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-one days. 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. Bats, cats, dogs, chick- 



