With this object in view an investigation was undertaken which should cover the life histories of a series of families with sufficient detail and extension to warrant at least tentative conclusions as well as also to indicate probable lines for future work. So far as possible, inquiries were pushed along collateral as well as direct lines of ancestry; and not only ill health but common habits and experiences were, so far as possible, given the consideration strictly their due. In every way the attempt was made to properly estimate the factors appertaining to the more intimate personal life as well as those that were more obvious and impersonal. Often, however, the completed record proved to be more or less broken; more often still, important items--the most important of all, in fact--could only be obtained under promise of absolute secrecy as to future use. So, as matters of absolute science, the following conclusions must stand chiefly as challenges for future confirmation or change. But, so far as they can be allowed to go, they may be accepted as pretty thoroughly based in ascertained fact and legitimate generalization. The very first conclusion, so far as the natural history of the steps toward insanity is concerned, is that the weak constitutional strands and tendencies have their beginnings in those ancestral marriages which, chiefly for educational reasons, I have chosen to call "unphysiological."[C] By an unphysiological marriage one need not mean a marriage between people obviously deformed or imbecile or insane, or otherwise permanently unfitted, but rather between people who are found to be not well adapted to each other in some important sense. Thus, too great physical disproportion; too great disparity of age, or of temperament, or of family or of natural tendencies; or, on the other hand, too near a sameness, either through consanguinity or other sources; or too fixed constitutional characteristics; or even too great differences of education, religion, taste, or ambition. In fact, it seems probable that anything and everything which difficultly amalgamates in marriage, and as surely fails to blend in progeny, may be considered as unphysiological in this connection. As I have said elsewhere: "The parties entering into such an unphysiological marriage may both be normal individually, but yet not physiologically marriageable, because they are either too distantly or too nearly, or in fact too unphysiologically, related, either physically or psychically. In such cases the ultimate outcome is almost absolutely certain, and is noted chiefly by a definite class of tensions and reactions of both mind and body which invariably impress themselves upon progeny, and which for the most part are made obvious in this particular way. No matter how unphysiological such marriages may be, however, they do not necessarily or very often result in the evolution of insanity in the parties contracting them, but rather they do lay