BACTERIUM ANTHRACIS. 515 



temperature of the incubator, spore-formation may be 

 easily observed. 



STAB- AND SLANT-CULTURES. Stab- and slant-cult- 

 ures on agar-agar present in general the appearances 

 given for the colonies, except that the growth is much 

 more extensive. The growth is always more pro- 

 nounced on the surface than down the track of the 

 needle. 



On gelatin it causes liquefaction, which begins on the 

 surface at the point inoculated and spreads outward and 

 downward. 



It grows best with access to oxygen, and very poorly 

 when the supply of that gas is interfered with. 



Under favorable conditions of aeration, nutrition, and 

 temperature its growth is rapid. 



Under 12 C. and above 45 C. no growth occurs. 

 Its optimum temperature is that of the human body, 

 viz., 37-38 C. 



The spores of bacterium anthracis are very resistant to 

 heat, though the degree of resistance varies with spores 

 of different origin. Von Esmarch found that anthrax 

 spores from some sources were readily killed by an ex- 

 posure of one minute to the temperature of steam, 

 whereas spores from other sources resisted this temper- 

 ature longer, in some cases as long as twelve minutes. 



STAINING. Anthrax bacteria stain readily with the 

 ordinary aniline dyes. In tissues their presence may 

 also be demonstrated by the ordinary aniline stain- 

 ing-fluids or by Gram's method. They may also be 

 stained in tissues with a strong watery solution of 

 dahlia, after which the sections are decolorized in 2 per 

 cent, sodium carbonate solution, washed in water, dehy- 

 drated in alcohol, cleared in xylol, and mounted in bal- 



