I 66 BACTERIA 



have been. Fields, hay, bristles, hides, manure, etc., have been 

 found to contain bacilli. Drinking water may be polluted by tan- 

 neries and the bodies of dead animals. Meadows and fields may 

 be contaminated for years. From the buried bodies of infected 

 animals anthrax spores may be brought to the top of the soil by 

 earth-worms. 



Cultures. Grows exceedingly well on all culture media in the 

 air. On gelatine it grows in whitish round colonies, rapidly sink- 

 ing into the gelatine, due to the liquefaction. The liquid medium is 

 turbid. The interior of the colony is crumbly. When magnified, 

 the colonies seem to be made up of tangled waving bundles, like 

 locks of hair, especially about the periphery. In gelatine stab 

 cultures the growth is luxuriant and rapid; the medium is liquefied 

 more rapidly at the top, and finally a crater is formed; before this 

 appears, lateral hair-like outgrowths are s*een in the gelatine. At 

 the bottom of the crater a white crumbly mass is formed, but no 

 pellicle. On agar plates, small whitish colonies develop -which 

 are elevated and round. When magnified, wavy hair-like growths 

 appear on the edge, caused by many twisted parallel chains of 

 bacilli. (Fig. 56.) 



In agar stab, the growth is 'more luxuriant near the top; lateral 

 filamentous branches are seen along the stab line. In agar streak 

 the colonies are abundant, thick and fatty; have tangled edges, 

 and the water of condensation is cloudy. In bouillon, it forms 

 homogeneous flocculi, which precipitate, leaving the bouillon clear. 

 A fragile pellicle is formed. In milk, it multiplies rapidly, the 

 proteids are coagulated, generally rendered acid, and later the coagu- 

 lum is dissolved. Potato cultures are likewise luxuriant. The 

 growth is elevated, dull in lustre, and the outline is wavy. 



Pathogenesis. The anthrax bacillus increases so rapidly, and 

 so luxuriantly, that it has been supposed to cause death merely by 

 mechanically overwhelming the animal: absorbing nutriment and 

 oxygen, and blocking capillaries. Its action is certainly not purely 

 toxic, as it causes, not a toxaemia, but a bacteraemia. It is especially 



