252 ABDOMEN 



/ Hernia is the term applied to the abnormal protrusion, 



\ \ through the wall of the abdomen, of a viscus, or a part of a 

 \ y viscus, or of a part of a peritoneal fold which supports or is 

 ^\\ | attached to a viscus. 



i-* It occurs most commonly where the peritoneal sac, or a 

 diverticulum of the peritoneal sac, was prolonged through 

 the abdominal wall at some period of intra-uterine develop- 

 ment. The two situations in which such prolongations are 

 always present are the inguinal region and the umbilicus ; and 

 it is stated that a small diverticulum is almost always met with 

 in the subinguinal region, dipping into the mouth of the 

 femoral canal of the femoral sheath. Those three regions, 

 therefore, are the situations in which hernia is most often met 

 with, and it is asserted that the most important factor in the 

 production of hernia is the presence of a more or less definite 

 persisting diverticulum of the peritoneum. 



The diverticulum which existed in the inguinal region was 

 the processus vaginalis described on pp. 234, 235. That 

 diverticulum passed obliquely through the wall of the 

 abdomen, producing the inguinal canal; and, although the 

 diverticulum disappears, the canal made by its passage may 

 be looked upon, to a certain extent, as a source of weakness 

 to the part of the wall through which it runs. The weakness, 

 however, is more apparent than real, for the canal is so 

 oblique in the adult that its abdominal opening, the abdominal 

 inguinal ring^ is one and a half inches distant from its super- 

 ficial opening, the subcutaneous inguinal ring; the opening is 

 therefore valvular, and the intra-abdominal pressure, forcing 

 the posterior wall against .the anterior wall, tends to close the 

 canal ; moreover, the constituent parts of the anterior and 

 posterior walls are so arranged that weakness of one wall 

 is compensated for by strength in the opposite wall. The 

 dissector should now proceed to demonstrate the truth of 

 these statements by making a special dissection of the inguinal 

 region on the left side of the body, which has been kept intact 

 for the purpose. 



Dissection, Begin by reflecting the aponeurosis of the 

 external oblique. Make a vertical incision through it, parallel 

 to the lateral border of the rectus abdominis, and carry the 

 incision downwards on the medial side of the superior crus of 

 the subcutaneous inguinal ring. The aponeurosis can then be 

 thrown downwards and laterally ; and, at the same time, the sub- 

 cutaneous ring is preserved. The internal oblique, the cremaster, 



