368 



Anthrax 



grayish-white, translucent, slightly wrinkled layer with irregular 



edges, from which curls of bacillary threads 

 extend upon the medium. When the cul- 

 ture is old, the agar-agar usually becomes 

 brown in color. Spore-formation is lux- 

 uriant. 



Bouillon. — In bouillon the anthrax bacU- 

 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 surf ace 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-seriun. — Blood-serum cultures 

 lack characteristic pecuUarities; the cul- 

 ture-medium is slowly Hquefied. 



Milk. — The anthrax bacillus grows well 

 in milk, which it coagulates and acidulates. 

 Later the coagulum is peptonized and dis- 

 solved, leaving a clear whey. 



Vital Resistance. — ^The bacillus grows 

 between the extremes of 12° and 4S°C., 

 best at 37°C. The exposure of the organ- 

 ism to the temperature of 42° to 43°C. 

 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 ioo°C. It is said by 

 some that spores subjected to 5 per cent. 

 carboHc acid can subsequently germinate 

 when introduced into susceptible 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 ex- 

 posure to I : 1000 bichlorid of mercury solution. 

 Metabolic Products. — The anthrax bacillus produces a curdling 



Fig_. 127.^ — 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). 



