I0 8 THE HORSE IN MOTION. 



centre of gravity, the spring of one fore leg lifts the anterior half 

 the body, and, the action of the posterior extremities immediately fol- 

 lowing, the whole body is projected into the air; but, the deer being in 

 more rapid motion, his feet take the ground at longer intervals and 

 more regular order, and so diminish the danger of stumbling, as well 

 as distribute the shock of contact and equalize the support of the 

 weight of the body. 



When the horse reduces his speed in running so that he can no longer 

 maintain his balance upon one foot, he will usually drop into a trot, which 

 is a gait having two feet as bases of support instead of one. The theory 

 of the trot is the same as that of the walk, but adapted to a higher rate 

 of speed. It differs from a walk in that the latter has always two feet 

 upon the ground, while in the trot there is always a space of time, of 

 greater or less amount, in which all the feet are off the ground. Other 

 differences will be noticed when we come to analyze the walk. They 

 correspond in that the weight of the body is borne by the diagonal 

 extremities alternately, and in the general co-relation of the limbs in 

 their mechanical action. The action in the trot is the more vigorous 

 as the distance in which the body moves unsupported is increased. 

 The definition of the word step in its general use is somewhat 

 ambiguous. It is often used synonymously with stride. In the step 

 of both quadrupeds and bipeds it is understood to mean the distance 

 spanned by the two feet both resting on the ground. This will vary 

 with the muscular energy, but is limited by anatomical proportions. 



The stride is here used to signify the distance passed over by one 

 foot from the time it leaves the ground until it reaches it again, 

 measured to corresponding points, and is equal to two steps ; but in 

 the trot this definition will not hold good, for there must be added a 

 certain distance, differing according to speed, in which neither of the 

 feet will be on the ground. If a represents the step in the walk, and 

 x the distance passed over by the foot after the other foot is raised, 

 the step in the trot would be expressed by a + x, and when a 

 constant, the step will vary as x. In the run, there being four steps, 

 and an interval when all the feet are off the ground equal to a step, 

 the stride would be expressed by 5 a. The stride is divided in the 



