TBE mmrihUAL 97 



a passive period in this form of locomotion which each 

 leg or set of legs experiences in alternate order. One leg, 

 a pair of legs or a set of three legs supports the weight 

 of the horse while the other leg or legs is executing a 

 stride. Hence, we can distinguish a supporting leg and a 

 striding leg, and we find that deviations in the way of going 

 may be accounted for by abnormalities operative during- 

 either or both periods. For instance, some lamenesses 

 are manifested only when the leg is supporting, while 

 others are characterized as striding or swinging leg lame- 

 ness. A horse may interfere because of a base^narrow, toe- 

 wide position, which places the fetlock of the supporting 

 leg so near the median plane as to insure its being 

 struck, but the likelihood of its being struck is greatly 

 enhanced by the fact that the same defective position of 

 leg which causes the fetlock to approach the median plane 

 is also responsible for the striding leg's being swung in a 

 circle inward. This of itself might be productive of in- 

 terfering, but to be added to the results of such a position 

 in the supporting leg makes interfering doubly certain. 

 On the other hand, the shortened stride of the spavined 

 horse involves a condition which manifests itself in the 

 striding leg only. 



91. The phases of the stride. — The evolution of the 

 stride involves five distinct phases, a preliminary, during 

 which the leg is undergoing flexion, but the foot has not 

 left the ground, — the point at which the real stride 

 begins ; next, the breaking over, in which the foot is raised 

 heel first and leaves the ground by being rocked up and 

 over at the toe, although at speed the foot springs directly 

 from the ground, not waiting to break over at the toe ; then 

 flight, during which the foot is describing a more or less 

 regular arc of a perpendicular circle ; followed by contact, 



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