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PATHOGENIC MICROOROANISxMS 



artificial media and to reproduce the disease experimentally by inocu- 

 lation with pure cultures. 



Morphology and Stainuig. — 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 con- 



FiG. 120. — Bacillus anthracis. From pure culture on agar. 



trast to the rounded ends of many other bacilli. The comers 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 l)cen not inaptly compared to a rod of bamboo. On 

 artificial m.edia the anthrax bacillus forms spores. Oxygen is necessary 

 for the formation of these spores and they are consequently not found 



