250 HAND-BOOK OF PHYSIOLOGY. 



just before it enters the prostate gland, through part of which it passes 

 to terminate in the urethra, gives oiT a side-branch, which bends back 

 from it at an acute angle: and this branch dilating, variously branching, 

 and pursuing in both itself and its branches a tortuous course, forms the 

 vesicula seminalis. 



Structure. Each of the vesiculae, therefore, might be unraveled 

 into a single branching tube, sacculated, convoluted, and folded up. The 

 structure of the vesiculse resembles closely that of the vasa deferentia. 

 The mucous membrane lining the vesiculse seminales, like that of the 

 gall-bladder, is minutely wrinkled and set with folds and ridges arranged 

 so as to give it a finely reticulated appearance. 



Functions. To the vesiculse seminales a double function may be 

 assigned; for they both secrete some fluid to be added to that of the tes- 



Fio. 406. Dissection of the base of the bladder and prostate gland, showing the vesiculae seminales 

 and vasa deferentia. a, lower surface of the bladder at the place of reflection of the peritoneum; 6, 

 the part above covered by the peritoneum; t, left vas deferens, ending in e, the ejaculatory duct; the 

 vas deferens has been divided near i, and all except the vesicle portion has been taken away ; s, left 

 vesicula seminalis joining the same duct; s, s, the right vas deferens and right vesicula seminalis, 

 which has been unraveled; p, under side of the prostate gland; m, part of the urethra; u, u, the 

 ureters (cut short), the right one turned aside. (Haller.) 



tides, and serve as reservoirs for the seminal fluid. The former is their 

 most constant and probably most important office; for in the horse, bear, 

 guinea-pig, and several other animals, in whom the vesiculaa seminales 

 are large and of apparently active function, they do not communicate 

 with the vasa deferentia, but pour their secretions, separately, though it 

 may be simultaneously, into the urethra. In man, also, when one testicle 

 is lost, the corresponding vesicula seminalis suffers no atrophy, though its 

 function as a reservoir is abrogated. But how the vesiculae seminales act 

 as secreting organs is unknown; the peculiar brownish fluid which they 



