CHAPTER VI 



THE ORGANS OF REPRODUCTION 



We have convincing evidence that the organs of 

 reproduction, or the "sexual" glands, produce both 

 an external * and an internal secretion ; in this re- 

 spect showing a similarity to the pancreas and the 

 small intestine. The external secretion contributes 

 to the reproduction of the species; the internal 

 secretion like the secretions from the other duct- 

 less glands that we have studied, contributes to the 

 molding of the species. In this chapter we are, of 

 course, primarily interested in the internal secre- 

 tion of the sexual glands, though the two secretions 

 cannot always be sharply separated. 



Proof of an internal secretion. The removal of 

 the testes or ovaries, an operation commonly known 

 as "castration," if carried out before puberty, pre- 

 vents the development of "secondary sex character- 

 istics." In the female the periodic act of menstrua- 

 tion from a very early age until perhaps her fiftieth 

 year, is indicative of a .functional ovary. The 



1 Some physiologists are opposed to regarding the external 

 secrefion of the reproductive system as a true secretion, on the 

 ground that the active constituents are not enzymes. 



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