30 iiorse-back: rtding. 



because it most disturbs the centre of gravity ; but it 

 is also, if we except the walk, the one which can be 

 indulged in longest, by both horse and rider, be- 

 cause of the great number of muscles brought into 

 action, and which seem to divide the labor and pre- 

 vent fatigue from being felt as soon as when the 

 number of muscles is smaller. 



The reader may judge from this explanation of the 

 communicated movements how complicated they are, 

 and those executed by the rider himself are not less 

 so, as the following analysis will show. 



The rider sits on the saddle with his thighs firmly 

 pressed against it, the knees also, though not too 

 hardly, the leg free, with the foot resting in the 

 stirrup in order to aid in supporting the knee, for on 

 the fixity of the point of support furnished by the 

 knee depends the solidity, as on the proper position 

 of the body and the centre of gravity does the firm- 

 ness 6f his seat. This pressure, which should be 

 stronger than in walking, since the disturbance is 

 greater, is effected as we have seen by the adductors 

 of the thighs. 



With the knees so fixed, the trunk no longer obeys 

 the forward impulse, or at least the displacement in 

 this direction is much diminished, and there is little 

 more than slight vertical movement, from below up- 

 wards, which takes place when the ischium leaves the 

 saddle to fall again by the force of gravity. This is 

 not the case with the superior portions of the body, 



