The facts when collected must, because they are many, be arranged. I believe that it would be found convenient by the political student to arrange them under three main heads: descriptive facts as to the human type; quantitative facts as to inherited variations from that type observed either in individuals or groups of individuals; and facts, both quantitative and descriptive, as to the environment into which men are born, and the observed effect of that environment upon their political actions and impulses. A medical student already attempts to master as many as possible of those facts about the human type that are relevant to his science. The descriptive facts, for instance, of typical human anatomy alone which he has to learn before he can hope to pass his examinations must number many thousands. If he is to remember them so that he can use them in practice, they must be carefully arranged in associated groups. He may find, for instance, that he remembers the anatomical facts about the human eye most easily and correctly by associating them with their evolutionary history, or the facts about the bones of the hand by associating them with the visual image of a hand in an X-ray photograph. The quantitative facts as to variations from the anatomical human type are collected for him in statistical form, and he makes an attempt to acquire the main facts as to hygienic environment when and if he takes the Diploma of Public Health. The student teacher, too, during his period of training acquires a series of facts about the human type, though in his case they are as yet far less numerous, less accurate and less conveniently arranged than those in the medical text-books. If the student of politics followed such an arrangement, he would at least begin his course by mastering a treatise on psychology, containing all those facts about the human type which have been shown by experience to be helpful in politics, and so arranged that the student's knowledge could be most easily recalled when wanted.