INTESTINAL DIGESTION 215 



The best known case of a modifying influence exerted 

 by the lining cells of the intestine is their action upon 

 the products of fat digestion. Glycerin and fatty 

 acids or soaps disappear from the canal but the cells 

 work a change which is the reverse of digestion and that 

 which enters the lymph, and later the blood, is neutral 

 fat in place of the compounds formed by its cleavage. 



The history of the foods after absorption can best be 

 followed when we shall have given some attention to the 

 blood in which they are represented and the main facts 

 of the circulation. It may be well to anticipate one 

 point. Material arriving within the villi must at first 

 be in the indefinite lymph spaces of the tissue. From 

 these crevices it may enter the capillaries as most of it 

 does or it may leave the vicinity by pursuing channels 

 of another order, the lymphatics. This latter course 

 is taken by most of the fat. 



