There  are  examples  of  congestion  of  the  capillaries  complicating  arach-
nitis ;  but  there  is  also  a  venous  congestion,  a  hyperasmia  of  the  cerebral
veins.  This  complication  is  not  often  alluded  to  by  systematic  writers,
but  it  is  an  important  one ;  it  is  usually  seen  as  the  sequel  of  all  habitual
congestive  states  of  the  brain,  but  is  never  so  constant  as  after  the  abuse
of  fdcohohc  drinks.  In  death  from  delirium  tremens,  the  venous  sinuses
are  not  only  turgid  with  blood,  but  the  veins  generally  even  to  the  small
branches  in  the  pia  mater  are  congested  and  turgid,  often  giving  rise  to
a  thin  lymphatic  exudation,  which  is  to  be  distinguished  from  inflam-
matory exudation,  and  not  confounded  with  it,  as  has  been  done  by  some
writers.  A  similar  exudation  takes  place  to  a  more  or  less  extent  in  all
parts  of  the  brain  as  well  as  into  the  ventricles.  The  symptoms  in  the
case  under  consideration  tally  with  those  which  might  be  expected  to
occur  in  such  a  pathological  state,  but  with  this  difference,  that  an  actively
inflammatory  condition  has  aggravated  the  state  of  congestion,  wliile  the
symptoms  of  the  former  have  been  masked  by  the  latter.  The  diagnosis
then  is  purulent  arachnitis  at  the  base  of  the  brain,  with  serous  effusion
into  the  ventricles,  caused  by  hypersemia  of  the  brain.
