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SYDENHAM    SOCIETY 


INSTITUTED 


MDCCCXLIII 


LONDON 


THE 

PRINCIPLES  OF  PHYSIOLOGY, 

BY 

JOHN  AUGUSTUS  UNZER; 


A  DISSERTATION 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM, 


BY 

GEORGE  PROCHASKA. 


TRANSLATED  AND  EDITED  BY 

THOMAS  LAYCOCK,  M.D.  (Gottingen), 

LICENTIATE  OF  THE  KOYAL  COLLEGE  OF  PHYSICIANS,  LONDON  ; 

PHYSICIAN  TO  THE  YOKK  DISPENSARY  ;  AND 

LECTUEEB  ON  THE  THEOKY  AND  PEACTICE  OF  MEDICINE  AT  THE  YOBK  MEDICAL  SCHOOL. 


LONDON 

PRINTED  FOR  THE  SYDENHAM  SOCIETY 

MDCCCLI. 


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C.    AND    J.    ADLARD,    PRINTERS, 

BAUTHOi-OMKW  CIOSK. 


CONTENTS. 

PAGE 

Preface     .......  xi 

Introduction.    By  the  Editor                      .               .               .  .         i 

Notice  of  the  Life  and  Writings  of  Unzer       .                .                .  i-viii 

Notice  of  the  Life  and  Writings  of  Prochaska        .                .  ix-xiv 
List  of   Words  and  Phrases  used  by  Unzer,  and  their  English 

Synonymes           .                .                .                .                .  .       xv 


PRINCIPLES  OF  A  PHYSIOLOGY  OF  THE  PROPER 
ANIMAL  NATURE  OF  ANIMAL  ORGANISMS. 

Preface  .  .  .  .  .  .  .3 

Introduction  .  .  .  .  .  .13 


PART  I. 

ANIMAL  NATURE  IN  ITS  CONNECTION  WITH  THE  SENTIENT 
FACULTY  OF  THE  SOUL  OF  THE  ANIMAL. 


CHAPTER  L 
The  Animal   Machines   in   general,   and  especially  as  they  are 

adapted  to  the  Animal-Sentient  Forces       .  .  .17 

CHAPTER  II. 
The  Animal  Forces  considered  abstractedly,  and  particularly  as 

Animal-Sentient  Forces  .  .  .  .  .21 

Sect.  I. — The  Functions  of  the  Vital  Spirits     ....       ib. 
II. — The  Animal  Forces  of  the  Brain  considered  abstractedly  as  Animal- 

Sentient  Forces  .  .  .  .  .23 


\I 


CONTENTS. 


III. — The  Animal  Forces  of  the  Nerves  considered  solely  in  their  relation 
with  the  Animal-Sentient  Forces  of  the  Brain 
Of  the  External  Impressions 
On  External  Sensations     . 
The  External  Senses 
The  Sensational  Conceptions 
Imaginations     . 
Expectations     . 
The  Understanding 
Sensational  Pleasure  and  Suffering 
Desires  and  Aversions 
Instincts, — Passions 
The  Free- Will  . 

Actions  excited  by  the  Mind,  or  Sentient  Actions 
Actions  of  Material  Ideas  in  the  Nervous  System 
Actions  of  Material  Ideas  in  the  Brain 
Actions  of  Material  Ideas  through  the  Nerves  generally 
Actions  of  the  Material  Ideas  in  the  Nerves  exclusively 


CHAPTER  III. 
On  the  Influence  of  the  Animal-Sentient  Forces  in  the  Mechanism 

OF  Animal  Organisms 
Actions  of  Material  Ideas  in  the  Mechanical  Machines  of  the  Brain 
Actions  of  Material  Ideas  in  the  Mechanical  Machines  through  the  Nerves      85 
Actions  of  External  Sensations  in  the  Mechanical  Machines 
Actions  of  Imaginations  in  the  Mechanical  Machines 
Actions  of  the  Sensational  Foreseeings  in  the  Mechanical  Machines 
Actions  of  Sensational  Pleasure  and  Pain  in  the  Mechanical  Machines 
Actions  of  the   Sensational  Desires  and  Aversions  in  the  Mechanical 

Machines  ..... 

Actions  of  the  Sensational  Instincts  in  the  Mechanical  Machines 
Self-Love  ..... 

Instinct  foi?  Food       ..... 
Instinct  to  perform  Sensational-voluntary  Movements 


CONTENTS. 


VIl 


Instinct  for  Repose  and  Exhilaration 

Instinct  of  Self-Defence 

Instinct  for  the  Propagation  of  the  Species 

Instinct  to  give  Suck 

The  Instinctive  Passions 

Actions  of  the  Passions  in  the  Mechanical  Machines 

Actions  of  the  Understanding  in  the  Mechanical  Machines 

Actions  of  Intellectual  Pleasure  and  Pain  in  the  Mechanical  Machines 

Actions  of  the  Will  in  the  Mechanical  Machines 


FAOB 
153 

155 
157 
158 
161 
166 
176 
178 
179 


CHAPTER  IV. 
The  Reciprocal  Connection  of  the  Body  with  the  Soul 


.     184 


PART  11. 

ANIMAL   NATURE  IN   RELATION  TO  ITS   PURELY   ANIMAL 

FORCES,  OR  VIS  NERVOSA. 
Introduction  .  .  .  .  .  .188 


CHAPTER  I. 
On  the  Vis  Nervosa,  and  on  Nerve-Actions  in  general 


189 


CHAPTER  II. 

On  the  Vis  Nervosa  of  External  Impressions        .  .  .     222 

Sect.  I. — On  the  Vis  Nervosa  of  External  Impressions  in  general    .  .       ib. 

II. — On  the  Vis  Nervosa  of  External  Impressions  in  Special  Relation  to 

direct  Nerve-Actions        ....  .    238 


CHAPTER  III. 
On  the  Vis  Nervosa  of  Internal  Impressions  (without  conceptions). 


Sect.  I. —        .  .  .  .  .  . 

II. — On  the  Vis  Nervosa  of  Internal  Impressions  in  particular 


"TnfCT 
.     262 


VIII  CONTENTS. 

CHAPTER  IV. 

PAGE 

Relations  of  the  Animal-Sentient  (Cerebral)  Forces  and  of  the 

Vis  Nervosa  to  each  other     .....  275 

Sect.  1. — On  the  Substitution  of  Nerve-Actions  for  Sentient  Actions  .  275 

II. — On  the  Substitution  of  Sentient  Actions  for  Nerve-Actions  .  299 

III. — The  Reciprocal  Connection  of  the  Animal-Sentient  (Cerebral)  Forces, 

with  the  Vis  Nervosa  in  the  Natural  State  .  .  .  302 


PART  III. 
ANIMAL  NATURE  CONSIDERED  AS  A  WHOLE. 

Introduction     .  .  .  .  .  .  .    308 

CHAPTER  I. 
On  Animal  Nature  in  General  ....     309 

CHAPTER  II. 
The  principal  Genera  of  Existing  Animals  .  .  .317 

CHAPTER  III. 
On  the  Origin  of  Animal  Nature  ....     327 

CHAPTER  IV. 
On  Animal  Life  ......    330 

CHAPTER  V. 
The  System  of  the  Forces  of  Animal  Life  .  .  .     337 

CHAPTER  VI. 
On  Old  Age  and  Death  .....     354 

e:nd  or  contents  to  vkzku's  'I'mncirLiis  oi'  physiology.' 


CONTENTS.  IX 

A  DISSERTATION   ON    THE    FUNCTIONS    OF   THE 
NERVOUS  SYSTEM. 

PAGE 

Introduction  .....  .    363 

CHAPTER  I. 
The    Principal  Opinions   of   Authors,   regarding    the   Uses    and 

Functions  of  the  Nervous  System,  concisely  stated. 

Sect.  I. — The  Opinions  of  Aristotle  .  .  .  .    365 

II.— The  Opinions  of  Galen     .  .  .  .  .366 

III.— The  Followers  of  Galen     .  .  .  .  .369 

IV. — The  Animal  Spirits  are  dislodged  from  the  Ventricles      .  .    370 

V. — Another  office  attributed  to  the  Ventricles  of  the  Brain,  by  Galen,  is 

also  shown  to  be  erroneous  .  .  .  .372 

VI. — It  is  proposed,  with  other  special  Functions  of  the  Nervous  System, 
that  the  Cortical  Portion  of  the  Brain  be  substituted  for  the 
Ventricles,  as  the  part  where  the  Animal  Spirits  are  secreted,  and 
that  the  Medullary  Matter  has  the  Function  of  collecting  and 
distributing  them  to  the  Nerves  ....  374 
VII. — Those  who  have  denied  the  existence  of  Animal  Spirits   .  .    378 

VIII. — The  Functions  of  the  Nwvous  System  are  explained  by  the  Vis 

Nervosa        .  .  .  .  .  .380 

CHAPTER  II. 
The  Nervous  System  in  general. 
I.— What  Parts  it  includes      .  .  .  .  .381 

II. — How  the  Nervous  System  is  constituted  in  other  Animals,  and  how 

far  it  extends  through  the  whole  Animal  Kingdom       .  .     384 

III. — What  is  understood  by  the  Vis  Nervosa,  and  what  are  its  general 

Properties     ......    389 

CHAPTER  III. 
The  Functions  of  the  Nerves. 
Sect.  I. — On  the  Action  of  the  Nerves  in  producing  Sensation  and  Motion    .    406 
II. — The  Action  of  the  Nerves  on  the  Vessels  and  Fluids        .  .    408 


X  CONTENTS. 

PAGE 

III. — By  this  Derivation  of  the  Fluids  to  the    stimulated  part,  the 
Muscles  are  made  to  contract,  and  many  other  phenomena  pro- 
produced       .  .  .  .  .  .413 

IV. — Does  an  opposite  Property  exist  in  the  Nerves,  so  that  they  can  repel 

the  Blood  from  the  Vessels  under  their  Influence  into  other  parts?     417 
V. — Have  the  Nerves  any  Influence  on  Secretion  '  .  .418 

VI. — Do  the  Nerves  exert  any  Influence  in  the  Production  of  Animal 

Heat?  .  .  .  .  .  .421 

VII. — Are  the  Nerves  necessary  to  Nutrition  ?  .  .  .     423 

CHAPTER  IV. 
The  Functions  of  the  SensoriuiiI  Commune. 
Sect.  I. — What  is  the  Sensorium  Commune ;  what  its  Functions,  and  what  its 

Seat?  .  .  .  .  .  .429 

II. — Does  every  Consensus  of  the  Nerves  take  place  through  the  Sen- 
sorium Commune  only  ?  .  .  .  .    433 

III. — Does  Consensus  of  the  Nerves  also  take  place  in  the  Ganglia  ?        .     435 

CHAPTER  V. 
The  Animal  Functions. 
Sect.  I. — A  short  Enumeration  of  them  ....     439 

II. — Is  the  faculty  of  Thought  the  special  property  of  the  Mind,  or  is  it 
necessary  to  Thought  that  the  Mind  use  the  hrain  as  an 
Instrument?  .....     442 

III. — Do  each  of  the  Divisions  of  the  Intellect  occupy  a  separate  portion 

of  the  Brain  .....    446 

IV. — "WTiat  movements  are  properly  termed  Animal  ?  .  .447 


Index  to  Unzer's  First  Principles     .  .  .  .  .451 

Index  to  Prochaska's  Dissertation  ....     460 


PREFACE. 

The  Introduction  which  1  have  written,  at  the  request 
of  the  Council  of  the  Sydenham  Society,  might  suffice  for  a 
Preface  also,  if  it  were  not  that  there  are  one  or  two  matters 
to  be  mentioned  which  a  Preface  only  can  include. 

In  the  first  place,  I  earnestly  request  the  reader's  close  at- 
tention to  the  works  contained  in  this  Volume ;  partly,  for  my 
own  sake,  that  I  may  not  lose  the  sweetest  reward  of  literary 
labour ;  but  principally  for  his  and  for  the  interests  of  medical 
science  and  art.  They  belong  to  a  field  of  research  not  yet 
fully  entered  upon  by  the  medical  profession.  Emigrants  from 
its  ranks  have  been  the  "  Pilgrim  Fathers"  of  many,  if  not 
most,  of  the  natural  history  sciences ;  but  there  is  one  that 
has  yet  to  be  perfected  by  its  labours — the  science  of  mind. 

The  study  of  Life  and  Organisation  is  confessedly  essential 
to  the  progress  of  medical  science  and  art ;  and  it  appears  to 
me,  that  that  true  intellectual  system  of  the  universe,  which 
will  and  must  comprehend,  in  orderly  arrangement,  all  the  phe- 
nomena of  Life  and  Mind,  ought,  therefore,  to  emanate  from 
the  medical  profession.  If  so  glorious  a  result  of  philosophical 
inquiry  be  within  its  scope  and  aim,  then  are  the  works  con- 
tained in  this  Volume  of  double  value  and  interest  to  it,  since 
they  not  only  powerfully  elucidate  the  Physiology  and  Patho- 
logy of  the  Nervous  System,  but  constitute  an  important  con- 
tribution to  Mental  Philosophy. 

Having  said  so  much  for  the  works  entrusted  to  my  care,  I 
must  now  say  something,  by  way  of  thanks,  to  those  who  have 


XII  PREFACE. 

assisted  me  in  bringing  them  out.  My  kind  friend,  Professor 
Marx  of  Gottingen,  has  not  only  readily  afforded  me  his 
advice  as  to  the  translation  of  Unzer's  work,  but  has  also  con- 
tributed much  valuable  and  interesting  information  respecting 
the  life  and  writings  of  his  countrymen,  which  I  have  embodied 
in  the  Introduction.  I  have  also  to  acknowledge  my  obliga- 
tions to  Professor  Sharpey,  and  Dr.  Adams  of  Banchory,  (so 
well  known  to  the  Sydenham  Society  for  his  translations  of 
Hippocrates  and  Paulus  ^  gin  eta,)  for  the  valuable  criticisms 
with  which  they  favoured  me  when  the  '  Dissertation  on  the 
Nervous  System^  was  going  through  the  press.  To  these 
three  gentlemen  both  reader  and  translator  owe  their  thanks. 

But  there  is  one  other  valued  name  I  cannot  omit  here  without 
injustice.  To  Dr.  Forbes  we  owe  the  first  substantial  intro- 
duction of  Unzer^s  work  to  the  English  reader ;  to  him,  there- 
fore, our  thanks  are  also  due; — and  not  for  this  service  only, 
but  for  many  others  rendered  to  the  medical  profession  and  to 
medical  science  and  literature,  the  value  of  which  have  yet  to 
be  acknowledged. 

Of  my  own  share  in  this  work  I  have  only  to  say,  that  I 
feel  I  had  an  important  trust  committed  to  me,  and  laboured 
accordingly; — laboured,  it  is  true,  with  the  usual  drawbacks 
of  an  active  professional  life; — and  if  this  be  admitted  by  the 
critic  as  an  excuse  for  errors  and  failures,  I  shall  be  grateful 
to  him. 

T.  L. 

York;  February  1851. 


INTEODUCTION 

BY  THE  TRANSLA.TOR. 


It  having  been  thought  expedient  to  facilitate  the  com- 
prehension of  the  Physiological  Systems  laid  down  in  this 
volume,  by  a  short  notice  of  the  labours  and  literary  course  of 
the  writers,  I  subjoin  the  following  remarks. 

John  Augustus  Unzer  (or  Untzer)  was  born  at  Halle, 
April  29,  1727,  and  commenced  the  study  of  medicine  at  the 
university  of  his  native  town,  when  only  12  years  old.  He 
showed  an  early  inclination  to  neuiJo-metaphysical  studies,  for,  at 
the  age  of  18  (while  yet  a  student),  he  attempted  to  elucidate 
mental  philosophy  by  the  physiology  of  the  nervous  system,  in  an 
essay,  published  anonymously,  entitled  '  New  Views  regarding 
the  Emotions,'  i  in  which  he  attributed  the  emotions  to  varying 
tension  of  the  nerves;  in  the  same  year  (1746,)  he  wrote  a 
defence  of  the  doctrines  of  Stahl,  entitled  '  Thoughts  on  the 
Influence  of  the  Soul  on  its  Body/^  also  '  Thoughts  on  Sleep 
and  Dreams,  together  with  a  Letter  showing  that  there  may 
be  Sensation  without  the  Head,'  under  the  somewhat  curious 
signature  of  '  S.  C.  I.  S/^  From  this  date  to  the  year  1771, 
when  the  work  now  translated  was  published,  a  quarter  of 
a  century  elapsed,  during  the  whole  of  which  period  his  at- 
tention was  continuously  directed  to  his  favorite  subject, 
as  is  shown  by  the  essays  and  treatises  he  gave  to  the  world 
during  that  period.  In  1747  he  published  a  '  Treatise  on 
Sighing.'  *  On  taking  his  Doctor's  degree,  in  the  following 
year,  he  defended -his  dissertation  '  De  Sternutatione ;'  and, 

'  Neue  Lehre  von  den  Gemiiths  Bewegungen. — Halle,  1746. 
'  Gedancken  vom  Einflusse  der  Seele  in  ihren  Kbrper. — 1746. 
^  Gedancken  vom  Schlafe  und  den  Traiimen  nebst  einera  Send-schreiben  dass  man 
ohne  Kopf  empfinden  konne.     Halle,  1746. 
*  Abhandlung  vom  Seufzen.      Halle,  1747. 

b 


ii  TRANSLATOR'S  INTRODUCTION. 

in  1749,  his  dissertation  '  De  Nexu  Metaphysices  cum  Medi- 
cina  generatim/  In  1750  he  published  a  '  Philosophical  View 
of  the  Human  Body  generally/  ^  in  which  the  germ  of  his 
future  views  may  be  distinctly  traced.  Towards  the  close  of 
this  year  he  left  Halle  to  reside  at  Hamburgh,^  where  he  im- 
mediately became  connected  with  the  *  Hamburgh  Magazine' 
(vide  vol.  vi),  and  communicated  to  it  various  essays  of  a 
neuro-metaphysical  character  :  amongst  them  was  one,  entitled 
'Reflections  on  the  fundamental  Principle  of  StahVs  Theory.'^ 
In  1759  he  established  a  weekly  medical  journal,  '  The 
Physician,'*  on  the  model  of  Addison's  '  Spectator,'  with  the 
view  of  securing  a  proper  estimate  of  physicians  and  of  the 
art  of  healing,  and  of  extending  sound  medical  knowledge,  re- 
moving prejudices,  and  checking  the  misdoings  of  ignorant 
practitioners ;  it  is  an  amusing  medley.  The  first  part  contains 
his  portrait  by  Tischbein.  This  journal  was  translated 
into  Danish,  Swedish,  and  Dutch,  and  was  published  during 
the  years  1759-64;  the  neuro-psychological  essays  he  inserted 
in  it  are  frequently  referred  to  in  the  present  work.  From 
1766  to  1769  he  published  '  Collections  of  Minor  Physical 
Essays  :'^  and  in  the  latter  year,  a  new  edition  of  '  Der  Arzt,' 
in  six  volumes.  His  portrait,  taken  in  the  42d  year  of  his 
age,  painted  and  engraved  by  H.  G.  Fritzsch,  fronts  the  title- 
page  of  the  first  volume.  In  1768  he  made  an  attempt  at  a 
better  and  more  systematic  arrangement  of  his  views,  in  a  work 
entitled  '  Outlines  of  a  System  treating  of  the  Sentiency  of 
Animal  Organisms;'^  and,  finally,  three  years  after,  he  pub- 
lished the  work  now  translated,  which  he  dedicated  to  his  brother. 
Dr.  J.  C.  Unzer,  and  which  may  be  looked  upon  as  a  new 
and  much  improved  edition  of  the  last-mentioned  publication. 
Thus  his  'Principles  of  a  Physiology  of  the  Animal  Nature  pro- 
per to  Animal  Organisms,'  was  given  to  the  world  at  the  mature 
age  of  44,  after  it  had  been  virtually  a  quarter  of  a  century 

*  Philosophische  Betrachtung  des  Menschlichen  Korpers  uberhaupt.     1750. 

^  Haller  makes  a  statement  in  his  '  Bibliotheca  Anatom.,'  (vol.  2,  p.  400),  which, 
on  careful  inquiry,  I  find  to  be  erroneous,  namely,  that  Unzer  was  Professor  of 
Medicine  at  the  University  of  Rinteln. 

3  Betrachtungen  iiber  Stahl's  theoretischen  Grundsatz. — Hamburg.  Magaz.  Bd.  10. 

*  Der  Arzt ; — eine  Medicinische  Wochenschrift. 

*  Saramlung  Kleiner  physicalischer  Schriften; — the  third  in  1769. 

^  Grundriss  eines  Lehrgebaudes  von  der  Sinnlichkeit  der  thierischen  Korper. 


TRANSLATOR'S  INTRODUCTION.  iii 

in  preparation,  and  may  therefore  be  considered  as  the  work  of 
a  powerful  metaphysical  intellect,  in  the  prime  of  its  strength, 
and  thoroughly  informed  on  the  subject  to  which  it  had  been 
so  long,  so  perseveringly,  and  so  assiduously  directed.  With 
the  exception  of  a  reply  to  various  reviews  of  the  work,^  Unzer 
wrote  no  more  on  his  favorite  subject,  but  turned  his  atten- 
tion to  the  pathology  of  contagion,  and  contagious  diseases, 
which  he  elucidated  with  his  usual  acuteness.  He  died,  rich, 
April  22,  1799,  being  a  week  less  than  72  years  old. 

Having  thus  given  a  brief  sketch  of  Unzer's  literary  career, 
I  will  notice,  as  shortly  as  possible,  the  origin  and  progress  of 
his  peculiar  views,  as  finally  perfected  in  this,  his  greatest  work. 
Although  he  must  have  been  eminently  qualified  by  natural 
endowments,  and  by  a  natural  bias  to  metaphysical  research 
for  grappling  successfully  with  the  profound  and  very  difficult 
questions  of  physiological  metaphysics,  it  is  probable,  that  to  his 
early  associations  at  the  University  of  Halle  we  owe  the  special 
direction  of  his  mind  to  the  subject.  Both  Hoffmann  and  Stahl 
were  professors  at  Halle  for  a  lengthened  period;  but  when 
Unzer  commenced  his  medical  studies,  the  former  was  still 
professor,  at  the  venerable  age  of  79,  and  died  at  Halle,  in 
his  83d  year,  so  that  Unzer  must  have  known  him  personally. 
It  was,  however,  as  the  pupil  of  Juncker,  an  avowed  Stahlian, 
that  he  specially  directed  his  attention  to  the  metaphysics  of 
vital  actions,  and  to  him  Unzer  dedicated  his  defence  of  the 
doctrines  of  Stahl,  in  a  long  and  highly  complimentary 
dedication.  At  this  time  physiology,  and  especially  the  phy- 
siology of  the  nervous  system,  was  fast  losing  its  purely 
hypothetical  character,  and  assuming  the  rank  of  a  science. 
Mental  philosophy  had  long  taken  cognisance  of  the  different 
kinds  of  motion  in  animals  of  which  every  man  is  led  to  dis- 
criminate at  least  three  : — namely ;  1st,  those  dependent  solely 
on  the  will ;  2d,  those  of  which  he  is  conscious,  but  which  are 
independent  of  the  will  as  the  exciting  cause;  3d,  those  of 
which  he  is  wholly  unconscious,  and  which  can  neither  be  excited 
nor  restrained  by  volition.  The  first  class  of  actions  could  be 
readily  ascribed  to  the  soul ;  but  the  second  and  third  classes, 

'  Physiologische  Untersuchungen  auf  Veranlassung  der  Gottingisclien,  Frank- 
furter, &c.    Recensionen  seiner  Physiologic  der  thierischen  Natur. — Leipzig,  1773. 


iv  TRANSLATOR'S  INTRODUCTION. 

although  independent  of  reason,  volition,  and  even  consciousness, 
were  equally  characterised  by  their  intelligent  and  exact  adap- 
tation to  the  wants  of  the  animal.  To  explain  the  origin  of 
these  adapted  acts,  and  to  determine  their  relations  to  those 
of  the  reason  and  will,  was  a  problem  which  had  occupied  and 
baffled  the  greatest  intellects,  from  Plato  downwards,  and  a 
satisfactory  solution  had  never  been  given  to  the  world.  In 
the  theory  of  Aristotle,  these  various  actions  were  considered 
to  result  from  the  operation  of  a  sentient,  or  intelligent 
principle,  endowed  with  certain  faculties  or  powers.  All  the 
faculties  that,  according  to  this  theory,  can  exist  in  a  living 
creature,  are  five: — namely;  1,  the  faculty  of  receiving  nu- 
triment ;  2,  of  sensation ;  3,  of  motion  in  place ;  4,  of  impulse 
or  desire ;  5,  of  intelligence :  so  that  soul,  considered  as 
endowed  with  only  the  nutritive  faculty  (which  is  present  in 
all  beings),  may  be  attributed  to  vegetables.  The  soul  of  man 
differs  from  the  soul  of  lower  beings,  in  being  endowed  with  the 
faculty  of  intelligence,  in  addition  to  all  the  others ;  consequently 
it  may  be  considered  as  containing  three  portions, — logically, 
not  materially,  separated, — one,  absolutely  without  reason ; 
a  second,  rational ;  a  third,  participant  of  reason. 

The  Aristotelian  philosophy  was  long  exclusively  current  in 
the  universities  and  schools ;  but,  with  the  revival  of  anatomy 
and  physiology,  the  outlines  of  various  systems  oi  physiological 
metaphysics  appeared,  and  anatomy,  physiology,  and  natural 
philosophy,  were  brought  into  direct  relation  with  psychology. 
Our  own  Willis  took  the  lead  in  this  new  department  of  medical 
science.  He  illustrated  the  human  and  comparative  anatomy 
of  the  brain  and  nervous  systems,  by  drawings  and  copper- 
plates ;  he  distinguished  two  kinds  of  souls,  namely,  the  corporeal 
or  sensitive  (the  anima — the  soul  of  brutes),  and  the  rational 
or  intellectual  (the  animus)  :  and  he  assigned  the  cerebrum 
to  the  latter,  and  the  cerebellum  to  the  former,  the  diseases, 
faculties,  and  operations  of  which  he  treated  of  specially  in  his 
two  discourses,  '  De  Anima  Brutorum.'^  The  first  discourse  is 
physiological,  and,  in  many  respects,  is  the  analogue  and 
prototype  of  Unzer's  work ;   the   second  is  pathological,   and 

*  De  Anima  Brutorum  quee  Hominis  vitalis  ac  sensitiva  est,  Exercitationes 
nvM  quarum  prior  Physiologic  a  ejus  naturam  Partes,  Potentias,  et  Affectiones 
tradit ;  altera  Pathologica,  &c. 


TRANSLATOR'S  INTRODUCTION.  v 

treats  of  the  diseases  of  the  brain  and  nervous  system.  In 
these,  as  well  as  in  his  other  neurological  works,  Willis  follows 
the  line  of  research  which  his  peculiar  position,  as  Sidley 
Professor  of  Natural  Philosophy  at  Oxford,  would  almost 
necessarily  incline  him  to  take.  According  to  Willis,  the  vital, 
sensitive,  or  corporeal  soul,  performs  two  principal  offices; 
namely,  first,  to  form  the  body  of  the  animal  and  its  organs, 
and  then  to  render  it  and  them  apt  and  fit  for  all  the  purposes 
of  the  life  of  the  individual.  The  better  to  illustrate  his  views, 
he  devotes  a  chapter  to  a  description  of  the  various  kinds  of 
lower  animals,  including  therein  zoology,  and  comparative 
anatomy  and  physiology.  To  this  corporeal  soul  he  ascribes 
all  the  emotional,  instinctive,  and  involuntary  acts.  Touching 
this  class  of  movements,  he  observes,  (I  quote  the  quaint, 
vigorous  language  of  Pordage's  translation,) — "  First,  as  to 
what  regards  natural  Instincts,  it  is  a  great  and  most  ancient 
Notion,  That  there  is,  in  all  Living  Creatures,  an  innate  Conser- 
vation of  themselves;  to  wit,  that  every  Individual  might 
preserve  itself  as  long  as  it  can.  This  is  a  Law  of  Divine 
Providence,  inbred  in  all  creatures,  which  gathers  together  the 
Principles  of  Life  like  a  Bond,  otherways  apt  to  be  dissipated 
and  to  depart  one  from  another,  and  on  which,  as  the  Basis, 
the  Duration  or  Continuance  of  the  whole  World  stands.^' 
"  This  being  supposed,  it  necessarily  follows,  that  all  Animals 
ordained  for  this  end,  are  furnished  also  with  certain  fit  means 
for  following  the  same,  wherefore  they  ought  to  know,  by 
Natural  Instinct,  whatsoever  things  are  Congruous  and  benign, 
and  what  are  incongruous  or  hurtful  to  them ;  and  that  they 
should  follow  these  with  hatred  and  aversion,  and  those  vdth 
Love  and  delight.  Hence  it  is,  that  every  one  of  them  are  able 
to  choose  Food  proper  for  themselves,  and  to  seek  it,  being 
absent,  and  remote  from  their  eyes ;  And,  from  an  implanted 
disposition  of  their  Nature,  are  skilful  to  know  and  oppose 
Enemies,  to  love  their  Friends,  to  get  a  female  fit  for  themselves, 
and  to  make  ready  whatever  may  conduce  to  the  Procreating 
and  Cherishing  their  young;  besides  many  other  Kinds  of 
powers  and  habits,  granted  to  us  not  without  Learning  and 
Study,  are  originally  fixed  on  the  prcecordia  of  the  Beast.'' ^ 

'  *'  Quod  autern  spectat  ad  imtinctus  naturales,  antiquissima,  et  maxime  generalis 
notio,  cunctis  animalibus  innata  est  sui  ipsius  conservatio,  nempe  ut  unumquodque 


vi  TRANSLATOR'S  INTRODUCTION. 

Willis  was  not_,  however,  solitary  in  his  doctrine  as  to  the 
existence  of  two  souls  in  man  ;^  Gassendus,  and  Dr.  Hammond, 
a  learned  English  divine  (both  his  contemporaries),  are  specially- 
quoted  by  him ;  nor  was  he  alone  in  his  direct  application  of 
natural  science  to  mental  philosophy,  for  Sylvius  was  diligently 
pursuing  at  Leyden  the  same  course  of  research  which  he  was 
following  at  Oxford.  Sylvius,  however,  followed  Descartes, 
while  Willis  was  influenced  in  the  formation  of  his  theories  by 
the  doctrines  of  Paracelsus.  There  was,  however,  yet  another 
neuro-psychologist,  whose  name  is  less  known  in  England,  but 
who  was  the  contemporary  of  Sylvius  and  WilUs,  and  taught 
identical  or  analogous  doctrines,  with  brilliant  success,  at  Jena, 
— this  was  G.  W.  Wedel,  the  teacher  of  Hoffmann  and  Stahl, 
— and  it  is  through  him  that  we  have  to  trace  the  views  of 
Unzer  in  a  direct  line  from  Willis. 

Hoffmann  and  Stahl  ran  a  singularly  parallel  course  through 
life.  They  were  born  in  the  same  year  (1660),  and  studied  at 
the  same  time  and  place,  under  Wedel,  at  Jena,  then  the 
most  renowned  university  in  Germany.  They  were  appointed 
professors  of  medicine  at  Halle,  in  the  same  year  (1694),  and 
at  the  same  age ;  and  both  became  physicians  to  the  king  of 
Prussia ;  Hoffmann  was  the  first  to  leave  HaUe,  and  fill  that 
office,  but,  in  three  years,  he  abandoned  court,  and  resumed 
his  professor's  chair,  where  he  died,  in  the  83d  year  of  his 
age.  Stahl  died  at  Berlin,  the  physician  to  royalty;  but, 
previously  to  his  removal  from  Halle,  he  was  a  professor 
for  twenty -two  years.  In  the  neuro-metaphysical  doctrines 
of  both  these  great  men,  the  influence  of  WiUis's  views  may 
be  traced,  but  the  purely  metaphysical  bias  of  StahFs  mind 
soon  showed  itself;  for  he  repudiated  all  histological,  ana- 
tomical, and  bio-chemical  researches,  as  worse  than  useless 
in  medicine.  The  foundation  of  his  theory  was  wholly  meta- 
physical; the  organism,  considered  as  matter,  had  no  power 
to  originate  movement ;  it  could  only  be  put  into  motion  by 
an  immaterial  principle, — the  soul;  and   the  laws  of  action 

individuum,  quamdiu  possit,  sese  tueatur:  hsec  divinae  providentise  lex  est,  creaturis 
omnibus  indita,  quae  vinculi  instar  vitae  priiicipia  alioqui  dissipari,  et  ab  invicem 
discedere  apta,  una  coUigat,  et  cui  tanquam  basi  totius  mundi  duratio  innititur,"  &c. 
De  Anima.  Brutorum,  Pars  Physiolog.  cap.  vi. 

'  Prochaska  gives  an  account  of  Willis's  views  on  this  and  other  points,  in  his 
*  Dissertation  on  the  Functions  of  the  Nervous  System,'  chap,  i,  §  vi. 


( 


TRANSLATOR'S  INTRODUCTION.  vii 

of  that  principle  were  alone  to  be  investigated.  According  to 
his  viewSj  the  involuntary,  instinctive,  and  habitual  acts  of  the 
organism,  are  produced  unconsciously  by  the  soul ;  being 
adapted,  they  result  ratione,  or  Xoyw,  but  not  ratiocinioy  or 
Xoyiafxw.  Hoffmann,  on  the  contrary,  seems  to  have  been 
eclectic,  and  to  have  constructed  his  system  by  modifying 
those  of  Sylvius,  Willis,  Wedel,  and  Stahl.  He  recognises  a 
sensational  soul,  or  anima  sensitivay  as  distinct  from  the  rational 
soul ;  and  an  etherial  fluid,  diffused  throughout  nature,  is  the 
means  by  which  this  soul  acts  on  the  body.  The  blood  receives 
this  ether  from  the  atmosphere ;  it  is  secreted  from  the  blood 
by  the  brain ;  and,  being  transmitted  thence  along  the  nerves, 
the  anima  sensitiva  is  enabled  thereby  to  produce  all  the  in- 
stinctive and  involuntary  acts  displayed  by  animal  organisms. 
The  conservative  and  remedial  powers  manifested  by  the  latter, 
which  Stahl  attributed  to  the  soul,  Hoffmann  considered  to  be 
a  law  of  life,  seated  in  the  general  organisation,  as  Willis  did 
before  him.  He  distinguished  the  nervous  tissue  from  the 
mus(5ular,  and  attributed  the  motive  power  of  the  former  to  a 
vis  nerve  a,  of  the  latter  to  a  vis  insita. 

Professor  Juncker,  the  disciple  and  successor,  at  Halle,  of 
Stahl,  and  to  whom  Unzer  attached  himself,  was  the  contem- 
porary of  Hoffmann,  and  therefore,  in  some  respects,  the 
antagonist.  Unzer  seems  to  have  attached  himself  to  his 
master  with  youthful  enthusiasm,  and  to  have  defended  the 
Stahlian  doctrines,  at  the  outset  of  his  literary  career,  rather 
from  feeling  than  conviction.  Perhaps  he  was  influenced  by 
the  doctrines  of  Hoffmann  unconsciously  to  himself; — it  is 
certain  that,  imbued  with  the  same  spirit  of  eclecticism,  he 
quickly  abandoned  the  Stahlian  system  and  method  of  phi- 
losophising, to  investigate  the  phenomena  of  life  and  mind  by 
anatomical  and  physiological  researches.  During  the  time  that 
he  was  a  student,  and  subsequently,  general  and  histological 
anatomy  and  experimental  physiology  were  assiduously  culti- 
vated, and  every  year  some  interesting  experiment  or  discovery 
was  made.  It  was  then,  or  a  few  years  previously,  that 
Lancisi,  Valsalva,  Pacchioni,  Baglivi,  Santorini,  Morgagni, 
and  Spallanzani  flourished  in  Italy, — Winslow  and  Vicq  d'Azyr 
in  France, — Albinus  in  Holland, — and  Lieberkiihn,  Haller, 
(his  distinguished  pupils,)  and  Sommerring  in  Germany  ;  while 


viii  TRANSLATOR'S  INTRODUCTION. 

Cowper,  Cheselden,  and  the  Monros,  laboured  in  Great  Britain. 
There  were  others,  who  made  the  structure  and  functions  of 
the  nervous  system  their  special  study, — as  Kriiger,  Wrisberg, 
Meckel,  Lobstein,  Walther,  de  Asche,  &c. ;  and  thus,  every 
year,  new  facts  and  opinions  were  brought  before  the  eclectic 
intellect  of  Unzer,  and,  every  year,  he  extended  and  perfected 
his  views.  John  Gottlieb  Kriiger  was  a  popular  professor  at 
Halle,  the  native  place  and  alma  mater  of  Unzer,  and  he, 
Haller,  and  Alexander  Monro,  appear  to  have  had  the  greatest 
influence  on  his  mind; — Kriiger,  by  his  doctrines  as  to  the 
involuntary  nature  of  purely  sensational  movements ;  HaUer, 
by  his  inquiries  into  the  nature  of  muscular  action ;  and 
Monro,  by  his  researches  into  the  anatomy  and  physiology  of 
the  nervous  system.  The  doctrines  of  Haller  as  to  the  powers 
and  properties  of  the  vis  insita,  he  extended  to  the  whole  class 
of  purely  automatic  movements  excited  by  mere  impressions  on 
the  nerves  or  nervous  centres;  the  doctrines  of  Kriiger  he 
adapted  to  the  preceding,  and  to  that  great  class  of  excited 
movements  accompanied  by,  but  not  necessarily  dependent  on, 
sensation :  the  ordinary  metaphysical  doctrines  of  the  day,  as 
propounded  by  Baumgarten,^  were  adapted  to  the  current 
physiology  of  the  cerebrum  ;  and,  finally,  with  all  were  incorpo- 
rated the  doctrine  of  Willis  and  Hoffmann,  as  to  the  nature  and 
seat  of  the  conservative  and  curative  powers  of  the  organism. 

Thus,  after  twenty-five  years  had  been  devoted  to  his  subject, 
Unzer  gave  to  the  world  his  system  of  physiological  meta- 
physics. He  lived  and  wrote  far  in  anticipation  of  his  age  and 
his  contemporaries.  That  which  he  established  hypothetically, 
but  logically,  has  since  been  demonstrated  by  dissection  and 
experiment;  what  he  thought  to  be  only  perceptible  to  the 
eye  of  reason,  has  been  revealed  to  the  eye  of  the  histologist ; 
what  he  discovered,  intuitively  but  speculatively,  has  been  duly 
enrolled  on  the  records  of  science  as  a  proved  thing.  Yet, 
after  the  lapse  of  eighty  years,  much  that  he  advanced  remains 
to  be  duly  appreciated;  and  the  present  age  has  still  to 
acknowledge,  that  his  work  is  a  model  of  psychological  inquiry, 
and  a  mine  of  suggestive  ideas. 

»  The  translation  from  the  Latin  into  German  by  Professor  Meier,  of  Halle  (1766), 
is  the  edition  of  Baumgarten's  *  Metaphysics,  to  which  Unzer  refers  in  his  work. 


TRANSLATOR'S  INTRODUCTION.  ix 

George  Prochaska  was  bom  at  Lospitz,  in  Moravia, 
April  10,  1749.  In  1776  he  graduated  at  Vienna;  in  1778 
he  became  Professor  of  Anatomy  and  Diseases  of  the  Eye,  at 
Prague;  and,  in  1791,  Professor  of  Anatomy,  Physiology,  and 
Diseases  of  the  Eye,  at  Vienna.  In  1805  he  was  appointed  a 
Regierungsrath,  and  died  on  July  17,  1820,  of  hydrothorax 
and  pulmonary  disease,  aged  71.  His  portrait  was  published, 
in  1812,  with  his  ^Disquisitio  Anatomico-physiologica  Organismi 
Corporis  humani.' 

At  the  commencement  of  his  career,  Prochaska  specially 
investigated  the  anatomy  and  physiology  of  the  muscular  and 
nervous  systems ;  and,  throughout  his  whole  life,  endeavoured 
to  elucidate  the  vital  processes.  His  first  essay  was  published 
at  Vienna,  in  1778,  and  entitled,  '  Qusestiones  Physiologicse  de 
Viribus  Cordis,^  and  was  followed,  in  the  same  year,  by  ^  De 
came  musculari;  Tractatus  Anatomico-physiologicus.'  In  1779 
he  published  a  histological  essay,  entitled  '  De  Structura 
Nervorum ;  Tractatus  Anatomicus  :'  and  this  was  followed  by 
his  'Adnotationes  Academicse.^  The  first  fasciculus,  published 
in  1780,  contained  anatomical  observations  (with  plates)  on 
the  wear  of  the  teeth,  and  an  elucidation  of  the  causes  of  the 
second  dentition ;  together  with  a  description,  dissection,  and 
plates,  of  a  human  bicephalous  monster  ;  the  second,  published 
in  1781,  contained  various  contributions  to  pathological  ana- 
tomy, a  description  of  four  monsters,  and  a  commentary  on 
their  mode  of  generation ;  the  third,  published  in  1784,  con- 
tained contributions  to  pathology  and  pathological  anatomy, 
together  with  a  dissertation,  '  De  Functionibus  Systematis 
Nervosi,*  the  translation  of  which  has  been  intrusted  to  me 
by  the  Sydenham  Society.^  In  1797,  he  repeated  the  views  ad- 
vanced in  this  essay,  with  certain  modifications,  in  a  class-book  he 
published,  for  the  use  of  his  pupils,  at  Vienna.^  The  text  of 
the  essay  sufficiently  shows,  that  the  works  of  Unzer  were  well 
known  to  him,  for  not  only  is  direct  reference  made  to  the 
*  Erste  Griinde,'  but  the  doctrines  as  to  the  functions  of  the 

•  This  was  republished,  with  few  alterations,  amongst  the  '  Opera  Minora* 
(Vienna,  1800,)  of  the  author ;  but  the  translation  is  from  the  first  edition. 

'  Lehrsatze  aus  der  Physiologic  des  Menschen,  2  vols.  1797.  A  second  edition 
appeared  in  1802,  and  a  third  in  1810.  This  work  was  also  published  in  Latin,  in 
two  volumes,  under  the  title  of  *  Institutiones  Physiologiae  Humanae,'  1805. 


X  TRANSLATOR'S  INTRODUCTION. 

sensorium  commune  contained  therein  are  but  a  synopsis  of 
the  views  in  Unzer's  great  work.  He  obviously  was  also 
familiar  with  the  views  of  Willis,  of  which  he  gives  a  synopsis. 
In  his  '  Lehrsatze/  (first  edition,)  Prochaska  adopts  the  prin- 
ciple of  a  general  sensorium  commune,  but  subdivides  it  so  as 
to  correspond  with  the  views  of  Willis  as  to  the  existence  of  a 
rational  and  a  corporeal  soul  in  man ;  he  therefore  constitutes 
it  of  two  separate  elements,  namely,  the  sensorium  commune 
of  the  soul,  which  is  seated  in  the  brain  only,  and  reflects 
those  impressions  of  which  we  are  conscious;  and  the  sensorium 
commune  of  the  body,  which  is  seated  in  the  brain,  spinal  cord, 
and  ganglia  and  plexuses  of  the  sympathetic  system.  A 
literal  translation  of  one  or  two  paragraphs  from  this  work 
will  more  distinctly  show  his  relations  to  Willis  and  Unzer. 

'^  XXXV.   The  relations  of  the  vis  nervosa  to  stimuli. 

"  §  1 78.  The  operation  of  the  nervous  system  and  of  its  vis  is  specially 
related  in  this  respect, — that  it  feels  external  impressions  by  means  of 
the  brain,  and  thereupon  causes  adapted  movements  by  means  of  the 
muscles.  The  transition  of  sensation  into  motion  takes  place  according 
to  the  law  of  self-conservation,  written,  as  it  were,  on  the  organisation 
of  the  nervous  system;^  for  sensations  that  are  agreeable,  and  con- 
ducive to  our  preservation,  cause  such  movements  as  are  adapted  to 
retain  the  impression ;  while  movements  result  from  unpleasant  im- 
pressions, such,  that  by  them  the  disagreeable  impression  must  be 
averted  from  us. 

"§  179.  This  transition  of  sensation  into  adapted  movements, 
occurs  partly  with  the  consciousness  of  the  soul,  whereby  it  is  taken, 
as  it  were,  into  counsel,  and  its  will  obeyed  ;  now  these  are  termed  the 
sentient  operations.  In  other  instances,  sensations  pass  into  adapted 
movements  without  the  consciousness  of  the  soul,  and  often  in  oppo- 
sition to  its  will;  and  this  transition  is  termed  simply  the  nerve - 
operations.  Following  out  this  fact,  Unzer  has  divided  sensation  into 
soul-sensation,  or  sensation  with  consciousness ;  and  corporeal  feeling, 
or  sensation  without  consciousness.^  By  this,  and  the  preceding  pro- 
position, the  relations  of  the  vis  nervosa  to  stimuli  can  be  easily 
determined."  ^ 

1  On  the  Functions  of  the  Nervous  System,  chap,  iv,  §  i,  in  Adnotat.  academ. 
Fasc.  iii,  p.  117. 

2  Grundriss  eines  Lehrgebaudes  von  der  Sinnlichkeit  der  thierischen  Korper. — 1 768. 

3  Op.  cit.  p.  113. 


translator's  introduction.  xi 


"  xxxvii.  Function  of  the  common  Sensorium. 

"§  215.  That  point  of  the  nervous  system  is  termed  the  common 
sensorium  (Sensorium  commune),  in  which  external  impressions  meet, 
and  from  which  internal  impressions  are  diffused  to  all  parts  of  our 
body ;  in  which,  consequently,  the  consensus  of  the  nerves  takes  place 
that  is  necessary  to  Life,  and  in  which  external  impressions  are  reflected 
into  internal  impressions,  according  to  the  law  of  self-conservation 
(178),  with,  or  without,  consciousness. 

"§  216.  That  sensorium  in  which  impressions  are  reflected  with 
the  consciousness  of  the  soul,  may  be  termed  the  soul-sensorium  ;  and 
the  other,  the  corporeal  sensorium ;  just  as  Willis  has  already  divided 
it,  into  the  rational  and  the  corporeal  soul. 

"§  217.  The  brain,  only,  is  the  seat  of  the  soul-sensorium;  the 
seat  of  the  body-sensorium  is  the  brain,  spinal  cord,  and  (as  all  obser- 
vation shows)  the  ganglia  and  plexuses  of  the  nerves.  That  external 
impressions  can  also  be  reflected  in  the  brain,  without  conscious- 
ness, is  shown  by  the  involuntary  convulsions  of  voluntary  muscles. 
Monsters,  born  without  brain  and  spinal  cord,  and  which  live  up  to 
the  moment  of  birth,  show  that  the  consensus  of  the  nerves  necessary 
to  this  form  of  life,  imperfect  though  it  be,  may  take  place,  and  that 
there  may  be  a  corporeal  sensorium  independently  of  the  brain  and 
spinal  cord,  and  which,  consequently,  must  be  constituted  by  the 
plexuses  and  ganglia  of  the  nerves.  The  movements  observed  to  take 
place  on  irritating  the  nerves  of  a  headless  frog,  and  seen  also  in 
decapitated  men,  prove  the  same  thing.  The  sympathetic  nerve  ap- 
pears likewise  to  reflect  its  impressions  in  its  ganglia  and  plexuses, 
without  the  consciousness  of  the  soul. 

"  §  218.  In  accordance  with  this  consensus  of  the  nerves,  as  well 
in  the  brain  as  in  the  spinal  cord,  ganglia,  and  plexuses,  the  operation 
of  a  stimulus  is  not  limited  to  the  nerves  immediately  irritated,  but  is 
extended  to  distant  nerves,  in  known  or  unknown  connection  with  the 
irritated  nerves  ;  and  this  is  demonstrated  by  innumerable  examples  of 
consensus  of  nerves  [consensus  nervorum],  as,  for  instance,  the  irri- 
tation in  the  pregnant  uterus  often  causes  nausea,  vomiting,  headache, 
toothache,  &c. 

"  §  219.  Both  the  soul-sensorium  and  body-sensorium  operate  ac- 
cording to  the  law  of  self-conservation  (178),  a  truth  which  may  be 
illustrated  by  numerous  examples.  For  instance,  the  irritation  or 
impression  of  too  strong  a  light  goes  to  the  optic  nerve,  from  whence 
it  can  only  get  at  the  ciliary  nerves  through  the  brain,  and  induce 


xii  TRANSLATOR'S  INTRODUCTION. 

contraction  of  the  pupil,  so  as  to  exclude  the  too  vivid  light  from  the 
eye,  and  obviate  its  unpleasant  impression." 

Prochaska  then  adds  other  illustrations,  which  he  explains 
in  a  similar  manner;  namely,  the  closure  of  the  eyelids  when 
a  finger  is  brought  near  to  the  eye ;  the  act  of  sneezing,  from 
irritation  of  the  nostrils ;  of  coughing,  from  irritation  of  the 
bronchi;  the  increased  action  of  the  heart  and  arteries,  from 
the  presence  of  a  poison  or  other  irritating  materies  in  the 
blood,  "  whereby  the  blood  is  circulated  more  rapidly,  and  all 
the  powers  of  those  structures  are  called  forth,  as  it  were,  to 
diminish  the  irritation,  to  render  it  harmless,  or  to  expel  it 
from  the  organism.^^      He  then  proceeds : 

"  §  220.  These  adduced  examples  sufficiently  show  that  the  sen- 
sorium  commune  acts,  in  all  its  operations,  strictly  according  to  the 
law  of  self-conservation,  and  that  it  is  ever  studious  to  do  the  best  for 
our  preservation,  so  long  as  it  is  not  prevented  by  disease,  or  the 
cessation  of  vital  action ;  in  which  cases  it  is  seen  that  it  is  thrown 
into  confusion,  and  no  longer  always  takes  the  best  steps  for  the  cure 
of  disease  ;  often,  indeed,  proving  itself  altogether  incompetent  thereto ; 
just  as  a  delirious  or  idiotic  person,  from  the  disordered  state  of  his 
soul-sensorium,  neither  knows  what  is  necessary  to  his  preservation, 
nor  does  it."  ^ 

In  his  details,  we  find  Prochaska  repeating  several  of  the 
views  of  Unzer,  although  they  are  mixed  up  with  opinions 
derived  from  the  writings  of  others,  or  his  own  researches. 
He  thus  notices  an  important  distinction  between  the  two 
great  classes  of  involuntary  and  voluntary  acts : 

**  §  175.  Nevertheless,  this  need  for  rest  seems  only  to  be  a  charac- 
teristic of  the  nerves  which  are  subordinate  to  the  will,  and  not  to  the 
involuntary,  which  have  to  provide  for  the  motion  of  the  heart,  respi- 
ration, and  digestion ;  and  whose  vis  nervosa  is  active,  without  inter- 
mission, during  the  whole  of  life,  although  it  may  be  weaker  or 
stronger.  Though  it  cannot  be  doubted  that  both  kinds  of  vis  have  a 
similar  origin  (§§  171,  173),  and  are  of  the  same  nature,  still  obser- 
vation shows,  that  the  one  belongs  to  the  will,  the  other  is  involuntary ; 
that  the  former  is  exhausted  by  sensation  and  motion,  and  requires 
rest  and  repose  ;  with  the  latter,  the  contrary  takes  place  ;  and,  finally, 
that  the  two  kinds  of  vis  are  independent  of  each  other.     This  dis- 

'  Op.  cit. 


TRANSLATOR'S  INTRODUCTION.  xii 

tinctoess  and  independence  of  the  voluntary  and  involuntary  vis  nervosa 
is  shown,  not  only  in  sleep,  but  also  in  apoplexy,  when  the  voluntary 
vis  nervosa  is  quite  arrested,  but  the  involuntary  performs  its  duty. 
So,  also,  in  cases  of  fever,  the  voluntary  vis  nervosa  is  quite  weakened, 
but  the  involuntary  so  much  the  more  active."  ' 

Subsequently  to  the  publication  of  this  work,  Prochaska, 
being  attracted  by  the  singularity  and  novelty  of  the  results  of 
the  experiments  of  Galvani  and  others,  laboured  diligently  to 
elucidate  the  nature  of  the  vital  processes  by  electro-galvanic 
theories  ;  he  also  published  numerous  works,  essays,  and 
observations,  on  physiology,  pathology,  pathological  anatomy, 
diseases  of  the  eye,  &c.  A  list  is  before  me,  supplied  to 
me  by  my  friend  Professor  Marx,  of  Gottingen,  containing  the 
titles  of  twenty-seven  works,  or  papers. 


A  few  explanatory  sentences  are  necessary,  with  regard  to 
the  translations.  The  Council  of  the  Society  having  required 
that  the  two  works  should  be  comprised  in  one  volume,  a 
question  arose  as  to  the  mode  in  which  this  condition  should 
be  accomplished.  It  was  obvious  that  one  of  the  two  must  be 
abridged ;  and  the  work  of  Unzer  being  an  octavo  of  800  pages, 
while  the  tract  of  Prochaska  is  very  short,  it  was  equally 
obvious  that  the  condition  could  only  be  fulfilled  by  abridging 
the  larger.  But  an  abridgment  implies  a  free  translation,  and 
a  free  translation  great  responsibility  on  the  part  of  the 
translator.  This  feeling  of  responsibility  was  not  diminished, 
when,  on  consultation  with  Professor  Marx,  that  accomplished 
scholar,  while  recommending  a  free  translation,  stated  that  the 
antiquated  style,  and  singular  phrases  of  the  work,  rendered  it 
somewhat  difficult  for  even  the  modern  German  physician  to 
comprehend. 

The  plan  I  finally  resolved  upon  was  this : — To  give  a  full 
and  literal  translation  of  the  ^  Dissertation^  of  Prochaska ; 
omitting  only  the  Appendix,  which,  being  on  a  controversial 
topic,  (that  the  brain  and  nerves  are  made  up  of  globules,)  and 

•  Op.  cit.  p.  110. 


xiv  TRANSLATOR'S  INTRODUCTION. 

having  reference  to  another  work  published  by  him,  '  De 
Structura  Nervorum/  had  no  immediate  connection  with  the 
dissertation  to  which  it  is  appended.  To  give  as  condensed  an 
abridgment  of  Unzer's  work  as  was  consistent  with  a  due  regard 
to  a  full  and  complete  exposition  of  the  writer's  views,  on  the 
following  principles  : — 1.  To  omit  all  quotations  from  Haller 
and  others,  except  such  as  were  absolutely  necessary  to  under- 
stand the  text.  2.  To  omit  all  controversial  matter,  on  points 
of  secondary  importance.  3.  To  leave  out  all  anatomical  and 
physiological  descriptions  and  disquisitions,  not  of  an  original 
character,  and  to  be  found  in  the  standard  works  of  the  day. 
4.  To  condense,  wherever  that  could  be  done  without  injury 
to  the  meaning  of  the  author,  and  to  avoid  numerous  repe- 
titions, which  he  thought  to  be  necessary  to  the  perfect  com- 
prehension of  his  views.  5.  Where  the  sense  was  doubtful, 
to  give  a  literal  translation.  6.  To  remodel  and  freely  trans- 
late various  words  and  phrases  used  by  the  author  in  a  special 
sense.  That  the  critical  reader  may  be  in  a  position,  however, 
to  judge  for  himself  on  this  point,  I  have  subjoined  a  glossary 
of  these  words  and  phrases,  and  a  reference  to  the  paragraphs, 
to  which  I  have  appended  my  reasons  for  the  adoption  of  the 
English  terms.  These  have  only  been  decided  upon  after  the 
most  mature  deliberation,  and  with  careful  reference  to  other 
writings  of  Unzer ;  I  therefore  venture  to  express  a  hope,  that 
the  reader  will  not  criticise  hastily,  nor  without  a  reference 
to  the  entire  scope  and  intent  of  the  work. 

T.  L. 


i 


XV 


List  of  German  words  and  phrases  used  by  Unzee,  and  their  English 
synonymes.  {The  figures  refer  to  paragraphs,  to  which  explana- 
tory notes  are  added  by  the  Translator.) 

Paragraph 

6.  Ein  Thierischer  K'drper — an  animal  organism,   or,  organism, 
simply. 

6,  10.   Vorstellungskrafty  and   Vorstellungskraft   der  Seele — the 
conceptive  force ;  the  sentient  force  ;  mind. 

6,25.   Vorstellung — act  of  mind  ;  conception. 
6,  25.  Thierische  Seelenkrafte—diXi\v[\?i\.  sentient  forces;  cerebral 
forces. 

6,  31.  Thierische  JTra/ife— animal  forces ;  vis  nervosa. 
6.  Seelenwirkungen — (actiones  aniince)   mental,  sentient,   or  sen- 
sational actions ;  actions,  simply. 

9.  Thierischen  Maschinen — the  nervous  system. 
27.  Naturlich — Physical,  corporeal,  organic,  natural. 
27.  Eigenm'dchtig,  Selbstth'dtig — arbitrary,  spontaneous. 
3 1 .  Thierische  Kr'dfte  der  Nerven,  Nervenkrdfte — vis  nervosa. 
31.  Sinnlicher   Eindruck — sensational   or   sense-like   impression; 
impression,  simply. 

31,  66,  262,  403.  Sinnlich — sensational,  sense-like,  impressional. 

32.  Sinnlichkeit — property  of  respondence  to  impressions  ;  sense- 
likeness  ;  impressibility. 

88.  Triebfedern  des  Gemiiths — excitants  of  the  feelings. 

121.  Inner e    sinnliche   Eindriicke — internal    impressions,    cerebral 
impressions. 

122,  359.  Inner e  sinnliche.  Eindriicke  der   Vorstellungen — concep- 
tional  impressions. 

191.  Der  naturlichen  Verrichtung  gem'dss — connatural. 

191.  Der  naturlichen  Verrichtung  nicht  gem'dss — contranatural. 

283.   Willkiihrlich — volitional,  sensational-voluntary,  voluntary. 

335.  Freiwillig — free-will  (adjectively). 

6,  349.  Beseelte,  and  Unbeseelte — sentient,  insentient. 


PRINCIPLES  OF  A  PHYSIOLOGY 


OF    THE    PROPER 


ANIMAL  NATURE  OF  ANIMAL  ORGANISMS. 


BY 


JOHN  AUGUSTUS  UNZER. 


PRINCIPLES    OF    PHYSIOLOGY. 


PREFACE. 


We  observe,  that  in  a  corpse,  purely  physical  and  mechanical 
forces  imitate  the  processes  of  our  bodies,  and  can  originate 
that  motion  in  its  machines,  of  which  in  virtue  of  their  structure 
and  composition  they  are  capable.  The  fluid  portions  are  com- 
bined and  separated  according  to  the  laws  of  gravity,  of  the 
power  of  attraction  and  repulsion,  and  remain  in  equilibrium 
according  to  the  laws  of  hydrostatics.  When  an  anatomist 
injects  the  vascular  system,  it  is  made,  by  merely  mechanical 
forces,  to  repeat  in  some  degree  its  former  natural  function, 
according  to  the  laws  of  hydraulics.  The  muscle,  the  fibres 
which  are  contracted  by  cold,  keeps  the  limb  in  the  same  posi- 
tion in  which  it  had  placed  it,  and,  by  a  mere  mechanical  action, 
the  arteries  of  a  corpse  contract  and  compress  the  finger  when 
pushed  into  them,  &c. 

These  purely  physical  and  mechanical  forces  are  not  the  pecu- 
liar forces  which  usually  move  the  living  animal  organism  in  its 
natural  condition,  but  there  are  other  forces  operating  in  it,  ac- 
cording to  a  fixed  arrangement,  and  according  to  laws  altogether 
different  from  the  physical  and  mechanical  laws  already  known; 
and  it  is  through  these,  that  the  organism  performs  those 
natural  processes  which  its  structure  renders  it  capable  of. 
That  stimulus,  which  excites  no  movement  in  the  lifeless  heart, 
or  in  the  perfectly  dead  muscle,  or  in  the  arteries  of  a  corpse, 
in  the  natural  or  living  condition  keeps  up  the  circulation, 
changes  the  pulse  in  the  arteries,  and  moves  the  muscles  and 
limbs.  Those  peculiar  motive  powers,  which  give  the  living 
organism  the  advantage  over  the  corpse,  although  they  may 
co-operate  with  the  purely  physical  and  mechanical  forces  com- 
mon to  both,  T  term  the  proper  animal  forces,  and  they 
communicate  to  the  living  animal  that  nature  which  I  call  the 

PROPER  ANIMAL  NATURE  OF  ANIMAL  ORGANISMS. 


4  PRINCIPLES  OF  PHYSIOLOGY. 

The  ordinary  science  of  physiology  considers  the  forces  of 
animal  organisms  in  their  natural  condition,  and  as  they  act 
together  in  connection  with  each  other,  but  without  distin- 
guishing the  simply  physical  and  mechanical  from  the  proper 
animal  forces.  This  presupposes  that  we  know  the  laws  accord- 
ing to  which  each  of  these  peculiar  forces  acts  separately ;  and, 
indeed,  as  to  the  physical  and  mechanical,  whose  laws  are  known, 
there  is  in  general  no  difficulty.  The  physiological  w^orks  of 
Haller  teach  us,  in  a  manner  almost  impossible  to  be  surpassed, 
the  mechanism  of  all  parts  of  the  animal  body,  of  which  the 
structure  developes  the  functions  according  to  the  laws  of  me- 
chanics, hydrostatics,  hydraulics,  optics,  acoustics,  &c.  But  do 
we  know  those  laws  by  which  the  proper  animal  forces  govern 
the  body  when  acting  separately  from  the  physical  and  me- 
chanical, and  independently  of  them  ?  Truly,  no  !  or  at  least 
very  imperfectly.  The  thoughts  and  desires  are  animal  moving 
forces  of  the  animal  organism.  But  do  we  at  this  moment 
know  anything  of  the  laws  by  which  these  forces  regulate  their 
appropriate  organs?  or  have  we  hitherto  troubled  ourselves  to 
observe  the  operation  of  these  laws  in  each  particular  class  of 
ideas  and  desires  ?  We  have  disputed  stoutly  enough,  whether 
the  soul  be  matter  or  brain;  whether  thought  be  an  electric  fire 
or  a  movement  of  the  vital  spirits ;  whether  souls  and  bodies 
exercise  a  real  or  an  ideal  influence  on  each  other ;  whether  souls 
form  their  bodies,  or  whether  they  are  diffused  through  them, 
or  dwell  only  in  the  head ;  whether  an  instinctive  impulse  or 
a  passion  belongs  to  the  body  or  the  soul ;  or  whether  the  vital 
spirits  be  elastic  or  inflexible,  electrical  or  ethereal,  &c.  All  these 
inquiries  will  remain  for  ever  inscrutable  mysteries,  and  do  not 
belong  to  our  subject;  they  can  remain  altogether  uninvestigated 
without  any  disadvantage  to  the  real  usefulness  of  theoretical 
medicine,  but  we  have  pursued  them  with  profitless  diligence, 
and  have  done  our  best  to  confuse  them  more  and  more.  How 
much  have  we  effected  in  resolving  questions  useful  to  our  art, 
as,  for  example,  in  determining  by  what  laws  the  mind  moves  the 
machinery  of  the  animal  organism?  Under  what  circumstances 
the  nerves  excite  sensation  ?  Under  what  the  sensation  becomes 
an  animal  moving  force,  so  as  to  move  this  or  that  limb,  in  such 
a  manner  and  not  otherwise?  After  what  laws  the  imaginations, 
the  conceptions  of  the  understanding,  pleasure,  pain,  the  in- 


PREFACE.  5 

stincts,  the  passions,  and  the  will,  impel  various  portions  of  the 
animal  to  perform  the  actions  intended  by  the  Creator  in  uniting 
the  machines  with  a  thinking  force  ?  If  the  doctrines  of  the  first 
part  of  this  work  (which  are,  however,  an  imperfect  sketch  of 
the  elements  of  the  science  of  the  laws  which  regulate  the  in- 
fluence of  the  mind  on  the  body)  be  compared  with  what  our 
physiologists  have  hitherto  produced,  it  will  be  seen  that^  as  yet, 
this  whole  science  has  been  in  some  degree  a  waste  field. 

As  regards  the  other  animal  motive  forces,  with  the  exception 
of  the  conceptions,  there  scarcely  was  a  notion  until  the  time 
of  Haller,  who  at  least  pointed  out  their  existence ;  and  yet  the 
doctrine  of  irritability,  which  that  great  man  has  taught,  com- 
prises only  a  portion  of  those  animal  motive  forces  which  are 
independent  of  the  mind,  as  the  whole  of  the  Second  Part  of 
this  work  will  sufficiently  prove.  The  laws  of  action  of  these 
forces  have  not  as  yet  been  illustrated  by  any  one,  and  the  first 
elements  thereof  which  this  Second  Part  contains,  exhibit  to  us 
a  large  and  fertile  branch  of  science  with  which  medical  art  can 
and  must  ultimately  be  enriched,  if  Physiology — that  science 
which  has  to  elucidate  the  mechanism  of  animal  bodies  com- 
pounded of  such  multifarious  motive  forces — is  ever  to  be  freed 
from  at  least  existing  defects.  It  was  always  premature  to 
attempt  to  explain  the  natural  actions  of  the  animal  body 
(which  are  brought  about  by  the  common  operation  of  physical, 
mechanical,  and  animal  forces),  by  the  laws   of  physics   and 

I  machines,  so  long  as  there  were  no  principles  by  which  to 
judge  of  the  co-operation  of  the  proper  animal  forces;  but 
especially  premature  to  attempt  their  elucidation  by  the  aid  of 
untenable,  imperfect  opinions,  and  inadmissible  suppositions, 
when  the  principles  of  physics  and  mechanics  were  found  to  be 
insufficient.  Thus  Stahl  erred,  who  knew  well  the  necessity 
there  was  for  the  co-operation  of  the  animal  forces  with  the 
mechanism  of  the  animal  body,  because  it  did  not  occur  to  him, 
that  it  possessed  other  animal  motive  forces  besides  the  influ- 
ence of  the  mind  on  the  body.  So  also  the  mechanical  phy- 
sicians erred,  who  would  deduce  all  natural  phenomena  from 
the  physical  and  mechanical  forces  of  the  elements  of  the  animal 
organism,  and  absolutely  deny  the  manifest  influence  of  the 
mind  and  of  the  other  purely  animal  forces  on  animal  acts. 
So  at  this  moment  physiologists  err,  when  they  exclude  the 


6  PRINCIPLES  OF  PHYSIOLOGY. 

co-operation  of  the  auimal  forces,  in  actions  wliich  they  attempt 
to  explain  mechanically;  or,  when  they  think  that  that  which 
cannot  be  explained  mechanically,  must  necessarily  be  attributed 
to  mind;  or  when  they  would  elucidate  the  animal  motive 
forces  by  the  laws  of  natural  philosophy  and  mechanics,  and 
never  know  how  to  determine  the  forces,  laws,  and  connection, 
by  and  through  which  the  moving  springs  of  animal  life,  so 
totally  different,  regulate  the  wonderful  machines  of  the  living 
organism. 

This  defect  in  Physiology  becomes  continually  the  more  ap- 
parent, now  that  inquiry  has  commenced  into  the  diseases 
of  the  proper  animal  forces  and  their  cure ;  and  the  present 
appears  to  be  the  proper  time  to  supply  it  by  carefully  con- 
sidering proper  animal  nature  in  its  uncomplicated  state,  and 
distinctly  deducing  the  laws  by  which  the  animal  forces,  as 
such,  act  in  animal  organisms.  The  pathology  of  the  mind, 
or  of  the  nervous  system,  and  of  other  diseases  of  the  animal 
forces,  ought  to  demonstrate  to  us  the  deviations  of  the  animal 
forces  from  their  proper  laws ;  but  what  can  be  really  expected 
from  pathology  so  long  as  we  have  no  distinct  idea  of  those 
laws,  and  are  even  ignorant  of  the  animal  forces  themselves  ? 
This  knowledge  will  never  be  rendered  in  any  degree  perfect, 
if  the  operations  of  the  proper  animal  forces  are  not  considered 
quite  separately  and  by  themselves,  and  the  laws  studied  by 
which  they  ensue  in  animal  organisms  independently  of  the 
physical  and  mechanical  forces  in  operation  at  the  same  time. 

From  these  considerations  originated  my  idea  of  a  physiology 
of  the  proper  animal  nature  of  animal  organisms,  of  which  the 
present  work  supplies  the  first  principles,  and  by  which  the  phy- 
siology of  the  whole  animal  economy,  which  hitherto  has  been 
extremely  deficient  in  these  principles,  may  for  the  future  be 
corrected,  completed,  and  extended.  Although  I  do  not  overlook 
the  imperfection  of  my  own  plan,  and  have  never  considered  it 
to  be  so  well  carried  out,  as  to  be  satisfied  with  my  performance, 
still  I  thought  it  deserved  to  be  made  public  even  in  its  imper- 
fect state ;  since  it  would,  for  the  first  time,  make  known  the 
utility  and  necessity  of  separating  the  proper  animal  physiology 
from  the  general  physiology  of  the  entire  animal  economy ;  of 
which  hitherto  no  one  seems  to  have  ever  thought.  If  I  am 
not  deceived  in  my  expectations,  some  better  student  of  animal 


PREFACE.  7 

nature  (and  there  are  at  present  many  with  whom  I  am  not 
to  be  placed  in  comparison),  being  stimulated  by  this  first  essay, 
will  project  and  carry  out  a  much  more  perfect  system ;  to  me 
it  will  be  a  matter  of  satisfaction  that  I  had  the  honour  of 
affording  the  first  ideas ;  and  if  I  might  flatter  myself  that  such 
an  one  would  also  publish  a  special  pathology  of  the  proper 
animal  nature,  according  to  these  principles  of  a  special  phy- 
siology, I  should  certainly  think  myself  fortunate  in  having  laid 
the  foundation  for  so  great  an  improvement  of  our  art.  Any 
one  who  is  acquainted  with  the  present  condition  of  medical 
science,  and  has  at  all  attempted  to  remedy  the  striking  defects 
in  the  theory  of  proper  animal  nature,  must  be  aware  it  was 
necessary  to  any  degree  of  progress  that  these  first  steps  should 
be  taken. 

I  will  now  briefly  describe  the  plan  of  my  work. 
The  primary  seat  of  the  animal  forces  is  in  the  so-called 
proper  animal  machines,  namely,  the  brain  with  its  animal  spirits, 
together  with  the  nerves,  through  which  the  latter  are  com- 
municated to  the  mechanical  machines.      I  originally  intended 
to  have  given  a  general  division,  containing  a  general  account 
of  the  animal  machines,  and  their  structure  and  moving  forces, 
in  which  I  should  have  included  an  anatomical  description  of 
the  brain  and  nerves ;  but  I  determined  to  omit  this  part,  so 
as  not  with  useless  prolixity  to  extend  a  simple  sketch,  inas- 
much as  this  description  of  the  animal  machines  is  already  to 
be  found  as   complete  as   possible   in  the  fourth  volume  of 
Haller's  larger  work  on  Physiology,  .and  1  have  nothing  to  add 
to  it.      I  have,  however,  made  extracts  from,  and  given  reference 
to,  the  most  indisputable   statements   with  reference  to  the 
animal  machines  and  properties  (most  of  which  will  be  noticed 
in  the  following  pages),  and  thus  originated  the  following  plan 
of  a  physiology  of  the  proper  animal  nature  of  animal  bodies. 

Animal  nature  is  the  aggregate  of  the  proper  animal  forces, 
and  the  science  of  these,  uncomplicated,  is  the  physiology  of 
animal  nature.  All  animal  forces  act,  when  untrammelled,  either 
necessarily  in  connection  with  the  mind  of  the  animal,  or  not ; 
and  thus  the  science  is  divided  into  two  great  divisions.  The 
first  treats  of  the  animal  nature  in  its  connection  with  mind, 
that  is,  in  other  words,  with  reference  to  the  animal-sentient 


8  PRINCIPLES  OF  PHYSIOLOGY. 

forces ;  but  the  second^  in  reference  to  the  nerve-forces^  inde- 
pendently of  the  mind;  out  of  these  a  third  division  arises, 
which  describes  the  animal  nature  as  an  independent  whole, 
compounded  of  these  two  animal  forces. 

The  First  Part  is  devoted  exclusively  to  the  animal-sentient 
forces  of  the  animal  machines  above-mentioned ;  and  an  epitome 
of  the  general  doctrines  applicable  to  the  brain  and  nerves, 
and  to  the  animal  spirits  and  their  general  properties,  is 
concisely  given  in  the  First  Chapter  and  the  beginning  of 
the  Second.  The  animal- sentient  forces  are  considered  with 
reference  to  their  action,  in  two  ways ;  namely,  partly  per  se, 
as  they  themselves  act  in  the  animal  machines, — the  brain 
and  nerves, — and  partly  in  reference  to  their  influence  on  the 
mechanical  machines,  with  which  the  nerves  are  incorporated. 
These  constitute  the  contents  of  the  Second  and  Third  Chapters ; 
to  these  may  be  added  the  Fourth,  in  which  the  connection  of 
the  conceptive  force  and  the  animal  moving  forces,  or  in  other 
words,  of  mind  and  body,  is  generally  set  forth. 

The  whole  philosophy  of  the  reciprocal  influence  of  body 
and  mind,  as  laid  down  in  our  works  on  Physiology,  is  as  yet 
imperfect,  being  without  true  principles,  and  partly  confusedly, 
partly  erroneously,  propounded.  Probably  this  has  arisen  from 
the  little  acquaintance  of  physicians  with  theoretical  philosophy 
except  physics,  and  still  less  with  psychology;  as  if  mental 
philosophy  were  not  necessary  to  the  science  of  the  nature  of 
man^s  organism.  Nevertheless,  our  physiologists  have  only 
worked  at  the  useless  subtilties  mentioned  before,  and  the 
only  useful  knowledge  which  they  teach  as  to  the  union  of 
body  and  soul,  refers  to  the  external  sensations,  and  also  to 
the  imaginations  and  passions.  There  are  others  who  aspire, 
with  Bonnet,  rather  to  analyse  the  different  mental  faculties 
by  means  of  movements  in  the  brain,  of  which  we  are  totally 
ignorant,  than  to  study  what  is  peculiarly  within  the  sphere  of 
the  physician,  and  investigate  the  laws  according  to  which  the 
faculties  act  in  the  body;  which,  nevertheless,  can  be  easily 
learnt  by  observation,  if  people  would  only  cease  from  the 
attempt  to  deduce  them  from  inscrutable  principles. 

These  doctrines  present  a  somewhat  different  appearance  in 
the  present  work.  I  have  endeavoured  to  define  the  laws  by 
which  the  various  faculties  of  the  mind  operate  either  through 


PREFACE.  9 

the  animal  motive  forces,  or  by  and  through  themselves  in  the 
entire  mechanism  of  the  body.  This  is  peculiarly  important 
with  reference  to  the  sensations,  and  the  instincts  and  passions, 
and  of  consequence  in  every  department  of  medical  science. 

In  the  Second  Part,  the  nerve-forces  are  treated  of  so  far 
as  they  act  independently  of  the  mind.  It  is  shown  that, 
besides  the  animal-sentient  forces  of  the  brain,  there  are  only 
two  kinds  of  forces  of  the  nerves  which  act  in  the  body  as 
animal- motive  forces,  namely,  the  sense-like  [sinnlich]  im- 
pressions, which  are  divided  into  internal  and  external  (Part  II, 
Chap.  I).  These  two  kinds  of  impressions  are  considered  in 
the  Second  and  Third  Chapters  respectively;  and  in  the  Fourth, 
their  relations  to  the  mental  forces  are  elucidated.  Modern 
physiologists,  whose  names  Europe  knows  and  honours, — Haller, 
Zimmermann,  Whytt,  and  Oeder, — have  rendered  much  ser- 
vice to  this  department  of  physiology  by  contributing  materials 
thereto.  Haller  has,  indeed,  begun  to  trace  out  the  plan  of 
this  new  department,  which  certainly  did  not  exist  before  him ; 
but  there  he  has  stopped.  I  have  ventured  to  extend  this 
outline,  with  the  hope  of  inducing  able  men  to  complete  it. 
The  most  important  progress  that  has  been  accomplished  in 
this  matter,  consists  in  the  following :  I  have  defined  the  two 
kinds  of  impressions,  and  the  entirely  diff'erent  laws  by  which 
they  move  the  body,  without  having  recourse  to  the  hypothesis 
of  vital  spirits  as  a  motive  power;  for  these  sense-like  [sinnlich] 
impressions  can  be  considered  simply  as  phenomena,  and  their 
laws  of  action  discovered  without  a  knowledge  of  their  nature. 
I  have  derived  primarily  from  the  nerves,  that  motive  force  of 
the  external  impression,  which  Haller  assigned  to  the  muscular 
fibres  under  the  designation  of  irritability,  but  denied  it  to  be 
a  property  of  the  nerves ;  I  have  demonstrated  the  deflection 
[declination]  and  reflection  of  the  impressions  in  the  nerves, 
whereby  many  phenomena  of  the  animal  economy,  hitherto 
inexplicable,  can  be  understood;  and  I  have  shown  how  the 
vis  nervosa  is  sufficient  of  itself  to  develope  those  movements 
in  bodies,  which  were  formerly  attributed  to  the  influence  of 
the  mind  or  soul,  and  vice  versa. 

I  have  added  the  Third  Part  to  describe  the  economy  of  the 
animal  forces  in  general,  and  trace,  as  it  were,  the  course  of 
life  in  animal  nature.      The  First  Chapter  contains  a  sketch 


10  PRINCIPLES  OF  PHYSIOLOGY. 

of  animal  nature ;  but  since  every  animal  is  not  provided  with 
those  animal  forces,  which  the  most  perfect  possess,  in  the 
Second  Chapter  the  different  genera  of  animals  are  classified 
from  the  irrational  to  the  rational.  I  have  taken  this  oppor- 
tunity to  state  reasons  for  the  possibility  and  existence  of 
animals  without  souls.  The  other  Chapter  of  this  Part  treats 
of  the  origin,  life,  maturity,  decline,  and  death  of  animal  nature. 
Hitherto  we  have  only  had  scattered  notices  of  these  various 
matters  in  our  physiological  works,  or,  at  most,  of  the  peculiar 
mechanism  of  generation ;  and  the  growth,  decline,  and  death 
of  animal  organisms  have  only  been  considered,  without  sepa- 
rating that  which  has  reference  to  the  proper  animal  nature 
from  the  other  portions  of  the  subject.  In  this  Part,  the  most 
interesting  chapters  are  the  last  three  on  the  periods  of  animal 
life,  the  system  of  animal  forces,  and  on  animal  death;  these 
have  a  wide  and  useful  application  to  the  pathology  of  proper 
animal  nature.  I  have  adopted  a  short,  simple,  dry,  and  me- 
thodical plan  of  writing,  that  the  reader  may  continually  be 
enabled  to  examine  and  thoroughly  understand  the  truth  of 
the  views  and  principles,  both  in  the  abstract  and  in  their 
application, — the  connection  and  consequences  of  the  doctrines, 
— and  the  whole  system  of  animal  physiology.  I  have  avoided, 
as  much  as  possible,  all  medical  researches  of  a  confusing,  imper- 
fect, or  merely  subtle  character,  and  all  hypotheses ;  or,  at  least, 
have  made  no  use  of  the  latter  in  establishing  my  own  prin- 
ciples ;  for  a  system  of  presupposed  ideas,  which  in  a  short 
time  must  itself  be  set  aside,  would  not  be  well  received  as  a 
commencement  in  this  new  division  of  medical  science,  instead 
of  true  natural  laws,  the  result  of  accurate  observations. 

As  to  the  doctrines  themselves,  and  the  various  controversies 
that  have  already  arisen  concerning  them,  I  can  only  most 
sincerely  beg  the  reader  to  examine  them  with  the  greatest 
rigour;  and  if  the  author  of  a  work  so  extensive,  and  attempted 
for  the  first  time  from  the  present  point  of  view,  have  described 
anything  untruly,  indistinctly,  or  incorrectly,  or  have  omitted 
anything,  not  to  blame  him  too  harshly.  The  justice  of  such 
an  exculpation  can  only  be  understood  by  those  who  have 
undertaken  to  write  on  such  a  subject,  and  experienced  the 
difficulty  of  avoiding  errors  and  omissions.  I  desire  no  in- 
dulgence for  the  doctrines  themselves.    Truth  has  been  sought. 


PREFACE.  11 

and  Avhere  I  have  not  found  it,  I  will  endeavour  to  find  it. 
Consequently,  I  can  only  ask  a  mature  consideration  for  those 
passages  of  my  principles  which  are  open  to  controversy,  or 
suspected  of  error.  I  am  confident  that  there  are  many  errors, 
and  still  more  defects,  in  this  work ;  but  I  have  thought  much 
and  written  little,  and  I  can  therefore  ask  that  the  critics  shall 
think  before  they  controvert.  If  any  one  would  reply  to  any 
of  the  doctrines,  whether  for  the  purpose  of  proving  them,  or 
limiting  them,  or  correcting  misunderstandings,  or  refuting  an 
error,  I  will  absolutely  act  only  as  the  interests  of  truth  re- 
quire, and  as  an  indifi'erent  reader,  who  has  no  feeling  for 
personalities,  whether  they  be  civilities  or  insults,  and  to 
whom  no  objecter  exists,  but  only  an  objection.  It  is  my 
general  rule  to  answer  no  attack  on  my  writings,  still  less  on 
my  character  and  conduct;  and  I  willingly  permit  many  a  one 
to  use  this  advantage,  who  may  think  me  a  very  troublesome 
person  to  attack,  and  who  I  would  not  for  the  world  should 
know  what  I  thought  on  the  matter.  Why  should  not  every 
one  be  at  liberty  to  criticise  another  as  much  as  he  likes,  if  he 
thinks  him  of  sufficient  importance  ?  And  why  should  the 
other  be  bound  to  answer  him,  if  he  do  not  think  it  of  suffi- 
cient importance  to  entertain  the  public  with  his  justification  ? 
It  is  seldom  that  controversial  writings  are  of  any  great  service 
to  science ;  but  it  is  difficult  to  avoid  explanations  with  a  newly- 
invented  science,  only  a  sketch  of  the  first  principles  of  which 
I  has  appeared,  not  supplied  with  ample  illustrations,  without 
any  of  the  advantages  of  an  introductory  discourse,  and  with 
the  disadvantages  of  unusual  terms  and  expressions,  which  at 
first  always  excite  subordinate  ideas  that  lead  the  reader  away 
from  the  meaning  of  the  author :  thus  explanations  may  not 
only  be  required,  but  cannot  be  withheld  without  disadvantage 
to  the  reception  of  the  science  itself. 
I  must  especially  ask  the  reader^ s  forgiveness  with  regard  to 
these  unusual  terms  and  phrases.  It  will  be  seen  that  they 
were  indispensable  to  an  accurate  exposition  of  the  ideas^ 
without  which  it  would  be  altogether  impossible  to  give  the 
physiology  of  animal  nature  that  first  degree  of  completeness 
which  it  now  possesses.  At  one  time  I  was  not  inclined  to 
seek  unusual  phrases;  but  when,  two  years  since,  I  used  the 
word   "feehng"'   [Gefiihl]   with   an  unusual  meaning,  from  a 


12  PRINCIPLES  OF  PHYSIOLOGY. 

similar  necessity^  in  a  little  work  I  published  on  '  The  Sense- 
likeness  [Sinnlichkeit]  of  Animal  Bodies/  I  found  that  this 
use  of  the  word  with  a  new  meaning  was  of  little  advantage, 
because  the  majority  of  the  critics  dwelt  too  much  on  the  ex- 
pression itself,  and  hardly  noticed  the  weightier  matters  to 
which  it  owed  its  origin.  In  the  present  work  I  have  avoided 
this  objectionable  word,  and  in  its  stead  selected  the  expression 
"  eocternal  and  internal  sense -like  [sinnlich]  infipressions,''  al- 
though I  have  shown  in  §  402,  &c.,  the  usefulness  and  propriety 
of  the  former.  At  any  rate,  the  reader  must  get  accustomed 
to  the  use  of  one  of  the  two  expressions. 

The  reader  will  be  reminded  in  many  places  that  I  have  not 
considered  any  of  my  principles  practically,  nor  shown  their 
application  to  the  practice  of  medicine,  although  I  well  knew 
that  this  step  would  not  only  have  been  useful  generally,  but 
would  have  also  disposed  many  to  grant  me  their  approval. 
But  my  principal  object  was  to  show  convincingly,  that  the 
physiology  of  the  proper  animal  nature  is  a  branch  of  science 
altogether  distinct  from  the  physiology  of  the  entire  mechanism 
of  the  body  ;  and  to  determine  satisfactorily  the  boundaries  of 
the  two,  which,  indeed,  are  generally  laid  down  in  this  work. 
A  mere  sketch  would  have  been  sufficient  for  this  purpose,  and 
it  would  have  been  much  shorter  if  it  had  not  contained  so 
many  new  views,  which  it  was  necessary  to  treat  somewhat  in 
full,  to  render  them  intelligible ;  nevertheless  I  have  quoted 
briefly  only  all  those  doctrines  belonging  to  peculiar  Animal 
Physiology,  which  are  contained  in  the  physiology  of  the  whole 
mechanism  of  animals,  so  as  to  indicate  their  places  in  the 
present  work.  Now  that  the  principles  of  a  proper  animal 
physiology  can  be  surveyed  connectedly,  it  will  be  found  much 
easier  to  separate  what  is  defective,  obscure,  confused,  un- 
intelligible, and  false,  from  what  is  really  useful,  and  to  bring 
the  whole  system  to  perfection.  For  this  reason  I  earnestly 
wish  that  this  sketch  may  not  be  read  and  judged  of  super- 
ficially and  unconnectedly ;  but  that  the  reader  will  endeavour 
to  follow  me  in  the  chain  of  ideas  from  the  beginning  throughout 
the  work. 


INTRODUCTION. 

1.  The  nature  of  a  body  is  the  aggregate  of  its  peculiar 
powers,  capabilities,  and  forces.  These  depend  upon  the  con- 
dition of  its  parts  and  the  manner  of  their  connection. 

2.  The  aggregate  of  the  forces  of  a  purely  physical  body  is 
termed  its  physical  nature. 

3.  The  general  forces  of  physical  bodies  belong  to  the  animal 
and  the  human  organism,  so  far  as  it  is  considered  in  its  con- 
stituent parts,  and  the  union  of  these  as  a  physical  body  only, 
and  not  as  a  machine ;  and  to  that  extent  we  can  philosophically 
apply  the  general  laws  of  natural  philosophy  to  the  fluids  and 
the  matter  of  the  solids.  To  these  general  forces  particularly 
belong  general  and  specific  gravity,  the  force  of  attraction, 
which,  in  the  matter  composing  the  solids  of  animals,  is  the 
so-called  contractility  [Reiz],  or  the  dead  force  of  Haller, 
and  which  is  simply  the  effect  of  cohesion; — also  heat,  elec- 
tricity, &c. 

4.  The  aggregate  of  the  forces  which  a  physical  body  pos- 
sesses, in  so  far  as  it  is  a  machine,  is  termed  its  mechanical 
nature,  and  depends  upon  the  physical  nature  and  the  kind 
of  union  of  its  parts,  whereby  it  becomes  a  machine.  [Its 
structure.) 

5.  In  addition  to  its  mechanical  nature,  the  animal  or 
human  organism  (so  far  as  it  is  not  a  living  body,  but  only  a 
mechanical  machine),  is  endowed  with  the  mechanical  forces  of 
the  machines,  and  to  that  extent  we  can  philosophically  apply 
the  laws  of  mechanics  to  the  machines  of  such  a  body.  The 
forces  of  the  lever,  of  hydraulic  machines,  of  the  force-pump, 
&c.,  belong  to  this  class  of  mechanical  forces. 

Mechanical  machines  may  be  divided  into  the  artistic  and 
natural  {organic).  The  latter  diff'er  principally  from  the 
former  in  having  a  highly  compound  structure,  so  that  the 
wdiole  machine,  even  to  its  minutest  details,  is  composed  of 


14  PRINCIPLES  OF  PHYSIOLOGY. 

other  machines,  which  by  their  union  communicate  equally 
compound  forces  to  the  general  machine.  On  the  other  hand,  in 
the  artistic  machines,  the  coarser  elements  are  either  not  me- 
chanical machines  at  all,  but  only  mere  physical  bodies,  or  else 
impart  to  the  whole  machinery  no  other  mechanical  forces  than 
those  which  they  would  still  have,  if  their  constituent  elements 
were  not  machines.  The  nature  of  the  organic  machines,  con- 
sidered as  such  only,  is  termed  their  organic  nature,  and  the 
continuance  of  organic  nature  is  organic  life,  which  is  common 
to  anim^als  and  vegetables. 

6.  Organic  (or  natural)  machines  are  termed  animal  ma- 
chines when,  in  addition  to  their  physical  composition,  organical 
structure,  and  the  general  forces  of  physical  and  mechanical 
bodies,  they  are  endowed  with  other  forces,  which  do  not  regu- 
late such  bodies  and  machines,  according  to  the  general  laws  of 
motion,  but  are  only  adapted  to  them  by  means  of  an  arrange- 
ment, the  nature  of  which  is  unknown.  These  forces  are  termed 
(primary)  animal  forces ;  and  the  movements  directly  produced 
by  them  are  (primary)  animal  movements.  When  animal  ma- 
chines are  combined  with  those  that  are  purely  mechanical,  and 
the  latter  are  moved  by  the  animal  forces  of  the  former,  they 
possess  communicated  animal  forces,  and  by  means  of  these  the}^ 
also  perform  animal  movements.  The  aggregate  of  the  animal 
forces  in  the  body  of  an  animal  is  termed  its  animal  nature. 
The  animal  nature  of  a  body  depends  on  the  peculiar  condition 
of  the  materials  of  which  the  animal  machines,  as  such,  consist ; 
on  the  structure  of  the  animal  machines ;  on  the  animal  forces 
themselves;  and  on  the  connection  of  the  animal  with  the  other 
organic  machines  of  the  organism,  whereby  the  forces  and 
movements  of  the  latter  are  stamped  with  the  animal  character. 
The  continuance  of  animal  nature  is  animal  life,  and  its  termi- 
nation animal  death.  In  all  living  animals  the  animal  forces 
act  either  in  perfect  accord  with  the  sentient  force  of  the  mind, 
or  not :  if  the  former,  then  a  distinct  class  of  animal  movements 
in  the  body  is  connected  with  each  class  of  ideas,  and  conse- 
quently both  reciprocally  contain  the  basis  of  their  twofold  ex- 
istence. These  united  animal  and  sentient  forces  are  termed 
animal-sentient  forces;  and  the  movements  they  produce  are 
sentient  actions  (actiones  animse).  When  the  animal  forces  act 
independently  of  the  sentient  force,  they  are  termed  pure  animal 


INTRODUCTION.  15 

forces  or  nerve  forces  [vis  nervosa],  and  their  movements  are 
purely  animal  or  nerve-actions} 

Note. — It  is  absolutely  necessary,  that  these  various  animal 
forces  and  their  modes  of  action  should  each  have  their  distin- 
guishing designations,  and  I  have  not  been  able  to  invent  more 
convenient  terms  than  the  preceding.  They  might  have  been 
termed  simply  mental  forces  and  nerve  forces ;  but  since  the 
former  term  is  already  applied  to  designate  the  powers  of  the 
mind,  the  affix  animal  must  be  used  to  distinguish  the  mental 
forces  of  the  sentient  animal  body. 

7.  By  virtue  of  their  animal  nature,  the  bodies  of  animals 
acquire  forces,  which  cannot  be  explained  by  the  physical  and 
mechanical  laws  applicable  to  the  motion  of  other  bodies  and 
machines,  and  which  can  act  only  through  the  proper  animal 
machines.  Their  workings  are  manifested  partly  in  the  latter, 
partly  in  the  other  machines  of  the  bodies,  upon  the  forces  and 
movements  of  which  they  stamp  the  animal  characteristics. 
With  these  (primary)  animal  forces  the  influence  of  the  soul 
on  the  body,  and  also  the  moving  forces  peculiar  to  the  animal 
machines,  are  to  be  classed. 

'  The  term  Thierischer  kbrper,  as  used  by  Unzer,  exactly  corresponds  to  the 
modern  phrase,  animal  organism.     The  word  kr'dfte  might  he  rendered  forces, 
powers,  properties,  faculties,  or  vis.     In  (3),  kraft  is  applied  to  express  the  force  of 
attraction  and  repulsion  ;  and  I  have,  therefore,  used  that  word  as  its  synonym, 
although  it   is   evident   that  Unzer  uses   the  word   rather   indefinitely ;   and   the 
Thierische  krdfte,  mentioned  in  the  text,  might  more  fitly  be  designated  powers  or 
properties  than  forces.     The  true  synonym  is  vis  nervosa  (639).     Thierische-seelen- 
krafte  is  a  compound  word,  for  which  it  is  impossible  to  find  an  English  synonym  ; 
it  is  used  to  signify  the  properties  or  functions  of  the  brain,  so  far  as  that  organ  is 
the  seat  of  consciousness,  or,  more  abstractedly,  the  combination  in  action  of  the 
purely  animal  force  {vis  nervosa)  with  the  mental.     In  either  case  the  term  implies 
the  action  of  mind  and  the  existence  of  consciousness  or  will.     When  used  in  the 
former  sense,  I  have  rendered  the  phrase  by  cerebral  forces  ;  when  in  the  latter,  by 
animal- sentient  forces.      Whenever  the  word  seele  is  used  in  the  original,  either 
adjectively  or  in  compound  words,  to  express  circumstances  dependent  on  the  exist- 
ence of  soul  or  mind,  as  in  beseelte,  &c.  (349,  603),  I  have  rendered  it  by  sentient. 
Vorstellung  is  used  indefinitely  in  the  sense  of  sensation,  perception,  conception, 
thought,  or  of  an  act  of  mind  generally  (vide  25,  34-36) ;  and  Vorstellungskraft  to 
signify  the  power  or  force  by  which  we  feel,  perceive,  think,  or  will.     I  have  trans- 
lated Vorstellung  generally  by  the  term  conception,  and  consequently  use  the  word 
conceptive  force  as  the  best  rendering  of  Vorstellungskraft ;  but  where  the  context 
required  or  allowed,  I  have  also  rendered  it  by  sentient  force,  or,  more  simply,  by 
mmrf.— Vide  note  to  $  25.— Ed. 


16  PRINCIPLES  OF  PHYSIOLOGY. 

8.  The  doctrines  of  animal  nature  presuppose  the  doctrine 
of  physical  and  organic  nature  (3,  5,  6),  and  must  contan : 

i.  A  description  of  the  animal  machines  in  the  bodies  of 
animals,  comprising  the  composition  and  structure  of  their 
parts,  and  of  their  system  of  relation  to  each  other. 

ii.  The  determination  of  the  animal  forces  proper  to  them 
alone,  and  without  reference  to  their  influence  on  the  other 
parts  and  functions  of  the  organism. 

iii.  The  determination  of  their  influence  on  these  other 
organs  and  functions. 

All  primary  animal  forces  are  either  animal-sentient  forces, 
or  nerve-forces  (purely  animal)  (6) ;  and  hence  arises  the  great 
divisions  of  the  entire  philosophy  of  animal  nature. 

The  First  Part  considers  animal  nature  in  its  connection  with 
the  thinking  power  of  the  soul  of  the  animal,  and  includes  : 

i.  The  animal  machines  in  general,  in  so  far  as  they  are 
capable  of  the  action  of  the  animal-sentient  forces  (6). — 
Part  I,  Chap.  I. 

ii.  The  animal  forces,  per  se,  without  reference  to  their 
influence  on  the  rest  of  the  mechanism,  and  considered  specially 
as  animal  sentient  forces  (6,  7). — Part  I,  Chap.  II. 

iii.  The  influence  of  the  animal- sentient  forces  on  the  rest  of 
the  mechanism  of  the  animal  body  (6,  7). — Part  I,  Chap.  III. 

iv.  The  connection  of  the  body  and  soul  generally. — Part  I, 
Chap.  IV. 

The  Second  Part  treats  of  animal  nature  with  reference  to  its 
simply  animal  forces,  according  to  which  the  animal  machines 
do  not  act  in  connection  with  the  sentient  faculty  of  the  animal 
(355). 

Lastly,  in  the  Third  Part,  animal  nature  is  treated  of  as  a 
whole  (599)  :  in  this  Part  we  consider  its  essential  characte- 
ristics in  the  difl'erent  kinds  of  animals,  its  origin,  continuance, 
and  state  of  perfection ;  its  entire  system  of  animal  forces,  its 
decline,  and  finally  its  cessation. 

Man  is  by  no  means  the  only  object  of  this  work,  although, 
as  the  most  perfect  of  animals,  he  is  its  principal  object ;  it 
contains  rather  the  principles  of  a  Zoology,  or  natural  history 
of  every  species  of  animal,  but  only  according  to  their  peculiar 
animal  forces;  and  as  to  these,  only  in  outline  (15). 


PAET    I. 

ANIMAL  NATURE  IN  ITS  CONNECTION  WITH 

THE    SENTIENT    FACULTY    OF   THE 

SOUL  OF  AN  ANIMAL. 


CHAPTER  I. 


I 


THE  ANIMAL  MACHINES  IN  GENERAL,  AND  ESPECIALLY  AS  THEY 
ARE  ADAPTED  TO  THE  ANIMAL-SENTIENT  FORCES. 

9.  The  proper  animal  macliines  in  animal  organisms  are  the 
brain  and  nerves/  in  which  the  vital  spirits  (the  nervous  fluid) 
are  produced  and  distributed,  with  the  object  of  constituting 
the  medium  of  the  functions  of  these  organs. 

10.  The  brain  is  the  seat  of  the  soul.  We  feel  that  we  think 
in  the  head ;  nowhere  else  are  we  conscious  of  our  existence ; 
in  no  other  organ  is  there  a  thought^  or  an  idea,  or  consci- 
ousness. Now,  since  the  sentient  faculty  [Vorstellungskraft^] 
of  animals  is  their  soul,  the  soul  can  have  its  seat  nowhere  else 
than  in  the  brain,  and  it  would  be  absurd  to  maintain  that  it 
is  diffused  throughout  the  body  (597).  It  is  sufficient  to  a 
physician  to  know,  that  the  thinking  faculty  can  have  no  other 
seat  than  the  medullary  matter  of  the  brain. 

11.  The  brain  is  the  laboratory  of  the  vital  spirits  (15,  i). 
"  It  appears  certain  that  there  is  such  a  fluid  essence  secreted 

'  As  the  phrase  thierischen  maschinen  is  used  for  the  most  part  by  Unzer  to 
indicate  the  nervous  system,  it  is  so  translated  throughout  the  work  wherever  the 
context  permits. — Ed. 

'•'  The  term  VorstellungsJcraft  is  of  very  frequent  occurrence,  and  has  been  trans- 
lated by  the  terms  sentient  faculty  or  force,  conceptive  faculty  or  force,  and  simply 
mind. — See  note  to  $  6,  25. — Ed. 

2 


18         THE  BRAIN  AND  NERVES  AS         [i. 

from  the  vessels  of  the  gray  matter  of  the  brain  into  the  hollow 
tubes  of  the  medullary  matter,  which  is  carried  in  the  tubes 
of  the  nerves  to  their  termination,  and  supplies  the  principle 
whereby  the  nerves  are  rendered  capable  of  being  the  organs  of 
the  senses  and  of  movements/^  (Haller's  ^Physiology/  sect.  383.) 
As  the  gray  or  cortical  substance  of  the  brain  is  the  secreting 
organ  of  the  vital  spirits,  the  medullary  substance  must  be  the 
seat  of  the  animal-sentient  forces.  The  secretion  and  action 
of  the  vital  spirits  will  be  considered  afterwards  (374). 

12.  The  brain  also  gives  origin  to  all  the  nerves,  which  are 
continuations  of  the  cortical  substance,  given  off  partly  from 
it  directly  in  small  bundles,  termed  the  cranial  nerves,  and 
partly  from  a  thick  cord  of  it,  termed  the  spinal  marrow,  which 
passes  downwards  through  the  spine,  whence  the  nerves  are 
distributed  to  all  parts  of  the  body. 

13.  The  nerves  generally  are  enclosed  in  an  investing  mem- 
brane, and,  like  the  blood-vessels,  divide  and  subdivide  in  the 
greater  part  of  the  body,  which  they  either  penetrate  or  form 
loops  in ;  or,  having  lost  their  investing  membrane,  are  so  incor- 
porated with  the  soft  parts,  that  they  can  be  no  longer  traced. 
Their  essential  element  is  the  medullary  matter  of  the  brain, 
or  the  soft  substance  enclosed  within  the  cortical  substance; 
whereas  their  investing  membrane  seems  to  have  no  share  in 
the  proper  animal  functions  allotted  to  them.  Every  nerve  is 
a  bundle  of  much  smaller  fibrils,  each  of  which  rims  an  inde- 
pendent course  to  and  from  the  brain.  Every  nerve  has  its 
special  point  of  origin  in  the  brain,  and  every  fibril  must  have 
its  special  origin  from  that  point,  from  whence  it  takes  an 
entirely  independent  and  separate  course  through  the  medulla 
oblongata  and  the  spinal  cord,  to  its  minutest  termination. 
According  to  all  probability,  the  fibrils  of  the  nerves  are  hollow 
canals. 

Since  these  propositions  are  of  very  great  importance  in 
the  present  work,  and  much  will  be  deduced  from  them,  it  isj 
proper  to  state  that  they  are  taken  from  the  Physiology  of  j 
Haller,  the  greatest  anatomist  and  physiologist  of  the  day. 

14.  The  nerves  so  terminate  externally,  that  either  they  are) 
incorporated  with  other  machines  of  the  organism  appropriated; 
to  certain  movements;  or  they  are  distributed  over  the  skin  or  ■ 
other  parts  of  the  body,  as  the  eyes,  ears,  &c.,  without  exciting 


CH.  I.]  ANIMAL  MACHINES.  19 

such  machines  to  motion,  if  they  be  appropriated  to  certain 
movements,  or  at  least  without  co-operating  therein.  The 
first  are  termed,  in  relation  to  their  function,  motor  nerves; 
the  other  are  sensitive  nerves.  They  are,  however,  identical 
in  structure,  and  only  differ  in  this  local  relation.  Each  nerve 
may  be  either  the  one  or  the  other,  according  to  its  distribu- 
tion ;  and  each  motor  nerve  is  at  the  same  time  endowed  with 
the  properties  of  the  sensitive.  The  motor  nerves  have  ganglia, 
composed  partly  of  their  own  fibres,  and  partly  of  other  nervous 
twigs  and  nerves  which  accompany  them,  whereby  the  direct 
course  of  the  fibrils  and  nerves  is  interrupted.  The  nerves  of 
the  senses,  which  have  no  motive  influence  on  the  mechanical 
machines  of  the  organism,  have  no  ganglia. 

15.  i.  All  the  phenomena  of  motion  and  sensation  mani- 
fested through  the  nerves,  render  probable  the  existence  of  a 
remarkably  subtle  fluid  essence,  which  is  present  invisibly  in 
the  medulla  of  the  brain  and  nerves,  and  is  the  means  whereby 
all  the  functions  of  both  are  performed.  It  is  termed  the 
vital  spirits  or  nervous  fluid,  but  it  is  not  known  how  and 
when  it  contributes  to  the  animal  actions.  It  is  not  that  fluid 
matter  which  is  seen  in  the  medulla  of  the  brain  and  nerves, 
but  a  much  more  subtle  spirit,  imperceptible  to  the  senses. 
It  is  inferred  from  the  phenomena  which  betray  its  existence, 
that  this  nervous  fluid  is  a  remarkably  mobile  fluid,  a  spirituous 
vapour,  which  can  be  neither  aqueous,  nor  glutinous,  nor 
elastic,  nor  etherial,  nor  electrical. 

ii.  Although  animal  machines  are  indeed  proper  to  all 
animals  (6),  still  every  species  does  not  possess  those  which 
have  been  just  described,  but  only  the  most  perfect,  namely, 
man  and  the  animals  immediately  below  him.  But  since  our 
object  is  not  to  lay  down  the  principles  of  a  physiology  of  the 
proper  animal  nature  of  man  only,  but  rather  of  animals  in 
general,  these  principles  will  be  found  applicable  to  an  expla- 
nation of  the  functions  of  animal  machines  in  the  various 
classes  of  animals,  a  detailed  description  of  which  may  be 
found  in  Haller^s  greater  Physiology,  and  in  his  ^  Opera 
Minora.^  ^ 

From  these  statements  we  may  draw  the  conclusion,  with 

*  The  author  here  gives  a  sketch  of  the  comparative  anatomy  of  the  nervous 
system,  as  known  in  his  day ;  this  has  been  omitted  for  the  sake  of  brevity. — Ed. 


20  THE  ANIMAL  MACHINES.  [i. 

reference  to  the  wliole  animal  kingdom,  that  the  general  animal 
machines  in  which  no  species  (so  far  as  is  known)  is  defective, 
and  which,  consequently,  are  the  most  essential  elements  of 
animal  life,  are  the  nerves,  the  ganglia,  and  the  spinal  cord, 
with  their  (probably)  accompanying  cortical  substance — or  the 
analogues  of  those  structures — in  which  the  vital  spirits  reside 
and  circulate ;  and  in  which,  in  those  cases,  there  is  no  cere- 
bral cortical  matter,  the  latter  must  be  secreted  directly  from 
the  blood  (11);  and  that  the  cerebrum  and  cerebellum,  to- 
gether with  their  cortical  substance  and  the  nerves  of  the 
external  senses,  are  not  so  general,  and  only  essentially  neces- 
sary to  certain  species  of  animals,  especially  those  endowed 
with  mind.  Those  only  of  the  cerebrate  animals,  however, 
which,  without  question,  think  and  desire,  are  supplied  with 
a  large  and  considerable  brain;  whilst  those  which  manifest 
ambiguous  traces  of  ideas  have  a  small,  simple,  and  irregular 
brain,  differing  little  from  the  spinal  cord,  to  which  it  appears 
to  be  an  appendage ;  and,  consequently,  has  probably  only  the 
same  functions. 

In  this,  the  First  Part  of  the  Physiology,  we  investigate  the 
animal  nature  of  the  most  perfect  animals,  in  which  all  these 
animal  machines,  or,  at  least,  the  most  important,  are  com- 
bined ;  and  which  render  them  capable  of  acting  in  connection 
with  the  thinking  force.  All  other  animals  only  differ,  in 
descending  the  scale,  in  a  continually  increasing  defect  in 
the  animal  organs  and  forces ;  and  there  are  some  whose  whole 
life  is  so  simple  and  mechanical,  that  they  scarcely  manifest 
any  traces  of  the  animal  forces.  In  the  Second  Part  of  this 
Physiology  it  will  be  shown  how  animal  life  can  equally  sub- 
sist in  these  with  only  the  most  general  and  most  essential 
animal  machines,  and  without  the  co-operation  of  those  pecu- 
liar to  more  perfect  animals ;  and  it  will  be  shown,  also,  how 
far  they  are  similar  or  inferior  to  the  latter.  Finally,  the 
Third  Part  will  exhibit  a  general  view  of  animal  nature,  and 
will  explain  how  the  forces  in  each  species  of  animal  connect 
the  machines  together,  and  complete  animal  life  in  each  (8). 


CHAPTER  II. 

THE    ANIMAL    FORCES    CONSIDERED    ABSTRACTEDLY,    AND 
PARTICULARLY  AS  ANIMAL-SENTIENT  FORCES. 

16.  To  what  end  are  the  animal  forces  peculiar  to  the 
animal  machines  only,  without  reference  to  their  influence  on 
the  other  portions  of  the  organism,  so  that  the  latter  would 
still  possess  them,  even  if  not  united  with  the  mechanical 
machines  which  move  the  body?  The  answer  to  this  question 
is  the  object  of  the  present  chapter. 


SECTTON  I.— THE  FUNCTIONS  OF  THE  VITAL  SPIRITS. 

17.  The  vital  spirits  originate  in  the  brain  (11).  If,  con- 
sequently, they  contribute,  in  some  degree,  to  the  functions  of 
the  nerves,  and  are  present  in  them,  or  carry  the  impressions 
made  on  the  brain  from  time  to  time  along  the  trunks,  twigs, 
and  terminating  fibrils  of  the  nerves,  they  must  flow  from  the 
brain  to  the  most  remote  termination  of  the  nerves,  or,  at 
least,  propagate  the  impression  on  the  brain  in  this  direction, 
namely,  downwards  to  the  termination  of  the  nerves;  and  have 
also  a  natural  motion  from  the  brain  downwards  along  the 
trunks,  branches,  and  terminating  fibrils  of  tl^e  nerves,  whereby 
they  become  the  medium  of  the  direct  action  of  the  brain  on 
the  nerves  (122). 

18.  If  the  vital  spirits  already  secreted  in  the  nerves  con- 
tribute somewhat  to  the  functions  of  the  brain,  and  carry  to 
it  the  impressions  received  from  time  to  time  by  the  termi- 
nations of  the  nerves  (11),  they  must  also  flow  from  the  latter 
to  the  former,  or  at  least  propagate  the  external  impression 
in  that  direction  upwards  to  the  brain,  and  possess  a  natural 
motion  from  the  terminating  fibrils  of  the  nerves  upwards  to 
the  brain,  whereby  they  become  the  medium  of  the  direct  action 
of  the  nerves  in  the  brain  (36 — Haller). 

19.  This  interposition  of  the  nervous  fluid  between  the  re- 


23  FUNCTIONS  OF  THE  VITAL  SPIRITS.  [i. 

ciprocal  actions  of  the  brain  and  nerves  on  each  other,  derives 
great  probability  from  all  observation  of  the  operations  of  the 
animal  forces,  and  takes  place  so  quickly  and  immediately, 
that  the  fluid  acts  with  inconceivable  rapidity,  either  as  to  its 
own  movements,  or  in  propagating  impressions  (Haller,  §  381), 

20.  It  is  a  natural  inference,  and  one  established  by  facts, 
that  the  vital  spirits  are  diminished,  or  rendered  unfit  for  their 
functions,  by  frequent  or  prolonged  use;  and,  consequently, 
the  animal  forces,  of  which  they  are  the  medium,  become 
weakened  or  disappear  (17,  18),  or  increase,  when  they  are  sup- 
plied to  the  brain  and  nerves. 

21.  If  the  vital  spirits  are  duly  secreted  from  the  blood  in 
the  brain,  and  their  influence  goes  uninterruptedly  thence  to 
the  nerves,  or  vice  versa,  the  functions  of  the  sentient  forces  or 
the  nerve-forces,  of  which  they  are  the  medium,  are  performed 
naturally;  and,  consequently,  those  forces  can  act  freely,  so 
far  as  they  are  influenced  by  the  vital  spirits. 

22.  The  free  action  of  the  animal-sentient  or  nerve-forces, 
in  so  far  as  it  is  dependent  on  the  vital  spirits,  is  prevented 
by  whatever  prevents  the  production  of  the  vital  spirits  in  the 
brain ;  by  whatever  destroys  their  normal,  but  to  us  unknown, 
condition ;  by  whatever  interrupts  their  influence  directed  from 
the  brain  to  the  nerves,  or  vice  versa ;  or,  finally,  by  whatever 
destroys  them  or  wears  them  out.  Obstruction  of  the  cerebral 
circulation,  the  compression  or  destruction  of  the  brain,  or  its 
entire  removal  from  the  body,  prevent  the  production  of  vital 
spirits.  A  general  corruption  of  the  fluids  must  also  neces- 
sarily destroy  their  natural  condition;  ligature,  or  compression, 
or  section  of  the  spinal  cord,  prevents  their  influence  being 
communicated  from  the  brain  to  the  nerves,  or  from  the  nerves 
to  the  brain  ;  and  an  undue  straining  of  the  powers  of  body 
and  mind  consumes  the  vital  spirits  (20). 

23.  Experience  teaches  us,  that  sleep,  wine  and  other  spiri- 
tuous drinks,  light  nourishing  food,  the  odour  of  spirituous 
vapours,  ablution  of  the  limbs  with  spirituous  fluids,  friction, 
gentle  bodily  exercise,  mental  enjoyment,  cheerful  society, 
moderate  and  agreeable  use  of  the  senses,  all  strengthen  and 
enliven  the  sentient  and  nerve-forces ;  and  it  is  probable  that 
this  occurs  either  from  an  increased  secretion,  or  a  renewed 
natui'al  good  state  of  the  nervous  fluid,  or  from   a  greater 


CH.  II.]  CEREBRAL  FORCES.  28 

facility  of  flux  and  reflux  which  it  acquires.  In  like  manner  it  is 
probable  that  prolonged  watching,  starvation,  debilitating  food 
and  drugs,  the  emotions,  and  the  active  elements  of  certain 
matters  which,  from  their  destructive  qualities,  are  injurious  to 
the  nervous  fluid,  as  opium,  for  example;  also  cold,  indolence, 
want  of  exercise,  fatigue,  vexation,  intense  application  of  the 
mind  or  of  the  senses,  all  interrupt  or  diminish  the  animal 
forces,  because  they  either  diminish  the  vital  spirits,  or  impede 
their  secretion,  or  render  them  morbid,  or  hinder  their  flux  and 
reflux. 

Note. — Although  little  is  known  of  the  nature  and  proper- 
ties of  the  forces  of  the  vital  spirits,  the  physician  can  content 
himself  therewith,  even  although  the  little  that  we  think  we 
know  is  doubtful,  and  at  the  best  only  probable :  for  they  may 
remain  undetermined  for  ever  without  any  loss  to  science,  be- 
cause we  are  under  no  necessity  to  show  the  origin  and  nature 
of  the  animal  forces,  inasmuch  as  we  learn  their  true  actions 
and  laws  from  observation  only. 

SECTION    II. THE    FORCES    OF    THE    BRAIN    CONSIDERED 

ABSTRACTEDLY  AS  ANIMAL-SENTIENT   FORCES. 

24.  The  brain  has  a  regular  double  movement,  which  is 
mechanical  only,  and  not  peculiar  to  its  animal  nature.  One 
movement  is  simply  the  motion  communicated  to  it  by  the 
arteries;  the  other  consists  in  an  alternate  eff'ort  to  expand 
and  contract,  which  Haller  attributes  to  the  connection  between 
the  respiration  and  the  cerebral  veins,  so  that  the  latter,  like 
the  brain  itself,  become  turgid  at  each  expiration,  and  flaccid 
at  every  inspiration  (Haller's  ^ Physiology^).  Although  this  me- 
chanical motor  power  of  the  brain,  as  well  as  the  consequent 
secretions,  together  with  the  cerebral  circulation  and  its  purely 
physical  forces,  do  not  properly  come  under  our  notice  here, 
but  belong  to  the  physiology  of  the  mechanical  nature  of  animal 
organisms,  still  it  is  necessary  to  remember  them  in  an  inquiry 
into  its  animal  forces,  so  far  as  the  existence  of  the  latter  pre- 
supposes their  existence.  Since  respiration  is  the  cause  of  the 
continual  movements  of  the  brain  just  mentioned,  and  without 
it,  indeed,  the  animal-sentient  forces  cannot  act,  because  their 
action  presupposes  the  existence  of  the  mechanical  forces  (6), 


24  CEREBRAL  FORCES.  [i. 

its  absence  appears  to  be  the  reason  why  the  embryos  of  animals 
endowed  with  a  sentient  brain,  display  no  trace  of  those  animal 
functions  for  which  the  animal-sentient  forces  of  the  brain  are 
absolutely  requisite. 

25.  The  seat  of  the  soul  is  the  brain  (10).  Whenever  the 
brain  is  destroyed,  or  its  natural  functions  interrupted,  the  sen- 
tient force  ceases  to  act.  So  soon  as  it  is  restored  to  its  natural 
functions,  conceptions  return.  The  whole  brain  is  not  imme- 
diately necessary  to  thought,  since  large  portions  of  it  may  be 
lost  or  be  defective,  or  be  compressed,  or  ossified,  or  its  functions 
otherwise  interrupted,  without  any  perceptible  influence  on  the 
mental  powers,  which,  as  to  the  cortical  substance  at  least,  is  not 
remarkable,  because  it  is  not  the  seat  of  mind  (11) ;  but  it  can- 
not be  deduced  from  any  observation  whatever,  that  the  whole 
brain  may  be  wanting  (as,  for  example,  when  the  head  is  re- 
moved, or  the  brain  entirely  destroyed,  or  the  functions  of  all 
its  parts  generally  interrupted),  and  the  slightest  trace  of  mental 
operations  ever  be  perceived.  Further,  when  a  thought  arises 
in  the  mind,  a  change  must  necessarily  occur  concurrently 
therewith  in  the  brain,  and  particularly  in  the  medullary  sub- 
stance, without  which  the  sentient  force  cannot  act ;  and  when 
this  change  occurs  in  the  brain,  the  sentient  force  is  necessarily 
excited  into  action.  Whatever  may  be  reasoned  on  the  matter, 
a  change  in  the  brain  must  consist  in  a  movement,  and  the 
medullary  matter  must  also  be  endowed  with  a  motive  force, 
which  acts  in  harmony  with  the  sentient  force.  So  that  each 
distinct  class  of  perceptions  is  always  connected  with  certain 
animal  movements  (6),  and  with  these  movements  a  certain 
class  of  perceptions ;  for  it  is  ascertained  from  numerous  ob- 
servations, that  after  certain  injuries  of  the  medullary  portion 
of  the  brain,  especially  of  that  part  from  which  nerves  of  sensa- 
tion arise  (14),  certain  kinds  of  perceptions  [Vorstellung] ,  as 
for  example,  certain  sensations,  are  prevented  or  disappear,  and 
together  with  them  all  the  ideas,  desires,  and  instincts,  dependent 
thereon,  as  well  as  other  faculties  of  the  mind.  (Haller.)  This 
motive  power  of  the  brain,  which  is  connected  with  the  sentient 
force  [mind],  is  an  animal-sentient  force,  and  hence  arises 
the  fundamental  general  principle  in  the  doctrines  of  the  con- 
nection between  body  and  mind,  that  the  medullary  matter  of 
the  brain  possesses  an  animal- sentient  force,  by  means  of  which. 


CH.  II.]  MATERIAL  IDEAS.  25 

at  every  act  of  mind,^  whether  it  be  a  sensation,  imagination, 
desire,  reflection,  or  conclusion,  there  is  produced  in  it  a  cer- 
tain animal  movement,  necessary  thereto,  without  which  the 
act  of  thought  [Vorstellung]  can  neither  arise  nor  continue, 
and  with  which  it  infallibly  arises  and  continues.  This  animal- 
sentient  force  is  peculiar  to  the  brain,  and  is  the  property  of 
no  other  portion  of  the  nervous  system^  because  in  none  other 
except  in  the  brain  does  an  animal  movement  develope  per- 
ceptions (10).  The  medullary  matter  of  the  brain  can  also,  with 
propriety,  be  designated  as  the  only  instrument  of  the  sentient 
force,  for  it  is  through  its  animal  movements  that  the  mind 
puts  its  force  into  action,  and  maintains  it,  and  without  which, 
it  would  absolutely  remain  inactive.  Philosophers  have  already 
introduced  the  phrase,  material  ideas,  to  express  those  move- 
ments in  the  brain  that  are  necessarily  connected  with  each 
act  of  thought.  (Baumgarten's  Metaphysics,  §  416.)  A  psy- 
chological materialist  considers  these  material  ideas  as  the  ideas 
of  the  mind  itself.  But  since  it  must  be  firmly  maintained, 
that  the  thinking  faculty  is  an  immaterial  substance  [Substanz), 
it  cannot  certainly  be  granted  that  these  material  changes  in 
the  brain  are  really  the  ideas  themselves ;  but  since  the  two 
are  inseparately  connected  with  each  other,  and  the  mind  never 
acts,  nor  can  act,  in  animals,  without  these  movements,  it  is 
fully  established  that  every  act  of  thought  presupposes  and 
causes  a  movement  in  the  brain  (material  idea),  and  every  such 
movement  in  the  brain  presupposes  and  causes  a  conception  in 
the  mind ;  that  the  same  or  a  similar  conception  excites  the 
same  or  a  similar  material  idea,  and  that  the  same  or  a  similar 
material  idea  excites  the  same  or  a  similar  conception  in  the 
mind ;  that  when  there  are  no  conceptions  excited  in  the  mind, 
there  are  no  material  ideas,  although  probably  similar  movements 
may  take  place  in  the  brain;  that  when  no  material  ideas  take 
place  in  the  brain,  no  conceptions  come  into  real  existence  in  the 
mind  (112) ;  and  that  the  perfection  or  imperfection  of  the  mental 

'  The  phrase  Vorstellung  der  Seele  is  here  translated  act  of  mind.  Vorstellung  is 
of  very  frequent  occurrence  throughout  the  work,  and  is  ordinarily  translated  con- 
ception. The  reader  must,  however,  bear  in  mind,  that  the  term  "  conception  "  does 
not  so  exactly  express  the  author's  meaning  as  "  act  of  mind,"  inasmuch  as  Vorstel- 
lung is  applied  to  signify  sensation,  perception,  and  thought  generally, — in  short, 
evert/  mental  operation ;  whereas  conception  has  a  more  limited  application.  No  other 
word  could  be  found,  however,  more  nearly  expressing  the  author's  meaning. — Ed. 


26  CEREBRAL  FORCES.  [i. 

powers  depends  very  mucli  on  the  natural  perfection  or  imper- 
fection of  the  brain,  or  on  the  full  or  faulty  development  of  the 
brain  at  birth,  or  during  growth,  &c.,  of  which  we  have  illus- 
trations in  the  deformed  and  compressed  heads  of  many  stupid 
races. 

Note. — The    reader    must    not    object    to    the    expression 
"  material  idea,^^  because  it  has  been  very  variously  misapplied. 
By  it  we  understand  no  hieroglyphical  figures  of  the  objects  of 
the   conceptions,   no   impressions   stamped   on  the   medullary 
substance  of  which  one  has  no  conception,  and  which  can  only 
be  considered  as  the  fancies  of  too  contemplative  philosophers. 
It  is  least  in  our  intention,  with  Bonnet,  to  analyse  the  faculties 
of  the  soul  by  means  of  their  altogether  unknown  qualities. 
It  need  only  be  granted,  that  the  change  which  takes  place 
in  the  medullary  substance  at  each  conception,  is  a  movement 
which,  since  it  is  unknown,  every  one  may  conceive  for  himself 
as  he  pleases;  and  that  we  term  these  movements  material  ideas , 
so  as  to  have  a  short  phrase  alreadj^  used  by  writers,  instead  of  a 
long  circumlocution.    It  will  be  seen,  that  throughout  the  work, 
we  use  this  expression  in  no  other  than  this  general  signification. 
26.  Since  every  continuous  conception  in  the  mind  is  to  be 
considered  at  each  moment  as  a  prolonged  action  of  the  sentient 
force,  and  no  act  of  the  latter  takes  place  without  material  ideas 
in  the  brain  (25),  it  follows  that  each  continuous  conception 
excites  continuous  movements  in  the  brain  which  are  usually 
considered  under  the  term  impressions,  or  representations  of  the 
conceptions.     The  more  a  conception  is  developed,  or,  in  other 
words,  the   clearer    it  becomes   (Baumgarten^s   'Metaphysics,' 
§  415),  by  so  much  the  more  fully  must  the  material  idea  be 
developed ;  if,  on  the  other  hand,  the  conceptions  be  obscure, 
there  are  only  imperfect  and  undeveloped  movements  in  the 
brain.      A  more  forcible   conception   requires    more  vigorous 
movements  (material  ideas)  in  the  brain,   and  more  vigorous 
material  ideas  develope  more  forcible  conceptions.      Since  every 
conception  is  the  origin  of  a  material  idea  in  the  brain,  and 
vice  versa  (25),  the  more  vigorous  conceptions  are  larger  con- 
ceptions so  far  as   they   are    the    origins    of  material  ideas. 
(Baumgarten's    'Metaphysics'    §  379).      A  large  conception 
contains  small  conceptions  as  its  constituent  parts,  and  con- 
sequently it  is   made  up   of  several,   each  of  which  causes  a 


CH.  II.]  MATERIAL  IDEAS.  27 

material  idea  in  the  brain  (25).  Consequently,  the  material 
ideas  of  more  vigorous  conceptions  are  more  compound  and  more 
vigorous  movements  than  those  of  the  weaker ;  and  for  similar 
reasons,  the  conceptions  of  more  vigorous  material  ideas  are  more 
compound  and  larger  conceptions  than  those  of  the  weaker. 

27.  All  conceptions  are  operations  of  the  sentient  force,  and 
consequently  acts  of  the  soul.  All  material  ideas  are  operations 
of  the  animal-sentient  force  of  the  brain  (25,  26),  consequently 
they  are  operations  of  the  animal  motor  forces  of  an  animal 
machine.  But  since  neither  can  exist  without  the  other,  the 
conceptions,  as  well  as  the  material  ideas  in  general,  are  effected 
by  means  of  the  two  co-operating  forces  of  the  soul  and  brain. 
When  the  animal  machines  produce  material  ideas  in  virtue 
of  antecedent  impressions  derived  from  without,  and  thus  induce 
the  co-operation  of  the  conceptive  force, — such  as  takes  place, 
for  example,  in  external  sensations, — conceptions  thus  origi- 
nated are  termed  purely  natural)-  (impressional)  conceptions^ 
which  arise  in  the  mind,  necessarily  and  physically  (Baum- 
garten^s  ^Metaphysics,'  §  522),  and  succeed  each  other  according 
to  the  laws  of  external  impressions,  so  far  as  they  put  the 
animal- sentient  force  of  the  brain  into  activity.  When,  on 
the  other  hand,  conceptions,  and  their  material  ideas,  are  de- 
veloped by  the  sentient  force,  independently  of  any  previous 
external  impressions  in  the  animal  machines,  and  thus  induce 
the  co-operation  of  the  animal-sentient  force  of  the  brain,  as, 
for  example,  in  volitional  acts, — these  conceptions  are  termed 
arhitrary , spontaneous,  physiologically  free^  (Baumgartner,  §520 ; 
Hallers's  'Physiology,'  §  570);  and  they  succeed  each  other  ac- 
cording to  the  laws  of  the  sentient  force.  Neither  the  purely 
impressional,  nor  the  spontaneous  conceptions,  can  have  a  real 
existence,  independently  of  material  ideas  (25),  and  when  they 
continue,  must  embody  their  impressions  in  the  brain  (26).  But 

*  The  term  naturlich,  here  translated  natural,  has  a  pecuUar  meaning,  being  used 
generally  in  the  sense  of  organic,  somatic,  or  corporeal,  or  to  express  something  antago- 
nistic to  spiritual.     I  have  ordinarily  translated  it  by  natural,  organic,  or  physical. 

*  The  reader  is  particularly  requested  to  observe,  that  the  words  "  arbitrary"  and 
'*  spontaneous"  are  used  here  and  elsewhere  throughout  the  work  in  their  strict 
etymological  and  metaphysical  sense,  and  indicate  conceptions  or  actions  caused  or 
excited  by  the  will,  as  a  faculty  of  mind.  This  remark  is  necessary,  because,  popu- 
larly, the  word  "  arbitrary,"  indicates  acts  that  are  despotic,  absolute,  or  capricious  ; 
while  "  spontaneous"  is  applied  to  acts  done  without  compulsion.  The  words  in 
the  original  are  eigenmdchtig  and  selhstthdtig. — Ed. 


28  CEREBRAL  FORCES.  [i. 

as  to  the  former,  the  mind  cannot,  by  its  own  power  alone, 
produce  the  material  ideas  in  the  brain,  but  must  wait  for 
the  external  impressions  which  form  them  in  the  brain ;  while,  on 
the  other  hand,  no  immediately  antecedent  impression  on  the 
nervous  system  is  necessary  to  the  latter — the  ideas  of  the 
intellect — but  the  soul  forms  them  by  its  own  proper  power, 
and  lets  them  follow  each  other  according  to  their  natural 
psychological  laws,  free  from  the  restraint  of  external  impressions. 
Note. — It  is  necessary  to  comprehend  clearly  this  difference 
between  the  conceptions,  otherwise  nothing  can  be  accurately 
distinguished  and  taught  in  the  physiology  of  the  connection 
between  body  and  soul ;  for  this  reason,  the  new  expressions 
must  be  excused,  and  their  subjoined  definitions  closely  adhered 
to  in  the  subsequent  portions  of  the  work;  and  there  is  nothing 
in  them  which  does  not  fully  harmonise  with  established  psy- 
chological ideas. 

28.  Probably  these  material  ideas  and  representations  of  the 
conceptions  in  the  brain,  consist  simply  in  a  play  of  the  vital 
spirits  in  it ;  for  when  the  brain  of  an  animal  is  examined,  there 
IS  nothing  visible,  of  all  the  animal  movements,  or  at  all  events 
of  the  material  ideas ;  and  its  purely  mechanical  movements  in 
no  wise  harmonise  with  the  conceptions,  but  are  much  more 
simple,  and  are  in  accordance  with  the  mechanism  of  the  cir- 
culation and  respiration. 

29.  This  fundamental  principle  of  the  animal  nature  of  all 
sentient  animals,  namely,  that  every  operation  of  the  soul 
originates,  continues,  ceases,  is  defective,  and  increases  or 
diminishes,  in  connection  with  an  operation  of  the  animal-sentient 
force  of  the  brain  (25,  26), — connects  the  souls  of  animals  most 
intimately  with  their  bodies,  and  the  conceptions  with  the  move- 
ments, and  lays  the  basis  for  the  whole  doctrines  of  the  animal 
nature  of  the  sentient  forces,  or  in  other  words,  of  the  union 
of  soul  and  body,  (compare  345).  This  union  is  known  to, 
and  conceded  by,  philosophers  and  physicians,  although  they 
explain  it  in  totally  different  ways  ;  which  explanations,  how- 
ever, are  unnecessary  and  foreign  to  medical  art,  because  it 
is  of  no  real  importance  whether  the  union  be  explained 
'^  materially,'^  ^*^  harmonically,"  '^influxionistically,''  or  ^^occa- 
sionalistically.'^  And  although  the  peculiar  relations  of  the 
movements  in  the  brain  (its  material  ideas),  which  accompany 
the  conceptions  be  unknown  (28),  nevertheless  their  existence 


CH.  II.]  EXTERNAL  IMPRESSIONS.  29 

is  rendered  evident  from  the  continual  operations  of  each  concep- 
tion on  the  body,  and  which  must  necessarily  have  their  origin 
in  the  brain,  where  the  mind  has  its  seat,  and  is  in  intimate 
relation  with  the  nervous  system. 

30.  The  doctrines  of  the  animal-sentient  forces  which  follow 
from  these  principles,  divide  naturally  into  two  principal  divi- 
sions; namely:  1st.  How  are  the  material  ideas  produced  in  the 
brain?  (31-112.)  2d.  What  functions  do  they  perform  in  the 
animal  economy?  (113-344.)  These  two  take  place  mainly 
through  the  connection  of  the  brain  with  the  nerves,  whereby 
the  animal  forces  of  the  nerves  keep  up  a  physical  relation  with 
the  animal-sentient  forces  of  the  brain. 

SECTION   III. THE   ANIMAL  FORCES  OF  THE   NERVES,  CONSIDERED 

SOLELY    IN    THEIR    RELATION    WITH    THE    ANIMAL-SENTIENT 
FORCES  OF  THE   BRAIN.^ 

Of  the  External  Impressions  [Aussern  sinnlichen  Eindriicke]  — 
[Nerve  feelings) . 

31.  Every  nerve  has  its  beginning  or  origin  in  the  brain  (12) ; 
and  if  an  impression  be  made  there,  and  propagated  along  the 
nerve,  it  must  necessarily  take  a  direction  from  the  brain  outwards 
towards  the  branches  and  their  terminations,  as  the  vital  spirits 
would  also  propagate  it  (17).  If,  on  the  contrary,  a  similar  im- 
pression be  made  on  the  terminations  and  propagated  along  the 
trunk  of  the  nerve,  its  direction  must  be  toward  the  brain  in  the 
same  course  as  the  vital  spirits  (18).  If  a  nerve  be  divided,  an  im- 
pression made  on  that  point  separated  from  the  terminating  fibrils, 
but  still  in  connection  with  the  brain,  takes  the  same  direction  if 
it  be  propagated,  just  as  if  it  had  been  made  on  the  terminating 
fibrils  themselves,  namely,  upwards  to  the  brain.  On  the  con- 
trary, if  an  impression  be  made  on  that  end  of  the  cut  nerve  which 
is  separated  from  its  connection  with  the  brain,  but  in  connection 
with  the  terminating  fibrils,  if  propagated,  it  will  go  towards  the 
terminating  fibrils.  If  an  impression  be  made  on  the  cerebral 
origin,  or  on  the  terminating  fibrils  of  the  nerve,  and  it  is 
propagated,  it  will  in  both  cases  traverse  the  nerve  only  as  far 
as  the  point  of  section ;  consequently,  when  an  impression  takes 

'  The  thierische  kr'dfte  of  the  nerves,  here  translated  animal  forces  of  the  nerves, 
are  termed  elsewhere  nervenkrdfte,  or  nerve-forces  ;  both  phrases  are  used  in  exactly 
the  same  sense  as  the  Latin  term  vis  nervosa^  which  has  therefore  been  preferred, 
wherever  possible,  to  the  literal  rendering. — Vide  note  to  §  353. 


30  CEREBRAL  FORCES.  [i. 

place  sideways  on  an  undivided  nerve,  that  is  to  say,  neither  at 
its  origin  nor  termination,  but  on  the  trunk  between  these  two 
points,  if  it  be  propagated,  it  can  pass  onwards  from  the  point 
of  impression  (not  from  its  termination  !)  upwards  to  the  brain, 
and  in  like  manner  from  the  same  point,  (and  not  from  the 
cerebral  origin  of  the  nerve !)  downwards  to  the  terminating 
fibrils.  When  by  a  touch  or  some  movement  communicated  to 
it,  or  by  any  other  agency  whatever,  an  animal  machine  (and 
consequently  a  nerve)  is  so  changed  that  it  produces  actions, 
which  cannot  be  satisfactorily  explained  by  the  physical  and 
mechanical  laws  of  motion,  or  in  other  words,  so  that  it  mani- 
fests animal  actions  (6) ;  the  change  thus  excited  in  it  is  termed 
a  sense-like  [sinnlich]  impression  {nerve-feeling).  A  sense-like 
impression  made  on  the  cerebral  origin  of  a  nerve  in  a  direction 
downwards,  or  on  its  trunk,  if  propagated,  passes  outwards  to- 
wards the  terminating  fibrils  of  the  nerve ;  on  the  contrary,  a 
sense-like  impression  made  on  the  terminating  fibrils  of  a  nerve, 
or  on  its  trunk,  in  a  direction  upwards  from  the  termination  to 
the  brain,  if  propagated,  is  transmitted  in  that  direction.^ 

»  The  indefinite  use  of  the  words  "  sinnlich,"  "  sensible"  "  sentient,"  and  "  sensa- 
tional," by  German,  French,  and  English  writers,  on  the  physiology  of  the  nervous 
system,  has  led  to  innumerable  misconceptions  by  both  authors  and  readers.  Agents 
frequently  change  the  condition  of  the  nervous  system,  and  excite  it  to  action  with- 
out being  felt :  that  is  to  say,  without  exciting  pleasure  or  pain,  or  the  feeling  of 
self-consciousness,  or  any  perception  whatever  of  the  agent  or  agents,  or  of  the  re- 
sults of  their  action ;  yet  movements  result  therefrom  as  much  adapted  to  attain  a 
definite  and  designed  end,  as  if  the  agents  were  felt,  and  the  mind  itself  acted.  In 
the  text,  Unzer  analyses  these  phenomena,  and  terms  the  change  which  takes  place 
in  a  nerve,  when  agents  so  act  upon  it,  a  sinnlich  impression  or  Nervengefuhl — 
nerve-feeling.  It  is  obvious  from  the  context,  that  to  render  sinnlich  by  sensational 
or  sentient  would  give  an  erroneous  idea  of  the  author's  meaning,  if  by  those  words 
we  mean  "  of  or  belonging  to  sensation  or  perception ;"  for  he  emphatically  dis- 
criminates, in  a  subsequent  paragraph  (34),  and  elsewhere,  between  the  property  of 
mere  respondence  to  impressions  seated  in  the  nerves  (**  nerve-feeling"),  and  the 
property  of  sensation  or  perception  requiring  a  special  organ, — a  cerebrum. 

There  is  no  English  word  which  corresponds  to  sinnlich  as  thus  used  by  Unzer, 
which  I  have  hitherto  rendered  by  sense-like.  The  term  sinnlicher  Eindruck  may 
be  very  correctly  rendered,  however,  by  the  word  '*  impression,"  as  used  by  modern 
neurologists ;  for  when  we  say  that  light  makes  no  impression  on  the  nerves  of  the 
skin,  we  mean  to  say  that  it  excites  no  change  in  their  medulla,  so  that  appropriate 
vital  movements  shall  follow.  I  therefore  propose  to  use  the  word  "impression" 
simply,  as  conveying  the  meaning  of  sinnlicher  EindrucA,  deducing  therefrom  the 
adjective  impressional. 

It  is  to  be  observed,  however,  that  sinnlich  is  used  by  Unzer  in  other  senses, 
when  it  may  be  rendered  by  sentient  or  sensational.     When  sinnlich  impressions 


CH.  ii.J  EXTERNAL  IMPRESSIONS.  31 

32.  When  an  impression  is  received  on  the  terminating  fibrils 
or  branches  of  a  nerve,  it  is  termed  an  external  impression  (a 
nerve-feeling  from  without  inwards)  (31,403),  to  distinguish  it 
from   an  impression  passing  from  within  outwards  (31,  121), 
and  which  must  not  be  confounded  with  the  sense  of  touch. 
Whether  the  impression  be  made  on  nerves  distributed  in  the 
interior  of  the  body  or  on  the  exterior,  it  is  the  same,  provided 
that  when  it  is  propagated,  it  passes  upwards  to  the  brain  (31). 
As  to  this  external  impression,  experience  teaches  us,  that  it  is 
developed  in  living  animals  by  every  touch  of  the  nerve,  or  by 
some  communicated  movement,   provided  it  excites  a  certain 
definite,  although  unknown,  change  in  the  medulla  of  the  nerve, 
and  is  transmitted  upwards  to  the  brain.      Every  impression  on 
the  terminating  fibres  of  a  nerve  is  not  an  external  impression, 
nor  causes  one,  but  only  those  which  so  act  on  the  medulla  of 
the  nerve,  that  animal  actions  directly  result  (31).   For  example, 
light  excites  no  external  impression  on  the  most  exposed  and 
most  delicate  nerves   of  the  skin,  &c.     The  most  undoubted 
observations  teach  us,  that  animal  actions  are  excited  by  the 
agency  of  contact  or  movement,   not  in  the  investing  mem- 
brane, but  in  and  through  the  medullary  matter  of  the  nerve. 
(Haller's  'Physiology,'  §§365,372,373.)    The  mode  in  which 
the  medulla  is  acted  upon  by  a  touch,  or  any  other  agent,  is 
purely  animal,  and  difi'ers  altogether  from  the  physical  and 
mechanical  laws  of  communicated  motion.     In  every  case  where 
a  touch  of  the  medulla  excites  most  vivid  animal  actions,  whether 
they  be  acts  of  mind,  or  motions  caused  by  the  animal- sentient 
forces,  or  simply  by  the  animal  forces  (6),  there  is  no  perceptible 
movement  in  the  medulla,  nor  any  change  visible  therein.    Nor 
are  the  animal  actions  resulting  from  such  a  touch  in  proportion 
to  its  nature  and  strength,  as  when  bodies  act  physically  on  each 
other  by  a  blow,  pressure,  &c.;  but  often  the  slightest  influences 
will,  in  the  same  nerve,  excite  the  most  energetic  actions,  and 
a  more  forcible  agent  the  weakest.      Certain  agencies  cannot 

reach  the  hrain  and  are  felt,  they  excite  an  act  of  mind,  or  a  Vorstellung,  as  sensa- 
tion, perception,  desire,  &c.  All  acts  of  mind  necessarily  and  directly  dependent 
upon  such  impressions  are  termed  by  him  sinnlich  ;  and  in  this  case  the  word  may 
be  rendered  by  sensational.  It  must  be  remembered,  however,  that  the  word  so 
used  implies  causation  as  well  as  condition, — vide  §  66,  and  would,  I  think,  be  as 
correctly  rendered  impressional  as  sensational. 


32  CEREBRAL  FORCES.  [i. 

stimulate  a  nerve  to  the  performance  of  its  function,  although 
in  reality  they,  act  strongly  physically ;  as,  for  example,  a  sound 
which  shakes  every  bone  in  the  head,  excites  no  animal  actions 
in  the  optic  nerves.  There  is  also  the  mode  in  which  a  nerve 
receives  an  external  impression  j  for  the  working  of  an  animal 
force  in  the  medulla  of  the  nerve  is  one  thing,  the  propagation 
to  the  brain  of  the  impression  received  by  the  nerve,  another. 
Then  there  is  nothing  in  the  medulla  whereby  this  transmission 
can  be  explained  according  to  mechanical  or  physical  laws.  The 
medulla  is  neither  hard  nor  elastic,  but  a  soft  body,  which 
according  to  the  laws  of  physics  must  prevent  or  arrest  the 
communication  of  motion.  Besides,  this  transmission  takes 
place  so  rapidly,  and  so  soon  after  the  external  impression  is 
received,  that  the  mind  can  perceive  no  space  of  time  to  occur 
between  the  stimulation  of  the  nerve,  and  the  animal  action 
excited  in  a  part  of  the  body  far  distant  from  the  point  where 
the  impression  was  made.  Nor  can  this  transmission  be  effected 
like  a  motion  in  fluids,  for  the  medulla  is  not  fluid  matter,  nor 
so  filled  with  fluid  as  to  have  the  mobility  of  fluids,  but  is  a  soft 
material  which  retards  motion.  Lastly,  the  properties  of  ethereal 
fluids  are  not  observable  in  the  medulla,  nor  even  in  the  vital 
spirits,  as,  for  example,  such  as  ether,  the  electric  fluid,  &c., 
which  transmit  motion  in  an  unknown  physical  way.  (Haller^s 
'  Physiology,'  §  379.)  Since  both  the  external  impression  and 
its  transmission  along  the  nerves  are  operations  of  the  vis  nervosa 
(6),  and  the  aggregate  of  the  animal  forces  in  animal  bodies  is 
termed  their  Senselikeness  \_Sinnlichkeit] ,  it  follows  that  the 
mode  in  which  the  medulla  of  the  nerve  receives  impressions 
generally,  and  external  impressions  particularly  (31),  as  well  as 
the  mode  in  which  it  transmits  them,  together  indeed  with  the 
impression  itself,  (it  being  an  animal  force,)  belong  to  the  Sense- 
likeness  [Sinnlichkeit]  of  animal  bodies,  and  cannot  be  deduced 
from  or  explained  by  the  mechanical  and  physical  laws  of  motion. 
33.  There  is  no  difference  between  the  nerves  of  motion 
and  sensation  in  respect  to  the  method  of  receiving  and  trans- 
mitting external  impressions  (14,  31). — See  Haller's  'Physiol./ 
§  384.  But  as  in  the  present  section  we  have  to  consider  the 
animal  forces  abstractedly,  and  without  reference  to  their  motive 
force  on  the  mechanical  machines  (16),  that  which  has  been 
stated  must  be  understood  to  apply  to  the  motor  nerves  only, 


CH.  II.]  EXTERNAL  SENSATIONS.  33 

in  so  far  as  they  are  at  the  same  time  sensitive  nerves.  In  the 
Third  Chapter  we  shall  state  how  far  the  animal  forces  of  both 
kinds  of  impressions  on  the  nerves  act  on  the  mechanical 
machines  appropriated  to  the  motion  of  animal  bodies^  and  in 
particular  how  far  they  regulate  these,  as  animal-sentient  forces 
of  the  nerves  (8).  But  how  do  the  impressions,  per  se,  act  on 
the  nervous  system  ?  And  what  animal  forces,  and  especially 
what  animal-sentient  forces,  become  thereby  participants  in  that 
action  ? 

On  External  Sensations. 

34.  When  a  nerve  of  a  sentient  animal  receives  an  external 
impression,  it  is  transmitted  along  it,  and  unanimous  observa- 
tions show,  that  at  each  impression,  certain  animal  actions 
result  therefrom,  either  in  the  brain,  from  which  the  nerve 
arises  (12),  or  in  those  parts  of  the  body  with  which  it  is  in 
connection ;  but  these  actions  no  longer  result,  even  when  the 
external  impression  is  made,  if  its  transmission  to  the  structure 
in  which  they  previously  took  place  be  prevented  by  section 
or  ligature  of  the  nerve  (43).  This  transmission  takes  place 
from  the  point  of  impression  upwards  (31,  32),  and  either 
arrives  at  the  brain  or  not.  Both  cases  occur  in  nature  (see 
illustrations  of  the  latter  in  47-51).  In*  the  former  case,  the 
external  impression  entering  the  brain,  instantaneously  develops 
that  material  idea  in  it  which  is  required  for  the  development 
of  the  conception  it  originates.  Since  the  conceptions  [Vorstel- 
lungen]  thus  excited  in  the  mind  by  external  impressions  are 
termed  ea^ternal  sensations,  this  animal  force  of  the  nerves, 
in  virtue  of  which  they  excite  sensations  by  means  of  external 
impressions,  is  termed  their  sensational  force,  or  sensibility 
[Empfindlichkeit], — (see  §  62). 

Note. — The  word  sensation  [Empfindung]  is  commonly  used 
in  a  threefold  sense.  1.  As  in  the  preceding  sentence,  where 
it  expresses  the  involuntary  sensations  [Vorstellungen],  which 
we  obtain  through  the  nerves  of  the  external  senses.  2.  When 
it  expresses  the  inner  feeling  of  the  soul, — its  consciousness 
of  itself  (80).  3.  When  it  denotes  generally  the  perception 
[Vorstellung]  of  the  existing  condition  indefinitely,  or  equally, 
whether  this  perception  be  excited  by  an  external  impression  or 
not.    It  is  of  the  highest  importance,  that  these  three  meanings 

3 


34  CEREBRAL  FORCES.  [i. 

be  distinguished^  for  otherwise  the  doctrines  as  to  the  recriprocal 
influence  of  body  and  soul  can  only  be  indistinctly  and  inde- 
finitely comprehended.  We  have,  therefore,  for  want  of  more 
elegant  expressions,  determined  to  designate  sensations  of  the  first 
c\a,ssea^ternalj  and  of  the  second  internal,  and  never  to  vary  from 
these  terms,  except  when  we  use  the  verb  to  feel,  in  the  third, 
general,  or  indefinite  meaning,  when  it  is  not  necessary  to  say 
whether  external  or  internal  sensations  are  meant.  The  reader 
will  sometimes  find  it  necessary  in  the  sequel,  to  remember  these 
remarks. 

35.  A  true  external  sensation  is  never  excited  without  there 
being  an  external  impression  on  the  nerves,  and  consequently 
the  latter  is  rightly  considered  the  only  primary  animal  force  (6), 
whereby  the  soul  feels.  But  since  external  sensations  are  con- 
ceptions which  cannot  possibly  arise  without  material  ideas  in 
the  brain  (25),  it  follows  that  in  each  case  an  external  impres- 
sion must  excite  a  material  external  sensation  in  the  brain,  and 
itself  develop  true  external  sensations,  independently  of  the 
co-operation  of  the  conceptive  force.^ 

»  The  Gottingen  reviewer  of  Unzer's  work,  referring  to  this  doctrine  as  to  the 
development  of  external  impressions  into  material  ideas  (the  "species"  of  Haller), 
objects  "that  nerves  pass  from  and  to  the  spinal  cord  and  enter  it,  and,  conse- 
quently, that  the  external  impressions  made  on  them  ought  to  be  developed  therein 
into  material  ideas ;  yet  it  is  certain  that  the  soul  neither  feels  nor  has  its  seat  in 
the  spine."  This  and  other  objections  raised  against  Unzer's  views  in  this  review 
are  the  more  interesting,  because  it  seems  probable  that  Haller  was  the  writer,  and 
because  it  gives  Unzer  an  opportunity  of  explaining  some  points  more  fully.  He 
then  replies  to  the  objection : — "  Although  this  is  hardly  advanced  as  an  objection, 
and  although  I  have  not  only  not  neglected  to  notice  the  matter  referred  to,  but 
have  entered  into  details  in  illustration ;  still  it  is  sufficiently  important  to  merit 
further  consideration.  It  is  not  merely  a  change  caused  at  the  origin  of  a  nerve  by 
impressions,  that  induces  sensation  and  thought,  but  it  is  always  necessary  thereto, 
that  there  be  a  cerebral  tissue  into  which  the  nerve  must  penetrate.  Since  new 
fibrils  frequently  pass  out  from  the  ganglia,  it  might  be  inferred  that  all  might  feel ; 
but  as  there  is  that  peculiar  structure  wanting  in  them,  which  is  present  in  the  brain, 
and  is  subservient  to  the  formation  of  material  ideas,  the  change  which  the  nerves 
undergo  in  the  ganglia  from  external  influences,  is  only  a  motor  force — a  reflexion 
of  the  impression  upon  other  nerve-fibrils, — and  which  has  been  fully  explained 
already  in  my  work  (399,  421).  It  is  the  same  with  the  nerves  which  arise  from 
the  spinal  cord,  and  which  probably  have  the  twofold  function  of  transmitting  to  the 
spinal  cord  the  impressions  they  receive,  that  they  may  be  sent  directly  forwards  to 
the  brain  and  subserve  to  sensation ;  or  that  they  may  be  reflected  in  the  spinal 
cord  on  other  nerves,  and  thus  induce  certain  movements  which  otherwise  would 
not  have  resulted  from  these  impressions." — Physiologische  Untersuchungen,  p.  24. 
Compare  also  §  624.— Ed. 


CH.  II.]  EXTERNAL  SENSATIONS.  35 

36.  True  external  sensations  are  conceptions  excited  by 
external  impressions  on  the  nerves.  Thereby  the  mind  dis- 
tinguishes at  each  act  of  attention  the  point  where  the  external 
impression  takes  place.  Consequently,  the  sphere  of  action  of 
the  external  impression,  which  causes  the  external  sensation,  is 
only  between  the  point  of  impression  and  the  material  external 
sensation  in  the  brain;  and  since  there  is  first  the  external 
impression,  and  then  its  transmission,  the  vital  changes  which 
cause  the  external  sensations  must  be  propagated  from  the 
point  of  impression  upwards  to  the  brain,  and  not  downwards, 
from  the  brain,  in  so  far  as  they  are  felt  (31).  If,  consequently, 
a  branch  of  a  nerve  is  irritated  at  a  point  nearest  to  the 
brain,  the  external  impression  which  ascends  thence  to  excite 
a  material  external  sensation,  can  excite  it  in  the  most  distant 
branches,  and  by  their  means  develope  impossible  animal  actions. 
And  if  these  actions  should  arise  in  the  distant  branches,  or 
through  them,  they  are  the  actions  resulting  from  an  impression 
occurring  contiguous  to  the  brain  which  is  sent  downwards, 
and  contributes  nothing  to  sensation.  The  probable  motion  of 
the  vital  spirits  accords  with  this  view. 

37.  It  may,  however,  be  quite  possible,  with  regard  to  many 
external  impressions,  that  the  impression  on  the  nerve  may  so 
take  place,  that  it  concusses  it,  or  its  lower  or  more  distant 
branches,  only  mechanically.  The  impressions  excited  by  this 
mechanical  concussion  of  the  nerves  are  sometimes  duly  received, 
and,  like  other  external  impressions,  propagated  to  the  brain, 
and  there  produce  external  sensations.  Thus,  an  external 
impression  may  appear  to  be  transmitted  downwards  without 
that  being  actually  the  case.  An  example  of  this  kind  is 
afforded  by  the  tingling  which  a  blow  of  the  elbow  causes  to 
be  felt  as  far  as  the  tips  of  the  fingers,  the  nerve  being 
mechanically  concussed ;  it  cannot  be  said  that  the  external 
impression  felt  at  the  elbow  had  been  propagated  backwards, 
and  felt  through  the  fingers. 

38.  The  mind  determines  the  point  of  external  impression 
in  external  sensations  by  an  act  of  the  judgment.  At  first 
it  learns  to  distinguish  the  point  of  contact  by  a  due  observa- 
tion of  its  external  sensations,  and  a  comparison  of  them  with 
the  place  where  the  external  impression  takes  place  ;  but  after 
frequent  repetition  it  determines  it  in  a  shorter  way,  by  analogy. 


36  CEREBRAL  FORCES.  [i. 

It  is  accustomed,  for  example,  to  decide  as  to  the  external 
sensations  which  it  feels  through  the  terminating  nerve-fibrils 
of  the  left  hand,  which  transmit  the  impressions  they  receive 
to  the  brain,  along  the  trunk  of  the  nerve,  that  they  take  place 
in  virtue  of  external  impression  on  the  left  hand.  But  if  this 
hand  be  amputated,  and  these  terminating  fibrils  be  altogether 
removed,  still  every  external  impression  made  on  the  cut  end 
of  the  trunk  of  the  nerve  of  the  left  arm,  being  likewise  trans- 
mitted to  the  brain,  seems  to  come  from  the  left  hand,  when, 
from  a  want  of  attention,  the  accustomed  method  of  estimating 
the  point  of  contact  is  adopted ;  and  the  mind  is  only  aware 
from  due  observation,  that  its  estimate  is  erroneous.  This 
case  (in  which  there  is  no  true  external  sensation  from  the  left 
hand)  cannot  prove  that  a  true  external  sensation  of  an  external 
impression  can  reach  the  mind  from  a  more  distant  spot  than 
the  true  point  of  impression  of  the  nerve ;  but  simply  that  the 
judgment  may  sometimes  err  respecting  the  external  sensations, 
which  error  is  a  defect  of  the  judgment,  and  not  of  sensation. 
In  this  way  a  thousand  phenomena  must  be  estimated,  as  when 
a  person  thinks  he  has  sensations  in  a  lost  limb,  or  when  he 
seeks  the  point  of  sensation  in  a  broken  limb,  in  a  natural 
direct  line,  and  finds  it  in  quite  another  place. 

39.  External  impressions  may  be  made  on  many  nerves  at 
the  same  time,  and  the  mind  can  distinguish  all  and  each  of 
the  external  sensations  thence  arising,  although  the  impressions 
come  from  the  most  distinct  nerves  into  a  common  trunk  (as 
for  example,  the  spinal  cord),  before  they  reach  the  brain,  and 
there  form  the  material  ideas  of  an  external  sensation.  In 
the  same  nerve,  and,  at  the  same  time,  different  impressions 
may  be  made,  yet  the  mind  accurately  distinguishes  them ;  so 
that  every  external  impression  on  each  point  of  a  nerve  takes 
also  an  uninterrupted  course  to  the  brain,  and  can  there  form 
the  material  sensation  peculiar  to  itself,  and  distinct  from  all 
others,  without  being  confounded  or  mingled,  either  on  its  way 
with  other  impressions  ascending  at  the  same  time,  along  the 
nerve,  or  with  the  material  sensations  which  arise  at  the  same 
time  in  the  brain.  The  reason  of  this  is,  that  the  terminating 
fibrils  ^hich  receive  the  impressions  run  a  distinct  course  to  their 
origin,  and  remain  quite  separate,  however  they  may  be  united 
with  other  fibrils  to  form  an  entire  nerve,  or,  however  the 


I 


CH.  II.]  EXTERNAL  SENSATIONS.  37 

latter  may  be  united  to  form  larger  trunks,  as  the  spinal  cord.^ 
Further,  at  the  place  of  origin  of  the  nerve  in  the  brain,  there 
is  a  distinct  point  where  the  material  ideas  must  be  developed 
from  the  external  impressions  which  it  brings  to  the  brain. 

40.  It  is  useless  to  attempt  an  arrangement  of  the  various 
kinds  of  external  impressions  according  to  the  variation  in  their 
external  sensations.  Everything  is  ordered  according  to  laws 
altogether  unknown,  and  which  we  can  never  fathom.  Pain, 
for  example,  is  a  sensation  which  usually  arises  from  very 
vehement  external  impressions  on  the  nerves;  nevertheless, 
the  most  violent  disturbance  of  a  nerve  is  not  always  the  most 
painful.  A  corrosive  fluid  can  excite  a  far  more  intolerable 
pain  in  a  nerve,  than  a  blow  which  shatters  the  bone  of  the 
limb.  Neither  is  it  the  separation  of  the  components  of  a 
nerve  by  the  corrosion,  which  causes  the  pain  to  be  so  acute, 
for  a  sharp  knife  divides  it  without  any  remarkable  pain.      It 

'  This  important  doctrine  of  the  distinct  course  of  each  nerve-fibril  was  taught 
at  Leyden  during  the  first  half  of  the  last  century.  The  following  quotation  will 
interest  the  reader : — '<  The  doctrine  of  Albinus, — indeed,  of  the  whole  school  of 
Boerhaave, — in  regard  to  the  nervous  system,  and,  in  particular,  touching  the  dis- 
tinction and  the  isolation  of  the  ultimate  nervous  filaments,  seems,  during  a  century 
of  interval,  not  only  to  have  been  neglected,  but  absolutely  forgotten  ;  and  a  counter- 
opinion  of  the  most  erroneous  character,  with  here  and  there  a  feeble  echo  of  the 
true,  to  have  become  generally  prevalent  in  its  stead.  For,  strange  to  say,  this  very 
doctrine  is  that  recently  promulgated  as  the  last  consummation  of  nervous  physiology 
by  the  most  illustrious  physiologist  in  Europe.  '  That  the  primitive  fibres  of  all 
the  cerebro-spinal  nerves  are  to  be  regarded  as  isolated  and  distinct  from  their 
origin  to  their  termination,  and  as  radii  issuing  from  the  axis  of  the  nervous 
system,'  is  the  grand  result,  as  stated  by  himself,  of  the  elaborate  researches  of 
Johann  Mueller;  and  to  the  earliest  discovery  of  this  general  fact  he  carefully 
vindicates  his  right  against  other  contemporary  observers,  by  stating  that  it  had 
been  privately  communicated  by  him  to  Van  der  Kolk,  of  Utrecht,  so  long  ago  as 
the  year  1830."  (Phys.,  pp.  596-603 ;  Supplementary  Dissertations  to  Reid's  Works, 
by  Sir  W.  Hamilton,  Bart.,  &c.,  note  D  ;  '  On  the  Distinction  of  the  Primary  and  Se- 
condary Qualities  of  Body,'  p.  874.) 

This  whole  essay  is  a  mine  of  suggestive  thought  to  the  neurologist,  but  is  specially 
interesting  from  containing  a  general  abstract  of  the  doctrines  taught  by  the  younger 
Albinus,  in  his  lectures  delivered  at  Leyden,  and  which  Sir  W.  Hamilton  has  obtained 
from  a  manuscript  copy  in  his  Ubrary  of  the  '  Dictata,'  of  Albinus,  taken  very  fully 
after  the  middle  of  the  last  century  by  Dr.  William  Grant,  and  collated  with  another 
copy  by  an  anonymous  hand  of  1741.  Having,  by  the  kindness  of  Sir  William 
Hamilton,  had  an  opportunity  of  perusing  a  portion  of  these  '  Dictata,'  I  cannot  but 
concur  with  that  profound  metaphysician  in  au  expression  of  regret  that  they  have 
never  been  printed. — Ed. 


38  CEREBRAL  FORCES.  [i. 

is  the  same  with  the  tickling  which  a  fine  feather,  or  particle 
of  dust,  can  excite,  for  it  is  a  state  of  the  nerve  allied  to  that 
of  pain,  and  sensations  much  pleasanter  than  it  require  much 
stronger  external  impressions.  Indeed,  the  more  indifferent 
external  sensations  of  heat  and  cold,  hardness  and  softness, 
moist  and  dry,  of  light,  of  dissolved  salts,  &c.,  are  so  totally- 
different  in  the  mind,  that  it  is  certain  the  external  impressions 
on  the  nerves  must  be  different  also ;  but  we  know  of  nothing 
generally,  as  to  this  difference,  which  may  serve  as  a  general  rule. 
41,  42.  It  is  equally  impossible  to  compare  the  material  ideas 
with  the  external  impressions,  or  both  these  with  the  external 
sensations  {vide  Haller^s  '  Phys.,'  §  556).  Every  external  im- 
pression does  not  necessarily  excite  external  sensations  (34), 
although  external  sensations  are  the  only  conceptions  it  can 
excite  (35).  Since  an  external  impression  differs  from  every 
other  in  this,  that  it  excites  animal  operations,  and  these  can 
be  either  in  the  mind  as  external  sensations,  or  only  in  the 
body,  and  consist  simply  in  animal  movements  (7)  j  and  since 
we  have  only  to  consider  here  the  operations  on  the  mind  of 
an  external  impression  (33),  we  must  inquire  under  what  con- 
ditions an  external  impression  develops  external  sensations,  and 
under  what  conditions  it  does  not. 

43.  If  a  nerve  of  special  sense  be  compressed  or  divided,  the 
sense  is  lost.  If  the  brain  be  compressed,  sensation  ceases  in 
the  whole  body ;  and  when  the  spinal  cord  is  compressed,  sen- 
sation ceases  in  the  part  below  the  point  compressed.  The 
reason  in  all  these  cases  is,  that  either  external  impressions  are 
not  transmitted  to  the  brain,  or,  if  transmitted,  do  not  excite 
in  it  the  material  ideas  requisite  to  sensation. 

44.  That  a  part  be  sensitive,  it  is  requisite  that  it  be  endowed 
with  nerves  capable  of  receiving  those  external  impressions, 
which  can  be  transmitted  uninterruptedly  to  the  brain,  and 
there  excite  the  material  idea  of  a  conception.  The  more  a 
part  is  endowed  with  such  nerves,  the  more  readily  it  receives 
an  external  impression ;  and  the  more  uninterruptedly  it  can  be 
transmitted  to  their  origin  in  the  brain  (43),  the  more  sensitive 
it  is.  The  less  a  part  is  supplied  with  such  nerves,  although 
it  may  have  many  others  of  a  different  kind,  and  the  more  diffi- 
cult it  is  to  convey  external  impressions  to  them,  that  is  to  say, 
the  more  they  are  covered  and  protected  from  contact,  and  the 


CH.  II.]  EXTERNAL  SENSATIONS.  89 

more  hindrances  there  are  to  an  uninterrupted  transmission  to 
the  brain,  of  an  external  impression,  in  the  same  proportion 
the  part  is  insensible  (34). 

45.  We  are  now  able  to  say  what  is  requisite  to  the  develop- 
ment of  an  external  sensation. 

i.  A  nerve  must  be  so  acted  on,  that  its  medulla  thereby 
receives  an  external  impression  (31,  32). 

ii.  This  impression  must  be  propagated  into  the  brain,  so 
far  as  the  origin  of  the  nerve  (43,  44) . 

iii.  It  must  there  excite  the  animal  movement  (a  material 
idea),  which  naturally  arises  from  this  external  impression  ;  and 
so  soon  as  this  takes  place,  the  conceptive  force  of  the  soul 
develops  the  external  sensation  (34,  25). 

46.  An  external  sensation  derived  from  a  given  nerve  may 
be  interrupted,  or  cannot  arise. 

i.  When  the  nerve  is  not  acted  on,  or  not  sufficiently  so, 
that  its  medulla  receives  an  external  impression  (45,  i) .  All  con- 
ceptions, consequently,  which  are  considered  to  be  such  external 
sensations,  but  which  arise  only  from  the  conceptive  force  with- 
out an  external  impression,  are  not  true  external  sensations : 
of  this  kind  are  imaginations,  recollections,  anticipations,  &c. 

ii.  When  the  external  impression  does  not  reach  the  brain  at 
all,  but  particularly  that  point  where  the  material  sensation  is  to 
be  developed.  It  does  not  follow  because  a  nerve  has  been  acted 
on,  and  an  external  impression  excited,  that  the  latter  must 
necessarily  be  felt  (42),  for  to  this  end  the  impression  must 
find  its  way  uninterruptedly  to  the  brain  (45,  ii). 

iii.  When  the  material  idea,  which  ought  naturally  to  result 
from  the  external  impression,  cannot  arise  in  the  brain  (45,  iii). 
The  brain  may  be  defective  at  those  points  whence  the  nerve 
arises,  and  thus  the  limb,  to  which  the  nerve  is  distributed,  may 
be  rendered  insensible  to  all  external  impressions,  although  their 
existence  along  their  whole  course  to  the  brain,  be  rendered 
manifest  by  other  animal  movements. 

47.  Since,  in  the  normal  condition  of  animal  organisms,  all 
external  impressions  do  not  excite  material  external  sensations, 
so  also  there  are  portions  amply  supplied  with  nerves  which 
have  little  sensation ;  so  that  the  amount  of  sensibility  of  a  part 
cannot  be  deduced,  from  the  number  of  nerves  without  certain 
limitations.  Nevertheless,  these  numerous  nerves  may  be  of  great 


40  CEREBRAL  FORCES.  [i. 

use  in  the  animal  economy,  by  means  of  other  animal  opera- 
tions (42) ;  and  as,  in  fact,  experience  teaches  us,  that  many  parts 
well  supplied  with  nerves  have  little  sensation,  feeling  but  rarely, 
and  only  a  few  external  impressions,  and  those  of  a  special  kind, 
as  the  heart,  stomach,  &c.,  it  is  very  probable,  that  in  animals 
in  a  state  of  health  many  external  sensations  are  prevented  by 
similar  natural  obstacles,  and  that  this  is  no  abnormal  condition 
of  many  nerves.  That  this  important  matter  may  be  placed 
in  its  proper  light,  we  will  endeavour  in  every  possible  way  to 
demonstrate  from  observations,  how  external  sensations  are 
prevented  naturally. 

i.  Nature  protects  many  nerves  from  contact  by  coverings, 
by  envelopes  of  cutis,  or  mucus,  or  so  distributes  them,  that  they 
are  only  exposed  to  slight  or  gentle  contact,  or  to  certain  im- 
pressions expressly  adapted  to  them,  and  little,  if  at  all,  to  any 
other.  By  this  means,  also,  external  sensations  are  so  moderated 
as  not  to  be  painful  (46,  i) . 

ii.  There  are  many  nerves,  so  situated  and  distributed,  that 
they  are  only  exposed  to  certain  agencies,  the  optic  for  example ; 
which,  in  general,  are  only  susceptible  of  external  impressions 
from  the  rays  of  light ;  while  the  nerves  of  the  skin  receive  no 
impressions  from  the  rays  of  light  (40).  In  the  same  way,  the 
undulations  of  the  atmosphere,  which  duly  act  as  impressions  on 
the  auditory  nerves,  cause  no  external  impression  on  the  delicate 
and  sensitive  nerves  of  vision.  The  odorous  particles  which  are 
so  perceptible  by  the  olfactory  nerves,  have  no  effect  on  the 
tactile,  gustatory,  auditory,  or  visual  nerves.  Sometimes  certain 
nerves  are  endowed  for  a  period  only,  with  the  capability  of 
receiving  external  impressions  from  certain  irritations  and 
influences,  which  they  afterwards  lose,  as,  for  example,  in  the 
sensational  instincts  (265). 

iii.  Further,  certain  external  impressions  act  so  feebly  on 
nerves  otherwise  sensitive,  that  they  do  not  go  onwards  to  the 
brain,  but  are  weakened  or  lost  in  their  course  thereto.  That 
this  feeble  influence  on  the  nerve  has  certainly  excited  an 
external  impression,  is  made  clear  by  other  animal  actions,  as, 
for  example,  by  certain  animal  movements  which  the  impression 
excites ;  and  the  cause  of  its  not  being  felt  must  be  in  its  not 
having  reached  the  brain.  Flatus  in  the  stomach  often  excites 
a  tension  of  the  nerves,  which  is  so  feeble,  that  we  do  not  feel 


CH.  II.]  EXTERNAL  SENSATIONS.  41 

it ;  although  the  external  impression  that  takes  place  at  the  same 
time,  betrays  itself  by  animal  actions,  namely,  contraction  of 
the  stomach,  as  is  proved  by  the  rumbling  of  the  flatus.  But 
the  transmission  of  the  external  impression  to  the  brain  is 
prevented  in  the  natural  state,  or  state  of  health,  in  a  way  which 
requires  a  copious  elucidation. 

48.  iv.  It  is  incontrovertible,  that  many  nerves,  although 
sensitive,  are  mainly  appropriated  to  certain  special  movements ; 
and  that  the  external  impressions  necessary  thereto,  are  seldom 
or  never  transmitted  to  the  brain,  or  only  those  of  a  certain 
kind ;  but  that,  for  the  most  part,  it  is  their  normal  condition 
to  remain  in  the  nerve.  The  nerves  of  the  stomach,  intestines, 
and  heart,  illustrate  this  point.  Food  which  gives  rise  to  a 
strong  sensation  in  the  mouth,  causes  no  sensation  whatever 
when  passed  into  the  stomach.  Whether  it  be  bitter,  sweet, 
or  salt,  it  is  the  same  in  the  stomach.  Yet  the  stomach  is 
more  amply  supplied  with  nerves  than  most  other  viscera,  and 
these  are  highly  sensitive  to  other  impressions,  as  those  of  acrid 
poisons,  for  example,  and  consequently  quite  susceptible  of  ex- 
ternal impressions.  As  food  comes  into  contact  with  them  as 
certainly  as  poisons,  and  excites  an  external  impression,  which 
undeniably  develops  the  animal  movements  of  digestion  that 
result  from  the  contact,  it  necessarily  follows,  that  the  external 
impressions  on  these  nerves  are  not  generally  transmitted  to 
the  brain,  but  are  lost  in  the  mechanical  machines,  to  the 
movement  of  which  they  are  specially  appropriate.  An 
acridity  in  the  stomach  will  be  felt  little,  if  at  all ;  but  if  it  be 
in  the  mouth,  it  almost  suffocates  us,  and  bites  the  tongue ;  on 
the  other  hand,  it  will  excite  a  gastric  spasm  in  the  gastric  nerves 
by  its  external  impression.  The  heart  is  abundantly  supplied 
with  nerves,  and  remarkably  sensitive.  The  impression  of  the 
blood  flowing  through  it  excites  its  movement,  which,  even 
when  it  has  ceased,  can  be  renewed  by  the  injection  of  warm 
fluids,  and  yet  the  mind  feels  nothing  of  this  external  impression. 
The  special  destiny  of  these  nerves  is  to  excite  the  motion  of 
the  heart,  which,  according  to  the  views  of  all  physicians,  is 
vital  and  not  mechanical  in  its  nature.  It  is  so  little  necessary 
that  the  external  impression  made  on  the  nerves  which  move  it 
be  felt,  that  motion  can  be  re-excited  in  a  heart  detached  from 
the  body  by  an  external  impression  on  the  terminating  fibrils 


42  CEREBRAL  FORCES.  [i. 

of  the  nerves,  as  when  salt  is  sprinkled  on  them ;  and  by  this 
experiment  all  probability  of  a  mere  mechanical  excitement  by 
the  impression,  (as  in  filling  the  heart  with  warm  fluids,  or  with 
air,)  is  taken  away.  Since,  also,  external  sensation  is  not  neces- 
sary to  the  ordinary  motion  of  the  heart,  there  must  be  natural 
hindrances  to  transmission,  in  virtue  of  which  certain  external 
impressions  are  retained  in  these  and  analogous  nerves,  so  that 
they  cannot  pass  upwards  to  the  brain  (see  §  55 — 61).  It  is  diffi- 
cult to  say,  in  what  these  hindrances  consist.  The  external  im- 
pression on  the  heart  is  really  there,  since  every  motion  of  the 
heart  is  excited  by  it.  It  is  also  in  the  stomach  after  taking  food, 
since  the  peristaltic  motion  of  the  latter  is  renewed  by  it.  What 
prevents  the  propagation  of  all  these  impressions  to  the  brain  ? 
There  is  nothing  to  be  found  in  the  nerves  adapted  to  this  end, 
except  certain  formations  found  scattered  on  the  motor  nerves, 
termed  ganglia  (14),  and  the  point  of  insertion  of  the  smaller 
fibrils  in  the  larger  trunks,  where  also  a  sort  of  ganglion  is 
formed.  At  these  points,  the  direct  course  of  the  fibrils  is 
interrupted,  and  here  the  external  impression  traversing  them 
can  be  deflected  from  its  course,  and  its  transmission  to  the  brain 
prevented  (13,  14);  the  more  especially,  as  the  outer  thick  coat 
of  the  ganglion  acts  in  some  degree  as  a  muscle,  and,  by  a  slight 
compression,  can  hinder  the  transmission  (Monro) .  But  is  it  not 
probable,  that  an  external  impression  on  motor  nerves  of  this 
kind,  is  expressly  intended,  when  it  reaches  the  ganglia,  to  be 
deflected  to  the  trunk  or  branch  of  another  nerve,  or  to  another 
fibril  of  the  same  nerve  interwoven  in  the  ganglion  ?  For  thereby 
it  would  cause  a  reflected  or  retrogressive  action  in  the  fibril, 
as  if  an  impression  were  excited  in  it,  and  sent  from  above 
downwards,  or,  as  if  sent  from  the  brain ;  when  thus  deflected, 
it  puts  certain  parts  into  movement,  just  as  an  impression  really 
transmitted  along  the  nerves  from  above  downwards,  and  so 
imitates  the  latter  by  this  reflected  course  (31,  121,  122,  137). 
If,  however,  this  conjecture  be  groundless,  still  the  fact  remains, 
that  external  impressions  on  certain  nerves,  not  received  directly, 
excite  movements  without  reaching  the  brain,  and  without  being 
felt. 

