II. In the next place, in order to understand the arrangement of the peritoneum in this lower larger compartment of the abdomen, disregard for the present the peritoneal connections of the stomach, liver, pancreas and spleen, and the folds of the great omentum entirely. This latter membrane is adherent in the adult human subject by its dorsal surface to the upper margin of the transverse colon, so that in turning the omentum up over the ventral chest wall the transverse colon will be carried with the omentum and the lower layer of the transverse mesocolon will be put upon the stretch. This membrane forms in adult man by its transverse attachment to the abdominal background the cephalic limit of the larger lower compartment of the abdomen, which is framed laterally by ascending and descending colon, continuous below with the pelvic cavity and occupied chiefly by the freely movable coils of the jejuno-ileum. Remember that the duodenum starting from the pyloric extremity of the stomach first turns cephalad and dorsad in contact with the caudal surface of the right lobe of the liver, forming the first portion or hepatic angle of the duodenum; that in the next place the second or descending portion of the duodenum passes down in front of the medial part of the ventral surface of the right kidney and the inferior vena cava, but _behind_ the right extremity (hepatic flexure) of what after rotation and formation of the ascending colon appears as the transverse colon; that consequently the descending duodenum is divided by its intersection with the transverse colon into a cephalic supra-colic and a caudal infra-colic segment. Also remember that the second angle of the duodenum (transition between the descending and transverse portions) is consequently situated to the right of the vertebral column below the level of the transverse colon and the secondary attachment presently to be considered of the transverse mesocolon to the background of the abdominal cavity. The third portion of the duodenum extends from this point more or less transversely--depending upon the type--to the left, across the vertebral column and aorta. This transverse portion, after the rotation of the primitive loop at the duodeno-colic angle, is crossed in the direction caudad and ventrad by the superior mesenteric vessels, which hence divide this portion of the intestine into a right and left segment. The latter turns cephalad and ventrad on the left side of the vertebral column (4th or ascending portion) to become continuous at the duodeno-jejunal angle with the free or floating small intestine (jejunum).