C. V. subclavia.—The subclavian vein enters the innominate at about the level of the first rib. Outside of the thorax it is called the axillary vein (j); this comes from the arm.

[Fig. 130].

Superficial Arteries, Veins, and Nerves on the Extensor Side of the Arm and Dorsum of the Hand.

a, V. cephalica; b, V. mediana cubiti; c, V. cephalica antibrachii; d, A. collateralis radialis superior; e, Aa. and Vv. digitales dorsales; f, A. radialis; g, superficial radial nerve; h, N. musculocutaneus; i, N. cutaneus medialis.

Veins of the Arm.—The blood is returned from the arm by two systems of veins,—a deep and a superficial system.

The deep system is composed of veins which correspond to the branches of the axillary artery, follow in general the same course, and receive the same names ([Fig. 122]). They unite to form the axillary vein. The brachial vein does not pass with the brachial artery through the supracondyloid foramen.

The superficial system comprises the vena cephalica and its branches.

V. cephalica ([Fig. 130]).—Several superficial branches lying in the palm of the hand unite to form a common trunk which curves about the radial side of the wrist and here unites with a similarly formed trunk from the dorsum of the hand. The vein formed by this union, vena cephalica (antibrachii) (c), passes to the elbow accompanying the radial nerve (g) and the collateral radial artery (d), and lying on the extensor carpi radialis longus muscle just beneath the integument. It receives small lateral superficial branches. At the elbow it divides into two: these are the vena cephalica (humeri) (a) and the vena mediana cubiti (b). The latter passes beneath the pectoantibrachialis muscle, across the biceps, and unites with the brachial vein in the concavity of the elbow.

The vena cephalica (humeri) passes at the elbow onto the upper arm, following the lateral border of the clavobrachial muscle. It thus reaches the acromiodeltoid muscle, where it divides into two branches. One passes inward beneath the acromiodeltoid, and joins the vena circumflexa posterior (a branch of the axillary). The second continues over the outer surface of the shoulder, and finally joins the vena transversa scapulæ (a branch of the external jugular).