BACILLAC-E^: THE SPOROGENIC AEROBES 281 



Bacillus (Bacterium) Anthracis. — Pollender in 1849 and 

 Davaine and Rayer in 1850, observed thread-like bodies in the 

 blood of animals dying of anthrax. Robert Koch in 1876 ob- 

 tained pure cultures of the organism, using the aqueous humor of 

 the ox's eye as culture medium. He saw the small rod-shaped 

 bodies found in the anthrax blood elongate into threads in this 

 medium, and observed, the formation of the bright refractive 

 bodies in these threads, which he correctly recognized as spores. 

 Finally by inoculating healthy animals with his cultures he pro- 





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Pig. III. — Anthrax bacilli in the capillaries of the liver of a mouse. 



duced typical anthrax in them, thus proving conclusively for the 

 first time the causal relation of a bacterium to a disease. 



The anthrax bacillus occurs in the blood and throughout the 

 tissues of animals suffering from anthrax, and in the excretions 

 of such animals. Its spores occur on hides and in wool derived 

 from anthrax animals. Furthermore, the soil of fields where 

 anthrax animals have grazed harbors these organisms for many 

 years. It seems probable that the bacilli multiply in the soil 

 during the warm wet seasons and it is certain that the spores 

 may lie dormant for as long as ten years in dry places. 



