FIG. 13.—OSCILLATIONS OF THE LEG OF A WALKING MAN.
FIG. 14.—SUCCESSIVE POSITIONS OF THE LIMBS
IN AN ELASTIC JUMP UPON THE BALL OF THE FOOT.
Using a disk pierced with five holes, which gives twenty-five images per second, the result shown in [Fig. 12], which shows in full detail the movements of the left half of the body, head, arm, and leg, was obtained by this method for the action of running. Every fifth image is a little stronger than the others. This is effected by making one of the apertures in the disk larger than the others. The time of exposure is thus increased, and the intensity of the image is greater. The object of this disposition is to furnish base marks, by means of which it is always easy to recognize traces corresponding to the same image, that is to say, to a given attitude of the runner. For detailed studies a part of the image is screened, as shown in [Fig. 13]. These diagrams are very well adapted for the comparison of two sorts of movements whose difference cannot be discerned by the eye. Thus, in jumping from an elevation the shock caused by the feet striking the ground is reduced in intensity by bending the legs, while the extensor muscles operate to sustain the weight of the falling body. Our next two engravings show two kinds of jumps: the [first], the flexure of the legs and the reduction of the shock; the [second], with the leg almost straight, which implies a severe shock by the feet striking the ground.
FIG. 15.—INELASTIC JUMP UPON THE HEELS.