movements. Nodding of the head with the catching up of weight by a sound
member in supporting-leg-lameness of a fore leg, constitutes the chief
symptom considered in detecting the lame leg.

Where supporting-leg-lameness affects a hind limb the head is raised at
the time weight is caught by the sound member--here the long axis of the
subject's body may be likened unto a lever of the first class. The
posterior part of the body, at the time weight is taken upon the sound
leg, is as the long arm: the fore limbs the fulcrum, and the subject's
head the weight, which is lifted. The head movements of a horse at a
trot, in supporting-leg-lameness of a front leg, synchronize with the
discharge of weight from a lame leg to the opposite one if sound; but in
pelvic limb affections, the head is thrown or jerked upward as weight is
caught by the sound member,--this peculiar nodding movement is
_opposite_ in the two instances.

In pacing horses, since front and hind legs of the same side are
advanced at the same time, there occurs in supporting-leg-lameness, a
nodding of the head with discharge of weight from the lame leg, and a
dropping of the hip as weight is caught by the sound pelvic member. In
observing animals that are limping, (as in supporting-leg-lameness) one
notices particularly the sacro-iliac region in hind leg affections and
the occipital region in lameness of the front legs.

Where there exists a bilateral affection, (such as characterizes some cases
of navicular disease or other affections causing supporting-leg-lameness)
there occurs no nodding of the head; weight is supported for an equal
length of time upon each one of the two legs, but the stride[4] is
shortened. The gait, in such cases, is peculiar, animals appearing stiff
and they are said, by horsemen, to have a "choppy" gait.