BEHAVIOR OF BACTERIOPHAGE IN EPIDEMICS 493 



Before discussing these control experiments I ought to mention that, 

 thanks to the kindness of the veterinarians of different regions invaded 

 by typhosis, I have been able to procure numerous specimens of blood 

 and excreta taken from sick chickens, from chickens which had died or 

 from those which had recovered, derived from eleven different foci scat- 

 tered throughout all France. This allows me to generahze from the 

 facts that I have personally observed. 



Control experiments 



The control experiments have been conducted in Paris, that is to say, 

 entirely outside of the epizootic area. 



Six chickens, procured from a region free of infection, were placed 

 under observation. Their excreta were examined daily for ten days for 

 the purpose of establishing the complete absence of a bacteriophage 

 active for B. gallinarum. 



Chicken No. 1 then received, per as, 1 cc. of a suspension of a race 

 of bacteriophage very active for B. gallinarum (+ + + +). 



Chicken No 2 received 0.5 cc. of the same suspension by subcutaneous 

 injection. 



The next day examination of the feces of these two animals showed 

 the presence of a bacteriophage strongly virulent for B. gallinarum. 

 Therefore, the bacteriophage passed into the intestine, whether ingested 

 or injected. This same fact has since been verified with man and with 

 different -animals. 



Chicken No. 1 next received per os daily for twenty-five days, 2 cc. 

 of a bouillon culture of B. gallinarum. The active bacteriophage per- 

 sisted in the intestine with its primary virulence (+ + + + ) and main- 

 tained itself up to nine days after the last dose of the pathogenic 

 organism. 



Chicken No. 2, which had received nothing after the inoculation of 

 the active bacteriophage ceased to show a race active for B. gallinarum 

 within three days after the injection. In other words, chicken No. 1, 

 subjected to repeated reinfections, retained an intestinal bacteriophage 

 active for B. gallinarum for thirty-four days, while chicken No. 2, not 

 infected, for only three days. 



It follows that the intestinal bacteriophage remains active only if it is 

 able to develop in the intestine at the expense of this bacterium, but in 

 such a case it remains active just so long as this condition is fulfilled. 

 Inversely, the presence in the intestine of a bacteriophage possessing 

 virulence for a given bacterium indicates that this bacterium was a short 

 time previously in the intestine. 



