The =mesogastrium= or peritoneal fold for the stomach passes from that part of the median dorsal line lying between the kidneys and the diaphragm, to the greater curvature of the stomach. It does not pass directly to the stomach, but passes first ventrad of the small intestine as far as the pelvis. Thence it turns craniad to reach the greater curvature of the stomach. The fold thus formed is called the =great omentum=. It forms the dorsal and ventral walls of a sac, the =omental sac=, the cavity of which is called the =lesser peritoneal cavity=. The descending limb of the fold forms the dorsal wall of the sac, and its ascending limb forms the ventral wall. Each of these walls is double like a mesentery, so that the great omentum consists of four sheets of peritoneum. Between the two sheets forming the descending limb lies the left half of the pancreas, which passes thence to the right into the duodenal mesentery. A transverse fold passes from the descending limb of the omentum along the cranial border of the pancreas to the duodenal mesentery. Farther to the right the descending limb of the omentum, which is here shorter, encloses the spleen and holds it in position parallel to the greater curvature of the stomach and about one centimeter from it. This part of the great omentum is sometimes called the =gastrosplenic= or =gastrolienal= omentum. The great omental sac communicates with the peritoneal sac by an opening, the =foramen epiploicum= or =foramen of Winslow=. This opening lies caudad and dextrad of the caudate lobe of the liver. This lobe itself lies within the sac. Along the ventral border of the foramen epiploicum pass the common bile-duct from the liver and the portal vein to the liver. The size of the great omental sac is increased by the =lesser omentum=. This is a double sheet of peritoneum which stretches horizontally from the liver to the duodenum and the lesser curvature of the stomach. It covers ventrad the caudate lobe of the liver. Its right border is at the foramen epiploicum. The part of it which stretches to the duodenum is called the =duodenohepatic= ligament and contains the bile-ducts and the portal vein. The part that stretches to the stomach is called the =gastrohepatic= ligament. The peritoneum covers the caudal and cranial surfaces of the liver and is reflected to the adjacent parts to form the ligaments of the liver.