TOW DO HORSES MOVE? 109 
exerted through the muscles and tendons, the latter pass- 
ing back of the fetlock. The power arm is F B, while the 
resistance arm is F A. The straighter and shorter the 
pastern, O F, the easier the animal maintains a standing 
position and the greater the power. The longer and more 
slanting the pastern, the greater the speed. Heavy draft 
horses have short, steep pasterns, while light, running 
and trotting horses have long slanting ones. 
7. The center of gravity—An object of uniform density 
does not topple over of its own weight, unless its center 
falls outside its base. 
The farther one must 
push an object to cause 
its center to fall out- 
side the base the more 
difficult it is to move it. 
If a horse is near the 
ground, and has its feet 
wide apart, its center of 
gravity does not read- ; 
ily fall outside its base. CENTER OF GRAVITY IN Horse 
In a horse that is tall It is evident that the center of gravity is not 
located at similar points in these two horses. 
and has its feet near 
together, this occurs easily. A draft horse is able to pull 
a great load, not alone because he has large muscles, but 
because he is near the ground and has his feet wide apart. 
On the other hand, a horse does not run fast simply 
because he has long legs, but because his body is farther 
from the ground and he is relatively shorter, bringing 
his feet closer together. The reason a boy cannot run 
when leaning backwards is because his center of gravity 
is in the wrong place. 
8. Gaits——The horse has four well-defined gaits—the 
walk, trot, pace and gallop. A horse or other animal 
