ABDOMINAL WALL 409 



peritoneum lining the inner surface of the abdominal wall. The testis is 

 developed in the lumbar region, and it projects forwards into the peritoneal 

 cavity covered with a layer of epithelium, which is continuous with the 

 peritoneal epithelium. It also invaginates a portion of the wall of the 

 peritoneal sac and so produces a mesentery connecting the testis and the 

 epithelium which covers its surface with the parietal peritoneum, this is 

 called the mesorchium. 



The testis and its mesorchium gradually descend in the wall of the 

 peritoneal sac to the inguinal region and, at the same time, a diverticulum 

 of peritoneum, the processus vaginalis^ is projected through the inguinal 

 portion of the abdominal wall into the scrotum, producing by its passage 

 the inguinal canal, and prolonging the cavity of the peritoneum into the 

 scrotum. During the latter part of the seventh and the early part of the 

 eighth month of foetal life the testis, with its epithelium and its mesorchium, 

 descends along the posterior wall of this diverticulum, and during the ninth 

 month it comes to rest near the lower end of the scrotum, where it projects 

 forwards in the posterior wall of the lower part of the processus vaginalis. 

 In the meantime the cavity of the upper part of the processus vaginalis 

 disappears and its peritoneal wall forms a solid fibrous cord (Rudimentum 

 processus vaginalis}. The lower part of the sac, thus cut off, is the tunica 

 vaginalis of the testis. Its cavity is now entirely separated from the 

 cavity of the peritoneum, but its wall is still connected, for a longer or 

 shorter time, with the peritoneum by the fibrous cord which is the remains 

 of the upper part of the processus vaginalis. In most cases, however, this 

 cord undergoes atrophy from below upwards, and in many cases, as already 

 mentioned, it entirely disappears. 



The orifice of communication between the processus vaginalis and the 

 peritoneal cavity is usually closed before birth, and the cavity of the upper 

 portion of the process, from the abdominal inguinal ring to the persistent 

 tunica vaginalis, is generally obliterated during the first month of extra- 

 uterine life. 



The cause of the descent of the processus vaginalis and the testis 

 is still a subject of dispute. It has been suggested : (i) that it is due to 

 different growth energy in adjacent parts ; (2) to traction from below 

 produced by a musculo-fibrous cord, the gubernaculum of the testis^ which 

 grows through the inguinal part of the abdominal wall and is attached to the 

 interior of the scrotum, whilst above it is attached to the testis and the 

 adjacent peritoneum ; (3) to the action of intra-abdominal pressure tending 

 to displace the testis downwards. 



Dissection. The coverings of the spermatic cord should now be 

 removed, and the parts which enter into its formation isolated from each 

 other. 



Constituent Parts of the Spermatic Cord. The following 

 are the structures which form the spermatic cord : 



i. The ductus deferens (O.T. vas deferens). 



{The internal spermatic. 

 The external spermatic. 

 The artery to the ductus deferens. 

 I Veins. The pampiniform plexus of veins. 

 3. Lymph vessels. 

 L Nerves / External spermatic. 

 " (Sympathetic twigs. 



These are all held together by loose areolar tissue which 



