Note 22 — Chapter VI · Digestion.

The Peritoneum. The intestines do not lie in a loose mass in the abdominal cavity. Lining the walls of this cavity, just as in a general way, a paper lines the walls of a room, is a delicate serous membrane, called the peritoneum. It envelops, in a greater or less degree, all the viscera in the cavity and forms folds by which they are connected with each other, or are attached to the posterior wall. Its arrangement is therefore very complicated. When the peritoneum comes in contact with the large intestine, it passes over it just as the paper of a room would pass over a gas pipe which ran along the surface of the wall, and in passing over it binds it down to the wall of the cavity. The small intestines are suspended from the back wall of the cavity by a double fold of the peritoneum, called the mesentery. The bowels are also protected from external cold by several folds of this membrane loaded with fat. This is known as the great omentum. The peritoneum, when in health, secretes only enough fluid to keep its surface lubricated so that the bowels may move freely and smoothly on each other and on the other viscera. In disease this fluid may increase in amount, and the abdominal cavity may become greatly distended. This is known as ascites or dropsy.