Each new field of scientific study goes through a period of development which may be likened to the development of a man child. Up to the age of six or seven a boy interests everybody intensely. In babyhood he is new and sweet and altogether charming because of the awakening qualities which bloom forth as he becomes a real person, and from then on up to seven or eight he is intensely interesting because he is revealing day by day what kind of a person he is likely to be. Then from say eight to thirteen he goes through a period in which he is in general best described as a whining brat who knows no law, is always against the government, and has no real friend except his mother. From about thirteen on he begins to find himself as a member of the human family, and by the time he is twenty-one is ready to don the toga and be admitted regularly into the ordered society of adults.