BACILLUS ANTHRACIS 109 



On Agar and Gelatine, small, more or less rounded opaque masses, 

 thicker at the periphery than in the centre, develop. 



In Milk it grows without changing the reaction or causing 

 coagulation. 



On Potatoes the growth is rapid. 



Pathogenesis. Pure cultures or pus injected into the peritoneal 

 cavity of a guinea-pig cause pseudo-tuberculosis of the peritoneum in 

 nine to twenty days, the characteristic tufted organisms being present 

 in the centre of the nodules. Intravenous inoculation causes a 

 generalized pseudo-tuberculosis. Intravenous inoculation of cattle 

 and sheep causes a slow-forming pseudo-tuberculosis. 



Subcutaneous inoculation in refractory animals causes an abscess 

 which heals quickly. 



BACILLUS ANTHRACIS. 



(Ger. Milzbrand bacillus ; Fr. Bacteridie du charbon). 



This organism is always present in the blood of animals affected 

 with anthrax, and can be isolated in pure cultures on artificial 

 media. When susceptible animals are inoculated with portions of 

 pure cultures, conditions similar to those found in the animal from 

 which the original cultures was obtained are produced. 



Microscopical Appearances. In the blood of animals recently 

 dead, the bacilli occur as large rods of variable size, from 3 to 10 /z long 

 and 1 to Ij fji broad, often arranged in threads formed by several rods 

 jointed together (see Photomicrograph, Fig. 34). In unstained specimens 

 examined by means of a hanging drop, the ends of the rods appear round ; 

 while in stained specimens the ends of the rods are square. Under a high 

 magnification the ends are found to be a trifle thicker than the body of 

 the bacillus, and occasionally somewhat indented and concave compared 

 by Fraenkel, when stained with methylene blue, to small pieces of 

 bamboo cane. 



Bacilli obtained from the blood of affected animals possess capsules 

 (see Photomicrograph, Plate I., Fig. 1, also Fig. 35). To demonstrate 

 the capsules, stain the specimens by Johne's special process (see 

 Technique, 22). Capsules can also be demonstrated when the 

 bacilli are cultivated in liquid blood serum medium. Giinther has also 

 found the capsules present in bacilli in sections stained with methylene 

 blue. The square ends and the presence of capsules help to distinguish 

 the Bacillus anthracis from certain other organisms that resemble it 

 morphologically, especially putrefactive bacteria. 



After death, the bacilli are only to be found in bloodvessels. In 



