THE BAR, THE EYE, THE SKIN, AND THE FOOT 177 



from the fact that they bring the body into communication with 

 objects which may be long distances away. 



THE SKIN 



The skin is the covering tissue which acts as a mechanical 

 protection to the surface of the body. On the back of horses 

 and cattle it is 34 inch thick and very strong; on the face it 

 is nearly as thin as paper. It consists of two main layers, the 

 epidermis or scarf skin being the outer, and the dermis or true 

 skin the inner. The epidermis is composed of several layers of 

 cells; the outer of these cells are horny, scale-like, and fall off in 

 the form of dandruff when horses are groomed. It contains the 

 coloring-matter or pigment of the skin. The dermis is a vascular 

 structure containing a network of white fibrous tissue with some 

 elastic fibers. Its inner face' adheres closely to the stratum of 

 fatty tissue which lies beneath it. Its external face is perfo- 

 rated by openings for the hairs and the ducts of the sebaceous 

 and sweat-glands, which he in the lower layers of the dermis. 



In health the skin feels pliable and elastic, and is easily movable 

 upon its underlying tissues. When a fold is drawn up between 

 the fingers, it quickly regains its normal position when released, 

 unless the animal is old or in a state of poor nutrition. 



The sebaceous glands have small openings into the hair f ollicles. 

 They secrete an oily substance known as sebum, which serves to 

 keep the hair glossy and the skin soft and pliable. 



The sweat or sudoriparous glands discharge sweat directly 

 upon the surface of the skin. They are more than 3,000,000 in 

 number. They occur over the entire surface of the horse's 

 body, but are confined to certain areas in some animals. Sweat 

 is a watery fluid, salty to the taste, of strong alkaline reaction, 

 and characteristic odor. Besides water it contains inorganic 

 salts, fatty acids, and waste products. It serves to keep the skin 

 moist and in good condition, to remove waste and poisonous or 

 irritating matters, and to regulate the body temperature by 

 evaporation. In order to keep the skin "pores" from clogging 

 up, the skin should be groomed daily and washed occasionally, 

 otherwise it will become dry, hard, and thick. 



The appendages of the skin comprise the hair, the chestnuts 

 and ergots on the legs, the hoofs of the feet, and the horns. 



Hair is a modification of the epithelium and covers all parts 



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