302 



ANTHRAX. 



■:^\ 



Fig. 107. — Surface colony of the anthrax 

 bacillus on an agar plate, showing the charac- 

 teristic appearances, x 30. 



6 to 8 yii 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 pro.ximal end of a phalanx. Their 



protoplasm is very finely granu- 

 lar, and sometimes appears sur- 

 rounded by a thin unstained 

 capsule. When several bacilli 

 He end to end in a thread, the 

 capsule seems common to the 

 whole thread (Fig. 1 11). They 

 stain well with all the basic 

 aniline dyes and are not de- 

 colorised 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 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. 1 14) 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. 



X 1000. 



