THE PERITONEUM 237 



the two layers pass upwards and backwards to reach the 

 anterior border of the pancreas, where they finally diverge 

 from one another. 



In Fig. 88 the lower part of the greater omentum is seen to 

 consist of four layers, but in the adult these layers are generally 

 fused to one another, and the anterior two layers, as they pass 

 in front of the transverse colon, are commonly adherent to the 

 gut. The short upper part of the greater omentum which 

 intervenes between the greater curvature of the stomach and 

 the transverse colon is termed the gastro-colic ligament. 



The fold which attaches the transverse colon to the inferior 

 border of the pancreas is known as the transverse mesocolon. 

 Its upper layer ascends over the posterior abdominal wall and 

 is ultimately reflected on to the liver. It subsequently forms 

 the posterior layer of the lesser omentum. The lower layer 

 of the transverse mesocolon descends from the pancreas, 

 and, after plastering the duodenum against the posterior 

 abdominal wall, it is drawn off the wall to form the mesentery, 

 which suspends the coils of the jejunum and ileum within the 

 peritoneal cavity. 



It will be seen from Fig. 88 that a part of the peritoneal 

 cavity is shut off behind the stomach. This portion is termed 

 the omental bursa (lesser sac) ; it forms a sac which is com- 

 pletely closed except at one point, where it communicates with 

 the rest of the peritoneal cavity (great sac). The communica- 

 tion lies behind the right free border of the lesser omentum 

 and is termed the epiploic foramen (of Winslow). 



Sagittal sections demonstrate the structures which constitute 

 the anterior and posterior walls of the omental bursa. The 

 anterior wall is formed, from above downwards, by the liver, 

 the lesser omentum, the posterior surface of the stomach and 

 the gastro-colic ligament. The posterior wall is formed, from 

 below upwards, by the transverse colon, the transverse meso- 

 colon, the anterior surface of the pancreas and the viscera on 

 the posterior abdominal wall. 



The left and right lateral boundaries can only be studied in 



