426 SPLANCHNOLOGY, OR ANATOMY OF THE VISCERA 



greater sac. At the transverse colon the layers of the greater 

 omentum separate and enclose the gut, meeting behind and 

 completing the transverse mesocolon, which extends to the 

 lower border of the pancreas. Here the inferior layer (from 

 the greater sac) runs down along the posterior abdominal 

 wall and blends with the mesentery as described, and the 

 superior layer (from the lesser sac) proceeds as already men- 

 tioned. 



The peritoneum forms certain pouches or cul-de-sacs, which 

 are essential to the surgeon, owing to their being sites for 

 the possible occurrence of retroperitoneal or intra-abdominal 

 hernia. They are the lesser sac; through the foramen of 

 Winslow, the duodenal fossae; the pericecal fossae; and the 

 intersigmoid fossae. 



The duodenal folds, or fossae: (1) The inferior duodenal 

 fossa, or fossa of Treitz, is present in from 70 to 75 per cent, 

 of cases. It is found opposite the third lumbar vertebra 

 on the left side of the ascending or fourth portion of the 

 duodenum; and is bounded by a thin free fold of peri- 

 toneum, called the inferior duodenal fold. (2) The superior 

 duodenal fossa is present in about 40 to 50 per cent, of the 

 cases. It is found to the left of the duodenum, bounded by 

 the thin free edge of the superior duodenal fold; to the right 

 it is blended with the peritoneum covering the ascending 

 duodenum, and on the left with the peritoneum covering the 

 perirenal tissues; behind is the second lumbar vertebra. (3) 

 The duodenojejunal fossa, or mesocolic fossa, is seen by pulling 

 the jejenum downward and to the right, after raising upward the 

 transverse colon. It is circular in shape, bounded above by 

 the free margins of peritoneum, called right and left duodeno- 

 mesocolic ligaments. Above is the body of the pancreas, to 

 the right the aorta, and to the left lies the left kidney, behind 

 the left renal vein. It is present in about 15 to 20 per cent, 

 of the cases. (4) The paraduodenal fossa, or fossa of Laudzert, 

 is very seldom seen, and usually in the infant when present. 

 It is found to the left of the ascending duodenum, the fold 

 of peritoneum bounding it above is formed by the inferior 

 mesenteric vein. Its lower boundary is a free edge, called the 

 mesentericomesocolic fold. (5) The retro duodenal fossa is a 

 peritoneal cul-de-sac, first described by Jonesco in 1893, and 



