362 BIOLOGY OF PNEUMOCOCCUS 



that previously had failed to agglutinate with immune serum of 

 the authors' preparation or with samples of serum from America. 

 Gillespie (1914) 516 reported that strains of Type I and II pneu- 

 mococci exhibited narrow zones of agglutination whereas organ- 

 isms of the other types showed broad zones, and ascribed the 

 variations to the differences in the hydrogen ion concentration of 

 the cultures used and to the greater susceptibility of pneumococci 

 of Types I and II to the inhibiting action of salts. Armstrong 

 (1921— 1922) 19 ~ 20 placed greater reliance on the method of agglu- 

 tinin-absorption than on simple agglutination in the classification 

 of strains of pneumococci, since he believed that the latter tech- 

 nique was not always sufficient for recognition of type. On the 

 basis of agglutinability, Olmstead, 10278 Griffith, 558 and later Cooper 

 and her associates 272 " 4 extended the serological classification of 

 pneumococci to include the present thirty-two separate and spe- 

 cific types. 



AGGLUTINABILITY OF PNEUMOCOCCAL VARIANTS 



The experiments of Stryker 1348 in 1916 demonstrated that the 

 biological changes produced in pneumococci by growth in homolo- 

 gous immune serum included alterations in agglutinative behavior. 

 In 1923, Blake and Trask 129 found that a similar treatment of 

 pneumococcal cultures resulted, along with loss of virulence, in 

 constant and distinct changes in agglutinability, with respect to 

 both the character of agglutination and the zone of optimal reac- 

 tion. The changes appeared to be not a gradual alteration of all 

 members of a culture, but to consist in a rapid and complete 

 change in individual organisms. Three main variants developed 

 after growth in immune serum, and all exhibited marked differ- 

 ences in agglutinability. Analogous changes in the agglutinability 

 of typical pneumococci after cultivation under unfavorable condi- 

 tions were reported in the same year by Yoshioka. 1564 Cultivation 

 on unsuitable media at 39° and long drying in the desiccator 



