INTESTINAL CANAL. 35 



mesentery, but allows to the middle of the large intestine very 

 considerable motion, up and down, according to the distention 

 of the stomach, while the lateral portions are very much confined. 

 For example, in the right iliac fossa the mesocolon is so'^hort 

 that the posterior surface of the gut is in contact with the iliac 

 fascia, and adheres to it by loose cellular substance ; in the right 

 and left lumbar regions the bowel is immoveably fixed in front 

 of the kidneys, but in the space between these two points, that 

 is to say, where the bowel traverses the hypochondriac and the 

 epigastric or umbilical regions, the peritoneal attachment, here 

 called, from its situation, the transverse mesocolon, is so long 

 and loose that it forms a complete and moveable septum between 

 the small intestine and the stomach. In the left iliac region, 

 again, the large intestine, after having been bound down to the 

 left lumbar, is suddenly loosened by an increased breadth of the 

 mesocolon, which permits it to form a large con volution, called 

 its sigmoid flexure. The mesocolon is then continued into the 

 pelvis in front of the sacrum, first of all a little to the left of the 

 middle line of the latter, and, as it descends, it gets directly in 

 front of the middle line. The portion of it in the pelvis is called 

 mesorectum, after the gut which it serves to attach. 



The composition of the mesocolon is precisely the same with 

 that of the mesentery, though it be not so thick: it, therefore, 

 consists in two laminas of peritoneum, which contain between 

 them some adipose and cellular matter, along with the arteries, 

 the veins, the nerves, and the lymphatic vessels and glands be- 

 longing to the large intestine. 



When the large intestine is inflated, it is rendered very ob- 

 vious that it decreases in size from its commencement to the 

 lower part of the sigmoid flexure, it then increases again in size 

 just above the anus. Its surface is arranged into three series or 

 longitudinal rows of projections, separated by transverse depres- 

 sions, the whole corresponding with an internal cellular arrange- 

 ment, by the latter surface being the reverse of the former. 



Its coats, like the small intestine, are four in number ; the pe- 

 ritoneal, the muscular, the cellular, and the mucous. 



The Peritoneal Coat prevails in its whole extent, with the 

 exception of the lower part of the rectum: on the ascending and 



