454 OF. RUNNING. 





merits, but by the pressure of the air, a fact that may be proved by very 

 simple experiments. If the pressure of the air be removed, as in an ex- 

 hausted receiver, spontaneous dislocation ensues. The trunk of the body 

 is like a rod balanced on an axis passing through the hip joints, and ad- 

 vancing with the movement of the legs like a rod balanced on the tip of 

 the finger. It is inclined forward or backward in correspondence with 

 the motion or with the resistance of the wind ; if the wind blows in front, 

 we lean forward; if behind, we lean backward; the angle of inclination be- 

 ing in proportion to its force. In walking there are two distinct periods : 

 the body is first poised on one of the limbs, and then rests for a moment 

 on both. The advancing limb swings like a pendulum, bending at the 

 knee so as to be shortened one ninth ; the other straightening at the knee 

 and hip joint, and so pushing the pelvis and trunk forward to be received 

 on the limb that has just advanced. It is only in slow walking that the 

 whole arc of motion is swung through, the time occupied being two thirds 

 of a second. In quick walking and running only half a vibration is ac- 

 complished, and this in half a second of time. In slow walking each foot 

 rests upon the ground one third of a second. The longest step made is 

 half the entire span of the two extremities. To prevent swaying from 

 side to side, the arms swing with the legs. 



In running there is a moment when both feet are off the ground at 

 once, and the body actually projected into the air. In walk- 

 '' ing there is a moment when both feet are on the ground to- 

 gether, the one not being raised till the other is planted. In running the 

 steps are, on an average, twice as long as in walking ; and the number 

 of steps made in a given time in running and walking respectively is as 

 3 to 2. 



