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ME.  J.  L.  CLAEKE  OK  THE  IKTIilATE  STErCTHEE  OF  THE  BEAIK. 
broad  band,  called  the  trapezium  or  inferior  pons  (*•),  which  in  the  Cat  and  other  ani- 
mals of  the  feline  species  is  very  prominent  on  each  side*.  Along  the  outer  border  of  the 
pyramid  is  a narrow  column,  which  is  not  so  distinct  in  some  animals.  This  is  the 
olivary  column  as  it  appears  at  the  surface.  It  bears  near  its  middle  a prominent  mass, 
which  is  oval  and  small  in  the  Sheep  and  Cat,  but  semilunar  and  larger  in  some  animals, 
as  the  Bear  and  Seal.  In  the  Tiger  it  resembles  that  of  the  Cat,  and  forms  a long  and 
somewhat  crescentic  band,  the  curve  of  the  crescent  embracing  a corresponding  con- 
vexity along  the  outer  side  of  the  pp’amid.  At  its  upper  end,  as  may  be  seen  in 
tigs.  7 and  8,  it  sinks  behind  the  pyramid,  but  is  continuous,  below,  uith  a distinct  but 
slender  fasciculus  [h)  of  the  antero-lateral  column.  In  the  tigui’es,  the  dots  along  its 
inner  border  indicate  the  attachment  of  the  hypoglossal  neiwe.  At  (?)  on  each  side,  the 
anterior  pyramid  commences,  and  suddenly  projects  forward  as  an  oblong  swelling, 
which  might  be  mistaken  for  an  enlargement  of  the  pyramid  itself.  But  if  a transverse 
section  (fig.  14,  Plate  XII.)  be  made  through  the  lower  part  of  the  protuberance,  it 
may  be  seen  that  the  decussation  has  already  ceased,  and  is  therefore  very  limited  in 
extent.  The  pyramids  [i,  i)  are  consequently  very  shallow,  but  rendered  prominent  by 
the  olivary  bodies,  which  are  chiefly  imbedded  behind  them,  and  appear  at  the  suiTace 
as  a narrow  column  only.  As  in  Man,  each  of  these  bodies  consists  of  a vesicular  sac 
enclosing  a central  nucleus ; but  the  convolutions  of  the  lamina  are  fewer  and  compa- 
ratively larger,  as  may  be  seen  in  fig.  26,  Plate  XV.,  which  represents  a transverse 
section  through  the  middle  of  the  protuberance  of  the  medulla  of  the  Sheep,  in  a plane 
passing  through  the  point  of  the  calamus  scriptorius.  It  rests  in  a conca'^ity  of  the 
pyramid,  with  one  extremity  at  the  side  of  the  raphe.  The  opposite  bodies  are  united 
by  a transverse  commissure,  composed  of  separate  bundles  which  undulate  through  them 
into  the  lateral  columns  to  be  continuous  with  the  arciform  system : immediately 
behind  the  pyramids  some  of  these  fibres  form  a very  regular  and  wa’cy  band.  Fig.  27, 
Plate  XV.  represents  a transverse  section  of  the  olivary  bodies  and  pp’amids  m the  Cat  ; 
those  of  the  Guinea  Pig  are  seen  in  fig.  17,  Plate  XIII.,  resting  on  the  back  of  the 
pyramids.  In  the  Simiadee,  the  vesicular  lamina,  or  corpus  dentatum,  is  tlnrouTi  into 
numerous  convolutions,  and  has  nearly  the  same  shape  and  appearance  as  in  Man. 
(33.)  The  cells  of  the  lamina  vary  somewhat  in  different  orders.  In  the  Ox,  Sheep 
and  Cat,  they  are  about  equal  to  those  of  Man,  but  many  are  more  elongated.  In  the 
Guinea  Pig  they  are  not  so  large. 
(34.)  In  Birds  the  cells  are  small  and  not  arranged  in  a lamina,  but  scattered  through 
the  side  of  the  anterior  column  (see  fig.  18,  Plate  XIII.). 
(36.)  On  the  outer  side  of  each  olivary  body,  and  separated  from  it  by  a groove  which 
lodges  the  hypoglossal  nerve,  is  another  vesicular  column  of  nearly  the  same  length,  but 
broader  externally.  It  is  rather  cylindrical  in  the  Cat  (fig.  4,  Plate  XII.),  fusiform  in 
the  Sheep  (figs.  7 and  8),  and  in  the  Dog  forms  a broad  swelling  at  its  lower  extremity. 
* The  trapezmm  is  found  in  all  the  Simiadse  except  the  Chimpanzee,  but  varies  in  size,  and  is  generally 
sunk  deeply  at  the  side  of  the  olive. 
