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+*** START OF THE PROJECT GUTENBERG EBOOK 78983 ***
+
+
+
+
+                       LITTLE BLUE BOOK NO. 1476
+                      Edited by E. Haldeman-Julius
+
+                          What You Should Know
+                         About Your Sensations
+
+                              Grace Adams
+
+                      HALDEMAN-JULIUS PUBLICATIONS
+                             GIRARD, KANSAS
+
+
+
+
+                            Copyright, 1929,
+                        Haldeman-Julius Company
+
+
+                PRINTED IN THE UNITED STATES OF AMERICA
+
+
+
+
+CONTENTS
+
+
+                                            Page
+
+ The Importance of Sensations                  5
+
+ The Nature of Sensations                      7
+
+ How Sensations Occur                          8
+
+ How We Feel                                  10
+
+ Visual Sensations                            13
+
+ Common Abnormalities of Vision               16
+
+ How We See in the Light and in the Dark      19
+
+ The Importance of the Sense of Smell         22
+
+ The True Sense of Taste                      24
+
+ The Complexity of Our Perceptions            26
+
+ Localization on the Skin                     28
+
+
+
+
+WHAT YOU SHOULD KNOW ABOUT YOUR SENSATIONS
+
+
+
+
+THE IMPORTANCE OF SENSATIONS
+
+
+Since man first became interested in the processes taking place in his
+own mind, his dreams and emotions and thoughts, he has wondered if
+he could understand these relatively elusive processes as thoroughly
+as he could the more stable facts of the material universe. And ever
+since Epictetus and Aristotle began to collect the facts of mental life
+and formulate them into the laws which were later to become the basis
+of the study of psychology, philosophers and theologians and natural
+scientists have debated whether or not this study of the human mind
+constituted a real science. The champions of both sides of the question
+are worthy of attention.
+
+Epictetus and Aristotle considered their psychological investigations
+strictly scientific. Yet as fascinating and as authoritative as their
+studies appeared to their contemporaries, their opinions lose value
+today, because none of the discipline with which they were familiar are
+accounted scientific by exact modern standards.
+
+From the scientific movement to which Descartes gave such impetus in
+the seventeenth century until the time of Herbert Spencer, psychology
+was not considered a science but a mystical preoccupation not unlike
+theology. In Diderot’s Encyclopedia of 1752 we find psychology defined
+as that branch of philosophy which “defines the human soul and gives
+an account of its activities.” Bacon also classified psychology as one
+of the philosophies of the soul. With it he included soothsaying and
+witchcraft which in his day were supposed to be the two most practical
+applications of psychology.
+
+Comte was the first authority to place psychology among the natural
+sciences instead of the philosophies. But curiously enough the one
+branch of psychology which he considered exact enough to be classified
+along with biology was the one branch of psychology which today is
+thought to be completely and absolutely unscientific--phrenology.
+
+Since the time of Spencer, who accepted psychology as an independent
+science following biology and preparatory to sociology, its scientific
+status has been fairly generally accepted. Still there have been some
+violent dissenters. Kant, in particular, prophesied that there could
+never be a science of psychology because mental phenomena could never
+be treated mathematically. And the old debate is still raging. John B.
+Watson when he adopted his behavioristic platform threw aside all of
+the laboriously got results of the introspectionists and functionalists
+because he considered them inexact, and irremediably so, when compared
+with the results of the biologists and chemists. Many of these same
+introspectionists and functionalists feel that the revolutionary and
+far-reaching theories of Freud and Jung and Adler are too hypothetical
+and too general ever to form the basis of an exact science.
+
+Yet in one field all but the most radically behavioristic admit that
+traditional psychology has justified its scientific claims. This field
+comprises the human sensations.
+
+
+
+
+THE NATURE OF SENSATIONS
+
+
+Sensations are the mental ultimates of the psychological universe just
+as the chemical elements are the ultimates of the chemical universe.
+Sensations are the colors that we see--the reds and greens and purples
+and blacks and whites and greys; the tactual experiences that we
+feel--the warmths and colds and tickles and pains and aches; the tones
+and noises that we hear; all the vast number of odors that we smell
+and our few simple tastes of salt, sweet, sour and bitter. Of course
+these simple experiences very seldom appear isolated. They come to
+us as integral parts of much more complex experiences, as the taste
+of lemonade, the smell of a flower or the colors of a landscape. In
+this they parallel the elements of the other sciences which must be
+separated out, artificially if necessary, before they can be adequately
+studied.
+
+It is a little ironical that at the very time Kant was denying
+that any mental phenomena could ever be treated mathematically the
+psychologists, themselves, were bringing the facts of sensation
+under mathematical laws and the natural scientists were accepting
+these laws as scientific, for it is to be assumed that biologists
+and physicists might be more jealous of the limits of an exact
+science than philosophers. The natural scientists, however, did
+more than complacently accept the psychologists’ own investigations
+of sensations; they verified and extended them and pointed out new
+fields for the psychologists to explore. This was, of course, no mere
+altruistic gesture. Natural scientists, themselves, have a real and
+pertinent interest in all sensory problems and it is in their solution
+that we come to understand the relations between the three sciences of
+physics, biology and psychology, the differences among them and their
+interdependence on one another.
+
+
+
+
+HOW SENSATIONS OCCUR
+
+
+One particular physiological organ or group of organs is responsible
+for each of our five senses: the internal ear for sound, the retina of
+the eye for color, the papillae of the tongue for taste, and so on.
+Each of these special organs responds to a definite type of physical
+stimulation: the retina to vibrations of the ether, the internal
+ear to sound waves, the tongue to chemical solutions. Every simple
+psychological sensation has, then, a rather complicated causal history
+and it depends not only on the form of the physical stimulus but also
+on the peculiar make-up of its special organ.
+
+Every physiological organ of the human body is, of course, subject to
+a wide range of individual differences. Some hearts are weaker than
+others, some livers more sluggish, and some lungs less efficient in
+their functions. It is only natural that the sense organs should differ
+also. And they do. Yet on the whole they are surprisingly uniform. All
+eyes react so typically to certain physical stimuli, and all noses to
+others, that physicists themselves call these stimuli by the names
+of the psychological sensations that they normally evoke. A light
+wave of 687 millimicrons, for example, is known as a red wave because
+when it impinges upon the normal retina it produces a red sensation,
+and a vibration of 527 is called a green wave for the same reason. A
+temperature of 12 degrees centigrade is marked as cold because when it
+stimulates the human skin it produces a cold sensation, and 45 degrees
+C. is hot because it produces the psychological experience of heat.
+Chemists are so familiar with the typical odors of certain substances
+that they accept these odors as invariable attributes of the substance.
+At times, however, our usually well behaved sense organs respond to
+the wrong type of stimuli and paradoxical sensations result. Neither
+ether vibrations nor sound waves are necessarily involved when we
+receive a severe blow on the head, yet such an accident can cause our
+ears to “ring” and our eyes to “see stars.” And a perfectly normal
+human being can feel a cold indistinguishable from normal cold when his
+skin is stimulated by a temperature of 45 degrees C. (or 113° F.). To
+understand this paradox it is necessary to familiarize ourselves with
+the anatomy and physiology of the skin.
+
+
+
+
+HOW WE FEEL
+
+
+The whole surface of the human skin is not equally sensitive to
+stimulation. In fact, a very large proportion of it is completely
+insensitive. But dotted throughout this insensitive area are hundreds
+of thousands of tiny sense organs. They are clustered together much
+thicker in some regions of the body than in others, and wherever
+they are more numerous the skin is, of course, more sensitive; yet
+everywhere there is a sufficient number of them to make us unaware,
+unless we investigate carefully, that there are any portions which are
+insensate. These organs are of three different kinds and each kind
+is responsible for a special type of sensation. The most numerous,
+the corpuscles of Meissner, give us our experiences of pressure, the
+bulbs of Kraus provide our sensations of cold and the corpuscles of
+Ruffini those of warmth. In a square centimeter of the skin there are
+approximately twenty pressure spots, thirteen cold spots and two warm
+spots.
+
+When a pressure spot is touched very lightly by a small narrow object
+it reacts with a sensation which may be described as a tickle. The same
+sensation can be got by gently moving a hair on the forearm or the
+back of the hand for the corpuscles of Meissner are situated directly
+beneath and to the windward of the hair bulbs and a movement of the
+hairs stimulates them adequately. If the pressure is made a little
+stronger, the tickle becomes a sensation of contact. Both the tickle
+and the contact are definitely experiences of pressure. If the same
+pressure spot is stimulated very carefully by either a cold or a warm
+object, the experience will still be one of pressure. The pressure will
+be neither warm nor cold for the pressure spots can respond only with
+tactual sensations. They are as insensitive to thermal stimulations as
+are the many other portions of the skin where there are no temperature
+spots. The warm and cold spots, alone, give us all our experience of
+temperature.
+
+When a cold spot is stimulated by an object whose temperature is
+between 12 and 15 degrees C., a cold sensation is felt. When a stimulus
+whose temperature is between 37 and 40 degrees C. is brought in contact
+with a warm spot, the typical sensation of warmth results. If, however,
+the cold stimulus is applied to the warm spot, nothing at all is felt.
+The warm spots do not respond at all until the temperature reaches 37
+degrees. Similarly the cold spots do not react to warm stimuli, warmth
+can be realized only from a warm spot. Yet when the temperature reaches
+45 degrees C. (113° F.) the cold spots do respond, but with neither
+warmth nor heat. They are cold spots, not warm spots, therefore they
+can react in only one way--with a cold sensation. So we find that
+due to the physiological functioning of an anatomical sense organ, a
+physically hot stimulus really feels cold.
