[Fig. 122].—Blood-vessels and the more Ventral Nerves of the Axilla, Ventral View.

The pectoral and clavobrachial muscles have been cut and laid aside, their ends being shown; only a part of the nerves are exhibited. 1, M. clavobrachialis; 2, cut end of M. pectoralis major; 3, cut end of M. pectoralis minor; 4, M. biceps; 5, M. teres major; 6, M. epitrochlearis, partly cut and turned back; 7, M. latissimus dorsi, partly cut; 8, M. pectoralis minor; 9, M. pectoralis major; 10, short portion of caput mediale of M. triceps brachii. a, branches of the thyrocervical axis to clavobrachial and clavotrapezius muscles; b, suprascapular nerve; c, first subscapular nerve; d, musculocutaneous nerve; e, median nerve; f, V. axillaris; f′, V. brachialis; g, A. axillaris; g′, A. brachialis; h, first anterior thoracic nerve, accompanied by the anterior thoracic artery and vein; i, V. subscapularis; j, large muscular branch (to subscapular muscle) of the subscapular vein and brachial artery; l, A. subscapularis; l′, A. circumflexa humeri anterior; m, radial nerve; n, ulnar nerve; o, medial cutaneous nerve; p, A. thoracica longa; q, r, second anterior thoracic nerve; s, V. longa thoracica; t, A. and V. thoracicodorsalis; u, A. profunda brachii; v, branch of brachial artery accompanying medial cutaneous nerve; w, branch of A. collateralis radialis superior; x, A. collateralis radialis superior; y, V. mediana cubiti; z, A. collateralis ulnaris.

A. thoracicodorsalis (t).—This arises from the subscapular a short distance from its origin and passes across the teres major to the latissimus dorsi (7), giving branches to both these muscles and to the epitrochlearis.

A. circumflexa humeri posterior.—The posterior circumflex artery arises from the A. subscapularis close to the origin of the latter. It passes between the subscapularis muscle and the teres major, close to the border of the biceps, then between the lateral and long heads of the triceps. It gives off a branch to the inner surface of the spinodeltoid and acromiodeltoid, then passes distad to supply the lateral and long heads of the triceps.

4. A. brachialis (g′).—The brachial artery is the continuation of the axillary (g) into the arm beyond the origin of the subscapular (l). It passes along that side of the biceps which lies next to the humerus. It passes thus, accompanied by the brachial vein (f′) and median and ulnar nerves, through the bicipital arch and afterwards between the biceps (4) and the intermediate division of the medial head of the triceps to the supracondyloid foramen of the humerus, through which it passes with the median nerve to reach the concavity of the elbow. It gives off the following branches:

a. A. circumflexa humeri anterior (l′).—The anterior circumflex artery usually leaves the brachial near its origin (but may arise from the subscapular (l) or one of its branches); it passes to the biceps (4) near the origin of the latter and sends a branch proximad to the head of the humerus.

b. A. profunda brachii or superior profunda (u).—This arises from the first part of the brachial or it may come off from one of the branches of the axillary (e.g., the subscapularis). It passes along with the radial nerve onto the dorsal side of the humerus and supplies the triceps muscle. It also sends branches to the epitrochlearis (6) and latissimus dorsi (7).

c. Rami musculares.—Muscular branches are given off near the supracondyloid foramen to the biceps (4), epitrochlearis (6), and brachialis muscles. A nutrient artery leaves the brachial proximad of the supracondyloid foramen, either separately or in common with the muscular branches, and passes into the nutrient foramen at the junction of the middle and distal thirds of the shaft of the humerus, supplying the bone.

d. A. collateralis ulnaris (superior) (or A. anastomotica magna) (z).—This leaves the brachial artery just proximad of the supracondyloid foramen and passes to the convexity of the elbow, supplying the structures about the olecranon.

e. A. collateralis radialis superior ([Fig. 130]).—This rises from the axillary artery just proximad of the supracondyloid foramen ([Fig. 122], x), in company with the vena mediana cubiti (y), passes across the surface of the biceps (4), beneath the pectoantibrachialis, into the concavity of the elbow. Here it gives branches to the pectoantibrachialis, clavobrachialis, and extensor muscles of the forearm. It then passes onto the ventroradial border of the forearm ([Fig. 130]) and runs along this border, in company with the vena cephalica ([Fig. 130], c) and the superficial radial nerve (g), to the wrist, sending off branches to the integument. At the wrist it turns onto the dorsum of the hand, passing in a gentle curve to the ulnar side and distad, and giving off a branch for the space between each pair of metacarpal bones. These branches ([Fig. 130], e) (Aa. digitales dorsales) pass distad and anastomose with branches coming from the palm.