138 APPLIED BACTERIOLOGY 



etc., while Algerian sheep, dogs, frogs,* and white rats, are 

 immune. If mice are inoculated with the smallest possible 

 quantity of a culture of anthrax bacilli, they die within 

 twenty-four hours. 



With other animals the fatality or severity of the attack 

 depends upon the age and weight of the animal, and the 

 virulence and quantity of the culture administered. Young 

 animals are more susceptible than old, and the fatal dose 

 also varies proportionately with the weight. 



Animals dead of anthrax present no marked peculiarities 

 to the naked eye ; the spleen is considerably enlarged, and 

 is dark and soft, the liver may be enlarged, and there may 

 be bloody discharges from the orifices of the body. 



In susceptible rodents the subcutaneous connective tissue 

 may be distended with blood serum of a gelatinous con- 

 sistency. Considerable inflammation extends from the 

 point of inoculation in the guinea-pig. If the tissue is 

 examined microscopically, the blood is found to be full 

 of bacilli, which in some places may have so distended the 

 capillaries as to have ruptured them and escaped into the 

 surrounding tissue. Anthrax once introduced may become 

 endemic in a field in the following manner : The infected 

 animal dies, the bacilli in the bloody discharges that come 

 in contact with the air develop spores, which may be blown 

 about on to the surrounding soil, where the organism can 

 lead a saprophytic life. Animals feeding on grass growing 

 about this spot would be liable to infection. The bacilli 

 might be killed in the stomach, but the spores could with- 

 stand its action and enter the circulation. 



People engaged in the woollen industries — wool-sorters, 



etc. — are liable to pulmonary anthrax (malignant pustule) 



from breathing the spores which have been shaken out 



of wool. Wool-sorter's disease is often associated with 



* Unless the frog is heated to 37° C. 



