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If you are not located in the United States, you -will have to check the laws of the country where you are located before -using this eBook. - -Title: Life and death - -Author: Albert Dastre - -Translator: William John Greenstreet - -Release Date: June 25, 2021 [eBook #65699] - -Language: English - -Character set encoding: UTF-8 - -Produced by: Turgut Dincer, Les Galloway and the Online Distributed - Proofreading Team at https://www.pgdp.net - -*** START OF THE PROJECT GUTENBERG EBOOK LIFE AND DEATH *** - - Transcriber’s Notes - -Obvious typographical errors have been silently corrected. Variations -in hyphenation and accents have been standardised but all other -spelling and punctuation remains unchanged. - -In the section on The Instinct of Life, fifth paragraph “and Flourens -has reduced the ratio to that of 5:1, which would still give us 120 -years.” the 120 has been corrected to 100. - -In Book V, Chapter III, Chemical Changes, “and at the same time would -transform an amido-group into an amido-group.” is as printed. - -Italics are represented thus _italic_, superscripts thus y^ and -subscripts thus y⌄. - - - - - LIFE AND DEATH. - - - - - LIFE AND DEATH - - BY - - A. DASTRE, - PROFESSOR OF PHYSIOLOGY AT THE SORBONNE. - - TRANSLATED BY - W. J. GREENSTREET, M.A., F.R.A.S. - - THE WALTER SCOTT PUBLISHING CO., LTD., - PATERNOSTER SQUARE, LONDON, E.C. - CHARLES SCRIBNER’S SONS, - 153-157 FIFTH AVENUE, NEW YORK. - 1911 - - - - - PREFACE. - - -The educated and inquiring public of the present day addresses to the -experts who have specialized in every imaginable subject the question -that was asked in olden times of Euclid by King Ptolemy Philadelphus, -Protector of Letters. Recoiling in dismay from the difficulties -presented by the study of mathematics and annoyed at his slow progress, -he inquired of the celebrated geometer if there was not some royal -road, could he not learn geometry more easily than by studying the -Elements. The learned Greek replied, “There is no royal road.” These -royal roads making every branch of science accessible to the cultivated -mind did not exist in the days of Ptolemy and Euclid. But they do exist -to-day. These roads form what we call Scientific Philosophy. - -Scientific philosophy opens a path through the hitherto inextricable -medley of natural phenomena. It throws light on facts, it lays bare -principles, it replaces contingent details by essential facts. And -thus it makes science accessible and communicable. Intellectually it -performs a very lofty function. - -There is virtually a philosophy of every science. There is therefore -a philosophy of the science which deals with the phenomena of life -and death—_i.e._, of physiology. I have endeavoured to give a summary -of this philosophy in this volume. I have had in view two classes of -readers. In the first place there are readers of general culture who -are desirous of knowing something of the trend of ideas in biology. -They already form quite a large section of the great public. - -These scholars and inquirers, with Bacon, believe that the only science -is general science. What they want to know is not what instruments we -use, our processes, our technique, and the thousand and one details of -the experiments on which we spend our lives in the laboratory. What -they are interested in are the general truths we have acquired, the -problems we are trying to solve, the principles of our methods, the -progress of our science in the past, its state in the present, its -probable course in the future. - -But I venture to think that this book is also addressed to another -class of readers, to those whose professional study is physiology. -To them it is dedicated. They have been initiated into the mysteries -of the science. They are learning it by practice. That is the right -method. Practice makes perfect. Claude Bernard used to say that in -order to be an expert in experimental science you must first be “a -laboratory rat.” And among us there are many such “laboratory rats.” -They are guided in the daily task of investigation by a dim instinct -of the path and of the direction of contemporary physiology. Perhaps -it may be of assistance to them to find their more or less unconscious -ideas here expressed in an explicit form. - - A. DASTRE. - - - - - CONTENTS. - - - BOOK I. - - THE FRONTIERS OF SCIENCE. GENERAL THEORIES OF - LIFE AND DEATH. THEIR SUCCESSIVE TRANSFORMATIONS. - - CHAP. PAGE - - I. EARLY THEORIES 1 - - II. ANIMISM 5 - - III. VITALISM 15 - - IV. THE MONISTIC THEORY 34 - - V. THE EMANCIPATION OF SCIENTIFIC RESEARCH FROM - THE YOKE OF PHILOSOPHICAL DOCTRINE 42 - - - BOOK II. - - THE DOCTRINE OF ENERGY AND THE LIVING WORLD. - GENERAL IDEAS OF LIFE. ALIMENTARY LIFE. - - I. ENERGY IN GENERAL 57 - - II. ENERGY IN BIOLOGY 97 - - III. ALIMENTARY ENERGETICS 116 - - - BOOK III. - - THE CHARACTERS COMMON TO LIVING BEINGS. - - I. DOCTRINE OF VITAL UNITY 146 - - II. MORPHOLOGICAL UNITY OF LIVING BEINGS 157 - - III. CHEMICAL UNITY OF LIVING BEINGS 173 - - IV. TWOFOLD CONDITIONS OF VITAL PHENOMENA. - IRRITABILITY 188 - - V. THE SPECIFIC FORM: ITS ACQUISITION, ITS REPARATION 199 - - VI. NUTRITION. FUNCTIONAL ASSIMILATION. FUNCTIONAL - DISTRIBUTION. ASSIMILATING SYNTHESIS 209 - - - BOOK IV. - - THE LIFE OF MATTER. - - I. UNIVERSAL LIFE (OPINIONS OF THE PHILOSOPHERS - AND POETS). CONTINUITY BETWEEN BRUTE BODIES - AND LIVING BODIES. ORIGIN OF THE PRINCIPLE OF - CONTINUITY 239 - - II. ORIGIN OF LIVING MATTER IN BRUTE MATTER 249 - - III. ORGANIZATION AND CHEMICAL COMPOSITION OF LIVING - MATTER AND BRUTE MATTER 255 - - IV. EVOLUTION AND MUTABILITY OF LIVING MATTER AND - BRUTE MATTER 259 - - V. THE COMPOSITION OF THE SPECIFIC FORM. LIVING - BODIES AND CRYSTALS. CICATRIZATION 281 - - VI. NUTRITION IN THE LIVING BEING AND IN THE - CRYSTAL 290 - - VII. GENERATION IN BRUTE BODIES AND LIVING BODIES. - SPONTANEOUS GENERATION 294 - - - BOOK V. - - SENESCENCE AND DEATH. - - I. THE DIFFERENT POINTS OF VIEW FROM WHICH DEATH - MAY BE REGARDED 307 - - II. CONSTITUTION OF THE ORGANISMS. PARTIAL DEATH. - COLLECTIVE DEATHS 312 - - III. PHYSICAL AND CHEMICAL CHARACTERISTICS OF - CELLULAR DEATHS. NECROBIOSIS 321 - - IV. APPARENT PERRENNITY OF COMPLEX INDIVIDUALS 330 - - V. IMMORTALITY OF THE PROTOZOA AND OF SLIGHTLY - DIFFERENTIATED CELLS 334 - - VI. LETHALITY OF THE METAZOA AND OF DIFFERENTIATED - CELLS 340 - - VII. MAN. THE INSTINCT OF LIFE AND THE INSTINCT OF - DEATH 345 - - INDEX 361 - - - - - LIFE AND DEATH. - - BOOK I. - - THE FRONTIERS OF SCIENCE—GENERAL THEORIES OF LIFE AND DEATH—THEIR - SUCCESSIVE TRANSFORMATIONS. - - Chapter I. Early Theories.—II. Animism.—III. Vitalism.—IV. Monism.—V. - Emancipation of Scientific Research from the Yoke of Philosophy. - - - CHAPTER I. - - EARLY THEORIES. - - Animism—Vitalism—The Physico-Chemical Theory—Their Survival and - Transformations. - - -The fundamental theories of science are but the expression of its -most general results. What, then, is the most general result of the -development of physiology or biology—that is to say, of that department -of science which has life as its object? What glimpse do we get of the -fruit of all our efforts? The answer is evidently the response to that -essential question—What is Life? - -There are beings which we call living beings; there are bodies which -have never been alive—inanimate bodies; and there are bodies which are -no longer alive—dead bodies. The fact that we use these terms implies -the idea of a common attribute, of a _quid proprium_, life, which -exists in the first, has never existed in the second, and has ceased -to exist in the last. Is this idea correct? Suppose for a moment that -this is so, that this implicit supposition has a foundation, and that -there really is something which corresponds to the word “_life_.” Must -we then wait for the last days of physiology, and in a measure for its -last word before we know what is hidden behind this word, “life”? - -Yes, no doubt positive science should be precluded from dealing with -questions of this kind, which are far too general. It should be limited -to the study of second causes. But, as a matter of fact, scientific men -in no age have entirely conformed to this provisional or definitive -antagonism. As the human mind cannot rest satisfied with indefinite -attempts, or with ignorance pure and simple, it has always asked, and -even now asks, from the spirit of system the solution which science -refuses. It appeals to philosophical speculation. Now, philosophy, in -order to explain life and death, offers us hypotheses. It offers us -the hypotheses of thirty, of a hundred, or two thousand years ago. -It offers us animism; vitalism in its two forms, unitary vitalism -or the doctrine of vital force, and dismembered vitalism or the -doctrine of vital properties; and finally, materialism, a mechanical -theory, unicism or monism,—to give it all its names—_i.e._, the -physico-chemical doctrine of life. There are, therefore, at the present -day, in biology, representatives of these three systems which have -never agreed on the explanation of vital phenomena—namely, animists, -vitalists, and monists. But it is pretty clear that there must have -been some change between yesterday and to-day. Not in vain has general -science and biology itself made the progress which we know has been -made since the Renaissance, and especially during the course of the -nineteenth century. The old theories have been compelled to take new -shape, such parts as have become obsolete have been cut away, another -language is spoken—in a word, the theories have become rejuvenated. The -neo-animists of our day, Chauffard in 1878, von Bunge in 1889, and more -recently Rindfleisch, do not hold exactly the same views as Aristotle, -St. Thomas Aquinas, or Stahl. Contemporary neo-vitalists, physiologists -like Heidenhain, chemists like Armand Gautier, or botanists like Reinke -do not between 1880 and 1900 hold the same views as Paracelsus in -the fifteenth century and Van Helmont in the seventeenth, as Barthez -and Bordeu at the end of the eighteenth, or as Cuvier and Bichat at -the beginning of the nineteenth century. Finally, the mechanicians -themselves, whether they be disciples of Darwin and Haeckel, as -most biologists of our own time, or disciples of Lavoisier, as most -physiologists of the present day, have passed far beyond the ideas of -Descartes. They would reject the coarse materialism of the celebrated -philosopher. They would no longer consider the living organism as a -machine, composed of nothing but wheels, springs, levers, presses, -sieves, pipes, and valves; or again of matrasses, retorts, or alembics, -as the iatro-mechanicians and would-be chemists of other days believed. - -All that is changed, at any rate in form. If we look back only thirty -or forty years we see that the old doctrines have undergone more or -less profound modifications. The changes of form, which have been -made necessary by the acquisitions of contemporary science, enable us -to appreciate its progress. They enable us to give an account of the -progress of biology, and for this reason they deserve to be examined -with some attention. It is into this examination that I ask my readers -to accompany me. - - - - - CHAPTER II. - - ANIMISM. - - The Common Characteristic of Animism and Vitalism: the Human - Statue—Primitive Animism—Stahl’s Animism—First Objection with - Reference to the Relation between Soul and Body—Second Objection: the - Unconscious Character of Vital Operations—Twofold Modality of the - Soul—Continuity of the Soul and Life. - - -Children are taught that there are three kingdoms in Nature—the mineral -kingdom and the two living kingdoms, animal and vegetable. This is the -whole of the sensible world. Then above all that is placed the world of -the soul. School-boys therefore have no doubts on the doctrines that we -discuss here. They have the solution. To them there are three distinct -spheres, three separate worlds—matter, life, and thought. - -It is this preconceived idea that we are about to examine. Current -opinion solves _a priori_ the question of the fundamental homogeneity -or lack of resemblance of these three orders of phenomena—the phenomena -of inanimate nature, of living nature, and of the thinking soul. -_Animism_, _vitalism_, and _monism_ are, in reality, different ways of -looking at them. They are the different answers to this question:—Are -vital, psychic, and physico-chemical manifestations essentially -distinct? Vitalists distinguish between life and thought, animists -identify them. In the opposite camp mechanicians, materialists, or -monists make the same mistake as the animists, but to that mistake they -add another: they assimilate the forces at play in animals and plants -to the general forces of the universe; they confuse all three—soul, -life, inanimate nature. - -These problems belong on many sides to metaphysical speculation. They -have been discussed by philosophers; they have been solved from time -immemorial in different ways, for reasons and by arguments which it is -not our purpose to examine here, and which, moreover, have not changed. -But on some sides they belong to science, and must be tested in the -light of its progress. Cuvier and Bichat, for example, considered that -the forces in action in living beings were not only different from -physico-mechanical forces, but were utterly opposed to them. We now -know that this antagonism does not exist. - -The preceding doctrines, therefore, depend up to a certain point on -experiment and observation. They are subject to the test of experiment -and observation in proportion as the latter can give us information -on the degree of difference or analogy presented by psychic, vital, -and physico-chemical facts. Now, scientific investigations have thrown -light on these points. There is no doubt that the analogies and the -resemblances of these three orders of manifestations have appeared more -and more numerous and striking as our knowledge has advanced. Hence it -is that animism can count to-day but very few advocates in biological -science. Vitalism in its different forms counts more supporters, but -the great majority have adopted the physico-chemical theory. - -Both animism and vitalism separate from matter a directing principle -which guides it. At bottom they are mythological theories somewhat -similar to the paganism of old. The fable of Prometheus or the story -of Pygmalion contains all that is essential. An immaterial principle, -divine, stolen by the Titan from Jupiter, or obtained from Venus by -the Cypriot sculptor, descends from Olympus and animates the form, -till then inert, which has been carved in the marble or modelled in -the clay. In a word, there is a human statue. It receives a breath of -heavenly fire, a vital force, a divine spark, a soul, and behold! it is -alive. But this breath can also leave it. An accident happens, a clot -in a vein, a grain of lead in the brain—the life escapes, and all that -is left is a corpse. A single instant has proved sufficient to destroy -its fascination. This is how all men picture to their minds the scene -of death. The breath escapes; something flies away, or flows away with -the blood. The happy genius of the Greeks conceived a graceful image -of this, for they represented the life or the soul in the form of a -butterfly (Psyche) leaving the body, an ethereal butterfly, as it were, -opening its sapphire wings. - -But what is this subtle and transient guest of the human statue, this -passing stranger which makes of the living body an inhabited house? -According to the animists it is the soul itself, in the sense in which -the word is understood by philosophers; the immortal and reasoning -soul. To the vitalists it is an inferior, subordinate soul; a soul, as -it were, of secondary majesty, the vital force, or in a word, life. - -_Primitive Animism._—Animism is the oldest and most primitive of the -conceptions presented to the human mind. But in so far as it is a -co-ordinated doctrine, it is the most recent. In fact it only received -its definitive expression in the eighteenth century, from Stahl, the -philosopher-physician and chemist. - -According to Tylor, one of the first speculations of primitive man, of -the savage, is as to the difference between the living body and the -corpse. The former is an inhabited house, the latter is empty. To such -rudimentary intellects the mysterious inhabitant is a kind of _double_ -or duplicate of the human form. It is only revealed by the shadow -which follows the body when illuminated by the sun, by the image of -its reflection in the water, by the echo which repeats the voice. It -is only seen in a dream, and the figures which people and animate our -dreams are nothing but these doubled, impalpable beings. Some savages -believe that at the moment of death the double, or the soul, takes up -its residence in another body. Sometimes each individual possesses, not -one of these souls, but several. According to Maspero, the Egyptians -counted at least five, of which the principle, the _ka_ or _double_, -would be the aeriform or vaporous image of the living form. Space is -peopled by souls on their travels, which leave one set of bodies to -occupy another set. After having been the cause of life in the bodies -which they animated, they react from without on other beings, and are -the cause of all sorts of unexpected events. They are benevolent or -malevolent spirits. - -Analogy inevitably leads simple minds to extend the same ideas to -animals and plants; in a word, to attribute souls to everything alive, -souls more or less nomadic, wandering, or interchangeable, as is -taught in the doctrine of metempsychosis. Mons. L. Errera points out -that this primitive, co-ordinated, hierarchized doctrine—meet subject -for the poet’s art—is the basis of all ancient mythologies. - -_The Animism of Stahl._—Modern animism was much more narrow in scope. -It was a medical theory—_i.e._ almost exclusive to man. Stahl had -adopted it in a kind of reaction against the exaggerations of the -mechanical school of his time. According to him, the life of the body -is due to the intelligent and reasoning soul. It governs the corporeal -substance and directs it towards an assigned end. The organs are its -instruments. It acts on them directly, without intermediaries. It -makes the heart beat, the muscles contract, the glands secrete, and -all the organs perform their functions. Nay more, it is itself the -architectonic soul, which has constructed and which maintains the body -which it rules. It is the _mens agitat molem_ of Virgil. - -It is remarkable that these ideas, so excessively and exaggeratedly -spiritualistic, should have been brought forward by a chemist and a -physician, while ideas completely opposed to these were admitted by -philosophers like Descartes and Leibniz, who were decided believers -in the spirituality of the soul. Stahl had been Professor of Medicine -at the University of Halle, physician to the Duke of Saxe-Weimar, -and later to the King of Prussia. He left an important medical and -chemical work, both theoretical and practical. He is the author of the -celebrated theory of phlogiston, which held its ground in chemistry up -to the time of Lavoisier. He died about 1734. - -Animism survived him for some time, maintained by the zeal of a few -faithful disciples. But after the witty mockery of Bordeu,[1] in 1742, -it began to decay. We must, however, point out that an attempt to -revive this theory was made in 1878 by a well-known doctor of the last -generation, E. Chauffard. While preserving the essential features of -the theory, this learned physician proposed to bring it into harmony -with modern science, and to free it from all the reproaches which had -been levelled at it. - - [1] In a thesis presented in 1742 at Montpellier, Bordeu, then only - twenty years of age, made game of the tasks imposed by animists on - the Soul, “which has to moisten the lips when required;” or, “whose - anger produces the symptoms of certain diseases;” or again, “which - is prevented by the consequences of original sin from guiding and - directing the body.” - -_The Animism of E. Chauffard._—These reproaches were numerous. The -most serious is of a philosophic nature. It rises from the difficulty -of conceiving a direct and immediate action of the soul, considered as -a spiritual principle, upon the matter of the body. There is such an -abyss—hewn by the philosophic mind itself—between soul and body, that -it is impossible to imagine any relation between them. We can only get -a glimpse of how the soul might become an instrument of action. - -This was the problem which sorely tried the genius of Leibniz. -Descartes, in earlier days, attacked it vigorously, like an Alexander -cutting the Gordian knot. He separated the soul from the body, and -made of the latter a pure machine in the government of which the soul -had no part. He attributed all the known manifestations of vital -activity to inanimate forces. Leibniz, also, was compelled to reject -all action, all contact, all direct relation, every real bond between -soul and body, and to imagine between them a purely metaphysical -relation—pre-established harmony:—“Soul and body agree in virtue of -this harmony, the harmony pre-established since the creation, and -in no way by a mutual, actual, physical influence. Everything that -takes place in the soul takes place as if there were no body, and so -everything takes place in the body as if there were no soul.” At this -point we almost reach a scientific materialism. It is easy for the -materialist to break this frail tie of pre-established harmony which so -loosely unites body and soul, and to exhibit the organism as under the -sole control of universal mechanics and physics. - -Thus the weak point of Stahl’s animism was the supposition of a -direct action exercised on the organism by a distinct, heterogeneous, -spiritual principle. - -Chauffard has endeavoured to avoid this pitfall. In conformity with -modern ideas, he has brought together what the ancient philosophers -and Stahl himself separated—the activity of matter and the activity of -the soul. “Thought, action, function, are embraced in an indissoluble -union.” This is the classical but not very lucid theory which has been -so often reproduced—_Homo factus est anima vivens_—which Bossuet has -expressed in the celebrated formula: “Soul and body form a natural -whole.” - -A second objection raised against animism is that the soul acts -consciously, with reflection, and with volition, and that its essential -attributes are not found in most physiological phenomena, which, on the -contrary are automatic, involuntary, and unconscious. The contradictory -nature of these characteristics has obliged vitalists to conceive of -a vital principle distinct from thought. Chauffard, agreeing here -with Boullieu, Tissot, and Stahl himself, does not accept this -distinction; he refuses to shatter the unity of the vivifying and -thinking principle. He prefers to attribute to the soul two modes of -action: the one which is exercised on the acts of thought, and hence -it proceeds consciously, with reflection, and with volition; the other -exercising control over the physiological phenomena which it governs, -“by unconscious impressions, and by instinctive determinations, obeying -primordial laws.” This soul is hardly in keeping with his definition of -a conscious, reflecting, and voluntary principle; it is a new soul, a -somatic soul, singularly akin to that _rachidian soul_ which, according -to Pflüger, a well-known German physiologist, resides in each segment -of the spinal marrow, and is responsible for reflex movements. - -_Twofold Modality of the Soul._—This twofold modality of the soul, this -duality admitted by Stahl and his disciples, was repugnant to many -thinkers, and it is this repugnance that gave rise to the vitalistic -school. It appeared to them to be a heresy tainted by materialism—and -so it was. In this lay the strength and the weakness of animism. It -admits of a unique animating principle for all the manifestations of -the living being, for the higher facts in the realm of thought, and for -the lower facts connected with the body. It throws down the barriers -which separate them. It fills up the gap between the different forms of -human activity, and assimilates them the one to the other. - -Now this is precisely what materialism does. It, too, reduces to -a single order the psychical and physiological phenomena, between -which it no longer recognizes anything but a difference of degree, -thought being only a maximum of the vital movement, or life a minimum -of thought. In truth, the aims of the two schools are diametrically -opposed; the one claims to raise corporeal activity to the dignity -of thinking activity, and to spiritualize the vital fact; the other -lowers the former to the level of the latter and materializes the -psychic fact. But, though the intentions are different, the result is -identical. Spiritualistic monism inclines towards materialistic monism. -One step more, and the soul, confused with life, will be confused with -physical forces. - -On the other hand, twofold modality has this advantage, that it -escapes the objection drawn from the existence of so many living -beings to which a thinking soul cannot be attributed; an anencephalous -fœtus, the young of the higher animals, the lower animals and plants, -living without thought, or with a minimum of real, conscious thought. -The advocate of animism replies that this physiological activity -is still a soul, but one which is barely aware of its existence—a -gleam of consciousness. In this theory, the knowledge of self, the -consciousness, is of all degrees. On the other hand, in the eyes of the -vitalist, it is an absolute fact which allows of no attenuation, of no -middle course between the being and the non-being. - -It is this conception of the continuity of the soul and life, it is -the affirmation of a possible lowering of the complete consciousness -down to a mere gleam of knowledge, and finally down to unconscious -vital activity, which saved animism from complete shipwreck. That is -why this ancient doctrine finds, even in the present day, a few rare -supporters. An able German scientist, G. von Bunge, well known for -his researches in physiological chemistry, professes animistic views -in a work which appeared in 1889. He attributes to organized beings a -guiding principle, a kind of vital soul. A distinguished naturalist, -Rindfleisch, of Lübeck, has likewise taken his place among the -advocates of what we may call neo-animism. - - - - - CHAPTER III. - - VITALISM. - - Its Extreme Forms—Early Vitalism, and Modern Neo-vitalism—Advantage - of distinguishing between Soul and Life—§ 1. _The Vitalism of - Barthez_—Its Extension—The Seat of the Vital Principle—The Vital - Knot—The Vital Tripod—Decentralisation of the Vital Principle—§ 2. - _The Doctrine of Vital Properties_—Galen, Van Helmont, Xavier Bichat, - and Cuvier—Vital and Physical Properties antagonistic—§ 3. _Scientific - Neo-vitalism_—Heidenhain—§ 4. _Philosophical Neo-vitalism_—Reinke. - - -_Extreme Forms: Early Vitalism and Modern Neo-vitalism._—Contemporary -neo-vitalism has weakened primitive vitalism in some important points. -The latter made of the vital fact something quite specific, irreducible -either to the phenomena of general physics or to those of thought. -It absolutely isolated life, separating it above from the soul, and -below from inanimate matter. This sequestration is nowadays much less -rigorous. On the psychical side the barrier remains, but it is lowered -on the material side. The neo-vitalists of to-day recognize that the -laws of physics and chemistry are observed within, as well as without, -the living body; the same natural forces intervene in both, only they -are “otherwise directed.” - -The vital principle of early times was a kind of anthromorphic, pagan -divinity. To Aristotle, this force, the _anima_, _the Psyche_, worked, -so to speak, with human hands. According to the well-known expression, -its situation in the human body corresponds to that of a pilot on a -vessel, or to that of a sculptor or his assistant before the marble or -clay. And, in fact, we have no other clear image of a cause external -to the object. We have no other representation of a force external to -matter than that which is offered by the craftsman making an object, or -in general by the human being with his activity, free, or supposed to -be free, and directed towards an end to be realized. - -Personifications of this kind, the mythological entities, the imaginary -beings, the ontological fictions, which ever filled the stage in the -mind of our predecessors, have definitely disappeared; no longer -have they a place in the scientific explanations of our time. The -neo-vitalists replace them by _the idea of direction_, which is another -form of the same idea of finality. The series of second causes in the -living being seems to be regulated in conformity with a plan, and -directed with a view to carrying it out. The tendency which exists -in every being to carry out this plan,—that is to say, the tendency -towards its end,—gives the impulse that is necessary to carry it out. -Neo-vitalists claim that vital force directs the phenomena which it -does not produce, and which are in reality carried out by the general -forces of physics and chemistry. - -Thus, the directing impulse, _considered as really active_, is the last -concession of modern vitalism. If we go further, and if we refuse to -the directing idea executive power and efficient activity, the vital -principle is weakened, and we abandon the doctrine. We can no longer -invoke it. We cease to be vitalists if the part played by the vital -principle is thus far restricted. At first it was both the author of -the plan and the universal architect of the organic edifice; it is -now only the architect directing his workmen, and they are physical -and chemical agents. It is now reduced to the plan of the work, and -even this plan has no objective existence; it is now only an _idea_. It -has only a shadow of reality. To this it has been reduced by certain -biologists. For this we may thank Claude Bernard; and he has thereby -placed himself outside and beyond the weakest form of vitalism. He -did not consider the _idea of direction_ as a real principle. The -connection of phenomena, their harmony, their conformity to a plan -grasped by the intellect, their fitness for a purpose known to the -intellect, are to him but a mental necessity, a metaphysical concept. -The plan which is carried out has only a subjective existence; the -directing force has no efficient virtue, no executive power; it does -not emerge from the intellectual domain in which it took its rise, and -does not “react on the phenomena which enabled the mind to create it.” - -It is between these two extreme incarnations of the vital principle, on -the one hand an executive agent, on the other a simple directing plan, -that the motley procession of vitalist doctrines passes on its way. -At the point of departure we have a vital force, personified, acting, -as we have stated, as if with human hands fashioning obedient matter; -this is the pure and primitive form of the theory. At the other extreme -we have a vital force which is now only a directing idea, without -objective existence, and without an executive rôle; a mere concept -by which the mind gathers together and conceives of a succession of -physico-chemical phenomena. On this side we are brought into touch with -monism. - -_The Reasons given by the Vitalists for distinguishing Soul from -Life._—It is, in particular, on the opposite side, in the psychical -world, that the early vitalists professed to entrench themselves. -We have just seen that their doctrines were not so subtle as those -of to-day; the vital principle to them was a real agent, and not an -ideal plan in the process of being carried out. But they distinguished -this spiritual principle from another co-existent with it in superior -living beings—at any rate, in man: the thinking soul. They boldly -distinguished between them, because the activity of the one is -manifested by knowledge and volition, while on the contrary, the -manifestations of the other for the most part escape both consciousness -and volition. - -In fact, we know nothing of what goes on in the normal state of our -organs. Their perfect performance of their functions is translated to -us solely by an obscure feeling of comfort. We do not feel the beating -of the heart, the periodic dilations of the arteries, the movements of -the lungs or intestine, the glands at their work of secretion, or the -thousand reflex manifestations of our nervous system. The soul, which -is conscious of itself, is nevertheless ignorant of all this vital -movement, and is therefore external to it. - -This is the view of all the philosophers of antiquity. Pythagoras -distinguished the real soul, the thinking soul, the _Nous_, the -intelligent and immortal principle, characterized by the attributes of -consciousness and volition, from the vital principle, the _Psyche_, -which gives breath and animation to the body, and which is a soul of -secondary majesty, active, transient, and mortal. Aristotle did the -same. On the one side he placed the soul properly so called, the _Nous_ -or intellect—that is to say, the understanding with its rational -intelligence; on the other side was the directing principle of life, -the irrational and vegetative Psyche. - -This distinction agrees with the fact of the diffusion of life. Life -does not belong to the superior animals alone, and to the man in whom -we can recognize a reasoning soul. It is extended to the vast multitude -of humbler beings to which such lofty faculties cannot be attributed, -the invertebrates, microscopic animals, and plants. The advantage is -compensated for by the inconvenience of breaking down all continuity -between the soul and life; a continuity which is the principle of the -two other doctrines, animism and monism, and which is, we may say, the -very aim and the unquestionable tendency of science. - -As for classical philosophy, it satisfies the necessity of establishing -the unity of the living being,—_i.e._, of bringing into harmony soul -and body,—but in a manner which we need not here discuss. It attributes -to the soul several modalities, several distinct powers: powers of -the vegetative life, powers of the sensitive life, and powers of the -intellectual life. And this other solution of the problem would be, in -the opinion of M. Gardair, in complete agreement with the doctrines of -St. Thomas Aquinas. - - - § 1. THE VITALISM OF BARTHEZ: ITS EXTENSION. - - -Vitalism reached its most perfect expression in the second half -of the eighteenth century in the hands of the representatives of -the Montpellier school—Bordeu, Grimaud, and Barthez. The last, in -particular, contributed to the prevalence of the doctrine in medical -circles. A man of profound erudition, a collaborates with d’Alembert -in the _Encyclopædia_, he exercised quite a preponderant influence -on the medicine of his day. Stationed at Paris during part of his -career, physician to the King and the Duke of Orleans, we may say -that he supported his theories by every imaginable influence which -might contribute to their success. In consequence of this, the medical -schools taught that vital phenomena are the immediate effects of a -force which has no analogues outside the living body. This conception -reigned unchallenged up to the days of Bichat. - -After Bichat, the vitalism of Barthez, more or less modified by the -ideas of the celebrated anatomist, continued to hold its own in all the -schools of Europe until about the middle of the nineteenth century. -Johannes Müller, the founder of physiology in Germany, admitted, about -1833, the existence of a unique vital force “aware of all the secrets -of the forces of physics and chemistry, but continually in conflict -with them, as the supreme cause and regulator of all phenomena.” When -death came, this principle disappeared and left no trace behind. One -of the founders of biological chemistry, Justus Liebig, who died in -1873, shared these ideas. The celebrated botanist, Candolle, who lived -up to 1893, taught at the beginning of his career that the vital -force was one of the four forces ruling in nature, the other three -being—attraction, affinity, and intellectual force. Flourens, in -France, made the vital principle one of the five properties of forces -residing in the nervous system. Another contemporary, Dressel, in 1883, -endeavoured to bring back into fashion this rather primitive, monistic, -and efficient vitalism. - -_The Seat of the Vital Principle._—Meanwhile, another question was -asked with reference to this vital principle. It was a question of -ascertaining its seat: or, in other words, of finding its place in -the organism. Is it spread throughout the organism, or is it situated -in some particular spot from which it acts upon every part of the -body? Van Helmont, a celebrated scientist at the end of the sixteenth -century, who was both physician and alchemist, gave the first and -rather quaint solution of this difficulty. The vital principle, -according to him, was situated in the stomach, or rather in the opening -of the pylorus. It was the _concierge_, so to speak, of the stomach. -The Hebrew idea was more reasonable. The life was connected with the -blood, and was circulated with it by means of all the veins of the -organism. It escaped from a wound at the same time as the liquid blood. -It is clear that in this belief we see why the Jews were forbidden to -eat meat which had not been bled. - -_The Vital Knot._—In 1748 a doctor named Lorry found that a very small -wound in a certain region of the spinal marrow brought on sudden -death. The position of this remarkable point was ascertained in 1812 -by Legallois, and more accurately still by Flourens in 1827. It is -situated in the rachidian bulb, at the level of the junction of the -neck and the head; or more precisely, on the floor of the fourth -ventricle, near the origin of the eighth pair of cranial nerves. This -is what was called the _vital knot_. Upon the integrity of this spot, -which is no bigger than the head of a pin, depends the life of the -animal. Those who believed in a localisation of the vital principle -thought that they had found the seat desired; but for that to be so the -destruction of this spot must be irremediable, and must necessarily -cause death. But if the _vital knot_ be destroyed, and respiration be -artificially induced by means of a bellows, the animal resists: it -continues to live. It is only the nervous stimulating mechanism of the -respiratory movements which has been attacked in one of its essential -parts. - -Life, therefore, resides no more in this point than it does in the -blood or in the stomach. Later experiment has shown that it resides -everywhere, that each organ enjoys an independent life. Each part of -the body is, to use Bordeu’s strong expression, “_an animal in an -animal_”; or to adopt the phrase due to Bichat, “_a particular machine -within the general machine_.” - -_The Vital Tripod._—What then is life, or, in other words, what is the -biological activity of the individual, of the animal, of man? It is -clearly the sum total, or rather, the harmony of these partial lives -of the different organs. But in this harmony it seems that there are -certain instruments which dominate and sustain the others. There are -some whose integrity is more necessary to the preservation of existence -and health, and of which any lesion makes death more inevitable. They -are the lungs, the heart, and the brain. Death always ensues, said -the early doctors, if any one of these three organs be injured. Life -depends, therefore, on them, as if upon a three-legged support. Hence -the idea of the _vital tripod_. It is no longer a single seat for -the vital principle, but a kind of throne on three-supports. Life is -decentralized. - -This was only the first step, very soon followed by many others, in the -direction of vital decentralization. Experiment showed, in fact, that -every organ separated from the body will continue to live if provided -with the proper conditions. And here, it is not only a question of -inferior beings; of plants that are propagated by slips; of the _hydra_ -which Trembley cut into pieces, each of which generated a complete -hydra; of the _naïs_ which C. Bonnet cut up into sections, each of -which reconstituted a complete annelid. There is no exception to the -rule. - -_Decentralization of the Vital Principle._—The result is the same in -the higher vertebrates, only the experiment is much more difficult. At -the Physiological Congress of Turin in 1901, Locke showed the heart -of a hare, extracted from the body of the animal, and beating for -hours as energetically and as regularly as if it were in its place. -He suspended it in the air of a room at the normal temperature, the -sole condition being that it was irrigated with a liquid composed of -certain constituents. The animal had been dead some time. More recently -Kuliabko has shown in the same way the heart of a man still beating, -although the man had been dead some eighteen hours. The same experiment -is repeated in any physiological laboratory, in a much easier manner, -with the heart of a tortoise. This organ, extracted from the body, -fitted up with rubber tubes to represent its arteries and veins, and -filled with the defibrinated blood of a horse or an ox taken from the -slaughter-house, works for hours and days pumping the liquid blood into -its rubber aorta, just as if it were pumping it into the living aorta. - -But it is unnecessary to multiply examples. Every organ can be made -to live for a longer or shorter period even though removed from its -natural position; muscles, nerves, glands, and even the brain itself. -Each organ, each tissue therefore enjoys an independent existence; -it lives and works for itself. No doubt it shares in the activity of -the whole, but it may be separated therefrom without being thereby -placed in the category of dead substances. For each aliquot part of the -organism there is a partial life and a partial death. - -This decentralization of the vital activity is finally extended in -complex beings from the organs to the tissues, and from the tissues -to the anatomical elements—the cells. The idea of decentralization -has given birth to the second form of vitalism, a softened down and -weakened form—namely, pluri-vitalism, or the theory of vital properties. - - - § 2. THE THEORY OF VITAL PROPERTIES. - - -The advocates of the theory of vital properties have cut up into -fragments the monistic and indivisible guiding principle of Bordeu and -Barthez. They have given it new currency—pluri-vitalism. This theory -maintains the existence of spiritual powers of a lower order, which -control phenomena more intimately than the vital principle did. These -powers, less lofty in their dignity than the rational soul of the -animists, or the soul of secondary majesty of the unitarian vitalists, -are eventually incorporated in the living matter of which they will -then be no longer more than the properties. Brought into closer -connection therefore with the sensible world, they will be more in -harmony with the spirit of research and with scientific progress. - -The defect of the earlier conceptions, their common illusion, rose from -their seeking the cause outside the object, from their demanding an -explanation of vital phenomena from a principle external to living, -immaterial, and unsubstantial matter. Here this defect is less marked. -The pluri-vitalists will in turn appeal to the vital properties as -modes of activity, inherent in the living substance in which and by -which they are manifested, and derived from the arrangement of the -molecules of this substance—that is to say, from its organization. This -is almost the conception of the present day. - -But this progress will only be realized at the end of the evolution -of the pluri-vitalist theory. At the outset this theory seems an -exaggeration of its predecessor, and a still more exaggerated form of -the mythological paganism with which it was reproached. The archeus, -the blas, the properties, the spirits—all have at first the effect -of the genii or of the gods imagined by the ancients to preside over -natural phenomena, of Neptune stirring up the waters of the sea, and -of Eolus unchaining the winds. These divinities of the ancient world, -the nymphs, the dryads, and the sylvan gods, seem to be transported to -the Middle Ages, to that age of argument, that philosophical period of -the history of humanity, and there metamorphosed into occult causes, -immaterial powers, and personified forces. - -_Galen._—The first of the pluri-vitalists was Galen, the physician of -Marcus Aurelius, the celebrated author of an Encyclopædia of which the -greater part has been lost, and of which the one book preserved held -its own as the anatomical oracle and breviary throughout the Middle -Ages. According to Galen the human machine is guided by three kinds -of spirits: _animal spirits_, presiding over the activity of the -nervous system; _vital spirits_ governing most of the other functions; -and finally, _natural spirits_ regulating the liver and susceptible -of incorporation in the blood. In the sixteenth century, in the time -of Paracelsus, Galen’s spirits became _Olympic spirits_. They still -presided over the functional activity of the organs, the liver, heart, -and brain, but they also existed in all the bodies of nature. - -_Van Helmont._—Finally, the theory was laid down by Van Helmont, -physician, chemist, experimentalist, and philosopher, endowed with -a rare and penetrating intellect. Here we find many profound truths -combined with fantastic dreams. Refusing to admit the direct action of -an immaterial agent, such as the soul, on inert matter, on the body, he -filled up the abyss which separated them by creating a whole hierarchy -of immaterial principles which played the part of mediators and -executive agents. At the head of this hierarchy was placed the thinking -and immortal soul; below was the sensitive and mortal soul, having for -its minister the _principal archeus_, the _aura vitalis_, a kind of -incorporeal agent, which is remarkably like the vital principle, and -which had its seat at the orifice of the stomach. Below again were the -subordinate agents, the _blas_, or _vulcans_ placed in each organ, and -intelligently directing its mechanism like skillful workmen. - -These chimerical ideas are not, however, so far astray as the theory -of vital properties. When we see a muscle contract, we say that this -phenomenon is due to a vital property—_i.e._, a property without any -analogue in the physical world, namely _contractility_, in the same -way the nerve possesses two vital properties, _excitability_ and -_conductibility_, which Vulpian proposed to blend into one, calling it -_neurility_. These are mere names, serving as a kind of shorthand; but -to those who believe that there is something real in it, this something -is not very far from the _blas_ of Van Helmont. _Vulcans_, hidden in -the muscle or the nerve, are here detected by attraction, there by -the production and the propagation of the nervous influx; that is to -say, by phenomena of which we as yet know no analogues in the physical -world, but of which we cannot say that they do not exist. - -_X. Bichat and G. Cuvier: Vital and Physical Properties -Antagonistic._—The archeus and the blas of Van Helmont were but a -first rough outline of vital properties. Xavier Bichat, the founder of -general anatomy, wearied of all these incorporeal entities, of these -unsubstantial principles with which biology was encumbered, undertook -to get rid of them by the methods of the physicist and the chemist. The -physics and the chemistry of his day referred phenomenal manifestations -to the properties of matter, gravity, capillarity, magnetism, etc. -Bichat did the same. He referred vital manifestations to the properties -of living tissues, if not, indeed, of living matter. Of these -properties as yet but very few were known: the irritability described -by Glisson, which is the excitability of current physiology; and the -irritability of Haller, which is nothing but muscular contractility. -Others had to be discovered. - -There is no need to recall the mistake made by Bichat and followed -by most scientific men of his time, such as Cuvier in France, and J. -Müller in Germany, for the story has been told by Claude Bernard. His -mistake was in considering the vital properties not only as distinct -from physical properties but even as opposed to them. The one -preserve the body, the others tend to destroy it. They are always in -conflict. Life is the victory of the one; death is the triumph of the -other. Hence the celebrated definition given by Bichat: “Life is the -sum total of functions which resist death,” or the definition of the -Encyclopædia: “Life is the contrary of death.” - -Cuvier has illustrated this conception by a graphic picture. He -represents a young woman in all the health and strength of youth -suddenly stricken by death. The sculptural forms collapse and show the -angularities of the bones; the eyes so lately sparkling become dull; -the flesh tint gives place to a livid pallor; the graceful suppleness -of the body is now rigidity, “and it will not be long before more -horrible changes ensue; the flesh becomes blue, green, black, one part -flows away in putrid poison, and another part evaporates in infectious -emanations. Finally, nothing is left but saline or earthy mineral -principles, all the rest has vanished.” Now, according to Cuvier, what -has happened? - -These alterations are the effect of external agents, air, humidity, and -heat. They have acted on the corpse just as they used to act on the -living being; but before death their assault had no effect, because it -was repelled by the vital properties. Now that life has disappeared -the assault is successful. We know now that external agents are not -the cause of these disorders. They are caused by the microbes of -putrefaction. It is against _them_ that the organs were struggling, and -not against physical forces. - -The mistake made by Bichat and Cuvier was inexcusable, even in their -day. They were wrong not to attach the importance they deserved to -Lavoisier’s researches. He had asserted, apropos of animal heat and -respiration, the identity of the action of physical agents in the -living body and in the external world. On the other hand, Bichat, by a -flash of genius, decentralized life, dispersing the vital properties -in the tissues, or, as we should now say, in the living matter. It was -from the comparison between the constitution and the properties of -living matter and those of inanimate matter that light was to come. - - - § 3. SCIENTIFIC NEO-VITALISM. - - -We can now understand the nature of modern neo-vitalism. It borrows -from its predecessor its fundamental principle—namely, the specificity -of the _vital fact_. But this specificity is no longer _essential_, it -is only _formal_. The difference between it and the physical fact grows -less and almost vanishes. It consists of a diversity of mechanisms or -executive agents. For example, digestion transforms the alimentary -starch in the intestines into sugar; the chemist does the same in his -laboratory, only he employs acids, while the organism employs special -agents, ferments, in this case a diastase. It is a particular form of -chemistry, but still it is a chemistry. That is how Claude Bernard -looked at it. The vital fact was not fundamentally distinguished from -the physico-chemical fact, but only in form. - -This expurgated and accommodated vitalism (Claude Bernard pushed his -concessions so far as to call his doctrine “physico-chemical vitalism”) -was revived a few years ago by Chr. Bohr and Heidenhain. - -Other biologists, instead of attributing the difference between the -phenomena of the two orders to the manner of their occurrence, seem to -admit the complete identity of the mechanisms. It is no longer then in -itself, individually, that the vital act is particularized, but in the -manner in which it is linked to others. The vital order is a series of -physico-chemical acts realizing an ideal plan. - -Neo-vitalism has therefore assumed two forms, one the more scientific -and the other the more philosophical. - -_Chr. Bohr and Heidenhain._—Its scientific form was given to it by -Chr. Bohr, an able physiologist at Copenhagen, and by Heidenhain, -a professor at Breslau, who was one of the lights of contemporary -German physiology. The course of their researches led these two -experimentalists, working independently, to submit to fresh -investigation the ideas of Lavoisier and those of Bichat, on the -relation of physico-chemical forces to the vital forces. - -It was by no means a question of a general inquiry, deliberately -instituted with the object of discovering the part played respectively -by physical and physiological factors in the performance of the various -functions. Such an investigation would have taken several generations -to complete. No; the question had only come up incidentally. Chr. Bohr -had studied with the utmost care the gaseous exchanges which take place -between the air and the blood in the lungs. The gaseous mixture and -the liquid blood are face to face; they are separated by thin membrane -formed of living cells. Will this membrane behave as an inert membrane -deprived of vitality, and therefore obeying the physical laws of the -diffusion of gases? Well! no. It does not so behave. The most careful -measurements of pressures and of solubilities leave no doubt in this -respect. The living elements of the pulmonary membrane must therefore -intervene in order to disturb the physical phenomenon. Things happen -as if the exchanged gases were subjected not to a simple diffusion, -a physical fact obeying certain rules, but to a real secretion, a -physiological or vital phenomenon, obeying laws which are also fixed, -but different from the former. - -On the other hand, Heidenhain was led about the same time to analogous -conclusions with respect to the liquid exchanges which take place -within the tissues, between the liquids (lymphs) which bathe the -blood-vessels externally and the blood which those vessels contain. -The phenomenon is very important because it is the prologue of the -actions of nutrition and assimilation. Here again, the two factors of -exchange are brought into relation through a thin wall, the wall of -the blood-vessel. The physical laws of diffusion, of osmosis, and of -dialysis, enable us to foretell what would take place if the vitality -of the elements of the wall did not intervene. Heidenhain thought he -observed that things took place otherwise. The passage of the liquids -is disturbed by the fact that the cellular elements are alive. It -assumes the characteristics of a physiological act, and no longer -those of a physical act. Let us add that the interpretation of these -experiments is difficult, and it has given rise to controversies which -still persist. - -These two examples, around which others might be grouped, have led -certain physiologists to diminish the importance of the physical -factors in the functional activity of the living being to the advantage -of the physiological factors. It would therefore seem that the vital -force, to use a rather questionable form of language, withdraws in -a certain measure the organized being from the realm of physical -forces—and this conclusion is one form of contemporary neo-vitalism. - - - § 4. PHILOSOPHICAL NEO-VITALISM. - - -Contemporary neo-vitalism has assumed another form, more philosophical -than scientific, by which it is brought closer to vitalism, properly -so called. We should like to mention the experiment of Reinke,[2] in -Germany. Reinke is a botanist of distinction, who distinguishes the -speculative from the positive domain of science, and cultivates both -with success. - - [2] Reinke, _Die Welt als That_; Berlin, 1899. - -His ideas are analogous to those of A. Gautier, of Chevreul, and of -Claude Bernard himself. He thinks, with these masters, that the mystery -of life is not to be found in the nature of the forces that it brings -into play, but in the direction that it gives them. All these thinkers -are struck by the order and the direction impressed upon the phenomena -which take place in the living being, by their interconnection, by -their apparent adaptation to an end, by the kind of impression that -they give of a plan which is being carried out. All these reflections -lead Reinke to attach great weight to the idea of a “directing force.” - -The physico-chemical energies are no doubt the only ones which are -manifested in the organized being, but they are directed as a blind man -is by his guide. It seems as if a _double_ accompanies them like a -shadow. This intelligent guide of blind, material force is what Reinke -calls a _dominant_. Nothing could be more like the blas and the archeus -of Van Helmont. Material energies would thus be paired off with their -blas, their dominants, in the living organisms. In them there would -therefore be two categories of force: “material forces,” or rather, -material energies obeying the laws of universal energetics; and in the -second place, intelligent “spiritual forces,” the dominants. When the -sculptor is working his marble, in every blow which elicits a spark -there is something more than the strong force of the hammer. There is -thought, the volition of the artist, which is realizing a plan. In a -machine there is more than machinery. Behind the wheels is the object -which the author had in view when he adjusted them for a determined -end. The energies spent in action are regulated by the adjustment—that -is to say, by the dominants due to the intellect of the constructor. - -Thus it is in the living machine. The dominants in this case are the -guardians of the plan, the agents of the aim in view. Some regulate -the functional activity of the living body, and some regulate its -development and its construction. Such is the second form, the -philosophical form, extreme and teleological, of contemporary -neo-vitalism. - - - - - CHAPTER IV. - - THE MONISTIC THEORY. - - Physico-chemical Theory of Life.—Iatro-mechanism.—Descartes, - Borelli.—Iatro-chemistry.—Sylvius le Boë.—The Physico-chemical Theory - of Life.—Matter and Energy.—Heterogeneity is merely the result of the - arrangement or combination of homogeneous bodies.—Reservation relative - to the world of thought.—The Kinetic Theory. - - -The unicist or monistic doctrine gives us a third way of conceiving -the functional activity of the living being, by levelling and -blending its three forms of activity—spiritual, vital, and material. -It was expressed in the seventeenth and eighteenth centuries in -“iatro-mechanism” and “iatro-chemistry,” conceptions to which have more -recently succeeded the physico-chemical doctrine of life, and finally -“current materialism.” - -Materialism is not only a biological interpretation; it is a universal -interpretation applicable to the whole of nature, because it is -based on a determinate conception of matter. Here we find ourselves -confronted by the eternal enigma discussed by philosophers relative -to this fundamental problem of force and matter. We know what -answers were given to the problem by the Ionic philosophers—Thales, -Democritus, Heraclitus, and Anaxagoras, who discarded the agency of -every spiritual power external to matter. The explanation of the -world, the explanation of life, were reduced to the play of physical -or mechanical forces. Epicurus, a little later, maintained that the -knowledge of matter and its different forms accounts for all phenomena, -and therefore for those of life. - -Descartes, sharply separating the metaphysical world—that is to say, -the soul defined by its attribute, thought—from the physical or -material world characterized by extension, practically came to the same -conclusions as the materialists of antiquity. To him, as to them, the -living body was a mere machine. - -_Iatro-mechanism. Descartes. Borelli._—This, then, is the theory of the -iatro-mechanicians, of which we may consider Descartes the founder, -instead of the Greek philosophers. These ideas held their own for two -centuries, and were productive of such fruitful results in the hands of -Borelli, Pitcairn, Hales, Bernoulli, and Boerhaave, as to justify the -jest of Bacon that “the philosophy of Epicurus had done less harm to -science than that of Plato.” The iatro-mechanic school tenaciously held -its own until Bichat came upon the scene. - -_Iatro-chemistry. Sylvius le Boë._—It was from a reaction against their -exaggerations that Stahl created animism, and the Montpellier school -created vitalism. We gather some idea of the extravagant character -of their explanations by reading Boerhaave. To this celebrated -doctor the muscles were springs, the heart was a pump, the kidneys -a sieve, and the secretions of the glandular juices were produced -by pressure; the heat of the body was the result of the friction of -the globules of blood against the walls of the blood-vessels; it was -greater in the lungs because the vessels of the lungs were supposed -to be narrower than those of other organs. The inadequacy of these -explanations suggested the idea of completing them by the aid of -the chemistry which was then springing into being. This chemistry, -rudimentary as it was, longed for a share in the government of living -bodies and in the explanation of their phenomena. Distillations, -fermentations, and effervescences are now seen to play their rôle, a -rôle which was premature and carried to excess. Iatro-chemistry from -the general point of view is only an aspect of iatro-mechanics; but it -is also an auxiliary. Sylvius le Boë and Willis were its most eminent -representatives. This theory remained in the background until chemistry -made its great advance—that is to say, in the days of Lavoisier. After -that, its importance has gradually increased, particularly in the -present day. Nowadays, the general tendency is to regard the organic -functional activity, or even morphogeny—_i.e._, whatever there is -that is most peculiar to and characteristic of living beings—as a -consequence of the chemical composition of their substance. This is a -point of capital importance, and to it we must recur. - -_The Physico-chemical Theory of Life._—Contemporary biological schools -have made many efforts to secure themselves from any slips on the -philosophical side. They have avoided in most cases the psychological -problem; they have deliberately refrained from penetrating into the -world of the soul. Hence, _the physico-chemical theory_ of life has -been built up free from spiritualistic difficulties and objections. -But this prudence did not exclude the tendency. And there is no doubt, -as Armand Gautier said, that “real science can affirm nothing, but -it also can deny nothing outside observable facts;” and again, that -“only a science progressing backwards can venture to assert that matter -alone exists, and that its laws alone govern the world.” It is none the -less true that by establishing the continuity between inert matter and -living matter, we thereby render probable the continuity between the -world of life and the world of thought. - -_Matter and Energy._—Besides, and without any wish to enter into -this burning controversy, it is only too evident that there is no -agreement as to the terms that are used, and in particular as to -“matter” and “laws of matter.” It is not necessary to repeat that the -geometrical mould in which Descartes cast his philosophy has long -since been broken. The celebrated philosopher, in defining matter by -one attribute—extension, does not enable us to grasp its activity, an -activity revealed by all natural facts; and in defining the soul by -thought alone, prevents us from seeking in it the principle of this -material activity. This purely passive matter, consisting of extension -alone, this _bare matter_ was to Leibniz a pure concept. A philosopher -of our own time, M. Magy, has called it a sensorial illusion. The -bodies of nature exhibit to us _matter clad_ with energy, formed by -the indissoluble union of extension with an inseparable dynamical -principle. The Stoics declared that matter is mobile and not immobile, -active and not inert. Leibniz also had this in his mind when he -associated it indissolubly with an active principle, an “entelechy.” -Others have said that matter is “an assemblage of forces,” or with P. -Boscovitch, “a system of indivisible points without extension, centres -of force, in fact.” Space would be the geometrical locus of these -points. - -In this conception the materialistic school finds the explanation of -all phenomenality. Physical properties, vital phenomena, psychical -facts, all have their foundation in this immanent activity. Material -activity is a minimum of soul or thought which, by continuous gradation -and progressive complexity, without solution of continuity, without -an abrupt transition from the homogeneous to the heterogeneous, rises -through the series of living beings to the dignity of the human soul. -The observation of the transitions, an imperfect tracing of the -geometrical method of limits, thus enables us to pass from material to -vital, and from thence to psychical activity. - -_Apparent Heterogeneity is the Result of the Arrangement or the -Combination of Homogeneous Bodies._—In this system, material energy, -life, soul would only be more and more complex combinations of the -consubstantial activity with material atoms. Life appears distinct from -physical force, and thought from life, because the analysis has not yet -advanced far enough. Thus, glass would appear to the ancient Chaldeans -distinct from the sand and salt of which they made it. In the same way, -again, water, to modern eyes, is distinct from its constituents, oxygen -and hydrogen. The whole difficulty is that of explaining what this -“arrangement” of the elements can introduce that is new in the aspect -of the compound. We must know what novelty and apparent homogeneity -the variety of the combinations, which are only special arrangements -of the elementary parts, may produce in the phenomena. But we do -not know, and it is this ignorance which leads us to consider them -as heterogeneous, irreducible, and distinct in principle. The vital -phenomenon, the complexus of physico-chemical facts, thus appears to us -essentially different from those facts, and that is why we picture to -ourselves “dominants” and “directing forces” more or less analogous to -the sidereal guiding principle of Kepler, which, before the discovery -of universal attraction, regulated the harmony of the movements of the -planets. - -_A Reservation relative to the Psychical Order._—The scientific mind -has shown in every age a real predilection towards the mechanical or -materialistic theory. Contemporary scientists as a whole have accepted -it in so far as it blends the vital and the physical orders. Objections -and contradictions are only offered in the realm of psychology. A. -Gautier, for example, has contested with infinite originality and -vigour the claims of the materialists who would reduce the phenomenon -of thought to a material phenomenon. The most general characteristic -of material phenomenality is—as we shall later see—that it may be -considered as a mutation of energy—_i.e._, it obeys the laws of -energetics. Now thought, says A. Gautier, is not a form of material -energy. Thought, comparison, volition, are not acts of material -phenomenality; they are states. They are realities; they have no -mass; they have no physical existence. They respond to adjustments, -arrangements, and concerted groupings of material manifestations of -chemical molecules. They escape the laws of energetics. - -_Kinetic Theory._—We shall lay aside for a moment this serious problem -relative to the limits of the world of conscious thought and of the -world of life. It is on the other side, on the frontiers of living and -inanimate nature, that the mechanical view triumphs. It has furnished a -universal conception agreeing with phenomena of every kind—viz., the -kinetic theory, which ascribes everything in nature to the movements of -particles, molecules, or atoms. - -The living and the physical orders are here reduced to one unique -order, because all the phenomena of the sensible universe are -themselves reduced to one and the same mechanics, and are represented -by means of the atom and of motion. This conception of the world, -which was that of the philosophers of the Ionic school in the remotest -antiquity, which was modified later by Descartes and Leibniz, has -passed into modern science under the name of the kinetic theory. The -mechanics of atoms ponderable or imponderable, would contain the -explanation of all phenomenality. If it were a question of physical -properties or vital manifestations, the objective world in final -analysis would offer us nothing but motion. Every phenomenon would be -expressed by an atomistic integral, and that is the inner reason of -the majestic unity which reigns in modern physics. The forces which -are brought into play by Life are no longer to be distinguished in -this ultimate analysis from other natural forces. All are blended in -molecular mechanics. - -The philosophical value of this theory is undeniable. It has exercised -on physical science an influence which is justified by the discoveries -which it has suggested. But to biology, on the other hand, it has lent -no aid. It is precisely because it descends too deeply into things, and -analyzes them to the uttermost, that it ceases to throw any light upon -them. The distance between the hypothetical atom and the apparent and -concrete fact is too great for the one to be able to throw light on the -other. The vital phenomenon vanishes with its individual aspect; its -features can no longer be distinguished. - -Besides, a whole school of contemporary physicists (Ostwald of Leipzig, -Mach of Vienna) is beginning to cast some doubt on the utility of the -kinetic hypothesis in the future of physics itself, and is inclined to -propose to substitute for it the theory of energetics. We shall see, -in every case, that this other conception, as universal as the kinetic -theory, _the theory of Energy_, causes a vivid light to penetrate into -the depths of the most difficult problems in physiology. - -Such are, with their successive transformations, the three principal -theories, the three great currents between which biology has been -tossed to and fro. They are sufficiently indicative of the state of -positive science in each age, but one is astonished that they are not -more so; and this is due to the fact that these conceptions are too -general. They soar too high above reality. More characteristic in this -respect will be particular theories of the principal manifestations of -living matter, of its perpetuity by generation, of the development by -which it acquires its individual form, on heredity. It is here that it -is of importance to grasp the progressive march of science—that is to -say, the design and the plan of the building which is being erected, -“blindly, so to speak,” by the efforts of an army of workers, an army -becoming more numerous day by day. - - - - - CHAPTER V. - -THE EMANCIPATION OF SCIENTIFIC RESEARCH FROM THE YOKE OF PHILOSOPHICAL - THEORIES. - - The excessive use of Hypothetical Agents in Physiological - Explanations—§ 1. _Vital Phenomena in Fully-constituted - Organisms_—Provisory Exclusion of the Morphogenic idea—The Realm - of the Morphogenic Idea as the Sanctuary of Vital Force—§ 2. _The - Physiological Domain properly so called_—Harmony and Connection - of Phenomena—Directive Forces—Claude Bernard’s Work—Exclusion - of Vital Force, of Final Cause, of the “Caprice” of Living - Nature—Determinism—The Comparative Method—Generality of Vital - Phenomena—Views of Pasteur. - - -The theories whose history we have just sketched in broad outline long -dominated science and exercised their influence on its progress. - -This domination has ceased to exist. Physiology has emancipated itself -from their sway, and this, perhaps, is the most important revolution -in the whole history of biology. Animism, vitalism, materialism, -have ceased to exercise their tyranny on scientific research. These -conceptions have passed from the laboratory to the study; from being -physiological, they have become philosophical. - -This result is the work of the physiologists of sixty years ago. It -is also the consequence of the general march of science and of the -progress of the scientific spirit, which shows a more and more marked -tendency to separate completely the domain of facts from the domain of -hypotheses. - -_Excessive Use of Hypothetical Agents in Physiological -Explanations._—It may be said that in the early part of the nineteenth -century, in spite of the efforts of a few real experimenters from -Harvey to Spallanzani, Hales, Laplace, Lavoisier, and Magendie, the -science of the phenomena of life had not followed the progress of -the other natural sciences. It remained in the fog of scholasticism. -Hypotheses were mingled with facts, and imaginary agents carried out -real acts, in inexpressible confusion. The soul (_animism_), the vital -force (_vitalism_), and the final cause (_finalism_, _teleology_) -served to explain everything. - -In truth, it was also at this time that physical agents, electric and -magnetic fluids, or, again, chemical affinity, played an analogous -part in the science of inanimate nature. But there was at least this -difference in favour of physicists and chemists, that when they had -attributed some new property or aptitude to their hypothetical agents -they respected what they attributed. The physiological physicians -respected no law, they were subject to no restraint. Their vital force -was capricious; its spontaneity made anticipation impossible; it acted -arbitrarily in the healthy body; it acted more arbitrarily still in the -diseased body. All the subtlety of medical genius was called into play -to divine the fantastic behaviour of the spirit of disease. If we speak -here of physiologists and doctors alone and do not quote biologists, it -is because the latter had not yet made their appearance as authorities; -their science had remained purely descriptive, and they had not yet -begun to explain phenomena. - -Such was the state of things during the first years of the nineteenth -century. It lasted, thanks to the founders of contemporary -physiology—Claude Bernard in France, and Brücke, Dubois-Reymond, -Helmholtz, and Ludwig in Germany—until a separation took place between -biological research and philosophical theories. This delimitation -operated in physiology properly so called—_i.e._ in a branch of the -biological domain in which as yet joint tenancy had been the rule. An -important revolution fixed the respective divisions of experimental -science and philosophical interpretation. It was understood that the -one ends where the other begins, that the one follows the other, -that one may not cross the other’s path. There is between them only -one doubtful region about which there is dispute, and this uncertain -frontier is constantly being shifted and science daily gains what -philosophy loses. - - - § 1. VITAL PHENOMENA IN CONSTITUTED ORGANISMS. - - -A displacement of this kind had taken place at the time of which we -speak. It was agreed, that as far as concerns the phenomena which take -place in _a constructed and constituted living organism_, it would -no longer be permissible to allow to intervene in their explanation -forces or energies other than those which are brought into play in -inanimate nature. Just as when explaining the working of a clock, the -physicist will not invoke the volition or the art of the maker, or -the design that he had in view, but only the connection of causes and -effects which he has utilized; so, for the living machine, whether -the most complex, such as the human body, or the most elementary, -such as the cell, we may not invoke a final cause, a vital force, -external to that organism and acting on it from without, but only the -connections and the fluctuations of effects which are the sole actual -and efficient causes. In other words Ludwig, and Claude Bernard in -particular, expelled from the domain of active phenomenality the three -chimeras—Vital Force, Final Cause, and the “Caprice” of Living Nature. - -But the living being is not only a _completely constructed and -completely constituted_ organism. It is not a finished clock. It is a -clock which is making itself, a mechanism which is constructing and -perpetuating itself. Nothing of the kind is known to us in inanimate -nature. Physiology has found—in what is called morphogeny—its temporary -limit. It is beyond this limit, it is in the study of phenomena by -which the organism is constructed and perpetuated, it is in the region -of the functions of generation and development, that philosophical -doctrines expand and flourish. This is the present frontier of these -two powers, philosophy and science. We shall presently delimit them -more precisely. W. Kühne, a well-known scientist whose death is -deplored, not in Germany alone, amused himself by studying the division -of biological doctrines among the members of learned societies and in -the world of academies. He summed up this kind of statistical inquiry -by saying in 1898 at the Cambridge Congress, that physiologists were -nearly all advocates of the physico-chemical doctrine of life, and that -the majority of naturalists were advocates of vital force, and of the -theory of final causes. - -_Domain of the Morphogenic Idea as the Last Sanctuary of Vital -Force._—We see the reason for this. Physiology, in fact, has taken -up its position in the explanation of the functional activity of -the constituted organism—_i.e._, on a ground where intervene, as we -shall show further on, no energies and no matter other than universal -energies and matter. Naturalists, on the other hand, have more -especially considered—and from the descriptive point of view alone, -at least up to the times of Lamarck and Darwin—the functions, the -generation, the development and the evolution of species. Now these -functions are most refractory and inaccessible to physico-chemical -explanations. So, when the time came to give an account of what they -had done, the zoologists had substituted for executive agents nothing -but vital force under its different names. To Aristotle it is the vital -force itself which, as soon as it is introduced into the body of the -child, moulds its flesh and fashions it in the human form. Contemporary -naturalists, the Americans C. O. Whitman and C. Philpotts, for example, -take the same line of argument. Others, such as Blumenbach and Needham, -in the eighteenth century, invoked the same division under another -name, that of the _nisus formativus_. Finally, others play with words; -they talk of heredity, of adaptation, of atavism, as if these were -real, active, and efficient beings; while they are only appellations, -names applied to collections of facts. - -This region was therefore eminently favourable to the rapid increase of -hypotheses, and so they abounded. There were the theories of Buffon, -of Lamarck, of Darwin, of Herbert Spencer, of E. Haeckel, of His, of -Weismann, of De Vries, and of W. Roux. Each biologist of any mark -had his own, and the list is endless. But here already this domain of -theoretical speculation is checked on various sides by experiment. -J. Loeb, a pure physiologist, has recently given his researches a -direction in which zoology believes may be found the explanation of -the mysterious part played by the male element in fecundation. On -the other hand, the first experiment of the artificial division of -the living cell (_merotomy_), with its light upon the part played by -the nucleus in the preservation and regeneration of the living form, -is also the work of a physiological experimenter. It dates back to -1852, and is due to Augustus Waller. This experiment was made on the -sensitive nervous cell of the spinal ganglions and on the motor cell -of the anterior cornua of the spinal cord. The effects were correctly -interpreted twelve or fifteen years later. All that zoologists have -done is to repeat, perhaps unconsciously, this celebrated experiment -and to confirm the result. - -Thus we see that the attack upon the vitalist sanctuary has commenced. -But it would be a grave mistake to suppose that final cause and vital -force are on the point of being dislodged from their entrenchments. -Philosophical speculation has an ample field before it. Its frontiers -may recede. For a long time yet there will be room for a more or less -modernized vitalism. - - - § 2. THE PHYSIOLOGICAL DOMAIN PROPERLY SO CALLED. - - -Vitalism is even found installed in the region of physiology, although -for the moment this science limits its ambition to the consideration -of the completely constructed organized being, perfected in its form. -The explanation of the working of this constituted machine cannot be -complete until we take into account the harmony and the adjustment of -its parts. - -_Harmony and Connection of Parts: Directive Forces._—These constituent -parts are the cells. We know that the progress of anatomy has resulted -in the cellular doctrine—_i.e._, in the two-fold affirmation that the -most complicated organism is composed of microscopic elements, the -cells, all similar, true stones of the living building, and that it -derives its origin from a single cell, egg, or spore, the sexual cell, -or cell of germination. The phenomena of life, looked at from the point -of view of the formed individual, are therefore harmonized in space; -just as, regarded from the point of view of the individual in formation -and in the species, they are connected in time. This harmony and this -connection are in the eyes of the majority of men of science the most -characteristic properties of the living being. This is the domain of -_vital specificity_, of the _directive forces_ of Claude Bernard and A. -Gautier, and of the _dominants_ of Reinke. It is not certain, however, -that this order of facts is more specific than the other. Generation -and development have been considered by many physiologists, and quite -recently by Le Dantec, as simple aspects or modalities of nutrition or -assimilation, the common and fundamental property of every living cell. - -_The Work of Claude Bernard. Exclusion of Vital Force, of Vital Cause, -of the “Caprice” of Living Nature._—It is not, however, a slight -advance or inconsiderable advantage to have eliminated vitalistic -hypotheses from almost the whole domain of present-day physiology, and -to have them, as it were, thrown back into its hinterland. This is the -work of the scientific men of the first half of the nineteenth century, -and particularly of Claude Bernard, who has thereby won the name of -the founder or lawgiver of physiology. They found in the old medical -school an obstinate adversary glorying in its sterile traditions. In -vain was it proved that vital force cannot be an efficient cause; that -it was a creation of the brain, an insubstantial phantom introduced -into the anatomical marionette and moving it by strings at the will of -any one—its adepts having only to confer upon it a new kind of activity -to account for the new act. All that had been shown with the utmost -clearness by Bonnet of Geneva, and by many others. It had also been -said that the teleological explanation is equally futile, since it -assigns to the present, which exists, an inaccessible, and evidently -ultimately inadequate cause, which does not yet exist. These objections -were in vain. - -_Determinism._—And so it was not by theoretical arguments that the -celebrated physiologist dealt with his adversaries, but by a kind of -lesson on things. In fact he was continually showing by examples that -vitalism and the theory of final causes were idle errors which led -astray experimental investigation; that they had prevented the progress -of research and the discovery of the truth in every case and on every -point in which they had been invoked. He laid down the principle of -_biological determinism_, which is nothing but the negation of the -“caprice” of living nature. This postulate, so evident that there was -no need to enunciate it in the physical sciences, had to be shouted -from the housetops for the benefit of supporters of vital spontaneity. -It is the statement that, under determined circumstances materially -identical, the same vital phenomena will be identically reproduced. - -_Comparative Method._—Claude Bernard completed this critical work by -laying down the laws of experiment on living beings. He commended as -the rational method of research the _comparative method_. This should -be, and is in fact, the daily instrument of all those who work in -physiology. It compels the investigator in every research bearing -on organized beings to institute a series of tests, such that the -conditions which are unknown and impossible to know may be regarded -as identical from one test to another; and when we are certain that a -single condition is variable, it compels him to discover the character -of the condition we are dealing with, and to learn to appreciate, and -to measure its influence. It is safe to say that the errors which are -daily committed in biological work have their cause in some infraction -of this golden rule. In physical science the obligation to follow -the comparative method is much less felt. In most cases the _witness -test_[3] is useless. In physiology the witness test is indispensable. - - [3] In an article on the experimental method recently published in the - _Dictionnaire de Physiologie_, M. Ch. Richet writes as follows:—“We - must therefore never cease to carry out comparative experiments. - I do not hesitate to say that this comparison is the basis of the - experimental method.” It is in fact what was taught by Claude - Bernard in maxim and by example. It is no exaggeration to assert - that nine-tenths of the errors which take place in research work - are imputable to some breach of this method. When an investigator - makes a mistake, save in the case of material error, it is almost - certainly due to the fact that he has neglected to carry out one - of the comparative tests required in the problem before him. The - following is an instance which happened since the above pages were - written:—Several years ago a chemist announced the existence in the - blood serum of a ferment, lipase, capable of saponifying fats—that is - to say, of extracting from them the fatty acid. From this he deduced - many consequences relative to the mechanism of fermentations. But on - the other hand, it has been since shown (April 1902) that this lipase - of the serum does not exist. How did the error arise? The author in - question had mixed normally obtained serum with oil, and he had noted - the acidification of the mixture; he assured himself of the fact by - adding carbonate of soda. He saw the alkalinity of the mixture, serum - + oil + carbonate of soda, diminish, and he drew the conclusion that - the acid came from the saponified oil. He did not make the comparative - test, serum + carbonate of soda. If he had done so, he would have - ascertained that it also succeeded, and that therefore as the acid did - not come from the saponification of the oil, since there was none, its - production could not prove the existence of a lipase. - -_Generality of Vital Phenomena._—If we add that Claude Bernard opposed -the narrow opinion, so dear to early medicine, which limited the -consideration of vitality to man, and the contrary notion of the -essential generality of the phenomena of life from man to the animal, -and from the animal to the plant, we shall have given very briefly an -idea of the kind of revolution which was accomplished about the year -1864, the date of the appearance of the celebrated _l’Introduction à la -médecine expérimentale_. - -The ideas we have just recalled seem to be as evident as they are -simple. These principles appear so well founded that in a measure they -form an integral part of contemporary mentality. What scientist would -nowadays deliberately venture to explain some biological fact by the -intervention of the evidently inadequate vital force or final cause? -And who, to account for the apparent inconsistency of the result, -would bring forward the “caprice” of living nature? And who again would -openly dispute the utility of the comparative method? - -What the physiologists of to-day, according to Claude Bernard, would no -longer do, their predecessors would do, and not the least important of -them. Longet, for example, at a full meeting of the Académie, apropos -of recurrent sensibility, and Colin (of Alfort), communicating his -statistical results on the temperature of two hearts, accepted more or -less explicitly the indetermination of vital facts. And why confine -our remarks to our predecessors? The scientists of to-day are much -the same. So here again we see the reappearance of the phantom of the -final cause in so-called scientific explanations. One fact is accounted -for by the necessity of the self-defence of the organism; another by -the necessity to a warm-blooded animal of keeping its temperature -constant. Le Dantec has recently reproached zoologists for giving as -an explanation of fecundation the advantage that an animal enjoys in -having a double line of ancestors. We might as well say, as L. Errera -has pointed out, that the inundations of the Nile occur in order to -bring fertility to Egypt. - -We must not therefore depreciate the marvellous work which has -emancipated modern physiology from the tutelage of early theories. -The witnesses of this revolution appreciated its importance. One of -them remarked as follows, on the appearance of _l’Introduction à la -médecine expérimentale_, which contained, however, only a portion of -the theory:—“Nothing more luminous, more complete, or more profound, -has ever been written upon the true principles of an art so difficult -as that of experiment. This book is scarcely known because it is on a -level to which few people nowadays attain. The influence it will have -on medical science, on its progress, and on its very language, will -be enormous. I cannot now prove my assertion, but the reading of this -book will leave so strong an impression that I cannot help thinking -that a new spirit will at once inspire these splendid researches.” -This was said by Pasteur in 1866. That is what he thought of the work -of his senior and his rival, at the moment when he himself was about -to inspire those “splendid researches” with the movement of reform, -the importance and the consequences of which have no equivalent in -the history of science. By their discoveries and their teaching, by -their examples and their principles, Claude Bernard and Pasteur have -succeeded in emancipating a portion of the domain of vital facts from -the direct intervention of hypothetical agents and first causes. They -were compelled, however, to leave to philosophical speculation, to -directing forces, to animism, to vitalism, an immense provisory field, -the field which corresponds to the functions of generation and of -development, to the life of the species and to its variations. Here we -find them again in various disguises. - - - - - BOOK II. - - THE DOCTRINE OF ENERGY AND THE LIVING WORLD. - - Summary: General Ideas of Life.—Elementary Life.—Chapter I. Energy - in General.—Chapter II. Energy in Biology.—Chapter III. Alimentary - Energetics. - - - GENERAL IDEAS OF LIFE. ELEMENTARY LIFE. - - -_Life is the Sum-total of the Phenomena Common to all Living Beings. -Elementary Life._—Living beings differ more in form and configuration -than in their manner of being. They are distinguished more by their -anatomy than by their physiology. There are, in fact, phenomena common -to all, from the highest to the lowest. This is because there is that -similar or identical foundation, that _quid commune_ which has enabled -us to apply to them the common name of “living beings.” Claude Bernard -gave to this sum-total of manifestations common to all (nutrition, -reproduction) the name of _elementary life_. To him _general -physiology_ was _the study of elementary life_; the two expressions -were equivalent, and they were equivalent to a longer formula which -the illustrious biologist has given as a title to one of his most -celebrated works—_The Study of the Phenomena Common to all Living -Beings, Animals, and Plants_. From this point of view each being is -distinguished from another being as a given _individual_ and as a -particular _species_; but all are in some way alike and thus resemble -one another: common life, elementary life, the essential phenomena of -life; it is _life itself_.[4] - - [4] Le Dantec has objected to this conception of phenomena common to - different living beings. He insists that all phenomena which take - place in a given living being are proper to him, and differ, however - slightly, from those of another individual. The objection is more - specious than real. - -The manifestations of life may therefore be regarded from the point -of view of what is most general among them. As we go down the scale -of anatomical organization, as we pass from apparatus (circulatory, -digestive, respiratory, nervous) to the _organs_ which compose them, -from the organs to the _tissues_, and finally from the tissues to the -_anatomical elements_ or _cells_ of which they are formed, we approach -that common, physiological dynamism which is _elementary life_, but we -do not actually reach it. The cell, the anatomical element, is still a -complicated structure. The elementary fact is further from us and lower -down. It is in the living matter, in the molecule of this matter, and -there we must seek it. - -Galen gave in days gone by as the object of researches on life, the -knowledge of the use of the different organs of the animal machine; -“de usu partium.” Later, Bichat assigned to them as their end the -determination of the _properties of tissues_. Modern anatomists and -zoologists try to reach the constituent element of these tissue—the -cell. Their dream is to construct a _cellular physiology_, a -_physiological cytology_; but we must go further than that. - -_General Physiology, Cellular Physiology, the Energetics of Living -Beings._—General physiology, as was taught by Pflüger and his school, -claims to go deeper down than the apparatus, or the organ, or even -the cell. As in the case of physics, general physiology endeavours to -reach, and really does in many cases reach, as far as the molecule. -It is not cellular, it is _molecular_. Already, in fact, the efforts -of modern science have succeeded in penetrating into the most general -phenomena of the living being—those attributable to living matter, -or, to speak more clearly, those which result from the play of the -universal laws of matter at work in this particular medium which is the -organized being. - -Robert Mayer and Helmholtz have the honour of having set physiology in -the right road. They founded _the energetics of living beings_—_i.e._, -they regarded the phenomena of life from the point of view of energy, -which is the factor of all the phenomena of the universe. - - - - - CHAPTER I. - - ENERGY IN GENERAL. - - Origin of the Idea of Energy.—The Phenomena of Nature bring into play - only two Elements, Matter and Energy.—§ 1. Matter.—§ 2. Energy.—§ 3. - Mechanical Energy.—§ 4. Thermal Energy.—§ 5. Chemical Energy.—§ 6. - The Transformations of Energy.—§ 7. The Principles of Energetics.—The - Principle of the Conservation of Energy.—§ 8. Carnot’s Principle.—The - Degradation of Energy. - - -_Origin of the Idea of Energy._—A new term, namely _energy_, has been -for some years introduced into natural science, and has ever since -assumed a more and more important place. It is owing to the English -physicists, and especially to the English electrical engineers, that -this expression has made its way into technology, an expression which -is part and parcel of both languages, and which has the same meaning -in both. The idea it expresses is, in fact, of infinite value in -industrial applications, and that is why its use has gradually spread -and become generalized. But it is not merely a practical idea. It is -above all a theoretical idea of capital importance to pure theory. It -has become the point of departure of a science, _energetics_, which, -although born but yesterday, already claims to embrace, co-ordinate, -and blend within itself all the other sciences of physical and living -nature, which the imperfection of our knowledge alone had hitherto kept -distinct and apart. - -On the threshold of this new science we find inscribed _the principle -of the conservation of energy_, which has been presented to us by -some as Nature’s supreme law, and which we may say dominates natural -philosophy. Its discovery marked a new era and accomplished a profound -revolution in our conception of the universe. It is due to a doctor, -Robert Mayer, who practised in a little town in Wurtemberg, and who -formulated the new principle in 1842, and afterwards developed its -consequences in a series of publications between 1845 and 1851. They -remained almost unknown until Helmholtz, in his celebrated memoir on -the conservation of force, brought them to light and gave them the -importance they deserved. From that time forward the name of the doctor -of Heilbronn, until then obscure, has taken its place among the most -honoured names in the history of science.[5] - - [5] Mayer’s claim to fame has been disputed. A Scotch physicist, P. - G. Tait, has investigated the history of the law of the conservation - of energy, which is the history of the idea of energy. The conception - has taken time to penetrate the human mind, but its experimental proof - is of recent date. P. G. Tait finds an almost complete expression - of the law of the conservation of energy in Newton’s third law of - motion—namely, “the law of the equality of action and reaction,” or - rather, in the second explanation which Newton gave of that law. In - fact, it was from this law that Helmholtz deduced it in 1847. He - showed that the law of the equality of action and reaction, considered - as a law of nature, involved the impossibility of perpetual motion, - and the impossibility of perpetual motion is, in another form, the - conservation of energy. - - At a meeting of the Academy of Science, at Berlin, 28th March 1878, - Du Bois-Reymond violently attacked Tait’s contention. The honour - of having been the first to conceive of the idea of energy and - conservation was awarded to Leibniz. Newton had no right to it, for - he appealed to divine intervention to set the planetary system on its - path when disturbed by accumulated perturbations. On the other hand, - Colding claims to have drawn his knowledge of the law of conservation - from d’Alembert’s principle. Whatever may be the theoretical - foundations of this law, we are here dealing with its experimental - proof. According to Tait, the proof can no more be attributed to R. - Mayer than to Seguin. The real modern authors of the principle of the - conservation of energy, who gave an experimental proof of it, are - Colding, of Copenhagen, and Joule, of Manchester. - -As for _energetics_, of which thermodynamics is only a section, it is -agreed that even if it cannot forthwith absorb mechanics, astronomy, -physics, chemistry, and physiology, and build up that general science -which will be in the future the one and only science of nature, it -furnishes a preparation for that ideal state, and is a first step in -the ascent to definite progress. - -Here I propose to expound these new ideas, in so far as they contain -anything universally accessible; and in the second place, I propose to -show their application to physiology—that is to say, to point out their -rôle and their influence in the phenomena of life. - -_Postulate: the Phenomena of Nature bring into play only two Elements, -Matter and Energy._—If we try to account for the phenomena of the -universe, we must admit with most physicists that they bring into play -two elements, and two elements only; namely, _matter_ and _energy_. All -manifestations are exhibited in one or other of these two forms. This, -we may say, is the postulate of experimental science. - -Just as gold, lead, oxygen, the metalloids, and the metals are -different kinds of matter, so it has been recognized that sound, light, -heat, and generally, the imponderable agents of the days of early -physics, are different varieties of energy. The first of these ideas -is older and more familiar to us, but it has not for that reason a more -certain existence. Energy is objective reality for the same reason that -matter is. The latter certainly appears more tangible and more easily -grasped by the senses. But, upon reflection, we are assured that the -best proof of their existence, in both cases, is given by the law of -their conservation—that is to say, their persistence in subsisting. - -The objective existence of matter and that of energy will therefore -be taken here as a postulate of physical science. Metaphysicians may -discuss them. We have but little room for such a discussion. - - - § I. MATTER. - - -It is certainly difficult to give a definition of matter which will -satisfy both physicists and metaphysicians. - -_Mechanical Explanation of the Universe. Matter is Mass._—Physicists -have a tendency to consider all natural phenomena from the point of -view of mechanics. They believe that there is a mechanical explanation -of the universe. They are always on the look out for it, implicitly or -explicitly. They endeavour to reduce each category of physical facts -to the type of the facts of mechanics. They have made up their minds -to see nowhere anything but the play of motion and force. Astronomy -is celestial mechanics. Acoustics is the mechanics of the vibratory -movements of the air or of sonorous bodies. Physical optics has become -the mechanics of the undulations of the ether, after having been the -mechanics of emission—a wonderful mechanics which represents exactly -all the phenomena of light, and furnishes us with a perfect objective -image of it. Heat, in its turn, has been reduced to a mode of motion, -and thermodynamics claims to embrace all its manifestations. As early -as 1812, Sir Humphry Davy wrote as follows:—“The immediate cause of -heat is motion, and the laws of transmission are precisely the same -as those of the transmission of motion.” From that time forth, this -conception developed into what is really a science. The constitution -of gases has been conceived by means of two elements—particles, and -the motions of these particles, determined in the strictest detail. -And finally, in spite of the difficulties of the representation of -electrical and magnetic phenomena after Ampère and before Maxwell and -Hertz, physicists have been able to announce in the second half of the -nineteenth century the unity of the physical forces realized in and -by mechanics. From that time forth, all phenomena have been conceived -as motion or modes of motion, only differing essentially one from the -other in so far as motions may differ—that is to say, in the masses of -the moving particles, their velocities, and their trajectories. The -external world has appeared essentially homogeneous; it has fallen a -prize to mechanics. Above all, there is heterogeneity in ourselves. It -is in the brain, which responds to the nervous influx engendered by the -longitudinal vibration of the air, by the specific sensation of sound, -which responds to the transverse vibration of the ether by a luminous -sensation, and in general to each form of motion by an irreducible -specific sensation. - -Forty years have passed since the mechanical explanation of the -universe reached its definite and perfect form. It dominates physics -under the name of the _theory of kinetic energy_. The minds of men -in our own time are so strongly impregnated with this idea that most -scientists of ordinary culture get no glimpse of the world of phenomena -but by means of this conception. And yet it is only an hypothesis. -But it is so simple, so intuitive, and appears to be so thoroughly -verified by experiment, that we have ceased to recognize its arbitrary -and unnecessarily contingent character. Many physicists from this -standpoint consider the kinetic theory as an imperishable monument. - -However, as in the case of H. Poincaré, the most eminent physicists and -mathematicians are not the dupes of this system; and without failing to -recognize the immense services which it has rendered to science, they -are perfectly well aware that it is only a system, and that there may -be other systems. Certain among them, such as Ostwald, Mach, and Duhem, -believe that the monument is showing signs of decay, and at present the -theory is opposed by another theory—namely, the theory of _energy_. - -The theory of _energy_ is usually considered and presented as a -consequence of the kinetic theory; but it is perfectly independent of -it, and it is, in fact, without relying on the kinetic theory, without -assuming the unity of physical forces, which are combined in molecular -mechanics, that we shall expound the general system. - -This is not the point at issue for the moment. It is not a question -of deciding the reality or the merit of this or that mechanical -explanation; it is a question of something more general, because upon -it depends the _idea of matter_. It is a question of knowing if there -are any explanations other than mechanical. The illustrious English -physicist, Lord Kelvin, does not seem willing to admit this. “I am -never satisfied,” he said, in his _Molecular Mechanics_, “until I have -made a mechanical model of the object. If I can make this model, I -understand; if I cannot, I do not understand.” - -This tendency of so vigorous a mind to be content only with mechanical -explanations, has been that of the majority of scientific men up to the -present day, and from it has arisen the scientific idea of matter. - -What is matter, in fact, to the student of mechanics? It is mass. All -mechanics is constructed of masses and forces. Laplace said: “The mass -of a body is the sum of its material points.” To Poisson, mass is the -quantity of matter of which a body is composed. Matter is therefore -confused with mass. Now, mass is the characteristic of the motion of -a body under the action of a given force; it defines obedience or -resistance to the causes of motion; it is the _mechanical parameter_; -it is the co-efficient proper to every mobile body; it is the first -_invariant_ of which a conception has been established by science. - -In fact, the word matter appears to be used in other senses by -physicists, but this is only apparently so. They have but broadened the -idea of the mechanicians. They have characterized matter by the whole -series of phenomenal manifestations which are _proportional to mass_, -such as weight, volume, chemical properties—so that we may say that the -notion of matter does not intervene scientifically with a different -signification from that of mass. - -_Two kinds of Matter. Ponderable and Imponderable._—In physics we -distinguish between two kinds of matter—ponderable, obeying the law of -universal attraction or weight, and imponderable matter or ether, which -we assume to exist and to escape the action of that force. Ether has no -weight, or extremely little weight. It is material in so far as it has -mass. It is its mass which confers existence on it from the mechanical -point of view—a logical existence, inferred from the necessity of -explaining the propagation of heat, light, or electricity. - -It may be observed that the use of mass really comes to bringing -another element, force, to intervene, and we shall see that force is -connected with energy; thus it comes to defining matter indirectly by -energy. The two fundamental elements are not therefore irreducible; on -the contrary, they should be one and the same thing. - -_Energy is the only Objective Reality._—This fusion into one will -become more evident still when we examine the different kinds of -energy, each of which exactly corresponds to one of the aspects of -active matter. Shall we define matter by _extension_, by the portion -of space it occupies, as certain philosophers do? The physicist will -answer that space is only known to us by the expenditure of energy -necessary to penetrate it (the activity of our different senses). And -then what is weight? It is _energy of position_ (universal attraction). -And so with the other attributes. So that if matter were separated -from the energetic phenomena by means of which it is revealed to -us—weight or energy of position, impenetrability or energy of volume, -chemical properties or chemical energies, mass or capacity for kinetic -energy—the very idea of matter would vanish. And that comes to saying -that fundamentally there is only one objective reality, _energy_. - -_Philosophical Point of View._—But from the philosophical point of view -are there objective realities? That is a wider question which throws -doubt upon matter itself, and which it is not our place to investigate -here. A metaphysician may always discuss and deny the existence of -the objective world. It may be maintained that man knows nothing -beyond his sensations, and that he only objectivates them and projects -them outside himself by a kind of hereditary illusion. We must avoid -taking sides in all these difficulties. Physics for the moment ignores -them—_i.e._, postpones their consideration. - -In a first approximation we agree to consider ponderable matter only. -Chemistry acquaints us with its different forms. They are the different -simple bodies, metalloids, metals, and the compound bodies, mineral -or organic. Hence we may say that chemistry is _the history of the -transformations of matter_. From the time of Lavoisier this science has -followed the transformations of matter, balance in hand, and ascertains -that they are accomplished without change of weight. - -_Law of the Conservation of Matter._—Imagine a system of bodies -enclosed in a closed vessel, and the vessel placed in the scale of a -balance. All the chemical reactions capable of completely modifying the -state of this system have no effect upon the scale of the balance. The -total weight is the same before, during, and after. It is precisely -this equality of weight which is expressed in all the equations with -which treatises on chemistry are filled. - -From a higher point of view we recognize here, in this _law of -Lavoisier_ or of the _conservation of weight_, the verification of one -of the great laws of nature which we extend to every kind of matter, -ponderable or not. It is the _law of the conservation of matter_, or -again, of the indestructibility of matter—“Nothing is lost, nothing -is created, all is transformation.” This is exactly what Tait held, -this impossibility of creating or destroying matter which at the same -time is a proof of its objective existence. This indestructibility -of ponderable matter is at the same time the fundamental basis of -chemistry. Chemical analysis could not exist if the chemist were not -sure that the contents of his vessel at the end of his operations ought -to be quantitatively, that is to say by weight, the same as at the -beginning, and during the whole course of the experiment.[6] - - [6] It must be added that the absolute rigour of this law has been - called in question in recent researches. It would only have an - approximate value. - - - § 2. ENERGY. - - -_The Idea of Energy Derived from the Kinetic Theory._—The notion of -energy is not less clear than the notion of matter, it is only more -novel to our minds. We are led to it by the mechanical conception which -now dominates the whole of physics, _the kinetic conception_, according -to which in the sensible universe there are no phenomena but those of -motion. Heat, sound, light, with all their manifestations so complex -and so varied, may, according to this theory, be explained by motion. -But then, if outside the brain and the mind which has consciousness and -which perceives, Nature really offers us only motion, it follows that -all phenomena are essentially homogenous among one another, and that -their apparent heterogeneity is only the result of the intervention of -our sensorium. They differ only in so far as movements are capable of -differing—that is to say, in velocity, mass, and trajectory. There is -something fundamental which is common to them and this _quid commune_ -is _energy_. Thus the idea of energy may be derived from the kinetic -conception, and this is the usual method of exposition. - -This method has the great inconvenience of causing an idea which lays -claim to reality to depend upon an hypothesis. And besides that, it -gives a view of it which may be false. It makes of the different forms -of energy something more than varieties which are equivalent to one -another. It makes of them _one and the same thing_. It blends into one -the modalities of energy and mechanical energy. For the experimental -idea of equivalence, the kinetic theory substitutes the arbitrary idea -of the equality, the blending, and the fundamental homogeneity of -phenomena. This no doubt is how the founders of energetics, Helmholtz, -Clausius, and Lord Kelvin understood things. But a more attentive study -and a more scrupulous determination not to go beyond the teaching -of experiment should compel us to reform this manner of looking at -it. And it is Ostwald’s merit that, after Hamilton, he insisted on -this truth—that the various kinds of physical magnitudes furnished -by the observation of phenomena are different and characteristic. In -particular, we may distinguish among them those which belong to the -order of _scalar_ magnitudes and others which are of the order of -_vector_ magnitudes. - -_The Idea of Energy derived from the Connection of Phenomena._—The idea -of energy is not absolutely connected with the kinetic theory, and it -should not be exposed therefore to the vicissitudes experienced by that -theory. It is of a higher order of truth. We can derive it from a less -unsafe idea, namely that of the _connection of natural phenomena_. To -conceive it we must get accustomed to this primordial truth, that there -are no _phenomena isolated_ in time and space. This statement contains -the whole point of view of energetics. - -The physics of early days had only an incomplete view of things, for it -considered phenomena independently the one of the other. - -Phenomena for purposes of analysis were classed in separate and -distinct compartments: weight, heat, electricity, magnetism, light. -Each phenomenon was studied without reference to that it succeeded or -that which should follow. Nothing could be more artificial than such a -method as this. In fact, there is a sequence in everything, everything -is connected up, _everything precedes and succeeds in nature_—in -nature there are only series. The isolated fact without antecedent or -consequent is a myth. Each phenomenal manifestation is in solidarity -with another. It is a metamorphosis of one state of things into -another. It is transformation. It implies a state of things anterior to -that which we are observing, a phenomenal form which has preceded the -form of the present moment. - -Now there exists a link between the anterior state and the succeeding -state—that is to say, between the new form which is appearing and the -preceding form which is disappearing. The science of energy shows -that something has passed from the first condition to the second, -but covering itself as it were with a new garment; in a word, that -something active and permanent subsists in the passage from one -condition to another, and that what has changed is only the aspect, the -appearance. - -This constant something which is perceived beneath the inconstancy and -the variety of forms, and which circulates in a certain manner from the -antecedent phenomenon to its successor, is energy. - -But still this is only a very vague view, and it may seem arbitrary. -It may be made more exact by examples borrowed from the different -categories of natural phenomena. There are energetic modalities in -relation with the different phenomenal modalities. The different orders -of phenomena which may be presented—mechanical, chemical, thermal, -electrical—give rise to corresponding forms of energy. - -When to a mechanical phenomenon succeeds a mechanical, thermal, -or electrical phenomenon, we say, embracing transformation in its -totality, that there has been a transformation of mechanical energy -into another form of energy, mechanical, thermal, or electrical, etc. - -This idea becomes more precise if we examine successively each of these -cases and the laws which regulate them. - - - § 3. MECHANICAL ENERGY. - - -Mechanical energy is the simplest and the oldest known. - -_Mechanical Elements: Time, Space, Force, Work, Power._—Mechanical -phenomena may be considered under two fundamental conditions—_time_ and -_space_, which are, in a measure, logical elements, to which may be -joined a third element, itself experimental, having its foundations in -our sensations—namely, _force_, _work_, or _power_. - -The ideas of force, work, and power, are drawn from the experience man -has of his muscular activity. Nevertheless the greatest mathematical -minds from from Descartes to Leibniz have been obliged to define and -explain them clearly. - -_Force_.—The prototype of force is weight, universal attraction. -Experiment shows us that every body falls as long as no obstacle -opposes its fall. This is so universal a property of matter that it -serves to define it. The _force_, weight, is therefore the name given -to the cause of the fall of the bodies. - -Force in general is the _cause of motion_. Hence force exists only in -so far as there is motion. There would be no force without action. This -is Newton’s point of view. It did not prevail, and was not the point -of view of his successors. The name of force has been given not only -to the cause which produces or modifies motion, but to the cause which -resists and prevents it. And then not only have _forces in action_ been -considered (dynamics), but _forces at rest_ (statics). Now, to Newton -there was no statics. Forces do not continue to exist when they produce -no motion; they are not in equilibrium, they are destroyed. - -The idea of force therefore is a metaphysical idea which contains the -idea of _cause_. But it becomes experimental immediately it is looked -upon as resisting motion, according to the point of view of Newton’s -opponents. Its foundations lie in the muscular activity of man. - -Man can support a burden without bending or moving. This burden is -a weight—that is to say, a mass acted on by the force of weight. -Man resists this force so as to prevent its effect. If it were not -annihilated by man’s _effort_, this effect would be the motion or -the fall of the heavy body. The _effort_ and the force are thus in -equilibrium, and the effort is equal and opposite to the force. It -gives to the man who exercises it the conscious idea of _force_. Thus -we know of force through effort. Every clear idea that we can have of -_force_ springs from the observation of our muscular effort. - -The notion of force is thus an anthropomorphic notion. When an effect -is produced in nature outside human intervention, we say that it is -by something analogous to what in man is effort, and we give to this -something a name which is also analogous, namely _force_. To give a -name to _effort_ and to compare efforts in magnitude, we need not know -all about them, nor need we know in what they essentially consist, of -what series of physical, chemical, and physiological actions they are -the consequence. And so it is with force. It is a resistance to motion -or the cause of motion. This cause of motion may be an anterior motion -(kinetic force). It may be an anterior physical energy (physical and -chemical forces). - -Forces are measured in the C.G.S. system by comparing them with the -unit called the Dyne.[7] In practice they are compared with a much -larger unit—the gramme, which is the weight, the force acting on a unit -of mass of one centimetre of distilled water at a temperature of 4° C. - - [7] The dyne is the force which applied to the unit of mass produces a - unit of acceleration. - -_Work._—The muscular activity of man may be brought into play in yet -another manner. When we employ workmen, as Carnot said in his _Essai -sur l’équilibre et le mouvement_, it is not a question of “knowing the -burdens that they can carry without moving from their position,” but -rather the burdens that they can carry from one point to another. For -instance, a workman may have to lift the water from the bottom of a -well to a given height, and the case is the same for the animals we -employ. “This is what we understand by force when we say that the force -of a horse is equal to the force of seven men. We do not mean that if -seven men were pulling in one direction and the horse in another that -there would be equilibrium, but that in a piece of work the horse alone -would lift, for example, as much water from the bottom of a well to a -given height as the seven men together would do in the same time.”[8] - - [8] These words spoil the statement, for time has nothing to do with - it. - -Here, then, we have to do with the second form of muscular activity, -which is called in mechanics, “work”—at least, if in the preceding -quotation we attach no particular importance to the words “in the same -time,” and retain the employment of muscular activity only “under -constant conditions.” Mechanical work is compared with the elevation of -a certain weight to a certain height. It is measured by the product of -the force (understood in the sense in which it was used just now—that -is to say, as causing or resisting motion) and the displacement due to -this motion. The unit is the Kilogrammetre—that is to say, the work -necessary to lift a weight of one kilogramme to the height of one -metre. - -It will be remarked that the idea of time does not intervene in our -estimation of work. The notion of work is independent of the ideas -of velocity and time. “The greater or less time that we take to do a -piece of work is of no more assistance in measuring its magnitude than -the number of years that a man may have taken to grow rich or to ruin -himself can help to estimate the present amount of his fortune.” - -Going back to Carnot’s comparison, an employer who employed his workmen -only on piece-work,—that is to say, who would only care about the -amount of work done, and would be indifferent to the time that they -took over it,—would be at the same point of view as the advocates of -the mechanical theory. M. Bouasse, whom we follow here, has remarked -that this idea of mechanical work may be traced back to Descartes. His -predecessors, and Galileo in particular, had quite a different idea of -the way in which mechanical activity should be measured; and so, among -the mathematicians of the eighteenth century, Leibniz and, later, John -Bernoulli were almost alone in looking at it from this point of view. - -_Energy._—Work thus understood is _mechanical energy_. It represents -the lasting and objective effect of the mechanical activity independent -of all the circumstances under which it was carried out. The same -work may be done under very different conditions of time, velocity, -force, and displacement. It is therefore the permanent element in the -variety of mechanical aspects. Work, for example, in the collision of -bodies when the motion of a body appears to be destroyed on impact -with another, reappears as indestructible _vis viva_. This, then, is -exactly what we call _energy_; and if we agree to give it this name, -we may say that the conservation of energy is invariable throughout all -mechanical transformations. - -_Distinction between Work and Force, and between Energy and Work._—The -history of mechanics shows us what trouble has been taken and what -efforts have been made to distinguish work (now mechanical energy) from -force. - -It is worth while insisting on this distinction. It could be easily -shown that force has no objective existence. It has no duration, -no permanence. It does not survive its effect, motion. There is no -conservation of force. It passes instantly from infinity to zero. -It is a _vectorial magnitude_—that is to say, it involves the idea -of direction. Work, on the other hand, is the real element; it is -a _scalar magnitude_ involving the idea of opposite directions, -indicated by the signs + and-. Work and force are heterogeneous -magnitudes. Energy, and this is the only characteristic by which it is -distinguished from work, is an _absolute magnitude_ to which we may not -even give opposite signs. - -An example may perhaps throw these characteristics into relief—namely, -the hydraulic press. We have on the platform exactly the work which has -been done on the other side. The machine has only made it change its -form. On the contrary, the force has been infinitely multiplied. We -may, in fact, consider an infinite number of surfaces equal to that of -a small piston, placed and orientated at will within the liquid; each, -according to Pascal’s principle, will support a pressure equal to that -which is exercised. As soon as we cease to support it, this infinity -falls at once to zero. Now what real thing could pass instantly from -infinity to zero? - -That skilful and very able physiologist, M. Chauveau, has endeavoured -to use the same term _energy of contraction_ for the two phenomena of -effort (force) and work. It seems, however, from the point of view -of the expenditure imposed on the organism, that these two modes of -activity, _static contraction_ (effort), and _dynamical contraction_ -(work), may be, in fact, perfectly comparable. But although this manner -of conceiving the phenomena may certainly be exact, and may be of great -value, the idea of force must none the less remain distinct from that -of work. The persistence of the author in violating established custom -in this connection has prevented him from enabling mechanicians and -even some physiologists to understand and accept very useful truths. - -_Power._—The idea of mechanical _power_ differs from those of force -and work. The idea of time must intervene. It is not sufficient, in -fact, in order to characterize a mechanical operation, to point to -the task accomplished. It may be necessary or useful to know how much -time it required. This is true, especially when we are concerned with -the circumstances as well as the results of the performance of the -work; and this is the case when we wish to compare machines. We say -that the machine which does the work in the shortest space of time is -the most powerful. The unit of power is the Kilogrammetre-second—that -is to say, the power of a machine which does a kilogrammetre in a -second. In manufactures we generally employ a unit 75 times greater -than this—a _horse-power_. This is the power of a machine which does -75 kilogrammetres a second. In the electrical industry we measure by -_kilowatts_, which are equivalent to 1.36 horse power, or by a _watt_, -a unit a thousand times smaller. - -Let us add that the power of a machine is not an absolute and permanent -characteristic of the machine. It depends on the circumstances under -which the work is carried out, and that is why, in particular, we -cannot appreciate the power of the human machine in comparison with -industrial machines. Experience has shown that the mechanical power -of living beings depends upon the nature of the work they are doing. -In this connection we may mention some very interesting experiments -communicated to the Institute, in the year VI., by the celebrated -physicist, Coulomb. A man of the average weight of 70 kilogrammes was -made to climb the stairs of a house 20 metres high. He ascended at the -rate of 14 metres a minute, and he performed this daily task for four -effective hours. This work was equivalent to 235,000 kilogrammetres. -But if, instead of climbing without a burden, the same man had had to -carry a load, the result would have been quite different. Coulomb’s -workman took up six loads of wood a day to a height of 12 metres in 66 -journeys, corresponding to a maximum work of 109,000 instead of 235,000 -kilogrammetres. The mechanical power of the human machine thus varied -in the two cases in the ratio of 235 to 109. - -_The Two Aspects of Mechanical Energy: Kinetic and Potential._—Energy, -or mechanical work, may present itself in two forms—kinetic energy, -corresponding to the mechanical phenomenon which has really taken -place, and _potential energy_, or the energy of reserve. - -A body which has been raised to a certain height will, if it be let -fall, perform work which can be exactly measured in kilogrammetres by -the product of its weight into the height it falls. Such work may be -utilized in many ways. In this way, for instance, public clocks are -worked. Now, as long as the clock-weight is raised and not let go, and -as long as it is motionless, the physics of early days would say that -there is nothing to discuss; the phenomenon is the fall; it is going to -take place, but at the present moment there has been no fall. - -In energetics we do not reason in this way. We say that the body -possesses a _capacity for work_ which will be manifested when the -opportunity arises, a storage of energy, a virtual or _potential -energy_, or again, an _energy of position_, which will be transformed -into actual energy or real work as soon as the body falls. - -Let us ask whence this energy arises. It proceeds from the previous -operation which has raised the weight from the surface of the soil -to the position it occupies. For example, if it is a question of the -weights of a public clock, which, by its fall, will develop in 15 -days the work that is necessary to turn the wheels, to strike the -bell, and to turn the hands, this work ought to bring to our minds the -exactly equal and opposite work done by the clockmaker, who has to -carry the clock-weight and to lift it up from the ground to its point -of departure. The work of the fall is the faithful counterpart of the -work of elevation. The phenomenon has therefore in reality two phases. -We find in the second exactly what was put into the first, the same -quantity of energy—_i.e._, the same work. Between these phases comes -the intermediary phase of which we say that it is a period of virtual -_or potential energy_. This is a way of remembering in some measure the -preceding phenomenon—_i.e._, the work of lifting up, and of indicating -the phenomena which will follow—_i.e._, the work of the fall. And thus -we connect by our thoughts the present situation with the antecedent -and with the consequent position, and it is from this consideration of -continuity alone that the conception of energy springs—that is to say, -of something which is conserved and is found to be permanent in the -succession of phenomena. This energy of which we lose no trace does -not appear to us new when it is manifested. Our imagination eventually -materializes the idea of it. We follow it as a real thing, having -an objective existence, which is asleep during the latent potential -period, and is revealed or manifested later. - -Among other examples, that of the coiled spring which is unwound is -particularly suitable for showing this fundamental character of the -idea of mechanical energy, an idea which is the clearest of all. -Machines are only transformers and not creators of mechanical energy. -They only change one form into another. - -In the same way, too, a stream of water or the torrent of a mountainous -region may be utilized for setting in motion the wheels and the -turbines of the factories situated in the valley. Its descent produces -the mechanical work which would be a creation _ex nihilo_ if we do not -connect the phenomenon with its antecedents. We look on it as a simple -restitution, if we think of the origin of this water which has been -transported and lifted in some way to its level by the play of natural -forces—evaporation under the action of the sun, the formation of -clouds, transport by winds, etc. And we here again see that a complex -energy has been transformed, in its first phenomenal condition, into -_potential energy_, and that this potential energy is always expended -in the second phase without loss or gain. - -_The Different Kinds of Mechanical Energy; of Motion, of -Position._—There are as many forms of energy as there are distinct -categories of phenomena or of varieties in these categories. Physicists -distinguish between two kinds of mechanical energy—energy of motion -and energy of position. The energy of position presents several -variants—energy of distance, which corresponds to force: of this we -have just spoken; energy of surface, which corresponds to particular -phenomena of surface tension; and energy of volume which corresponds -to the phenomena of pressure. Energy of motion, _kinetic energy_, is -measured in two ways: as work (the product of force and displacement, -W = _fs_) or as _vis viva_ (half the product of the mass into the square -of the velocity U = _mv^2_∕2.)[9] - - [9] We therefore notice that the measures of force and work bring in - mass, space, and time. The typical force, weight, is given by w = mg. - On the other hand, we have by the laws of falling bodies _v_ = _gt_; - _s_ = 1∕2_gt^2_; whence _g_ = 2_s_∕_t^2_; _w_ = _m_(2_s_∕_t^2_); or, - if F be the force, M the mass, L the space described, and T the time, - we have F = MLT^{-2}, which expresses what are called the dimensions - of the force—that is to say, the magnitudes with their degree, which - enter into its expression. We may thus easily obtain the dimensions of - work:— - - _Work_ = _f_ × _s_ = _mv^2_∕2 = ML^2T^{-2}. - - - § 4. THERMAL ENERGY. - - -In the elements of physics it is nowadays taught that mechanical -work may be transformed into heat, and reciprocally that heat may be -transformed into mechanical work. Friction, impact, pressure, and -expansion destroy or annihilate the mechanical energy communicated to -a body or to the organs of a machine. With the disappearance of motion -we note the appearance of heat. Examples abound. The tyre of a wheel -is heated by the friction of the road. Portions of steel are warmed -by the impact with stone, as in the old flint and steel. Two pieces -of ice were melted by Davy, who rubbed them one against the other, -the external temperature being below zero. The boiling of a mass of -water caused by a drill was noticed by Rumford in 1790, during the -manufacture of bronze cannon. Metal, beaten on an anvil, is heated. A -leaden ball flattened against a resisting obstacle shows increase of -temperature carried to the point of fusion. Finally, and symbolically, -we have the origin of fire in the fable of Prometheus, by rubbing -together the pieces of wood which the Hindoos called _pramantha_. -Correlation is constant between the thermal and mechanical phenomena, -a correlation that becomes evident as soon as observers have ceased to -restrict themselves to the determination in isolation of the one fact -or the other. There is never any real destruction of heat and motion -in the true sense of the word; what disappears in one form appears -again in another; just as if something indestructible were appearing in -a series of successive disguises. This impression is translated into -words when we speak of the metamorphosis of mechanical into thermal -energy. - -_The Mechanical Equivalent of Heat._—The interpretation assumes a -remarkable character of precision, which at once strikes the mind -when physics applies to these transformations the almost absolute -accuracy of its measurements. We then find that the rate of exchange -is invariable. Transformations of heat into motion, and of motion into -heat, take place according to a rigorous numerical law, which brings -into exact correspondence the quantity of each. Mechanical effect -is estimated, as we have seen, by work, that is in kilogrammetres. -Heat is measured in calories, the calorie being the quantity of heat -necessary to raise from 0°C to 1°C a kilogramme of water (Calorie) or -one gramme of water (calorie). It is found that whatever may be the -bodies and the phenomena which serve as intermediaries for carrying -out this transformation, we must always expend 425 kilogrammetres to -create a Calorie, or expend 0·00234 Calories to create a kilogrammetre. -The number 425 is the mechanical equivalent of the Calorie, or, as -is incorrectly stated, of the heat. It is this constant fact which -constitutes _the principle of the equivalence of heat and of mechanical -work_. - - - § 5. CHEMICAL ENERGY. - - -We cannot yet actually measure chemical activity directly, but we know -that chemical action may give rise to all other phenomenal modalities. -It is their most ordinary source, and it is to it that industries -appeal to obtain heat, electricity, and mechanical action. In the -steam engine, for instance, the work that is received arises from the -combustion of carbon by the oxygen of the air. This gives rise to the -heat which vaporizes the water, produces the tension of the steam, -and ultimately produces the displacement of the piston. The theory of -the steam engine might be reduced to these two propositions: chemical -activity gives rise to heat, and heat gives rise to motion; or to use -the language to which the reader by now will be accustomed, chemical -energy is transformed into thermal energy, and that into mechanical -energy. It is a series of phases and of instantaneous changes, and the -exchange is always affected according to a fixed rate. - -_The Measurement of Chemical Energy._—Our knowledge of chemical energy -is less advanced than that of the energies of heat and sensible motion. -We have not yet reached the stage of numerical verifications. We can -only therefore affirm the equivalence of chemical and thermal energies -without the aid of numerical constants, because we do not yet, in -the present state of science, know how to measure chemical energy -directly. Other known energies are always the product of two factors: -the mechanical energy of position, or work, is measured by the product -of the force _f_, and the displacement _s_; work = _fs_; the mechanical -energy of motion, U = 1∕2_mv^2_, is measured by the product of the mass -into half the square of the velocity. Thermal energy is measured by -the product of the temperature and the specific heat; electric energy -by the product of the quantity of electricity (in coulombs) and of the -electromotive force (in volts). As for chemical energy, we guess that -it may be valued directly according to Berthollet’s system, adopted by -the Norwegian chemists, Guldberg and Waage, by means of the product of -the masses and of a force, or co-efficient of affinity, which depends -on the nature of the substances which are brought together, on the -temperature, and on the other physical circumstances of the reaction. -On the other hand, the researches of M. Berthelot enable us in many -cases to obtain an indirect valuation in terms of the equivalent heat. - -_Its Two Forms._—It is interesting to note that chemical energy may -also be regarded from the two states of _potential_ and _kinetic -energy_. The coal-oxygen system, to burn in the furnace of the steam -engine, must be primed by preliminary work (local ignition), just as -the weight that is raised and left motionless at a certain height -requires a small effort to be detached from its support. When this -condition is fulfilled, energy is at once manifest. We must admit that -it existed in the latent state, in the state of _chemical potential -energy_. Under the impulse received, the carbon combines with the -oxygen and forms carbonic acid, C + 2O becomes CO⌄{2}; potential energy -is changed into actual chemical energy, and immediately afterwards into -thermal energy. We should have only a very incomplete and fragmentary -view of the reality of things if we were to consider this phenomenon -of combustion in isolation. We must consider it in connection with -what has actually created the energy which it is about to dissipate. -This antecedent fact is the action of the sun upon the green leaf. The -carbon which burns in the furnace of the machine comes from the mine in -which it was stored in the form of coal—that is to say, of a product -which was vegetable in its primitive form, and which was formed at the -expense of the carbonic acid of the air. The plant had separated, at -the expense of the solar energy, the carbon from the oxygen to which it -was united in the carbonic acid of the atmosphere. It had created the -system C + 2O. So that the solar energy produces the chemical potential -energy which was so long before it was utilized. Combustion expends -this energy in making carbonic acid over again. - -_Materialization of Energy._—The fertility of the idea of energy is -therefore, as we see from all these examples, due to the relations -it establishes between the natural phenomena of which it exhibits -the necessary relation, destroyed by the excessive analysis of early -science. It shows us that in the world of phenomena there is nothing -but transformations of energy. And we regard these transformations -themselves as the circulation of a kind of indestructible agent which -passes from one form of determination to another, as if it were -simply putting on a fresh disguise. If our intellect requires images -or symbols to embrace the facts and to grasp their relation, it may -introduce them here. It will materialize energy, it will make of it a -kind of imaginary being, and confer upon it an objective reality. And -for the mind, as long as it does not become the dupe of the phantom -which it itself has created, this is an eminently comprehensive -artifice which enables us to grasp readily the relations between -phenomena and their bond of affiliation. - -The world appears to us then, as we said at the outset, constructed -with singular symmetry. It offers to us nothing but transformations of -matter and transformations of energy; these two kinds of metamorphoses -being governed by two laws equally inevitable, the conservation -of matter and the conservation of energy. The first of these laws -expresses the fact that matter is indestructible, and passes from -one phenomenal determination to another at a rate of equivalence -measured by weight; the second, that energy is indestructible, and -that it passes from one phenomenal determination to another at a rate -of equivalence fixed for each category by the discoveries of the -physicists. - - - § 6. TRANSFORMATIONS OF ENERGY. - - -The idea of energy has become the point of departure of a science, -_Energetics_, to the establishment of which a large number of -contemporary physicists, among whom are Ostwald, Le Châtelier, etc., -have devoted their efforts. It is the study of phenomena, regarded -from the point of view of _energy_. I have said that it claims to -co-ordinate and to embrace all other sciences. - -The first object of energetics should be the consideration of the -different forms of energy at present known, their definition and their -measurement. This is what we have just done in broad outline. - -In the second place, each form of energy must be regarded with -reference to the rest, so as to determine if the transformation of this -into that is directly realizable, and by what means, and, finally, -according to what rate of equivalence. This new chapter is a laborious -task which would compel us to traverse the whole field of physics. - -Of this long examination we need only concern ourselves here with three -or four results which will be more particularly important in the case -of applications to living beings. They refer to mechanical energy, to -the relations of thermal energy and chemical energy, to the complete -rôle of thermal energy, and finally to the extreme adaptability of -electrical energy. - -1. _Transformation of Mechanical Energy._—Mechanical energy may change -into every other form of energy, and all others can change into it, -with but one exception, that of chemical energy. Mechanical effort does -not produce chemical combination. What we know of the part played by -pressure in the reactions of dissociation seems at first to contradict -this assertion. But this is only in appearance. Pressure intervenes in -these operations only as _preliminary work_ or _priming_, the purpose -of which is to bring the bodies into contact in the exact state in -which they must be for the chemical affinities to be able to enter into -play. - -2. _Transformation of Thermal Energy; Priming._—Thermal (or luminous) -energy does not change directly into chemical energy. In fact, heat and -light favour and even determine a large number of chemical reactions; -but if we go down to the foundation of things we are not long before -we feel assured that heat and light only serve in some measure for -_priming_ for the phenomenon, for preparing the chemical action, for -bringing the body into the physical state (liquid, steam) or to the -degree of temperature (400° C. for instance, for the combination of -oxygen and hydrogen) which are the preliminary indispensable conditions -for the entry upon the scene of chemical affinities. - -On the contrary, chemical energy may really be transformed into -thermal energy. We have an instance of this in the reactions which -take place without the aid of external energy; and again, in those -very numerous cases which, such as the combustion of hydrogen and -carbon, or the decomposition of explosives, the reactions continue -when once primed. I may make a further observation apropos of thermal -and photic energy. These are not two really and essentially distinct -forms, as was thought in the early days of physics. When we consider -things objectively, there is absolutely no light without heat; light -and heat are one and the same agent. According as it is at this or -that degree of its scale of magnitude, it makes a stronger impression -on the skin (sensation of heat) or on the retina (sensation of light) -of man and animals. The difference may be put down to the diversity of -the work and not to that of the agent. The kinetic theory shows us that -the agent is qualitatively identical. The words heat and light only -express the chance of the meeting of the radiant agent with a skin and -a retina. At the lowest degree of activity this agent exerts no action -on the terminations of the thermal cutaneous nerves, nor on the optic -nerve-terminations. As this degree is raised the former of these nerves -are affected (cold, heat) and are so to the exclusion of the nerves of -vision. Then they are both affected (sensation of heat and light), and -finally, beyond that, sight alone is affected. The transformation of -one energy into the other is therefore here reduced to the possibility -of increasing or decreasing the intensity of the action of this common -agent in the exact proportions suitable for passing from one of the -conditions to the other; and this is easy when it is a question of -going up the scale in the case of light, and, on the contrary, it is -not realizable directly, that is to say without external assistance, -when it is a question of going down the scale again, in the case of -heat. - -3. _Heat a Degraded Form of Energy._—We have seen that thermal energy -is not directly transformed into chemical energy. There is yet another -restriction in the case of this thermal energy if we study the laws -which govern the circulation and the transformations of thermal energy; -and the most important comes from the impossibility of transporting it -from a body at a lower temperature to a body at a higher temperature. -On the whole, and because of these restrictions, thermal energy is an -imperfect variety of universal energy, or, as the English physicists -call it, a degraded form. - -4. _Simple Transformations of Electrical Energy. Its Intermediary -Rôle._—On the other hand, electrical energy represents a perfected and -infinitely advantageous form of this same universal energy, and this -explains the vast development of its industrial applications within -less than a century. It is not that it is better known than the others -in its nature and in the secret of its action. On the contrary, there -is more dispute than ever as to its nature. To some, electricity, -which is transported and propagated with the speed of light, is a real -flux of the ether as was taught by Father Secchi, who compared it to a -current of water in a pipe. It would do its work, just as the water of -the mill does its work by flowing over a wheel or through a turbine. -Electricity, like water in this case, would not be an energy in itself, -but a means of transporting energy. - -To others, such as Clausius, Hertz, and Maxwell, it is not so; the -electric current is not a transport of energy. It is a state of the -ether of a peculiar, specific kind, periodically produced (electric -oscillation), and propagated with a speed of the order of that of light. - -However that may be, what constitutes the essential peculiarity -of electrical energy, and what causes its value, is that it is an -incomparable agent of transformation. Every known form of energy -may be converted into it, and inversely, electrical energy may be -changed with the utmost facility into all other energies. This extreme -adaptability assigns to it the part of an intermediary between the -other less tractable agents. Mechanical energy, for instance, lends -itself