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 aérobic 
—that is, its growth is considerably enhanced by the 
presence of oxygen—but it grows also under anaérobic 
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 
