86 



PHYSIOLOGY OF FARM ANIMALS 



[CH. 



The use of hair is to assist in heat retention. For this reason 

 animals which are subjected to severe climatic conditions have 

 thicker coats than those in warm countries. With horses the 

 thickness of the hair varies with the breed, and the better bred 

 the animal the finer the coat. There are about 4300 hairs to 



■ stratum cornei 



— st. lucidum 

 st. granulosun 



St. Malpighii 

 St. germinati- 



muscle of hai 



(lerniic coat o 

 hair 



- medulla of ha 



Fig. 43. Section of epidermis and dermis (from Gray). 



a square inch excepting on the muzzle and lips, the inside of the 

 ears, the inside of the thigh, the mammary glands and the 

 external generative organs where there are very few hairs. The 

 coat is changed twice a year, being alternately fine and thick. 

 Generally speaking this change is related to the temperature of 

 the air, and is not simply seasonal. Thus horses in a heated 



