152 THE HUMAN BOD Y. 



clearing the ground as the left did before. The Body is 

 meanwhile supported on the left foot alone, but when the 

 right completes its step the knee of that leg is straightened 

 and the foot thus placed, heel first, on the ground. Mean- 

 while the left foot has been gradually leaving the ground, 

 and its toes alone are at that moment upon it: from these' 

 a push is given, as before with the right foot, and the knee 

 being bent so as to raise the foot, the left leg swings for- 

 wards at the hip-joint to make a fresh step. 



During each step the whole Body sways up and down 

 and also from side to side. It is highest at the moment 

 when the advancing trunk is vertically over the foot sup- 

 porting it, and then sinks until the moment when the ad- 

 vancing foot touches the ground, when it is lowest. From 

 this moment it rises as it swings forward on this foot, until 

 it is vertically over it, and then sinks again until the other 

 touches the ground; and so on. At the same time, as its 

 weight is alternately transferred from the right to the left 

 foot and vice versa, there is a slight lateral sway, commonly 

 more marked in women than in men, and which when ex- 

 cessive produces an ugly "waddling" gait. 



The length of each step is primarily dependent on the 

 length of the legs; but can be controlled within wide lim- 

 its by special muscular effort. In easy walking, little mus- 

 cular work is employed to carry the rear leg forwards after 

 it has given its push. When its foot is raised from the 

 ground it swings on like a pendulum; but in fast walking 

 the muscles passing in front of the hip-joint, from the pel- 

 vis to the limb, by their contraction forcibly carry the leg 

 forwards. The easiest step, that in which there is most 

 economy of labor, is that in which the limb is let swing 

 freely, and since a short pendulum swings faster than a 

 longer, the natural step of short-legged people is quicker 

 than that of long-legged ones. 



In fast walking the advanced or supporting leg also 

 aids in propulsion; the muscles passing in front of the 

 ankle-joint contracting so as to pull the Body forwards 

 over that foot and aid the push from the rear foot. Hence 

 the fatigue and pain in front of the shin which is felt in 



