348 SURGICAL APPLIED ANATOMY. [Chap. xvn. 



In the left wall of this meso-colon, close to the 

 point where it lies over the iliac vessels, a fossa is 

 sometimes to be found. It is produced by the sigmoid 

 artery, and is about one and a half inches in depth. It 

 is called the intersigmoid fossa, and is the seat of 

 sigmoid hernia. Two cases of strangulated hernia in 

 this fossa have been recorded. 



The sigmoid flexure, or Omega loop, when empty, 

 normally occupies the pelvis. When distended this 

 piece of bowel may become so enormously dilated as 

 to reach the liver. The chief examples of extraor- 

 dinary dilatation of the colon concern this loop. 

 Faecal masses are very frequently lodged in the free 

 end of the loop, and certain intestinal concretions have 

 been met with in the same situation. 



I have shown by experiment that the " long tube," 

 when introduced through the anus, cannot be passed 

 beyond the sigmoid flexure in ordinary cases, and 

 with a normal disposition of the bowel. 



In cases of congenital absence, or deficiency of the 

 rectum, the sigmoid flexure is often opened in the 

 groin and an artificial anus established there. This 

 operation, known as Littre's operation, is, it must be 

 confessed, not very successful. One difficulty has 

 been said to depend upon the uncertain position of the 

 sigmoid flexure in cases of congenital deformity, it 

 being sometimes on the right side and sometimes in 

 the pelvis at the middle line. It is rarely, however, 

 found in these positions. Out of 100 post-mortem 

 examinations on young infants, Curling found the loop 

 on the left side in 85 cases. 



Congenital malformations of the colon. 

 These are of moment with regard to operative pro- 

 cedures. It may be very briefly said that in the foetus 

 the small bowel occupies at one time the right side of 

 the abdomen, while the large gut is represented by a 

 straight tube that passes on the left side vertically 



