43. In the last chapter we surveyed the deductive evidence, from which the conclusion was that Reflexion necessarily involves Sensibility, but not necessarily any one particular mode of Sensibility, such as Consciousness, Pain, Discomfort, Attention, or the reaction of any one of the special Senses. Although each or all of these modes may be involved in the sensorial process which determines a reflex act, each or all may be absent. Such is the fact of observation. This fact is interpreted on the hypothesis that Reflexion is the exclusive property of the spinal cord, as Sensation is of the brain. When we come to examine the evidence for this hypothesis, we find it to move in a circle: the brain is said to be the exclusive seat of sensation, because reflex actions can be effected after its removal; and reflex actions are said to be insentient because they take place in the absence of the brain.

A gentleman was one day stoutly asserting that there were no gold-fields except in Mexico and Peru. A nugget, dug up in California, was presented to him, as evidence against his positive assertion. He was not in the least disconcerted. “This metal, sir, is, I own, extremely like gold; and you tell me that it passes as such in the market, having been declared by the assayers to be undistinguishable from the precious metal. All this I will not dispute. Nevertheless, the metal is not gold, but auruminium; it cannot be gold, because gold comes only from Mexico and Peru.” In vain was he informed that the geological formation was similar in California and Peru, and the metals similar; he had fixed in his mind the conclusion that gold existed only in Mexico and Peru: this was a law of nature; he had no reasons to give why it should be so; but such had been the admitted fact for many years, and from it he would not swerve. He was not fond of new-fangled notions, which, after all, would only lead us back to the exploded errors of the past. To accept the statement that gold was to be found elsewhere than in Mexico and Peru, would be to return to the opinion of the ancients, who thought there was gold in the upper regions of Tartary!

Sensation is not tangible, assayable, like gold. We can understand, therefore, that the very men who would make merry with the auruminium, would accept easily such a phrase as “reflex action.” The decapitated animal defends itself against injury, gets out of the way of annoyances, cleans itself, performs many of its ordinary actions, but is said to do these things without that Sensibility which, if its head were on, would guide them. Even before the Reflex Theory was invented this line of argument was used. Gall, referring to the experiments of Sue, previously noticed, says that “Sue confounds the effects of Irritability with those of Sensibility.”246 Not gold, dear sir, but auruminium!

44. On investigating the phenomena we soon come upon two classes which must cause hesitation. We find that the brain has its reflex processes, of the same order as those of the cord; we find that these processes may be conscious or unconscious, voluntary or involuntary; so that we can no longer separate brain from cord on the ground of Reflexion. In this respect, at least, the two are mechanisms with similar powers. Turning now to the other class of phenomena, we find that precisely as the brain is an organ of Reflexion, the cord is an organ of Sensation. All the evidence we can have, from which to infer the presence of sensation, is furnished by the sensorial processes in the cord. Remove the brain, and the animal still manifests Sensibility, and this in degrees of energy and complexity proportional to the mechanisms still intact: some of these manifestations have the character of volitional actions, some of automatic actions, some of Memory, Judgment, and selective Adaptation. These we observe not indeed with the energy and variety of such manifestations when the brain co-operates, since the disturbance of the organism which is the consequence of the brain’s removal—or the meagreness of the organism which is the correlative of the brain never having been developed—must of course involve a corresponding difference in the observed phenomena; but the point here brought forward is that phenomena of the same order are manifested by organisms with or without a brain.

45. Let us go seriatim through the evidence of these two classes:—

CEREBRAL REFLEXES.

While Theory separated the actions of the cord from those of the brain on the ground of their being at times unconscious and involuntary, Observation disclosed that this distinction could not be maintained.

This step was taken by Dr. Laycock in 1840. In a striking paper247 read by him at the British Association in 1844, he brought together the evidence on which his view was founded. The idea has been adopted and illustrated in the writings of Dr. Carpenter, who now calls the action “unconscious cerebration.” “I was led to this opinion,” Dr. Laycock says in announcing his view, “by the general principle that the ganglia within the cranium, being a continuation of the spinal cord, must necessarily be regulated as to their reaction on external agencies by laws identical with those governing the spinal ganglia and their analogues in the lower animals. If, therefore, the spinal cord is a centre of reflexion, the brain must also be one.” It is a matter of regret that Dr. Laycock did not extend this principle, and declare that whatever was true of the properties of the cranial centres must also be true of the spinal centres; if the brain have Sensibility, the spinal cord must also have it.

Dr. Laycock refers to the curious phenomena of Hydrophobia in proof that reflex actions may be excited by the optic nerves, or by a mere idea of water. When a mirror was presented to a patient, the reflexion of the light acting on his retina, in the manner of a reflexion from the surface of water, produced a convulsive sobbing, as in the attempt to swallow water, and the patient turned aside his head with expressions of terror. Money was given him to induce him to look a second time, but before he had looked a minute the same effect was produced.

The idea of water excited similar convulsions. No sooner was it suggested that the patient should swallow a little water than he seemed frightened, and began to cry out. By kindly encouragements he was brought to express his willingness to drink, but the sound of the water, as it was poured out again, brought on convulsions. In another case, “on our proposing to him to drink, he started up, and recovered his breath by a deep convulsive inspiration. On being urged to try, he took a cup of water in one hand and a spoon in the other. With as expression of terror, yet with great resolution, he filled the spoon and proceeded to carry it to his lips; but before it reached his mouth his courage forsook him, and he was forced to desist. He repeatedly renewed the attempt, but with no more success. His arm became rigid and immovable whenever he tried to raise it to his mouth, and he struggled in vain against this spasmodic resistance.”

In 1843 Griesinger—who appears to have known nothing of Dr. Laycock’s paper—published his remarkably suggestive memoir on Psychical Reflexes,248 in which he extends the principle of Reflexion to all the cerebro-spinal centres. The whole course of subsequent research has confirmed this view; so that we may say with Landry, “L’existence du pouvoir rÉflexe dans l’encÉphale ou dans quelques unes de ses parties Établit une nouvelle analogie entre le centre nerveux cranien et la moelle ÉpiniÈre.”249 Indeed we have only to consider the Laughter which follows a ludicrous idea, or the Terror which follows a suggestion of danger,—the varying and involuntary expression of Emotion,—and the curious phenomena of Imitation and Contagion,—to see how large a place cerebral reflexion occupies.

46. The existence of cerebral reflexion having been thus made manifest, Dr. Carpenter classed all reflex actions under three heads: 1°, the excito-motor, determined by the spinal cord; 2°, the sensori-motor, determined by the ganglia at the base of the brain; 3°, ideo-motor, determined by the brain. From all these Consciousness is absent. From the first, he supposes Sensation to be absent. As an artifice, such a classification may have its value, but it is physiologically and psychologically misleading. It sustains the hypothesis of an imaginary excito-motor mechanism. It restricts Sensibility to one of its many modes. It fails altogether to connect Sensation with Thought, the Logic of Feeling with the Logic of Signs.

