ANTHRAX 55 



The true nature of a case which is examined post-mortem can 

 easily be determined bacteriologically ; the cut surface of the 

 liver or spleen should be rubbed upon a clean slide, and the films 

 treated secundum artem. They will probably show the bacilli in 

 large numbers. Sections may also be cut and stained by Gram's 

 method (see p. 172). 



In the later stages of any infection with anthrax the bacilli 

 may be found in the blood. They may be apparent on examina- 

 tion of stained films, or by cultural methods similar to those used 

 in the diagnosis of malignant pustule. 



The anthrax bacillus varies considerably in length, but is 

 always a large organism, and may be considerably longer than 

 the diameter of a red blood-corpuscle. It is much thicker than 

 the bacilli which have been dealt with hitherto, and it is invariably 

 straight. The ends of these bacilli are cut sharply at right angles 

 to the sides of the organism, and may be even somewhat concave ; 

 this is a most characteristic feature. The anthrax bacillus stains 

 by Gram's method (Plate I., Fig. 4). 



In cultures the appearances are somewhat different. Here the 

 bacilli are frequently arranged in long chains which have an 

 appearance which has been compared to that of a bamboo ; chains 

 occur in the blood or in the inflammatory exudate, but are usually 

 much shorter than those seen in cultures. But the most important 

 features in cultures of the anthrax bacillus is the development 

 of spores, which are oval, highly refractile bodies, and lie in or 

 near the centre of the bacilli, one in each. These spores are 

 possessed of tough capsules, which resist the action of the ordinary 

 stains much in the same way as the tubercle bacillus. Thus 

 it happens that in films of a cultivation of the anthrax bacillus 

 which have been stained with such a dye as weak methylene blue 

 the spores are readily seen as colourless and refractile oval areas 

 in the centre of the bacilli, the latter being stained blue. The 

 spores themselves may be stained by a modification of the 

 process used for the tubercle bacillus. The films are first stained 

 by heated carbol fuchsin, which penetrates slowly through the 

 capsule; they are then decolorized by a very rapid immersion 

 in very dilute sulphuric acid (i per cent.) or in methylated spirit, 

 and examined microscopically. If the red colour has been entirely 

 removed from the bacilli, but is still present in the spores, the films 

 are ready to be counterstained by methylene blue ; if not, they 

 must be dipped in the acid or spirit once more and re-examined. 



