THE SCIENTIFIC EQUITATION 



centric circles, as the center of gravity travels from 

 O to M ; otherwise the equilibrium will be lost. Evi- 

 dently, the two left legs must travel farther than 

 the two right legs. 



But the length of the stride does not affect the 

 velocity or the momentum; consequently, it does 

 not change the center of gravity. The left front leg, 

 if it is to gain more ground than the right, must be 

 unloaded, since the rule is that any leg cannot 

 leave the ground before the weight which it carries 

 has been transferred to another support. This we 

 accomplish by flexing the head slightly to the left, 

 arid at the same time we establish the fixed point of 

 the rhomboidus and mastoido-humeralis muscles at 

 the left side of the atlas region. Thereupon the un- 

 loaded left shoulder will cover the longer distance 

 CL while the loaded right shoulder is covering the 

 shorter distance DP and serving as pivot and sup- 

 port for the center of gravity, which remains on 

 OM. 



But for the impulsion of the hind quarters, both 

 the rider's legs are necessary. The left prevents the 

 haunches from yielding to the effect of the right, 

 and thus departing from the proper path ACL. 

 The right leg of the rider pushes forward the right 

 hind leg of the horse, and since this is prevented 

 from moving toward the left off the line BDP, the 

 center of gravity must remain on the line OM ; and 

 momentum, velocity, and equilibrium remain al- 

 tered. 



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