364 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



observed can only be a phenomenon linked with assimilation. When 

 the antigenic properties of the streptococcus undergo a change it must 

 mean that the substance of this streptococcus has changed, and that 

 change varies with the nature of the foodstuff. The assimilation is not 

 complete; the "substance" of a streptococcus which develops at the 

 expense of "horse substance," although becoming "streptococcus sub- 



NUMBER 



STRAINS OF STREPTOCOCCI 



I S6gala I Sauteur I Passe I A. 1179 I 



Medium: Bouillon, 4 cc. + guinea-pig blood, 1 cc. 



Medium: Bouillon, 4 cc. + rabbit blood, 1 cc. 



* Attention is called to the fact that the differences in the number of passages 

 are due to the fact that it was necessary, in some cases, to make isolations from 

 agar in order to separate the streptococci from associated organisms, which, 

 despite the precautions taken, occasionally contaminated their cultures through 

 blood stream invasions. In those instances in the table where the series is ter- 

 minated the loss of antigenic power was complete at the tenth passage. The 

 names applied to the strains of streptococci are the names of the horses from which 

 they were isolated. 



stance" retains, nevertheless, some of the characters of "horse sub- 

 stance," and the smaller the difference between the two substances, 

 the greater is the virulence.* The same thing takes place if the strep- 

 tococcus is subjected to passage through another animal. f 



* This relation between the virulence and the quality of the substance of the 

 bacterium is, without doubt, very simple. It may be associated with phagocy- 

 tosis, which may be the more active as the substance of the bacterium differs from 

 the substance of the animal invaded. 



t It should be observed that these authors have noted that in order to induce a 

 transformation in antigenic character by passages in artificial media, it is essen- 

 tial that the added animal product, — blood, — be unmodified by heating. In 

 effect, it is necessary that the animal substance be still "alive." 



