THE PERITONEUM. 



995 



Sometimes the fold is bound to the intestine and the fossa is then apparently 

 lacking. 



The vascular relations of this fossa are not close. The inferior mesenteric 

 vein is about one finger's breadth to the left and the art. colica sinistra is as far 

 below. The vessels have no causal relations and the fossa is non-vascular. Jon- 

 nesco met one case where the artery and vein were related to the fold. 



FIG. 617. Inferior and superior duodenal fossfe. 

 The inferior mesenteric vein is some distance from 

 the inferior fossa but near the left border of the su- 

 perior fossa. Transverse colon and mesocolon are 

 turned up. On the left is the descending colon, as- 

 cending duodenum on the right, and jejunum is 

 pulled to the right. (Jonnesco.) 



FIG. 618. Duodeno-jejunal fossa of Treitz. (From 

 Treitz in Jonnesco.) D. Ascending duodenum. P. 

 Duodenal fold. Vm. Inferior mesenteric vein. Ac. 

 Art. colica sinistra. Jft. Transverse mesocolon. Ifd. 

 Descending mesocolon. 



The fossa described by Treitz and known as the duodeno-jejunal fossa of 

 Treitz is this one, but it is "vascular," in which the inferior mesenteric vein 

 runs in the edge of the crescentic fold and the inferior extremity of the fossa is 

 formed by the colica sinistra artery. Treitz regarded the formation of the fossa 

 due to the presence of the vessels (Fig. 618). 



" The orifice of the fossa was limited on the right by the duodenum, on the 

 left by the free edge of the duodenal fold. The fossa lay on the third lumbar 

 vertebra left side, and in the bottom of a depression of the posterior abdominal 

 wall limited by the pancreas, left kidney and aorta." 



'2. The superior dnoJ- .rc.il fU-.*</ is present in about 50 per cent. It often co- 

 exists with the inferior one (Fig. 617). It is always at the level of the superior 

 extremity of the ascending duodenum, and its orifice looks downward, opposed to 

 the preceding. The orifice is limited by the edge of the superior duodenal fold, 

 which presents the free semilunar base turned below. The summit of the fold is 

 lost above in the inferior layer of the transverse mesocolon, its left side passes 

 over into prerenal peritoneum, and its right side on to the duodenum and left leaf 

 of mesentery. 



The fossa is limited in front by this fold, to the right by the duodenum and is 

 stopped above by the body of the pancreas and rests on the second lumbar verte- 

 bra in the angle formed by the left renal vein crossing the aorta. Its greatest 

 depth is 2 cm. This fossa is always vascular, i. e. is related to the inferior mesen- 

 teric vein which passes to its left along its adherent parietal border and disap- 

 pears under the pancreas : sometimes it enters the free fold covering the orifice. 



3. The duodeno-jejunal or mesocolic fossa. This is found in 16 per cent. ; it 

 does not coexist with anv other. Its existence necessitates that the duodeno- 



