BACILLUS ANTHRACIS. 297 



characters of the whole group of bacilli, and is therefore of 

 the greatest use to the student. Further, its behaviour 

 when inoculated in animals illustrates many of the points 

 raised in connection with such difficult questions as the 

 general pathogenic effects of bacteria, immunity, etc. 

 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 a cow, for example, which has 

 died from anthrax, and examined microscopically, it will 

 be found to contain a great number of large non-motile 

 bacilli. On making a cover-glass preparation from the 

 same source, and 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 8 //, 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 proximal end of a phalanx. 

 Their protoplasm is very finely granular, and sometimes 

 appears surrounded by a thin unstained capsule. When 

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

 common to the whole thread (Fig. 82). They stain well 

 with all the basic aniline dyes and are not decolorised by 

 Gram's method. 



Plate Cultures. From a source such as that indicated, 

 it is easy to isolate the bacilli by making gelatine or agar 

 plates. If, after twelve hours' incubation at 37 C, the 

 latter be examined under a low objective, 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. 78). The whole colony 

 is, in fact, probably one long thread. Such colonies are 

 very suitable for making impression preparations (vide p. 

 124) 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 



