have taken place in the animal he
has been accustomed to drive or ride, unless they are indeed slight and
limited to the last degree. But what is not always easy is the
detection, after discovering the fact of an existing irregularity, of
the locality of its point of origin, and whether its seat be in the near
or off leg, or in the fore or the hind part of the body. These are
questions too often wrongly answered, notwithstanding the fact that with
a little careful scrutiny the point may be easily settled. The error,
which is too often committed, of pronouncing the leg upon which the
animal travels soundly as the seat of the lameness, is the result of a
misinterpretation of the physiology of locomotion in the crippled
animal. Much depends upon the gait with which the animal moves while
under examination. The act of walking is unfavorable for accurate
observation, though, if the animal walks on three legs, the decision is
easy to reach. The action of galloping will often, by the rapidity of
the muscular movements and their quick succession, interfere with a nice
study of their rhythm, and it is only under some peculiar circumstances
that the examination can be safely conducted while the animal is moving
with that gait. It is while the animal is trotting that the
investigation is made with the best chances of an intelligent decision,
and it is while moving with that gait, therefore, that the points should
be looked for which must form the elements of the diagnosis.

[Illustration: PLATE XXIII.

SKELETON OF HORSE.]

[Illustration: PLATE XXIV.

SUPERFICIAL LAYER OF MUSCLES.]

Our first consideration should be the physiology of normal or healthy
locomotion, that thence we may the more easily reach our conclusions
touching lameness, or that which is abnormal, and by this process we
ought to succeed in obtaining a clew to the solution of the first
problem, to wit, in which leg is the seat of the lameness?

A word of definition is here necessary, in order to render that which
follows more easily intelligible. In veterinary nomenclature each two of
the legs, as referred to in pairs, is denominated a biped. Of the four
points occupied by the feet of the animal while standing at rest,
forming a square, the two fore legs are known as the anterior biped; the
two hinder, the posterior; the two on one side, the lateral: and one of
either the front or hind biped with the opposite leg of the hind or
front biped will form the diago