In “The Psychology of Suggestion,” I pointed out the conditions of normal and abnormal suggestibility. Among these conditions, monotony and the limitation of voluntary movements play an important r?le. Any arrangement of external circumstances, tending to produce monotony and limitation of voluntary movements, brings about a subconscious state of suggestibility in which the patient’s mental life can be influenced with ease.

I find that in the subconscious hypnoidal state consciousness is vague and memory is diffused, so that experiences apparently forgotten come in bits and scraps to the foreground of consciousness. Emotional excitement is calmed, voluntary activity is somewhat passive, and suggestions meet with little resistance.

The induced subconscious hypnoidal state is a rest state, a state of physical and mental relaxation. It is a state of rest and relaxation that is specially amenable to psychotherapeutic influences. The important results obtained by me led to a closer study[92] of what I then thought was a peculiar mental state designated by me as the subwaking, or the hypnoidal state.

The subwaking, or the hypnoidal state is essentially an intermediary state belonging apparently to the borderland of mental life. On the one hand, the hypnoidal state touches on the waking condition; on the other it merges into sleep and hypnosis. A close study of the hypnoidal state shows that it differs from the hypnotic state proper and that it can by no means be identified with light hypnosis.

In my years of work on patients and subjects, I have observed the presence of the hypnoidal state before the development of hypnosis and also before the onset of sleep. When again the hypnotic or sleep state passes into waking, the hypnoidal state reappears. The hypnoidal state then may be regarded as an intermediate and transitional state.

A somewhat related state has been long known in psychological literature as the hypnagogic state which precedes the oncome of sleep and is rich in hallucinations known under the term of hypnagogic hallucinations. In coming out of sleep, a closely related state may be observed, a state which I have termed hypnapagogic. In both states, hypnagogic and hypnapagogic, dream-hallucinations hold sway.

The hypnagogic and hypnapagogic states do not belong to light hypnosis, as it can hardly be claimed[93] that men fall into light hypnosis twice, or possibly more than that, every day of their life. We do not go into light hypnosis with every nap we take. We do, however, go into the hypnoidal state when we pass into sleep or come out of sleep. Every drowsy state has the hypnoidal state as one of its constituents; every sleep state is preceded and followed by the hypnoidal state.

Hypnosis may be regarded as belonging to the abnormal mental states, while the hypnoidal state is more closely allied to waking and sleep, and belongs to the normal, physiological, mental states. At first, I regarded the hypnoidal state as peculiar, but as I proceeded with my observations and experiments I could not help coming to the conclusion that the hypnoidal state is found in all the representatives of animal life and is as normal as waking and sleep.

The hypnoidal state may be said to partake not only of the nature of waking and sleep, but also to possess some characteristics of hypnosis, namely, suggestibility. It is clear that, from the very nature of its mixed symptomatology, the hypnoidal state is variable and highly unstable. The hypnoidal state may be regarded in the light of an equivalent of sleep. Like sleep, the hypnoidal state has many levels of depth. It differs, however, from sleep in the rapidity of oscillation from level to level.

In the experiments of various investigators, the depth of sleep is found to be represented by a rapidly[94] rising curve during the first couple of hours, and by a gradually descending curve during the rest of the hours of sleep. No such regularity of curve can be found in the hypnoidal state. The depth of the hypnoidal state changes very rapidly, and with it the passive condition and suggestibility of the patient.

For many years investigations of the hypnoidal state were carried out by me on subjects and patients, adults, and children. The work was entirely limited to the study of such states as found in man. Having found that during the hypnoidal state the condition of suggestibility is quite pronounced for therapeutic purposes, and having effected many cures of severe psychopathic maladies ranging throughout the whole domain of hysterical affections, neurasthenia, obsessions, drug habits, especially alcoholic ones, the hypnoidal state has become, in my practice, quite an important therapeutic agent. Other investigators have obtained some excellent results with the hypnoidal state in their treatment of various functional, psychopathic maladies.

Thus far, the work with the hypnoidal state has been confined entirely to observations and experiments on human subjects and patients, and also to the treatment of man’s psychopathic ailments. I undertook a series of experiments on sleep, both from a phylogenetic and ontogenetic standpoint, following up the conditions and manifestations of sleep[95] in the ascending scale of animal life, from the frog and the guinea pig, through the cat, the dog, to the infant and the adult.

My experiments clearly prove that the hypnoidal state is by no means confined to man, but is also present in animals. This is important since it indubitably shows how widely spread the hypnoidal state is throughout the domain of animal life. Moreover, the experiments clearly prove that the further down we descend in the scale of animal organization, the more prominent, the more essential, does the hypnoidal state become.

The conclusion is forced upon me that the hypnoidal state is the primitive rest-state out of which sleep has arisen in the later stages of evolution. We may say that sleep and hypnosis take their origin in the hypnoidal state.[8] Sleep and hypnosis are highly differentiated states; they have evolved out of the primitive, undifferentiated, hypnoidal state which is essentially a............