47. The view of Sensibility as common to the whole cerebro-spinal axis is by no means new. Robert Whytt maintained it. Prochaska held that the spinal cord formed the greater part of the sensorium commune; and he adduced, in proof, the familiar facts of sensibility manifested by headless animals. The next writer whom I can discover to have held this opinion is J. J. Sue,—the father of the celebrated French romance-writer,—who, in 1803, conceived that his experiments proved the spinal cord to be capable of replacing, to a certain extent, the functions of the brain.250 Next came Legallois,251 who undertook to show, by a series of experiments, that the principle of sensation and movement, in the trunk and extremities, has its seat in the spinal cord. The mere division of the cord, he said, produces “the astonishing result of an animal, in which the head and the body enjoy separate vitality, the head living as if the body did not exist, and the body living as if the head did not exist. Guinea-pigs, after decapitation, seem very sensitive to the pain caused by the wound in the neck; they alternately carry first one hind-leg and then the other, to the spot, as if to scratch it. Kittens also do the same.”

A few years afterwards, 1817, Dr. Wilson Philip concluded that “the spinal marrow possesses sensorial power, as appears from very simple experiments”; but he held the brain to be the chief source of sensorial power.252 The following year, Lallemand supported this opinion by the very curious phenomena exhibited by infants born without brains: these infants breathed, swallowed, sucked, squalled, and gave very unequivocal signs of sensibility. The value of such observations consists in disproving the objection frequently urged against the evidence of decapitated animals, namely, that in these animals the spinal cord preserves the remains of a sensibility endowed by the brain.

Longet here places an observation recorded by Beyer. A new-born infant, whose brain, during the birth, had been completely extirpated (to save the mother’s life), was wrapped in a towel, and placed in the corner of the room, as a lifeless mass. While the surgeon was giving all his care to the mother, he heard with horror a kind of murmur proceeding from the spot where the body had been placed. In three minutes a distinct cry was heard. The towel was removed, and, to the surprise of all, this brainless infant was seen struggling with rapid movement of its arms and legs. It cried, and gave other signs of sensibility for several minutes.253

In 1828 Calmeil arrived at the same conclusion as that reached by Legallois, Wilson Philip, and Lallemand. Indeed when, in 1833, the Reflex Theory appeared, this opinion was so firmly rooted, that we find Mr. Grainger combating it as the established error of the day. He takes as much pains to show that physiologists are wrong in attributing sensation to the spinal cord, as I am here taking to show that they were right.254 “It is, indeed, apparent,” he says, “that the whole question concerning the truth or falsehood of the theory which attributes the reflex power to the spinal cord hinges upon the correctness or incorrectness of the received doctrines respecting the seat of sensation and volition; so that until those doctrines are proved to be false, it is impossible to establish the hypothesis of Dr. Hall.”255

The reader is requested to take note of this, because when we come to the evidence which proves the spinal cord to be a centre of sensation, we shall find that the only ground for rejecting that evidence is the assumed truth of the Reflex Theory, coupled with the assumption of the brain being the exclusive seat of sensation. Whereas if the evidence proves that the spinal cord is a sensational centre, then the Reflex Theory is destroyed, and cannot be urged against such evidence.

48. Thus many of the facts which prove the sensational function of the spinal cord were known, and even a vague conception of their real significance was general, until the Reflex Theory came to explain all such facts as the results of mechanical adjustment, and of a new nervous principle called “Reflexion.” For many years this theory has reigned, and met with but little opposition. Yet the true doctrine has not wanted defenders in Germany. Nasse256 denied that decapitated animals showed no spontaneity; he asserted that they exhibited clear signs of mental activity. Carus sarcastically pointed out that the word “reflex” was replacing “irritability,” as a key to unlock all puzzles; and he took up a position which is very similar to the one occupied in these pages, namely, that the spinal cord being formed of gray matter as well as of fibres, it must have sensibility and power of reacting on nervous stimulus, no less than conductibility; that, in fact, it is a centre, and must act like all other nerve-centres.257 J. W. Arnold opposed the Reflex Theory in a very remarkable little work, in which he vindicates the claim of the spinal cord as a sensory and motor centre, although denying to its actions any volitional character.258 This was in 1844. Eleven years elapsed without any further opposition, when Edward PflÜger, in 1853, published his work on the Sensorial Functions of the spinal cord.259 In this work he recurred to the old views of Prochaska and Legallois; but although he attacked Marshall Hall with merciless severity, he did not point out the fundamental error of the Reflex Theory, which theory he seems to accept. Nor did he give his views that philosophical and anatomical basis which could alone render his interpretations acceptable. Added to this, the tone of asperity in which his work was written, created some prejudice against him; and thus, while many admitted his facts, they rejected his conclusions.260

In 1858 Professor Owen read a paper of mine at the Leeds meeting of the British Association, on “The spinal cord as a centre of Sensation and Volition,” in which a rapid indication of my point of view, and an account of some experiments to illustrate it, were given—not, I believe, conclusive to any of the audience. Indeed, the subject was too vast to be discussed in such a paper; and my object was rather to excite new inquiry, than to make converts to a view which could only be embraced after a thorough reinvestigation of the dominant theories.

In 1859 appeared Schiff’s work;261 and here we find a large space allotted to the discussion of PflÜger’s doctrine. Schiff, whose immense experience as an experimentalist, and whose acuteness and caution every one will highly estimate, frankly pronounces in favor of the sensational character of spinal actions; but he denies that they are volitional, and objects strongly to the introduction of any such idea as that of “psychical activity.” He thinks it utterly untenable to suppose that impressions have reactions in the brain which they have not in the spinal cord:—if one has sensibility, the other must have it; and he thinks that, so far from the actions of the cord being distinguishable from those of the brain by the character of “reflexion,” and depending on a mechanical arrangement—all actions, cerebral or spinal, are reflex; all depend on a mechanical arrangement.262

Since that time there has been the remarkable work of Goltz, so often cited in these pages,263 and his subsequent experiments on dogs, which (although he does not decisively adopt the views of PflÜger) furnish ample evidence that sensation and volition cannot be exclusively localised in the brain.

49. Heubel’s interesting experiments264 show that a frog may be thrown into a state of profound sleep by the withdrawal of all external stimulation, and in this state will remain lying on its back for hours. Now this position is one so very uncomfortable that, when awake, the frog will not retain it a moment, if free to turn round; and when asleep, a prick on the toe, a sudden noise, or a beam of light will awaken it, causing it to turn. That is to say, the withdrawal of the normal stimuli so lowers the sensibility of the frog’s nerve-centres, that he does not feel the effects of the unusual position, but feels them directly the centres are stimulated into activity. All this is intelligible enough on the supposition of the state of sleep being dependent on a lowering of the cerebral activity. But what shall we say on learning that precisely the same phenomena are manifested by a brainless frog? Every one knows that the brainless frog is intolerant of lying on its back, and immediately turns round, if placed on it. Yet the brainless frog may be thrown into deep sleep by the same exclusion of external stimuli; from which he also will be awakened by a prick, a noise, or a beam of light; and no sooner is he awakened than he at once turns round. Were the brainless frog incapable of sensation, a prick on his toe would cause a simple reflex withdrawal of the leg; but this is not the effect; on the contrary, the stimulus excites the whole spinal cord, and whatever sensation of discomfort may be caused by the abnormal position of the limbs in an uninjured awakened frog, is excited in the brainless frog.

