CHAPTER IX 



THE SKIN 



It is obvious that one important function the skin performs 

 is that of affording cover to the delicate parts beneath ; where- 

 ever the chance of injury is the greatest, the skin is the thickest, 

 while in those parts where sensibility is most required it is thinnest. 

 The skin of the back, quarters, and limbs are good examples of 

 the first type ; on the back especially, a protective covering is 

 found which, in some horses, is as much as J inch in thickness : 

 the face and muzzle are a good example of the latter variety, 

 the skin in some parts being as thin as paper. In those regions 

 not exposed to violence it is also thin, as on the inside of the 

 arms and thighs. In spite of the thinness of the skin its strength 

 is remarkable ; a horse's body may be dragged along by the 

 thin skin of the head. 



The skin as an organ of touch is of great importance. All 

 animals appear most sensitive to even slight skin irritation ; 

 flies will cause horses considerable suffering, and the elephant, 

 with its thick hide, is quite as intolerant of these tormentors 

 as is a well-bred horse. The skin is highly endowed with 

 sensory nerves, especially that part connected with the organs 

 of prehension ; the long hairs, ' feelers,' growing from the muzzle 

 of the horse end in special tactile structures in the skin (Fig. 89). 

 The skin is a bad conductor of heat, and this is considerably 

 assisted by the layers of fat found beneath or at no great distance 

 from it, as in the abdominal region ; it is the subperitoneal fat 

 which protects the viscera of animals living in the open and 

 lying in wet places. The epidermal covering of the skin relieves 

 the parts beneath from excessive sensitiveness ; through the 

 sebaceous secretion it assists in preventing loss of heat, while 

 the greasy covering helps the hair to throw off rain, prevents the 

 penetration of water, and so saves the epidermis from dis- 

 integration. Horn is skin which has undergone a modificatiQn. 

 Hair. — Not all parts of the body are covered by hair. There 

 is very little on the muzzle and lips, and it is very scanty on the 



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