All these relative positions would be altered in a dislocation 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 projection 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] =Bursæ.=--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 is also a small subcutaneous bursa over each of the condyles. The vertical extent of the elbow joint is limited, above by a line drawn from one condyle to the other; below, by a line corresponding to the lowest part of the head of the radius. 138. =Interosseous arteries.=--About one inch below the head of the radius, the ulnar artery gives off the common interosseous; and this divides, about half an inch lower, into the anterior and posterior interosseous. Thus, in amputating the forearm, say two inches below the head of the radius, four arteries at least would require ligature. By flexion of the elbow to the utmost, the circulation through the brachial artery can be arrested; but the position is painful, and can be tolerated only for a short time. =Lymphatic gland.=--There is a small lymphatic gland just above the inner condyle, in front of the intermuscular septum. It is the first to take alarm in poisoned wounds of the hand. _THE FOREARM AND WRIST._ 139. =Ulna.=--The edge of the ulna can be felt subcutaneous from the olecranon to the styloid process (in supination). Any irregularity could be easily detected. The styloid process of the ulna does not descend so low as the styloid process of the radius, or it would impede the free abduction of the hand. Its apex is on a level with the radio-carpal joint. The head of the ulna is plainly felt and seen projecting at the back of the wrist, especially in pronation of the forearm. It then lies between the tendons of the extensor carpi ulnaris and extensor minimi digiti. There is often a subcutaneous bursa over it. 140. =Radius.=--The upper half of the shaft of the radius is so covered by muscles that we cannot feel it; the lower half is more accessible to the touch, especially just above and just below the part where it is crossed by the extensors of the thumb. Its styloid process is readily felt, and made all the more manifest by being covered by the first two extensor tendons of the thumb. It descends lower, and lies more to the front than the corresponding process of the ulna. The relative positions of these styloid processes can be best examined by placing the thumb on one and the forefinger on the other.