240 THE BACTERIOPHAGE 



degree, attack the bacillus of Flexner, or that of Hiss, or both at 

 once. It is difficult to explain in any other manner the simul- 

 taneous appearance of virulence for several bacilli of the same 

 group. These co-virulences extend generally to the bacillary 

 species which show among themselves the phenomenon of co- 

 agglutination. 



With man, also, much less exposed to contagion because of 

 his mode of life, the activity of the bacteriophagous ultramicrobe 

 for the typhoid, paratyphoids, and dysentery bacilli is very fre- 

 quent. Each time that it occurs it can only be the indication of 

 an incipient infection, which usually passes undetected. The 

 bacteriophage, as a result of its rapid adaptation destroys the 

 invading bacilli before they can multiply. 3 



The ultramicrobial bacteriophage is a normal inhabitant of 

 the intestine of all animals. Furthermore, as we have seen, 

 it has a great vitality. Thanks to its minuteness it is able cer- 

 tainly to filter through soils which arrest bacteria. Everything 

 shows that it must be extremely widely disseminated in the ex- 

 ternal world. Everything which at any time may be contami- 

 nated by the excreta of any animal must contain it. It must be 

 particularly abundant where there are living organisms; in the 

 soil, in rivers, and in the ocean. 4 And everywhere it must be 

 the principal factor in the destruction of bacteria. 



* It seems then, even in animals considered refractory, that there occurs 

 at times a delay in the adaptation of the bacteriophage. This is noted, 

 for example, in cases of dysentery (Shiga bacillus) in horses in tropical 

 countries. 



4 1 have isolated a strain of the bacteriophage active for B. coli from a 

 specimen of sea-water taken off from the estuary of Mekong, and a second 

 taken from the Mediterranean off Marseilles. I was unable to isolate a 

 strain from a specimen of water from the Indian Ocean at a point approxi- 

 mately 60° East longitude and 10° North latitude. Dumas has isolated 

 strains from a specimen of garden soil and from the tap-water in Paris. 

 Beckerich and Hauduroy, at the Institute of Hygiene at Strasbourg, have 

 isolated a number of strains active for B. coli, for B. typhosus, and for dys- 

 entery organisms, from different specimens of soil, from the water of the 

 111, and from Rhine water after sand filtration. 



These findings allow us to draw an important conclusion, which has a 

 bearing on hygiene. The bacteriophage exercises a preponderant role in 

 the defense of the organism. It is therefore of great interest that drinking 



