An Experimental Study of Sleep. BORIS SIDIS. J. of Abnormal Psychology, 3, 1-32, 63-96, 170-199.

        Sleep and hypnosis can both be produced by monotony, by limitation of voluntary movements, limitation of the field of consciousness and inhibition. In hypnosis there is fixation of the attention and suggestibility, and an increased facility of reactions to external stimulations. In sleep there is relaxation of the attention, absence of suggestibility and almost complete suppression of the more complex reactions associated with mental processes.

        Sidis, by the method which he terms hypnoidization, induces states which are allied to sleep on the one hand, and to hypnosis on the other. He thus utilizes conditions favorable to both sleep and hypnosis, with the exception that the subject is asked to fixate his attention instead of relaxing it. After a time the patient's pulse and respiration are somewhat lowered. He is often cataleptic and is in an unstable condition that falls now into sleep, then into wakefulness and again into hypnosis. These facts were the basis of experiments were made on frogs, guinea pigs, cats, dogs, children and adults. The same methods were used with all of the animals. The condition induced in frogs was not typical sleep as observed in human beings. Before the frogs fell into a state of prolonged passiveness they went through an intermediate stage which was highly unstable and varied from catalepsy to lethargy, and again from passivity to activity. The general characteristics of the condition corresponded to those of the hypnoidal state in man. A hypnoidal state that more and more closely resembled the phenomena observed in man, as the animal advanced in the scale, was found to precede and succeed the sleep of guinea pigs, cats, dogs and children.