The method of hypnoidization, and the hypnoidal states induced by it, enable us to trace the history and etiology of the symptoms, and also to effect a synthesis and a cure. The hypnoidal state may not be striking and sensational in its manifestations, but it is a powerful instrument in psychopathology and psychotherapeutics. For many years my investigations of the hypnoidal state were carried out on subjects and patients, adults and children. Having found that during the hypnoidal state the condition of mental plasticity is quite pronounced for therapeutic purposes, and having effected many cures of severe psychopathic maladies, ranging throughout the whole domain of so-called hysterical affections, neurasthenia, obsessions, drug habits, especially alcoholic ones, the hypnoidal state has become in my practice quite an important therapeutic agent. Lately, others have obtained excellent results with the hypnoidal state in their treatment of various functional, psychopathic or neurotic maladies. Perhaps it may be opportune here for the sake of further elucidation to give a few extracts from the Presidential address on “The Hypnoidal State of Sidis,” given by Dr. T. W. Mitchell before the Psycho-Medical Society of Great Britain, January 26, 1911. “The history of science,” says Dr. Mitchell in his address, “affords us many instances in which the neglect of residual phenomena in experimental research has led to the overlooking of important facts, and prevented investigators from making discoveries which, had they paid attention to their residues, they could hardly have missed. The great chemist, Cavendish, probably missed the discovery of argon, because in his estimate of nitrogen of the air he neglected a residue which his experiments showed him could not be more than 1/120 part of the whole. More than a hundred years afterwards this residue was accounted for by the discovery of argon. “Now in the history of Psychotherapeutics, from its earliest beginning down to our own time, we find many cases where the circumstances under which curative results have been obtained render it difficult for us to range these results under the category of the therapeutics of suggestion.