PREFACE 



The study reported in the following pages was undertaken with the 

 purpose of sifting out the voluminous data which have accumulated 

 on the subject of diphtheroid organisms. 



The greatest impetus given to such an investigation has resulted, in 

 recent years, from the attempts of numerous workers to associate 

 Hodgkin's disease with a certain organism belonging to the diphtheroid 

 group. In a short time the literature on the subject assumed great 

 proportions. 



A survey of the field revealed immediately the fact that the group 

 as a whole has been indiscriminately used as a cover for any organ- 

 ism which bore some sort of morphological resemblance, real or 

 apparent, to the diphtheria type. The material presented in this study 

 is by no means exhaustive since a great many methods will have to be 

 tried before a clear-cut answer is to be given to the question as tc 

 what a true diphtheroid is and where it belongs in the comprehensive 

 group of which these bacteria are members. 



Of great moment is the idea of mutation introduced by Rosenow 

 and his school. This problem is fraught with such difficulties not 

 amenable to satisfactory control, that a reply to the findings of these 

 workers will have to be deferred. At present the outlook for a deci- 

 sive answer to this question seems to be found in at least one method 

 whereby we can control the constitution of our nutrient media by 

 means of H-ion concentration, and also in a phase of serological 

 technic which has not been studied heretofore. In the following 

 pages an effort will be made to attack the problem from these angles. 



I wish to thank Professor Hans Zinsser for much valuable advice 

 and suggestions and Dr. R. E. Buchanan of the Iowa State College 

 for his criticisms on nomenclature. F. E. 



Bacteriological Laboratory. Columbia University. 

 Xew York City, January," 1918. 



93754 

 08C150 



