MORPHOLOGY 521 



(i) The bacillary form. 



In the blood of animals infected with anthrax the bacilli occur as small 

 rods 5-10/A by 1-1 '5/x, straight, flexible, non-motile and staining uniformly. 



FIG. 249. Bacillus anthracis. Blood film from an ox dead of anthrax. 

 Gram's stain. (Oc. 2, obj. ^th, Zeiss.) 



The organisms are arranged singly or in short chains of two or three bacilli : 

 sometimes the individuals in the chains are separated from one another by 

 such a small space that they appear rather as one long filamentous bacillus. 



FIG. 250. Bacillus anthracis. Section of liver. Gram's method and eosin. 

 (Oc. -2, obj. y^th, Zeiss.) 



If unstained preparations be examined the bacilli appear transparent 

 like glass. 



In the gelatinous oedema the bacilli are a little longer than in blood ; it 

 is also to be noted that the length of the bacilli varies in different animals 

 and also according to the virulence of cultures. A slightly attenuated virus 

 gives long forms, more virulent organisms are shorter and thick-set. 



