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 Longet[271] 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