CHAPTER Lin. 

 PHYSIOLOGY OF THE MALE REPRODUCTIVE ORGANS. 



The sexual life of the male is longer than that of the female. 

 Puberty or sexual maturity begins somewhat later, in tem- 

 perate climates at about the fifteenth year; but there is no dis- 

 tinct limitation of the reproductive powers in old age correspond- 

 ing to the menopause of the female. At the time of puberty and 

 for 'a short preceding period the boy grows more rapidly in stature 

 and weight, and the assumption of its complete functions by the 

 testis exerts a general influence upon the organism as a whole. 

 One of the superficial changes at this period which is very evident 

 is the alteration in pitch of the voice. Owing to the rapid growth 

 of the larynx and the vocal cords the voice becomes markedly 

 deeper, and the change is in some cases sufficiently sudden to cause 

 the well-known phenomenon of the breaking of the voice. The 

 neuromuscular control of the vocal cords becomes for a time un- 

 certain. The completion of puberty can not be determined in the 

 boy with the same exactness as in the girl, in whom menstruation 

 furnishes a visible sign of sexual maturity. Much of the sexual 

 mechanism may be functional long before the time of puberty, 

 as is shown by the presence of sexual desire and the possibility 

 of erection; but fully developed spermatozoa are not produced 

 until this period, and indeed the presence of ripe and functional 

 spermatozoa in the testis is the only certain sign that sexual ma- 

 turity has been attained. Puberty consists in the maturation of 

 the testis in the male, and of the ovary in the female. 



The Properties of the Spermatozoa. The development and 

 maturation of the spermatozoa in the testis has been followed 

 successfully by histological means. The mother-cells of the sper- 

 matozoa, the spermatocytes, give rise to four daughter-cells, sper- 

 matids, each of which develops into a functional spermatozoon. 

 The process in this case is spmething more than mere cell division, 

 since in the spermatozoa eventually produced the number of 

 chromosomes present in the nucleus that is, the head of the sper- 

 matozoon are reduced by one-half. The process of production 

 of the spermatozoa is therefore quite analogous to the maturation 

 of the ovum during the formation of the polar bodies. The forma- 

 tion and maturation of the spermatozoa may be represented by 



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