OF THE UPPER EXTREMITY AXD THORAX. 663 



dorsal surface, and form two plexuses, an inner and outer, on the back of the 

 hand. The inner plexus is formed by the veins from the little finger (vena salva- 

 t> //'/). the ring finger, and the ulnar side of the middle finger ; from it the anterior 

 and posterior ulnar veins are derived. The outer plexus is formed by veins from 

 the thumb, the index finger, and radial side of the middle finger ; from it the 

 radial vein is derived. These two plexuses communicate on the back of the hand, 

 forming the superficial arch of veins in this situation. The superficial veins from 

 the palm of the hand form a plexus in front of the wrist, from which the median 

 vein is derived. 



The Anterior Ulnar Vein commences on the anterior surface of the ulnar side 

 of the hand and wrist, and ascends along the anterior surface of the ulnar side of 

 the forearm to the bend of the elbow, where it joins with the posterior ulnar vein 

 to form the common ulnar. Occasionally it opens separately into the median 

 basilic vein. It communicates with branches of the median vein in front and 

 with the posterior ulnar behind. 



The Posterior Ulnar Vein commences on the posterior surface of the ulnar side 

 of the wrist. It runs on the posterior surface of the ulnar side of the forearm, 

 and just below the elbow unites with the anterior ulnar vein to form the common 

 ulnar, or else joins the median basilic to form the basilic. It communicates with 

 the deep veins of the palm by a branch which emerges from beneath the Abductor 

 minimi digiti muscle. 



The Common Ulnar is a short trunk which is not constant. When it exists it 

 is formed by the junction of the two preceding veins, and, passing upward and 

 outward, joins the median basilic to form the basilic vein. When it does not 

 exis: the anterior and posterior ulnar veins open separately into the median 

 basilic vein. 



The Radial Vein commences from the dorsal surface of the wrist, communi- 

 cating with the deep veins of the palm by a branch which passes through the 

 first interosseous space. It forms a large vessel, which ascends along the radial 

 side of the forearm and receives numerous veins from both its surfaces. At 

 the bend of the elbow it unites with the median cephalic to form the cephalic 

 vein. 



The Median Vein ascends on the front of the forearm, and communicates with 

 the anterior ulnar and radial veins. At the bend of the elbow it receives a branch 

 of communication from the deep veins, and divides into two branches, the median 

 cephalic and median basilic, which diverge from each other as they ascend. 



The Median Cephalic, usually the smaller of the two, passes outward in the 

 groove between the Supinator longus and Biceps muscles, and joins with the 

 radial to form the cephalic vein. The branches of the external cutaneous nerve 

 pass beneath this vessel. 



The Median Basilic Vein passes obliquely inward, in the groove between the 

 Biceps and Pronator radii teres. and joins the common ulnar to form the basilic. 

 This vein passes in front of the brachial artery, from which it is separated by a 

 fibrous expansion (the bicipital fascia] which is given off from the tendon of the 

 Biceps to the fascia covering the Flexor muscles of the forearm. Filaments of 

 the internal cutaneous nerve pass in front as well as behind this vessel. 1 * 



Venesection is usually performed at the bend of the elbow, and as a matter of practice the 

 largest vein in this situation is commonly selected. This is usually the median basilic, and there 

 are anatomical advantages and disadvantages in selecting this vein. The advantages are, that 

 in addition to its being the largest, and therefore yielding a greater supply of blood, it is the 

 least movable and can be easily steadied on the bieipital fascia on which it rests. The disadvan- 

 are. that it is in close relationship with the brachial artery, separated only by the bieipital 

 fascia ; and formerly, when venesection was frequently practised, arterio-venous aneurism was 



1 Cruveilhier says: "Numerous varieties are observed in the disposition of the veins of the 

 elbow; sometimes the common median vein is wanting: but in those cases its two branches are fur- 

 nished by the radial vein, and the cephalic is almost always in a rudimentary condition. In other 

 .nly two veins are found at the bend of the elbow, the radial and ulnar, which are continuous, 

 without any demarcation, with the cephalic and bnsilic." 



