246 THE BACTERIOPHAGE AND ITS BEHAVIOR 



years 1918 and 1919, I isolated many strains of this bacillus and also 

 many races of virulent bacteriophages. All of these bacteriophages 

 caused bacteriophagy with all of the strains isolated, including some 

 American strains sent me through the kindness of Dr. Hadley. 



I have isolated, uniformly, races of the virulent bacteriophage from 

 the excreta of domestic animals which were resisting the infection on the 

 farms where the typhoid raged, even among those which were naturally 

 immune. The bacteriophage is extremely virulent in those animals 

 which have recovered from the typhoid. 



Outside of the epizootic foci, in spite of a great many examinations, 

 I have never been able to isolate a bacteriophage possessing any action 

 whatsoever for Eherthella sanguinaria from the excreta of chickens or 

 any other domestic animals. ^^^ 



I have also isolated races of the bacteriophage virulent for the related 

 bacilli,- — E. pfaffi, E. jeffersonii and Salmonella piillora.^^'^ The number 

 of experiments carried out with these organisms is not, however, suffici- 

 ently great to permit me to say whether these bacterial species are 

 homogeneous or heterogeneous. Nevertheless the following fact is 

 sufficient to suggest that E. pfaffi is heterogeneous and E. jeffersonii 

 on the contrary may be homogeneous. Some races of the bacteriophage 

 virulent for Eherthella sanguinaria are virulent for E. pfaffi, others are 

 not. This would not be the case if E. pfaffi were a homogeneous species. 

 On the contrary all of the races of the bacteriophage virulent for Eher- 

 thella sanguinaria are also virulent for E. jeffersonii. 



With regard to the question of crossed virulences among these different 

 bacteria the following may be stated. One race of the bacteriophage 

 presented the following virulences : for Eherthella sanguinaria, + + + + ; 

 for E. jeffersonii, + + + + ; for S. pullora A, + + ; for >S. pullora B, 

 + ; for E. pfaffi, 0; and for E. rettgeri, 0.* 



Another race isolated from the excreta of a chicken which had resisted 

 an epizootic due to E. jeffersonii showed the following virulences; 

 Eherthella sanguinaria, 0; E. jeffersonii, 0; S. pullora A, 0; S. pullora B, 

 + ; E. pfaffi, + + + + ; and ^. rettgeri, (d'Herelle ^^i). 



6. Pasteurella hovis 



I have isolated about 30 races of bacteriophage virulent for this 

 organism. About 12 of these were, when isolated, endowed with a very 



* + + + + = very strong virulence; + + + = strong virulence; ++ = mod- 

 erate virulence, + = weak virulence; = no virulence. 



