NOTE BY THE AMERICAN EDITOR. 



The study of " Immunity," once of merely theoretical interest and 

 purely scientific importance, is to-day no longer such. A realm of practical 

 considerations, considerations which are constantly coming up and enlisting 

 the attention of the busy practitioner have little by little supplanted those 

 phenomena at one time vaguely understood and mostly taken for granted. 

 Gradually have the uncertainties so long dominating and obscuring an 

 intelligent comprehension of the subject been cleared away; mistakes 

 explained; and hypotheses re-established as proven facts. The methods 

 employed for the necessary investigations have naturally improved and 

 increased with such extreme rapidity that a severe task presents itself to one 

 who desires to separate the more from the less valuable ones. It was 

 therefore with extreme satisfaction that I greeted the opportunity of bring- 

 ing out an English edition of this working hand-book on the various, but 

 most essential methods used in the applications of "Immunity." The 

 author of this volume has, by his exhaustive research and extensive practical 

 experience as a teacher, treated his field with such fulness and preciseness 

 of detail that it is of value not only to the laboratory student, but also to the 

 clinician. 



Its already favorable reception in Germany will, it is hoped, be extended 

 to it in America, especially by those whose lack of familiarity with the Ger- 

 man language has kept this work beyond their reach. 



The chapter on vaccines has been slightly revised and elaborated to 

 conform more closely with the most recently advocated methods of Sir A. E. 

 Wright, to whom the editor is indebted for his experience. Otherwise 

 there has been no need to alter the original text, with the exception that 

 here and there some features which may be of special interest to the English 

 reading public, have been inserted. 



I wish in the present connection to express my deep thanks to my teacher 

 Dr. Citron for offering me the privilege of this undertaking, and to the 

 publishers, Messrs. Blakiston & Co., without whose hearty cooperation 

 this would have been impossible, my sincere appreciation. 



A. L. GARBAT. 



IX 



