INTERNAL SECRETION OF TESTICLE 133 



developed seminiferous tubules full of spermatozoa, but with 

 underdeveloped interstitial cells. These animals had the penis 

 of a "castrate" (Figs. 67 to 72). 



Lacassagne (1913, p. 213) tried to support the view that the 

 endocrine function of the testicle is performed by the inter- 

 stitial cells, by the observation that the sexual ardour of the 

 rabbit becomes intensified after ligature of the vasa deferentia. 

 One might suppose that this was due to the proliferation of the 

 interstitial cells. Also Sand (19 18, p. 104) and Kuntz (1921) 

 remark that the sexual impulse is of a particular intensity when 

 there is a striking hypertrophy of the interstitial cells. Further, 

 Ancel and Boiiin (1904 b) have found a proportional relation 

 between the quantity of the interstitial cells in the retained 

 testicles and the degree of the development of the copulatory 

 apparatus in pigs in such a condition. Similar observations 

 have been recorded by Steinach and Sand in experiments on 

 rats with engrafted testicles (see Section 4). We shall see that 

 all these quantitative observations are insufficient for proving 

 the internal secretory function of the interstitial cells. First, 

 an increase of interstitial tissue after ligature may be some- 

 times only apparent, as was pointed out hy Myers (1915), who 

 ligatured the vas deferens in white rats ; the same may be often 

 true also for other experiments where an operative interference 

 with the testicle itself took place. Further, a normal develop- 

 ment of the sexual characters may be observed when an 

 extremely small number of interstitial cells is present, as we 

 showed in our own experiments. These two objections will be 

 discussed later. Thirdly, it seems to me impossible, as already 

 mentioned above, to make any certain statements as to the 

 intensity of the sexual ardour of small laboratory animals. 



The question as to why ligature of the vas deferens leads to a 

 degeneration of the seminiferous tubules is by no means 

 decided. One might suppose that degeneration is caused by an 

 interference with the blood supply of the testicle. This seems 

 very improbable, since in the rabbit and in the guinea pig the 

 ligature of the vas deferens can be made without any difficulty 

 and without interfering with the arteria spermatica interna. An 

 interference with the innervation of the testicle is more probable. 

 It is known [Brack, 192 1) that in cases of aplasia of the vas 

 deferens and of the cauda epididymidis in man there may be 

 full spermatogenesis. On the other hand, some workers have 



