368 THE BACTERIOPHAGE AND ITS BEHAVIOR 



of species idea,- — that there is "not one bacteriophage but a great many 

 bacteriophages, as different from each other as are the bacteria."^^ 



The arguments are four in number : 



First. The antigenic variabiHty of the bacteriophage races. 



Second. The variabihty in resistance to different destructive agents. 



Third. The fact that a bacterium which has developed a resistance 

 to one bacteriophage may be attacked by another. 



Fourth. Because different bacteriophage races may differ in the 

 form of their colonies. 



The reply to the first of these objections has already been given in 

 the preceding paragraph. Just so surely as the antigenic properties of a 

 bacterium like the streptococcus can be transformed by passages at 

 the expense of different animals, it is but natural that the same fact 

 should occur with the bacteriophage, and that the antigenic properties 

 should differ in accord with the bacteria at the expense of which it has 

 multiplied. 



It is not without significance that, as we know, each strain of B. coli 

 has its own individual antigenic properties, and that there are as many 

 coli antigens as there are strains of B. coli. Has anyone yet ventured to 

 advance the idea that each strain of B. coli represents an individual 

 species? It is obvious that all strains of B. coli belong to a single species 

 which is in a continual state of antigenic transformation. Upon what 

 basis, then, can anyone advance the fact of the antigenic variability 

 of the bacteriophage as an argument in favor of a plurality of species? 



As for variability in resistance, clearly if the resistance of each race 

 were a fixed property this argument would deserve consideration. But 

 this is not what is observed. The studies of all authors who have con- 

 sidered the question, even including the collaborators of Bruynoghe, 

 show that from one experiment to another a single bacteriophage pre- 

 sents considerable variations,^ — differences as great as are those observed 

 between the different races.* This argument is therefore without value. 



The argument based on the fact that one race of the bacteriophage 

 may attack a bacterial strain which has acquired a resistance toward 

 another race means nothing, for the same fact occurs with even a single 

 race 



* There is nothing strange in this, since with the bacteriophage as with patho- 

 genic bacteria, virulence disappears prior to their destruction. We know that 

 bacteria may become avirulent and yet remain alive. With the bacteriophage 

 the same thing occurs. Absence of bacteriophagy does not necessarily imply 

 total destruction of the being. With the bacteriophage an "apparent" destruc- 

 tion coincides with a loss in virulence, and this loss is effected through the action 

 of a physical or chemical agent the more readily when the virulence is weak. 



