CHAP. VII] 



RIDING AND SADDLES 



77 



the twelfth, and are of the same length from the 

 thirteenth to the eighteenth. They slope back- 

 wards from the first to the thirteenth or four- 

 teenth, the fourteenth or fifteenth is vertical, and 

 slope forward from the fifteenth or sixteenth to 

 the eighteenth. 



The twelfth or thirteenth is the smallest and 

 the thickest. The bodies of the vertebrae increase 

 in size as we pass back, because there is more 

 movement in the rear part of the back, and 

 therefore a greater curvature is required between 

 each body to allow for this twisting movement. 

 The spinal column consists of an arch with its 

 apex at the fourteenth or fifteenth dorsal ver- 

 tebra. The arch is trussed by powerful muscles 

 woven in between the spines, acting as ties, and 

 by a powerful muscle under the column (longus 

 colli), as well as by a large number of powerful 

 inelastic and elastic ligaments. This arch or 

 girder is not rigid, as will be clear to anyone 

 who has studied the horse ; it can be arched, 

 depressed, or bent to either side at will. 



298. The first six or eight of these spines 

 form what is called the withers. On top of the 

 spines there is a white, non-elastic ligament 

 (supra-spinous), but over the withers this liga- 

 ment is interwoven with the rear end of the 

 yellow elastic ligamentum nuchse that supports 

 the weight of the head. Pressure or friction on 

 any of these spines will cause diseased ligaments 

 and, eventually, diseased bone ; but, if over the 

 yellow ligament above the withers, the result 

 will be far more serious. It is for this reason 

 that fistulous withers are so common and so 

 difficult at times to heal. 



299. As stated above, the tops of the ribs must 

 be made to bear the weight. The top portion 

 is at a considerable angle in the front ribs, but 

 nearly horizontal in those at the back, so that 

 the pressure from the front of the saddle will 

 naturally tend to force a saddle downwards and 

 pinch the horse. The pressure is not taken 

 directly by the bones ; any pressure or friction 

 is first taken by the periosteum, a thin, highly 

 vascular skin covering the bone. This skin, if 

 damaged, dies, and causes necrosis, i.e. death 

 of the bone below. This shows the importance 

 of keeping all bony prominences free from 

 injury, and shows how much more careful we 

 must be when a horse is in poor condition and 

 has less muscle covering his bones, as, for 

 example, at the end of a campaign. The top 

 portion of the ribs on each side of the spinal 

 column is covered by a powerful muscle (longis- 

 simus dorsi), which is again covered by skin 

 and hair. It is this, then, that actually bears 

 the weight and acts as a cushion between the 

 bones and the saddle. 



300. We found above that the front part of 

 the saddle may tend to pinch the first few ribs 

 together, and, fortunately, the bottom ends of 

 these ribs are securely attached to the breast- 



bone, otherwise we should not be able to put a 

 saddle upon a horse without interfering with 

 the action of the heart and lungs. Whilst the 

 amount of muscle covering the bony back makes 

 a better cushion, it is the cause of sore backs, 

 being so difficult to treat surgically. The reason 

 is that when pus (matter) forms under the skin, 

 instead of its breaking out and the wound heal- 

 ing quickly, it burrows down between the layers 

 of muscle, carrying the infection wherever it 

 goes. In fistulous withers the pus will burrow 

 inside the muscles of the shoulder-blades, and an 

 incision for drainage may have to be made 

 below. Where the pus has burrowed down, 

 setons should be inserted and the holes kept 

 open until they heal from the top. If wounds 

 are allowed to heal from the bottom they will 

 not drain, and blood-poisoning will result. The 

 healing of bad saddle-sores cannot be hurried, 

 because if hurried worse consequences inevitably 

 result. The next point is how far the saddle 

 should extend to the front. We see that it must 

 not extend posterior to the ribs. In Chapter VI. 

 we saw that the shoulder-blade moved to and fro 

 as the horse moved. As this bone moves back, 

 the muscle bulges out. The foremost part of 

 the saddle must not in any way interfere with 

 the play of this bone or the action of the muscles. 



301. It is clear that the shape of the back 

 and shoulders will materially affect the position 

 of the weight, the amount of weight that can 

 be carried, and the extent to which the weight 

 will move when the horse is in motion. With 

 nearly all kinds of backs a saddle tends to work 

 forwards, hence a breastplate (now almost 

 abolished) is seldom of any use. On some horses 

 with large girths i.e. deep and wide over the 

 first few ribs and narrow behind, like a grey- 

 hound the saddle will tend to slip backwards, 

 and the use of a breastplate is advisable. Al- 

 though the saddle itself generally tends to work 

 forward, the blanket or numnah, under the 

 saddle, tends to work backwards in the direction 

 of the hair, so that if the numnah or blanket is 

 strapped to the saddle the tendency of the saddle 

 to work forward is greatly diminished. 



302. Backs. The front of the portions of the 

 saddle resting on the ribs must be embedded in 

 the hollow behind the shoulder blade, so as to 

 prevent the possibility of the saddle slipping 

 over these parts. These portions of the saddle 

 must be well padded to prevent injury. 



The conformation of the back varies greatly. 

 Short backs are stronger and generally wider in 

 the loin. A back cannot be too short, if it is 

 long enough to fit the saddle. A long back is 

 generally weak and narrow. A horse cannot be 

 too short above his body, but he must have 

 sufficient length underneath. High withers are 

 most liable to injury, as they are thinner and 

 less covered with flesh ; they, however, 

 generally, indicate good action in front, which 



