446 THE BACTERIOPHAGE AND ITS BEHAVIOR 



In this case the struggle was prolonged, with fluctuations due to the 

 mixed cultures formed in the intestine. The condition of the patient 

 registered faithfully the changes in the struggle. It may be noted 

 particularly that the bacteriophage manifests a transitory activity on 

 the eleventh day of the disease and the stools temporarily lose their 

 bloody character. But the baciUus increases its resistance and this 

 permits it to develop, and blood reappears in the stools. The disease 

 is only definitely overcome at a time when the virulence of the bacterio- 

 phage is sufficiently high to dominate the resistance of the bacterium. 



In addition to the five cases which have just been presented as il- 

 lustrating the manner in which the bacteriophage behaves, a number of 

 other cases have been followed, both in France and in Indo-China. Of 

 these other cases, 17 which varied materially in the severity of the in- 

 fection, were examined daily throughout the period of the disease, and 

 29 more were examined less frequently. 



In all of the cases the intestinal bacteriophage showed changes in its 

 virulence comparable to those recorded above. These changes may be 

 summarized as follows: 



1. In case of recovery, the virulence of the bacteriophage commences 

 to manifest itself in a marked manner toward B. coli. 



2. The virulence next extends to the type strain of the Shiga bacillus, 

 that is to say, toward a strain which has been for a long time under 

 artificial cultivation and which, for this reason, has been deprived of 

 much of its resistance. 



3. It manifests itself next, more or less quickly, toward the Shiga 

 bacillus isolated from the patient himself at the onset of the disease.* 



4. In all cases the fluctuations in the virulence, as well as the fluctua- 

 tions in the resistance of the bacteria, parallel the state of the patient, 

 and the onset of improvement coincides with the moment when the 

 virulence of the bacteriophage dominates clearly the resistance of the 

 bacterium. We thus see reproduced in vivo the same phenomena as 

 we have observed in vitro; permanent and complete dissolution, mixed 

 cultures with negative transfers, mixed cultures with alternations in the 

 dominating force. 



In Indo-China an opportunity was afforded to follow four fatal 



* Obviously it is necessary to preserve this strain without replanting. The 

 isolated colonies obtained on the original plates are planted on several agar tubes 

 and a portion is taken from these tubes for the tests conducted during the course 

 of the disease. It is well-known that resistance is attenuated by successive trans- 

 plantations. 



