718 PHYSIOLOGY OF DIGESTION AND SECRETION. 



the movements of the stomach. In this way they are mechanically 

 prepared so that the subsequent action of the pancreatic juice is 

 much favored. When, however, fats are ingested in emulsified 

 form, as in milk, for instance, the lipase of the stomach, according to 

 Volhard, may cause a marked hydrolysis. It is supposed that 

 this action may be important in the digestion of the milk-fat by 

 infants. Regarding the proteins, the practical point of interest 

 is as to how far they are digested during their stay in the stomach. 

 It seems probable that this question does not admit of a categorical 

 answer that is, the extent of the digestion varies under different 

 circumstances; with the consistency of the food, the duration of 

 its stay in the stomach, etc. In the liquid material (chyme) forced 

 through the pylorus into the duodenum one may find unchanged 

 proteins, primary or secondary proteoses, peptones, or even the final 

 split products of proteolytic action. The true value of peptic diges- 

 tion is not so much in its own action as in its combined action with 

 the trypsin of the pancreatic juice. The digestion of the proteins 

 of the food is accomplished by both enzymes, and normally we are 

 justified in considering them together as effecting a peptic-tryptic 

 digestion. The preliminary digestion in the stomach is important 

 as regards the protein foods from several standpoints: First, in the 

 matter of mechanical preparation of the food and its discharge in 

 convenient quantities easily handled by the duodenum. Second, 

 in the more or less complete hydrolysis to peptones and proteoses 

 whereby the action of the pancreatic juice must be greatly acceler- 

 ated. Indeed, in some cases, this preliminary action of the pepsin- 

 hydrochloric acid may be absolutely necessary. Native proteins, 

 such as serum-albumin, are not acted upon by trypsin, but if sub- 

 mitted first to pepsin-hydrochloric acid they are quickly digested by 

 this enzyme. Third, for some as yet unknown reason proteins sub- 

 mitted to peptic digestion are split by the trypsin in a way different 

 from its action on proteins without this preliminary treatment. 

 These and other facts seem to indicate that the peptic digestion is not 

 so much an end in itself as a preparation for subsequent intestinal 

 digestion. The stomach, therefore, may be removed without a 

 fatal result. Several cases are on record in which the stomach was 

 practically removed by surgical operation, the esophagus being 

 stitched to the duodenum.* The animals did well and seemed 

 perfectly normal, although special precautions were necessary in 

 the matter of feeding. 



Absorption in the Stomach. In the stomach it is possible that 

 there may be absorption of the following substances : Water ; salts ; 

 sugars and dextrins that may have been formed in salivary digestion 



*Ludwig and Ogata, "Archiv f. Physiologic," 1883, p. 89; Carvallo and 

 Pachon, "Archives de physiologie norm, et path.," 1894, p. 106. 



