HYPOTHESES CONCERNING NATURE OF BACTERIOPHAGE 317 



with the greater vigor the younger the bacteria and when the conditions 

 for life are at their optimum. And, as we Icnow, the phenomenon 

 takes place poorly, or may not occur at all, with suspensions of old 

 bacteria. 



The partisans of the autolytic theories are then, it seems to me, con- 

 fronted by an obhgation to explain the paradoxical fact presented by 

 their conceptions, namely, that the phenomenon of bact eriophagy occurs 

 with young bacteria which have no natural autolytic tendency, and 

 does not take place with old bacteria which autolyse spontaneously. 



But despite these contradictions, the fact that normal bacteria con- 

 tain autolytic ferments makes it imperative that we analyse this hy- 

 pothesis further. It is necessary to demonstrate, not that such an hy- 

 pothesis is improbable, but that it is impossible. I am the more inter- 

 ested in this hypothesis, since when I was the only one interested in 

 the phenomenon of bacteriophagy, and long before any of this discus- 

 sion developed, I carefully considered this hypothesis as a possible 

 explanation of the process which I was study ing,^^^ only to reject it 

 because it was contrary to the experimental facts. Although rejected 

 at that time because it failed to accord with certain demonstrated 

 experimental facts, the proof of its inadequacy is today on a distinctly 

 different plane, for we are now able to present direct evidence, demon- 

 strating that the lysogenic principle, the cause of bacteriophagy, is 

 distinct from the autolysins and that it can not be present in a normal 

 bacterium. 



Let us consider first the validity of the argument upon which the 

 hypothesis explaining bacteriophagy as being due to the action of a 

 normal autolysin has been built.* 



The argument advanced is correct, but it is open to several interpre- 

 tations. Beyond question it is possible to isolate, from some bacterial 

 strains, a principle which causes the phenomenon of bacteriophagy. 

 Indeed I have reported that such an isolation is possible, and I was the 

 firsf'^i to show how such mixed bacterial strains could almost uniformly 

 be obtained. It is only necessary to use strains of B. coli derived from 

 cases of infection of the urinary tract. This observation has been since 

 confirmed by several authors (among others, Tomaselli^^^ and 

 Hauduroy.^2° 



The question of natural mixed cultures has been discussed at length in 



* The hypothesis of "splitter" of Bail can be refuted on the same grounds as 

 that of an autolysin. 



