WALKING, RUNNING, JUMPING. 595 



the length of the leg, it is evident that each individual, in accordance with the 

 length of his leg, has a certain natural time of oscillation, which especially in- 

 fluences his accustomed rate of walking. In addition, however, the duration of 

 the step depends upon the length of time during which both feet touch the ground 

 simultaneously. Naturally, this can be increased voluntarily. With a "rapid 

 pace" the period of time is zero; that is, at the same moment that the active leg 

 is placed on the ground the passive leg is raised. (2) The length (or stretch) of 

 the step, which amounts to six or seven decimeters on the average, must be the 

 greater, the more the length of the hypothenuse of the passive leg exceeds the 

 cathetus of the active leg. Hence, in the longest steps the active leg is markedly 

 shortened by flexion at the knee, so that the trunk is carried at a lower level. 

 Similarly, long legs are especially able to make greater steps. 



According to Marey, Carlet, and H. Vierordt the pendulum-movement of the 

 passive leg cannot be regarded as a true pendulum-oscillation, because it possesses 

 a more nearly uniform rapidity, owing to muscular action. During the pendulum- 

 movement of the whole limb, the leg oscillates independently at the knee-joint, 

 as is especially evident in women. According to Ed. and Wm. Weber the head 

 of the femur of the passive leg is held in the acetabulum chiefly by air-pressure, 

 so that no muscular activity is necessary to carry the whole extremity. If all 

 the muscles and the joint-capsule be divided, the head still remains attached 

 to the acetabulum. By pulling on the thigh the borders of the cartilaginous 

 rim of the acetabulum are closely applied in a valve-like manner to the margin 



FIG. 203. Instantaneous Photographs of a High Jump (after Marey). The pictures partly overlap as soon as 

 the velocity of the forward movement diminishes on the descent after the jump. In the upper, left-hand 

 corner is a dial, the white radius of which has moved forward one division in one-twelfth of a second. The 

 base line represents the distance traversed, in meters. 



of the cartilage on the head of the femur. According to the statements of the 

 brothers Weber, the thigh is released from the acetabulum as soon as air is allowed 

 to penetrate the articular cavity by perforating the bottom of the socket. 



The brothers Weber showed that in walking on level ground an appreciable 

 amount of mechanical work is performed, as the weight of the body must be 

 lifted several centimeters with every step. Marey and Demery estimated that 

 the work performed by a person weighing 64 kilos, when walking slowly, is equal 

 to six kilogrammeters in a second; when running rapidly, it amounts to 56 kilo- 

 grammeters. The performance consists in raising the whole body and extremities, 

 in imparting rapidity of motion to them, and in maintaining the center of gravity. 

 According to Rziha the work performed in each second in walking slowly is 3.5 

 kilogrammeters, in walking at a medium gait 5.46, in walking rapidly 7.87, in a 

 short run 21.87, in a brisk run 42.87, and in a fast run 87.50 kilogrammeters. 



A bicycle-rider going at the rate of two meters in a second, performs 1.12 

 kilogrammeters, at a four-meter pace 4.51 kilogrammeters, at a five-meter pace 

 7.05, and at a six-meter pace 10.15 kilogrammeters. The normal capability of 



