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HOMER WHEELON 



usually larger than those of the normal testis (Fig. 5)-, otherwise their 

 structure is the same. The seminiferous tubules show marked abnormali- 

 ties; their basement membrane is thickened, and lined only by a single 

 layer of sustentacular cells. Sperm producing cells are not found in the 

 adult cryptorchid testis (Fig. 6). Similar pictures are seen in the cryp- 

 torchid human testis (Freiberg). In very young cryptorchid testes, how- 

 ever, large clear primary sperm cells are seen, but these apparently do not 

 develop, and soon disappear. . 



Fig. 7. The urogenital organs of a normal pig. (Hanes, 1911, Plate XXXIV, 

 Fig. 8.) 



No distinction can be made between the genitalia of normal and 

 cryptorchid animals possessing functional interstitial cells (Figs. 7, 8). 

 Complete sclerosis of the testes and castration, on the other hand, result in 

 immature development of the genitalia (Fig. 9). Hence, since the sexual 

 characters develop quite normally in the absence of sperm-forming cells, 

 they may be eliminated as possible factors in the elaboration of an internal 

 secretion by the testes. 



The sustentacular cells, in some instances, remain long after complete 

 degeneration of the sperm-producing cells in cases of vasectomy as well 

 as in testicular transplants and in cryptorchid testes. The following con- 

 siderations, however, relieve these cells of any responsibility in the pro- 

 duction of the testicular hormone. 



