214 R. R. HUMPHREY 



The assumption that the 'secretion' of this 'gland' is responsible 

 for the development of the secondary sex characters or sexual 

 instincts, or both, follows. The mass of evidence supporting 

 such an assumption is, however, entirely indirect, and is frequently 

 conflicting w^hen several forms are considered. The difficulties 

 lying in the path of the worker will be suggested by the following 

 comments upon several lines of investigation and experiment. 



The effects of castration are too well known to need description, 

 but the operation removes all testicular structures; the injection 

 of testicular extracts, though demonstrating clearly the presence 

 of elements capable of influencing sex characters and instincts, 

 does not limit the source of this element to the interstitial cells ; 

 vasectomy as practiced on laboratory animals and man (Myers, 

 '15) does not result in complete exclusion of other possible sources 

 of the secretion which causes retention of the sex characters and 

 instincts in animals so treated, since Sertoli cells as well as inter- 

 stitial cells are found to survive. The same may be said of 

 x-ray treatments, which, like vasectomy, destroy the germinal 

 epithelium, but do not eliminate the cells of Sertoli.- But as 

 histologic studies, in such cases, show apparent increases in 

 number or size of the interstitial cells, and partial or even com- 

 plete- degeneration of the Sertoli cells, it has been concluded 

 that the former rather than the latter must produce the secretion, 

 if any be produced. 



So, too, do the studies of cryptorchid testes and the organs of 

 hermaphrodites fail to give clearly convincing evidence. Hanes 

 ('11) believed that in cryptorchid pigs the evidence from the sex 

 characters of animals and histological studies of the testes 

 warrants the belief in the secretory function of the interstitial 

 cells; Whitehead ('08), from studies on a cryptorchid stallion, 

 inclined to the same opinion, and, further, considered that the 

 Sertoli cells had been ruled out as a possible source of secretion 

 because of their degenerate condition in the animal studied. 



2 Biedl, page 396, lists numerous workers in this field and summarizes their 

 findings. 



3 Tournade ('03-'04) has shown that degenerative destruction of the Sertoli 

 cells ultimately results from ligature of the vas deferens in rats. 



