ACTION OF THE GASTRIC JUICE. 199 



curdling is a physiologic process, and the only abnormality is its 

 regurgitation, which is usually due to overfeeding. 



Action of the Gastric Juice. Having considered the 

 composition of the gastric juice, we are now in a position to dis- 

 cuss its action upon the food. 



Action on Proteids. When proteids reach the stomach by 

 the process of deglutition they meet with the gastric juice, whose 

 hydrochloric acid converts them into acid-albumins. Some writers 

 use the term syntonin as synonymous with acid-albumins ; others 

 restrict its use to the special acid-albumin which results from the 

 action of the acid upon myosin. This change in the proteids is 

 more quickly and completely brought about by the acid when 

 pepsin is present than when the acid acts by itself. The acid- 

 albumin (syntonin) takes up water, and undergoes a "cleavage" 

 or splitting up, as a result of which two soluble proteids are 

 formed, proto-proteose and hetero-proteose, which are together 

 known as primary proteases. This is due to the action of the 

 pepsin, which is, therefore, a proteolytic enzyme. The process, 

 however, does not cease here ; the action of the pepsin continuing, 

 the primary proteoses take up water and in turn split, forming 

 secondary or deutero-proteoses. These in turn undergo hydrolytic 

 cleavage, forming as final products, peptones. Inasmuch as there 

 are doubtless two varieties of peptones, as will be seen in the dis- 

 cussion of the digestion of proteids by the pancreatic juice, these 

 are called ampho-peptones. For the distinguishing characteristics 

 of peptones and proteoses the reader is referred to p. 106. 



Action on Carbohydrates. Cane-sugar is undoubtedly inverted 

 in the stomach to dextrose and levulose, the hydrochloric acid 

 being the agent in the inversion. All the cane-sugar of the 

 food, however, does not undergo this change in the stomach, some 

 of it not being inverted until it reaches the small intestine. 



There is some evidence looking toward the presence in the 

 gastric juice of an amylolytic enzyme, but this is as yet too incom- 

 plete to require more than mention. 



The changes which starch undergoes during stomach digestion 

 are elsewhere described. 



Action on Fats. The temperature of the stomach, 38 C., ren- 

 ders the fats more fluid. If the fat is in the form of adipose tissue 

 that is, enclosed in adipose vesicles the walls of the latter being 

 proteid in character undergo proteid digestion, setting the fat free ; 

 but the latter is not emulsified. The evidence that fat is split up 

 and fatty acids liberated in the stomach is accumulating ; it is 

 believed that this is due to a lipolytic enzyme, whose action is in- 

 hibited by hydrochloric acid and pepsin. 



Action on Albuminoids. Of all the albuminoids which enter 

 into the food, gelatin is the most important. It is found in 



