ABSORPTION OF SPECIAL MATERIALS. 209 



cumstances of which we are ignorant cooperate in bringing about 

 the results which seem to us so simple. 



It is not the same, however, with the fatty food stuffs. A small 

 quantity of these may no doubt be split up into soluble glycerin 

 and fatty acids, which are at once changed into soluble soaps, 

 and in this condition are capable of simple osmotic transmission 

 into the blood vessels or lacteals. However, the greater portion 

 of the fat enters the lacteals as such in a condition of a fine 

 emulsion, i.e., composed of solid particles. This process is difficult 

 to reconcile with our physical experiences ; for, however finely 

 divided it may be, fat emulsified does not pass through an animal 

 membrane more freely than ordinary fluid fat. The fat emulsion 

 is chiefly taken up by the villi of the small intestines, as in the 

 stomach it exists only in large fluid masses or globules, and the 

 amount of fat found in the large intestine is small, unless used as 

 food in great excess. This can also be seen in examining the 

 absorbent vessels after a fatty meal, when those which carry mate- 

 rials from the stomach and large intestine are clear and trans- 

 parent, while those coming from the small intestines are filled 

 with the white milky fluid which gives them their special name 

 of lacteals. There is a limit to the absorbent capacity of the 

 intestine for fatty matters, for when a great excess of fat is eaten 

 it appears with the excrement, sometimes giving rise to adipose 

 diarrhoea, thus showing that the amount has exceeded this limit. 



The important question remains, How does the fat emulsion 

 make its way through the intestinal mucous membrane? That 

 it really does so there can be no shadow of doubt ; for it disap- 

 pears from the intestinal cavity, and can be detected in the chyle 

 with the aid of the microscope more easily than any other of the 

 intestinal contents that are absorbed. 



It has been shown that while a membrane moistened with 

 water acts as a complete barrier to a fat emulsion, and only after 

 prolonged exposure under high pressure allows traces of fats to 

 pass, the same membrane when saturated with bile will without 

 pressure permit the passage of a considerable amount of oil. It 

 has therefore been suggested that the epithelial cells of the mu- 

 cous membrane are more or less moistened with bile, and the par- 

 18 