+
+These three groups of sense organs, the pressure, cold and warm spots,
+are the only sense organs on the whole surface of the body. Even
+the pain which we feel when our skin is pricked or lacerated is not
+represented by a special organ. Pain is experienced whenever a nerve
+is stimulated directly and cutting the skin immediately exposes a
+nerve and pain results. The only other organs from which we receive
+any tactual sensations are the muscle spindles which produce aches and
+soreness, the spindles of the tendons from which come our sensations
+of strain, and the corpuscles of the joints which give us subcutaneous
+pressure. Yet think of the wealth of tactual experiences which we have
+every day, in fact, every few minutes. Not only such gross experiences
+as hunger and thirst and fatigue and dizziness, but simple perceptions
+of wetness and oiliness and smoothness and roughness and heaviness
+and lightness. There are no specific sense organs for any of these
+experiences. They are brought about by the six sense organs already
+mentioned and the free nerve endings of pain functioning singly or in
+combination, in greater or less degree.
+
+There are not even any special sense organs of heat. Yet heat appears
+as a unique sensation. It is different from warmth because warmth is
+essentially comfortable while heat has a distinct and disagreeable
+sting. The characteristic sting of heat is recognized whenever we
+refer to pepper and other spices as hot. Psychologically, of course,
+the sensation of heat is unique and simple, but on its biological
+side it is slightly complicated. It is occasioned by the simultaneous
+response of a warm spot and a cold spot, or several warm and cold
+spots, to a stimulus of more than 45 degrees C. And it can be produced
+in no other way. The warm spots, of course respond normally, the cold
+spots paradoxically. The normal response is more vigorous than the
+paradoxical, consequently we do not often realize the sensory quality
+of the cold, while the warmth comes into consciousness. Ordinarily,
+then, heat is warm. With particular stimuli and in certain regions of
+the body where cold spots are particularly numerous, however, trained
+psychologists are able to detect a heat which is cold. Also it is not
+an especially rare occurrence to feel cold when we plunge our hands
+unknowingly into very hot water.
+
+Wetness, which seems almost as simple as heat, is produced by the
+simultaneous stimulation of a cold spot and a pressure spot. It is
+really nothing more than a cold pressure. It is true that we speak of
+being wet when we are in a warm bath, but it is only when the water
+begins to cool that we get the typical wet perception. This explains
+why cold objects so often feel damp when there is actually no moisture
+on them and why it is very difficult to determine whether cloth is
+dry or not when it is held close to a hot fire, also why we are so
+generally unconscious of the continual moisture of our own bodies.
+
+
+
+
+VISUAL SENSATIONS
+
+
+The number of perceptions produced by the relatively few sense
+organs of the skin seems quite insignificant when compared to the
+many different colors occasioned by the activity of the retina of
+the eye, for the microscopic organs in the retina bring about all
+of our sensations of color and of light and shade. All of the rest
+of the rather elaborate apparatus of the eye has to do with spacial
+perceptions; with form and distance and movement and size.
+
+The normal human retina is sensitive to only some four hundred wave
+lengths of light. The others, like the ultra violet rays, lie outside
+the visible spectrum. Yet so efficient is that one small layer of
+the eye that it can convert these four hundred ether vibrations into
+approximately twelve million hues and tints and chromas. This number
+seems astounding because it would probably be impossible for anyone to
+name as many as twelve hundred separate colors. In fact, although the
+persons responsible for the new shades in women’s stockings seem to
+have an unlimited color-vocabulary, most of us get along satisfactorily
+with an extremely limited one. Yet the fact that only a very few of
+these twelve million hues and shades have common names does not mean
+that they cannot all be detected under suitable conditions. Take the
+one color, black, for instance. How many vastly different shades do you
+group under that one word?
+
+You can probably name immediately some ten, or maybe twenty objects
+which you would without hesitation describe as black. Black velvet,
+black satin, black cotton, black wood, coal, soot, ink, and so on. It
+is possible that it may never have occurred to you that these blacks
+are not identical. Yet a little critical attention to them will show
+you how very different they really are. The black paper looks decidedly
+grayish when placed beside the velvet. The velvet, itself, begins to
+pale when it is compared to the darkness of the inside of a black tube.
+The same variety holds for whiteness. White paper is different from
+white enamel and white paint. Indeed, it is somewhat difficult to find
+two kinds of paper whose whiteness is identical. And the white that is
+got from clear sky reflected in a mirror makes the white of any object
+look positively dirty.
+
+Without examining any true colors at all we have already collected a
+variety of shades. And this variety grows when we remember all of the
+various grays which are darker than the whites but lighter than the
+blacks. Von Kries, the German physiologist, found that there were two
+hundred and four different shades of gray between the blackest of black
+paper and the whitest of white paper. And Kulper, the psychologist,
+estimated that the best visible black is a thousand times darker than
+the best visible white.
+
+As soon as the true colors are added to the blacks and whites and
+grays, the possible visual sensations begin to multiply almost
+limitlessly. There are literally thousands of reds: dull reds, bright
+reds, yellowish reds, bluish reds. And there are bluish greens,
+greenish blues, yellowish greens and greenish yellows. But there is a
+limit to these color combinations. There are no reddish greens, no
+greenish reds, no yellowish blues and no bluish yellows.
+
+
+
+
+COMMON ABNORMALITIES OF VISION
+
+
+The astonishingly wide variation of hues and tints and chromas is
+visible to the majority of human beings. There is a large class,
+however, whose visual range is much narrower. About three percent of
+the male population is known to be partially color blind, that is
+insensitive to certain visual stimuli. To such individuals blue and
+yellow appear as they do to persons with normal color vision; but they
+see both red and green as grey, greenish yellow and orange as greyish
+yellow, and bluish green and purple as greyish blue. Partial color
+blindness is hereditary and although it usually occurs only in males,
+it is transmitted by females. Thus a partially color blind man may have
+both sons and daughters who are color normal. All of the children of
+his sons may also have normal color vision, but the male offspring of
+his daughters will be partially color blind.
+
+There are also a number of individuals who are totally color blind,
+who see no colors at all. Total color blindness is also hereditary and
+is also more prevalent among males than among females, but it is much
+rarer than partial color blindness and should be confused neither with
+that nor with true blindness. Blind persons see neither colors nor
+blacks nor whites nor greys. As Helmholtz put it they “see things in
+the same way in which we ourselves see what is behind our backs; that
+is to say, they do not see at all.” But totally color blind persons
+can see; in a dim light they can see exceptionally well. They can
+distinguish objects visually as well as persons with normal eyes, but
+for them these objects never possess any color. They always appear grey.
+
+The two forms of color blindness seem more creditable when we realize
+that everyone is often either partially or totally color blind. All
+of us are partially color blind to objects which we see in indirect
+vision, or “out of the corner of the eye.” Many of us, of course, never
+realize this deficiency, because we usually pay very little attention
+to our indirect vision. If an object interests us we immediately turn
+our eyes toward it and focus them upon it and its colors become clear.
+But if you will hold an orange or a greenish blue pencil parallel to
+and about a foot away from your right ear while your eyes are steadily
+focused directly in front of you, and move the pencil gradually until
+it is directly in front of your nose, you will find that at the side
+of your eye the orange pencil looks only yellow and the greenish blue
+pencil only blue. The red and green do not appear until the pencil is
+almost within the focus of your eyes. It is only at the very center
+then that the eye is color normal. It is partially color blind at the
+sides. And it is always totally color blind, of course, in the dark.
+
+If we wake up suddenly on a black night or go quickly from a brightly
+lighted room into one that is much darker, we at first seem to be
+quite blind--to be incapable of distinguishing anything. Gradually,
+however, our eyes become accustomed to the darkness--the psychologists
+say that they become dark adapted, and we can make out the outlines of
+familiar objects, can see that parts of the room are lighter and parts
+darker than others. But we cannot distinguish any colors. We do not
+even see any clear blacks or whites. Everything appears grey. And that
+is the way the whole world in daylight as well as in darkness looks to
+the totally color blind--as a series of darker or lighter greys.
+
+The inability to distinguish the hues of colors is not the only thing
+which differentiates the way we see in the dark from the way we see in
+daylight. We have already noted the fact that under good illumination
+the center of the eye is the area of clearest vision. Those objects
+upon which our eyes are focused are the ones which appear clearest to
+us. Offhand we would suspect that the same principle held in the dark.
+Yet it is very easy to demonstrate that it does not. Some night when
+you are out of doors look up at the sky and select one small isolated
+star and remember carefully just where it is. Then try to focus your
+eye upon it. You will find that this is impossible. As soon as you
+stare directly at it it disappears, but reappears as soon as you search
+for it. This process can be continued indefinitely--a disappearing and
+reappearing which is so rapid that the star actually seems to twinkle.
+Whenever you look directly at it it is gone, but as soon as you
+shift your eyes ever so slightly it is back again. Carefully verified
+experiments which elaborate this simple experience have convinced
+psychologists of the fact that at night all eyes are completely blind
+at the center where in daylight they have the clearest vision. And
+totally color blind eyes show this same deficiency in daylight as well
+as in the dark. They twitch continually when their possessors attempt
+to read.
+
+So much for the psychological side of visual sensations. If we wish an
+explanation of them, of their variety and of their peculiarities, we
+must turn once more to anatomy and physiology.
+
+
+
+
+HOW WE SEE IN THE LIGHT AND IN THE DARK
+
+
+The retina of the eye contains a quantity of microscopic structures,
+some of which may be roughly described as rods, others as cones. The
+cones are scattered over the entire retina but are thickest at the very
+center. The rods have about the same distribution except that they
+are entirely lacking at the center. From pathological cases and from
+histology the function of these tiny structures has been determined.
+
+A human eye which contains no rods has never been discovered but the
+eyes of fowls and pigeons show this defect, and these animals are
+apparently quite blind at night. All of their activities are carried
+on in the daylight. Hens do not even lay eggs in total darkness.
