e facets uniting the navicular
to the pedal bone, and offers for consideration two sacs. A large one
posteriorly running up behind the second phalanx to nearly adjoin the
sesamoidean bursae, and a small one, a prolongation of the synovial membrane
between the antero-lateral and postero-lateral ligaments of the same side.
This latter is often distended, and on account of its close proximity to
the seat of operation, is liable to be accidentally opened in excision of
the lateral cartilage for quittor.

C. THE TENDONS

In order to convey an intelligent understanding of the tendons it will be
wise to briefly describe the course of their parent muscles from their
commencement.

THE EXTENSOR PEDIS.--The extensor pedis arises from the lower extremity
of the humerus in two distinct portions of unequal size, a muscular and a
tendinous. These are succeeded by two tendons passing in common through a
vertical groove at the lower end of the radius. Lower in the limb these
tendons separate, the outer and smaller joining the tendon of the extensor
suffraginis, and the inner and main tendon continuing its course downwards.
With the exception of the navicular, it is attached to all the bones of the
foot, and is covered internally by the capsular ligaments of the joints
over which it passes, those with which we are concerned being the pastern
joint and the pedal joint. Before its attachment to the os pedis it
receives on each side of the middle of the first phalanx reinforcement in
the shape of a strong band descending obliquely over the fetlock from the
suspensory ligament. Widening out in fanlike fashion, it is inserted into
the pyramidal process of the os pedis.

_Action_.--The action of this muscle is to extend the third phalanx on the
second, the second on the first, and the first on the metacarpus. It also
assists in the extension of the foot on the forearm.

[Illustration: FIG. 10.--THE FLEXOR TENDONS AND EXTENSOR PEDIS. (AFTER
HAUeBNER.) 1, Tendon of flexor perforans; 2, its supporting check-band from
the posterior ligament of the carpus; 3, tendon of the flexor perforatus;
4, ring and sheath of the flexor perforatus; 5, widening out of the flexor
perforatus to form the plantar aponeurosis; 6, suspensory ligament; 7,
reinforcing band from the suspensory ligament to the extensor pedis; 8, the
extensor pedis.]

THE FLEXOR PEDIS PERFORATUS, OR THE SUPERFICIAL FLEXOR OF THE
PHALANGES.--In common with the perforans, this muscl