40 MANUAL FOR STABLE SERGEANTS. 



THE SKIN. 



101. The skin covers the external surface of the body. It 

 varies in thickness according to the amount of protection the dif- 

 ferent parts of the body require. The skin is the special organ of 

 touch and is supplied with sensory nerves, particularly at the muz- 

 zle and lips. The long hairs (feelers) growing from the muzzle, and 

 in special nerve structures in the dermis. 



102. The skin consists of two parts; the outer, called the epider- 

 mis, or cuticle; and the inner, the corium, dermis, or true skin. 



103. The epidermis is the outer protective covering. The hoof, 

 ergot, and chestnuts are modifications of the epidermis. 



104. The dermis lies beneath the inner surface of the epidermis 

 and continually replaces it as it is worm away. It contains the hair 

 follicles, the sebaceous and the sweat glands. 



105. Hairs grow from the hair follicles, and form the outer pro- 

 tective covering of the body known as the coat. The coat is shed 

 twice a year, in the spring and in the fall, and is replaced by a 

 lighter or heavier growth according to the season. 



108. The sebaceous glands secrete an oily substance which is 

 formed within them. Where the skin is covered with hair the 

 sebaceous fluid is discharged into the hair follicles. It softens and 

 waterproofs the hair and surrounding skin, keeping them flexible 

 and giving the hair the gloss that is seen in healthy animals. AVhere 

 no hair is present the glands discharge directly on the surface oi 

 the skin, keeping it soft and supple. 



107. The sweat glands are groups of cells which excrete sweat. 

 They communicate with the outer surface by simple tubes which 

 pour their excretions on the surface of the skin. Sweat consists of 

 water and various salts and waste materials from the blood. It 

 evaporates on the surface of the skin and assists in regulating the 

 temperature of the body. 



THE FOOT. 



108. The foot is composed oi four parts: the bones', the elastic 

 structures; the corium; and the hoof, the protective organ of the foot. 



