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Marine  Biological  Laboratory  Library 


Woods  Hole,  Mass. 


Presented  by 


Dr.   Wm.   Amber son 


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HUMAN   PHYSIOLOGY 


BY 

PROF.  LUIGI  LUCIANI 

TRANSLATED    BY 

FRANCES  A.  WELBY 

WITH    A    PREFACE    BY 

PROF.  J.  X.  LANGLEY,   F.R.S. 
In  5  vols.      Illustrated.      8vo. 

Vol.      I.   Circulation  and  Respiration.     18s.  net. 

Vol.    II.   Internal  Secretion  —  Digestion  —  Excretion  — The 

Skin.     18s.  net. 

Vol.  III.   Muscnlar  and  Nervous  Systems. 
Vols.  IV.  and  V.  [In  the  Press. 

LONDON  :  MACMILLAN  AND  CO.,   LTD. 


HUMAN    PHYSIOLOGY 


MACMILLAN  AND  CO.,   LIMITED 

LONDON  •  BOMBAY  •  CALCUTTA 
MELBOURNE 

THE    MACMILLAN    COMPANY 

NEW    YORK  •  BOSTON  •  CHICAGO 
DALLAS  •  SAN    FRANCISCO 

THE  MACMILLAN  CO.  OF  CANADA,  LTD. 

TORONTO 


HUMAN 
PHYSIOLOGY 


BY 

PROFESSOR   LUIGI    LUCIANI 

DIRECTOR   OF   THE   PHYSIOLOGICAL    INSTITUTE   OF   THE    ROYAL    UNIVERSITY    OF   ROMK 

TRANSLATED    BY 

FEANCES    A.    WELBY 


WITH    A    PREFACE    BY 

J.    K    LANGLEY,    F.E.S. 

PROFESSOR   OF   PHYSIOLOGY    IN   THE    UNIVERSITY   OP   CAMBRIDGE 


IN   FIVE  VOLUMES 
VOL.  Ill 

EDITED    BY 

GORDON  M.  HOLMES,  M.D. 


MUSCULAR  AND  NERVOUS  SYSTEMS 


MACMILLAN   AND    CO.,    LIMITED 
ST.    MARTIN'S    STREET,    LONDON" 

1915 


COPYRIGHT 


NOTE 

THE  third  volume  of  Professor  Luciani's  Human  Physiology, 
which  deals  with  the  muscular  and  nervous  systems,  has  been 
translated  from  the  fourth  Italian  edition,  which  has  appeared 
since  the  publication  of  the  English  translation  of  Vols.  I.  and  II. 

This  edition,  in  which  the  third  and  fourth  volumes  have 
been  enlarged  and  corrected  in  places  by  Professor  Luciaui,  wras 
brought  out  in  1913 — on  which  occasion  a  commemorative  medal 
and  an  album  containing  the  autographs  of  almost  all  the  world's 
most  eminent  physiologists  were  presented  to  the  Author. 

The  English  translation  of  the  preceding  volumes  was  edited 
by  Dr.  M.  Camis,  but  as  he  was  unable  to  act  again  in  this 
capacity  the  Editorship  of  the  present  volume  has  been  under- 
taken by  Dr.  Gordon  Holmes. 

LONDON,  1914. 


CONTENTS 


CHAPTER   I 

PAGE 

GENERAL  PHYSIOLOGY  OF  MUSCLE    .  .  .  .  .1 

1.  Skeletal  muscles  ;  excitability  and  the  conditions  which  regulate 
it.  2.  Curves  of  muscular  contraction.  3.  Theory  of  contraction  in 
tetanus  ;  the  muscle  sound.  4.  Propagation  of  excitatory  wave  along 
the  muscle  on  exciting  with  induced  or  constant  currents.  5.  Minute 
structure  of  striated  muscle  fibres  :  changes  during  contraction.  6. 
Muscular  tone,contracture,  and  capacity  of  muscle  for  active  elongation. 
7.  Chemical  composition  of  muscle  in  rest  and  activity.  8.  Metabolism 
in  muscle  and  sources  of  the  energy  developed.  9.  Muscular  work  and 
muscular  energy.  10.  Heat  production  in  muscle.  11.  Electrical 
changes  during  rest  and  activity.  12.  Origin  of  muscular  activity. 
Bibliography. 


CHAPTER   II 

MECHANICS  OF  LOCOMOTOR  APPARATUS        .  .  .  .96 

1.  General  remarks  on  the  structure  of  the  bones  and  their  articula- 
tions. 2.  Form,  attachments,  and  mechanics  of  muscles  in  relation  to 
bones.  3.  Line  and  centre  of  gravity  of  the  body  in  different  postures. 
4.  Mechanics  of  equilibration  in  different  postures.  5.  Movements  of 
the  body  in  walking.  6.  Movements  of  the  body  in  running.  7.  Move- 
ments of  the  body  in  swimming.  Bibliography. 


CHAPTER   III 

PHONATION  AND  ARTICULATION         .  .  .  .  .129 

1.  General  observations  on  the  fundamental  characters  of  sounds, 
and  their  formation  by  different  musical  instruments.  2.  Structure 
of  larynx  as  a  musical  instrument ;  functions  of  laryngeal  muscles. 

vii 


viii  PHYSIOLOGY 

PAGE 

3.  Nerves  and  centres  of  phonation.  4.  Mechanical  conditions  for  the 
production  of  laryngeal  sounds ;  function  of  different  parts  of  the 
phonatory  system.  5.  Principal  characteristics  of  the  singing  voice. 
6.  Difficulties  and  natural  imperfections  of  singing.  7.  The  vowel 
system  in  phonetic  language.  8.  Theory  of  physical  nature  of  vowel 
tones.  9.  System  of  semivowels  or  sounding  consonants,  middle  conso- 
nants, and  mute  consonants.  10.  Composition  of  syllables  and  words. 
11.  Writing,  or  graphic  language.  Bibliography. 


CHAPTER    IV 

GENERAL  PHYSIOLOGY  OF  THE  NERVOUS  SYSTEM      .  .175 

1.  Structural  elements  of  the  nervous  system.  Theory  of  inde- 
pendent neurones,  or  continuity  of  neuro-fibrils.  2.  Conditions,  laws, 
and  phenomena  of  conduction  in  nerve.  3.  Rate  of  conductivity : 
diphasic  character  of  the  impulse  arousing  it.  4.  Metabolism  of  nerve  : 
electromotive  phenomena  during  rest  and  excitation ;  demarcation 
current,  action  current.  5.  Excitation  of  nerve.  Natural  stimuli  and 
artificial  (chemical,  mechanical,  electrical)  stimuli.  6.  Factors  in  life 
and  death  of  nerve  :  conditions  of  excitability.  7.  Polar  effects  of 
constant  current  (electrotonus)  :  correlative  changes  in  excitability  and 
conductivity.  8.  Excitatory  action  of  electrical  currents.  Laws  of 
excitation.  9.  Theories  as  to  origin  of  neural  activity.  10.  General 
functions  of  nerve-centres.  Ganglion  cells  and  central  fibrillary  net- 
work. Bibliography. 


CHAPTER   V 

SPINAL  CORD  AND  NERVES.  .  .  .278 

1.  Grey  and  white  matter  of  the  spinal  cord.  2.  Extra-  and  intra- 
spinal  nerve-cells  ;  their  connections  with  the  root-fibres  and  tracts 
which  make  up  the  spinal  columns.  3.  Spinal  roots.  Bell-Magendie 
law  of  localisation  of  sensory  and  motor  tracts.  Waller's  law  of 
degeneration  after  section.  4.  Functional  relations  between  afferent 
and  efferent  roots.  5.  Segmental  arrangement  of  spinal  roots.  6. 
Reflex  activity  of  segments  of  cord  ;  shock  after  section  of  cord.  7. 
Short  and  long  spinal  reflexes  ;  laws  of  reflex  spread.  8.  Genesis  of 
spinal  reflexes  ;  central  factors  that  inhibit  or  promote  them.  9.  Tonic 
and  automatic  functions  of  spinal  cord  ;  "  knee-jerk  "  or  patellar  reflex. 
10.  Trophic  functions  of  spinal  cord.  11.  Sensory  functions  and 
Pfliiger's  "  spinal  soul."  12.  Spinal  cord  an  instrument  of  the  brain  ; 
spino-cerebral  and  cerebro-spinal  paths  of  conduction.  13.  Localisation 
of  principal  spinal  centres  ;  phenomena  of  spinal  deficiency  (dogs  with 
amputated  cord,  Goltz).  Bibliography. 


CONTENTS  ix 

CHAPTER    VI 

PAGE 

SYMPATHETIC  SYSTEM  ......     359 

1.  Anatomy  and  histology  of  fibres  and  ganglia  of  sympathetic 
system.  2.  Peripheral  distribution  of  sympathetic  system  to  the 
organs  which  it  innervates.  3.  Physiological  arrangement  of  con- 
stituent parts  of  sympathetic  system  ;  origin  and  course  of  efferent 
iibres.  4.  Origin  and  course  of  afferent  fibres,  o.  Function  of  peripheral 
ganglia.  Bibliography. 

CHAPTER   VII 

THE  MEDULLA  OBLONGATA  AND  CEREBRAL  NERVES  .  .     380 

1.  General  anatomy  of  the  brain  :  the  medulla  oblongata.  2.  Motor 
functions  of  hypoglossus  nerve.  3.  Vago- accessory  group  ;  motor 
functions  of  eleventh  nerve.  4.  Different  functions  of  vagus  nerve. 
5.  The  glosso-pharyngeal  exclusively  a  nerve  of  taste.  6.  Functions  of 
the  facial  and  acoustic  nerves.  7.  Functions  of  the  oculomotor  and 
trigeminal  nerves.  8.  The  medulla  oblongata  as  a  motor  centre.  9. 
The  medulla  oblongata  as  the  central  organ  of  locomotion  and  posture. 
10.  The  medulla  oblongata  as  a  sensory  centre.  Bibliography. 

CHAPTER   VIII 
THE  HIND-BRAIN    .  .  .  .  ...  .419 

1.  Anatomy  of  hind-brain  :  ati'erent  and  efferent  tracts  of  the 
three  cerebellar  peduncles.  2.  Preliminary  observations  on  cerebellar 
functions.  3.  Dynamic  phenomena  immediately  incident  on  removal 
of  cerebellum.  4.  Cerebellar  ataxy  in  dogs  and  monkeys  after  removal 
of  half  the  cerebellum.  5.  Cerebellar  ataxy  after  total  removal  of 
cerebellum.  6.  Cerebellar  ataxy.  7.  The  cerebellum  as  the  centre  of 
equilibrium ;  8.  And  the  co-ordinating  organ  of  voluntary  movements-; 
9.  And  the  organ  of  subconscious  sensations,  exercising  constant 
reinforcing  action  upon  the  other  nerve-centres.  10.  Localisation  of 
cerebellar  'functions.  Bibliography. 

CHAPTER   IX 

MID-BRAIN  AND  THALAMENCEPHALON  .  .  .  .486 

1.  General  structure  of  the  mesencephalon.  2.  The  thalamen- 
cephalon.  3.  Effects  of  total  extirpation  of  fore-,  inter-,  and  mid- 
brain  in  fishes ;  4.  In  amphibia  ;  5.  In  birds  ;  6.  In  mammals.  7. 
Effects  of  stimulating  the  mesencephalon.  8.  Effects  of  extirpating 
the  corpora  quadrigemina  alone.  9.  Effects  of  dividing  the  whole  or 
half  the  brain  stem  at  level  of  the  mid-brain.  10.  Effects  of  incom- 
plete or  total  removal  of  optic  thalami.  Bibliography. 


x  PHYSIOLOGY 

CHAPTER   X 

PAGE 

THE  FORE-BRAIN     .  .  .  .  .526 

1.  General  anatomy  of  telencephalon.  2.  Structure  of  the  cerebral 
cortex  or  pallium.  3.  History  of  cerebral  localisation.  4.  Excitable 
zone  of  the  cerebral  cortex  ;  localisation  in  dog,  monkey,  man.  5. 
Physiological  analysis  of  motor  reactions  of  cerebral  cortex.  6.  Inhibi- 
tory reactions.  7.  Organic  reactions  of  cortical  origin.  8.  Epilepsy 
from  cortical  excitation.  9.  The  sensory-motor  area,  deduced  from 
effects  of  partial  or  total  destruction  of  excitable  cortex.  10.  Functions 
of  basal  ganglia  or  corpora  striata  (caudate  and  lenticular  nuclei). 
11.  Visual  area.  12.  Auditory  area.  13.  Olfactory  and  gustatory 
areas.  14.  Association  areas  ;  division  of  cortex  into  thirty-six  areas, 
according  to  Flechsig's  embryological  method.  15.  Physiological  analysis 
of  speech  disorders  of  cerebral  origin.  16.  General  theory  of  the 
psycho- physical  functions  of  the  brain.  Bibliography. 

INDEX  OF  SUBJECTS     .  .  .  .  .  .637 

INDEX  OF  AUTHORS  651 


EEEATA 

Page    24,  par.  4,  line    5,  for  " idea- muscular"  read  " idio-muscular." 
,,       38,    ,,     3,     ,,      6,  for    "  zanthine,    hypozanthine "   read   "  xanthine,    hypo- 

xanthine." 

,,     102,    ,,     3,     ,,      5,  for  "  hypoglossus  "  read  "  hyoglossus. " 
,,     130,    ,,     4,     ,,      6,  for  "phonation  (speech)  "  read  "phonation  (voice)." 
,,     144,    ,,     2,     ,,    14,  for  "pitch  "  read  "timbre." 
,,     345,  Fig.  192,  for  "dorsal"  read  "thoracic  vertebra." 
,,     349,    ,,     5,    ,,      2,  for  "controlateral"  read  "contralateral." 
,,     510,    ,,     3,     ,,      3,  for  "  Macacus  rheus"  read  "  Macacus  rhesus. " 
,,     514,    ,,     5,     ,,      1,  for  "  opistothonus  "  read  "  opisthotonus." 


CHAPTEE   I 

GENERAL   PHYSIOLOGY   OF   MUSCLE 

CONTENTS. — 1.  Skeletal  muscles;  excitability  and  the  conditions  which 
regulate  it.  2.  Curves  of  muscular  contraction.  3.  Theory  of  contraction  in 
tetanus  ;  the  muscle  sound.  4.  Propagation  of  excitatory  wave  along  the  muscle 
on  exciting  witli  induced  or  constant  currents.  5.  Minute  structure  of  striated 
muscle  fibres  ;  changes  during  contraction.  6.  Muscular  tone,  contracture,  and 
capacity  of  muscle  for  active  elongation.  7.  Chemical  composition  of  muscle  in 
rest  and  activity.  8.  Metabolism  in  muscle  and  sources  of  the  energy  developed. 
9.  Muscular  work  and  muscular  energy.  10.  Heat  production  in  muscle. 
11.  Electrical  changes  during  rest  and  activity.  12.  Origin  of  muscular  activity. 
Bibliography. 

FROM  the  physiological  standpoint  the  higher  animal  organism 
may  be  treated  as  a  system  of  blood-forming  organs,  at  the  service 
of  a  sensory-motor  system.  The  first  of  these — the  vegetative  or 
involuntary  system — subserves  the  internal  life  of  the  body,  and 
its  function  is  to  prepare  and  keep  approximately  constant  the 
mass  and  constituents  of  the  blood  and  lymph  which  provide  the 
common  nutriment :  the  second — the  organic  or  voluntary  system- 
subserves  the  phenomena  of  external  life,  and  maintains  and  regu- 
lates the  relations  between  the  organism  and  its  environment. 

But  this  distinction,  proposed  by  Xavier  Bichat,  has  little 
intrinsic  value,  however  useful  it  may  be  in  the  classification  of 
functions.  The  two  systems  do  not  constitute  two  separate 
organisms,  like  the  two  primitive  layers  of  the  blastoderm,  but 
form  a  single  complex  indivisible  organism,  in  which  the  specific 
functions  of  both  systems  are  sharply  differentiated  and  localised. 
Bones,  tendons,  and  other  forms  of  connective  tissue  participate 
in  the  structure  of  the  organs  and  mechanisms  of  animal  life,  and 
although  they  remain  passive  during  the  activity  of  the  muscles 
and  nervous  system  they  make  the  functions  of  the  latter  possible, 
and  are  thus  important  constituents  of  the  sensory-motor  system. 
On  the  other  hand  motor  and  sensory  elements  contribute  to 
the  structure  of  the  organs  and  systems  of  vegetative  life  ;  among 
the  former  are  amoeboid  cells,  ciliated  epithelia  and  muscle 
fibres,  among  the  latter  not  only  the  nerve  plexuses  of  the 
VOL.  in  1  B 


2  PHYSIOLOGY  CHAP. 

sympathetic,  but  also  the  nerve-paths  and  centres  of  the  cerebro- 
spinal  system. 

Nevertheless  the  muscular  and  nervous  elements  which  play 
a  direct  part  in  the  functions  of  vegetative  life  have  usually 
certain  morphological  and  functional  characters  which  distinguish 
them  from  those  which  make  up  the  organs  of  animal  life,  and 
regulate  the  relations  of  the  organism  with  the  external  world  :— 

(a)  Voluntary  or  skeletal  muscles  are  almost  always  striated ; 
involuntary  muscles,  i.e.  those  of  vegetative  life,  are  almost  always 
non-striated. 

(&)  The  former  are  controlled  by  the  will,  and  only  come  into 
play  in  response  to  nervous  impulses ;  the  latter  are  nearly  always 
independent  of  the  will,  and  may  even  function  independently 
of  the  central  and  peripheral  nervous  systems. 

(c)  The  voluntary  muscles  consist  of  long  fibres,  grouped  into 
large  masses,  each  of  which  is  an  anatomical  unit ;  the  involuntary 
fibres,  which  are  not  grouped  into  separate  muscles,  almost  always 
form  smooth  layers  that  line  vessels  or  tubes,  or  constitute  sheaths 
that  surround  certain  special  cavities. 

(f/)  Finally  (and  this  appears  the  most  important),  the  first 
are  almost  always  skeletal  muscles,  attached  by  tendons  to  bony 
levers,  by  which  they  can  lift  weights  and  overcome  resistance, 
i.e.  perform  actual  mechanical  work ;  the  second,  on  the  con- 
trary, are  nearly  all  visceral  muscles,  and  perform  work  that  is 
entirely  confined  to  the  interior  of  the  body. 

The  nerves  that  control  the  involuntary  system,  again,  present 
certain  characters  which  distinguish  them  from  those  that 
innervate  the  voluntary  muscles.  The  latter  consist  of  medullated 
fibres  which  come  directly  from  the  spinal  roots ;  the  former  are 
exclusively  non-medullated,  and  come  principally  from  the  sym- 
pathetic system,  and  make  at  the  periphery  an  exceedingly  fine 
fibrillary  network  which  surrounds  the  separate  muscle  cells. 

I.  The  skeletal  muscles  constitute  the  principal  mass  of  the 
body.  Each  muscle  is  an  anatomical  unit,  a  separate  organ, 
which  can  assume  the  most  various  shapes  and  sizes,  but  usually 
consists  of  an  elongated  mass  provided  with  tendons  by  which 
it  is  attached  to  the  skeleton.  Each  muscle  consists  of  fibres 
which  are  generally  arranged  parallel  to  its  long  axis,  and  converge 
more  or  less  towards  the  tendinous  attachments.  The  muscle 
fibres  are  united  into  bundles  of  varying  size  by  connective 
tissue,  which  is  connected  with  the  sheath  or  perimysium  that 
surrounds  the  whole  muscle ;  the  blood  and  lymph  vessels  and 
the  nerves  run  through  this  connective  tissue. 

The  length  and  the  diameter  of  the  muscle  fibres  vary  con- 
siderably. On  an  average,  the  length  does  not  exceed  30-40  mm., 
but  according  to  some  authors  it  may  reach  30  cm.  The  diameter 
varies  considerably  even  in  the  same  muscle,  and  still  more  in 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  3 

different  muscles,  as  it  ranges  from  O'l  to  O'Ol  mm.  The  fibres  are 
cylindrical  or  prismatic  in  form,  with  rounded  angles  and  conical 
ends.  They  consist  of  a  striated  substance  of  soft  consistency 
(the  structure  of  which  we  shall  presently  examine)  enclosed  in 
a  tubular,  apparently  homogeneous  elastic  sheath,  called  the 
sarcolemma;  this  is  continued  at  both  ends  of  the  fibre  into 
connective  tissue  fibrils,  which  join  the  tendon  or  the  septa  of 
the  perirnysium. 

The  muscle  fibres  alone  become  active  when  the  muscle 
contracts  ;  the  sarcolemma,  the  connective  tissue  of  the  perimysium 
and  its  intermuscular  septa,  and  the  tendons  remain  passive. 
During  contraction  each  fibre  pulls  upon  the  tendon,  either 
directly  or  by  means  of  the  interfascicular  connective  tissue 
which  is  continued  into  the  tendon. 

Each  muscle  has  rnedullated  and  non-medullated  nerve  fibres ; 
the  former  innervate  its  fibres,  the  latter  the  walls  of  the  blood- 
vessels :  every  muscle  fibre  is  provided  with  at  least  one  nerve 
fibre,  which  usually  forms  an  end-plate  near  its  middle. 

Under  normal  conditions  the  skeletal  muscles  are  thrown 
into  activity  by  their  nerves,  and  after  section  of  these  all  move- 
ment of  the  muscle  is  arrested ;  this  indicates  that  neither  the 
muscles  nor  the  nerves  by  which  they  are  innervated  are  capable 
of  automatic  activity.  But  after  dividing  the  nerve  and  exposing 
the  muscle  an  effective  mechanical,  thermal,  chemical  or  electrical 
stimulus,  applied  either  to  the  nerve  or  directly  to  the  muscle, 
evokes  a  contraction  of  the  latter  in  response ;  so  that  both 
nerves,  when  severed  from  their  centre,  and  voluntary  muscles 
manifest  irritability  or  excitability,  i.e.  a  power  of  reacting  by  an 
explosion  of  energy  to  external  impulses  (Vol.  I.  p.  44).  The 
active  reaction,  or  contraction,  of  the  muscle  is  expressed  in  its 
rapid  change  of  form  and  displacement ;  excitation  of  the  nerve, 
on  the  contrary,  is  not  accompanied  by  any  direct  visible  change, 
and  consists  solely,  as  we  shall  see,  in  a  molecular  vibration,  by 
which  the  excitatory  impulse  is  transmitted  to  the  muscle. 

Since  the  natural  excitation  of  a  muscle  is  always  the  effect 
of  an  excitation  through  its  nerve,  it  is  legitimate  to  assume  that 
the  reaction  produced  artificially  by  its  direct  stimulation  is  also 
due  to  stimulation  of  the  nerve  fibres  that  run  between  the 
muscle  bundles.  Many  authors,  from  Borelli  and  Willis  onwards, 
have  regarded  the  muscles  as  the  passive  instruments  of  the 
nerves,  though  A.  Haller  maintained  the  opposite  view  in  his 
famous  theory  of  muscular  irritability,  which  was  based  on 
fallacious  arguments  (Vol.  I.  p.  299).  Although  Haller's  view 
has  now  only  an  historical  interest,  it  is  instructive  to  sum  up 
briefly  the  most  striking  arguments  that  were,  and  still  might  be, 
adduced  in  support  of  the  theory  of  direct  or  autonomous  excita- 
bility of  the  voluntary  muscles. 


4  PHYSIOLOGY  CHAP. 

In  1841,  Longet  resorted  to  a  very  simple  method  of  deciding 
the  question,  by  cutting  the  nerves  to  a  limb  of  a  mammal,  and 
testing  the  direct  and  indirect  excitability  of  its  muscles,  at 
various  intervals  after  the  operation.  He  found  that  the  nerves 
lost  their  excitability  to  all  stimuli  (mechanical,  chemical, 
electrical)  after  the  fourth  day ;  while  the  muscles  to  which  these 
nerves  were  distributed  reacted  to  direct  stimulation  as  long  as 
twelve  weeks  after  the  operation.  To  this  argument  in  favour 
of  autonomous  muscular  excitability  it  was  objected  that  the 
degeneration  and  loss  of  excitability  in  the  nerve  is  propagated  in 
a  centrifugal  direction,  i.e.  from  the  point  of  section  towards  the 
nerve-endings,  and  that  the  end-plates  might  consequently  retain 
their  excitability  after  total  degeneration  of  the  corresponding 
fibres.  Microscopical  investigation,  however,  shows  that  the  small 
muscular  nerves  are  already  altered  eight  to  ten  days  after  the 
section,  and  it  would  therefore  be  illogical  to  suppose  that  the 
end-plates  can  remain  intact  several  months  longer.  Clinical  ob- 
servations confirm  this  fact ;  the  muscles  of  the  face,  for  instance, 
preserve  their  direct  excitability  several  years  after  the  facial 
nerve  has  been  paralysed  (C.  Richet). 

Another  more  effective  method  of  showing  that  muscular 
excitability  is  independent  of  the  corresponding  nerves  was  dis- 
covered in  1850  by  Cl.  Bernard,  and  almost  simultaneously  by 
Ko'lliker.  The  strongest  stimuli  applied  to  the  nerves  of 
animals  paralysed  by  curare  are  unable  to  excite  any  contraction 
of  the  skeletal  muscles ;  but  the  muscles  preserve  their  direct 
excitability.  Curare  neither  paralyses  the  sensory  nerves  nor 
the  nerve-centres,  its  paralysing  action  being  limited  (except 
with  excessive  doses)  to  the  motor  nerve -endings.  In  fact,  if 
the  sciatic  nerve  of  a  frog  is  exposed  on  the  right  side,  and  that 
leg,  leaving  out  the  sciatic,  is  ligatured,  and  curare  is  then  injected 
under  the  skin  of  the  back,  the  right  leg  reacts  when  its  sciatic 
nerve  is  stimulated ;  but  when  the  left  sciatic  is  stimulated  no 
reaction  of  the  muscles  on  that  side  is  obtained  because  the  poison 
has  been  circulating  through  them,  while  there  are  reflex  move- 
ments from  the  right  leg.  The  section  of  a  motor  nerve  abolishes 
excitability  from  the  point  of  section  to  the  periphery,  but  the 
toxic  action  of  curare  begins  by  paralysing  the  motor  end-plates, 
and  then  extends  centripetally  along  the  nerve.  Curare  does  not 
therefore  alter  the  excitability  of  the  muscle  perceptibly  (at  any 
rate  in  small  doses  and  in  the  early  stages  of  its  action),  but  it 
paralyses  motor  nerves,  by  abolishing  the  conductivity  of  the  motor 
end-plates,  and  thus  interrupts  the  normal  link  between  the  nerve 
and  its  muscle. 

A  simpler  and  no  less  conclusive  argument  was  brought 
forward  by  Kiihne  (1859).  He  observed  that  the  sartorius  muscle 
of  the  frog  has  no  nerve  fibres  near  its  end,  for  about  ^  of  its 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  5 

total  length.  Yet  the  muscle  reacts  by  a  twitch  if  it  is  stimulated 
by  pinching  it  with  forceps  at  a  point  at  which  there  are  no  nerve 
fibres. 

Another  sound  argument  for  the  autonomous  excitability  of 
muscle  is  the  so-called  idio-  muscular  contraction  observed  by 
Schiff.  This  is  seen  in  fatigued  or  degenerating  muscle,  in  which 
conductivity  is  lowered.  On  stroking  the  exposed  muscle  obliquely 
to  the  direction  of  its  fibres  with  a  blunt  object,  or  tapping  it 
with  a  scalpel,  a  ridge  of  contraction  appears  at  the  point  of 
contact.  This  is  obviously  a  local  muscular  reaction,  independent 
of  the  nerve. 

These  direct  arguments  for  the  independent  excitability  of 
voluntary  muscles  are  confirmed  by  observations  which  demonstrate 
the  automatic  and  reflex  excitability  of  involuntary  muscle  fibres. 
(See  Vol.  I.  pp.  305-12.) 

Muscular  excitability,  independent  of  the  nerves,  is  controlled 
by  the  circulation  which  supplies  the  muscle  with  the  nutrient 
material  and  oxygen  indispensable  to  its  metabolism,  and  removes 
the  waste  products  as  fast  as  these  accumulate.  Nicolas  Stensen 
(1687)  first  observed  that  after  tying  the  abdominal  aorta  in 
mammals  paralysis  of  the  posterior  limbs  rapidly  set  in,  and  dis- 
appeared again  if  the  artery  were  reopened  after  a  short  period. 
In  this  experiment,  however,  the  paralysis  depends  not  only  on  the 
fall  of  muscular  excitability,  but  also  on  the  anaemia  of  the  lumbar 
cord  which  is  supplied  by  the  aorta  (Schiffer).  If  instead  of  the 
aorta  the  iliac  and  crural  arteries  of  one  limb  are  tied,  the  ex- 
citability of  the  muscles  cut  off  from  the  .circulation  survives  for 
many  hours  (Brown -Sequard) ;  as  the  vitality  of  the  muscle 
diminishes  it  shortens,  and  finally  becomes  rigid  (rigor  mortis). 
If  the  circulation  is  re-established  before  the  onset  of  complete 
rigor,  the  excitability  of  the  muscles  may  be  recovered. 

Brown-Sequard  demonstrated  by  a  long  series  of  experiments 
that,  after  death,  excitability  persists  for  a  longer  or  shorter  time 
in  different  muscles  of  the  same  animal ;  that,  generally  speaking, 
it  survives  longer  if  the  external  temperature  is  low,  although  the 
contrary  has  been  affirmed ;  and  that  the  longer  the  muscles  pre- 
serve their  excitability  after  death,  the  longer  are  they  capable 
of  recovering  it  on  the  artificial  circulation  of  arterial  blood. 

Claude  Bernard  stated  that  during  muscular  contraction  in 
the  living  animal  the  blood  flowing  away  from  the  muscles  is 
highly  venous.  Ludwig  further  observed  that  during  tetanisation 
of  the  muscles  of  any  limb,  by  stimulation  of  its  nerves,  the  flow 
of  blood  from  the  muscle  was  accelerated,  owing  to  the  active 
dilatation  of  the  vessels.  Chauveau  noted  an  acceleration  of  the 
circulation  in  the  masticator  muscles  of  calves  during  mastication, 
which  was  due  not  only  to  nervous  influence  but  also  to  the  active 
dilatation  of  the  muscular  vessels,  and  to  the  impetus  given  to  the 


6  PHYSIOLOGY  CHAR 

venous  stream  by  each  contraction  of  the  muscles.  But  in  curar- 
ised  animals  also  direct  excitation  of  the  muscles  dilates  the 
vessels  and  may  produce  minute  capillary  extravasations  owing  to 
excess  of  tension. 

The  nutrition  of  the  muscles,  and  indirectly  their  excitability, 
also  depend  on  the  trophic  influence  continually  exercised  upon 
them  by  the  nervous  system.  After  cutting  the  motor  nerves  the 
muscles  degenerate  as  well  as  the  peripheral  end  of  the  nerves 
severed  from  their  centre.  Their  excitability  falls  in  the  first  three 
or  four  days,  but  then  rises  to  mechanical  and  galvanic  excitation 
(Erb's  reaction  of  degeneration^),  while  it  decreases  still  further  to 
faradic  stimulation;  after  seven  weeks  muscular  excitability  is  much 
reduced,  and  within  six  to  seven  mouths  it  has  disappeared.  During 
the  first  week  after  section  fibrillary  contractions  are  observed  in 
the  degenerating  muscle,  which  are  due  to  the  excitation  of  the 
contractile  elements  by  intrinsic  chemical  changes  (Schiff). 

Use  and  disuse  again  have  great  influence  upon  the  nutrition, 
and  thus  upon  the  excitability  and  work-capacity,  of  muscle.  It 
is  a  common  observation  that  exercise  develops  and  strengthens 
the  muscles,  while  disuse  and  a  sedentary  life  render  them  weak 
and  flabby.  Absolute  enforced  rest  causes  the  muscles  in  time  to 
degenerate  and  atrophy. 

II.  The  physiology  of  muscle  was  not  really  known  till  after 
the  ingenious  researches  of  E.  Weber  (1846)  on  the  relations 
between  contractility  and  elasticity  ;  and  till  Helinholtz  (1850-52) 
applied  the  graphic  method  to  its  study  by  means  of  his  myograpli, 
which  traces  the  entire  curve  of  a  muscular  contraction  (myogram) 
and  indicates  the  exact  moment  of  the  application  of  the  stimulus 
to  the  nerve  or  to  the  muscle. 

A  Myograpli  is  an  apparatus  designed  to  show  by  a  tracing  on  a  smoked 
plate  or  revolving  cylinder  the  changes  in  length  (or  thickness)  which  a 
muscle  undergoes  during  excitation,  i.e.  the  active  state  into  which  it  is 
thrown  as  the  effect  of  .stimulation. 

There  are  a  great  variety  of  these  instruments,  invented  by  the  different 
authors  who  have  occupied  themselves  with  the  mechanical  functions  of  the 
muscles.  One  of  the  oldest  is  that  of  Pfliiger,  which  again  is  only  a  simpli- 
fication of  the  original  rnyograph  devised  by  Helmholtz.  Pfliiger's  apparatus 
(Fig.  1)  consists  of  an  arm  LL  which  moves  round  a  horizontal  axis,  and  can 
be  brought  into  equilibrium  by  the  counterpoise  C.  The  other  end  of  the  arm 
is  fitted  witli  a  lever,  which  also  rotates  round  an  axis  and  ends  in  a  metal 
point  P,  which  writes  on  a  moving  smoked  plate  or  drum  that  can  be  rotated 
at  varying  speeds.  The  writing-point  is  kept  in  contact  with  the  recording 
surface  by  a  small  weight  or  spring,  but  can  be  drawn  back  by  a  thread 
fastened  to  the  wheel  c.  A  freshly  excised  muscle  is  clamped  at  the  top,  and 
attached  below  by  a  thread  and  hook  to  the  middle  of  the  lever.  Below  the 
point  at  which  the  muscle  is  attached  is  a  small  scale-pin  />,  on  which  different 
weights  can  be  placed  to  examine  the  influence  of  different  loading  on  the 
contractility  of  the  muscle.  The  latter  is  kept  moist  in  a  glass  chamber  con- 
taining a  little  wet  filter  paper. 

Instruments  of  this  class  give  an  imperfect  record  because  the  myograms 


GENEEAL  PHYSIOLOGY  OF  MUSCLE 


do  not  correspond  with  the  true  movements  of  the  excited  muscle.  Owing, 
to  the  weight  of  the  lever  and  the  distance  from  the  axis  of  the  load  appliec 
to  the  muscle,  tin-  entire  mass 
is  accelerated  on  the  rapid  con- 
traction of  the  muscle,  and  the 
curve  altered,  because  the  ten- 
sion in  the  muscle  due  to  the 
load  is  greater  at  first,  and  then 
gradually  diminishes  —  instead 
of  being  constant.  To  avoid  this 
the  mass  raised  by  the  muscle 
and  the  height  to  which  it  is 
lifted  must  be  lessened,  so  as 
to  obviate  changes  of  tension 
during  the  contraction.  This 
is  done  by  using  a  very  light- 
lever,  and  making  the  height 
to  which  the  weight  is  raised 
as  small  as  possible  by  attach- 
ing it,  close  to  the  fulcrum,  to 
a  thread  which  passes  over  a 
wheel  fixed  at  the  axis  of  the 
lever.  By  this  arrangement 
the  acceleration  imparted  to 
the  weight  becomes  negligible, 
no  matter  how  rapid  and  ample 
the  movement  of  the  lever,  and 
the  passive  tension  of  the  muscle 
remains  constant  throughout 
the  experiment. 

Fig.  2  (which  is  only  a  modi- 


FIG.  1.— Pfliiger's  myograph.     Explanation  in  text. 


fication  of  Waller's  myograph)  gives  one  of  many  that  have  been  constructed 
on  this  principle.      It  is  adapted  to  show  on  the  same  muscle  the  effects 


FIG.  2. — Myograph  for  comparing  direct  and  indirect  excitation  on  the  same  muscle — loaded  or 
unloaded.  (Luciani.)  The  frog's  gastrocnemius  muscle  is  fixed  horizontally  over  the  surface 
nf  the  mercury  contained  in  a  hollow  of  the  cork  plate.  It  is  connected  by  a  thread  with  a 
jointed  lever  II,  the  axis  of  which  carries  a  small  wheel ;  a  thread  passes  round  this  to  hold 
the  scale-pan  for  the  weight  ji,  which  is  to  load  the  muscle.  The  vertical  arm  of  the  aluminium 
lever,  cm  which  the  muscle  pulls  directly,  works  the  movements  of  the  much  longer  horizontal 
arm,  which  consists  of  a  straw  ending  in  a  writing-point,  by  which  the  movement  is  traced 
on  a  revolving  cylinder.  The  relations  between  the  two  arms  can  be  easily  adjusted.  The 
electrodes  from  the  secondary  coil  of  an  induction  apparatus  can  be  applied  by  a  Pohl's 
commutator  without  cross-wires  to  the  muscle  or  the  nerve,  according  as  the  bridge  is  thrown 
over  to  the  left  M,  or  right  N. 

not  only  of  direct   and   indirect  excitation,  but   also  of  different  weights 
applied  to  the  muscle,  from  the  minimal  load  of  a  fine  straw  employed  as 


8 


PHYSIOLOGY 


CHAP. 


the  lever  to  progressively  increasing  weights  suspended  from  the  thread  and 
wheel  at  the  axis. 

The  errors  inseparable  from  the  use  of  a  lever  (inertia,  etc.)  have  more 
recently  been  eliminated  by  employing  the  photographic  method  (Blix,  1895  ; 

Brodie  and  Richardson,  1897 ;  Lucas, 
1903,  etc.)  The  principle  is  that  the 

contracting     muscle     deflects    a    small 

I  Te^V  §  IL£ — ^"X.        mirror,  from  which  a  beam  of  light  is 

reflected  on  to  a  travelling  sensitive 
surface  so  that  the  movement  of  con- 
traction is  photographed. 

