1004 THE ORGANS OF DIGESTION 



If figs. 593, 597, and 598 be exanuned, it Avill l)r understood that when the 

 rotation of the intestine takes plaee and tlie eolon rises uj) and crosses in front of the 

 duodenum, the peritoneum between the nieso-duo(Unium and meso-colon must be 

 folded upon itself. The folding is V-shaped, the ai)ex of the V l^eing placed below, 

 and the plication being in or about the median line. The two membranes on a 

 transverse section would have the relation to one another shown in fig. 598, C. 



The third part of the duodenum is brought closer to the posterior parietes; the 

 peritoneum in connection with it is curtailed; and the relations of the structures 

 around are readjusted. As a result of these changes, which can be followed in 

 many of the lower mammals, a distinct fold is produced which is connected 

 Svith the third and terminal parts of the duodenum, and is often of considerable 

 size. This fold can be well studied in jMnrropus. It appears to come off from 

 tliat margin of the bowel which is immediately opposite to the attachment of the 

 meso-duodenum (figs. 605, 606). It ends below in a free edge, and posteriorly it 

 either joins the peritoneum on the posterior parietes close to the origin of the 

 descending meso-colon, or it joins the meso-colon at some little distance from the 

 spine. 



The traction about this somewhat firmly held segment of bowel has been such 

 that it has been drawn between the layers of its own meso-duodenum. It is 

 by this fold that is ft)rmed the wall of the fossa duodeno-jejunalis (page 966, 

 fig. 572). 



