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: