THE STOMACH. 459 



it. It is furnished with a valve (the pyloric valve), formed by the union of the 

 cellular and mucous tunics, and the sudden disappearance of the circular muscular 

 fibres. 



Structure. — The parietes of the stomach are formed by three membranes : 

 an external, or serous ; a middle, or musniUtr ; and an internal, or mucous. 



1. Serous membrane. — This membrane, derived from the peritoneum, adheres 

 closely to the muscular layer, except towards the curvatures. At the lesser 

 curvature, it is constantly covered by an expansion of yellow elastic tissue, the 

 use of which appears to be to maintain the two extremities of the stomach near 

 each other ; for when this is destroyed, the lesser curvature l)ocomes considerably 

 elongated. Along the whole of the greater curvature is a triangular space 

 occupied by connective tissue ; this space disappears more or less completely as 

 the organ becomes distended. 



It has three folds, which are detached from the stomach and carried on to 

 the adjacent parts, and are formed in the manner indicated in the general 

 description of the peritoneum. These folds constitute the cardiac ligament, the 

 gastro-hepatic ligament or omentum, and the great omentum. 



The cardiac ligament is a short, serous band developed around the terminal 

 extremity of the oesophagus, and strengthened by fibres of yellow fibrous tissue. 

 It attaches the stomach to the posterior face of the diaphragm, and is continuous, 

 on each side, with the two folds about to be described. 



The gastro-hepatic (or lesser) ligament is a band composed of two layers, 

 which leave the lesser curvature of the stomach, and are inserted into the 

 posterior fissure of the liver. It is prolonged posteriorly, and to the right, along 

 the duodenum, where it constitutes a peculiar serous frtenum, which wall be 

 studied with the small intestine. 



The great or gastro-colic omentum, is detached from the whole extent of 

 the great curvature, from the cardia to the pylorus, beyond which it extends 

 to the duodenum. The portion surrounding the left cul-de-sac is excessively 

 short, and is carried to the sublumbar wall of the abdomen, to which it fixes the 

 stomach. For the remainder of its extent, this omentum is greatly developed, 

 and hangs freely in the abdominal cavity, among the intestinal convolutions. 

 The border opposed to the stomach is attached to the terminal portion of the 

 large colon, and to the origin of the floating colon. (For further details, see 

 the description of the peritoneum.) 



These three ligaments fix the stomach in the abdominai cavity, in addition 

 to the oesophagus and duodenum, which are continuous with it. 



2. Muscular membrane. — This tunic, comprised between the serous and 

 mucous layers, is lined internally by a covering of condensed connective tissue 

 which adheres intimately to it, and may be regarded as the fibrous membrane of 

 the stomach. Dissection shows this muscular tunic to be composed of three 

 superposed planes. 



The superficicd plane envelops all the right sac, and the majority of its fibres 

 are spread in loops around the left cul-de-sac, their extremities being lost on 

 the surfaces of the organ. Some of them even extend over the great curvature, 

 to the surface of the right sac ; while others are evidently continuous with the 

 superficial fibres of the oesophagus (Fig. 261, a). 



The middle plane (Fig. 261, b) is formed of circular fibres spread over the 

 whole of the organ. In the right sac, they are placed immediately beneath the 

 serous membrane ; in the left sac, they pass beneath the fibres of the superficial 