+Conversely the retinas of nocturnal animals, such as bats and owls and
+moles, are almost entirely lacking in cones but are richly supplied
+with rods. These and similar findings, together with the psychological
+differences of night and day vision, have led psychologists and
+biologists alike to conclude that the rods and cones, although they
+are very similar in structure, serve two very different functions. The
+cones provide us with daylight vision, apparently, while the rods,
+alone, are responsible for the manner in which we see in the dark. The
+rods are completely inactive in daylight but begin to respond to weak
+stimuli as soon as twilight (real or artificial) sets in. And the cones
+which are reacting continuously during every second that it is light,
+become functionally useless in the dark.
+
+The cones alone are responsible for true colors. Many theories have
+been advanced to explain their functioning, but they are too long and
+too complicated to be reviewed here. This much can be stated, however;
+only three photo-chemical substances reacting to light produce all
+of our many different hues. The same substance reacting in different
+ways gives us both red and green, another both blue and yellow, and a
+third both black and white. When more than one substance responds to
+stimulation we get the intermediate colors which resemble one or more
+of these primary colors, for instance, purple which resembles both blue
+and red, and orange which is like both red and yellow. In normal eyes
+all three substances are found only at the center and consequently it
+is only at the center that all colors are visible. In partially color
+blind eyes the red-green substance is absent from the center as well as
+the periphery and the partially color blind, therefore, can see only
+the colors which contain either yellow or blue. In the absence of blue
+or yellow stimuli they see only grey. The totally color blind eye is
+completely deficient in cones. The totally color blind use their rods
+for daylight as well as dark vision.
+
+
+
+
+THE IMPORTANCE OF THE SENSE OF SMELL
+
+
+We have spent so much time on visual and tactual sensations because
+they represent the two senses which have been investigated most
+thoroughly on the physical and biological side. We know not only just
+what these groups of sensations are psychologically but how they are
+physically and biologically produced. Vision has another claim to
+careful study. It, along with audition, is known as a higher sense
+and is used more by civilized man than the lower senses of touch,
+taste and smell. We depend upon our eyes and ears as guides throughout
+all of our practical life and they are the two senses which have the
+highest biological development. Aside from their original function of
+orientation, civilization has forced them to serve two still higher
+purposes. Our eyes and ears are responsible both for the language which
+we use in conversation and for our two special forms of culture--art
+and music. We have no highly developed gustatory or olfactory art and
+although both of these senses are very important in our daily lives,
+we never use them as conscious means of communication. Yet viewed in
+relation to the evolution of the race, smell is the most important of
+all our senses. In the extension of the olfactory organs of the reptile
+we find the first hint of the development of a brain. And in all
+animals which live on the land the sense of smell is highly specialized.
+
+Fish have no real olfactory sensations. The piscatorial organ which
+corresponds to the mammalian nose is really an organ of taste.
+Even animals which spend the greatest part of their lives in the
+water--whales, dolphins and seals--have very rudimentary olfactory
+organs and probably no real sensations of smell. Birds, also, contrary
+to common opinion, have a very poor sense of smell and exceedingly
+efficient eyes. The power which is usually attributed to their
+olfactory sensitivity is actually due to their extraordinarily keen
+sight. It has been proven by experiments that if a decaying animal
+carcass is carefully concealed carrion birds will pass directly by it
+without pausing to investigate. In all animals, however, who habitually
+live upon the ground, olfactory experiences are remarkably numerous and
+varied. It is easy to verify this fact by observing the behavior of
+insects and any four-footed mammals, especially dogs. But it is hard to
+believe that human beings are equally sensitive to odors. Yet they can
+be.
+
+The human olfactory sense has been extensively investigated but at the
+present time no one has been able to state the exact number of smells
+which the human nostrils are capable of detecting. The chief difficulty
+lies in the fact that while the tactual and visual senses, for example,
+are physically limited, new odorous stimuli are being discovered every
+day. Each slightly different chemical compound produces a new odor and
+each new species of plant life carries its own typical smell. Already
+there is reasonable experimental ground for assuming that there are
+sensations from all of the other sense departments put together.
+
+There are two principal reasons why we are generally unaware of this
+wealth of olfactory experiences. The first is that man habitually walks
+on two feet so that his nose, compared to that of other mammals, is
+very far from the ground and smells have a tendency to cling to the
+ground. Consequently, those smell stimuli which do reach his nostrils
+are very weak by the time they arrive there and are, therefore,
+generally ignored in favor of the more insistent visual and auditory
+tactual stimuli. In the second place, the most frequent and the
+strongest odors we experience we customarily ascribe to our sense of
+taste. We speak of the taste of our food when we are actually referring
+to its smell.
+
+It is very easy to prove by experiment how limited is our sense of
+taste but we even have a very strong hint of the fact during our
+everyday life, or rather during that part of our everyday life when
+we are afflicted by a severe cold in the head. At such times we think
+that even the most savory meal has very little taste. Yet common sense
+should tell us that our tongues, which in adult life contain almost
+all of the sense organs of taste, are not seriously impaired by a bad
+cold. We should know that it is our noses, in which the olfactory organ
+is situated, which are really affected. It is the sense of smell which
+we habitually confuse with that of taste which is weakened. It is not
+entirely out of commission, however. There is a small passage at the
+back of the mouth, leading to the nose, of which we are disagreeably
+conscious when we choke. In swallowing, air laden with odorous
+particles is pushed up through this passage, the posterior nares of
+the nostrils are immediately stimulated and smell is experienced. This
+arrangement is quite evident to us when we take medicine which has a
+particularly disagreeable odor. Holding the nose helps a great deal
+until the dose is actually swallowed. If you should continue to hold
+your nose and, instead of swallowing, rinse your mouth thoroughly,
+you would be surprised to find how very little unpleasant “taste” the
+medicine contained. A rather agreeable sweetness might be all that
+remained.
+
+
+
+
+THE TRUE SENSE OF TASTE
+
+
+When all odor is completely eliminated by stopping the nostrils
+with cotton and the surface of the tongue is stimulated directly,
+it has been discovered that there are only four fundamental tastes,
+sour, salt, sweet and bitter. A particular region of the tongue is
+responsible for each of these four tastes. It is very easy to find
+these specialized parts for, while the functional organ of the nose
+is so securely hidden that it is almost impossible to stimulate it
+directly, the gustatory organs are visible to the naked eye. They are
+contained in the tiny bright red spots, or papillae, that dot the
+duller surface of the tongue everywhere except in the center. Although
+any single papilla is apt to contain several kinds of taste buds and
+may, therefore, be sensitive to more than one taste, and although the
+buds which respond to salt are fairly equally distributed over the
+sensitive area of the tongue, those which react to sweet, sour and
+bitter are grouped on different regions. Language recognizes this
+distribution.
+
+We describe as a sweet expression one in which the lips are drawn
+toward the tip of the tongue and the tip, itself, is flattened out.
+The taste buds which respond to sweet stimuli are found clustered at
+the tip of the tongue. In a sour expression the lips are drawn back
+from the tip of the tongue and down toward the sides. And the sour
+taste buds are thickest on the sides of the tongue. When a face wears
+a bitter expression the tongue itself is pulled back until it is in
+contact with the roof of the mouth. And the bitter taste buds are found
+almost exclusively at the rear of the tongue.
+
+Testing these three facial expressions before the mirror will afford
+you a little innocent amusement, but remembering what they represent
+will help you to get the full effect of desirable tastes and to avoid
+the disagreeable qualities of others. A bitter tablet, for example,
+should not be placed at the rear of the tongue where you would get
+the full benefit of its bitterness, but rather in the center which is
+relatively insensitive to any taste.
+
+The manner in which children lick a stick of candy shows that they
+realize unconsciously how they can make the most of its sweetness. The
+taste buds also explain another habit of children which is usually
+frowned upon by their elders--that of taking large mouthfuls. Children
+have many more taste buds than adults. They are distributed not only
+over the whole surface of the tongue but on the insides of the cheeks
+as well. Consequently when children stuff their mouths until their jaws
+bulge, they actually get a great many more gustatory sensations than
+when they have only a dainty morsel on their tongues. If the taste buds
+in the cheeks did not atrophy early in life, there would probably be
+nothing ill mannered about large mouthfuls. As it is, large mouthfuls
+are quite useless to adults. The food has to be directly on their
+tongues before they can taste it. So, forgetting the days when bulging
+cheeks were so delightful, adults become intolerant of a habit which
+was once both pleasant and useful.
+
+
+
+
+THE COMPLEXITY OF OUR PERCEPTIONS
+
+
+Because it is possible to isolate particular sensations and study them
+in detail, as we have attempted to do here, it must not be assumed
+that we customarily experience them in so simple a manner. Even at
+birth the human nervous system is a tremendously complicated affair.
+There are cross connections among the senses. From the very first most
+of our sensations seem to us completely bound up with other processes.
+A pure sensation is a very rare occurrence. A color is nearly always
+the color of something--of cloth or leather or paper or liquid. All of
+the objects which have colors have textures also. They look rough or
+smooth or glossy or dull. And the color and texture seem inalterably
+mixed together. It is only when we look at a rainbow or the rays of
+a spectroscope that we see a color which does not appear to be an
+integral part of some object.
+
+Tones seem to belong less to the objects which produce them--to exist
+by themselves to a greater degree. Yet it is much more difficult to
+produce a simple tone than a pure color. In this case the trouble
+lies not so much with the nervous system as in the physical stimulus
+itself. There are not as many audible tones as there are discernible
+colors and odors, but there are some eleven thousand of them. The tone
+got from a musical instrument is not, however, a simple tone or a pure
+sensation. It is a combination of many tones, some of which are more
+intense than others. These extra tones or partials are produced by
+the musical instrument itself and they cannot be eliminated because a
+musical instrument is essentially a complicated vibrating body. With
+each vibration it produces over-tones as well as a principal tone. It
+is the different intensities of the partial tones which give timbre to
+instruments. It is by their characteristic timbres that we are able to
+distinguish a G struck on a piano from the G of an organ or a violin or
+a saxophone.