49.  V.  Amongst  the  natural  impediments  to  external  sensa- 
tions, those  also  may  be  classed  (according  to  46,  iii)  which 
prevent  the  external  impression  from  developing  in  its  proper 


CH.  II.]  EXTERNAL  SENSATIONS.  48 

place  the  material  idea  belonging  to  it,  although  it  has  arrived 
at  the  brain ;  that  there  are  such  impediments  is  certain,  and 
sleep  is  an  example.  This  is  a  periodic  state  of  insensibility 
natural  to  all  animals  endowed  with  sensation,  and  enables  them 
to  collect  new  strength  after  the  weariness  resulting  from  ac- 
tivity, and  which  arises,  as  some  think,  from  the  want  or 
weakness  of  the  vital  spirits ;  light  may  shine  into  the  eyes, 
sound  fall  on  the  ears,  and  the  nerves  may  be  stimulated  in  a 
thousand  waj^s,  and  yet  no  external  sensation  be  excited. 
Consequently,  either  the  external  impression  never  reaches 
the  brain  (and  for  this  conclusion,  there  is  not  the  slightest 
foundation),  or  else  no  material  ideas  are  formed  therein, 
or  at  least  only  imperfectly ;  and  this  is  probably  the  true 
doctrine,  since  a  compression  of  the  brain,  either  by  haemor- 
rhage, or  effusion,  or  depression  of  a  portion  of  the  cranium, 
or  even  excessive  distension  of  the  blood-vessels,  develops  the 
same  insensible  state,  and  induces  true  sleep.  It  appears  as  if 
the  brain  were  in  a  state  of  torpor  in  profound  sleep,  so  that 
the  material  ideas  are  prevented  being  developed  by  the  external 
impression  on  the  nerves ;  whilst  the  purely  animal  movements 
excited  by  the  impression  on  the  latter  only  appear  to  ex- 
perience no  change, — (see  §  182,  183.) 

50.  vi.  There  is  still  another  special  cause  which  prevents 
external  sensations  arising  in  the  mind,  in  one  or  other  of  the 
five  methods  described  (47-49) ;  and  this  is  the  frequent  repetition 
of  an  external  sensation.  By  this,  as  observation  teaches, 
many  external  sensations  become  gradually  weaker  and  weaker, 
and  at  last  cease  altogether,  although  the  impression  on  the 
nerve  still  takes  place.  This  diminution  and  destruction  of 
external  sensations  by  frequent  repetition,  is  termed  the  habit 
of  external  sensations,  and  since  it  cannot  be  explained  on 
mechanical  principles,  it  must  be  classed  with  the  properties 
peculiar  to  animal  bodies  (6). 

51.  Habit  weakens  or  destroys  external  sensations  in  the 
five  following  ways : 

i.  By  their  frequent  repetition  the  susceptibility  of  the 
nerve  may  be  weakened  or  prevented  (47,  i).  For  example,  a 
thick  cuticle  is  developed,  and  protects  the  terminating  fibrils, 
in  consequence  of  certain  oft-repeated  impressions  on  the  organs 
of  touch. 


44  CEREBRAL  FORCES.  [i. 

ii.  An  impression^  often  repeated  on  a  nerve,  may  render 
it  unfit  to  receive  that  particular  impression,  although  it  may 
receive  every  other;  as  when  one  who,  accustomed  to  cold, 
neither  feels  the  cold,  nor  has  goose-skin  produced,  and  yet 
would  feel  a  tickling  from  the  slightest  touch  of  a  feather. 

iii.  The  frequent  repetition  of  the  same  external  sensation 
may  render  a  nerve  insensible  (47,  iii.) 

iv.  When  the  frequent  repetition  of  the  same  external  im- 
pression (48),  renders  the  nerve  so  insensible,  that  thereby 
the  ganglia  and  points  of  anastomosis  are  so  changed  that 
they  retain  an  impression  which  they  previously  allowed  to 
pass.  This  may  only  be  observed  in  the  cases  in  which  an 
external  impression,  in  an  unweakened  nerve,  excites  both 
sensation  and  movements  at  the  same  moment ;  but  in  the  ab- 
normal condition  excites  the  latter  only.  In  such  a  case  the 
occurrence  of  the  animal  movement  (a  proof  wanting  in  other 
instances),  shows  that  the  external  impression  is  really  received 
by  the  nerve  and  transmitted  to  the  point,  where,  on  its  way 
to  the  brain,  it  is  reflected  and  sent  downwards  along  the 
trunk  of  the  nerve,  being  the  direction  taken  by  an  impression 
transmitted  from  the  brain  itself  (31,  122).  This  is  the  only 
explanation  admissible,  since  as  the  nerve  is  not  enfeebled,  the 
principle  just  laid  down  (iii)  cannot  apply.  Instances  will  be 
remembered  of  persons  who  experienced  spasms  in  their  limbs 
from  various  external  impressions  made  on  nerves  in  a  distant 
part,  and  in  whom  the  same  spasms  continue  to  occur, 
although  the  mind  has  become  at  last  habituated  to  the  pain, 
and  it  is  no  longer  felt.  So,  also,  many  epileptic  and  gouty 
patients — the  paroxysms  they  suffer  being  excited  by  worms  or 
gouty  humors,  causing  external  impressions  on  the  nerves  of 
the  stomach — can  foretell  an  attack  from  the  sensations  thus 
excited.  After  a  time,  however,  when  the  disease  is  rendered 
chronic,  these  sensations  are  no  longer  felt,  and  the  paroxysms 
come  on  quite  unexpectedly. 

V.  Lastly,  the  frequent  repetition  of  the  same  external  im- 
pression can  weaken  or  destroy  the  external  sensations.  The 
point  in  the  brain,  where  the  impression  ought  to  excite  the 
material' external  sensation,  undergoes  such  a  change,  that  the 
development  of  the  material  idea  is  prevented  (49).  This  is 
the  case  when  a  miller  becomes  so  accustomed  to  the  noise 


CH.  II.]  EXTERNAL  SENSATIONS.  45 

of  his  mill,  that  he  does  not  hear  it  at  all,  or  only  with  an  in- 
distinct consciousness.  Again,  we  know  that  when  the  mind 
is  abstracted  from  other  conceptions,  and  devotes  itself  to  one 
only  (an  act  termed  attention) ^  it  can  only  do  this  by  a  cessa- 
tion of  the  movements  in  the  brain;  or,  in  other  words,  of 
the  material  ideas  of  the  conceptions  from  which  it  is  ab- 
stracted (21).  Such  a  repose  of  the  brain  probably  takes 
place  in  cases  of  the  kind  under  consideration. 

52.  When  the  nerves  of  an  organism  receive  external  im- 
pressions with  greater  comparative  facility,  and  when  the  latter 
meet  with  fewer  or  less  important  natural  obstructions  to  their 
transmission  to  the  brain,  and  to  the  formation  of  material 
external  sensations  therein  (47,  51),  the  organism  is  termed 
sensitive,  in  a  special  sense  [excitablej  susceptible) ;  or,  if  the  con* 
trary,  insensible  (harsh,  unfeeling);  and  the  qualities  themselves 
are  termed  individual  sensibility  (94),  individual  insensibility. 
The  property  of  animal  nature,  in  relation  to  sensibility  and 
insensibility,  is  the  temperament  of  an  animal  body :  the  bodily 
constitution, — the  nature.  By  habit,  sensitive  organisms  become 
insensible ;  consequently  the  temperament  is  changed,  and  this 
may  take  place  in  all  the  modes  indicated  (51).  An  individual 
sensibility  towards  certain  external  impressions,  not  shown  by 
the  majority  of  persons  of  a  similar  temperament,  is  termed 


53.  Mental  philosophers  maintain,  that  external  sensations 
have  greater  strength  than  other  conceptions,  because  they 
consist  of  a  greater  number  of  elements  [merkmalen], 
(Baumgarten's  '  Metaphysics,'  §  402).  Now,  since  each  element 
of  a  conception  is  also  a  conception  itself,  and  every  conception 
requires  a  material  idea  in  the  brain  (25),  it  follows,  that  the 
material  ideas  of  external  sensations  are  compounded  of  more 
movements  in  the  brain,  than  the  material  ideas  of  all  other 
conceptions.  Consequently,  they  exceed  the  latter  in  intensity, 
that  is  to  say,  the  movements  in  the  brain  which  external 
sensations  produce,  are  greater,  and  consequently  have  greater 
results,  than  those  which  accompany  other  conceptions. 

54.  Every  thing  that  enfeebles  external  sensations,  diminishes 
also  the  force  of  their  material  ideas  in  the  brain,  and  of  their 
action  in  the  organism ;  and  this  diminution  of  force  can  take 
place  by  the  same  means,  that  enfeeble  the  external  sensations 


46  CEREBRAL  FORCES.  [i. 

themselves  (46,  50).  The  material  ideas  of  external  sen- 
sations, and  their  operation  on  the  body,  are  the  strongest 
when  they  are  recent  and  not  habitual,  provided  other  circum- 
stances are  the  same. 

The  External  Senses. 

55.  The  nerves  are  the  organs  of  external  sensations,  but 
only  by  means  of  the  brain  (43).  Those  parts  of  organisms 
wherein  the  nerves  are  distributed  that  are  susceptible  only  of 
special  external  impressions,  and  consequently  only  of  special 
external  sensations,  are  termed  organs  of  the  {external)  senses. 
In  man,  these  are  five;  other  animals  have  fewer,  a  few  have 
probably  more. 

56 — 64.  The  senses  are — 1st,  touch ;  which  has  its  seat  in  the 
tips  of  the  fingers,  but  it  is  mixed  up  with  general  sensation ; 
2d,  taste,  subservient  to  nutrition ;  3d,  smell,  in  many  animals 
much  more  acute  than  in  man ;  4th,  hearing ;  5th,  sight.  The 
anatomical  relations  are  to  be  found  in  works  of  anatomy ;  the 
metaphysical  questions,  as  for  example,  why  we  do  not  hear 
two  tones,  or  see  two  images,  or  perceive  the  rays  of  light  and 
the  undulations  of  the  air,  or  feel  the  forms  of  salts,  are  dis- 
cussed at  length  in  works  of  metaphysics,  and  therefore  need 
not  detain  us. 

The  Sensational  Conceptions. 

It  has  so  far  been  shown  how  material  ideas  are  produced 
in  the  brain  by  means  of  external  impressions.  In  this  way  the 
mind  receives  conceptions  corporeally,  necessarily,  and  involun- 
tarily (27),  in  consequence  of  the  animal  force  of  the  nerves 
developing  external  sensations.  But  the  mind  can  also  produce 
voluntarily,  in  itself,  many  kinds  of  conceptions,  and  through 
these,  material  ideas  are  formed  in  the  brain,  as  an  effect  of  the 
conceptive  force,  and  by  conceptions  only,  without  the  inter- 
vention of  any  external  impressions  (27).  This  other  kind  of 
material  ideas  so  produced  must  be  defined,  before  their  in- 
fluence on  the  animal  economy  can  be  explained.  Since, 
however,  some  of  these  voluntary  conceptions  induce  only 
material  ideas  of  a  kind  that  do  not  manifest  externally  to 
the  brain  any  perceptible  efiects  in  the  animal  economy,  and 


CH.  II.]  SENSATIONAL  CONCEPTIONS.  47 

nothing  therefore  can  be  stated  scientifically  regarding  them, 
we  will  only  consider  those,  of  whose  effects  we  know  something. 

65.  No  animal  thinks  without  feeling.  Those  which  have 
the  smallest  external  senses,  manifest  the  feeblest  mental 
power.  Sensations  precede  all  their  other  conceptions.  How- 
ever possible  it  may  appear,  that  animals  which  have  felt  for  a 
time,  can  still  continue  to  think  after  all  sensation  is  lost,  there 
is  no  well-established  example  of  this ;  much  less  of  an  animal 
possessing  conceptions  which  it  has  never  felt.  Thus  sensi- 
bility [Empfindlichkeit]  is  the  first  stimulus  of  the  conceptive 
force  in  animals,  and  to  this  extent  all  their  other  conceptions 
originate  in  their  external  sensations.  Now,  since  external  sen- 
sations presuppose  material  ideas,  produced  by  external  im- 
pressions on  the  nerves  (34),  it  follows  that  the  latter  must 
regulate  all  the  mental  phenomena,  either  directly  through 
external  sensations,  or  indirectly.  But  since  all  conceptions 
are  connected  with  material  ideas  in  the  brain,  the  material 
ideas  of  all  conceptions  must  depend  either  directly  or  in- 
directly, on  external  sensations  in  the  brain,  and  on  the  external 
impressions  on  the  nerves. 

66.  When,  therefore,  the  matter  is  very  closely  considered, 
we  find  that  even  the  most  spontaneous  conceptions  are  oc- 
casioned by  external  impressions  on  the  nerves ;  but  this  causa- 
tion occurs  in  many  so  very  indirectly,  that  the  connection 
becomes  imperceptible  ;  in  others,  on  the  contrary,  it  is  more 
direct,  often  immediate,  and  this  constitutes  an  important  dis- 
tinction in  that  class  of  conceptions  which,  in  our  arrangement 
of  external  sensations,  we  have  termed  spontaneous  (27) .  It  is 
necessary,  therefore,  to  bear  this  difference  well  in  mind,  and 
not  to  adhere  too  closely,  in  a  physiological  inquiry,  to  the 
ordinary  psychological  division  of  the  conceptions  and  desires, 
into  the  obscure,  the  indefinite,  and  the  definite;  a  division 
neither  precise  in  itself,  nor  tending  to  the  advancement  of 
physiology.  When  the  mind  is  compelled  to  set  in  operation 
and  exercise  its  conceptive  force  by  various  external  sensations, 
each  of  which  presents  to  it  many  sub-impressions  of  a  single 
object  (53),  it  soon  acquires  a  facility  of  conceiving  some  of  these 
sub-impressions  spontaneously,  although  it  can  never  attain  to 
the  power  to  renew  completely  an  external  sensation,  without  the 
aid  of  an  external  impression  (35).      Or  this  may  be  presented 


48  CEREBRAL  FORCES.  [i. 

in  another  aspect,  as  follows :  when  the  animal-  sentient  force 
of  the  brain  is  frequently  excited  into  action  by  various  material 
external  sensations  derived  from  external  impressions  (which  must 
be  very  compound  movements  in  the  brain,  since  they  consist 
of  so   many  sub-impressions),  it  partly  renews  these  material 
external  sensations  by  means  of  the  inner  animal  mechanism 
of  the  cerebral  medulla,  in  conjunction  with  the  free-will  opera- 
tion of  its  own  conceptive  force,  although  it  cannot  develope 
them  fully  without  the  aid  of  the  external  impressions.     These 
spontaneous  conceptions,  which  are  nothing  more  than  incom- 
plete  external    sensations,    are   imaginations ^    so    far    as   they 
appertain  to  antecedent  external  sensations^  and  anticipations, 
so  far  as  they  may  belong  to  future  external  sensations.      Con- 
sequently, so  soon  as  the  conceptive  force  has  attained  to  that 
degree  of  perfection  by  means  of  external  sensations,  that  it 
can  of  itself  form  imaginations  and  anticipations,  it  is  led  to 
re-perceive  an  antecedent  external  sensation  by  every  new  ex- 
ternal sensation  that  has  something  in  common  with  the  latter; 
the  material  ideas  of  the  antecedent  sensation  being  again,  in 
some  degree,  excited  into  activity.      It  can,  however,  conceive 
the  antecedent  sensation  again  only  so  far  as  is  possible  with- 
out the  aid  of  the  antecedent  external  impression;   and  the 
animal-sentient  force  of  the  brain  also  co-operates  therewith  in 
renewing  each  material  external  sensation,  but  only  so  far  as 
is  possible  without  the  entire  antecedent  external  impression ; 
there  being  only  some  of  its  sub-impressions  in  the  existing 
similar  impression.      Now  the  spontaneous  conceptions  which 
are  developed  by  external  sensations  in  the  way  just  described, 
whether  directly  or  secondarily,  are  termed  sensational  concep- 
tions in  the  true  sense  of  the  word  (32)  [sinnliche  im  eigentlichen 
Verstande].^    There  are  also  sensational  imaginations  ^ndi  fore- 
seeing s.     When  sensational  conceptions,  acting  in  the  same  way 
as  external  sensations,  excite  other  spontaneous  conceptions, 
the   conceptions   thus   produced   are   termed   less  sensational, 

'  The  word  sinnlich  may  clearly  be  used  here  in  the  sense  of  semational, — see 
ante  §  31  note,  and  §  34 ;  but  it  strictly  implies  that  the  class  of  conceptions  or  act 
of  thought  referred  to  are  sinnlich,  because  necessarily  dependent  upon  a  sinnlich 
impression.  Hence  the  term  "  sensational,"  as  used  in  this  work,  must  be  considered 
to  have  a  double  meaning,  expressive  both  of  the  origin  of  certain  acts  of  mind  (or 
conceptions),  and  of  their  nature. 


CH.  II.]  IMAGINATIONS.  49 

physiologically  more  free  (27) ;  these,  again^  may  induce  other 
conceptions,  still  more  free ;  and  when  at  length  conceptions 
arise,  so  far  removed  from  sensations  induced  hy  external 
impressions,  that  the  connection  between  them  is  no  longer 
traceable,  and  containing  only  few  elements  in  common  with 
all  the  sensational  conceptions  which  have  induced  them,  they 
are  termed  conceptions  of  the  understanding  or  reason ;  higher, 
abstract,  general  ideas.  In  proportion  as  a  conception  is  less 
sensational,  it  is  the  less  to  be  deduced  from,  and  explained  by 
the  sensations  induced  by  external  impressions;  and  the  less  it 
is  under  their  control,  the  more  it  is  to  be  referred  to  psycho- 
logical principles  (27).  On  the  other  hand,  when  the  mind 
collects  and  combines  from  external  sensations,  associated  sub- 
impressions,  which  it  perceives,  sua  sponte,  without  the  assist- 
ance of  their  external  impressions,  and  only  by  the  inducement 
of  similar  external  impressions,  it  causes  material  ideas  in  the 
brain,  such  that  they  have  something  in  common  with  the 
material  ideas  of  the  external  sensations  from  which  they  are 
compounded  or  drawn.  They  imitate  imperfectly  those  move- 
ments in  the  brain,  which  can  only  be  fully  developed  by  the 
co-operation  of  the  external  impressions  of  those  external  sen- 
sations from  which  the  sensational  conception  is  compounded; 
and  when  sensational  conceptions  of  this  kind  excite  any  actions 
in  the  animal  economy,  the  actions  must  in  part  correspond 
with  those  that  result  from  the  external  sensations  themselves. 


Imaginations  [Einbildungen] . 

67.  Sensational  imaginations  are  conceptions  of  past  external 
sensations  (66), — (Baumgarten^s  ^  Metaphysics,^  §  414),  which 
the  mind  renews  spontaneously,  so  far  as  it  is  able,  without  the 
assistance  of  external  impressions  (Baumgarten,  §  415).  Con- 
sequently, they  are  wholly  sensational  conceptions.  The  ma- 
terial ideas  of  imaginations  are  also  those  of  past  external 
sensations,  but  in  that  imperfect  condition,  which  necessarily 
results  from  the  want  of  an  external  impression  (35,  53);  iu 
other  words,  when  the  mind  excites  spontaneous  imaginations, 
movements  are  also  excited  in  the  brain,  which  are  partly  the 
material  ideas  of  former  external  sensations  [QQ).  Generally  con- 
sidered, the  material  ideas  of  imaginations  are  feebler  than  those 

4 


50  CEREBRAL  FORCES.  [i. 

of  external  sensations.  Some  may,  however,  surpass  the  latter,  if 
compounded  of  many  external  sensations  (53).  The  stronger  the 
imaginations,  the  more  effective  are  their  material  ideas  (26). 

68.  That  which  is  wanting  in  the  material  ideas  of  the 
imaginations,  so  that  they  do  not  form  the  perfect  material 
ideas  of  external  sensations,  is,  the  external  impression  trans- 
mitted along  the  nerves  to  the  brain ;  which  also  renders  the 
material  ideas  more  perfect,  and  consequently,  the  conceptions 
richer  in  sub-impressions  [merkmale]  than  those  which  the 
mind  can  produce  without  it  (53). 

69.  If  material  ideas  act  as  animal-sentient  forces  of  the 
brain  (6)  in  the  animal  economy,  and  excite  animal  actions,  the 
actions  excited  by  material  ideas  of  imaginations  must  partly 
accord  with  those  of  antecedent  external  sensations  {67,  66). 

70.  Since  dreams  are  often  imaginations  of  the  sleeping 
state  (sensational  conceptions),  which  in  somnambulism,  and 
during  the  waking  state  in  insanity,  become  so  distinct  that 
they  cannot  be  distinguished  from  external  sensations,  the 
rules  stated  previously  (67 — 69),  with  reference  to  imaginations, 
are  applicable  to  all  these.  When  the  mind  spontaneously 
combines  many  imaginations,  it  invents  poetically  [dichtet  sie] . 
(Baumgarten's  ^  Metaphysics,^  §  438.)  All  that  has  been 
stated  as  to  imaginations  and  their  material  ideas,  is  applicable 
also  to  fictions  (Erdichtungen). 

71.  All  conceptions  are  connected  with  their  proper  material 
ideas  (25).  But  for  the  mind  to  know  regarding  the  same 
conception  returning  at  different  times,  that  the  last  is  the 
same  as  the  first,  a  renewed  conception  is  requisite,  and  it 
remembers,  or  an  act  of  memory  takes  place;  but  it  is  not 
necessary  to  this  end,  that  the  first  should  be  continuous  with 
the  last.  So  little,  indeed,  is  this  continuity  necessary,  that 
a  long  period  may  elapse  before  the  renewal,  without  there 
being  a  trace  of  the  conception  in  the  mind,  and  still  when  re- 
developed, the  mind  knows  that  it  is  the  same  as  the  previously 
existing  conception.  It  is  equally  unnecessary  for  the  material 
idea  of  a  conception  thus  remembered  to  have  a  continuous 
impression  on  the  brain,  or  to  leave  traces  behind  it,  of  which 
the  mind  makes  use,  so  as  to  recognise  the  renewed  conception 
as  having  previously  been  present  to  it.  Each  recognition  of 
a  conception  is  much  rather  an  operation  of  the  mind  [con- 


CH.  II.]  FORESEEINGS— EXPECTATIONS.  61 

ceptive  force],  and  is  accompanied  by  its  own  proper  material 
ideas,  of  which  we  know  nothing,  and  of  which  we  can  trace  no 
action  in  the  rest  of  the  economy.  Granted,  however,  that  a 
certain  continuance  of  the  conceptions  is  necessary  to  the 
recollections  of  the  memory,  it  follows  that  the  material  ideas 
of  these  continuous  conceptions  must  continue  also  in  the 
brain  (26),  and  this  is  the  view  usually  taken  of  the  conceptions 
of  the  memory.  But  a  conception  may  continue  in  the  mind 
for  a  century,  and  be  never  remembered,  until  a  new  con- 
ception is  formed  to  the  effect  that  it  is  the  same  as  that 
which  formerly  existed. 

72.  Sensational  memory  induces  by  its  recollections  those 
material  ideas  in  the  brain,  which  have  something  in  common 
with  the  antecedent  material  sensations  (71,  66),  and,  in  so  far 
as  they  can  excite  animal  actions,  their  actions  will  accord 
in  some  degree  with  those  of  the  antecedent  sensations  or 
imaginations. 

Foreseeings. — Expectations. 

73.  The  sensational  foreseeings  and  expectations  arise  from 
true  present  external  sensations  and  the  renewal  of  former  sen- 
sations {Imaginations,  67),  which  have  an  element  in  common 
with  each  other;  if  the  mind  considers  that,  wherein  they 
differ  as  something  to  come,  it  foresees;  or  the  same  as  that 
which  is  actually  coming,  it  expects.  (Baumgarten,  §§  444,  454.) 
They  are  more  remotely  dependent  on  external  sensations  than 
are  imaginations,  because  they  depend  on  the  latter,  which  them- 
selves are  directly  derived  from  external  sensations  (66) .  Purely 
sensational  expectations  are  termed  forebodings  [Ahndungen] 
(Baumgarten,  §  454).  Foreseeings,  expectations,  and  fore- 
bodings are  consequently  conceptions  of  future  external  sensa- 
tions, which  have  also  their  proper  sub-impressions  [merkmale] 
on  the  brain.  Consequently  the  material  ideas,  also  of  all 
these  foreseeings,  must  be  those  of  future  external  sensations, 
but  still  very  imperfect  ones,  since  the  mind  can  develope  them 
spontaneously,  only  so  far  as  is  possible,  without  the  direct  aid 
of  external  impressions  on  the  nerves  (35,  36) ;  that  is  to  say, 
when  the  mind  developes  foreseeings,  movements  arise  in  the 
brain,  which  are  the  imperfect  material  ideas  of  future  external 
sensations.      Since  foreseeings  are  weaker  than  external  sensa- 


52  CEREBRAL  FORCES.  [i. 

tions,  or  the  imaginations  themselves  (Baiimgarten,  §§  445,  446), 
their  material  ideas  are  less  energetic  than  those  of  either  (53). 
Still,  the  stronger  the  foreseeings  are,  the  greater  the  strength 
of  their  material  ideas  (26). 

74.  When  the  material  ideas  of  sensational  foreseeings  and 
forebodings  excite  animal  actions,  the  actions  must  in  part 
accord  with  those  of  the  future  external  sensations,  and  be 
regulated  according  to  the  strength  of  the  ideas. 

75.  Sensational  foreseeings  and  forebodings  are  often  pro- 
duced in  dreaming  and  in  insanity  (Baumgarten,  §  458).  What 
has  been  already  stated  generally  with  reference  to  sensational 
foreseeings  (73,  74)  is  equally  applicable  to  this  class,  and 
especially  to  those  of  soothsayers, — persons  who  have  skill  in 
foreseeing  the  future  (Baumgarten,  §  456). 

Understanding, 

76.  The  aggregate  of  the  sensational  powers  of  the  mind  {^Q) 
is  termed  the  sensational  perceptive  power ;  and  the  true  ex- 
ternal sensations,  as  well  as  the  other  sensational  conceptions, 
are  sensational  perceptions  [Erkenntnisse] .  All  conceptions 
which  are  only  remotely  determined  by  external  sensations 
(65,  66),  are  termed  conceptions  of  the  understanding  [the 
higher  perceptive  faculty);  the  faculty  of  judgment,  of  intel- 
lectual memory,  of  prevision,  &c.,  belong  to  this  class.  The 
material  ideas  of  all  these  conceptions  are  not  developed  directly, 
either  by  external  impressions,  or  by  the  material  ideas  which 
they  produce;  but  are  impressed  on  the  brain  by  the  most 
spontaneous  action  of  the  mind,  and  are  developed  by  the  very 
obscure  mechanism  of  the  animal-sentient  forces  (6,  27). 

77.  Attention  (the  directing  of  the  mind  to  anything)  is 
such  an  application  of  the  mind,  that  it  retains  a  certain  con- 
ception, while  it  neglects  the  rest.  During  attention,  the 
material  ideas  of  a  certain  conception  are  retained  when  those 
of  the  other  conceptions  become  w^eak,  or  disappear ;  and  the 
greater  the  attention,  the  more  vigorous  are  the  material  ideas 
and  their  operations.  This  turning  of  the  conceptive  force  from 
other  inferior  conceptions,  in  behalf  of  that  to  which  the  mind 
attends,  is  termed  abstraction,  and  a  continuous  act  of  attention 
to  the  components  of  an  entire  conception  or  perception,  is 


CH.  II.]  PLEASURE  AND  SUFFERING.  53 

meditation,  reflection.  In  abstraction,  many  material  ideas  cease 
in  the  brain,  or  become  weaker;  the  weaker,  indeed,  in  proportion 
as  the  abstraction  is  deep.  In  reflection,  they  follow  each 
other  continuously,  and  each  is  immediately  determined  by  its 
predecessor. 

78,  79.  Since  material  ideas  of  the  understanding  develope 
actions  in  the  organism,  it  follows  that  the  acts  of  meditation, 
abstraction,  and  attention,  by  causing  those  material  ideas  to 
cease,  will  diminish,  or  abrogate  those  actions  {77). 


Sensational  Pleasure  and  Suffering. 

80.  The  mind  has  its  own  feeling  of  its  present  condition, 
or  a  feeling  of  its  own  conceptions,  which  has  been  termed  the 
inner  sense  ("  consciousness,^'  "  inner  feeling,''  ''  conscience," 
"self-feeling,"  Baumgarten,  §  396).  Under  circumstances 
which  metaphysical  writers  explain  (ibid.,  §  478),  many  a  con- 
ception is  agreeable  or  disagreeable,  or  in  other  words,  pleases, 
satisfies,  gives  pleasure  or  displeasure,  dissatisfies,  excites  un- 
easiness. This  feeling  is  a  property  of  the  conceptions,  and 
may  belong  to  all.  Conceptions  either  please  or  displease ;  that 
which  makes  them  agreeable  or  disagreeable  is  a  sub-impression 
in  them  [merkmal] ,  which  the  mind  perceives  at  the  same  time. 
But  since  no  conception  is  at  once  both  pleasing  and  dis- 
pleasing, except  when  considered  from  another  point  of  view, 
or  in  other  words,  when  it  becomes  a  new  conception,  an 
agreeable  conception  differs  in  its  nature  from  a  disagreeable 
conception ;  and  each  consequently  makes  its  characteristic 
impression  at  the  point  in  the  brain  where  the  material  ideas 
of  the  conception  are  (25),  and  which  can  have  also  its  peculiar 
and  distinct  action  in  the  animal  economy  (26).  This  is 
termed  the  impression  of  pleasure  (lust),  or  suffering  (unlust). 

This  difference  in  the  impressions  on  the  origin  of  the 
nerves  made  by  an  agreeable  or  unpleasant  conception,  implies 
that  there  is  also  a  distinct  external  impression,  when  pleasure 
or  suffering  accompanies  external  sensations,  which  it  forms 
in  the  brain  as  its  material  idea.  A  very  strong  pleasure  of 
the  external  senses  is  termed  sensual  gratification,  or  titilla- 
tion  [Kitzel],  a  very  strong  disagreeable  impression  is  pain 
[Schmertz].    Both  are,  therefore,  external  sensations,  differing 


54  CEREBRAL  FORCES.  [i. 

in  their  nature,  and  exciting  different  material  sensations  at 
the  origin  of  the  nerve  which  feels.  The  pleasure  or  suf- 
fering which  the  proper  sensational  conceptions  (66)  excite, 
is  termed  sensational  pleasure,  or  sensational  suffering;  and 
under  this  term  pleasure  or  pain  of  the  senses  is  often  in- 
cluded. The  more  sensational  the  spontaneous  conceptions 
are  in  their  character,  the  more  their  agreeableness  or  disagree- 
ableness  is  in  accordance  with  the  sensual  pleasure  or  pain  of 
the  external  sensations  from  which  they  are  derived,  or  to  which 
they  are  related ;  and  when  they  excite  actions  in  the  economy, 
the  latter  are  similar  to  those  of  the  external  sensations.  We 
can  know  and  understand  from  the  external  impressions  of 
the  sensations,  which  either  directly  or  proximately  excite  these 
sensational  conceptions,  why  the  conceptions  ensue ;  they  ensue, 
also,  according  to  the  same  laws  (66).  On  the  contrary,  pleasure 
or  suffering  of  the  intellectual  conceptions  is  developed  accord- 
ing to  purely  psychological  laws,  and  has  no  manifest  relation 
to  the  external  impressions  of  external  sensations,  which  excite 
them  quite  remotely.  From  an  unpardonable  confusion  of 
ideas,  even  modern  physicians  have  taught,  that  the  sensational 
kinds  of  pleasure  and  pain  have  their  seat  in  the  body,  those  of 
the  intellect  in  the  mind.  They  have  also  fallen  into  the  same 
error  as  to  the  passions,  of  which  more  afterwards  (579,  iii). 

Desires,  Aversions. 

81.  When  the  mind  foresees  anything  pleasing  to  it,  or 
(what  amounts  to  the  same  thing)  the  conception  of  anything 
pleasing,  it  exerts  its  conceptive  force,  it  endeavours  to  bring 
this  foreseen  agreeable  conception  forward,  to  make  it  pre- 
sent, or  to  accomplish  its  fulfilment,  that  is  to  say,  to  feel  it 
(in  the  third  sense  of  the  word,  §  34,  note) ;  and  to  develope 
the  contrary  conception  to  a  foreseen  unpleasant  conception 
(to  feel  it,  to  accomplish  its  fulfilment),  in  so  far  as  in  either  case 
it  expects  to  be  able  to  effect  these  objects  by  the  exertion  of 
its  forces.  This  effort,  this  straining  of  its  conceptive  force, 
which  it  makes  with  the  intention  of  realizing  a  foreseen 
external  or  internal  sensation  (34,  80),  is  termed,  in  the  first 
case,  desire,  in  the  second,  aversion.  When  the  foreseen 
agreeable  conception  (or  thing),  or  the  opposite  to  a  disagree- 


CH.  II.]  DESIRES,  AVERSIONS.  55 

able  conception,  becomes  present  (is  felt),  the  effort  terminates; 
that  is  to  say,  the  desires  and  aversions  are  satisfied  or  con- 
tented, or  the  foreseeings  are  fulfilled  (Baumgarten,  §  450). 
When  the  objects  of  these  are  true  external  sensations,  the 
mind  cannot  produce  them  independently  of  the  proper  ante- 
cedent external  impression  (34,  27) ;  consequently,  desires  and 
aversions  of  this  kind  cannot  be  fulfilled  or  satisfied  without 
the  external  impression  itself. 

Note. — It  will  be  necessary  to  bear  in  mind  the  definitions 
of  the  word  feeling,  as  given  in  the  Note  to  §  34. 

82.  The  efforts  of  the  conceptive  force  are  special  applications 
of  its  power  with  the  object  of  producing  a  certain  special  con- 
ception (81);  and  they  manifest  their  actions  on  the  brain 
through  similar  efforts  of  the  cerebral  forces^  to  develope  a 
certain  material  idea  suitable  to  the  conception  (26).  It  is, 
consequently,  the  same  also  in  the  desires  and  aversions  (81). 

83.  Since  pleasure  and  pain  are  the  motives  of  the  efforts, 
and  consequently  the  bases  of  the  desires  and  aversions  (80,  81), 
in  which  relation  they  are  incitements  of  the  feelings,  it  follows 
that  the  impressions  of  pleasure  or  pain  of  a  foreseen  conception 
excite  to  that  extent  an  effort  of  the  cerebral  forces  to  produce 
the  material  idea  of  this  future  conception  (81,  82),  and  this 
is  the  material  expression  of  the  desire  or  aversion  in  the  brain. 

84.  85,  86,  87.  In  every  desire  and  aversion,  consequently, 
we  must  distinguish  : 

i.  The  foreseeing  and  expectation  of  a  future  sensation,  or 
of  one  the  opposite  to  it,  which  therefore  consists  of  the  sub- 
impressions  of  the  future  sensation  [merkmale],  and  excites 
material  ideas  in  the  brain,  that  are  partly  the  material  ideas 
of  the  coming  sensation  or  its  opposite,  and  consequently  con- 
stitute an  imperfect  material  sensation. 

ii.  The  incitements  of  the  feelings — pleasure  or  pain — which 
communicate  the  impression  of  pleasure  or  pain  to  the  imperfect 
material  sensation  in  the  brain  (80). 

iii.  The  spontaneous  effort  of  the  mind  to  develope  the 
entire  foreseen  conception,  or  its  opposite,  which  is  connected 

'  As  the  animal-sentient  forces  [Thierische  seelenkrafte]  are  peculiar  to  the  brain, 
the  term  "  cerebral  force,"  here  used  by  Unzer  himself  in  that  sense,  will  be  used  to 
designate  them  whenever  it  maybe  most  in  accordance  with  previous  definitions,  25. 
—Ed. 


56  CEREBRAL  FORCES.  [i. 

with  the  effort  of  the  cerebral  forces  to  complete  the  imperfect 
material  sensation  which  the  soul  foresees,  or  in  other  words  to 
render  it  perfect,  and  realize  the  anticipation  (83,  83). 

If,  consequently,  a  desire  or  aversion,  by  its  influence  on  the 
brain,  manifests  actions  in  the  economy,  they  are  compounded : 
1.  Of  the  actions  excited  by  the  material  ideas  of  a  foreseeing 
and  expectation.  3.  Of  the  actions  excited  by  the  impression  of 
pleasure  or  pain  in  the  brain.  3.  Of  the  actions  resulting  from 
the  eflbrt  of  the  cerebral  forces  of  the  brain,  to  produce  the 
entire  material  sensation,  which  is  anticipated,  or  the  contrary 
to  it  (84)  j  and  the  stronger  all  these  are,  the  more  energetic 
the  actions  of  the  desire  or  aversion  (26). 

88.  The  conceptions  which  are  necessary  to  the  excitement 
of  desires  and  aversions,  namely,  the  incitements  of  the  feelings 
[Triebfedern  des  Gemiiths]  (83),  pleasure  and  pain,  are  in  so 
far  as  they  excite  the  effort  of  the  conceptive  force,  either  sen- 
sational (66)  or  intellectual  {76,  80).  When  they  are  sensa- 
tional, that  is  to  say,  when  they  are  true  external  sensations, 
or  other  sensational  conceptions  (67),  or  foreseeings  (73),  they 
are  termed  sensational  stimuli  {sensual  stimuli,  incitements  of 
the  flesh)  ;  if,  on  the  contrary,  they  belong  to  the  understand- 
ing, they  are  motives,  reasons.  Sensual  gratification  or  titilla- 
tion  [Kitzel],  and  smarting  are,  consequently,  sensational  sti- 
muli (80). 

89.  The  sensational  stimuli  (which  must  by  no  means  be  con- 
founded with  mere  impressions  or  nerve-feelings)  (31,  32,  121), 
excite  desires  and  aversions,  which  are  termed  sensational  (88); 
on  the  contrary,  motives  are  termed  intellectual  {desires  or 
aversions  of  the  will).  The  development  of  a  sensational  desire 
or  aversion  from  sensational  stimuli  may  be  considered  in 
various  ways.  Various  kinds  of  conceptions,  anticipations,  ex- 
pectations, and  efforts  of  the  conceptive  force  (84,  86),  are 
requisite,  all  which  impress  their  material  ideas  and  impres- 
sions in  the  brain  (25).  On  one  hand,  the  sensational  desires 
and  conceptions  may  result  from  sensational  stimuli,  organically 
and  necessarily  (as  external  sensations  result  from  their  external 
impressions),  according  to  the  laws  of  action  of  external  impres- 
sions, and  be  equally  sensational.  Or  the  sensational  desires 
and  aversions  do  not  result  from  these  stimuli  organically  and 
necessarily;  and  we  can  only  explain  their  excitation  by  at  the 


CH.  II.]  INSTINCTS,  PASSIONS.  57 

same  time  taking  into  consideration  the  intervention  of  the 
spontaneous  conceptions  which  they  produce  in  the  mind,  and 
which  commingle  with  the  former,  according  to  their  laws. 
Now,  when  the  sensational  desires  and  aversions  manifest  their 
workings  in  the  economy  as  in  the  former  case,  they  can  be 
explained  and  deduced  by  the  laws  of  action  of  the  external 
impressions  of  the  sensational  stimuli  on  the  cerebral  forces; 
but  in  the  latter  case,  we  must  bear  in  mind  the  concurrence 
of  the  spontaneous  intervention  of  the  conceptive  force.  The 
first  class,  therefore,  being  almost  as  fully  developed  as  external 
sensations,  may  be  termed  wholly  sensational^  but  the  latter 
being  more  like  conceptions  of  the  understanding  in  their 
origin,  are  more  spontaneous  or  more  physiologically  free  (27). 
In  the  latter,  the  mind  is  necessarily  conscious  of  the  inter- 
vening conceptions ;  in  the  former,  it  need  not  be  conscious 
of  either  the  conception  or  of  the  external  impressions  of  the 

;nsational  stimuli,  out  of  which  the  conceptions  are  formed. 
Note. — It  is  not  possible,  in  this  stage  of  the  work,  to  render 
this  matter  clearer ;   subsequently  (564,  579)  it  will  be  made 

lore  intelligible. 

Instincts,  Passions. 

90.  A  strong  and  wholly  sensational  desire,  which  arises  from 
[obscure  sensational  stimuli,  and  the  material  ideas  of  which  are 

jonsequently  little-  developed  in  the  brain  (26),  is  termed  a 
Hind  impulse  {instinct,  sympathy,  sensual  propensity,  sensual 
\inclination,  natural  instinct  generally),  (295) ;  an  analogous 
aversion  is  a  blind  abhorrence  {antipathy,  sensual  dislike,  enmity); 
I  both  are  sensational  instincts  (''the  flesh'^).  They  are  divided 
into  the  instincts  of  self-preservation,  self -maintenance,  the  pro- 
pagation of  the  species,  and  love  of  offspring. 

91.  Strong  desires  and  aversions  arising  from  confused  sen- 
sational stimuli,  of  which  there  is  a  consciousness,  although 
it  is  indefinite,  and  the  material  ideas  of  which  are  more  de- 
veloped in  the  brain  than  those  of  the  sensational  instincts  (26), 
are  termed  passions,  emotions,  affections.  Those  arising  from 
the  sensational  stimuli  of  pleasure  are  termed  pleasing ;  those 
from  the  sensational  stimuli  of  pain,  painful. 

92.  In  every  sensational  instinct,  and  in  each  passion,  we 
must  distinguish  : 


58  CEREBRAL  FORCES.  [i. 

i.  An  obscure  or  confused  anticipation  or  expectation  of  an 
internal  or  external  future  sensation,  produced  by  a  nearly  direct 
external  sensation  (34,  80),  which  anticipation  or  expectation 
consequently  contains  sub-impressions  of  the  future  sensation 
within  itself  (73),  and  developes  similar  material  ideas  in  the 
brain,  consisting  of  the  constituents  of  the  material  ideas  of 
the  future  sensation,  that  is  to  say,  they  are  imperfect  future 
material  sensations  (84,  66). 

ii.  The  sensational  stimuli  (84 — 88),  pleasure  or  pain,  which 
communicate  to  the  imperfect  material  sensation  in  the  brain, 
the  impression  of  pleasure  or  pain. 

iii.  The  spontaneous  strong  effort  of  the  mind  to  develope 
the  entire  foreseen  sensation  (81),  which  is  connected  with  a 
strong  endeavour  of  the  cerebral  forces  to  complete  the  im- 
perfect material  sensation  that  the  mind  foresees :  or,  in  other 
words,  to  develope  the  foreseeing  of  the  instinct  or  passion 
(82,  90,  91). 

93.  When  a  sensational  instinct  or  a  passion  excites  actions 
in  the  economy,  in  virtue  of  its  influence  on  the  brain,  they 
will  be  compounded  :  1.  Of  those  arising  from  the  material 
ideas  of  a  sensational  foreseeing  or  anticipation.  2.  From 
those  of  the  stronger  sensational  stimuli  in  the  brain.  3.  From 
those  of  the  more  active  endeavour  of  the  cerebral  forces  to 
develope  the  entire  material  sensation  which  is  foreseen  (92). 
The  stronger  each  of  these  are,  the  more  vigorous  its  actions 
in  the  economy  (85,  87,  90,  91). 

94.  The  proper  development  or  excitement  of  a  sensational 
instinct  or  of  a  passion  is  as  follows  :  Firstly,  there  is  an 
external  sensation  or  other  sensational  conception  in  the  mind. 
This  causes  the  obscure  and  confused  anticipation  and  expecta- 
tion of  a  complete  future  sensation,  that  is  highly  pleasing  or 
annoying,  which  indeed  is  no  other  than  a  portion, — a  collec- 
tion of  many  sub-impressions  (merkmale)  of  the  future  sen- 
sation, or,  in  other  words,  an  imperfect  sensation  with  its 
sensational  stimuli.  Hereby  the  mind  is  moved  to  apply  its 
spontaneous  conceptive  force  with  stronger  energy  to  produce 
this  foreseen  sensation  (whether  it  be  the  opposite  of  another 
or  not), — that  is,  to  produce  all  the  sub-impressions  wanting 
to  complete  the  true  sensation,  and  thereby  to  satisfy  the 
instinct  or  passion  (to  fulfil  its  anticipation)  (81) ;  this  cannot 


CH.  II.]  INSTINCTS,  PASSIONS.  59 

be  accomplished,  however,  when  it  refers  to  true  external  sen- 
sations, unless  the  appropriate  external  impression  be  attained. 
When  we  apply  this  doctrine  to  animal  functions  in  accordance 
with  the  principles  laid  down  in  §  25,  we  find  that  the  material 
element  of  a  sensational  instinct  or  passion  is  thus  developed : 
Firstly,  there  are  material  external  sensations,  imaginations,  or 
other  sensational  conceptions  in  the  brain.  Through  their 
action  arise  in  the  brain  the  material  ideas  of  the  anticipation 
or  expectation  of  a  future  sensation,  which  contains  within 
itself  the  impressions  of  pleasure  or  suffering.  With  this  is 
a  new  impulse  of  the  cerebral  forces  now  associated,  to  render 
this  incomplete  material  sensation  perfect,  either  because  it 
results  from  the  impression  organically  and  necessarily,  or 
because  the  mind  has  previously  spontaneously  resolved  to  com- 
plete its  foreseen  incomplete  sensation,  and  direct  its  efforts  to 
this  end  (89).  Next,  through  this  effort  of  the  animal-sen- 
tient force  of  the  brain,  an  endeavour  is  made  for  the  develop- 
ment of  the  whole  material  sensation,  a  portion  of  which  is 
actually  there, — partly  to  produce  more  of  its  elements,  to  which 
the  mind  can  add  spontaneously  the  sub-impressions  of  the 
anticipations, — partly  to  impress  the  elements  of  the  material 
sensations  already  present  more  forcibly,  and  render  them 
more  active,  until  the  remaining  elements  wanting  to  complete 
the  entire  material  sensation,  are  actually  produced  through 
this  effort  of  the  cerebral  forces.  The  effort  then  ceases,  the 
instinct  or  passion  being  satisfied;  or  the  effort  ceases  from 
enfeebling  of  the  instinct  or  passion,  without  the  completion 
being  achieved.  The  satisfaction  cannot,  however,  take  place, 
if  to  perfect  the  incomplete  sensation  it  must  become  a  true 
external  sensation,  unless  an  external  impression  be  also  added 
(35).  All  actions,  consequently,  which  the  instincts  and  pas- 
sions excite  directly  in  the  brain,  are  material  ideas  of  an 
anticipation  or  expectation,  which  constitute  portions  of  the 
perfect  material  idea  of  the  future  sensation,  together  with  the 
strong  sensational  impressions  of  pleasure  or  suffering  which 
belong  to  this  material  anticipation ;  and  when  these  material 
ideas  produce  actions  in  the  economy,  they  are  no  other  than 
those  of  the  imperfect  material  sensation  combined  with  the 
actions  of  the  superadded  impressions  of  pleasure  or  pain  ex- 
pressed with  unusual  force  (93). 


60  CEREBRAL  FORCES.  [i. 

95.  A  sensational  instinct  and  a  passion  cease,  or  are  pre- 
vented being  satisfied,  either  by  tlie  enfeebling  of  the  sensational 
stimuli  which  incite  the  mind  to  the  strong  effort,  and  this  may- 
occur  partly  psychologically,  partly  physiologically,  or — by  the 
contentment  of  the  anticipation,  or  by  the  prevention  of  the 
requisites  thereto  (81,  94). 

The  Free  Will. 

96.  The  motives  [Bewegungsgriinde]  add  the  impression  of 
pleasure  or  suffering  to  the  material  ideas  of  every  conception 
not  in  equilibrio  or  passive,  and  consequently  to  those  of  a 
similar  future  sensation,  which  must  be  stronger  in  proportion 
as  the  feeling  of  pleasure  or  suffering  is  greater,  and,  according 
to  these  views,  be  able  to  exercise  a  corresponding  influence  in 
the  animal  economy  (80,  88).  But  as  incitements  of  the 
mind,  they  also  excite  desires  and  aversions  (83),  which  are 
termed  intellectual  (to  will,  and  not  to  will,  intentions  of  the 
will)  free  conclusions  (89),  and  which  arise  from  an  anticipation 
and  expectation  of  the  understanding,  and  the  motives  it  con- 
tains (84,  86,  88).  The  laws  of  action  in  this  case  are  the 
same  as  laid  down  in  §  94 ;  the  effort  of  the  cerebral  forces  is 
strong  in  proportion  with  the  strength  of  the  will. 


The  Actions  excited  by  the  Mind,  or  Sentient  Actions. 
[Seelenwirkungen] . 

97 — 110.  All  material  ideas  (25,  26)  with  their  impressions 
of  pleasure  and  pain  (80)  and  all  efforts  of  the  cerebral  forces, 
so  far  as  they  are  based  on  the  conceptive  force  (27),  together 
with  all  real  animal  actions  in  the  body  dependent  thereon 
(Baumgarten,  §  224),  are  termed  actions  of  the  animal-sentient 
forces,  operationes  animce,  sentient  actions.  Sentient  actions 
in  the  body  may  be  divided  into  two  classes :  1 .  Those  of  the 
perceptive  faculty,  or,  in  other  words,  those  of  the  external  sen- 
sations, of  sensational  imaginations,  forcseeings,  and  of  the 
understanding  [017,  73,  70).  2.  Those  of  the  incitements  of 
the  feelings  (80,  83),  including  sensational  stimuli  and  motives 
(88),  the  desires  and  aversions  (81),  the  instincts  and  passions 
(90,  91),  and  the  will  (96).  The  sentient  actions  which  are 
excited  by  an  entire  conception  ("  tot  ale,"  Baumgarten,  §  378), 


CH.  11.]  SENTIENT  ACTIONS.  61 

without  the  intervention  of  another,  are  termed  direct  sentient 
actions ;  all  others  are  indirect  (incidental)  actions  of  this  entire 
conception.  The  nature  and  origin  of  these  various  sentient 
actions  may  be  learnt  from  the  paragraphs  to  which  reference 
is  made. 

111.  Although  the  sentient  actions  of  the  various  conceptions 
are  developed,  and  follow  each  other,  partly  according  to  the 
laws  of  action  of  external  impressions  on  the  cerebral  forces, 
partly  according  to  psychological  laws,  still  the  conceptive  force 
co-operates  in  each  as  well  as  the  cerebral  forces  (25);  and  con- 
sequently each  may  be   developed,   facilitated,   hindered,   and 
interrupted   in   two   different   ways ;   namely,   physiologically, 
because  the  actions  of  the  animal  machines  requisite  to  each 
are  partly  so  developed,  facilitated,  hindered,  or  interrupted; 
and  psychologically,  because  the  mind  has  a  similar  influence 
on  those  actions.     It  has  already  been  shown  (45,  46),  how  the 
sentient  actions  of  the  external  sensations,  and  consequently 
through  these,  those   of  the   sensational  conceptions,  desires, 
aversions,  instincts,  and  highly  sensational  passions  are  physio- 
logically   developed  and   prevented,  in  so   far  as  the  external 
sensations   themselves   are    physiologically   developed   or   pre- 
vented.     But  it  has  not  been  possible  hitherto  to  explain  how 
the  sentient  actions  of  the  conceptions,  desires,  &c.,  are  physio- 
logically developed  in  the  brain  out  of  each  other  as  material 
ideas,  and  transmitted  to  the  nerves,  for  we  know  nothing  of 
the  nature  of  the  cerebral  forces,  or  of  the  mode  in  which  the 
conceptions  excite  the   cerebral  functions.      Nevertheless,  we 
know  generally  under  what  conditions  these  sentient  actions 
are  physiologically  developed  or  prevented  in  the  animal  ma- 
chines external  to  the  brain,   as  we  shall  subsequently  show, 
(121,  &c.)      But  how  all  this  happens  psychologically,  is  taught 
by  metaphysics ;  and  therefore  in  both  ways,  and  on  principles 
entirely  dissimilar,  sentient  actions  may  be  produced,  facilitated, 
and  increased ;  and,  on  the   contrary,   in  both  ways,  and   on 
principles  as  widely  different,  they  may  be  prevented,  weakened, 
and  destroyed.      This  is  the  ground  of  difference  in  the  nature 
of  diseases  of  the  cerebral  forces  and  sentient  actions,  which 
arise  both  from  corporeal   and  mental  causes;    and   in  their 
therapeutical  and  psychological  treatment. 

112.  The  varying  degree  of  senselikeness  [Sinnlichkeit]  in  the 


62  CEREBRAL  FORCES.  [i. 

conceptions  raises  the  questions^  whether  the  external  sensations 
and  their  sentient  actions  depend  solely  on  the  body ;  whether 
the  sensational  perceptions,  stimuli,  desires,  aversions,  instincts, 
and  passions,  with  their  sentient  actions,  depend  partly  on  the 
body,  and  partly  on  the  mind;  and  whether  the  intellectual 
conceptions,  motives,  the  will,  and  the  unwill,  together  with 
their  actions,  depend  solely  on  the  mind.  Indeed,  properly, 
all  sentient  actions  are  produced  by  the  cerebral  forces  excited 
into  action  by  the  conceptions,  but  while  the  mind  produces 
all  its  conceptions  in  virtue  of  its  conceptive  force,  they  again 
are  dependent  on  the  material  ideas  in  the  brain  (25),  and 
consequently  on  sentient  actions  (97),  as  is  fully  shown  in 
metaphysics.  (Vide  §  119,  and  Baumgarten^s  'Metaphysics,^ 
§§  563,  567.) 

Action  of  the  Material  Ideas  in  the  Nervous  System. 

113.  We  have  hitherto  followed  the  arrangement  laid  down 
in  §  30,  and  shown  how  material  ideas  are  produced  in  the  brain, 
namely,  partly  by  external  impressions  on  the  nerves  (through 
external  sensations),  which  are  propagated  to  the  brain  (31 — 64) 
partly  by  the  influence  of  the  conceptions  which  the  mind, 
by  its  own  power,  produces  in  the  brain  (65 — 112).  There  is 
now  another  question  to  answer,  namely,  what  functions  do 
the  material  ideas  perform  in  the  economy?  In  this  chapter, 
according  to  §  16,  we  can  only  consider  them  in  their  relations 
to  the  animal  machines — the  brain  and  nerves — leaving  out 
any  reference  to  the  mechanical  machines. 

114.  The  material  ideas  are  animal  forces,  in  so  far  as  they 
manifest  their  operations  in  the  economy.  Now  since  they 
act  in  accord  with  the  mind  (97),  they  are  also  animal-sentient 
forces  (6). 

115.  All  material  ideas  are  solely  and  exclusively  in  the 
brain  (25).  Consequently,  they  produce  their  eff*ects  either 
directly  through  the  brain,  or  indirectly  through  the  nerves,  by 
means  of  which  the  brain  is  extended  through  the  entire 
animal  body  (12,  13) ;  because  the  nerves  are  the  only  animal 
machines  in  those  animals  which  possess  true  conceptions  (9); 
but  the  vital  spirits  are  only  the  means  by  which  they  perform 
their  functions  (17,  18). 


CH.  II.]  MATERIAL  IDEAS.  63 

116.  All  actions  of  the  material  ideas,  whether  arising  directly 
through  the  brain,  or  indirectly  through  the  nerves  (115),  are 
extended  solely  into  the  sensitive  or  animal  machines  (34,  14), 
which  are  the  brain  and  nerves  only,  or  they  at  the  same  time 
put  mechanical  machines  into  motion. 

117.  All  actions  of  the  material  ideas  are  therefore : — 1, 
directly  cerebral,  and  not  extended  either  to  the  mechanical 
machines  or  to  the  nerves;  2,  directly  cerebral,  but  extended 
to  the  mechanical  machines  without  the  intervention  of  the 
nerves ;  or  3,  cerebral  indirectly  through  the  nerves,  and  in  this 
case,  either  remain  simply  in  the  nerves,  so  far,  at  least,  as  not 
to  affect  mechanical  machines,  or  are  in  fact,  extended  to  the 
latter  at  the  same  time,  and  move  them  (115,  116).  Now 
since  we  have  only  to  consider  the  actions  of  the  material  ideas 
restricted  to  the  nervous  system  exclusively  (113),  they  may  be 
arranged  under  two  heads  : 

i.  The  direct  cerebral  actions  of  material  ideas  not  extended 
either  to  the  nerves  or  to  the  mechanical  machines ;   and — 

ii.  The  indirect  cerebral  actions  of  material  ideas  excited 
through  the  nerves,  so  far  as  they  do  not  put  mechanical  ma- 
chines into  motion. 

Actions  of  Material  Ideas  in  the  Brain. 

118.  All  material  ideas  are  movements  in  the  brain  (25); 
consequently,  their  actions  in  animal  bodies  can  be  none  other 
than  movements;  but  animal  (114)  and  sentient  actions  (97), 
which,  when  they  are  not  extended  beyond  the  brain,  are 
actions  of  its  own  animal- sentient  force  (114).  Now,  the  latter 
is  no  other  than  the  power  to  produce  the  material  ideas  of  the 
conceptions  (25,  26) .  Further,  the  direct  actions  of  the  material 
ideas  which  remain  in  the  brain,  and  are  not  extended  either 
to  the  nerves  or  to  the  mechanical  machines,  are  simply  other 
material  ideas,  which  produce  other  conceptions,  and,  con- 
sequently, can  be  developed  in  other  points  of  the  brain 
than  the  first,  as  is  certainly  the  case  with  various  external 
sensations  (43). 

119.  The  primary  material  ideas  in  the  brain,  which  are  pro- 
duced by  either  external  impressions  (31,  32),  or  by  spontaneous 
conceptions  of  the  mind  (27,  114),  excite,  consequently,  of  them- 
selves material  ideas  of  a  second  kind  which  are  necessary  to 


64  CEREBRAL  FORCES.  [i. 

those  conceptions  which  arise  directly  either  from  external  sen- 
sations, or  from  primary  spontaneous  conceptions  (118).  Or, 
in  other  words,  as  the  conceptions  arise  from  and  follow  the 
primary  material  ideas  ;  so,  also,  all  the  material  ideas  belong- 
ing to  the  secondary  conceptions  arise  from  and  succeed  each 
other  in  virtue  of  the  cerebral  force  put  into  action  by  the 
primary  material  ideas  (112).  We  are  ignorant,  however,  of 
these  processes. 

120.  So  soon,  however,  as  the  actions  of  the  material  ideas 
are  extended  beyond  the  brain  to  the  nerves,  whether  tliey  put 
mechanical  machines  into  motion  at  the  same  time  or  not,  many 
traces  of  them  can  be  discovered,  and  it  is  these  which  we  have 
now  to  consider  (117,  ii).  We  will  first,  however,  notice  the 
actions  of  material  ideas  through  the  nerves  generally;  or,  in 
other  words,  of  the  proper  cerebral  force  (121 — 111),  and 
afterwards  their  actions  as  manifested  solely  in  the  nerves,  and 
not  in  mechanical  machines. — (Vide  §§  142 — 152.) 

Actions  of  Material  Ideas  through  the  Nerves  generally :  the 
Internal  Lnpression  in  the  Brain. 

121.  Material  ideas  are  to  be  considered  as  impressions  made 
by  conceptions  (acts  of  mind)  on  the  brain,  for  even  those  pro- 
duced by  external  impressions  only  arise  when  the  latter  excite 
external  sensations ;  and  we  can  discover  no  other  source  for 
those  which  accompany  the  intellectual  conceptions,  than  the 
conceptions  themselves  (25,  112).  To  distinguish  these  im- 
pressions from  external  impressions,  we  will  term  them,  for  want 
of  a  better  phrase,  internal  senselike  impressions,  senselike  impres- 
sions on  the  brain — internal  nerve-feeling ;  and  include,  under 
these  terms,  all  impressions  made  on  the  cerebral  origin  of  a 
nerve,  or  on  its  trunk,  and  transmitted  downwards  from  the 
brain,  in  a  direction  contrary  to  that  taken  by  the  external  im- 
pi'ession  (31,  32,  406).^  Although  a  nerve  may  receive  an 
internal  impression  which  is  not  derived  from  the  brain,  just 
as  it  may  receive  an  external  impression  which  does  not  reach 
the  brain  (47,  199),  still  internal  impressions  on   the   nerves, 

>  The  reader  is  particularly  requested  to  refer  to  §  31,  and  the  foot-note  appended 
thereto,  for  an  explanation  of  the  word  sinnlich,  here  translated  senselike.  In  accord- 
ance with  the  views  there  stated,  the  word  sinnliche  Eindriick,  here  used,  will  be 
translated  simply  impression. 


CH.  II.]  CEREBRAL  IMPRESSIONS.  65 

caused  by  animal-sentient  forces, — material  ideas  (114), — take 
place  solely  through  the  brain,  and  may  very  properly  be  termed 
cerebral  impressions  (sinnliclie  Eindriicke  durchs  Gehirn).^ 

122.  The  actions  of  material  ideas  in  the  nerves  are  there- 
fore impressions  of  conceptions  propagated  along  the  nerves 
from  the  brain  downwards  to  the  terminating  fibrils  (31,  121); 
and  since,  in  this  respect,  the  material  ideas  act  as  animal- 
sentient  forces  (114),  their  actions  in  the  nerves  are  true 
sentient  actions  (97),  which  probably  are  extended  through  the 
system  of  nerves  by  means  of  the  vital  spirits.  (See  §  17 
and  §  28 ;  also  Haller's  '  Physiology,'  §  377.) 

123.  Since  no  other  animal  movements  in  animal  organisms 
are  sentient  actions  except  material  ideas  and  the  actions 
actually  resulting  from  them  (97) ;  it  follows  that,  to  every 
true  sentient  action,  a  conceptional  impression  is  necessary, 
which  is  either  confined  to  the  brain,  or  propagated  downwards 
along  the  nerves  (122). 

124.  Since  there  is  a  particular  point  in  the  brain  from 
which  each  nerve  arises  (13),  and  at  which  alone  the  material 
ideas  of  its  external  sensations  are  developed, — no  other  por- 
tion of  the  brain  having  a  part  therein — (43) ;  it  follows,  that 
the  impressions  of  the  conceptions  act  upon  the  origin  of  a 
nerve  when  they  excite  sentient  actions  in  it  (31,  118).  Con- 
sequently, the  whole  brain  will  not  be  put  into  action  by  each 
conception,  but  only  a  certain  locality,  or  that  point  in  which  the 
material  ideas  are  formed ;  and  this  action  is  directly  propagated 
only  along  the  nerve  and  its  branches  to  the  terminating  fibrils 
arising  from  this  point  of  the  brain,  although  it  m|iy  also  be 
communicated  indirectly  to  other  nerves  when  in  connection 
with  the  former  in  ganglia,  and  when,  in  both  cases,  there  is 
no  hinderance  to  this  transmission.  The  impressions  of  pleasure 
and  pain  are  only  difi'erent  conditions  of  the  material  ideas  of 
the  conceptions  which  please  or  displease  (80).  They  con- 
sequently take  place  at  the  same  point  as  the  material  ideas  of 
the  conceptions  themselves,  and  are  only  impressions  of  a 
difi'erent  kind  at  the  same  origins  of  nerves. 

125.  Just  as  an  external  impression, — whether  made  on 
trunks  of  nerves,  in  which  many  fibrils  are  collected,  or  on  the 

'  These  impressions,  caused  by,  or  accompanying,  acts  of  thought  or  feeling,  are 
also  termed  conceptional  impressions.  (Vide  §  359.) — Ed. 

5 


66  CEREBRAL  FORCES.  [i. 

common  trunk  of  nerves  altogether  different,  or  even  in  the 
spinal  cord  itself,  which  is  the  general  stem  of  a  great  number 
of  nerves — equally  reaches  the  brain  at  the  point  of  origin  of 
the  nerve  which  receives  it,  unmingled  with  any  of  the  other 
external  impressions  taking  place  at  the  same  time,  and  in  the 
same  direction,  and  there  forms  its  own  proper  material  ideas ; 
so,  also,  the  conceptional  internal  impressions  travel  from  the 
points  in  the  brain  in  which  they  take  place,  along  the  nerves 
arising  from  those  points,  and  are  propagated  downwards  through 
the  branches  and  terminating  fibrils  without  being  commingled 
with  other  conceptional  impressions  taking  place  in  the  brain  at 
the  same  time,  although  they  all  pass  together  along  one  and  the 
same  trunk,  or  rather  first  along  the  spinal  cord  to  the  larger 
branches,  and  thence  to  the  smaller  branches  and  fibrils  (124). 
The  cause  of  the  two  phenomena  is  identical  (39) .  The  fibrils 
of  a  nerve  are  already  separated  at  its  origin,  and  run  each  a 
separate  course  as  portions  of  the  same  larger  nerve  to  their 
allotted  termination  in  the  body  (13).  Each  complete  nerve 
has,  again,  its  special  point  of  origin  in  the  brain,  and  although 
it  passes  downwards  combined  with  many  others  into  a  large 
trunk,  such  as,  for  example,  the  spinal  cord,  it  is  afterwards 
given  off  again  and  remains  distinct,  and  continues  its  own 
special  course  to  its  final  termination  at  the  allotted  spot. 
Thus,  consequently,  an  impression  in  the  brain,  made  on  the 
origin  of  a  nerve,  or  on  one  of  its  fibrils,  takes  its  course  along 
the  fibril,  although  ten  other  impressions  may  have  been  made  in 
the  same  nerve,  or  on  other  fibrils  of  the  same  nerve,  and  pro- 
duces its  results  without  being  intermingled  with  the  others. 

126.  Although  at  the  same  time  that  conceptional  im- 
pressions are  transmitted  along  a  certain  nerve-fibril,  and  by  its 
means  perform  their  sentient  actions,  an  external  impression  is 
made  on  the  same  fibril,  and  takes  its  course  upwards  to  the 
brain  along  the  same  track,  as  far  as  the  origin  of  the  nerve 
from  whence  the  internal  impression  had  set  forth,  still  these 
two  impressions  are  in  no  wise  interrupted  in  their  course  to 
and  from  the  brain,  although  opposed  to  each  other,  but  each  are 
followed  by  their  proper  actions,  as  if  the  contrar}^  impression 
had  never  been  received  (§§  17, 18,  Haller's  ^Physiology,'  §  377). 
Is  it  not  highly  probable  from  this  statement  of  facts,  that  some 
of  the  numerous  fibrils  of  which  each  nerve  consists  (17),  are 


CH.  II.]  CEREBRAL  IMPRESSIONS.  67 

destined  solely  to  the  transmission  upwards  of  external  im- 
pressions made  on  the  terminating  fibrils  (perhaps  the  vital 
spirits  being  present  in  them),  while  on  the  other  hand,  other 
fibrils  are  destined  solely  to  the  transmission  downwards  to  the 
terminating  fibrils  of  internal  impressions  on  the  brain  (perhaps 
the  vital  spirits  being  present  at  the  cerebral  origin),  just  as 
there  are  two  classes  of  blood-vessels  having  similarly  opposed 
functions  ?  According  to  this  analogy  (which  comes  nearest  to 
the  idea  of  Borellus  (^De  Motu  Anim.,^  §  159,  and  which 
A.  Monro  does  not  entirely  disprove),  the  brain  that  produces 
the  vital  spirits  sends  them  downwards  through  certain  fibrilli 
in  a  nerve  to  the  terminal  points  (the  sensitive  papillae),  where 
they  are  received  by  the  terminating  points  of  other  nerves,  and 
transmitted  back  to  the  brain,  as  if  to  a  heart.  Although 
this  theory  cannot  be  fully  demonstrated,  it  has  a  great  degree 
of  probability,  since  by  it  we  can  comprehend  many  phenomena 
which  otherwise  would  remain  incomprehensible.  It  will  be 
worth  while  to  render  this  matter  more  explicit. 

127.  When  an  external  expression  has  been  made  on  a 
nerve  on  the  surface  of  the  body,  it  passes  upwards  if  there  be 
no  impediment  (13),  and  reaches  the  brain  at  the  point  of  origin 
of  the  nerve.  The  other  nerve-fibrils,  which  cannot  transmit 
the  impression  upwards,  are  not  affected  by  the  influence  from 
without.  At  the  point  of  origin  of  the  nerve  in  the  brain, 
the  transmitted  external  impression  produces  a  material  idea 
which  excites  an  external  sensation.  By  this  material  idea  (a 
movement)  at  the  origin  of  the  nerve,  those  fibrils  are  impressed 
that  propagate  the  internal  impression  downwards;  whilst  on 
the  other  hand,  those  fibrils  that  transmitted  the  external  im- 
pression to  the  brain,  receive  no  impression  from  the  external 
sensation.  The  former,  however,  propagate  the  conceptional 
impression  to  those  structures,  in  which  the  sentient  actions  of 
the  external  sensation  can  arise,  and  these  result  accordingly. 
It  is  now  more  intelligible,  how  these  opposite  movements, 
arising  from  opposite  impressions  in  the  same  nerve,  are  not 
impeded  by  each  other,  and  why  the  same  nerve  can,  at  the 
same  time  that  it  transmits  an  external  impression  to  the 
brain,  produce  a  sentient  action  in  some  organ  of  the  body,  as 
for  example,  a  voluntary  movement.  Since  a  nerve  in  its 
course  from  the  brain  is  divided  into  many  branches,  which 


68  CEREBRAL  FORCES.  [i. 

are  distributed  to  various  organs  of  the  body,  it  follows  that 
some  of  its  fibrils  that  transmit  the  impression  from  the  brain 
downwards  may  go  to  one  tissue,  and  some  of  those  which 
transmit  the  external  impression  upwards  again  into  other 
tissues  widely  distant,  and  thus  a  sensation  in  a  limb  trans- 
mitted along  the  same  principal  nerve,  may,  by  means  of  the 
cerebral  impression,  develope  a  sentient  action  (movement)  in 
limbs  far  distant  from  the  point  of  irritation.  This  connection 
between  the  sentient  actions  of  various  parts  is  termed  the 
sympathy  of  sentient  actions.  When  the  fibrilli  of  a  nerve 
which  transmits  external  impressions  to  the  brain,  to  pro- 
duce corresponding  material  ideas  at  the  point  of  its  origin 
in  the  brain,  have  experienced  some  injury  at  its  origin,  being 
compressed  or  stretched,  for  example,  in  such  a  way,  that  those 
fibrilli  only  have  their  function  interrupted  which  transmit  the 
cerebral  impression  downwards, — the  consequence  is,  that  the 
sentient  action  (as,  for  example,  a  voluntary  motion),  which 
formerly  resulted  from  this  external  sensation  (excited  by  the 
material  idea  in  the  brain),  ceases  to  be  excited,  until  the 
impediment  is  removed.  Thus,  it  is  intelligible,  how  a  nerve 
may  retain  its  sensibility  and  yet  have  lost  its  motor  power ; 
being  sensitive  and  yet  paralysed,  as  is  often  observed.  If,  on 
the  other  hand,  the  obstruction  involves  those  fibrils  only  at 
the  cerebral  origin  of  the  nerve  which  transmit  the  external 
impression  to  the  brain,  the  latter  will  develope  no  material 
idea  in  the  brain  and  no  sensation  in  the  mind ;  but  a  sponta- 
neous conception  can  excite  a  material  idea  (an  internal  im 
pression)  at  the  origin  of  the  nerve,  and  this  may  be  transmitted 
along  the  fibrils,  and  produce  actions  in  the  body,  such  as  a 
voluntary  movement,  for  example.  In  other  words,  the  same 
nerve  may  be  insensible,  and  still  the  channel  of  the  will. 
How  could  it  be  possible  to  explain  these  two  classes  of  phe- 
nomena, if  the  existence  of  this  diff*erence  in  the  fibrils  of  the 
same  nerve  be  not  admitted  ?  It  is  manifest  to  every  one,  that 
the  nervous  fibrils  are  distinct  and  separated  from  each  other 
at  their  origin.  From  these  and  other  considerations,  which 
will  be  stated  subsequently,  this  doctrine  of  two  distinct  classes 
of  nerve-fibrils  existing  in  the  same  nerve,  and  which  are  appro- 
priated to  the  two  kinds  of  internal  and  external  impressions 
respectively,  acquires  an  air  of  truthfulness  which  renders  it 


CH.  II.]  CEREBRAL  IMPRESSIONS.  69 

worthy  of  acceptance ;  still,  in  the  course  of  this  work,  I  shall 
only  consider  it  as  a  mere  opinion,  so  that  what  is  true,  and 
what  is  only  probable,  may  be  kept  perfectly  distinct. 

Note. — Haller  seems  to  object  to  this  doctrine,  but  his 
objections  appear  to  be  of  little  importance.  He  observes,  for 
example,  that  tubuli  of  two  kinds  in  the  same  nerve  are  not 
to  be  distinguished  by  our  senses,  and  all  ganglia  seem  to  be 
identical  with  each  other.  But  on  similar  grounds  we  may 
deny  the  existence  of  the  vital  spirits  themselves,  as  they  also 
are  invisible.  Other  arguments  of  no  greater  validity  are  also 
brought  forward  as  well  by  Haller  as  by  Monro.^ 

128.  When  a  nerve  is  compressed  by  a  ligature,  or  divided, 
sentient  actions  are  no  longer  produced  by  internal  impressions 
in  the  parts  separated  from  the  brain,  but  are  observed  only  in 
those  still  in  connection  with  the  brain  (31)  ;  but  if  the  ligature 
be  removed  from  the  nerve,  they  are  again  manifested  as  before, 
provided  the  ligature  have  not  destroyed  the  structure  of  the 
nerve.  (Haller's  ^  Physiology,^  §  367.)  But  if  the  nerve  be 
injured  by  the  ligature,  its  sensibility  is  destroyed  (43) ;  hence 
neither  class  of  impressions  can  be  propagated  along  either 
kind  of  fibril,  their  progress  being  impeded  by  the  divided  or 
ligatured  portion  of  the  nerve  (126,  127).  If  the  brain  itself 
be  compressed,  as  it  often  is,  that  portion  of  the  body  supplied 
with  nerves  from  the  compressed  part  of  the  brain,  becomes 
incapable  of  sentient  actions.  The  capability  returns,  however, 
so  soon  as  the  compression  of  the  brain  is  taken  off.  When 
the  whole  brain  is  compressed,  all  animal  operations  caused  by 
impressions  acting  on  the  brain,  cease  throughout  the  whole 

'  In  this  paragraph  and  elsewhere  ($§  487, 488),  Unzer  advances  the  hypothesis,  as 
he  terms  it,  of  afferent  (aufleitenden)  and  efferent  (ableitenden),  fibrils  in  the  same 
nerve.  His  Gottingen  reviewer  (probably  Haller)  thus  objects  to  it :  "  Herr  Unzer 
considers  that  it  is  probable  there  are  afferent  and  efferent  nerves  going  to  and  re- 
turning from  the  brain ;  and  that  the  objections  raised  against  the  doctrine  are  not 
of  much  weight.  He  forgets  that  the  proof  rests  with  himself,  for  neither  experi- 
mental nor  anatomical  researches  support  his  conjecture."  Unzer  replies :  "  Neither 
anatomy  nor  experiment  can  determine  the  question;  for  it  is  so  microscopically 
minute,  as  to  escape  the  cognisance  of  our  senses.  It  was  no  part  of  my  plan  to 
prove  the  existence  of  the  two  kinds  of  fibrils.  I  meditated  on  certain  phenomena, 
and  found  that  it  was  absolutely  impossible  to  explain  them,  except  by  assuming 
that  afferent  and  efferent  fibrils  do  exist.  The  doctrine  cannot  be  absolutely 
demonstrated;  it  is  but  a  hypothesis,  and  I  treated  it  as  such."  (Physiologische 
Uutersuchungen,  p.  26.) — Ed. 


70  CEREBRAL  FORCES.  [i. 

body.  (Haller's  '  Physiology/  §  368.)  The  cause  of  this  may 
be^  that  either  no  impression  can  be  made  in  the  brain,  on 
account  of  the  compression,  consequently  no  conceptions  can 
arise  in  the  mind  (121,  25)  because  the  pressure  entirely  destroys 
the  animal  force  and  consequently  the  sentient  force  of  the  brain 
(6),  and  then  no  operations  can  take  place  in  the  body ;  or,  it  may 
be,  that  by  pressure  on  individual  portions  of  the  brain,  as  when 
blood  or  water  overflows  it,  or  projecting  points  of  the  cranium 
are  forced  into  it,  only  those  fibrils  at  the  origin  of  certain 
nerves,  which  formerly  developed  sentient  actions  in  the  body, 
have  their  functions  arrested,  so  that  internal  impressions 
cannot  be  transmitted;  in  this  case,  the  external  sensations 
and  spontaneous  conceptions  are  unaffected,  but  the  sentient 
actions  resulting  from  them  can  no  longer  be  produced.  This 
opinion  is  based  on  the  doctrines  laid  down  in  §§  126, 127,  and 
without  this  it  is  impossible  to  explain  those  cases  in  which 
certain  limbs  are  paralysed  by  a  pressure  on  the  brain,  and  yet 
external  sensations  and  spontaneous  conceptions  continue.  It  is 
impossible  that  this  can  depend  upon  the  want  of  material  ideas 
of  the  external  sensations  and  other  conceptions,  for  without 
these  the  sensations  and  conceptions  could  not  exist  at  all  (25). 

129.  When  sentient  actions  are  produced  directly  through 
the  nerves  by  external  sensations,  it  is  necesssiry  thereto  : 

i.  That  there  be  all  that  is  requisite  for  the  production  of 
external  sensations  (45). 

ii.  That  the  external  material  sensation  duly  impress  the 
origin  of  that  individual  nerve  which  has  to  propagate  the  im- 
pression outwards  from  the  brain  (122,  124,  126,  127). 

iii.  That  this  cerebral  impression  be  actually  transmitted 
along  the  nerve  to  the  point  where  the  sentient  actions  are  to 
be  developed  (128). 

iv.  In  those  instances  in  which  the  sentient  action  consists 
in  a  movement  of  a  mechanical  machine  to  which  the  nerves 
are  distributed,  it  is  also  requisite,  that  the  mechanical  machines 
themselves  be  in  a  condition  to  perform  the  movements  which 
constitute  the  sentient  action. 

130.  When  sentient  actions  are  produced  through  the  nerves 
by  conceptions  of  the  mind,  it  is  necessary  thereto : 

i.  That  the  material  idea  of  the  conception  make  such  an 
impression  on  the  origin  of  the  nerve,  and  on  those  fibrilli  which 


CH.  II.]  CEREBRAL  IMPRESSIONS.  71 

are  appropriate  to  the  sentient  action,  as  to  be  transmitted  (121); 
in  this  case,  the  impression  must  be  made  on  those  fibrilli  of  the 
nerve  which  propagate  it  from  the  brain  outwards  (126,  127). 
ii.  That  the  further  transmission  take  place,  as  stated  in  iii 
and  iv  of  last  paragraph. 

131.  When  the  material  idea  of  an  external  sensation  makes 
an  impression  on  the  origin  of  another  nerve  than  its  own,  it 
becomes  the  material  idea  (121)  of  another  (118),  and  indeed 
of  a  sensational  conception ;  or  of  instincts  and  passions  by 
means  of  the  sensational  stimuli  of  thie  conception  (88,  90,  91) ; 
and,  consequently,  of  analogous  purer  conceptions,  which 
although  induced  by  means  of  external  sensations,  are  also 
spontaneously  (27)  developed,  as  stated  in  §  130. 

132.  The  medulla  of  the  nerves  is  naturally  adapted  to  the 
external  impressions  of  the  external  sensations  (31) ;  but  since 
it  is  no  other  than  cerebral  medulla,  the  latter  is  also  naturally 
adapted  to  external  impressions.  When,  consequently,  certain 
fibrilli  of  the  cerebral  medulla  are  touched  or  stimulated,  they 
receive  an  external  impression  (just  as  the  terminating  fibrilli 
of  the  nerves),  which  is  propagated  along  the  fibrilli  to  their 
cerebral  origin  (45,  ii),  and  there  excites  a  material  external 
sensation.  This  latter  causes  an  impression  on  the  brain, 
which  either  produces  sentient  actions  directly  by  means  of  a 
nerve  at  that  point,  or  in  the  way  stated  in  last  paragraph. 
Consequently  when  the  cerebral  medulla  of  living  animals  en- 
dowed with  conceptions  is  irritated,  an  external  material  sen- 
sation is  produced  (as  for  example  that  belonging  to  pain), 
which  produces  sentient  actions  through  the  nerves  (e.  g., 
convulsive  movements  from  pain),  in  the  same  way  as  other 
external  sensations  (129,  130,  '  Haller's  Physiol.'  §368). 

133.  In  proportion  as  the  cerebral  impressions,  and  the  forces 

I  which  excite  them,  namely,  the  external  sensations  (129),   and 
the  spontaneous  mental  conceptions  (130)  are  powerful,  in  the 
same  proportion  the  sentient  actions  which  they  excite  through 
the  nerves  are  vigorous  (121,  26). 
134.  A  sentient  action  produced  directly  through  the  nerves 
by  an  external  sensation  may  be  prevented : 
i.  By   everything  which    prevents    the    external    sensation 
(46,  129,  i.) 
ii.  By  this,  that   the   material   external  sensation  in  the 
I 


73  CEREBRAL  FORCES.  [i. 

braiu  cannot  so  duly  stimulate  the  origin  of  the  sensitive  nerve  as 
to  induce  the  propagation  outwards  of  the  impression  (129,  ii.). 
Supposing  that  the  material  external  sensation  makes  its  ap- 
propriate impression  in  the  brain  at  the  point  of  origin  of 
another  nerve^  and  not  of  that  which  brought  it  to  the  braiu; 
this  would  be  the  material  idea  of  another  conception  of  the 
mind,  and  the  sentient  action  which  it  excites  through 
the  nerve  would  not  be  similar  to  those  produced  directly  by 
the  external  sensation  (131).  Again,  supposing  the  external 
sensation  only  makes  such  an  impression  on  the  origin  of  the 
nerve,  that  it  cannot  be  propagated  downwards  from  the  brain 
along  the  same  nerve,  no  corresponding  direct  sentient  action 
can  be  produced  thereby  (129,  ii,  iii).  Further, — since  ex- 
ternal impressions  do  really  occur  which  develope  an  external 
sensation  in  the  mind  (a  material  external  sensation  in  the 
brain),  and  yet  do  not  thereby  excite  the  ordinary  direct  sen- 
tient actions  (Haller^s  '  Physiology,^  ^  384),  although  the 
origin  of  the  nerve  actually  possesses  the  material  external  sen- 
sation, which  is  proper  to  it,  and  which  constitutes  the  internal 
impression  on  the  origin  of  the  nerve  (121), — we  could  not 
explain  why  the  direct  sentient  action  of  the  external  sensation 
does  not  take  place  through  the  same  nerve,  unless  we  assume 
that  there  are  two  classes  of  fibrils  in  the  nerve,  according  to 
the  doctrines  previously  stated  (126, 127).  The  case  is  explained 
by  assuming  that  the  fibrils  of  the  nerve  which  receive  the 
cerebral  impression,  and  transmit  it  downwards,  are  rendered 
incapable,  in  consequence  of  there  being  some  of  the  impedi- 
ments to  the  reception  of  the  impression  described  above 
(127,  128).  (As  when  a  limb,  for  example,  which  the  mind 
governs  through  the  nerve  that  receives  the  impression,  remains 
motionless  and  paralysed  in  spite  of  its  external  sensations, 
although  the  same  sensation  can  excite  other  sentient  actions 
in  other  portions  of  the  body,  e.  g.,  certain  voluntary  move- 
ments by  means  of  other  spontaneous  conceptions,  and  the 
material  ideas  produced  by  them  at  the  origins  of  other 
nerves — §  128). 

iii.  The  direct  sentient  action  of  an  external  sensation 
caused  through  the  nerves  is  also  prevented,  when  the  appro- 
priate impression  received  at  the  cerebral  origin  of  the  sensitive 
nerve  cannot  be  transmitted  to  the  point  where  the  sentient 


CH.  II.]  CEREBRAL  IMPRESSIONS.  73 

action  ought  to  be  developed ;  as,  for  example,  when  the  spinal 
cord,  or  the  trunk  or  branch  of  a  nerve,  is  tied,  compressed,  or 
divided  below  the  point,  or  mechanical  machine,  to  which  the 
sensation  ought  to  be  transmitted  (128,  129,  iii). 

iv.  When  the  sentient  action  produced  by  a  nerve  consists 
in  a  movement  of  a  mechanical  machine,  to  which  the  nerve  is 
distributed,  its  production  is  prevented  when  the  machine  is 
not  in  a  condition  to  effect  the  movement  organically  ap- 
propriate to  it  (129,  iv). 

135.  When  sentient  actions  produced  by  means  of  the  nerves, 
are  caused  by  spontaneous  conceptions,  they  may  be  prevented 
as  follows : — 

i.  When  the  material  idea  of  the  conception  at  the  origin  of 
the  nerve  appropriate  to  the  sentient  action  cannot  so  make 
its  impression,  that  it  may  be  transmitted  (130,  i). 

ii.  When  the  further  transmission  cannot  take  place  (134, 
iii,  iv). 

136.  There  are  various  kinds  of  conceptions  which  do  not 
usually  develope  sentient  actions  in  the  body  through  the  nerves, 
as  inferences,  witty  thoughts,  &c. — (vide  238,  249,  330);  nay, 
many  external  sensations  and  other  conceptions  which  ordinarily 
develope  sentient  actions  through  the  nerves  do  not  do  it, 
although  the  animal  is  in  its  natural  condition.  Consequently, 
just  as  there  are  material  hinderances  which  prevent  the 
continuous  transmission  of  many  external  impressions  to  the 
brain  (47 — 51),  so  similar  hinderances  may  prevent  the  sentient 
actions  of  conceptions,  and  it  is  a  matter  of  importance  to 
know  every  possible  hinderance  of  this  kind. 

i.  Nature  has  so  distributed  the  origins  of  the  nerves  in  the 
brain,  that  every  material  idea  of  a  conception  has  not  neces- 
sarily relations  with  any  of  them,  or  if  it  excite  one  origin,  it 
does  not  necessarily  excite  all  the  others  at  the  same  time, 
or  even  any  one  origin.  Consequently,  when  material  ideas 
are  formed  at  points  of  the  brain  from  whence  no  nerves  arise, 
they  excite  no  sentient  action  through  the  nerves  (124).  Nay, 
when  the  material  ideas  of  external  sensations,  or  other  concep- 
tions duly  (sinnlich)  impress  the  origin  of  a  nerve,  and  excite 
sentient  actions  through  it,  all  other  origins  of  nerves  may 
remain  unaffected  thereby,  and  no  sentient  actions  result, 
unless  under  special  circumstances  (124). 


74  CEREBRAL  FORCES.  [i. 

ii.  It  may  be,  also,  that  many  nerves  are  not  adapted  natu- 
rally, or  become  unadapted  to  the  internal  impressions  of  many 
conceptions  (material  ideas),  although  the  change  caused  by 
the  material  ideas  really  involves  their  origin ;  and  that  only 
certain  kinds  of  conceptions  (material  ideas)  can  affect  them, 
just  as  certain  external  impressions  only  are  received  by  the 
nerves  (47,  ii).  An  agreeable  taste,  for  example,  or  the  imagi- 
nation or  anticipation  of  it,  cannot  excite  the  sentient  actions 
of  vomiting,  while  an  unpleasant  taste,  or  the  imagination  or 
anticipation  of  it,  produces  that  effect.  Although  both  sensations 
pass  along  the  same  nerve  to  the  same  origin  in  the  brain,  and 
there  excite  a  material  idea,  and  both  ideas  or  anticipations 
must  develope  their  material  ideas  or  impressions  at  the  same 
point  in  the  brain  (124),  yet,  from  the  one  kind  the  sentient 
action  of  vomiting  results,  but  nothing  from  the  other. 

iii.  Internal  sensations  and  other  conceptions  may  some- 
times be  so  feeble,  that  they  do  not  make  so  powerful  an  im- 
pression in  the  brain  as  is  necessary  to  the  production  of  a 
sentient  action ;  and  this  is  also  the  case  with  sensations  from 
without  (47,  iii).  A  slight  irritation  of  the  nose,  for  example, 
by  snuff,  does  not  produce,  as  a  stronger  would,  the  sentient 
action  of  sneezing  (80);  thus  it  is,  that  the  phantasies  being 
weak  in  dreams,  we  omit  many  voluntary  movements  which  we 
should  otherwise  perform,  if  the  latter  were  as  strong  as  in  the 
waking  state,  or  as  in  somnambulism.  In  these  cases  there 
is  doubtless  an  impression  in  the  brain  from  very  feeble  con- 
ceptions (25,  121),  only  it  is  not  propagated  along  the  nerves 
to  its  destined  point,  but  is  lost,  as  it  would  appear,  in  the  way. 

137.  iv.  The  bifurcations  and  the  ganglia  of  the  nerves  may 
act  as  impediments  to  the  transmission  of  internal  impressions 
and  to  the  consequent  production  of  sentient  actions,  just  as 
they  prevent  the  transmission  of  external  impressions,  and  the 
consequent  production  of  material  external  sensations  (48). 
That  this  must  be  the  case,  is  demonstrable  from  numerous 
facts.  The  acquisition  of  skill  in  the  manual  arts  depends  on 
a  removal  of  these  impediments.  It  is  falsely  termed  habit, 
but  it  is  really  eocpertness.  The  frequent  repetition  of  the  same 
impression  in  the  brain,  acts  each  time  on  the  natural  hinderance 
at  the  divisions  of  the  nerves,  just  as  occurs  in  the  action  of 
two  opposing  forces,  when  that  which  continually  repeats  its 


CH.  II.]  CEREBRAL  IMPRESSIONS.  75 

shocks  must  overcome  the  other  which  is  totally  unsupported ; 
in  like  manner,  the  natural  hinderance  is  destroyed,  and  the 
impression  takes  its  uninterrupted  course  to  the  production  of 
its  sentient  action. 

138.  V.  Lastly,  mechanical  machines  may  act  as  impediments 
to  the  production  of  sentient  actions,  when  a  change  in  them  is 
necessary  before  the  impression  in  the  brain  can  produce  its 
sentient  action.  This  is  the  case  with  the  mountebank,  whose 
gestures  and  postures  cannot  be  imitated  by  another  until  his 
joints  are  stretched,  his  muscles  practised,  and  even  his  viscera 
partly  displaced,  so  that  the  machines  can  instantaneously 
follow  the  act  of  willing. 

139.  The  sentient  actions  which  are  produced  directly  by 
external  sensations,  can  also  be  partly  enfeebled,  partly  pre- 
vented, in  various  ways,  by  the  habit  of  reception  of  sensations 
(50,  51,  134,  i,  54);  and  since  the  actions  of  sensational  con- 
ceptions depend  proximately  upon  external  sensations  (66),  the 
habitual  reception  of  external  sensations  may  have  a  consider- 
able influence  on  their  development.  But  it  is  unnecessary  to 
quote  instances  of  this  kind,  as  they  are  of  daily  occurrence. 

140.  The  sentient  actions  which  ideas  excite  through  the 
nerves  in  dreaming  and  in  insanity,  partly  accord  with  those 
of  former  external  sensations  (69) ;  so  also  those  of  sensa- 
tional memory  (72).  Those  of  the  sensational  foreseeings, 
expectations,  and  forebodings,  as  well  as  those  of  dreams  and 
of  mania  (75)  partly  produce  the  actions  of  coming  future 
external  sensations  (74).  These  actions  are  forcible  in  pro- 
portion to  the  strength  of  the  conceptions  exciting  them 
(69,  74) ;  abstraction  of  the  mind  can  cause  many  actions  of 
the  understanding  to  cease ;  attention  on  the  other  hand  can 
excite  and  maintain  many.  The  sentient  actions  of  pleasure 
or  suffering  are  powerful  in  proportion  to  the  strength  of  these 
internal  sensations  (80,  96).  The  sentient  actions  of  a  desire 
or  aversion  are  composed  of  those  of  a  foreseeing,  of  an 
expectation,  of  a  pleasure  or  pain,  and  of  an  effort  of  the 
conceptive  force ;  and  are  powerful  in  proportion  as  these  are 
vigorous  (85,87).  So,  also,,  those  of  the  sensational  instincts 
and  emotions  (93),  and  of  willing  and  not  willing  (96),  all 
these  sentient  actions  result  according  to  general  laws,  partly 
physiological,  partly  psychological  (111). 


76  CEREBRAL  FORCES.  [i. 

141.  Although  all  operations  through  the  nerves  of  impres- 
sions in  the  brain  are  movements  (122)^  it  is  not  a  necessary 
consequence,  that  these  movements  arise  in  proper  mechanical 
machines,  as  muscles,  glands,  viscera,  &c.,  for  they  may  occur  in 
nerves  of  sensation  which  are  not  distributed  to  these  machines 
(14) ;  or  may,  even  in  motor  nerves,  be  only  movements  of  the 
vital  spirits,  which  are  not  manifested  by  visible  movements; 
yet  they  are  as  certainly  operations  of  the  cerebral  impression 
acting  through  the  nerves  (sentient  actions,  §  123),  and  as 
certainly  cause  important  phenomena  in  the  animal  economy 
(as  we  shall  shortly  see),  as  those  which  are  manifested  by 
visible  movements  in  the  animal  machines.  (This  shows  inci- 
dentally the  correctness  of  the  division,  §  117). 


Actions  of  the  Material  Ideas  in  the  Nerves  exclusively ,  and 
when  not  extended  to  Mechanical  Machines. 

142.  After  the  general  consideration  of  the  actions  of  the 
material  ideas  on  the  nerves,  we  have  now  to  investigate  their 
special  action  in  the  nerves  exclusively,  without  reference  to 
their  extension  to  the  mechanical  machines.  Indeed  all  kinds 
of  nerves  are  subject  to  this  influence  of  the  material  ideas  in 
the  same  way.  But  while  internal  impressions  are  distinctly 
manifested  by  the  movements  of  mechanical  machines,  there 
are  only  shght  traces  of  movements  in  the  brain,  in  the  nerves 
themselves,  (no  action  in  a  mechanical  machine  following,)  or 
in  purely  sensitive  nerves,  with  which  no  mechanical  machines 
are  connected.  They  are  best  observed  in  the  nerves  of  the 
external  senses  which  simply  feel. 

143.  Every  nerve  in  animals  endowed  with  sensation  receives 
external  impressions,  some  of  which  at  least  are  transmitted 
onwards  to  the  brain,  where  they  produce,  at  the  origin  of  the 
nerve  in  the  brain,  a  material  external  sensation  (45,  124) ;  or, 
in  other  words,  an  internal  or  cerebral  impression,  which  must 
directly  excite  sentient  actions  in  the  nerve  itself,  even  if  it  only 
feels,  provided  it  be  a  nerve  capable  of  so  receiving  an  internal 
impression ;  and  it  must  be  so  capable,  if  the  impression  is  to 
be  propagated  outwards  from  the  brain  (129,  ii,  iii.)  That  every 
nerve,  whether  purely  sensitive,  or  both  sensitive  and  motor, 
must  possess  this  capability,  although  it  may  not  be  able  to 


CH.  II.]  SENSITIVE  NERVES.  77 

receive  and  transmit  both  kinds  of  impressions  (136,  ii),  is  as 
certain  as  that  the  vital  spirits  of  the  external  impressions  pass 
on  to  the  brain  (18,  36),  and  that  their  laboratory  is  in  the 
latter  (11).  Since  there  must  be  an  opening  at  the  point  of 
origin  of  the  nerve  in  the  brain,  at  which  the  vital  spirits  must 
enter  to  pass  along  the  sensitive  nerves  to  their  terminating 
fibrils,  for  the  purpose  of  receiving  external  impressions,  we 
conclude  that  this  is  the  course  which  the  internal  or  cerebral 
impression  takes.  In  other  words,  the  sensitive  nerves  have 
fibrils  like  the  motor  nerves,  which  transmit  internal  impres- 
sions from  the  brain  to  their  terminating  fibrils  (126,  127). 

144.  The  external  sensations  develope  their  direct  actions  in 
the  sensitive  nerves  themselves  (129,  ii,  143) .  But  all  sensational 
perceptions  (76)  with  their  sensational  stimuli  (88),  all  sensational 
instincts  (90),  and  all  the  passions  (91),  efi'ect  their  sentient 
actions  through  those  nerves  by  which  external  sensation  is 
received.  Now,  since  all  these  require  such  material  ideas  or 
impressions  in  the  brain,  as  the  material  external  sensations 
partly  develope,  and  by  which  they  are  proximately  determined 
{66,  88) ;  it  follows,  that  their  material  ideas  must  excite  at  the 
same  time  a  corresponding  impression  at  the  origin  of  the 
nerve,  which  is  propagated  downwards  along  the  nerve,  and 
developes  actions  in  it  (123).  On  the  other  hand,  the  intel- 
lectual conceptions,  motives,  volition,  and  involition  (which 
only  depend  remotely  upon  external  sensations),  have  less 
influence  on  the  sensitive  than  on  the  motor  nerves. 

145.  By  what  means  can  the  sentient  actions,  produced  in 
the  nerves  by  the  cerebral  impressions  of  all  these  sensational 
conceptions  be  ascertained,  when  their  influence  on  the  me- 
chanical machines  cannot  be  observed  ?  The  nerves  have  in 
themselves  no  visible  movements ;  yet  the  impressions  of  the 
sensational  conceptions  can  only  act  upon  them  as  movements. 
But  these  escape  observation  quite  as  much  as  those  of  external 
impressions  (31).  They  are  probably  only  movements  of  the 
vital  spirits  in  the  hollow  fibrilli  of  the  nerves  (13).  How  can 
the  existence  of  these  hidden  movements  be  demonstrated? 
VV^e  infer  their  existence  in  the  external  impressions  from  their 
action  on  the  brain,  inasmuch  as  they  produce  external  sensa- 
tions, and  because  compression  of  the  nerve,  in  its  course  to  the 
brain,  arrests  or  interrupts  the  propagation  upwards  of  the  im- 


78  CEREBRAL  FORCES.  [i. 

pression.  We  infer  it  to  be  in  the  motor  nerves  from  the 
actions  which  the  cerebral  impressions  of  conceptions  produce 
in  those  structures  to  which  these  nerves  are  distributed,  and 
because  compression  of  the  nerve  prevents  the  transmission  of 
internal  impressions  to  the  mechanical  machines.  As  to  the 
sensitive  nerves  which  simply  feel,  and  manifest  no  visible 
movements  from  either  kind  of  impression,  we  know  that  the 
cerebral  impression  is  in  them  by  its  operations,  which,  although 
certainly  taking  place,  are  not  visible. 

146.  The  cerebral  conceptional  impression  causes,  at  the 
origin  of  each  nerve  on  which  it  duly  acts,  a  movement  (of  the 
vital  spirits)  from  above  downwards  towards  the  terminating 
fibrils  which  feel  (122).  It  is  at  this,  the  extremest  point  of  the 
nerves,  that  this  movement  is  either  wholly  reflected,  or  ceases 
(126);  for  from  that  point  the  external  impression  causes  an 
opposite  movement  towards  the  brain.  Further  observation 
may  enable  us  to  determine  something  as  to  this  change,  as  for 
example,  when  a  strong  sensational  conception  acts  on  the 
nerve  with  unusual  vigour. 

147.  When  the  terminations  of  the  nerves  are  carefully 
observed  in  powerful  sensational  foreseeings,  particularly  in  the 
instincts  or  passions,  it  is  obvious  that  they  are  erected,  and 
become  more  prominent.  Thus  the  papillae  of  the  tongue,  in 
which  the  gustatory  nerves  terminate,  are  visibly  elevated  when 
the  expectation  or  desire  to  taste  a  piece  of  sugar  or  salt  is 
excited  by  bringing  it  near  to  the  tongue.  So  also  the  nerve- 
points  in  the  fingers  are  evidently  elevated,  when  one  attempts 
to  feel  something  more  distinctly,  which  is  the  foreseeing  in  a 
desire.  "  The  sensitive  points  of  the  fingers,^^  Haller  remarks, 
'^  are  slightly  elevated  during  an  act  of  attention  (an  expecta- 
tion), just  as  we  see  in  rigors,  in  the  nipple  of  the  mamma,  and 
in  a  portion  of  bowel  hanging  out  of  the  abdomen.^^  {'  Phys.,^ 
§431.)  Probably  shivering  ought  to  be  classed  with  the  sen- 
tient actions  produced  through  the  nerves  in  the  mechanical 
machines.  That  the  sensitive  points  in  the  nipple  are  elevated 
by  the  expectation  of  an  act  of  suckling,  or  simply  by  titillation, 
is  quite  certain.  With  regard  to  the  senses  of  feeling  and  taste 
many  similar  observations  have  been  made,  but  not  with  regard 
to  the  other  senses.  This  erection  of  the  nerve-points  is  there- 
fore a  true  sentient  action. 


CH.  II.]        IMPERFECT  EXTERNAL  SENSATIONS.  79 

148.  Erection  of  the  nerve-points  is  a  movement,  or  change, 
which,  when  strong  enough,  may  become  an  external  impres- 
sion (31),  and  on  arriving  at  the  brain,  may  excite  a  concep- 
tion similar  to  external  sensations ;  but  having  no  true  material 
impression  as  its  basis,  has  consequently  no  real  external  cir- 
cumstance. In  this  way,  remarkably  powerful  impressions  in 
the  brain  (from  very  vigorous  conceptions)  may  produce  an 
external  impression  on  the  nerves  to  which  they  have  reference, 
as  if  it  came  from  a  real  thing  without ;  this  reaching  the  brain 
will  excite  the  analogue  to  a  real  external  sensation,  and  some- 
times contains  so  much  of  the  real,  that  the  mind  can  only  dis- 
tinguish, by  great  attention,  this  class  of  sensations  and  their  con- 
comitant conceptions,  from  those  which  have  a  true  external 
origin.  To  distinguish  these  sensations  from  the  latter  class, 
we  shall  term  them  imperfect  external  sensations.  Hitherto 
they  have  been  confounded  with  very  vivid  imaginations ;  but 
their  extraordinary  distinctness  shows  that  they  differ  from 
these,  inasmuch  as  often  they  are  in  no  respect  dissimilar  from 
true  external  sensations.  They  are  necessarily,  however,  the 
results  only  of  very  powerful  impressions  in  the  brain  of  other 
conceptions,  as  shown  above ;  consequently,  they  can  be  the 
actions  of  a  too-active  imaginative  faculty,  and  may,  there- 
fore, accompany  insanity,  drunkenness,  impressive  dreams, 
strong  forebodings,  and  very  strong  and  violent  passions. 
These  imperfect  external  sensations  are  known  as  appearances^ 
apparitions,  delusions,  spectres,  ghosts,  &c.,  and  it  is  of  not 
less  importance  to  pathology  and  practical  medicine  than  to 
the  present  subject,  that  these  be  traced  to  their  origin,  and 
distinguished  from  the  feeble  images  of  imaginations  and 
foreseeings.  If  a  vigorous  effort  be  made  to  see  with  the  eye- 
lids closed,  a  red  colour  is  seen :  if  the  fear  of  a  sudden  fall 
from  a  height  excites  the  nerves  of  vision  to  give  a  false  im- 
pression of  surrounding  objects,  they  seem  to  move,  or  vertigo 
occurs :  a  loud  stunning  noise  is  heard  long  after  it  has  ceased, 
but  with  decreasing  indistinctness :  if  food  be  desired  with 
great  longing,  its  taste  is  perceived  beforehand :  if  a  delightful 
sensation  be  anticipated  earnestly,  the  nerves  become  so  sen- 
sitive, that  every  slight  impression  causes  it,  although  previously 
they  would  have  had  no  effect.  All  these  are  instances  of 
imperfect  sensations  of  this  kind,  which  happen  to  the  most 


80  CEREBRAL  FORCES.  [r. 

healthy  persons.      Consequently,  they  are  not  peculiar  to  an 
unnatural  condition  of  animal  bodies,  but  occur  in  the  natural. 
149.  It  will  be  worth  the  while  to  consider  more  closely  the 
origin  of  imperfect  external  sensations.    A  strongly  sensational 
conception  makes  a  forcible  impression  in  the  brain,  at  the  point 
of  origin  of  a  certain  nerve   (144,  26).      This  is   propagated 
along  the   nerve  to  its  terminating  fibrils,   which  are  thereby 
stimulated  and  erected  (147).     This  action  imparts  an  external 
impression  to  the  fibrils,  just  as  if  they  had   been   acted  upon 
from  without,  which  is  returned  to  the  brain,  and  becomes  an 
imperfect  external  sensation  (148).      But  inasmuch  as  the  real 
external  circumstance  is  wanting,  the   question  arises,  what  is 
really  felt  imperfectly  ?      The  answer  is  as  follows  :   The  sen- 
sational conception  from  which  the  whole  delusion  arises,  pos- 
sesses the  sub-impressions   (merkmale)  of  a  past  or  future  ex- 
ternal sensation  (66),  and  their  material  ideas  also  partly  excite, 
at  the  origin  of  the  nerve  which  they  impress,  the  corresponding 
material  external  sensation.      This,  which  is  a  movement  at  the 
cerebral  origin  of  the  nerve  (43),  and  is  now,  in  fact,  its  impres- 
sion (121),  is  transmitted  downwards  to  the  terminal  fibrils,  and 
there  makes  the  baseless  external  impression,  which  is  returned 
to  the  brain,  to  the  same  point  of  the  nerve  whence  it  came. 
The  imperfect  material   external  sensation  thus  excited  is  a 
movement  at  the  origin  of  the  nerve,  which  is  partly  the  same 
as  would  have  originated  if  the  actual  external  thing,  of  which 
the  sensational  conception  contains   sub-impressions,  had  made 
an  external  impression  on  the  terminal  fibrils,   and  which  is 
only  defective  in  that  which  the  external  impression  alone  can 
supply,  to  render  it  a  true   external   sensation.      Now,   since  a 
true   external   impression  takes   place,   although   without  the 
impression   of  a  real  external  object,  the   imperfect   external 
sensation  is  thereby  rendered  more  similar  and  equal  to  a  true 
external   sensation,  than   it   previously  was  by  the  sensational 
conception  alone.   Further,  the  apparent  object  of  the  imperfect- 
external  sensation  is  always  the  object  of  that  external  past  or 
future   sensation,   which   was   already   the   basis   of  the   con- 
ception  that   constitutes    the   first   element   of   the   delusion. 
Consequently,   the  maniac,   the   drunkard,    the   dreamer,    the 
soothsayer,  the  enamoured,  the  scorner,   &c.,  each  according 
to    their    delusion,   feel  what  their  imaginations,   foreseeings, 


CH.  II.]  MATERIAL  IDEAS.  81 

expectations,  forebodings,  instincts,   and  emotions  bring  into 
the  mind. 

150.  When  the  nerves  which  feel  these  imperfect  sensations 
are  distributed  to  mechanical  machines,  they  excite  the  same 
movements,  as  if  the  sensation  had  been  real.  But  these  im- 
perfect sensations  must  not  be  confounded  with  others  aiising 
from  circumstances  external  to  the  nerves,  although  not  external 
to  the  organs  of  the  senses ;  as  for  example,  when  sparks  are 
seen  in  inflammation  of  the  eye,  or  singing  and  humming  in 
inflammation  or  diseases  of  the  cavity  of  the  ear.  These  are 
true  external  sensations,  connected  with  an  erroneous  judgment. 
The  nerves  of  the  eye  and  ear  are  really  impressed  by  some- 
thing external  to  them,  but  it  is  within  the  organ  of  hearing 
or  of  vision  itself,  and  the  mind  judges  falsely,  that  the  sen- 
sations arise  from  objects  which  have  customarily  excited  them ; 
as,  for  example,  that  sparks  of  fire  are  seen,  that  bells  are 
heard  ringing,  water  rushing,  &c.  [Vide  §  378.) 

151.  Since  cerebral  impressions  excite  movements  at  the 
terminations  of  the  nerves,  where  their  course  is  obstructed 
or  reflected  (147),  it  is  highly  probable,  that  very  vivid  sensa- 
tional impressions  are  also  deflected  in  their  course  from  the 
brain  downwards  to  the  periphery,  either  at  the  bifurcations  of 
the  nerves,  or  in  the  ganglia,  especially  whei*e  nerves  are  given 
ofi*  to  other  parts,  or  to  surround  the  arteries,  and  excite  such 
gentle  movements,  as  may  have  an  influence  on  the  contiguous 
mechanical  machines. 


CHAPTER  III. 

ON  THE  INFLUENCE  OF  THE  ANIMAL-SENTIENT  FORCES  IN  THE 
MECHANISM  OF  ANIMAL  ORGANISMS. 

153.  In  the  foregoing  chapter,  we  have  treated  of  the  animal- 
sentient  forces  abstractedly,  without  reference  to  their  influence 
in  the  mechanical  machines  of  the  body.  We  must  now  bring 
this  influence  under  notice  (8),  as  being  the  second  class  of 
actions,  which  the  material  ideas  excite  in  the  animal  eco- 
nomy (16,  113).     According  to  §  117,  we  have  to  inquire  into  : 

i.  The  direct  actions  of  the  material  ideas,  which  they  alone 
perform  in  the  mechanical  machines  of  the  brain,  without  the 
aid  of  the  nerves  (153 — 159). 

ii.  The  indirect  actions  of  the  material  ideas  through  the 
nerves  in  the  mechanical  machines  generally  (344),  and  spe- 
cially the  material  ideas  of  all  the  various  kinds  of  conceptions. 

Actions  of  Material  Ideas  in  the  Mechanical  Machines 
of  the  Brain. 

153.  The  mechanical  machines  of  animal  organisms  are 
capable  of  many  kinds  of  movement,  in  virtue  of  their  struc- 
ture ;  but  they  are  put  in  motion  much  more  by  animal  than 
physical  and  mechanical  forces.  Since  the  animal  forces  are 
not  regulated  in  their  operation  according  to  physical  or  me- 
chanical laws  (7),  we  cannot  bring  them  into  the  same  category ; 
and  as  their  laws  are  unknown,  we  can  only  infer  their  actions 
in  the  animal  machines  from  observation. 

154.  The  influence  of  the  soul  on  the  body  is  exercised 
by  means  of  the  material  ideas,  or  the  impressions  of  their 
conceptions  in  the  brain  (25,  121),  and  all  the  movements 
of  mechanical  machines  which  are  actually  efi*ected  through 
these,  are  sentient  actions  (97).  All  sentient  actions  in  the 
mechanical  machines  are  excited  either  directly,  by  the  material 
ideas  developed  in  the  brain  itself,  or  indirectly,  by  means  of 


CH.  III.]  THE  BRAIN.  83 

the  nerves  along  which  conceptional  or  internal  impressions  are 
transmitted  from  the  brain. 

155.  To  understand  this  matter  rightly^  the  meaning  of  the 
term  mechanical  machines  used  in  this  whole  treatise,  must 
be  properly  comprehended ;  it  must  be  understood  to  include 
all  the  organs  of  the  body,  except  the  brain  and  nerves,  which 
are  proper  animal  machines.  Consequently  muscles,  tendons, 
membranes,  vessels,  glands,  bones,  cartilages,  viscera,  &c.,  are  all 
mechanical  machines.  Although  many  of  these  are  endowed 
with  animal  moving  forces,  they  are  so  endowed,  only  through, 
and  in  virtue  of,  the  nerves  with  which  they  are  supplied.  So 
also  the  organs  of  the  external  senses,  although  endowed  with 
sensitive  nerves,  are  only  mechanical  machines,  and  even  the 
brain  and  nerves  contain  the  latter. 

156.  There  are  no  other  mechanical  machines  in  direct  con- 
nection with  the  brain,  than  certain  glands,  the  meninges,  and 
the  circulating  and  lymphatic  vessels.  Consequently,  these  are 
the  only  machines,  in  which  material  ideas  can  develope  sentient 
actions  directly  in  the  brain  itself,  without  the  aid  of  the  nerves. 

157.  The  uses  of  the  glands  situate  on  the  membranes  of  the 
brain,  and  in  close  proximity  to  it,  are  altogether  unknown ;  but 
they  probably  constitute  a  part  of  its  mechanical  structure. 

158.  The  membranes  enclosing  the  brain,  and  partly  the 
nerves,  belong  to  the  same  class  (the  mechanical)  as  tendons, 
ligaments,  &c.  They  are  not  only  insensible,  but  the  brain 
itself  seems  to  have  no  influence  on  them,  except  in  commu- 
nicating the  mechanical  movement  (24)  which  it  possesses  itself. 

159.  The  tubes,  and  especially  the  vascular  system,  remain 
only  to  be  noticed  among  the  mechanical  machines  which  are 
in  connection  with  the  brain,  and  in  these,  material  ideas  can 
develope  true  sentient  actions.  The  cortical  substance  is  almost 
wholly  a  tissue  of  tubes ;  it  is  not  the  organ  of  the  conceptive 
faculty,  nor  the  seat  of  the  animal-sentient  forces,  but  the 
organ  for  secreting  the  vital  spirits,  which  it  supplies  to  the 
medulla  of  the  brain,  and  thence  to  the  entire  system  of  animal 
machines  (the  nervous  system)  (11) ;  in  this  respect  it  can  be 
considered  as  a  viscus  of  the  head,  whose  proper  function  is  the 
secretion  of  certain  fluids  from  the  blood;  which  fluids  con- 
stitute, however,  an  essential  part  of  the  animal  machines  (9) ; 
it  is,  therefore,  really  a  mechanical  machine  (155),  but  in  virtue 


84  ANIMAL-SENTIENT  FORCES.  [i. 

of  its  function  to  give  existence  to  the  animal  forces,  it  differs  as 
little  from  the  proper  animal  machines,  and  as  necessarily  be- 
longs to  them,  as  the  roots  of  a  tree  to  the  tree  itself  (9,  11). 
This  mechanical  machine  is  unique,  for  while  it  belongs  to  the 
animal  machines,  it  secretes  the  vital  spirits  from  the  blood 
in  its  infinitely  numerous  minute  canals,  just  as  other  secreting 
organs  secrete  other  fluids  in  their  minute  tubuli.  Secretion 
generally,  as  physiology  teaches  us,  takes  place  according  to 
physical  laws,  rather  than  animal.  But,  nevertheless,  since 
the  fluids  entering  the  tubuli  act  as  stimuli,  and  excite  them  to 
the  performance  of  their  natural  functions,  as  will  be  shown 
subsequently  (168, 172,  460),  the  natural  function  of  the  cortical 
substance  of  the  brain  must  be  considered  as  animal ;  only  its 
functions  do  not  belong  to  the  proper  sentient  actions,  however 
necessary  and  indispensable  to  them ;  for,  although  requisite  to 
the  production  of  material  ideas  in  the  cerebral  medulla,  it  is 
not  a  direct  result  of  these,  nor  is  it  in  itself  a  material  idea, 
since  the  secretion  of  the  vital  spirits  is  not  directly  caused 
by  conceptions  (25,  97).  Nevertheless,  the  cortical  substance 
can  be  influenced  indirectly  by  sentient  actions,  as  when  con- 
ceptions, desires,  &c.,  influence  the  heart  and  the  circulation ; 
and  thus,  either  by  increasing  or  diminishing  the  amount  of 
blood  sent  to  the  brain,  increases  or  diminishes  the  secretion  of 
vital  spirits ;  which  phenomena  are  rather  the  results,  however, 
of  sentient  actions,  than  sentient  actions  themselves.  It  is 
probable,  although  not  established,  that  the  material  ideas  in 
the  medullary  substance  exercise,  as  sentient  actions,  a  direct 
influence  on  the  vessels  of  the  brain.  The  brain  receives  at  each 
stroke  of  the  left  ventricle  at  least  a  sixth  part  of  the  whole 
mass  of  blood,  and  this  is  distributed  through  every  part  of 
•  the  brain,  by  means  of  the  almost  infinitely  numerous  capillaries 
which  enter  into  its  substance  (Haller),  so  that  the  smallest  move- 
ment in  the  brain  would  act  almost  necessarily  on  these  minute 
vessels.  The  vessels  w^hich  return  the  blood  to  the  heart,  the 
source  of  vital  movements  (Lebensbewegungen),  are  equally 
numerous.  It  is,  therefore,  probable,  that  the  material  ideas 
in  the  brain,  however  hidden  they  may  be  from  observation  (28), 
have  some  influence  on  the  vital  movements,  independently  of 
the  nerves,  and  that  this  may  be  one  of  the  causes,  why  so 
many   conceptions,    but   especially  painful    sensations  in   the 


CH.  III.]  NERVES  OF  BLOOD-VESSELS.  85 

brain  (headache),  change  the  circulation  of  the  blood,  and  some- 
times distend,  sometimes  empty,  the  vessels  of  the  head,  and 
render  the  colour  of  the  face  so  variable.  All  this  it  is 
true  is  conjecture,  but  it  is  probable;  we  cannot  decide  the 
question,  for  proper  observations  as  to  the  mode  are  impossible. 
We  see,  indeed,  that  some  species  of  conceptions  regularly 
and  powerfully  modify  the  vital  movements,  and  especially  the 
circulation  within  the  head ;  but  still  since  this  may  probably 
take  place  through  the  nerves  distributed  to  the  heart  (for  the 
impressions  of  such  conceptions  influence  its  movements  by 
means  of  its  nerves),  it  remains  undetermined  whether  the 
direct  action  on  the  cerebral  capillaries  of  the  cerebral  im- 
pression has  a  share  in  these  sentient  actions,  and  to  what  extent. 


Actions  of  the  Material  Ideas  in   the    Mechanical   Machines 
through  the  Nerves. 

160.  The  most  common  and  most  general  mode  of  connec- 
tion between  the  nerves  and  mechanical  machines  is  the  rami- 
fication and  subdivision  of  the  former  in  the  latter,  until  they 
become  imperceptible  (13).  Another  is,  however,  possible  :  the 
nerves  come  in  their  course  into  contact  with  various  me- 
chanical machines,  without  being  specially  distributed  to  or 
lost  in  them.  As  the  cerebral  impression  on  the  nerve  pro- 
duces no  visible  or  observable  movement  at  the  point  of  im- 
pression, so  neither  in  traversing  the  nerve  does  it  excite  any 
action  in  the  parts  with  which  in  its  direct  course  it  comes  into 
contact.  But  as  it  is  probable,  that  its  deflection  at  the 
points  where  it  is  turned  from  its  direct  course,  is  caused 
y  a  vivid  cerebral  impression  (151) ;  it  is  probable,  also,  in 
ch  a  case  it  may  communicate  some  movement  to  the  me- 
chanical machines  it  comes  into  contact  with  at  such  points, 
and  this  may  be  termed  a  sentient  action  (97).  This  conjecture 
is  very  probable  as  to  the  loops  of  nerves,  which  wind  round 
numerous  blood-vessels,  and  enclose  them,  certainly  not  without 
an  object.  Probably,  many  vivid  cerebral  impressions  slightly 
compress  the  vessels  by  this  means,  and  so  retard  the  circulation, 
as  Haller  has  supposed,  who  by  this  hypothesis  has  explained  the 
redness  of  the  face  in  blushing.  {'  Opera  Minora,'  tom.  i,  p.  513.) 
Subsequently,  however,  this  distinguished  man  discarded  the 


m 


86  ANIMAL-SENTIENT  FORCES.  [i. 

hypothesis,  and  other  learned  persons  have  rejected  it  entirely, 
on  the  ground  that  although  impressions,  whether  external  or 
internal,  may  excite  convulsions  in  muscles,  they  excite  no 
perceptible  movement  in  the  nerves.  Nevertheless,  as  the 
cerebral  impression  undoubtedly  excites  movement  in  the  ter- 
minal points  of  the  nerves  (147),  this  may  be  possible  and  pro- 
bable, wherever  else  it  is  deflected  from  its  direct  course  (151). 
Further  proofs  on  this  point  will  be  given  subsequently  (178). 

161.  Amongst  the  mechanical  machines,  in  which  the 
nerves  are  so  distributed  as  to  be  completely  incorporated  with 
them,  the  muscles  hold  the  first  place.  Nerves  penetrate  all 
muscles,  being  distributed  together  with  the  blood-vessels  through 
the  cellular  tissue,  losing,  however,  their  firm  coat,  and  be- 
coming soft,  before  they  become  so  minute  as  to  be  no  longer 
traceable  (^  Haller^s  Physiol.,^  §  398).  It  maybe  also  asserted, 
that  the  soft  medulla  of  the  nerve  is  lost  in  the  muscular  fibrils, 
and  incorporated  with  their  substance  (^  Monro  de  Nervis,^  §  22). 
When  a  muscle  is  thrown  into  contraction  by  an  impulse  sent 
along  the  nerve,  its  fibrils  are  contracted,  and  the  two  ends  are 
drawn  together,  so  that  the  whole  muscle  is  shortened;  con- 
sequently, it  also  draws  the  parts  together  to  which,  by  means 
of  its  tendons,  it  is  attached.  The  latter  are  passive,  and  are 
neither  contractile,  nor  capable  of  receiving  an  impression.  The 
muscle  may  be  moved  either  wholly  or  partly.  The  arteries 
which  are  distributed  to  muscles  are  necessary  to  their  com- 
pleteness, so  that  without  them  they  soon  become  unfit  for 
their  functions,  or  diseased  (129,  iv) ;  but  the  animal  actions 
themselves  do  not  immediately  cease  when  the  influence  of  the 
blood  ceases  {'  Monro  de  Nervis,^  §  44),  and  are  in  no  wise  pro- 
duced by  it  (Haller's  'Physiol.,'  §  406). 

162.  This  action  of  the  nerves  on  the  muscles  cannot  be 
explained  by  any  of  the  laws  of  mechanical  motion  (Haller's 
'  Physiol.,'  §  §  394, 412.)  It  is  also  manifest  from  all  phenomena, 
that  the  vibrations  transmitted  along  the  nerves,  and  com- 
municated to  the  muscles,  do  not  produce  the  movements  of  the 
latter  in  any  mechanical  way  (Ibid.,  §§  376,  377);  and  as  all 
other  methods  of  explaining  mechanically  these  movements  are 
insufficient,  we  must  turn  to  other  moving  forces.  The  move- 
ment in  the  muscle  which  it  receives  from  the  nerves,  only 
takes  place  after  an  impression  made  on  the  nerve, — it  may  be 


CH.  III.]  THE  NERVES  OF  MUSCLES.  87 

an  external  impression  transmitted  to  the  brain,  or  one  which 
does  not  reach  the  brain  (3i,  47),  or  a  cerebral  impression  from 
conceptions,  or  not,  or  an  internal  impression  in  the  medulla  of 
the  nerve  itself  in  its  course  (121).  An  irritation  of  the  nerve 
of  a  muscle  (an  external  impression)  produces  movement  in  the 
muscle  it  supplies ;  it  does  this  also  when  the  animal  is  de- 
capitated, or  with  its  nerves  tied  and  rendered  insensible,  nay, 
even  in  the  separated  muscle  itself  (Haller's  '  Physiol.,'  §  §  404, 
409,  575.)  If  the  medulla  of  a  nerve  be  irritated,  the  muscle 
or  muscles  to  which  it  is  distributed,  are  convulsively  con- 
tracted; and  this  so  long  as  the  animal  lives,  or  even  after 
death,  so  long  as  it  is  moist.  It  is  not  at  all  necessary  that 
the  nerve  be  entire,  since  if  it  be  divided  and  then  irritated, 
contractions  are  equally  excited.  If  a  nerve  be  compressed,  or 
tied,  the  muscles  to  which  it  is  distributed  are  paralysed,  and 
although  the  will  endeavours  to  act  on  them,  they  remain 
motionless.  But  if  the  ligature,  or  compression,  be  relaxed, 
the  muscles  regain  the  power  of  movement,  provided  the 
nerve  be  uninjured.  If  the  crura  cerebri  be  irritated  deeply 
in  their  substance,  the  most  violent  convulsive  movements  are 
excited  in  the  whole  body;  the  same  occurs  when  the  spinal 
cord  is  irritated.  If  the  brain  be  compressed,  that  portion 
of  the  body  is  deprived  of  motion,  the  nerves  of  which  arise 
from  the  compressed  portion :  in  injuries  of  the  spinal  cord 
it  is  more  distinctly  manifest,  that  convulsions  or  paralyses  are 
induced  in  that  part  of  the  body  supplied  with  nerves  from 
the  injured  portion.  When  the  spinal  cord  is  injured  in  the 
neck,  death  follows  immediately,  because  the  nerves  of  the 
heart  arise  from  this  portion  (Haller's  ^  Physiol.,^  §§  367,  368). 
An  impression  on  a  motor  nerve,  of  whatever  kind  it  may  be, 
developes  the  movements  proper  to  the  muscle  with  which  it  is 
incorporated  in  a  way  quite  incomprehensible.  It  is  a  movement 
caused  by  an  animal  force  (7),  and  in  so  far  as  it  is  produced 
by  the  impressions  of  conceptions  in  the  brain,  it  is  a  sentient 
action  (97) .  No  other  movement  of  a  muscle  is  such,  whether 
it  be  from  mechanical  or  physical  forces,  or  even  from  im- 
pressions (except  those  of  conceptions),  although  in  the  latter 
case  they  are  animal  (6,  7) .  On  the  other  hand,  the  volitional 
movements  must  not  be  considered  as  the  only  sentient  actions, 
— as  is  carelessly  taught  in  many  elementary  treatises,  causing 


88  ANIMAL-SENTIENT  FORCES.  [i. 

numerous  errors,  —  since  there  are  also  those  which  arise 
from  spontaneous  conceptions  and  from  external  sensations 
(97,  98,  351).  It  is,  consequently,  equally  incorrect  to  say,  that 
the  functions  of  certain  muscles,  as  the  heart,  intestinal  canal, 
&c.,  do  not  depend  on  the  mind,  because  the  mind  has  no 
control  over  them,  for  the  external  sensations,  imaginations, 
instincts,  and  passions  equally  change,  increase,  or  diminish 
them,  although  the  mind  exercises  at  the  same  time  no  vo- 
litional influence. 

Note. — Haller  seems  to  be  of  the  opinion,  that  no  movements 
except  the  voluntary  are  produced  by  the  soul,  "  ^Eterna  lege 
separatur  voluntatis  imperium  ab  irritabiiitatis  provincia'^ 
('Elem.  Phys.,^  torn,  iv,  p.  528).  He  recognises,  nevertheless, 
the  action  of  the  imaginations,  sensations,  instincts,  and  emo- 
tions, and  proves  somewhat  unnecessarily  that  they  are  not 
volitional  movements  (ibid.,  p.  525).  It  necessarily  follows 
that  the  sensational  conceptions,  desires,  instincts,  &c.,  are  not 
mental,  but  corporeal,  as  Haller,  in  his  *^  Physiology,'  §  564, 
and  other  places  in  his  writings,  seems  to  maintain.  But  no 
sound  metaphysician  can  grant  such  a  confusion  of  ideas,  as  we 
shall  subsequently  show  it  to  be  (579,  iii). 

163.  All  muscular  actions  are  animal  actions,  in  so  far  as 
they  are  excited  by  the  nerves;  they  are  only  sentient  when 
excited  by  conceptional  impressions  in  the  brain.  We  may 
enumerate  walking,  standing,  sitting,  flexion  and  extension 
of  the  limbs,  respiration  and  its  modifications,  as  speaking, 
laughing,  singing,  wailing,  sighing,  coughing,  sneezing,  de- 
glutition, digestion  in  the  stomach  and  intestines,  the  action 
of  the  heart,  and  the  circulation  in  connection  with  cardiac 
action,  as  animal  functions,  which  may  be  sentient  (167).  On 
the  other  hand  every  action  of  a  muscle,  which  takes  place  in 
virtue  of  its  physical  contraction,  or  of  physical  or  mechanical 
moving  forces,  or  by  the  influence  of  the  vessels,  or  through 
its  membranes  or  tendons,  or  other  impressions  than  the  ap- 
propriate ones,  is  neither  animal  nor  sentient  (162). 

164,  i.  When  a  muscular  movement,  or  an  action  resulting 
therefrom,  is  a  sentient  action,  a  special  impression  on  the 
cerebral  origin  of  the  nerve  that  controls  the  muscle  is  neces- 
sary thereto  (123,  124),  and  which  is  propagated  downwards 
through  special  fibrils  of  the  nerve  to  the  muscle  into  \vhich  it 


CH.  III.]  THE  NERVES  OF  MUSCLES.  89 

arrives,  together  with  the  nerve,  and  excites  it  to  that  action,  of 
which,  in  virtue  of  its  structure,  it  is  capable. 

ii.  The  same  nerve,  can  at  the  same  time  in  which  it  excites 
the  muscle  into  action,  receive  an  external  impression,  and 
transmit  it  to  the  brain,  there  to  excite  external  sensations, 
without  the  two  impressions  as  they  pass  in  opposite  directions, 
interrupting  each  other  in  their  course  (126). 

iii.  When  a  nerve  is  compressed,  or  divided,  in  its  course 
between  the  brain  and  the  muscle  to  which  it  is  distributed, 
the  latter  cannot  be  excited  into  action  by  cerebral  impressions 
until  the  compression  is  taken  off  (128.  Haller's  '  Physiology,^ 
§§  403,  367). 

iv.  If  the  brain  be  compressed,  all  sentient  actions  in  the 
muscles  cease,  and  all  actions  dependent  on  them  (128).  If 
only  a  portion  of  the  brain  be  compressed,  then  the  actions 
cease  in  those  muscles  which  receive  their  nerves  from  the 
compressed  portion,  inasmuch  as  they  can  no  longer  receive 
conceptional  impressions. 

V.  A  general  irritation  of  the  brain,  or  such  an  irritation 
that  the  origin  of  all  the  motor  nerves  is  implicated,  must 
excite  disorder  of  the  whole,  or  of  the  greater  part  of  the 
muscular  system  (128.  Mailer's  '  Physiology,'  §§  367-8,  568). 
165,  i.  If  a  muscle  be  directly  excited  into  action  by  external 
sensations,  the  nerve  which  perceived  the  latter  must  move  it 
(129,  131),  although  the  movement  may  take  place  through 
other  and  far  distant  branches  (127).  This  is  the  sympathy 
of  sentient  actions  in  the  muscles.  Direct  sentient  actions  of 
this  kind  frequently  take  place,  as  for  example,  if  by  a  powerful 
injury  the  muscles  are  excited  to  spasmodic  action,  or  cramps, 
other  sympathising  muscles  are  frequently  excited  into  similar 
movements. 

ii.  When    the    medulla   of  the   brain  is   irritated,   violent 

lovements  may  be  excited  in  the  muscles  by  the  pain  (132, 

Laller's  '  Physiology,'  §  308),  which  are  sentient  actions^  and 

•e  produced  in  the  same  way  as  those  resulting  from  external 

jnsations  (132). 
iii.  When  the  mind,  by  means  of  spontaneous  conceptions, 

lOves  the  muscles  and  other  parts   through   them,  the  con- 
jeptions  must  act  on  the  cerebral  origin  of  the  nerves  which 

jgulate  the  muscles  (130).      All  kinds   of  imaginations   and 


90  ANIMAL-SENTIENT  FORCES.  [i. 

foreseeings,  also  imperfect  external  sensations  (148),  internal 
sensations^  pleasure  or  pain,  desires,  aversions,  instincts,  emo- 
tions, and  ideas  of  the  understanding,  in  so  far  as  they  are 
mixed  up  with  sensational  conceptions,  or  are  pleasing  or 
painful  (330,  &c.),  and  the  desires  and  aversions  of  the  will, 
have  a  manifold  influence  on  some  muscles,  as  experience 
teaches,  and  the  domain  of  the  animal- sentient  forces  is  con- 
sequently very  general  in  the  muscular  system. 

iv.  The  more  energetic  the  impressions  of  all  these  concep- 
tions are,  the  more  energetic  are  the  movements  which  they 
can  produce  in  the  muscles  (133). 

V.  When  these  movements  are  caused  by  conceptions  wholly 
spontaneous,  as  for  example,  by  volitions,  the  principle  of  their 
sequence  must  be  sought  for  in  the  laws  of  the  conceptive 
faculty  (110).  On  the  other  hand,  the  muscular  actions  pro- 
duced by  sensational  conceptions  are  known  to  us,  partly 
through  the  sequence  of  external  sensations  and  their  external 
impressions. 

VI.  The  sentient  actions  of  the  muscular  system  may  be 
prevented  in  the  same  modes  as  all  other  sentient  actions  ex- 
cited through  the  nerves  (136 — 139). 

166.  The  muscular  action  excited  by  animal-sentient  forces, 
represents  the  thoughts  as  it  were  by  external  delineations, 
especially  in  the  face,  by  which  their  existence  may  be  dis- 
covered ;  and  by  a  frequent  repetition  of  these  movements,  in 
consequence  of  vivid  and  oft-repeated  conceptions,  certain 
marks  are  necessarily  traced  in  the  skin  covering  and  surround- 
ing the  muscles.  Hence  arises  the  art  of  discovering  the  modes 
of  thought,  and  the  predominant  mental  characteristics  of  men, 
from  the  lineaments  of  the  face,  termed  Physiognomy. 

167.  The  nerves  may  have  an  influence  on  the  blood-vessels, 
on  the  secretions,  and  on  the  whole  circulation,  in  various 
ways.  In  the  first  place,  through  the  heart,  a  compound  hollow 
muscle,  throughout  which  nerves  from  various  sources  are  dis- 
tributed as  in  other  muscles  (161).  These  nerves,  like  all  others, 
can  receive  external  impressions,  since  an  animal  feels  when  the 
heart  is  pricked  or  irritated  (32).  They  consequently  transmit 
external  impressions  in  Such  cases  to  the  brain,  and  produce 
therein  at  their  origin  external  sensations  (34,  25),  or  cerebral 
impressions  (129).     When    there    is    no    impediment,    these 


CH.  III.]  THE  CARDIAC  NERVES.  91 

are  propagated  downwards  along  the  same  nerve  (129,  131), 
and,  consequently,  may  not  only  have  an  influence  on  the 
movements  of  the  heart  (7),  but  may  excite  sentient  actions  (97). 
In  the  same  way,  the  sensational  conceptions,  desires,  and 
aversions,  sometimes  excite  cardiac  movements,  which  are 
sentient  actions  produced  through  the  nerves  by  various 
material  external  sensations  (66,  93) :  examples  of  this  kind 
are  numerous,  as  when  ideas,  foreseeings,  and  emotions  change 
the  movements.  It  is  acknowledged  by  the  most  eminent 
physiologists,  that  the  action  of  the  heart  generally  is  not 
mechanical,  but  animal;  yet  that  it  is  absolutely  a  sentient 
action  is  undoubtedly  erroneous,  since  it  will  continue  and 
be  re-excited  even  after  the  heart  has  been  removed  from 
the  body  (164,  iii).  Neither  is  it  any  proof  thereof,  that  an 
external  impression  on  the  terminal  fibrils  renews  the  move- 
ments of  the  heart,  since  the  action  of  that  impression  be- 
comes sentient  only  after  reaching  the  brain,  and  not  before 
(98,  1 62) .  If  it  be  asked,  whether  the  motion  of  the  heart  is 
not  sometimes  changed  by  numerous  impressions  made  on  the 
origin  of  its  nerves  in  the  brain,  and  consequently  that  many  a 
change  in  its  motion  maybe  a  sentient  action  (97)? — I  answer, 
— this  by  no  means  proves  the  contrary,  for  no  change  in  the 
heart's  movement  is  subject  to  the  will  (162,  163).  It  is  much 
more  indisputable,  that  such  a  change  is  a  sentient  action,  when 
an  external  sensation  or  another  spontaneous  conception  excites 
the  change.  Now  the  mind  actually  feels  many  external  im- 
pressions on  the  nerves  of  the  heart.  It  feels  its  palpitation, 
or  wounds  and  other  irritants ;  and  violent  actions  result  from 
these,  which  are  necessarily  direct  sentient  actions  of  its  ex- 
ternal sensations  (129).  That  its  nerves  do  not  respond  to  all 
stimuli,  is  a  peculiarity  they  have  in  common  with  all  other 
nerves.  Further,  it  is  indisputable,  that  although  the  will  has 
no  power  over  the  heart,  still  many  sensational  conceptions  have, 
and  particularly  the  instincts  and  emotions;  and  it  is  clear 
from  this,  that  many  changes  in  the  heart's  action  are  true 
sentient  actions,  in  so  far  as  they  are  produced  by  conceptions 
by  means  of  their  cerebral  impressions  (97,  163).  Lastly, 
although  the  movement  of  the  heart  is  neither  weakened  nor 
ceases,  when  the  brain  is  compressed,  or  the  nerves  tied, 
nothing  more  can  be  inferred  therefrom,  than  that  the  entire 


92  ANIMAL-SENTIENT  FORCES.  [i. 

movement  is  not  generally  a  sentient  action,  which  is  indeed 
the  fact ;  but  rather  that  the  undoubted  animal  force,  which  con- 
tinually produces  it,  is  not  derived  from  the  brain,  and  has  its 
seat  in  other  animal  machines  (the  nerves)  and  forces  (the  purely 
animal,  ^7),  which  will  be  treated  of  subsequently  in  the  Second 
Part  (448,  514).  But  in  so  far  as  the  heart  is  capable  of  certain 
sentient  actions  excited  through  the  brain,  no  one  would  deny 
that  they  must  cease,  when  the  brain,  or  the  origins  of  the 
nerves,  are  compressed,  or  the  nerves  tied,  or  divided  in  some 
part  of  their  course.  In  such  a  case,  the  external  sensation 
from  the  strongest  irritant  applied  to  the  heart,  or  any  emotion, 
would  fail  to  excite  its  action  (164,  i,  iii,  iv). 

168.  The  nerves  have  another  influence;  namely,  on  the 
vascular  system  generally,  since  they  are  incorporated  with  the 
coats  of  the  arteries,  and  thereby  probably  supply  animal  force 
to  the  muscular  fibres  which  they  surround.  This  influence 
of  the  nerves  on  the  blood-vessels  is  very  obscure,  and  they 
scarcely  appear  to  efi*ect  a  sentient  action,  for,  in  the  experi- 
ments which  have  been  instituted,  the  arteries  have  never  once 
shown  any  sensibility  (Haller's  'Physiology,^  §  32).  Neverthe- 
less, Haller  asks  whether  it  is  not  probable,  that  the  arteries 
derive  from  these  nerves  the  powder  of  contracting  ? — Compare 
what  has  been  already  stated  (160)  and  subsequent  statements 
(178.) 

1 69.  A  third  kind  of  influence  possessed  by  the  nerves,  is  on 
the  vessels  distributed  to  the  muscles.  It  almost  necessarily 
follows,  that  the  numerous  blood-vessels  distributed  in  them 
are  aff'ected  by  the  contractions  excited  by  the  nerves.  Con- 
sequently, the  latter  indirectly  favour  the  circulation  of  the 
blood  in  the  veins,  and  agitate  and  mix  that  in  the  arteries, 
thereby  favouring  its  course  towards  the  lungs.  They  regulate 
the  secretions  of  the  liver,  mesentery,  &c.,  and  diminish  or 
retard  them;  they  urge  on  the  blood,  and  the  large  muscles 
of  the  abdomen  impel  the  blood  contained  in  that  cavity  towards 
the  heart  (Haller^s  'Physiology,^  §  416).  Many  of  these  acts 
are  sentient,  nay,  are  even  volitional  (165) ;  and  if  to  aU  these 
actions  of  the  nerves  on  the  blood-vessels  and  the  circulation, 
the  direct  action  of  the  brain  on  its  multitudinous  capillaries 
be  added  (159),  it  is  clear  that  this  apparently  simple  me- 
chanical motion  of  the  heart  is  much  under  the  important 


CH.  III.]       THE  NERVES  OF  MUSCULAR  TUBES.  93 

influence  of  the  mind,  and  the  still  more  important  influence 
of  the  nerves. — (Compare  §  207.) 

170.  The  nerves  act  principally  in  the  other  canals  which 
have  a  muscular  structure,  and  numerous  nerves,  as  the 
oesophagus,  intestinal  canal,  &c.,  by  the  stimulus  of  muscular 
motion,  so  that  these  tubes  are  put  in  motion  by  the  nerves  for 
the  performance  of  those  acts,  of  which  their  structure  renders 
them  capable.  When  no  natural  obstacle  is  present  in  the 
perves  (47,  &c.)  to  prevent  the  transit  of  the  external  impres- 
Isions  to  the  brain,  and  they  are  really  sensitive  (34),  they  may 
be  stimulated  to  action  by  the  cerebral  impression  of  external 
sensations,  and  then  the  action  is  sentient  (97,  129,  131), 
although  their  actions  are  not  usually  sentient,  but  nervine 
(162,  163).  The  oesophagus  and  intestines  are  often  really  sen- 
sitive, and  are  then  affected  with  spasms,  as  is  proved  by  colic, 
which  has  its  seat  in  the  intestines.  Now,  since  in  these  cases, 
the  spasms  are  true  sentient  actions  from  external  sensations 
(from  pain),  these  tubes  do  actually  manifest  some  sentient 
actions;  although,  in  other  cases,  they  are  excited  wholly  by 
other  animal  forces,  and,  although  the  will  has  no  power  over 
them  (162,  163).  Nay,  since  the  other  sensational  conceptions, 
imaginations,  foreseeings,  &c.,  and  the  sensational  desires  and 
aversions,  can  partly  re-excite  the  material  external  sensations, 
of  which  the  sensitive  nerves  are  susceptible  at  their  origin 
(66,  &c.,  93),  so  in  like  manner,  they  can  excite  movements  in 
these  muscular  tubes  which  are  sentient  actions ;  as,  for  example, 
when  retching  is  excited  by  the  anticipation  of  a  nauseous  taste, 
and  when  the  bowels  are  acted  on  by  the  imagination  of  a 
purgative  being  taken. 

171.  The  membranes  of  the  human  body  differ  very  much  in 
structure, — glandular,  cellular,  vascular,  &c. ;  the  latter  will  be 
treated  of  subsequently  (208).  The  muscular  membranes,  as 
the  diaphragm  and  others  which  enclose  different  parts  of  the 
body,  particularly  certain  glands,  are  also  sensitive,  as  we  learn 
from  observation ;  the  diaphragm,  in  particular,  has  large  nerves 
which  influence  its  movements  by  means  of  external  im- 
pressions, and  the  ligature  of  which  causes  the  movements  to 
cease  (Haller's  ^  Physiology,^  §  403).  Further,  the  motion  of 
the  diaphragm  is  subject  to  the  will,  inasmuch  as  we  can 
change  the  respiration  at  pleasure.      The  remarks  previously 


94  ANIMAL-SENTIENT  FORCES.  [i. 

made  (161 — 168)  as  to  the  action  of  the  nerves  on  the  muscles 
and  blood-vessels,  are  equally  applicable  to  these  flat  muscles 
and  muscular  membranes. 

172.  The  glands  are  a  tissue  of  vessels  and  nerves,  and  their 
function  is  to  separate  the  secretions  from  the  blood.  The 
nerves  exercise  the  same  influence  on  these  as  on  other  vessels, 
and,  consequently,  secretion,  which  ordinarily  appears  to  be 
simply  physical,  is  not  only  animal,  but  is  also  sometimes  a 
sentient  action.  The  nerves  have  the  most  manifest  influence 
on  those  glands  which  are  surrounded  by  muscular  tissue,  or  so 
placed  between  muscles  that  the  latter,  by  their  action,  express 
the  fluid  from  the  glands  when  secreted ;  so  that  it  is  poured 
out.  Examples  of  this  kind  are  the  penis  [Geilen],the  urinary 
bladder,  the  bowels,  the  stomach;  also  the  parotid  glands, 
which  are  emptied  by  the  actiou  of  the  muscles  of  mastication 
(Haller^s  '  Physiology,^  §  233.)  Many  glands  pour  out  their 
secretions  from  external  sensations  (titillation — pain,  80) ;  many 
from  imaginations,  sensational  anticipations,  desires,  &c.,  as,  for 
example,  the  salivary  glands  from  the  recollection  or  expectation 
of  an  agreeable  taste,  or  in  hunger ;  many  from  passions,  as  the 
lachrymal  and  sexual  glands;  many  even  from  acts  of  will,  as 
when  the  saliva  is  stimulated  to  flow  by  voluntary  mastication, 
or  weeping  is  feigned. 

173.  The  action  of  the  nerves  in  the  viscera  is  yerj  complex, 
varying  with  the  number  of  the  nerves  distributed,  or  with  the 
various  impressions  of  which  the  latter  are  susceptible  (34,  47, 
121);  or,  as  they  are  influenced  by  the  muscles,  muscular  tissues, 
glands,  &c.,  which  surround,  or  are  in  relation  to  them ;  or,  as 
the  nerves  act  directly  or  by  sympathy  (127,  165).  We  can 
only  notice  some  of  the  most  important. 

174.  The  stomach  has  many  and  considerable  nerves,  and 
remarkable  sensibility.  When  the  trunk  of  these  nerves  (the 
eighth  pair)  is  tied,  the  powers  of  digestion  fail.  Its  nerves 
are  susceptible  of  special  external  impressions,  so  that  acrid 
substances  which  are  not  distinguishable  by  the  tongue  excite 
the  stomach.  On  the  contrary,  other  things  which  the  tongue 
perceives  most  sensibly,  cause  not  only  no  distinct  sensation, 
but  no  sensation  at  all,  although  it  is  manifest  from  the  move- 
ments which  they  sometimes  excite,  that  they  must  cause 
another  external  impression,  which  is  not  felt,  because,  probably. 


t  H.  III.]  THE  VISCERAL  NERVES.  95 

there  are  natural  obstacles  that  prevent  the  transmission  of  the 
impression  to  the  brain  (47);  of  these  we  shall  treat  in  the 
second  part  (428,  429) .  In  virtue  of  its  sensibility,  the  stomach 
is  susceptible  of  impressions  from  conceptions  in  the  brain  (98), 
which  are  sentient  actions,  as,  for  example,  a  violent  pain  causes 
spasms  of  the  stomach.  The  observations  made  with  reference 
to  the  action  of  the  sensational  conceptions  and  desires  on  the 
oesophagus  and  intestinal  canal,  are  equally  applicable  to  the 
stomach  (170);  they  induce  sentient  actions,  as,  for  example,  when 
by  an  imagination  or  anticipation  of  a  loathing,  its  action  is  in- 
verted, and  vomiting  is  excited;  or,  when  it  is  excited  to  motion  by 
hunger ;  or  is  thrown  into  spasmodic  action  by  violent  emotions. 
The  will  has  little  influence  over  it ;  but  the  connection  between 
disorders  of  the  mind  and  the  nervous  system,  and  disorder  of 
the  digestive  powers  of  the  stomach  and  bowels,  is  well  known. 

175.  Although  the  sensibility  of  the  liver  is  not  great,  and, 
consequently,  only  few  external  impressions  made  on  its  nerves 
reach  the  brain,  still  it  is  capable  of  sentient  actions.  They 
are  observable  only  in  the  most  vivid  external  sensations  and 
sensational  conceptions,  as,  for  example,  in  the  pain  of  inflam- 
mation, or  in  rage,  fury,  &c.,  inasmuch  as  it  can  be  inferred  from 
the  bilious  disorders  which  follow,  as  icterus,  &c.,  that  the 
secretion  of  bile  must  be  prevented  or  increased.  The  nerves 
can  also  exercise  an  indirect  influence  on  the  liver  through  the 
diaphragm,  and  the  abdominal  muscles,  and  the  other  organs 
in  relation  with  it,  and  the  results  are  also  sentient  actions. 

176.  The  kidneys  have  but  few  nerves,  and  are  only  afi'ected 
by  powerful  external  impressions  and  sensations,  as  when  there 
is  a  stone  or  inflammation  present ;  in  which  cases  only,  certain 
sentient  actions  occur,  as  spasms.  The  external  impressions 
made  by  the  urine,  and  which  excite  vivid  external  sensations 
in  the  nerves  of  the  tongue,  the  nose,  and  even  the  skin  itself, 
are  either  not  made  at  all  on  the  renal  nerves,  or  a  natural 
obstacle  (47,  &c.)  prevents  their  transmission  to  the  brain. 
The  urinary  bladder,  on  the  other  hand,  is  much  more  sensitive. 
Vivid  external  sensations  (pain)  cause  spasms  and  spasmodic 
discharge  of  urine,  which  are  sentient  actions.  The  sensational 
conceptions  and  foreseeings  act  upon  it,  whence  persons  are 
often  induced  to  pass  urine  in  dreams.  The  will  has  also  some 
influence  upon  it  through  the  sphincters. 


96  ANIMAL-SENTIENT  FORCES.  [r. 

177.  The  organs  of  the  external  senses,  considered  as  me- 
chanical machines  only  (155)  are  subject  to  the  same  laws  as 
others.  Through  external  sensations,  sensational  conceptions, 
instincts,  emotions,  and  even  through  the  will,  the  nerves  cause 
movement  in  the  tongue,  the  nose,  the  ears,  the  eyes — even  the 
skin  in  which  are  placed  the  nerves  of  touch,  is  contracted  by 
many  external  sensations  (as  cold);  all  which  movements  are 
true  sentient  actions. 

178.  The  sexual  organs  of  man,  and  especially  the  testes  and 
penis,  are  supplied  with  numerous  and  large  nerves,  which  are 
extremely  sensitive.  The  sensibility  of  the  testes  is  so  great, 
that  syncope  and  convulsions  are  induced  by  injuries  to  them, 
and  locked  jaw,  in  particular,  from  the  sympathy  of  their 
sentient  actions.  The  sensitive  nerves  of  the  penis,  which  every 
impression  excites,  afford  a  remarkable  example  of  the  action 
of  conceptional  impressions  on  the  vessels  through  the  nervous 
loops  around  them,  and  independently  of  muscular  action,  of 
which  mention  has  been  already  made  (160),  for  the  tume- 
faction of  the  corpora  spongiosa  must  be  caused  by  a  reten- 
tion of  the  blood  in  the  vessels ;  which  can  only  be  explained 
by  the  theory  that  the  nerves  induce  the  vessels  to  contract, 
in  fact,  this  tumefaction  is  excited  by  every  kind  of  external 
impression  on  these  nerves,  especially  by  external  sensations,  as 
when  urine  irritates  the  bladder;  semen  the  seminal  ducts; 
the  venereal  poison,  and  Spanish  flies  the  urethra, — which  is 
very  sensitive;  and  other  causes,  as  flogging,  and  friction  of 
the  glans  penis.  In  like  manner,  it  is  caused  by  imaginations, 
foreseeings,  sensational  desires,  instincts,  and  emotions,  as  is 
well  known,  and  altogether  independently  of  the  will.  Haller 
maintains  the  doctrine,  that  this  swelling  takes  place  without 
the  assistance  of  the  muscles,  and  solely  by  the  blood-vessels, 
finding  analogous  instances  in  the  erection  of  the  nipples  in 
sucking,  the  distension  of  the  wattle  of  the  turkey,  and  of  the 
organs  of  generation  in  lower  animals  ('Physiology,'  §  840), 
all  which  are  sentient  actions.  (Compare  §  274.) 

179.  The  numerous  nerves  distributed  to  the  female  organs 
of  generation,  render  them  extremely  sensitive,  and  the  re- 
marks in  the  preceding  section  are  equally  applicable  to 
them  (274). 

180.  It  is  the  most  important  mechanical  machines  of  animal 


CH.  III.]     EXTERNAL  SENSATIONAL  ACTIONS.  97 

bodies,  that  are  susceptible  of  the  sentient  actions  just  described, 
in  virtue  of  their  nerves.  We  will  now  consider,  in  what  me- 
chanical machines,  and  by  what  laws,  the  different  conceptive 
forces  of  the  soul  manifest  their  actions  externally  to  the  brain, 
in  animal  bodies,  and  in  what  these  consist.  We  will  begin 
with  the  sensational  perception  and  desires  {76,  89),  and 
afterwards  consider  those  of  the  intellect. 


The  Actions  of  External  Sensations  through  the  Nerves  in  the 
Mechanical  Machines. 

181.  It  is  not  so  easy  a  task  as  it  appears,  to  discover  the 
direct  sentient  actions  of  external  sensations  in  the  mechanical 
machines.  All  those  produced  by  an  irritation  of  a  nerve, 
or  by  the  external  impression  transmitted  along  the  nerve,  or 
even  by  its  propagation  to  the  brain,  or  deflection  thence,  are 
its  animal  actions ;  but  none  is  a  sentient  action  of  an  external 
sensation  (98),  unless  it  belong  to  the  class  caused  in  the  me- 
chanical machines  by  an  external  sensation,  or  by  the  material 
cerebral  sensation  acting  as  an  impression  in  the  brain  (121,  97). 
All  movements,  consequently,  in  the  mechanical  machines, 
which  the  external  impression  excites  by  its  own  proper  animal 
forces,  before  it  has  formed  external  sensations  in  the  brain, 
and  all  that  it  produces  in  other  nerves  and  mechanical  ma- 
chines in  its  course  to  the  brain,  in  virtue  of  the  motive  force 
peculiar  to  itself,  cannot  be  considered  as  the  sentient  actions 
of  external  sensations,  even  although  they  be  also  developed 
by  the  external  sensations  of  the  external  impressions.  All 
the  sentient  actions  produced  in  the  mechanical  machines 
through  the  nerves  only,  of  imaginations,  foreseeings,  sensa- 
tional instincts,  emotions,  intellectual  conceptions,  or  desires  and 
aversions  of  the  will,  excited  in  the  mind  by  external  sensations, 
are  not  true  direct  sentient  actions  of  the  external  sensations, 
although  all  the  material  ideas  of  the  conceptions  produced 
by  the  latter  are  their  indirect  sentient  actions  (97,  98). 

182.  Hitherto,  these  actions  (altogether  distinct)  have  been 
indiscriminately  considered  as  direct  sentient  actions  of  external 
sensations,  and  so  the  physiological  doctrines  of  external  sen- 
sations have  been  sadly  confused.     It  is,  consequently,  of  im- 

7 


98  ANIMAL-SENTIENT  FORCES.  [i. 

portance,  that  we  make  this  distinction  as  clear  as  possible ; 
and  to  this  end,  we  must  assume^ — what  will  be  demonstrated 
in  another  part  of  this  book  for  the  first  time,  namely, — 
that  the  external  impressions  on  the  nerves  (nerve-feeling,  §  32), 
becomes  itself  an  animal  motive  force,  before  it  reaches  the  brain, 
and  develops  external  sensations  therein.  The  most  certain 
answer  to  the  question,  whether  a  movement,  excited  in  a  me- 
chanical machine  by  the  external  irritation  of  a  nerve,  be  simply 
an  action  of  the  external  impression  (feeling),  or  whether  it 
result  from  an  external  sensation,  is  found  in  the  experiment 
of  repeating  the  irritation,  of  which  the  movement  is  the  result, 
after  the  nerve  is  cut  off  from  connection  with  the  brain ;  or,  for 
greater  security  against  sympathetic  action,  after  the  head  of 
the  animal  has  been  separated  entirely  from  the  body.  So 
long  as  traces  of  animal  life  remain  after  this  separation,  the 
same  movement  results  from  irritation  of  the  nerve,  although 
the  external  impression  is  no  longer  propagated  to  the  brain, 
and  no  longer  able  to  excite  a  material  sensation  therein ;  con- 
sequently, the  movement  cannot  be  a  sentient  action  caused 
by  the  external  sensation,  but  is  an  animal  action  produced  by 
the  motive  force  peculiar  to  the  external  impression.  When 
after  this  demonstration,  the  apparently  sentient  actions  of 
external  sensations  in  the  animal  machines  are  investigated, 
it  is  found,  that  the  animal  motive  force  of  unfelt  external 
impressions  can  produce,  although  somewhat  less  perfectly,  the 
greater  number  of  these  movements,  which  we  consider  as 
being  solely  sentient  actions  resulting  from  external  sensations, 
and  which  are  in  fact  sentient  actions  also,  as  will  be  shown  in 
the  second  division  of  the  work. 

183.  The  movements  developed  in  organisms  by  the  pe- 
culiar animal  moving  force  of  the  nervous  system,  not  being 
at  the  same  time  an  animal-sentient  force  (6),  are  termed 
nerve-actions i  to  distinguish  them  from  sentient  actions;  con- 
sequently, the  movements  excited  in  organisms  by  the  motive 
force  of  an  unfelt  external  impression,  are  nerve-actions.  The 
majority  of  the  sentient  actions  in  mechanical  machines  of 
external  sensations  are,  therefore,  at  the  same  time,  nerve- 
actions  (182);  and  the  following  propositions  must  be  rejected 
as  erroneous.  1,  That  an  animal  movement  in  the  mechanical 
machines,  which  is  a  sentient  action  of  external  sensations,  is 


CH.  III.]      EXTERNAL  SENSATIONAL  ACTIONS.  99 

never  a  nerve-action ;  2,  that  the  movement,  which  is  a  nerve- 
action,  is  never  a  sentient  action  of  external  sensations;  for 
there  is  nothing  more  certain  than  that  a  sentient  action  result- 
ing from  external  sensations  may  be  at  the  same  time  a  nerve- 
action,  and  vice  versa.  On  the  other  hand,  there  may  be 
nerve-actions  in  the  mechanical  machines,  which  are  not,  at  the 
same  time  sentient  actions,  nor  resulting  from  external  sensa- 
tions, because  the  external  impression  is  prevented  developing 
a  material  sensation  by  a  natural  or  other  obstacle  (47,  48,  199). 
Thus,  the  movement  of  the  heart  is  usually  a  nerve-action  only, 
and  seldom  a  sentient  action  (167),  for  we  but  rarely  feel  the 
external  impression  which  excites  the  movement,  although  we 
often  feel  the  stroke  itself,  which  is  the  nerve-action. — (Com- 
pare §225.)  It  is  not  necessary  to  inquire  here,  whether  there 
be  sentient  actions  in  the  mechanical  machines  from  external 
.sensations  which  are  not  also  nerve-actions. 

184,  i.  When  an  external  impression  on  the  nerves  is  not 
^felt,  then  the  movement  which  it  causes  in  the  machines  is 
^not  a  sentient  action  from  an  external  sensation.  If,  however, 
the  movement  itself  be  felt,  and  this  acts  as  an  external  sen- 
sation in  exciting  new  movements,  the  latter  are  sentient 
^actions  from  the  external  sensation  produced  by  a  nerve- 
faction  (183,  443). 

ii.  It  is  not  manifest  what  influence  is  exercised  by  feeling, 

|iOr  the  consciousness  of  an    impression   in   the  production  of 

Jsentient  actions  which  can  also  be  simply  nerve-actions,  more 

.than  by  the  external  impression  itself;  unless  it  be  that  the 

■actions  are  rendered  more  complete  and  regular  when  the  two 

:CO-operate.      Generally,  however,  the  feeling  or  consciousness 

;of  the  external  impression  seems  to  have  no  other  object  than 

to  excite  other  conceptions  in  the  mind,   and  other  sentient 

factions,  so  that  its  operation  is  extended  evidently  through  the 

organism   generally,  and  becomes  of  compound  utility.      For 

example,  if  the  movement  of  the  stomach  when  empty  from 

fasting,  remain  such  as  it  really  is, — a  nerve-action, — and  be 

f.not  a  sentient  action  at  the  same  time,  the  desire  cannot  be 

j^excited  which  we  term  hunger,  and  the  organism  is  neglected. 

(If  a  violent  spasm  of  a  muscle  were  a  nerve-action  only,  and 

fnot  also  a  sentient  action  from  pain,  the  functions  of  the  muscle 

.might  be  destroyed  without  our  taking  any  steps  to  prevent  it. 


100  ANIMAL-SENTIENT  FORCES.  [i. 

According  to  this  view^  external  sensations  must  be  considered 
as  watching  over  our  preservation. 

185.  Again,  we  often  confound  the  sentient  actions  in  the 
mechanical  machines,  resulting  from  other  conceptions,  with 
those  resulting  directly  from  external  sensations.  When  we 
smell  or  see  some  nauseous  article  of  food,  which,  on  some 
previous  occasion  has  made  us  vomit,  the  external  sensation 
excites  in  us  the  imagination  of  the  previous  vomiting,  and  it 
again  comes  on,  because  this  imagination  conjoins  with  it  in 
its  action  the  partially  re-excited  external  sensation  {67).  In 
this  case,  vomiting  is  not  the  immediate  result  of  the  smell,  or 
perception  (the  external  sensation)  of  the  article  of  food,  but 
of  the  imagination  thereby  excited.  When  we  see  a  stone 
coming  upon  us  and  try  to  avoid  it,  the  movement  is  not  a 
direct  sentient  action  excited  by  the  seeing  the  stone  (the  ex- 
ternal sensation),  but  is  the  result  of  the  abhorrence  of  the 
impending  danger,  which  the  sight  of  the  stone  occasions. 
Such  examples  are  infinitely  numerous,  and  if  we  compare 
them  with  those  mentioned  in  ^  182,  it  is  found  that  we  have 
mistaken  the  greater  number  for  the  movements  connected 
directly  with  external  sensations,  these  being  either  nerve- 
actions  also,  or  purely  nerve-actions  (182,  183),  or  sentient 
actions  of  other  mental  forces  which  are  excited  to  action  solely 
by  external  sensations  (219,  199). 

186.  It  is  to  be  understood,  however,  that  those  inner  sen- 
sations of  the  soul  of  pleasure  and  suffering  excited  by  external 
sensations  (80)  must,  on  no  account,  be  classed  with  the  con- 
ceptions produced  by  external  sensations,  the  sentient  actions  of 
which  are  so  often  confounded  with  those  belonging  to  external 
sensations ;  for  pleasure  and  suffering  are  only  qualities  in  the 
external  sensations  of  the  soul,  and  not  other  conceptions  excited 
by  them ;  their  sentient  actions  are  consequently  to  be  classed 
with  those  arising  directly  from  external  sensations,  and  they 
extend  their  influence  to  no  other  nerves  than  those  which  feel 
the  agreeable  or  disagreeable  (124).  But  since  the  two  distinct 
conditions  of  agreeable  and  disagreeable  external  sensations  con- 
stitute external  sensations  for  two  distinct  kinds  of  conceptions, 
and  these  presuppose  distinct  material  sensations  in  the  brain 
(80),  and,  consequently,  distinct  external  impressions  in  the 
nerves  (35),  they   certainly   constitute  two    perfectly  distinct 


CH.  III.]       EXTERNAL  SENSATIONAL  ACTIONS.  101 

kinds  of  external   sensations   which  develope  totally   distinct 
sentient  actions  in  the  body. 

187.  All  external  sensations  are  either  agreeable  or  dis- 
agreeable; and  if  they  be  intense,  the  one  is  gratification 
[Kitzel],  the  other  suffering  [Schmerz]  (80).  There  is  no  ex- 
ternal sensation  without  these  qualities  of  pleasure  or  suflfering. 
(See  Baumgarten's  'Metaphysics/  §  481,  405.)  Consequently 
all  direct  actions  of  external  sensations  comprise  at  the  same 
time  those  of  pleasure  and  pain,  and  cannot  be  separated  from 
them,  because  one  or  other  is  present  on  every  external  sen- 
sation. 

188.  All  direct  sentient  actions  in  the  mechanical  machines, 
are  efi'ected  through  the  same  nerve  which  produces  the  ex- 
ternal material  sensation  in  the  brain  (129,  131),  whether  it 
be  the  same  fibril  which  received  the  external  impression,  or 
another,  in  virtue  of  the  sympathy  of  sentient  actions  (165,  i), 
or  from  reflexion  (48,  iv).  But,  should  the  action  of  an  ex- 
ternal sensation  occur  in  the  same  machine  that  received  the 
external  impression,  the  material  sensation  must  necessarily 
excite  in  the  brain  the  efferent  fibrils  of  the  same  nerve  which 
is  distributed  to  the  affected  mechanical  machines  as  their 
motor  nerve  (129,  iii). 

189.  The  difference  in  the  nature  of  the  external  impressions 
on  the  terminating  fibrils  of  the  same  nerve,  causes  the  dif- 
ference between  agreeable  or  disagreeable  external  sensations. 
Now,  since  the  external  impression  is  itself  an  animal  moving 
force  of  the  mechanical  machines  (182),  it  follows,  that  the 
impression  exciting  agreeable  external  sensations,  and  the 
impression  exciting  disagreeable  external  sensations,  can  each 
develope  appropriate  movements  in  the  mechanical  machines. 

190.  Since  we  know  nothing  of  the  peculiar  nature  of  an  ex- 
ternal impression,  we  cannot  say  wherein  it  differs  when,  through 
the  same  nerve,  it  excites  in  the  mind  at  one  time  an  agreeable, 
at  another  a  disagreeable  external  sensation,  or  when  it  excites 
gratification  or  suffering  (40).  But  since  we  are  no  better  ac- 
quainted with  the  nature  of  material  external  sensations  in  the 
brain,  the  only  sources  of  actions  in  the  mechanical  machines, 
dependent  on  external  sensations  (55,  129),  the  resulting  move- 
ments can  only  be  known  by  observation ;  but  by  this,  we  are 
able  sufficiently  to  discriminate  between  nerve- actions  merely 


102  ANIMAL-SENTIENT  FORCES.  [i. 

(183),  and  sentient  actions  of  conceptions  dependent  on  external 
sensations  (181,  185). 

191.  It  appears  that  the  external  impression  for  agreeable, 
or  for  neutral  external  sensations,  if  such  there  be,  is  con- 
formable to  the  natural  function  (destination)  of  the  nerves, 
or  connatural ;  on  the  other  hand,  that  of  disagreeable  external 
sensations  is  not  conformable  to  the  animal  structure  and  pro- 
perties of  the  nerve,  but  does  them  violence  in  some  degree, 
or  is  contra-natural}  This  difference  arises  probably,  because 
it  is  in  the  nature  of  the  soul  to  be  adjusted,  as  it  were,  to 
all  which  relates  to  the  preservation  of  the  body,  and  finds 
nothing  to  be  agreeable  which  is  injurious  to  the  latter  (196). 

192.  So  far  as  is  known,  all  the  nerves  of  sentient  animals 
are  sensitive  to  at  least  some  external  impressions.  Con- 
sequently, all  have  the  power  to  receive  at  least  some  of  these 
sensationally,  and  transmit  them  to  the  brain,  where  they  are 
changed  into  material  external  sensations  (34).  Material  ex- 
ternal sensations  are  animal-sentient  forces  (114),  that  cause 
an  internal  impression  on  the  nerve  that  has  felt  the  external 
influence  (121),  which  internal  impression  is  propagated  down- 
wards from  the  brain  along  the  nerve  (143),  and  if  the  latter 
be  incorporated  with  any  mechanical  machines,  may  excite 
actions  which  are  direct  sentient  actions  of  external  sensations 
(160).  In  this  way,  all  those  mechanical  machines  of  sentient 
animals  which  are  supplied  with  nerves,  are  in  fact  capable  of 
at  least  some  direct  sentient  actions  of  external  sensations, 
although  they  may  be  incapable  of  a  greater  number  from 

1  Der  naturlichen  Verrichtung  gem'dss  and  nicht  gem'dss  are  terms  used  here  in 
the  same  sense  as  natiirlich  and  widernaturlich  used  elsewhere.  The  terms  natural 
and  unnatural  would  not,  however,  exactly  express  the  author's  meaning.  The 
doctrine  laid  down  in  the  text  is  as  profound  and  truthful  as  any  of  the  remarkable 
views  advanced  by  him ;  the  terms  referred  to  imply,  that  there  are  agents  to  which 
the  animal  organism  is  expressly  and  beneficially  adapted,  and  the  impressions  of 
which  excite  its  mechanism  beneficially,  in  accordance  with  that  scheme  of  adaptation; 
while  other  agents  act  upon  it  in  a  contrary  sense,  and  impair  or  derange  the  normal 
and  beneficial  working  of  the  organism.  In  the  former  case  the  term  connatural  best 
expresses  the  character  of  the  agents ;  in  the  latter,  the  term  contra-natural.  In 
the  Second  and  Third  Parts  of  the  work,  these  doctrines  have  an  important  appli- 
cation in  explaining  the  conservative  and  other  actions  resulting  from  the  operation 
of  the  vis  nervosa,  when  excited  into  action  by  impressions,  where  the  same  words  are 
used  with  the  same  meaning.  (Vide  §  546,  et  alia.) 


CH.  III.]      EXTERNAL  SENSATIONAL  ACTIONS.  103 

natural  or  other  hinderances  (47) .   Now,  since  it  is  not  observed 
of  other  conceptions,  and  of  the  desires  and  aversions  (which 
^come  next  to  external  sensations,  §§  68,  89),  that  they  can  extend 
bheir  influence  to  all  the   mechanical  machines  supplied  with 
lervesj  nay,  that  the  greater  number  seem  to  act  only  in 
jome,  and,  indeed,  many  to  act  on  none  (79),  it  results,  that  the 
sphere  of  the  sentient  actions  from  external  sensations  is  the 
lost  extensive  of  all,  and  that  those  mechanical  machines  supplied 
dth  nerves,  which  are  excited  at  all  by  animal- sentient  forces, 
ire  capable  of  certain  sentient  actions  from  external  sensations. 
193.  The    circumstance    which    is    common    to   all    move- 
Lcnts  of  mechanical  machines,  whether  they  be  nerve-actions 
>nly,  or  excited  by  cerebral  impressions,  or  sentient  actions 
[resulting  from  external  sensations,  or  from  other  conceptions, 
jand  in  which  they  differ  from  simply  mechanical  movements, 
iis  this, — that  the  stimulus  to  those  movements  to  which  the 
jmechanical  machines  in  virtue  of  their  structure  are  adapted, 
is  received  through  the  nerves  as  an  internal  or  external  im- 
^pression  (31).      The    movements    themselves,    would,    conse- 
quently, be  the  same  as  those  produced  by  simply  mechanical 
forces,  since  all  movements  excited  in  a  machine  by  whatever 
force,  must  necessarily  be   such  as  are  in  accordance  with  its 
structure.     It  follows,  therefore,  that  the  circumstance  which 
renders  the  movement  of  a  mechanical  machine  in  organisms 
simply  animal  is, — that  it  proceeds  solely  from  an  unfelt  im- 
pression on  the  nerve,  and  not  from  cerebral  impressions  caused 
by  conceptions ;  that  the  circumstance  which  renders  the  move- 
ment a  sentient  action  is,— that  it  is  excited  by  an  internal 
impression  arising  from  conceptions  (154);  and  lastly,  that  that 
which  constitutes  it  a  sentient   action  of  external  sensations 
is, — that   it   originates  from  the  internal    impression   in   the 
brain  of  external  sensations  (34,  121). 

194.  The  more  vivid  the  external  sensations  are,  the  more 
energetic  is  their  action  on  the  mechanical  machines,  and, 
therefore,  the  actions  they  excite  in  the  latter  are  vigorous  in 
the  same  proportion  (133). 

195.  All  movements,  of  which  a  mechanical  machine  is 
capable  in  virtue  of  its  structure,  are  either  normal,  or  in  ac- 
cordance with  its  natural  structure  in  a  state  of  health,  or  are 
abnormal,  and  opposed  to  that  natural  function.    Consequently, 


104  ANIMAL-SENTIENT  FORCES.  [i. 

all  sentient  actions  of  external  sensations  stimulate  the  me- 
chanical machines  to  which  they  are  extended,  either  to  those 
movements  that  are  their  natural  function^  in  which  case  they 
are  sentient  actions  of  agreeable,  or  at  least  of  neutral  sen- 
sationSj  or  to  those  which  deviate  from  their  natural  function, 
and  these  are  sentient  actions  of  disagreeable  external  sensations 
(191).  This  applies  also  to  the  sentient  actions  of  titillation 
[Kitzel]  and  pain  [Schmerz],  which  only  differ  in  degree 
from  the  preceding  (80). 

196.  To  understand  these  views  properly,  it  must  be  remem- 
bered, that  every  pain  and  every  unpleasant  external  sensation 
is  of  itself  something  contra-natural,  and  is  considered  as 
disease  (191),  whereas  the  healthy,  that  is,  the  natural  condition, 
is  maintained  so  long  as  either  pleasant  or  no  unpleasant  sen- 
sations are  felt.  But  since  effects  are  as  their  causes,  it  follows, 
that  the  actions  of  unpleasant  external  sensations  are  contra- 
natural,  while  those  of  pleasant  sensations  are  connatural.  All 
experience  supports  this  view,  and  since  suffering  is  to  be  con- 
sidered as  the  sentinel  of  our  preservation  (184),  so  also  its 
actions  are  to  be  considered  as  a  natural  medicine  which 
develops  contra-natural  changes  for  the  purpose  of  thereby 
expelling  contra-natural  disorders  of  the  organism. 

197.  Titillation  [Kitzel]  is  a  vivid  agreeable  external  sen- 
sation (80) ;  consequently,  its  sentient  actions  render  the  natural 
functions  of  the  mechanical  machines  violent  and  exaggerated 
(195,  193). 

198.  Pain  is  a  vivid  disagreeable  external  sensation  (80); 
consequently,  the  mechanical  machines  are  excited  by  its  sentient 
actions  to  very  violent  contra-natural  movements  (195). 

