ANTIBODIES TO PNEUMOCOCCUS 359 



tinin titer, but concluded that agglutination was specific only for 

 the strain used in the preparation of the serum employed in the 

 test. In the same year, Collins, 270 after immunizing rabbits succes- 

 sively with heat-killed and then with living broth cultures, tested 

 the serum so prepared against some seventy strains of Pneumo- 

 coccus. The serum of an animal immunized with one particular 

 strain of Pneumococcus agglutinated only seven of the organisms 

 when used in a dilution equalling that in which the homologous 

 organism agglutinated. 



Collins concluded from her study that pneumococci by reason of 

 their agglutinative properties exhibit a tendency to separate into 

 numerous groups, and also that by the reaction of agglutination 

 Pneumococcus mucosus forms a distinct and consistent variety. 

 The conclusions were based on results obtained by the method of 

 agglutinin-absorption, which indicated that the agglutinating sub- 

 stances consist of specific and group agglutinins. Collins, appre- 

 ciating that pneumococci showed marked differences in ability to 

 undergo agglutination, and believing that there existed different 

 types or groups as far as their agglutinative ability was con- 

 cerned, was convinced that it was not possible to establish a defi- 

 nite relationship between the agglutination reaction and other 

 characters of pneumococci except in the case of Pneumococcus 

 mucosus. 



Two other reports published before the serological classification 

 of pneumococci was established are those of Panichi (1907), 1047 " 8 

 and of Cotoni and Truche (1912). 284 The former author, after 

 testing the agglutinative property of a strain of Pneumococcus at 

 different stages of growth in bouillon when added to serum from 

 rabbits, sheep, and asses previously injected with the same culture, 

 concluded that agglutinability of the organism was greater during 

 the process of growth than after the cocci had attained full de- 

 velopment. Curative serums, including one prepared by Pane, did 

 not necessarily contain agglutinins. The experimental data sug- 

 gest that the serums employed were of low potency and, hence, the 



