THE REPRODUCTIVE ORGANS. 



751 



semen as well as the i:rine is discharged. The Prostate gland, the 

 exact function of which is not understood, is generally included in the 

 same class. 



The Testes. The secreting structure of the testicle and its duct 

 are disposed of in two contiguous, parts (1) the body of the testicle proper, 

 inclosed within a thick and tough white fibrous membrane, the tunica 

 albuginea, on the outer surf ace of which is the serous covering formed by 

 the tunica vaginalis, and (2) the epididymis and vas deferens. 



The Vas deferens, or duct of the testicle, which is about two feet 

 (60 cm.) in length, is constructed externally of connective tissue, and 

 internally is lined by a mucous membrane, covered with columnar epithe- 

 lium ; while between these two coats is a middle coat, very firm and tough, 

 made up of unstriped muscle, chiefly arranged longitudinally, but also 

 containing some circular fibres. When followed back to its origin, the 

 vas deferens is found to pass to the lower part of the epididymis, with 



Fig. 447. 



Fig. 448. 



Fig. 447. Plan of a vertical section of t^e testicle, showing the arrangement of the ducts. 

 The true length and diameter of the ducts have been disregarded, a a, tubuli seminiferi coiled 

 up in the separate lobes ; 6, tubuli recti or vasa recta ; c, rete testis ; d, vasa efferentia ending 

 in the coni vasculosi ; I, e, g, convoluted canal of the epididymis ; h, vas deferens ; /, section of 

 the back part of the tunica albuginea ; i, i, fibrous processes running between the lobes ; s, me- 

 diastinum. 



Fig, 448. Section of the epididymis of a dog. The tube is cut in several places, both trans- 

 versely and obliquely ; it is seen to be lined by a ciliated epithelium, the nuclei of which are 

 well shown, c, connective tissue. (Schofield.) 



which it is directly continuous (fig. 447), and assumes there a much smaller 

 diameter with an exceedingly tortuous course. 



The Epididymis, which is lined, except at its lowest part, by co- 



