140 MEDICAL BACTERIOLOGY 



Milk is acidulated and coagulated. 



Resistance. Bacillus anthracis is only slightly more resistant to heat and 

 chemical germicides than the typhoid bacillus. 



The spores are very resistant to all germicidal agents; exposure to strong 

 chemicals, direct sunlight and drying is withstood for a long time. 'An expo- 

 sure of several hours at i5oC. to 20oC. is required to destroy spores in a hot- 

 air sterilizer; boiling for i hour sometimes fails to kill them; steam under 15 

 pounds pressure destroys anthrax spores in a few minutes. 



Toxin. Bacillus anthracis produces no extracellular toxin. 



Agglutinins and lysins are not demonstrable in the blood of either infected 

 or immunized animals. 



Pathogenesis. Many domestic animals are very susceptible to anthrax, 

 usually contracting the infection through eating from pastures contaminated 

 with anthrax spores. The feces from such animals contains spores. Minute 

 amounts of bacillus anthracis or spores injected into rabbits or guinea-pigs 

 produce death. 



In man infection is almost entirely confined to those engaged in handling 

 hides, wool or cattle. 



Wool sorters are usually infected through the respiratory tract and suffer 

 pulmonic involvement, followed, in most cases, by bacteremia and death. 

 Those who handle hides are usually infected through abrasions of the skin, a 

 lesion known as malignant pustule developing at the point of inoculation. The 

 infection may remain localized or the bacteria may enter the blood-stream. 

 The mortality is high 25 per cent, or more. 



Infection through the alimentary canal in man is exceedingly rare. 



Diagnosis. When the disease is localized bacteria may be obtained from the 

 pustule and adjacent tissue; if bacteremia occurs organisms may be obtained 

 from any blood-vessels even capillaries are clogged with them. 



Bacillus anthracis is easily identified by its morphology and growth on plain 

 agar, gelatin or bouillon. 



