GASTRIC SECRETION AND DIGESTION 79 



be claimed that it is indispensable to man. It forms, as 

 already indicated, a convenient place of deposit for food 

 and a gradual feeder of the small intestine, but it is mean- 

 while the seat of preliminary digestive changes which 

 greatly facilitate the further advance of the process. 

 Attention has been called to the fact that salivary diges- 

 tion is continued for a time in the almost stationary con- 

 tents of the fundus. When this is stopped by the penetra- 

 tion of the acid gastric juice it is superseded by a new type 

 of digestion in which the proteins are the food-stuffs acted 

 upon. The gastric hydrolysis of proteins is generally re- 

 ferred to as peptic digestion. Before we discuss it in 

 detail we must consider the nature and the circumstances 

 of formation of the gastric juice. 



This secretion is the product of the numerous, relatively 

 simple glands with which the mucous coat of the stomach is 

 provided. Beaumont has vividly described the appearance 

 presented by the lining of St. Martin's stomach directly 

 after a meal. The surface, usually of a pale gray, flushed 

 deeply, and the gastric juice welled up in glistening beads 

 from the invisible mouths of the glands. Its manner of 

 breaking out resembled the rising of perspiration from the 

 pores of the skin. The empty stomach may have a well- 

 marked film of mucus upon its walls, but its active secre- 

 tion is limpid and free flowing. The volume which the 

 human stomach produces in twenty-four hours is ap- 

 parently very large; if we have a right to judge from what 

 is known of the dog, it may be 3 or 4 quarts. A dog, being 

 carnivorous, probably secretes a disproportionate quan- 

 tity, and our estimate for man should very likely be re- 

 duced. 



The Acid of the Gastric Juice. Repeated reference has 

 been made to the acidity of the stomach-contents. The 

 early investigators were surprised and puzzled when they 

 were forced to recognize that the acid in question is largely 

 free hydrochloric. When we consider that this acid can- 

 not be made industrially except by decomposing a chlorid 

 with the still stronger and more corrosive sulphuric acid 



