CHAPTER II 



The Ubiquity of the Bacteriophage 



1. THE bacteriophage IN THE INTESTINAL TRACT 



Throughout the remainder of this text the subjects under discussion 

 will involve, directly or indirectly, the question of the multiple viru- 

 lences which a race of the bacteriophage may show in the intestine. 

 But before presenting this material I must first reply to an objection 

 which has been raised by several authors, wherein they question whether 

 the activity which a filtrate of the stool manifests against different 

 bacterial species is due to the presence of one bacteriophage endowed 

 witn muiwple virulences, or whether it is a natural result of the simul- 

 taneous presence of several races of the bacteriophage. 



Anticipating somewhat the facts which are to be presented, we may 

 say at once that different races of the bacteriophage exist, and are found, 

 frequently, in any material which may have been, at any time, con- 

 taminated by the excreta of any animal whatever. For example, 

 drinking water, among other things, commonly contains the bacte- 

 riophage. This being the case, the ingestion of different races of the 

 bacteriophage must be a constant occurrence, both by man and by 

 animals. One would think, a -priori, that a specimen of excreta should, 

 therefore, contain bacteriophages belonging to different races. But as a 

 matter of fact, the experiments to be detailed in the following chapters 

 show that this is not the case, and that it is rare to find in the filtrate of a 

 stool from a given individual, not many races, but even two. 



How can we explain this finding which seems to be in conflict with 

 the fact that we daily ingest different races? 



Experiment shows that within the intestinal tract of each individual 

 there is, as a rule, one race of the bacteriophage Hving in a symbiotic 

 relationship with the B. coli present in the intestine of this individual. 

 Thus, of two possibiHties, one must occur; either the different races 

 ingested are not able to adapt themselves to the bacteriophagy of the 

 B. coli strain there present, with the result that they are quickly elim- 

 inated, or, the behavior of the bacteriophage is not the same m vuw as 

 in vitro, and that in the intestine the different races quickly lose their 

 particular distinctive characters and become uniform. It is difficult to 



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