The  myograms  best  suited  for 
analysis  and  study  are  those  ob- 
tained from  "  nerve -muscle  pre- 
parations "  of  the  frog  or  other 

Fio.   3.— Frog's    nerve -muscle    preparation.      Cold-blooded    animal,  ill  which    the 

muscle;    n,  sciatic    excitability    of    the    nerves    and 


t.a. 


nerve,  with  all  the  branches  cut  except 
that  to  the  muscle  ;  /,  femur  ;  p,  clamp  to 
fix  upper  end  of  muscle  with  femur  ;  (.a., 
tenclo  Achillis  with  hook  to  attach  lower 
end  of  muscle  to  myograph  ;  c.s/i.,  extreme 
end  of  spinal  cord. 


muscles    lasts    much    longer   than 
in  warm-blooded  animals  (Fig.  3). 
Whatever    the    nature   of   the 
stimulus  applied  to  the  muscle  or 

its  nerve,  the  contraction  which  is  recorded  by  the  myograph  may 

assume  the  form  of  a  twitch  or  of  tetanus.     The  twitch  is  the 

simplest  and  most  rapid  form  of  muscular  contraction ;  tetanus  is 

a  more  complex  and  persistent  contraction  which  results  from  the 

fusion  of  a  greater  or  less  number  of  twitches  in  rapid  succession. 
Fig.  4  gives  the  myogram  of  a  simple  twitch,  obtained  on  the 

momentary  stimulation  of  the   frog's  gastrocneinius  by  a   break 

shock  from   the  secondary  coil  of  an  induction   apparatus.      In 

order   to    determine    the    exact   moment   at  which   the    shock    is 

thrown   into    the  muscle    the 

recording  cylinder  itself,  at  a 

certain  point  of  its  revolution, 

is  arranged  to  open  a  contact 

(Helmholtz),  or  else  an  electric 

signal  which  is  interposed  in 

the  circuit   marks   the    exact 

moment   of  stimulation   upon 

the  recording  surface  (Marey 

and  others). 

In   Fig.   4   three    different 

periods  can  be  distinguished:— 

(a)  The    interval    a    b,   in 

which  no  visible  change  takes  place  in  the  muscle ;  this  is  the 
time  lost  between  the  application  of  the  stimulus  and  the  com- 
mencement of  the  contraction,  which  Helmholtz  termed  the  period 
of  latent  excitation  or  latent  period. 

(b)  The  interval  b  c,  during  which  the  muscle  shortens,  at  first 


PIG.  4. — Myogram  of  contraction  of  frog's  gastm- 
cnemius.  Time  tracing  from  tuning-fork,  giving 
10U  vibrations  per  second,  n,  li,  latent  period  ; 
li,  <•,  phase  of  contract-ion  ;  <•,  d,  phase  of  re- 
laxation. 


GENERAL  PHYSIOLOGY  OF  MUSCLE  9 

slowly,  then  more  rapidly,  then  more  slowly  again,  which  repre- 
sents the  contraction  period. 

(c)  The  interval  c  d,  during  which  the  muscle  relaxes  and 
lengthens,  slowly  at  first,  then  more  rapidly,  then  again  slowly, 
which  is  the  expansion  or  elongation  period. 

According  to  Helmholtz'  first  results  the  latent  period  in  the 
voluntary  muscles  of  the  frog  is  about  O'Ol  sec.,  but  later  work  has 
shown  it  to  be  much  shorter.  According  to  Yeo  it  is  0'005  sec. ; 
according  to  Burdou-Sanderson  0'0025  sec. ;  lastly,  according  to 
Tigerstedt  (who  made  many  comparative  experiments  on  the 
frog's  gastrocnemius  under  a  variety  of  conditions)  it  varies  between 
0-004  to  0-006  sec,,  but  is  generally  (41  per  cent)  0'005  sec. 

From  the  theoretical  standpoint  it  is  more  than  probable  that 
there  is  really  no  appreciable  interval  between  the  direct  stimula- 
tion of  a  muscle  and  the  commencement  of  contraction,  and  that 
the  apparent  latency  of  excitation  depends  on  the  fact  that  the 
contraction  does  not  begin  simultaneously  throughout  the  mass  of 
the  muscle,  but  advances  gradually  like  a  wave,  so  that  the  fibres 
which  first  contract  pull  upon,  and  passively  extend,  the  fibres 
that  have  not  yet  contracted,  and  thus  nullify  the  mechanical 
effect.  It  is  only  when,  with  the  advance  of  the  contraction  wave, 
the  active  shortening  of  the  mass  of  muscle  exceeds  its  passive 
elongation  that  the  lever  attached  to  the  muscle  begins  to  rise 
from  the  abscissa  (Gad). 

Apart  from  the  latent  period,  the  active  reaction  or  excitation 
of  the  muscle  consists  in  a  diphasic  process,  with  distinct  phases 
of  contraction  and  of  expansion,  which  may  vary  considerably 
under  different  circumstances.  For  instance  :— 

(it)  Tracings  of  a  muscle  twitch  vary  considerably  in  the 
duration  or  velocity  of  the  total  movement  and  that  of  the  two 
separate  phases,  according  to  the  character  of  the  muscles  which 
are  under  observation.  As  regards  speed  of  reaction,  there  is  an 
enormous  difference  between  the  plain  muscles,  which  react  so 
slowly  that  both  phases  are  visible  to  the  eye,  and  the  striated 
muscles,  which  react  so  quickly  that  the  graphic  method  is  indis- 
pensable for  their  demonstration.  The  cardiac  muscle  cells  come 
midway  as  regards  rate  of  response  between  the  unstriated  visceral 
and  the  striated  skeletal  muscles.  The  duration  of  the  contraction 
of  skeletal  muscles  is  variable,  not  only  in  the  muscles  of  different 
animals,  but  even  in  the  different  muscles  of  the  same  animal. 

Contraction  is  most  rapid  in  insects,  less  rapid  in  birds,  slower 
still  in  mammals  (about  O'l  sec.  on  an  average),  slowest  of  all  in 
the  cold-blooded  animals,  especially  in  the  tortoise. 

Eauvier  (1874)  first  noted  that  in  certain  birds  and  mammals 
two  kinds  of  muscles  can  be  distinguished,  red  and  pale,  and  that 
the  latter  contract  more  rapidly  than  the  former,  an  important 
fact  subsequently  confirmed  by  other  experimenters. 


10  PHYSIOLOGY  CHAP. 

According  to  Griitzner  (1883)  each  muscle  contains  rapidly 
contracting  and  slowly  contracting  fibres,  which  cannot  always  be 
distinguished  by  their  colour.  Speaking  generally,  he  holds  that 
the  latter,  which  are  less  excitable  and  less  easily  fatigued,  are 
richer  in  sarcoplasm,  darker  and  thinner ;  the  former,  on  the 
contrary,  are  more  excitable  and  more  easily  fatigued,  less  rich  in 
sarcoplasm,  lighter  and  thicker.  Easier  (1904-5),  in  Griitzner's 
laboratory,  afterwards  confirmed  and  extended  these  researches. 

Paukul  (1904),  who  examined  the  forms  of  twitch  from  almost 
every  muscle  of  the  rabbit,  came  to  the  conclusion  that  the 
different  modes  of  contraction  depend  on  the  arrangement  of  the 
muscle  fibrils  and  the  intervening  sarcoplasm ;  those  muscles  in 
which  fibrils  lie  uniformly  and  are  surrounded  by  little  sarcoplasm 
contract  rapidly,  while  those  in  which  the  fibrils  are  arranged  in 


FIG.  5. — Influence  of  temperature  on  amplitude  of  muscular  contraction.  (A.  D.  Waller.)  1,  con- 
traction of  normal  gastrocnemius  ;  2,  of  same  muscle,  slightly  cooled  ;  3,  of  same  muscle,  much 
cooled. 

groups  and  separated  by  a  large  amount  of  sarcoplasm  contract 
more  slowly. 

(6)  Temperature,  either  higher  or  lower  than  the  normal,  has 
a  marked  influence  upon  the  course  of  the  muscular  contraction. 
Cooling  always  lengthens  the  contraction,  and  raises  its  height 
when  the  degree  of  cooling  is  moderated,  but  lowers  it  if  more 
marked  (Fig.  5).  Warming  constantly  accelerates  contraction 
and  increases  its  height  when  moderate  in  degree,  but  lowers  it 
when  more  pronounced.  Gad  and  Heymans  found  the  maximum 
height  of  contraction  at  30°  C.  It  is  diminished  as  tbe  tempera- 
ture falls  to  19°  C,  and  subsequently  rises  again  at  0°  C. 

Patrizi  examined  muscular  contraction  in  the  marmot,  both 
in  the  hibernating  and  in  the  waking  state,  which  are,  of  course, 
distinguished  by  great  differences  of  temperature.  He  found  that 
contraction  is  about  three  times  more  rapid  when  the  animal  is 
awake  than  in  hibernation  ;  and  determined  the  latent  period  and 
duration  of  the  different  phases  of  the  twitch,  and  the  stimulation 
frequency  required  to  produce  tetanus,  in  both  these  states,  that  is, 
with  both  the  high  and  the  low  body-temperature. 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  11 

While  cold  diminishes  muscular  excitability  and  renders  the 
muscle  less  easily  fatigued  and  more  resistent,  heat,  after  a  brief 
rise  of  excitability,  leads  to  easy  exhaustion.  When  the  rise  of 
temperature  exceeds  40-50°  0.  the  muscle  enters  into  thermal  rigor, 
in  which  it  gives  its  maximal  contraction,  and  does  not  relax  again. 

(c)  The  duration  and  form  of  the  muscle  twitch  also  depend  on 
the  degree  of  fatigue.  If  a  series  of  twitches  from  a  frog's  muscle, 
uniformly  loaded  and  excited  at  equal  intervals  (1-2  sees.),  with 
uniform  shocks  from  make  or  break  induction  currents  are  recorded 
on  the  drum  of  the  myograph,  a  fatigue  curve  will  be  obtained  which 
shows  a  gradual  retardation  and  weakening  of  muscular  activity, 
preceded  by  a  short  phase  of  augmentation.  Fig.  6  shows  that  in 
a  preliminary  period,  consisting  of  some  ten  twitches,  the  tracings 
rise  in  height,  and  the  duration  of  both  contraction  and  elongation 
is  lengthened.  In  a  second  much  longer  period  the  height  drops, 


I  ;.  ti.— Curve  of  fatigue,  with  direct  stimulation  of  frog's  gastrocnemius.  (A.  D.  Waller.)  Tracing 
of  125  maximal  contractions  at  H  sees,  interval.  The  experiment  was  stopped  before  the  muscle 
became  fully  exhausted. 

while  the  duration  of  both  phases  increases,  but  particularly  that 
of  relaxation. 

Kronecker  (1871)  showed  that  when  a  frog's  muscle,  excited 
at  regular  intervals  with  maximal  induction  shocks,  is  loaded 
only  at  the  moment  at  which  it  commences  its  contraction  (after 
loading},  the  apex  of  the  twitches  forms  a  straight  line,  which 
drops  more  rapidly  towards  the  abscissa  in  proportion  as  the 
interval  between  the  single  stimulations  diminishes.  In  repro- 
ducing Kronecker's  experimental  conditions  it  is  necessary  first 
to  test  the  excitability  of  the  muscle  in  order  to  find  the  least 
stimulus  that  will  produce  a  maximal  effect ;  next,  the  single 
stimuli  must  succeed  each  other  at  long  intervals,  so  that  the 
muscle  shall  not  be  excited  again  before  the  phase  of  relaxation  is 
fully  completed,  which  takes  longer  and  longer  as  the  fatigue 
increases.  The  apparent  rise  of  activity,  often  seen  at  the  com- 
mencement of  muscular  fatigue,  is  probably  due  to  the  fact  that, 
owing  to  the  lengthening  of  the  phase  of  relaxation,  the  muscle 
receives  the  next  shock  before  it  has  completely  relaxed.  In 
this  case  each  new  excitation  summates  with  the  residue  of  the 
previous  contraction,  and  the  level  of  the  myogram  rises  in  conse- 
quence (Fr.  W.  Frohlich,  1905). 


12 


PHYSIOLOGY 


CHAP. 


The  study  of  fatigue  phenomena  in  muscle  is  simplified  and 
made  more  complete  if,  instead  of  sending  in  the  excitations  at 
regular  intervals,  the  muscle  is  stimulated  by  a  make  induction 
shock  directly  it  has  relaxed.  The  apparatus  can  be  arranged  so 
that  the  contraction  of  the  muscle  breaks  the  exciting  circuit,  and 
its  relaxation  closes  it  again.  The  muscle  thus  contracts  and 
relaxes  continuously  (Wundt,  1858  ;  Novi,  1879). 

Fig.  7  shows  the  curve  of  muscular  fatigue  passing  into 
complete  exhaustion.  It  exhibits  the  initial  phases  that  are  to 
be  seen  in  Waller's  incomplete  curve,  followed  by  a  much  longer 


Km.  7. — Complete  tracing  of  muscular  fatigue  from  frog's  gastrocnemins  ;  series  of  successive 
contractions  which  vary  in  frequency  with  the  varying  duration  of  the  contraction.  (I.  Novi.) 
Lines  1,  2,  3,  4  represent  successive  parts  of  one  tracing,  a,  b,  first,  very  brief  phase  con- 
sisting of  extremely  rapid  contractions  of  increasing  height ;  b,  <:,  second  phase,  four  to  five 
times  longer,  rapid  contractions  decreasing  in  height ;  c,  d,  third  phase,  less  rapid  contractions, 
approximately  equal  in  height ;  </,  c,  fourth  phase,  longer  than  preceding,  contractions  becoming 
slower  and  higher ;  e,  f,  fifth  phase,  the  longest  of  all,  contractions  decrease  regularly  in  height, 
and  become  increasingly  slower;  x,  y,  slowest  of  all  ;  y,  /,  minimum  height,  contractions 
gradually  die  away. 

final  phase,  in  which  the  height  of  the  twitches  regularly  decreases 
in  a  straight  line,  as  shown  by  Kronecker. 

By  Novi's  method  it  is  easier  to  analyse  the  changes  in  the 
functions  of  muscle  which  are  due  to  fatigue,  and  the  variations 
of  the  curve  of  fatigue  with  variations  of  temperature,  and  under 
the  influence  of  different  drugs  and  poisons. 

When  fatigue  has  been  pushed  to  complete  exhaustion  by 
very  frequent  stimulation  the  muscle  often  fails  to  regain  its 
normal  length,  and  remains  more  or  less  contracted,  thus  approxi- 
mating to  the  state  of  rigor  that  signalises  its  death. 

If  the  muscle  is  left  to  itself  for  a  certain  time  after  its 
excitability  is  so  exhausted  that  it  no  longer  reacts  to  stimuli, 
it  gradually  recovers,  i.e.  regains  its  excitability.  In  the  living 


i  GENEEAL  PHYSIOLOGY  OF  MUSCLE  13 

body  the  tired  muscle  rapidly  recovers  with  rest,  owing  to  the 
blood  circulation ;  but  excised  muscle,  too,  is  capable  of  a  partial 
restoration,  although  it  is  cut  off  from  the  circulating  tissue  fluids. 
Fatigue  is  the  effect  of  two  factors  which  act  simultaneously 
upon  contractile  protoplasm — the  consumption  of  the  dynamogenic 
materials  of  muscle,  and  the  accumulation  of  waste  matters  or 
decomposition  products.  Recovery  depends  on  the  supply  of 
further  nutritive  material  and  removal  of  the  waste  products,  as 
we  shall  presently  see  in  discussing  muscular  metabolism. 

(d~)  The  height  of  the  twitch  also  depends  on  the  form  or 
strength  of  the  stimulus.  It  is  advisable  in  studying  these 
relations  to  employ  the  make  or  break  shocks  of  an  induced 
current,  which  can  be  easily  graduated.  If  a  muscle  is  rhythmic- 
ally excited  by  break  shocks  of  gradually  increasing  strength, 
it  begins  to  respond  only  when  the  stimulus  reaches  a  certain 
intensity,  the  so-called  threshold  of  stimulation.  If  the  exciting 
current  is  then  further  strengthened,  a  series  of  contractions 
result  that  increase  in  height,  step  by  step,  up  to  a  certain  point, 
after  which  they  no  longer  increase  with  the  strength  of  the 
stimulus.  Stimulation  is  therefore  distinguished  as  effective  and 
ineffective  according  as  it  produces  or  does  not  produce  a  reaction ; 
effective  stimuli,  again,  may  be  minimal,  median,  maximal,  or 
super -maximal.  The  gradation  of  the  stimuli  alters,  moreover, 
according  as  the  muscle  is  directly  or  indirectly  excited.  When 
the  muscle  is  directly  excited  the  interval  between  the  minimal 
and  maximal  stimulus  is  greater,  but  as  this  interval  is  very  small 
it  requires  only  a  slight  increase  of  the  stimulus  above  the  threshold 
to  elicit  a  maximal  contraction.  The  gradation  of  the  response  to 
an  increasing  stimulus  is  not,  therefore,  easy  to  demonstrate. 
Certain  muscles,  e.g.  cardiac  muscle,  either  do  not  respond  at  all 
or  respond  to  each  shock  by  a  maximal  contraction — Bowditch's 
Law  of  "  all  or  nothing  "  (Vol.  I.  p.  318). 

According  to  Fick's  first  researches  (1862)  on  the  gradation  of 
response  to  indirect  stimulation  of  skeletal  muscle,  the  increase 
in  height  of  the  contractions  is  approximately  proportional  to  the 
increase  in  strength  of  the  stimulus ;  but  Tigerstedt  has  shown, 
with  direct  stimulation  of  curarised  muscles,  that  with  regular 
increase  in  the  strength  of  the  current  the  contractions  at  first 
increase  rapidly,  and  afterwards  more  slowly,  till  they  become 
maximal.  The  ascending  line  of  the  contractions  is  thus  not  a 
straight  line  but  a  hyperbola. 

At  the  maximum  height  of  the  muscle  twitch  obtained  on 
exciting  a  fresh  frog's  muscle  with  a  maximal  or  supermaximal 
stimulus  the  muscle  shortens  by  \  of  its  length,  as  measured  in 
the  resting  state. 

(e)  The  height,  duration,  and  form  of  the  contraction  are 
considerably  influenced  by  the  load  carried  by  the  muscle,  i.e. 


14  PHYSIOLOGY  CHAP. 

the  resistance  it  encounters  during  its  contraction.  Generally 
speaking,  it  is  said  that  the  weight  applied  to  the  muscle  impedes 
contraction  while  it  facilitates  relaxation.  It  is  further  assumed 
that  a  muscle  which  carries  no  load — i.e.  is  not  influenced  by 
external  resistance,  as  when  it  floats  on  mercury — shortens  with 
an  induced  shock,  and  remains  contracted  without  resuming  its 
initial  length.  If  this  were  accepted  unconditionally  it  would  be 
in  open  contradiction  with  a  number  of  experimental  observations, 
which  prove  that  both  contraction  and  relaxation  are  active  states 
of  the  muscle.  Kaiser  (1900)  showed  that  if  the  frog's  sartorius 
muscle  is  carefully  dissected  out  without  pulling  on  it,  and  dipped 
in  olive  oil  before  being  placed  on  the  mercury  to  minimise  friction, 
it  responds  to  each  shock  of  an  induced  -  current  by  a  single 
diphasic  contraction,  i.e.  after  contracting  it  relaxes  at  its  normal 
rate.  After  the  first  indirect  stimulation  the  muscle  regularly 


^D 

FIG.  8.— Diagram  of  isotonic  myograph.  L,  lever  connected  with  the  muscle  at  point  A,  traces  the 
movements  with  writing-point  p  on  the  recording  surface.  The  weight  P  that  pulls  on  the 
muscle  is  fastened  by  a  thread  to  a  little  wheel  attached  to  axis  «  of  the  lever. 

becomes  longer  than  it  was  before ;  but  if  the  stimuli  are 
applied  frequently  the  expansion  is  less  complete — a  muscle,  for 
instance,  35  mm.  long  in  the  initial  resting  state  fails  to  attain 
its  original  length,  but  becomes  successively  shorter  by  1,  2,  or 
3  mm. 

It  may  be  said  in  general  that  the  greater  the  load  or  the 
resistance  opposed  to  the  contractile  phase  of  muscular  activity 
the  less  is  the  shortening  and  the  greater  the  degree  of  tension 
in  the  muscle,  so  that  shortening  and  muscular  tension  are  in 
inverse  ratio.  On  stimulating  a  muscle  clamped  at  both  ends, 
the  tension  can  be  increased  to  a  maximum  without  any  shortening  ; 
conversely,  when  a  muscle,  clamped  at  one  end  only  and  loaded 
at  the  other  with  a  small  weight,  is  stimulated,  it  contracts 
maximally  with  the  least  possible  increase  of  tension.  A.  Fick 
(1887)  first  analysed  these  two  functions  of  muscular  activity, 
and  devised  a  comparatively  simple  method  by  which  it  was 
possible  to  a  large  extent  to  eliminate  the  alterations  of  tension, 
while  the  curve  of  shortening  was  simultaneously  recorded,  or 
vice  versa  to  minimise  the  alterations  in  the  length  of  the  muscle 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  15 

and  at  the  same  time  record  the  curve  of  muscular  tension.  To 
the  first  he  gave  the  name  of  isotonic,  to  the  second  of  isometric 
curves. 

Isotonic  curves  are  recorded  with  a  very  light  lever,  the  weight  being 
applied  near  the  fulcrum  by  a  thread  that  runs  over  a  wheel  during  the 
contraction  (Fig.  R). 

The  free  end  of  the  muscle  is  attached  by  a  hook  and  thread  to  a  point  of 
the  lever  at  greater  or  less  distance  from  the  fulcrum.  The  movements  of 
the  muscle  are  magnified  by  the  writing-point  according  as  the  muscle  is 
fixed  nearer  the  fulcrum.  Under  these  conditions  the  acceleration  of  the 
weight  is  negligible,  no  matter  what  the  amplitude  and  speed  of  the  move- 
ment, and  the  tension  of  the  muscle  remains  approximately  constant  through- 
out its  contraction. 

To  obtain  relatively  perfect  isometric  curves,  the  shortening  of  the  muscle 
must  be  reduced  to  a  minimum  by  causing  its  lower  end  to  work  against  a 
strong  elastic  resistance,  and  magnifying  the  excursion  of  the  lever  by  a  long 
arm  (Fig.  9).  The  muscle  is  fixed  at  its  upper  extremity,  and  is  connected 
by  a  long  inextensible  thread  with  a  metal  wheel,  to  which  a  steel  spring 


M 


FIG.  9.— Diagram  of  isometric  myograph.  The  muscle  is  directly  connected  with  the  wheel,  which 
carries  the  spring  .V;  by  pressing  on  the  supports  this  considerably  reduces  the  rotary 
movement  A,  although  the  latter  is  magnified  by  the  long  arm  of  the  lever  L  which  records  it. 

is  attached,  which  rests  on  a  support  at  its  free  end.  When  the  muscle 
pulls  on  the  thread  the  wheel  moves  slightly  round  the  axis  and  the  spring  is 
stretched  against  the  support.  The  least  movement  of  the  wheel  is  magnified 
by  a  long  light  lever,  the  point  of  which  traces  a  curve  upon  a  rotating 
drum  that  almost  perfectly  expresses  the  tension  of  the  muscle  during 
excitation,  but  not  its  change  of  form. 

Various  isotonic  and  isometric  myographs  have  been  invented,  but  the 
principle  is  the  same  as  in  Figs.  8  and  9. 

When  the  tension  of  the  muscle  remains  approximately  constant 
during  the  course  of  the  contraction  (isotonic]  the  height  of  the 
latter  generally  increases  with  diminution  of  the  load,  at  first 
rapidly,  then  more  slowly,  i.e.  not  in  proportion  with  the  load, 
while  the  work  done  by  the  muscle,  calculated  from  the  weight 
multiplied  by  the  height  to  which  it  is  raised,  increases  within 
certain  limits  with  each  increment  of  weight  (Santesson). 

There  are,  indeed,  exceptions  to  this  rule.  According  to  the 
observations  originally  made  by  Fick,  and  afterwards  confirmed 
by  others,  when  the  weight  applied  to  the  muscle  is  not  great, 
and  particularly  when  an  elastic  resistance  is  opposed  to  the 
muscle,  so  that  its  tension  increases  constantly  during  contraction, 


16  PHYSIOLOGY  CHAP. 

the  shortening  is  greater  when  the  weight  and  the  initial  resist- 
ance are  increased.  This  paradoxical  phenomenon  is  a  specific 
property  of  the  substance  of  living  muscle,  and  shows  that  the 
sudden  pull  of  the  muscle  and  increase  of  tension  during  shortening 
act  as  a  stimulus  on  the  contractile  substance,  and  increases  the 
effect  of  the  electrical  stimulation. 

With  the  isometric  method  the  tension  of  the  muscle  pre- 
vented from  shortening  is  far  greater  in  the  excited  than  in  the 
resting  state.  Comparison  of  the  curves  of  isotonic  and  isometric 
contraction,  obtained  from  the  same  muscle  under  uniform  con- 
ditions of  stimulation,  show  that  the  two  curves  differ  very  little 
at  medium  temperature.  When,  on  the  contrary,  the  temperature 
of  the  atmosphere  is  lowered  to  about  5°  C.  the  two  tracings 

present  distinctive  char- 
acters. Fig.  10  plainly 
shows  that  the  isometric 
curve  reaches  its  maximum 
more  rapidly  than  the  iso- 
tonic curve,  and  that  in 
the  former  maximal  tension 
persists  for  a  certain  time, 
while  in  the  second  it  passes 
suddenly  from  the  height  of 
the  contraction  phase  to  the 

FIG.  10.— Comparison  of  isotonic  (a)  and  isometric  (/-)  phase  of  relaxation. 

inyograms   from  the   same   muscle.     (Gad.)     The  eor.iv.o-nn     /"I  QOJA     cfnrliprl 

isometric  curve  is  reversed  because  in  Gad's  myo-  \J.yw±)     &LUI 

graph  the  lever  is  pulled  down  instead  of  up  by  foe     influence     of      the      load 
increasing  tension  of  the  muscle. 

upon    isometric    curves     by 

submitting  the  muscle  to  sudden  changes  of  tension  during  its 
contraction.  Such  changes,  whether  a  temporary  or  permanent 
increase  or  decrease,  always  induce  marked  diminution  of  tension 
in  the  muscle  in  a  degree  which  depends  not  on  the  magnitude, 
but  on  the  abruptness  of  the  change,  and  is  more  pronounced 
the  later  the  alteration  in  tension  occurs  in  the  contraction. 
In  the  body  these  conditions  of  isotonia  and  isometria  are,  of 
course,  seldom  realised.  A  certain  amount  of  contraction  is  nearly 
always  needed  to  overcome  the  resistance  that  diminishes  or 
increases  during  the  course  of  excitation.  The  muscles,  in  other 
words,  are  almost  always  employed  in  carrying  out  an  external 
mechanical  task  under  various  conditions,  which  differ  from  the 
experimental  conditions  of  isotonia  and  isometria.  The  isometric 
method  is  an  analytic  means  of  eliminating  the  complications  of 
changes  of  form  and  internal  friction,  so  as  to  obtain  the  simpler 
curve  of  the  changes  of  tension  or  of  longitudinal  molecular  attrac- 
tion, which  are  the  fundamental  effects  of  muscular  excitation. 

III.    The  activity  of  skeletal  muscle  in  the  body  differs  in 
another    respect    from    that    above    described.       Under   natural 


i  GENEEAL  PHYSIOLOGY  OF  MUSCLE  17 

conditions  the  movements  of  our  body  are  not  the  effects  of 
simple  muscular  contraction,  due  to  isolated  and  instantaneous 
stimulations,  but  almost  invariably  result  from  a  series  of  rapidly 
succeeding  stimuli,  which  produce  in  the  muscle  the  state  of 
permanent  and  apparently  uniform  contraction  known  as  tetanus. 

Volta  (1792)  was  the  first  who  recognised  that  frequently 
repeated  stimuli  were  able  to  produce  persistent  contraction  in 
muscle.  Matteucci  (1838)  first  termed  this  state  of  contraction 
tetanus,  and  the  interrupted  currents  which  produce  it,  tetanising 
currents.  Helmholtz  (1854)  first  demonstrated  that  tetanus  of 
the  skeletal  muscles  is  the  effect  of  the  summation  and  fusion  of 
a  rapid  succession  of  simple  contractions. 

On  sending  two  shocks  from  an  induced  current  into  the 
nerve  of  a  muscle  at  very  brief  intervals,  so  that  the  second 
stimulus  falls  011  the  muscle  during  the  period  of  latent  excitation, 
the  resulting  curve  does  not  differ  from  that  produced  by  a  single 
shock  if  the  current  is  maximal,  but  if,  on  the  contrary,  the 


Fin.  11. — Diagrammatic  superposition  of  two  contractions.  (Helmholtz.)  The  curves  a  b  c  and 
</  i:  /  represent  two  distinct  contractions  excited  by  two  shocks  rr'.  The  curve  a  g  h  i  k 
represents  the  superposition  and  fusion  of  the  two  preceding,  as  if  the  contractions  <l  ef  rose 
from  the  abscissa  line  g  i,  and  not  from  d  /. 

current  is  moderate  or  hardly  effective,  the  height  of  the  curve 
is  different.  Accordingly,  two  shocks  of  medium  strength  act 
in  this  case  like  a  single  maximal  or  supra -maximal  stimulus, 
showing  that  there  is  summation  of  the  two  excitations  (Helm- 
holtz). In  the  crab's  muscles  it  is  possible  also  to  observe  latent 
summation  of  several  shocks,  each  of  which  is  ineffective  in  itself, 
that  is,  incapable  of  producing  any  visible  sign  of  excitation 
(Richet). 

If  the  interval  between  two  stimuli  is  such  that  the  second 
induction  shock  falls  on  the  muscle  during  the  contraction 
induced  by  the  first,  the  second  shock  is  superposed  upon  the 
former,  as  if  the  muscle  were  at  the  moment  of  its  application  in 
the  natural  state  of  rest  (Helmholtz).  In  this  case,  accordingly, 
the  two  contractions  fuse  into  a  single  one  of  greater  height  and 
duration  (Fig.  11). 

If  the  interval  between  the  two  stimulations  is  such  that  the 
second  contraction  is  sent  in  when  the  muscle  is  at  the  height  of 
the  contraction  produced  by  the  first,  the  fusion  of  the  two  will  be 
maximal,  i.e.  almost  double  that  of  the  simple  twitch.  This 

VOL.  in  c 


18  PHYSIOLOGY  CHAP. 

maximal  effect  of  the  fusion  of  the  two  contractions  takes  place 
when  the  interval  between  the  two  shocks  is  about  oV  of  a  second 
(Sewall  and  others). 

Summation  of  contractions  takes  place  not  only  with  currents 
of  medium  strength,  but  also  with  maximal  or  supra-maximal 
stimulation.  The  maximal  contraction  of  a  muscle  is  therefore 
not  obtained  with  a  single  stimulation,  however  strong,  but  only 
with  repeated  stimuli  in  rapid  succession,  owing  to  the  summation 
of  excitation.  The  interpretation  of  this  phenomenon  will  be 
given  later  in  speaking  of  Contracture. 

When  a  series  of  stimuli  act  upon  a  muscle  in  rapid  succession, 
it  reaches  the  maximum  degree  of%  shortening,  owing  to  summation 
of  the  stimuli,  and  remains  in  the  state  of  persistent  contraction 
known  as  tetanus  so  long  as  the  stimuli  act  upon  it.  The  minimal 


•••.:*•••••.  '-..  ':,;••• 


- 

•.-;'  s 


Fin.  12. —Comparison  of  tetanus  curves  from  a  red  (;•)  and  pale  (yi)  muscle  of  rabbit.  (Kroneckor 
and  Stirling.)  At  A  both  muscles  were  excited  by  ten  induced  shocks  per  second  ;  at  B  by 
six  shocks  per  second. 

stimulation  frequency  necessary  to  produce  complete  tetanus 
varies  in  the  muscles  of  different  animals.  As  a  rule  it  is  less 
in  proportion  as  the  active  phase  of  the  muscular  contraction  is 
slower.  12-30  stimuli  per  second  suffice  for  frog  muscles,  while 
20-30  are  required  for  those  of  mammals.  The  red  muscles  of  the 
rabbit,  according  to  Kronecker  and  Stirling,  may  be  almost  com- 
pletely tetanised  with  10  stimuli  per  second,  while  the  pale  muscles 
of  the  same  animal  are  only  thrown  into  tetanus  with  20-30 
stimuli  per  second.  With  6  stimuli  per  second  the  pale  muscles 
exhibit  a  series  of  almost  wholly  isolated  contractions,  while 
the  same  frequency  throws  the  red  muscles  into  a  tremulous 
contraction  closely  resembling  tetanus  (Fig.  12). 

All  conditions  that  make  muscular  contraction  slower,  as 
fatigue,  fall  of  temperature,  etc.,  diminish  the  stimulation 
frequency  necessary  for  complete  tetanus.  On  the  cessation  of 
the  series  of  stimuli  that  induced  tetanic  contraction,  the  muscle 
never  resumes  its  original  length,  but  remains  a  little  shortened 
in  consequence  of  the  fatigue  and  the  abnormal  changes  which  the 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  1.9 

contractile  protoplasm  has  suffered.  The  degree  of  this  residual 
shortening  is,  of  course,  in  definite  relation  with  the  duration  of 
the  tetanus. 

It  follows  from  the  theory  of  summation  of  contractions  that 
in  tetanus  the  shortening  of  the  muscle,  and  thus  the  work  it  is 
able  to  accomplish,  is  greater  than  in  a  simple  contraction.  To 
this  rule  there  is,  however,  one  exception ;  according  to  von  Frey 
a  lightly  loaded  muscle  contracts  equally  both  to  a  single  shock, 
and  to  a  tetanisiug  current. 

The  degree  of  shortening  and  the  yield  of  work  from  the 
tetanised  muscle  depend  on  the  frequency  and  strength  of  the 
tetanising  current.  When  the  stimulation  frequency  exceeds 
300  per  second,  and  the  current  is  sufficiently  weak,  no  tetanus 
results  (Harless,  Heidenhain),  or  at  most  a  single  initial  twitch 
(Bernstein).  In  order  to  produce  tetanus  the  current  must  be 
strengthened  ;  this  is  due  to  the  fact  that  after  the  first  stimulation 
the  excitability  of  the  muscle  drops,  and  consequently  it  no  longer 
reacts  to  subsequent  stimuli  so  long  as  these  remain  minimal. 
According  to  Salomonson  (1904),  on  the  contrary,  this  is  merely 
a  physical  phenomenon. 

The  upper  limit  of  the  stimulation  frequency  that  can  produce 
tetanus  has  not  yet  been  ascertained.  Bernstein  obtained  it  with 
an  acoustic  interrupter  that  sent  2000-3000  induction  shocks  into 
the  muscle  per  second :  Kronecker  with  20,000  shocks  per  second. 

Tesla  and  d'Arsonval  discovered  that  high  frequency  alternating 
currents  sufficiently  intense  to  render  a  carbon  filament  in- 
candescent fail  to  excite  a  muscle  or  nerve.  While  a  constant 
current  of  5  milliamperes  excites  both  at  break  and  at  make 
of  the  circuit,  an  alternating  current  of  5  amperes,  of  high 
frequency  (about  one  million  per  second),  produces  no  effect,  motor 
or  sensory.  By  a  special  contrivance  this  current  can  be  passed 
through  one  or  more  persons  and  at  the  same  time  through  a 
series  of  incandescent  lamps ;  the  lamps  light  up,  while  the 
individuals  included  in  the  circuit  feel  neither  sensation  nor 
motion.  Eiuthoven  (1900)  subsequently  demonstrated  that  it  is 
possible  to  evoke  muscular  contractions  by  means  of  indirect 
stimulation,  even  with  alternating  currents  of  the  highest  frequency 
(up  to  a  million  per  second),  provided  the  strength  of  the  current 
is  enormously  increased  in  proportion  with  its  frequency. 

Comparison  of  the  rate  of  the  muscular  contractions  produced 
by  an  instantaneous  shock  from  an  induced  current  with  the  slow 
persistent  contractions  by  which  the  skeletal  muscles  are  usually 
thrown  into  voluntary  contraction,  has  led  to  the  conclusion  that 
the  latter  are  tetanic  in  character,  i.e.  are  the  effects  of  a  series  of 
impulses  from  the  nerve  centres.  To  support  this  theory  of  the 
discontinuity  of  excitation  in  voluntary  contraction,  Wollaston 
(1810)  adduced  the  sound  developed  by  the  muscle  in  contracting, 


20 


PHYSIOLOGY 


CHAP. 


in  which  one  tone  predominates.  On  introducing  one  finger  into 
the  auditory  meatus  and  then  forcibly  contracting  the  muscles  of 
the  arm,  a  dull  murmur  is  heard  similar  to  that  from  a  distant 
vehicle  moving  rapidly  along  the  surface  of  a  road.  He  regarded 
the  tremor  often  noticed  in  the  muscular  movements  of  old  people 
as  the  effect  of  an  abnormal  slowing  of  the  muscular  vibrations 
due  to  debility  and  age.  From  his  studies  of  voluntary  muscular 
contraction  Wollaston  concluded  that  the  sound  in  the  contracting 
muscle  corresponds  to  a  frequency  that  oscillates  between  14  and 
15  per  second  at  the  minimum,  35  and  36  at  the  maximum. 

Helmholtz  (1864)  investigated  the  subject  of  the  muscle  sound 
with  better  methods.  He  observed  that  if  in  the  dead  of  night 
the  auditory  meatuses  are  stopped  and  the  masseters  forcibly 
contracted,  a  murmur  is  heard  in  which  there  is  a  ground  tone 
that  lasts  as  long  as  the  voluntary  contraction,  and  does  not 
change  materially  with  increase  of  muscular  tension. 


n 
s 


,VAV/ fsrsfW\W't*w  AMAA AAA*WWy  / A- AM/ ./AAA/NAA/  /  A/. W\ '/ //v%A'V////>lAA''/-'////y/'^/yA'lAA/-/Wyv/v/yv.//1A/W 


Fn:.  13. — Vibrations  of  biceps  muscle  of  rabbit's  femur  on  stimulating  the  spinal  cord  or  sciatic 
nerve  with  forty-two  induction  shocks  per  second.  (Kronecker  and  Stanley  Hall.)  The  middle 
line  s  gives  the  vibrations  of  a  tuning-fork  in  TJn  sec.  ;  the  upper  line  n  is  the  tracing  of  the 
vibration  of  the  muscle  during  stimulation  of  the  sciatic  ;  the  lower  line  in,  the  vibrations  of 
the  muscle  during  stimulation  of  the  cord.  Both  tracings  were  obtained  by  applying  a 
sensitive  lever  to  the  surface  of  the  exposed  muscle. 

