1484 



WALKING. 



[BOOK in. 



actual curve described by the centre of gravity is therefore a 

 somewhat complicated one, being composed of vertical and hori- 

 zontal factors. 



The natural step is the one which is determined by the length 

 of the swinging leg, since this acts as a pendulum ; and hence the 

 step of a long-legged person is naturally longer than that of a 

 person with short legs. The length of the step however may be 

 diminished or increased by a direct muscular effort, as when a line 

 of soldiers keep step in spite of their having legs of different 

 lengths. Such a mode of marching must obviously be fatiguing, 

 inasmuch as it involves an unnecessary expenditure of energy. 



In slow walking, which Fig. 192 may be taken to illustrate, 

 there is an appreciable time during which, while one foot is 

 already in position to serve as a fulcrum, the other, swinging, foot 

 has not yet left the ground. In fast walking this period is so 

 much reduced, that one foot leaves the ground the moment the 

 other touches it ; hence there is practically no period during 

 which both feet are on the ground together; this might be 

 shewn by omitting b c and d e in Fig. 192. 



When the body is swung forward on the one foot acting as a 

 fulcrum with such energy that this foot leaves the ground before 

 the other, swinging, foot has reached the ground, as shewn in 

 Fig. 193, there being an interval, b c, d e in the figure, during 



R 



a be d e f g 



FlG. 193. DlAGKAM TO ILLUSTRATE EuNNING. 



L, the line of contact with the ground of the left, E of the right foot ; in each 

 case the curved portion of the line represents the time during which the foot 

 leaves the ground. 



which neither foot is on the ground, the person is said to be running, 

 not walking. 



In jumping this propulsion of the body takes place on both feet 

 at the same time ; in hopping it is effected on one foot only. 



