﻿462 
  J. 
  W, 
  JKNKINSON. 
  

  

  lifted 
  off 
  the 
  lowei* 
  layer 
  wliicli 
  forms 
  tlie 
  floor 
  of 
  the 
  central 
  

   circular 
  area. 
  

  

  I 
  next 
  tried 
  gelatin, 
  principally 
  a 
  solution 
  of 
  about 
  6 
  per 
  

   cent., 
  and 
  succeeded 
  in 
  producing 
  the 
  excurrent 
  aster 
  with 
  

   picric 
  acid, 
  either 
  alone 
  or 
  with 
  the 
  admixture 
  of 
  glycerin 
  

   or 
  cane 
  sugar 
  ; 
  with 
  chromic 
  acid 
  and 
  glycerin, 
  and 
  with 
  

   Flemming's 
  solution; 
  with 
  albumen 
  mixed 
  with 
  either 
  glycerin 
  

   or 
  cane 
  sugar 
  ; 
  with 
  a 
  crystal 
  of 
  either 
  ammonium 
  sulphate 
  or 
  

   sodium 
  chloride, 
  and 
  with 
  saturated 
  solutions 
  of 
  either 
  sub- 
  

   stance; 
  and 
  with 
  a 
  mixture 
  of 
  gum 
  and 
  sublimate. 
  As 
  before 
  the 
  

   results 
  are 
  far 
  superior 
  when 
  a 
  thin 
  layer 
  of 
  gelatin 
  is 
  used. 
  The 
  

   asters 
  retain 
  their 
  form 
  long 
  enough 
  for 
  the 
  gelatin 
  to 
  set; 
  

   they 
  may 
  then 
  be 
  fixed 
  in 
  alcohol 
  and 
  preserved 
  permanently. 
  

  

  Thirdly 
  I 
  experimented 
  with 
  yolk 
  of 
  egg. 
  If 
  a 
  small 
  crystal 
  

   of 
  ammonium 
  sulphate 
  be 
  immersed 
  in 
  a 
  drop 
  of 
  egg-yolk, 
  it 
  

   does 
  not 
  matter 
  how 
  large 
  or 
  thick, 
  a 
  clear 
  area 
  is 
  at 
  once 
  

   formed 
  round 
  it, 
  the 
  yolk-granules 
  being 
  driven 
  away. 
  This 
  

   can 
  be 
  seen 
  in 
  the 
  drop 
  and 
  is 
  easily 
  verified 
  by 
  the 
  aid 
  of 
  

   sections. 
  Soon 
  there 
  appears 
  internally 
  to 
  this 
  clear 
  area 
  a 
  

   thick 
  brown 
  wall 
  of 
  precipitate, 
  as 
  in 
  the 
  case 
  of 
  albumen 
  

   described 
  above, 
  and 
  inside 
  this 
  a 
  central 
  vacuole 
  as 
  the 
  

   crystal 
  finally 
  dissolves 
  away. 
  

  

  If 
  instead 
  of 
  ammonium 
  sulphate 
  a 
  small 
  crystal, 
  the 
  smaller 
  

   the 
  better, 
  of 
  salt 
  or 
  sugar 
  be 
  employed 
  no 
  precipitate 
  is 
  

   formed, 
  but 
  short 
  radial 
  tubes 
  grow 
  out 
  into 
  the 
  clear 
  zone 
  

   from 
  the 
  central 
  vacuole, 
  and 
  not 
  only 
  in 
  a 
  horizontal 
  plane. 
  

   It 
  is 
  important 
  to 
  observe 
  that 
  these 
  outgrowths 
  can 
  be 
  pro- 
  

   duced 
  as 
  easily 
  in 
  a 
  large 
  drop 
  as 
  in 
  a 
  small, 
  and 
  that 
  in 
  the 
  

   former 
  case 
  their 
  formation 
  is 
  quite 
  independent 
  of 
  any 
  con- 
  

   tact 
  with 
  the 
  lower 
  surface 
  of 
  the 
  drop 
  next 
  the 
  glass. 
  

  

  If 
  on 
  the 
  other 
  hand 
  a 
  thin 
  film 
  of 
  egg-yolk 
  be 
  employed 
  

   the 
  aster 
  is 
  much 
  more 
  fully 
  developed. 
  In 
  egg-yolk 
  I 
  have 
  

   made 
  asters 
  with 
  solutions 
  of 
  picric, 
  picric 
  and 
  cane 
  sugar, 
  

   cane 
  sugai', 
  glacial 
  acetic, 
  aceto-corrosive, 
  chromic, 
  chromic 
  

   and 
  acetic, 
  glycerin 
  and 
  sublimate, 
  glycerin 
  and 
  picric, 
  

   ammonium 
  sulphate 
  and 
  90 
  per 
  cent, 
  alcohol. 
  The 
  best 
  

   results 
  are 
  given 
  by 
  glacial 
  acetic 
  and 
  cane 
  sugar. 
  

  

  