The  same  tone  is  heard  on  firmly  contracting  the  eye-muscles 
or  applying  the  stethoscope  to  the  arm-muscles  during  voluntary 
contraction.  Helmholtz  pointed  out  that  the  vibrations  which 
give  rise  to  the  sounds  did  not  follow  in  regular  sequence  like 
those  of  a  musical  tone.  To  determine  the  frequency  objectively, 
he  applied  watch  springs  or  strips  of  paper  to  the  muscles  which 
were  vibrating  in  unison,  and  found  the  vibrations  to  be  18-20 
per  second.  He  confirmed  the  fact  previously  observed  by  Du  Bois- 
Keymond,  that  vibrations  of  the  same  frequency  as  those  of 
voluntary  contraction  are  produced  when  a  tetanising  current  of 
high  frequency  is  applied  not  only  to  the  nerve  or  muscle  but 
also  to  the  spinal  cord  of  an  animal.  Subsequently,  Helmholtz 
pointed  out  (1864)  that  the  tone  perceived  by  the  ear  corresponds 
not  to  the  effective  number  of  muscular  vibrations,  but  to  the 
resonance  tone  proper  to  the  ear  of  the  observer,  which  corresponds 
with  the  first  over-tone  or  the  octave  of  the  fundamental  tone  of 
the  muscle,  and  is  difficult  to  determine,  because  it  lies  at  the  limit 
of  the  perceptible  tones.  He  stated  in  effect  that  the  tone  heard 
on  voluntary  contraction  of  the  masseter  muscles  corresponds  to 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  21 

36-40  vibrations,  while  the  natural  vibration  of  the  human  muscles  is 
only  18-20  per  second.  Similar  results  were  obtained  by  Kronecker 
and  Stanley  Hall  (1879),  who  registered  the  oscillations  in  the 
mass  of  the  exposed  femoral  biceps  of  the  rabbit  by  applying  the 
lever  of  a  Marey's  tambour  to  its  surface,  and  tetanising  the  spinal 
cord  with  an  induced  current  of  43  shocks  per  second  (Fig.  13). 

Later  work  on  this  subject,  particularly  by  Loven,  von  Kries, 
Schafer,  Wedensky,  and  Stern  (1900),  however,  yielded  different 
and  apparently  contradictory  conclusions  in  certain  particulars, 
while  confirming  the  fact  that  all  voluntary  contractions,  and 
those  due  to  strychnine  and  to  reflex  or  direct  stimulation  of  the 
cerebral  centres,  are  discontinuous  phenomena,  i.e.  are  due  to  the 
summation  of  a  series  of  impulses  emanating  from  the  centres  and 
transmitted  to  the  muscles. 

It  is  difficult  on  the  generally  accepted  theory  of  Helmholtz, 
that  the  sound  heard  from  a  muscle  either  in  tetanus  or  in  per- 
sistent voluntary  muscular  contraction  depends  essentially  on  the 
displacement  of  the  contractile  substance,  to  explain  the  fact  that 
simple  twitches  or  contractions,  such  as  the  cardiac  systole,  can 
give  rise  to  a  murmur. 

Lastly,  it  should  be  added  that  Briinings  (1903)  made  an 
accurate  analysis  of  the  muscle  sound  produced  by  direct  and 
indirect  stimulation  with  faradic  currents  of  varying  frequency. 
He  found  that  it  always  has  the  character  of  a  simple  tone,  and 
that  its  frequency  never  differs  from  that  of  the  stimulus.  But  if 
on  direct  stimulation  the  frequency  of  the  faradic  currents  is 
constantly  increased,  the  intensity  of  the  muscle  sound  grows 
proportionately  less,  until  it  disappears  altogether  after  reaching  a 
certain  limit  of  frequency,  though  the  tetanus  still  continues. 
This  maximal  limit  is  higher  in  proportion  to  the  strength  of  the 
stimulus  and  the  freshness  and  the  temperature  of  the  muscle. 
Its  relation  to  the  temperature  in  particular  is  surprisingly 
regular.  While,  e.g.,  at  Y'5°  C.  3  stimuli  per  second  is  the  maximum 
at  which  an  isorhythmic  murmur  can  be  obtained,  no  sound  being 
heard  at  any  higher  frequency,  at  35°  C.  the  highest  perceptible 
tone  is  observed  with  435  vibrations. 

IV.  To  complete  the  analysis  of  the  mechanical  effects  of 
excitation  we  must  further  consider  the  variations  in  thickness  of 
the  muscle  and  the  propagation  of  excitation  along  its  fibres.  In 
excitation  the  long  axis  of  the  muscle  shortens,  and  its  transverse 
axis  increases,  while  the  surface  of  the  muscle  diminishes  during 
the  contraction  and  increases  in  relaxation.  But  the  question  was 
long  disputed  as  to  whether  the  volume  of  the  muscle  also  varied 
during  contraction,  and  diminished  during  tetanus.  This  question 
was  experimentally  investigated  long  since  by  Borelli,  Glisson, 
Swammerdam,  and  subsequently  with  better  methods  by  Barzel- 
lotti,  Erinan,  Joh.  Mu'ller,  E.  Weber,  and  many  others.  The 


22 


PHYSIOLOGY 


CHAP. 


results  were  contradictory.  Many  observers  were  unable  to  dis- 
cover any  variation  in  the  volume  of  the  muscle,  while  others  saw 
a  more  or  less  marked  diminution  in  volume  during  tetanus. 

Among   the   former  we    must 

mention  Barzellotti  (1795-96), 
who  invented  the  method  of 
introducing  the  muscles  of  a 
frog  into  a  closed  vessel  full  of 
water,  which  carried  a  capillary 
tube:  among  the  latter,  Erman 
(1812),  who  with  the  same 
method  observed  a  marked 
diminution  in  volume.  An 


Fin.  14.  —  Myograph  suitable  for  man,  to  record 
increased  bulk  of  the  muscles.  (Marey.)  Con- 
sists of  a  capsule  covered  with  a  rubber  mem- 
brane, pulled  out  by  a  spiral  spring.  A  metal 


rane,  pue     ou       y  a  spra    sprng.          mea  ,  .  11 

button  in  the  centre  of  the  membrane  carries  the  exhaustive    research    by 

exciting  current  to  the  skin  immediately  above  /1oq7\    wVir>    riprfppfpH     " 

the  muscle  to  be  explored.     The  compression  of  ViO°  '  )>  wn 


the  air  in  the  capsule  flunns  the  contraction  lis    lottl's     method    with     nce     a- 

tiansimtted  by  a  rubber  tube  to  the  lever  of  a     .  ., 

recording  tambour.  JUStUientS,  aiSO  jailed  to  Obtain 

even  minimal  variations  of 
volume  in  a  muscle  during  tetanisation. 

The  muscle  therefore  changes  in  form  and  extent  of  surface, 
but  not  in  density  and  volume,  during  activity.  Were  they  not 
sanctioned  by  use  it  would  be  better  to  give  up  the  inappropriate 
expressions  "  contraction  "  and  "  relaxation,"  to  indicate  the  two 
phases  of  muscular  activity. 

The  state  of  contraction  in  a  muscle  can  also  be  studied  by 
tracings  of  the  area  of  its  cross-section.  Marey  invented  special 
myographs  for  this  purpose  which  can  be  applied  to  man  in 
physiological  and  clinical  research.  The  simplest  of  these  are 
shown  in  Figs.  14  and  15.  Curves  of  simple  contraction  and  of 


FIG.  15. — Exploring  tambour  that  can  lie  used  as  a  myograph  to  transmit  the  phases  of  increasing 
thickness  of  a  contracting  muscle  to  a  tambour  with  writing  lever. 


tetanus  recorded  by  this  method  closely  resemble  those  we  have 
already  analysed  in  the  corresponding  changes  in  the  length  of  a 
muscle.  But  there  is  one  important  difference ;  while  the  former 
record  the  algebraic  sum  of  the  changes  in  length  in  all  tbe 
different  parts  of  the  muscle,  the  latter  only  trace  the  changes  in 


i  GENEKAL  PHYSIOLOGY  OF  MUSCLE  23 

thickness  of  the  particular  portion  of  the  muscle  to  which  the 
myograph  is  applied. 

The  rate  of  propagation  of  the  contraction  wave  can  be  calcu- 
lated from  the  interval  between  the  contraction  of  two  different 
points  of  an  isolated  muscle,  traced  by  two  myograph  levers  placed 
on  the  muscle  at  a  known  distance  from  each  other,  and  writing 
on  the  same  drum.  The  sartorius  muscle  of  the  frog,  in  which 
the  fibres  were  parallel  to  one  another,  is  the  most  suitable  for 
this  purpose.  Before  dissecting  it  out,  the  frog  should  be  curarised 
to  eliminate  the  action  of  the  stimulus  upon  the  intramuscular 
nerves.  When  an  induced  shock  is  applied  to  one  end  of  the 
muscle,  the  contraction  spreads  in  wave-form  to  the  other  end,  at 
a  velocity  which  can  be  calculated  by  means  of  the  two  curves. 

Fig.  16  shows  that  the  second  curve  rises  about  0-06  sec. 
after  the  commencement  of  the  first  curve :  in  passing  over  the 


Fir,.  16.— Two  myograms  of  thickening  from  the  same  frog's  muscle,  obtained  by  applying  two 
/(/'/UTS  myographiqves  at  a  distance  of  15  mm.  to  measure  the  velocity  of  the  excitation  wave. 
(Marey.)  Time  tracing  in  T£n  sec. 

part  of  the  muscle  between  the  two  rnyographs  the  wave  of  con- 
traction therefore  occupied  0'06  sec.  As  the  distance  between  the 
two  levers  was  15  mm.,  the  wave  travelled  at  a  rate  of  about  1  m. 
per  second. 

The  length  of  the  wave  can  also  be  calculated  from  the 
duration  of  the  thickening  of  the  fibres  (in  Fig.  16  about  seven 
vibrations  of  the  tuning-fork  =  O07  sec.),  and  from  the  rate  at 
which  the  wave  is  propagated.  Bernstein  stated  that  the  duration 
of  the  twitch  in  any  segment  of  the  muscle  (which  must  be  dis- 
tinguished from  the  duration  of  the  twitch  of  the  whole  muscle, 
which  usually  takes  longer)  is  from  0'05  to  01  sec.  Assuming 
Bernstein's  calculations  of  the  rate  at  which  the  wave  travels— 
3-4  m.  per  second,  to  be  correct — then  the  length  of  the  wave,  or 
the  part  of  the  muscle  over  which  it  passes  in  O'05-O'l  sec.,  is  on 
an  average  200-300  mm. 

As  the  length  of  each  muscle  fibre  rarely  exceeds  40  mm.  the 
entire  length  of  each  fibre  is  usually  involved  in  the  contraction. 
It  is  only  at  the  beginning  and  towards  the  end  of  the  contraction 
that  one  or  other  end  of  the  fibre  is  not  active;  throughout  the 


24  PHYSIOLOGY  CHAP. 

greater  part  of  the  duration  of  the  wave,  each  segment  of  the 
fibre  will  be  in  some  phase  of  activity,  which  is  more  advanced  in 
the  segments  nearer  to,  less  advanced  in  those  more  distant  from, 
the  points  at  which  the  stimulus  is  applied. 

The  rate  of  propagation  varies  considerably  in  the  muscles  of 
the  same  animal  according  to  the  method  adopted.  According  to 
Aeby  (1860),  who  first  applied  the  graphic  method  to  this  research 
in  the  gracilis  and  semi-membranosus  muscles  of  the  frog,  it  is 
about  1  m.  per  second  (1'2-1'G  in.).  Yon  Bezold's  and  Marey's 
results  were  much  the  same,  while  Bernstein,  who  compared  the 
moments  at  which  successive  waves,  travelling  in  the  same 
direction  from  different  points,  reached  a  particular  spot  at  a 
known  distance  from  each  of  them,  obtained  much  higher  values 
(3'2-4'4  m.  per  second).  Hermann  who  excited  the  two  sartorius 
muscles  in  a  curarised  frog  at  two  different  points,  and  simultane- 
ously, gave  the  rate  as  2-7  m.  per  second. 

Just  as  the  velocity  of  the  muscle  twitch  differs  considerably 
in  the  muscles  of  different  animals  (cold-blooded  and  warm- 
blooded), and  in  different  muscles  (pale  or  red,  quick  or  torpid),  so 
the  velocity  at  which  the  wave  of  excitation  or  contraction  travels 
also  varies.  In  the  retractor  collis  muscle  of  the  tortoise  the  rate 
at  which  excitation  is  transmitted  varies  between  05  and  T8  m. 
(Hermann  and  Aeby) ;  while  in  the  sterno-mastoid  muscle  of  the 
dog  it  is  equal  to  3-6  m.  (Bernstein  and  Steiner). 

The  rate  of  propagation  of  the  wave  may  v/iry  greatly  in  the 
same  muscle  with  the  strength  of  stimulus,  still  more  with  the 
state  of  its  excitability,  which  varies  largely  according  to  fatigue 
and  with  the  temperature.  Schiff  (1856-58)  first  studied  the 
interesting  phenomenon  known  as  the  ideo-muscular  contraction, 
which  directly  shows  the  transmission  of  a  contraction  excited  by 
mechanical  stimuli  along  mammalian  muscles  exposed  shortly 
after  death.  A  ridge  or  weal  forms  when  the  muscle  is  tapped 
or  stroked  with  a  blunt  object,  and  persists  for  a  certain  time ; 
two  contractile  waves  start  from  it,  and  spread  towards  the 
two  ends  of  the  muscle,  where  they  are  reflected  back  towards 
the  spot  stimulated,  and  collide  with  secondary  waves  from  the 
weal.  As  the  excitability  of  the  tissue  is  exhausted,  the  velocity 
of  this  wave  conduction  also  diminishes. 

These  observations  on  the  propagation  of  the  contraction  wave 
through  the  muscle  refer  to  artificial  direct  stimulation  at  one 
end.  With  natural  or  indirect  stimuli,  when  the  excitation 
reaches  the  muscle  through  the  end-plates  of  the  motor  nerves  that 
lie  towards  the  middle  of  each  fibre,  the  contraction  must  invade 
the  total  length  of  the  fibres  in  a  much  shorter  time.  In  fact  we 
assume  that  the  contraction  is  propagated  from  the  end-plates  in 
two  opposite  directions  towards  the  two  ends  of  the  fibres,  and 
therefore  has  only  to  traverse  half  its  length. 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


25 


When,  instead  of  using  make  and  break  shocks  from  an 
induction  coil,  a  muscle  is  excited  with  the  constant  current, 
it  contracts  at  each  closure  or  opening  of  the  current,  but  is 
relaxed  during  the  passage  of  the  current.  This  law  usually  holds 
good  if  a  current  of  medium  strength  is  employed,  but  if  the 
strength  of  the  current  exceeds  certain  limits,  the  make  or  break 
of  the  current  is  immediately  followed  by  a  tetanus  (closure  or 
opening  tetanus).  This  fact,  which  was  first  noted  by  Wundt, 
can  also  be  observed  on  man,  by  sending  a  strong  galvanic  current 
into  a  muscle,  or  even  a  comparatively  weak  current  when  the 
muscle  is  degenerated. 

Curarised  muscles  react  more  readily  to  the  closure  and  open- 
ing of  a  constant  current  than  to  the 
more  transitory  make  and  break  shocks 
of  an  induced  current.  Hence  in  ex- 
amining the  rate  of  transmission  of 
contraction,  the  constant  current  is  pre- 
ferable. 

The  excitation  at  make  of  the  con- 
stant current  is  greater  than  at  break, 
as  can  be  seen  by  varying  the  amount 
of  current  passed  through  the  muscle, 
by  means  of  a  rheochord. 

Von  Bezold,  Engelmann,  and  Hering 
showed  that  the  "law  of  contraction" 
which  Pfliiger  formulated  for  nerve  (see 
Chap.  IV.)  holds  for  muscle  also :  the 
closing  contraction  always  starts  from 
the  negative  pole,  while  the  opening 
contraction  is  set  up  at  the  positive 
pole ;  in  other  words  the  make  excita- 
tion is  kathodal,  the  break  excitation  is 

anodal.  This  law  may  be  demonstrated  by  placing  two  myograph 
levers  far  apart  on  a  curarised  muscle,  to  the  two  ends  of  which 
the  two  electrodes  are  applied.  At  make  and  break  of  the 
current  the  two  contractions  are  recorded  at  brief  intervals,  but 
the  kathodal  always  precedes  the  anodal  at  the  closure,  and  the 
anodal  the  kathodal  at  the  opening,  of  the  current. 

V.  In  order  to  understand  the  changes  in  form  which  the 
muscle  undergoes  during  activity,  it  is  necessary  to  examine  the 
structure  of  the  muscle  fibre  under  the  microscope,  and  the 
changes  which  it  undergoes  during  contraction. 

Each  muscle  fibre  consists  of  soft  protoplasm  enclosed  in  an 
elastic  tubular  sheath,  the  sarcolemma.  This  membrane  is  so 
resistant  that  it  is  uninjured  by  a  pull  strong  enough  to  rupture 
the  muscle  substance  (Fig.  17).  Oval  nuclei  parallel  with  the 
long  axis  of  the  fibre  generally  lie  immediately  under  the  sarco- 


Fi 


}.  17. — Sarcolemma  of  mammalian 
muscle.  (Schafer.)  Highly  magni- 
fied. The  sarcolemma  is  left  clear, 
owing  to  rupture  of  the  muscular 
substance. 


26 


PHYSIOLOGY 


CHAP. 


lemma,  but  they  belong  to  the  muscle  substance,  and  not  to  the 
sarcolemma.  Each  muscle  fibre  may  be  regarded  as  a  very 
elongated  cell,  provided  with  several  nuclei,  the  sarcolemma 
representing  the  cell  membrane.  The  diameter  of  the  fibres 
usually  varies  from  30  to  40  /*,  but  may  be  greater  or  less  in 
different  classes  of  animals. 

The  substance  proper  or  protoplasm  of  the  fibre  presents  a 
double  striation,  longitudinal  and  transverse,  owing  to  the  fact 
that  it  consists  of  a  bundle  of  numerous  primitive  fibrils  arranged 
parallel,  each  of  which  has  a  complex  transverse  structure. 

On  examining  a  fibre  in  cross-section,  each  primitive  fibril 
appears  as  a  rounded  spherical  granule,  comparatively  dark  in 
colour,  surrounded  by  a  lighter  non-differentiated  substance — the 
sarcoplasm.  The  amount  of  sarcoplasm  may  vary  considerably  in 


s , 


Fio.  18. — Traiivi'rsi-  section  of  two  striated  muscle  fibres  of  rabbit.  (S/.ymonowk-z.)  Magnified 
1000  diameters.  At  A  the  primitive  fibrils  (.S)  are  equally  distributed  in  the  sarcoplasm  (S^). 
At  B  they  form  polyliedric  segments  known  as  Cohnlu-im's  areas  (Cc). 

different  muscles,  just  as  the  mode  of  division  or  grouping  of  the 
primitive  fibrils  within  the  sarcoplasm  also  differs  (Fig.  18). 

On  examination  of  a  fre^h  muscle  fibre  in  serum,  a  longi- 
tudinal striation  is  seen  owing  to  the  parallel  arrangement  of  the 
primitive  fibrillae.  A  series  of  light  and  dark  striae  at  right 
angles  to  the  longitudinal  axis  of  the  fibre  are  also  visible,  which 
are  due  to  a  double  series  of  light  and  dark  parallel  bands  that 
alternate  regularly  through  the  entire  length  of  the  fibre.  The 
dark  striae  are  broader  than  the  light,  and  show  at  the  boundary 
of  the  clear  bands  a  darker  layer  which  seems  to  consist  of  a  series 
of  dots. 

On  teasing  out  dead  muscle  fibres  hardened  in  alcohol,  it  is 
possible  to  separate  the  primitive  fibrils.  This  is  easiest  in 
animals  which  have  the  most  abundant  sarcoplasm  (Fig.  20). 
Under  a  high  power,  each  fibril  is  seen  to  consist  of  alternating 
light  and  dark  bands  of  approximately  uniform  width.  But  in 
the  middle  of  the  clear  band  there  is  a  very  fine  dark  line, 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


27 


which  was  first  described  by  Aniici,  but  is  generally  known  as 
Krause's  membrane.  Krause  regarded  this  as  a  delicate  little 
membrane,  dividing  the  fibrils  into  a  series  of  segments  which  he 
called  sarcomeres.  In  the  muscles  of  certain  insects  as  well  as 
those  of  some  mammals,  a  further  differentiation  is  visible  with 
strong  magnification  in  both  light  and  dark  bands,  for  the 
description  of  which  the  reader  must  refer  to  text-books  of  modern 
histology. 

From  the  physiological  point  of  view  the  different  refracting 


:::::::-  •••••. 

:, !;ij;;;;;;; 


is 


•iiffjj     in  I, 

tmfl  &aiwis 
ii-j  3  !»»MwFfi» ; 

Dun  --/(({"'V't'/ 
jllHll  '."iinimTf/  -, 
-.'!'!'.'»  BjrnjHifijf  /' 
ufff  unniTinm  / 


FIG.  19. — (Left.)  Muscular  fibre  of  a  mammal  examined  fresh  in  .serum.  (Schiifer.)  Highly 
magnified. 

FIG.  20. — (Right.)  Fragment  of  frog's  muscle  fibre  in  which  a  few  fibres  have  been  isolated. 
(Szymonowicz.)  Magnified  about  650  diameters,  n,  nucleus ;  fp,  primitive  fibril ;  is, 
isotropous  layer;  an,  anisotropous  layer;  A,  Amici's  striae  or  intermediate  disc. 

power  of  the  respective  light  or  dark  bands  of  muscle  fibres  is 
more  important.  Boeck  of  Christiania  was  the  first  who  pointed 
out  that  certain  tissues,  among  them  the  muscles,  were  doubly 
refracting  or  anisotropous,  but  Briicke  (1857)  showed  that  the 
whole  fibre  is  not  anisotropous,  a  portion  of  its  substance  being 
singly  refracting  or  isotropous.  When  the  fibres  are  viewed  by 
polarised  light,  the  dark  striae  show  up  light  on  the  black  ground 
formed  by  crossed  Nicol  prisms  :  the  light  striae,  on  the  contrary, 
appear  dark.  The  former  are  doubly,  the  latter  singly  refracting. 
To  obtain  a  clear  idea  of  the  changes  which  the  striatiou  of 
the  muscle  fibre  undergoes  during  contraction,  it  is  necessary  to 
fix  the  muscle  as  the  contraction  wave  crosses  it,  in  order  to  study 


PHYSIOLOGY  CHAP. 

all  the  details  of  its  appearance  under  the  microscope.  This  is 
easily  accomplished  if  a  fresh  muscle  from  an  insect's  leg  is 
dropped  into  absolute  alcohol  or  solution  of  osmic  acid.  These 
reagents  excite  a  series  of  waves  in  the  muscle  fibre,  and  fix  it  at 
the  same  time,  so  that  on  teasing  out  some  bundles  of  fibres  for  a 
few  minutes  and  examining  them  under  the  high  power,  the  so- 
called  "fixed  wave  of  contraction "  can  be  seen  in  the  form  of 
nodes  or  fusiform  swellings.  In  some  fibres  it  is  also  possible  to 
see  the  so-called  "  lateral  waves,"  due  to  contraction  of  one  surface 
of  a  fibre  which  is  relaxed  on  the  opposite  side,  and  intermediate 
parts  between  the  two  surfaces  show  gradations  of  all  the 
intermediate  stages  between  the  phases  of  contraction  and  of 
relaxation. 

Engelmann  (1878)  made  the  most  important  contributions  to 
this  subject.  He  found  in  the  muscle  fibres  of  an  insect  (Thele- 
pliorus  melanurus)  treated  as  above,  that  the  optical  properties 
and  the  breadth  of  the  isotropous  and  anisotropous  bands  altered 
inversely  to  the  changes  in  the  form  of  the  fibres  during  contrac- 
tion. As  shown  by  Fig.  21  the  isotropous  layers  become  ?is  a 
whole  more  refracting,  i.e.  more  compact  and  darker,  while  the 
anisotropous  layers  become  less  refractive,  i.e.  more  fluid  and 
Lighter.  The  breadth  of  both  layers  diminishes  during  contraction, 
but  more  rapidly  in  the  isotropous  than  in  the  anisotropous  bands, 
so  that  the  latter  increase  in  volume  at  the  expense  of  the  former. 
Thus,  according  to  Engelmann,  we  must  assume  that  during 
contraction  the  anisotropous  substance  subtracts  water  from  the 
isotropous. 

The  same  fact  is  more  evident  in  Fig.  22,  which  represents  a 
lateral  contraction  wave,  observed  by  Eollet  near  a  motor  end-plate. 

Ranvier  (1880)  employed  an  ingenious  method  for  determining 
which  bands  of  the  sarcoplasm  contracted,  and  which  behaved 
passively,  when  stimulated.  He  put  two  muscles  of  a  frog  or 
rabbit  into  a  condition  of  absolute  isometry,  and  then  fixed  them 
by  absolute  alcohol  while  one  was  inactive,  the  other  in  tetanus 
produced  by  an  induced  current.  On  then  comparing  the  muscles 
under  the  microscope,  he  found  a  reduction  in  the  breadth  of  the 
dark  anisotropous  discs  in  the  fibres  of  the  tetanised  muscle,  which 
were  now  perceptibly  equal  to  the  clear  isotropons  discs,  while 
in  the  inactive  muscle  they  were  considerably  broader.  He 
further  pointed  out  that  there  was  in  the  fibres  of  the  tetanised 
muscle  a  considerable  increase  of  the  interfibrillar  sarcoplasm, 
which  appeared  to  break  up  the  fibre  into  fibrils. 

According  to  Eanvier,  therefore,  the  layers  of  anisotropous 
substance  diminished  in  volume.  Contrary  to  Engelmann's 
results,  water  does  not  pass  from  the  isotropous  to  the  anisotropous 
substance  during  tetanic  tension,  but  diffuses  from  the  latter  into 
the  interfibrillary  substance. 


GENEKAL  PHYSIOLOGY  OF  MUSCLE 


29 


Since  the  experimental  conditions  adopted  by  the  two  authors 
are  essentially  different,  these  apparently  contradictory  conclusions 
may  not  be  irreconcilable. 

Both   Engelmaim  and  Eanvier  agree,  though  from  different 


FIG.  21. — (Left.)  Fixed  wave  of  contraction  in  muscular  fibre  of  insect.  (Engelmann.)  The  right 
half  of  the  figure  shows  the  fibre  examined  under  polarised  light;  the  doubly  refracting  bands 
look  light  on  a  dark  ground  with  crossed  Nicols.  R,  segment  of  fibre  at  rest ;  //,  segment 
beginning  to  contract ;  C,  contracted  segment,  a,  intermediate  disc  of  Amici ;  b,  accessory 
disc  of  clear  or  isotropous  layer  ;  c,  dark  or  anisotropous  layer. 

Fio.  2'2. — (Right.)  Fixed  wave  of  lateral  contraction  near  a  motor  end-plate  (Pin)  obtained  by 
Rollett  from  a  muscle  fibre  of  Cassida  eifuestris.  Very  high  magnification. 

reasons,  in  regarding  the  anisotropous  disc  as  the  only  contractile 
part  of  the  muscle  fibre.  Engelmann  based  this  conclusion  on  a 
long  series  of  observations  which  showed  that  contractility  and 
double  refractivity  appear  simultaneously  during  the  ontogeiietic 
development  of  the  muscle  cells,  and  that  the  contractile  force  is 
greater  in  proportion  as  the  double  refractivity  is  more  intense. 


30  PHYSIOLOGY  CHAP. 

Kanvier  draws  the  same  conclusions  from  the  fact  brought  out 
directly  by  his  experiments,  viz.  that  the  anisotropous  discs  are 
the  only  ones  that  change  in  form  and  diminish  in  volume  during 
the  state  of  isomeric  tetanisation. 

More  recently  Schafer  (1891)  and  Hiirthle  (1901-4)  have 
studied  the  microscopic  variations  in  the  muscle  fibres  during 
contraction,  by  photography  and  cinematography.  Schiller's 
observation  in  particular,  according  to  which  minute  canals, 
parallel  with  one  another,  run  in  the  anisotropous  layer  in  the 
direction  of  the  fibres,  is  important.  During  contraction  the 
isotropous  substance  penetrates  these  canaliculi,  which  dilate  so 
that  the  muscular  segment  becomes  wider  and  shorter. 

It  is  in  any  case  certain  that  the  transverse  striatiou  due  to 
the  separation  of  the  doubly  refracting  from  the  singly  refracting 
tibres  is  not  indispensable  to  the  contractility  of  the  elements, 
because  the  unstriated  muscle  cells  are  contractile  although  much 
more  sluggishly  so  than  the  striated  fibres.  Kanvier  assumes  in  the 
latter  that  the  separation  of  the  doubly  refracting  substance  into 
distinct  masses  facilitates  and  makes  possible  a  quicker  displace- 
ment of  the  fluid  from  the  surrounding  parts  into  the  contractile 
layers. 

VI.  We  must  next  consider  the  phase  of  relaxation,  in  which 
the  shortened  muscle  elongates  and  describes  a  curve  which 
closely  resembles  the  curve  of  contraction.  The  sole  difference 
between  contraction  and  relaxation  lies  in  the  fact  that  the  latter 
is,  generally  speaking,  more  variable  in  its  duration  and  rate  of 
drop  towards  the  abscissa. 

Formerly  the  elongation  of  the  contracted  muscle  was  regarded 
as  a  physiologically  passive  phenomenon,  due  to  the  cessation  of 
the  process  of  contraction.  Very  few  admitted  that  both  the 
shortening  and  the  lengthening  of  the  muscle  were  due  to 
converse  physiological  processes :  yet  this  theory  of  the  con- 
tractive and  expansive  activity  of  skeletal  muscle,  which  we  have 
maintained  since  1871,  agrees  with  the  corresponding  theory  of 
the  properties  of  amoeboid  protoplasm,  cardiac  muscle,  and  the 
musculature  of  the  vessels  and  gut,  which  was  discussed  at  length 
in  Vol.  I. 

The  length  of  any  skeletal  muscle  in  the  resting  state  is  not 
constant,  but  varies  under  different  intrinsic  and  extrinsic 
conditions. 

When  any  muscle  or  the  tendon  by  which  it  is  attached  to 
the  bone  is  divided  in  the  living  animal,  the  two  segments  draw 
apart  or  retract,- as  though  the  muscle  were  normally  in  elastic 
tension  and  the  distance  from  the  points  of  its  insertion  were 
greater  than  the  natural  length. 

Cut  muscles  also  retract  after  death,  so  that  the  tension  of 
normal  skeletal  muscle  is  partly  an  effect  of  the  elasticity  of  the 


i  GENEEAL  PHYSIOLOGY  OF  MUSCLE  31 

muscle  and  the  stretching  to  which  it  is  mechanically  subjected. 
One  advantage  of  this  extension  is  that,  even  if  fully  relaxed,  the 
muscle  on  contraction  immediately  approximates  its  two  points 
of  insertion,  without  any  loss  through  mechanical  causes. 

The  elastic  tension  of  the  resting  muscle  under  normal  con- 
ditions is  not,  however,  explained  solely  by  this  passive  traction. 
During  life  it  undergoes  marked  oscillations  under  various 
conditions.  This  tension  of  the  muscle,  which  is  not  passively 
determined  by  the  distance  between  its  points  of  insertion  but 
is  the  expression  of  muscular  activity,  is  known  as  its  tone. 

Many  facts  show  that  the  natural  length  of  the  resting 
muscle,  on  which  its  natural  tone  depends,  is  directly  dependent 
on  the  nervous  system.  We  shall  elsewhere  study  the  mechanism 
of  this  constant  tonic  influence  which  the  nerve  exercises  upon 
the  muscle :  here  we  must  confine  ourselves  to  describing  the 
classical  experiment  of  Brondgeest  (1860)  which  demonstrates  it. 
If  the  lumbar  plexus  of  a  frog  is  cut  on  one  side,  after  its  spinal 
cord  has  been  divided  higher  up  so  as  to  paralyse  voluntary 
movements,  and  the  animal  is  suspended  vertically  by  its  head, 
the  two  hind-limbs  of  the  animal  take  up  essentially  different 
positions.  The  leg  of  the  side  on  which  the  nerves  were  cut 
hangs  fully  extended,  i.e.  the  muscles  are  flaccid,  while  that  of 
the  other  side,  on  which  the  nerves  are  intact,  is  slightly  flexed 
owing  to  the  tone  of  the  muscles.  A  similar  phenomenon  is 
observed  on  man  in  the  fairly  frequent  cases  of  facial  paralysis ; 
the  distortion  of  the  mouth  and  nose,  which  is  very  pronounced 
in  speaking,  is  also  obvious  even  in  the  state  of  absolute  inactivity 
of  all  the  facial  muscles ;  it  is  due  to  loss  of  tone  in  the  muscles 
of  the  paralysed  side  and  its  persistence  in  the  muscles  of  the 
sound  side,  owing  to  which  the  latter  pull  on  the  former. 

In  certain  abnormal  conditions  of  the  nervous  system — as  in 
hysteria,  somnambulism,  and  hemiplegia  of  long  standing — the 
tone  of  the  muscles  may  be  enormously  exaggerated  and  become 
contractured  (Brissaud  and  Eichet).  This  condition  is  essentially 
different  from  tetanus,  which  is  due,  as  we  have  seen,  to  summation 
and  fusion  of  muscular  contraction.  Simple  twitches  and  even 
a  true  tetanus  can  be  obtained  from  contractured  muscles,  by 
suitable  electrical  stimulation,  as  in  the  normal  resting  muscle : 
and  the  characteristic  muscle  sound  can  be  heard  during  tetanus, 
that  is  absent  in  simple  contracture  (Brissaud  and  Boudet). 

Independently,  again,  of  the  nervous  system,  contracture  may 
result  from  intrinsic  alterations  in  the  muscle,  caused  by  certain 
poisons.  This  is  a  tonic  state,  quite  distinct  from  the  rapid 
contractions  which  can  also  be  evoked  from  the  muscle  by  means 
of  make  or  break  shocks  during  contracture.  Among  the  poisons 
capable  of  producing  this  phenomenon,  veratrin  has  been  the 
most  studied,  particularly  by  von  Bezold,  Fick,  Bohm,  and  others. 


PHYSIOLOGY  CHAP. 

If  one  muscle  of  a  lightly  veratrinised  animal  (frog  or  toad) 
is  detached,  fixed  to  the  myograph,  and  stimulated  with  an 
induction  shock,  the  resulting  curve  will  be  very  different  from 
that  of  the  normal  twitch  (in  Fig.  23),  as  the  rapid  contraction  is 
followed  by  a  long  contracture  which  slowly  diminishes. 

Fick  endeavoured  to  explain  this  phenomenon  by  assuming 
that  the  rapid  primary  contraction  depends  on  the  indirect 
excitation  of  the  muscle  transmitted  by  the  intramuscular  nerves, 
and  the  subsequent  contracture  on  the  direct  excitation  by  the 
poison.  fBut  this  interpretation  is  contradicted  by  the  fact  that 
it  is  possible  to  obtain  the  same  form  of  curve  from  animals  that 
have  previously  been  curarised.  Griitzner  proposes  another 
explanation,  and  suggests  that  the  rapid  primary  and  slow 
secondary  contraction  depend  on  two  distinct  species  of  fibres 


FIG.  23. — Contracture  of  gastrocnemius  muscle  of  veratrinised  toad,  produced  by  simple  break 
shock  from  an  induced  current.  (Bottazzi.)  The  tracing  shows  that  the  veratrin  contracture 
is  preceded  by  an  ordinary  contraction,  which  is  suddenly  interrupted  at  the  commencement 
of  the  relaxation.  Time  tracing  in  half-seconds. 

(pale  and  red,  rapid  and  torpid)  in  the  muscle.  This  hypothesis 
is  contradicted  by  the  later  observations  of  Carvallo  and  Weiss, 
according  to  which  both  the  pale  muscles  and  the  red  exhibit 
the  characteristic  veratrin  contracture.  The  most  probable 
explanation  is  that  of  Bottazzi,  who  regards  the  coexistence  of  a 
rapid  and  a  slow  contraction  as  due  to  the  presence  in  the 
muscle  fibres  of  two  distinct  contractile  materials,  endowed  with 
different  degrees  of  excitability — anisotropous  and  isotropous 
substance. 

The  hypothesis  that  the  singly  refracting  substance  of  the 
sarcoplasrn  is  capable  of  causing  positive  and  negative  variations 
in  the  tone  of  the  muscle,  independently  of  the  simultaneous 
rhythmical  excitation  of  the  doubly  refracting  substance,  explains 
the  phenomenon  discovered  by  Fano  in  the  auricular  musculature 
of  Emys  europea  (Vol.  I.  p.  319),  which  exhibits  rhythmical 
oscillations  of  tone,  on  which  the  ordinary  cardiac  rhythm  is 
superposed.  The  plain  muscles  of  the  oesophagus  in  toad,  fowl, 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE 

Aplysia  (Bottazzi),  aud  those  of  the  dog's  stomach  also  show 
automatic  rhythmic  oscillations  of  tone,  similar  to  those  in  the 
tortoise  auricle,  and  may  be  explained  by  contractility  of  the 
sarcoplasrn,  which  certainly  predominates  in  these  muscles. 

