So  far  forwards  does  the  sacro-lumbar  union  project,  and  so
great  is  the  curve  of  the  sacrum,  that  a  line  let  fall  from  the
front  surface  of  the  third  lumbar  vertebra  strikes  the  upper
surface  of  the  symphysis  pubis.  The  inclination  of  the  pubis
is  such  that  it  helps  by  its  inner  surface,  which  looks  upwards
as  well  as  backwards,  to  support  some  of  the  abdominal
viscera,  and  during  the  latter  months  of  pregnancy  the  en-
larged uterus  rests  upon  it  in  part.
Bany  Wall  of  Pelvis  iviper/ect. — In  connexion  with  the
parturient  state,  it  is  a  fact  of  gi*eat  importance  that  no  portion
of  the  cavity  of  the  true  pelvis  has  a  bony  wall  completely
surrounding  it.  Opposite  nearly  the  whole  length  of  the
sacrum  and  on  the  same  horizontal  plane  with  it,  is  the  front


120      THE   MUSCLES  CONNECTED    WITH    THE  PELVIS.
