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
HAÜBNER.) 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 muscle arises from the inner
condyloid ridge of the humerus. It is reinforced at the lower end of the
radius by the superior carpal ligament, passes through the carpal and