SEXUAL ORGANS 627 



development on both sides. When pieces of testicle from normal 

 frogs are introduced under the skin of the castrated frogs, the 

 phenomena occur just as if the animals had not been castrated 

 (M. Nussbaum). 



The remarkable observations of Steinach indicate that the 

 internal secretion is not furnished by the proper reproductive 

 elements (those which form the spermatozoa), but by the interstitial 

 cells of Ley dig, which are distributed in groups throughout the 

 substance of the testes between the seminal tubules. When the 

 testes of a young- rat or guinea-pig are transplanted to another part 

 of its body (the peritoneal cavity or subcutaneous tissue), the 

 animal develops all the secondary sexual characters at the proper 

 time. The penis grows to the normal size. The seminal vesicles 

 and prostate develop in the ordinary way, and yield a plentiful 

 secretion. Sexual desire and potency appear in due season, and 

 in normal or, in not a few cases, indeed, increased intensity. Yet 

 histological examination shows that not a single spermatocyte or 

 spermatid (Chapter XIX.) has developed, while outside the 

 seminal tubules the interstitial cells form large masses which much 

 surpass in size the interstitial islands of the normal testis. Similar 

 changes are observed, though with less certainty and after a longer 

 interval, when the vas deferens is ligated, a method often recom- 

 mended and occasionally practised for the sterilization of the human 

 male. On account of the influence, thus demonstrated, of the inter- 

 stitial cells in producing the sexual development observed at puberty, 

 Steinach designates these cells collectively as the ' puberty gland.' 



When the ovaries of a young female rat or guinea-pig are 

 transplanted into the peritoneal cavity or under the skin of a pre- 

 viously castrated male animal of the same kind (preferably, to 

 facilitate accurate comparison, a male of the same litter), the graft 

 takes (in about half the cases), and the implanted ovaries grow 

 and mature in the male body. There is this difference in the fate 

 of the ovary and the testis when transplanted, that the generative 

 elements of the latter, the Graafian follicles, with the ova contained 

 in them, generally develop as well as the large interstitial cells rich 

 in protoplasm lying in the stroma, which cells appear to constitute 

 the female puberty gland. The strict isolation of the female 

 puberty gland is only realized in those cases in which by some 

 accident of healing the stroma of the transplanted ovary maintains 

 itself while the generative elements disappear. In these cases the 

 influence of the ovary on the development of the sexual characters 

 is the same as when the reproductive elements proper persist and 

 grow. Male animals into which successful implantation of ovaries 

 has been accomplished, instead of developing sexually in the way 

 observed even in castrated males, become feminized. The growth 

 of the external generative organs is inhibited, the mammary glands 



