THE ULNAR ARTERY. • 781 



The venae comites of the ulnar are closely attached to it, but may be included in 

 the ligature without danger, as the other venous channels of the forearm are amply 

 sufficient to carry on the circulation. 



The collateral circulation is maintained by means of the free anastomosis between 

 the branches of the radial and ulnar, those of the interosseous vessels, and those of 

 the carpal and palmar arches. 



1. The Anterior Ulnar Recurrent Artery. — The anterior ulnar recurrent 

 (a. recurrens ulnaris anterior) (Fig. 712) arises from the upper part of the ulnar 

 artery, frequendy in common with the posterior recurrent. It is usually a rather 

 slender branch, and is directed upward in the groove between the brachialis anticus 

 and the pronator radii teres towards the internal condyle, over which it terminates 

 in branches which anastomose with the inferior profunda and anastomotica magna of 

 the brachial. It gives of? branches to the neighboring muscles and a branch to the 

 anterior inner portion of the capsular ligament of the elbow-joint. 



2. The Posterior Ulnar Recurrent Artery. — The posterior ulnar recurrent 

 (a. recurrens ulnaris posterior) (Fig. 712) arises either immediately below the anterior 

 recurrent or by a common trunk with it. It is usually considerably larger than the 

 anterior recurrent, and passes at first almost horizontally inward and backward be- 

 tween the flexor sublimis and the flexor profundus digitorum, and then bends upward 

 along the side of the ulnar nerve between the two heads of the flexor carpi ulnaris. It 

 terminates upon the posterior surface of the internal condyle of the humerus in 

 branches which anastomose with the posterior branch of the inferior profunda and 

 with the anastomotica magna of the brachial. 



It gives branches to the adjacent muscles, to the skin, and to the posterior in- 

 ternal portion of the capsule of the elbow-joint. 



3. The Common Interosseous Artery. — The common interosseous (a. 

 interossea communis) (Fig. 710) arises from the outer and back part of the ulnar 

 artery, a short distance below the posterior ulnar recurrent. It is a short, stout 

 trunk which passes downward and outward and, having reached the upper border 

 of the interosseous ligament, divides into the anterior and posterior interosseous 

 arteries. 



Variations. — In cases in which a superficial brachial artery (page 774) exists, the true 

 brachial may be directly continuous below with the common interosseous, the radial and ulnar 

 arteries arising by the bifurcation of the superficial brachial. Such cases form what are usually 

 termed " high" origins of the common interosseous ; and, since the superficial brachial may arise 

 from the axillary, owing to the anastomosis with it of the aberrant branch of that artery, the 

 common interosseous may also appear to arise from the axillary. 



In cases of high origin of the radial the common interosseous may arise from that vessel 

 and give origin to the recurrent ulnar branches, and it may also give rise to these branches when 

 it has a normal origin. When it has a high origin, it may give off both the radial and ulnar 

 recurrent branches. • 



a. The Anterior Interosseous Artery. — The anterior interosseous (a. inter- 

 ossea volaris) (Fig. 712) descends from the point of bifurcation of the common inter- 

 osseous artery, along the anterior surface of the interosseous membrane, between the 

 adjacent edges of the flexor profundus digitorum and the flexor longus pollicis, and 

 divides at the upper border of the pronator quadratus into an anterior and a pos' 

 terior terminal branch (Fig. 715). 



Branches. — In addition to muscular branches to the adjacent muscles and to the ex- 

 tensor muscles of the thumb, — the latter perforating the interosseous membrane to reach their 

 destinations, — the anterior interosseous artery gives off a number of more or less important 

 branches. 



(aa) The median artery (a. comes nervi mediani) arises from the anterior surface of the ante- 

 rior interosseous, immediately below the origin of that vessel. It passes forward to join the 

 median nerve, which it accompanies down the arm, and in whose substance it is frequently 

 embedded. It continues its course with the nerve beneath the anterior annular ligament, and, 

 when well developed, may terminate by anastomosing directly with the superficial palmar 

 arch. 



{bb) A nutrient branch is usually given off to the radius and occasionally also to the ulna. 



