itated by the opposite rein exerting a strong
pressure on the neck.

[Illustration: Fig. 49.--Side view of Horse's lower jaw.]

In regulating the length of the running martingale, we should carefully
guard against making it so short that it would interfere with the
horse's mouth, when he is not carrying his head unnaturally high; for
such interference could have no good result, and would probably impede
the animal's movements. Although it is impossible to determine with
mathematical accuracy the exact length of this martingale, we find in
practice that it should not be shorter than a length which will allow
it, when drawn up, to reach as high as the top of the withers.
Lengthening it out another three or four inches will generally be an
improvement. The use of a running martingale shorter than the minimum I
have just laid down, more or less irritates the horse; because, even
when he holds his head in correct position, he cannot escape from its
disagreeable pressure. The employment of a short running martingale for
'cross country work is a very dangerous proceeding; for if the rider
does not leave the reins loose when jumping, the horse will be almost
certain to hurt his mouth, and consequently he will be afraid to face
his bit, or will become unmanageable from pain, either eventuality being
highly dangerous to horse and rider.

[Illustration: Fig. 50.--Angle made by the Cheeks of a Curb, when the
Reins are taken up.]

ADJUSTMENT OF THE BRIDLE.

The bit is placed in the horse's mouth, because there is a vacant space
(of about four inches in length) on the gums of his lower jaw, between
his back teeth and tushes (canine teeth or eye teeth), as we may see in
Fig. 49. A mare has no tushes, or possesses them in only a rudimentary
form. The tushes of a horse begin to appear through his gums when he is
about 4 years old. If horses had not this convenient gap (interdental
space) in their rows of teeth, we would probably have to guide and
control them by means of reins attached to a nose-band, which is a
method practised by many American cow-boys when breaking in young
horses. Owing to the fact that their nose-band (hackamore) does not hurt
the animal's mouth, and that it gives all the necessary indications,
excellent results, I believe, are obtained with it.

[Illustration: Fig. 51.--View of under-surface of Lower Jaw.]

As the pressure of the bit should be an indication of the wishes of the
rider and not a means of i