PAT Ml TABOMSM 691 



if vve mix 1 » i I * * with fresh pancreatic juice, which by itself only slowly 

 digests Eat, we shall find thai the bile very materially increases the lipo- 

 lytic activity of the pancreatic juice, li has been found that the salts 

 of cholalic acid, the so-called bile salts, are th< stituents of bile 



thai are responsible for this activation of lipase, this fad having bi 

 demonstrated with bile salts prepared in such a way thai then ■ no 

 possible chance of any other biliary constituenl being present as an 

 impurity. It is importanl to remember, however, that lipase itself be- 

 comes slowly activated on standing, which explains why it should be 



that bile added to pancreatic juice thai has si 1 for some time, ha 



less evident activating influence than bile added to fresh juice. It is 

 probable that the activating influence of bile salts is due to some physico- 

 chemical change induced in the digestion mixture. 



< >ne may ask how it happens that, when bile and pancreatic juic 

 both absenl from the intestine, the fat which appeals in the feces is not 

 neutral fal bu1 fatty acid. The reason is that the neutral fat that has 

 escaped digestion in the small intestine becomes acted on by the intestinal 

 bacteria, particularly in the large intestine. Under these conditio 

 however, the fatty acid that is split off is tiol absorbed, because the 

 epithelium of the lower parts on the intestinal tract can not perform this 

 function. 



Besides assisting the action of lipase, bile facilitates fat digestion in 

 other ways. Thus, by its containing alkali and mucin-like substai 

 it assists in the emulsification of fat. Although emulsification is no 

 sential part of fa1 absorption, yet it greatly facilitates the process by 

 breaking up the fa1 into small globules on which the lipase can act 

 much more efficiently. The alkali also combines with the fatty acids, 

 as they are liberated by the digestive process, to form water-soluble 

 s.»aps. which are readily absorbed by the epithelial cells. The bile salts 

 further assist in the solution of the fatty acids, and they lower the sur- 

 face tension ><\' fluids in which they are contained and so bring the fat 

 and lipase into closer itact. 



ABSORPTION OF FATS 



After its digestion fat lies in contacl with the intestinal border of the 

 epithelial cells as fatty acid and glycerine. The fatty arid is combi 



either wilh alkali to form a water soluhle soap, or with bill - to 



form a compound, which is also soluble. The glycerine and the dissol 



fatty acids are separately absorbed into the epithelial cells of the in- 

 testine, in the protoplasm of which after the fatly acid has b< 

 \'\e^ from the alkali or bile Ball they 1 ome united or resynt 



to form neutral fat. which graduallv finds iis way by the central lac- 



