THE GENERATIVE GLANDS 397 



Upon all essential points these investigators are unanimous. 

 It is the specific cells of the testis, the spermatogonias, which are 

 destroyed by the Rontgen rays; while Sertoli's cells, which take 

 no part in spermatogenesis, remain intact and the entire inter- 

 stitial tissue, with nerves and vessels, undergoes no change. 



Tandler and Gross experimented with roebuck with perfectly 

 developed secondary sex characters and found that, after exposure 

 of the testicles to the Rontgen rays, the antlers remained perfect ; 

 while it is well known that castration results in the loss of these 

 male characters. 



This elective destructive action of the Rontgen rays upon 

 the spermatic cells have recently been confirmed by Simmonds 

 by means of very careful experiments. He points out, however, 

 that even after prolonged exposure, isolated seminiferous tubules 

 remain intact. Of his conclusions the following deserve men- 

 tion : 



If the animal lives for a sufficient length of time after ex- 

 posure, regeneration of the seminiferous tubules will take place 

 and spermatogenesis may result. The destruction of the sper- 

 matic cells is almost invariably accompanied by proliferation of 

 the cells of Leydig, and this proliferation disappears after re- 

 generation of the spermatic cells. 



Where the testicle had become withered by the action of the 

 Rontgen rays, the animals frequently became very obese later. 

 This obesity, like that which follows castration, must be regarded 

 as the outcome of the destruction of the genital glands. 



From the results of his experiments, Simmonds concludes 

 that the maintenance of the sex characters, by means of an internal 

 secretion, is a function of both the spermatic cells and the cells 

 of Leydig; that under normal conditions the cells of Leydig are 

 few in number, but, after the destruction of the spermatic cells, 

 there is vicarious intervention on their part, in consequence of 

 which they undergo proliferation. 



If we summarize all that is known concerning the internal 

 secretory tissue of the male genital gland, we are led to the in- 

 evitable conclusion that the hormone which gives to the organism 

 its male characteristics, is elaborated in the cells of Leydig in the 

 interstitial tissue. In spite of their mesodermal origin, these cells 

 are able actively to produce certain specific substances and to 

 transfer these substances to the blood-stream ; such being the case 

 we are justified in describing them in their totality as an " inter- 

 stitial gland." 



It is highly probable that, by the agency of its secretory pro- 

 ducts, this gland is responsible for the development of the male 

 sexual gland from the indifferent genital trace. That it has a 

 determining influence upon the normal development and maturity 

 of the generative portion of the sexual gland, upon the formation 

 of the secondary genital organs, and upon the existence and. 



