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 apparatus of the os pedis, as well as to the villous tissue and the coronet. A branch of it is turned forwards to join with the coronary circle in forming the _circumflex artery of the coronet_. [Illustration: FIG. 14.--THE ARTERIES OF THE FOOT. The digital; 2, the perpendicular--(_a_) its ascending branch, (_b_) its descending branch; 3, circumflex artery of coronary cushion; 4, the preplantar (ungual) artery--this is seen issuing from the preplantar foramen, and distributing numerous ascending (_c_) and descending (_d_) branches (the latter concur in forming the circumflex artery of the toe); 5, the circumflex artery of the toe; 6, at the point marked (*) the terminal branch of the digital--namely, the plantar ungual--is hidden behind the lateral cartilage; 7, the lateral cartilage.]