468 INTERNAL SECRETIONS 



complicated one ; though the existence of an inhibitory action 

 of the female sexual hormones on the plumage cannot be 

 denied, the opposite effect also seems to occur, for some of the 

 dorsal feathers in the hen are even better developed than in the 

 cock {Goodale; personal communication). The larynx seems 

 to be influenced in an antagonistic manner. As to the head 

 apparel it is probable that both the ovary and the testicle act 

 in the same direction, but "furtherance" by male hormones is 

 much more pronounced than by female ones. 



Notwithstanding lack of detailed knowledge as to the 

 dependence of the various sex characters upon the hormones, 

 it seems clear that there is no sex character which can be 

 regarded simply as a furthered or inhibited character of the 

 asexual type, the problem being always a more complicated 

 one. But leaving aside details we may assume that in mammals 

 and birds the sexually differentiated type originates from an 

 asexual embryonic soma, the characters of which underwent 

 "furtherance" and inhibition by sex hormones or developed inde- 

 pendently. In the Genetic System show^n opposite I have tried 

 to represent this hypothesis schematically. 



The objection might be made that this genetic system based 

 on a critical consideration of the results of experimental 

 castration, feminization and mascuhnization relates only to 

 quantitative differences between the sexes. There is no place 

 in this system for the differences in psycho-sexual behaviour. But 

 this defect is merely occasioned by lack of knowledge ; further 

 investigations on the psycho-sexual reflexes should reveal that 

 in this field also sex differences are of a quantitative order. 



There are certain facts which seem to show the dependence 

 of the generative cells also upon sex specific hormones. Ancel 

 and Bouin (1904, p. 1041) were the first to lay stress on such a 

 dependence. These authors pointed out that male interstitial 

 cells are present in the gonad during embryonic development 

 even before there is a sexual differentiation of the generative 

 cells. Further, Tandler and Gross (1912) concluded from their 

 observations on the seasonal dimorphism of the mole that the 

 ripening of the generative cells depends upon the interstitial 

 cells. We have seen, especially in Chapter IV., that the 

 question as to the seat of endocrine function in the testicle is not 

 yet solved, and is even more complicated than formerly 

 appeared. The observations of Ancel and Bouin, and of 



