PREFACE. 



THE substance Protein, which constitutes the most important 

 part of the material basis of all animal and vegetable life, has 

 naturally attracted the attention and energy of numerous 

 investigators throughout the past century. Progress in the 

 study of this subject, on account of its difficulty, has been 

 exceedingly slow, and it is only of recent years that the 

 discovery of new methods by Emil Fischer has enabled us 

 to increase our knowledge to its present extent. By these 

 methods we have been able to advance from the conception 

 of " albumin " to its actual separation into numerous units, 

 and also to determine their arrangement in the molecule. On 

 this account a monograph embodying the results of the most 

 recent investigations, together with their connections with the 

 work of the other and earlier investigators, needs no excuse 

 for its appearance, as the subject is now being studied in 

 every direction. 



On account of the mass of material connected with the 

 subject, this monograph has exceeded the proposed limit in 

 length, and consequently it has become necessary to divide 

 it into two parts : 



f The Chemical Composition of the Protein Molecule. 

 'IThe Chemical Constitution of its Units. 



II. The Synthesis of the Proteins. 



R. H. A. P. 



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