33(5 



ANTHRAX 



tion, between and near the bacteria there is a varying amount of an 

 irregularly disposed amorphous or finely granular material of a violet or 

 reddish-purple tint. Frequently the colour reaction in the preparation 

 is so marked as to be recognisahle to the naked eye. McFadyean stales 

 that this reaction does not occur with putrefactive or other bacteria 

 which might be present under circumstances where the recognition of 

 the anthrax bacilli is the question under consideration. 



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

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

 twelve hours at 37° C, these be examined under a low objective, 

 colonies will be observed. They are to be recognised by beauti- 

 ful]wavy wreaths like locks of hair, radiating from the centre and 



apparently terminating 

 in a point which, how- 

 ever, on examination 

 with a higher power, is 

 observed to be a fila- 

 ment which turns upon 

 itself (Fig. 98). Gra- 

 t ham-Smith (vide- p. 4) 

 [ attributes the appear- 

 ance to the toughness 

 of the bacterial en- 

 velope, which prevents 

 the separation of in- 

 dividuals from one 

 another after division. 

 The colonies are suit- 



™ o , i * *v m, able for making im- 



Fio. 98. — Surface colony of the anthrax . ° , 



bacillus on an agar plate, showing the pression preparations 

 characteristic appearance. x30. (vide p. 134) which 



preserve permanently 

 the appearances described. On examining 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. 99). 



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 

 appearance at the margin, the colonies sometimes give off 

 radiating spikelets irregularly jointed, nodulated, and whorled, 

 which produce a star-like form. These spikelets are composed 

 of spirally twisted threads. 



