40 THE BACTERIOPHAGE 



ject to attack. For after a twenty-four hour stay in fluoride 

 bouillon a normal culture will be secured by transfer from this 

 medium into ordinary bouillon, and this culture is normally 

 lysed by the bacteriophage. 



This will be discussed later, accepting for the moment that here 

 is a medium in which the Shiga organism remains alive for at 

 least thirty-six hours, in which the bacteriophage likewise remains 

 alive, which exerts no inhibitory action on the diastases, but in 

 which the bacteriophage fails to multiply. 



THE EFFECT OF THE CONDITION OF THE BACTERIA 



These experiments have been conducted so as to determine the 

 effect of the state of the bacterium upon the lytic process. Since 

 lysis is the result of the multiplication of the ultramicrobes the 

 lytic process will not be complete unless all of the bacteria present 

 in the suspension are capable of being attacked. 



Instead of taking a suspension prepared from a young culture 

 we may inoculate the bacteriophage into a fifteen-day old broth 

 culture. A clearing of the medium, a partial lysis, results but a 

 certain degree of turbidity remains. Nevertheless, it is possible 

 to continue to use such a medium, making as many passages as 

 may be desired. Some tube of the series when planted on agar 

 or in bouillon will remain sterile, and a drop of this tube inoculated 

 into a suspension of young bacilli will produce perfect lysis. In 

 the old culture, then, the bacteriophage multiplies normally 

 but does not produce lysis, or at least, the lysis is incomplete. 

 What is the explanation of this reaction? To answer this it is 

 sufficient to compare the results of counting the total number of 

 bacilli existing in an old culture (this can be done by the method 

 of counting cells) with the results secured by counting the viable 

 organisms only (done by the plating method). For a confirma- 

 tion of this type, a Shiga culture in Martin's bouillon is made, 

 incubated for fourteen hours, and allowed to stand at laboratory 

 temperature for fifteen days. The total count of bacillary bodies 

 will be about 625 millions; that of the viable bacilli, that is, those 

 capable of yielding colonies when transferred to agar, will be 

 about two millions in each half cubic centimeter of culture. Now, 

 as we have seen, the bacteriophage is only able to develop at the 



