BACILLUS ANTHRACIS 



333 



common to the whole thread (Fig. 103). They stain well with all 

 the basic aniline dyes and are not decolorised by Gram's method. 



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 are 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. 113). 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' in- 

 cubation at 37 C., the 

 latter be examined under 

 a low objective, colonies 

 will be observed. They 

 are to be recognised by 

 1 MM ut if ul wavy wreaths 

 like locks of hair, radiat- 

 ing from the centre and 

 apparently terminating 

 in u point which, how- 

 ever, on examination 

 with a higher power, is 

 ol.xTved to be a fila- 

 ment which turns upon 

 itself (Fig. 99). Graham 

 Smith (vide p. 4) attri- 

 butes the appearance to 

 the toughness of the 

 bacterial envelope, which 



prevents the separation of individuals from one another after 

 division. Tin- whole colony is, in fact, probably one long thread. 

 Such colonies are very suitable for making impression prepara- 

 tions (vide p. 138) which preserve permanently the appearances 



FIG. 99. Surface colony of the anthrax 

 bacillus on an agar plate, showing the 

 characteristic appearance, x 30. 



