62 



ANIMAL LOCOMOTION. 



In order to enable the right leg to swing forward, it is 

 evident that it must be flexed, and that the left leg must be 

 extended^ and the trunk raised. The raising of the trunk 

 causes it to assume a more vertical position, and this prevents 

 the swinging leg from going too far forwards ; the swinging 



Fig. 28.— Preparing to run, from a design by Flaxman. Adapted. In the ori- 

 ginal of this figure the right arm is depending and placed on the right 

 thigh. 



leg tending to oscillate in a slightly backward direction as 

 the trunk is elevated. The body is more inclined forwards 

 in running than in walking, and there is a period when both 

 legs are off the ground, no such period occurring in walking. 



In quick walking, the propelling leg acts more obliquely on 

 the trunk, which is more inclined, and forced forwards more 

 rapidly than in slow walking. The time when both legs are 

 on the ground diminishes as the velocity increases, and it 

 vanishes altogether when the velocity is at a maximum. In 

 quick running the length of step rapidly increases, whilst the 

 duration slowly diminishes ; but in slow running the length 

 diminishes rapidly, whilst the time remains nearly the same. 

 The time of a step in quick running, compared to that in 

 quick walking, is nearly as two to three, whilst the length of 

 the steps are as two to one j consequently a person can run in 



