In undertaking to introduce a discussion on this very large and important question, I am conscious of my inability to do it justice. No one can possibly cover the wide range of subjects comprised in it; and I am anxious rather to elicit the convictions of more experienced men than to obtrude my own crude and imperfect ideas. My purpose is, therefore, to state the case as briefly as possible, and to introduce questions for discussion in preference to merely ventilating my own ideas. In this way we may arrive at some common points of agreement and materially advance our knowledge of the subject. There can be no two opinions as to the advantage of bringing to a focus the collective experience and conclusions of the various sections of our profession interested in this field of research, and the present opportunity is a particularly good one. The title of the discussion embraces a great deal, and yet does not strictly include topics which might be considered relevant, particularly therapeutics. My aim at the outset will be to invite your special attention to a few questions only, and in order to make the most of our time and concentrate the discussion as much as possible I propose to take each division separately. The subject, viewed as a whole, is so far-reaching and practical as to possess uncommon interest, for it links together medicine and psychological medicine, it gives an open field of discussion to general medicine, obstetrics, and psychology, and it views insanity on its less speculative side, because the more materialistic functions are brought out in strong relief, and sometimes even overshadow the characters of mental disease.