PHYSIOLOGY, CHEMISTEY AKD PATHOLOGY 443 



and functional integrity indefinitely, and as long as these remain, altera- 

 tions of the stigmata of sex do not occur (Myers, Wheelon). If these cells 

 disappear from the testes the results are the same as those following castra- 

 tion. Recent works indicate that occlusion of the vas, although causing 

 primary degenerative changes in the sperm producing tissues accompanied 

 by hyperplasia of the interstitial cells, does not prevent the subsequent 

 appearance of sperm cells in the uri.niferous tubules (Steinach, Kuntz, 

 Wheelon). 



The operation of vasectomy upon male horses in place of castration 

 does not produce the results of castration; these animals retain all of the 

 sex characteristics of the stallion. Similar results are observed in cryptor- 

 chids from which the greatly enlarged epididymis instead of the testis is 

 removed. Simple occlusion of the vas in Herdwick rams does not prevent 

 the normal development of the secondary sex signs (Shattock and Selig- 

 mann). Unilateral castration accompanied by ligation of the opposite 

 vas results, within six months, in a diminution of the testis left in situ; 

 the seminiferous tubules carry but few spermatogonia, and the susten- 

 tacular cells remain unchanged. At the end of a year the testis is com- 

 posed almost entirely of extremely hyperplastic interstitial tissue; the 

 seminiferous tubules are greatly shriveled and the sustentacular cells 

 degenerated. However, sex characters remain as before the operation. 



Such observations are of special interest in that both sperm producing 

 tissue and sustentacular cells are destroyed without destruction of the 

 interstitial cells. The fact that the accessory sexual organs and the 

 secondary characters of sex appear and are maintained in association with 

 the interstitial cells alone is strong evidence in support of the theory that 

 these cells, and not the sperm producing or nutrient cells, are responsible 

 for the hormone production of the testes. The loss of interstitial cells 

 and castration, therefore, are equivalent as far as the development and 

 maintenance of secondary sexual characters are concerned. 



Cryptorchism and the Interstitial Cells. Hyperplasia and hyper- 

 trophy of the interstitial cells appear always to accompany both imperfect 

 development and secondary atrophy of the seminiferous tubules (Diirck). 

 Cryptorchid animals, or those possessing imperfectly descended testi- 

 cles, may be considered intermediate between castrated and normal indi- 

 viduals in regard to the genital glands, sexual instincts and char- 

 acters. Not infrequently there is a minimal development or an entire 

 lack of interstitial cells ; consequently the apparent degree of male- 

 ness is determined by the degree of development of these cells (Bouin 

 and Ancel, Doolen, Regaud and Policard). Observations upon cryp- 

 torchid pigs, the testicles of which have remained at a primitive stage 

 of development, show an absence of the sustentacular cells,, while 

 the interstitial cells are well developed (Fig. 4). Such animals are typical 

 males in appearance, and the genital tracts are fully formed. . Bilateral 