50. I need not swell this chapter with examples of Sensibility in animals deprived of the brain; many have already been given, and any text-book of Physiology will supply more. No one disputes the observations, only the inference that these manifestations were sentient: they are said to have been merely mechanical reflexes. If, however, we can detect in them some evidence of what all recognize as peculiarly characteristic of Mind, the mechanical interpretation will be less plausible.

At the outset the reader must be warned against exaggerating and distorting the bearing of my remarks, and must not suppose that I disregard the vast differences between the Logic of Signs which belongs to Thought, and the Logic of Feeling which belongs to Sensation, nor suppose that I look upon the spinal cord as a mental organ having the same functions as the brain. All that I wish to establish is the common character of spinal and cerebral processes, modified as each is by the character of the actions initiated by the process.

51. This premised, let us begin with the evidence of

DISCRIMINATION.

Although this process is usually regarded as purely psychological, it must obviously have its physiological side; we find it in Sensation as in Ideation, and may expect to find it in unconscious as in conscious processes—in a word, in all sensorial processes whatever. Place a bit of marble on your tongue, and it will be touched, but not tasted: the sensations of contact and temperature will excite reflexes, but little or no reflexes from parotid and salivary glands. A difference in sensation has a corresponding difference in reflex action; which may be made evident by removing the tasteless marble, and replacing it by a pinch of carbonate of lime, i.e. the marble in another state reduced to a powder: this will excite a sensation of taste, and a secretion from the glands. In both cases your sentient organism was affected, but it reacted differently because the difference of the stimulation was discriminated: consciously or unconsciously, you felt differently. Again: touch the back of your mouth with your finger, or a feather, and a convulsive contraction of the gullet responds, followed by vomiting, if the excitation be renewed. Yet these same nerves and muscles respond by the totally opposite action of swallowing, if instead of the stimulation coming from your finger, it come from the pressure of food or drink. Analogous experiments on animals without their brains yield similar results.265 The salivary secretion and the ordinary reactions of Taste are provoked by sapid substances. Still more conclusive are the observations made on a dog whose spinal cord has been divided, and who therefore according to the reigning ideas is incapable of feeling any impression made on parts below the section. A pencil inserted in the rectum causes a reaction of the muscles energetically resisting the entrance of this foreign body; yet this rectum so sensitive in its reaction on the stimulus of the pencil, responds by the totally different reaction—the relaxation of the muscles—on the stimulus of fÆcal matters.

52. “This is all mechanical,” you say? Mechanical, no doubt, as all actions are; but the question here is whether among the conditions of the mechanical action Sensibility has a place? The answer can only be grounded on induction. The actions of the dog are analogous to the actions which you know were sentient in yourself. There was in both a discrimination, in both a corresponding reaction. I admit that what is here called “discrimination” is the application of a logical term to a mechanical process; I admit that if the spinal mechanism is insentient, the fact of discrimination may still be manifested; but I conceive that the many and coercive grounds for admitting that the mechanism is sentient gain further support in the evidence of discrimination. Every particular sensation has its corresponding reaction; and although this has been acquired during ancestral or individual experiences, so that in the majority of cases there is no consciousness accompanying the operation, this, as we have seen, is not a valid argument against the existence of a sensorial process. We have only to lower the Sensibility of the cord by anÆsthetics, or to preoccupy its energies by some other excitation, and the reaction fails.

MEMORY.

53. “But discrimination, if not a purely physical process, implies Memory?” No doubt. And what is Memory—on its physiological side—but an organized tendency to react on lines previously traversed? As Griesinger truly says: “There is Memory in all the functions of the central organs, including the spinal cord. There is one for reflex actions, no less than for sense-images, words, and ideas.” Gratiolet makes a similar assertion.266 Indeed if, as we have seen, reflex actions are partly connate, and partly acquired, it is obvious that the second class must involve that very reproduction of experiences, which in the sphere of Intellect is called Memory.

There is assuredly something paradoxical at first in this application of the terms of the Logic of Signs, yet the psychologist will find it of great service. But if the terms discrimination and memory be objected to, they may be replaced by some such phrase as the “adaptation of the mechanism to varying impulses.” On its objective side, Discrimination is Neural Grouping; on its subjective side, it is Association of experiences.

INSTINCT.

54. If we can detect evidences of Volition and Instinct in the absence of the brain, our thesis may be considered less questionable. And such evidence there is. Goltz decapitated a male frog (in the pairing season), and observed that it not only sought, grasped, and energetically embraced a female, but could always discriminate a female from a male. Thus when a male frog closely resembling a female in size and shape was presented to this decapitated animal, he clasped it, but rapidly let it go again, whereas even the dead body of a female was held as in a vice. Goltz tried to delude this brainless animal in various ways, always in vain. Only a female would be held in his embrace. Goltz then presented a female in a reversed position, so that the head was grasped by the male. Now here, had there been simply a reflex machine, incapable of sentient discrimination, the clutched female would have been held in this position, just like any other object which excited the reflex; there would have been no “sense of incongruity,” such as Goltz noticed in his frog, who at once began a series of movements by which he was enabled, without letting the female escape, to bring her into the proper position. To render this observation still more significant, I may add that Goltz did not find all male frogs act thus—many relinquished the female thus improperly presented to them. Such phenomena observed in frogs possessing brains, would be accepted as evidence of sexual instinct and volition.

Further: Goltz removed the brain from a frog, which he then held under water, gently pressing the body so as to drive the air out of its lungs; the body being then heavier than the water sank to the bottom, where it remained motionless. He repeated this procedure with another frog, not brainless but blinded. This one sank also, but in a few minutes rose to the surface to breathe. This difference naturally suggests that the brainless frog was insensible of the condition which in the other caused a movement of relief. The one felt impending suffocation, the other felt nothing. Such was the interpretation of a German friend in whose presence I repeated the experiment. But I had been instructed by Goltz, and bade my friend wait awhile. He did so, and saw the brainless frog slowly rise to the surface and breathe there like his blinded companion. So that the only difference observable was in the lessened sensibility of the brainless frog.