199.  Since  a  violent  and  exaggerated  natural  function  of  a 
mechanical  machine  borders  on  the  contra-natural,  the  actions 
from  very  vivid  titillations  are  nearly  allied  to  pain  (197, 198). 
Consequently,  a  violent  titillation,  like  pain,  often  produces 
convulsive  movements. 

200.  The  mechanical  machines  to  which  the  nerve  that  has 
felt,  is  distributed,  are  excited  to  those  movements  of  which 
they  are  capable,  in  virtue  of  their  structure  (193).  If  the 
external  sensations  be  agreeable,  the  movements  excited  are 
conformable  to  the  functions  of  the  mechanical  machine;  if 
disagreeable,  are  not  conformable  (195). 


CH.  III.]      EXTERNAL  SENSATIONAL  ACTIONS.  105 

201.  If  external  sensations  develope  actions  directly  in  me- 
chanical machines,  they  re-act  by  means  of  their  material  ideas 
along  the  same  nerve  that  received  the  impression  (188). 
Hence  it  would  follow  (contrary  to  observation),  that  all  me- 
chanical machines,  in  which  a  branch  of  the  same  nerve  is  dis- 
tributed, must  be  all  put  into  action  at  once  by  every  external 
sensation  of  the  nerve,  unless  it  be  granted,  either  that  the 
impression  which  excites  an  external  sensation  in  the  brain 
at  the  point  of  origin  of  the  nerve,  can  only  act  upon  certain 
fibrils  of  the  brain  in  connection  with  one  or  a  few  branches 
going  to  certain  mechanical  machines,  which  fibrils  do  not 
accompany  other  twigs  of  the  same  nerve  (188);  or,  that  (136 
et  seq.)  there  are  certain  natural  hinderances  to  the  transmis- 
sion of  the  cerebral  impressions  (136,  iii),  or,  that  it  is  turned 
aside,  or  conducted  away,  in  its  course  along  the  nerve  from 
various  mechanical  machines,  and  permitted  to  reach  only  those 
appropriate  to  it,  as  is  detailed  ante  (136 — 139,  also  165,  vi). 

What  influence  sleep  (49,  136,  iii),  and  habit  (51,  139),  and 
the  ganglia  (48,  137),  may  exercise  in  this  respect,  ought  also 
to  be  considered.  It  is  probable,  that  all  these  hinderances 
actually  occur  in  nature. 

202.  The  mechanical  machines  can  develope  nerve-actions 
(183),  but  no  sentient  actions,  if  the  brain,  or  the  cerebral 
origin  of  its  nerves,  or  of  those  special  fibres  of  the  nerve 
which  receives  and  transmits  the  external  impression  appropriate 
to  the  sensation  (126),  be  compressed,  or  their  function  des- 
troyed ;  or  if  the  course  of  the  nerve  or  of  the  fibrils  be  inter- 
rupted between  the  brain  and  their  terminating  fibrils  (128, 
164,  iii,  iv):  also  when  the  function  of  the  mechanical  machines 
themselves  are  interrupted  (129,  iv). 

208.  The  direct  sentient  actions  developed  in  the  various 
mechanical  machines  by  external  sensations,  are  as  varied  as 
the  adaptations  of  the  machines  themselves  to  impressions  (193). 
We  will  consider  their  functions  more  in  detail  with  reference 
to  this  point. 

204.  The  sentient  actions  of  external  sensations  excite  con- 
tractions in  muscular  tissue  which,  when  violent,  are  termed 
spasms.  Spasms,  frequently  repeated,  are .  convulsions ;  if  con- 
tinuous, they  are  tetanic  [Erstarrungen] .  The  limbs  moved 
by  the  muscles  thus  aff'ected,  and  the  other  functions  which  the 


106  ANIMAL-SENTIENT  FORCES.  [i. 

muscles  perform,  participate  naturally  in  all  these  movements, 
partly  from  sympathy,  partly  in  consequence  of  a  mechanical  con- 
nection (165,  i,  161, 169, 179).  Hence,  the  sensibility  of  muscles 
is  a  very  general  principle  in  animal  mechanism,  since  all  these 
movements  are  developed  at  each  external  impression  and  also 
when  it  is  felt,  and  the  more  vividly  it  is  felt,  the  stronger  the 
movements  (194,  165,  iv);  consequently,  they  must  all  be  con- 
sidered to  be  direct  sentient  actions  of  external  sensations  (163, 
98),  although  they  may  be  at  the  same  time  nerve-actions  (183, 
162).  The  muscles  are  excited  to  action  by  various  external 
impressions,  as,  for  example,  the  urinary  bladder  by  the  injection 
of  water,  the  heart  from  the  entrance  of  the  blood,  the  bowels 
by  inflation  with  air,  &c.  The  agreeable,  or  connatural  external 
sensations,  maintain,  sc^  far  as  they  act  on  muscles,  the  order 
and  degree  of  movements  and  functions  appointed  by  nature 
to  the  muscles,  and  to  the  parts  of  the  animal  body  regulated 
in  their  function  by  them  (195,  196).  On  the  other  hand,  the 
disagreeable  excite  contra-natural  movements  of  the  kind 
mentioned.  Tickling  [Kitzel]  excites  vivid  contractions;  pain 
excites  sometimes  violent  cramps  of  a  spasmodic  character, 
sometimes  tetanic  convulsions  [Erstarrungen],  which  are  also 
occasionally  caused  by  tickling.  How  direct  sentient  actions 
from  external  sensations  are  induced  in  the  muscular  system 
and  in  other  parts  of  the  body,  and  how  they  may  be  prevented, 
has  been  already  shown  (129,  13  i,  136) ;  and  the  doctrines  have 
an  extensive  application  to  pathology  and  therapeutics. 

205.  The  sentient  actions  which  external  sensations  excite 
in  the  other  mechanical  machines,  may  be  deduced  for  the^ 
most  part  from  the  preceding.     External  sensations  act  upoi 
the  blood-vessels,  either  through  the  heart,  which  is  a  muscle] 
(167),    or   through   their    muscular   fibres    (168),    or   directly] 
through  the  muscles  which  contain  blood-vessels  (169).     lv\ 
this  respect,  therefore,  they  can  change  the  circulation.    The 
action  on  the  blood-vessels,  through  their  muscular  fibres  and 
muscles,  consists  in  a  contraction  of  the  blood-vessels  (204), 
(as  is  manifest  in  spasmodic  attacks,  which  sometimes  excite 
congestion,    sometimes    accumulation  of  blood    in    parts    not 
implicated  in  the  spasms).     Probably,  the  nerves  themselves 
have  the  power  of  directly  causing  contraction  of  the  vessels, 
especially  at  their  capillary  terminations,  as  has  been  already 


CH.  III.]       EXTERNAL  SENSATIONAL  ACTIONS.  107 

observed  (160).  Although  the  distinguished  Haller  wishes  to 
withdraw  this  proposition  once  stated  by  him,  he  cannot  with- 
stand the  force  of  facts,  and  observes :  '^  Aliquid  autem  in 
luinimis  vasis  esse,  quod  laqueorum  nerveorum  similitudiuem 
certe  in  effectu  habeat,  adparet  ex  suppress©  sanguinis  venosi 
motu  in  pene,  analogo  effectui  vinculorum,  et  ex  tuberculis 
cutaneis,  quse  perinde  a  terrore  ut  ex  frigore  nascuntur.'^ 
(Element.  Physiol.,,  torn,  v,  p.  590.) 

206.  External  sensations  also  cause  contraction  of  the  mus- 
cular tubes,  as  the  oesophagus  and  intestines,  whereby  their 
natural  function — the  transmission  of  the  food  (170) — is  fur- 
thered. Pain  causes  a  spasm  in  these  organs  which  hinders 
their  natural  functions  (204). 

207.  All  observation  shows,  that  every  external  impression 
at  the  mouths  of  the  capillary  vessels,  whether  they  contain 
blood  or  other  fluids,  which  is  felt   (and  also  an  impression 
which  is    not  felt,    as  will  be   proved  in  the    Second  Part), 
attracts  their  fluid  contents  to  their  mouths,  where  the  fluid 
either    accumulates,  or  is  effused.     "  Dolori  multa  fere  cum 
voluptate  communia  sunt ;  fortior  nempe  sensus,  fortior  etiam 
sanguinis  confluxus  ad  eam  partem,  quse  vel  voluptate  emovetur 
vel  dolore;  exempla  sunt  in  venereis  organis,  in  ipsis  oculis 
acrius  tuentibus,  in  fricta   cute.^^      (Haller,  '  Elem.  Physiol.,' 
tom.  V,  p.  597.)    This  action  is  animal,  for  it  is  not  a  property 
of  other  mechanical  machines,  although  they  also  possess  similar 
canals ;  nor  is  it  observed  in  dead  animals ;  and,  consequently, 
does  not  result  from  mere  mechanism  (7) ;  and  so  far  as  it  usually 
follows  in  the  same  parts  on  external  sensation,  it  is  a  direct  sen- 
tient action  from  external  sensation  (98, 186).    The  direct  action 
of  external  sensations  on  the  blood-vessels,  is  a  contraction  (205). 
When  the  terminations  of  the  arterial  capillaries,  which  are  either 
continuous  with  the  venous  radicles,  or  open  into  cavities,  become 
contracted,  the  continually  flowing  stream  accumulates  in  them, 
and  they  are  stretched  and  dilated,  and  thus,  according  to  the 
mechanical  principles  of  pathology,  congestion,  swelling,  and  in- 
flammation arise.      It  is  in  this  way  that  those  arteries  are  ex- 
cited to  pulsation  by  the  pain  of  inflammation,  in  which  it  usually 
does  not  occur.  (Haller^s  '  Physiology,'  §  33.)    If  the  capillaries 
open  into  shut  sacs,  the  great  distension  of  their  mouths  dilates 
the  opening,  and  then  copious  effusion  of  the  congested  fluids 


108  ANIMAL-SENTIENT  FORCES.  [i. 

takes  place  into  the  cavities.  This  action  is  the  greater  in  pro- 
portion as  the  sensation  is  more  vivid.  Hence  contra-natural 
inflammations  and  swellings  in  the  muscles  and  other  me- 
chanical machines  arise  from  painful  external  sensations.  From 
pleasant  sensations,  as  warmth,  friction,  itching,  titillation,  arise 
a  gentle  glow  and  excitement ;  and  in  cavities,  such  as  the  nares, 
or  intestines,  in  which  the  capillaries  can  pour  out  their  con- 
tents, an  accumulation  of  fluid,  as,  for  example,  a  discharge  from 
tickling  of  the  nose  (199),  a  purging  from  colicky  pain,  purgatives, 
poison,  &c.  (198.)  This  afflux  of  fluids  to  the  mouths  of  these 
capillary  vessels,  when  an  external  sensation  stimulates  their 
own  nerves,  or  by  sympathy,  those  adjoining  (165),  constitutes 
the  basis  of  many  important  phenomena  in  the  animal  economy, 
and  has  the  most  important  bearing  on  the  instincts,  emotions, 
and  diseases  of  animal  organisms,  (Haller's  '  Physiol.,'  §  561.) 
The  greater  number  of  mechanical  machines  of  the  body  are 
as  thoroughly  interpenetrated  by  capillary  vessels  as  by  nerves  ; 
it  follows,  therefore,  that  this  particular  action  of  external  sen- 
sations is  observed  to  be  almost  always  coincident  with  all 
external  impressions  which  are  felt ;  and  thus  it  is  a  general 
physiological  law,  that  concurrently  with  each  external  sensation 
there  is  an  afflux  of  fluid  to  the  point  where  the  external  im- 
pression is  made.  This  is  not,  however,  the  sole  law,  nor  is  it 
quite  general,  since  this  afflux  cannot  take  place  as  a  consequence 
of  external  sensation  ia  those  parts  not  supplied  with  capillaries 
and  tubuli ;  nor  does  it  even  take  place  in  other  parts,  if  the 
external  sensation  be  not  of  a  certain  degree  of  intensity  or 
strength. 

208.  External  sensations  excite  direct  sentient  actions  in  the 
flat  muscles,  particularly  the  diaphragm  (171),  which  consist  of 
such  contractions,  or  other  movements,  as  they  are  capable  of, 
in  virtue  of  their  structure  (193).  Thus  a  painful  sensation 
from  inflammation  of  the  diaphragm,  causes  unnatural  respira- 
tion, in  consequence  of  the  convulsive  movement  excited  in  it. 
Those  membranes  of  the  organism,  which  do  not  consist  of  a 
true  muscular  tissue,  but  rather  of  minute  glands,  papillae,  cel- 
lular tissue,  and  capillaries  and  tubuli,  must  be  considered  quite 
difi'erently  with  reference  to  their  sensibility,  and  the  sentient 
actions  resulting  therefrom.  Some  of  these  membranes  have 
numerous  nerves,  and  are  very  sensitive,  as  the  skin,  and  the 


CH.  III.]     EXTERNAL  SENSATIONAL  ACTIONS.  109 

mucous  membrane   of  the  nostrils,   throat,   and   other  parts. 
It  appears  also,  that  nerves  are  intimately  incorporated  with 
these  tissues  (160),   for  every   portion   of  the   surface   which 
the   point   of  a  needle   touches,    is    sensitive,    and   the   final 
distribution  of  the  nerves  in   them  cannot   be   traced.      But 
since  their  structure  differs  from  that  of  the  muscles,  we  cannot 
expect    them  to  manifest    similar    sentient    actions.     Never- 
theless  external  impressions  on  their  nerves  can  proceed  to 
the  brain  without  exciting  a  visible  movement  in   the  point 
touched,  —  can  be  felt,  —  and  can  be  reflected  by  means  of 
the  internal  impressions  of  the  sensation  along  the  principal 
nerve  and  its  branches,  and  if  there  be  no  hinderances,  can 
excite  movements  in  the   mechanical  machines  to  which  the 
nerves  are  distributed,  and,   consequently,   develope    sentient 
actions  in  other  parts  by  means  of  the  external  sensation  thus 
excited  on  such  surface  (129).      Thus,  titillation  of  the  mucous 
membrane  of  the   nostrils  excites  sneezing,  and  a  convulsive 
movement  of  the  diaphragm  and  respiratory  muscles,  the  nerves 
of  which  are  in  natural  connection  with  those  of  the  nasal  mucous 
membrane :  thus  also  many  an  external  sensation  of  the  cu- 
taneous surface  excites,  by  means  of  the  nerves,  a  tremor  of  the 
muscles  in  relation  to  it,  which  is  termed  a  shudder.  Thus  also 
a  titillation  of  the  nasal  mucous  membrane  excites  eff'usion  of 
mucus,  which  is  a  sentient  action  of  titillation  in  the  capillaries 
or  terminating  tubuli  of  the  minute  glands  (207,   172)  :  thus 
also  the  cutaneous  surface  becomes  inflamed,  and  swells  from 
the  stimulus  of  an   acrid  irritant :   thus   also   cold   contracts 
the  respiratory  pores    by   a  sentient   action    on  the    minute 
terminations  of  the  arteries,  and  interrupts  perspiration  (168). 
Other  non-muscular  tissues  have  either  no  nerves  at  all,  or 
very  few  distributed  here  and  there  in  their  structure.    Hence 
their  sensibility  is  doubtful.      Of  this  kind,  according  to  Haller's 
researches,  are  the  serous  membranes  covering  the  thorax  and 
diaphragm,  the  pericardium,   peritoneum,   &c.     Nevertheless, 
experience  proves  that  they  are  susceptible  of  certain  actions  of 
external  sensations;  and  that  actions  may  also  be   excited  in 
other  parts  by  sensations  originating  in  their  nerves.      Thus 
it  is  seen,  that  if  a  nerve  be  injured  or  divided  which  traverses 
a  tendon,  or  the  periosteum,  paralysis  or  convulsive  movement 
is  induced  in  the  adjoining  limbs,  or  in  those  in  relation  with 


110  ANIMAL-SENTIENT  FORCES.  [i. 

the  injured  nerve,  which  may  be  considered  as  the  sentient  action 
of  pain  in  those  tissues,  although  their  proper  substance  be 
insensible.  Besides,  in  such  tissues,  an  injured  blood-vessel  or 
gland,  or  other  structure  supplied  with  nerves,  or  with  muscular 
fibrils,  may  excite  a  painful  inflammation,  and  therewith  the 
appropriate  sentient  actions,  as  an  afflux  or  effusion  of  fluids, 
congestions,  inflammations,  &c.  (168,  172),  from  which  as  ex- 
perience teaches,  neither  the  pleura  nor  peritoneum,  nor  other  in- 
sensible tissues,  are  exempt  (Vide  §§460 — 465,  470,  522 — 530.) 

209.  External  sensations  excite  the  functions  of  the  glands; 
namely,  the  excretion  of  fluids;  and  when  they  are  enclosed  in 
muscular  tissues,  the  evacuation  takes  place  according  to  their 
mode  of  action  on  muscular  tissues  (172) ;  but  when  there  is  no 
muscular  tissue,  they  excite  an  afflux  of  fluid,  in  virtue  of  their 
action  on  the  terminating  mouths  of  the  tubuli  (207).  Thus, 
a  strong  flavour  excites  the  secretion  and  discharge  of  the 
saliva ;  irritation,  or  pain  in  the  eye,  excites  a  flow  of  tears  ;  thus, 
also,  titillation  causes  parts  to  be  lubricated,  by  irritating  the 
nerves  of  the  glands,  and  favouring  a  secretion  and  discharge 
of  their  fluids ;  thus  also  irritation  and  pain  of  the  bronchi 
cause  a  mucous  discharge  from  the  irritated  glands, — all 
being  manifestly  sentient  actions  in  the  glands  from  external 
sensations. 

210.  The  direct  sentient  actions,  from  external  sensations 
in  the  viscera,  properly  so  called,  are  very  complicated  and 
varied,  inasmuch  as  these  machines  are  compounded  of  many 
others  in  which  external  sensations  act  very  variously.  We 
can  only  mention  some  of  the  more  important  in  this  sketch, 
referring  the  reader  to  §  §  204 — 209  for  general  principles. 

211.  The  heart,  as  a  compound  hollow  muscle,  is  stimulated 
by  external  sensations  (167)  to  the  performance  of  its  func- 
tion, namely  contraction,  whereby  the  circulation  of  the  blood 
through  the  body  is  kept  up.  Consequently  a  painful  sensation 
in  the  heart  causes  a  convulsive  contraction  and  an  accelerated 
circulation. 

212.  The  external  sensations  which  are  excited  in  and 
about  the  stomach,  stimulate  it  and  the  intestines  to  gentle 
writhings,  whereby  digestion  and  the  transmission  of  the  food 
onwards  is  attained.  There  is  a  movement  excited  in  the 
stomach  when  an  external  impression  is  made  on  it,  but  this 


CH.  III.]      EXTERNAL  SENSATIONAL  ACTIONS.  Ill 

takes  place,  for  the  most  part,  through  nerve- actions  (183),  for 
the  external  sensation  of  each  impression  is  seldom  perceived, 
only  the  vivid  external  impressions  being  felt,  when  the 
painful  actions  of  external  sensations  caused  in  it  are  contra- 
natural.  Thus  arises  the  violent  peristaltic  action  of  the 
stomach  and  bowels  from  griping  purgatives,  poisons,  inflamma- 
tions; hence  also  the  spasm  of  the  stomach  from  similar  causes, 
or  from  flatulency,  or  indigestible  food  painfully  pressing  the 
stomach.  The  muscles  of  the  limbs  participate  largely  in  such 
contra-natural  movements  of  the  stomach  and  bowels,  as  is 
shown  by  the  paralysis  which  supervenes  on  violent  colic. 
This  takes  place  in  virtue  of  the  sympathy  between  the  sentient 
actions  of  muscles,  but  the  question  belongs  properly  to  the 
pathology  of  organisms. 

213.  The  liver  and  gall-bladder  are  little  susceptible  of  ex- 
ternal sensations  :  an  external  impression  is  only  perceived  when 
it  is  remarkably  vivid,  and  also  contra-natural,  or  painful  (198). 
Violent  pain  in  the  region  of  the  liver  exercises  an  injurious 
influence  on  the  secretion  and  excretion  of  bile  (175).  Other 
conceptions,  like  external  sensations,  have  a  manifest  influence 
on  most  of  the  proper  viscera  of  the  body  by  sentient  actions 
on  their  nerves. 

214.  Ordinary  external  impressions  on  the  lungs  are  rarely 
felt;  when,  however,  they  experience  tickling  or  pain,  the 
respiration  is  partly  accelerated,  partly  rendered  contra-natural 
and  spasmodic,  as  in  cough ;  in  cases  of  this  kind  the  sentient 
actions  are  from  sympathy  (98,  165).  Respiration  is  not  excited 
solely  by  irritation  of  the  nerves  of  the  lungs,  but  also  by 
irritation  of  the  diaphragm,  and  of  the  respiratory  muscles 
of  the  thorax. 

215.  The  kidneys  also  are  susceptible  only  of  extraordinary 
and  unnatural  external  impressions ;  spasm  is  almost  the  only 
example  of  sentient  action  from  external  sensations  that  can  be 
deduced.      It  is  otherwise  with  the  bladder. 

216.  The  organs  of  the  senses,  considered  as  mechanical 
machines,  are  moved  by  external  sensations  in  various  ways, 
having  reference  to  their  particular  functions.  When  a  sound 
enters  the  ear,  and  is  heard,  the  muscles  which  stretch  the 
tympanum  are  so  put  into  action,  as  to  render  the  latter  tense 
in  accordance  with  the  tone :  so  when  light  enters  the  eye,  and 


112  ANIMALSENTIENT  FORCES.  [i. 

is  perceived,  the  muscular  pupil  of  the  eye  undergoes  a  change. 
The  light  has  no  more  such  effect  upon  the  pupil  of  the 
blind  than  in  a  corpse,  consequently  it  is  a  true  direct  sentient 
action  from  an  external  sensation.  When  a  savoury  drop 
or  two  is  tasted  posteriorly,  by  means  of  the  tongue,  the 
throat  is  stimulated  to  the  act  of  swallowing ;  and  when  the 
skin  is  affected  by  an  acute  external  sensation,  as  from  cold  or 
itching,  it  is  contracted,  and  its  exhalation  altered  (177). 
These  are  obviously  sentient  actions  in  the  organs  of  the  senses 
from  external  sensations,  rendering  them  more  fit  for  their 
functions,  and  testifying  to  a  fore-seeing  wisdom. 

217.  All  that  need  be  said  as  to  the  direct  sentient  actions 
of  external  sensations  in  the  sexual  organs  has  been  already 
stated ;  it  is  their  great  characteristic  that  they  render  the 
organs  fit  for  the  function  of  reproduction. 

218.  We  may  now  estimate  from  previous  considerations 
(204 — 207)  the  law  laid  down  by  Kriiger,  in  his  '  Physiology,' 
that  every  external  sensation  is  followed  by  a  movement  in  the 
body  proportionate  to  the  sensation.  In  the  ordinary  state  of 
the  body,  whenever  an  external  sensation  is  excited  in  the  mind 
through  a  nerve  which  is  distributed  to  mechanical  machines, 
such  movements  are  developed  in  the  machines  by  means  of  the 
nerve,  its  branches  and  fibrils,  provided  there  are  no  natural 
hinderances  there  (136,  199),  as  in  virtue  of  their  structure  they 
are  capable  of,  and  the  movements  are  the  stronger  in  propor- 
tion as  the  external  sensation  is  more  vivid  (194).  But  it  may  so 
occur  (as  will  be  demonstrated  in  another  part  of  this  work,) 
that  the  same  movements  may  result  from  an  external  im- 
pression which  is  not  felt,  and  thus  be  nerve-actions  (83,  462). 
This  law  is,  however,  not  to  be  understood,  to  the  effect  that 
the  movements  will  be  stronger  in  proportion  as  the  external 
contact  on  the  nerve  is  stronger,  or  according  to  the  measure 
of  physical  forces,  but  the  stronger  the  external  impression  is, 
which  may  sometimes  be  very  strong  from  a  slight  contact,  and 
vice  versa  (40). 

219.  Besides  the  direct  sentient  actions  of  external  sensations 
that  we  have  hitherto  considered  (204 — 218),  we  have  also  to 
consider  the  incidental^  [zufallig]  which  are  so  often  confounded 
with  the  former.  It  may  be  stated  generally,  that  the  sentient 
actions  of  both  kinds,  and  all  the  mental  forces  possessed 


CH.  III.]        INCIDENTAL  SENTIENT  ACTIONS.  113 

by  animals  in  addition  to  the  sensational  force,  are  indirect 
sentient  actions  of  external  sensations,  although  in  very  different 
degrees  of  connection  (65).  We  will  glance  at  the  most 
prominent  of  the  series. 

We  connect  with  our  external  sensations  the  conception  of 
another  like  to  it,  which  we  have  had  before,  and  thus  a  direct 
imagination  is  attached  to  our  external  sensation  (67),  that  com- 
mingles its  action  in  the  mechanical  machines  with  those  of  the 
external  sensation.  In  this  way  we  sigh  at  the  sight  of  a 
person  who  is  like  another,  with  respect  to  whom  we  have  had 
sorrowful  sensations.  This  sighing  is  the  sentient  action  of 
the  imagination,  and  only  indirectly  of  the  external  sensation 
(97,  99). 

220.  We  often  connect  with  our  external  sensations  the 
expectations  of  others  formerly  connected  with  them,  and  thus 
a  foreseeing  (73)  accompanies  our  external  sensation,  which 
mingles  its  actions  in  the  mechanical  machines  with  those 
arising  from  the  external  sensation.  A  certain  person  always 
faints  during  the  operation  of  venesection ;  some  time  after- 
wards he  meets  the  surgeon  in  the  street,  and  becomes  faint : 
this  faintness  was  the  sentient  action  of  a  foreseeing  of  the  blood- 
letting, and  only  incidental  to  the  external  sensation  (97,  99). 

221.  Since  all  our  external  sensations  are  made  vivid  by 
pleasure  or  suffering  (187),  and  accompanied  by  imaginations 
and  expectations  (219,  220),  so  they  are  also  associated  with 
desires  and  aversions,  which  unite  their  actions  in  the  mechanical 
machines  with  those  arising  directly  from  external  sensations, 
and  are  most  manifest  in  the  instincts  and  passions  (93).  Thus, 
an  agreeable  or  odious  countenance  instantaneously  renders  a 
man  enamoured  or  angry ;  in  animals,  an  odour,  or  a  sound, 
excites  the  sexual  instinct ;  or,  in  one  who  has  fasted,  the  sight 
of  food  excites  hunger.  Here  the  whole  process  of  the  instincts 
and  passions  is  set  forth,  and  it  is  by  no  mean^  the  external 
sensations  that  directly  excite  their  sentient  actions.  The  last 
will  serve  as  an  illustration  :  a  man  with  an  empty  stomach 
sees  bread,  and  he  recollects  that  under  similar  circumstances 
he  has  been  relieved  by  the  eating  of  bread.  From  this 
external  sensation  and  imagination,  there  arises  the  expectation 
that  the  same  result  would  follow  again  if  he  ate  bread,  and  now 
there  arises  the  seeking  to  eat,  whereby  the  mouth  fills  with 

8 


114  ANIMAL-SENTIENT  FORCES.  [i. 

water, — a  sentient  action  of  the  desire   (of  the  instinct)  inci- 
dentally produced  by  the  external  sensation  (97,  103). 

222.  The  strongest  sensational  conceptions  and  desires  most 
readily  excite  imperfect  external  sensations  (148).  Now  since 
true  external  sensations  excite  all  conceptions,  and  consequently 
the  strongest  conceptions  and  desires  (219-221),  they  can  inci- 
dentally give  rise  to  the  sentient  actions  of  phantoms,  visions, 
ghosts,  and  illusions  (148).  We  seek  with  the  greatest  anxiety 
to  lay  hold  of  the  object  which  threatens  us  with  imminent 
danger,  and  this  vivid  conception  works  so  intensely,  and  as  an 
aversion  so  contra-naturally  (195),  in  our  muscles,  that  the 
arm  remains  stiff,  swells,  and  inflames.  This  is  not  an  unusual 
circumstance  where  real  objects  are  concerned.  When  we  see 
a  form  in  the  dark,  which  we  take  for  a  ghost,  and  the  im- 
perfect external  sensation  excites  the  instinct  of  terror,  and  we 
reach  towards  it,  the  above-mentioned  condition  may  occur  to 
the  arm,  not  directly  through  the  real  external  sensation,  as, 
for  example,  the  sight  of  a  shadow,  but  incidentally,  inasmuch 
as  the  latter  excited  the  imperfect  external  sensation  which 
produced  the  phenomenon  of  the  ghost. 

223.  We  often  connect  thoughts  of  the  understanding  with  our 
external  sensations,  when  we  reflect  upon  objects  that  appear  to 
the  senses,  and  thus  a  reflection  {^"7^  accompanies  our  external 
sensation,  which  combines  the  action  it  probably  may  develope 
in  the  mechanical  machines  (330)  with  those  resulting  directly 
from  external  sensations  (100).  Thus  a  glance  may  quickly 
cause  deep  thoughts  in  us,  together  with  vertigo,  the  vertigo 
being  the  sentient  action  of  deep  thought,  and  only  incidentally 
that  of  the  external  sensation  (97,  100;  see  also  331). 

224.  We  connect  desires  and  aversions  of  the  will  with  oui' 
external  sensations,  and  so  the  actions  of  the  latter  accompany 
those  of  the  former  (96).  Thus,  at  the  sight  of  a  ravening 
beast,  we  exert  our  muscles,  and  flee.  This  flight  is  the  sentient 
action  of  the  conclusion  of  our  will,  and  only  incidentally  that 
of  the  external  sensation  (97,  104). 

225.  All  sentient  actions  of  external  sensations  consist  of 
movements,  in  which  all  those  structures  must  take  part  that 
are  incorporated  with  the  substance  of  the  organ  of  movement, 
and,  consequently,  the  nerves  (160).  When  these  nerves  receive 
an  external  impression  through  their  ultimate  ramifications  in 


CH.  III.]      SUBORDINATE  SENTIENT  ACTIONS.  115 

the  mechanical  machines,  from  a  movement  produced  in  the 
latter,  by  means  of  material  external  sensation  sent  from  the 
brain,  they  can  thereby  excite  new  external  sensations  (31), 
and  these  can  develope  sentient  actions,  either  in  the  same 
mechanical  machines  by  means  of  the  same  nerves,  or  their 
branches ;  or  in  other  machines  to  which  they  are  distributed, 
or  to  which  their  cerebral  impression  is  transmitted  (188). 
Sentient  actions  from  external  sensations  of  this  second  class 
are  subordinate,  or  secondary,  as  to  their  origin,  and  if  we 
would  avoid  many  errors  in  explaining  the  phenomena  of  the 
animal  economy,  they  must  be  carefully  distinguished  from 
those  which  arise  directly  from  external  sensations.  Pain  in 
a  muscle  excites  cramp  of  the  muscle,  its  direct  sentient  action. 
But  this  cramp  causes  also  a  violent  pain,  from  which  con- 
vulsions result,  involving  many  other  muscles.  These  con- 
vulsions are  subordinate  sentient  actions  of  the  primary  pain. 
A  poison  excites  a  burning  sensation  in  the  stomach  and  bowels, 
in  consequence  of  which  they  writhe,  and  are  spasmodically 
contracted.  These  are  the  primary  sentient  actions  of  the  ex- 
ternal sensations  of  burning  from  the  poison.  But  the  writhing 
and  spasmodic  contraction  cause  new  pain  (colic,  spasms  of  the 
stomach),  whereby  the  circulation  of  the  blood  in  the  abdomen, 
and  the  digestion  and  transmission  forwards  of  the  food,  are 
hindered,  the  bowels  constipated,  dysuria  induced,  and  the  legs 
paralysed  (212).  These  are  the  subordinate  or  secondary  actions 
of  the  sensation  of  burning  excited  by  the  poison,  and  the 
direct  sentient  actions  of  the  gastric  spasm  or  colic.  It  is 
obvious,  that  when  these  subordinate  actions  excite  new  sen- 
sations, new  sentient  actions  may  result  which  are  again  sub- 
ordinate. Thus,  therefore,  a  single  external  sensation  can,  by 
means  of  its  subordinate  and  continuous  direct  sentient  actions 
excite  most,  if  not  all,  the  mechanical  machines  of  the  body  to 
movement;  spasmodic  diseases,  from  titillation,  &c.,  present 
the  most  frequent  examples  of  this  kind.  It  must  therefore 
be  remembered,  (and  it  will  be  subsequently  advanced  in  treating 
of  the  actions  arising  from  other  sentient  forces,)  that  the 
subordinate  external  sensations  of  the  mind  constitute,  when 
combined  with  the  primary,  a  compound  external  sensa- 
tion (an  entire  or  complete  [conception]  external  sensation, 
— Baumgarten^s  '  Metaphysics,'  §  378),  which  consists  of  the 


116  ANIMAL-SENTIENT  FORCES.  [i. 

primary  and  all  its  subordinate  sensations;  and  that  the  pri- 
mary and  subordinate,  separately  considered,  are  the  elements 
of  an  entire  external  sensation.  The  same  principles  apply  to 
the  actions  of  compound  conceptions. 

226.  Just  as  the  subordinate  sensations  are  developed  at  the 
same  time  as  the  entire  external  sensations,  so  also  their  sentient 
actions  are  produced  in  the  machines  in  which  they  act  (225). 
But  since  the  subordinate,  like  all  other  external  sensations, 
do  not  necessarily  set  the  mechanical  machines  into  movement, 
to  which  the  nerve  is  distributed  that  has  received  their  cerebral 
impression,  on  account  of  natural  hinderances  (201),  it  follows, 
that  the  sentient  actions  of  a  complex  external  sensation  may 
occupy  sometimes  a  greater,  sometimes  a  less,  sphere  of  action, 
according  to  the  variety  in  the  impressions  in  the  brain,  which 
make  up  the  constituents  of  the  total  external  sensation,  and 
according  to  the  nature  of  those  normal  hinderances,  which  im- 
pede or  divert  the  course  of  the  impressions  from  the  brain  to 
the  machines  (165,  vi).  The  stronger,  however,  the  subordinate 
external  sensations,  the  stronger  are  the  actions  which  they 
actually  excite  (218,  225). 

227.  All  external  sensations  arc  entire  conceptions,  consist- 
ing of  many  elements.  (Baumgarten's  'Metaph.,'  §§  378,  405.) 
It  follows,  therefore,  that  all  their  direct  actions  may  consist 
of  many  elements,  and  this  may  occiu"  when  no  natural  hin- 
derances exist  to  the  transmission  of  their  cerebral  impres- 
sion (116) .  But  all  their  actions  do  not  depend  upon  subordinate 
sensations,  since  at  the  same  moment  distinct  primary  external 
sensations  may  be  in  the  mind,  which  manifest,  at  the  same 
time,  their  proper  sentient  actions,  according  to  the  laws  of 
primary  external  sensations ;  these  may  be  termed  co-ordinate 
external  sensations,  and  sentient  actions. 


Actions  of  Imaginations  on  the  Mechanical  Machines  through 
the  Nerves. 

228.  The  sensational  conceptions  are  external  sensations, 
spontaneously  imitated  or  repeated  by  the  soul,  the  external 
impression  which  can  give  them  the  reality  of  external  sensa- 
tions not  being  present  {Q7) ;  that  is  to  say,  in  each  imagination 
many  sub-impressions  [Merkmale]  of  the   external  sensation 


CH.  III.]  ACTIONS  OF  IMAGINATIONS.  117 

are  wanting,  tlie  conception  of  which  is  necessarily  induced  by 
the  external  impression,  and  which  are  not  perceived  therefore 
by  the  soul  (68).  The  material  idea,  which  the  external  im- 
pression develops  in  the  brain,  consists  of  more  numerous 
sub-impressions,  and  is  much  more  perfect,  than  that  which 
the  mind  when  it  repeats  it  can  develope  without  its  assistance. 
Further,  as  the  imaginations  are  only  imperfect  external  sen- 
sations, the  material  ideas  of  the  imaginative  force  are  only 
constituents  of  the  material  external  sensations,  which  the 
external  impression,  by  reaching  the  brain,  can  alone  render 
perfect  and  complete.  Both  are  conceptions  and  material  ideas 
of  one  and  the  same  kind,  but  the  imaginations  are  weaker 
and  more  imperfect  (68). 

229.  It  may  be  readily  inferred  from  these  views,  that  the 
sentient  actions  of  imaginations  in  the  mechanical  machines, 
correspond  generally  with  those  of  external  sensations;  that  their 
range  of  influence  is  equally  extensive ;  that  they  excite  similar 
kinds  of  movements  in  the  various  machines ;  and  that  they 
are  only  diff'erent  in  being  somewhat  less  complete.  Experience 
teaches  us  the  same  thing.  An  imagination  excites  in  the 
same  mechanical  machines,  the  same  movements  that  the 
previous  external  sensation  developed.  An  object  which  causes 
us  to  shudder,  produces  a  similar  eff'ect  when  we  recall  it  to 
recollection;  the  remembrance  of  some  food  that  has  caused 
us  to  vomit,  excites  vomiting  again ;  and  the  recollection  of  a 
gratification  excites  the  same  conditions  of  the  organs  as  that 
in  which  it  was  enjoyed.  The  diff'erence  is,  that  the  actions  of 
imaginations  are  weaker,  simpler,  and  more  imperfect  than  those 
of  external  sensations  (69).  And  all  this  could  not  be  other- 
wise, since  the  imaginations  produce  their  material  ideas  at  the 
cerebral  origins  of  those  nerves  afifected  by  those  of  external 
sensations  (124,67);  consequently,  the  same  machines  must  be 
put  into  movement  (129,  130),  for  the  same  kind  of  cerebral 
impression,  but  more  feebly,  is  made  at  the  origin  of  the  nerves, 
as  by  external  sensations  (67,  228) ;  and  the  resulting  movements 
are  similar,  but  feebler  (133). 

230.  An  entire  imagination  consists  only  of  some  of  the 
elements  of  a  previous  external  sensation,  and,  consequently, 
of  only  some  of  their  material  ideas  or  impressions  on  the 
origins  of  the  nerves.     The  law,  then,  of  the  sentient  actions 


118  ANIMAL-SENTIENT  FORCES.  [i. 

of  imaginations  in  the  mechanical  machines,  is  this: — whatever 
portions  of  the  elements  of  a  preceding  entire  (225)  external 
sensation  are  contained  in  an  imagination,  the  sentient  actions 
of  those  elements  are  repeated,  although  feebly,  in  the  same 
mechanical  machines  (229,  106.) 

231.  Since  many  elements  of  an  entire  external  sensation 
may  consist  of  subordinate  external  sensations,  and  an  imagination 
therefrom  be  made  up  principally  or  wholly  of  the  latter  (228, 
225),  it  follows,  that  an  imagination  may  produce  few  or  none 
of  the  sentient  actions  of  the  original  sensation,  but  principally 
or  solely  those  of  the  subordinate  (230).  Certain  food  formerly 
taken  excited  spasm  of  the  stomach ;  this  cramp  caused  a  new 
pain, — a  subordinate  external  sensation  (225),  from  which 
general  convulsions  arose,  or  subordinate  sentient  actions. 
Now  when  this  food  is  brought  to  the  recollection,  convulsions 
are  immediately  excited,  but  without  the  gastric  spasm  being 
excited  also.  In  this  case  the  imagination  excites  only  the 
subordinate  sentient  actions  of  the  antecedent  primary  external 
sensation,  passing  over  the  primary  sentient  actions. 

232.  Although  the  absence  of  the  external  impression  is  the 
cause  why  the  sentient  actions  of  imaginations  are  less  perfect 
and  more  feeble  than  those  of  external  sensations,  yet  strong 
imaginations  can  cause  imperfect  external  sensations  which 
imitate  the  action  of  external  impressions  on  the  nerves  (148); 
and  so  imaginations,  accompanied  by  imperfect  external  sensa- 
tions, may  develope  such  perfect  and  vigorous  sentient  actions, 
that  they  can  hardly  be  distinguished  from  those  of  real  external 
sensations  (229,  150).  Thus,  an  insane  person,  or  one  that 
dreams,  or  any  individual  with  a  vivid  imagination,  imagines  he 
has  swallowed  an  active  purgative,  and  is  purged  in  consequence; 
or  vomits  from  dreaming  of  taking  nauseous  food,  &c. 

233.  i.  A  mere  external  impression  can  excite  no  imagination 
if  it  be  not  felt ;  consequently  its  nerve-action,  as  such,  is  never 
at  any  time  a  sentient  action  of  an  imagination,  if  it  be  not  the 
sentient  action  of  its  sensation  (228,  184,  i).  But  such  a  nerve- 
action  may  be  felt  and  therefore  imagined,  and  this  imagination 
can  have  sentient  actions  in  the  mechanical  machines. 

ii.  The  external  impressions  often  excite  by  its  own  vis 
nervosa  (7)  those  movements  which  are  sentient  actions  of  the 
external  sensation,  in  which  case  they  are  nerve  actions  (183). 


CH.  III.]  ACTIONS  OF  IMAGINATIONS.  119 

Now,  as  the  external  impression  is  wanting  in  the  sentient 
actions  of  imaginations  (228,  229),  the  co-operation  of  its  vis 
^^ervosa  is  wanting,  and,  consequently,  the  movements  dependent 
^ftpon  it  do  not  enter  into  the  sentient  actions  of  imaginations, 
^Br,  at  least,  are  not  excited  by  it,  but  occur  only  incidentally. 
^Bf,  therefore,  an  imagination  repeats  the  sub-impressions  a,  h,  c, 
^Hf  a  preceding  external  sensation,  with  which  certain  movements 
in  the  mechanical  machines  are  connected,  but  which  are  not 
sentient  actions  of  the  external  sensations  «,  h,  c,  but  simply 
nerve-actions  of  the  co-operating  external  impression, — these 
actions  do  not  occur,  if  the  impression  itself  be  not  made. 
Thus,  an  external  impression  of  food,  although  not  felt,  will 
excite  a  movement  in  the  bowels  as  a  nerve-action  (183),  but 
the  imagination  of  food  not  actually  eaten  cannot  possibly  excite 
the  movement,  nor  can  a  mere  imagination  excite  any  subor- 
dinate action  resulting  as  a  nerve  action  from  the  impression,  as, 
for  example,  the  micturition  which  follows  the  taking  of  food. 

234,  i.  The  sentient  actions  of  imaginations,  like  those  of 
external  sensations,  extend  to  all  the  mechanical  machines 
which  can  be  moved  by  external  sensations  (192,  229),  and 
stimulate  them  to  the  same  movements,  although  more  feebly 
and  imperfectly ;  nay,  those  connected  with  imperfect  external 
sensations  excite  the  machines  to  these  movements,  with  a 
force  almost  equal  to  that  of  external  sensations  (232,  229). 

ii.  The  imaginations  of  agreeable  external  sensations  (186, 
228)  develope  connatural  actions  (195);  those  of  unpleasant 
external  sensations,  contra-natural  actions ;  those  of  titillation 
and  pain  excite  more  violent  movements  (197,  198). 

iii.  Just  as  external  sensations  do  not  actually  put  in  motion 
all  the  mechanical  machines  which  have  nerves  to  move  them 
(201),  so  also  it  is  with  imaginations  (228). 

iv.  Just  as  external  sensations,  in  developing  sentient  actions, 
act  on  the  mechanical  machines  according  to  the  capabilities 
of  each,  so  is  it  also  with  imaginations,  and  all  that  has  been 
stated  with  reference  to  the  former  (204-217),  applies  equally 
to  the  latter. 

235.  The  direct  sentient  actions  of  imaginations  (hitherto 
considered  exclusively)  are  often  accompanied,  in  addition  to 
those  of  true  external  sensations,  and  of  other  imaginations  not 
belonging  to  them,  by  incidental  actions  (219),  as  those  of  fore- 


120  ANIMAL-SENTIENT  FORCES.  [i. 

seeings  (73),  desires,  aversions,  passions  nay,  more  remotely,  by 
those  of  ideas  of  the  understanding,  and  of  intellectual  desires 
and  aversions  of  the  will.  All  these  actions,  which  are  either 
only  coincident  with  those  of  imaginations,  or  are  only  incidently 
connected  with  them,  must  be  carefully  distinguished  from 
those  proceeding  directly  from  imaginations.  Yesterday  a 
person  ran ;  at  night  he  dreams  that  he  is  running,  and  begins 
to  breathe  quickly.  This  is  the  sentient  action  of  his  imagi- 
nation. Then  he  thinks  he  is  falling  and  calls  out;  this  is 
the  sentient  action  of  his  foreseeing.  He  seeks  to  place  him- 
self upright,  and  strains  his  muscles  to  that  end ;  this  is  the 
sentient  action  of  a  desire  (223,  224) . 

236.  As  sometimes  in  dreaming,  and  especially  in  somnam- 
bulism and  insanity,  the  imaginations  are  so  vivid,  that  they 
equal  true  external  sensations,  so  also,  in  such  cases,  they  de- 
velope  the  same  sentient  actions  in  the  mechanical  machines, 
as  if  they  really  proceeded  from  the  latter  (70,  69) . 

237.  When  the  mind  is  in  reverie  [dichtet],  it  combines  the 
constituents  of  various  imaginations  with  each  other,  and  then 
each  develops  its  actions  in  the  mechanical  machines,  according 
to  the  laws  of  imaginations.  In  a  prolonged  reverie  [dichten], 
which  consists  of  the  most  vivid  imaginations  and  imperfect 
external  sensations,  as,  for  example,  in  somnambulism,  insanity, 
or  delirium,  the  sentient  actions  are  as  distinct  as  if  they  resulted 
from  real  external  sensations  (236),  only  they  are  not  so  per- 
fect, complete,  and  regular,  and  are  not  so  accordant  with  the 
natural  functions  of  the  body  (184),  so  that  there  arises  danger 
to  its  health  and  conservation.  The  principles  laid  down  as  to 
imaginations  (231 — 236)  are  also  applicable  to  reveries  of  the 
imagination  [Erdictungen] . 

238.  The  remembrance  of  a  conception  (71)  does  not  appear 
to  be  a  species  of  conception,  which  develops  actions  externally 
to  the  brain,  except  so  far  as  the  conception  which  is  remem- 
bered is  an  external  sensation  or  imagination  that  so  acts.  A 
person  sees  a  visionary  figure,  and  becomes  pale  with  fear.  It 
is  the  resemblance  of  an  individual  who  long  ago  caused  him 
bitter  vexation.  The  pallor  comes  on  before  it  is  remembered 
whom  the  figure  resembles,  and  simply  from  the  repeated  ex- 
ternal sensation,  without  the  recognition.  How  often  in  such 
cases  we  hear  persons  say :  "  this  appearance  terrifies,  affects. 


CH.  III.]  ACTIONS  OF  FORESEEINGS.  121 

aud  calms  me,  without  my  knowing  why,  some  subordinate 
ideas,  which  I  cannot  remember,  must  be  the  cause."  When 
the  person  whose  figure  we  have  seen,  actually  appears  also,  no 
other  action  results  than  as  stated  above;  we  become  pale  as 
before,  but  now  we  know  why.  Hence  it  appears,  that  the 
memory  itself  [das  eigentliche  Erinnern]  belongs  to  that  class 
of  conceptions,  the  sentient  actions  of  which  are  limited  to  the 
brain,  and  excite  only  material  ideas  of  another  kind ;  whereas 
the  conceptions  which  are  remembered  develope  their  usual 
actions  externally  to  the  brain  in  the  mechanical  machines. 


Actions  of  the  Sensational  Foreseeings  on  the  Mechanical 
Machines  through  the  Nerves. 

239.  The  sensational  foreseeings  are  future  external  sensa- 
tions, to  which  the  external  impression  must  supply  what  con- 
stitutes the  element  of  external  sensations  (73).  In  other 
words,  a  number  of  sub-impressions  of  the  external  sensation 
are  wanting  in  every  sensational  foreseeing,  the  conception  of 
which  must  be  induced  by  the  external  impression,  and  without 
which  the  mind  does  not  conceive  them.  The  material  idea 
excited  in  the  brain  by  the  external  impression  contains  many 
more  sub-impressions,  and  is  far  more  complete  than  that  which 
the  mind  can  impress  spontaneously  on  the  brain,  without  the 
aid  of  the  external  impression  (53,  73) ;  and  as  foreseeings  are 
only  imperfect  external  sensations,  more  imperfect,  indeed, 
than  imaginations  (73),  the  material  ideas  of  the  foreseeing  force 
are  only  portions  of  the  material  external  sensations,  which  the 
accession  of  the  external  impression  alone  can  render  complete 
and  perfect.  Both  are  conceptions  and  material  ideas  of  the 
same  kind,  but  the  foreseeings  are  much  more  feeble  and  im- 
perfect (73). 

240,  i.  The  material  ideas  of  foreseeings  arise  at  the  origins 
of  the  same  nerves,  as  those  of  the  foreseen  sensations  them- 
selves (73,  124) :  consequently,  their  sentient  actions,  external 
to  the  brain,  must  be  similar  (129,  130.) 

ii.  Foreseeings  cause  the  same  kind  of  impressions  (73,  121) 
in  these  cerebral  origins  of  the  nerves  as  the  foreseen  sen- 
sations, consequently  their  sentient  actions  in  the  mechanical 
machines  must  be  similar  to  those  of  the  future  sensations. 


122  ANIMAL-SENTIENT  FORCES.  [i. 

iii.  As  these  impressions  are  more  feeble  than  those  of  sen- 
sations^ and  even  of  imaginations,  so  also  must  be  the  resulting 
actions.  And  this  is  confirmed  by  observation.  When,  for 
example,  a  person  sees  another  eat,  and  himself  thinks  of 
eating,  this  foreseeing,  in  conjunction  with  the  accompanying 
desire,  stimulates  the  salivary  glands  as  food  itself  would  have  i 
done.  The  foreseeing  of  a  fall  from  a  height  excites  us  to 
hold  fast,  even  against  our  will  and  purpose,  as  we  should  do, 
if  the  fall  actually  took  place.  When  a  person  dreams  that 
he  will  empty  the  urinary  bladder,  the  act  often  takes  place. 
The  expectation  of  the  action  of  a  remedy  often  causes  us  to 
experience  its  operation  beforehand.  Yawning,  from  imitation, 
belongs  to  this  class  of  phenomena. 

241.  The  entirety  of  a  foreseeing  is  compounded  only  of 
certain  of  the  constituents  of  a  future  external  sensation; 
consequently,  its  material  ideas,  or  impressions  on  the  cerebral 
origin  of  the  nerves,  are  a  portion  of  those  of  the  future 
sensation,  and  therefore  its  sentient  actions  are  expressed  in 
the  same  mechanical  machines,  but  more  feebly  (240, 106). 

242.  Since  many  of  the  elements  of  a  complete  external 
sensation  may  be  subordinate  external  sensations,  and  a  fore- 
seeing arising  from  it  may  consist  wholly  or  principally  of  these 
(239,  225);  it  follows  that  a  foreseeing  may  develope  few  or 
none  of  the  primary  actions,  but  principally  or  wholly  those  of 
the  subordinate  sensations  (241).  A  cold  air  coming  in  contact 
with  the  cutaneous  nerves,  when  we  are  warm,  contracts  the 
pores,  and  drives  the  perspiration  inwards.  This  is  the  sentient 
action  of  the  primary  external  sensation  of  cold.  The  re- 
pressed acrid  perspiration  irritates  the  nerves  of  the  muscles, 
and  our  limbs  tremble,  and  our  teeth  chatter,  and  this  is  the 
sentient  action  of  the  subordinate  sensation  in  the  muscles 
which  move  the  limbs  and  the  lower  jaw  (225).  A  person  in 
a  warm  bed  dreams,  or  vividly  foresees,  that  he  falls  into  a 
river  full  of  floating  ice,  and  he  forthwith  shivers :  a  case  of 
this  kind  really  occurred,  and  may  be  found  in  the  '  Diction- 
naire  Encyclop.,^  article  "  Somnambule.^'  A  somnambulist 
once  fancied  in  winter,  that  as  he  was  walking  by  the  side 
of  a  river,  he  saw  a  child  fall  in  and  drown.  The  bitter  cold 
did  not  restrain  him  from  saving  it.  He  threw  himself  out 
of  bed  in  the  posture,  and  with  the  movements  of  a  person 


CH.  III.]  ACTIONS  OF  FORESEEINGS.  123 

swimming,  and  when  he  had  laboured  diligently,  he  seized 
the  bed-clothes  with  one  hand,  thinking  it  was  the  child,  while 
with  the  other  he  attempted  to  swim  to  the  imaginary  shore. 
Then  he  laid  his  burden  down,  shivered  with  cold,  his  teeth 
chattering,  as  if  he  had  come  out  of  an  ice-cold  river.  He 
said  that  he  was  stiff  with  cold,  and  asked  for  a  glass  of 
brandy.  The  dreamer  had  not  really  felt  the  ice-cold  river, 
nor  had  repressed  perspiration  irritated  the  nerves  of  the 
muscles.  The  whole  mental  action  of  his  foreseeing  of  both, 
manifested  itself  only  by  shivering  and  chattering  of  the  teeth. 
In  this  case,  the  foreseeing  develops  the  subordinate  sentient 
action  of  the  future  external  sensation  only,  omitting  the 
primary,  because  the  mind  thought  principally,  in  its  foreseeing, 
of  the  subordinate  external  sensation, — the  irritation  of  the 
muscles,  —  and  did  not  combine  with  it  the  foreseeing  the 
antecedent  primary  sensation  in  the  cutaneous  nerves  (241). 

243,  The  cause  why  the  sentient  actions  of  foreseeings  are 
more  imperfect  and  more  feeble  than  those  of  external  sen- 
sations, is  the  want  of  the  external  impression  (239,  240). 
Still,  very  strong  sensational  foreseeings  may  cause  imperfect 
external  sensations,  which  resemble  the  external  impression 
(74,  148)  ;  and  foreseeings,  accompanied  by  their  imperfect 
external  sensations,  may  develope  such  perfect  sentient  actions 
in  the  mechanical  machines,  that  they  are  generally  similar  to 
the  sentient  actions  of  true  external  sensations  (150,  240). 
Thus,  a  person  who  dreams  vividly  that  he  hears  it  thundering, 
may  start  so  violently  in  the  bed  as  to  shake  it.  Thus,  also, 
an  infant  in  the  cradle  sucks  the  air  with  all  its  might,  from 
the  foreseeing  that  it  is  sucking  the  breast. 

244,  i.  An  impression  can  excite  no  foreseeing  if  not  felt, 
for  it  is,  of  course,  not  imagined  (233,  i) ;  consequently  its 
nerve-action,  purely  as  such,  is  never  at  the  same  time  the 
sentient  action  of  a  foreseeing,  until  it  is  the  sentient  action 
of  its  sensation  (239,  184,  i.)  On  the  other  hand,  the  mind 
can  feel  and  imagine  (223),  and,  consequently,  foresee  such  a 
nerve-action  (73),  and  these  foreseeings  can  excite  sentient 
actions  in  the  mechanical  machines. 

ii.  The  external  impressions  often  excite  by  its  own  vis 
nervosa  (7)  those  movements  which  are  sentient  actions  of  the 
external  sensation,  in  which  case  they  are  nerve  actions  (183). 


124  ANIMAL-SENTIENT  FORCES.  [i. 

Now,  as  the  external  impression  is  wanting  in  the  sentient 
actions  of  foreseeings  (228,  229),  the  co-operation  of  its  vis 
nervosa  is  wanting,  and,  consequently,  the  movements  dependent 
upon  it  do  not  enter  into  the  sentient  actions  of  foreseeings, 
or,  at  least,  are  not  excited  by  it,  but  occur  only  incidentally. 
If,  therefore,  a  foreseeing  repeats  the  sub-impressions  «,  b,  c, 
of  a  preceding  external  sensation,  with  which  certain  movements 
in  the  mechanical  machines  are  connected,  but  which  are  not 
sentient  actions  of  the  external  sensations  a,  h,  c,  but  simply 
nerve-actions  of  the  co-operating  external  impression, — these 
actions  do  not  occur,  if  the  impression  itself  be  not  made. 

245,  i.  The  sentient  actions  of  foreseeings,  as  well  as  those 
of  external  sensations  (192)  and  imaginations  (234,  i),  take 
place  in  all  those  mechanical  machines  which  can  be  moved  by 
external  sensations  and  imaginations,  and  excite  the  same  move- 
ments as  the  latter,  but  more  feebly  and  imperfectly  (193). 
Nay,  even  the  foreseeings  connected  with  imperfect  external 
sensations,  excite  the  mechanical  machines  to  the  same  move- 
ments as  are  excited  by  true  external  sensations  (240,  243). 

ii.  The  foreseeings  of  agreeable  or  disagreeable  sensations 
contain,  in  some  degree,  the  impressions  of  pleasure  or  pain 
(186),  and  develope  such  actions  as  are  in  accordance  with,  or 
opposed  to,  their  normal  function  (195,  197,  198). 

iii.  As  external  sensations  do  not  excite  to  movement  all 
those  mechanical  machines  which  the  nerves  can  move  (201, 
239),  so  is  it  also  with  regard  to  foreseeings. 

iv.  As  external  sensations,  when  they  produce  actions  in 
the  mechanical  machines,  act  upon  them  according  to  their 
respective  capabilities,  so  is  it  also  with  regard  to  foreseeings, 
so  that  the  principles  laid  down  previously  under  this  head 
(204 — 217)  are  also  applicable  to  the  latter. 

246.  There  are  often  connected  with  the  sentient  actions  of 
foreseeings  certain  others  of  an  incidental  kind,  as,  for  instance, 
those  of  desires,  aversions,  and  even  more  remotely,  those  of 
understanding  and  efforts  of  the  will  (65),  and  in  addition 
to  the  sentient  actions  of  co-existing  true  external  sensations, 
imaginations,  and  other  foreseeings.  All  these  actions,  whether 
co-existent,  or  incidentally  connected  with  those  of  foreseeings, 
must  be  distinguished  from  the  latter.  The  foreseeing  of  a 
lascivious  action  acts  directly  on  the  organs  which  have  to  per- 


CH.  III.]      ACTIONS  OF  PLEASURE  AND  PAIN.  125 

form  it.  Therewith  is  combined  the  emotion  of  shame,  and 
the  face  reddens.  This  reddening  is  incidental.  A  philosopher 
studies  from  a  foreseeing  of  fame,  until  he  is  hypochondriacal 
and  loses  his  digestive  powers.  This  action  of  deep  thought 
(vide  §  332)  is  only  incidental  to  the  anticipation  of  fame,  &c. 

247.  Since  sensational  foreseeings  and  prophetic  visions  are 
occasionally  so  vivid  in  dreams,  and  especially  in  somnambulism, 
as  well  as  in  insanity  and  prophetic  ecstasy,  that  they  equal  true 
sensations,  particularly  as  they  become  usually  in  such  persons 
imperfect  external  sensations,  and  constitute  the  greater  number 
of  apparitions,  spectres,  &c.  (148,  243), — they  develope  the  same 
actions  as  are  produced  by  true  external  sensations. 

248.  The  poetic  faculty  [Dichtungskraft]  is  occupied  with 
foreseeings  as  well  as  imaginations,  and  according  to  the  same 
laws.  Hence  it  is  that  somnambulists,  visionaries,  lunatics, 
inspired  persons,  soothsayers,  &c.,  are  as  much  deluded  by  the 
foreseeings  of  their  bodings  and  expectations  as  by  their  ima- 
ginations, taking  both  for  true  sensations,  while  their  sentient 
actions  are  equally  erroneous  (237). 

249.  The  true  expectations  differ  from  the  foreseeings  in 
this,  that  their  sentient  actions  are  confined  to  the  brain,  and 
do  not  extend  to  the  mechanical  machines. 


Actions  of  Sensational  Pleasure  and  Pain  through  the  Nerves 
on  the  Mechanical  Machines. 

250.  So  soon  as  a  sensation,  or  other  conception  of  the  mind, 
pleases  or  displeases,  or  contains  the  excitants  of  the  feelings 
(88),  it  is  said  that  they  touch  the  heart,  that  the  heart  sympa- 
thizes, &c.  This  mode  of  expression  has  its  rise  in  the  universal 
experience,  that  the  movements  of  the  heart,  and  especially 
those  actions  termed  vital  by  physiologists,  are  manifestly 
affected  by  all  conceptions  which  please  or  displease.  It  is 
said  of  the  pleasant  external  sensation  excited  by  food,  drink, 
or  medicine,  that  it  goes  to  the  heart,  enlivens,  strengthens  the 
heart.  A  beautiful  sight,  or  music,  soothes  the  soul  and 
exhilarates  the  heart.  Tickling  excites  convulsive  respiration 
and  laughter,  and  accelerates  the  whole  circulation.  Pain 
causes  fever,  and  sighing,  groaning,  and  weeping.  Pleasant 
condolence,  or  a  kind  visit,  refreshes  the  heart ;  a  reproof  that 


126  ANIMAL.SENTIENT  FORCES.  [i. 

we  feel  to  be  merited,  goes  to  the  heart ;  the  recollection  of  a 
cruel  action  shocks  the  heart ;  the  anticipation  of  a  joyous 
thing  causes  it  to  beat  more  freely  and  easily.  And  in  short, 
every  sensational  and  intellectual  conception  which  awakens 
happiness  or  misery  in  the  mind,  causes  changes  in  the  pulse 
and  in  the  action  of  the  heart,  in  which  the  respiration  also 
participates,  and  thereby  exercises  an  important  influence  on 
the  whole  economy,  which  a  mere  perception  or  a  neutral  ex- 
ternal sensation,  imagination,  or  foreseeing  entirely  wants.  It 
is  consequently  a  general  law  of  animal  nature,  that  all  excitants 
of  the  feelings  add  a  special  sentient  action  to  the  other  sentient 
actions  of  the  conceptions,  so  that  they  modify  the  functions  of 
the  mechanical  machines  subservient  to  vital  movements.  But 
since  the  sensational  stimuli,  or  in  other  words,  the  pleasure  or 
pain  of  the  external  senses  (80),  and  of  the  sensational  con- 
ceptions, imaginations,  foreseeings  (88),  are,  from  their  nature, 
stronger  stimuli  than  mere  motives  [Bewegungsgrunde]  (53,88), 
it  follows,  that  their  action  on  the  vital  movements  is  more 
obvious  and  powerful. 

251.  The  direct  sentient  actions  of  the  excitants  of  the 
feelings  generally,  and  considered  per  se,  are  consequently  the 
impressions  in  the  brain  of  pleasure  and  pain,  in  so  far  as 
being  special  conditions  of  the  material  ideas  of  each  neutral 
sensational  conception,  they  excite  the  origin  of  those  nerves  in 
the  brain  by  which  the  vital  movements  are  regulated;  and  this 
applies,  in  particular,  to  the  sentient  actions  of  the  pleasure  or 
pain  of  the  senses  (80),  and  to  all  other  sensational  stimuli,  and 
to  motives  [Bewegungsgrunde]  (88,  250).  In  addition,  there- 
fore, to  the  direct  sentient  actions  hitherto  described,  as  resulting 
from  external  sensations,  imaginations,  and  foreseeings,  the  latter 
excite  other  direct  and  special  actions  in  virtue  of  these  excitants 
of  the  feelings,  whenever  they  become  agreeable  or  painful,  so 
that  they  modify  the  vital  movements,  and  in  consequence  of 
the  physical,  mechanical,  and  vital  inter-connection  of  the  latter, 
powerfully  influence  the  whole  animal  economy,  and  this  pro- 
portionately to  the  degree  of  excitation.  This  doctrine  applies 
also  to  the  motives  of  the  intellect.  As  to  the  cause  of  this 
action  of  the  sensational  stimuli  on  the  vital  movements,  we 
can  only  say,  that  these  inner  sensations  of  the  soul  must  make 
an  impression  peculiar  to  themselves  on  the  cerebral  origin  of 


) 


Lii.  III.]      ACTIONS  OF  PLEASURE  AND  PAIN.  127 

le  nerves  distributed  to  the  vital  organs  (124),  and  it  is  pro- 
bable that  by  exciting  the  mind  into  action  (81),  the  numerous 
capillaries  of  the  brain  are  stimulated,  and  thus  by  a  change  in 
so  large  a  portion  of  the  mass  of  the  blood,  a  change  is  pro- 
duced in  the  action  of  the  heart,  in  the  respiration,  and  in  all 
the  vital  movements  (159). 

252.  The  sentient  actions  of  the  pleasure  of  the  senses  are 
movements  in  accordance  with  the  natural  functions  of  the 
mechanical  machines;  those  of  annoyance  of  the  senses  are 
contrary  to  the  natural  functions  (80).  The  same  apphes  to 
the  sentient  actions  resulting  from  pleasing  or  displeasing 
sensational  conceptions,  imaginations,  and  foreseeings  (234,  ii; 
245,  ii).  But  since  a  very  active  and  inordinate  discharge  of  a 
function  borders  on  the  contra-natural,  the  sentient  actions  of 
very  vivid  pleasurable  stimuli  are  in  some  degree  contra- 
natural  (199).  Consequently,  a  state  of  gentle  calm  pleasure  is 
more  favorable  to  the  maintenance  of  life  and  to  health,  than 
excess  in  pleasurable  sensations,  or  than  distressing  painful 
sensations. 

253.  All  experience  establishes  this  doctrine.  A  person 
describes  a  condition  of  health,  by  saying  that  he  is  well ; — of 
sickness,  by  the  expression  he  is  ill.  This  being  well  and  ill, 
are  sensations  of  what  is  pleasant  and  unpleasant  (80).  One 
perfectly  in  health  says,  that  not  a  finger  aches,  one  out  of 
health,  that  nothing  goes  right  with  him ;  obviously  expressions 
of  what  is  pleasant  and  unpleasant,  whereby  we  designate  a 
natural  or  contra -natural  condition  of  the  body.  In  particular, 
it  is  also  observed,  that  the  change  in  the  vital  movements  ex- 
cited by  moderate  pleasures,  are  favorable  to  the  organism, — 
the  immoderate  on  the  painful  are  unfavorable.  Moderate 
laughter  is  beneficial,  immoderate  is  hurtful.  Agreeable  exer- 
cise of  the  understanding  is  favorable  to  health;  and  it  was 
for  this  reason  that  the  ancient  philosophers  maintained,  that 
the  study  of  nature  favoured  the  attainment  of  old  age; 
while,  on  the  contrary,  excessive  study  and  tiresome  subtle 
meditations  led  to  premature  decrepitude,  and  caused  nervous 
diseases. 

254.  The  general  law,  whereby  the  direct  sentient  actions  of 
the  excitants  of  all  the  feelings  are  regulated,  is  this : — ^just  as 
a  sensational  or  intellectual  conception  pleases  or  displeases,  so 


128  ANIMAL-SENTIENT  FORCES.  [i. 

are  the  nerves  acted  on  in  the  brain,  and  corresponding  vital 
movements  excited  thereby  in  the  vital  organs ;  in  the  former 
case  in  accordance  with  their  natural  functions ;  in  the  latter, 
in  opposition  thereto  (252),  but  always  in  another  way  than 
when  the  conception  is  neutral. 


Actions  of  the  Sensational  Desires  and  Aversions  in  the 
Mechanical  Machines  through  the  Nerves. 

255.  The  direct  sentient  actions  of  the  sensational  desires 
and  aversions,  are  produced  according  to  the  laws  already  laid 
down  (80 — 88).  They  are  made  up  by  the  sentient  actions: 
— 1,  of  the  sensational  foreseeings  of  a  coming  sensation,  or 
its  opposite,  expected  by  the  mind  (239 — 247);  2,  by  those  of 
this  expectation  (249);  3,  by  those  of  the  impressions  of  sen- 
sational pleasure  and  pain  (84 — 87,  250). 

256.  The  same  doctrines  apply  equally  to  the  sensational 
instincts  and  passions,  since  these  are  only  desires  and  aversions 
of  a  greater  intensity,  arising  out  of  obscure  or  simple  sensa- 
tional stimuli  (90,  91). 

257.  In  each  sensational  instinct  and  emotion,  there  is  a 
sensational  foreseeing  of  coming  sensations,  the  sentient  actions 
of  which  are  none  other  than  those  of  the  imperfect  material 
sensation  which  is  foreseen ;  when  it  is  external,  the  actions  are 
developed  in  those  mechanical  machines  external  to  the  brain, 
which  the  foreseen  external  sensation  sets  in  motion,  &c. 
(240,  i,  ii.) 

258.  There  are  strong  sensational  stimuli  conjoined  in  every 
sensational  instinct  and  emotion,  the  actions  of  which  are  the 
same  as  those  arising  from  the  impressions  of  sensational 
pleasure  or  pain,  which  impressions  depend  on  the  foreseen 
material  sensation.  These  stimuli  change  the  vital  actions  in 
a  remarkable  manner,  and  excite  the  animal-sentient  force  of 
the  brain  to  render  perfect  the  imperfect  actions  of  the  coming 
sensation.  In  all  these  cases,  if  the  objects  of  the  instinct  or 
emotion  be  true  external  sensations,  the  efforts  of  the  soul 
cannot  attain  them,  and  consequently  the  instincts  or  emotion 
cannot  be  satisfied  without  the  appropriate  external  impressions 
(81,256);  and  in  the  sensational  instincts  and  emotions,  there- 
fore, only  those  sentient  actions  of  the  future  sensation  can  be 


CH.  iii.J      ACTIONS  OF  DESIRES  OR  AVERSIONS.        129 

excited,  which  are  not  dependent  on  the  external  impression 
(81,  94). 

259.  The  effects  of  the  pleasing  or  distressing  instincts  and 
emotions  on  the  organism,  are  regulated  by  the  same  laws  as 
those  of  simple  pleasure  or  pain  (191 — 199),  or  of  the  agree- 
able  or  distressing  foreseeings,  (245,  ii,  252,  &c.)  Consequently, 
every  kind  of  joy  is  beneficial  to  health,  all  sorrow  injurious ; 
but  the  former  may  be  injurious  too,  if  excessive  (252). 

260.  The  direct  sentient  actions  of  the  sensational  pro- 
pensities and  emotions,  are  produced  according  to  the  same  laws 
as  those  of  sensational  pleasure  and  pain.  (Compare  254,  199.) 

261.  It  may  be  useful  to  illustrate  these  views  by  special 
facts. 

i.  Observations  prove,  that  in  the  propensities  and  emotions, 
the  actions  of  the  coming  foreseen  external  sensation  therein 
imperfectly  expressed,  are  produced  (257).  In  the  appetite  for 
food,  the  gratification  of  which  is  the  taking  of  nutriment,  saliva 
is  poured  out  into  the  mouth,  as  if  nutriment  were  taken ;  in 
the  sexual  appetite,  the  gratification  of  which  is  copulation,  the 
organs  of  generation  are  put  into  a  condition  suitable  to  its 
gratification  ;  in  the  desire  to  give  suck,  the  satisfaction  for  which 
is  the  discharge  of  milk  from  the  nipples  during  suckling,  the 
nipples  become  erect,  and  there  is  a  flow  of  milk  towards  them. 
In  the  desire  of  children  to  suck,  the  lips  are  placed  in  a  pro- 
per position,  and  the  child  sucks  the  air.  In  the  desire  for 
revenge,  the  satisfaction  of  which  is  an  injury  to  the  individual 
who  has  offended,  the  natural  weapons  partly  manifest  the 
functions  whereby  they  inflict  injury ;  animals  put  their  stings 
or  claws  into  action ;  they  eject  or  pour  forth  their  poison ; 
they  endeavour  to  bite,  to  strike,  to  tear ;  man  doubles  his  fist, 
stamps,  and  gnashes,  as  he  would  do  if  actually  taking  revenge. 
In  terror,  the  satisfaction  of  which  is  the  averting  of  a  great 
impending  danger,  the  struggles  for  preservation  are  seen  in 
starting  back,  stooping,  leaping,  standing  still,  &c.  In  shame, 
the  satisfaction  of  which  emotion  is  the  avoidance  of  the  glance 
of  the  person  whose  contempt  we  fear  to  perceive,  we  drop  the 
eyelids,  and  endeavour  to  withdraw  ourselves  as  much  as  possible 
from  that  glance,  &c. 

ii.  That  the  propensities  and  emotions  connected  with  im- 
perfect  external   sensations,    excite   the   mechanical   machines 

9 


130  ANIMAL-SENTIENT  FORCES.  [i. 

appropriate  to  them  to  almost  as  perfect  functions  as  when 
they  act  normally  (257),  is  manifest  from  various  facts.  In 
lascivious  feelings,  an  emission  not  unfrequently  takes  place; 
when  we  lament  for  a  deceased  friend,  he  so  often  appears 
before  our  eyes,  that  we  believe  we  see  him,  speak  with  him, 
embrace  him ;  when  afraid  of  ghosts,  an  individual  is  often  in 
the  same  condition  as  if  a  ghost  had  actually  appeared,  &c. 

iii.  It  is  equally  a  general  and  undoubted  observation,  that 
in  all  the  instincts  and  emotions,  as  well  as  in  all  the  desires  and 
aversions,  the  vital  movements  of  the  organism  (the  respiratory 
and  cardiac  movements)  are  modified.  And  this  change  is  the 
greater,  the  more  powerfully  the  instincts  and  emotions  operate. 

iv.  That  this  change  in  the  agreeable  instincts  and  emotions, 
is  in  accordance  with  nature  and  with  healthy  action,  or  con- 
natural, and  in  the  disagreeable  is  opposed  thereto,  or  contra- 
natural  is  established  by  universal  experience  (Haller^s  '  Phy- 
siology,^ §  565). 

V.  Lastly,  that  those  sensational  instincts  and  emotions, 
whose  objects  are  true  external  sensations  (258),  cannot  be 
satisfied  without  the  adjunct  of  the  external  impression,  is 
proved  by  all  the  pleasures  of  the  senses.  The  satisfaction 
of  the  instincts  and  emotions  must  not,  however,  be  con- 
founded with  their  enfeebling.  {Vide  §  95.) 

Actions  of  the  Sensational  Instincts  in  the  Mechanical  Machines 
through  the  Nerves. 

262.  The  sensational^  instincts  in  particular  may  be  arranged 
under  four  heads : 

i.  Strong  desires  which  arise  from  obscure  sensational  stimuli, 
and  whose  object  is  our  preservation  and  well-being.  This  is 
the  instinct  of  self-preservation. 

ii.  Powerful  aversions,  which  arise  from  obscure  sensational 

1  The  word  sinnlich  is  here  translated  sensational,  for  want  of  a  better  term ;  but 
the  reader  will  please  to  remember  the  special  meaning  attached  to  the  word  {vide 
notes,  §§  31,  66).  It  is  obvious  from  the  context  (§§  263 — 269)  that  these  instincts 
are  not  sensational,  because  sensation  is  the  cause  oiihe  instinctive  acts,  but  because 
sensation  accompanies  the  cause,  namely,  the  external  senselike  impressions.  With 
this  understanding,  that  the  word  sensational  does  not  indicate  the  cause  of  the 
instincts,  but  simply  a  certain  condition  of  the  cause, — it  may  be  properly  used 
here. — Ed. 


CH.  III.]  ACTIONS  OF  INSTINCTS.  131 

stimuli,  and  whose  object  is  to  prevent  our  destruction  or  ill- 
being.     The  instinct  of  self-defence, 

iii.  Strong  desires,  which  arise  out  of  obscure  sensational 
stimuli,  and  whose  object  is  the  propagation  of  the  species  by- 
means  of  copulation.      The  instinct  of  propagation. 

iv.  Strong  desires  and  aversions,  which  arise  from  obscure 
sensational  stimuli,  and  whose  object  is  the  preservation  and 
well-being  of  the  offspring,  and  the  prevention  of  its  destruction, 
or  its  ill-being.      The  instinct  for  offspring. 

263.  Since  the  natural  instincts  of  self-preservation,  of  well- 
being,  and  of  propagation,  are  specially  implanted  in  animals 
by  nature,  that  these  objects  may  be  attained  certainly  and 
infallibly,  they  are  distinguished  from  all  other  desires,  aversions, 
and  passions,  firstly,  because  nature  has  so  placed  them  under 
the  control  of  external  impressions,  and  so  arranged  the  natural 
functions  of  organs,  that  animals  cannot  prevent  their  mani- 
festation; while,  on  the  contrary,  the  others  are  more  left  to 
the  proper  power  of  the  animal  to  develop,  or  suppress,  increase 
or  diminish,  or  even  to  prevent  altogether  (89,  90).  Secondly, 
the  animals  themselves,  and  tte  whole  of  nature  around  them, 
are  so  reciprocally  adapted,  that  these  instincts  never  become 
inactive  until  their  object,  or,  in  other  words,  the  satisfaction 
of  the  instinct  is  fully  attained,  which  is  also  the  object 
and  will  of  the  Creator  (95).  Consequently,  there  is  in  the 
instincts  of  animals  a  something  that  points  to  the  attainment 
of  a  great  object  of  the  Creator,  a  sufiicient  origin  of  which 
is  not  to  be  found  in  the  conceptive  force  alone,  but  in  certain 
predetermined  adaptations  external  to  animals,  whereby  they 
are  necessitated  to  follow  their  instincts  according  to  their 
organism :  this  is  termed  the  wonderful,  the  magical  [Be- 
zauberung],  the  divine  in  instincts.  Consequently,  to  this  ex- 
tent the  blind  instincts  bear  the  same  relation  to  other  desires 
and  aversions,  as  external  sensations  bear  to  spontaneous  con- 
ceptions (27,  89).  Both  are  excited  conceptions,  which  cannot 
arise  nor  be  satisfied,  independently  of  an  external  impression  on 
the  nerves,  and  which  nature  has  preordained,  especially  for  the 
former.     This,  however,  requires  a  more  minute  investigation. 

264.  In  animals  which  think,  or  in  all  animals,  if  it  be 
maintained  that  all  have  conceptions,  the  acts  to  which  they 
are  excited  by  their  natural  instinct,  or  in  other  words,  the 


132  ANIMAL-SENTIENT  FORCES.  [i. 

movements  of  the  mechanical  machines_,  are  sentient  actions  of 
certain  pleasing  or  unpleasing  sensational  conceptions  (262, 
81).  NoWj  since  the  natural  instincts  have  for  their  objects, 
the  preservation  and  well-being  of  animals,  and  of  their  offspring, 
but  the  means  to  these  ends  are  not  taught  to  animals,  nor 
even  to  man  himself  by  experience,  it  follows  that  the  concep- 
tions are  imparted  to  them  without  their  knowledge  and  choice, 
nay,  even  against  their  inclination,  by  means  of  previously 
arranged  inducements  (external  impressions  on  the  nerves), 
dispersed  throughout  nature  by  the  Creator,  wherein  the 
sensational  stimuli  lie  concealed,  which  by  means  of  their  im- 
pression on  the  brain  develop  those  sentient  actions  in  the 
mechanical  machines  according  to  the  laws  of  the  actions  of 
desires  and  aversions,  that  have  as  their  object,  and  in  accord- 
ance with  the  views  of  the  Creator,  the  preservation  and  well- 
being  of  animals  or  their  offspring.  Why  the  Creator  has  not 
so  restricted  the  mental  faculty,  that  it  could  only  develop 
those  conceptions  which  are  in  accordance  with  these  objects, 
and  none  other,  is  hidden  from  our  knowledge.  It  is  enough 
that  it  is  not  so  in  nature ;  but  it  has  been  determined  so  to 
use  the  obscurest  sensational  faculty  [Sinnlichkeit]  of  animals, 
as  to  force  upon  them,  as  it  were,  as  often  and  when  it  appears 
necessary,  such  conceptions  as  must  develop  in  them  instinctive 
actions  in  accordance  with  the  objects  of  the  Creator ;  for  the 
obscure  sensational  conceptions,  and  especially  external  sensa- 
tions, which  are  the  principal  means  used  by  nature  to  this  end, 
are  the  only  conceptions  that  the  mind  cannot  develop  inde- 
pendently and  at  pleasure,  but  must  receive  from  the  external  im- 
pression on  the  nerves,  which  nature  transmits  to  them  (35,  66). 
265.  The  double  object  of  nature,  namely,  the  excitement 
and  the  satisfaction  of  the  instincts,  is  attained  thereby ;  for  the 
obscure  feelings  which  excite  them  and  the  external  circum- 
stances which  satisfy  them  by  means  of  their  external  impres- 
sion, are  so  numerous  at  the  fixed  times  and  for  the  appointed 
objects  of  each  instinct,  and  the  natural  hindrances  whereby 
desires  and  aversions  are  weakened  and  do  not  attain  to  satis- 
faction, so  few,  that  the  great  object  of  nature  in  general  is 
always  fully  attained.  Experience  proves  this  irrefragably. 
At  the  moment,  when,  according  to  the  order  of  nature,  an 
instinct  should  be  put  into  action,  the  nerves  are  certain  to 


CH.  in.]  ACTIONS  OF  INSTINCTS.  133 

receive  the  external  impressions  necessary  thereto,  and  which 
are  appointed,  as  it  were,  to  this  end.  For  example,  when 
nutriment  is  necessary  to  the  body,  the  fluids  collected  in  the 
empty  stomach  must  impress  on  it  an  external  impression, 
which  excites  the  sensational  instinct  of  hunger ;  when  animals 
ought  to  propagate  their  kind,  the  male  inhales  from  the  female 
during  heat  an  odour  which  causes  the  instinct  of  copulation  to 
be  active.  On  such  occasions,  even  certain  external  sensations 
become  sensational  stimuli  to  the  animal  that  formerly  were 
not  so,  or  had  even  a  contrary  effect,  as,  for  example,  the  sight 
or  smell  of  the  sexual  organs,  previously  unnoticed  or  even 
disagreeable  and  disgusting,  become  the  sensational  stimuli 
of  the  strongest  sensual  pleasure.  At  the  same  time,  when  the 
instincts  are  regularly  excited  into  activity  in  accordance  with 
the  object  of  nature,  the  circumstances  whereby  they  can  be 
satisfied  are  so  carefully  provided  for  previously,  that  the  satis- 
faction of  the  instincts  can  hardly  fail.  Thus,  hunger  is  rarely 
excited  in  animals  that  lie  dormant  through  the  winter,  until 
they  can  find  food  in  the  fields.  So  also  the  instinct  of  self- 
preservation  operates,  when  they  fatten  themselves  towards 
winter,  or  return  into  a  warmer  climate,  or  creep  into  a  retreat 
from  the  cold,  no  sooner  than  they  have  occasion.  Lastly, 
when  once  the  natural  instincts  are  excited,  it  is  difficult  to 
cause  them  to  cease,  by  means  of  psychological  or  physiological 
hindrances,  before  they  are  satisfied,  which  may,  however,  be 
done  as  to  desires,  aversions,  and  even  emotions.  A  hungry, 
or  vindictive,  or  enamoured  person  is  not  easily  appeased  by 
artful  management,  but  the  satisfaction  of  the  instinct  must 
be  effected,  that  is  to  say,  repletion  of  the  stomach,  or  accom- 
plishment of  copulation,  or  wreaking  of  vengeance.  Nature, 
indeed,  seems  to  have  actually  weakened  or  diminished  those 
hindrances  which  on  previous  occasions  moderated  or  prevented 
sensational  stimuli  (47),  so  that  the  instincts  might  break  forth 
without  restraint  and  overcome  all  obstacles,  and  continue  their 
appointed  time  until  their  satisfaction  has  been  sufficiently  re- 
peated. In  other  desires  and  even  in  emotions,  the  animal  with- 
draws the  sensational  stimulus  voluntarily,  being  conscious  of  it, 
and  its  effects ;  but  in  the  instinct  it  is  not  conscious  of  the 
stimulus  as  it  is  only  obscurely  perceived  (262) ;  consequently,  its 
effects  are  unknown,   and  the  animal  is  carried  blindly  on  by 


134  ANIMAL-SENTIENT  FORCES.  [i. 

the  instinct.     In   cases   of  this  kind,  the  nerves  themselves 
appear  to  change  their  nature  and  to  favour  the  instinct,  since 
they  receive  new  impressions   and  stimuli,  from  which  they 
were  previously  secured ;  and,  lastly,  experience  also  sufficiently 
shows  to  us,  how  little  all  psychological  means  avail  in  weak- 
ening the  desires  and  aversions,  when  moralists  apply  them  to 
human  nature,  with  the  object  of  preventing  the  outbreak  or  satis- 
faction of  its  feelings,  or  restraining  them  within  certain  limits. 
266.  The  sensational  instincts  act  in  the  mechanical  machines 
in  accordance  with  this  preordained  arrangement,  established 
by  the  wisdom  of  the  Creator  in  the  whole  creation,  as  well  as 
in  the  animal  kingdom,  for  their  development  and  for  the 
attainment  of  their  main  objects.    They  are  in  no  way  dependent 
upon  an  innate  wisdom  present  in  the  mind  of  the  animal,  by 
which  it  spontaneously  and  voluntarily  excites  these  instincts, 
and  their  operations  in  the  body  (89,  90).     And  indeed,  those 
actions  which  in  true  sensational  animals  are  sentient  actions  of 
the  sensational  instincts,  are  excited  in  other  animals,  or  in  the 
former  under  circumstances  in  which  they  can  no  longer  be  sen- 
tient actions,  by  precisely  the  same  external  impressions  (183) : 
as,  for  example,  when  a  decapitated  animal  being  brought  to 
another,  copulates  and  lays  eggs ;  when  a  decapitated  frog  with- 
draws its  leg  on  its  foot  being  pinched,   and  leaps  away,  in 
accordance  with  the  instinct  of  self-preservation,  &c.,  of  which 
more  in  the  Second  Part  of  the  work.     It  is  manifest,  also,  that 
although  these  animals,  in  which  the  instinctive  actions  are  sen- 
tient actions,  feel  the  sensational  stimuli  so  strongly,  although 
obscurely,  as  to  long  for  their  gratification,  they  have  not  the 
least  knowledge  of  the  objects  of  the  instincts,  or  why  these 
movements  are  produced;  but,  on  the  contrary,  their  other 
actions  are  not  in  harmony  with  those  objects,   and  this  is  the 
reason  why  so  much  surprise  is  felt  at  the  stupidity  of  animals, 
which  otherwise  display  so  much  apparent  sagacity  in  the  actions 
appropriate  to  their  natural  instincts ;  as,  for  example,  when  a 
hen,  which  has  trod  upon  her  chicken,  hearing  its  cry,  calls  it 
to  some  food,  without  at  the  same  time  lifting  its  foot ;  or  when 
a  lobster  having  one  of  its  legs  fixed  in  and  pinched  by  one  of 
its  claws,  excited  by  the  pain,  violently  tears  away  the  limb, 
instead  of  opening  its  claw ;  or,  when  a  lark,  while  over  the  sea, 
blindly  following  its  instinct  to  ascend  into  the  air,  and  to  fall 


i 


CH.  III.]  ACTIONS  OF  INSTINCTS.  135 

again,  descends  to  the  sea,  and  is  drowned.  Lastly,  experience 
teaches  us,  that  when  men  attempt  to  develop  the  instincts  in 
themselves  or  other  animals  voluntarily,  or  to  regulate,  limit, 
or  extend  them,  they  usually  fail,  and  miss  the  object  of  nature, 
which  would  more  rarely  happen,  if  the  instincts  were  blindly 
allowed  to  act,  without  the  interference  of  their  own  notions. 

267.  Nevertheless,  it  is  also  certain,  that  the  operations  of 
the  blind  instincts  do  not  appear  to  harmonise  in  all  cases  with 
the  objects  of  nature  :  this  may  arise  possibly  from  the  fact,  that 
we  do  not  sufficiently  comprehend  those  objects ;  or  else  that  the 
instincts  are  rendered  incapable  of  their  attainment,  where  their 
actions  are  influenced  volitionally  by  the  intermingling  of  the 
actions  of  other  sentient  forces.  It  is  observed,  for  example, 
that  many  animals  are  not  sufficiently  taught  by  their  instinct, 
not  to  eat  or  do  certain  things  which  are  injurious  to  them. 
Some  eat  poisonous  herbs  without  suspicion,  and  are  poisoned. 
Many  exceed  their  strength  so  much  in  the  accomplishment  of 
their  instincts,  that  they  become  quite  enfeebled  and  die.  In 
cases  of  this  kind  we  are  ignorant  what  are  the  designs  of  nature 
in  the  implantation  of  instincts,  or  what  is  the  object  in  limiting 
the  sphere  of  their  utility  to  the  personal  weal  of  the  animal, 
and  not  extending  it  to  all  possible  cases.  To  what  extent  we 
ourselves  hinder  the  designs  of  nature  in  the  instincts,  and  limit 
their  operations  by  the  interference  of  our  will,  is  shown  by 
their  great  uncertainty  in  mankind,  and  their  much  greater  cer- 
tainty in  those  animals  which  follow  them  blindly ;  but  especially 
is  it  shown  in  disease,  when  we  attribute  that  to  an  instinct  of 
nature,  which  is  only  the  consequence  of  intellectual  desires. 

268.  It  is  requisite  to  the  attainment  of  the  objects  of  the 
instincts,  that  the  inducements  previously  appointed  by  nature, 
shall  excite  the  pleasure  or  suffering,  which  will  develop  a  cer- 
tain foreseen  future  agreeable  or  unpleasant  sensation  (94,  262). 
These  sensational  stimuli  excite  that  effort  which  is  the  instinct 
itself  (80,83),  and  the  satisfaction  of  which  nature  afterwards  pro- 
vides by  means  prepared  beforehand  (262) .  In  this  development, 
the  natural  inducements  of  the  instinct  are  to  be  most  carefully 
distinguished  from  its  sensational  stimuli,  — the  latter  from  the 
instinct  itself, — and  the  instinct  from  its  contentment  or  satis- 
faction. It  is  thus  that  we  find  the  whole  order  of  the  pheno- 
mena of  instinct  to  occur  in  nature.     With  the  object  of  causing 


136  ANIMAL-SENTIENT  FORCES.  [i. 

an  animal  to  think  of  supplying  itself  with  food,  at  certain  fixed 
periods  the  stomach  is  emptied  of  all  the  food  taken  into  it,  and 
from  this  emptiness  an  unpleasant  external  sensation  arises, 
termed  hungriness.  This  is  the  sensational  stimulusofthe  instinct 
of  hunger,  which  is  communicated  to  the  mind  by  means  of  the 
emptiness  of  the  stomach  naturally  and  necessarily ;  nay,  even 
contrarily  to  the  wish  of  the  animal  (27).  This  unpleasant 
external  sensation  reminds  it  of  the  contrary  pleasant  sensation 
experienced  when  the  stomach  was  full.  From  this  com- 
bination arises  the  foreseeing  and  expectation  (73)  of  the  agree- 
able sensation  of  a  fall  stomach,  and  the  effort  of  the  mind  to 
develop  it  (81),  which  is  the  instinct  of  hunger,  and  the  con- 
tentment of  which  by  eating  to  satiety,  is  the  object  nature  had  in 
view  in  exciting  the  instinct,  so  as  to  provide  for  the  nutrition 
of  the  animal  (262).  When  an  animal  has  remained  motionless 
for  a  length  of  time,  the  body  becomes  sickly,  because  the 
functions  of  all  organs  go  on  imperfectly.  This  is  the  pre- 
ordained cause  of  the  instinct  of  muscular  activity,  because  the 
sickliness  excites  unpleasant  external  sensations,  which  the 
animal  cannot  avoid,  and  which  are  the  sensational  stimuh  of 
the  instinct.  Out  of  this  unpleasant  external  sensation  of  the 
animal,  and  the  recollection  of  the  well-being  experienced  when 
the  limbs  were  moved,  arise  the  foreseeing  and  expectation  of 
the  opposite  pleasant  sensation  of  a  future  movement,  and  thus 
results  an  effort — the  instinct  of  movement — the  satisfaction  of 
which  by  bodily  exercise  is  the  design  of  nature,  so  as  to  pro- 
vide for  the  well-being  of  the  animal.  The  same  mechanism 
and  series  of  phenomena  may  be  readily  traced  in  the  develop- 
ment of  other  natural  instincts. 

269.  In  thinking  animals,  all  the  sentient  instincts,  together 
with  the  sentient  actions  that  accompany  them,  are  thus 
developed,  although  obscurely  enough,  from  the  natural  in- 
ducements pre-ordained  by  the  Creator,  according  to  the  laws 
of  the  conceptive  force  and  of  the  animal  sentient  forces;  but 
only  on  the  condition  that  the  animals  have  lived  so  long,  and 
felt,  thought,  and  compared  so  much  as  to  be  able  to  associate 
imaginations  with  the  sensations  induced,  and  which  must  de- 
velop the  foreseeing  into  instinct  (66,  89) .  But  it  is  impossible 
to  suppose  that  this  takes  place  with  newly  born  animals,  that 
have  scarcely  begun  to  feel,  and  seem  to  have  no  other  concep- 


(II.  III.]  ACTIONS  OF  INSTINCTS.  137 

tionSj  yet  perform  with  remarkable  readiness  and  completeness, 
all  the  movements,  that,  as  sentient  actions,  are  appropriate  to 
the  development  and  satisfaction  of  the  instincts.  No  one 
will  be  persuaded  that  the  mind  of  an  animal  which  has  never 
eaten,  is  led  by  the  sensation  of  an  empty  stomach  to  the  idea 
of  agreeable  repletion,  and  that  from  this  is  formed  the  desire 
to  eat;  that  the  mind  of  an  animal  which  moves  voluntarily 
for  the  first  time,  is  led  by  the  unpleasant  sensation  of  repose, 
to  the  idea  that  movement  has  removed  this  sensation,  and  out 
of  this  is  formed  the  desire  to  move  its  limbs;  or  that  the 
mind  of  an  animal  which  as  yet  knows  nothing  of  an  enemy, 
of  violence,  or  of  danger,  is  reminded  of  the  use  of  its  natural 
weapons  (not  yet  in  fact  grown),  by  the  sight  of  an  enemy, 
and  that  out  of  this  is  formed  the  desire  to  defend  itself.  But 
since  at  the  same  time,  an  instinct  cannot  be  developed  natu- 
rally in  the  mind,  in  any  other  mode  than  that  just  described 
(268),  according  to  premises  already  advanced  (94),  it  follows 
that  in  the  inexperienced  animals,  and  in  all  not  endued  with 
mind,  no  instincts  are  developed ;  but  that  those  movements, 
which  by  the  analogy  of  our  own  nature  we  conclude  to  be 
sentient  actions,  and  which  in  many  thinking  animals  really  are 
such,  may  continually  be  at  least  true  nerve-actions  excited  by 
external  impressions  (183,  89),  and  that  the  sensation  itself  of 
the  external  impressions  contributes  nothing  essential  towards 
the  production  of  these  movements.  It  is  undoubted,  that  the 
regular  and  adapted  development  of  conceptions  and  of  the  entire 
instinct,  accompanies  in  thinking  animals  these  nerve-actions, 
which  are  also  developed  regularly  and  adaptively,  in  accordance 
with  the  designs  of  nature  (268),  and  this  with  special  designs 
which  have  been  already  noticed  (184,  ii).  In  this  way  these 
nerve-actions  are  to  be  considered  as  sentient  actions ;  as  nerve- 
actions  solely,  they  will  be  again  treated  of  (439,  454,  551,  &c.) 
270.  The  stimuli  of  the  instincts  are  obscure  sensational  fore- 
seeings  (262),  either  pleasing  or  unpleasing,  being  the  imperfect 
elements  of  a  coming  agreeable  sensation,  or  of  the  opposite  to 
a  disagreeable  sensation,  which  becomes  perfect,  when  the 
instinct  is  fulfilled,  or  satisfied  (94).  Foreseeings  of  this  kind 
are  highly  sensational  conceptions,  almost  as  involuntary  and 
as  necessarily  produced  as  external  sensations  themselves,  of 
which,  as  obscure  conceptions,  the  mind  is  never  conscious; 


138  ANIMAL-SENTIENT  FORCES.  [i. 

which  are  scarcely  regularly  developed  in  the  depths  of  the  mind, 
to  the  special  astonishment  of  the  animal  when  conscious  of 
their  operations;  and  which  consequently  give  rise  to  the  magical 
(bezauberung)  in  instincts  (263).  Consequently,  just  as  they 
differ  from  the  corporeal  inducements  of  the  instincts  (264),  so 
they  must  be  distinguished  from  the  instinct  itself,  which  is 
the  effort  of  the  conceptive  force  excited  by  them,  to  develop 
the  foreseen  agreeable  sensation,  or  the  contrary  to  the  dis- 
agreeable sensation,  although  they  act  in  and  with  it  at  the 
same  time  (80).  Thus  satiety  is  the  agreeable  foreseen  sen- 
sation in  hunger ;  in  the  instinct  of  self-defence,  the  foreseen  sen- 
sation is  the  contrary  to  the  sensation  of  danger ;  in  the  instinct 
of  propagation  of  the  species,  that  of  copulation ;  and  in  the 
instinct  to  give  suck,  that  of  emptying  of  the  mammae  (94,  268). 

271.  The  sentient  actions  of  the  stimuli  of  the  instincts,  as 
such,  are  those  of  sensational  pleasure  and  pain  (88),  and  con- 
sidered alone,  change  consequently  the  respiratory  and  cardiac 
movements  (250),  but  as  foreseeings,  they  express  imperfectly 
the  sentient  action  of  the  coming  sensation  (241).  Conse- 
quently, the  vital  movements  are  very  strikingly  altered  in  each 
instinct  (262,  258),  and  movements  are  partly  excited  in  the 
mechanical  machines,  similar  to  those  which  are  fully  developed 
when  the  instinct  is  satisfied  (257). 

272.  The  instinct  itself,  (which  is  only  the  effort  of  the 
conceptive  force  to  develop  the  foreseen  sensation,)  manifests 
its  influence  in  the  mechanical  machines,  so  as  to  develop  the 
sentient  actions  of  the  coming  sensation  as  powerfully  as  it 
possibly  can,  short  of  the  actual  contentment  of  the  instinct, 
or  without  the  intervention  of  the  true  sensation  therein  fore- 
seen. Their  nature,  laws,  and  characteristics,  may  be  learnt 
from  previous  statements.   (Compare  257 — 261 ;  also  274.) 

273.  To  each  kind  of  sensational  conceptions  are  usually 
superadded  others,  which  the  mind  connects  therewith  spon- 
taneously, and  at  pleasure,  and  which  develop  their  sentient  ac- 
tions at  the  same  time,  and  incidentally  to  the  preceding  (219 
— 224,  235,  246),  nay,  the  direct  sentient  actions  of  the  external 
sensations,  which  play  so  important  a  part  in  the  instincts,  are 
often  felt,  and  induce  subordinate  sentient  actions  of  sensations 
(225,  226),  and  subordinate  instincts  which  are  often  conjoined 
with  other  instincts,  as,  for  example,  the  instincts  of  jealousy. 


CH.  III.]  ACTIONS  OF  INSTINCTS.  139 

or  of  solitude,  accompany  the  instinct  of  .love,  whilst  in  man, 
the  understanding  and  will  often  co-operate  with  the  instincts. 
It  follows  from  hence  that  many  movements  occur  conjointly 
with  the  actions  of  the  instincts,  particularly  in  those  animals, 
which  are  capable  of  conceptions  only  remotely  connected  with 
external  sensations  (27) ;  and  thus  a  highly  compound  and 
complicated  condition  of  the  mind  and  the  body  may  arise, 
which  can  never  be  explained  by  the  nature  of  the  instincts,  as 
has  been  often  uselessly  attempted,  so  long  as  the  subordinate 
conceptions,  together  with  their  accompanying  actions,  are  not 
carefully  distinguished  from  the  instinct  itself  and  its  acts.  If 
the  acts,  for  example,  resulting  from  the  satisfaction  of  the 
instinct,  be  confounded  with  those  of  the  instinct  itself,  the 
greatest  mistake  is  made.  And  one  great  reason  why  the 
nature  and  operations  of  the  instincts  and  passions  have  been 
hitherto  so  imperfectly  elucidated  is,  that  they  have  been  cha- 
racterised confusedly.  It  will,  therefore,  be  worth  while  to 
take  an  instinct  as  an  example  for  analysis ;  and  for  this  pur- 
pose I  select  the  instinct  of  propagation,  as  the  most  important 
and  the  most  complicated. 

274.  In  this  instinct,  nature  in  the  first  instance  impart 
certain  inducements  to  the  animal, — external  impressions 
which  surprise  it  (in  Staunen  setzen),  and  by  means  of  a  pe- 
culiar action  in  the  sexual  organs,  prepare  the  latter  for  the 
sensational  stimulus  of  the  instinct,  so  that  their  nerves  become 
more  sensitive  to  touch,  so  as  to  receive  the  gentle  titillation 
which  constitutes  the  incitement  of  the  instinct.  This  peculiar 
impression  causes  in  the  minds  of  animals  during  heat  only, 
and  at  no  other  time,  certain  external  sensations,  and  other  sen- 
sational conceptions,  in  accordance  with  the  prearrangement  of 
nature  (265).  For  example,  the  odour  of  an  animal  of  the  oppo- 
site sex,  a  sound,  a  song,  a  whining,  a  chirp,  a  look,  or  a  sensa- 
tional conception,  imagination,  or  foreseeing  of  them  by  an  animal 
in  a  state  of  heat,  &c.,  develops  the  sentient  actions  in  the  me- 
chanical machines  (sexual  organs)  assigned  to  them  by  nature ; 
for  example,  an  increased  flow  of  fluids  to  those  organs,  and 
the  increased  secretion  of  the  seminal  fluid,  and  its  accumula- 
tion in  the  vesciculse  seminales,  in  consequence  of  which  they 
become  gently  distended  and  excited ;  and  thus  the  agreeable 
external  sensation  in  the  sexual  organs  (the  gentle  titillation). 


3arts^>^jv 


140  ANIMAL-SENTIENT  FORCES.  [i. 

is  produced,  that  constitutes  the  sensational  stimulus  of  the 
instinct  of  propagation,  and  excites  it  in  the  mode  described 
above  (268),  together  with  all  its  sentient  actions. — ( Vide 
Haller^s  'Physiology,^  §  870).  It  is  manifested  by  the  strong 
effort  of  the  conceptive  force  to  attain  the  complete  development 
of  the  highly  pleasurable,  obscure,  foreseen  sensation  of  copula- 
tion (94),  and  by  the  sentient  actions  which  accompany  this  effort 
(255).  The  vital  movements,  consequently,  are  powerfully  in- 
fluenced by  the  instinct  itself  (251,  258).  The  heart  beats  with 
greater  force,  the  heated  blood  circulates  violently,  the  respiration 
becomes  a  sighing,  or  a  corporeally-produced  languishing  and 
moaning,  as  occur  from  any  other  similar  heated  state  of  the 
blood :  at  the  same  time,  the  actions  of  the  future  sensation, 
in  the  satisfaction  of  the  instinct  (in  this  case  copulation),  become 
vividly,  although  incompletely  manifested  (257),  so  that  the 
sexual  organs  are  in  the  same  condition  as  in  copulation,  and 
only  the  external  impression  is  wanting  to  the  satisfaction  of 
the  instinct,  which  the  animal  often  procures  incidentally, 
often  experiences  normally  in  copulation.  These  only  are  the 
true,  direct,  sentient  actions  of  the  instinct.  It  hardly,  how- 
ever, excites  these  only  in  the  mind;  for  other  conceptions 
are  conjoined  therewith,  as  subordinate  sensations  (225),  and 
in  particular,  spontaneous  conceptions,  imaginations,  foreseeings, 
imperfect  sensations  (148),  other  instincts  and  emotions,  and 
in  men  even  reflections,  and  desires,  and  aversions  of  the 
intellect,  of  which  the  object  that  gives  pleasure  is  the  exciting 
cause.  For  example,  similar  circumstances  are  remembered 
in  the  instinct  with  their  subordinate  impressions,  scenes  from 
favorite  romances  are  recollected,  new  images  for  the  fore- 
seeing faculty  are  produced,  and  pleasurable  anticipations  ex- 
cited, which  often  grow  into  imperfect  external  sensations,  so 
that  the  individual  l^ias  the  beloved  object  before  his  eyes,  and 
thinks  that  he  converses  with  it  (148).  All  movements  of  the 
animal  in  accordance  with  these  conceptions,  and  even  all 
influences  which  these  conceptions  exercise  according  to  their 
nature,  on  the  mechanical  machines  of  the  body, — as  singing, 
chirping,  crowing,  whining,  and  all  spontaneous  enticements  to 
copulation,  are  not  direct  actions  of  the  instinct  (103),  but  inci- 
dental sentient  actions,  contingent  on  secondary  sensations,  or 
on  ideas  excited  spontaneously,  or  on  secondary  conceptions. 


CH.  III.]  ACTIONS  OF  INSTINCTS.  141 

and  sensational  or  intellectual  desires  and  aversions,  and  their 
satisfaction,  which  have  nothing  further  in  common  with  the 
instinct  than  that  they  are  usually  connected  with  and  accom- 
pany it.  The  spontaneous  and  voluntary  song  of  birds,  the 
chirping  of  insects,  the  whine  of  dogs,  &c.,  whereby  they  allure 
to  sexual  congress,  may  be  no  more  considered  as  direct  sen- 
tient actions  of  their  instinct,  than  the  suicide  of  a  lover ;  for 
all  these  are  sentient  actions  of  voluntary  resolves,  induced 
and  occasioned  in  the  mind  by  the  instinct,  but  which  may 
certainly  take  place  without  it,  although  not  usually.  Gratifica- 
tion of  the  instinct  ends  it  (95).  The  intense  longing  then 
ceases,  the  vital  movements  become  quiescent,  the  sexual 
organs  return  to  their  former  condition,  and  they  lose  their 
excitability,  for  the  parts  formerly  distended  and  irritated  have 
become  empty.  But  so  long  as  the  period  of  heat  continues, 
the  natural  inducements  and  the  secondary  conceptions  accom- 
panying them  and  the  instinct,  exercise  a  continually-renewed 
influence  on  the  mind  and  body  of  the  animal,  and  often  re- 
excite  the  instinct,  until  at  last,  either  from  its  repeated  gra- 
tification, or  its  enfeeblement  (95),  it  is  no  longer  re-excited, 
and  its  natural  inducements  in  accordance  with  the  designs  of 
nature,  lose  their  magical  influence  (263).  Hence  animals 
allure  to  sexual  congress  during  the  whole  period  of  heat,  be- 
cause their  minds  are  continually  occupied  with  secondary 
conceptions  and  instincts,  having  reference  to  the  predominant 
instinct,  derived  from  the  natural  inducements  continually 
acting,  and  from  the  sensational  stimuli  and  instincts  repeatedly 
renewed.  Hence  also  man  even  often  desires  amorously  the 
satisfaction  of  the  instinct,  and  is  inclined  to  solitude  and 
jealousy,  so  long  as  he  is  held  in  enchantment  by  the  object  of 
his  passion ;  all  which  were  impossible,  if  these  conceptions, 
with  their  actions,  belonged  to  the  gratification  of  the  instinct, 
and  were  its  direct  actions  (94,  95). 

275.  The  gratification  of  the  instinct  is  the  actual  de- 
velopment of  the  foreseen  sensation,  and  to  attain  which  end 
the  conceptive  force  and  the  animal- sentient  forces  of  the 
instinct  are  excited  (81,  90).  The  mental  eifort  consequently 
ceases,  and  the  sensational  stimuli  (pleasure  or  pain)  are  weakened 
so  soon  as  satisfaction  is  attained  (83).  Consequently,  also, 
the    sentient    actions  cease,    the    vital   movements    return  to 


142  ANIMAL-SENTIENT  FORCES.  [i. 

their  usual  order,  and  the  imperfect  expressions  of  move- 
ments, which,  during  the  gratification  of  the  instinct,  become 
perfect,  are  abolished.  But  inasmuch  as  the  gratification  of 
the  instinct  is  itself  a  sensation,  it  also,  like  a  true  sensation, 
develops  special  sentient  actions  in  the  mechanical  machines, 
and  these  do  not  belong  to  the  instinct.  To  this  class  belong 
the  convulsions  that  occur  during  the  satisfaction  of  the  instinct 
of  sexual  congress,  being  excited  by  the  excessive  titillation. 
When,  as  in  this  case,  and  in  all  the  true  blind  instincts,  the 
satisfying  sensation  is  an  external  sensation,  the  external 
impression  can  excite  special  nerve-actions  in  the  mechanical 
machines  (183),  which  are  altogether  foreign  to  the  instinct, 
and  never  belong,  as  such,  to  its  gratification  (184,  i). 

276,  i.  Although  strong  sensational  desires  and  aversions, 
may  and  do  frequently  occur,  which  are  not  induced  or  satisfied 
by  external  sensations,  nor  require  to  those  ends  an  external 
impression,  but  which  are  based  on  imaginations,  fictions, 
visions,  appearances,  forebodings,  &c.,  and  are  satisfied  by  them, 
yet  still  they  all  arise  from  sensational  stimuli,  and  are  indirectly 
determined,  both  as  to  their  excitation  and  satisfaction,  by  ex- 
ternal impressions  (66).  But  as  regards  the  regular  and  truly 
natural  instincts,  imparted  by  the  Creator  to  animals  for  the 
conservation  of  their  existence  and  well-being  (262),  all,  so  far  as 
we  observe  them,  are  excited  and  satisfied  by  external  sensations, 
which  require  true  external  impressions  (258);  these  are  provided 
before-hand  by  nature,  and  so  brought  into  connection  with  the 
whole  phenomena  of  life,  that  they  must  aff'ect  the  animal  at 
the  right  time  and  place,  at  such  a  period,  with  such  intensity, 
and  in  such  a  way,  too,  that  the  instinct  is  duly  excited,  and  at 
last  satisfied  in  the  way  already  illustrated  (265 — 268). 

ii.  Since  pleasurable  and  painful  feelings  derived  from  ex- 
ternal impressions  constitute  the  stronger  sensational  stimuli 
(80,  88),  such  constitute  also  the  most  suitable  stimuli  of  the 
peculiarly  natural  instincts  of  animals  (262,  90),  and  nature  has, 
therefore,  specially  made  use  of  them  for  the  development  of 
the  absolutely  necessary  instincts,  so  that  the  latter  may  be 
kept  in  action  in  animals  in  the  most  eff'ectual  manner. 

iii.  No  disagreeable  external  sensation,  and  therefore  no 
pain,  is  ever  an  object  of  satisfaction  to  an  instinct,  but  only 
the  agreeable  sensation  that  is  the  contrary  thereof  (262,  80,  81). 


CH.  III.]  ACTIONS  OF  INSTINCTS.  143 


tf° 


Even  excessively  pleasurable  feelings,  which  border  upon  the 
contra-natural  (199),   cease  to    be   an   object  of  gratification, 
d  are  abhorred  (191,  80,  81). 

iv.  The  sentient  actions  of  the  agreeable  sensational  instincts 
all  agree  in  this,  that  if  not  excessive_,  they  are  conformable 
with  the  welfare  of  the  body,  but  if  excessive,  they  are  like 
the  sentient  actions  of  the  unpleasant  instincts,  and  are  opposed 
to  it  (259).  But  inasmuch  as  all  have  the  best  interests  of  the 
animal  in  view  (263),  the  latter  are  only  serviceable  so  far  as  they 
act  like  medicine,  and  compel  the  animal  by  abnormal  actions  to 
pass  from  a  condition  injurious  to  it,  and  therefore  opposed  to 
their  object  (as,  for  example,  a  state  of  indifference,  of  pleasure,  or 
of  misery),  into  the  opposite  and  more  salutary  condition  (196). 

V.  The  sensational  stimuli,  whether  pleasurable  or  painful, 
which  have  to  excite  the  curative  instincts  of  the  animal 
(270,  271),  operate  sometimes  in  this  way,  by  maintaining  the 
health  of  the  animal,  of  sometimes  contrarily  thereto,  according 
as  they  are  either  pleasurable  or  painful  (252).  Thus  fasting, 
which  is  the  sensational  stimulus  of  hunger,  makes  us  ill,  and 
compels  us  to  think  of  feeding  ourselves. 

vi.  Since  the  gratification  of  all  instincts  is  an  agreeable  ex- 
ternal sensation  (276,  iii),  their  sentient  actions  in  the  body  are 
generally  in  accordance  with  its  nature  and  welfare  (196),  pro- 
vided they  are  not  excessive  (199).  Thus  the  gratification  of  the 
appetite  for  food, for  sexual  congress,  &c.,  conduces  to  health,  pro- 
vided the  appetites  are  not  excessive ;  in  the  latter  case,  however, 
they  cease  to  be  agreeable,  and  are  abhorred  (excite  disgust). 

277.  The  combination  of  so  many  corporeal  influences  in 
each  instinct  (which  act  partly  from  without  through  the 
nerves,  and  are  partly  sentient  actions  of  various  kinds),  renders 
the  explanation  of  the  resulting  corporeal  phenomena  pecu- 
liarly difficult ;  a  knowledge  of  the  peculiar  sources  of  each  of 
these  influences  is,  however,  of  considerable  assistance.  These 
influences  are : 

i.  The  actions  of  the  natural  inducements  of  the  instinct. 
These  inducements  are  external  impressions  on  the  nerves, 
which  they  prepare  before-hand,  in  a  peculiar  way,  to  receive  the 
sensational  stimuli  proper  to  the  instinct  (264). 

ii.  The  sentient  actions  of  the  sensational  stimuli  on  the 
vital  movements  (271). 


144  ANIMAL.SENTIENT  FORCES.  [i. 

iii.  The  effort  of  the  animal-sentient  forces  to  develop  the 
complete  sensation  wherein  the  sensational  stimulus  is  (272). 

iv.  The  sentient  actions  of  all  subordinate  conceptions  (273, 
274). 

V.  The  development  of  the  complete  sensation,  or  the 
satisfaction  of  the  instinct,  when  it  is  fulfilled,  for  which,  in 
the  true  instincts,  an  external  impression  is  requisite,  and 
which  impressions  themselves  excite  actions  (275). 

Since  the  mind  cannot  voluntarily  satisfy  the  greater  number 
of  the  instincts,  but  must  await  to  this  end  an  external  im- 
pression, which  cannot  possibly  occur  immediately  (276,  i),  we 
can  understand  the  reason,  why  the  instincts  and  all  other 
sensational  desires  and  aversions  in  general,  to  which  an  ex- 
ternal impression  is  necessary  for  their  satisfaction,  often  require 
so  long  and  fruitless  an  effort  of  the  mind,  and  such  a  com- 
bined effort  of  the  animal  sentient  forces ;  while  others,  as  the 
instinct  to  voluntary  movement  (283),  and  the  desires  and 
aversions  of  the  will,  are  much  calmer,  and  are  satisfied, 
apparently,  with  much  less  effort  of  the  mind  and  motor  forces; 
for  a  limb  may  be  moved,  as  soon  as  the  motion  is  willed. 
In  the  latter  class,  the  satisfying  sensation  is  not  an  external 
sensation,  but  a  spontaneous  conception  of  the  mind,  to  the 
perfect  development  of  which  no  external  impression  on  the 
nerves  need  be  awaited.      {Vide  336). 

278.  We  have  now  to  consider  the  instincts  in  detail,  in 
accordance  with  this  general  view:  with  the  object  of  inquiring 
in  what  mechanical  machines  each  kind  manifests  sentient 
actions ;  to  what  end  these  are  manifested ;  according  to  what 
laws;  and  what  is  the  great  result  they  have  in  the  animal 
economy  by  means  of  the  connection  between  the  physical, 
mechanical,  and  animal  forces  of  the  part  in  which  they  act. 
But  since  each  sensational  instinct  may  be  numerously  sub- 
divided, we  will  take  only  the  chiefest  into  consideration,  so  as  to 
give  the  elementary  principles  of  a  more  detailed  doctrine 
respecting  the  actions  of  the  instincts. 

279.  The  sensational  instincts  of  self-preservation  and  self- 
defence,  may  be  classed  together  in  reference  to  their  objects 
and  natural  intent,  namely,  the  preservation  and  well-being 
of  the  animal,  and  the  modes  in  which  those  objects  are 
attained  (262) .     In  this  class,  indeed,  we  place  the  instincts  of 


CH.  III.]  SELF-LOVE.  145 

animals  to  seek  dwellings,  to  keep  themselves  warm,  to  escape 
the  dangers  of  winter,  to  avoid  or  avert  oppressive  sensations, 
&c.,  just  as  properly  as  the  instincts  for  food,  for  movement, 
for  rest,  &c.,  although,  at  the  same  time,  they  are  defen- 
sive instincts.  But  since  certain  natural  organs  have  been 
given  to  each  animal,  as  >veapons  for  its  defence  against  inju- 
rious attacks,  and  inasmuch  as  for  the  proper  use  of  these 
weapons,  it  possesses  special  instincts,  which,  although  defen- 
sive, are  different  from  those  of  self-preservation,  we  will  at 
least  class  the  war-instinct  (Wehrtrieb)  with  the  defensive 
instincts,  but  consider  all  others,  which  have  the  maintenance 
and  well-being  of  the  animal  as  their  object,  amongst  the 
instincts  of  self-preservation,  although  their  object  be  at  the 
same  time  the  averting  of  dangers,  and  attained  by  means  of 
aversions. 


Self-love  [Selbstliebe] . 

280.  All  the  changes  in  an  animal  organism,  which  tend  to 
its  preservation  and  well-being,  must  ensue  in  accordance  with 
its  natural  functions,  or,  at  least,  terminate  in  their  full 
attainment  (263).  Corporeal  changes  which  thus  ensue  and 
terminate  are  agreeable,  if  felt  or  perceived,  or  else  soon 
terminate  in  agreeable  conceptions  or  sensations  (276,  iv,  252). 
On  the  same  grounds  all  contra-natural  changes  tend  to  the 
ill-being  and  destruction  of  the  body  (263),  and  if  felt,  are 
painful.  Consequently,  all  instincts  for  the  preservation  and 
well-being  of  the  animal,  are  efforts  of  the  conceptive  force  to 
attain  to  agreeable  sensations,  and  to  avoid  the  painful  (262,  257). 
This  general  effort  in  the  instincts  is  termed  the  instinct  for 
enjoyment  (80);  and  since  its  objects  cannot  be  attained  without 
the  continuance  of  the  forces,  or,  in  other  words,  independently 
of  the  existence  of  the  animal,  it  follows  that  the  instinct  termed 
love  of  life  is  the  fundamental  instinct  in  all  animals;  so 
that  the  instinct  for  life  and  for  enjoyment,  that  is  to  say, 
sensational  self-love  (selfishness  [Eignliebe] ),  instigates  all  the 
others. 


10 


146  ANIMAL-SENTIENT  FORCES.  [i. 

Instinct  for  Food. 

281.  By  the  pre-arrangement  of  nature  (263),  whenever  food 
is  wanting,  there  arises  in  the  stomach  of  the  animal  an  uneasy 
sensation  termed  hungriness  [Nuchternheit],  and  one  which 
ever}'  animal  dislikes  (280).  This  is  the  sensational  stimulus  of 
the  instinct  for  food  (Hunger),  which  consists  in  a  strong  effort 
to  excite  the  sensations  in  the  stomach  antagonistic  to  this 
unpleasant  external  sensation,  or,  in  other  words,  to  feel  the 
stomach  filled  with  food ;  this  being  the  design  of  the  Creator 
in  the  instinct  and  its  object  in  the  animal,  although  the  latter 
knows  nothing  whatever  of  that  object  (266).  Everything 
that  excites  an  unpleasant  external  sensation  in  the  stomach 
develops  the  sensational  stimulus  of  the  instinct,  as  long  fast- 
ing, a  too  quick  digestion,  acrid  fluids  in  the  stomach,  sto- 
machic remedies,  &c.  The  sensational  stimulus  manifests  its 
sentient  actions  in  the  vital  movements,  which  it  influences  the . 
more  powerfully  in  proportion  as  it  is  excessive  (271),  as  is 
shown  by  faintness,  in  which  the  movements  of  the  heart,  of 
the  blood,  and  of  respiration  are  manifestly  changed,  and  these 
actions  are  contra-natural  (276,  iv).  In  so  far  as  the  sensa- 
tional stimulus  is  a  foreseeing  of  a  future  repletion  of  the 
stomach,  it  manifests  its  sentient  actions  therein,  so  that  it 
produces  imperfectly  in  the  stomach,  and  in  the  mechanism 
of  the  instinct,  the  same  movements  which  actual  repletion 
or  the  satisfaction  of  the  instinct  excites  (271-72).  Hunger, 
therefore,  acts  on  the  mechanical  machines  appointed  to  re- 
ceive food,  and  to  co- operate  in  nutrition,  as  the  stomach, 
bowels,  throat,  salivary  glands,  &c. ;  for  it  stimulates  them  to 
discharge  their  natural  functions  (170 — 174),  and  which  reple- 
tion of  the  stomach  in  particular  develops  in  them.  Hence, 
in  hunger,  the  stomach  and  intestines  are  more  vividly  moved, 
and  rumble  (212),  the  salivary  glands  pour  out  fluid,  so  that 
the  mouth  waters,  and  the  other  digestive  fluids,  including  the 
bile,  are  discharged,  &c.  We  purposely  avoid  noticing  in  this, 
as  well  as  all  other  special  instincts,  the  sentient  actions  of  all 
the  associated  secondary  conceptions,  so  as  to  avoid  confusion 
in  stating  the  sentient  actions  proper  to  the  instinct  itself. 
We  pass  over,  also,  the  processes  of  digestion,  although  partly 
belonging  to  the  subject,  inasmuch  as  it  is  already  discussed 
in  physiological  works.   ( Vide  Haller's  '  Physiology.^) 


II.  III.]  INSTINCT  FOR  FOOD.  147 

282.  By  the  pre-ordination  of  nature  (263),  animals  that 
drink,  feel  a  painful  external  sensation  (280)  in  the  gullet, 
throat,  and  mouth,  whenever  their  bodies  require  more  fluids. 
This  is  the  sensational  stimulus  of  thirsty  which  consists  in  an 
eff'ort  to  produce  the  sensation  antagonistic  to  this  painful 
sensation;  or,  in  other  words,  to  feel  moisture  of  the  parts, 
which  is  the  intent  of  nature  in  the  instinct,  and  its  object  in 
animals,  although  it  is  concealed  from  them,  and  they  are 
quite  ignorant  why  the  parts  should  be  moistened  (266). 
Everything  which  induces  this  unpleasant  sensation,  as  heat, 
dust,  want  of  fluids  and  of  saliva,  salts,  wine,  spices,  &c.,  in  a 
word,  everything  which  dries  and  heats,  excites  the  sensational 
stimulus  and  the  instinct  to  drink.  The  sensational  stimulus 
manifests  its  sentient  actions  more  strongly  and  contra-naturally 
(271,  276,  iv)  in  proportion  as  it  is  excessive,  as  is  shown  by 
the  oppressive  thirst  of  fevers,  &c.  Inasmuch  as  the  sensational 
stimulus  is  a  foreseeing  of  a  moistening  of  the  mouth  and  throat, 
it  manifests  its  sentient  actions  in  the  parts  by  a  frequent  swal- 
lowing of  the  saliva,  for  the  purpose  of  moistening  the  mouth  and 
throat,  and  thereby  attaining  the  object  which  results  from  the 
real  act  of  drinking,  or  the  satisfying  of  the  instinct :  the  efi'ort 
of  the  animal- sentient  forces  to  excite  these  movements  is  the 
sentient  action  of  thirst,  or  the  instinct  for  drink  itself.  Thirst 
acts  consequently  on  the  organs  predetermined  to  be  moistened, 
— the  tongue,  the  muscles  of  deglutition, the  throat,  &c., — so  that 
it  develops  certain  movements  necessary  to  the  act  of  drinking, 
according  to  the  laws  of  the  sentient  actions  of  the  sensational 
instincts  (277),  which  movements  become  perfect  during  the 
resulting  quenching  of  the  thirst  (257);  and  in  such  cases 
have,  as  a  consequence,  beneficial  actions  in  the  animal  economy, 
in  accordance  with  the  connection  of  the  physical,  mechanical, 
and  animal  forces  of  the  body,  constituting  the  design  of  nature 
in  the  drinking  of  animals,  and  which  are  specially  described  in 
works  on  the  physiology  of  the  peculiar  mechanism  of  animal 
bodies.   {Vide  Haller's  'Physiology,'  §  639.) 

Loathing  is  just  the  opposite  to  the  instinct  for  food.  The 
unpleasant  external  sensation,  or  idea,  of  an  overloaded  or  cor- 
rupted stomach,  excites  the  mind  to  develop  the  antagonistic 
sensation,  the  emptying  of  the  stomach,  which  is  accomplished 
by  abstaining  from  food,  and  by  the  act  of  vomiting,  &c. 


148  ANIMAL-SENTIENT  FORCES.  [i. 

The  Instinct  to  perform  Sensational  Voluntary  Movements 
[Zur  willkuhrlichen  Bewegung].^ 

283.  Nature  has  ordained  bodily  exercise  to  be  a  means  of 
the  preservation  and  well-being  of  animals,  and  thereby  they 
are  kept  in  the  best  health.  When  therefore  to  its  injury, 
exercisfe  of  the  body  is  too  long  neglected,  a  number  of  unpleasant 
sensations  are  excited,  termed  indisposition  or  sickliness,  and 
which  all  animals  abhor  (280).  These  constitute  the  sensational 
stimulus  of  the  instinct  for  bodily  exercise,  in  which  the  vital 
movements  are  more  or  less  morbid,  according  to  the  strength 
of  the  stimulus,  the  pulse  becoming  feverish,  and  the  respiration 
impeded.  By  this  unpleasant  sensational  stimulus  (induced  by 
long  repose,  too  much  sleep,  too  great  corpulency,  and  many  other 
causes),  the  animal  is  induced  to  make  an  effort  for  the  opposite 
agreeable  sensations,  which  it  foresees  will  be  obtained  by  the 
movement  of  its  muscles  and  limbs,  and  this  is  the  intent  of 
nature  and  the  object  of  the  instinct,  although  the  animal  does  not 
know  for  what  ulterior  purpose  it  makes  the  movements  (266). 
The  sentient  actions  of  this  sensational  stimulus,  in  so  far  as  they 
are  a  foreseeing  of  corporeal  exercise  are,  consequently,  developed 
in  the  muscles  of  voluntary  motion,  that  is  to  say,  in  those 
which  conceptional  impressions  can  excite  to  movement  inde- 
pendently of  any  other  impression,  so  that  it  stimulates  those 
muscles  to  the  same  movements  that  are  fully  performed  during 
bodily  exercise  (271).  In  the  effort  of  the  animal-sentient  forces 
to  perform  these  movements  imperfectly  consists  the  sentient 
actions  of  the  instinct  to  bodily  exercise  itself  (272).  This 
instinct  acts,  therefore,  in  the  mechanical  machines  which 
formerly  exercised  the  body,  namely,  the  muscles  of  voluntary 
motion,  for  it  excites  them  to  the  performance  of  their  natural 
functions  (161 — 166),  and  which  especially  the  gratification  of 

*  In  a  note  to  §  335,  Unzer  distinguishes  two  classes  of  voluntary  movements, 
namely,  the  willkiihrlich,  or  sensational,  which  accompany  the  sensations  and  all 
sensational  conceptions ;  and  the  freiwillig,  or  intellectual,  which  are  excited  by  the 
will  of  the  understanding.  Wille  and  Willkiihr  are  also  sometimes  used  to  dis- 
tinguish these  two  kinds  of  will,  but  more  frequently  Willkuhr  is  used  to  express 
both,  as  in  the  note  referred  to,  where  Unzer  distinguishes  between  the  sensational 
and  intellectual  Willkuhr.  I  know  of  no  English  word  which  corresponds  to 
Willkuhrlich ;  I  have,  therefore,  termed  the  actions  of  voluntary  muscles  to  which 
Unzer  uses  it  in  the  stricter  sense,  sensational  voluntary  movements;  but  where 
it  is  used  indefinitely,  I  have  translated  it  by  voluntary  simply,  or  volitional. — Ed, 


CH.  III.]  SENSATIONAL  MOVEMENTS.  149 

the  instinct,  or  bodily  exercise,  will  develop  fully  (204).  Con- 
sequently, in  this  instinct  the  muscles  contract,  the  limbs  are 
moved  irregularly,  and  the  animal  often  attempts  to  hop,  leap, 
soar,  sit  upright,  &c.,  just  as  actually  occurs  during  the  grati- 
fication of  the  instinct  for  corporeal  -exercise ;  and  if  there  be 
no  extraneous  impediment,  it  usually  takes  place  instantaneously, 
because  a  conception  only,  is  enough  to  excite  movement  in  the 
voluntary  muscles.  In  such  cases,  there  results,  in  virtue  of 
the  connection  between  the  physical,  mechanical,  and  vital 
forces  of  the  muscles  appropriated  to  voluntary  motion,  the 
further  operations  in  the  animal  economy,  such  as  a  modification 
of  the  fluids,  promotion  of  secretion  and  excretion,  increase 
of  muscular  strength,  and  of  the  animal  force  itself  (204),  as  is 
the  design  of  nature  in  the  instinct.  For  details  on  the  subject, 
works  on  physiology  may  be  consulted.  {Vide  Haller^s  ^Phy- 
siology,' §  11.) 

281.  The  instincts  of  animals  for  particular  kinds  of  sensa- 
tional voluntary  movements,  are  easily  understood  from  the 
principles  laid  down  in  the  previous  paragraph.  The  instinct 
for  song  of  birds,  which  is  usually  a  secondary  instinct  of  the 
instinct  for  propagation,  arises  from  the  sensational  stimulus 
of  an  unpleasant  sensation  in  the  chest,  produced  by  changes 
in  the  respiration  and  circulation  resulting  from  the  primary 
instinct,  as  is  also  the  case  in  man  and  other  animals  in 
the  acts  of  sighing,  sobbing,  weeping,  moaning,  talking,  &c. 
Every  inducement  of  such  external  sensations,  excites  the 
instinct  of  similar  movements.  Warmth,  which  accelerates 
the  movements  and  impedes  respiration,  stimulates  birds  to 
sing  even  in  winter,  in  heated  rooms,  and  compels  other 
animals  to  sigh  and  pant  [lechzen].  Wine,  not  less  an  ex- 
citant of  the  vital  movements,  causes  talkativeness ;  a  too  crass 
state  of  the  blood  causes  melancholy,  and  weeping,  sighing, 
sobbing,  &c.  All  these  movements  constitute  generally  the 
satisfaction  of  the  instinct  itself,  the  proper  sentient  actions 
of  which  are  only  previous  imperfect  manifestations  of  them, 
as,  for  example,  instead  of  singing,  a  frequent  chirping;  instead 
of  sighing,  sobbing,  or  weeping,  a  deep  inspiration ;  instead  of 
speech,  a  mere  sound,  &c.  To  this  class  belongs  also  the 
instinct  of  laughter  in  man,  which  is  often  secondary  to  other 
agreeable    instincts   and    sensations,    and   is   also   an   accom- 


i 


150  ANIMAL-SENTIENT  FORCES.  [i. 

paniment  of  various  pleasures  of  the  senses  (250).  Its  sen- 
sational stimulus  is  an  agreeable  external  sensation,  resembling 
titillation,  about  the  diaphragm,  which  originates  from  the 
vital  movements  being  altered  by  a  vivid  feeling  of  pleasure, 
particularly  of  the  senses  (titillation,  §  80).  Sensational  stimuli 
to  laughter  result  from  everything  which  excites  this  sensation 
at  the  diaphragm,  even  by  flatulency  of  the  stomach.  The 
instinct  is  manifested  by  the  well-known  contractions  of  the 
diaphragm  and  thoracic  and  facial  muscles,  and  its  gratification 
is  actual  laughter.  Further,  to  this  class  belong  other  move- 
ments, as  the  migration  and  hybernation  of  animals,  the  acts  of 
cleaning,  bathing,  swimming,  pluming,  revolving;  the  seeking 
the  sun^s  rays  and  a  warmer  climate,  the  manufacture  of  clothing 
which  many  animals  undertake  (as  in  forming  cocoons),  the 
preparation  of  habitations,  the  establishment  of  republics 
amongst  beavers,  bees,  and  ants,  if  we  presuppose  that  these 
animals  all  think.  All  these  follow  the  laws  of  the  primary 
instinct  for  bodily  movement,  and  have  all  as  a  basis,  certain 
obscure  pleasant  or  unpleasant  sensations,  whereby  the  animal 
is  induced  to  attempt  certain  movements  without  knowing  the 
ulterior  object  to  be  gained,  but  which,  according  to  the  plans  of 
nature,  are  actually  accomplished  with  the  co-operation  of 
external  impressions,  for  the  purpose  of  securing  the  pre- 
servation and  well-being  of  the  animal. 

285.  It  has  not  been  to  this  day  decided,  whether  the  respi- 
ratory movements  are  mechanical  or  volitional.  Generally, 
they  are  neither  the  one  nor  the  other  (Haller^s  ^  Physiology,' 
§  274),  but  manifestly  the  sentient  actions  of  an  instinct.  So 
soon  as  they  are  suspended,  a  distressing  external  sensation 
arises  in  the  chest,  which  is  abhorred  (280).  This  is  the  sen- 
sational stimulus  of  the  instinct  of  respiration,  namely,  the 
strong  desire  to  produce  the  opposite  to  this  anxious  state, 
which  we  remember  to  be  attained  by  respiring.  The  desire  to 
breathe  consequently  arises,  the  performance  of  which  function  is 
the  design  of  nature  and  the  object  of  the  animal  in  the  instinct, 
although  of  its  further  ends  the  animal  is  quite  ignorant  (266). 
The  sensational  stimulus,  namely,  the  unpleasant  external  sen- 
sation, manifests  its  action  on  the  vital  movements  (which  are 
the  more  widely  influenced  in  proportion  as  it  is  excessive,  §  271) 
by  a  contra-natural  and  powerful  beating  of  the  heart  (276,  iv. 


CH.  III.]  RESPIRATORY  MOVEMENTS.  151 

252),  and  in  as  far  as  it  is  a  foreseeing  of  a  future  agreeable 
sensation  of  respiration,  causes  the  necessary  respiratory  movC' 
ments  imperfectly  (271).      The  instinct  itself  brings  forth  the 
^effort   of  the   animal- sentient   forces   to   produce   these   same 
imperfect  respiratory  movements  (272),  and  acts  consequently 
m  the   parts  subservient  to  respiration,   the   diaphragm,  the 
luscles,  &c.,  since  it  stimulates  these  to  their   natural  fiinc- 
ions,   and   which    the    satisfaction   of   the   instinct,    namely, 
ispiration  produces  perfectly  (208,  214).      The  result  is,  that 
this  instinct  the  mouth  is  opened,  the  muscles  exert  them- 
jlves  to  raise  the  ribs,  and  the  diaphragm  is  forced  downwards, 
)eing  evidently  the  movements  necessary  to  respiration,  which 
jontinue,  according  to  the  laws  of  the  actions  of  sensational 
instincts,   until   respiration    is   actually  restored   (257);    then 
there   results,    according  to  the   connection   of  the   physical, 
lechanical,  and  animal  forces  of  the  parts  subservient  to  re- 
spiration, further  actions  in  the  animal  economy,  namely,  the 
expansion  and  contraction  of  the  lungs,  the  determination  of 
the  circulation  of  the  blood,  the  cooling  of  the  blood,  perhaps 
the  transformation   of  the  chyle  into  blood,  and  many  other 
uses,   in  accordance   with   the   design   of  nature,   which  may 
be  learnt  in  detail  in  works  on  physiology.  {Vide  Haller,  §  8.) 
Since  in  the  natural  condition,  animals  are  able  to  satisfy  this 
instinct  volitionally  almost  instantaneously  after  birth,  it  does 
not  continue  so  long  a  mere  instinct  as  others,  and  probably 
this  is  the  sole  reason  why  respiration  has  not  been  hitherto 
recognised  as  the  sentient  action  of  an  instinct.      Haller  has 
fully  shown,  that  it  is  a  sentient  action,  {vide  §§  268,  273,  of 
that  great   man^s  ^  Physiology,'  for  a  lucid  explanation  of  the 
question;)  and  it  is  surprising,  that  his  doctrine  has  not  only 
been  opposed,  but  he  has  even  been  blamed  for  advancing  it. 

Other  questions  arising  out  of  this  subject  will  be  referred 
to  again  (526),  or  may  be  solved  by  the  principles  already 
stated.  Of  this  kind  are  the  questions,  whether  respiration  be 
not  at  first  and  in  the  newly-born  a  nerve-action,  or  whether 
it  be  not  rather  a  nerve  action  in  them  (269)  continued 
afterwards  by  the  co-operation  of  a  sentient  instinct  (183), 
resulting  from  the  habit  of  sensation  in  the  machines  (51);  or 
whether  it  is  not  so  little  mechanical,  that  at  each  retardation 
of   the   respiration   the   instinct   scarcely   induces   its    recom- 


152  ANIMAL-SENTIENT  FORCES.  [i. 

mencement^  but  it  is  regulated  by  sensational  and  intellectual 
volitions,  according  to  the  requirements  of  other  instincts, 
emotions,  intellectual  desires,  &c.,  into  laughing,  or  weeping, 
or  sighing,  speaking,  &c.  It  is  incontrovertible,  that  these, 
together  with  groaning,  sobbing,  cooing,  moaning,  screaming, 
coughing,  whistling,  sneezing,  and  all  other  changes  of  the 
respiratory  movements  which  are  caused  by  external  sensations 
or  obscure  complex  conceptions,  are  in  so  far  true  sentient 
actions  of  satisfied  instincts,  since  the  respiratory  actions  gene- 
rally belong  to  this  class. 

286.  It  is  manifest  from  the  considerations  already  advanced, 
that  there  are  two  classes  of  instincts ;  the  one  comprising 
those  in  which  the  acts  are  under  the  control  of  the  animal, 
so  that  they  can  be  induced  or  intermitted  at  will  (283^ — 285) ; 
the  other,  comprising  those  in  which  the  acts  are  the  purely 
corporeal  functions  of  the  mechanical  machines,  as  in  hunger 
and  thirst  (281,  282).  There  are  some  instincts  of  both  classes, 
however,  which  gradually  change  into  one  or  the  other  class. 
Thus,  at  first,  in  children  and  animals  the  unpleasant  external 
sensations  resulting  from  accumulation  in  the  bladder  and 
rectum,  and  which  bring  the  appropriate  instinct  into  opera- 
tion, are  relieved  in  a  natural  and  necessary  manner,  because 
the  sphincter  muscles  are  compelled  by  mere  physical  pressure 
to  permit  the  exit  of  accumulated  excretions ;  afterwards,  how- 
ever, this  takes  place  when  the  unpleasant  external  sensation 
is  again  felt,  by  a  voluntary  relaxation  of  the  sphincters.  In 
the  same  way,  the  first  respiratory  movement  in  a  newly-born 
animal  is  probably  the  natural  and  necessary  result  of  a  very 
obscure  external  sensation ;  but,  afterwards,  it  takes  place  by 
a  voluntary  movement  of  the  thorax  on  the  recurrence  of  the 
unpleasant  sensation  (285).  And,  on  the  contrary,  we  seek 
at  first  to  avoid  many  pains  and  other  unpleasant  external  sensa- 
tions by  voluntary  movements,  which  afterwards  become  purely 
automatic,  as,  for  example,  shouting,  writhing,  and  retracting 
when  in  pain;  the  quickened  walk  and  the  drawing  up  of  the  legs 
to  the  body  in  severe  cold ;  the  contraction  of  the  eyelids  in  a 
strong  light;  and  a  thousand  other  movements,  the  objects  of 
instincts,  formerly  volitional,  but  become  mechanical  from 
frequent  repetition.  Neither  can  we  infer  that  the  sentient 
actions  of  an  instinct  which,  in  us  or  in  another  animal,  are 


CH.  III.]  REPOSE  AND  EXHILARATION.  153 

volitional  movements,  must  have  been   such  formerly,  or  will 
be  for  the  future,  or  are  such  in  any  other  creature. 


The  Instinct  for  Repose  and  Exhilaration, 

287,  i.  The  animal-sentient  forces  are  exhausted  by  long 
activity,  and  the  destruction  of  the  animal  would  result  there- 
from if  nature  had  not  previously  provided  against  this  cause  of 
exhaustion.  When  the  animal-sentient  forces  (that  is  to  say, 
the  forces  of  the  material  ideas,  as  they  may  be  now  considered, 
in  so  far  as  they  cause  conceptions  or  sentient  actions,)  have 
been  uninterruptedly  used  by  the  animal  for  so  long  a  time 
that  any  further  effort  would  be  injurious,  it  feels  during 
thought  or  during  the  performance  of  the  sentient  actions  in 
the  body  an  unpleasant  difficulty,  which  has  been  termed  lassi- 
tude, weariness,  ov  fatigue  (280).  This  unpleasant  sensation  is 
the  natural  stimulus  of  the  instinct  for  repose  or  sleep,  which 
instinct  consists  in  an  effort  to  develop  the  contrary  to  this 
unpleasant  sensation,  that  is,  the  withdrawal  of  the  mind  from 
the  wearying  thoughts,  and  letting  the  animal-sentient  forces 
be  inactive,  so  as  to  experience  the  sweetness  of  repose,  and 
thereby  collect  new  forces,  as  is  the  design  of  the  Creator  in 
the  instinct  and  its  object  with  the  animal,  although  the  latter 
knows  nothing  of  the  actual  intent,  namely,  the  renewal  of  the 
strength  (266) .  Everything  which  causes  the  unpleasant  sensation 
of  lassitude  develops  the  sensational  stimulus  for  repose,  and  the 
instinct  itself,  the  longing  for  repose.  Causes  of  this  kind  are 
hardships,  every  long-continued  movement,  meditation,  and  all 
long-continued  thought,  attention,  reflection,  and  abstraction  {77) ; 
also  articles  of  food,  or  medicines,  which  interrupt  the  animal-sen- 
tient forces,  as  wine,  opium,  heavy  meals,  pressure  in  or  upon  the 
brain,  the  plethoric  state,  various  poisons,  and  numerous  others. 
The  sensational  stimulus,  namely,  the  disagreeable  external 
sensation  of  weariness,  manifests  its  sentient  action  in  the  car- 
diac and  respiratory  movements  (271),  which  are  at  first  languid 
almost  to  faintness ;  but  in  a  higher  degree  the  stimulus  becomes 
feverish,  and  these  actions  become  contra-natural  (276,  iv.  See 
also  Haller  ^  Physiology,^  §  580).  In  so  far  as  the  sensational 
stimulus  is  a  foreseeing  of  the  future  sweet  repose  (the  contrary 
to  the  disagreeable  feeling  of  lassitude),  it  manifests  its  sentient 


154  ANIMAL-SENTIENT  FORCES.  [i. 

actions  in  the  parts  appropriated  to  the  animal-sentient  forces, 
so  that  it  develops  imperfectly  the  future  state  of  repose  (271); 
and  in  fact,  in  the  straining  of  the  animal-sentient  forces  and 
the  effort  of  the  mind  to  withdraw  as  much  as  possible  from 
all  external  sensations,  and  spontaneous  conceptions,  and  thereby 
to  interrupt  all  their  sentient  actions  in  the  body,  consists  the 
sentient  actions  of  the  instinct  to  repose  itself  (272),  so  that 
the  organs  which  co-operate  in  the  act  of  thinking,  and  which 
produce  sentient  actions,  are  compelled  involuntarily,  by  the 
soul  and  by  a  purely  corporeal  process,  to  cease  their  functions 
(270,  49,  51).  Consequently,  during  the  instinct  to  repose  and 
sleep,  the  external  sensations  derived  from  external  impressions, 
and  from  the  spontaneous  conceptions  are  gradually  lost,  in 
consequence  of  the  enfeebling  of  their  material  ideas  in  the 
brain;  the  muscles,  in  so  far  as  they  perform  sentient  actions, 
move  heavily,  and  let  the  limbs  sink ;  the  eyelids  shut,  and  the 
whole  body  totters.  In  short,  the  instinct  induces  imperfectly 
that  condition  which  comes  on  when  the  instinct  is  satisfied  by 
rest  or  sleep,  and  there  results  from  the  connection  between 
the  physical,  mechanical,  and  animal  forces,  the  repose  and 
renewal  of  the  forces  appropriate  to  sentient  actions,  in  accord- 
ance with  the  object  of  nature  in  establishing  the  instinct  {vide 
Haller's  'Physiology,'  §§  578—590). 

ii.  Yawning  and  stretching  are  rather  sentient  actions  of  the 
instinct  for  exhilaration,  than  for  rest.  For  when  we  feel  the 
unpleasant  condition  of  languor  and  weariness,  we  can  attain 
its  opposite  by  new  efforts  of  the  animal-sentient  forces,  as  well 
as  by  their  periodical  relaxation  during  sleep.  If,  therefore,  the 
obscure  stimulus  leads  us  to  the  former,  we  then  express  the 
anticipated  condition  of  renewed  activity  of  the  animal-sentient 
forces,  by  imperfect  efforts,  to  which  the  agreeable  obscure 
foreseeing  of  the  condition  of  activity  excites  us.  Consequently, 
although  these  movements  are  doubtless  signs  of  weariness,  and 
of  the  need  for  sleep,  yet  they  are  not  sentient  actions  of  the 
instinct  for  sleep,  but  of  the  instinct  for  activity,  or  the  waking 
state.  All  circumstances  that  excite  the  obscure  foreseeing  of 
pleasing  exhilaration,  and,  consequently,  the  above-mentioned 
causes  of  weariness  render  the  instinct  active,  if  we  desire 
the  antagonistic  condition,  namely  exhilarated  activity.  Now, 
as  the  sight  of  another  person  who  yawns  or  stretches   him- 


CH.  III.]  SELF-DEFENCE.  155 

self,  reminds  us  of  this  condition  antagonistic  to  disagreeable 
weariness,  it  leads  us  to  the  instinct  for  exhilaration,  and  we 
stretch  and  yawn  with  the  person. 

iii.  It  still  remains  to  state  specially,  with  reference  to  the 
instinct  for  repose,  that  the  physical  and  mechanical  forces  of 
the  machines  of  animal  bodies,  as  also  the  vis  nervosa  on  which 
nerve- actions  are  dependent,  in  so  far  as  they  are  not  also 
at  the  same  time  sentient  actions,  are  not  subject  to  this  law 
of  nature,  namely,  that  their  uninterrupted  activity  shall  cause 
unpleasant  external  sensations,  and,  consequently,  induce  the 
stimuli  of  the  instinct  for  repose  and  sleep.  The  formation  of 
the  blood,  and  its  continuous  internal  movement,  together  with 
its  circulation ;  the  working  of  the  elasticity  and  other  purely 
physical  and  mechanical  forces  of  the  machines ;  nay,  all  those 
processes  of  the  mechanical  machines  which  during  the  waking 
state  are  sentient  actions,  but  at  the  same  time  may  be  and 
commonly  are,  even  during  the  waking  state,  purely  nerve- 
actions  (183),  as,  for  example,  the  movements  of  the  heart,  sto- 
mach, intestines,  and  various  muscles,  particularly  the  muscles 
of  respiration  (285),  all  these,  as  such,  are  never  accompanied 
by  a  sensation  of  fatigue,  never  excite  the  instinct  for  repose, 
never  stand  in  need  of  repose,  are  never  changed  by  this 
instinct,  nor  directly  by  its  satisfaction  during  the  deepest 
sleep,  but  go  on  continuously,  and  take  no  further  part  in  it 
unless  they  are  at  the  same  time  sentient  actions,  or  indirectly 
influenced  through  the  general  connection  of  all  the  forces  of 
the  animal  (Haller's  '^  Physiology,'  §  579).  On  these  principles, 
all  the  phenomena  of  the  animal  economy,  which  depend  upon 
the  sensational  stimulus  to  sleep,  on  the  instinct  itself,  and  on 
the  satisfaction  of  the  instinct,  or  the  act  of  sleeping,  may  be 
very  readily  explained. 

The  Instinct  of  Self-Defence. 

288.  Just  as  nature  has  supplied  every  animal  with  me- 
chanical machines  (organs),  which  serve  as  the  instruments  of 
the  instincts  for  self-preservation,  for  they  receive  both  the 
external  sensational  stimuli  that  excite  these  instincts  and  the 
external  sensations  that  satisfy  them  (281 — 285) ;  nay,  just  as 
every   creature  is  taught  and  enjoined  by   other  instincts  to 


156  ANIMAL-SENTIENT  FORCES.  [i. 

furnish  themselves  with  such  instruments  for  self-preservation 
as  spiders,  for  example,  which  weave  nets  to  take  their  food 
more  readily,  or  caterpillars,  which  spin  a  net  around  themselves 
for  the  purpose  of  undergoing  their  transformations  undisturbed, 
&c.,  so  also  she  has  fitted  out  every  animal  with  special  instru- 
ments (mechanical  machines)  for  the  other  instincts  of  self- 
defence  and  propagation  of  the  species,  which  are  partly 
adapted  to  receive  the  sensational  stimuli  that  excite  these 
instincts  and  partly  subservient  to  the  gratification  of  the 
instincts,  without  the  animal  knowing  their  objects,  or  tlie 
causes  of  the  movements  (266).  The  instruments  appropriated 
to  the  instinct  of  self-defence  (262)  are  termed  the  natural 
weapons  of  the  animal,  and  each  is  provided  with  particular 
kinds  of  weapons,  adapted  to  avert  its  greatest  and  most  pro- 
bable dangers,  and  appropriate  to  the  objects  of  nature  in  the 
satisfying  the  instinct  of  self-defence.  Thus,  the  soft  animals, 
which  are  easily  crushed,  are  surrounded  with  hard  shells ; 
those  which  are  appointed  to  be  pursued  and  eaten  by  other 
animals  possess  instruments  whereby  they  can  inflict  as 
much  injury  on  their  pursuers,  as  may  be  necessary  to 
check  the  pursuit ;  teeth  for  biting,  poisons,  stings,  talons  for 
wounding,  hoofs  for  striking,  claws  for  lacerating,  &c.  The 
animals  themselves  are  ignorant  that  they  possess  these  weapons, 
or,  at  least,  of  the  object  of  nature  in  furnishing  them  (266). 
They  do  not  make  use  of  them  with  a  deliberate  design,  but 
are  impelled  by  their  instinct  to  undertake  blindly  the  other- 
wise voluntary  movements  of  the  organs  which  are  furnished 
with  weapons,  whereby  these  become  subservient  to  self  defence 
without  the  knowledge  of  the  animal.  Consequently,  many 
animals,  when  they  find  themselves  in  danger,  make  such 
defensive  movements,  although  their  limbs  are  not  yet  supplied 
with  the  weapons,  or  have  lost  them,  and  although  the  weapons 
are  useless  against  such  dangers;  they  bite  at  a  stone,  they 
sting  at  the  air,  they  spurt  out  their  poison  without  knowing 
where,  they  strike  at  a  thorn-bush  or  a  wall,  they  even  scratch 
or  bite  themselves,  &c.  Now,  since  the  instincts  of  self-defence 
are  really  none  other  than  instincts  to  voluntary  movements 
manifested  in  armed  organs,  they  are  subject  to  the  same  laws 
as  that  class.    {Vide  §§  283,  284.) 


CH.  III.]        PROPAGATION  OF  THE  SPECIES.  157 


The  Instinct  for  the  Propagation  of  the  Species. 

289.  By  the  pre-ordination  of  nature  (263),  with  a  view  to 
the  continuation  of  the  species,  there  arises  in  animals  an 
agreeable  external  sensation,  the  sensational  stimulus  of  the 
instinct  for  propagation,  the  sentient  actions  of  which  are 
manifested  by  remarkably  active  vital  movements  (253, — 
Haller's  *  Physiology,^  §  870),  and  this  arises  at  a  time  when 
the  organism  is  in  the  most  suitable  state,  at  a  certain  age, 
during  a  fixed  period  of  existence,  for  the  most  part  periodically, 
in  the  sexual  organs  given  by  nature  for  this  express  object,  by 
means  of  natural  inducements  prepared  beforehand,  and  already 
described  (268,  874);  these  depend  on  a  plethoric  state,  nutri- 
tious food,  or  food  stimulating  the  nerves  of  the  sexual  organs, 
wine,  condiments,  much  rest,  idleness,  good  living,  freedom  from 
care,  and  various  external  sensations  and  other  conceptions.  In 
man,  who,  as  regards  his  instincts,  is  subject  to  the  same  laws 
as  brutes,  this  sensational  stimulus  is  induced  by  a  glance,  an 
imagination,  a  foreseeing,  which  surprises  him  without  his 
desire  or  even  against  it ;  and  he  terms  this  operation  which 
amazes  him,  this  wonderful  change  (263),  the  enchantment  of 
love.  He  is  so  little  informed  as  to  the  design  of  nature  in 
this  wondrous  emotion,  that  at  first  he  considers  it  to  be  the 
feeling  of  friendship  or  of  great  esteem,  in  short,  to  be  a  noble 
instinct,  not  arising  from  sensual  stimuli,  until  at  last  he  learns, 
from  its  influence  on  the  sexual  organs,  that  it  tends  to  an 
object  not  observed  by  him,  the  excitement  of  the  flesh  (88), 
and  that  it  is  the  instinct  for  sexual  congress,  to  which  all  the 
stimuli  converge.  In  both  sexes,  the  instinct  consists  in  the 
desire  to  enjoy  this  sensual  pleasure  in  the  greatest  degree  which 
takes  place  in  coitu.  Consequently,  just  as  sexual  congress  is 
the  design  of  nature  in  this  instinct  (265),  so  is  it  also  its  object 
in  animals,  which  know  nothing  more  of  the  ulterior  object, 
namely,  the  propagation  of  the  species  (266).  The  sentient 
actions  of  the  obscure  foreseeing  of  an  agreeable  external  sen- 
sation, are  manifested  imperfectly  as  they  actually  occur  (271), 
and  in  the  eff'ort  of  the  animal-sentient  forces  to  attain  to  these 
imperfect  movements  consist  the  sentient  actions  of  the  instinct 
itself.       The   instinct   acts,  consequently,  in   the   mechanical 


158  ANIMAL-SENTIENT  FORCES.  [i. 

machines  which  have  to  accomplish  sexual  congress,  namely, 
the  organs  of  generation,  since  it  stimulates  them  to  their  ap- 
propriate functions  (178-179),  and  in  particular  is  developed 
fully  the  satisfaction  of  the  instinct,  namely,  sexual  congress. 
Hence  we  understand  why  in  this  instinct  the  organs  of  gene- 
ration fall  into  the  same  state  as  in  coitus  (217),  that  state 
being  induced  according  to  the  laws  of  the  sentient  actions  of 
sensational  instincts.  These  incomplete  movements  becoming 
complete  in  the  satisfaction  of  this  instinct,  in  accordance  with 
the  designs  of  nature,  other  phenomena  having  reference  to  the 
propagation  of  the  species,  result,  as  impregnation,  conception, 
the  formation  and  nutrition  of  the  embryo,  and,  lastly,  its  birth, 
an  account  of  which  may  be  found  in  works  on  the  Physiology 
of  the  Special  Mechanism  of  Animal  Bodies.  (Haller's  '  Physio- 
logy,' 28th  Division.) 

The  Instinct  to  give  Suck, 

290.  The  instinct  to  suckle  is  one  of  the  most  remarkable 
of  the  instincts  of  parent  animals  for  their  offspring.  It  arises 
by  the  prevision  of  nature  in  the  maternal  animal,  which  gives 
suck  even  at  the  period  when  a  young  creature  is  about  to  be 
born,  and  in  consequence  of  an  unpleasant  external  sensation 
from  the  distension  of  the  mammse  with  milk,  which  is  the 
sensational  stimulus  of  the  instinct.  Everything  that  induces 
this  sensation  in  the  mammae,  excites  the  instinct  to  give  suck  ; 
so  that  bitches,  whose  mammse  swell  about  the  time  when  they 
ought  to  whelp,  have  the  instinct  fully  developed,  although  not 
in  pup  at  the  time,  and  willingly  allow  a  strange  dog  to  suckle 
them.  The  instinct  itself  is  a  strong  desire  to  attain  to  the 
sensation  contrary  to  that  of  painful  distension,  or  in  other 
words,  a  desire  to  empty  the  mammse,  which  is  the  design  of 
nature,  as  well  as  the  object  of  the  animal,  although  it  is  other- 
wise ignorant  to  what  end  the  suckiug  of  its  mammae  subserves. 
The  painful  sensational  stimulus  changes  the  vital  movements 
contra-naturally  (271,  276,  iv),  as  is  proved  by  the  great  un- 
easiness, and  by  the  milk  fever ;  and,  as  a  foreseeing  of  a  future 
agreeable  sensation  of  suckling,  manifests  its  sentient  actions 
in  such  a  way,  that  it  stimulates  the  mammae  to  similar  func- 
tions, and  partly  develops  them  according  to  the  laws  of  the 


CH.  III.]  SUCKLING.  159 

actions  of  sensational  instincts  (271-72,  277),  as  sentient 
actions  actually  requisite  to  suckling,  and  resulting  from  the 
completion  of  the  instinct ;  so  that,  for  example,  the  milk  fever, 
whereby  the  milk  is  produced,  supervenes,  and  the  nipples  are 
erected  (105,  247).  The  sentient  actions  of  the  instinct  itself 
consist  in  the  effort  of  the  animal-sentient  forces  to  attain 
these  same  imperfect  movements  (272),  and  through  these,  by 
means  of  the  connection  of  the  physical,  mechanical,  and  animal 
forces  of  the  organs  adapted  for  suckling,  the  further  operations 
in  the  animal  economy  are  attained,  as  the  emptying  of  the 
mammae,  a  more  free  circulation  in  them,  the  further  quiet 
secretion  of  good  milk  from  the  glands,  and  the  prevention  of 
induration  and  impaction,  all  in  accordance  with  the  design  of 
nature  in  the  instinct.  {Vide  Haller's  'Physiology,^  §  133.) 
It  is  obvious  from  common  experience,  how  this  instinct  is 
adapted  to  another  in  the  offspring,  namely,  the  instinct  to 
suck;  but  inasmuch  as  this  is  only  a  particular  form  of  the 
instinct  for  food  already  treated  of  at  length  (281-82)  it  is 
unnecessary  to  enter  here  into  detail. 

291.  It  would  be  equally  unnecessary  (and  perhaps  wearying) 
to  go  through  the  other  instincts  in  detail,  inasmuch  as  the 
preceding  explanations  and  principles  are  applicable  to  all. 
We  need  only  here  state  the  general  laws  by  which  the 
phenomena  must  be  explained,  which  the  sensational  instincts 
develop  in  the  animal  economy.  Whether  all  these  pheno- 
mena be  always  true  sentient  actions  from  sentient  instincts, 
or  always  such  in  all  animals,  or  whether  they  are  in  some 
degree,  or  altogether,  nerve-actions  (183),  as  has  been  often 
mentioned  (266,  269,  285),  all  these  questions  must  be  left 
undetermined,  until  we  come  to  the  Second  Part  of  the  work. 
It  is  sufficient  to  state  at  present,  that  the  phenomena  of  the 
instincts,  in  so  far  as  they  are  true  sentient  actions,  can  be  ex- 
plained on  no  other  principles  than  those  hitherto  laid  down. 
Nevertheless,  it  will  not  be  useless  to  prepare  the  reader  for  the 
doctrines  of  the  Second  Part  by  a  few  general  statements  and 
deductions. 

292.  It  is  indubitably  clear,  from  the  nature  of  the  instincts, 
that  the  true  sensational  instincts,  together  with  their  sentient 
actions,  result  naturally  and  necessarily  from  external  im- 
pressions, much  in  the  same  way  as  external  sensations  and 


160  ANIMAL-SENTIENT  FORCES.  [i. 

their  sentient  actions  arise  from  external  impressions,  trans- 
mitted to  the  brain  (266,  269;  281 — 290).  Although  they 
appear  to  be  actions  meditated  on,  and  willed  for  a  special 
object,  they  occur  without  any  other  aim  than  those  that  relate 
to  the  external  sensation  of  satisfaction  of  the  instinct,  there 
being  no  knowledge  of  the  inducements  or  incitants, — of  the 
ulterior  objects  of  the  instinct, — or  of  the  intention  of  nature. 
It  would  be  most  erroneous  to  infer,  that  the  skilfully  adapted 
actions  of  animal  instincts  are  the  operations  of  a  sensational 
uaderstanding  or  wisdom,  and  the  result  of  thought.  The 
animal  is  not  only  ignorant  of  the  inducements  of  its  instincts, 
but  they  act  in  spite  of  it.  The  obscure  sensational  stimuli 
of  the  instinct  spring  from  these  inducements,  also  without  the 
knowledge  or  preference  of  the  animal,  and  without  its  being 
able  to  reason  regarding  them  (264,  270).  From  these  stimuli 
the  instinct  results,  according  to  the  eternal  laws  of  the  con- 
ceptive  force  (81,  94),  naturally  and  necessarily,  since  no 
animal  can  prevent  itself  desiring  or  avoiding  sensationally 
that  which  has  once  become  unavoidably  pleasant  or  unpleasant 
(80,  81).  This  effort  of  the  mind  is  forcibly  directed  to 
the  attainment  of  the  satisfaction  of  the  instinct  without  a 
knowledge  of  the  means,  or,  at  least,  of  their  use  (266) ;  nature 
provides  them  for  the  animal,  and  brings  them  so  near  to  it, 
that  it  cannot  avoid  them;  consequently  it  cannot  suppress 
the  instinct,  or  avoid  its  gratification,  by  means  of  the  reason 
or  the  will,  as  man,  in  many  instances,  is  able  to  do.  Lastly, 
the  animal  enjoys  the  pleasing  external  sensation  accompanying 
the  gratification  of  the  instinct  blindly  and  quietly,  without  a 
knowledge  of  its  ulterior  objects,  and  without  troubling  itself 
in  the  least  about  them  (266).  Now,  since  all  this  applies  to 
the  sensational  instincts,  it  is  equally  applicable  to  their 
voluntary  movements  (283,  284),  and  consequently  it  is  also  a 
mistake  to  consider  these  as  the  result  of  reason  and  reflection. 
293.  But  this  is  not  all;  for  it  can  be  proved,  that  these 
various  instinctive  actions  are,  under  varying  circumstances, 
only  nerve-actions  (183,  269),  and  can  take  place  without  any 
external  sensations  or  conceptions  whatever,  as  will  be  demon- 
strated in  the  Second  Part  of  this  work  (see  §  561),  and  that 
it  is  consequently  an  error  to  conclude,  that  the  apparent 
care   of  animals   for   themselves   and   their   young,   the   wise 


i 


CH.  III.]  INSTINCTIVE  PASSIONS.  161 

use  of  means  to  these  ends,  &c.,  prove  the  existence  of  a  soul  in 
them. 

294.  The  instincts  of  self-preservation  and  of  the  propaga- 
tion of  the  species  are  common  to  all  animals,  and  there  are 
therefore  general  instincts,  as  the  love  of  life,  of  pleasure, — 
the  instinct  for  food,  for  sexual  congress,  &c.  There  are  also 
special  instincts,  which,  are  peculiar  to  certain  animals,  as 
the  instinct  to  breathe,  to  incubate,  to  take  care  of  offspring, 
&c. ;  these  are  regulated  in  their  development  by  the  special 
wants  of  the  animal,  and  hence  a  manifestation  in  instinct  of 
the  Godlike,  the  adapting.  An  animal,  for  example,  which  has 
not  to  seek  its  food  in  water,  has  no  instinct  and  no  adaptation 
for  swimming  :  the  animal,  whose  eggs  are  hatched  by  the  sun, 
has  no  instinct  for  incubation :  the  animal,  which  has  not  to 
seek  its  food  underground,  has  neither  the  instinct  to  dig,  nor 
the  claws  to  dig  with,  &c. 

295.  Every  instinct  excites  the  development  of  a  special  class 
of  conceptions,  which  constitute  the  object  and  satisfaction  of  the 
instinct,  and  are,  at  the  same  time,  either  in  accordance  with 
the  desires  of  nature  or  not  (263).  If  they  be  the  former, 
they  are  natural  instincts ;  if  the  latter,  unnatural  (90) ;  as  the 
instinct  for  self-torture,  for  suicide,  sodomy,  &c.  The  latter 
never  occur  in  animals  left  solely  to  nature,  and  only  in  those 
which  have  the  power  to  combine  them  with  volitional 
conceptions.  The  instinct  of  an  animal  for  that  class  of  con- 
ceptions which  are  most  common  to  it,  because  it  finds  the 
greatest  pleasure  in  them,  and  whereby  its  volitional  actions 
are  determined,  is  termed  its  leading  instinct ;  and  this  gives 
rise  to  the  peculiar  characteristics  of  the  animal,  or  its  animal 
or  sensational  character  [Character  seiner  sinnlichkeit] . 
According  as  the  instincts  are  vigorous  or  weak,  the  animal  is 
said  to  be  active,  vigorous,  &c.,  or  dull,  lazy,  inactive. 

The  Instinctive  Passions  [Affectentriebe] . 

296.  The  primary  passions  are  not  excited,  nor  their  satis- 
faction designedly  attained,  by  inducements  prepared  before- 
hand by  nature,  as  is  the  case  with  the  true  instincts  (263). 
We  are  affected  by  passions  for  the  most  part  incidentally, 
certainly  not  periodically,  nor  by  a  corporeal  compulsory  cause 

11 


162  ANIMAL-SENTIENT  FORCES.  [i. 

unknown  to  us^  but  volitionally^  and  with  the  consciousness  of 
the  sensational  impulses.  We  can  often  avoid  or  weaken  the 
sensational  stimuli  at  will^  so  as  to  prevent  the  passion ;  or,  on 
the  contrary,  seek  and  strengthen  them  so  as  to  excite  it. 
During  the  access  of  the  passions,  we  have  often  more  power 
than  in  the  instincts  to  increase  or  diminish  them  at  will,  and 
more  means  of  weakening  them  without  satisfying  them, 
because  we  know  their  objects.  An  angry  man  can  more 
readily  mitigate  his  passion  without  avenging  himself,  than  a 
hungry  man  can  quiet  his  instinct  without  taking  food.  A 
man  can  often  avoid  at  will  every  inducement  to  anger,  but 
hunger  arises  naturally  and  necessarily,  without  our  know- 
ledge, as  soon  as  its  cause  is  induced  in  the  stomach.  And 
here  it  must  be  observed,  that  the  passions  are  often  not  pri- 
mary, but  are  excited  in  us  by  sensational  instincts,  and  as 
these  are  in  close  relation  with  the  instincts,  they  may  be 
termed  instinctive  passions  (affectentriebe) . 

297.  The  main  difference  between  the  passions  and  instincts 
consists  in  this,  that  in  the  former  we  are  conscious  of  the 
sensational  excitants,  in  the  latter  we  are  unconscious  (90,91). 
The  secondary  conceptions  in  the  former  may  be  weakened  by 
abstraction,  or  antagonised,  or  rendered  more  vivid  at  will; 
whereas  in  the  instincts;  their  object  cannot  be  brought 
voluntarily  into  relation  with  the  secondary  conceptions,  since 
the  object  is  unknown  (273,  304). 

298.  When  in  the  course  of  an  instinct  in  an  animal  capable 
of  pure  conceptions,  the  obscure  sensational  stimulus  is  com- 
prehended, although  it  is  still  sensational  and  confused,  a 
passion  is  excited  in  and  by  the  instinct,  or  an  instinctive 
passion  (90,  91).  The  instinctive  passions  are  at  first  instincts, 
which  become  passions  during  their  continuance.  Conse- 
quently they  arise  from  the  natural  excitants  of  the  instinct, 
and  manifest  like  them  the  Wonderful  (263) ;  but  with  this 
difference,  that  during  their  continuance  the  sensational  volition 
of  the  animal  is  combined  with  the  natural  impulse  to  obtain 
the  satisfaction  of  the  instinct :  thus  a  voluntary  power  over  it 
is  attained.  We  will  consider  briefly  the  more  prominent 
instinctive  passions  from  this  point  of  view. 

299.  Animals  are  impelled  by  nature  to  a  love  of  life, 
without   knowing  why;    they   are   blindly  led  to    abhor  the 


CH.  III.]  INSTINCTIVE  PASSIONS.  163 

danger  of  destruction.  Nature^  without  their  aid,  has  prepared 
beforehand  for  them  the  means  of  defending  their  life  without 
any  knowledge  of  the  object  to  be  attained  (285,  266,  280). 
But  when  they  become  conscious  of  the  object  of  their  aver- 
sion, namely,  the  danger  of  death,  the  designs  of  nature 
hitherto  blindly  followed  become  their  own,  and  nature  and 
the  sensational  volition  of  the  animal  co-operate  to  attain  the 
same  object,  so  that  the  sentient  actions  now  result  as  well 
from  the  sensational  inclination  of  the  animal,  as  naturally  and 
necessarily  from  the  instinct.  Yet,  although  the  animal  still 
follows  the  impulse  of  nature,  it  follows  it  willingly,  since 
from  a  consciousness  of  the  abject  of  the  blind  instinct  of  life, 
the  latter  is  changed  into  an  instinctive  emotion,  the  fear  of 
\death.  It  is  led  by  this  knowledge  to  a  sensational  volition, 
whereby  it  brings  other  conceptions,  desires,  instincts,  and 
emotions,  which  arise  from  it,  according  to  the  laws  of  the 
conceptive  force  (273),  to  bear  on  the  object  now  known,  so 
as  to  obtain  the  fulfilment  of  the  instinct.  It  is  thus  we 
understand  the  differences  between  passions  and  instincts.  In 
the  primary  passions,  the  natural  impulse  which  characterises 
the  instinct  is  not  present  (263)  :  in  pure  instincts,  the  voli- 
tional element  is  wanting :  in  the  instinctive  passions  (or 
emotional  instincts),  both  are  united. 

300.  In  the  instincts  of  hunger  and  thirst,  animals  eat  and 
drink  before  they  can  know  that  food  and  drink  induce  that 
pleasant  external  sensation,  which  constitutes  the  satisfaction 
of  the  instinct.  But  if  the  animal  become  conscious  of  the 
object  of  the  instinct,  the  volitional  element  is  added,  and  the 
blind  impulse  of  nature  co-operates  with  the  inclination  of  the 
animal  to  attain  it.  The  blind  instinct  is  become  the  volitional 
instinct  for  food,  the  appetite,  gluttony,  longing  for  drinks. 
The  perception  of  the  object  leads  to  a  sensational  volition, 
and  thus  other  conceptions,  desires,  instincts,  and  passions  are 
brought  to  bear  on  its  attainment,  and  the  volitional  actions  of 
voracity  and  rapacity  are  manifested. 

301 .  The  war-instinct,  a  form  of  the  instinct  of  self-defence, 
stimulates  animals  to  the  blind  use  of  the  natural  weapons 
which  nature  has  supplied,  together  with  skill  to  use  them. 
They  know  nothing  of  the  object  (the  injury  of  another)  to 
be   gained   by  their  use,   so  that  they  perform   the   requisite 


164  ANIMAL-SENTIENT  FORCES.  [i. 

movements  before  they  actually  possess  the  weapons  (288, 
266,  269).  But  if  a  knowledge  of  the  object  of  the  in- 
stinct be  added,  namely,  an  infliction  of  an  injury  upon 
another,  the  volitional  element  is  added,  so  that  the  will  and 
the  impulse  of  nature  co-operate  for  the  attainment  of  the 
same  object,  and  the  blind  instinct  becomes  the  instinctive 
passion  of  self-defence.  A  sensational  volition  follows  this 
perception  of  the  object  of  the  instinct,  and  other  conceptions, 
desires  and  passions  are  brought  to  bear  on  its  attainment, 
whereby  the  volitional  actions  of  the  desire  of  revenge  are  mani- 
fested in  the  skilful  and  revengeful  use  of  the  natural  weapons, 
as,  for  example,  in  selecting  the  most  dangerous  point  to 
inflict  injury,  in  the  most  crafty  and  violent  infliction  of  it,  &c., 
and  in  discriminating  the  objects  which  should  be  feared  and 
avoided,  or  pursued  and  seized. 

Anger  [Zorn]  is  always  a  passion,  and  never  an  emotional 
instinct,  because  it  consists  in  an  abhorrence  of  a  known 
injury,  of  which  consequently  we  are  conscious.  Animals 
that  possess  no  pure  conceptions,  and  are  incapable  of  primary 
passions,  never  experience  it ;  nor  is  it  even  an  emotional 
instinct  in  them,  as  the  desire  of  revenge  is  [Rachgier],  but  a 
passion  subordinate  to  the  latter,  developed  by  the  instinct  of 
self-defence.  Anger  can  excite  the  desire  of  revenge  as  a 
subordinate  passion,  and  then  the  latter  is  not  an  emotional 
instinct,  but  a  passion  combined  with  another  passion,  namely, 
anger.  The  special  sentient  action  of  anger  on  the  liver,  &c., 
will  be  considered  subsequently  (see  §  325). 

