t is easy to
understand why the condition is so painful.

_Chronic laminitis_ is a sequel of acute inflammation of the sensitive
laminae. It varies as to intensity and the exact manner of its
manifestation depends upon preexisting disturbances.

In some mild cases of laminitis there are recurrent attacks wherein no
particular structural change exists, and diagnosis is established
chiefly by noting the character of the pulse at the bifurcation of the
large metacarpal (or metatarsal) artery just above the fetlock. The same
manifestation of pain is present when weight is supported by one foot,
though in a lesser degree. There is less local heat to be detected by
palpation than in the acute cases.

Chronic laminitis as it occurs following acute attacks which have
resulted in structural changes of the foot, present the same symptoms
just described and, in addition, the peculiar alterations in structure
exist. When, owing to acute inflammation of the sensitive laminae, there
has resulted necrosis of this sensitive tissue together with
infiltration between the anterior surface of the distal phalanx (os
pedis) and the contacting hoof, the lower portion of the distal phalanx
is turned downward and backward (rotated upon its transverse axis).
Because of the traction which is exerted by the deep flexor tendon
(perforans), as it attaches to the solar surface of the distal phalanx,
this rotation is facilitated. With hyperplasia of lamina, at the
anterior portion of the distal phalanx, there results a thick "white
line." Rotation of the distal phalanx necessitates a descent of its
apical portion and there occurs a "dropped sole."

In time, partly because of excessive wear of hoof at the heel, owing to
an altered condition in the normal antagonistic relation between the
flexor and extensor tendons, the toe makes an excessive growth, and the
concavity of the anterior line is accentuated owing to this abnormal
length of hoof. The hoof, because of recurrent inflammatory attacks, is
corrugated--elevations of horn in parallel rings are usually present.

[Illustration: Fig. 33--The hoof in chronic laminitis. Note the
concavity. This animal was serviceable for any work that could be
performed at a walk.]

Animals that are so affected in traveling strike the heel first and the
toe is later contacted with the ground surface. Rotation of the distal
phalanx upon its transverse axis produces a condition, with respect to
this peculiar imped