55. But Goltz records a still more conclusive case. In a large vessel of water he inverted a glass jar also containing water, which could then only be retained in the jar by atmospheric pressure. Through the neck of this inverted jar he thrust a blinded frog, not having pressed the air out of its lungs. It rose at once in the jar, touching the inverted bottom with its nose, and when the necessity of fresh air was felt, the frog began restlessly feeling about the surface of its prison till an issue was found in the neck of the jar, through which it dashed into the vessel, and at once rose to the surface of the water to breathe. In this observation are plainly manifested the stimulation of uneasy sensation, the volition of seeking relief, and the discrimination of it when found. If this frog was a sentient mechanism, what shall we say to the fact that a brainless frog was observed to go through precisely the same series of actions? Goltz pertinently remarks: “So long as physiologists satisfied themselves that the brain was the sole organ of sensation, it was easy to declare all the actions of the brainless animal to be merely reflex. But now we must ask whether the greater part of these actions are not due to the power of adaptation in the central organs, and are therefore to be struck out of the class of simple reflexes? If I bind one leg of a brainless frog and observe that he not only sees an obstacle, but crawls aside from it, I must regard these movements as regulated by his central power of adaptation; but now suppose I unbind the leg and remove the obstacle, then if I prick the frog he hops forward. Must I now declare this hop to have been a simple reflex? Not at all. In both cases the physiological processes have been similar.”

56. There are no doubt readers who will dismiss all evidence drawn from experiments on frogs, as irrelevant to mammals and man. Let us therefore see how the evidence stands with respect to animals higher in the scale, endowed with less questionable mental faculties. In a former chapter (Problem II. §29) we recorded the marked results of removing the cerebral hemispheres; and at the same time suggested that these by no means justified the conclusion usually drawn respecting the hemispheres as the exclusive seat of sensation. And this on two grounds: First, because the absence of some sensitive phenomena does not prevent the presence of others: the mutilated organism is still capable of manifesting Sensibility in those organs which remain intact. Secondly, because were the mutilation followed by total destruction of Sensibility, this would not prove Sensibility in the normal organism to have its seat in the part injured. If the removal of a pin will destroy the chronometric action of a watch, we do not thence infer that the chronometric action was the function of this pin. And this objection has the greater force when we remember that one hemisphere may be removed without the consequent loss of a single function, and both may be removed without the loss of several functions usually ascribed to cerebral influence.267 57. Consider the analogous effects of injuries to or removal of the Cerebellum, in causing disturbance of locomotion, whence the conclusion has been drawn that the Cerebellum is the exclusive organ of muscular co-ordination, in spite of the unquestionable evidence that very many muscular co-ordinations still persist after this organ is removed. What is the part played by the Cerebellum I do not pause here to examine.268 I only say that the movements of swimming, sucking, swallowing, breathing, crying, micturition, defecation, etc., are co-ordinated as well after removal of the Cerebellum as they were before, and that consequently their co-ordination has not its seat in the Cerebellum. The parallelism is obvious. Removal of the Cerebrum causes a disturbance in the combination of sensations, and the execution of certain sense-guided actions, but causes little appreciable disturbance in others. Removal of the Cerebellum causes a disturbance in the combination of certain muscular sensations, and the execution of certain co-ordinated actions, with little appreciable disturbance in others.

58. So little have the facts been surveyed and estimated in their entirety that there is perhaps no subject on which physiologists are more agreed than on the function of the Cerebellum being that of co-ordination. Yet consider this decisive experiment. I etherized three healthy frogs, from one I removed the entire cranial centres; from another I removed only the cerebellum; and, leaving the third in possession of an intact encephalon, I made two sections of the posterior columns of the spinal cord. The two first hopped, swam, used their legs in defence, and exhibited a variety of muscular co-ordinations, although in both the supposed organ of co-ordination was absent. Whereas the third, which had this organ intact, and was capable of moving each limb separately, and each pair of limbs separately, was utterly incapable of moving all four simultaneously. Why was this? Obviously because in the first two frogs the motor mechanism remained intact, and only the cerebral and cerebellar influence was removed; in the third frog the sensory part of the motor mechanism had been divided, and no combination of the limbs was possible.

59. Physiological induction agrees with anatomical induction in assigning to the cerebrum and cerebellum the office of incitation and regulation rather than of innervation; for, as we have seen, no nerve issues directly from them (Problem II. §7). Consequently the effects of injuries to these centres are losses of spontaneity and of complexity in the manifestations. Inasmuch as in the intact organism all sensory impressions are propagated throughout the nervous centres, the reactions of these highest centres will enter into the complex of every adjusted movement; so the abolition of these centres will be the dropping of a link in the chain, the abolition of a special element in the complex group. The organs which are still intact will react, each in its own way, on being stimulated; but the reaction will be without the modifying influence of the absent centres. For instance, the retinal stimulation from a luminous impression normally calls up a cluster of associated feelings derived originally from other senses, and a perception of the object is associated with emotions of desire, terror, etc., according to the past history of the organism, and its organized reactions, due to hereditary or acquired experiences. It is these which form the complex feeling discharged in the particular movement of prehension, or flight. Remove the brain, and there can be no longer this cluster of associated neural groups excited; there will be therefore no emotion, simply the visual sensation, and such a movement as is directly associated with it. The brainless dog moans when hurt, it does not bark at the cat which it nevertheless sees, and avoids as a mere obstacle in its path; the cat will cry, it will not mew. The present pain moves the vocal organs, but does not revive associated experiences. All those combinations by which a series of dependent actions result from a single stimulation are frustrated when the mechanism is disturbed, so that the mutilated animal can no longer recognize its prey or its enemy, to feed on the one and fly from the other; no longer builds its habitation, or rears its offspring. It can still live, feed, sleep, move, and defend itself against present discomfort; it cannot find its food, or protect itself against prospective discomfort. We must supply the place of its Intelligence. We must give it the food, and protect it from injuries.

There is therefore ample evidence to show that what is specially known as Intelligence is very imperfect after the cerebral influence has been abolished; but this does not prove the Cerebrum to be the exclusive seat of Intelligence, it only proves it to be an indispensable factor in a complex of factors. Still less does it prove the Cerebrum to be the exclusive seat of Sensation, Instinct, Volition; for these may be manifested after its removal, although of course even these will be impaired by the loss of one factor.