with difficulty to the production of light, that is to say, to -a metamorphosis into photic energy (a variety of thermal energy). A -fall of water cannot be directly utilized for lighting purposes. The -mechanical work of this fall, which cannot be exploited in its present -form, serves to set in motion in industrial lighting the installations, -the electric machines, and the dynamos which feed the incandescent -lamps. Mechanical work is changed into electrical energy, and it, in -its turn, into thermal or photic energy. Electricity has here played -the part of a useful intermediary. - -The last part of energetics must be consecrated to the study of the -general principles of this science. These principles are two in number, -the principle of the _conservation of energy_, or Mayer’s principle, -and the principle of the transformation of energy, or Carnot’s -principle. The doctrine of energy thus reduces to two fundamental laws -the multitude of laws, often known as “general,” to which natural -science is subject. - - - § 7. THE PRINCIPLE OF THE CONSERVATION OF ENERGY. - - -In all that precedes, the principle of conservation has intervened at -every step. In fact, the very idea of energy is connected with the -existence of this principle. We first discover the idea in the work of -the philosophical mathematicians who established the foundations of -mechanics:—Newton, Leibniz, d’Alembert, and Helmholtz; or of inductive -physicists such as Lord Kelvin. Its experimental proof, sketched by -Marc Seguin and R. Mayer, is due to Colding and Joule. - -_It is Independent of the Kinetic Theory._—Mayer’s law states that -energy is indestructible; that all phenomenality is nothing but a -transformation of energy from one form to another, and that this -transformation takes place either at equal values, or rather, at a -certain rate of equivalence. This is what takes place when thermal -energy is transformed into mechanical energy (equivalent 425). This -rate of equivalence is fixed by the researches of physicists for each -category of energy. - -It will be noticed that this law and this theory of energy, which -is always presented by authors of elementary books as a consequence -of the kinetic theory, is quite independent of it. In the preceding -lines we have not even mentioned its name. We have not assumed that -all phenomena are movements or transformations of movements, whether -sensible or vibratory; we have not affirmed that what was passing from -one phenomenal determination to another was the _vis viva_ of the -motion, as is the case in the impact of elastic bodies. No doubt the -kinetic theory affords us a very striking image of these truths which -are independent of it; but it may be false: and the theory of energy -which assumes the minimum of possible hypotheses would yet be true. - -_It contains a great many other Principles._—The principle of the -conservation of energy contains a large number of the most general -principles of science. It may be shown without much difficulty that, -for example, it contains the principle of the inertia of matter, laid -down by Galileo and Descartes; that of the equality of action and -reaction, due to Newton; and even that of the conservation of matter, -or rather of mass, due to Lavoisier. And finally, it contains the -experimental law of equivalence connected with the name of the English -physicist Joule, from which may be derived the Law of Hess and the -principle of the initial and final states which we owe to Berthelot. - -_It involves the Law of Equivalence._—Here we may be content with -noticing that the law of the conservation of energy involves the -existence of relations of equivalence between the different varieties. -A certain quantity of a given energy, measured, as we have seen, by -the product of two factors, is equivalent to a certain fixed quantity -of quite a different form of energy into which it may be converted. -The laws which govern energetic transformations therefore contain, -from both the qualitative and the quantitative points of view, all the -connections of the phenomena of the universe. To study these laws in -their detail is the task that physics must take upon itself. - -The conversion one into the other of the different forms of energy by -means of equivalents is only a possibility. It is subject, in fact, to -all sorts of restrictions, of which the most important are due to the -second principle. - - - § 8. CARNOT’S PRINCIPLE. ITS GENERALITY. - - -The second fundamental principle is that of the transformations of -equilibrium, or of the conditions of reversibility, or again, Carnot’s -principle. This principle, which first assumed a concrete form in -thermodynamics, has been very widely extended. It has reached a degree -of generality such that contemporary theoretical physicists such as -Lord Kelvin, Le Châtelier, etc., consider it the universal law of -physical, mechanical, and chemical equilibrium. - -Carnot’s principle contains, as was shown by G. Robin, d’Alembert’s -principle of virtual velocities, and according to physicists of -to-day, as we have just remarked, it contains the laws peculiar to -physico-chemical equilibrium. The application of this principle -gives us the differential equations from which are derived numerical -relations between the different energies, or the different modalities -of universal energy. - -_Its Character._—It is very remarkable that we cannot give a general -enunciation of this principle which by its revealing power has changed -the face of physics. This is because it is less a law, properly so -called, than a method or manner of interpreting the relations of the -different forms of energy, and particularly the relations of heat and -mechanical energy. - -_Conversion of Work into Heat and Vice-versâ._—The conversion of -work into heat is accomplished without difficulty. For example, the -hammering of a piece of iron on an anvil may bring it to a red heat. -A shell which passes through an armour plate is heated, and melts and -volatilizes the metal all round the hole it has made. By utilizing -mechanical action under the form of friction all energy can be -converted into heat. - -The inverse transformation of heat into work, on the contrary, cannot -be complete. The best motor that we can think of, and _à fortiori_ the -best we can realize, can only transform a third or a fourth of the heat -with which it is supplied. - -This is an extremely important fact. It is of incalculable importance -to natural philosophy, and may be ranked among the greatest discoveries. - -_Higher and Degraded Forms of Energy._—Of these we may give an account -by distinguishing among the forms of universal energy _higher forms_, -and _lower_ or _degraded forms_. Here we have the principle of the -_degradation of energy_ on its trial, and it may be regarded as a -particular aspect of the second principle of energetics, or Carnot’s -principle. Mechanical energy is a higher form. Thermal energy is -a lower form, a degraded form, and one which has degrees in its -degradation. Higher energy, in general, may be completely converted -into lower energy; for example, work into heat: the slope is easy to -descend, but it is difficult to retrace our steps; lower energy can be -only partially transformed into higher energy, and the fraction thus -utilizable depends upon certain conditions on which Carnot’s principle -has thrown considerable light. - -Thus, although in theory the thermal energy of a body may have its -equivalent in mechanical energy, the complete transformation is only -realizable from the latter to the former, and not from the former to -the latter. This is due to a condition of thermal energy which is -called _temperature_. The same quantity of thermal energy, of heat, -may be stored in the same thermal body at different temperatures. If -this quantity of thermal energy is in a very hot body we can utilize -a large portion of it; if it is in a relatively cold body we can only -convert a small portion of it into mechanical work. Thus the value of -energy,—_i.e._, its capacity of being converted into a higher and more -useful form,—depends on temperature. - -_The Capacity of Conversion depends on Temperature._—The conversion -of heat into work assumes two bodies of different temperatures, the -one warm and the other cold; a boiler and a condenser. Every thermal -machine conveys a certain amount of heat from the boiler to the -condenser, and what is not thus carried is changed into work. This -residue is only a small fraction, a quarter, or at most a third of the -heat employed, and that, too, in the theoretically perfect machine, in -the ideal machine. - -This output, this utilizable fraction depends on the fall of -temperature from the higher to the lower level, just as the work of a -turbine depends on the height of the waterfall which passes through it. -But it also depends on the conditions of this fall, on the accessory -losses from radiation and conduction. However, Carnot has shown that -the output is the same, and a maximum for the same fall of temperature, -whatever be the working agent (steam, hot air, etc.), and whatever be -the machine—provided that this agent, this substance which works is not -exposed to accessory losses, that it is never in contact with a body -having temperature different to its own—or again, that it is connected -only with bodies impermeable to heat. - -This is Carnot’s principle in one of its concrete forms. - -A machine which realizes this condition, that the agent (steam, -alcohol, ether) is in relation, at all phases of its function, with -bodies which can neither take heat from it nor give heat to it, is a -_reversible machine_. Such a machine is perfect. The fraction of heat -that it transforms into motion is constant; it is a maximum; it is -independent of the motor, of its organs, of the agent: it accurately -expresses the transformability of the heat agent into a mechanical -agent under the given conditions. - -_The Degradation and Restoration of Energy._—The fraction not utilized, -that which is carried to the condenser at a lower temperature, is -_degraded_. It can only be used by a new agent, in a new machine in -which the boiler has exactly the same temperature as the condenser in -the first machine, and the new condenser has a lower temperature, and -so on. The proportion of utilizable energy thus goes on diminishing. -Its utilization requires conditions more and more difficult to -realize. The thermal energy loses its potential and its value, and is -further and further degraded as its temperature approaches that of the -surrounding medium. - -The degraded energy, theoretically, has kept its equivalent value but, -practically, it is incapable of conversion. However, it is shown in -physics that it can be raised and re-established at its initial level. -But for that purpose another energy must be utilized and degraded for -its benefit. - -_The End of the Universe._—What we have just seen with respect to -heat and motion is to some degree true of all other forms of energy, -as Lord Kelvin has shown. The principle of the degradation of energy -is very general. Every manifestation of nature is an energetic -transformation. In each of these transformations there is a degradation -of energy—_i.e._, a certain fraction is lowered and becomes less easily -transformable. So that the energy of the universe is more and more -degraded; the higher forms are lowered to the thermal form, the latter -increasing at temperatures which become more and more uniform. The -end of the universe, from this point of view, would then be unity of -(thermal) energy in uniformity of temperature. - -_Importance of the Idea of Energy in Physiology._—I have said that the -application of Carnot’s principle furnished numerical relations between -the different energetic transformations. - -The science of living beings has not yet reached that point of -development at which it is possible for us to obtain its numerical -relations. However, the consideration of energy and the principle of -conservation has altered the outlook of physiology on many questions -which are of the highest importance. - -The determination of the sources from which plants and animals draw -their vital energies; the mediate transformation of chemical energy -into animal heat in nutrition, or into motion in muscular contraction; -the chemical evolution of foods; the study of soluble ferments—all -these questions are of considerable importance when we wish to -understand the mechanisms of life. They are therefore departments of -physiological energetics in which great advances have already been -made. - - - - - CHAPTER II. - - ENERGY IN BIOLOGY. - - § 1. Energy in Living Beings.—§ 2. The First Law of Biological - Energetics:—All Vital Phenomena are Energetic Transformations.—§ - 3. Second Law:—The Origin of Vital Energy is in Chemical Energy. - Functional Activity and Destruction.—§ 4. Third Law:—The Final Form of - Energetic Transformation in the Animal is Thermal Energy. Heat is an - Excretum. - - -The theory of energy was thought of and utilized in physiology before -it was introduced into physics, in which it has exercised such an -extraordinary influence. Robert Mayer was a physicist and a doctor. -Helmholtz was equally at home in physiology and in physics. From -the outset both had seen in this new idea a powerful instrument of -physiological research. The volume in which Robert Mayer expounded, -in 1845, his remarkable views on organic movement in relation to -nutrition, and Helmholtz’ commentary leave us in no doubt in this -respect. The essay on the mechanical equivalent of heat, of a more -particularly physical character, is six years later than the earlier -work. - -_The Relations between Energetics and Biology._—The theory of energy is -therefore only returning to its cradle; and to that cradle it returns -with all the sanction of physical proof, as the most general theory -ever proposed in natural philosophy, and the theory least encumbered -with hypotheses. It reduces all particular laws to two fundamental -principles—that of the conservation of energy, which contains the -principles of Galileo and Descartes, of Newton, of Lavoisier, Joule’s -law, Hess’s law, and Berthelot’s principle of the initial and final -states; and also Carnot’s principle, from which are deduced the laws -of physico-chemical and chemical equilibrium. These two principles -therefore sum up the whole of natural science. They express the -necessary relation of all the phenomena of the universe, their -uninterrupted gentic connection, and their continuity. - -_A priori_ there would be little likelihood that a doctrine, so -universal and so thoroughly verified in the physical world, could be -restricted, and thus be useless to the living world. Such a supposition -would be contrary to the scientific method, which always tends to the -generalization and the explanation of elementary laws. The human mind -has always proceeded thus: it has applied to the unknown order of -living phenomena the most general laws of contemporary physics. - -This application has been found legitimate, and has been justified by -experiment whenever it has been a question of the laws or of the really -fundamental or elementary conditions of phenomena. It has, on the other -hand, however, been unfortunate when it has stopped short of secondary -characteristics. When we now concede the subjection of living beings -to these general laws of energetics, we are following a traditional -method. There is no doubt that this application is legitimate, and that -experiment will justify it _a posteriori_. - -I will therefore grant, as a provisional _postulate_, the consequences -of which will have to be ultimately justified, that the living and -inanimate world alike show us nothing but _transformations of matter_ -and _transformations of energy_. The word phenomenon will have no -other signification, whatever be the circumstances under which the -phenomenon occurs. The varied manifestations which translate the -activity of living beings thus correspond to transformations of energy, -to conversions of one form into another, in conformity with the rules -of equivalence laid down by the physicists. This conception may be -formulated in the following manner:—_The phenomena of life have the -same claim to be energetic metamorphoses as the other phenomena of -nature_. - -This postulate is the foundation of biological energetics. It may be -useful to give some explanation relative to the signification, the -origin, and the scope of this statement. - -Biological energetics is nothing but general physiology reduced to the -principles that are common to all the physical sciences. Robert Mayer -and Helmholtz gave the best description of this science, and laid -down its limits by defining it as “the study of the phenomena of life -regarded from the point of view of energy.” - - - § 1. ENERGY AT PLAY IN LIVING BEINGS. COMMON OR PHYSICAL ENERGIES. - VITAL ENERGIES. - - -Our first object will be to define and to enumerate the energies -at play in living beings; to determine their more or less easy -transformations from one to another, to bring to light the general -laws which govern those transformations, and finally to apply them to -the detailed study of phenomena. This programme may be divided into -four parts. - -In the physical world the specific forms of energy are not numerous. -When we have mentioned mechanical, chemical, radiant (thermal and -photic) energies, electrical energy, with which is blended magnetic -energy, we have exhausted the catalogue of natural agents. - -But is this list for ever closed? Are vital energies comprised in this -list? These are the first questions which we must ask ourselves. - -The iatro-mechanical school, on _a priori_ grounds give an affirmative -answer. No doubt there are in the living organism many manifestations -which are pure physical manifestations of known energies, mechanical, -chemical, thermal, etc. But are all the manifestations of the living -being of this order? Are they all, henceforth, reducible to the -categories and varieties of energy which are investigated in physics? -This is the claim of the mechanical school. But the claim is rash. Our -fundamental postulate affirms, in principle, that universal energy is -manifested in living beings; but, as a matter of fact, there is no -reason for the assertion that it does not assume particular forms, -according to the circumstances peculiar to the conditions under which -they are produced. - -These _special forms of energy_ manifested in the conditions suitable -to living beings would swell the list drawn up by the physicists. And -it would not be the first instance of an extension of this kind. The -history of science records many remarkable cases. Scarcely a century -has passed since we first heard of electrical energy. This discovery -in the world of energy, which took place, so to speak, before our very -eyes, of an agent which plays so large a part in nature, clearly leaves -the door open to other surprises. - -We shall therefore concede that there may be other forms of energy -at work in living beings than those we already know in the physical -world. This reservation would enable us to discover at once the -essential characteristics by which vital phenomena are henceforth -reduced to universal physics, and the purely formal differences still -distinguishing them. - -If there are really special energies in living beings, our monistic -postulate leads us to assert that these energies are homogeneous with -the others, and that they do not differ from them more than they differ -among themselves. It is probable that some day they will be discovered -external to living bodies, if the material conditions (which it is -always possible to imagine) are realized externally to them. And if we -must admit that the peculiarity of the medium is such that these forms -must remain indefinitely peculiar to living beings, we may assert with -every confidence that these special energies do not obey special laws. -They are subject to the two fundamental principles of Robert Mayer -and Carnot. They are exchanged according to fixed laws with the other -physical forms of energies at present known. - -To sum up, then, we must establish three categories in the forms of -energy which express the phenomena of vitality. - -In the first place, most of these energies are those which have -already been studied and recognized in general physics. They are -the same energies: chemical, thermal, mechanical, with their -characteristics of mutability, their lists of equivalents, and their -actual and potential stales. - -In the second place, it may happen, and it probably will happen, as it -happened in the last century in the case of electricity, that some new -form of energy will be discovered belonging to the universal order as -to the living order. This will be a conquest of general physics as well -as of biology. - -And finally we may rigorously and provisionally admit a last category -of _vital energies properly so called_. - -It is difficult to give much precision to the idea of _vital energies -properly so called_. - -It will be easier to measure them by means of equivalents than to -indicate their nature. Besides, this is the ordinary rule in the case -of physical agents. We can measure them, although we know not what they -are. - -_Characteristics of Vital Energies._—We see why we cannot exhibit -with precision, _a priori_, the nature of vital energies. In the -first place, they are expressed by what takes place in the tissues -in activity, and this cannot at present be identified with the known -types of physical, chemical, and mechanical phenomena. This is a first, -intrinsic reason for not being able to distinguish them readily, since -what takes place is not distinguished by the phenomenal appearances to -which we are accustomed. - -There is a second, intrinsic reason. These vital phenomena are -intermediary, as we shall see, between manifestations of known -energies. They lie between a chemical phenomenon which always precedes -them, and a thermal phenomenon which always follows them. They are -lost sight of, as it were, between manifestations which strike our -attention. Generally speaking, intermediary energies often escape us -even in physics. Only the extreme manifestations are clearly seen. -In the presence of the organism we are, as it were, in electric -lighting works which are run by a fall of water, and at first we only -see the mechanical energy of the falling water, of the turbine and -dynamo at work, and the photic energy of the lamps which give the -light. Electrical energy, an intermediary, which has only a transient -existence, does not impose itself on our attention. - -And so _vital energies_ for this twofold reason, intrinsic and -extrinsic, are not readily apparent. To reveal them, the careful -analysis of the physiologists is required. They are acts, in most -cases silent and invisible, which we should scarcely recognize but -by their effects, after they have terminated in familiar, phenomenal -forms. This is, for example, what goes on in the muscle in process of -shortening, in the nerve carrying the nervous influx, in the secreting -gland. And this is what constitutes the different forms of energy -which we call _vital properties_. M. Chauveau and M. Laulanié use -the phrase _physiological work_ to distinguish them. _Vital energy_ -would be preferable. It better expresses the analogy of this special -form with the other forms of universal energy; it helps us better to -understand that we must henceforth consider it as exchangeable by means -of equivalents with the energies of the physical world just as they are -exchangeable one with another. - - - § 2. FIRST LAW OF BIOLOGICAL ENERGETICS. - - -It is easy to understand, after these remarks, the significance and -the scope of this assertion which contains the first principle of -biological energetics—namely, that the phenomena of life have the same -claim to be called energetic metamorphoses as the other phenomena of -nature. - -_Irreversibility of Vital Energies._—However, there is one -characteristic of vital energies which deserves the closest attention. -Their transformations have a direction which is in some measure -inevitable. They descend a slope which they never re-ascend. They -appear to be irreversible. Ostwald has rightly insisted on this -fundamental characteristic, which no doubt is not that of all the -phenomena of the living being without exception, but which is certainly -that of the most essential phenomena. There are reversible phenomena -in organisms; there are energetic transformations which may take -place from one form of energy to another, or _vice versâ_. But the -most characteristic phenomena of vitality do not act in this way. We -shall presently see that most functional physiological acts begin -with chemical and end with thermal action. The series of energetic -transformations takes place in an inevitable direction, from chemical -to thermal energy. The order of succession of ordinary energies is -thus determined in the machine of the organism, and therefore by -the conditions of the machine. The order of transformation of vital -energies is still more rigorously regulated, and the phenomena of life -evolve from childhood to ripened years, and thence to old age, without -a possible return. - -The laws of biological energetics are three in number. First of all, -there is the fundamental principle which we have just developed, and -which is, so to speak, laid down _a priori_; and there are two other -principles, those established by experiment and summing-up, as it were, -the multitude of known physiological effects. Of these two experimental -laws, one refers to the _origin_ and the other to the _termination of -the energies developed in living beings_. - - - § 3. SECOND LAW OF BIOLOGICAL ENERGETICS. - - -_The Origin of Vital Energy._—Vital energies have their origin in one -of the _external or common energies_—not in any one we choose, as might -be supposed, but in one only: chemical energy. The third principle will -show us that they terminate in another energy or a few others, also -completely fixed. - -It follows that the phenomena of life must appear to us to be a -circulation of energy which, starting from one fixed point in the -physical world, returns to that world by a few points, also fixed, -after a transient passage through the animal organism. - -Or more precisely, it is a transposition from the realm of matter -into the world of energy, of the idea of the _vital vortex_ of -Cuvier and the biologists. They defined life by its most constant -property—nutrition. Nutrition was exactly this current of matter which -the organism obtains from without by alimentation, and which it throws -out again by excretion; and the even momentary interruption of which, -if complete, would be the signal of death. The cycle of energy is the -exact counterpart of this cycle of matter. - -The second truth taught us by general physiology, a truth which -physiology learned from experiment, is enunciated as follows:—_The -maintenance of life consumes none of its energy. It borrows from the -external world all the energy which it expends, and borrows it in the -form of potential chemical energy._ This is a translation into the -language of energetics of the results acquired in animal physiology -during the last fifty years. No comment is needed to exhibit the -importance of such a truth. It reveals the origin of animal activity. -It reveals the source from which proceeds that energy which at some -moment of its transformations in the animal organism will be a _vital -energy_. - -The _primum movens_ of vital activity is, therefore, according to this -law, the chemical energy stored up in the immediate principles of the -organism. - -Let us try to follow, for a moment, this energy through the organism -and to specify the circumstances of its transformations. - -_Organic Functional Activity, and the Destruction of -Reserve-stuff._—Let us suppose then, for this purpose, that our -attention is directed to a given limited part of this organism, to -a certain tissue. Let us seize it, so to speak, by observation at a -given moment, and let us make an examination of the functional activity -starting from this conventional moment. This functional activity, -like all other vital phenomena, will be the result, as we have just -explained, of a transformation of the potential chemical energy -contained in the materials held in reserve in the tissue. This is our -first perceptible fact. This energy, when disengaged, will furnish to -the vital action the means by which it may be prolonged. - -There is, then, a _functional destruction_. There is, at the beginning -of the functional process, and by a necessary effect of that very -process, a liberation of chemical energy; and that can only take place -by a decomposition of the immediate principles of the tissue, or, as we -may say, by a destruction of organic material. Claude Bernard insisted -on this consideration, that the vital function is accompanied by a -destruction of organic material. “When a movement is produced, when a -muscle is contracted, when volition and sensibility are manifested, -when thought is exercised, when a gland secretes, then the substance -of the muscles, of the nerves, of the brain, of the glandular tissue, -is disorganized, is destroyed, and is consumed.” Energetics enables us -to grasp the deeply-seated reason of this coincidence between chemical -destruction and the functional activity, the existence of which Claude -Bernard intuitively suspected. A portion of organic material is -decomposed, is chemically simplified, becomes less complex, and loses -in this kind of descent the chemical energy which it contained in its -potential state. It is this energy which becomes the very texture of -the vital phenomenon. - -It is clear that the reserve of energy thus expended must be replaced, -because the organism remains in equilibrium. Alimentation provides for -this. - -How does it provide for it? This is a question which deserves detailed -examination. We cannot incidentally treat it in full; we can only -indicate its main features. - -_How the supply of Reserve Stuff is kept up._—We know that food does -not directly replace the reserve of energy consumed by the functional -activity. It is not its potential chemical energy which replaces, -purely and simply, the energy brought into play, consumed, or, better -still, transformed in the active organ, or tissue. Food as it is -introduced, inert food, does not, in fact, take up its place _as it -is_, without undergoing changes in that organ and that tissue, in order -to restore the _status quo ante_. - -Before building up the tissue it will have undergone various -modifications in the digestive apparatus. It will have also undergone -changes in the circulatory apparatus, in the liver, and in the -very organ we are considering. It is after all these changes that -assimilation takes place. It will find its place and will have then -passed into the state of _reserve_. - -The food digested, modified, and finally incorporated as an integral -part in the tissue in which it will be expended, is therefore in a new -state, differing more or less from its state when it was ingested. It -is a part of the living tissue in the state of constitutive reserve. -Its potential chemical energy is not the same as that of the food -introduced. It may differ from it very remarkably in consequence of -sudden alterations. - -We do not know for certain at the expense of what category of foods -this or that given organ builds up its reserve stuff. There is a -belief, for instance, according to M. Chauveau, that the muscle does -its work at the expense of the reserve of glycogen which it contains. -The potential chemical energy of this substance would be a source of -muscular mechanical energy. But we do not know exactly at the expense -of what foods, albumenoids, fats, or carbohydrates the muscle builds -up the reserve of _glycogen_ expended during its contraction. It is -probable that it builds it up at the expense of each of the three -categories after the various more or less simple alterations undergone -by the materials in the digestive tube, the blood, the liver, or other -organs. - -This building up of reserve stuff, the complement and counterpart of -_functional destruction_, is not chemical synthesis. It is, on the -contrary, generally, and on the whole, a simplification of the food -that has been introduced. This is true, at least as far as the muscle -is concerned. However, to this operation, Claude Bernard has given the -name of _organizing synthesis_, but the phrase is not a happy one. But -in no case was the eminent physiologist deceived as to the character of -the operation. “The organizing synthesis,” says he, “remains internal, -silent, hidden in its phenomenal expression, gathering together -noiselessly the materials which will be expended.” - -These considerations enable us to understand the existence of the -two great categories into which the eminent physiologist divides -the phenomena of animal life: the phenomena of the _destruction of -reserve-stuff_ corresponding to _functional facts_—that is to say -expenditures of energy; and the _plastic phenomena_ of the _building-up -of reserves_ of organic regeneration, corresponding to _functional -repose_—_i.e._, to the supply of food to the tissues. - -_Distinction between Active Protoplasm and Reserve-stuff._—If it is not -exactly in these terms that Claude Bernard formulated this fruitful -idea, it is at any rate in this way that it is to be interpreted. -This can be done by giving it a little more precision. We apply -more rigorously than that great physiologist the distinction drawn -by himself between _really active and living protoplasm_ and the -_reserve-stuff_ which it prepares. To the latter is restricted the -destruction by the functional activity and the building up by repose. - -The classification of Claude Bernard is strictly true for -reserve-stuff. It is easy to criticize the wavering and, as it were, -dimly groping expressions in which the celebrated physiologist has -shrouded his ideas. The old adage will excuse him: _Obscuritate rerum -verba obscurantur_. In the depths of his ignorance he had a flash -of genius; perhaps he did not find the definitive and, as it were, -clearly-cut formula defining what was in his mind. But, in this -respect, he has left his successors an easy task. - -_The Law of Functional Assimilation._—The progress of physiological -knowledge compels us therefore to distinguish in the constitution of -anatomical elements two parts—the materials of _reserve-stuff_ and the -_really active_ and _living protoplasm_. We have just seen how the -reserve-stuff behaves, alternately destroyed by functional activity, -and built up afterwards by the ingestion of food, followed by the -operations of digestion, elaboration, and assimilation. It remains to -ask how this really living and protoplasmic matter behaves. Does it -follow the same law? Is it destroyed during the functional activity, -and is it afterwards replaced? As to this we can express no opinion. -M. le Dantec fills a gap in our knowledge, in this respect, by an -hypothesis. He assumes that this essentially active matter grows during -functional activity, and is destroyed during repose. This is what -he calls the _law of functional assimilation_. The protoplasm would -therefore behave in an exactly contrary manner to the reserve-stuff. -It will be its counterpart. But this is only an hypothesis which, in -the present state of our knowledge, cannot be verified by experiment -We are at liberty to assert either that the protoplasm increases by -functional activity or that it is destroyed. Neither the arguments nor -the objections pro or con have any decisive value. The facts alleged on -either side are capable of too many interpretations.[10] - - [10] The reason is to be found in the large number of indeterminates - in the problem we have to solve. It will be sufficient to enumerate - them: the two substances which exist in the anatomical element, - protoplasm and reserve-stuff, to which are attributed contrary roles; - the two conditions attributable to the protoplasm, of manifested or - latent activity; the faculty possessed by both of being prolonged for - an indeterminate period, and of encroaching each on its protagonist - when its existence is at stake. Here are more elements than are - necessary to explain the positive or negative results of all the - experiments in the world. - -The only favourable argument (not demonstrative) is furnished by -energetics. It is this. The _re-building of the protoplasm_ is not -like the _organisation of reserve-stuff_, a slightly complicated or -even simplified phenomenon, as happens in the case of the reserve of -muscular glycogen. The glycogen, in fact, is built up at the expense -of foods chemically more complex. It is, on the contrary, a clearly -synthetic phenomenon, certainly of chemical complexity, since it ends -in building up the active protoplasm which is, in some measure, of -the highest scale of complexity. Its formation at the expense of the -simplest alimentary materials requires, therefore, an appreciable -quantity of energy. - -The assimilation which organizes the active protoplasm therefore -requires energy for its realization. Now, at the moment of functional -activity, and by a necessary consequence thereof, the chemical -destruction or simplification of the substance of reserve takes place. -Here is something that meets the case, and we may note the coincidence. -It does not mean that the disposable energy is really used to increase -the protoplasm, nor that the protoplasm itself is thereby increased. -It merely signifies that the wherewithal exists to provide for that -increase if it takes place. - -It is therefore _possible_ that the active protoplasm follows the law -of functional assimilation; but it is _certain_ that the reserve-stuff -follows the law laid down by Claude Bernard. - -All these considerations definitely result in the confirmation of this -second law of general physiology, according to which all vital energies -are borrowed from the potential chemical energy of the reserve-stuff of -alimentary origin. - - - § 4. THE THIRD LAW OF BIOLOGICAL ENERGETICS. - - -The third law of biological energetics is also drawn from experiment. -It relates no longer to the point of departure of the cycle of animal -energy, but to its final position. _The energetic transformations of -the animal end in thermal energy._ - -This is the most novel part of the theory, and, if we may say so, that -least understood by physiologists themselves. The energy resulting -from the chemical potential of food, having passed through the -organism (or simply through the organ which we are considering in -action), and having given rise to phenomenal appearances more or less -diversified, more or less dim or clear, obscure or obvious, which are -the characteristic or still irreducible manifestations of vitality, -finally returns to the physical world. This return takes place (with -certain exceptions which will be presently indicated) under the -ultimate form of thermal energy. This we are taught by experiment. The -phenomena of functional activity are exothermal. - -Real vital phenomena thus lie between the chemical energy which gives -rise to them, and the thermal phenomena to which they in their turn -give rise. The place of the vital fact in the cycle of universal energy -is therefore completely determined. This conclusion is of the utmost -importance to biology. It may be expressed in a concise formula which -sums up in a few words all that natural philosophy can teach as to -energetics applied to living beings. “Vital energy is a transformation -of chemical energy into thermal energy.” - -_Exceptions._—There are some exceptions to the rigour of this -statement, but they are not many in number. We must first of all remark -that it applies to _animal life_ alone. - -In the case of vegetables, looked at as a whole, the law must be -modified. Their vital energy has another origin, and another final -form. Instead of being the destroyers of chemical potential energy, -they are its creators. They build up by means of the inert and simple -materials afforded them by the atmosphere and the soil, the immediate -principles by which their cells are filled. Their vital functional -activity forms by synthesis of the reserves, carbo-hydrates (sugars and -starches), fats, albuminoid nitrogenous materials—that is to say, the -same three principal categories of foods as those used by animals. - -And to return to the latter, it should be observed that thermal energy -is not the only final form of vital energy, as this dogmatic statement -would have it supposed. It is only the principle of the final forms. -The cycle of energy occasionally terminates in mechanical energy -(phenomena of motion) and in a less degree in other energies; such -as, for example, the electrical energy produced by the functional -activity of the nerves and muscles in all animals, or in the functional -activity of special organs in rays, torpedo-fish, and the malapterurus -electricus, or finally, in the photic energy of phosphorescent animals. -But these are secondary facts. - -_Heat is an Excretum._-The third principle of biological energetics -may be therefore thus enunciated:—_Vital energy in its final form -becomes thermal energy._ This principle teaches us that if chemical -energy is the primitive generating form of vital energies, thermal -energy is the form of waste, of emunctory, the degraded form as the -physicists would say. Heat is in the dynamical order an excretion of -animal life, as urea, carbonic acid and water, are excreta in the -substantial order. By a false interpretation of the principle of the -mechanical equivalence of heat, or through ignorance of Carnot’s -principle, certain physiologists have fallen into error when they -still speak of the transformation of heat into motion or into into -electricity in the animal organism. Heat is transformed into nothing -in the animal organism. It is dissipated. Its utility arises not from -its energetic value, but from the part it plays as a primer in the -chemical reactions, as has been explained with reference to the general -characteristics of chemical energy. - -_The Effect of Energetics on our Knowledge of the Relations of -the Universe._—The consequences of these principles of energetic -physiology, which give us so much and which are so clear, are of the -greatest importance from the practical as well as from the theoretical -point of view. - -In the first place, they show us the position and the rank of the -phenomena of life in the universe as a whole. They throw fresh light on -the noble harmony of the animal and vegetable kingdoms which Priestley, -Ingenhousz, Senebier, and the chemical school of the beginning of the -nineteenth century discovered, and which was expounded by Dumas with -incomparable lucidity and brilliance. Energetics is expressed in a -line. “The animal world expends the energy accumulated by the vegetable -world.” It extends these views beyond the living kingdoms. It shows how -the vegetable world itself draws its activity from the energy radiated -by the sun, and how animals restore it again, in dissipated heat, -to the cosmic medium. It extends the harmony of the two kingdoms to -the whole of nature. The new science makes of the whole universe one -connected system. - -From a more limited point of view, and so that we may not restrict -ourselves to a consideration of the domain of animal physiology, -the laws of energetics sum up and explain a multitude of facts and -of experimental laws—for example, the law of the intermittence of -physiological activity, the facts of fatigue, the rôle and the general -principles of alimentation, and the conditions of muscular contraction. - - - - - CHAPTER III. - - ALIMENTARY ENERGETICS. - - Various Problems of Alimentation. § 1. _Food the source of Energy - and Matter._ The two forms of Energy afforded by Food—Vital Energy, - Thermal Energy. Food the source of Heat. The rôle of Heat.—§ 2. - _Measure of the output of Energy_—by the Calometric Method—by the - Chemical Method.—§ 3. The regular type of Food, Biothermogenic, and - the irregular type, Thermogenic.—§ 4. Food considered as the source - of Heat. The Law of Surfaces. The limits of Isodynamics.—§ 5. Plastic - rôle of Food. Preponderance of Nitrogenous Foods. - - -Among the problems on which energetics has thrown a vivid light we have -mentioned alimentation, muscular contraction, and, more general still, -the intermittence of vital functional activity. We shall begin with the -study of alimentation. - -_The Different Problems of Alimentation._—What is a food? In what does -alimentation consist? The dictionary of the _Académie_ will give us -our first answer. It tells us that the word food is applied to “every -kind of matter, whatever may be its nature, which habitually serves -or may serve for nutrition.” This is very well put, but here again -we must know what nutrition is, and that is not a simple matter; in -fact, it practically means whatever is usually placed on the table in -a civilized and polished society. But it is just the profound reasons -for this traditional practice that we are trying to discover. - -The problem of alimentation may be looked at in a thousand ways. It -is culinary, no doubt, and gastronomic; but it is also economical and -social, agricultural, fiscal, hygienic, medical, and even moral. But -first and foremost, it is physiological. It comprises and assumes the -knowledge of the general composition of foods, of their transformations -in the digestive apparatus, and their comparative utility in the -maintenance and the sound functional activity of the organism. To -this first group of subjects for our discussion are attached others -relating to the effects of inanition, of insufficient alimentation, and -of over-feeding. And in order to throw light on all these aspects of -the problem of alimentation, we have to lay bare the most intimate and -delicate reactions by which the organism is maintained and recruited, -and, in the words of a celebrated physiologist, “to penetrate into -the kitchen of vital phenomena.” And here neither Apicius, nor -Brillat-Savarin, nor Berchoux, nor the moralists, nor the economists -are of any use to us as guides. We must appeal to the scientists, who, -following the example of Lavoisier, Berzelius, Regnault, and Liebig, -have applied to the study of living beings the resources of general -science, and have thus founded _chemical biology_. - -This branch of science developed considerably in the second half of -the nineteenth century. It has now its methods, its technique, its -chairs at the universities, its laboratories, and its literature. -It has particularly applied itself to the study of the “material -changes” or the _metabolism_ of living beings, and with that object in -view it has done two things. In the first place, it has determined -the composition of the constituent materials of the organism; then -analyzing qualitatively and quantitatively all that penetrates into -that organism in a given time—that is to say, all the alimentary or -respiratory ingesta, and all that issues from the organism, _i.e._, -all the excreta, all the _egesta_,—it has drawn up _nutritive balance -sheets_, corresponding to the various conditions of life, whether -naturally or artificially created. And thus we can determine the -alimentary régimes which give too much, and which give too little, and -which finally restore equilibrium. - -We do not propose to give a detailed account of this scientific -movement. This may be done in monographs. All we wish to indicate -here is the most general result of these laborious researches—that is -to say, the laws and the doctrines which are derived from them, and -the theories to which they have given birth. It is by this alone that -they are brought into relation with general science, and may therefore -interest the reader. The facts of detail are never lacking to the -historian; it is more profitable to show the movement of ideas. The -theories of alimentation bring into conflict very different conceptions -of the vital functional activity. And here we find a confused medley of -opinions on which it is not without interest to endeavour to throw some -light. - - - § 1. FOOD, A SOURCE OF ENERGY AND MATTER. - - -_Definitions of Food._—Before the introduction into physiology of the -notion of energy, no one had succeeded in giving an exact idea and a -precise definition of food and alimentation. Every physiologist and -medical man who attempted it had failed, and this for various reasons. - -The general cause of this failure was that most definitions, popular or -technical, interposed the condition that the food must be introduced -into the digestive apparatus. “It is,” said they, “a substance which -when introduced into the digestive tube undergoes, etc., etc.” -But plants draw food from the soil, and they possess no digestive -apparatus; many animals have no intestinal tube; and in the case of -certain rotifera, the females possess a digestive apparatus, while the -males have none. Nevertheless all animals feed. - -On the other hand, there are other substances than those which use the -digestive tract for the purpose of entering the organism, and which are -eminently useful or necessary to the maintenance of life. In particular -we may mention oxygen. - -The distinctive feature of food is its _utility_—when conveniently -introduced or employed—to the living being. Claude Bernard’s definition -is this:—A substance taken in the external medium “necessary for the -maintenance of the phenomena of the healthy organism and for the -reparation of the losses it constantly suffers.” “A substance which -supplies an element necessary for the constitution of the organism, or -which _diminishes its disintegration_” (stored-up food); this is the -definition of C. Voit, the German physiologist. M. Duclaux says, in -his turn, but in far too general terms, that it is a substance which -contributes to assure the sound functional activity of any of the -organs of the living being. None of these ways of describing food gives -a complete idea. - -_Food, the Source of Energy and Matter._—The intervention of the -notion of energy enables us more completely to understand the true -nature of food. We must, in fact, have recourse to the energetic -conception if we desire to take into account all that the organism -requires from food. It not only requires _matter_, but also, and most -important of all, energy. - -Investigators so far concentrated their thoughts exclusively on the -necessity of a supply of matter—that is to say, they only looked upon -one side of the problem. The living body presents, at each of its -points, an uninterrupted series of disintegrations and reconstitutions, -the materials being supplied from without by alimentation, and rejected -by excretion. Cuvier gave to this unceasing circulation of ambient -matter throughout the vital world the name of _vital vortex_, and he -rightly saw in it the characteristic of nutrition, and the distinctive -feature of life. - -This idea of the _cycle of matter_ has been completed in our own -time by that of the _cycle of energy_. All the phenomena of the -universe, and therefore those of life, are conceived of as energetic -transformations. We now look at them in their relationship instead of -considering them individually as of old. Each has an antecedent and a -consequent unity with which it is connected in magnitude by the law of -equivalents taught us by contemporary physics. And thus we may conceive -of their succession as the cycle of a kind of indestructible agent, -which changes only apparently, or assumes another form as it passes -from one to the other, but its magnitude remains unaltered. This is -energy. Thus, in the living being there is not only a circulation of -matter, but also a circulation of energy. - -The most general result of research in physiological chemistry -from the time of Lavoisier down to our own day has been to teach us -that _the antecedent of the vital phenomenon is always a chemical -phenomenon_. The vital energies are derived from the potential chemical -energy accumulated in the immediate constituent principles of the -organism. In the same way _the consequent phenomenon of the vital -phenomenon is in general a thermal phenomenon_. The final form of vital -energy is thermal energy. These three assertions as to the nature, the -origin, and the final form of vital phenomena constitute the three -fundamental principles, the three laws, of biological energetics. - -_Food, a Source of Heat. It is not quâ source of heat that food is -the source of vital energy._—The place of vital energy in the cycle -of universal energy is completely determined. It lies between the -chemical energy which is its generating form and the thermal energy -which is its form of disappearance, of breakdown, the “degraded form,” -as the physicists say. Hence we have a result which can be immediately -applied in the theory of food—namely, that heat is in the dynamical -order an excretum of the animal life rejected by the living being, -just as in the substantial order, urea, carbonic acid and water, are -the materials used up and again rejected by it. We therefore must -not think of the transformation in the animal organism of heat into -vital energy, as certain physiologists always do. Nor must we think, -with Béclard, of its transformation into muscular movement; or, as -others have maintained, into animal electricity. This is not only -an error of doctrine but an error of fact. It proceeds from a false -interpretation of the principle of the mechanical equivalent of heat -and a misunderstanding of Carnot’s principle. Thermal energy does not -repeat the course of the energetic flux in the animal organism. The -heat is not transformed into anything. It is simply dissipated. - -_The Part played by Animal Heat as a Condition of Physiological -Manifestations._—Does this mean that heat is useless to life in the -very beings in which it is most abundantly produced—_i.e._, in man -and in the warm-blooded vertebrates? So far from this being so, it is -necessary to life. But its utility has a peculiar character which must -neither be misunderstood nor exaggerated. It is not transformed into -chemical or vital reactions, but merely creates for them a favourable -condition. - -According to the first principle of energetics, for the vital fact -to be derived from the thermal fact, the heat must be preliminarily -transformed into chemical energy, since chemical energy is necessarily -an antecedent and generating form of vital energy. Now this regressive -transformation is impossible according to the current theories of -general physics. The part played by heat in the act of chemical -combination is that of a primer to the reaction. It consists in -placing the reacting bodies, by changing their state or by modifying -their temperature, in the condition in which they ought to be for the -chemical forces to come into play. For example, in the combination of -hydrogen and oxygen by setting light to an explosive mixture, heat -only acts as a primer to the phenomenon, because the two gases which -are passive at ordinary temperatures, require to be raised to 400° -C. before chemical affinity comes into play. And so it is with the -reactions which go on in the organism. They have a maximum temperature, -and the part played by animal heat is to furnish them with it. - -It follows that heat intervenes in animal life in two capacities—first -and foremost as _excretum_, or end of the vital phenomenon, of -_physiological work_; and on the other hand, as a _condition_ or -_primer_ of the chemical reactions of the organism; and generally, -as a favourable condition for the appearance of the physiological -manifestations of living matter. Thus, it is not dissipated in sheer -waste. - -I was led to adopt these views some years ago from certain experiments -on the rôle played in food by alcohol. I did not then know that they -had already been expressed by one of the masters of contemporary -physiology, M. A. Chauveau, and that they were related in his mind to -a series of conceptions and of researches of great interest, in the -development of which I have since then taken a share. - -_Two Forms of Energy supplied to Animals by Food._—To say that food is -simultaneously a supply of energy and a supply of matter, is really to -express in a single sentence the fundamental conception of biology, in -virtue of which life brings into play no substratum or characteristic -dynamism. According to this, the living being appears to us as the seat -of an incessant circulation of matter and energy, starting from the -external world and returning to it. All food is nothing but this matter -and this energy. All its characteristics, our views as to its rôle, its -evolution, all the rules of alimentation are simple consequences of -this principle, interpreted by the light of energetics. - -And first of all, let us ask what forms of energy are afforded by food? -It is easy to see that there are two—food is essentially a source of -chemical energy; and secondarily and accessorily, it is a source of -heat. Chemical energy is the only energy, according to the second -law of energetics, which may be transformed into vital energy. It is -true at any rate for animals; for in plants it is otherwise. There the -vital cycle has neither the same point of departure nor the same final -position. The circulation of energy does not take place in the same -manner. - -On the other hand, and this we are taught by the third law, energy -brought into play in vital phenomena is finally liberated and restored -to the physical world in the form of heat. We have just said that this -release of heat is employed in raising the temperature of the living -being. It is animal heat. - -Thus there are two forms of energy supplied by food, chemical and -thermal. - -It must be added that these are not the only forms, but the principal, -and by far the most important. It is not absolutely true that heat is -the only outcome of the vital cycle. It is only so in the subject in -repose, contented to live idly without doing external mechanical work, -without lifting a tool or a weight, even that of its own body. And -again, speaking in this way, we neglect all the movements and all the -mechanical work which is done without exercise of the volition, by the -beating of the heart and of the arteries, the movements of respiration, -and the contractions of the digestive tube. - -Mechanical work is, in fact, another possible termination of the cycle -of energy. But there is no longer anything necessary or inevitable -in this, since motion and the use of force are in a certain measure -subordinated to the capricious volition of the animal.[11] - - [11] There is another reason why the rôle of mechanical energy, - compared with that of thermal energy, is reduced, in the partition of - afferent, alimentary energy—at least, in animals which have not to do - excessive work. The unit of heat, the Calorie, is equivalent to 425 - units of work—_i.e._, to 425 kilogrammetres. In the animal at rest, - the number of kilogrammetres representing the different quantities - of work done is small, the number of corresponding Calories is 425 - times smaller. It becomes almost negligeable in comparison with the - considerable number of Calories dissipated in the form of heat. - -At other times, again, it is an electrical phenomenon which terminates -the vital cycle, and it is, in fact, in this way that things happen -in the functional activity of the nerves and muscles in all animals, -and in the functional activity of the electrical organ in fish, such -as the ray and the torpedo. Finally, the termination may be a photic -phenomenon, and this is what happens in phosphorescent animals. - -It is idle to diminish the power of these principles by proceeding -to enumerate the whole of the exceptions to their validity. We know -perfectly well that there are no absolute principles in nature. Let -us say, then, that the energy which temporarily animates the living -being is furnished to it by the external world under the exclusive -form of potential chemical energy; but that, if there is only one door -of entry, there are two exits. It may return to the external world -in the principal form of thermal energy and in the accessory form of -mechanical energy. - - - § 2. MEASUREMENT OF THE SUPPLY OF ALIMENTARY ENERGY. - - -_Calorimetric Method._—From what has preceded it is clear that if the -energetic _flux_ which circulates through the animal emerges, _in -toto_, in the state of heat, the measurement of this heat becomes the -measurement of the vital energy itself, for the origin of which we -must go back to the food. If the flux is divided into two currents, -mechanical and thermal, they must both be measured and the sum of their -values taken. If the animal does not produce mechanical work, and all -ends in heat, we have only to capture, by means of a calorimeter, -this energetic flux as it emerges, and thus measure in magnitude and -numerically the energy in motion in the living being. Physiologists use -for this purpose various types of apparatus. Lavoisier and Laplace used -an ice calorimeter—that is to say, a block of ice in which they shut up -a small animal, such as a guinea-pig; they then measured its thermal -production by the quantity of ice it caused to melt. In one of their -experiments, for instance, they found that a guinea-pig had melted 341 -grammes of ice in the space of ten hours, and had therefore set free 27 -Calories. - -But since those days more perfect instruments have been invented. -M. d’Arsonval employed an air calorimeter, which is nothing but a -differential thermometer very ingeniously arranged, and giving an -automatic record. Messrs. Rosenthal, Richet, Hirn and Kaufmann, -and Lefèvre have used more or less simplified or complicated air -calorimeters. Others, following the example of Dulong and Despretz, -have used calorimeters of air and mercury, or with Liebermester, -Winternitz, and J. Lefèvre (of Havre), have had recourse to baths. -Here, then, there is a considerable movement of research which has led -to the discovery of very interesting facts. - -_Measurement of the Supply of Alimentary Energy by the Chemical -Method._—We may again reach our result in another way. Instead of -surprising the current of energy as it emerges and in the form of -heat, we may try and capture it at its entry in the form of potential -chemical energy. - -The evaluation of potential chemical energy may be effected with the -same unit of measurement as the preceding—that is to say, the Calorie. -If we consider man and mammals, for example, we know that there is -only apparently an infinite variety in their foods. We may say that -they feed on only three substances. It is a very remarkable fact that -all the complexity and multiplicity of foods, fruits, grains, leaves, -animal tissues, and vegetable products of which use is made, reduce to -so great a simplicity and uniformity, that all these substances are of -three types only: albuminoids, such as albumen or white of egg—foods of -animal origin or varieties of albumen; carbo-hydrates, which are more -or less disguised varieties of sugar; and finally, fats. - -Here, then, from the chemical point of view, leaving out certain -mineral substances, are the principal categories of alimentary -substances. Here, with the oxygen that is brought in by respiration, is -everything that penetrates the organism. - -And now, what comes out of the organism? Three things only, water, -carbonic acid, and urea. But the former are the products of the -combustion of the latter. If we consider an adult organism in perfect -equilibrium, which varies throughout the experiment neither in -weight nor in composition, we may say that the receipts balance the -expenditure. Albumen, sugar, fat, plus the oxygen brought in, balance -quantitatively the water, carbonic acid, and urea expelled. Things -happen, in fact, as if the foods of the three categories were burned up -more or less completely by the oxygen. - -It is this combustion that we have known since the days of Lavoisier -to be the source of animal heat. We can easily determine the quantity -of heat left by albumen passing into the state of urea, and by the -starch, the sugars, and the fats reduced to the state of water and -carbonic acid. This quantity of heat does not depend on the variety -of the unknown intermediary products which have been formed in the -organism. Berthelot has shown that this quantity of heat which measures -the chemical energy liberated by these substances is identical with -the quantity obtained by burning the sugar and the fats in a chemical -apparatus, in a calorimetric bomb, until we get carbonic acid and -water, and by burning albumen till we get urea. This result is a -consequence of Berthelot’s _principle of initial and final states_. -The liberated heat only depends on the initial and final states, and -not on the intermediary states. The heat left in the economy by the -food being the same as that left in the calorimetric bomb, it is easy -for the chemist to determine it. It has thus been discovered that -one gramme of albumen produces 4.8 Calories, one gramme of sugar 4.2 -Calories, and one gramme of fat 9.4 Calories. We thus gather what a -given ration—a mixture in certain proportions of these different kinds -of foods—supplies to the organism and what energy it gives it, measured -in Calories. - -The calculation may be carried out to a high degree of accuracy if, -instead of confining ourselves to the broad features of the problem, we -enter into rigorous detail. It is only, in fact, approximately that we -have reduced all foods to albumen, sugar, and fat, and all excreta to -water, carbonic acid, and urea. - -The reality is a little more complicated. There are varieties of -albumen, carbo-hydrates, and fatty bodies, the heats of combustion of -which in the organism oscillate in the neighbourhood of the numbers -4.8, 4.2, and 9.4. Each of these bodies has been individually examined, -and numerical tables have been drawn up by Berthelot, Rubner, Stohmann, -Van Noorden, etc. The tables exhibit the thermal value or energetic -value of very different kinds of foods. - -In our climate, the adult average man, doing no laborious work, daily -consumes a maintenance ration composed, as a rule, of 100 grammes of -albuminoids, 49 grammes of fats, and 403 grammes of carbo-hydrates. -This ration has an energetic value of 2,600 Calories. - -It is therefore, thanks to the victories won in the field of -thermo-chemistry, and to the principles laid down since 1864 by M. -Berthelot, that this second method of attack on nutritive dynamism has -been rendered possible. Physiologists, by the aid of these methods, -have drawn up _balance-sheets of energy_ for living beings just as they -had previously established _balance-sheets of matter_. - -Now, it is precisely researches of this kind that we have indicated -here as a consequence of biological energetics, which in reality have -helped to build up that principle. These researches have shown us -that, in conformity with the _principles of thermodynamics_, there -was not, in fact, in the organism, any transformation of heat into -mechanical work, as the physiologists for a short time supposed, on -the authority of Berthelot. With the help of our theory this mistake -is no longer possible. The doctrine of energetics shows us in fact -the current of energy dividing itself, as it issues from the living -being, into two divergent branches, the one thermal and the other -mechanical, external the one to the other although both issuing from -the same common trunk, and having between them no relation but this, -that the sum of their discharges represents the total of the energy -in motion. Let us now translate these very simple notions into the -more or less barbarous jargon in use in physiology. We shall be -convinced as we go on of the truth of the saying of Buffon, that -“the language of science is more difficult to learn than the science -itself.” We shall say, then, that chemical energy, that the unit of -weight of the food which may be placed in the organism, constitutes -the alimentary _potential_, the _energetic value_ of this substance, -its _dynamogenic power_. It is measured in units of heat, in Calories, -which the substance may leave in the organism. The evaluation is made -according to the principles of thermo-chemistry, by means of the -numerical tables of Berthelot, Rubner, and Stohmann. The same number -also expresses the _thermogenic power_, virtual or theoretical, of the -alimentary substance. This energy being destined to be transformed -into _vital energies_ (Chauveau’s _physiological work_, _physiological -energy_), the dynamogenic or thermogenic value of the food is at the -same time its biogenetic value. Two weights of different foods which -supply the organism with the same number of Calories,—_i.e._ for which -these numerical values are the same,—will be called _isodynamic_ or -_isodynamogenic_, _isobiogenetic_, _isoenergetic_ weights. They will -be equivalent from the point of view of their alimentary value. And -finally, if, as is usually the case, the cycle of energy ends in the -production of heat, the food which has been utilized for this purpose -has a real _thermogenic value_, identical with its theoretical -thermogenic value. In this case it might be determined experimentally -by direct calorimetry, measuring the heat produced by the animal -supposed absolutely unchanged and identical before and after the -consumption of the food. - - - § 3. DIFFERENT TYPES OF FOODS. THE REGULAR, BIOTHERMOGENIC TYPE AND - THE IRREGULAR, THERMOGENIC TYPE. - - -Food is a source of thermal energy for the organism because it is -decomposed within it, and undergoes within it a chemical degradation. -Physiological chemistry tells us that whatever be the manner in which -it is broken up, it always results in the same body and always sets -free the same quantity of heat. But if the point of departure and the -point of arrival are the same, it is possible that the path pursued is -not constantly identical. For example, one gramme of fat will always -give the same quantity of heat, 9.4 Calories, and will always come -to its final state of carbonic acid and water; but from the fat to -the mixture of carbonic acid gas and water there are many different -intermediaries. In a word we get the conception of varied cycles of -alimentary evolutions. - -From the point of view of the heat produced it has just been said that -these cycles are equivalent. But are they equivalent from the vital -point of view? This is an essential question. - -Let us imagine the most ordinary alternative. Food passes from the -natural to the final state after being incorporated with the elements -of the tissues, and after having taken part in the vital operations. -The chemical potential only passes into thermal energy after having -passed through a certain intermediary phase of vital energy. This -is the normal case, _the regular type of alimentary evolution_. It -may be said in this case that the food has fulfilled the whole of -its function, it has served for the vital functional activity before -producing heat. It has been _biothermogenic_. - -_The irregular or pure thermogenic type._—And now let us conceive of -the most simple _irregular or aberrant type_. Food passes from the -initial to the final state without incorporation in the living cells of -the organism, and without taking part in the vital functional activity. -It remains confined in the blood and the circulating liquids, but it -undergoes in the end, however, the same molecular disintegration as -before, and sets free the same quantity of heat Its chemical energy -changes at once into thermal energy. Food is a _pure thermogen_. It -has fulfilled only one part of its work. It has been of slight vital -utility. - -Does this ever occur in reality? Are there foods which would be only -_pure thermogens_—that is to say, which would not in reality be -incorporated with the living anatomical elements, which would form no -part of them either in a state of provisory constituents of the living -protoplasm, or in the state of reserve-stuff; which would remain in the -internal medium, in the blood and the lymph, and would there undergo -their chemical evolution? Or again, if the whole of the food does not -escape assimilation, would it be possible for part to escape it? Would -it be possible for one part of the same alimentary substance to be -incorporated, and for the rest to be kept in the blood or the lymph, -in the circulating liquids _ad limina corporis_, so to speak? In other -words, can the same food be according to circumstances a _biothermogen_ -or a _pure thermogen_? Some physiologists—Fick of Wurzburg, for -instance—have claimed that this is really the case for most -nitrogenous elements, carbohydrates, and fats; all would be capable -of evolving according to the two types. On the other hand, Zuntz and -von Mering have absolutely denied the existence of the aberrant or -pure thermogenic type. No substances would be directly decomposed in -the organic liquids apart from the functional intervention of the -histological elements. Finally, other authors teach that there is a -small number of alimentary substances which thus undergoes direct -combustion, and among them is alcohol. - -_Liebig’s Superfluous Consumption._—Liebig’s _theory of superfluous -consumption_ and Voit’s _theory of the circulating albumen_ assert -that the proteid foods undergo partial direct combustion in the -blood vessels. The organism only incorporates what is necessary for -physiological requirements. As for the surplus of the food that is -offered it, it accepts it, and, so to speak, squanders it; it burns it -directly; and we have a “sumptuary” consumption, consumption _de luxe_. - -In this connection arose a celebrated discussion which still divides -physiologists. If we disengage the essential body of the discussion -from all that envelops it, we see that it is fundamentally a question -of deciding whether a food always follows the same evolution whatever -the circumstances may be, and particularly when it is introduced in -great excess. Liebig thought that the superabundant part, escaping -the ordinary process, was destroyed by direct combustion. He affirmed, -for instance, that nitrogenous substances in excess were directly -burned in the blood instead of passing through their usual cycle of -vital operations. We might express the same idea by saying that they -then undergo an accelerated evolution. Instead of passing through the -blood in the anatomical element, to return in the dismembered form from -the anatomical element to the blood, their breaking up takes place in -the blood itself. They save a