302.  In  the  sexual  instinct,  as  in  the  preceding,  nature 
impels  animals  to  the  blind  use  of  the  organs  with  which  she 
has  supplied  them,  as  well  as  with  the  knowledge  how  to  use 
them ;  without  their  being  aware  that  they  will  thereby  pro- 
pagate the  species.  It  would  appear,  indeed,  that  no  animal, 
except  man,  is  aware  of  this  object.  But  even  the  immediate 
object  of  nature  in  the  instinct,  namely,  pleasure,  is  unknown 
to  many  animals,  so  that  they  are  stimulated  solely  by  the 
blind  instinct  to  the  use  of  the  organs  of  generation  (269). 
But  when  an  animal  is  conscious  of  this  immediate  object  of 
the  instinct,  namely,  pleasure  in  sexual  congress,  the  blind 
instinct  is  combined  in  its  action  with  the  sensational  will  of 
the  animal,  and  becomes  the  instinctive  passion   of  physical 


CH.  III.]  INSTINCTIVE  PASSIONS.  165 

love  (not  the  passion  of  love,  §  308).  Other  conceptions, 
desiresj  instincts,  and  passions,  are  brought  to  bear  upon  the 
object  by  the  sensational  volition  of  the  animal,  so  that  the 
fulfilment  of  the  instinct  may  be  attained.  Thus  the  volitional 
actions  of  lasciviousness,  jealousy,  amorous  enticements,  as  well 
as  the  discrimination  of  the  beloved  object  and  its  sensational 
selection  from  all  others,  are  to  be  explained.  As  a  pure 
instinct,  there  is  no  knowledge  of  its  object  and  intent;  so 
that,  even  man,  so  long  as  it  does  not  attain  to  be  an  in- 
stinctive passion,  does  not  know  how  to  investigate  the  origin  of 
his  enchantment  and  mental  disorder  (263).  He  never  imagines, 
that  the  final  object  of  the  strange  disquiet  which  thrills 
through  his  whole  frame  is  sexual  congress;  and  amidst  the 
effort,  he  literally  does  not  know  what  he  wishes,  until  the 
blind  instinct  becomes  an  emotional  instinct,  and  opens  his 
eyes  (289).  If  amorousness  were  a  primary  passion,  it  would 
not  be  accompanied  by  the  natural  impulse;  it  would  be  a 
sensational  desire  for  sexual  congress  more  gentle  and  more 
volitional,  never  found  in  animals,  although  sometimes  in  man. 

303.  The  maternal  instinct  is  usually  excited  blindly  and 
naturally.  The  parent  animal  knows  neither  why  she  broods, 
nor  what  she  hatches  or  gives  birth  to.  She  tends,  allures, 
covers,  nourishes,  and  protects  her  young,  blindly :  nay,  will 
perform  these  offices  for  young  animals  she  has  never  known 
before,  and  which  require  attentions  entirely  different  from 
those  she  affords,  consequently,  without  any  knowledge  of  the 
objects  or  aims  of  the  instinct.  When,  however,  an  animal 
becomes  conscious  of  these,  the  volition  co-operates  with  the 
impulse  of  the  instinct,  and  we  have  the  emotional  instinct  of 
love  of  offspring.  This  consciousness  induces  acts  of  sen- 
sational volition,  whereby  other  conceptions,  desires,  instincts, 
and  passions  are  directed  towards  the  attainment  of  the  objects 
of  the  instinct,  and  thus  the  various  actions  connected  with  the 
care  of  the  young  are  developed. 

304.  But  although  in  the  instinctive  passions  or  emotional 
instincts,  animals  readily  perform,  by  acts  of  sensational  will, 
that  which  nature  works  in  them,  naturally  and  necessarily, 
by  means  of  the  instinct,  and  whether  they  will  co-operate  or 
not ;  still,  as  is  to  be  shown  subsequently  (348),  the  mind  has 
not  only  no  command  over  the  conceptions  and  desires  which  it 


166  ANIMAL^SENTIENT  FORCES.  [i. 

directs  by  sensational  volitions  towards  the  objects  of  the 
instinct,  but  it  is  prevented  applying  them  in  any  other  way 
than  in  advancing  the  sensational  pleasure,  and  in  attaining 
the  object  of  the  instinct,  by  the  general  instinct  for  enjoyment 
(280),  by  the  power  of  the  spell  of  the  instinct  (263),  and  by 
the  close  dependence  of  all  complex  sensational  desires  and 
aversions,  particularly  of  the  emotional  instincts  (298),  upon 
the  sensational  faculty  (Sinnlichkeit)  (89).  By  these  views  we 
can  explain,  why  all  animals,  endowed  though  they  be  with 
sensational  volition  and  with  free-will,  when  in  circumstances  to 
encourage,  excite,  increase,  or  ennoble  certain  morally  good 
emotional  instincts,  or  to  avoid,  repress,  diminish,  or  counteract 
the  morally  evil,  have  a  natural  infirmity  to  lean  to  the  side  of 
instinct,  and  not  to  deduce  from  its  morality  any  motives  for 
their  voluntary  conduct. 


Actions  of  the  Passions  through  the   Nerves  in   the 
Mechanical  Machines. 

305.  The  primary  passions  arise  from  pure  but  still  con- 
fused sensational  stimuli,  of  which  we  are  conscious,  and  not 
from  instincts  (91).  They  are  free  from  the  powerful  impulse 
of  the  latter,  or,  at  least,  more  free  than  the  emotional  instincts  ; 
and  constitute,  therefore,  an  entirely  different  class  of  desires, 
more  volitional,  and  less  under  the  control  of  the  sensational 
faculty,  although  always  sensational,  and  only  half  spontaneous 
conceptions  (27,  66,  89).  The  direct  sentient  actions  of  these 
desires,  and  their  general  laws,  have  been  already  laid  down 
(255,  261).  The  incidental  are  in  all  respects  analogous  to 
the  incidental  conceptions  in  the  instincts,  and  subject  to 
the  same  laws  (273).  The  desires  and  subordinate  conceptions, 
which  are  spontaneous,  volitional,  and  incidental,  influence  the 
passions  more,  either  in  strengthening  or  restraining  them, 
according  to  the  pleasure  of  the  animal,  although  they  seldom 
act  in  any  other  way  than  that  most  favorable  to  the  instinct 
of  self-love  (304).  It  is,  therefore,  only  necessary  here,  to 
distinguish  the  sentient  actions  peculiar  to  each  passion ;  and 
we  will  limit  our  inquiry  to  the  principal  of  them. 

306.  Every  agreeable  passion  {joy^  §  259),  is  a  strong  desire 
arising  from  confused  sensational  incitements  (91,  94),  developed 


€ 


H.  III.]     ACTIONS  OF  THE   JOYOUS   PASSIONS.         167 


cording  to  the  general  laws  of  the  passions.  It  must  be 
distinguished  from  the  instinct  for  enjoyment  (380),  in  which 
the  object  of  the  pleasure  is  neither  known  nor  distin- 
guished (262),  while  in  every  kind  of  joy  the  animal  is  con- 
scious of  the  object,  although  imperfectly.  In  joyousness, 
there  is  a  future  agreeable  thing  anticipated  from  the  pre- 
sent, in  contentment^  from  the  past,  in  hope,  from  the  future, 
(Baumgarten's  'Metaphysics,'  §  505  :)  and  since,  consequently, 
the  various  species  of  joy  do  not  arise  out  of  instincts  (262), 
they  are  never  instinctive  passions.  Their  sentient  actions  are 
compounded  of  those  of  a  sensational  pleasure  and  a  confused 
sensational  foreseeing  (257,  258).  Joy  for  honour  is  termed 
ambition ;  for  the  perfections  of  another,  love  (the  passion) ; 
in  the  various  relations  of  the  beloved  to  the  loved,  grati- 
tude, compassion,  kindness,  benevolence,  &c.  (Baumgarten's 
*  Metaphysics/  §  506.) 

307.  In  as  far  as  every  kind  of  joyous  passion  is  pleasure, 
their  sentient  actions  act  upon  the  vital  movements  beneficially 
for  the  health  (259).  They  excite  the  circulation,  and  further 
all  the  natural  functions  and  secretions,  especially  that  of 
insensible  transpiration,  and  give  a  sensation  of  lightness  of  the 
body  :  the  last  is  more  particularly  felt  in  joy,  contentment, 
and  hope.  If  violent,  however,  they  act  contra-naturally  (259), 
so  that  great  and  sudden  joy  renders  the  transpiration  ex- 
cessive, or  the  heart  acts  too  violently,  and  so  brings  on  an 
apopletic  fit,  or  causes  paralysis  of  the  heart  by  excessive 
distension,  and  sudden  death  is  induced.  The  gentle  calm 
feelings  of  satisfaction  and  contentment,  maintained  continu- 
ously and  equally,  and  the  practice  of  the  gentler  virtues, 
conduce,  consequently,  to  health  and  long  life,  more  than  vio- 
lent emotions  of  joy  and  happiness  (252).  Nevertheless,  various 
diseases  of  the  body,  dependent  upon  contra-natural  changes,  or 
upon  enfeebled  vital  movements,  maybe  cured  by  joyous  emotion. 

The  sentient  actions  of  joyous  emotions,  which  result  from  the 
foreseeing  of  their  object,  imperfectly  express  the  condition  of 
their  satisfaction  (257),  and  are  for  the  most  part  volitional 
movements,  such  as  dancing,  leaping,  laughing,  singing,  speak- 
ing, and  similar  actions  which  accompany  the  actual  enjoyment 
of  a  vivid  sensational  pleasure,  and  the  secondary  conceptions 
and  desires  thereby  excited.      These  volitional  movements  are 


168  ANIMAL-SENTIENT  FORCES.  [i. 

excited  in  the  emotions  and  instincts  in  a  similar  manner 
{vide  §  283 — 5).  Everythiug  that  excites  a  vivid  sensational 
pleasure  can  induce  the  joyous  emotions,  as  wine,  music, 
society,  jests,  the  gratification  of  other  desires,  stimulating 
sensations,  imaginations,  foreseeings,  &c. 

308.  Every  form  of  the  emotion  of  love,  as  kindness,  friend- 
ship, gratitude,  pity,  and  the  benevolent  virtues,  are  a  species 
of  gentle  joy  for  the  perfection  of  another  (306),  and  manifest 
the  sentient  actions  of  the  joyous  emotions  in  a  moderate 
degree.  Inasmuch  as  these  are  very  favorable  to  health  and 
long  life  (307),  it  is  a  truth  established  by  experience,  that  a 
misanthropic  or  malicious  person  is  his  own  enemy,  and  that 
goodness  is  its  own  reward.  These  nobler  passions  must  not  be 
confounded,  however,  with  the  instincts  or  the  instinctive 
emotions  of  love,  for  they  arise  primarily  from  pure  perceptions 
(91),  and  have  sensational  stimuli  and  objects  of  satisfaction, 
altogether  difi*erent  from  those  of  the  latter.  Every  kind  of 
perfection  which  we  observe  in  another  can  excite  in  us  the 
passion  of  love,  while  there  is  only  one  sensational  stimulus  of 
the  instinctive  passion  of  love, 

309.  Every  painful  emotion  {distress,  §  259),  is  a  strong 
abhorrence  excited  by  confused  sensational  impulses  (91), 
developed  according  to  the  general  laws  of  the  passions  (94), 
and  consequently  belonging  neither  to  the  class  of  instincts  or 
of  instinctive  emotions.  Their  mental  actions  are  made  up  of 
those  of  a  sensational  annoyance  and  a  sensational  confused 
foreseeing  (257-— 8).  Distress  for  the  past,  in  reference  to 
future  consequences,  is  regret ;  for  the  present  in  reference  to 
the  future,  is  grief;  and  for  the  future  itself,  is  anxiety, 
care,  dread,  despair.  To  this  class  belong  also  the  passion 
excited  by  the  delay  of  what  is  longed  for,  longing  ;  or  by  the 
imperfection  of  another,  sympathy;  or  by  contempt  inflicted 
or  anticipated,  shame  ;  or  by  the  perfection  of  another,  hatred ; 
or  by  a  coveted  perfection,  envy ;  or  by  an  offence,  anger ; 

i  or  by  the  desire  to  retaliate  on  the  off'ender,  revenge;  or, 
I  lastly,  by  a  sudden,  unexpected,  and  great  evil,  terror 
\  (Baumgarten's  'Metaphysics,'   §§  507,  508).     Each  of  these 

passions  have  their  peculiar  sentient  actions   in  the   animal 

economy. 

310.  The   sentient  actions   of   the  distressing   passions  in 


CH.  III.]       ACTIONS  OF  THE  PAINFUL  PASSIONS.      169 

general,  and  of  sorrow  in  particular,  are  vital  movements 
antagonistic  to  the  natural  movements,  in  so  far  as  they  depend 
upon  a  sensational  annoyance  (259).  The  blood  is  retained 
and  accumulates  in  the  lungs,  as  is  shown  by  sighing,  prse- 
cordial  anxiety,  pallor  of  the  face,  small  pulse,  and  coldness  of 
the  extremities.  Does  this  congestion  take  place  in  consequence 
of  feebleness  of  the  heart  ?  or  is  it  over  dilated  at  each  stroke, 
and  contracts  again  too  feebly?  or  does  it  beat  irregularly,  not 
expelHng  a  mass  of  blood  equal  to  that  which  it  receives  ?  The 
latter  is  the  more  probable  state,  since  in  no  true  passion  are 
those  movements  which  constitute  its  direct  sentient  actions, 
weaker  than  in  health,  but  stronger  (94),  although  in  the 
distressing  class  they  are  tumultuous  and  contra-natural  (209). 
This  is  the  more  manifest,  when  the  passion  of  sorrow  is 
distinguished  from  that  condition  of  the  mind,  in  which  there 
are  unpleasant  conceptions  without  a  full  development  of  the 
instincts  or  emotions, — and  termed  a  sorrowful,  low-spirited, 
melancholic  state  of  mind,  for  in  this,  the  continued  annoyance 
can  debilitate  the  vital  movements  (254,  261,  iii).  To  this  class 
belongs  a  continued  state  of  secret  anxiety,  sorrow,  carking 
care,  jealousy,  hatred,  envy,  &c.,  which  consists  in  a  continued 
state  of  suffering,  seldom  or  never  attaining  the  force  of  an 
instinct  or  passion,  and  in  which  the  vital  movements  are 
obviously  rendered  weaker.  But  in  a  true  passion  of  the 
distressing  class,  the  movements  do  not  indicate  debility ;  but, 
on  the  contrary,  the  restlessness,  the  loud  cries,  the  wringing 
of  the  hands,  the  tearing  of  the  hair,  &c.,  indicate  increased 
activity. 

311.  The  disturbance  of  the  hearths  action,  in  sorrow  and 
in  all  the  painful  passions,  leads  to  disturbance  of  all  the 
functions  of  the  body,  and,  as  experience  teaches,  to  disease 
and  death.  If  these  emotions  or  passions  remove  or  alleviate 
many  diseases,  it  is  only  by  their  direct  sentient  actions,  or  by 
those  of  the  secondary  conceptions  (259). 

312.  Those  sentient  actions  of  regret,  that  depend  upon  the 
foreseeing  of  its  object,  and  which  imperfectly  express  its  fulfil- 
ment (257),  are  closely  accompanied  by  those  of  an  imagination, 
since  the  emotion  is  felt  for  some  thing  passed  (309,  67),  and 
this  imagination  is  often  so  vivid,  that  it  becomes  an  imperfect 
sensation  (148).     Thus  it  is  that  the  form  of  a  beloved  indi- 


170  ANIMAL-SENTIENT  FORCES.  [i. 

vidual  deceased  still  hovers  around  the  mourner,  and  seems 
to  accompany  him  everywhere,  while  the  latter  acts  accordingly, 
addressing  and  embracing  the  shadowy  form.  As  foreseeings 
do  not  readily  become  so  vivid,  this  circumstance  takes  place 
more  frequently  in  passions  having  reference  to  the  past  rather 
than  to  the  future.  But  still  it  may  be  observed  in  the  latter 
class,  by  a  careful  analysis.  When,  for  example,  we  are  in 
sorrow,  from  the  expectation  of  bad  news  respecting  a  dear 
friend  separated  from  us,  and  the  sentient  actions  of  sorrow 
are  excited,  those  of  an  expectation  (foreseeing)  of  dreadful 
news  respecting  him  are  distinctly  connected  with  the  sentient 
actions  of  a  recollection  of  the  affectionate  parting  from  him, 
and  of  his  last  proceedings,  so  that  we  remember  his  farewell, 
his  tears,  his  gestures,  while,  at  the  same  time,  the  expectation 
of  evil  tidings  causes  us  to  feel  all  the  workings  of  a  dismaying 
fear. 

313.  Grief,  care,  fear,  anxiety,  despair,  are  distressing  pas- 
sions, of  whose  causes  we  are  conscious  (309),  whereby  they 
are  distinguished  as  well  from  instincts,  as  from  the  instinctive 
emotions  (263 — 5,  296 — 8).  They  follow  the  laws  of  other 
passions  in  every  respect,  and,  for  the  most  part,  differ  from 
each  other  in  degree  only. 

314.  These  emotions  of  grief,  and  every  kind  of  fear,  cer- 
tainly exhibit  the  sentient  actions  of  a  sensational  suffering  in 
common  with  every  kind  of  afflictive  emotion  (309,  313),  but 
the  close  observer  will  mark  differences  in  each  (254).  The 
pulse  is  altered,  is  less  full  than  usual,  tremulous,  and  varying 
in  frequency  and  force;  there  is  a  feeling  of  constriction  of 
the  chest  from  congestion,  paleness  of  the  face,  cold  extremi- 
ties, corrugated  skin,  and  the  sense  of  constriction  of  the  chest 
often  ends  in  syncope,  and  even  death,  as  historical  details 
show.  All  these  are  the  sentient  actions  of  the  vital  move- 
ments contra-naturally  altered  by  the  sensational  suffering 
(259),  because,  probably,  an  irregular  influence  of  the  vital 
spirits  on  the  nerves  of  the  heart  renders  its  movements  at 
one  time,  excessive,  at  another  enfeebles  them  even  to  syncope, 
whence  various  secondary  phenomena  result  [vide  §§310,  311). 
It  is  in  consequence  of  these  results,  and  especially  the  repres- 
sion of  an  injurious  humour,  in  consequence  of  the  suppression 
of  the  cutaneous  functions,  that  fear,  grief,  and  all  the  depressing 


ill.  III.]    ACTIONS  OF  THE  DISTRESSING  PASSIONS.    171 

passions  are   so   dangerous,   when  the  plague  and  contagious 
diseases  are  prevalent. 

315.  The  sentient  actions  which  accompany  a  foreseeing 
in  these  passions,  and  whereby  they  are  the  most  distinctly 
distinguished  from  all  other  kind  of  distress,  exhibit  imperfectly 
that  state  of  the  body  which  would  arise  during  the  fulfilment 
of  the  foreseeing  (257).  A  timid  person  abhors  most  strongly 
that  condition  which  he  foresees ;  hence  a  secondary  instinct 
is  usually  conjoined  with  the  passion,  namely,  that  of  self- 
preservation  (288),  the  sentient  actions  of  which  are  combined 
with  those  of  the  foreseeing  (241,  273).  These  subordinate 
instincts  of  self-preservation  or  defence,  accompany  all  kinds 
of  fear,  and  excite  the  corresponding  volitional  actions,  ac- 
cording to  the  laws  of  instinct,  as  running,  shouting,  seizing, 
&c.,  only  they  are  specially  directed  to  an  object  by  the  fore- 
seeing itself.  Thus,  when  a  person  fears  he  will  perish  by  the 
fall  of  a  house,  he  runs  away  in  virtue  of  the  instinct  of  self- 
preservation,  but  with  his  head  bent  down,  or  his  hands  lifted 
over  it,  induced  to  act  thus  by  the  foreseeing  of  the  evil,  exactly 
as  he  would  do  if  the  house  were  falling  upon  him.  In  the 
same  way  he  would  cover  the  heart  if  he  feared  being  run 
through  with  a  sword. 

316.  Certain  phenomena  result  from  all  the  sentient  actions 
of  these  passions  combined,  which  specially  characterise  them, 
although  only  effected  by  the  connection  of  all  other  forces  of 
the  body  with  the  animal  sentient  forces,  and  are  to  be  con- 
sidered, not  as  direct  actions  of  the  passions,  but  as  purely 
physical,  mechanical,  or  animal  movements  caused  thereby. 
Thus  all  kinds  of  fear  have  this  peculiarity,  that  they  cause 
the  bowels  to  be  moved ;  that  they  contract  the  skin,  causing 
the  phenomenon  of  shuddering ;  and  that  they  induce  a  peculiar 
contortion  (ausschlag)  of  the  mouth ;  fear,  like  grief,  will  also 
soon  turn  the  hair  gray.  Alexander  Drummond  attributes  the 
change  of  colour  in  the  chameleon  to  its  remarkable  timidity. 

317.  Everything  that  can  excite  a  strong  sensational  un- 
pleasant feeling  respecting  present  or  future  circumstances, 
favours  grief  and  all  kinds  of  fear.  The  mind  can  be  thus 
injured  by  education,  particularly  by  ghost-stories,  which  terrify 
children.  All  causes  of  low  spirits  render  the  mind  disposed 
to    grief   or    fear.      The   sensations,    and    other    conceptions. 


172  ANIMAL-SENTIENT  FORCES,  [i. 

instincts,  and  passions,  which  excite  this  kind  of  unpleasant 
feeling,  naturally  induce  a  disposition  to  sorrow,  grief,  and  fear, 
while  the  contrary  prevent  them.  Similar  results  follow  from 
habits  of  life,  diseases,  and  other  circumstances  that  injure  the 
health,  and  cause  the  same  sensations  as  the  depressing 
emotions. 

318.  Terror  is  a  violent  emotion  analogous  to  fear,  but 
much  more  intense  and  sudden.  For  this  reason,  it  is  one  of 
the  most  dangerous  to  life  (359).  The  action  of  the  heart  is 
so  rapidly  and  contra-naturally  affected,  that  diseases  of  the  vital 
forces  are  thereby  instantaneously  produced,  which  not  unfre- 
quently  induce  immediate  death.  The  pulse  is  not  continu- 
ously full,  but  remarkably  quick,  consequently  the  hearths  action 
is  very  irregular,  and  sometimes  the  contractions  become  so 
convulsive  and  violent,  that  the  arteries  burst ;  there  is  great 
dyspnoea ;  the  complexion  is  deathly ;  the  extremities  cold ; 
and  there  are  often  dangerous  fain  tings,  and  even  instant 
death.  The  other  phenomena  are  analogous  to  those  produced 
by  fear  (314). 

319.  The  actions  arising  from  a  foreseeing  in  terror,  are 
similar  to  those  of  fear,  and  are  developed  in  the  same  way 
(compare  §  315). 

320.  The  special  actions  produced  in  the  animal  economy 
by  the  direct  actions  of  terror,  are  in  some  respects  similar  to 
those  of  fear  (316),  although  with  many  there  is  an  opposite 
condition,  namely,  spasmodic  closure  of  the  sphincters  of  the 
rectum,  bladder,  &c.,  arising  probably  from  the  peculiar  in- 
fluence of  terror  on  the  muscular  system,  its  effect  being  to 
excite  spasms  and  convulsions  (Haller^s  'Physiology,^  §  565). 
On  the  other  hand,  terror  does  not  turn  the  hair  gray,  like 
grief  and  fear. 

321 .  Whatever  excites  fear,  predisposes  to  terror  :  whatever 
prevents  the  one,  prevents  the  other  (309,  317).  The  habitua- 
tion of  youth  to  endure  adversity ;  that  habitual  lightness  of 
spirit,  which  meets  great  evils  courageously ;  the  steady  fortitude 
which  anticipates  the  distressing  strokes  of  fortune ;  and  the 
happy  deception  whereby  an  impending  danger  is  made  to 
appear  yet  distant ; — these  are  the  true  means,  by  which  many 
may  be  preserved  from  terror,  or  at  least  from  a  timid  temper. 
Instead  of  terrific   stories,  the  history  of  heroic   deeds  should 


CH.  III.]  ACTIONS  OF  THE  DISTRESSING  PASSIONS.    173 

occupy  tlie  memory ;   cheerful  society,  travelling,  excitement, 
wine,  &c.,  are  all  beneficial. 

322.  Anger  and  revenge,  are  depressing  passions,  we  being 
undoubtedly  conscious  of  their  stimuli ;  they  are  therefore  to 
be  distinguished  from  the  general  instinct  of  self-defence,  and 
from  the  war-instinct  in  particular  (309,  301).  They  are 
developed  according  to  the  general  laws  previously  stated 
(94),  and  their  sentient  actions  are  composed  of  those  of  a 
sensational  unpleasant  feeling,  and  of  a  sensational  confused 
foreseeing  (257,  258). 

323.  The  actions  of  suffering  [Unlust]  in  these,  as  in 
all  the  depressing  passions,  are  contra-natural  and  violent 
(259)  ;  but  they  differ  generally  in  this,  that  they  attain  a 
greater  degree  of  intensity,  while  the  action  of  the  heart 
differs  from  that  of  anxiety  and  terror,  in  being  characterised 
by  a  continuous  frequency  and  violence  of  movement.  In 
anger  and  revenge,  the  blood  is  impelled  into  the  smallest 
capillaries,  so  that  those  which  seldom  carry  red  blood  are 
injected,  and  hence  redness  of  the  face,  increased  temperature 
of  the  whole  body,  haemorrhages,  a  full  pulse,  rapid  and  violent 
breathing  and  panting,  livid  lips,  and  analogous  phenomena. 
Both  passions  are  highly  injurious  to  health,  and  sometimes 
fatal,  as  experience  shows.  In  virtue  of  the  general  connection 
of  the  physical,  mechanical,  and  animal  forces  of  the  body,  there 
arise  also  from  this  great  disturbance  of  the  vital  movements,  a 
profuse  perspiration,  an  immoderate  agitation  of  the  blood, 
suffocative  catarrh,  inflammations  of  the  viscera  and  of  the 
skin  (roseola),  apoplectic  seizures  from  rupture  of  the  cerebral 
vessels,  delirium  from  inflammation,  particularly  of  the  brain, 
violent  fevers,  &c.  On  the  other  hand,  diseases,  particularly 
those  of  the  chronic  land,  and  visceral  obstructions  have  been 
cured  by  these  emotions  (259). 

324.  The  sentient  actions  of  the  foreseeings  in  these  pas- 
sions, and  their  subordinate  conceptions,  instincts,  and  emo- 
tions, may  have  an  equally  injurious  or  beneficial  influence  on 
health  and  life,  since  the  greater  proportion  are  of  equal  inten- 
sity (259).  In  general,  revenge  is  combined  with  anger  as  a 
secondary  passion,  yet  as  it  is  usually  an  instinctive  emotion 
conjoined  with  the  instinct  of  self-defence  (301),  and  inasmuch 
as  in  this  case  it  is  a  violent  desire  excited  by  anger,  to  inflict 


174  ANIMAL-SENTIENT  FORCES.  [i. 

injury  on  the  offending  person  (309),  and,  consequently,  to 
make  use  of  the  means  most  suitable  to  this  end,  it  follows 
that  these  efforts  commingle  with  those  of  the  foreseeing  in 
anger,  and  the  actions  of  the  two  commingle  with  each  other, 
independently  of  those  of  many  other  subordinate  conceptions. 
The  angry  individual  acts,  therefore,  as  he  would  if  inflicting 
revenge :  he  strains  all  the  organs  subservient  to  self-defence 
and  combat,  particularly  the  hands,  arms,  tongue,  voice,  often 
as  if  really  in  conflict  with  his  enemy;  so  that  convulsions, 
tetanus,  and  paralysis,  or  even  epileptic  paroxysms,  may  result. 
As  the  foreseeings  differ  in  character,  so  also  do  the  various 
motions  excited  thereby,  and  offensive  words,  grimaces,  gnash- 
ing of  the  teeth,  blows,  &c.,  are  excited. 

325.  The  special  changes  (316)  produced  in  the  animal 
economy,  by  the  sentient  actions  of  anger  and  revenge,  are  an 
increased  secretion  of  bile,  often  hepatic  inflammation,  or  such  a 
morbid  state  of  the  bile,  that  it  sometimes  inflames  the  stomach, 
induces  sometimes  a  malignant  bilious  fever;  a  peculiar  poison- 
ous state  of  the  saliva  is  also  induced,  so  that  it  is  not  only  in- 
jurious to  the  angry  person  who  swallows  it,  but  if  mixed  with 
the  blood,  or  applied  to  the  nerves  of  another,  poisons  him, 
exciting  madness,  or  deranging  the  whole  nervous  system. 
This  peculiar  and  inexplicable  influence  of  anger  on  the  liver 
and  gall-bladder,  the  bile  and  the  saliva,  is  observed  also  in  the 
war-instinct  and  revenge  of  many  animals ;  and  when  biting  is 
the  means  used  for  the  satisfaction  of  the  instinct,  they  have 
either  a  special  poisonous  fluid,  which  is  inserted  into  the 
wound  made  by  the  bite,  or  their  saliva  is  poisoned  at  each 
outbreak  of  the  instinct,  as  stated  above.  Hence  arise  the 
horrible  consequences  caused  by  the  bite  of  enraged  animals  or 
men ;  for  hydrophobia  is  nothing  else  than  a  disease,  in  which 
the  animal  is  excited  to  anger  by  very  slight  causes,  and  its 
body  is  permanently  in  such  a  condition,  that  it  may  be  excited 
to  the  highest  degree  of  rage  and  revenge.  All  kinds  of  anger, 
— as  vexation,  hatred,  envy,  &c., — have  a  marked  influence  on 
the  liver  and  its  secretion,  whence  jaundice,  congestion  of  the 
liver,  bilious  vomitings,  and  diarrhoea,  &c.,  result.  In  many 
animals  and  in  men,  the  hair,  and  in  birds  the  feathers,  are 
erected  and  bristle  up  in  the  instincts  of  war  and  anger. 

326.  Since   man  himself  has  the  war-instinct,   exciting  in 


CH.  III.]  ACTIONS  OF  THE  DISTRESSING  PASSIONS.    175 

him  the  instinctive  emotion  of  revenge  (301),  and  as  instincts 
and  instinctive  emotions  are  little  under  control,  we  possess 
few  means  of  guarding  against  their  influence,  although  the 
passion  of  anger  is  more  under  control.  The  excitement  of 
antagonistic  ideas,  instincts,  and  emotions,  dissipation  of  the 
mind,  and  abstraction  of  the  thoughts,  are  the  best  psychological 
means.  Amongst  the  physiological,  are  those  which  prevent 
the  too  great  secretion  and  heating  of  the  bile,  since  it  is 
actually  the  case,  that  those  animals  are  least  prone  to  anger, 
and  to  quarrelling,  which  have  the  least  bile. 

327.  Longiiig  is  a  gentle  passion,  generally  considered  as 
painful ;  its  sentient  actions  are,  therefore,  injurious  to  health, 
and  consist  in  palpitation,  thoracic  congestion,  sighing,  weep- 
ing, &c.  Its  foreseeing  manifests  imperfectly  the  fulfilment  of 
the  emotion  (257),  so  that  he  who  longs  to  embrace,  often  ex- 
tends his  arms  as  if  about  to  embrace  the  object  of  his  longing; 
if  he  longs  for  a  conversation,  he  talks  loudly  to  himself,  &c. 
Its  special  action  (316)  in  the  animal  economy  is  the  absorption 
of  the  fat ;  hence  probably  the  sunken  appearance  of  the  eyes, 
and  their  slower  movements,  termed  a  languishing  expression. 

328.  Shame  is  the  slightest  of  the  painful  passions.  It 
nevertheless  causes  palpitation  of  the  heart.  The  foreseeing 
excites  a  casting-down  of  the  eyes,  and  an  averting  of  the  face; 
a  further  result  of  its  operations  is  a  redness  of  the  face,  as  if 
the  vessels  below  were  tied. 

329.  Just  as  every  thinking  animal  has  its  predominant 
instinct  and  peculiar  sensational  character  (295),  so  also  each 
possesses  a  predominant  passion,  which  in  so  far  as  it  deter- 
mines principally  its  volitional  actions,  co-operates  to  form  its 
sensational  character  (295),  whereby  the  latter  is  made  more 
volitional,  and  more  in  the  power  of  the  animal,  and  thus 
receives  a  moral  relation  (296,  297) .  And  since  the  passions,  as 
well  as  the  instincts,  but  especially  the  latter,  are  dependent 
proximately  on  the  sensibility  of  the  nerves  (90,  91,  66),  both 
the  predominant  instincts  and  emotions  presuppose  a  definite 
sensibility  of  the  nerves  of  an  animal  towards  sensational 
stimuli,  and  thus  temperament  mainly  determines  the  sen- 
sational faculty  [Sinnlichkeit]  of  an  animal,  and  its  principal 
inclinations,  emotions,  and  sensational  character,  and  may 
modify  them  by  habit  in  various  ways  (51,  52). 


176  ANIMAL-SENTIENT  FORCES.  [i. 


Actions  of  the  Understanding  in  the  Mechanical  Machines. 

330.  The  sentient  actions  of  the  intellectual  concep- 
tions {7Q>,  89,  180)  when  acting  alone,  and  uncombined 
with  sensational  conceptions,  nor  being  at  the  same  time 
sensational  stimuli  of  pleasure  or  pain  [Triebfedern  des 
Gemuths],  are  not  extended  beyond  the  brain,  neither 
into  the  nerves,  nor  through  them  into  the  mechanical 
machines  (115,  116) ;  at  least  we  have  no  traces  of  such 
actions.  Being  excited  in  the  hidden  mechanism  of  the  brain 
by  the  mind,  according  to  psychological  laws  (111),  and  without 
the  co-operation  of  an  external  impression,  they  have  no  direct 
action  on  the  origin  of  the  nerves  in  the  brain  (124),  but  their 
impressions  are  made  on  the  brain  itself,  so  as  to  develop 
material  ideas  of  another  kind  there,  which,  according  to  the 
laws  of  cerebral  sentient  actions,  must  accompany  the  chain 
of  intellectual  conceptions  excited  by  the  mind  (119).  That 
this  is  correct,  is  proved  by  the  fact,  that  during  the  deepest 
thought,  or  the  most  complete  abstraction,  no  action  in  the 
nerves  is  observed  similar  to  a  direct  action  of  intellectual 
conceptions,  or  like  those  of  sensational  conceptions,  provided 
there  be  nothing  sensational  commingled  therewith,  or  no 
sensational  incitements  of  pleasure  or  pain  [Triebfedern  des 
Gemuths],  So  little  is  this  the  result,  that  if  the  deepest 
meditation  be  free  from  what  is  sensational,  the  natural  move- 
ments go  on  as  in  deep  sleep,  while  the  volitional  movements 
are  forgotten,  and  the  body  is  motionless  as  a  statue. 

331.  It  does  not  follow,  because  certain  conceptions  do  not 
excite  direct  actions  externally  to  the  brain,  that  they  have 
no  influence  on  the  body,  since,  in  the  first  place,  the  de- 
velopment of  material  ideas  in  the  brain  is  an  operation  of  its 
animal  forces,  which,  from  their  connection  with  all  other  forces, 
must  have  its  results.  Secondly,  although  the  material  ideas 
do  not  act  upon  the  cerebral  origin  of  any  nerves,  they  act 
upon  other  portions  of  the  brain  (124),  and  also  on  the  me- 
chanical machines  (159)  which  enclose  it,  and  through  these 
may  exercise  an  important  influence  on  the  animal  economy. 
Thirdly,  material  ideas  may  readily  develop  unknown  actions 
in  the  nerves,  which  have  their  results  in  the  animal  economy. 


(II.  III.]         ACTIONS  OF  THE  UNDERSTANDING.        177 

although  we  do  not  see  their  connection,,  nor  recognise  them  as 
the  results  of  sentient  actions  (141).  Fourthly,  since  the  vital 
spirits  are  necessary  for  all  animal  functions,  and  consequently 
to  the  production  of  the  material  ideas  of  intellectual  concep- 
tions (15),  and  since  long  and  deep  thought  may  waste  or 
destroy  them  (20),  and  thus  the  free  action  of  the  other  animal 
forces  be  restricted  (22),  it  follows  that  in  this  way  the  con- 
ceptions of  the  understanding  may  act  powerfully  in  the  animal 
economy.  Lastly,  since  they  certainly  develop  some  actions 
in  the  body  through  the  nerves,  partly,  as  internal  sensations, 
(or  as  sensational  incitements,)  in  so  far  as  they  are  pleasing 
or  unpleasing  (80),  partly,  because  they  are  commingled  each 
time  with  sensational  elements,  it  cannot  be  matter  for  sur- 
prise, that  many  and  important  changes  are  produced  in  the 
body  by  the  exercise  of  the  intellect,  although  the  intellectual 
conceptions,  purely  as  such,  do  not  act  directly  on  the  nerves. 
(Compare  §§136—141.) 

332.  The  corporeal  phenomena  which  are  manifestly  the 
results  of  the  effort  of  the  intellect  must  be  investigated  on 
these  principles.  By  deep  and  intense  thought,  the  body 
wastes,  the  muscles  become  weaker,  the  blood  is  determined 
to  the  head,  the  extremities  become  cold;  the  blood  is 
changed  in  composition,  the  sensational  property  of  the  nerves 
is  altered,  and  they  become  too  sensitive,  and  excite  irregular 
sentient  actions,  which  derange  the  sentient  action  of  the 
other  sensational  conceptive  forces:  the  functions  of  the  viscera 
are  irregularly  performed,  and  in  particular  the  digestion  is 
much  impaired.  Hence  it  follows,  that  deep  studies  and  scien- 
tific pursuits  are  not  the  natural  objects  of  man,  but  opposed 
to  his  health  and  well-being.  Thus  it  is,  that  those  learned 
men  who  cultivate  the  abstract  sciences  are  generally  feeble, 
meagre,  sensitive,  splenetic,  hypochondriacal,  and  fanciful,  and 
have  impaired  digestion.  On  the  contrary,  the  strongest  and 
healthiest  men,  with  good  digestion,  are  little  given  to  study 
the  abstract  sciences,  and  little  capable  of  comprehending  them. 
These  principles  have  an  important  bearing  on  pathology. 


12 


178  ANIMAL-SENTIENT  FORCES.  [i. 

Actions  of  Intellectual  Pleasure  and  Pain  through  the  Nerves 
on  the  Mechanical  Machines. 

333.  The  pleasure  and  pain  which  are  connected  with  the 
intellectual  conceptions^  and  render  them  motives  to  action,  act 
in  virtue  of  their  impressions  in  the  brain  (121,  80)  on  the 
the  vital  movements,  which  are  changed  in  proportion  to  the 
strength  of  the  impressions  (250,  251).  It  is  a  well-known 
and  undoubted  fact,  that  deep  thought  on  abstract  subjects 
causes  a  manifest  change  in  the  circulation  of  the  blood ;  the 
extremities  become  cold,  while  contrarily  the  vessels  of  the 
head  are  filled,  so  that  they  beat  more  powerfully,  and  cause 
redness  and  heat  of  the  face,  swelling  of  the  head,  headache, 
perspiration  on  the  forehead.  Of  the  changes  mentioned,  those 
which  are  most  contra-natural  are  observed  principally  when 
the  thoughts  are  unpleasing,  but  even  the  pleasing  may  excite 
such,  if  they  be  excessive.  If  a  pleasing  meditation  be  not 
too  deep,  it  excites  only  a  vivid  colour  in  the  cheeks,  and 
favours  the  transpiration  from  the  head ;  a  deep  meditation  on 
painful  subjects,  on  the  contrary,  causes  vertigo,  strong  pulsa- 
tion of  the  vessels,  and  a  profuse  perspiration,  so  that  it  is  said 
the  head  smokes.  But  since  sensational  stimuli  accompany  all 
motives,  and  therefore  all  intellectual  pleasure  and  pain  (251), 
it  is  not  easy  to  determine,  whether  this  operation  of  the 
motives  depends  specially  on  intellectual  pleasure  and  pain,  or 
on  the  accompanying  sensational  stimuli  (252).  Still  the  dif- 
ference between  the  changed  vital  movements  of  deep  thought 
and  those  of  sensational  stimuli  is  so  great,  as  to  induce  us  to 
doubt,  whether  they  both  spring  from  the  same  source.  The 
determination  of  the  blood  to  the  head,  in  operations  of  the 
understanding,  is  not  like  that  resulting  from  sensational  stimuli, 
for  the  blush  of  shame,  and  the  violent  derivation  of  the  blood 
to  the  head  in  anger,  and  in  other  instincts  and  passions,  are 
changes  in  the  circulation  of  quite  a  different  kind.  Besides 
these  operations  of  the  motives  are  weaker  than  those  of  the 
sensational  stimuli  (250),  and  have  this  peculiarity,  that  they  are 
not  excited  either  directly  or  proximately  by  external  sensational 
out  according  to  the  laws  of  the  intellect  (110).  The  intel- 
lectual conceptions  please  or  displease,  according  as  they  are 
considered   to  be  good  or  bad;   the  sensational   conceptions 


CH.  III.]  ACTIONS  OF  THE  WILL.  179 

please  or  displease,  according  as  the  external  impressions  from 
which  they  directly  or  indirectly  arise,  are  in  accordance  with, 
or  contrary  to,  the  natural  function  of  the  nerves. 

334.  From  an  error  of  the  understanding,  the  mind  may 
esteem  something  to  be  good  or  to  be  evil,  which  is  the  contrary. 
But  since  in  either  case,  nevertheless,  the  pleasure  or  pain  there- 
from is  felt,  it  follows,  according  to  the  laws  of  the  sentient 
actions  of  both  (254),  that  the  agreeable  motives  will  originate 
changes  favorable  to  health,  while  the  disagreeable  originate 
unfavorable  changes.  Hence  error  and  truth  may  alike  some- 
times advance,  sometimes  detract  from,  the  well-being  of  an 
animal ;  so  that  in  this  respect,  as  is  the  case  generally,  it  is  not 
every  truth  that  is  propitious, nor  every  error  that  is  unpropitious. 


Actions  of  the  Will  through  the  Nerves  in  the  Mechanical 
Machines, 

335.  When  the  mind  wills  in  reference  to  the  pleasure  or  pain 
in  a  distinct  foreseeing  of  the  understanding,  it  exercises  its 
conceptive  force  to  produce  the  foreseeing  or  its  opposite  (81) ; 
and  thus  it  wills,  or  not  wills,  from  motives  (88,  96).  The 
eflPorts  of  the  cerebral  forces  connected  with  this  act  of  willing 
or  not  willing,  partly  express  the  perfect  material  idea  of  the 
foreseen  sensation  (96) .  If  the  circumstance  in  the  intellectual 
desire  or  aversion  be  only  another  spontaneous  conception, 
which  has  no  direct  influence  on  the  mechanical  machines, 
as,  for  example,  a  general  proposition  (330),  then  the  efforts 
are  limited  to  the  development  of  the  corresponding  material 
ideas,  and  the  desires  and  aversions  of  the  will  have  no 
perceptible  sentient  actions,  at  least,  on  the  mechanical 
machines  (332).  But  if  the  object  of  the  act  of  willing,  or 
not  willing,  be  a  conception,  that  should  act  on  the  mechanical 
machines,  fitting  material  ideas  are  developed  (96),  and  thus 
the  desires  and  aversions  of  the  will  have  some  sentient  actions 
in  the  mechanical  machines  (104,  110).  For  example,  the 
desire  to  comprehend  a  truth  is  manifested  by  no  actions 
exterior  to  the  brain,  but  the  desire  to  perform  a  certain  act, 
as,  for  instance,  to  rise  and  take  hold  of  anything,  is  followed 
by  the  proper  movements.  The  sentient  actions,  which  intel- 
lectual   desires    and    aversions   develop  directly  through   the 


180  ANIMAL-SENTIENT  FORCES.  [i. 

nerves,    are  termed  free-will   movements   [freywillige  Bewe- 
gungen]. 

Note. — The  free  will  [freywillige]  movements  are  almost 
always  confounded  with  the  sensational  voluntary  movements 
[willkiihrlichen] .  Volition  [Willkiihr]  may  be  either  sensa- 
tional or  intellectual.  Free-will  movements  are  sentient  actions 
of  the  intellectual,  and  not  of  the  sensational  will  [Willkiihr] . 
Consequently,  there  is  an  infinite  number  of  volitional  [will- 
kiirliche]  movements  (the  sensational),  which  are  not  free-will 
movements.^ 

336.  In  the  sensational  desires  and  aversions,  especially  in 
the  instincts,  neither  their  sensational  stimuli,  nor  their  grati- 
fication, is  within  the  powers  of  the  mind  (292).  It  is 
otherwise  with  the  intellectual  desires  and  aversions.  As  the 
mind  can  choose  for  itself  the  favorable  side  of  a  thing,  or 
decide  in  what  way  it  shall  consider  it,  it  can  cause  it  either 
to  be  pleasing,  and  therefore  desires  it;  or,  contrarily,  dis- 
pleasing, and  therefore  abhors  it.  And  since  the  mind  chooses 
such  conceptions  for  the  objects  of  desire  and  aversion  as  it 
has  the  full  power  to  develop,  as,  for  example,  the  direction 
of  the  muscles  to  voluntary  movements  (283),  it  satisfies  its 
desires  as  soon  as  they  are  excited ;  and  if  these  conceptions 
produce  sentient  actions  (free-will  movements),  the  latter 
result  the  moment  they  are  desired.  This  is  the  reason  why 
the  free-will  movements,  as  well  as  all  volitional  movements 
generally  (283),  follow  so  implicitly  the  thoughts,  so  that  the 
simple  pleasure  of  the  mind  is  sufficient  for  their  production. 
A  comparison  of  this  power  of  volition  (Willkiihrlichkeit)  of 
the  will  with  the  natural  impulse  of  the  sensational  desires, 
instincts,  and  passions,  explains  why  the  former,  taken  alone, 
has  entirely  moral  relations :  the  latter,  either  no  moral  rela- 
tions whatever,  or  only  in  a  subordinate  degree  (297) . 

337.  When  sensational  stimuli  cause  intellectual  motives, 
and  both  refer  to  one  and  the  same  object,  or  vice  versa, 
and  with  both  it  is  either  agreeable  or  unpleasant,   the  will 

1  In  an  early  work  on  Human  Physiology,  and  which  contains  the  germ  of  many 
ideas  more  fully  developed  in  this,  Unzer  distinguishes  (as  in  this  place)  between 
sensational  and  intellectual  will,  and  characterises  the  movements  resulting  there- 
from respectively  as  willkuhrlich  and  freiwilUg.  (Philosoph.  Betrachtung  des 
Menschlichen  Korpers  iiberhaupt.    Halle,  1750.)     See  also  note  to  §  283. — Ed. 


III.  III.] 


ACTIONS  OF  THE  WILL. 


181 


unbines  with  the  seusational  faculty,  and  free-will  movements 

[■are  conjoined  with  the  sentient  actions  of  the  sensational  desires 

|for  the  attainment  of  the  object.      In  this  way,  the  will  urges 

[a  lover  to  go  to  his  beloved,  since,  at  the  same  time,  the  instinct 

rorks  for  its   satisfaction,   and  develops  the  sentient  actions 

lecessary  thereto  (289) .     If,  on  the  contrary,  in  a  case  of  this 

dnd,  the  object  is  desired  on  the  one  hand  and  avoided  on  the 

)ther,  there  arises  a  conflict  between  the  sensational  faculty 

[[Sinnlichkeit]   and  the  will  (the  flesh,  §  88,  warring  against 

the  spirit) ;  in  this,  the  victory  is  usually  on  the  side  of  the 

msational  faculty,  because  its  incitements  are  the  stronger 

(251).    Thus  the  instinct  of  love  will  be  victorious,  in  the  case 

where  our  intellectual  motives  are  in  conflict  therewith,  and 

teach  us  to  avoid  the  beloved  object.      Video  meliora  prohoque, 

deteriora  sequor. 

338.  When  the  conception  of  the  object  of  the  mil  is  either 
sensational,  or   of  that  character  that  it  cannot  be  produced 

[solely  by  the  conceptive  force,  the  satisfaction  of  the  will  does 
not  take  place  as  in  the  above  cases  (336) ;  nor  can  the  will 

^perfectly  perform  the  free-will  movements  desired  (335).  Thus 
the  most  imperious  will  completes  nothing  to  which  external 
sensation  is  necessary,  so  long  as  no  external  impression  takes 
place ;  nor  can  the  mind  force  itself  into  the  belief  of  an 
absurdity,  nor  can  any  effort  of  the  muscles  fulfil  the  desires  of 
the  will,    when  we   would  leap  over  a  tower,   because   such 

^.fulfilment  is  an  impossibility. 

339.  All  our  intellectual  motives  are  intimately  associated 
I  with  sensational  stimuli,  and  all  the  intellectual  desires  and 

aversions  are  also  sensational  (65,  Baumgarten^s  '  Metaphysics,' 
§  512).  Consequently,  our  will  is  not  so  free,  that  it  does  not 
either  combine  its  efforts  with  the  sensational,  or  antagonise 
them  (337)  ;  and  must,  therefore,  in  some  degree  receive  its 
contentment  from  them.  We  therefore  do  nothing  by  a  pure 
will;  the  flesh  has  always  a  part  in  our  efforts,  conclusions, 
and  virtues,  because  it  always  makes  them  either  more  agreeable 
or  more  difficult. 

340.  The  muscles  are  the  mechanical  machines  which  are 
under  the  influence  of  the  will,  and  the  origins  of  their  nerves 
must  be  stimulated  by  the  efforts  of  the  cerebral  forces,  excited 
by  the  intellectual  desires  and  aversions  (164,  i). 


182  ANIMAL-SENTIENT  FORCES.  [i. 

341.  The  reason  why  the  free-will  movements  take  place  in 
a  given  series^  and  in  no  other_,  can  only  be  sought  in  the 
arbitary  and  spontaneous  production  by  the  mind  of  the  intel- 
lectual desires  and  aversions,  and  no  external  inducements  are 
necessary  thereto_,  as  in  the  sentient  actions  of  the  sensational 
desires  and  aversions,  except  in  so  far  as  the  will  depends  on 
the  sensational  faculty  (109,  339). 

342.  The  free-will  movements  are  produced  by  a  special 
impression  of  an  intellectual  desire  or  aversion  in  the  brain, 
which  acts  on  the  origin  of  the  nerves  distributed  to  the 
muscles,  and  is  propagated  outwards  from  the  brain  (164,  i). 
Everything  hinders  the  free-will  movement,  in  spite  of  the 
will,  which  prevents  this  impression  being  made  or  transmitted, 
or  which  diverts  it  from  its  course  to  the  muscles  (164,  iii,  iv), 
or  renders  the  muscle  unfit  to  perform  its  proper  function 
(165,  vi).  On  the  other  hand,  an  impression  may  be  made  on 
the  origin  or  trunk  of  a  motor  nerve  independently  of  the 
will,  and  if  it  be  propagated  to  the  muscle,  and  the  latter  be  in 
a  fit  state  to  perform  its  functions,  may  excite  movements, 
usually  voluntary,  in  spite  of  the  will  (162).  It  is,  therefore, 
erroneous  to  say,  that  a  movement  of  the  extremities,  usually 
voluntary,  must  always  depend  on  the  will,  or  that  all  free-will 
movements  must  always  take  place  whenever  the  mind  wills. 
Daily  experience  contradicts  both  propositions,  for  a  natural 
and  incidental  hindrance  in  the  body,  may  prevent  a  movement 
that  we  will,  from  taking  place  (see  §  165,  vi) ;  and  further, 
movements  that  are  usually  voluntary,  may  be  produced  by 
external  sensations,  or  as  nerve  actions  (183),  not  only  without 
an  act  of  the  will,  but  in  spite  of  it  (162). 

343.  The  free-will  movements  have  a  very  important  and 
general  influence  in  the  whole  animal  economy,  through  the 
mutual  connection  of  all  the  forces.  Works  on  physiology 
may  be  consulted  as  to  the  details  {vide  Haller^s  '  Physiology,^ 
§  416). 

344.  Just  as  every  animal  has  its  predominent  instinct  and 
passion  (295,  329),  so  those  that  possess  an  understanding  and 
will  have  their  pj'edominant  inclination,  or,  in  other  words, 
intellectual  desires  for  that  class  of  conceptions  which  are  most 
usual  with  them,  because  the  mind  finds  the  most  pleasure 
therein  ;  and   according  to  which  its  voluntary  actions  are  for 


CH.   Til.] 


ACTIONS  OF  THE  WILL. 


183 


the  most  part  determioed,  or  its  mental  character  constituted. 
Since  all  intellectual  desires  are  the  most  voluntary  and  free, 
as  compared  with  the  sensational^  although  always  closely 
connected  with  the  latter  (295,  329,  339),  they  are  the  most 
closely  related  to  morals,  and  the  mental  character  is  termed 
the  moral  character.  In  reference  to  their  moral  relations,  the 
)redominant  inclinations  are  termed  cardinal  virtues  or  great 

ices,  both  which,  however,  are  connected  closely  with  the  sensa- 
tional faculty  (Sinnlichkeit),  as  is  shown  by  their  names,  which 

:e  derived  from  leading  instincts  and  passions,  as  avarice,  or 

lordinate  desire  for  gold ;  ambition,  or  inordinate  desire  for 
lonour,  sensuality,  selfishness,  self-love,  &c.  Like  the  instincts 
md  passions,  therefore,  they  may  be  greatly  but  psychologi- 

lUy  changed  by  exercise  and  habit  (329,  iii,  111).      As  most  of 

le  conceptions,  and  all  the  desires  and  aversions,  are  charac- 
terised by  special  movements  in  the  mechanical  machines  (as 

las  been  shown  throughout  this  entire  chapter),  we  may  by 
^hem  and  by  physiognomy  know  the  mental  capacities,  the 

;ading  instincts  and  passions,  the  principal  virtues  and  vices, 
md  the  sensational  and  moral  character,  on  which  that  physio- 

)gical  science  which  investigates  the  human  mind  is  based. 


CHAPTER  IV. 

THE  RECIPROCAL  CONNECTION  \_GEMEimCHAFT]  OF  THE  BODY 
WITH  THE  SOUL. 

345.  When  by  the  action  of  one  thing,  a  change  can  be 
perceived  extending  into  another,  the  former  is  said  to  exercise 
an  influence  on  the  latter  (Baui/igarten's  '  Metaphysics/  §  140, 
141),  and  the  connection  in  which  they  stand  to  each  other,  by 
their  reciprocal  influence,  is  their  reciprocal  connection  (ibid., 
§  328). 

346.  It  is  sufficiently  obvious,  why,  from  an  external 
impression  on  the  nerves,  which  produces  material  external 
sensations  in  the  brain,  and  consequently  from  the  motive 
force  of  the  animal  organism,  an  external  sensation  arises  in 
the  mind  (35) ;  the  animal  organism,  therefore,  acts  upon  its 
soul,  and  has  an  influence  upon  it  (345)  by  its  sensibility  (34). 
(Baumgarten's  'Metaphysics,'  §  540). 

347.  All  conceptions,  without  exception,  have  their  foundation 
in  their  external  sensations  (65),  and  are,  therefore,  partly  sen- 
sational. Now,  since  this  sensational  element  of  every  conception 
is  produced  by  the  influence  of  the  body  on  the  soul  (346,  66), 
it  follows  that  the  body,  by  means  of  its  sensibility  [Empfind- 
lichkeit],  exercises  an  influence  on  the  mind  in  all  its  concep- 
tions, without  exception  :  and  in  virtue  of  the  animal- sentient 
force  of  sensibility  (or  the  sensational  force),  the  animal  or- 
ganism is  constituted  a  co-operating  force  of  all  conceptions  of  the 
mind.  Consequently,  the  following  depend  more  immediately 
on  the  influence  of  the  body  on  the  mind,  namely,  the  sensa- 
tional conceptions,  imaginations,  and  foreseeings;  sensational 
memory ;  the  sensational  expectations  and  forebodings ; 
dreams;  poetic  inventions  [Erdictungen],  and  imperfect  ex- 
ternal sensations  ;  also  pleasure  and  pain  of  the  senses,  and  all 
other  sensational  stimuli,  the  sensational  desires  and  aversions, 
the  instincts,  the  instinctive  emotions,  and  the  passions.  On 
the  other  hand,  conceptions  of  the  understanding  and  of  the 
reason,  intellectual  motives,  and  the  intellectual  desires  and 


CH.  IV.]      CONNECTION  OF  BODY  AND  SOUL.  185 

aversions,  depend  only  remotely  on  the  influence  of  the  body 
on  the  mind. 

348.  When  sentient  actions  are  excited  in  an  animal  organism, 
it  is  sufficient  to  know  that  they  proceed  from  the  conceptive 
force  (97).  Since  all  conceptions  are  connected  with  certain 
actions  (25,  97),  the  mind  acts  on  the  body  and  exercises  an 
influence  on  it,  which  extends  to  all  those  of  its  movements  with- 
out exception  that  have  an  origin  in  conceptions.  The  free-will 
movements  depend,  however,  more  immediately  on  free-will  (336) . 
This  dependence  of  the  movements  of  the  body  on  the  will  is 
termed  the  dominion  of  the  soul  over  the  body,  (Baumgarten^s 
*  Metaphysics,'  §  538),  but  the  actions  of  the  sensational  per- 
ceptions, pleasure  and  pain,  desires  and  aversions,  are  not  directly 
or  immediately  under  the  power  of  the  soul,  although  they  are 
altogether  produced  by  its  influence. 

349.  The  animal  organism  and  the  soul  have  a  reciprocal 
connection  with  each  other  (345),  and  since  the  influence  of  the 
body  is  extended  to  all  the  conceptions  by  means  of  external 
impressions  on  the  nerves  transmitted  to  the  brain  (347,  113), 
and  since  also  the  influence  of  the  soul  is  extended  to  all  the 
sentient  actions  of  the  body,  by  means  of  the  impression  of  the 
conceptions  on  the  brain  (113,  121),  it  follows,  that  this  reci- 
procal connection  is  more  intimate  and  complete  than  that  of 
another  animal  with  the  soul,  or  of  another  soul  with  the 
animal  body.  In  virtue  of  this  reciprocal  connection,  the  body 
is  also  most  closely  united  to  its  soul  in  the  brain,  and  this 
united  whole  is  a  sentient  [beseeltes]  animal  {vide  §§  6,  7),^ 
the  idea  of  which  consists  in  the  closest  reciprocal  connection 
of  a  body  and  a  soul. 

350.  Those  therefore  are  in  error,  who,  with  Stahl,  wholly 
deny  the  influence  of  the  animal  body  on  its  soul ;  as  also  are 
those  who  limit  that  influence  to  the  sensational  perceptions, 
and  the  feelings  of  pleasure  and  pain,  and  to  the  desires, 
aversions,  instincts,  and  passions ;  inasmuch  as  the  conceptions 

'  The  exact  meaning  of  the  terras  leseelte  and  unbeseelte  is  given  in  the  text 
(§  605,  et  seq.),  and  the  two  kinds  of  sentient  or  beseelte  animals  defined.  A  literal 
translation  of  the  words  might  have  been  made  in  strict  accordance  with  the  idiom 
of  the  English  language ;  but  the  term  sentient  seems  to  me  to  express  as  fully  the 
author's  meaning  as  besouled  would. — Ed. 


180  CONNECTION  OF  BODY  AND  SOUL.  [i. 

of  the  understanding,  the  motives,  and  the  desires  and  aversions 
of  the  will,  share  in  the  influence  of  the  body. 

351.  Those  also  are  in  error,  who  wholly  deny  the  influence 
of  the  soul  over  its  body,  as  some  mechanical  physicians ;  nor 
are  those  less  in  error,  who  limit,  the  power  of  the  soul  to  the 
free-will  movements,  and  deny  that  the  involuntary  movements 
are  under  its  influence,  for  the  action  of  the  heart,  arteries, 
stomach,  and  bowels,  are  manifestly  influenced  by  it. 

352.  Lastly,  those  are  also  in  error,  who  would  explain 
sentient  actions  by  the  physical  and  mechanical  laws  of  motion 
(7,  97),  as  well  as  those  who  would  explain  them  by  the  laws 
of  other  animal  forces  than  the  conceptive  force,  although 
connected  with  conceptions.  Nevertheless,  movements  identi- 
cally the  same,  may  take  place  without  being  accompanied  by 
conceptions,  and  since  in  this  case,  they  are  not  sentient  actions, 
but  take  place  independently  of  the  influence  of  the  soul,  they 
can  be  explained  on  other  principles,  yet  not  by  the  mechanical 
and  physical  laws  of  motion,  but  rather  by  the  laws  of  motion 
of  the  animal  forces  (7). 


PART    II. 

ANIMAL  NATURE  IN  RELATION  TO  ITS  PURELY 

ANIMAL  FORCES,  OR  VIS  NERVOSA 

[NERVENKRAFTE]. 


INTRODUCTION. 

353.  Animal  forces  acting  without  the  co-operation  of  the 
conceptive  force,  are  termed  nerve-forces  (vis  nervosa),  or 
purely  animal  forces  (183,  186),  and  their  actions  are  nerve- 
actions  [Nervenwirkungen],  ov  purely  animal  movements. 

354.  In  virtue  of  the  vis  nervosa^  the  animal  body  becomes 
capable  of  functions,  which  cannot  be  explained  either  by  the 
mechanical  and  physical  laws  of  motion,  or  by  the  laws  of  the 
animal-sentient  forces,  but  which  are  performed  by  the  animal 
machines,  supplied  according  to  special  laws  with  vital  spirits 
(6,183).  To  these  belong  the  purely  animal  movements  caused  1 
by  an  external  impression  on  the  nerves  before  it  excites  a 
material  external  sensation  in  the  brain  (98,  i),  with  which  the 
muscular  irritability  [Muskelreiz]  of  Haller  must  be  classed 
[vide  §  388),  as  well  as  those  excited  by  internal  impressions 
on  the  medulla  of  the  nervous  system  and  which  excite  no  con- 
ceptions ;  or  by  other  stimuli  than  conceptions,  including  many  i 
actions  attributed  to  nervous  irritability  [Nervenreiz]  by  Haller. 
(See  §  386.) 

The  following  is  the  plan  of  this,  the  Second  Part : 
In  Chapter  I,  the  vis  nervosa  and  the  nerve-actions  are 
considered  generally.  In  Chapter  II,  the  vis  nervosa  of  the 
external  impression ;  and  in  Chapter  III,  the  vis  nervosa  of  the 
internal  impression  in  the  medulla  of  the  brain  and  nerves,  are 
considered ;  and  lastly,  in  Chapter  IV,  the  relations  of  the  vis 
nervosa  and  of  the  cerebral  forces  are  reviewed. 


CHAPTER  I. 

ON  THE  VIS  NERVOSA  AND  ON  NERVE-ACTIONS  IN  GENERAL. 


^H  356.  Only  two  primary  animal  forces  of  the  animal  machines 
^^[the  brain  and  nerves)  are  known;  namely,  the  two  kinds  of 
impressions  on  the  nerves  (33,  121).  These  animal  machines 
being  incorporated  with  the  mechanical  machines  (155),  render 
them  capable  of  animal  operations;  and  it  is  from  the  action 
of  the  animal  forces  on  the  former,  and  through  them  on  the 
latter,  that  all  the  phenomena  of  animal  organisms  are  produced. 
These  animal  forces  constitute  the  animal- sentient  forces  when 
acting  in  and  through  the  brain  of  an  animal  endowed  with 
mind,  and  are  the  means  whereby  the  reciprocal  connection  of 
the  body  and  mind  is  effected.  It  is  the  external  impression 
which  supplies  the  mind  with  all  its  external  sensations,  but  on 
the  condition  that  it  reaches  the  brain,  and  produces  there 
material  external  sensations  (46) ;  while  the  internal  impression 
excites  all  the  sentient  actions  of  the  body,  with  the  condition, 
however,  that  it  be  caused  by  conceptions  (123).  But  if  these 
conditions  fail,  that  is  to  say,  if  the  external  impression  be  not 
transmitted  to  the  brain,  or  at  least  do  not  excite  materi^  ex- 
ternal sensations  therein;  or  if  an  internal  impression  at  the 
cerebral  origin,  or  on  the  medulla  of  the  nervous  trunks,  is  not 
caused  by  conceptions,  but  by  other  irritants,  the  two  kinds  of 
impressions  still  excite  actions  in  the  organism,  and  these  are 
the  nerve-actions  of  the  vis  nervosa  (353) .  Every  animal  move- 
ment is,  in  reference  to  the  animal  force  that  develops  it, 
either  a  sentient  action  or  a  nerve  action;  and  if  it  be  pro- 
duced at  the  same  time  by  both  the  cerebral  forces  and  the  vis 
nervosa,  it  belongs  to  both  classes  of  actions  (193).  Under  such 
circumstances,  it  would  be  erroneous  to  consider  the  one  class 
as  distinct  from  the  other,  since  they  are  identical  in  both  cases, 
just  as  a  musical  clock  is  the  same,  whether  put  in  motion  by 
a  performer  or  by  machinery.  "A  muscle,  when  its  nerve  is 
irritated,  contracts  and  performs  a  movement  the  same  as  that 


190  ANIMAL  FORCES.  [ii. 

which  nature  has  appointed^  and  bends  or  extends  the  limb,  &c/^ 
(Haller.)  It  now  remains  to  prove,  that  the  animal  movements 
which  the  cerebral  forces  excite  by  means  of  the  impressions 
caused  by  conceptions  (as  has  been  demonstrated  in  the  First 
Part)  can  be  excited  by  impressions  not  produced  by  concep 
tions.  In  the  first  place,  we  will  prove  by  facts  that  this 
actually  occurs,  and  we  will  then  investigate  the  nature  and 
properties  and  the  conditions  and  laws  of  these  peculiar  animal 
forces,  and  how  they  act  in  co-operation  with  the  cerebral 
forces. 

357.  If  a  nerve,  which  certain  external  impressions,  when 
felt,  usually  stimulate  to   produce  certain  movements  in  the 
organism,  be  cut  off  from  its  connection  with  the  seat  of  the 
conceptive  force,  namely,  the  brain,  or  in  other  words,  if  it 
be  cut  or  tied,  or  the  head  of  the  animal  be  entirely  separated 
from  the  body,  undoubted  observations  prove,  that  the  same 
external  impression  from  the  point  of  impression  to  the  point 
of  division  acts  as  a  stimulus  to  the  same  movements  so  long 
as  any  traces  of  life  remain  in  the  body,  although    the   ex- 
ternal impression  never  arrive  at  the  brain,  but  only  as  far  as 
the  point  of  division  (31),  and,  consequently,  is  neither  felt  nor 
excites  material  external  sensations  in  the  brain  (46,  ii).    This 
is  the  first  fundamental  principle,  on  which  the  doctrines  to  be 
taught    in  this    Second    Part  of  the    Physiology  of  Animal 
Nature,  are  based.     The  experiment  is  successful  in  numerous 
inst£g:ices  with  the  most  varied  external  impressions  on  the  most 
dissimilar  nerves;  and  it  would  be  successful  still  more  frequently, 
if  the  decapitation  or  destruction  of  the  brain  were  not  so  rapidly 
fatal,  for  it  is  to  be  remembered,  that  the  structure  of  the  nerves 
experimented  on  must  be  unaltered,  they  must  also  still  con- 
tain vital  spirits,  they  must  be  able  to  transmit  the  impression,] 
and  the  parts  must  also  retain  some  of  their  natural  warmth  o: 
moisture,  &c.  (Haller's  ^Physiology,'  §§  367,  960.)    The  large 
mammalia  bleed  so  profusely  when  experimented  on,  that  th 
circulation  soon  ceases,  and  the  natural  warmth  and  moistun 
of  the  parts  disappear;  but  so  long  as  these  conditions  con 
tinue,  the  experiment  is  successful  with  them,  but  still  mo 
so  with  smaller  animals,  as  birds,  worms,  and  insects*      In  th 
Second  Section  of  the  next  Chapter,  it  will  be  shown,  that  th 
vis  nervosa  of  the  external  impression  regulates  the  animal  ma-j 


{ 


cu.  1.]  NERVE  ACTIONS  IN  GENERAL.  191 


liines ;  in  the  meanwhile  it  will  be  sufficient  to  prove  its  exist- 
ce  and  reality  by  detailing  a  few  of  the  most  instructive  and 
most  obvious  facts.    Thus,  an  external  impression  made  on  the 
nerves  of  a  portion  of  a  muscle,  or  of  the  heart,  or  of  the  in- 
testines separated  from  the  body  (as  when,  for  example,  the 
outer  or  inner  surface  is  burnt  with  acid,  or  pricked,  or  other- 
wise irritated),  excites  the  movements  proper  to  the  part,  or 
renews  them  for  a  time  if  they  have  already  ceased,  just  as 
when,  in  the  natural  condition  of  the  animal,  it  was  felt  (167, 
170).    Thus,  also,  if  immediately  after  decapitation,  the  body 
be  struck  forcibly,  the  part  struck  becomes  suffused  with  blood, 
precisely  as  it  would  have  been  in  the  natural  condition  from 
the  external  sensation  of  a  blow  (207).    Thus,  also,  the  glands 
in  an  excised  portion  of  intestine  secrete  on  an  external  stimulus 
being  applied ;  thus  also  the  external  impression  of  the  gastric 
juice,  which  in  the  natural  condition  excited  the  instinct  of 
hunger,  stimulates  the  decapitated  animal  to  rise  up  and  seek 
food,  an  act  which  is  properly  a  sentient  action  of  the  instinct ; 
thus,   also   decapitated  insects   allure  with   chirping  wings  to 
sexual  congress  from  the  external  irritations  of  the  nerves  of 
their  sexual  organs ;  thus,  also,  in  decapitated  butterflies,  move- 
ments necessary  to  copulation  are  excited,  and  the  act  itself 
completed  by  the  external  stimuli  proper  to  the  instinct,  while 
decapitated  female  butterflies,  flies,  &c.,  are  in  the  same  way 
excited  to  deposit  their  ova ;  and  thus,  also  the  pinching  of  the 
toe  of  a  decapitated  frog  causes  the  same  muscular  contractions 
and  the  same  movements  of  the  instinct  of  self-preservation,  as 
pain   ordinarily   excites   in   the   natural  condition.    (Compare 
Haller's  '  Physiology,'  §  402.) 

Note. — These  facts  (of  which  a  great  number  may  be  found 
scattered  through  the  writings  of  observers)  are  stated  here 
without  reference  to  authorities,  being  generally  known  and 
undoubted.  If  further  proofs  be  required  by  the  reader, 
especially  as  to  the  irritability  of  muscles,  he  is  referred  to  the 
works  of  Haller,  Zimmerman,  and  Oeder,  for  it  will  be  shown 
subsequently,  that  the  experiments  which  demonstrate  the 
irritability  of  a  muscle,  establish  also  that  the  animal  motive 
force  of  an  external  impression  acts  independently  of  the 
cerebral  forces  (338).  (Compare  Haller's  'Opera  Minora,^ 
torn,  i,  pp.  368,  seq.) 


192  ANIMAL  FORCES.  [ii. 

358.  The  external  impression  on  the  nerves  can  produce  the 
same  movements  in  the  body  as  if  it  were  felt,  although  it  is  not 
feltj  nor  transmitted  to  the  brain. — These  movements  are 
animal,  inasmuch  as  they  do  not  result  from  physical  and 
mechanical  forces  only  (32,  42),  (as  Haller  has  shown,  particu- 
larly with  reference  to  muscular  movevent  (162),  ('  Physiology,^ 
§  412).  They  do  not  necessarily  occur  in  accordance  with 
conceptions,  because  the  impression  is  not  felt,  and,  therefore, 
there  are  no  sentient  actions  excited  by  it,  that  is  to  say,  no 
actions  from  external  sensations  (98,  46);  although  in  the 
natural  condition  the  two  kinds  of  actions  may  occur  together, 
and  often  do  (183).  Consequently,  there  are  nerve-actions 
excited  by  the  vis  nervosa  of  the  external  impression  (353), 
and  whether  the  external  sensation  of  the  mind  co-operates 
with  it,  or  not. 

359.  If  a  nerve,  ordinarily  stimulated  to  excite  certain 
movements,  by  conceptional  impressions^  acting  on  its 
origin  in  the  brain,  be  stimulated  at  its  origin  by  other 
internal  impressions  which  are  not  material  ideas  (121) ;  or  if 
its  medulla  be  irritated  by  some  other  internal  impression,  at 
any  point  of  its  course  downwards,  after  its  connection  with  its 
cerebral  origin,  or  with  the  brain  generally,  has  been  severed, 
either  by  ligature  or  division  of  the  nerve,  or  by  the  separation 
of  the  head  from  the  body, — in  either  case  the  same  move- 
ments are  excited  (provided  animal  life  continues,  and  with  the 
other  conditions  previously  stated,  §  357),  by  the  internal  im- 
pression simply,  as  are  usually  excited  by  internal  impressions 
caused  by  conceptions.  This  is  also  an  irrefragable  principle, 
and  is  of  tbe  greatest  importance  in  understanding  the  doc- 
trines to  be  taught  in  this  second  part.  In  the  Second  Section 
of  the  Third  Chapter,  abundant  examples  will  be  given  of  the 
action  of  the  vis  nervosa  of  the  internal  impression :  we  can 
here  give  only  some  of  the  most  prominent.  If  the  nerve 
of  a  limb  be  irritated  with  a  needle,  movements   take  place 

•  By  the  term  internal  impressions  of  conceptions,  Unzer  means  to  express  the 
material  ideas  or  changes  which  take  place  at  each  act  of  mind  in  the  hrain,  and 
which  are  referred  to  in  the  First  Part  (§  121,  foot-note,  et  alia).  For  brevity's 
sake,  I  have  termed  these  impressions  conci^ ^iowa/,  becanse  I  have  already  translated 
Vorstellung  by  conception ;  but  it  is  of  importance  to  remember  the  wide  and  in- 
definite meaning  attached  to  the  term.  {Vide  §  25.) — Ei' 


CH.  I.]  NERVE-ACTIONS  IN  GENERAL. 

exactly  similar  to  those  produced  in  the  natural  condition  by 
the  volitional  conceptions :  thus,  the  diaphragm  renews  its 
motions  as  in  respiration,  if  the  trunk  of  its  nerve  be  irritated  : 
thus,  the  body  of  a  dog,  or  of  an  ox,  (nay,  even  of  a  man,  as 
is  seen  in  executions  by  decapitation,)  will  be  thrown  into  the 
most  violent  volitional  movements,  when  the  spinal  cord  is  cut 
through :  if  in  such  an  one  the  cord  be  irritated  inferiorly, 
the  movements  involve  the  feet  only;  if  superiorly,  panting 
respiration,  palpitation,  deglutition,  and  vomiting  result.  When 
an  irritation  of  the  spinal  cord  produces  spasmodic  convulsions 
of  the  whole  body,  but  a  particular  nerve  has  been  previously 
divided,  the  limb  to  which  that  nerve  is  distributed  is 
unaffected  by  spasmodic  action,  because  the  irritation  cannot 
be  transmitted  to  it :  thus  also,  a  decapitated  frog  rises  up  and 
springs  forward,  and  if  thrown  into  water  begins  to  swim,  so 
soon  as  its  spinal  cord  is  irritated  by  a  needle  in  the  cer- 
vical region,  just  as  if  it  knew  what  it  had  to  do.  Bilguer 
relates  a  somewhat  similar  case,  in  which  if  a  certain  part  of 
the  neck  where  suppuration  had  taken  place,  was  irritated, 
the  patient  was  obliged  to  stand  upright  in  spite  of  himself,  &c. 
A  great  variety  of  well-authenticated  facts  of  this  kind  may 
be  found  in  Haller^s  *  Physiology.' 

360.  An  internal  impression  on  the  nerves  can  produce  ike 
same  animal  movements  in  the  body,  as  the  co7iceptions  produce 
by  means  of  material  ideas,  although  not  caused  by  conceptions, 
nor  even  taking  place  in  the  brain. — These  movements  are 
animal,  for  they  do  not  result  from  physical  and  mechanical 
forces  only  (§  121.  Haller's  'Physiology,'  §  412).  They  do 
not  necessarily  occur  in  connection  with  conceptions,  be- 
cause the  internal  impression  which  excites  them  need  not 
be  a  material  idea,  and  it  is  in  no  degree  necessary  that 
conceptions  cause  it.  These  are  not,  therefore,  sentient 
actions  (123),  although  the  two  kinds  of  actions  may  occur 
at  the  same  time,  and  often  do  (183).  Consequently,  there 
are  nerve  actions  which  the  vis  nervosa  of  the  internal  im- 
pressions produces  (353),  whether  a  conception  co-operates  with 
it  or  not. 

361.  The  following  irrefragable  truth  follows  from  these 
two  leading  principles  :  while  the  animal  machines  are  endowed 
by  nature  with  the  property  of  conducting  external  impressions 

13 


194  ANIMAL    FORCES.  [n. 

to  the  brain,  so  that  they  may  there  excite  material  ideas, 
giving  rise  to  sensations,  and  of  receiving  internal  impressions 
caused  by  conceptions,  they  also  possess  another  and  entirely 
different  property,  and  are  intended  by  nature  to  effect  by  means 
of  the  external  impressions  they  receive,  whether  the  latter  reach 
the  brain  and  are  felt  or  not,  the  same  movements  which  are 
effected  when  they  do  reach  the  brain  and  are  felt ;  and  to  effect 
by  means  of  an  internal  impression,  which  they  receive  from  a 
touch  or  irritant  caused  by  no  conception  whatever,  the  same 
movements  as  are  effected  by  means  of  the  cerebral  forces,  when 
the  same  internal  imp^^ession  is  produced  by  a  conception.  The 
animal  machines  are  mysteriously  and  inscrutably  endowed  by 
the  Creator  with  these  two  distinct  motor  forces  derived  from 
impressions,  in  addition  to  the  equally-inscrutable  animal  force 
originating  also  from  them,  partly  that  they  may  put  the 
animal-sentient  forces  into  action,  and  partly  that  through 
these  they  may  move  the  organism  animally ;  and  the  greater 
proportion  of  animal  movements  are  so  closely  dependent  upon 
them,  even  when  these  are  at  the  same  time  sentient  actions, 
that  they  must  be  considered  as  the  most  fundamental  and  most 
general  principium  of  the  whole  animal  mechanism.  But  it  is 
also  obvious,  that  these  two  kinds  of  vis  nervosa  have  an  essen- 
tially distinct  nature :  that  they  produce  their  nerve  actions  in 
some  degree  in  an  antagonistic  manner;  that  the  external 
impression,  considered  also  as  simply  a  vis  nervosa,  is  neverthe- 
less a  force  as  entirely  different  from  that  of  the  internal  im- 
pression as  it  is  from  the  cerebral  forces  (32,  121)  :  that  the 
two  kinds  of  vis  nervosa  are  excited  into  action  in  opposite 
ways :  that  they  are  regulated  by  different  laws  in  their  opera- 
tions :  and  that  all  nerve  actions  of  one  and  the  same  kind 
cannot  be  all  explained  by  one  kind  only  of  the  vis  nervosa, 
nor  that  the  existence  of  the  one  kind  implies  or  excludes  the 
existence  of  the  other.  Hitherto,  both  have  been  generally 
confounded  too  much  with  each  other.  Nevertheless,  both 
kinds  oivis  nervosa  have  certain  properties  in  common,  which 
are  now  to  be  considered :  those  which  are  peculiar  to  each, 
will  be  investigated  in  a  subsequent  chapter. 

362.  No  vis  nervosa  requires  necessarily  the  co-operation  of 
the  cerebral  forces  (358,  360).  Further,  all  nerve-actions  may 
take  place  in  the  animal  machines  [the  brain  and  nerves],  and 


CH.  I.]  NERVE-ACTIONS  IN  GENERAL.  195 

by  their  means  in  the  mechanical  without  the  co-operation  of 
the  cerebral  force,  and  in  fact  may  take  place  without  any 
brain  whatever.      Consequently,  we  cannot  infer, 

i.  That  those  actions  cannot  originate  from  a  sentient  brain 
which  are  not  animal  actions  or  nerve-actions ;  or  if  the  sen- 
tient brain  be  separated  from  the  body,  that  no  animal  actions 
or  nerve-actions  can  take  place  in  the  latter. 

ii.  That  those  impressions  which  are  not  felt,  and  do  not 
reach  the  brain^  cannot  develop  animal  or  nerve-actions. 

iii.  That  those  impressions  which  are  not  produced  by  con- 
ceptions, and  do  not  depend  upon  material  ideas,  cannot  cause 
animal  actions,  or  nerve- actions. 

There  is  an  important  distinction  to  be  noted  in  all.  Nerve- 
actions  require  the  presence  and  free  action  of  the  vital  spirits 
in  the  animal  machines  (357,  359).  The  cortical  substance 
of  the  brain  secretes  the  vital  spirits  from  the  blood,  and  dis- 
tributes them  to  the  nervous  system.  To  this  extent,  the  vital 
spirits  and  the  brain  can  be  considered  as  being  necessary  to 
the  two  kinds  of  vis  nervosa.  But  again,  the  brain  is  not  the 
secreting  organ  of  the  vital  spirits  in  all  animals,  since  there 
are  some,  in  the  first  place,  that  have  no  brain  or  head  distinct 
from  the  trunk,  yet  are  nevertheless  endowed  with  vis  nervosa, 
and  in  which  in  all  probability  the  vital  spirits  are  secreted  in 
every  part  of  the  system,  —  in  every  nerve,  and  probably  in 
every  ganglion — for  their  limbs  often  retain  animal  life,  and 
have  an  independent  existence,  when  separated  from  the  body. 
Secondly,  in  those  that  have  a  distinct  brain  secreting  nervous 
fluid,  it  is  not  the  medullary  substance,  the  seat  of  the  cerebral 
forces  (11)  that  is  necessary  to  the  vis  nervosa,  but  the  con- 
nected cortical  substance.  Lastly,  even  in  these  the  cortical 
substance  is  only  necessary,  because  it  prepares  and  supplies 
for  the  vis  nervosa  its  animal  nourishment,  namely,  the  vital 
spirits,  and  is,  consequently,  unnecessary  so  long  as  the  nerves 
retain  a  sufficient  supply  of  the  latter  (1 59) ;  just   as  animals 

I  will  live  for  some  time  without  food,  or  plants  survive  after  being 
separated  from  the  stem.      The  reader  will  better  understand 
what  follows  by  keeping  this  view  in  mind. 
363.  Although  the  two  kinds  of  vis  nervosa  be  thus  inde- 
pendent  of  the   brain   and  of  the   cerebral   forces,   they   can 


196  ANIMAL  FORCES.  [ii. 

action^  through  the  same  nerves.  External  impressions  can  pro- 
duce nerve-actions  in  their  way  upwards,  before  they  reach  the 
brain  (98,  i),  and  at  the  same  time  reach  the  brain  and  be  felt, 
although  their  nerve-actions  are  independent  of  the  brain  and 
of  conceptions  (362).  The  movements  which  a  conceptional 
internal  impression  excites  as  sentient  actions,  may  be  equally 
produced  by  other  internal  impressions.  Movements  may,  there- 
fore, have  a  twofold  origin,  for  an  external  impression  may  be 
felt  and  excite  sentient  actions,  which  are  also  excited  by  it  as 
nerve-actions.  In  the  same  way  an  internal  impression  may,  as 
the  result  of  conceptions,  excite  sentient  actions,  and  as  the  re- 
sult of  an  irritant  applied  to  the  cerebral  origin  of  the  same 
nerve,  or  in  any  part  of  its  course,  excite  the  same  movements  as 
nerve-actions.  When  a  nerve  going  to  the  trunk  of  a  decapitated 
animal  is  irritated,  movements  like  those  arising  volitionally  are 
excited  by  the  irritation  (359).  It  would  be,  therefore,  erroneous 
to  conclude  that  movements  might  not  be  at  the  same  time  both 
sentient  actions  and  nerve- actions,  or  that  actions  exactly  similar 
to  sentient  actions  in  every  respect  may  not  be  exclusively  nerve- 
actions,  and  vice  versa. 

364.  The  possibility  that  nerve-actions  may  be  at  the  same 
time  sentient  actions,  is  manifest  from  a  simple  consideration 
of  circumstances. 

i.  All  animal  movements  in  the  mechanical  machines  (7), 
consequently  all  sentient  actions  and  nerve- actions,  are  produced 
through  the  nerves.  The  impressions  of  the  material  ideas  also 
act  as  stimuli  to  the  nerves  (130),  and  produce  the  appropriate 
movements  (193)  :  but  any  other  stimulus  acting  on  the  same 
nerves,  either  at  their  cerebral  origin  or  on  any  part  of  their 
course  dow  nwards,  must  necessarily  have  a  similar  effect  (359)  ; 
the  two  kinds  of  stimuli  may  occur  therefore  simultaneously, 
and  co-operate  in  exciting  the  same  movements. 

ii.  If  an  external  impression  produces  a  sentient  action,  it 
must  act  by  producing  a  material  external  sensation  in  the 
brain,  the  latter  exciting  the  movement  by  its  internal  im- 
pression on  the  cerebral  origin  of  the  nerves.  But  if  this 
external  impression  on  its  way  to  the  brain  be  reflected  in 
the  ganglia,  or  at  the  points  where  branches  are  given  off, 
on  the  same  fibrils,  as  it  would  have  acted  on  if  it  had 
actually  reached  the  brain  (48,  151),  movements  must  result 


CH.  I.]  NERVEACTIONS  IN  GENERAL.  197 

exactly  resembling  the  sentient  actions  produced  by  the  ex- 
ternal impression. 

iii.  Hence  follows  the  general  principle  (361),  that  those 
movements  in  bodies  which  are  most  usually  nerve-actions, 
may  at  another  time,  or  in  another  animal,  be  sentient  actions, 
or  vice  versa;  or  they  may  be  at  the  same  time  both  sentient 
and  nerve  actions ;  in  every  case  being  the  same  movements, 
but  only  excited  by  different  stimuli. 

365,  i.  If  a  sentient  action  cannot  be  also  at  the  same  time 
a  nerve-action,  no  unfelt  or  non-conceptional  impression  can 
cause  it  as  a  nerve-action. 

ii.  If  a  nerve- action  cannot  be  also  a  sentient  action,  no  im- 
pression, either  felt  or  produced  by  conceptions,  can  excite  it  (362). 

iii.  If  a  sentient  action  can  be  also  a  nerve-action,  the  im- 
pression exciting  it  can  act  in  both  ways  (364,  i,  ii). 

366.  Since  sentient  actions  and  nerve-actions  are  analogous 
animal  movements  from  impressions  on  the  nerves,  and  differ 
only  in  this,  that  in  the  former  the  impressions  are  felt  or 
originate  from  conceptions,  but  in  the  latter  not,  (193,  364, 
iii,)  it  follows  that  all  those  movements  which  in  one  animal 
are  sentient  actions  only,  or  both  sentient  actions  and  nerve- 
actions,  may  be  nerve-actions  only  in  another,  excited  by  im- 
pressions; so  that  the  external  impressions  are  never  felt,  and 
the  internal  never  produced  by  conceptions,  but  by  other  sti- 
muli ;  in  this  way  an  animal  may  not  require  for  all  its  animal 
actions,  either  material  ideas,  or  a  sentient  brain,  or  conceptions, 
or  mind.  This  appears  to  be  the  case  with  those  creatures 
which  have  no  brain,  but  only  nerve-like  fibrils,  as  polypes,  in 
which  there  is  no  brain,  but  the  nerves  are  interwoven  in 
ganglia  only.  In  animals  with  a  sentient  brain,  every  external 
impression  which  is  felt  passes  directly  to  it,  and  excites  therein 
a  material  idea,  and  in  the  mind  a  conception  (35).  Having 
reached  the  brain,  it  is  turned  iDack  or  reflected,  as  it  were,  and 
goes  back  as  an  internal  impression  of  a  conception,  into  those 
nerve-fibrils  that  move  the  limb,  which  the  external  impression 
is  enabled  to  control  by  means  of  a  sentient  action  of  its  sen- 
sation (129)  .j  At  the  moment  of  this  reflection,  when  the  ex- 
ternal impression  is  changed  into  the  internal,  thought  takes 
place  in  the  mind,  and  thereby  the  movement  which  the  ex- 
ternal impression  excites  becomes  a  sentient  action  (97)1  When 


198  ANIMAL  FORCES.  [ii. 

a  polype  receives  external  impressions,  they  pass  onwards  (31) 
to  the  nearest  ganglion,  whence  they  are  reflected  as  if  from  a 
brain,  either  entirely,  or  in  such  a  way,  that  they  only  partly 
reach  other  ganglia,  and  thus  they  can  be  reflected  many  times. 
(Compare  §  48.)  It  is  sufficient  that  at  these  points  the  external 
impressions  are  transformed  into  internal,  and  pass  again  from 
the  ganglia  along  the  nerves  to  the  mechanical  machines,  which 
they  put  in  motion,  no  act  of  thought  taking  place  during  the 
transformation,  because  there  is  no  brain  (for  in  that  only  is 
the  seat  of  the  conceptive  force),  nor  are  the  internal  impres- 
sions adapted  to  excite  a  sentient  action  (97).  In  this  way, 
poises  may  be  enabled  to  perform  all  their  animal  movements, 
solely  by  means  of  external  impressions  on  their  nerves,  without 
having  feeling,  or  thought,  and  without  either  brain  or  soul. 
But  inasmuch  as  all  this  is  accomplished  by  means  of  animal 
forces  (32,  121),  these  animals  do  not  act  as  mere  machines,  as 
Descartes  supposed,  but  according  to  purely  animal  laws,  which 
cannot  be  deduced  from  either  mechanical  or  physical  principles, 
or  explained  by  them.  As  Haller  observes  on  the  last  page 
of  his  introduction  to  the  translation  of  Biiflijn^s^^  History 
of  Nature,'  they  are  animals  whose  life  consists  simply  in 
irritability. 

367.  Other  conclusions  follow  from  the  preceding  propositions. 
i.  If  the  agency  of  material  ideas  on  the  cerebral  origin  of 
the  nerves,  whereby  they  develop  sentient  actions  in  the  me- 
chanical machines,  be  sufficiently  ascertained — that  is  to  say,  if 
it  be  known  on  what  nerve-fibrils,  with  what  kind  of  stimulus 
or  movement,  and  in  what  direction  and  force,  each  received 
material  idea  operates  to  produce  certain  sentient  actions  on 
the  muscles — another  stimulus  may  be  applied  to  the  cerebral 
origin  of  the  nerves,  or  deeply  in  their  trunks,  instead  of  that 
of  conceptions,  and  thereby  all  the  movements  which  the  animal 
performs  as  sentient  acts,  may  be  artificially  produced  without 
brain,  or  mind,  or  conceptions,  just  as  nature  produces  them  in 
anencephalous  animals,  by  the  transformation  of  the  external 
impression  into  the  internal  without  any  conceptions  being 
experienced.  Thus,  if  the  spinal  cord  or  foot  of  a  decapitated 
frog  be  irritated,  it  moves  from  one  place  to  another  as  if 
acting  volitionally,  although  deprived  of  both  consciousness 
and  will  (357,  359). 


I 


CH.  I.]  NERVE-ACTIONS  IN  GENERAL.  199 

ii.  It  is  possible,  that  in  animals  with  a  sentient  brain, 
movements  are  transformed  from  sentient  actions  into  nerve- 
actions,  as  is  probably  the  case  with  the  respiratory  and  other 
movements  (285-86);  and  vice  versa  from  nerve-actions  into 
sentient  actions,  as  in  the  sentient  actions  of  the  instincts  of 
newly-born  animals  (269);  or  become  both  when  previously 
they  were  only  one  or  the  other,  or  vice  versa,  become  only 
one  or  the  other,  when  previously  they  were  both.  To  establish 
the  possibility  of  these  changes,  each  example  must  be  specially 
considered. 

368,  i.  A  sentient  action  may  be  changed  into  a  nerve- 
action,  when  the  transmission  of  the  external  impression  to 
the  brain  is  prevented,  which  may  take  place  from  natural  or 
contra-natural  hindrances.  (Compare  §  51,  iii,  iv,  v.) 

ii.  A  sentient  action  from  a  conceptional  impression  may  be 
changed  into  a  nerve-action  when  the  conception  ceases  (136 — 
139)  and  other  stimuli,  having  a  similar  mode  of  action,  are 
applied  to  the  conducting  nerves  (123,  360).  Thus,  the  mere 
physical  irritation  of  an  acrid  humour  acting  upon  the  motor 
nerves  at  their  origin  in  the  brain  or  along  their  course,  will 
excite  contractions  of  the  muscles  which  ordinarily  are  volitional. 
The  same  may  take  place  automatically,  as  when  an  external 
impression  which  does  not  reach  the  brain,  stimulates  the  nerves 
in  the  same  way  as  a  volitional  conception,  in  consequence  of 
being  reflected  downwards  in  the  ganglia,  or  at  the  points  of 
division  of  the  fibrils,  thus  producing  movements  as  nerve- 
actions,  which  are  exactly  identical  with  those  excited  by  voli- 
tion (48,  151).  The  closure  of  the  sphincter  of  the  bladder, 
whereby  the  urine  is  retained,  is  usually  a  voluntary  act ;  but 
when  the  volition  ceases,  and  even  when  the  contrary  state  is 
willed,  an  irritation  in  the  bladder,  which  is  not  felt,  causes  it 
to  be  spasmodically  closed,  even  until  death ;  in  this  case,  the 
former  volitional  action  is  changed  by  the  vis  nervosa  of  an 
external  impression  into  a  nerve-action. 

iii.  A  nerve-action  may  be  transformed  into  a  sentient 
action,  if  it  results  from  an  external  impression,  when  the 
natural  obstacle  to  the  transmission  of  the  latter  to  the  brain 
is  removed  (45);  if,  for  example,  a  limb  (as  the  leg),  being 
deprived  of  sensation  by  an  injury  to  the  nerve,  and  being 
scourged,  becomes  inflamed,  as  a  nerve-action  (207,  357),  and 


200  ANIMAL  FORCES.  [ii. 

then  the  power  of  sensation  being  restored,  is  inflamed  in 
consequence  of  the  pain  excited  by  the  scourging,  the  inflam- 
mation is  a  sentient  action  from  an  external  sensation  (207). 

iv.  A  nerve-action  proceeding  from  an  internal  non-concep- 
tional  impression  may  be  changed  into  a  sentient  action  by 
the  addition  of  conceptional  impressions,  which  act  upon  the 
fibrils  of  the  motor  nerves  conducting  the  impression  itself 
(130,  360).  Thus,  in  convulsions  proceeding  from  mechanical 
irritants  applied  to  the  motor  fibrils  at  their  origin,  or  in  their 
course,  or  from  worms  in  the  stomach,  the  external  impression 
is  not  perceived,  and  the  convulsions  are  simply  nerve-actions 
(162,  360);  but  if  a  fright,  or  pain,  or  other  powerful  external 
sensation,  be  superadded,  which  also  excites  convulsions,  but  as 
sentient  actions  by  means  of  conceptional  impressions,  then 
the  convulsive  paroxysm  is  re-excited  by  the  latter  as  a  sen- 
tient action.  In  this  way  epileptic  paroxysms,  originally  purely 
nerve- actions,  may  be  reproduced  as  sentient  actions,  by  fear, 
or  pain,  or  other  violent  conceptions  capable  in  themselves  of 
exciting  convulsive  attacks. 

V.  An  action  may  be  both  a  nerve-action  and  sentient  action 
at  the  same  time,  if  the  causes  of  a  change  into  one  or  the 
other  are  superadded,  as  in  the  instances  above  mentioned, 
yet  neither  ceasing  to  be  what  it  was.  If,  after  both 
are  excited,  the  causes  of  the  one  kind  only  cease,  then  the 
other  class  remains  (364). 

369.  There  naturally  arises  a  question  out  of  the  preceding 
considerations  (362 — 368),  as  to  the  advantages  which  animals 
endowed  with  mind  and  brain  derive  from  their  movements 
being  often  at  the  same  time  both  nerve-actions  and  sentient 
actions,  and  produced  by  a  twofold  cause ;  since  in  fact,  mere 
impressions  without  the  co-operation  of  the  brain  or  mind  may 
be  sufficient  to  produce  the  animal  functions,  as  in  anencephalous 
animals.  Although  this  question  has  been  noticed  already 
(184,  ii),  it  requires  further  consideration  here. 

370.  To  the  end  that  an  impression  be  felt,  it  is  changed  in 
the  brain  into  an  internal  impression  (121,  129).  But  this 
change  of  an  external  into  an  internal  impression  may  take 
place  also  by  means  of  ganglia,  or  in  some  other  way  usual  or 
possible  with  animals ;  only  in  such  cases,  the  external  impres- 
sion will  have  no  other  reflex  action  in  the  animal  machines 


CH.  I.]  NERVE-ACTIONS  IN  GENERAL.  201 

than  that  of  which  it  is  capable  in  virtue  of  its  purely  animal 
force,  which  it  reflects  upon  the  motor  nerves   (364,  ii);  and 
the  whole  of  tliis  action  is  purely  corporeal  and  automatic,  and 
cannot  be   changed,  or  induced,  or   extended,   or  limited,   or 
directed  volitionally.      If,  on  the  other  hand,  the  external  im- 
^pression  be  also  felt,  then  the  mind,  according  to  its  psycho- 
logical laws,  connects  volitionally  with  it  many  other  conceptions 
(2 1 9 — 224) ,  the  internal  impression  s  of  which  can  produce  through 
the  motor  nerves  such  sentient  actions  as  the  unfelt  external 
impression  could  not  have  developed  at  all,  or,  at  least,  not  in 
(combination  with  the  will  of  the  animal.      It  is  for  this  reason, 
!that  we  find  animals  without  brain  and  without  any  traces  of 
Imind,  to  be  capable  of  very  few  kinds  of  animal  movements ; 
that  those  of  which  they  are  capable  are  excited  by  the  external 
'impressions  automatically  and  necessarily ;  and  that  they  are  so 
.far  from  being  under  the  control  of  the  animal,  as  to  be  excited 
ind  continue  just  the  same  whether  they  be  injurious  or  bene- 
icial.      In  animals  endowed  with  mind,  on  the  contrary,  every 
external  sensation  develops  by  means  of  the  series  of  secondary 
conceptions  caused  by  it,  yet  spontaneously  or  volitionally,  a 
number  of  new  movements,  which  would  not  have  resulted  from 
the  unfelt  external  impression  in  this  connection,  and  perhaps 
not  at  all.      Now,  if  nature  has  compensated  brainless  animals 
for  the  want  of  spontaneous  and  volitional  conceptions  adapted 
[to   their   preservation   and   well-being,   by  the  automatic  and 
necessary  results   of  mere  impressions,  as  is  particularly  the 
case  in  the  instincts  (266) ;  it  is  obvious,  that  it  is  with  the 
same  object  in  view  that  nature  has  endowed  other  animals 
capable  of  so  much  more  varied  animal  motor  forces,  with  the 
faculty  of  both  feeling  the  external  impressions  and  acting  in 
accordance  with  the  resulting  sensations.    (Compare  §  184,  ii.) 
371.  The  same  relations  exist  with  regard  to  internal  im- 
pressions.    When  they  are  not  produced  by  conceptions,  they 
originate  automatically  and  corporeally  from  mere  animal  stimuli 
of  the  nerve- medulla,  either  at  the  cerebral  origin,  or  in  the 
trunk  of  the  nerves ;  and  nerve- actions  in  the  machines  result 
just  as  automatically  and  corporeally ;  either  because  a  purely 
physical   influence    suitably   irritates    the   nerves   from   above 
downward,  or  else,  because  unfelt  external  impressions  reflected 
in  their  course  to  the  brain  act  in  the  same  way.    If,  however. 


202  ANIMAL  FORCES.  [ii. 

tlie  animal  itself  produces  internal  impressions^  and  arranges 
them  by  means  of  spontaneous  or  volitional  or  even  free-will 
conceptions^  the  sentient  actions  result  according  to  laws  entirely 
different  from  those  of  the  automatic  necessity  just  described 
(119,  121),  and  are  subject  to  the  will  and  reason  of  the  animal. 
When  a  lobster  gets  one  of  its  legs  accidentally  fixed  in  one  of 
its  claws,  and  the  claw  is  then  made  to  contract  by  a  mere 
stimulus  solely,  the  leg  is  crushed,  and  the  animal  is  excited  to 
tear  away  the  leg  by  the  external  impression  of  the  forcible  crush- 
ing, and  is  thereby  mutilated  for  a  long  time  without  suffering. 
But  if  the  closure  of  the  claws  and  the  insertion  of  the  leg 
between  them  were  sentient  actions  from  conceptions,  its  mind 
would  readily  have  deduced  a  third  conception,  namely,  to  open 
the  claws,  and  withdraw  the  leg.  But  as  this  does  not  occur, 
the  purely  automatic  actions  are  excited,  and  the  animal  loses 
a  limb  in  virtue  of  the  working  of  a  piece  of  mere  animal 
machinery,  which  it  need  not  have  lost,  if  the  movements  re- 
sulting from  its  external  impressions  had  been  at  the  same 
time  sentient  actions  from  its  conceptive  force.  In  such 
cases,  in  sentient  animals,  the  conceptive  force  regulates  the 
movements  by  means  of  internal  impressions,  although  im- 
pressions from  mere  animal  stimuli  may  have  the  same  effect 
automatically. 

372.  Having  considered  the  relation  of  the  vis  nervosa  to 
the  animal-sentient  forces,  it  becomes  necessary  to  show  the 
special  seat  of  the  former.  The  animal- sentient  forces,  whose 
seat  is  the  sentient  brain,  extend  their  operations  as  well  into 
the  animal  machines,  as  (through  these)  into  the  mechanical 
(117).  The  proper  seat  of  the  vis  nervosa  is  the  nerves,  for  all 
primary  animal  forces  have  their  seat  in  animal  machines  only 
(6),  although  they  are  transmitted  through  the  animal  machines 
into  the  mechanical,  and  excite  animal  actions  therein  (7).  The 
proper  animal  machines  are  the  brain  and  nerves,  in  which  the 
vital  spirits  are  contained  (9) .  But  the  operations  of  the  brain  as 
a  sentient  animal  machine,  are  for  the  most  part  only  sentient 
actions  (25).  Consequently,  its  peculiar  animal  forces  are  animal- 
sentient  forces  (6).  Now,  the  two  kinds  of  vis  nervosa  are  not 
animal-sentient  forces  (356),  consequently,  are  not  peculiar  to 
the  brain ;  and  since  the  nerves  supplied  with  vital  spirits  are 
the  only  true  animal  machines,  except  the  sentient  brain  and 


CH.  I.]  NERVE-ACTIONS  IN  GENERAL.  203 

the  cortical  substance  which  surrounds  it  (159),  it  follows,  that 
the  principal  seat  of  the  primary  vis  nervosa  must  be  specially 
in  the  nerves. 

373.  Nevertheless,  it  cannot  be  denied,  that  the  medullary 
substance  of  the  brain  itself  has  some  share  in  the  vis  nervosa. 
We  cannot,  however,  determine  by  experiment,  whether  an  ex- 
ternal impression  which  reaches  the  brain  but  is  not  felt,  does 
not  develop  some  animal  action  through  the  medullary  matter 
of  the  brain,  although  it  causes  no  material  external  sensation 
(46,  iii).  For,  although  it  excites  the  most  energetic  movements 
through  the  nerves,  yet  the  same  phenomena  occur  when  the 
head  is  wholly  severed  from  the  body  (357),  consequently  the 
external  impression  is  changed  into  an  internal  lower  down, 
probably  in  the  ganglia  (48),  to  produce  the  nerve-actions,  for 
it  would  appear  as  if  the  condition  absolutely  requisite  to  the 
change  of  the  external  impression  into  an  internal  in  the  brain 
and  its  reflection  is,  that  it  develops  therein  a  material  external 
sensation  (25).  Nevertheless,  there  are  cases  in  which  it  must 
remain  doubtful  whether  an  external  impression  does  not  produce 
purely  nerve-actions  through  the  medullary  substance  of  the 
brain,  for  when  the  latter  is  injured  in  an  animal,  the  body  is 
convulsively  agitated  (Haller^s  ^  Physiology,^  §  368).  It  has 
been  already  shown  (132),  that  this  may  constitute  sentient 
actions  of  an  external  sensation  of  pain,  because  the  medullary 
substance  also  transmits  external  impressions  to  the  origins  of 
the  fibrils  of  the  irritated  nerve,  or  of  the  fibrils  of  the  cerebral 
medulla,  and  can  excite  therein  material  external  sensations 
which  may  act  reflexly  by  means  of  their  internal  impression 
on  the  brain,  and  through  it  on  the  nerves  in  the  mechanical 
machines.  But  if  a  similar  external  impression  on  the  medul- 
lary substance  should  not  be  felt,  and  yet  excite  movements 
(convulsions),  would  not  these  be  no  other  than  mere  nerve- 
actions  of  an  external  impression  on  the  brain,  and  must  not 
the  brain,  consequently,  possess  a  vis  nervosa  of  external  impres- 
sions in  addition  to  its  animal-sentient  forces  ?  It  is  difficult  to 
determine,  whether  external  impressions  be  felt  or  not,  and  in 
the  latter  case,  whether  they  produce  the  same  movements  as 
in  the  former.  Although  indeed  many  injuries  of  the  brain 
are  not  at  all  painful  or  manifest,  and  foreign  bodies  may  lodge 
therein  for  a  lengthened  period  without  the  knowledge  of  the 


204  ANIMAL  FORCES.  [ii. 

patient,  still  it  is  probable  that  sometimes  external  impressions 
on  the  brain  itself  excite  nerve-actions,  and  it  may  really  be 
capable  in  some  degree  of  the  vis  nervosa  of  external  impres- 
sions. Many  facts  appear  to  corroborate  this.  ^'^A  certain 
person  had  a  piece  of  bone  driven  into  his  brain.  For  a  long 
time  no  results  followed,  but  at  last  spasms  and  death  took 
place  from  a  large  ulcer  of  the  brain.'^  (Haller.)  Still  nothing 
certain  can  be  stated  on  this  point  (624,  iv).  It  is  more 
probable,  however,  that  an  internal  impression  on  the  brain, 
not  proceeding  from  conceptions,  excites,  as  nerve-actions,  the 
same  movements  that  it  would  have  excited  if  it  had  proceeded 
from  a  conception,  since  this  continually  takes  place  in  the 
spinal  cord,  which  is  analogous  to  the  brain  (12^).  Indeed,  in 
the  case  just  mentioned,  when  an  external  impression,  though 
not  felt,  excites  animal  movements  in  the  body,  they  must  have 
been  caused  by  the  external  impression  reflected  independently 
of  the  animal-sentient  force,  and  without  the  intervention  of  a 
conception,  and  acting  as  a  mere  internal  impression.  But 
without  laying  much  stress  on  this  doubtful  case,  there  are 
many  other  reasons  for  recognising  the  existence  of  a  vis 
nervosa  in  impressions  on  the  brain  not  caused  by  conceptions. 
When  in  a  plethoric  person  the  brain  becomes  congested,  as  in 
stooping,  and  the  small  arteries  in  the  optic  nerves  are  dis- 
tended, and  stimulate  the  origin  or  trunk  of  the  nerves,  this 
internal  impression  in  the  brain  is  transmitted  downwards  to 
the  termination  of  the  nerve  in  the  eye,  and  there  causes 
an  external  impression  which  is  transmitted  upwards  (31),  and 
excites  in  the  mind  an  imperfect  external  sensation  (148).  This 
imperfect  external  sensation  of  various  false  appearances  before 
the  eyes,  is  a  manifest  proof,  that  internal  impressions  which  do 
not  depend  on  conceptions,  are  transmitted  through  the  brain, 
and  have  the  same  actions  as  those  which  proceed  from  con- 
ceptions ;  for  just  as  v&ry  vivid  imaginations,  or  passions,  cause 
(as  sentient  actions)  imperfect  external  sensations  of  various 
appearances  before  the  eyes  (148),  so  in  this  case,  the  pressure 
of  blood  in  the  optic  nerves  at  their  cerebral  origin  acts  as  a 
nerve-action,  and  sparks  and  motions  are  seen  before  the  eyes 
as  vividly  as  if  they  were  real.      Now  since  the  optic  nerve  is 

•   Fide  foot-note  to  §  34.— Ed. 


CH.  1.1  NERVE-ACTIONS  IN  GENERAL.  205 

I! 
in  the  brain,  constitutes  a  portion  of  it,  and  is  close  to  it  in  its 

course,  this  fact  can  be  received  as  a  proof,  that  there  is  a  vis  ' 

nervosa   seated  in  the  brain  itself,  which   develops  the  same 

jinovements  as  if  a  conception  irritated  in  a  similar  manner  the 

ime  spot  in  the  brain,  and,  consequently,  as  if  the  action  were 

jffected  by  the  animal-sentient  force  of  the  brain. 

374.  The  medullary  matter  of  the  brain  having  some  share 
Jn  the  vis  nervosa,  it  is  certain  that  the  cortical  substance  also 

endowed  with  it,  since  its  peculiar  function  is  to  secrete  the 
ital  spirits  from  the  blood,  and  supply  them  to  the  other 
dmal  machines  (11).  Like  all  secretions,  this  process  is  at 
jast  partly  animal,  and  not  a  sentient  action  (159);  it  is  there- 
fore a  nerve-action  of  the  vis  nervosa  of  the  cortical  substance 
(353),  and  subject  to  the  same  laws  as  other  secretions,  which, 
is  we  shall  subsequently  show,  are  effected  simply  by  means  of 
ihevis  nervosa.  (Vide  §§  471,  530.)  As  the  secretion  and  dis- 
dbution  of  the  vital  spirits  is  a  process  of  the  highest  import- 
ice  to  animal  life,  this  vis  nervosa  of  the  brain  demands  great 
jonsideration  in  animal  physiology. 

375.  The  nerves,  however,  must  be  considered  as  the  prin- 
sipal  seat  of  the  vis  nervosa,  and  rightly  give  it  its  peculiar 
lesignation.  But  the  question  arises,  whether  the  nerves  are 
mdowed  with  their  vis  nervosa  universally  and  without  limita- 
tion, or  whether  only  in  virtue  of  their  relations  to  the  me- 
jhanical  machines  with  which  they  are  incorporated.  As, 
lowever,  the  sensory  nerves  possess  a  vis  nervosa  as  well  as  the 
lotor,   it    must  be  a  general  property  of  the  nerves,   or  in 

>ther  words,  the  two  kinds  of  vis  nervosa  are  primary  animal 
Forces  proper  to  the  nerves. 

376.  An  external  impression  on  a  sensory  nerve  passes  directly 
[upwards  to  the  brain  (31),  and  is  not  readily  reflected  on  its 

>urse,  or  changes  into  a  non-conception al  internal  impression, 

)ecause  this  class  of  nerves  has  no  ganglia,  in  which  the  course 

>f  the  impression  could  be  changed  and  reflected  (14,  48).  The 

|pnly  way  in  which  this   occurs  is  the  reflection  in  the  brain, 

diere  the  external  impression,  when  the  mind  feels  it,  is  trans- 

[formed  into  a  material  idea  for  the  internal  impression  of  a 

Iconception  (121,  129,  ii).   But  in  this  way,  it  produces  sentient 

actions  only  (97).  It  is  not  yet  determined  whether  there  be       /' 

hases  in  which  an  impression,  when  transmitted  along  sensory    ^ 


206  ANIMAL    FORCES.  [ii. 

nerves,  excites  visible  animal  actions  in  the  brain,  without 
producing  a  material  external  sensation  at  the  origin  of  its 
nerves.  At  least  such  actions  are  not  observed  in  syncope,  or 
profound  sleep  (49),  when  light  streams  into  the  open  eye,  or 
a  loud  noise  strikes  on  the  ear  without  being  felt.  Yet  in  these 
cases  some  animal  actions  in  the  nerve  must  result,  because 
the  external  impression  made  on  it  goes  to  the  brain,  which  is 
of  itself  an  animal  movement  (32),  and  because  the  sensational 
force  of  the  nerves  may  be  impaired  at  their  cerebral  origin,  when 
in  cases  of  this  kind,  the  external  impressions  are  too  violent, 
although  they  are  not  felt.  Thus,  for  example,  deafness 
gradually  comes  on  in  persons  who  sleep  in  a  mill,  and  blindness 
from  the  gleaming  of  the  moon's  rays  into  the  eyes  during 
sleep,  &c.  Only,  these  are  not  perceptible  nerve- actions,  but 
are  probably  only  irregularities  of  the  vital  spirits,  or  imper- 
ceptible changes  in  the  medulla  of  the  nerves,  and  consequently 
no  definite  conclusion  can  be  drawn  as  to  the  vis  nervosa  of 
external  impressions  situate  in  the  sensory  nerves. 

377.  A  non-conceptional  internal  impression  on  purely  sensory 
nerves,  displays  the  traces  of  its  actions  distinctly  enough,  as 
in  the  case  of  the  nerves  of  vision  previously  mentioned  (373). 
All  the  visual  and  auditory  phenomena  so  often  noticed  on 
stooping,  or  whirling  round  too  rapidly,  or  binding  the  neck 
too  tightly,  are,  in  fact  none  other  than  animal  actions  (namely, 
imperfect  external  sensations)  in  purely  sensory  nerves,  excited 
by  non-conceptional  impressions,  which  are  usually  produced  by 
conceptions,  and  exciting  similar  actions  (148).  Analogous 
phenomena  are  manifested  in  the  nerves  of  taste,  and  smell, 
and  touch,  so  that  persons  of  great  sensibility,  and  especially  in 
certain  morbid  states,  think  they  perceive  tastes  or  odours  which 
are  not  present,  and  are  not  caused  by  any  conception. 

378.  It  was  previously  observed  (150),  that  true  external 
sensations  may  be  regarded  as  being  imperfect,  when  an  ex- 
ternal impression  is  really  made  on  the  sensory  nerves,  but  by 
something  within  the  organ  of  sense;  as,  for  example,  when 
in  inflammation  of  the  eyes,  or  in  retention  of  air  in  the  ears, 
phenomena  are  seen  or  heard  which  are  not  in  fact  so  real  as 
it  is  thought.  These  may  be  termed  generally  imperfect  ex- 
ternal sensations  from  an  erroneous  judgment ;  those  mentioned 
in  the  preceding  section  may  be  termed  imperfect  external 


CH.  1.]  NERVE-ACTIONS  IN  GENERAL.  207 

sensations  from  non-conceptional  internal  impressions,  and  those 
in  §  148  imperfect  external  sensations  from  conceptional  internal 
impressions.  It  is  manifested^  that  the  first  of  these  may  be 
easily  but  erroneously  confounded  with  the  second. 

Note. — It  may  be  permitted  just  to  state  here,  a  bearing 
which  these  views  have  on  pathology.  Since  the  phenomena 
mentioned,  as  arising  from  the  causes  aforesaid,  may  be  excited 
the  more  readily  in  proportion  as  the  nerves  are  more  sensitive, 
and  the  conceptions  vivid  (148),  it  is  obvious,  why  persons  of 
irritable  temperaments  and  nerves,  and  patients  in  whom  the 
nerves  are  unusually  susceptible  of  all  kinds  of  impressions, 
have  those  phenomena  so  frequently,  and  how  erroneously  they 
are  attributed  to  a  too-vivid  power  of  the  imagination.  * 

379.  Now  since,  therefore,  both  the  brain  and  sensory 
nerves  are  endowed  with  vis  nervosa,  it  must  be  understood, 
that  its  actions  are  developed  independently  of  the  brain 
(375,  358,  360),  although  they  can  be  rarely  rendered  visible, 
as  they  can  scarcely  communicate  any  visible  movement  (151) 
to  a  mechanical  machine.  But  it  is  quite  otherwise  with 
[motor  nerves  ;  and  as  almost  all  movements  of  animal  machines 
are  either  muscular  movements,  or  effected  by  means  of 
muscles,  or  at  least  by  muscular  fibrils,  the  vis  nervosa  would 
appear,  although  erroneously  (375,  377),  to  be  peculiar  to 
muscles  and  muscular  fibrils  only.  This  has  probably  given 
rise  to  the  new  doctrine  in  physiology  propounded  by  the 
otherwise  correct  observer,  Haller,  who  has  laid  down  the 
principle,  that  the  muscular  fibre  possesses  in  itself  a  primary 
animal  motor  force,  which  he  has  termed  vis  insita,  muscular 
irritability  [die  angeborne  kraft],  {Vide  Haller's  ^Physiology,' 
§  400,  402.)  It  is,  therefore,  of  importance  to  investigate  the 
subject,  and  see  whether  this  opinion  be  well  founded  or  not. 

380.  To  prove  that  the  muscular  fibre  possesses  an  animal 
motor  force  peculiar  to  itself,  it  must  be  shown  to  put  itself  in 
action  without  the  co-operation  or  assistance  of  other  animal 
machines  or  forces.  A  probable  way  of  doing  this,  would  be 
to  separate  a  muscle  from  all  other  animal  machines,  and  then 
demonstrate  the  existence  of  an  animal  motor  force.   But  since 

j every  muscle  has  its  nerves  (161),  and  is  therefore  connected 
with  animal  machines,  which  enter -into  its  substance,  and  are 
so  intimately  incorporated    therewith  and   so    constituting   a 


208  ANIMAL  FORCES.  [ii. 

whole,  that  no  one  has  been  able  hitherto  to  trace  them  to 
their  terminations,  it  follows  that  it  is  impossible  to  separate 
the  muscular  fibrils  from  the  nerve-fibrils,  and  so  afford  the 
proof  required;  so  that  when  it  is  affirmed,  that  a  muscle 
retains  its  animal  force  after  being  separated  from  its  nerves, 
it  is  first  of  all  necessary  to  show  how  this  separation  has  been 
eff'ected. 

381 .  The  trunks  of  the  nerves  distributed  to  a  muscle  have 
been  divided,  and  the  latter  have  nevertheless  been  excited  to 
movement  by  an  external  irritant.  Is  this  the  required  proof? 
Certainly  not.  The  division  of  the  trunks  does  not  destroy 
the  infinitely  numerous  twigs  distributed  to  the  muscle,  and  so 
long  as  it  retains  these,  the  vis  nervosa  is  incorporated  with 
it.      Further : 

i.  Nerves  retain  their  purely  animal  motor  force  derived 
from  external  impressions  from  the  point  of  impression  to 
the  point  of  bisection  (357,  358).  So  long,  therefore,  that  it 
cannot  be  shown,  that  the  irritant  which  moves  a  muscle  after 
its  nerves  have  been  divided,  cannot  act  impressionally  on  the 
nerve-twigs  in  the  muscle,  and  that  the  animal  movement  in 
the  latter  is  not  excited  thereby,  the  peculiar  animal  force  of 
the  muscular  fibre  is  not  demonstrated  by  the  experiment. 
Consequenth^,  although  the  movement  of  a  heart  separated 
from  the  body  be  renewed  and  increased  by  puncture  with  a 
needle,  by  acrid  irritants,  by  injections  of  water,  &c.,  still  this 
does  not  prove  that  the  irritation  induced  this  activity  through 
the  muscular  fibrils  only,  without  the  co-operation  of  the 
nerves,  for  it  is  incontrovertible  that  it  can  produce  them  in 
virtue  of  the  impression  on  the  nerves  of  the  heart,  because 
every  point  of  a  muscle,  and  consequently  of  the  heart,  both 
its  inner  and  outer  surface,  which  the  needless  point  touches, 
can,  in  the  healthy  state,  so  receive  the  irritation,  that  it  is 
felt,  which  is  only  possible  by  means  of  nerves ;  while  further, 
the  same  increased  activity  of  the  heart  results  as  an  animal 
action  excited  by  the  external  impression  which  this  irritation 
causes,  whether  it  goes  to  the  brain  or  not  (357,  358). 

ii.  The  nerves  retain  also  their  vis  nervosa,  excited  by  non- 
conceptional  internal  impressions  from  the  point  of  impression 
(whether  it  be  at  the  origin  of  the  nerves,  or  on  their  trunks), 
to  the  terminating  fibrils  (359,  360).     When,  consequently,  the 


I 


.  I.]  NERVE-ACTIONS  IN  GENERAL.  209 


a  separated  muscle  is  irritated  by  a  physical  irritant  applied  to 
the  medulla  of  the  trunk,  or  when  an  external  impression  is 
reflected  in  the  muscle  itself  and  becomes  an  internal  im- 
pression, ia  either  case  movement  of  the  muscle  may  result, 
without  it  necessarily  following  that  the  motor  force  is  situate 
in  the  muscular  fibres,  independently  of  the  nerves.  Unless 
it  can  be  proved  that  the  irritant  which  moves  a  muscle,  whose 
nerves  are  divided,  cannot  have  excited  a  non-conceptional  im- 
pression in  the  medulla  of  the  nerve,  whether  by  causing  a 
mere  physical  irritation  of  the  latter,  constituting  an  internal 
impression,  or  by  the  reflexion  of  an  external  impression  in 
the  muscle  itself,  and  that  the  movement  of  the  muscle  is  not 
produced  by  such  impression,  it  cannot  be  allowed  that  the 
peculiar  animal  force  of  the  muscular  fibre  is  demonstrated  by 
the  experiment  (380). 

382.  But  perhaps,  it  may  be  urged,  a  muscle  may  be  so 
irritated,  as  to  be  excited  to  movement  without  the  irritant 
causing  at  the  same  time  an  impression  on  its  nerves,  for  it 
is  not  every  excitant  which  causes  an  impression  (32) ;  and 
possibly  the  muscular  fibres  are  excited  to  movement  by 
irritants  which  do  not  animally  affect  the  nerves. 

This  proposition  would  be  of  importance,  if  it  had  been  pre- 
viously shown  that  muscular  fibres  are  capable  of  movement, 
independently  of  their  nerves ;  but  this  condition  is  wanting. 
Besides,  facts  prove  that  the  impressions  which  move  muscles 
affect  also  the  nerves,  because  they  can  be  felt.  We  will,  how- 
ever, notice  the  leading  points  which  Haller  advances  in 
defence  of  his  doctrine. 

383.  Haller  observes  that  muscle  is  excited  to  movement 
when  touched,  but  nerve  is  not.  Consequently,  this  irritability, 
or  the  property  to  be  moved  animally,  from  a  certain  contact, 
is  proper  to  muscular  fibres  rather  than  to  nerves.  May  not, 
however,  they  possess  this  property  simply  through  their  nerves  ? 
If  the  muscular  fibres  constitute  a  mechanical  machine,  excited 
to  movement  by  suitable  impressions  on  its  nerves,  it  is  the 
machine  that  possesses  this  capability  of  movement  rather 
than  the  nerves  themselves,  for  an  impression  never  visibly 
excites  movement  in  the  nerves,  but  in  the  mechanical  machines 
with  which  they  are  incorporated  (153).  The  same  applies  to 
all  movements  of  muscle  excited  by  conceptions,  or  by  the  will. 

14 


210  ANIMAL  FORCES.  [ii. 

The  spring  of  a  watch  produces,  by  an  invisible  movement, 
the  visible  movements  of  the  wheels.  But  should  the  primary 
force  which  sets  them  in  motion  be  therefore  attributed  to 
them? 

384.  Haller  observes,  that  it  cannot  be  proved  that  from  so 
few  nerves  as  are  distributed  in  a  muscle,  so  many  fibrils  can 
arise  as  there  are  muscular  fibrils;  consequently  the  latter 
cannot  be  considered  as  prolongations  of  the  former.  But  this 
is  not  necessary ;  it  is  enough  that  every  part  of  a  muscle  is 
supplied  with  nerves,  and  that  every  muscular  fibril,  where- 
soever irritated  by  the  point  of  a  needle,  is  sensitive.  And 
if,  as  Haller  thinks,  the  nervous  fluid  communicates  this  irri- 
tability, the  fluid  is  derived  through  the  nerves. 

385.  Haller  advances  (§§  402,  407),  that  animals  without 
brain,  spinal  cord,  or  nerves,  such  as  polypes,  are  equally  ex- 
cited to  motion  by  an  irritant,  and  thus  show  that  the  structure 
of  the  muscle  alone  is  sufficient  for  animal  movement.  The 
vital  movements  of  plants  lead  to  the  same  conclusion. 

The  movements  of  plants,  even  those  of  the  sensitive  plant, 
are  regulated  according  to  the  mechanical  laws  of  movement  of 
organised  bodies.  The  fibrils  in  insects,  which  a  touch  excites 
to  animal  movements,  are  not  such  nerves  or  muscles  as  ours, 
but  still  animal  machines  (6),  which  are  capable  of  receiving 
external  impressions  (31,  32),  whereby  they  stimulate  the 
mechanical  machines  of  insects  to  animal  movements  (7,  162), 
and,  consequently,  a  species  of  motor  nerves  (14),  and  thus 
aff'ord  no  proof  of  the  existence  of  the  primary  motor  force  of 
muscular  fibre. 

386.  The  heart  (it  is  advanced  by  Haller)  and  the  intes- 
tinal canal  are  regulated  by  the  vis  insita,  or  muscular  force, 
and  by  stimuli,  for  their  movements  are  independent  of  the 
mind,  whilst  the  movements  of  the  muscles  actually  dependent 
upon  the  nerves  are  under  the  control  of  the  will. 

The  error  here  is  very  manifest :  the  great  man  has  not 
properly  distinguished  between  sentient  actions  and  nerve- 
actions.  If,  'according  to  Haller,  when  movements  are  excited 
in  muscles  through  their  nerves,  they  must  be  excited  in  con- 
nection with  the  brain,  or  the  mind,  or  the  will,  then  it  follows 
that  animal  movements  excited  after  division  or  ligature  of 
the   nerve   going  to  the   muscle,   are  not   produced  through 


I 


ti.  I.]  NERVE-ACTIONS  IN  GENERAL.  211 

the  nerves.    (Compare  362,  iv,  and  367,  ii,  for  a  further  cor- 
rection.) 

387.  The  movements  dependent  on  nerves  (Haller  states) 
cease  with  life,  those  on  the  vis  insita  continue  after  death; 
destruction  of  the  brain,  or  ligature  of  the  nerves,  prevents  the 
former,  the  latter  continue  without  brain.  Parts  that  have  no 
sensation  are  moved,  others  that  have  are  not  moved;  the 
will  excites  or  arrests  the  nerve-motions,  it  has  no  power  over 
the  actions  of  the  vis  insita. 

All  this  only  demonstrates  the  difference  between  the  cere- 
bral [animal -sentient]  forces  and  the  nerve -forces,  between 
sentient  actions  and  nerve-actions.  It  does  not  prove,  how- 
ever, that  the  nerve-actions  are  not  produced  through  the 
nerves,  but  that  they  are  not  produced  through  the  brain  or 
the  mind. 

388.  It  does  not  appear  then,  that  this  doctrine  of  Haller 
can  be  supported  by  valid  arguments.  There  are  other  ob- 
jections to  it.  No  irritant  applied  to  parts  un supplied  with 
nerves,  can  excite  movements.  Then  irritability  is  peculiar 
to  muscular  fibre,  but  all  muscular  movements  are  motions  of 
mechanical  machines  intimately  connected  with  the  nerves,  and 
the  latter  cannot  be  entirely  separated  from  them  without  at 
the  same  time  destroying  their  structure.  Every  impression 
which  excites  the  muscle  irritates  also  the  nerves.  An  internal 
impression  on  the  medulla  of  the  nerves,  excites  the  same  move- 
ments as  when  the  muscular  fibres  are  irritated.  Opium, 
which  if  applied  to  a  nerve  deprives  it  at  the  point  where  ap- 
plied of  its  vis  nervosa  J  also  suddenly  renders  a  muscle  unirri- 
table  at  the  point  of  application  (Whytt's  Works).  Every  nerve 
retains  the  animal  motor  force,  even  if  cut,  or  tied,  or  otherwise 
so  treated  that  an  external  impression  on  it  can  no  longer  be 
felt  (381,  i);  and,  in  fact,  the  same  muscular  action  is  excited 
by  an  irritant,  whether  it  be  felt  or  not  (204,  357).  Now  since, 
therefore,  all  muscular  movements  which  are  attributed  without 
adequate  grounds  to  the  irritability  of  muscles  can  also  take 
place  in  virtue  of  impressions  on  their  nerves,  and  in  undoubted 
instances  actually  do  so  take  place,  and  as  there  is  no  reason 
why  they  should  not  occur  in  every  case,  so  soon  as  the  muscular 
fibre  is  irritated,  it  is  probable  that  no  truth  in  all  physiology 
is  so  physically  certain  as   this ;  that  all  animal  movements  of 


212  ANIMAL  FORCES.  [ii. 

muscles  are  primarily  effected  through  the  nerves  only,  whether 
in,  or  without  connection  with,  the  brain  and  the  mind. 

389.  The  two  kinds  oivis  nervosa  then,  like  the  cerebral  forces, 
are  primary  properties  of  the  true  animal  machines,  and  especially 
of  the  nerves  (372 — 388),  and  cause  the  same  workings  in  the 
mechanical  machines,  whether  they  be  caused  at  the  same  time 
by  cerebral  forces  or  not  (362 — 371).  That  which  renders  a 
mechanical  machine  external  to  the  brain  capable  of  sentient 
actions,  namely,  the  nerve  incorporated  with  it,  also  renders  it 
capable  of  nerve-actions,  and  there  is  not  a  single  animal  motor 
force,  independently  of  it,  nor  even  in  muscular  fibre. 

390.  The  mechanical  machines  that  are  not  endowed  with 
nerves,  as  tendons  and  tendinous  tissues,  bone  and  cartilage, 
&c.,  are  not  adapted  to  the  vis  nervosa,  and  primarily  their 
movements  are  neither  sentient  actions  nor  nerve-actions, 
although  from  their  mechanical  relations  they  are  either  or 
both.  All  such  parts  of  the  body  without  exception  have 
neither  irritability  nor  sensibility,  being  deficient  in  nerves. 

391.  On  the  other  hand,  those  mechanical  machines  that  are 
supplied  with  nerves  become  thereby  not  only  capable  of  sen- 
sation and  sentient  actions  (162 — 179),  but  also  of  nerve-actions, 
as  will  be  shown  subsequently. 

392.  It  has  been  already  shown,  that  the  muscles  are  moved 
by  the  vis  nervosa  as  well  as  by  cerebral  forces  (162,  204); 
the  experiments  already  detailed  prove  this  amply  (357,  359). 
The  action  of  the  heart  (as  proved  also  by  experiment — §  357), 
is  usually  a  nerve-action,  although  it  is  likewise  changed  by 
sentient  actions  (161,  211).  The  action  of  the  blood-vessels  can 
be  renewed  and  continued  in  decapitated  animals  that  do  not 
bleed  to  death  too  quickly,  by  purely  animal  irritants.  The 
phenomena  previously  detailed  (168,  207)  may  all  take  place 
as  nerve-actions. 

393.  The  natural  functions  of  the  oesophagus,  stomach,  in- 
testines, and  other  muscular  canals,  are  ordinarily  (as  has  been 
already  stated)  rather  nerve-actions  than  sentient  actions  (170, 
174,  212),  and  experiments  on  portions  separated  from  the 
body  confirm  the  statement.  These  remarks  apply  to  the 
diaphragm,  and  similar  muscular  structures  (171,  359). 

394.  The  glandular  and  other  secreting  tissues  belong  to  the 
same  class  as  the  preceding ;  their  functions  going  on  without 


IH.  I.]  ACTION  OF  THE  VIS  NERVOSA.  213 

msation  and  after  decapitation.  {Vide  §§  172 — 176  and  209 — 
115.)  The  cortical  substance  of  the  brain  is  to  be  classed  with 
le  secreting  organs. 

395.  The  functions  of  the  sexual  organs  both  in  the  male 
id  female  are  carried  on  not  solely  by  means  of  the  cerebral 

"forces^  but  often  through  the  vis  nervosa  only,  as  experiments 
on  decapitated  animals  demonstrate  (357). 

396.  The  movements  of  the  limbs  display  the  influence  of 
the  vis  nervosa  strikingly,  because  its  action  is  greatest  on  the 
muscular  portion  of  the  organism.  These,  as  a  thousand  ex- 
periments prove,  may  arise  as  nerve-actions,  although  they 
usually  occur  as  sentient  actions  from  external  sensations  and 
sensational  conceptions,  instincts,  and  passions,  as  well  as 
volitionally.  Thus,  a  decapitated  animal  will  stand,  move  for- 
wards, raise  itself  up,  leap,  fly,  or  flutter  its  wings,  seek  food, 
clean,  defend  or  conceal  itself,  copulate,  &c.  A  decapitated 
man  immediately  after  decapitation  struggles  to  free  his  hands, 
attempts  to  stand  upright,  and  to  stamp  with  his  feet ;  if  the 
head  of  a  pigeon  be  cut  ofi*  whilst  it  is  running,  it  continues 
to  run  on  for  some  distance,  until  it  knocks  against  something ; 
a  frog  leaps  forward  without  its  head,  so  also  a  headless  fly  flies, 
a  snake,  a  fish,  a  worm,  writhes  and  twists  about,  if  touched, 
although  wholly  deprived  of  sensation ;  a  fly  makes  the  move- 
ment of  brushing  its  eyes  by  a  natural  instinct,  although  its 
head  be  cut  off^;  a  headless  snail  seeks  its  food  by  its  usual 
plan  of  feeling  about;  a  decapitated  tortoise  does  the  same 
thing,  and  will  live  for  half  a  year  after  decapitation,  and  raise 
itself  up,  or  endeavour  to  do  so  if  placed  on  its  back ;  an  ear- 
wig nips  with  the  nippers  of  its  abdomen  at  its  own  separated 
head,  when  the  head  bites  the  abdomen;  the  abdomen  of  a 
wasp  will  sting;  animals  that  fight  with  their  hind  feet  use 
them  vigorously  when  decapitated,  at  every  irritation  applied  to 
the  nerves;  butterflies,  caterpillars,  and  silk-worms  copulate 
after  decapitation,  and  they  and  flies  deposit  their  ova;  in 
short,  all  the  instinctive  actions  of  animals  are  sometimes  seen 
to  occur  as  nerve-actions;  and  it  naturally  follows  that  they 
occur  at  first  in  newly-born  animals  as  such,  and  that  it  is  only 
after  the  perception  of  external  sensations  that  they  become 
sentient  actions  (269). 

397.  Thus  the  dominion  of  the  vis  nervosa  is  in  reality  as 


214  ANIMAL  FORCES.  [ii. 

extensive  as  that  of  the  cerebral  forces,  and  it  would  be  difficult 
to  discover  a  movement  which  occurs  as  a  sentient  action,  which 
may  not  be  also  effected  by  the  vis  nervosa,  although,  in  many 
cases  it  is  not  practicable  to  show  this  by  satisfactory  experi- 
ments. The  greater  number  of  movements  take  place  by  means 
of  muscles  or  muscular  tissues,  whether  they  be  sentient  or 
not  (379).  That,  however,  which  a  muscle  can  effect  when 
stimulated  by  the  cerebral  forces,  it  can  also  effect  very  easily 
solely  by  means  of  an  unfelt  internal  or  external  impression 
on  its  nerves  (364,  i),  for  in  either  case  it  is  stimulated  to  the 
same  movement  (356).  It  is  not  surprising,  therefore,  that 
suitable  impressions  on  the  motor  nerves  can  act  as  the  primary 
iucitants  to  all  nerve-actions  independently  of  sensation  or 
thought,  and  maintain  the  whole  machinery  of  an  animal  body 
in  continued  working  and  reciprocal  functional  activity,  just  as 
is  effected  by  external  sensations  and  their  sensational  concep- 
tions by  means  of  internal  impressions  on  the  brain.  For  we 
must  remember  that  an  impression  not  only  develops  the  same 
movement  as  it  develops  when  felt,  or  as  when  excited  by  con- 
ceptions ;  but  that,  just  as  from  external  sensations  and  their 
sentient  actions,  other  sensational  conceptions  and  their  sen- 
tient actions  are  produced  and  combined  together,  whence  the 
connected  acts  of  the  cerebral  forces  arise,  so  also  unfelt  external 
impressions  cause  unfelt  internal  impressions,  from  which  some- 
times other  external  impressions  originate;  all  which  have 
unitedly  their  special  nerve-actions,  constituting  connected  and 
combined  acts.  To  show  this  more  distinctly,  and  to  render  it 
by  successive  proofs  more  probable  and  obvious,  how  an  animal 
body  can  be  regulated  and  excited,  as  well  to  automatic  as  to 
what  are  usually  volitional  movements,  independently  of  mind, 
as  regularly  and  connectedly  as  if  directed  by  thought  and  sen- 
sation, we  must  now  consider  the  relations  of  the  two  kinds  of 
vis  nervosa  to  each  other ;  and  thus  facilitate  a  comprehension 
of  this  important  matter,  which  will,  for  the  first  time,  be  placed 
in  its  proper  light  in  the  succeeding  Chapters. 

398.  Either  of  the  two  kinds  of  impressions  may  reciprocally 
excite  the  other,  without  the  intervention  of  the  conceptive 
force ;  and  both  can  excite  the  same  or  other  movements,  either 
consentaneously  or  consecutively;  and  from  their  reciprocal 
connection  whole  series  of  acts  may  take  place  as  the  result  of 


CH.  I.]  RELATIONS  OF  IMPRESSIONS.  215 

a  single  impression,  and  be  combined  together  by  the  proper 
animal  force  of  the  body ;  although  there  be  neither  sensation 
nor  thought,  even  although  the  animal  possess  neither  brain 
nor  mind,  or,  if  it  possess  mind,  without  the  mind  in  any  way 
influencing  the  acts.    Consequently,  the  general  principles  that 

I  we  shall  lay  down  as  to  the  connection  and  reciprocal  influence 
bf  the  two  kinds  of  vis  nervosa  with  and  on  each  other  are 
equally  valid,   whether  or  no  external  impressions  be  felt  or 
pternal  impressions  be  excited  by  conceptions. 
«    399.  An  external  impression  is  changed  into,  or  develops  an 
internal  impression,   whenever  its   course  which   is   naturally 
towards  the  brain  from  the  terminating  fibrils,  is  so  reflected 
or  turned  back,  that  it  returns  in  the  direction  from  the  brain 
downwards  to  the  branches  and  terminations  of  the  nerves  (32, 
121).   This  usually  takes  place  in  the  brain  in  animals  endowed 
with  cerebral  forces,  by  means  of  the  external  sensation  of  the 
external  impression  (129).    But  since  the  external  impression 
without  either  being  felt,  or  without  either  the  presence  of  the 
brain  or  of  mind,  causes  the  same  movements  as  are  excited  by 
the  internal  impression  of  its  external  sensation  (358),  it  must 
become  a  non-conceptional  impression  without  this  transition 
into  a  sentient  action  taking  place,  because  it  is  turned  back 
and  reflected  in  its  course  to  the  brain,  before  it  forms  the 
material  external  sensation  in  the  latter.     There  are  grounds 
for  supposing  that  this  can  take  place  in  the  brain  itself  (373, 
376).    In  the  nerves,  however,  there  is  no  place  in  which  it  can 
occur,  except  the  ganglia  of  the  motor  nerves  (14),  and  at  their 
separation  into  branches  and   fibrils   (48).    According  to  all 
probabihty,  these  ganglia  and  points  of  division  of  the  nerves, 
perform  in  the  motor  nerves  the  office  of  the  brain  in  relation 
to  the  external  impressions,  since  they  deflect  these  from  their 
course  upwards,  and  communicate  an  internal  impression,  either 
to  other  nerves  and  their  branches,  or  to  different  fibrils  in  the 
same  nerve,  conducting  in  the  direction  from  the  brain  down- 
wards ;  whereby  these  twigs  and  fibrils  are  suitably  stimulated, 
and  such  muscular  movements   excited,  as  would  have  been 
caused  if  the  external  impression  had  reached  the  brain  and 
had  been  turned  back  or  reflected  from  thence  by  the  inter- 
vention of  an  external  sensation  (364,  ii).     If  this  reflexion  of 
the  external  impression  be  made  upon  the  same  efi'erent  fibrils, 


216  ANIMAL  FORCES.  [ii. 

as  transmit  internal  impressions,  then  the  nerve-actions  produced 
by  the  two  kinds  of  impressions  are  the  same,  and  also  identical 
with  the  direct  sentient  actions  of  the  external  sensations  (188). 
If,  however,  other  nerves,  or  nerve  fibrils,  be  the  channel  of  the 
reflexion,  other  nerve-actions  are  excited,  which  accord  with 
the  sentient  actions  of  the  external  sensation  produced  by  th( 
impression  so  reflected  (97,  124;  compare  also  435,  436). 

400.  In  so  far  as  an  external  impression  can  excite  a  non-con- 
ceptional  internal  impression,  it  may  also  induce  all  such  nerve- 
actions  as  can  be  produced  by  the  latter.  Now,  these  are  in 
fact  the  same  as  sentient  actions  (363) .  Consequently,  an  external 
impression  although  unfelt,  can  induce  the  same  movements 
which,  when  felt,  it  induced  as  sentient  actions  (364,  i).  In  the 
animals  destitute  of  brain,  as  sea-anemones,  tape-worms,  &c., 
and  in  microscopic  animals,  polypes,  &c.,  external  impressions, 
although  unfelt,  can  be  the  incitants  of  the  machines,  whereby 
they  are  incited  to  all  those  movements  which  arise  as  sentient 
actions  from  sensation,  when  the  impressions  are  felt  by  these 
or  other  animals  (366).  If,  therefore,  brainless  animals  like 
those  alluded  to,  are  so  formed  by  nature,  that  all  their  external 
impressions  are  reflected,  and  changed  into  non-conceptional 
internal  impressions,  in  the  plexuses,  ganglia,  and  points  of 
division  of  the  nerves,  and  which  move  their  Hmbs  just  as  they 
would  have  been  moved  by  sentient  actions,  it  ought  not  to 
be  matter  for  surprise,  that  such  animals  although  without 
thought  or  sensation,  appear  to  act  as  designedly,  spontaneously, 
thoughtfully,  and  volitionally,  as  animals  really  endowed  with 
mind. 

401.  A  non-conceptional  impression  can  develop  obvious 
animal  movements  in  the  purely  sensitive  nerves  (377).  Still 
more  can  it  put  muscles  into  action  by  means  of  the  motor 
nerves  (360).  These  muscular  movements  in  the  healthy  con- 
dition of  the  individual  (225),  are  often  felt,  and  consequently 
cause  an  external  impression  on  the  nerves  of  the  muscles  (35), 
and  which,  even  if  not  felt,  can  excite  the  same  movements 
as  if  they  were.  In  this  way  non-conceptional  impressions 
can  produce  external  impressions,  which,  although  not  felt, 
still  imitate  in  the  mechanical  machines  the  sentient  action  of 
their  external  sensation.  Thus,  if  the  spinal  cord  of  a  headless 
frog  be  irritated  with  a  needle,  the  internal  impression  thus 


!H.  I.]  RELATIONS  OF  IMPRESSIONS.  217 

)roduced  acts  in  the  same  way  as  a  volition^  and  the  animal  is 
jxcited  to  raise  itself  up.  Whilst  the  muscles  are  contracted 
this  end^  their  nerves  have  an  external  impression  commu- 
licated  to  them  by  the  movement,  which  irritates  them  and 
rther  muscles  to  new  movements_,  so  that  the  animal  either 
)laces  itself  upright,  or  balances  itself,  or  turns  round,  retreats, 
lakes  a  spring,  swims,  &c.,  according  as  the  irritation  of  the 
jpinal  cord  has  excited  the  first  movement. 

402.  To  determine  more  definitely  the  relationship  which  the 
two  kinds  of  impressions  bear  to  external  and  internal  sensations, 
re  will  still  further  consider  their  relations.  An  external  im- 
)ression  is  necessarily  required  for  all  external  sensations  (35), 
id,  consequently,  constitutes  a  portion  of  them,  but  only  in  so  far 
it  is  felt,  for  the  entire  external  sensation  is  in  the  mind — is 
conception  (34) .  Taken  alone,  it  is  a  portion  of  the  material 
external  sensation,  but  only  in  so  far  as  it  forms  therewith  a 
material  idea  at  the  origin  of  the  nerves  which  have  received 
it  (34).  Popularly,  and  indeed  in  books  also,  external  sensation 
generally,  and  in  its  widest  signification,  is  termed  feeling 
[Gefiihl],  and  attributed  to  the  five  senses,  for  it  is  said  that 
the  eye  feels  the  rays  of  light,  the  ear  feels  the  undulations  of 
the  atmosphere,  &c.  It  is  also  customary  to  apply  the  term 
sensation  and  feeling  to  animal  bodies,  for  it  is  said  that  the 
hand,  the  flesh,  a  nerve,  feels  and  has  sensation.  According 
to  this  established  signification  of  the  terms,  it  may  be  said 
that  the  external  impression  is  an  element  in  feeling  (the 
material  external  sensation),  and  since  it  produces  the  same 
phenomena,  whether  it  reaches  the  brain  to  form  material 
ideas  in  it  or  not,  the  name  is  derived  from  a  part,  and  the 
external  impression  thus  becomes  to  be  designated  the  external 
feeling  [Gefiihl]  of  the  nerves  (32).  In  this  way,  the  external 
impression  and  the  material  external  sensation  in  the  brain 
may  be  distinguished  by  convenient  terms,  both  of  which  are 
figurative,  the  latter  being  termed  sensation  [Empfindung],  the 
sentiment  of  Buff'on ;  the  former,  the  external  feeling  of  the 
nerves  —  sensation  of  Buff'on.  Thus  it  is  said,  that  the 
tongue,  the  hand,  the  ear,  have  sensation,  whilst  a  decapitated 
animal,  or  an  excised  heart,  or  portion  of  intestine,  so  long  as 
it  is  excited  to  motion  by  a  purely  external  impression,  is  said 
to  have  feeling  left  in  it,  or  that  the  acephalous  embryos,  which. 


218  ANIMAL  FORCES.  [ii. 

are  born  destitute  alike  of  head  and  brain,  but  are  moved, 
nevertheless,  by  external  impressions,  have  feeling ^  &c. 

403.  The  external  feeling  of  the  nerves,  or  what  is  identical 
therewith,  the  external  impression,  is  that  animal  force  of  the 
nerves,  the  properties  of  which  have  been  already  stated  (32, 
34,  and  364,  iii).  According  to  the  laws  and  principles  pre- 
viously established,  it  is  in  no  degree  mental,  although  it  excites 
external  sensations,  being  neither  conception  nor  sensation 
[Empfindung],  but  seated  externally  to  the  mind  in  the  nerves 
(98,  i,  &c.)  Neither  is  it  a  sentient  action,  but  a  property 
independent  of  the  conceptive  force,  peculiar  to  and  innate  in 
the  nerves,  of  being  excited  to  this  wonderful  movement  by  an 
irritation  of  their  medulla,  which  is  the  case  with  no  other 
bodies,  nor  with  any  purely  mechanical  machines,  and  is 
wholly  independent  of  the  physical  and  mechanical  laws  of 
motion ; — a  movement  which  penetrates  the  brain,  and  awakes 
the  soul  to  sensations,  and  at  the  same  moment  puts  the  ma- 
chines of  the  body  into  motion,  in  a  way  that  no  other  force 
in  nature  can  attain  to. 

Note. — So  important  an  animal  force  merits  well  to  be 
specially  distinguished  as  well  from  sensation,  which  is  a  pro- 
perty of  mind,  as  from  the  physical  and  mechanical  forces  of 
inorganic  machines.  I  have  termed  it  for  the  reasons  previously 
stated  (402),  the  feeling  of  the  nerves,  but  the  expression  is  so 
new,  that  although  quite  correct,  it  may  lead  the  reader  to  mis- 
apprehend its  meaning  and  application.  I  have,  therefore,  in 
this  work  used  the  term  external  senselike  (sinnlich)  impression 
in  its  stead.^ 

404.  If  this  difference  between  external  feeling  (the  external 
impression)  and  external  sensation  had  been  better  observed, 
that  erroneous  proposition  of  the  ancients  (renewed  by  Whytt) 
would  have  been  long  ago  forgotten,  which  propounded  that 
the  soul  was  diffused  throughout  the  entire  organism,  because 
in  sensation  the  mind  determined  and  fixed  the  point  where 
the  nerves  received  an  external  impression,  or  in  other  words, 
where  it  felt.  Even  a  materialist  cannot  defend  so  fundamental 
an  error.  If  the  mind  be  that  which  has  self-consciousness, 
or  which  forms  ideas,  the  nerves  can  constitute  no  part  of  it ; 

'  The  reader  is  particularly  referred  to  the  note  to  §  31  for  an  explanation  of  this 
term. — Ed. 


CH.   I.] 


NATURE  OF  IMPRESSIONS. 


219 


for  they  at  least,  can  neither  conceive  nor  perceive,  if  we  grant 
khat  the  brain  can ;  nor  can  sensation  [das  Empfinden]  be  con- 
nived to  be  a  property  of  the  nerves,  by  those  who  maintain 
fchat  the  brain  is  the  soul.      From  the  point  of  impression  at 
the  termination  of  the  nerves  to  their  origin  in  the  brain,  the 
external  impression  (external  feeling)  is  nothing  more  than  a 
ddden  movement  in  the  nerve,  which,  at  the  point  where  it 
forms  a  material  idea,  is  only  first  perceived,  conceived,  felt, 
)bserved  by  the  soul  (80).    If,  therefore,  the  materialist  main- 
lins,  that  it  is  the  materies  (Stoff)  of  external  sensation,  still 
it  does  not  become  an  external  sensation  until  it  enters  this 
)oint  of  sensation  [Fiihlpunkt]  in  the  brain ;  and  it  cannot  be 
[antecedently  to  this,  while  in  the  trunk  of  the  nerve  from  whence 
puts  the  animal  machines  which  it  can  regulate  into  motion, 
[either  an  external  sensation  or  sentient  moving  force ;  but  is  a 
[pure  vis  nervosa  [eine  blosse  Nervenkraft] ,  and  all  its  operations 
:e  purely  nerve-actions  and  not  sentient  actions  from  external 
sensation  (98,  i). 

405.  The  distinction  between  internal  impressions  with  con- 
sciousness and  without,  is  equally  as  great  as  that  between  an 
external  impression  and  external  sensation.  The  conceptional 
internal  impression,  which  operates  in  the  mechanical  machines, 
is  a  material  idea  at  the  point  of  origin  of  a  nerve  in  the 
brain,  where  the  mind  felt  in  virtue  of  its  self-consciousness 
[Selbstgefiihl]  ;  (80)  and  so  soon  as  this  hidden  movement  at 
the  origin  of  the  nerve  (the  material  idea)  passes  onward  from  this 
[point  of  consciousness  [Fiihlpunkt  der  Seele]  over  to  the  nerves, 
[to  the  end  that  they  may  put  the  mechanical  machines  into 
motion,  the  internal  impression  becomes  nothing  more  than 
what  the  external  impression  is  before  it  enters  the  point  of 
consciousness  in  the  brain ;  it  is  therefore  neither  a  sensation 
nor  conception,  but  a  hidden  movement  in  the  nerve,  which 
continues  downwards  from  the  brain  towards  the  terminations 
of  the  nerves,  and  puts  the  mechanical  machines  into  motion 
to  which  they  are  distributed.  In  so  far  as  a  conception  was 
the  basis  of  this  animal  movement,  and  in  so  far  as  the  impres- 
sions passed  from  the  brain  downwards  from  the  point  of  con- 
sciousness, at  which  the  mind  perceived  the  conception  of  this 
material  idea,  to  that  extent  the  movement  is  a  sentient  action 
(97) ;   and  the  internal  impression  (the  material  idea)  is   an 


220  ANIMAL  FORCES.  [ii. 

animal-sentient  force.  But  if  an  irritation  of  the  medulla  of 
the  nerve  constituted  the  internal  impression,  and  if  it  did  not 
depart  from  the  point  of  consciousness,  that  is  to  say,  from  the 
locality  of  the  material  idea  of  a  conception,  then  it  is  not  an 
animal-sentient  force,  and  the  resulting  movements,  although 
similar  to  sentient  actions,  are  not  such,  but  nerve-actions  of  a 
vis  nervosa.  This  may  be  termed  the  internal  feeling  of  the 
nerves,  to  distinguish  it  from  internal  sensations  (80,  121). 

406.  This  internal  feeling  of  the  nerves,  or  what  is  identical 
therewith,  the  internal  impression  not  produced  by  concep- 
tions, is  that  animal  force  of  the  nerves,  in  virtue  of  which 
they  receive  in  their  medulla  a  certain  impression,  not  mental 
in  its  origin,  and  communicated  to  them  in  the  direction 
from  above  downwards ;  transmit  the  impression  thus  received 
in  the  same  direction  to  their  minutest  fibrils ;  and  excite  in 
the  mechanical  machines  with  which  their  fibrils  are  incor- 
porated, the  same  movements  as  would  have  occurred  if  the 
impression  had  originated  from  conceptions.  It  is  a  property 
peculiar  to  and  innate  in  the  nerves,  in  virtue  of  which  a 
stimulus  applied  to  their  medulla  in  the  direction  from  above 
downwards  excites  hidden  movements  in  them,  which  no  other 
bodies  and  no  purely  mechanical  machines  could  acquire  from 
such  a  stimulus,  and  which  are  not  subject  to  the  physical 
and  mechanical  laws  of  motion.  These  hidden  movements 
are  propagated  by  the  nerves  to  the  mechanical  machines  to 
which  they  are  distributed,  if  no  hindrance  arise,  and  move 
them  in  the  same  way  as  they  are  usually  moved  by  con- 
ceptions. 

407.  According  to  these  views  as  to  the  distinction  between 
the  cerebral  force  and  the  internal  feeling  of  the  nerves,  it 
follows,  that  it  is  manifestly  erroneous  to  say  (as  is  said  in  our 
elementary  works),  that  the  animal  movements  excited  by  the 
internal  impression  are  mental,  or  at  least,  cerebral.  Hence 
have  arisen  the  erroneous  views,  which  have  had  so  injurious 
an  influence  on  pathology  and  therapeutics ;  to  the  effect  that 
the  phenomena  of  fevers,  spasmodic  diseases,  epilepsy,  paralysis, 
and  all  nervous  diseases  in  general,  depend  upon  some  aff^ection 
of  the  brain,  and  that  they  must  be  cured  by  remedies  which 
act  upon  that  viscus.  On  the  contrary,  an  internal  impression 
excited  in  nerves  far  distant  from  the  brain  by  various  irritating 


CH.   1.] 


NATURE  OF  IMPRESSIONS. 


221 


jents  in  the  body,  especially  by  reflected  external  impressions 
rhich  are  not  felt,  may  induce  all  these  affections  quite  inde- 
mdently  of  the  brain,  and  must  be  cured  by  the  removal  of 
lese  agents. 

It  is  manifest,  too,  with  what  justice  we  have  controverted 
le  doctrine  of  Haller,  that  the  motor  force  of  the  nerves  can 
leither  arise  nor  continue  independently  of  the  brain,  and  how 
)rejudicial  such  views  must  be  to  pathology  and  the  practice  of 
nedicine,  especially  when  advocated  by  so  eminent  a  physio- 
logist.    It  has  simply  escaped  his  notice,  however,  for  it  could 
be  shown  by  a  hundred  passages  in  his  writings  that  the  truth 
was  known  to  him. 


CHAPTER  II. 

ON  THE  VIS  NERVOSA  OF  EXTERNAL  IMPRESSIONS. 

408.  After  having  considered  the  two  kinds  of  vis  nervosa  in 
general  (355),  we  will  consider  them  separately,  and,  firstly,  the 
vis  nervosa  of  the  external  impressions,  generally  and  specially. 


SECTION  I. ON  THE  VIS  NERVOSA  OF  EXTERNAL  IMPRESSIONS 

IN   GENERAL. 

409.  An  impression  passes  upwards  to  the  brain,  along  the 
nerves,  from  the  point  of  impression.  If  it  reaches  the  cerebral 
origin  of  the  nerves,  it  develops  there  an  external  sensation, 
and  the  actions  which  it  thus  produces  in  the  body  are  sentient 
actions  from  external  sensations  (32,  34) .  On  the  other  hand, 
all  actions  which  it  produces  before  it  reaches  the  brain,  or  in 
other  words,  before  it  becomes  an  external  sensation,  are  nerve- 
actions  of  its  vis  nervosa  (98,  i,  and  353).  It  is  the  latter  which 
we  have  to  consider  here. 

410.  When  a  nerve  is  irritated  with  a  needle,  it  receives 
both  an  internal  and  external  impression ;  if,  for  example,  it  be 
a  motor  nerve,  the  latter  acts  on  the  muscles  above  the  point 
irritated,  and  the  former  (or  the  non-conceptional  internal  im- 
pression) on  the  muscles  situated  below,  or  in  a  direction  from 
the  brain.      Both  kinds  of  movement  are  equally  nerve-actions. 

411.  If  when,  as  in  many  external  sensations,  the  irritation 
is  so  applied  that  the  nerve  is  mechanically  concussed  below 
the  point  of  irritation,  and  this  concussion  of  the  lower  portion 
of  the  nerve  acts  as  another  external  impression,  and  thus 
develops  movements  in  the  parts  below,  they  will  be  the  same 
as  those  induced  by  the  first  irritation  (37). 

412.  Since  the  external  impressions  that  are  made  at  the 
same  time  on  several  nerves,  do  not  hinder  or  confuse  each 
other  in  their  course  to  the  brain,  but  pass  along  the  same 
nerve,  or  through  the  spinal  cord,  unmingled  with  each  other 
(39) ;  it  follows,  that  they  can  produce   their  corresponding 


cii.  II.]    VIS  NERVOSA  OF  EXTERNAL  IMPRESSIONS.  223 

nerve-actions,  without  the  one  kind  interfering  with  the  other. 
Experiments  on  decapitated  animals  establish  this  fact. 

413.  It  is  as  difficult  to  discriminate  the  various  kinds  of 
impressions  from  their  nerve- actions  as  from  their  external  sen- 
sations (40,  41).  An  irritant  may  often  act  when  we  cannot 
detect  it,  or  when  we  think  it  not  an  irritant ;  and  hence  it  is 
that  the  phenomena  of  idiosyncrasies  are  so  inscrutable  (52). 
The  heart  is  more  stimulated  by  blood  than  by  acrid  irri- 
tants, the  urinary  bladder  by  water,  the  intestinal  canal  by  air 
(Haller's  'Physiology,'  §402).  An  irritant  which  a  priori 
would  be  expected  to  be  more  active  than  another  apparently 
less  irritating,  is  in  fact  less  active :  many  parts  that  remain 
unchanged  when  the  most  acrid  chemical  spirits  are  applied 
to  them,  are  excited  to  convulsive  movements  on  being  irritated 
by  the  point  of  a  needle.  It  is  in  fact  impossible  to  infer  from 
mechanical  or  physical  laws,  what  nerve-actions  will  follow  on 
certain  kinds  of  irritants ;  the  laws  of  their  action  can  only  be 
known  by  experiment  and  observation. 

414.  It  is  not  every  impression  on  the  nerves  that  is  adapted 
to  their  structure,  but  only  that  which  excites  animal  actions 
(31,  32)  ;  nor  is  it  adapted  if  it  be  not  made  so  as  to  excite  that 
hidden  movement  in  the  nerves,  which  when  propagated  to  the 
brain,  excites  external  sensations ;  or  excites  movements  in  the 
mechanical  machines  when  propagated  to  them.  We  have 
already  discussed  the  former  (42,  et  seq.)  :  we  will  now  treat  of 
the  hidden  movements  in  the  latter,  as  disclosed  by  nerve- 
actions,  and  inquire  under  what  circumstances  they  take  place. 

415.  i.  If,  at  the  point  where  a  nerve  receives  an  external 
impression,  it  be  completely  incorporated  with  a  mechanical 
machine  which  is  capable  of  performing  certain  movements  at 
that  point,  as  in  muscles  for  example  (161),  it  excites  these 
directly  to  perform  their  animal  movements ;  and  the  nerve- 
action  thus  excited  requires  nothing  more  than  the  external 

I  impression,  whether  it  proceeds  further  or  not.  Thus  a  mus- 
cular fibre  in  an  excised  muscle  contracts  immediately  at  the 
point  where  a  point  of  a  needle  irritates  it,  or  a  particle  of  salt 
is  dissolved  upon  it. 
ii.  If  a  nerve  causes  nerve-actions,  by  means  of  an  external 
impression  in  parts  remote  from  the  point  of  impression,  or  even 


224  ANIMAL  FORCES.  [ii. 

primarily  received  the  impression,  or  through  its  own  efferent 
fibrils  (127),  the  impression  is  transmitted  along  the  nerve 
upwards  to  the  brain ;  but  ere  it  reaches  there,  it  is  turned 
from  its  course,  and  so  reflected  downwards,  that  it  excites  (as 
an  internal  impression)  the  nerve  of  the  other  remote  parts,  or 
the  nerve-twigs  or  efferent  nerve-fibrils  of  the  part  receiving 
the  impression ;  and  this  internal  impression,  which  is  nothing 
else  than  the  reflected  external  impression,  thus  reaches  the 
mechanical  machine  which  has  to  perform  the  nerve-action. 
This  is  proved  by  undoubted  experiments.  If  the  toe  of  a  frog 
at  rest  be  pricked,  the  external  impression  thus  made  goes  to 
the  brain.  From  thence  it  is  reflected  upon  the  limbs,  and 
the  animal  rises  up  and  springs  forward.  But  if  the  head  be 
cut  off,  and  the  toe  be  again  pricked,  the  same  motions  take 
place  (357).  In  this  case,  the  external  impression  on  the  toe, 
must  pass  upwards  towards  the  brain,  although  it  cannot  reach 
it,  for  if  the  nerve  be  divided  in  the  thigh,  so  as  to  prevent 
its  transmission,  the  motion  does  not  take  place.  Further,  it 
is  obvious  that  it  is  reflected  on  the  nerves  of  the  limbs,  as  an 
internal  impression,  and  along  their  twigs  to  their  muscles, 
because  no  other  part  of  the  body,  except  this  single  toe 
which  was  pricked,  receives  an  external  impression.  Again, 
supposing  while  one  toe  is  pinched,  that  the  nerve  of  the  other 
leg  be  divided ;  in  this  case,  the  movements  will  be  repeated  in 
all  the  parts  except  that  whose  nerve  is  cut  through.  This 
explains  what  takes  place  in  similar  circumstances,  when  an 
impression  is  made  on  the  spinal  cord,  and  spasms  and  con- 
vulsive movements  are  excited  in  all  parts  below  the  point  of 
irritation,  except  those  the  nerves  of  which  are  cut  through. 
The  reflected  external  impression  passes  as  an  internal  im- 
pression to,  and  only  excites  movements  in  those  muscles  to 
which  it  can  be  transmitted  from  the  point  of  reflexion. 

iii.  Examples  of  this  class  of  nerve-actions  are  to  be  met 
with  daily,  which  sometimes  are  mistaken  for  sentient  actions 
(which  they  often  accompany),  sometimes  for  special  operations 
of  unfelt  external  impressions  acting  through  the  brain,  some- 
times for  inexplicable  sympathies.  Numerous  instances  of  this 
kind  may  be  found  in  Haller^s  '  Physiology,'  vol.  iv,  p.  529, 
and  B.  10,  Absch.  vii,  ^  30-31. 

416.  As   the    brain    secretes    the   vital  spirits,    and   as  in 


II.]   VIS  NERVOSA  OF  EXTERNAL  IMPRESSIONS.  225 

mimals  endowed  with  brain,  it  is  requisite  that  the  nerves  be 
supplied  with  these,  as  the  medium  for  the  transmission  of 
impressions,  the  brain  must  be  considered  as  being  necessary 
at  least  to  the  continued  production  of  nerve-actions;  unless 
the  animal  be  so  constituted,  that  the  vital  spirits  are  secreted 
in  the  medulla  of  the  nerves  themselves,  or  in  their  ganglia, 
as  is  the  case  in  avertebrate  animals  (362).  Compare  also 
§  673.  This  is  one  of  the  reasons  why  in  animals  endowed 
with  brain,  the  vis  nervosa  is  abolished  so  soon  after  de- 
capitation ;  for  the  vital  spirits  gradually  flow  out  of  the  nerve- 
medulla,  and  are  not  re-produced.  So  long,  however,  as  a 
sufficiency  of  vital  spirits  remain  in  the  nerves,  their  vis  nervosa 
continues  to  act  with  vigour,  thus  establishing  its  independence 
of  the  brain.  In  many  animals,  the  vis  nervosa  is  retained  after 
decapitation  for  days  and  weeks,  and  in  turtles  for  half  a  year. 
The  destruction  or  removal  of  the  brain,  which  destroys  con- 
sciousness, hinders  therefore  the  continuance  of  the  vis  nervosa, 
but  only  so  far  as  it  prevents  the  influence  of  the  blood  in  the 
muscles  (161) ;  or,  in  other  words,  in  proportion  as  the  nerves 
thereby  become  gradually  more  feeble  and  dead,  but  not  because 
the  co-operation  of  the  brain  is  a  part  of  the  vis  nervosa, 

417.  Those  portions  of  animals  which  are  supplied  with 
nerves  highly  susceptible  of  impressions  (160),  are  endowed 
with  more  acute  external  feeling,  and  a  stronger  vis  nervosa 
from  external  impressions  (403)  than  others ;  as  for  example, 
the  heart,  stomach,  and  intestines.  Structures  with  few  nerves, 
or  nerves  little  irritable,  are  endowed  with  a  feebler  vis  nervosa 
from  external  impressions ;  and  those  to  which  no  nerves  are 
distributed,  have  neither  external  impressions,  nor  vis  nervosa 
(390).  Thus  bones,  tendons,  cartilages,  and  ligaments,  however 
they  may  be  irritated,  display  no  traces  of  movement.  A  part, 
to  possess  the  vis  nervosa  of  external  impressions  must  have 
nerves  that  can  receive  an  impression,  fully  incorporated  with 
it ;  the  more  numerous  such  nerves,  the  more  varied  the  im- 
pressions, and  the  more  susceptible  they  are  to  these  impressions, 
the  more  vivid  its  external  feeling,  and  vice  versa  (44,  47) . 

418.  When  an  external  impression  in  a  nerve  distributed  to 
a  mechanical  machine,  excites  a  nerve-action  in  the  latter  at 
the  point  where  the  impression  is  received,  it  is  termed, 
whether  the  impression  be  transmitted  onwards  or  not  (415,  i), . 

15 


226  ANIMAL  FORCES.  [ii. 

in  so  far  as  it  is  independent  of  that  transmission^  its  direct  nerve  , 
action.    The  conditions  requisite  to  the  production  of  this  are — • 

i.  That  the  mechanical  machine  be  endowed  with  nerves 
(160,  417). 

ii.  That  its  nerves  be  so  touched,  that  an  external  impression 
be  communicated  to  their  medulla  (414). 

iii.  That  the  mechanical  machines  be  capable  at  the  point  of 
impression  of  such  movement  as  the  impression  can  excite. 

419.  The  direct  nerve-actions  are  to  be  distinguished  from 
the  indirect,  which  are  induced  either  remotely  from  the  point 
of  impression,  or,  if  they  arise  in  the  machines  whose  nerves 
are  irritated,  are  not  excited  through  those  nerves,  but  through 
some  other,  or  else  through  the  efferent  fibrils  of  the  irritated 
nerve  (127) .  The  conditions  under  which  they  arise,  are  more 
numerous  than  the  preceding,  and  to  understand  them  the 
following  must  be  premised. 

420.  Take  a  nerve  which  pursues  a  direct  course  from 
the  brain  to  a  limb,  and  penetrates  tissues,  without  giving 
off  a  single  branch  to  any  organs  or  structures  in  its  course, 
having  neither  ganglia  nor  plexuses,  and  instead  of  ending  in 
numerous  fibrils,  gives  off  one  only  to  a  simple  muscular  fibre. 
If  the  latter  be  irritated  with  the  point  of  a  needle,  and  the 
nerve  thus  receive  an  external  impression,  the  fibril  contracts, 
and  so  a  direct  nerve-action  is  produced,  whether  the  im- 
pression be  transmitted  upwards  or  not  (161,  204).  But  sup- 
pose it  to  be  so  transmitted,  what  then  happens  ?  Since  there 
are  no  ganglia  or  plexuses,  in  which  the  impression  can  be 
reflected,  and  since  there  are  no  branches  whatever  given  off, 
the  tissues  it  penetrates  cannot  be  excited  to  action;  but  the 
impression  must  go  on  to  the  brain,  in  which,  if  it  reach  the 
brain,  it  causes  sensation,  and  can  then  be  reflected  from  the 
brain  as  the  internal  impression  of  an  external  sensation,  and 
thus  again  move  the  fibrils  it  moved  before  (188,  127).  This 
result  is,  however,  a  sentient  action,  and  not  a  nerve-action. 

421.  When,  therefore,  an  external  impression  on  a  nerve  ex- 
cites, in  addition  to  its  direct  nerve-actions,  a  movement  in  remote 
machines,  or  in  the  same  machine,  to  which  it  is  distributed  by 
fibrils  of  nerves  distinct  from  that  which  received  the  impression^ 
or  by  efferent  fibrils  ;  or,  in  other  words,  when  it  develops  indirect 
nerve-actions,  it  follows  that  either  the  nerve  itself  is  deflected, 


KJJ. 

I 


tf 


CH.  II.]   NERVE^ACTIONS,  EXTERNAL  IMPRESSIONS.  227 

from  its  course,  or  it  must  have  ganglia,  plexuses,  or  points  of 
division,  in  which  the  impression  itself  may  be  deflected  in  its 
course  upwards.  In  this  case,  the  impression  is  reflected  either 
in  the  nerve  itself,  or  on  its  eff'erent  fibrils,  or  in  the  ganglia 
and  plexuses,  on  altogether  diff'erent  nerves,  and  thus  it  passes 
downwards,  as  a  reflected  internal  impression,  but  unfelt,  and, 
as  such,  can  excite  nerve-actions  in  those  machines  suppliied 
with  the  nerves,  along  which  it  is  reflected. 

422.  The  conditions,  then^  which  are  requisite  to  the  pro- 
duction of  indirect  nerve-actions  by  an  external  impression, 
are — 

i.  The  external  impression  must  be  transmitted  upwards,  to 
that  point  of  the  nerve  where  it  is  reflected,  and  changed  into 
a  non-conceptional,  internal  impression  j  as^  for  example,  to 
that  point  where  the  efferent  fibrils  of  the  nerve  are  excited  by 
the  external  impression,  or  where  the  nerve-fibrils  are  given  off 
which  subserve  to  the  required  nerve-action ;  or  to  the  ganglia, 
or  to  the  plexuses  which  contain  them  (415,  ii). 

ii.  Reflexion  of  the  external  impression,  or  its  change  into  a 

n-conceptional  impression,  must  actually  take  place  there, 
'y  in  other  words,  must  duly  affect  the  efferent  or  other  fibrils 
bove  mentioned  (121). 

iii.  This  new  internal  impression  must  also  be  transmitted 
to,  and  reach,  the  mechanical  machines  to  which  the  fibrils  are 
istributed  (128,  415). 

The  indirect  nerve-actions  of  external  impressions  are,  con- 
sequently, no  other  than  nerve-actions  of  non-conceptional  in- 
ternal impressions,  originating  from  external  impressions  turned 
back  from  their  course  towards  the  brain,  and  unfelt. 

423.  Although  this  reflexion  of  external  impressions  fre- 
uently  takes  place,  and  always  in  certain  circumstances  or- 

ined  by  nature  (48),  yet  it  does  not  follow  that  it  takes  place 
solutely  in  every  case.  On  the  contrary,  it  is  often  seen 
at  an  external  impression,  which  excites  in  certain  machines 
ct  or  indirect  nerve-actions,  excites  also,  at  the  same  time, 
the  same  movements  in  other  machines  regulated  by  other 
nerves ;  nay,  is  even  felt,  and  produces  them  as  sentient  actions 
of  the  internal  impression  of  the  external  sensation  (363,  364,  ii), 

424.  An  indirect  nerve-action  from  an  external  impression 
cannot  arise,  or  is  prevented, — 


228  ANIMAL  FORCES.  [ii. 

i.  If  the  meclianical  macliines  which  ought  to  be  its  seat, 
are  not  endowed  with  nerves. 

ii.  If  their  nerves  be  not  irritated,  or  only  so  irritated  that  the 
nerve-medulla  does  not  receive  thereby  an  external  impression 
(418,  ii).  Something  more  than  mere  irritation  is  required  to 
this  end,  as  a  strong  excitant  fails  to  excite  the  nerve-actions, 
if-  it  be  not  such  an  one  as  stimulates  the  nerve  suitably. 
(Compare  413,  414.) 

iii.  If  the  mechanical  machines  be  unfit,  at  the  point  of 
impression,  to  manifest  the  nerve-actions  to  which  they  are 
stimulated  (418,  iii).  In  such  cases,  the  impression  has  no 
direct  action ;  but  leaving  the  machines  unchanged,  acts  upon 
them  indirectly,  and  causes  an  indirect  nerve-action,  or,  if  it  be 
felt,  a  sentient  action.  Thus,  a  stimulus  applied  to  a  muscle, 
excites  no  contraction,  if  it  be  already  affected  with  spasm, 
although  it  may  be  felt,  and  excite  spasmodic  movements  in 
many  other  muscles.   (See  §§  208,  464.) 

425.  An  indirect  nerve-action  from  an  external  impression 
cannot  arise,  or  will  be  prevented, — 

i.  If  the  external  impression  do  not  reach  to  the  point, 
where  it  can  be  so  turned  as  to  be  reflected  (422,  i),  as  when 
the  nerve  is  tied,  or  divided. 

ii.  If  the  external  impression,  although  it  reach  this  point, 
be  not  changed  into  a  non-conceptional  impression,  or,  in  other 
words,  at  least  partly  deflected  from  and  hindered  in  its  course 
to  the  brain ;  as  when  there  is  induration,  or  other  disease,  of 
the  ganglia,  or  plexuses,  or  of  points  of  branching. 

iii.  If  the  transmission  of  the  reflected  impression  downwards 
to  the  machines  be  prevented,  as  by  ligature ;  it  being  under- 
stood that  the  machines  themselves  are  capable  of  the  actions 
(422,  iii). 

