886 HUMAN ANATOMY. 



operation, as elevation of the clavicle may then be followed by the entrance of air 

 into the vein (Henlej. Obstruction of the subclavian at the point of junction with 

 the internal jugular results in compression of the orifice of the thoracic duct. 



. THE VEINS OF THE UPPER EXTREMITY. 



Instead of following distally the various branches which return the blood from 

 the upper limb it will be more convenient to begin with the peripheral branches and 

 trace the vessels proximally towards the subclavian. 



The veins of the upper extremity may be divided into a superficial and a deep 

 set. The latter follow in general the course of the arteries, of which they are, as a 

 rule, the venae comites. They anastomose frequently with the superficial veins and 

 are more richly supplied with valves than are the latter. 



THE DEEP VEINS. 

 The Deep Veins of the Hand. 



The deep veins of the hand are all relatively small and are of less importance 

 than the superficial ones in returning the blood. Each of the palmar arterial 

 arches is accompanied by venae comites, and into those of the superficial arch (arcus 

 volaris venosus superficialis) the superficial digital veins (vv. digitales volares com- 

 munes) open, while those of the deep arch (arcus volaris venosus profundus) receive 

 the veins (vv. metacarpeae volares) which accompany the aa. princeps pollicis, radialis 

 indicis, and interossei palmares. 



Upon the dorsum of the hand even more than on its volar surface the chief 

 part is played by the superficial veins. Three or four pairs of dorsal interosseous 

 veins occur, however, accompanying the corresponding arteries and opening event- 

 ually partly into the radial veins and partly, through the veins corresponding to the 

 posterior carpal net- work, into the superficial veins of the dorsum of the wrist (rete 

 venosum dorsale manus). As in the case of the arteries, the deep veins of the dorsal 

 and volar surfaces of the hand are connected by perforating veins, and both make 

 numerous connections with the superficial veins. 



The Deep Veins of the Forearm. 



The deep veins of the forearm are the venae comites which accompany the radial 

 and ulnar arteries and their branches. The radial veins (vv. radiales) are the 

 upward continuation of the veins of the deep palmar arch and are relatively slender. 

 The ulnar veins (vv. ulnares) are larger and are formed by the union of the ulnar 

 ends of the venae comites of both the superficial and deep palmar arches. Usually 

 they have a large communication from the superficial veins of the dorsum of the hand, 

 and receive near the elbow the veins which accompany the interosseous artery and 

 its branches, and also a strong communicating branch, the deep median vein, from 

 the superficial median (page 890). Both the ulnar and radial veins are well supplied 

 with valves, and they unite at the elbow to form the brachial veins. 



The Brachial Veins. 



The brachial veins (vv. brachiales) (Fig. 762) are the companion veins of the 

 brachial artery and receive tributaries corresponding to the branches of the artery. 

 They are formed at about the elbow-joint by the union of the radial and ulnar veins, 

 and extend upward, one on either side of the brachial artery, to the lower border of the 

 pectoralis major muscle^ at about which level they unite to form a single trunk, termed 

 the axillary vein. 



As is usual with venae comites, the two brachial veins are united by numerous 

 anastomoses and occasionally unite through portions of their course, especially above, to 

 form a single trunk. At the elbow one of the veins frequently lies in front of the artery 

 and sometimes the two veins pursue a spiral course around it. In addition to the 

 tributaries which accompany the branches of the brachial artery, the brachial veins, or 

 rather the inner one of the two, receive near their termination the basilic vein (page 8qo). 



