600 MOTION. 



Now it is evident that by the time the body has assumed 

 the position No. 3, it is time that the right leg should be 

 brought forward to support it and prevent it from falling 

 prostrate. This advance of the other leg (in this case the 

 right) is effected partly by its mechanically swinging for- 

 wards, pendulum- wise, and partly by muscular action ; 

 the muscles used being, Tst, those on the front of the 

 thigh, which bend the thigh forwards on the pelvis, espe- 

 cially the rectus femoris, with the psoas and the iliacus ; 

 zndfy,. the hamstring muscles, which slightly bend the leg 

 on the thigh ; and ^rdly, the muscles on the front of the 

 leg, which raise the front of the foot and toes, and so pre- 

 vent the latter in swinging forwards from hitching in the 

 ground. Anybody who has attentively watched the help- 

 less flapping action of the foot and leg in cases of partial 

 paralysis affecting the muscles of the leg, or who will, in 

 his own case, note the act of bringing the leg forward in 

 walking, will be convinced of the large share which the 

 muscles take in the act in question ; although, of course, 

 their work is rendered much easier by the pendulum-like 

 swinging forward of the leg by its own weight. 



The second part of the act of walking, which has been 

 just described,, is shown in the diagram (4, fig. 159). 



When the right foot has reached the ground the action 

 of the left leg has not ceased. The calf-muscles of the 

 latter continue to act, and by pulling up the heel, throw 

 the body still more forwards over the right leg, now bearing 

 nearly the whole weight, until it is time that in its turn 

 the left leg should swing forwards, and the left foot be 

 planted on the ground to prevent the body from falling 

 prostrate. As at first, while the calf-muscles of one leg 

 and foot are preparing, so to speak, to push the body 

 forward and upward from behind by raising the heel, the 

 muscles on the front of the trunk and of the same leg (and 

 of the other leg, except when it is swinging forwards) are 

 helping the act by pulling the legs and trunk, so as to make 



