292 PHYSIOLOGY OF ALIMENTATION 



entirely possible that the appearance of butyric and other 

 fatty acids in diseases of the stomach is attributable in part 

 at least to the activity of the lipase normally present here. 



But even if under normal circumstances little or no diges- 

 tion of fats occurs in the stomach, active digestion of this 

 food begins as soon as the gastric contents are neutralized 

 in the duodenum and have poured out upon them the pan- 

 creatic juice and the bile. The function of the latter we will 

 ignore for the present. Let us ask first of all how much of 

 the fat will be split under the influence of the pancreatic juice 

 as the mixture of the two moves down the intestine. It is 

 clear that if the intestine were replaced by a glass tube, by 

 no means all of the fat would be split, but only a portion of 

 it, or to put it more technically, fat would undergo cleavage 

 until an equilibrium had been established between this sub- 

 stance on the one hand and fatty acid and alcohol on the 

 other. In other words, we recognize here again an equa- 

 tion similar to the one given on page 107: 



Fat + Fatty acid + Alcohol. 



In the animal body conditions are somewhat different than 

 in a glass tube. While in a glass tube the products of the 

 cleavage accumulate, this does not occur in the intestine, for 

 here the fatty acid and alcohol diffuse into the intestinal 

 mucosa as soon as formed. Evidently, therefore, the state 

 of equilibrium outlined above never comes to pass in the in- 

 testine, and the cleavage of the fat continues until all has 

 been split, in other words, all has been absorbed. This really 

 occurs, for under normal circumstances no fat, or practically 

 none, is found in the faeces. 



Let us see now what becomes of the fatty acid and alcohol 

 which have diffused into the lining cells of the intestine. At 

 the beginning of a meal these cells contain no fat, but they 

 do contain lipase. As the fatty acid and alcohol diffuse 

 into them evidently the reverse of what occurred in the lumen 