60. And here an objection must be anticipated. In spite of the familiar experience that one mode of Sensibility may be destroyed without involving the destruction of other modes, there is a general belief—derived from a mistaken conception of what is really represented by the unity of Consciousness—that Consciousness disappears altogether when it disappears at all; and hence, since Sensation is supposed to imply Consciousness, it also cannot be divisible, but must vanish altogether if it vanish at all. The first answer is that Sensation as an abstraction is neither divisible nor indivisible; but as a generalized expression of concrete sensorial processes it is reducible to these processes, and divisible as they are. No one doubts that we may lose a whole class of special sensations—sight, hearing, pain, temperature, etc.—yet retain all the others. No one doubts that we may lose a whole class of registered experiences—forget a language, or lose memory of places so familiar as the streets of the small town we inhabit, or of faces so familiar as those of friends and relatives, while the names of these streets and friends are still remembered when the sounds are heard. Yet sensation and intelligence are not wholly lost. The mind is still erect amid these ruins.269

61. This premised, let us consider the experimental evidence. Flourens declares that when he removed the whole of the Cerebrum from pigeons and fowls, they lost all sensation, all perception, all instinct, and all volition. They lived perfectly well for months after the operation, if the food were placed in their mouths; but they never sought their food; they never took it, even when their beaks were plunged into it: they could swallow, and digest the grains; but they had no instinct to make them seek, no volition to make them pick up the grains. They saw nothing, although the iris remained irritable; they heard nothing; they could not smell. A state of stupor came on, resembling that of deep sleep. All voluntary action ceased. If they were thrown into the air, they flew; if irritated, they moved away; but if left to themselves, they remained motionless, with the head under the wing, as in sleep. Now, inasmuch as these effects always ensue when the Cerebrum is removed, and never when only the Cerebellum is removed, he concludes that all instincts, volitions, and sensations “belong exclusively to the cerebral lobes.”

But all experimenters do not agree in other points named by Flourens; nor in the conclusions he has drawn. On the contrary, it is very certain, and we find evidence even in Flourens himself, that all instincts and all sensations are not destroyed by the removal of the cerebral lobes.

62. Let us hear Bouillaud on this subject.270 He repeated the experiment of Flourens, removing the whole of the Cerebrum from the Brain of a fowl; and he thus records his observations: “This fowl passes the greater part of her time asleep, but she awakes at intervals, and spontaneously. When she goes to sleep, she turns her head on one side and buries it in the feathers of the wing; when she awakes, she shakes herself, flaps her wings, and opens her eyes. In this respect there is no difference observable between the mutilated and the perfect bird. She does not seem to be moved at all by the noise made round about her, but a very slight irritation of the skin suffices to awaken her instantaneously. When the irritation ceases, she relapses into sleep. When awake, she is often seen to cast stupid glances here and there, to change her place, and walk spontaneously. If put into a cage, she tries to escape; but she comes and goes without any purpose, or rational design. When either foot, wing, or head is pinched, she withdraws it; when she is laid hold of, she struggles to escape, and screams; but no sooner is she liberated than she rests motionless. If severely irritated, she screams loudly; but it is not only to express pain that she uses her voice, for it is by no means rare to hear her cackle and cluck a little spontaneously; that is to say, when no external irritation affects her. Her stupidity is profound; she knows neither objects nor places, nor persons, and is completely divested of memory in this respect: not only does she not know how to seek or take food, she does not even know how to swallow it when placed in her beak—it must be pushed to the throat. Nevertheless her indocility, her movements, her agitation, attest that she feels the presence of a strange body. Inasmuch as external objects excite in her no idea, no desire, she pays no attention to them; but she is not absolutely deprived of the power of attention, for if much irritated her attention is awakened. She knows not how to escape an enemy, nor how to defend herself. All her actions, in a word, are blind, without reflexion, without knowledge.”

In this recital, the evidence both of sensation and instinct is incontestable, to any unprejudiced mind. Bouillaud, in commenting on his observations, remarks, that assuredly all sensation was not destroyed, since the sensibilities of touch and pain were very manifest. Nor is it certain, he says, that the fowl heard nothing, saw nothing. It is true that she stumbled against objects, and knew not how to avoid them. She opened her eyes on awaking, looked about, and showed a sensibility in the pupil to light; which, he thinks, is incompatible with the absence of all sensation of sight

63. The experiments of Longet271 seem decisive on this latter point. Having removed the whole of the Cerebrum from a pigeon, he observed that whenever he approached a light brusquely to its eyes, there was contraction of the pupil, and even winking; but, what was still more remarkable, “when I gave a rotatory motion to the candle, and at such a distance that there could be no sensation of heat, the pigeon made a similar movement with its head. These observations, renewed several times in the presence of persons who were at my lectures, left no doubt of the persistence of sensibility to light after removal of the cerebral lobes.” We have only to think of the baby following with its eyes the light moved before it, to understand the kind of impression produced by the candle on the pigeon. Longet also declares that his experiments prove the existence of sensations of sound, after removal of the whole cerebrum.

64. Dr. Dalton, giving the results of numerous experiments he performed, says that removal of the Cerebrum plunges the animal in “a profound stupor, in which he is almost entirely inattentive to surrounding objects.... Occasionally the bird opens its eyes with a vacant stare, stretches his neck, perhaps shakes his bill once or twice, or smoothes down the feathers upon his shoulders, and then relapses into his former apathetic condition. This state of immobility, however, is not accompanied by the loss of sight, of hearing, or of ordinary sensibility. All these functions remain, as well as that of voluntary motion. If a pistol be discharged behind the back of the animal, he at once opens his eyes, moves his head half round, and gives evident signs of having heard the report; but he immediately becomes quiet again, and pays no further attention to it. Sight is also retained, since the bird will sometimes fix its eye on a particular object, and watch it for several seconds together.”272

While, therefore, Flourens concludes from his experiments that the Cerebrum is the seat of all sensation and all volition; and Bouillaud concludes that it is most probably the seat of none; Dr. Dalton concludes that the functions of the Cerebrum are restricted to those usually classed as intellectual. “The animal,” he says, “is still capable, after removal of the hemispheres, of receiving sensations from external objects. But these sensations appear to make upon him no lasting impression. He is incapable of connecting with his perceptions any distinct succession of ideas. He hears, for example, the report of a pistol, but he is not alarmed by it; for the sound, although distinctly perceived, does not suggest any idea of danger or injury. The memory is altogether destroyed, and the recollection of sensations is not retained from one moment to another. The limbs and muscles are still under the control of the will; but the will itself is inactive, because apparently it lacks its usual mental stimulus and direction.”273

Dr. Dalton reminds us how disturbance of the cerebral functions in human beings recalls these observations on animals. “In cases of impending apoplexy, or of softening of the cerebral substance, among the earliest and most common phenomena is a loss or impairment of the memory. The patient forgets the names of particular objects, or particular persons; or he is unable to calculate numbers with his usual facility. His mental derangement is often shown in the undue estimate which he forms of passing events. He is no longer able to appreciate the true relation between different objects and different phenomena. Thus he will show an exaggerated degree of solicitude about a trivial occurrence, and will pay no attention to other matters of importance. As the difficulty increases, he becomes careless of the directions and advice of his attendants, and must be watched and managed like a child or an imbecile. After a certain period he no longer appreciates the lapse of time, and even loses the distinction between day and night. Finally, when the injury to the hemispheres is complete, the senses may still remain active and impressible, while the patient is completely deprived of intelligence and judgment.”274

65. Having seen how far other experimenters are from confirming the conclusions of Flourens, let us glance at his record of observations, and we shall find there evidence that all sensation and all volition cannot be localized in the Cerebrum. Speaking of a fowl whose Cerebrum was removed the day before, he says: “She shakes her head and feathers, sometimes even she cleans and sharpens them with her beak; sometimes she changes the leg on which she sleeps, for, like other birds, she sleeps habitually resting upon one leg. In all these cases she seems like a man asleep, who, without quite waking, changes his place, and reposes in another, from the fatigue occasioned by the previous posture: he selects one more comfortable, stretches himself, yawns, shakes himself a little, and falls asleep again.... On the third day the fowl is no longer so calm; she comes and goes, but without motive and without an aim; and if she encounters an obstacle on her path, she knows not how to avoid it.”275 In his second work he remarks of a Duck operated on in the same way: “As I mentioned last year À propos of fowls, the duck walks about oftener, and for a longer time together, when it is fasting, than when it is fed.”

