THE UPPER LIMB 35' 



ment of the posterior ulnar vein, and is known as the vena salvatdla 

 or ' saving vein.' The blood is conveyed away from the outer side 

 of the dorsal venous plexus by the radial vein, and from the inner 

 side by the posterior ulnar vein. The radial vein receives a com- 

 municating branch from the venae comites of the deep palmar arch 

 at the proximal end of the first interosseous space. The posterior 

 ulnar vein receives a communicating branch from the venae comites 

 of the profunda branch of the ulnar artery, which passes beneath the 

 abductor minimi digiti muscle. 



The anterior venous plexus receives its radicles from the palm, 

 and the blood is conveyed away from it by the median vein . The 

 anterior ulnar vein, as stated, commences on the inner aspect of the 

 front of the wrist. 



Deep Fascia of the Forearm. — The deep fascia is of considerable 

 strength, its fibres being principally transverse, though some are 

 disposed longitudinally and obliquely. Superiorly, below the 

 internal epicondyle, it receives the semilunar fascia of the biceps, 

 and behind it gets an accession of fibres from the tendon of the 

 triceps. In front of the elbow it presents an opening for the passage 

 of the deep median vein. In the region of the epicondyles it serves 

 as a common tendon of origin to the muscles arising from these 

 prominences, and it sends between them strong intermuscular septa 

 which afford additional origin to them, and are readily recognised on 

 the surface by white hues. It is attached above to the epicondyles 

 of the humerus and the margins of the triangular surface on the back 

 of the olecranon process of the ulna, and along the forearm to the 

 posterior border of the latter bone. Anteriorly it sends an ex- 

 pansion between the superficial and deep muscles, and it acts in a 

 similar manner on the posterior aspect, where the fascia is stronger 

 than in front. At the wrist it blends with the anterior annular liga- 

 ment, and posteriorly it forms the posterior annular ligament. 



FRONT OF THE FOREARM. 



Muscles. — The muscles of the front of the forearm are arranged 

 in three layers — first or superficial, second or intermediate, and 

 third or deep. 



First Layer. — The muscles comprising this layer are, in order from 

 without inwards, the pronator radii teres, flexor carpi radialis, 

 palmaris longus (inconstant), and flexor carpi ulnaris. 



I. Pronator Radii Teres. — This muscle arises by two heads — 

 superficial or humeral, and deep or coronoid. The superficial head, 

 which is of large size, arises from (i) the front and upper part of the 

 internal epicondyle, and lower part of the internal supracondylar 

 ridge, of the humerus ; (2) the common tendon ; and (3) the inter- 

 muscular septa between it and the flexor carpi radialis externally, 

 and flexor sublimis digitorum deeply. The deep head, which is of 

 small size, arises from the inner margin of the coronoid process of the 



