38 SUPERFICIAL ANATOMY OF THE UPPER LIMB. 



THE FOREARM. 



From the olecranon, the sinuous posterior border of the ulna is to be followed 

 down the forearm, corresponding to a superficial furrow between the ulnar flexor 

 and extensor muscles of the wrist ; the border becomes rounded off in the lower 

 third, but a narrow strip of the bone is still subcutaneous, leading down to the 

 styloid process. When the hand is supinated, the styloid process of the ulna is 

 exposed at the inner and posterior pjfrt of the wrist ;, but if the hand be pronated, 

 then the skin is stretched over the opposite (outer) part of the head of the ulna, 

 which projects between the extensor carpi ulnaris and extensor minimi digiti 

 muscles. Close below the outer condyle of the humerus the head of the radius may 

 be felt moving beneath the muscles, more distinctly when the elbow is bent, as the 

 forearm is alternately pronated and supinated. The upper half of the shaft of the 

 radius is too thickly covered by muscles to be distinctly made out ; the lower half 

 is nearer to the surface, and can be readily examined between and through the 

 surrounding muscles and tendons ; at the lower end, the styloid process, which 

 descends rather lower than the styloid process of the ulna, is superficial in front and 

 behind, being covered externally by the tendons of the extensor ossis metacarpi and 

 extensor brevis (ext. primi internodii) pollicis muscles ; and the prominent tubercle 

 on the outer side of the groove for the extensor longus pollicis (ext. secundi inter- 

 nodii) is also to be distinguished. 



Along the inner and fore part of the forearm is the prominence formed by the 

 pronato-flexor muscles, the great mass covering the ulna internally being formed by 

 the flexor profundus digitorum beneath the flexor carpi ulnaris. A short distance 

 below the internal condyle, a slight groove runs obliquely downwards and inwards 

 across the muscles, caused by the prolongation of the fibres of the bicipital fascia. 

 Near the wrist, the tendon of the flexor carpi ulnaris can be felt, passing down to 

 the pisiform bone, and immediately external to the tendon the beating of the ulnar 

 artery is perceptible : when the wrist is extended a groove marks the position of 

 the tendon. About the centre of the front of the wrist the tendon of the palmaris 

 longus descends, being the moet prominent of all the tendons here, and a little 

 external to this, the tendon of the flexor carpi radialis is also visible. It will 

 however be remembered that the palmaris longus is often wanting. Outside the 

 tendon of the flexor carpi radialis is a hollow in which the radial vessels are placed, 

 and where the pulse is commonly felt : immediately internal to the tendon lies the 

 median nerve. 



Along the outer border of the forearm, the long supinator and radial extensor 

 muscles of the wrist descend, becoming tendinous and smaller below the middle ; 

 and in the lower third of the forearm a smaller prominence, directed obliquely 

 downwards, outwards and forwards, results from the presence of the extensor 

 muscles of the thumb crossing over the long tendons. On the back of the forearm 

 are the extensors of the fingers, the extensor carpi ulnaris, and the anconeus, all of 

 which may be individually distinguished in thin persons. 



Numerous cutaneous veins are seen on the forearm, arising principally from the 

 network on the dorsum of the hand, and forming two main trunks, the posterior 

 ulnar and the radial, which ascend respectively along the inner and outer borders 

 of the limb, and incline forwards to their terminations in front of the elbow ; in 

 many cases another large vein is present (assisting or even replacing the radial 

 vein), which turns round the outer border of the forearm below the middle to join 

 the median vein. The subcutaneous veins of the lower part of the front of the 

 forearm (also those of the palm) are small, and terminate in the median and anterior 

 ulnar veins. It occasionally happens that the ulnar artery, having been derived 

 from the brachial at a higher level than usual, descends over the pronato-flexor 