More  recently  (1901)  Bottazzi  lias  endeavoured  to  extend  his 
hypothesis  to  all  contractile  protoplasm,  including  the  striated 
muscles  of  the  skeleton.  Why,  he  asked,  should  the  muscular 
tetanus  due  to  the  fusion  of  elementary  twitches  reach  a  height 
considerably  greater  than  that  of  a  single  twitch  obtained  from 
the  same  muscle  with  maximal  stimulation  ?  This  is  explained 
by  assuming  that  owing  to  the  tetauising  stimulus  and  the 
weight  applied  to  the  muscle  the  muscular  tone  is  exaggerated 
into  a  contract ure,  which  represents  a  form  of  "  internal  support " 
maintained  as  long  as  the  muscle  remains  shortened,  while  the 
rhythmical  contractions  rise  above  the  level  of  this  contracture 
(v.  Kries,  v.  Frey,  Griitzner).  v.  Frey  (1877)  had  demonstrated 


Fin.  24.— Myogram  of  frog's  gastrocnemius  loaded  with  10'5  grins,  (v.  Frey.)  t,  t,  myograms  of 
tetanus;  *•. i. ,  s.i. ,  myograms  of  .simple  contractions  obtained  with  single  shock  of  the  same 
induced  current;  x.in.s.,  myograms  of  a  group  of  contractions  obtained  with  the  muscle 
supported,  i.e.  relieved  of  the  weight  during  relaxation. 

that  on  exciting  the  muscle  of  a  frog  by  a  series  of  induction 
shocks,  while  the  muscle  is  so  supported  that  in  relaxing  it  is  not 
stretched  by  the  weight  which  it  lifts  in  contracting,  the  con- 
tractions rise  in  proportion  as  the  lever-support  is  raised  by  a 
screw,  till  they  eventually  reach  the  same  height  as  the  tetanus 
of  the  same  muscle,  loaded  and  not  supported  (Fig.  24). 

But  v.  Frey's  explanation  is  not  sufficient.  We  still  ask- 
on  what  does  the  contracture  depend '{  It  cannot  be  due  to 
activity  of  the  same  contractile  substance  as  that  on  which  muscle 
twitches  depend,  for  it  would  then  be  unable  to  function  as  an 
internal  stimulus.  Bottazzi  holds  that  it  can  only  he  interpreted 
on  his  hypothesis  of  the  contractility  of  the  sarcoplasm.  He 
assumes  that  the  rhythmical  faradic  stimuli  (and  in  our  opinion 
the  weight  which  stretches  the  muscle  as  well)  are  capable,  in 
addition  to  the  rapid  twitches  that  su inmate  in  the  curve  of 
tetanus,  of  evoking  a  further  excitation  and  contracture  of  the 
sarcoplasm,  which  constitutes  an  internal  support.  If  after  induc- 
ing "  veratrin  contracture  "  in  a  muscle  it  is  excited  with  a  maximal 
induction  shock,  the  resulting  twitch  rises  above  the  level  of 

VOL.  Ill  D 


34  PHYSIOLOGY  CHAP. 

contracture  to  the  same  height  to  which  it  rose  above  the  abscissa 
of  the  base  line,  previous  to  contracture  (Fig.  25).  Probably, 
therefore,  the  rapid  shortening  of  the  muscle  in  contraction  is 
independent  of  the  slow  and  persistent  shortening  in  contracture. 
The  former,  depends  on  the  activity  of  the  anisotropous,  the  latter 
on  that  of  the  isotropous  substance. 

The  fact  that  the  tetanus-curve  of  a  muscle  rises  normally 
above  the  maximal  twitch  is,  however,  capable  of  a  far  more  simple 
interpretation.  We  have  seen  that  the  excitation  spreads  over 
the  muscle  like  a  wave.  Hence  even  after  a  maximal  shock  all  parts 
of  the  muscle  cannot  be  simultaneously  thrown  into  contraction. 
On  the  contrary,  the  parts  first  excited  already  begin  to  relax  before 
the  others  reach  the  maximum  of  contraction  (Fig.  16,  p.  23).  So 
that  with  maximal  shocks  the  extent  of  the  muscular  shortening 


FIG.  25. — Two  contractions  of  toad's  gastrocnemius,  before  (1)  and  after  (2)  veratrin  contracture 
(I')  on  exciting  by  maximal  induction  shocks.     (Bottazzi.) 

depends  on  the  point  of  excitation,  the  rate  at  which  the  contrac- 
tion wave  travels,  and  the  rapidity  with  which  the  individual 
portions  of  the  muscle  contract  and  relax.  If,  on  the  other  hand, 
a  series  of  excitation-waves  are  sent  in  rapid  succession  through 
the  muscle,  all  its  parts  will  finally  be  in  maximal  contraction  at 
the  same  time,  which  must  obviously  result  in  a  much  more 
pronounced  contraction  (Fr.  W.  Frohlich). 

The  general  conclusion  that  can  be  deduced  from  this  discussion 
of  the  tone  of  the  skeletal  muscles  is  that  tonicity  may  undergo 
positive  or  negative  oscillations,  which  are  probably  the  expression 
of  corresponding  changes  in  the  elastic  forces  intrinsic  to  the 
muscular  protoplasm.  These  changes  may  be  due  to  the  tonic 
influence  exercised  by  the  nerves  011  the  muscles,  or  to  stimuli 
acting  directly  on  the  latter.  After  section  or  paralysis  of  the 
nerves  or  motor  end-plates  the  tone  of  the  skeletal  muscles  is 
abolished ;  it  is  normal  in  healthy  individuals  in  whom  the 
antagonist  muscles  exert  reciprocal  traction ;  it  becomes  more  or 
less  strongly  exaggerated  under  certain  special  abnormal  conditions 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  35 

of  the  nervous  system,  some  of  which  may  also  he  produced 
artificially  in  healthy  subjects,  and  by  curtain  poisons  which  act 
directly  upon  muscle. 

It  should  be  added  that  muscle  tone  may  be  inhibited  under 
special  conditions ;  i.e.  it  may  suffer  a  negative  variation  in  which 
the  length  of  the  muscle  is  exaggerated  beyond  the  normal. 

An  interesting  example  of  obvious  lengthening  of  the  muscles 
after  direct  excitation  of  their  motor  nerves  was  first  observed  by 
Eichet  (1882)  on  the  muscles  of  the  crab's  claw.  This  organ  for 
the  capture  of  prey  and  weapon  of  offence  and  defence  consists  of 
two  arms,  one  of  which  is  fixed,  the  other  movable  by  means  of 
two  muscles  of  antagonist  action,  the  one  a  very  delicate  abductor, 
the  other  a  much  thicker  and  stronger  adductor.  If  the  rigid 
branch  of  the  claw  be  fixed  in  a  clamp,  and  a  thread  attached  to 
the  movable  arm,  it  is  easy  (either  by  direct  transmission  to  a 
writing-lever,  or  by  indirect  transmission  through  a  couple  of 
Marey's  tambours  joined  together)  to  record  on  a  moving  drum 
the  reactions  of  the  claw-muscles  to  induced  or  constant  currents, 
acting  directly  on  the  nerves  of  the  claw,  or  on  one  or  other  of  the 
muscle.?. 

On  exciting  the  nerve  with  a  weak  current,  Eichet  saw  that 
the  claw  opened ;  on  exciting  with  a  strong  current,  on  the 
contrary,  it  closed.  In  the  first  case  the  action  of  the  abductor 
prevailed,  in  the  second,  of  the  adductor. 

Eichet's  observation  was  confirmed  by  Luchsinger,  and 
elucidated  by  further  experiments  of  Biedermann  (1887-88).  If 
the  abductor  is  divided  before  exciting  the  nerve  of  the  claw,  the 
result  is  the  same  as  in  Eichet's  experiments ;  with  weak  stimula- 
tion the  claw  opens,  with  stronger  excitation  it  closes.  In  the 
first  case,  therefore,  there  is  elongation  or  relaxation  of  the  adductor, 
in  the  second,  contraction.  If,  on  the  contrary,  the  adductor  be 
cut,  a  weak  current  causes  opening  of  the  claw,  or  contraction  of 
the  abductor,  a  stronger  current  closing  of  the  claw  and  lengthen- 
ing of  the  muscle.  The  elongation  of  the  muscle  apparent  in  the 
first  experiment  with  weak  stimulation,  in  the  second  with  strong, 
was  interpreted  by  Biedermann  as  an  inhibition  of  muscle  tone, 
similar  to  that  produced  in  cardiac  muscle  by  excitation  of  the 
vagus. 

Piotrowrski  (1893)  confirmed  the  fact  already  noted  by  Bieder- 
mann that  to  produce  the  inhibitory  effect  it  is  essential  that  the 
preparation  should  be  in  a  state  of  considerable  tonic  excitation ; 
in  fact  it  can  never  be  obtained  in  summer,  when  the  tone  of  the 
muscles  is  low.  He  noted  further  that  the  same  current  may 
evoke  now  contraction  and  now  inhibition,  according  as  the  tone 
of  the  preparation  is  low  or  high.  Temperature  has  a  marked 
effect  on  the  phenomenon ;  high  temperatures  abolish  the 
inhibitory  effect ;  low  temperatures  favour  it ;  the  optimum  for 


36  PHYSIOLOGY  CHAP. 

obtaining  the  inhibitory  effect  is  about  8°  C.  For  both  claw 
muscles  he  saw  that  the  latent  period  of  the  inhibition  produced 
by  a  minimal  stimulus  is  shorter  than  that  which  precedes  con- 
traction evoked  by  a  similar  stimulus.  Lastly,  he  found  on 
stimulating  the  nerve  with  simple  induction  shocks  that  when  the 
tone  of  the  muscle  was  very  pronounced  the  contraction  was 
preceded  by  a  brief  depression  of  tone.  The  same  was  noted  by 
(lad,  and  later  by  Nagy  von  Eegeczy  and  by  Cowl,  for  nerve- 
muscle  preparations  of  the  frog  under  special  conditions. 

All  these  researches  on  the  reaction  of  striated  crustacean 
muscles  to  stimuli  present  numerous  analogies  with  the  phenomena 
of  cardiac  muscle.  Certain  histological  observations  of  Biedermann 
justify  the  conjecture  that  there  are  two  different  species  of  nerve- 
fibres  in  the  crab's  claw-muscles,  as  in  the  heart,  some  of  which 
may  excite  the  assimilatory  or  anabolic  processes,  others  dis- 
similatory  or  katabolic  changes.  The  former  function  like  the 
vagus  fibres,  the  latter  like  the  sympathetic  fibres,  on  the  heart. 
Mangold  (1905)  has  recently  confirmed  this  hypothesis  of  a  double 
in  nervation  of  these  muscles. 

VII.  Alterations  of  form  (contraction  and  relaxation,  positive 
and  negative  variations  in  tone)  are  only  the  external  expression 
of  the  physiological  processes  that  take  place  within  the  muscle. 
To  obtain  a  clear  idea  of  these,  we  must  next  investigate  the 
chemical  composition  of  muscle,  and  the  changes  which  it  under- 
goes during  activity  and  in  rest. 

Muscle  undergoes  a  profound  physico-chemical  alteration  after 
death,  which  is  termed  rigor  mortis.  Muscles  excised  from  the 
body  of  the  living  animal,  or  merely  cut  off  from  the  circulation, 
become  rigid  after  a  certain  time  (varying  from  ten  minutes  to 
several  hours)  i.e.  they  are  less  soft  and  elastic,  less  extensible  and 
at  the  same  time  shorter,  thicker,  darker,  and  less  transparent. 
Their  alkaline  or  neutral  reaction  becomes  acid.  As  early  as  1833 
Sommer  regarded  cadaveric  rigidity  as  a  coagulation  phenomenon. 
Briicke  accepted  the  same  theory,  but  proof  was  afforded  for  the 
first  time  in  1859  by  Kiibne.  He  showed  that  when  the  living 
muscles  of  the  frog  were  completely  deprived  of  blood  by  an 
endovascular  injection  of  salt  solution,  and  gradually  cooled  to 
-  7°  C.  rubbed  into  fragments  and  squeezed  under  high  pressure,  it 
was  possible  at  a  temperature  of  0°  to  separate  off  a  fluid  which 
filtered  slowly,  was  of  syrupy  consistency  and  slightly  alkaline 
reaction,  which  he  termed  muscle  plasma. 

At  the  temperature  of  the  air,  muscle  plasma  clots  as  easily  as 
blood  plasma,  and  takes  on  a  gelatinous  consistency.  A  fluid 
afterwards  separates  out,  owing  to  the  contraction  of  the  clot. 
The  substance  that  clots  was  termed  my o sin  by  Kiihne,  and  the 
liquid  that  separates  off,  muscle  serum.  Muscle  plasma,  like  blood 
plasma,  begins  to  clot  at  the  points  of  contact,  and  the  process  of 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  37 

coagulation  is  accelerated  by  agitation  and  by  rise  of  temperature. 
Cold  checks  coagulation  ;  above  0°  C.  it  proceeds  very  slowly  ;  at 
higher  temperatures  it  becomes  faster,  and  at  40°  very  rapid. 
Addition  of  distilled  water  or  acids  causes  instantaneous  co- 
agulation. 

It  is  obvious  that  the  coagulation  of  muscle  plasma  corresponds 
to  the  rigor  that  develops  after  the  death  of  the  muscle.  Muscle 
plasma  indeed  contains  the  whole  of  the  soluble  proteins  of  living 
muscle,  and  as  on  cooling  muscle  to  -  7°  C.  its  excitability  is  not 
abolished,  but  merely  becomes  latent,  it  may  reasonably  be 
concluded  that  extraction  of  muscle  plasma  at  a  low  temperature 
destroys  its  structure,  but  produces  no  chemical  alteration  in  the 
substance  of  living  muscle. 

Kiihne's  discoveries  on  frog's  muscle  were  extended  to  the 
muscles  of  warm-blooded  animals  by  Halliburton  (1887),  who  nob 
only  employed  cooling  to  check  the  coagulation  of  muscle  plasma, 
but  also  added  neutral  salts  (sodium  chloride,  sodium  and 
magnesium  sulphate),  as  in  the  preparation  of  salted  blood 
plasma  (Vol.  I.  Chap.  V.)  The  addition  of  water  to  salted  muscle 
plasma  causes  it  to  coagulate  like  blood  plasma  when  the  fluid 
is  at  body  temperature,  while  it  does  not  clot  at  0°  C.  When 
coagulation  sets  in  the  reaction  of  the  plasma  becomes  acid.  In 
blood  plasma  fibrin  is  formed  from  fibrinogen  by  the  action  of  an 
enzyme,  and  similarly  in  muscle  plasma  myosin  is  formed  by  the 
action  of  an  analogous  enzyme  from  a  mother-substance,  which 
Kiilme  and  Halliburton  termed  myosinogen.  As  in  blood, 
fibrinogen,  not  fibrin,  is  pre-existent,  so  in  muscle  myosinogen  pre- 
exists, not  myosin.  0.  v.  Fiirth  (1902-3),  however,  denies  this 
analogy  between  the  coagulation  of  blood  and  of  muscle,  as  he 
failed  to  obtain  experimental  proof  that  the  rigor  mortis  of  muscle 
depends  on  the  action  of  any  ferment. 

Myosin  has  the  same  chemical  composition  as  globulin ;  it  is 
insoluble  in  distilled  water,  soluble  in  solutions  of  neutral  salts 
(sodium  chloride,  sodium  and  magnesium  sulphate),  and  it  coagu- 
lates at  a  temperature  of  55°-60°  C.  Myosin  when  dissolved  in 
neutral  salts  has  all  the  properties  of  myosinogen,  and  can  easily 
be  reconverted  into  myosin  on  simple  dilution  (Halliburton). 

The  fact  that  myosin  dissolved  in  a  weak  salt  solution  at  a  low 
temperature  is  doubly  refracting  in  polarised  light,  justifies  the 
assumption  that  the  anisotropous  discs  that  are  actively  concerned 
in  muscular  contraction  are  principally  composed  of  myosinogen 
(C.  Schipiloff  and  A.  Danilewsky). 

Halliburton  succeeded  by  means  of  fractional  heat  coagulation, 
and  by  salt  solutions  of  different  concentrations,  in  separating  five 
different  proteins  from  the  muscle  plasma,  four  of  which  are 
coagulable  at  different  degrees  of  temperature,  and  one  is  un- 
coagulable.  This  last  is  a  proteose,  and  is  apparently  identical 


38  PHYSIOLOGY  CHAP. 

with  the  eozyme  which  effects  the  coagulation  or  transformation 
of  myosinogen  into  myosin.  Of  the  four  coagulable  proteins,  two 
(inyosinogen  and  the  paramyosinogen  or  musculin  of  Hammarsten) 
form  the  clot,  while  the  two  found  in  the  muscle  serum  (myo- 
globulin  and  -myoalbumiii)  closely  resemble  or  are  identical  with 
those  present  in  blood  serum. 

Muscle  serum  holds  the  pigments  to  which  the  muscles  owe 
their  colour  in  solution.  The  normal  pigment  of  the  red  muscles 
is  due  to  haemoglobin,  identical  with  that  of  the  erythrocytes,  as 
was  proved  by  Kiihne  (1865)  from  the  spectrum  of  muscles 
(diaphragm)  that  had  been  entirely  freed  from  blood  by  prolonged 
washing  with  saline.  MacMunn  (1884-87)  afterwards  investi- 
gated the  muscles  of  different  classes  of  vertebrates  and  inverte- 
brates, and  found  that  they  exhibited  a  variety  of  absorption 
spectra,  due  in  his  opinion  to  a  group  of  pigments  which  he 
named  myohae matin.  According,  however,  to  Hoppe-Seyler  and 
Levy  (1889)  myohaematin  is  only  a  decomposition  product  of  the 
haemoglobin  of  the  muscle.  That  haemoglobin  is  an  intrinsic 
product  of  the  muscle  cells  or  fibres  is  shown  by  the  fact  that  it 
exists  in  the  muscles  of  invertebrates  which  have  no  haemoglobin 
in  their  circulating  fluids. 

When  the  muscles  of  recently  killed  animals  are  treated  with 
boiling  water  the  proteins  coagulate,  and  the  extract  contains  all 
the  soluble  nitrogenous  and  non-nitrogenous  organic  substances  of 
the  muscle.  The  first  form  a  group  of  compounds  which  represent 
different  disintegration  products  of  the  proteins  (creatine  and 
creatinine — zanthine,  hypozanthine,  carnine,  uric  acid  and  urea— 
taurine  and  glycocoll).  The  second  belong  to  the  carbohydrate 
group  and  its  derivatives  (glycogen,  dextrin,  glucose,  maltose, 
inosite,  lactic  acid,  and  lactates). 

Quantitatively  speaking,  creatine  and  glycogen  (which  we  have 
already  discussed,  Vol.  II.  pp.  391,  310)  predominate  among  these 
groups  of  substances  in  the  muscle. 

Nothing  definite  is  known  at  present  about  the  physiological 
importance  of  creatine  and  creatinine.  They  are  certainly  formed 
by  katabolic  processes  from  the  proteins  in  the  muscle.  In  fact 
they  are  more  abundant  in  muscles  which  have  been  overworked 
previous  to  the  death  of  the  animal  (Monari,  1888)  than  in  muscles 
analysed  after  rest.  Nawrocki  and  Sarokin,  however,  found  that 
the  creatine-content  is  no  larger  in  tetanised  than  in  resting 
muscle.  Another  striking  fact  was  discovered  by  Demant  (1879) 
in  Hoppe-Seyler's  laboratory.  In  the  muscles  of  pigeons  starved 
until  they  have  consumed  all  the  non-nitrogenous  reserve  materials 
contained  in  the  muscles,  so  that  metabolism  proceeds  at  the 
expense  of  protein  disintegration,  the  content  of  creatine  and 
creatinine  amounts  to  three  times  that  in  normal  pigeon  muscle. 

Glycogen  and  its  derivatives  are  the  principal  reserve  material 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  39 

utilised  by  the  muscle  during  work.  Nasse  (1869)  first  poiuted 
this  out,  as  he  found  that  the  glycogen  content  of  muscle  is  in 
inverse  ratio  with  the  work  performed.  The  best  evidence  for  it 
lies  in  the  fact  that  all  muscles  prevented  from  working  by  section 
of  their  nerves  or  tendinous  attachments  contain  an  excess  of 
glycogen,  as  compared  with  the  symmetrical  muscles  that  have 
remained  intact  (MacDonnel,  Chandelon,  Manche,  Weiss,  E. 
Krauss).  At  the  same  time  it  is  a  striking  fact  that  muscular 
glycogen  diminishes  far  more  slowly  than  hepatic  glycogen  in 
fasting  (Weiss,  Aldehoff,  Luchsinger) ;  this  is  not  due  to  the  fact 
that  the  liver  normally  supplies  the  muscles  with  glycogen,  since 
even  when  the  liver  has  been  excised  the  glycogen-content  of  the 
muscles  can  be  increased  by  feeding  with  cane-sugar.  Muscles 
have  therefore  an  amylogenic  and  glycogenic  function  which  is 
perfectly  independent  of  that  of  the  liver  (Prausnitz). 

Helmholtz  (1845)  observed  that  during  tetanus  the  extractives 
of  muscle  which  are  soluble  in  water  diminish,  while  those  soluble  in 
alcohol  increase,  which  depends  at  least  in  part  on  the  reduction  of 
glycogeu  and  increase  of  glucose  coincident  with  muscular  activity. 

Lactic  (or  sarcolactic)  acid  is  an  important  constituent  of 
muscle;  during  rigor  mortis  it  may  amount  to  O'l-l'O  percent 
(Bohm,  Demant).  Living,  resting  muscle  has  a  neutral  or  feebly 
alkaline  reaction,  while  rigid  muscle  has  a  distinctly  acid  reaction. 
Muscle  plasma,  too,  is  first  neutral  or  feebly  alkaline,  and  becomes 
acid  after  coagulation.  The  cause  of  this  reaction  has  been  the 
subject  of  much  controversy.  Some  authors  have  tried  to  replace 
Liebig's  early  theory  (1847)  that  it  is  due  to  a  development  of 
lactic  acid,  by  the  hypothesis  that  the  acidity  of  muscle  is  caused 
exclusively  by  mono-phosphate  of  potassium.  This  can  only  be 
proved  by  excluding  the  formation  of  lactic  acid  during  the  life  of 
the  muscle.  It  may,  however,  be  assumed  that  the  free  lactic 
acid,  acting  on  the  potassium  bi-phosphate  of  normal  living 
muscles,  is  converted  into  potassium  lactate,  by  reduction  of  the 
neutral  into  acid  phosphate,  which  may  partly  account  for  the 
acidity  of  dead  muscle. 

It  was  formerly,  and  is  still  sometimes  held  (Araki),  that 
lactic  acid  arises  from  disintegration  of  the  glycogen.  But  this 
is  obviously  controverted  by  the  work  of  Bohni  and  of  Demant. 
Bohm  (1880)  showed  that  the  amount  of  lactic  acid  formed  during 
the  death  of  the  cat's  muscle  is  in  no  relation  with  the  glycogen 
content,  since  the  latter  gradually  disappears  during  starvation, 
while  the  proportion  of  lactic  acid  is  not  less  than  normal.  Demant 
(1879)  showed  that  glycogen  entirely  disappears  in  the  pectoral 
muscle  of  pigeon  after  eight  days  of  fasting,  while  there  is  a  free 
formation  of  lactic  acid.  From  these  results  they  concluded  that 
the  mother-substances  of  the  lactic  acid  formed  by  muscle  must 
be  sought  in  its  proteins. 


40  PHYSIOLOGY  CHAP. 

Lactic  acid  has  been  proved  experimentally  to  be  one  of  the 
normal  katabolites  of  muscle,  formed  not  only  in  dead  but  also 
in  living  muscle  during  rest,  and  still  more  during  work.  On 
artificially  circulating  defibrinated  blood  for  three  hours  through 
the  muscles  of  the  lower  limbs  of  a  dog,  the  amount  of  lactic  acid 
that  can  be  extracted  from  the  blood  that  has  repeatedly  passed 
through  the  resting  muscle  amounts  to  about  1-5  grms.  Tetanisa- 
tion  of  living  muscle  certainly  increases  lactic  acid  formation ; 
the  amount  of  lactates  present  in  the  blood  (Spiro)  or  excreted  by 
the  kidneys  (Colasanti  and  Moscatelli)  increases.  The  muscles 
do  not,  however,  acquire  an  acid  reaction,  because  the  lactic  acid 
is  given  off  as  fast  as  it  is  formed  to  the  blood  -  stream,  where 
it  is  saturated  with  alkali.  When,  on  the  contrary,  a  group  of 
muscles  previously  cut  off  from  the  circulation  is  tetanised  they 
become  acid  owing  to  accumulation  of  lactic  acid,  while  the 
corresponding,  non-excited  muscles  of  the  opposite  side  remain 
neutral  or  alkaline  and  contain  little  lactate  (Marcuse,  Werther). 
In  excised  frog's  muscle  slight  electrical  excitation,  which  causes 
no  violent  contraction,  suffices  to  convert  the  neutral  into  an  acid 
reaction  (Gotschlich). 

From  these  and  other  experimental  researches  it  may  be  con- 
cluded that  the  formation  of  lactic  acid  is  associated  with  the  life 
of  muscle,  and  not  with  its  death,  as  many  believe.  The  con- 
vincing evidence  of  this  lies  in  the  fact  that  when  a  muscle  with 
normal  circulation  is  tetanised,  then  excised,  it  forms  less  acid 
during  its  death  than  the  corresponding  muscle  which  was  not 
excited,  showing  that  the  mother-substance  of  the  acid  has  been 
used  up,  and  that  the  amount  of  acid  developed  by  a  muscle  in 
dying  corresponds  with  the  quantity  of  mother-substance  con- 
tained in  it. 

In  addition  to  protein  and  glycogen  the  fats  may  be  regarded 
as  reserve  materials;  these  are  found  not  only  in  the  inter- 
muscular  connective  tissue,  but  also  within  the  fibres  and  in  the 
sarcoplasm,  and  especially  in  the  fibres  of  the  red  muscles,  in  the 
form  of  droplets  which  give  them  a  turbid  appearance  (Ph.  Knoll). 
Some  of  these  droplets  stain  black  with  osmic  acid,  others  remain 
unstained  and  probably  consist  of  lecithin.  During  starvation 
they  disappear,  and  return  on  feeding.  In  morbid  degenerative 
changes,  as  after  phosphorus  poisoning,  the  amount  of  fat  in- 
creases enormously,  and  it  must  therefore  be  due  not  to  storage, 
but  to  regressive  metamorphosis  of  the  proteins. 

The  part  played  by  the  fats  in  muscular  metabolism  is  un- 
known. The  small  fat-content  of  normal  fibres  is  no  reason  for 
regarding  it  as  unimportant,  since  in  all  probability  fat  does  not 
accumulate  normally  because  it  is  consumed  as  soon  as  formed. 
According  to  Bogdanow  the  fat  of  muscle-substance  is  richer  in 
volatile  fatty  acids  than  that  of  the  interniuscular  connective 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  41 

tissue.  It  seems  to  us  uot  improbable  that  tbe  development  of 
latty  acids  contributes  to  the  acidification  of  muscle  during  its 
death. 

The  inorganic  compounds  of  muscle  are  water  and  the  salts 
contained  in  the  ash. 

The  amount  of  water  in  human  muscle  is  not  less  than  70  per 
cent  and  may  rise  to  72-74  per  cent.  It  varies  to  some  extent 
in  different  classes  of  muscle.  Generally  speaking,  embryonic 
muscles  and  those  of  young  persons  are  richer  in  water  than 
those  of  adults  and  old  people.  During  starvation  the  water 
diminishes  considerably  ;  it  is  increased,  on  the  contrary,  by  work, 
which  suggests  that  during  the  discharge  of  the  energy  accumu- 
lated in  the  muscle  water  is  one  of  the  end-products  of  the  carbo- 
hydrate metabolism. 

Of  the  mineral  salts  contained  in  the  ash  of  muscle  the  pre- 
dominance of  potash  over  soda  among  the  bases,  and  of  phosphoric 
acid  among  the  acids,  is  remarkable.  According  to  Bunge  the 
ash  of  100  parts  of  muscle  contains  on  an  average  :— 

K,0  .  .  .  4-407  Fe.,03  .         .         .  O057 

Na.,0  .  .  .  0-790  P.,63  .        .         .  4-612 

C.,0"  .  .  .  0-079  01  ...  0-682 

MgO  .  .  .  0-396  S03  .         .         .  0-100 

It  is  certain  that  in  living  muscle  these  mineral  compounds  are 
not  all  present  in  the  form  of  simple  solutions,  but  are  in  organic 
combination.  The  sulphuric  acid  is  formed  from  the  sulphur  of 
the  proteins  during  combustion.  The  phosphoric  acid  is  only  pre- 
existent  to  a  very  small  extent  in  living  muscle,  the  greater  part 
arises  from  the  combustion  of  the  lecithin  and  the  nucleins. 
The  ferric  oxide  results  from  the  disintegration  of  the  muscular 
haemoglobin. 

The  gases  of  muscle  consist  in  a  considerable  amount  of  carbon 
dioxide  and  traces  of  nitrogen.  The  mercury  pump  has  failed 
to  separate  any  trace  of  oxygen  from  muscles  when  carefully 
washed  free  of  blood,  obviously  because  the  oxygen  combined  with 
the  haemoglobin  is  dissociated  and  carried  away  in  the  washing. 
According  to  Hermann  (1867),  2-74  per  cent  free,  and  1*95 
per  cent  combined  C02  can  be  extracted  from  muscle  which  is 
bled,  minced  up,  and  triturated  previous  to  the  onset  of  rigor. 
Stiutzing  found  that  on  prolonged  boiling  of  muscle  another 
substance  decomposes,  which  gives  rise  to  a  free  development  of 
CO.,.  It  is  probable  that  the  carbonic  acid  developed  in  tetanus 
and"  during  rigor  is  derived  from  the  same  substance  as  is  decom- 
posed by  boiling. 

We  have  already  reviewed  the  principal  facts  of  muscular 
respiration  (Vol.  I.  p.  393).  The  important  fact  is  that  the  gas 
exchanges  of  muscle  are  exaggerated  during  activity,  i.e.  both 


42  PHYSIOLOGY  CHAP. 

elimination  of  C02  and  absorption  of  02  are  increased ;  but  the 

CO 

value  of  the  respiratory  quotient  — p  increases  also,  because  the 

2 

output  of  C09  is  greater  than  the  intake  of  0.,  (Ludwig  and 
Sczelkow,  1862,  Ludwig  and  Schmidt,  1868,  v.  Frey,  1885). 

Hans  Winterstein  (1907)  demonstrated  that  the  rigor  mortis 
of  mammalian  muscle  is  essentially  due  to  the  loss  of  oxygenation, 
owing  to  arrest  of  the  vascular  circulation  ;  it  is  thus  an  asphyxia 
phenomenon.  In  fact,  if  a  mammalian  muscle,  excised  from  the 
body,  is  kept  in  Einger's  solution  at  an  oxygen  pressure  of  2-4 
atmospheres,  at  a  temperature  of  36-38°  C.,  its  excitability  may 
be  preserved  for  twenty-seven  hours  after  dissecting  it  out,  with 
no  appearance  of  rigor.  If  rigor  sets  in,  it  may  be  kept  off  by 
successive  strong  doses  of  oxygen.  When  it  is  once  established, 
however,  further  oxygenation  is  useless. 

VIII.  There  can  be  no  doubt  that  the  chemical  processes 
which  come  into  play  during  the  activity  of  muscle  are  the  source 
of  the  physical  energy  which  the  muscle  develops,  and  the  external 
mechanical  work  which  it  performs.  This  is  a  direct  corollary  to 
the  law  of  the  conservation  of  energy.  Muscular  excitation  is  the 
most  classical  instance  in  the  living  world  of  the  explosive  dis- 
charge of  energy,  i.e.  the  rapid  transformation  of  potential  chemical 
energy  iuto  kinetic  energy,  in  the  form  of  work,  heat,  and 
electricity.  As  in  the  steam-engine  the  mechanical  work  depends 
on  the  combustion  of  coal,  so  the  mechanical  work  of  the  muscular 
machine  results  from  the  katabolic  processes  of  disintegration  and 
oxidation  of  the  organic  compounds  which  build  up  the  muscle. 

Having  now  discussed  the  chemical  changes  that  go  on  in 
living  muscle  during  rest  and  in  activity,  we  must  next  turn  to 
the  problem  of  the  origin  of  muscular  energy,  that  is,  which  of  the 
food  stuffs  introduced  into  the  body  and  assimilated  by  the  muscles 
furnishes  the  necessary  energy  for  their  activity. 

Starting  from  the  fact  that  proteins  represent  the  chief  con- 
stituents of  muscle,  and  that  a  full  meat-diet  increases  the  work- 
capacity  of  muscle,  while  a  diet  poor  in  protein  depresses  it, 
Liebig  (1857-70)  assumed  that  the  source  of  muscular  energy 
must  be  sought  in  the  proteins.  There  can  be  no  doubt  that  the 
nitrogenous  exchanges  of  muscle  are  very  active,  much  protein 
being  consumed  both  in  rest  and  in  activity ;  but  Liebig  showed 
no  direct  experimental  proof  that  the  activity  of  muscle  depends 
mainly  upon  increased  protein  metabolism. 

Bischoff  and  Voit  (1860)  thought  the  question  could  be  solved 
by  comparing  the  urea  content  and  the  total  nitrogen  content 
of  urine  during  hard  muscular  work,  with  that  eliminated  during 
rest,  the  same  quantity  and  quality  of  food  stuffs  being  ingested. 
In  both  man  and  dogs  they  obtained  a  nitrogenous  equilibrium  after 
a  few  days  of  uniform  dieting,  i.e.  equivalence  between  the  nitrogen 


r  GENEKAL  PHYSIOLOGY  OF  MUSCLE  43 

introduced  and  that  eliminated  with  the  urine.  They  found  that 
this  equilibrium  was  not  much  affected  by  days  of  rest,  as  com- 
pared with  working  days,  i.e.  no  perceptibly  greater  quantity  of 
nitrogenous  substances  was  consumed  during  work. 

This  result  was  confirmed  by  the  later  and  more  accurate 
researches  of  Voit  (1870-81).  He  found  not  only  in  dogs  kept  on 
a  constant  diet,  but  in  starving  animals  also,  that  the  amount  of 
nitrogen  excreted  was  not  much  increased  by  work,  and  that  the 
increment  was  in  no  case  in  ratio  with  the  amount  of  work  done. 

Experiments  made  on  themselves  by  Fick  and  Wislicenus 
(1685)  supported  this  result.  They  climbed  the  Faulhorn,  1906  m., 
in  six  hours,  during  which  time  they  collected  all  the  urine  passed. 
During  the  twelve  hours  preceding  the  climb  and  on  the  ascent 
they  took  no  nitrogenous  foods,  and  lived  solely  on  starch,  fat,  and 
sugar.  From  the  amount  of  nitrogen  contained  in  the  urine  they 
deduced  the  amount  consumed  during  the  climb.  They  further 
calculated  the  amount  of  mechanical  work  accomplished  by  the 
leg  muscles  of  each,  multiplying  the  body-weight  by  the  height  of 
the  mountain  ;  the  work  done  by  the  other  muscles  was  not  calcu- 
lated. From  the  combustion  heat  of  the  protein  consumed  during 
the  ascent  they  calculated  the  maximal  yield  that  could  be 
obtained  if  the  whole  of  the  protein  in  the  body  were  burned  up. 
The  result  showed  that  the  work  done  on  the  climb  far  exceeded 
that  which  could  be  performed  by  the  decomposition  and  oxida- 
tion of  the  protein  consumed.  From  this  they  concluded  that  the 
non-nitrogenous  substances  introduced  with  the  food  or  stored  in 
the  body  as  reserve  materials  supply  energy  which  can  be  utilised 
during  work. 

The  direct  proof  that  it  is  principally  the  non-nitrogenous 
substances  (carbohydrates  and  fats)  that  are  consumed  during 
work  is  derived  from  experiments  on  the  respiratory  gas-exchanges, 
which  show  that  while  the  elimination  of  nitrogen  does  not 
increase  perceptibly  the  excretion  of  carbonic  acid  and  absorption 
of  oxygen  do  increase  considerably  during  work  (Pettenkofer  and 
Voit,  1866,  and  others).  This  agrees  perfectly  with  what  was 
stated  above  in  regard  to  the  consumption  of  glycogen  and  fat  in 
muscular  activity. 

What  part,  then,  does  the  protein  of  muscle  play  in  the  per- 
formance of  its  functions  ?  Since  muscle  consists  principally  of 
proteins,  which  are  the  fundamental  substrate  of  all  living  tissues, 
it  must  be  recognised  that  these  substances  play  an  active  part  in 
all  the  internal  processes  that  go  on  in  muscle. 

Traube  suggested  that  the  proteins  of  living  matter  have  the 
task  of  carrying  oxygen  to  the  nou- nitrogenous  combustible 
materials,  but  are  not  themselves  decomposed.  This  agrees  with 
PHiiger's  general  theory  of  the  oxidation  processes  of  the  animal 
body,  according  to  which  the  intra-molecular  oxygen,  chemically 


44  PHYSIOLOGY  CHAP. 

bound  up  in  the  molecules  of  living  matter,  is  the  source  of  the 
disintegrative  and  oxidising  changes  that  go  on  in  all  the  tissues. 
We  may  therefore  assume  that  the  proteins  of  muscle  absorb  and 
combine  with  oxygen  during  rest,  and  pass  it  on  during  activity 
to  nitrogen-free  molecules,  while  they  once  more  take  up  fresh 
oxygen  in  the  resting  period  which  follows.  On  this  hypothesis 
the  proteins  of  muscle  fulfil  the  same  function  as  an  enzyme 
during  work.  But  the  inadequacy  of  this  explanation  is  evident 
from  the  fact  that  muscle,  independently  of  rest  or  activity,  is  the 
seat  of  an  active  nitrogenous  metabolism,  which  must  therefore  be 
heightened  during  work.  Further,  intense  muscular  work  is 
possible  on  an  exclusively  flesh  diet.  Voit  showed  that  dogs  can 
be  kept  alive  under  normal  conditions  on  an  exclusive  diet  of 
meat.  In  his  latest  researches  (1892)  Ffliiger  fed  a  great  Dane 
of  30  kgrm.  for  nine  months  on  horseflesh,  which  was  almost  free 
of  fat,  and  made  it  do  hard  work  for  weeks  by  dragging  a  heavy 
cart  for  13  km.  in  two  to  three  hours.  During  this  time  the 
animal  remained  exceptionally  well  and  vigorous.  Under  these 
conditions  almost  the  whole  of  the  energy  developed  in  the 
animal's  muscles  must  be  derived  from  disintegration  of  protein, 
since  the  small  quantity  of  glycogen  and  fat  ingested  is  negligible. 

Nevertheless,  on  comparing  the  amount  of  nitrogen  given  off 
by  the  animal  in  periods  of  work  and  of  rest,  Pfliiger  could  only 
confirm  the  fact  that  it  did  not  vary  conspicuously,  and  that  the 
increase  was  never  in  proportion  with  the  work  performed. 

