The Nervous System. 103 



these depressions are well supplied with nutriment, and 

 are lined with cells from which are developed hairs. 

 Hairs are placed obliquely (on the slant), and by means 

 of a little muscle placed close to their roots, are brought 

 into the upright position, the effects of which are seen 

 in boars and dogs when excited, other conditions, such 

 as ill-health, cold, etc., have the same effect. Each hair 

 is enlarged at the enclosed end, and is lodged in a hair 

 follicle. The whiskers or cat hairs seen on the lips of 

 horses and cats are furnished with nerves which render 

 these hairs very sensitive. The term horse hair refers 

 to the hair of the mane, forelock, tail and fetlocks, and 

 in some breeds, notably Shires, to the strong coarse hair 

 at the knee and hock. In the pig the term "bristles" 

 denote hair; in sheep, where it is very fine, long and 

 wavy, it is known as wool; in the mule and ass, the 

 forelock and mane are either lacking or else only partially 

 developed, the hair of the tail in these animals being- 

 limited in quantity; in cattle, the development of hair at 

 the end of the tail is known as "the switch. " The 

 escutcheon of cows, held by some to be an indication of a 

 cow's milking qualities, is formed by the two-way-direc- 

 tion of the hair on the back part of .the thighs; from the 

 udder, the hair being directed upwards, on the outside 

 of the thighs it takes the opposite directions; the oppo- 

 site directions of the hair on the backs of pigs constitute 

 swirls. The color of the hair varies in animals at dif- 

 ferent periods of their lives, e. g., the iron gray horse as 

 -it ages grows whiter; the color is also affected by wounds, 

 old scars often growing white or gray hairs; the foal is 

 generally an entirely different color to what it is at ma- 



