The schizophrenic problem is a many-sided one and easily the most outstanding and important of this era. In the field of preventive psychiatry it offers many complexities and difficulties. The funda- -mental concepts of medical science are inadequate to its full understanding - an inadequacy that may be due to their impersonality. The study of mental disorders in general is to -day a very complicated one: one may consider ex- -elusively the principles which dominate the study of the organic psychoses, or use the point of view which has thrown so much light on hysteria and the other psychoneuroses or try to correlate both. Symptoms may be considered as defects or anomalies dependent on some structural or toxic damage to the nervous system, or each symptom and syndrome may be regarded as possibly having some significance, and as being part of an attempted adjustment to a life situation. The one attitude does not necessarily exclude but should supplement the other. A symptom may have its origin in certain hereditary structural or toxic factors, while at the same time it may be utilised for adaptive purposes: the severity and duration of the symptom may only be intelligible in the light of the actual situation and of the strivings of the individual Despite the fact that schizophrenia has been known under one or other name for centuries, the natur of the disorder, even at the descriptive level, remain in no small measure yet to be determined. The pro -. -gress made in the study of the psychoneuroses stimulated a revival of the study of the functional psychoses, and the stimulus given to this revival by the formulations of Adolf Meyer and of Jung on the schizophrenic group has done much to direct the work of the last two decades. The technical difficulties in the accurate analysis of material are considerable and while the main principles were clearly outlined twenty years ago the schizophrenic group of psychoses is by no means easy to delimit, and there is no general consensus of opinion as to the exact criteria which entitle a case to be included in this group. It has been divided into four sub -groups by Kraepelin (1), (1) simple, (2) hebephrenic, (3) catatonic, (4) paranoidal.