+
+Because it is so difficult to produce simple tones, psychologists have
+been unable to discover a great deal about our sense of audition. The
+physical side of sound has been adequately investigated, but we have to
+resort to musical terminology when we try to describe the sensations
+which are produced.
+
+We have already discovered, then, in the case of the three lower
+senses, our perceptions appear so unified that we seldom realize that
+they are complex. Wetness seems to be a unique experience until we
+recognize that it is composed of cold and pressure. So completely
+blended are our tastes and smells that a severe cold in the head is
+required for their conscious separation. And psychologists had to wait
+for years, until a soldier had a strange cortical injury, before they
+learned how complicated a process is tactual localization.
+
+
+
+
+LOCALIZATION ON THE SKIN
+
+
+Localizing a spot on the surface of the skin seems to be the very
+simplest of matters. An itch occurs on the hand and automatically we
+scratch it. Sometimes, it is true, the itch comes in the small of the
+back and we cannot quite reach it. But we can at least point out its
+approximate position to some other person. Both the scratching and
+the pointing seem to be as simple as reflex actions. This apparent
+simplicity led the psychologist Loetze to believe that every single
+spot on the body had a special attribute which he called a “local
+sign.” According to his doctrine we know exactly where we have been
+touched the instant that we are aware of the touch itself. Henri,
+another psychologist, discovered, however, that if he was stimulated on
+the skin when his eyes were closed and tried to locate the exact spot
+before he opened his eyes again, he made large errors of localization
+and the errors were as great on the finger as on the forearm. This
+discovery cast grave doubt on the doctrine of the local sign.
+
+During the late war two psychologists, Gelb and Goldstein, were
+attached to a German army hospital. One day a patient was brought in,
+who had had both of his occipital lobes destroyed, but the rest of his
+nervous system was still intact. This meant that he had absolutely no
+visual cognitions but the rest of his mental functions were unimpaired.
+Gelb and Goldstein immediately began to experiment with him and they
+got some rather startling results.
+
+If the patient was lying quietly with his eyes shut and was touched
+on some part of his body, perhaps his left foot, he knew that he had
+been touched but he had no idea of the place. He did not know whether
+it was on the leg or the forehead or the chest or the hand. It made no
+difference how intense the stimulus was or how long it was continued.
+As long as he remained motionless he could not tell where it was.
+If, however, he was allowed to move his body as much as he wished, he
+could localize the place touched almost exactly but he did it in a very
+strange way. He at first wriggled about so that he set his entire body
+in motion. Then gradually he would move less and less. If the stimulus
+was applied to his right index finger, he would, after a few squirms
+of his whole body, move only his trunk, then only his right arm, then
+just his forearm, his right hand, his fingers, and finally only the
+stimulated finger. Then he could say just where the pressure was felt.
+
+If he was touched in two places at once, as long as he was quiet, he
+would feel only one. If the two stimuli happened to be very close
+together, for instance both on the same finger, even by wriggling he
+could not discover that they were two. But if they were rather widely
+separated he could by the proper movements locate first one and then
+the other.
+
+When he was allowed to touch the place stimulated, his method was the
+same as when he wriggled his body. At first he would run his finger
+aimlessly over his skin, gradually bringing it closer and closer to the
+stimulated area until the exact spot was hit upon.
+
+These results led Gelb and Goldstein to the conclusion, which was
+foreshadowed by Henri, that immediate localization is always a function
+of vision. And they agreed with the findings of some rather different
+experiments which had been carried on at Cornell University several
+years before. The subjects of these experiments had to be real
+scientific martyrs. They were required to swallow a rubber tube in
+which there was an electric coil. The tube reached from the mouth to
+the bottom of the stomach and at intervals there were openings in it
+through which the experimenter could send an electric shock. All of
+the subjects had the greatest difficulty in locating the shocks; they
+could feel them clearly enough but they could not discover in which
+part of their digestive tracts they were. A stimulation might be at the
+extreme end of the tube and the subject would report that it was in his
+thorax. A shock at the esophagus would be referred to the bottom of the
+stomach, and so on.
+
+If localization is primarily a matter of vision, these errors are
+easily accounted for. No one has a very complete mental picture of the
+inside of his own digestive tract. When we localize sensations there we
+must do so by reference to the more familiar external body. But since
+the sensations are felt internally, not on the outside, it is only
+natural that the reference should often be erroneous. Doctors recognize
+this. They accept a patient’s statement that he has a pain but they
+are not so quick to take his word for its exact location. Instead
+they investigate. And when they thump about first at one place then
+at another, they are using the same method of localization which Gelb
+and Goldstein’s soldier employed when he ran his finger over his body.
+Fortunately, this method, though much slower than visual localization,
+is usually successful.
+
+
+
+
+Transcriber’s Note:
+
+- Inconsistencies in hyphenation have been standardized.
+
+- Minor punctuation errors have been changed without notice.
+
+- Spelling was retained as in the original except for the following
+changes:
+
+  Page 21: “spent so much time is” to “spent so much time on”
+  Page 27: “most of our sensations some” to “most of our sensations
+  seem”
+  Page 27: “a pure sensation. It it” to “a pure sensation. It is”
+
+
+
+*** END OF THE PROJECT GUTENBERG EBOOK 78983 ***
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+      What You Should Know About Your Sensations | Project Gutenberg
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+<body>
+<div style='text-align:center'>*** START OF THE PROJECT GUTENBERG EBOOK 78983 ***</div>
+
+
+<figure class="figcenter illowp45" id="cover">
+  <img alt="" class="w100" src="images/cover.jpg" id="img_images_cover.jpg">
+</figure>
+
+<p><span class="pagenum" id="Page_1">[Pg 1]</span></p>
+
+<p class="ph2">LITTLE BLUE BOOK NO. 1476</p>
+<p class="ph3">Edited by E. Haldeman-Julius</p>
+
+<h1>What You Should Know<br>
+About Your Sensations
+</h1>
+
+<p class="ph2">Grace Adams</p>
+<br><br>
+<p class="ph3">HALDEMAN-JULIUS PUBLICATIONS</p>
+<p class="ph3">GIRARD, KANSAS</p>
+<br><br>
+<p><span class="pagenum" id="Page_2">[Pg 2]</span></p>
+
+<p class="ph3">Copyright, 1929,</p>
+<p class="ph3">Haldeman-Julius Company</p>
+<br><br>
+<p class="ph4">PRINTED IN THE UNITED STATES OF AMERICA</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_3">[Pg 3]</span></p>
+
+  <h2 class="nobreak" id="CONTENTS">
+    CONTENTS
+  </h2>
+</div>
+
+<table class="autotable">
+<tr>
+<td class="tdl"></td>
+<td class="tdc">Page</td>
+</tr>
+<tr>
+<td class="tdl">The Importance of Sensations</td>
+<td class="tdr"><a href="#THE_IMPORTANCE_OF_SENSATIONS">5</a></td>
+</tr>
+<tr>
+<td class="tdl">The Nature of Sensations</td>
+<td class="tdr"><a href="#THE_NATURE_OF_SENSATIONS">7</a></td>
+</tr>
+<tr>
+<td class="tdl">How Sensations Occur</td>
+<td class="tdr"><a href="#HOW_SENSATIONS_OCCUR">8</a></td>
+</tr>
+<tr>
+<td class="tdl">How We Feel</td>
+<td class="tdr"><a href="#HOW_WE_FEEL">10</a></td>
+</tr>
+<tr>
+<td class="tdl">Visual Sensations</td>
+<td class="tdr"><a href="#VISUAL_SENSATIONS">13</a></td>
+</tr>
+<tr>
+<td class="tdl">Common Abnormalities of Vision</td>
+<td class="tdr"><a href="#COMMON_ABNORMALITIES_OF_VISION">16</a></td>
+</tr>
+<tr>
+<td class="tdl">How We See in the Light and in the Dark</td>
+<td class="tdr"><a href="#HOW_WE_SEE_IN_THE_LIGHT_AND_IN_THE">19</a></td>
+</tr>
+<tr>
+<td class="tdl">The Importance of the Sense of Smell</td>
+<td class="tdr"><a href="#THE_IMPORTANCE_OF_THE_SENSE_OF_SMELL">22</a></td>
+</tr>
+<tr>
+<td class="tdl">The True Sense of Taste</td>
+<td class="tdr"><a href="#THE_TRUE_SENSE_OF_TASTE">24</a></td>
+</tr>
+<tr>
+<td class="tdl">The Complexity of Our Perceptions</td>
+<td class="tdr"><a href="#THE_COMPLEXITY_OF_OUR_PERCEPTIONS">26</a></td>
+</tr>
+<tr>
+<td class="tdl">Localization on the Skin</td>
+<td class="tdr"><a href="#LOCALIZATION_ON_THE_SKIN">28</a></td>
+</tr>
+</table>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum"><a id="Page_4"></a><a id="Page_5"></a>[Pg 5]</span></p>
+
+
+<p class="halftitle">WHAT YOU SHOULD KNOW ABOUT YOUR SENSATIONS</p>
+  <h2 class="nobreak" id="THE_IMPORTANCE_OF_SENSATIONS">
+    THE IMPORTANCE OF SENSATIONS
+  </h2>
+</div>
+
+<p>Since man first became interested in the
+processes taking place in his own mind, his
+dreams and emotions and thoughts, he has
+wondered if he could understand these relatively
+elusive processes as thoroughly as he
+could the more stable facts of the material
+universe. And ever since Epictetus and Aristotle
+began to collect the facts of mental life
+and formulate them into the laws which were
+later to become the basis of the study of psychology,
+philosophers and theologians and natural
+scientists have debated whether or not
+this study of the human mind constituted a real
+science. The champions of both sides of the
+question are worthy of attention.</p>
+
+<p>Epictetus and Aristotle considered their
+psychological investigations strictly scientific.
