

LOCOMOTION ON SOLIDS. RUNNING. 175 



ground together ; the length of the step may be either shortened or 

 increased. In the case of a man, walking at the rate of 4 miles an 

 hour, and whose legs were 34 inches in length, the number of steps 

 taken in 15 minutes was 2000, the length of each step 2.64 feet, and 

 the period of each step .45 of a second (Vasey). In very quick walk- 

 ing, the rate has been nearly 5J miles per hour, or about 7.9 feet per 

 second. It has been shown that, whilst in slow walking, the advancing 

 limb performs as complete an oscillation as its length will permit, and 

 is off the ground for two-thirds of a second, in very quick walking, and 

 in running, the limb performs only half an oscillation, but in much 

 less time, that is, in less than half a second : again, in slow walking, 

 the supporting limb is in contact with the ground one-third of a second, 

 but, in quickened walking, a shorter and shorter time, until at length, 

 in running, the duration of such contact is only a small fraction of 

 the time in which the other leg is swinging. 



To the act of running, which, like walking, consists of unsymmet- 

 rical movements, there is a transition from rapid walking, in the step 

 known as " the double." In true running, which might perhaps be 

 confounded with quick walking, the distinguishing character is that 

 both feet are never on the ground together, the hinder foot being 

 raised a brief interval before the advancing foot comes 'to the ground ; 

 so that in running, there is a short interval, during which one foot 

 only is on the ground, and then a longer interval in which both feet 

 are off the ground, and the body, instead of being alternately pro- 

 pelled, is continuously swung forwards in the air. The centre of 

 gravity not only advances, but oscillates in the same manner as in 

 walking, the curve described in ascending and descending, varies from 

 three-quarters of an inch to an inch and a quarter, and the lateral 

 oscillations are less than in walking, in consequence of the advancing 

 foot being brought more nearly under the middle line of the body. In 

 running, it has been shown that, just as the forward foot reaches the 

 ground, the centre of gravity is exactly over it : an arrangement 

 necessary to counteract the tendency of the body to fall forward, 

 which is very much increased at high velocities ; if the foot is pre- 

 vented advancing, as in the act of tripping, then the person either 

 stumbles or falls. In any increase of pace, whether of walking or 

 running, the mean height of the centre of gravity is often slightly 

 diminished by an increased flexion of the lower limbs, which also 

 increases the possible length of the step. The ordinary rate of quick 

 running is about 10 miles an hour ; but, for short distances, the rate 

 may be 13 miles an hour, or about 18.8 feet in a second. 



In both walking and running, it has been found that the trunk is 

 inclined forwards from the vertical line at an angle, which gradually 

 increases as the step becomes more rapid. In both progressive move- 

 ments, too, the lateral disturbance of the centre of gravity, which 

 depends on the alternate forward movement of the lower limbs, drags 

 the pelvis first after one and then after the other limb, and so leads to a 

 rotation of the trunk. This is compensated for, or counteracted by, a 

 corresponding forward movement of the opposite arm, accomplished 



ot by muscular exertion, but by a swinging or pendulum-like action 



