160 APPLIED BACTERIOLOGY 



Pathogenesis. — It occurs in great numbers in the blood of 

 animals wbich have died of anthrax. In one instance it 

 was found in the mud at the bottom of a well in Southern 

 Kussia. Animals drinking at this particular well had 

 become infected, and a search was accordingly made for 

 the specific organism. 



Both bacilli and spores remain in fleeces, and may 

 thus transmit the disease to those engaged in handling 

 them. 



The Bacillus anthracis produces anthrax or splenic fever 

 in cattle and man, and malignant pustule, or wool-sorter's 

 disease, in man. It is pathogenic to the following animals, 

 which are arranged roughly in order of their susceptibility : 

 mice, guinea-pigs, rabbits, cattle, horses, human beings, 

 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 

 * Unless the frog is heated to 37° C. 



