THE SKIN 31 1 



perature rises above the normal during work, in some cases, 

 it is said, as much as 2-5° to 3 C. (4 to 5 Fahr.), and remains 

 so for some time afterwards. Another peculiarity in sweating 

 of the horse is the patchy perspiration observed occasionally, 

 such as a wet patch on the side or quarter which dries slowly, 

 or may remain for days or weeks, even months, in a wet or damp 

 condition. This must be a paralytic secretion, but nothing is 

 known of its true nature. Finally, there is no drug, so far as 

 we are aware, which produces sweating in horses ; this is perhaps 

 an explanation of the common use of nitre in veterinary practice, 

 the kidneys being made to do the work of the skin. 



Sebaceous Secretion, or Sebum, is a fatty material formed in 

 the sebaceous glands of the skin, which in the horse are freely 

 distributed over the whole surface of the body. Though it is 

 spoken of as a secretion, yet the process involved is not secretory, 

 inasmuch as the cellular elements of the gland are not actively 

 employed pouring out material, but are themselves shed after 

 undergoing fatty metamorphosis. The greasy material thus 

 produced saves the epithelium from the disintegrating influence 

 of wet, keeps the skin supple, and gives the gloss to the groomed 

 coat ; from its greasy nature it assists in preventing the pene- 

 tration of rain, and thereby saves, to some extent, undue loss of 

 heat. 



Dandruff. — The material removed from horses by grooming 

 consists of a white or grey powder which can readily be moulded 

 by pressure into a dough-like mass ; it has a curious smell, 

 which can only be described as ' horse-like.' It consists of epi- 

 thelial scales, fat, largely in the form of lanolin, colouring matter, 

 salts, and a considerable amount of silica and dirt, the two latter 

 depending upon the cleanliness of the animal. The amount of 

 dandruff lost in an ordinary grooming varies from 1*25 to 

 375 grammes (20 to 60 grains) for clean horses, and 11 to 13 

 grammes (170 to 200 grains) for very dirty animals. An analysis 

 of dandruff from the horse gave the following composition :* 



Water - - - 1796 



Fat- ... 1240 



Organic matter - 56*22 containing roj of urea. 



Ash- - 13" 42 „ 2- 45 of silica. 



ioo-oo 



The fatty matter in the skin proves to be lanolin, the same 

 as that found in the fleece of sheep ; it explains the reason why 

 horses living in the open should not be too freely groomed, and 



* ' Dandruff from the Horse, and its Pigment,' Journal of Physiology, 

 vol. xv., 1893. 



