CHAPTER V

The Induction of Sleep-States

OWING to the kindness of Dr. Walter B. Cannon, Professor of Physiology at the Harvard Medical School, I was given the opportunity and facilities to perform some experiments at the Physiological Laboratory of that institution. I wish to thank Dr. Cannon for all the kindness and consideration he has shown me in the carrying out of the experiments on sleep at his laboratory.*

            Guided by the work, on account of which was given in the previous chapters, I undertook a series of experiments on the induction of sleep in different animals. I thought it might be well, since sleep belonged to animals as well as to man, to start my experiments on animal life, beginning with lower animals and ending with man. My experiments were carried out on frogs, guinea pigs, cats, dogs, infants and adults. It occurred to me to use the same methods to bring about sleep under the conditions of normal and abnormal suggestibility in all those various representatives of the ascending scale of animal life. I consequently tried to induce sleep under the conditions favorable for the bringing about of the intermediary, subwaking, hypnoidal states. Now I pointed out above, that the transient character of the subwaking hypnoidal states was due to the variability of the conditions under which they were induced. Hence the fact of oscillation or instability of such states, the subject now plunging into hypnosis, now into sleep, and then again emerging into the light of the waking state. Hence the mixed manifestations observed in the subjects, when in the hypnoidal state now presenting the traits of hypnosis and now of sleep. My point therefore was to induce sleep and its allied states, subwaking and hypnoidal, keeping as closely as possible to the conditions of normal and abnormal suggestibility.

            Now I found in my experiments on the induction of the intermediary hypnoidal states in man that the conditions of monotony, limitation of the voluntary movements, limitation of the field of consciousness were of the utmost consequence. In my present experiments on animals I followed the same line of work and as far as possible reproduced the same conditions. I tried to limit the incoming sensory impressions, to limit the voluntary movements and thus produce a monotonous state by the continuous inhibition of new and varied stimulations. After narrowing down the animal’s psychophysiological activity I invariably found that when I succeeded in maintaining closely the same conditions which had been found favorable in human subjects for the induction of subwaking states, the animal uniformly fell into a passive condition closely analogous to the subwaking state and in many instances into a deep sleep. The condition of the animal was often strikingly similar to the one observed in the human subject. The respirations and pulse were lowered, while mental activity in the higher animals, alertness of sensory and motor reactions to external stimulations in the lower animals became greatly reduced and even completely suppressed. In the higher animals, such as dogs, a transitory cataleptic state, a state in which the voluntary muscles retained the position given to them, could be observed accompanied by a disturbance of respiration and heart beat. The slight disturbance then subsided and calmness supervened. The calm lasted but for a brief period of time and the disturbances reappeared. The latter were once more succeeded by calm which ended by full waking state or by a deep sleep. In other words, the experiments, the details of which are adduced further on, allow me to draw the conclusion that I had here the typical manifestations observed under the same conditions in my human subjects. I found here the manifestations characteristic of the intermediary hypnoidal states, the animal now passing into waking and now falling into sleep.

            Of course, in the case of the frogs the interpretation of the manifestations is rather uncertain. Still even in the frogs as the course of the experiments advanced the results stood out more clear and distinct, especially when viewed in the light of the experiments performed on the higher animals.

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* I take here the opportunity to acknowledge my obligations to Dr. Morton Prince and to Dr. W. B. Cannon for the many helpful suggestions given to me m the revision of the manuscript.

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