GENITAL ORGANS OF THE MALE. 



625 



Genital Organs of the Male. Testes. The testes or 

 testicles (Fig. 403), two in number, are situated in the scrotum. 

 They are composed of lobules, the number of which in each testis 

 is variously estimated at from two hundred and fifty to four 

 hundred. In each lobule are convoluted seminiferous tubules, 

 tubuli seminiferi, varying in number from one to three. 



These tubules contain epithelial cells of two varieties, susten- 

 tacular cells, or Sartoli's columns, and spermatogenic cells, the latter 

 being related only to the formation of spermatozoa. These two 

 varieties of cells are sometimes described as the parietal cells. 

 Internal to these are the mother-cells, which are derived from the 

 spermatogenic cells by the process of mitosis or karyokinesis 



Globus Major 



Vaga Efferentia 



Globus Minor 



Pio. 403. Vertical section of the testicle to show the arrangement of the ducts 



(Leroy). 



. 28). These give rise to a third and more internal layer of 

 'aughter-cells, from whose nuclei, by the disappearance of the 

 cell-body, the spermatoblasts are developed. These in turn become 

 spermatozoa. This process by which spermatozoa are formed is 

 known as spermatogenesis. 



Spermatozoa (Fig. 404). A human spermatozoon is about 50 p. 

 in length, and consists of a head from 3 fj. to 5 p. long, a body and 

 a tail, the last terminating in the end-piece of Retzius, which is the 

 end of the axial fiber which runs through the center of the body 

 and tail. The tail during the living condition is in rapid motion, 

 by virtue of which the spermatozoon can travel quite rapidly. The 

 vitality of spermatozoa is considerable, as they can live for several 



40 



