LOCOMOTION. 627 



prefers one gait, as pacing, for Ms easy, slow movements, will 

 break into a trot when pushed to a higher rate of speed. 



Trotting can not be considered the natural gait for high 

 speed in the horse, yet, by a process of "artiflcial selection" 

 (by man) from horses that have shown capacity for great speed 

 by this mode of progression, strains of racers have been bred, 

 showing that even an acquired mode of locomotion may be 

 hereditary ; while that galloping is the more natural mode of 

 locomotion of the horse is evident, among other things, by the 

 tendency of even the best trotting racers to break into a gallop 

 when unduly pushed — an instance also of an hereditary tend- 

 ency of more ancient origin prevailing over one more recent. 



The bipedal modes of progression of birds are naturally very 

 like those of man. 



