54 



(soldiers in the same camp; children in a children's home) were 

 proved to be distinct from one another. This was the case even 

 in a family, the culture being taken from different members who 

 fell ill almost simultaneously. In the absorption experiments 3-4 

 times the bacterial concentration necessary to completely absorb 

 the agglutinin of the homologous serum, was used, but practically 

 none of the agglutinin in the serum corresponding to the other 

 strains was absorbed. In some special experiments on the effect of 

 bacterial concentration it could even be considerably further in- 

 creased without absorbing any of the heterologous agglutinin. 



Povitzky & Denny tested 100 strains obtained from influenza 

 cases in 1918, and 90 strains from a later outbreak, against 30 sera 

 prepared with strains obtained in 1918 and also before and during 

 the last oulhreak. These authors also found nearly all their strains 

 different from one another. 



The greatest number of strains in Valentine & Cooper's, and 

 Povjtzky & Denny's material collectively, which were identical 

 with one another, was 5. 



Bell tested 36 strains with 27 sera, — just as the three pre- 

 ceding groups of authors did by agglutination and absorption of 

 agglutinin — and found the majority were different from one another. 

 There was however a gradual change from one to another as regards 

 the power to absorb agglutinin. 



Cooke obtained similar results in complement fixation experi- 

 ments with 16 strains against 48 sera. 



Riyers & Kohn examined 13 meningeal strains which were 

 isolated in the course of 7 years and found 2 groups of 3 and 

 7 identical strains. 1 occupied an intermediate position between 

 the 2 groups, and 2 stood quite apart. 4 strains cultivated from 

 the blood of children with pneumonia were all different from one 

 another. 



7 of Riyers & Kohn's 13 meningeal strains had previously 

 been examined by Poyitzky & Denny, who in fact, had found 

 another grouping. (In one or two other cases also it is reported 

 that 2 investigators obtained different results with the same strains. 

 Whether this was due to confusing the strains or to other causes, 

 it is hardly possible to determine). 



Among other workers who have also found marked differences 

 between strains of Pfeiffer's bacillus may be mentioned Fleming 

 & Clemenger, Small & Stangl, Seligmann & Wole, Bieling 

 & Joseph, Bieling, Bieling & Weiciirrodt, Coca & Kelley, 

 Chesney, Maitland & Cameron, Skajaa. 



No distinct grouping on the strength of the serological 

 reactions has been effected. 



In opposition to the previous authors, Huntoon & Hannvm 

 found that some strains, from places far apart, both by direct 



