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  The 
  Flicker 
  Photometer 
  and 
  the 
  Iris. 
  

  

  or 
  a 
  coarse 
  flicker 
  for 
  one 
  observer 
  with 
  the 
  speed 
  of 
  rotation 
  

   of 
  the 
  disk, 
  when 
  a 
  second 
  observer 
  described 
  the 
  flicker 
  in 
  

   the 
  same 
  terms 
  as 
  the 
  first. 
  The 
  speed 
  of 
  the 
  motor 
  was 
  

   regulated 
  by 
  means 
  of 
  a 
  brake. 
  

  

  On 
  January 
  18, 
  1913, 
  an 
  experiment 
  was 
  performed 
  in 
  

   which 
  the 
  irides 
  of 
  both 
  eyes 
  of 
  the 
  author 
  and 
  those 
  of 
  

   C. 
  D. 
  Livingstone 
  were 
  paralysed 
  with 
  a 
  solution 
  * 
  of 
  homa- 
  

   tropine 
  sulphate. 
  When 
  the 
  pupil 
  ceased 
  to 
  change 
  in 
  size 
  

   with 
  changing 
  intensities 
  of 
  light, 
  the 
  observers 
  observed 
  

   the 
  flickering 
  fields 
  through 
  the 
  tube 
  of 
  the 
  apparatus 
  with 
  

   each 
  eye 
  separately 
  and 
  determined 
  the 
  rate 
  of 
  the 
  motor 
  

   which 
  caused 
  the 
  flicker 
  to 
  disappear. 
  In 
  order 
  to 
  make 
  

   sure 
  that 
  the 
  reaction 
  of 
  the 
  pupil 
  to 
  light 
  was 
  totally 
  

   abolished 
  so 
  as 
  not 
  even 
  to 
  remain 
  residnally, 
  the 
  pupils 
  of 
  

   both 
  eyes 
  of 
  both 
  observers 
  were 
  tested, 
  with 
  the 
  aid 
  of 
  a 
  

   bi-convex 
  lens 
  which 
  magnifies 
  about 
  two 
  times, 
  bv 
  S. 
  Karrer, 
  

   whose 
  eyes 
  were 
  normal. 
  No 
  visible 
  reaction 
  remained 
  in 
  

   the 
  eyes 
  of 
  either 
  observer 
  when 
  tested 
  before 
  and 
  after 
  the 
  

   experiment. 
  Under 
  these 
  conditions, 
  the 
  appearance 
  of 
  the 
  

   flicker 
  was 
  not 
  changed 
  in 
  any 
  observable 
  particular 
  from 
  

   the 
  appearance 
  of 
  the 
  flicker 
  to 
  the 
  normal 
  eyes. 
  All 
  degrees 
  

   of 
  flicker 
  remained 
  as 
  before 
  the 
  atropine 
  was 
  placed 
  in 
  the 
  

   eyes, 
  and 
  it 
  is 
  to 
  be 
  noted 
  also 
  that 
  the 
  disagreeable 
  quality 
  

   of 
  the 
  coarse 
  flicker 
  persisted 
  undiminished. 
  To 
  make 
  

   certain 
  that 
  both 
  observers 
  were 
  observing 
  the 
  same 
  

   phenomenon, 
  the 
  rate 
  of 
  rotation 
  of 
  the 
  disk 
  which 
  was 
  

   necessary 
  just 
  to 
  obliterate 
  the 
  flicker 
  was 
  determined 
  for 
  

  

  Table 
  I. 
  

  

  

  H. 
  C. 
  S. 
  

  

  C. 
  D. 
  L. 
  

  

  Left 
  eye. 
  

  

  9*8 
  rvs. 
  per 
  second 
  

   or 
  

   39*2 
  flashes 
  per 
  second. 
  

  

  9 
  9 
  rvs. 
  per 
  second. 
  

   39 
  6 
  flashes 
  per 
  second. 
  

  

  Eight 
  eye. 
  

  

  10'4 
  rvs. 
  per 
  second 
  

  

  or 
  

   41 
  - 
  6 
  flashes 
  per 
  second. 
  

  

  10 
  - 
  9 
  rvs. 
  per 
  second. 
  

   43 
  6 
  flashes 
  per 
  second. 
  

  

  each 
  eye 
  and 
  for 
  each 
  observer. 
  The 
  results 
  are 
  shown 
  in 
  

   Table 
  I. 
  Both 
  the 
  number 
  of 
  revolutions 
  of 
  the 
  disk 
  per 
  

   second 
  and 
  the 
  number 
  of 
  flashes 
  of 
  light 
  are 
  given 
  in 
  the 
  

   table. 
  

  

  * 
  The 
  piescription 
  for 
  the 
  preparation 
  is 
  here 
  given. 
  As 
  will 
  be 
  seen^, 
  

   the 
  stienglh 
  of 
  tLe 
  solution 
  is 
  somewhat 
  less 
  than 
  1 
  per 
  cent. 
  

   Homatropirre 
  sulphatis 
  i. 
  gr. 
  Aquas 
  Destillatse 
  ii. 
  5- 
  

  

  