CLASSIFICATION OF PNEUMOCOCCI 105 



authors and reviewers. She prepared agglutinative serum by im- 

 munizing rabbits with repeated doses, first of killed, then of living, 

 and finally of killed broth cultures of pneumococci. The strain used 

 as an antigen must have belonged to a type other than I or II, 

 since the serum agglutinated only a few of the seventy strains 

 tested. Collins' results may be summarized as follows: Pneumo- 

 cocci by reason of their agglutinating properties exhibit a tend- 

 ency to separate into numerous groups ; Pneumococcus mucosus 

 forms a distinct and consistent race, and the resistance of the ag- 

 glutinins produced by it to absorption by streptococci indicates a 

 nearer relation to Pneumococcus than to Streptococcus. There 

 was considerable uniformity of reaction of the various strains in 

 low dilutions, but this uniformity was not continued as the animal 

 became more highly immunized, and it was not possible for Collins 

 to establish a definite relationship, between the agglutination reac- 

 tion and the other characters of Pneumococcus except in the case 

 of Pneumococcus mucosus. 



In 1906, Eyre, Leathern, and Washbourn 372 suggested the sepa- 

 ration of pneumococci into two groups according to the reaction 

 of rabbit tissue to infection, that is, a fibrinous type and a cellu- 

 lar type, but this idea apparently was never pursued. 



It remained for Neufeld and Haendel 991 in 1910 to demonstrate 

 the full significance and the differential value of these phenomena. 

 With a collection of pneumococcal strains isolated from a series of 

 pneumonia patients the authors obtained, by the immunization of 

 rabbits, asses, and horses, monovalent serums of high potency. 

 With a culture isolated in 1909 a serum was prepared that pro- 

 tected mice against the majority of the other strains, and this 

 strain was called "Pneumococcus I." All the pneumococci against 

 which the serum protected mice were classed as "typical," and all 

 others as "atypical." Among the latter was one strain, "Franz," 

 that was later found to be Type II. The "typical" antiserum had 

 no effect on the "Franz" strain, and a "Franz" antiserum failed 

 to protect mice against the Type I culture. Neufeld and Haendel 



