Absorption. 189 



mesentery, passing through the mesenteric glands, where 

 certain additions are made to the stream in the shape of 

 cells, and the whole is poured into the general circulation. 

 It is a well-known fact in human surgery that fat embolism 

 is not an infrequent accompaniment of certain injuries, 

 fractures, etc. The fat of the body is taken into the blood- 

 vessels and blocks the capillaries, especially those of the 

 lungs. Fat embolism in lacteal absorption is prevented by 

 the fine emulsion produced in the intestines, for no emul- 

 sion can occur in any other part of the body, in spite of 

 the alkaline nature of the blood, owing to the fact that the 

 body fat is neutral, and neutral fats can only be emulsified 

 by free alkalies, and not by their carbonates (Bunge). 



Absorption of Sugar. — The sugar formed in the bowel is 

 said to reach the general circulation via the portal vein 

 and liver. We have reason, however, to believe that some 

 portion of it may find its way into the lacteals ; but the 

 bulk of it must of necessity be absorbed by the blood- 

 vessels, and pass by the portal vein into the liver. We 

 have seen, in speaking of the liver, how important is the 

 function of this gland in regulating the supply of sugar 

 to the system, and the method it possesses of storing 

 it up. 



The Absorption of Proteids is said to be exclusively by 

 the bloodvessels, from whence they are conveyed to the liver 

 by the portal vein ; but here a curious point arises : little or 

 no peptone can be found in the portal vein or even in the 

 general mass of blood. If peptone be experimentally in- 

 jected into the blood it is rapidly excreted by the kidneys, 

 so that it is evident the pe ptone taken up from the intestinal 

 canal must undergo some important and rapid change before 

 entering the portal system. Hofmeister's work in this 

 direction has shown that the peptone is converted once 

 more into proteid, and that this change occurs in the 

 intestinal mucous membrane, so that peptones enter the 

 system in the form of proteid. The process is analogous 

 to that we have previously dealt with in speaking of 

 glycogen, where the starch enters the blood as sugar, but is 



