ALIMENTARY TRACT AS AN ABSORPTIVE SYSTEM. 295 



Some fat seems, however, to be carried from the intestine 

 by way of the blood-vessels, and when the thoracic duct has 

 been ligated the amount carried in this way is much increased. 

 MUNK and FRIEDENTHAL found that the fat in the blood 

 may under circumstances rise to six times the normal amount 

 when the thoracic duct is occluded. A thick layer of fat 

 forms upon the blood collected from a vein even though 

 the entire amount of fat absorbed from the intestine may 

 be less than half that absorbed when the thoracic duct is 

 open. 



The total amount of fat absorbed is dependent upon the 

 kind of fat fed an animal. We know from MUNK and 

 MULLER'S observations that fats having a low melting-point 

 are more perfectly absorbed than those having a higher one. 

 97.7 percent of the olive-oil fed an animal is absorbed. 

 97.5 percent of fats melting between 25 and 34 C. (goose- 

 and pork-fat), 90 to 92. 5 percent of fats melting between 49 

 and 51 C. (mutton- tallow), and only 89.4 percent of a mix- 

 ture of stearin and almond-oil melting at 55 C. are absorbed. 

 Of pure stearin, which does not melt until 60 C. is reached, 

 only 9 to 14 percent is absorbed. 1 When a mixture of fats 

 having different melting-points is fed, those having the lower 

 melting-points are absorbed more completely than those 

 having the higher. Fat is also more perfectly absorbed 

 when it is free in the form of butter or lard than when it is 

 enclosed in cells, as in fat meat or bacon. Under these cir- 

 cumstances the digestive juices must first dissolve the walls 

 of the cells. 



The velocity with which different fats are absorbed is also 

 determined in large part by their melting-points. MUNK 

 and ROSENSTEIN found that the lymph obtained from their 

 patient with a lymphatic fistula became milky in appear- 

 ance two hours after feeding a mixture of olive-oil containing 

 6 percent oleic acid, and in the fifth hour after feeding con- 



1 MUNK: Ergebnisse d. Physiol., 1902, 1, lie Abth., p. 323. 



