Fig. 161 shows the abdominal cavity of Nasua rufa, the brown Coati-mundi, a South American arctoid carnivore, with the intestines everted and turned to the left side. In this animal the large intestine is very short, there is no caecum, the ileo-colic junction is only marked on the surface by a pyloric-like constriction of the tube and in the interior by the projection of a ring-valve (Fig. 408). The duodenal fold is very well developed, passing between the convex surface of the duodenal loop and the adjacent right leaf of the short mesocolon. In Primates, in which complete rotation of the intestine, on the plan of the human development, takes place, still further and more extensive agglutination of the serous surface of the duodenum to the peritoneum of the mesocolon occurs. Fig. 162 shows the condition in _Hapale vulgaris_, one of the marmosets. The ascending and descending mesocola and the mesoduodenum of this animal are still free, but the surface of the duodenum has become fastened to the opposed mesocolon. With fixation of the hepatic flexure and adhesion of the ascending colon, such as occurs in man, the duodenum is carried dorsad against the ventral surface of the right kidney, and now anchoring of the duodenum, by obliteration of the mesoduodenum and adhesion to the prerenal parietal peritoneum, takes place as already detailed above. To return now to the formation of the duodeno-jejunal fossa by means of this fold, as illustrated in the cat. Perform the manipulations already described in rotation of the intestine. The appearance of the parts then will be as shown in Fig. 163. The large intestine is drawn over so as to represent the human ascending and transverse colon in one segment, the descending colon in the other, and the mesocolon appears correspondingly as transverse and descending. In other words the cat's intestines as arranged in the figure would represent the stage in the human development in which caecum and beginning of large intestine are still subhepatic in position ventrad of the right kidney, before differentiation of ascending and transverse colon by descent of caecum into right iliac fossa. [Illustration: FIG. 162.--Abdominal viscera of _Hapale vulgaris_, the marmoset. (Columbia University Museum, No. 1818.)] [Illustration: FIG. 163.--Abdominal viscera of cat; intestines rotated and turned to the right to show duodenal fold. (From a fresh dissection.)] In the human subject, as we have seen, the transverse mesocolon obtains a secondary attachment to the background of the abdominal cavity, its caudal surface remaining free.