IMMUNIZATION WITH BACTERIOPHAGE SUSPENSIONS 525 



We have seen in the discussion of the phenomenon of antiphylaxis 

 that the serum of rabbits which have received several injections of 

 bacteriophage suspension possesses the property of sensitizing the 

 animals against the bacteria for which the bacteriophage injected was 

 active. The delay in the establishment of the immunity as a result 

 of the injection of large doses of Barbone-bacteriophage 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 dose inoculated. With a small 

 dose the first surpasses the second which disappears quickly; with a 

 large dose, on the contrary, the inhibitive action persists for a very 

 long time — about sixty days for an injection of 20 cc. 



The experiments further show that the immunity conferred by the 

 injection of suspensions of the bacteriophage is absolute when once 

 established, and is negative during the period of incubation. There 

 is no intermediary state. The animals, young or old, which receive 

 the test inoculation during the period of incubation die, with very 

 few exceptions, in the same time as the controls, even if this inocula- 

 tion is made at a time very close to that where all the immunized 

 animals resist. On the other hand, all those which are tested after 

 the incubation period resist without presenting any apparent malaise, 

 whatever the test dose may be. It seems indeed, as a result of these 

 findings, that after an incubation time, more or less protracted ac- 

 cording to the amount of bacteriophage injected, a period during 

 which the animal remains as sensitive as a normal animal, the im- 

 munity increases very rapidly once its manifestation has commenced. 

 In a word, the release of immunity is abrupt. 



Effect of the age of the animals on the acquisition of immunity 



We have seen that thirty-two animals, steers, young buffaloes, or 

 adult buffaloes of less than twelve years, have all acquired an immunity 

 that approaches the refractory condition within twenty days following 

 the injection of 0.25 cc. of the bacteriophage suspension. We wished 

 to see how this would compare with the results obtained in old animals. 



Three buffaloes between fourteen and sixteen years and five very old 

 animals no longer working and certainly more than twenty years old* 



* The buffalo usually lives about twenty-five or thirty years. The Annamite 

 never kills a buffalo; old and no longer able to work, it is fed and cared for as 

 well as are the younger animals. The attachment of the natives for these buff a- 



