THE COELOM, DIGESTIVE, AND RESPIRATORY SYSTEMS 191 



the greater part of it first descends posteriorly, forming a bag, the greater omentum. 

 This is a very large and extensive sheet in the cat, covering the intestine ventrally 

 as noted above. In the rabbit it is a short membrane dependent from the greater 

 curvature of the stomach. The greater omentum is to be thought of as formed 

 in the following way. Suppose one should grasp the mesogaster and pull it pos- 

 teriorly, drawing it into a sac. Such a sac would have two walls, each double, 

 i.e., composed of the two layers of the mesogaster; the sac would contain a 

 cavity which is known as the lesser peritoneal sac and would open anteriorly (this 

 opening will be seen later) (see Fig. 50, p 198.). By manipulating the omentum 

 determine that it consists of two separate walls. Having formed the greater 

 omentum the mesogaster returns to the stomach wall and passes onto the stomach 

 along the greater curvature. The spleen is inclosed in the ventral wall of the 

 great omentum just before the latter passes to the stomach. The portion of the 

 great omentum between the spleen and the stomach is called the gastrosplenic 

 (or gastrolienal) ligament. Posterior to the spleen, near the left kidney, a second- 

 ary fusion, the gastrocolic ligament, has formed between the mesogaster and the 

 mesentery of the intestine (see Fig. 50). 



The greater omentum owes its origin in part to the rotation of the stomach. 

 The line of attachment of the omentum to the greater curvature is the original 

 dorsal surface of the stomach, while the lesser curvature is the original ventral 

 surface. The mesogaster passes over the stomach, forming the visceral peri- 

 toneum of the stomach, and inclosing the stomach between its walls, and at 

 the lesser curvature is continued by a strong ligament, the lesser omentum, which 

 passes to the liver. 



The liver may be studied next. It presents a convex anterior surface, fitting 

 against the posterior surface of the diaphragm, and a concave posterior surface, 

 fitting over the stomach and first part of the small intestine. The liver is divided 

 into right and left lobes, each of which is subdivided into two lobes, a median and a 

 lateral. The left lateral and right median lobes are larger than the others. In 

 the cat the right lateral lobe is deeply cleft into two lobules. The large elongated 

 gall bladder is imbedded in the right median lobe, on its dorsal surface in the 

 rabbit, in a cleft in this lobe in the cat. On raising the liver and looking between 

 the liver and the stomach another small lobe, the caudate lobe, will be seen. It is 

 situated between the two layers of the lesser omentum. The lesser omentum, 

 or gastro-hepato-duodenal ligament, is the ligament passing from the lesser curva- 

 ture of the stomach to the posterior surface of the liver. It is divisible into two 

 portions: the gastrohepatic ligament from the lesser curvature to the liver, and 

 the hepatoduodenal ligament from the liver to the first part of the small intestine. 

 That portion of the gastrohepatic ligament which contains the caudate lobe of 

 the liver forms a sac which continues anteriorly the cavity of the greater omen- 

 tum. In the hepatoduodenal ligament runs the bile duct which should be traced 

 from the gall bladder by gently dissecting in the ligament. Note the cystic duct 



