THE COLON. 



1669 



not rest against the under side of the diaphragm, according to its distention and 

 that of the stomach. It rests behind and below on the small intestine. It may or 

 may not be in immediate relation to the tail of the pancreas. 



The descending colon descends partly in front, but still more external to the 

 kidney, and after passing the kidney rests wholly on the quadratus lumborum. 

 Although more externally placed than the ascending colon, it does not usually project 

 beyond that muscle. It may be very much contracted and sacculated. 



The sigmoid flexure (colon sigmoideum), the continuation of the large intestine, 

 begins at the crest of the ilium as a loop of very varying length, which is attached by 



FIG. 1418. 



Left side of abdomen ; small intestine turned to right, exposing mesentery, mesocolon of descending colon, and 



mesosigmoid. 



a mesentery, and ends at the middle of the third sacral vertebra. Its usual length is 

 from 25-56 cm. (10-18 in.), but is occasionally much longer. While it is true that the 

 gut does not always become free at the crest of the ilium, but may descend, bound 

 down closely, to the iliac fossa for some distance, it is best to regard the sigmoid 

 flexure as beginning at a definite although arbitrary point rather than at the less 

 certain one at which the gut really has a mesentery. Moreover, there is no great 

 inaccuracy in the statement that this generally occurs at the crest of the ilium or 

 just below it. The simplest form of the sigmoid flexure is a loop. If it be a small 

 one, it usually is made of the last part of this section of the gut ; very often the first 

 part is but slightly free while the last part is very much so. Short sigmoid flexures, 



