BACILLUS ANTHRACIS. 313 



immune; white ones always succumb, at least to a manifold 

 infection. Swine, dogs, hens, and pigeons enjoy a very 

 considerable, and the adult animals not infrequently a 

 complete, immunity. (Regarding the variation of the 

 same, see p. 96. ) Frogs are killed, when kept warm, by 

 ordinary anthrax; or, without warming, by anthrax 

 adapted to cold temperatures (Dieudonne) (p. 45). For 

 the susceptible animals, every possible method of intro- 

 duction of anthrax bacilli and spores is successful. Feed- 

 ing spore-free bacilli is especially uncertain (gastric juice 

 kills); subcutaneous, intravenous, intraperitoneal, espe- 

 cially respiratory introductions of bacilli or spores are suc- 

 cessful. After subcutaneous inoculation the animals 

 show no symptoms for several hours. Frank and Lu- 

 barsch found that in the inoculation of guinea-pigs with 

 an anthrax culture, which killed in thirty-four hours 

 after subcutaneous infection of the animal, the bacilli 

 first appeared in the blood seventeen to twenty-two hours 

 after the infection. The section of the infected animal 

 usually presents the picture of a septicemia. Besides 

 hemorrhagic edema of the subcutaneous tissue (especially 

 in the region of the point of inoculation), effusion into 

 the body cavities, and splenic tumor, there are no espe- 

 cially characteristic changes. The bacilli are found in the 

 blood, local edema, and in all the organs, especially in the 

 spleen, but in variable numbers. 



Variations in the virulence of the B. anthracis have 

 been especially carefully studied. The virulence in ordi- 

 nary cultivation is not very easily nor very much reduced, 

 yet it is very easily attenuated by heat, chemicals, etc., 

 until no virulence remains. (See p. 94.) Tavel once 

 observed an anthrax bacillus (originating from smoked 

 ham) which killed mice only after many as much as 

 thirty- two days, and yet a man was killed from eating 

 this ham. 



By inoculation of cows and sheep with cultures of little 

 virulence there is obtained a slight, and by subsequent 

 inoculation with more virulent cultures a pronounced, 

 immunity (similar experiments fail in mice and guinea- 

 pigs, but sometimes succeed in rabbits), which, indeed, 

 does not protect against the deleterious effect of feeding 