+Yet as fascinating and as authoritative as their
+studies appeared to their contemporaries, their
+opinions lose value today, because none of the
+discipline with which they were familiar are
+accounted scientific by exact modern standards.</p>
+
+<p>From the scientific movement to which Descartes
+gave such impetus in the seventeenth
+century until the time of Herbert Spencer,
+psychology was not considered a science but a
+mystical preoccupation not unlike theology.
+<span class="pagenum" id="Page_6">[Pg 6]</span>In Diderot’s Encyclopedia of 1752 we find
+psychology defined as that branch of philosophy
+which “defines the human soul and gives
+an account of its activities.” Bacon also classified
+psychology as one of the philosophies
+of the soul. With it he included soothsaying
+and witchcraft which in his day were supposed
+to be the two most practical applications of
+psychology.</p>
+
+<p>Comte was the first authority to place psychology
+among the natural sciences instead of
+the philosophies. But curiously enough the one
+branch of psychology which he considered exact
+enough to be classified along with biology was
+the one branch of psychology which today is
+thought to be completely and absolutely unscientific—phrenology.</p>
+
+<p>Since the time of Spencer, who accepted psychology
+as an independent science following
+biology and preparatory to sociology, its scientific
+status has been fairly generally accepted.
+Still there have been some violent dissenters.
+Kant, in particular, prophesied that there
+could never be a science of psychology because
+mental phenomena could never be treated
+mathematically. And the old debate is still
+raging. John B. Watson when he adopted his
+behavioristic platform threw aside all of the
+laboriously got results of the introspectionists
+and functionalists because he considered them
+inexact, and irremediably so, when compared
+with the results of the biologists and chemists.
+Many of these same introspectionists and
+functionalists feel that the revolutionary and
+far-reaching theories of Freud and Jung and
+<span class="pagenum" id="Page_7">[Pg 7]</span>Adler are too hypothetical and too general ever
+to form the basis of an exact science.</p>
+
+<p>Yet in one field all but the most radically
+behavioristic admit that traditional psychology
+has justified its scientific claims. This field
+comprises the human sensations.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="THE_NATURE_OF_SENSATIONS">
+    THE NATURE OF SENSATIONS
+  </h2>
+</div>
+
+<p>Sensations are the mental ultimates of the
+psychological universe just as the chemical elements
+are the ultimates of the chemical universe.
+Sensations are the colors that we see—the
+reds and greens and purples and blacks and
+whites and greys; the tactual experiences that
+we feel—the warmths and colds and tickles and
+pains and aches; the tones and noises that we
+hear; all the vast number of odors that we
+smell and our few simple tastes of salt, sweet,
+sour and bitter. Of course these simple experiences
+very seldom appear isolated. They
+come to us as integral parts of much more
+complex experiences, as the taste of lemonade,
+the smell of a flower or the colors of a landscape.
+In this they parallel the elements of
+the other sciences which must be separated out,
+artificially if necessary, before they can be adequately
+studied.</p>
+
+<p>It is a little ironical that at the very time
+Kant was denying that any mental phenomena
+could ever be treated mathematically the psychologists,
+themselves, were bringing the facts
+of sensation under mathematical laws and the
+natural scientists were accepting these laws as
+scientific, for it is to be assumed that biologists
+<span class="pagenum" id="Page_8">[Pg 8]</span>and physicists might be more jealous of
+the limits of an exact science than philosophers.
+The natural scientists, however, did
+more than complacently accept the psychologists’
+own investigations of sensations; they
+verified and extended them and pointed out
+new fields for the psychologists to explore.
+This was, of course, no mere altruistic gesture.
+Natural scientists, themselves, have a real and
+pertinent interest in all sensory problems and
+it is in their solution that we come to understand
+the relations between the three sciences
+of physics, biology and psychology, the differences
+among them and their interdependence
+on one another.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="HOW_SENSATIONS_OCCUR">
+    HOW SENSATIONS OCCUR
+  </h2>
+</div>
+
+<p>One particular physiological organ or group
+of organs is responsible for each of our five
+senses: the internal ear for sound, the retina
+of the eye for color, the papillae of the tongue
+for taste, and so on. Each of these special organs
+responds to a definite type of physical
+stimulation: the retina to vibrations of the
+ether, the internal ear to sound waves, the
+tongue to chemical solutions. Every simple
+psychological sensation has, then, a rather
+complicated causal history and it depends not
+only on the form of the physical stimulus but
+also on the peculiar make-up of its special
+organ.</p>
+
+<p>Every physiological organ of the human body
+is, of course, subject to a wide range of individual
+differences. Some hearts are weaker
+<span class="pagenum" id="Page_9">[Pg 9]</span>than others, some livers more sluggish, and
+some lungs less efficient in their functions. It
+is only natural that the sense organs should
+differ also. And they do. Yet on the whole
+they are surprisingly uniform. All eyes react
+so typically to certain physical stimuli, and all
+noses to others, that physicists themselves call
+these stimuli by the names of the psychological
+sensations that they normally evoke. A light
+wave of 687 millimicrons, for example, is known
+as a red wave because when it impinges upon
+the normal retina it produces a red sensation,
+and a vibration of 527 is called a green wave
+for the same reason. A temperature of 12 degrees
+centigrade is marked as cold because
+when it stimulates the human skin it produces
+a cold sensation, and 45 degrees C. is
+hot because it produces the psychological experience
+of heat. Chemists are so familiar with
+the typical odors of certain substances that
+they accept these odors as invariable attributes
+of the substance. At times, however, our usually
+well behaved sense organs respond to the
+wrong type of stimuli and paradoxical sensations
+result. Neither ether vibrations nor
+sound waves are necessarily involved when we
+receive a severe blow on the head, yet such
+an accident can cause our ears to “ring” and
+our eyes to “see stars.” And a perfectly normal
+human being can feel a cold indistinguishable
+from normal cold when his skin is stimulated
+by a temperature of 45 degrees C. (or
+113° F.). To understand this paradox it is
+necessary to familiarize ourselves with the
+anatomy and physiology of the skin.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+
+<p><span class="pagenum" id="Page_10">[Pg 10]</span></p>
+
+  <h2 class="nobreak" id="HOW_WE_FEEL">
+    HOW WE FEEL
+  </h2>
+</div>
+
+<p>The whole surface of the human skin is not
+equally sensitive to stimulation. In fact, a
+very large proportion of it is completely insensitive.
+But dotted throughout this insensitive
+area are hundreds of thousands of tiny
+sense organs. They are clustered together much
+thicker in some regions of the body than in
+others, and wherever they are more numerous
+the skin is, of course, more sensitive; yet
+everywhere there is a sufficient number of
+them to make us unaware, unless we investigate
+carefully, that there are any portions
+which are insensate. These organs are of
+three different kinds and each kind is responsible
+for a special type of sensation. The
+most numerous, the corpuscles of Meissner, give
+us our experiences of pressure, the bulbs of
+Kraus provide our sensations of cold and the
+corpuscles of Ruffini those of warmth. In a
+square centimeter of the skin there are approximately
+twenty pressure spots, thirteen cold
+spots and two warm spots.</p>
+
+<p>When a pressure spot is touched very lightly
+by a small narrow object it reacts with a sensation
+which may be described as a tickle. The
+same sensation can be got by gently moving a
+hair on the forearm or the back of the hand for
+the corpuscles of Meissner are situated directly
+beneath and to the windward of the
+hair bulbs and a movement of the hairs stimulates
+them adequately. If the pressure is
+made a little stronger, the tickle becomes a
+<span class="pagenum" id="Page_11">[Pg 11]</span>sensation of contact. Both the tickle and the
+contact are definitely experiences of pressure.
+If the same pressure spot is stimulated very
+carefully by either a cold or a warm object, the
+experience will still be one of pressure. The
+pressure will be neither warm nor cold for
+the pressure spots can respond only with tactual
+sensations. They are as insensitive to
+thermal stimulations as are the many other
+portions of the skin where there are no temperature
+spots. The warm and cold spots,
+alone, give us all our experience of temperature.</p>
+
+<p>When a cold spot is stimulated by an object
+whose temperature is between 12 and 15 degrees C.,
+a cold sensation is felt. When a stimulus
+whose temperature is between 37 and 40
+degrees C. is brought in contact with a warm
+spot, the typical sensation of warmth results.
+If, however, the cold stimulus is applied to the
+warm spot, nothing at all is felt. The warm
+spots do not respond at all until the temperature
+reaches 37 degrees. Similarly the cold
+spots do not react to warm stimuli, warmth can
+be realized only from a warm spot. Yet when
+the temperature reaches 45 degrees C. (113° F.)
+the cold spots do respond, but with neither
+warmth nor heat. They are cold spots, not
+warm spots, therefore they can react in only
+one way—with a cold sensation. So we find
+that due to the physiological functioning of an
+anatomical sense organ, a physically hot stimulus
+really feels cold.</p>
+
+<p>These three groups of sense organs, the pressure,
+cold and warm spots, are the only sense
+organs on the whole surface of the body. Even
+<span class="pagenum" id="Page_12">[Pg 12]</span>the pain which we feel when our skin is pricked
+or lacerated is not represented by a special
+organ. Pain is experienced whenever a nerve
+is stimulated directly and cutting the skin immediately
+exposes a nerve and pain results.
