52.^ 



CHAPTER XX. 



SKIN, COLOUR, AND HAIR. 

 General Remarks — SUin — Colour — Hair. 



General Remarks.— The body of the horse is 

 invested with a covering, the structure and functions of 

 which vary according to its position. It acts more or 

 less as a filter for the watery portion of the blood in its 

 neighbourhood ; has the power to effect certain changes 

 in the excreted material ; and thus provides itself with a 

 protective layer (epidermis), which takes the respective 

 forms of cuticle (outer skin or scarf skin), hair, and horn. 

 The material for this epidermal layer is derived from the 

 fluid which has been exuded from the superficial blood 

 vessels, and is more abundant when the circulation is 

 slow, than when it is fast. Consequently, horses in cold 

 chmates have tliicker coats and hoofs than those in hoi 

 countries. Dr. W. H. Willcox kindly points out to me 

 that various forms of disease in which the circulation is 

 slow, are characterised by growth of the epidermis. Thus, 

 in human tuberculosis, the hair of the scalp and the eye- 

 lashes tend to grow long ; the skin gets coarse and thick ; 

 and the body often becomes covered with tine, downy 

 hair. In cases of myxoedema with weak circulation, and 

 in those of congenital heart disease, the skin is thick and 

 the hair coarse. On the other hand, high fever is often 

 accompanied by loss of hair. In heavy cart horses, we 

 hnd the growth of hair and horn, especially that of the 

 chestnuts and ergots (p. 319), much more profuse than 



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