BACILLUS ANTHRACIS 
409 
develop rapidly, and liquefaction commences within thirty hours as a 
rule. At this stage of development the edges of the colonies are com- 
posed of tangled, radiating chains of bacilli which extend into the 
surrounding medium, and the colony itself is composed of a mass of 
twisted filaments which has been likened to a Medusa head. Few, 
if any, pathogenic bacteria present such an appearance. The growth 
in stab cultures in gelatin is also characteristic; the organisms grow- 
away from the line of inoculation into the medium as spikelets which 
resemble an "inverted pine tree." Liquefaction soon takes place. 
Milk is rendered acid, and the casein precipitated and slowly liquefied. 
A pellicle forms upon the surface of broth which readily becomes 
detached from the sides of the tube and settles to the bottom. No 
turbidity is produced in fluid media. 
Fig. 58. 
-Bacillus anthracis, section from kidney, semi-diagrammatic. X 500. 
(Kolle and Hetsch.) 
B, anthracis is a strongly aerobic bacillus, but growth will take place 
under anaerobic conditions. Growth is very slow at 18° C, and ceases 
below 15° C. The optimum is about 37° C, and development does 
not take place at 45° C. 
The vegetative (sporeless) organisms are not particularly resistant to 
heat or drying. The spores are very resistant. Dried spores have 
remained viable and virulent for eighteen years. ^ Fresh blood con- 
taining anthrax bacilli may remain viable for two months if relatively 
thick layers are prepared. Dry heat at 160° C. kills anthrax spores 
within one and a half hours; live steam (100° C.) kills them within 
ten minutes. Carbolic acid is not very effective as a germicide, but 1 to 
1000 bichloride of mercury kills the spores within half an hour. Direct 
sunlight kills them within six hours.^ 
Products of Growth.— C/^e?»^ca/.— Martin^ found protoalbumose, 
deuteroalbumose, a trace of peptone, an alkaloidal substance, and 
1 V. Szekely: Ztschr. f. Hyg., 1903, 44, 359. 
">■ Moment: Ann. Inst. Pasteur, 1892, 6, 21. 
3 Proc. Roy. Soc, London, May 22, 1890; British Med. Jour., 1892, i, 641, 696, 755; 
Annual Report Local Goverment Board, Supplement, 1890-1891, 20, 255-266. 
