180 RELATIONSHIPS OF THE COCCACE^E 



with the problems of infection and immunity, and their 

 chief result from the systematic standpoint has been to 

 make clear the existence of virulent and non-virulent 

 types, both of orange and of white staphylococci. The 

 Aurococcus produces both a hemolysin and a substance 

 which acts specifically on the white blood cells, first de- 

 scribed by Van de Velde (1894) and called by him a Leu- 

 cocidin. Neisser and Wechsberg (1901) in an elaborate 

 study showed that these were distinct bodies, the strength 

 of one varying independently of the other, and they held 

 the formation of hemolysins and leucocidins to be impor- 

 tant aids in differentiating pathogenic staphylococci from 

 other types. 



Kolle and Otto (1902) studied the agglutination reac- 

 tions of Aurococcus and Albococcus and concluded that 

 the serum of immunized guinea pigs would serve to dis- 

 tinguish the true pus-formers from allied types. Klop- 

 stock and Bockenheimer (1903) confirmed the general 

 results of Kolle and Otto. They found that a serum 

 prepared by injecting a pathogenic Aurococcus or Albo- 

 coccus would generally agglutinate other pathogenic forms 

 but not saprophytic ones. Some saprophytic cocci failed 

 to stimulate the production of agglutinins at all. Some, 

 on the other hand, when injected, produced sera which 

 would agglutinate other saprophytic strains but did not 

 affect pathogens. Van Durme (1903) also found that 

 hemolytic power was generally greatest in cultures of 

 ,albococci and aurococci freshly isolated from pathogenic 



