Reasoning shows clearly that this velocity is far from 

 being uniform.' 



The hind foot which forms the first step of the stride 

 strikes the ground only with the remaining velocity of 

 the preceding stride; as it strikes, a part of this remain- 

 ing momentum should be neutralized by the reaction of 

 the ground ; the whole of the first phase of the rotation 

 of the body around this hind foot should therefore be 

 executed with a relatively low velocity. But as soon as 

 the hind leg has passed the vertical it should begin to 

 contribute its prepulsive force and the velocity should 

 increase. It should tend to diminish in the second step 

 of the stride when the other hind foot is grounded ; it 

 should reach its maximum as soon as the two hind legs 

 shall have combined their propulsive effort during the 

 formation of the diagonal base and until the third step or 

 the grounding of a fore foot. From this third step on, 

 the velocity should decrease during the whole time of 

 rotation of the body around the fore feet and especially 

 at the fourth step when the base becomes unipedal on one 

 of the fore feet and when part of the motion is absorbed 

 by the reaction by the earth and also by the w^ork of com- 

 pression of the spring which is to produce the period of 

 suspension. This last phase of the stride, therefore, also 

 should be executed at reduced speed. 



It was interesting to verify by experiment these the- 

 oretical conceptions. To do this we used the series of 



^Although the gait of the gallop is well known, it will perhaps not 

 be useless to recall its mechanism here. 



The racing gallop is a gait of four steps followed by a period of 

 suspension. 



Suppose the horse to be galloping on the left foot ; the first step 

 is the grounding of the right hind foot ; the second the grounding 

 of the left hind foot ; the third, the grounding of the right fore foot, 

 and the fourth, the grounding of the left fore foot ; then comes the 

 period of suspension and the series is repeated in the same order. 

 The supports are in the following order : 

 Unipedal right posterior 

 Bipedal posterior 

 Bipedal right diagonal 

 Bipedal anterior 

 Unipedal left anterior 



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