252 THE BACTERIOPHAGE 



subcutaneous injection 0.25 cc. of bacteriophage culture. They were 

 tested 25 days later by the inoculation of 2000 surely fatal doses of barbone 

 culture. They resisted without showing the slightest reaction. The 

 controls died in from 18 to 22 hours after the inoculation. 



The injection of the bacteriophage did not produce in any of 

 the animals, even in twenty cubic centimeter doses, the slightest 

 reaction, either local or general. The temperature curve follow- 

 ing the immunizing injection could be superimposed throughout 

 on the curves of normal untreated animals. From this it is clear 

 that, contrary to general belief, an immunity bordering on the 

 refractory state may be acquired without the manifestation of 

 the slightest reaction. 



During the course of these experiments aphthous fever made 

 its appearance at Saigon. The animals in the course of immuniza- 

 tion contracted it but this complication in no instance exerted 

 any influence upon the development of immunity to barbone. 



From these different experiments it may be deduced that with 

 a large dose of bacteriophage culture the immunity is slow in 

 being established ; about forty to sixty days with a dose of twenty 

 cubic centimeters, more than twenty-eight days with 5 cc. With 

 0.25 cc. it is not effective for all animals until about the twentieth 

 day. It then permits them to resist without apparent discomfort 

 two thousand surely fatal doses of the culture of barbone, that 

 is to say, the immunity conferred borders on the refractory state. 

 With the minimal dose of 0.04 cc, or less than a normal drop, a 

 solid immunity is acquired by the fourth day. We are not con- 

 cerned for the moment with the steers which have resisted after 

 twenty-four hours; the immunity which they enjoy is of a differ- 

 ent order, as we will see later. 



We have seen in Part I of this text that the serum of rabbits 

 which have received four injections of bacteriophage culture 

 possesses the property of sensitizing the animals against the bac- 

 teria for which the bacteriophage injected was active. The de- 

 lay in the establishment of the immunity as a result of the in- 

 jection of large doses of antibarbone bacteriophage culture ought 

 to induce this same phenomenon. The injection produces in 

 the animals two phenomena of different orders: an immunity 

 and a sensitization which varies in intensity according to the 



