112 BITS AND BITTING. 



an analysis .of their mode of action, we find them to 

 consist in the application of the principles of the lever 

 and of equilibrium, matters belonging respectively to 

 the domains of statics and dynamics. 



The great difficulty in the rational application of 

 these principles arises partly from the complexity of all 

 problems connected with " equilibrium in motion," and 

 partly on account of the very great diversity in the 

 details of the construction and the relative proportions 

 of these animated machines. If we take the horse's 

 neck, for instance, it may be compared to the tiller of 

 a boat ; it is the lever by which the whole animal is 

 steered, or, in a state of nature, steers itself the reins 

 being the tiller-ropes. The lever formed by the neck 

 acts on that part of the dorsal vertebrae we have shown 

 to be the centre of motion ; and when the horse is in 

 motion, the lever action of the limbs, derived from the 

 muscles, is propagated to this same point, the neck and 

 the tail being the regulators of the movement ; for by 

 means of the neck, the animal, as has been shown 

 in Part I., adjusts its equilibrium according to the 

 degree of velocity it requires, and according to whether 

 it wishes to move on straight or on curved lines ; and 

 a little attention to the movements of young horses, 

 when perfectly uncontrolled, will suffice to show that 

 the position of the neck is constantly varied to suit the 

 exigencies of the moment, the tail following its move- 

 ments in the most graceful manner as a counterpoise. * 



It is precisely for this reason that a proper command 

 over the horse's neck is of such value to the rider, 



* It would be easy to show that breeds of horses employed con- 

 stantly for one particular movement have their tails differently 

 seated and developed from those that are employed for a variety 

 of purposes. Our English race-horse is an instance. 



