190 THE CAT. [chap. vi. 



omenta ; and folds wliicli pass from tlie abdominal wall to viscera 

 which, do not form parts of the alimentary tube itself, are spoken of 

 as ligaments. 



The peritoneum forms a truly closed sac in the male, but in the 

 female it has two small openings, which indirectly communicate with 

 the external surface of the body. These openings are the mouths 

 of the " Fallopian tubes." 



Of the MESENTERIES, the mesentery par excelknce is that which 

 connects the small intestine with the dorsal abdominal wall, and 

 conveys vessels to it. It contains numerous mesenteric glands (to 

 be noticed hereafter in connexion with the lymphatic system) and 

 vessels. Its vertebral border is very short, but its intestinal border 

 is of course drawn out nearly to the length of the small intestine. 

 Other folds attach the large intestine to the back of the abdominal 

 wall, and are respectively called the mcso-colon and meso-rectum. 



The OMENTA are three in number, and the first and largest 

 of these, the great or gastro-coUc omentum, is really a modified 

 mesentery, being an enormous extension of that membrane which 

 primitively connected the stomach with the body- wall, and which is 

 produced and folded on itself so as to form a great sac, constituting 

 that apron-like fold which was before spoken of as covering the 

 intestines when the abdominal cavity is laid open in front. 



Anteriorly, the great omentum is attached to the stomach along 

 its greater curvature ; posteriorly, it is attached to the dorsal 

 surface of the abdominal wall. Thus, this great omental sac con- 

 sists really of four layers. 



That it must do so is plain, since every mesentery consists of two 

 layers (which hold between them the viscus they suspend), and, the 

 great omentum being a pouch formed by the bulging out of a 

 mesentery in a sac-like manner, each wall of the sac (being a part 

 of a mesentery) must consist of two layers. 



The second, gastro-hepatic, or lesser omentum, passes backwards 

 from the hinder surface of the liver to the pyloric part of the 

 stomach, and the beginning of the duodenum. Its two folds extend 

 from the two sides of the portal fissure, and have between them the 

 portal vein and hepatic artery, as well as the gaU-duct. 



The third, or gastro-sjjlenic omentum, proceeds from the cardiac 

 region of the stomach to the hilus of the spleen. There it divides, 

 one layer passing all round the outer surface of the spleen, and 

 returning to the other side of the hilus, whence the two layers pro- 

 ceed side by side to the diaphragm ; forming what might be called 

 a mesentery of the spleen. Between these layers the blood-vessels 

 proceed to the spleen and to the stomach, shomng that the gastro- 

 splenic omentum is the remains of the proximal part of what was 

 originally the gastric mesentery. 



By the folding of the peritoneum upon itself with the development 

 of the viscera, the edge of the gastro-hepatic omentum is brought 

 so near the posterior abdominal wall that but a small space is left 

 between. This space is called the foramen of Winslow, and the 



