“Such cases as these may be regarded as the residual phenomena of the therapeutics of suggestion, and just as Cavendish and his successors too readily assumed that all the so-called nitrogen of the air was the same as the nitrogen of nitre, so we may be missing some important truth, if we too readily assume that all these therapeutic results are due solely to suggestion. The value of suggestion during hypnosis is well attested, and the possibility of effecting physiological and psychological changes by its means is supported by a large amount of experimental evidence. But evidence of this kind is lacking in regard to suggestion without hypnosis, and until it is forthcoming, we are justified in receiving with some suspicion the account of the therapeutic efficacy of suggestion in the waking state. We seem bound to consider whether some state of consciousness intermediate between waking and hypnosis may not be artificially induced and utilized for the purpose of giving therapeutic suggestion. “The scientific investigation of states of consciousness intermediate between waking and hypnosis is a contribution to psychology and psychotherapy which we owe practically to one man--Dr. Sidis. A research into the nature of suggestibility led him to formulate certain laws and conditions of normal and abnormal suggestibility.... “By keeping the patient for a short time under the conditions of normal suggestibility we induce a peculiar mental state which Sidis named _Hypnoidal state_. The process by which it is induced is what Sidis calls, _hypnoidization_. “By the use of various methods a state of consciousness is induced which differs from full waking, but is not hypnosis or ordinary sleep. “The hypnoidal state is an intermediary territory, on the borderland of waking, sleep and hypnosis. In the course of a valuable experimental investigation of sleep in man and the lower animals, Sidis discovered that the hypnoidal state is a phase of consciousness which is passed through in every transition from one of these states to another. In passing from the waking state to ordinary sleep or hypnosis, there is always a longer or shorter hypnoidal stage. In the practice of hypnoidization the patient sometimes drops into hypnosis, or he may fall asleep without touching on hypnosis. And so also in awaking from sleep or from hypnosis, the hypnoidal state has to be passed through. Sidis found that the further we descend in the scale of animal life, the more important does the hypnoidal state become in relation to bodily rest and recuperation, and he concludes that it is the primitive rest-state out of which both sleep and hypnosis have been evolved.