Il6 THE HORSE IN MOTION. 



quadruped uses the diagonal feet alternately, so that the centre of 

 gravity always falls within the quadrangle formed by them, and near 

 the intersection of the lines connecting their diagonal feet. 



The theory of the walk in quadrupeds is that there should be 

 two feet always upon the ground while the diagonal ones are being 

 advanced, and if the legs moved synchronously in pairs, there must be 

 four on the ground for a brief time at each step, for from the defi- 

 nition of the walk one foot does not rise until the other is upon the 

 ground; it follows that in two pairs of feet the two feet cannot rise 

 until the other two are upon the ground. This, one would think, 

 should be proved by the camera; but it shows that sometimes three 

 feet are on the ground, but never four at the same time. How is 

 this ? Is the definition of the walk incorrect ? It is so when applied 

 to quadrupeds. In fact, the diagonal limbs do not act synchronously 

 in the slow movements of the walk, for it is more difficult to maintain 

 an equilibrium in a slow movement than a fast, as a top falls when 

 its revolutions are slow, and for the reason that a horse never rests 

 on two legs, but always on the two anterior and one posterior, so 

 that the centre of gravity always falls within a triangle ; so in the 

 walk one of the reserve feet holds the ground for a brief time until 

 the other has the start, in order to shorten the time in which the 

 centre of gravity has but two points of support. 



The walk, being the slowest pace of the horse, has been best 

 observed and most discussed, but chiefly as to the order in which the 

 feet are moved. There can be little doubt that habit in the horse, as 

 in man, determines which foot shall be the first to move ; and it may 

 often be determined by. their accidental relation to each other at the 

 instant that he has occasion to move one of them, though it would 

 be doing no injustice to the brute to suppose him to have a suffi- 

 cient freedom of will to choose which foot he should put forward 

 if he waited to think of it. 



When the horse quickens his walk, he does not at once change his 

 pace, but extends his strides and makes them more uniform, until 

 further extension becomes difficult, when he will break into a trot, in 

 which there are never more than two feet upon the ground at a time, 



