﻿Dr. 
  H. 
  Eltringham 
  on 
  Butterfly 
  Vision. 
  29 
  

  

  I 
  have 
  tried 
  several. 
  For 
  some 
  purposes 
  the 
  well- 
  

   known 
  saturated 
  solution 
  of 
  corrosive 
  subhmate 
  in 
  

   water 
  to 
  which 
  is 
  added 
  50 
  % 
  of 
  alcohol 
  was 
  found 
  

   very 
  good. 
  About 
  1 
  % 
  glacial 
  acetic 
  acid 
  may 
  be 
  added 
  if 
  

   required. 
  Sections 
  thus 
  prepared 
  and 
  stained 
  for 
  twenty- 
  

   four 
  hours 
  in 
  anihn-water-saffranin 
  followed 
  by 
  a 
  short 
  

   immersion 
  in 
  a 
  2 
  % 
  solution 
  of 
  hght 
  green 
  in 
  alcohol, 
  give 
  

   a 
  very 
  beautiful 
  differentiation 
  of 
  the 
  cones. 
  For 
  showing 
  

   the 
  pecuhar 
  structure 
  of 
  the 
  trachaeal 
  distributor 
  at 
  the 
  

   base 
  of 
  the 
  rhabdom 
  the 
  ordinary 
  combined 
  methyl 
  blue 
  and 
  

   eosin 
  (Mann's 
  stain) 
  is 
  the 
  best, 
  and 
  this 
  also 
  gives 
  good 
  

   preparations 
  of 
  the 
  general 
  nervous 
  arrangement. 
  One 
  of 
  

   the 
  best 
  fixatives 
  of 
  high 
  penetrative 
  power 
  is 
  " 
  Picro- 
  

   chlor-acetic 
  acid 
  " 
  made 
  up 
  as 
  follows 
  : 
  — 
  

  

  1 
  % 
  Picric 
  acid 
  in 
  alcohol 
  ... 
  6 
  parts 
  

  

  Chloroform 
  1 
  part 
  

  

  Glacial 
  acetic 
  acid 
  . 
  . 
  . 
  . 
  | 
  

  

  Fix 
  for 
  twenty-four 
  hours 
  and 
  wash 
  well 
  in 
  90 
  % 
  alcohol. 
  

  

  The 
  nerve 
  fibres 
  passing 
  from 
  the 
  periopticon 
  to 
  the 
  

   retinulae 
  are 
  very 
  well 
  shown 
  by 
  Heidenhain's 
  haemato- 
  

   xylin. 
  Potassium 
  bichromate 
  and 
  solutions 
  containing 
  

   formalin 
  are, 
  as 
  a 
  rule, 
  of 
  very 
  httle 
  use, 
  as 
  they 
  render 
  any 
  

   chitinous 
  parts 
  exceedingly 
  brittle, 
  and 
  the 
  softer 
  parts 
  are 
  

   also 
  made 
  hable 
  to 
  pulverise 
  at 
  a 
  touch. 
  One 
  of 
  the 
  great 
  

   difficulties 
  in 
  all 
  insect 
  eye 
  preparations 
  is 
  the 
  pigment. 
  

   If 
  any 
  fixative 
  containing 
  osmic 
  acid 
  be 
  used 
  all 
  pigment 
  

   cells 
  are 
  intensified 
  and 
  the 
  pigment 
  cannot 
  be 
  removed. 
  

   The 
  same 
  apphes 
  in 
  great 
  measure 
  to 
  silver 
  nitrate. 
  For 
  

   depigmentation 
  after 
  fixation 
  the 
  following 
  solution 
  works 
  

   very 
  well 
  : 
  — 
  

  

  80 
  % 
  alcohol 
  2 
  parts 
  

  

  Glycerine 
  1 
  part 
  

  

  Hydrochloric 
  acid 
  . 
  . 
  . 
  .2% 
  

  

  Sections 
  after 
  removal 
  of 
  paraffin 
  or 
  celloidin 
  or 
  both 
  

   are 
  put 
  into 
  this 
  solution, 
  and 
  the 
  pigment 
  disappears 
  in 
  

   a 
  few 
  hours 
  or 
  less. 
  

  

  Buxton 
  (Trans. 
  Ent, 
  Soc, 
  1917, 
  p. 
  144) 
  obtained 
  good 
  

   results 
  with 
  insect 
  brain 
  tissue 
  by 
  putting 
  material 
  into 
  

   a 
  1 
  % 
  solution 
  of 
  silver 
  nitrate 
  in 
  water 
  for 
  ten 
  days 
  in 
  

   the 
  dark 
  and 
  then 
  washing. 
  The 
  material 
  is 
  embedded 
  

   in 
  paraffin 
  and 
  sections 
  cut. 
  After 
  removal 
  of 
  the 
  paraffin 
  

  

  