UNICITY OF BACTERIOPHAGE PROTOBE 



363 



TABLE i2— Continued 



Passages through guinea pigs 



* These experiments were carried out on the only two strains of the strepto- 

 coccus which were sufficiently virulent to kill the rabbits. The same is true for 

 the guinea-pig experiments. 



adapts itself to the new organism which harbors it, and the more quickly 

 it loses its equine character to become a streptococcus of the mouse, 

 the rat, the rabbit, or the guinea pig. 



It is certain, as these authors say, that the rapidity of the transforma- 

 tion is a function of resistance, but is it the resistance of the animal 

 itself which is responsible, or may it be some other phenomenon ac- 

 companying resistance? The following experiments, made by these 

 same investigators, suggest an answer. 



A few years ago, in some experiments performed with Le Louet, I 

 observed that the virulence of a bacterium for a given animal is exalted 

 by cultivation in an artificial medium, a bouillon, prepared with the 

 flesh of this animal,* The same thing has been found to occur with the 

 strangles streptococcus for by cultivating this organism in Martin's 

 bouillon to which the blood of some laboratory animal was added Brocq- 

 Rousseu, Urbain and Forgeot observed that the virulence was increased 

 for this animal. They further noted that this increase in virulence 

 was associated with a transformation in antigenic properties, just as 

 though the passages had been made through the animal itself. Table 

 43 summarizes their experiments. 



These experiments solve the question. The explanation given by the 

 authors, namely, that the transformation is a function of the resistance 

 of the animal, can not be invoked. The alteration in properties here 



* d'Herelle, F. and LeLouet, G.— Sur la vaccination antibarbonique par virus 

 atUnn6. Ann. Inst. Pasteur, 1921, 35, 741. 



