'3. Veins of the upper extremity. — These veins are arranged in two series, a superficialand a deep; both of which are provided with valves, but the deep veins the most abundantly.
Superficial Veins. In the fore-arm and hand these veins are distributed with great minuteness in the subcutaneous areolar tissue, and anastomose freely with one another ; but their larger branches chiefly occupy the radial and ulnar (the lateral) aspects of the fore-arm.
The radial or external superficial veins ema nate from numerous venules on the thumb and dorsum of the fore-finger, and are joined in the fore-arm by many cutaneous branches from either side. Opposite the elbow joint these tributaries have ended in one vessel of considerable size, the cephalic vein, which, being joined by a branch from the median vein (median cephalic), ascends between the biceps and supinator loops muscles, follows the outer margin of the biceps, traverses the interspace between the pectoralis major and the deltoid, and ultimately having arrived in the subclavieular triangle, bends over the upper edge of the pectoralis minor, penetrates the thin expansion of the "fascia clavicularis" (ligamentunz bicorne), and enters the axillary vein immediately beneath the clavicle. In some instances a branch is continued upwards from the cephalic vein, which passes over the clavicle and communicates with the external jugular vein.
The ulnar or internal superficial veins have their origins from veins which ramify on the dorsum of the hand and of the two inner fingers, one of which from the little finger has been long known as the " vena salvatella ;" others arise anteriorly from subcutaneous veins on the front of the wrist. In the vici nity of the elbow both sets of branches unite to form one principal trunk, the basilic vein, which is reinforced almost at the moment of its formation by the median basilic vein, a branch of very considerable size from the median.
The basilic vein, now much enlarged, as cends along the inner margin of the biceps muscle, parallel to the brachial artery, but more superficially than that vessel, (for the deep fascia intervenes,) until it arrives oppo site the centre of the arm, when it pierces the brachial aponeurosis, and joins one or other of the vena' comites of the brachial artery. In a few instances the vein ascends as high as the axilla, and entering that space joins the trunk of the axillary vein. The
superficial veins in the front of the upper part of the fore-arm unite to form a short trunk termed median vein, which by its lateral branches connects the radial and ulnar super ficial veins ; near the bend of the elbow the median vein receives a large communicating branch from the venm comites of the brachial artery, and terminates by dividing into two very considerable veins, termed median basilic and median cephalic veins respectively : the latter passes obliquely upwards and outwards, over the tendon of the biceps, and joins the cephalic vein ; the former, which is the largest, inclines inwards, and in its course to join the basilic trunk passes across the bra chial artery, separated from it only by the " semilunar fascia" of the biceps tendon.
The deep veins of the upper extremity ac company the ramifications of the larger arteries chiefly, which in the lower as well as in the tipper extremity, are invariably attended by two veins, one on either side, hence called vena' comites; transverse branches at short intervals maintain a free communication between these vessels.
The vena comites of the ulntar artery are de rived from veins which correspond to the di gital arteries, and which form a superficial pa/mar arch of veins, which at its outer ex tremity receives branches from the deep radial veins, through which the venm comites of the radial and ulnar arteries are brought into com munication with each other. The associate veins of the interosseous artery unite with the venm comites of the ulnar artery.
The vence comites of the radial artery com mence from the pa/mar interosseal veins, which form a deep palmar arch across the heads of the metacarpal bones, and are joined by veins from the muscles of the thumb, and by branches of the superficial arch which follow the course of the arteria superficialis volw. The venue comites of both the radial and ulnar arteries receive numerous tributaries from the veins of the adjacent muscles, and ultimately unite to form the Satellite veins of the brachial artery. The brachial vena: comites are joined by veins which correspond to the branches of the brachial artery in the arm (superior and inferior profunda and anastomotica magna), and also by the basilic vein. At the lower part of the axilla, these veins, by their union, form the axillary vein.