Preface Need of Sex Knowledge The Awakening of the Nation to the problems pertaining to Personal Purity, Sex-Hygiene and Eugenics, has created a demand for an authoritative series of instructions, presenting scientific facts written in such a language as to bring the subjects within the understanding of the great number of people that go to constitute our home life. Government investigation has sounded the alarm calling attention to the neglect of the greatest of life's interests. Fathers, Mothers, Teachers, Educators, Preachers, Physicians and leading Scientists are appalled at the conditions of degeneracy resultant from this widespread ignorance. Human Life, the most sacred of all life, depends on the proper teaching of Personal Purity, Sex-Hygiene and the Science of Eugenics; therefore, as moral instruction is the dominant educational need of the present generation, so the solving of sex problems transcends all others in importance. Many generations have joined in the "Suicidal Policy of Silence" in matters pertaining to Sex and Reproduction. The result is widespread ignorance of matters of the utmost importance to the individual and the race - ignorance of which many good people feel proud, but might well be ashamed. The social conditions of today demand the raising of the standard of human life; to develop wiser and better trained parenthood; to bring into closer relations the home and the school that parent and teacher may co-operate intelligently in the education of the young; to better fit young people for the duties of parenthood; to develop the childhood of the whole world into good citizens instead of law breakers and degenerates; to foster all that concerns childhood in the home, school, church, state and legislation, and to interest men and women to co-operate in the work for social purity. Dangers of Ignorance Sacredness of the body should be taught early to children. It is through ignorance on this very important subject that too often the young are entrapped to their ruin. Parents frequently act too much as ix