450 



MYOLOGY 



and slightly downward, to be inserted into the lower fourth of the lateral border 

 and the volar surface of the body of the radius. The deeper fibers of the muscle 

 are inserted into the triangular area above the ulnar notch of the radius an 

 attachment comparable with the origin of the Supinator from the triangular area 

 below the radial notch of the ulna. 





Tendon of Ext. 

 carpi rad. longus 



Tendon of Ext. 

 digitorum communis 



Tendon of Extensor indicts 

 proprius 



First Lumbricalis 



Vincida brevia 



Tendon of Abductor 



pollicis longus 

 Greater multangular bone 



Radial artery 



Tendon of Ext. pollicis brevis 



-Tendon of Ext. pollicis longus 



'lexor digitorum sublimis 

 Flexor digitorum profundus 



FIQ. 416. Tendons of forefinger and vincula tendina 



Variations. Rarely absent; split into two or three layers; increased attachment upward or 

 downward. 



Nerves. All the muscles of the superficial layer are supplied by the median nerve, excepting 

 the Flexor carpi ulnaris, which is supplied by the ulnar. The Pronator teres, the Flexor carpi 

 radialis, and the Palmaris longus derive their supply primarily from the sixth cervical nerve; 

 the Flexor digitorum sublimis from the seventh and eighth cervical and first thoracic nerves, 

 and the Flexor carpi ulnaris from the eighth cervical and first thoracic. Of the deep layer, the 

 Flexor digitorum profundus is supplied by the eighth cervical and first thoracic through the 

 ulnar, and the volar interosseous branch of the median. The Flexor pollicis longus and Pronator 

 quadratus are supplied by the eighth cervical and first thoracic through the volar interosseous 

 branch of the median. 



Actions. These muscles act upon the forearm, the wrist, and hand. The Pronator teres 

 rotates the radius upon the ulna, rendering the hand prone; when the radius is fixed, it assists 

 in flexing the forearm. The Flexor carpi radialis is a flexor and abductor of the wrist; it also 

 assists in pronating the hand, and in bending the elbow. The Flexor carpi ulnaris is a flexor and 

 adductor of the wrist; it also assists in bending the elbow. The Palmaris longus is a flexor of the 

 wrist-joint; it also assists in flexing the elbow. The Flexor digitorum sublimis flexes first the 

 middle and then the proximal phalanges; it also assists in flexing the wrist and elbow. The 

 Flexor digitorum profundus is one of the flexors of the phalanges. After the Flexor sublimis 

 has bent the second phalanx, the Flexor profundus flexes the terminal one; but it cannot do so 

 until after the contraction of the superficial muscle. It also assists in flexing the wrist. The 



