WEIGHT-BEARING SURFACES. 117 



small recesses in which the ends of the points of the tree 

 rest. Ds are small semicircular metal rings which are 

 attached by chapes (short straps) to the front and back of 

 the saddle for strapping on a coat, shoe-case, etc. Staples 

 are somewhat similar in size and shape to Ds, but are firmly 

 fixed to the front of the tree, and are used to afford attach- 

 ment for the breast-plate. 



WEIGHT-BEARING SURFACES OF A HORSE'S BACK 



AND LOINS. 



If we examine a horse's skeleton, we shall find that his 

 spinal column is composed of a large number of short bones 

 called vertebrae. There are seven vertebrae of the neck, 

 eighteen of the back, six of the loins, five of the croup, and 

 from thirteen to twenty of the tail. In the middle of each 

 vertebra there is a more or less upright bony projection 

 (spine), which is only thinly protected from injury by skin 

 and ligaments. At the withers, these projections or spines 

 attain their greatest length. On each side there are eighteen 

 ribs attached, above, to the eighteen vertebrae of the back, 

 and below, to the breast-bone ; thus forming a strong case 

 or barrel, which is capable of offering considerable resist- 

 ance to pressure applied to its upper surface. The last few 

 ribs have a decided slope to the rear ; in fact, in a well- 

 ribbed-up horse, the end of the last rib would come within 

 three or four inches of the point of the hip. The vertebrae of 

 the loins have long side projections of bone (transverse pro- 

 cesses) but no ribs. Consequently the loins are not as well 

 fitted to bear weight as the back. The space on each 

 side of the back and loins is occupied by a large mass of 

 muscle. The rearmost portion of the shoulder-blade lies 

 immediately below the withers, and is covered by a lump of 

 muscle which is known to saddlers as the " saddle muscle." 

 During movement, the top of the shoulder-blade rotates back- 



