1020 



THE MALE ORGANS OF GENERATION. 



and tail, the latter projecting into the lumen of the tube. Ultimately the heads 

 are separated and the spermatozoa are set free. 



Spermatogenesis. The stages in the development of the spermatozoa are as 

 follows : The spermatogonia become enlarged to form the sperm atocytes, and 

 each spermatocyte subdivides into two cells, and each of these again divides into 

 two spermatids or young spermatozoa, so that the spermatocyte gives origin to 

 four spermatozoa. 



The process of spermatogenesis bears a close relation to that of maturation of 

 the ovum. The spermatocyte is equivalent to the immature ovum. It undergoes 

 subdivision, and ultimately gives origin to four spermatozoa, each of which con- 

 tains, therefore, only one- fourth of the chromatin elements of the nucleus of the 

 spermatocyte. In the process of maturation of the ovum its nucleus divides, one 

 half being extended as the first polar body. The remaining half of the nucleus 

 again subdivides, one half being extended as the second polar body. The portion 

 of the nucleus which is retained to form the female pronucleus of the now 

 matured ovum contains, therefore, only one-fourth of the chromatin elements of 

 the original nucleus, and thus the spermatozoon and the matured ovum, so far as 

 their nuclear elements are concerned, may be regarded as of the same morpho- 

 logical value. 



The tubules are enclosed in a delicate plexus of capillary vessels, and are held 

 together by anintertubular connective tissue, which presents large interstitial spaces 

 lined by endothelium, which are believed to be the rootlets of lymphatic vessels 

 of the testis. 



In the apices of the lobules the tubuli become less convoluted, assume a nearly 

 straight course, and unite together to form from twenty to thirty larger ducts, of 

 about -gig- of an inch in diameter, and these, from their straight course, are called 

 vasa recta. 



The vasa recta enter the fibrous tissue of the mediastinum, and pass upward 

 and backward, forming, in their ascent, a close network of anastomosing tubes, 



which are merely channels in the fibrous stroma, 

 lined by flattened epithelium, and having no 

 proper walls ; this constitutes the rete testis. At 

 the upper end of the mediastinum the vessels of 

 the rete testis terminate in from twelve to fifteen 

 or twenty ducts, the vasa efferentia : they per- 

 forate the tunica albuginea, and carry the sem- 

 inal fluid from the testis to the epididymis. Their 

 course is at first straight ; they then become en- 

 larged and exceedingly convoluted, and form a 

 series of conical masses, the coni vasculosi, which, 

 together, constitute the globus major of the epi- 

 didymis. Each cone consists of a single con- 

 voluted duct from six to eight inches in length, 

 the diameter of which gradually decreases from 

 the testis to the epididymis. Opposite the bases 

 of the cones the efferent vessels open at narrow 

 intervals into a single duct, which constitutes, 

 by its complex convolutions, the body and globus 

 minor of the epididymis. When the convolutions 

 of this tube are unravelled, it measures upward 

 of twenty feet in length, and it increases in diam- 

 eter and thickness as it approaches the vas def- 

 erens. The convolutions are held together by fine 

 areolar tissue and by bands of fibrous tissue. 



The vasa recta are of smaller diameter than the seminal tubes, and have very 

 thin parietes. They, like the channels of the rete testis, are lined by a single 

 layer of flattened epithelium. The vasa efferentia and the tube of the epididymis 



Tunica Vaginalis. 



Tunica Aibuglnea 



FIG. 567. Vertical section of the testi- 

 cle, to show the arrangement of the ducts. 



