394 



THE MUSCULAR SYSTEM. 



of the preceding muscle, by tendinous fibres, from the transverse carpal ligament 



and from the hamulus of the os hamatum. 



It is inserted into the medial margin and medial half of the volar surface of the 



fifth metacarpal bone in its distal 

 three-fourths (Fig. 351, p. 392). 



Nerve -Supply. Deep branch of the 



ulnar nerve (C. 8. (T. 1.)). 



Action. The muscle acts only on the 

 metacarpal bone, drawing it forward, so as 

 to deepen the hollow of the hand. 



M. Flexor Digit! Quinti Brevis. 

 The flexor digit! quint! brevis 



may be absent or incorporated with 

 either the opponens or abductor digiti 

 quinti. It arises, by tendinous fibres, 

 from the transverse carpal ligament 

 and from the hamulus of the os 

 hamatum (Fig. 351, p. 392). 



It is inserted along with the ab- 

 ductor into the medial side of the 

 first phalanx of the little finger. 



Nerve -Supply. The deep branch of 

 the ulnar nerve (C. 8. (T. 1.)). 



Actions. Flexion of the little finger 

 at the carpo-metacarpal and metacarpo- 

 phalangeal joints. 



FIG. 352. THE VOLAR INTEROSSEOUS MUSCLES 

 (Right Side). 



V 1 , first ; V 2 , second ; and V 3 , third volar interosseous 

 muscles. 



The Interosseous Muscles. 



The interosseous muscles of the hand occupy the spaces between the metacarpal 

 bones. They are arranged in two sets, volar and dorsal. 



Mm. Interossei Volares. The volar (O.T. palmar) interossei are three in 



Extensor carpi ulnaris (insertion) 



Fourth dorsal interosseous 

 muscle (origin) 



Third dorsal inter- 

 osseous muscle 

 (origin) 



Extensor carpi radialis 

 brevis (insertion) 



Extensor carpi radialis 

 /longus (insertion) 



First dorsal inter- 

 osseous muscle 

 (origin)' 



Second dorsal interosseous 

 muscle (origin) 



FIG. 353. MUSCLE -ATTACHMENTS TO THE DORSAL ASPECT OF THE RIGHT METACARPUS. 



number, occupying the medial three interosseous spaces. Each arises by a single head ; 

 the first from the medial side of the body of the second metacarpal bone ; the second 

 and third from the lateral sides of the bodies of the fourth and fifth metacarpal 



