212 THE BACTERIOPHAGE 



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 os, 1 cc. of a culture of a strain 

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



Chicken no. 2 received 0.5 cc. of the same culture 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 bac- 

 teriophage persisted in the intestine with its primary virulence 

 (+ + ++) and maintained itself up to nine days after the last 

 dose of the pathogenic organism. 



Chicken no. 2, which had received nothing after the inocula- 

 tion of the active bacteriophage ceased to show an active strain 

 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. 



In the course of the preceding experiment chickens nos. 3 and 

 4 were placed in contact with chicken no. 1. They all ate and 

 drank from the same containers, the more so since they were 

 changed about in the pens in such a manner as to simulate condi- 

 tions of life analogous to those of the chicken-yard. Two days 

 after the first contact, in the case of chicken no. 3, three days after 

 with chicken no. 4, their excreta contained a bacteriophage very 



