514 THE BACTERIOPHAGE AND ITS BEHAVIOR 



2 or 3 fowls, each ingested about 1 cc. of the bacteriophage suspension. 

 Seven months later no new case had developed since the time of the 

 ingestion. 



B. The same test was performed on October 15 on about 100 chickens 

 on a neighboring farm where typhosis had been present for several 

 months. The epizootic was immediately and completely checked. 



In both of these cases the disease continued to spread throughout 

 the neighboring poultry-yards that were held as controls. 



It appears needless to multiply such examples. In all cases the 

 picture has been the same. The epizootic disappeared from the time 

 that the bacteriophage virulent for the pathogenic bacterium, the 

 cause of the epizootic, had been introduced into the organism of the 

 susceptible animal, whether this introduction was by injection or inges- 

 tion. We will see later that this last mode of administration is some- 

 what less efficient than injection. 



On the contrary, injections of a suspension of a bacteriophage active 

 for B. gallinaru7n, the specific cause of typhosis, had in general, no 

 effect when the epizootic was a paratyphosis, particularly in the case 

 of infections due to B. pfaffi. In practise, it is only necessary to inject 

 a mixture of different races of bacteriophage active for the various 

 pathogenic bacteria that may produce the epizootic. This mixture 

 should also include a race active for chicken cholera. It will be very 

 easy to accomplish this, for the dose of 0.5 cc. which I have arbitrarily 

 adopted is indeed much larger than necessary, as we will see. Even 

 in mixing five or six different strains of bacteriophage, the quantity 

 necessary to effect immunization is not more than a fraction of a 

 cubic centimeter. 



In the course of the experunents cited there has been no selection. 

 All of the animals of the poultry-yard, even though they were mori- 

 bund, received the immunizing injection. About 100 sick chickens 

 have therefore been injected, and the mortality among these has been 

 5 per cent. This is an appreciable reduction since the mortality 

 among affected animals varies from 100 per cent at the beginning of 

 the epizootic to 95 per cent, when, after some weeks, the disease 

 appears only in sporadic cases. 



A suspension of the bacteriophage, as we have shown in several 

 ways, is composed of bacteriophage corpuscles suspended in a medium 

 containing the dissolved bacterial substance, the bacteria which have 

 been destroyed by the action of the protobes. What, among these 

 different principles, is the one which plays the active role in the protec- 