426.  Since  we  can  prevent  the  action  of  irritants  and  of  ex- 
ternal impressions,  and  hinder  their  course,  reflexion,  and  trans- 
mission downwards,  so  also  nature  herself  regulates  them ;  and 
the  impressions  do  not  act  blindly  and  necessarily,  being  pre- 
vented in  various  ways,  and  guided  so  as  to  excite  the  mechanical 
machines  for  specific  objects,  just  as  various  external  sensations 
are  prevented  by  various  means,  to  the  end  that  the  conceptive 
force  be  not  excited  by  every  irritant  applied  to  the  body 
(47 — 51).     It  is  of  importance  to  comprehend  all  the  modes 


[CH.  II.]    NERVE- ACTIONS,  EXTERNAL  IMPRESSIONS.  229 

which,  in  the  natural  condition,  the  nerve-actions  of  external 
ipressions  can  possibly  be  prevented,  and  we  will  therefore  go 
[through  them. 

427.  All  those  natural  obstacles  which  hinder  external  im- 
jressions  arising,  prevent  them  also  from  developing  direct 
lerve-actions  (47,  i,  ii,  iii). 

i.  If  a  part  be  not  supplied  with  nerves,  nerve-actions  cannot 
ike  place  in  them  :  of  this  kind  are  bone,  cartilage,  8zc. 

ii.  If  the  nerves  of  a  part  be  so  protected  by  nature,  by 

leans  of  membranes,  mucus,   &c.,  that  they  cannot  receive 

irious  impressions,  they  cannot  excite  the  corresponding  nerve- 

jtions,  although  they  may  be  moved  by  internal  impressions, 

md  manifest,  through  these,  either  sentient  actions  or  nerve- 

ictions. 

iii.  If  a  nerve  is  naturally  susceptible  of  certain  impressions 
mly,  these  alone  can  excite  the  direct  or  indirect  nerve-actions, 
id  none  others  (424,  ii ;  47,  ii) .  Various  insects,  as  spiders, 
5ndure  the  application  of  very  acrid  irritants,  from  which  other 
limals  would  experience  violent  inflammation  and  convulsions, 
md  yet  feel  the  slightest  irritation  of  another  kind  (413,  414) .  It 
often  observed,  in  animals  endowed  with  sensation,  that  some 
lerves  are  only  susceptible  of  certain  impressions  for  a 'given 
jeriod,  consequently  the  nerve-actions  dependent  thereon  cease 
soon  as  the  period  of  susceptibility  terminates  (265).  The 
)henomena  of  idiosyncrasy  belong  to  this  class. 

iv.  If  a  mechanical  machine  be  endowed  with  nerves,  and 

'^et  is  naturally  incapacitated  for  animal  movement  at  the  point 

[of  impression,  no  direct  nerve-  actions  can  arise  therein  (424,  iii) . 

^he  liver,   spleen,  &c.,   are  incapable  of  motion  at  the  point 

firritated,  namely,  the  substance  of  the  viscus,  and  therefore  no 

external  impression  excites  movement  in  them. 

428,  V.  If  the  external  impression  be  too  feeble  to  reach  a 
point  of  reflexion,  to  be  there  changed  into  an  internal  impres- 
sion, it  may  excite  a  direct,  but  not  an  indirect  nerve-action, 
although  the  body  be  in  the  natural  state  (425,  i).  Thus,  in 
a  decapitated  animal,  a  slight  irritation  of  a  muscle  excites  a 
gentle  contraction  of  its  fibres,  without  any  of  those  convulsions 
resulting  in  other  parts,  which  a  more  powerful  irritation  gene- 
rally produces. 

vi.  Doubtless  there  are  cases  in  which,  in  the  natural  state 


230  ANIMAL  FORCES.  [ii. 

of  the  body,  a  certain  external  impression  is  not  reflected  in 
its  course  to  the  brain,  or  changed  into  a  non-conceptional 
impression,  and  in  which  direct  actions  result,  but  not  those 
indirect  actions  as  would  have  occurred  had  not  the  reflexion 
been  prevented  (425,  ii).  There  are  numerous  instances  of 
this  kind,  in  which  the  impression  is  naturally  not  felt,  and 
not  transmitted  to  the  brain,  and  which  render  it  probable  that 
there  are  secondary  points  in  the  nerves,  whence  it  must  be 
reflected,  and  sent  in  a  certain  direction,  where  it  is  to  be 
changed  into  a  non-conceptional  internal  impression.  A  great 
number  of  external  sensations,  and  also  of  unfelt  external  im- 
pressions on  the  stomach  and  intestinal  canal,  are  never  com- 
municated to  the  muscles  of  the  limbs,  although  these  two 
kinds  of  nerves  are  in  close  connection  :  there  are  also  impres- 
sions of  this  kind,  which  are  not  felt  (48),  yet  excite  the  most 
violent  convulsions.  Here  we  can  only  say,  with  reference  to 
the  greater  number  of  these  impressions  on  the  nerves  of  the 
stomach  and  intestinal  canal,  that  the  points  where  the  latter 
come  into  contact  with  the  nerves  of  the  muscles,  are  not  duly 
excited,  or  do  not  reflect  the  external  impression.  Since  many 
of  these  impressions  are,  in  fact,  felt,  it  is  certain  that  they 
reach-  the  brain,  and  if  they  had  been  reflected,  they  would 
also  have  excited  the  muscles  to  action;  unless  it  be  that  the 
impressions  actually  reflected  do  not  reach  the  muscles,  being 
interrupted  (as  shown  in  the  next  section)  in  their  course  be- 
tween the  point  of  reflexion  and  the  mechanical  machines. 
In  the  examples  above  quoted,  this  is  neither  demonstrable 
nor  probable. 

429,  vii.  Wlien  an  external  impression  on  its  way  to  the 
brain  is  actually  reflected  and  transformed  into  a  non-concep- 
tional internal  impression,  but  is  not  transmitted  back  again 
along  the  nerve  which  received  it,  or  on  account  of  a  natural 
deflection  by  means  of  intervening  ganglia,  or  plexuses,  or  is 
reflected  upon  a  certain  other  nerve,  the  nerve-actions  which 
usually  result  from  it,  do  not  take  place,  but  those  mechanical 
machines  are  put  into  motion  in  connection  with  the  nerve 
along  which  the  impression  is  deflected  (425,  iii).  This  case 
often  occurs  naturally  (137),  but  the  proof  is  difficult.  When 
an  external  impression  has  caused  an  external  sensation,  we 
know  that  it  has  reached  the  brain,  and  that  the   cerebral 


lilt 


CH.  II.]  NERVE-ACTIONS,  EXTERNAL  IMPRESSIONS.  231 

origin  of  the  nerves  has  received  the  internal  impression  of  the 
conception ;  and  if  the  ordinary  sentient  actions  do  not  result, 
we  conclude  that  the  internal  impression  cannot  have  reached 
the  mechanical  machines  (137).  But  with  regard  to  the  non- 
pnceptional  internal  impressions,  we  have  not  the  direct  proof 

brded  hy  sensation,  but  only  secondary  evidence,  when  their 

direct  nerve-actions  remain  unperformed,  whether  they  be 
"reflected  at  the  point  of  reflexion  [Reflexionspunkte]  of  their 
nerve ;  and,  consequently,  whether  the  cause  of  the  failure  is  in 
their  course  to  the  mechanical  machines  or  not.  We  can  only 
incidentally  conclude  in  a  case  of  this  kind,  that  the  reflexion 
has  taken  place,  if  another  organ  situate  below  the  point  of 
reflexion,  and  receiving  its  innervation  from  the  same  nerves, 
is  excited  to  action  by  the  same  external  impression  which 
ordinarily  excites  the  other  organ,  but  now  fails  to  do  so.  It 
is  difficult  to  adduce  instances,  hut  reasoning  from  analogy, 
(compare  §§  138,  360,)  it  is  probable  that  the  reflexion  takes 
place,  and  it  is  the  transmission  downwards  of  the  reflected 
impression  that  is  arrested. 

430.  Just  as  habit  enfeebles  and  prevents  many  sensations 
and  their  sentient  actions,  in  like  manner  it  influences  nerve- 
actions  from  external  impressions,  as  follows : 

i.  The  terminating  fibrils  may  be  so  changed  by  the  frequent 
repetition  of  an  external  impression,  that  they  are  no  longer 
capable  of  the  irritation  requisite  to  the  production  of  the  im- 
pression j  and,  consequently,  no  nerve-actions  result  from  the 
application  of  the  stimulus. 

ii.  The  sensibility  to  certain  stimuli  only,  may  be  destroyed 
by  frequent  repetition  of  them,  whilst  with  regard  to  others  it 
is  unaltered  (51,  ii),  and  thus  the  former  are  no  longer  able  to 
excite  nerve-actions  (427,  ii,  iii). 

iii.  The  frequent  repetition  of  the  same  external  impression 
on  the  same  part  of  a  nerve,  may  so  enfeeble  it,  that  whereas 
previously  it  could  reach  the  point  where  it  was  reflected,  and 
thereby  excite  indirect  nerve-actions,  after  long  habit  it  cannot 
reach  that  point,  and  thus  its  indirect  nerve-actions  cease, 
while  its  direct  continue  (428,  v) . 

iv.  Frequent  repetition  of  the  same  external  impression  on 
the  same  nerve,  can  so  afi'ect  the  point  of  reflexion,  that  re- 
flexion and  transformation  of  the  impression  no  longer  take 


232  ANIMAL  FORCES.  [ii. 

place  (137,  iv) ;  and  thus,  althougli  its  direct  nerve-actions  con- 
tinue, the  indirect  no  longer  occur  (428,  vi). 

V.  Lastly,  in  consequence  of  this  frequent  repetition  of  an 
external  impression,  the  reflexion '  and  transformation  may- 
take  place  so  imperfectly,  that  it  is  not  transmitted  as  a  non- 
conceptional  internal  impression,  with  sufficient  force  to  reach 
the  accustomed  mechanical  machines  (138) ;  and  thus  the 
indirect  nerve-actions  cease,  although  the  ordinary  direct 
actions,  or  other  direct  actions  still  occur  (429) 

431.  That  continued-frequent  repetition,  or  habit ,  has  con- 
siderable influence  on  nerve-actions  excited  by  external  im- 
pressions, as  well  as  on  external  sensations  and  their  actions, 
is  proved  not  only  by  the  analogy  of  all  experience  as  regards 
the  latter  (51),  but  also  by  experience  in  all  instances  in  which 
the  external  impression  is  not  felt.  The  habituation  to  various 
foods,  poisons,  &c.,  are  examples  of  this  kind.  The  movements 
excited  by  these,  until  a  person  is  habituated  to  them,  are 
usually  nerve-actions  of  their  external  impressions,  and  con- 
tinue to  be  such,  although  they  may  be  felt  (364,  ii) ;  but  these 
movements  often  cease  from  constant  repetition  of  the  stimulus. 

432.  The  organisms  of  those  animals,  whose  organs  beiag 
well  supplied  with  nerves,  have,  as  compared  with  other 
animals,  a  vivid  sensibility  (417),  are  termed  irritable  organisms 
(animals)  :  those  which  are  the  contrary,  are  inirritable.  Sen- 
sibility [empfindlichkeit]  may  co-exist  with  irritability,  and 
insensibility  with  inirritability ;  but  irritability  does  not  always 
imply  sensibility,  because  a  very  irritable  organ,  as  the  heart 
or  stomach,  may  be  endowed  with  a  less  sensibility  than  a  less 
irritable  one,  as  the  tongue.  But  as  sensibility  implies  irrita- 
bility, the  latter  enters  also  into  the  temperament^  or  corporeal 
constitution  (52),  and  like  the  former,  is  influenced  by  habit, 
and  thus  forms  the  basis  of  all  the  peculiarities  of  idiosyncrasy 
(Haller  ^Elem.  Phys/  tom.  iv,  p.  576). 

Note. — That  which  Haller  terms  vis  insita  [angeborne 
Kraft],  is  really  only  a  part  of  the  same  property  of  animal 
organisms,  and  has  the  same  relations  to  sensibility  and  habit ; 
for,  according  to  our  views,  it  is  nothing  else  than  the  vis 
nervosa  of  external  impressions  exciting  direct  nerve-actions. 
Let  the  reader  compare  Mailer's  ^  Physiology,'  §  400,  with 
other  parts  of  his  works,  and  with  our  own  views,  and  it  will 


CH.  II.]  NERVE-ACTIONS,  EXTERNAL  IMPRESSIONS.  233 

be  seen  that  the  latter  afford  a  ready  explanation  of  all  the 
phenomena  which  he  refers  to  the  vis  insita. 

433.  When  an  external  impression  is  felt,  it  is  also  felt  to  be 
either  pleasing  or  displeasing  (187).  This  difference  lies  in  the 
impression  itself  (186) ;  consequently,  the  external  impression, 
which  when  felt  is  pleasing,  is  totally  different  in  its  nerve- 
actions,  and  is  of  quite  another  kind,  than  the  impression 
which  when  felt  is  displeasing  (189).  Now  since  the  nerve- 
actions  of  an  external  impression  are  the  same,  whether  it  be 
felt  or  not  (364,  iii),  it  follows  that  the  impression  which  can 
cause  a  pleasing  sensation  will  excite  the  same  animal  move- 
ments as  the  pleasing  sensation  itself  will  excite ;  and  so  in 
regard  to  the  external  impression  of  a  displeasing  external  sen- 
sation. Consequently,  external  impressions  produce,  as  nerve- 
actions,  the  same  movements  which  their  external  sensations, 
accompanied  with  sensual  pleasure  and  pain,  would  develop  as 
sentient  actions  (186,  80). 

434.  By  means  of  the  same  force,  an  external  impression 
also  produces  the  sentient  actions  of  smarting,  or  tickling, 
although  not  felt,  provided  it  occur  under  the  circumstances 
when  it  would  have  caused  titillation  or  pain  (80).  It  cannot, 
consequently,  be  inferred  from  the  occurrence  of  those  move- 
ments which  usually  accompany  an  external  sensation,  par- 
ticularly tickling  or  smarting,  that  the  latter  are  felt,  but  only 
that  there  is  that  present  in  the  external  impression  which 
can  cause  tickling  or  smarting.  If  an  acephalous  foetus, 
or  the  headless  trunk  of  a  worm  or  insect,  be  irritated,  the 
same  movements  result  as  would  have  been  considered  the 
direct  and  incidental  sentient  actions  of  the  irritation,  if  it  had 
been  felt,  although  this  is  impossible  (25,  34).  If  it  be  so 
irritated,  that  pain  under  ordinary  circumstances  would  have 
been  caused,  then  those  movements  result  which  are  the 
ordinary  direct  and  indirect  sentient  actions  of  pain.  The 
injured  part  contracts,  is  congested  with  blood,  and  swells  and 
inflames,  and  the  animal  writhes,  tries  to  escape,  leaps,  flies, 
defends  itself,  and  exhibits  all  the  signs  of  suffering,  although 
it  is  incapable  of  sensation.  Titillation  has  a  similar  effect 
imder  similar  circumstances,  so  that  decapitated  animals  may 
be  excited  to  the  performance  of  sexual  acts,  by  the  external 
stimuli  appropriate  thereto  (274,  396). 


234  .        ANIMAL  FORCES.  [ii. 

435.  If  we  would  compreliend  more  distinctly  how  the 
nerve-actions  of  an  external  impression  can  resemble  all  the 
sentient  actions,  whether  direct  or  indirect,  of  its  external  sen- 
sation, we  must  take  into  consideration  that  the  direct  nerve- 
actions  in  the  part  irritated  result  immediately  from  the  appli- 
cation of  the  external  impression,  and  before  it  can  be  felt ;  to 
this  class  the  internal  impression  is  not  required.  With  regard 
to  the  indirect  nerve-actions  of  external  impressions,  the  matter 
is  as  follows : 

436.  When  an  external  sensation,  either  from  sympathy  or 
natural  deflexions,  develops  direct  sentient  actions,  or  excites 
incidental  sentient  actions  by  means  of  subordinate  concep- 
tions, imaginations,  foreseeings,  desires,  &c.,  through  other 
branches  of  the  nerve  which  has  received  the  external  impres- 
sion, or  by  means  of  nerves  quite  different  (131),  it  is  requisite 
to  these  series  of  phenomena,  that  the  external  impression  be 
changed  into  a  conceptional  internal  impression  before  it  can 
suitabl}^  excite  the  cerebral  origin  of  the  nerve,  or  be  reflected 
in  its  course  downwards  on  the  other  branches  or  nerves,  as 
an  internal  impression  (123,  124).  If  the  same  nerves  be 
suitably  excited  in  the  same  manner,  by  a  reflexion  or  turning 
back  of  the  (External  impression,  exactly  the  same  phenomena 
are  excited,  as  if  they  had  resulted  from  secondary  sensational 
conceptions,  foreseeings,  desires,  &c. 

437.  It  is  thus  we  comprehend,  how  it  is  possible  for  head- 
less animals  to  exhibit  on  a  stimulus  being  applied  (as  proved 
by  experiment),  the  same  adapted  movements  as  are  produced 
by  sensation,  and  by  the  ideas,  foreseeings,  desires,  &c.,  resulting 
therefrom ;  as  when  a  fly  deprived  of  its  head,  flies  away  if 
irritated,  or  as  when  a  headless  snake  quickly  withdraws  its 
body  from  whatever  comes  in  contact  with  it,  or  a  headless 
fish  strikes  the  boiling  water  it  is  put  into  with  its  tail,  &c. 

438.  It  appears  really  wonderful  that  a  blind  external  im- 
pression is  so  reflected  on  other  nerve-fibrils  in  its  way  to  the 
brain,  as  to  produce  those  movements  which  the  mind  produces 
in  virtue  of  its  sensational  volitions.  The  wonder  arises, 
however,  from  our  ignorance  of  the  laws  of  animal  nature,  and 
from  our  prejudice  in  concluding  that  all  which  results  from 
sensation,  can  result  in  no  other  way.  The  nerve- actions  pro- 
duced by  external  impressions,  are  referred  by  the  mind  to 


cu.  II.]   NERVE- ACTIONS,  EXTERNAL  IMPRESSIONS.  235 

ieir  external  sensations,  and  to  the  pleasure  or  pain  they  excite, 
or  to  the  secondary  conceptions  they  produce.  There  must  be 
then  a  sub-element  [Merkmal]  for  the  mind  in  the  external 
sensation  of  an  external  impression,  so  that  it  feels  co-ordinately 
the  reflexion  of  the  latter,  and  also  the  force  required  for 
the  resulting  indirect  nerve-action;  and  it  is  thereby  led  by 
the  sensational  secondary  desires  to  eff'ect  the  movements 
volitionally,  which  then  take  place  the  more  readily,  because 
the  mind  can  of  itself  satisfy  the  desires  for  volitional  movements 
(283).  In  this  way,  the  indirect  nerve-action  becomes  at  the 
same  time  the  incidental  sentient  action  of  the  external  sensa- 
tion excited  by  the  same  external  impression  (97,  221).  But 
having  observed,  that  adapted  motions  excited  after  decapitation 
were  always  previously  volitional,  we  are  led  to  presuppose 
that  they  must  be  volitional  in  their  nature,  and,  therefore, 
always  volitional ;  and  are  astonished  when  we  find  that  they 
can  take  place  independently  of  the  will.  It  is  so  in  every 
instance ;  but  it  is  those  motions  only  that  excite  astonishment, 
which  from  their  nature  we  have  always  been  accustomed  to 
consider  as  wholly  dependent  on  the  will.  "We  are  little  sur- 
prised at  seeing  a  muscle  in  a  decapitated  animal  contract  when 
irritated,  because  we  often  feel  the  irritation  without  at  the 
same  time  feeling  or  observing  the  contraction;  but  when  we 
see  the  animal  rise  up  and  leap  away  when  strongly  irritated,  we 
are  surprised,  because  a  similar  sensation  was  always  previously 
connected  with  the  determination  to  escape,  made  by  a  sensa- 
tional act  of  will.  If  the  movement  to  escape  were  not  always 
connected  with  the  painful  sensation  in  the  uninjured  animal, 
we  should  see  it  produced  in  the  decapitated  animal  without 
thinking  it  resembled  a  volitional  movement,  and  without  being 
surprised. 

439.  It  is  clear  from  the  preceding  statements  (366,  and 
398 — 401),  that  brainless  animals,  although  without  sensation, 
because  not  endowed  with  mind,  nevertheless  by  means  of  ex- 
ternal impressions  which  operate  incessantly  in  them,  perform 
all  the  acts  and  manifest  all  the  activity  of  the  sentient  animal ; 
everything,  in  short,  that  is  effected  sensationally  and  voli- 
tionally they  effect  by  means  of  the  organic  forces  of  the 
impressions  ;  and  since  they  can  act  as  orderly,  judiciously,  and 
rationally  as  it  were,  as  if  they  thought,  it  has  been  inferred 


236  ANIMAL  FORCES.  [ii. 

erroneously,  that  the  apparent  voluntariness  of  these  acts 
depended  on  sensational  conceptions,  even  although  they  might 
be  only  external  sensations.  That  which  is  termed  voluntary 
motion,  we  term  so  only  in  ourselves ;  the  voluntariness  is  not 
in  the  movements — which  remain  the  same  whether  sensational 
conceptions  produce  them  or  not — but  simply  in  this,  that  we 
produce  them  by  spontaneous  sensational  conceptions.  But 
who  has  proved  that  animals  thus  produce  their  movements  ? 
or  who  can  demonstrate,  in  the  face  of  ocular  proof  to  the 
contrary,  that  these  movements  can  be  effected  by  no  other 
animal  force  than  conceptions  (400)  ?  That  these  animals  act  in 
this  way  according  to  the  preordained  objects  of  nature,  especially 
in  the  instincts,  is  undeniable  (262) ;  but  of  these  objects  even 
the  greater  number  of  thinking  animals  themselves  know  nothing 
(265).  They  are  the  objects  of  nature,  not  theirs  (266);  and 
nature  has  so  provided  when  their  adapted  acts  should  take 
place,  or  their  instincts  ought  to  be  in  operation,  that  certain 
external  impressions  are  imparted  in  a  naturally  necessary 
manner,  which  pass  along  their  nerves,  and  are  so  reflected 
and  changed  into  internal  impressions  (399),  that  the  animal 
must  perform  those  apparently  adapted  and  volitional  movements; 
and  which  are  intended  also  for  the  gratification  of  an  instinct, 
if  it  exist,  but  which  are  nevertheless  just  as  fully  eflPected 
without  it  (269).  Thus  it  is  from  erroneous  views  that  our 
astonishment  arises,  inasmuch  as  we  think  that  these  acts 
cannot  be  developed  by  any  other  animal  force  than  the  con- 
ceptive  force  of  the  mind.  For  the  same  reason  we  erroneously 
infer,  that  because  the  acts  of  bees,  ants,  flies,  polypes,  and  other 
insects  and  worms,  are  regulated  to  ends  and  in  agreement  with 
preordination  of  nature,  they  are  dependent  upon  the  conceptive 
force  (266).  It  is  quite  possible,  however,  that  the  external  im- 
pressions manifestly  provided  by  nature  for  the  instincts  in  a 
preordained  manner,  and  which  excite  the  organs  according  to 
a  pre-established  order  of  sequence,  cause  in  them  all  those 
wonderful  and  apparently  voluntary  acts,  without  a  conception 
being  at  all  necessary  thereto  (286,  292,  293). 

440.  We  know  as  little  how  and  wherein  external  impressions 
on  the  nerves  diff'er  from  each  other  as  we  know  with  regard  to 
the  various  external  sensations  which  they  excite  (413).  An  ex- 
ternal impression  produces  as  nerve -actions  the  same  movements 


4 


H.  II.]  NERVE-ACTIONS,  EXTERNAL  IMPRESSIONS.  237 


hicli  it  would  excite  if  it  were  felt  and  caused  a  painful  or 
pleasing  sensation;  but  we  know  no  more  in  what  it  differs 
from  an  impression  which  produces  the  contrary  effect,  than  in 
what  sensations  themselves  differ  (190).  Nevertheless,  it  is  very 
probable,  that  the  external  impression  which  would  have  excited 
pleasing  sensations,  operates  upon  the  nerves  connaturally  or  in 
a  way  that  is  in  accordance  with  their  normal  and  appointed 
functions ;  while  on  the  contrary,  those  which  would  have  caused 
a  painful  sensation,  act  upon  the  nerves  contra-naturally 
[widernatiirlich]  ;  consequently,  the  resulting  nerve-actions 
themselves  are  either  connatural  or  contra-natural  (191,  195). 
Experiment  supports  this  view.  If  a  decapitated  animal  be 
irritated,  so  that  in  its  ordinary  state  the  irritation  would  have 
caused  pain,  it  fights  with  its  natural  weapons,  as  if  the  pain 
were  really  felt;  a  headless  wasp  stings,  a  headless  earwig 
attacks  with  its  nippers,  &c.  All  these  movements  are  violent, 
convulsive,  and  contra-natural,  just  as  they  are  in  the  ordinary 
state  of  the  animal.  An  acrid  irritant  causes  a  convulsive  con- 
traction in  the  excised  intestine  of  an  animal,  just  as  usually 
occurs  in  the  painful  colic  excited  by  ths  same  acrid  poison. 
Gentle  stimuli,  on  the  contrary,  excite  in  headless  animals 
gentle  movements  only;  when  a  decapitated  cricket  receives 
the  external  impressions  which  ordinarily  excite  the  insect  to 
the  act  of  sexual  congress,  a  disordered  and  half- convulsive 
manifestation  of  the  sexual  instinct  is  excited,  which  borders 
closely  on  a  contra-natural  state,  because  its  sensational  stimulus 
is  a  titillation  of  the  sexual  organs  (274).  It  chirps  incessantly 
with  its  wings,  and  allures  to  se:8;ual  congress  with  unusual 
energy  and  activity. 

441.  Consequently,  just  as  external  impressions  follow  upon 
each  other,  so  also  the  same  movements  result  as  nerve-actions, 
which  take  place  as  sentient  actions,  when  the  external  im- 
pression excites  pleasing  or  unpleasing  external  sensations,  pain 
or  tickling ;  and  these  nerve-actions  are  in  like  manner,  either 
in  accordance  with  the  natural  destination  of  the  mechanical 
machines,  or  opposed  thereto. 

442.  It  is  not  necessary  that  an  external  impression  shall 
always  develop  indirect  nerve-actions  in  the  mechanical  ma- 
chines supplied  with  fibrils  from  the  nerve  which  received  the 
impression,  or  from  others  in  connection  with  the  latter,  for 


238  ANIMAL  FORCES.  [ii. 

the  same  reasons  as  laid  down  in  §  201  with  reference  to 
external  sensation. 

443.  The  nerve-actions  of  an  unfelt  external  impression  may 
be  felt,  and  induce  external  sensations  (184).  This  constitutes 
in  sensational  animals,  a  new  link  between  the  nerve-actions  of 
external  impressions  and  the  sentient  actions  of  external  sen- 
sations. A  loaded  state  of  the  stomach,  worms,  or  poisons 
cause  therein  external  impressions,  which  usually  are  not  felt. 
These  have  their  direct  nerve-actions  in  the  stomach,  producing 
in  it  a  contraction  and  contra-natural  movement,  and  this 
nerve-action  it  is  which  we  feel,  when  we  say  that  we  are  ill. 
Vomiting  follows  upon  this  external  sensation,  as  its  sentient 
action,  and  as  the  result  of  a  nerve-action  of  an  unfelt  impres- 
sion. So  the  headaches  accompanying  disorder  of  the  stomach, 
are  felt  nerve-actions  from  unfelt  external  impressions  (419). 
Examples  of  this  kind  are  of  daily  occurrence. 

In  specially  considering  the  nature  of  the  nerve-actions  in 
the  different  mechanical  machines,  it  must  not  be  forgotten 
that  the  latter  are  by  nature  peculiarly  adapted  to  certain 
movements,  and  to  none  other  (193). 


SECTION  IT. THE  VIS  NERVOSA  OF  AN  EXTERNAL  IMPRESSION   IN 

SPECIAL  RELATION   TO  DIRECT  NERVE-ACTIONS. 

444.  The  nerve-actions,  produced  indirectly  by  an  external 
impression,  are  really  nerve-actions  of  a  non-conceptional 
internal  impression  (422).  As  these  will  be  considered  in  the 
next  Chapter,  our  inquiry  as  to  the  vis  nervosa  of  an  external 
impression  need  not  extend  beyond  the  direct  actions  it  produces 
in  the  mechanical -machines  (418). 

415.  Muscular  fibre  of  all  the  tissues  is  most  eminently  that 
in  which  an  external  impression  excites  direct  nerve-actions. 
The  structure  is  peculiarly  adapted  to  the  latter,  since  the 
fibrilli  are  easily  excited  to  movement  at  any  point  of  their 
length,  when  the  two  ends  either  approach  or  separate  from  each 
other  (161).  An  external  irritation  which  duly  excites  the  nerve- 
medulla  distributed  through  the  muscle  can  therefore  very 
readily  impart  an  obvious  movement  at  the  irritated  point,  and 
produce  a  direct  nerve-action  (418).  An  external  impression 
cannot  so  easily  excite  motion  in  other  mechanical  machines. 


I 


H.  II.]      EXTERNAL  DIRECT  NERVE-ACTIONS.        239 


ot  constituted  of  longitudinal  fibrils  like  those  of  muscles 
(161),  although  supplied  with  nerves ;  as  the  substance  of  the 
liver,  the  osseous  medulla,  the  glands,  and  the  membranes  not 
made  up  of  sensitive  muscular  tissue,  as  the  mucous.  When 
such  a  tissue  is  irritated,  no  immediate  movement  results; 
nevertheless,  an  external  impression  is  transmitted  along  the 
nerves,  and  felt  or  reflected  in  its  course  upwards,  and  can 
produce  indirect  nerve-actions  and  sentient  actions  of  external 
sensations  in  the  same  or  other  mechanical  machines  (424,  iii). 
Note. — This  peculiar  capability  of  muscular  fibre  for  direct 
nerve-actions,  as  compared  with  other  machines,  has  probably- 
been  the  principal  source  of  the  erroneous  doctrine,  that  the 
animal  motor  force  of  an  external  impression,  or,  in  other 
words,  their  irritability,  is  a  property  peculiar  to  the  tissue, 
and  independent  of  the  nerves.  It  is  probable,  however,  that 
it  is  not  the  only  seat  of  direct  nerve-actions,  as  wiU  be  shown 
subsequently  (463). 

446.  When  many  muscular  fibres  are  united  together,  so  as 
to  form  bundles,  the  motion  excited  in  one  readily  extends  to 
others,  and  puts  the  whole  bundle  into  action ;  or,  if  a  viscus 
be  made  up  wholly  of  such  bundles,  the  whole  machine  may  be 
thus  excited  to  action,  as  is  the  case  with  the  heart,  stomach, 
intestines,  &c.  This  compound  and  communicated  action  is  as 
much  a  direct  nerve-action,  as  if  only  one  fibril  had  been 
excited  to  contract;  consequently,  when  the  motions  of  the 
heart,  or  of  portions  of  intestine,  are  renewed  after  their 
removal  from  the  body,  by  pricking  with  a  needle,  direct 
nerve-actions  are  produced.  {Vide  Haller's  'Elem.  Physiol.,^ 
tom.  iv,  p.  467.) 

447.  Nevertheless,  it  is  not  advisable  thus  to  consider  them. 
For,  firstly,  the  movements  excited  in  the  fibrils  connected  with 
those  primarily  irritated,  is  only  a  mechanical  result.  Secondly, 
it  may  be  considered  as  a  nerve-action,  the  direct  result  of  an 
internal,  or  the  indirect  nerve-action  of  an  external  impression, 
and  this  may  take  place  as  follows.  The  nerve  entering  a 
muscle  is  distributed  to  every  fibril  of  it,  otherwise  every 
portion  would  not  be  sensitive  (35).  Consequently,  there  must  be 
numerous  points  of  division  of  the  nerve  in  the  substance  of 
the  muscle,  at  which  an  external  impression  on  its  way  upwai'ds 
can  be  reflected,  and  changed  into  a  non-conceptional  impression 


240  ANIMAL  FORCES.  [ii. 

(48).  This  reflexion  of  the  impression  can  excite  indirect  nerve- 
actions  in  all  other  parts  of  the  muscle.  It  is  difficult  to  decide 
which  of  these  two  modes  of  action  takes  place,  when  an  entire 
muscle,  or  muscular  viscus,  is  excited  to  movement  by  the 
irritation  of  a  single  point ;  but  it  is  necessary  for  the  sake  of 
establishing  the  correctness  of  the  doctrine,  that  the  possible 
distinction  be  known. 

448.  The  motion  of  which  a  muscular  fibril  is  capable,  is 
alternate  cqntractiop  and  relaxation.  According  to  the  views 
stated  in  the  previous  paragraph,  irritation  of  a  single  fibril 
may  excite  entire  muscles,  or  bundles  of  fibrilli,  into  action, 
and  by  means  of  the  latter,  entire  viscera  and  limbs  be  put 
into  motion.  When  an  impression  produces  this  motion  it  is 
animal,  whether  it  arise  from  a  conception,  or  from  an  irritation 
applied  to  the  nerves  of  the  fibrilli  (161 — 163,  193).  Thus,  in  a 
decapitated  animal,  an  external  impression  produces  contrac- 
tions, spasms,  &c.,  in  a  muscle,  by  a  direct  nerve-action,  and 
thereby  puts  those  limbs  into  movement  to  which  it  is  attached, 
just  as  a  volition  would.  And  thus,  many  movements  which 
are  or  may  be  sentient  actions,  result  from  the  direct  nerve- 
actions  of  external  impressions  on  the  muscles ;  as  when  the 
irritated  muscle  moves  a  limb  by  its  contractions,  or  closes  a 
cavity,  or,  as  in  the  intestines,  causes  peristaltic  movements  and 
numerous  writhings. 

449.  Neither  the  mind,  nor  internal  impressions  on  the 
brain  or  nerves,  are  necessary  to  direct  nerve-actions  in  the 
muscles.  They  occur,  although  the  brain  be  compressed,  or 
even  the  head  removed  from  the  body,  and  although  the  nerve 
going  to  the  muscle  be  divided,  or  the  muscle  itself  excised. 
All  these  are  points  of  distinction  between  direct  nerve-actions 
and  sentient  actions  generally,  but  especially  those  of  external 
sensations  (164,  204). 

450.  Although,  therefore,  after  the  functions  of  the  brain  are 
arrested,  or  the  nerve  divided  or  tied,  the  muscle  is  excited  to 
motion  neither  by  the  cerebral  force,  nor  by  any  other  internal 
impression  above  the  point  of  division,  but  remains  paralysed 
(415,  ii)  to  all  impressions,  still  the  nerve  itself  retains  the 
power  of  producing  direct  nerve-actions  in  it,  by  means  of  an 
external  impression. 

451.  It  is  not  every  irritation  that  excites  direct  nerve- 


I 


II.]     EXTERNAL  DIRECT  NERVE-ACTIONS.  241 


actions  in  a  muscle  (424);  nor  is  it  to  be  inferred,  that  because 
certain  irritants  fail  to  excite  movement  in  a  muscle,  it  is  de- 
fective in  the  vis  nervosa  of  an  external  impression;  or  because 
it  is  excited  to  movement  by  some,  it  must  necessarily  be  so 
excited  by  all.  Every  muscle,  like  the  nerves,  has  its  own 
special  external  impressions,  which  directly  irritate  it  rather 
than  others,  and  that  whether  they  be  felt  or  not.  And  the 
same  irritant  of  the  nerves  in  a  muscle  may  cause  an  external 
impression,  be  transmitted  upwards,  be  felt,  or  be  reflected 
downwards,  and  consequently  produce  sentient  actions,  or  in- 
direct nerve- actions,  and  all  without  having  produced  a  direct 
nerve-action  in  the  muscle  itself  (424,  iii). 

452.  Those  external  impressions  on  the  muscular  fibre  which 
can  excite  an  agreeable  external  sensation,  excite  the  muscles 
to  movements  in  accordance  with  their  healthy  functions,  as 
the  sensations  themselves  would  ;  on  the  other  hand,  those 
which  would  be  painful  to  the  animal  under  ordinary  circum- 
stances, excite  the  irritated  muscle  to  spasmodic  and  convulsive 
actions,  and  convulse  the  limbs  (204,  440) .  Thus  acrid,  irritant 
poisons,  excite  violent  writhings  in  an  excised  portion  of  intes- 
tine, and  render  an  excised  muscle  hard,  and  permanently 
contracted;  the  excised  heart  beats  irregularly,  if  strongly 
irritated,  &c. 

4<53.  The  direct  nerve -actions  of  an  external  impression  on 
the  muscles  are  the  same  as  the  direct  sentient  actions  of  its 
external  sensation,  and  can  cause  the  same  series  of  movements 
which  these  latter  excite  by  their  pleasure  and  pain,  and  the 
resulting  sensational  conceptions  as  incidental  sentient  actions ; 
so  that  external  impressions  may  thus  excite  a  whole  chain  of 
apparently  volitional  acts,  without  one  of  them  being  felt,  or  any 
conception  whatever  excited  (437-8).  Hence  an  animal  may, 
by  external  impressions  only,  perform  all  the  organic  and  appa- 
rently volitional  movements  necessary  to  its  existence,  without 
having  either  brain  or  mind,  if  its  body  be  so  constituted  (as  is 
quite  possible)  that  all  external  impressions  on  its  nerves  can 
produce  their  direct  and  indirect  nerve-actions,  without  having 
to  excite  material  ideas  in  the  brain,  or  conceptions  in  the 
mind,  connected  therewith. 

454.  Although  muscular  movements  be,  for  the  most  part, 
excited  volitionallv,  either  by  external  sensations  or  volitional 

16 


242  ANIMAL  FORCES.  [ii. 

conceptions  (163),  still  an  infinite  number  of  instances  are  ob- 
served in  the  natural  state,  in  which  they  take  place  solely 
by  means  of  the  vis  nervosa,  and,  in  particular,  that  of  external 
impressions.  A  limb  is  often  moved,  not  only  against  our 
wish,  but  often  without  any  feeling  of  the  irritation  that  causes 
the  involuntary  movement.  It  often  happens  that  an  impres- 
sion in  the  intestinal  canal,  which  is  not  felt,  causes,  in  virtue 
of  an  indirect  nerve-action,  the  most  violent  movements  of  the 
limbs;  as  is  proved  by  epileptic  paroxysms  dependent  on  worms, 
and  the  presence  of  which,  in  the  intestinal  canal,  is  not  indi- 
cated to  either  the  physician  or  patient,  by  any  peculiar  phe- 
nomena (470).  Thus,  also,  an  irritant  poison  causes  spasmodic 
action  of  the  intestines,  which  is  only  indicated  by  the  rumbling 
of  flatus,  but  not  felt.  So,  also,  the  stimulus  of  light  causes 
contraction  of  the  iris,  as  an  indirect  nerve-action,  without  any 
accompanying  sensation.  Consequently,  there  are  many  move- 
ments considered  to  be  sentient  actions  of  external  sensations 
only,  which  are  nevertheless,  at  the  same  time,  direct  or  indirect 
nerve-actions  of  an  external  impression  which  is  felt;  and  in 
this  way  may  be  explained  many  movements  made  during  sleep, 
particularly  by  somnambulists,  and  those  habitual  voluntary 
movements  which  are  induced  by  external  impressions  that  are 
not  felt.  But  the  principal  point  is,  that  on  this  depends  the 
secret  of  the  instincts  in  those  animals  which  probably  do  not 
feel  the  sensational  stimuli  of  the  instincts ;  as,  for  example, 
animals  in  utero,  or  in  ovo,  which  already  know  how  to  aid 
their  birth  before  they  seem  to  have  felt  anything;  or  animals 
which  are  stimulated  to  undertake  movements  the  most  skil- 
fully adapted  to  their  preservation,  without  having  been  taught 
by  experience  (269) ;  or  animals  which,  during  their  whole  life, 
do  nothing  that  shows  the  least  trace  of  ideas,  and,  conse- 
quently, of  external  sensations,  as  polypes  and  oysters,  &c. 
In  all  these  examples,  the  external  impressions  which  are  ordi- 
narily the  sensational  elements  of  the  instincts,  seem  to  act  as 
a  vis  nervosa  in  producing  the  movements  of  the  so-called  in- 
stincts; and  many  of  these  are  undoubtedly  true,  direct,  nerve- 
actions,  although  it  is  equally  certain  that  others  are  indirect. 
In  animals  which  gradually  learn  to  feel,  and  to  form  volitions, 
these  external  impressions  become,  in  time,  to  be  external  sen- 
sations, and  the  movements,  hitherto  nerve-actions,  become  to 


CH.  II.]     EXTERNAL  DIRECT  NERVE-ACTIONS.  243 

be  also  sentient  actions,  as  has  been  already  shown  in  detail, 
in  Part  I.    (Compare  §§  269,  285—293,  &c.) 

455.  The  heart  is  a  muscular  viscus,  which  can  be  excited 
into  direct  nerve-actions  by  an  external  impression  (357),  applied 
either  externally  or  internally;  and  even  when  it  has  been  re- 
moved from  the  body,  and  its  action  has  already  ceased  for  a 
lengthened  period.    (Haller*s  '  Physiology/  §  102.) 

456.  Since  the  cardiac  movements,  thus  excited,  are  neces- 
sarily independent  of  the  mind  or  the  brain,  and  are,  therefore, 
in  no  respect  sentient,  they  are  direct  nerve-actions  excited  by 
an  external  impression,  and  would  still  be  such  if  they  were 
also  felt,  and  occurred  (as  they  sometimes  do)  as  sentient 
actions  of  external  sensations  (452,  512). 

457.  The  external  stimuli  which  more  especially  excite  direct 
nerve- actions  in  the  heart,  are  the  blood  and  other  fluids,  and 
the  air  itself,  if  in  contact  with  the  inner  surface.  (Haller^s 
'  Physiology,'  §  101,  and  'Opera  Minora,'  tom.  ii,  pp.  389,  390.) 
Various  stimuli,  applied  externally,  have  also  the  same  effect ; 
the  heart  is,  indeed,  the  organ  which,  of  all  others,  possesses 
the  greatest  irritability  (Haller's  '  Physiology,'  §  102) ;  or,  in 
other  words,  which  is  the  most  readily  excited  to  violent,  direct 
nerve- actions,  by  the  greatest  number  of  external  impressions. 

458.  Just  as  painful  or  pleasing  sensations  excite  the  heart's 
action  contrarily  to,  or  in  accordance  with,  its  natural  func- 
tions (211,  204),  so,  also,  are  the  nerve-actions,  when  excited  by 
those  external  impressions,  which,  if  felt,  would  excite  painful 
or  pleasing  sensations  (452).  An  excised  heart  is  irritated  to 
convulsive  movements,  if  the  irritant  be  violent,  or  such  as 
would  have  been  painful.  Now,  inasmuch  as  the  circulation 
of  the  blood  is  closely  connected  with  the  motions  of  the  heart, 
it  may  be  either  in  accordance  with  the  well-being  of  the 
organism,  or  opposed  to  it,  just  as  the  external  impressions  on 
the  heart  differ;  and  it  thus  appears  that  an  abnormal  com- 
position or  temperature  of  the  blood  renders  the  stroke  of  the 
heart  contranatural,  in  fevers  and  other  diseases. 

459.  The  ordinary  and  natural  stimuli,  or  the  external  im- 
pressions of  the  heart,  are  not  felt  by  animals  (167);  conse- 
quently, their  transmission  beyond  the  heart  is  not  necessary 
to  the  excitation  of  its  action,  although  it  seems  to  be  necessary, 
in  many  animals,   to  the  more   certain   maintenance   of  the 


244  ANIMAL  FORCES.  [ii. 

movements.    (See  §  515.)     It  follows^  therefore^  that  the  heart's 
action  is,  for  the  most  part,  purely  a  nerve-action  of  an  external 
impression,  and  direct,  although,  at  the  same  time,  a  sentient 
action  also  (167),  especially  of  external  sensations,  and,  therefore, 
may  be  also  an  indirect  nerve-action  (421 — 423) .   Consequently, 
in  animals  without  either  sensation  or  brain,  the  movements  of 
the  heart  may  go  on  just  as  in  sentient  animals,  and  be  either 
connatural  or  contranatural,   according  to  the  nature  of  the 
external  impressions  exciting  them;  and  the  change  thus  in- 
duced in  the   circulation  may  induce   the   same  movements, 
which,  when  the  animal  felt  it,  constituted  incidental  sentient 
actions  of  the  external  sensation  exciting  the  movements  (453). 
460.  The   pulse,   or  the  contraction  and  dilatation  of  the 
arteries,  and  the  entire  circulation  of  the  blood  through  the 
blood-vessels,  are,  for  the  most  part,  nerve-actions  only,  although 
they  may  sometimes  be  also  sentient  actions  (167,  205),  and 
indirect  nerve-actions.      They  may  take  place  independently  of 
the  brain   or  of  sensation.      The  action  of  the  arteries,  inde- 
pendently of  the   heart,   seems  to  be  rather  mechanical  than 
animal.      They  are  endowed  with  the  force  of  contractility,  as 
is  shown  when  they  contract  on  a  finger  inserted  into  them, 
and  when  they  contract  again,  so  soon  as  they  are  distended 
with  the  blood  sent  from  the  heart.      This  force  is,  in  all  pro- 
bability,  purely  mechanical,  for  the  arteries  are  always  con- 
tracted in  the  corpse ;  and  if  fluids  be  injected,  so  as  to  distend 
them,  they  contract  again  so  soon  as  the  pressure  is  withdrawn. 
They  have  also  a  natural  elasticity,  for  they  retract  very  consi- 
derably when  divided.   (Haller's  'Physiology,'  §  33.)      But  they 
have  no  sensibility,  if  their  nerves  be  not  irritated,  which,  how- 
ever, are  certainly  not  distributed  to  their  fibrous  tissue  :   even 
Haller  himself  denies  that  they  have  any  visible  irritabihty. 
{'  Physiology,'  §  32,  and  'Opera  Minora,'  torn,  i,  pp.  377,  418.) 
Nevertheless,   they   are   surrounded  with  muscular  fibres  and 
nerves,  that  have  both  properties.      It  appears,  however,  that 
these  are  supplied  by  nature,  to  the  end  that  their  ordinary  me- 
chanical stroke  may  be  changed  by  means  of  direct  nerve-actions, 
when  certain  external  impressions,  which  are  unusual  or  contra- 
natural,  are  received.     This  is  observed,  when  an  artery,  being 
so  wounded,  that  its  nerves  or  muscular  fibres  are  injured,  be- 
comes inflamed  at  the  spot,  and  pulsates  strongly.     Probably 


CH.  II.]     EXTERNAL  DIRECT  NERVE-ACTIONS.  245 

the  alteration  of  the  pulse,  when  the  blood  is  at  a  higher  tem- 
perature, or  has  undergone  a  morbid  change,  is  connected 
therewith,  the  nerves  and  muscular  fibres  being  irritated  by  the 
morbid  blood,  so  that  the  arteries  contract  more  forcibly  and 
quickly;  which  action  must  be  a  direct  nerve-action,  excited  by 
an  external  impression  of  an  unnatural  kind.  The  reader  is 
recommended  to  take  into  consideration  the  proofs  of  the  irri- 
tability of  arteries,  adduced,  from  his  own  researches,  by 
Verschuir,  in  his  excellent  dissertation,  "  De  Arteriarum  et 
Venarum  vi  irritabili/^  &c. — Groningen,  1766.  However, 
whether  the  natural  movement  of  the  arteries  be  simply  me- 
chanical, or  whether  it  be  a  direct  nerve-action  of  external 
impressions  received  from  the  in-streaming  blood,  in  either 
case  it  is  independent  of  the  brain  or  the  mind.  Lastly,  since 
every  assistance  which  is  given  to  the  circulation  in  the  blood- 
vessels of  the  muscles  by  muscular  action  (169),  maybe  as  often 
the  result  of  a  direct  nerve-action  of  an  external  impression  on 
the  muscles  as  of  a  sentient  action;  it  may  be  asserted,  that 
the  entire  circulation  of  the  blood,  and  the  functions,  and 
changes  in  organs  mechanically  connected  therewith,  may  be 
carried  on  without  the  co-operation  of  either  the  brain  or  the 
mind,  and,  in  fact,  are  so  carried  on,  even  in  animals  endowed 
with  consciousness. 

461.  This  is  proved  by  experiment.  In  animals  which  do 
not  bleed  to  death  immediately  after  decapitation,  the  beat  of 
the  heart  and  the  pulse,  and  the  entire  circulation  (so  far  as 
the  great  disturbance  of  the  organism  admits  of)  goes  on  un- 
interruptedly for  a  considerable  period  (Haller  ^  Opera  Minora,^ 
torn,  i,  p.  425),  and  are  altered  by  external  stimuli,  especially 
by  the  various  qualities  of  the  blood.  The  arterial  pulse,  in 
cases  of  suffocation,  when  life  is  restored  by  artificial  means, 
returns  only  after  the  hearths  action  is  established,  and  is  first 
felt  in  the  vessels  nearest  to  the  heart.  In  the  dying  and  in 
syncope,  the  pulse  continues  in  the  latter  vessels,  when  it  can 
be  no  longer  perceived  in  the  more  distant. 

462.  The  arterial  capillaries,  as  has  been  already  shown 
(207),  are  capable  of  special  movements,  which  although  some- 
times sentient,  belong  properly  to  the  class  of  direct  nerve- 
actions,  excited  by  external  impressions  on  the  nerves  which 
surround  these  vessels.     They  consist  in  this,  that  an  external 


246  ANIMAL  FORCES.  [ii. 

impression  on  these  capillaries,  attracts  the  contained  fluids  to 
them,  which  are  thence  in  many  cases  effused,  but  in  many 
other  cases  rendered  motionless,  and  thus  redness,  swelling, 
and  inflammation  are  caused.  That  this  is  a  purely  direct 
nerve-action  of  external  impressions  is  proved  by  the  fact,  that 
if  a  portion  of  the  body  be  struck  after  decapitation  it  becomes 
congested,  just  as  if  the  animal  had  felt  the  blow.  And  we 
often  perceive  similar  effusions,  redness,  congestions,  swellings, 
and  inflammations,  take  place  in  sleep,  syncope,  convulsions, 
delirium,  &c.,  without  the  external  impression  having  been  felt 
that  caused  them,  so  that  the  principle  that  at  each  external 
sensation  a  flow  of  fluids  to  the  irritated  part  takes  place  pro- 
portionate to  the  external  impression,  must  have  a  wider  appli- 
cation, and  be  extended  to  every  external  impression,  whether 
it  be  felt  or  not  (218). 

463.  The  question  has  been  raised,  whether  this  direct 
nerve- action  in  the  capillaries  takes  place  through  muscular 
fibrilli,  or  through  the  irritation  of  the  nerves.  Without 
attempting  to  solve  this  difficult  problem,  it  is  sufficient  to  ob- 
serve, that  it  may  be  analogous  to  the  sentient  actions  de- 
scribed §  147;  that  is,  an  external  impression  on  the  capillaries 
causes  a  slight  movement,  whereby  it  immediately  induces  a 
closure  of  their  mouths,  and  so  the  other  phenomena  described 
(207)  result. 

464.  The  flat  muscles  and  muscular  membranes,  are  capable 
of  direct  nerve-actions  independently  of  the  brain  and  of  mind, 
just  as  other  muscles :  this  has  been  fully  established  by  ex- 
periments with  reference  to  the  diaphragm.  '^  Caro  diaphrag- 
matis  per  integram  horam  tremuit,  et  mansit  irritabilis,  cum 
intestina  jam  quievissent,'^  &c.  (Haller,  '  Opera  Minora,'  tom.  i, 
p.  368:  Exp.  181,  182,  194). 

Those  tissues  which  have  no  muscular  element,  as  the  skin 
and  mucous  membranes,  are  not  capable  of  movements  from 
external  impressions  at  the  point  of  irritation,  although  they 
be  felt  (208,  445) ;  but  since  they  contain  numerous  blood- 
vessels and  glandular  structures,  which  are  capable  of  direct 
nerve-actions,  it  follows  that  these  membranes,  however  little 
irritable  they  may  be  of  themselves,  will  still  exhibit  certain 
movements,  which  will  sometimes  occur  in  them  at  the  irritated 
spot,  as  sentient  actions  (208).     When  a  painful  irritation  of 


(  H.  II.]     EXTERNAL  DIRECT   NERVE-ACTIONS.  247 

the  skin  causes  redness,  it  is  the  sentient  action  of  an  ex- 
ternal sensation  at  the  irritated  part;  but  when  the  same  takes 
place  after  decapitation,  it  is  the  direct  nerve-action  of  an 
external  impression  on  the  terminations  of  the  capillaries  of 
the  skin  (462) .  When  an  irritation  of  the  mucous  membrane 
of  the  nares,  causes  a  flow  of  mucus,  a  sentient  action  of  an 
external  sensation  takes  place;  but  if  the  same  occurs  after 
removal  or  destruction  of  the  brain,  it  is  a  direct  nerve-action 
in  the  capillaries,  or  the  glandular  tissues  of  the  mucous 
membrane. 

On  account  of  the  deficiency  of  nerves  in  the  insensible 
fibro-serous  tissues  of  the  thorax  and  abdomen  (208),  no  other 
nerve-actions  occur  than  those  produced  in  the  sensitive  nerves. 
Thus  a  repelled  transpiration  from  cold  excites  the  capillaries 
of  the  pleura  to  contract,  and  thereby  induces  congestion  and 
inflammation,  although  no  sensation  is  excited  by  this  external 
impression ;  for  the  pain  results  from  the  inflammation  (208, 
note) . 

465.  Although  the  broad  muscles  and  muscular  tissues  are 
sensitive  (171),  and  an  external  impression  excites  their  natural 
functions  as  sentient  actions  (as,  for  example,  when  an  irritation 
causes  spasmodic  action  of  the  diaphragm) ;  yet  it  often  happens 
that  the  excited  functions  are  the  direct  or  indirect  nerve- 
actions  of  the  same  external  impression,  or  even  mechanical 
results  of  the  direct  nerve-action  (447,  464).  Thus,  the 
external  irritation  which  excites  the  diaphragm  to  motion,  and 
that  which  irritates  the  muscular  tissue  of  the  glands,  when 
they  pour  out  their  secretions,  are  very  seldom  felt.  It  is  the 
same  with  the  indirect  nerve-actions  in  the  membranes  devoid 
of  muscular  tissue ;  although  they  sometimes  arise  from  ex- 
ternal sensations,  yet  general  observation  shows,  that  small 
suff'usions,  inflammations,  congestions,  induration,  effusion,  &c., 
take  place  in  the  pleura,  peritoneum,  &c.,  which  necessarily 
result  from  external  impressions  on  those  tissues  that  are 
altogether  unfelt;  just  as  occurs  in  various  diseases,  namely, 
erysipelas,  catarrh,  cough,  pleurodynia,  cutaneous  eruptions,  &c. 

466.  The  large  muscular  viscera,  particularly  the  oesophagus, 
stomach,  and  intestines,  are  not  only  directly  excited  by  ex- 
ternal impressions,  but  in  virtue  of  their  peculiar  structure,  and 
by  means  of  their  direct  nerve-actions,  are  so  excited  through- 


248  ANIMAL  FORCES.  [ii. 

out  their  whole  extent  (446),  that_,  like  the  heart,  they  move 
actively  on  being  irritated,  when  separated  even  for  a  lengthened 
period  from  the  body  (357).  See  Haller's  '  Physiology,'  §  402, 
and  '  Opera  Minora,'  torn,  i,  pp.  384,  199,  390,  &c. 

467.  The  co-operation  of  neither  the  cerebral  forces  nor  the 
mind  is  necessary  to  the  natural  functions  of  the  oesophagus, 
stomach,  and  intestines,  excited  as  nerve-actions  by  external 
impressions  ;  they  can  take  place  in  animals  deprived  of  both 
(418). 

468.  The  oesophagus  and  gastro-intestinal  canal  are  directly 
excited  by  numerous  external  stimuli.  Food  of  various  kinds, 
air,  medicines,  poisons,  injuries,  &c.,  excite  contractions  at  the 
point  of  irritation,  which  are  propagated  to  their  whole  extent 
as  a  result  of  the  direct  nerve-actions  of  the  external  impression 
(446).  Those  excitants,  which  can  excite  an  agreeable  external 
sensation,  produce  only  natural  movements  in  these  viscera : 
those  which  would  excite  pain,  excite  convulsive  contractions, 
as  in  muscles  (compare  §  452). 

469.  In  accordance  with  these  views,  it  follows  that  the 
entire  process  of  digestion,  considered  as  an  animal  function, 
is  the  result  of  the  nerve-actions  of  the  external  impressions 
derived  from  the  food  in  contact  with  the  digestive  organs,  and 
it  may,  therefore,  take  place  quite  independently  either  of 
brain  or  mind.  The  movement  of  the  chyle  in  the  chyliferous 
ducts  belongs  also  to  this  class  of  functions.  See  Haller's 
'  Opera  Minora,'  torn,  i,  pp.  378-9. 

470.  The  ordinary  stimuli  of  the  vermicular  motions  of  the 
alimentary  canal,  are  not  felt  or  propagated  beyond  its  tissues. 
We  feel  nothing  of  the  food  after  it  has  passed  beyond  the 
tongue :  the  violent  irritants,  which  excite  spasmodic  action 
and  convulsive  movements,  are  so  little  felt,  that  their  presence 
is  only  inferred  from  the  rumbling  of  flatus,  or  from  their 
indirect  nerve- actions,  or  from  the  external  sensations  excited 
thereby  in  widely  distant  parts  (212);  as  when  w^orms  in  the 
stomach  or  bowels  excite  convulsions,  paralysis,  pleurodynia, 
frequent  nausea  and  vomiting,  &c. 

471.  The  functions  of  glandular  secretion  and  excretion 
are,  for  the  most  part,  regulated  by  physical  laws  (159);  but 
since  a  gland  is  a  tissue  compounded  of  blood-vessels  and 
nerves,  these  functions  must  depend  upon  the  influence  of  the 


I 


CH.  II.]      EXTERNAL  DIRECT  NERVE- ACTIONS.  249 

vis  nervosa,  and  are,  consequently,  animal  (6,  9).  It  has  been 
already  shown,  that  they  are  sometimes  sentient  actions,  espe- 
cially of  external  sensations  (172,  209).  Can  they  occur  also 
as  nerve-actions  ?  Experiments,  as  to  this  point,  are  not 
decisive ;  but,  it  has  been  observed,  that  the  glands  of  excised 
portions  of  the  intestines  may  be  excited  to  pour  out  fluid,  which 
act  is  undoubtedly  a  nerve-action  (Haller,  '  Opera  Minora,^ 
torn,  i,  pp.  390,  &c.  "  Humorum  a  purgante  medicamento 
copiosior  adfluxus,^^  p.  401.) 

472.  Granting,  however,  that  the  doctrine  is  not  proved  by 
direct  experiment,  the  principles  already  established  as  to  the 
action  of  external  impressions  on  the  blood-vessels  and  their 
terminations  (4G0 — 463)  and  on  muscular  fibre  (which  also 
enters  into  the  composition  of  several  secreting  organs,  §  §  448, 
454),  sufficiently  prove  that  secretion  and  excretion  may  be 
simply  direct  nerve-actions  of  external  impressions. 

473.  An  additional  proof,  that  secretion  and  excretion  in 
animals  endowed  with  mind,  are  nerve-actions  of  external  im- 
pressions, is  found  in  the  fact  that  they  are  rarely  sentient 
actions  of  external  sensations,  and,  consequently,  the  external 
stimuli  are  not  usually  felt ;  and  as  nerve-actions  can  only 
occur  in  so  far  as  the  functions  of  the  capillaries  and  the  action 
of  the  muscular  fibres  and  muscles  are  directly  excited  (472), 
it  follows  that  secretion  and  excretion  from  glands  are  nerve- 
actions  of  an  external  impression  acting  directly  on  their  nerves 
{vide  Haller's  'Physiology,^  §  233).  Hence  we  conclude  that 
the  whole  of  these  phenomena  may  take  place  perfectly  in 
animals  unendowed  with  brain  or  mind,  and  difi*er  in  being 
either  in  accordance  with  the  objects  of  nature  or  opposed 
thereto,  just  as  in  animals  endowed  with  consciousness.  (Com- 
pare Haller^ s  '  Elements  of  Physiology,^  tom.  iv,  p.  575.) 

474.  The  viscera  are  compound  mechanical  machines,  made 
up  of  muscular  fibres  and  coats,  muscles,  vessels,  glands,  or 
secreting  vessels,  which  are,  in  fact,  the  mouths  of  capillaries; 
consequently,  the  statements  already  made  (445 — 473),  apply 
equally  to  them  in  every  respect.  We  need  only  mention  a 
few  experiments  to  establish  this  truth. 

475.  As  to  the  heart  {vide  §§  455 — 459),  the  alimentary  canal 
(^  466 — 470),  the  diaphragm  (§§  464,  4^66),  ffla?idular  struc- 
tures (§^  471 — 473),  fibrous  tissues  (§§  460,   461),  muscular 


250  ANIMAL  FORCES.  [ii. 

structures  (§§  448 — 454).  The  lungs  have  mechanical  functions 
(Haller's  'Phys/  §263*),  in  which  their  nerves  have  httle  share ; 
neither  are  they  endowed  with  much  sensibiUty  or  irritability. 
[Ibid.  §  245.)  Yet  the  bronchial  tubes,  far  into  the  lungs,  are 
supplied  with  muscular  fibrilli,  a  very  sensitive  membrane,  and 
numerous  glands.  Hence,  external  impressions  excite  many 
direct  nerve-actions,  as  spasmodic  contraction  of  the  tubes,  and 
a  flow  of  fluids  from  the  irritated  glands  and  the  mouths  of  the 
capillaries.  Respiration  is  carried  on  by  means  of  the  muscles 
of  the  thorax,  back,  abdomen,  and  diaphragm;  but  many 
changes  are  caused  in  it,  as  in  singing,  speaking,  coughing,  by 
means  of  the  upper  portion  of  the  air-tubes  which  are  regulated 
by  muscles,  and  by  the  mouth,  lips,  tongue,  and  nose,  all 
which  are  muscular  structures.  Now,  since  all  these  organs 
are  usually  moved  by  means  of  direct  nerve-actions  of  external 
impressions,  it  follows  that  the  whole  function  of  respiration 
may  take  place  independently  of  either  the  brain  or  mind 
{Vide  Haller^s  experiments,  'Opera  Minora,'  tom.  i,  pp.  368, 
&c.),  and  be  either  connatural  or  contranatural  (454),  although 
it  may  be,  at  the  same  time,  a  volitional  act,  and  the  result  of 
an  instinct ;  or,  in  other  words,  an  incidental  sentient  action  of 
external  sensations  (221,  285).  It  is  thus  that  unfelt  external 
impressions  re-excite  this  highly  complex  process,  in  cases  of 
suspended  animation,  by  stimulating  the  nose,  air-passages,  and 
respiratory  muscles.  It  is  not  to  be  forgotten,  that  some  of 
these  act  as  internal  impressions,  producing  indirect  nerve- 
actions.    (Compare  §  525.) 

476.  The  liver  is  only  capable  of  the  nerve-actions,  which 
are  produced  through  the  nerves  that  accompany  its  blood- 
vessels. Experiments  are  not  easily  instituted  on  this  viscus. 
The  irritability  of  the  gall-bladder  is  somewhat  doubtful. 

477.  Various  remedies,  and  articles  of  food,  act  quickly,  in 
increasing  the  secerning  function  of  the  kidneys.  The  external 
impressions  they  cause  on  the  kidneys  are  not  felt ;  the  func- 
tion, therefore,  is  a  nerve-action,  and  the  doctrines  already  laid 
down  with  regard  to  secretion  and  excretion  are  applicable  to 
the  kidneys. 

478.  The  urinary  bladder  is  opened,  contracted,  and  shut, 
by  muscular  fibres ;  consequently  these  processes  may  be  and 
are  nerve-actions  of  external  impressions,  inasmuch  as  the  latter 


CH.  n.]     EXTERNAL  DIRECT  NERVE-ACTIONS.  251 

e  often  not  felt^  although  usually  the  natural  functions  of  the 
bladder  are  volitional,  and  therefore  sentient  actions. 

479.  The  spleen,  being  composed  of  vessels,  is  in  the  same 
^^ategory  with  the  liver. 
^B    480.    The  organs  of  the  senses   (considered   as  mechanical 
^fciachines,  and  not  as  organs  of  sensation),  being  supplied  with 
^fcauscles,  are,  to  that  extent,  capable  of  nerve- actions  :  the  spas- 
^Biodic  affections  of  the  tongue  and  of  the  muscles  of  the  orbit, 
horripilation,  and,  in  lower  animals,  twitchings  of  the  ears,  are 
manifest  examples  of  these.     Are  not  the  actions  of  the  iris  in 
contraction  and  dilatation,  and  the  tension  of  the  muscles  of 
the  ossicula  auditus,  although  usually  sentient  actions,  caused  by 
external  sensation,  at  the  same  time  also  nerve-actions  caused 
by  the  same  external  impressions  ?    It  is  difficult  to  decide  the 
question.     (Compare  Haller's  '  Physiology,^  §§  494,  496,  513.) 
481.   The  functions  of  the  sexual  organs  in  mammalia,  and 
in  animals  of  a  similar  organisation  in  this  respect,  are  usually 
sentient  actions ;   but,  nevertheless,  there  are  some  reasons  for 
thinking,  that  the  cerebral  forces  only  co-operate,  and  that  they 
may  be  induced  by  the  vis  nervosa  alone,  as  direct  nerve-actions 
of  external  impressions.     Erection  of  the  penis  will  take  place 
in  sleep,  or  in  disease,  without  any  external  sensation,  and  is, 
therefore,  a  direct  nerve-action.     The  uterus  is  endowed  with 
as   much    irritability   as    the    intestinal    canal :     and,    lastly, 
Bibiena^s  experiments,   lately  instituted,  show  that  butterflies 
and  silkworm-moths  copulate,  and  deposit  their  eggs,  after  de- 
capitation ;  and  thus  a  natural  instinct  is  fulfilled  by  nerve- 
actions  alone.    (Compare  §  269.) 


CHAPTER  III. 

ON  THE  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS 
(WITHOUT  CONCEPTIONS). 

SECTION  I. 

482.  Every  internal  impression  is  transmitted  along  the 
nerves,  in  a  direction  from  the  brain  downwards^,  and  is  a  mo- 
tor force  not  subject  to  physical  or  mechanical  laws  (32,  121). 
If  it  be  caused  by  conceptions  at  the  cerebral  origin  of  the 
nerves,  the  movements  it  excites  are  sentient  actions  (122), 
but  if  it  be  not  caused  by  conceptions,  then  the  movements  it 
excites  are  nerve-actions  of  its  vis  nervosa,  and  it  is  of  these  we 
propose  to  discourse. 

483.  Non-conceptional  impressions,  that  is  to  say,  internal 
impressions  not  caused  by  conceptions,  consequently  not  origi- 
nating from  a  material  idea  in  the  brain  (123),  can  take  place 
at  any  point  of  a  nerve,  even  at  its  cerebral  origin,  but  always 
excepting  the  terminal  fibrils,  for  it  would  then  be  an  external 
impression  (32,  121).  Consequently,  the  indirect  nerve-actions 
of  external  impressions  are  nerve-actions  of  non-conceptional 
internal  impressions  (422). 

484.  Since  every  internal  impression  on  the  nerves  is  pro- 
pagated downwards  only  (141) — if  made  on  a  nerve  between  its 
origin  and  termination,  it  cannot  be  transmitted  as  an  internal 
impression  upwards  to  the  brain,  nor  can  it  excite  any  animal 
actions  in  the  parts  situate  above  the  point  of  impression;  and 
if  such  result,  they  must  be  considered  as  being  excited  by  a 
concurrent  external  impression,  transmitted  upwards  to  the 
brain,  and  consequently  are  either  sentient  actions  of  external 
sensations,  or  indirect  nerve-actions  of  the  external  impression; 
although,  in  the  latter  case,  nerve-actions  of  another  internal 
impression  (419,  422).  Supposing  the  trunk  of  a  motor  nerve 
is  irritated  by  a  needle,  its  medulla  receives  an  external  im- 
pression, which  is  transmitted  upwards,  and,  if  it  reaches  the 
brain,  excites  sentient  actions  by  means  of  an  external  sensa- 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  253 

tion ;  or  is  reflected  downw wards,  and  develops  indirect  nerve- 
actions  of  the  external  impression ;  or  else,  both  results  take 
place :  at  the  same  time,  however,  the  irritation  made  by  the 
needle  is  transmitted  downwards  to  the  terminating  fibrils  of 
the  nerve,  as  a  non-conceptional  internal  impression,  and  excites 
nerve-actions  in  the  parts  to  which  the  terminating  fibrils  are 
istributed. 

485.  An  internal  impression,  unconnected  with  conceptions, 
acts  downwards  from  the  point  where  the  impression  is  made 
along  the  twigs  and  branches  of  the  nerves,  and  if  there  be  no 
obstacle  to  its  course,  operates  in  those  mechanical  machines 
connected  with  the  fibrils.  It  may  also  (as  when  produced  by 
conceptions)  be  communicated  to  other  nerves  and  to  other 
mechanical  machines,  if  the  fibrils  be  interwoven  in  ganglia 
beneath  the  point  irritated  (124). 

486.  As  the  action  is  the  same  in  the  mechanical  machines, 
whether  the  internal  impression  be  produced  by  conceptions  or  by 
other  irritants,  so  also  is  its  transmission;  so  that,  just  as  internal 
impressions  from  conceptions  are  transmitted  along  the  trunks 
of  the  nerves  to  the  terminal  fibrils,  without  being  commingled 
with  each  other,  although  passing  along  the  same  trunk,  as,  for 
example,  the  spinal  cord,  or  principal  branch  of  a  nerve  (125), 
so  also  the  non-conceptional  internal  impressions  have  their 
independent  course,  and  are  not  confused  by  or  commingled  with 
each  other ;  whence  it  is  inferred,  that  every  internal  impression 
takes  place  in  a  special  fibril,  running  an  independent  course  to 
a  distinct  mechanical  machine,  as  has  been  previously  shown  (125). 
If  we  knew  which  particular  fibrils  were  excited  by  a  certain 
conception,  when  it  produced  a  certain  movement  of  a  mecha- 
nical machine,  as  a  sentient  action,  we  might  be  able  to  excite 
the  same  movement  as  a  nerve-action,  by  irritating  the  special 
fibrils,  and  thus  causing  an  internal  impression,  either  in  the 
spinal  cord  or  in  the  branches  given  off  from  it.  It  is  not 
possible,  however,  to  perform  this  experiment,  because  we  can- 
not distinguish  the  various  efferent  fibrils  on  which  a  special 
conception  acts;  and  because  the  irritation  of  a  single  efferent 
fibril  would  probably  require  much  more  delicate  instruments 
than  we  possess. 

487.   The  non-conceptional  internal  impressions  will  be  as 
little  interrupted  in  their  course  to  the  terminal  fibrils,  by  ex- 


254  ANIMAL  FORCES.  [ii. 

ternal  impressions  taking  the  opposite  direction,  as  the  concep- 
tional  internal  impressions  (126),  because  it  is  indifferent 
whether  the  stimulus  be  a  material  idea,  or  some  other  irritant 
in  the  brain,  or  on  the  course  of  the  nerve ;  and  because  the 
apparent  reason  of  this  phenomenon,  namely,  the  natural  dis- 
tinction between  the  afferent  and  efferent  nerve  fibrils  remains 
the  same  (126,  127).      Experiments  confirm  this  doctrine. 

488.  The  doctrine  laid  down  in  §  126,  as  to  the  existence 
of  two  kinds  of  fibrils  in  each  nerve, ^  the  one  transmitting  ex- 
ternal impressions  upwards,  and  the  other  internal  impressions 
downwards,  enables  us  to  explain  how  it  may  happen,  that  in 
a  natural  or  contranatural  condition  of  the  nerve,  certain  me- 
chanical machines  may  be  excited  into  action  by  the  one,  and 
not  by  the  other ;  although  it  may  be  excited  to  action  by  both 
kinds  of  impressions.  For  example,  the  terminal  nerve-fibrils, 
in  a  mechanical  machine,  may  not  be  duly  excited  by  certain 
external  excitants  (424),  or  a  natural  or  contranatural  impedi- 
ment may  take  place  in  the  fibrils  which  have  to  transmit  the 
external  impression  upwards  (425),  and,  consequently,  neither  a 
direct  nor  indirect  nerve-action  results  (427 — 431).  But,  if 
there  is  no  such  impediment  in  the  efferent  fibrils  of  the  same 
nerve,  a  nerve-action  may  take  place  in  the  mechanical  machine 
from  an  internal  impression  on  the  medulla  of  the  nerve,  and 
vice  versa.  Except  on  the  hypothesis  of  such  a  difference  in 
the  nerve-fibrils,  it  is  very  difficult  to  understand  phenomena 
of  this  kind.  That  such  phenomena  really  take  place  is  un- 
doubted ;  for  a  limb  which  has  become  insensible  to  all  external 
impressions,  and  never  once  manifests  nerve-actions,  as  in  the 
case  of  a  paralysed  limb,  which  neither  feels  nor  even  contracts 
when  scourged  with  nettles,  may  be  stimulated  to  contractions, 
independently  and  even  in  spite  of  the  will,  by  irritation  of  the 
trunk  of  its  nerve;  or  when  some  internal  agent  causes  a 
morbid  change  in  it ;  and  these  contractions  are  manifestly 
nerve-actions  of  a  non-conceptional  internal  impression.  Again, 
there  are  instances  in  which  the  limb  is  not  moved  either  by 
conceptional  internal  impressions,  or  other  internal  stimuli  of 
the  nerves,  although  it  is  sensible  of  external  impressions  on 
the    terminal    nerve-fibrils,    and    nerve-actions    are    produced 

'  See  note  to  §  126,  with  reference  to  this  point. — Ed. 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  255 

thereby.  This,  it  would  appear,  is  the  normal  condition  of 
the  heart ;  for  it  is  not  only  not  sensitive,  but  is  excited  to  the 
most  violent  movements  by  external  impressions  on  its  nerves 
(455,  456).  It  is  also  excited  to  movements  by  the  internal 
impressions  of  some  conceptions  (167,  211).  Nevertheless,  the 
will  exerts  no  influence  over  it;  and  the  internal  irritation  of  the 
trunks  of  its  nerves  never  causes,  so  far  as  has  been  observed, 
any  internal  impression  in  them,  and  develops  no  nerve-actions 
in  it;  on  the  contrary, the  hearths  action  remains  unchanged,  and, 
if  separated  from  the  body,  is  not  re-excited  thereby,  although 
this  readily  results  from  an  external  irritation.  {Vide  §  515, 
and  Haller^s  'Physiology,'  §  101.)  If  it  be  conceded  that, 
from  natural  impediments,  the  efferent  fibrils  of  the  cardiac 
nerves  transmit  only  few  kinds  of  internal  impressions,  and  are 
capable  only  of  certain  conceptions,  being  at  the  same  time 
incapable,  for  the  most  part  at  least,  if  not  wholly,  of  other 
kinds,  and  particularly  of  non- conception al  internal  impressions; 
whilst,  on  the  other  hand,  the  afferent  fibrils  are  readily  sus- 
ceptible of  an  infinite  number  of  external  impressions,  we  can 
thus  comprehend  the  phenomena,  without  having  recourse  to 
the  erroneous  doctrine  that  the  cardiac  movements  result  from 
an  animal  motive  force  innate  in  the  muscular  fibre,  and  inde- 
pendent of  the  nerves  (380 — 388). 

489.  The  ordinary  natural  stimuli  of  the  nerves  causing  in- 
ternal impressions,  are, — I,  the  conceptions  which  produce 
sentient  actions  (121,  123) ;  and,  2,  reflected  external  impres- 
sions (399),  which  excite  indirect  nerve-actions  of  external 
impressions,  and,  consequently,  nerve-actions  of  non-concep- 
tional  internal  impressions  (399,  421-2).  Both  can  effect  the 
same  movements  in  the  mechanical  machines,  or  one  only,  as 
well  as  both  (360,  364).  These  movements  may  be  nerve- 
actions,  excited  by  reflected  external  impressions  only,  and  be 
as  connected  and  adapted  as  if  they  were  sentient  actions  ex- 
cited by  conceptions  (438).  Nature  has  endowed  sentient 
animals  with  both  kinds  of  stimuli,  but  to  those  which  exhibit 
no  conceptive  faculty,  she  has  only  given  the  last  mentioned ; 
and  she  thereby  attains,  in  both,  the  same  end,  namely,  to 
impart  to  them  internal  impressions,  which,  together  with  the 
direct  vis  nervosa  of  the  external  impressions,  constitute  the 
proper  natural  incitants  of  the  animal  movements  of  the  me- 


256  ANIMAL  FORCES.  [ii. 

chanical  machines.  For  all  conceptions  are  primarily  produced 
by  external  sensations,  that  is,  by  means  of  external  impres- 
sions (65);  and  by  means  of  these  identical  impressions,  when 
reflected  ere  they  reach  the  brain,  can  those  movements  be 
excited,  as  simply  nerve- actions  of  non-conceptional  impressions, 
which  are  sentient  actions  of  conceptions;  or  they  may  act 
concurrently  with  conceptions  (421-2).  This  great  truth  will 
be  amply  established,  by  what  will  be  laid  down  in  this  and 
the  following  chapter,  as  to  the  vis  nervosa  of  non-conceptional 
internal  impressions. 

490.  Nevertheless,  there  are  other  irritants  that  act  as  non- 
conceptional  impressions.  When  the  medulla  of  a  nerve  is 
irritated,  as  by  pricking,  pinching,  cutting,  &c.,  the  same  move- 
ments take  place  in  the  mechanical  machines  to  which  the 
nerve  is  distributed,  as  if  a  conceptional  internal  impression  j 
had  produced  them;  or  as  if  they  were  the  indirect  nerve-action 
of  an  external  impression.  Thus,  a  decapitated  frog  retracts 
its  leg  when  its  spinal  cord  is  irritated,  just  as  it  did  when, 
during  life,  it  willed  to  make  a  spring,  and  as  also,  if  decapitated, 
when  its  toe  is  pinched  (359).  So  also  a  muscle  contracts,  when 
its  nerve  is  cut  through.  (Haller^s  '  Physiology,^  §§  403,  &c.) 
Suppose  that  instead  of  this  artificial  irritation,  some  materies 
so  irritates  a  nervous  trunk  in  the  direction  downwards  from 
the  brain,  that  the  muscles  which  the  nerve  regulates  are 
thereby  put  into  motion;  the  resulting  movements  are  then 
nerve-actions  of  a  non-conceptional  internal  impression,  which 
are  not  in  the  first  place  indirect  nerve-actions  of  an  external 
impression,  but  are  produced  by  2i  primary  internal  impression. 
Such  irritants,  while  exciting  movements  in  a  direction  down- 
wards from  the  brain,  may  be  also  felt ;  but  in  this  case 
sensation  contributes  nothing  to  the  movements  which  are  j 
excited  at  the  same  time  by  the  primary  internal  impression.     % 

491.  Observation  teaches,  that  this  class  of  nerve-actions 
occurs,  but  the  most  distinct  are  usually  contra-natural.  Various 
contractions,  spasms,  convulsions,  and  cramps  of  muscles  and  of 
limbs,  occur  in  disease,  without  being  induced  by  a  conception 
or  an  external  sensation,  or  even  by  an  external  impres- 
sion on  the  motor  nerves,  and  are  therefore  neither  sentient 
actions,  nor  indirect  nerve-actions  of  external  impressions, 
and  have  no  other  origin,  than  that  some  acrid  irritant  matter 


tf 


III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  257 


18  applied  to  the  trunk  of  the  nerves,  and  develops  in  them 
primary  internal  impressions,  which  cause  these  nerve-actions. 
Movements  of  this  kind  are  observed_,  for  the  most  part,  in 
persons  in  whom  the  whole  mass  of  humours  is  acrid,  so  that 
when  they  come  into  contact  with  the  medulla  of  the  nerves, 
they  stimulate  it.  Of  this  class  also  are  the  movements  which 
occur  if  the  trunk  of  a  nerve  be  ulcerated,  and  the  limbs  to 
which  it  is  distributed  are  moved  in  various  contra-natural 
ways ;  or  when  a  tumour,  a  foreign  body,  &c.,  irritates  the 
nervous  trunks,  and  thereby  excites  the  muscles  to  contra- 
natural  movements.  Examples  of  primary  non-conceptional 
impressions  will  be  given  subsequently,  (515,  525,  532,  &c.) 

492.  We  are  as  ignorant  what  peculiar  irritation  of  the  me- 
dulla in  the  nervous  trunks  must  be  excited,  to  produce  a  certain 
kind  of  internal  impression  and  thereby  certain  definite  nerve- 
actions,  as  we  are  with  reference  to  external  impressions  (413). 
Thus  much  is  known,  however,  that  it  is  not  every  irritation 
or  impression  on  the  trunk  of  a  nerve  that  is  effective 
[sinnlich]  ;  or,  in  other  words,  it  is  not  every  irritation, 
although  directed  from  the  brain  downwards,  that  causes  in 
the  nerve  itself  that  mysterious  movement  which  is  propagated 
downwards  in  the  nerve,  and  puts  the  mechanical  machines  to 
which  it  is  distributed  into  motion.  Every  irritation  which  is 
adapted  to  act  on  the  nerves  [or  is  sinnlich],  develops  animal 
actions  (121),  and  all  others  act  simply  as  physical  or  mechanical 
forces  (7) .  We  have  in  the  heart  an  example,  in  what  a  minor 
degree  many  nerves  receive  certain  internal  impressions  (488); 
it  is  also  known  that  nitric  acid  applied  to  a  nervous  trunk 
corrodes  the  medulla,  but  does  not  excite  the  muscle  to  which 
the  nerve  is  distributed,  although  irritation  of  the  same  nerve 
with  a  needle  will  throw  the  muscle  into  convulsions  (Haller, 
'  Opera  Minora,^  torn,  i,  p.  364).  The  action  of  impressions  can 
be  learnt  only  by  experiment  and  observation. 

493.  Just  as  a  conceptional  internal  impression  on  a  tied  or 
cut  nerve  does  not  pass  beyond  the  injured  point  (128),  so 
also  no  other  internal  impression  made  above  the  injured  point, 
nearer  the  brain,  passes  beyond  the  ligature  or  section,  to  excite 
nerve-actions  in  those  parts  only  which  are  supplied  with  twigs 
from  the  trunk  between  the  point  of  irritation  and  of  injury. 
But  if  an  internal  impression  be  made  on  the  nerve  below  the 

17 


258  ANIMAL  FORCES.  [ii 


< 


ligature  or  section,  it  is  transmitted  to  all  the  terminal  fibrils, 
and  nerve-actions  are  excited  in  all  the  organs  supplied  with 
twigs  given  off  from  the  trunk  below  the  point  of  injury,  provided 
there  be  no  impediment  to  the  course  of  the  impression  (359). 
These  are  principles  well  known  to  physiologists  (Haller^s 
'Physiology/  §§367,  403). 

494,  i.  Non-conceptional  internal  impressions  excite  nerve- 
actions  only,  when  duly  transmitted  from  the  point  of  irritation 
to  the  mechanical  machines  (493).  Consequently,  the  brain 
may  be  destroyed,  or  even  the  head  wholly  separated  from  the 
body,  and  yet  an  internal  impression  made  on  the  spinal  cord, 
or  the  trunk  of  a  nerve,  will  develop  nerve-actions  in  those 
mechanical  machines  which  receive  their  nerves  from  the  cord, 
or  from  the  nervous  trunk  from  below  the  point  of  irritation, 
provided  there  be  no  impediment  to  its  transmission  downwards 
(483) .  Thus,  a  frog,  although  headless,  will  leap  forward,  when 
its  spinal  cord  is  irritated  with  a  needle,  so  that  the  brain  and 
the  conceptive  force  are  as  little  necessary  to  the  nerve-actions 
of  internal  impressions  as  of  external,  with  the  condition,  how- 
ever, that  the  vital  spirits  be  present  in  the  nerves  as  stated 
in  §  416. 

ii.  Nevertheless,  there  are  cases  in  which  the  existence  of  the 
brain  and  its  uninterrupted  connection  with  the  limb  are  neces- 
sary to  the  nerve-actions  of  internal  impressions,  although  the 
cerebral  forces  and  the  mind  do  not  come  into  action.  In  the 
natural  condition  of  the  animal,  certain  functions  are  per- 
formed by  both  kinds  of  vis  nervosa  acting  at  the  same  time,  so 
that  ordinarily  they  are  both  direct  nerve- actions  of  external 
impressions  and  nerve-actions  of  non-conceptional  internal 
impressions.  The  heart,  diaphragm,  and  muscular  system 
generally,  will  be  subsequently  referred  to,  as  exhibiting  ex- 
amples (575,  524,  514).  In  instances  of  this  kind,  a  shock 
may  easily  injure,  enfeeble,  or  interrupt  the  functions  so  com- 
pounded, by  causing  one  of  the  two  kinds  of  vis  nervosa  to  cease 
to  operate ;  although  the  other  is  able  of  itself  to  restore  the 
disturbed  functions,  when  after  this  interruption  its  influence 
on  the  mechanical  machines  be  renewed.  Consequently,  if 
the  trunk  of  a  nerve  distributed  to  a  mechanical  machine,  the 
natural  function  of  which  is  at  the  same  time  both  a  direct 
nerve-action  of  an  internal  impression  and  a  nerve-action  of  an 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  259 

internal  impression,  be  tied  or  divided,  the  function  may  cease 
or  be  interrupted,  because  the  co-operation  of  the  internal  im- 
pression ceases ;  although  the  same  function  can  be  renewed,  if 
an  external  impression  be  made,  or  a  new  internal  impression 
be  communicated  to  the  nerve  below  the  ligature  or  section. 
If,  however,  the  usual  non-conceptional  impression  stimulus  be 
applied  to  the  nerve  near  its  cerebral  origin,  whether  directly, 
or  whether  as  an  external  impression  reflected  and  changed 
there  into  a  non-conceptional  impression,  then  the  presence 
of  the  brain  and  its  unbroken  connection  with  the  nerves  of 
the  machines  are  requisite  to  the  continuance  of  the  natural 
functions  of  the  latter;  although  they  may  be  renewed  by  a 
renewed  impression,  or  by  the  renewal  of  one  or  of  both  im- 
pressions. Thus,  a  muscle  is  enfeebled,  or  the  natural  move- 
ments of  the  heart,  diaphragm,  &c.,  interrupted,  so  soon  as  the 
connection  of  their  nerves  with  the  brain  is  broken ;  yet  their 
functions  can  be  renewed  so  soon  as  one  of  the  two  kinds  of  vis 
nervosa  communicates  a  new  impulse,  and  the  heart  receives  an 
external  impression  below  the  ligature,  or  the  diaphragm  an 
internal  impression,  or  the  muscle  either  or  both. 

iii.  Nevertheless,  the  brain  and  the  conceptive  force  are 
necessary  to  these  movements  of  the  non-conceptional  internal 
impression,  when,  to  continue  in  their  natural  order,  they  must 
be  at  the  same  time  sentient  actions ;  for  the  removal  of  the 
brain  interrupts  this  natural  order,  although  it  does  not  abolish 
it  irreparably. 

iv.  That  the  brain  is  necessary  to  the  prolonged  continuance 
of  the  nerve-actions  of  non-conceptional  internal  impressions, 
in  so  far  as  its  medullary  substance  supplies  vital  spirits  to  the 
nerves,  has  been  already  stated ;  it  is  also  necessary  in  those 
cases,  in  which  the  nerve-action  depends  on  an  internal  im- 
pression made  near  to  or  at  the  cerebral  origin  of  the  nerve, 
but  not  by  conceptions.     But  it  is  manifest,  that  in  none  of 

i these  cases,  the  action  of  the  cerebral  forces  or  of  the  conceptive 
force  is  necessary  to  nerve-actions,  and  that  even  in  the  in- 
stances mentioned  in  par.  iii,  neither  contributes  to  the  sole 
production  of  the  movements  as  nerve-actions. 
495.  When  an  internal  impression  is  not  a  primary,  but  a 
reflected  external  impression,  it  causes  nerve-actions,  as  if  it 
■■■——-— 


260 


ANIMAL  FORCES. 


[II. 


the  brain  and  the  conceptive  force.  When  a  decapitated  frog 
leaps  from  pinching  of  its  toe,  the  action  is  a  nerve-action  of 
an  internal  impression  derived  from  a  reflected  external  im- 
pression .(419j  415,  ii).  The  external  impression  in  this  case 
can  pass  uninterruptedly  from  the  point  of  irritation  in  the  toe 
to  the  point  of  injury  in  the  spinal  cord,  where  it  is  reflected, 
and  passes  uninterruptedly  back  again,  and  thus  the  same 
nerve-action  is  caused  by  it,  as  if  a  primary  internal  impression 
had  excited  the  spinal  cord  (494). 

496.  A  non-conceptional  internal  impression  can  excite  nerve- 
actions  under  the  following  conditions  only  : 

i.  The  medulla  of  the  trunk  of  the  nerve  must  receive  an 
internal  impression  in  one  direction  downwards  from  the  brain, 
independently  of  any  conception  (121,  4SS). 

ii.  This  internal  impression  must  be  transmitted  downwards, 
along  the  trunk  and  its  branches  through  the  efferent  fibrils,  to 
the  mechanical  machines  which  have  to  perform  the  nerve-action. 

iii.  The  mechanical  machines  must  be  capable  of  performing 
that  nerve-action,  which  the  received  internal  impression  can 
effect  in  virtue  of  its  nature ;  just  as  is  necessary  in  sentient 
actions  excited  by  conceptional  internal  impressions  (130,  ii, 
129,  iv). 

The  conditions  under  which  those  nerve-actions  of  internal 
impressions  take  place,  that  are  caused  by  a  reflected  external 
impression,  have  been  already  stated  (419,  422). 

497.  The  nerve-actions  of  non-conceptional  internal  impres- 
sions are  quite  independent  of  the  brain  and  the  conceptive 
force ;  nevertheless,  at  another  time,  or  in  other  animals,  they 
may  be  sentient  actions  of  impressions  caused  by  conceptions 
(364,  i);  and  this  applies  especially  to  indirect  nerve-actions  of 
external  impressions  (423).  Thus,  the  volitional  movement  of 
a  limb  (a  sentient  action)  may  occur  as  the  nerve-action  of  a 
primary  internal  impression,  when  an  acrid  humour  irritates  the 
trunk  of  the  nerve  going  to  the  limb ;  and  although  this  acrid 
humour,  as  in  gouty  diseases,  may  cause  pain,  yet  this  external 
sensation  of  pain  is  not  the  motor  force  of  the  limb,  but  the 
concurrent  internal  impression  (484).  See  a  previous  paragraph 
for  examples  of  this  class  (423) . 

498.  A  nerve-action  of  a  primary  internal  impression  cannot 
take  place,  or  will  be  prevented : 


I 


CH.  HI.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  261 


i.  If  an  irritation,  although  applied  to  the  medulla  of  a  nerve 

the  direction  downwards  from  the  brain,  excites  no  internal 
impression  therein.  Thus,  in  disease,  there  are  often  traces  of 
putrid  humours  collected  about  the  points  where  the  trunks  of 
nerves  occur,  without  any  motions  resulting  in  the  muscles; 
either  because  the  putrid  fluids  do  not  penetrate  to  the  medulla 
of  the  nerve,  but  remain  externally  to  it,  or  else  because  they 
are  of  a  kind  which  excites  no  internal  impression  in  it  (492) . 

ii.  If  the  transmission  of  a  primary  internal  impression  is 
prevented  by  some  impediment,  so  that  it  cannot  reach  the 
mechanical  machines  which  it  regulates  (496,  ii).  Thus,  an 
acrid  humour  in  the  axilla  may  irritate  the  nerves,  which  regulate 
the  forearm  and  hand,  and  so  excite  convulsive  movements 
therein.  But  if  there  be  a  tumour  at  the  elbow-joint  com- 
pressing the  nerves,  or  if  some  external  pressure  be  made  on 
them  (as  when  a  limb  goes  to  sleep),  then  the  transmission  of 
the  primary  internal  impression  from  above  downwards  is 
prevented,  and  no  nerve-actions  take  place. 

iii.  If  the  mechanical  machines  are  rendered  incapable  of 
the  requisite  nerve-action.  Thus,  when  an  acrid  humour  irri- 
tates the  nerves,  a  bandaging  of  the  muscles  of  the  convulsed 
limb,  will  prevent  their  action,  and  so  the  patient  may  obtain 
sleep  and  rest.  (Compare  also  §  425.) 

499.  There  must  be  natural  obstacles  to  the  development  of 
the  nerve-actions  of  non-conceptional  internal  impressions,  as 
well  as  of  sentient  actions  (136 — 138).  Those  already  enume- 
rated as  preventing  the  indirect  nerve-actions  of  external  im- 
pressions, act  also  in  preventing  the  nerve-actions  of  primary 
internal  impressions  (428,  vi;  429).  The  following  is  a  short 
statement  of  some  others. 

500.  A  natural  impediment  to  the  production  of  certain 
nerve-actions  from  primary  internal  impressions,  occurs — 

i.  When  a  nerve,  by  nature,  is  but  slightly  or  not  at  all 
susceptible  of  certain  primary  natural  stimuli  (492,  498,  i) ; 
consequently,  if  it  do  receive  an  impression,  the  latter  is  too 
weak  to  be  propagated  to  the  mechanical  machines.  It  is  quite 
certain  that  there  are  stimuli,  which,  when  applied  to  the 
medulla  of  the  nerve  in  its  normal  condition,  do  not  excite 
nerve-actions.  The  nerves  are  in  close  relation  with  many 
tissues,  and  their  medulla  is  penetrated  by  capillaries  and  fluids. 


262  ANIMAL  FORCES.  [ii. 

all  which  must  often  necessarily  act  as  active  stimuli,  but  they 
seem  to  act  as  such,  for  the  most  part,  extraordinarily  and 
abnormally  only,  otherwise  they  would  incessantly  stimulate 
our  limbs  to  movements. 

ii.  When  certain  internal  impressions  on  the  nerves  are  not 
naturally  transmitted  to  certain  mechanical  machines  (498,  ii). 
This  hindrance  is  principally  constituted  by  the  ganglia  and  points 
of  division  of  the  nerves  (137,  429),  which  sometimes  so  receive 
internal  impressions  of  a  certain  kind,  that  they  go  forwards ; 
but  also,  sometimes,  so  that  the  nerves  are  not  excited  inter- 
nally by  them,  and  consequently  the  impressions  have  no  in- 
fluence on  the  mechanical  machines  innervated  by  the  nerves. 

iii.  When  the  mechanical  machines  are  as  yet  naturally 
incapacitated  for  the  animal  movement  which  a  certain  internal 
impression  can  communicate  to  it,  or  becomes  so  incapacitated. 
This  impediment  is  observed  in  young  animals,  or  in  the  very 
old,  which  are  excited  to  certain  movements  simply  by  their 
blind  instincts,  in  virtue  of  the  vis  nervosa  (439) . 

501 .  Habit,  and  the  frequent  repetition  of  internal  impres- 
sions, can  act  as  impediments  to  this  class  of  nerve-actions,  in 
the  way  already  laid  down  (430,  431). 

502.  Since  the  nerve-actions  of  non-conceptional  impressions 
are,  for  the  most  part,  indirect  nerve-actions  of  external  im- 
pressions (which  determine  the  sensibility  of  animals),  the 
vis  nervosa  of  internal  impressions  has  also  its  influence  in 
determining  the  irritability  and  vital  constitution  of  animal 
bodies. 


SECTION     II. ON    THE    VIS    NERVOSA    OF    INTERNAL    IMPRESSIONS 

IN    PARTICULAR. 

503.  Nerve-actions  of  internal  impressions,  whether  the  latter 
be  primary  internal  impressions,  or  reflected  external  impres- 
sions changed  into  internal,  can  be  developed  in  all  the  organs 
that  are  capable  of  sentient  actions ;  for  the  whole  diff'erence 
of  the  two  consists  in  this, — that  in  the  development  of  the 
latter,  the  nerves  are  excited  by  conceptions,  and  solely  at  their 
origin  in  the  brain ;  of  the  former,  by  other  stimuli  applied  to 
the  whole  nervous  system,  except  the  terminal  fibrils  (121,  483). 
Both  kinds  of  stimuli  consist  in  the  same  changes  in  the  nervous 


CH.  111.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  263 

system  [the  animal  machines]  ;  both  kinds  of  impressions  are 
transmitted  in  the  same  way  through  the  nerves,  and  move  the 
mechanical  machines  with  which  they  are  incorporated  (360). 
We  have  now  to  show,  by  facts,  in  what  structures  this  class  of 

trve-actions  are  produced  in  the  normal  condition. 
504.  Conceptions  act  on  the  brain  and  nerves,  so  as  either 
put  mechanical  machines  into  motion  or  not  (117).  In  the 
latter  case,  they  are  manifested  specially  in  the  brain "  and 
sensitive  nerves.  It  is  already  established  by  experiment,  so 
far  as  the  difl&culty  of  investigating  this  profound  subject  will 
allow,  that  there  are  also  other  stimuli  than  conceptions,  which 
excite  nerve-actions  in  and  limited  to  the  brain  itself,  by  means 
of  their  internal  impressions  (374).  It  has  also  been  shown 
(377,  378),  that  internal  impressions  not  caused  by  conceptions, 
excite  in  the  purely  sensitive  nerves,  as  nerve-actions,  the  same 
changes  which  the  internal  impressions  of  conceptions  produce, 
as  sentient-actions,  inasmuch  as  both  induce  imperfect  external 
sensations  (148,  377).  Hence  it  follows,  that  the  internal  im- 
pressions not  caused  by  conceptions,  are  subject  to  the  same 
law  of  deflexion,  and  excite  the  same  changes  in  the  nerves,  as 
the  internal  impressions  derived  from  conceptions  {vide  §  151). 
The  question  is,  however,  so  recondite,  that  it  is  difficult  to 
institute  experiments  in  regard  to  it. 

505.  Conceptions  act  on  the  mechanical  machines  (155) 
either  directly  through  the  brain,  or  through  the  nerves.  Now, 
as  non-conceptional  internal  impressions  develop  changes  in  the 
brain,  they  can  also  thereby  put  mechanical  machines  into 
motion.  It  is  properly,  however,  the  vessels,  and  especially  the 
blood-vessels,  that  experience  this  change  (156 — 159),  enabling 
them  to  alter  the  cerebral  circulation  and  the  vital  movements 
generally.  It  is  not,  however,  possible  to  show  clearly,  that 
non-conceptional  internal  impressions  cause  the  same  changes 
in  the  cerebral  capillaries,  since  it  is  impossible  to  determine 
whether  a  certain  stimulus  of  the  brain  acts  through  the  nerve- 
fibrils  in  the  brain,  according  to  §  132;  or  directly  on  the 
membranes  and  mouths  of  the  capillaries  of  the  brain,  accord- 
ing to  §  392 ;  or  whether  in  either  of  these  two  cases  it  acts 
as  an  external  impression  by  means  of  direct  or  indirect  (418, 
419)  nerve-actions,  or  through  the  sentient  action  of  an  external 
sensation  (132) ;  or  (much  more  probably)  as  a  primary  internal 


264  ANIMAL  FORCES.  [ii. 

impression  not  induced  by  conceptions  (490).  The  obscurity  in 
wbich  these  changes  in  the  brain  are  involved,  is  an  apology 
for  the  want  of  experiments.    (Compare  §  159.) 

506.  Except  in  the  example  stated,  §  504,  non-conceptional 
internal  impressions  act  on  the  mechanical  machines,  only  so  { 
far  as  the  latter  have  nerves  incorporated  with  them.     Their 
nerve-actions,  as  well  as  the  sentient  actions  of  the  conceptional 
impressions,  are  effected  through  the  nerves  (160). 

507.  The  laws  of  action  on  the  muscular  system  of  the  im- 
pressions derived  from  conceptions,  are  applicable  to  the  in- 
ternal impressions  not  derived  from  conceptions,  whether  they 
be  primary  or  reflected  in  their  origin  (161,  162,  204).  The 
primary  are  illustrated  §  498 ;  those  from  a  reflected  external 
impression  §§  415,  495. 

508.  Since  non-conceptional  impressions  act  on  the  muscular 
system,  they  must  also  excite  movements  of  the  limbs.  Examples 
of  this  kind  are  seen,  when  a  decapitated  man,  either  from  the 
primary  internal  impression  of  the  sword- stroke  in  his  spinal 
cord,  or  from  the  reflected  external  impression  of  the  injury, 
makes  those  movements,  which  a  conception  of  danger,  or  an 
external  sensation  of  the  injury,  would  have  led  him  to  make ; 
or  when  an  animal,  decapitated  while  moving,  still  goes  on,  and 
continues  its  former  sentient  actions  in  the  muscles  of  locomo- 
tion, as  nerve-actions,  &c. 

509.  A  nerve-action  in  a  muscle  from  an  internal  impres- 
sion implies  the  transmission  of  the  impression  along  the  nerve, 
in  the  direction  from  the  brain  downwards  to  the  muscle  which 
is  excited  to  movement.  If  the  movement  be  the  indirect 
nerve-action  of  an  external  impression,  it  implies  that  an  ex- 
ternal impression,  is  reflected  in  its  course  upwards  to  the  brain, 
and  transmitted  from  the  point  of  reflexion  downwards,  as  an 
internal  impression,  to  the  muscle  excited  to  movement  (422, 
496). 

510.  The  same  nerve  of  a  muscle  may  receive  external  im- 
pressions, at  the  same  time  that  internal  impressions  on  it 
excite  muscular  action,  and  this  external  impression  may  be 
either  felt,  or  develop  nerve-actions,  without  the  two  antago- 
nistic impressions  impeding  each  other^s  action  (487). 

511.  When  a  nerve  is  tied,  divided,  or  compressed,  an  in- 
ternal impression  (whether  primary  or  reflected  in  its  origin)  if 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  265 

applied  above  the  point  of  injury,  cannot  excite  a  nerve-action 
in  the  machines  to  which  the  nerve  is  distributed.  Nevertheless, 
the  brain  and  conceptive  force  are  not  necessary  to  nerve-actions, 
although  in  many  cases  nerve-actions  cannot  take  place  without 
the  brain;  not,  however,  because  the  cerebral  forces  or  the 
conceptive  force  are  requisite,  but  because  it  contains  the 
origins  of  the  nerves,  and  without  it  non-conceptional  impres- 
sions cannot  be  applied  to  that  portion  of  the  nerves.  If  the 
brain  be  excited  by  some  general  stimulus,  in  which  the  roots 
of  all  or  the  greater  number  of  the  motor  nerves  participate,  its 
influence  must  be  extended  to  the  greater  part  or  the  whole  of 
the  muscular  system,  as  occurs  with  internal  impressions  caused 
by  conceptions  (164,  v).  The  same  doctrine  applies  to  the 
spinal  cord.  Consequently,  in  experiments  made  on  animals 
when  the  brain  and  spinal  cord  are  irritated  mechanically,  some- 
times partial,  sometimes  general  convulsions  are  excited  (359). 

512.  The  nerve-actions  from  the  two  kinds  of  internal  im- 
pressions are  liable  to  the  impediments  that  have  been  already 
indicated  (428 — 431,  &c.),  and  hence  it  is  not  every  internal 
impression  which  can  excite  nerve-actions  in  the  muscles  (50Q). 

513.  Unfelt  external  impressions  in  the  muscles  can  be 
reflected  in  the  muscles  themselves,  and  then  cause  nerve- 
actions  in  them  by  means  of  internal  impressions  (447);  so 
that  various  movements  of  the  limbs  and  the  viscera,  which 
appear  to  be  nerve-actions  of  external  impressions  only,  are  at 
the  same  time  nerve-actions  of  an  internal  impression  induced 
by  external  impressions  (448,  423).  The  excited  motion  of  the 
heart  and  intestinal  canal  may  be  taken  as  examples  (446). 

514.  A  direct  nerve-action  of  an  external  impression  may 
at  the  same  time,  or  at  another  time,  or  in  another  animal,  be 
indirect,  or  the  nerve-action  of  internal  impressions,  or  a  sen- 
tient action  of  external  sensations,  or  of  other  conceptions,  nay, 
may  even  be  volitional;  and  vice  versa.  Consequently,  those 
go  too  far  who  maintain  that  the  irritability  of  muscles  is  their 
only  or  principal  motor  force.  It  would  rather  appear,  that 
although  the  greater  number  of  muscular  actions  can  be  directly 
excited  by  external  impressions,  in  the  natural  condition  of 
animals  endowed  with  a  brain  and  conceptive  force,  yet 
internal  impressions,  whether  primary  or  originating  in  a  re- 
flected external  impression,  may  co-operate  therewith ;  so  that  the 


266  ANIMAL  FORCES.  [u. 

muscular  movements  may  be  either  sentient  or  nerve-actions 
only,  or  both  at  once.  It  is  this  common  action  of  the  two 
kinds  of  vis  nervosa  in  the  muscular  movements  of  animals 
which  renders  the  presence  of  the  brain  and  its  uninterrupted 
connection  with  the  muscles,  necessary  to  the  development  of 
many  nerve-actions ;  the  co-operation  of  the  cerebral  forces  or 
of  the  conceptive  force  being  unnecessary  (494,  ii).  Haller 
referring  to  the  instinctive  acts  of  animals,  observes  that  the 
causes  of  muscular  action  in  these  instances  depend  on  a  law 
given  by  God,  and  not  on  the  mind  (^Physiology,'  §  408). 

515.  External  sensations  and  other  conceptions  in  many 
ways  change  the  action  of  the  heart  by  means  of  their  internal 
impressions  (167,  211) — that  action  being  for  the  most  part  an 
indirect  nerve-action  of  external  impressions  on  the  heart  (457, 
459).  Can  internal  impressions  not  caused  by  conceptions  also 
exercise  a  motor  power  over  it  ?  It  is  a  priori  probable,  for 
the  heart  is  a  muscle.  It  is  much  more  probable,  however, 
from  another  consideration  deduced  from  experiment,  namely, 
that  when  in  animals  endowed  with  brain  the  cardiac  nerves 
are  tied,  the  movements  of  the  heart  cease,  even  although  all 
the  nerves  are  not  tied  at  the  same  time  (Haller's  '  Physiology,' 
§  100).  Consequently,  although  the  natural  movements  of  the 
heart  be  a  direct  nerve-action  excited  by  external  impressions,  yet 
it  must  be  maintained  by  a  co-operating  internal  impression,  and 
this  must  depend  either  on  conceptions  or  other  stimuli.  Now, 
although  the  ordinary  natural  stimuli  of  the  heart's  action  be 
unfelt,  they  are  not  the  less  sentient  actions  of  other  conceptions 
(457 — 459).  Perhaps  the  natural  motion  of  the  brain,  which 
synchronises  with  the  respiratory  movements,  may  be  enume- 
rated amongst  these,  although  that  motion  is  itself  dependent 
on  the  heart's  action,  and  acts  by  communicating  non-concep- 
tional  internal  impressions  to  the  cerebral  origins  of  the  cardiac 
nerves ;  yet,  on  the  other  hand,  the  heart  beats  in  the  foetus 
in  utero,  or  in  the  embryo  in  ovo,  and  also  in  animals  which 
have  no  respiratory  movements.  Or  the  heart's  action  may  be 
influenced  by  primary  internal  impressions,  communicated  to 
the  cardiac  nerves  by  the  arteries  of  the  brain  (505).  In  this 
way  we  may  understand  why  the  connection  of  the  brain  with 
the  heart,  is  necessary  to  the  movements  of  the  latter,  without 
the  cerebral  forces  being  requisite.     But  reflected  external  im- 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  267 

pressions  may  constitute  this  co-operating  force  in  the  action  of 
the  heart ;  the  external  impressions  being  reflected  downwards 
in  the  ganglia  on  their  way  to  the  brain^  or  changed  into  internal 
impressions  in  the  spinal  cord,  and  so  acting  reflexly  in  the 
heart ;  for  it  is  quite  certain  that  external  impressions  made  on 
the  cardiac  nerves  are  transmitted  upwards  to  the  brain,  be- 
cause they  are  sometimes  felt  (35).  The  object  of  nature  in 
thus  providing  that  internal  impressions  shall  co-operate  in  the 
natural  movement  of  the  heart,  although  external  impressions 
alone  may  fully  efi'ect  it  (457),  seems  to  be  simply  this,  that 
the  continuance  of  an  action  so  important  to  life  may  be  the 
more  certainly  maintained,  and  in  the  less  danger  of  being 
interrupted  than  it  would  otherwise  be,  if  wholly  dependent 
upon  the  usual  external  impression,  namely,  the  stimulus  of  the 
inflowing  blood  on  the  heart.  When  this  ceases  momentarily, 
or  acts  only  feebly,  as  in  syncope,  still  the  heart  is  not  left 
without  a  stimulus  to  its  continued  action.  Observation  seems 
to  corroborate  this  opinion,  for  the  enfeebled  or  interrupted 
stroke  may  be  restored  or  invigorated  in  a  moment  by  the  ex- 
ternal impression  of  irritating  vapours  on  the  nerves  of  the 
nose,  and  which  are  reflected  upon  the  cerebral  origin  of  the 
cardiac  nerves.  It  is  not  probable,  that  any  other  end  is 
gained  from  this  co-operation  of  internal  impressions,  for  they 
only  strengthen  the  motion  of  the  heart,  and  if  it  be  interrupted, 
a  slight  irritant  re-excites  it,  as  has  been  shown  by  experiments, 
when  by  means  of  an  irritation  (a  non-conceptional  internal 
impression)  applied  to  the  eighth  pair,  to  the  brain,  or  to  the 
spinal  cord,  the  stroke  of  the  heart  has  been  rendered  stronger 
(Haller's  '  Physiology,^  §  100),  although  by  no  means  able  to 
maintain  it  continuously.  Farther,  although  the  ligature  or 
section  of  the  cardiac  nerves  enfeebles  the  heart's  action,  it 
never  quite  abolishes  it  (Haller,  loco  citato) ;  whilst  a  slight  ex- 
ternal impression  (its  principal  excitant)  will  re-excite  the 
movement. 

516.  Without,  however,  entering  further  into  this  obscure 
part  of  the  subject,  we  conclude  that  the  heart  is  susceptible 
of  nerve-actions  from  non-conceptional  internal  impressions, 
although  the  principal  motive  force  consists  in  unfelt  external 
impressions  (459).  Additional  proofs  will  be  found  in  §  519. 
Further  researches  are  much  to  be  desired,  for  the  properties 


268  ANIMAL  FORCES.  [ii. 

of  the  cardiac  nerves  are  peculiar,  and  the  action  of  impressions  on 
the  heart  differs  from  that  on  other  muscles.  The  number  of  the 
cardiac  nerves,  their  origin  from  such  different  points,  their  in- 
tricate combination,  and  their  ganglia  and  remarkable  plexus 
all  merit  the  closest  attention.  Probably,  the  results  of  external 
impressions  would  be  very  different,  according  as  the  nerves 
were  irritated,  or  tied,  or  divided,  above  or  below  the  ganglia 
and  plexuses  and  points  of  division  into  branches ;  and  that  the 
different  results  observed  when  the  cardiac  nerves  are  imtated 
— the  hearths  action  being  sometimes  increased,  sometimes  un- 
altered— may  be  dependent  upon  some  such  difference  in  the 
mode  of  experimenting  (Haller^s  'Physiology,^  loco  citato). 

517.  Since  the  heart  is  compounded  of  several  muscles,  and 
since  these  can  be  excited  to  action  independently  of  each 
other,  as  has  been  shown  in  excised  hearts,  it  is  more  probable, 
that  the  stroke  of  the  heart,  or  the  combined  action  of  all  the 
muscular  structures,  is  an  indirect  nerve-action  of  external  im- 
pressions, they  being  reflected  in  the  heart  itself  (513),  than 
that  it  is  simply  a  mechanical  result  of  their  direct  nerve- 
actions  (447);  for  in  the  latter  case,  the  whole  heart  must  be 
excited  to  action  by  an  external  impression  which  acts  only  on 
certain  of  its  fibres — a  conclusion  opposed  to  the  results  of  ex- 
periments (Haller's  'Physiology,'  §  101). 

518.  Although  the  preceding  propositions  are  well  founded, 
still  many  a  change  in  the  heart's  action  is  either  a  sentient  ac- 
tion, or  at  the  same  time  both  a  sentient  and  a  nerve-action;  and 
consequently,  it  is  erroneous  to  infer,  because  the  heart's  action 
is  usually  a  direct  nerve-action  of  external  impressions,  or  in 
other  words,  a  result  of  irritability,  that  it  is  always  such,'  or 
such  only,  or  such  in  all  animals.  Lastly,  in  so  far  as  the 
circulation  is  dependent  on  the  heart,  each  kind  of  impression 
contributes  something  thereto,  so  that  the  whole  of  the  circula- 
tion derives  some  stimulus  to  its  continuance  and  maintenance 
from  every  kind  of  animal  motor  force,  although  the  customary 
and  principal  stimuli  consist  in  unfelt  external  impressions  (459). 

519.  The  arterial  pulse,  in  so  far  as  it  is  dependent  on  the 
heart's  action  and  the  circulation,  may  be  a  nerve-action  of 
every  kind  (518).  Many  of  the  stimuli  used  in  cases  of 
suspended  animation  to  restore  life  by  re-exciting  the  action  of 
the  heart,  the  circulation,  and  the  pulse,  act  as  non-concep- 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  269 

tioiial  internal  impressions ;  although  it  may  be  easily  conceived 
that  these  re-excited  movements  are  simply  direct  nerve-actions 
of  external  impressions  on  the  heart,  arising  from  inflation  of 
the  lungs,  and  from  the  various  stimuli  applied  to  the  throat, 
stomach,  intestinal  canal,  &c.  But  as  these  stimuli  are  applied 
to  the  nerves  adjacent  to  the  heart,  and  which  have  a  much 
less  degree  of  irritability  than  the  cardiac  nerves,  they  must  be 
applied  strongly  and  for  a  lengthened  period,  before  the  external 
impressions  they  receive  are  transmitted  upwards  to  the  points 
of  reflexion,  and  hence  sent  downwards ;  and  when  the  result 
follows,  the  heart  makes  only  a  few  strokes  and  then  stops,  so 
that  the  stimuli  must  be  renewed  continually  to  keep  up  its 
action.  But  if  the  heart  be  excited  by  stimuli  applied  directly 
to  its  nerves,  all  this  takes  place  more  readily  and  actively. 

520.  The  changes  in  the  pulse,  resulting  from  the  action  of 
the  muscular  fibres  and  nerves  of  the  arteries,  independently  of 
the  heart,  are  direct  nerve-actions  from  external  impressions 
derived  from  the  blood,  as  in  the  case  of  the  heart  (460) .  Why 
should  not  these  impressions  on  the  muscular  fibrils  be  pro- 
pagated to  the  nerves,  and,  although  not  felt,  nevertheless,  at 
least  in  some  cases,  be  reflected  so  as  to  change  the  circulation 
by  means  of  indirect  nerve-actions  ?  The  possibility  of  this  is 
hardly  doubtful,  yet  it  is  as  difficult  to  demonstrate  by  experi- 
ments, since  the  phenomena  of  direct  nerve-actions  from  ex- 
ternal impressions  on  the  blood-vessels  are  scarcely  perceptible 
(460).  As  conceptional  internal  impressions,  and  particularly 
those  of  external  sensations  (147,  151),  excite  changes  in  the 
pulse  and  circulation,  the  same  may  result  from  primary  in- 
ternal  impressions,  or  from  external  impressions  reflected  be- 
fore they  are  felt  (360,  503). 

521.  Lastly,  in  so  far  as  muscular  action  changes  the  pulse, 
all  those  non-con ceptional  internal  impressions  which  excite 
muscular  action  will  influence  the  pulse.  Every  effort,  or  bodily 
movement,  whether  convulsive  or  volitional,  accelerates  the 
circulation,  and  often  the  causes  of  the  movements  are  neither 
felt  nor  perceived. 

522.  The  mouths  of  the  capillaries  are  as  subject  to  changes 
from  non-conceptional  internal  impressions,  as  from  external 
impressions,  whether  felt  (207),  or  uufelt  (462).  The  action  of 
certain  remedies  on  the  capillaries  proves  this :  as  Avhen  certain 


270  ANIMAL  FORCES.  [ii. 

haemorrhages  are  cured  by  external  applications.  Sleeping  with 
a  pillow  of  oak-chips  beneath  the  loins,  or  having  a  decoction 
of  gall-nuts  applied  to  the  abdomen,  cures  a  haemorrhage  from 
the  hsemorrhoidal  veins ;  cold  water  to  the  forehead  or  nape  of 
the  neck,  cures  a  bleeding  from  the  nose ;  a  blister  applied 
externally,  relieves  inflammation  of  the  subjacent  parts,  &c. 
The  external  impressions  made  by  such  remedies  on  the  nerv^es 
they  are  brought  into  immediate  contact  with,  are  in  many 
cases  transmitted  upwards,  since  they  are  felt;  but  in  other 
cases  in  which  they  excite  no  external  sensation  they  must 
be  reflected  downwards  on  the  nerves  distributed  to  the  capil- 
laries, and  excite  contraction  of  their  bleeding  mouths. 

523.  That  the  diaphragm  may  be  excited  to  action  by  non-con- 
ceptional  internal  impressions  made  on  its  nerves, has  been  proved 
by  experiments.  (Haller,  ^  Opera  Minora,'  tom.  i,  pp.  365, 199.) 
Further,  the  irritants,  which  when  applied  to  the  nose,  excite 
sneezing — a  convulsive  action  of  the  diaphragm — as  the  sen- 
tient action  of  an  external  sensation  (208),  contribute  much  to 
the  restoration  of  life  in  cases  of  suspended  animation;  and 
since  they  are  not  felt  for  some  time  after  the  action  of  the 
heart  and  lungs  is  re-excited,  it  follows  that  they  act  in  virtue 
of  a  reflexion  of  their  external  impressions  on  the  trunk  of  the 
phrenic  nerve,  and  thus  excite  the  movements  of  this  muscle  as 
their  indirect  nerve-action.  Consequently,  we  can  infer  that 
the  same  movements  will  result  from  non-conceptional  internal 
impressions. 

524.  The  ordinary  and  natural  movement  of  the  diaphragm, 
does  not  arise  from  external  stimuli  that  are  felt,  although  it  is 
very  much  influenced  by  such  (208) ;  nor  is  it  ordinarily  a  sen- 
tient action  from  external  sensations ;  and  inasmuch  as  it  takes 
place  without  our  consciousness,  and  even  without  any  know- 
ledge on  our  part  of  its  existence,  it  is  not  a  sentient  action 
from  other  conceptions,  although  these  can  change  it  volition- 
ally  (171).  Consequently,  the  usual  stimulus  to  the  continued 
natural  movement  of  the  diaphragm,  acts  by  means  of  non-con- 
ceptional impressions,  and  it  is  either  a  direct  nerve- action  of 
the  latter,  or  of  external  impressions  (356)  :  if  from  the  non- 
conceptional,  it  may  be  either  from  primary  internal  im- 
pressions or  reflected  external  impressions  (419,  483).  Granted 
that  it  arises  from  external  impressions,  still  as  in  the  instance 


cH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  271 

of  the  heart's  movement,  the  co-operation  of  an  internal  im- 
pression is  necessary  to  its  maintenance,  and  probably  with  the 
same  object  (515),  for  so  soon  as  the  phrenic  nerve  is  tied,  the 
movement  of  the  diaphragm  is  interrupted  (171). 

525.  Although  the  motion  of  the  diaphragm  is  influenced 
by  volitional  conceptions  and  external  sensations,  still  its 
natural  action  in  respiration  is  a  nerve-action.  Nevertheless, 
while  the  cerebral  forces  and  the  mind  are  not  requisite  to  that 
action,  the  connection  of  its  nerves  with  the  brain  is,  inasmuch 
as  non-conceptional  internal  impressions  co-operate  in  exciting 
it.  This  doctrine  is  equally  applicable  to  the  respiratory  move- 
ments, in  which  the  diaphragm  plays  so  important  a  part.  The 
morbid  changes  in  the  respiratory  movements  arising  from 
contra-natural  nerve-actions  in  distant  parts,  especially  the  ab- 
domen, sufficiently  prove  this  influence  of  the  vis  nervosa  of 
non-conceptional  internal  impressions  on  the  nerves  of  the 
thoracic  muscles,  and  of  the  structures  subservient  to  respira- 
tion. 

526.  We  can  hence  confirm  the  proposition  already  mooted 
(285)  as  to  the  respiratory  function ;  namely,  that  at  first  in  the 
newly  born,  it  is  a  nerve-action  of  external  impressions,  or  at 
the  most  a  sentient  action  excited  by  obscure  external  sensa- 
tions (525) ;  that  subsequently  it  continues  both  as  a  sentient 
action  excited  by  an  instinct  originating  in  those  obscure  ex- 
ternal sensations  (364,  285),  but  being  also,  from  the  habitual 
recurrence  of  those  stimuli,  a  direct  or  indirect  nerve-action  of 
external  impressions  (51),  occurring  mechanically  (475) ;  and  is 
continually  changed  into  a  sentient  action  by  new  instincts,  or 
volitional  conceptions,  constituting  the  acts  of  laughing,  weep- 
ing, sighing,  singing,  speaking,  &c.  (285).  According  to  all 
probability,  this  is  the  true  nature  of  the  respiratory  move- 
ments in  animals  endowed  with  consciousness.  In  those  not 
so  endowed,  their  mechanism  is  altogether  diff'erent,  and  they 
consist  solely  of  nerve-actions. 

527.  The  skin  and  mucous  membranes  have  not  a  structure 
capable  of  movements  from  external  sensations,  and,  conse- 
quently, cannot  manifest  nerve-actions  from  non-conceptional 
internal  impressions.  Their  vessels,  and  the  glandular  struc- 
tures imbedded  in  them  are,  however,  capable  of  their  proper 
nerve-actions.  (Compare  §^  520 — 522.) 


272  ANIMAL  FORCES.  [ii. 

528.  The  functions  of  glandular  structures   generally  must 
be  comprised  in  the  same  proposition,  except  in  those  cases  in 
"which  secretion  or  excretion  is  effected  by  means  of  muscular  A 
tubes,  or  the  action  of  adjoining  muscles  (172).  Since  secretion 

is  effected  by  the  action  of  stimuli  on  the  mouths  of  the  capil- 
laries, the  general  views  already  stated  are  applicable  to  it. 
Thus,  by  means  of  the  vis  nervosa  of  non-conceptional  internal 
impressions,  certain  external  impressions  of  food  and  poisons  in 
the  stomach  which  are  not  felt,  excite  a  flow  of  saliva  and  a 
discharge  from  the  bronchial  tubes,  as  an  indirect  nerve- 
action  (419). 

529.  The  glands,  whose  functions  are  regulated  by  muscular 
action,  are  subject  to  laws  previously  stated  (172,  473). 

530.  Although  the  glandular  system  is  excited  to  the  per- 
formance of  its  functions  by  cerebral  forces  (172,  209),  as  well 
as  by  the  vis  nervosa,  yet  the  latter  is  the  most  general  and 
most  usual  excitant.  Many  glandular  functions  go  on  in  de- 
capitated animals,  so  long  as  they  possess  vis  nervosa  and  the 
functions  are  not  interrupted  by  deep  sleep,  syncope,  &c.  They 
are  observed,  too,  in  many  animals  not  endowed  by  nature 
with  cerebral  forces. 

531.  The  oesophagus,  stomach,  and  intestinal  canal,  are 
capable  of  nerve-actions  from  non-conceptional  internal  im- 
pressions. Vomiting,  from  injury  of  the  brain,  is  an  illustrative 
example  (490) ;  colic  or  diarrhoea,  produced  by  the  application 
of  poisons  externally  to  the  umbilical  region,  is  another ;  ver- 
micular action  excited  by  puncture  of  a  portion  of  the  intestinal 
canal,  another  (513). 

532.  Although  the  movement  of  the  digestive  apparatus  is 
usually  a  direct  nerve  action  of  external  impressions,  and  con- 
sequently requires  neither  the  cerebral  forces,  nor  the  concep- 
tive  force  (466,  467),  nevertheless,  not  only  conceptional  internal 
impressions  often  change  it  (170,  174,  206,  212),  but  it  also 
requires  the  co-operation  of  non-conceptional  internal  impres- 
sions for  its  continuance,  just  as  is  required  in  the  movements 
of  the  heart,  diaphragm,  and  other  parts;  for  the  moving 
power  of  the  stomach  is  abolished,  when  the  trunk  of  its 
nerves  is  tied.  Hence  the  continued  connection  of  its  nerves 
with  the  brain  is  necessary  to  the  movement  of  the  digestive 
apparatus,  although  independent  of  the   cerebral  forces  and 


CH.  III.]  VIS  NERVOSA  OF  INTERNAL  IMPRESSIONS.  273 

the  conceptive  force.  External  impressions  on  the  stomach 
and  intestines  are  the  principal  motor  forces,  and  the  peri- 
staltic motion  may  be  excited  in  those  viscera  when  separated 
from  the  body.  The  point  whence  the  co-operating  internal 
impressions  proceed,  as  well  as  the  natural  stimuli  which  cause 
lem,  are  as  yet  unknown. 

533.  The  entire  process  of  digestion,  although  peculiarly  a 
direct  nerve-action  of  external  impressions,  is  changed  in 
various  ways  by  non-conceptional  internal  impressions.  It  is 
by  no  means  correct  to  conclude,  that  because  a  certain  altera- 
tion in  the  digestive  process  is  usually  a  direct  nerve-action  of 
external  impressions,  it  cannot  originate  in  other  animals  from 
primary  non-conceptional  impressions,  or  even  that  it  may  not 
be  a  sentient  action.  It  is  also  a  great  mistake,  to  refer  all 
such  changes  to  the  great  irritability  of  the  intestinal  canal. 

534.  The  muscular  fibres  of  the  lungs  are  as  capable  of 
nerve-actions  from  non-conceptional  internal  impressions  as 
muscular  fibres  generally ;  and  since  their  capillaries  and  glan- 
dular tissues  are  in  this  respect  under  the  same  general  laws, 
as  the  skin  and  glands  at  large,  no  further  illustrations  are 
here  necessary. 

535.  The  capillaries  of  the  liver,  like  those  of  the  lungs, 
and  probably  the  ductus  communis  choledochus,  are  influenced 
by  non-conceptional  internal  impressions.  Is  it  probable  that 
the  animal  poisons,  introduced  by  the  fangs  or  stings  of  en- 
raged or  poisonous  animals,  thus  excite,  by  means  of  reflected 
external  impressions,  contraction  of  the  gall- duct  and  jaundice, 
just  as  they  excite  spasmodic  nerve-actions  of  the  oesophagus 
and  the  muscles  of  deglutition?  or  are  they  the  direct  nerve- 
actions  of  the  external  impressions,  derived  from  the  poisons 
introduced  with  the  blood  into  the  viscus  ? 

536.  The  kidneys  are  liable  to  the  same  changes  in  function- 
as  the  liver.  Is  the  change  in  the  urinary  secretion  which 
occurs  when  cantharides  are  simply  held  in  the  hand,  but  not 
so  as  to  excite  any  manifest  external  sensation,  a  nerve-action 
of  a  reflected  impression  ?  or  is  it  not  rather  a  direct  nerve- 
action,  excited  by  the  poison  itself  being  carried  to  the  kidneys  ? 
The  latter  is  the  more  probable. 

537.  The  urinary  bladder  is  capable  of  many  sentient 
actions  (176),  and,  consequently,  of  many  nerve-actions  from 

18 


274  ANIMAL  FORCES.  [ii. 

non-conceptional  internal  impressions,  although  it  is  excited 
for  the  most  part  by  unfelt  external  impressions.  This  is 
shown  by  the  development  of  various  spasmodic  phenomena 
involving  the  bladder. 

538.  The  nerve-actions  of  non-conceptional  internal  im- 
pressions in  other  viscera,  as  the  spleen,  pancreas,  are  either 
the  same  as  those  of  the  glands,  blood-vessels,  &c.,  or  else 
experimental  researches  have  not  thrown  light  on  the  subject. 

539.  The  organs  of  the  senses  are  the  seat  of  the  same 
nerve-actions,  as  the  muscular  system  generally;  it  is  there- 
fore not  necessary  to  give  special  illustrations. 

540.  The  sexual  functions  in  animals  not  far  removed  from 
quadrupeds,  are  undoubtedly,  for  the  most  part,  nerve-actions. 
The  seminal  emission,  which  takes  place  in  epilepsy,  and  in 
which  all  sensation  and  consciousness  is  abolished,  is  of  this 
nature,  as  also  the  sexual  congress  of  decapitated  animals 
before  alluded  to  (481). 


CHAPTER  IV. 

RELATIONS  OF  THE  ANIMAL-SENTIENT  [CEREBRAL]  FORCES,  AND 
OF  THE  VIS  NERVOSA  TO  EACH  OTHER. 


JECTION    I. ON     THE     SUBSTITUTION     [eRSETZUNg]     OF     NERVE- 
ACTIONS    FOR    SENTIENT    ACTIONS. 

541.  When  an  internal  impression,  caused  by  conceptions, 
levelops  sentient  actions  in  the  mechanical  machines  by  means 
)f  the  nerves,  the  material  ideas  must,  firstly,  be  suitably  in 
contact  with  the  cerebral  origin  of  the  nerve  which  regulates 
the  machine ;  secondly,   the  internal  impression  must  go  un- 

jinterruptedly  downwards  along  the  same  nerve  to  the  machine 

itself;  and,  thirdly,  there  must  be  no  impediment  in  the  latter, 

^hen  duly  excited,  to  its  performing  the  movements,  which 

'e  in  accordance  with  its   structure  (129,  130).      When  an 

iternal  impression,    not   derived  from   conceptions,    develops 

lerve-actions  in  the  mechanical  machines,  it  acts  under  the 

fsame  conditions  (422,  496) ;  only  it  is  not  necessary  that  it  be 

lade  at  the  cerebral  origin  of  the  nerve,   or   by  means  of 

laterial  ideas  there,  but  it  may  be  made  at  any  point  of  the 

lerve,  provided  it  can   go  uninterruptedly  from  the  point  of 

impression  to  the  mechanical  machine,  which  it  moves  (493). 

In  either  case,  the  movement  excited  is  the  same,  whether  it 

he  a  sentient  action  or  a  nerve-action  (360). 

542.  When  an  internal  impression,  from  external  sensations, 
|;  develops  direct  sentient  actions  by  means  of  the  nerves,  and, 

even,  at  the  point  where  the  external  impression  of  the  sen- 
sations has  taken  place,  it  must  be  reflected,  and  sent  downwards 
.along  the  same  nerve  which  received  the  external  impression 
(188).  When  an  internal  impression,  by  means  of  an  indirect 
nerve-action  of  an  external  impression,  causes  movements  at 
.the  point  where  the  external  impression  has  taken  place,  it 
-produces  the  same  movements  as  nerve-actions  (422),  which,  as 
sentient  actions,  were  produced  under  the  circumstances  just 
mentioned;    these  are  also  produced  by  a  reflected  external 


276  ANIMAL  FORCES.  [ii. 

impression  (399,  422,  360),  and  may  likewise  result  as  direct ' 
norve-actions,  from  the  vis  nervosa  of  external  impressions 
(435).  These  principles  have  already  been  fully  established 
by  the  details  of  experiments  on  decapitated  animals,  and  by 
an  analysis  of  the  phenomena  of  muscular  contractioD.  Com- 
pare §§  201,  357,  445,  453,  &c. 

543.  When  an  internal  impression,  from  external  sensations, 
excites  direct  sentient  actions  in  mechanical  machines,  which 
have  not  received  the  external  impression,  it  is  reflected  at  the 
cerebral  origin  of  the  nerve  along  fibrils  which  were  not 
impressed  (188,  129,  iv).  If  a  non-conceptional  impression,  by 
means  of  a  direct  nerve-action  of  an  external  impression,  de- 
velops movements  in  another  machine  than  that  duly  im- 
pressed by  the  external  sensation,  or  excites  them  in  the  same 
machine  by  means  of  other  fibrils,  it  operates  exactly  as  in 
the  preceding  case.  A  non-conceptional  primary  internal  im-  i 
pression  produces  the  same  effects  under  conditions  already  | 
stated  (436,  496).  If,  therefore,  such  an  impression  excite  a 
nerve-fibril,  in  the  same  way  as  it  is  excited  by  the  internal 
impression  of  an  external  sensation,  then  the  same  changes 
take  place,  as  a  nerve-action,  that  usually  accompanied  the 
felt  external  impression,  and  constituted  a  sentient  action  of 
the  external  sensation. 

544.  When  external  sensations  excite  incidental  sentient 
actions,  the  material  external  sensation  impresses  the  origins 
of  other  nerves  in  the  brain,  which  have  not  received  the 
external  impression  (124,  131),  since  it  causes  material  ideas 
in  the  brain  for  other  conceptions  (97).  Consequently,  the 
incidental  sentient  actions  of  external  sensations  differ  only 
in  the  mode  of  causation,  from  those  of  other  and  spontaneous 
conceptions  (219,  &c.),  and  are  not  really  different.  But 
just  as  in  a  similar  manner  felt  external  impressions,  acting 
through  nerves  indirectly,  induce  sentient  actions  of  spon- 
taneous conceptions,  so  also  unfelt  external  impressions  induce 
nerve-actions  of  non-conceptional  internal  impressions,  con- 
stituting the  same  movements  which  the  spontaneous  sensa- 
tional conceptions  caused  by  sensation  would  develop ;  provided 
only,  that  the  unfelt  external  impressions  be  so  deflected  from 
their  course  before  they  reach  the  cerebral  origin  of  their 
nerve,  as  to  impress  the  same  nerves  as  the  spontaneous  con- 


CH.  IV.]      SUBSTITUTION  OF  NERVE^ACTIONS.  277 

ceptions  would  have  impressed,  and  in  the  same  way ;  and 
provided  also,  that  they  be  transmitted  thence  as  non-concep- 
tional  internal  impressions  to  the  same  mechanical  machines, 
as  the  spontaneous  conceptions  would  have  set  in  motion  (436). 
It  has  already  been  demonstrated,  that  the  bodies  of  animals 
may  be  so  constituted,  that  external  impressions,  while  being 
transmitted  to  the  brain,  are  reflected  here  and  there  upon 
other  fibrils  of  the  same  nerve,  or  upon  other  and  different 
nerves,  and  thereby  cause  an  indirect  nerve-action;  that  a 
part  [Merkmal]  of  this  reflexion  may  be  present  in  the 
external  sensation  caused  by  the  external  impression,  and 
induce  the  conceptive  force  acting  with  the  sensation  to  form 
a  certain  spontaneous  conception,  foreseeing,  imagination,  &c., 
of  which  the  indirect  nerve-action,  excited  as  aforesaid,  is  the 
ordinary  sentient  action;  and  that  thus  the  same  animal 
movement  may  be  at  the  same  time  both  an  indirect  nerve- 
action  of  an  external  impression,  and  the  sentient  action  of  a 
volitional  or  incidental  spontaneous  conception,  connected  by 
the  mind  with  the  sensation  of  the  external  impression  (438,439). 
There  are  phenomena  which  accord  with  the  view  of  the 
constitution  of  animal  bodies,  and  render  it  probable ;  but  this 
probability  is  rendered  much  greater,  when  it  is  recollected 
that  in  each  kind  of  spontaneous  sensational  conceptions,  (all 
which  are  proximately  induced  by  external  sensations)  (66), 
phenomena  are  actually  observed,  that  indicate  that  their  sen- 
tient actions  are  not  solely  developed  by  primary  non-concep- 
tional  internal  impressions,  but  that  also  in  virtue  of  their  con- 
nection with  the  impression  from  whence  the  sensations  which 
excite  them  originate,  they  are  excited  as  indirect  nerve-actions 
of  those  external  impressions.  This  will  be  subsequently  shown 
more  distinctly. 

545.  The  material  ideas  of  the  sensational  conceptions 
arising  out  of  external  sensations,  namely,  imaginations,  fore- 
seeings,  imperfect  external  sensations,  &c.  (67,  73,  148),  are 
simply  imperfect  material  external  sensations,  which  the  cere- 
bral force  produces  of  itself,  without  the  assistance  of  external 
impressions  derived  from  external  stimuli  (228,  239).  Their 
sentient  actions  are  those  of  the  external  sensations  to  which 
they  refer,  only  they  are  less  complete  (229,  240,  ii,  iii). 
Now,  since  unfelt  external  impressions  and  non-conceptional 


278  ANIMAL  FORCES.  [ii. 

internal  impressions  imitate  tlie  complete  sentient  actions  of 
external  sensations,  so  also  their  nerve-actions  resemble  the 
sentient  actions  of  all  other  sensational  exceptions :  and  inas- 
much as  the  dominion  of  the  vis  nervosa  extends  over  all 
the  mechanical  machines  capable  of  any  sentient  actions,  it 
follows,  that  all  the  sentient  actions  of  imaginations  and  fore-  « 
seeings  are  imitated  by  the  vis  nervosa  only.  This  view  is  ■ 
supported  by  observation.  A  gouty  person  dreams  that  he 
has  an  attack  of  gout,  and  this  foreseeing  is  accompanied  by 
the  sentient  action  of  retraction  of  the  limb  :  in  this  case,  the 
obscure  external  sensation  caused  by  pressure  of  the  toe 
against  the  bed-post,  induced  the  foreseeing.  But  if  the  toe 
of  a  decapitated  frog  be  pinched,  it  makes  the  same  movement, 
although  the  irritation  is  quite  unfelt.  The  same  movement 
is  a  sentient  action  in  the  one  case,  and  a  nerve-action  in  the 
other. 

546.  By  the  same  cause  that  a  sensational  conception  is 
rendered  agreeable  or  disagreeable,  but  especially  by  means  of 
the  impressions  of  sensational  pleasure  or  suffering,  its  sentient 
actions  are  also  so  ordered,  that  at  the  same  time  they  cause 
changes  in  the  vital  movements  (251);  and  these  changes  are 
connatural,  if  resulting  from  a  moderate  sensational  pleasure, 
and  contra-natural,  if  from  an  immoderate  sensational  pleasure, 
or  from  sensational  suffering  (252).  The  vis  nervosa  can 
induce  similar  changes.  Examples  of  this  kind  are  afforded 
by  changes  in  the  heart's  movements — especially  in  the 
circulation  through  the  thorax — and  in  the  mechanism  of  re- 
spiration (519,  520,  525). 

547.  A  change  is  caused  in  the  vital  movements — a  sentient 
action — by  external  sensations,  in  so  far  as  they  are  pleasant 
or  unpleasant,  or  cause  titillation  or  pain  (80,  250).  Now,  the 
cause  why  an  external  sensation  is  pleasing  or  unpleasing,  con- 
sists in  a  difference  in  the  external  impression  itself,  and  this 
difference  exists  whether  it  be  felt  or  not  (189).  Consequently, 
the  vis  nervosa  of  external  impressions  alone  causes  those 
changes  in  the  vital  movements,  which  were  caused  when  its  sen- 
sation was  titillation  or  pain.  For  illustrations,  see  §§  433, 434, 
but  the  number  might  be  readily  increased. 

548.  Spontaneous  sensational  conceptions,  imaginations,  fore- 
seeings,  &c.,  are  only  portions  of  external  sensations  (228,  239), 


( H.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  279 

and,  consequently,  the  pleasing  or  unpleasing  internal  feelings 
they  excite  in  the  mind,  depend  on  the  difference  in  the  nature 
of  the  external  sensation  to  which  they  are  related.  Now, 
since  sensational  pleasure  or  pain  depends  on  a  difference  in 
the  nature  of  the  impressions  which  are  felt  (80),  so  also  the 

Ileasure  or  pain  excited  by  all  spontaneous  sensational  concep- 
fons,  differs  accordingly  as  the  external  impressions  differ  that 
Kcite  the  external  sensations  to  which  they  are  related  (88). 
jhe  sentient  action  of  sensational  pleasure  or  pain  is  either  a 
Dnnatural  or  contra-natural  change  in  the  vital  movements 
^51,  252) ;  and  an  imagination,  foreseeing,  &c.,  in  so  far  as 
;  is  agreeable  or  disagreeable,  produces  also  a  connatural  or 
Dntra-natural  change  by  means  of  its  internal  impressions  of 
pleasure  or  pain,  just  as  the  external  impression  whereon  it 
depends  produces  change  by  means  of  its  vis  nervosa  alone 
(546,  547).  The  imagination  or  foreseeing  of  a  titillation  or 
pain,  changes  the  vital  movements  in  the  same  way,  but  less 
perfectly,  as  the  titillation  or  pain  itself.  From  hence  we 
conclude,  that  the  vis  nervosa  of  the  external  impressions,  by 
which  the  pleasure  or  pain  in  the  imaginations,  conceptions,  &c., 
is  indirectly  excited,  can  of  itself  excite  vital  changes,  which 
constitute  the  sentient  action  of  the  imaginations,  foreseeings, 
&c.,  themselves.  In  the  example  already  given  of  the  dream- 
ing gouty  patient,  we  have  an  illustration  of  this  view;  de- 
capitated animals  and  acephalous  foetuses  seem  also  to  be  as 
much  distressed  by  violent  external  impressions  merely,  as  they 
would  have  been  if  those  impressions  had  been  felt,  so  that  the 
heart  palpitates,  and  the  pulse  is  manifestly  quickened.  This 
doctrine  will  be  also  fully  illustrated,  when  we  consider  the 
relations  of  the  instinctive  and  emotional  acts  to  the  vis 
nervosa. 

549.  From  the  preceding  considerations  (542 — 548),  it 
follows,  that  the  actions  of  external  sensations,  or  of  imagina- 
tions, or  foreseeings,  or  of  their  sensational  pleasure  or  pain, 
may  at  the  same  time  be  both  sentient  actions  and  nerve- 
actions,  or  may  at  another  time  be  nerve-actions  only ;  or  in 
other  animals,  they  may  be  solely  nerve-actions  resulting  from 
impressions  independently  of  the  co-operation  of  the  cerebral 
forces,  so  that  neither  head,  nor  brain,  nor  mind,  is  absolutely 
necessary  to  their  development;  nay,  if  there  be  animals  altogether 


280  ANIMAL  FORCES.  [ii. 

devoid  of  cerebral  forces,  and  so  constituted  that  the  impressions 
made  on  their  nerves,  are  communicated  to  the  mechanical  ma- 
chines, as  they  are  when  felt,  or  produced  by  spontaneous  sensa- 
tional conceptions,  these  animals  can  perform  all  the  sentient 
actions  of  pleasurable  or  painful  sensations,  imaginations,  fore- 
seeings,  &c.  (437 — 439);  and  the  actions  themselves  vj^ill  have 
all  the  favorable  or  unfavorable  influence  on  the  economy,  which 
they  would  have  had  if  they  had  been  true  sentient  actions. 

550.  The  efiPort  of  the  conceptive  force,  arising  out  of  the 
pleasurableness  or  painfulness  of  sensational  foreseeings,  is 
termed  desire  or  aversion  (81,  89);  and  by  it  the  cerebral  forces 
are  strained  to  develop  fully  the  material  idea  of  a  certain  fore- 
seen conception  (83).  Ail  the  sentient  actions  of  the  sensational 
desires  and  aversions  are  compounded  of  those  of  a  sensational 
foreseeing  and  of  its  pleasure  or  pain  (255).  Now,  since  all 
these  sentient  actions  can  be  caused  also  by  the  vis  nervosa 
(549),  it  follows  that  the  sentient  actions  of  the  sensational 
desires  and  aversions  can  be  caused  in  like  manner. 

551.  The  blind  instincts  and  emotions  are  sensational  desires 
and  aversions  dififering  from  the  latter  only  in  this,  that  they 
manifest  a  higher  degree  of  intensity,  that  they  are  wholly 
sensational,  and  that  the  mind  has  only  an  obscure  and  confused 
knowlege  of  their  objects  (90) ;  their  sentient  actions  diff'er  also 
in  attaining  a  high  degree  of  intensity,  often  bordering  on  the 
contra-natural  (256).  Now,  since  the  vis  nervosa  can  of  itself 
cause  the  actions  of  the  sensational  desires  and  aversions,  it 
follows,  that  it  can  also  cause  those  of  the  sensational  instincts 
and  emotions. 

552.  Nature  leads  animals  by  means  of  sensational  instincts, 
to  perform  the  acts  necessary  to  self-preservation  and  self- 
defence,  to  the  propagation  of  the  species,  and  to  the  care  of 
their  young,  by  means  of  external  impressions  which  she  places 
in  their  way  at  the  proper  time,  if  necessary  (262 — 265) ;  and 
which  impel  even  rational  animals  by  very  obscure  sensations 
to  the  fulfilment  of  these  duties  (266 — -269).  Hence  it  is  so 
much  the  less  surprising,  that  external  impressions  so  wisely 
prepared  beforehand  and  produced  by  nature,  can  excite  the 
sentient  actions  of  the  natural  instincts,  as  nerve-actions ;  and 
attain  to  and  accomplish  their  object  without  their  being  felt, 
and  without  the  cerebral  forces  taking  any  share  therein  (89). 


IH.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  281 


I 

^^Wut  direct  sentient  actions  of  the  instincts  are  none  other  than 
l^^bianges  in  the  vital  movements  arising  from  pleasure  and  pain, 
combined  with  those  movements  which  take  place  more  com- 
pletely during  the  satisfaction  of  the  instinct,  and  which  are 
properly  the  sentient  actions  of  a  foreseeing  (271,  272).  To 
these  may  be  added  a  number  of  incidental  sentient  actions  of 
the  instincts,  which  the  vis  nervosa  can  develop  as  regularly 
and  as  providently  as  those  of  the  instincts  themselves  (436 — 
439).  Lastly,  the  sentient  actions  of  the  satisfaction  of  the 
instinct,  are  simply  those  of  the  foreseeing  and  of  the  actual 
sensation,  or  of  other  sensational  conceptions  (275,  276),  and 
these  also  can  be  developed  by  the  vis  nervosa.  We  will  de- 
monstrate these  views  with  reference  to  some  of  the  principal 
instincts. 

553.  The  external  impressions  on  the  stomach,  which  excite 
the  instinct  of  hunger,  excite  an  unpleasant  external  sensation 
in  the  stomach  of  faintness,  which,  being  a  painful  sensation, 
changes  the  vital  movements  contra-naturally,  and  otherwise 
stimulates  to  the  performance  of  their  functions,  all  the  me- 
chanical machines  which  co-operate  in  the  mechanism  and  func- 
tion of  digestion  (281).  Incidental  sentient  actions  accompany 
these  direct  sentient  actions  of  the  instinct,  as,  for  example, 
that  the  animal  shall  go  out  to  seek  food,  seize  it,  and  carry  it 
to  the  stomach.  Satiety,  or  the  satisfaction  of  the  instinct  by 
these  means,  is  an  external  sensation  in  the  stomach,  which  has 
also  its  peculiar  direct  and  incidental  sentient  actions,  subser- 
vient to  the  whole  process  of  digestion.  AU  these  actions  may 
be  excited  by  the  vis  nervosa  only,  especially  in  those  animals 
whose  organisms  are  so  constituted  that  the  vis  nervosa  can 
take  the  place  of  the  cerebral  forces  (439) .  A  headless  tortoise 
lives  several  months ;  it  cannot  possibly  feel  the  sensation  of 
faintness  from  emptiness  of  the  stomach,  yet  the  external  im- 
pressions must  change  the  vital  movements  contra-naturally 
like  that  painful  sensation,  because  it  becomes  feeble  and  faint 
from  starvation.  The  digestive  organs  must  be  excited  to  the 
movements  which  are  requisite  to  digestion,  by  the  external 
impressions  of  emptiness,  just  as  by  the  instinct,  since  the 
bowels  are  moved  peristaltically,  and  the  digestive  fluids  are 
secreted,  so  long  as  life  continues  (468).  The  most  convincing 
proof,  however,  of  the  general  principle  is,  that  those  movements 


282  ANIMAL  FORCES.  [ii. 

are  excited  as  nerve-actions,  which  usually  are  volitional;  for 
the  animal  raises  itself,  and  creeps  about  to  seek  food.  In 
animals  in  whom  the  existence  of  a  conceptive  force  is  more 
doubtful,  the  same  thing  is  observed,  for  it  appears  from 
Schaffer's  experiments,  that  decapitated  snails  can  obtain  food, 
and  satisfy  the  instinct  of  hunger.  (Schaffer,  Versuche  mit 
Schnecken.)  He  placed  headless  snails  under  a  glass,  with 
some  bean-leaves ;  on  the  following  day  he  observed  traces, 
showing  that  they  had  crept  about;  on  the  fourth  day,  the 
leaves  were  eaten  into  holes ;  by  the  end  of  the  month  a  new 
head  had  grown. 

554.  It  must  be  remembered,  however,  that  direct  proofs  of 
the  production  as  nerve-actions  of  sentient  actions,  by  the  vis 
nervosa  only,  are  not  always  possible.  In  many  cases,  de- 
capitation arrests  certain  functions,  which  although  purely 
nerve-actions,  require  some  influence  from  the  vis  nervosa  pro- 
duced in  the  head  and  cerebrum.  (Compare  §§  515,  524,  532.) 
Again,  when  the  head  is  separated,  many  nerve-actions  cannot 
possibly  take  place,  because  the  organs  in  which  they  ordinarily 
occur  as  sentient  actions,  are  removed  with  the  head.  Thus, 
the  flow  of  saliva  cannot  be  excited  in  a  headless  animal,  by 
the  sensational  stimulus  of  hunger.  Further,  the  proof  in 
many  cases  can  only  be  indirect,  or  an  inference,  as  in  the  ex- 
ample of  the  headless  tortoise  just  mentioned,  which,  after  long 
fasting,  crept  about  as  if  in  search  of  food.  Certain  actions 
result  from  certain  stimuli  previously  to  decapitation ;  the  same 
results  follow  on  the  same  stimuli  after  decapitation ;  hence 
we  conclude,  that  in  both  cases  the  actions  result  equally  from 
the  stimuli. 

555.  The  external  impressions  that  develop  the  instinct  to 
voluntary  movements,  excite  unpleasant  external  sensations  of 
weariness,  lassitude,  indisposition,  &c.,  which,  being  strong  sensa- 
tional painful  feelings  cause  the  vital  movements  to  be  feverish, 
and  stimulate  the  muscles  of  voluntary  motion  to  perform  their 
proper  functions,  so  that  they  jerk,  move  the  limbs,  and  produce 
complete  movements.  When  the  instinct  is  satisfied  by  the 
performance  of  the  movements,  the  agreeable  sensation  thence 
resulting  has  also  its  peculiar  results  in  the  economy,  and  in- 
duces a  general  healthy  tone  of  the  system  (283).  The  instincts 
for  particular  kinds  of  movements,  as  walking,  sighing,  laughing. 


(II.  TV.]      SUBSTITUTION  OF  NERVE- ACTIONS.  283 

yawning,  crying,  singing,  striking,  swimming,  spinning,  building, 

&c.  (284),  have,  as  their  inducements,  various  external  sensations, 

imaginations,  foreseeings,  and  other  instincts ;  and  it  is  an  esta- 

)lished  fact  in  the  whole  animal  kingdom,  that  all  the  actions 

these  instinct  for  voluntary  movements  may  be  produced  by 

le  vis  nervosa  only.     Various  experiments  and  observations 

lade  on  decapitated  frogs  and  other  animals  already  detailed, 

rove  this  amply.    An  acephalous  child  retracts  its  limbs  when 

winched  or  burnt,  exactly  as  an  ordinary  child  would  have  done. 

[t  is  related,  that  a  decapitated  man,  being  thrust  through  the 

)reast  with  a  sword,  threw  his  arms  together, — a  movement 

^bich  under  ordinary  circumstances  would  have  been  the  sen- 

ient  action  of  the  instinct  of  self-preservation.    The  movements 

ide  by  a  decapitated  man,  immediately  after  decapitation,  are 

Tor  the  most  part  volitional  in  character.    He  struggles  violently 

dth  his  arms,  that  he  may  free  bis  hands  from  their  bonds,  and 

10  be  able  to  use  them  to  save  himself.     He  grasps  with  his 

lands,    and    endeavours   to    turn,   to  stand  on  his  feet,   &c. 

Jimilar  movements  in  great    variety  may  be   seen   daily    in 

lecapitated  animals,  as  turtles,  snakes,  snails,  flies,  centipeds, 

:c.    Many  of  this  class  of  movements,  as  singing,  sighing,  &c., 

jannot,  however,  be  excited  as  nerve-actions,  because  decapita- 

ion  renders  the  experiment  impossible,  the  organs  themselves 

)eing  removed. 

556.  From  the  preceding  and  other  considerations  already 

idduced  (435 — 439),  it  is  extremely  probable,  that  these  actions 

)f  the  instincts,  ordinarily  voluntary  movements  in  all  animals 

'^hich  feel  true   instincts,    often  take    place   as   pure   nerve- 

|actions  (269);  that  they  are  sometimes  of  the  one  kind,  some- 

Itimes  of  the  other  (286) ;  and,  consequently,  that  animals  which 

[are  endowed  with  neither  sensation  nor  true  instincts,  being 

Simulated  solely  by  unfelt  external  impressions,  can  apparently 

[act  volitionally,  and  as  if  endowed  with  sensation.     Respiration 

pas  already  been  quoted  as  an  example  of  this  kind  (285,  526). 

iWhen  the  instinct   of  an   animal  excites  it  to   walk    or   run 

[Toluntarily  in  a    certain    locality,    the  muscles    of  the  legs 

[are  only  sentiently  excited  at  first  to  the  suitable  movements, 

id,    subsequently,    an    external    impression   is    sufiicient    to 

^excite  the   same    movements.     Thus   there   are   examples   of 

^persons  who  continually  traverse  the  same  streets,  who  fall  fast 


284  ANIMAL  FORCES.  [ii. 

asleep  on  tlie  way,  are  conscious  of  nothing,  observe  nothing 
that  they  meet,  and  yet  reach  their  destination.  If  it  be 
advanced,  that  these  movements  depend  on  obscure  sensations, 
(which,  however,  is  not  the  case,)  there  are  innumerable  illus- 
trations in  lower  animals,  that  are  unanswerable.  A  frog  uses 
its  legs  quite  differently,  when  it  swims  than  when  it  leaps. 
If,  when  decapitated,  it  be  pinched,  it  leaps  away,  not  because 
an  external  sensation  excites  an  instinct,  but  simply  in  virtue 
of  the  nerve-action  of  an  external  impression.  If,  in  leaping, 
it  falls  into  the  water,  it  then  uses  its  legs  to  swim,  not  because 
the  external  sensation  of  the  water  excites  the  instinct  to  swim, 
but  because  the  external  impression  from  the  contact  of  the 
water  excites  the  movement  as  a  nerve-action.  This  being 
undoubted,  why  should  it  be  presupposed  that  a  living  frog 
leaps  or  swims  only  in  consequence  of  the  excitement  of  the 
instinct  by  external  sensations  ?  It  is  clear  that  it  may  do 
both  without  external  sensations,  and  without  the  development 
of  the  instinct.  Thus,  it  is  manifest,  that  the  movements  are 
probably  often  nerve-actions  only,  which  we  constantly  suppose 
to  be  sentient  actions,  because  they  are  such  in  ourselves  and 
in  other  animals. 

557.  We  can  manifestly  see  from  these  considerations,  what 
truth  there  is  in  the  inference  made  from  the  performance  of 
volitional  motions  of  animals,  especially  of  those  which  are 
instinctive,  as  to  the  existence  of  mind,  and  of  sensations,  and 
volitional  conceptions.  If  the  most  voluntary  instinctive  ac- 
tions of  animals  really  sentient  and  endowed  with  true  instincts 
can  be  excited  by  means  of  mere  external  impressions,  and  can 
go  on  after  their  organism  has  been  subjected  to  so  great  an 
injury  as  decapitation, — or  if  volitional  movements  can  be 
excited  and  regulated  under  such  circumstances,  by  various 
and  successive  external  impressions,  just  as  if  they  were  felt, 
and  so  excite  new  instincts  into  operation  (555,  556),  it  were 
altogether  unreasonable  to  infer  from  the  apparently  voluntary 
movements  of  many  animals,  whose  whole  conceptive  force  is 
of  doubtful  existence,  that  those  movements  in  them  are  sen- 
tient actions  of  true  instincts,  and  the  results  of  external  sen- 
sations; or  to  accept  these  as  the  sole  decisive  proof,  that 
they  possess  conceptions.  When  we  consider  how  carefully 
nature  has  provided,  that  in  the  apparent  instincts  of  animals. 


en.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  285 

the  external  impressions  shall  be  applied  in  such  order,  and 

with  such  energy,  that  in  a  like  order  and  with  proportionate 

vigour,  those  voluntary  movements  are  excited,  which  we  con- 

jsider  as  the  sentient  actions  of  the  instincts  (265),  remembering 

the  same  time  how  closely  these  are  related  to  the  ordinary 

lerve-actions  caused  by  these  impressions,  it  can  hardly  be  a 

latter  of  surprise,  that  the  latter  take  place  as  regularly  and 

adaptively,  as  if  they  were  sentient  actions.      Our  astonish- 

lent,   as  we  have  already  shown,   arises   from   our  erroneous 

►Delusions  (438).     Is  not  that  which  appears  to  be  performed 

laptively,  volitionally,   and  in  a   definite  order,   by  a  worm 

dthout  a  head  or  brain,  by  an  insect,  or  by  any  other  animal 

^hose  structure  is  widely  different  from  that  of  sentient  beings, 

Ithough  in  such  we  can  scarcely  trace  vegetative  life — is  not 

the  whole  life  of  an  oyster,   a  sea-worm,   a  polype,   a  snail, 

spider,  a  flea,  an  ant,  a  bee,  &c. — is  not  the  whole  of  their 

lets,  or  part  of  them,  solely  an  operation  of  the  vis  nervosa  ? 

[ay,  are  they  not  such  even  in  sentient  animals  ?      We  know 

)f  no  reason  why  it  should  be  doubted,  that  such  is  the  case 

dth  those  animals  whose  organisms  are  not  constructed  to  be 

le  seat  of  mind,  like  the  bodies  of  sentient  animals,  but  are 

lanifestly  so  formed  as  to  lead  to  the  conclusion,  that  the 

lervous  ganglia,  so  numerous  in  many,  perform  the  office  of 

brain,  and  that  the  external  impressions  which  nature  sup- 

)lies,  are  so  reflected  from  them  to  the  limbs,  that  the  latter 

ire  excited  thereby  to  perform  those  movements,  according  to 

the  pre-ordained  intent  of  nature,  which,  in  sentient  animals, 

khe  material  ideas  of  the  instinct  develop  in  like  manner  by 

leans  of  the  cerebral  force. 

558.  The  external  impressions,  which  cause  the  sensation  of 

[weariness,  lassitude,  and  fatigue,  whence  the  instinct  for  repose 

ind  sleep  arises,  develop  the  sentient  actions  of  this  instinct,  as 

[nerve-actions ;  namely,  a  relaxation  in  the  activity  of  the  cerebral 

forces,  and  the  weakening  of  their  action  on  the  mechanical 

lachines  (287,  i),  without  the  instinct  itself  being  excited,  and 

dthout  being  felt.      A  sudden  pressure  on  the  brain  arrests 

[in  a  moment  the  operation  of  the  cerebral  forces,  without  the 

^nstinct  for  sleep  being  previously  developed,  and  all  conceptions 

[and   sentient   actions   suddenly   cease.      Opium,   when   taken, 

texcites  this  instinct,  and  not  only  changes  the  vital  movements 


286  ANIMAL  FORCES.  [ii. 

thereby,  but  the  sentient  actions  gradually  cease,  in  conse- 
quence of  the  brain  being  rendered  unfit  for  the  performance  of 
its  functions,  and  no  material  sensations  being  excited  in  the 
brain.  Opium  acts  on  the  nerves,  as  on  the  brain,  and  renders 
the  vis  nervosa  as  inefficient  as  the  cerebral  forces.  When 
opium  is  applied  to  the  nerves  of  a  decapitated  animal,  it 
changes  and  arrests  the  movements  of  the  heart,  but  somewhat 
more  slowly  than  if  taken.  According  to  Whytt,  a  muscle 
suddenly  loses  its  irritability,  if  opium  be  applied  to  its  nerve. 
But  the  power  of  the  vis  nervosa  to  excite  indirect  nerve- actions, 
as  well  as  the  direct,  is  abolished  by  opium,  since  all  the  nerves 
of  the  body  are  rendered  insensible,  as  well  as  those  with  which 
it  comes  in  contact;  so  that  external  impressions  are  neither 
transmitted  upwards  along  the  nerves,  nor  reflected  downwards. 
Very  frequently,  not  a  particle  of  opium  or  other  narcotic 
poison,  reaches  the  brain  in  narcotization ;  for  it  acts  when  it 
has  scarcely  come  in  contact  with  the  stomach,  and  even  when 
applied  externally,  or  when  the  heart  is  excised,  and,  conse- 
quently, the  circulation  of  the  blood  arrested  (Whytt).  It  is 
often  impossible,  that  narcotics  can  excite  sleep  by  causing  ex- 
ternal sensations,  since  their  impressions  on  the  stomach  and 
intestines  are  rarely  felt  (470),  for  they  deprive  the  terminal 
points  of  the  nerves  with  which  they  come  in  contact,  of  both 
their  sensibility  and  vis  nervosa  at  the  same  time,  and  thus,  in 
a  moment  abolish  the  most  violent  external  sensation  of  a 
nerve,  namely,  pain.  It  would  appear,  that  Whytt  (whose 
experiments  we  have  just  quoted)  was  correct  in  concluding, 
that  the  sleep  which  opium  induced,  was  much  more  probably 
the  result  of  a  diminution  of  the  general  sensibility  of  the 
nerves  caused  by  it,  or  in  other  words,  of  the  cerebral  forces 
and  the  vis  nervosa,  than  of  the  excited  instinct  for  sleep ; 
although  when  the  opium  acts  at  the  same  time  on  the  brain, 
this  instinct  may  be  developed. 

559.  The  war-instinct,  by  which  animals  are  motived  to  use 
their  natural  weapons  when  exposed  to  danger,  is  really  only 
another  form  of  the  instinct  to  voluntary  movement ;  and,  con- 
sequently, its  sentient  actions  may,  under  suitable  circumstances, 
be  nerve-actions,  excited  by  the  same  external  impressions, 
which,  when  felt,  excite  the  instinct.  Insects,  as  the  earwig 
and  bee,  thus  use  the  natural  weapons,  placed  in  their  abdomen, 


'cii.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS. 


287 


Fter  being  decapitated.  A  horse  with  his  head  shot  off  by  a 
jannon-ball  kicks  when  it  is  struck  down,  just  as  it  usually 
loes  when  its  war-instinct  is  otherwise  excited.  Examples  of 
ithis  kind  are  numerous. 

560.  It  scarcely  requires  proof,  that  the  sentient  actions  of 
the  instinct   of  propagation  may  take  place  as  nerve-actions 

'om  external  impressions  only.  Crickets  allure  to  sexual 
[congress,  after  decapitation,  by  the  vibration  of  their  wings; 
land  Kedi,  Bibiena,  and  others,  have  observed  that  butterflies, 
[after  having  copulated  but  once  in  their  lives,  repeat  the  func- 
ition  perfectly  when  decapitated,  and  the  females  after  sexual 
jcongress,  deposit  their  eggs  as  carefully  as  if  excited  thereto  by 
[their  instinct. 

561.  The  preceding  statements  fully  estabhsh  the  general 
[fact,  that  all  this  class  of  sentient  actions  are  only  animal 
imovements,  which  may  be  produced  as  perfectly  by  the  vis 

wsa  only,  as  by  the  cerebral  forces ;  in  many  animals  they 
[are  the  preordained  and  adapted  results  of  external  impressions 
^made  by  nature  on  the  nerves  for  the  express  purpose ;  in  many 
)thers,  are  at  the  same  time  sentient  actions,  being  produced 
|by  the  co-operation  of  the  cerebral  forces,  and  in  this  class  are 
-at  one  time  excited  as  nerve-actions  only,  at  another  as  both 
sentient  actions  and  nerve-actions ;  and  in  newly-born  animals, 
which  are  insensible  to  the  external  impressions  of  the  instincts, 
are  developed  as  nerve-actions  only.  Further,  the  acts  which 
btake  place  in  connection  with  its  principal  and  secondary 
/instincts,  characterise  an  animal,  and  determine  its  sensational 
-character  and  leading  propensities  (295),  constitute  no  proof 
^that  such  animals  are  controlled  by  true  instincts,  or  are  en- 
dowed with  the  sensational  faculty  or  with  mind  (437 — 440). 

562.  The  instinctive  passions  originate  like  instincts  from 
obscure  sensational  stimuli;  differing  only  in  this,  that  the 
latter  are  perceived  during  their  continuance  (298).  Their 
sentient  actions  are  the  same  as  those  of  the  instincts,  but  the 
incidental  sentient  actions  are  developed  rather  according  to 
psychological  laws  (297).  But  inasmuch  as  they  arise  in  the 
instinct  itself,  and,  consequently,  in  close  connection  with  the 
external  impressions  which  excite  it,  and  since  the  sentient 
actions  of  the  instinct  are  excited  by  the  vis  nervosa  only,  and 

,  can  take  place  in  the  same  order  as  if  excited  volitionally  (552), 


288  ANIMAL  FORCES.  [ii. 

it  appears  that  the  incidental  sentient  actions  of  the  instinctive 
actions,  stand  in  the  same  relation,  and  may  be  equally  excited 
by  the  vis  nervosa.  All  the  actions  which  a  sentient  animal 
performs  under  the  influence  of  the  instinctive  passions  (299 — 
303,  &c.),  may  be  excited  in  another  animal  by  the  vis  nervosa  of 
external  impressions  in  the  order  and  succession  preordained 
by  nature.  Decapitated  insects  supply  illustrative  examples. 
In  many  animals  these  actions  take  place  naturally  as  nerve- 
actions. 

563.  That  the  sentient  actions  of  the  passions  can  be  excited 
as  nerve-actions,  by  means  of  non-conceptional  internal  im- 
pressions, does  not  admit  of  doubt  (503).  All  the  passions 
modify  the  circulation,  the  action  of  the  heart,  the  respiration, 
and  the  vital  movements  in  general  (307,  310).  Internal  im- 
pressions do  the  same  in  a  thousand  instances,  simply  by  means 
of  the  vis  nervosa  (515 — 521,  525).  The  other  sentient  actions 
of  the  passions  are  often  volitional  movements,  often  changes 
in  the  natural  functions  of  the  viscera  (307 — 325),  and  these 
also  can  be  produced  by  the  vis  nervosa  of  internal  impressions 
(508,  532 — 540).  But  an  important  question  arises,  whether  the 
sentient  actions  of  a  passion,  considered  as  incidental  actions 
of  the  primary  external  sensation,  can  be  excited  by  the  vis 
nervosa  of  the  external  impression  proper  to  the  latter,  according 
to  the  doctrines  stated,  §  544. 

564.  Animals  not  endowed  with  reason  are  peculiarly  main- 
tained in  the  performance  of  their  natural  functions  by  the 
blind  instincts ;  and  it  is  only  the  most  skilful  in  which  we  see 
the  latter  attain  to  the  stage  of  instinctive  passions,  because 
their  brain  is  capable  of  containing  a  greater  number  or  a 
greater  development  of  material  ideas  (26);  for  it  is  certain, 
that  a  more  perfect  conceptive  force  which  can  form  wholly 
pure  conceptions  and  a  higher  degree  of  sensational  perceptions, 
are  necessary  to  the  development  of  the  passions  in  general 
(305),  and  these  are  possessed  only  by  the  more  perfect  animals. 
A  true  passion  never  results  so  directly  from  external  sensations, 
however  pure  [klar]  they  may  be,  as  the  natural  instincts  and 
instinctive  passions  (276,  i,  298).  The  former  usually  require 
entire  series  of  other  pure  [klar]  sensational  conceptions,  often 
only  distantly  related  to  external  sensations,  which  the  mind 
connects  together  according  to  psychological  laws,  and  of  w^hich 


CH.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  289 

a  very  imperfect  and  obscure  conceptive  force  is  not  capable 
(89^  108).  It  is  only  necessary  to  compare  an  instinct  and  a 
passion,  ia  one  point,  to  be  assured  of  this.  Any  painful  external 
sensation  immediately  excites  the  war-instinct,  and  the  move- 
ments proper  to  the  instinct  as  instantaneously  follow,  even  in 
man  himself,  and  before  the  cause  of  the  sensation  is  known. 
Between  the  external  sensation  exciting  the  instinct  and  its  sen- 
tient actions,  no  traces  of  conceptions  can  be  discovered,  con- 
sequently there  are  no  material  ideas  of  imaginations,  foreseeings, 
&c.,  produced  by  the  external  sensation ;  so  that  there  appears 
to  be  a  direct  transition  [Uebergang]  of  the  latter  into  the 
instinct  itself,  and  the  material  ideas  proper  to  it  to  take  effect 
in  the  sentient  actions  of  the  other.  So  that  it  may  in  some 
degree  be  asserted,  that  in  the  instincts  the  brain  turns  back 
[umwendete]  the  felt  impression,  and  reflects  it  on  the  nerves 
appropriate  to  the  sentient  actions  of  the  instinct,  just  as  an 
unfelt  external  impression  is  reflected  in  the  ganglia,  and  this 
without  the  material  ideas  of  the  conceptions  necessary  to  the 
instinct  becoming  an  object  of  special  thought,  they  being  too 
little  developed;  and  without  its  sentient  actions  being  obviously 
excited  and  connected  with  each  other,  according  to  psycho- 
logical laws.  If,  on  the  contrary,  a  man  be  excited  to  anger 
by  a  pain  inflicted  by  another,  between  the  passion  which 
excites  to  combat,  and  the  painful  sensation,  a  number  of 
connected  sensational  conceptions  arise,  which  are  psychological 
and  volitional  in  their  character.  He  perceives  clearly  that  an 
injury  has  been  done  him;  he  resolves  to  retaliate  on  the 
offender;  is  undecided  as  to  the  means  by  which  he  should  do 
this;  chooses  that  which  comes  first  to  hand,  and  by  a  con- 
tinually repeated  and  magnified  conception  of  the  injury,  is 
more  and  more  irritated  against  his  enemy.  Just  as  these 
sensational  conceptions,  excited  by  the  external  sensations,  are 
developed  in  the  mind,  and  excite  the  instinct  (94),  so  also  are 
the  material  ideas  which  produced  the  material  external  sensa- 
tion developed  in  the  brain ;  so  that  in  this  case  there  is  not 
that  apparently  direct  transition  of  the  external  sensation  into 
the  passion  itself,  and  of  the  material  ideas  of  the  former  into 
the  sentient  actions  of  the  latter.  To  comprehend  the  sentient 
actions  of  the  passion,  in  their  connection  with  the  external 
impression  which  first  excited  it,  the  course  of  all  the  sensational 

19 


290  ANIMAL    FORCES.  [ii. 

conceptions  and  their  sentient  actions  must  be  traced  as  far  as 
the  outbreak  of  the  passion  and  its  sentient  actions,  so  that  it 
may  be  noted  how  they  are  developed  from  each  other,  according 
to  psychological  laws  (108). 

565.  Amongst  those  sensational  conceptions  induced  by  an 
external  sensation,  and  which  must  be  generally  developed  ere 
they  form  the  passions  (94),  there  are  in  many  passions  some 
which  are  incidental  and  as  little  related  to  the  primary  sensa- 
tion, as  conceptions  of  the  understanding;  and,  consequently, 
are  not  really  produced  by  the  external  impression  which 
excites  the  sensation,  but  are  excited  in  successive  series,  accord- 
ing to  psychological  laws.  But  since  these  conceptions  are 
nevertheless  the  incitements  [Triebfedern]  of  the  passion  which 
they  excite  into  activity,  it  follows  that  the  sentient  actions  of 
the  passion  so  excited  are  not  really  produced  by  the  primary 
material  sensation,  and,  consequently,  not  by  its  external  im- 
pression; and  therefore  cannot  be  developed  either  as  its 
sentient  action  or  nerve-action.  An  example  will  illustrate 
this.  An  individual  sees  another  who  resembles  a  deceased 
friend.  This  constitutes  the  primary  external  sensation  of  all 
that  follows.  In  accordance  with  psychological  laws  the  mind 
perceives  the  resemblance,  and  this  is  the  first  intermediate 
conception  which  is  not  connected  with  the  sensation  according 
to  the  laws  of  the  vis  nervosa.  Thence  arises  the  imagination 
of  the  deceased  friend,  which  has  only,  in  common  with  the 
sensation,  those  sub-impressions  of  the  two  persons  in  which 
they  are  alike.  Next  arises  the  recollection  of  the  death  of  the 
friend,  and  all  its  accompanying  circumstances,  with  which  the 
primary  sensation  has  nothing  in  common.  Lastly,  the  fore- 
seeing arises,  that  death  has  cut  off  all  possibility  of  future 
converse  with  him.  This  foreseeing  is  painful,  and  the  mind 
endeavours,  according  to  psychological  laws,  to  develop  the 
conception  antagonistic  to  this  painful  one.  In  the  effort  of 
the  conceptive  force  to  effect  this,  consists  the  passion  of  sorrow, 
which  was  excited  by  the  sight  of  the  individual.  All  the 
conceptions  thus  excited  are  as  far  removed  from  the  primary 
sensation,  as  many  an  abstract  conception  induced  by  sensations, 
consequently,  the  sensation  has  really  contributed  nothing  to 
the  sentient  actions  of  the  sorrow.  But  the  vis  nervosa  of  the 
external  impression  of  the  sensation  can  only  develop  as  nerve- 


CH.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  291 

actions,  those  movements  which  its  external  sensation  would 
have,  or  had,  excited  as  its  sentient  actions  (542,  543).  Con- 
quently,  the  vis  nervosa  of  the  external  impression  which  induced 
the  emotion  of  sorrow,  cannot  excite  as  nerve- actions,  the  sen- 
tient actions  of  the  emotion.  The  same  doctrine  applies  to 
many  other  passions. 

