2. In the forms which possess in the adult an adherent duodenum and mesoduodenum, as in man, the foramen of Winslow obtains a secondary caudal limit by the agglutination of the descending duodenum and the parietal prerenal peritoneum. This is the secondary and inconstant factor referred to above in the caudal boundary of the foramen. The result of this anchoring of duodenum and mesoduodenum is to bring the margin of the foramen further to the right and to bury the hepatic artery still further from view. Thus in the adult human subject the structures bounding the foramen at the margin of the entrance into the narrow channel would be above caudate lobe of liver, behind postcava, below duodenum adherent to ventral surface of right kidney, in front first portion of duodenum and lesser omentum. The hepatic artery will be felt on introducing the finger through the foramen in its original position, but it will be seen that the actual boundaries of the foramen have been moved so to speak a little further to the right by the duodenal adhesion. [Illustration: FIG. 296.--Dissection of adult liver, pancreas, spleen, and duodenum, with vessels, to show structures concerned in the formation of the foramen of Winslow. (Columbia University, Study Collection.)] Fig. 296 shows a complete dissection of the adult human viscera and vessels concerned in the formation of the foramen, hardened in situ. The stomach is removed, dividing of course the coronary artery and vein and the left gastro-epiploic artery. The portal vein, hepatic artery and bile-duct are seen entering and leaving the liver at the transverse fissure. Behind them and to the right the vena cava enters the liver. The hepatic artery distributes its pancreatico-duodenal branches to the duodenum and pancreas. The left angle of the Spigelian lobe and the fissure for the ductus venosus appear to the left of the portal vein and hepatic artery. The right angle of the Spigelian lobe and its continuation into the right lobe by means of the caudate lobe is hidden by the structures occupying the transverse fissure. We would enter the beginning of the foramen of Winslow by passing between the vena cava behind, the structures in the transverse fissure (portal vein, hepatic artery and duct) in front, caudate lobe of liver above and duodenum below, the latter in the undisturbed condition of the parts adherent to the right kidney. Continuing to the left the finger would pass between aorta behind, coeliac axis and hepatic artery below and in front, and liver above. These structures bound the permanent and primary narrow channel of communication between the retrogastric or lesser peritoneal space and the general peritoneal cavity, which exists even if a free duodenum and mesoduodenum allow us to lift the intestine away from vena cava and right kidney.