356 



Anthrax 



grayish-white, translucent, slightly wrinkled layer with irregular 

 edges, from which curls of bacillary threads 

 extend upon the medium. When the 

 culture is old, the agar-agar usually be- 

 comes brown in color. Spore-formation 

 is luxuriant. 



Bouillon. In bouillon the anthrax bacil- 

 lus grows chiefly upon the surface, where 

 a thick felt-like pellicle forms. From this, 

 fuzzy extensions descend into the clear 

 bouillon below. After a few days some 

 wooly aggregations can be seen in the 

 bottom of the tube. In the course of time 

 the growth ceases and the surface pellicle 

 sinks. If, by shaking, it is caused to sink 

 prematurely, a new, similar surface growth 

 takes its place. Spore-formation is rapid 

 at the surface. 



Potato. Upon the potato the growth is 

 white, creamy, and rather dry. Sporula- 

 tion is marked. 



Blood-serum. Blood-serum cultures 

 lack characteristic peculiarities; the cul- 

 ture-medium is slowly liquefied. 



Milk. The anthrax bacillus grows well 

 in milk, which it coagulates and acidulates. 

 Later the coagulum is peptonized arid dis- 

 solved, leaving a clear whey. 



Vital Resistance. The bacillus grows 

 between the extremes of 12 and 45C., 

 best at 37C. The exposure of the organ- 

 ism to the temperature of 42 to 43C. 

 slowly diminishes its virulence. 



When dried upon threads, the spores 

 retain their vitality for years, and are 

 highly resistant to heat and disinfectants. 

 The spores of anthrax are killed by five 

 minutes' exposure to iooC. It is said 

 by some that spores subjected to 5 per 

 cent, carbolic acid can subsequently 

 germinate when introduced into suscepti- 

 ble animals, their resistance to this 

 strength carbolic solution being so great 

 that they are not destroyed by it under 

 twenty-four hours. They are killed in 



two hours by exposure to i : 1000 bichlorid of mercury solution. 

 Metabolic Products. The anthrax bacillus produces a curdling 



Fig. 131. Bacillus an- 

 thracis; gelatin stab cul- 

 ture, showing character- 

 istic growth with com- 

 mencing liquefaction and 

 cupping (from evapora- 

 tion) at the surface of the 

 medium (Curtis). 



