IMMUNIZATION BY MEANS OF THE BACTERIOPHAGE 249 



The strain of bacteriophage employed for the preparation of 

 the cultures destined for use in the immunization experiments 

 had been isolated from the feces of a buffalo which had passed 

 unaffected through the epizootic mentioned in the preceding 

 chapter. This bacteriophage possessed, when derived from the 

 organism, a strong virulence (+ + +) for the bacterium of bar- 

 bone. After about ten passages in vitro the virulence became 

 extreme (+ + + +), and at this time it was used. 



A fairly turbid bouillon culture of the bacterium of barbone 

 about 12 hours old received one drop of the previously described 

 active (+ + + +) culture of anti-barbone bacteriophage. After 

 about 12 hours the medium became perfectly limpid. This 

 culture was filtered through a Chamberland filter (L 3 ) and dis- 

 tributed into ampoules, which were sealed. I would call atten- 

 tion to the necessity of employing only cultures with which the 

 lysis of the bacteria has been complete. Such cultures ought, 

 moreover, to be filtered because of the fact that a secondary 

 culture may develop in some of the tubes. 



The cultures of anti-barbone bacteriophage have been used 

 after a variable length of time, — from twenty days to five months 

 after their preparation. No difference nas ever been observed 

 in their mode of action, whatever the time elapsed between the 

 date of preparation and the time of use. 



All of the experiments, except those dealing with the effect of 

 the age of the animal upon the development of immunity, have 

 been effected on steers of the indigenous race, in a perfect state 

 of health, aged from twelve to eighteen months, and of an average 

 weight of 100 kgms., 3 and on buffaloes aged from one to twelve 

 years. The bovine race and the buffalo are equally susceptible 

 to barbone. In Egypt, Piot has seen the herds of cattle deci- 

 mated to the same extent as the herds of buffalo. According 

 to our observations the buffalo may be rather easier to immunize 

 than cattle. 



Let us consider first the experiments conducted for the purpose 

 of determining what conditions control the development of the 

 immunity resulting from the injection of a culture of the bacterio- 



3 The race in Indo-China is of small size. 



