The author’s aim in writing this book was to write a complete Encyclopædia on the sexual sciences, and it will probably be acknowledged by all who study its pages that the author has accomplished his intention in a very scholarly manner, and in such form as to be of great value to the professions for whom this translation is intended. The subject is no doubt one which appeals to and affects the interests of all adult persons, but the publishers have, after very serious and careful consideration, come to the conclusion that the sale of the English translation of the book shall be limited to members of the legal and medical professions. To both these professions it is essential that a knowledge of the science of Sex and the various causes for the existence of “abnormals” should be ascertained, so that they may be guided in the future in their investigations into, and the practice of attempts to mitigate, the evil which undoubtedly exists, and to bring about a more healthy class of beings. It is the first time that the subject has been so carefully and fully gone into in the English language, and it is believed that the very exhaustive examination which the author has made into the matter, and the various cases to which he has called attention, will be of considerable use to the medical practitioner, and also to the lawyer in criminal and quasi-criminal matters, and probably in matrimonial disputes and cases of insanity.