524 THE BACTERIOPHAGE AND ITS BEHAVIOR 



fatal doses of culture. All resisted without showing any reaction. 

 Five control animals died, all between 16 and 23 hours after the inocu- 

 lation of culture. 



IV. Eight steers received 0.04 cc. of bacteriophage suspension. 

 They were tested after a variable number of days by the inoculation of 

 5 surely fatal doses of virulent culture. The results are shown in 

 table 64. The last steer, No. 102, was tested 60 days after the injec- 

 tion of the immunizing dose by the inoculation of 50 surely fatal doses 

 of culture. It resisted without showing any disturbance. 



V. A last experiment, as a control, was performed with a view to 

 testing the practical application of immunization of buffaloes against 

 barbone by M. Le Louet after my departure from Saigon. Twelve 

 steers received by subcutaneous injection 0.25 cc. of bacteriophage 

 suspension. 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 20 cc. doses, the slightest reaction, either local or 

 general. The temperature curve following 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 im- 

 munity 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 immunization 

 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 suspension the immunity is slow in being 

 estabUshed; about forty to sixty days with a dose of 20 cc, 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 concerned for the moment with the steers which have re- 

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

 different order, as we will see later. 



