412 PA THOGENIC BA CTERIA. 



Pasteur discovered that when cultures are allowed to 

 remain undisturbed for several months, their virulence 

 is greatly lessened, and new cultures planted from these 

 are also attenuated. When chickens are inoculated with 

 such cultures, no other change occurs than a local in- 

 flammatory reaction by which the birds are protected 

 against virulent bacilli. From this observation Pasteur 

 worked out a system of protective vaccination in which 

 fowls can first be inoculated with very weak, then with 

 stronger, and finally with highly virulent cultures, with 

 a resulting protection and immunity. Unfortunately, 

 the method is too complicated to be very practical. Use 

 has, however, been made of the ability of this bacillus 

 to kill rabbits, and in Australia, where they are pests, 

 they are being exterminated by the use of bouillon cul- 

 ture. It is estimated that two gallons of bouillon culture 

 will destroy 20,000 rabbits irrespective of infection by 

 contagion. 



The bacillus of chicken-cholera seems not only to be 

 specific for that disease, but seems able, when properly 

 introduced into various other animals, to produce several 

 different diseases. Indeed, no little confusion has arisen 

 in bacteriology by the description of what is now pretty 

 generally accepted to be this very bacillus under the 

 various names of bacillus of rabbit-septicemia (Koch), 

 Bacillus cuniculicida (Fliigge), bacillus of swine-plague 

 (Loffler and Schiitz), bacillus of lt Wildseuche" (Hiippe), 

 bacillus of " Biiffelseuche " (Oriste-Armanni), etc. 



