﻿1874.] 
  On 
  the 
  Development 
  of 
  the 
  Teeth 
  of 
  Ophidia. 
  95 
  

  

  the 
  base 
  of 
  the 
  dentine-germ 
  furnishes 
  lateral 
  prolongations, 
  just 
  as 
  has 
  

   been 
  observed 
  to 
  be 
  the 
  case 
  in 
  man. 
  

  

  The 
  dentine-organs 
  conform 
  closely 
  with 
  those 
  of 
  mammals 
  ; 
  the 
  

   odontoblast 
  layer 
  is 
  very 
  distinct, 
  and 
  the 
  processes 
  passing 
  from 
  these 
  

   cells 
  into 
  the 
  dentine-tubes 
  are 
  often 
  visible. 
  

  

  The 
  enamel-organs 
  consist 
  only 
  of 
  the 
  outer 
  and 
  inner 
  epithelia, 
  with- 
  

   out 
  any 
  stellate 
  intermediate 
  tissue 
  ; 
  as, 
  in 
  some 
  instances, 
  enamel 
  is 
  

   certainly 
  formed, 
  the 
  existence 
  of 
  the 
  stellate 
  tissue 
  is 
  obviously 
  non- 
  

   essential. 
  When 
  a 
  tooth 
  is 
  moving 
  to 
  displace 
  its 
  predecessor, 
  its 
  sac 
  

   travels 
  with 
  it, 
  remaining 
  intact 
  until 
  the 
  actual 
  attachment 
  of 
  the 
  tooth 
  

   to 
  the 
  bone 
  by 
  ankylosis. 
  

  

  II. 
  " 
  On 
  the 
  Structure 
  and 
  Development 
  of 
  the 
  Teeth 
  of 
  

   Ophidia." 
  By 
  Charles 
  T. 
  Tomes, 
  M.A. 
  Communicated 
  by 
  

   John 
  Tomes, 
  F.R.S. 
  Received 
  October 
  5, 
  1874. 
  

  

  (Abstract.) 
  

  

  Contrary 
  to 
  the 
  opinion 
  expressed 
  by 
  Professor 
  Owen 
  and 
  endorsed 
  

   by 
  Giebel 
  and 
  all 
  subsequent 
  writers, 
  the 
  author 
  finds 
  that 
  there 
  is 
  no 
  

   cementum 
  upon 
  the 
  teeth 
  of 
  snakes, 
  the 
  tissue 
  which 
  has 
  been 
  so 
  named 
  

   proving, 
  both 
  from 
  a 
  study 
  of 
  its 
  physical 
  characters 
  and, 
  yet 
  more 
  con- 
  

   clusively, 
  from 
  its 
  development, 
  to 
  be 
  enamel. 
  The 
  generalization 
  that 
  

   the 
  teeth 
  of 
  all 
  reptiles 
  consist 
  of 
  dentine 
  and 
  cement, 
  to 
  which 
  is 
  occa- 
  

   sionally 
  added 
  enamel, 
  must 
  hence 
  be 
  abandoned. 
  

  

  Without 
  as 
  yet 
  pledging 
  himself 
  to 
  the 
  following 
  opinion, 
  the 
  author 
  

   believes 
  that 
  in 
  the 
  class 
  of 
  Reptiles 
  the 
  presence 
  of 
  cementum 
  will 
  be 
  

   found 
  associated 
  with 
  the 
  implantation 
  of 
  the 
  teeth 
  in 
  more 
  or 
  less 
  com- 
  

   plete 
  sockets, 
  as 
  in 
  the 
  Crocodiles 
  and 
  Ichthyosaurs. 
  

  

  The 
  tooth-germs 
  of 
  Ophidia 
  consist 
  of 
  a 
  conical 
  dentine-germ, 
  resem- 
  

   bling 
  in 
  all 
  save 
  its 
  shape 
  that 
  of 
  other 
  animals, 
  of 
  an 
  enamel-organ, 
  

   and 
  of 
  a 
  feebly 
  expressed 
  capsule, 
  derived 
  mainly 
  from 
  the 
  condensation 
  

   of 
  the 
  surrounding 
  connective 
  tissue. 
  

  

  The 
  enamel-organ 
  consists 
  only 
  of 
  a 
  layer 
  of 
  enamel-cells, 
  forming 
  a 
  

   very 
  regular 
  columnar 
  epithelium, 
  and 
  of 
  a 
  few 
  compressed 
  cells 
  external 
  

   to 
  this, 
  hardly 
  amounting 
  to 
  a 
  distinct 
  layer 
  ; 
  the 
  enamel-organ 
  is 
  coex- 
  

   tensive 
  with 
  the 
  dentine-germ. 
  There 
  is 
  no 
  stellate 
  reticulum 
  separating 
  

   the 
  outer 
  and 
  inner 
  epithelia 
  of 
  the 
  enamel-organ. 
  

  

  The 
  successional 
  teeth 
  are 
  very 
  numerous, 
  no 
  less 
  than 
  seven 
  being 
  

   often 
  seen 
  in 
  a 
  single 
  section 
  ; 
  and 
  their 
  arrangement 
  is 
  peculiar, 
  and 
  

   quite 
  characteristic 
  of 
  the 
  Ophidia. 
  

  

  The 
  tooth 
  next 
  in 
  order 
  of 
  succession 
  is 
  to 
  be 
  found 
  at 
  the 
  inner 
  side 
  

   of 
  the 
  base 
  of 
  the 
  tooth 
  in 
  place, 
  where 
  it 
  lies 
  nearly 
  horizontally 
  ; 
  but 
  

   the 
  others 
  stand 
  more 
  nearly 
  vertically, 
  parallel 
  with 
  the 
  jaw 
  and 
  with 
  

   the 
  tooth 
  in 
  place, 
  the 
  youngest 
  of 
  the 
  series 
  being 
  at 
  the 
  bottom. 
  

  

  i 
  2 
  

  

  