On the other hand, it may be argued that equal risk to the patient is run
in allowing him to remain with a disease (and that disease a progressive
one) of the structures so closely antiguous to the navicular bursa and the
pedal articulation.

If only for that reason we give the operation brief mention here.

The animal is prepared in the usual way for the operating bed; the foot
soaked for a day or two previously in a strong antiseptic solution, the
patient cast and chloroformed, and the operation proceeded with.

[Illustration: FIG. 106.--'CURETTE,' OR VOLKMANN'S SPOON.]

An Esmarch's bandage should be first applied, and a tourniquet afterwards
placed higher up on the limb. The foot is then secured as described in an
earlier chapter, and the whole of the horny structures of the lower surface
of the foot (the sole, the frog, and the bars) pared until quite near the
sensitive structures, or, if under-run with pus, stripped off entirely. An
incision is then made in each lateral lacuna of the frog, the two meeting
at the frog's point. Each incision thus made should be carried deep enough
to cut through the substance of the plantar cushion. A tape is then passed
through the point of the frog, tied in a loop, and given to an assistant to
draw backwards. The plantar cushion itself is then incised in a direction
from before backwards, and pulled on by the assistant, so as to expose the
plantar aponeurosis.

Should this be found at all necrotic, it may be taken that purulent
inflammation of the navicular bursa and of the navicular bone itself
exists. The operator must then proceed to resection of the tendon in order
to treat the deeper structures thus affected. At its point of insertion
into the semilunar crest the tendon is severed and afterwards reflected.
This exposes the inferior face of the navicular bone. Instead of the
glistening and clear appearance it ordinarily presents, its glenoid
cartilage is found to be showing haemorrhagic or even purulent spots of
necrosis. The terminal portion of the tendon must then be excised.

To effect this a clean transverse incision is made at the extreme upper
border of the navicular bone. Here we are in close contact with the pedal
articulation, and great care is necessary in making this last incision, in
order that the synovial sac may not be penetrated.

All structures showing spots of necrosis should now be carefully removed,
either with the knife or with the curette. The kniv