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PATHOGENIC MICROORGANISMS 



this last observer to isolate the bacillus upon artificial media and 

 to reproduce the disease experimentally by inoculation with pure 

 cultures. 



Morphology and Staining. The anthrax bacillus is a straight 

 rod, 5 to 10 micra in length, 1 to 3 micra in width. It is non-motile. 

 In preparations made from the blood of an infected animal, the 

 bacilli are usually single or in pairs. Grown on artificial media they 

 form tangles of long threads. Their ends are cut off squarely, in 

 sharp contrast to the rounded ends of many other bacilli, The 



FIG. 78. BACILLUS ANTHRACIS. From pure culture on agar. 



corners are often sharp and the ends of bacilli in contact in a chain 

 often touch each other only at these points, leaving in consequence 

 an oval chink between the ends of the organisms. The appearance 

 of a chain of anthrax bacilli therefore, has been not inaptly com- 

 pared to a rod of bamboo. On artificial media the anthrax bacillus 

 forms spores. Oxygen is necessary for the formation of these spores 

 and they are consequently not found in the blood of infected sub- 

 jects. The spores are located in the middle of the bacilli and are 

 distinctly oval. They are difficult to stain, but may be demonstrated 

 by any of the usual spore-staining procedures, such as Holler's or 

 Novy's methods. The bacilli themselves are easily stained by the 

 usual anilin dyes, and gentian- violet or fuchsin in aqueous solution 



