ACTION OF THE GASTRIC JUICE. 227 



first changed by the gastric juice into an acid-albumin or albuminate ; this is 

 farther changed into propeptone, or as it is called by Kuhne, hemialbumose ; 

 and the final action is a change into the true peptones. These intermediate 

 processes have been studied in artificial digestion, and the acid-albumin and 

 propeptone differ, in some of their chemical properties which it is not neces- 

 sary to describe in detail, from both albumin and peptone. A temperature 

 near that of the body is necessary to the various changes just mentioned. 



Action of the Gastric Juice on Fats, Sugars and Amylaceous Substances. 

 Most of the fatty constituents of the food are liquefied at the temperature 

 of the body ; and when taken in the form of adipose tissue, the vesicles in 

 which the fatty matters are contained are dissolved, the fat is set free, is 

 melted and floats in the form of drops of oil on the alimentary mass. The 

 action of the stomach, then, seems to be to prepare the fats, chiefly by dis- 

 solving the adipose vesicles, for the complete digestion which takes place in 

 the small intestine. 



The varieties of sugar of which glucose is the type undergo little if any 

 change in digestion and are probably in greatest part directly absorbed by 

 the mucous membrane of the stomach. This is not the case, however, with 

 the varieties of sugar classed with cane-sugar. It has been shown that cane- 

 sugar injected into the veins of a living animal is not assimilated by the sys- 

 tem but is immediately rejected by the kidneys. When, however, it has been 

 changed into glucose by the action of a dilute acid or by digestion in the gas- 

 tric juice, it no longer behaves as a foreign substance and does not appear in 

 the urine. Experiments have shown that cane-sugar, after being digested 

 for several hours in the gastric juice, is slowly converted into glucose. This 

 action does not depend upon any constituent of the gastric juice except the 

 free acid ; and a dilute mixture of hydrochloric acid had an equally marked 

 effect. Experiments in artificial digestion have shown that cane-sugar is 

 transformed into glucose by the gastric juice very slowly, the action of this 

 fluid in no way differing from that of very dilute acids. In the natural pro- 

 cess of digestion, this action may take place to a certain extent ; but it is not 

 shown to be constant or important. 



The action of gastric juice, unmixed with saliva, upon starch is entirely 

 negative, as far as any transformation into sugar is concerned. When the 

 starch is enclosed in vegetable cells, it is set free by the action of the gastric 

 juice upon the nitrogenized parts. Raw starch in the form of granules 

 becomes hydrated in the stoniach, on account of the elevated temperature 

 and the acidity of the contents of the organ. This is not the form, however, 

 in which starch is generally taken by the human subject ; but when it is so 

 taken, the stomach evidently assists in preparing it for the more complete 

 processes of digestion which are to take place in the small intestine. 



Cooked or hydrated starch, the form in which it exists in bread, fari- 

 naceous preparations generally and ordinary vegetables, is not affected by 

 the pure gastric juice and passes out at the pylorus unchanged. It must be 

 remembered, however, that the gastric juice does not entirely prevent a con- 

 tinuance of the action of the saliva ; and experiments have shown that gastric 



