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extensive!}^ spread disease in Russia, Holland, and England, and for 

 the last century has been gradually spreading in the Americas; more 

 so in South America. In 1804, in the five governments of Petersburg, 

 Novgorod, Olonetz, Twer, and Jaroslaw, in Russia, over ten thousand 

 horses and nearly one thousand persons perished from the disease. 



The causes of anthrax were for a long time attributed entirelj' to 

 climatic influence, soil, and atmospheric temperature, and they are 

 still recognized as most important predisposing factors in the develop- 

 ment of the disease, for it is usually found, especially when outbreaks 

 over any number of animals occur, in low, damp, marshy countries 

 during the warm seasons. It is more frequent in districts where 

 marsh}- lands dry out during the heat of summer and are then covered 

 with light rains. Decaying vegetable matter seems most favorable for 

 nourishing and preserving the virus. 



The direct cause of anthrax is always contagion or infection of a pre- 

 viously sound animal, either directly from a diseased animal or through 

 various media which contain excretions or the debris from the body of 

 a previously infected animal. The specific virus of anthrax was first 

 discovered by Davaine in 1851. He recognized in the blood of animals 

 suffering from anthrax microscopic bodies in the form of little rods 

 with bright spots at their extremities. It ^vas not, however, till a 

 quarter of a century later that Pasteur defined the exact nature of the 

 bacillus, the mode of its propagation, and its exact relationship to 

 anthrax as the sole cause of the disease. The bacillus of Davaine, or 

 the virus of anthrax, is a low organism, in the form of a rod with a 

 bright spot or spore at either end, which develops in the blood of an 

 animal, or in other favorable media, as chicken broth or meat jellies 

 kept at the temperature of the animal body. In the animal body the 

 bacilli have a tendency to be filtered from the blood by the tissues of 

 the organs through which the fluid passes, and to accumulate in the 

 spleen, liver, and elsewhere, so that these organs are much more viru- 

 lent than the muscles or less vascular tissues. AVhen eliminated from 

 the animal in the excretions, or when exposed to outside influences by 

 the death of the animal and the disintegration of the tissues, the body 

 of the rod is destroyed and the spores only remain. These spores, 

 which are the germs of the ^irus, retain their vitality for a long period; 

 they resist ordinary putrefaction; they are unchanged by moisture, 

 and they are not afleeeted by moderate heat. If scattered with the 

 debris of a dead animal on the surface of the ground, they may remain 

 around the roots of -the grass in a pasture, or may be washed to the 

 nearest low-lying ground or marsh. If buried in the body of an ani- 

 mal dead from anthrax, they may be washed deep in the ground, and 

 in later years (in one proven case seventeen years) be brought to the 

 surface and infect other animals. They are frequently brought to 

 the surface of the earth, having been swallowed by earthworms, in the 

 bodies of which they have been found. 



