180 CASTRATION. 



3. The spermatic fascia, continuous with the tendon of the external 

 oblique muscle. 



4. The cremasteric fascia, continuous with the internal oblique muscle. 



5. The infundihuliform fascia, continuous with the transversalis fascia. 

 (). The tunica vaginalis reflexa, a layer of serous membrane continuous 



with the peritoneum. 



Sir John McFadyean remarks of layers 3, 4 and 5 that the dissector 

 will probably be unable to discriminate between them. These three layers. 

 being more or less adherents, are often referred to as the common vaginal 

 sheath. 



The tunica vaginalis reflexa is sack-like in form ; above, where it lies 

 in the inguinal canal, it is much narrower than below, where it surrounds 

 the testicle. Its narrowest point is rather more than an inch below the 

 inner inguinal ring, thence it gradually dilates as it descends ; as a whole 

 its outline resembles that of an hour glass. In the space (vaginal sac) 

 enclosed by this prolongation of the peritoneal tunic are found the 

 testicle and spermatic cord ; in the horse the testicle lies horizontally ; 

 in ruminants vertically, with the epididymis pointing downwards. 



7. The testicular cord is a flattened, elongated, fan-shaped structure. 

 connected at its lower, broader end to the testicle, whilst its upper portion 

 extends into the abdominal cavity. It is invested by the tunica vaginalis 

 propria, a prolongation of the visceral peritoneum, and consists of the vas 

 deferens, spermatic vessels and nerves, and the cremaster muscle. 



The vas deferens, which is placed at the posterior part of the 

 spermatic cord, is a thick-walled tube, representing the excretory duct of 

 the testicle, in large animals of the size of a goose-quill, surrounded by a 

 fold of peritoneum and situated on the inner side of the spermatic cord ; by 

 its convolutions it forms the epididymis, the anterior enlargement of which 

 is termed the globus major on account of its greater size, the posterior the 

 globus minor : the intermediate part is called the body. The vas deferens 

 enters the abdominal cavity through the inguinal canal, passes backwards, 

 surrounded by a special fold of peritoneum, towards the upper surface of 

 the urinary bladder and empties by the ejaculatory duct into the 

 urethra. 



The spermatic artery lies in the front part of the spermatic cord and 

 is accompanied by the artery of the cord, and the large and tortuous 

 spermatic veins, the convolutions of which form the plexus pampiniform is. 

 The anterior portion of the cord (the vascular portion) therefore contains 

 the important blood-vessels, whilst the posterior is comparatively poor in 

 vessels, a point of great importance in connection with castration. 



The inguinal canal consists of a flattened, funnel-shaped space between 

 the abdominal coats, communicating above through the medium of the 

 inner abdominal ring with the peritoneal cavity, and below by the outer 

 abdominal ring with the interior of the scrotum. The outer abdominal 

 ring, an oval opening between the inner and outer limbs of the tendon of 

 the external oblique abdominal muscle, can be enlarged by drawing back 

 the hind limb of the corresponding side. The ring can then be felt by 

 passing the hand gently upwards along the inner surface of the thigh and 

 some estimate of its size can be made, a matter of importance under certain 

 circumstances. 



In the horse the inner abdominal ring is an opening about | inch to 

 H inches long, between the posterior border of the inner oblique muscle 



