522 PATHOGENIC MICROORGANISMS 



Types of Meningococci. Until 1909 it was believed that the men- 

 ingococcus group, was homogeneous, and that no essential difference 

 between individual members of the group existed. In this year, 

 Dopter 20 found that some of the meningococci isolated from cases 

 which occurred in Paris and environment, could be distinguished "by 

 specific agglutination reactions from the ordinary or normal type. 

 This para-meniiigococcus, as Dopter called it, opened the way for 

 investigations aimed at the serological classification of the group, and, 

 as was to be expected, it was found that there were a considerable 

 number of different meiiingococcus sub-types. Wollstein 21 confirmed 

 Dopter 's work and found, among other things, that the various para- 

 meningococeus strains were not wholly homologous, and suggested 

 their possible further subdivision. Gordon 22 examined a large num- 

 ber of meningococci from cases occurring among British and Canadian 

 troops, and found that all the organisms studied by him could be 

 divided into four definite types. He used not only the agglutination 

 reaction, but controlled them with absorption tests. Tulloch, 23 follow- 

 ing up Gordon's work on a considerable material, found that, out of 

 356 cocci investigated, 234 gave specific results with the four type sera 

 used by Gordon's laboratory. He found that, with remarkably few 

 exceptions, the organisms responsible for the outbreaks among British 

 troops were comprised in the four Gordon types. He did, however, 

 find some organisms in the nasopharyngeal cultures of carriers which, 

 though closely resembling meningococci, did not react with any of the 

 type sera. There was some question, however, in his mind as to 

 whether these represented true virulent meningococci. An important 

 result of Gordon's investigations was to show that very many of the 

 organisms obtained from carriers belong to one of the four types 

 known to exist in actual cases of meningeal infection. 



In America, Flexner 24 and his associates have investigated the 

 group relationships of the meningococci very carefully, and their 

 results indicate that there are probably two main types, the normal 

 and the para-meningococcus of Dopter; and, in addition to this, a 

 considerable number of heterogeneous intermediate types which are 

 related to each other and to the fixed types more or less in the same 



20 Dopter, Cdmpt. Eend. de la Soc. de Biol., 67, 1909, 74. 



21 Wollstein, Jour. Exper. Med., 20, 1914. 



22 Gordon, Brit. Med. Res. Commit. Eeports, London, 1915 and 1917. 

 28 Tulloch, Jour. Royal Medical College, February, 1918, p. 9. 



24 Flexner, Bulletin, Rock. Inst. for Med. Res., 1917. 



