MAKGE. 187 



is the reverse of this ; the malady spreads slowly, attacking the 

 skin as it were, inch by inch. 



Mange, in its spontaneous form, usually commences upon 

 the limbs between the coronet and the knee, or between the 

 coronet and the hock, and their appearance when affected is 

 characteristic of the malady. The hair is broken and uneven in 

 its length ; portions of the skin are covered with short, scanty, 

 down-like hair, which appears as thougli dusted with a pale 

 mixture of flour and soot. Sometimes filthy looking sores are 

 present, surrounded by thick crusts of scurf ; in other cases 

 the skin and sub-textures are deeply ploughed with long 

 ragged sores. 



The general health of horses thus affected may be good or 

 it may not. I have known horses to be affected with Mange of 

 the extremities for years, and remain stout and vigorous the 

 whole time ; while the general health of others, diseased to all 

 appearance in a precisely similar way, was indifferent, and their 

 appearance unthrifty and mean-looking. 



Cause of Mat^tge. — The immediate cause of Mange is now 

 ascertained beyond all doubt to depend upon the existence of 

 a species of insect denominated by naturalists Acari Equi, 

 being present upon the skin in immense numbers ; and 

 which are known, under conditions favourable to their increase, 

 to spread vsdth excessive rapidity. 



The annexed figures are exact representations of this insect 

 as it appears upon the stage of a microscope, when viewed 

 with the aid of a good one-inch object glass. These figures 

 are copied from engravings, after drawings by Erasmus "Wilson. 

 The figure at the top of the page represents the insect as it 

 appears when placed upon its back ; the lower figure represents 

 the dorsal surface of the same, or as the insect is seen when 



