INTERNAL SECRETION OF TESTICLE 193 



whereas the seminiferous tubules increase further and enter 

 upon spermatogenesis. At the age of eight months the inter- 

 stitial cells have almost disappeared. Pezard supposes that the 

 development of the sexual characters in the cock is not parallel 

 to the development of the interstitial tissue: the discordant 

 growth of the comb and the development of the sexual in- 

 stincts take place at a time when the interstitial tissue is 

 already nearly at the minimum. As the discordant growth of 

 the comb and the development of the sexual instincts can take 

 place only when the hormones of the testicle enter without 

 interruption into the blood, Pezard concluded from his ob- 

 servations that the sexual characters in the cock are formed 

 and preserved by hormones arising not in the interstitial cells 

 but in the generative part of the testicle. 



Against the conclusions of Boring, Pearl and Pezard the 

 same objection can be made as in the cases of the mole and 

 Rana esculenta, i.e., that the decrease of the interstitial tissue 

 in the testicle of the growing cock is only an apparent one. 

 The testicle increases enormously owing to the development 

 of the seminiferous tubules, and if the volume of the interstitial 

 tissue remains unaltered or even markedly increases, a single 

 microscopical preparation will always give the impression that 

 the insterstitial tissue decreases as compared with what is found 

 in the just hatched or young chicken, whereas there may be in 

 reality only a distribution of the interstitial tissue in an enlarged 

 space. 



A detailed study of the interstitial tissue in the cock as made 

 by Benoit (1922) showed that this objection is justified. Benoit 

 claims that the investigators drew erroneous conclusions about 

 the interstitial cells in the cock, owing to an insufficiency in 

 their methods. According to Benoit the interstitial cells of the 

 cock acquire the appearance of glandular cells at an age of about 

 three months. A quantitative study of the question reveals 

 that the total mass of interstitial tissue increases enormously, 

 though there is seemingly a decrease when judged from a single 

 microscopical preparation. Benoit (1922 d) stated that at an 

 age of two and a half months when, according to Pezard, the 

 interstitial tissue decreases, there is in reality an increase of 

 about three times compared to that at an age of two weeks. 

 At about seven months the total mass of glandular interstitial 

 cells is about 24 times greater, and in the fully-grown cock the 



