THE SYNTHESIS OF THE PROTEINS 57 



d-Alanyl-l-serine anhydride (?) in silk-fibroin. 



Glycyl-1-leucine anhydride in elastin. 



d-Alanyl-1-leucine anhydride in elastin. 



d-Alanyl-1-leucine in elastin. 



d-Alanyl-proline anhydride in elastin. 



Glycyl-valine anhydride in elastin. 



Leucinimide in caseinogen. 



1-Phenylalanyl-d-alanine anhydride in caseinogen. 



1-Leucyl-d-valine anhydride in caseinogen. 



1-Leucyl-d-glutamic acid in gliadin. 



Dipeptide (proline + phenylalanine) in gliadin. 



Dipeptide (proline + glycine) in gelatin. 



Tetrapeptide (2 glycine + i alanine + I tyrosine) in silk-fibroin. 



It is only by the knowledge of the properties of the synthetical com- 

 pounds that Fischer has been able to invent methods for isolating 

 them from the mixtures which result by the hydrolysis of the proteins 

 and to identify these compounds. The extension of the study of the 

 higher polypeptides, more especially of the mixed polypeptides, will 

 lead without doubt to the isolation of greater complexes from the pro- 

 ducts of partial hydrolysis of the proteins, such as the separation of the 

 proteoses and peptones, which from the results so far obtained appear to 

 be more simple than was previously supposed, if salting out by am- 

 monium sulphate of polypeptides containing four and six units, of 

 which tyrosine is one, be taken as a typical example. 



