PREFACE 



must be attended by privacy, dignity and romance. It is a 

 good tradition, provided we add a fourth attribute, namely 

 understanding; for otherwise the fundamental life activities 

 concerned in sex may become involved in fears, inhibitions 

 and blind taboos. I emphasize the importance — nay even the 

 necessity — of instruction and understanding in matters of 

 sex, in case there are still among my readers some who are 

 troubled by our free discussion of intimate functions, and 

 especially in case it seems to them that the dignity and the 

 romance of life are threatened by frank acceptance of the 

 animal nature of mankind or by our use of other creatures to 

 explain human affairs. There is of course no denying that 

 man is an animal, and since human physiology cannot always 

 be subjected to direct experiment (particularly in this field 

 of investigation), we must study the lower animals not only 

 for their own intrinsic interest but also in order to under- 

 stand ourselves. It is equally true that man is more than an 

 animal. The ape, the tiger, and the worm mate and reproduce 

 their kind, and so do human beings, but only man tries to 

 understand what he is doing and why he does it. In such 

 understanding and in right living based upon knowledge lies 

 our best hope of attaining dignity, honor and beauty in the 

 physical life of mankind. 



A book of this kind rests upon the laborious work of many 

 scientific^ investigators. The author, in drawing freely upon 

 the writings of his colleagues, has endeavored to acknowledge 

 their contributions as fully as possible, by mention in the 

 text, footnotes and legends. References however are neces- 

 sarily limited; readers who wish to consult the original 

 literature will find full bibliographies in Appendix II, note 1. 



Many fellow workers who have generously permitted the 

 use of illustrations, as indicated in text and legends, deserve 

 especial thanks. 



