CONTAGIOUS AND EPIZOOTIC DISEASES. .^ 



or brown mucous membranes, enlargement, or even rupture of 

 the spleen (milt), and a very high mortality. 



Causes. — It is propagated by contagion but tends to die out 

 whan i^roduced in this way only. It is transmitted by contact 

 with the blood, liquid exudations, portions of the diseased 

 carcass, fat, skins, hair, wool, bristles, feathers, and bowel 

 evacuations, and rarely or not at all through the atmosphere. 

 Simple contact of these matters with the healthy skin of a 

 susceptible subject is enough to produce the disease. The 

 virus is most potent when received from an animal still living 

 or only recently dead, and yet may be preserved for months in 

 all conditions of cUmate, temperature, and humidity. 



Eating of the flesh of animals killed while suffering in this way 

 has often conveyed the disease in spite of the cooking to which 

 it was subjected. Fifteen thousand of the inhabitants of St 

 Domingo once perished in six weeks from this cause, and a 

 whole family was poisoned a few years ago in Aberdeenshire. 

 The Tartars perish in great numbers from eating their anthrax 

 horses. Mosquitoes and other insects with perforating appar 

 atus to the mouth probably help to communicate it, as nearly 

 all cases in man occur on exposed parts of the body. 



Its development in a locality is determined : — i. fey the rich 

 surface soil abounding in organic matter, and the impervious 

 subsoil preventing natural drainage. 2. The frequent in- 

 undations of banks of rivers flowing through level countries and 

 the drying up of ponds and lakes leaving much organic deposit 

 in their basins. 3. A continuation of warm, dry weather which 

 favours organic emanations from such places as the. above. 4. 

 A condition of the system of the animal predisposing to the 

 reception and growth of the poison, and consisting in the loading 

 of the blood with plastic or waste organic matter, as in over- 

 fed plethoric animals, in those making flesh most rapidly, in the 

 young and rapidly growing, in those rendered unhealthy by 

 overwork, impure air, unsuitable food or water. 5. Sudden 



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