THE REPRODUCTIVE SYSTEM. 655 



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 

 contain 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 func- 

 tions are exercised at only one season of the year, the vesiculae seminales, 

 whether they communicate with the vasa deferentia or not. enlarge 

 commensurately with the testicles at the approach of that season. 



That the vesiculae are also reservoirs in which the seminal fluid may 

 lie for a time previous to its discharge, is shown by their commonly con- 

 taining 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 vesiculae in straining during defaecation, com- 

 monly contains seminal filaments. But no reason can be given why this 

 office of the vesiculae should not be equally necessary to all the animals 

 whose testicles are organized like those of man, or why in many animals 

 the vesiculae 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 approach 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 procrea- 

 tive power ceases. 



The fluid part of the semen or liquor seminis has not been satisfac- 

 torily analyzed: but Henle says it contains fibrin, because shortly after 

 being discharged, flocculi form in it by spontaneous coagulation, 'and 

 leave the rest of it thinner and more liquid, so that the filaments move 

 in it more actively. 



Nothing has shown what it is that makes this fluid with its corpuscles 

 capable of impregnating the ovum, or (what is yet more remarkable) of 

 giving to the developing offspring all the characters, in features, size, 

 mental disposition, and liability to disease, which belong to the father. 

 This is a fact wholly inexplicable: and is, perhaps, only exceeded in 

 strangeness by those facts which show that the seminal fluid may exert 

 such an influence, not only on the ovum which it impregnates, but, 

 through the medium of the mother, on many which are subsequently 

 impregnated by the seminal fluid of another male. 



