222 



MICROBIOLOGY 



lender x who happened to examine the blood of a cow that had 

 died from anthrax. The same observation was made inde- 

 pendently by Brauell 2 and Davaine. 3 The organism did not 

 receive special attention until Davaine published his further 

 researches in 1863. Until this time, many ridiculed the theory 

 of these little rods being the cause of the disease. Consider- 

 able interest is attached to this organism historically, as it was 

 the first bacterium that was demonstrated as bearing a definite 

 etiological relation to an infectious disease of animals. It has 

 l)een stated that Bacterium anthracis laid as it were the corner 

 stone of modern bacteriology. 



Morphology. The an- 

 thrax bacterium i s a 

 straight rod, 5 to 10 ju. 

 in length, and from 1.0 

 to 2.5 /ji in width. In 

 preparations made from 

 the blood of an infected 

 animal, the bacteria are 

 usually single or in 

 pairs. Grown on artifi- 

 cial media they form 

 skeins of long threads. 

 The ends are square cut. 

 When in pairs or short 

 chains the ends are 

 often depressed so that 

 the corners are sharp 



and the . ends of the bacteria touch each other only at these 

 points, leaving in consequence an oval space between the ends 

 of the organisms. On artificial media the anthrax bacteria 

 form spores. The spore, one in each bacterium, appears as a 

 small, highly refractile spot in the center of the individual 

 bacterium. As this enlarges, the body of the bacterium around 



Fig. 49. Bacterium anthracis. Im- 

 pression preparation from a gelatin 

 colony. 



1 Pollender. Vierteljahrschar Ger. Med., Bd. VIII (1855). 



2 Brauell. Virchow's Archiv, Bd. II (1857). 



3 Davaine. Compt rendu de 1'Acad. des Sci., Vol. LVII (1863). 



