up" the hand (Fig. 13). The counterbalancing
digital extensor inserts into the two most distal
phalanges and, on contraction, rigidly extends
the entire finger. Coordinated action
between extensor and flexor groups, however,
permits fixed intermediate positions of each
segment of the system.
Two common postures of this system may
be pictured. In palmar prehension (Fig. 13),
the carpal and metacarpal segments commonly
fix the wrist in moderate extension, while the
digital configuration, mostly metacarpophalangeal
flexion coupled with only slight phalangeal
flexion, indicates action of the long
flexors, strongly modified by the lumbricals
and interossei, which are in position not only
to contribute to the metacarpophalangeal
flexion but also to maintain the phalangeal