ETIOLOGY 131 



§ 118. Geographical distribution. Anthrax is a widel}* 

 disseminated disease. The continent of Europe has perhaps 

 suffered most from its ravages. It occurs, also, in Northern, 

 Eastern and Central Africa, where in recent years it has 

 become a great plague. In Siberia, it has caused fearful des- 

 truction, and in that country it is still known as the "Siberian 

 Plague." It has frequently appeared in England. Russia, 

 India and Australia are also infected. South America is also 

 reported to suffer much from its ravages. In the United States 

 it has been reported from at least fifteen states. In fact there 

 are very few, if any, countries where this disease has not been 

 found. A knowledge of its specific cause, with the methods 

 of properly disposing of dead animals, isolation and disinfec- 

 tion, as well as the preventive inoculations now in vogue, have 

 made it possible to prevent wide-spread epizootics. In 

 America it is looked upon as a comparatively rare disease, 

 excepting in certain infected districts. 



§ 119. Etiology. Anthrax is due to the presence of a 

 microorganism known as Bacterium anthracis. This organism 

 is found in the diseased tissues and organs of aflfected animals. 

 On account of its spores, it is very resistant to the normal 

 destructive agencies in nature. Consequently when it is once 

 introduced into a locality it tends to remain there for many 

 years, possibly causing from time to time a few cases of anthrax 

 or serious epizootics or epidemics. The spores are also fre- 

 quently carried in the wool, hair, hides, hoofs and horns taken 

 from animals sick or dead of anthrax. Thus the afifection has 

 been introduced into far distant localities. 



Bacterium anthracis is a rod-shaped organism varying in 

 length from i to 4 /^, but having a quite uniform breadth of 

 about one micron. In a suitable medium it grows out in long 

 flexible filaments which combine to form thread-like bundles. 

 When examined, the ends of the rod seem to be square cut. 

 In preparations from animal tissues there appear sometimes to 

 be slight concavities in the ends of the segments when two of 

 them are united. In cultures spores are formed. These are 



