594 



WALKING, RUNNING, JUMPING. 



(i, 2, thick line). The center of gravity is transferred to this, the hence- 

 forth active leg, which at the same time assumes a vertical position, 

 somewhat flexed at the knee. The first act is now begun again. 



In walking, the trunk also exhibits some characteristic secondary movements : 

 (i) It inclines each time toward the active leg, as a result of traction of the glu- 

 teal muscles and the tensor vaginae femoris, with the object of transferring the 

 center of gravity. In heavy, short persons with broad pelves this produces the 

 "waddling" gait. (2) In order to overcome the resistance of the air, especially 



FIG. 201. Slow Walking, Photographed in Instantaneous Pictures (after Marey). Only the side direct toward 

 the observer is represented. From the vertical position of the right active leg (7) the entire phase of the 

 movement of this leg follows in six pictures (from / to VI); after VI the vertical position is again reached. 

 The Arabic numerals denote the simultaneous corresponding positions of the left leg, thus i = /, 2 = 77, 

 etc., so that, for example, during position IV of the right leg the left leg at the same time has the 

 position 7. 



FIG. 202. Instantaneous Photographs of a Runner (after Marey). Ten pictures in a second; 

 sents the distance traversed in meters. 



the base line repre- 



in rapid walking, the trunk is balanced at a forward inclination. (3) During the 

 " pendulum. "-motion the trunk rotates slightly about the head of the active 

 femur. This rotation is compensated, especially in rapid walking, by the arm 

 on the same side as the oscillating leg swinging in the opposite direction; while 

 that on the other side at the same time swings in the same direction as the oscil- 

 lating leg. 



O. Fischer has accurately determined the movement of the center of gravity 

 of the body. The external forces to be considered are the weight, the resistance 

 of the ground, the friction on the latter, and the resistance of the air. 



The time-relations of walking are influenced by the following conditions: (i) 

 The duration of the step. As the rapidity of the pendulum-motion depends upon 



