190 



CHAPTER XXIV. 



DIGESTION CONTINUED. THE STOMACH. ITS COATS, PARTICULARLY 



THE MUCOUS COAT. STOMACH CELLS AND TUBES. PYLORIC TUBES. 



MOVEMENTS OF THE STOMACH. THE GASTRIC JUICE, ITS NATURE 



AND PROPERTIES. PEPSINE. STOMACH DIGESTION. 



THE alimentary canal below the diaphragm is naturally divided 

 into the stomach, the small intestine, and the large intestine, all of 

 which are lined by mucous membrane, have, like the oesophagus, a 

 double muscular coat, and are, besides, invested with a serous mem- 

 brane, the peritoneum, which facilitates the motion by which the 

 contained matters are propelled from end to end. 



The stomach, of which we have first to speak, is an elongated 

 curved pouch, very dilatable and contractile, fitted to receive the 

 food from the oesophagus, to retain it while acted on by the gastric 

 fluid secreted from the lining membrane, and then to transmit it to 

 the duodenum or first part of the small intestine. It is expanded 

 into an ample cul-de-sac at its left extremity, and becomes gradually 

 narrower towards the pylorus, where it joins the duodenum. A cir- 

 cular constriction is often apparent three or four inches from the 

 pylorus, partially dividing the pyloric region from the rest of the 

 cavity. It has an anterior and posterior surface, which become re- 

 spectively rather upper and lower during repletion of the organ 

 (owing to its change of bulk, and its being fixed at its two ori- 

 fices), and an upper and lower curvature, called also lesser and 

 greater, which undergo a corresponding alteration, becoming rather 

 posterior and anterior. The peritoneum invests both surfaces, and 

 passes from them to the liver (forming the gastro-hepatic omentum), 

 to the spleen (forming the gastro-splenic omentum), and to the 

 transverse colon (forming first the anterior and then the posterior 

 layers of the great omentum). This peculiar arrangement of the 

 serous membrane is probably intended to allow of the extreme 

 changes of bulk to which this organ is liable. The muscular fibres 

 of the stomach are continuous with those of the oesophagus ; but, in 

 consequence of its irregular shape and its bulging from the cardia 

 towards the left hypochondrium and the umbilical region, these 



