148 INTERNAL SECRETIONS 



not impossible, therefore, that in the animals mentioned 

 testicular secretory products were no longer present, though 

 the effects of castration were not yet visible. 



The knowledge of the fact that the absence of the higher 

 stages of spermatogenesis or of spermatozoa in the retained 

 testicle does not hinder the normal endocrine function of this 

 organ, has found practical application in human pathology. 

 We learned in Chapter III. that the results of castration can 

 be counteracted by the implantation of a retained testicle. In 

 a case reported by Lichtenstern, the microscopical examination 

 of a particle of the engrafted testicle showed that the semini- 

 ferous tubules were atrophic, and that no spermatozoa were 

 present. Thorek (1923) succeeded in restoring potency in an 

 ape previously castrated a year ago by engrafting a human 

 crypt orchic testicle. 



4. The Engrafted Testicle. 



We referred above (p. 82) to the experiments of Steinach 

 on rats where testicles were transplanted; in many cases the 

 transplantation was successful, and the animals reached full 

 maturity. But the histological examination (Steinach, 1916) 

 of the engrafted testicle showed that the generative part was 

 not normally developed. If there are originally fully developed 

 seminiferous tubules, or if these develop, they degenerate 

 afterwards. This is shown by the histological examination of 

 grafts at different intervals after transplantation. The greater 

 the interval after transplantation the greater the atrophy of the 

 generative part. The diameter of the atrophying seminiferous 

 tubules decreases. According to Steinach the ceUs of Sertoli 

 are finally the only part of the cellular elements of the semin- 

 iferous tubules which persists (Fig. 76). It may be, as Benda 

 (1921) has pointed out, that the cells forming the wall of the 

 degenerate tubules are really not cells of Sertoli, but primitive 

 cells of a generative character, which can enter into a new 

 phase of spermatogenesis. I sometimes found degenerate 

 tubules in a condition identical \nth that of young tubules. 

 This is why I suggested that degeneration of semi- 

 niferous tubules implies really something which might be 

 characterised as "backward development" (1921 d, 1922 c), to 

 use an expression of the Russian zoologist, Eugen Schultz (1908) 

 The changes observable in a degenerating tubule are, indeed. 



