PREFACE. 



IN the following pages an attempt is made to review the 

 chief properties of the proteins, with the object of determining 

 how far they are of value for devising methods of isolation 

 and identification of individual members of the class. 



In view of the limited scope of the essay, certain aspects 

 of the subject have been purposely treated in a somewhat 

 empirical manner. No attempt, for example, has been made 

 to explain such processes as " salting out " or heat coagula- 

 tion ; subjects such as these may be more fittingly discussed 

 in a monograph dealing with the general chemical physics of 

 colloids. 



In spite of the great advances recently made in the know- 

 ledge of the physics and of the constitution of proteins, the 

 methods available for their isolation and identification are 

 still very unsatisfactory in character. This fact may serve 

 as an apology for the tentative treatment of certain sections 

 of this book ; the importance of the subject, however, both 

 to chemists and physiologists, may warrant the issue of 

 this monograph, dealing, as it does, with a part of protein 

 chemistry still in a rudimentary state of development. 



S. B. S. 



vii 



