Problems of Life and Mind. Second series, George Henry Lewes [e book reading free TXT] 📗

“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