554 BACTERIOLOGY. 
ated virus’’ by keeping his cultures for a considerable 
time before replanting them upon fresh soil. Cham- 
berland and Roux have shown that cultivation in the 
presence of certain chemical substances added to the 
culture medium, as bichromate of potassium, causes an 
attenuation of virulence. Attenuation of pathogenic 
power is also effected by cultivation in the body of a 
non-susceptible animal, like the frog (Lubarsch, Pe- 
truschky); or in the blood of a rat (Behring); by ex- 
posure to sunlight (Arloing); to heat, 50° C. for 
eighteen minutes; and by compressed air (Chauveau). 
Anthrax cultures containing spores retain their vital- 
ity for years; in the absence of spores the vitality is 
much more rapidly lost. When grown in liquids rich 
in albumin the bacilli attain a considerable degree of 
resistance; thus dried anthrax blood has been found to 
retain its virulence for sixty days, while dried bouillon 
cultures only did so for twenty-onedays. Dried anthrax 
spores may be preserved for many years without losing 
their vitality or virulence. They also resist a com- 
paratively high temperature. Exposed in dry air they 
require a temperature of 140° C. maintained for three 
hours to destroy them; but suspended in a liquid they 
are destroyed in four minutes by a temperature of 
100° C. The bacilli, in the absence of spores, are de- 
stroyed in ten minutes by a temperature of 54° C. 
Anthrax spores in a desiccated condition are destroyed 
in four hours when exposed to the action of direct 
sunlight, only after several weeks in diffuse daylight 
(Kruse). 
Pathogenesis. The anthrax bacillus is pathogenic for 
cattle, sheep (except the Algerian race), horses, swine, 
mice, guinea-pigs, and rabbits. Rats, cats, dogs, chick- 
