right diagonal pair), the thrust of the left diagonal pair will be the greater, and, since the thrust acts in the direction of the other diagonal, the right shoulder" will gain more ground than the left. From this there results, after a certain length of time, a disagreeable irregularity in the gait.
The results explained in the second remark above may be practically utilized. If the rider discovers that his horse trots unevenly and advances one shoulder more than the other, he should rise habitually on the shoulder that gains less ground until the fault is corrected.
These results may also be utilized to correct the fault of a horse always leading with the same foot at a gallop. Suppose, for instance, a horse that always gallops on the right foot: to lead with the right foot the horse sets the right shoulder in advance of the left. If, therefore, the rider persists, for a certain length of time, in rising from the left diagonal pair, the left shoulder, as has been explained above, will be pushed further forward than the right and the horse will be in a position at a trot that will induce him to lead with the left foot at a gallop.
From the preceding explanations it is evident that the rider should know how to trot his horse on either shoulder and to change shoulders without changing gait if he wishes to develop the animal's efficiency equally and have him always perfectly straight.
The only exception is when the legs of one diagonal pair have been injured and they can be saved by rising from the other.
Lengthening and shortening the gait at a walk and trot.—Lengthening and shortening of gaits must be executed gradually and by the steady use of the aids. The lowering of the head and the extending of the neck assist in producing a lengthened gait. The raising of the head and curving of the crest favor a shortening of the gait.
