The  Movements. — Movements  of  the  carpal  articulations
between  bones  of  the  same  row  are  very  limited  indeed,  and
consist  only  of  slight  gliding  one  upon  the  other.  Yet  these
gliding  movements,  slight  as  they  are,  give  sufficient  elas-
ticity to  the  carpus  to  break  the  jars  and  shocks  which  result
from  blows  or  falls  upon  the  hand.  The  movements  of  one  row
of  bones  upon  the  other,  at  the  medio-carpal  articulation,  are
much  more  extensive,  especially  in  the  direction  of  flexion
and  extension,  so  that  the  hand  enjoys  a  greater  range  of  these
movements  than  is  permitted  at  the  wrist-joint  alone.  In
the  wrist-joint  extension  is  more  free  than  flexion,  owing  to
the  greater  extent  of  the  articular  surface  upon  the  dorsal
than  upon  the  palmar  aspect  of  the  scaphoid,  lunar,  and  cunei-
form bones.  But  this  limitation  of  flexion  is  compensated  for
by  the  greater  freedom  of  flexion  than  of  extension  at  the
medio-carpal  joint,  and  by  the  flexion  permitted  at  the  carpo-
metacarpal joint,  so  that  on  the  whole  the  degree  of  flexion  of
the  hand  is  greater  than  that  of  extension.
Flexion  and  extension  are  not  the  only  movements  which
are  permitted  at  this  joint.  A  slight  amoimt  of  lateral  motion,
ie.,  abduction  and  adduction,  accompanied  with  a  limited  degree
of  rotation,  takes  place.  This  rotation  of  the  hand  consists  in
a  rotation  of  the  head  of  the  os  magnum,  and  of  the  superior
and  outer  angle  of  the  unciform  in  the  socket  formed  by  the
three  bones  of  the  upper  row,  and  in  a  gliding  forwards  and
backwards  of  the  trapezium  and  trapezoid  upon  the  scaphoid.
