166 



ANIMAL MECHANISM. 



In this series of movements the ear has, therefore, dis- 

 tinguished three sounds , at nearly equal intervals. The first 

 sound is produced by a hinder foot, the second by a diagonal 

 biped, the third by a fore-foot. Between the single impact of 

 the fore-foot, which constitutes the third sound, and the first 

 beat of the pace which follows, reigns a silence whose dura- 

 tion is exactly equal to that of the three impacts taken 

 together ; then the series of movements recommences. 



By the inspection of the curves, we see that the pressure 

 of the feet on the ground must be more energetic in the 

 gallop than in the other paces already represented, for the 

 height of the curves is evidently greater than for the trot, 

 and especially so as compared with the walk. In fact, the 

 animal must not only support the weight of its body, but give 

 it violent forward impulses. The greatest energy seems to 

 belong to the first impact. At this moment, the body, raised 

 for an instant from the ground, falls again, and one leg 

 alone sustains this shock. 



Fig. 56.— Gallop in three-time. (A) indication of three-time. B. indication 

 of the number of feet which form the support of the body at each instant 

 of the gallop in three-time. 



If we wish to take account of the successive pressures which 

 sustain the body during each of the steps in the gallop, we 

 have only to divide the duration of this pace into successive 

 instants in which the body is sometimes supported on one or 

 on several feet, and sometimes suspended. The notation (fig. 

 56) allows us to follow in (A) the succession of impacts, and 

 shows in (B) the succession of the limbs which cause these 

 pressures on the ground. 



If we wish to ascertain what are the re-actions produced at 

 the withers, we see them represented in fig. 55 (upper line R). 

 We find an undulatory elevation, which lasts all the time 



