248 DIGESTION. 



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

 does not say much with regard to the changes which fatty substances undergo in the stom- 

 ach, except that they are '* digested with great difficulty." All the recent observations 

 on this subject show that these principles, when taken in the condition of oil, pass out 

 at the pylorus unchanged. 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 little vesi- 

 cles in which the oleaginous matter is contained are dissolved, the fat is set free and 

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

 of the stomach, then, seems to be to prepare the fats for digestion, chiefly by dissolving 

 the adipose vesicles, for the complete digestion which takes place in the small in- 

 testine. 



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

 digestion and are probably for the most 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 system 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 gastric juice, it no longer behaves as a foreign substance and does not appear in the 

 urine. This leads to a consideration of the changes which cane-sugar undergoes in the 

 stomach. Experiments have shown that this variety of 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 an exceedingly 

 dilute mixture of hydrochloric acid had an equally marked efiect. Experiments in arti- 

 ficial 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 process of digestion, this action may take place to a certain ex- 

 tent ; but it is not shown to be constant or important, and we must look to intestinal di- 

 gestion for the rapid and efficient transformation of cane-sugar. 



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 vege- 

 table 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 stomach, 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. 



Gooked or hydrated starch, the form in which it exists in bread, farinaceous prepara- 

 tions 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 prevent a continuance of the action induced by the saliva ; and experi- 

 ments have shown that gastric juice taken from the stomach, when it contains a notable 

 quantity of saliva, has, to a certain extent, the power of transforming starch into sugar. 

 It has already been remarked that, with regard to this question, experiments on dogs, as 

 these animals do not naturally take starch as food, do not correspond with observations 

 on the human subject. 



The changes which vegetable acids and salts, the various inorganic constituents of 

 food, and the liquids which come under the head of drinks undergo in the stomach are 

 very slight. Most of these principles can hardly be said to be digested; for they are 

 either liquid or in solution in water and are capable of direct absorption and assimila- 

 tion. With regard to most of the inorganic salts, they either exist in small quantity in 

 the ordinary water taken as drink or are united with organic nitrogenized principles. 

 In the latter case, they become intimately combined with the organic principles result- 

 ing from stomach-digestion. We have already seen that the various peptones have been 