To  explain  this  fact  he  assumed  that  the  excretion  of  nitrogen 
does  not  increase  definitely  after  work,  because  though  the  muscles 
consume  more  protein,  other  tissues  consume  less,  by  a  sort  of 
adaptation  due  to  the  lesser  amount  of  protein  circulated. 

Verworn,  however,  pointed  out  that  this  hypothesis  cannot 
explain  Voit's  observation  on  the  dog,  that  even  in  the  fasting 
state  when  the  amount  of  circulating  protein  at  the  disposal 
of  the  muscles  and  other  tissues  is  minimal,  nitrogen  elimination 
does  not  increase  proportionately  with  hard  work  (making  a  wheel 
revolve  on  its  axis). 

Pfliiger  suggested  later  that  the  increased  disintegration  of 
protein  effected  by  the  muscle  during  work  does  not  show  a 
larger  excretion  of  nitrogen  in  the  urine,  because  the  nitrogenous 
waste  products  are  regenerated  synthetically  into  the  complex 
molecules  of  protein,  by  combining  with  non-nitrogenous  atoms 
lost  during  the  work,  at  the  expense  of  nutrition,  or  of  the  reserve 
materials.  In  other  words,  it  is  possible  and  even  probable  that 
the  nitrogenous  products  of  proteolysis,  which  is  increased  in 
muscular  work,  do  not  leave  the  body  like  the  non-nitrogenous 
products,  which  are  excreted  principally  in  the  form  of  carbohydrate 
and  water,  but  are  stored  up  and  partially  utilised  again  in  the 
synthetic  regeneration  of  protein  :  this  is  to  some  extent  analogous 


i  GENERAL  PHYSIOLOGY"  OF  MUSCLE  45 

to  the  process  by  which  the  proteoses  and  peptones  are  regenerated 
into  protein  by  the  intestinal  epithelium,  and  the  amino-acids 
(which  are  the  final  products  of  the  digestive  decomposition  of  the 
proteins)  restore  and  build  up  the  tissues,  after  being  reabsorbed 
into  the  lymph  and  blood.  So  that  muscular  proteolysis,  which 
is  stimulated  or  increased  by  work,  in  its  turn  promotes  the 
genesis  of  protein — and  consequently  the  quantity  of  nitrogenous 
products  in  the  urine  does  not  materially  increase  during  work. 

This  hypothesis  appears  to  us  acceptable  in  view  of  recent 
researches  on  the  complex  structure  of  the  proteins  which  build 
up  living  matter,  and  the  different  cleavage  products  that  can  be 
isolated  by  the  action  of  enzymes.  Pick's  studies  (1899)  on  the 
proteolytic  products  into  which  fibrin  can  split  under  the  action 
of  pepsin  are  of  first  importance.  Of  these  products  he  was  able 
to  isolate  :— 

(a)  A  proteoalbumose,  which  contains  no  carbohydrate  group,  but 
has  much  tyrosine  and  indole,  gives  off  no  glycocoll  among  its 
decomposition  products,  and  holds  sulphur  only  in  unstable 
equilibrium. 

(&)  A  heteroalbumose,  which  contains  no  carbohydrate  group 
and  hardly  any  tyrosiue  and  indole,  is  rich  in  leuciue,  with  some 
glycocoll,  and  holds  sulphur  only  in  unstable  combination. 

(c)  A  deuteroalbumose,  which  contains  no  carbohydrates. 

(V)  Two  deuteroalbuminoses  rich  in  carbohydrates. 

(e)  Two  peptones  containing  carbohydrates. 

The  importance  of  these  results  consists  in  the  fact  that  it  is 
comparatively  easy  to  separate  the  protein  molecule  from  the 
carbo-hydrate  group  (which  is  oxidised  during  muscular  work) 
without  loss  of  the  fundamental  chemical  properties  of  the  pro- 
teins, which  therefore  retain  their  capacity  for  synthetic  regenera- 
tion into  protein  under  the  influence  of  the  anabolic  activity  of 
the  living  tissue -cells.  If  we  admit  an  anabolic  proteogenic 
activity  in  the  intestinal  epithelium,  it  seems  reasonable  also  to 
assume  that  it  exists  in  muscle  (Vol.  II.  p.  328). 

IX.  We  have  said  that  muscular  contraction  is  the  most 
classical  and  hence  the  best  investigated  instance  of  an  explosive 
discharge  of  energy  in  the  living  world.  The  potential  chemical 
energy  stored  up  in  the  muscle  is  converted  during  excitation 
into  kinetic  energy,  which  appears  in  the  forms  of  mechanical 
work,  heat,  and  electricity,  each  of  which  must  be  considered 
separately. 

The  work  done  by  muscle  is  measured  by  the  product  of  the 
weight  raised  by  the  muscle  into  the  height  to  which  it  is  raised, 
w  x  h.  If,  therefore,  the  muscle  contracts  without  lifting  a  weight 
or  overcoming  any  resistance,  it  performs  no  mechanical  work. 
This  supposition  is,  however,  purely  theoretical  since  the  muscle 
always  has  to  carry  its  own  weight,  which  may  indeed  be  reduced 


46 


PHYSIOLOGY 


CHAP. 


to  a  minimum  if  the  muscle  is  laid  horizontally  on  mercury,  after 
first  dipping  it  into  oil  to  diminish  the  surface  friction. 

Again,  the  muscle  does  110  work  when  it  is  loaded  with  such 
a  heavy  weight  that  it  is  unable  to  raise  it.  In  the  first  case  the 
energy  developed  by  the  excitation  is  exhausted  in  the  contraction, 
in  the  second  in  the  tension  of  the  muscle ;  but  in  both  cases 
no  external  mechanical  work,  but  only  internal  mechanical  work 
is  done. 

On  calculating  the  external  work  done  by  a  muscle  in  raising 
regularly  increasing  weights,  it  is  found  that  it  increases  quickly 
at  first,  and  then  more  slowly,  until  it  reaches  a  certain  maximum, 
after  which  it  diminishes  again  and  finally  becomes  nil  on  reaching 
the  weight  which  the  muscle  is  unable  to  lift. 


Fig.  26  illustrates 


grms.  0 

•  i  50 

..  100 

..  <50 

..  200 

.'  250 

"  300 

..  350 

•i  400 

..  450 

>,  500 


min.  5 


6 
5 

4 
3 

2    5 
2 


grin.  mm.    0 

..    550 

»       ..    700 

..  900 

,.«000 

N<000 

•>        i.    900 

"       ••  675 

ii        .,  800 

••       ,,675 

,,   BOO 


Fio.  26. — Diagram  showing  work  done  by  muscle — frog's  gastrocnemius.     (A.  D.  Waller.) 

these  experimental  results,  which  can  be  verified  on  every  muscle 
that  is  loaded  and  stretched  before  contraction,  or  merely  while  it 
contracts. 

It  may  thus  be  stated  that  there  is  a  given  weight  for  every 
muscle,  at  which  it  reaches  its  maximal  yield  of  work,  and  that 
with  diminution  or  increase  of  the  load  the  work  becomes 
gradually  less  till  it  finally  reaches  zero.  This  law  of  course 
applies  also  to  all  groups  of  muscles  which  co-operate  in  the  work 
performed. 

The  resistances  encountered  by  the  different  muscles  concerned 
in  complicated  action  vary ;  the  degree  of  shortening  which  they 
undergo  varies  also.  Generally  speaking,  the  strength  of  a  muscle, 
i.e.  the  weight  it  is  able  to  lift,  increases  in  proportion  to  its 
diameter,  that  is,  the  number  of  fibres  it  contains.  Since  work  is 
the  product  of  the  weight  and  the  height  to  which  it  is  raised,  it 
follows  that,  other  things  being  equal,  the  work  of  a  muscle  is  in 
proportion  with  the  product  of  its  length  and  cross-section,  viz. 


GENEKAL  PHYSIOLOGY  OF  MUSCLE 


47 


the  volume  or  mass  of  the  muscle.     These  relations  between  the 
size    of   a   muscle    and    the    energy  it  is  capable  of  developing : 


between  the  length  of  a  muscle  consisting  of  parallel  fibres  and  its 
degree  of  contraction  ;  and  finally  between  the  weight  of  the 
muscle  and  the  useful  work  it  is  capable  of  yielding — were  all 
noted  by  Borelli  in  the  early  half  of  the  eighteenth  century,  and 
were  fully  considered  and  cleared  up  by  Weber  in  1845. 

The  absolute  force  of  a  muscle  is  measured  by  the  minimal 
weight  that  it  is  unable  to  lift  under  maximal  excitation  (Weber). 
Since  it  is  proportional  to  the  cross-section  or  diameter  of  the 
muscle,  a  universal  standard  is  obtained  by  calculating  the  absolute 
force  of  a  square  centimetre  of  the  muscle  section.  The  absolute 
force  of  the  muscles  varies  in 
different  animals  and  even  in 
different  muscles  of  the  same 
animal.  It  varies  for  a  square 
cm.  of  frog's  muscle  between  7 
and  8  kgrms.  (Henke  and  Knorz) 
or  even  9  and  10  k grins.  (Koster, 
Haughton). 

Attempts  have  also  been  made 
to  determine  the  absolute  force 
of  a  sq.  cm.  of  human  muscle  by 
measuring  the  cross -section  on 
a  dead  subject  of  the  same 
physique  and  muscular  develop- 
ment as  the  subject  of  experi- 
ment. Here,  again,  the  values 
obtained  were  very  different : 
2-8-3  kgrms.  (Eosenthal),  5-10 
kgrms.  (other  experimenters).  It 
should  be  noted,  however,  that  these  experiments  on  man  were  made 
not  with  artificial  tetanisation,  but  with  a  voluntary  yield  of  work, 
in  which  the  energy  developed  may  be  double,  or  at  least  a  third 
more  than  that  developed  on  stimulation  with  a  tetanising  current. 

From  the  clinical  point  of  view,  investigation  of  the  relative 
strength  of  certain  groups  of  human  muscles  is  far  more  practicable. 
The  dynamometer  is  usually  employed  for  this  purpose.  It  consists 
of  a  strong  oval  steel  spring,  which  is  compressed  by  the  hand,  while 
an  index  moves  along  an  empirically  graduated  scale  to  indicate 
the  amount  of  compression  and  thus  of  the  power  developed  in  the 
group  of  muscles  which  come  into  play  when  the  hand  is  closed. 

The  figures  obtained  by  this  instrument  are,  however,  of  little 
value,  since  they  can  be  modified  by  practice,  attention  on  the  part 
of  the  subject,  and,  above  all,  degree  of  voluntary  effort,  which  may 
vary  considerably,  even  independently  of  the  conscious  will  of  the 
subject. 


FIG.  27.— Dynamograph.    (A.  D.  Waller.) 


48 


PHYSIOLOGY 


CHAP. 


Morselli  added  a  contrivance  for  air- transmission,  which  made 
it  possible  to  record  the  compression  of  the  spring  upon  a  revolving 
cylinder,  and  which  transformed  the  dynamometer  into  a  dynamo- 
graph,  by  which  the  tracing  of  a  series  of  maximal  voluntary 
contractions  of  the  flexor  muscles  of  the  hand,  at  regular  intervals 
measured  by  the  beats  of  a  metronome,  can  be  recorded.  Such 


FIG.  28.— Tracing  from  Waller's  dynainograph,  to  show  elli-cls  of  fatigue  and  recovery. 

curves  show  not  only  the  comparative  force  of  the  muscles,  but 
also  their  resistance,  or  the  ease  with  which  they  become  fatigued. 
Still  more  simple  is  Waller's  dynarnograph  (Fig.  27),  in  which 
the  pull  of  the  hand  upon  a  strong  steel  spring  is  registered 
directly  by  a  long  lever.  Fig.  28  shows  the  tracing  of  six  groups 
of  maximal  contractions,  at  regular  intervals  ;  between  each  group 


Fn..  '_".!. — Mosso'x  c]  i;oi;Tapli. 


there  is  a  uniform  pause  for  rest.  The  drop  in  the 
line  uniting  the  apices  in  each  group  shows  the 
fatigue  of  the  muscle ;  the  return  to  the  original 
executed  height  in  the  next  group  represents  its 
recovery  during  rest. 

The  dynamographs  of  Morselli  and  Waller  are 
based  on  the  isometric  method,  and  consequently  record  the  maxi- 
mal tensions  of  the  flexors  of  the  hand,  and  the  correlative  internal 
work ;  Mosso's  ergograph  (Fig.  29)  is  an  instrument  based  on  the 
isotonic  method,  and  it  records  the  maximal  contraction  of  the 


GENEEAL  PHYSIOLOGY  OF  MUSCLE 


49 


flexors  of  the  middle  tinger,  on  loading  with  a  given  weight,  and 
therefore  the  external  work  (in  kilogranimetres)  performed  during 
maximal  voluntary  effort.  The  arm  is  placed  in  the  supine  position 
and  h'xed  to  a  horizontal  support.  A  leather  ring  is  applied  to  the 
middle  finger,  which  carries  a  string  that  runs  over  a  pulley  and  is 
weighted  at  the  end.  Raising  the  weight  displaces  a  lever,  the 
point  of  which  records  the  amount  of  flexion  of  the  finger.  Mosso 
attached  a  supporting  screw  or  stop  to  the  indicator  of  the  ergo- 
graph,  by  which  the  flexor  muscle  of  the  finger  can  be  relieved  of 
its  load  during  rest,  and  the  weight  only  pulls  on  the  muscle 
during  its  contractions. 


FIG.  30. — Two  tracings  of  different  types  from  Mosso's  ergograph,  taken  from  two  boys  of  the  same 
age  and  habit ;  in  both  a  weight  of  3  kgrms.  was  lifted  every  two  seconds. 

The  most  striking  results  obtained  in  the  earliest  researches 
of  Mosso  and  his  collaborators  (1890)  by  the  study  of  the  ergograph 
tracings  in  a  series  of  voluntary  maximal  efforts  at  regular  intervals 
are  as  follows  :— 

(a)  There  is  no  common  type  for  the  ergograph  fatigue  curve, 
but  each  individual  has  a  personal  type — i.e.  under  good  physio- 
logical conditions,  in  a  state  of  repose,  with  a  given  load  and 
definite  rate,  each  individual — even  at  long  intervals — exhibits 
the  same  fatigue  curve,  although  the  amount  of  external  mechanical 
work  may  vary  widely  (Fig.  30). 

(6)  The  personal  type  of  the  fatigue  curve  persists  even  when 
the  fatigue  is  produced,  not  by  voluntary  effort,  but  by  rhythmic 
electrical  stimulation  of  the  nerve  or  muscle. 

(c)  Pronounced  mental  fatigue  or  fatigue  of  all  the  muscles  of 

VOL.  in  E 


50  PHYSIOLOGY  CHAP. 

the  body  produces  rapid  exhaustion  on  the  ergograph,  even  if  the 
curve  is  obtained  by  electrical  excitation. 

(oT)  Ergograph  work  may  alter  the  elasticity  of  the  muscle, 
increasing  or  diminishing  it ;  in  certain  individuals  it  may  excite 
contracture,  which  is  the  more  readily  produced  in  proportion  with 
the  strength  and  frequency  of  the  stimulus,  and  the  weight  the 
muscle  has  to  raise. 

The  ergograph  curve  depends  on  the  combined  effects  of 
fatigue  of  the  nerve-centres  and  fatigue  of  the  muscle,  though  the 
latter  always  predominates.  "  The  characteristic  phenomena," 
Mosso  writes,  "  are  peripheral,  since  the  muscle  exhibits  its  char- 
acteristic fatigue  curve  even  with  artificial  stimulation.  ...  It  is 
not  the  will  nor  the  nerves,  but  the  muscle  that  is  weakened  after 
arduous  brain-work." 

Maggiora  subsequently  brought  out  the  great  importance  of 
the  varying  conditions  under  which  external  mechanical  work  is 
performed  on  the  ergograph  :— 

(a)  There  is  a  certain  weight  which  elicits  the  maximum  of 
utility ;  with  weights  below  a  certain  value,  no  sign  of  fatigue  is 
perceptible. 

(6)  With  every  load,  the  slower  the  rhythm  of  contraction  the 
more  external  work  can  be  performed,  and  the  more  the  onset  of 
fatigue  is  delayed.  For  any  given  weight  there  is  a  rate  at  which 
the  contractions  can  proceed  for  a  long  time  with  no  trace  of 
fatigue. 

(c)  If  a  muscle  is  contracting  at  a  given  rate  slow  enough  to 
allow  of  its  complete  recovery  at  each  contraction,  and  the  load  is 
then  doubled,  it  is  not  sufficient  to  reduce  the  rate  to  half  its 
original  frequency  in  order  to  obtain  the  same  yield  of  mechanical 
work  from  the  muscle. 

(d)  The    interval    which    must    elapse    between    two    ergo- 
graphic  curves  in  order  to  obtain  normal  fatigue  curves  during 
the  whole  day  is  from  1|  to  2  hours.     The  weight  of  the  load  is  a 
matter  of  indifference  between  certain  limits  (2-4  kgrms.). 

(e)  The  work  performed  by  a  muscle  that  is  already  fatigued  is 
far  more  injurious  to  that  muscle  than  a  greater  amount  of  work 
performed  under  normal  conditions. 

In  these  studies  Mosso,  Maggiora,  and  other  investigators,  in 
calculating  the  work  effected  by  the  muscle,  neglected  the  end 
part  of  the  tracing — which  consists  of  low,  long-drawn-out  con- 
tractions. Lombard  (1890)  investigated  this  terminal  phase, 
and  discovered  that  when  the  ergogram  appeared  to  stop,  it 
usually  continues  as  a  new  series  of  contractions,  in  which  the 
rise  and  fall  of  the  curve  were  approximately  regular.  According 
to  Lombard  these  periods  are  only  to  be  seen  in  the  voluntary 
ergogram,  and  are  due  to  spinal  fatigue. 

Owing  to  the  ease  with  which  the  ergograph  can  be  used  it  is 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  51 

employed  by  psychologists  and  clinicians  as  well  as  physiologists. 
The  method  is  universally  allowed  to  make  functional  isolation  of 
a  limited  group  of  muscles  possible  ;  average  weights  (.'5-4  kgrms.) 
should  be  used  to  ensure  the  better  graduation  of  the  work  and 
curves  that  are  neither  too  short  nor  too  long ;  and  it  is  assumed 
that  the  output  of  work  with  this  load  and  under  the  right  experi- 
mental conditions  for  the  ergograph  is  a  true  expression  of  the 
physiological  capacity  of  the  muscle  in  relation  to  the  weight. 
Above  all,  psychologists  and  psychiatrists  sought  -  -  on  the 
strength  of  Mosso's  results,  and  obviously  going  farther  than  he 
originally  attempted — to  emphasise  that  both  central  and  peri- 
pheral or  muscular  fatigue  were  shown  in  the  curve.  Kraepelin 
affirmed  that  in  the  ergographic  curve  the  height  of  lift  expresses 
muscular  fatigue ;  the  number  of  contractions,  on  the  contrary, 
gives  the  measure  of  mental  fatigue.  This  proposition  includes 
the  conception  that  the  cessation  of  the  ergograph  curve  is  due  to 
muscular  exhaustion,  i.e.  functional  incapacity  of  the  nerve-muscle 
apparatus,  caused  in  all  probability  by  the  curarising  action 
of  the  fatigue  products,  owing  to  which  the  psychical  impulses 
encounter  an  increasing  resistance. 

In  fact,  the  experiments  of  many  workers  upon  the  influence 
on  the  ergograph  curve  of  different  external  conditions  (as 
temperature,  pressure,  time  of  day,  etc.),  as  well  as  of  many  internal 
states  (state  of  nutrition,  period  of  digestion,  special  diet,  exhibi- 
tion of  stimulating  agents,  of  organic  extracts,  etc.),  have  always 
yielded  very  uncertain  results.  The  output  of  external  mechanical 
work  never  varied  perceptibly  from  the  ordinary  physiological 
limits. 

U.  Mosso  attempted  by  a  series  of  experiments  to  determine 
whether  the  administration  of  foods — sugar  in  particular — could 
restore  the  potential  capacity  of  the  muscle  depressed  by  work. 
The  most  definite  conclusion  was  that  the  action  of  sugar  was  only 
beneficial  with  the  ergograph  when  the  individual  was  in  a  condition 
of  extreme  fatigue. 

Generally  speaking,  the  ergograph  is  not  suitable  for  solving 
these  questions — Zuntz  and  his  pupils  utilised  it,  but  only  as  an 
index  to  the  state  of  fatigue  on  certain  occasions  when  the  subject 
was  executing  a  definite  piece  of  work  that  involved  the  musculature 
of  the  whole  body.  If  the  subject  is  made  to  do  a  known  quantity 
of  work  in  the  interval  between  the  ergographic  records,  a  per- 
ceptible recovery  is  seen  in  the  next  ergogram  if  small  quantities 
of  food  are  administered. 

The  value  of  the  ergograph  curve  as  an  index  of  muscular 
fatigue  on  the  one  hand  and  mental  fatigue  on  the  other,  as 
Kraepelin  has  used  it,  is  very  doubtful. 

In  1898  Treves,  working  in  the  Physiological  Institute  of 
Turin  on  the  laws  of  muscular  activity  in  man  and  animals,  made 


52 


PHYSIOLOGY 


CHAP. 


certain  modifications  in  the  methods  of  investigation,  and  obtained 
results  which  frequently  contradicted  previous  conclusions.  His 
first  experiments  were  carried  out  on  the  rabbit,  with  direct  and 
indirect  excitations  of  the  muscles  once  a  second.  The  tendon  of 
the  muscle  was  not  separated  from  its  insertions,  but  the  resistance 


cjr.  1150 


Fio.  31. — Ergogram  of  rabbit's  gastrocnemius,  loaded  with  1150  gnus,  (maximal  weight).     The 
sciatic  was  excited  every  two  seconds.     (Treves.) 

of  the  weight  was  transmitted  to  the  muscle  by  means  of  the 
natural  bony  lever  of  the  rabbit's  leg,  the  end  of  which  is  connected 
with  the  writing  point  of  the  ergograph.  He  used  maximal 
tetauising  stimuli  of  very  brief  duration,  in  imitation  of  voluntary 
impulses.  Before  taking  the  ergograph  curves,  Treves  ascertained 
at  what  weight  the  muscle  was  able  to  contract,  with  maximal 


FIG.  32.— Ergograph  tracings  from  same  muscle  as  preceding  figure.  The  initial  maximal  weight  was 
gradually  diminished  so  as  to  determine  the  maximal  terminal  weight  at  which  the  rhythmic 
lifts  no  longer  make  a  descending  curve,  but  form  a  horizontal  line  (constant  phase  of  ergogram). 
(Treves.) 

excitation,  so  as  to  serve  up  maximal  work.  As  he  did  away  with 
the  supporting  screw  of  Mosso's  ergograph,  the  weight  pulled 
continuously  upon  the  muscle,  and  not  merely  during  contraction. 
Under  these  conditions  Treves  obtained  an  ergogram  in  which 
the  height  of  the  contractions  regularly  diminished,  but  more  and 
more  slowly,  till  they  became  almost  inappreciable,  and  below 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


53 


this  they  showed  no  tendency  to  further  diminution  (Fig.  31). 
On  the  usual  interpretation  of  ergograph  curves  it  would  be  said 
that  the  muscle  had  become  incapable  of  any  further  work  at  this 
point.  But  this  is  not  the  case ;  the  muscle  is  still  capable  of 
serving  up  a  considerable  amount  of  external  work.  For  if  the 
weight  is  gradually  reduced,  the  height  of  the  contraction  again 
increases  until  a  new  maximal  weight  is  found  which  yields 


Fn:.  33.— Ergograph  tracing  of  rabbit's  gastrocnemius,  after  ten  minutes'  rest,  during  phase 

of  constant  work.     (Treves.) 

the  maximum  of  work  (Fig.  32)  and  corresponds  to  about 
400  grms.,  i.e.  much  less  than  the  original  weight,  which  was 
1150  grms.  If  the  rhythmical  maximum  excitation  is  continued 
with  this  new  load  (which  may  be  called  the  terminal  maximal 
load),  an  endless  series  of  contractions  is  obtained,  which  correspond 
with  the  production  of  constant  work.  The  series  of  contractions 
following  on  a  falling  curve  exhibits  similar  constancy,  irrespective 
of  the  load  which  is  carried.  Fig.  32  reproduces  a  few  cm.  only 
of  the  tracings  obtained  with  different  loads  in  testing  for  the 


Fin.  34.— Ergogram  of  rabbit's  gastrocnemius,  loaded  with  600  grms.,  after  twenty  minutes'  rest, 
during  phase  of  constant  work.  (Treves.)  Before  resting  the  muscle  gave  at  each  lift  a 
constant  yield  of  400  grms.  x  4  mm.  =  1600  grm.  mm.  After  resting  the  maximal  work  was 
600  grms.  x  11  mm.  =6600  grm.  mrn. 

terminal  maximal  load — in  the  second  phase  of  the  ergogram. 
This  constant  phase  may  preserve  its  regularity  at  a  rhythm  of 
1  sec.  for  over  2000  consecutive  contractions,  each  representing 
work  that  may  amount  to  2500  gr.  mm. 

If  the  muscle  is  allowed  a  longer  or  shorter  pause  for  rest 
during  the  period  of  constant  work,  the  maximal  work  of  which  it 
is  capable  at  each  contraction  increases  again,  in  proportion  as  the 
resting-pause  has  been  longer.  This  partial  recovery  of  power  is 
shown  in  the  capacity  of  the  muscle  to  trace  a  new  ergogram  with 


54  PHYSIOLOGY  CHAP. 

diminishing  heights  of  contraction  which  is  followed  by  the 
constant  phase  with  uniform  values  (Figs.  33  and  34). 

If  the  falling  portion  of  the  ergogram  is  obtained  with  a 
sub-maximal  load,  the  tracing  passes  into  the  constant  phase 
without  altering  the  weight,  in  which  case  each  contraction 
represents  a  sub-maximal  yield  of  work  (Fig.  35). 

The  level  of  constant  work  may  be  maintained  for  several  hours 
without  any  sign  of  the  characteristic  modifications  of  fatigue 


Fn;.  3.x — Kilogram  of  gastrocnemius  showing  decreasing  and  constant  phase,  at  a 
sub-maximal  load.     (Treves.) 

(Fig.  36),  but  finally  there  comes  a  moment  at  which  the  muscle  can 
no  longer  yield  any  mechanical  work  owing  to  the  gradual  onset  of 


rigor. 


In  the  ergogram  of  the  gastrocnemius  obtained  with  electrical 
stimulation  and  an  initial  maximal  load,  the  curve  of  the  contraction 
heights  sinks  rapidly  to  zero,  or  to  a  very  low  level.,  because  after 
a  certain  number  of  contractions  the  load  becomes  super-maximal. 
If  the  weight  could  be  gradually  adjusted  as  the  muscle  weakens 
so  as  to  be  maximal  at  each  fresh  contraction,  the  ergogram  would 
show  no  intervening  stage  of  complete  or  almost  complete  cessation 
of  work,  which  is  solely  due  to  imperfect  mechanical  conditions. 
A  more  important  curve  would  stand  out  as  a  whole — namely  the 


FIG.  36.— Ergograph  tracing  of  rabbit's  gastrocnemius  (phase  of  constant  work)  after  two  hours' 
rhythmical  maximal  excitation.  (Treves.)  The  tracing  shows  a  slight  irregularity  of  the  base 
line  of  the  contractions,  but  the  work  remains  fairly  constant. 

work  curve,  represented  by  a  series  of  rhythmical  contractions 
executed  under  conditions  of  maximal  work.  Treves  endeavoured 
to  approximate  to  such  conditions  in  his  experiments,  and  con- 
structed a  diagrammatic  work  curve}  the  course  of  which  recalls 
the  form  of  a  muscle  twitch,  with  an  ascending  and  a  descending 
phase,  passing  gradually  into  the  period  of  constant  work. 

Treves  was  the  first  to  apply  these  methods  of  research  to  the 
human  subject.  He  did  away  with  the  support  of  the  ergograph 
lever,  and  made  the  subject  lift  a  weight  of  4-5-6  kgrms.  (accord- 
ing to  the  individual)  every  two  seconds  by  a  voluntary  maximal 
effort.  In  consequence  the  constant  level  was  always  obtained  on 


GENERAL  PHYSIOLOGY  OF  MUSCLE  55 


the  ergogram,  and  forms  an  essential  part  of  it.  This  proves  that 
supporting  of  the  ergograph  lever  creates  artificial  work  conditions, 
which,  together  with  the  variations  in  elasticity  and  tone  which 
the  muscle  suffers  during  work,  cause  a  more  or  less  rapid 
decline  in  the  successive  contractions,  and  shorten  the  ergogram 
prematurely. 

In  extending  his  investigation  to  voluntary  work,  Treves  found 
it  necessary  to  alter  his  system  of  loading,  and  to  apply  the 
principle  of  maximal  loading  in  this  case  also — that  is  of  gradually 
altering  the  weight  as  the  muscular  power  declines.  In  this  study 
he  employed  the  flexor  muscles  of  the  forearm,  and  invented  a 
new  ergograph  for  the  purpose  which  may  be  studied  in  his 
original  memoir. 

A  minute  analysis  of  Treves'  results  is  beyond  the  scope  of 
this  text-book.  We  must  confine  ourselves  to  a  few  of  the  most 
important  principles  that  can  be  deduced  from  them  :— 

(a)  During  voluntary  work  on  the  ergograph  the  height  of 
contraction  remains  constant  so  long  as  the  conditions  of  work  are 
favourable,  and  above  all  so  long  as  the  load  is  not  excessive. 

(6)  The  maximal  load  that  can  be  raised  by  voluntary  effort 
corresponds  with  the  load  which  necessitates  the  maximum  of  work. 

(c)  The  maximum  load  diminishes  gradually  in  a  hyperbolic 
curve  till  it  reaches  a  value  which  varies  with  the  rate  of  work,  but 
is  practically  constant.  The  curve  of  voluntary  work,  like  that 
obtained  by  artificial  stimulation,  consists  of  two  phases — a 
descending  and  a  constant  part.  The  differences  seen  in  the  two 
curves  arise  from  the  fact  that  in  the  case  of  work  elicited  by 
artificial  stimuli  the  stimulus  is  constant ;  in  voluntary  work,  on 
the  contrary,  the  effort  varies  since  it  diminishes  independently  of 
the  will,  according  to  the  resistance  experienced  in  carrying  out 
the  movement. 

(d}  The  ergograph  tracing  consists  of  a  series  of  vertical  lines 
approximately  equal  in  height,  with  no  feature  characteristic  of 
the  individual  or  of  the  experimental  conditions.  The  true 
ergogram  is  the  line  according  to  which  the  work  diminishes  with 
the  maximal  load. 

(e)  The  main  factor  which  determines  the  rapid  fall  of  the 
curve  with  a  constant  load  is  the  appearance  of  unfavourable 
mechanical  conditions.  To  obviate  this  the  muscles  must  be  left 
perfectly  free  to  contract,  and  the  contraction  of  other  muscles 
connected  with  those  under  investigation  must  not  be  hindered. 
It  suffices  to  see  that  the  graphic  apparatus  records  only  the 
movements  of  the  bony  lever  in  question.  Further,  the  normal 
conditions  under  which  the  muscle  acts  must  be  respected,  and 
the  gradual  unloading  of  the  muscle  during  contraction  permitted, 
as  would  happen  by  the  displacement  of  the  bony  lever  on  which 
the  muscle  naturally  works. 


56  PHYSIOLOGY  CHAP. 

(/)  The  will  as  a  psychical  factor  has  no  influence  on  the  fall 
of  the  curve  with  a  constant  load.  Directly  the  load  is  adjusted 
the  tracing  is  prolonged  by  an  unlimited  number  of  contractions 
with  a  considerable  production  of  work.  All  other  hypotheses  are 
superfluous,  on  which  the  functional  incapacity  which  appears  in 
the  ergograph  curve  only  with  the  constant  load  has  been 
explained  by  assuming  a  sort  of  antagonism  between  the  height 
and  the  number  of  the  contractions. 

(<?)  In  order  to  elicit  the  whole  work  of  which  a  muscle  is 
capable,  in  regard  both  to  time  and  to  amount,  care  must  be  taken 
that  the  muscle  is  always  engaged  in  maximal  work.  At  whatever 
load  the  work  begins,  the  time  necessary  for  attaining  a  constant 
level  is  always  the  same.  Still  the  muscle  working  under  the 
influence  of  the  will  with  sub-maximal  loads  economises  part  of 
the  materials  at  its  disposal,  and  may  accumulate  a  fresh  supply. 

(h~)  Given  uniform  conditions,  the  value  of  the  initial  maximal 
load  is  constant  in  the  same  person  on  different  days,  and  the 
height  of  the  contractions  varies  but  little.  The  work  curves 
vary  very  slightly  in  the  amount  of  work  that  can  be  obtained 
with  the  initial  maximal  load,  the  terminal  maximal  load,  and, 
lastly,  the  total  amount  of  work. 

(i)  Fasting  does  not  perceptibly  alter  the  value  of  the  initial 
maximal  load,  but  it  accelerates  the  fall  of  the  curve,  and  lowers 
the  value  of  the  terminal  maximal  load  considerably.  Practice 
and  training,  on  the  contrary,  render  the  muscle  capable  of  accom- 
plishing much  more  work.  After  practice  the  initial  maximal 
load  increases  within  limits,  while  the  value  of  the  terminal 
maximal  load  increases  from  day  to  day,  without,  however,  delaying 
the  fall  of  the  curve  to  the  constant  level. 

(A-)  If  the  work  is  begun  with  the  maximal  terminal  load 
as  determined  by  the  previous  experiments,  the  ergograph  curve 
forms  a  horizontal  line.  From  this  we  must  not  conclude  that 
work  under  these  conditions  produces  no  appreciable  fatigue  in 
the  nerve-muscle  apparatus.  Fatigue,  according  to  Treves,  can 
be  studied  simultaneously  with  the  production  of  external  work, 
by  determining  the  manner  in  which  the  nervous  energy 
diminishes.  This  is  represented  by  the  product  of  a  given  weight 
into  the  time  in  seconds  for  which  the  weight  can  be  held  up  by 
the  voluntary  tetanus,  continued  to  exhaustion,  of  a  given  group 
of  muscles.  The  line  indicating  the  alterations  of  nervous  energy 
falls  much  more  rapidly  than  that  showing  the  variations  of 
the  maximal  load,  and  is  in  a  marked  degree  independent  of  the 
production  of  external  work. 

At  the  Fifth  International  Congress  of  Physiology  at  Turin 
Treves  proposed  certain  modifications  of  his  original  ergograph, 
by  which  he  wras  enabled  to  control  these  observations  and  to 
extend  his  research  to  the  flexor  muscles  of  the  fingers  (Fig.  37). 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


57 


In  the  first  place  he  investigated  the  conditions  which  determine 
the  spontaneous  rhythm  of  contraction  in  voluntary  ergograph 
work.  This  rhythm  depends  essentially  upon  perception  of  resist- 
ance, and  not  upon  the  amount  of  work  accomplished  by  the 
subject  nor  his  state  of  fatigue. 


Fie.  37.—  Treves'  new  ergograph,  in  which  the  weight  can  be  gradually  reduced,  to  obtain  a  tracing 
under  constant  conditions  of  maximal  load  and  maximal  work.  Platform  (a)  to  support  the 
forearm,  and  Mosso's  recording  apparatus  (l>)  are  retained,  but  the  contrivances  for  fixing  the 
arm  and  fingers  that  are  not  working  are  discarded.  The  arrangement  for  applying  the  weight 
is  altered.  The  cord  passes  over  the  pnlley  d,  the  axis  of  which  ends  in  a  small  crank  which 
revolves  round  the  axis  with  the  flexion  of  the  middle  finger.  The  lower  part  of  the  apparatus 
serves  to  graduate  the  weight  h  and  keep  it  maximal  by  running  it  along  a  metal  bar  one  metre 
long,  which  moves  upon  the  axis  k.  It  is  obvious  that  the  resistance  opposed  to  the  flexion  of 
the  finger  must  decrease  regularly,  in  proportion  as  the  weight  is  farther  from  the  point  100, 
and  nearer  the  zero  at  axis  /,-. 

The  "  constant  phase  "  of  the  work  curve  was  investigated  by 
other  authors,  and  appreciated  at  its  proper  value.  Some  physio- 
logists, however,  while  recognising  the  theoretical  accuracy  of  the 
isotonic  method  and  Treves'  application  of  the  principle  of  the 
maximal  load,  regard  the  isometric  method  as  more  practical  and 
better  adapted  to  the  study  of  voluntary  muscular  activity. 


58  PHYSIOLOGY 


CHAP. 


Schenck  justly  remarks  of  Treves'  method  that,  while  it  corrects 
certain  faults  of  the  original  ergograph,  it  introduces  new  corn- 
plications.  Obviously,  as  Treves  himself  admits,  contractions 
against  different  loads  cannot  be  compared,  because  with  variations 
of  the  weight  raised  the  energy  of  inner vation  must  also  vary, 
other  conditions  being  equal. 

Schenck  resumed  the  study  of  muscular  fatigue  (1900)  in 
voluntary  effort  by  applying  the  isometric  method  to  the  abductor 
of  the  index  finger.  For  this  purpose  he  used  the  apparatus 
devised  by  Fick  in  1887  (Spannungszeichner),  with  the  addition 
of  certain  useful  modifications.  The  subject,  working  by  the 
beats  of  a  metronome,  throws  this  muscle  into  maximal  tension 
for  one  second,  and  relaxes  it  for  the  next  second.  Each  series 
lasts  for  twenty-five  minutes,  and  therefore  consists  of  750  alter- 
nate contractions  and  relaxations. 

The  results  of  these  researches  may  be  summed  up  as  follows : 
The  curve  of  the  isometric  contractions  of  the  abductor  indicis, 
made  with  maximal  voluntary  effort,  generally  presents  three 
distinct  stages  :— 

(a)  In  the  first  stage  the  tension  which  the  muscle  reaches  in 
the  first  contractions  (which  may  exceed  14  kgrms.)  diminishes 
rapidly,  and  drops  to  about  two-thirds  (i.e.  to  8400  grms.)  after 
about  five  minutes. 

