146 THE BACTERIOPHAGE 



to question. Each of them has taken simply a particular fact, 

 suited to support his thesis, and has neglected entirely the great 

 group of experimental facts which render this hypothesis inad- 

 missible, forgetting that that which accords with experiment is, 

 for a theory, the sole and indispensable criterion of its truth. 



But the strangeness of their procedure is not restricted to the 

 interpretation of their experimental findings, but extends to the 

 experiments themselves. These experiments correctly performed 

 react against their hypotheses. I have called attention to these 

 errors and Kabeshima seems to be converted by the evidence, 

 for he has published nothing for two years. As for Bordet, he 

 does not maintain that his fundamental experiment, called that 

 of leucocytic exudates, may be repeated. He has recognized 

 that the specificity of the bacteriophage, a condition sine qua 

 non for his hypothesis, is contrary to fact, but he nevertheless 

 continues to support a hypothesis thenceforth without foundation. 



THE POSSIBLE HYPOTHESES 



The number of possible hypotheses is limited, and after a con- 

 sideration of these fundamental hypotheses it is only necessary 

 to select that which accords with the observed experimental facts 

 which have been contradicted by no one. These hypotheses 

 were carefully reviewed prior to all publication in an attempt to 

 determine the nature of the principle which I had discovered. 



Three fundamental hypotheses can be formulated and any 

 other view must be a modification or a combination of one or 

 more of these three. Discussion of these three must necessarily 

 dispose of any subsidiary hypotheses that may be advanced. 



What, then, are these three fundamental hypotheses which 

 comprise all that can possibly be formulated? 



First hypothesis 



The bacteriophage is derived from the superior organism in 

 its reaction to the bacterial invasion by the production of a prin- 

 ciple which provokes the destruction of the bacterium. 



This first hypothesis admits of two solutions. 



1. The principle in question is a substance of diastatic nature. 

 The single fact of the serial action of the principle is sufficient to 



