THE MECHANISM OF MOVEMENT 529 



swings forward as a pendulum for the next thrust. The exact changes 

 which take place during rapid movement have been analyzed by 

 taking a succession of instantaneous photographs on a film. Such a 

 film passed at a correct speed through the cinematograph lantern 

 faithfully reproduces the movement; the different photographs 

 succeed each other so rapidly that they fuse together and give the 

 sensation of a moving object. In real life we only get a fused impres- 

 sion of the position of a moving animal. If an artist drew a horse 

 in some of the attitudes revealed by instantaneous photography it 

 would be deemed unnatural. 



The position of the feet in walking and running can be well seen 

 .in the footprints made in the firm, wet sand left by the receding tide. 



