BACTERIUM DIPHTHERIA 497 



2. By immunizing an animal from any one of a large 

 number of strains of genuine bacillus diphtherise a certain 

 number of the varieties in the group will agglutinate with 

 the serum of that animal in very high dilutions; while others 

 will either not agglutinate at all with that serum or only in 

 very low dilutions. 



3. These agglutination reactions are specific for the several 

 groups, i. e., cross-reactions are not observed. 



4. There is a sharp distinction between the agglutining 

 antigenic component and the antitoxin antigenic component 

 in bacillus diphtherise. 



5. The antitoxin produced through the use of the several 

 groups are not so sharply distinguished from one another 

 as are the agglutinins, though they manifest specific rela- 

 tionship to their homologous antigens. 



The bearing of all this on the recognition of bacillus 

 diphtheria and on the production of antitoxin is obvious. 1 



Bacterium Pseudodiphtheriticum. For a long time bac- 

 terium pseudodiphtheriticum was looked upon as being 

 entirely harmless, and the only particular in which it was 

 regarded as being of importance was in the fact that it was 

 likely to be mistaken for bacterium diphtherise. The wide 

 dissemination of this class of organisms and the demon- 

 stration of pathogenic effects in isolated instances has led 

 to the more systematic study of members of this group of 

 organisms. 



Bacterium pseudodiphtheriticum, as found under different 

 conditions, varies markedly in its morphologic and biologic 

 characters. Some of the varieties have definite chromogenic 



1 See Langer, Die Agglutination der Diphtherie bacillen, Centralbl. f. 

 Bact., Abt. I, Originale, 1916, vol. Ixxviii, p. 117. Havens, Biologic Studies 

 of the Diphtheria Bacillus, Jour. Infect. Dis., 1920, vol. xxvi, p. 38$, Addi- 

 tional literature given .in these papers. 

 32 



