464 



MYOLOGY 



I 



The Flexor digiti quinti brevis (Flexor brevis minimi digiti) lies on the same 

 plane as the preceding muscle, on its radial side. It arises from the convex surface 

 of the hamulus of the hamate bone, and the volar surface of the transverse carpal 

 ligament, and is inserted into the ulnar side of the base of the first phalanx of the 

 little finger. It is separated from the Abductor, at its origin, by the deep branches 

 of the ulnar artery and nerve. This muscle is sometimes wanting; the Abductor 

 is then, usually, of large size. 



The Opponens digiti quinti (Opponens minimi digiti) (Fig. 426) is of a tri- 

 angular form, and placed immediately beneath the preceding muscles. It arises 

 from the convexity of the hamulus of the hamate bone, and contiguous portion 

 of the transverse carpal ligament; it is inserted into the whole length of the meta- 

 carpal bone of the little finger, along its ulnar margin. 



Variations. The Palmaris brevis varies greatly in size. The Abductor digiti quinti may be 

 divided into two or three slips or united with the Flexor digiti quinti brevis. Accessory head from 

 the tendon of the Flexor carpi ulnaris, the transverse carpal ligament, the fascia of the forearm 

 or the tendon of the Palmaris longus. A portion of the muscle may insert into the metacarpal, 

 or separate slips the Pisimetacarpus, Pisiuncinatus or the Pisianmdaris muscle may exist. 



Nerves. All the muscles of this group are supplied by the eighth cervical nerve through the 

 ulnar nerve. 



Actions. The Abductor and Flexor digiti quinti brevis abduct the little finger from the ring 

 finger and assist in flexing the proximal phalanx. The Opponens digiti quinti draws forward 

 the fifth metacarpal bone, so as to deepen the hollow of the palm. The Palmaris brevis corrugates 

 the skin on the ulnar side of the palm. 



3. The Intermediate Muscles. 



Lumbricales. 



Interossei. 



The Lumbricales (Fig. 427) are four small fleshy fasciculi, associated with the 

 tendons of the Flexor digitorum profundus. The first and second arise from the 

 radial sides and volar surfaces of the tendons of the index and middle fingers 

 respectively; the third, from the contiguous sides of the tendons of the middle and 

 ring fingers; and the fourth, from the contiguous sides of the tendons of the ring 

 and little fingers. Each passes to the radial side of the corresponding finger, and 

 opposite the metacarpophalangeal articulation is inserted into the tendinous 

 expansion of the Extensor digitorum communis covering the dorsal aspect of the 

 finger. 



Variations. The Lumbricales vary in number from two to five or six and there is considerable 

 variation in insertions. 



The Interossei (Figs. 428, 429) are so named from occupying the intervals 

 between the metacarpal bones, and are divided into two sets, a dorsal and a volar. 



The Interossei dorsales (Dorsal interossei) are four in number, and occupy the 

 intervals between the metacarpal bones. They are bipenniform muscles, each arising 

 by two heads from the adjacent sides of the metacarpal bones, but more exten- 

 sively from the metacarpal bone of the finger into which the muscle is inserted. 

 They are inserted into the bases of the first phalanges and into the aponeuroses 

 of the tendons of the Extensor digitorum communis. Between the double origin 

 of each of these muscles is a narrow triangular interval ; through the first of these 

 the radial artery passes; through each of the other three a perforating branch from 

 the deep volar arch is transmitted. 



The first or Abductor indicis is larger than the others. It is flat, triangular in 

 form, and arises by two heads, separated by a fibrous arch for the passage of the 

 radial artery from the dorsum to the palm of the hand. The lateral head arises 

 from the proximal half of the ulnar border of the first metacarpal bone; the medial 

 head, from almost the entire length of the radial border of the second metacarpal 

 bone; the tendon is inserted into the radial side of the index finger. The second 



