﻿THE 
  CRITERIA 
  OF 
  LIVINGNESS 
  87 
  

  

  food, 
  have 
  time 
  for 
  agency, 
  and 
  that 
  we 
  have 
  time 
  for 
  

   thinking 
  about 
  it 
  all. 
  

  

  We 
  are 
  familiar 
  with 
  the 
  self-preservative 
  devices 
  and 
  

   reactions 
  of 
  higher 
  animals 
  and 
  with 
  the 
  self-preservative 
  

   way 
  in 
  which 
  the 
  various 
  organs 
  of 
  the 
  body 
  work 
  into 
  each 
  

   other's 
  hands 
  ; 
  and 
  it 
  is 
  a 
  remarkable 
  fact 
  that 
  a 
  specific 
  

   activity 
  in 
  a 
  nervous 
  system 
  may 
  be 
  restored 
  after 
  the 
  de- 
  

   struction 
  of 
  the 
  particular 
  nerve-elements 
  on 
  which 
  the 
  activ- 
  

   ity 
  previously 
  depended. 
  This 
  vicarious 
  functioning 
  is 
  all 
  

   the 
  more 
  remarkable 
  inasmuch 
  as 
  there 
  is 
  not 
  in 
  higher 
  

   animals 
  any 
  regeneration 
  or 
  replacement 
  of 
  nerve-cells 
  after 
  

   birth. 
  But 
  deeper 
  than 
  all 
  this 
  is 
  the 
  correlation 
  of 
  chemical 
  

   processes 
  in 
  the 
  individual 
  units, 
  so 
  that 
  down-breaking 
  leads 
  

   to 
  up-building, 
  so 
  that 
  up-building 
  makes 
  further 
  down-break- 
  

   ing 
  possible, 
  the 
  pluses 
  balance 
  the 
  minuses, 
  and 
  the 
  creature 
  

   goes 
  on. 
  The 
  unicellular 
  organism 
  spends 
  its 
  substance 
  and 
  

   yet 
  has 
  it, 
  through 
  its 
  fundamental 
  capacity 
  for 
  self-renewal. 
  

   If 
  the 
  living 
  creature 
  is 
  a 
  machine, 
  it 
  is 
  a 
  self-stoking, 
  self- 
  

   repairing 
  machine, 
  and 
  it 
  can 
  take 
  a 
  rest 
  betimes. 
  

  

  Several 
  saving-clauses 
  must 
  be 
  appended 
  :--(!) 
  The 
  or- 
  

   ganism 
  shows 
  persistent 
  functionality, 
  but 
  it 
  is 
  not 
  known 
  

   to 
  offer 
  any 
  exception 
  to 
  the 
  law 
  of 
  the 
  conservation 
  of 
  

   energy. 
  In 
  living 
  it 
  expends 
  energy, 
  and 
  suffers 
  wear 
  and 
  

   tear; 
  it 
  cannot 
  continue 
  unless 
  it 
  captures 
  more 
  energy 
  and 
  

   is 
  able 
  to 
  repair 
  its 
  structure. 
  Fatigue 
  and 
  the 
  dying 
  of 
  

   parts, 
  such 
  as 
  leaves, 
  not 
  to 
  speak 
  of 
  senescence 
  and 
  death 
  

   itself, 
  show 
  that 
  the 
  fundamental 
  capacity 
  for 
  self-main- 
  

   tenance 
  is 
  not 
  perfect. 
  But 
  the 
  broad 
  fact 
  is 
  that 
  the 
  capacity 
  

   has 
  for 
  a 
  variable 
  time 
  a 
  very 
  considerable 
  degree 
  of 
  per- 
  

   fection. 
  The 
  organism's 
  chemical 
  activities 
  (and 
  repair- 
  

   processes) 
  are 
  so 
  correlated 
  that 
  it 
  remains 
  for 
  a 
  considerable 
  

   time 
  a 
  going 
  .concern. 
  As 
  we 
  shall 
  afterwards 
  see, 
  some 
  

  

  