96 THE SUPERIOR EXTREMITY 



tion between the radius and the humerus. Immediately distal 

 to it the head of the radius lies near to the surface, and can 

 readily be felt, especially when it is made to roll under the 

 finger by inducing alternately the movements of pronation 

 and supination. The head of the radius is placed about 

 25 mm. (one inch) distal to the lateral epicondyle. 



Venae Superficiales. Portions of two large cutaneous 

 veins are met with in the arm, the cephalic vein and the 

 basilic vein. They were dissected and studied when the 

 cutaneous nerves of the superior extremity were examined 

 (see p. 63). Their positions in the arm should now be 

 revised. Both ascend from the back of the hand, and they 

 communicate with one another across the fascial roof of the 

 cubital fossa at the front of the elbow, by means of the 

 median cubital vein. 



In the arm the cephalic vein ascends along the groove at 

 the lateral border of the biceps or along the lateral part of 

 the eminence caused by the biceps muscle, to the delto- 

 pectoral sulcus. There it pierces the deep fascia, and it 

 continues upwards to the delto- pectoral triangle where it 

 turns medially, crosses superficial to the pectoralis minor, 

 pierces the costo-coracoid membrane, under cover of the 

 pectoralis major, and terminates in the axillary vein. 



The portion of the basilic vein which lies in the arm 

 ascends in the groove along the medial border of the biceps 

 muscle. At the middle of the arm it pierces the deep fascia, 

 and runs along the medial side of the brachial artery to the 

 axilla, where it becomes the axillary vein. 



Nervi Cutanei. The cutaneous nerves found in the 

 region of the arm at a previous stage of the dissection were : 



Nn. supraclaviculares (the posterior group) from the 



cervical plexus. 



N. cutaneus brachii lateralis from the axillary nerve. 

 N. intercosto-brachialis from the second intercostal 



nerve. 



N. cutaneus brachii medialis from the brachial plexus. 

 N. cutaneus antibrachii medialis from the brachial plexus. 

 N. cutaneus brachii posterior from the radial nerve. 

 N. cutaneus antibrachii dorsalis from the radial nerve. 

 N. cutaneus antibrachii lateralis from the musculo- 



cutaneous nerve. 



