﻿Brown 
  

  

  REFRACTION 
  

  

  247 
  

  

  . 
  This 
  may 
  be 
  done 
  by 
  measuring 
  at 
  room 
  temperature 
  (70 
  

   F.) 
  the 
  volume 
  of 
  200 
  drops 
  of 
  each 
  of 
  the 
  oils 
  used 
  in 
  the 
  mix- 
  

   ture. 
  By 
  this 
  means 
  a 
  drop 
  of 
  castor 
  oil 
  was 
  found 
  to 
  have 
  a 
  

   volume 
  equal 
  to 
  that 
  of 
  1.8 
  drops 
  of 
  clove 
  oil, 
  and 
  i 
  drop 
  of 
  naph- 
  

   ^ 
  thalene 
  a 
  monobromated, 
  0.95 
  the 
  volume 
  of 
  a 
  drop 
  of 
  clove 
  oiL 
  

  

  ARATION 
  

  

  In 
  preparing 
  tissues 
  for 
  the 
  measurment 
  of 
  their 
  refraction 
  the 
  

   following 
  schedule 
  was 
  adopted. 
  

  

  1. 
  Cut 
  as 
  many 
  sections, 
  10-40 
  /x 
  thick, 
  as 
  there 
  are 
  refractive 
  

   liquids 
  in 
  the 
  series, 
  and 
  wash 
  in 
  water 
  for 
  10 
  minutes 
  or 
  longer. 
  

  

  2. 
  Transfer 
  each 
  section 
  to 
  a 
  separate 
  slide 
  and 
  cover 
  with 
  a 
  

  

  glass 
  slip. 
  

  

  3. 
  Dry 
  for 
  at 
  least 
  fifteen 
  minutes 
  at 
  loo"" 
  C. 
  An 
  electric 
  oven 
  

   is 
  useful 
  for 
  this 
  purpose. 
  

  

  4. 
  Remove 
  the 
  slides 
  one 
  at 
  a 
  time 
  from 
  the 
  oven 
  and 
  mount 
  

   each 
  section 
  in 
  a 
  different 
  refractive 
  liquid 
  of 
  the 
  series. 
  The 
  

   samples 
  of 
  tissue 
  are 
  then 
  ready 
  for 
  microscopic 
  examination. 
  

  

  3. 
  Determination 
  of 
  relative 
  refraction 
  . 
  

  

  For 
  this 
  purpose, 
  an 
  apochromatic 
  microscope 
  with 
  Abbe 
  

   condenser 
  and 
  movable 
  sub-stage 
  diaphragm 
  was 
  used, 
  but 
  any 
  

   microscope 
  with 
  the 
  usual 
  accessories 
  will 
  answer 
  for 
  ordinary 
  

   purposes. 
  A 
  magnification 
  of 
  about 
  800 
  diameters 
  was 
  usually 
  

   used 
  in 
  the 
  examination. 
  The 
  refraction 
  of 
  the 
  object 
  relative 
  

   to 
  that 
  of 
  the 
  liquid 
  was 
  determined 
  in 
  each 
  case 
  by 
  one 
  or 
  more 
  of 
  

   the 
  following 
  methods. 
  

  

  A, 
  By 
  oblique 
  illumination 
  

  

  The 
  partly-closed 
  sub-stage 
  diaphragm 
  is 
  shifted 
  to 
  one 
  side. 
  

   If 
  the 
  refraction 
  of 
  the 
  tissue 
  mass 
  is 
  above 
  that 
  of 
  the 
  liquid, 
  the 
  

   outlines 
  appear 
  dark 
  on 
  the 
  side 
  toward 
  which 
  the 
  diaphragm 
  is 
  

   shifted. 
  But 
  if 
  the 
  refraction 
  of 
  the 
  tissue 
  mass 
  is 
  below 
  that 
  of 
  

   the 
  liquid, 
  the 
  outlines 
  appear 
  dark 
  on 
  the 
  side 
  away 
  from 
  which 
  

   the 
  diaphragm 
  is 
  shifted. 
  In 
  Table 
  I 
  the 
  refraction 
  of 
  the 
  

   tissue 
  or 
  body 
  examined 
  is 
  indicated 
  as 
  + 
  (above) 
  o*" 
  — 
  (below) 
  

   with 
  respect 
  to 
  the 
  refractive 
  index 
  of 
  the 
  liquid 
  in 
  which 
  it 
  is 
  

   immersed. 
  

  

  