BACTERIOPHAGY IN A FLUID MEDIUM 41 



and the minute quantity adhering to the wire is inoculated into the 

 prepared bacterial suspension. Within a few hours the suspension 

 is clear; all of the bacteria have disappeared. To all appearances they 

 have dissolved in the bouillon, just as sugar becomes dissolved in 

 water. At this time, a bacterial suspension, prepared as was the first, 

 is made and the tip of the platinum wire is immersed in the clear fluid 

 which originally was the first suspension, and thus a minute quantity 

 is transferred to the second turbid suspension. Again after a few 

 hours, this second suspension will in turn have become Hmpid. A needle 

 dipped in this second cleared suspension inoculated into a third results in 

 a repetition of the process. In each successive suspension the bacteria 

 become dissolved, and in this way it is possible to continue "serial 

 passages" of the bacteriophage principle as long as may be desired. 

 After some thousands of passages comparable to those described above 

 the last suspension, once it has become clear, represents a "bacterio- 

 phage fluid" just as active as that originally employed to cause bac- 

 terial dissolution in the first passage. By this procedure I have main- 

 tained for almost ten years several particularly active bacteriophage 

 races, certain of them having undergone several thousand passages at 

 the expense of the appropriate susceptible bacterium. 



The phenomenon of bacteriophagy is then, in reahty, a double 

 phenomenon. A dissolution of the bacterial cells takes place, and, in 

 the course of this dissolution, the bacteriophage principle regenerates, 

 reproduces itself. 



It is unnecessary to give here experimental protocols supporting 

 these statements. No one has questioned them, and, as a matter of 

 fact, this entire text is simply an exposition of the manner and the 

 results of this reproductive capacity of the bacteriophage. 



3. ENVIRONMENTAL CONDITIONS FAVORING BACTERIOPHAGY 



General conditions 



Of the many culture media devised up to the present time none 

 possess the composition requisite to the multiplication of the bacterio- 

 phage. The sine qua non for multipKcation of the bacteriophage 

 principle, thus permitting a dissolution of the bacteria, in itself a 

 direct result of this multiplication, is the medium provided by living 

 bacteria. It is further necessary, but this is evident a priori, that the 

 bacteriophage principle which one opposes to this bacterium be active 

 against the latter. 



