62 THE AMINO ACIDS 



blood under ordinary conditions. If proteoses were 

 present normally in the blood it is probable that this 

 enzyme would also be a normal constituent of the 

 blood. 



THE SYNTHESIS, OR REGENERATION OF PROTEIN, BY 

 THE INTESTINE 



If it is accepted that protein is not absorbed in the 

 form of proteoses or peptones the query naturally 

 arises, In what form is it absorbed ? An answer to this 

 question must necessarily determine also the place of 

 protein regeneration so long as the conception of nutri- 

 tion obtains that metabolic changes in the organism 

 demand the formation of new material to replace that 

 broken down. If one maintains that protein gets into 

 the blood stream in the form of a molecule larger than 

 the amino acid, proteose or peptone molecule, it is self- 

 evident that the intestine must be regarded as capable 

 of synthesizing amino acids to protein. On the other 

 hand if amino acids are regularly present in the sys- 

 temic circulation, the place of protein regeneration 

 must be relegated to the cellular elements of the dif- 

 ferent tissues. 



Abderhalden. In the past various theories have been 

 maintained. In view of the failure to find amino acids 

 in the blood, Abderhalden put forward the view that 

 the intestinal wall possessed the power during the act 

 of absorption to synthesize the amino acids to proteins, 

 probably serum proteins, to meet the needs of the 



