BACILLUS ANTHRACIS 



343 



capsule seems common to the whole thread (Fig. 107). They 

 stain well with all the basic aniline dyes and are not decolorised 

 by Gram's method. To demonstrate the capsule the preparation 

 is well stained with aniline-oil gentian violet solution, rapidly 

 differentiated in water acidulated with acetic acid, and mounted 

 in water. 



Methylene-blue Reaction. This was introduced independently by 

 McFadyean and by Heim with a view to the easy recognition of the 

 bacilli in blood or other bodily fluids, and depends on a disintegration of 

 the bacillary capsules which occurs when these arc imperfectly fixed. 

 Imperfect fixation is attained by drying a blood film on a slide and hold- 

 ing it three times for a second in a flame, film upwards (too great heating 

 fixes the capsules and prevents the reaction from occurring). The pre- 

 paration is stained for a few seconds with an old solution of methylene- 

 blue, 1 per cent, in water (i.e., with a methylene-blue possessing poly- 

 chromatic qualities, see p. 114). It is washed in water and dried with 

 filter paper, preferably a cover-glass is not applied. In such a prepara- 

 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 recognisable naked -eye. McFadyean states 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 gelatin or agar 

 plates. If, after twelve 

 hours' incubation at 37 

 C., the latter be ex- 

 amined under a low 

 objective, colonies will 

 be observed. They are 

 to be recognised by 

 beautiful wavy wreaths 

 like locks of hair, radiat- 

 ing from the centre and 

 apparently terminating 

 in a point which, how- 

 ever, on examination 

 with a higher power, is 

 observed to be a filament which turns upon itself (Fig. 103). 

 Graham-Smith (vide p. 4) attributes the appearance to the tough- 

 ness of the bacterial envelope, which prevents the separation of 



FIG. 103. Surface colony of the anthrax 

 bacillus on an agar plate, showing the 

 characteristic appearance. x30. 



