chap, xvii.) ABDOMINAL VISCERA. 347 



where gall stones have been lodged within the gall 

 bladder, the walls of that structure have ulcerated 

 from pressure, the ulceration has involved the sub- 

 jacent transverse colon, and thus a fistula has been 

 established between the gall bladder and the gut, 

 through which large stones have been passed. Hepatic 

 abscesses also have discharged themselves through the 

 transverse colon. 



The sigmoid flexure. The segments of gut termed 

 the sigmoid flexure and "the first part of tho 

 rectum," form together a single simple loop that 

 cannot be divided into parts. This loop begins where 

 the descending colon ends, and ends at the commence- 

 ment of the so-called " second part of the rectum ; " at 

 a spot, in fact, where the meso-rectum ceases, opposite 

 about the third piece of the sacrum. This loop, when 

 unfolded, describes a figure that, if it must be com- 

 pared to a letter, resembles the capital Omega. It may 

 well be termed the Omega loop, and the term rectum 

 be limited to the short piece of practically straight gut, 

 that is now described as the second and third parts of 

 the rectum. The average length of the loop in the 

 adult is seventeen and a half inches. The two ex- 

 tremities of the loop are about three or four inches 

 apart. If they are approximated to one another, as 

 by contracting peritonitis at the root of the sigmoid 

 meso-colon, a kind of pedicle is established, about 

 which the loop may readily become twisted. Such a 

 twist of the bowel constitutes a volvulus of the 

 sigmoid flexure ; and it may be here said that volvulus 

 of the intestine is more commonly met with in this 

 loop than in any other part of the canal. 



The line of attachment of the meso-colon of the 

 Omega loop (the sigmoid meso-colon) crosses the psoas 

 muscle and the iliac vessels near their bifurcation ; it 

 then turns abruptly down, and running nearly ver- 

 tically, terminates at the middle line. 



