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  ORGANISM 
  AND 
  MECHANISM 
  

  

  trace 
  it 
  through 
  the 
  ordinary 
  metabolic 
  phenomena 
  in 
  living 
  

   organisms, 
  as 
  well 
  as 
  through 
  the 
  phenomena 
  of 
  senescence, 
  

   death, 
  and 
  reproduction' 
  (p. 
  21). 
  

  

  The 
  everyday 
  life 
  of 
  any 
  common 
  animal 
  is 
  an 
  extraor- 
  

   dinarily 
  complex 
  affair. 
  " 
  For 
  what 
  is 
  a 
  creature 
  but 
  a 
  

   great 
  and 
  well-disciplined 
  army 
  with 
  battalions 
  which 
  we 
  

   call 
  organs, 
  and 
  brigades 
  which 
  we 
  call 
  systems 
  ? 
  It 
  advances 
  

   insurgently 
  from 
  day 
  to 
  day, 
  always 
  into 
  new 
  territory 
  of 
  

   time 
  and 
  space 
  often 
  inhospitable 
  or 
  actively 
  unfriendly 
  ; 
  

   it 
  holds 
  itself 
  together, 
  it 
  forages, 
  it 
  makes 
  good 
  its 
  ex- 
  

   penditure 
  of 
  explosives, 
  it 
  even 
  recruits 
  itself, 
  it 
  pitches 
  a 
  

   camp 
  and 
  strikes 
  it 
  again, 
  it 
  goes 
  into 
  entrenchments 
  and 
  

   winter-quarters, 
  it 
  retreats 
  and 
  lies 
  low, 
  it 
  recovers 
  itself, 
  it 
  

   has 
  a 
  forced 
  march, 
  it 
  conquers 
  ? 
  (Thomson, 
  Wonder 
  of 
  Life, 
  

   1914, 
  p. 
  627). 
  What 
  the 
  biologist 
  wishes 
  is 
  not 
  merely 
  

   a 
  complete 
  ledger 
  of 
  all 
  the 
  osmotic 
  and 
  capillary 
  proc- 
  

   esses 
  in 
  the 
  body, 
  all 
  the 
  oxidations 
  and 
  reductions, 
  all 
  the 
  

   solutions 
  and 
  fermentations, 
  though 
  that 
  will 
  be 
  a 
  great 
  

   achievement 
  he 
  wishes 
  a 
  description 
  of 
  the 
  organism's 
  

   daily 
  march 
  which 
  will 
  not 
  ignore 
  the 
  correlated 
  organismal 
  

   tactics 
  or 
  the 
  strategy 
  which, 
  in 
  some 
  cases 
  at 
  least, 
  lies 
  

   behind 
  these. 
  

  

  5. 
  Criticism 
  of 
  Mechanistic 
  Descriptions 
  of 
  Animal 
  

  

  Behaviour. 
  

  

  Let 
  us 
  pass 
  from 
  the 
  everyday 
  functions 
  of 
  the 
  body 
  

   to 
  a 
  connected 
  series 
  of 
  external 
  activities 
  to 
  animal 
  'be- 
  

   haviour, 
  .a 
  subject 
  to 
  which 
  we 
  shall 
  return 
  in 
  the 
  sixth 
  

   lecture. 
  We 
  know 
  that 
  a 
  young 
  British-born 
  swallow 
  which 
  

   leaves 
  us 
  for 
  the 
  south 
  towards 
  the 
  end 
  of 
  summer 
  may 
  

   return 
  the 
  following 
  spring 
  to 
  the 
  parish, 
  even 
  to 
  the 
  farm- 
  

   steading, 
  of 
  its 
  birth, 
  moved, 
  who 
  shall 
  say 
  by 
  what 
  deep 
  

  

  