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BACTERIOLOGY FOR NURSES 



noticed in the supposedly germ-free blood. Further research 

 showed that animals might become infected by feeding them with 

 spores. This fact together with a knowledge of the prolonged 

 vitality of these bodies in the soil explained the persistence of the 

 disease in certain localities and its reappearance in once-infected 

 pastures after many years. 



Morphology and Staining. The bacillus is one of the largest 

 of the pathogenic bacteria; it ranges from 2 to 20 ft in length 



and 1 to 1.2 /* in width. In 

 stained film preparations the 

 organisms may appear singly 

 or joined end to end in chains 

 of varying length. The free 

 ends of the rods are rounded, 

 while those coming in contact 

 with one another are square or 

 slightly swollen and concave, 

 the latter giving the chain 

 somewhat the appearance of a 

 bamboo rod. In preparations 

 from albuminous material a 

 thin capsule may be seen surrounding the cell. (Fig. 31.) 



Spores are formed only in the presence of free oxygen ; hence 

 they do not develop in the blood while it remains in the body. 

 They are oval in shape and appear in the center of the rod. As 

 the spore develops it occupies more and more of the parent cell 

 until the latter appears as a thin envelope which finally ruptures 

 and sets the spore free. Sporeless strains of B. anthracis have been 

 produced by growing the organisms on media containing anti- 

 septics or by cultivation at their maximum temperature (43 C.). 

 The bacilli stain with the usual dyes and are Gram positive. 



Cultivation. The organism grows well on ordinary culture 

 media under aerobic conditions ; vegetative forms are facultative 

 anaerobes. Development will occur between 14 C. and 43 C., 

 the optimum being about 34 C. ; under the minimum and above 

 the maximum temperature sporulation does not take place. 



FIG. 31. Anthrax Bacilli. 



