Of course one must realize that just as, in the period of childhood, the plastic state of life, changes of structure and appearance are more rapid than in the mature man, after {70} traits and characters have become more fixed, so by analogy we may assume that this was the way of the human race and that in the earlier period changes were more rapid than they are to-day. Thus in the cross-fertilizations and amalgamation of races we would expect a slower development than under these earlier conditions, yet when we realize the persistence of the types of Irish and German, of Italian and Greek, of Japanese and Chinese, even though the races become amalgamated, we must infer that the racial types were very slow in developing. If we consider the variations in the structure and appearance of the several tribes and races with which we come in contact in every-day life, we are impressed with the amount of time necessary to make these changes. Thus the Anglo-American, whom we sometimes call Caucasian, taken as one type of the perfection of physical structure and mental habit, with his brown hair, having a slight tendency to curl, his fair skin, high, prominent, and broad forehead, his great brain capacity, his long head and delicately moulded features, contrasts very strongly with the negro, with his black skin, long head, with flat, narrow forehead, thick lips, projecting jaw, broad nose, and black and woolly hair. The Chinese, with his yellow skin, flat nose, black, coarse hair, and oblique, almond-shaped eyes, and round skull, marks another distinct racial type. Other great races have different characteristics, and among our own race we find a further separation into two great types, the blonds and the brunettes.