OF    THE  ACINI.  97

It  is  asserted  by  several  microscopical  observers,  that  a  minute
branch  of  each  of  the  aforesaid  vessels  can  be  traced  into  each
of  the  acini.  It  is  also  declared,  that  if  each  of  these  vessels
be  injected  separately  with  mercury,  oil  of  turpentine  colored,
or  a  saturated  aqueous  solution  of  gutta  gamba,  there  is  no  part
of  the  glandular  mass  as  large  as  a  grain  of  mustard  seed  in
which  those  vessels  will  not  be  found.
Several  anatomists  of  the  first  character  have  likewise  declared,
that  a  fluid  properly  injected  into  one  of  these  vessels,  will  occa-
sionally pass  into  all  of  them.  Thus  an  injection  will  not  only
pass  from  the  vena  portarum  to  the  biliary  duct,  but  to  the  hep-
atic artery  and  veins  also.  It  will  likewise  pass,  in  a  retrograde
course,  from  the  biliary  ducts  to  the  vena  portarum,  and  to  the
hepatic  artery  and  the  hepatic  veins  ;  or  from  any  one  of  the
four  orders  of  vessels  into  the  three  others.*

The  great  peculiarity  of  the  liver  is,  that  venous  blood,
instead  of  arterial,  is  brought  to  it  for  the  purpose  of  secretion.
