Psychiatry, during the past fifty years, has had a phenomenal but in some respects a rather unfortunate growth. Long in what Auguste Comte called the mystical state of the evolution of a science, psychiatry rapidly entered into its taxonomic phase when, as one of the later repercussions of the romantic reaction to eighteenth century materialism, the rightful place of psychiatry among the sciences of the humanities began to be appreciated. Almost simultaneously, however, premature efforts began to be made by students in the field to achieve higher levels of scientific development, with the result that the facts of psychiatry soon became almost lost in rigid and increasingly complex systems of classification. Fortunately, in recent years there has arisen a salutary tendency among psychiatrists to review the data of their discipline, and to re-examine the pragmatic and heuristic validity of certain formulations that too readily, perhaps, had been taken for granted. Among these attempts at re-orientation may be mentioned: as to ætiology and psychopathology, the work of Freud and the psycho-analytic school; as to a valid nosology, the statistical researches of T. V. Moore and others; and as to clinical application, the objective, critical studies of the results of various methods of diagnosis and therapy appearing with increasing frequency in the recent literature. We hope that the present work will be a contribution to the movement of fundamental reorganization now evident in psychiatry and its related fields of study.