BRACHIAL OR HUMERAL ARTERY (arteria brachzalis, humeraria. Germ. die Ar marterie.) This artery is the continuation of the trunk of the axillary. It commences at the inferior margin of the tendons of the teres ma jor and latissimus dorsi, whence it extends to about an inch below the bend of the elbow, where it usually divides into the radial and ulnar arteries ; but not unfrequently this divi sion takes place high in the arm.
The brachial artery lies on the internal side of the arm above, but in its course downwards it gradually advances in an oblique direction until it gets completely to the anterior surface of the limb, where it is found situated nearly midway between the condyles of the humerus in front of the elbow joint ; it is superficial in the whole line of its course, in every part of which its pulsations can easily be felt, and sometimes, in the arms of thin persons, are distinctly visible.
Relations.—Anteriorly the brachial artery is overlapped, for about its upper fourth, by the coraco-brachialis muscle and the median nerve; for the greater part of its course down the arm it is covered by the brachial aponeurosis, to which is added, where it crosses the elbow, the falciform expansion sent off from the tendon of the biceps to the internal condyle : the median basilic vein also lies in front of it opposite the bend of the elbow. Posteriorly, for about a third of its length from its commencement it lies in front of the triceps, from which it is se parated by a quantity of loose cellular tissue which envelopes the musculo-spiral nerve ; in its inferior two-thirds it rests on the brachiams anticus. Internally it is covered by the bra chial aponeurosis at its superior part, where the ulna'. nerve is also in contact with it. The me
dian nerve which crosses it, sometimes super ficially, and at other times passing more deeply, in the middle of the arm gets to its internal side, and continues to hold this relation to it in the remainder of its course. Externally it lies at first on the internal side of the humerus, from which it is separated as it descends by the thin muscular expansion in which the coraco-brachi alis terminates at the lower part of its insertion ; in the remainder of its course the inner edge of the biceps bounds it. The fleshy belly of this muscle also partially covers it in front, a little below the middle of the arm. At the bend of the elbow, the relations of the brachial artery become more numerous and complicated; here it inclines obliquely outwards and backwards, and sinks into a space which is bounded on the inner side by the origins of the pronator and flexor muscles of the forearm, and on the out side by those of the supinators and extensors, the floor of which space is formed by the bra chimus anticus muscle, from which the artery is separated by a layer of adipose cellular mem brane. The artery is accompanied in its passage into this space by the tendon of the biceps and the median nerve, the former being situated to its radial side, the latter to its ulnar ; and it is at the bottom of this space, opposite the coro noid process of the ulna, that the subdivision of the artery into radial and ulnar usually takes