mention, for
the reason that we shall be afterwards concerned with it in the operation
of neurectomy. Its point of origin is the inside of the inferior extremity
of the radius. Descending in company with the flexor tendons, and passing
behind the carpus and beneath the carpal sheath, it continues its descent,
in company with the internal plantar nerve and the internal metacarpal
vein, on the inner side of the flexor tendons until just above the fetlock.
At this point it bifurcates into the digital arteries.

From the carpus downwards the large metacarpal artery, the internal
metacarpal vein, and the internal plantar nerve are in close relation with
each other. The vein holds the anterior position. The artery is between the
two, and has the nerve in close contact with it behind.

THE DIGITAL ARTERIES, OR COLLATERAL ARTERIES OF THE DIGIT.--These are of
large volume, and carry the blood to the keratogenous apparatus of the
foot. They separate from each other at an acute angle, and pass over the
side of the fetlock, one to the inside, the other to the outside, to reach
the internal face of the basilar process of the os pedis, where they
bifurcate to form the _Plantar_ and _Preplantar_ arteries. In the whole
of their course the digital arteries follow the flexor tendons, and are
related in front to the digital vein, and behind to the posterior branch of
the plantar nerve. This is the nerve implicated in the lower operation of
neurectomy, and its relation to adjoining structures will be detailed
under Section F. of this chapter. During its course the digital artery
gives off branches in the following positions:

1. _At the Fetlock_ numerous branches to the metacarpo-phalangeal
articulation, the sesamoid sheath, and the tendons.

2. _At the Upper Extremity of the First Phalanx_ branches for the supply of
the surrounding tissues, and for the tissues of the ergot.

3. _Towards the Middle of the Third Phalanx_, the _Perpendicular_ artery
of Percival. This arises at a right angle from the main vessel, and
immediately divides into two series of ramifications--an ascending and
a descending. The ramifications of these series freely anastomose with
corresponding vessels of the opposite side.

4. _At the Superior Border of the Lateral Cartilage_, the _Artery of the
Plantar Cushion_. This is directed obliquely downwards and backwards, under
cover of the cartilage, and is distributed to the middle portion of the
complementary appar