256 A MANUAL OF BACTERIOLOGY 



Certain anthrax-like bacilli have been described and 

 have to be distinguished from B. anthracis, e.g. B. pseudo- 

 anthracis, B. anthracoides, B. anthracis similis. These are 

 non-pathogenic and are haemolytic for rabbit, sheep, horse, 

 and ox corpuscles, while the B. anthracis is non-hsemolytic. 1 

 The former form no capsule in the animal nor when 

 cultivated in an inactivated serum, anthrax forms a 

 capsule in such circumstances. 



Pathogenicity. The anthrax bacillus is pathogenic for 

 man, cattle, sheep, goats, rabbits, guinea-pigs, and mice. 

 The horse and the pig are also susceptible ; but adult 

 white rats are partially, 2 and dogs, cats, and Algerian 

 sheep are completely, immune. 



Inoculated anthrax is rarely fatal to cattle in India 

 (Holmes). 



Young white rats, or rats fatigued by muscular work, 

 can be infected, and frogs and fish, though immune under 

 ordinary conditions, can be rendered susceptible by raising 

 the temperature of their environment. Birds, such as 

 fowls and pigeons, are also almost insusceptible, but may 

 be rendered susceptible by lowering their temperature ; 

 smaller birds, such as sparrows, are more susceptible. 

 The virulence varies considerably and may be artificially 

 modified in many ways : by passing through a series of 

 susceptible animals it is heightened, by growing in the 

 body of an insusceptible animal it is lowered, and the 

 latter result is also obtained by cultivating for two or 

 three weeks at a temperature of 42 to 45 C., or by the 

 addition of certain chemical substances to the culture 

 medium for example, O01 per cent, of potassium bi- 

 chromate. These methods of " attenuation," as it is 

 termed, are practically applied in the preparation of the 

 anthrax vaccine. 



1 Jarmai, Centr. f. Bakt., Abt. I (Orig.), Ixx, 1913, p. 72 



2 Hall, Ibid. Ixvi, 1912, p. 293. 



