mesentery of the vermiform appendix, and the mesenteries occasionally found in connection with the ascending and descending portions of the colon. The term ligament is given to folds which connect viscera which are not parts of the intestinal canal to the walls of the abdomen, or which bind viscera of any kind to the diaphragm. Examples of these are to be found in the peritoneal ligaments of the liver, bladder, and uterus, and also in the lieno-renal, the phrenico-colic, and the gastro-phrenic ligaments. Let us now endeavour to follow the peritoneal membrane in the vertical direction (Fig. 107). The best point to start from is the great omentum, or large apron-like fold which hangs down from the stomach, and is spread out over the coils of the small intestine. This omentum is composed of four layers-two anterior layers and two posterior layers, and these are continuous with each other at the lower free margin of the fold. Trace the two anterior layers upwards. They lead to the greater curvature of the stomach, and here they separate from each other so as to enclose this viscus between them-one passing in front and the other passing behind it. The smooth glistening appearance presented by the surface of the stomach is due to the peritoneal coating which it thus acquires. At the lesser curvature of the stomach the two layers come together, and are prolonged upwards to the liver as a distinct fold, which receives the name of the gastro-hepatic or lesser omentum. Reaching the transverse fissure of the liver the two layers again separate, this time to enclose the liver. The one layer is directed forwards over the under surface of the organ round its anterior border, and then onwards over its anterior and superior surfaces. On reaching the point where the liver and diaphragm are in contact, it is reflected on to the diaphragm, and proceeds forwards upon its under surface to reach the anterior wall of the abdomen. The other layer turns backwards, and, clothing the lobus Spigelii on the posterior surface of the liver, is reflected on to the back part of the diaphragm, and turns downwards on the posterior wall of the abdomen. We shall now leave these layers for a little and trace the two posterior layers of the omentum. For this purpose it is necessary to turn up the great omentum over the ribs. Its two posterior layers in proceeding upwards come to the transverse colon. This they enclose, the one passing in front and the other behind, and coming in contact with each other again on the other side o the gut, they are prolonged backwards to the posterior wall of the abdomen, as the transverse meso-colon. They reach the back wall of the abdomen along the anteroinferior border of the pancreas, and here they separate. The one layer turns upwards over the pancreas to become continuous with the layer which we left upon the posterior wall of the abdomen. The other turns downwards over the third part of the duodenum, and is almost immediately led away from the posterior wall of the abdomen by the superior mesenteric vessels, which, spreading out in a fanlike manner, conduct it to the small intestine. Turning round the gut so as to invest it, the peritoneum proceeds upwards upon the posterior aspect of the superior mesenteric vessels to the spine. In this manner the mesentery proper is formed. The peritoneum is now carried downwards over the posterior abdominal wall into the pelvis, where it may be traced over the rectum and bladder,1 to both of which it gives partial coverings, and then on to the anterior abdominal wall, where it becomes continuous with the layer which we left there. The two anterior layers of the great omentum therefore proceed upwards to the under surface of the diaphragm, and there separate, the one passing forwards over the anterior portion of its under surface to reach the anterior wall of the abdomen, whilst the other is directed backwards over the posterior part of its under surface to reach the posterior wall of the abdomen. On their way up to the diaphragm these layers enclose the stomach, form the gastro-hepatie omentum, and partially enclose the liver. On the other hand, the two 1 In the female it also gives a covering to the uterus, but the disposition of the peritoneum in the pelvis, both male and female, will be fully described in connection with the pelvic viscera. posterior layers are directed backwards to the spine, and there separate. In passing back, they enclose the transverse colon, and form the transverse meso-colon. The one layer then ascends to become continuous with the layer on the posterior abdominal wall. The other layer passes downwards, doubles upon itself to enclose the small intestine and form the mesentery proper, enters the pelvis, and then reaches the anterior abdominal wall. A reference to Fig. 107 will show that the peritoneal sac is arranged in two pouches,-a large pouch in front and a smaller pouch situated behind it. The large pouch is the one into which we have opened in opening the cavity of the abdomen. Now it must be clearly understood that these are simply compartments of one serous sac, and that they communicate freely with each other through a narrow channel called the Foramen of Winslow (foramen epiploicum). The best way to find the foramen of Winslow is to lay hold of the fundus of the gall-bladder with the left hand, and then pass the forefinger of the right hand backwards along it towards its neck. The finger will slip behind the gastro-hepatic omentum into the foramen. The foramen of Winslow has the following boundaries :in fron, the right free margin of the gastro-hepatic omentum, between the two layers of which are the hepatic artery, the portal vein, the hepatic duct, and some nerves; behind, the vena cava inferior, and the right crus of the diaphragm, covered by the layer of the transverse meso-colon, which passes upwards on the posterior wall of the abdomen; below, the duodenum and hepatic artery; and above, the lobus caudatus of the liver. The lesser bag of the peritoneum extends downwards into the omentum, upwards to the posterior surface of the Spigelian lobe of the liver and back part of the diaphragm, and to the left as far as the spleen. It is closed in the following manner :-in front, by the two anterior layers of the great omentum, by the stomach, by the gastro-hepatic omentum, and the lobus Spigelii of the liver; behind, by the two posterior layers of the great omentum, by the stomach. aorta. parietal peritoneum. spleen. transverse colon, by the transverse meso-colon, and by the omentum. : In a favourable subject these points can be made out by dividing the two anterior layers of the great omentum along the greater curvature of the stomach, and introducing the hand into the lesser sac. The entire gastro-hepatic omentum. FIG. 108.-Section through the peritoneal cavity at the extent of the pouch can thus be explored, and its continuity with the The peritoneal lining of the abdomen must also be traced right kidney. |