PERITONEUM (Gr. perilancin, to extend around), a serous membrane, and, like all membranes of this class, a shut sae, which, however, in the female, is not completely closed, as the Fallopian tithes communicate with it by their free extremities. The peri toneum more or less completely invests all the viscera lying in the abdominal and pelvic cavities, and is then reflected upon the walls of the abdomen, so that there Is a visceral and a parietal layer. Numerous folds are formed by the visceral layer as it passes from .one organ to another. They serve kl'hold the parts in position, and at the same time euelo;e vessels and nerves. Some of these folds are termed ligaments, from their serving to support the organs. Thus we nave ligaments of the liver, spleen, bladder, and uterus formed by peritoneal folds. Others are termed mesenteries (from the Gr. meson, the middle, and enteron, the intestine), and connect the intestines with the vertebral column They are the mesentery proper (q.v.), which has been already described, the ascending transverse, and descending mego-colon, and the meso-rectum. Lastly, there are folds called omenta, which proceed from one viscus to another They are three in number— viz.. the lesser or 081).o-hepatic omentam, which extends from the under-surface of the
liver to the lesser curvature of the stomach; the gastro-splenic omentum ; and the great (or gastro-colic) omentum, which consists of four layers of peritoneum, the two which descend from the stomach, and the same two returning upon themselves, and ascending as high as the transverse colon, where they separate, and inclose that organ: These separate layers may be easily seen in the young subject, but in the adult they are more or less blended. The great omentum always contains some adipose tissue, which, in persons inclined to corpulency, often accumulates to an. enormous extent. Its use appears to be (1) to protect the intestines from cold by covering them anteriorly as with an apron, and (2) to facilitate their movement upon each other during their vermicular action.
Like all the serous membranes, the peritoneum readily takes on inflammation from various exciting causes. This inflammation is termed peritonitis (q