THE PNEUMOCOCCUS . 289 



Types of Pneumococci. Kruse and Pansini 1 as early as 1891 called 

 attention to the differences, both cultural, morphological and in 

 virulence, which they observed in studying eighty-four strains of 

 pneumococci isolated from many cases of pneumonia. They believe 

 that there was no sharp line of demarcation between the pneumo- 

 coccus and Streptococcus pyogenes, because their various strains 

 included all variants between the two types of organisms. Recently 

 Rosenow 2 has reported the transmutation of typical pneumococci to 

 Streptococcus pyogenes by a series of animal passages and cultural 

 manipulations. Cole 3 has been unable to confirm this observation 

 in any one of several hundred strains, but it should be stated that 

 he has not employed Rosenow's procedure in detail. 



Much light has been shed upon the apparent variability of strains 

 of pneumococci by the observations of Neufeld and Handel, 4 and 

 Dochez, 5 and Dochez and Gillespie. 6 These observers have shown 

 by serological reactions that pneumococci may be divided into four 

 groups or types, each of which fails to agglutinate with sera other 

 than the homologous serum. These groups have been tentatively 

 designated I to IV inclusive. Groups I and II are typical virulent 

 pneumococci. Group III comprises the organism formerly known 

 as Streptococcus mucosus, now called Pneumococcus mucosus; and 

 Group IV includes relatively avirulent strains which are commonly 

 found in the mouths of healthy persons. Group IV is somewhat 

 more heterogenous, judging from agglutination reactions, than Groups 

 I to III. Group III contains the most virulent organisms. A study 

 of the distribution of the various types in seventy-two cases of pneu- 

 monia illustrates this point. 7 



Infection type. No. cases. No. deaths. Per cent. 



1 34 8 24 



2 13 8 61 



3 10 6 60 



4 15 17 



Total 72 23 32 



It is possible that "mixed infections" will be found when more 

 cases are carefully studied. The same general types have since been 

 reported in Europe and in Philadelphia. 8 



Loc. cit. 2 Jour. Am. Med. Assn., 1913, Ixi, 2007. 3 Loc. cit. 



Zeit, f. Immunitatsforsch., 1909, iii, 159; Berl. klin. Woch., 1912, xlix, 680. 

 Jour. Exp. Med., 1912, xvi, 680. Jour. Am. Med. Assn., 1913, Ixi, 727. 



Cole, Arch. Int. Med., 1914, xiv, 33. 

 Cole, New York Med. Jour., January 2 and 9, 1915. 

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