The translation of this book will be welcomed by men and women from many different professions, but alike in the need of preparation to guide the sex-life of boys and girls and to meet emergencies caused by its corruption by weakness within or attack from without. Of the clergymen in this country who are in real touch with the lives of their charges, there is hardly a one who does not, every so often, have to minister to a mind whose moral and religious distress depends on an unfortunate sex history. Conscientious and observant teachers realize, in a dim way, that they cannot do justice to even the purely intellectual needs of pupils without understanding the natural history of those instinctive impulses, which, concealed and falsified as they are under our traditional taboos, nevertheless retain enormous potency. The facts, so clearly shown in the present volume, that the life of sex begins long before its obvious manifestations at puberty, and that the direction of its vaguer and less differentiated habits in these earlier years is as important as its hygiene at the more noticeable climax of the early 'teens, increase the teacher's responsibility. Moreover, there is probably not a teacher of ten years' standing who has not faced--or by ignorance neglected--some emergency where moderate insight into the laws whereby the vague instincts of sex are turned into healthy and unhealthy habits, and form right and wrong attitudes, could have rescued a boy or girl from years of wretched anxiety, or degraded conduct, or both. The social worker, still more emphatically, knows his or her need of a surer equipment for the wise direction of the life of sex in childhood and its protection from the abominable suggestions of those who are themselves sexually diseased or depraved. The casual questioning of medical or legal friends, reminiscences of vague references in the Bible or classic literature, and the miscellaneous experiences which life itself throws in one's way, are hopelessly inadequate.