within the hoof. In such cases the only treatment of any use is that
of neurectomy.

CHAPTER XII

DISEASES OF THE JOINTS[A]

[Footnote A: Properly speaking, we have in the foot of the horse but _one_
joint--namely, the corono-pedal articulation.

Although not a joint in the strict sense of the word, we, nevertheless,
intend here to consider the navicular bursa as such. In this apparatus,
although we have no articular cartilage proper, and no apposition of bone
to bone, we still have a large synovial cavity, and in close proximity to
it bone. We may, in fact, and do get in it exactly similar changes to those
termed 'synovitis' and 'arthritis' elsewhere. Therefore, we include the
changes occurring in it in this chapter, and hence the plural use of the
word to which this note refers.]

A. SYNOVITIS.

_Definition_.--By the term 'synovitis' is indicated an inflammation of the
synovial membrane. It may be either (_a_) _Simple_ or _Acute_, or it may be
(_b_) _Purulent_ or _Suppurative_.

In the simple form there is little or no tendency for the affection to
implicate the other structures of the joint, whereas in the suppurative
form the joint capsule, the ligaments, and the bones soon come to
participate in the diseased processes, giving us a condition which we shall
afterwards describe as acute arthritis.

(_a_) SIMPLE SYNOVITIS.

1. _Acute--(Causes)_.--Simple or acute synovitis is nearly always brought
about by injury to the joint--by blows or bruises, or by sprains of the
ligaments. At other times it occurs without ascertainable cause, and is
then put down to the influence of cold, or to poisonous materials (as, for
example, that of rheumatism) circulating in the blood-stream.

_Pathology_.--Uncomplicated acute synovitis never causes death. The
pathological changes in connection with it have therefore been studied in
cases purposely induced, and the animal afterwards slaughtered. It is then
found that, as in inflammation elsewhere, the synovial membrane is showing
the usual inflammatory phenomena--that it is thick and swollen as a result
of the inflammatory hyperaemia and commencing exudation. Later, the synovial
fluid becomes increased in quantity, is thin and serous, and after a time
is seen to be mixed with the inflammatory exudation poured into it. We then
find that it has lost its clear appearance, has become thick and muddy, and
has floating in it flakes of fibrin.

If the case progresses favoura