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

 a previously infected animal. The specific virusof anthrax was first dis- 

 covered by Davaine in 1851. He recognized in the blood of animals suf- 

 fering from anthrax microscopic bodies in the form of little rods with 

 bright spots at their extremities. It was 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 ani- 

 mal 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 virulent than the muscles or less vascular 

 tissues. When eliminated from the animal in the excretions, or when 

 exposed to outside influences by the death of the animal and the disinte- 

 gration of the tissues, the body of the rod is destro^'ed and the spores 

 only remain. These spores, which are the germs of the virus, retain 

 their vitality for a long period ; they resist ordinary i^utrefaction ; they 

 are unchanged by moisture, and they are not affected by moderate heat. 

 If scattered with the d6bris of a dead animal on the surface of the 

 ground, they may remain around the roots of the grass in a i^asture, or 

 may be washed to the nearest low-lying ground or marsh. If buried in 

 the body of an animal 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 earth- 

 worms, in the bodies of which they have been found. 



This accounts for the outbreaks at the time of the first rains after a 

 dry season. During the latter the earthworm goes deep in the ground 

 in search of moisture ; it finds the spore which has been washed there 

 in past years, swallows it, and brings it to the surface, when the rain 

 furnishes the moisture which drives the worm itself from its deeper 

 home. The virus is carried with the wool from infected sheep and re- 

 mains in it through the process of manufacture into cloth. The spores 

 remain in the hides of animals which have died of anthrax and retain 

 their vitality throughout months of soaking in the tanners' pits, the 

 working of the harness-maker or the cobbler and after the oiling of the 

 completed leather. The dried spores in the dust from any of these prod- 

 ucts may be carried by the atmosphere. 



Infection of an animal takes place through inoculation or contact of 

 the-bacillus or its spores with an abraded surface or mucous membrane 

 on a sound animal. In an infected district "horses may eat the rich 

 pasturage of spring and early summer with impunity, but when grass 

 becomes low they croi) it close to the ground, pull up the roots around 



