BACILLUS ANTHRACIH 
407 
tion, obtained the organism in pure culture, and reproduced the disease 
with these cultures in other animals, thus establishing the etiology of 
anthrax. He also demonstrated spore formation by B. anthracis 
u])on artificial media. 
Morphology.— B. anthracis is a rod-shaped organism measuring from 
1 to 1.5 microns in diameter and from 2 to 4 microns in length. 
Occasionally filaments 20 to 25 microns in length are observed, which 
exhibit no demonstrable septation; these long rods may be single cells 
or chains of cells in which septation is imperfect. The ends of the 
bacilli are square cut and often appear to be concave, particularly 
when the organisms are examined in a stained preparation made 
directly from the blood of an infected animal. Occasionally the ends 
are somewhat thickened, giving the bacillus an appearance which sug- 
gests a segment of bamboo. B. anthracis produces short chains of 
three to eight elements in the bloodvessels of infected animals, and 
Fig. 56.— Bacillus anthracis, spore formation. X 1000. (Gtinther.) 
in artificial media it produces long, coiled chains of bacilli which give a 
characteristic filamentous appearance to the colonies upon solid media. 
The organism is non-motile, and possesses no flagella. A capsule^ is 
formed around the bacilli in the animal body and also in cultures con- 
taining albuminous substances, as uncoagulated blood serum.- Spores 
are produced in media freely exposed to the air between the tempera- 
tures of 15° C. and 40° C. The lower limit of spore formation has a 
practical bearing upon the presence of anthrax spores in soil. In the 
temperate zones a temperature exceeding 15° C. in midsummer is 
not found at depths greater than 5 feet, hence anthrax carcasses 
buried deeply are not likely to cause infection of the soil. It has been 
1 The capsule was first seen by Serafini (Progresso Medico, 1888), but Johne (Deutsch. 
Ztschr. f. Tiermed. u. vergl. Path., 1893, 19, 244; 1894, 20, 426) first called attention 
to the diagnostic importance of the capsule in the diagnosis of anthrax of the domestic 
animals. 
2 Haase: Deutsch. Ztschr. f. Tiermed. u. vergl. Path., 1894, 20, 429. Johne: Ibid., 
1894, 21, 142. 
