110 BITS AND BITTING. 



altogether mechanical in their nature ; and on entering 

 into 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 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. 



