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ME.  J.  L.  CLAEKE  OX  THE  IXTIMATE  STEUCTUEE  OE  THE  EE  A TV. 
spinal-accessory  nuclei,  at  the  bottom  of  the  median  fLssm’e,  is  a transA'erse  commissural 
band  divided  on  each  side  by  a longitudinal  column  into  two  portions,  which  again 
unite,  and  becoming  continuous  vnth  cells,  either  single  or  in  linear  series,  run  partly 
behind  and  partly  through  the  nucleus  and  network  in  the  lateral  column  as  fibres  of 
the  accessory  nerve.  In  front  of  the  canal  are  the  first-formed  cells  of  the  hypoglossal 
nucleus ; and  a little  further  forward  is  the  ^zow-decussating  portion  (I)  of  the  anterior 
pyramid,  consisting  of  that  outer  and  deep  part  of  the  anterior  column  at  the  side  of 
the  sulcus  (I,  figs.  11, 12  and  19)  which  remained  unmixed  Avith  the  decussating  bundles 
from  the  opposite  lateral  column,  but  is  now  crossed  at  its  posterior  half  by  those  of  its 
own  side,  which  divide  it  into  smaller  fasciculi.  The  anterior  cornu  which  lay  on  its 
outer  side  is  wholly  resolved  into  network  (represented  in  the  left  half  of  the  figure  23) ; 
but  amongst  this  nerivork  (omitted  on  the  right  side)  may  still  be  obseiwed  a number  of 
small  fusiform  cells,  sometimes  pigmentary,  and  joined  in  linear  series;  and  with  these 
are  a few  others  that  are  larger,  oval,  fusiform  and  triangular,  and  lie  mostly  AAuth  theii’ 
longer  axes  and  processes  parallel  with  a multitude  of  fine  fibres,  which  running  ob- 
liquely outwards,  in  part  form  the  roots  of  the  hypoglossal  nerve.  Traced  backwards, 
these  fibres  are  found  to  have  various  destinations.  Some  of  the  innermost  layer  bend 
forward  round  the  root  of  the  pyramid  and  join  in  the  decussation ; a feAV  run  obliquely 
backwards  round  the  opposite  side  of  the  canal,  in  front  of  which  they  first  decussate  Avith 
their  opposite  fellows,  and  become  continuous  Avith  cells  that  are  often  darkened  by  pig- 
ment ; the  rest  take  their  origin  from  the  cells  of  the  nucleus.  Scattered  in  part  amongst 
these  fibres,  and  partly  resting  in  masses  on  the  back  of  the  pyramid,  is  a multitude  of 
cells  much  smaller  than  the  rest,  which  form  the  commencement  of  the  olivary  lamma. 
In  the  posterior  part  of  the  lateral  column,  amongst  the  netAvork  in  front  of  the  caput 
cornus  posterioris,  is  seen  a remarkable  group  of  large  stellate,  pyriform  and  fusiform 
cells  {p),  which  send  out  their  processes  to  a great  length  betAveen  the  longitudinal 
bundles  enclosed  in  the  meshes;  and  nearer  the  anterior  and  outer  part  of  the  same 
column  is  another  curious  group  [g],  to  be  described  further  on.  The  decussation  of 
the  anterior  pyramids,  though  still  considerable,  is  very  much  reduced ; for  the  fibres  it 
derives  from  the  lateral  columns,  Avhich  at  first  Avere  its  principal  source,  have  become 
comparatively  feAV,  Avhile  those  that  proceed  from  the  posterior  columns  and  central 
grey  substance  have  been  gradually  increasing  in  number,  though  not  in  a correspond- 
ing inverse  proportion.  From  before  backAAurds  the  decussating  bundles  may  be  traced 
round  the  sides  of  the  central  canal,  Avhere  the  fibres  of  each  spread  out  and  interlace  Avith 
the  rest  in  a series  of  curves  and  undulations.  Some  are  continuous  Avith  the  deep  lon- 
gitudinal bundles  of  the  lateral  columns ; others  run  outAvards  to  the  plexus  or  iietAA’ork 
at  the  root  or  base  of  the  caput  cornus  posterioris ; the  rest  extend  baclvAA'ards,  and  of 
these,  some  wander  amongst  and  end  in  the  cells  of  the  central  grey  substance,  Avhile 
others  are  prolonged  through  the  posterior  columns. 
