400 



THE MUSCULATURE 



Relations. — The belly of the muscle is covered by the pronator teres, flexor carpi radialis, 

 and palmaris longus, but is superficial along a narrow strip between the flexor carpi ulnaris and 

 the palmaris longus, and on each side of the tendon of the flexor carpi radiahs. The muscle 

 rests on the flexor polhcis longus and flexor digitorum profundus, the median nerve (see de- 

 scription given above) and ulnar vessels. The median nerve emerges from beneath the radial 

 border of the muscle in the lower third of the forearm. In the palm the tendons lie beneath the 



Fig. 372. — Front of the Forearm: Third Layer of Muscles. 



Biceps 



Muscles of the first and second 

 layers 



Flexor digitorum profundus 



Pronator quadratus 

 Flexor carpi ulnaris 



Brachio-radialis 



Brachialis 



Extensor carpi radialis longus 

 Supinator 



Flexor pollicis longus 



Brachio-radialis 



Abductor pollicis longus 



Extensor pollicis brevis 



palmar apoiicurosi.s, the suix-rficiul palmar arch, and tiie l)ranchcs of the median nerve, while 

 they lie m front of the teri(ioiis of tlie flexor profundus, with which they are closely associated 

 into a common bundle by loose fibrous tissue. Tlic digital relations of the tendons arc described 

 above. 



Variaiions. — The whole muscle may be rendered digastric by a transverse tendon. A 

 fasciculus of the flexor sublimis may replace the palmaris longus or the two may coexist. A 

 fasciculus may terminate in tiie fascia of tlu; forciann or in the transverse carpal ligament, the 

 palmar aponeurosis, etc. Various parts of the muscle nuiy be absent or more inde|)endent than 

 usual. The extent of the radial attachnient varies greatly and may be missing. A special 

 fasciculus may be received from the; coronoid proeiess of the ulna. A fasciculus may be sent to 

 the flexor profundus or to otlicr inusrlcs. There niiiy i)e some fusion with neighbouring 

 muscles. 