displacement, and therefore in reality -remain external to the construction of the living edifice. Their -energy, crossing the intermediary vital stage, passes with a leap from -the chemical to the thermal form. Liebig’s doctrine reduced to this -fundamental idea deserved to survive, but mistakes in minor details -involved its ruin. - -_Voit’s Circulating Albumen._—A few years later C. Voit, a celebrated -physiological chemist of Munich, revived it in a more extravagant form. -He held that almost the whole of the albuminoid element is burned -directly in the blood. He interpreted certain experiments on the -utilization of nitrogenous foods by imagining that these substances -when introduced into the blood were divided as a result of digestion -into two parts: the one very small, which was incorporated with the -living elements, and passed into the stage of _organized albumen_, the -other, corresponding to the greater part of the alimentary albumen, -remained mingled with the blood and lymph, and was subjected in this -medium to direct combustion. This was _circulating albumen_. In this -theory the tissues are almost stable; the organic liquids alone are -subjected to oxydizing transformations, to nutritive metabolism. The -accelerated evolution, which Liebig considered as an exceptional case, -was to C. Voit the rule. - -_Current Ideas as to the Rôle of Foods._—The ideas of to-day are not -those of Voit; but they do not, however, differ from them essentially. -We no longer admit that the greater part of the ingested and digested -albumen remains confined in the circulating medium external to the -anatomical elements. It is held, with Pflüger and the school of Bonn, -that it penetrates the anatomical element and is incorporated in it; -but in agreement with Voit it is believed that a very small part is -assimilated to the really living matter, to the protoplasm properly -so called; the greater part is deposited in the cellular element as -reserve-stuff. The material, properly so called, of the living machine -does not undergo destruction and reparation as extensively as our -predecessors supposed. There is no need for great reparation. On the -contrary, the physiological activity consumes to a great extent the -reserve-stuff. And the greater part of the food, after having undergone -suitable elaboration, serves to replace the reserve-stuff destroyed in -each anatomical element by the vital functional activity. - -_Experimental Facts._—Among the facts which brought physiologists -of the school of Voit to believe that most foods do not get beyond -the internal medium, there is one which may well be mentioned here. -It has been observed that the consumption of oxygen in respiration -increases notably (about a fifth of its value) immediately after a -meal. What does this mean? The interval is too short for the digested -alimentary substances to have been elaborated and incorporated in the -living cells. It is supposed that an appreciable time is required -for this complete assimilation. The products of alimentary digestion -are therefore in all probability still in the blood, and in the -interstitial liquids in communication with it. The increase of oxygen -consumed would show that a considerable portion of these nutritive -substances absorbed and passed into the blood would be oxydized and -then and there destroyed. But this interpretation, however probable -it may be, does not really fit in with the facts in such a way that -we may consider it as proved. Certain experiments by Zuntz and Mering -are opposed to the idea that combustion in the blood is easy. These -physiologists injected certain oxydizable substances into the vessels -without being able to detect any instantaneous oxidation. It is only -fair to add that against these fruitless attempts other more fortunate -experiments may be quoted. - -_Category of Purely Thermogenic Foods, with Accelerated Evolution. -Alcohol. Acids of Fruits._—The accelerated evolution of foods—an -evolution which takes place in the blood, that is to say outside the -really living elements—remains, therefore, very uncertain as far as -ordinary food is concerned. It has been thought that it was a little -less uncertain as far as the special category of alcohol, acids of -fruits, and glycerine is concerned. - -Some authors consider these bodies as pure thermogens. When alcohol -is ingested in moderate doses, they say that about a tenth of the -quantity absorbed becomes fixed in the living tissues; the rest is -“circulating alcohol.” It is oxidized directly in the blood and in -the lymph, without intervening in the vital functions other than by -the heat it produces. From the point of view of the energetic theory -these are not real foods, because their potential energy is not -transformed into any kind of vital energy, but passes at once to the -thermal form. On the other hand, other physiologists look upon alcohol -as really a food. According to them everything is called a food which -is transformed in the organism with the production of heat; and they -measure the nutritive value of a substance by the number of Calories -it can give up to the organism. So that alcohol would be a better food -than carbohydrated and nitrogenous substances. A definite quantity of -alcohol, a gramme for instance, is equivalent from the thermal point of -view to 1.66 grammes of sugar, 1.44 of albumen, or 0.73 of fat. These -quantities would be _isodynamic_. - -Experiment has not entirely decided for or against this theory. -However, the first tests have not been very favourable to it. -The researches of C. von Noorden and his pupils, Stammreich and -Miura, have clearly and directly established that alcohol cannot -be substituted in a maintenance ration for an exactly isodynamic -quantity of carbohydrates. If the substitution is effected, a ration -only just capable of maintaining the organism in equilibrium becomes -insufficient. The animal decreases in weight. It loses more nitrogenous -matter than it can recover from its diet, and this situation cannot be -sustained for long. On the other hand, the celebrated researches of -the American physiologist, Atwater, would plead, on the contrary, in -favour of almost isodynamic substitution. Finally, Duclaux has shown -that alcohol is a real food, biothermogenic for certain vegetable -organisms. But urea is also a food for _micrococcus ureæ_. It does not -follow that it is a food for mammals. We have not reached the solution -yet—_adhuc sub judice_. - -_Conclusion: The Energetic Character of Food._—To sum up we have -confined ourselves, in what has been said, to the consideration of a -single character of food, and really the most essential, its energetic -character. Food must furnish energy to the organism, and for that -purpose it is decomposed and broken up within it, and issues from it -simplified. It is thus, for instance, that the fats, which from the -chemical point of view are complicated molecular edifices, escape in -the form of carbonic acid and water. And so it is with carbo-hydrates, -starchy and sugary substances. This is because these compounds descend -to a lower degree of complexity during their passage through the -organism, and by this drop, as it were, they get rid of the chemical -energy which they contained in the potential state. Thermo-chemistry -enables us to deduce from the comparison of the initial and final -states the value of the energy absorbed by the living being. This -energetic, dynamogenic or thermogenic value, thus gives a measure -of the alimentary capacity of the substance. A gramme of fat, for -instance, gives to the organism a quantity of energy equivalent to 9.4 -Calories; the thermogenic value of the albumenoids is 4.8 Calories. -The thermogenic or thermal value of carbohydrates is less than 4.7 -calories. This being so, we understand why the animal is nourished by -foods which are products very high in the scale of chemical complexity. - - - § 4. FOOD CONSIDERED EXCLUSIVELYY AS SOURCE OF HEAT. - - -We have seen that food is, in the first place, a source of _chemical -energy_; and, in the second place, a source of _vital energy_—finally, -and consequently, a source of thermal energy. It is this last point -of view which has exclusively struck the attention of certain -physiologists, and hence has arisen a peculiar manner of conceiving the -rôle of food. It consists in looking on food as a source of thermal -energy. - -This conception is easily applied to warm-blooded animals, but to them -exclusively—and this is where it first fails. The animal is warmer than -the environment in general. It is constantly giving out heat to it. To -repair this loss of heat it takes in food in exact proportion to the -loss it sustains. When it is a question of cold-blooded vertebrates, -which live in water and in most cases have an internal temperature -which is not distinguishable from that of the environment, we see less -clearly the thermal rôle of food. It seems then that the production of -heat is an episodic phenomenon, not existing for itself. - -However that may be, food is in the second place a source of thermal -energy for the organism. Can it be said, inversely, that every -substance which we introduce into the economy, and which is there -broken up and gives off heat, is a food? This is a moot point. We dealt -just now with purely thermogenic foods. However, most physiologists -are inclined to give a positive answer. In their eyes the idea of food -cannot be considered apart from the fact of the production of heat. -They take the effect for the cause. To these physiologists everything -ingested is called food, if it gives off heat within the body. - -To be heated by food is, indeed, an imperious necessity for the higher -animals. If this need be not satisfied the functional activities -become enervated; the animal falls into a state of torpor; and if it -is capable of attenuated, of more or less latent, life it sleeps in -a state of hibernation; but if it is not capable of this, it dies. -The warm-blooded animal with a fixed temperature is so organized that -this constancy of temperature is necessary to the exercise and to the -conservation of life. To maintain this indispensable temperature there -must be a continual supply of thermal energy. According to this, the -necessity of alimentation is confused with the necessity of a supply -of heat to cover the deficit which is due to the inevitable cooling -of the organism. This is the point of view taken up by theorists, and -we cannot say that they have no right to do so. We can only protest -against the exaggeration of this principle, and the subordination -of the other rôles of food to this single role as a thermogen. It -is the magnitude of the thermal losses which, according to these -physiologists, determines the need for food, and regulates the total -value of the maintenance ration. From the quantitative view it is -approximately true. From the qualitative point of view it is false. - -Such is the theory opposed to the theory of chemical and vital energy. -It has on its side a large number of experts, among whom are Rubner, -Stohmann, and von Noorden. It has been defended in an article in -the _Dictionnaire de Physiologie_ by Ch. Richet and Lapicque. They -hold that thermogenesis absolutely dominates the play of nutritive -exchanges; and it is the need for the production of heat that -regulates the total demand for Calories which every organism requires -from its ration. It is not because it produces too much heat that -the organism gets rid of it peripherally: it is rather because it -inevitably disperses it that it is adapted to produce it. - -_Rubner’s Experiments._—This conception of the rôle of alimentation -is based on two arguments. The first is furnished by Rubner’s last -experiment (1893). A dog in a calorimeter is kept alive for a rather -long period (two to twelve days); the quantity of heat produced in this -lapse of time is measured, and it is compared with the heat afforded by -the food. In all cases the agreement is remarkable. But is it possible -that there should be no such agreement? Clearly no, because there is a -well-known regulating mechanism which always exactly proportions the -losses and the gains of heat to the necessity of maintaining the fixed -internal temperature. This first argument is, therefore, not conclusive. - -The second argument is drawn from what has been called the _law of -surfaces_, clearly perceived by Regnault and Reiset in their celebrated -memoir in 1849, formulated by Rubner in 1884, and beautifully -demonstrated by Ch. Richet. In comparing the maintenance rations -for subjects of very different weights, placed under very different -conditions, it is found that the food always introduces the same -number of Calories for the same extent of skin—_i.e._, for the same -cooling surface. The numerical data collected by E. Voit show that, -under identical conditions, warm-blooded animals daily expend the same -quantity of heat per unit of surface—namely, 1.036 Calories per square -yard. The average ration introduces exactly the amount of food which -gives off sensibly this number of Calories. Now, this is an interesting -fact, but, like the preceding, it has no demonstrative force. - -_Objections. The Limits of Isodynamism._—On the contrary, there are -serious objections. The thermal value of the nutritive principles only -represents one feature of their physiological rôle. In fact, animals -and man are capable of extracting the same profit and the same results -from rations in which one of the foods is replaced by an _isodynamic_ -proportion of the other two—that is to say, a proportion developing the -same quantity of heat. But this substitution has very narrow limits. -Isodynamism—that is to say, the faculty that food has of supplying _pro -ratâ_ its thermal values—is limited all round by exceptions. In the -first place, there are a few nitrogenous foods that no other nutritive -principle can supply; and besides, beyond this minimum, when the -supply takes place, it is not perfect. Lying between the albuminoids -and the carbohydrates relatively to the fats, it is not between these -two categories relatively to nitrogenous substances if the thermal -power of food were the only thing that had to be considered in it, the -isodynamic supply would not fail in a whole category of principles such -as alcohol, glycerin, and the fatty acids. Finally, if the thermal -power of a food is the sole measure of its physiological utility, -we are compelled to ask why a dose of food may not be replaced by a -dose of heat. External warming might take the place of the internal -warming given by food. We might be ambitious enough to substitute for -rations of sugar and fat an isodynamic quantity of heat-giving coal, -and so nourish the man by suitably warming his room. In reality, food -has many other offices to fulfill than that of warming the body and -of giving it energy—that is to say, of providing for the functional -activity of the living machine. It must also serve to provide for -wear and tear. The organism needs a suitable quantity of certain -fixed principles, organic and mineral. These substances are evidently -intended to replace those which have been involved in the cycle of -matter, and to reconstitute the organic material. To these materials we -may give the name of _histogenetic_ foods (repairing the tissues), or -of _plastic_ foods. - - - § 5. THE PLASTIC RÔLE OF FOOD. - - -_Opinions of the Early Physiologists._—It is from this point of view -that the ancients regarded the rôle of alimentation. Hippocrates, -Aristotle, and Galen believed in the existence of a unique nutritive -substance, existing in all the infinitely different bodies that man -and the animals utilize for their nourishment. It was Lavoisier -who first had the idea of a dynamogenic or thermal rôle of foods. -Finally, the general view of these two species of attributes and their -marked distinction is due to J. Liebig, who called them _plastic_ and -_dynamogenic_ foods. In addition he thought that the same substance -should accumulate the same attributes, and that this was the case with -the albuminoid foods, which were at once _plastic_ and _dynamogenic_. - -_Preponderance of Nitrogenous Foods._—Magendie, in 1836, was the -pioneer who introduced in this interminable list of foods the first -simple division. He divided them into proteid substances, still called -albuminoids, nitrogenous, quaternary, and _ternary substances_. Proteid -substances are capable of maintaining life. Hence the preponderant -importance given by the eminent physiologist to this order of foods. -These results have since been verified. Pflüger, of Bonn, gave a -very convincing proof of this a few years ago. He fed a dog, made it -work, and finally fattened it, by giving it nothing at all to eat but -meat from which had been extracted, as thoroughly as possible, every -other substance.[12] The same experiment showed that the organism can -manufacture fats and carbo-hydrates at the expense of the nitrogenous -food, when it does not find them ready formed in the ration. The -albumen will suffice for all the needs of energy and and matter. To -sum up, there is no necessary fat, no carbohydrate is necessary; -albuminoids alone are indispensable. Theoretically, the animal and man -alike could maintain life by the exclusive use of proteid food; but, -practically, this is not possible for man, because of the enormous -amount of meat which would have to be used (3 kilogrammes a day). - - [12] It is not certain, however, that all the precautions taken - have the desired result. You cannot entirely deprive meat of its - carbohydrates. - -Ordinary alimentation comprises a mixture of three orders of -substances, and to this mixture albumen brings the plastic element -materially necessary for the reparation of the organism; it also is -the source of energy. The two other varieties only bring energy. In -this mixed regimen the quantity of albumen must never descend below a -certain minimum. The efforts of physiologists of late years have tended -to fix with precision this minimum ration of albuminoids—or as we may -briefly put it, of _albumen_—below which the organism would perish. -Voit had found 118 grammes of albumen necessary for the average adult -man weighing 70 kilos. This figure is certainly too high. The Japanese -doctors, Mori, Tsuboï, and Murato, have shown that a considerable -portion of the population of Japan is content with a diet much poorer -in nitrogen, and suffers no inconvenience. The Abyssinians, according -to Lapicque, ingest, on the average, only 67 grammes of albumen per -day. A Scandinavian physiologist, Siven, experimenting on himself, -found that he could reduce the ration of albumen necessary to the -maintenance and equilibrium of the organism to the lowest figures -which have been yet reached—namely, from 35 to 46 grammes a day. These -experiments, however, must be confirmed and interpreted. Besides, it -is important to point out that the most advantageous ration of albumen -requires to be a good deal above the strictly sufficient quantity. - -It only remains to refer to several other recent researches. The most -important of many are those published by M. Chauveau, on the reciprocal -transformation of the immediate principles in the organism according -to the conditions of its functioning and the circumstances of its -activity. To deal with these researches with as much detail as they -deserve, we must study the physiology of muscular contraction and of -movement—that is to say, of muscular energetics. - - - - - BOOK III. - - THE CHARACTERS COMMON TO LIVING BEINGS. - - Chapter I. Summary: The doctrine of vital unity.—Chapter II. The - morphological unity of living beings.—Chapter III. The chemical unity - of living beings.—Chapter IV. The mutability of living beings.—Chapter - V. The specific form, its acquisition, and reparation.—Chapter VI. - Nutrition. - - - CHAPTER I. - - THE DOCTRINE OF VITAL UNITY. - - Phenomena common to all living beings—Theory of vital duality—Unity in - the formation of immediate principles—Unity in the digestive acts—The - common vital fund. - - -When we ask the various philosophical schools what life is, some show -us a chemical retort, and others show us a soul. Whether vitalists -or of the mechanical school, these are the adversaries who since -philosophy began have vainly contested the possession of the secret -of life. We need not concern ourselves with this eternal quarrel. We -need not ask Pythagoras, Plato, Aristotle, Hippocrates, Paracelsus, -Van Helmont, and Stahl what idea they formed of the vital principle; -nor need we probe to the depths the ideas of living nature held by -Epicurus, Democritus, Boerhaave, Willis, and Lamettrie; nor need we -apply to the iatromechanicians nor to the chemists. We may do better -than that. We may ask nature itself. - -_Phenomena Common to Living Beings._—Nature shows us an infinite number -of beings, animal or vegetable, described in ordinary language as -_living beings_. This language implicitly assumes something common to -them all, a universal manner of being which belongs to them without -distinction, without regard to differences of species, types, or -kingdoms. On the other hand, anatomical analysis teaches us that -animated beings and plants may be divided into parts ever decreasing -in complexity, of which the last and the simplest is the _anatomical -element_, the _cell_, the microscopic organic unit which, too, is -alive. Common opinion suspects that all these beings, whether entire -as in the case of animal and vegetable individuals, or fragmentary as -in the case of cellular elements, have the same manner of being, and -present the same body of common characteristics which rightly gives -them this unmistakable title of living beings. Life then essentially -would be this manner of being, common to animals, vegetables, and their -elements. To seize in isolation these common, necessary, and permanent -features, and then to synthetize them into a whole, will be the really -scientific method of defining life, and of explaining its nature. - -And here then immediately arises a fundamental question which gives -one pause, a question of fact which must be solved before we can -go further. Is there really a common manner of being in all these -things? Are _animal life, vegetable life_, and the life of the -elements or _elementary life_, all the same? Is there a sum total of -characteristics which may define life in general? - -The physiologists, following in the steps of Claude Bernard, respond in -the affirmative. They accept as valid and convincing the proof given of -this vital community by the illustrious experimentalist. However there -are some rare exceptions to this universal assent. In this concert -of approval there is at least one discordant voice, that of M. F. Le -Dantec.[13] - - [13] M. Le Dantec, of whose philosophical and rigorously systematic - mind I have the highest opinion, has laid down a new conception of - life, the essential basis of which is this very distinction between - elementary life and ordinary life; between the life of the elements - or of the beings formed from a single cell, protophytes and protozoa, - and the life of ordinary animals and plants, which are multicellular - complexes, and for that reason called _metazoa_ and _metaphytes_. - - Further, in the _elementary life_ peculiar to monocellular beings - (protozoa and cellular elements), M. Le Dantec distinguishes three - manners of being:—The first condition, which is elementary life - manifested in all its perfection, cellular health; the second - condition is deteriorated elementary life, _cellular disease_; and the - third condition, which is _latent life_. I should say at once that in - so far as the fundamental distinction of the phenomena of _elementary - life_ and those of the general life of animals and ordinary plants, - metazoa or metaphytes is concerned, we find it neither justified nor - useful. And further, _manifested elementary life_, as M. Le Dantec - understands it, would only belong to a small number of _elementary - beings_—for the protozoa, starting with the infusoria, are not among - the number—and to a still smaller number of _anatomical elements_, - since among the vertebrates we recognize as almost the only elements - satisfying it, the ovule, and perhaps the leucocyte. Physiologists, - therefore, do not agree with M. Le Dantec as to the utility of adding - one condition more to those we all admit—namely, manifested animal - life and latent life. - -_The Doctrine of the Vital Duality of Animals and Plants._—There are, -therefore, biologists who, in the domain of theory and in virtue of -more or less well-founded conceptions or interpretations, separate -_elementary life_ from other vital forms, and thus break the bond of -vital unity proclaimed by Claude Bernard. This monistic doctrine at the -outset met with other opponents, and that, too, in the domain of facts. -But it triumphed over them and became established. We have to deal with -scientists like J. B. Dumas and Boussingault, who drew a dividing line -between _animal life_ and _vegetable life_. - -But let us in a few words recall to the reader this victorious struggle -of the monistic doctrine against the dualism of the two kingdoms. If -we consider an animal in action, said the champions of vital dualism, -we agree that it feels, moves, breathes, digests, and finally, that -it destroys by a real operation of chemical analysis the materials -afforded to it by its ambient world. It is in these phenomena that are -manifested its activity, its life. Now, added the dualists, plants do -not feel, do not move, do not breathe, and do not digest. They build -up from immediate principles, by an operation of chemical synthesis, -the materials they borrow from the soil which bears them, or from the -atmosphere which surrounds them. There is, therefore, nothing in common -between the representatives of the two kingdoms if we confine ourselves -to the examination of the actual phenomena which take place in them. -To find a resemblance between the animal and the vegetable, said the -dualists, we must set aside what they _do_, for they do different, -or even contrary things. We must consider whence they come and what -they _become_. Both originate in organisms similar to themselves. -They grow, evolve, and generate as they themselves were generated. -In other words, while their acts separate plants from animals, their -mode of origin and evolution alone bring them together. Such analogies -are of no slight importance; but they were neutralized by their -dissimilarities, which were exaggerated by the dualistic school. - -It is clear that the word _life_ would lose all actual significance to -those who would reduce it to the faculty of evolution, and who would -separate all its real manifestations in animated beings and in plants. -If there are two lives, the one animal and the other vegetable, there -are no more; or, what comes to the same thing, there is an infinite -number of lives which have nothing in common but the name, or at most, -the possession of some secondary characteristics. There are as many of -them as there are different beings, for each has its own particular -evolution. Here the specific is the negation of the general and it -destroys it instead of being subordinate to it. The principle of life -becomes for each being something as individual as its own evolution. -And this, if we think it out, is how the philosophers look at life, -and it is the real reason of their disagreement with the physiological -school. - -_Proof of the Monistic Theory._—On the other hand, under the -disguise of living forms, the physiologist recognizes the existence -of an identical basis. His trained ear marks amid the overcharged -instrumentation of the vital work the recognizable undertones of -a constant theme. It was the work of Claude Bernard to bring this -common basis to light. He shows that plants live as animals do, that -they breathe, digest, have sensory reactions, move essentially like -animals, destroy and build up in the same manner the immediate chemical -principles. For that purpose it was necessary to pass in review, -examining them from their foundation and distinguishing the essential -from the secondary, the different vital manifestations—digestion, -respiration, sensibility, motility, and nutrition. This is what Claude -Bernard did in his work _Sur les Phénomènes de la vie communs aux -animaux et aux plantes_. We need only to sketch in broad outline the -characteristic features of his lengthy demonstration. - -_Unity in the Formation of Immediate Chemical Principles._—The first -and most important of the differences pointed out between the life of -animals and that of plants was relative to the formation of immediate -principles. On this ground, indeed, vital dualism raised its fortress. -The animal kingdom was considered in its totality as the parasite of -the vegetable kingdom. To J. B. Dumas, animals, whatever they may be, -make neither fat nor any elementary organic matter; they borrow all -their foods, whether they be sugars or starches, fats or nitrogenous -substances, from the vegetable kingdom. About the year 1843 the -researches of the chemists, and of Payen in particular, succeeded in -proving the presence, almost constant, of fatty matters in vegetables; -and, further, these matters existed there in proportions more than -sufficient to explain how the beast which fed upon them was fattened. -The chemists attributed to nature as much practical sense as they -themselves possessed; and since the hay and the grass of the ration -brought fat ready made to the horse, the cow, and the sheep, they -declared that the animal organism had nothing whatever to do but to -put this food into the tissues, or to arrange for it to pass into the -milk. But nature is not so wise and economical as was supposed at -the Académie des Sciences. After a memorable debate, in which Dumas, -Boussingault, Payen, Liebig, Persoz, Chossat, Milne-Edwards, and -Flourens took part, and, later on, Berthelot and Claude Bernard, it was -agreed that the animal does not grow fat from the fatty food which is -supplied it, and that it makes its own fat just as the vegetable does, -but in another manner. In the same way sugar, the normal constituent -substance necessary for the nutrition of animals and plants, instead of -being a vegetable product passing by alimentation from the herbivorous -animals and thence to the carnivorous, is manufactured by the animal -itself. Generally speaking, immediate principles have an equal claim -to existence in the two kingdoms. Both form and destroy the substances -indispensable to life. - -Here, then, one of the barriers between animal life and vegetable life -is overthrown and destroyed. - -_Unity of Digestive Acts in Animals and Plants._—Similarly, another -barrier falls if we show that digestion, long considered the exclusive -function of animals, and, in particular, of the higher animals, is in -reality universal. - -Cuvier pointed out the absence of a digestive apparatus as a very -general and distinctive characteristic of plants. But the absence -of a digestive apparatus does not necessarily imply the absence of -digestion. The essential act of digestion is independent of the -infinite variety of the organs, just as a reaction is independent of -the form of the vessel in which it takes place. It is, in fact, a -chemical transformation of an alimentary substance. This transformation -may be realized outside the organism, _in vitro_, just as it can in -the living being without masticating organs, without an intestinal -apparatus, without glands, in a vessel placed in a stove, simply by -means of a few soluble ferments—pepsine, trypsine, amylolytic diastases. - -All alimentary substances, whether taken from without or borrowed -from the reserves accumulated in the internal stores of the organism, -must undergo preparation. This preparation is digestion. Digestion is -the prologue of nutrition. It is over when the reparative substance, -whether food or reserve-stuff, is brought into a state enabling it to -pass into the blood, and to be utilized by the organism. - -_The Identity of Categories of Foods in the Two Kingdoms._—Now the -alimentary substances are the same in the two kingdoms, and so -is their digestive preparation. Alimentary materials are of four -kinds: albuminoid, starchy, fatty, and sugary substances. The animal -takes them from without (food properly so-called), or from within -(reserve-stuff). Man obtains starch, for instance, from different -farinaceous dishes. It may, however, equally well be borrowed from -the reserve of flour that we carry within us in our liver, which is a -veritable granary, full of floury substance, glycogen. And so it is -with vegetables. The potato has its store of flour in its tuber just as -the animal has in its liver. The grain which is about to germinate has -it in reserve-stuff in its cotyledons, or in its albumen. The bud which -is about to develop into a tree or a flower carries it at its base. - -The same conclusions are true for another class of substances, the -sugars. They may be a food taken from without, or a reserve deposited -in the tissues. The animal takes from without, in fruits for instance, -the ordinary sugar which pleases its taste. Beetroot, when flowering -and fructifying, draws this substance from its roots in which stores -have been amassed. The sugar cane when running to seed takes the sugar -from the stores which it possesses in its cane. Brewer’s yeast, the -_saccharomyces cerevisiæ_, the agent of alcoholic fermentation, finds -this same substance in the sugary juices favourable to its development. - -In the same way, identically fatty substances, either in the -form of food or of reserve-stuff, serve for nutrition to animals -and vegetables; and that is again true of the substances of the -fourth class, albuminoids, identical in the two kingdoms, foods or -reserve-stuff, equally utilizable in both after digestion. - -_Identity of the Digestive Agents and Mechanisms in Plants and -Animals._—Now, the results of contemporary research have been to -establish a surprising resemblance in the modifications experienced -by these foods, or reserve stuffs, in animals and plants; and even -resemblances in the agents which realize them, and in the mechanisms by -which they are performed. There is a real unity. The flour accumulated -in the tuber of the potato is liquefied and digested on the appearance -of the buds or of the flower, just as the starch of the liver or the -alimentary flour is digested by the animal. The fatty matter which -is stored up in the oleaginous grain is digested at the moment of -germination, just as the fat during a meal is digested in the animal’s -intestine. As the beetroot begins to run to seed, the root gives up -part of its store of sugar, and this reserve stuff is distributed -throughout the stalk after having been digested, exactly as would have -been the case in the digestive canal of man. - -Vegetables, then, really digest. The four classes of substances -mentioned above are really digested in order to pass from their -actual form, a form unsuitable for interstitial exchanges, to another -form suitable for nutrition. As there are four kinds of foods, so -there are four kinds of digestions, four kinds of ferment-producing -agents—amylolytic,[14] proteolytic,[15] saccharine, and lipasic[16] -diastases, identical in the animal and the plant. Identity of ferments -implies identity of digestions. Going down to the very basis of things, -the digestive act is nothing but the action of this ferment. This -is the crux of the whole question. All else is only difference in -scene, varying in the means of execution and in the accessories. The -difference arises from the stage on which it takes place, but the piece -which is being played is the same, and the actors are the same, and so -is the action of the play. - - [14] Amylolytic ferments change starch and glycogen (_amyloses_) into - sugar.—TR. - - [15] Proteolytic ferments change proteids into peptones and - proteoses.—TR. - - [16] The enzyme known as lipase splits the fat or oil in germinating - seeds into a fatty acid and glycerine.—TR. - -This identity between animal and vegetable life is found in the -phenomena of respiration and of motility. The limits of this book do -not allow of our entering into the details of facts. Besides, the facts -are well known, and may be found in any treatise on general physiology. -This science, therefore, enables us to perceive the imposing unity of -life in its essential manifestations. - -The community of the phenomena of vitality in animals and plants being -thus placed beyond a doubt, we must now discover the reason why. This -reason is to be found in their anatomical and in their chemical unity. -The fundamental phenomena are common because the composition is common, -and because the universal anatomical basis, the cell, possesses in all -cases a sum total of identical properties. - -If we appeal to physiology for the characteristics common to living -beings, it will generally give us the following:—A structure or -organization; a certain chemical composition which is that of _living -matter_; a specific form; an evolution which in the earliest stage -occasions the being to grow and develop until it is divided, and -which in the highest stage includes one or more evolutive cycles -with growth, the adult stage, senility, and death; a property of -increase or nutrition, with its consequence—namely, a relation of -material exchanges with the ambient medium;—and finally, a property of -reproduction. It is important to pass them rapidly in review. - - - - - CHAPTER II. - - MORPHOLOGICAL UNITY OF LIVING BEINGS. - - § 1. The cellular theory. First period: division of the organism—§ - 2. Second period: division of the cell—Cytoplasm—The nucleus—§ 3. - Physical constitution of living matter—The micellar theory—§ 4. - Individuality of complex beings—The law of the constitution of - organisms. - - -The first characteristic of the living beings is _organization_. -By that we mean that they have a structure; that they are complex -bodies formed of smaller aliquot parts and grouped according to a -certain disposition. The most simple elementary being is not yet -homogeneous. It is heterogeneous. It is organized. The least complex -protoplasms, those of bacteria, for example, still possess a physical -structure; Kunstler distinguishes in them two non-miscible substances, -presenting an alveolar organization. Thus animals and plants present an -organization, and it is sensibly constant from one end to the other of -the scale of beings. There is a _morphological unity_. - - - § 1. THE CELLULAR THEORY. FIRST PERIOD: DIVISION OF THE ORGANISM INTO - CELLS. - - -_Cellular Theory. First Period._—Morphological unity results from the -existence of a universal anatomical basis, the _cell_. The cellular -theory sums up the teaching of general anatomy or histology. - -At the beginning of the nineteenth century anatomy was following a -routine dating from ancient times. It divided animal and vegetable -machines into units in descending order, first into different forms -of apparatus (circulatory, respiratory, digestive, etc.); then the -apparatus into organs examined one by one, figuring and describing each -of them from every point of view with scrupulous accuracy and untiring -patience. If we think of the duration of these researches—the _Iliad_, -as Malgaigne says, already containing the elements of a very fine -regional anatomy—and especially of the powerful impulse they received -in the seventeenth and eighteenth centuries, we shall understand the -illusion of those who, in the days of X. Bichat, could fancy that the -task of anatomy was almost ended. - -As a matter of fact this task was barely begun, for nothing was known -of the intimate structure of the organs. X. Bichat accomplished a -revolution when he decomposed the living body into tissues. His -successors, advancing a step in the analysis, dissociated the -tissues into elements. These elements, which one would have thought -were infinitely varied, were reduced in their turn to one common -_prototype_, the cell. - -The living body, disaggregated by the histologist, resolves under the -microscope into a dust, every grain of which is a cell. A cell is an -anatomical element the constitution of which is the same from one -part to the other of the same being, and from one being to another; -and its dimensions, which are sensibly constant throughout the whole -of the living world, have an average diameter of several thousandths -of a millimetre—_i.e._, of several _microns_. This element, the cell, -is a real organ. It is smaller, no doubt, than those described by the -ancient anatomists, but it is not less complex. Its complexity is only -revealed later. It is an organic unit. Its form varies from one element -to another. Its substance is a semi-fluid mass, a mixture of different -albuminoids. In the mean value of its dimensions, so carefully -measured—_exceptis excipiendis_—we have a condition the significance of -which has not yet been discovered, but which may be of great value in -the explanation of its peculiar activities. - -Such is the result to which have converged the researches of the -biologists who have examined plants or the lower animals, as well as -of the anatomists who have been more especially occupied with the -vertebrates and with man. All their researches have brought them to the -same conclusion—the cellular theory. Either living beings are composed -of a single cell—as is the case with the microscopic animals called -_protozoa_, and the microscopic vegetables called _protophytes_—or, -they are cellular complexes, _metazoa_ or _metaphytes_—that is to say, -associations of these microscopic organic units which are called cells. - -_The Law of the Composition of Organisms._—The law of the composition -of organisms was discovered in 1838 by Schleiden and Schwann. From that -time up to 1875 it may be said that micrographers have spent their -time in examining every organ and every tissue, muscular, glandular, -conjunctive, nervous, etc., and in showing that in spite of their -varieties of aspect and form, of the complexity of structures due to -cohesion and fusion, they all resolve into the common element, the -cell. Contemporary anatomists, Koelliker, Max Schultze, and Ranvier, -have thus established the generality of the cellular constitution, -while zoologists and botanists confirm the same law for all animals and -vegetables, and exhibit them all as either unicellular or multicellular. - -_The Cellular Origin of Complex Beings._—At the same time embryogenic -researches showed that all beings spring from a corpuscle of the same -type. Going back in the history of their development to the most remote -period, we find a cell of very constant constitution—namely, the -_ovule_. This truth may be expressed by changing a word in Harvey’s -celebrated aphorism—_omne vivum ex ovo_; we now say omne _vivum e -cellula_. The myriads of differentiated anatomical elements whose -association forms complex beings are the posterity of a cell, of the -_primordial ovule_, unless they are the posterity of another equivalent -cell. The second task of histology in the latter half of the nineteenth -century consisted in following up the filiation of each anatomical -element from the cell-egg to its state of complete development. - -The whole cellular theory is contained in the two following statements, -which establish the morphological unity of living beings:—_Everything -is a cell, everything comes from an initial cell_; the cell being -defined as a mass of substance, protoplasm or protoplasms, of an -average diameter of a few microns. - - - § 2. THE SECOND PERIOD: THE DIVISION OF THE CELL. - - -_Second Period: Constitution of the Cell._—This was, however, only the -first phase in the analytical study of the living being. A second -period began in 1873 with the researches of Strassburger, Bütschli, -Flemming, Kuppfer, Fromann, Heitzmann, Balbiani, Guignard, Kunstler, -etc. These observers in their turn submitted this anatomical, this -infinitely small cellular microcosm, to the same penetrating dissection -their predecessors had applied to the whole organism. They brought -us down one degree lower into the abyss of the infinitely small. And -as Pascal, losing himself in these wonders of the imperceptible, saw -in the body of the mite which is only a point, “parts incomparably -smaller, legs with joints, veins in the legs, blood in the veins, -humours in the blood, drops in the humours, vapours in these drops,” so -contemporary biologists have shown in the epitome of organism called a -cell, an edifice which itself is marvellously complex. - -_The Cytoplasm._—The observers named above revealed to us the extreme -complexity of this organic unit. Their researches have shown us the -structure of the two parts of which it is composed—the cellular -protoplasm and the nucleus. They have determined the part played by -each in genetic multiplication. They have shown that the protoplasm -which forms the body of the cell is not homogeneous, as was at first -supposed. The idea which was mooted later, that this protoplasm was -formed, to use Sachs’ words, of a kind of “protoplasmic mud,”—_i.e._, -of a dust consisting of grains and granules connected by a liquid,—is -no longer accurate. There is a much simpler view of the case. According -to Leydig and his pupils, we must compare the protoplasm to a sponge in -the meshes of which is lodged a fluid, transparent, hyaline substance, -a kind of cellular juice, hyaloplasm. From the chemical point of -view this cellular juice is a mixture of very different materials, -albumens, globulins, carbohydrates, and fats, elaborated by the cell -itself. It is a product of vital activity; it is not yet the seat of -this activity. The living matter has taken refuge in the spongy tissue -itself, in the _spongioplasm_. - -According to other histologists, the comparison of protoplasm to a -spongy mass does not give the most exact idea, and, in particular, it -does not furnish the most general idea. It would be far better to say -that the protoplasm possesses the structure of foam or lather. As was -seen by Kunstler in 1880, a comparison with some familiar objects gives -the best idea. Nothing could be more like protoplasm physically than -the culinary preparation known as _sauce mayonnaise_, made with the aid -of oil and a liquid with which oil does not mix. Emulsions of this kind -were made artificially by Bütschli. He noted that these preparations -mimicked all the aspects of cellular protoplasm. Thus, in the living -cell there is a mixture of two liquids, non-miscible and of unequal -fluidity. This mixture gives rise to the formation of little cells. The -more consistent substance forms their supporting framework (Leydig’s -spongioplasm), while the other, which is more fluid, fills its interior -(hyaloplasm). - -However that may be, whether the primitive organization of the cellular -protoplasm be that of a sponge, as is asserted by Leydig, or that of -a _sauce mayonnaise_, as is claimed by Bütschli and Kunstler, the -complexity does not rest there. Further recourse must be made to -analysis. Just as the tissue of a sponge, when torn, shows the fibres -which constitute it, so the spongioplasm, the parietal substance, -is exhibited as formed of a tangle of fibrils, or better still, of -filaments or ribbons (in Greek, _mitome_), which are called _chromatic -filaments_, because they are deeply stained when the cell is plunged -into aniline dye. In each of these filaments, the substance of which -is called chromatin, the devices of microscopic examination enable -us to discover a series of granulations like beads on a string, the -_microsomes_ or bioblasts, connected one with the other by a sort of -cement, Schwartz’s _linin_, which is a kind of nuclein. - -And let us add, to complete this summary of the constitution of -cellular protoplasm, that it presents, at any rate at a certain moment, -a remarkable organ, the _centrosome_, which plays an important part -in cellular division. Its pre-existence is not certain. Some writers -make it issue from the nucleus. At the moment of cellular division it -appears like a compressed mass of granulations, which may be deeply -stained. Around it is seen a clear unstainable zone, called the -attraction-sphere; and finally, beyond this is a crown of striæ, which -diverge like the rays of a halo—_i.e._, the _aster_. In conclusion, -there are yet in the cellular body three kinds of non-essential bodies: -the vacuoles, the leucites, and various inclusions. The _vacuoles_ are -cavities, some inert, some contractile; the _leucites_ are organs for -the manufacture of particular substances; the _inclusions_ are the -manufactured products, or wastes. - -_The Nucleus_.—Every cell capable of living, growing, and multiplying, -possesses a _nucleus_ of constitution very analogous to the cellular -mass which surrounds it. The anatomical elements in which no nucleus -is found, such as the red globules of blood in adult mammals, are -bodies which are certain, sooner or later, to disappear. There is -therefore no real cell without a nucleus, any more than there is a -nucleus without a cell. The exceptions to this law are only apparent. -Histologists have examined them one by one, and have shown their purely -specious character. We may therefore lay aside, subject to possible -appeal from this decision, organisms such as Haeckel’s _monera_ and -the problem of finding out if bacteria really have a nucleus. The very -great, if not the absolute generality of the nuclear body, must be -admitted. - -It hence follows that there is a nuclear protoplasm and a nuclear -juice, just as we have seen that there is a protoplasm and a cellular -juice. What was just said of the one may now be repeated of the other, -and perhaps with even more emphasis. The nuclear protoplasm is a -filamentary mass sometimes formed of a single mitome or cord, folded -over on itself and capable of being unrolled. The mitome in its turn -is a string of microsomes united by the cement of the linin. These are -the same constituent elements as before, and the language of science -distinguishes them one from the other by a prefix to their name of -the words _cyto_ or _karyo_, which in Greek signify cell and nucleus, -according as they belong to one or the other of these organs. These -are mere matters of nomenclature, but we know that in the descriptive -sciences such matters are not of minor importance. - -We have just indicated that in a state of repose,—that is to say, under -ordinary conditions,—the structure of a nucleus reproduces clearly the -structure of the cellular protoplasm which surrounds it. The nuclear -essence is best separated from the spongioplasm. It takes more clearly -the form of a filamentary thread, and the filaments themselves -(mitome) show very thick chromatic granulations, or microsomes, -connected by the linin. - -At the moment of reproduction of the cell these granulations blend -into a stainable sheath which surrounds the filaments, and the latter -dispose themselves so as to form a single thread. This chromatic -filament, which has now become a single thread, is shortened as -it thickens (_spireme_); it is then cut into segments, twelve or -twenty-four in the case of animals and a larger number in the case of -plants. These are _chromosomes_, or _nuclear segments_, or _chromatic_ -loops. Their part is a very important one. They are constant in number -and permanent during the whole of the life of the cell. Let us add that -the nucleus still contains accessory elements (nucleoli). - -_The Rôle of the Nucleus_.—Experiment has shown that the nucleus -presides over the nutrition, the growth, and the conservation of -the cell. If, following the example of Balbiani, Gruber, Nussbaum, -and W. Roux of Leipzig, we cut into two a cell without injuring the -nucleus, the fragment which is denuded of the nucleus continues to -perform its functions for some time in the ordinary manner, and in -some measure in virtue of its former impulse. It then declines and -dies. On the contrary, the fragment provided with the nucleus repairs -its wound, is reconstituted and continues to live. Thus the nucleus -takes a very remarkable part in the reproduction of the cell, but it -is still a matter of uncertainty whether its rôle is here subordinated -to that of the cellular body, or if it is pre-eminent. However that -may be, it follows from this experiment that the nucleus presents all -the characteristics of a vigorous vitality, and that it is in its -protoplasm that the chemists should be able to find the compounds, the -special albuminoids, which, _par excellence_, form living matter. - - - § 3. THE PHYSICAL CONSTITUTION OF LIVING MATTER. THE MICELLAR THEORY. - - -_Physical Constitution of Living Matter_.—Microscopic examination -does not take us much farther. The microscope, with the strongest -magnification of which it is capable at present, shows us nothing -beyond these links of aligned microsomes forming the species of -protoplasmic thread or mitome, whose cellular body is a confused -tangle or a very tangled ball. It is not probable that direct sight -can penetrate much farther than this. No doubt the microscope, which -has been so vastly improved, is capable of still further improvement. -But these improvements are not indefinite. We have already reached a -linear magnification of 2000, and theory tells us that a magnification -of 4000 is the limit which cannot be passed. The penetrating power of -the instrument is therefore near its culminating point. It has already -given almost all that we have a right to expect from it. - -We must, however, penetrate beyond this microscopic structure at which -the sense of sight has been arrested. How is this to be done? When -observation is arrested, hypothesis takes its place. Here there are two -kinds of hypotheses, the one purely anatomical, the other physical. -Anatomically, beyond the visible microsomes there have been imagined -invisible hyper-microscopic corpuscles, the plastidules of Haeckel, -the idioblasts of Hertwig, the pangenes of de Vries, the plasomes of -Wiesner, the gemmules of Darwin, and the biophores of Weismann. - -Biologists who have not got all that they hoped from microscopic -structure are therefore thrown back on hyper-microscopic structure. - -It is very remarkable that all this profound knowledge of structure has -been so sterile from the point of view of the knowledge of cellular -functional activity. All that is known of the life of the cell has -been revealed by experiment. Nothing has resulted from microscopic -observation but ideas as to configuration. When it is a question of -giving or imagining an explanation of vital facts, of heredity, etc., -biologists unable to supply anything beyond the details of structure -revealed by anatomy have had recourse to hypothetical elements, -gemmules, pangenes, biophores, and different kinds of determinants. - -Anatomy never has explained and never will explain anything. “Happy -physicists!” wrote Loeb, “in never having known the method of research -by sections and stainings! What would have happened if by chance a -steam engine had fallen into the hands of a histological physicist? -How many thousands of sections differently stained and unstained, how -many drawings, how many figures, would have been produced before they -knew for certain that the machine is an engine, and that it is used for -transforming heat into motion!” - -The study of physical properties, continued on rational hypotheses, has -also thrown some light on the possible constitution of living matter. -The gap between microscopical structure and molecular or chemical -structure has thus been filled. - -The consideration of the properties of _turgescence_ and of _swelling_, -which very generally belong to organized tissues, and therefore to the -organic substance of protoplasm, has enabled us to obtain some idea of -its ultra-microscopic constitution. If we wet a piece of sugar or a -morsel of salt, before they are dissolved they absorb and imbibe the -water without sensibly increasing their volume. It is quite otherwise -with a tissue (_i.e._, with a protoplasm) when weakened in water as a -preliminary. The tissue, plunged into the liquid, absorbs it, swells, -and often grows considerably. And this water does not lodge in the -gaps, in pre-existing lacunar spaces, for organic matter presents no -gaps of this kind. It does not resemble a porous mass with capillary -canals, such as sandstone, tempered mortar, clay, or refined sugar. -The molecules of water interpose between and separate the organic -molecules, thus increasing by a sort of intussusception the intervals -separating the one from the other—molecular intervals escaping the -senses, as do the molecules themselves because they are of the same -order of magnitude. - -_Micellar Theory._—While pondering over this phenomenon, an eminent -physiologist, Nägeli, was led in 1877 to propose his _micellar theory_. -Micellæ are groups of molecules in the sense in which physicists -and chemists use the word. They are molecular structures with a -configuration. They rapidly absorb water and are capable of fixing a -more or less thick and adherent layer of it to their surface. In a -word, they are aggregates of organic matter and water. - -There is therefore every reason for believing that the _microsomes_ of -spongy protoplasm, the physical support or basis of cellular life, -are _groups of micellæ_ formed of albuminoid substances and water. -These clustered forms, these micellæ, are not absolutely peculiar to -organized matter. Pfeffer, the learned botanist, has pointed them -out under another name, _tagmata_, in the membranes of chemical -precipitates. - -Beyond this limit analysis finds nothing but the chemical molecule -and the atom. So that if we wish to reconstruct the hierarchy of the -materials of constitution of the protoplasm in order of ascending -complexity, we shall find at the foundation the atom or atoms of simple -bodies. They are principally carbon, hydrogen, oxygen, nitrogen, the -elements of all organic compounds, to which may be added sulphur -and phosphorus. At the head we have the albuminoid molecule, or the -albuminoid molecules, aggregates of the preceding atoms. In the third -stage the micellæ or tagmata, aggregates of albuminoids and water, are -still too small to be observed by the senses. They unite in their turn -to form the microsomes, the first elements visible to the microscope. -The microsomes, cemented by linin, form the filaments or links which -are called mitomes. The living protoplasm is therefore nothing but a -chain, or tangled skein, or a spongy skeleton formed by its filaments. - -Such is the typical constitution of living matter according to -microscopic observation, supplemented by a perfectly reasonable -hypothesis, which is, so to speak, only a translation of one of its -most evident physical properties. This relatively simple scheme has -become a complex scheme in the hands of later biologists. On the -micellar hypothesis, which seems almost inevitable in its character, -new hypotheses have been grafted, merely for the sake of convenience. -Hence, we are led farther and farther from the real truth, and this is -why, in order to explain the phenomena of heredity, we find ourselves -compelled to intercalate hypothetical elements between micellæ and the -microsome in the higher hierarchy quoted above—gemmules, pangenes, -plasomes, which are only mental pictures or simple images to represent -them. - - -§ 4. THE INDIVIDUALITY OF COMPLEX BEINGS. LAW OF THE CONSTITUTION OF -ORGANISMS. - - -_Individuality of Complex Beings._—From the cellular doctrine follows a -remarkably suggestive conception of living beings. The metazoa and the -metaphytes—that is to say, the multicellular living beings which may be -seen with the eyes and do not require the microscope to reveal them—are -an assemblage of anatomical elements and the posterity of a cell. -The animal or the plant, instead of being an individual unity, is a -“multitude,” a term which is used by Goëthe himself when pondering, in -1807, over the doctrine taught by Bichat; or, according to the equally -correct expression of Hegel, it is a “nation”; it springs from a common -cellular ancestor, just as the Jewish people sprang from the loins of -Abraham. - -We now picture to ourselves the complex living being, animal or plant, -with its configuration which distinguishes it from every other being, -just as a populous city is distinguished by a thousand characteristics -from its neighbour. The elements of this city are independent and -autonomous for the same reason as the anatomical elements of the -organism. Both have in themselves the means of life, which they neither -borrow nor take from their neighbours nor from the whole. All these -inhabitants live in the same way, are nourished and breathe in the -same manner, all possessing the same general faculties, those of man; -but each has besides, his profession, his trade, his aptitudes, his -talents, by which he contributes to social life, and by which in his -turn he depends on it. Professional men, the mason, the baker, the -butcher, the manufacturer, the artist, carry out different tasks and -furnish different products, the more varied, the more numerous and the -more differentiated, in proportion as the social state has reached a -higher degree of perfection. The living being, animal or plant, is a -city of this kind. - -_Law of the Constitution of Organisms._—Such is the complex animal. -It is organized like the city. But the higher law of this city is -that the conditions of the elementary or individual life of all the -anatomical citizens are respected, the conditions being the same for -all. Food, air, and light must be brought everywhere to each sedentary -element; the waste must be carried off in discharges which will free -the whole from the inconvenience or the danger of such debris; and that -is why we have the different forms of apparatus in the circulatory, -respiratory, and excretory economy. The organization of the whole -is therefore dominated by the necessities of cellular life. This is -expressed in _the law of the constitution of organisms_ formulated by -Claude Bernard. The organic edifice is made up of apparatus and organs, -which furnish to each anatomical element the necessary conditions and -materials for the maintenance of life and the exercise of its activity. -We now understand what is the life, and at the same time what is the -death, of a complex being. The life of the complex animal, of the -metazoon, is of two degrees; at the foundation, the activity proper -to each cell, _elementary life_, cellular life; above, the forms of -activity resulting from the association of the cells, _the life of the -whole_, the sum or rather the complex of elementary partial lives. -There is a solidarity between them produced by the nervous system, -by the community of the general circulatory, respiratory apparatus, -etc., and by the free communication and mixture of the liquids which -constitute the media of culture for each cell. We shall have an -opportunity of recurring to current ideas as to the morphological -constitution of organisms. - - - - - CHAPTER III. - - THE CHEMICAL UNITY OF LIVING BEINGS. - - The varieties and essential unity of the protoplasm—Its affinity for - oxygen—The chemical composition of protoplasm—Its characteristic - substances.—§ 1. The different categories of albuminoid - substances—Nucleo-proteids—Albumins and histones—Nucleins.—§ - 2. Constitution of nucleins.—§ 3. Constitution of histones and - albumins—Schultzenberger’s analysis of albumin—Kossol’s analysis—The - hexonic nucleus. - - -The chemical unity of living beings corresponds to their morphological -unity. - -_The Varieties and Essential Unity of the Protoplasm._—One essential -feature of the living being is that it is composed of matter peculiar -to it, which is called _living matter_, or _protoplasm_. But this is -a somewhat incorrect way of expressing the facts. There is no unique -living matter, no single protoplasm; their number is infinite, there -are as many as there are distinct individuals. However like one man may -be to another, we are compelled to admit that they differ according to -the substance of which they are constituted. That of the first offers -a certain characteristic personal to the first, and found in all his -anatomical elements; similarly for the second. With Le Dantec we shall -say that the chemical substance of Primus is not only of the substance -of man, but in all parts of his body and in all his constituent cells -it is the exclusive substance of Primus; and, in the same way, the -living matter of another individual Secundus will carry everywhere his -personal impress, which differs from that of Primus. - -But it is none the less true that this absolute specificity is based -with certainty only on differences which from the chemical point -of view are exceedingly slight. All these protoplasms have a very -analogous composition. And, if we regard as negligible the smallest -individual, specific, generic, or ordinal variations we may then speak -in a general manner of _protoplasm_ or _living matter_. - -Experiment shows us, in fact, that the real living substance—apart -from the products it manufactures and can retain or reject—is in every -cell tolerably similar to itself. The fundamental chemical resemblance -of all protoplasms is certain, and thus we may speak of their typical -composition. We may sum up the work of physiological chemistry for the -last three quarters of a century by affirming that it has established -the chemical unity of all living beings—that is to say, a very notable -analogy in the composition of their protoplasm. - -This living matter is essentially a mixture of the proteid or -albuminoid substances, to which may be added other categories of -immediate principles, such as carbohydrates and fatty matters. But -the latter are of secondary importance. The essential element is the -proteid substance. The most skilful chemists have tried for more than -half a century to discover its composition. Only during the last few -years—thanks to the researches of Kossel, the German chemist, following -on those of Schultzenberger and Miescher—we are beginning to know the -outer walls or the framework of the albuminoid molecule; in other -words, its chemical nucleus. - -_Physical Characters of Protoplasm._—About 1860 Ch. Robin thought -that he had defined living matter sufficiently—or, at least, as -perfectly as could be expected at that time—by attributing to it -three physical characteristics. They were:—Absence of homogeneity, -molecular symmetry, and the association of three orders of immediate -principles—albuminoids, carbohydrates and fats. These characteristics -assist, but do not suffice, to define the organization. - -No doubt the characteristics must be completed by the addition of a -certain number of more subtle physical features. - -One of them refers to the structure of protoplasm as revealed by the -microscope. Throughout the whole of the living kingdom, from the -bacteria studied by Kunstler and Busquet to the most complicated -protozoa, protoplasmic matter presents the same constitution, and in -consequence, this structure of the protoplasm must be considered as -one of its distinctive characters. It is not homogeneous; it is not -the last term of the visible organization: it is itself organized. -Experiment shows that it does not resist breaking up or crushing. -Mutilations cause it to lose its properties. As for the kind of -structure that it presents, it may be expressed by saying that it is -that of a foamy emulsion. - -We saw above that our knowledge as to the physical condition of -protoplasm has been completed by the theories of Bütschli’s micellæ or -Pfeffer’s tagmata. - -_Properties of the Protoplasm. Its Affinity for Oxygen._—From the -chemical point of view, living matter presents a very remarkable -property—namely, a great affinity for oxygen. It absorbs it -so greedily that the gas cannot remain in a free state in its -neighbourhood. Living protoplasm, therefore, exercises a reducing -power. But it does not absorb oxygen in this way for its own advantage; -oxygen is not absorbed, as was supposed thirty years ago, to supply -fuel wherewith to burn the protoplasm. The products are not those of -its oxidation, of its own disintegration. They are the products of -combustion of the reserve-stuff which is incorporated in it. These -substances have been supplied to it from without, like the oxygen -itself, with the blood. This was proved by G. Pflüger in 1872 to -1876. The protoplasm is only the focus, the scene, or the factor of -combustion. It is not its victim, it does not itself furnish the fuel. -It works like the chemist, who obtains a reaction with the substances -that are given to him. - -As for the reducing power of protoplasm, A. Gautier in 1881 and Ehrlich -in 1890 have given fresh proofs. A. Gautier in particular has insisted -that the phenomena of combustion take place, so to speak, outside the -cell, and at the expense of the products which surround it; while on -the contrary the really active and living parts of the nucleus and of -the cellular body, work protected by the oxygen, as in the case of -anaerobic microbes. - -This result is of great importance. Burdon Sanderson, the late -learned professor of physiology at the University of Oxford, has not -hesitated to compare it to the discovery of respiratory combustion -by Lavoisier. There is no doubt some exaggeration in the comparison; -but there is, on the other hand, no less exaggeration in supposing -that it is not of great importance. We may no longer in these days -speak without reservation of the vital vortex of Cuvier, and of the -incessant twofold movement of assimilation and dissimilation which is -ever destroying living matter and building it up again. In reality, the -living protoplasm varies very little; it only undergoes oscillations of -very slight extent; it is the materials, the reserve stuff on which it -operates, which are subject to continual transformations. - -_Chemical Composition of Protoplasm._—One of the the three -characters attributed by Ch. Robin to living matter was its chemical -composition, of which little was known in his time. He insisted on -the constant presence in the living elements of three orders of -immediate principles—proteid substances, carbohydrates, and fatty -bodies. In reality the proteid substances, or albuminoids, alone are -characteristic. The two other groups, carbohydrates and fatty bodies, -are rather the signs and the products of the vital activity, than -constituents of the matter on which it is exercised. - -It is therefore on the knowledge of the proteid substances that all the -sagacity of biological chemists has been exercised. Their efforts for -thirty years, and particularly in the last few years, have not been -barren; they enable us to give a first rough sketch of the constitution -of these substances. - - - § 1. THE CHARACTERISTIC SUBSTANCES OF THE PROTOPLASM. THE - NUCLEO-PROTEIDS. - - -_The Different Categories of Albuminoid Substances._—Albuminoid or -proteid substances are extremely complex compounds, much more so than -any of those which are being constantly studied by the chemist. -They also are to be found in great variety. It has been difficult to -separate them one from the other, to characterize them rigorously, -or, in other words, to classify them. However, it has been done now, -and we distinguish three classes which are differentiated at once -from the physiological and from the chemical points of view. The -first comprises the complete or typical albuminoids. They are the -_proteids_ or _nucleo-albuminoids_. They are to be found in the most -active and most living parts of the protoplasm, and therefore in the -spongioplasm of the cell and around the nucleus. The second group -is formed of _albumins_ and _globulins_, compounds already simpler, -fragments derived from the destruction of the preceding, into which -they enter as constituent elements. In the isolated state they do not -belong to the really living protoplasm; they exist in the cellular -juice, in the interstitial and circulating liquids in the blood -and in the lymph. The third category comprises real but incomplete -albuminoids. They are to be found in the portions of the economy which -have a specialized or attenuated life, and are destined to serve as -a support to the more active elements—_i.e._, they contribute to the -building up of the bony, cartilaginous, conjunctive, elastic tissues. -They are called _albumoids_. It is naturally the first group, that of -the proteids—_i.e._, of the complete and characteristic compounds of -the living substance—upon which the attention of the physiologists -must be fixed. It is only quite recently that the clear definition of -these substances has been given, and proteid compounds detected in the -confused mass. - -_The Nucleo-proteids._—This progress in the characterization and -specification of the proteids required in the first place a knowledge -of two particular compounds, the _nucleins_ and the _histones_. This -did not become possible until after the researches of Miescher and -Kossel on the nucleins, which went on from 1874 to 1892, and those of -Lilienfeld and d’Yvor Bang on the histones, from 1893 to 1899. The -complete albuminoids are constituted by the combination of two kinds of -substances—albumins or histones on the one hand, and nucleins on the -other. By combining solutions of albumins or histones with solutions -of nuclein, the synthesis of the proteid is effected. The study of -the properties and characteristics of these nucleo-albumins and -nucleo-histones is going on at the present moment. It is being carried -out with much method and with wonderful patience by the German school. - -All the proteids contain phosphorus in addition to the five chemical -elements, carbon, oxygen, hydrogen, nitrogen, and sulphur, which are -common to the other albuminoids. Another interesting feature in their -history is that the action of the gastric juice divides them into -their two constituents:—the nuclein, which is deposited and resists -the destructive action of the digestive liquid, and the albumin or -histone, which on the contrary experiences this action with the usual -consequences. Thus the gastric juice furnishes a process which is very -simple and very convenient in the analysis of the proteids. - -_Localization of the Nucleo-Proteids._—What we said before as to -the important physiological rôle of the cellular nucleus may arouse -the expectation that in it will be found the living matter which -is chemically the most differentiated, the albuminoids of highest -rank—_i.e._, the nucleo-proteids and their constituents. Not that they -would not be found in the protoplasm of the rest of the