526 THE BACTERIOPHAGE AND ITS BEHAVIOR 



received 0.25 cc. of the suspension of bacteriophage. All eight were 

 tested forty-three days later by the inoculation of 1000 surely fatal 

 doses of bacterium barbone culture at the same time as a normal con- 

 trol animal. This last died in seventeen hours. One of the three 

 youngest buffaloes showed no reaction other than a transitory edema 

 at the site of the inoculation, the other two showed a voluminous edema 

 and were obviously sick, but all three recovered and could be considered 

 normal six days after the test inoculation. The five very old buffaloes 

 succumbed after 48, 53, 54, 60, and 142 hours; that is, after a time 

 considerably longer than the control. Fifteen young animals im- 

 munized and tested at the same time failed to show any reaction to 

 the test injection. 



It is evident that although the test dose was enormous, that did not 

 alter the fact that in the old animals the acquisition of immunity was 

 much more difficult, somewhat in proportion to the age. The relative 

 immunity against an extremely severe experimental test is observed 

 only in these old animals; with the young or with adults in the prime 

 of life, the immunity, as we have seen, is absent during the incubation 

 period and complete once it has appeared at all. 



The duration of the im7nunity 



After my departure from Indo-China, my collaborator M. Le Louet, 

 continued the experiments with a view to ascertaining the duration 

 of the immunity produced by the inoculation of a suspension of the 

 bacteriophage. In January, 1921, he injected 15 steers, aged about 

 one year, with a cubic centimeter of a suspension of the bacteriophage 

 that was about one month old, that is, a bouillon culture of the bacterium 

 of barbone which had been dissolved by the bacteriophage one month 

 before use. In March, 1922, all of the animals were tested, along with 

 nine controls, by the inoculation of 0.1 cc. of a virulent culture of the 

 bacterium of barbone. The virulence of this culture was such that in 

 amounts of 0.002 cc. it regularly killed steers in less than thirty-six 

 hours. Of the animals thus infected all of the controls died in from 

 seventeen to twenty-three hours after the injection, while of the vac- 

 cinated animals ten resisted without any evident reaction and five died 

 in from two to five days after inoculation. 



loes is such that it is difficult to find a person who will sell one of these animals. 

 Those which served in the experiments were procured, some through the agency 

 of the Governor of Cochin-China, M. le Gallen; others by M. Priv4, Director of 

 the plantations of An Loc and Suzannah, without considering the possible loss. I 

 offer them my sincere thanks. 



