AND ABSORPTION 47 



that half of these peptones were further acted on by 

 the trypsin of the pancreatic juice and broken down 

 into two aminoacids called leucin and ty rosin, whose 

 fate was in doubt. The modern view is very different. 

 The researches of Fischer, Kossel, and others have 

 thrown a flood of light on the composition of the 

 protein molecules. We now know that protein con- 

 sists of a complicated chain of the bodies called 

 aminoacids (that is, organic acids of which a hydrogen 

 has been replaced by the NH 2 group). These may 

 be classified as monoamines (as leucin, glycin), 

 diamines (as arginin, lysin), and aromatic amines 

 (as tyrosin, tryptophan). By the trypsin of the 

 pancreatic juice proteins are resolved into their 

 various components, and consequently a mixture, in 

 differing proportions, of these aminoacids is found 

 in the intestine. Peptone is only a stage on the way 

 to this final dissolution, and is not absorbed at all. 

 It would appear, however, that some of it is never 

 broken down to aminoacids. 



The ferment which brings about the full dissolution 

 is the trypsin of the pancreatic juice, which converts 

 albumin into aminoacids. Pepsin can carry the 

 action only as far as peptones, unless its action is 

 unnaturaUy prolonged, and consequently there is no 

 absorption of protein material in the stomach. There 

 is a ferment in both the pancreatic and intestinal 

 juices called erepsin, which completes the action of 

 the gastric juice by converting peptones into amino- 

 acids. 



Neither albumin nor peptone can be absorbed by 

 the intestine. They must first be converted into 



