66 



MECHANISM OF EQUINE LOCOMOTION. 



legs, there would be no displacement of it from side to side. As however the 

 impetus derived from the hind limb is greater than that from the fore leg, 

 and as the centre of gravity is nearer the latter than the former, there is a 

 certain tendency to lateral displacement, which has to be corrected by 

 muscular effort. This tendency to a rocking movement from side to side is 

 naturally greater in the amble than it is in the trot. In the gallop there is a 

 strong tendency to lateral displacement ; for at this pace each leg gives its 

 own separate stroke {see p. 112). When either of the near ones act, the centre 

 of gravity is canted to the right ; when the off ones make their respective 

 effort, it is thrown to the left. The retention of the centre of gravity in a 

 more or less straight line, entails a certain expenditure of muscular work, and 

 consequent fatigue. 



It is evident that the nearer {sec Fig, 28) a is to h, and d to e, the less 



-,& 



€L, 



Fig. 28. — Lateral Displacement of Body. 



will be the lateral displacement of the centre of gravity, and the smaller 

 the loss of speed from this cause. Hence we find that in animals of great 

 speed, like the cheetah, antelope, greyhound, and race-horse, both the fore 

 and hind legs are respectively placed much closer together than in animals of 

 comparatively greater strength, but of slower movement. The faster the 

 pace {see p. 124), the more do the footprints of the horse tend to come into 

 the line of the direction in which movement is taking place. This principle 

 is well exemplified in man ; for all fast walkers, runners, and skaters try to 

 place the feet, at each step, as nearly as possible, in one straight line. 



