INTERNAL SECRETION OF TESTICLE 187 



It has been shown by different observers that the interstitial 

 tissue in vertebrates other than mammals undergoes cychc 

 changes. 



Among fishes observations have been made by Courrier (1921, 

 1922) on Gasterosteus aculeatus. According to this observer 

 the connective tissue cells of the interstitial tissue in April begin 

 to assume the appearance of glandular cells surrounding 

 the blood vessels. This transformation of connective tissue 

 cells into true interstitial cells takes place only after spermato- 

 genesis is accomplished. Spermatogenesis begins long before, 

 and as early as the end of March spermatozoa are to be found 

 in great number in the seminiferous tubules. In May and 

 June Gasterosteus assumes the features characteristic of heat, 

 i.e., long after spermatogenesis has been accomplished, and when 

 the testicle contains a well developed tissue of glandular cells. 

 From these observations Courrier concludes that the inter- 

 stitial cells produce the internal secretion upon which the 

 nuptial transformations depend. It is also of great interest 

 that in cases where spermatogonia and spermatocytes only 

 were found in the testicle, and no interstitial cells, the nuptial 

 transformations fail to take place. Further, Courrier concluded 

 that the interstitial tissue cannot be considered as a trophic 

 organ in relation to the seminiferous tubules, as the former 

 does not develop until after the latter. Van Oordt {ig2^) and 

 Champy (1923), however, consider that these statements are 

 insufficient to prove the dependence of the nuptial changes 

 upon the interstitial cells. It may be pointed out that 

 Courrier's observations can be explained also in the light 

 of the "follicular theory" developed in the foregoing section 

 of the chapter. 



3. Amphibians. 



For amphibians the statements are very contradictory. 

 The question has been studied both histologically and experi- 

 mentally. Harms (19 14, p. 117) claimed to have demon- 

 strated that in Bufo vulgaris the Bidder's organ is a factor in 

 the development of the finger callosities. As this organ can be 

 considered as a rudimentary female sexual gland, in which, 

 according to Harms, interstitial cells do not occur, one might 

 conclude that in this case the degenerating female generative 

 cells present in Bidder's organ produce male sexual hormones. 