Here he observes the unmistakable evidence of feelings of Hunger, Fatigue, and Discomfort in animals which, according to him, have lost all sensation. He also observes the operation of instinct (cleaning the feathers), and of spontaneous activity (walking about), in animals said to have lost all instinct and all volition.

66. Still more decisive are the observations recorded by other experimenters. Leyden removed the hemispheres and the ganglia at their base from a hen; yet this hen moved about and clucked. Meissner noticed that a pigeon whose hemispheres had been removed always uttered its coo, and showed restlessness at the usual feeding-time.276 Voit carefully extirpated the cerebrum from some pigeons, and kept them for many months in health. For the first few weeks they exhibited the well-known stupor. Then they began to shake this off, open their eyes, walk, and fly about spontaneously. They gave unmistakable signs of seeing and hearing. But the chief defect was in the inability to feed themselves, and the complete insensibility to danger. They also manifested signs of sexual feeling with lively cooings; though quite unable to gratify their desires.277 Vulpian having removed the cerebrum, optic thalami, and corpora striata from a young rabbit, found that on pinching its tail it cried out and struggled to escape; and a rat thus mutilated not only struggled and cried when pinched, but manifested strong emotion. “Il est trÈs craintif, trÈs impressionable; il bondit pour peu qu’on le touche; le moindre bruit le fait tressaillir. Un certain bruit d’appel fait avec les lÈvres, ou un soufflet brusque imitant celui qu’emettent les chats en colÈre excitent chez le rat une vive Émotion.”278

67. There are several well-authenticated cases on record of children born without a vestige of brain, and others with only a vestige, who nevertheless manifested the ordinary signs of sensation. I will cite but one, and it shall be one for which an illustrious physiologist, Panizza, is the guarantee. A male infant, one of twins, who lived but eighteen hours, during that period manifested such unquestionable signs of Sensibility as the following: the pupils contracted under light, sharp sounds caused flutterings, and a bitter solution when placed in the mouth was instantly rejected. This infant had not a vestige of cerebrum, cerebellum, or cerebral ganglia. The medulla oblongata was normal. There were no olfactory nerves, and the optic nerves terminated in a little mass of membrane.279

68. The observations of Lussana and Lemoigne are both extensive and precise, and the conclusion at which they arrive is that the removal of the Cerebrum is the abolition of Intelligence and Instinct, but is not the abolition of Sensation. Whereas Rolando, and after him Renzi, consider that only the Intelligence is abolished, the supposed loss of Instinct being really nothing more than the loss of the directive influence which makes the Instinct to be executed.

69. Here it becomes needful to understand

THE MECHANISM OF INSTINCT.

Were we dealing with an ordinary mechanism, and the disturbances produced in its actions by the removal of any part, we should attribute all observed effects to interference with the conditions of dependent sequence: we should infer that the actions were imperfectly performed, or wholly abolished, because their requisite mechanical conditions were disturbed. Let us be equally precise in dealing with the physiological mechanism. If we have deprived it of an organ in which certain combinations are effected, we must expect to find all actions which were dependent on such combinations to be now impossible; but all the actions which are not directly dependent on these combinations may still be possible. The actions of feeding, for example, are determined by certain sensations, when these are present in a particular sequence, but not otherwise; the sensation of sight does not suffice, because the animal must not only see the food, he must perceive it. The action of defence and flight are also determined by certain sensations, but only when these are connected in a certain sequence: the brainless animal will defend itself, or move out of the way, under the stimulus of unpleasant sensation; but will not be moved by a prospective injury, because he fails to associate it with the sight of the threatening object. In the same way a blind man shrinks at the actual contact of the heated poker, but does not shrink at the approach of that poker which he does not see. We do not deny him the possession of the so-called instinct of Self-preservation on this ground; why deny it to the brainless animal? The brainless fish or frog swims when placed in the water, because the sensation from the moving water280 sets going the swimming mechanism. To call this a “swimming instinct” may seem extravagant; yet it is as fully entitled to the name as Self-defence is, or the Alimentary Instinct. In all three cases there is a connate mechanism set going by appropriate feelings.

70. Since all admit that there is an Alimentary Instinct, let us see what kind of mechanism it implies. There must be a state of feeling called Hunger, which—combined with other feelings—determines certain muscular adjustments in the search, recognition, capture, and finally the swallowing of the food:—a very complex series of actions, which lead to and sustain one another until the desire is gratified. On the mental side there are three constituents, all indispensable: the hunger must be felt, the food must be discriminated, the desire must be gratified; on the physical side there are also the indispensable arrangements of the motor mechanism. Now it is obvious that the entire mechanism of this instinct cannot be localized in the brain, even if its mental elements are localized there; and there is reason to believe that even the mental elements—the feelings of hunger, discrimination, and gratification—are not exclusively localized there. The brainless animal manifests if not the feeling of Hunger, at any rate that feeling of discomfort which is the basis of Hunger. The restlessness is that of a hungry animal. Now we know that some of the Systemic Sensibility is preserved, for we see the animal breathing, swallowing, urinating, sleeping, preening its feathers, changing its attitude, resting on one leg after the fatigue of the other, etc. We may therefore infer that other systemic sensations, such as Hunger and Thirst, arise under the usual conditions.

71. We have noted an indication of Hunger; but on further observation we discover that although the food is eaten, if brought within reach of that portion of the feeding mechanism which is still intact, yet the second step—the feeling of recognition—is wanting. The animal fails to perceive the food brought under his eyes, or even placed in his mouth; unless the back part of the mouth be touched, no swallowing takes place. Hence the animal can no longer feed himself, and is therefore said to have lost his instinct. But although the mechanism of the instinct has been disturbed, its action is not wholly abolished. The brain is necessary for that combination of adjustments which normally accompany the perception of food through sight and scent; and its absence of course frustrates such combination; but we shall presently see that although certain sensible marks by which a perception is guided are absent, others may still be present, and suffice.

72. Before adducing examples let me say that we cannot legitimately attribute the abeyance of an instinct solely to the absence of the brain, 1°, because we observe a similar abeyance of the instinct and frustration of perception, even when the brain is present, and the animal is in its normal state. 2°. On the other hand, some instincts are unmistakably manifested, and some perceptions excited, after the brain has been removed. In fact, all that is needful is that some of the mental elements of such perception and such instinct be preserved; and this is the case so long as the leading element is present.