cell, but there -is certainly a risk that they would be less concentrated there and more -blended with accessory products; they are there connected with much -more secondary vital functions. This conclusion inspired the early -researches of Professor Miescher, of Basle, in 1874, and, twenty years -later, those of Professor Kossel, one of the most eminent physiological -chemists in Germany. - -In fact, these compounds have been found in all tissues which are rich -in cellular elements with well-developed nuclei. The white globules -of the blood furnished to Lilienfeld the first nucleo-histone ever -isolated. The red globules themselves, when they possess a nucleus, -which is the case in birds and reptiles as well as in the embryo of -mammals, contain a nucleo-proteid which was easily isolated by Plosz -and Kossel. Hammarsten, the Swedish chemist, who has acquired a -great reputation from his researches in other domains of biological -chemistry, prepared the nucleo-proteids of the pancreas in 1893. They -have been obtained from the liver, from the thyroid gland (Ostwald), -from brewers’ yeast (Kossel), from mushrooms, and from barley (Petit). -They have been detected in starchy bodies and in bacteria (Galeotti). - - - § 2. CONSTITUTION OF NUCLEINS. - - -_Constitution of Nucleins._—Our path is already marked out if we wish -to penetrate farther into the constitution of these proteids, which are -the immediate principles highest in complexity among those which form -the living protoplasm. We must analyze the two components, the albumins -and the histones on the one hand, and the nucleins on the other. As for -the nucleins, this has already been done, or very nearly so. - -Kossel, in fact, decomposed the nuclein by a series of very carefully -arranged operations, and has reduced it step by step to its -crystallizable organic radicals. At each stage that we descend in the -scale of simplification a body appears which is more acid and more rich -in phosphorus. At the third stage we come to phosphoric acid itself. -The first operation divides the nuclein into two substances: the new -albumin and nucleinic acid. After separating these elements they can -be reunited: a solution of albumin with a solution of nucleinic acid -reconstitutes the nuclein. A second operation separates the nucleinic -acid in its turn into three parts. One is a body of the nature of -the sugars—_i.e._, a carbohydrate. The appearance of a sugar in this -portion of the molecule of nucleinic acid is an interesting fact and -fertile in results. The second part is constituted by a mixture of -nitrogenous bodies, well known in organic chemistry under the name of -_xanthic bases_ (xanthin, hypoxanthin, guanin, and adenin). The third -part is a very acid body and full of phosphorus—thymic acid. If in a -third and last operation the thymic acid is analyzed, it is finally -separated into phosphoric acid and into thymene, a crystallizable base, -and thus we are brought back to the physical world, for all these -bodies incontestably belong to it. - - - § 3. THE CONSTITUTION OF HISTONES AND ALBUMINS. - - -_Constitution of Histones._—But we are only half-way through our task. -We are acquainted in its origin with one of the genealogical branches -of the proteid, the nucleinic branch. We must also learn something -of the other branch, the albumin or histone branch. But on this side -the problem assumes a character of difficulty and complexity which is -admirably adapted to discourage the most untiring patience. - -The analysis of albumin for a long time baulked the chemist “Here,” -said Danilewsky, “we come to a closed door which resists all our -efforts.” We know how vastly interesting what is taking place on the -other side must be, but we cannot get there. We get a mere glimpse -through the cracks or chinks which we have been able to make. - -This analysis of albuminous matter at first requires great precautions. -The chemist finds himself in the presence of architecture of a very -subtle kind. The molecule of albumin is a complex edifice which has -used up several thousand atoms. To perceive the plan and structure, it -must be dismantled and separated into parts which are neither too large -nor too small. Such careful demolition is difficult. Processes too -rough or too violent will reduce the whole to the tiniest of fragments. -It is a statue which may be reduced to dust, instead of being separated -into recognizable fragments, easily fitted in place along their -fractured faces. - -_Analysis of Albumin by Schützenberger._—Schützenberger, a chemist -of great merit, attempted (about 1875) this thankless task. Others -before him had experimented in various ways. Two Austrian scientists, -Hlasitwetz and Habermann, in 1873, and a little later Drechsel in 1892, -had used concentrated hydrochloric acid to break down albumin. They -also employed bromine for the same purpose. More recently Fuerth had -used nitric acid with a similar object. Schützenberger tried another -way. The battering ram which he used against the edifice of albumin -was a concentrated alkali, baryta. He warmed the white of an egg with -barium hydrate in a closed vessel at a temperature of 200°. The albumin -of egg then divides into a certain number of simpler groups. The -difficulty is to isolate and to recognize each part in this mass of the -materials of demolition. That can be done by the aid of the processes -of direct analysis. By mentally combining these different fragments, -the original building is reconstructed. This method of demolition is -certainly too rough and violent. Schützenberger’s operation gives us -very fine fragments—small molecules of free hydrogen, of ammonia, of -carbonic, acetic, and oxalic, acids which reveal extreme pulverization. -These products represent about a quarter of the total mass. The other -three-quarters are formed of larger fragments, the examination of which -is most instructive. They belong to four groups. The first comprises -five or six bodies, amido-acids or _leucins_. It proves the existence -in the molecule of albumin of compounds of the series of fats—_i.e._, -arranged in an open chain. The second group is formed by tyrosin and -kindred products—_i.e._, by the bodies of the aromatic series, which -force us to acknowledge the presence in the molecule of albumin of a -benzene nucleus. The third group forms around the nucleus known to -chemists under the name of pyrrol. The fourth comprises bodies such as -the glucoproteins, connected with the sugars, or carbohydrates. - -Does the fact that the molecule of albumin is destroyed in producing -these compounds raise the question as to whether it implies the idea -that in reality they pre-exist in it? Chemists are rather inclined to -admit this. However, the conclusion does not appear to be permissible. -Duclaux considers it doubtful. It is not certain that all these -fragmentary bodies pre-exist in reality, and it is no more certain that -a simple bringing of them together represents the primitive edifice. -Materials of demolition from a house that has been pulled down give no -idea of its natural architectural character. There is only one way of -justifying the hypothesis, and that is to reconstitute the original -molecule of albumin by bringing the fragments together. We have not got -to that stage yet. The era of syntheses of such complexity is more or -less near, but it has certainly not yet begun. - -Moreover, it is not correct to say that the simple juxtaposition of the -surfaces of fracture will reproduce the initial body. The fragments, so -far as analysis has obtained them, are not absolutely what they might -have been in the original structure. There they adhered the one to the -other, not only by the mere contact of their surfaces of fracture, as -is supposed, but in a slightly more complex manner. The fragments of -the molecule are joined by bonds. We can picture them to ourselves -by supposing these bonds to be like hooks. The hooks, which could -only be broken by violence, are called by the chemists _satisfied -atomicities_. These atomicities, set free by the breaking up, cannot -remain in this condition; they must be satisfied anew. The hook tries -to attach itself. In Schützenberger’s experiment the addition of water -provides for this necessity. A molecule of water (H⌄{2}O) splits -into two, the hydrogen (H) on the one side and the hydroxyl (OH) on -the other. These two elements cling to the liberated bonds of the -fragments of the molecule of albumin, and thus the bodies were found -complete. Schützenberger’s experiment was too violent, too radical, -and it gave too large a number of fragments, with their free hooks and -atomicities unsatisfied, for rather a large proportion of the water -added disappeared during the experiment. In one case this quantity was -as much as 17 grammes per 100 grammes of albumin. The molecules of this -water were employed in the reparation of the incomplete fragmentary -molecules of the albumin. - -It follows that Schützenberger’s experiment gave too large a number of -very small pieces corresponding to far too great a pulverization. The -very small fragments are the molecules of acids such as acetic acid, -oxalic acid, carbonic acid, molecules of ammonia, and even of hydrogen, -which we know we are setting free. - -But, apart from these products which represent a quarter of the -molecule of albumin submitted to analysis, the other three quarters -represent larger fragments which may be considered as the real -constituents of the building. Thus we find four kinds of groups which -may be accepted as natural. The first of these groups is that of the -leucins or amido-acids. It proves the existence in the molecule of -albumin of compounds of the fatty series. There is also an aromatic -group—a pyridine group—and a group belonging to the category of sugars. -Imagine a certain grouping of these four series. This would be the -nucleus of the molecule of albumin. If we graft on to this nucleus, on -to this framework as it were, so many annexes, or lateral chains, the -building will be loaded with embellishments; it will have been made -unstable and _ipso facto_ appropriate for the part that it plays in the -incessant transformations of the organism. - -_Kossel’s Analysis. Hexonic Nucleus._—Kossel has approached the -problem in another fashion. He did not attempt to attack the albumin -of the egg. This body is, in fact, a heterogeneous mixture as complex -as the needs of the embryo of which it forms the food. Kossel tried -a physiologically simpler albuminoid. He got it from an anatomical -element having no nutritive rôle, of a very elementary organization -and physiological functional activity, and yet one of energetic -vitality—the male generating cell. Instead of the hen’s egg he -therefore analyzed the milt of fish, and, in the first place, of -salmon. As was to be expected from what has been said of the proteids, -this living matter gives a combination of the nuclein, already known, -with an albumin. The latter is abundant, forming a quarter of the -total mass. Its reaction is strongly alkaline, which is the general -characteristic of the variety of albumin known by the name of histones. -Miescher, the learned chemist of Basle, who had noticed this basic -albumin when working on the Rhine salmon, gave it the name of protamin. -This is the substance submitted by Kossel to analysis in preference -to the albumin of egg, so dear to the chemists who had preceded him. -The disintegration of this molecule, instead of giving the series of -bodies obtained by Schützenberger, gave but one, a real chemical base, -_arginin_. At the first trial the albumin examined was reduced to a -simple crystallizable element. The conclusion was obvious. The protamin -of salmon is the simplest of albumins. To form this elementary proteid -substance a hexonic base with water is all that is required. - -Continuing on these lines other male generating cells were examined -and a series of protamines constructed on the same type was found, -and these albuminous bodies proved to be formed of a base or mixture -of analogous hexonic bases: arginin, histidin, and lysin—all bodies -closely akin in their properties and entirely belonging to the physical -world. - -Once aware of the existence of this fundamental nucleus, chemists -found it in the more complex albumins where it had been missed. It was -found in the albumin of egg hidden under the mass of other groups. -It was recognized in all animal or vegetable albumins. The nuclei -of Schützenberger may be missing. Hexonic bases are the constant -and universal element of all varieties of albumins. They prevail in -the chemical nucleus of the albuminous molecule, and perhaps as is -suggested by Kossel, they may form it exclusively. All the other -elements are superadded and accessory. The essential type of this -molecular edifice, sought for so long, is known at last. - -_Conclusion._—To sum up, the chemical unity of living beings is -expressed by saying that living matter, protoplasm, is a mixture or a -complex of proteid substances with an hexonic nucleus. - - - - - CHAPTER IV. - - THE TWOFOLD CONDITIONING OF VITAL PHENOMENA. IRRITABILITY. - - Appearance of internal activity of the living being—Vital phenomena - regarded as a reaction of the ambient world.—§ 1. Extrinsic - conditions—The optimum law.—§ 2. Intrinsic conditions—The structure - of organs and apparatus—How experiment attacks the phenomena of life. - Generalization of the law of inertia—Irritability. - - -_Instability. Mutability. The Appearance of Internal Activity of the -Living Being._—One of the most remarkable characteristics of the living -being is its instability. It is in a state of continual change. The -simplest of the elementary beings, the plastid, grows and goes on -growing and becoming more complex, until it reaches a stage at which it -divides, and thus rejuvenated it commences the upward march which leads -it once again to the same segmentation. Its evolution is thus betrayed -by its growth, by the variations of form which correspond to it, and by -its division. - -If it be a question of beings higher in organization than the cellular -element the evolutionary character of this mutability becomes more -obvious. The being is formed, it grows; then in most cases, after -having passed through the stages of youth and adult age, it grows old, -declines and dies, and is disorganized after having gone through -what we may call an ideal trajectory. This march in a fixed direction -with its points of departure, its degrees, and its termination, is a -repetition of the path that the ancestors of the living being have -already followed. - -Here, then, is a characteristic fact of vitality, or rather there -are two facts. The one consists in this morphological and organic -evolution, the negation of immutability, the negation of the indefinite -maintenance of a permanent state or form which is regarded, on the -contrary, as the condition of inert, fixed stable bodies, eternally at -rest. The other consists in the repetition, realized by this evolution, -of the similar evolution of its ancestors; this is a fact of heredity. -Finally, evolution is always in a cycle—that is to say, that it comes -to an end which brings the course of things to their point of departure. - -This kind of internal activity of the living being is so striking, that -not only does it serve us to differentiate the living being from the -inert body, but it gives rise to the illusion of a kind of internal -demon, vital force, manifested by the more or less apparent acts of the -life of relation, of the motricity, of the displacement, or by the less -obvious acts of vegetative life. - -_Vital Phenomena regarded as a Reaction of the Ambient World. Their -Twofold Conditioning._—In reality, as the doctrine of energetics -teaches us, the phenomena of vitality are not the effect of a purely -internal activity. They are a reaction of the environment. “The idea -of life,” says Auguste Comte, “constantly assumes the necessary -correlation of two indispensable elements:—an appropriate organism and -a suitable environment. It is from the reciprocal action of these two -elements that all vital phenomena inevitably result.” The environment -furnishes the living being with three things:—its matter, its energy, -and the exciting forces of its vitality. All vital manifestation -results from the conflict of two factors: the extrinsic factor which -provokes its appearance; the intrinsic factor, the very organization -of the living body, which determines its form. Bichat and Cuvier saw -in the phenomena of life the exclusive intervention of a principle of -action entirely internal, checked rather than aided by the universal -forces of nature. The exact opposite is true. The protozoan finds the -stimuli of its vitality in the aquatic medium which is its habitat. -The really living particles of the metazoan—that is to say, its -cells, its anatomical elements—meet these stimuli in the lymph, in -the interstitial liquids which bathe them and which form their real -external environment. - -Auguste Comte thoroughly understood this truth, and has clearly -expressed it in the passage we have just quoted. Claude Bernard has -fully developed it and given it its classical form. - -In order to manifest the phenomena of vitality, the elementary being, -the protoplasmic being, requires from the external world certain -favourable conditions; these it finds there, and they may be called the -stimuli, or extrinsic conditions of vitality. This being possesses no -initiative or spontaneity in itself, it has only a faculty of entering -into action when an external stimulus provokes it. This subjection of -the living matter is called _irritability_. The term expresses that -life is not solely an internal attribute, but an internal principle of -action. - - - § 1. EXTRINSIC CONDITIONS. - - -_Extrinsic Conditions._—By showing that every vital manifestation -results from the conflict of two factors: the extrinsic or -physico-chemical conditions which determine its appearance, and the -intrinsic or organic conditions which regulate its form, Claude -Bernard dealt a mortal blow at the old vitalist theories. For he has -not only asserted the close dependence of the two kinds of factors, -but he has shown them in action in most physiological phenomena. The -study of the extrinsic or physico-chemical conditions necessary to -vital manifestations teaches us our first truth—namely, that they -are not infinitely varied as might be supposed. They present, on the -contrary, a remarkable uniformity in their essential qualities. The -fundamental conditions are the same for the animal or vegetable cells -of every species. They are four in number:—_moisture_, the air, or -rather _oxygen_, _heat_, and a certain _chemical constitution_ of the -medium, and the last condition, the enunciation of which seems vague, -becomes more precise if we look at it a little closer. The chemical -constitution of media favourable to life, the media of culture, obeys -three general laws. It is the knowledge of these laws which formerly -enabled Pasteur, Raulin, Cohn, and Balbiani to provide the media -appropriate to the existence of certain relatively simple organisms, -and thus to create an infinitely valuable method for the study of -nutrition, etc.,—namely, the _method of artificial cultures_, numerous -developments of which have been shown us by microbiology and physiology. - -_The Optimum Law._—It has been said, and it is more than a play on -words, that the conditions of the vital medium were the conditions -of the _juste milieu_. Water is wanted, there must not be too much or -too little. Oxygen is necessary, and also in certain proportions. Heat -is required, and for that, too, there is an optimum degree. Certain -chemical compounds are needed and, in this respect too, there must also -be _optima_ proportions. - -Water is a constituent element of the organisms. They contain fixed -proportions for the same tissue, proportions varying from one tissue to -another (between 2∕3 and 9∕10). The cell of a living tissue requires -around it an aqueous atmosphere, formed by the different juices of the -organism, the interstitial liquids, the blood, and the lymph. We are -deceived by appearances when we distinguish between aerial, aquatic, -and land-dwelling animals, and when we speak of the air, the water, -and the land as their natural environment. If we go to the bottom -of things, and fix our attention on the real living unities, on the -cells of which the organism is composed, we shall find around them -the juices, rich in water, which are their real environment. If these -juices are diluted or concentrated the least in the world, life stops. -The cell, the whole animal, falls into a state of latent life, or -dies. “All living beings are aquatic,” said Claude Bernard. “Beings -that live in the air are in reality wandering aquariums,” said another -physiologist. “No moisture, no life,” wrote Preyer. The environment -must contain water, but it must contain it in certain proportions. In -the higher animals there is a mechanism which works automatically to -keep at a constant level the quantity of water in the blood. Researches -on the lavage of the blood (A. Dastre and Loye) have clearly shown -this. - -Oxygen is also necessary to life. It is the _pabulum vitæ_. But the -discovery of the beings called by Pasteur _anaerobia_ appears to -contradict this statement. Pfeffer, the illustrious botanist, was -certain, in 1897, that the dogma of the necessity of oxygen no longer -held good. This is no longer tenable. In 1898 Beijerinck carried out -most careful researches on anaerobia said to have been cultivated in a -vacuum, such as the _bacteria of tetanus_ and the _septic vibrion_; or -on those to which oxygen seems to be a poison, such as the _butyric_ -and the _butylic ferments_, the anaerobia of putrefaction, the reducing -spirilla of the sulphates. All use free oxygen. They consume very -little it is true; they are micro-aerobia. The other organisms, on -the contrary, need more. They are macro-aerobia or simply _aerobia_. -Besides, if the so-called anaerobia take little or no free oxygen, it -matters little. They take the oxygen in combination. It may be said -with L. Errera that they have an affinity for oxygen, for they extract -it from its combinations, and that “they are so well adapted to this -mode of existence that life in the open air being too easy no longer -suits them.” There are for the different animal species different -optima of oxygen. - -Living beings require a certain amount of heat. Life, which could not -have existed on the globe when it was incandescent, will not be able to -exist when it is frozen. For each organism and each function there is a -maximum and a minimum of temperature compatible with activity. There is -also an optimum. For instance, the optimum is 29° C for the germination -of corn. - -The condition of the optimum exists in the same way for the chemical -composition of the vital medium—and for the other ambient physical -conditions, such as atmospheric pressure. - -It is therefore a law of _universal_ scope, a regulating law, as it -were, of life. Life is a function of extrinsic variables, water, air, -heat, the chemical composition of the medium, and pressure. “Every -vital phenomenon begins to be produced, starting from a certain -stage of the variable (minimum), becomes more and more vigorous as -it increases up to a determinate value (optimum), weakens if the -variable continues to increase, and disappears when it has reached -a certain limiting value (maximum).” This law, proved by Sachs, the -German botanist, in 1860, apropos of the action of temperature on the -germination of plants, by Paul Bert in 1875, apropos of the action of -oxygen and of atmospheric pressure on animals, and already formulated -at that time by Claude Bernard, was illustrated by Leo Errera in 1895. -It is a law of moderation. It expresses La Fontaine’s “_rien de trop_” -Terence’s “_ne quid nimis_,” the μηδὲν ἄγαν of Theognis, and the -biblical phrase “_omnia in mensura et numero et pondere_.” L. Errera -sees the profound cause of this optimum law in the properties of the -living protoplasm, which are mean properties. It is semi-liquid. It is -composed of albuminoid substances, which can stand no extremes either -from the physical or from the chemical points of view. - - - § 2. INTRINSIC CONDITIONS. THE LAW OF THE CONSTITUTION OF ORGANS AND - APPARATUS. - - -_Law of the Constitution of Organs and Apparatus._—If we consider -more highly organized beings, the influence of the intrinsic -conditions appears quite as clearly. As we have seen, this is so that -the requisite fundamental materials may be spent by each element in -suitable proportions,—water, chemical compounds, air, and heat,—that -organs may be added to organs, and that apparatus may be set to work in -complex structures. Why a digestive apparatus? To prepare and introduce -into the internal medium liquid materials which are necessary to -life. Why a respiratory apparatus? To impart the vital gas necessary -to the cells, and to expel the gaseous excrement, the carbonic acid -which they reject. Why a circulatory apparatus? To transport and renew -this medium throughout. The apparatus, the functional wheels, the -vessels, the digestive and respiratory mechanisms do not exist for -themselves, like the random sketches of an artistic nature. They exist -for the innumerable anatomical elements which people the economy. -They are arranged to assist and more rigorously to regulate cellular -life with respect to the extrinsic conditions which it demands. They -are, in the living body, as in civilized society, the manufactories -and the workshops which provide for the different members of society -dress, warmth, and food. In a word, the _law of the construction of -organisms_ or of the _bringing to perfection of an organism_ is the -same as the law of cellular life. It is otherwise suggestive as the -law of _division of physiological labour_ formerly enunciated by Henry -Milne-Edwards; and in every case it has a more concrete significance. -Finally, it brings the organic functional activity into relation with -the conditions of the ambient medium. - -_How Experiment acts on the Phenomena of Life._— The two orders of -conditions, the one provided by the being itself, the other by external -agents, are equally indispensable—and therefore of equal importance or -dignity. But they are not equally accessible to the experimentalist. -It is not easy to exercise on the organization direct and measurable -actions. On the contrary, the physical conditions are in the hands -and at the discretion of the experimenter. By them he may reach the -vital manifestations as they appear, stimulate or check them, defer -or precipitate them. Thus, for instance, the physiologist suspends -or re-establishes at his will full vital activity in a multitude of -reviviscent or hibernating beings, such as grains, the infusoria -capable of _encystment_, the vibrio, the tardigrade, the cold-blooded -animals, and perennial plants. - -The ambient world therefore furnishes to the animal and to the -vegetable, whole or fragmentary, those materials of its organization -which are at the same time the stimuli of its vitality. That is to say, -the vital mechanism would be a dormant and inert mechanism if nothing -in the surrounding medium could provoke it to action or give it a -check. It would be a kind of steam engine without coal and fire. - -Living matter, in other words, does not possess real spontaneity. As I -have shown elsewhere, the law of inertia which it is supposed it obeys -with inert bodies is not special to them. It is applied to the living -bodies whose apparent spontaneity is only an illusion contradicted by -physiology as a whole. All the vital manifestations are responses to a -stimulus of acts provoked, and not of spontaneous acts. - -_Generalization of the Law of Inertia in Living Bodies. -Irritability._—In fact, vulgar prejudice opposes this view. The -opinion of the average man distrusts it. It applies the law of inertia -only to inert matter. This is because the vital response does not -always immediately succeed the external stimulus, and is not always -proportional to it. But it is sufficient to have seen the flywheel of a -steam engine to understand that the restitution of a mechanical force -cannot be instantaneous. It is sufficient to have had a finger on the -trigger of a firearm to know that there is no necessary proportion -between the intensity of the stimulus and the magnitude of the force -produced. Things happen in the living just as in the inert machine. - -The faculty of entering into action when provoked by an external -stimulus has received, as we have said, the name of _irritability_. -The word is not used of inert matter. However, the condition of the -latter is the same. But there is no need to affirm its irritability, -because no one denies it. We know perfectly well that brute matter -is inert, that all the manifestations of activity of which it is the -theatre are provoked. Inertia is for it the equivalent of irritability -in living matter. But while it is not necessary to introduce this idea -into the physical sciences, where it has reigned since the days of -Galileo, it was, on the contrary, necessary to affirm it in biology, -precisely because it was in biology that the opposing doctrine of vital -spontaneity ruled supreme. - -Such was the view held by Claude Bernard. He never varied on this -point. _Irritability_, said he, is the property possessed “by every -anatomical element (that is to say, the protoplasm which enters into -its constitution) of being stimulated into activity and of reacting -in a certain manner under the influence of the external stimuli.” He -could not claim that this was a distinguishing characteristic between -living bodies and brute bodies, and that all the less because he always -tried to efface on this point the distinctions which were current in -his time, and which were established by Bichat and Cuvier. And so also -Le Dantec does not seem to have thoroughly grasped the ideas of the -celebrated physiologist on this point when he asserts, as if he were -thereby contradicting the opinion of Claude Bernard and his school, -that irritability is not something peculiar to living bodies.[17] - - [17] These ideas are clearly brought to light in a series of articles - in the _Revue Philosophique_, published in 1879 under the title of “La - problème physiologique de la vie,” and endorsed by A. Dastre in his - commentary on the _Phénomènes communs aux animaux et aux plantes_. - - - - - CHAPTER V. - - THE SPECIFIC FORM. ITS ACQUISITION. ITS REPARATION. - - § 1. Specific form not special to living beings—Connected with the - whole of the material conditions of the body and the medium—Is it a - property of chemical substance?—§ 2. Acquisition and re-establishment - of the specific form—Normal regeneration—Accidental regeneration in - the protozoa and the plastids—In the metazoa. - - - § 1. THE SPECIFIC FORM. - - -_The Specific Form is not Peculiar to Living Beings._—The position of -a _specific form_—the acquisition of this typical form progressively -realized—the re-establishment when some accident has altered it—these -are the features which we consider distinctive of living beings, from -the protophytes and the lowest protozoa to the highest animals. Nothing -gives a better idea of the unity and the individuality of the living -being than the existence of this typical form. We do not mean, however, -that this characteristic belongs to the living being alone, and is by -itself capable of defining it. We repeat that this is not a case with -any characteristic. In particular the _typical form_ belongs to crystal -as well as to living beings. - -_The Specific Form depends on the sum of Material Conditions of the -Body and the Medium._—The consideration of mineral bodies shows us -form dependent on the physico-chemical conditions of the body and the -medium. The form depends mainly on physical conditions in the cases -of a drop of water falling from a tap, of the liquid meniscus in a -narrow tube, of a small navel-shaped mass of mercury on a marble slab, -of a drop of oil “emulsioned” in a solution, and of the metal which -is hardened by hammering or annealed. In the case of crystals the -form depends more on chemical conditions. It is crystallization which -has introduced into physics the idea that has now become a kind of -postulate—namely, that the specific form is connected with the chemical -composition. However, it is sufficient to instance the dimorphism -of a simple body, such as sulphur, sometimes prismatic, sometimes -octahedric, to realize that substance is only one of the factors of -form, and that the physical conditions of the body and of the medium -are other factors quite as influential. - -_Is the Specific Form a Property of the Chemical Substance?_—How much -truer this restriction would be if we consider, instead of a given -chemical compound, an astonishingly complex mixture, such as protoplasm -or living matter, or the more complex organism still—the cell, the -plastid. - -Are there not great differences between the substance of the cellular -protoplasm, or cytoplasmic substance, and that of the nucleus? Should -we not distinguish in the former the hyaloplasmic substance; the -microsomic in the microsomes; the linin between its granulations; the -centrosomic in the centrosome; the archoplasmic in the attraction -sphere; not to mention the different leucins, the vacuolar juice, and -the various inclusions? And in the nucleus must we not consider the -nuclear juice, the substance of the chromosomes, and that of the -nucleoles? And is not each of these probably a very complex mixture? - -However, it is to this mixture that we attribute the possession -of a form, in virtue of and by extension of the principles of -crystallization, which definitely teach us that these mixtures cannot -have form; that form is the attribute of pure bodies, and is only -obtained by the separation of the blended parts—_i.e._, by a return -to homogeneity. There are therefore very good reasons for hesitating -before we transfer the absolute principle of the dependence between -chemical form and composition, as some philosophical biologists have -done, from the physical sciences—where it is already subject to serious -restrictions—to the biological sciences. - -Le Dantec, however, has made this principle the basis of his biological -system. He therefore finds in the crystal the model of the living -being. He thus gives a physical basis to life. - -Is it a question in this system of explaining this incomprehensible, -this unfathomable mystery, which shows the egg cell attracting to -itself materials from without and progressively building up that -amazing structure which is the body of the animal, the body of a -man, of any given man, of Primus, for example? It is said that the -substance of Primus is specific. His living substance is his own, -special to him; and that, too, from the beginning of the egg to the end -of its metamorphosis. It only remains to apply to this substance the -postulate, borrowed from crystallography, of the absolute dependence -of the nature of substance on the form it assumes. The form of the -body of the animal, of the man, of Primus, is the crystalline form of -their living substance. It is the only form of equilibrium that this -substance can assume under the given conditions, just as the cube is -the crystallized form of sea salt, the only state of equilibrium of -chloride of sodium in slowly evaporated sea water. Thus the problem -of the living form is reduced to the problem of the living substance, -which seems easier; and at the same time the biological mystery is -reduced to a physical mystery. It is clear that this way of looking -at things simplifies prodigiously—and, we must add, simplifies far -too much—the obscure problem of the relation of form to substance, -simultaneously in the two orders of science. This may be summed up in a -single sentence: There is an established relation between the specific -form and the chemical composition: the chemical composition _directs_ -and implies the specific form. - -We need not now examine the basis of this opinion. If it is nothing but -a verbal simplification, a unification of the language applied to the -two orders of phenomena, it implies an assimilation of the mechanisms -which realize them. To the organogenic forces which direct the -building up of the living organisms it brings into correspondence the -crystallogenic forces which group, adjust, equilibrate, and harmonize -the materials of the crystal. - -When it is a question of the application of a principle such as -this, in order to test its legitimacy we must always return to the -experimental foundations. Let us imagine, for example, a simple body, -such as sulphur, heated and brought to a state of fusion—that is to -say, homogeneous, isotropic, in an undisturbed medium the only change -in which will be a very gradual cooling down. These are the typical -crystallogenic conditions. The body would take a given crystalline -form. It is from experiments such as this that we derive the idea of _a -specific form connected with a chemical constitution_. - -But in drawing this conclusion our logic is at fault. The real -interpretation suitable to this case, as in all others, is that the -specific form is suitable to the substance, and also to the physical, -chemical, and mechanical conditions in which it is placed. And the -proof is that this same substance, sulphur, which takes the prismatic -form immediately after fusion, will not retain that form, but will pass -on to the quite different octahedral form. - -It is so with the specific form of the living being—that is to say, -with the assemblage of its constituent materials co-ordinated in a -given system—in a word, with its organization. This is suitable to its -substance, and to all the material, physical, chemical, and mechanical -conditions in which it is placed. This form is the condition of -material equilibrium corresponding to a very complex situation, to a -sum of given conditions. The chemical condition is only one of these. -And further, it is hardly proper to speak of a “chemical substance” -when we refer to an astonishingly complex mixture which is in addition -variable from one point to the other of the living body. When we thus -reduce phenomena to their original signification, false analogies -disappear. To say with Le Dantec that the form of the greyhound is -the condition of equilibrium of the “greyhound chemical substance” is -saying much; and too much, if it means that the body of the greyhound -has a substance which behaves in the same way as homogeneous, isotropic -masses like melted sulphur and dissolved salt. It were better to say -much less, if it means, as it will in the minds of the physiologists, -that the body of the greyhound is the condition of equilibrium of a -heterogeneous, anisotropic, material system, subjected to an infinite -number of physical and chemical conditions. - -The idea of connecting form, and by that we mean organization, with -chemical composition did not arise in the minds of chemists or -physiologists. Both have expressed themselves very clearly on this -point. - -“We must distinguish,” said Berthelot, “between the formation of the -chemical substances, the assemblage of which constitutes organized -beings, and the formation of the organs themselves. This last problem -does not come into the domain of chemistry. No chemist will ever -claim to have formed in his laboratory a leaf, a fruit, a muscle, or -an organ.... But chemistry has a right to claim that it forms direct -principles—that is to say, the chemical materials which constitute the -organs.” And Claude Bernard in the same way writes:—“In a word, the -chemist in his laboratory, and the living organism in its apparatus, -work in the same way, but each with its own tools. The chemist can make -the products of the living being, but he will never make the tools, -because they are the result of organic morphology.” - - - § 2. THE ACQUISITION AND RE-ESTABLISHMENT OF THE SPECIFIC FORM. - - -_Acquisition of the Typical Form._—The acquisition of the typical -form in the living being is the result of ontogenic work which cannot -be examined here. In the elementary being, the plastid, this work is -blended with the work of nutrition. It is _directed nutrition_. It -consists of a simple increase from the moment the element is born by -the division of an anterior element, and of a necessarily restricted -differentiation. It is a rudimentary embryogeny. In the complex being, -metazoan or metaphyte, the organism is constituted, starting from the -egg, by the growth, by the bipartition of the elements, and their -differentiation, accomplished in a certain direction and in conformity -with a given plan. This, again, is directed nutrition, but here the -embryogeny is complex. The directing plan of operations is no doubt -the consequence of the material conditions realized each moment in the -organism. - -_Normal Regeneration._—Not only do living beings themselves -construct their typical architecture, but they re-establish it -and continually reconstitute it, according as accidents, or even -ordinary circumstances, tend to destroy it; in a word, they become -rejuvenescent. This regeneration consists in the reformation of the -parts that are altered or carried away in the normal play of life, or -by the accidents which disturb its course. - -Thus there is a _normal physiological regeneration_, which is, so to -speak, the prolongation of the ontogenesis—_i.e._, of the work of -formation of the individual. We have examples in the reconstitution -of the skin of mammals—in the throwing off of the epidermic products -constantly used up in their superficial and distal parts and -regenerated in their deeply-seated parts; in the loss and the renewal -of teeth at the first dentition and in certain fish in the fact of -successive dentitions; in the periodical renewal of the integument -in the larvæ of insects, and in the crustaceæ; and finally in the -destruction and the neo-formation of the globules of the blood of -vertebrates, of the glandular cells, and of the epithelial cells of the -intestine. - -_Accidental Regeneration in Protozoa and Plastids._—There is also an -_accidental regeneration_ which more or less perfectly renews the parts -that are lost. This regeneration has its degrees, from the simple -cicatrization of a wound to the complete reproduction of the part cut -off. It is very unequally developed in zoological groups even when they -are connected. In the elementary monocellular beings—_i.e._, in the -anatomical elements and in the protozoa,—the experiments in merotomy, -_i.e._, in _partial section_, enable us to appreciate the extent of -this faculty of regeneration. These experiments, inaugurated by the -researches of Augustus Waller in 1851, were repeated by Gruber in 1885, -continued by Nussbaum in 1886, Balbiani in 1889, Verworn in 1891, and -have been reproduced by a large number of observers. They have shown -that the two fragments cicatrize, and are repaired, building up an -organism externally similar to the primitive organism, but smaller. -The two new organic units do not, however, behave in the same way. -That which retains the nucleus possesses the faculty of regeneration, -and of living as the primitive being lived. The protoplasmic fragment, -which does not contain the nucleus, cannot rebuild this absent organ; -and though it has functional activity in most respects, just as the -nucleated fragment, yet it is distinguished from it in others of great -importance. The anucleated fragment of an infusorian behaves as the -nucleated, and as the whole animal so far as the movements of the body, -the cilia, prehension of food, evacuation of fæces, and the rhythmical -contraction of the pulsatile vesicules are concerned. But Balbiani’s -researches in 1892 have shown us that secretion, complete regeneration, -and the faculty of reproduction by fission can take place only in the -nucleated fragment—_i.e._, in the nucleus. - -_Accidental Reproduction in the Metazoa._—Among multicellular beings -the faculty of reproduction is met with in the highest degree in -plants, where we find it in the process of propagation by slips. In -animals it is the most marked in Cœlenterata. Trembley’s experiments -are a striking instance. We know that when the hydra is cut into -tiny pieces it reproduces exactly as many complete beings. Among the -worms, Planaria afford a similar example. Every fragment, provided its -volume is not less than a tenth of that of the whole, can reproduce -a complete, entire being. The snail can produce a large part of its -head, including the tentacles and the mouth. Among the Tritons and -the Salamanders the faculty of regeneration reproduces the limbs, the -tail, and the eye. In the Frog family, on the contrary, the work of -regeneration does not go beyond cicatrization, and it is the same with -Birds and Insects. - -It is really startling to see in a vertebrate like the Triton the stump -of an arm with its fragment of humerus reproducing the forearm and -the hand in all their complexity, with their skeleton, blood vessels, -nerves, and teguments. We say that the limb has _budded_, as if there -were a germ of it which develops like the seed of a plant, or as if -each transverse portion of the limb, each slice, so to speak, could -re-form the slice that follows. - -The mechanism of generation and that of regeneration alike raise -problems of the highest importance. Does the part become regenerated -just as it was formed at first? Does the regeneration repeat the -ontogeny? Is it true that a lost organ is never regenerated (the -kidney for instance)? Does the symmetrical organ enjoy a compensating -and hypertrophic development, as Ribbert has asserted? And further, -if the organ be removed and transplanted to another position, can it -be grafted there, as Y. Delage maintains? These are very important -questions; but if we dwell upon them, we shall be diverted from our -immediate object. Our task is to look at these facts from the point -of view of their significant and characteristic meaning in vitality. -Flourens invoked on their behalf the intervention of vital forces, -_plastic_ and _morphoplastic_. But, as we shall see later, these -phenomena of cicatrization, of reparation, of regeneration, these more -or less complete efforts for the re-establishment of the specific form, -although they are found in all living beings in different degrees, -are not exclusively confined to them. We find them again in some -representatives of the mineral world—in crystals, for instance. - - - - - CHAPTER VI. - - NUTRITION. - - FUNCTIONAL ASSIMILATION. FUNCTIONAL DESTRUCTION. ORGANIC DESTRUCTION. - ASSIMILATING SYNTHESIS. - - The extreme importance of nutrition—§ 1. Effect of vital - activity—Destruction or growth—Distinction between the living - substance and the reserve-stuff mingled with it—Organic - destruction—Destruction of reserve-stuff—Destruction of living - matter—Growth of living matter—§ 2. The two categories of vital - phenomena—Foundations of the idea of functional destruction—The two - kinds of phenomena of vitality—Criticism of Claude Bernard—Current - views—Criticism of Le Dantec’s new theory of life.—§ 3. Correlation of - the two kinds of vital facts—Law of connection—Contradictions in the - new theory.—§ 4. The characteristics of nutrition—Its definition—Its - permanence—Erroneous idea of the vital vortex—Formative assimilation - of reserve-stuff—Formative assimilation of protoplasm—Death, real and - apparent. - - -_The Immense Importance of Nutrition._—We now come to the important -feature of vitality. All other characteristics of living matter, its -unstable equilibrium, its chemical and anatomical organization, the -acquisition and the maintenance of a typical form, are only secondary -properties, so to speak, subordinate with reference to _nutrition_. -Generation itself is only a mode. _Nutrition_ is the essential -attribute of life. It is life itself. - -Before we define it a few preliminary explanations are necessary. - -The most striking thing in living matter is its _growth_. An animal, a -vegetable, is something which is first more or less minute, and which -grows. Its characteristic is to expand—from the spore, the seed, the -slip, the egg—it grows. - -Whether we are dealing with a cellular element, a plastid, or a complex -being, their condition is the same in this respect. No doubt when the -animal or plant has reached a certain stage of development its growth -is stopped, and for a more or less lengthy period it remains in the -adult stage, in what seems to be equilibrium. But even then there is no -check in the manufacture of living matter; there is only a compensation -between its production and its destruction. - -It is important to reduce to order the ideas on this important subject, -which at present are confused, inconsistent, and contradictory. In -biology grievous confusion reigns. - - - § 1. EFFECT OF THE VITAL ACTIVITY. DESTRUCTION OR GROWTH? - - -_Distinction between the Living Substance and the Reserve-stuff mingled -with it._—The physiology of nutrition has given rise to a vast body -of research during the last half-century. Physiological schools, -masters and pupils, such as the school at Munich under Voit and -Pettenkofer, Pflüger’s at Bonn, Rubner’s, and those of Zuntz and von -Noorden at Berlin, and a large number of zootechnical and agricultural -laboratories through the whole world have for years past been engaged -in analyzing ingesta and egesta, in drawing up schedules of nutrition, -in order to determine the course of decomposition and reconstitution of -the living material. - -If I were asked what, in my opinion, is the most general result of -all this labour, I would reply that it has affirmed and corroborated -the important distinction which must be drawn between _living -substance, properly so called_, and _reserve-stuff_. The latter, -the _reserve-stuff_ of albuminoids, carbohydrates, and fats, are so -intimately intermingled with the living substance that they are in most -cases very difficult to distinguish from it. - -_Organic Destruction._—A second point, which is placed equally -beyond doubt, is that the vital functional activity is accompanied -by a destruction of the immediate principles of the organism, in the -direction of their simplification. This functional destruction cannot -be doubted in the case of differentiated organs in which the functional -activity is evident, intermittent, and in some measure distinct from -the other vital phenomena which take place in them. For example, in the -case of contracting muscles the respiratory carbonic acid and urinary -carbon are the irrefutable proofs of this destruction: weak in repose, -abundant during activity, and in proportion to it. There can be no -doubt on this point. The truth laid down by Claude Bernard under the -name of the _law of functional destruction_ has been doubly consecrated -by experiment and theory. According to the energetic theory, in fact, -mechanical and thermal energies manifested in the vital functional -activity can only have their source in the chemical energy set free by -the destruction of the immediate principles of the organism, reduced -to a lower degree of complexity. - -_Destruction of Reserve-stuff._—But now the disagreement begins. What -are these decomposed, destroyed principles? Do they belong to the -cellular reserve-stuff or to the living matter properly so called? -There is no doubt that most of them belong to the reserve-stuff. -For example, this is especially true of glycogen, which is consumed -in muscular contraction just as coal is consumed in the furnace of -the locomotive; and glycogen is a reserve-stuff of muscle. These -reserve-stuffs destroyed in the functional activity can be built up -again only during repose. - -But it is not yet certain whether the living matter itself, the -active protoplasm, the muscular protoplasm, takes part in this -destruction, whether it provides it with elements. Experiments have -proved contradictory. Experimenters have isolated the nitrogenous -wastes (urea) after muscular labour, and they have compared them with -the wastes of the period of repose. These nitrogenous wastes bear -witness to the destruction of albuminoid substances, and the latter are -the constituent principles of living matter. If—under conditions of -sufficient alimentation—the muscular functional activity involves more -nitrogenous waste, _i.e._, a greater destruction of albuminoids, it -might be supposed that the living material properly so called has been -used up and destroyed for its own purposes. (And here again there might -be a reserve-stuff of albuminoids, distinct from the living protoplasm -itself, and more or less incorporated with it.) - -But experiment so far has not given decisive results. The latest -experimental researches, such as those of Igo Kaup, of Vienna, which -date from 1902, tell us as uncertain a tale as their predecessors. -The increase in the destruction of albumen has not been constant; the -conditions of the observations do not justify our making an assertion -either _pro_ or _con_. - -_Destruction of Living Matter._—As no certain answer is supplied by -experiment, theory intervenes and gives two conflicting answers. The -majority of physiologists are inclined to believe in _the destruction -of the living substance as the result of its own functional activity_. -The functional activity would therefore destroy not only the -reserve-stuff, but also the protoplasmic material. This is the current -view. Only this opinion is strongly challenged by the positive teaching -of science. It is certain that this material, in the muscle, is but -little attacked, if it is attacked at all. We have seen above that the -physiologists, with Pflüger and Chauveau, are agreed on this point. -The vital functional activity in particular is destructive to the -reserve-stuffs. It does not destroy them much; it destroys the organic -material still less. Both would be repaired in functional repose. - -_Growth of Living Matter._—The second assertion is diametrically -opposed to this. Not only, says Le Dantec, is the muscle not destroyed -in the functional activity, but it grows. Contrary to universal -opinion, the protoplasmic material increases by activity, and it is -destroyed in repose. There would thus be a general law—_the law of -functional assimilation_. “A cell of brewers’ yeast when introduced -into a sugared must makes this must ferment, and at the same time, so -far from destroying it, it increases it. Now, the fermentation of the -must is exactly the same as the functional activity of the yeast.” It -is, says the same author, a mistake to believe that the phenomena of -functional activity, of _vital activity_, only takes place at the price -of organic destruction. Here, then, are these two competing views. -They are not so very far apart as a matter of fact, since the question -at issue is one of deciding between a slight destruction and a slight -growth, but theoretically they are strongly opposed. Moreover, they are -arbitrary, and _experiment_ has not decided between them. - - - § 2. THE TWO CATEGORIES OF VITAL PHENOMENA. - - -_Foundation of the Idea of Functional Destruction. Claude Bernard._—The -doctrine of functional destruction has been laid down with remarkable -power by Claude Bernard. But the terms in which he has expressed it -in a measure betray the thoughts of the great physiologist, or, at -any rate, overstep the immediate fact he had in view. “The phenomena -of destruction are very obvious. When movement is produced, when the -muscle contracts, when volition and sensibility are manifested, when -thought is exercised, when the gland secretes, then the substance -of the muscles, of the nerves, of the brain, of the glandular -tissue, becomes disorganized, destroyed, and consumed. So that every -manifestation of a phenomenon in the living being is necessarily -connected with an organic destruction.” To Claude Bernard organic -destruction is a truth. To Le Dantec it is an error. Which is right? -Clearly Claude Bernard. He bases his conviction on the analyses of -the materials excreted in the process of physiological work. The -excreta bear witness to a certain organic demolition. Generalizing -this teaching of experiment the illustrious biologist divined the -fundamental law of energetics before the idea of energetics had made -much way in France. Every act which expends energy, which produces heat -or motion, any manifestation whatever that may be looked upon as an -energetic transformation, necessarily expends energy, and that energy -is borrowed from the substance of the organism. These substances are -simplified, broken up, and destroyed. Now the functional activity of -the muscle produces heat and movement in warm-blooded as well as in -cold-blooded animals. The functional activity of the glands produces -heat, as has been shown by the celebrated experiments of C. Ludwig on -the salivary secretion, and as is also shown by the study of thermal -topography in the vertebrates. The functional activity of the nerves -and the brain produces a slight quantity of electricity and heat, as -most observers have agreed. The functional activity of the electrical -and of the photic apparatus also expends energy. Finally, the eye -which receives the photic impression destroys the purple matter of the -retina, and that purple matter, as we well know, is recuperated in -the dark during the repose of the organ. Everything that is expressed -objectively, everything that is a phenomenon in the living being—with -the exception of growth and formation, which are generally slow -phenomena, and of which we can only get an idea by the comparison -of successive states—all these energetic manifestations suppose a -destruction of organic matter, a chemical simplification, the source -of the energy manifested. And that is why material destruction does -not merely coincide with functional activity, but is its measure and -expression. - -_The Two Kinds of Phenomena of Vitality._—Another point on which -Claude Bernard is right and his opponent is wrong is not less -fundamental. What are we to understand by functional phenomena? -This is the very point at issue. Now, in the mind of physiologists, -this expression has a perfectly definite meaning. It is not so with -Le Dantec. Physiologists who have studied animals rather high in -organization—in which the differentiation of phenomena enables us to -grasp the fundamental distinction—have readily recognized that the -phenomena of living beings are divided into two categories. There are -some which are intermittent, alternative, which take place, or grow -stronger at certain moments, but which cannot be continuous—they are -the _functional acts_; there are others in which this characteristic of -explosives, energetic expenditure and intermittence, do not appear—they -are, in general, the _nutritive acts_. The muscle which contracts shows -functional activity. It has an activity and a repose. During this -apparent repose we must not say that it is dead; it has a life, but -that life is obscure as far as the salient fact of functional movement -is concerned. The salivary gland which throws up waves of saliva when -the food is introduced and masticated in the mouth, or when the chord -of the tympanum is at work, is in a state of functional activity; this -is the salient phenomenon. But before, though nothing, absolutely -nothing, was flowing through the glandular canal, yet the gland was -not reduced to the condition of a dead organ: it was living a more -obscure, a less evident life. The microscopical researches of Kühne, -Lea, and Langley, now universally verified, show us that during this -time of apparent repose the cells were loading up their granulations -and getting ready the materials of secretion, as just now the muscle -at rest was accumulating glycogen and the reserve-stuff which are to -be expended and destroyed in contraction. Similarly, with regard to -the functional activity of the other glands, of the brain, etc. Claude -Bernard was, therefore, perfectly right, when he took as his model -the chemists who distinguished between exothermic and endothermic -reactions, and who classed the phenomena of life into two great -divisions: those of functional activity, and those of functional repose. - -1st. _The phenomena of functional activity_ “are those which ‘leap to -the eyes,’ and by which we are inclined to characterize life. They are -conditioned by the effects of wear and tear, of chemical simplication, -and of the organic destruction which liberates energy.” And it must -be so, because these functional manifestations expend energy. These -phenomena, which are the most obvious, are also the least specific -phenomena of vitality. They form part of the general phenomenality. - -2nd. The _phenomena_ which accompany _functional repose_ correspond to -the building up of the reserve-stuff destroyed in the preceding period, -to the organizing synthesis. The latter remains “internal, silent, -concealed in its phenomenal expression, noiselessly gathering together -the materials which will be expended. We do not see these phenomena -of organization directly. The histologist and the embryogenist alone, -following the development of the element or of the living being, sees -the changes and the phases which reveal this silent effort. Here is a -store of substance; there, the formation of an envelope or a nucleus; -there, a division or multiplication, a renewal.” This type of phenomena -is the only type which has no direct analogues: it is peculiar, special -to the living being: what is really vital is this evolutive synthesis. -Life is creation. - -_Criticism of Claude Bernard._—All this is perfectly true. Thirty years -of the most intensive scientific development have run by since these -lines were written, and have not essentially changed the ideas therein -expressed. His work in its broad lines remains intact. Does that imply, -however, that everything is perfect in detail and expression, and that -there is no reason for making it more precise or for giving it fresh -form? No doubt this is not so. Although Claude Bernard contributed to -establish the essential distinction between the real living protoplasm -and the materials of reserve-stuff which it contains, he has not drawn -a sufficiently clear distinction between what belongs to each of the -categories. He has not specified, in relation to organic destruction, -what bearing it has on the organic materials of reserve-stuff. -Sometimes he uses the term “organic destruction,” which is correct, and -sometimes “vital destruction,” which is of doubtful import. Further, he -employs an obscure and paradoxical formula to characterize the obvious -but nevertheless not specific phenomena of organic destruction, and he -says: “life is death.” - -_Current Views._—Nowadays, if I may express a personal opinion on -this important distinction between functional activity and functional -repose, I should say that after having distinguished between the -two categories of phenomena we must try to correlate them. We must -try to discover, for instance, what there is in common between the -muscle in repose and the muscle in contraction, and to perceive in the -_muscular tonus_ a kind of bridge thrown between these two conditions. -The functional activity would be uninterrupted, but it would have -its degrees of activity. The muscular tonus would be the permanent -condition of an activity which is capable only of being considerably -raised or lowered. Similarly for the glandular functional activity; -the periods of charge must be connected with the periods of discharge. -In a word, following the constant path of the human mind in scientific -knowledge, after having drawn the distinctions that are necessary to -our understanding of things, we must obliterate them. After having -dug our ditches we must fill them up again. After having analyzed we -must synthesize. The distinction between the phenomena of _functional -activity_ and the phenomena of _functional repose_ or _purely -vegetative_ and nutritive _activity_, though only valid in the case of -a provisional and approximate truth, none the less throws light on the -obscure regions of biology. - -The succession of energy and repose, of sleep and awakening, is a -universal law, or at least a very general law, connected with the laws -of energetics. The heart, the lungs, the muscles, the glands, the brain -obey in the most obvious manner this obligation of rhythmical activity. -The reason is clear. It is because the functional activity involves -what is generally a sudden expenditure of energy, and this has to be -replaced by what is generally a slow process of reparation. Functional -activity is an explosive destruction of a chemical reserve which is -built up again more or less slowly. - -_Criticism of Le Dantec’s “New Theory of Life.”_—Let us now examine the -antithesis of Claude Bernard’s views. There are evidently rudimentary -organisms in which the differentiation of the two categories of -phenomena is but little marked; in which, apart from the movement, -it is impossible to recognize intermittent, functional activities -clearly distinct from morphogenic activity. It is not in this domain -of the indistinct that we must seek the touchstone of physiological -distinctions. Clearly, we must not choose these elementary plastids -to test the doctrine of functional assimilation and functional -destruction. But is not this exactly what Le Dantec did when he began -his researches on brewers’ yeast? When we try to examine things, -we must choose the conditions under which they are differentiated, -and not those in which they are confused. And this is why, in the -significant words of Auguste Comte, “the more complex living beings -are, the better known they are to us.” The philosopher goes still -farther in this direction, and adds “directly it is a question of the -characteristics of animality we must start from the man, and see how -those characteristics are little by little degraded, rather than start -from the sponge and endeavour to discover how these characteristics are -developed. The animal life of the man assists us to understand the life -of the sponge, but the converse is not true.” - -When, moreover, we consider a vegetable organism such as yeast, which -derives its energy, not from itself, not from the potential chemical -energy of its reserve-stuff, but directly from the medium—that is to -say, from the potential chemical energy of the compounds which form -its medium of culture,—we then find ourselves in the worst possible -situation for the recognition of organic destruction. Further, it is -doubly wrong to assert that in so ill-chosen a type the functional -phenomena do not result from an organic destruction—for at first there -are no very distinct functional phenomena here—and, in the second -place, there certainly is organic destruction. The phenomena of the -morphogenic vitality detected in the yeast are the exact concomitants, -or the results, of the destruction of an organic compound, which in -this case is sugar. The yeast destroys an immediate principle, and -this is the point of departure of its vital manifestations; only, it -has not, as a preliminary, clearly incorporated and assimilated this -principle. When, therefore, the functional phenomena are effaced and -disappear, we none the less find phenomena of destruction of organic -compounds which are in a measure, a preface to the phenomena of growth. -This is what happens in the case of brewers’ yeast: and here, again, -the two categories of facts exist. Once more, we find, in the first -place, the phenomena of destruction (destruction of sugar, reduced -by simplification to alcohol and carbonic acid)—phenomena which this -time no longer respond to obvious functional manifestations; and, in -the second place, the phenomena of chemical and organogenic synthesis, -corresponding to the growth of the yeast and the multiplication of its -protoplasm. The former are no longer detected, as we have just said, by -striking manifestations. However, it is not true that everything which -is visible and which may be isolated outside the activity of the yeast -is part of those phenomena. The boiling of the juice or the mash, -the heat given off by the copper, all this phenomenal apparatus is -but the consequence of the production of the carbonic acid and of its -liberations—_i.e._, the consequence of the act of destruction of the -sugar. Here is organic destruction with its energetic manifestations! - -This example of the life of brewers’ yeast, of the saccharomyces, -specially chosen by Le Dantec as being absolutely clear and giving the -best illustration of his argument, contradicts him at every point. The -general thesis of this vigorous thinker is that we cannot distinguish -between the two parts of the vital act, organic destruction, and -assimilating synthesis; that these two acts are not successive; that -they give rise to phenomenal manifestations equally evident, apparent, -or striking. Now, in the case of yeast, the phenomenon of destruction -is clearly distinct from that of the assimilating synthesis which -multiplies the substance of the saccharomyces. In fact, the action is -realized by means of an alcoholic diastase manufactured by the cell; -and Büchner succeeded in isolating this alcoholic ferment which splits -up the sugar into alcohol and carbonic acid, and also _in vitro_ and -_in vivo_, makes the vat boil and heats the liquid. All the yeast is at -work at once, says M. Dantec. No, and this is the proof. - -And, further, Pasteur himself, who had shown the relation of the -decomposition of the sugar to the fact of the growth of the yeast and -of the production of accessory substances such as succinic acid and -glycerine, always referred to _correlation_ between these phenomena. -The destruction of the sugar is the _correlative_ of the life of the -yeast. This was his favourite formula. It never entered his head -that there could be a confusion instead of a correlation, and that -there might be only one and the same act, the phases of which would -be indistinguishable. This unfortunate idea, which was fated to be so -rapidly contradicted, is due to Le Dantec. Far from it being the case, -Pasteur had distinguished the _ferment function_ from the life of the -yeast. According to him, the yeast may exist sometimes as a ferment and -sometimes otherwise. - - - § 3. CORRELATION OF TWO ORDERS OF VITAL FACTS. - - -It is this correlation between acts _distinct in themselves_ but -_usually connected_ that was announced by Claude Bernard. And, -_mirabile dictu_—and this is the natural outcome of the perfect sanity -of mind of this great physiologist—it happens that not only Pasteur’s -researches, but the development of a new science, Energetics, and -Büchner’s discovery lend support to his views, and that, too, in a -field where one would have thought they had no application. Le Dantec -is wrong when he declares that these ideas only apply to vertebrates. -“It is clear,” he says on several occasions, “that the author has -in view the metazoa and even the vertebrates.” Well! no. All that -is general, universally applicable, and universally true. So that -there are two orders of distinct phenomena energetically opposed and -certainly connected. We need only repeat Claude Bernard’s own words -quoted by Le Dantec in order to confute them. - -_Law of Connection of Two Orders of Vital Facts._—“These phenomena [of -organic destruction and of assimilating synthesis] are simultaneously -produced in every living being, in a connection which cannot be broken. -The disorganization or dissimilation uses up living matter [by this -we must understand the reserve-stuff, as will be seen later on in the -quotation] in the organs _in function_: the assimilating synthesis -regenerates the tissues; it gathers together the reserve-stuff which -the vital activity must expend. These two operations of destruction -and renovation, inverse the one to the other, are absolutely connected -and inseparable, in this sense at any rate, that destruction is -the necessary condition of renovation. The phenomena of functional -destruction are themselves the precursors and the instigators of -material regeneration, of the formative process which is silently going -on in the intimacy of the tissues. The losses are repaired as they take -place; and equilibrium being re-established as soon as it tends to be -broken, the body is maintained in its composition.” - -It is perfectly right and wise to say with Claude Bernard that the two -orders of facts are successive, and that one is normally the inciting -condition of the other. The possibility of the development of the yeast -when fermentation fails, and the weakness of this development on the -other hand under these conditions, are an excellent proof of this. The -one proves the essential independence of the two orders of facts, the -other the inciting and provoking virtue of the first relatively to the -second. The experimental truth is thus expressed with a minimum of -uncertainty. We know the facts which led Le Dantec to formulate his -law of functional assimilation—namely, that the functional activity is -useful or indispensable to the growth of the organ; that the organs -which are functionally active grow, and those which do not act -become atrophied. We are only expressing the facts when we say that -the organic destructions that go on in the living being (whether at -the expense of its reserve-stuff or at the expense of its medium, or -whether it be even slightly at the expense of the plastic substance -itself) are the antecedent, the inciting agent or the normal condition -of the chemical and organogenic syntheses which create the new -protoplasm. - -On the other hand, we are wrong if we hold with Le Dantec that -instead of two chemical operations there is only one, that which -creates the new protoplasm. The obvious destruction is neglected; it -is deliberately passed over. He does not see that it is necessary to -liberate the energy employed in the construction, by complication, of -this highly complex substance which is the new protoplasm. He really -seems to have made up his mind not to analyze the phenomenon. If we -decline to admit that to the first act of functional destruction -succeeds a second, assimilation or organogenic synthesis, we are -looking at elementary beings, in which the succession cannot be -grasped, as we look on brewers’ yeast. We not only mean that the -morphogenic assimilation results from the functional activity; we -mean that it results from it directly, immediately, that it is the -functional activity itself. Experiment tells us nothing of all this. -It shows us the real facts, the facts of the destruction of an organic -immediate principle, the sugar, and the fact that an assimilating -synthesis is the correlative of this destruction. Besides, if it is -impossible in examples of this kind to exhibit the succession, it is -perfectly easy in beings of a higher order. It is, then, clearly seen -that the preliminary destruction of a reserve-stuff (and perhaps of -a small quantity of the living substance) precedes and conditions the -formation of a greater quantity of this living matter—in other words, -the growth of the protoplasm of the organ. - -_Contradictions in the New Theory._—Moreover, these mistakes involve -those who make them in a series of inextricable contradictions. Here, -for example, is life; it is found, they say, in three forms:—Life -manifested, or condition 1º; latent life, or condition 3º. So far -this is the classical theory; but they add a condition 2º, which -is what might be called _pathological or incomplete life_. This -is defined by the following characteristic:—That its functional -phenomena are identical with those in the first form, but that they -are not accompanied by assimilation and by protoplasmic growth, But -since, they say, growth is the chemical consequence of the functional -activity, since it is so to speak its metabolic aspect, since it is -confused with it, and inseparable from it, by the argument—then it is -contradictory and logically absurd to speak of condition 2º. It would -be acknowledging in the case of the anucleated merozoite, for example, -a functional activity unaccompanied by assimilation, yet identical -with the functional activity which is accompanied by assimilation in -the nucleated merozoite. The general movement, that of the cilia, the -taking of food, the evacuation of the fæces, the contraction of the -pulsatile vacuoles, are the same. And this fact is the best proof that -this vital functional activity (with the organic destruction which is -its energetic source) must be distinguished from the assimilation which -usually follows it, and which in exceptional cases may not follow it. - -We shall carry this discussion no farther. We have examined at some -length Le Dantec’s views, and we have contrasted them with the doctrine -which has been current in general physiology since the time of -Claude Bernard, and this comparison does not turn out quite to their -advantage. It was inevitable that the experimental and realistic spirit -which inspired the doctrine of the celebrated physiologist made his -work really too systematic. His formula, “life is death,” and the form -he gave his ideas, are not always irreproachably correct. They lend -themselves at times to criticism. Sometimes they require commentary. -These are errors of detail which Le Dantec has summarized somewhat -roughly. There is no necessity to do this in his own case. We pay our -tribute to the clearness of his language, although we believe the -foundations of his system are false and ill-founded. Their rigour is -purely verbal. Their external qualities, their careful arrangement -are well adapted to the seduction of the systematic mind prepared -by mathematical teaching. This new theory of life is presented with -pedagogic talent of the highest order. We think we have shown that the -foundations are entirely fallacious, in particular the following:—Vital -condition No. 2º; the confusion between functional activity and -assimilating synthesis; the so-called absolute connection between -morphogeny and chemical composition; the fundamental distinction -between elementary life and individual life. - - - § 4. CHARACTERISTICS OF NUTRITION. - - -_Definition of Nutrition._—As we have just seen, the organism is the -scene of chemical reactions of two kinds, the one destructive and -simplifying, the other synthetic, constructive, or assimilating. This -totality of reactions constitutes nutrition. Hence the two phases -that it is convenient to consider in this function—_assimilation_ and -_disassimilation_. This twofold chemical movement or _metabolism_ -corresponding to the two categories of vital phenomena, of destruction -(catabolism) and of synthesis (anabolism) is therefore the chemical -sign of vitality in all its forms. But it is clear that disassimilation -or organic destruction, which is destined to furnish energy to the -organism for its different operations, reappears in the plan of the -general phenomena of nature. It is not specifically vital in its -principle. Assimilation, on the other hand, is in this respect much -more characteristic. - -To some physiologists nutrition is only assimilation. Of the two -aspects of metabolism they consider only one, the most typical, -_Ad-similare_, to assimilate, to restore the substance borrowed -from the ambient medium, the alimentary substances, _similar_ to -living matter, to make living matter of them, to increase active -protoplasm—this is indeed the most striking phenomenon of vitality. -To grow, to increase, to expand, to invade, is the law of living -matter. Assimilation, nutrition in its essentials, is, according to -the definition of Ch. Robin, “the production by the living being of a -substance identical with its own.” It is the act by which the living -matter, the protoplasm of a given being, is created. - -_Permanence in Nutrition._—Nutrition presents one quite remarkable -character—permanence. It is a vital manifestation, a property if -we look at it in the cell, in the living substance, a function if -we consider it in the animal or in the plant as a whole, which is -never arrested. Its suspension involves _ipso facto_ the suspension -of life itself. It is, in the words of Claude Bernard, that property -of nutrition “which, as long as it exists in an element, compels us -to believe that this element is alive, and which, when it is absent, -compels us to believe that it is dead. It dominates all others by its -generality and its importance. In a word, it is the absolute test of -vitality.” - -_Biological Energetics shows the Importance of Nutrition._—We have -indicated in advance the reason of its importance, showing that its two -phases, disassimilation and assimilation, are the energetic condition -of the two kinds of vital phenomena which we can distinguish. - -Nutrition is a manufacture of protoplasm at the expense of the -materials of the cellular ambient medium, which are assimilated—_i.e._, -made chemically and physically similar to living matter and to the -reserves it stores up. This operation, which is peculiarly chemical, -is therefore indicated by the borrowing of materials from the external -world, a borrowing which is always going on, because the operation is -permanent, and, let me add, because of the continual rejection of the -waste products of this manufacture. Our formula is:—Nutrition is a -chemistry which persists. - -_The Idea of the Vital Vortex is Erroneous._—Here the effect has hidden -the cause from the eyes of the biologists. They have been struck by -the incessant entry and exit, by the never-ceasing passage, by the -_cycle_ of matter through the living being without guessing its why -and wherefore; and they have taken as a picture of the living being a -vortex in which the essential form is maintained while the matter, -which is accessory, flows on without a check. This is Cuvier’s _vital -vortex_. But for what purpose is this circulating matter used? They -thought that it was employed entirely for the reconstitution of the -living substance, continually and inevitably destroyed by the vital -Minotaur. - -_Destruction of Reserve-stuff_.