i86 INTERNAL SECRETIONS 



time when the sexual characters cease to develop further, or 

 continue to develop in so far only as they do so " concordantly " 

 with the general growth of the body and independently of the 

 hormonic apparatus of the testicle, or when they continue their 

 ** discordant" growth at a very low level. 

 * * * 



These conclusions are founded mostly on experimental 

 evidence taken in conjunction with clinical evidence such as 

 that derived from the study of cryptorchism. Further 

 clinical evidence, as, for instance, that afforded by some cases 

 of eunuchoidism in man, and especially cases of hermaphrodit- 

 ism, seem to militate against the theory elaborated above. 

 This evidence will be discussed later on. 



B. INTERSTITIAL CELLS IN THE TESTICLE OF 

 OTHER SPECIES. 



We have so far confined our discussion of the question as to 

 the seat of the endocrine testicular function to the mammals. 

 It is, however, a matter of great interest to go deeper into the 

 problem from the standpoint of comparative physiology, as we 

 have indicated when comparing the rabbit and the guinea pig 

 (Section Ai). We shall now consider the question as to whether 

 there are other animals besides mammals, in which the genera- 

 tive cells of the testicle can be considered as having no direct 

 connection with the internal secretion of the testicle, and in 

 which certain other elements of the latter can be regarded as 

 endocrine organs. As we said above, systematic investigations 

 on this question have been made only recently upon fishes, 

 amphibians and birds. 



I. Invertebrates. 



We know that in the earthworm the development of the male 

 sexual characters depends upon the sexual gland. As in the 

 testicle of the earthworm, besides the generative cells, only 

 connective tissue can be found, Harms (1914, pp. 117, 158) has 

 concluded that in this animal the generative cells alone produce 

 the sexual hormones. 



2. Fishes. 



Observations on interstitial cells in fishes have recently been 

 made by Coiirrier (1921, 1922) and by Kolmer and Scheminzky 

 (1922), who state that they are present in numerous species. 



