THE SEXUAL ORGANS. 231 



epididymis, form beneath the tunica adnata beautiful plexuses, 

 ultimately 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 endeavoured to follow their course in the interior, 

 where it but rarely happens that dark-bordered nerves are 

 seen, even accompanying the larger arteries 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 — 1|'", the walls being ± — §"' thick, 

 and the cavity \ — \" in diameter, and composed, most exter- 

 nally, 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 — 06'" 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 Q'V" in length, and having an 

 average width of 0*004 — 006'", intermixed with some connec- 

 tive tissue, and a few very pale elastic fibrils. The mucous mem- 

 brane, 0*1 2'" thick, is white, longitudinally plicated, and in the 

 last, broadest and widest portions of the duct, presents numerous 

 larger and smaller fossa, 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 tesselated epithelium, 

 constituted of cells 0*005 — 0-008"' in size, and which almost in- 

 variably contain a certain number of brownish pigment-granules, 

 from which the internal surface of the mucous membrane ac- 

 quires 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'" in diameter. According 

 to Swan {< Nerves of the Human Body/ PI. V, 82 ; PI. VI, 



