S02 SPLANCHNOLOGY. 



anterior is related with tlie diaphragm and liver, the posterior with- 

 the diaphragmatic flexure of the colon. The spleen lies along; 

 the inferior and external part of the greater cul-de-sac, its base 

 being directed backwards and somewhat upwards ; the pyloric 

 extremity, which is placed lower than the cardiac, is related with 

 the right lobe of the liver and the intestines. 



The walls of the stomach are composed of three coats — an 

 external serous, a middle muscular, and an internal mucous coat. 



The serous coat, a reflection of the peritoneum, is smooth and 

 elastic, adhering intimately to the muscular, except at the lesser 

 curvature, where, strengthened by addition of yellow elastic tissue, 

 it forms a ligament, which appears to support the two extremities 

 of the stomach ; forming around the cardiac orifice a circular 

 fold, which surrounds the oesophagus and passes to the dia- 

 phragm ; this is the gastro-phrenic, or coronary ligament 

 The peritoneum also passes in a double fold from the greater 

 curvature to the spleen, as the gastro-splenic, to the colon as the 

 gastro-colic, or great omentum ; and from the lesser curvature 

 to the liver, as the gastro-hepatio omentum. 



In the m,uscular coat are three sets of fibres — an external 

 longitudinal, a middle circular, and an internal oblique layer. 

 The longitudinal are continuous with those of the oesophagus, 

 and radiate from the cardiac orifice ; they are thickest at the 

 curvatures, and are thinly scattered over the surfaces ; towards 

 the pyloric end they again converge, and form a uniform layer^ 

 which is continuous with that of the duodenum. The middle 

 layer consists of circular fibres, which cover the entire organ ; 

 near the pylorus they thicken into a circular ring, which projects 

 into the orifice, and forms with a doubling of the mucous mem- 

 brane, a sphincter, called the pyloric valve, which by contraction 

 prevents crude food from passing into the intestine. The inner 

 layer, is composed of oblique fibres, continuous with the circular 

 oesophageal ones ; they are confined to the cardiac portion, 

 descend obliquely over either surface, and disappear towards the 

 central constriction. All these layers are composed of pale or 

 involuntary tissue; the longitudinal layer, by contracting, enables 

 the stomach to dilate ; the circular produces vermicular motion, 

 while the oblique layer tends to force the food from the left into 

 the right cavity ; thus there is produced a kind of churning 

 motion, which macerates the food and brings each portion of it- 

 into contact with ths mucous surface. 



