UBIQUITY OF BACTERIOPHAGE 



425 



living in regions where this bacterium is lacking, a corresponding viru- 

 lence of the intestinal bacteriophage can never be detected. 



All of these facts show that if the intestinal bacteriophage of domestic 

 animals manifests, with very few exceptions, a virulence for the dysen- 

 tery bacilli and for the paratyphoid organisms, it is simply because these 

 bacteria must be extremely abundant in the environment and that 



their ingestion by the animals is not an exceptional occurrence 

 (d'Herelle^i"). 



The results of some of the studies which I have made upon the dis- 

 tribution of the bacteriophage among different anunal species^^"' ^^®' ^^i 

 and the virulences which these races of the bacteriophage possess are 

 presented in the following sections. 



