Microscopic.  Changes  are  found  both  in  tissues  of
mesodermogenic  and  of  ectodermogenic  origin.  The  pia
mater  in  most  areas  is  normal.  Where  it  is  involved  it  is


■-■■ '-^t'  ■-.►-;'■*■-■■  :--%/i.;^V  ■  — .r.  ^■i     -


A:"  ■'^^'  ^■l■■'


Fig.   7.— Thalamus.      Diffuse   Crllular    1  nliltiation.
thickened,  its  laj^ers  being  separated  by  edema,  cellular
infiltration,  and  at  times  red  blood  cells  which  have  es-
caped from  the  pial  capillaries.  In  the  substance  of  the
brain  there  is  diffuse  capillary  congestion  which  is  most
marked  in  the  involved  areas.  The  Virchow-Robin  spaces


STUDIES  OF  SELECTED  CASES


87


1'  ^


^  ■»■■


■%    #'


■'  ■     *  •  -  ■'  ?*■


A   ■


■  •■<  .  '*^'  ■<  -^  • ', '

i'lii.   >. —  I  naiaimis.      i'loudy   iSwollinu;  m    .\curuc\i('s.
88


EPIDEMIC    ENCEPHALITIS


of  the  vessel  wall  may  contain  red  blood  cells  but  more
frequently  show  moderate  distension  with  lymphocytes.
Occasionally  polymorphonuclear  leucocytes  are  seen
in  the  adventitial  lymph  spaces,  but  almost  all  of  the
cells  are  similar  to  the  lymphocytes  of  the  blood.  The


Fig.  9. — Thalamus.     Acute  Cloudv  Swelliuii;  of  Xerve  Cells.
hemorrhages  are  frequently  perivascular,  that  is,  largely
confined  to  the  perivascular  space  of  His.  Some  of  them
are  larger,  irregularly  infiltrating  the  surrounding  tissue.
In  some  areas  small  collections  of  cells  are  seen  which  may
be  in  either  the  gray  or  white  matter  and  have  no  appar-


STUDIES  OF  SELECTED  CASES


89


Fig.   10. — Thalamus.     Higher    Magnification.     Severe  Degenera-
tive Changes  and  Neuronophagy  in  Some  of  the  Nerve  Cells.
