THE ABDOMINAL CAVITY 303 



made longer than is necessary ; in order to guard against 

 subsequent obstruction, because, as a general rule, the patient 

 puts on weight after this operation, and much fat may be 

 deposited in the greater omentum. 



Occasionally in loop operations a kink or spur may form 

 and obstruct the outlet into the distal limb of the anastomosis. 

 The bile collects in the proximal limb and together with the 

 food is prevented from passing onwards. If the pylorus is 

 patent, this may set up a vicious circle. It is therefore usual to 

 carry out entero-anastomosis in addition to the loop operations, 

 and the jejunum on the proximal side of the gastro-enterostomy 

 is joined to the jejunum on the distal side. This allows the bile 

 to short-circuit into the small intestine at some distance from 

 the gastric anastomosis. 



After this second step, peptic ulceration occasionally occurs 

 in those portions of the jejunum between the gastric anastomosis 

 and the entero-anastomosis, since in this area the hyperacid 

 chyme is not neutralised by the alkaline bile. 



Development of the Stomach and the Omental Bursa (Lesser Sac). 



The first indication of the stomach is a fusiform dilatation, which appears 

 in the caudal part of the foregut during the fourth week. It is median in 

 position and is moored to the anterior and posterior abdominal walls by a 

 ventral and a dorsal mesentery. The dorsal aspect of the stomach grows 

 more rapidly than the ventral, and the lower or pyloric end is first thrust 

 forwards and is then rotated to the right side. In this way what was origin - 

 nlly the left surface of the stomach now becomes anterior, and it carries the 

 left vagus nerve with it. The rotation of the stomach produces a fossa 

 between it and the dorsal wall ; this is the site of the omental bursa. 



The lower part of the dorsal mesentery of the stomach grows rapidly 

 and sags downwards into the abdomen, converting the fossa into a bursal 

 sac which has a widely open mouth looking to the right. At the same time 

 the mesentery of the duodenum shortens and then disappears, so that the 

 lower margin of the epiploic foramen becomes defined. 



The spleen develops as a condensation of the mesoderm between the two 

 layers of the dorsal mesentery in its upper part and divides it into the gastro- 

 splenic and lieno-renal ligaments. 



The Duodenum extends from the pylorus to the duodeno- 

 jejunal flexure. It forms a C-shaped bend, which encloses the 

 head of the pancreas, and its total length is about ten inches. 



When the body is in the supine position, the Superior or 

 First Part of the duodenum passes backwards and slightly 

 upwards from the pylorus to the neck of the gall-bladder, and 

 is in relation to the inferior surface of the liver. When the 

 body is in the erect position, this part passes vertically upwards 

 owing to the descent of the pylorus (p. 290), and the level of the 