—Here again there is a mistake. Really -living substance is but little destroyed, and consequently requires -very little renewal by the functional activity of the animal machine. -Its metabolism—destruction and renewal—is in every case infinitely less -than is supposed in the classical image of the vital vortex. It is -the merit of physiologists, and particularly of Pflüger and Chauveau, -to have worked for nearly forty years to establish this truth. They -have proved it, at least as far as the muscular tissue is concerned. -Protoplasm, properly so-called, is only destroyed as the organs of a -steam engine are destroyed—its tubes, its boiler, its furnace. And -it matters little. We know that such an engine uses much coal, and -we know very little of its machinery and its metallic frame. And so -it is with the cell, the living machine. A very small portion of the -food introduced will be assimilated in the living substance. By far -the greater part of it is destined to be worked up by the protoplasm -and placed in reserve under the form of glycogen, albumen, and fat, -etc.—_i.e._, compounds which are not the really living substance, the -hereditary protoplasm, but the products of its industry, just as they -are or may be the products of the industry of the chemist working in -his laboratory. They will be expended for the purpose of furnishing -the necessary energy to the vital functional activity, muscular -contraction, secretion, heat, etc., just as coal is expended to set -the steam engine going. The proof as far as the muscle is concerned -does not stand alone. There are other examples. In particular, -micrographic physiologists who have studied nervous phenomena say -that the anatomical elements of the brain last indefinitely, and that -they continue as they are, without renewal from birth to death. The -permanence of the consciousness, be it said in passing, is connected by -them with the permanence of the cerebral element (Marinesco). - -Thus destruction is very restricted. There is only a very slight -disassimilation of the living matter, properly so-called, in the course -of the vital functional activity. We may even go farther than this -experimental fact. This is what Le Dantec has done when he claims that -there is even an assimilation, an increase of the protoplasm. Strictly -speaking, this is possible, but there is no certain proof of it; and -in any case we cannot agree with him when he affirms that the increase -is the _direct result_ of the functional activity and blends with -it in one single, unique operation. We must, on the contrary, agree -with Claude Bernard that it is only a _consequence_ of it, that it -is produced in consequence of the existence of a bond of correlation -between organic destruction and assimilating synthesis. - -Why is there this bond? That is easily understood if we reflect that -the assimilating synthesis, an operation of endothermic, chemical -complexity, naturally requires an exothermic counterpart, the organic -destruction which will set free this necessary energy. - -_Formative Assimilation of Reserve-stuff. Formative Assimilation of -Protoplasm._—It follows that there are in nutritive assimilation -itself two distinct acts. The one consisting of the manufacture -of reserve-stuff is the more obvious but the less specific; the -other, really essential, is assimilation properly so-called, the -reconstitution of the protoplasm. The former is indispensable to the -production of the most prominent acts of vitality—movement, secretion, -production of heat. If it is suspended, functional activity is -arrested. We get _apparent death_, or _latent life_. But if the real -assimilation is arrested, we have _real death_. - -According to this there would be a fundamental distinction between real -and apparent death. The former would be characterized by an _arrest -of the protoplasmic assimilation_ which is externally indicated by -no sign. On the other hand, apparent death would be characterized -by _the arrest of the formation and destruction of reserve-stuff_. -It would be externally manifested by two signs:—The suppression of -material exchanges with the medium (respiration, alimentation) and the -suppression of the functional acts (production of movement, of heat, of -electricity, of glandular excretion). - -Such would be the most expedient test for apparent or real death. The -question occurs in the case of grains of corn in Egyptian tombs, and -also of hibernating animals and reviviscent beings, and, in general, in -the case of what has been called the state of _latent life_. But from -the practical point of view it is extremely difficult to apply this -test and to decide if the phenomena which are arrested in the grain -at maturity, in Leeuwenhoek’s tardigrada,[18] and in the dried-up -Anguillulidæ[19] of Baker and Spallanzani, in the encysted colpoda[20] -that a drop of warm water will revive, in the animals exposed by E. -Yung and Pictet to a cold of more than a 100° C. below zero, are due -to the general arrest of the two forms of assimilation, or to the -arrest of the manufacture and utilization of reserve-stuff alone, or -finally, to the arrest of protoplasmic assimilation alone. The latter, -which is already very restricted in beings in a normal condition whose -growth is terminated, may fall to the lowest degree in the being which, -having no functional activity, is assimilating nothing. So that, to -cut the question short, the experimenter who measures the value of -the exchanges between the being and the medium has seldom to do more -than decide between little and nothing. Hence his perplexity. But if -experiment hesitates, theory affirms: it admits _a priori_ that the -movement of protoplasmic assimilation, an essential sign of vitality, -is neither checked nor renewed, but proceeds continuously. - - [18] Bear-animalcules, Sloth-animalcules. An order of Arachnida.—TR. - - [19] Minute thread worms, known as paste-eels and vinegar-eels.—TR. - - [20] Genus of Infusoria. Colpodea cucullus is found in infusions of - hay.—TR. - - -_Is Nutrition, the Assimilating Synthesis, interrupted?_—Nevertheless, -there are many reasons for suspending all judgment as to this -interpretation. It is questioned by most biologists. According to A. -Gautier, the preserved grain of corn and the dried up rotifera are not -really alive; they are like clocks in working order, ready to tell the -time, but awaiting in absolute repose the first vibration which will -set them going. As for the grain, it is the air, heat, and moisture -which supply the first impulse. In other words, the organization -proper to the manifestation of life remains, but there is no life. The -so-called arrested life is not a life. - -It must be said, however, that the majority of physiologists refuse -to accept this interpretation. They believe in an attenuation of the -nutritive synthesis and not in its complete destruction. They think -that this total suppression would be contrary to current ideas relative -to the perpetuity of the protoplasm and the limited duration of the -living element. The natural medium is variable, and even the mineral -cannot remain eternally fixed. Still less is perennity a property of -the living being. If ordinary life is for each individual of limited -duration, the arrested life must also be of limited duration. We cannot -believe that after an indefinitely prolonged sleep the grain of corn, -or the paste-eel, or the colpoda, emerging from their torpor can resume -their existence, like the Sleeping Beauty, at the point at which it -was interrupted, and thus pass with a bound, as it were, through the -centuries. - -In fact the maintenance of the vitality of grains of corn from the -Egyptian tombs and their aptitude to germinate after thousands of -years are only fables or the result of imposture. Maspero, in a letter -addressed to M. E. Griffon on the 15th July 1901, has clearly summed up -the situation by saying that the grains of corn bought from the fellahs -almost always germinate, but that this is never the case with those -that the experimenter himself takes from the tombs. - -To sum up, we must use the same language of nutrition and of life, -of their uninterrupted progress, of their continuity, of their -permanence, of their activity, and of their slackening. Living -matter is always growing, much or little, slowly or quickly, in its -reserve-stuff or in its protoplasm, for expenditure or accumulation. -This inevitability of growth defines it, characterizes it, and sums up -its activity. Development and the evolution of growth are consequences -or aspects of nutrition. - - - - -BOOK IV. - -THE LIFE OF MATTER. - - Summary: Chap. I. Universal life—Opinions of philosophers and - poets—Continuity between brute and living bodies—Origin of this - principle.—Chap. II. Origin of brute matter in living matter.—Chap. - III. Organization and chemical composition of brute and living - bodies.—Chap. IV. Evolution and transformation of brute and living - bodies.—Chap. V. Possession of a specific form—Living bodies and - crystals—Cicatrization.—Chap. VI. Nutrition in the living body - and in the crystal.—Chap. VII. Generation in brute and in living - bodies—Spontaneous generation. - - -_Apparent Differences between Living and Brute Bodies. The Two -Kingdoms._—It seems at first impossible that there should be any -essential similarity between an inanimate object and a living being. -What resemblance can be discovered between a stone, a lion, and an -oak? A comparison of the inert and immovable pebble with the leaping -animal, and with the plant extending its foliage gives an impression -of vivid contrast. Between the organic and the inorganic worlds there -seems to be an abyss. The first impressions we receive confirm this -view; superficial investigation furnishes arguments for it. There is -thus aroused in the mind of the child, and later in that of the man, a -sharply marked distinction between the natural objects of the mineral -kingdom on the one hand, and those of the two kingdoms of living beings -on the other. - -But a more intimate knowledge daily tends to throw doubt upon the -rigour or the absolute character of such a distinction. It shows that -brute matter can no longer be placed on one side and living beings on -the other. Scientists deliberately speak of “the life of matter,” which -seems to the average man a contradiction in terms. They discover in -certain classes of mineral bodies almost all the attributes of life. -They find in others fainter, but still recognizable indications of an -undeniable relationship. - -We propose to pass in review these analogies and resemblances, as has -already been done in a fairly complete manner by Leo Errera, C. E. -Guillaume, L. Bourdeau, Ed. Griffon, and others. We will consider the -fine researches of Rauber, of Ostwald, and of Tammann upon crystals -and crystalline germs—researches which are merely a continuation of -those of Pasteur and of Gernez. These show that crystalline bodies -are endowed with the principal attributes of living beings—_i.e._, -a rigorously defined form; an aptitude for acquiring it, and for -re-establishing it by repairing any mutilations that may be inflicted -upon it; nutritive growth at the expense of the mother liquor which -constitutes its culture medium; and, finally—a still more incredible -property—all the characteristics of reproduction by generation. Other -curious facts observed by skilful physicists—W. Roberts-Austen, W. -Spring, Stead, Osmond, Guillemin, Charpy, C. E. Guillaume—show that -the immutability even of bodies supposed to be the most rigid of all, -such as glass, the metals, steel, and brass, is apparent rather than -real. Beneath the surface of the metal that seems to us inert there -is a swarming population of molecules, displacing each other, moving -about, and arranging themselves so as to form definite figures, and -assuming forms adapted to the conditions of the environment. Sometimes -it is years before they arrive at the state of ultimate and final -equilibrium—which is that of eternal rest. - -However, in order to understand these facts and their interpretations, -it is necessary to pass in review the fundamental characteristics of -living beings. It will be shown that these very characteristics are -found in inanimate matter. - - - - - CHAPTER I. - - UNIVERSAL LIFE. OPINIONS OF PHILOSOPHERS AND POETS. - - § 1. Primitive beliefs; the ideas of poets.—§ 2. Opinions of - philosophers—Transition from brute to living bodies—The principle of - continuity: continuity by transition: continuity by summation—Ideas of - philosophers as to sensibility and consciousness in brute bodies—The - general principle of homogeneity—The principle of continuity as a - consequence of the principle of homogeneity. - - - § 1. PRIMITIVE BELIEFS. IDEAS OF THE POETS. - - -The teaching of science as to the analogies between brute bodies and -living bodies accords with the conceptions of the philosophers and -the fancies of the poets. The ancients held that all bodies in nature -were the constituent parts of a universal organism, the macrocosm, -which they compared to the human microcosm. They attributed to it a -principle of action, the _psyche_, analogous to the vital principle, -and this psyche directed phenomena; and also an intelligent principle, -the _nous_, analogous to the soul, and the _nous_ served for the -comprehension of phenomena. This universal life and this universal soul -played an important part in their metaphysical systems. - -It was the same with the poets. Their tendency has always been to -attribute life to Nature, so as to bring her into harmony with our -thoughts and feelings. They seek to discover the life or soul hidden in -the background of things. - - “Hark to the voices. Nothing is silent. - - Winds, waves, and flames, trees, reeds, and rocks - All live; all are instinct with soul.” - -After making proper allowance for emotional exaggeration, ought we -to consider these ideas as the prophetic divination of a truth which -science is only just beginning to dimly perceive? By no means. As -Renan has said, this universal animism, instead of being a product -of refined reflection, is merely a legacy from the most primitive of -mental processes, a residue of conceptions belonging to the childhood -of humanity. It recalls the time when men conceived of external things -only in terms of themselves; when they pictured each object of nature -as a living being. Thus, they personified the sky, the earth, the sea, -the mountains, the rivers, the fountains, and the fields. They likened -to animate voices the murmur of the forest:— - - “ ... The oak chides and the birch - Is whispering.... - And the beech murmurs.... - The willow’s shiver, soft and faint, sounds like a word. - The pine-tree utters mysterious moans.” - -For primitive man, as for the poet of all times, everything is alive, -and every sound is due to a being with feelings similar to our own. -The sighing of the breeze, the moan of the wave upon the shore, the -babbling of the brook, the roaring of the sea, and the pealing of the -thunder are nothing less than sad, joyous, or angry living voices. - -These impressions were embodied in ancient mythology, the graceful -beauty of which does not conceal its inadequacy. Then they passed -into philosophy and approached the realm of science. Thales believed -that all bodies in nature were animate and living. Origen considered -the stars as actual beings. Even Kepler himself attributed to the -celestial bodies an internal principle of action, which, it may be -said in passing, is contrary to the law of the inertia of matter, -which has been wrongly ascribed to him instead of to Galileo. The -terrestrial globe was, according to him, a huge animal, sensitive to -astral influences, frightened at the approach of the other planets, and -manifesting its terror by tempests, hurricanes, and earthquakes. The -wonderful flux and reflux of the ocean was its breathing. The earth had -its blood, its perspiration, its excretions; it also had its foods, -among which was the sea water which it absorbs by numerous channels. -It is only fair to add that at the end of his life Kepler retracted -these vague dreams, ascribing them to the influence of J. C. Scaliger. -He explained that by the soul of the celestial bodies he meant nothing -more than their motive force. - - - § 2. OPINION OF THE PHILOSOPHERS. - - -_Transition from Brute to Living Bodies._—The lowering of the barrier -between brute bodies and living bodies began with those philosophers -who introduced into the world the great principles of continuity and -evolution. - -_The Principle of Continuity._—First and foremost we must mention -Leibniz. According to the teaching of that illustrious philosopher, -as interpreted by M. Fouillée, “there is no inorganic kingdom, only -a great organic kingdom, of which mineral, vegetable, and animal -forms are the various developments.... Continuity exists everywhere -throughout the world; everywhere is life and organization. Nothing is -dead; life is universal.” It follows that there is no interruption -or break in the succession of natural phenomena; that everything is -gradually developed; and finally, that the origin of the organic being -must be sought in the inorganic. Life, properly so called, has not, -in fact, always existed on the surface of the globe. It appeared at a -certain geological epoch, in a purely inorganic medium, by reason of -favourable conditions. The doctrine of continuity compels us, however, -to admit that it pre-existed on the globe under some rudimentary form. - -The modern philosophers who are imbued with these principles, MM. -Fouillée, L. Bourdeau, and A. Sabatier, express themselves in similar -language. “Dead matter and living matter are not two absolutely -different entities, but represent two forms of the same matter, -differing only in degree, sometimes but slightly.” When it is only -a matter of degree, it cannot be held that these views are opposed. -Inequalities must not be interpreted as contrary attributes, as when -the untrained mind considers heat and cold as objective states, -qualitatively opposed to each other. - -_Continuity by Transition._—The argument which leads us to remove the -barrier between the two kingdoms, and to consider minerals as endowed -with a sort of rudimentary life, is the same as that which compels -us to admit that there is no fundamental difference between natural -phenomena. There are transitions between what lives and what does not, -between the animate being and the brute body. And in the same way there -are transitions between what thinks and what does not think, between -what is thought and what is not thought, between the conscious and -the unconscious. This idea of insensible transition, of a continuous -path between apparent antitheses, at first arouses an insuperable -opposition in minds not prepared for it by a long comparison of facts. -It is slowly realized, and finally is accepted by those who, in the -world of things, follow the infinity of gradations presented by natural -phenomena. The principle of continuity comes at last to constitute, -as one may say, a mental habit. Thus the man of science may be led, -like the philosopher, to entertain the idea of a rudimentary form of -life animating matter. He may, like the philosopher, be guided by -this idea; he may attribute _a priori_ to brute matter all the really -essential qualities of living beings. But this must be on the condition -that, assuming these properties to be common, he must afterwards -demonstrate them by means of observation and experiment. He must show -that molecules and atoms, far from being inert and dead masses, are in -reality active elements, endowed with a kind of inferior life, which -is manifested by all the transformations observed in brute matter, -by attractions and repulsions, by movements in response to external -stimuli, by variations of state and of equilibrium; and finally, by the -systematic methods according to which these elements group themselves, -conforming to those definite types of structure by means of which they -produce different species of chemical compounds. - -_Continuity by Summation._—The idea of summation leads by another path -to the same result. It is another form of the principle of continuity. -A sum total of effects, obscure and indistinct in themselves, produces -a phenomenon appreciable, perceptible, and distinct, apparently, -but not really, heterogeneous in its components. The manifestations -of atomic or molecular activity thus become manifestations of vital -activity. - -This is another consequence of the teaching of Leibniz. For, according -to his philosophical theory, individual consciousness, like individual -life, is the collective expression of a multitude of elementary lives -or consciousnesses. These elements are inappreciable because of their -low degree, and the real phenomenon is found in the sum, or rather -the _integral_, of all these insensible effects. The elementary -consciousnesses are harmonized, unified, integrated into a result that -becomes manifest, just as “the sounds of the waves, not one of which -would be heard if by itself, yet, when united together and perceived at -the same instant, become the resounding voice of the ocean.” - -_Ideas of the Philosophers as to Sensibility and Consciousness in -Brute Bodies._—The philosophers have gone still further in the way -of analogies, and have recognized in the play of the forces of brute -matter, particularly in the play of chemical forces, a mere rudiment -of the appetitions and tendencies that regulate, as they believe, the -functional activity of living beings—a trace, as it were, of their -sensibility. To them reactions of matter indicate the existence of a -kind of _hedonic consciousness_—_i.e._, a consciousness reduced simply -to a distinction between comfort and discomfort, a desire for good and -repulsion from evil, which they suppose to be the universal principle -of all activity. This was the view held by Empedocles in antiquity; -it was that of Diderot, of Cabanis, and, in general, of the modern -materialistic school, eager to find, even in the lowest representatives -of the inorganic world, the first traces of the vitality and -intellectual life which blossom out at the top of the scale in the -living world. - -Similar ideas are clearly seen in the early history of all natural -sciences. It was this same principle of appetition, or of love and of -repulsion or hate that, under the names of affinity, selection, and -incompatibility, was thought to direct the transformations of bodies -when chemistry first began; when Boerhaave, for example, compared -chemical combinations to voluntary and conscious alliances, in which -the respective elements, drawn together by sympathy, contracted -appropriate marriages. - -_General Principle of the Homogeneity of the Complex and its -Components._—The assimilation of brute bodies to living bodies, and -of the inorganic kingdom to the organic, was, in the mind of these -philosophers, the natural consequence of positing _a priori_ the -principles of continuity and evolution. There is, however, a principle -underlying these principles. This principle is not expressed explicitly -by the philosophers; it is not formulated in precise terms, but is more -or less unconsciously implied; it is everywhere applied. It, however, -may be clearly seen behind the apparatus of philosophical argument It -is the assertion that no arrangement or combination of elements can -put forth any new activity essentially different from the activities -of the elements of which it is composed. Man is living clay, say -Diderot and Cabanis; and, on the other hand, he is a thinking being. -_As it is impossible to produce that which thinks from that which -does not think_, the clay must possess a rudiment of thought. But is -there not another alternative? May not the new phenomenon, thought, -be the effect of the arrangement of this clay? If we exclude this -alternative, we must then consider arrangement and organization as -incapable of producing in arranged and organized matter a new property -different from that which it presented before such arrangement. Living -protoplasm, says another, is merely an assemblage of brute elements; -“these brute elements must therefore possess a rudiment of life.” This -is the same implied supposition which we have just considered; if life -is not the basis of each element, it cannot result from their simple -assemblage. - -Man and animals are combinations of atoms, says M. le Dantec. It is -more natural to admit that human consciousness is the result of the -elementary consciousness of the constituent atoms than to consider -it as resulting from construction by means of elements with no -consciousness. “Life,” says Haeckel, “is universal; we could not -conceive of its existence in certain aggregates of matter if it did not -belong to their constituent elements.” Here the postulate is almost -expressed. - -The argument is always the same; even the same words are used: -the fundamental hypothesis is the same; only it remains more or -less unexpressed, more or less unperceived. It may be stated as -follows:—Arrangement, assemblage, construction, and aggregation are -powerless to bring to light in the complex anything new and essentially -heterogeneous to what already exists in the elements. Reciprocally, -grouping reveals in a complex a property and character which is the -gradual development of an analogous property and character in the -elements. It is in this sense that there exists a collective soul in -crowds, the psychology of which has been discussed by M. G. Le Bon. In -the same way, many sociologists, adopting the views advanced by P. de -Lilienfeld in 1865, attribute to nations a formal individuality, after -the type of that possessed by each of their constituent members. M. -Izolet considers society as an organism, which he calls a “hyperzoan.” -Herbert Spencer has developed the comparison of the collective organism -with the individual organism, insisting on their resemblances and -differences. Th. Ribot has dwelt, in particular, on the resemblances. - -The postulate that we have clearly stated here is accepted by many as -an axiom. But it is not an axiom. When we say that there is nothing -in the complex that cannot be found in the parts, we think we are -expressing a self-evident truth; but we are, in fact, merely stating -an hypothesis. It is assumed that arrangement, aggregation, and -complicated and skilful grouping of elements can produce nothing really -new in the order of phenomena. And this is an assertion that requires -verification in each particular case. - -_The Principle of Continuity, a Consequence of the Preceding._—Let us -apply this principle to the beings in nature. All beings in nature are, -according to current ideas, arrangements, aggregates, or groupings of -the same universal matter, that is to say, of the same simple chemical -bodies. It results from the preceding postulate that their activities -can only differ in degree and form, and not fundamentally. There is -no essential difference of nature between the activities of various -categories of beings, no heterogeneity, no discontinuity. We may pass -from one to another without coming to an hiatus or impassable gulf. -The law of continuity thus appears as a simple consequence of the -fundamental postulate. And so it is with the law of evolution, for -evolution is merely continuity of action. - -Such are the origins of the philosophical doctrine which universalizes -life and extends it to all bodies in nature. - -It may be remarked that this doctrine is not confined to any particular -school or sect. Leibniz was by no means a materialist, and he endowed -his mundane elements, his _monads_, not only with a sort of life, but -even with a sort of soul. Father Boscovitch, Jesuit as he was, and -professor in the college of Rome, did not deny to his _indivisible -points_ a kind of inferior vitality. St. Thomas, too, the angelical -doctor, attributed, according to M. Gardair, to inanimate substances a -certain kind of activity, inborn inclinations, and a real appetition -towards certain acts. - - - - -CHAPTER II. - -ORIGIN OF BRUTE MATTER IN LIVING MATTER. - - Spontaneous generation: an episode in the history of the - globe—Verification of the identity between brute and living - matter—Slow identification—Rapid identification—Contrary - opinion—Hypothesis of cosmozoa; cosmic panspermia—Hypothesis of - pyrozoa. - - -There should be two ways of testing the doctrine of the essential -identity of brute and living matter—one slow and more laborious, the -other more rapid and decisive. - -_Identification of the Two Matters, Brute and Living._—The laborious -method, which we will be obliged to follow, consists in the attentive -examination of the various activities by which life is manifested, and -in finding more or less crude equivalents for them in all brute beings, -or in certain of them. - -_Rapid Verification. Spontaneous Generation._—The rapid and decisive -method, which, unhappily, is beyond our resources, would consist in -showing unquestionable, clearly marked life, the superior life, arising -from the kind of inferior life that is attributed to matter in general. -It would be necessary completely to construct in all its parts, by a -suitable combination of inorganic materials, a single living being, -even the humblest plant or the most rudimentary animal. This would -indeed be an irrefutable proof that the germs of all vital activity are -contained in the molecular activity of brute bodies, and that there is -nothing essential to the latter that is not found in the former. - -Unhappily this demonstration cannot be given. Science furnishes no -example of it, and we are forced to have recourse to the slow method. - -The question here involved is that of spontaneous generation. It is -well known that the ancients believed in spontaneous generation, -even for animals high in the scale of organization. According to Van -Helmont, mice could be born by some incomprehensible fermentation in -dirty linen mixed with wheat. Diodorus speaks of animal forms which -were seen to emerge, partly developed, from the mud of the Nile. -Aristotle believed in the spontaneous birth of certain fishes. This -belief, though rejected as to the higher forms, was for a long time -held with regard to the lower forms of animals, and to insects—such as -the bees which the shepherd of Virgil saw coming out from the flanks -of the dead bullock—flies engendered in putrefying meat, fruit worms -and intestinal worms; finally, with regard to infusoria and the most -rudimentary vegetables. The hypothesis of the spontaneous generation of -the living being at the expense of the materials of the ambient medium -has been successively driven from one classificatory group to another. -The history of the sciences of observation is also a history of the -confutation of this theory. Pasteur gave it the finishing stroke, when -he showed that the simplest microorganisms obeyed the general law which -declares that the living being is formed only by _filiation_—that is -to say, by the intervention of a pre-existing living organism. - -_Spontaneous Generation an Episode in the History of the Globe._—Though -we have been unable to effect spontaneous generation up to the present, -it has been referred by Haeckel to a more or less distant past, to -the time when the cooling of the globe, the solidification of its -crust, and the condensation of aqueous vapour upon its surface created -conditions compatible with the existence of living beings similar -to those with which we are acquainted. Lord Kelvin has fixed these -geological events as occurring from twenty to forty million years ago. -Then circumstances became propitious for the appearance of the first -organisms, whence were successively derived those which now people the -earth and the waters. - -Circumstances favourable to the appearance of the first beings -apparently occurred only in a far distant past; but most physiologists -admit that if we knew exactly these circumstances, and could reproduce -them, we might also expect to produce their effect—namely, the creation -of a living being, formed in all its parts, developed from the -inorganic kingdom. To all those who held this view the impotence of -experiment at the present time is purely temporary. It is comparable to -that of primitive men before the time of Prometheus; they, not knowing -how to produce fire, could only get it by transmitting it from one to -another. It is due to the inadequacy of our knowledge and the weakness -of our means; it does not contradict the possibility of the fact. - -_Contrary Opinion. Life did not Originate on our Globe._—But all -biologists do not share this opinion. Some, and not the least eminent, -hold it to be an established fact that it is impossible for life to -arise from a concurrence of inorganic materials and forces. This was -the opinion of Ferdinand Cohn, the great botanist; of H. Richter, the -Saxon physician, and of W. Preyer, a physiologist well known from his -remarkable researches in biological chemistry. According to these -scientists, life on the surface of the globe cannot have appeared as a -result of the reactions of brute matter and the forces that continue to -control it. - -According to F. Cohn and PI. Richter, life had no beginning on our -planet. It was transported to the earth from another world, from the -cosmic medium, under the form of cosmic germs, or _cosmozoa_, more -or less comparable to the living cells with which we are acquainted. -They may have made the journey either enclosed in meteorites, or -floating in space in the form of cosmic dust. The theory in question -has been presented in two forms:—_The Hypothesis of Meteoric Cosmozoa_, -by a French writer, the Count de Salles-Guyon; and that of _cosmic -panspermia_ brought forward in 1865 and 1872 by F. Cohn and H. Richter. - -_Hypothesis of the Cosmozoa._—The hypothesis of the cosmozoa, living -particles, protoplasmic germs emanating from other worlds and reaching -the earth by means of aerolites, is not so destitute of probability -as one might at first suppose. Lord Kelvin and Helmholtz gave it the -support of their high authority. Spectrum analysis shows in cometary -nebulæ the four or five lines characteristic of hydro-carbons. Cosmic -matter, therefore, contains compounds of carbon, substances that are -especially typical of organic chemistry. Besides, carbon and a sort -of humus have been found in several meteorites. To the objection -that these aerolites are heated while passing through our atmosphere, -Helmholtz replies that this elevation of temperature may be quite -superficial and may allow micro-organisms to subsist in their interior. -But other objections retain their force:—First, that of M. Verworn, who -considers the hypothesis of cosmic germs as inconsistent with the laws -of evolution; and that of L. Errera, who denies that the conditions -necessary for life exist in interplanetary bodies. - -_Hypothesis of Cosmic Panspermia._—Du Bois-Reymond has given the name -of _cosmic panspermia_ to a theory very similar to the preceding, -formulated by F. Cohn in 1872. The first living germs arrived on our -globe mingled with the cosmic dust that floats in space and falls -slowly to the surface of the earth. L. Errera observes that if they -escape by this gentle fall the dangerous heating of meteorites, they -still remain exposed to the action of the photic rays, which is -generally destructive to germs. - -_Hypothesis of Pyrozoa._—W. Preyer declined to accept this cosmic -transmigration of the simplest living beings, nor would he allow -the intervention of other worlds into the history of our own. Life, -according to him, must have existed from all time, even when the globe -was an incandescent mass. But it was not the same life as at present. -Vitality must have undergone many profound changes in the course of -ages. The _pyrozoa_, the first living beings, vulcanians, were very -different from the beings of the present day that are destroyed by -a slight elevation of temperature. No doubt this theory of pyrozoa, -proposed by W. Preyer in 1872, seems quite chimerical, and akin -to Kepler’s dreamy visions. But in a certain way it accords with -contemporary ideas concerning the life of _matter_. It is related -to them by the evolution which it implies in the materials of the -terrestrial globe. - -According to Preyer, primitive life existed in fire. Being igneous -masses in fusion, the pyrozoa lived after their own manner; their -vitality, slowly modified, assumed the form which it presents to-day. -Yet, in this profound transformation their number has not varied, and -the total quantity of life in the universe has remained unchanged. - -Here we recognize the ideas of Buffon. These cosmozoa, these pyrozoa, -have a singular resemblance to the _organic molecules_ of “live matter” -of the illustrious naturalist—distributed everywhere, indestructible, -and forming living structures by their concentration. - -But we must leave these scientific or philosophical theories, and come -to arguments based upon facts. - -It is in a spirit quite different from that of the poets, the -metaphysicians, and the more or less philosophical scientists that -the science of our days looks at the more or less obscure vitality of -inanimate bodies. It claims that we may recognize in them, in a more or -less rudimentary state, the action of the factors which intervene in -the case of living beings, the manifestation of the same fundamental -properties. - - - - -CHAPTER III. - -ORGANIZATION AND CHEMICAL COMPOSITION OF LIVING AND BRUTE MATTER. - - Laws of the organization and of the chemical composition of living - beings—Relative value of these laws; vital phenomena in crushed - protoplasm—Vital phenomena in brute bodies. - - -_Enumeration of the Principal Characters of Living Beings._—The -programme which we have just sketched compels us to look in the brute -being for the properties of living beings. What, then, are, in fact, -the characteristics of an authentic, complete, living being? What are -its fundamental properties? We have enumerated them above as follows:—A -certain chemical composition, which is that of living matter; a -structure or organization; a specific form; an evolution which has a -duration, that of life, and an end, death; a property of growth or -nutrition; a property of reproduction. Which of these characters counts -for most in the definition of life? Are they all equally necessary? If -some of them were wanting, would that justify the transference of a -being, who might possess the rest, from the animate world to that of -minerals? This is precisely the question that is under consideration. - -_Organization and Chemical Composition of Living Beings._—All that we -know concerning the constitution of living matter and its organization -is summed up in the laws of the _chemical unity_ and the _morphological -unity of living beings_ (v. Book III.). These laws seem to be a -legitimate generalization from all the facts observed. The first -states that the phenomena of life are manifested only in and through -living matter, protoplasm—_i.e._, in and through a substance which -has a certain chemical and physical composition. Chemically it is a -proteid complexus with a hexonic nucleus. Physically it shows a frothy -structure analogous to that resulting from the mixture of two granular, -immiscible liquids, of different viscosities. The second law states -that the phenomena of life can only be maintained in a protoplasm which -has the organization of the complete cell, with its cellular body and -nucleus. - -_Relative Value of these Laws. Exceptions._—What is the signification -of these laws of the chemical composition and organization of living -beings? Evidently that life in all its plenitude can only exist and be -perpetuated under their protection. If these laws were absolute, if -it were true that no life were possible but in and through albuminous -protoplasm, but in and through the cell, the problem of “the life of -matter” would be decided in the negative. - -May it not happen, however, that fragmentary and incomplete vital -manifestations, progressive traces of a true life, may occur under -different conditions; for example, in matter which is not protoplasm, -and in a body which has a structure differing from that of a cell—that -is to say, in a being which would be neither animal nor plant? We must -seek the answer to this question by an appeal to experiment. - -Without leaving the animal and vegetable kingdoms—_i.e._, real living -beings—we already see less rigour in the laws governing chemical -constitution and cellular organization. - -Experiments in merotomy—_i.e._, in amputation—carried out on the -nervous element by Waller, on infusoria by Brandt, Gruber, Balbiani, -Nussbaum, and Verworn, show us the necessity of the presence of the -cellular body and the nucleus—_i.e._, of the integrity of the cell. But -they also teach us that when that integrity no longer exists death does -not immediately follow. A part of the vital functions continues to be -performed in denucleated protoplasm, in a cell which is mutilated and -incomplete. - -_Vital Phenomena in Crushed Protoplasm._—It is true also that grinding -and crushing suppress the greater part of the functions of the cell. -But tests with pulps of various organs and with those of certain -yeasts also show that protoplasm, even though ground and disorganized, -cannot be considered as inert, and that it still exhibits many of its -characteristic phenomena; for example, the production of diastases, -the specific agents of vital chemistry. Finally, while we do not -know enough about the actions of which the secondary elements of -protoplasm—its granulations, its filaments—are capable, which this or -that method of destruction may bring to light, at least we know that -actions of this kind exist. - -To sum up, we are far from being able to deny that rudimentary, -isolated vital acts may be produced by the various bodies that result -from the dismemberment of protoplasm. The integrity of the cellular -organization, even the integrity of protoplasm itself, are therefore -not indispensable for these partial manifestations of vitality. - -Besides, biologists admit that there exist within the protoplasm -aliquot parts, elements of an inferior order, which possess special -activities. These secondary elements must have the principle of their -activity within themselves. Such are the _biophors_ to which Weismann -attributes the vital functions of the cell, nutrition, growth, and -multiplication. If there are biophors within the cell, we may imagine -them outside the cell, and since they carry within themselves the -principle of their activity they may exercise it in an independent -manner. Unhappily the biophors, and other constituent elements of -that kind, are purely hypothetical. They are like Darwin’s gemmules, -Altmann’s bioblasts, and the pangens of De Vries. They have no relation -to facts of observation and to real existence. - -_Vital Phenomena in Brute Bodies._—There is no doubt that certain -phenomena of vitality may occur outside of the cellular atmosphere. -And carrying this further, we may admit that they may be produced in -certain slightly organized bodies (crushed cells), and then in certain -unorganized bodies in certain brute beings. In every case it is certain -that effects are produced at any rate similar to those which are -characteristic of living matter. It is for observation and experiment -to decide as to the degree of similarity, and their verdict is that the -similarity is complete. The crystals and the crystalline germs studied -by Ostwald and Tammann are the seat of phenomena which are quite -comparable to those of vitality. - - - - - CHAPTER IV. - - EVOLUTION AND MUTABILITY OF LIVING MATTER AND BRUTE MATTER. - - Supposed immobility of brute bodies—Mobility and mutability of the - sidereal world.—§ 1. The movement of particles and molecules in brute - bodies—The internal movements of brute bodies—Kinetic conception of - molecular motion—Reality of the motion of particles—Comparison of the - activity of particles with vital activity.—§ 2. Brownian movement—Its - existence—Its character—Its independence of the nature of the bodies - and of the nature of the environment—Its indefinite duration—Its - independence of external conditions—The Brownian movement must be the - first stage of molecular motion.—§ 3. Motion of particles—Migration of - material particles—Migration under the action of weight; of diffusion; - of electrolysis; of mechanical pressure.—§ 4. Internal activity of - alloys—Their structure—Changes produced by deforming agencies—Slow - return to equilibrium—Residual effect—Effect of annealing; effect of - stretching—Nickel steel—Colour photography—Conclusion—Relations of the - environment to the living or brute matter. - - -One of the most remarkable characteristics of a living being is its -evolution. It undergoes a continuous change. It starts from something -very small; it assumes a configuration and grows; in most cases -it declines and disappears, having followed a course which may be -predicted—a sort of ideal trajectory. - -_Supposed Immobility of Brute Bodies._—It may be asked whether this -evolution, this directed mobility, is so exclusively a feature of the -living being as it appears, and if many brute bodies do not present -something analogous to it. We may answer in no uncertain tones. - -Bichat was wrong when he contrasted in this respect brute bodies with -living bodies. Vital properties, he said, are temporary; it is their -nature to be exhausted; in time they are used up in the same body. -Physical properties, on the contrary, are eternal. Brute bodies have -neither a beginning nor an inevitable end, neither age, nor evolution; -they remain as immutable as death, of which they are the image. - -_Mobility and Mutability of the Sidereal World._—This is not true, -in the first place, of the sidereal bodies. The ancients held the -sidereal world to be immutable and incorruptible. The doctrine of -the incorruptibility of the heavens prevailed up to the seventeenth -century. The observers who at that epoch directed towards the heavens -the first telescope, which Galileo had just invented, were struck with -astonishment at discovering a change in that celestial firmament which -they had hitherto believed incorruptible, and at perceiving a new star -that appeared in the constellation Ophiuchus. Such changes no longer -surprise us. The cosmogonic system of Laplace has become familiar to -all cultivated minds, and every one is accustomed to the idea of the -continual mobility and evolution of the celestial world. “The stars -have not always existed,” writes M. Faye; “they have had a period of -formation; they will likewise have a period of decline, followed by -final extinction.” - -Thus all the bodies of inanimate nature are not eternal and immutable; -the celestial bodies are eminently susceptible of evolution, slow -indeed with that we observe on the surface of our globe; but this -disproportion, corresponding to the immensity of time and of cosmic -spaces as compared with terrestrial measurements, should not mislead us -as to the fundamental analogy of the phenomena. - - - § 1. THE MOVEMENT OF PARTICLES AND MOLECULES IN BRUTE BODIES. - - -It is not only in celestial spaces that we must search for that -mobility of brute matter which imitates the mobility of living matter. -In order to find it we have only to look about us, or to inquire from -physicists and chemists. - -As far as geologists are concerned, M. le Dantec tells us somewhere of -one who divided minerals into _living rocks_—rocks capable of change -of structure, of evolution under the influence of atmospheric causes; -and _dead rocks_—rocks which, like clay, have found at the end of all -their changes a final state of repose. Jerome Cardan, a celebrated -scientist of the sixteenth century, at once mathematician, naturalist, -and physician, declared not only that stones live, but that they suffer -from disease, grow old, and die. The jewellers of the present day use -similar language of certain precious stones; the torquoise, for example. - -The alchemists carried these ideas to an extreme. It is not necessary -here to recall the past, to evoke the hermetic beliefs and the dreams -of the alchemists, who held that the different kinds of matter lived, -developed, and were transmuted into each other. - -I refer to precise and recent data, established by the most expert -investigators, and related by one of them, Charles Edward Guillaume, -some years ago, before the _Société helvétique des Sciences -naturelles_. These data show that determinate forms of matter may -live and die, in the sense that they may be slowly and continuously -modified, always in the same direction, until they have attained an -ultimate and definitive state of eternal repose. - -_The Internal Movements of Bodies._—Swift’s reply to an idle fellow who -spoke slightingly of work is well known. “In England,” said the author -of _Gulliver’s Travels_, “men work, women work, horses work, oxen work, -water works, fire works, and beer works; it is only the pig who does -nothing at all; he must, therefore, be the only gentleman in England.” -We know very well that English gentlemen also work. Indeed, everybody -and everything works. And the great wit was nearer right than he -supposed in comparing men and things in this respect. Everything is at -work; everything in nature strives and toils, at every stage, in every -degree. Immobility and repose in the case of natural things are usually -deceptive; the seeming quietude of matter is caused by our inability -to appreciate its internal movements. Because of their minuteness we -do not perceive the swarming particles that compose it, and which, -under the impassible surface of the bodies, oscillate, displace each -other, move to and fro, and group themselves into forms and positions -adapted to the conditions of the environment. In comparison with these -microscopic elements we are like Swift’s giant among the Lilliputians; -and this is far from being a sufficiently forcible comparison. - -_Kinetic Conception of Molecular Motion._—The idea of this peculiar -form of motion is by no means new to us. We were familiarized with -it in scientific theories during our school days. The atomic theory -teaches us that matter behaves, from a chemical point of view, as if it -were divided into molecules and atoms. The kinetic theory explains the -constitution of gases and the effects of heat by supposing that these -particles are endowed with movements of rotation and displacement. -The wave theory explains photic phenomena by supposing peculiar -vibratory movements in a special medium—the ether. But these are merely -hypotheses which are not at all necessary; they are the images of -things, not the things themselves. - -_Reality of the Motion of Particles._—Here there is no question of -hypotheses. This internal agitation, this interior labour, this -incessant activity of matter are positive facts, an objective reality. -It is true that when the chemical or mechanical equilibrium of bodies -is disturbed it is only restored more or less slowly. Sometimes days -and years are required before it is regained. Scarcely do they attain -this relative repose when they are again disturbed, for the environment -itself is not fixed; it experiences variations which react in their -turn upon the body under consideration; and it is only at the end of -these variations, at the end of their respective periods, that they -will attain together, in a universal uniformity, an eternal repose. - -We shall see that metallic alloys undergo continual physical and -chemical changes. They are always seeking a more or less elusive -equilibrium. Physicists in modern times have given their attention to -this internal activity of material bodies, to the pursuit of stability. -Wiedemann, Warburg, Tomlinson, MM. Duguet, Brillouin, Duhem, and -Bouasse have revived the old experimental researches of Coulomb and -Wertheim on the elasticity of bodies, the effects of pressures and -thrusts, the hammering, tempering, and annealing of metals. - -The internal activity manifested under these circumstances presents -quite remarkable characteristics which cannot but be compared to the -analogous phenomena presented by living bodies. Thus have arisen even -in physics, a figurative terminology, and metaphorical expressions -borrowed from biology. - -_Comparison of the Activity of Particles with Vital Activity._—Since -Lord Kelvin first spoke of the _fatigue_ of metals, or the _fatigue_ -of elasticity, Bose has shown in these same bodies the fatigue of -electrical contact. The term _accommodation_ has been employed in the -study of torsion, and according to Tomlinson for the very phenomena -which are the inverse of those of fatigue. The phenomena presented by -glass when acted on by an external force which slowly bends it, have -been called facts of adaptation. The manner in which a bar of steel -resists wire-drawing has been compared to _defensive_ processes against -threatened rupture. And M. C. E. Guillaume speaks somewhere of “the -heroic resistance of the bar of nickel-steel.” The term “defence” has -also been applied to the behaviour of chloride or iodide of silver when -exposed to light. - -There has been no hesitation in using the term “memory” concurrently -with that of hysteresis to designate the behaviour of bodies acted -on by magnetism or by certain mechanical forces. It is true that -M. H. Bouasse protests in the name of the physico-mathematicians -against the employment of these figurative expressions. But has he not -himself written “a twisted wire is a wound-up watch,” and elsewhere, -“the properties of bodies depend at every moment upon all anterior -modifications”? Does not this imply that they retain in some manner the -impression of their past evolution? Powerful deformative agencies leave -a trace of their action; they modify the body’s condition of molecular -aggregation, and some physicists go so far as to say that they even -modify its chemical constitution. With the exception of M. Duhem, the -disciples of the mechanical school who have studied elasticity admit -that the effect of an external force upon a body depends upon the -forces which have been previously acting on it, and not merely upon -those which are acting on it at the present moment. Its present state -cannot be anticipated, it is the recapitulation of preceding states. -The effect of a torsional force upon a new wire will be different from -that of the same force upon a wire previously subjected to torsions -and detorsions. It was with reference to actions of this kind that -Boltzmann, in 1876, declared that “a wire that has been twisted or -drawn out remembers for a certain time the deformations which it has -undergone.” This memory is obliterated and disappears after a certain -definite period. Here then, in a problem of static equilibrium, we find -introduced an unexpected factor—time. - -To sum up, it is the physicists themselves who have indicated the -correspondence between the condition of existence in many brute bodies -and that in many living bodies. It cannot be expected that these -analogies will in any way serve as explanations. We should rather -seek to derive the vital from the physical phenomenon. This is the -sole ambition of the physiologist. To derive the physical from the -vital phenomenon would be unreasonable. We do not attempt to do this -here. It is nevertheless true that analogies are of service, were it -only to shake the support which, from the time of Aristotle, has been -accorded to the division of the bodies of nature into _psuchia_ and -_apsuchia_—_i.e._, into living and brute bodies. - - - § 2. THE BROWNIAN MOVEMENT. - - -_The Existence of the Brownian Movement._—The simplest way of judging -of the working activity of matter is to observe it when the liberty of -the particles is not interfered with by the action of the neighbouring -particles. We approximate to this condition when we watch, through the -microscope, grains of dust suspended in a liquid, or globules of oil -suspended in water. Now what we see is well known to all microscopists. -If the granulations are sufficiently small, they seem to be never at -rest. They are animated by a kind of incessant tremor; we see the -phenomena called the “Brownian movement.” This movement has struck -all observers since the invention of the magnifying glass or simple -microscope. But the English botanist, Brown, in 1827, made it the -object of special research and gave it his name. The exact explanation -of it remained for a long time obscure. It was given in 1894 by M. -Gouy, the learned physicist of the Faculty of Lyons. - -The observer who for the first time looks through the microscope at -a drop of water from the river, from the sea, or from any ordinary -source—that is to say, water not specially purified—is struck with -surprise and admiration at the motion revealed to him. Infusoria, -microscopic articulata, and various micro-organisms people the -microscopic field, and animate it by their movements; but at the same -time all sorts of particles are also agitated, particles which cannot -be considered as living beings, and which are, in fact, nothing but -organic detritus, mineral dust, and debris of every description. Very -often the singular movements of these granulations, which simulate up -to a certain point those of living beings, have perplexed the observer -or led him to erroneous conclusions, and the bodies have been taken for -animalcules or for bacteria. - -_Characters of this Movement._—But it is as a rule quite easy to avoid -this confusion. The Brownian movement is a kind of oscillation, a -stationary, dancing to-and-fro movement. It is a Saint Vitus’s dance -on one and the same spot, and is thus distinguished from the movements -of displacement customary with animate beings. Each particle has its -own special dance. Each one acts on its own account, independently of -its neighbour. There is, however, in the execution of these individual -oscillations a kind of common and regular character which arises from -the fact that their amplitudes differ little from each other. The -largest particles are the slowest; when above four thousandths of a -millimetre in diameter, they almost cease to be mobile. The smallest -are the most active. When so small as to be barely visible in the -microscope, the movement is extremely rapid, and can only occasionally -be perceived. It is probable that it would be still more accelerated in -smaller objects; but the latter will always escape our observation. - -_Its Independence of the Nature of the Bodies and of the -Environment._—M. Gouy remarked that the movement depends neither on the -nature nor on the form of the particles. Even the nature of the liquid -has but little effect. Its degree of viscosity alone comes into play. -The movements are, indeed, more lively in alcohol or ether, which are -very mobile liquids; they are slow in sulphuric acid and in glycerine. -In water, a grain one two-thousandth of a millimetre in diameter -traverses, in a second, ten or twelve times its own length. - -The fact that the Brownian movement is seen in liquors which have been -boiled, in acids and in concentrated alkalies, in toxic solutions of -all degrees of temperature, shows conclusively that the phenomenon -has no vital significance; that it is in no way connected with vital -activity so called. - -_Its Indefinite Duration._—The most remarkable character of this -phenomenon is its permanence, its indefinite duration. The movement -never ceases, the particles never attain repose and equilibrium. -Granitic rocks contain quartz crystals which, at the moment of their -formation, include within a closed cavity a drop of water containing -a bubble of gas. These bubbles, contemporary with the Plutonian age -of the globe, have never since their formation ceased to manifest the -Brownian movement. - -_Its Independence of External Conditions._—What is the cause of this -eternal oscillation? Is it a tremor of the earth? No! M. Gouy saw the -Brownian movement far away from cities, where the mercurial mirror of -a seismoscope showed no subterranean vibration. It does not increase -when the vibrations occur and become quite appreciable. Neither is -it changed by variation in light, magnetism, or electric influences; -in a word, by any external occurrences. The result of observation -is to place before us the paradox of a phenomenon which is kept up -and indefinitely perpetuated in the interior of a body without known -external cause. - -_The Brownian Movement must be the First Stage of Molecular -Motion._—When we take in our hands a sheet of quartz containing a -gaseous inclusion, we seem to be holding a perfectly inert object. When -we have placed it upon the stage of the microscope, and have seen the -agitation of the bubble, we are convinced that this seeming inertia is -merely an illusion. - -Repose exists only because of our limited vision. We see the objects as -we see from afar a crowd of people. We perceive them only as a whole, -without being able to discern the individuals or their movements. -A visible object is, in the same way, a mass of particles. It is a -molecular crowd. It gives us the impression of an indivisible mass, of -a block in repose. - -But as soon as the lens brings us near to this crowd, as soon as the -microscope enlarges for us the minute elements of the brute body, -then they appear to us, and we perceive the continual agitation of -those elements which are less than four thousandths of a millimetre -in diameter. The smaller the particles under consideration, the more -lively are their movements. From this we infer that if we could -perceive molecules, whose probable dimensions are about one thousand -times less, their probable velocity would be, as required by the -kinetic theory, some hundreds of metres per second. In the case of -objects we can only just see, the Brownian velocity is only a few -thousandths of a millimetre per second. No doubt, concludes M. Gouy, -the particles that show this velocity are really enormous when compared -with true molecules. From this point of view the Brownian movement -is but the first degree, and a magnified picture of the molecular -vibrations assumed in the kinetic theory. - - - § 3. THE INTERNAL ACTIVITY OF BODIES. - - -_Migration of Material Particles._—In the Brownian movement we -take into account only very small, isolated masses, small free -fragments—_i.e._, material particles which are not hampered by their -relations to neighbouring particles. Any one but a physicist might -believe that in true solids endowed with cohesion and tenacity, in -which the molecules were bound one to the other, in which form and -volume are fixed, there could be no longer movements or changes. This -is a mistake. Physics teaches us the contrary, and, in late years -especially, has furnished us characteristic examples. There are real -migrations of material particles throughout solid bodies—migrations -of considerable extent. They are accomplished through the agency -of diverse forces acting externally—pressures, thrusts, torsions; -sometimes under the action of light, sometimes under the action of -electricity, sometimes under the influence of forces of diffusion. -The microscopic observation of alloys by H. and A. Lechatelier, J. -Hopkinson, Osmond, Charpy, J. R. Benoit; researches into their physical -and chemical properties by Calvert, Matthiessen, Riche, Roberts Austen, -Lodge, Laurie, and C. E. Guillaume; experiments on the electrolysis -of glass, and the curious results of Bose upon electrical contact of -metals, show in a striking manner the chemical and kinetic evolutions -which occur in the interior of bodies. - -_Migration under the Action of Weight._—An experiment by Obermeyer, -dating from 1877, furnishes a good example of the motions of solid -bodies through a hardened viscid mass, taking place under the influence -of weight. The black wax that shoemakers and boatbuilders use, is a -kind of resin extracted from the pine and other resinous trees, melted -in water, and separated from the more fluid part which rises from it. -Its colour is due to the lampblack produced by the combustion of straw -and fragments of bark. At an ordinary temperature it is a mass so hard -that it cannot always be easily scratched by the finger-nail; but if it -is left to itself in a receptacle, it finally yields, spreads out as -if it were a liquid, and conforms to the shape of the vessel. Suppose -we place within a cavity hollowed out of a piece of wood a portion of -this substance, and keep it there by means of a few pebbles, having -previously placed at the bottom of the cavity a few fragments of some -light substance, such as cork. The piece of wax is thus between a light -body below and a heavy body above. If we wait a few days, this order -is reversed—the wax has filled the cavity by conforming to it; the -cork has passed through the wax and appears on the surface, while the -stones are at the bottom. We have here the celebrated experiment of the -flask with the three elements, in which are seen the liquids mercury, -oil, and water superposed in the order of their density, but in this -case demonstrated with solid bodies. - -_Influence of Diffusion._—Diffusion, which disseminates liquids -throughout each other, may also cause solids to pass through other -solids. Of this W. Roberts Austen gave a convincing proof. This -ingenious physicist placed a little cylinder of lead upon a disc of -gold, and kept the whole at the temperature of boiling water. At this -temperature both metals are perfectly solid, for the melting point of -gold is 1,200° C., and of lead is 330°. Still, after this contact has -been prolonged for a month and a half, analysis shows that the gold has -become diffused through the top of the cylinder of lead. - -_Influence of Electrolysis._—Electrolysis offers another no less -remarkable means of transportation. By its means we may force metals, -such as sodium or lithium, through glass walls. The experiment may be -performed as indicated by M. Charles Guillaume. A glass bulb containing -mercury is placed in a bath of sodium amalgam, and a current is then -made to pass from within outward. After some time it can be shown that -the metal has penetrated the wall of the bulb, and has become dissolved -within it. - -_Influence of Mechanical Pressure._—Mechanical pressure is also capable -of causing one metal to pass into another. We need not recall the -well-known experiment of Cailletet, who, by employing considerable -pressure, caused mercury to sweat through a block of iron. In a more -simple manner W. Spring showed that a disc of copper could be welded -to a disc of tin by pressing them strongly one against the other. Up to -a certain distance from the surfaces of contact a real alloy is formed; -a layer of bronze of a certain thickness unites the two metals, and -this could not take place did not the particles of both metals mutually -interpenetrate. - - - § 4. INTERNAL ACTIVITY OF ALLOYS. - - -_Structure of Alloys._—Metallic alloys have a remarkable structure, -which is essentially mobile, and which we have only now begun to -understand by the aid of the microscope. Microscopical examination -justifies to a certain degree Coulomb’s conjecture. That illustrious -physicist explained the physical properties of metals by imagining them -to be formed of two kinds of elements—integral