MANGE. 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 afiected 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 though 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. 



Causes op Mange. — 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 lEquir 

 being present upon the skin in immense numbers, and which 

 are known, under conditions favourable to their increase, to 

 spread with excessive rapidity. 



The figures on the following page 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 ; and 

 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 



