﻿THE 
  MIDDLE 
  EAR 
  AND 
  COLUMELLA 
  OF 
  EIRDS. 
  

  

  19 
  

  

  sensibly 
  the 
  same 
  position 
  as 
  in 
  the 
  five-day-chick. 
  It 
  is 
  

   quite 
  clear 
  from 
  Figures 
  4 
  and 
  5 
  that 
  no 
  considerable 
  out- 
  

   growth 
  from 
  the 
  auditory 
  capsule 
  can 
  have 
  taken 
  place 
  to 
  

   complete 
  the 
  continuity 
  of 
  hyoid 
  and 
  auditory 
  capsule. 
  There 
  

   is 
  no 
  evidence 
  of 
  such 
  an 
  outgrowth, 
  and 
  even 
  if 
  it 
  occurs 
  

   between 
  the 
  stages 
  Figs. 
  4 
  and 
  5, 
  the 
  outgrowth 
  can 
  only 
  

  

  AUD 
  CAPS 
  

  

  n 
  E 
  R 
  1 
  R 
  /T' 
  ? 
  ^ 
  V'SWri 
  :'M°%' 
  'A 
  J 
  U 
  G 
  V 
  E 
  1 
  N 
  

  

  i-^ 
  

  

  Fig. 
  6. 
  — 
  Ditto 
  ; 
  a 
  more 
  median 
  section 
  to 
  show 
  continuity 
  of 
  stapes 
  with 
  

   auditory 
  capsule. 
  

  

  Letters 
  used 
  in 
  Figs. 
  4, 
  5, 
  and 
  6 
  : 
  

  

  I. 
  E. 
  Internal 
  ear. 
  aud. 
  caps. 
  Auditory 
  ca])sule. 
  stap. 
  Stapes, 
  cons. 
  

   Constriction 
  in 
  hyoid 
  arch. 
  iiY. 
  Hyoid 
  arch. 
  cm. 
  Cavity 
  of 
  middle 
  ear. 
  

   JUG. 
  VEIN. 
  Jugular 
  vein, 
  vii 
  gn. 
  Geniculate 
  ganglion, 
  vii. 
  Seventh 
  nerve. 
  

  

  Figs. 
  4, 
  5, 
  and 
  G 
  drawn 
  with 
  camera 
  under 
  Zeiss 
  4, 
  aa. 
  

  

  occupy 
  a 
  very 
  small 
  part 
  of 
  the 
  space 
  subsequently 
  occupied 
  

   by 
  the 
  stapes, 
  unless 
  we 
  imagine 
  it 
  bodily 
  thrusting 
  the 
  

   hyoid 
  arch 
  before 
  it, 
  a 
  process 
  which 
  is 
  not 
  easy 
  to 
  imao-ine 
  

   in 
  ill-defined 
  pro-cartilaginous 
  structures, 
  and 
  for 
  which 
  there 
  

   is 
  not 
  the 
  least 
  shadow 
  of 
  evidence. 
  

  

  During 
  the 
  sixth 
  aud 
  seventh 
  days 
  of 
  incubation 
  chondrifi- 
  

   cation 
  sets 
  in. 
  In 
  the 
  seven-day 
  chick 
  auditory 
  capsule 
  and 
  

   hyoid 
  are 
  both 
  perfectly 
  chondrified 
  and 
  perfectly 
  continuous 
  

  

  