73. On the first point consider this unequivocal example. A healthy, hungry frog may be placed in a vessel in which lie a quantity of dead flies. He sees these flies, but sight is not enough; to him they are only so many black spots, in which he does not recognize his food, because the flies do not move, and the leading element in his perception of food is not a colored form, but a moving form. Hence this frog, in spite of brain and an intact organism, will starve amidst appropriate food. Whereas the frog that will not snap at motionless flies snaps at any other small moving object, though it be not his food. Goltz observed one incessantly snapping at the moving tentacles of a slug which was in the vessel—as if that were possible food! Not only the stupid frog, but the more intelligent carnivora will starve in the presence of appropriate food which is unrecognized, because the leading element in the recognition is absent. The cat will not eat a dead mouse, unless she has killed it herself. Predatory animals must capture their food—unless the scent of blood excites their alimentary instinct. So intimately is this sensation of a moving object connected with the predatory impulse, that the cat which is unexcited by the dead mouse cannot resist springing on a moving ball. We need not suppose the cat to mistake this ball for food; but we must suppose that, accustomed to pounce upon moving food, it is unable to resist the impulse of this leading sensation.

74. The presence of the brain not sufficing, in the absence of the leading sensation, we shall now see that the absence of the brain will not prevent the execution of the instinctive action, if the leading sensation be present. The brainless bird sees a heap of grain, or a pan of water, but no more recognizes them by sight alone than the frog recognizes the dead flies; yet if the bird’s feet be placed in the water, this sensation will suffice to make him drink; if placed amid the grain, this sensation will (sometimes) suffice to make him feed. Lussana and Lemoigne state that their brainless pigeons ate and drank with avidity when their feet were placed in grain and water.281 M. Krishaber removed the hemispheres from a pigeon, and observed that when his beak was thrust into a heap of hempseed the head was quickly withdrawn, whereas when the beak was plunged into water the bird drank eagerly. Every day he was forced to feed the bird by pouring the seed into its throat, but every day it drank when the beak was thrust into the pan of water.282 BrÜcke noticed that his brainless hen, which made no attempt to peck at the grain under her very eyes, began pecking if the grain were thrown on the ground with force, so as to produce a rattling sound. The sensation of hearing was here more perfect than that of vision, and sufficed to awaken the state of feeling necessary to initiate the pecking movement.283 75. Somewhat analogous phenomena are observed in Aphasia. The patient can see printed or written letters, and even copy them; but he cannot read, i.e. interpret, these symbols; as the birds see the grain, but cannot connect this sensation with others. These letters and words, which the patient cannot interpret when seen, he can interpret when heard; he can not only understand them when spoken, but write them if they are dictated to him. The birds recognize the grain and water (or act as if they did) when other sensations than those of sight are excited. Sound is the leading element in Language, both spoken and written. We hear the words even when we see them, but we do not see them when we hear them. The visible symbols are accessory and subordinate. But to the born deaf the visible symbols dominate. How one sensation will determine a particular group of movements which cannot be effected by any other stimulus is abundantly illustrated in disease no less than in experiment. Here is a very luminous example: Gratiolet had a patient for six months under his eye incapable of articulating a single word, owing to the incoherence of her incessant utterance—she babbled sounds, but could not group the syllables into a recognizable word. Yet she could sing the words of any song she knew, the musical sensations being sufficient to guide her vocal organs. “Ainsi la mÉmoire, infidÈle dans le cas oÙ les mots Étaient des idÉes, devenait claire et prÉcise quand les mots Étaient des chansons.”284

76. These illustrations plainly tell how the brainless animal may starve amid his food, failing to perceive it because the leading sensation is not excited; and how the same animal may manifest his feeding instinct if the mechanism be set going by a leading sensation. We are told, indeed, that in the absence of the brain the actions are mechanical reflexes from impressions, and not comparable with the complex processes determined by perception. I think, however, that the only difference is in degree of complexity: a combination of touch, temperature, and muscular movement will be simpler than one which also combines sight, smell, and the revived images of associated sensations. The sight of a sheep affects the instinctive mechanism of a wolf only when combined with the leading element of smell. Place a stuffed sheep in a field, and no wolf will approach and spring on it, whereas the blind wolf will find and capture the real sheep; and I believe that were it practicable to remove the brain without injury to the organ of scent and the powers of locomotion, the wolf would track and capture the living sheep.

77. The outcome of this discussion is that the mechanism of each instinct is the adjustment of the organs which effect the instinctive action; and this adjustment is not simply a cerebral process, but a complex of many sensorial processes; consequently the instinct cannot be exclusively localized in the brain, although the cerebral process may be a very important element in the adjustment. This is true even on the supposition that in speaking of Instinct we refer only to the state of feeling which originates the action—separating the psychological from the physiological aspect of the phenomenon. For the brain minus the organism is obviously incapable of feelings; whereas the organism minus the brain is obviously capable of sensibilities adequate to determine the actions. Thus the feeling of hunger which prompts the alimentary actions does not arise if the animal is satiated, nor does the sexual feeling which prompts generative actions arise when the animal is castrated; but each arises when the organism is in a particular state. In vain will food be placed before the satiated animal, or a female before the castrated male; food and female are seen and recognized, but no desires are excited, in spite of the brain and its supposed instincts. On the contrary, when the brain is removed, the need of the organism for food is felt, and this need determines restless movements, which are directed by certain other sensations, and the instinctive action of feeding is finally effected; although, of course, the removal of the brain has so disturbed the normal mechanism of the instinct that the action is imperfect. Renzi says that an animal deprived of its brain has lost the intelligence which enables it to seek and seize its food, but not the instinct, since it still has the desire for food. The following experiment may illustrate this. Renzi wounded superficially one optic thalamus of a frog without injuring the external margin, or optic tract. The frog showed no appreciable loss of sight, but hopped timidly away whenever approached. Then both thalami were divided transversely, the optic tract still being spared. This frog remained motionless under every threat. It manifested no alarm, and even when directly irritated, only crawled or hopped away like a brainless frog. Sight still so far remained that obstacles were avoided.285 Now since this animal’s brain was intact, and its organs of movement were capable of responding to stimulation, how are we to explain the loss of its instinct of self-preservation? The frog perceived no danger in a threatening approach, yet perceived an obstacle and avoided it, getting under it if there were room enough, crawling beside it if that was the easier escape. Why did one vision prompt the movements of escape, and another fail? Was it not that in the one case the normal pathway was still open, in the other closed? We know that one injury will destroy the perception of color without destroying that of light and shadow; so one injury may destroy the combination of neural processes necessary for the perception of a danger, without destroying those necessary for the perception of a hindrance. If all actions depend on their mechanical conditions, they must be disturbed according to the disturbance of the conditions. Nothnagel found that after removing the nucleus lentiformis on both sides of a rabbit, leaving all the rest of the encephalon intact, the rabbit hopped when its tail was pinched; yet although starting at the sound when hands were loudly clapped, did not hop as a normal rabbit does; nor although closing his eyes when a light was brought near them, did he ever move aside. No feeling of danger was excited by sound or sight. In striking contrast are the phenomena manifested by a rabbit whose corpora striata have been removed: it is with difficulty made to hop by pinching its skin, whereas noises and sights cause it to make terrified bounds.286 78. No sooner do we analyze the conditions of an instinct than we see the error of regarding instincts as localized in the brain. The cerebral process is only one factor in the product—an important factor, no doubt, since the cerebrum is the supreme centre of incitation and regulation; but its absence does not wholly carry away the activity of the mechanism, sentient and motor, on which the instincts depend, it only carries away one source of stimulation and regulation.

