532 THE BACTERIOPHAGE AND ITS BEHAVIOR 



cubation of the organic immunity, which develops under the influence 

 of the soluble products contained in the culture of the bacteriophage. 

 Once this organic immunity is established the animal is refractory. 



We will see in connection with dysentery, that when a suspension 

 of the bacteriophage is injected the organism responds by the production 

 of an antitoxin. It is probable that the same thing takes place in 

 barbone and that the protective principle present in the blood, since 

 it is neither an amboceptor nor an opsonin, is likewise an antitoxin; 

 the response of the organism to the injection of the modified substance 

 of the dissolved bacterial cells contained in the suspension of the 

 bacteriophage. 



To summarize: the injection of the buffalo or of cattle, with a sus- 

 pension of the bacteriophage active for the bacterium of barbone confers : 



1. An heterologous immunity, solely due to the presence in the body 

 of bacteriophage protobes virulent for the bacterium of barbone, which 

 assures the destruction of the bacteria upon their introduction into the 

 organism. This immunity terminates just as soon as the protobes are 

 eliminated from the body. In the absence of frequent reinfections this 

 elimination is very rapid, since the continued growth and the mainte- 

 nance of virulence can not persist. 



2. An homologous, or organic and powerful immunity, induced by a 

 reaction of the tissues of the animal to the soluble principles con- 

 tained in the bacteriophage suspension injected. This organic immun- 

 ity is characterized principally by the appearance in the blood of an 

 extremely potent immunizing substance — probably an antitoxin. The 

 organic immunity establishes itself abruptly after an incubation period, 

 which varies with the dose injected, being longer as the amount of in- 

 jected culture is increased. 



A single injection of 0.04 cc, or less than a normal sized drop, into 

 a steer of 100 kgm. weight places the animal within 4 days in a condition 

 where it can withstand a test inoculation of five fatal doses. Sixty days 

 later the animal resists a test inoculation representing fifty surely fatal 

 doses. 



The blood of an immunized animal injected into a normal animal 

 confers on the latter a passive immunity as solid as that enjoyed by the 

 actively immunized one itself, even if this last one has received but a 

 single injection of 0.04 cc. of bacteriophage suspension. And this pas- 

 sive immunity, under experimental conditions at least, is still intact 

 forty-five days after the injection of the blood.^-^ 



As stated above, after my departure from Indo-China Le Louet 



