PREFACE TO THE GERMAN EDITION. 



This book is to serve a purely practical purpose. The methods of 

 serum diagnosis, on account of their growing clinical significance, are 

 constantly stimulating greater interest in all branches of medical science. 

 While giving instruction in this subject, I realized that it would be of great 

 help to both the medical student and physician if they possessed a short 

 text-book which would review in a purely critical form the various methods 

 of immunity diagnosis, especially those relating to tuberculosis and syphilis. 



The two systems of Kolle and Wassermann, and R. Kraus and Levaditi 

 are doubtless the standards on the subject in German medical literature. 

 On account of their size and price, however, these volumes come to be 

 sought only by the specialist. 



It was therefore my aim in this book to so present the subject of immu- 

 nity that the general medical man, who is even slightly acquainted with 

 laboratory work, can learn the details of the various reactions and their 

 significance. In selecting the different methods, I have taken up those 

 which are used in the clinic for diagnostic, therapeutic, or prophylactic 

 purposes. In addition there are herein included certain fundamental 

 considerations of questions on immunity which for the present are only of 

 theoretical interest, but which owing to the rapid development of the subject, 

 may soon become of practical importance. 



I have endeavored especially to place before the reader a critical review 

 of the results of the various methods. In the description of technical details, 

 the original articles of the author have been selected; modifications having 

 been considered, only provided they exhibit distinct advantages over the 

 original method. 



I here wish to express my thanks to my teacher Prof. Wassermann, 

 under whose guidance and stimulus I gained my laboratory experience; also 

 to my chief Prof. Kraus whose clinical genius proved to me the practical 

 importance that this subject of immunity commands. 



To the publishers as well, whose kind cooperation in all my plans as 

 regards publication and illustration, greatly simplified my work, I extend 

 my heartiest appreciation. 



JULIUS CITRON. 



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