52 THE AMINO ACIDS 



it may be possible that the transport of the foreign 

 material through the tissue has carried with it into the 

 blood enzymes already existing in other parts of the 

 organism. Be this as it may, it is very probable that 

 protein retained in the body after parenteral intro- 

 duction or even perhaps after absorption from the 

 intestinal canal without profound disintegration even- 

 tually undergoes decomposition into simpler products 

 after reaching the blood stream. It would appear from 

 this statement, therefore, that the tissues must prefer, 

 to say the least, their pabulum in the form of relatively 

 simple compounds rather than as complex molecules 

 like the native proteins. 



Absorption of Proteases and Peptones 



It was early discovered that peptone left in contact 

 with the living intestinal wall disappeared or at least 

 failed to show its characteristic reactions. From these 

 observations Hofmeister formulated the theory that 

 the peptones were taken up by the leucocytes of the 

 intestine after absorption and by them transformed 

 into protein and distributed to the tissues. This 

 hypothesis failed to meet with the approval of Heiden- 

 hain, who, although believing in the conversion of pep- 

 tone to protein, assigned to the intestine itself the 

 important role of this transformation. In confirmation 

 of the correctness of this idea may be cited the experi- 

 ments of Hofmeister and Neumeister who demon- 

 strated that peptone introduced directly into the blood 



