542 HILDA HEMPL HELLER 



relationships, can later be erected. We are not yet ready to 

 declare where the limits of variation for the organisms of our 

 group may lie. But I am decidedly of the opinion that in general 

 the old conception of species as accepted for the anaerobic group 

 must in future be taken as the conception of genera, and that 

 we must be more exact in our examination and analysis of these 

 organisms. To do otherwise, and classify as the same species 

 organisms which regularly and consistently show marked quanti- 

 tative differences in their behavior, would be to distinguish our 

 system of classification sharply from those of the botanists and 

 zoologists and to set up our own meanings of ''species" and 

 "genus." The application and use of the characters here sug- 

 gested will be described more fully in a future paper. 



Perhaps the first-noted definite "character," splitting up a 

 so-called species into a number of groups, is the agglutination 

 reaction. Thus TuUoch by this method demonstrated the exist- 

 ence of four types of the group recognized under the name of 

 B. tetani. Robertson thus subdivided her vibrion septique 

 strains into four groups, and Henry divided the species of B. 

 sporogenes into two groups on the basis of the agglutination 

 reaction. It has been found by various workers that agglutinat- 

 ing anti-sera formed against various strains of B. Welchii do 

 not agglutinate heterologous strains of the same organism, though 

 Werner found a serum that agglutinated one out of several 

 heterologous strains. When one thinks, however, of the com- 

 paratively numerous cases of cross agglutination recognized in 

 other groups, some of which may, and some of which may not 

 be modified in their importance by absorption-of-agglutinin 

 tests, and when one considers the Weil-Felix reaction, one is 

 ready to look for a more highly specific character than that of 

 the agglutination reaction by which to analyze his strains. 

 The Medical Research Committee term the agglutination reac- 

 tion "ultra specific" (1919). I personally regard this reaction 

 as of sub-generic rank, and not as of sub-specific rank in 

 the anaerobic group. The agglutination reaction has not yet 

 been investigated thoroughly enough to determine its value as 

 a systematic character for anaerobic bacteria. 



