In spite of the great amount of attention that has been devoted to that protean condition termed “dementia præcox,” it is not yet possible to say that any sort of agreement has been attained regarding its aetiology, pathology, or even its distinctiveness as a clinical entity. Opinion has wavered between the two extremes of the psychogenic and the physiogenic views, and extravagant speculation has risen from a limited foundation of fact. It is interesting to note Freud's (1) remarks in his recently published Introductory Lectures on Psycho-analysis, in which he says—“The edifice of psycho-analytic doctrine which we have erected is in reality but a superstructure which will have to be set on its organic foundation at some time or other.” A pronouncement of such a kind and from such a source gives one furiously to think, and invites a thorough scrutiny of our present position with regard to the problem of dementia praecox. The biological conception of mental disorders is capable of wide application, and has the additional advantage of linking psychiatry with other better established sciences. Already the study of reaction types has proved most helpful in explaining much that was hitherto obscure. Also, in the field of pathology, although it is too soon to judge of the exact significance of Sir F. Mott's (2) work on the changes found in the gonads of cases of dementia praecox and other psychoses, it is nevertheless quite clear that the conception of an inborn germinal defect has opened a new vista for research. Endocrinology, that somewhat precocious offspring of medicine, has not been neglected by psychiatrists. Langdon Brown (3) made a most helpful simile when he compared the vital process to a projectile travelling with a constantly diminishing velocity, but supplied with certain regulators capable of exerting a considerable measure of control upon this velocity. These regulators are the endocrine glands and the autonomic nervous system. He supposes that a deficient equipment of endocrines, especially the gonads, may explain the infantile outlook of the dementia praecox patient, as well as such abnormalities in bodily structure as the atavistic, monkey-like hands. He quotes Stragnell as saying, “No endocrine inferiority can be present without a psychological change, a retreat or a compensation.” It will be remembered that Adler considered that the symptoms of dementia praecox were largely the results of a sort of consciousness of organ inferiority, and that they are really methods or attempts at compensation, though ineffective, vain and misdirected. Centuries ago Lucretius (4) pointed out that the “mind is begotten with the body, grows up together with it, and becomes old along with it.” “The psyche,” says Kempf (5), “is not something which has been added in the course of evolution, its history is that of the history of the body.”