3i4 APPLIED ANATOMY. 



The median nerve runs down the middle of the forearm, lying beneath the 

 groove separating the palmaris longus and flexor carpi radialis tendons. The ulnar 

 nerve runs from the groove between the medial (internal) condyle and olecranon 

 process above to the radial or outer side of the pisiform bone below. It lies to the 

 ulnar side of the ulnar artery in the lower half of the forearm. The rounded mus- 

 cular mass between the edge of the flexor carpi ulnaris and the palmaris longus is 

 formed by the flexor sublimis digitorum muscle (Fig. 327). 



Posterior Surface. The posterior surface differs from the anterior in the 

 bones being more conspicuous they are subcutaneous. Of the two the ulna is the 

 more evident. At the elbow the olecranon and the capitellum to its outer side are 

 well marked and some distance inwardly is the medial (internal) condyle. By pal- 

 pation the ulna can be traced down the forearm almost subcutaneous, running from 

 the olecranon process, in a gentle curve toward the median line, down to its styloid 

 process at the back of the wrist. It is covered only by the skin and superficial and 

 deep fascias. About 3 cm. ( i ^ in. ) to the outer side of the olecranon can be felt 

 the lateral (external) condyle and capitellum. If the elbow is extended a dimple 

 is seen just below the capitellum ; it marks the position of the head of the radius, 

 and by pressure the groove separating the head from the capitellum can be felt. 



By placing the thumb of one hand in the dimple on the head of the radius, and 

 rotating the hand of the patient with the other, one can feel the bone rotate and thus 

 be assured that the radius is intact. Whenever fracture of the radius is suspected 

 this is the procedure resorted to in order to determine whether or not it is broken. 



The radius can be followed only for an inch or so below the dimple, when it 

 disappears beneath the muscles to again become subcutaneous on the outer side of 

 the forearm, about its middle, from thence it can be followed more or less distinctly 

 down to the styloid process on the outer side of the wrist. 



The ulna being subcutaneous, fracture can be determined by palpating it from 

 the olecranon down the back of the forearm to the styloid process. 



The line of the ulna is usually marked by the presence of a groove. To the 

 ulnar side of the groove lie the flexor carpi ulnaris and the other flexors; to the 

 radial side lie the extensor carpi ulnaris and the other extensors (Fig. 328). 



From the dimple marking the head of the radius a groove in the muscles can be 

 felt which runs to the middle of the outer surface of the radius. Anterior or to the 

 palmar side of this groove lie the brachioradialis and extensor carpi radialis longior 

 with the supinator (brevis) beneath. The muscles posterior or between the groove 

 and the ulna are the extensor carpi radialis brevior, extensor communis digitorum, 

 and extensor carpi ulnaris. Passing over the lower third of the outer side of the 

 radius are the tendons of the extensor ossis metacarpi pollicis and extensor brevis 

 pollicis muscles. As they are here subcutaneous, this is the point at which creaking 

 can be felt when they are affected with tenosynovitis. 



ARTERIES OF THE FOREARM. 



A knowledge of the arteries of the forearm is necessary on account of the trouble- 

 some hemorrhage which they cause when wounded. 



At the bend of the elbow, a finger's breadth below the crease and opposite the 

 neck of the radius, the brachial artery divides into the radial and ulnar arteries. 

 These are continued through the forearm to enter the hand, the ulnar anteriorly over 

 the annular ligament and the radial posteriorly through the " anatomical snuff-box. " 



The ulnar artery is larger than the radial and in its upper half it describes a 

 curve with its convexity toward the ulnar side passing beneath the pronator radii 

 teres and superficial flexor muscles arising from the medial (internal) condyle. It is 

 accompanied by venae comites but not by any nerve in this portion of its course. 

 Just above the middle of the forearm the ulnar nerve joins the artery, lying to its 

 ulnar side, and accompanies it down into the hand. In the lower half of its course 

 the ulnar artery lies to the radial side of the flexor carpi ulnaris muscle, being slightly 

 overlapped by it. The flexor sublimis on the radial side also tends to overlap it. 

 The covering of the artery, partially at least, by these muscles, together with the 

 thickness of the deep fascia and the lack of a proper bony support beneath, cause the 



