PREFACE, THIRD E])ITION 



excuse any errors that properly belong on 

 the editor's doorstep. He has learned as he 

 has gone along, but finds himself reacting 

 very much as he usually does at the end of a 

 lecture — if it were to be given again, parts 

 of it would be done differently. To the 

 contributors, there is a feeling of the deepest 

 gratitude for the time and thought they 

 have given to the preparation of their 

 chapters. The editor is indebted, too, to the 

 National Institute of Mental Health, Na- 

 tional Institutes of Health, for a research 

 grant, M-4648, which has taken care of a 

 number of the costs of publication. Justifica- 

 tion for this action is believed to have been 



given by the expansion of the section on the 

 gonadal regulation of reproductive behavior. 

 This development, in turn, would have 

 pleased Robert M. Yerkes. He was sensitive 

 to the need for truly scientific studies of 

 sexual behavior, the mechanisms which par- 

 ticipate in its expression, in the determina- 

 tion of its character, in its regulation, and 

 in its development. But he was equally aware 

 of the importance of investigations that 

 are purely physiologic, biochemical, and 

 morphologic, and in a quiet but effective 

 way did much to encourage many that are 

 recorded in the first two as well as in the 

 present edition of this book. 



