ABSORPTION FROM THE ALIMENTARY CANAL I2Q 



It is supposed also that syntonin at least can itself be spar- 

 ingly absorbed from the alimentary canal, while the phe- 

 nomena of rectal absorption would point to the conclusion 

 that proteid absorption in other shapes is possible. Prac- 

 tically, however, proteoses and peptones may be regarded as 

 the products cf proteid digestion, and their production as 

 the object of proteolysis. 



But, although these substances are absorbed by the blood- 

 vessels, the artificial injection of them into the veins occa- 

 sions untoward effects, or at least their rejection through 

 the organs of excretion. Furthermore, proteoses and pep- 

 tones cannot be detected in the blood during alimentary ab- 

 sorption. It follows, then, that in their passage from the 

 alimentary canal to the blood they undergo some change 

 whereby they lose their identity and are no longer recognis- 

 able as such. It is claimed that they are converted into 

 serum-albumin, and this is probably true. One effect at 

 least of the change is that they are now (in the blood) less 

 diffusible, more complex, and consequently remain more 

 easily a constituent part of that fluid. 



The proteids enter the radicles of the portal vein. 



3. Carbohydrates. The sugar of the blood is dextrose, 

 and if cane sugar be introduced into the -veins it is rejected 

 by the urine without being changed. It may be said that, 

 with a few exceptions, all the carbohydrates are converted 

 into dextrose or dextrose and levulose, before entering the 

 blood. This form of sugar is easily oxidized in the tissues. 

 It is conveyed directly to the liver by the portal vein. 



4. Fats. The digestive end of the fats has been seen to 

 be emulsions and soaps. . They pass into the intestinal lym- 

 phatics, or lacteals. Their absorption is a mechanical pro- 

 cess. They enter and pass through the epithelial cells and 

 basement membrane of the villus. Having thus passed into 

 the stroma of the villus, their entrance into the lacteal is 

 easy ; for undoubtedly lymph spaces in the stroma .are con- 

 nected with the stomata of the central lymph capillary, and 



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