818 THE MALE GENITAL TRACT. 



accompanying the blood-vessels, they, by division and frequent branching, 

 become more numerous and very much smaller, until finally, after having 

 reached the capillaries, they are extremely thin and transparent, and almost 

 escape the observer's eye in the fresh and unstained specimen. In success- 

 ful sections* however, they can still be observed to preserve the plexif orm 

 arrangement. When found in the proximity of a seminiferous tubule, they 

 are generally situated between a capillary and the basement-membrane. As 

 they penetrate this membrane, the nerve-fibers, still including several axis- 

 cylinders, break up into their ultimate fibrillse, at first pass along between 

 the several layers of endothelia of which the basement-membrane is composed, 

 and, after having emerged from its inner wall, they, as it were, line its interior 

 with a plexus consisting of the ultimate axis-fibrillge, being interrupted only by 

 variously shaped bodies, most of which present a pyramidal shape. This plexus 

 thus lining the inner surface of a seminiferous tubule is best observed in the 

 testicles of animals in which the membrana propria is very thin and is com- 

 posed of but one layer of endothelia, such as the mouse and the rat. From this 

 plexus, best seen in gold preparations, viz. : longitudinal sections which have 

 lost most of their epithelium, so as to expose the inner surface of the semi- 

 niferous tubule, the axis-fibrillse pass upward at acute angles in a direction 

 toward the center of the tubule. Between the epithelia superimposed upon 

 the membrana propria, the fibrillsB anastomose in every direction, and hold, 

 so to say, the epithelia in a mesh-work. The best and most clearly defined 

 pictures are represented in specimens of the testicle of the young rat. 



The cement-substance between the epithelia is the plan of the ultimate termina- 

 tion of the axis-fibrilla in the testicle. 



I have never seen a nerve-fiber penetrate into the interior of an epithe- 

 lium, although it might seem so when one of them crosses an epithelium and 

 is interrupted in its course. 



The ultimate axis-fibrillse, having been traced traversing the cement- 

 substance between the epithelia, and being connected with the filaments or 

 prickles crossing them, we are at once in a position to understand how the func- 

 tion of the epithelia within the seminiferous tubules viz.: the production 

 of spermatozoids is under the direct control of the sympathetic system. 



(2) The epididymis is composed of a single tubule with numer- 

 ous convolutions, with which the seminiferous tubules unite after 

 leaving the corpus Highmori, and producing the convoluted coni 

 vasculosi. These tubules are now termed efferent. They all 

 have a circular coat of smooth muscle-fibers, external to the mem- 

 brana propria. The epithelia are columnar, ciliated, numerous 

 smaller, wedged plastids being present between their pointed feet. 

 Toward the cauda epididymidis the wall of the efferent vessel in- 

 creases in thickness, and is supplied with longitudinal muscle- 

 bundles. A delicate, adventitial connective tissue, rich in elastic 

 fibers, supports the convolutions of the tubule of the epididymis, 

 being rich in capillary blood- and lymph- vessels. These circulate 

 through the adventitial coat, penetrate the muscle-layer, and pro- 

 dace a terminal capillary plexus above the epithelia. 



