342 



THE ORGANS 



their protoplasm mingling with the intercellular substance, their 

 nuclei becoming lost and the cells finally disappearing. According to 

 this theory the tuft-hke arrangement of the spermatozoa about the 

 ends of the Sertoli cells is due to pressure by surrounding spermato- 

 genic cells (Figs. 236, h and 238, /). 



^v-f:-\;^ 





^^^- ^^^^'^3^ 





— SI 



sp 

 sc 



sp 





m 



•sp' 



si 



■i^^mm'] 



in 



sp 



L^ ^ 



y 



Fig. 236. — Parts of Transverse Section of three Seminiferous Tubules from Testis of 

 White Mouse. X600. (Szj-monowicz.) 5, Sertoh cell with nucleus; 5/), spermatogone, 

 resting state; sp' , spermatogone in mitosis; sc, spermatocyte; si, spermatid; sj, spermatid 

 developing into spermatozoon; h, head of spermatozoon; t, tails of developing sper- 

 matozoa; h, blood-vessel; c, interstitial cell; m, basal membrane;/, fat droplets. 



The appearance which the spermatogenic cells present depends 

 upon the functional condition of the tubule. In the resting state the 

 epithelium consists of several layers of spherical cells containing 

 nuclei which stain with varying degrees of intensity. In the active 

 state several distinct layers of spermatogenic cells can be dift'eren- 

 tiated. These from without inward are as follows:. 



(i) S^i^XMa-logau^s (Figs. 235 and 236, sp). — These are small cu- 

 boidal cells which lie against the basement membrane. Their nuclei are 

 spherical andrich in chromatin. By mitotic division of the spermat- 

 ogones are formed the cells of the second layer, the spermatocytes. 



