4 THE CHEMICAL CONSTITUTION OF THE PROTEINS 



This long list is sufficient evidence of the complexity of the protein 

 molecule ; and, as yet, it seems to be still incomplete, for several 

 other products have been described. They are not here included, 

 since their presence in the molecule still requires confirmation. 



These amino acids are known as the foundation-stones or units 

 of the protein molecule. Before the constitution of a protein can be 

 determined, it is essential that both the amount of any of these units 

 and their chemical composition be known with certainty. The com- 

 bination together of these amino acids has then to be determined. 

 Consequently the study of the chemical constitution of the protein 

 molecule must be divided into three main sections : 



I. The Chemical Composition of the Protein Molecule. 

 II. The Chemical Constitution of its Units. 

 III. The Synthesis of the Proteins. 



