92 INTERNAL SECRETIONS 



been made by Guyenot and his co-workers, Ponse (1922) and 

 Welti (1923). 



But do all these experiments really afford sufficient proof 

 that the sexual glands act on the sexual characters by internal 

 secretions ? I mentioned above that we are confronted with an 

 objection here. We cannot exclude the possibility that centri- 

 petal nervous fibres have grown into the graft and that a 

 nervous path was re-established between the sexual gland and 

 the central nervous system. Nussbaum seems to have been 

 the first to have called attention to this. He pointed out that 

 by testicular or ovarian transplantation a new logical position 

 is not thereby created, and that there is nothing to decide the 

 question whether the graft is acting on the sexual characters 

 by the intermediation of a nervous path or by some chemical 

 substances. As far as I know the question whether nerves 

 also enter into the graft along with blood vessels has 

 not yet been studied anatomically. But observations certainly 

 show that a nervous connection between the engrafted sexual 

 gland and the central nervous system is established. A man on 

 whom a testicular transplantation was made by Lichtenstern 

 (1916) said, about five weeks after the operation, that bending 

 low (and pressing on the graft placed on the obliquus externus) 

 gave him the same pain as formerly when his own testicles were 

 pressed upon. The same thing was told me by another patient 

 also operated on by Lichtenstern. Els (1920) also describes 

 a case. where the sensitiveness of the testicular graft was like 

 that of a normal testicle. In view of these observations it seems 

 certain that the graft really becomes connected by nerves to 

 the central nervous system and that transplantation experi- 

 ments cannot absolutely decide the question whether the 

 sexual glands act by nervous reflexes or by internal secretions 

 discharged into the circulating blood. 



B. FEEDING WITH SEXUAL GLAND. 



Unlike the experiments with transplantation, those upon 

 feeding with testes or ovary should supply satisfactory proof 

 of an endocrine action on the part of the sexual glands 

 if proved to be successful in preventing the symptoms of 

 castration. The important part played by feeding experiments 

 with thjnroid gland or its extracts in contributing to our know- 

 ledge of internal secretion in general may be mentioned here 



