154 HUMAN PHYSIOLOGY 



V. The testes. In addition to their function as repro- 

 ductive organs, the testes stand in close connection with the 

 whole body. This connection is, no doubt, brought about 

 by substances furnished by the glands to the blood, which 

 modify the vital processes. Extirpation of the testes (castra- 

 tion) in a boy is followed by disturbances in development. 

 The voice does not change at puberty, the muscles remain 

 soft, and there is no development of manly strength and 

 character. Also in adult man, castration, or premature 

 atrophy of the testes, is followed by disturbances in the 

 nervous system and psychical life. It is said that subcu- 

 taneous injection of testes-extract increases manly strength 

 and thereby increases the bodily and psychical well-being. 

 Nothing is known concerning the nature of the active sub- 

 stance. 



Functions of a similar nature to those of the above-described 

 organs have been attributed to the ovaries, prostate, hypophyses, 

 and kidneys, but nothing certain is known about them. 



