RADIAL AND ULNAR ARTERIES. (Arteres radiale et ulnaire — Speiehenpulsader und Ellenbogenpulsader.)— The nomenclature of the different branches of the systemic cir culation is based upon two principles. Ac cording to one of these, the distinction of appellation is grounded upon the tubes them selves ; their different ramifications being designated by as many names, which usually more or less connote the ultimate destination of the vital fluid they contain. Where this method fails, another remains, which, though essentially arbitrary, is yet of the highest im portance : a method which, in order to their stricter contemplation by the anatomist, and their more accurate recognition by the sur geon, isolates different lengths of one and the. same tube, according to changes in its position and relations with respect to neigh bouring parts.
The radial and ulnar arteries, whose anato. my is here to be considered, are included in the first of these categories ; being the branches which result from the bifurcation of the artery for the upper extremity. Com mencing in their ordinary distribution, oppo site and anterior to the elbow joint, they continue along the whole front of the forearm, each in tolerably close proximity to the bone whose name it bears.* The ulnar, by simply continuing this course, arrives at the hand, but the radial previously turns round the outer side of the wrist to reach the first meta carpal interval, which it perforates. Each now takes a curved course in the palm ; a curve, whose convexity is forwards, whose situation—superficial or deep—follows that of the artery with which it is more imme diately continuous, and which, completed by a branch or branches from its fellow, forms that from the ulnar the superficial, that from the radial the deep, palmar arch.
Since either of' these arches has a share from both vessels, it might at first sight be supposed that we are here presented with a rare peculiarity in the uninterrupted artery traceable from the radial through its palmar arch to the ulnar, or vice vers'a.. But their apparent mutual continuity offers no difficulty to the exact nominal definition of each vessel and, obviously, the anastornosis differs from that common to all arteries only in degree : viz., in the greater freedom of communication which is the consequence of the larger size of the branches effecting it.
The brachial artery, inclining somewhat forwards in the lower part of its course so as to gain the angle of flexion of the limb, lies at its termination on the brachialis anticus, where this muscle becoming tendinous, covers the coronoid process of the ulna previously to its insertion into the apex of the rough non articular surface of this prominence. Here it
divides.
The radial artery. Its relations. — The radial artery begins as the outer of the two divaricatina branches, and. ends as the deep palmar arch : in this course it offers three chief variations of regional anatomy, which vvill require a separate consideration. The first of these divisions may be regarded as terminating at the lower border of the radius, the second at the superior extremity of the first metacarpal space in the back of the hand, and the third at the point where, after break ing up into the radialis indicis, ma,,ana pollicis, and palmaris profunda vessels, the latter of these, lying deeply in the inner side of the palm, unites with the communicating branch from the ulnar artery.
(a.) In the forearnz, the artery is directed at first downwards and externally, but afterwards more vertically, so as to exhibit a slight curve, whose convexity is upwards and outwards. It thus corresponds for a very short distance —say one third of an inch —to the coronoid process of the ulna, and lies on the brachialis anticus ; but in the whole of the remainder of its length it is related to the anterior sur face of the radius, and is situated on the muscles which immediately cover it. Crossing the inner surface of the tendon of the biceps as this sinks to its insertion, it by turns comes into contact with the cellular tissue 011 the supinator radii brevis, and lies upon the pronator radii teres, as this passes outwards to its insertion ; then for a short distance the radial origin of the flexor sublimis digitorum sustains it, and next the flexor longus pollicis; by the passage of whose muscular fibres in wards to their tendon, it is left opposed to the pronator quadratus, but scarcely touching it from the depth at which this muscle is placed. To its outer side is the tendon of the biceps, and, at first distantly', afterwards more closely, the supinator radii longus, which maintains the relation throughout the remain der of this portion of the vessel : in this situation is also found the musculo-spiral nerve, which descends under cover of the inner border of the muscle, and passes away from the lower part of the artery towards the back of the wrist. To its inner side are suc sessively, the pronator radii teres in about the upper half of the region, in the lower, the tendon of the flexor carpi radialis ; and be neath this for a very short distance, that of the flexor longus pollicis. The coverings of the artery are merely the integuments and fascia of the forearm, so that in the whole of its length it is comparatively superficial : and the ordinary cellular tissue surrounds the vessel, while two venw comites accompany its course.