210 THE BACTERIOPHAGE 



amined on May 24, a bacteriophage endowed with a considerable 

 activity for the pathogenic agent. 



Here is a second example of the same general nature, giving 

 the results secured on farm M. . . . at Vericourt (Aube). The 

 epizootic first appeared among the flock of twenty-five chickens 

 in May, 1919. The first animal died on May 18. On the next 

 day twelve specimens of excreta were collected at random. Three 

 only contained a bacteriophage, and that of feeble activity, for 

 B. gallinarum. From May 19 to 26 twelve birds contracted the 

 disease and of these eleven died. One, which became sick on 

 May 23, showed on May 25 a strongly active bacteriophage 

 (H- + H- for B. gallinarum) and recovered. The epidemic stopped 

 abruptly. On May 27 twelve specimens were taken at random. 

 In all a bacteriophage active for B. gallinarum was found (in 1 

 + + + + , in 9 + + +-, in 2 ++). 



A third example may be mentioned, in which the infection was 

 a paratyphosis. 6 On October 15 strains of B. pfaffi were isolated 

 from two specimens of blood, taken from animals which had died 

 in a chicken-yard where for about a month there had been an 

 infection presenting the characters of typhosis. From specimens 

 of the feces taken from two healthy animals living in the same 

 yard two strains of bacteriophage were isolated, one showing a 

 low virulence (+) for B. pfaffi, the other showing no activity for 

 this bacillus. Towards the end of the month three chickens 

 became sick, recovered after an interval of two or three days, and 

 then the epizootic ceased. Six specimens of feces examined at 

 this time all showed a bacteriophage of high virulence (+ + +) 

 for B. pfaffi. Against B. gallinarum four were inactive and two 

 showed a weak virulence (-}-). 



B. pfaffi was therefore the cause, for when the epizootic broke 

 out three months later the eighty chickens which had survived 

 received a subcutaneous injection of 0.5 cc. of a culture of the 

 anti-pfaffi bacteriophage and the epidemic stopped abruptly 

 and permanently from the time of the injection. We will see 

 later that this abrupt cessation is the rule following immuniza- 

 tion by means of a culture of the bacteriophage. 



6 These experiments were carried out with the assistance of M. Micheau, 

 D. V. M. at Trainel (Aube). 



