218 HANDBOOK OF ANATOMY 



The line of the median nerve is the same as that of the brachial 

 artery. The course of the ulnar nerve is mapped out by a line 

 extending from the posterior fold of the axilla behind coraco- 

 brachialis to the back of the internal condyle of the humerus. 



The course of the musculo-spiral nerve is mapped out by a line 

 drawn from the point where it pierces the intermuscular septum 

 (the junction of the upper and middle thirds of a line extending* 

 from the insertion of the deltoid to the external condyle) to the 

 front of the external condyle; and obliquely upwards to the 

 point where the posterior fold of the axilla joins the upper arm. 



The Elbow. 



The head of the radius can be felt 1 inch below the external 

 condyle of the humerus when alternately pronating and supinating 

 the flexed forearm. 



The median vein is seen to bifurcate J inch below the middle 

 of the bend of the elbow ; deep to this, beneath the fascia, is the 

 bifurcation of the brachial artery. 



The biceps tendon can be traced vertically through the centre 

 of the bend of the elbow with the forearm flexed. 



The Forearm and Hand. 



The lower half of the radius is easily felt, and the anterior 

 border of the lower extremity forms a ridge 1 inch above the 

 ball of the thumb, and just below is the radio-carpal articulation. 

 Upon the middle of the posterior border of the lower extremity 

 is the radial tubercle between the tendons of extensor longus 

 pollicis and extensor carpi radialis brevior. 



The posterior border of the ulna is subcutaneous throughout, 

 and its lower extremity forms a rounded prominence anterior to 

 which is the styloid process. Between the two lies the tendon of 

 extensor carpi ulnaris. 



The carpal bones form an arch bridged by the anterior annular 

 ligament; the bony attachments of the latter form important 

 landmarks. 



The tubercle at the base of the third metacarpal can be felt 

 If inches below the tubercle on the back of the lower end of the 

 radius. 



