ANIMAL LOCOMOTION. 



th >r secured by a pendulum movement in the arms as well as 

 in the legs, the right arm swinging before the body when the 

 right leg swings behind it, and the converse. The right leg 

 and left arm advance simultaneously, and alternate with the 

 left leg and right arm, which likewise advance together. This 

 gives rise to a double twisting of the body at the shoulders 

 and loins. The legs and arms when advancing move in 

 curves, the convexities of the curves made by the right leg 

 and left arm, which advance together when a step is being 

 made, being directed outwards, and forming, when placed 

 together, a more or less symmetrical ellipse. If the curves 

 formed by the legs and arms respectively be united, they 

 form waved lines which intersect at every step. This arises 

 from the fact that the curves formed by the right and left 

 legs are found alternately on either side of a given line, the 

 same holding true of the right and left arms. Walking is 

 consequently to be regarded as the result of a twisting diagonal 

 movement in the trunk and in the extremities. Without this 

 movement, the momentum acquired b}^ the different portions 

 of the moving mass could not be utilized. As the momentum 

 acquired by animals in walking, swimming, and flying forms 

 an important factor in those movements, it is necessary that 

 we should have a just conception of the value to be attached 

 to weight when in motion. In the horse when walking, the 

 stride is something like five feet, in trotting ten feet, but in 

 galloping eighteen or more feet. The stride is in fact deter- 

 mined by the speed acquired by the mass of the body of the 

 horse j the momentum at which the mass is moving carry- 

 ing the limbs forward.^ 



In the swimming of the fish, the body is thrown into double 

 or figure-of- 8 curves, as in the walking of the biped. The twist- 

 ing of the body, and the continuity of movement which that 

 twisting begets, reappear. The curves formed in the swimming 



A According to Sainbell, the celebrated horse Eclipse, when galloping at 

 liberty, and with its greatest speed, passed over the space of twenty-five feet 

 at each stride, which he repeated 2^ times in a second, being nearly four 

 miles in six minutes and two seconds. The race-horse Flying Childers was 

 computed to have passed over eighty-two feet and a half in a second, or nearly 

 a mile in a minute." 



