CHEMISTRY OF DIGESTION AND NUTRITION. 253 



Water. Experiments of the character just described show that water when 

 taken alone is practically not absorbed at all in the stomach. Von Mering's 

 experiments especially show that as soon as water is introduced into the 

 stomach it begins to pass out into the intestine, being forced out in a series 

 of spirts by the contractions of the stomach. Within jji comparatively short 

 time practically all the water can be recovered in this-way, none or very little 

 having been absorbed in the stomach. For example, in a large dog with a 

 fistula in the duodenum, 500 cubic centimeters of water were given through 

 the mouth. Within twenty-five minutes 495 cubic centimeters had been 

 forced out of the stomach through the duodenal fistula. The result was not 

 true for all liquids ; alcohol, for example, was absorbed readily. 



Salts. The absorption of salts from the stomach has not been investigated 

 thoroughly. According to Brandl, sodium iodide is absorbed very slowly or 

 not at all in dilute solutions. Not until its solutions reach a concentration of 

 3 per cent, or more does its absorption become important. This result, if 

 applicable to all the soluble inorganic salts, would indicate that under ordi- 

 nary conditions they are practically not absorbed in the stomach, since it can- 

 not be supposed that they are normally swallowed in solutions so concentrated 

 as 3 per cent. It was found that the absorption of sodium iodide was very 

 much facilitated by the use of condiments, such as mustard and pepper, or 

 alcohol, which act either by causing a greater congestion of the mucous mem- 

 brane or perhaps by directly stimulating the epithelial cells. 



Sugars and Peptones. Experiments by the newer methods leave no doubt 

 that sugars and peptones can be absorbed from the stomach. In Von Mering's 

 work different forms of sugar dextrose, lactose, saccharose (cane-sugar), maltose, 

 and also dextrin were tested. They were all absorbed, but it was found 

 that absorption was more marked the more concentrated were the solutions. 

 Brandl, however, reports that sugar (dextrose) and peptone were not sensibly 

 absorbed until the concentration had reached 5 per cent. With these sub- 

 stances also the ingestion of condiments or of alcohol increased distinctly the 

 absorptive processes in the stomach. On the whole it would seem that sugars 

 and peptones are absorbed with some difficulty from the stomach. 



Fats. As we have seen, fats undergo no digestive changes in the stomach. 

 The process of emulsification is supposed to be a necessary preliminary step to 

 absorption, and, as this process takes place only after the fats have reached the 

 small intestine, there seems to be no doubt that in the stomach fats escape 

 absorption entirely. 



Absorption in the Small Intestine. The soluble products of digestion 

 sugars and peptones or proteoses, as well as the emulsified fats are mainly 

 absorbed in the small intestine. This we should expect from a mere a priori 

 consideration of the conditions prevailing in this part of the alimentary canal. 

 The partially-digested food sent out from the stomach meets the digestive 

 secretions in the beginning of the small intestine. As we have seen, the diifer- 

 ent enzymes of the pancreatic secretion act powerfully upon the three important 

 classes of food-stuffs, and we have every reason to believe that their digestion 



