376 THE LARGE INTESTINE. 



coat take no part in the formation of the valve, but are stretched across 

 it uninterruptedly from one intestine to the other. 



The Colon. — The ascending colon, situated in the right lumbar 

 and hypochondriac regions, commencing at the ctecum opposite to the 

 ileo-cffical valve, ascends vertically to the under surface of the liver, near 

 the gall-bladder, where it proceeds forwards and then turns abruptly to 

 the left, forming what is named the Impatic flexure of the colon. The 

 ascending colon is smaller than the c;ecum, but larger than the trans- 

 verse colon. It is overlaid in front by some convolutions of the ileum, 

 and is bound down firmly by the peritoneum, which passes over its 

 anterior surface and its sides, and generally leaves an interval in which 

 its posterior surface is connected by areolar tissue with the fascia cover- 

 ing the quadratus lumborum muscle, and with the front of the right 

 kidney. In some cases, however, the peritoneum passes nearly round it, 

 and forms a distinct though very short right meso-colon. 



The TRANSVERSE COLON passcs across from the right hypochondrium, 

 through the upper part of the umbilical region, into the left hypochon- 

 drium. Sometimes it is found as low as the umbilicus or even lower. 

 At each extremity it is situated deeply towards the back part of the 

 abdominal cavity, but in the middle it curves forwards, and lies close to 

 the anterior wall of the abdomen. Hence it describes an arch, the con- 

 cavity of which is turned towards the vertebral column ; and it has 

 accordingly been named the arch of the colon. 



Above, the transverse colon is in contact with the under surface of 

 the liver, the gall-bladder, the great curvature of the stomach, and the 

 lower end of the spleen. Below it are the convolutions of the small 

 intestine, the third portion of the duodenum being behind it. It is 

 invested by the general peritoneum, which forms a separate fold for 

 it behind, the transverse meso-colon, and in front it adheres to the sac 

 of the omentum. 



The DESCENDING COLON is contiuuous with the left extremity of the 

 transverse colon by a sudden bend named the sjjlenic flexure. At this 

 bending there is found a remarkable fold of peritoneum, the cosfo- 

 colic or pleuro-colic l/'i/anienf, which stretches with a lunated free border 

 to the colon from the diaphragm, opposite the 10th or II th rib. As 

 was pointed out by Haller, it supports the spleen although uncon- 

 nected with that organ, and might be termed " sustentaculum 

 lienis." The colon then descends almost perpendicularly through the 

 left hypochondriac and lumbar regions to the left iliac fossa, where it 

 ends in the sigmoid flexure. The peritoneum affords a covering to it 

 only in front and at the sides, whilst behind it is connected by areolar 

 tissue to the left crus of the diai3hragm, the quadratus lumborum, and 

 the left kidney. It is usually concealed behind some convolutions of 

 the jejunum. 



The SIGMOID FLEXURE of the colon, situated in the left iliac fossa, 

 consists of a double bending of the intestine upon itself in the form of 

 the letter S, immediately before it becomes continuous with the rectum 

 at the margin of the pelvis opposite to the left sacro-iliac articulation. 

 It is attached by a distinct meso-colon to the iliac fossa, and is very 

 movable. It is placed iuimediately behind the anterior parietes, or is 

 concealed only by a few turns of the small intestine. The sigmoid 

 flexure is the narrowest part of the colon. 



The Rectum. — The lowest portion of the large intestine, named the 



