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  ORGANISM 
  AND 
  MECHANISM 
  

  

  and 
  particularly 
  of 
  physical 
  chemistry, 
  has 
  furnished 
  ex- 
  

   planations 
  of 
  these 
  processes. 
  This 
  is 
  most 
  certainly 
  not 
  

   the 
  case. 
  What 
  physical 
  chemistry 
  has 
  helped 
  us 
  to 
  do 
  is 
  

   to 
  obtain 
  measures 
  of 
  the 
  processes 
  in 
  the 
  living 
  body; 
  but 
  

   the 
  results 
  of 
  measurements 
  have 
  been 
  to 
  show 
  with 
  ever- 
  

   increasing 
  clearness 
  that 
  the 
  processes 
  in 
  the 
  living 
  body 
  

   do 
  not 
  correspond 
  with 
  our 
  conceptions 
  of 
  those 
  in 
  non- 
  

   living 
  structures, 
  and 
  that 
  we 
  are 
  not 
  remotely 
  in 
  sight 
  of 
  

   mechanical 
  explanations 
  of 
  the 
  former. 
  

  

  " 
  As 
  an 
  example, 
  I 
  need 
  only 
  take 
  the 
  case 
  of 
  the 
  exqui- 
  

   sitely 
  thin 
  and 
  delicate 
  living 
  membrance 
  which 
  separates 
  the 
  

   blood 
  in 
  the 
  lung 
  capillaries 
  from 
  the 
  air 
  in 
  the 
  alveoli 
  or 
  

   air-cells 
  of 
  the 
  lungs. 
  A 
  short 
  time 
  ago 
  it 
  was 
  assumed 
  

   that 
  this 
  membrane 
  plays 
  only 
  a 
  passive 
  part 
  which 
  we 
  

   regard 
  a 
  non-living 
  membrane 
  as 
  playing, 
  and 
  allows 
  oxygen 
  

   to 
  diffuse 
  through 
  it 
  just 
  as 
  a 
  non-living 
  membrane 
  would. 
  

   On 
  applying 
  accurate 
  methods 
  of 
  measurement 
  we 
  found 
  

   that, 
  whenever 
  there 
  is 
  need 
  for 
  an 
  extra 
  supply 
  of 
  oxygen, 
  

   as, 
  for 
  instance, 
  during 
  muscular 
  exertion, 
  the 
  membrane 
  

   assumes 
  an 
  active 
  role 
  and 
  pushes 
  oxygen 
  inwards, 
  without 
  

   regard 
  to 
  the 
  mechanical 
  laws 
  of 
  diffusion. 
  In 
  this 
  respect 
  

   the 
  alveolar 
  epithelium 
  acts 
  just 
  like 
  the 
  epithelium 
  of 
  the 
  

   swim-bladder, 
  or 
  that 
  of 
  the 
  kidney 
  or 
  any 
  other 
  gland, 
  or 
  

   the 
  alimentary 
  canal. 
  The 
  progress 
  of 
  physical 
  chemistry 
  

   is 
  enabling 
  us 
  to 
  distinguish 
  sharply 
  between 
  physiological 
  

   activity 
  and 
  the 
  processes 
  occurring 
  in 
  non-living 
  structures 
  ; 
  

   and 
  the 
  establishment 
  of 
  the 
  distinction 
  is 
  sweeping 
  away 
  

   the 
  easy-going 
  mechanistic 
  explanations 
  which 
  became 
  cur- 
  

   rent 
  during 
  the 
  latter 
  half 
  of 
  last 
  century." 
  " 
  On 
  the 
  whole, 
  

   there 
  is 
  no 
  evidence 
  of 
  real 
  progress 
  towards 
  a 
  mechanistic 
  

   explanation 
  of 
  life." 
  

  

  The 
  inadequacy 
  of 
  the 
  mechanical 
  description 
  is 
  apparent 
  

  

  