IMMUNIZATION WITH BACTERIOPHAGE SUSPENSIONS 527 



This experiment shows that fourteen months after the immunizing 

 injection two-thirds of the animals possessed an immunity sufficiently 

 strong to enable them to withstand a massive dose of the pathogenic 

 bacterium. 



The immunizing pr'inciple 



Under the conditions of the experiment, that is to say, in a non- 

 , contaminated area, what, in the bacteriophage suspension, is the princi- 

 ple which brings about the immunization? 



A preparation of the bacteriophage contains, as we know: 



1. The bacteriophage protobes and 



2. The soluble substances contained in the culture medium. These 

 are the soluble substances derived from the bacterial bodies at the 

 expense of which the bacteriophage has developed, the "products 

 resulting from bacteriophagy," and the metabolic products elaborated 

 by the bacteria prior to their dissolution. 



The course of the phenomenon alone, has shown us already that the 

 immunizing principle must be different according as the immunity is 

 developed in a contaminated area, as was the case in the experiments 

 made on typhosis, or in a non-contaminated area, as in those on barbone. 

 In the first, the immunity is acquired immediately; in the second, it 

 becomes effective only after an incubation period. However, direct 

 experiment allows us to confirm this idea. 



1. If one injects steers, by the subcutaneous route, with from 5 to 

 20 cc. of Barbone-bacteriophage it is possible to isolate the active 

 protobes from the blood throughout the first twenty-four hours after 

 the injection. After this period they have disappeared. Experiment fur- 

 ther shows that the protobes pass quickly into the intestine. They can 

 be isolated from the intestine within about twelve hours after 

 the injection and they persist there for a somewhat longer time than 

 in the circulation: for two or three days (up to six days in a single 

 case) . In all instances they have disappeared long before the immunity 

 is established. Let us repeat that this applies only to the case where 

 the introduction of the bacteriophage into the organism takes place in a 

 territory free from the infection. We have seen, for example, that 

 five months after the termination of an epizootic of barbone it is still 

 possible to isolate a bacteriophage active for the pathogenic bacterium 

 from the excreta of buffaloes which have resisted. On the other hand 

 experimentation in the chicken has shown us that the activity of the 

 bacteriophage for the pathogenic bacillus is maintained just as long as 

 the experimental animal continues to ingest these bacteria. 



