132 ENGLAND'S HORSES, 



CHAPTER XL 



Limits of the Horse's Power — Centre of Gravity. 



Having fixed the seat of tliat power it is the business of the 

 riding-master to apply to the most advantage, let us next 

 endeavour to ascertain the limits to its operation. The utmost 

 measure of extension of which the limb is capable, will evidently 

 constitute the limit of this power on the one hand, and the utmost 

 measure of contraction on the other. 



The first hint may be easily fixed, depending, as it does, on 

 the natural conformation of the limb. In most instances the 

 greatest angle which the femur can form with the haunch bone is 

 limited to about 130'^ ; again, the feviur and tibia joined at the 

 stifle joint can rarely form an angle greater than 140° ; and the 

 tibia and shank bone joined at the hock open out to their fullest 

 extent at from 150° to 165°, in proportion to the prominence of 

 the OS calcis. In these maximum amounts of opening, there- 

 fore, we have the limit of the animal's progressive energy on the 

 side of extension ; in the other direction they are not quite so 

 easily ascertained. 



It is obvious that if the joints of the limb were sufficiently 

 flexible to admit of its being brought to the ground in that very 

 high state of contraction in which the parts ai-e almost in contact, 

 we should have the muscular energy of which the parts are 

 capable brought into play in their extension, and consequently 

 would attain the highest velocity that such an apparatus is 

 capable of communicating : but not only are the limbs of the 

 horse incapable of this extreme degree of flexibility, but their 



