viii PREFACE TO THE GERMAN EDITION. 



stances, whether or not they are made up of two parts possessing 

 different functions; (2) the union of specific amboceptors with the 

 complements; (3) the plurality of complements. I am convinced 

 that the near future will furnish so many additional arguments for 

 the correctness of my views that all of these questions, as well as 

 numerous others, will be decided in my favor. And the decision, I 

 believe, will not be merely in favor of my views in general, but will 

 extend even to the details. 



In a way, therefore, my position is like that of a chess-player who. 

 even though his game is won, is forced by the obstinacy of his opponent 

 to carry it on move by move until the final "mate.'' 



For the means to carry on these experiments, I am indebted first 

 of all to the intelligent support which my scientific aims have received 

 at the hands of my superiors, the Prussian Ministry of Education. 

 I am especially grateful to the ministerial director, Dr. Althoff, who 

 aided me in every way possible, and exerted himself to lighten my 

 scientific labors. I may say that I was first spurred on to the im- 

 munity studies contained in "Die Werthbemessung des Diphtherie- 

 heilserums/' and which L have led to the formulation of the side-chain 

 theory, by the remarks addressed to me by Dr. Althoff when the 

 Institute was founded. It was he who begged that my first problem 

 be an exhaustive study whereby the difficulties which had arisen 

 in titrating and standardizing diphtheria antitoxin might be overcome. 

 To this kind and able friend I have therefore dedicated this volume as 

 a token of my gratitude and esteem. 



PAUL EHKLICH. 

 FRANKFURT A. M., February 1904. 



