52 THE BACTERIOPHAGE 



The quantity of the bacteriophagous germs inoculated into 

 the suspension is without influence on the final result. 



Experiment X. The following tubes containing suspensions of the Shiga 

 bacillus are prepared. 



Tubes 1 and 5 contain 250 million per cubic centimeter 

 Tubes 2 and 6 contain 500 million per cubic centimeter 

 Tubes 3 and 7 contain 1000 million per cubic centimeter 

 Tubes 4 and 8 contain 2000 million per cubic centimeter 



Tubes 1 , 2, 3, and 4 are inoculated with . 001 cc . of a culture of the bacte- 

 riophage. Tubes 5, 6, 7, and 8 are inoculated with 0. 5 cc. of the same culture 

 of bacteriophage, or, 500 times as much as in the first set. After eight 

 hours tubes 1 and 5 are limpid. After fourteen hours tubes 1, 2, 5, and 

 6 are limpid. After four days tubes 1, 2, 5, and 6 are still limpid, tube 3 is 

 very slightly cloudy, tubes 4 and 7 are cloudy, and tube 8 is turbid. 



It is thus apparent that lysis is not affected by the number of 

 the ultramicrobes inoculated. We will see in a subsequent 

 chapter which treats of the resistance of the bacteria to the 

 bacteriophage, that contrary to what one would a priori suppose, 

 lysis of a culture is even more perfect when the amount of the 

 bacteriophage added to the suspension is rather small. 



Quite aside from the quantitative relationships, a suspension 

 may vary in "quality." One may work with bacteria of different 

 ages, or with organisms of different strains. In so far as differ- 

 ence in strains is concerned, the course of the phenomenon remains 

 essentially the same — at least in so far as the Shiga bacillus is 

 concerned. We shall see that it is not the same with certain other 

 bacteria, B. typhosus for example. 



With reference to the question of the age of the bacilli subjected 

 to the action of the bacteriophage we have already seen that the 

 younger the bacillus the more readily it is attacked. This dif- 

 ference is due solely to the state of the bacillus itself and not to 

 the soluble substances resulting from its activity; — such substances 

 as result in a "vaccination" of the medium, to use a common ex- 

 pression. The bacteria vaccinate the medium for themselves 

 through the products of their activity. The bacteriophage does 

 the same thing. But the soluble products resulting from their 

 respective activities have nothing in common. 