+The only other organs from which we receive
+any tactual sensations are the muscle spindles
+which produce aches and soreness, the
+spindles of the tendons from which come our
+sensations of strain, and the corpuscles of the
+joints which give us subcutaneous pressure.
+Yet think of the wealth of tactual experiences
+which we have every day, in fact, every few
+minutes. Not only such gross experiences as
+hunger and thirst and fatigue and dizziness,
+but simple perceptions of wetness and oiliness
+and smoothness and roughness and heaviness
+and lightness. There are no specific sense organs
+for any of these experiences. They are
+brought about by the six sense organs already
+mentioned and the free nerve endings of pain
+functioning singly or in combination, in greater
+or less degree.</p>
+
+<p>There are not even any special sense organs
+of heat. Yet heat appears as a unique sensation.
+It is different from warmth because
+warmth is essentially comfortable while heat
+has a distinct and disagreeable sting. The
+characteristic sting of heat is recognized whenever
+we refer to pepper and other spices as hot.
+Psychologically, of course, the sensation of
+heat is unique and simple, but on its biological
+side it is slightly complicated. It is occasioned
+by the simultaneous response of a warm spot
+and a cold spot, or several warm and cold
+<span class="pagenum" id="Page_13">[Pg 13]</span>spots, to a stimulus of more than 45 degrees
+C. And it can be produced in no other way.
+The warm spots, of course respond normally,
+the cold spots paradoxically. The normal response
+is more vigorous than the paradoxical,
+consequently we do not often realize the sensory
+quality of the cold, while the warmth comes
+into consciousness. Ordinarily, then, heat is
+warm. With particular stimuli and in certain
+regions of the body where cold spots are particularly
+numerous, however, trained psychologists
+are able to detect a heat which is cold.
+Also it is not an especially rare occurrence to
+feel cold when we plunge our hands unknowingly
+into very hot water.</p>
+
+<p>Wetness, which seems almost as simple as
+heat, is produced by the simultaneous stimulation
+of a cold spot and a pressure spot. It is
+really nothing more than a cold pressure. It
+is true that we speak of being wet when we
+are in a warm bath, but it is only when the
+water begins to cool that we get the typical wet
+perception. This explains why cold objects so
+often feel damp when there is actually no moisture
+on them and why it is very difficult to
+determine whether cloth is dry or not when
+it is held close to a hot fire, also why we are
+so generally unconscious of the continual moisture
+of our own bodies.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="VISUAL_SENSATIONS">
+    VISUAL SENSATIONS
+  </h2>
+</div>
+
+<p>The number of perceptions produced by the
+relatively few sense organs of the skin seems
+quite insignificant when compared to the many
+<span class="pagenum" id="Page_14">[Pg 14]</span>different colors occasioned by the activity of
+the retina of the eye, for the microscopic organs
+in the retina bring about all of our sensations
+of color and of light and shade. All of
+the rest of the rather elaborate apparatus of
+the eye has to do with spacial perceptions;
+with form and distance and movement and
+size.</p>
+
+<p>The normal human retina is sensitive to only
+some four hundred wave lengths of light. The
+others, like the ultra violet rays, lie outside
+the visible spectrum. Yet so efficient is that
+one small layer of the eye that it can convert
+these four hundred ether vibrations into approximately
+twelve million hues and tints and
+chromas. This number seems astounding because
+it would probably be impossible for anyone
+to name as many as twelve hundred separate
+colors. In fact, although the persons responsible
+for the new shades in women’s stockings
+seem to have an unlimited color-vocabulary,
+most of us get along satisfactorily with
+an extremely limited one. Yet the fact that
+only a very few of these twelve million hues
+and shades have common names does not mean
+that they cannot all be detected under suitable
+conditions. Take the one color, black, for instance.
+How many vastly different shades do
+you group under that one word?</p>
+
+<p>You can probably name immediately some
+ten, or maybe twenty objects which you would
+without hesitation describe as black. Black
+velvet, black satin, black cotton, black wood,
+coal, soot, ink, and so on. It is possible that
+<span class="pagenum" id="Page_15">[Pg 15]</span>it may never have occurred to you that these
+blacks are not identical. Yet a little critical
+attention to them will show you how very different
+they really are. The black paper looks
+decidedly grayish when placed beside the velvet.
+The velvet, itself, begins to pale when it
+is compared to the darkness of the inside of
+a black tube. The same variety holds for
+whiteness. White paper is different from white
+enamel and white paint. Indeed, it is somewhat
+difficult to find two kinds of paper whose
+whiteness is identical. And the white that is
+got from clear sky reflected in a mirror makes
+the white of any object look positively dirty.</p>
+
+<p>Without examining any true colors at all we
+have already collected a variety of shades. And
+this variety grows when we remember all of
+the various grays which are darker than the
+whites but lighter than the blacks. Von Kries,
+the German physiologist, found that there were
+two hundred and four different shades of gray
+between the blackest of black paper and the
+whitest of white paper. And Kulper, the psychologist,
+estimated that the best visible black
+is a thousand times darker than the best visible
+white.</p>
+
+<p>As soon as the true colors are added to the
+blacks and whites and grays, the possible visual
+sensations begin to multiply almost limitlessly.
+There are literally thousands of reds:
+dull reds, bright reds, yellowish reds, bluish
+reds. And there are bluish greens, greenish
+blues, yellowish greens and greenish yellows.
+But there is a limit to these color combinations.
+<span class="pagenum" id="Page_16">[Pg 16]</span>There are no reddish greens, no greenish
+reds, no yellowish blues and no bluish
+yellows.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="COMMON_ABNORMALITIES_OF_VISION">
+    COMMON ABNORMALITIES OF VISION
+  </h2>
+</div>
+
+<p>The astonishingly wide variation of hues and
+tints and chromas is visible to the majority of
+human beings. There is a large class, however,
+whose visual range is much narrower.
+About three percent of the male population
+is known to be partially color blind, that is
+insensitive to certain visual stimuli. To such
+individuals blue and yellow appear as they do
+to persons with normal color vision; but they
+see both red and green as grey, greenish yellow
+and orange as greyish yellow, and bluish
+green and purple as greyish blue. Partial
+color blindness is hereditary and although it
+usually occurs only in males, it is transmitted
+by females. Thus a partially color blind man
+may have both sons and daughters who are
+color normal. All of the children of his sons
+may also have normal color vision, but the male
+offspring of his daughters will be partially
+color blind.</p>
+
+<p>There are also a number of individuals who
+are totally color blind, who see no colors at
+all. Total color blindness is also hereditary
+and is also more prevalent among males than
+among females, but it is much rarer than partial
+color blindness and should be confused
+neither with that nor with true blindness.
+Blind persons see neither colors nor blacks nor
+whites nor greys. As Helmholtz put it they
+<span class="pagenum" id="Page_17">[Pg 17]</span>“see things in the same way in which we ourselves
+see what is behind our backs; that is
+to say, they do not see at all.” But totally
+color blind persons can see; in a dim light they
+can see exceptionally well. They can distinguish
+objects visually as well as persons with
+normal eyes, but for them these objects never
+possess any color. They always appear grey.</p>
+
+<p>The two forms of color blindness seem more
+creditable when we realize that everyone is
+often either partially or totally color blind.
+All of us are partially color blind to objects
+which we see in indirect vision, or “out of the
+corner of the eye.” Many of us, of course,
+never realize this deficiency, because we usually
+pay very little attention to our indirect
+vision. If an object interests us we immediately
+turn our eyes toward it and focus them
+upon it and its colors become clear. But if
+you will hold an orange or a greenish blue
+pencil parallel to and about a foot away from
+your right ear while your eyes are steadily
+focused directly in front of you, and move the
+pencil gradually until it is directly in front
+of your nose, you will find that at the side of
+your eye the orange pencil looks only yellow
+and the greenish blue pencil only blue. The
+red and green do not appear until the pencil
+is almost within the focus of your eyes. It is
+only at the very center then that the eye is
+color normal. It is partially color blind at
+the sides. And it is always totally color blind,
+of course, in the dark.</p>
+
+<p>If we wake up suddenly on a black night or
+go quickly from a brightly lighted room into
+<span class="pagenum" id="Page_18">[Pg 18]</span>one that is much darker, we at first seem to
+be quite blind—to be incapable of distinguishing
+anything. Gradually, however, our eyes
+become accustomed to the darkness—the psychologists
+say that they become dark adapted,
+and we can make out the outlines of familiar
+objects, can see that parts of the room are
+lighter and parts darker than others. But we
+cannot distinguish any colors. We do not even
+see any clear blacks or whites. Everything
+appears grey. And that is the way the whole
+world in daylight as well as in darkness looks
+to the totally color blind—as a series of darker
+or lighter greys.</p>
+
+<p>The inability to distinguish the hues of colors
+is not the only thing which differentiates
+the way we see in the dark from the way we
+see in daylight. We have already noted the
+fact that under good illumination the center
+of the eye is the area of clearest vision. Those
+objects upon which our eyes are focused are the
+ones which appear clearest to us. Offhand
+we would suspect that the same principle held
+in the dark. Yet it is very easy to demonstrate
+that it does not. Some night when you are out
+of doors look up at the sky and select one small
+isolated star and remember carefully just where
+it is. Then try to focus your eye upon it. You
+will find that this is impossible. As soon as
+you stare directly at it it disappears, but reappears
+as soon as you search for it. This
+process can be continued indefinitely—a disappearing
+and reappearing which is so rapid
+that the star actually seems to twinkle. Whenever
+you look directly at it it is gone, but as
+<span class="pagenum" id="Page_19">[Pg 19]</span>soon as you shift your eyes ever so slightly
+it is back again. Carefully verified experiments
+which elaborate this simple experience
+have convinced psychologists of the fact that
+at night all eyes are completely blind at the
+center where in daylight they have the clearest
+vision. And totally color blind eyes show
+this same deficiency in daylight as well as in
+the dark. They twitch continually when their
+possessors attempt to read.</p>
+
+<p>So much for the psychological side of visual
+sensations. If we wish an explanation of
+them, of their variety and of their peculiarities,
+we must turn once more to anatomy and
+physiology.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="HOW_WE_SEE_IN_THE_LIGHT_AND_IN_THE">
+    HOW WE SEE IN THE LIGHT AND IN THE
+    DARK
+  </h2>
+</div>
+
+<p>The retina of the eye contains a quantity of
+microscopic structures, some of which may be
+roughly described as rods, others as cones. The
+cones are scattered over the entire retina but
+are thickest at the very center. The rods have
+about the same distribution except that they
+are entirely lacking at the center. From pathological
+cases and from histology the function
+of these tiny structures has been determined.</p>
+
+<p>A human eye which contains no rods has
+never been discovered but the eyes of fowls
+and pigeons show this defect, and these animals
+are apparently quite blind at night. All
+of their activities are carried on in the daylight.
