CHAPTER V 



THE EFFECTS OF CASTRATION AND OF TRANSPLAN- 

 TATION ON THE SECONDARY SEXUAL CHARACTERS 



IN several of the preceding chapters I have spoken in 

 some detail of sex-linked inheritance. In sex-linked 

 inheritance we deal with a class of characters that are 

 transmitted to one sex alone in certain combinations, 

 and have for this reason often been called sex-limited 

 characters ; but these same characters can be trans- 

 ferred by other combinations, as we have seen, to the 

 other sex, and are therefore not sex-limited. 



In contrast to these characters Secondary sexual char- 

 acters appear in one sex only and are not transferable 

 to the other sex without an operation. For instance, 

 the horns of the stag and the colors and structures of 

 certain male birds are in nature associated with one 

 sex alone. 



It has long been recognized in mammals and birds 

 that there is a close connection between sexual maturity 

 and the full development of the secondary sexual char- 

 acters. This relation suggests some intimate correla- 

 tion between the two. It has been shown, in fact, in 

 some mammals at least, that the development of the 

 secondary sexual characters does not take place, or 

 that they develop imperfectly, if the sex glands are 

 removed. It may appear, therefore, that we are deal- 

 ing here with a purely physiological process, and that 



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