WALKING, RUNNING, JUMPING. 



593 



each instantaneous photograph equals T - ff V(j of a second. When placed in a 

 stroboscope, these series reproduce the natural movements; and by projection 

 with the aid of a kinematograph they may also be shown as "moving pictures." 

 Figs. 201, 202, and 203 represent such series of instantaneous photographs ob- 

 tained in the manner described. Braune and O. Fischer, between 1895 ano ^ I &99> 

 introduced a new method of recording the motor process in walking by means 

 of bilateral chronophotographic exposures on an extensive coordinating system. 



In the act of walking the legs are alternatively active. While one, 

 the "supporting" or "active" leg, carries the body, the other, the "hang- 

 ing," "swinging," or "passive" leg, is inactive. Thus, each leg in regu- 

 lar alternation goes through an active and a passive phase. The motion 

 of walking may be divided into the following acts : 



First Act (Fig. 200, 2). The active leg is vertical, slightly flexed at 

 the knee, and supports alone the center of gravity of the body. The 

 passive leg is fully extended, and touches the ground only with the tip of 

 the great toe (z). This position of the legs corresponds to a right-angle 

 triangle, in which the active leg and the ground form the two sides 

 (catheti), and the passive leg the hypothenuse. 



FIG. 200. Phases of the Movement of Walking. The thick lines represent the active, the thin lines the passive 

 leg: h, hip- joint; k a, knee-joint; / b, ankle-joint; c d, heel; m e, ball of the metatarso-phalangeal joint; 

 z g, tip of the great toe. 



Second Act. To advance the trunk, the active leg tilts from its ver- 

 tical position (cathetus) into an oblique position (3) inclined forward 

 (hypothenuse). In order that the trunk may remain at the same height, 

 it is necessary for the active leg to be lengthened. This is accomplished 

 first by complete extension of the knee (3, 4, 5), then by elevation of the 

 heel from the ground (4, 5), so that the foot rests on the ball formed by 

 the heads of the metatarsal bone, and finally by elevation of the foot on 

 the joint of the great toe (2, thin line). As both sections of the foot are 

 successively raised from the ground, like the links of a measuring chain 

 that is lifted from the ground ("unwound"), the elevation of the foot 

 from the ground has also been termed "unwinding" of the foot. . During 

 the extension and forward inclination of the active leg the tips of the 

 toes of the passive leg have been compelled to leave the ground (3). 



While this leg now becomes slightly flexed at the knee for the pur- 

 pose of shortening, it executes at the same time a "pendulum-like" 

 movement (4, 5), by means of which its foot is moved just as far in front 

 of the active foot as it was previously behind the latter. 



When it attains this position, the foot is placed flat upon the ground 

 38 



