﻿THE 
  MIDDLE 
  EAR 
  AND 
  COLUMELLA 
  UE 
  BIRDS. 
  13 
  

  

  The 
  extra-columelUi 
  is 
  supplied 
  witli 
  one 
  ligament 
  in 
  all 
  

   birds, 
  Platuer's 
  ligaraeutj 
  which 
  stretches 
  across 
  the 
  cavity 
  

   of 
  the 
  middle 
  ear 
  to 
  the 
  posterior 
  face 
  of 
  the 
  quadrate 
  bone 
  

   {Pit., 
  Figs. 
  1 
  and 
  3). 
  In 
  Gallus 
  there 
  are 
  present 
  two 
  

   other 
  ligaments 
  attached 
  to 
  the 
  extra- 
  and 
  infra-stapedials 
  

   which 
  are 
  in 
  part 
  concentrations 
  of 
  the 
  fibrous 
  constituents 
  

   of 
  the 
  tympanic 
  membrane 
  ; 
  I 
  can 
  only 
  find 
  these 
  erroneously 
  

   described 
  by 
  Parker 
  (3) 
  as 
  being 
  attached 
  to 
  the 
  quadrate. 
  

   In 
  reality 
  they 
  pass 
  beneath 
  the 
  quadrate, 
  are 
  continued 
  

   beyond 
  the 
  region 
  of 
  the 
  tympanic 
  membrane 
  into 
  the 
  lining 
  

   of 
  the 
  Eustachian 
  tube, 
  and 
  are 
  finally 
  attached 
  to 
  the 
  walls 
  

   of 
  the 
  bony 
  Eustachian 
  groove 
  near 
  the 
  point 
  where 
  it 
  

   debouches 
  into 
  the 
  mouth 
  (Fig. 
  2). 
  This 
  is 
  a 
  peculiar 
  dis- 
  

   position, 
  not 
  found 
  in 
  other 
  birds 
  that 
  I 
  have 
  examined. 
  

  

  The 
  Seventh 
  Nerve. 
  — 
  This 
  nerve 
  has 
  three 
  branches, 
  

   wh'ich 
  are, 
  counting 
  in 
  order 
  from 
  the 
  root 
  of 
  the 
  nerve 
  

   outwards, 
  the 
  sphenopalatine, 
  the 
  chorda 
  tympani, 
  and 
  the 
  

   main 
  branch 
  of 
  the 
  seventh. 
  In 
  Gallus 
  the 
  sphenopalatine 
  

   and 
  the 
  chorda 
  tympani 
  come 
  off 
  together 
  from 
  the 
  geniculate 
  

   ganglion 
  and 
  do 
  not 
  take 
  up 
  any 
  intimate 
  relation 
  to 
  the 
  middle 
  

   ear. 
  The 
  chorda 
  tympani, 
  after 
  its 
  origin 
  from 
  the 
  seventh 
  

   nerve, 
  runs 
  a 
  little 
  Avay 
  with 
  it 
  in 
  the 
  Fallopian 
  tube, 
  then 
  

   enters 
  a 
  bony 
  canal 
  of 
  its 
  own 
  and 
  so 
  gains 
  the 
  posterior 
  face 
  

   of 
  the 
  quadrate. 
  The 
  cross 
  in 
  Fig. 
  3 
  shows 
  the 
  approximate 
  

   point 
  at 
  Avhich 
  the 
  chorda 
  tympani 
  comes 
  off 
  the 
  seventh 
  nerve 
  

   in 
  the 
  fowl. 
  After 
  giving 
  off 
  the 
  chorda 
  the 
  main 
  branch 
  of 
  

   the 
  seventh 
  crosses 
  the 
  stapes 
  externally 
  and 
  dorsally 
  to 
  it 
  in 
  

   the 
  cancellated 
  bone, 
  and 
  then 
  leaves 
  the 
  skull 
  by 
  the 
  stylo- 
  

   mastoid 
  foramen. 
  

  

  In 
  other 
  birds, 
  e. 
  g. 
  Columba, 
  the 
  chorda 
  has 
  a 
  quite 
  

   different 
  disposition 
  (Fig. 
  3). 
  It 
  leaves 
  the 
  seventh 
  nerve 
  by 
  

   a 
  special 
  foramen 
  in 
  the 
  Fallopian 
  tube 
  just 
  before 
  the 
  seventh 
  

   nerve 
  makes 
  its 
  exit 
  from 
  the 
  skull 
  by 
  the 
  stylo-mastoid 
  

   foramen; 
  it 
  then 
  traverses 
  a 
  small 
  piece 
  of 
  cancellated 
  bone 
  

   and 
  enters 
  the 
  cavity 
  of 
  the 
  middle 
  ear 
  quite 
  superficially, 
  

   viz. 
  between 
  the 
  extra-columellaand 
  the 
  tympanic 
  membrane. 
  

   It 
  now 
  crosses 
  the 
  extra-columella, 
  keeping 
  this 
  same 
  relation 
  

  

  