ABSORPTION FROM THE ALIMENTARY CANAL 1 29 



while the phenomena of rectal absorption would point to the 

 conclusion that proteid absorption in other shapes is possible. 

 Practically, however, proteoses and peptones may be regarded 

 as the products of 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 occasions 

 untoward effects, or at least their rejection through the organs of 

 excretion. Furthermore, proteoses and peptones cannot be 

 detected in the blood during alimentary absorption. 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 recognizable as such. It is claimed that they are con- 

 verted 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 lymphatics, 

 or lacteals. Their absorption is a mechanical process. They 

 enter and pass through the epithelial cells and basement mem- 

 brane 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 connected with the stomata of 

 the central lymph capillary, and there is a more or less constant 

 flow of lymph through these spaces toward the lacteal. The 



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