The Skin. 195 



the secretion that the vaso- dilator fibres should be in 

 operation, for we know that sweating will occur in a nearly 

 bloodless skin, as in the cold sweats following on ruptures 

 of such viscera as the stomach : and against this we have 

 the fact that in many cases of arterial thrombosis of the 

 hind limbs the sweat is pouring off the general surface of 

 the body (probably from pain), whilst the quarters and 

 hind extremities remain dry. 



The special secreting fibres supplying the cells of the 

 sweat glands have centres in the cord for the body and 

 limbs, and in the cervical sympathetic for the head. There 

 is also, probably, a sweat centre in the medulla. Dupuy 

 divided the cervical sympathetic of the horse, and obtained 

 sweating of the head and neck on the operated side.* 



The changes occurring in the secreting cells of the sudo- 

 riferous glands of the horse are described by Renaut.f 

 When charged the cells are clear and swollen, the nucleus 

 being situated near their attached ends ; when discharged 

 they are smaller, granular, and their nucleus more central. 



The amount of sweat secreted daily can only be roughly 

 guessed at : there are many conditions which affect it, such as 

 the length of coat, nature of the work, and pace. I should 

 think a minimum secretion would be about 1 pint, and this 

 I arrived at by brushing a horse lightly over with water. 



Doubtless the compensating action existing between the 

 kidneys and skin observed in men exists also in the horse, 

 viz., when the skin is acting freely less water passes by the 

 kidneys, and vice versa. 



Sebaceous secretion or sebum is very extensive in the 

 horse ; its action is protective to the skin. The glossy coat, 

 which is due to the natural skin fat, throws off a con- 

 siderable amount of water before penetration occurs.^ In 

 certain places, as in the prepuce, considerable quantities of 

 this secretion are found. The sebaceous secretion of the 

 prepuce of the horse consists of 50 per cent, fat, and also 

 contains calcium oxalate (Lehmann).§ The secretion of 



* Landois and Stirling. f Quoted by Halliburton. 



I I have found that the dandruff removed from horses by grooming 

 contains a large quantity of fat. § Quoted by Halliburton. 



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