302 



ANTHRAX 



protoplasm is very finely granular, and sometimes appears sur- 

 rounded by a thin unstained capsule. When several bacilli lie 

 end to end in a thread, the capsule seems common to the whole 

 thread (Fig. 108). They stain well with all the basic aniline dyes 

 and are not decolorised by Gram's method. 



Plate Cultures. From a source such as that indicated, it is 

 easy to isolate the bacilli by making gelatin or agar plates. If, 

 after twelve hours' incubation at 37 C., the latter be examined 

 under a low objective, colonies will be observed. They are to 

 be recognised by beautiful wavy wreaths like locks of hair, 

 radiating from the centre and apparently terminating in a point 



which, however, on ex- 

 amination with a higher 

 power is observed to be a 

 filament which turns upon 

 itself (Fig. 104). The whole 

 colony is, in fact, probably 

 one long thread. Such 

 colonies are very suitable 

 for making impression pre- 

 parations (vide p. 118) 

 which preserve perman- 

 ently the appearances de- 

 scribed. On examining 

 such with a high power, 

 the wreaths are seen to be 

 made up of bundles of 

 FIG. 104. Surface colony of the anthrax l n g filaments lying par- 

 bacillus on an agar plate, showing the allel with one another, each 

 characteristic appearances, x 30. filament consisting of a 



chain of bacilli lying end 

 to end, and similar to those observed in the blood (Fig. 105). 



On gelatin plates, after from twenty-four to thirty-six hours 

 at 20 C., the same appearances manifest themselves, and later 

 they are accompanied by liquefaction of the gelatin. In gelatin 

 plates, however, instead of the characteristically wreathed appear- 

 ance at the margin, the colonies sometimes give off radiating 

 spikelets irregularly nodulated, which produce a star-like form. 

 These spikelets are composed of spirally twisted threads. 



From such plates the bacilli can be easily isolated, and the 

 appearances of pure cultures on various media studied. 



In bouillon, after twenty-four hours' incubation at 37 C., 

 there is usually the appearance of irregularly spiral threads 

 suspended in the liquid. These, on being examined, are seen 



