THE PERITONEUM. 



1753 



the pancreas along the lower border of that gland to the left kidney (Fig. 1477). Its 

 greatest breadth is some five or six inches. (For a fuller description, see peritoneal 

 relations of the colon, page 1670.) The breadth of the transverse mesocolon is from 

 1215 cm. (5-6 in.). In the adult it is fused with the greater omentum, as already 

 described. The superior mesenteric artery enters this mesentery under the pancreas, 

 and gives from its left or convex side the branches for the small intestine. From 

 its right, just after its origin, it gives off the inferior pancreatico-duodenal and the 

 branches for the caecum and the ascending and transverse colon. In the adult the 

 right colic artery runs behind the permanent posterior parietal peritoneum. 



The Posterior Mesentery : Part III. The region of the inferior mesen- 

 teric artery is very simple. Starting at the left of the permanent mesentery of the 

 small intestine, the peritoneum is traced over the posterior abdominal wall, over 



Csecum 



FIG. 1478. 



Small intestine 



Transverse colon 



Ascending colon 

 Lower end of ileum 



Mesentery 



Duodenum 



Descending colon 

 Mesentery 



Posterior wall of abdom 



Bladder 



Mesenterium commune in child of three years ; the usual relations would be restored by bringing upper dotted line 



in contact with lower. 



the lower part of the left kidney, and over the descending colon, which, although 

 touching that organ, lies chiefly external to it. The posterior surface of the gut is 

 retroperitoneal. The descending colon has fallen over to the left, so that the peri- 

 toneum of the left side of its mesentery has fused with that of the abdominal wall, 

 and the permanent serous covering of the posterior wall is derived from that of the 

 right side of the original mesentery. This fusion ceases at the crest of the ilium, and 

 the sigmoid flexure retains at least a part of the original mesentery (Fig. 1478). The 

 line of its attachment runs in more than one direction, according to the amount of 

 freedom of the fold, from that point to the middle of the third sacral vertebra. (The 

 chief forms are described on page 1671.) Beyond the latter level the rectum is 

 partly uncovered behind, where the mesentery ceases, and its gradually diverging 



