l62 ANIMAL MANAGEMENT. 



melting of the muscles on the back bringing the skeleton beneath into 

 view. 



It is this metamorphosis of the back which has to be so anxiously 

 watched on service. It is this which renders all previous saddle fittings 

 useless, for the impoverished back is as different from the well-nourished 

 one as anything can possibly be ; it is as though we compared the 

 skeleton to the living subject. 



We dwell upon and emphasise this question of back muscle ; it is the 



foundation of a clear conception of sore backs and their causes, and it is 



the basis of all preventive measures. 



Effect of We have previously mentioned something of the structure of the skin, 



pressure but have now to deal with certain features in its construction which 



°U" f influence, to a considerable degree, the production of sore backs. We 



the"back have described the blood-vessels in the skin and how readily pressure 



acts in keeping these vessels empty ; the illustration which was given 



being the white mark on the back of the hand after pressure with a finger. 



The lay mind does not readily grasp the fact that quite a considerable 

 portion of the blood of the body is circulating in the skin, and that one 

 object of this is to ensure the rapid renewal of the skin, which being 

 exposed to friction, would soon wear away to the sensitive parts unless 

 constantly replaced. There are other functions the blood and the skin 

 performs, but these are not germane to our subject and may be 

 neglected. 



If the blood supply of any part of the body be cut off, the part dies. 

 Whether it dies rapidly or slowly depends upon the thoroughness with 

 which the blood stream has been cut off; if complete, the death of the 

 part will only be a matter of a few hours, if incomplete it may take a few 

 days. This statement holds good whether it be the question of a limb or 

 a small piece of skin on the back. 



Pressure will kill any of the tissues of the body ; a leg may be 

 completely amputated, skin, muscles, and bone, without the use of a knife 

 or saw— a simple piece of elastic cord will do in the course of weeks 

 what a knife can do in a minute or two. The pressure of the cord cuts 

 off the blood supply, the part dies, and is gradually cast off. 



The limb amputated by an elastic cord is an exaggerated example of 

 the influence of pressure ; for the purpose of the subject we are 

 considering we have not to think of any pressure greater than that 

 produced by a man's weight, or any structure to die as the result of 

 this pressure other than those found in the back. 



The skin of the horse's back is subjected to pressure when the man 

 mounts, and in consequence less blood circulates through it than before. 



