64 MECHANISM OF EQUINE LOCOMOTION 



draught, moves his load with his hind limbs in a more or less bent condition 

 {see Fig. 72), which will give his hind quarters the crouching appearance 

 which must be familiar to us all. Sloping pasterns from a load-pulling point 

 of view are objectionable in the cart-horse ; for the more oblique they are, the 

 greater is the mechanical disadvantage at which they work {see p. 6g). 

 Sloping shoulders, also, from the same point of view, are undesirable. 



Action of the Muscles which extend the Vertebrae. — 



When a horse prepares to kick, he, as a general rule, lowers his head and 

 arches his loins (" puts his back up " ), by doing which he relieves his hind 

 quarters of weight and puts it on his forehand. When, on the contrary, he 

 prepares to rear, he raises his head and neck and more or less hollows his 

 loins, so as to lighten his forehand and put more weight on his hind quarters. 

 If we examine Figs. 81 and 82 of the canter. Figs. 90 to 94 of the gallop, 

 and Figs. 140 to 144 of the leap, we shall see that the muscles which 

 enable a horse to rear, greatly aid the forward reach of the fore legs in 

 the canter and gallop. Also, the heavier the forehand, the greater difficulty 

 will they have to raise it. In the leap, they assist the leading fore leg in 

 raising the forehand. If the horse carries a rider, these muscles will have an 

 increased amount of work to do on account of extra weight being put in front, 

 and W'ill tire in a proportionately rapid rate. On examining the drawings 

 of horses in Chapter XII. at the various paces, we shall see that the faster 

 the movement, the more will these muscles be taxed, on account of the greater 

 distance of the centre of gravity from the hind feet, while one or both of which 

 support and propel forward the weight of the body. Hence we find that to 

 gallop fast or to jump " big," a horse must have good " rearing muscles," which 

 consist principally of those which straighten the hock, draw back the thigh, 

 and extend the vertebrce of the loins. These muscles also help to " lighten " 

 the forehand in the flying trot and fast " pacing," in both of which there is a 

 period of suspension, which will vary in length according to the weight that is 

 on the forehand. From these considerations I may lay down the law that the 

 faster the speed required, the stronger should the " rearing muscles " be. The 

 pair of them (one on each side) that is most readily noticed, is the loin 

 muscles, which in the ox constitute the upper cut of a sirloin, and which, in 

 the horse, we may see just behind the cantle of the saddle. I need hardly 

 say that the heavier the shoulder, the sooner will these muscles become tired ; 

 the shorter will be the stride ; and the slower will be the pace. Consequently, 

 horses for fast work ought to have light shoulders. Carrying out the same 

 train of reasoning, we may see that the longer a horse's body, the greater will 



