960 GENERATIVE APPARATUS. 



out as for as the bladder and anus, the cellulo-adipose tissue being removed from the bottom 

 of the pelvis, taking care to leave the peritoneum, where it passers on to the pelvic organs. The 

 portion of the ischium to whicli no organ rei^uiied for this study is attached, may be sawn oft'. 



In detaching the skin from the inner surface of the thigh, and as far as the middle line, 

 the fixed portion of the penis and one of the dartos sacs are exposed. The separation of the 

 scrotum from tlie dartos is a laborious operation, because of tiie fineness and the adlierence of 

 the skin; it ought to be effected by means of a good scalpel, and with every precaution. Tlie 

 preparation is completed by dissecting the suspensory ligaments of the corpus cavernosum, the 

 penis, and tiie prepuce (sheatii), about which there is nu difficulty. 



(The dart'is and other layers within the scrotum are more easilly dissected, if the skin be 

 drawn tight over the testicle and tied between the latter and the abdomen, so as to keep it 

 tense on the surface of the organ.) 



The Testicles, or Secretory Organs of the Semen, 



The testicles (testes) are two glands suspended on each side of the penis, 

 between the thighs, where each occupies a particular serous pouch — the tunica 

 iwjinalis. We will commence by describing this cavity, and afterwards the 

 organ it contains. 



1. Tunica Vaginalis. 



The tunica vaginalis, in the domesticated animals, is only a diverticulum of 

 the abdominal cavity, the serous membrane of which — the peritoneum — becomes 

 hernied in the inguinal canal — passing, as it does, through the upper (internal) 

 inguinal ring, and prolonged below the inferior (external) ring, so as to form a 

 serous sac, which is enveloped by membranous walls. 



We have to study, in the tunica vaginalis : 1. Its interior. 2. The enveloping 

 membrafies which form the external wall, and to which we give the common 

 name of scrotum. 



J?iterior. — The serous sac constituting the tunica vaginalis is vertically 

 elongated, and slightly inclined downwards, inwards, and backwards. Its 

 inferior extremity, forming the bottom, or cul-de-sac, is pear-shaped, and lodges 

 the testicle and its epididymis. Its middle portion, contracted into a narrow 

 canal, contains the spermatic cord. The superior extremity, or entrance, is open, 

 to maintain communication with the abdominal cavity ; through it pass the 

 spermatic vessels and vas deferens.^ 



As has been said, the peritoneum forms this vaginal sac. As in the abdomen, 

 it is divisible into two layers — parietal and visceral. The latter {tunica vagincdis 

 propria) covers the testicle and the cord ; while the former {tunica vaginalis 

 communis, or reflexa) lines the innermost of the membranous coverings which 

 serve as a wall to the tunica vaginalis. These two layers are made continuous 

 by a serous fraenum, analogous to the mesentery which sustains the floating 

 colon ; like it, it is formed by the junction of the two layers. Flat, elongated 

 from above to below, and extending vertically from one end of the sac to the 

 other, this fraenum is attached, by its upper border, behind the spermatic cord ; 

 its lower extremity passes over the epididymis, and from it on to the testicle ; 

 above, it is continued into the abdominal cavity, in accompanying the different 

 vessels composing the cord. 



(A small quantity of serous fluid is usually present in the tunica vaginalis. 

 When in excess it gives rise to hydrocele.) 



Enveloping Membranes. — The stratified layers that form the external walls 



' If this opening be abnormally dilated, a loop of intestine may enter it, and lie alongside 

 ;he testicle in the sue, constituting inguinal hernia. 



