THIS is a new sort of book, and unique. That is why I look upon the permission to write a brief preface for it as a rare privilege. Writings on children are frequent. When, in 1875, I contributed, for Karl Gerhardt’s immense Handbuch, my Hygiene of the Child, I quoted seven hundred treatises or pamphlets on that subject. There are now at least seven thousand of the kind, and the number of text-books on the diseases of children and infants do no longer lead a pardonable, rarely a laudable, existence. A few monographs on special subjects, or modern publications, as Erich Wulffen’s The Child: His Nature and Degeneration (Berlin, 1913), or the two large anthropological volumes by H. Ploss, The Child in the Customs and Morals of Nations (third edition by B. Renz, 1911), are praiseworthy examples of useful books. But while these are instructive they do not rouse historical interest.