FOREWORD 



intermingling of ideas from various fields. 

 It is not merely by chance that among the 

 American workers on the hypophysis two 

 names stand out, those of a surgeon, Harvey 

 Gushing, and a zoologist-anatomist, Philip 

 E. Smith. 



The central achievement of this half 

 century of intensive work can be summarized 

 in one sentence. It was, first, recognition, 

 description and explication of the reproduc- 

 tive cycle of mammals and man; and, 

 second, identification of the chemical sub- 

 stances that serve to integrate the cycle and 

 preside over gestation. Those who took part 

 in these investigations recognized, of course, 

 that in due time their work must be ex- 

 tended in two directions, downward to the 

 domain of molecular chemistry and ul- 

 timately of ionic physics in order to un- 

 derstand the basic nature of hormone action, 

 and upward to the field of animal and 

 human behavior, where sex gland hormones 

 join with other forms of bodily and mental 

 integration in directing the life and be- 

 havior of the organism. 



Once the histologists and embryologists 

 had identified the sex gland hormones it 

 was inevitable that further investigation of 

 these remarkable substances should be taken 

 over by biochemists, as can be seen from the 

 successive editions of this book. The chief 

 unsolved problems now demanding atten- 

 tion relate largely to the sites of action of 

 the hormones and the precise molecular 

 effects which they exert upon their target 

 organs. Recent indications that estrogens 

 take part in hydrogen transfer in the citric 

 phase of carbohydrate metabolism, and that 

 progesterone affects uterine muscle cells 

 by altering their permeability to potassium 

 ions, show clearly that there is hope of 

 understanding th(^ action at molecular level 

 of these remarkably specific and powerful 

 substances, which were bai'ely beginning 

 to be known when the first edition of this 

 book appeared in 1932. 



As the investigators of the future leai'n 

 exactly where the sex gland hormones exert 

 their chemical action, and just what they 

 do to the fundamental elements of th(> 

 cells of their target organs, we may con- 

 fidently expect ever-increasing knowledge 

 even of the most complex sexual and repro- 

 ductive activities. Running over the chapter 



headings of this third edition of Sex and 

 Internal Secretions, we see indeed that al- 

 most every author concerns himself with one 

 or another aspect of sex and reproduction in 

 the light of what is already known about 

 endocrine regulation. Chapter after chapter 

 deals with cyclic events determined by sex 

 gland hormones. Phenomena which in the 

 first edition could be explained only sup- 

 positionally on a hormonal basis, for ex- 

 ample the "free martin" state in domestic 

 cattle, and menstruation in primates, are 

 now much better understood. Others which 

 seemed hardly within the scope of endo- 

 crinology are now seen to be in some degree 

 influenced by hormone action, and thus 

 to call for discrimination between endocrine 

 effects and other types of regulation such 

 as gene action and control through the 

 nervous system. The experimental embry- 

 ologists, for example, seek to understand 

 the respective effects of genes and hormones 

 in determining the development of the 

 internal accessory sex organs; students of 

 animal psychology likewise are beginning 

 to discriminate between the action of hor- 

 mones and neuro-psychologic factors in de- 

 termining the patterns of sex behavior. 



Among the subjects discussed in this 

 book, only psychiatry and anthropology are 

 as yet not greatly influenced by our recently 

 acquired stores of endocrinologic informa- 

 tion. The complex, high-level patterns of 

 human thought and behavior with which 

 these sciences deal are presumably far less 

 subject to chemical regulation than to the 

 integrative control of the nervous system 

 as it affects learning, memory, and racial 

 tradition. Yet when we consider the extent 

 to which daily life and ethnic customs are 

 bound up with the sexual and reproductive 

 activities of mankind, we are prepared to 

 find this edition of Sex and Internal Secre- 

 tions not only advancing greatly beyond its 

 predec(>ss()rs in the study of animal be- 

 havioi-, but also looking forward, through 

 exploi'niory chaptcn-s on psychiatric and 

 anthi'opologic asix'cts of liuninn s(\\ Ix^- 

 liavior, to a time when we shall more fully 

 understand the interrelations of all the con- 

 trolling factors even of these most complex 

 activities, upon which the continuation and 

 renewal of life dcp(>nd. 



