ME.  J.  L.  CLAEKE  ON  THE  INTIMATE  STEUCTUEE  OF  THE  BEAIN. 
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of  the  vesicular  nucleus  of  the  hypoglossal  nerve,  or  the  commencement  of  t\ie  fasciculm 
teres,  from  which,  higher  up,  facial  and  the  abducens  or  sixth  nerve  have  a common 
origin : it  is  filled  with  cells,  which  vary  considerably  in  size,  and  are  smaller  than  those 
of  the  hypoglossal  nucleus:  those  nearest  the  raphe  are  the  largest,  and  mostly  oval 
or  spherical.  Proceeding  from  the  front  of  this  nucleus  are  two  or  three  considerable 
bundles  of  fibres  and  several  smaller  ones,  which  run  forwards  and  take  nearly  the  same 
course  as  the  hypoglossal  nerves  towards  the  olivary  body : near  their  origin  the  network 
in  the  antero-lateral  column,  through  which  they  pass,  is  crowded  with  cells,  of  all  shapes 
and  sizes,  which  send  out  their  processes  in  every  direction  between  the  longitudinal  fasci- 
culi, and  probably  establish  a most  intimate  union  of  the  parts  amongst  which  they  lie. 
Some  of  the  fibres  of  these  bundles,  as  well  as  separate  fibres  issuing  from  the  white 
column,  may  be  traced  into  this  nucleus ; but  others  turn  inwards,  and  after  running 
along  the  border  of  the  white  column  and  lower  part  of  the  nucleus,  they  decussate 
through  the  raphe  with  their  opposite  fellows.  Along  each  side  of  the  raphe  runs  a 
considerable  blood-vessel,  which  sends  out  lateral  branches  to  follow  the  bundles  of  the 
plexus  and  anastomose  with  the  vessels  that  accompany  the  antero-posterior  bundles  just 
described. 
(57.)  The  glossopharyiigeal  nerve  passes  inwards  and  backwards,  in  two  or  three 
bimdles,  through  the  gelatinous  substance  and  across  the  arciform  fibres.  On  reaching 
the  group  of  longitudinal  fasciculi,  Avhich  lie  at  the  extremity  of  the  vagal  nucleus  and 
now  adjoin  the  network  of  the  posterior  pyramid,  its  outer  portion  separates,  in  a 
brush-like  manner,  into  many  smaller  bundles,  which  subdivide  the  fasciculi  into  a cor- 
responding number  of  parts,  and  interlace  between  and  around  them : many  of  its  fibres 
at  this  point  appear  to  become  longitudinal ; some  turn  into  the  auditory  ganglion,  along 
the  lateral  border  of  which  they  may  be  traced  in  part  through  the  network  of  the 
posterior  pyramid  (5);  the  middle  fibres  of  the  nerve  proceed  to  the  remaining  cells 
of  the  vagal  nucleus,  and  many  of  them  appear  to  extend  as  far  as  the  group  of  cells 
that  form  the  commencement  of  i\\e  fasciculus  teres  and  the  continuation  of  the  hypo- 
glossal nucleus : as  in  the  case  of  the  vagus,  the  anterior  portion  of  the  nerve,  forming  a 
distinct  bundle,  turns  inwards  round  the  summit  of  the  antero-lateral  column,  and  pass- 
ing through  the  most  anterior  and  largest  cells,  sends  forward  a series  of  returning 
loops,  first  through  the  antero-posterior  bundles  along  the  inner  border  of  the  caput 
cornus  posterioris,  and  then  in  succession  through  the  network  of  the  lateral  column,  as 
it  makes  its  way  towards  the  raphe  (see  fig.  36,  Plate  XVII.) ; but  in  this  course  its 
fibres  lie  side  by  side  with  those  which  have  been  already  described  as  proceeding  from 
the  antero-lateral  column  in  the  same  direction  to  decussate  through  the  raphe  with  their 
opposite  fellows,  so  that  it  becomes  almost  impossible  to  identify  them  and  ascertain  if 
they  share  in  the  decussation ; that  they  do  so,  however,  is  rendered  extremely  probable 
by  the  fact  that  in  Birds  all  the  fibres  of  the  eighth  pair  of  nerves,  of  which  the  highest 
correspond  to  the  glossopharyngeal,  may  be  distinctly  seen  to  decussate  through  the 
