770 



PATHOGENIC MICROORGANISMS 



to be Grain-positive at least when taken from the animal body. 32 

 Cultivation. The bacillus is a strict anaerobe. It was obtained 

 in pure culture first by Kitasato. 33 Under anaerobic conditions it is 

 easily cultivated upon the usual laboratory media, all of which are 

 more, favorable after the addition of glucose, glycerin, or nutrose. 

 In all media there is active gas formation, which, 

 owing to an admixture of butyric acid, is of a foul, 

 sour odor. The bacillus is not very delicate in its 

 requirements of a special reaction of media, grow- 

 ing equally well on those slightly acid or slightly 

 alkaline. 



On gelatin plates, at 20 C., colonies appear in 

 about twenty-four hours, usually round or oval, 

 with a compact center about which fine radiating 

 filaments form an opaque halo. The gelatin is 

 liquefied. 



Surface colonies upon agar plates are circular 

 and made up of a slightly granular compact center, 

 from which a thinner peripheral zone emanates, 

 containing microscopically a tangle of fine threads. 

 In agar stabs, at 37.5 C., growth appears within 

 eighteen hours, rapidly spreading from the line 

 of stab as a diffuse, fine cloud. Gas formation, 

 especially near the bottom of the tube, rapidly leads 

 to the formation of bubbles and later to extensive 

 splitting of the medium. In gelatin stab cultures 

 growth is similar to that in agar stabs, though less 

 FIG. 77. BA- rapid. 



CILLUS OF SYMP- Pathogenicity. Symptomatic anthrax bacilli 

 TOMATIC ANTHRAX. 



Culture in glucose are P ath genic for cattle, sheep, and goats. By far 

 agar. the largest number of cases, possibly the only spon- 



taneous ones, appear among cattle. Guinea-pigs are 

 very susceptible to experimental inoculation. Horses are very little 

 susceptible. Dogs, cats, rabbits, and birds are immune. Man also 

 appears to be absolutely immune. Spontaneous infection occurs by 

 the entrance of infected soil into abrasions or wounds, usually of 

 the lower extremities.- Infection depends to some extent upon the 

 relative degree of virulence of the bacillus a variable factor in this 



32 ,'on Hibler, Kolle, Wassermann, etc,., p. 792, vol. iv. 

 **Kitasaio, Woch. f. Hyg, 1889. 