particles, to which -the metal owes its elastic properties, and a _cement_ which binds the -particles, and to which it owes its coherence. M. Brillouin has also -taken up this hypothesis of duality of structure. The metal is supposed -to be formed of very small, isolated, crystalline grains, embedded in -an almost continuous network of viscous matter. A more or less compact -mass surrounding more or less distinct crystals is the conception which -may be formed of an alloy. - -_Changes of Structure produced by Deforming Agencies._—It has been -shown that profound changes of crystalline structure can be produced -by various mechanical means, such as hammering, and the stretching -of metallic bars carried to the point of rupture. Some of these -changes are very slow, and it is only after months and years that -they are completed, and the metal attains the definite equilibrium -corresponding to the conditions to which it is exposed. Though there -may be discussions concerning the extent of the transformations to -which it is subjected, though some believe they affect the chemical -condition of the alloy, while others limit its power to physical -effects, it is nevertheless true—and this brings us back to our -subject—that the mass of these metals is at work, and that it only -slowly attains the phase of complete repose. - -_The Slow Re-establishment of Equilibrium. Residual Effect._—These -operations by which the physical characters of metals are changed, and -by which they are adapted to a variety of industrial needs—compression, -hammering, rolling, stretching, and torsion—have an immediate, very -apparent effect; but they have also a consecutive effect, slowly -produced, much less marked and less evident. This is the “residual -effect,” or “Nachwirkung” of the Germans. It is not without importance, -even in practical applications. - -Heat also creates a kind of _forced equilibrium_. This becomes but -slowly modified, so that a body may remain for a long time in a state -which is, however, not the most stable for the conditions under which -it is considered. The number of these bodies _not in equilibrium_ is as -great as that of the substances which have been exposed to fusion. All -the Plutonic rocks are in this condition. Glass presents a condition of -the same kind. Thermometers placed in melting ice do not always mark -the zero Centigrade. This displacement of the zero point falsifies all -records if care is not taken to correct it. The correction usually -requires prolonged observation. The theory of the displacement of the -thermometric zero is not entirely established; but we may suppose, -with the author of the _Traité de Thermométrie_, that in glass, as -in alloys, are to be found compounds which vary according to the -temperature. At each temperature glass tends to assume a determinate -composition and a corresponding state of equilibrium; but the previous -temperature to which it has been subjected clearly has an influence -on the rapidity with which it attains its state of repose. The effect -of variation is more marked when we observe glass of more complicated -composition. We can understand that those which contain comparable -quantities of the two alkalies, soda and potash, may be more subject to -these modifications than those having a more simple composition based -on a single alkali. - -_Effects of Annealing._—A piece of brass wire that has been drawn and -then heated is the scene of certain very remarkable internal changes, -and these have been only recently recognized. The violent treatment -of the metallic thread in forcing it through the hole in the die has -crushed the crystalline particles; the interior state of the wire is -that of broken crystals embedded in a granular mass. Heating changes -all that. The crystals separate, repair themselves, and are built -up again; they are then hard, geometrical bodies, in an amorphous, -relatively soft and plastic mass; their number keeps on increasing; -equilibrium is not established until the entire mass is crystallized. -We may imagine how many displacements, enormous when compared with -their dimensions, the molecules have to undergo when passing through -the resisting mass, and arranging themselves in definite places in the -crystalline structures. - -In the same way, too, in the manufacture of steel, the particles of -coal at first applied to the surface pass through the iron. - -This _faculty of molecular displacement_ enables the metal in some -cases to modify its state at one point or another. The use made of this -faculty under certain circumstances is very curious, greatly resembling -the adaptation of an animal to its environment, or the methods of -defence against agents that might destroy it. - -_Effect of Stretching. Hartmann’s Experiment._—When a cylindrical -rod of metal, held firmly at either end—a test-piece, as it is -called in metallurgy—is pulled sufficiently hard, it often elongates -considerably, part of the elongation disappearing as soon as the strain -ceases, and the other part remaining. The total elongation is thus the -sum of an “elastic elongation,” which is temporary, and a “permanent -elongation.” If we continue the stretching, there appears at some point -of the rod a local extension with contraction of sectional area. It is -here that the rod will break. - -But in place of continuing the stretching, Mr. Hartmann suspends it. -He stops, as if to give the “metal-being” time to rally. During this -delay it would seem that the molecules hasten to the menaced point -to reinforce and harden the weak part. In fact the metal, which was -soft at other points, at this spot looks like tempered metal. It is no -longer extensible. - -When the experimenter begins the stretching again after this rest, and -after the narrowed bar has been rolled and become cylindrical again, -the local extension and sectional contraction is forced to occur at -another point. If another rest is given at this point the metal will -also become hardened. - -If we repeat the experiment a sufficient number of times, we shall find -a total transformation of the rod, which becomes hardened throughout -its entire extent. It will break rather than elongate if the stretching -is sufficiently severe. - -_Nickel Steels—their “Heroic” Resistance._—Nickel steels present this -phenomena in an exaggerated degree. The alternation of operations which -we have just described, bringing the various parts of an ordinary -steel rod into a tempered state, is not necessary with nickel steel. -The effect is produced in the course of a single trial. As soon as -there is any tendency to contraction the alloy hardens at that precise -place; the contraction is hardly noticeable; the movement is stopped at -this point to attack another weak point, stops there again and attacks -a third, and so on; and, finally, the paradoxical fact appears that -a rod of metal which was in a soft state and could be considerably -elongated has now become throughout its whole extent as hard, brittle, -and inextensible as tempered steel. It is in connection with this point -that M. C. E. Guillaume spoke of “heroic resistance to rupture.” It -would seem, in fact, as if the ferro-nickel bar had reinforced each -weak point as it was threatened. It is only at the end of these efforts -that the inevitable catastrophe occurs. - -_Effect of Temperature._—When the temperature changes, it is seen that -these ferro-nickel bars elongate or retract, modifying at the same time -their chemical constitution. But these effects, like those which occur -in the glass bulb of a thermometer, do not occur at once. They are -produced rapidly for one part, and more slowly for a small remaining -portion. Bars of ferro-nickel which have been kept at the same -temperature change gradually in length in the course of a year. Can -we find a better proof of internal activity occurring in a substance -differing so greatly from living matter? - -_Nature of the Activity of Particles._—These are examples of the -internal activity that occurs in brute bodies. Besides, these facts -that we are quoting merely to refute Bichat’s assertion relative to -the immutability of brute bodies, and to show us their activity, also -afford us another proof. They show that this activity, like that of -animals, wards off foreign intervention, and that this parrying of -the attack, again like that of animals, is adapted for the defence -and preservation of the brute mass. So that if we consider of special -importance the adaptative, teleological characteristic of vital -phenomena, a characteristic which is so easily made too much of in -biological interpretations, we may also find it again in the inanimate -world. To this end we may add to the preceding examples one more which -is no less remarkable. This is the famous case of Becquerel’s process -for colour-photography. - -_Colour-Photography._—A greyish plate, treated with chloride or iodide -of silver and exposed to a red light, rapidly becomes red. It is then -exposed to green light, and after passing through dull and obscure -tints it becomes green. To explain this remarkable phenomenon, we -cannot improve on the following statement:—The silver salt protects -itself against the light that threatens its existence; that light -causes it to pass through all kinds of stages of coloration before -reducing it; the salt stops at the stage which protects it best. It -stops at red, if it is red light that assails it, because in becoming -red by reflection it best repels that light—_i.e._, it absorbs it the -least. - -It may then be advantageous, for the comprehension of natural -phenomena, to regard the transformation of inanimate matter as -manifestations of a kind of internal life. - -_Conclusion. Relations of the Surrounding Medium to the Living Being -and the Brute Body._—Brute bodies, then, are not immutable any more -than are living bodies. Both depend on the medium that surrounds them, -and they depend upon it in the same way. Life brings together, brings -into conflict, an appropriate organism and a suitable environment. -Auguste Comte and Claude Bernard have taught us that vital phenomena -result from the reciprocal action of these two factors which are -in close correlation. It is also from the reciprocal action of the -environment and the brute body that inevitably result the phenomena -which that body presents. The living body is sometimes more sensitive -to variations of the ambient medium than is the brute body, but at -other times the reverse is the case. For example, there is no living -organism as impressionable to any kind of stimulus whatever as the -bolometer is to the slightest variations of temperature. - -There can only be, then, one chemically immutable body—namely, the atom -of a simple body, since, by its very definition, it remains unaltered -and intangible in combinations. This notion of an unalterable atom -has, however, itself been attacked by the doctrine of the ionization -of particles due to Sir J. J. Thomson; and besides, with very few -exceptions—those of cadmium, mercury, and the gases of the argon -series—the atoms of simple bodies cannot exist in a free state. - -Thus, as in the vital struggle, the ambient medium by means of -alimentation furnishes to the living being, whether whole or -fragmentary, the materials of its organization and the energies which -it brings into play. It also furnishes to brute bodies their materials -and their energies. - -It is also said that the ambient medium furnishes to the living being -a third class of things, the _stimuli_ of its activities—_i.e._, its -“provocation to action.” The protozoon finds in the aquatic environment -which is its habitat the stimuli which provoke it to move and to absorb -its food. The cells of the metazoon encounter in the same way in the -lymph, the blood, and the interstitial liquids which bathe them, the -shock, the stimulus which brings their energies into play. They do not -derive from themselves, by a mysterious spontaneity without parallel in -the rest of nature, the capricious principle which sets them in motion. - -Vital spontaneity, so readily accepted by persons ignorant of biology, -is disproved by the whole history of the science. Every vital -manifestation is a response to a stimulus, a provoked phenomenon. It -is unnecessary to say this is also the case with brute bodies, since -that is precisely the foundation of the great principle of the inertia -of matter. It is plain that it is also as applicable to living as to -inanimate matter. - - - - - CHAPTER V. - - SPECIFIC FORM. LIVING BODIES AND CRYSTALS. - - § 1. Specific form and chemical constitution—The wide distribution - of crystalline forms—Organization of crystals—Law of relation - between specific form and chemical constitution—Value of form as a - characteristic of brute and living beings—Parentage, living beings and - mineral parentage—Iso-morphism and the faculty of cross-breeding—Other - analogies. § 2. Acquisition and re-establishment of the specific - form—Mutilation and regeneration of crystals—Mechanism of reparation. - - -§ 1. _Specific Form and Chemical Constitution._—In the enumeration -which we have made of the essential features of vitality there are -three that are, so to speak, of the highest value. They are, in -the order of their importance:—The possession of a specific form; -the faculty of growth or nutrition; and finally, the faculty of -reproduction by generation. By restricting our comparison between -brute bodies and living bodies to these truly fundamental characters -we sensibly restrict the field, but we shall see that it does not -disappear. - -_Wide Distribution of Crystalline Forms._—The consideration of specific -forms shows us that in the mineral world we need only consider -crystallized bodies, as they are almost the only ones that possess -definite form. In restricting ourselves to this category we do not -limit our field as much as might be supposed. Crystalline forms are -very widely distributed. They are, in a measure, universal. Matter -has a decided tendency to assume these forms whenever the physical -forces which it obeys act with order and regularity, and when their -action is undisturbed by accidental occurrences. In the same way, too, -living forms are only possible in regulated environments, under normal -conditions, protected from cataclysms and convulsions of nature. - -The possession of a specific form is the most significant feature of -an organized being. Its tendency, from the time it begins to develop -from the germ, is toward the acquirement of that form. The progressive -manner in which it seeks to realize its architectural plan in spite of -the obstacles and difficulties that arise—healing its wounds, repairing -its mutilations—all this, in the eyes of the philosophical biologist, -forms what is perhaps the most striking characteristic of a living -being, that which best shows its unity and its individuality. This -property of organogenesis seems pre-eminently the vital property. It is -not so, however, for crystalline bodies possess it in an almost equal -degree. - -The parallel between the crystal and a living being has been often -drawn. I will not reproduce it here in detail. My sole desire, after -sketching its principal features, is to call attention to the new -information that has been brought out by recent investigations. - -_Organization of Crystals. Views of Haüy, Delafosse, Bravais, and of -Wallerant._—In botany, zoology, and crystallography we understand by -form an assemblage of material constituents co-ordinated in a definite -system—_i.e._, the organization itself. The body of man, for example, -is an edifice in which sixty trillion cells ought each to find its own -predetermined place. - -In crystallography also we understand by form the organization which -crystals present. The grouping of the elements of crystals is, perhaps, -more simple. They are none the less organized, in the same sense that -living bodies are. - -Their organization, while more uniform than that of living bodies, -still shows a considerable amount of variation. It should not be -assumed that the area of a crystal is completely filled, with -contiguous parts applied one to the other by plane faces, as might -be supposed from the phenomenon of cleavage which dissociates the -parts of the crystalline body into solids of this kind. In reality, -the constituent parts are separated from each other by spaces. They -are arranged in a quincunx, as Haüy put it, or along the lines of a -network, to use the terms of Delafosse and Bravais. The intervals left -between them are incomparably larger than their diameters. So that in -the organization of a crystal it is necessary to take into account two -quite different things:—An element, the crystalline particle, which -is a certain aggregate of chemical molecules having a determinate -geometrical form; and a more or less regular, parallelopipedic network, -along the edges of which are arranged in a constant and definite manner -the aforesaid particles. The external form of the crystal indicates the -existence of the network. Its optical properties depend upon the action -of the particles, as Wallerant has shown: Thus we must distinguish in -a crystal between two kinds of geometrical figures—that of the network -and that of the particle—and their characters of symmetry may be either -concordant or discordant. - -The crystalline particle, the element of the crystal, is therefore -a certain molecular complex that repeats itself identically and is -identically placed at the nodes of the parallelopipedic network. It has -been given different names well calculated to produce confusion-the -crystallographic molecule of Mallard, the complex particle of other -authors. Some have separated this element into subordinate elements -(the fundamental particles of Wallerant and of Lapparent). - -These very general outlines will suffice to show how complex and -adjustable is the organization of the crystalline individual, which in -spite of its geometric regularity and its rigidity, may be compared -with the still more flexible organization of the living element. The -mineral individual is more stable, more labile—_i.e._, less prone -to undergo change than is the living individual. We may say with -M. Lapparent that “crystallized matter presents the most perfect -and stable orderly arrangement of which the particles of bodies are -susceptible.” - -_Law of Relation of Specific Form to Chemical -Constitution._—Crystallization is a method of acquiring specific form. -The geometrical architecture of the mineral individual is but little -less wonderful or characteristic than that of the living individual. -Its form is the result of the mutual reactions of its substances and -of the medium in which it is produced; it is the condition of material -equilibrium corresponding to a given situation. This idea of a specific -form belonging to a given substance under given conditions must be -borne in mind. We may consider it as a kind of principle of nature, -an elementary law, which may serve as a point of departure for the -explanation of phenomena. A particular substance under identical -conditions of environment, must always assume a certain form. - -This close linking of substance and form, admitted as a postulate in -physical sciences, has been carried into biology by some philosophical -naturalists, by M. Le Dantec, for instance. - -Let us imitate them for a moment. Let us cease to seek in the living -being for the prototype of the crystal; let us, on the contrary, seek -in the crystal the prototype of the living being. If we succeed in -this, we shall then have found the physical basis of life. - -Let us say, then, with the biologists we have mentioned, that the -substance of each living being is peculiar to it; that it is specific, -and that its form—that is to say its organization—follows from it. -The morpholpgy of any being whatever, of an animal—of a setter, for -example—or even of a determinate being—of Peter, of Paul—is the -“crystalline form of their living matter.” It is the only form of -equilibrium that can be assumed under the given conditions by the -substance of the setter, of Peter, or of Paul, just as the cube is the -crystalline form of sea-salt. In this manner these biologists have -supposed that they could carry back the problem of living form to the -problem of living substance, and at the same time reduce the biological -mystery to the physical mystery. I have shown above (Chap. V. pp. -199-204) how far this idea is legitimate, and how far and with what -restrictions it may be welcomed and adopted. - -_Value of Form as a Characteristic of Living and Brute Beings._—However -this may be, we may say, without fear of exaggeration, that the -crystalline form characterizes the mineral with no less precision than -the anatomical form characterizes the animal and the plant. In both -cases, form—regarded as a method of distribution of the parts—indicates -the individual and allows us to diagnose it with more or less facility. - -_Parentage of Living Beings and Mineral Parentage._—Still another -analogy has been noted. In animals and plants similarity in form -indicates similarity in descent, community of origin, and proximity in -any scheme of classification. In the same way identity of crystalline -form indicates mineral relationship. Substances chemically analogous -show identical, geometrically superposable forms, and are thus arranged -in family or generic groups recognizable at a glance. - -_Isomorphism and the Faculty of Cross-breeding._—And further, the -possibility in the case of isomorphous bodies, of their replacing each -other in the same crystal during the process of formation and of thus -mingling, so to speak, their congenital elements, may be compared -with the possibility of inter-breeding with living beings of the same -species. Isomorphism is thus a kind of faculty of crossing. And as the -impossibility of crossing is the touchstone of taxonomic relationship, -testing it, and separating stocks that ought to be separated, so the -operation of crystallization is also a means of separating from an -accidental mixture of mineral species the pure forms which are blended -therein. Crystallization is the touchstone of the specific purity of -minerals; it is the great process in chemical purification. - -_Other Analogies._—The analogies between crystalline and living forms -have been pushed still further even to the verge of exaggeration. - -The internal and external symmetry of animals and plants has been -compared to that of crystals. Transitions or intergradations have been -sought between the rigid and faceted architecture of the latter and the -flexible structure and curved surface of the former; the utricular form -of flowers of sulphur on the one hand, and the geometrical structure -of the shells of radiolarians on the other, have shown an exchange of -typical forms between the two systems. An effort has even been made -to draw a parallel between six of the principal types of the animal -kingdom and the six crystalline systems. If carried as far as this, our -thesis becomes puerile. Real analogies will suffice. Among these the -curious facts of crystalline renewal come first. - - - § 2. CICATRIZATION IN LIVING BEINGS AND IN CRYSTALS. - - -We know that living beings not only possess a typical architecture -which they have themselves constructed, but that they defend it against -destructive agencies, and that if need arise they repair it. The -living organism cicatrizes its wounds, repairs losses of substance, -regenerates more or less perfectly the parts that have been removed; -in other terms, when it has been mutilated it tends to reconstruct -itself according to the laws of its own morphology. This phenomenon of -reconstitution or reintegration, these more or less successful efforts -to re-establish its form and its integrity, at first appear to be a -characteristic feature of living beings. This is not the case. - -_Mutilation and Re-integration of Crystals._—Crystals—let us say -crystalline individuals—show a similar aptitude for repairing their -mutilations. Pasteur, in an early work, discussed these curious facts. -Other experimenters, Gernez a little later and Rauber more recently, -took up the same subject, but could do no more than extend and confirm -his observations. Crystals are formed from a primitive nucleus, as the -animal is formed from an egg; their integral particles are disposed -according to efficient geometrical laws, so as to produce the typical -form by a constructive process that may be compared to the embryogenic -process which builds up the body of an animal. Now this operation -may be disturbed by accidents in the surrounding medium or by the -deliberate intervention of the experimenter. The crystal is then -mutilated. Pasteur saw that these mutilations repaired themselves. -“When,” said he, “a crystal from which a piece has been broken off -is replaced in the mother liquor, we see that while it increases in -every direction by a deposit of crystalline particles, activity occurs -at the place where it was broken off or deformed; and in a few hours -this suffices not only to build up the regular amount required for the -increase of all parts of the crystal, but to re-establish regularity -of form in the mutilated part.” In other words, the work of formation -of the crystal is carried on much more actively at the point of lesion -than it would have been had there been no lesion. The same thing would -have occurred with a living being. - -_Mechanism of Reparation._—Gernez some years later made known the -mechanism of this reparation, or, at least, its immediate cause. He -showed that on the injured surface the crystal becomes less soluble -than on the other facets. This is not, however, an exceptional -phenomenon. It is, on the contrary, quite frequently observed that the -different faces of a crystal show marked differences in solubility. -This is what happens in every case for the mutilated face in comparison -with the others; the matter is less soluble there. The consequence -of this is clear; the growth must preponderate on that face, since -there the mother liquor will become super-saturated before being -super-saturated for the others. We may explain this result in another -way. Each face of the crystal in contact with the mother liquor is -exposed to two antagonistic actions: The matter deposited upon a -surface may be taken away and redissolved if, for any reason whatever, -such matter becomes more soluble than that of the liquid stratum in -contact with it; in the second place, the matter of this liquid stratum -may, under contrary conditions, be deposited, and thus increase the -body of the crystal. There is, then, for each point of the crystalline -facet, a positive operation of deposit which results in a gain, and a -negative operation of redissolution which results in a loss. One or -the other effect predominates according as the relative solubility is -greater or less for the matter of the facet under consideration. On the -mutilated surface it is diminished, deposition then prevails. - -But this is only the immediate cause of the phenomenon; and if we wish -to know why the solubility has diminished on the mutilated surface -Ostwald explains it to us by showing that crystallization tends to form -a polyhedron in which the surface energy is a relative minimum. - - - - -CHAPTER VI. - -NUTRITION IN THE LIVING BEING AND IN THE CRYSTAL. - - Assimilation and growth in the crystal.—Methods of growth - in the crystal and in the living being; intussusception; - apposition.—Secondary and unimportant character of the process of - intussusception. - - -I have already stated (Chap. VI. p. 209) that nutrition may be -considered as the most characteristic and essential property of living -beings. Such beings are in a state of continual exchange with the -surrounding medium. They assimilate and dissimilate. By assimilation -the substance of their being increases at the expense of the -surrounding alimentary material, which is rendered similar to that of -the being itself. - -_Assimilation and Growth in the Crystal._—There exists in the crystal -a property analogous to nutrition, a kind of nutrility, which is -the rudiment of this fundamental property of living beings. The -development of a crystal starts from a primitive nucleus, the germ -of the crystalline individual that we will presently compare to -the ovum or embryo of a plant or an animal. Placed in a suitable -culture-medium—_i.e._, in a solution of the substance—this germ -develops. It assimilates the matter in solution, incorporates the -particles of it, and increases, preserving at the same time its form, -reproducing its specific type or a variety of it. Its growth proceeds -without interruption. The crystalline individual may attain quite a -large size if we know how to nourish it properly—we might say, to -fatten it. Very frequently, at a given time, a new particle of the -crystal serves in its turn as a primitive nucleus, and becomes the -point of departure for a new crystal engrafted upon the first. - -Taken from its mother liquor, placed where it cannot be nourished, -the crystal, arrested in its growth, falls into a condition of rest -not without analogy to that of a seed or of a reviviscent animal. Its -evolution is resumed with the return of favourable conditions—the bath -of soluble matter. - -The crystal is in a relation of continual exchange with the surrounding -medium which feeds it. These exchanges are regulated by the state of -this medium, or, more exactly, by the state of the liquid stratum -which is in immediate contact with the crystals. It loses or it gains -in substance if, for example, this layer becomes heated or cooled -more rapidly than the crystal. In a general way, it assimilates or -dissimilates according as its immediate environment is saturated or -diluted. Here, then, we have a kind of mobile equilibrium, comparable, -in some measure, to that of the living being. - -_Methods of Growth of the Crystal and of the Living Being. -Intussusception. Apposition._—In truth, there seems to be a complete -opposition between the crystal and the living being as regards -their manner of nutrition and growth. In the one case the method -is intussusception; in the other it is apposition. The crystalline -individual is all surface. Its mass is impenetrable to the nutritive -materials. Since only the surface is accessible, the incorporation of -similar particles is possible only by external juxtaposition, and the -edifice increases only because a new layer of stones has been added to -those which were there before. On the contrary, the body of an animal -is a mass essentially penetrable. The cellular elements that compose -it have more or less rounded and flexible forms. Their contact is by -no means perfect. They have neither the stiffness nor the precision -of adjustment that the crystalline particles have. Liquids and gases -can insinuate themselves from without and circulate within the meshes -of this loose construction. Assimilation can therefore take place -throughout its whole depth, and the edifice increases because each -stone is itself increasing. - -_The Secondary and Commonplace Character of the Process of -Intussusception._—The apparent opposition of these two processes is -doubtless diminished if we compare the simple mineral individual -with the elementary living unit, the crystalline particle with the -protoplasmic mass of a cell. Without carrying analysis so far as -this, it is yet easy to see that apposition and intussusception are -mechanical means that living beings employ at one and the same time and -combine according to their necessities. The hard parts of the internal -and external skeleton increase both by interposition and superposition, -at once. It is by the last method that bones increase in diameter, -and the shells of molluscs, the scales of reptiles and fishes, and -the testae of many radiate animals are formed. In these organs, as in -crystals, life and nutrition occur at the surface. - -Apposition and intussusception are then secondary, mechanical -arrangements having relation to the physical characters of the -body—solidity in the crystal, semi-fluidity in the cellular protoplasm. -If we compare the inorganic liquid matter with the semi-fluid organized -matter, we recognize that the addition of substance takes place in -the same manner in each—_i.e._, by interposition. If we add a soluble -salt to a fluid, the molecules of the salt separate themselves and -interpose themselves between those of the fluid. There is, therefore, -nothing especially mysterious or particularly vital about the process -of intussusception. Applied to fluid protoplasm, it is merely the -diffusion that ordinarily occurs in mixed liquids. - - - - -CHAPTER VII. - -GENERATION IN BRUTE BODIES AND LIVING BODIES. SPONTANEOUS GENERATION. - - Protoplasm a substance which continues—Case of the - crystal—Characteristics of generation in the living being—Property of - growth—Supposed to be confined to the living being—Fertilization of - micro-organisms—Fertilization of crystals—Sterilization of crystalline - and living media—Spontaneous generation of crystals—Metastable and - labile zones—Glycerine crystals—Possible extinction of a crystalline - species—Conclusion. - - -We have not yet exhausted the analogies between a crystal and the -living being. The possession of a specific form, the tendency to -re-establish it by redisintegration and the existence of a kind of -nutrition are not sufficient to constitute complete similarity. It -still lacks a fundamental character, that of generation. Chauffard -some time ago, in an attack which he made upon the physiological ideas -of his day, aptly exhibited this weak point. “Let us disregard,” -he said, “those interesting facts relative to the acquisition of a -typical form—facts that are common to the mineral world as well as -to living beings. It is none the less true that the crystalline type -is in no way derived from other pre-existing types, and that nothing -in crystallization recalls the actions of ascendants and the laws of -heredity.” - -This gap has since been filled. The work of Gernez, of Violette, of -Lecoq de Boisbaudran, the experiments of Ostwald and of Tammann, the -observations of Crookes and of Armstrong—all this series of researches, -so lucidly summarized by M. Leo Errera in his essays in botanical -philosophy, had for their result the establishment of an unsuspected -relation between the processes of crystallization and those of -generation in animals and plants. - -_Protoplasm is a Substance which Continues. The Case of the -Crystal._—Under present conditions a living being of any kind springs -from another living being similar to itself. - -Its protoplasm is always a continuation of the protoplasm of an -ancestor. It is an atavic substance of which we do not see the -beginning; we only see it continue. The anatomical element comes from a -preceding anatomical element, and the higher animal itself comes from -a pre-existing cell of the material organism, the ovum. The ladder of -filiation reaches back indefinitely into the past. - -We shall see that there is something analogous to this in certain -crystals. They are born of a preceding individual; they may be -considered as the posterity of the antecedent crystal. If we speak of -the matter of a crystal as the matter of a living being is spoken of, -in cases of this kind we would say that the crystalline substance is an -atavic substance of which we see only the continuation, as in the case -of protoplasm. - -_Characters of Generation in the Living Being._—Growth of the living -substance, and consequently of the being itself, is the fundamental -law of vitality. Generation is the necessary consequence of growth (p. -210). - -Living elements or cells cannot subsist indefinitely without increasing -and multiplying. The time must come when the cell divides, either -directly or indirectly; and then, instead of one cell, there are -two. This is the method of generation for the anatomical element. -In a complex individual it is a more or less restricted part of the -organism, usually a simple sexual cell, that takes on the formation -of the new being, and assures the perpetuity of the protoplasm, and -therefore of the species. - -_Property of Growth. Its Supposed Restriction to Living Beings._—At -first it would appear that nothing like this occurs in inanimate -nature. The physical machine, if we furnish it matter and energy, could -go on working indefinitely, without being compelled to increase and -reproduce. Here, then, there is an entirely new condition peculiar to -the organized being, a property well adapted, it would seem—and this -time without any possible doubt—for separating living matter from brute -matter. It is not so. - -It would not be impossible to imagine a system of chemical bodies -organized like the animal or vegetable economy, so that a destruction -would be compensated for by a growth. The only thing impossible is to -suppose, with M. le Dantec, a destruction that would at the same time -be an analysis. And an additional perplexity occurs when he supposes -that in the successive acts exchanges of material may occur. - -There is no necessity for making this impossible chemistry a -characteristic of the living being. The chemistry of the living being -is general chemistry. Lavoisier and Berthelot enforced this view. We -should not lose sight of the teachings of the masters. - -Let us return to generation, properly so called, and find in it the -characteristics of brute bodies and of crystals. - -_The Sowing of Micro-organisms._—When a microbiologist wishes to -propagate a species of micro-organisms, he places in a culture medium -a few individuals (one is all that is actually necessary), and soon -observes their rapid multiplication. Usually, if only the ordinary -microbes in atmospheric dust are wanted, the operator need not trouble -to charge the culture; if the culture tube remains open and the medium -is suitably chosen, some germ of a common species will fall in and the -liquid will become colonized. This has the appearance of spontaneous -generation. - -_The Sowing of Crystals._—Concentrated solutions of various substances, -supersaturated solutions of sodium magnesium sulphate, and sodium -chlorate are also wonderful culture media for certain mineral organic -units—certain crystalline germs. Ch. Dufour, experimenting with water -cooled below 0° C., its point of solidification; Ostwald, with salol -kept below 39°.5, its point of fusion; Tammann, with betol, which -melts at 96°; and, before them, Gernez, with melted phosphorus and -sulphur—all these physicists have shown that liquids in superfusion are -also media specially appropriate for the culture and propagation of -certain kinds of crystalline individuals. - -Some of these facts have become classic. Lowitz showed in 1785 that a -solution of sodium sulphate could be concentrated by evaporation so -as to contain more salt than was conformable with the temperature, -without, however, depositing the excess. But if a solid fragment, a -crystal of salt, is thrown into the liquor, the whole of the excess -immediately passes into the state of a crystallized mass. The first -crystal has engendered a second similar to itself; the latter has -engendered a third, and so on from one to the other. If we compare -this phenomenon with that of the rapid multiplication of a species of -microbes in a suitable culture medium, no difference will be perceived. -Or perhaps we may note one unimportant difference—the rapidity of -the propagation of the crystalline germs as opposed to the relative -slowness of the generation of the micro-organisms. - -Again, the propagation of crystallization in a supersaturated -or superfused liquid may be delayed by appropriate devices. The -crystalline individual gives birth, then, to another individual that -conforms to its own type, or even to varieties of that type when such -exist. Into the right branch of a U tube filled with sulphur in a state -of superfusion Gernez dropped octahedric crystals of sulphur, and into -the left branch prismatic crystals. On either side were produced new -crystals conforming to the type that had been sown. - -_Sterilization of Crystalline Media and Living Media._—Ostwald varied -these experiments by using salol. He melted the substance by heating -it above 39∙5°C.; then, protecting it from crystals of any kind, he -let the solution stand in a closed tube. The salol remained liquid -indefinitely—until it was touched with a platinum wire that had been -in contact with solid salol—_i.e._, until a crystalline germ was -introduced. But if the platinum wire has been previously sterilized by -passing it, as the bacteriologists do, through a flame, it can then be -introduced into the liquor with impunity. - -_The Dimensions of Crystalline Germs Comparable to those of -Microbes._—We may dilute the solid salol with inert powder—lactin, -for example—dilute the first mixture with a second, the second with a -third, and so on; then, throwing into the solution of surfused salol -a tenth of a milligram from one of these various mixtures, we find -that the production of crystals will not take place if the fragment -thrown in weighs less than a millionth of a milligram, or measures -less than ten thousandths of a millimetre in length. It would seem, -then, that these are the dimensions of the crystalline particle or -crystallographic molecule of salol. In the same way Ostwald satisfied -himself that the crystalline germ of hyposulphite of soda weighs -about a thousand-millionth of a milligram, and measures a thousandth -of a millimetre; that of chlorate of soda weighs a ten-millionth of -a milligram. These dimensions are entirely comparable with those of -microbes. - -All these phenomena have been studied with a detail into which it -is impossible to enter here, and which clearly shows more and more -intimate analogies between the formation of crystals and the generation -of micro-organisms. - -_Extension and Propagation of Crystallization. Optimum Temperature -of Incubation._—Crystallization which has commenced around a germ is -propagated more or less rapidly, and ends by invading the whole of the -liquor. - -The rapidity of this movement of extension depends upon the conditions -of the medium, especially upon its temperature. This is shown very -well by Tammann’s experiments with betol. This body, the salicylic -ester of naphthol, fuses at 96° C. If it is melted in tubes sealed -at a temperature of 100° C., it may be cooled to lower and lower -temperatures—to + 70°, to + 25°, to + 10°, to-5° without solidifying. -Let us suppose that by some combination of circumstances a few centres -of crystallization—that is to say, of crystalline germs—have appeared -in the solution. Solidification will extend slowly at the ordinary -temperature, at 20° to 25° and thereabouts. On the other hand, it will -be propagated with great rapidity if the liquor is kept at about 70°. -This point—70°—is the thermal optimum for the propagation of germs. -It is the most favourable temperature for what may be called their -incubation. As soon as the germs find themselves in a liquor at 70° -they increase, multiply, and show that they are in the best conditions -for growth. - -_Spontaneous Generation of Crystals. Optimum Temperature for the -Appearance of Germs._—If we consider various supersaturated solutions -or liquids in superfusion, we shall soon discover that they can be -arranged in two categories. Some remain indefinitely liquid under -given conditions unless a crystalline germ is introduced into them. -Others solidify spontaneously without artificial intervention, and such -crystallization may even be propagated very rapidly under determinate -conditions. This implies that these are conditions favouring the -spontaneous appearance of germs. - -This distinction between substances of crystalline generation by -filiation and substances of spontaneous crystalline generation is not -specific. The same substance may present the two methods of generation -according to the conditions in which it is placed. Betol furnishes a -good example of this. Liquefy it at 100° in a sealed tube and keep -it by means of a stove above 30°, and it will remain liquid almost -indefinitely. On the other hand, lower its temperature and leave it -for one or two minutes at 10°, and germs will appear in the liquor; -prolong the exposure to this degree of heat and the number of these -spontaneously appearing germs, appearing in isolation, will rapidly -increase. On the other hand, you will observe that propagation by -filiation—that is to say, by extension from one to another—is almost -absent. The temperature of 10° is not favourable to that method of -generation; and we have just seen, in fact, that it is at a temperature -of about 70° that extension of crystallization from one to another -is best accomplished. The temperature of 70° was the optimum for -propagation by filiation. Inversely, the temperature of 10° is the -optimum for spontaneous generation. Above and below this optimum the -action is slower. We may count the centres of crystallization, which -slowly extend further and further, as in a microbic culture one counts -the colonies corresponding to the germs primitively formed. To sum -up, if there is an optimum for the formation of crystals, there is a -different optimum for their rapid extension. - -_The Metastable and Labile Zones._—This phenomena is general. There -is for each substance a set of conditions (temperature, degree of -concentration, volume of the solution) in which the crystalline -individuals can be produced only by germs or by filiation. This is what -occurs for betol above the temperature of 30°. The body is then in what -Ostwald has called a _metastable_ zone. There is, however, for the same -body another set of circumstances more or less complete, in which its -gems appear simultaneously. This is what happens for betol at about the -temperature of 10°. These circumstances are those of the _labile zone_ -or zone of spontaneous generation. - -_Crystals of Glycerine._—We may go a step further. Let us suppose, with -L. Errera, that we have a liquid in a state of metastable equilibrium, -whose labile equilibrium is as yet unknown. This is what actually -occurs for a very widely known body, glycerine. We do not know under -what conditions glycerine crystallizes spontaneously. If we cool it, -it becomes viscous; we cannot obtain its crystals in that way. It was -not found in crystals until 1867. In that year, in a cask sent from -Vienna to London during winter, crystallised glycerine was found, -and Crookes showed these crystals to the Chemical Society of London. -What circumstances had determined their formation? We knew not then, -and we know not now. It may be observed that this case of spontaneous -generation of the crystals of glycerine has not remained the solitary -instance. M. Henninger has noted the accidental formation of glycerine -crystals in a manufactory in St. Denis. - -It may be remarked that this crystalline species appeared, as living -species may have done, at a given moment in an environment in which a -favourable chance combined the necessary conditions for its production. -It is also quite comparable to the creation of a living species; -for having once appeared we have been able to perpetuate it. The -crystalline individuals of 1867 have had a posterity. They have been -sown in glycerine in a state of superfusion, and there they reproduced -themselves. These generations have been sufficiently numerous to -spread the species throughout a great part of Europe. M. Hoogewerf -showed a great flask full to the Dutch biologists who met at Utrecht -in 1891. M. L. Errera presented others in June 1899, to the Society of -Medical and Natural Sciences at Brussels. To-day the great manufactory -of Sarg & Co., of Vienna, is engaged in their production on a large -scale for industrial purposes. - -Thus we are able to study this crystalline species of glycerine and to -determine with precision the conditions of its continued existence. It -has been shown that it does not resist a temperature of 18°, so that -if precautions were not taken to preserve it, a single summer would -suffice to annihilate all the crystalline individuals existing on the -surface of the globe, and thus the species would be extinguished. - -_Possible Extinction of a Crystalline Species._—As these crystals -melt at 18°, this temperature represents the point of fusion of solid -glycerine or the point of solidification of liquid glycerine. But the -liquor does not solidify at all if its temperature falls below 18° C., -as we well know, for it is at that temperature we use it. Nor does it -solidify at zero, nor even at 18° below zero; at 20°, for instance, it -merely thickens and becomes pasty. We only know glycerine, then, in a -state of superfusion, a fact which chemists have not learned without -amazement. Under these conditions, so analogous to the appearance of -a living species, to its unlimited propagation and to its extinction, -the mineral world offers a quite faithful counterpart to the animal -world. The living body illustrates here the history of the brute body -and facilitates its exposition. Inversely, the brute body in its -turn throws remarkable light on the subject of the living body, and -on one of the most serious problems relative to its origin, that of -spontaneous generation. - -_Conclusion._—These facts lead to one conclusion. Until the concourse -of propitious circumstances favourable to their spontaneous generation -was brought about, crystals were obtained only by filiation. Until the -discovery of electro-magnetism, magnets were made only by filiation, -by means of the simple or double application of a pre-existing magnet. -Before the discovery which fable attributes to Prometheus, every new -fire was produced only by means of a spark from a pre-existing fire. -We are at the same historical stage as regards the living world, -and that is why, up to the present, there has never been formed a -single particle of living matter except by filiation, except by the -intervention of a pre-existing living organism. - - - - -BOOK V. - -SENESCENCE AND DEATH. - - Chap. I. The different points of view from which death may - be regarded.—Chap. II. Constitution of the organisms—Partial - death—Collective death.—Chap. III. Physical and chemical - characteristics of cellular death—Necrobiosis.— Chap. IV. Apparent - perennity of complex individuals.—Chap. V. Immortality of the protozoa - and of slightly differentiated cells. - - -We grow old and we die. We see the beings which surround us grow old -and disappear. At first we see no exceptions to this inexorable law, -and we consider it as a universal and inevitable law of nature. But -is this generalization well founded? Is it true that no being can -escape the cruel fate of old age and death, to which we and all the -representatives of the higher animality are exposed? Or, on the other -hand, are any beings immortal? Biology answers that, in fact, some -beings are immortal. There are beings to whose life no law assigns a -limit, and they are the simplest, the least differentiated and the -least perfect. Death thus appears to be a singular privilege attached -to organic superiority, the ransom paid for a masterly complexity. -Above these elementary, monocellular, undifferentiated beings, -which are protected from mortality, we find others, higher in their -organization, which are exposed to it, but with whom death seems but -an accident, avoidable in principle if not in fact. The anatomical -elements of this higher animal are a case in point. Flourens once tried -to persuade us that the threshold of old age might be made to recede -considerably, and there are biologists in the present day who give us -some glimpse of a kind of vague immortality. We may, therefore, ask our -readers to follow us in our examination of these re-opened if not novel -questions, and we shall explain the views of contemporary physiology as -to the nature of death, its causes, its mechanisms, and its signs. - - - - -CHAPTER I. - -VARIOUS WAYS OF REGARDING DEATH. - - Different meanings of the word death—Physiological distinction between - elementary and general death—Non-scientific opinions—The ordinary - point of view—Medical point of view.—The signs of death are prognostic - signs. - - -_Different Meanings of the Word Death._—An English philosopher has -asserted that the word we translate by “cause” has no less than -sixty-four different meanings in Plato and forty-eight in Aristotle. -The word “death” has not so many meanings in modern languages, but -still it has many. Sometimes it indicates an action which is taking -place, the action of dying, and sometimes a state, the state which -succeeds the action of dying. The phenomena it connotes are in the eyes -of many biologists quite different, according as we watch them in an -animal of complex organization, or on the other hand, in monocellular -beings, protozoa and protophytes. - -_Physiological Distinction between Elementary Death and General -Death._—We distinguish the death of the anatomical elements, -_elementary death_, from the death of the individual regarded as -a whole, _general death_. Hence we recognize an _apparent death_, -which is an incomplete and temporary suspension of the phenomena of -vitality, and a _real death_, which is a final and total arrest of -these phenomena. When we consider it in its essential nature (assumed, -but not known) we look on it as the _contrary of life_, as did the -Encyclopædia, Cuvier, and Bichat; or we regard it with others either as -the consequence of life, or simply as the end of life. - -_Non-scientific Opinions._—What is death to those outside the realm of -science? First of all we find the consoling solution given by those -who believe death to be the commencement of another life. We next find -ourselves involved in a confused medley, an infinite diversity of -philosophical doubt and superstition. “A leap into the unknown,” says -one. “Dreamless and unconscious night,” says another. And again, “A -sleep which knows no waking.” Or, with Horace, “the eternal exile,” or -with Seneca, annihilation. _Post mortem nihil; ipsaque mors nihil._ - -The idea which is constantly supervening in the midst of this conflict -of opinion is that of the _breaking up_ of the elements, the union -of which forms the living being. It has, as we shall see, a real -foundation which may perhaps receive the support of science. We shall -not find that the best way of defining death is to say that it consists -of the “dissolution of the society formed by the anatomical elements, -or again, in the dissolution of the consciousness that the individual -possesses of himself—_i.e._, of the existence of this society.” It is -the rupture of the social bond. The old idea of dispersion is a variant -of the same notion. But the ancients evidently could not understand, -as we do, the nature of these elements which are associated to form -the living being, and which are liberated or dispersed by death. -We, as biologists, can see microscopical organic unity with a real -objective existence. The ancients were thinking of spiritual elements, -of principles, of entities. To the Romans, who may be said to have held -that there are three souls, death was produced by their separation -from the body. The first, the breath, the _spiritus_, mounting towards -celestial regions (_astra petit_); the second, the _shade_, regaining -on the surface of the earth and wandering around the tombs; the third, -the _manes_, descending to the lower regions. The belief of the Hindoos -was slightly different. The body returned to the earth, the breath to -the winds, the fire of the glance to the sun, and the ethereal soul to -the world of the pure. Such were the ideas of mortal dispersion formed -by ancient humanity. - -Modern science takes a more objective point of view. It asks by -what facts, by what observable events death is indicated. Generally -speaking, we may say that these facts interrupt an interior state of -things which was life and to which they put an end. Thus death is -defined by life. It is the cessation of the events and of the phenomena -which characterize life. We must, therefore, know what life is to -understand the meaning of death. How wise was Confucius when he said to -his disciple, Li-Kou:—“If we do not know life, how can we know death?” -According to biology there are two kinds of death because there are two -kinds of life; elementary life and death correspond just as general -life and death do, and this is where scientific opinion diverges from -commonly received opinion. - -What cares the man who reasons as most human beings do, about this life -of the anatomical elements of his body, the existence and the silent -activity of which are in no way revealed to him. What does their death -matter to him? To him there is but one poignant question, that of being -separated or not being separated from the society of his fellows. Death -is no longer to feel, no longer to think; it is the assurance that one -will never feel, one will never think again. Sleep, dreamless sleep, -is already in our eyes a kind of transient death; but, when we fall -asleep we are sure of waking again. There is no awaking from the sleep -of death. But that is not all. Man knows that death, this dreamless -sleep that knows no waking, will be followed by the dissolution of his -body. And what a dissolution will there be for the body, the object -of his continual care! Remember the description of Cuvier—the flesh -that passes from green to blue and from blue to black, the part which -flows away in putrid venom, the other part which evaporates in foul -emanations, and finally, the few ashes that remain, the tiny pinch of -minerals, saline or earthy, which are all that is left of that once -animated masterpiece. - -_The Popular View._—To the man afraid of death it seems, in the -presence of so great a catastrophe, that the patient analysis of the -physiologist scrupulously noting the succession of phenomena and -explaining their sequence is uninteresting. He will only attach the -slightest importance to knowing that vestiges of vitality remain in -this or that part of his body, if they do not re-establish in every -part the _status quo ante_. He cares not to hear that a certain time -after the formal declaration of his death his nails and his hair will -continue to grow, that his muscles will still have the useless faculty -of contraction, that every organ, every tissue, every element, will -oppose a more or less prolonged resistance to the invasion of death. - -_Medical View._—It is, however, these very facts and details, this -why and wherefore, which interest the physiologist. The state of -mind of the doctor in this respect, again, is different. When, for -instance, the doctor declares that such and such a person is dead, -he is really making not so much a statement of fact as a prediction. -How many elements are still living and will be capable of new birth -in this corpse that he has before his eyes? That is not what he asks -himself, nor is it what we should ask of him. He knows, besides, that -all these partial survivals will be extinguished and will never find -the conditions necessary to reviviscence, and that the organization -will never be restored to its primal activity; and this is what he -affirms. The fear of premature burial which haunts so many imaginations -is the fear of an error in the prediction. It is to avoid this that -practical medicine has devoted so much of its attention to the -discovery of a _certain_—and early—sign of death. By this we understand -the discovery of a _certain prognostic sign of general death_. We want -a prognostic sign enabling us to assert that the life of the brain is -now extinguished and will never be reanimated. And yet there are in -that organism many elements which are still alive. Many others even -may be born anew if we could give them suitable conditions which they -no longer meet with in the animal machine now thrown out of gear. -What finer example could we give than the experiment of Kuliabko, the -Russian physiologist, who kept a man’s heart working and beating for -eighteen hours after the official verification of his death. - - - - -CHAPTER II. - -THE PROCESS OF DEATH. - - Constitution of organisms.—Partial lives.—Collective life.—The - rôle of apparatus.—Death by lesion of the major apparatus.—The - vital tripod.—Solidarity of the anatomical elements.—Humoral - solidarity.—Nervous solidarity.—Independence and subordination of the - anatomical elements. - - -_Partial Lives._ _Collective Life._—With the exception of the -physiologist, no one, neither he who is ignorant nor he who is -intellectual, nor even the doctor, troubles his head about the life -or the death of the element, although this is the basis, the real -foundation, of the activity manifested by the social body and by its -different organs. The life of the individual, of the animal, depends -on these elementary partial lives just as the existence of the State -depends upon that of its citizens. To the physiologist, the organism -is a federation of cellular elements unified by close association. -Goethe compared them to a “multitude”; Kant to a “nation”; and others -have likened them to a populous city the anatomical elements of which -are the citizens, and which possesses an individuality of its own. So -that the activity of the federated organism may be discussed in each -of its parts, and then it is _elementary life_, or in its totality, -and then it is _general life_. Paracelsus and Bordeu had a glimpse -of this truth when they considered a life appropriate to each part -(_vita propria_) and a collective life, the life of the whole (_vita -communis_). In the same way we must distinguish the _elementary death_, -which is the cessation of the vital phenomena in the isolated cell, -from the _general death_, which is the disappearance of the phenomena -which characterised the collectivity, the totality, the federation, the -nation, the city, the whole in so far as it is a unit. - -These comparisons enable us to understand how general life depends on -the partial lives of each anatomical citizen. If all die, the nation, -the federation, the total being clearly ceases to exist. This city -has an enormous population—there are thirty trillion cellules in the -body of man; it is peopled with absolutely sedentary citizens, each -of which has its fixed place, which it never leaves, and in which -it lives and dies. It must possess a system of more or less perfect -arrangements to secure the material life of each inhabitant. All have -analogous requirements: they feed very much the same; they breathe in -the same way; each in fact has its profession, industry, talents, and -aptitudes by which it contributes to social life, and on which, in its -turn, it depends. But the process of alimentation is the same for all. -They must have water, nitrogenous materials and analogous ternaries; -the same mineral substances, and the same vital gas, oxygen. It is no -less necessary that the wastes and the egesta, very much alike in every -respect, should be carried off and borne away in discharges arranged so -as to free the whole system from the inconvenience, the unhealthiness, -and the danger of these residues. - -_Secondary Organization in Organs._—That is why, as we said above, the -secondary organizations of the economy exist:—the digestive apparatus -which prepares the food and enables it to pass into the blood, into the -lymph, and finally into the liquid medium which bathes each cell and -constitutes its real medium; the respiratory apparatus which imports -the oxygen and exports the gaseous excrement, carbonic acid; the heart -and the circulatory system which distributes through the system the -internal medium, suitably purified and recuperated. The organization -is dominated by the necessities of cellular life. This is the law of -the city, to which Claude Bernard has given the name of the _law of the -constitution of organisms_. - -_Death by Lesion of the Major Organs. Vital Tripod._—Thus we understand -what life is, and at the same time what is the death of a complex -living being. The city perishes if its more or less complicated -mechanisms which look after its revictualling and its discharge are -seriously affected at any point. The different groups may survive for -a more or less lengthy period, but progressively deprived of the means -of food or of discharge, they are finally involved in the general -ruin. If the heart stops, there is a universal famine; if the lungs -are seriously injured, we are asphyxiated; if the principal organ of -discharge, the kidney, ceases to perform its allotted task, there is a -general poisoning by the used-up and toxic materials retained in the -blood. - -We understand how the integrity of the major organs,—the heart, the -lungs, the kidney,—is indispensable to the maintenance of existence. We -understand that their lesion, by a series of successive repercussions, -involves universal death. We always die, said the doctors of old, -because of the failure of one of these three organs, the heart, the -lungs, or the brain. Life, they said in their inaccurate language, -depends upon these as upon three supports. Hence the idea of the _vital -tripod_. But it is not only this trio of organs which maintain the -organism; the kidney and the liver are no less important. In different -degrees each part exercises its action on the rest. Life is based in -reality on the immense multitude of living cells associated for the -formation of the body; on the thirty trillion anatomical elements, -each part is more or less necessary to all the rest, according as the -bond of solidarity is drawn more or less closely in the organism under -consideration. - -_Death and the Brain._—There are indeed more noble elements charged -with higher functions than the rest. These are the nervous elements. -Those of the brain preside over the higher functions of animality, -sensibility, voluntary movement, and the exercise of the intellect. The -rest of the nervous system forms an instrument of centralization which -establishes the relations of the parts one with the other and secures -their solidarity. When the brain is stricken and its functions cease, -man has lost the consciousness of his existence. Life seems to have -disappeared. We say of a man in this plight that he no longer lives, -thus confusing general life with the cerebral life which is its highest -manifestation. But the man or the animal without a brain lives what may -be called a vegetative life. The human anencephalic foetus lives for -some time, just as the foetus which is properly formed. Observation -always shows that this existence of the other parts of the body cannot -be sustained indefinitely in the absence of that of the brain. By a -series of impulses due to the solidarity of the grouping of the parts, -the injury received by the brain affects by repercussion the other -organs, and leads in the long run to the arrest of elementary life in -all the anatomical elements. The death of the whole is then complete. - -Doctors have therefore a two-fold reason for saying that the brain -may cause death. The death of the brain suppresses the highest -manifestation of life, and, in the second place, by a more or less -remote counter stroke, it suppresses life in all the rest of the system. - -_Death is a Process._—Besides, the fact is general. The death of one -part always involves the death of the rest—_i.e._, universal death. A -living organism cannot be at the same time alive and a cemetery. The -corpses cannot exist side by side with the living elements. The dead -contaminates the living, or in some other way involves it in its ruin. -Death is propagated; it is a progressive phenomenon which begins at one -point and gradually is extended to the whole. It has a beginning and a -duration. In other words, the death of a complex organism is a process. -And further, the end of a simple organism, of a protozoan, of a cell, -is itself a process infinitely more shortened. - -The very perfection of the organism is therefore the cause of its -fragility. It is the degree of solidarity of the parts one with another -which involves the one set in the catastrophe of the rest, just as in -a delicate piece of mechanism the derangement of a wheel brings nearer -and nearer the total breakdown. The important parts, the lungs, the -heart, the brain, suffer no serious alteration without the reflex being -felt throughout. But there are also wheels less evident, the integrity -of which is scarcely less necessary. - -_The Solidarity of the Anatomical Elements._—The cause of the mortal -process—_i.e._, of the extension and the propagation of an initial -destruction—is therefore to be found in the solidarity of the parts -of the organism. The closer it is the greater do the chances of -destruction become, for the accident which has happened to one will by -repercussions affect the others. - -Now the solidarity of the parts of the organism may be carried out in -two ways; there is a _humoral solidarity_ and a _nervous solidarity_. - -_Humoral Solidarity._—Humoral solidarity is realized by the mixture -of humours. All the liquids of the organism which have lodged in the -interstices of the elements and which soak the tissues, are in contact -and in relation of exchange one with another, and through the permeable -wall of the small vessels they are in relation with the blood and the -lymph. - -All the liquid atmospheres which surround the cells and form their -ambient medium have intercommunication. A change having taken place in -one cellular group, and therefore in the corresponding liquid, modifies -the medium of the further or nearer groups, and therefore these groups -themselves. - -_Nervous Solidarity._—But the real instrument of the solidarity of the -part is the nervous system. Thanks to it in the living machine the -component activities of the cellular multitude restrain and control -one another. Nervous solidarity makes of the complex being not a mob -of cells, but a connected system, an individual in which the parts are -subordinated to the whole and the whole to the parts; in which the -social organism has its rights just as the individual has his rights. -The whole secret of the vital functional activity of the complex -being is contained in these two factors:—the independence and the -subordination of the elementary lives. General life is the harmony of -the elementary lives, their symphony. - -_Independence and Subordination of the Anatomical Elements._—The -independence of the anatomical elements results from the fact that -they are the real depositaries of the vital properties, the really -active components. On the other hand the subordination of the parts -to the whole is the very condition of the preservation of form in -animals and plants. The architecture which is characteristic of -them, the morphological plan which they realize in their evolutive -development which they are ever preserving and repairing, form a -striking proof of this. This dependence in no way contradicts the -autonomy of the elements. For when with Claude Bernard and Virchow -we study the circumstances we see that the element accommodates -itself to the organic plan without violence to its nature. It behaves -in its natural place as it would behave elsewhere, if elsewhere it -were to meet around it the same liquid medium which at once is a -stimulant and a food. This at least is the conclusion we may draw from -experiments on transplanting, or on animal and vegetable grafting. -Neither the neighbouring elements, nor the whole system act on it at -a distance by a kind of mysterious induction, according to the ideas -of the vitalists, in order to regulate the activity of the element. -They contribute solely to the composition of the liquid atmosphere -which bathes it. They intervene in order to provide it with a -certain environment whose very characteristic physical and chemical -constitution regulates its activity. This constitution may be some day -imitated by the devices of experiment. When that result is achieved -the anatomical element will live in isolation exactly as it lives in -the organic association, and the mysterious bond which causes its -solidarity with the rest of the economy will become intelligible. In -fact, we may defer more or less the maturity of this prophecy, but -there is no doubt that we are daily nearing its fulfilment. - -The general life of the complex being is therefore the more or less -perfect synergy, the _ordered process_ of elementary lives. General -death is the destruction of these partial lives. The nervous system, -the instrument of this harmony of the parts, represents the social -bond. It keeps most of the partial elements under its sway, and is -thus the intermediary of their relations. The closer this dependence, -the higher the development of the nervous apparatus, and the better, -also, is assured the universal solidarity and therefore the unity of -the organism. Cellular federation assumes the characteristic of a -unique individuality in proportion to the development of this nervous -centralization. With an ideal perfect nervous system the correlation -of the parts would also attain perfection. As Cuvier said: “None could -experience change without a change in the rest.” - -But no animal possesses this extreme solidarity of the parts of the -living economy. It is a philosopher’s dream. It is the dream of Kant, -to whom the perfect organism would be “a teleological system,” a system -of reciprocal ends and means, a sum total of parts each existing for -and by the rest, for and by the whole. An organism so completely -connected would be unlikely to live. In fact, living organisms show -a little more freedom in the interplay of their parts. Their nervous -apparatus fortunately does not attain this imaginary perfection; their -unity is not so rigorous. The idea of individuality, of individual -existence, is therefore not absolute but relative. There are all -degrees of it according to the development of the nervous system. What -the man in the street and the doctor himself understand by death is the -situation created by the stopping of the general wheels, the brain, the -heart, and the lungs. If the breath leaves no trace on the glass held -to the mouth, if the beating of the heart is no longer perceptible by -the hand which touches or the ear which listens, if the movement and -the reaction of sensitiveness have ceased to be manifest, these signs -make us conclude that it is death. But this conclusion, as we have said -before, is a prognostic rather than a judgment of fact. It expresses -the belief that the subject will certainly die, and not that it is from -this moment dead. To the physiologist the subject is only on the way to -die. The process has started. The only real death is when the universal -death of all the elements has been consummated. - - - - -CHAPTER