112 THE HORSE IN MOTION. 



natural. The walk, trot, and run are all equally natural, and each is 

 best adapted to each of the three degrees of speed which the animal 

 finds it convenient or necessary to employ in his feral or unbroken 

 state. 



It will be seen that the theory of the trot is the same as that in the 

 run, namely, that the centre of gravity shall be supported constantly 

 and propulsion made uniformly by all the extremities from the time 

 they reach the grotuid until they leave it, but by two alternate limbs 

 at a time, and not by one as in the run. The action of the limbs in 

 shortening and extending, to enable them to begin the support early 

 and continue it late, and permit the centre of gravity to pass over them 

 without being deflected, is the same in both paces. The action is 

 the same, differing only in degree. The undulations are greatest in 

 the slow trot, and diminish as the speed is increased. Every rider 

 knows this from experience ; the uncomfortable trot is the slow one. 

 The reason for this was explained when treating of the run in the last 

 chapter. In the slow trot the action of the muscles is not sustained, 

 and the bony levers are allowed to resume their normal angles. At 

 each half-stride the centre of gravity regains nearly, if not quite, its 

 elevation ; but as the horse increases his speed he lowers the centre of 

 gravity, and, in so doing, enables the extremities to reach farther and 

 sustain the weight longer, while the rapidity of the movement of the 

 body gives it a momentum that forces the suspensory ligament to yield 

 and the angles to close to the requisite degree to prevent the alternative 

 of deflection of the trajectory, or crushing of the limb ; and if measure- 

 ments be taken of the height of the horse at different portions of 

 the stride, it will be found that it is least when it would seem that 

 it should be the greatest, tliat is, when it passes the perpendicular, or 

 that point where the supporting limbs are shortest, as was shown in 

 the last chapter when analyzing the action in the run. 



While the action of the limbs in the two paces is similar, the co- 

 ordination of them presents some interesting points for consideration. 

 Instead of the great impulse being given by the fore leg, as in the 

 run, it acts in a lesser degree, raising the centre of gravity only so far 

 as to give its co-operating posterior extremity an opportunity to use its 



