NATURE OF THE BACTERIOPHAGE 159 



of this hypothesis would be strict specificity, and experiment 

 demonstrates that this does not obtain. All authors are actu- 

 ally in accord on this point and have confirmed the observation 

 that a single bacteriophage is able to attack diverse bacterial 

 species. 



REFUTATION OF THE HYPOTHESIS OF SALIMBENI 



The hypothesis of Salimbeni is merely mentioned. Admitting 

 that the bacteriophage is an autonomous microorganism, he 

 considered it a Myxomycete, presenting itself in visible forms, 

 and visible even to the naked eye. His observations have been 

 contradicted by all who have studied the bacteriophage. More- 

 over, Salimbeni himself, has not continued to maintain this hy- 

 pothesis. Possibly the observation upon which he based his 

 hypothesis was due to the use of contaminated cultures. 



CONCLUSIONS 



All of the authors who have advanced hypotheses other than 

 that of an ultramicrobe parasitizing the bacteria have forgotten 

 that a hypothesis ought always to account for the entire mass of 

 facts; that it is necessary, not only to demonstrate that it suffices 

 to justify the phenomena, but it must also prove that these phe- 

 nomena can not be justified if this hypothesis is abandoned or if 

 it is modified. 



After all, the whole controversy on the subject of the nature 

 of the bacteriophage is only the renewal of the old discussion 

 which we had for a long time thought terminated. With the new 

 ideas of diastases capable of multiplication, or of co-ferments or 

 catalyzers playing with the metaphysics of ubiquity, or of se- 

 cretory immunity transmissible by communicated motion; it 

 is only taking up anew the old theory of Stahl, that "any body 

 brought to a state of putrefaction transmits very easily this 

 state to another body still free of corruption." This theory of 

 the multiplication of a principle of communicating motion had 

 been held by Liebig in his discussion with Pasteur concerning 

 the mechanism of fermentation. Pasteur demonstrated experi- 

 mentally that it was false, and we were lead to believe the fact 

 definitely acquired. With vital phenomena or communicating 