79. An instinct depends on a connate mechanism. Let us glance for a moment at a parallel case of an ordinary reflex action, also dependent on a connate mechanism, say that of sneezing. When the inner surface of the nose is stimulated by snuff, or other irritant, the nasal branch of the trigeminus is excited, and the effects are first a deep inspiration, then a closure of the respiratory orifices by the tongue, which in turn excites a spasmodic expiration. But the same effects are producible from quite different stimulations—namely, that of the ciliary nerves on sudden exposure to a glare of sunshine—or of the skin nerves on a sudden draught of cold air. BrÜcke remarks that there is perhaps no spot on the surface of the body from which this reflex may not be excited in very sensitive people. He knew a gentleman who always sneezed when in winter he laid hold of a cold door-bell; and the fit of sneezing was only arrested by giving him a crust of bread or something hard to gnaw. Now just as the connate mechanism of sneezing may be set in action by a variety of stimulations, so may the connate mechanism of an instinct.

80. Not only may Discrimination and Instinct be manifested in the absence of the brain, but even the acquisition of new modes of reaction, such as are classed under Learning through Experience. The objection is sometimes urged that animals without their brains only manifest single reactions on stimulation—the pinched foot is withdrawn, and then remains motionless until again pinched. But although the stimulation does not excite a consecutive series of movements, because there is no cerebrum to react in successive stimulation, this does not prove the absence of sensation in the one movement which is excited. If my hand be lying on the table, and something irritates it, my hand is withdrawn, and then remains as motionless as the limb of the brainless animal, until some fresh stimulation, external or internal, moves it. Although removal of the brain causes a manifest reduction in the variety and succession of the movements, all experimenters are agreed that animals acquire a certain dexterity in executing actions which they had previously failed to carry out after removal of their brains. “There is,” says Freusberg, “a decided improvement acquired in the reactions of the motor centres after division of the spinal cord, not indeed in vigor, but in delicacy. Removed from the regulating influence of the brain, the legs acquired through practice a power of self-regulation.” Nor is this wonderful: pathways are made easy by repetition of impulses, and new adaptations form new adjustments. It is thus all learning is effected—intelligent, and automatic. Nor is there any force in the objection that the power thus acquired speedily disappears, so that if the stimulations are effected at long intervals the reactions do not manifest their acquired dexterity. The spinal centres forget, as the cerebral centres forget; but they also remember, i.e. they learn. Because an animal shows to-day none of the aptitude it acquired three days ago, we are not to deny that it had once acquired the aptitude it has now lost. Attempt to teach a child to read by giving it spelling lessons of two or three minutes at intervals of two or three months, and little will the acquisition be!

81. Hitherto we have been considering phenomena manifested in the absence of the cerebral hemispheres, because it is in these that the majority of writers place the sensorium. There are, indeed, many authoritative writers who regard the ganglionic masses at the base of the cerebrum, and even those of the medulla oblongata, as participating in this sensorial property, which they refuse to the lower ganglia in the spinal cord. I cannot follow their logic. The cerebrum is by its position as a centre of centres, and its detachment from all direct innervation of organs, so different from the rest of the neural axis, that we can understand how it should be assigned a special function; although being of the same tissue as the other ganglionic masses, it must have the same property. And what that special function is I shall hereafter endeavor to set forth. But that the upper region of the spinal axis should differ so profoundly from the lower region as to be the seat of psychical processes, while the lower region is simply the seat of mechanical processes, is what I cannot understand, so long as the anatomical structure and physiological properties of the two regions are seen to be identical. The various centres innervate various organs, and have consequently various functions. As each centre is removed, we observe a corresponding loss of function—the organism is truncated, but continues to manifest such functions as have still their mechanisms intact. Let us suppose the brain or upper regions of the cord detached from the lower regions by a section of the cord; the animal will still live, and perform almost all its functions in the normal way, but there will be little or no consensus between the lower and the upper regions. Granting Sensibility to both, we must still see that the sensation excited in one will not be felt in the other. And this is the ground on which physiologists deny that the lower regions have Sensibility. Without pausing here to examine this point, which will occupy us in the next chapter, I assume that the positive evidence of Sensibility suffices to discredit that argument; and in furtherance of that assumption will cite an example of sensation and volition manifested by the lower portion of the cord when separated from the brain and upper portion.

82. The function of Urination is one which notoriously belongs to the voluntary class, in so far as it is initiated or arrested by a voluntary impulse, and it is one which, according to the classic teaching, has its centre in the brain. The grounds on which this cerebral centre is assigned are very similar to those on which other functions are assigned to cerebral centres, namely, observation of the suppression of the function when the pathway between certain organs and the brain is interrupted. But the careful experiments of Goltz287 have demonstrated that the “centre” of Urination is not in the brain, but in the lower region of the cord. When the cord is completely divided, Urination is performed in the normal way—not passively, not irregularly, but with all the characters of the active regular function. And, what is also noticeable, this function is so intimately dependent on Sensibility that it will be arrested—like any other function—by a sensation excited from the periphery—to be resumed when the irritation ceases. Now this arrest from a stimulation of sensory nerves takes place when the brain is cut off from the spinal centre, just as when the brain is in connection with it.

The same is true of Defecation, and the still more complex functions of Generation and Parturition. I can only refer the reader to the very remarkable case of Goltz’s bitch with the spinal cord divided in the lumbar region, if evidence be wanted for the performance of complex functions so long as the spinal centres were intact. It is true that Goltz considers these functions to have been independent of sensation; but that is because he has not entirely emancipated himself from the traditional views; for my purpose it is enough that he admits the functions to be dependent on sensorial processes.

83. To sum up the evidence, we may say that observation discloses a surprising resemblance in the manifestations of the cord and brain. In both there are reflex processes, and processes of arrest; in both there are actions referable to conscious and unconscious processes; in both depression and exaltation are produced by the same drugs; in both there are manifestations interpretable, as those of Discrimination, Logic, Instinct, Volition, Acquisition, Memory; in both there is manifestation of Sensibility—how then can we deny Sensation to the one if we accord it to the other?