ABSORPTION OF CARBOHYDRATES 303 



only favor the secretion of the digestive fluids, they further the absorption 

 of the digested foodstuffs. Whether this action is due to a stimulating influ- 

 ence of these substances on the absorbing elements of the mucous membrane, 

 or to vasodilatation caused by them, must for the present be regarded as 

 undecided, although in the opinion of the author the former supposition is 

 the more probable. 



Comparison of absorption in the stomach with that in the intestine brings 

 to light this fact, which is important for our understanding of the gastric 

 functions : that the stomach tolerates much more highly concentrated solutions 

 of .the foodstuffs than does the intestine. The stomach acts as a reservoir 

 for the ingested food, in order that the gruelly contents, properly diluted, 

 may be discharged into the intestine gradually. But the latter plays the 

 chief part in absorption. 



In this connection we may mention also the experiments of Ogata in which 

 the absorption of proteid was investigated after meat feeding, once when the 

 meat was fed by the mouth, and another time when it was brought directly into 

 the duodenum through a stomach fistula. The nitrogen output in the urine was 

 taken as an expression of the absorption. It was shown that after direct intro- 

 duction of meat into the duodenum the N-output rose much more rapidly and 

 exhibited greater variations than when the meat had first to undergo digestion 

 in the stomach. The absorption of proteid therefore takes place much more 

 rapidly when it is placed directly in the intestine, than when it must pass through 

 the stomach. We have then to add to what we have already learned about the 

 importance of the stomach, that in virtue of its function as a storehouse, the 

 absorption of ingested proteid is distributed more uniformly than it would be 



otherwise. 



t 



2. ABSORPTION OF CARBOHYDRATES 



We have no exact information as to how the carbohydrates are removed 

 from the intestinal cavity (cf. page 302). 



That they are carried off chiefly by the blood vessels, and not by the 

 lymphatics, appears to be shown by a number of observations. For example, 

 after a meal rich in carbohydrates, the amount of sugar in the chyle is no 

 greater than after one poor in carbohydrates, while the portal blood shows a 

 considerable increase in the former case. On the basis of these results and of 

 the location of the blood vessels in the villi, Heidenhain has made the general 

 statement that all substances soluble in water pass for the most part into the 

 roots of the portal vein. Only when the quantity of fluid is very great does 

 any sugar enter the lacteals. 



This conclusion is confirmed in its entirety by observations on a young 

 girl who had a fistula in the receptaculum chyli, from which all the chyle 

 flowed out of the body. In this patient it was found that not more than 

 five-tenths per cent of the absorbed sugar was taken up by the lymphatics 

 (I. Munk and Rosenstein). 



