420 ABDOMEN 



latter until he exposes the lower part of the kidney, below the level of the 

 last rib, and the adjacent part of the colon which lies along the lower and 

 lateral part of the kidney. After this has been done the dissector of the 

 abdomen ceases work till the body is re-turned, when he will re-examine 

 the anatomy of the inguinal region in association with the formation of 

 hernia, and afterwards proceed to the investigation of the abdominal cavity 

 and its contents. 



HERNIA. 



The anatomy of the abdominal wall, in the regions where 

 hernia most frequently occurs, is of such great importance to 

 the practical surgeon that special attention must be paid to it 

 by the dissector. 



Hernia is the term applied to the abnormal protrusion, 

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

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

 attached to a viscus. 



It most commonly occurs 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. These 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. 408, 409. This 

 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 inch distant from its super- 

 ficial opening, the subcutaneous inguinal ring; the opening is, 

 therefore, valvular and the intra-abdominal pressure, forcing 

 the posterior against the anterior wall, tends to close the canal ; 



