332 



VETERINARY BACTERIOLOGY 



work of Dr. Robert Koch, published in 1876. Methods of vac- 

 cination were developed by Toussaint in 1880, and by Pasteur 

 in 1881. 



Distribution. Anthrax has been recorded in Europe since 

 ancient times. It is known also from Africa, Asia, Australia, 

 and South America. It has been reported from about one-third 

 of the States of the United States, and probably occurs sporadically 

 in most of them. The disease in this country is not common, ex- 

 cept in a few thoroughly infected localities. 



Morphology and Staining. Bacillus anthracis is a large rod, 

 straight, usually with truncate ends, 1 to 1.25 by 4.5 to 10 /w, in 

 short chains when examined in tissues or blood and in long chains 



in culture-media. It is non- 

 motile. Capsules may be 

 demonstrated in smears from 

 blood and other tissues. 

 Spores are produced only 

 when the organism is grown 

 in the presence of free oxygen. 

 They do not, therefore, occur 

 in the bacillus as found in the 

 blood and the tissues. The 

 single spore produced by a 

 cell is oval or spherical, oc- 

 cupies the middle of the cell, 

 and is of almost the same 

 diameter. The spores are 



much more refractive than the protoplasm of the non-sporulating 

 cells. The spores germinate on being brought under favorable 

 growth conditions by breaking through the spore-wall at the pole. 

 They may be demonstrated by a contrast spore stain. The 

 vegetative rod stains readily with the aqueous anilin dyes and 

 is gram-positive. Metachromatic granules may rarely be demon- 

 strated. 



Isolation and Culture. B. anthracis may be readily isolated 

 in pure culture upon any of the common laboratory media by 

 direct inoculation from the blood of an infected animal or from 

 the internal organs, particularly the spleen or liver. Plate cul- 



Fig. 135. Bacillus anthracis, rods with- 

 out spores (Giinther). 



