312 



CHORDATE ANATOMY 



of skin comparable with the labia majora of the female, the line of fusion 

 being marked externally by a ridge, the raphe. Included in the wall of 

 the scrotum is a cremaster muscle, the fibers of which are striped and by 

 contraction lift the scrotum and testes. 



The testes are oval glands which have migrated into the scrotum from 



the body cavity through the paired 

 inguinal canals, and which have both 

 reproductive and endocrinal func- 

 tions. Attached to the posterior 

 border of each testis is a mass of 

 efferent tubules forming the 

 epididymis. Each testis is enclosed 

 in a tough connective-tissue capsule, 

 the tunica albuginea, which pene- 

 trates into the substance of the testis 

 as septula and divides the testis into 

 lobules. 



The testis is a compound tubu- 

 lar gland composed of convoluted 

 seminiferous tubules which are held 

 together by interstitial connective 

 tissue. In each lobule several of 

 the seminiferous tubules unite into a 

 common efferent tubular outlet. 

 These efferent tubules, the tubuli 

 necting piece; ch.p., chief piece; g.c, galea recti, in turn combine into a network 



capitis; n, nucleus; nk., neck; p., proto- ^ i-r ^ ^ i j. j. *: 



plasm; />.c., posterior centrosome. (From of efferent tubulCS, the fCte teStlS. 

 Bremer's "Text Book of Histology," after Yvom the rete testis paSS the efferent 



M^GVCS ) 



ducts which convey the sperm from 

 the testis into the ductus epididjnnidis. These relations are shown in 

 Fig. 278. 



The seminiferous tubules are Uned with an irregular many-layered 

 epithehum from which the spermatozoa are proliferated, the multiplica- 

 tion of cells beginning in the basal layers. During this process a reduc- 

 tional or maturation division takes place previous to the metamorphosis 

 of the cells into mature spermatozoa. All transitional stages in the 

 conversion of epithelial cells into spermatozoa may be seen in a cross 

 section of the seminiferous tubules. The Sertoli cells which occur 

 among the germ-cells are usually assumed to have a nutritive function. 

 As the spermatozoa lose connexion with the epithelium, they pass into 

 the lumen of the tubules, and thus find their way to the epididymis, 

 in which they may be retained for some time. They are contained in 

 a mucous alkaline liquid, also secreted by the epithelium of the seminifer- 



C E F 



Fig. 277. — Diagrams of the develop- 

 ment of spermatozoa, a.c, anterior 

 centrosome; a.f., axial filament; c.p., con- 



