302 



ANTHRAX. 



FlG. 107. Surface colony of the anthrax 

 bacillus on an agar plate, showing the charac- 

 teristic appearances. X 30. 



6 to 8 //. long, though both shorter and longer forms also occur. 

 The ends are sharply cut across, or may be slightly dimpled so 

 as to resemble somewhat the proximal end of a phalanx. Their 



protoplasm is very finely granu- 

 lar, 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. 1 1 1 ). They 

 stain well with all the basic 

 aniline dyes and are not de- 

 colorised by Grain'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 objec- 

 tive, 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 examination with a higher 

 power is observed to be a fila- 

 ment which turns upon itself 

 (Fig. 107). The whole colony 

 is, in fact, probably one long 

 thread. Such colonies are very 

 suitable for making impression 

 preparations (vide p. 114) which 

 preserve permanently the ap- 

 pearances described. On ex- 

 amining such with a high power, 

 the wreaths are seen to be made 

 up of bundles of long filaments 

 lying parallel with one another, 

 each filament consisting of a 

 chain of bacilli lying end to end, and similar to those observed 

 in the blood (Fig. 108). 



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



FIG. 108. Anthrax bacilli, arranged 

 in chains from a twenty-four hours' culture 

 on agar at 37 C. Stained with fuchsin. 

 Xiooo. 



