SEC. 3. THE MALE ORGANS. 



The Testis. 



938. We have seen that the ovum is an epithelium cell 

 which, like other epithelium cells, is eventually shed ; though it is 

 prepared and nurtured in a way very different from that in which 

 other epithelium cells are cared for, we may in a broad way speak 

 of the discharge of ova as a ' secretion.' The history of the male 

 element, the spermatozoon, much more strikingly suggests the idea 

 of secretion. The semen containing the spermatozoa is formed in 

 epithelium lined tubules, the seminiferous or seminal tubules, tubuli 

 seminiferi, which have all the appearance of secreting tubules, and 

 is carried off thence by conducting tubules uniting into a duct, the 

 two sets of tubules making up together the secreting gland which 

 is called the testis. The distinction which we have more than 

 once pointed out between the secreting and the conducting 

 portion of a gland is remarkably salient in the testis. Not only 

 do the seminiferous tubules, which alone form the secreting portion, 

 differ markedly from the rest of the testis in structure, but they also 

 have a wholly different origin. The male embryo developes on each 

 side of the body cavity a patch of germinal epithelium, which is at 

 first apparently identical with that of the female embryo, and con- 

 tains primordial ova. As in the female, the epithelium cells are 

 separated into clusters by mesoblastic growths, but these clusters 

 become not Graaffian follicles with enduring ova, but tubules from 

 which the primordial ova disappear, and which eventually become 

 the seminiferous tubules, the secreting portion of the testis. The 

 rest of the testis, the conducting portion, is derived from a wholly 

 different source, namely, the Wolffian body ; the two portions 

 become connected to form the whole organ. In the female the 

 Wolffian body also joins the germinal epithelium to form part 

 of the whole ovary ; but the connection is not a functional one, 

 and in the adult ovary remnants only of the Wolffian body are 

 found at the hilus ( 929). 



939. In the adult the testis proper is an oval body surmounted 

 by a cap ; the latter, which is the coiled up main duct of the 

 organ, receives the name of epididymis. 



