THE BACTERIOPHAGE IN DISEASE 185 



at the beginning of the disease. From all the organs a bacteriophage 

 was isolated presenting the same characters as that which had been 

 isolated from the stools and whose virulence has been indicated. 



This case, altogether exceptional (I believe that it is the first 

 case reported of a B. dysenteriae Hiss septicemia) is very interest- 

 ing for it shows in an unquestioned manner the role that the bac- 

 teriophage plays in the defense of the organism. In all of the 

 cases examined heretofore we have seen, either recovery starting 

 from the time when the bacteriophage had acquired sufficient 

 virulence to dominate the pathogenic bacillus, or death in the 

 case of the failure of adaptation. In this last case, the bacteria 

 developed a refractory condition, the bacteriophage was overcome 

 and remained without action whatever its virulence may have 

 been. The barrier thus being lacking, the bacteria developed 

 freely and invaded the entire organism. The patient succumbed 

 to a septicemia with the Hiss bacillus. 



This exceptional case provides us with new information. A 

 bacterium is pathogenic for a given organism if it secretes sub- 

 stances toxic for the cells of this organism. It is the more viru- 

 lent the more capable it is of development at the expense of this 

 organism. The dysentery bacilli are pathogens because of this 

 secretion of toxic substances, for they do not invade the organism, 

 but remain localized in the intestine and in the intestinal mucosa. 

 Nevertheless, in the case of the woman Desp. . . . the Hiss 

 strain was accidentally endowed with an extreme virulence, 

 and this solely because the bacteriophage had been overcome. 

 This suggests an idea which we will have occasion to confirm in 

 the following chapters, — that the virulence of a bacterium at 

 any given moment is the greater if its resistance to the bacterio- 

 phage is at this time high. 



The case Desp. ... is exceptional. As a general rule death 

 occurs in dysentery, not because of the acquisition by the bac- 

 terium of a refractory condition, but by a failure of the bacterio- 

 phage to adapt itself to bacteriophagy toward the pathogenic 

 organism. In the four cases mentioned above which Were fatal, 

 a bacteriophage active for I the Shiga bacillus could not be 

 isolated at any period of the disease. 



