THE BACILLUS OP ANTHRAX. 343 



a small quantity of agar to a gelatin medium prevents liquefaction 

 of the gelatin (Fliigge). 



Upon blood serum a rather thick, white layer is formed and 

 liquefaction slowly occurs. 



Upon potato the growth is abundant as a rather dry, grayish- 

 white layer, of limited extent, having a somewhat rough surface and 

 irregular margins. 



Spores are formed only in the free presence of oxygen, as in sur- 

 face cultures upon potato or nutrient agar, or in shallow cultures in 

 liquid media, and at a temperature of 20 to 35 C. They are not 

 formed during the development of the bacilli in the bodies of living 



FIG. 103. Colonies of Bacillus anthracis upon gelatin plates : a, at end of twenty-four hours; 

 6, at end of forty -eight hours, x 80. (Flugge.) 



animals, but after the death of the animal the bacillus continues to 

 multiply for a time, and spores may be formed where the fluids 

 containing it come in contact with the air as, for example, in 

 bloody discharges from the nostrils or from the bowels of the dead 

 animal. 



Varieties incapable of spore production have been produced arti- 

 ficially, by several bacteriologists, by cultivating the bacillus under 

 unfavorable conditions. Roux was able to produce a sporeless va- 

 riety by successive cultivation in media containing a small quantity 

 of carbolic acid 1 : 1,000. 



Varieties differing in their pathogenic power may also be pro- 

 duced by cultivation under unfavorable conditions. Thus Pasteur 



