ME.  J.  L.  CLAEKE  ON  THE  INTIMATE  STEECTEEE  OE  THE  BEAIN. 
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anterior  than  of  the  posterior  median  sulcus ; for  the  grey  substance  behind  it  has  be- 
come more  ample  than  in  any  region  of  the  medulla  spinalis’,  so  that  with  the  lateral 
portions  it  presents  a kind  of  quadrilateral  mass,  which  is  prolonged  in  front  and  behind, 
on  either  side,  to  form  the  anterior  and  posterior  cornua.  The  anterior  cornu  is  thick, 
club-shaped,  short,  yet  reaches  nearly  to  the  surface,  for  the  corresponding  white  column 
is  extremely  shallow.  The  posterior  cornu,  on  the  contrary,  is  very  slender  and  long, 
and  projects  obliquely  backwards  to  within  a line  or  two  of  the  surface,  where  it  expands 
into  a kind  of  tuft,  or  irregularly  oval  mass(y*),  which  is  frequently  broken  into  two 
parts,  of  which  the  most  anterior  is  sunk,  as  it  were,  in  the  lateral  column.  This  tuft 
or  expanded  portion  might  be  termed  the  caput  cornus,  and  its  long  and  narrow  por- 
tion, the  cervix.  The  outer  part,  or  border  of  the  caput  cornus,  is  the  gelatinous  sub- 
stance ; its  interior  is  more  opake,  and  pierced  by  a multitude  of  longitudinal  bundles. 
The  cervix  cornus  is  also  intersected  by  a number  of  nearly  flat  longitudinal  bundles, 
which  in  a transverse  section  appear  as  fusiform  streaks  in  its  course.  Many  of  the 
fibres  of  the  posterior  nerve-roots  (/'),  after  traversing  the  gelatinous  substance,  run 
out  and  disperse  through  the  posterior  column  (see  fig.  11  y*'");  some  cross  over  to  the 
opposite  side,  behind  the  central  canal ; the  rest,  between  the  flat  longitudinal  bundles, 
curve  forward  to  the  anterior  cornu,  and  in  part  run  out  at  intervals  through  the  antero- 
lateral column.  The  gelatinous  substance  contains  numerous  small  and  large  cells, 
which  are  spherical,  oval,  fusiform,  and  triangular ; and  the  cervix  cornus  abounds  with 
others  of  small  average  size  and  which  are  often  extremely  minute : these  are  oval  in 
various  degrees,  or  exceedingly  fusiform  in  the  direction  of  the  fibres,  with  which  their 
processes,  extending  to  a great  length,  run  side  by  side,  or  parallel.  The  whole  lateral 
portion  of  the  central  grey  substance  (figs.  10  and  11)  contains  cells  of  the  same  kind, 
with  a crowd  of  others  that  are  spherical,  oval  or  angular,  but  of  great  disparity  in  size : 
the  smallest  are  less  than  the  4-^0  qth  of  an  inch  in  diameter,  while  some  of  the  largest 
are  nearly  equal  to  those  of  the  anterior  cornu. 
(12.)  From  the  lateral  border  of  the  entme  grey  substance  (figs.  10  and  11),  a beau- 
tiful network  of  blood-vessels  and  fibres  is  prolonged  through  the  lateral  column,  which 
is  divided  by  its  meshes  into  a multitude  of  separate  fasciculi  of  different  shapes  and 
thickness.  With  the  fibres,  which  at  first  are  but  few,  a number  of  cells,  like  those  of 
the  grey  substance,  extend  through  the  network,  and  are  apparently  connected  with 
each  other  between  the  fasciculi  of  the  white  columns.  Those  of  the  anterior  part 
(fig.  10),  in  Man,  are  by  far  the  most  abundant  and  the  largest ; they  are  oval,  fusiform, 
triangular  or  variously  branched,  and  may  not  only  be  traced  uninterruptedly  to  the  very 
centre  of  the  anterior  cornu,  but  many  of  the  most  distant,  off  the  skirts  of  the  network, 
are  connected  with  it  by  processes  of  remarkable  length. 
(13.)  It  is  from  the  fasciculi  of  the  lateral  column,  enclosed  in  the  meshes  of  this 
network,  that  the  fibres  proceed  in  a transverse  direction,  with  others  from  the  grey 
substance,  to  form  the  chief  portion  of  the  opposite  anterior  pyramid  (see  figs.  11  and  12). 
As  they  bend  round  to  take  this  direction,  they  interlace  and  intertwine  in  a very  intri- 
