192 A Manual of Veterinary Physiology. 



The epidermal covering of the skin relieves the part from 

 excessive sensitiveness, such as would occur to an exposed 

 sensory surface, and through the sebaceous secretion it 

 assists in preventing loss of heat, whilst the greasy covering 

 throws off the rain, prevents the penetration of water, and 

 thus saves the epidermis from disintegration. 



By means of the hair growing from the skin the heat of 

 the body is maintained and prevented from passing off too 

 rapidly. The thickness of the hairy covering varies con- 

 siderably with the class of horse : the better bred the animal 

 the finer the coat. I have obtained from draught horses 

 between 7 lbs. and S lbs. of hair by clipping : in a well-bred 

 horse this would be reduced to 10 ozs., or even less. 



It is a well-known fact that, excepting the hair of the 

 mane and tail, that of every other part of the body has 

 only a temporary existence, and is changed twice a year — 

 once for a thick, and once for a fine coat. It is found that 

 the heavy coat grown by horses is the cause of considerable 

 sweating at work, and the general practice of clipping has 

 been introduced. Of its value there can be no doubt : it 

 considerably reduces the risk of cold and chest disease, 

 for animals, instead of coming in from work with a wet 

 skin — which in some cases will not dry for hours — are 

 readily dried and easily protected against inclement weather. 



Animals Avhich sweat freely at work lose condition. 1 

 have shown that this is due to the proteid lost by the skin, 

 for, as we shall presently see, proteids are regularly found in 

 the sweat of the horse ; clipping largely prevents this loss. 

 As to the influence of clipping on temperature, see 'Animal 

 Heat.' 



The loss of epidermis by the skin from grooming and 

 other causes is something considerable, and is an explana- 

 tion of the nitrogen deficit met with in experiments on the 

 body-waste. The amount of epidermis lost during an 

 ordinary grooming will vary considerably, depending on the 

 cleanliness of the animal and the state of the coat ; in fairly 

 clean horses it, has nraounted to between '2~> to 60 grains, 

 and in very dirty animals from 170 grains to '220 grains. 



