1758 HUMAN ANATOMY. 



Cancer of the peritoneum is occasionally primary, but is usually due to exten- 

 sion from the stomach, uterus, ovaries, liver, or other organs. The irregular mass of 

 a carcinomatous omentum cannot be distinguished by touch from the similar tumor 

 due to chronic peritonitis. 



The peritoneal cavity as a whole the interval between adjacent visceral surfaces 

 or between such surfaces and the parietes may be scarcely more than a potential 

 space, containing enough serous fluid for purposes of lubrication, or may be more or 

 less distended by an effusion of the same fluid, ascites. Such effusion may result 

 from (a) infection followed by chronic inflammation ; (b) abdominal tumors, causing 

 irritation and pressure ; (c) obstruction of the portal circulation, either terminal, as 

 in hepatic cirrhosis, or by pressure on the vein itself in the gastro-hepatic omen- 

 tum, as from certain pancreatic or duodenal growths, aneurism, or the exudate of 

 a chronic peritonitis (vide supra}; or (d} from conditions producing a general 

 dropsy (of which the ascites is but a part), such as cardiac or renal disease, chronic 

 empyema, or pulmonary sclerosis. Ascites is recognized by (a) a flat abdomen 

 bulging at the flanks, with prominent umbilicus ; (b} dulness in the flanks varying 

 with change of posture ; (c) resonance over the uppermost part of the abdomen 

 in either dorsal or lateral decubitus (from floating upward of the intestine) ; (d) fluc- 

 tuation. Sudden withdrawal of ascitic fluid may cause syncope in persons with 

 pre-existing cardiac lesions by diminishing intra-abdominal pressure, permitting a 

 dilatation of the deep circumflex iliac, the deep epigastric, the lumbar and other 

 deep abdominal veins, and thus suddenly lessening cardiac blood-pressure. 



The difference between the peritoneal cavity and the abdominal cavity should 

 not be overlooked by the student. A number of the abdominal viscera are not intra- 

 peritoneal, but lie more or less completely behind that membrane. Thus the kidney 

 and pancreas and certain aspects of the ascending and descending colon and duode- 

 num may be wounded, or may be the subject of infectious disease, without involve- 

 ment of the peritoneum, while similar wounds or infections of the liver, spleen, stom- 

 ach, or small intestine would necessarily include it to some extent. 



The parietal peritoneum, the least sensitive portion of the membrane (vide 

 supra}, is thickest below and posteriorly, and is there connected loosely with the 

 abdominal wall by relatively abundant subperitoneal cellular tissue containing fat. 

 This loose connection permits it to be stripped forward, as in some operations on 

 the kidneys or ureters or on the iliac vessels. About the umbilicus and along 

 the mid-line of the abdomen it adheres much more closely. It is strong, bearing 

 a weight of fifty pounds (Huschke) ; distensible, as shown by the gradual stretch- 

 ing it undergoes in ascites, during pregnancy, or in a hernial sac ; and elastic, as in 

 such cases it returns to its normal dimensions when the distending cause is removed. 

 It may be ruptured by sudden force without injury being done to the underlying 

 viscera. 



From its superficial position, the greater omentum is often involved in penetrating 

 wounds of the abdominal wall. Wounds of the omentum are not in themselves seri- 

 ous, except from hemorrhage. The rapid adhesive inflammation which follows injury 

 to the omentum, as to other parts of the peritoneum, may act beneficially by leading 

 to the closure of an intestinal wound or perforation before extravasation occurs, or by 

 favoring the localization of an area of infection. It is sometimes utilized by the sur- 

 geon to reinforce an intestinal suture or to cover intestinal defects, especially in the 

 caecum (E. Senn) ; or to protect the general peritoneal cavity, as in some operations 

 on the bile-ducts. Through inflammatory adhesions, portions of the omentum may 

 act as bands beneath which a loop of gut may be strangulated, or such a loop may 

 pass through an aperture in the omentum itself and become strangulated. The 

 omentum is constantly found in sacs of ordinary hernia? or may constitute their only 

 contents (epiplocele), especially in umbilical and frequently in femoral hernia?. It 

 almost always contracts adhesions to the neck or other portion of a hernial sac, if the 

 hernia is not kept permanently reduced. It then prevents reduction. It is found 

 oftener in left -sided hernia?, because it was developed from the mesogastrium and 

 inclines somewhat towards that side. It is very vascular, and has through acci- 

 dental adhesions -maintained the blood-supply of an ovarian tumor the pedicle of 

 which has been twisted so as to occlude its vessels. Its vascularity and rapid adhe- 



