IMMUNIZATION WITH BACTERIOPHAGE SUSPENSIONS 531 



specific amboceptor in detectable quantity. In conducting the reac- 

 tion of Bordet with even 0,5 cc. one obtains an exactly comparable 

 hemolysis, of the same intensity and in the same time, as that which 

 occurs in a control tube containing the same quantity of normal serum. 



Examination of the opsonic power of two of these sera gave indices 

 of 0.3 and 0.4; indices which are essentially negative. 



The serum containing the protective principle does not contain 

 destructive substances or even substances delaying the growth of the 

 bacterium of barbone. Bouillon, mixed with such a serum, in any 

 proportion (from 0.05 cc. to 3 cc. per 10 cc. of bouillon), with or without 

 the addition of fresh guinea pig serum, furnishes a medium which, 

 when inoculated, gives luxuriant cultures of the bacterium of barbone. 



Finally, the serum contains no traces of agglutinins. 



Organic immunity, then, is not due to the presence of an amboceptor, 

 nor to the presence of an opsonin in the blood of the vaccinated sub- 

 jects. The blood contains neither agglutinins nor inhibiting sub- 

 stances. The immunity is most probably antitoxic. 



We have seen in the experiments performed on avian typhosis, 

 that, in an infected area, the protection of the animal is immediate and 

 that this protection is assured only by the presence of bacteriophage 

 corpuscles virulent for the pathogenic bacterium. We have again found 

 this immediate immunity in the case of barbone. It is that which 

 protected steers Nos. 103 and 107 against the inoculation of five fatal 

 doses of culture when given only twenty-four hours after the injection 

 of the bacteriophage. 



In typhosis, this heterologous immunity has been permanent, for 

 the daily reinfections which occur in the infected area allow the bac- 

 teriophage to multiply at the expense of the pathogenic bacteria in- 

 gested and thus to maintain its virulence for this bacterium. In 

 barbone, this same thing takes place in an infected area, since we have 

 seen that the bacteriophage virulent for the bacterium of barbone was 

 present in the intestine of buffaloes five months after the complete 

 disappearance of the epizootic. 



In a non-injected region, and this was the case in the experiments 

 performed on barbone, the mechanism is not same. In the absence of 

 reinfection the bacteriophage active for the bacterium is eliminated 

 very rapidly, since it is not able to multiply at the expense of this 

 bacterium. The heterologous immunity disappears with ,it,- — ^that is 

 to say, after one or two days, — and the animal then becomes susceptible. 

 It remains in this condition throughout the entire duration of the in- 



