vi PREFACE 



first issued shall deal with the pure chemistry of physiological 

 products and with certain general aspects of the subject. 

 Subsequent monographs will be devoted to such questions 

 as the chemistry of special tissues and particular aspects of 

 metabolism. So the series, if continued, will proceed from 

 physiological chemistry to what may be now more properly 

 termed chemical physiology. This will depend upon the 

 success which the first series achieves, and upon the divisions 

 of the subject which may be of interest at the time. 



R. H. A. P. 

 F. G. H. 



PREFACE. 



MORE work has perhaps been done upon the digestion and 

 assimilation of proteins than upon any of the other branches 

 of metabolism. A monograph on Protein Metabolism would 

 therefore be the first of a series, and it is to be hoped that 

 volumes dealing with the other particular aspects of metabolism 

 will soon be forthcoming which will furnish us with a complete 

 survey of the present position of this portion of chemical 

 physiology. 



The present monograph does not pretend to cover the 

 whole literature of protein metabolism ; it consists rather of 

 the discussion of the more important results published during 

 the last decade and their bearing upon the work of the earlier 

 investigators. The majority of recent writers have devoted 

 their attention to the study of the metabolism of particular 

 constituents of the protein molecule ; an attempt has been 

 made in this monograph to avoid laying undue stress on the 

 fate of these since it is felt that a truer picture of the real 

 course of protein metabolism can thus be drawn. 



It is a pleasant duty to express my indebtedness to Miss 

 G. D. Bostock, M.B., for her valuable assistance in the revision 

 both of the manuscript and the proofs. 



E. P. C. 



