284 GENERATIVE SYSTEM. 



purse, denominated the septum scroti ; which consequently ex- 

 tends from the raphe to the under and posterior part of the penis, 

 and serves to prevent one testscle from encroaching upon or in- 

 terfering with the other. 



Cellular Structure. — The celhilar membrane of the scrotum 

 (vvliich may be considered as the third l|yer of substance enter- 

 ing into its composition) is interposed in the greatest abundance 

 between the fibrous expansion and the peritoneaLcoverings of the 

 testicles. Being very long and loose in its texture, and desti- 

 tute of any adipose matter, the parts it connects are extremely 

 moveable upon each other, at the same time that it admits itself 

 of considerable extension. 



Testicles. 



Coverings. — The first or external covering of the testicle, one 

 common both to it and the chord, is a borrowed one from the pe- 

 ritoneum, known as the tunica vaginalis. The acquisition and 

 reflection of this covering will not be clearly understood until the 

 descent of the testicle has been explained ; though it may be ob- 

 served here, that it is a production of peritoneum formed into a 

 loose vagina or sheath, which originates at the internal ring, pro- 

 ceeds with and loosely envelopes the chord, and, lastly, covers 

 in the same lax manner the testicle and epididymis ; so that if 

 the bag (it forms) be punctured, and air or liquid be impelled into 

 the cavity, the fluid will not only distend it, but mount into the 

 abdomen, since both cavities have a free communication at the 

 internal ring. The elongated membrane, however, does not end 

 in single investment of the testicle. Along the superior and an- 

 terior border of the eididymis, we find it firmly attached, but not 

 terminated ; for here it becomes reflected, first upon the epididy- 

 mis itself, next over the testicle, and lastly upon the chord, so 

 as to give them all a second covering, which only differs from the 

 first in being every where in close adhesion with the parts it in- 

 vests : this last production is called, by way of distinction, the 

 tunica reflexa or tunica vaginalis testis : it must not be forgot- 

 ten, however, that they arc ho\\\ peritoneal productions — one and 

 the satne continuous membrane. The vaginal cavity possesses 

 a smooth polished surface, and this is constantly bedewed with a 

 limpid, colourless, serous fluid, which in the operation for castra- 

 tion spirts out the instant the knife or cautery has penetrated the 

 tunica vaginalis. It is an accumulation of this fluid that con- 

 stitutes hydrocele; a disease that has no existence, I believe, in 

 the horse, abstractedly from abdominal dropsy. 



THE TESTICLES, with their appendages, the epididymes, 



