BEHAVIOR OF BACTERIOPHAGE IN EPIDEMICS 491 



lected on May 22, did not contain a bacteriophage active for B. galli- 

 narum. On the morning of May 24 the chicken which had been taken 

 sick on May 22 and which had resisted showed in its intestinal contents 

 a bacteriophage of extreme activity (+ + + +) toward the patho- 

 genic bacillus. On May 26 the fourth chicken, one of those whose 

 feces had not showed an active bacteriophage when examined on May 

 22, was affected. It resisted, and on May 28 its symptoms had dis- 

 appeared. The disease disappeared suddenly and during the next three 

 months no new cases developed. 



On May 30 the feces of thirty chickens were examined and the fol- 

 lowing results were obtained : 



Virulence for B. gallinarum; in five + + + +, in twenty-one + + + , 

 in four + + • 



We see, then, on May 22, four animals among thirty in which the 

 intestinal bacteriophage lacked activity for the pathogenic bacillus. 

 These four animals contracted the disease during the four following days. 

 In the twenty-six specimens collected on May 22 and showing positive 

 results, the bacteriophage showed a relatively weak virulence. Nine 

 days later this activity was very much greater, that is, at the time when 

 the epizootic ceased. What, then, took place in this interval? The 

 bird which became sick on May 22 and which resisted showed in its 

 feces, when examined 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 bacterio- 

 phage, 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 (+ + + for 5. gallinanmi) 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.* On October 15, strains of B. pfaffi were isolated from 

 two specimens of blood, taken from animals which had died in a chicken- 



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

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



