Chapter D: SPECIAL MUSCLES OF THE SECOND DIGIT (THE INDEX).--=M. flexor brevis

digiti secundi= (or indicis).--This name may be applied to M. interosseus of the second digit (Fig. 89, _c_).

=M. abductor digiti secundi.=--This name might be applied to a portion of the interosseus of the second digit which is sometimes differentiated from the remainder.

_Origin_ from the radial and ventral surfaces of the base of the second metacarpal, and from the ventral surface of the trapezium.

_Insertion_ into the radial side of the base of the first phalanx of the second digit and into its sesamoid.

=M. adductor digiti secundi= (Fig. 89, _d_).

_Origin_ from the ventral surface of the os magnum.

_Insertion_ into the ulnar side of the base of the first phalanx of the second digit.

E. SPECIAL MUSCLES OF THE FIFTH DIGIT.--=M. abductor digiti quinti= (Fig. 89, _i_).--A thick, small, conical bundle.

_Origin_ from the distal surface of the pisiform bone and from the transverse ligament on the ulnar side of the pisiform. It ends in a slender tendon which runs along the ulnar side of the fifth metacarpal to its

_Insertion_ into the ulnar side of the base of the first phalanx of the fifth digit.

=M. flexor brevis digiti quinti= (Fig. 89, _h_; Fig. 88, _e_).--This covers the ventral surface of the fifth metacarpal, and is really the interosseus of this digit.

_Origin_ by fleshy fibres from the ventral surface of the base of the fifth metacarpal; from the ventral process of the unciform bone, and from the transverse ligament proximad of the fifth metacarpal.

_Insertion_ by fleshy fibres into the ventral border of the proximal end of the first phalanx of the fifth digit.

=M. opponens (adductor) digiti quinti= (Fig. 89, _g_).

_Origin_ by a flat tendon from the ventral surface of the os magnum on the ulnar side of the adductor pollicis (_b_). It passes toward the ulnar side and distad, the fibres diverging to their

_Insertion_ (1) into nearly the whole of the radial surface of the fifth metacarpal, (2) into the base of its first phalanx.