518 THE BACTERIOPHAGE AND ITS BEHAVIOR 



Yard No. 1. The 100 survivors received an injection of 0,5 cc. of 

 bacteriophage suspension. Five chickens died immediately after the 

 injection, and then there were no further deaths. 



Yard No. 2. Here there were 3 deaths per day. The 24 survivors, 

 despite the fact that the majority of them were already infected and 

 showed the symptoms of the disease, received an injection of 0.5 cc. 

 of bacteriophage suspension. The animals that were very sick died, 

 then the epizootic was arrested. 



Yard No. 3. The disease had not yet invaded this yard, in which 

 there were 100 chickens. All of them received as a prophylactic 

 measure an injection of 4 cc. of an anti-galhnarum serum. Four 

 days after this injection the epizootic began, 4 or 5 animals dying 

 each day. Five days later, when 80 chickens still remained alive, each 

 one received 0,5 cc. of bacteriophage suspension. The epizootic 

 stopped at once. 



Observation 13. Epizootic due to B. gallinarum. 



The race of bacteriophage used in this experiment had but a weak 

 virulence for a strain of B. gallinarum isolated from the blood of one 

 of the chickens dying in the henyard. The 100 survivors received an 

 inoculation of 0.5 cc. of the suspension of bacteriophage of low viru- 

 lence. There was no effect. Two weeks later a second injection was 

 given. The mortality diminished, but the disease did not disappear. 

 This experiment is extremely interesting for it shows two things: 



First: That immunization does not take place if the bacteriophage 

 inoculated does not possess a virulence sufficient to overcome the 

 pathogenic organisms; 



Second: That it is clearly the bacteriophage which is effective, and 

 effective as a parasite of the pathogenic bacteria. If the active princi- 

 ple were some soluble substance of the bacteria, the virulence of the 

 bacteriophage, with the associated possibility of secondary cultures, 

 would be of Httle consequence. 



Observation 14- Enzootic due to B. gallinarwn. 



The infection here had lasted throughout several months. An in- 

 jection of 0.5 cc. of a bacteriophage suspension was given to each of the 

 200 survivors. The enzootic stopped abruptly and finally. 



Observation 15. Epizootic due to an atypical B. gallinarum. 



In this epizootic there had been 3 or 4 deaths per day. Isolation of 

 the pathogenic bacterium showed that the causative agent was an 

 atypical strain of B. gallinarum, but the race of bacteriophage available 

 possessed a very high virulence for this bacillus. The 317 survivors 



