Hence  the  bones  of  an  aged  person  are  more  brittle  and  easily
broken  than  those  of  a  child.  The  bones  of  a  young  child
are  in  fact  tolerably  flexible  and  may  be  distorted  by  any  con-
tinued strain ;  therefore  children  should  never  be  kept  sitting
for  hours,  in  school  or  elsewhere,  on  a  bench  which  is  so  high
that  the  feet  are  not  supported.  If  this  be  insisted  upon  (for
no  child  will  continue  it  voluntarily)  the  thigh-bones  will  al-
most certainly  be  bent  over  the  edge  of  the  seat  by  the  weight
of  the  legs  and  feet,  and  a  permanent  distortion  may  be  pro-
duced. For  the  same  reason  it  is  important  that  a  child
be  made  to  sit  straight  while  writing,  to  avoid  the  risk  of
producing  a  lateral  curvature  of  the  spinal  column.  The
facility  with  which  the  bones  may  be  moulded  by  prolonged


8TRUGTUBE  AND  COMPOSITION  OF  BONE.    JOINTS.     91

pressure  in  early  life  is  well  seen  in  the  distortion  of  the
feet  of  Chinese  ladies,  produced  by  keeping  them  in  tight
shoes;  and  in  the  extraordinary  forms  which  some  races  of
man  produce  in  their  skulls,  by  tying  boards  on  the  heads  of
the  children.
