CHAPTER VII

Experiments on Guinea-Pigs

WITHOUT going into physiological speculations let us once more return to our facts.

            In the pathological Institute of the New York State hospitals, I had occasion to carry on a few experiments on guinea-pigs. One of the guinea-pigs was put into a cataleptic condition by gentle stroking, while another was put into a similar state by simply seizing him suddenly. The guinea-pigs lost the control of their extremities and could not move even when stimulated by strong electric currents. After a few minutes left in the same position the guinea-pigs recovered the use of their extremities. The holding down of the animal to one position of the limbs, the gentle stroking, or the strong emotion of fear favored the condition of monotony and inhibition. In my present experiments I tried something similar, namely, to put the guinea-pig under the same conditions of experimentation under which I put the frogs and my human subjects.

            A guinea-pig was bound with straps and plaster strips and was left in this condition over night. In the morning he was found in the same place,—he could not free himself. He was very much weakened and paralyzed. He did not struggle much and could easily be put into a passive state. Unfortunately it was hard to say whether the passive state was due to his weakness or to the conditions under which he was artificially put.

            Young guinea-pig, of a few days old; very lively. I took him in my hands and kept him quietly and then put a blind on his eyes as I did in the case of the frogs. At first he struggled, then became very quiet. Respiration fell from 120 to 90 per minute. He remained in the same posture for about 35 minutes. He did not respond to stimuli such as intense noises. After fifteen minutes respiration was regular and fell to 60 per minute. The guinea-pig looked like a ball of immovable matter,—the only thing indicating life was the regularity of the respirations. After a few minutes I found that he started at intense stimuli, but still did not change posture. As he was near the end of the board his foot slipped from relaxation of the limbs, he changed posture, but remained immovable. After half an hour he began to stir and move his head slightly.

            On closing the pig’s eyes there was a difference in respiration,—the respiration fell and became more uniform. I tried now to modify somewhat the experiments. I found that the pigs were extraordinarily lively animals and struggled a good deal.           

            Now in my experiments on human beings where there was too much opposition to the induction of subwaking states, I could reduce the opposition by the use of hypnotics and anaesthetics. I tried similar experiments on my frogs, but the results were not satisfactory. The anaesthetized frogs either reacted very much like normal animals, or when given a somewhat larger and more effective dose soon died. I attempted to paint the skin of the frog with collodion to exclude stimulations of the skin, but the frogs died in convulsions. When I soaked their skin in chloroform or ether I had the same results. Evidently the skin of the frog absorbed the chloroform or ether and produced undesirable poisonous effects. Since however I did have success with my human subjects under similar conditions, I thought I might have some favorable result in the case of the guinea-pigs.

            A guinea-pig was put under chloroform for a few seconds. Respiration fell to 48 per minute. Reflex movements were well preserved. Eyes were partly closed. The guinea-pig started every time, but did not react to sound or light-stimuli, and very sluggishly reacted to pain-stimuli. He shivered and then closed his eyes. About 15 minutes later he began to react to stimuli. The reactions conformed to Pflüger’s law*. Stimulations called forth reactions on the same side. About half an hour later the pig began to feel pain, cried on sharp pinching of the front paw. Respiration was still greatly reduced. By closing his eyes and by continuous gentle stroking of his back, it was easy to make him fall asleep. He rolled up in a ball and seemed to sleep quite comfortably.

            Guinea-pig under ether for about a minute. Respiration and heart-beat greatly lowered. Muscles were relaxed; eyes were half closed in sleep. Later on he awoke and was fully alive to external stimulations, though not so lively as usual. I put him in my hand, kept him very quiet and closed his eyes. He evidently fell asleep as he did not open his eyes when I removed my hand from them; on the whole the pig kept unusually quiet without stirring a muscle.

            A guinea-pig was put under ether for 30 seconds. Reflex of wiping with forepaws was present. Reactions to stimuli were rather sluggish. After a few minutes the pig awoke, but had a tendency to go to sleep again when I put him in my hand, kept him very quiet and closed his eyes. He fell into a quiet sleep, his muscles relaxed; respiration and heart-beat were much lowered. When disturbed, he became fully awake and began to eat, but went immediately to sleep again, when put in my hand and kept quiet. Now and then a passing state of resistance of limbs was observed. The limbs once changed often retained the posture given them. This state however was far from being as marked as it was found in the case of the frog.

            When light was excluded from one of the eyes of the animal the other eye began to contract and close; the animal became unusually quiet. Anything that excluded visual sensory stimuli and brought about limitation of the voluntary activity of the pig produced a state very much akin to sleep with now and then a slight catalepsy quickly followed by relaxation of the limbs.

            A guinea-pig was fixed on a board,—he kicked violently. Collodion was used to fasten his eyelids together and as in the case of the frog, he became quiet and ceased to make attempts at fighting.

            A guinea-pig breathed chloroform for two seconds only. It seemed to have affected the animal sufficiently to make him quiet. He did not fight; lost a good deal of his liveliness. I put my hand on him, restricting his movements. He did not resist; I then closed his eyes; he remained without stirring in the same posture. When I closed one eye of the animal, the other closed also and the animal seemed to have gone to sleep, the limbs being in a relaxed condition.

            After some time he opened his eyes again; chewing movements were present; active, lively and restless, sniffing about in all directions. I once more took him in my hand, kept him very quietly, but firmly,—his activity subsided, he ceased to struggle, eyes became contracted as well as pupils; finally eyes closed very slowly. The animal sank into a state of turpitude. Respiration and heart-beat fell.

            Thus far we may say that the experiments on guinea-pigs gave results somewhat similar to those of the frogs, though the cataleptic states were not so pronounced,—in fact they were very transient. Still the induction of sleep was brought about under conditions of monotony, limitation and inhibition. It was far more difficult to bring about rest or passive states in guinea-pigs than in frogs, on account of the great liveliness and ceaseless activity of the pigs. It may be objected that the anaesthetics somewhat modified the result, because it might be claimed that the sleep-states induced were really due to the anaesthetics used. This objection however can be easily obviated by the rejoinder that the action of the anaesthetic was only to reduce the extraordinary activity and restlessness of the animal and thus make it easier to induce sleep. The sleep-states themselves were really produced under the same conditions as were the ones induced in frogs and in my subjects. In fact even when the guinea-pigs were really lively and active it was sufficient to subject them to the conditions described, when they gradually fell into a state very much of the character of hypnoidal states and sleep. The phenomena though were not so well marked as in the frogs.

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*See Chap. XI, footnote.

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