' CHAPTER XXI 



BACILLUS ANTHRACIS. BACILLUS MALLEI. BACIL- 

 LUS PYOCYANEUS. BACILLUS PROTEUS. 



B. Anthracis. Anthrax or splenic fever is a disease occurring 

 especially in sheep and cattle, although many of the lower animals 

 are susceptible. Infection occasionally appears in human beings, 

 but it is never transmitted from man to man ; it is always con- 

 tracted directly or indirectly from animals. 



Anthrax has undoubtedly occurred among cattle from the 

 earliest times. It was the first infectious disease shown to be 

 caused by a specific microorganism and consequently it has been 

 one of the most studied of all bacterial diseases. Pollender in 

 1849 described rod-shaped bodies which were contained in the 

 blood of infected animals and suggested that they might be the 

 cause of the disease. In 1863 Davaine demonstrated by inocula- 

 tion experiments that blood containing these bodies invariably 

 produced anthrax. He therefore concluded they were bacteria 

 and suggested the name B. anthracis. Later, in 1877, Koch 

 confirmed Davaine's work by isolating the organism, growing 

 it in pure culture, and with the pure culture producing the char- 

 acteristic disease. Koch's observations explained many apparent 

 paradoxes that had greatly puzzled previous workers. Blood 

 from infected animals which appeared to be free from bacteria 

 had been found to produce the specific disease when inoculated 

 into susceptible animals and also the disease was sometimes 

 found to appear without any known means of infection. Koch 

 discovered that very soon after blood is drawn the anthrax bacillus 

 forms spores which are highly refractive and seen with difficulty, 

 and that consequently they must have been present but not 



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