CHAPTER VIII 



THE AMINO ACIDS AND SIMPLER NITRO- 

 GENOUS COMPOUNDS AS FOODSTUFFS 



VALUE OP AMINO ACIDS AS FOODSTUFFS 



The dictum of Liebig that the animal organism is 

 endowed with very limited capacities for processes of 

 synthesis was accepted for a great many years with- 

 out serious question. A partial reason for this assump- 

 tion is to be found in the great difficulties to be over- 

 come in putting the question to experimental proof. 

 The discovery of erepsin by Cohnheim with the con- 

 sequent readjustment of ideas relative to the extent 

 and character of digestion processes and the form of 

 products absorbed casts doubt upon the inability of the 

 animal body to synthesize. It was reasonable to 

 assume that the disintegration of the protein molecule 

 to the stage of amino acids is with a purposeful object 

 and that the absorption of such relatively small com- 

 pounds as amino acids predicates the probability that 

 synthesis must occur if the organism is obliged to 

 reconstruct new protoplasm to replace that worn away 

 through the many metabolic activities. 



About a dozen years ago the first attempt to deter- 

 mine the possibility of positive protein synthesis was 