566.  Nevertheless,  all  passions  are  not  excited  so  remotely, 
and  with  the  intervention  of  so  many  purely  psychological  con- 
ceptions ;  for  there  are  some  which,  from  their  closer  connection 
with  external  sensations,  are  similar  in  their  origin  and  de- 
velopment to  the  instincts.  With  regard  to  this  class,  it  must 
often  remain  doubtful,  whether  they  belong  to  the  passions,  or 
to  the  instincts,  or  instinctive  passions.  Thus  fear,  alarm,  and 
terror  (313,  318),  which  an  external  stimulus  excites  in  us, 
without  an  intervening  series  of  irrelevant  and  purely  psycho- 
logical conceptions,  is  usually  rather  a  form  of  the  instinct  of 
self-preservation  (299) :  the  anger  and  revenge  of  the  dog  rather 
a  modification  of  self-defence  (326).  The  affection  of  many 
animals  for  their  ofPspring,  which  sometimes  (as  in  monkeys), 
appears  to  be  a  passion,  is  but  a  form  of  the  instinct  to  tend 
offspring  (303)  ;  the  frolicsomeness  and  cheerfulness  of  many 
animals  rather  an  iiistinctive  passion  for  enjoyment  (299).  The 
sentient  actions  of  emotions  of  this  class  do  not  differ  from 
those  of  true  instincts,  except  in  being  accompanied  with  the 
sentient  actions  of  some  other  conceptions,  which  the  conceptive 
force  intermingles  according  to  its  own  laws  (297 — 304).  Now, 
since  all  these  may  be  excited  by  the  vis  nervosa  only  (549,  552), 
no  repetition  of  proofs  from  observation  (compare  553 — 562)  is 
necessary  to  demonstrate,  that  the  same  external  impressions, 
which,  when  felt,  excite  the  sentient  actions  of  these  instinctive 
passions,  will  also  excite  them  by  means  of  the  vis  nervosa  only, 
as  nerve-actions.  We  will,  however,  analyse  the  emotion  of 
terror.  In  this,  the  external  impressions  cause  a  painful 
external  sensation;  or  such  a  sensation  as  induces  a  strong 
sensational  unpleasantness  [Uulust] ,  because  it  excites  a  sudden 
secondary  sensational  conception :  as,  for  example,  when  an 
individual  hears  a  noise,  he  immediately  imagines  it  to  be 
thunder,  or,  if  he  receives  a  blow,  he  conceives  it  to  be  given 
by  a  robber.  This  disagreeable  sensation  changes  the  vital 
movements  contra-naturally,  and  violently  (314,  318),  and  puts 


292  ANIMAL  FORCES.  [ii. 

those  machines  into  motion,  which  must  act  in  flight  and 
defence  from  the  foreseen  danger  (315,  319),  whence  all  the 
other  phenomena  result  (316,  320).  All  these  sentient  actions 
may  be  excited  as  nerve-actions,  in  decapitated  animals,  insects, 
or  frogs,  or  in  a  decapitated  man,  or  in  an  acephalous  foetus. 

567.  Not  even  the  same  kind  of  passions  arise  always  from 
external  sensations  in  the  same  way,  but  sometimes  directly 
from  them,  sometimes  with  the  intervention  of  many  psycho- 
logical conceptions.  When  a  dog  is  frightened  by  a  sudden 
blow,  so  that  it  excites  its  muscles  for  the  purpose  of  running 
away,  it  connects  with  the  external  sensation  of  the  blow,  the 
foreseeing  excited  by  frequent  experience,  that  many  more 
blows  will  follow,  and  thus  the  emotion  of  fear  arises,  without 
the  intervention  of  other  conceptions.  This  sentient  action  of 
fear  can  be  developed  by  the  vis  nervosa  only  of  the  same  ex- 
ternal impression,  and  would  be  manifested  if  the  animal  were 
decapitated  (555).  If,  on  the  other  hand,  fear  is  excited  in  a 
man  by  a  sudden  blow,  it  may  arise  from  a  sensational  concep- 
tion, which  has  little  in  common  with  the  sensation.  He  judges, 
for  example,  that  the  blow  must  have  been  inflicted  by  a  man  : 
he  looks  about,  and  sees  no  one.  This  excites  surprise  and 
thought,  and  he  now  concludes  from  probabilities :  firstly,  he 
thinks  it  may  have  been  from  a  concealed  robber,  and  thus  fear 
incites  him  to  those  sentient  actions  which  can  protect  him  : 
then  he  conceives  it  was  a  ghost,  and  fear  incites  him  to  run 
away :  lastly,  he  attributes  the  blow  to  some  missile,  and  fear 
incites  him  to  hide  himself,  &c.  The  impression  of  the  blow 
could  not  possibly  excite  all  these  various  kinds  of  sentient 
actions,  since  so  many  volitional  conceptions  influence  them ; 
the  external  sensation  only  excites  the  will  into  action. 

568.  We  conclude,  therefore,  from  the  preceding  statements  : 
i.  That  the  sentient  actions  of  the  passions  generally  may 
be  excited  by  means  of  the  vis  nervosa  only  (563) ;  but  that 
the  same  external  impressions,  which  by  means  of  their  corre- 
sponding external  sensation  induce  the  passions,  however 
remotely  (66,  90),  can  only  excite  by  the  vis  nervosa  the  move- 
ments constituting  the  sentient  actions  of  the  latter,  in  so  far  as 
these  actions,  although  always  incidental  to  the  external  sensa- 
tion excited,  are  not  produced  by  intermediate  conceptions,  in- 
duced by  other  sensations  differing  altogether  from  it,  and  only 


CH.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  293 

in  so  far  as  the  movements  are  at  least  in  part  dependent 
on  it. 

ii.  That  the  reason  why  the  sentient  actions  of  the  instincts, 
although  only  incidental,  are  much  more  frequently  excited  as 
nerve-actions  by  the  vis  nervosa  of  the  external  impression 
only,  than  those  of  the  passions,  is  this :  namely,  that  the  ex- 
ternal sensation  which  excites  an  instinct,  being  seldom  or 
hardly  an  object  of  consciousness  to  the  animal,  is  in  closer 
relation  with  the  sensational  volition  of  the  conceptive  force 
than  in  the  passions ;  in  which  other  sensational  conceptions, 
altogether  foreign  to  the  primary  external  sensation,  are  so 
widely  removed  from  it,  that  the  sentient  actions  are  quite 
incidental  and  excited  by  them  according  to  psychological  laws. 

569.  Although  the  vis  nervosa  can  excite  the  sentient 
actions  of  the  passions  generally,  it  cannot  imitate  the  opera- 
tions of  the  cerebral  forces,  in  the  order  in  which  they  are 
developed  psychologically,  from  the  primary  external  sensation 
to  the  outbreak  of  the  passion,  unless  the  latter,  like  instincts, 
depend  directly,  or  for  the  most  part,  on  the  sensation.  Now 
since  the  other  results  in  the  animal  economy,  which  peculiarly 
characterise  each  passion,  are  caused  by  the  sentient  actions  of 
the  passion,  by  means  of  the  natural  connection  of  all  the 
forces  of  the  animal  body,  they  can  be  induced  by  the  vis 
nervosa  of  the  external  impressions  which  excite  the  passion 
only  under  the  same  conditions.  Thus,  the  sentient  actions  of 
joy,  namely,  the  quicker  and  more  vigorous  action  of  the  heart, 
the  half-convulsive  movement  of  the  diaphragm  in  laughter, 
and  the  volitional  movements  of  dancing,  singing,  &c.,  may  all 
be  induced  by  the  vis  nervosa  only,  as  has  been  already  fully 
shown.  But  if  the  attempt  be  made  to  trace  the  greater 
number  of  the  joyous  emotions  to  their  primary  sensations, 
and  to  deduce  their  sentient  actions  and  their  other  animal 
movements  from  their  impression  alone,  as  for  example,  from 
the  nerve-actions  caused  by  wine,  or  by  music,  or  by  a  look, 
or  conversation,  observation  will  not  afford  an  instance  in  which 
these  flow  directly  from  the  external  impression,  except  in 
those  cases  in  which  the  emotion  arises  directly  from  external 
sensation,  like  the  instinct  for  pleasure.  Such  is  the  case  when 
a  chrysalis  writhes  and  turns  about  if  placed  in  the  sun,  as  if 
from  the  pleasurable  sensation   of  warmth ;  or  when  a  torpid 


294  ANIMAL    FORCES.  [ii. 

newly-born  child,  after  being  washed  with  wine,  moves  its 
limbs,  having  its  circulation  accelerated,  &c.,  just  as  would 
have  followed  from  the  taking  of  wine;  or  when  a  headless 
butterfly  is  excited  to  copulation,  by  the  fluttering  of  the 
female,  just  as  if  the  sexual  sensation  had  been  excited  in  it. 

570.  Who  can  doubt,  that  the  sentient  actions  of  sorrow 
(310,  312)  may  be  induced  by  the  vis  nervosa  only  ?  Yet  if 
we  were  to  trace  them  back  in  the  majority  of  cases  to  the 
primary  sensation,  and  attempt  to  deduce  them  from  their 
external  impressions  only,  namely,  from  the  nerve-actions  of 
black  bile  in  the  stomach  and  bowels,  of  imperfect  digestion, 
&c.,  in  the  order  in  which  they  arise,  together  with  their 
material  results  in  the  economy,  such  as  diminished  transpira- 
tion, weeping,  wailings,  &c.,  we  should  find  no  examples  in 
which  it  could  be  done,  except  in  instances  in  which  they 
arise  directly  from  the  external  sensation.  In  this  way,  a  child 
cries  from  the  first  external  impression  of  the  air,  as  if  suffering 
pain,  a  decapitated  man  clasps  his  hand,  when  wounded,  as  if 
lamenting,  &c. 

571.  The  sentient  actions  of  all  kinds  of  fear,  anguish, 
despair,  and  terror  (314 — 320),  may  also  be  excited  by  the 
vis  nervosa  solely ;  still,  as  in  the  preceding  cases,  they  cannot 
be  traced  directly  back  in  the  order  in  which  they  arise  to  the 
primary  sensation,  and  thence  to  the  external  impressions 
causing  them,  except  in  the  instances  in  which  they  arise  (as 
in  instinctive  actions)  immediately  from  the  external  sensation, 
and  of  which  illustrations  have  been  already  given  (566). 

572.  Lastly,  the  sentient  actions  of  all  kinds  of  anger  and 
revenge  (323 — 325),  may  be  excited  by  the  vis  nervosa  only; 
still,  as  in  the  preceding  instances,  they  cannot  be  traced  back 
to  their  primary  exciting  impression,  except  when  they  are 
instinctive  in  their  nature,  and  arise  directly  from  an  external 
sensation. 

573.  In  investigating  the  sentient  actions  of  all  the  other 
passions,  and  other  desires  and  aversions,  the  material  ideas  of 
all  the  intervening  sensational  conceptions  must  be  considered 
(111,  568,  i,  ii).  The  sentient  actions  of  the  true  passions 
(306,  309),  can  never  occur  in  decapitated  animals,  solely  by 
means  of  the  vis  nervosa,  or  in  those  not  endowed  with  mind, 
or  capable  at  most  of  only  feeble  and  obscure  external  sensa- 


I 


(II.  IV.]      SUBSTITUTION  OF  NERVE-ACTIONS.  295 

tions.  The  apparent  instances  adduced  to  the  contrary,  are 
really  only  examples  in  which  the  sentient  actions  are  instinctive 
in  their  nature,  and  have  arisen  from  direct  external  sensations. 

574.  The  material  ideas  of  the  conceptions  of  the  understanding, 
are  not  excited  like  those  of  sensational  conceptions  by  external 
impressions  (66) ;  consequently,  they  cannot  be  excited  by 
the  vis  nervosa  of  the  latter,  in  the  order  in  which  they  are 
developed  psychologically.  But  as  all  material  ideas,  and,  con- 
sequently, those  of  the  intellectual  conceptions  are  internal 
impressions  on  the  cerebral  origin  of  the  nerves  (121),  it  follows 
that  their  actions  may  be  developed  by  the  vis  nervosa  of  non- 
conceptional  internal  impressions  (360).  Still,  as  they  manifest 
no  visible  direct  sentient  actions  (330),  except  in  so  far  as  they 
are  either  at  the  same  time  sensational  (and  then  the  vis  nervosa 
can  excite  them)  or  incitements  of  the  mind,  and  excite  the 
will,  it  follows  that  no  direct  actions  of  the  intellectual  con- 
ceptions can  be  induced  as  nerve-actions  by  the  vis  nervosa 
acting  through  the  nerves. 

575.  The  incidental  influence  of  the  understanding  on  the 
animal  economy  arises  in  various  ways  (331),  and  can  only  be 
replaced  by  the  vis  nervosa  acting  alone,  in  so  far  as  it  consists 
in  sentient  actions  from  sensational  conceptions,  or  from  plea- 
sure or  pain  of  the  desires  and  aversions,  whether  sensational 
or  intellectual  (574).  In  so  far,  however,  as  the  eflPort  of  the 
intellectual  power  involves  and  disorders  the  entire  organism 
(331,  332),  and  an  abuse  of  the  cerebral  forces  must  necessarily 
have  this  effect, — to  this  extent  the  effects  of  the  abuse  of  the 
vis  nervosa  are  identical,  whether  the  latter  co-operate  with  the 
former  or  not  (356 — 360).  For  example,  just  as  study  en- 
feebles the  body,  wastes  it,  and  disorders  its  natural  functions, 
so  also  does  an  excessive  indulgence  of  the  sensational  instincts 
(261,  iv).  Thus,  an  abuse  of  the  sexual  instinct  has  the  same 
injurious  effect  as  excessive  study. 

576.  The  gentle  influence  which  the  intellectual  conceptions, 
in  so  far  as  they  are  agreeable,  or  the  contrary,  have  on  the 
vital  movements  (333),  may  be  exercised  by  non-conceptional 
internal  impressions ;  and  in  this  way  the  movements  of  the 
muscles  which  the  intellectual  desires  and  aversions,  and 
their  satisfaction,  develop  as  direct  sentient  actions  (340), 
are    often    incidentally   mere    nerve-actions    of    impressions 


296  ANIMAL  FORCES.  [ii. 

(342,  445,  507).  But  since  the  mind  produces  all  these  kinds 
of  motives  [Bewegungsgriinde]  and  desires  of  the  will,  according 
to  purely  psychological  laws,  and  independently  of  external 
impressions  (333,  341),  the  movements  resulting  cannot  be 
induced  like  the  sentient  actions  of  sensational  conceptions, 
feelings,  and  desires,  by  the  vis  nervosa ;  and,  although  those 
movements  which  are  excited  by  the  will,  in  intellectual  beings, 
may  and  do  occur  in  decapitated  animals,  or  in  purely  sen- 
sational animals,  still  they  are  induced  by  impressions,  and  not 
psychologically. 

577.  The  incidental  influence  which  the  will  exercises,  by 
means  of  its  acts  on  the  animal  economy  (compare  336,  337,  343), 
can  be  exercised  also  by  the  vis  nervosa,  in  so  far  as  that  in- 
fluence consists  in  sentient  actions  directly  dependent  on  the 
internal  impressions  of  sensational  conceptions,  incitements, 
and  desires. 

578.  The  intellectual  conceptions  (330),  the  motives  con- 
tained in  them  (333),  and  all  desires  and  aversions  of  the  will 
(339),  in  addition  to  their  remote  connection  with  sensation 
(65),  possess  a  special  connection  in  virtue  of  the  sensational 
conceptions,  incitements,  and  desires,  intermingled  with  them. 
Hence  all  their  sentient  actions  have  a  sensational  character,  and 
to  this  extent  can  sometimes  be  induced  by  the  vis  nervosa  of 
external  impressions,  although  always  very  imperfectly.  When 
the  external  sensation  of  a  tune  excites  our  instinct  to  dance, 
the  desire  of  the  will  to  dance  a  rhythmical  dance  is  combined 
with  the  instinct,  and  by  dancing  we  satisfy  that  desire.  In  so 
far  as  this  free-will  act  is  a  sentient  action  of  the  instinct,  it  can 
be  excited  purely  as  a  nerve-action  of  other  impressions :  those 
affected  with  chorea  St.  Viti,  for  example,  dance  involuntarily 
and  convulsively,  even  when  sleeping,  but  certainly  not  ryth- 
mically,  since  this  is  an  action  of  the  will. 

579.  The  following  conclusions  may  be  drawn,  as  to  the 
substitution  of  nerve-actions  for  sentient  actions.  All  move- 
ments which  can  be  sentient  actions  may  be  excited,  either 
as  nerve-actions  only  by  the  vis  nervosa  alone,  or  as  the  latter 
at  the  same  time  that  they  are  sentient  actions  (503);  and  so 
far  as  it  is  possible  to  illustrate  the  question  by  observations  and 
experiments,  the  latter  establish  this  principle  without  exception. 
If,  however,  the  sentient  actions  be  considered  in  reference  to 


CH.  IV.]      SUBSTITUTION  OF  NERVE- ACTIONS.  297 

their  exciting  cause,  namely,  the  conceptions  of  the  mind,  and 
in  connection  with  the  order  in  which  they  are  developed,  and 
succeed  each  other,  we  find  there  are  two  kinds : 

i.  Certain  conceptions,  namely,  the  sensational,  are  induced 
in  the  mind  by  external  impressions  corporeally  and  necessarily 
(65,  66),  and  are  developed  by  the  mind,  so  as  to  succeed 
each  other  only  in  the  same  order  as  the  external  impressions 
succeed  each  other,  and  determine  the  conceptions  to  act, 
according  to  the  laws  of  the  vis  nervosa.  These  sensational 
conceptions  are — the  external  sensations,  imaginations,  fore- 
seeings,  &c. — the  sensational  incitements  they  contain,  and  the 
sensational  desires  and  aversions,  particularly  the  instincts 
and  passions.  External  sensations,  together  with  sensational 
pleasure  and  pain  (80),  and  the  blind  instincts  (263),  are  the 
most  directly  induced  of  all  these  by  external  impressions,  and 
are  developed  and  succeed  each  other  just  as  the  impressions 
succeed  each  other,  according  to  the  laws  of  the  vis  nervosa,  and 
develop  their  material  ideas  in  the  brain;  and  the  sentient 
actions  of  these  sensational  conceptions  are  also  developed  in 
like  manner,  (542,  543,  547,  552,  &c.)  The  remaining  sensa- 
tional conceptions,  incitements,  and  desires,  namely,  the 
imaginations,  foreseeings,  &c.,  with  their  sensational  pleasure 
and  pain  (66,  80),  and  the  passions  (305),  are  somewhat  more 
free  from  the  natural  and  necessary  influence  of  external  im- 
pressions, and  are  developed  and  succeed  each  other  more 
according  to  psychological  laws ;  nevertheless  they  are  not  to  be 
confounded  with  recollections,  expectations,  &c.  (238  249), 
considered  as  simply  imperfect  external  sensations,  and  not 
directly  dependent  on  external  impressions.  Hence  the  sentient 
actions  of  imaginations,  foreseeings,  &c.,  are  in  fact  those  of  the 
external  sensations  to  which  they  are  related  (237,  247),  and  as 
such  (as  experience  teaches)  may  be  induced  by  the  vis  nervosa 
only  (545,  547).  It  is  only  the  sentient  actions  of  the  higher 
passions,  and  of  the  higher  sensational  desires  and  aversions, 
which  are  formed  and  developed  rather  according  to  psycho- 
logical laws  than  the  laws  of  the  vis  nervosa,  and  which  cannot 
be  induced  by  it  as  nerve-actions  (573). 

ii.  The  other  class  of  conceptions  is  the  intellectual.  This 
comprises  those  perceptions  which  are  not  sensational,  the 
motives  they  contain,  and  the  desires,  aversions,  and  satisfactions 


298  ANIMAL  FORCES.  [ii. 

of  the  will.  Their  material  ideas  are  formed,  and  connected 
with  each  other,  in  the  brain,  solely  according  to  psychological 
laws,  and  their  sentient  actions  are  developed  and  succeed  each 
other  independently  of  external  impressions :  consequently, 
they  cannot  be  induced  by  the  vis  nervosa  as  nerve-actions, 
except  incidentally,  and  then  not  in  the  same  sequence  as  that 
in  which  the  mind  develops  them  (574 — 576). 

iii.  This  difference  in  the  two  classes  of  conceptions,  as 
regards  their  relations  to  external  impressions,  has  led  eminent 
men  into  the  singular  error  of  placing  the  seat  of  the  first  class 
in  the  body,  and  that  of  the  second  in  the  mind.  The  occasion 
of  the  error  is  so  obvious,  that  further  explanation  is  not 
necessary.  All  that  is  conception,  consciousness,  thought,  is  in 
the  mind  [in  der  Seele].  External  sensations  are  conceptions 
of  external  impressions  on  the  nerves;  all  sensational  concep- 
tions are  only  repetitions,  or  anticipations  of  these ;  the  feeling 
of  that  which  is  pleasing  or  displeasing  in  a  sensational  con- 
ception constitutes  sensational  pleasure  or  pain  [Unlust]  ;  hence 
are  developed  sensational  desires,  instincts,  and  passions ;  and 
although  all  these  take  place  from  the  impulse  of  external  im- 
pressions, still  it  is  always  in  the  mind  that  these  conceptions, 
pleasures,  and  desires,  are  forcibly  developed.  They  are  as 
certainly  sentient  as  the  most  voluntary  sensational  conceptions 
and  desires,  or  the  most  abstract  ideas,  and  the  noblest  motives, 
passions,  and  conclusions  of  the  will.  But  the  external  im- 
pressions which  excite  sensational  conceptions,  pleasures,  and 
passions  in  the  mind,  can,  nevertheless,  if  they  do  not  develop 
these,  excite,  by  means  of  their  vis  nervosa,  the  same  movements 
in  the  animal  economy,  and  in  the  same  order  and  series,  as  if 
they  were  excited  as  sentient  actions.  In  cases  of  this  kind, 
the  organism  performs  the  sensational  acts  of  desires,  of  instincts, 
of  passions,  without  these  being  really  in  the  mind ;  but  how 
can  it  be  inferred  from  hence  that  they  are  present  in  the 
body  ?  There  is  a  force,  it  is  true,  which  imitates  their  work- 
ings, whether  it  co-operates  with  them  or  not;  but  the  crude 
matter  cannot  feel  pleasure  and  disgust ;  or  desire,  or  shun 
anything. 


CH.  IV.]      SUBSTITUTION  OF  SENTIENT  ACTIONS.      299 

SECTION    II. ON    THE    SUBSTITUTION    OF    SENTIENT    ACTIONS   FOR 

NERVE-ACTIONS. 

580.  There  are  three  principal  kinds  of  nerve-actions  in  the 
mechanical  machines  :  firstly,  those  of  primary  internal  impres- 
sions, not  caused  by  conceptions  (419);  secondly,  those  of 
unfelt  reflected  external  impressions ;  and  thirdly,  those  of  direct 
external  impressions  (418). 

581.  The  nerve-actions  of  primary  non-conceptional  internal 
impressions  may  be  excited  by  the  impressions  of  conceptions, 
since  the  two  kinds  develop  the  same  animal  movements  (541). 
The  non-conceptional  internal  impressions  may  be  divided  into 
the  contra-natural,  to  which  class  the  experimental  belong,  and 
the  natural.  The  experimental  internal  impressions  are  those 
made  on  the  brain,  spinal  cord,  or  nervous  trunks,  by  various 
stimuli  in  experimental  researches.  There  is  no  nerve-action 
caused  by  impressions  of  this  class,  which  is  not  induced  also 
as  a  sentient  action ;  and  it  is  because  we  know  them  as  the 
latter,  that  they  surprise  us  so  much  when  excited  artificially 
(486).  Nerve-actions  are  often  excited  in  the  usual  condition 
of  an  animal,  by  contra-natural  internal  impressions,  as  when 
the  cerebral  origin  of  the  nerves,  the  spinal  cord,  or  the  trunk 
of  a  nerve  is  irritated  by  stimuli,  which  are  not  conceptions, 
and  so  cause  nerve-actions;  as,  for  example,  when  efiused 
fluid  in  the  brain  partly  paralyses,  partly  causes  spasmodic 
action  in  the  extremities ;  or  when  an  acrid  humor  is  determined 
to  the  spinal  cord ;  or  it  has  been  injured ;  or  a  tumour  or  growth 
on  nerves  causes  contra-natural  movements  in  the  parts  regu- 
lated by  the  afi'ected  nerves.  These  are  also  similar  to  move- 
ments which  occur  as  sentient  actions  in  the  natural  condition, 
or  at  least,  as  contra-natural  sentient  actions.  Thus,  a  fright 
will  paralyse  or  convulse  the  limbs,  as  much  as  a  paralytic 
stroke  from  effusion;  the  convulsions  excited  by  an  acrid 
humor  determined  to  the  nerves  are  excited  also  by  anger  or 
anxiety;  and  the  most  violent  convulsions  may  accompany 
intense  passion  in  sensitive  persons,  &c. 

582.  When  reflected  unfelt  external  impressions  produce 
nerve-actions,  they  act  in  the  same  way  as  internal  impressions, 
and  the  same  animal  movements  are  excited.  Consequently, 
the  observations  made  in  the  last  paragraph  apply  equally  to 


300  ANIMAL  FORCES.  [ii. 

them.  But  the  question  arises,  whether  the  unfelt  external 
impression,  which,  by  its  reflection  causes  an  indirect  nerve- 
action,  can,  when  felt,  excite  the  same  movement  as  a  direct  or 
indirect  sentient  action  of  its  sensation  ?  It  is  not  easy  to 
answer  this  question  without  going  into  details. 

583.  When  the  toe  of  a  decapitated  frog  is  pinched,  it 
places  its  limbs  in  a  position  for  leaping,  and  actually  leaps,  in 
consequence  of  the  indirect  nerve-action  caused  by  the  external 
impression  on  the  toe  (415,  ii) ;  and  the  question  arises  whether 
the  same  impression,  when  felt,  would  cause  the  same  leap  as 
a  sentient  action  of  the  pain  caused,  either  indirectly  or 
incidentally,  in  consequence  of  the  excitement  of  an  instinct  ? 
Probably  it  is  so,  for  a  healthy  frog  leaps  when  it  feels  the  pain 
caused  by  pinching  its  toe ;  but  in  this  case  is  the  leap  neces- 
sarily a  sentient  action  caused  by  the  pain?  for  although  it 
may  take  place  as  such  at  the  same  time  that  it  occurs  as  a 
nerve-action  (364),  still  it  does  not  follow,  that  in  the  case  of 
the  healthy  frog,  the  leap  is  so  produced.  How  can  it  be  shown, 
experimentally,  whether  it  occurs  from  the  sensation  of  the  ex- 
ternal impression,  or  from  the  impression  only?  Everything 
which  prevents  the  action  of  the  external  impression,  also 
partly  prevents  its  being  felt,  and  if  felt,  partly  prevents  the 
same  movement  being  excited  as  a  sentient  action  of  the  sen- 
sation. Other  difficulties  might  be  mentioned,  and,  in  fact, 
there  is  only  one  means  of  solving  the  problem. 

584.  The  sensational  conceptions,  namely,  imaginations, 
foreseeings,  &c.,  are  imperfect  external  sensations,  which  are  in 
relation  to  an  external  impression ;  and  their  sentient  actions 
are  the  same  as  the  actions  of  the  external  sensations,  but  are 
imperfectly  so,  since  the  external  impression  and  all  its  nerve- 
actions  are  wanting  (68 — 74).  Now,  if  an  imagination  or  fore- 
seeing of  a  sensation  excites  imperfectly  as  sentient  actions,  the 
same  movements  which  the  external  impression  of  the  sensation 
usually  excites,  as  its  indirect  nerve-action,  the  conclusion  is 
obvious,  that  the  sensation  of  the  impression  itself  will  produce 
the  same  animal  movement ;  particularly,  as  in  the  normal  con- 
dition it  always  accompanies  sensation,  which  would  not  be  the 
case  if  it  were  always  a  nerve-action  only  of  the  external  im- 
pression. Now,  the  former  proposition  is  established  by  ob- 
servation ;  and  the  latter  must  be  true,  since  it  does  not  appear 


CH.  IV.]      SUBSTITUTION  OF  SENTIENT  ACTIONS.      301 

that  any  objection  can  be  raised.  If  a  frog  could  dream,  and 
dreamed  of  a  pinching  of  its  toe,  the  imagination  would  certainly 
induce  it,  if  not  to  take  a  leap,  at  least  to  place  its  limbs  in  the 
necessary  state  of  preparation  for  leaping.  Animals  endowed 
with  sensational  conceptions  and  instincts  afford  a  thousand 
proofs  of  this  doctrine,  since  all  their  imaginations  and  fore- 
seeings  express,  although  imperfectly,  the  sentient  actions  of  the 
sensation  to  which  they  are  related;  while  many  of  these  actions 
are  at  the  same  time  nerve-actions  of  the  external  impression 
which  causes  the  sensation  (543,  545).  A  person  dreams  that 
his  finger  is  touching  red  hot  iron,  and  withdraws  his  whole 
arm,  as  if  he  really  touched  it.  This  retraction  is  the  imper- 
fect sentient  action  of  the  imagined  sensation,  and  may  occur 
as  a  nerve-action,  being  analogous  to  the  retraction  of  its  foot 
by  a  decapitated  frog,  when  its  toe  is  pinched.  Illustrations 
of  this  kind  could,  in  fact,  be  multiplied  to  any  extent  in  support 
of  the  proposition,  that  the  indirect  nerve-actions  of  external 
impressions  are,  when  the  latter  are  felt,  at  the  same  time 
direct  or  incidental  actions  of  the  sensations  of  those  impressions; 
and  that  the  feeling  itself  is  nothing  superfluous  in  the  pro- 
duction of  these  movements,  which  the  impressions  themselves 
can  excite  as  indirect  nerve-actions. 

585.  The  direct  nerve-actions  of  an  external  impression,  or 
in  other  words,  the  movements  of  irritability  (432),  can,  in 
general  be  replaced  by  sentient  actions.  Since  they  take  place 
principally  in  muscular  fibres  (445),  which  are  moved  by  all 
cerebral  forces  from  external  sensations  to  free-will  acts  in- 
clusive, the  movements  of  the  muscles  are  the  same,  whether 
they  be  nerve-actions  or  sentient  actions  (161-162);  and  no 
result  of  irritability  can  be  mentioned,  which  cannot  be  a 
sentient  action.  Innumerable  illustrations  might  be  advanced 
(445_448,  204,  229,  &c.) 

586.  But  since  the  direct  nerve-actions  of  external  impres- 
sions are  developed  at  the  point  where  the  impression  is  made 
when  it  is  not  transmitted  to  the  brain,  or,  if  transmitted  along 
the  nerves,  before  it  reaches  the  brain — the  question  arises, 
whether  the  impression  can  produce,  when  felt,  the  same  direct 
nerve-actions  it  produced  when  unfelt  ?  This  question  offers 
the  same  difficulties  as  that  mooted  in  a  previous  paragraph, 
regarding  indirect  nerve-actions. 


302  ANIMAL  FORCES.  [ir. 

587.  The  answer  must,  as  in  the  preceding  paragraph,  be 
deduced  from  a  consideration  of  the  sensational  conceptions, 
and  mutatis  mutandis,  the  line  of  argument  is  the  same.  When 
we  imagine  that  we  have  swallowed  an  emetic,  and  the  imagi- 
nation excites  retching  and  vomiting,  as  if  an  emetic  had  been 
really  taken,  the  conclusion  is  obvious,  that  the  felt  external 
impression  on  the  stomach  of  such  an  emetic,  or  its  felt  nerve- 
actions  (413),  must  have  produced  the  same  movement,  namely, 
vomiting,  as  a  sentient  action  of  the  external  sensation  at  the 
irritated  point,  which  the  same  external  impression  had  excited 
there  at  the  same  time,  as  a  direct  nerve-action.  This  occurs 
also  when  purgation  takes  place,  simply  from  dreaming  that  a 
purgative  has  been  taken;  when  we  shiver  from  the  imagination 
of  intense  cold;  when  suffusion  and  blue  marks  take  place,  at  the 
spot  where  we  dream  that  we  have  received  a  blow,  pinch,  &c. 

588.  Although  the  direct  nerve-actions  of  external  impres- 
sions, or  in  other  words  the  results  of  irritability  (432),  do  not 
require  the  co-operation  of  the  cerebral  forces  for  their  produc- 
tion, still,  in  cases  where  the  impression  is  felt,  they  may  occur 
also  as  sentient  actions  of  the  sensation.  Consequently,  it 
would  be  erroneous  to  conclude,  that  a  result  of  irritability 
could  not  be  at  another  time  a  sentient  action  of  the  sensation 
caused  by  the  irritant,  or  that  it  may  not  depend  on  sensibility. 
This  conclusion  can  only  be  made  when  the  external  impression 
which  causes  the  movement  is  not  felt  nor  cannot  be. 

589.  We  conclude  therefore,  that  all  nerve-actions  of  non- 
conceptional  internal  impressions  can  be  altogether  replaced  by 
sentient  actions,  that  is  to  say,  induced  by  internal  impressions 
caused  by  conceptions  (581).  With  reference  particularly  to 
those  excited  directly  by  external  impressions,  it  may  be  stated, 
that  they  are  developed  as  sentient  actions  by  the  external 
sensation  of  the  external  impressions  which  excite  them  (584, 
588). 


SECTION  III. THE  RECIPROCAL  CONNECTION  OF  THE  ANIMAL- 
SENTIENT  [cerebral]  FORCES  WITH  THE  VIS  NERVOSA  IN 
THE    NATURAL  STATE. 

590.  When  an  external  impression  is  not  felt,  and  a  primary 
internal  impression  is  not  excited  by  conceptions,  the  movements 


CH.  IV.]  RELATION  OF  CEREBRAL  &  NERVE  FORCES.  303 

resulting  from  either  are  only  nerve-actions,  since  they  cannot 
be  also  at  the  same  time  sentient  actions  (97),  and  there  are 
no  other  animal  forces  than  the  vis  nervosa  (356),  inasmuch  as 
in  this  case  it  does  not  signify,  whether  the  unfelt  external  im- 
pression can  be  felt  or  not ;  or  whether  the  primary  internal 
impression  not  caused  by  conceptions  can  be  caused  by  con- 
ceptions or  not.  It  follows,  that  no  combined  action  of  the 
cerebral  forces  and  vis  nervosa  effects  these  animal  movements, 
even  in  sensational  and  thinking  animals,  and  a  fortiori  in  those 
which  have  no  sensational  faculty,  and,  consequently,  no  mind. 
Since  the  latter  class,  in  common  with  all  animals,  without 
exception,  are  endowed  at  least  with  the  vis  nervosa,  it  alone 
must  be  sufficient  for  all  the  objects  of  their  existence.  According 
to  this  view,  the  acts  of  all  anencephalous  [hirnlosen]  animals 
(to  all  which,  as  far  as  can  be  observed,  they  are  excited  by 
external  impressions),  are  partly  direct  nerve-actions,  partly 
dependent  on  the  reflexion  of  the  impressions  in  the  ganglia 
and  plexuses,  and  thereby  are  rendered  similar  to  sentient 
actions  and  volitional  acts  (438-439) ;  while,  on  the  other  hand, 
their  vital  movements  and  the  indispensable  functions  of  their 
mechanical  machines,  are  maintained  by  non-conceptional  im- 
pressions, as  occurs  in  sensational  animals  (515,  519,  525,  532). 
These  views  apply  also  to  the  acts  of  sensational  animals,  in  as 
far  as  the  impressions  which  excite  them  are  unfelt,  or  not 
induced  by  conceptions,  for  as  they  all  possess  the  two  kinds 
of  vis  nervosa,  the  acts  must  necessarily  be  nerve-actions,  inas- 
much as  the  mind  cannot  act  (353,  356). 

591.  When  an  external  impression  is  felt,  the  resulting 
animal  movements  are  both  nerve-actions  of  its  vis  nervosa  and 
sentient  actions  of  its  external  sensations.  The  first — because 
they  equally  result,  even  if  the  sensation  be  wanting  (542 — 547): 
the  last — because  the  sensation  of  an  external  impression 
excites  material  ideas  at  the  cerebral  origin  of  the  sensitive 
nerves;  the  internal  impression  thus  caused  is  transmitted  down- 
wards, and  excites  movements  in  those  machines  to  which  the 
nerve  is  distributed,  and  these  are  the  direct  sentient  actions  of 
the  external  sensation,  and  identical  with  the  direct  or  indirect 
nerve-action  of  the  external  impression,  which  gave  rise  to  the 
sensation  (418,  419,  358).  But  since  the  transmission  of  the 
internal  impression,  caused  })y  a  material  external  sensation. 


304  ANIMAL  FORCES.  [ii. 

may  be  prevented  by  natural  obstacles,  and  thus  the  movements 
may  never  take  place  (136 — 139),  it  follows  that  animals  may, 
in  the  natural  state,  exhibit  direct  or  indirect  nerve-actions  of 
external  impressions,  which  never  occur  as  sentient  actions  of 
their  external  sensation,  and  never  can.  Direct  physiological 
illustrations  are  almost  impossible,  for  the  reasons  stated,  §§  583 
and  586,  and  the  proofs  can  only  be  argumentative.  The 
morbid  condition  affords  an  illustration  in  those  cases  in  which 
a  limb,  still  possessed  of  sensation,  cannot  be  excited  to  those 
movements  by  external  impressions,  of  which  in  a  natural  con- 
dition it  is  capable  (127). 

592.  When  an  internal  impression  depends  on  sensational 
conceptions,  as  imaginations,  foreseeings,  feelings  [Reizungen], 
desires,  aversions,  instincts,  instinctive  emotions,  and  various 
passions,  the  movements  it  excites  are  both  sentient  actions  of 
the  conceptions  and  nerve-actions  of  the  external  impression 
that  causes  the  external  sensation  upon  which  they  depend. 
They  are  nerve-actions,  because  they  can  be  excited  when  there 
is  no  sensation;  they  are  sentient  actions,  because  all  these 
sensational  conceptions  develop  no  other  sentient  actions  than 
movements  that  are  identical  with  those  excited  by  the  external 
sensation  itself.  The  probable  object  of  nature,  in  thus  uniting 
the  action  of  the  cerebral  forces  and  of  the  vis  ne^^vosa,  in  the 
movements  of  external  sensations,  and  of  sensational  conceptions, 
desires,  and  aversions,  has  been  already  referred  to  (184,  ii, 
370,  371). 

593.  When  an  internal  impression  arises  from  the  higher 
passions,  from  intellectual  conceptions  and  motives,  and  from 
desires  and  aversions  of  the  will  and  their  satisfaction,  the 
movements  it  excites,  in  so  far  as  these  intellectual  conceptions, 
&c.,  are  unmingled  with  sensational  conceptions,  are  solely 
sentient  actions,  and  there  is  no  combined  action  of  the  cere- 
bral forces  and  the  vis  nervosa  in  their  production.  They  are 
not  dependent  on  any  external  impression,  and  consequently 
cannot  be  nerve-actions  induced  by  the  vis  nervosa,  and  the  only 
other  animal  forces  are  the  cerebral  (353 — 356).  Nature  has 
granted  this  higher  species  of  conceptions  to  the  most  perfect 
animals  only,  whose  souls  are  not  simply  sensational  [Sinnlich] , 
but  spiritual  [Geister],  (Baumgarten^s  ^  Metaphysics,^  §'  590). 

594.  Those  err  who  conclude,  that  because  an  animal  per- 


CH.iv.]  RELATION  OF  CEREBRAL  &  NERVE  FORCES.  305 

rms  animal  acts,  it  must  necessarily  therefore  be  endowed  with 
cerebral  forces,  or  with  a  soul,  or  with  will ;  for  it  is  undeniably- 
possible,  that  the  vis  nervosa  alone  can  cause  the  greater  num- 
ber of  the  animal  acts  (590).  The  majority  of  philosophers 
have  been  led  by  this  error  to  consider  all  animals  without 
exception  as  endowed  with  souls ;  but  it  is  highly  probable,  that 
many  have  neither  consciousness  nor  feeling. 

595.  It  cannot  be  correctly  inferred,  that,  because  in  a 
sensitive  or  thinking  animal,  movement  is  excited  in  virtue  of 
irritability,  or  by  the  vis  nervosa  of  external  impressions  gene- 
rally, it  cannot  be  a  sentient  action  of  the  external  sensation 
caused  by  the  impression ;  or,  vice  versa,  that  because  it  is  a 
sentient  action  of  the  external  sensation  of  an  external  im- 
pression, it  cannot  be  a  nerve- action  of  the  impression  only. 
The  first  is  the  error  of  some  recent  writers,  who,  since  Haller 
recognised  the  agency  of  the  vis  nervosa  of  external  impressions 
in  exciting  direct  nerve-actions,  and  taught  it  under  the  term 
irritability,  wished  to  maintain,  that  all  animal  movements  not 
resulting  from  volition  are  dependent  on  irritability,  and 
erroneously  deny  those  dependent  on  sensation.  The  latter 
error  is  that  of  the  Stahlians,  when  they  maintain,  that  in  ex- 
ternal sensations  the  body  is  purely  passive,  and  does  not  co- 
operate by  means  of  its  own  proper  forces. 

596.  It  cannot  be  correctly  inferred,  that  because  in  a 
sensitive  or  thinking  animal  the  movements  which  accompany 
the  sensational  conceptions,  incitements,  desires,  aversions,  &c., 
are  sentient  actions,  for  this  reason  they  cannot  be  nerve- 
actions  j  and  vice  versa,  that  they  cannot  be  sentient  actions  of 
these  sensational  conceptions  (592).  From  this  error,  taken  in 
connection  with  the  second  mentioned  in  the  preceding  para- 
graph, the  old  error  has  probably  arisen,  and  which  the  author 
of  the  article  '^Sensibilite,^^  in  the  'Dictionnaire  Encyclopedique' 
has  lately  reproduced,  namely,  that  there  are  two  kinds  of  souls 
in  reasoning  animals,  the  one  being  the  rational  soul,  by  which, 
sentient  actions  are  developed  according  to  psychological  laws; 
and  the  other  a  sensational  soul,  by  which  the  sentient  actions 
of  the  external  sensations  and  other  sensational  conceptions  are 
developed  according  to  the  laws  of  the  vis  nervosa.  We  have 
shown,  however,  that  to  the  action  of  the  latter  no  soul  is 
necessary. 

20 


306  ANIMAL  FORCES.  [ii. 

597.  Lastly,  those  also  are  in  error,  who  conclude  that 
because  an  animal  performs  movements,  which  are  effected  by 
the  cerebral  forces  alone,  without  the  co-operation  of  the  vis 
nervosa,  all  its  animal  forces  are  actions  of  the  cerebral  forces 
(590,  593).  This  is  the  error  of  the  Stahlians,  who  consider 
all  animal  movements  to  be  sentient  actions,  nay,  to  be  medi- 
tated acts  of  a  will,  of  which  the  soul  is  necessarily  unconscious. 
The  old  error,  lately  renewed  by  Whytt,  is  also  connected  with 
this  erroneous  supposition,  namely,  that  the  souls  of  animals  are 
distributed  throughout  their  bodies  by  means  of  the  nerves, 
because  animal  movements,  which  are  usually  sentient  actions, 
can  be  excited  in  decapitated  animals,  thus  assuming  that  no 
other  force  than  the  mental  can  effect  this. 


PAET   III. 

ANIMAL  NATURE  CONSIDERED  AS  A  WHOLE. 


INTRODUCTION. 

598.  The  cerebral  forces  and  the  vis  nervosa  are  essential 
constituents  of  the  proper  animal  nature  of  animal  organisms 
(6,  356)^  and  in  the  more  perfect  animals  are  in  close  connection 
(591 — 593).  The  aggregate  of  those  animal  forces,  which  act  na- 
turally in  connection  in  an  animal  body,  constitute  its  whole 
animal  nature,  and  this  whole  is  now  to  be  considered;  its  two 
essential  constituents  even  in  the  most  perfect,  having  been  dis- 
cussed in  the  two  preceding  parts. 

599.  The  arrangement  of  this  part  is  as  follows  : — first,  the 
character  of  the  whole  animal  nature  of  an  animal  will  be 
sketched  ;  secondly,  the  existence  of  distinct  classes  of  animals 
will  be  proved ;  then  the  origin  of  animals  according  to  their 
nature  will  be  considered ;  next,  animal  life  and  its  natural 
periods  up  to  its  full  development ;  then  the  system  of  forces 
necessary  to  animal  life,  or  how  they  act  with  and  through  each 
other  for  its  maintenance  and  perfection ;  and,  finally,  old  age 
and  death  will  be  treated  of  in  succession. 


I 


CHAPTER  I. 

ON  ANIMAL  NATURE  IN  GENERAL. 

600.  An  organism,  which,  in  its  entire  and  natural  condition^ 
is  regulated  by  the  animal  moving  forces  of  its  own  proper 
animal  machines,  is  termed  a  living  animal  organism^  an  animal 
endowed  with  life,  an  animal  in  the  widest  sense.  In  deter- 
mining the  general  characteristic  distinction  of  plants  and 
animals,  by  which  we  decide  whether  an  organism  belongs  to 
the  one  or  the  other  division,  we  have  to  determine  whether  it 
is  moved  in  its  natural  condition,  according  to  the  known 
physical  or  mechanical  laws  of  gravity,  of  the  force  of  attrac- 
tion, of  elasticity,  of  the  mechanism  of  its  structure,  &c. ;  or, 
according  to  peculiar  laws : — whether  a  touch,  or  an  external 
impression  upon  it,  excites  it  to  the  movement  that  we  should 
be  led  to  expect  from  the  known  physical  and  mechanical  laws 
of  motion,  or  whether  a  movement  is  excited  thereby,  which 
compels  us  to  recognise  the  phenomena  of  a  peculiar  force  put 
into  action  by  this  external  impression ;  and  which  regulates  it 
according  to  other  and  widely  different  laws.  It  is  not  denied 
that  this  distinction  is  always  somewhat  indefinite,  still  it 
exists  in  nature,  and  we  universally  form  a  judgment  thereon ; 
but  we  only  become  more  definite,  when  we  have  become 
acquainted  with  the  laws  of  the  animal  moving .  forces.  If 
some  persons  distinguish  animals  from  plants  by  their  volun- 
tary movements,  others  by  their  instinctive  actions,  and  others 
by  their  external  sensations,  it  all  comes  to  the  same  thing; 
inasmuch  as  we  recognise  a  moving  force  in  animals  differing 
altogether  in  its  nature  from  physical  and  mechanical  forces, 
and  acting  according  to  altogether  different  laws.  But  these 
distinctions  are  wholly  deduced  from  the  phenomena  of  the  cere- 
bral forces,  while  the  nerves  themselves  possess  peculiar  animal 
forces,  which  are  not  taken  into  consideration;  so  that  they  who 
adopt  this  as  an  universal  distinction,  are  at  a  loss  when  they 
come  to  decide,   whether  a  certain    organism  which   cannot 


310  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

possibly  be  endowed  with  cerebral  forces^  be  a  plant  or  an 
animal.  Hence  the  confusion  of  ideas,  caused  by  the  researches 
on  decapitated  animals,  moved  solely  by  the  vis  nervosa, — by 
the  phenomena  of  anencephalous  infants  bom  alive — and  by 
animals  so  constituted  by  nature,  as  to  live  without  head  or 
brain,  and  which  manifest  no  traces  of  mind;  regarding  all 
which  no  definite  opinion  can  be  stated.  If,  however,  the  above 
general  distinction  be  adopted,  no  difficulty  arises  in  such  cases ; 
for,  although  entirely  without  conceptions,  all  these  organisms 
are  regulated  by  external  impressions,  in  a  way  wholly  different 
from  plants,  and  according  to  wholly  different  laws.  Now, 
since  we  recognise  the  existence  of  the  vis  nervosa  of  external 
impressions  in  animal  machines  [the  brain  and  nerves],  and 
know  that  it  is  adapted  to  sentient  animals,  and  excites  in  them 
the  same  movements,  according  to  the  same  peculiar  laws  as 
external  impressions  excite  in  these  organisms;  and  since  we 
find  machines  in  the  latter,  which  are  very  similar  to  the 
animal  machines  [brain  and  nerves]  of  sentient  animals,  we 
can  positively  decide,  that  all  these  organisms  are  moved 
animally  by  nature,  by  means  of  animal  machines,  and  that 
they  also  belong  to  the  class  of  animal  bodies. 

601.  Still,  as  has  been  said,  the  line  of  distinction  is  always 
indefinite,  and  the  limits  of  the  animal  and  vegetable  kingdoms 
run  so  into  each  other,  that  they  cannot  be  defined.  The 
fault,  however,  is  not  in  the  want  of  grounds  of  distinction, 
but  in  the  difficulty  of  discovering  them  in  many  cases.  The 
movements  excited  in  the  sensitive  plant  by  a  touch,  leads  us 
to  the  conclusion  that  it  is  a  zoophyte;  so  fixed  is  the  principle 
in  us,  that  an  organism  must  be  an  animal  which  is  moved  by 
certain  impressions — not  according  to  physical  and  mechanical 
laws — but  according  to  the  laws  of  movement  in  animals.  But 
these  movements  are  neither  sentient  actions  nor  nerve-actions, 
for  upon  investigating  the  structure  of  the  leaf,  it  is  found  that 
the  closing  of  the  leaves  is  simply  a  mechanical  action,  excited 
by  a  touch. 

602.  The  question  may  arise,  however,  whether  a  body  may 
not  be  animal  in  its  nature,  and  yet  not  be  an  animal ;  as,  for 
example,  in  the  case  of  a  decapitated  animal.  A  man,  deprived 
of  his  limbs,  is  not  the  less  a  man ;  and  so  if  the  vis  nervosa 
continue  in  a  mutilated  creature,  it  is  still  an  animal.    Besides, 


cu.  I.]  ANIMAL  NATURE  IN  GENERAL.  311 

our  definition  is  based  on  the  condition,  that  the  organism  be 
entire,  and  in  its  natural  state.  A  decapitated  animal  is  a 
living  animal  body,  and  not  a  living  animal. 

603.  A  living  animal  is  regulated  in  its  natural  state  by  the 
animal  moving  forces  of  its  own  animal  machines.  These  are 
the  analogues  of  our  nerves  and  our  brain,  at  least  we  know 
of  no  other;  and  their  animal  forces  are  the  impressions  of  which 
they  are  susceptible,  when  touched,  or  when  a  movement  is 
communicated  to  them  (31,  32,  121).  Further,  every  living 
animal  is  regulated,  either  by  the  vis  nervosa,  or  by  the  cere- 
bral forces,  or  by  both  (356) .  If  by  cerebral  forces,  then  it  is 
by  means  of  external  sensations  and  conceptional  impressions 
(65,  121),  and,  consequently,  also  by  the  vis  nervosa  of  the 
external  and  internal  impressions  (35,  32,  358,  360).  That  the 
vis  nervosa  alone  regulates  living  animals  is  fully  proved  in  the 
Second  Part.  Now,  since  the  cerebral  forces  imply  the  action 
of  a  conceptive  force,  or  mind,  it  follows  that  the  animals 
endowed  with  the  former  have  also  the  latter,  or  are  sentient 
animals;  while  those  which  are  regulated  solely  by  the  vis 
nervosa  are  insentient,  or  simply  living  animals. 

604.  Every  insentient  animal  must  possess  nerves,  or  their 
analogues,  to  which  the  vis  nervosa  is  adapted  by  nature.  But 
since  their  external  impressions  are  not  felt,  and  their  internal 
impressions  never  produced  by  conceptions,  and  as  they  require 
no  animal  sentient  forces,  it  follows,  that  in  so  far  as  the  brain 
is  the  seat  of  the  latter,  and  of  mind,  or  the  conceptive  force,  it 
may  be  entirely  wanting,  and  yet  they  may  perform  all  the 
acts  necessary  to  their  existence. 

605.  Every  sentient  animal  must  not  only  be  endowed  with 
mind,  or  the  conceptive  force,  but  also  with  the  vis  nervosa 
and  nerves,  and  with  the  cerebral  forces  and  a  brain :  if  the 
soul  be  spiritual,  that  is  to  say,  if  the  animal  be  endowed  with 
understanding  and  will  (574),  it  is  termed  a  reasoning  animal, 
but  if  the  soul  be  simply  sensational,  then  the  animal  is  a 
sensational  or  unreasoning  animal  (a  brute) . 

606.  Insentient  animals  are  moved  solely  by  means  of  the 
nerves;  and  if,  also,  in  sentient  animals,  the  cerebral  forces  do  not 
act,  still  the  greater  number  of  their  vital  movements,  natural 
functions,  and  sentient  actions,  can  be  produced  by  the  vis 
nervosa  ;  and  when  in  such  the  brain  does  co-operate,  it  is  by 


312  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

means  of  its  vis  nervosa  (373,  374),  and  not  by  the  animal- 
sentient  forces.  But,  on  the  other  hand,  when  the  latter  act 
on  the  body,  they  are  excited  into  action  by  the  conceptive 
force  (Baumgarten's  ^Metaphysics',  §  554). 

607.  The  vis  nervosa  is  distributed  to  every  portion  of  a 
nerve  (31).  The  seat  of  the  animal-sentient  forces  is  in  the 
brain,  or  the  nerves  dependent  on  it  (25).  The  seat  of  the 
animal-moving  forces  in  insentient  animals  is  in  their  nervous 
system,  and  this  is  the  case  with  sentient  animals,  in  so  far  as 
they  also  possess  the  nature  of  the  insentient.  But  the  seat  of 
the  animal-moving  forces  of  sentient  animals,  peculiarly  as  such, 
is  in  the  brain,  the  seat  of  mind  (10). 

608.  All  the  animal  movements  of  an  insentient  animal  Eire 
dependent  on  the  vis  nervosa,  and  all  the  animal  acts  take 
place  according  to  its  laws  of  action.  This  is  the  case  also  with 
sentient  animals,  in  so  far  as  their  movements  are  dependent 
on  the  vis  nervosa;  but  in  so  far  as  they  are  sentient  actions  of 
those  conceptions  which  the  conceptive  force  forms  and  de- 
velops in  the  mind,  according  to  psychological  laws,  indepen- 
dently of  the  vis  nervosa,  they  flow  from  the  cerebral  forces, 
which  the  conceptive  force  regulates  (6).  But  if  the  movements 
be  both  sentient  actions  and  nerve-actions,  they  follow  the 
laws  of  both  kinds  of  forces  acting  in  co-operation  (Part  II, 
Chap.  IV,  Sect.  in.     Compare  also  §  579). 

609.  Insentient  animals  are  moved  animally  by  the  vis  ner- 
vosa of  external  or  internal  impressions,  according  to  their 
nature  (31,  32, 121).  The  external  impressions  act  upon  them, 
either  by  means  of  direct  nerve-actions  (418),  or  indirect;  when 
they  are  reflected  in  the  ganglia,  or  points  of  division  of  the 
nerves,  along  which  they  pass  upwards  upon  other  nerves,  and 
thereby  put  the  organs  to  which  the  latter  are  distributed  into 
motion  (419,  421).  Nature  herself  causes  in  insentient  animals 
such  external  impressions  as  are  necessary  to  the  maintenance 
in  them  of  those  animal  acts  on  which  their  preservation  and 
the  objects  of  their  existence  depend;  and  to  this  end  their 
animal  acts  are  as  adaptively  excited,  arranged,  and  connected 
with  each  other,  as  in  sentient  animals  by  means  of  their 
natural  instincts  (435 — 439),  although  neither  the  sentient  nor 
insentient  act  from  consciousness  (266).  The  natural  primary 
internal  impressions,  in  insentient  animals,  excite  those  move- 


CH.  I.]  ANIMAL  NATURE  IN  GENERAL.  313 

ments  which  either  cannot  be  caused  by  external  stimuli,  or 
else  require  the  co-operation  of  others  that  they  may  go  on 
uninterruptedly;  their  continuance  being  necessary  to  the  main- 
tenance of  life  in  the  animal.  Consequently,  they  are  to  be 
particularly  observed  in  the  vital  movements  and  in  the  viscera, 
the  functions  of  which  are  the  most  necessary  to  the  preserva- 
tion of  the  animal  (515,  525,  532).  The  stimuli  to  the  move- 
ments thus  induced,  being  deeply  hid  in  the  interior  of  the 
medulla  of  the  nerves,  and  traceable  to  no  external  cause,  we 
infer  erroneously  that  the  movements  themselves  are  the  re- 
sult, either  of  obscure  sensations,  or  of  other  and  volitional 
conceptions. 

610.  The  movements  necessary  to  existence,  preservation, 
and  other  objects  of  nature,  in  insentient  animals,  are  effected 
wholly  in  them  by  means  of  the  vis  nervosa,  and  in  some  degree 
in  the  same  way  as  in  sentient  animals;  so  that  they  are  capable 
of  movements,  which  experience  and  observation  prove  may  be 
effected  without  the  co-operation  of  the  cerebral  forces ;  that  is 
to  say,  they  are  capable  of  muscular  action,  and  the  appa- 
rently voluntary  movements,  the  movements  of  the  heart,  and 
the  circulation  of  the  fluids  ;  the  arterial  pulse ;  the  flow  of 
humors  to  an  irritated  part ;  the  movements  of  the  diaphragm ; 
the  animal  mechanism  of  respiration ;  digestion  and  peristaltic 
action ;  glandular  secretion  and  excretion  ;  and  the  animal 
functions  of  the  lungs, — of  the  liver  in  the  secretion  and  excre- 
tion of  the  bile, — of  the  kidneys  and  urinary  bladder  in  the 
secretion  and  excretion  of  urine, — and  of  the  sexual  organs  in 
the  propagation  of  the  species  (445 — 481,  507 — 540) . 

611.  Insentient  animals  can  also  excite,  by  the  vis  nervosa 
alone,  according  to  its  animal  laws,  all  those  animal  movements 
which  are  excited  in  sentient  animals  by  means  of  the  animal- 
sentient  forces  of  the  sensational  faculty  [Sinnlichkeit]  ;  de- 
veloping them  in  the  same  order,  connecting  them  with  each 
other  in  the  same  way,  and  just  as  consecutively  as  when  the 
movements  constitute  sentient  actions  of  sensational  concep- 
tions; that  is  to  say,  the  vis  nervosa  excites  the  same  move- 
ments in  insentient  animals,  as  constitute  the  sentient  actions 
of  external  sensations  (433,  439) ;  of  imaginations  and  of  fore- 
seeings;  of  sensational  desires,  aversions,  and  instincts;  namely, 
of  the  alimentative  instinct,  of  the  instincts  for  volitional  move- 


314  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

ments,  for  repose  and  playfulness,  for  combat,  for  self-defence, 
for  propagation  of  the  species  and  care  of  offspring  ;  and  of  the 
instinctive  emotions,  as  rapacity,  revenge,  lasciviousness,  and  all 
the  passions  closely  allied  to  them  (542 — 573).  On  the  other 
hand,  the  sentient  actions  of  sentient  animals,  which  arise  as 
free-will  movements,  from  desires,  aversions,  and  passions,  de- 
veloped in  the  mind  according  to  psychological  laws  (564 — 573), 
or  from  pleasing  or  displeasing  conceptions  of  the  understand- 
ing, or  from  desires  or  aversions  of  the  will  (564,  576),  cannot 
be  developed  in  insentient  animals  by  means  of  the  vis  nervosa, 
unless  there  be  a  sensational  element  in  the  conceptions  them- 
selves (578). 

612.  Since  sentient  animals  are  endowed  with  the  vis  ner- 
vosa, in  common  with  the  insentient,  and  which  sometimes  acts 
in  them  alone,  sometimes  in  connection  and  in  harmony  with 
the  cerebral  forces,  they  are  capable,  under  certain  conditions, 
of  all  those  movements  of  which  insentient  animals  are  capable. 

613.  Sentient  animals  are  moved  according  to  their  nature, 
not  only  by  the  vis  nervosa,  but  by  the  forces  of  material  ideas 
in  the  brain.  These  material  ideas  are  those  either  of  external 
sensations,  and  other  sensational  conceptions  and  desires,  or  of 
intellectual  conceptions  :  the  former  are  regulated  according  to 
the  laws  of  the  vis  nervosa,  the  latter  according  to  the  psycholo- 
gical laws  of  the  conceptive  force.  By  means  of  these  cerebral 
forces  of  conceptions,  the  movements  iu  sentient  animals  in  the 
natural  condition  are  developed,  arranged,  and  changed,  in  ac- 
cordance with  the  conceptions  in  their  mind :  this,  however,  is 
so  done,  that  in  purely  sensational  animals,  and  in  the  reason- 
ing animals  also,  in  so  far  as  their  sensational  conceptive  force 
acts,  the  conceptions  are  caused  and  connected  in  the  mind  by 
means  of  the  vis  nervosa  of  external  impressions.  On  the  other 
hand,  they  arise  and  are  linked  together  in  rational  animals, 
when  the  conceptive  force  acts  solely  according  to  psychological 
law  (60,  i,  579,  i,  ii). 

614.  Purely  sensational  animals  are  capable  of  all  the  vital 
actions  just  enumerated  in  §  600  (compare  161 — 179,  207,  &c), 
in  virtue  of  the  cerebral  force  of  the  sensational  material  ideas, 
which  external  impressions  excite  and  connect  in  the  brain,  and 
which  develop  the  vital  actions  as  sentient  actions. 

615.  Purely  sensational  animals  perform  as  sentient  actions, 


CH.  I.]  ANIMAL  NATURE  IN  GENERAL.  315 

by  means  of  various  external  sensational  conceptions,  and 
enumerated  in  §  611,  those  animal  movements  which,  although 
they  can  be,  and  often  are,  in  unreasoning  animals,  mere  nerve- 
actions,  can,  nevertheless,  be  developed,  arranged,  and  modified 
by  the  cerebral  forces  solely  (581 — 592). 

616.  Reasoning  animals,  in  addition  to  the  preceding,  are 
capable  of  performing  as  sentient  actions  all  movements  vrhich 
the  higher  emotions,  intellectual  pleasure  or  suffering,  and 
the  desires,  aversions,  and  satisfyings  of  the  will  develop 
through  the  free-will  movements;  and  this  by  means  of  the 
cerebral  force  of  the  material  ideas  connected  with  the  under- 
standing and  the  will.  And  since  these  animal  monements  are 
neither  sensational  actions,  nor  nerve-actions  (336,  593),  they 
are  the  peculiar  privilege  of  reasoning  animals,  and  distinguish 
them  from  all  others. 

617.  The  animal  nature  (1)  of  an  insentient  animal  is  the 
aggregate  of  its  two  kinds  of  vis  nervosa :  that  of  a  sentient 
animal  is  the  aggregate  of  its  two  kinds  of  vis  nervosa  and  its 
cerebral  forces ;  and  implies  also  the  animal  nature  of  the 
insentient.  The  animal  nature  of  a  purely  sensational  animal, 
is  the  aggregate  of  its  two  kinds  of  vis  nervosa,  and  of  the 
cerebral  forces  of  its  sensational  conceptions,  desires,  &c.  The 
animal  nature  of  a  reasoning  animal  is  the  aggregate  of  the 
cerebral  force  of  sensational  and  intellectual  conceptions  and 
desires,  &c.,  and  presupposes  the  nature  of  the  sensational 
animal,  which  includes  that  of  the  insentient  animal. 

618.  The  animal  natures  of  all  other  animals  are  conjoined 
in  a  reasoning  animal,  as  well  as  the  two  essential  principles 
[principien]  of  all  animal  movements,  namely,  the  vis  nervosa 
and  the  cerebral  forces.  The  physician  need  not  seek  to  explain 
the  mode  in  which  the  vis  nei^vosa  excites  sensational  concep- 
tions and  desires,  and  in  which  these,  together  with  those  of  the 
intellect,  excite  animal  movements,  for  it  is  inexplicable :  con- 
sequently he  need  not  investigate  psychological  explanations  of 
the  union  of  body  and  soul;  or  the  hypothesis  of  physicians  as 
to  the  nature  of  the  vital  spirits,  of  the  medulla  of  the  brain  and 
nerves,  and  of  material  ideas ;  his  business  is  with  general  facts, 
from  whence  he  must  deduce  his  principles  of  theory  and  prac- 
tice. The  whole  physiology  of  animal  nature  must  be  based 
upon  the  following  general  principles  : 


316  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

i.  The  nerves  receive  external  impressions  in  a  manner 
peculiar  to  themselves ;  that  is^  according  to  their  peculiar  laws, 
which  accord  with  neither  the  physical  nor  mechanical  laws  of 
any  other  bodies,  than  animal  bodies ;  these  impressions  are 
transmitted  along  the  nerves  to  the  brain,  and  laterally  by  means 
of  branches  or  ganglia  to  other  nerves,  and  thereby  become 
animal-motor  forces  of  the  mechanical  machines  with  which  the 
nerves  are  incorporated,  as  well  as  animal-sentient  forces  by 
means  of  the  brain,  for  the  development  of  external  sensations 
and  sensational  conceptions,  desires,  aversions,  instincts,  &c., 
which  are  developed  and  connected  with  each  other  in  the  mind, 
according  to  the  animal  laws  of  the  vis  nervosa  of  the  external 
impressions. 

ii.  The  conceptions  of  the  mind  communicate  internal  im- 
pressions to  the  brain,  which  it  receives  in  a  peculiar  manner, 
according  to  the  laws  of  its  own  peculiar  animal-sentient  forces, 
and  transmits  along  the  nerves,  whose  cerebral  origins  these  con- 
ceptions excite,  to  the  mechanical  machines  in  which  the  nerves 
are  distributed,  or  along  their  branches,  or  by  means  of  their 
ganglia  along  other  nerves  going  to  mechanical  machines,  and 
thereby  the  impressions  become  motor  animal-sentient  forces  of 
these  machines,  and  are  developed  and  connected  with  each 
other  in  them,  according  to  the  psychological  laws  of  the  con- 
ceptive  force ;  but  which  are  themselves  nevertheless  necessarily 
regulated  in  the  sensational  conceptions,  by  the  animal  laws  of 
the  vis  nervosa  of  external  impressions. 

iii.  The  vis  nervosa  of  external  impressions  can  produce  all 
the  sentient  actions  which  sensational  conceptions  excite,  even 
if  the  conceptions  themselves  do  not  ensue. 

iv.  The  animal-sentient  forces  can  reproduce  the  nerve- 
actions  of  impressions,  when  the  impressions  themselves  do  not 
actually  take  place. 

V.  Lastly,  the  movements  excited  by  unfelt  external  im- 
pressions are  purely  nerve-actions  :  those  excited  by  the  higher 
passions,  intellectual  conceptions,  desires,  aversions,  and  satis- 
fyings  of  the  will,  are  purely  sentient  actions,  and  all  others  are 
excited  by  the  combined  operation  of  the  animal-sentient  forces 
and  the  vis  nervosa. 


CHAPTER  II. 

THE  PRINCIPAL  GENERA  OF  EXISTING  ANIMALS. 

619.  Man  is  an  example  of  a  reasoning  being,  and  all  the 
principal  forms  of  existing  animals  are  combined  in  him,  namely, 
the  insentient,  the  sensational,  and  the  reasoning;  he  is  also 
capable  of  all  the  animal  functions  proper  to  these. 

620.  The  nature  of  a  reasoning  being  implies  the  presence 
of  the  natures  of  merely  sensational  and  insentient  animals,  but 
the  last  two  do  not  necessarily  require  the  former.  There  is  a 
great  number  of  sentient  but  purely  sensational  beings,  endowed 
with  neither  understanding  nor  will;  and  even  a  reasoning  being 
may,  by  poisons  or  disease,  or  in  the  early  periods  of  life,  exist 
only  as  a  purely  sensational  animal,  without  any  use  of  the 
reason  or  the  will,  and  usually  capable  only  of  those  functions, 
of  which  purely  sensational  and  insentient  animals  are  capable 
(612—615). 

621.  A  sentient  animal  may  be  entirely  deprived  of  its  animal 
sentient  forces  (for  by  separating  the  head  from  the  body,  the 
brain  and  soul  are  removed),  and  yet  may  live  for  some  time  as 
an  insentient  animal,  and  continue  all  those  functions  of  which 
as  an  insentient  animal  it  is  capable.  But  do  true  insentient 
animals  exist  ?  We  will  state  the  arguments  for  the  affirma- 
tive and  negative,  leaving  the  reader  to  decide. 

622.  It  is  unquestionable  that  every  animal  does  not  require 
to  have  a  soul :  the  definition  that  an  animal  is  a  whole  com- 
pounded of  soul  and  body  is  a  petitio  principiij  for  no  one  has 
ever  proved  that  a  soul  is  requisite,  and  we  therefore  base  one 
false  proposition  upon  another.  Many  eminent  men  have 
doubted,  whether  unreasoning  animals  possess  a  soul;  although 
like  others  they  have  been  educated  in  the  dogma,  that  body  and 
soul  constitute  an  animal. 

623.  It  is  incontrovertible,  that  the  nature  of  an  insentient 
animal  can  only  be  requisite  to  the  existence  and  continuance 
of   an  animal  absolutely;  firstly,    because  all   the    processes 


318  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

required  for  the  life  and  preservation  of  an  animal  organism,  can 
be  effected  by  the  vis  nervosa  only;  nay,  even  the  greater  num- 
ber of  the  actions  of  sensational  conceptions,  desires,  instincts, 
&c.,  may  be  induced  by  it,  simply  as  nerve-actions ;  secondly, 
because  experiments  on  decapitated  animals  prove  it. 

624.  As  to  a  large  class  of  animals,  it  has  never  been  proved 
that  they  are  endowed  with  animal-sentient  forces,  and  it  is 
highly  improbable  that  they  are  : 

i.  Because  we  can  detect  no  traces  of  mind  or  a  conceptive 
force  with  which  their  animal  forces  can  co-operate  (6).  If 
those  movements  of  sensation  and  volition,  which  occur  in  de- 
capitated animals,  as  results  of  the  vis  nervosa  solely,  are  all 
that  can  be  adduced  as  proofs  of  the  existence  of  an  external 
sensation,  then  an  oyster,  a  sea- worm,  a  snail,  a  polype,  do  not 
manifest,  during  their  whole  existence,  a  single  movement 
which  renders  the  existence  of  conceptive  force  in  them  at  all 
probable. 

ii.  Because  many  animals,  unlike  those  undoubtedly  sentient, 
have  not  a  head  distinct  from  the  body  (15,  ii).  We  may  con- 
clude from  analogy,  with  some  probability,  that  since  all  animals 
to  which  we  can  undoubtedly  attribute  the  possession  of  a  con- 
ceptive force  and  consciousness,  have  heads  distinct  from  the 
body,  it  follows  that  the  former  must  be  governed  by  forces  alto- 
gether different  from  the  latter ;  and  since  these  are  regulated 
by  animal-sentient  forces,  the  others  must  be  governed  by  the 
vis  nervosa,  for  there  is  no  other  force  (356).  The  relations  of 
mental  endowments  to  the  cerebral  development  is  specially 
noticed  by  Haller.    ('Physiology,'  vol.  iv,  p.  634<.) 

iii.  Because,  although  all  animals  possess  the  analogues  of 
nerves,  the  most  numerous  genera  have  nothing  analogous  to  a 
brain,  even  when  they  have  a  head  distinct  from  the  body;  or, 
indeed,  a  part  which  in  movements  all  others  are  accustomed  to 
follow.  This  principle  is  of  very  great  importance.  In  those 
animals  undoubtedly  endowed  with  sensation,  there  is  a  distinct, 
complete  brain,  the  seat  of  mind  (10)  :  all  observations  establish 
this  doctrine — none  are  opposed  to  it — none  render  it  even 
doubtful.  Yet  this  undoubted  dwelling-place  of  the  soul  is  not 
a  necessary  portion  of  many  animals;  nor  necessary  to  the  per- 
formance of  numerous  acts,  performed  in  virtue  of  the  vis 
nervosa,  by  animals  after  decapitation,  in  the  same  order,  with 


cH.ii.]  PRINCIPAL  GENERA  OF  EXISTING  ANIMALS.  319 

the  same  connection,  and  from  the  same  external  impressions, 
as  before  decapitation.  A  single  series  of  experiments,  having 
such  results,  would  be  sufficient  to  refute  the  proposition,  that 
to  every  animal  life  a  body,  soul,  and  brain  are  necessary.  Yet 
nature  presents  millions  of  such  examples :  the  whole  creation, 
nay,  every  drop  of  water  is  full  of  them ;  numerous  genera  of 
animals  exhibit  no  trace  of  a  brain,  or  its  analogues ;  all  their 
acts,  as  in  sentient  animals,  can  be  simply  nerve-actions ;  their 
bodies  are  so  constructed,  that  these  acts  can  take  place  with- 
out any  co-operation  of  a  conceptive  force.  Their  souls  must 
be  extended,  and  be  everywhere  present  in  their  bodies,  since 
polypes  may  be  cut  into  pieces,  and  each  piece  becomes  a  new 
animal.  Contrary  to  all  analogy,  there  must  be  consciousness 
in  various  parts  of  their  organism,  or  they  must  consist  of  many 
souls.  How  opposed  is  all  this  to  sound  theory  and  to  com- 
mon sense  ! 

iv.  Because,  although  some  trace  of  a  brain,  or  its  analogue, 
be  found  in  animals,  as  in  worms,  snails,  crabs,  spiders,  mites, 
caterpillars,  lice,  ants,  fleas,  bees,  and  other  insects  and  worms, 
no  indications  of  animal-sentient  force  can  be  detected  in  them. 
In  none  of  the  animals  undoubtedly  sentient  is  the  brain  ever 
the  organ  of  the  animal- sentient  forces  only;  but  it  is  endowed 
also  with  the  vis  nervosa  necessary  to  all  animal  life,  even  of  an 
insentient  animal,  since  to  it  belongs  the  function  of  separating 
the  vital  spirits  from  the  blood,  and  distributing  them  to  all 
parts  of  the  nervous  system,  for  without  these  the  mere  vis 
nervosa  cannot  act  in  any  animal  (21,  22).  It  is  true,  that  this 
is  only  the  function  of  the  cortical  substance  of  the  brain  (159, 
374) ;  but  who  has  proved  that  in  the  animals  in  question,  the 
brain  consists  of  any  other  than  this  cortical  substance  ?  More- 
over it  is  probable,  that  the  medullary  substance  of  the  brain, 
even  in  sentient  animals,  possesses  the  vis  nervosa,  in  virtue  of 
which,  like  the  ganglia  and  spinal  cord,  it  reflects  external  im- 
pressions, receives  non-conceptional  internal  impressions,  and 
by  means  of  both  moves  the  mechanical  machines  (373).  It  is 
extremely  probable,  that  the  structure  considered  to  be  brain 
in  these  animals  is  either  only  cortical  substance,  or  only  a 
general  ganglion, — an  addition  to  the  spinal  cord,  in  which  the 
vital  spirits  are  separated  from  the  blood,  and  thence  trans- 
mitted through  all  the  nerves ;  in  which  also,  as  in  the  spinal 


320  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

and  other  ganglia/  unfelt  external  impressions  are  reflected, 
in  accordance  with  the  objects  of  nature,  upon  those  nerves 
through  which  the  nerve-actions  appropriate  to  the  impressions 
are  induced,  and  in  which  certain  non-conceptional  internal 
impressions  (internal  stimuli  of  the  nervous  fluid)  induce  or 
maintain,  by  means  of  the  mechanism  of  the  animal,  various 
animal  movements  necessary  to  its  existence,  well-being,  &c.; 
but  which  cannot  be  induced,  at  least  solely,  by  external  im- 
pressions. Such  a  brain  could  be  no  more  the  seat  of  mind, 
than  the  spinal  cord  or  the  ganglia.  Haller,  quoting  the  ob- 
servations of  Swammerdam  and  Lyonnet,  as  to  the  great 
simplicity  of  structure  of  the  small  ganglion  in  lobsters  and 
caterpillars,  termed  a  brain,  and  its  great  similarity  to  the  other 
ganglia,  adds,  that  even  in  fishes  and  cold-blooded  animals,  the 
brain  appears  to  be  only  an  appendage  to  the  spinal  cord. 
('Physiology,^  vol.  iv,  p.  6.) 

V.  Because,  all  the  proofs  which  are  adduced  to  show  that 
certain  nerve-actions  in  sentient  animals  are  not  sentient  actions 
(129,  130),  are  equally  valid  here.  All  the  conditions  necessary 
to  sentient  actions  are  wanting  in  animals  without  a  brain,  or 
with  a  brain  of  the  kind  just  referred  to,  and  in  which  no  ma- 
terial ideas  are  produced.  There  is  medullary  substance  in  all 
the  nerves ;  the  spinal  cord  is  for  the  most  part  made  up  of  it, 
and  yet  in  neither  are  the  material  ideas  of  conceptions  ever 
formed. 

625.  All  these  grounds  taken  together,  render  it  extremely 
probable,  that  such  animals  are  constituted  insentient  by  nature, 
and  endowed  with  vis  nervosa  only,  so  as  to  be  fitted  for  all  the 
objects  of  their  existence.  We  will  deduce  no  arguments  in 
favour  of  this  doctrine,  from  the  nature  of  the  soul,  so  totally 
unknown  to  us,  nor  will  we  answer  any  objections  brought 
against  it  from  the  same  source,  for  what  can  be  adduced  where 
we  are  so  completely  in  the  dark  ?  There  is  the  same  difficulty 
in  explaining  how  a  pure  soul  develops  animal  movements, 
whether  the  body  through  which  it  operates  be  a  skilfully  con- 
structed mechanism,  or  mere  matter.  Nature  has  prescribed 
this  law  to  them,  on  grounds  entirely  unknown  to  us,  and  it 
remains  with  her,  whether  all  or  only  a  few  animals  be  endowed 

'  Compare  note  to  §  35. — Ed. 


cH.ii.]  PRINCIPAL  GENERA  OF  EXISTING  ANIMALS.  321 

with  mind.  We  can  only  infer  the  true  condition  of  animals, 
in  this  respect,  from  their  organisms  and  their  acts.  We  have 
conclusively  shown,  that  animals  unendowed  with  mind  perform, 
by  the  vis  nervosa  only,  in  the  highest  degree  of  completeness, 
those  acts  (with  certain  exceptions)  which  are  performed  by 
sentient  animals.  Consequently,  nature  was  not  obliged  to 
render  all  animals  sentient,  if  she  were  willing  to  be  satisfied  with 
those  which  could  sufficiently  perform  the  natural  functions  of 
alimentation,  defence,  and  propagation  of  the  species,  although 
not  capable  of  the  more  perfect  acts  of  sentient  animals.  If,  then, 
there  are  animals  defective  in  the  higher  order  of  passions,  in 
reason,  and  will ;  animals,  which  do  not  possess  the  organ  of  the 
conceptive  force  peculiar  to  sentient  beings;  whose  whole  life  is  so 
uniform,  simple,  and  unvaried,  that  they  do  not  possess  even  the 
vis  nervosa,  so  perfectly  as  sentient  animals  possess  it  after  de- 
capitation ;  animals,  which  can  continue  in  life,  almost  as  per- 
fectly, when  that  is  removed  which  is  considered  the  machine  (if 
the  phrase  may  be  allowed)  of  the  conceptive  force,  namely,  the 
entire  head  wherein  their  mind  must  dwell  (621 — 624)  as  before; 
we  are  necessarily  led  to  the  conclusion,  that  it  has  pleased 
nature  not  to  place  a  considerable  portion  of  the  animal  creation 
in  closer  connection  with  a  thinking  essence,  or  to  endow  it 
uselessly  with  mind.  Still  it  would  be  well  to  notice  the  op- 
posing arguments,  few  of  which,  however,  are  of  much  weight. 

i.  The  objection  that  the  definition  of  an  animal  includes  the 
idea  of  the  existence  of  mind,  has  been  answered  already  (622). 

ii.  But  it  is  advanced,  "  that  all  animals  feel  when  they 
receive  external  impressions,  and  since  external  sensations  are 
conceptions,  they  must  therefore  have  mind.'^  To  this  we  reply, 
that  we  have  no  knowledge  that  they  feel  external  impressions, 
but  only  that  the  latter  induce  animal  movements.  It  is 
allowed,  that  all  direct  and  incidental  sentient  actions  of  ex- 
ternal sensations  may  be  excited  in  animals  endowed  with 
mind,  by  the  vis  nervosa  of  their  external  impressions,  both 
during  Kfe  and  after  decapitation  (542 — 544)  ;  and,  in  fact,  it 
is  more  difficult  to  prove,  that  these  movements  are  sentient 
actions  of  the  external  sensations  of  the  impressions,  than  that 
they  are  nerve-actions  of  the  impressions  solely  (582 — 588) . 

iii.  It  is  also  objected,  that  "  many  insects,  worms,  &c., 
which  must  be  considered  unendowed  with  mind,  have  never- 

21 


822  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

theless  organs  of  sense,  particularly  organs  of  vision;  and, 
since  tliese  nerves  are  purely  nerves  of  sensation,  these  animals 
must  possess  a  conceptive  force /^  But  are  the  organs  of  the 
senses  in  these  animals  analogous  to  ours  ?  Are  they — like  ours 
— without  ganglia  ?  Or  is  it  not,  that  their  brain  can  reflect 
external  impressions  in  the  same  way  as  the  ganglia?  (624,  iv). 
We  see  in  the  senses  of  taste  and  touch  external  senses,  the 
nerves  of  which  are  also  motor  nerves,  and  accomplish,  by 
their  vis  nervosa  alone,  all  those  movements  which  they  can 
excite  as  sentient  actions  (Haller's  '  Physiology/  vol.  iv,  pp.  615, 
sqq.).  Now,  since  the  organs  of  the  senses  in  insects  and 
worms  are  very  different  from  those  of  animals  endowed  with 
mind  (15,  ii),  it  is  possible  that  their  nerves  are  altogether 
motor,  like  the  nerves  of  touch  in  sentient  animals,  and  thus 
they  may  regulate  an  animal  without  there  being  any  sensation. 
It  cannot  be  maintained,  that  the  organs  of  the  senses  are  con- 
stituted for  the  sole  purpose  of  exciting  certain  special  kinds  of 
external  sensations  — as  the  eye  for  seeing,  the  ear  for  hearing, 
&c.  Their  proper  function  is  to  render  the  nerves  capable  of, 
receiving  certain  external  impressions,  which  could  not  be 
received  without  the  aid  of  such  machinery  (55,  42) .  If  these 
impressions  are  felt,  the  nerves  certainly  develop  a  particular 
kind  of  external  sensation ;  but  if  they  act  as  motor  nerves, 
they  excite  a  particular  class  of  movements  only,  for  they  are 
the  same  that  the  sensation  caused  by  the  impression  would 
excite  (358),  and  this  is  their  function  in  animals  not  endowed 
with  mind.  In  cases  of  this  kind,  the  animal  would  not  see 
with  its  eyes,  nor  hear  with  its  ears,  nor  smell  with  its  nose, 
but  only  have  the  same  animal  movements  excited  by  the  special 
external  impressions,  as  would  result  if  they  were  actually  felt 
(542 — 544).  The  external  impression  of  light  in  the  eye,  which 
sentient  animals  perceive,  and  through  which  they  are  excited 
to  a  thousand  volitional  movements,  can  imitate  the  actions  of: 
the  instinct  to  volitional  movements  in  insentient  animals,  and 
excite  them  directly  as  nerve-actions  (555).  Impressions  on 
the  ear  can  excite  as  nerve-actions  the  actions  of  the  instincts 
of  self-defence,  sexual  congress,  &c.  (559,  560,  566).  So  also 
the  actions  of  the  instinct  for  food  may  be  excited  in  insentient 
animals  as  nerve-actions,  by  external  impressions  on  the  nerves 
of  taste  and  smell  (552,  553). 


CH.ii.]  PRINCIPAL  GENERA  OF  EXISTING  ANIMALS.  323 

iv.  But  it  is  further  objected : — all  these  animals  appear  to 
be  moved  and  excited  by  external  sensations,  and  to  act  voli- 
tionally,  rationally,  and  designedly.  Ants  like  sugar,  bees 
Hke  the  juice  of  certain  plants,  and  each  species  of  insects  and 
worms  has  its  peculiar  food,  which  they  seek,  avoiding  others. 
They  are  guided  by  certain  sounds,  as  when  they  are  allured 
by  sexual  intercourse  (in  the  case  of  crickets),  or  when  bees 
would  swarm ;  they  fly  away  when  they  see  any  thing  unex- 
pectedly; they  smell  the  odour  of  their  food,  and  go  towards  it. 
In  these  actions,  an  effort  to  satisfy  an  instinct  is  shown,  which 
is  directed  volitionally,  and  an  animal  that  so  acts  must  be  sen- 
tient. The  argument  has  much  plausibility;  it  has,  however, 
been  demonstrated  already,  that  external  impressions  will  excite 
voUtional  acts  simply  as  nerve-actions,  whether  the  animal  feels 
them  or  not,  and  independently  of  any  reference  to  the  gratifi- 
cation of  any  desire  or  instinct  (263 — 269,  552,  561).  The 
phenomena  manifested  by  newly-born  and  decapitated  animals, 
some  of  which  have  been  already  stated  (555,  &c.),  amply  prove 
that  such  apparently  volitional  acts  may  take  place,  under  cir- 
cumstances which  altogether  exclude  the  idea  of  mind.  What 
in  them  appears  to  be  volitional,  only  appears  so,  because  we 
draw  conclusions  as  to  other  animals  from  the  nature  and  work- 
ing of  our  own  minds  (436 — 439) .  What  appears  to  be  designed, 
arises  from  the  preordination  of  nature,  and  in  no  case  enters 
into  the  minds  of  even  sentient  animals  (266,  609) . 

V.  But  it  is  further  objected, — that  these  animals  act  de- 
signedly and  volitionally,  without  the  incitement  of  external 
impressions,  and  consequently  they  must  be  under  the  influence 
of  conceptions.  The  answer  is,  that  the  movements  alluded  to 
result  from  primary  internal  impressions  not  caused  by  con- 
ceptions (609),  and  it  would  be  indeed  difficult  to  show,  that 
these  animals  had  such,  independently  of  external  impressions. 
(Compare  §  553.) 

vi.  It  is  further  objected,  that  many  of  these  animals,  as 
bees,  ants,  &c.,  act  socially  and  in  combination,  for  the  purpose 
of  attaining  certain  objects.  They  assist  each  other  in  their 
labours,  get  out  of  each  other^s  way,  take  each  other's  burdens, 
appear  to  apprize  each  other  of  danger,  combat  their  common 
enemies,  &c.  This  is  really  the  most  weighty  argument  that 
can  be  advanced  in  support  of  the  doctrine,  that  these  animals 


B2i  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

are  endowed  with  mind.  Granted  that  bees,  ants,  and  other 
social  animals,  are  endowed  with  mind,  and  have  external  sensa- 
tions, and  other  conceptions,  and  true  instincts,  all  their  social 
acts  would  be  sentient  actions  of  their  sensational  instincts,  and 
these  are  almost  the  direct  results  of  external  sensations  (276,  i, 
579,  i).  These  social  acts  are,  therefore,  either  direct  or 
incidental  actions  of  the  sensations  of  their  external  impressions. 
Now,  it  is  indubitable,  that  all  such  may  be  also  nerve-actions 
of  the  impressions  only,  and  consequently,  these  social  acts  may 
be  excited  solely  by  the  vis  nervosa,  even  if  the  animals  be 
endowed  w^ith  mind.  That  this  actually  is  so  in  other  animals 
is  fully  established  by  observation  (555 — 557) ;  how  then  can 
we  infer  the  existence  of  mind  from  these  social  acts  ?  If  the 
acts  of  an  animal  are  required  to  follow  each  other,  or  other 
acts,  in  a  certain  order,  the  impressions  which  excite  them  must 
be  received  in  the  same  order,  and  the  former  will  result, 
whether  the  latter  be  felt  or  not.  Which  method  nature  has 
adopted  in  social  animals  must  be  determined  by  the  question, 
whether  they  are  endowed  with  mind  or  not ;  but  it  would  be  a 
perversion  of  the  argument  to  say,  that  because  the  acts  may 
occur  in  two  ways,  they  therefore  are  dependent  on  mind.  The 
probability  is,  that  these  animals  are  not  endowed  with  mind, 
because  they  have  no  brain,  or  at  least  not  a  brain,  constituted 
like  those  of  animals  undoubtedly  endowed  with  mind.  If  it  be 
replied,  that  bees  and  ants  no  longer  perform  social  acts  when 
deprived  of  their  heads,  it  must  not  be  forgotten  that  the  eyes  of 
the  insects  are  removed  at  the  same  time,  and  that  it  is  by  means 
of  the  eyes  that  all  these  external  impressions  are  received  which 
excite  social  acts.  They  yet  can  and  do  perform  former  move- 
ments, although  headless,  but  not  in  a  definite  order,  and  in  rela- 
tion to  and  in  connection  with  the  labours  of  others,  because  the 
impressions  which  excite  them  are  merely  accidental,  whilst 
previously  the  impressions  were  made  through  the  organs  of 
vision,  in  a  given  order  predetermined  by  nature.  The  won- 
derful concord  in  the  acts  of  these  social  animals,  is  much  more 
probably  a  result  of  that  wisdom  which  is  manifested  in  the 
sensational  instincts  of  the  whole  animal  kingdom,  and  in  virtue 
of  which  animals,  even  the  sensational  and  thinking,  perform 
acts  according  to  a  design  and  preordination  of  nature  (561, 
263 — 270).  When  the  acts  of  republican  insects  are  considered 


CH.ii.]  PRINCIPAL  GENERA  OF  EXISTING  ANIMALS.  325 

from  this  point  of  view,  it  is  readily  seen  how  the  operation  of 
the  mysterious  and  God-like  element  of  the  instincts  (263),  may 
lead  us  to  erroneous  conclusions  in  attributing  them  to  mind 
and  external  sensations. 

626.  An  argument  for  the  existence  of  animals  endowed 
with  mind  may  be  drawn  from  analogy.  In  the  scale  of  crea- 
tion, nature  ascends  by  successive  degrees  of  perfection.  From 
physical  bodies  she  constructs  natural  mechanical  machines,  as 
elastic  matter,  capillaries.  To  these,  by  means  of  the  intimate 
connection  and  combined  action  of  many  mechanical  machines 
for  a  common  object,  or  in  other  words,  by  means  of  organisa- 
tion, she  communicates  organic  forces,  and  thus  from  them  she 
forms  organised  bodies,  such  as  plants  and  growths.  Organised 
bodies  are  undoubtedly  capable  of  three  successive  degrees  of 
perfection.  If  by  means  of  animal  machines,  they  be  endowed 
with  the  vis  nervosa,  they  attain  the  grade  of  insentient 
animal  (609 — 611).  If  to  this  a  brain  be  superadded,  and 
the  vis  nervosa  determine  and  act  in  accord  with  a  conceptive 
force,  it  becomes  then  a  purely  sensational  animal  (605,  620) ; 
and  when  in  this  class  the  conceptive  force  attains  to  that  per- 
fection, that  it  regulates  itself  and  its  body  independently  of 
the  vis  nervosa,  then  it  is  a  rational  animal,  such  as  is  man 
(619).  If  there  were  no  insentient  animals,  the  scale  of  nature 
would  be  defective  in  that  one  point.  Now  this  is  very  im- 
probable, and,  consequently,  it  is  in  accordance  with  a  perfect 
creative  scale,  to  consider  microscopic  creatures,  conchifera, 
and  insects,  as  insentient  animals. 

627.  There  are  degrees  of  perfection  in  every  genus  of 
animal.  A  mathematician  and  a  hottentot,  equally  belong  to 
the  class  of  rational  beings.  Both  comprehend  the  multipli- 
cation table,  both  can  think  of  God,  and  distinguish  between 
right  and  wrong ;  both  in  short  are  capable  of  ideas  and  acts, 
to  which  the  most  intelligent  monkey  can  never  attain.  But 
what  a  difference  between  the  two,  and  how  much  the  one  is 
more  nearly  allied  to  the  brute  than  the  other !  A  bee,  an  ant, 
a  cheese-mite,  are  in  the  same  class  of  insentient  animals  as  a 
snail,  an  oyster,  or  a  microscopic  animal,  but  how  intelligently 
and  perfectly  the  vis  nervosa  acts  in  the  former,  how  imper- 
fectly and  awkwardly  in  the  latter !  Those  are  nearly  allied 
to   the    sensational    animals,    whose   actions   they   imitate   so 


326  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

closely,  these  are  little  above  the  sensitive  plant.  Yet  the  line 
of  demarcation  is  never  passed.  The  monkey  never  acts  from 
general  principles,  or  ever  meditates  on  an  abstract  truth.  All 
its  actions  are  such  as  a  man  might  perform  independently  of 
his  reason  and  will,  in  virtue  of  the  high  perfection  of  his  sen- 
sational perceptions  and  sensational  will.  However  cleverly 
the  ant  or  bee  acts,  it  so  acts  independently  of  perception  or 
sensation  ;  and  its  actions  are  those  which  a  sensational  animal 
could  perform  after  decapitation,  and,  therefore,  independently 
of  mind,  and  in  virtue  of  the  high  perfection  of  its  vis  nervosa. 
However  animal-like  the  movements  of  the  sensitive  plant 
may  be,  they  do  not  take  place  according  to  the  laws  of  im- 
pressions on  the  nerves  of  sentient  animals. 

Note, — The  question  as  to  the  existence  of  insentient 
animals,  must  not  be  considered  as  quite  decided,  and  it  has 
no  very  important  bearing  on  the  other  doctrines  of  proper 
animal  physiology.  Animals  placed  in  this  class  must  be  con- 
sidered to  be  those  which  either  have  no  brain  at  all,  or  else  a 
brain  of  very  simple  construction,  widely  different  from  the 
brain  of  undoubtedly  sentient  animals,  and  which  is  capable 
only  of  those  movements  that  sentient  animals  can  execute 
after  decapitation,  and  independently  of  their  animal-sentient 
forces. 


CHAPTER  III. 

ON  THE  ORIGIN  OF  ANIMAL  NATURE. 

628.  The  commencement  of  animal  nature  is  termed  its 
generation  ov procreation.  (Baumgarten^s  'Metaphysics/ §  311.) 

Consequently,  an  animal  in  the  widest  sense  of  the  term  is 
[produced  so  soon  as  au  organised  body  is  capable  of  being 
[moved  by  means  of  the  animal-motor  forces  of  its  proper  animal 
lachines.  No  animal  can  thence  arise,  not  even  the  insen- 
ient,  unless  provided  at  least  with  nerves  and  vital  spirits,  or 
[their  analogues,  of  which  the  vis  nervosa  of  impressions  is  a 
[peculiar  property  (1 5,  604) .  No  insentient  animal  can  become 
I  sensational,  unless  furnished  with  brain  and  its  vital  spirits,  or 
an  analogue,  and  of  which  the  animal -sentient  forces  (10),  are 
a  peculiar  property.  A  sensational  animal  can  only  become  a 
rational  animal  when  it  attains  to  the  power  of  regulating  its 
jbody  by  intellectual  conceptions  and  volitions  (76,574,  96). 

629.  Every  animal  springs  from  one  like  itself.  The  mi- 
nutest, with  few,  if  any,  organs  and  functions,  and  a  very  brief 
life,  are  generated  after  a  very  simple  mode.  They  are  pro- 
duced without  any  difference  of  sex  by  fissiparous  generation. 
In  others,  the  mode  is  oviparous,  and  of  these  a  large  class  is 
hermaphrodite,  the  same  individual  containing  both  male  and 
female  organs.  In  a  larger  class,  the  two  sexes  are  distinct. 
The  females  of  cold-blooded  animals  deposit  their  ova,  and  then 
they  are  fructified  by  the  male ;  in  warm-blooded  animals,  the 
ova  are  fructified  in  the  uterus,  and  may  be  incubated  either 
within  or  without  that  viscus ;  in  some  genera  and  species  of 
animals  either  method  is  followed,  and  they  are  both  oviparous 
and  viviparous. 

630.  The  generation  of  an  animal  always  takes  place  by  one 
similar  to  it,  and  by  which  the  essential  constituents  of  its 
animal  nature  are  communicated  to  it.  The  origin  of  an  animal 
machine  and  its  vital  spirits,  whether  it  be  nerve  or  brain,  is 
one  of  the  hidden  secrets  of  nature,  of  which  we  are  totally 
ignorant. 


328  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

631.  The  organs  of  generation  are  very  different  in  different 
animals.  In  the  higher  classes  in  which  there  are  two  sexes 
the  instinct  of  propagation  of  species  is  requisite,  its  satisfac- 
tion (or  copulation)  having  no  other  natural  object  than  the 
fertilization  of  the  ovum.  The  objects  aimed  at  in  the  various 
modes  of  generation  are  concealed  from  us,  but  in  animals 
endowed  with  mind,  the  intent  of  the  difference  of  the  two 
sexes  seems  to  be  this,  that  the  sexes  may  be  led  to  associate 
in  protecting  their  offspring,  and  providing  for  their  various 
wants. 

633.  So  far  as  our  observations  on  the  development  of  the 
ovum  extend,  we  find  that  the  new  animal  is  a  portion  sepa- 
rated from  the  parent,  duly  furnished  with  both  animal  and 
mechanical  machines  necessary  to  its  existence  and  develop- 
ment. With  regard  to  those  animals  which  produce  their 
young  like  themselves,  we  find  that  their  offspring  is  furnished 
with  all  the  essential  animal  structures,  so  soon  as  separated 
from  the  parent. 

633.  The  whole  process  of  generation  is  a  masterpiece  of 
nature,  and  animal  bodies  are  constructed  most  skilfully  to  this 
end,  so  that  even  the  most  intelligent  animals  do  not  possess 
the  least  knowledge  of  the  varied  arrangements  and  plans  of 
nature  in  carrying  it  on  (289,  290).  This  is  not  the  place, 
however,  for  details. 

634.  The  period  of  development  comprised  between  the 
time  of  conception  and  of  birth,  is  a  period  of  imperfection, 
and,  consequently,  no  animal  can  be  expected  to  have  the  full 
use  of  its  natural  animal  forces ;  it  is  for  this  reason  that  insen- 
tient animals  and  even  sections  of  polypes  are  inactive  during 
this  period,  until  full  development  be  attained.  In  the  more 
perfect  animals  it  is  different  after  the  appearance  of  the 
pundum  saliens,  for  this  movement  is  a  direct  nerve-action  of 
the  external  impression  of  the  blood  on  the  heart  (459),  and, 
consequently,  sentient  animals  have  at  least  the  use  of  the  vis 
nervosa  to  some  extent,  and,  therefore,  possess  the  nature  of 
living  organisms.  The  intestines  of  the  chick  in  ovo  are  not 
irritable  during  the  first  fourteen  days,  but  subsequently  they 
become  more  and  more  irritable  every  day.  (Haller^s  '  Opera 
Minora,'  p.  401,  tom.  ii,  pp.  364,  398.)  As  development  ad- 
vances, (in  man  about  the  fourth  month,)  the  foetus  is  excited 


cii.  iii.J  ORIGIN  OF  ANIMAL  NATURE.  329 

by  external  impressions  to  movements,  which  are  usually  sen- 
sational voluntary  [Willkiihrlich]  ,^  but  are  probably  only  nerve- 
actions,  since,  besides  that  there  is  no  proof  of  senations  being 
felt  by  the  foetus  in  utero,  the  brain  seems  to  be  unfit  for  the 
operation  of  the  animal-sentient  forces,  inasmuch  as  its  natural 
movement  is  dependent  on  respiration  (24).  So  that  the  foetus 
is  analogous  to  an  insentient  animal  in  its  nature,  and  becomes 
sensational  at  the  moment  of  birth. 

635.  Since  an  animal  is  procreated  by  one  like  itself,  so  the 
structure  of  the  two  are  in  accordance ;  a  resemblance  in  inci- 
dental peculiarities  of  structure  may  accompany  a  similarity  in 
outward  form,  and  as  the  embryo,  whether  in  uiero  or  in  the 
shell,  receives  all  its  fluid  elements  from  the  female  parent, 
peculiarities  in  the  condition  of  the  fluids,  as  well  as  of  the 
sohds,  may  be  thus  communicated  from  parent  to  ofi'spring; 
hence  the  hereditary  predispositions  to  various  states  and  condi- 
tions of  health  and  disease. 

636.  Original  defects  in  the  structure  of  the  germ,  an  un- 
natural condition  of  the  fluids  which  nourish  it,  violent  move- 
ments of  the  latter  in  the  germinal  tissues,  injuries  to  its 
structure  by  external  force,  the  unnatural  connection  in  growth 
of  two  or  more  germs,  and  many  other  incidental  causes,  give 
rise  to  various  monstrosities  (Haller,  ^Oper.  cit.,'  tom.  iii).  In 
some  of  these  ways,  violent  emotions  or  sensations  of  the  mother 
may  influence  the  foetus,  and  to  this  extent  the  former  can  act 
upon  the  latter;  but  the  doctrine  of  a  harmony  between  the 
sentient  actions  of  the  mother  and  foetus  is  fabulous. 

637.  Merely  organised  natural  bodies  can  never  be  developed 
into  living  or  sentient  beings,  as  Needham  erroneously  taught. 
The  existence  of  an  animal  pre-supposes  that  it  originated  from 
an  animal  germ,  and  that  this  was  secreted  by  an  animal 
similar  to  itself,  (Compare  Spallanzani  and  Haller.) 

»  See  note  to  §  283.— Ed. 


CHAPTER  IV. 

ON  ANIMAL  LIFE. 

638.  The  continuance  of  animal  nature  is  animal  life,  (The 
life  of  an  animal^  as  such,  Baumgarten's  'Metaph./  §  311.)  So 
long  as  an  animal  force  operates  in  the  animal,  and  there  is  the 
smallest  animal  action  left,  so  long  the  animal  lives  (5,  6). 

639.  The  continuance  of  the  animal  nature  of  an  insentient] 
animal    may  be  termed  simply  animal  life,  just    as   the  vi 
nervosa  is  termed  a  simply  animal  force.     This  mere  animt 
nature  implies  the  existence  of  the  organic  nature,   and  the 
existence  of  the  latter  implies  the  existence  of  the  mechanical 
and  physical  natures  :   consequently,  the  entire  nature  of  an 
insentient   animal  (598)  is  made  up  of  these;   but  since  the 
last  mentioned  may  continue  independently  of  animal  life,  it 
may  cease,  or  in  other  words,  the  animal  may  die,  and  yet  the 
organic,  mechanical,  and  physical  nature  remain.    Consequently, 
the  continuance  of  the  vis  nervosa  is  solely  necessary  to  animal 
life,  and  so  long  as  there  are  the  minutest  traces  of  the  vis 
nervosa,  life  remains. 

640.  The  continuance  of  the  animal  nature  of  a  sentient 
animal,  and  especially  of  a  purely  sensational  animal,  may  be 
termed  sensational  life.  Such  an  animal  nature  implies  the 
existence  of  the  animal  nature  of  insentient  beings,  and  con- 
sequently it  is  a  whole,  compounded  of  the  two  animal  natures. 
But  a  sentient,  and  particularly  a  sensational  animal,  may  lose  its 
sensational  life,  and  still  be  a  living  creature  (603) ;  or  in  other 
words,  it  may  die  sensationally ,  and  still  live.  Consequently,  so 
long  as  it  retains  in  the  slightest  degree  that  animal  sentient 
force  which  characterises  it,  so  long  it  remains  sentient,  and 
exists  sensationally.  Again,  sensational  life  only  continues  so 
long  as  the  soul  is  in  such  connection  with  the  body,  that  it  per- 
forms any  one  of  its  movements  as  a  sentient  action  :  when  this 
connection  is  broken,  mere  animal  life  may  still  continue  (621). 

641.  The  continuance  of  the  animal  nature  of  a  reasoning 
being  may  be  termed  its  spiritual  life  [geistiges  Leben]  :  this 


CH.  IV.]  ANIMAL  LIFE.  331 

animal  nature  implies  the  existence  of  the  sensational  animal 

nature,   and  is  consequently  compounded  of  these  two — the 

intellectual  and  sensational.     But  inasmuch  as  sensational  life 

;an  continue  independently  of  the  intellectual  (620),  it  follows 

lat  a  reasoning  animal  may  lose  its  intelleccual  life,  and  yet 

>ntinue  to  be  a  sensational  animal : — it  may  die  mentally,  and 

ive  sensationally,  or  merely  animally.      So  long  as  the  higher 

limal-sentient  forces  continue  in  action  in  the  slightest  degree, 

lental  life  continues.     As  this  life   depends  on  the  intimate 

lion  of  the  soul  and  body,  when  this  union  is  broken,  that  is 

say,  when  reason  and  will  are  abolished,  mental  life  ceases, 

mt  sensational  life  may  still  go  on  (620). 

642.  All  these   differences  in  the   liie  of  animals  exist  in 
lature  (638 — 641) ;  but  their  nomenclature  does  not   accord 

with  the  terms  in  ordinary  use,  so  that  their  specific  designa- 
tion enables  us  to  analyse  our  ideas  more  correctly.  Ordinarily, 
sensational  life  and  intellectual  life  (made  up  of  the  sensational 
and  natural)  are  both  designated  by  the  term  proper  animal 
life,  or  the  life  of  an  animal  (Baumgarten^s  'Metaphysics/ 
§§  575,  576),  which  can  only  be  understood  to  mean,  the  actual 
continuance  of  the  union  of  soul  and  body.  This  idea  is  too 
narrow,  and  is  founded  on  the  erroneous  notion,  that  every 
animal  is  endowed  with  a  soul,  and  consequently  excludes  the 
idea  of  mere  animal  life  (639) ;  but  since  insentient  animals 
may  exist,  the  definition  must  include  these,  and  thus  various 
errors  will  be  avoided  :  as  for  example,  that  decapitated  animals 
still  possess  souls,  or  that  the  soul  is  extended  throughout  the 
body,  or  that  a  sentient  animal  must  have  several  souls,  or  that 
all  animal  movements  are  sentient  actions,  &c. 

643.  If,  therefore,  the  usual  phraseology  be  adopted,  sentient 
animals  alone  (640 — 642)  possess  proper  animal  life,  and  there 
remains  a  special  class  of  animals,  intermediate  creatures  pos- 
sessed of  mere  animal  life  solely  (639).  We  would  designate 
the  aggregate  in  sentient  animals  of  the  two  kinds,  namely, 
of  the  proper  animal  life  and  the  mere  animal  life — complete 
[ganze]  animal  life,  or  the  continuance  of  their  complete  animal 
nature  (598).  We  should  not,  consequently,  infer  that  an  animal 
had  lost  its  complete  animal  life,  because  its  proper  animal  life 
— the  connection  of  body  and  soul — had  ceased ;  nor  that  no 
sentient  actions  could  take  place  in  it;  otherwise  we  should 


332  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

fall  into  the  error  of  those  who  thus  argue  (Baumgarten^s 
'  Metaphysics/  §  576),  and  say — contrary  to  the  ordinary 
meaning  of  terms — that  a  tortoise,  which  crept  about  for  six 
months,  deprived  of  its  head;  or  that  a  headless  butterfly, 
which  had  sexual  intercourse,  and  deposited  its  ova ;  or  that  a 
snail,  similarly  mutilated,  which  sought  about  for  food,  and  had 
its  head  regenerated ;  or  that  a  lizard  that  ran  about  in  the 
grass  for  several  days  after  decapitation,  &c.,  was  a  dead 
animal,  or  a  corpse. 

644.  The  life  of  every  animal  is  divided  into  four  periods. 
The  first  is  the  period  of  development^  and  extends  from  the 
moment  at  which  the  germ  is  separated  from  the  parent,  to  the 
time  when  it  is  so  far  developed  as  to  be  capable  of  an  inde- 
pendent existence.  In  the  majority  of  animals  this  occurs  at 
birth. 

645.  The  second  period  is  i\LQ  period  of  growth,  and  extends 
from  the  moment  of  birth  to  the  time  when  the  animal  is  fully 
developed,  and  fit  for  the  performance  of  the  entire  range  of 
its  functions,  and  of  those  duties  which  nature  has  assigned  it. 
During  this  period  the  animal  is  unfit  for  many  functions  which 
it  performs  afterwards,  when  fully  developed. 

Qi^Qt.  Neither  nutrition  nor  growth  are  purely  animal  func- 
tions, nor  do  they  involve  animal  machines  only,  but  are  effected 
by  the  common  action  of  the  forces  of  all  parts  of  the  entire 
nature  of  an  animal, — the  physical,  mechanical,  organic,  and 
animal — and  in  sentient  animals — the  animal-sentient  forces — 
all  acting  in  wonderful  union  to  that  end. 

Note. — The  laws  of  nutrition  and  growth  are  laid  down  in 
physiological  works,  and  we  refer  to  them  here  only  in  so  far 
as  they  bear  on  proper  animal  nature,  and  influence  the  proper 
animal  machines,  and  the  proper  animal  forces. 

647.  Neither  the  nerves,  nor,  in  sentient  animals,  the  brain, 
are  fully  developed  at  first,  or  are  fully  capable  of  the  vis 
nervosa,  or  of  all  the  animal-sentient  forces.  Innumerable 
facts  show,  not  only  that  the  nerves  continue  to  grow  after 
birth,  but  are  developed  in  new  growths.  This  is  most  clearly 
seen  in  insentient  animals,  as  in  insects ;  in  the  metamorphoses 
they  undergo  during  the  various  stages  of  their  development ; 
and  in  animals  in  which  entire  limbs,  or  entire  segments  of  the 
body,  have  been  reproduced  after  mutilation. 


cH.  IV.]  ANIMAL  LIFE.  333 


^ 


648.  In  fact,  we  see  that  all  animals  perform  more  numerous 
and  perfect  acts  as  they  approach  the  period  of  perfect  de- 
velopment.     Many  animals,  especially  the  insentient,  act  from 

e  beginning  with  great  skill  and  adaptiveness,  but  they  can- 
t  perform  those  movements  which  belong  to  a  more  perfect 
stage.  A  caterpillar  acts  principally  from  the  instinct  for  nutri- 
tion ;  it  must  undergo  several  changes,  before  it  is  capable  of  the 
animal  act  of  spinning :  it  is  only  when  fully  developed  into  a 
butterfly,  that  it  can  perform  the  acts  necessary  to  propagation 
of  the  species.  No  signs  of  a  desire  to  perform  motions  of 
this  kind  are  manifested  before  the  organs  requisite  to  their 
performance  are  developed.  (Compare  Spallanzani,  '  Phys. 
Abhand.,^  p.  167,  for  examples  in  the  infusoria.) 

649.  The  brain  is  always  imperfect  at  first  in  sentient  animals. 
During  the  period  of  growth,  it  becomes  larger  and  firmer,  and 
receives  a  movement  from  the  respiratory  act,  which  it  had  not 
before,  and  which  seems  to  have  an  influence  on  the  actual  use 
of  the  cerebral  forces.  The  nerves  also  increase  in  sentient 
animals  after  birth,  not  less  than  in  the  insentient,  and  parts 
become  sensitive  and  irritable  which  were  not  so  formerly. 

650.  In  sentient  animals,  as  w  ell  as  in  insentient,  we  observe 
a  progressive  development  of  the  animal  forces ;  although  from 
the  moment  of  birth  many  of  these  display  a  readiness  in  the 
use  of  the  vis  nervosa,  and  a  perfection  in  the  instincts  necessary 
to  their  maintenance,  so  as  greatly  to  surpass  man  in  these 
respects.  Still  many  of  their  sensational  and  motor  faculties 
are  so  imperfect,  that  the  earliest  portion  of  their  existence  is 
only  the  vague  dream  of  an  almost  continuous  sleep. 

651.  Since  it  is  during  the  period  of  growth  that  the  nervous 
system  and  its  forces  are  developed,  it  is  at  that  time  that  they 
determine  the  temperament  of  the  animal  (52,  502),  together 
with  its  animal  and  even  moral  character,  if  capable  of  such 
(65,  295,  344).  Now,  as  every  genus  and  species  of  animal 
has  originally  the  capabilities  of  its  parents,  and  these  only  be- 
come more  perfect  and  fixed  during  the  period  of  growth,  it 
follows  that  every  genus  and  species  have  each  their  special 
characteristics.  These  capabilities  and  endowments  may  be 
changed  in  numerous  ways,  by  habit,  education,  and  accidental 
modifications  of  development  (52,  431,  501). 

652.  The  third  period,  or  that  of  propagation  of  the  species. 


334  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

is  the  perfect  or  adult  stage  of  life.  In  some  animals  it  is  ex- 
tremely short,  in  others  prolonged;  but  without  it  no  animal 
is  complete,  and  so  soon  as  it  terminates,  the  animal  begins  to 
decline.  This  period  is  also  the  great  object  of  natiu-e  in  the 
animal  creation,  and  to  this  there  is  no  exception  from  man  to 
the  simplest  animalcule. 

653.  In  sentient  animals  the  propagation  of  the  species 
takes  place  by  means  of  the  satisfaction  of  the  instinct  for 
sexual  congress  (289)  :  in  insentient  animals  which  propagate 
by  copulation,  this  instinct  is  replaced  by  nerve-actions.  It  has 
been  already  illustrated  fully  (274,  289,  290,  481,  540,  560) ; 
and  we  have  only  to  consider  here  the  changes  which  take 
place  at  this  period  in  animal  nature. 

654.  All  animals  are  not  bom  with  sexual  organs :  some 
only  acquire  them  after  undergoing  a  succession  of  transforma- 
tions, as  insects.  But  these  organs  in  those  animals  which 
possess  them  at  birth,  as  well  as  the  body  generally,  undergo 
such  great  changes,  as  the  period  of  propagation  of  the  species 
approaches,  that  the  period  itself  becomes  of  the  greatest  and 
most  general  importance.  The  whole  body  is  invigorated,  the 
seminal  fluid  is  secreted,  and  often  communicates  its  odour  to 
the  whole  animal ;  smooth  parts  become  hairy,  horns  grow,  the 
voice  alters,  &c.  In  the  female  equally  important  changes 
take  place. 

655.  It  is  a  necessary  result,  that  great  modifications  of 
the  nervous  system  accompany  these  important  changes  in  the 
animal.  The  nerves  of  the  whole  body,  and  particularly  of  the 
sexual  organs,  become  susceptible  of  new  impressions,  and  in 
sentient  animals  this  occurs  so  extensively,  that  it  appears  as 
if  a  wholly  new  sense  of  feeling  had  been  developed.  A  look, 
a  tone,  an  odour,  a  touch,  which  the  sentient  animal  had  ex- 
perienced a  thousand  times  before,  without  any  other  than 
ordinary  results,  cause  an  emotion  during  this  period,  which 
excites  the  instinct  to  sexual  congress,  while  the  sexual  organs 
themselves  undergo  analogous  changes  (274,  289).  The  external 
impressions  of  these  sensations  in  sentient  animals  excite  the 
same  unusual  operations  in  the  insentient  (481).  Without 
exciting  a  sensation,  they  are  so  reflected  as  to  act  upon  the 
sexual  organs,  as  if  they  had  excited  a  sensation  (540).  That 
external  impressions  are  so  reflected  on  the  nerves  of  the  sexual 


CH.  TV.]  ANIMAL  LIFE.  835 

organs,  even  when  these  are  not  directly  irritated,  and  act  as 
though  they  were  felt,  is  shown  by  the  fact  that  the  fluttering 
of  the  wings,  whereby  the  female  butterfly  allures  the  male  to 
sexual  congress,  irritates  the  nerves  of  the  decapitated  male 
butterfly  generally,  and  not  those  of  the  sexual  organs  in  par- 
ticular, as  any  other  fluttering  would ;  yet  it  has  the  same 
eff'ect  on  the  sexual  organs  of  the  male  as  if  they  felt  it,  and  it 
was  reflected  as  a  conceptional  internal  impression.  It  is 
shown,  however,  that  this  reflexion  of  the  external  impressions 
on  the  sexual  organs,  purely  by  means  of  the  vis  nervosa,  takes 
place  for  the  first  time  at  this  period  of  propagation,  and  be- 
cause the  route  thereto  is  as  it  were  laid  down,  from  the  fact, 
that  the  external  impressions  made  by  the  fluttering  of  the 
female  on  the  decapitated  male  butterfly,  are  not  thus  reflected, 
unless  they  have  copulated  at  least  once  before  decapitation 
(560). 

656.  The  internal  impressions  caused  by  conceptions  in  sen- 
tient animals,  or  independently  of  conceptions  in  the  insentient, 
manifest,  at  this  period,  the  same  new  powers  of  action  on  the 
sexual  organs  as  external  impressions.  The  remembrance  of 
a  sensation,  that  in  the  child  would  excite  no  attention  what- 
ever to  sexual  congress,  now  becomes  a  sensational  excitant  of 
the  instinct,  and  it  is  probable  that  the  mind  repeats  the  for- 
mer pure  sensation,  increased  by  new  sub-impressions  [Merk- 
male]  that  excite  this  new  instinct,  and  from  which  the  former 
sensation  was  entirely  free.  This  also  appears  to  be  imitated 
in  insentient  animals  by  the  vis  nervosa,  when  the  female  of 
insects,  if  decapitated  at  the  period  of  sexual  excitement,  not 
only  continue  the  sexual  functions,  without  any  apparent  ex- 
ternal excitement,  but  frequently  recommence  them  after  a 
period  of  repose,  fluttering  with  their  wings,  to  call  as  it  were 
the  male  to  sexual  congress. 

657.  In  reasoning  animals  this  period  of  life  is  not  distin- 
guished by  all  these  new  movements  in  the  vis  nervosa  and  in 
the  cerebral  forces,  as  is  the  case  in  sensational  animals,  but 
the  understanding  and  will  attain  to  new  and  higher  powers. 
Every  one  is  aware  that  these  attain  the  greatest  perfection 
of  which  they  are  capable,  with  adult  age.  The  brain  also 
acquires  a  higher  and  more  perfect  development,  in  accordance 
with  the  greater  perfection  of  the  mental  powers. 


336 


ANIMAL  NATURE  AS  A  WHOLE. 


[III. 


658.  As  this  period  of  perfection  of  all  the  functions  is 
attained  sooner  in  some  animals  than  in  others,  and  continues 
for  a  shorter  period,  it  determines  the  duration  of  life  in 
different  classes  of  animals ;  and  in  this  there  is  the  greatest 
difference,  the  period  in  which  the  sexual  organs  are  active, 
varying  from  a  day  to  a  hundred  years.  The  interval  between 
the  cessation  of  sexual  activity  and  death,  seems  only  to  be  an 
addition  to  life, — a  something  given  over  and  above ;  and  we 
will  term  it  the  period  of  decline.  But  before  entering  on  the 
consideration  of  this  period,  we  must  consider  the  whole  plan 
of  perfect  animal  life,  the  proper  knowledge  of  which  is  the 
great  object  of  this  system  of  physiology. 


CHAPTER  V.      - 

THE  SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE. 

659.  The  mode  and  method  by  ,whicli,  in  the  perfect  con- 
dition of  animal  life,  tlie  animal  forces  act  with  and  by  each 
other,  and  are  co-ordinate  and  subordinate,  is  termed  the  system 
of  the  forces  of  animal  life. 

660.  The  order  in  which  a  watchmaker  constructs  a  watch, 
when  at  one  time  he  forms  a  wheel,  at  another  a  chain,  now  the 
hands,  the  face,  and  the  spring,  and  then  connects  these  separate 
pieces,  and  inserts  the  spring,  cannot  enable  a  spectator  to  dis- 
cover how  each  of  them  will  contribute  its  share  to  the  perform- 
ance of  the  whole  machine,  although  well  known  to  the  master- 
workman,  who  has  worked  according  to  a  previous  plan.  But 
when  the  watch  is  put  together,  wound  up,  and  set  in  motion ; 
in  short,  when  the  mechanism  is  completed  and  finished,  the 
spectator  can  understand  how  all  the  separate  pieces  and  the 
motor  powers  co-operate  with  each  other,  so  as  to  attain  the 
intent  of  the  machine,  namely,  to  divide  the  time  accurately. 
Hitherto,  we  have  seen  how  the  machines  and  forces  of  the 
animal  are  more  and  more  developed,  as  it  approaches  the  period 
of  maturity.  It  is  at  that  period  that  the  complete  machine 
can  be  investigated  in  all  its  relations,  and  the  connection 
of  all  its  machinery  and  forces,  as  a  system,  be  comprehended. 

661.  The  animal  functions  of  animals  are  effected  generally 
by  means  of  the  nervous  system  and  the  vital  spirits  it  contains. 
These  do  not  constitute  the  only  parts  which  develop  animal 
movements,  but  in  virtue  of  their  relation,  are  the  first  that  are 
capable  of  them.  Then  all  animal  functions  take  place  in  virtue 
of  impressions  on  the  animal  machines  (356).  It  is  necessary 
to  the  reception  of  an  internal  or  external  impression  by  a 
nerve,  that  it  be  communicated  to  it  in  a  certain  direction,  that 
it  be  impressed  on  the  medulla  of  a  nerve,  and  be  propagated 
therein  by  means  of  the  vital  spirits  (32,  121) ;  and  if  the 
brain  is  to  receive  impressions  from  conceptions  or  other  causes 
of  irritation,  they  must  take  place  in  virtue  of  a  current 
[Antrieb]  of  the  vital  spirits  in  its  minute  tubes  (28, 121).    But 

22 


338  ANIMAL  NATURE  AS  A   WHOLE.  [m. 

all  these  conditions  cannot  possibly  be  coincident  in  an  isolated 
portion  of  the  brain,  or  of  a  nerve,  since  they  are  dependent 
on  the  connection  of  the  whole,  and  imply  the  existence  of 
the  natural  structure  of  the  animal  machines. 

662.  Hence  it  follows,  that  although  the  nerves  and  brain 
[the  animal  machines]  daily  receive  new  elements  by  nutrition 
and  growth,  and  wear  away  by  daily  use,  still  they  can  continue 
their  functions,  so  long  as  this  increase  or  change  of  their 
elements  neither  alters  their  structure,  so  as  to  render  them 
incapable  of  their  functions,  nor  prevents  the  action  of  the  ani- 
mal-motor forces,  for  their  individual  constituent  parts  have  no 
share  in  these  functions,  except  under  these  conditions.  Indeed, 
so  far  from  the  gradual  and  imperceptible  growth  and  change, 
which  the  brain  and  nerves  undergo  from  continued  use,  ren- 
dering them  unfit  for  their  functions,  and  preventing  the  action 
of  the  animal-motor  forces,  they  are  the  rather  rendered  more 
and  more  capable  of  new  functions  (644 — 648).  All  plants 
which  daily  lose  old  elements  and  receive  new,  their  organic 
functions  going  on  uninterruptedly,  are  illustrations  of  these 
views;  the  heart  in  animals,  considered  as  a  mere  mechanical 
machine,  is  another,  for  although  the  heart  of  the  old  man  con- 
tains not  one  of  the  constituents  which  made  up  the  heart  of 
the  child,  the  general  change  of  all  its  constituent  parts  has  in 
no  degree  interfered  with  its  functions,  they  having  gone 
on  without  a  moment^s  interruption.  Thus  also  it  is  with  the 
brain  and  nerves. 

663.  The  structure  of  the  brain  and  nerves  renders  them 
capable  of  their  proper  and  natural  functions,  and  is  necessary 
to  animal  life  in  general,  but  it  does  not  excite  those  functions. 
This  is  the  case  with  all  machines,  whether  mechanical,  organic, 
or  animal.  A  watch  or  a  mill  does  not  go  merely  because  its 
machinery  is  complete  in  all  its  parts,  but  the  action  of  the 
motor  force  appropriate  to  the  machinery  is  requisite.  The 
whole  body  of  the  animal  is  so  constructed  in  its  perfect  state, 
that  it  can  perform  all  the  movements  to  which  nature  has  des- 
tined it,  but  it  is  endowed  with  true  animal  life,  solely  in  virtue.: 
of  the  animal  forces  which  put  it  into  motion ;  and  so  soon  as 
these  cease  to  act,  animal  life  ceases,  although  its  nervous  struc- 
ture has  undergone  no  change  whatever  (638). 

664.  There  may  be  also  such  a  condition  of  the  animal,  that 


CH.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.   339 

the  nervous  system  cannot,  either  wholly  or  in  part,  perform  its 
functions,  independently  of  any  defect  of  structure;  as,  for 
example,  before  the  animal  has  an  independent  existence.  It 
is  also  a  mistake  to  refer  the  true  animal  functions  solely  to 
the  structure  of  the  animal,  since  that  only  renders  the  func- 
tions possible.  But  while  the  accomplishment  of  the  functions 
by  the  animal  forces  implies  the  existence  of  the  requisite 
structures,  the  absence  or  injury  of  the  structures,  and  every- 
thing which  renders  them  incapable  of  performing  their  func- 
tions, interrupts  life,  and  brings  it  to  a  termination.  Thus,  if 
the  brain  be  removed  or  destroyed,  sensational  life  ceases ;  and 
animal  life  would  cease  too,  if  all  the  nerves  were  destroyed,  or 
all  the  vital  spirits,  or  their  circulation  through  the  nerves  en- 
tirely arrested,  or  any  means  used  by  which  the  nerves  were 
rendered  unfit  to  receive  any  impression,  although  the  same 
impressions  may  still  be  made,  which  make  ordinary  circum- 
stances constitute  true  animal  motor  forces  (356). 

665.  The  animal  forces,  which  give  vitality  to  the  whole 
animal  kingdom,  are  all  those  impressions  of  which  animal 
machines  are  capable,  in  virtue  of  their  proper  animal  structure. 
These  impressions  have  been  already  fully  considered,  as  well 
as  their  co-ordinate  and  reciprocal  action  (31,  &c.,  121,  356, 
590,  &c.)  We  must,  however,  note  more  specially  their  mutual 
subordination,  or  their  dependence  on  each  other. 

666.  An  animal  function  (the  action  of  an  animal  force) 
which  is  based  on  another,  is  subordinate  to  it  (Baumgarten^s 
'Metaphysics,^  §  25).  Consequently,  this  subordinate  function 
implies  another  animal  function  and  force,  namely,  that  to 
which  it  is  subordinate.  Now,  as  many  animal  functions  are 
based  on  others,  as,  for  example,  sentient  actions  or  imagina- 
tions, these  latter  on  sensations,  and  sensations  on  external 
impressions,  there  is  doubtless  a  subordination  of  animal  forces 
in  animal  life;  and  if  they  can  act  in  the  natural  condition  in 
no  other  way  than  subordinately,  it  is  a  natural  subordination} 

667.  There  are  certain  animal  forces  which  are  not  naturally 
subordinate  to  any  others,  namely, — i.  External  impressions 
when  not  in  themselves  animal  actions ;  for  the  nerves  receive 

'  The  term  natural  has  here  and  elsewhere  a  peculiar  meaning,  and  refers  to  the 
mode  of  action  of  the  organism,  as  resulting  necessarily  from  its  organisation.  See 
note  to  §  27.— Ed. 


340  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

impressions  without  a  previous  animal  action  being  necessarily 
implied  (33).  ii.  Primary  internal  impressions,  independent  of 
conceptions,  with  the  condition  just  stated.  In  these  no  pre- 
vious animal  action  is  necessarily  implied  (490).  iii.  The  in- 
ternal impressions,  arising  from  those  conceptions,  desires, 
aversions,  &c.  that  are  mental,  and  not  sensational  in  their 
nature,  when  considered  independently  of  their  remote  sensa- 
tional origin,  since  in  these  the  brain  receives  impressions  from 
conceptions  formed  solely  according  to  psychological  laws,  and 
not  necessarily  in  dependence  on  any  other  animal  action  {76). 

668.  All  the  remaining  forces  are  naturally  subordinate  to 
others,  as  for  example, — i.  The  internal  impression  developed 
from  unfelt  and  reflected  external  impressions ;  for  in  this  case, 
the  internal  impressions  on  the  nerve  implies  the  reflexion  of 
an  external  impression  (421).  ii.  The  internal  impression  from 
external  sensations  and  sensational  conceptions,  desires,  in- 
stincts, &c. ;  since  these  are  dependent  on  animal- sentient 
forces  excited  from  without  (66).  iii.  All  those  mentioned, 
§  667,  if  the  condition  there  stated  as  necessary  be  wanting. 

669.  The  animal  forces  which  are  naturally  subordinate  to 
others,  are, — i.  Unfelt  external  impressions,  which,  by  being  re- 
flected, excite  internal  impressions,  ii.  Those  external  impres- 
sions which  excite  sensations,  sensational  desires,  aversions,  &c. 
iii.  Internal  impressions  not  connected  with  conceptions,  in  so 
far  as  they  are  reflected  on  other  nerves  in  their  course  down- 
wards (500) :  and  iv.  The  internal  impressions  of  conceptions, 
but  with  similar  conditions  (137). 

670.  Those  animal  forces  which  are  not  naturally  subordi- 
nate to  any  other,  are  all  those  just  mentioned,  when  the 
conditions  are  not  present ;  or,  in  other  words,  when  unfelt  ex- 
ternal impressions  cause  unfelt  direct  nerve-actions  simply  (418, 
443) ;  or  if,  when  they  excite  no  direct  nerve- actions  (445),  are 
prevented  naturally  from  being  transmitted  along  the  nerve, 
and  are  either  reflected  (426,  199),  or  felt  (47,  &c.),  or,  in  so 
far  as  internal  impressions  not  dependent  on  conceptions,  or 
those  of  conceptions,  are  not  reflected  on  other  nerves  in  their 
course  downwards  (485,  124). 

671 .  The  animal  machines  of  an  animal  are  all  in  connection 
with  each  other,  and  constitute  a  special  system  of  animal  ma- 
chines.    In  those  endowed  with  brain,  the   nerves  are  only 


CH.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.  341 

prolongations  of  it,  and  the  current  of  the  vital  spirits  passes 
upwards  and  downwards  in  both  (21)  ;  in  others,  all  the  animal 
lachines  are  in  general  connection,  by  means  of  ganglia, 
)ranches,  and  plexuses.  Nevertheless,  every  portion  of  the 
lystem  of  animal  machines  is  of  itself  capable  of  animal  forces 
(31).  The  brain  receives  its  own  impressions  at  points  quite 
.different  from  those  at  which  the  external  impressions  which 
are  felt  are  received  (124) ;  as  well  as  those  from  other  con- 
ceptions (130,  i).  In  like  manner,  every  nerve,  every  portion 
of  the  system  of  nerves,  has  the  capability  of  receiving  both 
internal  and  external  impressions,  and  when  there  are  no  na- 
tural obstacles  present,  of  transmitting  them  to  other  branches, 
or  other  nerves,  either  through  the  ganglia  or  plexuses,  or  com- 
municating nerves,  or  through  the  brain  itself,  by  means  of 
conceptions  (31,  32,  121).  But  if  the  action  of  an  animal  force 
in  this  system  of  animal  machines  shall  have  another  subordinate 
to  it,  it  must  excite  another  animal  force  either  in  the  same 
portion  of  the  system — as  when  an  external  impression  excites 
an  internal  impression  in  the  same  nerve,  or  vice  versa;  or  else 
it  must  excite  an  animal  force  in  another  portion — as  when  an 
external  impression  on  one  nerve  excites  either  an  internal  or 
external  impression  in  other  nerves,  or  other  branches,  &c. 

672.  This  natural  subordination  of  the  animal  forces  does  not, 
therefore,  occur  in  each  and  every  point  of  the  system  of  animal 
machines,  but  (as  experience  proves)  certain  points  are  destined 
by  nature  to  this  end ;  these  may  be  termed  the  natural  con- 
necting points  of  the  animal  forces,  inasmuch  as  in  these  the 
forces  communicate  and  combine  with  each  other.  The  external 
impression  continues  its  course  along  the  nerve,  until  it  arrives 
where  a  branch  is  given  off,  and  which  receives  it  as  an  internal 
impression,  and  thereby  other  animal  actions  may  be  produced ; 
or  until  the  nerve  is  intermingled  with  others  in  the  ganglia 
or  plexuses,  where  its  external  impression  can  be  received,  and 
act  as  an  internal  impression  (421)  ;  or  in  sentient  animals, 
until  the  external  impression  reaches  the  origin  of  its  nerve  in 
the  brain,  and  there,  by  means  of  a  conception  (sensation), 
excites  the  animal-sentient  force  to  send  it  back  again  along 
the  nerve  (35,  121,  124) ;  or  until  one  of  its  nerve-actions 
excites  external  impressions,  which  cause  corresponding  sensa- 
tions and  sentient  actions  (184,  i,  443).      An  internal  impres- 


342  ANIMAL  NATURE  AS   A  WHOLE.  [in. 

sion,  whether  arising  from  conceptions  or  other  stimuli,  con- 
tinues its  course  onwards  in  the  system  of  animal  machines 
from  the  place  of  its  origin,  whether  that  be  in  the  brain,  or  in 
a  ganglion  or  plexus,  or  at  the  point  of  division  of  a  nerve,  or 
any  other  point  of  the  nerve-medulla,  without  putting  any  other 
animal  force  into  action,  until  it  is  conducted  along  other 
branches  or  nerves  (which  duly  receive  it),  either  in  a  ganglion, 
a  plexus,  or  point  of  division,  and  thus  excites  animal  actions 
(124,  485) ;  or  until  its  own  action  excites  external  impressions 
in  the  nerves,  which  again  have  their  peculiar  course  and 
operation  (225). 

673.  Those  portions  of  the  system  of  animal  machines  which 
combine  several  natural  connecting  points  of  the  animal  forces, 
are  termed  centres  of  the  animal  forces.  A  number  of  animal 
machines  are  put  into  action,  by  means  of  these  centres,  when 
external  or  internal  impressions  reach  them.  We  will  mention 
the  principal  of  these  centres.  The  brain  deserves  the  name  in 
a  two-fold  manner.  Firstly,  in  its  relation  to  the  vital  spirits, 
of  which  it  is  the  secreting  organ,  partly  sending  them  to  all 
other  animal  machines,  or  communicating  internal  impressions 
not  caused  by  conceptions :  partly  receiving  them  back  again 
from  the  machines,  or  having  external  impressions  commimi- 
cated  to  it  from  the  latter  (11,  17,  18,  31).  Now,  although 
many  insentient  animals  have  no  proper  brain,  still  all  must 
have  animal  machines  performing  this  function,  because  there 
can  be  no  animal  life  without  the  intervention  of  the  vital 
spirits,  and  consequently  without  their  secretion  and  circula- 
tion. The  ganglia  and  plexuses  are  probably,  in  this  respect, 
the  analogues  of  the  brain  ;  and  in  those  animals,  a  mere  section 
of  which  has  an  independent  existence,  as  polypes,  or  in  those 
in  which  the  head  and  brain  may  be  removed  without  injury 
to  life,  since  they  are  reproduced,  as  snails  [vide  Spallanzani), 
either  the  whole  nerve-medulla  of  the  entire  system  of  animal 
machines,  or  a  special  portion  in  each  limb,  has  the  same  func- 
tion as  ganglia  and  plexuses;  so  that  animals  of  this  class 
possess  several  analogues  of  the  brain  (362,  vide  Haller's 
'Physiology,'  part  iv,  vol.  x,  sect,  vii,  §  36).  Now,  although 
a  brain  of  this  kind  may  not  be  so  constituted,  as  to  be  also 
capable  of  the  animal-sentient  forces,  as  in  sentient  animals, 
still  it  possesses  so  much  of  the  structure  of  a  brain,  as  to  be 


CH.  v.]     SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.   343 

an  animal  secreting  organ,  and  consequently  may  be  very  pro- 
perly termed  a  brain ;  and  thus  the  unnecessary  multiplication 
of  terms  be  avoided.  Many  eminent  men,  seeing  that  the 
ganglia  are  supplied  with  numerous  capillaries,  have  concluded 
that  they  have  some  beneficial  function  with  reference  to  the 
nerves.     {Vide  Haller,  vol.  cit.  sect.  10,  §  32.) 

In  the  second  place,  the  brain  merits  the  designation  of 
centre  of  animal  forces,  inasmuch  as  it  is  so  constructed  in 
sentient  animals,  that  it  is  adapted  to  the  animal-sentient 
forces ;  and  external  impressions  which  are  felt,  are  generally 
so  reflected  in  it  by  the  intervention  of  conceptions,  that  they 
put  internal  impressions  from  external  sensations  and  sensa- 
tional conceptions  into  action  (34,  66) ;  the  operation  of  which 
can  be  extended  throughout  the  animal  machines  [nervous 
system]  of  the  whole  body.  (Part  I,  Chap.  III.) 

Another  centre  of  animal  forces  found  in  all  animals  is  the 
hearty  and  which  is  specially  adapted  to  be  such  by  the  number 
of  its  nerves  and  the  varied  composition  of  its  plexuses  (516). 
When  it  is  remembered  that  all  conceptions,  in  so  far  as  they 
are  pleasant  or  disagreeable,  modify  its  movement  (250) ;  that 
a  great  number  of  animal  actions  in  the  entire  economy  of 
the  organism  are  thus  developed,  as  is  particularly  shown  in 
the  sensational  instincts  and  passions  (258) ;  that  its  natural 
movement  is  maintained  by  means  of  unfelt  external  and  in- 
ternal impressions  (459,  515) ;  and  that  by  means  of  the  circu- 
lation the  greater  number  of  the  processes  necessary  to  the 
preservation  of  the  individual  are  maintained,  there  can  be  no 
doubt  as  to  the  importance  of  this  centre  of  animal  forces. 
Although  such  a  heart  as  the  larger  animals  possess  is  not  de- 
veloped in  all  animals,  still  there  is  always  a  machine  which 
regulates  the  circulation  of  the  fluids,  and  to  which  the  term 
heart  may  be  very  fairly  assigned.  The  region  of  the  diaphragm 
and  of  the  stomach  is  not  unreasonably  considered  to  be  a 
centre  of  animal  forces,  because  numerous  nerves  meet  and 
unite  there  (171,  174) ;  and  because  it  is  observed  that  the 
impressions  reaching  there  develop  nerve-actions  and  sentient 
actions  in  most  parts  of  the  body  {vide  §  688).  Lastly,  the 
sexual  organs  occupy  an  important  position  amongst  the  centres 
of  animal  forces  (687) . 

674.  We  know  of  no  animal  with  a  general  centre  of  animal 


344  ANIMAL  NATURE   AS  A   WHOLE.  [in. 

forces,  that  is  to  say  a  centre  wherein  all  the  natural  connect- 
ing points  of  the  animal  forces  are  collected  together,  since  in 
all,  there  are  found,  at  very  distinct  portions  of  the  nervous 
system,  larger  and  smaller  ganglia,  plexuses,  and  general  points 
of  division  of  nervous  trunks  into  branches.  If,  however,  those 
centres  of  the  animal  forces  ought  to  be  termed  general,  which 
are  common  to  all  animals  without  exception,  then  there  are 
many  such  (673) ;  or  if  by  the  expression  is  meant  a  certain 
portion  of  the  animal  machines  [the  nervous  system],  the 
injury,  destruction,  or  removal  of  which  terminates  life,  then 
there  certainly  are  such  general  centres,  as  we  shall  shortly 
show  (675) ;  but  those  are  in  general  in  greatest  number  which 
are  mutually  subordinate  to  each  other. 

675.  The  heart  and  brain  are  essential  to  animal  life  in  all 
animals,  the  latter  as  the  secreting  organ  of  the  vital  spirits, 
the  former  as  the  first  cause  of  the  circulation.  Both  are  the 
most  important  and  the  first  visible  portions  of  the  germ.  It 
is  true,  that  the  brain  in  the  embryo  of  sentient  animals  has 
no  apparent  function,  for  its  natural  visible  movement  seems 
to  be  requisite  to  the  action  of  its  animal-sentient  force,  be- 
cause it  only  occurs  with  respiration,  and  consequently  not 
before  birth  (24) ;  anteriorly  to  which  no  animal-sentient  force 
can  be  shown  to  be  in  operation  (634).  On  the  other  hand, 
the  secretion  of  the  vital  spirits  is  an  invisible  function  (28), 
and  in  so  far  as  it  is  animal  is  a  pure  vis  nervosa  (374,  159), 
which  may  without  doubt  be  active  in  utero.  The  heart,  or  its 
analogue,  manifests  a  distinct  movement  in  the  earliest  stage  of 
development  of  the  embryo :  these  two  centres  must  conse- 
quently be  considered  to  be  the  primary  and  essential  portions 
of  the  system  of  animal  machines.  We  therefore  term  the 
secreting  faculty  of  the  brain  and  the  natural  force  of  the 
heart,  the  primary  vital  forces.  We  exclude  from  this  desig- 
nation the  animal-sentient  force  of  the  brain,  which  is  not  com- 
mon to  all  animals,  and  understand  solely  the  two  mentioned, 
the  one  being  that  on  which  all  animal  forces  depend,  without 
exception;  and  the  other  that  on  which  the  circulation,  the 
secretions,  and  nutrition  are  dependent 

676.  It  may  happen,  that  before  birth  an  animal  receives  its 
fluids  from  its  mother,  elaborating  none  by  its  own  forces,  and 
secreting  none  until  it  has  an  independent  existence.  The  vital 


CH.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.    345 

spirits  is  the  only  one  of  these  secretions  absolutely  necessary 
to  the  action  of  the  other  animal  forces  in  the  economy  (21); 
and  as  they  are  secreted  from  the  blood,  this  primary  vital  force 
of  the  adult  and  perfect  animal  is  dependent  upon  the  cardiac 
force.  But  the  influence  of  the  vital  spirits  on  the  heart  keeps 
up  its  continuous  action,  by  means  of  its  unfelt  external  impres- 
sions (515,  532,  note) ;  and  unless  the  cardiac  nerves  be  filled 
with  the  vital  spirits,  they  cannot  respond  to  the  impressions 
made  on  them  by  the  blood,  and  consequently  cannot  excite 
its  whole  motor  force  (665,  457).  The  two  primary  forces  are 
therefore  reciprocally  subordinate  to  each  other :  neither  can 
continue  uninterruptedly,  independently  of  the  other,  and  if 
the  one  ceases,  so  must  also  the  other.  Therefore,  if  there  be 
a  common  point  of  union  of  the  two  forces  in  an  animal,  that 
point  is  also  the  general  centre  of  the  animal  forces  in  the  sense 
already  referred  to  (674).  According  to  Lorry's  observations, 
this  point  is  situate  in  that  part  of  the  meduUa  oblongata  cor- 
responding to  the  second  cervical  vertebra.  Animal  life  sud- 
denly ceases  if  this  portion  be  injured,  destroyed,  or  removed. 
( Vide  Haller's  ^  Physiology,'  part  iv,  vol.  x,  sect.  7,  §  36.) 

677.  The  objections  to  this  doctrine  of  the  reciprocal  sub- 
ordination of  the  two  forces  to  each  other  are  easily  met.—— 
i.  It  may  be  advanced,  that  in  the  germ  one  of  the  forces  must 
necessarily  begin  to  act  before  the  other,  and  consequently 
either  the  heart  can  act  independently  of  the  vital  spirits,  or 
the  latter  may  be  produced  independently  of  the  heart.  As 
to  the  former  objection,  we  answer,  that  both  may  commence 
at  once;  as  to  the  latter,  the  assertion  is  only  applicable  to 
animals  enjoying  an  independent  existence,  inasmuch  as  the 
fluids  may  circulate  before  birth  in  virtue  of  extraneous  forces, 
and  not  of  those  proper  to  the  germ  (Haller's  '  Physiology,' 
§  891). 

ii.  It  is  objected,  that  in  sentient  animals  the  heart's  action 
will  continue  for  some  time  after  decapitation.  The  reply  is,  that 
the  vital  spirits  do  not  drain  away  immediately  after  removal 
of  the  brain ;  and  so  long  as  the  cardiac  nerves  respond  to  im- 
pressions, so  long  are  the  vital  spirits  retained  in  them  (515). 

iii.  It  is  further  objected,  that  the  brain  can  perform  sen- 
tient actions  after  the  heart  has  been  removed  from  the  body. 
This  may  occur  for  a  short  time,  but  only  so  long  as  the  brain 


346  ANIMAL  NATURE  AS  A   AVHOLE.  [iii. 

contains  the  blood  sent  to  it  from  the  arteries,  which  can  con- 
tinue to  act  for  a  short  time  after  excision  of  the  heart. 

iv.  Another  objection  is,  that  insentient  animals  exist  with- 
out either  brain  or  heart.  According  to  all  probability,  in 
these  the  vital  spirits  are  not  secreted  in  what  is  ordinarily 
termed  a  brain,  but  from  the  nerve-medulla  at 'several  points  of 
the  nervous  system,  and  consequently  the  organs  of  these 
animals  retain  their  whole  animal  life  until  either  their  fluids 
are  exhausted  from  the  want  of  nutrition,  or  can  no  longer 
contribute  the  material  of  the  vital  spirits  (362,  416).  Animals 
of  this  kind,  which  are  not  only  nourished  by  what  may  be 
termed  the  head,  but  also  by  several  organs,  or  by  the  entire 
surface  of  the  body,  can  perfectly  retain  their  whole  animal 
life,  and  each  separate  portion  of  their  body  must  be  considered 
as  a  whole,  having  the  two  centres  of  primary  vital  forces,  in 
which  an  analogue  of  the  brain  secretes  vital  spirits,  and  acts 
in  reciprocal  subordination  with  an  animal  machine,  the 
analogue  of  the  heart  having  the  function  of  carrying  on  the 
circulation  [vide  §  699). 

678.  The  proper  motor  force  of  the  heart  in  the  natural 
adult  condition  of  an  animal,  is  the  external  impression  which 
the  in-flowing  blood,  or  some  other  general  fluid,  excites  in  its 
nerves,  and  whereby  the  movement  of  the  heart  is  peculiarly  a 
direct  nerve-action  (456) ;  but  at  the  same  time  it  is  continued 
in  its  natural  order  by  the  internal  impression,  which  the 
influence  of  the  vital  spirits  makes  on  the  nerves.  The  life  of 
the  heartj  therefore,  continues, — i.  So  long  as  its  nerves  are 
capable  of  responding  to  external  impressions,  especially  those 
made  by  the  blood,  ii.  So  long  as  these  external  impressions 
actually  act  upon  them.  These  two  conditions  are  alone  neces- 
sary. But  since  the  cardiac  nerves  lose  this  capability,  if  the 
continued  flow  of  the  vital  spirits  into  them  be  interrupted,  or 
the  secretion  arrested,  the  vitality  of  the  heart  is  extinguished  as 
soon  as  the  supply  of  vital  spirits  contained  in  them  is  exhausted, 
and  this  is  the  reciprocal  subordination  of  the  two  forces. 

679.  The  primary  vital  force  of  the  cortical  substance  of  the 
brain  (362),  (not  the  animal-sentient  force,  375),  in  the  perfect 
condition  of  an  animal,  is  the  impression  made  by  the  in- 
streaming  blood  on  its  secretory  vessels,  whereby  they  are  sti- 
mulated to  perform  their  proper  function,  in  so  far  as  it  is 


CH.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.    347 


I 


nimal,  namely,  to  secrete  and  transmit  the  vital  spirits  (374). 

t  is  naturally  subordinate  to  the  animal  force  of  the  heart,  and 
continues  so,  firstly,  so  long  as  the  blood  continues  to  flow 
through  the  vessels  in  virtue  of  the  hearths  action ;  and  secondly, 
so  long  as  the  vessels  respond  to  the  impressions  made  by  the 
blood  circulating  through  them.  These  two  conditions  are 
alone  requisite  to  the  maintenance  of  this  natural  vital  force 
of  the  brain  (663,  664).  But  when  the  secretion  of  the  vital 
spirits  is  arrested,  or  their  flow  to  the  cardiac  nerves  cut  ofi", 
then  the  hearths  movements  are  easily  interrupted,  and  at  last 
stop,  so  that  when  the  circulation  of  the  vital  spirits  in  the 
cardiac  nerves  ceases,  (which  may  result  from  the  interruption 
of  all  the  cerebral  functions,  of  the  connection  between  the  heart 
and  brain,  &c.,)  this  primary  vital  force  of  the  brain  ceases. 

680.  All  other  animal  forces  are  naturally  subordinate  to 
these  two  primary  vital  forces,  in  so  far  as  the  operation  of  all 
in  the  animal  machines  presupposes  the  influence  of  the  vital 
spirits  which  render  the  animal  machines  fit  for  their  func- 
tions, and  which  they  cannot  be,  without  the  natural  subordina- 
tion of  both  j  and  again,  in  so  far  as  every  animal  machine  is 
nourished  and  developed  by  the  circulation  of  the  blood,  their 
natural  functions  are  eff'ected  also  by  it. 

681.  In  especial,  the  natural  functions  of  all  parts  of  animal 
organs  are  naturally  subordinate  to  the  combined  action  of  the 
two  primary  vital  forces  of  the  heart  and  brain,  as  may  be 
easily  shown.  This  is  manifest  with  reference  to  the  animal 
force  of  the  arteries,  in  forwarding  the  general  circulation  of 
the  fluids,  since  they  become  fit  for  their  function  in  virtue  of 
the  vital  spirits,  and  are  dependent  on  the  heart  for  receiving 
the  impressions  which  excite  their  stroke  (460). 

682.  The  animal  forces  of  the  capillaries  and  their  termina- 
tions stand  in  the  same  natural  subordination,  whereby  they 
excite  a  flux  towards  parts  duly  irritated  (207).  The  circula- 
tion must  supply  the  fluids  which  constitute  the  flux,  and  it 
is  through  the  vital  spirits  that  they  are  rendered  capable  of 
responding  to  stimuli  (462,  463).  But  a  co-operating  or  co- 
ordinate force  is  necessary  to  this  flux,  and  the  subordination 
of  this  animal  function  is  also  conditional,  inasmuch  as  it  only 
results  when  an  external  impression  takes  place  at  the  same 
time  on  the  capillaries,  or  their  mouths  (207,  462). 


348  ANIMAL  NATURE  AS  A   WHOLE.  [in. 

683.  The  natural  subordination  of  excretion  and  secretion 
to  the  two  primary  vital  forces  is  less  direct,  because  they 
imply  the  action  of  the  arteries,  for  the  latter  must  carry 
those  materies,  the  external  impressions  of  which  excite  them 
to  the  functions  of  secretion  and  excretion,  and  subserve 
thereto  (472). 

684.  The  movements  of  muscular  fibrils,  of  membranes,  of 
muscles,  and  of  muscular  viscera  and  organs  (162),  are  also 
subordinate  to  the  two  primary  vital  forces.  The  influence 
both  of  the  vital  spirits  and  of  the  blood  is  necessary  to  the 
natural  actions  of  all  these.  Although  the  subordination  is 
more  direct  than  in  the  glandular  system  and  excretory  viscera, 
co-ordinate  forces  are  required,  inasmuch  as  all  muscular  action 
requires  also  an  internal  or  external  impression  (162,  448). 

685.  The  function  of  respiration  in  breathing  animals, 
being  effected  by  muscular  tissue,  follows  the  law  of  subordina- 
tion of  muscular  action  in  general. 

686.  Lastly,  all  compound  functions  of  the  viscera  are 
subordinate  to  the  primary  vital  forces,  in  accordance  with  the 
preceding  laws.  The  functions  of  the  sexual  organs,  whether 
male  or  female, — as  copulation,  &c.,  include  those  of  arteries, 
capillaries,  muscles,  glands,  &c.,  and  are  subordinate,  according 
to  the  age  and  conditions  of  the  constituent  parts. 

687.  But  even  these  compound  animal  functions,  as  respira- 
tion, digestion,  generation,  have  a  number  of  functions  subor- 
dinate to  them,  inasmuch  as  their  effects  extend  through  the 
entire  animal  economy.  This  is  very  remarkably  the  case 
with  the  function  of  generation,  which,  in  those  which  have 
sexual  congress  (633),  puts  animal  forces  into  operation  that 
are  subordinate  to  it  in  a  wonderful  manner. 

688.  The  diaphragm  and  the  stomach  (which  forms  with 
the  intestines  one  canal)  stand  in  very  close  relation  to  each 
other,  and  attentive  observers  have  recognised  the  region  in 
which  they  are  situate,  as  a  very  general  centre  of  animal  forces ; 
not  only  because  many  nerves  meet  and  communicate  there, 
but  because  many  phenomena  prove  it  to  be  such.  Violent 
injury  of  this  region  causes  great  general  changes  in  the  body, 
and  diseases  of  these  parts  derange  many  animal  functions. 
Thus,  worms  and  mucus  in  the  stomach  excite  convulsions  of 
the  extremities ;  colic  induces  paralysis ;   bad  digestion  causes 


cii.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.    349 

hypochondria;  inflammation  of  the   diaphragm  induces   fatal 
delirium  and  nervous  attacks,  &o. 

689.  There  are  many  other  subordinations,  but  it  is  not 
possible  to  give  all  in  detail  in  this  general  sketch ;  it  is  easy, 
however,  to  deduce  them  from  the  general  principles  laid  down. 

690.  The  natural  subordination  of  all  animal  forces  we  have 
considered  hitherto,  has  been  considered  with  reference,  it  is 
true,  to  the  most  perfect  type  of  animal  organisation;  but, 
nevertheless,  it  is  applicable  to  every  species  of  animal,  whether 
sentient  or  insentient,  provided  only  that  they  have  some  of 
the  organs  belonging  thereto ;  for,  in  the  Second  Part  of  this 
work  it  has  been  shown,  that  the  animal  functions  in  question 
may  be  performed  as  well  by  the  vis  nervosa  only,  as  by  the 
animal-sentient  forces;  or  by  both  acting  conjointly.  But  in 
sentient  animals,  the  brain  is  a  special  organ  and  centre  of  the 
animal  sentient  forces,  and  of  this  we  have  now  to  treat. 

691.  The  brain  is  not  capable  of  an  animal -sentient  force, 
without  vital  spirits  (21, 22).  Further,  its  animal-sentient 
forces  are  subordinate  to  the  primary  vital  forces,  as  regards  the 
secretion  of  the  vital  spirits.  The  proper  animal-sentient  forces 
of  the  brain  are  the  material  ideas  of  conceptions  (25),  which 
are  always  induced  primarily  by  means  of  external  impressions 
(65),  although  some  of  them,  namely  those  of  intellectual  con- 
ceptions, desires,  &c.  are  impressed  on  the  brain  by  the  mind, 
without  their  being  more  immediately  dependent  on  external 
impressions  (579,  ii.) 

692.  As  the  animal-sentient  forces  of  the  brain  depend  upon 
external  forces  that  are  felt,  and  all  sentient  operations  in  the 
system  are  effected  through  them  (97,  6),  it  follows  that  the 
brain,  in  so  far  as  it  is  adapted  to  them,  is  the  centre  of  the 
animal-sentient  forces  (673) ;  although  the  latter  are  themselves 
naturally  subordinate  to  the  primary  vital  forces. 

693.  Proper  animal  life  endures  so  long,  as,  i.  The  natural 
functions  of  tbe  primary  vital  forces  continue,  at  least  in  some 
degree,  namely,  the  secretion  of  the  vital  spirits  in  the  brain, 
and  the  circulation  of  the  blood  (640,  641).  ii.  So  long  as  the 
brain  is  not  prevented  receiving  external  impressions,  or  internal 
impressions  from  certain  conceptions,  iii.  So  long  as  external 
impressions,  or  sensational  or  intellectual  conceptions,  induce 
material  ideas  in  the  brain  (663,  664.) 


350  ANIMAL  NATURE  AS  A  AVHOLE.  [i"- 

694.  Proper  animal  life,  or  in  other  words  the  connection 
of  body  and  soul,  ceases, 

i.  When  the  primary  vital  forces  cease,  that  is  to  say  when 
the  circulation  is  altogether  arrested,  so  that  no  blood  is  sent 
to  the  brain,  and  that  already  sent  is  no  longer  retained  in  it ; 
or  when  the  functions  of  those  portions  of  the  brain  which 
secrete  the  vital  spirits  is  altogether  abolished,  so  that  no  more 
is  secreted,  and  that  already  circulating  in  the  nervous  system 
is  used  up  or  destroyed. 

ii.  When,  although  the  circulation  of  the  blood  and  secretion 
of  vital  spirits  go  on,  the  brain  itself  is  so  changed,  that  neither 
an  external  impression,  even  if  it  reach  the  cerebral  origin  of 
the  nerves,  nor  a  conception,  can  produce  a  material  idea  in  it. 
This  takes  place,  when  the  brain  is  entirely  removed  or  de- 
stroyed, or  so  under  the  influence  of  poisons,  that  its  functions 
are  abolished, — circumstances  which  change  the  animal  into 
an  insentient  animal  machine. 

iii.  When  an  animal  no  longer  has  in  the  slightest  degree, 
either  an  external  sensation,  or  a  sensational  or  intellectual 
conception,  or  when  neither  these,  nor  external  impressions, 
develop  any  material  ideas  whatever ;  for  under  these  circum- 
stances the  soul  has  no  connection  with  the  body,  whether  it 
have  an  independent  existence  or  not,  and,  consequently,  the 
life  of  the  sentient-animal  terminates  (610). 

Note.  —  In  these  conditions  consist  the  first  principles 
of  our  knowledge  of  the  causes  of  death;  of  the  fatality 
of  wounds,  poisons,  and  other  injurious  agents;  and  the 
question  of  life  or  death  in  disease  and  in  doubtful  cases, 
(vide  §  710,  &c.) 

695.  All  natural  functions  are  subordinate  to  the  animal- 
sentient  forces,  in  so  far  as  they  are  sentient  actions  and  forces 
of  other  sentient  actions  subordinate  to  them;  and  result  (sub- 
ject to  the  general  conditions  of  proper  animal  life)  from  all 
conceptions,  in  so  far  as  they  are  excited  by  external  impres- 
sions, or  the  sensational  or  conceptive  force. 

696.  In  particular,  all  the  sentient  actions  enumerated 
§  §  97 — 100,  and  considered  in  detail  in  subsequent  chapters ; 
and  all  those  developed  in  the  tissues  and  organs,  considered 
§§  160 — 179,  and  in  the  capillaries  (207),  are  subordinate  to 
the  animal-sentient  forces. 


N 


H.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.    351 


697.  So  soon  as  the  connection  of  body  and  mind  is  abolished, 
and,  consequently,  proper  animal  life  ended,  all  these  animal 
operations  cease  to  be  sentient  actions,  although,  in  conse- 
quence of  the  maintenance  of  mere  animal  life,  they  may  still 
be  produced  by  the  vis  nervosa  only.  (Part  II,  Chap.  IV,  sect,  i.) 
They  may  be  produced,  however,  in  virtue  of  the  natural  co- 
ordination of  the  forces  of  the  mind  and  the  nerves,  by  both 
acting  at  the  same  time  in  parallel  subordination.  (Part  II, 
Chap.  IV,  sect,  ii,  iii.)  But  as  the  animal-sentient  forces  are 
subordinate  to  the  primary  vital  forces  towards  the  close  of 
mere  animal  life,  the  animal  functions  cannot  be  produced  by 
the  former,  but  all  proper  animal  life  must  cease  at  the  same 
time  (640). 

698.  Thus  then,  in  tbe  perfect  condition  of  the  animal,  all 
its  animal  forces  are  both  subordinate  and  co-ordinate  in  the 
most  wonderful  manner ;  whence  in  the  system  of  all  the  forces 
of  the  complete  animal  nature,  the  concurrence  of  merely 
physical,  mechanical,  or  organic  forces  come  into  consideration ; 
as,  for  example,  of  the  commingling  of  fluid  elements,  of  rigidity 
or  flexibility,  shock,  compression,  elasticity,  &c.,  to  which  the 
action  of  the  animal  forces  is  often  incidentally,  naturally,  or 
contra-naturally  co-ordinate  and  subordinate.  All  animal 
operations  are  naturally  subordinate  to  impressions,  through 
which  the  primary  vital  forces  are  maintained  in  activity,  but 
only  so  long  as  animal  life  remains  (678,  679).  It  depends  on 
these  forces  whether  an  animal  life  can  exist  and  continue  in 
perfection,  be  the  animal  endowed  with  mind  or  not,  and  that 
a  thousand  impressions  on  every  part  of  the  nervous  system 
(which  act  with  them  in  a  co-ordination,  partly  fixed  by  nature 
and  naturally  necessary,  and  partly  incidental)  can  develop  at 
one  time  whole  series  of  natural  and  subordinate  animal  pro- 
cesses, from  distinct  centres  of  animal  forces  (673,  687 — 689); 
at  another  one  such  process  only,  but  all  subservient  to  the 
preservation  of  the  animal  and  the  attainment  of  the  ends 
designed  by  nature  (674,681 — 686).  In  animals  endowed  with 
mind,  the  animal- sentient  forces  are  subordinate  to  the  primary 
vital  forces,  the  former  being,  in  fact,  impressions  of  a  peculiar 
kind  (356)  which  act  through  the  brain,  (the  centre  of  the 
animal-sentient  forces,)  by  means  of  the  production  or  operation 
of  conceptions   and   material  ideas,    and   which   can   thereby 


352  ANIMAL  NATURE   AS  A   WHOLE.  [in. 

develop  the  same  series  of  subordinate  or  single  processes,  pro- 
duced by  the  other  impressions  necessary  to  the  preservation  of 
the  animal  and  the  attainment  of  nature's  objects ;  and  with 
the  same  partly  necessary  and  natural  and  partly  incidental 
co-ordination  (696).  All  this  takes  place,  in  order  that  these 
processes  may  be  caused  also  at  the  same  time  by  sensation, 
perception,  volition,  effort,  desire,  aversion,  reflection,  and  choice 
and  satisfaction  of  the  animal,  and  thus  it  be  rendered  more 
perfect,  and  capable  of  a  more  independent  carrying  out  of  its 
proper  objects  (370,  371). 

699.  The  doctrine,  as  to  the  general  subordination  of  all 
animal  forces  to  the  primary  vital  force  of  the  brain,  may  excite 
doubts  which  require  a  solution.  In  this  entire  work,  we  have 
taught  that  the  most  essential  and  the  greater  proportion  of  the 
animal  processes  necessary  to  life,  may  go  on  perfectly,  even  in 
sentient  animals,  not  only  absolutely,  but  also  in  their  natural 
connection,  without  the  assistance  or  co-operation  of  the  brain ; 
and  that  it  is  possible  animals  may  and  do  exist,  that  have 
neither  brain  nor  head,  nor  conceptive  force,  and  yet  can 
perfectly  perform  all  the  functions  necessary  to  their  animal 
life,  by  means  of  the  vis  nervosa  only.  How  can  t)iis  agree 
with  the  doctrine,  that  the  brain  is  the  centre  of  all  the  animal 
forces  of  animals  ?  and  that  the  secretion  of  vital  spirits  in  it, 
and  their  circulation  through  the  whole  system  of  animal 
machines,  is  a  primary  vital  force  of  all  (675)?  The  animal 
machine  which  secretes  the  vital  spirits,  is  not  in  all  animals 
the  same  as  that  which  is  capable  of  animal-sentient  forces, 
although  the  term  brain  has  been  applied  to  both  kinds  (673). 
All  animal  functions  require  the  primary  vital  force  of  the 
brain,  because  it  is  necessary  to  the  secretion  and  transmis- 
sion through  the  nerves  of  the  vital  spirits ;  but  all  do  not 
require  the  animal-sentient  forces,  inasmuch  as  they  can  be 
replaced  by  the  vis  nervosa  only.  In  those  animals  not  en- 
dowed with  animal-sentient  forces,  the  secretion  and  diffusion 
of  the  vital  spirits  is  necessary  to  their  animal  processes ;  and, 
consequently,  a  brain  endowed  with  a  primary  vital  force  is  also 
necessary,  since  all  the  processes  are  subordinate  to  it  (680, 
690).  But  this  brain  may  be  diffused  throughout  the  body,  and 
every  part  may  have  its  own  brain ;  and  their  animal  processes 
may  be  in   subordination  to  the  primary  vital  force  of  this 


CH.  v.]    SYSTEM  OF  THE  FORCES  OF  ANIMAL  LIFE.    353 

diffused  brain  (677,  iv).  If,  however,  the  nerve-medulla  in  the 
head  secretes  and  transmits  the  vital  spirits  only,  then  life 
ceases  with  the  removal  of  the  head,  except  in  so  far  as  vital 
spirits  already  secreted  and  transmitted  may  still  remain  in 
the  nerves  (661,  677,  ii);  until  these  are  exhausted,  various 
processes  may  go  on  in  the  body  in  their  natural  co-ordination, 
although  no  sentient  actions  can  take  place  in  sentient  animals. 
The  functions  of  the  brain  may  be  compared  with  a  fountain 
supplied  from  a  brook,  which  waters  flowers  and  plants :  the 
latter  are  the  nerves ;  the  fountain  represents  the  animal-sen- 
tient force,  and  the  brook  the  primary  vital  force.  The  fountain 
may  be  removed,  and  still  the  flowers  may  flourish,  provided 
the  sources  of  the  brook  be  not  cut  off",  but  the  flowers  and 
plants  live  only  so  long  as  the  supply  of  water  already  in  the 
garden  holds  out. 


23 


CHAPTER  VI. 
ON  OLD  AGE  AND  DEATH. 

700.  After  an  animal  has  attained  its  growth,  and  all  its 
natural  transformations  being  completed,  it  has  remained  for  a 
period  in  its  state  of  full  development,  everything  in  its  nature 
tends  to  decline.  Its  fluid  elements  are  used  up,  and  become 
more  inspissated  and  earthy ;  its  solid  constituents  are  partly 
destroyed,  partly  rendered  harder  and  denser;  its  canals  are 
filled  up  and  ossified.  All  this  occurs  from  natural  causes 
existing  throughout  the  organism,  and  for  the  most  part  in 
virtue  of  physical  and  mechanical  forces.  The  consideration 
of  these  belongs  to  the  physiology  of  mechanical  nature;  we 
have  only  to  discuss  the  decay  of  the  proper  animal  forces. 

701.  In  old  age,  the  brain  and  nerves  appear  to  dry  up,  and 
become  flaccid ;  the  nerves  even  of  the  organs  of  sense  become 
hebete  from  constant  use  and  the  growth  of  impediments  to 
their  functions,  so  that  external  impressions  are  less  felt,  and 
external  sensations  are  less  readily  excited.  Hence  the  dimi- 
nished activity  of  the  sexual  instincts  and  desires,  the  diminished 
muscular  energy,  the  insensibility  and  dullness  of  age.  Internal 
impressions  following  the  same  rule  as  external,  the  mental 
powers  become  enfeebled,  the  memory  fails,  the  judgment  is 
impaired  and  becomes  slow  and  undecided.  Hence  the  appear- 
ance of  greater  wisdom  and  prudence  than  the  old  really 
possess,  &c. 

702.  Since  every  kind  of  animal  force  decays,  whether 
manifested  in  the  insentient,  the  merely  sensational,  or  the 
reasoning  animal,  destruction  naturally  impends  over  aU  animals, 
and  every  animal  is  naturally  mortal.  The  natural  necessity 
of  this  interruption  of  animal  life  is  not  only  shown  by  the 
laws  of  the  economy,  but  also  by  the  operation  of  remote  phy- 
sical and  mechanical  causes,  which  partly  destroy — insensibly 
and  gradually — the  structure  of  the  animal  machines,  partly  inter- 
rupt the  natural  action  of  their  forces,  as  well  in  themselves  as 
in  the  mechanical  machines,  in  a  way  not  known.  The  subject 
belongs,  however,  to  the  physiology  of  the  mechanism  of  animal 
bodies  (Haller's  'Physiology,'  §  31). 


CH.  VI.]  OLD  AGE  AND  DEATH.  355 

703.  The  termination  of  animal  life  is  death,  which  there- 
fore occurs  when  no  animal  force  whatever  exercises  the  slightest 
action  on  the  organism  (638). 

704.  The  spiritual  death  of  a  reasoning  animal  is  the  end  of 
its  intellectual  life,  and  takes  place  when  not  a  single  higher 
animal-sentient  force  exercises  the  slightest  action  in  the 
organism.  In  this  kind  of  death,  sensational  life  and  the 
union  of  body  and  soul  may  still  continue  (641). 

705.  Sensational  death  comprises  also  spiritual  death,  and 
takes  place  when  not  a  single  sensational  force  exercises  the 
slightest  action  in  the  organism.  It  has  been  termed  peculiarly 
the  death  of  the  animal,  or  the  deprivation  of  life,  since  it 
completely  destroys  the  connection  of  body  and  soul  (640); 
mere  animal  life  may,  however,  continue. 

706.  Complete  death  takes  place  when  not  one  of  all  the 
animal  forces  any  longer  acts  in  the  slightest  degree,  or  when 
the  vis  nervosa  has  ceased  to  act.  The  popular  mistake  as  to 
this  kind  of  death  has  been  already  noticed  (643) , 

707.  Natural  death  occurs  from  the  natural  death  of  the 
animal  forces,  after  the  animal  has  attained  its  full  growth  and 
perfection,  and  takes  place  necessarily.  Few  animals,  and  least 
of  all  mankind,  die  a  natural  death,  and  death  occurring  under 
other  circumstances  is  termed  accidental,  the  causes  of  which 
may  be  found  in  Haller^s  ^  Physiology,'  §  959. 

708.  Animal  death  in  the  strict  sense,  or  the  separation  of 
the  soul  from  the  body,  whether  accidental  or  natural,  takes 
place,  either  when  the  natural  functions  of  the  primary  vital 
forces  altogether  cease,  others  being  subordinate  to  them,  or 
when  the  animal-sentient  forces  are  abolished.  In  the  former 
case,  it  results  in  consequence  of  the  entire  death  of  the  animal, 
which  includes  the  separation  of  the  soul  and  body;  in  the 
latter  case,  mere  animal  life  may  continue  after  such  separation 
(640).     We  will  consider  the  modes  in  which  it  may  occur. 

709.  710.  The  union  of  body  and  mind  is  sundered  when 
the  animal  ceases  wholly  to  exist.  An  animal  wholly  ceases  to 
exist  when  its  vis  nervosa  is  abolished,  together  with  all  its 
natural  effects  in  the  economy.  No  portion  of  the  animal 
machines  is  susceptible  of  vis  nervosa  without  a  suitable 
structure,  and  without  vital  spirits  (661,  663);  and  cannot 
be  supplied  with  the  latter  independently  of  the  primary 
vital  force  of  the  brain  or  nerves,  by  which  the  vital  spirits 


356  ANIMAL  NATURE  AS  A  WHOLE.  [m. 

are  secreted  and  diffused  (678);  and  the  brain  cannot  be 
active  if  the  heart  do  not,  in  virtue  of  its  primary  vital 
force,  transmit  the  blood  to  it,  so  that  the  vital  spirits  may 
be  secreted.  Further,  the  primary  vital  force  of  the  heart  is 
inoperative,  if  the  vital  spirits  do  not  flow  to  it,  and  if  external 
impressions  be  not  duly  received  by  it  (678,  679). 

711.  Firstly,  complete  death  may  take  place  when  the  heart 
wholly  ceases  to  act,  and  all  the  functions  dependent  on  the 
circulation  are  entirely  abolished;  so  long,  however,  as  the  hearths 
action  continues,  in  however  slight  a  degree,  the  animal  still 
lives ;  or  so  long  as  the  arteries  maintain  the  circulation,  which 
may  occur  longer  in  the  capillaries  than  in  the  larger  vessels, 
independently  of  the  direct  action  of  the  heart ;  or  so  long  as 
there  is  blood  remaining  in  the  brain,  from  which  vital  spirits 
may  be  secreted ;  or,  so  long  as  vital  spirits  remain  in  the  nerves, 
and  render  them  capable  of  duly  receiving  impressions.  It  is 
thus  we  can  understand,  why  certain  animals  survive  after  the 
heart's  action  has  ceased,  or  even  when  that  viscus  has  been 
entirely  removed  from  the  body. 

712.  Secondly,  complete  death  may  result  from  whatever 
destroys  the  primary  vital  force  of  the  brain,  or  of  its  analogue, 
and  prevents  the  secretion  of  the  vital  spirits,  and  their  diffu- 
sion through  the  entire  system  of  animal  machines;  so  soon 
as  the  functions  dependent  thereon  are  quite  abolished,  the 
animal  is  perfectly  lifeless.  If,  however,  the  primary  vital 
force  of  the  brain  continues  to  act  in  the  slightest  degree,  or 
if  there  be  any  vital  spirits  remaining  in  the  animal  machines 
after  the  removal  or  destruction  of  the  brain,  so  that  they  are 
capable  of  duly  receiving  impressions,  the  animal  is  not 
absolutely  dead. 

