THE .\\THRAX BACILLUS 333 



times short, isolated rods are seen, and, again, shorter or longer chains 

 or threads made up of several rods joined end to end. In suitable 

 culture media very long, flexible filaments may be observed, which 

 are frequently united in twisted or plaited cord-like bundles. (See 

 Fig. 116 and Fig. 13, p. 29, and Fig. 17, p. 33.) These filaments in 

 hanging-drop cultures, before the development of spores, appear to 

 be homogeneous or nearly so; but in stained preparations they are 

 seen to be composed of a series of rectangular, deeply stained segments. 

 When obtained directly from the blood of an infected animal the free 

 ends of the rods are slightly rounded, but those coming in contact with 

 one another are quite square. In cultures the ends are seen to be a 

 trifle thicker than the body of the cell and somewhat concave, giving 

 the appearance of joints of bamboo. At one time much stress was 

 laid upon these peculiarities as distinguishing marks of the anthrax 



FIG. lie 



Anthrax bacillus. X 900 diameters. Agar culture. 



bacillus; but it has been found that they are the effects of artificial 

 cultivation and not necessarily characteristic of the organism under 

 all conditions. Another peculiarity of this bacillus is that it is enclosed 

 in a transparent envelope or capsule, which in stained preparations 

 may be distinguished by its taking on a lighter stain than the deeply 

 stained rods which it surrounds. 



Under favorable conditions in cultures spores are developed in the 

 bacilli. These spores are elliptical in shape and about one and a half 

 times longer than broad. They first appear as small, refractive granules 

 distributed at regular intervals, one in each rod. As the spore develops 

 the mother-cell becomes less and less distinct, until it disappears alto- 

 gether, the complete oval spore being set free by its dissolution. (See 

 Fig. 117, Fig. 13, p. 29, and Fig. 17, p. 33.) Irregular sponilation 

 sometimes takes place, and occasionally there is no spore formation, 

 as in varieties of non-spore-bearing anthrax. 



