186 THE BACTERIOPHAGE 



During the course of the epidemic of dysentery which occurred 

 in the region of Paris during the early autumn of 1918, an oppor- 

 tunity was given to observe twenty-nine cases of benign diarrhea. 

 In all of these cases a bacteriophage of very high or extreme ac- 

 tivity for the Shiga bacillus was isolated from stools taken the 

 day after the malaise. This bacillus was the cause of all the 

 severe cases studied at this same time. 



Living at this time in a locality (Meulan) where several severe 

 cases of dysentery were noted together with a large number of 

 cases of transitory diarrhea, I examined the stools of nine per- 

 sons who were healthy, but who lived in contact with individuals 

 who had had dysentery. From these nine individuals a bacterio- 

 phage of average or high activity for the Shiga bacillus was iso- 

 lated. We have noted above that the same fact was observed 

 in the institution where Germaine Mel. . . . had contracted 

 dysentery. Individuals who are exposed to infection and who 

 resist show therefore in their intestine a bacteriophage virulent 

 for the causative pathogenic bacillus, exactly like the affected 

 individuals who recover. 



As a result, in an epidemic period the simple cases of diarrhea 

 must in reality be cases of aborted bacillary dysentery, thanks 

 to the rapidity with which the intestinal bacteriophage adapts 

 itself to bacteriophagy against pathogenic bacteria. And healthy 

 individuals, living in contact with affected people, are only spared 

 by virtue of a still more rapid adaptation occurring before mor- 

 bid symptoms appear. We will find comparable facts in all the 

 diseases which we will discuss. 



To summarize : the pathogenesis and the pathology of bacillary 

 dysentery are dominated by two factors, operating in different 

 directions; the dysentery bacillus as the pathogenic agent and 

 the bacteriophage as the agent of immunity. The history of a 

 case of dysentery is only the story of the struggle, occurring with- 

 in the body, between these two factors, and the condition of the 

 patient faithfully reflects the vicissitudes of the struggle. 



In case of a rapid enhancement in the virulence of the intestinal 

 bacteriophage toward a pathogenic bacillus, the latter is unable 

 to develop a resistance and is destroyed in the struggle, so that 

 the disease aborts before the appearance of any symptoms or 

 manifests itself only in a transitory disturbance. 



