To have a correct notion of the manner in which the hand operates on
the horse’s mouth, it must be understood that the reins, being held
as described, are collected to such definite length, that bracing the
muscles of the hand would rein the horse back, and easing them permit
him freely to advance; the hand, for preserving a medium effect on the
mouth, being only half shut, and the knuckles near the wrist nearly
open. The hand, then, being connected to the reins, the reins to the
bit, the bit operating in the curb on the bars, and in the snaffle on
the lips, the rider cannot move the hand, and scarcely even a finger,
without the horse’s mouth being more or less affected. This is called
the CORRESPONDENCE.
If, moreover, the hand be held steady, as the horse advances in the
trot, the fingers will feel, by the contraction of the reins, a slight
tug, occasioned by the cadence of every step; and this tug, by means of
the correspondence, is reciprocally felt in the horse’s mouth. This is
called the APPUY.
While this relation is preserved between the hand and mouth, the horse
is in perfect obedience to the rider, and the hand directs him, in any
position or action, with such ease, that the horse seems to work by the
will of the rider rather than by the power of his hand. This is called
the SUPPORT.
Now, the correspondence or effective communication between the hand
and mouth,--the appuy, or strength of the operation in the mouth,--the
support, or aid, the hand gives in the position or action,--are always
maintained in the manège and all united paces. Without these, a horse
is under no immediate control, as in the extended gallop, or at full
speed, where it may require a hundred yards to pull before we can stop
him.