THE SKIN 313 



loss of temperature, and show signs of weakness. The effect of 

 varnishing the skin is to cause the capillaries to dilate, and so 

 produce a great discharge of heat. 



For absorption from the skin, see ' Absorption,' p. 282. 



The Chestnuts and Ergots are considered to be the remains of 

 hoofs belonging to digits long since lost by the horse ; the former 

 can be distinctly seen in the foetus. The ergot grows from the 

 back of the fetlock ; the chestnut is found on the inside of the 

 arms and hocks, and is always larger in the former position. In 

 the heavy type of horse it may grow to* a considerable size. The 

 horn of which it is composed is tubular in structure, and produced 

 by the papillae of the skin. After growing a certain size they 

 drop or are pulled off. Both ergots and chestnuts are found 

 larger in horses wanting in quality than in those better bred ; 

 in the donkey and mule the chestnut forms no outgrowth of 

 horn, but a hairless black patch represents its position. 



Pathological. 



The chief pathological conditions of the skin are those due to 

 parasitic invasion ; this may produce widespread disease in all 

 animals. 