(&)  In  a  second  much  longer  period  (about  fourteen  minutes) 
the  tension  reached  by  the  muscle  is  approximately  constant. 

(c)  In  a  third  period  the  tension  drops  again,  but  slightly  (to 
about  7700  grms.)to  the  end  of  the  series, which  may  exceed  twenty- 
five  minutes,  without  any  further  evidence  of  fatigue  in  the  muscle. 

If  these  results  are  compared  with  those  of  Treves,  it  is  seen 
at  once  that  Schenck's  first  stage  corresponds  with  the  descending 
phase  of  Treves'  ergogram,  and  the  second  stage  with  the  constant 
phase  which  Treves  obtained  with  the  so-called  "  terminal  maximal 
load,"  with  this  difference,  that  in  Schenck's  method  the  maximal 
energy  of  innervation  is  exerted  from  the  beginning  to  the  end, 
while  in  Treves'  method  the  energy  of  innervatiou  gradually 
declines.  Accordingly,  there  is  never  any  sign  of  fatigue  after 
the  constant  phase,  and  the  third  stage,  which  is  prominent  in 
the  isometric  method,  does  not  appear. 

The  functional  constancy,  that  is,  the  comparative  non-fatigu- 
al  >ility  and  inexhaustibility  of  muscle,  contracting  rhythmically 
both  with  Treves'  ergographic  and  Schenck's  isometric  method, 
recalls  the  continuous  rhythmic  activity  of  the  heart  and  respira- 
tory muscles.  This  certainly  depends  on  the  blood-supply  that 
restores  the  muscle  and  nerve-centres  as  fast  as  they  become 
fatigued,  and  carries  off  the  waste-products.  In  fact,  when  excised 
muscles  of  the  frog  are  used,  the  so-called  fatigue  curve  passes 
into  complete  exhaustion  (Fig.  7,  p.  12). 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  59 

This  exhaustion  depends  on  the  absence  of  a  proper  supply  of 
oxygen  and  nutrient  material  to  repair  the  waste  of  substance  in 
the  active  muscle  and  nerve-centres,  and  to  the  accumulation  of 
metabolites  which  paralyse  the  tissue  owing  to  the  arrest  of  the 
blood  and  lymph  circulation.  Ranke,  in  fact,  showed  that,  on 
merely  circulating  a  saline  solution  that  contained  no  nutrient 
restorative  matters  through  fatigued  frog-muscle,  the  signs  of 
fatigue  disappeared.  If,  on  the  other  hand,  an  aqueous  extract  of 
the  fatigued  muscle  of  one  frog  were  circulated  through  the  fresh 
muscle  of  another,  fatigue  phenomena  at  once  set  in. 

Mosso  continued  these  researches  on  warm-blooded  animals, 
and  showed  that  transfusion  of  the  blood  of  a  fatigued  into  the 
vessels  of  a  normal  dog  induced  symptoms  of  respiratory,  cardiac, 
and  general  fatigue  in  the  latter.  Clearly,  therefore,  the  waste 
products  of  muscular  activity  act  as  toxic  substances,  and  cause 
muscular  fatigue  and  exhaustion. 

The  inexhaustibility  of  the  flexor  muscles  of  the  middle  finger 
or  the  abductors  of  the  index  linger,  under  the  experimental 
conditions  adopted  by  Treves,  Schenck,  and  others,  is  not  sur- 
prising, and  seems  indirectly  to  confirm  Eanke's  theory  of  the 
causes  of  muscular  fatigue  and  exhaustion. 

X.  Only  a  small  part  of  the  potential  energy  liberated  in 
muscular  contraction  is  used  up  in  the  form  of  external  work ; 
the  other,  considerably  larger,  part  is  converted  into  internal  work, 
which  is  accompanied  by  the  development  of  heat. 

It  is  a  common  observation  that  after  vigorous  effort  or 
repeated  contractions  of  the  muscles  the  temperature  of  the  body 
rises ;  every  one  knows  that  muscular  activity  is  the  best  way  of 
warming  oneself  in  cold  weather.  In  walking  and  running  the 
rectal  temperature  may  rise  some  tenths  of  a  degree.  In  tetanus 
the  fever  may  reach  a  high  degree  (45 '3°  C.,  according  to  Wunder- 
lich).  The  same  is  seen  in  strychnine  poisoning  (44°  C.,  Vulpian). 

On  the  other  hand  it  has  long  been  known  that  in  a  state  of 
absolute  muscular  rest,  as  in  sleep,  the  internal  temperature  falls 
about  half  a  degree  centigrade,  and  rises  again  rapidly  on  waking. 
The  mere  immobilisation  of  an  animal,  or  its  curarisation,  cools  it 
to  30-7°  C.  (Ricliet),  and  a  subsequent  injection  of  strychnine  is 
no  longer  able  to  evoke  spasms  or  to  raise  the  temperature,  which 
must  therefore  depend  on  the  tetanising  action  of  the  strychnine. 

Since  the  muscles  represent  about  40  per  cent  of  the  total  body 
weight  in  vertebrates,  and  after  removal  of  the  skeleton  (which 
can  only  develop  a  negligible  amount  of  heat)  certainly  represent 
more  than  50  per  cent,  and  since  katabolism  is  more  active  in 
muscle  than  in  any  other  tissue,  we  are  justified  in  assuming 
that  the  muscles  have  a  preponderating  influence  on  the  heat  pro- 
duction of  the  body,  in  comparison  with  that  of  all  other  tissues. 

We  shall   elsewhere   discuss    thermogenesis   and    the    thermal 


60 


PHYSIOLOGY 


CHAP. 


balance  of  the  organism  as  a  whole ;  here  we  must  confine  our- 
selves to  the  study  of  muscle  as  a  thermogenic  organ  by  the  direct 
examination  of  its  temperature  both  during  contraction  and  in  the 
resting  state. 

The  first  observations  were  made  in  1835  by  Becquerel  and 
Brechet.  They  attached  one  couple  of  a  thermo-electric  battery 
to  the  biceps  muscle  of  a  human  arm,  while  the  second  couple 
was  kept  at  constant  temperature.  After  a  few  contractions  the 
temperature  of  the  muscle  was  raised  05°,  and  after  five  minutes 
of  energetic  alternate  contraction  and  relaxation  (working  a  saw) 
1°  C.  Gierse  (1842)  was  the  first  who  noted  in  the  dog,  with  the 


v_ 


Fio.  38. — D'Arsonval's  thermo-electric  couples  with  sheathed  junctions,  to  avoid  the  electrical 
currents  liable  to  be  set  up  by  the  contact  of  two  different  metals  with  fluid.  1,  Section  of 
finely-pointed  conical  tube  of  German  silver,  into  which  an  iron  wire  has  been  soldered  ;  2, 
section  of  cylindrical  tube  of  German  silver,  closed  and  pointed  at  one  end  at  the  junction 
with  an  iron  wire,  and  protected  above  this  by  a  non-conducting  sheath  ;  3  and  4,  a  pair  of 
thermo-electric  needles  composed  of  two  wires,  iron  and  German  silver,  soldered  together  at 
the  points,  and  covered  with  an  insulating  varnish. 

thermometer,  that  the  cutaneous  temperature  of  a  limb  rose  during 
the  contraction  of  its  muscles.  Zienissen  (1857)  and  Bee-lard 
(1860-61)  observed  the  same  on  man.  The  objection  that  the 
rise  of  temperature  depends  on  increased  flow  of  blood  to  the  skin 
may  be  met  by  saying  that  the  skin  becomes  warmer,  but  not 
redder,  during  the  contraction  of  the  subjacent  muscles.  Another 
objection,  that  the  heating  may  depend  on  the  hyperaernia  of  the 
muscle  during  its  contraction,  is  less  easily  met. 

The  ordinary  thermometric  or  thermo-electric  methods  are  used  in  investigat- 
ing muscular  thermogenesis.  If  the  bulb  of  a  highly  sensitive  thermometer 
covered  with  a  thick  layer  of  non-conducting  material  (cotton-wool)  to  prevent 
the  dispersion  of  heat  is  applied  to  the  human  skin  above  the  muscle  to  be 
examined  ;  or  better,  if  the  bulb  of  the  thermometer  is  inserted  between  the 
muscles  of  the  animal,  it  is  possible  to  measure  the  alterations  of  temperature. 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  61 

Baudin  has  recently  carried  tlie  construction  of  mercury  thermometers  with 
small  bull >s  for  physiological  purposes  to  such  perfection  that  he  has  obtained 
a  scale  in  which  each  degree  is  divided  into  fifty  parts.  But  even  with  an 
ordinary  clinical  thermometer,  divided  into  tenths  of  a  degree,  it  is  possible 
on  reading  the  scale  under  the  microscope  to  estimate  differences  of  a  hundredth 
of  a  degree. 

The  thermo-electric  method  has,  as  compared  with  the  thermometric 
method,  the  great  advantage  of  almost  instantaneously  indicating  rapid 
alterations  in  the  temperature  of  the  muscle.  On  the  other  hand  it  is  more 
difficult  and  delicate  of  application,  and  may  lead  to  fallacies  if  not  employed 
very  cautiously. 

The  thermo-electric  method  is  founded  on  the  following  principle  :  If  two 
different  metals  united  by  two  junctions  are  included  in  the  circuit  of  a 
low  resistance  galvanometer,  the  heating  or  cooling  of  one  of  the  junctions 
gives  rise  to  an  electric  current,  which  deflects  the  needle  of  the  galvanometer 
in  the  positive  or  negative  direction,  in  proportion  with  the  rise  or  fall  of 
temperature  in  the  first  junction,  if  that  of  the  second  remains  unchanged. 
To  investigate  muscular  therniogenesis  it  is  best  to  take  needle-shaped 
thermo-electric  couples  (Fig.  38),  which  are  plunged  into  two  symmetrical 
muscles  of  the  frog,  one  of  which  is  at  rest,  the  other  contracting  (Helmholtz). 


(HUM 


mmn^nmx^f  "^""^'^^^tHasnr: 


FIG.  39. — Photograph  of  positive  and  negative  variations  of  temperature  obtained  with  two 
thermo-electric  needles  pushed  into  the  two  gastrocnemius  muscles  of  a  frog,  and  connected 
with  a  low  resistance  galvanometer ;  the  sciatic  nerve  was  excited  alternately  on  either  side. 
(A.  D.  Waller.)  The  excursions  of  the  galvanometer  mirror  are  photographed  by  a  beam  of  light 
reflected  on  to  the  sensitive  surface  of  a  moving  drum.  Each  tetanising  excitation  of  the 
sc-iatics,  respectively,  lasted  one  minute  as  indicated  by  the  break  of  the  abscissa  line.  During 
tetanus  the  curve  falls  or  rises,  according  as  the  right  or  left  sciatic  was  excited. 

To  measure  the  rise  of  temperature  developed  in  a  simple  twitch  a  Melloni's 
thermopile  is  used,  which  consists  of  several  elements,  the  two  muscles  of 
the  frog  being  placed  in  contact  with  the  two  surfaces  at  which  are  the 
junctions  of  the  elements  of  the  pile  (Heidenhain). 

If  a  mirror  is  attached  to  the  magnet  of  the  galvanometer,  its  deflections 
can  be  photographed  by  the  reflection  of  a  ray  of  light  upon  a  sensitive 
surface  (Waller,  Fig.  39). 

The  first  experiments  that  proved  incontestably  that  muscle 
is  concerned  in  the  production  of  heat  as  well  as  motion  were 
performed  on  cold-blooded  animals  by  Helmholtz  (1847).  By 
employing  the  thermo-electric  method  he  saw  that  the  muscles  of 
the  frog's  thigh  developed  heat  during  indirect  or  direct  tetanisa- 
tion  (0-14°-0-18°  C.). 

In  later  experiments  (1864)  Heidenhain  measured  the  rise  of 
temperature  (1-5  hundredths  of  a  degree)  in  the  isolated  gastro- 
cnemius of  the  frog  after  a  simple  twitch. 

There  is  therefore  no  doubt  that  muscular  contraction  is 
accompanied  by  a  development  of  heat,  which  is  due  to  an  increase 
of  exothermal  processes  within  the  contractile  organ,  by  which  the 
greater  part  of  the  store  of  accumulated  energy  is  dispersed. 


62  PHYSIOLOGY  CHAP. 

Even  in  rest,  however,  muscle  develops  more  heat  thaii  other 
tissues.  An  indirect  proof  of  this  is  obtained  from  the  experi- 
ments in  which  Claude  Bernard  attempted  to  estimate  the  oxygen 
content  of  the  hlood  flowing  respectively  to  and  from  the  muscle, 
in  rest  and  during  tetanus.  According  to  Bernard  the  blood  of 
the  artery  of  the  anterior  rectus  muscle  of  the  dog's  leg  carries 
9'31  c.c.  oxygen,  the  blood  that  flows  from  the  veins  8'21  c.c.  when 
the  muscle  is  at  rest,  3'31  during  tetanus.  During  its  activity, 
therefore,  the  muscle  consumes  much  more  oxygen  than  during 
rest ;  but  even  in  the  resting  state  it  consumes  a  certain  amount, 
and  must  therefore  develop  heat. 

These  results  were  confirmed  in  Ludwig's  laboratory  by  Meade 
Smith  (1881),  who  made  numerous  direct  estimations  of  tempera- 
ture, both  on  the  blood  of  the  artery  and  vein  of  the  muscle,  and 
on  the  resting  or  tetanised  muscle  itself.  The  general  conclusion 
was  that  the  temperature  in  the  artery  is  less  than  in  the  vein 
and  in  the  muscle  in  the  resting  state,  and  that  the  difference 
increases  considerably  during  tetanus. 

Beclard  was  the  first  who  studied  heat  production  in  muscle 
from  the  point  of  view  of  the  mechanical  theory  of  heat  (1861). 
He  tried  first  on  the  frog  by  the  thermo-electric  method,  and  then 
on  his  own  biceps  muscle,  to  estimate  with  an  air-thermometer, 
graduated  in  fiftieths  of  a  degree,  the  amount  of  heat  developed 
during  static  (isometric)  contraction,  in  which  the  mechanical  work 
is  nil,  with  that  produced  during  dynamic  (isotonic)  contraction, 
which  is  accompanied  by  mechanical  work  that  can  be  measured 
in  kilogrammetres.  He  stated  positively  that  when  the  muscular 
contraction  results  in  muscular  work,  much  less  heat  is  evolved  in 
the  muscle  than  when  a  contraction  of  the  same  strength  is  not 
accompanied  by  external  mechanical  effects. 

This  fact,  despite  the  imperfections  of  Beclard's  method,  proves 
that  muscular  activity  is  subject  to  the  great  law  of  the  conserva- 
tion of  energy.  When  the  whole  of  the  energy  liberated  by  the 
muscle  is  expressed  in  the  form  of  heat,  more  heat  is  evolved  than 
when  part  of  the  energy  is  converted  into  muscular  work. 

Beclard  further  demonstrated  that  the  amount  of  energy  trans- 
formed into  mechanical  work  during  the  lifting  of  the  weight  by 
the  muscle  is  reconverted  into  heat  when  the  raising  is  succeeded 
by  the  lowering  of  the  weight,  i.e.  when  the  positive  is  followed 
by  negative  work.  The  experiment  consists  in  comparing  the 
heat  developed  when  a  certain  weight  is  held  up  for  a  given  time 
by  the  static  contraction  of  the  biceps,  with  that  developed  during 
the  same  time  when  the  arm  loaded  with  the  same  weight  makes 
up  and  down  movements.  Under  these  conditions  (according  to 
Beclard)  the  development  of  heat  indicated  by  the  thermometer  is 
equal,  whether  the  arm  be  kept  in  equilibrium  or  executes  move- 
ments. The  positive  work  of  raising  the  weight  is  therefore 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


03 


cancelled  by  the  negative  work  of  lowering  it,  so  that  in  this  case 
the  heat  production  in  static  contraction  is  equal  to  that  in  dynamic 
contraction. 

But  apart  from  the  imperfections  of  the  method  Beclard's 
results  were  incomplete.  He  neglected  the  influence  exerted  by 
differences  of  load  on  muscular  thermogenesis,  as  well  as  the  degree 
of  stimulation  and  the  state  of  fatigue  of  the  muscles.  In  1864 
Heidenhain  investigated  the  question  again  from  a  wider  point  of 
view  and  by  more  exact  methods.  He  employed  the  isolated 
muscles  of  the  frog,  with  different  loads,  and  recorded  the  height 
of  the  contractions,  from  which  he  calculated  the  work,  and 
measured  the  changes  of  temperature  with  a  thermo-electric  pile. 

Since  we  know  that  with  increase  of  load  the  mechanical  work 
of  the  muscle  increases  within  certain  limits  (Fig.  26,  p.  46)  it 
seems  natural  to  suppose  that  the  simultaneous  development  of 
heat  takes  place  inversely  and  diminishes  with  increment  of  work, 
so  that  the  sum  of  energy  liberated  by  the  katabolic  processes  in 
the  muscle  remains  constant  for  the  same  stimulus,  its  division 
into  work  and  heat  alone  being  variable.  Heidenhain's  researches, 
however,  demonstrated  that  when  the  intensity  of  the  stimulus 
remains  constant,  the  sum  of  energy  developed  by  the  muscle 
increases  up  to  a  certain  point  with  increase  of  load,  i.e.  the 
increase  of  work  is  accompanied  by  increased  heat-production. 

This  important  conclusion  is  represented  by  the  following 
table,  which  gives  Heidenhain's  data  from  one  of  his  experiments 
on  the  gastrocuemius  of  the  frog  loaded  with  different  weights :— 


Increased  warmth 

Number 
of  test. 

Weights  applied 
to  the  muscle. 

Summated 
height  of  three 
contractions. 

Mechanical 
work  of  the  three 
contractions. 

of  the  muscle 
expressed  in 
degrees  of  the  scale 
of  the  thernio- 

multiplier. 

1 

grms. 
10 

mm. 
10-6 

gr.  mm. 
106 

8-5 

2 

30 

10-4 

312 

11-5 

3 

90 

8-5 

761 

18-0 

4 

60 

9-6 

573 

11-5 

5 

30 

10-6 

318 

9-5 

6 

10 

10-8 

108 

7-0 

During  three  successive  contractions  the  muscle  was  loaded 
with  the  weight  during  both  contraction  and  relaxation ;  thus  the 
mechanical  work  given  out  by  the  muscle  during  contraction  was 
restored  to  it  in  the  form  of  heat  during  relaxation.  The  rise  of 
temperature  shown  in  the  table  therefore  expresses  the  total  sum 
of  the  energy  developed  by  the  muscle  during  the  three  successive 
contractions.  This  is  not  a  constant  but  varies  with  the  external 
mechanical  work :  it  increases  with  the  increment  of  this  work 


64  PHYSIOLOGY  CHAP. 

and  declines  with  its  decrement.  The  facts  collected  by  Heiden- 
haiu,  however,  show  that  the  rise  and  fall  of  temperature  in  the 
muscle  are  not  strictly  proportionate  to  the  increase  and 
diminution  of  the  mechanical  work  which  it  performs ;  generally 
speaking,  the  thermal  increase  is  much  less  than  the  increase  of 
work.  This  proves  that  the  muscle  works  more  economically 
when  it  lifts  a  moderate  weight  than  when  it  lifts  a  lighter  one. 

The  property  which  the  muscle  possesses  of  adjusting  the 
quantity  of  energy  which  it  develops  under  a  constant  stimulus 
to  the  greater  or  less  resistance  which  it  has  to  overcome,  is  very 
important.  If  the  strength  of  its  reaction  depended  only  on  the 
strength  of  the  stimulus,  and  was  independent  of  the  load,  then 
the  development  of  muscular  energy — the  nerve  impulses  remain- 
ing uniform — would  not  be  in  proportion  with  the  external  work 
that  had  to  be  performed.  Heidenhaiu's  discovery  that  the  total 
sum  of  energy  developed  by  the  muscle  depends  on  the  degree  of 
tension  due  to  the  resistance  it  encounters  in  contracting,  shows 
that  it  possesses  a  mechanism  in  itself  which  is  capable — inde- 
pendently of  the  nervous  impulses — of  partially  regulating  its 
intrinsic  metabolism  according  to  the  needs  of  the  moment. 

Again,  when  the  load  remains  constant,  and  the  strength  of 
stimulation  is  progressively  increased,  the  development  of  heat 
increases  —  within  certain  limits — with  the  height  of  the  con- 
tractions and  the  mechanical  work  performed,  till  it  reaches  a 
maximum.  So  that  the  metabolism  and  heat  production  of 
muscle  are  regulated  not  only  by  tension,  but  also  by  the  nervous 
system,  owing  to  the  varying  intensity  of  the  impulses  which  it 
transmits  to  the  muscle. 

It  should,  however,  according  to  the  results  of  Heidenhain  and 
Nawalichin,  be  observed  that,  just  as  we  have  seen  with  constant 
stimulus  and  increasing  load,  so  too  with  a  constant  load  and  a 
progressively  increased  stimulus,  the  increase  in  heat  and  work 
development  are  not  parallel,  but  the  maximum  production  of  heat 
is  always  reached  before  the  maximum  of  work,  i.e.  the  heat  pro- 
duction increases  more  rapidly  than  the  height  of  the  contractions. 
This  proves  that  the  muscle  works  more  economically  whenever  it 
is  more  strongly  excited  from  the  nerve,  and  forced  to  do  more 
work. 

But  when  the  same  amount  of  work  is  performed  by  a  muscle, 
on  the  one  hand  by  many  small  contractions,  on  the  other  by 
fewer  but  larger  contractions,  less  heat,  according  to  Heidenhain, 
is  developed  in  the  first  case  than  in  the  second.  This  agrees 
with  the  common  observation  that  it  is  more  fatiguing  to  ascend  a 
rapid  incline  with  long  steps,  than  a  less  steep  slope  of  the  same 
height,  with  shorter  steps. 

Heidenhaiu  brought  out  another  interesting  fact  which  is  not 
easy  to  explain.  When  the  same  amount  of  work  is  performed  by 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  65 

a  fresh  muscle  and  a  fatigued  muscle,  the  former  develops  more 
heat  than  the  latter,  as  if  the  chemical  activity  necessary  for 
developing  the  same  amount  of  useful  external  work  were  greater 
in  the  fresh  muscle  and  less  in  the  fatigued.  In  a  series  of 
successive  contractions  of  equal  height,  carried  out  by  a  muscle 
loaded  with  the  same  weight,  so  that  each  contraction  performs 
the  same  amount  of  work,  the  development  of  heat  diminishes 
between  the  first  and  the  last  of  the  series.  This  shows  that 
fatigue  can  be  detected  in  the  diminished  heat-production  before 
it  becomes  evident  in  the  lessened  height  of  contraction.  Accord- 
ingly, as  it  becomes  fatigued,  the  muscle  functions  more  economi- 
cally— i.e.  a  less  amount  of  energy  is  transformed  into  heat. 

When  the  impulses  that  reach  the  muscle  follow  so  rapidly  as 
to  give  rise  to  tetanic  fusion  of  the  contractions,  the  production  of 
heat  increases  progressively  up  to  a  certain  maximum,  in  propor- 
tion to  the  increasing  height  to  which  the  weight  is  raised. 

The  heat  developed  in  tetanus  increases  with  increment  of  the 
load  and  corresponding  tension  of  tjhe  muscle.  When  the  weight 
is  so  great  as  to  inhibit  contraction  altogether,  more  heat  is 
developed  than  when  the  load  is  less  and  the  muscle  can  shorten 
a  little.  During  the  development  of  tension  the  heat  production 
is  greater  than  when  the  tetanic  rise  is  complete.  During  a  brief 
tetanus  the  same  amount  of  heat  is  liberated  at  each  instant.  But 
during  the  contraction,  and  possibly  during  the  relaxation,  that 
precede  and  follow  tetanus,  a  much  larger  quantity  of  heat  is 
developed. 

Heidenhain's  work  on  muscular  thermogeuesis  was  extended 
and  completed  by  Fick  and  his  pupils.  Fick  in  his  first  experi- 
ments (1884)  resumed  the  study  of  the  question  already  investigated 
by  Beelard.  Heidenhain's  discovery  that  the  sum  of  the  energy 
(work  and  heat)  developed  by  the  muscle  is  proportional  to  its 
tension  during  its  activity,  does  not  contradict  Beclard's  view,  as 
Hermann  also  pointed  out,  that  with  constant  tension  the  sum  of 
energy  developed  by  the  muscle  (work  and  heat)  is  in  direct  ratio 
with  the  intensity  and  duration  of  its  activity,  so  that,  caeteris 
paribiis,  the  energy  liberated  in  the  form  of  work  is  inversely 
proportional  to  that  liberated  in  the  form  of  heat — conformably 
with  the  law  of  conservation  of  energy. 

In  order  to  prove  this  theory  experimentally,  Fick  employed 
Heidenhain's  method  on  the  excised  muscles  of  the  frog.  To 
compare  the  thermal  production  in  useful  work  with  that  of  con- 
traction by  which  no  external  work  was  performed,  he  invented 
an  ingenious  apparatus  which  he  termed  "  Arbeitssammler."  This 
is  a  small  windlass  which  the  muscle  turns  on  contracting  'against 
the  constant  resistance  of  a  weight,  which  can  be  prevented  from 
dropping  again  during  relaxation  by  putting  a  brake  on  the  wheel 
(Fig.  40).  When  this  is  applied  the  muscle  is  unloaded,  i.e.  freed 

VOL.  in  F 


66 


PHYSIOLOGY 


CHAr. 


from  the  weight,  when  it  begins  to  relax,  and  the  work  done  in 
contraction  is  utilised ;  when  the  break  is  removed,  the  work  done 
is  cancelled  and  converted  into  heat  when  the  muscle  relaxes. 

Tick's  results  confirmed  Beclard's  hypothesis.  In  a  series  of 
contractions  produced  by  stimuli  of  uniform  strength,  while  the 
muscle  is  performing  useful  work,  less  heat  is  evolved  than  in  a 


Fir..  40. — Kick's  Arbeitssammler,  by  which  the  muscle  is  loader!  with  a  weight  during  contraction, 
and  unloaded  during  relaxation.  While  contracting,  the  muscle  (frog's  gastrocnemius)  lifts 
the  lever  r  rj,  which  in  itself  offers  little  resistance,  as  it  is  almost  balanced  by  the  small 
counterpoise  /.  But  owing  to  the  support  /(,  which  presses  on  the  edge  of  the  graduated  disc 
m  M  (which  revolves  round  the  same  axis  as  the  lever),  the  disc  turns  as  the  lever  rises,  along 
with  the  concentric  pulley  that  carries  the  thread  to  which  the  weight  is  attached.  The 
muscle  is  thus  loaded  during  contraction,  and  lifts  the.  weight  to  a  height  that  can  be  exactly 
measured  by  the  degree  of  rotation  of  the  disc  shown  on  the  scale  ./'.  In  relaxing,  the  muscle 
is  freed  from  its  load,  because  the  disc  and  pulley  cannot  drop  back  owing  to  the  stop  /ij. 
The  weight  remains  up,  and  the  lever  sinks  to  its  original  position  owing  to  the  slight  pre- 
ponderance of  arm  r  over  arm  )-j.  At  each  succeeding  contraction  the  weight  is  lifted  higher, 
so  that  from  the  total  rotation  of  the  disc  it  is  easy  to  calculate  the  total  sum  of  work  per- 
formed by  the  muscle  in  a  given  number  of  contractions.  When  the  stop  /ij  is  removed  from 
the  edge  of  the  disc,  the  apparatus  can  be  used  as  a  simple  isotonic  lever.  At  each  contraction 
the  muscle  rotates  the  disc  and  lifts  the  weight ;  but  at  each  successive  relaxation  the  work 
done  is  cancelled,  because  the  disc  retracts  with  the  lever  owing  to  the  pull  of  the  weight. 

second  series  of  uniform  contractions,  produced  by  stimuli  of  the 
same  strength,  in  which  the  muscle  performs  no  useful  work. 

The  later  work  of  Danilewsky,  Blix,  and  Chauveau  leads  to  the 
same  conclusion. 

On  comparing  the  heat  developed  by  a  series  of  maximal 
muscular  contractions  in  a  given  time  without  useful  work,  with 
that  developed  by  the  same  muscle  in  the  same  time  with  maximal 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  67 

stimuli  so  frequent  as  to  produce  complete  tetanus,  Fick  observed 
that  in  the  first  case  there  was  a  much  greater  development  of  heat 
than  in  the  second.  From  this  he  concluded:— 

(a)  That  the  amount  of  heat  developed  at  each  contraction 
during  tetanus  is  in  inverse  ratio  to  the  frequency  of  the  stimuli. 

(b)  That  in  a  series  of  single  contractions  due  to  momentary 
stimuli,  the  theriiiogenetic  effect  of  each  twitch  far  exceeds  that 
of  each  contraction  of  a  series  of  such  frequency  as  to  result  in 
tetanus. 

Fick  tried  to  express  the  amount  of  heat  liberated  during 
muscular  activity  in  absolute  values.  He  found  that  the  maximum 
heat  which  a  gram  of  muscle  may  develop  during  a  simple  con- 
traction may  reach  the  value  of  3'1  microcalories,  a  microcalorie 
being  the  amount  of  heat  required  to  raise  the  temperature  of 
1  mgrm.  of  water  1°  C.  With  his  pupils  he  determined  the  relative 
rates  at  which  the  development  of  heat  and  of  work  increased,  by 
a  series  of  tests  on  frog  muscle  excited  with  maximal  stimuli,  and 
loaded  with  regularly  increasing  weights. 

The  general  result  as  a  rule  was  that  the  greater  part  of  the 
potential  chemical  energy  liberated  by  the  muscle  during  its 
activity  appeared  in  the  form  of  heat.  But  with  increase  of  load 
the  ratio  between  heat  and  work  alters  regularly,  as  an  increasingly 
larger  part  of  the  potential  chemical  energy  is  set  free  in  the  form 
of  work,  and  a  comparatively  smaller  part  as  heat.  This  proves 
that  the  muscle  in  doing  more  work  functions  more  economically 
than  in  doing  little  work. 

Zuntz,  Lehmann,  and  Hagemann  (1889)  tried  to  ascertain  what 
proportion  of  the  total  energy  developed  in  the  muscles  of  warm- 
blooded animals  is  utilised  in  the  form  of  mechanical  work.  This 
question  has  only  been  solved  approximately  by  calculating  the 
total  chemical  energy  developed  by  the  estimation  of  the  reciprocal 
gas-exchanges  which  take  place  in  any  given  work  of  the  muscles. 
It  was  shown  by  experiments  on  horses  that  about  J  of  the 
energy  is  transformed  into  work,  and  f  into  heat.  If  we  con- 
sider that  in  the  best  steam-engines  man  is  able  to  construct 
only  jL  or  TV  part  of  the  energy  liberated  can  be  utilised  in 
mechanical  work,  all  the  rest  being  lost  in  the  form  of  heat,  we 
see  that  the  muscle  is  a  living  machine  which  functions  more 
economically  than  any  steam-engine.  On  the  other  hand,  an 
electric  motor  fed  from  a  battery  is  capable  of  utilising  y9^ 
of  the  energy  developed  by  the  oxidisation  of  the  zinc  of  the  cell 
in  external  mechanical  work,  so  that  it  is  a  more  perfect  machine 
than  the  muscle.  We  must  not,  however,  forget  that  in  homoio- 
thermic  animals  the  development  of  heat  must  not  be  regarded  as 
a  loss,  since  it  is  as  useful  to  the  organism  as  mechanical  work. 
A  muscle  is  not  merely  an  apparatus  for  the  production  of  external 
work,  but  it  also  serves  to  heat  the  body  of  warm-blooded 


68  PHYSIOLOGY  CHAP. 

animals,  and  raise  their  temperature  to  a  given  height,  inde- 
pendently of  the  variations  of  external  temperature.  From  this 
physiological  standpoint  it  may  be  held  that  the  muscle  utilises 
all  the  energy  which  it  develops,  either  in  the  form  of  work  or  of 
heat. 

XL  A  portion  of  the  potential  chemical  energy  liberated 
during  the  activity  of  the  muscle  appears  not  as  heat,  but  as 
electricity. 

A  discovery  of  great  importance  in  physics — galvanism,  and  in 
physiology — animal  electricity,  originated  in  Galvani's  observations 
that  muscles  of  a  recently  killed  frog  were  thrown  into  convulsions 
on  closing  the  circuit  between  the  muscles  and  the  nerves  by 
means  of  two  metals.  From  this  Galvaiii  concluded  that  the 
muscles  of  the  frog  were  normally  charged  like  a  Leyden  jar,  with 
positive  electricity  inside  and  negative  electricity  outside  each 
muscle.  Hence  he  assumed  that  on  making  connection  between 

the  inside  and  outside  of  a 
muscle,  a  current  was  produced 
which  gave  rise  to  the  con- 
traction. 

Volta  at  once  recognised 
that  this  interpretation  was 
erroneous,  because  the  circuit 

FIG.  41. — Galvani's  second  experiment,  without  •    •  j-™»  t    i 

metais.  comprising  two  different  metals 

in  itself  contained  a  source  of 

electromotive  force.  The  long  controversy  between  Volta,  who 
affirmed  the  existence  of  metallic  currents,  and  Galvani,  who 
maintained  the  contrary  and  endeavoured  to  explain  everything 
by  muscle  currents,  is  certainly  one  of  the  most  remarkable 
incidents  in  the  history  of  experimental  science.  The  contrary 
statements  of  the  two  protagonists  were  true ;  their  negations 
were  false.  Volta's  theory  led  to  the  discovery  of  the  pile ; 
Galvani's  to  the  first  demonstration  that  living  tissues  in  general, 
and  the  muscles  in  particular,  may,  under  given  conditions,  be  the 
seat  of  the  development  of  electrical  currents. 

The  observation  of  Galvani  and  his  nephew  Aldini  was 
based  on  the  fact  that  contraction  takes  place  in  the  muscles  of 
a  recently  killed  frog,  not  only  when  a  circuit  is  made  between  a 
muscle  and  its  nerve  by  a  bridge  consisting  of  two  metals  or  even 
of  one  metal,  but  also — though  in  a  less  degree — when  the  circuit 
is  made  without  any  metal.  This  experiment,  famous  in  the 
annals  of  medicine,  consists  in  laying  the  nerve-muscle  preparation 
of  a  frog  upon  a  glass  plate  (Fig.  41),  and  bringing  the  surface  of 
the  muscle  into  contact  with  the  end  of  the  freshly-cut  nerve  by 
a  glass  rod.  At  the  moment  of  contact  the  muscle  contracts. 
Eepeated  and  confirmed  by  Valli  (1794)  and  Alexander  v. 
Humboldt  (1798),  this  experiment  underlies  the  general  theory 


i  GENEEAL  PHYSIOLOGY  OF  MUSCLE  69 

that  living  tissues  are  under  special  conditions  the  seat  of 
electromotive  forces,  which  may  excite  muscular  contractions  on 
the  closure  of  non-metallic  circuits. 

Direct  proof  of  this  was  not  available  till  after  the  invention 
of  the  galvanometer  by  Nobili  (1824),  when  it  became  possible 
not  only  to  demonstrate  the  existence  of  the  comparatively 
weak  currents  present  in  living  tissues,  but  also  to  measure  them. 
In  1827  Nobili  made  use  of  Schweigger's  rnultiplicator  to  demon- 
strate the  so-called  "  natural  current "  of  the  frog,  directed  from 
the  foot  towards  the  head. 

On  repeating  and  varying  Nobili's  experiment  in  different 
ways,  Matteucci  (1838-40)  discovered  the  phenomenon  known 
later  as  the  "current  of  rest"  in  muscle.  He  amputated  the 
thigh  of  a  skinned  frog  by  a  transverse  incision,  and  brought  it 
into  the  circuit  of  a  galvanometer,  by  applying  one  electrode  to 
the  cut  surface  and  the  other  to  the  outer  surface  of  the  thigh 
muscles.  On  closing  the  current  the  galvanometer  needle  was 


Fin.  42. — Matteucci's  experiment  of  secondary  contraction  and  tetanus. 

deflected,  showing  a  current  in  the  muscle  from  within  outwards, 
i.e.  from  the  cut  surface  to  the  natural  surface  of  the  muscle,  in 
the  galvanometer  circuit  from  the  natural  to  the  cut  surface.1 

In  1842  Matteucci  communicated  to  the  Academic  des  Sciences 
in  Paris  another  discovery,  which  Biedermann  reckons  among  the 
most  important  in  experimental  physiology.  When  the  nerve  of 
a  frog's  leg  is  placed  on  the  muscle  of  the  opposite  leg,  and  the 
nerve  of  the  latter  is  excited  by  certain  stimuli,  a  vigorous  primary 
contraction  results  in  the  muscles  of  this  excited  limb,  accom- 
panied by  a  less  vigorous  secondary  contraction  in  the  muscles  of 
the  other  limb  (Fig.  42). 

This  observation  was  the  first  demonstration  of  an  electrical 
phenomenon  concomitant  with  the  state  of  muscular  activity. 
Matteucci  interpreted  it  wrongly ;  the  true  explanation  was  only 
possible  after  the  law  of  the  current  of  rest  in  muscle  and  its 
negative  variation  had  been  discovered  by  du  Bois-Keymond  (1843). 

1  To  avoid  the  confusion  that  frequently  arises  between  the  current  in  the 
outer  (galvanometer)  circuit  and  that  flowing  within  the  tissue,  it  might  be  well, 
as  suggested  by  Waller,  to  replace  the  ambiguous  term  "  negative  "  (more  correctly 
"  electro-positive  ")  by  the  term  "zincative,"  which  would  serve  as  a  reminder  that 
the  current  flows  from  the  excited  to  the  unexcited  portion  of  the  tissue,  as  from 
zinc  to  copper  in  a  Daniell  cell. — Translator. 


70  PHYSIOLOGY  CHAP. 

Du  Bois-Keymond's  researches  began    in   1841,  shortly   after 


Fin.  43. — Thomson's  galvanometer.     To  the  left  is  the  galvanometer,  in  the  centre  a  .shunt,  to  the 
right  the  scale,  illuminated  by  a  beam  reflected  from  a  lamp  to  the  galvanometer  mirror. 


those  of  Matteucci. 


