﻿22 
  INTRODUCTION. 
  

  

  tions 
  between 
  the 
  lymph-sacs 
  that 
  exist 
  on 
  both 
  the 
  

   dorsal 
  and 
  ventral 
  surfaces 
  immediately 
  beneath 
  the 
  

   integument. 
  

  

  The 
  lymph, 
  fed 
  by 
  the 
  moisture 
  absorbed 
  through 
  

   the 
  skin, 
  is 
  pumped 
  into 
  the 
  veins 
  by 
  two 
  pairs 
  of 
  

   lymph-hearts, 
  contractile 
  muscular 
  sacs, 
  the 
  anterior 
  

   of 
  which 
  are 
  situated 
  in 
  the 
  muscular 
  tissue 
  close 
  to 
  

   the 
  transverse 
  processes 
  of 
  the 
  third 
  vertebra, 
  the 
  

   posterior 
  on 
  the 
  sides 
  of 
  the 
  urostyle 
  near 
  its 
  extre- 
  

   mity 
  ; 
  their 
  pulsations 
  may 
  be 
  observed 
  on 
  the 
  back 
  

   of 
  the 
  living 
  frog. 
  

  

  The 
  number 
  aud 
  extent 
  of 
  the 
  lymph-sacs 
  varies 
  in 
  

   the 
  different 
  genera. 
  In 
  Rana 
  and 
  Felodytes 
  there 
  

   are 
  22, 
  4 
  unpaired 
  and 
  9 
  pairs. 
  The 
  dorsal 
  sac 
  

   extends 
  from 
  the 
  tip 
  of 
  the 
  snout 
  to 
  above 
  the 
  vent, 
  

   and 
  is 
  limited 
  by 
  the 
  line 
  of 
  attachment 
  which 
  corre- 
  

   sponds 
  to 
  the 
  canthus 
  rostralis, 
  the 
  supra-orbital 
  

   border, 
  the 
  supra-temporal 
  fold, 
  and 
  the 
  glandular 
  

   dorso-lateral 
  fold. 
  The 
  lateral 
  sac 
  is 
  limited 
  below 
  by 
  

   a 
  band 
  on 
  each 
  side 
  of 
  the 
  belly, 
  which 
  may 
  be 
  marked 
  

   externally 
  by 
  a 
  shght 
  groove 
  ; 
  the 
  abdominal 
  surface 
  of 
  

   the 
  head 
  and 
  body 
  is 
  divided 
  into 
  three 
  sacs, 
  gular, 
  

   pectoral, 
  and 
  abdominal, 
  with 
  partitions 
  across 
  the 
  

   prascoracoid 
  and 
  coracoid 
  regions. 
  The 
  further 
  sacs 
  

   (brachial, 
  subbrachial, 
  femoral, 
  supra-femoral, 
  inter- 
  

   femoral, 
  crural, 
  supra- 
  and 
  sub-plantar) 
  belong 
  to 
  the 
  

   limbs. 
  In 
  Hyla 
  there 
  is 
  besides 
  a 
  close 
  areolar 
  attach- 
  

   ment 
  of 
  the 
  abdominal 
  integument. 
  The 
  Discoglos- 
  

   sidse 
  differ 
  in 
  the 
  absence 
  of 
  coracoid 
  attachment, 
  

   or 
  if 
  such 
  exists,' 
  as 
  in 
  Discoglossus, 
  it 
  is 
  widely 
  

   interrupted 
  on 
  the 
  middle 
  line 
  ; 
  there 
  is, 
  therefore, 
  

   no 
  distinct 
  pectoral 
  lymph-sac. 
  In 
  Pelohates 
  the 
  skin 
  

   of 
  the 
  belly 
  is 
  attached 
  in 
  its 
  posterior 
  half. 
  In 
  

   Bitfo 
  the 
  ventral 
  integument 
  is 
  more 
  or 
  less 
  broadly 
  

   attached, 
  together 
  with 
  the 
  whole 
  of 
  the 
  dorsal 
  

   integument. 
  

  

  One 
  of 
  the 
  most 
  remarkable 
  peculiarities 
  connected 
  

   with 
  the 
  integument 
  of 
  Batrachians 
  is 
  the 
  cutaneous 
  

   respiration, 
  or 
  the 
  power 
  which 
  the 
  surface 
  of 
  the 
  

  

  