PREFACE TO THE GERMAN EDITION. 



THE present volume embraces the greater portion of the studies 

 in immunity published during the past few years by myself and my 

 collaborators. While the publication of these studies in a single 

 volume meets the request of numerous workers in immunity, it is 

 hoped that the collection will at the same time fulfill another purpose, 

 namely, to show clearly that my theory of immunity rests on so 

 broad an experimental basis that it is practically identical with a 

 summary of generalizations derived from an enormous mass of experi- 

 mental data. 1 



When Behring's great discovery of antitoxin opened new paths 

 for the study of immunity it was at once clear that further progress 

 could be attempted in two ways. The first of these, having practical 

 therapeutic results in mind, consists in bending all efforts to the pro- 

 duction of various individual curative sera. The other method con- 

 sists in seeking a deeper insight into the nature of immunity phe- 

 nomena, and discovering the general principles underlying the same, 

 for these in turn will aid practical progress. 



By pursuing the latter method it has been found that the immunity 

 reaction is merely a repetition of certain processes of normal meta- 

 bolism, and that what is apparently a wonderful adaptation to the 

 purpose is nothing more than the ever-recurring manifestation of 

 primeval wisdom inherent in the protoplasm. I have endeavored to 

 establish this experimentally and to show that the bond between 



1 With a view of giving the reader a better idea of the technique ordinarily 

 employed, and thereby to facilitate his introduction to this subject, I have had 

 my colleagues, Dr. Morgenroth and Prof. Neisser, present the result of their ex- 

 tensive technical experiences with hsemolytic and bacteriolytic test-tube experi- 

 ments, in two special chapters. (Chapters XXIX and XXX.) 



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