Jl 


FIG.  44. —  Diagram  of  galvano- 
meter, n  s  and  s  n,  pair  of 
magnets  with  opposite  poles, 
circular  mirror  fixed  to  upper 
magnet ;  1 1,  end  of  wire  that 
surrounds  the  magnets  ;  N  S, 
third  magnet,  which  controls 
the  two  lower  magnets. 


equilibrium 

theory  "). 


He  devoted  many  years  to  the  study  of 
animal  electricity,  and  his  great  merit  lies 
in  the  introduction  of  exact  methods.  His 
discovery  of  unpolarisable  electrodes,  com- 
bined with  the  method  of  compensating 
by  means  of  a  rheochord,  enabled  him  to 
separate  the  tissue  currents  from  those  of 
metallic  origin,  and  to  measure  them,  both 
in  the  resting  state  of  the  muscles  and 
nerves  and  during  their  activity. 

In  1807  Hermann's  investigations 
opened  up  a  new  chapter  in  electro- 
physiology.  He  overthrew  clu  Bois- 
Reymond's  theory,  according  to  which 
electrical  currents  are  pre  -  existent  in 
normal  living  tissues  in  the  resting  state 
(" pre-existence  theory"].  By  the  experi- 
ments we  are  about  to  discuss,  which  were 
to  a  large  extent  confirmed  by  subsequent 
observers  (Hering,  Engelmaun,  Bieder- 
mann,  and  others),  Hermann  proved  that 
muscles  and  other  tissues,  so  long  as 
they  are  at  rest  and  intact,  give  off  no 
currents  to  the  galvanometer.  When 
currents  appear  they  are  due  solely  to 
the  effects  of  artificial  alteration  of  the 
tissues,  or  to  the  disturbance  of  chemical 
which  accompanies  functional  activity  ("  alteration 


GENEEAL  PHYSIOLOGY  OF  MUSCLE 


71 


Owing  to  (lie  high  resistance  of  animal  tissues  (which  is  millions  of  times 
greater  than  the  resistance  of  metals)  and  their  low  potential,  it  is  necessary 
in  electrophysiological  research  to  employ  galvanometers  or  multipliers  with 


FIG.  45. — Various  forms  of  unpolarisable  electrodes.     D  and  C,  du  Bois-Reymond's  pattern  ; 
E,  Burden-Sanderson's  ;  B,  von  Fleischl's  ;  A,  d'Arsouval's. 


astatic   magnets,  so   as  to   render   the  vibrations   as 

have  a  high  internal  resistance 
the  instrument  can  be  decreased 


These  galvanometers 


of 


,9,99 

1  oTFu 


many  coils   and  with 
a-periodic  as  possible. 
(5,000-20,000  ohms).     The  sensitiveness 
by  a  shunt,  which  cuts  off  -j9^,  -fifa,  or 
of  the  current.     The  principle  on  which  gal- 
vanometers are  constructed  is  that  a  magnet, 
suspended    and   surrounded  by  a  conducting 
wire,  is  deflected  in  the  direction  of  a  current 
passing  through   the  wire,   in  proportion   to 
the  strength  of  the  current. 

Both  in  Wiedemann's  (with  detachable 
and  interchangeable  spools)  and  in  Thomson's 
galvanometer  (Figs.  43,  44)  the  deflections  of 
the  magnet  suspended  by  a  thread  of  raw  silk 
are  more  or  less  magnified  by  a  mirror  which 
reflects  a  ray  of  light  on  to  a  horizontal  scale. 
These  deflections  can  be  photographed  on  a 
moving  sensitive  surface. 

The  ends  of  the  galvanometer  wires  must 
not  be  directly  applied  to  the  tissues,  on 
account  of  their  polarisability.  Unpolarisable 
electrodes  are  indispensable  in  experimenting 
with  muscle  and  nerve  (du  Bois-Eeymond). 
These  usually  consist  of  a  little  rod  or  disc  of 
amalgamated  zinc  dipping  into  solution  of 
zinc  sulphate  in  a  glass  tube,  the  other  end 
of  which  is  closed  by  a  plug  of  china  clay 
saturated  with  physiological  saline,  which  is  in  contact  with 
protects  it  from  the  caustic  action  of  the  zinc  sulphate  (Fig.  45). 

Nowadays,  however,  all  these  imperfect  electrodes  may  be  replaced  by  the 
so-called  "normal  electrodes"  of   Ostwald,  in  which  potassium  chloride    is 


FIG.  46. — Ostwald's  normal  electrode, 
adapted  to  physiological  research 
by  Oker  Blom. 


the  tissue  and 


PHYSIOLOGY 


CHAP. 


substituted  for  sodium  chloride.  A  suitable  adaptation  of  these  to  physio- 
logical purposes  is  the  model  of  Oker  Blom  (1900).  Two  glass  tubes  are 
sealed  at  the  bottom  in  the  flame,  with  a  little  mercury  on  the  base,  by  which 
contact  is  made  with  two  platinum  wires  that  pass  through  the  sealed  ends. 
Pure  calomel  is  placed  on  the  mercury,  and  above  that  physiological  salt 
solution,  which  is  brought  into  contact  with  the  muscle  by  a  tag  of  cotton 
saturated  with  the  solution  (Fig.  46). 

The  galvanometer  can  be  replaced  by  Lippmann's  capillary  electrometer, 
which  has  the  advantage  of  reacting  to  very  rapid  oscillations  of  current,  with 


FN;.  47. — Lippmamf  s  capillary  electrometer.  A,  viewed  as  a  whole  (pressure  bulb,  capillary,  and 
microscope) ;  1',  tube  (Hg)  and  capillary  (<•)  which  dips  into  the  tube  of  sulphuric  acid 
(HoSO.|) ;  C,  mercury  in  capillary  tube  under  the  microscope. 

no  lost  time  and  no  periodic  vibrations.  Moreover,  as  the  resistance  in  the 
capillary  is  enormous  and  the  current  passing  through  it  is  practically  abolished, 
nnpolarisable  electrodes  can  be  dispensed  with.  As  seen  in  Fig.  47,  the 
instrument  consists  of  a  glass  tube  drawn  out  in  the  flame  at  one  end  to  a 
capillary  20-30  mm.  diameter.  This  tube  is  filled  with  mercury  and  joined  to 
an  apparatus  by  which  the  pressure  can  be  regulated.  The  open  end  of  the 
capillary  dips  into  10  per  cent  sulphuric  acid  solution.  Two  platinum  wires  con- 
nect the  mercury  and  sulphuric  acid,  respectively,  to  the  points  of  the  organ  under 
investigation.  Under  the  microscope  the  excursions  of  the  mercury  meniscus 
—which  is  brought  into  the  field  by  means  of  the  pressure  apparatus — can  be 
seen  plainly  on  closure  of  the  circuit.  The  meniscus  advances  or  recedes  towards 
the  end  of  the  capillary  according  as  the  potential  rises  or  falls  on  the  side  of 
the  mercury  tube,  and  vice  versa  as  regards  the  reservoir  of  sulphuric  acid. 
In  the  capillary  electrometer  the  excursions  of  the  meniscus  do  not 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  73 

indicate  the  strength  of  current,  but  the  electromotive  force  or  <li (Terence  of 
potential  between  the  two  electrodes.  It  is  thus  an  electrical  manometer, 
the  sensitiveness  of  which  is  so  great  that  it  reacts  to  TUT&UTT  volt.  The  dis- 
placements of  the  mercury  surface  can  be  photographed. 

Eiiithoven  (1905-6)  introduced  the  string  galvanometer  which  has  distinct 
advantages  over  its  predecessors. 

This  instrument  has  a  fine  thread  of  silvered  quartz  or  platinum  stretched 
between  the  two  poles  of  a  strong  magnet.  On  passing  a  weak  current 
through  the  string,  it  moves  laterally  in  proportion  to  the  strength  of  the 
current.  The  poles  of  the  magnet  are  pierced  by  holes  so  that  the  thread  may 
be  illuminated  by  an  electric  light  from  the  one  side,  and  observed  from  the 
other  by  means  of  a  microscope  ;  or  a  magnified  image  may  be  thrown  on  a 
screen,  or  moving  sensitive  surface  on  which  it  is  photographed. 

Einthoven  devised  this  apparatus  for  the  special  purpose  of  studying 
the  electrical  variations  of  the  human  heart.  But  it  may  be  substituted 
advantageously  for  all  purposes  instead  of  the  apparatus  described  above. 

We  will  briefly  consider  the  principal  electromotive  phenomena 
in  muscle,  keeping  distinct  the  electrical  manifestations  of  the 
resting  and  the  active  states. 

When  a  muscle  with  parallel  fibres,  e.g.  the  frog's  sartorius,  is 
dissected  out,  and  the  tendinous  end  trimmed  neatly  with  a  razor, 
a  regular  cylinder  of  muscle  substance  is  obtained,  with  a  natural 
longitudinal  surface  and  two  artificial  cross-sections.  If  any  two 
points  of  this  muscle  are  connected  with  the  galvanometer  by 
unpolarisable  electrodes  there  is  nearly  always  a  deflection  of  the 
galvanometer  needle,  showing  that  the  two  points  led  off  are  not 
isoelectric,  but  that  there  is  a  difference  in  potential. 

If  the  electrodes  are  applied  to  points  on  the  natural 
longitudinal  and  the  artificial  transverse  surfaces,  the  former  is 
found  to  be  "  positive"  in  relation  to  the  latter,  which  is  "  negative." 
Du  Bois-Keymond  made  a  minute  study  of  the  different  degrees 
to  which  the  galvanometer  needle  was  deflected  by  altering  the 
position  of  the  electrodes  upon  the  muscle  cylinders,  and  drew  up 
the  following  laws  of  the  muscle  current  :— 

(a)  Strong  currents  appear  on  leading  off  to  the  galvano- 
meter from  the  natural  longitudinal  surface  and  artificial  cross- 
section  of  the  muscle.  The  current  is  strongest  when  a  point  in 
the  equatorial  median  line  of  the  longitudinal  surface  is  connected 
with  the  axial  point  of  an  artificial  cross-section,  and  decreases 
regularly  with  increased  distance  from  these  points. 

(&)  Weak  currents  are  obtained  when  two  points  at  unequal 
distance  from  the  equator  of  the  longitudinal  section  are  united  ; 
still  weaker  currents  when  two  points  of  the  cross-section  at  un- 
equal distances  from  the  ends  of  its  axis  are  connected. 

(c)  No  current  is  obtained  on  connecting  two  points  of  the 
equator  or  any  two  points  at  equal  distance  from  the  same ;  nor  on 
connecting  the  two  axial  points  of  the  cross-section,  or  any  two 
points  of  the  cross  -  section  equidistant  from  the  axial  points 
(Fig.  48). 


74 


PHYSIOLOGY 


CHAP. 


These  observations  show  that  the  natural  surface  of  the  muscle 
has  a  positive  electrical  charge,  which  is  maximal  along  the 
equatorial  Hue  and  decreases  regularly  away  from  it;  and  that  the 
two  artificial  cross-sections  have  a  negative  electrical  charge  which 
decreases  regularly  from  the  axial  point  of  the  muscle  cylinder, 


4- 


•f 


!  + 

— t — 


Fie.  48. — Diagram  of  direction  of  currents  that 
can  be  led  off  to  a  galvanometer  from 
different  points  of  the  surface  of  a  muscle 
cylinder. 


-f 


Fia.  4;t.  —  Distribution  of  positive  electrical 
charge  on  natural  longitudinal,  and  negative 
electrical  charge  on  artificial  transverse 
sections  of  a  muscle  cylinder. 


where  it  is  maximal,  to  the  more  peripheral  points  of  the  cross- 
section  (Fig.  49). 

If  the  section  is  made  obliquely  through  the  muscle  cylinder, 
the  potential  at  the  different  points  of  the  natural  surface  and  the 
artificial  surfaces  varies  according  to  another  law.  The  galvano- 
meter shows  that  the  most  positive  points  of  the  longitudinal 
surface  lie  much  nearer  the  obtuse  angles  of  the  rhombus,  and  the 
more  negative  points  close  to  the  acute  angles.  The  strongest 
current  is  obtained  on  leading-off  from  these  opposite  points ;  on 


4- 


\ 


FIG.  50. — Diagram  of  direction  of  currents  led 
off  from  surface  of  a  muscle  rhombus. 


-f-     + 


Kici.  51.  —  Positive  and  negative  electrical 
charges  at  longitudinal  and  transverse 
sections  of  a  muscle  rhombus. 


connecting  points  more  remote  from  these  the  currents  become 
increasingly  weaker  ;  lastly,  there  is  no  current  on  joining  up 
honionymous  points  on  the  natural  or  artificial  surfaces  (Fig.  50). 

There  is  thus  in  the  oblique  muscle  cylinder  a  displacement  of 
the  isoelectric  equatorial  and  axial  points  in  the  direction  indicated 
in  Fig.  51. 

The  longitudinal  surface  of  a  muscle  shows  a  positive  charge 


i  GENEKAL  PHYSIOLOGY  OF  MUSCLE  75 

as  compared  with  the  artificial  transverse  or  oblique  section,  even 
when  it  is  not  the  natural  external  surface  covered  with  periinysium, 
but  the  surface  of  a  bundle  of  fibres  artificially  dissected  out,  but 
otherwise  intact.  On  the  other  hand,  the  natural  transverse  or 
oblique  section,  consisting  of  the  ends  of  the  fibres  where  they  are 
connected  with  the  tendon  or  aponeurosis,  is  not — like  the  artificial 
surface  produced  by  a  cut — negative  to  the  longitudinal  surface. 
The  negative  charge  first  makes  its  appearance  after  removal  of 
the  tendon,  i.e.  on  the  formation  of  an  artificial  cross-section. 

The  gastrocnemius  muscle,  which  is  generally  employed  for  a 
nerve-muscle  preparation  from  the  frog,  shows  marked  differences 
of  potential  at  different  points  of  its  natural  surface,  which  do  not 
altogether  conform,  to  the  laws  of  the  current  of  rest  in  straight  or 
oblique  muscle  cylinders.  This  is  due  to  the  complicated  structure 


Fio.  52. — Measurement  of  electromotive  force  of  current  of  rest  in  muscle  by  method  of  compensa- 
tion. V  )•,  rectilinear  rheochord  (monochord)  consisting  of  a  long  wire  connected  at  the  ends 
to  the  battery.  The  runm-r  *•  is  movable  along  it,  so  that  any  fraction  of  the  battery  current 
can  be  thrown  into  the  galvanometer  to  compensate  the  muscle  current  which  is  opposite 
in  direction. 

of  the  muscle,  which  consists  not  of  parallel  fibres,  but  of  fibres  that 
run  obliquely  (Kosenthal). 

The  electromotive  force  which  a  frog's  muscle  is  capable  of 
developing  may  be  measured  by  the  compensation  method,  i.e.  by 
introducing  into  the  circuit  that  connects  the  two  oppositely 
charged  points  of  the  muscle  with  the  galvanometer  a  current 
from  a  Daniell  cell  in  the  direction  opposite  to,  and  of  the  same 
strength  as,  the  muscle  current.  This  is  easily  effected  by  means  of 
a  rheochord  (Fig.  52).  The  electromotive  force  has  been  known  to 
exceed  O'OS  volt  (du  Bois-Eeymond,  Chapman).  But  it  may  be 
concluded  that  the  portion  of  the  current  led  off  to  the  galvano- 
meter is  only  a  small  fraction  of  the  total  current  developed 
within  the  muscle,  which  we  are  not  in  a  position  to  measure 
(Bernstein). 

The  electrical  phenomena  of  the  resting  muscle  depend  on  the 
state  of  vitality  of  the  tissues.  Muscles  that  are  dead  or  in  rigor 
mortis  are  electrically  inactive.  Muscles  treated  with  ether  vapour, 


76  PHYSIOLOGY  CHAP. 

or  swollen  with  water,  which  are  totally  inexcitable  and  apparently 
dead  do,  on  the  contrary,  manifest  differences  of  electrical 
potential. 

Another  important  fact  discovered  by  Hermann  and  confirmed 
by  Biedermann  and  others  is  that  wholly  uninjured  muscles 
are  isoelectric,  i.e.  manifest  no  difference  in  potential  at  their 
surface  in  the  resting  state.  When  the  hind -leg  of  a  frog  is 
very  carefully  skinned,  precaution  being  taken  to  avoid  contact 
between  the  cutaneous  secretion  and  the  exposed  surface  of  the 
muscle,  no  current  can  be  led  off  from  the  latter  to  the  galvano- 
meter. When,  on  the  contrary,  an  exposed  muscle  is  injured  at 
any  point  of  its  surface  by  cauterisation,  chemical  burns,  partial 
poisoning  with  potassium  salts,  mechanical  crushing,  etc.,  the 
injured  spot  invariably  becomes  negative  to  the  intact  parts  of  the 
surface.  So  that  injured  points  react  like  transverse  or  oblique 
surfaces  produced  by  section.  Hermann,  therefore,  formulated  the 
general  law  which  is  applicable  to  all  cases,  that  "  In  every  injured 
muscle  fibre  the  surface  of  demarcation  between  the  living  and 
dead  portions  of  the  fibre  is  the  seat  of  an  electromotive  force 
directed  towards  the  living  part."  He  gave  the  name  of  demarca- 
tion current  to  the  so-called  "  current  of  rest,"  because  it  does  not 
pre-exist  in  the  normal  muscle,  but  first  appears  when  any  part  of 
the  latter  suffers  alteration.  [Current  of  injury  :  Hering.] 

Another  phenomenon  brought  out  by  Hermann  is  that  a 
general  rise  of  temperature  increases  the  strength  of  the  demarca- 
tion current  up  to  a  certain  limit,  beyond  which  it  decreases 
again,  till  it  disappears  with  the  onset  of  heat  rigor.  A  drop  in 
the  temperature,  on  the  contrary,  lowers  the  e.m.f.  Again,  in 
intact  muscle  heated  points  are  electro-positive  to  cooler  parts 
(Hermann  and  Worm-Mliller).  Finally,  fatigue  from  protracted 
muscular  activity  weakens  the  demarcation  current  (Eb'ber),  and 
abolishes  it  if  pushed  as  far  as  rigor. 

Another  fact  in  favour  of  Hermann's  views  is  that  in  muscle 
prisms  or  cylinders  freshly  cut  with  a  razor  and  connected  with 
the  galvanometer  the  demarcation  current  is  absent,  or  almost 
absent,  during  the  first  moments,  but  increases  rapidly  to  its 
maximum.  This  phenomenon  can  only  be  explained  by  assuming 
that  the  surface  of  the  section  alters  with  exposure  to  air,  and 
that  its  negative  potential  increases  in  proportion  with  this 
change.  The  alteration  shown  in  the  acidification  of-  the  muscle 
gradually  extends  over  the  whole,  till  it  becomes  perfectly  rigid. 
The  demarcation  current  as  shown  on  the  galvanometer  suffers 
a  parallel  slow  diminution,  till  it  eventually  disappears. 

We  must  next  study  the  phenomena  of  active  muscle.     If  the 

nerve  of  a  muscle-nerve  preparation  that  is  showing  a  demarcation 

current  on  the  galvanometer  is  tetanised,  the  current  is  diminished 

—the  galvanometer  needle  swings  back  towards  the  zero  of  the 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  77 

scale  during  the  tetanus.  This  is  the  "  negative  variation  "  referred 
to  above.  On  a  sensitive  galvanometer  it  can  be  shown  during 
single  twitches  as  well  as  in  tetanus.  If  the  current  of  rest  is 
compensated,  and  the  nerve  is  then  excited,  the  negative  variation 
will  appear  on  the  galvanometer  as  an  autonomous  current,  in 
the  opposite  direction  to  the  current  of  rest — showing  that  the 
e.m.f.  of  the  muscle  is  diminished  by  excitation  (du  Bois-Pieyrnond). 

The  phenomena  of  secondary  contraction,  or  induced  contraction 
as  it  was  termed  by  Matteucci,  and  secondary  tetanus,  which  can 
be  seen  in  a  frog's  leg  when  its  nerves  are  laid  across  the  muscles 
of  another  leg,  so  that  the  muscle  current  produced  in  the  latter 
on  contraction  passes  through  the  nerves  of  the  former  (Fig.  42), 
depend,  as  du  Bois-Eeymond  showed,  on  the  exciting  action  of 
the  negative  variation  of  the  current.  The  secondary  twitch  is 
the  simplest  and  most  convincing  proof  that  a  single  contraction 
can  elicit  a  negative  variation  of  sufficient  intensity  to  stimulate 
the  nerve.  Secondary  tetanus  further  shows  that  the  negative 
variation  of  the  primary  tetanus  is  a  discontinuous  process, 
although  the  variations  in  the  current  are  too  rapid  to  be 
followed  by  the  galvanometer  needle,  and  their  mean  value  only 
is  recorded. 

The  oscillating  character  of  the  muscle  current  in  tetanus  can 
also  be  demonstrated  by  the  telephone,  which  Hermann  regards 
as  more  sensitive  than  the  "  galvanoscopic  leg."  When  the 
muscle  current  is  led  off  to  a  telephone,  a  sound  is  heard  during 
tetanisation  which  results,  as  Bernstein  and  Wedensky  demon- 
strated, from  a  number  of  vibrations  equal  to  the  rate  of  the  break 
or  make  shocks  of  the  tetanising  current. 

Bernstein  was  able  by  an  ingenious  apparatus  known  as  the 
differential  rheotome  to  analyse  the  negative  variation  during  a 
simple  contraction. 

The  negative  variation  in  a  nerve-muscle  preparation  during 
tetanus  can  be  photographed  by  reflecting  a  beam  of  light  from 
the  galvanometer  magnet  on  to  a  sensitive  surface  moving  by 
clockwork.  Fig.  53  records  the  tetanic  contraction  and  accom- 
panying negative  variation. 

The  galvanometer  does  not  react  quickly  enough  to  show  the 
oscillations  that  accompany  tetanus,  but  if  the  capillary  electro- 
meter is  used,  they  can  be  photographed  by  letting  the  shadow 
of  the  meniscus  fall  on  a  slit  behind  the  sensitive  paper,  which 
travels  in  a  direction  vertical  to  the  oscillations  of  the  mercury 
(Burdon-Sanderson  and  others). 

The  negative  variation  increases  to  a  maximum  with  the 
intensity  of  the  tetanising  current.  According  to  Bernstein  it 
never  reaches  the  zero  point,  i.e.  never  cancels  the  demarcation 
current.  According  to  Gotch  and  Sanderson,  on  the  contrary, 
the  negative  variation  may  pass  beyond  the  zero  point,  and 


78 


PHYSIOLOGY 


CHAP. 


exceed  the  value  of  the  demarcation  current ;  for  instance,  the 
demarcation  current  may  equal  O04  volt,  the  negative  variation 
0'08  volt.  The  negative  variation  also  increases  up  to  a  certain 
maximum  with  increase  of  the  elastic  tension  or  load  of  the 
muscle,  parallel  with  the  development  of  work  and  of  heat. 

In  order  to  understand  the  nature  of  the  negative  variation 
of  the  demarcation  current  in  muscle  when  the  nerve  is  tetanised, 


FIG.  53.— Myogram  of  tetanic  contraction  of  frog's  gastrocnemius  (white  line  on  black  ground)  ,-md 
simultaneous  photograph  of  negative  variation  (black  line  on  white  ground).  (A.  D.  Waller.) 
u,  gradually  diminishing  demarcation  current;  &,  its  sudden  decrease  during  tetanus  (negative 
variation) ;  c,  subsequent  positive  variation  on  cessation  of  tetanus  ;  d,  return  of  slowly 
declining  demarcation  current. 

it  must  be  remembered  that  in  consequence  of  stimulation  the 
whole  mass  of  the  muscle  undergoes  an  explosive  chemical  change 
associated  with  the  passage  from  the  state  of  rest  to  the  state  of 
activity,  which  is  greater  in  the  normal  than  in  the  altered  parts 
of  the  muscle.  This  effect  of  excitation  sets  up  a  difference  of 
electrical  potential  and  gives  rise  to  the  action  current,  which 
neutralises  the  demarcation  current,  and  may  even  exceed  it 
(Gotch  and  Sanderson). 


GENEEAL  PHYSIOLOGY  OF  MUSCLE 


In  studying  the  current  of  action  developed  by  stimulation 
it  is  best  to  employ  an  intact  muscle  with  no  current  of  rest, 
for  as  this  would  pass  in  the  opposite  direction,  it  would  be 
unfavourable  to  the  demonstration  of  the  action  current,  which 
would  then  seem  to  be  only  the  negative  variation  of  the  current 
of  rest.  When  the  galvanometer  electrodes  are  applied  to  both 
ends  of  an  intact  and  freshly  excised  muscle,  as  in  Fig.  54,  A,  B, 
and  the  muscle  is  stimulated  at  C  by  an  induction  shock,  the 
reaction  does  not  take  place  simultaneously  all  over  the  muscle, 
but  it  is  propagated,  as  we  saw  above  (Fig.  16,  p.  23),  like  a  wave 
from  the  point  stimulated  to  the  more  distant  points.  So  that 
the  end  A  of  the  muscle  which  is  near  the  point  of  application  of 


B 


Fir:.  54. — Apparatus  for  study  of  diphasic- 
action  current. 


FIG.  55. — Myogram  of  a  contraction  of  frog's  gastro- 
enrmius,  in  m,  and  simultaneous  photograph  of 
diphasic  electrical  variation,  e  e.  (A.  D.  Waller.) 


the  stimulus  C  will  be  thrown  into  activity  first,  and  the  end  B 
last.  Since  the  active  points  of  the  muscle  become  galvano- 
metrically  negative  to  the  inactive  points,  the  galvanometer  needle 
reacts  in  a  diphasic  oscillation.  In  the  first  phase  A  will  be 
negative  to  B,  in  the  second  phase  B  will  be  negative  to  A.  The 
first  phase  coincides  with  the  transmission  of  the  contractile  wave 
from  A  to  B ;  the  second  phase  coincides  with  the  contraction  of 
B,  as  A  begins  to  relax.  The  slower  the  transmission  of  the 
wave  along  the  muscle,  the  more  prolonged  will  be  the  negativity 
of  A  at  the  beginning,  and  of  B  at  the  close  of  the  contraction. 
Hence  the  diphasic  variation  of  the  action  current  is  more  easily 
demonstrated  on  the  frog's  heart,  where  the  systolic  wave  is 
propagated  on  an  average  at  O'l  m.  per  second,  than  in  skeletal 
muscle,  where  the  wave  of  contraction  is  propagated  at  about 
1  m.  per  second. 

Pig.  55  gives  the  myogram  of  a  contraction  produced  in  the 
frog's  gastrocneuiius  when  an  induction  shock   is  sent    through 


80 


PHYSIOLOGY 


CHAP. 


the  sciatic  nerve,  with  a  synchronous  photograph  of  the  diphasic 
current  of  action.  In  this  case  the  muscle  was  indirectly  stimu- 
lated, and  the  contractile  wave  started  from  the  end-plates  which 
usually  lie  about  midway  in  the  fibres,  and  spread  from  there 
towards  the  two  ends,  one  electrode  connected  with  the  sulphuric 


Fir;.  56. — Cardiogram  of  spontaneous  beat  of  frog's  heart,  It,  and  simultaneous  photograph  of 
diphasic  variation,  e.     (A.  D.  Waller.) 

acid  of  the  electrometer  being  applied  near  the  middle  of  the 
muscle,  and  the  other,  connected  with  the  mercury,  to  the 
tendinous  end.  Fig.  56  gives  the  spontaneous  cardiogram  of  the 
frog's  heart  with  a  synchronous  photograph  of  the  diphasic 
variation,  the  sulphuric  acid  electrode  being  applied  to  the  apex 


FIG.  57. — Apparatus  for  leading  off  diphasic  action  current  from  the  muscles  of  the  human  fore- 
arm. (Hermann.)  To  light  of  figure  an  unpolarisable  bracelet  electrode ;  r,  »•',  points  of 
stimulation  of  brachial  plexus. 

of  the  heart,  and  the  mercury  electrodes  to  the  base  of  the 
ventricle.  In  the  first  experiment  there  is  a  positive  oscillation 
of  the  electrometer  at  the  first  phase,  and  a  negative  oscillation 
at  the  second  phase,  because  in  the  first  phase  the  end  of  the 
muscle  is  positive  to  its  middle  part,  which  was  first  thrown 
into  contraction — negative  to  it  in  the  second  phase.  In  the 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


81 


experiment  on  the  heart,  on  the  contrary,  there  is  a  negative 
oscillation  in  the  first  phase,  which  expresses  the  negativity  of 
the  base  to  the  apex  at  the  commencement  of  systole,  and  a 
positive  oscillation  in  the  second  phase,  which  expresses  the 
positivity  of  base  to  apex  at  the  close  of  systole  and  commence- 
ment of  diastole. 

Hermann  succeeded  in  demonstrating  the  diphasic  variation  in 


I 


I 


Fie;.  58. — Distribution  of  electrical  potential  to  different  parts  of  the  human  body  at  the  moment 
at  which  the  diphasic  action  current  of  the  heart  arises.  (A.  D.  Waller.)  A,  apex  ;  B,  base  of 
ventricles  ;  0  0,  equatorial  line  or  plane  in  which  the  electrical  potential  is  nil ;  a,  a,  a  and 
6,  ft,  b  are  the  equipotential  curves  of  A  and  L. 

the  muscles  of  the  fore-arm  of  a  man  by  stimulating  the  brachial 
plexus  in  the  axilla.  The  current  was  led  off  by  special  electrodes, 
applied  one  between  the  middle  and  upper  third  of  the  fore-arm, 
the  other  to  the  wrist  or  elbow  (Fig.  57). 

In  the  first  case  there  is  a  descending-ascending,  in  the  second 
case  an  ascending-descending  diphasic  current,  as  shown  by 
arrows  1,  2  of  the  diagram.  This  diphasic  action  current  is  the 
only  electrical  phenomenon  which  can  be  positively  demonstrated 
for  skeletal  muscle  on  living  man. 

The  ascending  current  in  the  arm  after  a  voluntary  contraction 
of  the  muscles  (du  Bois-Eeymond)  is  not  a  muscular  action 

VOL.  Ill  G 


82 


PHYSIOLOGY 


CHAP. 


current,  but  a  secretory  skin  current,  as  was  shown  by  Hermann 
and  Lucb singer. 

A.  D.  Waller  succeeded  in  demonstrating  the  electrical  changes 
that  accompany  contraction  of  cardiac  muscle  in  intact  animals 
and  man.  He  used  Lippmann's  capillary  electrometer,  by  which 
he  was  able  to  record  not  only  the  diphasic  variation  that  accom- 
panies the  beats  of  the  human  heart,  but  also  the  simultaneous 
distribution  of  electrical  potential  in  the  remainder  of  the  body. 
In  connecting  the  different  points  of  the  cutaneous  surface  witli 
the  capillary  electrometer,  he  obtained  the  results  shown  in 
Fig.  58.  If  the  two  electrodes  are  placed  on  the  two  points  A 
and  B,  or  other  more  remote  points  ab,  situated  at  either  side  of 
the  oblique  equatorial  line  00,  along  which  the  potential  is  zero, 
the  mercury  of  the  capillary  moves  synchronously  with  the  beats 


FIG.  59.— Cardiograms  of  human  heart,  c  c,  and  simultaneous  diphasic  variations.  (A.  D.  Waller.) 
Time  tracing,  1 1,  in  T\,  sec.  The  electrode  connected  with  the  sulphuric  acid  went  to  the 
mouth,  that  with  the  mercury  to  the  left  foot. 

of  the  heart.  This  does  not  occur  if  the  electrodes  are  applied  to 
two  points  on  the  same  side  of  the  equatorial  plane.  If  the 
oscillations  of  the  mercury  are  closely  watched  or  photographed 
it  can  be  seen  that  a  diphasic  variation  corresponds  with  each 
systole  (Fig.  59). 

We  have  elsewhere  described  Gaskell's  important  discovery  on 
the  cardiac  muscle  of  the  tortoise  when  arrested  by  Stanuius' 
upper  ligature  (Vol.  I.  p.  332).  He  found  on  leading  off  a 
demarcation  current  excited  by  injury  of  the  surface  to  the 
galvanometer,  and  then  exciting  a  branch  of  the  vagus,  that  the 
variation  was  not  negative,  but  positive,  i.e.  the  demarcation 
current  was  reinforced,  not  weakened.  From  this  observation  he 
concluded  that  the  vagus  has  an  anabolic  action  on  the  heart,  as 
opposed  to  the  katabolic  action  of  the  sympathetic.  As  dis- 
integrative  explosive  stimuli  produce  a  negative  potential  in  the 
active  segments  of  the  tissue  as  compared  with  the  non-active,  so 
integrative  processes  which  spread  as  a  wave  of  inhibition,  after 


GENERAL  PHYSIOLOGY  OF  MUSCLE 


83 


stimulation  of  the  diastolic  nerves,  produce  a  positive  potential  in 
the  inhibited  segments  in  relation  to  those  at  rest. 

At  the  International  Congress  of  Physiology  in  Turin  (1901) 
Fano  communicated  another  interesting  observation  on  the  tortoise 
heart,  which  agrees  well  with  Gaskell's  theory,  and  also  helps  to 
interpret  the  diphasic  character  of  the  current  of  action.  If  while 
the  photograph  of  the  normal  diphasic  current  or  electrical  beat 
of  the  heart  is  being  recorded  the  vagus  is  excited  by  a  slight 
stimulus,  which  does  not  arrest  the  heart  completely  but  only 


FIG.  60. — Electrical  beat  of  right  auricle  of  tortoise  heart,  and  its  reversal  during  excitation  of 
vagus.  (Fano.)  Ad,  photograph  of  beat  of  right  auricle  ;  Pe,  photograph  of  its  electrical  beat 
or  diphasic  variation  ;  Vd,  line  showing  duration  of  gentle  stimulation  of  right  vagus. 

slows  down  the  beat  and  diminishes  the  amplitude  of  the  systole, 
there  is  usually  a  profound  alteration  in  the  form  of  the  photo- 
graph, which  consists  in  the  marked  diminution,  sometimes  the 
almost  total  disappearance,  of  the  negative  phase,  with  a  simul- 
taneous increase  in  the  second  or  positive  phase.  There  is,  in  fact, 
a  complete  reversal  of  the  electrical  beat  of  the  heart  (Fig.  60). 

The  same  sometimes  occurs  after,  instead  of  during,  the 
stimulation  of  the  vagus,  when  the  systolic  wave  is  gradually 
increasing  towards  its  normal. 

This  reversal  of  the  electrical  beat  during  or  after  vagus 
excitation  depends  on  the  inhibitory  or  diastolic  action  of  this 
nerve,  since  it  does  not  occur  after  the  application  of  atropine  to 
the  heart. 


84  PHYSIOLOGY  CHAP. 

According  to  Fano  the  reversal  of  the  diphasic  curve  proves 
that  it  does  not  depend  solely,  as  is  usually  assumed,  on  a  wave  of 
negativity  spreading  from  the  near  points  to  those  more  remote 
from  the  stimulus,  but  is  due  to  a  wave  of  positivity  immediately 
following  the  former.  In  the  normal  electrical  tracing,  too,  the 
relations  between  the  two  phases,  negative  and  positive,  vary— 
the  first  predominating  in  some  cases,  the  second  in  others.  It  is 
not  improbable  that  these  different  types  of  the  electrical  curve 
depend  on  the  relations  between  the  katabolic  and  anabolic 
processes  of  cardiac  muscle,  and  that  stimulation  of  the  vagus 
exaggerates  the  latter. 

XII.  The  innumerable  physical,  chemical,  and  histological 
researches  011  muscle  which  have  thus  been  briefly  summarised 
have  yielded  an  extraordinary  wealth  of  physiological  data,  from 
which  some  solution  of  the  difficult  problem  of  the  origin  of 
muscular  force  may  be  constructed — some  hypothesis  able  to 
explain  the  internal  mechanism  on  which  the  contraction  and 
relaxation  of  the  muscle  depends,  or  more  generally,  its  capacity 
for  passing  suddenly  from  the  state  of  comparative  rest  to  that  of 
activity,  and  vice  versa. 

An  exhaustive  theory  of  the  mechanism  of  muscular  excita- 
bility must  cover  a  series  of  difficult  problems,  among  which  are 
the  following  :— 

(a)  How  is  the  excitation  of  the  nerve  end-plate  transmitted 
to  the  muscle  fibre  ? 

(6)  On  what  does  the  sudden  contraction  (isotonic)  and  elastic 
tension  (isometric)  depend  ? 

(c)  What  process  gives  rise  to  the  sudden  relaxation  of  the 
muscle,  i.e.  the  cessation  of  the  elastic  tension  on  which  shortening 
depends  and  the  production  of  the  elastic  tension  to  which  lengthen- 
ing is  due  ? 

(rf)  How  are  the  excitatory  impulse  and  the  wave  of  contraction 
and  relaxation  conducted  along  the  muscle  fibre  ? 

Speaking  generally,  it  may  be  said  that  these  and  other 
problems  have  at  present  received  no  proper  scientific  solution, 
so  we  must  confine  ourselves  to  a  critical  investigation  of  the 
principal  hypotheses  that  have  been  put  forward. 

It  is  now  universally  agreed  that  the  physiological  combustion 
of  certain  chemical  constituents  of  the  tissue  which  are  bound  up 
with  the  protein  molecule  or  intimately  connected  with  it,  are  the 
prime  source  of  muscular  energy,  and  that  the  transformation  of 
potential  chemical  energy  into  mechanical  energy,  either  in  the 
form  of  elastic  tension  or  in  that  of  external  work,  is  performed 
according  to  the  law  of  the  conservation  of  energy.  There  is  a 
general  tendency  to  consider  the  chemical  state  of  the  resting 
muscle  substance  as  one  of  unstable  equilibrium,  in  which  the 
atoms  of  oxygen  and  the  groups  of  combustible  atoms  which  form 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  85 

part  of  the  great  protein  molecule  are  so  close  together  that  a  very 
weak  stimulus  suffices  to  bring  about  an  explosion,  in  which  most, 
of  the  oxygen  atoms  combine  with  atoms  of  carbon  and  hydrogen 
to  form  carbonic  acid  and  water.  It  is  more  difficult  to  explain 
why  the  explosion  is  confined  to  a  small  part  of  the  explosive 
mass  instead  of  discharging  it  completely,  as  in  the  case  of  a 
loaded  tire-arm.  But  the  universally  accepted  principle  is  that 
the  potential  chemical  energy  of  the  muscle  substance  is  the  primary 
source  of  muscular  energy  in  all  its  manifestations. 

