The peritoneum, which is stretched over many organs and possesses many recesses and pouches, has a superficies said to be equal to the surface of the body. It is a large lymphatic sac and fluid is constantly circulating through it. Experiments (especially those of Wegner) have shown that the peritoneum possesses great powers both of the transudation and absorption of fluid. Thus the injection of concentrated solution of sugar or of glycerine causes an exudation of serous fluid amounting in three quarters of an hour to from 3 to 8 per cent, of the weight of the body. Again, watery fluids and even urine, bile, oil, etc., are absorbed with great rapidity without injury to the membrane, and such medicaments as morphia and choral are absorbed much more rapidly than when injected subcutaneously. Finely divided solid matter is also readily absorbed and carried into the lymphatics. The absorption is effected presumably by stomata, by which the sac communicates with the lymphatic vessels. Whilst all parts of the peritoneum doubtless possess the power of absorption, there are two localities in which this presents points of special interest.
From certain facts to be afterwards referred to in connection with tuberculosis and cancer of the peritoneum, it may be inferred that the Great omentum is specially concerned in the process of absorption. This double layer of peritoneum, lying free in the cavity, may be regarded as a drain by means of which the fluid is drawn off.
Again, the lymphatics of the Diaphragm communicate on the one hand with the peritoneal sac, and on the other with the pleural cavity, so that fluid and finely-divided solids-may be carried through from one to the other. It is probable that the general course of the current is-from peritoneum to pleura, although it may be reversed.
This great power of absorption is very important, especially in relation to septic processes. The products of septic decomposition are readily absorbed; sometimes in such quantity as to produce fatal results before they have had time to induce any considerable local effects. This. is especially the case in rupture of the intestine, where death may occur within twenty-four hours without definite symptoms of peritonitis, and apparently from absorption of the septic. poison. After death, however, signs of inflammation are usually visible in the peritoneum.
The fluid in the peritoneal sac is not at rest, but circulates, and the movements of the intestines doubtless have to do with its transportation from place to place. Hence any pathogenic agent introduced into the peritoneal cavity is generally carried to every part of the sac and produces its effects in every region. Abundant examples of this are afforded by such conditions as tuberculosis of the peritoneum, inflammations, und cancer.
The mesenteries are sometimes too long or too short. The former condition is supposed to have to do with the causation of hernias. The latter causes the intestine to be unduly controlled in its movements. In a case recorded by Lawson Tait the peritoneum passed from loop to loop without any proper mesentery. There are also dermoid cysts found in the peritoneum of congenital origin.