713.  Thirdly,  death  is  complete,  when  either  both  the  primary 
vital  forces  are  abolished  at  once,  or  when  the  one  is  so  arrested, 
that  the  other  is  destroyed.  So  soon  as  the  operations  of  one 
or  both  cease  entirely,  the  animal  dies  absolutely,  because  they 
are  mutually  subordinate  to  each  other.  But  if  the  centres  of 
one  of  these  vital  forces  be  removed  from  the  body  or  destroyed, 
without  the  other  being  entirely  abolished,  then  death  is  not 
complete.  Such  is  the  case  in  those  animals  in  which  the 
arterial  system  keeps  up  the  circulation  for  a  lengthened  period, 
after  removal  of  the  heart ;  or  in  those  in  which  several  points 
of  the  nervous  system  secrete  vital  spirits,  and  thereby  maintain 


CH.  VI.]  OLD  AGE  AND  DEATH.  357 

the  action  of  the  heart  after  removal  of  the  head ;  or  in  those 
in  which  the  vital  spirits  remain  for  a  lengthened  period  dif- 
fused through  other  portions  of  the  nervous  system.  Thus, 
merely  animal  life  may  continue  after  the  removal  of  both  the 
heart  and  the  brain. 

714.  Fourthly,  an  animal  is  absolutely  dead,  when  its  entire 
system  of  animal  machines  is  rendered  wholly  incapable  of  per- 
forming its  functions  (639) .  But  so  long  as  the  structure  of  that 
system  is  not  completely  destroyed  or  changed,  or  the  vital  spirits 
contained  in  it  exhausted,  so  long,  in  short,  as  any  portion  of  the 
system  retains  the  property  of  duly  responding  to  impressions, 
the  animal  is  not  absolutely  dead.  It  is  thus  we  understand, 
how  animals  may  be  frozen,  and  yet  retain  animal  life.  (Vide 
Spallanzani.) 

715.  The  destruction,  division,  or  injury  of  portions  of  the 
system  of  animal  machines,  and  the  exhaustion  of  the  contained 
vital  spirits,  are  necessarily  followed  by  the  complete  death  of  the 
whole  organism,  when  the  primary  vital  forces  of  one  or  both 
centres  of  animal  forces  are  abolished  (711 — 713).  Hence 
mortification,  or  the  loss  of  entire  limbs,  only  causes  death, 
when  it  involves  one  or  other  of  these  centres. 

716.  Lastly,  death  is  absolutely  complete,  when  those  im- 
pressions are  no  longer  made  on  the  animal  machines  which 
maintain  the  primary  animal  functions.  Thus,  if  the  heart 
becomes  empty  from  haemorrhage,  its  movements  cease,  the 
natural  stimulus  derived  from  the  blood  being  wanting.  Death 
will  not  take  place,  however,  so  long  as  either  of  the  primary 
vital  forces  are  kept  active,  in  some  degree  at  least,  by 
supplying  the  defective  impressions :  and  this  is  the  art  of 
restoring  persons  to  life  apparently  dead ;  for  all  animals, 
whether  sentient  or  insentient,  which  perish  suddenly,  as  those 
drowned,  frozen,  strangled,  stunned,  suffocated,  &c.,  die  from  a 
want  of  those  natural  impressions  that  excite  the  primary  vital 
forces  to  the  performance  of  their  functions. 

717.  Sentient  animals  may  die  in  any  of  the  modes  in  which 
absolute  animal  death  occurs,  but  none  of  these  are  necessary 
for  proper  animal  death,  or  the  disseverance  of  soul  and  body, 
because  animal  life  may  continue  after  the  latter  has  taken 
place  (708),  just  as  it  existed  in  the  earliest  germ  independently 
of  mental  life  (634);  and  a  sentient  animal  may  thus  be  capable, 
after  death  in  the  ordinary  sense  has  taken  place,  of  those 


358  ANIMAL  NATURE  AS  A  WHOLE.  [in. 

animal  functions  which  insentient  animals  perform  as  perfectly 
as  sentient  (609 — 611).  Hence  we  can  comprehend  the  asto- 
nishing persistence  of  mere  animal  life  in  many  animals  after 
decapitation,  which,  inasmuch  as  'they  have  a  head  and  a  brain, 
and  seem  to  feel,  may  be  considered  to  be  very  imperfect  sen- 
sational animals,  such  as  turtles,  frogs,  &c.  It  cannot  be 
doubted  that  poisons  may  possibly  be  administered,  which  shall 
put  an  end  to  proper  animal  life  alone,  and  only  dissever  the 
connection  between  the  soul  and  body,  so  that  a  mere  Uving 
machine  is  left,  which,  if  supplied  with  nutriment,  will  continue 
to  live  on,  and,  like  an  anencephalous  infant,  be  excited  to 
movement  without  having  the  least  sensation  or  any  conception 
whatever.  But  the  bodies  of  sentient  animals  are  not  con- 
structed by  nature  so  as  to  be  capable  of  this  continued  animal 
existence,  but  require,  for  their  preservation  and  perfection,  the 
co-ordinate  action  of  both  the  animal-sentient  forces  and  the 
vis  nervosa. 

718.  The  separation  of  soul  and  body  may  occur :  i,  from 
everything  which  completely  interrupts  the  functions  of  the 
brain  (708),  so  far  as  it  is  the  centre  of  the  animal- sentient 
forces  (692) .  The  interruption  must  be,  however,  complete,  as, 
for  example,  by  the  entire  separation  of  the  head  from  the  body, 
the  destruction  of  the  brain,  every  injury  which  absolutely  stops 
the  formation  of  material  ideas  in  it  &c.,  but  the  injury  or 
removal  of  portions  only  is  not  sufficient. 

719.  No  one  knows  how  the  structure  of  the  brain  is  adapted 
to  material  ideas,  how  these  ideas  are  formed  in  it,  or  what  is 
their  nature,  or  how  the  vital  spirits  assist  in  forming  them,  or 
in  what  the  animal-sentient  force  of  the  brain  differs  from  its 
primary  vital  force  (679,  692).  It  is  only  possible  to  suppose, 
with  great  probability,  however,  that  the  gray  portion  is  the 
seat  of  the  latter,  and  appropriated  to  the  secretion  and  diffusion 
of  the  vital  spirits ;  while  the  white  matter  is  the  seat  of  the 
animal-sentient  forces ;  and  that  the  distribution  of  the  vital 
spirits  through  the  entire  system  of  animal  machines  is  a 
continuous  and  slow  movement,  whilst  that  by  which  material 
ideas  are  produced  and  their  sentient  actions  excited,  is 
altogether  different,  being  extremely  rapid,  not  continuous, 
and  dependent  on  the  stimulus  of  impressions  (11).  {Vide 
Haller^s  'Physiology,^  §  383.)  It  is  known,  that  the  animal- 
sentient  forces  are  active  at  the  origins  of  all  the  nerves  in 


CH.  VI.]  OLD  AGE  AND  DEATH.  359 

the  brain  (124,  130,  i),  but  it  is  not  known,  whether  there 
be  one  point  only  in  the  whole  brain  appropriated  to  con- 
sciousness and  the  conceptive  force,  and  which  can  be  termed 
the  seat  of  the  mind.  (Consult  Haller's  '  Physiology,'  §  370, 
sqq.)  The  difficulties  in  the  way  of  a  correct  theory,  render 
it  impossible  to  give  any  details  as  to  the  modes  in  which 
the  separation  of  body  and  soul  may  take  place. 

720,  ii.  The  separation  of  the  soul  and  body  may  occur  inde- 
pendently of  entire  animal  death  when  the  conceptive  force  ceases 
to  act ;  that  is  to  say,  when  those  impressions  are  absolutely 
wanting,  which  the  brain  can  duly  receive  in  virtue  of  its  animal- 
sentient  forces.  If  the  soul  be  considered  as  a  substance  distinct 
from  the  body,  cases  may  be  imagined,  in  which  it  may  separate 
itself  from  the  body,  the  animal-sentient  forces  of  the  brain 
being  altogether  unaffected,  as  is  supposed  to  occur  in  the  trans- 
migration of  souls.  But  it  is  fixed  by  the  eternal  laws  of 
nature,  that  no  conception  can  occur  without  the  co-operation 
of  the  animal-sentient  force,  and  no  material  ideas  arise  in  the 
brain,  without  the  co-operation  of  the  conceptive  force.  Con- 
sequently, all  possible  modes  of  dissolution  in  the  ordinary 
acceptation  of  the  word,  are  comprised  in  those  stated,  §  718. 

721 — 726.  Dissolution  of  the  connection  between  body  and 
mind  must  take  place,  whenever  complete  animal  death  occurs, 
and  will  be  caused — 

i.  By  whatever  entirely  arrests  the  action  of  the  heart  (711), 
and  thereby  arrests  the  functions  of  the  brain  and  its  animal- 
sentient  forces  (718).  But  so  long  as  interruption  of  the  cardiac 
action  fails  completely  to  effect  this,  the  animal  is  neither 
absolutely  nor  mentally  dead.  ii.  By  whatever  abolishes  the 
primary  vital  force  of  the  brain,  and,  consequently,  the  secre- 
tion and  distribution  of  the  vital  spirits,  so  that  the  action 
of  the  animal-sentient  force  is  quite  arrested  (712).  iii.  By 
whatever  abolishes  both  the  primary  vital  forces  at  once,  or  by 
abolishing  one  destroys  the  other,  and  thus  complete  animal 
death  takes  place  (713).  iv.  By  whatever  at  once  renders  the 
whole  system  of  animal  machines  unfit  for  its  function,  and, 
consequently,  for  the  animal-sentient  forces  (714).  If  this 
occurs  gradually,  the  dissolution  of  the  connection  of  body 
and  soul,  may  precede  complete  animal  death.  In  death 
by  lightning,  both  take  place  at  the  same  time.  If  the 
animal  machines    be  only  rendered  partially  unfit    for    their 


360  ANIMAL  NATURE  AS  A  WHOLE.  [iii. 

function,  separation  of  the  body  and  soul  can  only  take  place, 
when  those  parts  of  the  brain  are  involved  which  constitute 
the  centre  of  its  animal-sentient  forces.  But  inasmuch 
as  these  are  scattered  throughout  the  brain,  often  injury 
of  the  cerebral  medulla  only  destroys  a  certain  class  of  animal- 
sentient  forces,  and  others  not  naturally  subordinate  to  them, 
remain  uninjured.  Thus,  it  is  possible  in  injuries  of  the  head, 
or  in  old  age,  that  one  kind  of  external  sense,  or  the  memory, 
understanding,  judgment,  &c.,  may  be  enfeebled  or  abolished, 
while  other  faculties  are  unaffected,  v.  By  whatever  entirely 
prevents  those  impressions,  which  put  the  primary  vital  forces 
into  action,  or  maintain  them  in  action,  in  so  far  as  the  animal- 
sentient  forces  of  the  brain  (which  are  subordinate  to  them) 
are  abolished  (716). 

727.  All  these  various  kinds  of  death  are  usual  in  nature. 
Often  mental  death  precedes  mere  animal  dissolution;  often 
both  occur  at  the  same  time ;  but  in  every  case,  traces  of  mere 
animal  life  remain  after  the  soul  is  separated  from  the  body. 
When  all  conceptions  are  abolished,  and  all  sentient  actions  have 
ceased,  the  body  still  manifests  signs  of  the  vis  nervosa  ;  peri- 
staltic motion  continues,  the  heart  makes  a  few  feeble  strokes 
(the  right  ventricle  retaining  the  power  of  motion  the  longest), 
and  the  muscles  are  still  irritable.  Even  when  all  other  tissues 
are  no  longer  capable  of  stimulation,  the  heart's  action  may  be 
renewed  by  external  impressions,  so  that  to  this  extent  we  may 
consider  with  Haller  (Physiology,  §  961),  that  the  moment  the 
heart  loses  its  irritability  is  the  moment  of  complete  animal 
death.  That  the  moment  of  interruption  of  the  heart's  action 
is  not  that  moment,  is  manifest  from  what  has  been  already 
stated  (711 — 721).  Undoubtedly,  every  trace  of  the  vis  nervosa 
disappears  as  soon  as  the  parts  become  cold,  or  deprived  of 
moisture. 

728.  After  absolute  death  comes  the  end  of  the  remaining 
part  of  the  entire  nature  of  the  dead  body,  that  is,  of  the 
organic,  mechanical,  and  physical  forces,  and  is  termed  putre- 
faction. It  resolves  all  the  animal  machines, — the  brain  and 
nerves, — together  with  all  the  other  components  of  the  animal 
organism,  into  their  primary  elements. 

END  OF  "PRINCIPLES  OF  PHYSIOLOGY." 


DISSERTATION 


ON    THE 


FUNCTIONS  OF  THE  NERVOUS  SYSTEM 

BY 

GEORGE  PROCHASKA,  M.D. 


A  DISSERTATION 


TUNCTIONS  OF  THE  NERVOUS   SYSTEM. 


INTRODUCTION. 

The  nervous  system^  in  which  term  we  comprise  the  cere- 
brum, cerebellum,  medulla  oblongata,  and  medulla  spinalis,  and 
the  nerves  thence  distributed  throughout  the  whole  body,  is  of 
all  organs  of  the  animal  economy  the  most  important.  It  is 
the  seat  of  the  rational  soul,  and  the  link  by  which  it  is  united 
to  the  body ;  it  is  the  instrument  by  which  the  soul,  so  long 
as  it  is  united  to  the  body,  produces  its  own  actions,  termed 
animal,  and  by  which  it  acts  on  the  rest  of  the  body,  and  the 
body  in  turn  acts  upon  it.  But,  however  great  may  be  the 
importance  of  the  nervous  system  in  these  respects,  it  is  of  fur- 
ther importance,  because  it  possesses  in  addition  the  singular 
faculty  of  exciting  in  the  human  body  various  movements  with- 
out the  consciousness  or  assistance  of  the  soul;  nay,  plainly  against 
its  will  it  can  and  does  excite  them  without  intermission  through 
the  whole  of  life.  The  nervous  system  also  influences  other 
functions  of  the  human  body,  as  digestion,  nutrition,  and  secre- 
tion, which  functions  do  not  remain  long  undisturbed  if  the 
nerves  be  injured.  I  say  nothing  of  the  share  which  the 
nervous  system  is  well  known  to  have  in  almost  every  disease. 

Prom  all  this  it  is  manifest  how  valuable  results  would  follow 
on  sedulous  inquiry  into  the  structure  and  functions  of  the 
nervous  system,  inasmuch  as  much  light  might  be  expected 
to  be  thrown  on  medical  art;  nor  ought  it  to  be  lightly 
esteemed  as  to  its  results,  with  reference  to  those  who  desire  to 
know  themselves.  For  he  who  desires  to  understand  more 
thoroughly  his  own  mind, — the  nobler  portion  of  himself, — can 
understand  it  only  from  its  operations.     But  these  are  never 


36 1  INTRODUCTION. 

so  pure  and  so  unmixed,  that  the  nervous  system, — the  imme- 
diate instrument  of  the  mind, — has  no  part  in  them  ;  and 
consequently  it  is  necessary  that  the  structure  and  functions 
of  the  nervous  system  should  be  well  understood  by  those  who 
would  determine  what  should  be  ascribed  in  animal  actions  to 
the  operations  and  structure  of  the  nervous  system,  and  what 
should  be  clearly  assigned  to  the  immaterial  soul  alone. 

After  all  the  earnest  attempts  of  the  greatest  philosophers 
and  physicians  from  the  earliest  ages,  to  explain  the  functions 
of  the  nervous  system,  we  can  hitherto  only  say  with  Haller,^ 
it  is  but  a  little  that  we  certainly  know,  that  much  remains 
unknown,  and  if  we  may  judge  of  the  future  by  the  past,  that 
no  httle  will  remain  unknown  for  ever.  Nevertheless,  I  do 
not  think  all  hope  should  be  abandoned,  especially  if  we  should 
be  able  to  detect  and  remove  the  cause  of  that  slow  progress 
hitherto  made ;  and  this,  in  my  opinion,  partly  consists  in  the 
difficulties  of  the  subject,  which  nothing  but  great  labour  can 
overcome;  and  partly  in  the  love  of  hypotheses,  which 
have  been  devised  to  explain  the  functions  of  the  nervous 
system.  Many,  content  with  these  false  resemblances  of  truth, 
neglect  to  inquire  into  the  truth  itself,  and  they  who  do  inves- 
tigate, unless  they  discard  the  prejudices  which  spring  from 
hypothesis,  often  fail  to  perceive  the  truth,  even  when  it  is 
plain  before  them. 

I  have  therefore  entered  on  this  attempt,  to  explain  the 
natural  functions  of  the  nervous  system,  without  any  hypothesis, 
and  by  simple  facts  only;  and  should  the  attempt  be  approved, 
and  by  additions  and  emendations  be  rendered  more  complete 
(and  these  I  well  know  my  labours  to  stand  in  need  of),  it 
may  be  readily  and  usefully  applied  to  an  explanation  of  the  pre- 
ternatural functions  of  the  same  system.  I  have  taken  certain 
observations  and  experiments  of  celebrated  men  as  a  founda- 
tion ;  I  have  spoken  doubtfully  of  what  was  doubtful,  and  I 
have  preferred  to  acknowledge  my  ignorance  of  what  was  inex- 
plicable, rather  than  with  the  itch  of  explaining  everything  to 
have  recourse  to  improbable  hypotheses.  How  nearly  I  have 
attained  to  the  truth  in  other  respects  let  the  indulgent  reader 
decide. 

'  Elem.  Physiol.,  torn,  v,  p.  529. 


CHAPTER  I. 

THE  PRINCIPAL  OPINIONS  OF  AUTHORS,  REGARDING  THE  USES  AND 
FUNCTIONS  OF  THE  NERVOUS  SYSTEM,  CONCISELY  STATED. 

SECTION   I. THE    OPINIONS    OF    ARISTOTLE. 

It  is  remarkable  how  widely  Aristotle  with  many  others  of  the 
philosophers  and  stoics  have  erred  in  assigning  a  use  for  the  brain, 
having  described  it  as  an  inert  viscus,  cold  and  bloodless,  an  organ 
sui  generis,  not  to  be  enumerated  amongst  other  organs  of  the 
body,  seeing  that  it  is  of  no  use  except  to  cool  the  heart.  He 
thus  explained  how  the  brain  might  be  the  refrigeratory  of  the 
heart  :^ — Inasmuch  as  vapours  arise  from  the  waters  and  earth, 
and  when  they  reach  the  cold  middle  region  of  the  air  are  con- 
densed into  water,  which,  falling  upon  the  earth,  cools  it ;  so 
also,  the  hot  spirits  carried  from  the  heart  to  the  brain  with 
the  blood,  and  there  being  cooled,  are  condensed  into  water, 
which  again  descends  to  the  heart  for  the  purpose  of  cooling  it. 
He  placed  the  seat  of  the  rational  soul  in  the  heart,  where  it 
can  exercise  all  its  functions,  and  he  therefore  made  the  nerves 
(of  the  use  of  which,  in  sensation  and  motion,  he  was  not  igno- 
rant) to  arise  from  the  heart.  This  opinion  of  Aristotle  as  to 
the  heart  being  the  seat  of  the  soul,  appears  to  be  preserved,  even 
to  our  own  days,  in  the  popular  modes  of  expression,  as  when  a 
man  of  a  good  disposition  is  said  to  have  a  good  heart,  and  the 
writers  on  moral  science  speak  of  '^  the  cultivation  of  the  heart.'' 

It  would  appear,  that  anteriorly  to  Aristotle,  Hippocrates 
had  formed  a  more  correct  opinion  as  to  the  functions  of  the 
brain,  for  in  his  book  ^  de  Insania/  he  observes,  that  that  man 
is  sane  whose  brain  is  undisturbed  ;  although,  in  another  book, 
'  de  Corde,'  referred,  however,  to  the  spurious  works,  he  places 
the  mind  of  man  in  the  left  ventricle  of  the  heart.  Plato,  the 
preceptor  of  Aristotle,  also  thought  differently,  for  he  recog- 
nised three  distinct  faculties  of  the  mind,  having  three  distinct 
seats  :  one  was  the  concupiscent,  whose  seat  was  in  the  liver ; 
the  second,  the  irascible,  seated  in  the  heart ;  the  third,  the 


I 


De  Animal,  partib.,  lib.  ii,  cap.  vii. 


366        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,    [ch.  i. 

rational,  seated  in  the  brain.  In  this  doctrine  he  was  followed 
by  Galen,  Vesalius,  Fernelius,  and  others,  who  hence  acknow- 
ledged three  spirits  :  the  natural,  which  pass  from  the  liver  with 
the  blood ;  the  vital,  which  are  carried  from  the  heart  to  every 
part  of  the  body  through  the  arteries;  and  the  animal,  which 
are  transmitted  from  the  brain  through  the  whole  body  by 
means  of  the  nerves. 

SECTION  II. THE  OPINIONS  OF  GALEN. 

Erasistratus  and  Herophilus  abandoned  the  doctrine  of 
Aristotle  their  master,  as  to  the  functions  of  the  brain ;  the 
former  taught,  when  young,  that  the  sensory  nerves  arise  from 
the  meninges,  and  the  motor  from  the  cerebrum ;  but  when 
old,  he  taught  that  both  classes  of  nerves  arise  from  the  me- 
dullary matter  of  the  brain ;  that  the  animal  spirit  was  from 
the  head,  the  vital  from  the  heart.  Herophilus  maintained, 
that  the  ventricle  of  the  cerebellum,  the  calamus  scriptorius,  is 
the  chief  of  all  the  ventricles  of  the  brain,  and  that  the  nerves 
of  volition  spring  from  the  brain  and  medulla  spinalis.  The 
most  important  doctrines,  however,  are  those  laid  down  by 
Galen  in  the  books  de  placitis  Hippocratis  et  Platonis  and  de 
usu  pari'ium,  and  which  it  will  be  well  to  notice  more  in  detail. 

In  the  first  place,  Galen  refutes  the  doctrines  of  Aristotle, 
by  showing  that  the  refrigeration  assigned  to  the  brain  is 
abundantly  effected  by  the  respiration ;  that  he  himself  had 
always  found  the  brain  of  animals  hot  to  the  touch ;  and  that 
it  must  be  so,  is  proved  by  the  numerous  blood-vessels  dis- 
tributed over  the  pia  mater  and  throughout  the  brain.  More- 
over, in  contradiction  to  the  assertion  of  Aristotle,  that  all  the 
organs  of  the  senses  are  not  centered  in  the  brain,  he  shows 
that  nerves  are  given  off  to  both  ears,  to  both  sides  of  the  nose, 
to  both  eyes  and  their  motor  muscles,  and  not  only  four  to  the 
tongue,  but  also  nerves  to  the  pharynx,  larynx,  gullet,  and 
all  the  viscera,  as  well  as  all  parts  of  the  face.  Consequently 
he  asks,  if  the  brain  be  only  a  refrigeratory,  of  what  use  are  the 
various  parts  of  the  brain,  as  for  example,  the  choroid  bodies, 
the  retiform  plexus,  the  pineal  gland,  the  pelvis,  the  infundi- 
bulum,  the  fornix,  the  processus  vermiformis,  the  two  meninges, 
their  processes  to  the  spinal  marrow,  and  the  branches  of  the 
nerves?     It  would  have  been   suflBcient  for  the  purposes  of 


SECT.  II.]  OPINIONS  OF  GALEN.  367 

refrigeration,  if  the  brain  had  been  made  Hke  a  rude  and  form- 
less sponge,  nor  need  there  have  been  so  much  artificial  con- 
struction as  is  found  in  the  brain. 

Subsequently,  when  he  is  about  to  indicate  generally  the 
use  of  the  cerebrum  and  cerebellum,  he  observes  that  the  brain 
is  of  the  same  substance  as  the  nerves,  but  softer,  as  it  neces- 
sarily should  be,  inasmuch  as  it  receives  all  the  sensations,  per- 
ceives all  the  imaginations,  and  then  has  to  comprehend  all  the 
objects  of  the  understanding,  for  what  is  soft  is  more  easily 
changed  than  what  is  hard.  Since  double  nerves  are  necessary, 
the  soft  for  sensation,  the  hard  for  motion,  so  specially  also  the 
brain  is  double,  the  anterior  being  the  softer,  the  posterior  the 
harder,  which  is  also  termed  parencephalis.  These  two  cerebra 
are,  therefore,  separated  from  each  other  by  nature,  because  it 
would  not  be  at  all  safe,  that  the  soft  should  be  exposed  to  the 
contact  and  pressure  of  the  hard. 

The  use  of  the  anterior  or  superior  ventricles,  he  says,  is  as 
follows  :  Firstly,  to  receive  air  through  the  nostrils,  the  ethnoid 
bone,  and  the  mamillary  processes,  and  mixing  this  with  the  vital 
spirit  brought  into  the  ventricles  through  the  arteries  from  the 
heart,  to  prepare  the  animal  spirits  transmitted  from  the  brain  to 
the  nerves  for  the  purposes  of  motion  and  sensation.  Moreover, 
that  the  brain  had  a  double  movement : — a  diastoHc,  by  which 
it  receives  the  air  and  vital  spirit  into  the  ventricles ;  and  a  sys- 
tolic, by  which  it  distributes  the  animal  spirits  to  the  nerves. 
Secondly,  by  the  same  entrance,  sensible  objects,  and  objects  of 
the  faculty  of  smell,  are  introduced.  Thirdly,  the  excrementa  from 
the  bodies  contained  in  the  ventricles  collect  there,  the  accumu- 
lation of  which  excites  apoplexy,  unless  a  suitable  outlet  be  pro- 
vided ;  this,  however,  is  double,  the  one  through  the  meatus  of 
the  nostrils,  the  other  through  the  infundibulum,  or  pituitary 
gland,  with  its  two  ducts  opening  into  the  palate  and  cavity  of 
the  mouth.  The  superior  ventricles  are  double,  in  the  same 
way  as  other  parts  are  ordained  to  be  double  by  nature,  for  the 
purpose,  doubtless,  that  if  the  one  suffers,  the  other  may  serve  j 
for  this  reason,  also,  the  brain  is  double,  and  every  sensorium  is 
double.  He  mentions  the  case  of  a  youth  he  saw  at  Smyrna,  to 
prove  the  usefulness  of  double  ventricles :  this  youth  had  one 
ventricle  wounded,  and  was  thought  to  have  escaped  death  by 
the  help  of  God,  but  Galen  says  that  he  certainly  could  only  have 
lived  a  short  time,  if  he  had  been  wounded  in  both  ventricles. 


368        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,    [ch.  i. 

The  animal  spirits,  he  says,  are  transmitted  from  the 
anterior  ventricles  to  the  fourth  through  the  opening,  now 
termed  the  aqueduct  of  Sylvius.  But  he  afterwards  says, 
[lib.  8,  de  usu partium,)  that  the  animal  spirits  are  not  contained 
in  the  ventricles  only,  but  are  diffused  throughout  the  whole 
substance  of  the  cerebrum  and  cerebellum. 

The  use  of  the  fornix,  to  which  also  the  corpus  callosum 
belongs,  is  the  same,  he  says,  as  of  the  arches  of  buildings; 
namely,  to  support  commodiously  and  safely  the  whole  of  the 
superjacent  part  of  the  brain. 

The  eminences,  termed  nates  and  testes,  and  the  vermiform 
process  of  the  cerebellum,  serve  to  open  and  shut  the  passage 
by  which  the  animal  spirits  are  transmitted  from  the  anterior 
ventricles  to  the  posterior  ventricle.  Some  have  attributed  this 
function  of  a  janitor  to  the  conarium  [pineal  gland]  also,  but 
erroneously,  since  it  is  not  a  portion  of  the  cerebrum,  but 
merely  a  gland,  and  hence,  doubtless,  the  conarium  has  the 
same  functions  as  other  glands,  namely,  to  support  the  ramified 
veins  amongst  which  they  are  introduced. 

He  agrees  with  Erasistratus  in  the  opinion,  that  the  plexuses 
and  convolutions  are  larger  in  man  than  in  other  animals,  but 
he  does  not  admit  that  the  intellect  of  men  depends  on  this, 
because  asses  also  have  a  brain  much  convoluted. 

Although  Galen  asserts  passim,  that  the  function  of  the 
nerves  consists  in  transmitting  the  animal  spirits  from  the 
brain  to  the  other  parts  of  the  body,  for  the  purposes  of  sen- 
sation and  motion,  because  parts  are  deprived  of  motion  and 
sensation  when  the  nerve  is  cut,  tied,  compressed,  bruised,  or 
aflPected  with  scirrhus,  still  he  does  not  appear  to  have  been 
quite  certain  as  to  the  correctness  of  his  doctrine,  since  he 
raises  some  doubts  in  the  seventh  book  de  Placitis  Hipp,  et 
Platonis.  Firstly,  whether  the  nerves  contain  animal  spirits 
like  the  cavities  of  the  brain  ?  Secondly,  whether  this 
spirit  is  innate  in  the  nerves,  and  when  a  limb  is  to  be  moved, 
is  excited  only  when  acted  upon  by  the  spirit  contained  in 
the  cerebrum?  Thirdly,  whether  this  spirit  be  innate  in  the 
nerves  at  all,  but  rather  when  we  seek  to  move  a  limb, 
whether  it  does  not  flow  from  the  brain  into  the  nerve? 
Fourthly,  whetlier  the  matter  of  the  spirits  flows  into  the 
nerves  from  the  brain  in  any  way  ?  or  is  it  not  rather  its  force, 
virtue,  or  faculty,  just  as  the  substance  of  the  sun  remaining 


SECT.  III.]  FOLLOWERS  OF  GALEN.  369 

motionless,  its  light-giving  property  is  poured  forth  into  the 
ambient  air  ?  He  observes,  however,  that  he  cannot  decide  ab- 
solutely on  these  questions,  but  only  proposes  them  for  general 
discussion. 

SECTION    III. THE  FOLLOWERS  OF  GALEN. 

The  Arabs  distributed  the  animal  functions  amongst  the 
ventricles  of  the  brain,  so  that  one  of  the  anterior  ventricles 
they  made  the  seat  of  common  sensation,  the  other  of  the 
imaginative  faculty,  the  third  ventricle  was  the  seat  of  the 
understanding,  and  the  fourth  of  memory.  This  was  also  the 
doctrine  of  Benivenius,  who,  in  confirmation  of  it,  relates 
the  case  of  a  certain  thief,  often  caught  stealing,  who  never 
remembered  his  previous  offences ;  after  death  it  was  found 
that  he  had  no  cerebellum.  This  doctrine  was  also  main- 
tained by  Duns  Scotus,  Thomas  Aquinas,  and  other  theo- 
logians ;  and  although  disavowed  by  Vesalius  and  other  phy- 
sicians, was  again  adopted  by  others. 

The  Italian  and  other  anatomists  who  flourished  after  the 
Arabians  and  the  revival  of  learning,  scarcely  deviated  from 
Galenas  views  in  assigning  the  function  of  the  nervous  system, 
and  in  particular  of  the  encephalon.  Berengarius,  Massa, 
Fernelius,  Vesalius,  Stephanus,  Fuchsius,  Columbus,  Valverda, 
Fallopius,  Goiter,  Vidus  Vidius,  Varolius,  Felix  Platerus, 
Piccolhomineus,  Laurentius,  Riolanus,  Spigelius,  Cartesius, 
&c.,  agree  with  Galen  passim^  although  some  have  their 
peculiarities.  Fernelius  followed  the  doctrine  advocated  by 
Erasistratus  in  his  youth,  that  the  sensory  nerves  arise  from 
the  membranes  and  the  motor  from  the  substance  of  the  brain. 
Vesalius  was  not  anxious  to  determine  whether  the  animal 
spirit  is  conducted  through  certain  channels  of  the  nerves,  or 
along  the  sides  of  the  nerves,  or  whether  the  vis  cerebri  reaches 
the  parts  merely  by  the  continuity  of  the  nerves.  Fallo- 
pius denied  that  the  brain  is  moved  by  a  systole  and  diastole, 
since  he  had  never  witnessed  the  movement,  either  in  animals 
or  in  wounded  men.  Columbus  said  that  the  use  of  the  cir- 
cumvolutions of  the  brain  was  for  the  sake  of  lightness,  so  that 
it  might  the  more  readily  be  agitated  by  systole  and  diastole ; 
and  that  the  animal  spirits  derived  from  the  air  drawn  in 
through  the  nostrils  and  commingled  with  the  vital  spirit,  arise 

24 


370        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,    [ch.  i. 

into  the  upper  ventricles  from  the  motion  of  the  brain  and  of 
the  plexus  choroides ;  this  he  published  as  his  own  discovery, 
for  which  he  was  reproved  by  Piccolhomineus.  Des  Cartes 
maintained  that  the  animal  spirits  were  secreted  from  the 
brain  through  pores  opening  into  the  ventricles,  and  that 
there  accumulating,  the  slightest  disturbance  of  them  excites 
the  soul  seated  in  the  pineal  gland ;  and  contrarily  that  the 
animal  spirits  in  the  ventricles  are  moved  by  the  will  acting 
through  the  pineal  gland,  and  distributed  thence  through  the 
nerves  to  all  parts  of  the  body. 

SECTION    IV. THE    ANIMAL    SPIRITS    ARE    DISLODGED    FROM 

THE  VENTRICLES. 

Caspar  Bauhin  was  amongst  the  first  who  denied  that  the 
ventricles  are  the  laboratory  and  storehouse  of  the  animal  spirits_, 
and  who  taught  that  these  are  generated  in  the  substance  of 
the  brain,  and  dispensed  directly  from  thence  through  the 
nerves  to  the  organs  of  sensation  and  motion.  He  maintained 
that  the  ventricles  are  more  properly  accidental  structures, 
which  have  no  other  use  than  to  receive  the  excreta  and 
residuum  formed  in  the  nutrition  of  the  brain  and  in  the  pro- 
duction of  the  animal  spirits,  and  to  pass  them  away  through 
the  infundibulum  to  the  fauces.  Platerus,  Varolius,  Spigelius, 
Moebius,  &c.,  were  also  of  this  opinion. 

Caspar  Hoffmann,  Professor  at  Altorf,  more  particularly 
opposed  the  ancient  doctrine  as  to  the  use  of  the  ventricles  in 
preparing  and  retaining  the  animal  spirits,  and  used  six  leading 
arguments  against  it,  which  he  considered  to  be  wholly  irre- 
fragible.  1  st.  That  all  the  nerves  of  the  body  and  cerebrum  arise 
from  the  spinal  cord,  either  within  or  external  to  the  cerebrum. 
2dly.  That  if  it  be  necessary  to  the  action  of  the  spirits  that  they 
be  under  the  control  of  the  mind  in  the  vessels,  what  compels 
them  into  the  straits  of  the  nerves  after  having  entered  into 
the  ocean  of  the  ventricles  ?  3dly.  That  the  ventricles  are  lined 
internally  with  the  pia  mater  which  prevents  ingress  and  egress. 
4thly.  That  since  the  two  superior  ventricles  open  into  the  third, 
and  the  third  into  the  infundibulum,  and  this  into  the  palate^ 
who  will  say  that  the  spirits  might  not  pass  out  by  this  way  ? 
5thly.  That  the  ventricles  are  not  continuous  with  the  nerves, 
but  with  the  body.     6thly.  That  the  ventricles  have  already  a 


sECT.iv.]  ANIMAL  SPIRITS  NOT  IN  THE  VENTRICLES.  371 

function  incompatible  with  that  of  the  spirits,  namely,  to  collect 
and  excrete  the  effete  matters.  These  arguments,  whatever 
validity  they  might  have,  were  sufficient  to  lead  many  from  the 
doctrines  of  Galen,  and  to  convince  them  that  the  ventricles  of 
the  brain  are  not  the  factories  and  storehouses  of  the  spirits, 
but  only  established  for  the  collection  and  expulsion  of  the  effete 
matters.  Riolanus  the  son,^  endeavoured  to  remedy  this  neglect 
of  the  doctrine,  and  tried  to  weaken  and  explode  the  arguments 
of  Hoffmann,  and  while  he  defended  the  doctrine  of  Galen,  he 
in  some  measure  adopted  that  of  Aristotle.  He  taught  that 
the  animal  spirits  are  generated  from  the  vital  in  the  ventri- 
cles of  the  brain  alone,  and  diffused  thence  through  the  whole 
cerebrum ;  that  the  air  inspired  through  the  nostrils  does  not 
enter  the  ventricles,  nor  is  it  mixed  with  the  spirits,  but  being 
diffused  round  the  dense  membrane  [dura  mater]  cools  the 
brain,  as  the  inspired  air  cools  the  lung ;  and  that  the  convo- 
lutions are  so  constructed  for  the  sake  of  lightness  and  the 
distribution  of  the  arteries.  He  more  particularly  blamed 
Hoffmann,  and  charged  him  with  ignorance,  because  that  by 
his  new  dogma  he  unsettled  both  the  whole  pathology  and 
therapeutics  of  the  brain,  for  he  fixed  the  seat  of  epilepsy 
and  apoplexy  in  the  whole  substance  of  the  brain,  and  not  in 
the  ventricles,  as  Galen  taught.  And  this  argument  is  that 
with  which  physicians  are  accustomed  to  meet  new  dogmas, 
when  opposed  to  their  own,  even  if  true,  lest  they  should  be 
compelled  by  shame  to  unlearn  when  old  those  things  which  they 
have  learnt  in  youth.  Harvey  was  met  with  almost  a  similar 
argument,  and  considered  as  an  audacious  man,  a  disturber  of 
medical  peace,  and  a  seditious  citizen  of  the  medical  republic, 
who  first  dared  to  unsettle  the  doctrine  established  by  unanimous 
assent  for  many  ages,  confirmed  by  the  writings  of  so  many 
physicians,  and  handed  down,  as  it  were,  from  generation  to 
generation,  as  if  no  one  knew  any  thing  for  so  many  ages.^ 

Wepfer  fully  refuted  Riolan  in  his  'Auctarium  Historiarum 
Apoplecticorum  et  Exercitationis  de  loco  Apoplexia  affecto,^ 
and  duly  interred  the  doctrines  as  to  the  use  of  the  ventricles 
in  producing  and  retaining  the  animal  spirits. 

'  Enchirid.  Anat. 

'  In  Zacchar.  Sylvii  praefat.  ad  Harveii  Exercit.    Anat.  de  Circulatione  Sanguinis. 
Vide  Biblioth.  Anatom.  Mangeti. 


372        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,    [ch.  i. 

SECTION   V. ANOTHER    OFFICE   ATTRIBUTED    TO    THE  VENTRICLES 

OF  THE  BRAIN  BY  GALEN,  IS    ALSO   SHOWN  TO   BE  ERRONEOUS. 

After  it  had  been  fully  decided,  tliat  llie  animal  spirits  are 
not  generated  in  the  ventricles  of  the  brain,  nor  generated  in 
the  brain,  to  be  collected  in  the  ventricles,  still  all  believed 
in  this  use  of  the  ventricles  at  least,  that  they  are  cloacae, 
and  receptacles  appointed  to  receive  the  effete  matters  which 
flow  towards  the  ventricles  after  the  secretion  of  the  spirits 
and  the  nutrition  of  the  brain.  They  asserted  that  the  finer 
portion  of  these  excreta  escape  through  the  sutures  of  the 
cranium,  but  that  the  denser  portion  trickle  down  partly 
through  the  mamillary  processes  and  cribriform  bone  into  the 
nostrils,  partly  through  those  peculiar  ducts  pointed  out  by 
Galen  and  Vesalius,  which  lead  from  the  pituitary  gland  through 
the  sphenoid  bone  to  the  fauces.  It  then  became  the  theory 
of  the  day,  that  these  effete  matters  passing  down  continually 
formed  the  mucus  of  the  nostrils  and  fauces;  coryza  and  catarrh 
were  said  to  be  caused  by  these  effete  matters  trickling  down 
more  freely  and  in  larger  quantity,  and  that  the  brain  in  those 
affections  purged  itself  from  humidities,  which  if  left  to  ac- 
cumulate in  the  ventricles,  induce  cold  in  the  head,  vertigo, 
headache,  epilepsy,  apoplexy,  &c. 

Conrad  Victor  Schneider,  professor  at  Wittenberg,  whom 
Haller  has  praised  in  the  highest  terms,^  essayed  to  refute  these 
errors  in  the  happiest  manner  by  means  of  anatomy.  In  his 
tract  'De  Osse  Cribriformi,^  he  combats  by  dissection  two 
epidemic  errors,  as  Haller  terms  them,  the  one  which  taught 
that  odoriferous  particles  enter  the  ventricles  of  the  brain,  and 
there  excite  sensation  ;  the  other,  that  the  effete  matters 
descend  from  the  brain  through  the  cribriform  bone ;  for  the 
olfactory  nerves  are  not  hollow  in  man,  as  they  are  in  brutes. 
In  his  work  '  De  Catarrhis/  he  fully  demonstrates  by  anatomy, 
that  nothing  could  pass  from  the  nostrils  into  the  ventricles 
of  the  brain,  neither  air  nor  fumes,  because  all  the  foramina 
of  the  cribriform  bone  are  closed,  and  the  dura  mater  adheres 
strongly  everywhere  to  the  bones  and  also  to  the  cribriform 
plate;  that  nothing  could  pass  down  to  the  fauces  through 
the  infundibulum,  through  the  pituitary  gland,  or  through  its 
»  Bibl.  Anat.,  torn,  i,  p.  413. 


SECT,  v.]    ANOTHER  OFFICE  OF  THE  VENTRICLES.  373 

imaginary  ducts ;  that  no  vapours  could  exhale  from  the  ven- 
tricles through  the  sutures  of  the  cranium ;  that  catarrhs  never 
collect  in  the  ventricles  of  the  brain,  but  have  their  seat  in  the 
pituitary  membrane  of  the  nares  and  fauces,  which,  from  being 
more  exactly  described  by  him,  was  called  the  Schneiderian 
membrane.  In  confirmation  of  this,  he  states  a  case  of  coryza 
equina,  in  which  both  the  anterior  and  posterior  portion  of  the 
pituitary  membrane  was  affected,  but  the  mamillary  processes 
of  the  brain  were  perfectly  healthy. 

This  demonstration  by  Schneider,  however  lucid,  could  not 
convince  every  one,  and  there  were  still  some  who  preferred 
the  old  doctrine;  amongst  these,  were  Diemerbroeck,  Bartholin,^ 
and  Otto  Horstius.^  Lower,^  Willis  and  others,  were  convinced 
indeed,  that  nothing  could  pass  from  the  ventricles  to  the 
nostrils,  or  trickle  through  the  infundibulum  and  pituitary 
gland  to  the  fauces,  but  they  thought,  nevertheless,  that  the 
serum  of  the  ventricles  passed  through  the  infundibulum  to 
the  pituitary  gland,  and  hence  through  peculiar  ducts  to  the 
jugular  veins,  where  it  was  mixed  with  the  blood.  With  these 
Adolphus  Murray  may  be  classed,*  who  found  the  infundibulum 
hollow,  and  transmitting  a  serous  fluid  from  the  ventricles ;  but 
what  change  this  serum  underwent  in  the  pituitary  gland  he 
found  it  difficult  to  say ;  yet  he  affirms  that  he  once  found  two 
ducts,  which  arose  on  each  side  of  the  pituitary  gland,  and 
terminated  in  the  cavernous  sinus.  He  therefore  thought  it 
possible,  that  the  superfluous  serum  of  the  brain  might  pass  off 
by  this  route ;  but  on  his  repeating  the  experiment,  he  did  not 
succeed  in  finding  these  ducts.  The  opinion  of  Haller  as  to 
this  controversy,^  whether  the  infundibulum  be  hollow  or 
solid,  is,  that  we  must  agree  with  Murray,  who  found  it 
hollow,  but  that  he  strongly  suspected  the  two  ducts  passing 
from  the  pituitary  gland  to  the  cavernous  sinuses  were  only 
veins ;  nor,  in  fact,  do  the  ventricles  require  a  special  outlet, 
by  which  the  serum  may  be  evacuated,  because  in  every  part 
of  the  body  a  secreted  vapour  is  reabsorbed  by  its  proper  veins, 

'  Anat.  Reform. 

^  Presid.  Slevogtio  defendit.     Vid.  Halleri  disput.  Anat.,  torn,  ii,  p.  849. 

^  Tract,  de  Corde,  Capite  de  Catarrhis. 

*  Dissert.  Inaug.  de  Infundibulo  Cerebri,  &c.     Upsal,  1772. 


De  Usu  et  Fabrica  Part.  Corp.  Human.,  tom.  viii,  p.  92,  &c. 


374        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,     [ch.  i. 

and  just  as  the  fluid  of  the  pericardium,  thorax,  abdomen, 
scrotum,  generated  from  the  arterial  exhalation,  does  not  require 
special  excretory  ducts,  but  is  absorbed  by  the  absorbent  veins, 
so  also  beyond  all  doubt,  is  it  with  the  fluid  of  the  ventricles 
of  the  brain.  Haller  conjectures,  with  probability,  that  the 
pituitary  gland  is  an  appendix  of  the  brain,  as  in  fishes  he 
has  seen  filaments  like  those  of  nerves  to  pass  out  of  it. 

SECTION  VI. IT  IS    PROPOSED,  WITH    OTHER  SPECIAL    FUNCTIONS 

OF  THE  NERVOUS  SYSTEM,  THAT  THE  CORTICAL  PORTION  OF 
THE  BRAIN  BE  SUBSTITUTED  FOR  THE  VENTRICLES  AS  THE 
PART  WHERE  THE  ANIMAL  SPIRITS  ARE  SECRETED,  AND 
THAT  THE  MEDULLARY  MATTER  HAS  THE  FUNCTION  OF 
COLLECTING  AND  DISTRIBUTING  THEM  TO  THE  NERVES. 

The  animal  spirits,  being  ejected  from  the  ventricles,  were 
placed  in  the  cerebral  substance  ;  so  that  Malpighi,  "Willis,  and 
Sylvius  de  le  Boi,  were  unanimous  that  they  are  secreted  in  the 
cortical  substance  of  the  brain ;  that,  when  secreted,  they  are 
received  into  the  medullary  substance,  and  distributed  thence 
through  the  nerves  to  the  whole  body ;  and  this  doctrine  is 
maintained  by  many  physiologists  and  pathologists  to  the  pre- 
sent day.  The  faculties  of  the  mind,  such  as  perception,  imagi- 
nation, understanding,  and  memory,  were  banished  from  the 
ventricles  together  with  the  vital  spirits,  and  were  located  by 
some  in  the  solid  mass  of  the  brain ;  by  others  were  afl&rmed 
to  be  properties  of  the  immaterial  and  rational  soul  alone,  and 
in  no  wise  dependent  on  the  body.  Lest  I  should  weary  the 
reader  by  a  lengthened  enumeration  of  the  almost  innumerable 
authors  of  this  opinion,  I  will  only  adduce  the  doctrines  of 
Malpighi  and  Willis,  and  then  state,  in  general  terms,  how  far 
their  successors  followed  these  celebrated  men,  and  how  far 
they  departed  from  their  doctrine. 

Marcellus  Malpighi,  in  his  letters  to  Fracassatus, '  De  Cerebro 
et  Cortice  Cerebri,^  maintains  that  the  cortical  portion  secretes, 
by  means  of  a  glandular  structure,  which  he  pretends  it  con- 
tains, a  coagulable  serum  from  the  arterial  blood,  and  that  it 
is  necessary  to  sensation  and  movement,  that  this  fluid  be 
transmitted  from  the  cortical  to  the  medullary  matter.  It 
does  not  seem  possible  to  him,  that  there  can  be  a  reflux  of 
this  serum  in  the  nerves  to  the  brain  so  as  to  cause  sensation, 


\ 


SECT.  VI.]  SUBSTITUTION  OF  BRAIN  FOR  VENTRICLES.  375 

since  the  new  serum  perpetually  secreted  resists  the  retrograde 
movement. 

He  confirms  the  ancient  opinion  of  Plato,  that  the  brain  is 
an  appendage  to  the  spinal  cord_,  in  which  medullary  fibres, 
collected  together,  radiate  towards  the  brain,  until  they  end  in 
the  cortical  portion,  just  as  the  fibres  in  the  stem  of  a  cauli- 
flower radiate  into  the  leaves.  Confirmatory  of  this  doctrine 
are  the  small  brain  and  large  spinal  cord  of  fishes.  Fracassatus 
also  adopted  this  opinion,  and  Thomas  Bartholin,  in  his  '  Ana- 
tome  quartum  renovata,'  says  this  opinion  is  both  new  and 
peculiar,  and  that  by  it  he  can  understand  how  fishes,  on 
account  of  their  small  brain,  are  dull  as  to  sensation,  but  agile 
as  to  movement,  from  their  large  spinal  cord  ;  especially  since  in 
the  incubated  egg  also  the  anterior  part  of  the  brain  is  developed 
at  a  much  later  stage  than  that  in  which  if  the  chick  be  touched 
it  contracts.  It  is  well  known,  however,  that  Plato  had  already 
stated,  that  the  spinal  cord  is  first  formed,  and  the  brain  is  an 
appendix  to  it.^ 

Thomas  Willis,  a  celebrated  member  of  the  chemical  sect, 
advanced,  with  some  ingenuity,  many  new  hypotheses  as  to  the 
uses  of  the  nervous  system ;  with  these  he  commingled  some 
ancient  doctrines,  as  for  example,  that  serous  effete  matter  in 
the  ventricles  trickles  partly  through  the  olfactory  nerves  into 
the  nostrils,  partly  through  the  infundibulum  to  the  pituitary 
gland,  and  thence  by  peculiar  ducts  to  the  veins  which  return 
the  blood  to  the  heart  from  the  brain ;  he  also  agreed  with  Galen 
in  considering  the  use  of  the  fornix  to  consist  in  supporting  the 
hemispheres.  His  own  peculiar  doctrines  chiefly  are  :  that  the 
cerebrum  subserves  to  the  animal  functions  and  the  voluntary 
motions,  the  cerebellum  to  the  involuntary ;  that  a  perception 
of  all  the  sensations  takes  place  in  the  ascending  fibres  of  the 
corpora  striata,  and  that  through  the  descending,  voluntary  move- 
ments are  excited ;  that  the  understanding  is  seated  in  the  corpus 
callosum,  and  memory  in  the  convolutions,  which  are  its  store- 
houses ;  that  the  animal  spirits  are  generated  in  the  cortex  of 
the  cerebrum  and  cerebellum  from  the  arterial  blood ;  that  they 
collect  in  the  medulla,  are  variously  distributed  and  arranged 
to  excite  the  animal  actions,  and  distil  through  the  fornix 
as  if  through  a  pelican  :  that  the  animal  spirits  secreted  in 

'  Ilaller,  Bib.  Anat.,  torn,  i,  p.  30. 


376        FUNCTIONS  OF  THE  NERVOUS  SYSTEM,     [ch.  i. 

the  cerebellum  are  ever  flowing,  equably  and  continuously, 
into  the  nerves  which  regulate  involuntary  movements;  but 
those  of  the  cerebrum  tumultuously  and  irregularly,  according 
as  the  animal  actions  are  vehemently  performed  or  quiescent. 
To  excite  sensation,  the  spirits  flow  along  the  nerves  to  the 
brain.  He  distinguishes  between  a  thick  nervous  fluid,  suit- 
able to  nutrition,  and  the  extremely  volatile  animal  spirits, 
subservient  to  sensation  and  movement,  and  commingled  in  the 
preceding  as  their  vehicle.  He  maintains,  that  there  are  two 
souls  in  man,  the  one  rational,  the  other  corporeal ;  the  latter 
alone  is  given  to  brutes.  The  corporeal,  or  brute  soul,  consists 
partly  of  a  fiery  or  sulphureous  element,  which  is  located  in 
the  blood;  and  partly  of  an  ethereal  element,  which  is  the 
animal  spirit  secreted  in  the  cerebrum.  That  the  corporeal  soul, 
thus  composed,  forms  a  foetus  from  the  semen  of  the  parents 
like  to  the  parents,  increases  with  the  body,  preserves  the  body 
until  death,  causes  the  perception  of  sensations  in  the  corpora 
striata,  and  thence  reflected,  excites  desires  and  voluntary 
movements;  in  the  corpus  callosum  excites  imagination,  and 
in  the  convolutions  memory.  It  diff'ers  from  the  rational  soul 
in  this,  that  the  latter  uses  the  corporeal  soul  as  the  instrument 
whereby  it  performs  all  things  more  quickly  and  readily  in  man 
than  they  are  done  in  brutes,  and  because  in  virtue  of  the 
rational  soul  man  is  rendered  capable  of  contemplating  things 
not  belonging  to  the  senses,  as  God,  angels,  himself,  infinity, 
eternity,  &c.  He  explains  the  unity  of  the  nerves  by  their 
communications  and  connections  with  each  other,  or  their  anas- 
tomoses, as  anatomists  term  them :  and  he  also  explains,  that 
the  union  of  the  cerebrum  and  cerebellum  is  attained  by  the 
tubercula  quadrigemina,  or  nates  and  testes.  As  to  the  loops 
of  nerves  with  which  the  arteries  here  and  there  are  encircled, 
he  states  their  use  to  be,  to  relax  or  close  the  arteries,  and 
thus  during  various  emotions  of  the  mind  to  admit  the  blood 
in  greater  or  less  quantity  to  certain  parts.  He  decided  that 
the  pineal  gland  is  not  the  seat  of  the  soul,  but  a  lymphatic 
gland,  having  no  relation  with  the  substance  of  the  brain, 
which  absorbs  lymph,  aud  carries  it  ofi*  again  through  other 
vessels,  and  keeps  the  plexus  choroides  expanded. 

His  successors,  especially  of  the  school  of  Boerhaave,  em- 
braced some  of  these  doctrines  of  Willis,  but  some  were  exploded. 


i 


sECT.vi.]  SUBSTITUTION  OF  BRAIN  FOR  VENTRICLES.  377 

For  example,  it  was  shown  by  anatomy,  that  all  the  nerves  are 
not  of  involuntary  motion  which  arise  from  the  cerebellum,  as  the 
fifth  pair  of  cerebral  nerves  is  wholly  derived  from  the  medulla 
of  the  cerebellum,  the  pons  varolii.  Ruysch,  in  opposition  to 
Malpighi,  earnestly  endeavours  to  prove,  by  his  injections,  that 
the  cortex  of  the  brain  is  not  glandular,  but  consists  of  parallel 
vessels  :  however,  Albinus  clearly  showed,  that  it  was  not  alto- 
gether vascular.  Mayow  attempted  to  show,  that  the  animal 
spirits  consist  of  nitro-aerial  particles ;  Boerhaave,  that  they 
consist  of  a  very  refined  aqueous  fluid,  having  also  a  nutrient 
property,  which  was  disputed  afterwards  by  Haller.  Some 
thought  they  are  aether,  some  electron ;  Vieussens  placed  the 
seat  of  imagination  in  his  centrum  ovale  ;  Lancisi  and  Peyronie 
maintained,  that  all  sensation  is  felt  and  motion  excited  in  the 
corpus  callosum.  Meyer  placed  the  seat  of  memory  in  the 
cortical  matter,  sensation  at  the  origin  of  the  nerves,  and 
abstract  ideas  in  the  cerebellum  ;  many,  however,  acknowledged 
that  it  was  not  possible  to  determine  the  seat  of  the  mental 
faculties  with  any  accuracy,  although  there  could  be  no  doubt 
that  nature  had  not  formed  so  many  and  so  various  divisions  of 
the  cerebrum  and  cerebellum  without  an  object.  Haller  thought 
that  the  only  prospect  of  attaining  to  any  knowledge  of  the 
uses  of  these  portions  (if  it  were  possible)  was  in  diligently 
availing  ourselves  of  every  opportunity  for  dissecting  fatuous, 
oblivious,  or  maniacal  persons,  or  in  accurately  comparing  the 
cerebra  of  animals  whose  faculties  are  well  known  with  the 
human  brain,  &c.^  Meckel,  Gasser,  and  others  agreed  with 
WilHs  in  affirming,  that  the  consentience  of  the  nerves  is 
effected  by  the  communicating  branches;  Whytt,  Kaauw, 
Astruc,  objected  to  this  doctrine,  and  maintained  that  con- 
sentience  takes  place  in  the  sensorium  commune  only,  and 
Haller  adopted  this  opinion.  Haller,  and  some  of  his  dis- 
ciples, amongst  whom  the  celebrated  Meckel,  also  conjectured 
that  the  nervous  loops  had  the  function  attributed  to  them  by 
Willis,  but  Haller  subsequently  retracted  this  opinion,  being 
taught  by  his  own  experiments,  that  nerves  when  torn  or 
irritated  do  not  contract  in  the  least.  Vieussens,  Ridley,  Nuck, 
and  others,  following  Willis  (and  this  indeed  was  the  opinion  of 
Galen)  classed  the  pineal  gland  with  the  lymphatic  glands. 

'  Elem.  Phys.,  torn,  v,  p.  529. 


378         FUNCTIONS  OF  THE  NERVOUS  SYSTEM,     [ch.  i. 

Nuck  plainly  subscribes  to  this  doctrine  in  his  '  Epistola  Ana- 
tomica  de  novis  inventis/  but,  however,  in  the  present  day  we 
are  certain,  that  the  pineal  gland  is  really  a  part  of  the  cortical 
substance  of  the  brain,  connected  by  two  medullary  peduncles 
with  the  thalami  nervorum  opticorum,  and,  consequently,  not  a 
lymphatic  gland. 

The  ganglia  of  the  nerves  were  known  to  Galen,  Fallopius, 
Eustachius,  and  Willis,  but  their  function  was  first  taught  by 
Vieussens ;  who  considered  them  to  be  receptacles  of  the  animal 
spirit,  in  which  it  could  be  nourished,  preserved,  and  rectified, 
by  the  arterial  blood  flowing  through  them ;  others,  however, 
amongst  whom  was  Winslow,  looked  upon  them  as  little  brains, 
from  which  fresh  animal  spirits  are  secreted,  and  new  nerves 
given  ofi^.  Lancisi  assigned  to  them  a  muscular  coat,  by  which 
the  animal  spirits  contained  in  them  might  be  impelled  for- 
wards; Tarin  considered  them  to  be  accidental  callosities; 
Meckel  and  Zinn  were  of  opinion  that  they  divided  the  larger 
nerves  into  smaller,  and  gave  them  another  direction.  Johnstone 
maintained  that  ganglia  were  peculiar  to  those  nerves  not  sub- 
ject to  volition.  Various  objections  were  raised  against  this 
doctrine,  especially  by  the  illustrious  Haller,  and  Haase,  but 
Tissot  and  Pfeffinger  approved  of  it.  There  will  be  an  oppor- 
tunity of  discussing  this  again;  and  since  Tissot  has  fully 
treated  of  the  matter  in  his  work  on  the  nerves,  I  will  not 
abuse  the  patience  of  the  indulgent  reader  by  the  repetition  of 
things  well  known. 


SECTION  VII. THOSE  WHO   HAVE   DENIED  THE  EXISTENCE  OF 

ANIMAL  SPIRITS. 

The  existence  of  the  animal  spirits  being  received,  from  the 
most  remote  period,  descending  by  tradition,  as  it  were,  no  one 
proved  or  attempted  to  prove  it  as  it  ought  to  be.  Celebrated 
men  began,  however,  to  call  in  question  the  existence  of  these 
animal  spirits,  especially  since  the  doctrine  seemed  to  be  a  gra- 
tuitous assumption ;  amongst  whom  were  Argenter,  Alexander 
Benedictus,  Quercetanus,  Nymman,  Fernel,  Avicenna,  Felix 
Plater,  Helmont,  Cabroli,  Back,  Bidloo,  Lister,  Brini,  Parisinus, 
and  many  others  :  of  these  some  attempted  to  substitute  for  the 
discarded  hypothesis  one  not  more  demonstrable,  namely,  that 


SECT. VII.]  EXISTENCE  OF  ANIMAL  SPIRITS  DENIED.  879 

the  nerves  acted  as  solid  tense-cords,   alternately  contracting 
and  relaxing,  or  only  oscillating.     But  it  was  easy  to  demon- 
strate to  these,  that  the  nerves  are  soft,  pulpy,  and  not  tense- 
cords,  and  therefore  unsuitable  to  the  functions  assigned  to 
them :    this    hypothesis  being  rejected,  the   authority  of  the 
other,  as  to  the  animal  spirits,  increased.     In  the  next  place, 
opponents  of  the  animal  spirits  were  found  in  the  Stahlians,  who 
maintained  that  all  the  functions  of  the  nerves  depended  directly 
on  the  soul,  and  who  rejected  the  animal  spirits  (whose  exist- 
ence was  not  proved)  as  useless.     But  the  defenders  of  the 
animal  spirits  silenced  these  opponents  also,  not  by  proving  the 
existence  of  the  spirits,  but  because  they  overturned  the  foun- 
dations of  the  Stahlian  doctrines,  which,  it  appears  to  me,  Haller 
especially  accomplished.    After  this  second  victory  over  the  op- 
ponents of  the  animal  spirits,  some  distinguished  men  of  the 
mechanical  school  attempted  to  prove  their  existence  by  various 
and  far-fetched  arguments ;    the    principal   were   Boerhaave, 
Haller,  and  Tissot,  the  latter  plainly  endeavouring  to  establish 
the  hypothesis  as  a  truth.     Notwithstanding  the  authority  of 
these  great  names,  the  love  of  truth  excited  distinguished  men, 
who  advanced  doubts  as  to  this  hypothesis  of  the  animal  spirits, 
and  who  showed  that  the  arguments  adduced  in  its   favour 
proved  nothing  when  carefully  analysed,  and  that  the  whole 
hypothesis  was  altogether  devoid  of  truth.      Of  these  the  illus- 
trious Caldani,  so  highly  esteemed  by  Haller,   on  account  of 
his  great  merit  in  medical  art,  led  the  way ;   and  whose  argu- 
ments have,  I  think,  the  greater  weight,  because,  although  a 
most  dear  friend  to  Haller,  yet  led  by  the  love  of  truth,  he  did 
not  hesitate,  in  this  case,  to  think  and  act  in  opposition  to  him. 
Afterwards  Metzger,^  Azzoguidi,^  Mayer,^  Michelitz,^  Marzari,^ 
and  Fiorati,  in  the  notes  to  his  Italian  edition  of  ^  Tissot  on 
the  Nerves,'  joined  their  arguments  to  undermine  and  entirely 
overthrow  the  hypothesis;  and  if  we  consider  these  with   a 
mind  free  from  prejudices,  we  cannot  but  forget  the  hypothesis 
as  we  would  a  dream,  and  be  excited  to  inquire  after  truth  in 
another  way  than  through  hypotheses  and  conjectures. 

*  Adversar.  Med. 
«  Instit.  Med. 

^  Abhand.  vom  Gehirn,  Ruckenmark,  und  Ursprung  der  Nerven. 

*  Scrutin.  hypoth.  Spirit.  Anim. 

*  Dissertazioni  Accadem.  delle  Ipotesi,  &c. 


380        FUNCTIONS  OF  THE  NERVOUS  SYSTEM.    [cH.  i. 

SECTION  VIII. THE  FUNCTIONS  OF  THE   NERVOUS  SYSTEM  ARE 

EXPLAINED  BY  THE    VIS  NERVOSA. 

At  length  we  abandon  the  Cartesian  method  of  philoso- 
phising in  this  part  of  animal  physics  also,  and  adopt  the 
Newtonian,  being  persuaded  that  the  way  to  truth  through 
hypotheses  and  conjectures  is  tedious  and  altogether  uncertain, 
but  far  more  certain,  more  excellent,  and  shorter,  through  the 
inductive  method.  Newton  designated  the  mysterious  cause 
of  physical  attraction  by  the  term  vis  attractiva,  observed  and 
arranged  its  effects,  and  discovered  the  laws  of  motion ;  and 
thus  it  is  necessary  to  act  with  reference  to  the  functions  of 
the  nervous  system :  we  will  term  the  cause  latent  in  the  pulp 
of  the  nerves,  producing  its  effects,  and  not  as  yet  ascertained, 
the  vis  nervosa :  we  will  arrange  its  observed  effects,  which  are 
the  functions  of  the  nervous  system,  and  discover  its  laws ;  and 
thus  we  shall  be  able  to  found  a  true  and  useful  doctrine,  which 
will  undoubtedly  afford  a  new  light,  and  more  elegant  character 
to  medical  art.  The  illustrious  Haller  has  already  used  the 
phrase  vis  nervosa,  in  designating  the  agent  which  the  nerves 
employ  in  exciting  muscular  contractions ;  but  the  celebrated 
and  ingenious  J.  A.  Unzer  has  thrown  the  greatest  light  on 
the  subject  -^  for  although  he  continues  the  use  of  the  term 
animal  spirits,  that  he  may  the  more  conveniently  and  intel- 
ligibly express  himself,  yet,  as  he  himself  observes,  his  whole 
system  is  complete  without  them.^ 

•  Vid.  Grundrisz  eines  Lehrgebaudes  von  der  Sinnlichkeit  der  thierischen  Korper, 
&c.  1768.  Also,  Erste  Griinde  einer  Physiologic  der  eigentlichen  thierischen  Natur 
thierischer  Korper,  1771. 

^  Prochaska  thus  explains  in  what  sense  he  uses  the  term  vis  nervosa,  in  the 
"  Address  to  the  Reader,"  prefixed  to  the  edition  of  this  dissertation,  pubUshed  in 
his  '  Opera  Minora,'  part  2.  (Vienna,  1800.)  "I  had  already  (in  1780)  published 
this  dissertation,  in  the  third  fasciculus  of  my  *  Adnotationes  AcademiccB  ;^  at  which 
time  many  philosophers,  and  the  distinguished  Tissot  himself,  still  used  the  hy- 
pothesis of  a  nervous  fluid,  to  explain  the  functions  of  the  nervous  system  in  accord- 
ance with  the  opinion  of  Boerhaave.  Convinced  of  the  insufficiency  of  this  hypothesis,  I 
resolved  to  use  the  inductive  method  in  this  dissertation,  and  explain  those  functions 
by  facts  only ;  using  the  term  *  vis  nervosa'  to  designate  that  agent  (as  yet  unknown) 
by  which  the  nervous  system  is  rendered  fit  for  the  performance  of  its  functions, 
and  which  I  have  used  more  extensively  in  my  pubUc  lectures,  and  in  my  institutes 
of  human  physiology  ('  Lehrsatze  aus  der  Physiologic  des  Menschen,'  1797)." — Ed. 


CHAPTER  II. 

THE  NERVOUS  SYSTEM  IN  GENERAL. 


SECTION   I. WHAT  PARTS  IT  INCLUDES. 

The  nervous  system,  as  well  in  man  as  in  the  animals  in 
any  way  d:'elated  to  him,  comprises  the  cerebrum,  cerebellum, 
medulla  oblongata,  medulla  spinalis,  and  all  the  nerves  dis- 
tributed thence  to  every  part  of  the  body.  These  divisions  are 
manifestly  dissimilar  in  structure;  those  portions  whose  functions 
are  more  numerous  and  complicated  seem  to  require  a  more 
composite  and  complicated  structure  than  those  whose  functions 
in  the  animal  economy  are  of  a  simpler  kind ;  in  particular, 
the  brain  of  man  is  larger  and  of  a  more  complex  structure 
than  the  cerebellum,  and  other  portions  of  the  nervous  system. 
This  large  cerebrum  is  divided  into  two  hemispheres,  united 
in  the  middle  principally  by  the  corpus  callosum  :  the  gray  cor- 
tical matter  entirely  surrounds  the  white  internal  medullary 
matter,  which  is  in  much  greater  quantity  in  the  cerebrum  than 
in  the  cerebellum :  the  external  surface  appears  as  if  divided 
into  convolutions,  having  a  resemblance  to  the  intestines.  The 
cerebrum  has  three  cavities,  or  ventricles,  in  the  two  superior 
of  which  are  seen  the  plexus  choroides,  then  the  corpora  striata 
and  thalami  nervorum  opticorum ;  behind  these,  are  the  pineal 
gland  and  corpora  quadrigemina.  The  septum  lucidum  divides 
these  ventricles,  beneath  which  is  the  fornix  divided  posteriorly 
into  two  crura,  termed  pedes  hippocampi  and  cornua  am- 
monis.  In  the  third  ventricle,  are  the  anterior  and  posterior 
commissures;  also,  posteriorly,  the  opening  into  the  fourth 
ventricle,  which  is  in  the  cerebellum,  and,  anteriorly,  the  orifice 
into  the  infundibulum,  which  is  inserted  into  the  pineal  gland. 
Posteriorly  to  the  infundibulum,  are  seen  the  corpora  mamil- 
laria,  and  here  are  also  situate  the  two  great  crura  cerebri  into 
which  all  the  medullary  matter  from  both  hemispheres  seems 
to  be  collected.  The  cerebellum  is  much  less  than  the  cere- 
brum, and  presents  on  its  surface  highly-curved  and  slender 
convolutions;  its  medullary  matter  is  much  less  in  proportion  to 


382  THE  NERVOUS  SYSTEM  IN  GENERAL,     [ch.  ii. 

the  cortical  than  in  the  brain,  and  gives  off  its  medulla,  partly 
upwards  to  the  corpora  quadrigemina,  and  partly  downwards  to 
the  medulla  oblongata,  but  principally  to  the  pons  varolii  of 
which  it  constitutes  the  greater  portion.  Beneath  the  pons 
varolii  the  caudex  medullaris  takes  its  origin,  and  passes  through 
the  occipital  foramen.  It  has  been  specially  designated  the  me- 
dulla oblongata  by  late  anatomists,  and  consists  of  the  anterior 
and  posterior  pyramids,  with  the  olivary  bodies  between  them, 
in  which  the  cortical  matter  is  so  peculiarly  interwoven,  that  a 
transverse  section  of  an  olivary  body  presents  serpentine  lines, 
having  somewhat  the  appearance  of  a  small  tree.  The  composi- 
tion of  the  medulla  oblongata  is  of  a  simpler  character ;  it  is  a 
thick  nervous  cord,  occupying  the  cavity  of  the  vertebral  column: 
on  its  anterior  surface  there  is  a  groove  (some  call  it  a  fissure) 
which  divides  it  perpendicularly  into  two  columns,  internally 
in  its  centre  there  is,  as  some  think,  something  of  a  cortical 
substance.  The  origin  of  the  nerves  of  the  brain,  and  of  the 
medulla  spinalis,  is  different  as  to  situation  and  size,  more 
simple  in  some,  in  others  compounded  of  many  roots ;  of  these 
are  some  which  are  enlarged  near  their  origin  by  a  ganglion, 
as  in  the  fifth  pair  of  cerebral  nerves,  and  in  all  the  spinal 
nerves,  but  others  more  distantly,  as  is  particularly  the  case  in 
the  intercostal  nerves.  As  to  other  points,  all  the  nerves 
passing  out  from  the  cranium  and  vertebral  canal  are  furnished 
with  a  double  investing  membrane,  and  contain  a  continuation 
of  the  medullary  substance  of  the  brain  and  spinal  cord,  but 
are  of  a  firmer  consistence.  In  their  course  to  various  parts, 
the  fasciculi  of  which  they  are  composed  enter  into  remarkable 
plexuses  and  connections,  until  they  terminate  variously  in 
various  parts ;  in  the  eye,  the  optic  nerve  expands  into  a  mem- 
brane ;  in  the  ears,  in  the  Schneiderian  membrane,  in  the  pa- 
pillae of  the  tongue,  in  the  skin,  in  muscles,  and  in  various 
secreting  viscera  they  probably  terminate  differently ;  but  as  to 
this  point  nothing  is  known,  for  they  escape  the  most  acute 
vision. 

All  these  portions  of  the  nervous  system,  which  I  have  only 
cursorily  enumerated  for  the  sake  of  brevity,  and  of  which 
anatomy  furnishes  an  accurate  description  and  delineation,  ^ 

•  Monro,  Winslow,  and  Haller,  have  published  most  accurate  descriptions  of  the 
nerves ;  and  their  works  are  so  well  known  and  received  with  such  general  approval, 


SECT.  I.]  PARTS  INCLUDED  IN  THE  NERVOUS  SYSTEM. 383 

abundantly  shows  how  wonderfully  and  diversely  the  machine 
of  the  nervous  system  is  constituted,  and  how  skilfully  pro- 
tected j  and  if  it  be  compared  with  any  other  part  or  organ  of 
the  body,  testifies  that  nature  nowhere  else  has  adopted  such  a 
variety  and  number  of  parts,  nowhere  else  framed  such  sin- 
gular forms,  nowhere  else  used  such  a  delicate  and  fragile  ma- 
terial, no  other  structures  so  skilfully  protected  as  that  system ; 
whence  it  follows  that  its  functions  in  the  animal  economy 
must  be  of  the  highest  importance,  and  at  the  same  time  the 
most  complicated.  However  composite  the  machine  of  the 
nervous  system  may  be,  I  think  it  may  be  divided  into  three 
portions,  just  as  its  functions  are  most  conveniently  arranged 
in  three  divisions  :  namely,  in  the  first  place,  the  animal  organs, 
or  the  organs  of  the  mental  faculty,  the  cerebrum  and  cere- 
bellum ;  secondly,  the  general  sensorium  which  appears  to  con- 
sist of  the  medulla  spinalis  and  medulla  oblongata,  together 
with  that  portion  of  the  medulla  of  the  cerebrum  and  cere- 

that  it  would  be  superfluous  to  quote  them.  Besides  these,  a  most  accurate  de- 
scription of  the  nerves  of  the  humau  body,  containing  all  the  recent  discoveries 
appropriately  arranged,  may  be  read  in  the  new  Latin  edition  of  the  *  Institutiones 
Neurologicse,'  1781,  by  Martini,  President  of  the  Royal  Academy  of  Sciences  of 
Sweden,  and  formerly  Professor  of  Anatomy  and  Surgery.  They  who  desire  to  see 
correct  delineations  of  the  nervous  system,  may  consult,  for  this  purpose,  the  17th 
to  the  23d  inclusive  of  Eustachius's  plates,  and  the  '  Anatoraica  Adversaria'  of  Tarin 
(Paris,  1750).  Mayer,  the  celebrated  anatomist  and  professor  of  Frankfort,  in  his 
work  entitled  *  Anatomisch-Physiologische  Abhandlung  vom  Gehirn,  Ruckenmark, 
und  Ursprung  der  Nerven'  (Berlin,  1779),  as  also  in  another  on  the  vessels  of  the 
human  body,  has  published  most  beautiful  and  accurate  views  of  the  cerebrum, 
medulla  oblongata,  and  medulla  spinalis,  together  with  the  origin  of  the  nerves. 
Consult  also  the  excellent  work  of  S.  T.  Soemmering,  *  De  Basi  Encephali  et  Ori- 
ginibus  Nervorum  Cranio  Egredientium '  (Gottingse,  1778).  The  celebrated  Meckel, 
in  his  'Tractatus  de  quinto  pare  Nervorum  Cerebri'  (Gott.,  1748),  and  his  tract  'De 
Nervis  Faciei'  (Berolini,  1755),  has  dissected  the  most  minute  filaments  with  inimitable 
skill,  and  most  admirably  depicted  it.  Neubauer,  Professor  at  Jena,  snatched  away 
by  premature  death,  published  (1772)  a  work  entitled  *  Sectio  prima  Nervorum  Car- 
diacorum,*  which  could  only  have  come  from  the  hands  of  one  equally  skilled  as  an 
anatomist  and  draughtsman ;  also  Camper's  *  Demonstrationes  Anatomico-Patholo- 
gicae  ;*  Lobstein's  *  Dissert,  de  Nervo  Spinali  ad  par  Vagura  Accessorio '  in  Sandifort's 
Thesaurus,  1 :  George  Asch's  '  Diss,  de  primo  pare  Nervorum  Spinalium ;  Wrisberg's 
'Observ.  Anatomicae  de  5to  pare  Nervor.  Cer.'  (Gott.,  1777);  Boehmer's  '  Com- 
mentatio  de  nono  pare  Nervor.  Cerebri  (Gott,  1777).  To  these  might  be  subjoined 
my  tract '  De  Structura  Nervorum '  (Viennae,  1 779).  Consult  also  Ludwig's  *  Dissert, 
de  Cinerea  Cerebri  Substantia'  (Lipsiae,  1779),  and  the  beautiful  plates  of  the  nerves 
lately  published  by  Walther,  Professor  at  Berlin. 


384  THE  NERVOUS  SYSTEM  IN  GENERAL,     [ch.  ii. 

bellum,  from  which  the  nerves  directly  arise ;  and,  thirdly,  the 
nerves  distributed  from  the  general  sensorium  to  all  parts  of 
the  body. 


SECTION     II. HOW    THE    NERVOUS    SYSTEM     IS    CONSTITUTED    IN 

OTHER    ANIMALS,    AND     HOW    FAR    IT    EXTENDS    THROUGH    THE 
WHOLE   ANIMAL  KINGDOM. 

That  the  nervous  system  is  not  constituted  in  all  animals  as 
in  man,  is  proved  by  the  observations  of  eminent  men;  but 
all  the  differences  which  the  almost  innumerable  species  of 
animals  present,  have  not  as  yet  been  fully  investigated :  to 
observe  and  tabulate  all  would  require  almost  an  age,  although 
much  light  might  be  hoped  to  be  thrown  by  them  upon  the 
functions  of  the  nervous  system.  Many  of  the  able  observers, 
who  have  undertaken  the  investigation  of  these  differences  by 
means  of  comparative  anatomy,  have  directed  their  attention 
solely  to  the  cerebrum,  and  the  sum  of  their  observations  has 
been  set  forth  by  Ludwig,  in  his  dissertation  '  De  Cinerea  Ce- 
rebri Substantia.'  For  the  sake  of  brevity,  I  will  only  glance 
at  the  more  manifest  differences  derived  from  the  trustworthy 
observations  of  distinguished  men. 

Man  has  the  largest  brain ;  all  other  animals  have  less,  except 
certain  apes,  in  which  the  brain  is  not  less  proportionally  than  that 
of  man.^  In  fishes  and  animals  of  cold  blood,  the  brain  is  so 
small,  that  some  writers  have  not  hesitated  to  look  upon  it  as  only 
an  appendix  to  the  spinal  cord.  There  is  a  great  difference  in 
the  structure  and  composition  of  the  brain  of  animals  :  in  many 
the  olfactory  nerves  are  thick  and  hollow,  and  termed  mam- 
millary  processes,  while  the  contrary  is  observed  in  man ;  the 
convolutions  are  absent  in  dormice  and  birds  ;^  in  birds  and 
fishes,  the  thalami  nervol'um  opticorum  are  hollow  and  distinct 
from  the  cerebrum ;  birds  and  many  fishes  have  no  true  corpus 
callosum,  or  fornix,  or  pineal  gland;  according  to  the  obser- 
vations of  Haller,^  birds  and  fishes  have  bodies  similar  to  the 
corpora  quadrigemina,  but  of  simpler  character  than  those  of 
quadrupeds.  Other  divisions  of  the  brain,  as  the  medullary  and 

'  Haller,  de  Part.  Corp.  Hum.  Fab.,  torn.  vii. 

2  Ludwig,  Diss.  cit. 

'  Oper.  Mill.,  torn,  iii,  p.  214. 


SECT. II.]  CONSTITUTION  OF  THE  NERVOUS  SYSTEM.  385 

cortical  substance,  the  ventricles,  together  with  the  calamus 
scriptorius,  the  plexus  choroides,  commissures,  &c.,  are  more 
constantly  present,  and  from  this  Haller  concludes  that  these 
divisions  are  the  most  essential.^  The  brain  is  of  the  simplest 
form  in  insects,  in  which  there  is  little  medullary  matter,  except 
at  the  origin  of  the  optic  nerves;^  in  some,  it  is  bifid ;  in  others, 
semibifid ;  and,  in  others,  only  a  nodule,  called  a  brain,  little 
different  from  the  nodules  of  the  spinal  cord.^  When  it  is  of 
this  great  degree  of  simplicity,  it  follows,  that  in  the  lowest 
class  of  insects  it  is  altogether  wanting,  and  these  also  have  no 
eyes,  according  to  Haller,  nor  does  he  think  that  in  any 
animal,  eyes  are  unaccompanied  by  brain,  or  brain  by  eyes. 

It  is  manifest  from  these  observations,  that  nature  proceeds 
gradually  from  the  most  perfect  and  highly  complex  brain  to 
the  simpler  and  the  simplest ;  and  that  at  last  animals  exist 
altogether  devoid  of  brain ;  but  what  variety  is  there  in  the 
nerves  of  various  animals?  or  whether  in  all  animals  their 
structure,  number  of  fibrils,  plexuses,  and  ganglia  are  the  same 
as  in  man?  or  whether  (as  it  is  probable)  they  become  more 
simple  ?  We  have  not  as  yet  collected  sufiicient  observations 
to  answer  these  questions.  What  proportion  the  brain  bears 
to  other  parts  of  the  body  has  been  attempted  to  be  shown  by 
observations  and  experiments,  but  what  proportion  the  nerves 
bear,  as  well  to  the  brain,  as  to  those  parts  not  nerves,  remains 
unsolved.  It  was  a  conjecture  only  of  Boerhaave  and  other 
distinguished  men,  who  taught  that  the  brain  in  the  foetus  is 
larger  in  proportion  to  the  rest  of  the  body  than  in  the  adult, 
and  that  this  is  the  case  also  as  respects  the  nerves,  of  which 
they  believed  the  whole  foetus,  at  its  first  formation,  to  consist, 
so  that  the  bones,  cartilages,  ligaments,  muscles,  tendons,  and 
all  the  viscera  at  their  origin  were  merely  nerves.  Haller 
scouted  this  doctrine,*  while  many  distinguished  men  adopted 
it  too  much,  and  he  observes :  "  Nor  do  the  nerves  constitute 
the  common  material  from  which  nature  fabricates  the  other 


'  Oper.  Min.,  torn,  iii,  p.  214. 

^  Haller,  de  Part.  Corp.  Hum.  Fabr.,  torn,  viii,  p.  3. 

3  Ibid.,  p.  6. 

*  El.  Phys.,tom.  iv,  p.  271.  Marherr  also  rejected  the  opinion  in  his  *  Praelect.  ad 
Boerhaavii  Instit.,'  torn,  iii,  pp.  9 — 11,  &c. ;  and  A.  Murray,  in  his  *  Diss,  de  Sensibi- 
litate  Ossium  morbosa.'     Upsalae,  1780. 

25 


886         THE  NERVOUS  SYSTEM  IN  GENERAL,     [ch.  tt. 

parts  of  the  embryo^  but  from  all  time,  doubtless,  the  bones, 
muscles,  and  membranes  had  each  their  own  material/^ 

Seeing  that  sensation  and  voluntary  motion  in  man,  and 
many  animals,  are  obtained  through  the  nerv^ous  system,  we 
conclude  from  analogy,  that  all  animals  which  feel  and  have 
voluntary  motion,  possess  a  nervous  system ;  and  so  essential  is 
that  structure,  that  no  animal  exists  without  it,  from  man 
down  to  the  smallest  microscopic  insect.  Haller,  however, 
correctly  shows,  that  this  analogy  does  not  hold  good,  and 
observes,^  that  in  some  animals,  as  polypi  and  zoophytes,  no 
nervous  system  has  been  discovered ;  and  since  these  animals 
manifestly  belong  to  the  animal  kingdom,  their  difference  from 
vegetables  does  not  consist  in  having  nerves.  Spallanzani  more 
fully  illustrates  the  abuse  of  the  argument  from  analogy .2  He 
says  that  if  w*e  examine  the  whole  animal  chain,  it  will  appear 
to  us  at  first,  passing  from  man  to  quadrupeds,  that  each  have 
their  organs  of  digestion,  circulation,  various  secretions;  and 
each  also  their  nervous  system,  muscles,  bones,  and  organs  of 
the  senses ;  and  although  they  diverge  not  a  little  from  man  as 
to  form  and  structure,  yet  as  they  agree  in  their  essential  use, 
the  analogy  may  still  be  allowed ;  but  if  we  gradually  descend 
to  fishes,  insects,  and  infusory  microscopic  animalcules,  the  force 
of  the  analogy  is  very  much  weakened  or  altogether  lost,  for 
we  see  that  in  insects,  the  bones,  the  heart,  arteries,  and  veins, 
carrying  red  blood,  are  wanting ;  they  have,  besides,  no  brain, 
although  endowed  with  nerves,  and  their  organs  of  respiration 
resemble  those  of  vegetables.  But  if  we  descend  the  animal  scale 
still  lower,  we  find  creatures  in  whom  this  entire  apparatus  of 
organs  is  wanting,  and  which  are  entirely  destitute  of  nerves  as 
well  as  of  brain.  This  is  seen  in  such  animals  as  many  polypes, 
whose  body  is  nothing  more  than  an  oblong  sac  made  up  of  small 
granules;  or  such  as  many  aquatic  animalcules,  whose  whole 
body  is  simply  a  membrane,  or  vesicle ;  or  such  as  many  marine 
zoophytes,  whose  whole  body  consists  only  of  a  sort  of  simple 
jelly.  This  astonishing  simplicity  of  structure  induced  Bonnet 
and  Needham  to  conclude,  that  these  animalcules  are  not  true 
animals  endowed  with  an  immaterial  sentient  principle,  but 
merely  living  entities  endowed  with  irritability  only.    But  they 

'  De  Part.  Corp.  Hum.  Fabr.,  lib.  x,  sect,  vi,  §  1. 

'  Opuscules  de  Physique  Animal,  et  Vegetal.,  tom.  i,  chap.  xii. 


» 


SECT.  II.]   CONSTITUTION  OF  THE  NERVOUS  SYSTEM.  387 

are  clearly  proved  to  be  true  animals  by  Spallanzani,  who  says: 
"  I  am  much  more  inclined  to  look  upon  them  as  true  animals, 
rather  than  as  being  solely  vital  and  irritable,  and  I  think  my 
opinion  well  founded,  because  I  find  in  them  that  union  of 
qualities,  which  constitute  (as  I  have  previously  stated)  the  cha- 
racteristics of  a  true  animal  nature.  I  have  already  had  occasion 
to  state  some  of  those  qualities  in  my  Essay,  and  I  include  amoug 
them  the  power  of  avoiding  any  obstacles,  or  individuals  of  their 
own  kind,  that  they  may  meet  with ;  of  suddenly  changing  their 
course  and  taking  the  opposite  direction ;  of  passing  suddenly 
from  movement  to  rest,  without  any  apparent  external  shock. 
I  spoke  of  their  darting  towards  particles  in  the  infusions,  of 
the  property  they  possess  of  turning  incessantly  upon  them- 
selves, of  going  contrary  to  the  course  of  the  fluid,  of  going  to 
the  spots  where  a  little  moisture  is  left,  and  collecting  there  in 
numbers,  when  the  infusion  has  been  dried  up.^^  Erom  these 
and  other  facts  advanced  by  the  author,  it  is  manifest  that  these 
infusory  animalcules  feel,  and  have  volition,  and  possess  the  cha- 
racter of  the  true  animal ;  consequently,  they  are  endowed  with 
a  sentient  and  volitional  principle,  however  destitute  they  may 
be  of  a  nervous  system. 

Such  being  the  facts,  it  follows  that  a  nervous  system  is  not 
present  in  all  animals,  but  that  many  insects  have  not  cerebra, 
and  that  infusory  animals  and  creatures  much  larger  than  these, 
are  destitute  of  brain  and  nerves.  But  because  these  creatures 
feel  and  move  voluntarily  like  other  animals,  we  must  not  con- 
clude that  the  nervous  system  in  man  and  many  other  animals, 
is  not  the  immediate  instrument  of  sensation  and  animal  motion. 
Man  and  other  animals  endowed  with  that  system,  feel  and 
move  by  means  of  that  system,  nor,  their  organism  being  such 
as  it  is,  would  sensation  and  motion  be  possible  without  nerves. 
Insects,  that  have  no  cerebra  naturally,  are  nevertheless  en- 
dowed with  nerves,  and  perform  their  functions  by  means  of 
nerves  only,  and  by  the  vis  nervosa  contained  in  them,  which 
exists  without  a  brain ;  and  by  this  vis  nervosa  the  acephalous 
foetus  lives  in  utero,  and  when  born  gives  no  slight  signs  of  life. 
Polypes,  zoophytes,  and  other  infusory  animalcules  that  have 
neither  brain  nor  nerves,  feel  and  move  without  a  nervous 
system,  because  the  Author  of  Nature  appears  to  have  endowed 
the  pulp  of  which  their  bodies  are  composed  with  the  facidty 


388        THE  NERVOUS  SYSTEM  IN  GENERAL,      [ch.  ii. 

of  sensation  and  motion ;  just  as  tlie  medullary  pulp  of  the 
nervous  system  alone,  of  all  organs  of  our  body_,  is  endowed  witli 
that  faculty,  the  muscular  machine  being  an  auxiliary  hereto. 
It  cannot  be  correctly  objected  to  these  remarks,  that  insects 
have  a  cerebrum,  and  that  a  complete  nervous  system  exists 
even  in  infusory  animalcules,  and  that  it  is  their  minuteness 
alone  which  conceals  them  from  our  researches,  however  aided 
by  the  microscope,  for  Haller  meets  these  objections  at  once 
with  the  statement,^  that  in  the  larger  insects  at  least,  in  tsenise, 
in  sea-nettles,  and  other  zoophytes,  the  cerebrum  could  scarcely 
escape  observation,  inasmuch  as  they  are  large,  and  their  other 
organs  are  obvious  enough,  even  without  the  microscope ;  and 
since  we  can  distinguish  nodules  or  globules  in  polypes  by  the 
microscope,  and  in  others  fibrils  also,  there  seems  no  reason  why 
the  cerebrum  should  not  be  observed  as  well.  Bohadsch  clearly 
illustrates  this  in  his  description  of  the  lernsea,^  an  animal  six  or 
eight  inches  long  and  three  in  breadth,  which  has  many  stomachs, 
an  intestinal  canal,  sexual  organs,  a  heart,  and  a  circular  spinal 
cord,  furnished  with  many  knots  or  ganglia,  from  which  nerves 
are  sent  ofi'to  adjoining  structures,  but  no  cerebrum.  It  appears 
to  possess  very  small  eyes,  but  these  probably  are  not  true  organs 
of  vision.  In  this  creature,  in  which  so  many  organs  are  con- 
spicuous, and  the  medulla  spinalis  itself,  the  cerebrum  would  be 
visible  also,  if  there  was  anything  more  than  the  ganglionated 
spinal  cord.  In  the  fimbria,  an  animal  six  inches  long,  he 
detected  a  tubular  mouth,  oesophagus,  stomach,  furnished  Avith 
muscular  fibres,  intestines,  uterus,  epididymis,  but  no  eyes,  or 
lungs,  or  heart,  no  vessels  or  nerves  :  he  observes,  however,  that 
these  may  have  escaped  his  observation.  In  the  hydra,  called 
by  others  mentula  maris  [holothuria] ,  with  a  cylindrical  body  a 
foot  long  and  an  inch  broad,  he  could  not  detect  either  heart, 
cerebrum,  or  spinal  cord,  nor  any  viscus  except  the  oesophagus, 
intestinal  canal,  and  anus.  If  then  a  nervous  system  can  be 
discovered  in  much  smaller  animals,  it  would  not  have  escaped 
observation  in  those  of  a  sufiicient  size,  if  it  had  existed. 
Therefore,  although  nature  produces  sensation  and  animal 
motion  in  man  and  many  other  animals  by  means  of  a  nervous 
system,  there  are  nevertheless  not  a  few  creatures  to  which  it 

'  De  Part.  Corp.  Hum.  Fabr.,  torn,  viii,  p.  2. 

'  De  quibusdam  Animalibus  Marinis.    Dresdae,  1761. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.         389 

has  known  how  to  assign  these  animal  faculties  without  the 
aid  of  a  nervous  system  :  nay  more ;  nature  has  granted  even 
to  certain  irritable  vegetables  a  sort  of  sensation  and  motion, 
analogous  to  the  motion  and  sensation  of  animals,  and  that 
without  a  nervous  system. 

SECTION   III. WHAT  IS  UNDERSTOOD   BY   THE  VIS  NERVOSA,  AND 

WHAT  ARE  ITS  GENERAL  PROPERTIES. 

All  the  functions  of  the  nervous  system  are  as  dependent 
upon  its  structure  and  nature,  as  the  accurate  indication  of  time 
upon  the  construction  of  the  chronometer.  In  inquiring  into 
the  structure  of  the  nervous  system,  our  senses,  however  well 
assisted  by  the  microscope,  teach  us  nothing  more  than  that  the 
principal  portion  of  it,  the  medullary,  is  supplied  with  numerous 
arterial  and  venous  capillaries,  distributed  both  to  the  cerebrum 
and  to  the  nerves.  We  cannot  say,  however,  that  the  whole  is 
vascular,  because,  after  the  most  successful  injection  of  a 
coloured  fluid  into  the  cortical  substance  of  the  brain,  and  the 
medullary  substance  of  the  brain  and  nerves,  the  larger  portion 
remains  uninfected;  and  this  is  not  vascular,  but  inorganic  in  a 
manner,  being  composed  of  a  mass  of  very  small  globules  as  seen 
under  the  microscope, not  unlike  the  globules  seen  to  compose  the 
whole  organism  of  polypes  and  zoophytes,  and  the  pulp  of  fruits. 
Albinus  long  ago  refuted  the  doctrine  of  Ruysch,^  that  every 
part  of  the  body  is  composed  of  nothing  but  vessels,  by  showing 
that  in  bone,  cartilage,  muscle,  nerve,  and  in  the  medullary  and 
cortical  portions  of  the  brain,  there  was  a  large  proportion  of 
matter  which  was  not  vascular.  Malpighi  seems  to  intimate  the 
same  opinion,  with  reference  to  the  cortex  of  the  brain,  and  also 
the  medulla,^  when  he  says,  that  he  found  no  organisation  in 
the  cortex,  except  in  the  sanguiferous  vessels  with  which  it  is 
pervaded ;  and  if  a  parenchymatous  substance  should  be  at  any 
time  assigned  to  the  brain,  in  which  the  vessels  and  other 
organised  products  might  be  supported,  the  cortex  is  the  proper 
part,  inasmuch  as  it  would  seem  to  resemble  moss  mixed  with 
deep  coloured  clay.  In  another  epistle,  however,  he  tries  to 
show  that  it  is  glandular. 

If  any  reliance  is  to  be  placed  on  our  senses,  the  structure 

>  Adnot.  Acad.,  lib.  iii,  cap.  i ;  et  lib.  i,  p.  52. 

'  Epist.  ad  Fracassatum  de  Cerebro.     In  Bib.  Anat.  Mangeti, 


890         THE  NERVOUS  SYSTEM  IN  GENERAL,      [ch.  ii. 

of  the  medullary  pulp  of  the  nervous  system  is  almost  inor- 
gauic  j  but  much  is  still  wanting,  to  enable  us  to  understand 
its  admirable  functions.  We  may  assert,  however,  without 
fear  of  contradiction,  that  an  invisible  element  enters  into  its 
composition,  and  that  this  constitutes  the  producing  cause  of 
all  the  functions  of  the  nervous  system.  Since  this  is  as 
mysterious  and  unknown  as  the  vis  attractiva  of  matter,  it 
seems  to  me  that  it  may  be  termed  with  propriety  the  vis 
nervosa.  I  leave  the  inquiry,  as  to  its  nature,  to  the  very 
sagacious  and  ingenious  men  already  engaged  in  philosophical 
experiments.  I  shall  only  attempt  to  determine  some  of  its 
general  properties,  before  I  enter  upon  the  special  functions 
of  the  nervous  system.^ 

1.  A  stimulus  is  necessary  to  the  action  of  the  vis  nervosa. — 
i.  Although  this  vis  nervosa  is  a  property  inherent  in  the  me- 
dullary pulp,  it  is  not  the  chief  and  sole  cause  that  excites  the 
actions  of  the  nervous  system,  but  is  ever  latent,  and  exists  as 
a  predisposing  cause,  until  another  exciting  cause,  which  we 
term  stimulus,  is  brought  to  bear.  As  the  spark  is  latent  in 
the  steel  or  flint,  and  is  not  elicited,  unless  there  be  friction 
between  the  flint  and  steel,  so  the  vis  nervosa  is  latent,  nor 
excites  action  of  the  nervous  system  until  excited  by  an  applied 
stimulus,  which  continuing  to  act,  it  continues  to  act,  or  if 
removed,  it  ceases  to  act,  or  if  re-applied,  it  acts  again. 

ii.  This  stimulus  is  divided  into  stimulus  of  the  body  and  of 
the  mind, — This  stimulus  is  double :  either  it  is  some  fluid  or 
solid  body  applied  internally  or  externally  to  the  nervous 
system,  and  termed  corporeal,  or  mechanical  stimulus ;  or  else 
is  a  mental  stimulus  present  in  a  portion  of  the  nervous  system, 
and  by  means  of  this  portion  controls  the  rest  of  the  nervous 
system,  and  the  rest  of  the  body,  as  far  as  it  is  allowed. 
Whether  this  mental  stimulus  takes  place  through  a  system  of 
occasional  causes,  or  pre-established  harmonies  [harmonia  prae- 
stabilita] ,  or,  as  assumed  by  many,  by  a  physical  influx,  matters 
little  to  our  object;  it  is  sufficient  for  us  that  the  soul  can 
excite  the  nervous  system  to  the  performance  of  certain  actions, 
and  this  power  we  call  a  mental  stimulus. 

iii.  The  relations  of  the  actions  of  the  nervous  system  to  the 

1  I  have  conjectured,  however,  that  there  is  an  analogy  between  the  vis  nervosa 
and  electricity,  in  my  Inst.  Physiol.  $  206. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.         391 

vis  nervosa  and  stimulus,  generally  considered, — As  effects  are 
proportionate  to  their  causes,  so  the  operations  of  the  nervous 
system  are  proportionate  to  the  vis  nervosa  and  the  vis  stimuli. 
The  operations  of  the  nervous  system_,  for  example,  will  be  the 
more  powerful  and  extensive  in  proportion  as  the  vis  nervosa  is 
more  active  and  the  stimulus  efficient :  and  contrarily  in 
proportion  as  the  vis  nervosa  is  less  active  and  the  stimulus 
feebler,  in  that  proportion  will  the  operations  of  the  nervous 
system  be  more  languid.  A  less  energetic  stimulus  is  suffi- 
cient for  a  more  active  vis  nervosa,  just  as  a  more  powerful 
stimulus  will  compensate  for  a  less  active  vis  nervosa ;  so  that 
in  both  cases,  the  effect  on  the  operations  of  the  nervous  system 
may  be  equal.  The  vis  nervosa  is  not,  however,  indifferent  to  the 
kind  of  stimulus,  for  it  is  more  readily  excited  by  one  than  by 
another,  although  they  may  appear  to  be  equally  forcible ;  nay, 
it  sometimes  responds  more  actively  to  apparently  a  very  mild 
than  to  a  very  powerful  stimulus.  Thus  the  heart  and  intes- 
tinal canal,  according  to  Haller,^  are  thrown  into  more  powerful 
contractions  by  inflated  air  than  by  water,  or  any  poison ;  and, 
on  the  other  hand,  a  drop  of  water  getting  into  the  trachea 
excites  a  violent  cough,  while  the  air  is  insensibly  inspired  and 
expired  through  it.  I  shall  adduce  many  such  examples 
hereafter  as  illustrations  of  idiosyncrasy. 

iv.  Under  what  circumstances  the  vis  nervosa  is  increased. — 
It  is  evident  that  the  stimulus  may  be  greater  or  less,  longer 
or  shorter,  more  or  less  general,  or  quite  local;  and  the  same 
is  true  of  the  vis  nervosa.  This,  in  fact,  differs  in  degree 
according  to  the  difference  of  age,  sex,  temperament,  climate, 
the  condition  of  the  body  as  to  health  or  disease,  and  other 
circumstances,  and  in  a  portion  of  the  nervous  system  as  well 
as  in  the  whole,  which  it  will  suffice  to  prove  by  a  few  examples. 

a.  In  the  first  place,  the  vis  nervosa  is  generally  greater  in 
childhood  than  adult  age ;  for  a  slight  stimulus  at  that  age  will 
act  violently  upon  the  nervous  system,  which  scarcely  affects 
the  nerves  in  more  advanced  years,  a  truth  abundantly  proved 
by  the  testimony  of  celebrated  men.  Young  animals  are 
the  more  sensitive,^  and  organs  which  in  the  newly-born  are 
irritable,  become  insensible  through  age,^  and  languid  in  motion 

'  El.  Phys.,  torn,  iv,  p.  575.  =»  Haller,  Ibid.,  p.  456. 

3  Whytt  apiid  Haller,  Ibid.,  p.  184. 


392  THE  NERVOUS  SYSTEM  IN  GENERAL,     [ch.  ii. 

and  sensation.      Sensation  is  more  acute  in  the  young  man 
than  in  the  aged.^    The  pupil  is  more  contractile  in  the  infant, 
less  readily  acted  on  by  light  in  the  aged.     And  the  same 
principle  illustrates  the  cause  of  senile  impotence.     That  the 
sensibility   of  the   genital  organs   is   diminished  with   age  is 
proved  by  the  fact,  that  the  seminal  emissions  so  readily  excited 
in  youth,  cease  to  take  place  about  the  fiftieth  year  or  some- 
what later,   even  in  able  and  strong  men.      Since  the  female 
sex  has  a  more  excitable  nervous  system,  it  is  established  as  a 
general  rule  that  the  feeble,  or  rather  the  tender  organisms, 
feel  more  acutely  than  the  robust.^     Observations  also  show, 
that  the  amount  of  vis  nervosa  varies  with  the  climate,  since 
those   who  inhabit  hot  climates  indulge    more   in  ease    and 
pleasure  than  the  inhabitants  of  colder  regions ;  Montesquieu^ 
thinks  we  may  distinguish  climates  by  the  degrees  of  sensibility, 
just  as  we  distinguish  by  degrees  of  latitude.    Often  in  diseases, 
the  sensibility  or  vis  nervosa  of  the  whole  nervous  system,  is 
increased  in  a  very  remarkable  manner ;  whence  it  happens,  I 
think,  that  we  cannot  then  bear  a  slight  degree  of  cold  in  the 
atmosphere,  on  account  of  the  shiverings  and  unpleasant  sen- 
sations excited  through  the   whole   body,   that  in  health  we 
should  not  notice.      Thus,   also,  a  moderate   draught  of  wine 
greatly  increases  the  fever  of  a  fever-patient,   but  which,  if 
taken  by  a  person  in  health,  would  produce  no  change  what- 
ever in  the  pulse.      For  the  same  reason  it  happens,  that  in 
hemicrania,  gout,  or  any  painful  aifection,  we  are  impatient,  and 
cannot  endure  any  noise  or  light,  or  a  variety  of  objects.     All 
nerves  that  have  become  too  sensitive  can  no  longer  tolerate 
even  the  most  common  impressions.*     If  it  were  not  altogether 
superfluous,  many  other  instances  of  increased  vis  nervosa  in 
the  whole  nervous  system  might  be  adduced. 

h.  Frequently  an  increased  degree  of  vis  nervosa  is  observed 
in  a  portion  only  of  the  nervous  system,  and  not  in  the  whole ; 
in  the  animal  organs  alone,  or  only  in  the  sensorium  commune, 
or  in  one  or  other  of  the  nerves.  Thus,  I  imagine,  there  is  an 
increased  degree  of  vis  nervosa  in  the  delirious  and  maniacal, 

'  Haller,  El.  Phys.,  torn,  iv,  pp.  293,  294. 
«  Battle  apud  Haller,  El.  Phys.,  torn,  iv,  p.  459. 

^  Esprit,  de  Loix.     Vid.  La  Roche,  *  Analyse  de  Fonctions  du  Systeme  Nerveux/ 
torn.  i. 

*'  Tissot.  von  Nerv.,  2  Band,  ii  Th.,  §  77,  s,  165. 


SECT.  iii.J    PROPERTIES  OF  THE  VIS  NERVOSA.  393 

which  keeps  them  fixed  to  their  ideas.  That  condition  of  some 
decrepid  old  people,  in  which  they  are  more  pusillanimous  and 
timid  and  ready  to  weep  than  children,  seems  to  be  referable  to 
this  increased  decree  of  the  vis  nervosa.  So  also  may  be  ex- 
plained the  case  of  a  man  of  weak  mind  in  health,  who  was  ren- 
dered talented  by  a  blow  on  the  head,  but  when  cured  relapsed 
into  his  previous  simple-mindedness.^  The  serene  state  of  mind 
of  dying  persons,  which  has  been  aptly  compared  with  the 
crackling  of  a  dying  taper,^  seems  dependent,  for  the  moment 
at  least,  on  increased  vis  nervosa.  When  the  vis  nervosa  is 
increased  in  the  general  sensorium,  it  seems  also  to  have  this 
effect, — that  external  impressions  made  on  the  sensitive  nerves, 
and  transmitted  to  the  sensorium,  are  too  suddenly  and  violently 
reflected,  and  pass  over  into  the  motor  nerves,  and  excite  move- 
ment and  convulsions  in  spite  of  the  will,  as  happens  in  the 
frights  of  infants,  and  also  of  some  adults,  who  are  terrified  by 
any  slight  crash  or  noise.  Further,  that  the  vis  nervosa  may 
be  locally  increased  in  one  nerve  or  another,  is  proved  by  innu- 
merable examples  of  contused,  lacerated,  wounded,  and  in- 
flamed parts,  a  slight  touch  of  which  excites  much  suffering, 
although  in  the  natural  condition  it  would  scarcely  have  been 
felt,  and  this  while  other  sound  parts  of  the  body  possess  their 
natural  sensibility.  Thus  the  amount  of  vis  nervosa  is  greatly 
increased  in  the  gouty  foot,  but  the  other  limbs  are  in  their 
natural  condition.  Inflammation  is  the  most  frequent  cause 
of  a  topical  increase  of  the  vis  nervosa,  as  Haller  observes,  who 
says^  that  the  increase  of  the  sentient  nature  in  nerves  is  won- 
derful, as  observed  in  inflamed  parts,  in  certain  acute  diseases, 
in  inflammation  of  the  brain,  or  in  rabies  canina;  that  the 
younger  Albinus  experienced  the  greatest  annoyance  from  sounds 
so  slight,  as  not  to  be  audible  to  other  persons ;  and  that  a  cer- 
tain man  could  see  by  night  so  long  as  his  eye  was  inflamed,  but 
lost  the  faculty  along  with  the  inflammation.  Nor  were  these 
very  remarkable,  for  parts  of  the  body  in  which  sensation  in  the 
natural  state  is  so  imperfect  that  it  may  scarcely  be  said  to  exist, 
experience  from  disease  such  an  increase  of  the  vis  nervosa  in  the 

»  Haller,  El.  Phys.,  torn,  iv,  pp.  293,  294. 

2  Kemrae  von  der  Heiterkeit  des  Geistes  bey  einigen  Sterbenden.     Halle,  1774, 
Seit.  89. 

^  Loco  citato. 


394        THE  NERVOUS  SYSTEM  IN  GENERAL.      [ch.  ii. 

very  few  nerves  distributed  to  them,  that  they  become  extremely 
painful:  of  this  class  are  tendons,  ligaments,  and  the  bones,  which 
in  the  natural  state  have  no  sensation,  but  when  diseased,  become 
so  sensitive  that  a  touch  gives  pain.  Thus  in  a  case  observed 
by  Martini,^  a  denuded  tendon  had  no  feeling,  but  being  ren- 
dered black  by  an  ointment  applied  to  it,  it  became,  at  the 
same  time,  so  sensitive,  that  a  touch  could  not  be  borne,  and 
not  without  great  pain  could  the  black  and  dead  fibre  be  torn 
from  the  healthy.  Since,  then,  mortification  in  this  tendon 
rendered  its  nerves  so  very  sensitive,  the  same  result  may  be 
expected  in  the  ligaments  of  the  joints,  when  a  gouty  matter 
is  deposited  in  them.  Richter  is  of  this  opinion.^  A  man 
having  many  schirrous  tumours  beneath  the  skin,  one  was 
removed  from  the  dorsum  of  the  hand  by  Klinkosch,^  on  account 
of  its  hindering  the  movements  of  the  fingers.  The  patient 
bore  the  removal  of  the  tumour  tolerably  well,  but  not  the 
denudation  of  the  tendon,  the  irritation  of  which  caused  such 
a  trembling  of  the  body  generally,  that  he  would  for  no 
consideration  suffer  a  repetition  of  the  experiment.  In  this 
case  it  appears,  that  the  tendon  had  acquired  greater  sensibility 
from  disease  of  the  superjacent  skin.  Plenk  also  asserts,*  that 
a  divided  tendon  at  first  causes  no  bad  symptoms,  but  when, 
after  a  while,  it  becomes  inflamed,  it  is  then  painful.  Adolph 
Murray  confirms  the  remark,^  observing,  that  if  healthy  liga- 
ments be  pricked,  wounded,  or  burnt,  they  feel  no  pain ;  but 
if  the  structure  of  the  ligament  be  affected,  either  by  fungus 
or  pus,  or  any  other  acrid  humour,  then  incisions  into  them  are 
not  only  painful,  but  often  cause  so  much  suffering  that  it  ex- 
cites convulsions.  And  thus  also  bones,  when  not  diseased,  have 
no  sensation,  although  nerves  are  manifestly  distributed  here 
and  there ;  and  this  he  ingeniously  explains  by  the  hypothesis, 
that  the  nerves  are  constricted  by  the  accumulation  of  earthy 
matter  in  the  foramina,  through  which  they  enter  the  bone ; 

'  Versuche  und  Erfahrungen  iiber  die  Empfindlichkeit  der  Sehnen.  Copenhagen, 
1770. 

»  Chirurg.  Biblioth.,  Ite  Band,  Ite  Stuck. 

3  Observ.  de  Sensibilitate  tendinis  et  raro  Cutis  Aibrbo.  It  is  in  his  *  Collectio 
Diss.  Select.  Med.  Pragensium.' 

*  Chirurg.  Lehrsatze. 

^  Diss,  de  Sensibilitate  Ossium  morbosa.     Upsalae,  1780. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  395 

but  when  tlie  bones  are  softened  by  some  morbific  cause,  the 
constriction  of  the  foramina  is  relaxed,  and  the  nerves  no  longer 
strangulated  again  become    sensitive.     That  bones   morbidly 
softened  are  rendered  sensitive,  is  proved  by  the  observations 
of  Deidier  and  Petit.     He  also  found  that  the  slightest  touch 
of  a  carious  bone  excited  intense  pain.^     Murray  rightly  ob- 
serves, that  the   following  questions   are  worthy  the  diligent 
investigation  of  physiologists  : — how  does  it  happen  that  nerves 
entering  the  substance  of  bones,  are  compressed  and  strangu- 
lated in  the  narrow  foramina  for  many  years,   and  thus  ren- 
dered unfit  to  excite  sensation,  yet  when  the  bone  is  softened 
and  the  constriction  of  the  nerves  diminished,  they  again  become 
fit  for  sensation,  nay,   acquire  the  most  exquisite  sensibility  ? 
If  the  nerves  be  small  channels  for  a  nervous  fluid,  they  are 
compressed  so  long  that  the  channels  ought  to  coalesce,  and  the 
nerves  be  impermeable  ever  after  to  the  nervous  fluid.   Then  this 
author  seems  to  ask,  why  is  it  that  in  disease  of  the  bones  we 
often  find  so  much  more  sensibility  than  could  be  expected  from 
so  few  and  such  minute  nerves  ?     The  increased  sensibility,  or 
vis  nervosa,  seems  to  compensate  for  this  paucity  of  the  nerves. 
V.    When  the  vis  nervosa  is   diminished. — The  vis  nervosa 
is  diminished  in   proportion  as    we  observe  the  vital  powers 
which  are  dependent  on  the  vis  nervosa,  to  be  diminished  and 
weakened;  and  which  becomes  so  weak  in  death,  that  the  natural 
stimuli,  as  for  example,  the  influence  of  the  inspired  air,  and  of 
the  blood  in  the  heart,  can  no  longer  excite  it,  and  a  mortal 
repose  of  all  the  vital  and  animal  movements  results.    In  this 
ordinary  termination  of  life,  the  vis  nervosa  is  undoubtedly  at 
a  minimum,  but  it  is  not  quite  lost,  for  a  few  sparks  can  still 
be  excited,   if  a   strong  stimulus  be  applied    to  the   nerves. 
Vesalius  was  taught  this  fact  by  sorrowful  experience,  for  when 
dissecting  a  body  shortly  after  death,  he  excited  the  heart  to 
renewed  action.      Brunner^  succeeded  in  doing  the  same  thing 
in  the  bodies  of  men  and  various  animals,  by  forcing  air  into 
the  heart,  through  the  thoracic  duct  or  veins.     In  many  expe- 
riments on  frogs,  I  observed,  that  when  the  heart  was  still  and 

*  Brambilla,  Surgeon  in  Ordinary  to  the  Emperor  Joseph  II,  and  First  Surgeon  to  the 
Guards,  &c.,  also  demonstrated  the  sensibility  of  diseased  bones  before  the  author  at 
Vienna. 

*  Parerg.  Anat.  Genevae,  1681.  Miraculum  anatomicum  in  cordibus  resusci- 
tatis,  &c. 


396  THE  NERVOUS  SYSTEM  IN  GENERAL,      [ch.  ii. 

could  no  longer  be  excited  by  a  stimulus,  that  the  muscles  of 
the  thigh  continued  to   be   slightly  contracted,  whenever  the 
sciatic  nerve  was  punctured  or  compressed.  We  hence  conclude, 
that  a  certain  portion  of  the  vis  nervosa  remains  for  a  time  in 
the  nerves  after  death,  which,  although  insufficient  to  maintain 
life,  is  sufficient  to  develop  movements  in  the  heart  and  some 
muscles,  if  excited  by  a  powerful  stimulus.     For  they  contract, 
although  so  feebly,  that  weak  jerking  rather  than  contractions 
are  only  produced,  and  these  cease  after  awhile,  however  strongly 
the  nerves  or  muscles   may  be  stimulated.      When  after  death 
no  muscle  responds  to  a  stimulus,  are  we  to  conclude  that  all 
vis  nervosa  has  left  the  nerves,  or  is  it  that  it  cannot  display 
itself  on  account  of  the  muscles  being  rendered  unfit  for  action? 
We  cannot  determine  these  questions.     The  vis  nervosa  is  also 
diminished  by  opium,  according  to  the  observations  of  Whytt. 
Haller  and  Sprogel^  found  that  opium  destroyed  the  vis  irrita- 
bills  of  the  stomach  and  intestinal  canal,  and  since  (as  will  be 
hereafter  shown)  irritability  presupposes  a  vis  nervosa,  the  vis 
nervosa  is  also  diminished  by  it.      Smith2  observed,  that  opium 
or  nitre  applied  to  the  nerves  destroyed  the  irritability  of  the 
muscles  to  which  the  nerves  were  distributed.     Monro  also  ob- 
ser\ned,  that  narcotics  diminished  the  contractility  of  the  heart.^ 
Many  celebrated  men,  and  amongst  them  Tralles,  were,  on  the 
other  hand,    of  opinion,  that  opium  had  not  a  cooling  but  a 
heating  property,  increasing  the  motion  of  the  humours,  and 
they  attempted  to  prove  the  doctrine  by  experiments.  Wirtenson 
advanced  a  curious  and   ingenious  argument  for  the  purpose 
of  reconciling  these  conflicting  statements :  it  was  certain,  he 
said,  as  proved  by  his  own  experiments,  that  opium  diminished 
the  power  of  the  heart,  but  since  it   also  had  the  remarkable 
property  of  relaxing  the  capillaries  or  terminations  of  the  arte- 
ries, thus  by  a  diminution  of  resistance,  the  circulation  might 
be  increased,  although  at  the  same  time  the  force  of  the  heart 
were  somewhat  diminished.      Opium    does  not    increase    the 
motion  of  the  humours  in  the  Turks  habituated  to  it,  nor  heats 
them,  but  refrigerates  them,  because  their  capillaries,   being 
already  relaxed  by  the  climate  and  by  the  continual  use   of 
opium,  are  not  susceptible  of  further  relaxation  ;  the  resistance 

'  Haller,  Op.  Min.,  torn,  i,  p.  485. 

'  Diss,  de  Motu  Musculari.     Edinburg.,  1767. 

'  Act.  Gotting.,  vol.  ii,  pp.  147,  154. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  397 

being  therefore  undiminished,  a  slower  motion  of  the  humours 
and  an  agreeable  coolness  from  the  diminished  action  of  the 
heart  only  ensues.^  The  celebrated  Fontana  infers,  from  his 
experiments,  that  opium  does  not  diminish  the  amount  of  that 
power  by  which  the  nerves  move  the  muscles,  but  that  it  is  the 
spirit  of  wine  which,  whether  used  as  a  solvent  of  opium,  or  alone, 
renders  them  insensible  to  irritation,  and  destroys  that  property 
of  the  nerves  which  controls  the  muscles. ^  The  latest  opinion 
of  Haller  as  to  these  experiments  is,  that  they  partly  require 
confirmation,  and  partly  admit  of  another  explanation ;  and  he 
ends  his  opinion  with  these  words  :  "  Lastly,  from  the  remark- 
able effect  which  opium  produces  on  the  stomach  and  intestine, 
there  is  ground  for  suspecting  that  the  vis  insita  is  diminished 
by  opium  as  well  as  the  vis  nervosa.''^  But  it  has  already  been 
abundantly  proved  by  distinguished  men  (and  it  will  be  shortly 
rendered  more  evident),  that  the  vis  insita  of  Haller,  or  irrita- 
bility, is  dependent  upon  the  vis  nervosaj  and  cannot  exist 
without  it;  and,  consequently,  as  opium  diminishes  the  vis 
nervosa,  it  is  thus  only  that  it  diminishes  irritability,  or  the 
vis  insita. 

vi.  The  vis  nervosa  is  divisible,  and  exists  in  the  nerves  in- 
dependently  of  the  brain, —  Vis  nervosa  is  as  divisible  as  the  ner- 
vous system,  so  that  it  remains  in  each  portion  of  a  bisected 
nerve,  as  if  it  were  still  entire  and  connected  with  the  brain. 
Nor  does  the  vis  nervosa  of  the  nerves  require  continual  supplies 
from  the  brain,  since  nerves  possess  their  own  vis  nervosa, 
which  never  had  a  connection  with  the  brain.  The  experiments 
that  prove  this  have  long  been  perfectly  well  known ;  namely, 
that  if  a  nerve  be  cut  or  tied,  although  by  these  means  its 
connection  with  the  brain  be  destroyed,  it  is  still  as  able,  if 
irritated,  to  cause  the  muscles  to  contract  as  if  its  connection 
with  the  brain  were  entire.  Haller  clearly  states  this  fact  in 
many  places.*  He  observes  :  "  a  nerve  compressed  or  tied,  and 
then  irritated  below  the  ligature,  excites  those  muscles  to  con- 
vulsive contraction,  to  which  it  is  distributed,  just  as  if  it  was 

•  Dissert.  Demonstrans  Opium  vires  Fibrarum  cordis  Debilitare,  et  Motum  tameii 
sanguinis  augere.     Monasterii,  1775. 

2  Vid.  Halleri  Oper.  Min.,  torn,  i,  p.  487. 

3  De  Part.  Corp.  Hum.  Fabr.  et  Usu,  tom.  ii,  pp.  391,  392. 

*  El.  Phys.,  tom.  iv,  p.  337. 


398  THE  NERVOUS  SYSTEM  IN  GENERAL,      [ch.  ii. 

perfectlj  free/^  And  elsewhere  :  "  if  the  nerve  of  a  muscle  be 
compressed,  or  tied,  or  divided,  and  then  irritated,  provided 
it  be  fresh  and  moist,  the  irritation  will  produce  in  the  muscle 
to  which  the  nerve  is  distributed  the  same  movements  as  it 
would  have  produced,  if  the  continuity  of  the  nerve  with  the 
brain  had  remained  unbroken.  This  proposition  having  been 
proved  with  regard  to  the  voluntary  nerves,  is  here  shown  to 
be  applicable  to  the  organic  nerves.'^^  In  the  same  work 
(p.  237),  he  observes  :  "  it  is  not  necessary  to  the  excitation  of 
muscular  action  by  irritation  of  the  nerves,  that  the  nerve  be  in 
connection  with  either  the  brain  or  spinal  cord ;  for  irritation  of 
a  nerve  entirely  separated  from  the  spinal  cord  and  brain,  ex- 
cites the  same  muscular  contractions  as  irritation  of  a  nerve  in 
unbroken  connection  wdth  them.^'  And  in  a  sentence  before 
quoted,^  he  remarks  :  "  Thus,  when  after  the  destruction  of 
that  part  of  the  spinal  cord  from  which  it  proceeds,  a  nerve  is 
irritated,  it  still,  as  before,  throws  the  limb  into  contractions, 
to  which  it  is  distributed.  The  same  thing  takes  place  in  the 
medulla  spinalis  after  division  of  the  medulla  oblongata.  In 
short,  if  the  head  or  whole  brain  be  removed,  and  the  heart 
taken  away,  and  the  animal  be  apparently  dead,  on  irritating  in- 
dividual nerves,  or  the  spinal  cord,  the  muscles  are  convulsed.^' 
This  vis  nervosa,  which  remains  in  the  nerves  when  separated 
from  the  brain,  is  not  exhausted  by  one  or  two  muscular  con- 
tractions they  excite  when  irritated,  but  is  equal  to  the  produc- 
tion of  numerously  repeated  movements,  as  I  observed  in  a  frog, 
the  spinal  cord  of  which  I  divided  in  the  back»  It  survived  this 
wound  several  days,  and  during  the  whole  of  that  period,  by 
irritating  that  portion  of  the  spinal  cord  which  was  below  the 
section,  I  excited  innumerable  convulsions  in  the  lower  extremi- 
ties, nor  did  these  die  sooner  than  the  whole  frog.  I  am  com- 
pelled to  defer  a  more  detailed  and  accurate  account  of  these  and 
similar  experiments  to  another  opportunity,  as  this  is  not  the 
proper  place.  That  the  vis  nervosa  can  remain  a  long  time  in  the 
nerves,  independently  of  the  brain,  seems  to  be  proved  by  the 
state  of  paralytic  limbs,  the  nerves  of  which  are  deprived  of  all 
connection  with  the  brain  on  account  of  some  preternatural  com- 
pression, and  yet  for  a  long  period  the  paralysed  muscles  are 

•  Memoires  sur  la  Nature  Sensible  et  Irritable,  torn,  i,  p.  245,  exper.  225. 
=  Elem.  Phys.,  torn,  iv,  pp.  337,  338. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  399 

convulsed  by  the  stimulus  of  the  electric  spark. ^  The  vis  nervosa 
of  the  spinal  cord,  and  of  the  nerves  given  off  by  it,  remained  in  a 
case  after  atheroma  of  the  medulla  oblongata,  pons  varolii,  and 
entire  cerebellum  had  destroyed  the  connection  between  the 
spinal  cord  and  a  dropsical  brain.^  Moreover,  the  vis  nervosa 
not  only  continues  in  the  spinal  cord  and  nerves  long  separated 
from  their  connection  with  the  brain,  but  exists  in  nerves  that 
never  had  any  connection  with  the  brain  whatever.  This  is 
proved  by  the  histories  of  acephalous  foetuses,  which  lived 
during  the  whole  period  of  intra-uterine  life,  were  nourished, 
increased  in  growth,  and  when  bom  evinced  no  obscure  signs 
of  vitality,  without  having  a  brain,  and  by  the  sole  vis  of  the 
nerves  and  spinal  cord,  if  the  latter  was  not  also  defective. 
Animals  which  have  nerves  but  no  cerebrum  also  demonstrate 
the  same  fact. 

From  these  facts  it  is  obvious,  that  the  vis  nervosa  remaining 
in  the  nerves  after  the  severance  of  their  connection  with  the 
brain,  must  be  considered  as  the  cause  whereby  the  heart  was 
able  to  continue  its  movements,  in  the  experiments  instituted 
by  Haller  and  other  distinguished  men,  after  the  brain  and 
cerebellum  were  destroyed,  the  head  cut  off,  and  even  all  the 
nerves  of  the  heart  divided.  For  the  stimulus  of  the  blood,  alter- 
nately flowing  into  the  cavities  of  the  heart,  irritated  its  nerves 
still  endowed  with  vis  nervosa,  although  separated  from  the 
brain,  and  thus  excited  it  to  alternate  contractions.  But 
another  interpretation  has  been  given  to  these  facts;  and  espe- 
cially by  Haller,  namely,  that  it  is  manifest,  that  if  the  heart's 
action  continues  after  decapitation,  or  destruction  of  the  whole 
cerebrum  and  cerebellum,  the  cardiac  movements  are  not  in 
connection  with  the  nerves,  but  with  an  irritability  innate  in 
the  heart,  and  not  dependent  on  the  nerves.  But  the  fallacy 
in  this  conclusion  is  most  manifest,  since  it  can  only  be  fairly 
inferred  that  the  heart  can  continue  its  action  without  the  brain 
and  spinal  cord,  but  not  without  its  own  nerves,  which,  although 
entirely  separated  from  the  brain,  are  still  united  to  the  heart, 
and  still  as  endowed  with  the  vis  nervosa,  and  as  impatient  of  a 

'  Caldani  excited  movements  of  paralysed  muscles  by  the  electric  spark.  Consult 
Haller's  Bib.  Anat. 

2  De  Haen.  Rat.  Med.  Contin.,  torn,  iii,  section  i,  cas.  ix,  the  dissection  of  which 
I  performed  before  my  lamented  teacher. 


400         THE  NERVOUS  SYSTEM  IN  GENERAL.       [ch.  ii. 

stimulus,  as  wlien  in  connection  with  the  brain.  If  any  other 
muscle,  the  nerve  of  which  is  divided,  contracts  when  the  nerve 
is  irritated,  why  not  also  should  the  heart  alternately  contract, 
though  its  nerves  be  divided,  when  alternately  stimulated  by  the 
inflowing  venous  blood  ?  These  same  nerves  are  the  cause  why 
the  heart,  or  any  other  muscle,  when  separated  from  the  body, 
or  even  when  cut  into  pieces,  continues  to  contract  at  each 
irritation;  for  with  each  portion  there  are  nerves  also  cut  away, 
since  they  cannot  be  separated  from  the  substance  of  the 
muscle,  beiQg  lost  in  it  as  invisible  filaments.  These  minute 
invisible  nerves  are  also  endowed  with  their  own  vis  nervosa, 
are  irritated  when  the  muscle  is  irritated,  and  feel  the  stimulus, 
and  cause  the  muscle  or  fragment  of  a  muscle  to  contract. 
This  continues  longer  in  the  heart  and  intestines,  according  to 
the  experiments  of  Haller,  than  in  other  muscles,  and  only 
ends  when  the  animal  heat  being  dissipated,  the  cold  coagulates 
the  fat,  and  seems  also  to  diminish  the  flexibility  of  the  fibres, 
to  lessen  the  fluidity  of  the  blood  remaining  in  the  vessels  of 
the  muscle,  and  to  fix  the  vis  nervosa  itself.  It  is  now  placed 
beyond  doubt  by  many  distinguished  men,  that  the  irritability 
of  muscles  is  dependent  on  the  nerves,  and  cannot  exist  without 
them  ;^  although  it  is  certain  that  some  have  incon-ectly  con- 
founded irritability  with  sensibility.  Irritability  belongs  solely 
to  muscle,  and  sensibility  to  nerve;  but  irritability  is  the  eff'ect 
of  the  muscle  as  a  compound  instrument,  into  the  composition 
of  which    enter    muscular  fibres   enveloped    in    their    proper 

'  Whytt,  'Essays.  Phys.;*  also,  'Von  den  Nerven  und  Hypochondrischen  K>ank.' 
(Leipzig,  1766),  Seit.  4;  Unzer,  'Erste  Griinde  einer  Physiologie,'  Seit.  435 — 437, 
und  §§  382 — 387  ;  Rehfeld,  '  Diss,  an  Vis  Irritabilis  Fibrarum  Muscularum  Innata  ipsis 
inhaereat,  an  aliunde  accedat'  (Gryphiae,  1770).  Winterl,  *  Inflammationis  theoria 
Nova'  (Viennae,  1767),  cap.  iii;  Crantz  in  'Trabucchy  Diss,  de  Mechanis.  et  Usu 
Respirationis '  (Viennae,  1768);  Trzebiczky,  'Diss,  de  firitabilitate  et  Sensibilitate' 
(Pragae,  1770);  Marherr,  'Praelect.  in  Boerliaavii  Instit.  Med.,'  torn,  ii,  p.  131; 
Thaer,  'Diss,  de  Actione  Systematis  Nervosi  in  Febribus'  (Gott.,  1774);  Isenflamm, 
'Praktische  Anmerkungen  iiber  die  Nerven'  (Erlang.,  1774),  §  16;  also  'Praktische 
Anmerkungen  uber  die  Muskeln'  (Erlang.,  1778),  Seit,  73.  Ern.  Platner,  'De 
Principio  Vitali'  (1777),  also  speaks  of  it  in  'Anton  von  Haen's  Heilungsmethode,' 
3ten  Band,  1781 ;  iibersetzt  von  Ern.  Platner,  Prof,  zu  Leipzig,  ira  1  Aufsatze  iiber 
einige  Scbwierigkeiten  des  Hallerischen  Systems;  Prochaska,  '  De  Carne  Musculari' 
(Viennae,  1778);  La  Roscb,  'Analyse  des  Fonctions  du  Sys.  Nerv.'  (Geneve,  1778), 
torn,  i ;  Cremadel's  '  Nova  Elem.  Physiol.'  (Romae,  1779) ;  and  many  others  who  are 
quoted  in  Haller's  '  Elem.  Phys.,'  torn,  iv,  p.  456. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  401 

sheaths,  arteries  and  veins,  together  with  their  fluid  contents, 
and  nerves.  Not  only  can  no  part  of  this  machine  be  wanting, 
but  it  is  also  necessary  to  its  due  action  that  there  be  flexibility 
of  the  fibres,  fluidity  of  the  fluids  contained  in  the  vessels,  and 
vis  nervosa  remaining  in  its  nerves,  which  may  perceive  the 
stimulus,  and  excite  contractions  of  the  muscle.  The  cele- 
brated Tissot  recognised  this  truth  ;^  for  although  he  main- 
tained irritability  to  be  a  property  innate  in  muscles,  and 
independent  of  the  nerves,  yet  he  observes,  that  it  is  probable 
no  muscle  is  perfectly  organised  without  nerve.  Consequently, 
if  irritability  be  the  efiPect  of  a  well-organised  muscle,  irritability 
cannot  exist  without  nerve  in  the  muscle.  The  illustrious 
Haller  seems  also  to  have  felt  the  force  of  truth,  for  he  altered 
much  of  par.  ii,  section  v,  book  iv,  in  the  new  edition  of  his 
'  Elementa  Physiol.^  :^  and  although  he  heads  it  with  '*  cordis 
motus  non  a  nervis/'  he  nevertheless  says,  that  it  must  be 
granted,  when  his  own  and  the  opposing  experiments  are  well 
weighed,  that  "  it  is  possible  that  some  property  of  the  nerves 
is  necessary  to  the  due  action  of  the  heart,  and  to  maintain  the 
power  of  the  fibres.  Nevertheless,  another  motive  power  is  more 
influential  in  the  heart,  namely,  its  irritability,  which  cannot  be 
excited  when  the  nerves  are  entirely  wanting.^'  And  in  many 
other  places  he  acknowledges,  that  the  motion  of  the  heart 
depends  on  the  nerves,  which,  however,  he  elsewhere  declares  is 
independent  of  the  nerves.^  So  long  as  a  nerve  is  continuous 
with  the  brain,  if  it  be  irritated,  it  produces  sensation,  and  excites 

'  Abhandl.  uber  die  Nerven,  &c.,  Ite  Band,  2  Th.,  Seit.  176,  §  267. 

2  De  Part.  Corp.  Hum.  Fabrica  et  Usu,  torn,  ii,  p.  392. 

^  Ibid.,  p.  439,  Haller  further  says  :  "  Another  conjecture  is,  that  the  heart  is  more 
irritable,  because  the  sentient  nerves  of  the  heart  being  in  close  relation  with  the 
inner  membrane  of  the  heart,  are  stimulated  by  the  contact  of  the  blood ;  and  that 
thence  a  more  active  movement  arises  than  from  irritation  of  the  external  portion 
of  another  muscle.  The  external  surface  of  the  intestines  is,  in  like  manner,  almost 
insensible  to  stimuli,  the  internal  most  sensitive,  and  when  irritated,  continually  ex- 
cites extensive  movements.  Is  it  that  the  auricles  are  more  excitable  than  the  heart, 
and  more  apt  for  motion,  because  being  so  delicate  the  nerves  are  almost  naked,  and 
consequently  exposed  to  the  immediate  stimulus  of  the  blood?  If  any  one  will 
advance  any  other  cause  for  the  greater  aptness  of  the  heart  for  motion  on  being 
irritated,  I  will  willingly  listen,"  &c. 

At  page  158  of  vol.  iv  of  this  same  work,  he  continues:  "Lastly,  another  cause 
of  the  more  rapid  and  frequent  contraction  of  the  heart  is  latent  in  the  stimulus. 
"Whether  the  nerves  be  vehemently  excited  by  any  cause  whatsoever,  or  whether  the 
vis  sanguinis  bv  which  the  heart  is  put  in  motion,  shall  have  been  increased.   Conse- 

26 


402  THE  NERVOUS  SYSTEM  IN  GENERAL,      [ch.  ii. 

motion  in  tlie  muscle  under  its  control ;  no  sooner,  however,  is  it 
tied  or  cut,  than  it  loses  the  power  of  producing  sensation  when 
irritated,  but  retains  the  power  of  exciting  the  muscles  to  move- 
ment. No  one  will,  I  think,  infer  from  this,  that  by  that 
division  any  portion  of  the  vis  nervosa  escapes  when  the  power 
of  exciting  sensation  is  taken  away :  certainly  the  power  to 
produce  both  motion  and  sensation  remains  in  the  divided 
nerve,  but  it  cannot  excite  sensation,  because  on  account  of  the 
division  or  ligature,  it  cannot  communicate  its  external  im- 
pressions to  the  brain,  in  which  organ  the  perception  of  sen- 
sations takes  place.  It  is  certain  that  the  divided  nerve  retains 
the  power  of  producing  motion,  but  it  is  necessary  to  this,  that 
there  be  an  uninterrupted  connection  between  the  muscle  and 
the  irritated  point  of  the  nerve ;  if  this  be  broken  by  division 
or  ligature,  no  movement  is  excited  in  the  muscle,  however 
much  the  nerve  may  be  irritated  above  the  ligature  or  section ; 
and  the  same  holds  good  as  to  the  production  of  sensation. 

vii.  A  peculiar  affection  of  the  vis  nervosa,  or  idiosyncrasy, 
— That  state,  termed  idiosyncrasy,  is  evidently  a  peculiar  affec- 
tion of  the  nervous  system,  which  may  indeed  be  referred 
to  an  increase  or  diminution  of  the  vis  nervosa,  yet  not  in 
respect  to  all,  but  rather  to  certain  peculiar  stimuli.  This 
causes  us  to  regard  some  things  with  the  greatest  love,  and 
with  an  insatiable  longing,  and  others  with  the  greatest 
aversion ;  the  one  is  termed  sympathy,  the  other  antipathy. 
That  idiosyncrasies  are  diverse  in  different  men  is  evident 
from  this,  that  some  desire  just  what  others  are  averse  to. 
There  are  idiosyncrasies  proper  to  each  age,  temperament,  and 
sex ;  or,  more  properly,  to  each  individual ;  some  of  these  are 
altered  by  time,  the  manner  of  life  or  temperament  being 
changed  in  some  respects ;  many  are  modified  by  habit,  and 
some  remain  companions  for  life ;  some  again  are  excited  by 
pregnancy,  and  others  by  diseases,  and  disappear  when  these 
are  removed.  Consequently,  it  would  appear  that  idiosyncra- 
sies may  be  divided  into  idiosyncrasies  of  the  healthy,  of  the 
pregnant,  and  of  the  sick.     As  to  other  points,  if  we  be  igno- 

quently,  the  pulse  is  accelerated  by  affections  of  the  mind,  anger,  terror,  shame,  and 
various  passions.  Van  Helmont  was  not  ignorant  of  the  quicker  pulse,  which  is  said 
1 0  accompany  every  violent  pain,  as  in  the  instance  of  a  thorn  sticking  in  the  finger," 

&c.  And  in  'Elem.  Physiol.,'  tom.  iv,  p.  356,  he  adds:  "  In  many  (acephalous 
foetuses)  there  was  only  so  much  of  the  spinal  cord  as  was  sufficient  to  maintain  the 

motions  of  the  heart,"  &c. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  403 

rant  of  the  nature  of  the  vis  nervosa  in  general,  much  more  may 
this  peculiar  vis  nervosa  be  unknown  to  us,  the  visible  eflPects 
of  which  can  only  be  observed.  If  any  person  would  collect 
these  from  his  personal  observation  and  from  medical  writings, 
and  arrange  them  well,  he  would  certainly  accomplish  a  useful 
work,  from  which  we  might  hope  to  obtain  much  light  for 
understanding  the  functions  of  the  nervous  system,  and  much 
for  the  cm^e  of  its  diseases.  And  Haller  spoke  truly  of  idio- 
syncrasy, when  he  said  :  "  As  yet  this  field  has  certainly  not 
been  sufficiently  cultivated,  and  there  is  the  prospect  of  an 
abundant  harvest  from  it.^^  ^  As  in  this  dissertation  I  propose 
only  to  give  an  introduction  to  the  functions  of  the  nervous 
system,  rather  than  to  work  out  a  complete  treatise,  I  shall 
only  enumerate  a  few  examples  of  idiosyncrasy,  hoping  from 
others  a  full  systematic  account. 

It  happens  to  some  men,  in  other  respects  perfectly  healthy, 
that  they  cannot  see,  taste,  or  even  hear  certain  things,  but  they 
are  affected  unpleasantly,  and  sometimes  to  fainting.  Some 
cannot  be  present  at  a  venesection,  and  see  the  blood  flow,  with- 
out fainting  away.  I  know  a  female  who,  when  young,  could 
never  see  the  beet-root  that  is  usually  placed  on  the  table,  without 
swooning  and  fainting;  she  was  at  last  by  habit  enabled  to  look  at 
it,  but  could  never  eat  it.  The  exhalations  of  a  cat,  although 
concealed,  excite  in  some  men  disquietude,  perspiration,  and 
fainting ;  an  example  of  this  kind  is  narrated  by  Kaaw;^  and  also 
the  history  of  a  man  who  was  always  affected  with  a  bleeding 
at  the  nose,  from  the  odour  of  cheese.  Fainting,  in  some,  is 
induced  by  the  fragrance  of  roses ;  and  the  pale  rose  of  a 
pleasant  odour,  the  red,  unpleasant. "*  Fainting  has  also  been 
excited  by  the  odour  of  apples.^  Strawberries  have  produced 
remarkable  symptoms.^  Musk  and  civet  can  excite  in  some 
persons  violent  hysterical  attacks,  which  in  others  are  induced 
by  the  fetid  gums.  We  may  meet  every  day  with  illustrations 
of  idiosyncrasy  of  taste,  for  we  see  some  persons  esteem  articles 
of  diet  as  delicacies  which  others  abhor  :  I  myself,  when  young, 
had  such  an  aversion  for  spinach,  beet-root,  and  cod-fish,  that 

•  Elena.  Phys.,  torn,  iv,  p.  575. 

2  Impet.  Faciens  dictum  Hippocrati,  §  408,  p.  358. 
^  Eph.  Nat.  Cur.,  Dec.  ii,  An.  v,  observ.  8. 

*  Ibid,,  An.  I,  observ.,  72. 
Ibid.,  An.  v,  observ.,  214. 


404.        THE  NERV^OUS  SYSTEM  IN  GENERAL.       [ch.  ii. 

by  taking  the  smallest  particle  of  them,  I  could  have  excited 
nausea  and  vomiting;  becoming  habituated  to  them  all,  that 
disposition  gradually  disappeared.  Tissot  observed  in  one  of 
his  friends,  that  he  could  not  bear  the  smallest  quantity  of 
sugar,  and  would  presently  vomit  it,  even  if  taken  unknow- 
ingly.^ Music,  so  pleasant  to  us,  is  very  disagreeable  to  most 
dogs,  as  is  shown  by  their  disquietude  and  bowlings.  I  knew 
a  female,  on  whose  skin  a  plaster  of  any  kind  excited  redness, 
swelling,  and  pustules.  Many  persons  cannot  sit  with  their  back 
to  the  horses  in  a  carriage  without  experiencing  vertigo,  nausea, 
vomiting,  and  swooning.  Tissot  rightly  maintains,  that  the  anti- 
pathy between  certain  animals,  as  for  example,  between  the  hare 
and  the  dog,  the  cat  and  the  mouse,  depends  on  idiosyncrasy  of 
the  nerves ;  ^  and  he  shows  that  the  sympathies  and  antipathies 
between  men  are  due  to  the  same  cause,  as  when  a  person  at 
the  first  glance  finds  something  in  another  person  which  pleases 
or  displeases  him,  and  impels  him  to  love  or  hate  that  person. 

Pregnancy  frequently  induces  idiosyncrasy  of  the  nerves  of  the 
pregnant,  so  that  they  are  affected  with  a  dislike  for  various  foods 
and  drinks,  or  have  the  greatest  desire  for  other  things,  even 
the  most  absurd.  Many  recorded  examples  of  this  extraordinary 
appetite,  which  is  termed  pica,  or  malacia,  are  current.  Schenk 
relates  the  history  of  a  pregnant  female,  in  whom  the  sight  of 
the  bare  arm  of  a  baker  excited  such  an  inexphcable  desire  to 
bite  and  devour  it,  that  she  compelled  her  husband  to  offer 
money  to  the  baker  to  allow  her  only  a  bite  or  two  from  his  arm. 
He  also  mentions  another  female,  who  had  such  an  urgent 
desire  to  eat  the  flesh  of  her  husland  that  she  killed  him,  and 
pickled  the  flesh,  that  it  might  serve  her  for  several  banquets. 
But  it  is  also  true  that  this  detestable  appetite  for  human  flesh 
has  affected  men  and  unimpregnated  females,  as  well  as  the 
pregnant,  and  these  have  also  been  impelled  to  commit  murder, 
when  not  restrained  by  reason  or  humanity.  This  happened 
with  Elizabeth  of  Milan,  who  allured  boys  to  her  by  caresses, 
killed  them,  and  ate  their  pickled  flesh  every  day.  A  Scotch 
girl,  the  daughter  of  an  anthropophagous  robber,  had  the  same 
wicked  desires  as  her  father,  and  although  long  separated  from 
him,  and  educated  apart,  she  still,  from  an  innate  depraved  dis- 
position remained  prone  to  the  same  crime.^    We  have  a  recent 

'  Von  Nerven,  2  Band,  2  Th.,  §  58.  ^  Lqc^  cjt.,  ^$  58,  59. 

^  See  Gaubius  in  Orat.  I,  de  Regimine  Mentis,  quod  Medicorum  est. 


SECT.  III.]    PROPERTIES  OF  THE  VIS  NERVOSA.  405 

example  in  the  case  of  a  cannibal  of  Berg  [Westphalia],  who 
being  a  man  in  other  respects  of  a  depraved  disposition,  and 
incited  by  an  appetite  for  human  flesh,  did  not  hesitate  to  slay 
certain  innocent  persons,  namely,  a  girl,  and  a  traveller.^ 

Idiosyncrasies  have  been  frequently  observed  to  arise  from 
disease ;  thus,  a  person  aflPected  with  fever  arising  from 
internal  putrescence,  dislikes  flesh,  fish,  eggs,  and  broths  made 
from  them,  but  has  a  great  desire  for  acids ;  as  the  disease  de- 
clines, the  appetite  returns  for  the  things  that  were  previously 
rejected.  Persons,  who  in  health  esteem  tobacco  as  a  great 
luxury,  when  sick,  neglect  and  dislike  it,  but  with  returning 
health,  regain  their  desire  for  it.  Pale  girls,  commonly  aff'ected 
with  acidity,  have  a  taste  for  chalk  or  lime,  or  for  charcoal  and 
ashes,  or  for  vinegar  and  salt.  Hydrophobic  patients  are 
horrified  even  at  the  sight  of  water.  To  this  class  of  examples, 
belong  those  cases  in  which  remedies  having  been  applied  in 
vain,  suddenly  an  appetite  is  excited  for  some  particular  thing, 
which,  being  taken,  the  patients  are  happily  cured. 

The  influence  of  habit  on  the  vis  nervosa^  and  especially  on 
idiosyncrasy,  deserves  to  be  noticed  here.  By  means  of  this 
the  nerves  become  easily  tolerant  of  those  things,  by  which 
they  were  at  first  violently  aff'ected.  Thus,  those  who  are 
habituated  to  wine  and  the  smoke  of  tobacco,  can  imbibe  a 
large  quantity  with  impunity,  while  in  those  unaccustomed  to 
their  use,  they  excite  vertigo,  drunkenness,  and  other  unpleasant 
symptoms.  Thus,  also,  a  seaman  habituated  to  the  sea  is  not 
annoyed  with  the  nausea  and  vomiting  which  the  motion  of 
the  ship  will  excite.  These  and  many  other  instances  show, 
that  the  degree  of  sensibility  of  the  nerves  is  diminished  by 
habit,  not  indeed  with  regard  to  any  stimuli,  but  only  in  re- 
spect of  those  which  are  frequently  applied,  the  nerves  remaining 
equally  sensitive  to  other  stimuli.  Thus,  also,  an  idiosyncrasy 
may  be  diminished,  or  entirely  overcome  by  habit  alone ;  just 
as  on  the  other  hand,  by  habit  alone,  the  nervous  system  becomes 
accustomed  to  certain  things,  and  acquires  a  true  idiosyncrasy, 
so  that  we  cannot  easily  do  without  those  things,  as,  for  example, 
in  the  case  of  a  man  accustomed  to  the  use  of  tobacco.  It  is 
from  hence,  that  the  proverb  has  originated — "  habit  is  second 
nature.^' 

See  this  history  in  the  inaugural  dissertation  of  Jacobi,  defended  at  Jena  in  1781. 


CHAPTER  III. 

THE  FUNCTIONS  OF  THE  NERVES.  - 

Inasmuch  as  I  have  already  divided  the  nervous  system  into 
three  principal  portions,  namely,,  the  animal  organs,  sensorium 
commune,  and  the  nerves  properly  so  called,  I  shall  also  divide 
its  functions  into  three  classes,  namely,  into  animal  operations, 
operations  of  the  sensorium,  and  operations  of  the  nerves.  The 
functions  of  the  nerves  are  first  to  be  considered;  then  the 
operations  of  the  common  sensory,  and  lastly,  the  animal 
operations. 

SECTION     I. ON     THE    ACTION     OF    THE     NERVES     IN     PRODUCING 

SENSATION  AND  MOTION. 

Since  the  nerves  represent  cords  commencing  in  the  cerebrum, 
medulla  oblongata,  and  medulla  spinalis,  and  thence  extended 
throughout  the  whole  body,  two  extremities  are  noted  in  each 
nerve;  of  these,  the  one  is  internal  and  continuous  with  the 
cerebrum,  or  medulla  oblongata,  or  medulla  spinalis,  and  termed 
the  origin  or  beginning  of  the  nerve ;  the  other  is  external  where 
the  nerves  terminate  in  various  parts  of  the  body,  and  termed, 
therefore,  the  end  of  the  nerve.  It  is  besides  certain,  that  the 
nerves  have  the  property  of  most  readily  receiving  impressions, 
however  great  or  of  whatever  kind  they  may  be,  and  of  trans- 
mitting them  when  received  with  great  rapidity  along  their 
whole  length.  Consequently,  if  an  impression  be  made  at  the 
termination  of  a  nerve,  which  is  termed  an  external  impression, 
it  is  very  rapidly  transmitted  along  the  whole  length  of  the  nerve 
quite  to  its  origin ;  and  vice  versa,  if  the  impression  be  made 
at  the  commencement  of  the  nerve,  which  is  termed  an  internal 
impression,  it  is  transmitted  with  the  same  rapidity  to  the 
termination  of  the  nerve.  But  if  the  impression  be  made 
midway  on  the  trunk  of  the  nerve,  it  is  rapidly  transmitted  a 
the  same  moment  to  both  its  origin  and  termination.     This 


SECT.  I.]  ACTION  OF  THE  NERVES  ON  IMPRESSIONS.  407 

aptitude  of  the  nerves  to  receive  impressions,  and  when  received 
of  transmitting  them  either  way  with  great  rapidity,  appears  to 
be  that  called  the  vis  nervosa  of  the  nerves,  which  is  also  cor- 
rectly designated,  the  sensibility  or  mobility  of  the  nerves,  and 
which  is  also  well  designated  by  Unzer,  "  corporeal  sensation 
without  concomitant  perception.^^ 

This  property  of  the  nerves  does  not  depend  solely  on  their 
medullary  pulp,  (which  possibly  is  capable  of  some  slight  vibra- 
tion, or  oscillation,  although  the  nerves  do  not  appear  at  all 
tense,)  but  it  appears,  as  I  have  already  observed  in  §  3  of 
the  preceding  Chapter,  to  be  rather  some  other  principle  added 
to  the  medullary  pulp,  the  conjunction  of  the  two  constituting 
the  whole  vis  nervosa  j  and  possibly  the  diligence  of  the  very 
sagacious  observers  of  nature  may  discover  whether  that  prin- 
ciple be  electricity,  or  phlogiston,  or  some  species  of  air,  or  the 
matter  of  light,  or  a  something  compounded  of  these.  That  other 
principle,  whatever  it  may  be,  seems  to  come  to  the  nerves  with 
the  arterial  blood,  by  means  of  the  numerous  blood-vessels  which 
accompany  the  nerves  of  the  whole  body  throughout  their  whole 
course ;  or  to  be  attracted  from  the  air  through  inorganic  pores; 
or  in  both  these  ways,  and  not  to  be  sent  into  the  nerves 
from  the  brain,  as  its  only  source,  although  the  brain  itself 
appears  to  acquire  a  suitable  portion  of  the  same  principle 
through  its  own  vessels.  For,  as  I  have  before  shown,  the 
nerves  when  separated  from  the  brain  have  equally  vis  nervosa 
as  the  nerves  in  connection  with  the  brain,  and  in  proof 
hereof  may  be  mentioned  the  nerves  of  acephalous  foetuses 
and  of  brainless  animals,  which  are  endowed  with  the  vis 
nervosa,  although  they  could  not  possibly  derive  it  from  a  brain. 
Nevertheless,  a  certain  cohesion  of  the  medullary  pulp  of  the 
nerves  is  necessary  to  the  vis  nervosa,  because  if  we  so  injure 
the  pulp  of  a  nerve  by  strong  compression,  that  the  connection 
of  its  globules  is  destroyed,  and  their  relations  broken  up,  the 
vis  nervosa  ceases  in  the  portion  of  the  nerve  thus  compressed, 
neither  can  impressions  be  propagated  through  it,  nor  can  that 
portion  of  the  nerve  produce  motion  or  sensation,  if  pricked  or 
irritated. 

Although  a  nerve  be  necessary  to  sensation  and  motion,  it  does 
not  excite  motion  or  feel  alone,  but  feels  by  means  of  the  brain, 
which,  when  an  impression  made  on  a  nerve  is  brought  to  it, 


408  FUNCTIONS  OF  THE  NERVES.  [ch.  hi- 

communicates  the  impression  to  the  mind ;  and  the  nerve  pro- 
duces motion  by  means  of  a  muscle,  when  an  impression  made 
on  the  nerve  descends  to  the  muscle/  and  excites  it  to  move- 
ment. Consequently,  a  nerve  separated  from  the  brain,  and  no 
longer  able  to  communicate  impressions  to  it,  can  no  longer 
produce  sensation,  just  as  a  nerve  separated  by  division  from  a 
muscle  can  no  longer  excite  motion  in  the  muscle,  however 
much  it  may  be  irritated.  Consequently,  a  nerve  has  a  similar 
office  in  exciting  sensation  and  motion,  namely,  to  receive  the 
impression  of  a  stimulus,  and  to  transmit  it  with  the  greatest 
rapidity  along  its  whole  length,  which,  when  it  arrives  at  the 
brain,  produces  the  perception  of  a  sensation,  but  when  it 
arrives  at  a  muscle,  excites  its  contraction. 


SECTION  II. THE   ACTION   OF   THE   NERVES  ON    THE    VESSELS  AND 

THEIR  FLUIDS. 

Another  function  of  the  nerves  consists  in  a  certain  power 
over  the  blood-vessels,  and  specially  the  capillaries,  in  virtue 
of  which,  when  the  nerves  are  stimulated,  they  excite  in  that 
part  to  which  they  are  distributed  a  much  more  copious 
accumulation  of  blood  than  would  have  taken  place  in  the 
normal  condition  of  the  circulation.  This  phenomenon  is 
termed  congestion  of  the  humours,  afflux,  derivation,  abnormal 
direction,  descent  of  the  humours.  Stahl  termed  it  the  tide  of 
the  microcosmic  sea,  or  the  ebb  and  flow  of  the  blood. 

The  causes  that  determine  a  more  copious  derivation  of  the 
humours  into  any  part  of  the  body,  are  usually  considered  to  be 
twofold ;  the  one,  a  mere  mechanical  cause,  consists  in  a  dimi- 
nished resistance  of  the  vessels  of  the  part,  so  that  the  humours 
contained  in  the  vessels  being  forced  on  by  the  power  of  the 
heart  and  the  vessels  themselves,  flow  to  the  point  of  least 
resistance,  according  to  the  laws  regulating  other  fluids,  and 
cause  congestion  of  the  humours ;  for  this  reason,  when  a  vein 
or  artery  is  divided,  the  blood  rushes  from  the  adjoining  vessels, 
even  against  its  natural  direction  and  gravity;  for  this  reason, 
also,  congestion  takes  place,  when  vessels  are  relaxed  by  emol- 
lient cataplasms  and  pediluvia.^     Thus  also  the  blood  is  cou- 

'  Haller,  De  Part.  Corp.  Hum.  Fabr.,  torn,  iv,  pp.  93,  289. 


SECT. II.]  ACTION  OF  THE  NERVES  ON  THE  VESSELS.  409 

gested  under  a  cupping-glass  when  the  usual  atmospheric  pres- 
sure is  removed  from  the  part ;  a  local  derivation  of  the  humours 
takes  place  also  when  a  compression  of  the  vessels  occurs  in  any 
part,  and  the  blood  is  repelled  into  other  parts ;  as  occurs,  for 
example,  when  the  stomach  is  filled,  by  which  the  abdominal 
vessels  are  compressed  and  the  lungs  forced  into  less  room, 
and,  consequently,  a  greater  quantity  of  blood  goes  to  the  head, 
rendering  the  face  redder.     The  other  cause  is  a  stimulus  to 
the  nerves  ;    which  when  applied  to  the  nerves  excites  a  more 
copious  flow  of  humours.     Innumerable  phenomena  of  daily 
occurrence  show  this.  Thus  a  stimulus  applied  to  the  nerves  is 
the  cause  why  the  cheeks,  ears,  and  nose,  become  intensely  red, 
and  a  sense  of  heat  is  felt  when  exposed  to  a  cold  wind  in  winter. 
No  one  is  ignorant  how  much  the  stimulus  of  sinapisms  and 
blisters  cause  derivation  of  the  humours  to  the  stimulated  part; 
an  acrid  smoke  or  fine  powder  getting  into  the  eyes  excites  a 
copious  flow  of  tears,  and  the  vessels  of  the  conjunctiva,  pre- 
viously invisible,  become  distended  with  blood.     The  smoke  of 
tobacco,  or   any  other  acrid  aroma,  retained  in   the   mouth, 
excites  a  copious  flow  of  saliva ;  purgatives  and  emetics  bring 
off*  much  gastric  and  intestinal  mucus ;  titillation  of  the  nipple 
of  the  mamma  causes  it  to  become  turgid  and  erect ;  the  touch, 
or  the  stimulus  of  the  semen  or  urine,  or  a  gonorrhoea,  cause 
the  penis  to  be  distended  and  erected  by  exciting  a  more  copious 
flow  of  blood  into  the  corpora  cavernosa.     These  phenomena 
take  place  if  the  nerves  be  stimulated  locally ;  but  the  same 
thing  happens  when  the  nerves  are  excited  not  directly,  but 
indirectly,  through  the  brain.     We  know,  that  thus  the  face  is 
suffused  with  the  blush  of  modesty ;  grief  causes  a  copious  flow 
of  tears,   congestion  of  the  vessels  of  the  conjunctiva,   and 
redness  and  swelling  of  the  whole  face.     The  sight  of  agree- 
able food  provokes  a  flow  of  saliva ;  it  is  not  unusual  for  some 
persons  to  vomit,  or  be  purged  by  only  seeing  a  medicine ;  a 
lascivious  idea  erects  the  penis,  &c. 

Although  it  is  placed  beyond  a  doubt,  that  stimulated 
nerves  cause  congestion  and  derivation  of  the  humours  to  the 
part  stimulated,  the  mode  in  which  the  nerves  accomplish  this  is 
as  yet  unknown.  Distinguished  writers  have  advanced  various 
conjectures,  by  which  they  have  attempted  to  explain  this  in- 
fluence of  the  nerves  on  the  vessels.    Some  have  supposed  that 


410  FUNCTIONS  OF  THE  NERVES.  [ch.  in. 

there  are  nervous  loops  and  nooses  at  the  termination  of  the 
arteries  and  roots  of  veins,  similar  to  those  which  are  seen  to  sur- 
round the  larger  arteries  in  many  places ;  and  they  opined  that 
these  loops  could  be  tightened  or  relaxed,  and  so  be  able  to 
admit  blood  to  the  part  or  retain  it.  Haller,  together  with  some 
of  his  disciples,  followed  Willis  in  adopting  this  opinion ;  but 
when  he  learnt,  from  experiments,  that  the  nerves  do  not  con- 
tract when  stimulated,  he  rejected  the  doctrine.  Some  located 
muscular  sphincters  at  the  terminations  of  the  arteries  and 
roots  of  the  veins,  which  constricting  the  vessels,  and  causing 
the  blood  to  accumulate  above  the  constriction,  so  inundated 
the  lateral  vessels :  Boerhaave  in  particular  propounded  this 
opinion  in  his  theory  of  obstruction,^  and  also  founded  his 
theory  of  inflammation  upon  it.  But  many  and  weighty  ob- 
jections have  been  raised  against  this  production  of  accu- 
mulation and  inflammation  by  obstruction  and  constriction 
only;  for  obstruction  of  a  vessel  does  not  cause  such  an 
accumulation  of  fluid,  anterior  to  the  obstruction,  because  it 
easily  finds  an  exit  through  the  lateral  vessels  so  obvious  in  every 
part  of  the  body ;  and  the  comparison  of  a  river  swelling  from  an 
obstruction,  and  inundating  the  adjoining  parts,  does  not  apply 
to  our  vessels ;  for  if  one,  or  even  many  of  them,  be  obstructed, 
there  still  remain  innumerable  lateral  vessels,  through  which 
the  fluids  find  a  free  outlet.  For  this  reason,  Haller  found  that 
the  trunk  of  an  artery,  when  tied,  became  swollen  indeed  for  a 
moment,  between  the  ligature  and  the  heart,  and  manifested 
T)ne  or  two  pulsations ;  but  so  far  is  it  from  the  fact,  that 
the  impetus  of  the  fluids  is  directed  against  the  ligature,  that 
rather  the  canal  is  contracted,  and  it  impels  the  blood  into 
the  communicating  arteries,  until  that  which  was  tied  is  quite 
empty.  The  same  thing  is  shown  by  the  umbilical  arteries, 
which  also  become  empty,  and  impervious.  WinterP  fully 
sets  forth  these  and  other  arguments  of  distinguished  men, 
and  proves  that  the  fluids  do  not  rush  towards  an  obstruction, 
but  rather  prefer  to  pass  away  by  the  lateral  and  unobstructed 
vessels ;  consequently,  no  congestion  and  no  inflammation  can 
arise  from  an  obstruction  only,  but  the  stimulus  of  the  nerves 
is  the  cause,  which  immediately  excites  the  fluids  to  accumulate 
more  copiously  in  the  vessels  subjected  to  them.  Moreover, 
'  Aphoris.,  113.  ^  Nova  Theoria  Inflammationis,  p.  19. 


SECT.  11.]  ACTION  OF  THE  NERVES  ON  THE  VESSELS.  411 

that  distinguished  man  propounds  a  peculiar  and  singular  con- 
jecture, which  appears  to  me,  however,  unfounded,  to  the  effect 
that  since  a  stimulus  has  quite  a  different  result  on  the  mus- 
cular arteries,  than  on  the  heart  and  other  muscles — inasmuch 
as  the  arteries  appear  to  be  dilated  by  a  stimulus,  whereas  we 
see  that  the  heart  and  other  muscles  to  be  contracted — he 
thinks  that  the  blood  is  attracted,  and  flows  from  all  sides  into 
the  arteries  dilated  by  a  stimulus.  An  opinion  of  other  eminent 
men,  as  to  the  cause  of  the  derivation  of  the  fluids  to  a  stimu- 
lated part  is,  that  the  stimulus  renders  the  arterial  action 
more  frequent  and  powerful,  consequently  that  the  arteries  carry 
a  greater  quantity  of  the  fluids  onwards  than  the  veins  can  return, 
and  thus  they  explain  why  the  fluids  should  accumulate  more 
copiously  in  a  stimulated  part.^      But  even  this  doctrine  does 

*  I  may  be  permitted  to  make  some  observations  here  on  the  irritability  and  mus- 
cular contraction  of  arteries.  The  experiments  of  Haller  appeared  to  render  the  irri- 
tability of  arteries  doubtful,  as  he  never  found  them  irritable ;  and  to  show  that  the 
systole  of  the  pulsating  arteries  in  the  natural  state  arises  solely  from  their  elasticity, 
by  which  they  are  restored  to  their  former  condition  after  being  distended  by  the 
blood  projected  from  the  heart,  and  enabled  to  transmit  the  blood  thus  received 
inwards  into  the  veins,  so  that  along  with  the  eminent  men  who  have  repeated  the 
experiments,  I  expressed  my  assent  to  their  validity  in  *  Controversis  Quaestionibus 
Physiologicis,'  p.  30.  The  experiments  of  Verschuir  on  the  irritability  of  arteries, 
were  not  then  known  to  me ;  they  are  contained  in  his  Dissertation  '  De  Arteriarum 
et  Venarum  vi  irritabili  ejusque  in  vasis  excessu ;  et  inde  oriunda  Sanguinis  direc- 
tione  abnormi,'  printed  at  Grbningen  in  1766,  and  fully  demonstrate  that  some- 
times arteries  and  veins  manifestly  contract  on  the  application  of  a  powerful 
stimulus,  as  scraping  with  a  scalpel,  oil  of  vitriol,  spirit  of  sal  ammoniac,  &c. ;  but 
generally  the  contractions  were  very  indistinct,  and  not  unfrequently  neither  re- 
sponded to  these  acrid  stimulants,  nor,  as  in  the  experiments  of  Haller,  could 
irritability  be  detected.  It  is  also  shown  from  all  these  experiments  of  Verschuir, 
when  properly  collated,  that  although  arteries  were  found  to  respond  to  these 
acrid  stimulants  in  one  or  more  places,  in  another  part  of  the  same  animal  it 
was  the  least  possible.  Further,  it  is  to  be  observed,  that  those  contractions  which 
were  excited  continued  for  some  time  before  they  ceased,  and  the  artery  was  re- 
stored to  its  former  condition ;  consequently  the  contraction  and  relaxation  of  the 
artery  did  not  follow  each  other  so  quickly  as  the  systole  and  diastole  of  the  artery 
in  its  natural  condition,  nor  as  quickly  as  the  heart,  when  irritated,  contracts  and 
then  immediately  relaxes.  Lastly,  it  also  appears  from  the  experiments  of  this  dis- 
tinguished physiologist,  that  a  portion  of  an  artery,  which  an  acrid  poison  had 
caused  to  contract,  was  hard  and  rigid,  and  no  longer  pulsated ;  while,  at  the  same 
time,  other  portions  of  the  same  artery,  untouched  by  the  acrid  stimulus,  continued 
to  repeat  their  pulsations.  But  are  the  results  of  these  experiments  opposed  to  the 
doctrine,  that  the  elasticity  of  the  arteries  is  the  cause  of  their  systole  ?  By  no 
means ;  for  the  elasticity  of  the  arteries  is  ever  demonstrable  in  any  animal,  whether 


412  FUNCTIONS  OF  THE  NERVES.  [ch.  iii. 

not  appear  to  have  the  real  stamp  of  truth,  which  I  leave, 
however,  to  be  decided  on  by  other  perspicacious  men,  to 
whose  attention  I  would  also  commend  this  conjecture,  namely, 
whether  when  the  vis  nervosa  is  increased  by  a  stimulus,  it 
does  not  render  the  force  of  attraction  of  the  fluids  circulating 
through  the  vessels  greater,  so  that  by  this  means  the  fluids  are 
attracted  from  every  side  to  the  centre  of  stimulation,  as  occurs, 
for  example,  when  sealing-wax  is  gently  rubbed  on  a  piece  of 
cloth,  and  made  electrical,  and  attracts  sand  and  particles  of 
various  kinds?  Speculations  of  this  kind  are  not  vain  and 
useless,  because  if  the  true  reason  be  known  why  the  nerves 
when  stimulated  cause  accumulation  of  the  fluids  in  the  tissues 
to  which  they  are  distributed,  much  light  will  be  thrown  on 
the  nature  of  the  vis  nervosa  itself,  for  one  truth  leads  to  another. 

living  or  dead,  and  is  so  great  that  it  appears  to  be  a  power  quite  sufficient  to  restore 
the  artery  to  its  former  condition  after  being  dilated  by  the  blood  sent  into  it  from 
the  heart,  and  to  pass  that  blood  onwards  to  the  veins  :  it  is  by  this  elasticity  only, 
that  the  systole  of  the  arteries  so  immediately  and  quickly  follows  the  systole  of  the 
heart,  as  happens  in  the  regular  and  natural  pulse ;  while,  on  the  contrary,  the  irri- 
tability of  arteries  is  small,  requiring  the  strongest  stimulus,  and  not  always  respond- 
ing to  this,  so  that  it  obviously  appears  inadequate  to  the  repeated  natural  systole 
of  the  arteries.  According  to  the  experiments  of  Haller  (De  Part.  Corp.  Hum.  Fabr. 
et  Funct.,  tom.  iv,  pp.  93,  289),  it  is  only  the  elasticity  of  the  arteries,  which,  after 
the  death  of  an  animal,  impels  the  blood  from  every  point  through  a  wound,  since 
all  irritability  had  disappeared.  As  the  irritability  of  arteries,  according  to  the  ex- 
periments of  Verschuir,  is  hardly  excited  even  by  very  acrid  stimuli,  it  will  scarcely 
be  developed  by  the  unstimulating  blood  sent  from  the  heart  into  the  artery ;  but  it 
seems  to  presuppose  great  disturbance  of  the  nervous  system,  by  which  it  is  excited. 
This  takes  place  differently  in  different  parts,  and  to  it,  perhaps,  ought  to  be  ascribed 
those  abnormal  pulsations,  diflferent  in  different  parts,  and  even  complete  pulse- 
lessness ;  examples  of  which,  given  by  authors  worthy  of  credit,  are  cited  by  Verschuir 
in  the  Dissertation  just  noticed,  and  by  Gruber  in  his  Dissertation  *  De  Excessu  Vis 
Vitalis,'  published  in  Klinkosh's  collection  of  disputations  at  the  University  of 
Prague.  Consequently,  it  appears  to  me,  that  the  natural  systole  of  the  arteries 
ought  to  be  attributed  to  their  elasticity  only ;  but  as  to  the  cause  of  the  different 
pulses  in  different  parts,  observed  in  the  same  individual  at  the  same  time,  and  also 
as  to  the  want  of  pulsation  in  pulselessness,  it  is  clearly  demonstrated  by  the  experi- 
ments of  Verschuir  to  be  the  irritability  of  the  arteries.  Whence  it  therefore  follows, 
that  arteries  in  their  natural  condition  react  solely  by  their  elasticity,  and  are  not 
irritable ;  but  that  they  become  irritable  and  contract,  in  a  preternatural  condition, 
when  the  vis  nervosa  of  the  nerves  distributed  to  the  arteries  is  preternaturally  in- 
creased ;  or  when  a  very  powerful  stimulus,  as  in  the  experiments  of  Verschuir,  is 
applied  to  them ;  and  we  have  additional  confirmation  of  this,  when  we  remember 
that  some  parts  of  our  bodies,  which  are  without  sensation  in  the  natural  state,  be- 
come extremely  sensitive  in  disease. 


SECT.  111.]      CONTRACTION  OF  THE  MUSCLES.  413 


SECTION     III. BY     THIS     DERIVATION     OF    THE     FLUIDS    TO    THE 

STIMULATED     PART,     THE     MUSCLES    ARE     MADE    TO     CONTRACT, 
AND  MANY  OTHER  PHENOMENA  PRODUCED. 

The  fasciculi  of  the  muscles  are  made  up  of  fibres  and 
carneous  filaments,  and  bound  together  by  sheaths,  and  are  so 
traversed  by  blood-vessels,  that  these  are  everywhere  inter- 
mingled with  the  fibres  and  filaments,  and  decussate  with  them 
more  or  less  transversely;  and  since  the  fibres  and  carneous 
filaments  are  closely  compressed  together  by  their  sheaths,  the 
least  congestion  and  distension  of  the  vessels  distributed  amongst 
them  cannot  take  place  without  the  filaments  and  the  fibres 
which  they  constitute  being  thrown  into  many  serpentine  in- 
flexions, and  thus  their  length  be  diminished.  Since,  therefore, 
irritation  of  the  nerves  causes  congestion  of  humours  in  the 
vessels,  it  is  easy  to  infer  that  in  this  same  manner  nerves,  when 
irritated,  excite  the  muscles  to  which  they  are  distributed  to  con- 
traction, that  is  to  say,  by  the  greater  accumulation  of  the 
humour  alone,  caused  in  the  vessels  of  the  contracting  muscle. 
When  the  cause,  originating  in  the  nerves,  which  attracts  fluids 
more  freely  to  the  muscle,  ceases  to  act,  the  distended  vessels 
and  deflected  fibres  react  by  their  elasticity  on  the  accumulated 
fluids,  and  propel  them  into  the  larger  blood-vessels  not  en- 
tangled amongst  fibrils  and  muscular  filaments ;  this  process  is 
facilitated  by  the  raising  of  the  weight,  which  resists  the  con- 
traction of  the  muscle  that  raises  it,  by  the  action  of  the  over- 
stretched muscles  antagonistic  to  it ;  and  thus  the  contracted 
muscle  is  again  relaxed.  It  is  now  four  years  since  I  sub- 
mitted this  theory  of  muscular  action  to  the  criticism  of  the 
learned  public,  in  my  Tract,  ^De  Carne  Musculari.^  It  is 
founded  on  the  intimate  anatomy  of  the  muscular  tissues,  is 
well  adapted  to  the  phenomena,  and  I  am  not  aware  that  any 
one  has  opposed  the  theory,  or  advanced  any  doubts  regarding 
it ;  nor  in  meditating  upon  it  myself  have  I  been  able  to  dis- 
cover any  arguments  against  it,  except  that  irritability  exists 
more  extensively  than  muscular  structure.  But  it  appears 
to  me  that  this  argument,  when  rightly  considered,  is  not 
an  objection  to  my  theoiy ;  for  if  we  observe  that  polypes 
and   other    zoophytes   are    irritable,    in  whose    structure   the 


414  FUNCTIONS  OF  THE  NERVES.  [ch.  hi. 

microscope  enables  us  to  detect  only  a  granular  mass,  but 
no  muscle,  no  bones,  no  vessels,  no  nerves ;  if,  more- 
over, there  are  vegetables,  and  portions  of  vegetables,  which 
display  no  doubtful  irritability,  and  yet  cannot  be  suspected  of 
containing  muscles  and  nerves,  it  does  not,  therefore,  follow, 
that  the  irritability  of  muscles  is  not  produced  by  the  mechan- 
ism described  above ;  it  does  follow,  however,  that  that  irrita- 
bility, which  in  the  greater  and  more  perfect  animals  ought  to 
be  adapted  to  the  development  of  greater  strength,  is  neces- 
sarily dependent  on  the  mechanism  described  by  me ;  while, 
again,  irritability  in  plants  and  polypes  is  not  so  powerful,  and 
can  be  produced  by  the  Author  of  Nature  by  another  and  dif- 
ferent mechanism  than  that  of  muscles.  If  this  appear  incre- 
dible to  any  one,  let  him  reflect  that  the  function  of  generation 
is  more  widely  extended  than  irritability,  yet,  nevertheless,  that 
Nature  accomplishes  it,  not  in  one  way  always,  but  by  many 
and  by  the  most  varied  methods.  Some  animals  are  viviparous, 
others  oviparous ;  and  of  these  latter  some  have  the  ova  fecun- 
dated by  the  male  after  extrusion  from  the  female,  and  some 
before  extrusion ;  some  incubate  their  ova,  some  abandon  them 
to  be  incubated  by  others ;  some  deposit  fecundated  ova, 
without  the  coitus  of  the  sexes ;  some  propagate  by  shoots ;  the 
polypus  tintinabuliformis  is  reproduced  by  dividing  its  body 
into  two ;  ^  the  poh^pus  plumosus  propagates  both  by  shoots  and 
by  ova,  which  are  always  fecundated  without  coitus.  2  Why, 
then,  might  not  nature  be  able  to  produce  irritability  by  dif- 
ferent mechanisms — in  muscles  by  the  method  described  by 
me — and  in  polypes,  zoophytes,  and  plants,  devoid  of  muscular 
fibre,  in  some  other  way  as  yet  unknown  ?  I  am  persuaded 
that  these  things  being  weighed,  my  theory  of  muscular  con- 
traction is  very  near  the  truth;  and  I  should  be  much  delighted 
if  any  attempts  of  mine  should  avail  anything  in  elucidating 
such  a  difficult  subject,  since  I  am  not  ignorant  of  the  very 
great  anxiety  of  very  learned  men  to  understand  the  cause  of 
muscular  contraction ;  who  to  this  end  have  not  only  spared 
no  labour,  but  have  also  endeavoured  to  stimulate  other  in- 
quirers by   great  and  most  honorable  rewards  to  perfect  this 

•  Spallanzani  Opus.  Physique,  Tom.  i,  tab.  i,  fig.  vii.     (This  figure  represents  a 
vorticella. — Ed.) 
'^  lleaumur. 


