40 THE .THEORY OF IONS 



relatively simple molecules, which can be split by 

 hydrolysis, resulting in the production of amino-acids. 

 During recent years Fischer, Siegfried and others 

 have been able to unite synthetically the amino- 

 acids into longer or shorter chains, that is of trans- 

 forming them or constructing amide-like anhydrides 

 with the formation of peptides and polypeptides 

 having the same properties and reactions as the 

 natural peptones.* The synthesis of peptones and 

 albumoses in the laboratory may therefore be looked 

 for, and this will probably throw light upon the 

 mode of proteid construction in the living organism. 

 The whole series of proteins appears to consist of 

 amino-acids, but these are grouped into chains 

 which vary both quantitatively and qualitatively. 

 The importance of the amino-acids is very great ; 

 some of the acids being present in all and others 

 in most proteins. 



If little is known of the formation of protein bodies 

 in living organisms there is evidence to show that 

 the assimilation of nitrates, sulphates and phos- 

 phates containing the necessary elements for protein 

 formation can only take place in plants in the 

 presence of light ; and that the first stage in protein- 

 formation by plants is the production of the com- 

 paratively simple amino-acids, leucin and asparagin. 

 The next step is the formation of the protein mole- 

 cule, in the construction of which the amino-acids 

 occupy such an important place. It is conceivable 

 that, besides the amide-like chains, other modes of 

 union of the elements of the protein-molecule occur, 



* Prof. Barker's address at British Medical Association meet- 

 ing, Toronto, 1906. 



