DIGESTION. QI 



GASTRIC DIGESTION. 



The Stomach. Immediately beyond the termination of the esophagus 

 the alimentary canal expands and forms a receptacle for the temporary re- 

 tention of the food. To this dilatation the term stomach has been applied. 

 This organ is somewhat pyriform in outline, and occupies the upper part of 

 the abdominal cavity. It is about 13 inches long, 5 deep, and 3^ wide, and 

 has a capacity of about five pints. It presents two orifices, the cardiac or 

 esophageal, and the pyloric; two curvatures, the lesser and the greater. 



The left or cardiac end of the stomach is enlarged, and forms the fundus; 

 the right end is much narrower, and forms the pylorus. The stomach pos- 

 sesses three coats: 



1. The serous, or reflection of the peritoneum. 



2. The muscular, the fibers of which are arranged in a longitudinal, a circular, 

 and an oblique direction. As the pyloric end the circular fibers increase in 

 number and form a thick ring or band, which is known as the sphincter of 

 the pylorus. 



3. The mucous, which is somewhat larger than the muscular coat, and in 

 consequence is thrown into folds or rugae. The surface of the mucous coat 

 is covered by tall, narrow, columnar epithelium. 



Gastric Juice. During the period of time the food remains in the stomach 

 it is subjected to the disintegrating action of an acid fluid, the gastric juice. 

 This fluid, secreted from glands in the mucous membrane, is thoroughly 

 incorporated with the food in consequence of the contractions of the muscular 

 coat. The food is gradually liquefied and reduced to a form which partly 

 fits it for passage into the small intestine and for absorption into the blood. 

 Gastric juice, when obtained in a pure state, is a clear, colorless fluid, decid- 

 edly acid in reaction, with a specific gravity of 1005. It is composed of the 

 following ingredients: 



COMPOSITION OF GASTRIC JUICE. 



Water 994-44 



Hydrochloric acid 2.000 



Organic matter 3- z 95 



Inorganic salts 2.201 



1000.000 



The water forms by far the largest part of this fluid, and serves the purpose 

 of holding the other ingredients in solution, and by its saturating power 

 brings them into relation with the constituents of the food. Of the inorganic 

 salts the sodium and potassium chlorids are the most abundant and important. 



