THE TESTES. 



1943 



causes are much less marked than in animals, in which sexual activity is limited to 

 definite periods. Seen in sections of the mature human testicle (Fig. 1656), the epi- 

 thelium lining the seminiferous tubules includes two chief kinds of cells, the support- 

 ing and the spermatogenetic. The former the cells of Sertoli take no active part 

 in the production of the spermatozoa, but serve chiefly as temporary supports for the 

 more essential elements during certain stages of spermatogenesis. They are elongated 

 elements of irregularly pyramidal form that rest by expanded bases upon the mem- 

 brana propria, and project towards the lumen of the tubule between the layers of the 



Eptdidymi 



FIG 1652. 



Convolutions of duct of epididymis in globus major 



^^ 



, Coni vasculpsi 

 (convolutions of 

 efferent ducts; 



Digital fossa- 

 Serous surface of testis 



Sect jons of duct of 

 epididymis 



g^Uyw . 



iwgS^fi&SsB'^fe^^i^w^bn^ * - '-'' r-'" ; 

 '^iWilmi^^Mi^Pn^ f^A^'- 



*'JMI^^^&^-^^^W ; ' - ' ' / y . .^ Blood-vessels 



W^ 



' v :^Hf^K ' 



yVy' . Rete testis in tnediastin 



Interlobular septum 

 Tunica albuginea 



Lobules of gland-tissue 



Convolutions of duct of 

 epididymis in globus minor 



Sagittal section of testicle of child, showing general arrangement of framework and 

 gland-tissue and of canals connecting epididymis with testis. X 10. 



surrounding spermatogenetic cells. The large oval nuclei of the Sertoli cells are con- 

 spicuously meagre in chromatin, and lie towards the middle of the cell at some distance 

 from its base. The outer part of the protoplasm contains fat-droplets, the inner zone 

 being granular or often longitudinally striated. Where the tubuli contorti pass into 

 the straight tubules the supporting cells become reduced in height and form a layer 

 of simple columnar cells continuous with the low cuboidal epithelium lining the rete 

 testis. 



The spermatogenetic cells include three forms that stand in the relation of suc- 

 ceeding generations to one another, those representing the oldest lying nearest the 



