THE ABSORPTION OF PROTEINS 55 



or lymph could not be detected the theory of their 

 synthesis to protein coincident with their absorption 

 was promulgated. To Folin we owe the first indirect 

 proof of the absorption of amino acids from the intes- 

 tines. By a set of delicate methods adapted for the 

 partition of different forms of nitrogen he has suc- 

 ceeded in demonstrating an appreciable increase in the 

 "non-protein" portion of the blood, after introduction 

 of amino acids into a loop of intestine. Although the 

 amino acids themselves were not isolated the non- 

 protein fraction of the blood was so significant as to 

 leave no doubt of amino acid absorption. Van Slyke 

 and Meyer strongly fortified the view by the use of a 

 different method. The quantity of amino acids in the 

 circulation at one time is so small as to have escaped 

 detection by methods previously in use. It remained 

 for Abderhalden to demonstrate the presence of amino 

 acids in the blood under normal circumstances and 

 actually to isolate them. This he accomplished by 

 employing fifty liter lots of blood. From such large 

 volumes he succeeded in separating and identifying 

 proline, leucine, valine, aspartic acid, glutamic acid, 

 alanine, glycocoll, arginine, histidine, and lysine. In 

 no instance did he obtain more than 0.5 gram of any 

 one substance. The absorption of amino acids as such 

 is, therefore, an assured fact. 



ABSORPTION FROM THE LARGE INTESTINE 



Recalling to mind the heterogenous mixture of sub- 

 stances that may reach the large intestine one at once 



