26 THE AMINO ACIDS 



ment. For this purpose he employed a mild hydrolysis 

 which only partially broke up the large aggregates 

 formed and he succeeded in isolating from the pro- 

 ducts peptides identical with those made synthetically. 

 Since then other investigators have separated similar 

 compounds. One of the best proofs that proteins are 

 built up of these amino acid complexes is that, also 

 furnished by Fischer, of the action of various enzymes 

 upon the synthetical products. It was found that with 

 the exception of pepsin the various enzymes of the 

 body are quite capable of hydrolyzing the polypeptides 

 into amino acids. 



Although these investigations prove beyond doubt 

 that amino acids are linked together in protein in the 

 form of polypeptides, there are possibilities of other 

 forms of combination which will be revealed only by 

 future research. For the present we are justified in 

 accepting the hypothesis of the protein molecule as a 

 huge complex polypeptide. 



REFERENCES TO LITERATURE 



Abderhalden: Text Book of Physiological Chemistry. 1914. 



Abderhalden and Weil: Zeitschrift fur physiologische chemie. 

 1913, 88, p. 272. [Norleucine.] 



Hammarsten: Text Book of Physiological Chemistry. 1914. 



Kossel: The Chemical Composition of the Cell. The Harvey 

 Lectures. 1911-1912. 



