THE SEXUAL ORGANS. 627 



there is a similar though less abundant plexus, in the formation of which 

 the artery of the vas deferens also participates (Fig. 257), whilst the 

 scrotum and the t. vaginalis are richly supplied with vessels from the 

 aa. scrotales and spermatica externa. The veins accompany the arte- 

 ries, and with respect to the lymphatics, not only are those of the 

 scrotum and vaginal tunics extremely numerous, but, according to the 

 beautiful researches of Panizza (" Osservazioni," Tab. VIII.), confirmed 

 by Arnold, those of the testis are also very much developed. They pro- 

 ceed partly from the interior, partly from the surface of the testis and 

 epididymis, form beneath the tunica adnata beautiful plexuses, ulti- 

 mately connected by several trunks in the spermatic cord, and, together 

 with those of the vaginal tunics, communicate with the lumbar glands. 



The few nerves of the testis are derived from the internal spermatic 

 plexus, and accompany the arteries to the gland. I have in vain endea- 

 vored to follow their course in the interior, where it but rarely happens 

 that dark-bordered nerves are seen, even accompanying the larger arte- 

 ries of the parenchyma. 



200. Vasa deferentia, vesiculce seminales, accessory glands. The 

 spermatic ducts, or vasa deferentia, are cylindrical canals, having a mean 

 width of 1-1J lines, the walls being J-f of a line thick, and the cavity 

 J-J of a line in diameter, and composed, most externally, of a thin 

 fibrous membrane, then of a strong, smooth-muscular layer, and most, 

 internally, of a mucous membrane. The muscular tunic, which is 0-38 

 0*6 of a line thick, consists of an external, strong layer of longitudinal 

 fibres, a middle one, also strong, of transverse and oblique fibres, and 

 an internal thinner longitudinal layer, constituting not more than Jth of 

 the whole muscular tunic. The tissue is constituted of stiff and pale 

 fibre-cells, as much as 0-1 of a line in length, and having an average 

 width of 0-004-0-006 of a line, intermixed with some connective tissue, 

 and a very few pale elastic fibrils. The mucous membrane, 0-12 of a line 

 thick, is white, longitudinally plicated, and in the last, broadest and 

 widest portions of the duct, presents numerous larger and sm&ller fossce, 

 disposed in a reticular manner. Its external two-thirds are whiter, and 

 contain one of the closest felted tissues of elastic fibrils with which I am 

 acquainted; whilst towards the interior is found a more transparent, 

 thinner layer, composed of an indistinctly fibrous connective tissue, with 

 nuclei, upon which rests a single layer of tessellated epithelium, consti- 

 tuted of cells 0-005-0-008 of a line in size, and which almost invariably 

 contain a certain number of brownish pigment-granules, from which the 

 internal surface of the mucous membrane acquires a yellowish hue. The 

 vessels of the vas deferens are very distinct in the external fibrous tunic, 

 but also penetrate into the muscular and mucous coats, constituting in 

 each, loose plexuses of capillaries 0-003-0-005 of a line in diameter. 