SECT.  III.]      CONTRACTION  OF  THE  MUSCLES.  415 

department  of  physiology :  I  need  only  mention  the  prizes 
offered  by  the  Royal  Academy  of  Prussia,^  and  William  Croon 
of  London.^ 

Verschuir,  in  the  dissertation  already  quoted,  has  attempted 
to  explain  the  flow  of  the  menses  hy  this  same  derivation  of  the 
blood,  excited  every  month  through  the  nerves,  since  this  pheno- 
menon cannot  be  accounted  for  either  by  the  theory  of  a  general 
plethora,  which  Van  Swieten  has  ah'eady  fully  refuted  in  his 
'  Comments  on  Boerhaave^s  Aphorisms,'  or  by  the  notion  of  a 
partial  uterine  plethora.  Marherr  in  particular,  following 
Haller,  has  attempted  to  show,  that  the  cause  of  the  flow  of  the 
menses  is  a  special  plethora  of  the  uterus.  He  asserts,  for 
instance,  that  the  arteries  of  the  uterus  are  more  capacious  and 
less  contractile  than  the  veins,  consequently  the  arteries  receive 
more  blood  than  the  veins  can  return ;  that  the  veins  have  no 
valves,  and  consequently,  as  the  veins  cannot  so  well  support 
the  pressure  of  the  blood,  its  return  from  the  uterus  is  rendered 
more  difficult ;  and  thus,  from  these  causes,  the  blood  accumu- 
lates for  a  period  in  the  uterine  arteries  and  venous  capillaries, 
until  by  that  time  a  sufficient  quantity  being  present,  it  bursts 
forth.  But  these  distinguished  writers  do  not  appear  to  have 
considered  how  much  the  weight  and  size  of  the  uterus  must  be 
increased  every  month  before  the  flow  of  the  menses,  if  it  con- 
tains the  whole  quantity  of  blood  that  is  thus  discharged.  If 
we  estimate  its  weight  at  4,  5,  6,  7,  10,  12  ounces,  and  this  be 
accumulated  in  the  uterine  arteries  just  before  menstruation,  the 
uterus  ought  at  that  period  to  appear  manifestly  increased  in 
weight  and  size,  a  fact  which  has  not  been  as  yet  observed  or 
recorded  by  anatomists.  It  is  thus  manifest,  that  the  menstrual 
blood  is  not  contained  in  the  uterine  vessels  previously  to 
menstruation,  but  is  derived  to  the  vessels  and  cavity  of  the 
uterus  at  the  time  of  menstruation,  and  this  by  means  of  the 
nerves,   which  seem  to  be  irritated  by  some  stimulus  as  yet 

•  Vide  M.  Le  Cat's  '  Dissertation,  qui  a  remporte  le  prix  propose  par  I'Academie 
Royale  de  Prusse,  sur  le  principe  de  TAction  des  Muscles/  &c.     Berlin,  1753. 

2  Lectures  are  delivered  every  year  at  the  College  of  Physicians  of  London,  on 
the  nature  of  the  muscles  and  the  functions  of  the  nerves,  a  handsome  sum  heing 
bequeathed  to  the  Lecturer.  See  Thomas  Lawrence,  *  De  Natura  Musculorum 
Praelectiones  tres  in  Theatre  CoUegii  Medicorum  Londinensium  habitae  anno  1759.' 
Recusje  Venetiis,  1766. 


416  FUNCTIONS  OF  THE  NERVES.  [ch.  hi. 

unknown, recurring  periodically,  and  thus  produce  the  derivation 
of  blood  to  the  uterus.  Probably  it  is  some  latent  peculiarity 
of  the  vis  nervosa,  which  recurs  periodically,  and  causes  a  deriva- 
tion of  blood  to  the  uterus,  just  as  we  observe  intermittent  fevers 
to  return  periodically. 

Not  only  is  dilatation  of  the  minute  radiated  vessels  of  the 
iris  produced  by  congestion,  but  also  elongation  and  deflection 
from  a  serpentine  to  a  straight  line,  in  consequence  of  which 
the  iris  is  dilated  and  the  pupil  contracted,  when  the  retina  is 
irritated  by  a  strong  light,  and  this  again  acts  on  the  ciliar,y 
nerves  by  consentience.^  The  cause  ceasing,  which  through  the 
nerves  induced  congestion,  the  congested  fluids  appear  to  be 
driven  into  the  larger  vessels  by  the  elastic  and  tense  capillaries, 
and  thus  the  minute  radiated  vessels  of  the  iris  are  again  short- 
ened, and  arranged  in  serpentine  folds,  and  so  the  iris  is  con- 
tracted and  the  pupil  dilated. 

By  a  similar  but  greater  accumulation  of  blood  in  the  cor- 
pora cavernosa  of  the  penis  and  clitoris,  excited  by  the  nerves, 
these  parts  become  turgid,  hard,  and  erect,  when  their  nerves 
are  excited,  either  locally  by  a  mechanical  stimulus,  or  by 
lascivious  ideas.^ 

Thus  also  the  papillae  of  the  mammae  swell,  become  hard, 
and  those  which  are  retracted  into  their  fossae  protrude,  when 
rubbed  with  the  tip  of  the  finger,  or  taken  within  the  lips  of 
the  infant,  because  their  nerves  being  vellicated,  excite  a  greater 
flow  of  fluids  into  the  vessels  (for  a  corpus  cavernosum  is  not 
found  in  them),  and  produce  the  whole  phenomenon.^ 

That  appearance  of  the  human  skin  termed  cutis  anserinaj 
arises  also  from  a  greater  derivation  of  the  fluids  caused  by  the 
cutaneous  nerves,  for  the  spongy  bulbs  of  the  hairs  become 
turgid  by  the  blood  attracted  more  copiously  to  them,  and  pro- 
duce those  small  eminences  on  the  skin,  from  which  the  term 
cutis  anserina  is  derived,  and  by  which  also  the  hairs  proceeding 
from  them  are  rendered  erect.     When  that  greater  derivation 

»  Haller,  *Elem,  Phys.,'  torn,  v,  lib.  xvi,  sect,  ii,  §  xii;  Caldani,  'Instit.  Physiol.,' 
Nro.  320 ;  and  my  tract,  •  De  Carne  Muscular!,'  may  be  consulted,  p.  10. 

2  Caldani,  loc.  cit.,  Nro.  494 ;  Winterl,  '  Inflamm.  Theor.  Nov.,'  p.  143. 

'  Kolpin's  Dissertation,  *  De  Structura  Mammarum,'  may  be  consulted,  translated 
into  German  (Berlin,  1767),  p.  16,  where  the  translator  in  a  note  supposes  a  con- 
gestion of  humours  into  the  irritated  part,  by  oscillation  of  the  vessels  increased 
through  the  nerves. 


SECT.  IV.]    OPPOSITE  PROPERTY  IN  THE  NERVES.       417 

to  the  bulbs  of  the  hairs  ceases,  the  small  prominences  subside 
and  disappear,  and  in  their  place  there  are  little  depressions,  in 
consequence  of  which  the  hairs  cease  to  be  erect. 

Other  phenomena,  occurring  in  the  natural  state,  besides  those 
mentioned  in  the  preceding  paragraphs  are  intelligible  by  this 
congestion  arising  in  the  irritated  part.  And  in  diseases  there 
are  frequently  opportunities  for  observing  the  operation  of  that 
nervous  influence  on  the  vessels,  in  virtue  of  which  fluids  flow 
more  copiously  and  immediately  to  the  irritated  part.  Inflamma- 
tion itself  is  nothing  else  than  a  powerful  attraction  and  deriva- 
tion of  blood  from  a  stimulus,  by  which  the  vessels  become  filled, 
swell,  are  rendered  tense,  red,  painful,  &c.j  for  eminent  writers^ 
have  already  demonstrated  the  incorrectness  of  the  doctrine  of 
Boerhaave,  that  obstruction  is  the  only  cause  of  inflammation, 
and  all  recognise  the  cause  to  be  a  stimulus  which  attracts  the 
fluids  more  powerfully  to  the  stimulated  part,  and  produces 
inflammation.  If  this  stimulus  be  suflSciently  powerful,  it 
draws  the  nerves  of  the  heart  into  sympathetic  action,  and  by 
increasing  the  movements  of  the  latter  produces  fever,  the  con- 
comitant of  inflammation.  Eminent  men  have  already  taught, 
that  the  motion  of  the  blood  cannot  be  so  much  accelerated 
through  free  vessels  by  the  obstruction  alone  of  other  vessels,  as 
to  excite  fever.  Thus  also  haemorrhoids  continually  arise  from 
the  stimulus  of  hard  and  acrid  faeces  in  the  rectum  and  other 
similar  causes,  since  the  vessels  gradually  give  way,  and  dilate 
into  varices,  from  the  frequent  derivation  of  blood  to  that  part. 
And  those  deposits,  termed  metastases  by  physicians,  are  pro- 
bably owing  in  a  great  degree  to  a  stimulation  of  the  nerves. 


SECTION      IV. DOES     AN     OPPOSITE      PROPERTY      EXIST     IN     THE 

NERVES,  SO  THAT  THEY  CAN   REPEL  THE   BLOOD   FROM  THE  VES- 
SELS UNDER  THEIR   INFLUENCE   INTO  OTHER   PARTS? 

The  face  of  a  man  struck  with  sudden  terror  is  pale,  and 
some  men  become  pale  when  in  a  paroxysm  of  rage,  which  pale- 
ness is  without  doubt  owing  to  a  repulsion  of  the  blood  from 
the  cutaneous  blood-vessels,  to  those  in  the  interior  of  the  body. 
Inasmuch  as  the  nervous  system  is  afiPected  in  terror  or  rage, 

'   Galen,   Senac,   Gorter,  Haller,  in  Winterl's  *  Inflamraationis  Theoria   Nova, 
(Viennae,  1767) ;  and  Caldani  in  his  '  Institutiones  Pathologiae,'  cap.  ix. 

27 


418  FUNCTIONS  OF  THE  NERVES.  [ce.  iii. 

the  question  arises  whether  the  cutaueous  nerves  then  affected 
completely  repel  the  blood  from  the  cutaneous  vessels,  by  con- 
tracting them,  to  the  inner  vessels  of  the  body?  or  whether, 
the  heart  disturbed  at  the  time  and  not  contracting,  ceases  for 
a  moment  to  impel  the  blood  to  the  surface  of  the  body,  the 
cutaneous  vessels  acting  at  the  same  time  as  in  fainting,  and  by 
virtue  of  their  own  elasticity  repelling  the  blood  to  the  internal 
organs  ?  Often  if  one  kidney  be  affected  with  calculus,  or  in- 
flammation, a  true  ischuria  comes  on,  for  the  other  kidney, 
although  healthy,  ceases  to  secrete  urine.  Physicians  are  aware 
that  this  takes  place  from  sympathy  of  the  nerves  of  the  two 
kidneys.  Do  the  renal  nerves  in  this  case  drive  away  and  repel 
the  blood  that  comes  to  the  kidneys  to  be  subservient  to  the 
secretion  of  urine  ?  or  do  they  not  rather  totally  prevent  the 
secretion  from  the  blood  by  causing  spasm  of  the  secreting  ves- 
sels? Truly,  although  there  are  numerous  facts  which  teach 
us  that  a  stimulus  may  cause  the  fluids  to  be  drawn  to  a 
locality,  there  is  hardly  one  to  show  that  the  nerves  have  the 
opposite  property  of  repelling  the  fluids. 

SECTION  V. HAVE   THE   NERVES  ANY  INFLUENCE  IN   SECRETION  ? 

In  considering  the  causes  which  operate  in  producing  such 
varied  secretions  from  the  same  blood,  Boerhaave  does  not 
detail  how  great  a  share  the  nerves  may  have  in  that  function 
of  the  animal  economy.^  The  illustrious  Haller,  in  his  notes  to 
the  lectures  of  Boerhaave,^  conjectures  that  the  nerves  operate 
in  the  secretion  of  the  fluids,  since  they  surround  the  vessels 
of  the  viscera  like  sphincters,  and  thus  either  delay  or  pro- 
mote secretion.  It  has  already  been  stated  why  tliis  eminent 
man  withdrew  the  doctrine  as  to  the  sphincters  and  loops  of 
the  nerves,  but  he  shows  that  the  secretions  and  excretions 
have  a  close  connection  with  the  nerves,  when  he  treats  on 
the  greater  or  less  irritability  of  the  excretory  ducts.^  The 
celebrated  Tissot  also  devotes  an  entire  section  of  his  work  on 
the  functions  and  diseases  of  the  nerves,  to  the  secretions,  for 
the  purpose  of  demonstrating  how  much  these  latter  are  de- 
pendent on  nervous  influence. 

»  Instit.  Med.,  Nro.  253.  »  Note  (14)  vi. 

'  De  Part.  Corp.  Hum.  Fabr.  et  Ubu,  lib.  vii,  sect,  iii,  §  xii. 


SECT,  v.]    INFLUENCE  OF  NERVES  IN  SECRETION.       419 

In  truths  since  it  has  been  shown  how  great  is  the  influence 
of  the  nerves  on  the  vessels,  in  virtue  of  which  stimuli  can 
excite  a  more  copious  flow  of  fluids  to  a  part,  we  infer  that  the 
same  thing  occurs  in  the  secreting  viscera,  which  consist 
almost  entirely  of  vessels.  So  soon,  therefore,  as  by  nervous 
action  the  fluids  are  more  copiously  attracted  to  secreting 
viscera,  the  secretions  are  necessarily  increased.  Moreover, 
since  the  nerves  have  the  property  of  causing  spasms,  or  con- 
traction of  the  capillaries,  it  is  manifest  that  the  secretions 
may  be  diminished,  or  entirely  interrupted  by  the  influence  of 
the  nerves,  the  secreting  vessels  being  entirely  closed  by  con- 
striction. Illustrations,  confirmatory  of  this  doctrine,  have 
been  already  brought  forward. 

But  it  may  further  be  asked,  is  the  influence  of  the  nerves 
on  the  fluids  so  great,  either  at  the  time  of  secretion,  or  when 
secreted,  that  it  can  modify,  or  alter  them,  or  entirely  change  their 
nature  ?  Thaer^  seems  to  have  held  an  opinion  somewhat  to  this 
eff'ect,  when  he  observes,  that  in  fevers  the  blood  becomes  some- 
times putrid  and  dissolved,  sometimes  acrid,  again  imperfectly 
coagulable,  or  in  some  other  way  altogether  changed  from  the 
healthy  condition  preceding  the  fever.  Musgrave^  attempts 
to  prove,  from  many  facts,  that  the  fluids  are  vitiated  by 
irritation  of  the  nerves.  In  the  first  place,  he  brings  forward 
the  experiments  of  Haller,  who  observed  the  contents  of 
the  stomachs  of  rabbits  to  become  putrid  and  thoroughly 
tainted,  in  a  short  time,  after  tying  the  eighth  pair  of  nerves ; 
and  that  a  very  ofi*ensive  suppuration  was  also  brought  on  in 
the  foot  by  tying  the  nerve.  Next,  he  shows  that  a  vomiting 
of  fetid  bilious  matter  has  been  excited  by  an  afi'ection  of  the 
head,  and  by  the  irritation  of  calculi  passing  along  the  ureters. 
Further,  diarrhoea  is  often  excited  by  mental  emotion,  and  this, 
indeed,  because  that  afi'ection  of  the  nerves  renders  the  secre- 
tions more  acrid  and  loose.  The  milk  of  a  nurse,  aff'ected 
with  anger,  immediately  acquires  an  unpleasant  taste,  and 
becomes  injurious  to  the  child.  The  bite  of  an  enraged  animal 
is  difficult  to  cure,  and  is  often  followed  by  bad  consequences. 
He  thinks  he  can  explain  why,  when  blood  is  drawn,  it  is 
often  inflammatory  in  the  first  cups,  and  less  so  in  the  later, 

'   De  Usu  System.  Nervosi  in  Febribus,  §  xxxviii. 
*  Betrachlung  iiber  die  Nerven,  3ten  Hauptst. 


420  FUNCTIONS  OF  THE  NERVES.  [cii.  in. 

on  the  liypothesis  that  the  febrile  irritation  being  diminished 
after  the  first  cupfuls  are  drawn^  the  blood  that  remains  in  the 
body  is  very  similar  to  healthy  blood.  Clearer  illustrations 
are  given  by  the  celebrated  Gaubius,  and  ^hich  prove  that  all 
the  fluids  of  the  body  may  be  rapidly  altered  and  vitiated 
through  the  nerves.  He  observes/  "  Ye  wonder,  my  hearers, 
and  justly,  at  the  great  number  of  evils,  which  anger  only 
sheds  over  the  body,  as  from  Pandora's  box.  Nor  is  it 
difficult  to  discover  the  origin  of  so  great  an  evil,  for  in 
addition  to  the  fact,  well  established,  that  the  motive  forces 
diffused  through  all  the  organs  of  the  body  are  very  powerfully 
excited  by  that  affection  of  the  mind,  and  consequently  that 
the  whole  organism  and  the  internal  viscera,  as  well  as  the 
vessels  and  their  contained  fluids,  are  agitated  by  most  violent 
movements,  it  is  shown,  beyond  doubt,  by  an  almost  incredible 
number  of  observations,  that  the  natural  properties  of  the 
juices  may  be  so  altered,  that  with  astonishing  rapidity,  the 
bland  becomes  acrid,  and  the  salubrious,  hurtful, —  nay,  truly 
virulent.  Do  you  doubt  this  ?  I  give  you  the  example  of  a 
hysterical  woman,  who  being  seized,  when  in  a  passion,  with 
her  disease,  vomits  vitiated  bile  of  every  colour  and  acridity; 
of  a  nurse,  whose  breasts,  when  angry,  supply  poison  instead 
of  food  to  the  infant,  causing  death  with  horrid  convulsions. 
Tame  domestic  animals,  when  provoked,  not  only  contract  rabies 
themselves,  but  transfuse  it  with  the  foaming  poison  of  their 
saliva  into  the  man  bitten  by  them.  Two  dunghill  cocks  fight 
ferociously  with  each  other,  as  is  their  habit ;  a  man  interferes 
to  separate  them;  he  is  bit  by  one  of  them,  and  dies  of 
hydrophobia.  You  will,  perhaps,  allege  in  reply,  that  there  is 
a  difference  between  man  and  brutes ;  I  will  therefore  give  you 
examples  of  our  own  species.  A  soldier  quarrels  with  a  woman, 
who  bites  him  in  the  hand;  he  is  seized  with  rigor  and  dies.  An 
Italian  youth,  excited  by  rage,  and  unable  to  revenge  himself, 
bites  his  own  hand,  and  is  seized  with  a  deadly  fear  of  water, 
as  if  bitten  by  a  rabid  dog.  I  am  aware,  and  I  do  not  hesitate 
to  confess  it,  that  I  am  ignorant  of  the  mode  in  which  such 
pestilent  corruptions  of  the  fluids  are  so  suddenly  excited ;  but 
this  I  think  to  have  been  attained  by  me,  that  you  can  under- 
stand that  the  whole  foundations  of  life  are  shaken  by  this 
*  Sermo  alter  de  Regimine  Mentis  quod  Medicorura  est.    Edit.  Argent.,  1776,  p.  96. 


SEC.  VI.]   INFLUENCE  OF  NERVES  ON  ANIMAL  HEAT.  421 

passion,  and  consequently  that  there  is  no  function  of  the 
human  economy,  which  can  easily  resist  so  great  an  evil." 
It  seems,  indeed,  possible,  that  the  nerves,  when  irritated  by 
anger,  may,  in  virtue  of  their  influence  on  the  secreting 
viscera,  render  the  secretions  irregular,  disordered,  and  impure, 
although  we  cannot  determine  in  what  that  impurity  may 
consist,  which  is  added  to  the  secretions  by  the  nerves,  when 
irritated  by  anger ;  and,  consequently,  the  saliva  secreted  and 
excreted  under  such  circumstances,  and  inserted  in  a  wound 
inflicted  by  an  enraged  animal,  may  possibly  prevent  its  cica- 
trization, and  subsequently  induce  horrid  evils.  Thus,  also, 
the  milk  of  an  angry  nurse  being  disordered  and  rendered  im- 
pure, may  become  hurtful  to  the  infant.  It  appears  more  diffi- 
cult to  explain  what  share  the  nerves  have  in  inducing  a  morbid 
coagulation  of  the  blood,  or  a  putrid  deliquescence,  acrimony, 
putridity,  and  impurity  of  the  fluids  in  a  cancerous  or  gan- 
grenous part,  &c. ;  these  things  posterity  may  inquire  into. 


SECTION   VI. DO  THE   NERVES  EXERT  ANY  INFLUENCE   IN   THE 

PRODUCTION  OF  ANIMAL  HEAT? 

What  opinions  various  authors  have  expressed  concerning  the 
source  and  maintenance  of  animal  heat  are  well  known;  I  think, 
therefore,  I  need  not  detail  them.  Among  them  all,  that  was  best 
received  which  maintained  that  animal  heat  arises  from  the 
attrition  of  the  particles  of  blood  with  each  other,  and  with  the 
walls  of  the  vessels.  After  Haller  had  weighed  all  the  various 
views,  he  adopted  the  theory  of  Boerhaave,  according  to  which 
animal  heat  is  acquired  by  friction,  observing :  ''  Hitherto  it 
seems  to  me  by  far  the  most  probable,  that  the  blood  acquires 
heat  from  motion.^' ^  In  the  meanwhile,  he  appears  not  to 
have  disagreed  altogether  with  the  opinion  of  those  who  main- 
tained that  the  nerves  have  some  share  in  the  production  of 
animal  heat ;  for  he  observes,  in  another  place  :  "  I  refer  heat, 
which  arises  from  friction,  to  stimulus.^^^  The  objections  to  the 
doctrine,  that  friction  is  the  sole  cause  of  animal  heat,  raised 
by   De    Haen,^  seem  to    have    particularly  influenced  recent 

'  De  Part.  Corp.  Hum.  Fabr.  et  Usu,  torn,  iv,  p.  253. 

^  Ibidtm,  p.  159. 

3  Rat.  Med.,  torn.  iv.  p.  248. 


422  FUNCTIONS  OF  THE  NERVES.  [ch.  hi. 

eminent  writers,  who  have  sought  for  the  source  of  animal 
heat  in  the  nerves^  and  not  in  the  friction  of  the  particles  of 
the  blood  with  each  other,  or  with  the  sides  of  the  vessels. 
Amongst  these  were  Caverhill^  and  Roederer.^  Wrisberg^ 
followed  the  latter,  and  seems  to  have  wished  to  corroborate 
his  doctrine  by  his  own  arguments  and  observations.  In 
comparing  animals  with  vegetables,  he  saw  that  it  was  the 
nervous  system  that  was  wanting  in  the  one  and  present  in 
the  other ;  and  since  animal  heat  was  enjoyed  by  animals,  and 
not  by  vegetables,  it  seemed  to  him  that  there  existed  some 
connection,  between  a  nervous  system  and  animal  heat. 
Further,  he  thought  this  was  confirmed  by  the  fact,  that  the 
passions,  which  excite  the  nervous  system,  increase  animal 
heat,  but  that  those  which  depress  the  nervous  system  induce 
cold.  In  further  corroboration  he  observes,  that  if  the  back  be 
turned  towards  the  fire,  and  the  spinal  marrow  warmed,  warmth 
is  rapidly  transmitted  along  the  nerves  arising  from  it  to  all 
parts  of  the  body ;  while,  on  the  contrary,  if  the  front  of  the 
body  be  towards  the  fire,  the  body  is  not  warmed  so  quickly. 
Thaer  also  thought  that  this  theory  of  the  dependence  of  the 
animal  heat  upon  the  operation  of  the  nerves,  was  not  deficient 
in  probability.*  Musgrave  also  maintained,  that  animal  heat 
arises  neither  from  the  intestine  motion  of  the  fermenting 
blood,  nor  from  the  friction  of  the  blood  against  the  sides  of 
the  vessels,  but  from  irritation  of  the  nerves,  whether  from  an 
external  agent  applied  to  the  nerves,  as  in  inflammation,  or  an 
internal  irritant,  as  anger.^  La  Roche  was  of  the  same  opinion, 
and  attempted  to  reconcile  his  views  with  those  of  Haller,  for 
he  conjectured,  with  Newton,  that  the  nervous  fluid  is  aetherial, 
and  that  its  oscillatory  motion  in  the  nerves  is  the  proximate 
cause  of  animal  heat,  the  circulatory  motion  of  the  blood  in 
the  vessels  being  only  secondary,  and  by  continually  stimulating 
the  nerves,  exciting  the  oscillation  of  the  nervous  fluid  in  them; 

1  In  Haller.  de  Part.  Corp.  Hum.  Fabr.  et  Usu,  torn,  iv,  p.  248. 

2  In  Programmate  de  Animalium  Galore.  Ad  Diss.  CI.  Grimm,  de  Visu.  Got- 
tingse,  1758. 

3  In  Program,  de  Respiratione  prima,  Nervo  phrenico,  et  Calore  animali. 
Gottingae,  1763.  It  has  also  been  printed  in  Sandifort's  ♦Thesaurus  Diss.  Med.,' 
tom.  ii. 

*  De  Actione  Systematis  Nervosi  in  Febribus.     Gottingae,  1774,  p.  83. 
'  Op.  citato. 


SECT. VII.]  NECESSITY  OF  NERVES  TO  NUTRITION.      423 

which  oscillatory  motion  is  the  proximate  cause  of  heat.^ 
Cremadells^  may  be  also  mentioned,  who  maintained  that 
animal  heat  is  directly  generated,  kept  up,  and  increased  by 
the  vital  principle,  by  which  principle  he  explains  all  those 
phenomena  of  the  animal  economy,  which  by  others  are  attri- 
buted to  the  nervous  system.  Schaffer  ^  is  another  writer,  who 
rejecting  the  doctrine  that  the  cause  of  animal  heat  consists  in 
the  fermentation  of  the  blood,  or  in  its  friction  against  the 
sides  of  the  vessels,  refers  it  to  a  certain  vital  principle,  which 
is  in  the  nerves. 

Although  the  doctrine,  which  teaches  that  the  nerves  have 
a  share  in  the  production  of  animal  heat,  is  not  destitute  of 
probability,  yet  the  arguments  hitherto  advanced  do  not  fully 
establish  it.  Perhaps  the  cause  of  animal  heat  is  more  complex, 
and  cannot  be  attributed  to  the  nerves  only.  Undoubtedly 
there  remain  many  things  to  be  known  before  we  can  determine 
what  is  the  true  cause.  Especially  we  ought  to  wnit  and  see 
what  the  industry  of  distinguished  men  may  discover"^  respecting 
inflammable  bodies,  fire,  light,  heat  in  general,  and  animal  heat 
in  especial;  taught  by  these,  posterity  may  be  enabled  to 
decide  more  accurately  respecting  the  cause  of  animal  heat. 

SECTION   VII. ARE   THE   NERVES  NECESSARY  TO  NUTRITION  ? 

By  the  term  nutrition,  all  physiologists  understand  the  con- 
servation of  the  body,  which  is  accomplished  by  the  action  of 
certain  powers  inherent  in  our  body,  and  which  have  the  power 
of  converting  food  and  drink  iuto  a  fluid,  analogous  to  the 
constituents  of  our  body,  termed  the  nutritive  juice,  and  thereby 

'  Analyse  de  Fonct.  du  Syst.  Nerv.,  torn,  ii,  chap,  xviii,  xix.     Geneve,  1778. 

»  Nova  Elem.  Physiol.     Romae,  1779. 

^  Erster  Versuch  aus  der  theoretischen  Arzneikunde  iiber  Bewegung  und  Mischung 
der  Safte.     Nurnberg,  1782. 

*  Crawford, '  Experiments  and  Observations  on  Animal  Heat,  and  the  Inflammation 
of  Combustible  Bodies.'  London,  1779.  This  little  work  is  reviewed  in  the  Got- 
tingen  Magazine,  part  v,  of  the  past  year.  The  celebrated  Forster  also  quotes  it  in 
a  very  beautiful  article  inserted  in  the  same  periodical.  (See  Getting.  Magazin,  Iten 
Jahrgangs,  2tes  Stiick :  *'  A  theory  proposed  to  explain  the  cause  which  occasions 
the  leaves  of  plants  to  purify  the  foul  air  in  sunlight,  but  to  vitiate  the  air  in  the 
shade.")  The  celebrated  Baldinger  promises  (in  the  new  Magazine)  that  the  illus- 
trious Landriani  is  about  to  give  his  experiments  on  light  and  animal  heat. 


424  FUNCTIONS  OF  THE  NERVES.  [ch.  hi. 

to  maintain  its  continued  existence  by  restoring^  the  solid 
and  fluid  particles  worn  away  and  dissipated  by  the  movements 
going  on.  It  is  necessary  to  the  proper  performance  of  this 
function,  that  there  be  not  only  a  due  supply  of  food  of  a  proper 
quality,  but  also  that  those  various  viscera  be  healthy,  which 
carry  on  digestion,  and  by  the  combined  function  of  which,  the 
food  is  converted  into  chyle,  and  rendered  fit  to  be  mixed  with 
the  blood.  Yet  when  this  process  is  completed,  nutrition  is 
not  accomplished,  but  only  the  nutritive  materials  supplied  to 
the  blood,  from  which  the  wasted  portion  of  our  body  may 
be  restored;  and  the  reparation  of  the  lost  material  takes 
place  by  some  admirable  arrangement,  and  by  a  power  as  yet 
unknown,  which  knows  how  to  restore  to  each  portion  of  the 
body  its  lost  particles,  to  apply  them,  and  cause  them  to 
adhere. 

Many  physiologists,  both  ancient  and  modern,  have  main- 
tained that  nutrition  is  carried  on  through  the  nerves.  Thus 
Sylvius,  Willis,  Glisson,  and  others,  considered  that  there  were 
two  fluids  in  the  nerves,  one  thick  and  albuminous,  subservient 
to  nutrition,  the  other  very  thin  and  spirituous,  intimately 
connected  with  the  former,  and  subservient  to  sensation  and 
movement.  The  school  of  Boerhaave  allowed  one  nervous  fluid 
only,  and  that  most  refined  and  active ;  and  held,  not  only  that 
sensation  and  motion  were  performed  by  this,  but  nutrition  also 
accomplished,  when  that  fluid  experienced  the  final  elaboration 
by  which  it  was  rendered  similar  to  our  organism.  Haller 
denied  this  nutritive  property  of  the  nervous  fluid,  because  he 
thought  that  our  body  must  be  nourished  with  a  less  spiritual 
and  more  viscid  fluid  than  the  nervous  fluid. ^  Marherr  followed 
Haller,  and  maintained  the  same  doctrine.^  Tissot  also  adopted 
it,*  although  in  another  place  he  attributes  with  Boerhaave  a 

•  This  doctrine  of  attrition,  and  the  destruction  of  the  solid  particles  thence 
arising,  has  been  maintained  by  many  distinguished  persons,  but  too  exclusively, 
T  think,  as  has  been  correctly  shown  by  Kemme  in  his  Essay  entitled,  '  Zweifel  und 
Errinnerungen  wider  die  Lehre  der  Aerzte  von  der  Ernahrung  der  festen  Theile.' 
Halle,  1778.  This  wearing  away  and  loss  of  substance  manifestly  does  not  occur  in 
the  nerves  and  brain,  since  the  abrasion  of  so  sensitive  a  substance  could  not  occur 
without  pain,  or,  at  least,  without  an  unpleasant  sensation. 

2  Elem.  Phys,,  tom.  iv,  p.  405. 

3  Prajlect.  ad  Boerh.  Inst.,  torn.  ii. 

<  Yon  Nerven,  Iten  Bandes,  2ter  Theil,  §  271. 


sECT.vii.]  NECESSITY  OF  NERVES  TO  NUTRITION.      425 

nutritive  property  to  the  nervous  fluid,  observing:^  "  If  the  nerves 
were  not  tubuli  pervious  to  the  nervous  fluid,  they  could  not  be 
nourished ;  for  the  vessels  surrounding  the  nerves  on  all  sides 
give  nutrition  to  their  cellular  investment  only,  but  the  medullary 
tubuli  are  nourished  by  the  nervous  fluid/'  Tissot,  moreover, 
specifies  three  modes  in  which  the  nerves  co-operate  in  nutrition. 
In  the  first  place,  they  pour  animal  spirits  into  the  stomach, 
intestine,  lacteal  vessels,  &c.,  carry  on  digestion  conjointly  with 
the  gastric  juice,  impress  an  animal  character  on  the  food,  and 
act  as  a  stimulus  to  the  stomach  itself.  Secondly,  they  cause 
the  animal  spirits  to  concur  in  nutrition  by  exciting  muscular 
action,  and  promoting  digestion :  thirdly,  they  promote  the 
secretion  of  gastric  juice,  saliva,  &c.^  Tralles  has  lately  again  pro- 
mulgated the  doctrine  denied  by  Haller  and  others,  of  a  nutrient 
property  in  the  nervous  fluid,  observing  that  if  a  nerve  be  tied, 
compressed,  or  destroyed,  not  only  are  motion  and  sensation 
in  the  muscle  destroyed,  but  also  nutrition,  and  atrophy  comes 
on ;  whence  he  thinks,  the  conclusion  is  undoubted,  that  some 
fluid  passes  from  the  brain  along  the  nerves  to  the  muscles,  by 
which  not  only  the  muscles  but  the  nerves  also  are  nourished.^ 
But  all  theories  founded  on  the  hypothesis  of  a  nervous  fluid 
are  untenable,  if  the  hypothesis  itself  be  demonstrated  to 
be  untrue. 

For  the  better  understanding  what  share  the  nerves  have 
in  nutrition,  it  is  advisable  with  Tissot  to  divide  the  nutritive 
process  into  the  two  processes  of  assimilation,  and  the  ap- 
plication of  the  nutrient  materials.  No  one  can  deny  that 
the  nerves  concur,  at  least  remotely,  in  the  assimilation  and 
transformation  of  food  into  nutrient  material ;  promoting,  for 
example,  the  secretion  of  saliva,  of  the  gastric,  intestinal, 
and  pancreatic  juice,  and  of  bile;  by  producing  action  of  the 
muscles  subservient  to  mastication  and  deglutition ;  by  exciting 
the  movements  of  the  stomach  and  intestines,  nay,  even  those 
of  the  heart,  of  respiration,  and  of  the  whole  body,  inasmuch 
as  all  these  actions  concur  in  the  elaboration  of  the  nutrient 
fluid.  But  the  question  arises,  have  the  nerves  also  a  share 
in  restoring   the  lost  particles,  and  therefore  in  forming  and 

'  I])id.  ill  Iten  Bande,  Itcn  Theile,  §  153. 

^  Iteii  Bandes,  2ter  Theil,  j  269. 

^  See  Kemme's  Zwcifel  uud  Eniiinerun}?en. 


4.26  FUNCTIONS  OF  THE  NERVES.  [ch.  hi. 

repairing  our  bodies?  Wonderful,  indeed,  is  that  property 
whereby  the  adaptation  of  nutrient  material  to  each  portion  of 
the  body  is  effected.  This  is  done  with  such  skill  and  wisdom, 
that  suitable  and  analogous  particles  are  applied  to  every 
part,  and  thus  neither  the  composition  nor  character  of  their 
constituent  particles,  nor  the  form  or  structure  of  the  nourished 
parts  themselves,  are  disturbed  by  the  continuous  apposition  of 
new  molecules.  Particles  which  are  adapted  to  the  composition 
of  muscles  or  cartilage,  are  not  deposited  in  bones,  otherwise 
bones  would  gradually  lose  their  proper  character,  and  become 
cartilaginous  or  muscular.  For  these  reasons,  Blumenbach 
correctly  maintains,^  that  generation,  nutrition,  and  reproduc- 
tion are  effects  or  modifications  of  one  and  the  same  force, 
which  forms  in  the  first,  maintains  in  the  second,  and  restores 
in  the  third. ^ 

'  Von  dem  Bildungstriebe,  ^  7.    Gottingen,  1781. 

2  This  expression,  that  the  foetus  is  formed  by  generation,  and  not  evolved  from  a 
germ  created  from  the  beginning  of  the  world,  should  not  appear  to  the  indulgent 
reader  altogether  new ;  for  Casper  F.  Wolff  has  long  ago  much  weakened  the  system 
of  evolutions  set  up  by  Bonnet  and  Haller,  and  established  in  its  place  the  doctrine 
of  epigenesis  of  the  ancients.  Haller,  it  is  true,  continued  to  maintain  his  views  in 
his  *  Element.  Physiol.,'  tom.  viii ;  but  after  having  carefully  weighed  his  arguments, 
I  do  not  think  them  sufficient  to  estabUsh  the  doctrine  of  evolution,  and  confute  that 
of  epigenesis.  Hybrid  animals,  malformations  of  the  parent  transmitted  to  the  off- 
spring, the  reproduction  of  whole  structures,  especially  of  certain  animals,  as  well  as 
the  generation  of  polypes  and  certain  vegetables  by  cuttings,  all  confute  the  doctrine 
of  evolution,  and  prove  that  those  germs  in  which,  from  all  time,  entire  animals  or 
parts  of  them  are  marked  out,  do  not  exist;  but  that  there  must  be  some  vis 
structrix,  which  constructs  the  bodies  of  animals,  however  complicated,  from  suit- 
able materials  that  it  has  ready  at  hand.  I  have  treated  of  this  more  fully  in  my 
dissertation  on  the  system  of  generation,  inserted  in  the  Second  Fasciculus  of  my 
*  Adnotationes  Acaderaicae'  for  1781.  In  the  same  year  in  which  my  dissertation 
appeared,  that  elegant  tract  by  Blumenbach,  Professor  at  Gottingen,  was  published, 
in  which  this  vis  structrix,  or  nisus  formativus,  as  he  terms  it,  is  proved  to  exist, 
and  the  doctrine  of  evolution  by  germs  is  rejected.  This  essay  gives  the  greater 
support  to  the  doctrine  of  epigenesis,  because  the  distinguished  author  himself 
brought  forward  much  in  favour  of  the  hypothesis  of  evolution  in  his  work '  De  Generis 
Humani  Varietate  Nativa,'  (Gotting.,  1776 ;)  but  now,  having  had  an  opportunity  of 
observing  the  phenomena  of  reproduction  in  polypes,  and  feeling  the  weight  of  the 
arguments  in  favour  of  epigenesis,  has  adopted  it  in  place  of  the  system  of  evolution. 
He  maintains  that  in  every  animal  and  vegetable  organism,  there  is  intimately 
connected  with  it,  during  its  whole  life,  a  certain  innate  and  ever-acting  instinct, 
which  he  terms  the  nisus  formativus,  in  virtue  of  which  animals  and  vegetables  at- 
tain their  proper  and  fixed  form ;  when  this  is  attained,  the  same  force  maintains  it ; 


SECT. VII.]  NECESSITY  OF  NERVES  TO  NUTRITION.      427 

For  that  wondrous  force,  which  forms  a  foetus  similar  to  the 
parents,  out  of  the  semen  of  the  male  projected  into  the  uterus, 
and  that  part  which  the  female  contributes,  whether  it  be  an 
ovum  or  semen — that  force,  I  say,  is  not  exhausted  in  the  forma- 
tion of  a  puny  foetus,^  but  continues  active  in  it,  and  thus 
carries  forward  the  human  body  through  all  its  phases  of  growth 
and  age,  to  the  perfect  state,  fittingly  replaces  from  the  nutrient 
material,  the  particles  worn  away  and  dissipated  by  the  con- 
tinual movements  and  operations  of  life,  nay,  regenerates  in  a 
great  measure  portions  of  skin  lost  by  violence,  consolidates 
wounds,  forms  the  callus  of  bones,  &c.  To  this  are  owing 
those  so-called  efforts  of  nature,  by  which  she  attempts  to 
preserve  health  and  remove  disease.  In  some  animals,  as 
lizards,  for  example,  this  vis  structrix  is  so  efficient,  that  it  repro- 
duces in  them  tails,  extremities,  and  jaws,  together  with  their 
bones,  muscles,  vessels,  and  nerves.^  Eminent  philosophers 
readily  perceived,  that  these  and  many  other  phenomena  observed 
in  the  animal  organism,  and  also  in  the  vegetable,  can  be 
referred  neither  to  the  wisdom  of  a  rational  soul,  nor  to  any 
mechanical  and  physical  laws  as  yet  known ;  and,  consequently, 
they  have  very  properly  termed  that  wonderful  cause  innate  in 
the  animal  and  vegetable  organism,  the  vital  principle,  inas- 
much as  to  that,  as  a  proximate  cause,  both  animal  and  vegetable 
owes  its  life ;  which  is  also  distinct  from  the  thinking  principle, 
for  it  far  excels  this  in  wisdom,  and  is  not  subject  to  it,  and 
has  higher  faculties,  than  it  has  hitherto  been  agreed  that 
bodies  possess.  The  vital  principle  is  not  some  simple  force, 
but  seems  to  be  compounded  of  various  unknown  forces  co- 
operating together ;  amongst  which  unknown  forces  so  co-ope- 

and  when  injured,  repairs  it  as  much  as  may  be.  Very  lately,  also,  Metzger,  Professor 
at  Kbnigsberg,  in  the  first  volume  of  his  work  entitled  '  Vermischte  Medicinische 
Schriften,'  (Konigsberg,  1782,)  weakens  the  force  of  the  arguments  adduced  by 
Haller  in  favour  of  evolution  ;  and  in  the  supplement  to  the  second  volume,  declares 
his  assent  to  the  views  of  Blumenbach.  He  differs,  however,  in  thinking  that  the 
nisus  formativus  cannot  be  considered  as  distinct  from  the  vis  plastica  of  the  ancients 
and  the  vis  essentialis  of  Wolff,  since  it  so  much  resembles  them ;  so  that  the  vis 
essentialis  is  primary,  and  analogous  to  the  vis  vitalis  of  physiologists,  which  con- 
stitutes life,  both  in  animals  and  vegetables:  secretion,  nutrition,  generation,  and 
reproduction,  are  portions,  or  rather  branches,  of  this. 

'  See  Fasciculus  ii  of  my  '  Acad.  Adnot.,'  p.  31. 

^  See  my  *  Comment,  de  System.  Generat.* 


428  FUNCTIONS  OF  THE  NERVES.  [ch.  iti. 

rating  for  the  formation  of  the  vital  principle  in  man  and  many 
animals,  the  vis  nervosa  seems  to  claim  an  important  position, 
since  in  many  operations  ascribed  to  the  vital  principle,  the 
function  of  the  nerves  is  predominant.  The  nerves  appear 
also  necessary  to  the  application  of  nutrient  material,  and  the 
reproduction  of  cut  off  parts,  because  if  the  nerves  of  a  part  be 
injured,  its  nutrition  is  impaired,  and  because  the  animals 
which  are  tenacious  of  life  and  of  irritability,  also  possess  a 
remarkable  property  of  reproducing  separated  parts. 

Since  vegetjibles  and  some  animals  generate,  are  nourished, 
and  reproduce  cut-off  parts,  and,  consequently,  possess  a  vital 
principle,  although  they  appear  to  be  destitute  of  a  nervous 
system,  it  follows  that  the  vital  principle  may  exist  independently 
of  the  vis  nervosa  in  plants  and  certain  animals  not  endowed  with 
nerves ;  but  it  does  not  hence  follow,  that  the  vital  principle  can 
exist  without  the  vis  nervosa  in  man  and  animals  endowed  with 
a  nervous  system.  For  nature  seems  to  have  bound  all  parts 
of  our  body  together  by  such  an  agreement  and  combination, 
that  one  part  assists  another,  and  one  cannot  easily  exist  without 
another ;  and  especially  the  vis  nervosa  seems  to  be  necessary 
to  the  constituting  of  the  vital  principle  in  our  own  body  and 
in  the  bodies  of  animals  endowed  with  a  nervous  system, 
although  it  appears  that  the  principle  may  exist  without  the 
vis  nervosa  in  plants  and  animals  that  have  no  nervous  system. 
There  are  certain  animals  and  vegetables  which  reproduce  their 
kind  without  distinction  of  sex,  but  is  the  congress  of  both 
sexes,  therefore,  not  necessary  to  generation  in  man  and  other 
animals  and  vegetables? 


CHAPTER  IV. 

THE  FUNCTIONS  OF  THE  SENSORIUM  COMMUNE. 


SECTION   I. WHAT  IS  THE   SENSORIUM    COMMUNE,  WHAT    ITS 

FUNCTIONS,   AND    WHAT  ITS   SEAT? 

The  external  impressions  which  are  made  on  the  sensorial 
nerves  are  very  quickly  transmitted  along  the  whole  length  of 
the  nerves,  as  far  as  their  origin  j  and  having  arrived  there,  they 
are  reflected  by  a  certain  law,  and  pass  on  to  certain  and 
corresponding  motor  nerves,  through  which,  being  again  very 
quickly  transmitted  to  muscles,  they  excite  certain  and  definite 
motions.  This  part,  in  which,  as  in  a  centre,  the  sensorial 
nerves,  as  well  as  the  motor  nerves,  meet  and  communicate, 
and  in  which  the  impressions  made  on  the  sensorial  nerves  are 
reflected  on  the  motor  nerves,  is  designated  by  a  term,  now 
adopted  by  most  physiologists,  the  sensorium  commune. 

Distinguished  men  have  not  agreed  as  to  the  seat  of  the 
sensorium  commune.  Bontekoe,  Lancisi,  De  La  Peyronie 
have  placed  the  sensorium  commune  in  the  corpus  callosum ; 
Willis  derived  the  perception  of  sensation  and  the  source  of 
movements  from  the  corpora  striata ;  Des  Cartes  attributed  the 
function  of  the  sensorium  commune  to  the  pineal  gland ; 
Vieussens  to  the  centrum  ovale  j  Boerhaave  decided  that  aggre- 
gate of  points  to  be  the  sensorium  commune,  in  which  all  the 
sensory  nerves  terminate,  and  from  which  all  the  motor  nerves 
arise,  and  accordingly  placed  it  in  the  medulla  fornicata,  sur- 
rounding the  cavity  of  the  ventricles.^  In  a  later  work,  '  De 
Morbis  Nervorum,^  Boerhaave  places  the  sensorium  commune 
in  the  boundary  line  of  the  medullary  and  cortical  substance, 
which  opinion  Tissot  thought  to  be  extremely  probable,  regarding 
it  as  confirmed  by  the  observations  of  Wepfer.^  Mayer  seems 
to  place  the  sensorium  commune  in  the  medulla  oblongata;^ 
that  distinguished  man,  J.  D.  Metzger,  appears  to  be  also  of 

'  Praelect.  Acad,  in  proprias  Inst,  cum  Notis  Halleri,  torn,  iv,  §  574. 

'■'  Abhandl.  iiber  Neiven  und  Nervenkrankh.  Iten  Bandes,  2ter  Tlieil,  §  236. 

3  Abhandlung  vom  Gehirn,  Ruckenmark,  &c.,  Seite  34 — 38. 


430  FUNCTIONS  OF  THE  SENSORIUM  COMMUNE,  [ch.iv. 

the  same  opinion;^  the  celebrated  Camper  said,  that  if  the 
sensorium  commune  has  a  seat  at  all,  it  ought  to  be  in  the 
pineal  gland,  and  in  the  nates  and  testes,  and  that,  therefore, 
the  opinion  of  Des  Cartes  was  not  so  very  absurd.^  It  certainly 
does  not  appear  that  the  whole  of  the  cerebrum  and  cerebellum 
enters  into  the  constitution  of  the  sensorium  commune,  which 
portions  of  the  nervous  system  seem  rather  to  be  the  instru- 
ments that  the  soul  directly  uses  for  performing  its  own  actions, 
termed  animal ;  but  the  sensorium  commune,  properly  so  called, 
seems  not  improbably  to  extend  through  the  medulla  oblongata, 
the  crura  of  the  cerebrum  and  cerebellum,  also  part  of  the 
thalami  optici,  and  the  whole  of  the  medulla  spinalis;  in  a 
word  it  is  co-extensive  with  the  origin  of  the  nerves.  That 
the  sensorium  commune^  extends  to  the  medulla  spinalis  is 
manifest  from  the  motions  exhibited  by  decapitated  animals, 
which  cannot  take  place  without  the  consentience  and  interven- 
tion of  the  nerves  arising  from  the  medulla  spinalis ;  for  the 
decapitated  frog,  if  pricked,  not  only  withdraws  the  punctured 
part,  but  also  creeps  and  leaps,  which  cannot  be  done  without 
the  consensus  of  the  sensorial  and  motor  nerves,  the  seat  of 
which  consensus  must  necessarily  be  in  the  medulla  spinalis 
— the  remaining  portion  of  the  sensorium  commune. 

The  reflexion  of  sensorial  into  motor  impressions,  which 
takes  place  in  the  sensorium  commune,  is  not  performed  ac- 
cording to  mere  physical  laws,  where  the  angle  of  reflexion  is 
equal  to  the  angle  of  incidence,  and  where  the  reaction  is  equal 
to  the  action ;  but  that  reflexion  follows  according  to  certain 
laws,  writ,  as  it  were,  by  nature  on  the  medullary  pulp  of  the 
sensorium,  which  laws  we  are  able  to  know  from  their  eff'ects 
only,  and  in  nowise  to  find  out  by  our  reason.  The  general 
law,  however,  by  which  the  sensorium  commune  reflects  sen- 
sorial into  motor  impressions,  is  the  preservation  of  the  individual; 
so  that  certain  motor  impressions  follow  certain  external  impres- 
sions calculated  to  injure  our  body,  and  give  rise  to  movements 
having  this  object,  namely,  that  the  annoying  cause  be  averted 

'  Advers.  Med.,  p.  15 ;  Vermisch.  Schrift.,  Iten  Bandes,  Seite  56. 

'  Kleine  Schriften,  (Leipzig,  1782,)  Iter  Band;  Nachricht  von  der  Zergliederung 
eines  jungen  Elephanten.,  §  21. 

^  Marherr  contends  that  the  medulla  spinalis  ought  also  to  be  referred  to  the 
sensorium  commune  in  *  Praelect.  ad  Inst.  Med.  Boerhaavii,'  tom.  ii,  p.  404. 


SECT.  I.]       SEAT  OF  THE  SENSORIUM  COMMUNE.        431 

and  removed  from  our  body ;  and  vice  versa,  internal  or  motor 
impressions  follow  external  or  sensorial  impressions  beneficial 
to  us,  giving  rise  to  motions  tending  to  the  end  that  the 
agreeable  condition  shall  be  still  maintained.  Very  many 
instances  which  might  be  adduced,  undoubtedly  prove  this 
general  law  of  the  reflexions  of  the  sensorium  commune,  of 
which  it  may  be  sufficient  to  mention  a  few.  Irritation  being 
made  on  the  internal  membrane  of  the  nostrils  excites  sneezing, 
because  the  impression  made  on  the  olfactory  nerves  by  the 
irritation  is  conducted  along  them  to  the  sensorium  commune, 
there  by  a  definite  law  is  reflected  upon  motor  nerves  going  to 
muscles  employed  in  respiration,  and  through  these  produces  a 
strong  expiration  through  the  nostrils,  whereby  the  air  passing 
with  force,  the  cause  of  the  irritation  is  removed  and  ejected. 
In  like  manner  it  happens  that  when  irritation  is  caused  in  the 
trachea  by  the  descent  of  a  particle  of  food,  or  a  drop  of  fluid, 
the  irritation  excited  is  conducted  to  the  sensorium  commune, 
and  there  reflected  on  the  nerves  devoted  to  the  movement  of 
respiration,  so  that  a  violent  cough  is  excited,  a  most  suitable 
means  for  expelling  the  cause  of  irritation,  which  does  not 
cease  until  the  irritant  be  ejected.  If  a  friend  brings  his 
finger  near  to  our  eye,  although  we  may  be  persuaded  that 
no  injury  is  about  to  be  done  to  us,  nevertheless  the  impres- 
sion carried  along  the  optic  nerve  to  the  sensorium  commune 
is  there  so  reflected  upon  the  nerves  devoted  to  the  motion 
of  the  eyelids,  that  the  eyelids  are  involuntarily  closed,  and 
prevent  the  offensive  contact  of  the  finger  with  the  eye.  These 
and  innumerable  other  examples  which  might  be  brought 
forward,  manifestly  show  how  much  the  reflexion  of  sensorial 
impressions  into  motorial,  effected  through  the  sensorium  com- 
mune, has  reference  to  maintaining  the  conservation  of  the  body. 
Wherefore,  Tissot  justly  enumerates  the  action  of  the  sen- 
sorium commune  amongst  those  powers,  the  sum  and  co- 
ordination of  which  constitute  the  nature  of  our  living  body.^ 

Since  the  principal  function  of  the  sensorium  commune  thus 
consists  in  the  reflexion  of  sensorial  impressions  into  motor, 
it  is  to  be  noted,  that  this  reflexion  may  take  place,   either 

'  Von  Nerven,  2ten  Bandes,  2ter  Theil,  §  55,  in  the  first  note;  and  ibidem,  §  6 
No.  6  ;  Thaer's  dissertation  already  referred  to,  '  De  Actione  Systematis  Nervosi  in 
Febribus,'  and  especially  §§  viii,  ix,  &c,,  should  also  be  read. 


432    FUNCTIONS  OF  THE  SENSORIUM  COMMUNE,  [ch.iv. 

with  consciousness  or  without  consciousness.  The  movements 
of  the  heart,  stomach,  and  intestines,  are  certainly  in  nowise  de- 
pendent on  the  consciousness  of  the  soul,  for  whilst  no  muscular 
movement  can  be  excited,  unless  a  stimulus  applied  to  the  sen- 
sorial nerves  passes  by  a  peculiar  reflexion  to  the  motor  nerves, 
and  excites  contraction  of  the  muscle,  it  is  at  the  same  time 
certain  that  the  reflexion  of  the  impressions  suitable  for  exciting 
those  movements,  if  it  takes  place  in  the  sensorium  commune, 
is  effected  without  consciousness.  But  it  is  a  question  whether 
these  impressions,  in  order  that  they  may  be  reflected,  do  really 
travel  so  far  as  the  sensorium  commune,  or,  without  taking  this 
long  circuit,  are  reflected  nearer  in  the  ganglia,  from  whence 
these  parts  derive  many  nerves  ?  This  matter  is  further  to  be 
considered  afterwards.  But  that  reflexions  of  sensorial  im- 
pressions into  motor  are  effected  in  the  sensorium  commune 
itself  while  the  mind  is  altogether  unconscious,  is  shown  by  cer- 
tain acts  remaining  in  apoplectics  deprived  entirely  of  conscious- 
ness ;  for  they  have  a  strong  pulse,  breathe  strongly,  and  also 
raise  the  hand,  and  very  often  unconsciously  apply  it  to  the 
affected  part.  The  sensorium  commune  also  acts  independently 
of  consciousness  in  producing  the  convulsive  movements  of  epi- 
leptics, and  also  those  which  are  sometimes  observed  in  persons 
buried  in  profound  sleep,  namely,  the  retractions  of  pricked  or 
irritated  limbs,  to  say  nothing  of  the  motion  of  the  heart  and 
the  respiratory  acts.  To  this  category  also  belong  all  those 
motions  which  remain  some  time  in  the  body  of  a  decapitated 
man,  or  other  animal,  and  are  excited  when  the  trunk,  and  par- 
ticularly the  medulla  spinalis,  are  irritated,  which  motions  cer- 
tainly take  place  without  consciousness,  and  are  regulated  by 
the  remaining  portion  of  the  sensorium  commune  existing  in 
the  medulla  spinalis.  All  these  actions  flow  from  the  organism, 
and  by  physical  laws  peculiar  to  the  sensorium  commune ;  and 
are,  therefore,  spontaneous  and  automatic.  The  actions  taking 
place  in  the  animal  body,  with  accompanying  consciousness,  are 
either  such  as  are  independent  of  volition,  or  such  as  the  mind 
can  restrain  and  prohibit  at  pleasure ;  the  former  being  governed 
by  the  sensorium  commune  alone,  independently  of  the  mind, 
are  as  much  automatic  as  those  of  which  the  soul  is  unconscious. 
Of  this  character  are  sneezing  from  an  irritant  applied  to  the 
nostrils,  cough  from  an  irritant  fallen  into  the  trachea,  vomiting 


SECT.  II.]  CONSENSUS  OF  THE  NERVES.  433 

from  a  titillation  of  the  fauces^  or  after  taking  an  emetic ;  the 
tremors  and  convulsions  in  St.  Vitus^s  dance,  and  in  a  paroxysm 
of  intermittent  fever,  &c.  Those  actions,  however,  which  the 
soul  directs  or  limits  by  its  own  power,  even  although  the 
sensorium  commune  has  its  share  in  producing  them,  are  never- 
theless called  animal,  and  not  automatic,  and  concerning  them 
we  treat  in  the  next  chapter. 


SECTION     II. DOES    EVERY     CONSENSUS    OF    THE     NERVES    TAKE 

PLACE   THROUGH  THE   SENSORIUM  COMMUNE  ONLY? 

Since  the  nerves  depend  so  much  on  each  other  in  performing 
their  functions,  so  that  one  is  required  to  regulate  the  action  of 
another,  and  one  to  come  to  the  help  of  another  as  it  were, 
it  is  manifest  how  necessary  it  is  that  there  should  be  a  consensus 
of  the  nerves,  and  how  necessary  is  that  part  of  the  nervous 
system  in  which  this  consensus  takes  place ;  for  if  this  part  be 
destroyed,  presently  all  those  actions  to  the  production  of  which 
the  consensus  of  many  nerves  is  required  necessarily  cease.  I 
will  not  waste  time  in  narrating  examples  of  consensus  of  the 
nerves,  for  the  latter  is  abundantly  treated  of  in  physiology  and 
pathology,  and  examples  of  it  are  ex  professo  related  by  those 
highly  distinguished  men  Whytt^  and  Tissot.^  I  will,  however, 
direct  consideration  to  one  question,  namely,  whether  the  nerves 
communicate  with  each  other  in  the  sensorium  commune  only, 
or  whether  there  be  other  localities  besides  the  sensorium  com- 
mune, in  which  the  consensus  of  at  least  some  nerves  takes 
place?  Willis  taught,  that  the  consensus  took  place  not  only 
through  the  brain,  but  through  the  connections  and  com- 
municating branches  of  the  nerves,  which  we  perceive  to  be 
pretty  numerous  in  their  course ;  Vieussens  ascribed  the  con- 
sensus of  the  nerves  to  both  their  ganglia  and  anastomoses, 
and  Boerhaave,  Bergen,  Vater,  Buchner,  &c.,  were  also  of  a 
similar  opinion,  as  well  as  the  celebrated  Meckel  in  his  essays, 
'  De  Nervo  Quinti  Paris,'  and  '  de  Nervis  Faciei.'  Gasser 
followed  him  -^  and  lastly,  Camper  also  explained  the  consensus 
of  the   nerves  by  their   communicating  branches.      Eminent 

1  On  Diseases  of  the  Nerves.     See  all  his  practical  works  in  German. 

»  Von  Nerven,  2ten  Bandes  2ter  Theil,  lOtes  Kapit. 

^  In  the  dissertation  of  George  Egger,  '  De  Consensu  Nervorum.'  Viennae,  1766, 

38 


434  FUNCTIONS  OF  THE  SENSORIUM  COMMUNE,  [ch.iv. 

men  were  also  of  a  contrary  opinion ;  that  is  to  say,  that  the 
nerves  do  not  communicate  with  each  other  through  their 
anastomoses,  but  in  the  brain  only.  Amongst  these  were 
Perault,  Astruc,  Kau  Boerhaave,  Haller,  Whytt,  Van  Swieten, 
Monro,  Marherr,  Thaer,  La  Roche,  and  Martin  j^  add  to  these 
Tissot,^  who  specially  lays  stress  on  the  following  arguments  of 
Whytt:  firstly,  that  all  the  nerve-fibrils  from  their  commence- 
ment to  their  termination  are  entirely  separate  from  each 
other,  so  that  they  have  no  communication,  and  are  connected 
with  each  other  by  their  investing  membrane  only.  Secondly, 
that  there  is  sympathy  between  parts,  the  nerves  of  which 
have  no  anastomoses  with  each  other.  Thirdly,  that  there 
ought  to  be  many  sympathies  of  parts,  the  nerves  of  which 
are  seen  to  be  closely  interwoven  and  connected  with  eacli 
other,  and  yet  no  such  sympathies  are  manifested.  Fourthly,  he 
adds  also  to  these  arguments  of  Whytt,  another,  namely,  that 
if  the  trunk  of  a  nerve  be  divided,  the  consensus  of  its 
branches  is  destroyed.  That  eminent  man,  therefore,  attempts 
by  these  arguments  to  establish  the  doctrine,  that  consensus 
of  the  nerves  takes  place  in  the  sensorium  commune  only,  and 
in  no  degree  in  the  nerves.  Yet  nevertheless,  in  the  next 
page^  he  observes,  that  it  may  be  assumed  as  a  demonstrated 
truth,  that  consensus  is  most  frequently  noted  in  the  nerves 
between  which  the  communicating  branches  are  numerous; 
still  he  does  not  believe  that  consensus  takes  place  through 
these  communicating  branches,  but  that  they  contribute  some- 
thing to  it,  of  the  nature  of  which  we  are  as  yet  ignorant. 

It  is  difficult  to  decide  on  a  point  regarding  which  so  many 
persons  have  disagreed,  and  which  is  as  yet  involved  in  so  much 
obscurity.  The  first  glance  at  the  anastomoses  or  communi- 
cations of  the  nerves  leads  us  to  think,  that  they  are  consti- 
tuted to  maintain  some  consensus  and  interchange  of  their 
functions,  and  no  other  probable  reason  can  be  assigned  for  so 
many  anastomoses  of  the  nerves  and  of  their  funiculi.*  With 
regard  to  the  arguments  which  eminent  men  have  advanced  in 
favour  of  a  contrary  doctrine,  they  establish  nothing  as  far  as  I 

1  Instit.  Neurolog.,  sect,  i,  p.  87. 

^  Loc.  cit. 

3  2ten  Bandes  2ter  Theil,  §  6,  Nro.  4. 

*  These  may  be  seen  delineated  in  my  treatise  *  De  Structura  Nervorum.' 


SEC.  III.]  CONSENSUS  OF  NERVES  IN  THE  GANGLIA.  435 

perceive,  for  the  first  argument  of  Whytt  is  founded  on  this, 
that  every  nerve-fibril  is  a  canal  continued  from  its  commence- 
ment to  its  termination  without  any  connection  with  another ; 
but  since  this  supposition  is  nothing  more  than  an  improbable 
conjecture,  to  which  anatomy  is  opposed,  for  the  pulp  of  the 
nerves  is  found  to  be  rather  granular  than  tubular,  we  cannot 
allow  it  to  have  any  demonstrative  force.  The  second  argument, 
which  alleges  that  there  are  nerves  which  are  consentient 
in  their  functions,  but  have  no  anastomoses  in  their  whole 
course,  proves,  indeed,  that  these  nerves  communicate  only  in 
the  sensorium  commune^  but  does  not  prove  that  the  anastomoses 
of  other  nerves  do  not  contribute  to  their  necessary  inter- 
communication. As  to  the  third  argument,  that  there  should 
be  many  sympathies  displayed  by  those  nerves  which  have 
many  anastomoses,  and  yet  are  these  not  displayed,  we  would 
answer  in  the  words  of  Tissot  himself,^  that  we  are  not  as  yet 
informed  as  to  all  the  sympathies  and  consensus  of  nerves, 
and  therefore  there  may  be  many  which  have  hitherto  escaped 
the  diligence  of  observers.  From  which,  therefore,  I  think  we 
may  conclude,  that  although  the  principal  and  greatest  consensus 
of  the  nerves  takes  place  in  the  sensorium  commune,  it  is  not 
possible  to  deny  some  share  in  connecting  and  combining  the 
functions  of  the  nerves  to  their  anastomosing  and  communicating 
branches. 

SECTION  III. DOES  CONSENSUS  OF  THE  NERVES  ALSO  TAKE  PLACE 

IN  THE   GANGLIA? 

The  functions  of  the  ganglia  of  the  nerves  have  also  been 
hitherto  involved  in  much  obscurity;  so  that,  after  the  labours 
of  such  great  men  to  determine  their  nature  and  use,  scarcely  a 
spark  of  the  light  necessary  to  elucidate  that  mystery  of  nature  has 
appeared.  The  celebrated  Tissot^  has  so  learnedly  and  elegantly 
treated  of  this  matter,  as  well  as  of  the  consensus  of  the  nerves, 
that  I  think  it  altogether  superfluous  to  consider  the  structure 
and  functions  of  the  ganglia  in  complete  detail.  Having 
weighed  all  the  opinions  that  have  been  advanced  regarding  the 
functions  of  the  ganglia,  he  esteems  that  which  Johnston  has 
propounded  as  the  most  probable,  namely,  that  the  ganglia  ren- 

•  Instit.  Neurolog.,  §  6,  No.  5. 

'  Iten  Bandes  2ter  Theils,  Eilfter  Artikel. 


436  FUNCTIONS  OF  THE  SENSORIUM  COMMUNE,  [ch.iv. 

der  the  nerves  -whicli  arise  from  tliem  independent  of  the  will, 
and  therefore  that  the  heart  and  intestinal  canal  are  not  subject 
to  volition,  since  they  receive  their  nerves  from  the  ganglia  of 
the  intercostal  [great  sympathetic]  nerve.  Tissot  thinks,  that 
the  doubts  advanced  by  Haller,  and  more  fully  entered  into  by 
Haase,  are  not  at  all  unanswerable,  and  are  indeed  of  that  cha- 
racter, that  they  may  be  easily  made  to  comport  with  the  doc- 
trine of  Johnston.  Pfeffinger  has  also  studiously  investigated 
this  theory  as  to  the  uses  of  the  ganglia,  and  approved  of  it  in 
an  elegant  dissertation,  ^De  Structura  Nervorum,^  published 
in  1782. 

It    is    not    an    improbable  conjecture,  therefore,  that  the 
ganglia  found  around  the  nerves  act  as  a  sort  of  gentle  ligature 
or  compress,  so  that  the  connection  between  the  two  extremities 
of  a  nerve  is  so  far  interrupted,  as  to  prevent  the  impressions 
made  on  the  one  extremity  of  the  nerve  being  communicated 
through  the  ganglion  to  the  other  extremity ;  yet  the  com- 
munication  of  all    impressions    is  apparently   not    altogether 
interrupted;   for  if  they   be    powerful,   they   appear    to    pass 
through  the  ganglia,  and  to  be  transmitted  forward  along  the 
length  of  the  nerves,  but  with  broken  and  diminished  force. 
From  this  it  appears  to  be  possible  to  understand,  why  the 
mind   has  no  immediate  control  over  the  movements   of  the 
heart,  stomach,  and  intestines,  namely,  because  the  impressions 
made  by  the  will  on  the  origins  of  the  nerves  do  not  appear  to 
pass  through  the  ganglia  of  the  intercostal,  or  great  sympathetic 
nerve,  to  the  parts  mentioned,  which  derive  their  nerves  princi- 
pally from  the  intercostal.     For  this  reason  it  also  appears,  that 
although,  when  the  medulla  spinalis  is  irritated,  all  the  muscles 
are  spasmodically  contracted,  yet  the  movements  of  the  heart, 
stomach,  and  intestines,  are  scarcely,  if  at  all,  accelerated,  since 
the  impression  of  the  stimulus  applied  to  the  medulla  spinalis 
cannot  be  transmitted  to  the  intercostal  [great  sympathetic] 
nerve  through  its  ganglia.      But  eminent  men  testify,  that  they 
have  seen  the  motion  of  the  heart  increased,  and  the  heart  when 
at  rest  excited  into  action  by  irritation  of  the  medulla  spinalis,  as 
also  certainly  that  from  too  great  emotion, — anger,  for  example, 
— the  hearths  action  is  immediately  accelerated ;  whence  it  neces- 
sarily follows,  that  the  impressions  of  a  stimulus  from  the  brain 
and  spinal  cord  may  pass  through  the  ganglia  of  the  intercostal 


SEC.iii.]  CONSENSUS  OF  NERVES  IN  THE  GANGLIA.  437 

nerve  j  but  that  it  is  necessary  that  these  impressions  be  more 
powerfuh  Hence  we  have  an  explanation,  why  the  heart  is  so 
obtuse  as  regards  sensation,  and  the  stomach  and  intestine  not 
acute,  namely,  because  impressions  made  on  the  nerves  of  those 
parts  do  not  penetrate  the  ganglia  of  the  intercostal  nerve  to 
reach  the  brain,  where  the  perception  of  sensations  takes  place. 
As  regards  the  impressions,  however  obtuse  they  may  be,  that  do 
reach  the  brain  from  the  heart,  stomach,  and  intestines,  is  it 
not  rather  that  they  reach  the  brain  through  the  branches  of 
the  eighth  pair  distributed  to  those  viscera,  than  that  they  pass 
through  the  intercostal  [great  sympathetic]  ganglia?  The 
conjecture  is  difficult.  Further,  the  structure  of  the  ganglia,  as 
described  by  eminent  inquirers,  is  not  opposed  to  this  doctrine 
of  the  functions  of  the  ganglia,  but  if  anything  rather  appears 
to  confirm  it.  Meckel,  Haase,  and  Zinn  maintain,  that  the 
ganglia  are  made  up  of  the  nerves  entering  into  them,  which 
divide  into  very  minute  filaments,  so  that  they  are  variously 
subdivided,  and  make  a  sort  of  net-work.  Condensed  cellular 
tissue  is  intermingled  with  this  net-work  of  nervous  filaments, 
and  the  whole  is  enveloped  in  a  somewhat  tense  external  mem- 
brane; whence  may  arise  a  somewhat  gentle  compression  of  the 
nerves  entering  the  ganglion,  which  is  sufficient  to  stifle,  or 
rather  intercept  the  less  powerful  impressions  propagated  along 
the  nerves,  and  manifestly  to  obtund  the  more  powerful.  The 
whole  of  this  doctrine,  as  to  the  uses  of  the  ganglia,  can  how- 
ever be  brought  forward  only  as  a  conjecture  not  manifestly 
improbable,  but  meriting  the  investigation  of  the  learned,  and 
possibly  containing  a  spark  of  truth,  from  which  some  acute 
genius  may  be  able  to  produce  greater  light  for  us.  He  who 
shall  unravel  the  uses  of  the  ganglia  will  also  give  a  reason 
why  the  fifth  pair  of  cerebral  nerves  pass  through  the  semi- 
lunar [Gasserian]  ganglia,  with  the  exception  of  a  fasciculus 
which  joins  the  third  division  without  touching  the  ganglion;* 
and  why  only  the  posterior  roots  of  the  spinal  nerves  enter  the 
ganglia,  whilst  the  anterior  roots  pass  by  without  any  com- 
munication with  them.^ 

Further,  it  may  be  asked,  whether  the  external  impressions 
made  on  the  terminations  of  the  nerves  and  passed  onwards  to 

'  See  my  treatise  '  De  Structura  Nervorum,'  tab.  ii,  figs,  v,  \i. 
'  Ibidem,  tab.  iii,  figs,  i,  ii. 


438    FUNCTIONS  OF  THE  SENSORIUM  COMMUNE,  [ch.  iv. 

the  ganglia  are  extinguished  in  the  ganglia  themselves?  or 
whether  being  reflected  there  by  a  fixed  law,  they  return 
again  along  the  nerves  to  the  parts  to  be  moved  ?  The  cele- 
brated Unzer/  and  the  eminent  Winterl  taught,  that  ex- 
ternal impressions  are  reflected  in  the  ganglia,  as  they  are 
reflected  in  the  sensorium  commune,  and  that  the  ganglia  are 
special  sensoria, — a  doctrine  which  does  not  appear  altogether 
destitute  of  probability.  For,  if  we  consider  that  the  minute  and 
invisible  nerves  disseminated  over  the  internal  membrane  of  the 
heart  and  auricles,  perceive  the  stimulus  of  the  inflowing  venous 
blood/  and  although  they  cannot  transmit  the  impression  of 
that  stimulus  to  the  sensorium  commune  through  the  ganglia  of 
the  intercostal  [great  sympathetic]  nerve,  yet  communicate  it 
to  the  motor  nerves  distributed  through  the  substance  of  the 
heart  [ventricles]  and  auricles,  it  follows  that  there  is  neces- 
sarily a  consensus  between  the  sensory  nerves  distributed  on 
the  inner  membrane  of  the  heart  and  the  motor  nerves  dis- 
seminated through  the  substance  of  the  heart  [ventricles]  and 
auricles,  which  must  take  place  either  in  the  ganglia  of  the 
intercostal  nerve  or  below  them,  in  the  communicating  branches 
or  plexuses  of  nerves.  It  seems  probable,  therefore,  that 
besides  the  sensorium  commune,  which  we  conjecture  to  be  in 
the  medulla  oblongata,  medulla  spinalis,  pons  varolii,  and  crura 
of  the  cerebrum  and  cerebellum,  there  are  special  sensorna  in 
the  ganglia  and  plexuses  of  the  nerves  in  which  external  im- 
pressions ascending  along  the  nerves  are  reflected,  that  need 
not  ascend  all  the  way  to  the  sensorium  commune,  to  be  reflected, 
thence. 


'  Erste  Griinde  einer  Physiologic,  &c. 
2  Haller,  De  Part.  Corp.  Hum.  Fabr. 


CHAPTER  V. 

THE  ANIMAL  FUNCTIONS. 


SECTION  I. A  SHORT  ENUMERATION  OF  THEM. 

In  that  portion  of  the  nervous  system  which  we  have  termed 
the  sensorium  commune^  such  a  mechanism  lies  concealed,  that 
external  sensory  impressions  of  the  nerves  are  reflected  in  it 
upon  the  motor  nerves  in  a  singular  manner,  and  by  unerring 
and  peculiar  laws,  so  that  they  produce  distinct  and  definite 
movements  of  the  muscles.  It  has  already  been  stated,  that 
many  motions  truly  automatic  take  place  in  man  by  means  of 
this  vis  nervosa  of  the  sensorium  commune  only;  nevertheless, 
although  many  animals  which  are  destitute  of  brain,  and  the 
higher  endowments  of  animals  are  regulated  and  live  only 
through  this  vis  of  the  sensorium  commune,  and  therefore  may 
be  termed  true  automata,  in  man  and  many  allied  animals  the 
nervous  system  is  increased  by  the  addition  of  a  brain;  and 
moreover,  with  a  certain  principle  which  we  call  the  soul,  an  ens 
of  incorporeal  origin,  and  which  we  are  taught  by  faith  to  have 
been  granted  to  man  alone,  to  constitute  him  an  immortal  crea- 
ture by  the  special  favour  of  God.  So  long  as  the  soul  is  joined 
with  the  body,  it  manifestly  produces  no  operation  which  depends 
solely  and  exclusively  upon  itself,  but  all  take  place  by  means 
of  the  nervous  system  as  the  instrument;  so  that  in  all  the  animal 
functions,  the  nervous  system  has  a  share  as  the  instrument, 
and  the  mind  a  share  as  the  acting  and  determining  principle. 

Animal  actions  under  the  name  of  internal  senses,  or  under 
the  name  of  faculty  of  thought,  or  of  reason,  or  of  intellect, 
come  continually  under  the  observation  of  physicians.  I  by 
no  means  propose  to  treat  of  these  so  accurately  and  profoundly 
as  has  been  done  by  metaphysicians  and  psychologists,  but 
only  to  touch  on  those  points  with  which  it  behoves  physicians 
to  be  fully  acquainted.  The  principal  divisions  into  which  the 
animal  functions  may  be  conveniently  divided,  are  perception, 
understanding,  and  will,  to  which  may  be  added  imagination  and 
recollection,  or  memory, 


440  THE  ANIMAL  FUNCTIONS.  [ch.  v. 

The  mind  perceives  the  external  impressions  made  on  the 
nerves,  and  communicated  to  the  sensorium  commune,  by 
acquiring  certain  notions  and  images  of  them  termed  ideas.^ 
These  differ  according  as  they  are  brought  from  the  various 
organs  of  the  senses  to  the  sensorium  commune,  for  vision  excites 
one  kind  of  ideas  in  the  mind,  hearing  another  kind,  taste, 
smell,  and  touch  other  kinds.  Ideas  also  differ  in  their  degree  of 
vividness,  for  the  more  vivid  ideas  presuppose  a  more  impres- 
sible nervous  system,  that  many  impressions  are  not  commu- 
nicated at  the  same  time  to  the  sensorium,  (for  the  mind  clearly 
perceives  one  idea  after  another,)  or  an  impression  more  powerful, 
repeated,  continuing  longer,  or  new  and  unusual. 

Whilst  engaged  in  the  examination  of  ideas,  the  mind  judges 
whether  there  be  discrepancy  or  agreement  amongst  them, 
whether  they  be  new  or  often-repeated  ideas — whether  they 
threaten  anything  injurious  to  our  body,  or  promise  anything 
beneficial.  When  engaged  in  this  judgment,  the  mind  must 
remember  the  idea  first  perceived,  when  it  compares  it  with 
another  for  the  purpose  of  seeing  their  agreement  or  discrepancy, 
and  consequently  the  faculty  of  judging  presupposes  memory. 
If  many  compound  ideas  be  compared  one  with  another,  a 
compound  judgment  is  made,  and  this  is  termed  reasoning. 

The  mind  wills,  when  it  endeavours  to  retain  or  remove  that 
which  by  the  ideas  is  understood  to  be  good  or  evil. 

It  imagines,  when  the  ideas  of  things  formerly  present  but 
now  absent  are  excited,  voluntarily  or  involuntarily,  either 
from  some  internal  disposition  of  the  brain,  or  from  some 
similar  or  associated  idea  excited  in  the  mind.      Those  ideas 

•  I  do  not  here  treat  of  the  hypotheses  as  to  the  formation  of  ideas  in  perception 
and  imagination,  whether  they  be  impressions  traced  on  the  brain,  which  Haller 
defends  in  his  '  Elem.  Phys.,'  torn,  v,  p.  541,  &c. ;  or  whether  they  are  a  certain 
motion  and  minute  vibrations  or  oscillations,  which,  being  different,  are  suitable  to 
the  excitation  of  different  ideas,  as  Bonnet  ingeniously  supposes.  (See  his  '  Analy- 
tischer  Versuch  uber  die  Seelenkrafte.')  Reimarus  (see  Gbttingen  Magazine  for  the 
past  year,  part  vi,)  strongly  disapproves  of  the  doctrine,  that  there  are  material 
tracings  of  the  ideas  impressed  on  the  brain,  since  the  memory  being  lost  in  disease 
could  never  be  restored,  as  it  often  is,  if,  indeed,  the  tracings  of  the  ideas,  once 
obliterated,  cannot  be  restored  when  the  disease  terminates,  with  the  same  facility 
as  the  fibres  of  the  brain  can  be  re-excited  into  similar  oscillations  on  the  oppor- 
tunity being  afforded;  and  because,  as  the  traces  are  always  present,  there  could 
be  no  reason  why  the  representation  of  ideas  should  cease  during  profound  sleep. 
In  this  matter  those  more  acute  than  I  will  decide. 


SECT.  I.]  ENUMERATION.  441 

which  arise  from  imagination  are  less  vivid  than  those  from 
perception ;  but  by  continual  meditation  and  fixing  of  the 
attention  upon  them,  they  become  gradually  more  and  more 
vivid,  until  at  last  they  may  become  equal  to  those  ideas  which 
arise  from  perception;  so  that  the  mind  cannot  distinguish  them, 
and  confounds  things  present  with  things  absent,  when  it  is 
said  to  wander. 

When  an  idea  arising  from  perception  or  imagination,  is 
accompanied  with  the  consciousness  that  it  is  not  new,  but  has 
been  perceived  by  us  formerly,  the  circumstances  also  occurring 
in  which  it  was  formerly  perceived,  the  mind  is  said  to  remember 
or  recollect. 

We  are  conscious,  when  the  animal  actions  are  in  actual 
operation  (as  takes  place  during  waking);  and  consciousness  is 
abolished  in  the  same  proportion  that  the  animal  functions 
cease  to  be  exercised,  as  for  example,  in  sleep,  apoplexy,  or 
fainting.  Thus  consciousness  seems  properly  to  belong  to  the 
actual  exercise  of  the  faculty  of  thought. 

The  mind  does  not  enjoy  an  equal  degree  of  freedom  in  all 
these  mental  operations.  It  does  not  perceive  voluntarily  but 
compulsorily,  since  it  is  not  able,  for  example,  not  to  see  if  the 
object  be  placed  properly  before  it.  Nor  does  the  mind  per- 
ceive the  harmony  or  discordance  of  ideas  more  voluntarily. 
The  mind  has  the  greatest  freedom  in  willing,  for  it  can  desire 
a  pleasing  object,  or  neglect,  or  refuse  it ;  nevertheless,  if  what 
is  pleasing  or  displeasing  becomes  an  object  of  any  great  pleasure 
or  pain,  the  mind  loses  much  of  its  freedom  in  willing,  nay,  is 
compelled  to  desire  or  dislike,  and  passions  arise  of  which  we 
are  not  the  masters  but  the  obsequious  slaves,  since  we  may 
often  see  and  approve  the  better,  and  yet  unwillingly  follow  the 
worse.  For  this  reason  they  are  rightly  termed  passions  of  the 
mind,  since  in  them  the  mind  scarcely  acts,  but  is  impelled  to 
action  by  the  body.  I  avoid  adducing  here  special  instances  of 
the  passions,  and  examining  them  with  reference  to  their 
causes  and  effects,  since  I  think  that  this  has  already  been 
fully  done  by  others,  nor  can  I  add  anything  new  or  par- 
ticular; I  will  only  treat  on  some  questions  relating  to  the 
animal  functions,  respecting  which  distinguished  men  have 
entertained  opposing  opinions. 


442  THE  ANIMAL  FUNCTIONS.  [ch.  v, 


SECTION  II. IS  THE  FACULTY  OF  THOUGHT  THE  SPECIAL  PRO- 
PERTY OF  THE  MIND,  OR  IS  IT  NECESSARY  TO  THOUGHT  THAT 
THE   MIND  USE  THE  BRAIN  AS  AN   INSTRUMENT? 

Many  pliilosophers  and  physicians  have  asserted,  that  the 
mind  alone  thinks,  and  the  body  takes  no  part  in  that  opera- 
tion ;  on  the  other  hand,  some  have  maintained  that  thought 
itself  is  a  faculty  belonging  to  matter,  and  denied  that  the  soul 
is  immaterial ;  others,  thinking  that  both  were  far  wide  of  the 
truth,  have  imagined  they  could  set  the  matter  at  rest  by 
stating  that  certain  operations  of  the  thinking  faculty  are  partly 
owing  to  the  body,  as  memory,  for  example,  but  that  others 
are  performed  by  the  mind  alone,  and  independently  of 
the  body. 

If  we  consult  daily  observation,  we  learn  that  the  faculty  of 
thought  is  subject  to  various  viscissitudes,  and  corresponds 
closely  with  the  condition  of  the  brain.  The  foetus  hid  in  the 
uterus  of  its  mother,  neither  sees,  nor  hears,  nor  tastes,  nor 
smells,  nor  scarcely  feels  the  fluids  that  surround  it.  Thus 
destitute  of  ideas,  it  neither  judges  nor  imagines,  nor  remem- 
bers. On  emerging  into  light,  the  fcetus,  indeed,  begins  to 
perceive  objects  through  the  organs  of  the  external  senses,  but 
it  cannot  as  yet  correctly  judge  between  ideas,  and  quickly 
forgets  its  perceptions,  for  the  semi-fluid  brain  seems  unfit  to 
retain  them,  and  consequently,  we  remember  nothing  of  that 
period.  The  same  mind  in  the  youth,  with  a  firmer  and  more 
condensed  brain,  retains  ideas  readily  and  with  remarkable 
facility,  and  is  endowed  with  somewhat  of  the  power  of  judg- 
ment as  to  serious  matters,  although  but  feebly.  In  manhood, 
the  solids  generally,  and  therewith  the  brain,  being  consolidated, 
it  commits  new  ideas  to  memory,  and  retains  them  with  less 
facility,  but  enjoys  by  so  much  the  more  a  riper  judgment.  In 
old  age,  new  ideas  are  retained  with  still  greater  difficulty,  but 
the  old  being  indurated,  as  it  were,  like  the  brain,  pertinaciously 
adhere  to  it ;  yet  some  aged  persons  lose  even  these,  and 
return  to  the  state  almost  of  plants,  oblivious  of  the  world, 
their  friends,  and  themselves.^     The  mental  endowments  diff"er 

^  Haller,  in  his  notes  to  the  *  Prselect.  Instit.  Med.'  of  Boerhaave,  and  in  his 
'  Elem.  Phys.,'  torn,  v,  p.  538. 


SECT.  II.]        THE  BRAIN  THE  ORGAN  OF  MIND.         443 

not  only  according  to  age,  but  also  in  persons  of  every  age, 
according  to  the  varying  constitution  of  the  brain  proper  to 
each  individual ;  for  just  as  an  equally  vigorous  stomach,  lungs, 
and  other  viscera  is  not  seen  in  all  men,  so  the  brain  does  not 
acquire  the  same  strength  and  perfection  in  all  men;  and  hence 
we  should  expect  a  diversity  in  the  faculty  of  thought,  of  which 
the  brain  is  the  instrument,  in  different  men ;   and  this,  in  fact, 
we  daily  find  to  be  the  case.      For  some  persons  endowed  with 
a  more  fortunate  condition  of  the  brain,  are  quick  in  perception, 
sound  in  judgment,  prompt  in  willing,  happy  in  retaining  and 
recalling  ideas ;  others  with  little  talent,  as  the  phrase  is,  owing 
to  a  less  fortunate  condition  of  the  brain,  are  dull  in  perception, 
weak  in  judgment,  slow  to  action,  unfortunate  and  imperfect  in 
the  exercise  of  memory.     Some,  again,  perceive   quickly,   and 
remember  most  felicitously,  but  judge  foolishly;  whilst  others 
who  are  endowed  with  an  excellent  judgment,  have  by  so  much 
the  more  imperfect  a  memory.      Some,   in  consequence   of  a 
congenital  defect  of  the  brain,  are  stupid  and  fatuous  through- 
out their  whole  life ;  ^'  many  of  whom,^^  says  Haller,^  '^  have  a 
face  scarcely  human,  large  mouth,  dribbling  saliva,  numerous 
strumous  swellings,  harsh  voice,  and  a  mind  unfit  for  all  the 
duties  of  life.      Another  equally  numerous  class  spend   their 
whole  life  in  bed,  incapable  of  any  corporeal  movement :  they 
pass   a  long  life  in  a  condition  not   much   superior  to  brute 
animals,  and  having  rather  less  intelligence  for  the  functions 
of  life ;  and,  indeed,  their  senses  are  so  dull,  that  lately  one  of 
them  perished  from  a  collection  of  fseces,  which  distended  the 
rectum  to  the  diameter  of  a  foot  and  a  half,  and  of  which  he 
felt  nothing.^^     This  effect  of  a  vitiated  state  of  the  brain  in 
depraving  the  intellect  is  so  well  known   that  it   cannot  be 
doubted  that  if  the  state  of  the  brain  of  Newton  and  Alexander 
had  been  changed  in  infancy  by  slight  concussion  or  compres- 
sion, the  one  might  have  been  a  stupid  man,  and  the  other  a 
wise  king.     Who,  in  short,  does  not  daily  observe  the  faculty 
of  thought  to  be  disturbed,  impaired,  and  even  extinguished  by 
disease,  and  all  consciousness  for  a  time  abolished?     If  his 
kinsfolk  be  placed  before  a  man  delirious  in  fever,  he  often 
does  not  recognise  them,  for  either  the  perception  is  affected, 

'  Elem.  Phys.,  torn,  v,  p.  570. 


444  THE  ANIMAL  FUNCTIONS.  [ch.  v. 

or  tlie  understanding,  or  the  memory,  which  does  not  retain  the 
old  idea  of  the  kinsfolk  to  be  compared  with  the  new  perception. 
The  organ  of  the  understanding  seems  to  have  been  especially 
affected  in  the  patient  of  Wepfer,  ^  who  mistook  a  piece  of  paper 
for  a  handkerchief,  and  the  handle  of  the  spoon  for  the  bowl.  The 
organ  of  memory  is  not  unfrequently  so  disordered  by  disease 
that  individuals  lose  the  recollection  of  their  past  life,  and  forget 
acquired  knowledge;  of  this,  the  illustrious  Linnaeus  lately 
afforded  an  example.  Not  unfrequently,  all  the  organs  of  the 
animal  functions  are  so  affected  that  none  of  them  can  be 
exercised,  and  for  the  time  at  least  consciousness  is  entirely 
abolished,  as  is  seen  not  only  in  persons  affected  with  apo- 
plexy, earns,  fainting,  and  epilepsy  (during  the  paroxysm),  but 
also  in  profound  sleep  in  which  all  the  animal  functions  enjoy 
a  full  holiday,  since  the  brain  requires  rest  for  itself  after 
having  been  wearied  with  the  exercise  of  thought  throughout 
the  day.  Nay,  frequent  use  has  no  slight  effect  in  changing 
and  perfecting  the  animal  functions.  By  use  alone  the  per- 
ception becomes  more  acute,  for  the  musician  perceives  the 
least  discord,  and  is  annoyed  by  that  which  a  person,  not  a 
musician,  never  notices ;  use  renders  the  memory  more  tena- 
cious, the  judgment  more  acute,  the  will  more  prompt;  all 
which  may  also  be  observed  in  musicians,  who  acquire  so  much 
readiness  and  facility  by  practice,  that  they  perceive  the  notes, 
judge  what  time  and  tone  they  denote,  will,  and  apply  the 
fingers  in  fulfilment  of  the  volition,  almost  at  the  same  moment. 
From  all  these  things  it  evidently  follows,  that  thought 
cannot  depend  solely  and  entirely  upon  the  mind,  nor  is  the 
whole  essence  of  the  soul  exempted  from  thought ;  otherwise 
we  must  conclude  that  a  soul  of  an  inferior  nature  is  given  to 
dull  persons,  and  of  a  superior  to  the  intelligent ;  that  it  can 
increase  with  age,  be  perfected  by  exercise,  become  sick,  and  be 
deprived  of  one  faculty  or  another, — as  memory,  for  example, 
and  consequently,  that  the  substance  is  material,  and  may  be 
increased  or  diminished.  But  these  changes  and  defects  may 
be  attributed  to  the  brain,  when  in  a  state  more  or  less  im- 
perfect, as  being  the  instrument  of  the  soul,  and  necessary  to 
thought,  so  long  as  the  soul  is  connected  with  the  body;  if  it 

'  Hist.,  98. 


SECT.  III.]       THE  BRAIN  A  COMPOUND  ORGAN.         445 

be  injured,   thought  is  injured;  if  destroyed,  thought  is  de- 
stroyed, and  consciousness  abolished. 

Eminent  men  of  all  ages  have  acknowledged  this  dependence  of 
the  faculty  of  thought  upon  the  body:  of  these  I  need  onlymention 
Hippocrates \  Galen, ^  Des  Cartes,^  Abraham  Kau  Boerhaave,'^ 
and  Gaubius^.  The  force  of  truth  also  made  Tralles  subscribe  to 
this  opinion^,  for  although  he  carried  the  doctrine  that  the 
mind  is  independent  of  the  body  too  far,  yet  he  observes  :  "  It 
is  indeed  certain  that  experience  teaches  us  that  so  long  as  the 
soul  is  connected  with  the  body,  a  well-constituted  brain  is 
absolutely  necessary  for  it  to  think,  imagine,  reproduce  ideas, 
and  judge  concerning  them.^'  Ernest  Platner,  also,  in  his 
elegant  essay,  '  De  Vi  Corporis  in  Memoria,^'^  observes  :  "  Since 
such  are  the  facts,  it  is  manifest  from  the  observations  already 
made  as  to  the  mode  of  perception,  that  every  one  of  our  senses 
is  put  in  action  by  the  common  agency  of  the  body  and  mind, 
so  that  no  sensation  or  thought  can  be  produced  by  the  mind 
without  the  body,  nor  by  the  body  without  the  mind."  And 
this  doctrine,  that  the  soul,  so  long  as  it  is  connected  with  the 
body,  can  neither  think,  nor  have  self-consciousness  without  a 
properly-constituted  brain,  derogates  certainly  in  no  degree 
from  the  immateriality  and  immortality  of  the  soul,  which  God, 
by  special  favour,  can  endow  with  an  eternal  consciousness  of 
itself  and  of  things  external  to  it,  although  the  body  it  had  in- 
habited be  destroyed, — a  doctrine  we  are  taught  to  believe  by 
religion,  which  also  in  every  age  has  been  desired  by  mankind^ 
and  which  great  philosophers  have  approved  by  their  assent^. 

'  In  the  Epistle  of  Democritus,  •  De  Natura  Hominis,'  which  is  extant  among  the 
works  of  Hippocrates. 

2  Cap.  ix,  Libri  quod  anirai  mores  corporis  temperamenta  sequantur. 

3  Diss,  de  Meth.,  n.  vi,  p.  m.  38. 

*  Impetum  faciens  dictum.  Hippocrati,  cap.  i,  he  says :  "  The  Supreme  Ruler 
has  associated  the  mind  with  the  body  by  such  a  law,  that  without  a  suitable  state 
of  body  the  mind  is  evidently  inactive,  and  becomes  so  disconsolate  and  unlike  itself, 
that  you  in  vain  search  for  mind  in  the  mind  itself." 

^  De  Regimine  Mentis  quod  Medic,  est,  Sermo  i. 

^  De  Animse  existentis  Immaterialitate  et  Immortalitate,  p.  31. 

'  In  Baldinger,  Syloge  Selector.  Opusculor.  Argum.  Medico-Pract.,  vol.  iii,  p.  86. 

8  This  closing  sentence  is  omitted  in  the  edition  published  in  the  Opera  Minora  ; 
the  reference  to  the  doctrines  of  Christianity  at  the  commencement  of  Section  I, 
is  also  omitted. — Ed. 


446  THE  ANIMAL  FUNCTIONS.  [ch.  v. 


SECTION  III. DO   EACH   OF  THE   DIVISIONS  OF  THE   INTELLECT 

OCCUPY  A  SEPARATE   PORTION  OF  THE   BRAIN? 

It  is  our  consciousness  and  a  certain  peculiar  feeling  which 
convinces  every  one  that  he  thinks  with  his  brain.  But  since 
the  brain,  as  well  as  the  cerebellum,  is  composed  of  many 
parts,  variously  figured,  it  is  probable,  that  nature,  which 
never  works  in  vain,  has  destined  those  parts  to  various  uses, 
so  that  the  various  faculties  of  mind  seem  to  require  different 
portions  of  the  cerebrum  and  cerebellum  for  their  production. 
Since,  however,  the  sensorium  commune  reflects  the  sensorial 
impressions  into  motor  by  definite  laws  peculiar  to  itself, 
and  independently  of  consciousness,  and  since  we  have  laid 
down  that  the  sensorium  commune  comprises  the  medulla  ob- 
longata, medulla  spinalis,  and  the  origin  of  all  the  nerves,  it 
follows  that  the  cerebrum  and  cerebellum,  together  with  their 
connections,  the  sensorium  commune  excepted,  constitute  the 
organs  of  the  faculty  of  thought ;  and  as  in  some  animals 
these  organs  are  entirely  wanting,  it  is  fair  to  conjecture  that 
the  faculty  of  thought  is  also  wanting,  and  that  they  exist 
solely  in  virtue  of  the  vis  nervosa  of  the  sensorium  commune  and 
of  the  nerves  with  which  they  are  endowed.  Hitherto  it  has 
not  been  possible  to  determine  what  portion  of  the  cerebrum 
or  cerebellum  are  specially  subservient  to  this  or  that  faculty 
of  the  mind.  The  conjectures  by  which  eminent  men^  have 
attempted  to  determine  these  are  extremely  improbable,  and 
that  department  of  physiology  is  as  obscure  now  as  ever  it  was ; 
and  we  think  with  Haller  that  no  light  can  be  thrown  upon  it 
in  any  other  way  than  by  a  careful  dissection  of  the  brains  of 
fatuous  persons,  apoplectics,  and  such  as  have  other  disorders 
of  the  understanding.  There  are  indeed,  many  observations 
extant  bearing  upon  this  point,  but  few  have  been  rightly  made, 
and  with  many  there  is  interwoven  a  preposterous  judgment  on 
what  has  been  observed.  As  hitherto  there  has  been  so  much 
reason  to  lament  the  dearth  of  judiciously-made  observations, 
I  hope  more  ingenious  men  may  be  incited  to  note,  as  occasion 

*  The  sentiments  of  the  Arabians  may  be  seen  in  §  iii  of  chap,  i;  and  in  §  vi,  the 
opinion  of  WilUs,  Lancisi,  De  la  Peyronie,  and  Mayer. 


SECT.  IV.]       THE  PROPER  ANIMAL  MOVEMENTS.        447 

offers,  what  has  been  observed  during  life  in  cases  of  this  kind, 
and  having  duly  examined,  after  death,  the  cerebrum  and 
cerebellum,  together  with  the  remainder  of  the  nervous  system, 
to  make  the  facts  public,  with  or  without  a  suitable  judg- 
ment on  the  case.  The  distinguished  Metzger  has  promised^ 
to  watch  diligently  for  such  observations,  and  has  raised  our 
hopes,  since  much  may  be  expected  from  his  genius  and 
dexterity. 

It  is,  therefore,  by  no  means  improbable,  that  each  division 
of  the  intellect  has  its  allotted  organ  in  the  brain,  so  that  there 
is  one  for  the  perceptions,  another  for  the  understanding,  pro- 
bably others  also  for  the  will,  and  imagination,  and  memory, 
which  act  wonderfully  in  concert  and  mutually  excite  each  other 
to  action.  The  organ  of  the  imagination,  however,  amongst 
the  rest,  will  be  far  apart,  I  should  think,  from  the  organ  of 
perceptions,  since  the  organ  of  perceptions  being  asleep  and 
at  rest,  the  organ  of  the  imaginations  may  be  in  action,  a  con- 
dition which  produces  dreams.  There  is  this  peculiarity  in 
dreams,  however,  that  the  ideas  represented  are  often  very 
absurd,  and  are  continually  combined  and  judged  of  erroneously, 
and  we  are  not  convinced  of  their  falsity  and  emptiness,  until 
all  these  phantasms  are  discovered  to  be  false  and  corrected 
by  the  waking  up  of  the  organ  of  the  perceptions. 


SECTION  IV. WHAT  MOVEMENTS  ARE  PROPERLY  TERMED  ANIMAL? 

There  are  only  two  kinds  of  muscular  action  in  the  human 
body,  according  to  the  cause  which  excites  it ;  the  one  kind 
is  termed  voluntary  or  animal,  because  according  as  the  mind 
commands  and  wills,  it  may  be  excited,  increased,  diminished, 
and  arrested;  the  other  involuntary,  of  which  the  mind  is 
either  unconscious,  or  if  conscious,  the  motion  is  performed 
without  its  consent,  and  is  excited  only  by  a  mechanical  cor- 
poreal stimulus  applied  to  the  nervous  system,  for  which  reason 
it  is  also  termed  spontaneous  and  automatic.  Nerves  are 
necessary  to  produce  both  kinds  of  movement.^  The  nerves 
do  not  act,  however,  without  a  stimulus,  which  is  either  pro- 
duced by  the  mind  willing,  or,  if  unconscious  and  unwilling,  by 

'  Vermischte  Medicinische  Schriften,  Iten  Bandes,  Seite  58. 
*  See  Chap.  II,  §  in,  (6). 


448        >  THE  ANIMAL  FUNCTIONS.  [ch.  v. 

some  body  applied  to  the  nerves.  Whence,  therefore,  it  is 
manifest,  that  those  movements  ought  alone  to  be  termed 
animal  which  depend  upon  the  untrammelled  control  of  the 
soul,  and  which  it  produces  or  restrains  by  its  own  free  will; 
on  the  other  hand,  those  which  in  no  degree  depend  on  the 
will,  but  are  performed  when  the  mind  is  unconscious  or  un- 
willing, cannot  be  termed  animal,  but  are  purely  mechanical 
and  automatic. 

Observation  teaches,  that  there  are  some  muscles  in  the 
human  body  over  which  the  mind  has  no  control  whatever, 
and  the  movements  of  which  are  purely  automatic  during  the 
whole  of  Ufe;  these  are  the  heart  [the  ventricles],  the  auricles, 
oesophagus,  stomach,  and  intestinal  canal;  with  these  may  be 
mentioned  the  motion  of  the  iris.  There  are  other  muscles 
which  are  ordinarily  subject  to  the  control  of  the  will,  and 
for  this  reason  are  termed  voluntary,  such  as  the  muscles  of 
the  limbs,  trunk,  head,  face,  eyes,  tongue,  genitals,  and  the 
sphincter  of  the  anus  and  urinary  bladder.  It  sometimes 
happens,  however,  that  all  these  muscles  renounce  the  authority 
of  the  miud,  and  while  it  is  either  unconscious  or  unwilling,  are 
violently  agitated  by  some  preternatural  mechanical  stimulus, 
as  is  seen  in  hysterical,  epileptic,  or  infantile  convulsions,  or 
in  those  affected  with  St.  Vitus^s  dance;  and  these  movements, 
although  performed  by  muscles  designated  voluntary,  can  only 
be  termed  automatic.  In  the  foetus  in  utero  and  in  the  newly- 
born  these  muscles  are  not  moved  voluntarily,  but  for  the  most 
part  automatically,  for  at  that  age  the  cerebrum  is  not  as  yet 
capable  of  thought,  until  the  organs  of  the  faculty  of  thought 
being  gradually  evolved,  the  mind  learns  to  think,  and  to  use 
the  muscles  subjected  to  its  control.  The  raising  of  the  hand 
and  the  application  of  it  to  the  head  in  apoplexy  belong  also 
to  the  class  of  automatic  movements,  also  the  turning  of  the 
body  in  sleep,  and  partly  even  somnambulism  itself,  which, 
however,  it  would  seem  is  partly  also  to  be  ascribed  to  obscure 
sensations  and  vohtions  which  the  mind  instantly  forgets.  In 
the  third  place,  there  are  muscles  which  continually  act  in- 
dependently of  the  will,  being  excited  thereto  by  a  mechanical 
stimulus  only,  but  over  which  the  mind  possesses  voluntary 
command,  and  can  at  will  accelerate,  or  retard,  or  entirely  stop 
their  movements  for  a  time;  the  action  of  these  is  termed 


SECT.  IV.]  NATURE  OF  THE  SOUL.  449 

mixed.  Of  this  kind  are  the  muscles  of  respiration,  which 
almost  constantly  act  automatically,  but  over  which,  however, 
the  mind  has  such  control,  that  it  can  accelerate,  retard,  or  even 
stop  the  respiratory  movements  for  a  time.  But  if  a  mechanical 
stimulus  be  too  powerful,  then  the  muscles  of  respiration  are 
excited  into  action  in  spite  of  the  will;  for  example,  if  a 
crumb  slips  into  the  trachea,  a  violent  cough  ensues  altogether 
uncontrollable  by  the  will;  thus  also  the  mind  cannot  prevent 
sneezing  when  the  pituitary  membrane  of  the  nostrils  is  stimu- 
lated by  an  acrid  stimulus. 

In  establishing  that  no  action  and  no  movement  can  be 
termed  animal,  of  which  the  mind  is  not  conscious,  and  which 
does  not  depend  upon  its  free  will,  I  shall  possibly  seem  to  have 
restricted  the  influence  of  the  soul  over  the  body  too  much,  since 
there  are  very  distinguished  men,  especially  of  the  Stahlian  School, 
who  have  taught  that  not  only  every  movement  is  directly  re- 
gulated by  the  soul,  but  also  other  functions  of  the  animal  body ; 
adopting  this  fundamental  principle,  that  consciousness  is  not 
necessary  to  each  function  of  the  mind.  But  it  is  certain  that 
as  yet  we  know  nothing  more  of  the  human  soul  than  that  it 
thinks,^  and  that  it  cannot  do  this,  so  long  as  it  is  connected 
with  the  body,  without  the  assistance  of  the  brain.  It  is  not 
proved,  as  assumed  by  the  Stahlians,  that  the  soul  is  the  im- 
mediate cause  of  other  animal  functions  which  do  not  involve 
thought.  But  although  we  were  to  concede  the  assumption, 
deductions  follow  from  it  which  must  be  pronounced  absurd, 
and  which  admit  of  no  defence,  as  has  been  fully  shown  by 
Haller,^  and  Platner,^  who,  although  an  eminent  supporter  of 
the  Stahlian  doctrine,  says  that  it  is  true  that  muscles  continue 
to  act,  the  nerves  of  which  have  been  tied,  or  divided,  and  that 
some  Stahlians  have  gone  too  far,  since  they  wished  to  attribute 
these  movements  also  to  the  soul,  which  to  this  end  they 
maintain  to  be  diflPused  through  the  body,  and  spoke  of  the 
remaining  portions  of  the  soul  as  if  it  were  divisible,  and  as  if 
they  continued  the  movement  that  originated  from  the  divided 


'  See  "Van  Swieten's  Commentary,  torn,  i,  $  1. 
^  Elem.  Physiol. 

^  See  De  Haen's  Heilungsmethode,  3ter  Band.     In  the  first  division,  on  some 
difficulties  in  the  system  of  Haller. 

29 


450  NATURE  OF  THE  SOUL.  [ch.  v. 

nerves.  Moreover,  that  he  was  of  opinion  that  Stahl  either 
held  the  soul  to  be  material,  or  confounded  the  rational  soul 
with  the  anima  sensitiva  or  vegetativa  of  the  ancients,  which 
alone  we  can  affirm  to  be  diflfused  through  the  whole  body. 

Si  quid  novisti  rectius  istis 
Candidas  imperii ;  si  non,  his  utere  mecum. 


END  OF  'FUNCTIONS  OF  THE  NERVOUS  SYSTEM. 


INDEX 


UNZER'S  PRINCIPLES  OF  PHYSIOLOGY. 


[N.B. — The  figures  in  this  Index  refer  to  the  numbers  of  .the  paragraphs.] 


Abstraction,  definition  of,  77  ;  many  ma- 
terial ideas  cease,  or  become  weaker  in, 
77,  140 
Action,  muscular,  animal  when  excited 
by  nerves,   163;   from   external  im- 
pressions  and  their  direct  nerve-ac- 
tions, 452-465 ;    from   internal   non- 
conceptional  impressions,   507 ;   may 
be  a  sentient  action  or  a  nerve  action, 
or  both,  514  ;  nature  of  investigated, 
161,    380;    effected    solely    through 
nerves,  388 
Action,   reflex,  see   Reflexion,  and  Im- 
pressions, external  and  internal. 
Actions,  animal,  see  Animal  actions. 
Actions,  sentient,  defined,  6 ;  are  direct 
and  indirect,  97-110;  the  conceptive 
force  co-operates  in,   111;  how  pro- 
duced, 112;  a  conceptional  impression 
necessary   to,    123 ;    when  produced 
directly  by  external  sensations,  129; 
when  produced  by  conceptions,  130 ; 
chai'acter  of  those  excited  by  cerebral 
impressions,  133 ;  when  produced  by 
external  sensations,  how    prevented, 
134 ;    when   caused   by    spontaneous 
conceptions,  hindrances  to,  136,  138 ; 
when  produced  by  external  sensations, 
how    enfeebled,   or  prevented,    139 ; 
occur  in  the  oesophagus  and  intestinal 
canal,    170;    occur   in   the   stomach, 
174  ;  in  the  liver,  175  ;  in  the  kidneys, 
176;  in  the  urinary  bladder,  ib.\  in 
the  organs  of  the  external  senses,  177  ; 
in  the  sexual  organs,  178 ;  when  not 
direct  results  of  the  external  sensa- 
tions, 181 ;   when  at  the  same  time 
nerve-actions,  183,  363 ;   how   influ- 
enced by  the  consciousness  of  an  im- 
pression,184,ii;  from  other  conceptions, 
often  confounded  with  those  from  ex- 
ternal sensations,  185 ;   of  agreeable 
and  disagreeable  external  sensations, 
195 ;   of  gratification,  197 ;  of  pain, 
198  ;  developed  even  in  the  non-mus- 
cular membranes,  208 ;   of  external 


Actions  {continued) 

sensations  in  the  heart,  stomach,  &c., 
204-218;  the  incidental  [zufallig], 
219-224;  the  subordinate,  225;  the 
co-ordinate,  227  ;  of  imaginations,  see 
Imaginations ;  of  the  memoiy,  238  ; 
of  the  foreseeings,  see  Foreseeings ;  of 
the  sensational  desires  and  aversions, 
255 ;  of  the  sensational  propensities 
and  emotions,  260 ;  of  the  instincts, 
281-292;  of  the  passions,  306-329; 
of  the  intellectual  conceptions,  330; 
may  all  be  produced  without  brain,  or 
mind,  or  conceptions,  367 ;  transfor- 
mation of,  into  nerve-actions,  or  vice 
versa,  367,  368 ;  often  result  from 
direct  nerve-actions  of  external  im- 
pressions on  the  muscles,  448 ;  substi- 
tution of,  for  nerve-actions,  580-593 
Affections,  91 
Affectentriebe,  the  instinctive  passions, 

296-304 
Afferent  and  efferent  fibrils  in  the  same 
nerve,   doctrine  of,   127    note,    486- 
488 
Age,  old,  its  phenomena,  701 
Ahndungen,  73.     See  Forebodings. 
Albinus,  his  doctrine  of  the  anatomical 
distinctness  of  the  nerve-fibrils  anti- 
cipating Miiller,  39  note;  MSS.  of,  in 
possession  of  Sir  W.  Hamilton,  ib. 
Anger,  always   a  passion,  301 ;   a  de- 
pressing one,  322  ;  its  sentient  actions 
how   composed,   ib. ;    its   union  with 
revenge,  324 ;  the  special  changes  its 
sentient  actions  produce,  325  ;  means 
of  controlling,  326 ;    its  sentient  ac- 
tions   may    be  induced    by   the  vis 
nervosa  only,  572 
Animal,  a  purely  sensational,  see  Sensa- 
tional animal. 
Animal,  a  reasoning,  see  Reasoning  ani- 
mal. 
Animal,  a  sentient,  see  Sentient  animal. 
Animal,   an   insentient,    see    Insentient 
animal. 


453 


INDEX  TO  UNZER'S 


Animal,  an,  characteristic  distinction  of, 
600 ;  distinction  indefinite,  GOl ;  its 
life  divided  into  four  periods,  644 

Animal  actions  defined,  6 ;  how  excited,  32 

Animal  death,  6.     See  Death. 

Animal  forces,  their  natural  subordina- 
tion, 666 ;  certain,  not  naturally  sub- 
ordinate to  any  other,  667, 670 ;  those 
subordinate  to  others,  668,  669  ;  their 
natural  connecting  points,  672 ;  their 
centres,  673;  no  general  centre  of, 
674 ;  primary,  defined,  6 ;  only  two 
known,  356;  communicated,  defined, 
6  ;  pure,  see  Nerve  forces. 

Animal  function,  the  action  of  an  animal 
force,  666 

Animal  life,  defined,  6 ;  its  most  essen- 
tial elements,  15,  i;  sensational,  640; 
spiritual,  641 ;  complete,  643 ;  its  four 
periods,  641-658;  the  system  of  its 
forces,  659;  the  heart  and  brain  es- 
sential to,  675 ;  conditions  of  its 
duration,  693 ;  cessation  of,  694 ;  may 
continue  after  proper  animal  death,  717 

Animal  machines,  defined,  6,  9 ;  the, 
general,  15,  ii ;  in  no  species  defective, 
ib.;  constitute  a  special  system,  671 ; 
are  centres  of  the  animal  forces,  673 

Animal  movements,  primary,  defined,  6 ; 
when  purely  animal,  193 ;  from  non- 
conceptional  impressions,  356 

Animal  nature  defined,  6 ;  gives  animal 
bodies  peculiar  forces,  7 ;  philosophy 
of  its  great  divisions,  8 ;  treated  of  in 
general,  600-728  ;  the  general  princi- 
ples on  which  its  whole  physiology 
must  be  based,  618 ;  its  origin,  628-637 

Animals,  distinguished  into  sentient  and 
insentient,  603  ;  all,  do  not  require  to 
have  a  soul,  622 

Animal  sentient  forces,  see  Forces. 

Anticipation,  or  expectation,  92-95 ;  of 
the  understanding,  96 

Anxiety,  a  distressing  passion,  313 

Apparitions,  imperfect  external  sensa- 
tions, 148 

Arbitrary,  as  applied  to  conceptions,  27 

Arteries,  their  contraction  and  dilation 
explained,  460 

Artistic  machines,  differ  from  natural  or 
organic,  5 

Attention,  definition  of,  51,  v,  77;  can 
excite  and  maintain  many  sentient 
actions,  140 

Aversions,  how  developed,  81 ;  if  active, 
three  things  to  be  distinguished  in, 
81-87 ;  sensational  and  intellectual, 
89;  may  be  wholly  sensational,  or 
more  spontaneous,  ib. ;  when  a  Wind 
abhorrence,  or  antipathy,  90;  intel- 
lectual, 96 


Beseelte,  rendered  sentient,  349  note. 

Bewegungsgriinde,  the  motives,  96.  See 
Motives. 

Bezauberung,  the  wonderful  in  instincts, 
263,  270 

Bladder,  the  gall,  little  susceptible  of  ex- 
ternal sensations,  213 ;  the  efl'ect  of 
anger  and  revenge  on,  325  ;  its  irrita- 
bility somewhat  doubtful,  476 

Bladder,  the  urinary,  effect  of  vivid  ex- 
ternal sensations  on,  176 ;  the  effect  of 
sensational  conceptions  and  foresee- 
ings  on,  ib.;  its  functions  may  be 
nerve-actions  of  external  impressions, 
478 ;  how  situate  as  to  nerve-actions 
from  non-conceptional  internal  im- 
pressions, 537 

Blood-vessels,  how  external  sensations 
act  upon,  205 

Body,  definition  of  a,  1 ;  physical  nature 
of  a  purely  physical,  2  ;  its  mechanical 
nature,  4 ;  reciprocal  connection  of, 
with  the  soul,  345-352 

Brain,  the  seat  of  the  soul  and  of  con- 
sciousness, 10,  25 ;  if  imperfect,  the 
mind  imperfect,  25  ;  the  laboratory  of 
the  vital  spirits,  11;  gives  origin  to 
all  the  nerves,  12 ;  has  a  double  move- 
ment, 24  ;  the  whole  not  immediately 
necessary  to  thought,  25 ;  its  medul- 
lary matter  possesses  an  animal-sen- 
tient force  peculiar  to  itself,  ib. ;  every 
act  of  mind  in  connection  with  its 
force,  29 ;  the  whole  not  put  into 
action  by  each  conception,  124;  com- 
pression of,  the  results  and  cause, 
128 ;  certain  fibrilli  of  the  medulla 
receive  external  impressions,  132  ;  the 
mechanical  machines  in  connection 
with  the,  156-159;  its  cortical  sub- 
stance can  be  influenced  indirectly  by 
sentient  actions,  159  ;  may  not  be  re- 
quired for  all  animal  movements,  366  ; 
its  medullary  and  cortical  substance 
have  some  share  in  the  vis  nervosa, 
373-4;  when  necessary  to  the  con- 
tinued production  of  nerve-actions, 
416;  when  requisite  to  nerve-actions, 
511;  always  imperfect  at  first,  649; 
the  effect  of  daily  waste  and  repair  on 
its  functions,  662 ;  as  a  centre  of  the 
animal  forces,  673;  whether  one  point 
of  it  the  seat  of  mind,  doubtful,  719 


Capillary  vessels,  effect  of  external  im- 
pressions on,  207,  462 ;  their  animal 
forces,  682 

Care,  a  distressing  passion,  313 

Cerebral  forces,  see  Forces. 

Cerebral  impressions,  121-141 


PRINCIPLES  OF  PHYSIOLOGY. 


453 


Conceptions,  how  caused,  25 ;  impressions 
or  representations  of,  26 ;  definition  of 
natural,  or  organic  and  arbitrary  voli- 
tions, 27  ;  dependent  on  material  ideas, 
ib.\  preceded  by  sensations,  65;    of 
the  understanding,  7^ ;    of  the  me- 
mory, 71 ;  their  relation  to  attention, 
abstraction,  meditation,  and  reflection, 
77 ;   either  please  or  displease,   80 ; 
their  relation  to   material  ideas,  97- 
151 ;    necessary  to  true  sentient  ac- 
tions, 123,  see  Actions  sentient ;  their 
course   independent  of   others,    125; 
sensational  and  intellectual,  347 ;  in- 
ternal impressions  of,  359  note. 
Conceptive  force  [Empfindhchkeit],  65 
Congestion,  theory  of,  207,  462 
Connatural,  as  applied  to  agreeable  ex- 
ternal sensations,  191,  196,  440 
Connection,  reciprocal,  defined,  345 
Consciousness,  80 
Contractility,  so  called  [Reiz],  3 
Contranatural,  as  applied  to  disagreeable 

external  sensations,  191,  196,  200 
Convulsions,  their  nature,  204 

Death,  definition  of,  703 ;  the  spiritual 
of  a  reasoning  animal,  704;  sensa- 
tional, 705  ;  complete,  706 ;  natural, 
707 ;  animal,  708 ;  from  what  com- 
plete, may  result,  711  716;  animal 
life  may  continue  after  proper,  717 

Desires,  how  developed  in  the  mind,  81 ; 
three  things  to  be  distinguished  in, 
84-87 ;  may  be  sensational  or  intel- 
lectual, wholly  sensational,  or  more 
spontaneous,  89 ;  sensational,  nature 
of,  90 ;  intellectual  nature  of,  96 

Despair,  a  distressing  passion,  313;  its 
sentient  actions  may  be  induced  by 
the  vis  nervosa  only,  571 

Diaphragm,  the,  is  sensitive,  and  sub- 
ject to  the  will,  171 ;  its  sentient  ac- 
tions from  external  sensations,  208 ; 
is  capable  of  direct  nerve-actions,  464  ; 
may  be  excited  by  non-conceptional 
internal  impressions,  523;  its  natural 
action  in  respiration,  525  ;  a  centre  of 
animal  forces,  673,  688 

Dichtungskraft,  the  poetic  faculty,  248 

Distress,  how  excited  and  developed, 
309;  its  mental  actions  and  various 
forms,  ib. 

Dreams,  the  rules  applicable  to,  67-69 ; 
70,  236 ;  sensational  foreseeings  often 
produced  in,  75,  247 

Emotions,  the,  nature  of,  91 ;  their  effect 
on  the  penis,  178  ;  strong  sensational 
stimuli  conjoined  in,  258  ;  effects  of 
the  pleasing  or  distressing,  how  regu- 
lated, 259 


Empfindung,  commonly  used  in  a  three- 
fold sense,  34  note. 
Empfindlichkeit,  see  Sensibility. 
Erdichtungen,  fictions,  70 
Ersetzung,  see  Substitution. 
Excitants  of  the  feelings,  see  Peelings. 
Exhilaration,  the  instinct  for,  287,  ii 
Expectations,  see  Anticipations. 
External  impressions,  see  Impressions. 
External  sensations,  see  Sensations. 

Faculty,  the  higher  perceptive,  76;  the 
poetic,  228 

Fear,  a  distressing  passion,  313,  in  what 
resembles  and  differs  from  terror,  320  ; 
may  be  induced  by  the  vis  nervosa 
only,  571 

Feelings,  incitements  of  the,  83 ;  are 
sensational  or  intellectual,  88 ;  add  a 
special  sentient  action  to  those  of  con- 
ceptions, 250 ;  excite  the  origin  of 
those  nerves  by  which  vital  move- 
ments are  regulated,  251 

Flesh,  the,  90  ;  warring  against  the  spi- 
rit, 337 

Food,  the  instinct  for,  its  sensational 
stimulus,  281 ;  its  effects  as  a  foresee- 
ing, 282 

Forces  of  physical  bodies,  the  general,  3 ; 
their  aggregate,  4 

Forces,  animal,  see  Animal  forces. 

Forces,  animal-sentient,  or  cerebral,  na- 
ture of,  6  note,  82  and  note;  their 
actions,  97-110 ;  their  relations  to  the 
vis  nervosa,  541-597  ;  their  reciprocal 
connection,  590-597 

Forces,  nerve,  defined,  6 ;  depend  on  the 
vital  spirits,  21 ;  what  retard  the  ac- 
tion of,  22 ;  what  strengthen  and  en- 
liven, 23 

Forces,  primary  vital,  nature  of  the,  675 ; 
the  two  reciprocally  subordinate,  676 

Forebodings,  the  nature  of,  73 

Foreseeings,  nature  of,  73,  23^;  relations 
of,  to  desires  and  aversions,  81 ;  rela- 
tions of,  to  instincts  and  passions,  90- 
94  ;  in  what  differ  from  true  expecta- 
tions, 249;  accompanying  the  depres- 
sing passions,  315-328 

Free  will,  96.     See  Will. 

Gall-bladder,  see  Bladder. 

Ganglia,  are  possessed  by  the  motor 
nerves,  14 ;  do  not  possess  true  cere- 
bral tissue,  35  note-,  624,  iv;  their 
probable  use,  48,  iv;  their  functions 
maybe  changed  through  habit,  49,  iv; 
probably  deflect  external  impressions, 
48,  iv,  399 ;  to  the  motor  nerves  per- 
form the  office  of  brain,  399 

GefiJhl,  the  external  feeling  of  the 
nerves,  402 


454 


INDEX  TO  UNZER'S 


Generation,  definition  of,  628 ;  fissipa- 

rous,  oviparous,  and  viviparous,  629 
Glands, the,  their  nature  and  function,  172 
Gratification,  nature   of,  80,  187,   195 ; 

its  actions,  when  very  vivid,  allied  to 

pain,  199 
Grief,  a  distressing  passion,  313 ;  what 

favour,  317 

Habit,  distinct  from  expertness,  137 

Haller,  the  dead  force  of,  3 ;  probably 
the  Gottingen  reviewer  of  Unzer's 
work,  35  note-,  his  objection  to  the 
hypothesis  of  afferent  and  efferent 
fibrils  in  the  same  nerve,  127  note', 
seems  to  think,  the  voluntary  move- 
ments alone  produced  by  the  soul, 
162  note\  has  shown  that  respiration 
is  a  sentient  action,  285 ;  his  terms  of 
muscular  and  nervous  irfltability,  354 ; 
his  doctrine  of  vis  insita  refuted,  379, 
388 

Hamilton,  Sir  W.,  his  abstract  of  the 
doctrines  of  Albinus,  39  note. 

Heart,  the,  its  action  animal,  167;  Hal- 
ler's  theory  of  its  motion  confuted, 
386  ;  the  effect  of  sensations  on,  211, 
250 ;  its  action  in  grief  and  fear,  314  ; 
its  action  in  anger  and  revenge,  anxiety 
and  terror,  323;  its  stroke  probably  an 
indirect  nerve-action,  517  ;  a  centre  of 
animal  forces,  673 ;  its  proper  motor 
force,  678 

Hunger,  the  sensational  instinct  of,  how 
excited,  265  ;  stimulates  the  machines 
which  receive  food  to  discharge  their 
functions,  281 

Incitements  of  the  feelings,  see  Feelings. 

Ideas,  material,  the  nature  of,  25 ;  neces- 
sary to  thought,  ib. ;  their  relations  to 
thought,  26 ;  in  what  probably  consist, 
28 ;  higher,  abstract,  or  general,  66 ; 
of  imaginations,  67 ;  of  anticipations, 
94 ;  act  either  directly  or  indirectly, 
115;  their  actions  on  the  nervous 
system,  117,  122,  142-151 ;  their  ac- 
tions in  the  brain,  118,  159;  the  pri- 
mary excite  those  of  a  second  kind, 
119;  their  action  in  the  mechanical 
machines,  160-180 

Idiosyncrasy,  52 

Imaginations,  nature  of  the  sensational, 
66;  their  relation  to  external  sensa- 
tions, 68,  230-233 ;  relations  to  in- 
sanity, 69,  70;  their  action  on  the 
mechanical  machines,  228-238 

Impression,  a  sense-like,  defined,  31,  and 
note 

Impressional,  sinnlich,  31,  66 

Impressibility,  SinnlicMeit,  32 

Impressions,  cerebral,  121, 133 


Impressions,    conceptional,   121    note; 
359 ;  characters  of,  31 ;  their  course         ■ 
along  the    nerves,   ib. ;   respondence        1 
to,  a  property  of  nerves,  or  "  nerve-         i 
feeling,"   31   note;   of  pleasure   and 
pain,  the  bases  of  the  desires,  82 

Impressions,  external, — why  so  termed; 
32 ;  a  definite  change  in  the  nerve, 
ib. ;  how  developed,  32-36  ;  to  be  felt, 
must  be  propagated  upwards  to  the 
brain,  36,  37  ;  all  determined  by  the 
mind,  38  ;  conditions  requisite  to  their 
developing  external  sensations,  45; 
the  cause  of  all  conceptions,  65,  66 ; 
their  course  in  animals,  with  a  sen- 
tient brain,  366 ;  by  their  reflexion, 
sentient  acts  may  be  performed  without 
brain,  367  ;  their  vis  nervosa  in  general, 
409, 443 ;  every  muscle,  like  the  nerves, 
has  its  own  special,  451 ;  their  action 
on  the  muscles  and  heart,  452-517 

Impressions, internal, — their  nature,  121 ; 
propagated,  without  being  commingled, 
125  ;  non-conceptional  can  produce  the 
same  movements  as  the  conceptive 
force,  360 ;  the  reflexion  of  external 
into,  366,  399;  how  non-concep- 
tional originate;  371;  their  relation 
to  external  and  internal  sensations, 
402  ;  course  of  the  non-conceptional, 
486,  487 ;  when  the  brain  and  cere- 
bral forces  necessary  to  the  nerve- 
actions  of  the  non-conceptional,  494  ; 
non-conceptional  subject  to  the  same 
law  of  deflection  as  those  from  con- 
ceptions, 504  ;  reflex  action  of,  on  the 
heart,  515;  action  of  non-conceptional 
on  the  capillaries,  diaphragm,  viscera, 
&c.,  522-537;  each  of  the  two  kinds 
may  reciprocally  excite  the  other,  398 ; 
excite  whole  series  of  acts,  ib. 

Inflammation,  theory  of,  207,  462 

Insanity,  the  rules  apphcable  to,  67-69, 
70,  236  ;  sensational  foreseeings  and 
forebodings  often  produced  in,  75, 247 

Insentient  animal,  an,  its  nature,  604; 
how  moved,  606;  all  their  animal 
movements  dependent  on  the  vis  ner- 
vosa, 608 ;  excite  all  sentient  move- 
ments by  the  vis  nervosa  alone,  611 

Instincts,sensational,  their  different  kinds, 
90  ;  their  actions  in  the  economy,  93 ; 
how  developed,  94  ;  how  cease,  or  are 
prevented,  95  ;  doctrines  applicable  to, 
256-259;  arrangement  of,  262;  in 
what  differ  from  all  other  desires, 
aversions,  and  passions,  263-265 ; 
depend  on  no  innate  wisdom,  266; 
the  order  of  their  phenomena,  268; 
their  stimuli,  270 :  general  and  special, 
natural  aindunnatural,29b ;  the  felt  im- 
pression in,  reflected  by  the  brain,  564. 


PRINCIPLES  OF  PHYSIOLOGY. 


455 


Intellect,  see  Understanding. 
Intestinal  canal,  how  the  nerves  act  on 
the,  170;  often  really  sensitive,  ib. 

Joy,  the  nature  of,  306 ;  how  far  bene- 
ficial or  contranatural,  307 

Judgment,  the,  may  err  respecting  ex- 
ternal sensations,  38  ;  to  what  class  of 
conceptions  it  belongs,  76 

Kidneys,  the,  have  but  few  nerves,  176 ; 
susceptible  only  of  extraordinary  ex- 
ternal impressions,  215  ;  their  secern- 
ing function,  a  nerve-action,  477  ;  how 
situate  as  to  nerve-actions  from  non- 
conceptional  internal  impressions,  526 

Kitzel,  titillation,  or  gratification,  80, 
187,  195-197 

Krijger,  his  law  as  to  the  movements  fol- 
lowing external  sensations,  218 

Laughter,  the  instinct  of,  284 

Life,  the  love  of,  the  fundamental  in- 
stinct in  all  animals,  280 

Liver,  the,  its  sensibility  not  great,  175 ; 
is  little  susceptible  of  external  sensa- 
tions, 213;  the  effects  of  anger  on, 
325  ;  how  far  capable  of  nerve -actions, 
476,  535 

Loathing,  282 

Longing,  its  sentient  and  special  actions, 
327 

Love,  the  enchantment  of,  289 ;  phy- 
sical, 302 ;  of  offspring,  303;  the  passion 
of,  306 ;  the  instinctive  emotions  of, 
308 

Lungs,  the,  little  susceptible  to  ordinary 
external  impressions,  214;  congestion 
of,  in  the  distressing  passions,  310; 
how  situate  as  to  nerve-actions,  475, 
534 

Machines,  animal,  see  Animal  machines. 

Machines,  mechanical, — meaning  of  the 
term,  4, 155-159  ;  divided  into  artistic 
and  organic,  5 ;  how  put  in  motion, 
153,  505,  506  ;  actions  of  the  material 
ideas  in,  160-180  ;  actions  of  external 
sensations  in,  181-227;  actions  of 
imaginations  on,  228-238 ;  actions  of 
the  sensational  foreseeings  on,  250- 
254 ;  actions  of  sensational  desires  and 
aversions  in,  255-261 ;  actions  of  sen- 
sational instincts  in,  262-304 ;  actions 
of  the  passions  on,  305-329 ;  actions 
of  the  understanding  in,  ib. ;  actions  of 
intellectual  pleasure  and  pain  in,  334- 
335  ;  actions  of  the  will  in,  335-344  ; 
direct  actions  produced  by  the  vis 
nervosa  in,  444-481 

Material  ideas,  see  Ideas. 


Meditation,  the  act  of,  77 

Membranes,  the,  are  sensitive,  171 ;  effect 
of  external  impressions  on  the  non 
muscular,  208 ;  the  serous,  how  situate 
as  to  external  sensations,  208  ;  nerve- 
actions  in  the  muscular,  mucous,  and 
fibro-serous,  464,  527 

Memory,  an  act  of  the,  71 ;  the  material 
ideas  induced  by  sensational,  72 ;  to 
what  class  of  conceptions  it  belongs, 
238 

Merkmahlen,  elements,  53 

Merkmale,  sub-impressions,  68,  73,  &c. 

Mind,  an  act  of  the,  6  note;  25,  34-36; 
effect  of  injury  of  the  medulla  of  the 
brain  on  the,  25 ;  material  ideas  are 
not  the  ideas  of  the,  25  ;  determines 
the  point  of  impression  in  external 
sensations,  30 ;  can  produce  voluntarily 
many  kinds  of  conceptions,  64 ;  its 
inner  sense,  80;  actions  excited  by 
the,  97-111;  not  necessary  to  direct 
nerve-actions  in  muscles,  449 

Monstrosities,  origin  of,  636 

Motives,  the  nature  of,  88,  89 ;  the  im- 
pressions they  add  to  passive  concep- 
tions, 96 ;  as  stimuli,  250 ;  excite  the 
origin  of  certain  nerves,  251 

Movements,  the  respiratory,  generally 
neither  mechanical  nor  volitional,  285. 
See  Respiration. 

Movements,  voluntary,  distinguished  into 
sensational  and  intellectual,  283  note ; 
the  instinct  to  perform  the  sensa- 
tional, 283 ;  instincts  for  particular 
kinds  of  sensational,  284 

Movements,  the  free-will,  with  what 
often  confounded,  335  ;  how  produced 
and  hindered,  336,  342 ;  why  take 
place  in  a  given  series,  341 ;  their  im- 
portant influence  in  the  economy, 
343;  power  of  the  soul  not  to  be 
limited  to,  351 

MiiLLER,  J.,  anticipation  of  his  neurolo- 
gical views  by  Albinus,  39  note. 

Muscles,  as  mechanical  machines,  161 ; 
the  nature  of  the  action  of  the  nerves 
on,  162;  their  vis  insita,  379-388; 
have  each  their  own  special  external 
impressions,  451;  reflexion  of  unfelt 
external  impressions  in,  514 

Natural,  as  applied  to  mechanical  ma- 
chines, 5 ;  conceptions,  27  ;  instinct, 
90 ;  subordination  of  animal  functions, 
666 

Nerve-actions,  definition  of,  6 ;  which 
may  be  at  the  same  time  sentient 
actions,  183,  184,  233,  364,  368,  441 ; 
from  the  external  impression,  358 ;  from 
the  internal  impression,  359, 360  ;  may 


456 


INDEX  TO  UNZER'S 


Nerve-actions  {continued) 

occur  without  cerebral  force,  or  brain, 
362  ;  change  of  sentient  actions  into, 
367;  advantages  to  reasoning  animals 
from,  370 ;  machines  must  be  supplied 
with  nerves,  to  be  capable  of,  390, 391 ; 
of  the  heart,  392 ;  of  the  oesophagus, 
stomach,  &c.,  393 ;  of  the  glandular 
tissues,  394 ;  of  the  sexual  organs,  395^ 
of  the  instincts,  396 ;  of  unfelTln- 
ternal  impressions,  397  ;  of  reflected 
impressions,  398 ;  of  the  brain's  vis 
nervosa,  409 ;  from  several  external 
impressions  at  the  same  time,  do  not 
confuse  each  other,  412;  different  kinds 
of  impressions  difficult  to  be  discrimi- 
nated from  their,  413  ;  from  a  reflected 
external  impression  occur  in  the  proper 
machine,  415,  ii;  from  reflected  im- 
pression often  misunderstood,  415,  iii; 
how  far  the  brain  necessary  to,  416, 
494, 511 ;  direct  and  indirect,  419, 425  ; 
how  enfeebled  or  prevented,  427-430; 
their  relation  to  external  sensations, 
433,  438 ;  how  resemble  the  sentient, 
435-437  ;  why  they  excite  our  wonder, 
438  ;  are  connatural  or  contra-natural, 
440 ;  muscular  fibre  peculiarly  adapted 
to  direct,  445 ;  in  muscles,  449-453, 
513;  in  the  heart,  455,  517,  518;  in 
the  membranes,  464  ;  in  the  capillaries, 
463  ;  of  the  stomach,  469,  470 ;  of  the 
viscera,  475-479;  of  the  senses,  480; 
of  the  sexual  organs,  481 ;  of  non-con- 
ceptional  internal  impressions,  483, 
494, 506, 507, 524-544  ;  produced  by  a 
primary  internal  impression,  490,  496, 
498 ;  of  imaginations  or  foreseeings, 
549 ;  of  the  sensational  desires  and 
aversions,  530 ;  of  the  blind  instincts 
and  emotions,  551 ;  of  the  sensational 
instincts,  552,  561 ;  of  the  instinctive 
passions,  562  ;  of  the  passions,  563- 
567 ;  three  principal  kinds  of,  in  the 
mechanical  machines,  580;  threefold 
division  of  those  of  primary  non-con- 
ceptional  internal  impressions,  581; 
substitution  of,  for  sentient  actions  and 
vice  versa,  541,  589 ;  from  a  sensational 
conception,  591 ;  in  the  foetus,  634 

Nerve  feeling,  its  nature,  31 ;  from  with- 
out inwards,  32  ;  internal,  121 

Nerve  forces,  see  Forces. 

Nervous  fluid,  see  Vital  spirits. 

Nerves,  all  arise  from  the  brain,  12  ;  their 
course,  13  ;  their  external  terminations, 
14 ;  division  of,  into  motor  and  sensitive, 
14;  contain  the  vital  spirits,  15 ;  dif- 
ferent efl"ects  of  impressions  on  different 
parts  of,  31;  how  animal  actions  ex- 
cited in  their  medulla,  32  ;  of  motion 


Nerves  (continued) 

and  sensation,  no  difference  of  in 
receiving  and  transmitting  impressions, 
33 ;  sensational  force  of,  34  ;  external 
impressions  on,  35-39,  55 ;  impressions 
on  the  cerebral  origin  of,  121 ;  action  of 
material  ideas  in,  122,  142-151,  405; 
impressions  of  the  conceptions  on,  124, 
125 ;  probably  have  aflferent  and  efferent 
fibrils,  126-127 ;  hidden  movements 
in  them  inferred,  145,  404,  405 ;  erec- 
tion of  their  terminations,  147-150; 
vivid  impressions  probably  deflected  at 
their  bifurcations,  151;  effect  of  a 
cerebral  impression  at  their  loops,  160; 
their  action  on  the  muscles,  162-164, 
510 ;  various  ways  in  which  may  in- 
fluence the  secretions  and  circulation, 
167-180  ;  the  action  of  external  sensa- 
tions through  them,  181-227;  actions 
of  imaginations  through  them,  228- 
238  ;  actions  of  the  sensational  foresee- 
ings through  them,  239-249 ;  actions  of 
sensational  pleasure  and  pain  through 
them,  250-254 ;  actions  of  the  sensa- 
tional desires  and  aversions  through 
them,  255-261 ;  actions  of  the  sensa- 
tional instincts  through  them,  262-304 ; 
actions  of  the  passions  through  them, 
305-329  ;  actions  of  intellectual  plea- 
sure and  pain  through  them,  333-334  ; 
actions  of  the  will  through  them,  335- 
336  ;  the  principal  seat  of  the  primary 
vis  nervosa,  372 ;  vis  nervosa  must  be 
a  general  property  of,  375  ;  impressions 
on  the  sensory,  376,  377;  external 
feeling  of,  402  ;  internal  feehng  of,  405- 
407;  secondary  points  in  them,  probable 
for  the  reflexion  of  impressions,  428 ; 
nerve-actions  explained  from  the  doc- 
trine of  afferent  and  eflferent  fibrils  in, 
486-488  ;  their  ordinary  stimuli  caus- 
ing internal  impressions,  489 ;  the  pe- 
culiar kind  of  irritation  of  their  medulla 
to  produce  a  certain  kind  of  internal 
impression,  unknown,  492 ;  changes  in, 
from  non-conceptional  internal  impres- 
sions, 504  ;  eflfect  of  opium  on,  558 ; 
their  growth,  and  development  in  new 
growths,  647 ;  their  daily  wear  and 
repair,  662 


(Esophagus  the,  action  of  the  nerves  on, 

170:  direct  nerve-actions  of,  466-468; 

nerve-actions    from    non-conceptional 

internal  impressions,  531 
Offspring,  the  instinct  for,  262,  iv 
Organic  life,  what,  5 
Organic  machines,  in  what  diflfer  from 

artistic,  5 ;  when  termed  animal,  6 


PRINCIPLES  OF  PHYSIOLOGY. 


457 


Organism  the,  how  far  the  general  forces 
of  physical  bodies  belong  to,  3 ;  to 
what  extent  the  laws  of  mechanics 
applicable  to,  5;  a  sensible  and  in- 
sensible, 52  ;  an  irritable  and  inirritable, 
432  ;  as  a  living  animal,  600 

Organs,  of  the  external  senses,  55  ;  as 
mechanical  machines,  subject  to  same 
laws,  177  ;  effect  of  external  sensations 
on,  216 ;  seat  of  the  same  nerve-actions 
as  the  muscular  system,  539 

Organs, the  sexual,are  extremely  sensitive, 
178;  their  functions  may  be  induced 
by  the  vis  nervosa  alone,  481 ;  nerve- 
actions  from  non-conceptional  internal 
impressions  on,  340  ;  all  animals  born 
with,  654 ;  as  centres  of  animal  forces, 
673 

Pain,  in  what  consists,  80;  sensational 
and  intellectual,  88 ;  action  of,  on  the 
organism,  136-200;  its  actions  on  the 
mechanical  machines,  204 ;  its  action 
on  the  vital  movements,  250,  333 

Passions,  the,  91 ;  each  of,  how  com- 
pounded, 93 ;  what  doctrines  apply 
to,  256 ;  instinctive,  302 ;  incidental 
action  of  the  primary,  305  ;  actions  of 
the  joyous,  306-308 ;  actions  of  the 
painful  and  distressing,  309-328 ;  the 
instinctive  as  nerve-actions,  562 ;  their 
sentient  actions  as  nerve-actions,  563- 
573 

Penis,  effect  of  foreseeings  and  desires  on 
the,  178;  Haller's  opinion  on  the 
swelling  of  its  corpora  spongiosa,  178 

Perceptions,  sensational,  76 

Physiognomy,  166 

Physiologically  free,  as  applied  to  con- 
ceptions, 27,  89 

Pleasure,  impression  of,  distinct  from 
that  of  pain,  80 ;  sensational  and  in- 
tellectual, 89 ;  its  action  on  the  organ- 
ism, 191 ;  its  action  on  the  vital  move- 
ments, 250,  333;  calm,  more  favorable 
to  health  and  life  than  when  in  excess, 
252,  253 

Pleasure  and  pain,  nature  of  their  im- 
pressions, 124 

Preservation,  pain  the  sentinel  of,  184  ; 
impressions  necessary  to,  in  insentient 
animals  given  by  nature,  609 ;  move- 
ments, necessary  to,  effected  by  the  vis 
nervosa,  610 

Procreation,  see  Generation. 

Propagation  of  the  species,  instinct  of, 
262,  iii,  289  ;  its  excitement  and  satis- 
faction, 263  ;  analysed,  273 ;  its  sensa- 
tional stimulus,  289 ;  its  sentient  as 
nerve-actions,  560  ;  as  a  period  in  the 
life  of  an  animal,  652-657 


Propensities,  actions  of  the  sensational, 
260,  261 

Pulse,  the  arterial, how  far  may  be  a  nerve- 
action,  519, 520 ;  influenced  by  all  non- 
conceptional  impressions  exciting  mus- 
cular action,  521 

Reasoning  animal,  a,  605 

Reasons,  88 

Reciprocal  connection,  defined,  345 ;  of 
the  animal-sentient  forces  with  the  vis 
nervosa,  590-597 

Reflection,  the  act  of,  77 

Reflex  action,  of  an  external  impression 
on  the  heart,  515 ;  of  the  brain  in  the 
instincts,  564 

Reflexion,  of  an  external  impression  in  a 
sentient  brain,  or  ganglion,  365,  415, 
ii ;  see  also  Nerve-actions  and  impres- 
sions, external  and  internal 

Regret,  its  nature  and  sentient  actions, 
312 

Reiz,  so  called  contractility,  3 

Repose,  the  instinct  for,  its  nature  and 
natural  stimulus,  287;  its  nerve-actions, 
558 

Respiration,  the  instinct  of,  285;  how 
far  a  nerve-action  in  thenewly-bom,285, 
286, 526 ;  may  take  place  independently 
of  brain  or  mind,  475 

Revenge,  the  desire  of,  an  instinctive 
passion,  301 ;  a  depressing  passion,  322 ; 
the  heart's  action  in,  323;  its  union 
with  anger,  324 ;  the  special  changes 
by  its  sentient  actions,  325 ;  means  of 
controlling  it,  326 ;  may  be  induced 
by  the  vis  nervosa  only,  572 

Reverie,  [dichtet,]  237 

Schmerz,  suffering,  80,  187,  195 

Secretion,  animal,  but  sometimes  a  sen- 
tient action,  172;  may  be  a  direct  nerve- 
action,  471-473 

SeelenwirJcungen,  mental,  sentient,  or  sen- 
sational acts,  6,  99,  iii 

Self-defence,  the  instinct  of,  262,  ii,  288 

Self-love,  sensational,  280 

Self-preservation,  the  instinct  of,  262,  ii, 
263 

Sense-like  impression,  a,  31 

Senselikeness,  32  ;  its  varying  degree  in 
the  conceptions,  112 

Sensation,  the  term  used  in  a  threefold 
sense,  34  note\  precedes  all  other 
conceptions,  65  ;  a  certain  use  of  the 
term  proposed,  402 

Sensation,  as  used  by  Buffon,  402 

Sensational,  31  note',  force,  or  sensi- 
bility, 34  ;  memory,  72  ;  foreseeings 
and  expectations,  see  Foreseeings  and 
Expectations;  pleasure  and  suffering. 


458 


INDEX  TO  UNZER'S 


Sensational  (continued) 

see  Pleasure  and  Pain  ;  stimuli,  88 ; 
instincts,  see  Instincts ;  desires  and 
aversions,  see  Desires  and  Aversions. 
Sensational  animal,  a,  605  ;  of  what  vital 
actions  capable,  614  ;  perform  nerve- 
actions  as  sentient  actions,  624 
Sensations,  external,  nature  of,  34-36 ; 
what  requisite  to  their  development, 
45 ;  what  interrupts  or  hinders  them, 
46-51 ;  the  material  ideas  of,  53,  54  ; 
their  organs,  54 ;  special,  55 ;  their 
relation  to  the  material  ideas  of  ima- 
ginations, 67 ;  of  pleasure  and  suffer- 
ing, 80 ;  material,  how  excited,  132 ; 
imperfect,  148,  378;  actions  of,  on 
the  mechanical  machines,  181-227; 
the  majority  of  their  sentient  actions 
at  the  same  time  nerve-actions,  183 ; 
agreeable  and  disagreeable,  189,  190  ; 
of  imaginations  and  instincts,  229- 
276 ;  external  feeling  of  the  nerves  to 
be  distinguished  from,  402-404  ;  their 
nerve-actions,  436-452 
Senses,  the,  their  number  and  seat,  55- 

64  ;  their  nerve-actions,  480 
Sensible,  meaning  of  the  term,  as  used 

by  the  French,  31  note. 
SensibiUty,  34,  65 ;   may  co-exist  with 

irritability,  432 
Sensual  gratification,  or  titillation,  80, 

88  ;  propensity,  or  inclination,  90 
Sentient  actions,  see  Actions,  sentient. 
Sentient  animal,  a,  the  idea  of,  349  ;  how 

moved,  612,  613 
Sentient  faculty,  what,  10 
Shame,its  nature  and  sentient  actions,  328 
Shivering,  how  ought   probably  to   be 

classed,  147 
Sinnlich,  in  what  sense  used  by  Unzer, 

31  note,  66  note. 
Sleep,  as  an  impediment  to  external  sen- 
sations, 49,  v;    the  instinct   for,  see 
Repose. 
Somnambulism,  the  rules,  67-69  ;  appli- 
cable to,  70, 236 ;  foreseeings  in,  247  ; 
the  movements  during  it   explained, 
454 
Sorrow,  its  nature  and  actions,  310;  in- 
jurious to  health  and  life,  311 
Soul,  the  seat  of  the,  10, 25  ;  acts  of  the, 
27;  its  union  with  the  body,  29;  its 
reciprocal  connexion  with  the  body, 
345-352 ;  error  of  the  ancients  con- 
cerning the,  404  ;  not  indispensable  to 
animal    acts,    594 ;    its    disseverance 
from  the  body,  717-726 
Spasms,  their  nature,  204 
Spleen,  its  nerve-actions,  479 
Spinal  cord,  reflexion  of  impressions  in, 
35  note. 


Spontaneous,  as  applied  to  conceptions, 
27 

Stomach,  the,  has  many  and  considerable 
nerves,  174;  is  susceptible  of  impres- 
sions from  conceptions,  ib. ;  the  exter- 
nal sensations  excited  in  and  about, 
212 ;  its  direct  nerve-actions,  466, 
468,  531;  a  centre  of  animal  forces, 
673,  688 

Substitution  of  nerve- actions  for  sen- 
tient, and  vice  versa,  541-589 

Suck,  the  instinct  to  give,  290 ;  the  in- 
stinct to,  ib. 

Suffering,  impression  of,  80 ;  a  sentinel 
of  our  preservation,  184 ;  a  natural 
medicine,  196 

Sympathy,  90 ;  of  sentient  actions  in  the 
muscles,  165 

Temperament  of  an  animal  body,  defined, 
52 ;  mainly  determines  the  sensational 
faculty,  329;  how  and  when  deter- 
mined, 651 

Terror,  its  nature  and  actions,  318 ;  in 
what  resembles  and  differs  from  fear, 
320 

Thierische-seelen  KrUfte,  rendered  by 
"  cerebral  forces,"  or, "  animal-sentient 
forces,'  6  note,  82  and  note. 

Thierischer  Kbrjjer,  the  equivalent  of 
animal  organism,  6  note. 

Thierischer  Krdfte,  the  vis  nervosa,  6 
note. 

Thierischer  Maschinen,  what  used  for, 
9  note. 

Thirst,  the  sensational  stimulus  of,  282 

Thought,  on  what  dependent,  25  ;  effect 
of,  on  abstract  subjects,  333 

Titillation,  80;    excites    vivid   contrac- 
tions in   muscles,   204 ;   as  a  nerve- 
action,  434 
Triebfedem  des  GemUths.     See  Feelings. 

Understanding,  conceptions  of  the,  76 ; 
their  sentient  actions,  331,  332,  380; 
the  direct  cannot  be  induced  as  nerve- 
actions,  574  ;  the  motives  and  desires 
of  the,  cannot  be  induced  by  the  vis 
nervosa,  576 

Viscera,  action  of  the  nerves  in  the,  very 
complex,  1 73 ;  their  nerve-actions, 
474-479 

Vis  nervosa,  its  synonyms,  6  and  note;  the 
functions  the  body  is  rendered  capa- 
ble of,  by  the,  354  ;  of  the  external  im- 
pression, its  nerve-actions,  358  ;  of  the 
internal  impression,  its  most  prominent 
examples,  359 ;  properties  of  both 
kinds  of,  361 ;  does  not  necessarily 
require  the  cerebral  force,  362 ;  seat 
of  the  primai-y,  372-374 ;  of  nerves. 


PRINCIPLES  OF  PHYSIOLOGY. 


459 


Vis  nervosa  (continued) 

excited  by  non-conceptional  internal 
impressions,  381,  ii ;  no  animal  motor 
force  independent  of,  389 ;  machines 
not  endowed  with  nerves  not  adapted 
to,  390 ;  of  the  heart,  392 ;  of  the 
oesophagus,  stomach,  &c.,  393  ;  of  the 
glandular  tissues,  394 ;  of  the  sexual 
organs,  395  ;  in  the  movements  of  the 
limbs,  396;  either  kind  of,  may  be 
excited  without  the  conceptive  force, 
398 ;  of  external  imprjessions,  409- 
413 ;  of  non-conceptional  internal  im- 
pressions, 482-540;  all  the  sentient 
actions  of  imaginations  and  fore-see- 
ings,  sensational  conceptions,  desires, 
and  aversions,  instincts,  and  emo- 
tions, imitated  by,  545-553  ;  effect  of 
opium  on,  558 ;  how  far  the  passions 
may  be  imitated  by,  562-573 ;  intel- 
lectual conceptions  and  motives  can- 
not be  induced  by,  575,  576;  how 
far  the  influence  of  the  will  can 
be  induced  by,  577 ;  as  possessed 
by  sentient  and  insentient  animals, 
604-617;  causes  movements,  neces- 
sary to  the  preservation  of  animals, 
610 ;  of  a  reasoning  animal,  618,  626 ; 
a  large  class  of  animals  endowed  alone 
with,  621-624 ;  of  a  purely  sensational 
animal,  626;  abolition  of,  709,  710 

Vital  spirits,  the,  how  secreted,  11,  362, 
416;  their  existence  probable,  15,  i; 


Vital  spirits  (continued) 

course  of  the  impressions  propagated 
by,  17,  18;  how  weakened,  20;  func- 
tions of  the  sentient  forces  dependent 
upon,  21 ;  the  movements  of  the  nerves 
probably  only  movements  of,  145; 
effect  of  an  irregular  influence  of,  314. 

Vorstellung,  generally  translated  by  "con- 
ception," 5  note,  25  note. 

Forstellungskraft,  conceptive  force,  sen- 
tient force,  or  mind,  6 


War-instinct,  the,  its  nature,  301,  326; 
its  sentient  actions  may  be  nerve-ac- 
tions, 559 

Whytt,  his  renewal  of  an  erroneous  pro- 
position of  the  ancients,  404 

Will,  the  free,  96 ;  sentient  actions  of  its 
desires  and  aversions,  335 ;  conflict 
between  the  sensational  faculty  and, 
337 ;  satisfaction  of,  prevented,  338 ; 
the  flesh  has  always  a  part  in,  339 ; 
how  far  its  incidental  influence  may  be 
exercised  by  the  vis  nervosa,  577  ;  how 
far  its  desires  and  aversions  may  be 
induced  by  vis  nervosa,  378 ;  move- 
ments of,  see  Movements. 

Wille  and  WillMhr,  how  used,  283  note. 

Willkiihrlich,  how  rendered,  283  note, 
335  note. 


Yawning,  its  nature,  287,  ii. 


INDEX 


PROCHASKA  ON  TPIE  NERVOUS  SYSTEM. 


[N.B. — The  figures  in  this  Index  refer  to  the  pages.] 


Albinus  shows  the  cortex  of  the  brain 
not  altogether  vascular,  377,  389 

Anatomy  of  the  nervous  system  —  its 
bibliography,  383  note. 

Animal  functions,  see  Functions. 

Animalcules  shown  by  Spallanzani  to 
be  true  animals,  386 ;  how  feel  and 
move,  387 

Arabs,  the,  located  the  animal  functions 
in  the  ventricles,  369 

Aristotle,  his  opinion  as  to  the  use  of 
the  brain  and  heart,  365 

Arteries,  irritability  and  muscular  con- 
traction of,  411 

AsTRuc,  quoted,  377 

Anger,  its  effect  on  the  secretions,  419- 
421 

Bartholin,  373 

Bauhin  Caspar,  the  first  to  deny  the 
doctrines  of  Galen,  370 

Benevenius,  his  doctrine  as  to  the  ani- 
mal functions,  369 

Blood-vessels,  action  of  the  nerves  on 
the,  408-412 

Blumenbach,  his  hypothesis  of  a  nisus 
formativus,  426 

Boerhaave,  doctrines  of  his  school  on 
the  brain,  377  ;  his  opinion  on  the 
animal  spirits,  377 ;  where  places  the 
sensorium  commune,  429 

BoHADSCH,  his  description  of  the  lernaea, 
388 

Bones,  morbid,  sensibility  of,  394 ; 
Murray  on,  394 ;  Brambilla  on 
395  note. 

Bonnet,  386 

Brain,  its  use,  according  to  Aristotle, 
365 ;  the  opinions  of  Hippocrates, 
Plato,  Galen,  and  others,  as  to  its 
functions,  365-369 ;  its  systole  and 
diastole,  367,  369  ;  intellect,  according 
to  Galen,  does  not  depend  on  its 
convolutions,  368 ;  case  of  injury  of, 
by  Galen,  367 ;  the  use  of  its  cir- 
cumvolutions, according  to  Columbus, 


Brain  (continued) 

369 ;  its  cortical  substance  secretes  the 
animal  spirits,  374;  Malpighi  and 
Willis  support  this  opinion,  375  j 
man  has  the  largest,  except  certain 
apes,  384;  structure  and  composition 
of,  in  animals,  ib. ;  the  proportion  it 
bears  to  other  parts  of  the  body,  385  ; 
its  medullary  matter  not  wholly  vas- 
cular, 389 ;  is  the  organ  of  the  mind, 
442 ;  is  probably  a  compound  organ, 
446,  447 

Caldani  opposed  the  doctrine  of  animal 
spirits,  379 

Camper,  his  opinion  on  the  consensus 
of  the  nerves,  433 

Capillaries,  action  of  the  nerves  on 
the,  408-412 

Cerebellum,  use  of  the  vermiform  process 
of  the,  according  to  Galen,  368  ;  the 
seat  of  involuntary  motions,  according 
to  Willis,  375;  description  of  the, 
381 

Cerebrum,  why  softer  than  the  nerves, 
and  double,  according  to  Galen,  367; 
its  use,  according  to  Willis,  375 ;  de- 
scription of  the,  381  ;  what  portion  of, 
subservient  to  this  or  that  faculty,  un- 
known, 446 

Circulation,  influence  of  the  nerves  on,  in 
the  capillaries,  408  ;  excited  by  a  sti- 
mulus to  the  nerves,  409 ;  can  it  be 
repelled  by  the  nerves?  417 

Columbus,  his  opinion  on  the  use  of  the 
circumvolutions  of  the  brain,  369 

Conarium,  see  Pineal  Gland. 

Congestion  caused  by  the  action  of 
nerves,  409  ;  theories  of,  410 ;  various 
phenomena  caused  by,  416 

Consensus  of  the  nerves,  inquiry  into, 
433  ;  where  it  takes  place,  ib. ;  when 
in  the  ganglia,  435 

Consciousness,  to  what  it  belongs,  441 

Corpora  striata,  functions  of  their  ascend- 
ing and  descending  fibres,  375 


ON  THE  NERVOUS  SYSTEM. 


461 


Corpus  callosum,  seat  of  the  understand- 
ing, 375  ;  the  centre  of  sensation  and 
motion  according  to  Lancisi,  &c., 
377,429 

Cremadells,  his  theory  of  animal  heat, 
423 

Cutis  anserina  explained,  416 

CRAWFOKD,his  theory  of  animalheat,  423 

De  Haen  on  animal  heat,  421 
Des  Cartes,  his  opinion  on  the  animal 
spirits,   370 ;    placed  the   sensorium 
commune  in  the  pineal  gland,  429 
Diemerbroeck,  373 

Erasistratus,  his  opinion  as  to   the 

functions  of  the  brain,  366 
Erectile  tissue,  influence  of  nerves  on,  416 

Fallopius,  denies  the  systole  and  dias- 
tole of  the  brain,  369 

False  resemblances  of  truths,  injurious 
influence  of,  on  science,  364 

Fernelius,  a  follower  of  Plato,  366 ; 
his  doctrine  as  to  the  origin  of  the 
sensory  and  motor  nerves,  369 

FiORATi,  his  edition  of  Tissot  on  the 
Nerves,  379 

Foetus,  the,  formed  by  generation,  not 
evolution,  426 ;  acephalous,  in  utero 
lives  by  vis  nervosa,  387,  399 

FoNTANA,  his  experiments  on  opium,  397 

Fornix,  the,  its  use,  according  to  Galen, 
368 

Functions,  the  animal,  distributed 
amongst  the  ventricles  of  the  brain  by 
the  Arabs,  369;  enumeration  of, 
439-441 

Galen  recognised  three  faculties  of  the 
mind  and  three  spirits,  365,  366 ; 
refutes  Aristotle's  doctrine  on  the 
brain,  366 ;  his  opinion  as  to  the  use 
of  the  cerebrum,  cerebellum,  &c.,  367- 
369 ;  doctrines  held  by  his  followers, 
369 ;  the  use  assigned  by  him  to  the 
ventricles  shown  to  be  erroneous, 
372,  373 

GangUa,  known  to  Galen  and  others, 
378;  functions  of,  first  taught  by 
ViEussENs,  &c.,  ib. ;  opinions  as  to 
their  probable  use,  378,  436 ;  con- 
sidered to  be  little  cerebra,  378  ;  con- 
sensus of  the  nerves  takes  place  in, 
435  ;  act  as  ligatures  on  the  nerves, 
436 ;  are  special  sensoria  for  reflexion 
of  impressions,  438 

Gasser  quoted,  377 

Gaubius,  his  account  of  the  effects  of 
anger  on  the  secretions,  420 


Habit, its  influence  on  the  vis  nervosa,  405 

Haller,  his  opinion  as  to  the  infundi- 
bulum,  373,  and  pituitary  gland,  374 ; 
his  error  as  to  irritability  in  muscle, 
390 ;  supports  the  doctrine  of  animal 
spirits,  379 ;  the  inconsistency  of  his 
doctrines  on  the  motion  of  the  heart, 
401  ;  his  opinion  on  animal  heat,  421; 
denied  the  nutritive  property  of  the 
nervous  fluid,  424 

Harvey,  nature  of  opposition  to  his 
views,  371 

Heart,  the  seat  of  the  soul,  according  to 
Aristotle,  365 ;  movements  depend- 
ent on  the  vis  nervosa,  399  ;  the  doc- 
trine of  its  irritability  controverted, 
407 ;  reflexion  of  impressions  on  the, 
438 

Heat,  animal,  its  production,  421-3 

Herophilus,  his  doctrine  as  to  the 
functions  of  the  brain,  366 

Hippocrates,  his  opinion  as  to  the 
functions  of  the  brain,  365 

Haase  on  the  ganglia,  378 

Hoffman  opposes  the  doctrine  as  to  the 
use  of  the  ventricles  in  preparing  the 
animal  spirits,  370 

Humours,  cause  of  a  more  copious  de- 
rivation to  any  one  part,  408 

Ideas,  their  nature,  440 

Idiosyncrasy,  its  nature,  and  various  ex- 
amples of,  402-5;  dependent  on  a 
change  in  the  vis  nervosa,  402 ;  of 
pregnant  women,  404  ;  a  cause  of  Pica, 
404-5  ;  influence  of  habit  on,  405 

Impressions,  mode  of  their  transmission 
along  nerves,  406 ;  reflexion  of  senso- 
rial into  motor,  in  the  sensorium  com- 
mune, 430;  reflexion  of,  in  the 
gangha,  438 

Inflammation,  its  nature  explained,  417 

Infundibulum,  its  use  according  to 
Lower,  Willis,  &c.,  373 ;  found  hol- 
low by  Murray,  ib. 

Insects  perform  their  functions  by  nerves 
only,  387 

Intellect,  probably  each  division  of,  has 
its  organ  in  the  brain,  447 

Intercostal  nerve,  how  far  impressions 
from  the  brain  and  spinal  cord  reach 
the,  436 

Iris,  the,  how  dilated,  416 

Irritability  of  muscles  dependent  on  their 
nerves,  401 

Klinkosch,  case  by  him,  394 
KoLPiN,  his  theory  of  congestion,  416 

La  Roche,  theory  of  animal  heat,  422 


462 


INDEX  TO  PROCHASKA 


Lancisi,  where  sensation  and  motion 

centered,  by,  577 
Lectures,  Croonian,  415 
LiNNiEus,  case  of,  referred  to,  444 

Malpighi,  his  opinion  on  the  anatomy, 
&c.,  of  the  brain,  374,  375,  389 

Mammae,  erection  of  the  papillae  of  the, 
explained,  416 

Martini  on  the  susceptibility  of  ten- 
dons, 394 

Mayow,  his  opinion  on  the  animal 
spirits,  377 

Meckel  quoted,  377-8 

Memory,  the  nature  of,  441 

Menses,  the  influence  of  the  nerves  on 
the  flow  of,  415 ;  not  dependent  on 
congestion,  ib. ;  caused  by  vis  nervosa, 
416 

Metzger  quoted,  379;  his  promised 
inquiries  into  the  functions  of  the 
brain,  447 

Meyer,  where  the  mental  faculties 
located,  by,  377 

Mind,  three  distinct  faculties  of  the, 
recognised  by  Plato,  365  ;  whether  it 
alone  thinks,  442;  faculties  of,  located 
in  the  brain,  374  ;  influenced  by  vary- 
ing states  of  the  brain,  442 

Movements,  what  properly  termed  ani- 
mal, 448-9 ;  automatic,  ib. 

Murray,  his  anatomy  of  the  infundi- 
bulum,  373 ;  on  the  morbid  sensi- 
bility of  bones,  394 

Muscles,  their  irritability  dependent  on 
the  nerves,  400  ;  theory  of  their  con- 
traction, 413;  the  automatic,  448 

Muscular  action,  the  two  kinds  of,  448  ; 
theory  of,  413 

Musgrave,  theories  of,  as  to  secretion, 
419  ;  as  to  animal  heat,  422 

Nates,  see  Tubercula  Quadrigemina. 

Needham,  quoted,  386 

Nerves,  the,  Galen's  doubts  as  to  their 
function  in  transmitting  the  animal 
spirits,  368 ;  unity  and  use  of  the 
loops  of,  according  to  Willis  and 
others,  376,  377;  their  origin,  &c., 
described,  382 ;  their  medulla  not 
wholly  vascular,  389;  vis  nervosa 
exists  in,  independently  of  the  brain, 
397 — 402  ;  their  action  in  sensation 
and  motion,  406;  on  what  their  pro- 
perty of  receiving  and  transmitting 
impressions  depends,  407  ;  their  oflSce 
as  respects  the  brain  and  muscles,  407, 
408 ;  their  action  on  the  vessels  and 
their  fluids,  408—412;  have  they  the 
property  of  repelling  fluids  ?  417 ;  their 


Nerves  (continued) 
influence  in  secretion,  418 — 421 ;  do 
they  exert  any  influence  in  the  produc- 
tion of  animal  heat  ?  421 — 423 ;  how 
far  necessary  to  nutrition,  423 — 428  ; 
consensus  of,  probably  not  wholly  in 
the  sensorium  commune,  435 

Nervous  system,  what  parts  it  includes, 
381 ;  bibliography  of  its  anatomy,  383 
note;  the  author's  threefold  division 
of,  383  ;  comparative  anatomy  of,  384 ; 
in  some  animals,  does  not  exist,  386  ; 
not  always  necessary  to  sensation  and 
animal  motion,  388 

Newton  on  the  nervous  fluid,  422 

NucK  quoted,  377 

Nutrition,  how  effected,  423—428 ;  ac- 
tion of  the  nisus  formativus  in,  426 

Opium,   experiments   by  Whytt  with, 

396 
Otto  Horstius,  373 

Parencephalis,  a  term  of  Galen,  367 

Passions,  the,  441 

Penis,  its  erection  explained,  416 

Perception,  its  nature,  440 ;  is  a  com- 
pelled act,  441 

PiccoLHOMiNEus  quotcd,  370 

Pineal  gland,  its  use  according  to  Galen 
and  Willis,  368,  376 

Pituitary  gland,  its  use  according  to 
LowER,WiLLis,  Haller,&c., 373,374 

Plato,  recognised  three  distinct  faculties 
of  the  mind,  365  ;  his  opinion  on  the 
brain,  375 

Platner,  his  opinion  on  the  union  of 
body  and  mind,  445,  449 

Polypes,  how  feel  and  move  without  a 
nervous  system,  387  ;  their  irritability 
produced  by  other  mechanism  than 
that  of  muscles,  414 

Preservation,  the,  of  the  individual,  the 
general  law  of  reflexion  of  impres- 
sions, 430 

Recollection,  its  nature,  441 

Reflexion,of  impressions,  in  the  sensorium 
commune,  described,  430 ;  general  law 
of,  ib. ;  illustration  of,  431 ;  indepen- 
dent of  mind  or  consciousness,  432 ; 
in  the  ganglia,  438 

RiOLANUs,  the  son,  defends  the  doc- 
trines of  Galen,  371 

RuYscH,  tries  to  prove  cortex  of  the  brain 
not  glandular,  377 

Schneider,  proves  that  the  ventricles 
of  the  brain  are  not  cloacae,  372  ;  his 
work, '  De  Catarrhis.'  quoted,  372 


ON  THE  NERVOUS  SYSTEM. 


463 


Secretion,  influence  of  the  nerves  in,  418 ; 
Musgrave's  doctrines  on,  419 

Sensorium  commune,  its  functions  and 
seat,  429—432 ;  centre  of  motor  and 
sensorial  nerves,  429 ;  its  law  of 
action,  consensus  of  nerves  in,  433 — 
435 ;  its  function  is  the  reflexion  of 
external  sensory  impressions  of  the 
nerves  upon  the  motor,  429,  430,  431. 

Soul,  the  rational,  seat  of,  according  to 
Aristotle,  365 ;  the  rational  and 
corporeal,  according  to  Willis,  376  ; 
its  union  with  the  body,  439  ;  all  we 
know  of  the,  449 

Spallanzani,  his  remarks  on  animal- 
cules, 386 

Spirits,  three  acknowledged  by  Galen 
and  others,  366 ;  the  animal,  their 
origin  and  seat,  according  to  Galen, 
367,  368 ;  Des  Cartes'  opinion  on 
the  secretion  of,  370  ;  dislodged  from 
the  ventricles  of  the  brain,  370,  371 ; 
said  by  Malpighi,  &c.,  to  be  secreted 
by  the  cortical  substance  of  the  brain, 
374;  their  existence  denied,  378 

Stahlians,  opponents  of  the  animal 
spirits,  379  ;  their  error  as  to  the  soul, 
449 

Tarin  quoted,  378 

Tendons,  morbid  sensibility  of,  394 

Testes,  see  Tubercula  Quadrigemina. 

Thought,  cannot  depend  solely  on  the 
mind,  442;  organs  of  the  faculty  of, 
446 ;  its  acknowledged  depijdence 
upon  the  body,  445 

TissoT,  supports  the  doctrine  of  animal 
spirits,  379;  his  views  as  to  the  ne- 
cessity of  nerves  to  nutrition,  424 ; 
lays  stress  on  "Whytt's  arguments  on 
the  consensus  of  the  nerves,  434 ; 
his  opinion  on  the  functions  of  the 
ganglia,  378,  435 

Tralles  quoted,  396 ;  his  opinion  on 
the  union  of  soul  and  body,  445 

Tubercula  quadrigemina,  their  use  ac- 
cording to  Galen  and  Willis,  368, 
376 

Understanding,  one  of  the  animal  func- 
tions, 439 

Unzer,  J.  A,  value  of  his  doctrines  as  to 
vis  nervosa,  380 ;  on  the  reflexion  of 
impressions  in  the  ganglia,  438 

Ventricles  of  the  brain,  the  use  of  the 
anterior    or    superior,    according    to 


Ventricles  of  the  brain  {continued) 
Galen,  367;  the  animal  functions 
distributed  amongst  the,  by  the  Arabs, 
369 ;  the  animal  spirits  dislodged  from 
the,  370, 371 ;  shown  not  to  be  cloacae, 
372—374 

Verschuir,  his  experiments  on  arteries, 
412;  his  theory  of  the  flow  of  the 
menses,  415 

Vesalius,  a  follower  of  Plato,  366; 
indifi'erent  as  to  the  course  of  the 
animal  spirits,  369 

ViEussENs,  where  the  seat  of  imagina- 
tion placed  by,  377  ;  first  taught  the 
function  of  the  ganglia,  378 ;  where 
placed  the  sensorium  commune,  429; 
his  opinion  on  the  consensus  of  the 
nerves,  433 

Vis  nervosa,  in  what  sense  the  term  is 
used,  380 ;  the  cause  of  the  functions 
of  the  nervous  system,  380;  a  stimulus 
necessary  to  its  action,  389 ;  is  not 
indifferent  to  the  kind  of  stimulus, 
391 ;  how  increased,  391 — 395 ;  in- 
creased locally,  392 ;  when  diminished, 
395 — 397;  action  of  opium  on,  396; 
is  divisible  and  exists  in  the  nerves 
independently  of  the  brain,  397 — 402 ; 
is  the  cause  of  the  heart's  movements, 
399;  its  action  modified  in  idiosyn- 
crasies, 402;  is  a  substitute  for  the 
mind,  446 

Vital  principle,  compounded  of  various 
forces,  427 ;  may  exist  independently 
of  vis  nervosa  in  plants  and  certain 
animals,  428 

Whytt,  his  arguments  on  the  consensus 
of  the  nerves,  377,  435 ;  his  experi- 
ments on  the  nerves,  396 ;  his  doc- 
trines on  consensus  of  the  nerves,  435 

Will,  definition  of  the,  440 

Willis,  his  opinion  on  the  functions 
of  the  brain,  373,  375 ;  and  on  the 
animal  spirits,  375 ;  his  opinion  on 
the  consensus  of  the  nerves,  433 

WiNSLow,  his  doctrine  that  the  ganglia 
are  little  brains,  378 

WiNTERL,  his  conjecture  on  the  nature 
of  the  action  of  nerves  on  the  vessels, 
410 

WiRTENSON,  his  dissertation  on  opium, 
396 

ZiNN  quoted,  378 

Zoophytes,  how  feel  and  move  without  a 
nervous  system,  387. 


THE  END. 


PRINTED  BY  C.  AKD  J.  ADLARD, 

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