THE ARM. 63 



On the outer side of the olecranon, just below the external 

 condyle, is a pit in the skin, constant even in fat persons 

 (when the elbow is extended). This pit is considered one of 

 the beauties of the elbow in a graceful arm ; it is seen in a 

 child as a pretty little dimple. To the surgeon it is most 

 interesting, as in this valley behind the supinator longus and 

 the radial extensors of the wrist he can distinctly feel the 

 head of the radius rolling in pronation and supination of the 

 forearm. It is, therefore, one of the most important land- 

 marks of the elbow, since it enables us to say whether the 

 head of the radius is in its right place, and whether it rotates 

 with the shaft. 



Can the tubercle of the radius be felt ? Yes, but only on 

 the back of the forearm in extreme pronation. Its projection 

 is then distinctly perceptible just below the head of the 

 bone. 



Relations of olecranon and condyles. To examine 

 the relative positions of the olecranon and condyles in the 

 different motions of the elbow joint, place the thumb on one 

 condyle, the tip of the middle finger on the other, and the tip 

 of the forefinger on the olecranon. In extension, the highest 

 point of the olecranon is never above the line of the condyles ; 

 indeed, it is just in this line. With the elbow at right angles 

 the point of the olecranon is vertically below the line of the 

 condyles. In extreme flexion the point of the olecranon lies 

 in front of the line of the condyles. 



All these relative positions would be altered in a disloca- 

 tion of the ulna, but not (necessarily) in a fracture of the 

 lower end of the humerus. 



Sometimes, though rarely, we meet with a hook-like pro- 

 jection of bone above the internal condyle. It is called a 

 ' supra-condyloid ' process ; it can be felt through the skin, 

 with its concavity downwards, and is a rudiment of the bony 

 canal which, in many mammalia, transmits the median nerve 

 and ulnar artery. A third origin of the pronator teres is 

 always attached to it ; this origin covers the brachial artery. 10 



Bursce. The subcutaneous bursa over the olecranon, if 

 distended, would be as large as a walnut. A second bursa 

 sometimes exists a little lower down upon the ulna. There 



