THE VESICUL^: SEMINALES. 577 



the testicles, 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 vesiculse seminales are large and of ap- 

 parently 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 abro- 

 gated. But how the vesiculse seminales act as secreting or- 

 gans is unknown ; the peculiar brownish fluid which they con- 

 tain after death does not properly represent their secretion, for 

 it is different in appearance from anything discharged during 

 life, and is mixed with semen. It is nearly certain, however, 

 that their secretion contributes to the proper composition of 

 the impregnating fluid ; for in all the animals in whom they 

 exist, and in whom the generative functions are exercised at 

 only one season of the year, the vesiculse seminales, whether 

 they communicate with the vasa deferentia or not, enlarge 

 commensurately with the testicles at the approach of that 

 season. 



That the vesiculse are also reservoirs in which the seminal 

 fluid may lie for a time previous to its discharge, is shown by 

 their commonly containing the seminal filaments in larger 

 abundance than any portion of the seminal ducts themselves 

 do. The fluid-like mucus, also, which is often discharged from 

 the vesiculse in straining during defecation, commonly contains 

 seminal filaments. But no reason can be given why this office 

 of the vesiculse should not be equally necessary to all the 

 animals whose testicles are organized like those of man, or 

 why in many animals the vesiculse are wholly absent. 



There is an equally complete want of information respecting 

 the secretions of the prostate and Cowper's glands, their nature 

 and purposes. That they contribute to the right composition 

 of the impregnating fluid, is shown both by the position of the 

 glands and by their enlarging with the testicles at the ap- 

 proach of an animal's breeding-time. But that they contribute 

 only a subordinate part is shown by the fact, that, when the 

 testicles are lost, though these other organs be perfect, all 

 procreative power ceases. 



The mingled secretions of all the organs just described, 

 form the semen or seminal fluid. Its corpuscles have been 

 already described (p. 574) ; its fluid part has not been satis- 

 factorily analyzed; but Henle says it contains fibrin, because, 

 shortly after being discharged, flocculi form in it by sponta- 



