﻿196 
  

  

  The 
  Properties 
  of 
  Colloidal 
  Systems. 
  IV 
  ' 
  .—Reversible 
  Gelation 
  in 
  

  

  Living 
  Protoplasm. 
  

   By 
  W. 
  M. 
  Bayliss, 
  F.R.S. 
  

  

  (Received 
  February 
  2, 
  1920.) 
  

   (From 
  the 
  Institute 
  of 
  Physiology, 
  University 
  College, 
  London.) 
  

  

  Protoplasm 
  itself, 
  using 
  the 
  name 
  to 
  express 
  living 
  substance 
  in 
  its 
  

   simplest, 
  undifferentiated 
  form, 
  is 
  generally 
  recognised 
  as 
  having 
  the 
  pro- 
  

   perties 
  of 
  a 
  somewhat 
  viscous 
  liquid. 
  This 
  fact 
  was 
  realised 
  as 
  long 
  ago 
  

   as 
  1864 
  by 
  Kuhne 
  (1864). 
  As 
  usually 
  seen 
  under 
  the 
  microscope, 
  it 
  contains 
  

   suspended 
  in 
  it 
  a 
  number 
  of 
  granules 
  of 
  a 
  great 
  variety 
  of 
  dimensions 
  and 
  

   properties. 
  But 
  in 
  the 
  pseudopodia 
  of 
  an 
  amoeba 
  or 
  of 
  a 
  leucocyte, 
  when 
  

   examined 
  by 
  the 
  ordinary 
  method 
  of 
  illumination 
  with 
  transmitted 
  light, 
  it 
  

   appears 
  completely 
  devoid 
  of 
  contents 
  or 
  structure. 
  As 
  Hardy 
  (1899) 
  

   showed, 
  the 
  various 
  networks 
  and 
  similar 
  arrangements 
  seen 
  in 
  fixed 
  pre- 
  

   parations 
  are 
  produced 
  by 
  the 
  action 
  of 
  the 
  reagents 
  used, 
  although 
  they 
  

   indicate 
  that 
  protoplasm 
  contains 
  matter 
  in 
  the 
  colloidal 
  state. 
  

  

  The 
  use 
  of 
  the 
  method 
  of 
  brilliant 
  lateral 
  illumination 
  on 
  a 
  dark 
  ground 
  

   (so-called 
  " 
  ultra-microscope 
  ") 
  has 
  led 
  to 
  the 
  detection 
  of 
  particles 
  in 
  

   protoplasm 
  which 
  are 
  too 
  minute 
  to 
  be 
  visible 
  by 
  ordinary 
  illumination. 
  

   Of 
  course, 
  these 
  particles, 
  being 
  comparable 
  in 
  dimensions 
  with 
  the 
  mean 
  

   wave-length 
  of 
  light, 
  are 
  not 
  seen 
  in 
  their 
  true 
  dimensions 
  or 
  form, 
  but 
  by 
  

   their 
  diffraction 
  discs. 
  Remembering 
  that 
  the 
  late 
  Lord 
  Rayleigh 
  showed 
  

   that 
  the 
  more 
  intense 
  the 
  illumination, 
  the 
  more 
  minute 
  are 
  the 
  particles 
  

   that 
  it 
  is 
  possible 
  to 
  detect, 
  I 
  tested 
  the 
  result 
  of 
  increasing 
  the 
  intensity 
  of 
  

   the 
  dark-ground 
  illumination 
  applied 
  to 
  the 
  apparently 
  clear 
  and 
  structure- 
  

   less 
  pseudopodia 
  of 
  large 
  amoeba?. 
  The 
  broad 
  flat 
  pseudopodia 
  of 
  a 
  species, 
  

   which 
  appeared 
  to 
  correspond 
  to 
  Amoeba 
  princeps 
  (Leidy), 
  were 
  found 
  to 
  be 
  

   most 
  appropriate 
  for 
  the 
  purpose. 
  A 
  paraboloid 
  condenser, 
  made 
  by 
  Zeiss, 
  

   was 
  used 
  in 
  most 
  cases. 
  The 
  source 
  of 
  light 
  was 
  the 
  positive 
  crater 
  of 
  

   a 
  small 
  arc 
  lamp 
  with 
  carbons 
  at 
  right 
  angles 
  to 
  one 
  another. 
  The 
  rays 
  

   were 
  made 
  parallel 
  by 
  a 
  condenser, 
  and 
  passed 
  through 
  a 
  cell 
  with 
  parallel 
  

   sides, 
  about 
  5 
  cm. 
  apart, 
  before 
  falling 
  on 
  the 
  mirror 
  of 
  the 
  microscope. 
  

   The 
  water-cell 
  was 
  found 
  to 
  be 
  necessary 
  on 
  account 
  of 
  the 
  heat 
  otherwise 
  

   transmitted 
  being 
  sufficient 
  to 
  kill 
  the 
  organisms. 
  In 
  order 
  to 
  obviate 
  the 
  

   injurious 
  effect 
  of 
  any 
  ultra-violet 
  rays 
  which 
  might 
  be 
  transmitted 
  through 
  

   the 
  system, 
  quinine 
  sulphate 
  was 
  added 
  to 
  the 
  water. 
  The 
  objective 
  used 
  

   for 
  the 
  majority 
  of 
  the 
  observations 
  was 
  an 
  excellent 
  i-inch 
  dry 
  lens 
  made 
  

  

  