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 prac- 

 tical considerations, considerations which are constantly coming up and 

 enlisting the attention of the busy practitioner have little by little sup- 

 planted 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 bringing out an English edition of this work- 

 ing 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 ex- 

 tended to it in America, especially by those whose lack of familiarity 

 with the German 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. Other- 

 wise 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 coopera- 

 tion this would have been impossible, my sincere appreciation. 



A. L. GARBAT. 



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