BACILLUS ANTHRACIS. 551 



only a few bacilli are present this method is not always 

 reliable, as some of the bacilli are generally decolorized. 



Biological Characters. The anthrax bacillus grows 

 easily in a variety of nutrient media at a temperature 

 from 18 to 43 C., 37 C. being the most favorable 

 temperature. Under 12 C. no development takes 

 place, as a rule, though by gradually accustoming the 

 bacillus to a lower temperature it may be induced to 

 grow under these conditions. Under 14 C. and above 

 43 C. spore-formation ceases. The lower limit of 

 growth and sporulation is of practical significance in 

 determining the question whether development can 

 occur in the bodies of animals dead from anthrax 

 when buried at certain depths in the earth. Kitasato 

 has shown that at a depth of 1.5 metres the earth in 

 July has a temperature of 15 C. at most, and that 

 under these conditions a scanty sporulation of anthrax 

 bacilli is possible, but that at a depth of 2 metres sporu- 

 lation no longer occurs. The anthrax bacillus is aerobic 

 that is, its growth is considerably enhanced by the 

 presence of oxygen but it grows also under anaerobic 

 conditions, as is shown by its growth at the bottom of 

 the line of puncture in stick cultures in solid media; 

 but under these conditions it no longer produces the 

 peptonizing ferment which it does with free access of 

 air. Furthermore, the presence of oxygen is absolutely 

 necessary for the formation of spores, while carbonic 

 acid gas retards sporulation. This explains, perhaps, 

 why sporulation does not take place within the animal 

 body either before or after death. 



This bacillus grows best in neutral or slightly alka- 

 line media. It may be cultivated in infusions of meat 

 or of various vegetables, in urine ; etc,, provided the 



