20 ELEMENTS OF MAMMALIAN ANATOMY. 



variety of the cat. The Mombus cat of Africa has short 

 stiff hair, while the Angora or Persian cat is remarkable for 

 the length and delicacy of its soft fur. The hair, like the 

 nails, is an extreme modification of the epidermis. Each 

 hair grows from a .papilla at the bottom of a small sac, the 

 follicle, which is a depression in the corium. The central 

 part of the hair is the pith, and the external portion, formed 

 of thin overlapping scales, the cuticle. The coloring-matter 

 lies in the superficial scales, and may be disposed in such an 

 irregular manner that one-half of a hair is white, and the 

 other half yellow. 



The large hairs on either side of the nose are known 

 as vibrissce. Their roots are provided with delicate nerve- 

 endings of touch, so that the animal may find its way with 

 ease through dark narrow passages. There are a few long 

 hairs above the eyes, forming the eyebrows, but no eye- 

 lashes are present. 



Most of the hairs are inserted obliquely into the skin, 

 but when angered the cat can erect them by the contraction 

 of a small muscle passing from the skin to the hair-bulb. 



On some mammals the hairy covering is partial and 

 limited to particular regions ; in others, as the hippopotamus 

 and the Sirenia, it is very scanty, but scattered over the 

 whole surface; while in the Cetacea it is reduced to a few 

 small bristles about the mouth. 



Some kinds of hair, as those of the mane and tail of the 

 horse, are shed and renewed annually. Most mammals 

 have a long hairy coat in winter which gives place in spring 

 to a short coat. The Arctic fox, hare, ermine, and numer- 

 ous other animals of the colder regions undergo a complete 

 change of color in the two seasons, being white in winter 

 and brown or gray in summer. By this protective colora- 

 tion they escape many of their enemies. 



