ME.  J.  L.  CLAEKE  ON  THE  INTIM:ATE  STEHCTUEE  OF  THE  BEAIN. 
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they  lie  chiefly  m the  inner  portion  of  the  nucleus,  contain  distinct  nuclei,  and  are 
remarkable  for  their  transparency,  which  gives  to  the  ganglion  a peculiar,  pearly  aspect ; 
but  some,  towards  its  outer  extremity,  are  fllled  with  dark  brown  or  blood-red  pigment- 
granules,  and  contain  no  nuclei  (see  flg.  23). 
(42.)  In  Mammalia  the  form  and  colour  of  the  ganglion  are  nearly  the  same  as  in 
Man ; but  the  cells  are  larger,  more  elongated  and  less  delicate,  and  none  of  them  are 
filled  with  pigment-granules,  as  in  the  human  medulla. 
(43.)  Like  the  vesicular  columns  just  described,  the  postpyramidal  and  restiform 
ganglia  continue  to  increase  as  they  ascend,  and  by  their  lateral  extension  form  nearly 
one  continuous  mass  on  each  side  of  the  medulla  (fig.  28  et  sey.  Plate  XVI.).  The  cells 
of  the  former  spread  through  the  whole  of  the  pyramid,  and  are  most  numerous  near 
the  surface.  In  the  superficial  portion  of  the  restiform  body  the  interlacement  of  its 
own  fibres  with  those  radiating  from  its  grey  substance  is  extremely  intricate  (see 
fig.  36) ; it  is  loose  and  irregular,  like  that  of  a sponge,  and  contains  in  its  interspaces 
a variable  number  of  cells,  which  send  out  their  processes  to  be  continuous  with  fibres 
in  all  directions. 
(44.)  Figs.  23,  28,  29,  30,  31,  32  and  36,  Plates  XVI.,  XVII.,  represent  a series  of 
transverse  sections,  from  the  lower  ends  of  the  olivary  bodies  to  the  fourth  ventricle. 
The  caput  cornus  posterioris  is  pierced  at  its  root  by  longitudinal  bundles,  enclosed  in 
the  meshes  of  a plexus  of  the  deep  arciform  fibres  which  proceed  from  the  posterior 
columns  (figs.  32  and  36).  These  longitudinal  bundles  are  exceedingly  interesting,  for 
I have  traced  the  continuity  of  some  with  the  descending  root  of  the  trifacial  nerve : 
in  the  angular  spaces  around  them  cells  are  imbedded,  and  between  them  the  roots  of 
the  vagus  and  glossopharyngeal  nerves  proceed  inwards  to  their  ganglia. 
(45.)  The  ganglia  or  nuclei  of  par  vagum  commence  with  the  fourth  ventricle,  and 
are  directly  continuous  with  the  vesicular  columns  from  which  the  accessory  nerves  take 
their  origin.  These  vesicular  columns,  by  encroaching  on  the  bases  and  inner  sides  of 
the  posterior  pyramids,  gradually  rise  to  the  surface,  and  diverging  to  form  the  point  of 
the  calamus  scriptorius,  enlarge  into  two  pyriform  masses  along  the  inner  border  of  the 
pjTamid,  from  which  they  are  partly  developed  * (rr,  fig.  5,  Plate  XII.).  Each  has  the 
same  form  as  the  spinal-accessory  nucleus,  and  in  the  same  way,  its  deeper  portion,  which 
lies  beneath  the  pyramid,  is  divided  into  two  horns  by  longitudinal  bundles  of  the  lateral 
column  (see  r,  figs.  29,  30,  31,  Plate  XVI.).  Its  cells  also  are  similar  to  those  of  the  ac- 
cessory nucleus,  but  more  abundant  (see  fig.  37,  Plate  XVII.).  I can  find  no  other  dif- 
ference. At  the  point  of  the  calamus  scriptorius  the  two  nuclei  are  joined  by  the  upper 
* These  pyriform  bodies  are  represented  in  Gall’s  plates,  but  were  first  described  by  Eolando  as  a 
portion  of  the  central  grey  substance : — “ Ces  tubercules  ne  sont  rien  autre  qu’une  portion  de  la  substance 
cendree  renfermee  dans  la  moelle  epiniere  et  la  moeUe  allongfe,  qu’on  pent  suivre  vers  le  haut,  jusqu’au 
quatrieme  ventricule,  ou  elle  se  montre  sous  la  forme  de  deux  feudles  lanceolees  de  substance  cendree.” — 
Eecherches  Anatomiques  sur  la  Moelle  Allongee,  4to,  p.  22.  Stilling,  however,  has  the  merit  of  having 
first  shown  them  to  be  the  nuclei  of  the  par  vagum. 
MDCCCLVIII.  2 L 
