BACTERIOLYSIS 



43 



Neutrality to litmus corresponds to about — 16, thus it may- 

 be concluded that the bacteriophage ceases to grow when the 

 medium presents even the slightest acidity. The ultramicrobial 

 elements detected in the slightly acid tubes — those where lysis 

 is not produced — is not an indication of multiplication. They 

 are simply the ultramicrobes which were inoculated, still living. 

 When the medium is decidedly acid even these elements 

 are destroyed. 



The following experiment demonstrates this still better and 

 further confirms the fact that the bacteria constitute the only 

 culture medium for the bacteriophage. 7 



7 As will be shown in a later chapter, bacteria in general are destroyed 

 after exposure for a very short time in physiological saline. On the other 

 hand, the different strains of dysentery bacilli present a variable resistance. 

 Certain races are no longer cultivable in bouillon after an exposure of five 

 to six hours, others remain cultivable up to 45 to 50 days. Experiments 

 involving lysis in physiological saline ought to be performed with strains 

 of the last type. Moreover, it is necessary to employ an extremely active 

 bacteriophage, capable of exerting its action in the minimum length of 

 time — if possible, one capable of producing complete lysis in about three 

 hours. A saline suspension of a bacterial strain of weak vitality may be 

 already sterile after four to five hours, that is to say, the great majority of 

 the bacteria are dead before the lytic process is able to be effected . And the 

 bacteriophage is without action on dead bacteria. 



