A full review of the German version of this book was published in this JOURNAL (Vol. II, p. 143, 1921). The author has now performed the feat of writing it in English, and it has been revised by Professor Marshall. This English edition differs very considerably from the German one inasmuch as the author has recast much of it, and has incorporated into it the recent work of subsequent years. We need only remind the reader that it is a standard work on this subject and also contains the most accessible reference in English to the work of foreign writers. The importance of the subject for all students of sexuality, where psychology is particularly hard to separate from physiology, is evident.