To  counteract  the  effects  of  the  forward  disposition  of  the
viscera  on  the  spine  there  are  several  provisions.  In  those
parts  of  the  trunk  in  which  the  largest  viscera  are  placed,  the
column  itself  curves  backwards ;  the  ribs  also  curve  consider-
ably back  before  they  arch  forwards,  and  tliereby  allow  of
some  portions  of  the  viscera  being  placed  at  the  sides  of,  and
even  on  a  posterior  plane  to,  tlie  column.
The  position  of  the  scapula  upon  the  posterior  surfaces  of
the  most  backward  projecting  ribs  tlirows  back  the  weight  of
the  shoulders,  wliile  powerfid  and  extensive  muscles  pass  to
the  upper  extremity  from  the  whole  series  of  spinous  processes
between  the  occiput  and  coccyx.
If  then  the  ligamenta  subflava  are  not  required,  and  cannot
act  to  restore  and  preserve  the  erect  posture,  what  are  the
uses  of  these  wonderful  little  structures  ?

1.  They  complete  tlie  roofing  in  of  the  vertebral  canal  in
the  interlaminar  spaces,  and  yet  at  the  same  time  they  permit
constant  variations  in  the  width  of  the  interspaces — ^varia-
tions required  by  tlie  shifting  of  the  articulating  jjrocesses  upon
one  another,  and  tlierefore  of  the  laminai  in  relation  to  one
another.
2.  Tliey  restore  the  articulating  surfaces  to  their  normal
position  with  respect  to  each  otlier  after  tliey  have  been  dis-
turbed therefrom  by  muscular  action,  either  in  antero-posterior,
lateral,  or  rotatory  movements.
86  THE   LIGAMENTS  AND  JOINTS

Tliis  normal  position  of  the  articular  surfaces  in  the
cervical  and  dorsal  vertebne  is  one  of  almost  complete  appo-
sition ;  but  in  the  lumbar  region,  the  superior  processes  are  so
much  wider  apart  than  the  inferior  of  the  veitebne  next  above
with  wliich  they  articulate,  that  complete  apposition  is  not
possible  on  both  sides  at  the  same' time.
