[Sidenote: Mechanical assistance of jockey.]
The question whether a jockey can mechanically assist his horse, does not rest on the same footing. I believe he can, thus. If a man sits astride of a chair, with his feet off the ground, and clasps the chair with his legs, by the muscular exertion of his lower limbs he can jump the chair along. The muscular force is there employed on the foreign fulcrum, the ground, through the medium of the legs of the chair. The muscular action strikes the chair downward and backward, and if the chair was on ice it would recede, so also would the feet of a horse in attempting to strike forward. If the chair was on soft ground, it would sink, so also would a horse, in proportion to the force of the muscular stroke. But if the resistance of the ground is complete, the reaction, which is precisely equal and in a contrary direction to the action, will throw the body of the man upward and forward, and by clasping with his legs he will draw the chair also with him. But he can only accomplish in this way a very little distance with a very great exertion. If the jockey made this muscular exertion every time that his horse struck with his hind feet, his strength would be employed on the foreign fulcrum, the ground, through the medium of his horse’s bony frame. Thus the jockey would contribute to the horizontal impulse of his own weight, and exactly in proportion to the muscular power exerted by the jockey, the muscular system of the horse would be relieved. At the same time no additional task is thrown on the bony frame of the horse, since, if the jockey had not used his muscular power on it in impelling his own weight, the muscular system of the horse must have been so employed. It is true, that not much is done after all with a prodigious exertion, but if that little gains six inches in a hardly contested race it may make the difference of its being lost or won. Thus an easy race is no exertion to a jockey, but after a hardly contested one, he returns with his lips parched, his tongue sticking to the roof of his mouth, and every muscle quivering.
The working a horse up with both hands on his mouth is easier to the jockey than using the whip, and more effective in rousing the horse to his greatest exertion.