BACILLUS CHAW EI 501 
there is in it a sanguineous exudate which contains relatively few 
leukocytes. The edematous area is crepitant, due to accumulated 
gas bubbles, and there is a rather strong odor of butyric acid. The 
incubation period is from one to three days. 
Sporulation does not take place in the tissues of the living animal, 
but it is said to take place in from twenty-four to forty-eight hours 
after death. If the spores are washed free from toxin anrl other bac- 
teria they are said not to be infective for experimental animals, accord- 
ing to Leclainche and Vallee.^ 
Vaccine.— One attack of symptomatic anthrax appears to confer 
immunity to subsequent attacks. Young cattle are usually infected; 
older ones appear to be more resistant to infection. A Aaccine has been 
prepared which protects the animal from infection. The general pro- 
cess of manufacture is to remove the infected tissues of animals dead 
of symptomatic anthrax and dry them under aseptic conditions at 
37° C.- From this dried tissue two vaccines are made up, the first 
being prepared by mixing the dried powder with sterile water^ to form 
a paste, which is heated to 100° C. for six hours. This is the first 
vaccine, which will not kill experimental animals. It is injected at the 
tip of the tail. In seven days a second vaccine (prepared from the 
same powder and heated to 94° C. for four hours) is injected in the 
same manner. This vaccine will ordinarily kill small experimental 
animals. These two vaccines or modifications of them are widely used 
for protecting cattle against blackleg. 
1 Ann. Inst. Pasteur, 1900, 14, 202. 
2 This temperature does not diminish the virulence of the bacteria; the potency of 
the dried virus remains unimpaired for eighteen to twenty-four months. 
3 Two parts sterile water to 1 part of dried powder. 
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