588 APPLICATION OF METHODS OF BACTERIOLOGY 



inoculation. On potato, at the temperature of the incubator, 

 spore-formation may be easily observed. 



Stab- and slant-cultures 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 pronounced 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 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. It has been found repeatedly that 

 anthrax spores from some strains are readily killed by an 

 exposure of one minute to the temperature of steam, whereas 

 spores from others resist this temperature for as long as 

 twenty minutes and sometimes longer. 



Staining. Anthrax bacteria stain readily with the 

 ordinary aniline dyes. In tissues their presence may also 

 be demonstrated by the ordinary aniline staining fluid 

 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, dehydrated in alcohol, cleared 

 in xylol, and mounted in balsam. This leaves the bacilli 

 stained, while the tissues containing them are decolorized; 