+Hens do not even lay eggs in total
+<span class="pagenum" id="Page_20">[Pg 20]</span>darkness. Conversely the retinas of nocturnal
+animals, such as bats and owls and moles, are
+almost entirely lacking in cones but are richly
+supplied with rods. These and similar findings,
+together with the psychological differences
+of night and day vision, have led psychologists
+and biologists alike to conclude that
+the rods and cones, although they are very
+similar in structure, serve two very different
+functions. The cones provide us with daylight
+vision, apparently, while the rods, alone, are
+responsible for the manner in which we see
+in the dark. The rods are completely inactive
+in daylight but begin to respond to weak stimuli
+as soon as twilight (real or artificial) sets
+in. And the cones which are reacting continuously
+during every second that it is light,
+become functionally useless in the dark.</p>
+
+<p>The cones alone are responsible for true
+colors. Many theories have been advanced to
+explain their functioning, but they are too long
+and too complicated to be reviewed here. This
+much can be stated, however; only three photo-chemical
+substances reacting to light produce
+all of our many different hues. The same substance
+reacting in different ways gives us both
+red and green, another both blue and yellow,
+and a third both black and white. When more
+than one substance responds to stimulation we
+get the intermediate colors which resemble
+one or more of these primary colors, for instance,
+purple which resembles both blue and
+red, and orange which is like both red and yellow.
+In normal eyes all three substances are
+found only at the center and consequently it is
+<span class="pagenum" id="Page_21">[Pg 21]</span>only at the center that all colors are visible. In
+partially color blind eyes the red-green substance
+is absent from the center as well as the
+periphery and the partially color blind, therefore,
+can see only the colors which contain
+either yellow or blue. In the absence of blue
+or yellow stimuli they see only grey. The totally
+color blind eye is completely deficient in
+cones. The totally color blind use their rods
+for daylight as well as dark vision.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="THE_IMPORTANCE_OF_THE_SENSE_OF_SMELL">
+    THE IMPORTANCE OF THE SENSE OF SMELL
+  </h2>
+</div>
+
+<p>We have spent so much time <ins title="Original has 'is'" id="on">on</ins> visual and
+tactual sensations because they represent the
+two senses which have been investigated most
+thoroughly on the physical and biological side.
+We know not only just what these groups of
+sensations are psychologically but how they are
+physically and biologically produced. Vision
+has another claim to careful study. It, along
+with audition, is known as a higher sense and
+is used more by civilized man than the lower
+senses of touch, taste and smell. We depend
+upon our eyes and ears as guides throughout
+all of our practical life and they are the two
+senses which have the highest biological development.
+Aside from their original function
+of orientation, civilization has forced them to
+serve two still higher purposes. Our eyes and
+ears are responsible both for the language
+which we use in conversation and for our two
+special forms of culture—art and music. We
+have no highly developed gustatory or olfactory
+art and although both of these senses are very
+<span class="pagenum" id="Page_22">[Pg 22]</span>important in our daily lives, we never use them
+as conscious means of communication. Yet
+viewed in relation to the evolution of the race,
+smell is the most important of all our senses.
+In the extension of the olfactory organs of the
+reptile we find the first hint of the development
+of a brain. And in all animals which live
+on the land the sense of smell is highly specialized.</p>
+
+<p>Fish have no real olfactory sensations. The
+piscatorial organ which corresponds to the
+mammalian nose is really an organ of taste.
+Even animals which spend the greatest part of
+their lives in the water—whales, dolphins and
+seals—have very rudimentary olfactory organs
+and probably no real sensations of smell. Birds,
+also, contrary to common opinion, have a very
+poor sense of smell and exceedingly efficient
+eyes. The power which is usually attributed to
+their olfactory sensitivity is actually due to
+their extraordinarily keen sight. It has been
+proven by experiments that if a decaying animal
+carcass is carefully concealed carrion birds
+will pass directly by it without pausing to investigate.
+In all animals, however, who habitually
+live upon the ground, olfactory experiences
+are remarkably numerous and varied.
+It is easy to verify this fact by observing the
+behavior of insects and any four-footed mammals,
+especially dogs. But it is hard to believe
+that human beings are equally sensitive
+to odors. Yet they can be.</p>
+
+<p>The human olfactory sense has been extensively
+investigated but at the present time no
+one has been able to state the exact number of
+<span class="pagenum" id="Page_23">[Pg 23]</span>smells which the human nostrils are capable
+of detecting. The chief difficulty lies in the
+fact that while the tactual and visual senses,
+for example, are physically limited, new odorous
+stimuli are being discovered every day.
+Each slightly different chemical compound produces
+a new odor and each new species of plant
+life carries its own typical smell. Already
+there is reasonable experimental ground for assuming
+that there are sensations from all of
+the other sense departments put together.</p>
+
+<p>There are two principal reasons why we are
+generally unaware of this wealth of olfactory
+experiences. The first is that man habitually
+walks on two feet so that his nose, compared
+to that of other mammals, is very far from the
+ground and smells have a tendency to cling to
+the ground. Consequently, those smell stimuli
+which do reach his nostrils are very weak by
+the time they arrive there and are, therefore,
+generally ignored in favor of the more insistent
+visual and auditory tactual stimuli. In the second
+place, the most frequent and the strongest
+odors we experience we customarily ascribe to
+our sense of taste. We speak of the taste of
+our food when we are actually referring to its
+smell.</p>
+
+<p>It is very easy to prove by experiment how
+limited is our sense of taste but we even have a
+very strong hint of the fact during our everyday
+life, or rather during that part of our
+everyday life when we are afflicted by a severe
+cold in the head. At such times we think
+that even the most savory meal has very little
+<span class="pagenum" id="Page_24">[Pg 24]</span>taste. Yet common sense should tell us that
+our tongues, which in adult life contain almost
+all of the sense organs of taste, are not seriously
+impaired by a bad cold. We should know
+that it is our noses, in which the olfactory
+organ is situated, which are really affected.
+It is the sense of smell which we habitually
+confuse with that of taste which is weakened.
+It is not entirely out of commission, however.
+There is a small passage at the back of the
+mouth, leading to the nose, of which we are
+disagreeably conscious when we choke. In
+swallowing, air laden with odorous particles
+is pushed up through this passage, the posterior
+nares of the nostrils are immediately stimulated
+and smell is experienced. This arrangement
+is quite evident to us when we take medicine
+which has a particularly disagreeable odor.
+Holding the nose helps a great deal until the
+dose is actually swallowed. If you should continue
+to hold your nose and, instead of swallowing,
+rinse your mouth thoroughly, you
+would be surprised to find how very little unpleasant
+“taste” the medicine contained. A
+rather agreeable sweetness might be all that
+remained.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="THE_TRUE_SENSE_OF_TASTE">
+    THE TRUE SENSE OF TASTE
+  </h2>
+</div>
+
+<p>When all odor is completely eliminated by
+stopping the nostrils with cotton and the surface
+of the tongue is stimulated directly, it has
+been discovered that there are only four fundamental
+tastes, sour, salt, sweet and bitter. A
+<span class="pagenum" id="Page_25">[Pg 25]</span>particular region of the tongue is responsible
+for each of these four tastes. It is very easy
+to find these specialized parts for, while the
+functional organ of the nose is so securely hidden
+that it is almost impossible to stimulate it
+directly, the gustatory organs are visible to the
+naked eye. They are contained in the tiny
+bright red spots, or papillae, that dot the duller
+surface of the tongue everywhere except in the
+center. Although any single papilla is apt to
+contain several kinds of taste buds and may,
+therefore, be sensitive to more than one taste,
+and although the buds which respond to salt
+are fairly equally distributed over the sensitive
+area of the tongue, those which react to sweet,
+sour and bitter are grouped on different regions.
+Language recognizes this distribution.</p>
+
+<p>We describe as a sweet expression one in
+which the lips are drawn toward the tip of
+the tongue and the tip, itself, is flattened out.
+The taste buds which respond to sweet stimuli
+are found clustered at the tip of the tongue.
+In a sour expression the lips are drawn back
+from the tip of the tongue and down toward
+the sides. And the sour taste buds are thickest
+on the sides of the tongue. When a face wears
+a bitter expression the tongue itself is pulled
+back until it is in contact with the roof of
+the mouth. And the bitter taste buds are
+found almost exclusively at the rear of the
+tongue.</p>
+
+<p>Testing these three facial expressions before
+the mirror will afford you a little innocent
+amusement, but remembering what they represent
+<span class="pagenum" id="Page_26">[Pg 26]</span>will help you to get the full effect of desirable
+tastes and to avoid the disagreeable
+qualities of others. A bitter tablet, for example,
+should not be placed at the rear of the
+tongue where you would get the full benefit of
+its bitterness, but rather in the center which
+is relatively insensitive to any taste.</p>
+
+<p>The manner in which children lick a stick
+of candy shows that they realize unconsciously
+how they can make the most of its sweetness.
