BACILLUS ANTHRACIS 335 



outside the body, and, by inoculating animals with, them, produced the 

 disease artificially. Koch's observations were, shortly afterwards, con- 

 firmed in the main by Pasteur, though controversy arose between them 

 on certain minor points. Moreover, further research showed that the 

 disease could be produced in animals by feeding them with spores, 

 and thus the way in which the disease might spread naturally was 

 explained. 



Bacillus Anthracis. — Anthrax as a disease in man is of 

 comparative rarity. Not only, however, is the bacillus 

 anthracis easy of growth and recognition, but in its growth it 

 illustrates many of the general morphological characters of the 

 whole group of bacilli, and it is therefore of great use to the 

 student. Further, its behaviour when inoculated in animals 

 illustrates many of the points raised in connection with the 

 general pathogenic effects of bacteria. Hence an enormous 

 amount of work has been done in investigating it in all its 

 aspects. 



If a drop of blood is taken immediately after death from an 

 auricular vein of an ox, for example, which has died from 

 anthrax, it will be found to contain a great number of large 

 non-motile bacilli. On staining with watery methylene-blue, 

 the characters of the bacilli can be better made out. They are 

 about 1 - 2 /a thick or a little thicker, and 6 to 8u long, though 

 both shorter and longer forms also occur. The ends are sharply 

 cut across, or may be slightly dimpled so as to resemble some- 

 what the proximal end of a phalanx. Their protoplasm is very 

 finely granular, and very frequently appears surrounded by a 

 capsule whose external margin is often not, however, so well 

 denned as is the case with, e.g., the pneumococcus. When 

 several bacilli lie end to end in a thread, the capsule seems 

 common to the whole thread. They stain well with all the 

 basic aniline dyes and are Gram-positive. 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 Reacliun.— 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- 

 ins; 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. 111). It is washed in water and dried with 

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



