THE ANTERIOR RADIOULNAR REGION 205 



the condyles of the humerus, olecranon, and fascia over the 

 biceps and triceps. The anterior part is weaker than the pos- 

 terior, and continuous below into the anterior annular ligament 

 (ligamentum carpi volare, p. n.) ; it sends in a thin layer between 

 the superficial and deep muscles. The posterior portion sends 

 off septa between the muscles and forms the posterior annular 

 ligament (ligamentum carpi dorsale, p. n.). The tendon of 

 the palmaris longus muscle is the only one passing in front 

 of the anterior annular ligament. 



The Anterior Radioulnar Region 



Eight muscles, five superficial and three deep. 

 Superficial Layer. All from a common tendon in the follow- 

 ing order from without in: 



1. M. pronator teres rises by two heads, the larger from the 

 upper part of the inner condyle above the common tendon 

 and from the common tendon and intermuscular septum; 

 second head, thin and deep, from the inner margin of the 

 coronoid process; insertion, by a flat tendon on the middle 

 of the outer surface of the radius. The ulnar artery is beneath 

 this muscle, and the median nerve between its heads. 



2. M. flexor carpi radialis (M. radialis internus) rises from 

 the common tendon and septa between it and the pronator 

 teres, palmaris longus, and flexor sublimis; tendon begins 

 below the middle of the forearm, passes through a special 

 compartment of the anterior annular ligament through a groove 

 in the trapezium; inserted into the base of the second meta- 

 carpal bone, anterior surface, and usually by a small slip to 

 the base of the third. 



3. M. palmaris longus is placed between the ulnar and radial 

 flexors of the carpus, resting upon the flexor sublimis; rises 

 from the common tendon, fascia, and septa, forming a short 

 muscular belly ending in a slender tendon, inserted into the 

 palmar fascia, and sends a slip to the abductor pollicis, some- 

 times one to the little finger muscle. 



Most variable muscle of the body, lacking on both sides 

 in one-third of the cases, on one side in one-half of the cases 

 (Hallett). Muscular belly may occupy the middle of the ten- 

 don, lower end, both ends, or be absent; may be double or 

 have additional origin from the coronoid or the radius. Inserted 



