IMMUNIZATION BY MEANS OF THE BACTERIOPHAGE 259 



on the production of therapeutic sera in animals immunized by a 

 single injection of an active bacteriophage, not only for barbone, 

 but for other diseases as well. 



One might conceive that the "principle" which is contained 

 in the blood of the immunized animal and which confers the pas- 

 sive immunity does not differ from the culture of the bacteriophage 

 which persists for a certain length of time in the circulation. 

 But this is impossible, for if the blood is taken at a time sufficiently 

 close to the immunizing injection of the bacteriophage it is in 

 no way effective. That is, blood taken during the incubation 

 period confers no immunity to the transfused animal. 



Steers nos. 89 and 90 received on December 19, 0.25 cc. of the bacte- 

 riophage culture subcutaneously. Sixteen days later 500 cc. of blood were 

 withdrawn from each animal and transfused into steers nos. 92 and 93. 

 The four animals, tested the next day, died with no greater delay than the 

 controls. Steer no. 46 received on November 5, 20 cc. of the culture of 

 bacteriophage. On November 19, 500 cc. of blood were taken and trans- 

 fused into steer no. 42. These two animals died in the same time as the 

 control after a test injection. 



As is to be seen, the incubation period of immunity in animals 

 which receive the immunizing injection of bacteriophage culture 

 parallels the appearance of the protective power in their blood. 

 Immunity develops abruptly; in the same way the protective 

 power of the blood manifests itself suddenly, and at the same 

 moment. 



What then, is the immunizing principle which makes its sudden 

 appearance in the blood at the moment when immunity is es- 

 tablished, even in animals which have received only the minimal 

 dose of a single drop of the culture of the bacteriophage? Can 

 it be an amboceptor? By no means, for the complement fixa- 

 tion reaction shows that the sera of animals immunized with 

 cultures of the bacteriophage do not contain a specific ambo- 

 ceptor in detectable quantity. In conducting the reaction of 

 Bordet with even 0.5 cc. one obtains an exactly comparable he- 

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

 occurs in a control tube containing the same quantity of normal 

 serum. 



