BACILLUS ANTHRACIS. 145 



Immunization. Pasteur has demonstrated that attenuated 

 cultures of the Bacillus antliracis when injected into susceptible 

 animals are capable of protecting the same against the action 

 of the virulent bacillus, subsequently inoculated, and against 

 an attack of the disease itself. His inoculation or vaccination 

 consists in using cultures that have been attenuated by means 

 of heat. For that purpose the bacteria are cultivated in 

 large Erlenmeyer flasks at a temperature of between 42 

 and 43 C., for a period of time varying from ten to thirty 

 days, when they do not form spores. The pathogenic power 

 of these cultures is tested every few days on guinea-pigs 

 and rabbits, and when a small dose of the culture will kill 

 a mouse and a guinea-pig, but fails to kill a rat, it is called 

 vaccine No. 2. In a lew days more this same culture will 

 fail to kill a guinea-pig, but will still kill a mouse ; it is 

 then vaccine No. 1. 



In veterinary practice large animals, as sheep, cattle, and 

 horses, are inoculated with aseptic precautions with 3 c.c. of 

 vaccine No. 1. Then they show little or no reaction. In ten 

 days or two weeks more they are inoculated with vaccine 

 No. 2, when they again show some little reaction ; and a few 

 days after this second vaccination they are able to withstand 

 an inoculation of virulent cultures of the bacilli. This mode 

 of vaccination has been of inestimable value by making it 

 possible to stop the ravages of epidemics of anthrax. It is 

 practised extensively in countries like France, Germany, and 

 Russia, where the disease is very prevalent among sheep and 

 cattle. In the Southern States the author has had occasion 

 to use it extensively during the last few years, with decided 

 benefit. 



The manner of infection among animals with the bacilli has 

 not been fully demonstrated. It seems to occur in the ma- 

 jority of cases from the soil, possibly from the fact that 

 animals which have died of the disease have been buried too 

 near the surface. It is therefore advisable that animals dead 

 from anthrax be buried at a depth not less than six feet from 

 the surface, as the soil at that depth is 15 C. even in sum- 

 10 M. B. 



