BACILLUS ANTHRACIS AND ANTHRAX 775 



may be conveniently employed. They are not decolorized by Gram's 

 method. 



In preparations from animal tissues or blood, stained by special 

 procedures, the anthrax bacillus may occasionally be seen to possess 

 a capsule. The capsule is never seen in preparations from the 

 ordinary artificial media. Some observers have demonstrated them 

 in cultures grown in fluid blood serum. In chains of anthrax bacilli, 

 the capsule when present seems to envelop the entire chain and not 

 the individual bacteria separately. 



Isolation. Isolation of the anthrax bacillus from infected ma- 

 terial is comparatively simple, both because of the ease of its cultiva- 

 tion and because of the sharply characteristic features of its mor- 

 phological and cultural appearance. 



Cultivation. The anthrax bacillus is an aerobic, facultatively 

 anaerobic bacillus. While it may develop slowly and sparsely under 

 anaerobic conditions, free oxygen is required to permit its luxuriant 

 and characteristic growth. 



The optimum temperature for its cultivation ranges about 37.5 

 C. It is. not, however, delicately susceptible to moderate variations 

 of temperature and growth does not cease until temperatures as low 

 as 12 C. or as high as 45 C. are reached. By continuous cultivation 

 at some of the temperatures near either the higher or the lower of 

 these limits, the bacillus may become well adapted to the new 

 environment and attain luxuriant growth. 4 



The anthrax bacillus may be cultivated on all of the usual 

 artificial media, growing upon the meat-extract as well as upon the 

 meat-infusion media. 



It may be cultivated also upon hay infusion, various other 

 vegetable media, sugar solutions, and urine. While moderate acidity 

 of the medium does not prevent the growth of this bacillus, the 

 most favorable reaction for media is neutrality or slight alkalinity. 



On gelatin plates, colonies develop within twenty-four to forty- 

 eight hours as opaque, white disks, pin-head in size, irregularly 

 round and rather flat. As- the colonies increase in size their outlines 

 become less regular and under the microscope they are seen to be 

 made up of a hair-like tangle of threads spreading in thin wavy 

 layers from a more compact central knot. The microscopic appear- 

 ance of these colonies has been aptly described as resembling a 



4 Dieudonne, Arb. a. d. kais, Gesundheitsamt, 1894. 