+The taste buds also explain another habit of
+children which is usually frowned upon by
+their elders—that of taking large mouthfuls.
+Children have many more taste buds than
+adults. They are distributed not only over the
+whole surface of the tongue but on the insides
+of the cheeks as well. Consequently when children
+stuff their mouths until their jaws bulge,
+they actually get a great many more gustatory
+sensations than when they have only a dainty
+morsel on their tongues. If the taste buds in
+the cheeks did not atrophy early in life, there
+would probably be nothing ill mannered about
+large mouthfuls. As it is, large mouthfuls are
+quite useless to adults. The food has to be
+directly on their tongues before they can taste
+it. So, forgetting the days when bulging cheeks
+were so delightful, adults become intolerant of
+a habit which was once both pleasant and useful.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="THE_COMPLEXITY_OF_OUR_PERCEPTIONS">
+    THE COMPLEXITY OF OUR PERCEPTIONS
+  </h2>
+</div>
+
+<p>Because it is possible to isolate particular
+sensations and study them in detail, as we
+<span class="pagenum" id="Page_27">[Pg 27]</span>have attempted to do here, it must not be assumed
+that we customarily experience them in
+so simple a manner. Even at birth the human
+nervous system is a tremendously complicated
+affair. There are cross connections among the
+senses. From the very first most of our sensations
+<ins title="Original has 'some'" id="seem">seem</ins> to us completely bound up with
+other processes. A pure sensation is a very
+rare occurrence. A color is nearly always the
+color of something—of cloth or leather or paper
+or liquid. All of the objects which have colors
+have textures also. They look rough or smooth
+or glossy or dull. And the color and texture
+seem inalterably mixed together. It is only
+when we look at a rainbow or the rays of a
+spectroscope that we see a color which does not
+appear to be an integral part of some object.</p>
+
+<p>Tones seem to belong less to the objects
+which produce them—to exist by themselves
+to a greater degree. Yet it is much more difficult
+to produce a simple tone than a pure
+color. In this case the trouble lies not so much
+with the nervous system as in the physical
+stimulus itself. There are not as many audible
+tones as there are discernible colors and odors,
+but there are some eleven thousand of them.
+The tone got from a musical instrument is not,
+however, a simple tone or a pure sensation. It
+<ins title="Original has 'it'" id="is">is</ins> a combination of many tones, some of which
+are more intense than others. These extra
+tones or partials are produced by the musical
+instrument itself and they cannot be eliminated
+because a musical instrument is essentially a
+complicated vibrating body. With each vibration
+it produces over-tones as well as a principal
+<span class="pagenum" id="Page_28">[Pg 28]</span>tone. It is the different intensities of the
+partial tones which give timbre to instruments.
+It is by their characteristic timbres that we are
+able to distinguish a G struck on a piano from
+the G of an organ or a violin or a saxophone.</p>
+
+<p>Because it is so difficult to produce simple
+tones, psychologists have been unable to discover
+a great deal about our sense of audition.
+The physical side of sound has been adequately
+investigated, but we have to resort to musical
+terminology when we try to describe the sensations
+which are produced.</p>
+
+<p>We have already discovered, then, in the case
+of the three lower senses, our perceptions appear
+so unified that we seldom realize that they
+are complex. Wetness seems to be a unique
+experience until we recognize that it is composed
+of cold and pressure. So completely
+blended are our tastes and smells that a severe
+cold in the head is required for their
+conscious separation. And psychologists had
+to wait for years, until a soldier had a strange
+cortical injury, before they learned how complicated
+a process is tactual localization.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+  <h2 class="nobreak" id="LOCALIZATION_ON_THE_SKIN">
+    LOCALIZATION ON THE SKIN
+  </h2>
+</div>
+
+<p>Localizing a spot on the surface of the skin
+seems to be the very simplest of matters. An
+itch occurs on the hand and automatically we
+scratch it. Sometimes, it is true, the itch
+comes in the small of the back and we cannot
+quite reach it. But we can at least point out
+its approximate position to some other person.
+<span class="pagenum" id="Page_29">[Pg 29]</span>
+Both the scratching and the pointing seem to
+be as simple as reflex actions. This apparent
+simplicity led the psychologist Loetze to believe
+that every single spot on the body had a
+special attribute which he called a “local sign.”
+According to his doctrine we know exactly
+where we have been touched the instant that
+we are aware of the touch itself. Henri, another
+psychologist, discovered, however, that if
+he was stimulated on the skin when his eyes
+were closed and tried to locate the exact spot
+before he opened his eyes again, he made large
+errors of localization and the errors were as
+great on the finger as on the forearm. This
+discovery cast grave doubt on the doctrine of
+the local sign.</p>
+
+<p>During the late war two psychologists, Gelb
+and Goldstein, were attached to a German army
+hospital. One day a patient was brought in,
+who had had both of his occipital lobes destroyed,
+but the rest of his nervous system was
+still intact. This meant that he had absolutely
+no visual cognitions but the rest of his mental
+functions were unimpaired. Gelb and Goldstein
+immediately began to experiment with him and
+they got some rather startling results.</p>
+
+<p>If the patient was lying quietly with his eyes
+shut and was touched on some part of his body,
+perhaps his left foot, he knew that he had been
+touched but he had no idea of the place. He
+did not know whether it was on the leg or the
+forehead or the chest or the hand. It made
+no difference how intense the stimulus was
+or how long it was continued. As long as he
+<span class="pagenum" id="Page_30">[Pg 30]</span>remained motionless he could not tell where it
+was. If, however, he was allowed to move his
+body as much as he wished, he could localize
+the place touched almost exactly but he did
+it in a very strange way. He at first wriggled
+about so that he set his entire body in motion.
+Then gradually he would move less and less.
+If the stimulus was applied to his right index
+finger, he would, after a few squirms of his
+whole body, move only his trunk, then only his
+right arm, then just his forearm, his right
+hand, his fingers, and finally only the stimulated
+finger. Then he could say just where
+the pressure was felt.</p>
+
+<p>If he was touched in two places at once, as
+long as he was quiet, he would feel only one.
+If the two stimuli happened to be very close
+together, for instance both on the same finger,
+even by wriggling he could not discover that
+they were two. But if they were rather widely
+separated he could by the proper movements
+locate first one and then the other.</p>
+
+<p>When he was allowed to touch the place
+stimulated, his method was the same as when
+he wriggled his body. At first he would run
+his finger aimlessly over his skin, gradually
+bringing it closer and closer to the stimulated
+area until the exact spot was hit upon.</p>
+
+<p>These results led Gelb and Goldstein to the
+conclusion, which was foreshadowed by Henri,
+that immediate localization is always a function
+of vision. And they agreed with the findings
+of some rather different experiments
+which had been carried on at Cornell University
+several years before. The subjects of these
+<span class="pagenum" id="Page_31">[Pg 31]</span>experiments had to be real scientific martyrs.
+They were required to swallow a rubber tube
+in which there was an electric coil. The tube
+reached from the mouth to the bottom of the
+stomach and at intervals there were openings
+in it through which the experimenter could
+send an electric shock. All of the subjects
+had the greatest difficulty in locating the
+shocks; they could feel them clearly enough
+but they could not discover in which part of
+their digestive tracts they were. A stimulation
+might be at the extreme end of the tube
+and the subject would report that it was in his
+thorax. A shock at the esophagus would be
+referred to the bottom of the stomach, and
+so on.</p>
+
+<p>If localization is primarily a matter of vision,
+these errors are easily accounted for. No one
+has a very complete mental picture of the inside
+of his own digestive tract. When we localize
+sensations there we must do so by reference
+to the more familiar external body. But
+since the sensations are felt internally, not on
+the outside, it is only natural that the reference
+should often be erroneous. Doctors recognize
+this. They accept a patient’s statement
+that he has a pain but they are not so quick
+to take his word for its exact location. Instead
+they investigate. And when they thump about
+first at one place then at another, they are
+using the same method of localization which
+Gelb and Goldstein’s soldier employed when
+he ran his finger over his body. Fortunately,
+this method, though much slower than visual
+localization, is usually successful.</p>
+
+<hr class="chap x-ebookmaker-drop">
+<div class="chapter">
+<div class="tnote">
+<h2 class="nobreak" id="Transcribers_note">
+Transcriber’s Note:
+</h2>
+
+<p>Inconsistencies in hyphenation have been standardized.</p>
+
+<p>Minor punctuation errors have been changed without notice.</p>
+
+<p>Spelling was retained as in the original except for the following changes:</p>
+
+<table class="autotable">
+<tbody>
+
+<tr>
+<td class="tdl"></td>
+<td class="tdl">Page <a href="#on">21</a>: “spent so much time is”</td>
+<td class="tdl">to</td>
+<td class="tdl">“spent so much time on”</td>
+</tr>
+
+<tr>
+<td class="tdl"></td>
+<td class="tdl">Page <a href="#seem">27</a>: “most of our sensations some”</td>
+<td class="tdl">to</td>
+<td class="tdl">“most of our sensations seem”</td>
+</tr>
+
+<tr>
+<td class="tdl"></td>
+<td class="tdl">Page <a href="#is">27</a>: “a pure sensation. It it”</td>
+<td class="tdl">to</td>
+<td class="tdl">“a pure sensation. It is”</td>
+</tr>
+</tbody></table>
+</div></div>
+<div style='text-align:center'>*** END OF THE PROJECT GUTENBERG EBOOK 78983 ***</div>
+</body>
+</html>
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+[Project Gutenberg](https://www.gutenberg.org) public repository for eBook [#78983](https://www.gutenberg.org/ebooks/78983)