viii PREFACE 



The chapter on Colloids was written especially for the book by 

 Prof. Stewart W. Young, of Stanford University. Since so many 

 analogies between serum reactions and those taking place between 

 colloidal substances generally have been observed, it has seemed best 

 to devote this chapter entirely to the elucidation of the principles 

 governing colloidal reactions, so that its contents may be utilized 

 as explanatory of the many allusions made to colloids in the rest of 

 the text. 



All available sources of information have been freely used. In 

 the large majority of cases we have had access to the original papers 

 and monographs. However, we acknowledge much aid from care- 

 ful reading of the admirable summaries, written by acknowledged 

 authorities, in the works edited by Kolle and Wassermann, and 

 by Kraus and Levaditi. Similar acknowledgment is made to 

 equally important sources in Weichhardt's Jahresbericht, the Bulle- 

 tins of the Pasteur Institute, and in such text-books as those of Paul 

 Theo. Miiller, Emery, Adami, Gideon Wells, Marx, Dieudonne, and 

 others. It is needless to acknowledge the use of such classics as that 

 of Metchnikoff or of the many critical writings of Bordet and of 

 Ehrlich masters who have helped to shape the thoughts of all men 

 working in this field. 



The writer takes pleasure in acknowledging many helpful sugges- 

 tions from his associates, Drs. Hopkins and Ottenberg, and much 

 aid, in the verification of references, from Mr. Walter Bliss, Fellow 

 in the Department of Bacteriology. 



