52 



VERTEBRATE REPRODUCTIVE CYCLES 



endocrine organ to produce the male hormone, or 

 androgen. This substance is described in the next section, 

 and the only question to be dealt with here is that of its 

 site of formation. For a long time it has been suspected 

 that the interstitial cells, which are glandular in appear- 

 ance, may be the main source of the testis hormone. The 



Spermatozoon 



^ Part oF sperm- 

 atic tubule 



Connect/Ve 

 y tissue 



Secretory inter- 

 stitial cell 



Lymph space 



Lipoid inter- 

 stitial cell 



Fig. 4. — The structure of the testis of a chaf- 

 finch, showing part of a spermatic tubule and 

 some of the interstitial tissue (after Sluiter and 

 van Oordt). 



early work of Benoit^^. 24, 25 supported this view, and 

 showed that hormone secretion in the cock is not 

 interfered with when the spermatic tubules are destroyed 

 by x-rays. Thus, Benoit was driven to assume that the 

 male hormone is formed somewhere in the interstitial 

 cells. Much recent work on this subject has been done 



