MUSCLES ON ANTEKIOK AND MEDIAL ASPECTS OF FOKEABM. 389 



Bracliialis muscle (insertion) 

 Supinator nmscle 

 (ulnar origin) 



Flexor digitorum sub- 

 limis (ulnar origin) 

 Pronator teres 

 (ulnar origin) 

 Flexor pollicislongus 

 (occasional origin) 



Biceps brachii 

 (insertion) 



Flexor digi 



torum sublimis 



(radial origin) 



Pronator teres 

 (insertion) 



Flexor pollicis 

 longus (origin 



Flexor digitorum 

 profundus (origin) 



process. It arises laterally from the medial half of the interosseous membrane in 

 its middle third (Figs. 348, p. 389, and 349, p. 390), and medially from the deep 

 fascia of the forearm dorsal to the origin of the flexor carpi ulnaris. 



The muscle forms a broad thick tendon which passes beneath the transverse 

 carpal ligament, covered by the tendons of the flexor digitorum sublimis, and 

 enveloped in the same mucous sheath, and divides, in the palm, into four tendons 

 for insertion into the terminal phalanges of the fingers. The tendon associated with 

 the forefinger is usually separate 

 from the rest of the tendons in 

 its whole length. 



Each tendon enters the 

 digital sheath of the finger 

 deep to the tendon of the flexor 

 digitorum sublimis, which it 

 pierces opposite the first phalanx, 

 and is finally inserted into the 

 base of the terminal phalanx. 

 Like the tendons of the flexor 

 sublimis, those of the deep flexor 

 are provided with vincula, viz., 

 vincula brevia attached to the 

 capsule of the second inter - 

 phalangeal articulation, and 

 vincula longa, which are in this 

 case connected to the tendons 

 of the subjacent flexor digitorum 

 sublimis. 



Mm. Lumbricales. The 

 lumbricales are four small 

 cylindrical muscles associated 

 with the tendons of the flexor 

 digitorum profundus in the palm 

 of the hand. The two lateral 

 muscles arise, each by a single 

 head, from the radial sides of the 

 tendons of the flexor digitorum 

 profundus destined respectively 

 for the fore and middle fingers. 

 The two medial muscles arise, each 

 by two heads, from the adjacent 

 sides of the second and third, and 

 third and fourth tendons. 



From their origins the mus- 

 cles are directed distally to 

 the lateral side of each of the 

 metacarpo-phalangeal joints, to 

 be inserted into the capsules of 

 these articulations, the lateral 

 border of the first phalanx, and 

 chiefly into the lateral side of the 

 extensor tendon on the dorsum of the phalanx. The lumbricales vary considerably 

 in number, and may be increased to six or diminished to two. 



Nerve-Supply. The flexor digitorum profundus is supplied in its lateral part by the volar 

 interosseous branch of the median nerve (C. 7. 8. T. 1.); and in its medial part by the ulnar 

 nerve (C. 8. T. 1.). The lateral two lumbricales are supplied by the median nerve (C. 6. 7.), and 

 the -medial two muscles by the ulnar nerve (C. 8. (T. 1.)). 



Actions. The flexor digitorum profundus is a powerful flexor of the wrist. It also flexes 

 the fingers at the metacarpo-phalangeal joint, and acts in a similar way at both the inter- 

 phalangeal joints. 



The lumbrical muscles act as flexors of the fingers at the metacarpo-phalangeal joints, and 



Pronator quad- 

 ratus (insertion) 



Brachioradialis 

 (insertion) 



Pronator quadratus 

 (origin) 



FIG. 348.- 



-MUSCLE-ATTACHMENTS TO THE RIGHT RADIUS 



AND ULNA (Volar Aspects). 



