SPLENIC FEVER 311 



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, 1 and dogs, cats, and Algerian 

 sheep are said to be completely, immune. The chief 

 Veterinary Officer states, however, that a dog and a cat 

 died or anthrax in 1914. 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 tempera- 

 ture ; 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, 0-01 per cent, of potassium 

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

 termed, are practically applied in the preparation of the 

 anthrax vaccine. 



Symptoms of the disease in cattle are not very marked. 

 A beast may appear a little out of sorts and the next 

 day be found dead, or after suffering for a day or two 

 with general malaise, fever, and rigors, and with a san- 

 guineous discharge from the nostrils and bowel, it dies 

 suddenly. Post-mortem, the chief feature that attracts 

 attention is enlargement of the spleen ; the organ may 

 be two or three times larger than normal, is highly con- 



1 Hall, Centr. f. Bakt., Abt. I (Orig.), Ixvi, 1912, p. 293. 



