PATHOGENICITY FOR EXPERIMENTAL ANIMALS 201 



between virulence and electrophoretic potential of different strains 

 and serological types of Pneumococcus has been studied by Falk 

 and his associates, Gussin and Jacobson. 379 According to the au- 

 thors the highest potentials were uniformly found for Type III 

 organisms, while the most probable sequence of decreasing poten- 

 tials was from Type III to I to II and then to Group IV strains. 

 The order corresponded to the decreasing sequence of virulence of 

 the cultures for white mice. Washing the cultures increased elec- 

 trophoretic velocities, but the order remained the same. From the 

 results obtained with stock cultures, the authors anticipated that 

 strains isolated from fatal cases of pneumonia might show higher 

 potentials than would strains of the same type isolated from non- 

 fatal cases. The experimental data confirmed the assumption for 

 Types II and III, and Group IV, but contradicted it for Type I 

 strains. Falk, Gussin, and Jacobson 379 concluded that electropho- 

 retic potential was related in some fundamental manner to viru- 

 lence "as well as to phagocytability, agglutinability, capsule for- 

 mation, and other characters of microorganisms. In a later com- 

 munication, Jacobson and Falk, 675 after a study of this electrical 

 phenomenon in pneumococcal variants, reported that in all cases 

 studied alterations in virulence were accompanied by parallel al- 

 terations in electrophoretic potential and by reciprocal alterations 

 in agglutinability. 



The results obtained by Thompson (1931 ) 1396 in some respects 

 contradict those reported by Falk and his colleagues. While the 

 electrophoretic migration of representatives of the first three 

 pneumococcal types was observed to decrease in the order III, I, 

 II, as previously noted by Falk, Gussin, and Jacobson, exaltation 

 or degradation of virulence respectively by mouse passage and by 

 growth in increasing concentrations of ox bile were unaccompa- 

 nied by any constant differences in the original velocity of migra- 

 tion. 



Welikanow and Michailowa (1930) 1513 claimed that variation 

 in the ability of pneumococci to ferment glucose is an indicator 



