TRANSLATOR'S PREFACE TO THE FIRST EDITION. 



No apology is needed for presenting this translation of Ehrlich's 

 classic studies in immunity, for a thorough knowledge of the master's 

 work is indispensable to all workers in this field. 



Attention is called to the fact that the important work done since 

 the publication of the German edition has been included by the 

 addition of three chapters, two by Ehrlich and Sachs and one, written 

 expressly for this translation, by Prof. Ehrlich. The subject is thus 



brought up to about March, 1906. 



CHARLES BOLDUAN. 



PREFACE TO THE SECOND EDITION. 



THE exhaustion of the first edition of this work affords the 

 translator the welcome opportunity to add, not only Professor 

 Ehrlich's new studies, but also some of his earlier papers which 

 the recent publication of Bordet's Studies on Immunity renders 

 desirable. 



The translator may be pardoned for a feeling of gratification 

 at the cordial reception extended this book both by the medical 

 press and the profession at large. The appreciation shown has 

 made the arduous, and usually thankless, work of translation one 

 of great pleasure. 



An exhaustive index has been added to this, edition and will, 

 it is hoped, greatly enhance its value as a work of reference. 



For kind permission to reproduce articles from their publica- 

 tions, thanks are due to Messrs. August Hirschwald, Georg Thieme, 

 J. F. Lehmann, and Gustav Fischer. 



CHARLES BOLDUAN. 



NEW YORK, February 1, 1010. 



iii 



