﻿386 
  PROFESSOR 
  ALISON'S 
  DEFENCE 
  

  

  material 
  facts 
  on 
  which 
  this 
  important 
  discovery 
  is 
  founded 
  : 
  — 
  " 
  Nature 
  has 
  

   catenated 
  together 
  organic 
  beings, 
  and 
  made 
  them 
  mutually 
  dependent 
  on 
  each 
  

   other 
  for 
  their 
  existence, 
  and 
  all 
  dependent 
  on 
  light. 
  A 
  privation 
  of 
  light 
  would 
  

   be 
  immediately 
  destructive 
  to 
  organic 
  existence; 
  vegetation 
  would 
  cease; 
  the 
  

   supply 
  of 
  oxygen 
  gas 
  would 
  be 
  quickly 
  cut 
  off 
  from 
  animals 
  ; 
  the 
  lower 
  strata 
  of 
  

   the 
  atmosphere 
  would 
  become 
  composed 
  of 
  carbonic 
  acid 
  ; 
  and 
  perception 
  and 
  

   volition 
  would 
  exist 
  no 
  longer."* 
  

  

  The 
  following 
  description 
  of 
  the 
  circulation, 
  in 
  which 
  all 
  the 
  matter 
  destined 
  

   by 
  Nature 
  to 
  the 
  maintenance 
  of 
  organised 
  creation 
  on 
  the 
  earth's 
  surface 
  is 
  con- 
  

   tinually 
  engaged, 
  is 
  merely 
  an 
  amplification 
  of 
  the 
  expressions 
  of 
  Dumas 
  ; 
  and 
  

   although 
  part 
  of 
  the 
  statements 
  contained 
  in 
  it 
  are 
  liable 
  to 
  objection, 
  its 
  general 
  

   import 
  is 
  such 
  as 
  amply 
  to 
  fulfil 
  the 
  expectation 
  of 
  a 
  great 
  discovery 
  which 
  I 
  

   had 
  expressed. 
  

  

  Vegetables, 
  under 
  the 
  influence 
  of 
  light 
  and 
  of 
  a 
  certain 
  temperature, 
  are 
  

   continually 
  abstracting 
  from 
  the 
  atmosphere, 
  directly 
  or 
  indirectly, 
  a 
  part 
  of 
  its 
  

   constituents, 
  in 
  the 
  form 
  of 
  water, 
  carbonic 
  acid, 
  a 
  little 
  nitric 
  acid, 
  and 
  ammonia. 
  

   The 
  radicals 
  of 
  this 
  inorganic 
  matter 
  (matiere 
  brute) 
  are 
  gradually 
  organised 
  in 
  vege- 
  

   tables, 
  which 
  are 
  a 
  true 
  reducing 
  apparatus, 
  while 
  a 
  part 
  of 
  its 
  oxygen 
  is 
  set 
  free 
  ; 
  

   and, 
  after 
  being 
  formed 
  into 
  organic 
  principles, 
  those 
  radicals 
  are 
  yielded 
  directly 
  

   or 
  indirectly 
  to 
  animals. 
  This 
  matter 
  is 
  applied, 
  without 
  farther 
  change, 
  to 
  the 
  

   maintenance 
  of 
  the 
  functions 
  of 
  animal 
  life 
  ; 
  particularly 
  it 
  furnishes 
  the 
  condi- 
  

   tions, 
  and 
  becomes 
  the 
  instrument, 
  of 
  mental 
  acts 
  ; 
  after 
  which, 
  as 
  if 
  exhausted 
  

   by 
  the 
  effort 
  which 
  it 
  has 
  made, 
  it 
  falls 
  again 
  under 
  the 
  influence 
  of 
  oxygen, 
  

   in 
  the 
  animal 
  body, 
  which 
  is 
  a 
  true 
  apparatus 
  of 
  combustion 
  ; 
  and 
  either 
  before 
  

   or 
  after 
  the 
  death 
  of 
  the 
  animal 
  structure, 
  returns 
  as 
  inorganic 
  matter, 
  under 
  

   the 
  name 
  of 
  manure, 
  to 
  the 
  great 
  reservoir 
  from 
  which 
  it 
  came. 
  In 
  this 
  eternal 
  

   circuit, 
  life 
  is 
  the 
  chief 
  agent, 
  and 
  by 
  these 
  changes 
  it 
  makes 
  itself 
  known 
  ; 
  but 
  

   the 
  matter 
  that 
  is 
  thus 
  employed 
  undergoes 
  only 
  a 
  change 
  of 
  place. 
  I 
  apprehend 
  

   we 
  must 
  add, 
  that 
  the 
  properties 
  as 
  well 
  as 
  the^ 
  positio?i 
  of 
  this 
  matter 
  are 
  conti- 
  

   nually 
  altered 
  and 
  resumed, 
  and 
  that 
  it 
  is 
  the 
  modification 
  which 
  the 
  properties 
  of 
  

   this 
  matter 
  undergo, 
  in 
  the 
  course 
  of 
  this 
  circulation, 
  which 
  constitutes 
  the 
  pre- 
  

   cise 
  object 
  of 
  all 
  physical 
  inquiries, 
  both 
  in 
  vegetable 
  and 
  animal 
  physiology, 
  so 
  

   far 
  as 
  the 
  organic 
  functions 
  of 
  animals 
  are 
  concerned. 
  

  

  The 
  final 
  cause 
  of 
  all 
  these 
  changes 
  is 
  already 
  obvious. 
  We 
  know 
  that 
  it 
  has 
  

   pleased 
  the 
  Author 
  of 
  our 
  being 
  to 
  connect 
  with 
  a 
  world 
  previously 
  existing, 
  and 
  

   consisting 
  of 
  matter 
  already 
  long 
  endowed 
  with 
  all 
  its 
  physical 
  properties, 
  an 
  in- 
  

   finite 
  number 
  and 
  variety, 
  and 
  eternal 
  succession, 
  of 
  sensitive 
  creatures, 
  and 
  ulti- 
  

   mately 
  a 
  race 
  of 
  beings 
  " 
  formed 
  after 
  his 
  own 
  image." 
  The 
  acts 
  of 
  sensation 
  

   and 
  thought 
  which 
  characterise 
  these, 
  he 
  has 
  placed 
  in 
  immediate 
  connection 
  

  

  * 
  Works, 
  vol. 
  i.. 
  p. 
  106. 
  

  

  