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  THE 
  CRITERIA 
  OF 
  LIVINGNESS 
  

  

  from 
  their 
  non-living 
  environment. 
  What 
  are 
  these 
  charac- 
  

   teristics 
  ? 
  What 
  are 
  the 
  criteria 
  of 
  living 
  organisms 
  ? 
  What 
  

   is 
  essential 
  in 
  the 
  admitted 
  contrast 
  between 
  the 
  living 
  and 
  

   the 
  not-living 
  ? 
  

  

  2. 
  The 
  Essential 
  Characteristics 
  of 
  Living 
  Organisms. 
  

  

  In 
  the 
  most 
  general 
  way 
  what 
  we 
  see 
  is 
  plain 
  enough. 
  

   We 
  see 
  organisms 
  acting 
  on 
  their 
  environment 
  displacing 
  

   it, 
  changing 
  it, 
  eating 
  it, 
  and 
  so 
  on 
  ; 
  and 
  again 
  we 
  see 
  that 
  

   the 
  environment 
  acts 
  upon 
  the 
  organism 
  displacing 
  it, 
  

   changing 
  it, 
  stimulating 
  it, 
  oxidising 
  part 
  of 
  it, 
  and 
  so 
  on. 
  

   So 
  that 
  living 
  is 
  a 
  twofold 
  relation 
  between 
  organisms 
  and 
  

   their 
  environment 
  a 
  twofold 
  relation 
  of 
  action 
  and 
  reaction, 
  

   of 
  thrust 
  and 
  parry, 
  of 
  doing 
  and 
  suffering. 
  At 
  one 
  moment 
  

   the 
  organism 
  is 
  relatively 
  the 
  more 
  active, 
  at 
  another 
  the 
  

   environment. 
  Living 
  is 
  a 
  continual 
  adjustment 
  between 
  

   these 
  two 
  relations. 
  

  

  When 
  we 
  look 
  at 
  the 
  facts 
  a 
  little 
  more 
  closely 
  we 
  see 
  

   that 
  all 
  living 
  creatures 
  plants 
  as 
  well 
  as 
  animals 
  are 
  

   active 
  towards 
  two 
  main 
  results, 
  their 
  own 
  self-maintenance 
  

   and 
  the 
  continuance 
  of 
  their 
  race. 
  Organisms 
  have 
  in 
  their 
  

   living 
  just 
  two 
  main 
  businesses 
  caring 
  for 
  themselves 
  and 
  

   caring 
  for 
  their 
  offspring. 
  But 
  all 
  this 
  is 
  living 
  rather 
  than 
  

   life 
  ; 
  we 
  are 
  only 
  hiding 
  the 
  problem 
  behind 
  the 
  word 
  organ- 
  

   ism. 
  What 
  are 
  the 
  marks 
  of 
  a 
  living 
  creature 
  ? 
  that 
  is 
  the 
  

   question. 
  What 
  is 
  the 
  best 
  answer 
  we 
  can 
  give 
  for 
  the 
  time 
  

   being 
  ? 
  Many 
  answers 
  have 
  been 
  given, 
  but 
  none 
  has 
  found 
  

   wide 
  acceptance, 
  which 
  doubtless 
  means 
  that 
  biologists 
  have 
  

   not 
  yet 
  seen 
  the 
  insignia 
  of 
  organisms 
  in 
  their 
  entirety, 
  or 
  

   in 
  proper 
  perspective. 
  

  

  One 
  of 
  the 
  best 
  statements 
  is 
  that 
  of 
  Roux, 
  who 
  recognises 
  

   five 
  " 
  elementary 
  functions 
  " 
  : 
  

  

  