622 COMPARATIVE PHYSIOLOGY. 



Walking. — ^In this gait the body rests on diagonal feet alter- 

 nately with the two of the same side ; the center of gravity 

 being shifted to one side, then returned to its original position, 

 to be moved next to the opposite side. In drawing heavy loads 

 the body is supported on three limbs. The rate of movement is 

 one to two metres per second. 



Amble. — In this mode of progression, most common in the 



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Fig. 471.— Movements (oscillation) of an extended hind-leg (Colin). The hip-joint 

 describes the arc of a circle, ABC, while the foot is on the ground, the lines A D, 

 B D, and C D representing the changing axis of the hind-leg. 



giraffe and camel tribe, occasional in ruminants and solipeds, 

 the body is supported by the two legs on the same side, as in the 

 walk, but the two opposite legs are elevated simultaneously and 

 not separately. In horses this gait is often termed pacing, and 

 is frequently very fast. Only two strokes of the feet are heard 

 in this gait. 



In racking the hind-leg leaves the ground sooner than the 

 corresponding fore-leg, hence four strokes of the feet are heard. 



The Trot. — The diagonal feet act together, two strokes of the 

 feet being heard at each complete step. In the fast trot there 

 is an interval in which all four feet are in the air. The hind- 

 feet strike the ground in front of the fore-feet. The speed in 



