THE GAITS IN PARTICULAR. 545 



In the types of locomotion already studied, the canter excepted, the 

 beats of eacli one of the pedestrians were always isochronous, — that is 

 to say, separated by equal intervals of time, whether the gait was 

 marched or leaped, lateral or diagonal. The member in contact ful- 

 filled by itself the double role of dispersion and impulsion, although 

 in a dij[ferent degree according to its position in relation to the centre 

 of gravity. 



Th^ rhythm in the gallop is entirely different. Each biped pre- 

 cipitates its falling on the ground in such a manner as to render the 

 beats irregular, heterochronous, and then it rises to be projected forward, 

 two phenomena which give to this mode of progression a jerking and 

 leaping character which we have so far not met. 



Here, the member in contact with the soil is far from having ter- 

 minated this phase when its congener begins to assume the same phase. 

 Hence there exists a somewhat long period in which both feet rest simul- 

 taneously, exerting this action against the centre of gravity, either to 

 deaden the concussion or to propel the body forward. It will be under- 

 stood that, in this case, the motor power is increased in considerable 

 proportions, and that the animal becomes capable of taking longer 

 strides and acquiring greater speed. 



The Gallop to the Right and the Gallop to the Left. — A 

 biped is said to gallop upon the right foot or upon the left foot according 

 to the foot which strikes the o;round last. 



True Gallop and False Gallop. — It matters little, if the trail 

 be rectilinear, whether the gallop is effected upon the one foot or upon 

 the other. The members are even seen, from time to time, to reverse 

 their order of succession, in order to rest themselves better. The 

 member which reaches the soil first, being a destroyer of the reactions 

 rather than a propeller, takes, at a certain moment, the place of its con- 

 gener, which was principally the propeller. The changing of the feet 

 relieves the biped by equalizing the work of its constituent parts. 



It is quite different, however, when the trail is curvilinear. We 

 know then that a centrifugal force is developed, which is so much 

 stronger as the velocity of the gait is greater and the curve shorter. 

 The animal is therefore obliged to incline himself towards the inner 

 side of the trail to counteract this force, an attitude which consequently 

 predisposes him to fall inside of the tract described. Hence, in view 

 of a fall which is always imminent, he must steady his equilibrium on 

 that side by the foothold of the corresponding propelling member, the 

 right if the trail turn to the right, the left if it turn to the left. 



The gallop is called true when it is effected upon the right foot, for 



35 