III. - -PHYSICAL AND CHEMICAL CHARACTERS OF CELLULAR DEATH. NECROBIOSIS. -GROWING OLD. - - Characteristic of elementary life—Changes produced by death in the - composition and the death of the cell—Schlemm; Loew; Bokorny; Pflüger; - A. Gautier; Duclaux—The processive character of death—Accidental - death—Necrobiosis—Atrophy—Degeneration—So-called natural - death—Senescence—Metchnikoff’s theory of senescence—Objections. - - -Elementary death is nothing but the suppression in the anatomical -elements of all the phenomena of vitality. - -_Characteristics of Elementary Life._—The characteristic features of -elementary life have been sufficiently fixed by science. First of -all, there is _morphological unity_. All the living elements have -an identical morphological composition. That is to say that life is -only accomplished and sustained in all its fulness in organic units -possessing the anatomical constitution of the cell, with its cytoplasm -and its nucleus, constituted on the classical type. In the second -place, there is _chemical unity_. The constituent matter, the matter of -which the cell is built up, diverges but little from a chemical type—a -proteid complex, with a hexonic nucleus, and from a physical model -which is an emulsion of granulous, immiscible liquids, of different -viscosities. The third character consists in the possession of a -_specific form_ acquired, preserved, and repaired by the element. -The fourth character, and perhaps the most essential of all, is _the -property of growth_ or _nutrition_ with its consequence, namely, a -relation of exchanges with the external medium, exchanges in which -oxygen plays considerable part. Finally, there is a last property, -that of _reproduction_, which in a certain measure is a necessary -consequence of the preceding,—_i.e._, of growth. - -These five vital characters of the elements are most in evidence -in cells living in isolation, in microscopical beings formed of a -single cell, protophytes and protozoa. But we find them also in -the associations formed by the cells among one another—_i.e._, in -ordinary plants and animals, multicellular complexes, called for this -reason metaphytes and metazoa. Free or associated, the anatomical -elements behave in the same way—feed, grow, breathe, digest in the -same manner. As a matter of fact, the grouping of the cells, the -relations, proximity and contiguity, which they assume, introduce -some variants into the expression of the common phenomena; but these -slight differences cannot disguise the essential community of the vital -processes. - -The majority of physiologists, following Claude Bernard, admit as -valent and convincing the proof that the illustrious experimenter -furnished of this unity of the vital processes. There are, however, a -few voices crying in the wilderness. M. Le Dantec is one. In his new -theory of life he amplifies and exalts the differences which exist -between the elementary life of the proteids and the associated life of -the metazoa. In them he can see nothing but contrasts and deviations. - -If this is elementary life, let us ask what is _elementary -death_—_i.e._, the death of the cell. And in this connection let us -ask the questions which we have to examine in the case of animals high -in organization, and of man himself. What are the characteristics -of elementary death? When the cell dies, is its death preceded by a -growing old or senescence? What are the preliminary signs and the -acknowledged symptoms? - -_Changes Produced by Death._—The state of death is only truly realized -when the fundamental properties of living matter enumerated above have -entirely disappeared. We must follow step by step this disappearance in -all the anatomical elements of the metazoan. - -Now the properties of the cell are connected with the physical and -chemical organization of living matter. For them to disappear entirely, -this organization must be destroyed as far as all that is essential in -it is concerned. We cannot admit with the vitalists that there is any -material difference between the dead and the living, and that only an -immaterial principle which has escaped into the air distinguishes the -corpse from the animated being. In fact, the external configuration may -be almost preserved, and the corpse may bear the aspect and the forms -of the preceding state. But this appearance is deceptive. Something in -reality has changed. The structure, the chemical composition of the -living substance, have undergone essential changes. What are these -changes? - -_Physical Changes._—Certain physiologists have endeavoured to determine -them. Klemm, a botanist, pointed out in 1895 the physical changes -which characterize the death of vegetable cells—loss of turgescence, -fragmentation of the protoplasm, the formation of granules, and the -appearance of vacuoles. - -_Chemical Changes._—O. Loew and Bokorny laid great stress in 1886 and -1896 on the chemical changes. The living protoplasm according to them -is an unstable proteid compound. A slight change would detach from the -albuminoid molecule a nucleus with the function of aldehyde, and at the -same time would transform an amido-group into an amido-group. This -would suffice for the transition of the protoplasm from the living to -the dead state. This theory is based on the fact that the compounds -which exercise a toxic action on the living cell, without acting -chemically on the dead albumin, are easily fixed by the aldehydes; and -on the fact that many of them, which attack simultaneously the living -albuminoids and the dead albumin, easily combine with the amido-group. - -E. Pflüger, a celebrated German scientist, has considered living matter -as an albumin spontaneously decomposable, the essential nucleus of -which is formed by cyanogen. Its active instability would be due to the -penetration into the molecule of the oxygen which fixes on the carbon -and separates it from the nitrogen. Armand Gautier has not confirmed -this view. Duclaux (1898) has stated that the difference between the -living and the dead albumin would be of a stereochemical order. - -_Progressive Character of Death. Accidental Death._—We have seen that -in general the disappearance of the characteristics of vitality is not -instantaneous, at least in the natural course of things, in complex -organisms. It is the end of a more or less rapid process. But death -is not instantaneous in the isolated anatomical element any more than -it is in the protozoan or protophyte. We must have recourse to very -violent devices of destruction to kill the cell at a blow, to leave -absolutely nothing of its organization existing. The protoplasm of -yeast when violently crushed by Büchner still possessed the power of -secreting soluble ferments. A powerful action, a very high temperature, -is necessary to obtain the result. _A fortiori_, the difficulty -increases in the case of complex organisms, all of whose living -elements cannot be attacked at the same moment by the destructive -cause. A mechanical action, capable of destroying at one blow all the -living parts of a complex being, of an animal, of a plant, must be of -almost inconceivable power. The blow of a Nasmyth hammer would not be -strong enough. - -The chemical alteration produced by a very toxic substance distributed -throughout the blood, and thus brought into contact with each element, -would produce a disorganization which, however rapid it were, could not -be called instantaneous. And the same holds good of physical agents. - -But these are not the processes of nature under normal circumstances. -They are accidents or devices. We shall leave on one side their -consideration and we shall only deal here with the natural processes of -the organism. - -Imagine it placed in a medium appropriate to its needs and following -out without intervening complications the evolution assigned to it by -its constitution. Experiment tells us that this natural evolution in -every case known to us ends in death. Death supervenes sooner or later. -For beings higher in organization, which we can bring into closer -and closer resemblance to man, we find that they die of disease, -by accident, or of old age. And as disease is an accident, we may -naturally ask if what we call old age is not also a disease. - -However that may be, the mortal process, being never instantaneous, has -a duration, a beginning, a development, an end—in a word, a history. -It constitutes an intermediary phase between perfect life and certain -death. - -_Necrobiosis._ _Atrophy._ _Degeneration._—The process according to -the circumstances may be shortened or prolonged. When death is the -result of violence events are precipitated. The physical and chemical -transformations of the living matter constitute a kind of acute -alteration called by Schultze and Virchow _necrobiosis_. According -to the pathologists, there are two kinds of _necrobiosis_:—that by -_destruction_, by _simple atrophy_, which causes the anatomical -elements to disappear gradually without undergoing appreciable -modifications; and _necrobiosis by degeneration_, which transforms the -protoplasm into fatty matter into calcareous matter, into granulations -(fatty degeneration, calcification, granulous degeneration). There is -no disagreement as to the causes of this necrobiosis. They are always -accidental; they originate in external circumstances:—the insufficiency -of the alimentary materials, of water, of oxygen; the presence in the -medium of real poisons destroying the organized matter; the violent -intervention of physical agents, heat, electricity; the reflex on the -composition of the cellular atmosphere of a violent attack on some -essential organ, the heart, the lungs, the kidneys. - -_Senescence._ _Old Age._—In a second category we must place the -mortal processes, slow in their movement, in which we cannot see the -intervention of clearly accidental and abnormal disturbing agents. -Death appears to be the termination of a breaking-up proceeding by -insensible degrees in consequence of the progressive accumulation -of very small inappreciable perturbations. This slow breaking up -is adequately expressed by the term—growing old, or senescence. -The alterations by which it is betrayed in the cell are especially -_atrophic_, but they are also accompanied, however, by different -forms of degeneration. An extremely important question arises on this -subject, and that is whether the phenomena of senility have their cause -in the cell itself, if they are inevitably found in its organization, -and therefore if old age and death are natural and necessary phenomena. -Or, on the other hand, should we consider them as due to a progressive -alteration of the medium, the character of which would be accidental -although frequent or habitual? This, in a word, is the problem which -has so often engaged the attention of philosophical biologists. Are old -age and death natural and inevitable phenomena? - -The recent experiments of Loeb and Calkins, and all similar -observations, tend to attribute to the phenomenon of growing old the -character of a remediable accident. But the remedy has not been found, -and the animal finally succumbs to these slow transformations of its -anatomical elements. We then say that it _dies of old age_. - -_Metchnikoff’s Theory of Senescence. Objections._—Metchnikoff has -proposed a theory of the mechanism of this general senescence. The -elements of the conjunctive tissue, phagocytes, macrophages, which -exist everywhere around the specialized and higher anatomical elements -would destroy and devour them as soon as their vitality diminishes, -and would take their place. In the brain, for example, it would be the -phagocytes which, attacking the nervous cellules, would disorganize the -higher elements, incapable of defending themselves. This substitution -of the conjunctive tissue, which only possesses vegetative properties -of a low order, for the nervous tissues, which possesses very high -vegetative properties, results in an evident breaking-up. The gross -element of violent and energetic vitality stifles the refined and -higher element. - -This expulsion is a very real fact. It constitutes what is called -senile sclerosis. But the active _rôle_ attributed to it by Metchnikoff -in the process of degeneration is not so certain. An expert observer -in the microscopic study of the nervous system, M. Marinesco, does not -accept this interpretation as far as the senescence of the elements of -the brain is concerned. Diminution of the cell, the decrease in the -number of its stainable granulations, chromatolysis, the formation of -inert, pigmented substances—all these phenomena which characterize the -breaking-up of the cerebral cells would be accomplished, according to -this observer, without the intervention of the conjunctive elements, -the phagocytes. - -The characteristic of extensive and progressive process presented -by death necessitates in a complex organism, which is a prey to it, -the existence side by side of living and dead cells. Similarly, in -the organism which is growing old, there are young elements and -elements of every age side by side with senile elements. As long as -the disorganization of the last has not gone too far, they may be -rejuvenated. All we have to do is to restore to them an appropriate -ambient medium. The whole question is one of knowing and being able -to realize, for this or that part which we wish to reanimate and to -rejuvenate, the very special or very delicate conditions that this -medium must fulfil. As we have said, success is attained in this -respect as far as the heart is concerned, and this is why we are able -to reanimate and to revive the heart of a dead man. It is hoped that -ideas along these lines will extend with the progress of physiology. - -After this sketch of the conditions and of the varieties of cellular -death we must return to the essential problem which is engaging the -curiosity of biologists and philosophers. Is death unavoidable, -inevitable? Is it the necessary consequence of life itself, the -inevitable issue, the inevitable end? - -There are two ways of endeavouring to solve this question of the -inevitability of death. The first is to examine popular observation, -practised, so to speak, unintelligently and without special -precautions. The second is to analyze everything we know relative to -the conditions of elementary life. - - - - -CHAPTER IV. - -THE APPARENT PERENNITY OF COMPLEX INDIVIDUALS. - - Millenary trees—Plants with a definite rhizome—Vegetables - reproduced by cuttings—Animal colonies—Destruction due to extrinsic - causes—Difficulty of interpretation. - - -Popular opinion teaches us that living beings have only a transient -existence, and as a poet has said: “Life is but a flash between two -dark nights.” But, on the other hand, simple observation shows us, or -appears to show us, beings whose duration of existence is far longer, -and practically illimitable. - -_Millenary Trees._—We know of trees of venerable antiquity. Among these -patriarchs of the vegetable world there is a chestnut tree on Mount -Etna which is ten centuries old, and an ivy in Scotland which is said -to be thirty centuries old. Trees of 5000 years old are not absolutely -unknown. We may mention among those of that age the famous dragon -tree[21] at Orotava, in the island of Teneriffe. Two other examples are -known in California—the pseudo-cedar, or _Tascodium_, at Sacramento, -and a _Sequoïa gigantea_. We know that the olive tree may live 700 -years. There are cedars 800 years old and oaks of the age of 1,500 -years. - - [21] Lately destroyed in a storm. [Tr.] - -_Plants with a Rhizome._—Vegetable species of almost unlimited -duration of life are known to botanists. Such, for instance, are plants -with a definite rhizome, such as colchicum. Autumnal colchicum has a -subterranean root, the bulb of which pushes out every year fresh axes -for a new bloom; and as each of these new axes stretches out an almost -constant length, a botanist once set himself the singular problem of -discovering how long it would take such a foot, if suitably directed, -to travel round the world. - -_Vegetables Reproduced by Cuttings._—Vegetables reproduced by slips -furnish another example of living beings of indefinite duration. The -weeping willows which adorn the banks of sheets of water in the parks -and gardens throughout the whole of Europe have sprung, directly or -indirectly, from slips of the first _Salix Babylonica_ introduced to -the West. May it not be said that they are the permanent fragments of -that one and the same willow? - -_Animal Colonies._—These examples, as well as those furnished to -zoologists by the consideration of the polypi which have produced by -their slow growth the reefs, or _atolls_, of the Polynesian seas, -do not, however, prove the perennity of living beings. The argument -is valueless, for it is founded upon a confusion. It turns on the -difficulty that biologists experience in defining the individual. The -oak and the polypus are not simple individuals, but associations of -individuals, or, to use Hegel’s expression, the nations of which we see -the successive generations. We give to this succession of generations -a unique existence, and our reasoning comes to this, that we confer on -each present citizen of this social body the antiquity which belongs to -the whole. - -_Destruction of the Social Individual due to Extrinsic Causes._—As -for the destruction, the death of this social individual, of this -hundred-year-old tree, it seems indeed that there is no ground for -considering it a natural necessity. We find the sufficient reason of -its usual end in the repercussion on the individual of external and -contingent circumstances. The cause of the death of a tree, of an oak -many centuries old, is to be found in the ambient conditions, and not -in some internal condition. Cold and heat, damp and dryness, the weight -of the snow, the mechanical action of the rain, of hail, of winds -unchained, of lightning; the ravages of insects and parasites—these are -what really work its ruin. And further, the new branches, appearing -every year and increasing the load the trunk has to bear, increase the -pressure of the parts, and make more difficult the motion of the sap. -But for these obstacles, external, so to speak, to the vegetable being -itself, it would continue indefinitely to bloom, to fructify, and as -each spring returned to show fresh buds. - -_Difficulty of Interpretation._—In this as in all other examples we -must know the nature of the beings that we see lasting on and braving -the centuries. Is it the individual? Is it the species? Is it a living -being, properly so called, having its unity and its individuality, -or is it a series of generations succeeding one another in time and -extending in space? In a word, the question is one of knowing if we -have to do with a real tree or with a genealogical tree. We are just -as uncertain when we deal with animals. What is the being that lasts -on—a series of generations or an individual? This doubt forbids us to -draw any conclusion from the observation of complex beings. We must -therefore return from them to the _elementary being_; and we must -examine it from the point of view of perennity or of vital decay. Let -us then ask the questions that we have already examined with reference -to animals high in organization and to man himself. Is the death of the -cell an inevitable characteristic? Are there any cells, protophytes, -protozoa, which are immortal? - - - - -CHAPTER V. - -THE IMMORTALITY OF THE PROTOZOA. - - Impossibility of life without evolution—Law of increase and - division—Immortality of the protozoa—Death, a phenomenon of adaptation - which has appeared in the course of the ages—The infusoria—The - death of the infusoria—Two kinds of reproduction—The caryogamic - rejuvenescence of Maupas—Calkins on rejuvenescence—Causes of - senescence—Impossibility of life without evolution. - - -We take into account, _a priori_, the conditions that must be fulfilled -by the monocellular being in order to escape the inevitability of -evolution, of the succession of ages, of old age, and of death. It must -be able indefinitely to maintain itself in a normal régime, without -changing, without increasing, maintaining its constant morphological -and chemical composition, in an environment vast enough for it to -be unaltered by the borrowings or the spendings resulting from its -nutrition—_i.e._, it must remain constant in the presence of the -constant being. We might conceive of a nutrition perfect enough, of -exchanges exact enough, and regular enough, for the state of things to -be indefinitely maintained. This would be absolute permanence realized -in the vital mobility. - -_The Law of Growth and Division._—This model of a perfect and -invariable machine does not exist in nature. Life is incompatible with -the absolute permanence of the dimensions and the forms of the living -organism. - -In a word, it is a rigorous law of living nature that the cell can -neither live indefinitely without growth, nor grow indefinitely without -division. - -Why is this so? Why is there this impossibility of a regular régime in -which the cell would be maintained in magnitude without diminution or -increase? Why has nutrition as a necessary consequence the growth of -the element? This is what we do not positively know. - -Things are so. It is an irreducible fact, peculiar to the protoplasm, a -characteristic of the living matter of the cell. It is the fundamental -basis of the property of generation. That is all we can say about it. -Real living beings have therefore inevitably an evolution. They are not -unchangeable. In its simple form this evolution consists in the fact -that the cell grows, divides, and diminishes by this division, begins -the upward march which ends in a new division. And so on. - -_Immortality of the Protozoa._—It may happen, and it does happen -in fact, that this series of acts is repeated indefinitely at any -rate unless an accidental cause should interrupt it. The animal thus -describes an indefinite curve, constituted by a series of indentations, -the highest point of which corresponds to the maximum of size, and the -lowest point to the diminution which succeeds the division. This state -of things has no inevitable end if the medium does not change. The -being is immortal. - -In fact, the compound beings of a single cell, protophytes and -protozoa, the algae and the unicellular mushrooms, at the minimum stage -of differentiation, escape the necessity of death. They have not, as -Weismann remarks, the real immortality of the gods of mythology, who -were invulnerable. On the contrary, they are infinitely vulnerable, -fragile, and perishable; myriads die every moment. But their death is -not inevitable. They succumb to accidents, never to old age. - -Imagine one of these beings placed in a culture medium favourable to -the full exercise of its activities, and, moreover, wide enough in -its extent to be unaffected by the infinitely small quantities of -material which the animal may take from it or expel into it. Suppose, -for example, it is an infusorian in an ocean. In this invariable medium -the being lives, increases, and grows continually. When it has reached -the limits of a size fixed by its specific law, it divides into two -parts, which are indistinguishable the one from the other. It leaves -one of its halves to colonize in its neighbourhood, and it begins its -evolution as before. There is no reason why the fact should not be -repeated indefinitely, since nothing is changed, either in the medium -or in the animal. - -To sum up. The phenomena which take place in the cell of the protozoan -do not behave as a cause of check. The medium allows the organism -to revictual and to discharge itself in such a way and with such -perfection that the animal is always living in a regular régime, and, -with the exception of its growth and later on of its division, there is -nothing changed in it. - -_Death a Phenomenon of Adaptation—It appeared in the Course of the -Ages._—This immortality belongs in principle to all the protista which -are reproduced by simple and equal division. If it be remarked that -these rudimentary organisms endowed with perennity are the first living -forms which have shown themselves on the surface of the globe, and -that they have no doubt preceded many others—the multicellular, for -instance, which are liable, on the contrary, to decay—the conclusion -is obvious:—Life has long existed without death. Death has been a -phenomenon of adaptation which has appeared in the course of the ages -in consequence of the evolution of species. - -_The Death of Infusoria._—We may ask ourselves at what moment in the -history of the globe, at what period of the evolution of its fauna, -this novelty, death, made its appearance. The celebrated experiments of -Maupas on the senescence of the infusoria seem to authorize us to give -a precise answer to this question. By means of these experiments we are -led to believe that death must have appeared at the same time as sexual -reproduction. Death became possible when this process of generation was -established, not in all its plenitude, but in its humblest beginnings, -under the rudimentary forms of unequal division and of conjugation. -This happened when the infusoria began to people the waters. - -_The Two Modes of Multiplication._—Infusoria are, in fact, capable of -multiplication by simple division. It is true to say that in addition -to this resource, the only one which interests us here, because it -is the only one which confers immortality, they possess another. -They present and exercise under certain circumstances a second mode -of reproduction, caryogamic conjugation. It is a rather complicated -process in its detail, but it is definitively summed up as the -temporary pairing of two individuals, which are otherwise very much -alike, and which cannot be distinguished as male and female. They -become closely united on one of their faces; they reciprocally exchange -a semi-nucleus which passes into the conjoint individual; and then -they separate. But infusoria can be prevented from this conjunction by -regularly isolating them immediately after their birth. Then they grow, -and are constrained after a lapse of time to divide according to the -first method. - -Maupas has shown that the infusoria could not accommodate themselves -to this régime indefinitely; they could not go on dividing for ever. -After a certain number of divisions they show signs of degeneration -and of evident decay. The size diminishes, the nuclear organs become -atrophied, all the activities fail, and the infusorian perishes. -It succumbs to this kind of senile atrophy unless it is given an -opportunity of conjugation with another infusorian in the same plight. -In this act it then derives new strength, it grows larger, attains its -proper size, and builds up its organs once more. Conjugation gives it -life, youth, and immortality. - -_Alimentary Rejuvenescence._—Recent observations due to Mr. G. N. -Calkins, an American biologist, and confirmed by other investigators, -have shown that this method of rejuvenescence is not the only one, -and is not even the most efficacious. Conjugation has no mysterious, -specific virtue. The infusoria need not be married in order to be -rejuvenated. It is sufficient to improve their food. In the case of -the “tailed” paramecium we may substitute beef broth and phosphates -for conjugation. Calkins observed 665 consecutive generations without -blemish, without exhaustion, and without any sign of old age. Plenty of -food and simple drugs have successfully resisted senility and the train -of atrophic degenerations which it involves. - -_Causes of Senescence._—As for the causes of senescence which have -been remedied with such success, they are not exactly known. Calkins -thinks that senescence results from the progressive losses to the -organism of some substance essential to life. Conjugation or intensive -alimentation would act by building up again this necessary compound. -G. Loisel believes on the contrary that it is a matter of the -progressive accumulation of toxic products due to a kind of alimentary -auto-intoxication. - - - - -CHAPTER VI. - -LETHALITY OF THE METAZOA AND OF DIFFERENTIATED CELLS. - - Evolution and death of metazoa.—Possible rejuvenescence of the - differentiated cells by the conditions of the medium.—Conditions of - the medium for immortal cells.—The immortal elements of metazoa.—The - element in accidental and remediable death.—Somatic cells and sexual - cells. - - -_Evolution and Death of Metazoa._—We have seen that the infusoria -are no longer animals in which material exchanges take place with -sufficient perfection, and in which cellular division, the consequence -of growth, is produced with sufficient precision and equality for -life to be carried on indefinitely in a perfect equilibrium in the -appropriate medium without alteration or check. _A fortiori_ we no -longer find the perfect regularity of nutritive exchange in the classes -above them. In a word, starting from this inferior group, there are -no animated beings in the state of existence which Le Dantec calls -“condition Iº of manifested life?” Living matter, instead of being -continually kept identical in conditions of identical media, is -modified in the course of existence. It becomes dependent on time. It -describes a declining trajectory; it experiences evolution, decay, -and death. Thus the fundamental condition of invariable youth and of -immortality fails in all metazoa. The vital wastes accumulate in all -through the insufficiency or the imperfection of nutritive absorption -or of excretion. Life decays; the organism progressively alters, and -thus is constituted that state of decrepitude by atrophy or chemical -modification which we call senescence, and which ends in death. To sum -up, old age and death may be attributed to cellular differentiation. - -_Possible Alimentary Rejuvenescence of the Differentiated -Cells—Conditions of Medium._—We must add, however—as the teaching -of experiments in general and in particular as the teaching of the -experiments of Loeb and of Calkins—that a slight change of the -environment, made at the right time, is capable of re-establishing -equilibrium and of completely rejuvenating the infusorian. Senescence -has not in this case a definitive any more than an intrinsic character; -a modification in the composition of the alimentary medium will -successfully resist it. If we are allowed to generalize this result, it -may be said that senescence, the declining trajectory, the evolution -step by step down to death, are not for the cells considered in -isolation an inevitable and essentially inherent in the organism, and -a rigorous consequence of life itself. They preserve an accidental -character. In senescence and death there is no really natural, internal -cause, inexorable, and irremediable, as was claimed in the past by J. -Müller, and more recently by Cohnheim in Germany and Sedgwick Minot in -America. - -_Conditions of the Medium for Immortal Cells._—As for the cells which -are less differentiated, the protophytes and the protozoa situated -one degree lower in the scale than the infusoria, we must admit the -possibility of that perfect and continuous equilibrium which would -save them from senile decrepitude. And it is quite understood that -this privilege remains subordinated to the perfect constancy of the -appropriate medium. If the latter changes, the equilibrium is broken, -the small insensible perturbations of nutrition accumulate, vital -activity decays, and in sole consequence of the imperfection of the -extrinsic conditions or of the medium, the living being finds itself -once more dragged down to decay and to death. - -_Immortal Elements of the Metazoa._—All the preceding facts and -considerations refer to isolated cells, to monocellular beings. -But, and this is what makes these truths so interesting, they may -be extended to all cells grouped in collectivity—i.e., to all the -animals and living beings that we know. In the complicated edifice -of the organism, the anatomical elements, at any rate the least -differentiated, would have a continual brevet of immortality. Generally -speaking, this would be the case for the egg, for the sexual elements, -and perhaps, too, for the white globules of the blood, the leucocytes. -And, further, around each of these elements must be realized the -invariably perfect medium which is the necessary condition. This does -not take place. - -_Elements in Accidental and Remediable Death._—As for the other -elements, they are like the infusoria, but without the resource of -conjugation. The ambient medium becomes exhausted and intoxicated -around each cell, in consequence of the accidents which happen to the -other cells. Each therefore undergoes progressive decay, and finally -they perish—the decay and destruction being perhaps in principle -accidental, but, in fact, they are the rule. - -The different anatomical elements of the organism are more or less -sensitive to those perturbations which cause senescence, necrobiosis, -and death. There are some more fragile and more exposed. Some are more -resisting, and finally, there are some which are really immortal. We -have just said that the sexual cell, the ovum, is one. It follows that -the metazoan, man for instance, cannot entirely die. Let us consider -one of these beings. Its ancestors, so to speak, have not entirely -disappeared; each has left the fertile egg, the surviving element from -which has issued the being of which we speak; and when it in its turn -has developed, part of that ovum has been placed in reserve for a new -generation. The death of the elements is not therefore universal. The -metazoan is divided from the beginning into two parts. On the one -hand are the cells destined to form the body, _somatic_ cells. They -will die. On the other hand are the _reproductive_, or _germinal_, or -_sexual_ cells, capable of living indefinitely. - -_Somatic and Sexual Cells._—In this sense we may say with Weismann -that there are two things in the animal and in man—the one mortal, -the _soma_ the body, the other immortal, the _germen_. These germinal -cells, as in the case of the protozoa we mentioned above, possess a -conditional immortality. They are imperishable, but on the contrary, -are fragile and vulnerable. Millions of ova are destroyed and are -disappearing every moment. They may die by accident, but never of old -age. - -We now understand that if the protistae are immortal, it is because -these living beings, reduced to a single cell, accumulate in it the -compound characters of the somatic cell and germinal cell, and enjoy -the privilege which is attached to the latter. - - - - -CHAPTER VII. - -MAN. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH. - - The miseries of humanity: 1. Disease; 2. Old age.—Old age considered - as a chronic disease.—Its occasional cause.—3. The disharmonies of - human nature; 4. The instinct of life and the instinct of death. - - -Man’s unhappy plight is the constant theme of philosophies and -religions. Without referring to its moral basis, it has a physical -basis due to four causes—the physical imperfection or disharmony of -nature, disease, old age, and death—or rather of three, for what we -call old age is perhaps a simple disease. These are the great sorrows -of man, the sources of all his woes. Disease attacks him, old age -awaits him, and death must tear him from all the ties which he has -formed. All his pleasures are poisoned by the certain knowledge that -they last but for a moment, that they are as precarious as his health, -his youth, and his life itself. - - - § 1. DISEASE. - - -Disease, frequent, constant, and inevitable as it is, is, however, -nothing but a fact outside the natural order. Its character is clearly -accidental, and it interrupts the normal cycle of evolution. Medical -observation teaches us, on the other hand, that the health of the body -reacts on that of the mind; and therefore man as a whole, moral and -physical, is affected by disease. Bacon described a diseased body as a -jailer to the soul, and the healthy body as a host. Pascal recognized -in diseases a principle of error. “They spoil our judgment and our -senses.” - -I am not expressing a chimerical hope when I predict that science will -conquer disease. Medicine has at last issued from the contemplative -attitude of so many centuries; it has engaged in the struggle, and -signs of victory are already appearing. Disease is no longer the -mysterious power which it was impossible to escape. Pasteur gave to it -a body. The microbe can be caught. In the words of Schopenhauer, an -alteration of the atmosphere so slight that it is impossible to detect -it by chemical analysis may bring on cholera, yellow fever, the black -plague, diseases which carry off thousands of men; and a slightly -greater alteration might endanger all life. The at once mysterious -and terrifying spectacle of the cholera at Berlin in 1831 had such -an effect on the philosopher that he fled in terror to Frankfort. It -has been said that this was the origin of his pessimism, and that -but for this he would have continued to teach idealistic philosophy -in some Prussian university. L. Hartmann, another celebrated leader -of contemporary pessimism, has also said that disease will always be -beyond the resources of medicine. Facts have given the lie to these -sombre prognostics. The microbic origin of most infectious diseases has -been recognized. The discovery of attenuated poisons and serums has -diminished their gravity. An exact knowledge of methods of contagion -has enabled us to erect against them impregnable barriers. Cholera, -yellow fever, the plague knock in vain at our doors. Diphtheria, -dreaded by every mother, has partially lost its deadly character. -Puerperal fever and blindness of the new-born child are tending to -disappear. Legend tells us that Buddha in his youth, frightened at -the sight of a sick man, expressed in his father’s presence the wish -to be always in perfect health and sheltered from disease. The King -answered: “My son! you are asking the impossible.” But it is towards -the realization of this impossibility that we are on our way. Science -is repelling the attacks of disease. - - - § 2. OLD AGE. - - -Old age is another sorrow of humanity. The stage of existence in -which the strength grows less and never grows greater, and in which -a thousand infirmities appear, is not, however, a stage universal in -animals. Most of them die without our perceiving in them any apparent -signs of senile weakness. On the other hand, some vegetables exhibit -these signs. Some trees are old; but it is in birds and mammals that -this decay, with the train of evils which accompanies it, becomes a -very marked phase of existence. In man to debility is added a bodily -shrinkage, grey hairs, withered skin, and the wearing out and loss of -teeth. The exhausted and atrophied organism offers a favourable field -to all intercurrent diseases and to every cause of destruction. It is -this discrepitude which makes old age so hateful. All desire to be old, -said Cicero; and when they are old, they say that old age has come -quicker than they expected. La Bruyère expresses it in an apothegm, -“We want to grow old, and we fear old age.” One would like longevity -without old age. - -But can life be prolonged without senility diminishing its value? -Metchnikoff thinks it can. He more or less clearly catches a glimpse -of a normal evolution of existence which would make it longer and -nevertheless exempt from senile decay. - -It is remarkable that we have so few scientific data on the old age of -man, and we have still fewer on that of animals. The biologist knows -no more than the layman. The old age of the dog is betrayed by its -gait. Its coat loses its lustre, just as in disease. The hair whitens -around the forehead and the muzzle. The teeth grow blunt and drop out. -The character loses its gaiety and becomes gloomy; the animal becomes -indifferent. He ceases to bark, and often becomes blind and deaf. - -It is admitted that senile degeneration is due to an alteration -affecting most of the tissues. The cells, the special anatomical -elements of the liver, the kidney, and the brain are reduced by atrophy -and degeneration. At the same time, the conjunctive woof which serves -them as a support develops, on the contrary, at the expense in a -measure of the higher elements. For this reason the tissues harden. -We know that the flesh of old animals is tough. We know in pathology -that this is happening to the tissues. It is due to growth, to injury -to the active and important elements, to the elements of support of -the organs. They form a tissue sometimes called packed tissue, to -show its secondary rôle with reference to the elements which are -deposited in it. This kind of degeneration of the organs is known as -sclerosis. It constitutes the characteristic lesion of a certain number -of chronic diseases; and these diseases are serious, for the stifling -of the characteristic elements by the less important elements of the -conjunctive or packed tissue results in the more or less complete -reduction or suppression of the function. - -The blood vessels also undergo this transformation, and what we -may call universal trouble and danger ensue. This sclerosis of the -arteries, this arterio-sclerosis, not only deprives the walls of the -blood vessels of the suppleness and elasticity which are necessary for -the proper irrigation of the organs, but it makes them more fragile. -Thus it becomes a cause of hemorrhage, which is a very serious matter -as far as the brain and lungs are concerned. - -It is remarkable that the alteration of the tissues during old age -should be exactly similar to this. This is inferred from the few -researches that have been made on the subject—from those of Demange in -1886, of Merkel in 1891, and finally from the researches of Metchnikoff -himself. It is a generalized sclerosis. As its consequence we have -the lowering of the proper activity of the organs and the danger of -cerebral hemorrhage created by arterio-sclerosis. The transformations -of the tissues in old men are therefore summed up in the atrophy of the -important and specific elements of the tissues, and their replacement -by the hypertrophied conjunctive tissue. This sclerosis is comparable -to that of chronic diseases; it is a pathological condition. Thus old -age, as we understand it, is a chronic disease and not a normal phase -of the vital cycle. - -On the other hand, if we ask ourselves what is the origin of the -scleroses which engender chronic diseases, we find that they are due -to the action of various poisons, among which syphilitic poison and -the immoderate use of alcohol take the first place. These are also the -usual causes of senile degeneration. But there must be some other, -some very general cause to explain the universality of the process of -senescence. Metchnikoff thinks that he has found this cause in the -microbes which swarm in man’s digestive tube, particularly in the -large intestine. Their number is enormous. Strassburger has given -an approximate calculation, but words fail to express it. We have -to imagine a figure followed by fifteen zeros. This microbic flora -is composed of “bacilli” and of “cocci,” and comprises a third of -the rejected matter. It produces slow poisons, which, being at once -reabsorbed, pass into the blood and provoke the constant irritation -from which results arterio-sclerosis and the universal sclerosis of old -age. Instead of enjoying a healthy and normal old age, in which the -faculties of ripening years are preserved, we drag out a diminished -life, a kind of chronic disease, which is ordinary old age. This is -due, according to Metchnikoff, to the parasitism and the symbiosis -of microbic flora, lodged in a part of the economy in which it finds -all the conditions favourable to its prolific expansion. Such is the -specious theory, held to the verge of intrepidity, by which this -investigator explains the misery of our old age, and which inspires him -with the idea of a remedy. For his observations conclude with a régime, -a series of prescriptions by which the author fancies that life may be -lengthened and the evils of old age swept from our path. The dangerous -flora must be transformed into a cultivated and selected flora. -Although the organ in question may be of doubtful utility, and although -its existence, the legacy of atavic heredity, must be considered as -a disharmony of human nature, Metchnikoff does not go so far as to -propose that it should be cut away, and that we should call in surgery -to assist in making mankind perfect! But the rational means he proposes -will be endorsed by the most judicious students of hygiene; and their -effect, if it is not as wonderful as one hopes for, cannot fail to -ameliorate the conditions of old age and make it more vigorous. - - - § 3. DISHARMONIES IN HUMAN NATURE. - - -Another misery in the condition of man is due to the dissidencies -of his nature—that is to say, to his physical imperfections and the -discordancies which exist between the physiological functions and the -instincts which should regulate them. - -This discordance reigns throughout the physical organism. The body of -man is not the perfect masterpiece it was once supposed to be. It is -encumbered with annoying inutilities, with rudimentary organs that have -neither rôle nor function, unfinished sketches which nature has left -in the different parts of his body. Such are the lachrymal caruncle, a -vestige of the third eyebrow in mammals; the extrinsic muscles of the -ear; the pineal gland of the brain, which is only the rudiment of an -ancestral organ; the third eye, or the Cyclopean eye of the saurians. -The list is interminable. Wiedersheim has counted in man 107 of these -abortive hereditary organs, the useless vestiges of organs useful -to our remote animal ancestors, atrophied in the course of ages in -consequence of modifications that have taken place in the external -medium. - -These rudimentary organs are not only useless; they are often -positively harmful. - -But the most serious discordance is that which exists between the -physiological functions and the instincts which regulate them. In a -well-regulated organism slowly developed by adaptation the instincts -and the organs alike should be in relation with the functions. All -really natural acts are solicited by an instinct, the satisfaction -of which is at once a need and a pleasure. The maternal instinct is -awakened at the proper moment in animals, and it disappears as soon as -the offspring requires no more assistance. A craving for milk is shown -in all newborn children, and often disappears at an early age. - -Nature has endowed man as well as the other animals with peculiar -instincts, destined to preside over the different functions and to -ensure their accomplishment. And, at the same time, it has enabled him -in a measure to deceive those instincts and to satisfy them by other -means than the execution of the physiological acts with a view to which -they exist. Love and the instinct of reproduction exist in man before -the age of puberty. Canova felt the spur of love at the age of five. -Dante was in love with Beatrice at nine; and Byron, then scarcely -seven, was already in love with Maria Duff. On the other hand, puberty -has no necessary relation to the general maturity of the organism. - -The family instinct is subject to the same aberrations. Man limits -the number of his children. The Turks of to-day follow the ancient -Greeks in the practice of abortion. Plato approved of the custom, and -Aristotle sanctioned its general prevalence. In the province of Canton -the Chinese of the agricultural classes kill two-thirds of their girl -children, and the same is done at Tahiti. All these customs co-exist -with the perfect love and tender care of the living children. - -Because of these different discordancies the physical life of man is -insufficiently regulated by nature. Neither the physiological instinct, -nor the family instinct, nor the social instinct is, in general, -sufficiently imperative and precise. Hence, since the internal impulse -has not sufficient power, the necessity arises for a rule of conduct -exercising its influence from without. Philosophies, religions, and -legislation have provided for this. They have regulated man’s hygiene -and the carrying out of his different physiological functions. Their -control has, moreover, had its hygienic side. The scientific hygiene of -to-day has inherited their rôle. - -The idea of the fundamental perversity of human nature is born of our -cognizance of its discordancies, unduly amplified and exaggerated. Soul -and body have been considered as distinctly discordant and hostile -elements. The body, the shroud of the soul, the temporary host, the -prison, the present source of miseries, has been subjected to every -kind of mortification. Asceticism has treated the body and all the -innate instincts as our mortal foes. - -This suspicion, this depreciation of human nature was the great -error of the mystics. This view was as fatal as the inverse view -of pagan antiquity. The model of the perfect life according to -Greek philosophy is a life in conformity with nature. To aim at the -harmonious development of man was the precept of the ancient Academy, -formulated by Plato. The Stoics and the Epicureans had adopted the -same principle. Physical nature is considered as good. It gives us -the type, the rule, and the measure. The moral rule itself is exactly -appropriate to the physical nature. We may say that pagan morality was -hygiene, the hygiene of the soul and the body alike; the _mens sana in -corpore sano_ gave individual and social direction. The Rationalists, -the philosophers of the eighteenth century, such as Baron d’Holbach -and later W. Von Humboldt, Darwin, and Herbert Spencer, have adopted -analogous views. If these views have been contested, it is because of -the imperfections or aberrations of the natural instincts of man. Also, -if we wish to base individual family or social morality on the natural -instincts of man, it must be specified that these instincts are to be -regularized. We must necessarily appeal from the imperfect instincts of -the present to the perfected instincts of the future. Their perfection, -moreover, will only be a more exact approximation to the real nature of -man, and he, having avoided by the aid of science the accidents which -cause disease and senile decrepitude, will enjoy a healthy youth and an -ideal old age. - -The reason of the discrepancies between instinct and function in man is -given by the natural history of his development. We know that man has -within him original sin—his long atavism. He has sprung, according to -the transformists, from a simian stock. He is a cousin, the successful -relation, of a type of antinomorphic monkeys, the chimpanzees. He -has “arrived,” they have remained undeveloped. Probably he had a -common ancestor with them, some dryopithecan of an extinct species. -From that type sprang a new type already on the way to progress, the -_Pithecanthropus erectus_. Finally, the anthropoid ancestor became -one fine day the father of a scion, clearly superior to himself, a -miraculously gifted being, man. Here, then, is no sign of the slow -evolution and gradual progress, which is the doctrine held at present -by Transformists. The Dutch botanist De Vries has shown us, in fact, -that nature does leap: _natura facit saltus_. There would thus be -crises, as it were, in the life of species. At certain critical epochs -considerable differences of a specific value appear in their offspring. -It is at one of these critical periods in the simian life that man -has appeared as the phenomenal child of an anthropoid. He was born -with a brain and an intellect superior to those of his humble parents; -and on the other hand, he has inherited from them an organization -which is only inadequately adapted to the new conditions of existence -created by the development of his sensitiveness and his brain power. -This intellect is not proportioned to his organization, which has not -developed at the same rate; it protests against the discordances which -adaptation has not yet had time to efface. But it will efface them in -the future. - - - § 4. THE INSTINCT OF LIFE AND THE INSTINCT OF DEATH. - - -The greatest discrepancy of this kind is the knowledge of inevitable -death without the instinct which makes it longed for. - -There are immortal animals. Man is not of the number. He belongs, -like all highly organized beings, to the class of beings which have -an end. They die from accident or from disease. They perish in the -struggle with other animals, or with microbes, or with external -conditions. There are certainly very few, if there are any, which die a -really natural death. And so it is with man. We see old men gradually -declining who appear to doze gently off into the last sleep, and become -extinguished without disease, like a lamp whose oil is exhausted. But -this is in most cases only apparently so. Besides the fact that the old -age to which they seemed to succumb is really a disease, a generalized -sclerosis, autopsy always reveals some lesion more or less directly -responsible for the fatal issue. - -Man, like all the higher animals, is therefore subject to the law -of lethality. But while animals have no idea of death and are not -tormented by the sentiment of their inevitable end, man knows and -understands this destiny. He has with the animals the instinct of -self-preservation, the instinct of life, and at the same time the -knowledge and the fear of death. This contradiction, this discordance, -is one of the sources of his woes. - -Whether it be an accident or the regular term of the normal cycle, -death always comes too soon. It surprises the man at a time when he -has not yet completed his physiological evolution; hence the aversion -and the terror it inspires. “We cannot fix our eyes on the sun or on -death,” said La Rochefoucauld. The old man does not regard death with -less aversion than the young man. “He who is most like the dead dies -with most regret.” Man knows that he is not getting his full measure. - -Further, all the really natural acts are solicited by an instinct, the -satisfaction of which is a need and a joy. The need of death should -therefore appear at the end of life, just as the need of sleep appears -at the end of the day. It would appear, no doubt, if the normal cycle -of existence were fulfilled, and if the harmonious evolution were not -always interrupted by accident. Death would then be welcomed and longed -for. It would lose its horror. The instinct of death would replace at -the wished for moment the instinct of life. Man would pass from the -banquet of life with no other desire. He would die without regret, -“being old and full of days,” according to the expression used in the -Bible in the case of Abraham, Isaac, and Jacob. No doubt there are some -analogies to this in the insects which only assume the perfect form -for the purpose of procreation and immediately perish in their full -perfection. In these animals the approach of death is blended with the -intoxication of hymen. Thus we see some of them, the ephemerae, lose at -that moment the instinct of life and the instinct of self-preservation. -They allow themselves to be approached, taken, and seized, and make no -effort at flight. - -But what is this full measure of life which is imparted to us? -Metchnikoff holds that the ages attributed to several persons in the -Bible are very probable. Abraham lived 175 years, Ishmael 137, Joseph -110, Moses 120. Buffon believed in the existence of a ratio between the -longevity of animals and the duration of their growth. He fixed it at -7:1. The animal whose development lasts two years would thus have 14 -years of life. This law would give us 140 years, but the figure is too -high, and Flourens has reduced the ratio to that of 5:1, which would -still give us 100 years. Plato died in the act of conversation at 81; -Isocrates wrote his _Panathenaïcus_ at 94; Gorgias died in the full -possession of his intellect at 107. - -To reach the end of the promised longevity we must neither count on the -elixir of life nor on the potable gold of the alchemists, nor on the -stone of immortality which did not prevent its inventor, Paracelsus, -from dying at the age of 58, nor on transfusion, nor on Graham’s -celestial bed, nor on King David’s gerocomy, nor on any nostrum or -remedy. _Contra vim mortis non est medicamen in hortis_, said the -Salernian school. What Feuchtersleben said is most true, “The art of -prolonging life consists in not cutting it short,” and it is a hygiene, -but a brilliant hygiene, such as that of which Metchnikoff traces us -the future lines, which will realize the desires of nature. - -And now shall we find that physiology has solved the enigma proposed by -the Sphinx, and that it has answered these poignant questions:—Whence -do we come? whither do we go? what is the end of life? The end of life -is, to the physiologist as well as to Herbert Spencer, the tendency -towards an existence as full and as long as possible, towards a life -in conformity with real nature freed from the discordancies which -still remain; it is the accomplishment of the harmonious cycle of our -normal evolution. This ideal human nature, without discordancies, no -longer vitiated as it is at present but improved, will be the work of -time and science. Realized at last it will serve as a solid basis for -individual, family, and social morality. Healthy youth fit for action; -prolonged, adult age, the symbol of strength; normal old age, wise in -council, these would have their natural places in harmonious society. -“Great actions,” said one of old, “are not achieved by exertions -of strength, or speed, or agility, but rather by the prudence, the -authority, and the judgment which are found in a higher degree in old -age.” The old age of which Cicero here speaks is the ideal old age, -regular and normal, and not the premature, deformed, incapable and -egoistic old age which results from a pathological condition. At the -end of this full life, the old man being full of days, will crave for -the eternal sleep and will resign himself to it with joy.... - -Death, then, “the last enemy that shall be destroyed,” to use the -expression of St. Paul, will yield to the power of science. Instead of -being “the king of terrors,” it will become after a long and healthy -life, after a life exempt from morbid accidents, a natural and longed -for event, a satisfied need. Then will be realized the wish of the -fabulist:— - - “_I should like to leave life at this age, just as one leaves a - banquet, thanking the host, and departing._” - -Has this physiological solution of the problem of death the virtue -attributed to it by Metchnikoff? Is it as optimistic as he thinks -it is? The instinct of death supervening at the end of a normal and -well-filled cycle will no doubt facilitate to the aged their departure -on the great voyage. The wrench will no longer exist for the dead. -Will it not exist for those who are left behind? And since the instinct -of death can only exist about the time at which death is expected, -will the young man and the man of ripened years look with less horror -than to-day at the law which cannot be escaped, when they are in full -possession of the instinct of life, but warned of the inevitability of -death? - - - - - INDEX OF AUTHORS. - - - Altmann, 258 - - Anaxagoras, 34 - - Aquinas, St. Thomas, 3, 19, 248 - - Aristotle, 3, 15, 18, 143, 146, 307 - - Armstrong, 295 - - Atwater, 137 - - - Bacon, vi., 35, 346 - - Baker, 233 - - Balbiani, 161, 165, 191, 206-7, 257 - - Bang, d’Yvor, 179 - - Barthez, 3, 19, 24 - - Beclard, 121 - - Becquerel, 278 - - Beijerinck, 193 - - Benoit, 271 - - Bernard, Claude, vi., 17, 27, 29, 32, 48, 50-4, 107, 109, 112, 119, - 148, 150-1, 171, 190-2, 194, 197, 204, 210, 214-218, 220 _et seq._, - 310, 318 - - Bernoulli, John, 35, 73 - - Bert, Paul, 194 - - Berthelot, 91, 98, 128-130, 152, 204, 296 - - Berthollet, 82 - - Berzelius, 117 - - Bichat, 3, 6, 20, 22, 27-30, 35, 55, 158, 170, 198, 308 - - Blumenbach, 46 - - Boë, Sylvius Le, 35-6 - - Boerhaave, 35, 147, 245 - - Bohr, 29-30 - - Bokorny, 324 - - Boltzmann, 265 - - Bonnet, 23, 49 - - Bordeu, 3, 10, 19, 22, 24, 312 - - Borelli, 35 - - Boscovitch, 37, 248 - - Bose, 264 - - Bossuet, 11 - - Bouasse, 73, 264-5 - - Boullier, 12 - - Bourdeau, 237, 242 - - Boussingault, 149 - - Brandt, 257 - - Bravais, 282 - - Brillouin, 264, 273 - - Brown, 266 _et seq._ - - Brücke, 44 - - Büchner, 325 - - Buffon, 46, 254, 357 - - Bunge, von, 3, 14 - - Burdon, Sanderson, 176 - - Busquet, 175 - - Bütschli, 161-2, 175 - - - Cabanis, 245, 246 - - Cailletet, 272 - - Calkins, 327, 338 - - Calvert, 271 - - Candolle, 20 - - Cardan, 261 - - Carnot, 72-3, 89, 92 _et seq._, 101, 114, 121 - - Charpy, 237, 271 - - Chauffard, 3, 10, 11, 294 - - Chauveau, 75, 103, 108, 123, 130, 145, 213 - - Chevreul, 32 - - Chossat, 152 - - Cicero, 347, 359 - - Clausius, 67, 88 - - Cohn, 191, 252 - - Cohnheim, 341 - - Colding, 58 _note_, 90 - - Colin, 52 - - Comte, 189-190, 310 - - Confucius, 309 - - Coulomb, 76, 264, 273 - - Crookes, 295, 302 - - Cuvier, 3, 6, 27-8, 105, 120, 152, 190, 198, 308, 310, 319 - - - D’Alembert, 20, 59 _note_, 90, 92 - - Dantec, Le, 48, 52, 55 _note_, 110, 148, 173, 198, 201, 203, 213, 216, - 220, 223 _et seq._, 231, 246, 261, 285, 296, 340 - - D’Arsonval, 126 - - Darwin, 3, 46, 167, 258, 354 - - Dastre, A., 192, 198 _note_ - - Davy, Sir Humphry, 61, 80 - - Delafosse, 282 - - Delage, 208 - - Demange, 349 - - Democritus, 34, 146 - - Descartes, 3, 9, 35, 37, 40, 73, 91, 98 - - Despretz, 126 - - Diderot, 245, 246 - - Drechsel, 183 - - Dressel, 20 - - Dubois-Reymond, 44, 58 _note_, 253 - - Duclaux, 119, 137, 184, 324 - - Dufour, 297 - - Duguet, 264 - - Duhem, 62, 264, 265 - - Dulong, 126 - - Dumas, 115, 149, 151-2 - - - Epicurus, 35, 146 - - Ehrlich, 176 - - Errera, 52, 193-4, 237, 153, 295, 302 _et seq._ - - Euclid, v. - - - Faye, 260 - - Feuchterslehen, 358 - - Flemming, 161 - - Flourens, 20-1, 152, 208, 306, 358 - - Fouillée, 242 - - Fromann, 161 - - Fuerth, 183 - - - Galen, 25, 55, 143 - - Galeotti, 180 - - Galileo, 73, 91, 98, 197, 241, 260 - - Gardair, 19, 248 - - Gautier, A., 3, 32, 36, 39, 176, 233, 324 - - Gernez, 237, 288, 295 _et seq._ - - Glisson, 27 - - Goethe, 170, 312 - - Gouy, 266, 268 - - Grimaud, 19 - - Gruber, 165, 206, 257 - - Guignard, 161 - - Guillaume, 237, 262, 264, 271, 277 - - Guillemin, 237 - - Guldberg, 83 - - - Harbermann, 183 - - Haeckel, 3, 46, 164, 167, 246, 251 - - Hales, 43 - - Haller, 27 - - Hamilton, Sir W. Rowan, 67 - - Hammarsten, 180 - - Hartmann, 276, 346 - - Harvey, 43, 160 - - Haüy, 282 - - Hegel, 170, 331 - - Heidenhain, 3, 29, 30-1 - - Heitzmann, 161 - - Helmholtz, 44, 56, 58, 67, 90, 97, 99, 252 - - Helmont, van, 3, 21, 26, 33, 146, 250 - - Henninger, 302 - - Heraclitus, 34 - - Hertwig, 167 - - Hertz, 88 - - Hess, 91, 98 - - Hippocrates, 146 - - Hirn, 126 - - His, 46 - - Hlasitwetz, 183 - - Holbach, d’, 354 - - Hoogewerf, 303 - - Hopkinson, 271 - - Humboldt, W. von, 354 - - - Ingenhousz, 115 - - Izolet, 247 - - - Joule, 53 _note_, 90-1, 93, 133 _et seq._, 143, 152 - - - Kant, 312, 319 - - Kaup, 213 - - Kaufmann, 126 - - Kelvin, Lord, 63, 67, 90, 92, 251-2, 264; - and the idea of energy, 66 - - Kepler, 29, 241 - - Klemm, 323 - - Koelliker, 160 - - Kossel, 174, 179, 130-1, 136 _et seq._ - - Kuhne, 45 - - Kuhm, 216 - - Kuliabko, 23, 311 - - Kunstler, 157, 161-2, 175 - - Kuppfer, 161 - - - Lammettrie, 147 - - Lamarck, 46 - - Lapparent, 284 - - Lapicque, 140, 145 - - Langley, 216 - - Laplace, 43, 63, 126, 260 - - Laulanié, 103 - - Laurie, 271 - - La Rochefoucauld, 356 - - Lavoisier, 3, 28, 30, 36, 43, 65, 117, 121, 126, 128, 143, 176, 296 - - Lea, 216 - - Le Châtelier, 85, 92 - - Lechatelier, H. and A., 271 - - Lecocq de Boisbaudran, 295 - - Leeuwenhoek, 232 - - Lefèvre, 126 - - Legallois, 21 - - Leydig, 161-2 - - Liebermeister, 136 - - Liebig, 26, 53 _note_, 117 - - Lilienfeld, 179, 247 - - Locke, 23 - - Lodge, 271 - - Loeb, 43, 167, 327, 341 - - Loew, 324 - - Loisel, 339, 341 - - Lorry, 21 - - Longet, 52 - - Lowitz, 297 - - Loye, 192 - - Ludwig, 44, 215 - - - Mach, 41, 62 - - Magendie, 43, 143 - - Magy, 37 - - Malgaigne, 153 - - Mallard, 284 - - Marinesco, 231, 328 - - Markel, 349 - - Maspero, 3, 234 - - Matthiesson, 271 - - Maupas, 337 - - Maxwell, 88 - - Mayer, R., 56, 58, 89, 90, 97, 99, 101 - - Mering, von, 133, 136 - - Metchnikoff, 327 _et seq._ - - Miescher, 174, 179 - - Milne-Edwards, 152, 195 - - Minot, 341 - - Miura, 137 - - Mori, 145 - - Müller, 20, 27, 341 - - Murato, 45 - - - Naegeli, 168 - - Needham, 46 - - Newton, 58 _note_, 70, 90-1, 93 - - Noorden, van, 129, 137, 140, 210 - - Nussbaum, 165, 206, 215, 217 - - - Obermeyer, 271 - - Osmond, 237, 271 - - Ostwald, 41, 62, 67, 85, 104, 237, 258, 289, 295 _et seq._ - - - Paracelsus, 26, 146, 312 - - Pascal, 74, 161 - - Pasteur, 53, 191, 222 _et seq._, 237, 250, 288, 346 - - Payen, 151 - - Persoz, 152 - - Petit, 180 - - Pettenkofer, 210 - - Pfeffer, 175, 193 - - Pflüger, 12, 56, 135, 144, 176, 210, 213 - - Philpotts, 46 - - Pictet, 233 - - Pitcairn, 35 - - Plato, 35, 307 - - Plosz, 180 - - Poincaré, 62 - - Poisson, 63 - - Preyer, 192, 252 _et seq._ - - Priestley, 115 - - Ptolemy, v. - - Pythagoras, 18 - - - Rauber, 237, 288 - - Raulin, 191 - - Regnault, 117 - - Reinke, 3, 32 - - Renan, 240 - - Ribbert, 208 - - Ribot, 247 - - Riche, 271 - - Richet, 50, 126, 140 - - Richter, 252 - - Rindfleisch, 4 - - Roberts-Austen, 237, 271-2 - - Robin, 62, 177 - - Rosenthal, 126 - - Rouvier, 160 - - Roux, 46, 165 - - Rubner, 129, 130, 140 _et seq._, 210 - - Rumford, 80 - - - Sabatier, 242 - - Sachs, 161, 194 - - Salles-Guyon, 252 - - Sanderson, Burdon, 176 - - Scaliger, 241 - - Schleiden, 159 - - Schopenhauer, 346 - - Schwartz, 162 - - Schultze, 160, 326 - - Schultzenberger, 174, 162 _et seq._ - - Secchi, 88 - - Seguin, 58 _note_, 90 - - Senebier, 115 - - Siven, 145 - - Spallanzani, 43, 233 - - Spencer, Herbert, 46, 247, 354, 358 - - Spring, 272 - - Stahl, 3, 9, 12, 35, 146 - - Stammreich, 137 - - Stead, 237 - - Stohmann, 129, 130, 140 - - Strassburger, 161, 350 - - Swann, 159 - - Swift, 262 - - - Tait, 53 _note_, 66 - - Tammann, 237, 253, 295 _et seq._ - - Thales, 34 - - Thomson, Sir J. J., 279 - - Tissot, 12 - - Tomlinson, 264 - - Trembley, 22, 206 - - Tsuboï, 145 - - Tylor, 8 - - - Verworn, 206, 252, 257 - - Violette, 295 - - Virchow, 318, 326 - - Voit, 119, 133 _et seq._, 210 - - Vries, de, 46, 258, 355 - - Vulpian, 24 - - - Waage, 83 - - Waller, 47, 206 - - Wallerant, 282-3 - - Warburg, 264 - - Watt, 76 - - Weismann, 46, 167, 336, 343 - - Wertheim, 264 - - Whitman, 46 - - Widersheim, 351 - - Wiedermann, 264 - - Wiesner, 167 - - Willis, 36, 147 - - Winternitz, 126 - - - Yung, 233 - - - Zuntz, 133, 136, 210 - - - - - INDEX OF SUBJECTS. - - - Activity, functional and vital, 106 _et seq._, 217 _et seq._ - - Aerobia, 193 - - Age, old, Book v. - - Albumin, 178 - - Albuminoids, 178 - - Alcohol, 136 - - Alimentation, 116 _et seq._ - - Alloys, structure of, 273 - - Anærobia, 193 - - Animism, 6, 7, Chap. ii., _passim_ - - Annealing, 275 - - Apposition, 291 - - Archeus, the, 25, 26, 33 - - Arginin, 187 - - Assimilation, law of functional, 110, 213 - - Atomicities, satisfied, 185 - - Atrophy, 326 - - Attraction, energy of position, 64 - - - Balance, sheet, nutritive, 118 - - Beliefs, primitive, 239 - - Bioblasts, 253 - - Biophors, 167 - - Blas, the, 25, 33 - - Blood, lavage of, 192 - - Brain, and death, 315 - - Butylic ferments, 193 - - Butyric ferments, 193 - - - Calorie, 125 _note_ - - Calorimeter, ice, 126; - bomb, 128 - - Caprice, of Nature, 45 - - Cause, final, 45 - - Cells, 48, 147; - somatic and sexual, 343 - - Cellular theory, 158 _et seq._ - - Centrosome, 163 - - Chromosome, 165 - - Cicatrization, 287 - - Complex, homogeneity of the, 245 - - Conductibility, 26 - - Consciousness, in brute bodies, 244 _et seq._ - - Continuity, principle of, 242, 247 - - Contractility, 26 - - Contraction, energy of static and dynamic, 75 - - Conservation, of energy, 58; - of force, 58 - - Crystals, 200 _et seq._, 237 _et seq._, 281 _et seq._ - - Cytoplasm, 161 _et seq._ - - - Death, apparent, 232; - senescence of, 305 _et seq._; - cellular, 321 _et seq._ - - Decentralization, 24 - - Degeneration, 326 - - Destruction, functional, 106; - organic, 211; - of living matter, 213 - - Determinism, 49 - - Digestion, of plants and animals, 152 _et seq._ - - Direction, idea of, 16 - - Dominants, 33, 39, 45 - - Dyne, the, 71 - - - Effort, of force, 71 - - Electrolysis, 272 - - Energetics, 39, 56; - laws of biological, 105 _et seq._, 229; - alimentary, 116 _et seq._ - - Energy, 37, Book ii., _passim_; - origin of idea of, 57; - theory of, 62; - the only objective reality, 64-5; - and kinetic conception, 67; - mechanical, 69, 73; - of contraction, 75; - kinetic, 76, 83; - potential, 76, 83; - virtual, 77; - of motion and position, 79; - thermal, and its measurements, 80-2; - chemical, and its measurements, 81-2; - chemical and potential, 83; - materialization of, 84; - transformations of, 85 _et seq._; - luminous, 86 _et seq._; - conservation of, 90 _et seq._; - capacity of conversion of, 93; - in biology, 97; - in living beings, 99 _et seq._; - physical, 99 _et seq._; - vital, 99 _et seq._ - - Ether, 89 - - Equivalence, law of, 91 - - Excitability, 26-7 - - - Fatigue, of metals, 264 - - Ferments, butylic and butyric, 193 - - Filiation, 250 - - Finalism, 43 - - Food, a source of energy, 118 _et seq._; - thermogenic and biothermogenic types of, 131 _et seq._; - dynamogenic type of, 143; - nitrogenous, 143; - of animals and plants, 153 _et seq._ - - Force, directive, 16 _et seq._, 32, 39, 48; - vital, 45; - an anthromorphic notion, 71; - and work, 74; - measurement of, 71; - plastic, 143; - plastic and morphoplastic forces, 208 - - Form, specific, 199 _et seq._, 281 - - Fruits, acids of, 136 - - - Gemmules, 167, 258 - - Generation, spontaneous, 249 _et seq._, 294 _et seq._ - - Globulin, 178 - - Glycerine, crystals of, 302 - - Glycogen, 108, 153 _et seq._ - - Gramme, 71 - - - Heat, a mode of motion, 61; - rôle of animal heat, 122; - mechanical equivalent of, 81; - an excretum, 114; - a degraded form of energy, 88; - converted into work, 92 - - Heterogeneity, 38, 61 - - Histones, 179, 182 _et seq._ - - Horse-power, 75 - - Hyaloplasm, 161 - - - Iatro-chemistry and mechanics, 34-5 - - Idioblasts, 167 - - Infusoria, death of, 337 - - Instability, 188 _et seq._ - - Instinct, of life and death, 345 _et seq._ - - Intussusception, 291 - - Invariant, mass the first, 63 - - Irreversibility, of vital energies, 104 - - Irritability, 27, 196 _et seq._ - - Isodynamism, 142 - - Isomorphism, 286 - - - Ka, the, 8 - - Kilogrammetre, 72, 75; - per second, 75 - - Kilowatt, 76 - - Kinetic theory, 39, 62 - - Knot, the vital, 21 - - - Leucines, 183 - - Leucites, 163 - - Life, defined, 28; - latent, 233; - physico-chemical theory of, 36; - elementary, 321 - - Linin, 163 - - - Mass, and matter, 63 - - Materialism, 34 - - Matter, 37, 60, 62; - and mass, 63; - two kinds of, 63; - life of, 236 _et seq._; - brute and living, 249 _et seq._; - organization and constitution of, 255 _et seq._; - defined as extension, 64; - conservation of, 65 - - “Memory,” of metals, etc., 265 - - Merotomy, 47 - - Metabolism, 117 - - Metazoa, evolution and death of, 340 _et seq._ - - Meteoric cosmozoa, 252 - - Micellar theory, 166 _et seq._ - - Microcosms, 163 - - Micro-organisms, culture of, 297 - - Mitomes, 169 - - Mobility of stars, 260 - - Modality, twofold, of soul, 12 - - Molecules, organic, 254 - - Monism, 34, Chap. iv. _passim_, 63 - - Montpellier, the school of, 35 - - Motion, cause of, 71; - kinetic conception of molecular, 263 - - Morphogenesis, idea of, 46 - - Movements, internal of bodies, 262; - Brownian, 266 _et seq._ - - Mutability, 80, 188 _et seq._; - of living matter, 259 _et seq._; - of brute bodies, 259 _et seq._ - - - Necrobiosis, 326 - - Neo-vitalism, 15, 29, 32 - - Neurility, 27 - - Nickel, steels, 277 - - Nisus _formativus_, 46 - - Nous, the, 18, 239 - - Nucleins, 179, 180 _et seq._ - - Nucleo-albuminoids, 178; - -proteids, 177 _et seq._ - - Nucleus, 163 _et seq._; - hexonic, 186 - - Nutrition, directed, 205, 209 _et seq._, 227 _et seq._, 290 _et seq._ - - - Organogenesis, 282 - - Organs, organization of, 314; - death of, 315; - perfect, 319 - - - Pangenes, 167 - - Panspermia, 252 - - Parameter, mass the mechanical, 63 - - Phenomena, vital, 44, 51, 189; - modes of motion, 61 - - Photography, colour, 277 - - Physiology, general, 56; - cellular, 56 - - Plants, and immortality, 330 - - Plasomes, 167 - - Plurivitalism, 25 - - Power, 70, 75 - - Principle, vital, 15 _et seq._ - - Properties, vital, 25, 103 - - Proteids, 178 - - Protoplasm, 109 _et seq._, 175 _et seq._, 231 _et seq._; - life in crushed, 257 _et seq._ - - Protozoa, immortality of, 352 _et seq._ - - Psyche, 239 - - Pyrozoa, 253 - - - Regeneration, normal, 205; - accidental, 206 - - Reparation, mechanism of, 288 - - Repose, functional, 109, 217 _et seq._ - - Reserve stuff, 106 _et seq._, 212, 230 _et seq._ - - Rachidian, soul, 12 - - - Senescence, 305 _et seq._ - - Sensibility, in brute bodies, 244 - - Solidarity, of anatomical elements, humoral and nervous, 317 - - Soul, the, 7 _et seq._ - - Space, 69 - - Specificity, vital, 48 - - Spireme, 165 - - Spongioplasm, 162 - - States, initial and final, 128 - - Swelling, 167 - - Synthesis, organizing, 109 - - - Tagmata, 169, 175 - - Teleology, 43 - - Tetanus, bacteria of, 193 - - Thermogenesis, 140 - - Time, 69 - - Tonus, muscular, 119 - - Trees, and immortality, 330 _et seq._ - - Tripod, vital, 2, 314 - - Turgescence, 168 - - - Universe, the, mechanical explanation of, 60; - the end of the, 95 - - Unity, chemical, of living beings, 173 _et seq._, 321; - morphological, 321 - - - Vacuoles, 113 - - Vibrion, septic, 193 - - Vis viva, 73 - - Vital properties, theory of, 29 _et seq._ - - Vitalism, 6, 7, Chap. iii. _passim_; - physico-chemical, 29 - - Vitality, phenomena of, 216 - - Vortex, vital, 105, 120, 229 _et seq._ - - Vulcans, 26-7 - - - Weight, energy of position, 64; - conservation of, 65; - movement under action of, 271 _et seq._ - - Work, 70, 72; - and force, 74, 77; - converted into heat, 92; - physiological, 103 - - - Xanthic bases, 180 - - - Zones, metastable and labile, 301 - - - THE WALTER SCOTT PUBLISHING COMPANY, LTD., FELLING-ON-TYNE. - -*** END OF THE PROJECT GUTENBERG EBOOK LIFE AND DEATH *** - -Updated editions will replace the previous one--the old editions will -be renamed. - -Creating the works from print editions not protected by U.S. copyright -law means that no one owns a United States copyright in these works, -so the Foundation (and you!) can copy and distribute it in the -United States without permission and without paying copyright -royalties. 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