344 



THE BACTERIOPHAGE AND ITS BEHAVIOR 



IV. I have found that the bacteriophage can develop a tolerance to 

 the action of acids.^'^^ jf successive passages are made in media with 

 increasing degrees of acidity a point is reached where the bacterio- 

 phage is perfectly active in media, which, with an unadapted bacterio- 

 phage of the same race, prevents multiplication. 



Asheshov-^ has performed the following experiments, which likewise 

 demonstrate the acquisition of a tolerance to acidity. He chose a race 



* The degree of turbidity of the liquid, represented in millions of bacteria 

 per cubic centimeter, based on comparison with titrated control tubes, obviously 

 shows the degree of bacteriophagic action, or the inhibition of this action. 



of bacteriophage (Flexner) which caused a weak clearing of a bacterial 

 suspension in a neutral (pH 7.0) medium, and which was completely 

 inactive in acidified media (glucose) . The effectiveness of the bacterio- 

 phage in these media is shown in table 33. 



After seven passages in bouillon with an initial reaction of pH 7.0 

 this bacteriophage reached the point where it would induce almost as 

 complete a bacteriophagy as that occurring in alkaline bouillon. At the 



