PREFACE TO SECOND EDITION. 



THREE years have elapsed since the appearance of the first 

 edition of this monograph. During these years there has been 

 continuous work on the chemistry of the proteins. What is 

 the result ? No startling discovery has been made, but we have 

 a better and deeper view of what is known. Emil Fischer, 

 our master, has entrusted his ester method to his former pupil, 

 Abderhalden, and has himself studied the more difficult question 

 of the synthesis of the proteins (the polypeptides) and the 

 peculiar optical properties of the amino acids. These properties, 

 he thinks, give us an insight into chemical substitution in 

 general. 



Abderhalden has analysed, it would seem, as many proteins 

 as possible, and has also devoted much labour to the polypeptides 

 and the action of enzymes ; in fact, the amount of work which 

 he has accomplished is extraordinary. His analyses of the 

 proteins are of great physiological interest, and are for the 

 purpose of ascertaining whether proteins of similar origin are 

 identical and whether they differ at different times of life. His 

 chemical work on the polypeptides is intimately connected with 

 the synthesis of the proteins and must lead later to a knowledge 

 of those ill-defined substances, the proteoses and peptones. His 

 physiological work on these compounds is concerned with the 

 enzyme action of various tissues and the problem of nutrition. 



Osborne is giving us as complete an analysis of his vegetable 

 proteins as he has given us of their preparation and properties. 

 From his careful and critical study of the data obtained by the 

 ester method he comes to the conclusion that only about 5-15 

 per cent, of some of these proteins remains to be accounted for. 