How  does  the  explosive  reaction  of  the  muscle  produce  its 
shortening  or  elastic  tension  ?  The  answers  to  this  question  are 
by  no  means  unanimous,  and  physiologists  differ,  according  as  the 
one  or  the  other  sign  of  muscular  activity  receives  the  more  con- 
sideration from  them. 

We  need  not  discuss  the  earlier  hypotheses  which  are  collected 
in  the  classical  text-books  of  Haller  (1792)  and  Johannes  Miiller 
(1844),  but  may  confine  ourselves  to  the  later  and  more  probable 
theories,  commencing  with  that  of  E.  Weber. 

Schwann  had  already  suggested  that  muscle  acts  by  elastic 
forces,  but  Weber  was  the  first  to  clear  up  the  obscurity  that 
prevailed  as  to  contractility  and  elasticity  in  his  classic  work  on 
Muskelphysik,  published  1846.  According  to  the  theory  formulated 
by  Eontana  elasticity  is  an  inherent  physical  property  which  tends 
to  preserve  the  natural  form  of  the  muscle,  and  thus  acts  in  the 
contrary  sense  to  contractility,  i.e.  it  limits  the  contraction  and 
brings  the  muscle  back  to  equilibrium  as  soon  as  the  active  state 
ceases.  But  Weber  pointed  out  that  the  natural  form  of  the 
muscle  which  depends  on  its  elastic  equilibrium  is  not  constant, 
but  rnrii-s  freely  with  the  external  and  internal  conditions  of  the 
life  of  the  muscle.  As  a  metal  rod  lengthens  when  heated,  and 
shortens  again  on  cooling,  because  different  degrees  of  temperature 
alter  the  equilibrium  of  its  atoms  and  produce  a  reaction  of  its 
elastic  forces  which  expand  in  the  first  case  and  contract  in  the 
second,  so  the  molecular  arrangement  differs  in  the  muscle  accord- 
ing as  it  is  at  rest  or  excited,  and  its  external  form  differs 
accordingly.  The  active  muscle  is  short  and  thick,  the  inactive 
long  and  thin,  and  in  suddenly  passing  from  one  state  to  the 
other  the  muscle  contracts  or  expands,  not  against  the  elasticity, 
but  by  an  elastic  reaction  in  order  to  assume  the  natural  form  of 
equilibrium  which  corresponds  to  its  active  or  inactive  state.  On 
Weber's  view  the  extension  of  a  muscle  by  a  weight  is  not  com- 
parable with  the  shortening  due  to  a  stimulus  :  the  weight  stretches 
the  muscle  against  its  elastic  forces  ;  the  stimulus,  on  the  contrary, 
causes  a  sudden  alteration  in  its  chemical  equilibrium,  and  therefore 
in  the  elastic  forces,  which  are  the  immediate  cause  of  contraction. 

Weber  was  the  first  who  submitted  the  elasticity  of  muscle, 
and  the  changes  it  undergoes  in  various  conditions,  to  strict 


86 


PHYSIOLOGY 


CHAP. 


investigations.  He  found  that  muscle  has  a  low  but  perfect 
elasticity ;  it  can  be  readily  extended  by  small  weights,  but 
promptly  returns,  under  normal  conditions,  to  its  initial  length, 
when  the  extending  force  ceases  to  act  on  it.  He  recognised 
that,  unlike  inorganic,  but  like  certain  organic  substances,  the 
elongation  of  the  muscle  is  not  proportional  to  the  weight,  and 
becomes  less  so  as  the  load  increases ;  so  that  the  curve  of  extensi- 
bility obtained  when  the  weights  are  plotted  on  the  abscissae, 
and  the  elongations  taken  as  ordinates,  is  not  a  straight  line  but 
a  curve,  which  Wertheim  subsequently  recognised  as  a  hyberbola. 
Weber  compared  the  elasticity  of  the  resting  hyoglossus 
muscle  of  the  frog  with  that  of  the  same  frog  'when  tetanised,  by 


m 


FIG.  61. — Diagram  to  show  elasticity  of  muscle  in  rest  and  in  activity.  A  B,  length  of  unloaded 
resting  muscle  ;  A  b,  same  muscle  in  activity.  A'  B',  A"  B",  length  of  resting  muscle  loaded 
with  regularly  increasing  weights  ;  A'  b',  A"  b",  length  reached  by  active  muscle  loaded  with 
same  weights.  The  line  B  B'  B"  .  .  .  y  x  gives  the  elasticity  curve  of  resting,  b  If  b"  .  .  .  y,  of 
contracting  muscle. 

comparing  the  curves  of  extensibility  to  regularly  increasing 
weights  during  rest  and  in  tetanus.  He  found  that  the  active 
muscle  is  less  elastic,  i.e.  more  extensible  than  the  inactive 
(Fig.  61).  '^Therefore  the  extensibility  curve  of  active  muscle 
falls  more  rapidly  than  that  of  resting  muscle.  With  progressive 
increase  of  load  a  point  is  reached  at  which  the  two  curves  meet. 
This  happens  when  the  weight  is  sufficiently  great  to  hinder 
contraction,  i.e.  when  the  elastic  tension  in  the  muscle  due  to 
the  weight  is  in  complete  equilibrium  with  the  opposite  elastic 
tension  which  is  actively  set  up  by  the  stimulus.  If,  after 
reaching  this  point,  the  muscle  is  further  overloaded  and  then 
stimulated,  there  will  not  only  be  no  contraction,  but,  on  the 
contrary,  a  certain  degree  of  elongation  due  to  the  decrease  in 
muscular  elasticity  after  stimulation,  so  that  the  elasticity  curve 
of  the  active  state  crosses  the  elasticity  curve  of  the  resting  state 
(Weber).  But  this  has  not  been  confirmed  by  later  workers,  who 


i  GENEEAL  PHYSIOLOGY  OF  MUSCLE  87 

hold  with  Tick  that  the  two  curves  tend  to  converge  asymptotic- 
ally without  meeting. 

These  studies  of  Weber  on  the  elasticity  curve  of  resting  and 
active  muscle  were  subsequently  confirmed  and  extended  with 
better  methods  by  Marey  (1868)  and  Blix  (1874)  on  excised  frog 
muscles ;  by  Bonders  and  Van  Mansvelt  (1863)  and  by  Chauveau 
and  Laulanie  (1899)  on  human  muscles. 

Other  work  on  muscular  elasticity  has  shown  that  it  varies 
under  the  influence  of  different  toxic  and  medicinal  substances. 
In  this  connection  Eossbach's  and  Anrep's  observations  (1880)  on 
the  frog  are  striking.  These  showed  that  the  changes  which  the 
elasticity  of  muscles  loaded  with  low  weights  (2  grms.)  undergoes 
by  the  action  of  certain  poisons  may  be  utilised  as  a  good  method 
of  toxicological  analysis.  They  found  that  curare  and  cocaine, 
which  paralyse  the  motor  or  sensory  nerve -endings,  produce 
elongation  of  the  muscle  (lowering  of  tone)  without  perceptibly 
affecting  elasticity ;  pliysostigmine,  in  addition,  causes  an  increase 
of  elasticity  by  acting  on  the  contractile  substance ;  digitaline 
causes  elongation  of  the  muscle  and  increase  of  its  elasticity, 
independent  of  the  action  of  the  nerves,  i.e.  by  direct  action  on 
the  contractile  substance ;  veratrin  (injected  in  doses  of  1-5  mgrms.) 
produces  first  elongation,  then  contracture  of  the  muscle,  inde- 
pendently of  the  nerve,  and  in  both  stages  depresses  the  elasticity 
and  makes  it  imperfect ;  lastly,  potassium  salts  shorten  the  muscle 
and  simultaneously  increase  its  excitability,  while  sodium  salts  in 
the  same  dose  and  same  concentration  produce  no  visible  change 
either  in  the  length  or  the  elasticity  of  the  muscle. 

Progressive  muscular  fatigue,  too,  alters  elasticity  in  the  same 
way  as  poisons,  raising  it  in  the  first  stage,  and  subsequently 
decreasing  it  in  proportion  as  contracture  sets  in.  After  death, 
when  rigor  mortis  begins,  muscle  is  highly  elastic,  that  is,  but  little 
extensible,  and  its  elasticity  simultaneously  diminishes,  for  when 
the  traction  is  removed  it  no  longer  returns  to  its  initial  length. 

All  these  and  other  experimental  observations  confirm  Weber's 
theory,  and  show  that  elasticity  is  not  a  constant  physical  property 
of  the  muscle,  but  is  perhaps  the  most  variable  and  least  stable  of 
all  its  properties. 

But  Weber's  assertion  that  the  contraction  of  the  muscle 
is  only  the  result  of  a  sudden  change  in  its  elasticity,  due  to 
the  chemical  changes  produced  by  excitation,  is  no  more  than 
a  schematic  restatement,  whatever  its  theoretical  value.  Its 
simplicity,  however,  signalises  a  considerable  advance  in  mechanical 
notions  of  muscular  activity ;  for,  by  excluding  Fontana's  theory, 
which  assumes  contractility  and  elasticity  to  be  two  opposite  or 
antagonistic  properties,  it  leads  on  logically  to  the  formulation  of 
a  more  exact  idea,  harmonising  better  with  the  facts,  of  the  process 
by  which  relaxation  follows  on  the  contraction  of  the  muscle. 


PHYSIOLOGY  CHAP. 

By  many  authors  muscular  relaxation  has  been,  and  still  is, 
regarded  as  a  simple  effect  of  the  cessation  of  contraction.  This 
is  Fontana's  theory  that  contraction  throws  the  muscle  into 
elastic  tension,  so  that  when  the  contraction  ceases  the  muscle 
lengthens  owing  to  its  elasticity.  But  if  contraction  is  not  con- 
trary to  elasticity,  it  is  plain  that  the  muscle  can  only  relax  by  a 
chemical  process  which  is  opposed  to  that  of  contraction,  owing 
to  which  its  form  changes  in  a  direction  opposite  to  that  of  the 
contraction  phase.  As  early  as  1874  \\e  pointed  out  this  logical 
consequence  of  Weber's  theory,  and  added  further,  "  If  the  con- 
traction, which  is  due  to  a  fresh  molecular  arrangement  to  which 
a  shorter  natural  form  of  the  muscle  corresponds,  be  termed  actin  , 
we  are  equally  justified  in  calling  the  elongation  of  the  muscle 
active,  since  it  too  is  associated  with  a  new  molecular  equilibrium 
which  accompanies  the  process  of  relaxation."  Years  after  (1887) 
Gaskell  made  the  important  discovery  that  electrical  phenomena 
accompany  the  inhibition  of  cardiac  muscle  by  the  vagus,  and 
disproved  the  hypothesis  that  the  contraction  of  this  muscle  is 
due  to  kat<tl>»/ir  and  its  relaxation  to  un<tl>uli<:  chemical  processes 
(Vol.  I.  p.  332).  More  recently  Fano  (1901)  extended  this  theory 
(see  p.  83),  which  in  our  opinion  applies  not  merely  to  the  heart, 
but  to  all  other  muscular  tissues. 

No  special  advance  upon  Weber's  hypothesis  has  been  made 
by  the  physiologists  who  refer  the  transformation  of  the  potential 
chemical  energy  developed  in  muscle  after  excitation  into 
mechanical  energy,  to  the  direct  effect  of  a  special  form  of 
chemical  alteration.  Pfliiger,  in  his  famous  memoir,1  accepts 
this  theory  of  the  origin  of  muscular  energy  without  enlarging 
on  it.  Pick  2  expresses  himself  more  clearly,  and  states  that  "  the 
chemical  forces  of  attraction  must  a  2»'iori  be  more  or  less  pre- 
disposed in  the  direction  of  the  mechanical  action  which  is  to 
follow,  and  participate  directly  in  the  same."  Chauveau 3  remarks 
that  "muscular  contraction  is  a  derivative  of  chemical  work." 

This  theory  seems  no  less  artificial  than  that  of  Weber. 
According  to  Engelmann,  moreover,  it  is  irreconcilable  with  the 
fact  that  during  contraction  an  infinitely  small  portion  of  the 
muscle  substance  is  chemically  active  as  compared  with  the  total 
mass  of  the  muscle  which  remains  passive.  He  points  out  that 
the  muscle  contains  70-80  per  cent  water,  and  that  the  greater 
part  of  the  20-30  per  cent  of  the  organic  substances  and  minerals 
of  which  it  is  composed  take  no  chemical  part  in  the  process.  Of 
the  carbo-hydrate  group  associated  with  the  protein  molecule, 
which  gives  rise  during  excitation  to  the  formation  of  C02  and 
H.,0,  only  small  proportions  are  simultaneously  affected.  On 

1  Ueber  die  pJiysiologische  Verbrennung  in  den  lebcndif/en  Organismen  (1875). 

2  Mechanische  Arbeit  und  Wcirmeentwickluny  lei  der  Muskcltatiykeit  (1882). 

3  Publications  on  Muscular  Work  and  Energy  (1891). 


i  GENEKAL  PHYSIOLOGY  OF  MUSCLE  89 

Engelmanu's  calculation  the  source  of  the  energy  necessary  to 
produce  a  contraction  amounts  to  about  four  uiillionths  of  the 
entire  mass  of  the  muscle.  It  is  inconceivable  to  Engelmann 
that  the  movement  of  the  relatively  enormous  mass  of  inert 
substance  should  be  effected  by  the  direct  chemical  attraction  of 
this  minimal  fraction  of  active  substance,  no  matter  what  the 
natural  form  or  magnitude  of  the  vibrations  or  the  particular 
arrangement  of  the  few  active  molecules.  He  further  objects  that 
the  hypothesis  of  direct  chemical  attraction  does  not  take  into 
account  the  tibrillary  structure  of  the  contractile  apparatus,  the 
differentiation  of  the  fibrils  into  isotropous  and  anisotropous 
portions,  the  opposite  variations  in  volume,  form,  refrangibility, 
extensibility,  etc.,  of  these  parts,  and  a  number  of  other  facts 
which  are  in  more  or  less  open  contradiction  to  it. 

Engelmaun  holds  the  thermodynamic  theory  propounded  by 
J.  K.  Mayer  (1845),  according  to  which  the  muscle  is  compared 
with  a  steam  engine  which  transforms  the  heat  evolved  in  com- 
bustion into  mechanical  work,  to  be  far  more  probable. 

In  reply  to  Solway's  criticism  that  the  muscle  works  more 
economically  than  any  engine,  Engelmann  remarks  that  the 
muscle  is  an  apparatus  whose  combustible  materials  burn  in 
direct  contact  with  the  parts  that  perform  the  mechanical  work, 
so  that  it  works  under  far  more  favourable  conditions  than  Watt's 
thermodynamic  machine. 

Another,  apparently  more  serious,  objection  to  the  theory  of 
the  thermal  origin  of  muscular  energy  put  forward  by  Fick  (1882), 
and  repeated  by  Gad,  is  that  it  is  irreconcilable  with  the  second 
of  Glausius'  fundamental  laws  of  thermodynamics.  According  to 
this  law,  heat  can  only  perform  work  when  it  passes  from  a  warmer 
body  (A}  to  a  cooler  body  (B},  and  its  potential  is  proportional  to 
the  difference  of  temperature  between  A  and  B.  So  that  before 
we  can  assume  that  muscle  works  like  a  thermodynamic  machine, 
we  must  first  prove  that  there  is  in  it  a  marked  difference  between 
A  and  B,  or  between  the  source  of  heat  and  the  surrounding 
medium. 

Fick  held  that  this  is  not  the  case  with  muscle,  which  only 
exhibits  slight  differences  of  temperature,  proving  conclusively 
that  it  does  not  act  as  a  thermodynamic  motor. 

Engelmann  replied  to  this  objection  that  Pflliger  had  already 
pointed  out  in  1875  that  body-temperature  is  only  an  arithmetic 
mean  which  comprises  innumerable  very  different  temperatures 
at  innumerable  different  points  of  an  organ,  and  that  the  molecules 
formed  in  physiological  combustion  have,  at  least  at  the  moment 
of  formation,  an  extremely  high  temperature,  which  they  lose  at 
once  by  giving  off  heat  to  the  cooler  matter  that  surrounds  them. 

Pfliiger's  conclusions  in  so  far  as  muscle  is  concerned  are  con- 
firmed, according  to  Engelmann,  by  the  fact  that  the  combustion 


90 


PHYSIOLOGY 


CHAP. 


of  a  comparatively  small  number  of  molecules  suffices  to  produce 
contraction,  which  can  only  be  explained  on  the  assumption  that 
at  the  moment  of  oxidation  they  acquire  a  temperature  so  high 
that  their  minute  size  and  low  number  are  perhaps  the  only  reason 

why    they  do   not    appear 
b  incandescent.     The  rise  of 

temperature  in  the  total 
mass  of  the  muscle,  even 
granting  that  it  only 
amounts  to  O'OOl0  C.  for 
one  contraction,  is  when  we 
consider  the  great  specific 
heat  of  the  muscle  sub- 
stance--i.e.  the  large 
quantity  of  heat  necessary 
to  raise  its  temperature- 
conceivable  only  on  the 
supposition  that  each  heat- 
producing  molecule  has  at 
its  birth  an  enormous  tem- 
perature in  comparison 
with  the  immense  mass  of 
substance  able  to  conduct 
and  permeable  to  heat,  by 
which  it  is  surrounded. 
In  this  assumption  it  is 
implicitly  recognised  that 
the  muscle  presents  to  a 
high  degree  the  funda- 
mental condition  for  the 
conversion  of  heat  into 
mechanical  work.  This 
conversion  —  according  to 
Engelmann — is  effected  by 
the  anisotropous  substance 
which  forms  the  positive, 
doubly  refracting  elements 
with  one  axis  parallel  to 
the  direction  of  contraction 
which  he  terms  inotagmata. 
He  supposes  that  in  mus- 
cular excitation  the  inotag- 
mata, warmed  by  the  heat 

generated  in  the  thermogenic  molecules,  swell  up  and  shorten, 
owing  to  imbibition  of  the  more  fluid  isotropous  substance  that 
surrounds  them.  This  alternate  swelling  and  shortening  of  the 
inotagmata  arranged  in  longitudinal  series  results  in  the  whole 


Fio.  62. — Engelmann's  apparatus  for  imitating  the  con- 
traction and  relaxation  of  muscle  on  a  violin  string. 
A  string  5  cm.  long  soaked  in  water  is  fixed  by  its 
lower  end  a  to  a  rigid  support  b,  and  connected  above 
by  a  strong  silk  thread  to  the  short  arm  of  the  lever 
H,  which  moves  round  the  axis  c.  By  means  of  the 
movable  weights  d  and  d'  the  string  can  be  thrown 
into  the  desired  tension,  and  the  position  of  the  lever 
regulated  by  screw  e.  The  string  is  surrounded  by  a 
thin  platinum  wire  /,  which  turns  spirally  round  it, 
and  is  soldered  at  the  end  to  thick  copper  wires  con- 
nected with  the  poles  of  two  Grove  or  Bunsen  cells. 
The  string,  platinum  wire,  and  support  are  placed  in 
a  wide  low  beaker  filled  with  water,  into  which  a 
thermometer  is  introduced.  When  stretched  by  at 
weight  of  25-50  grms.  the  string  after  a  few  minutes 
ceases  to  expand,  and  the  end  of  the  lever  remains 
steady.  If  a  current  is  then  passed  through  the 
spiral  for  a  few  seconds,  the  lever  rises  at  once  with 
great  rapidity,  and  on  breaking  the  circuit  it  returns 
almost  to  its  original  level,  while  the  thermometer  is 
either  stationary  or  shows  a  hardly  appreciable  rise 
of  temperature. 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  91 

muscle  in  the  formation  and  propagation  of  the  contraction  wave, 
by  which  a  part  of  the  heat  is  transformed  into  mechanical  work. 

To  strengthen  this  ingenious  hypothesis  Engelmann  devised 
an  experiment,  in  which  the  contraction  of  the  muscle,  owing  to  the 
swelling  and  shortening  of  doubly  refracting  particles  in  the  long 
axis  in  accordance  with  the  therrnodynamic  law,  is  imitated  on 
a  violin  string.  He  started  from  the  fact  that  the  property  of 
contracting  in  heat  is  not  peculiar  to  muscle,  but  is  inherent  in 
different  degrees  in  all  living  tissues,  and  even  in  other  organic 
substances  that  contain  a  doubly  refracting  substance,  e.g.  a  violin 
string  or  specially  prepared  string  of  non- vulcanised  indiarubber. 
Engelmann's  model  is  shown  in  Fig.  62.  He  proved  that  under 
definite  experimental  conditions  a  moistened  violin  string,  thrown 
into  tension  by  a  weight,  thickens  and  shortens  and  does  a  certain 
amount  of  work  when  heated  by  a  coil  of  platinum  wire  traversed 
by  an  electrical  current,  and  lengthens  again  on  cooling  when 
the  current  is  interrupted.  In  this  experiment  the  violin  string 
which  contains  the  doubly  refracting  substance  represents  the 
inotagma  or  anisotropous  element  of  the  muscle ;  the  vessel 
filled  with  water  the  aqueous,  isotropous  muscle  substance;  the 
platinum  coil  the  thermogenic  molecules;  the  closure  of  the 
galvanic  current  the  excitation  of  the  inotagrnata  which  gives 
rise  to  contraction ;  the  opening  of  the  circuit  the  cessation  of 
excitation  from  which  relaxation  results.  Nothing  but  the 
transmission  of  excitation  along  the  series  of  inotagmata  which 
causes  the  transmission  of  the  contractile  wave  is  absent  in  this 
ingenious  model. 

On  recording  the  contractions  and  subsequent  elongations  of 
the  violin  string  on  a  revolving  drum,  Engelmann  obtained 
chordogra/ns  which  resemble  myograms  to  a  surprising  degree 
(Fig.  63).  This  proves  that  they  depend  on  a  cyclic  process — as 
after  the  warming  which  leads  to  shortening,  the  string  lengthens 
and  returns  (at  least  approximately)  to  its  initial  state  on  cooling. 

It  may  be  objected  to  Engelmann's  theory  that  it  takes  no 
account  of  the  electrical  phenomena  that  occur  in  the  muscle. 
Before  meeting  this  objection  it  is  well  to  consider  the  different 
hypotheses  that  have  been  put  forward  in  favour  of  an  electrical 
origin  of  muscular  energy. 

Prevost  and  Dumas,  Meyer  and  Amici  compared  the  muscle, 
owing  to  its  striated  structure,  with  a  Volta's  pile,  which  also 
consists  of  discs.  Voit,  starting  from  the  negative  variation, 
assumes  that  the  muscle  current  diminishes  in  contraction,  because 
a  part  of  the  electricity  developed  in  the  muscle  is  transformed 
into  movement.  Krause  and  Kiihne  compared  the  motor  end- 
plates  to  the  electrical  organs  of  Torpedo,  and  the  action  of  nerve 
on  muscle  to  the  discharge  of  a  Leyden  jar.  According  to  du 
Bois-Reymond,  on  the  contrary,  it  is  the  wave  of  negative 


92 


PHYSIOLOGY 


CHAP. 


variation  (i.e.  the  current  of  action)  which  causes  the  transmission 
of  excitation  from  the  nerve  to  the  muscle,  and  the  spread  of  the 
contraction  in  the  latter.  According  to  d'Arsonval  the  thermal 
phenomenon  and  mechanical  work  of  the  muscle  are  the  effects  of 
the  electrical  phenomenon ;  the  chemical  energy  is  transformed 


FIG.  63. — Chordograms  obtained  by  Engelmann  with  the  apparatus  described  in  preceding  figui '<', 
with  the  violin  string  loaded  with  50  grins,  and  a  lever  that  magnified  fifty  times.  /,  At  a  a 
strong  current  was  passed  through  the  spiral  for  2-3  sees.  ;  at  b  a  weak  current  for  a  longer 
time,  a  shows  a  shorter  latent  period,  a  sharper  and  more  rapid  rise,  and  a  steeper  descent 
than  b.  II  and  ///,  Uniform  strength  of  current,  but  the  temperature  of  the  water  was  35°  C. 
in  //,  45°  C.  in  ///.  IV,  After  removing  the  water  the  warmth  of  the  spiral  was  conveyed  to 
the  string  by  the  air  which  was  at  a  temperature  of  1S°  C.  At  a  a  stronger  current  was  passed 
than  at  b.  As  the  cooling  of  the  string  had  been  accelerated,  it  expanded  more  rapidly. 
]',  The  curve  falls  still  more  rapidly,  owing  to  accelerated  cooling  of  the  string  due  to  a 
stronger  current  of  air.  Time  marking  =  0'5  sec. 

into  electrical  energy,  and  this  again  into  thermal  and  mechanical 
energy. 

All  these  hypotheses  are  too  vague  and  indefinite,  and  they 
neglect  certain  well-established  experimental  facts. 

G.  E.  Miiller  of  Gottingen  (1889)  put  forward  a  pyro-electrical 
theory  of  the  origin  of  muscular  force,  which,  although  partially 


i  GENERAL  PHYSIOLOGY  OF  MUSCLE  93 

founded  on  arbitrary  hypotheses,  is  certainly  more  definite.  He 
attributes  the  contraction  of  the  muscle  to  the  electrical  attraction 
and  repulsion  of  the  doubly  refracting  crystalloids,  the  poles  of 
which  undergo  a  change  of  electrical  state  owing  to  the  heat  that 
is  generated.  On  this  theory  the  muscle  shortens  as  its  tempera- 
ture rises ;  and  when  the  temperature  of  the  crystalloids  becomes 
constant  it  lengthens,  because  the  electrical  changes  subside. 
Engelmann's  experiments  show,  however,  that  the  length  of  the 
muscle  does  not  depend  on  the  rate  at  which  the  temperature 
rises,  but  on  the  absolute  temperature  present  at  the  moment  in 
the  doubly  refracting  discs.  They  further  show  that  when  the 
temperature  in  these  discs  is  constant,  the  muscle  does  not 
lengthen,  but  remains  indefinitely  shortened. 

Certain  well-authenticated  facts  prove  that  there  is  a  direct 
association  between  the  electrical  and  mechanical  phenomena  in 
muscle.  As  long  ago  as  1855  Helmholtz  showed  by  an  exact 
chronometric  method  that  the  electrical  wave  precedes  the 
mechanical  in  skeletal  muscle.  The  same  fact  was  demonstrated 
in  1856  by  Kiilliker  and  H.  Miiller  by  the  experiment  of  secondary 
contraction,  and  by  Bernstein  with  his  differential  rheotome.  In 
the  nerve-fibres,  in  which  no  sign  of  mechanical  phenomena  can 
be  detected,  and  little  heat  development  or  chemical  activity, 
electrical  phenomena  similar  to  those  of  the  muscle  occur,  which 
proves  them  to  be  quite  independent  of  the  phenomena  of  con- 
tractility. Certain  important  researches  of  Biederniann  (1880) 
favour  the  same  conclusion,  since  they  prove  that  frog  muscles 
which  have  lost  their  power  of  contracting  by  imbibition  of  water 
or  the  effect  of  ether  vapour  preserve  their  electrical  excitability 
and  capacity  for  conducting  intact.  From  this  Biederrnanu 
concludes  that  the  capability  of  actively  changing  its  form  at  the 
seat  of  direct  stimulation  is  not  an  indispensable  condition  of  the 
excitation  of  muscle. 

The  independence  of  the  electrical  phenomena  from  muscular 
contractility  is  also  demonstrated  by  the  fact  that  the  majority 
of  electric  and  pseudo-electric  organs  develop  at  the  expense  of 
the  striated  muscle  fibres,  and  that  during  this  development, 
according  to  Ewart,  contractility  is  gradually  lost,  while  the 
electromotive  function  develops  in  proportion.  According  to 
Baglioni  (1906)  the  chemical  composition  of  the  electrical  organs 
differs  fundamentally  from  that  of  the  muscles. 

On  the  strength  of  all  these  facts  Engelmann  founded  his 
hypothesis  that  in  muscle  the  particles  on  which  the  development 
of  the  electrical  phenomena  depends  are  quite  distinct  from  those 
which  supply  heat  by  combustion  (thermogenic],  and  those  which 
subserve  mechanical  work  (inogenic  particles'). 

The  first  are  solely  concerned  with  excitation  and  its  con- 
duction and  propagation,  as  Hermann  also  concluded  from  the 


94  PHYSIOLOGY  CHAP. 

fact  that  the  wave  of  negativity  at  the  point  of  the  muscle 
stimulated  appears  hefore  and  precedes  the  wave  of  contraction. 
These  particles  probably  lie  chiefly  in  the  isotropous  layers  which 
take  no  active  part  in  contraction.  The  thermogenic  particles, 
on  the  contrary,  are  in  close  contiguity  with  the  inogcnic  particles, 
which  are  represented  by  the  doubly  refracting  elements  of  the 
anisotropous  layers,  on  which  the  specific  function  of  the  muscle, 
i.e.  contraction,  depends.  According  to  Engelinann's  theory  this 
is  due  to  the  conversion  of  heat  into  work. 

Verworn  (1895),  starting  from  a  hypothesis  put  forward  by 
Berthold  (1886),  has  formulated  another  theory  of  contraction, 
which  includes  all  the  movements  of  all  forms  of  living  matter, 
from  amoeba  to  muscle.  On  this  theory  movement  is  due  to 
changes  in  the  surface  tension  of  the  histological  elements  of 
which  the  muscle  fibrils  consist  (isotropous  and  anisotropous 
discs) ;  these  changes  in  surface  tension  are  due,  according  to 
Verworn,  to  chemical  processes. 

A  similar  theory,  by  which  muscular  contraction  is  referred  to 
changes  of  surface  tension,  has  been  put  forward  by  other  physio- 
logists, as  d'Arsonval,  Imbert,  Bernstein,  Jensen,  and  Galeotti. 
Galeotti  holds  (1906)  that  the  changes  in  surface  tension  of  the 
different  muscle  elements  are  due  to  electrochemical  phenomena. 

None  of  these  theories,  however,  take  into  account  the  whole 
of  the  active  changes  concomitant  with  muscular  activity. 


BIBLIOGRAPHY 

Structure  of  Muscle  and  its  Visible  Changes  during  Activity  :— 

ENGELMANN.     Pfliiger's  Archiv,  xi.,  1875,  xxv.,  1881. 

RANVIER.     Lemons  d'anatoniie  gunerale  sur  le  systeme  musculaire.     Paris,  1880. 

ROLLET.     Denkschr.  der  AViener  Akademie,  xlix.  and  li.,  1885,  Iviii.  1891. 

Mechanical,  Thermal,  and  Electrical  Activity  of  Muscle:  — 

HERMANN.     Handbuch  der  Physiologic,  i.  1879. 

CH.  RICHET.     Physiologic  des  muscles  et  des  nerfs.     Paris,  1882. 

BIEDERMANN.     Elektrophysiologie.     Jena,   1895.     (English  translation  by  F.  A. 

Welby,  1896.)     Ergebnisse  d.  Physiol.,  II.  Part  2,  1903. 
A.    FICK.      Mechan.    Arbeit   und   Warmeentwickelung   bei   der    Muskeltatigkeit. 

Internat.  wiss.  Bibliothek,  1882. 

ROSENTHAL.     Allgemeine  Physiol.  der  Muskeln  und  Nerven.     Leipzig,  1899. 
W.  EINTHOVEN.     Pfliiger's  Archiv,  lx.,  1905  ;  Arch,  intern,  d.  Physiol.,  iv.  1906. 
I.  BERNSTEIN.     Pfliiger's  Archiv,  Ixxxi.,  1901. 
G.  GALEOTTI.     Zeitschr.  f.  allg.  Physiol.,  vi.,  1906. 
HOFMANN.     Pfliiger's  Arch.,  xciii.,  xcv.,  ciii.,  1902-4. 
BORUTTAU.     Pfliiger's  Arch.,  cv.,  1904. 
0.  FRANK.     Thermodynamik  des  Muskels.  Ergeb.  d.  Physiol.,  III.   Part  2,  1904. 

Chemical  Composition  and  Metabolism  of  Muscle  : — 

HALLIBURTON.     Text-book  of  Chemical  Physiology  and  Pathology,  1891. 

NEUMEISTER.     Lehrbuch  der  physiologischen  Chemie,  1895. 

H.  WINTERSTEIN.     Pfliiger's  Archiv,  cxx.,  1907. 

v.  FURTH.     Ergeb.  d.  Physiol.,  I.   Part  1,  1902  ;  II.  Part  1,  1903. 


i  GENEKAL  PHYSIOLOGY  OF  MUSCLE  95 

Ergograph  work  :— 

A.  Mosso.     Arch.  ital.  de  biologic,  xiii.,  1890. 

A.  MAGGIORA.     Ibidem. 

P.  W.  LOMBARD.     Ibidem. 

PATUIZI.     Archives  ital.  de  biologic,  1892,  1893,  1901. 

Z.  TREVES.     Ibidem,  xxix.,  xxx.,  xxxi.,  1898-1900. 

F.  SCHENCK.     Pfliiger's  Archiv,  Ixxxii.,  1900. 

General  Theory  of  the  Genesis  of  Muscular  Force,  in  addition  to  the  treatise  by 
Hermann,  see  : — 

TH.  W.  ENGELMANN.    Snr  1'origine  de  la  force  mnsculaire.    Archives  neerlandaises, 

xxvii.,  1893. 

VERWORN.     Allg.  Physiologie,  4th  Ed.     Jena,  1903. 
JENSEN.     Pfliiger's  Arch.,  Ixxx. ,  1900. 
BERNSTEIN.     Pfliiger's  Arch.,  Ixxxi.,  1901  ;   cv.,  1905.     Die  Krafte  der  Bevvegung 

in  der  lebenden  Substanz.     Brunswick,  1902. 
GALEOTTI.     Zeitschr.  f.  allg.  Physiol.,  vi. ,  1906. 

Recent  English  Literature  :— 

MAoDoNALD.  The  Structure  and  Function  of  Striated  Muscle.  Quart.  Journ.  of 
Experiment.  Physiol.,  1909,  ii.  5. 

LANGLEY.  On  the  Contraction  of  Muscle,  chiefly  in  relation  to  the  Presence  of 
"Receptive"  Substances.  Journ.  of  Physiol.,  1907,  xxxvi.,  347;  1908, 
xxxvii.  165  and  285  ;  1909,  xxxix.  235. 

KEITH  LUCAS.     On  the  Refractory  Period  of  Muscle  and  Nerve.     Journ.  of  Physiol., 

1909,  xxxix.  331. 

KEITH  LUCAS.     All-or-None  Contraction  of  the  Amphibian  Skeletal  Muscle  Fibre. 

Journ.  of  Physiol.,  1908,  xxxviii.  113. 
KEITH  LUCAS.     On  the  Relation  between  the  Electric  Disturbance  in  Muscle  and 

the  Propagation  of  the  Excited  State.     Journ.  of  Physiol.,  1909,  xxxix.  207. 
A.  V.  HILL.     The  Absolute  Mechanical  Efficiency  of  the  Contraction  of  an  Isolated 

Muscle.     Journ.  of  Physiol.,  1913,  xlvi.  435. 
BANCROFT..     The  Electrical  Stimulation  of  Muscle  as  dependent  upon  the  Relative 

Concentration  of  the  Calcium  Ions.     Journ.  of  Physiol.,  1909,  xxxix.  1. 
LILLIE.      The    Relation    of    Ions    to   Contractile    Processes.      Amer.    Journ.    of 

Physiol.,  1909,  xxiv.  459. 
KEITH  LUCAS.     Summation  of  Adequate  Stimuli  in  Muscle  and  Nerve.     Journ.  of 

Physiol.,  1910,  xxxix.  461. 

MINES.     Summation  of  Contractions.     Journ.  of  Physiol.,  1913,  xlvi.  1. 
KEITH  LUCAS.     On  the  Transference  of  the  Propagated  Disturbance  from  Nerve  to 

Muscle,    with    special    reference    to   the   apparent    Inhibition   described    by 

Wedensky.     Journ.  of  Physiol.,  1911,  xliii.  46. 
MAcDouoALL.      Mental  and  Muscular  Fatigue.     Reports,  80th  Meeting,   British 

Assoc.,  1911,  292. 
BURRIDGE.     An  Inquiry  into  some  Chemical  Factors  of  Fatigue.    Journ.  of  Physiol., 

1910,  xli.  285. 

KEITH   LUCAS.     On  the  Recovery  of  Muscle  and   Nerve  after  the   Passage  of  a 

Propagated  Disturbance.     Journ.  of  Physiol.,  1910,  xli.  368. 
A.  V.  HILL.     The  Energy  degraded  in  the  Recovery  Processes  of  Stimulated  Muscle. 

Journ.  of  Physiol.,  1913,  xlvi.  28. 
HILL.     The  Heat  produced  in  Contraction  and  Muscular  Tone.     Journ.  of  Physio!., 

1910,  xl.  389. 
MEIGS.     Heat  Coagulation  of  Smooth  Muscle.     Amer.   Journ.  of  Physiol,,   1909, 

xxiv.  1. 


CHAPTER   II 

MECHANICS   OF    LOCOMOTOR   APPARATUS 

CONTENTS. — 1.  General  remarks  on  the  structure  of  the  bones  and  their 
articulations.  2.  Form,  attachments,  and  mechanics  of  muscles  in  relation  to 
bones.  3.  Line  and  centre  of  gravity  of  the  body  in  different  postures. 
4.  Mechanics  of  equilibration  in  different  postures.  5.  Movements  of  the  body 
in  walking.  6.  Movements  of  the  body  in  running.  7.  Movements  of  the  body 
in  swimming.  Bibliography. 

THE  muscles  are  the  active  organs — the  bones,  cartilages,  ligaments, 
etc.,  which  build  up  the  skeleton  to  which  the  muscles  are  attached 
represent  the  passive  organs — of  a  highly  complex  system  to  which 
Marey  correctly  applied  the  term  animal  machine.  In  industrial 
machines  also  it  is  usual  to  distinguish  between  the  active  parts 
which  are  the  seat  of  the  production  or  development  of  the  energy 
destined  to  be  transformed  into  useful  work,  and  the  passive  parts 
which  transmit  it,  and  which  consist — as  in  the  animal  machine— 
of  levers,  pulleys,  inclined  planes,  pumps,  etc. 

Our  principal  task  in  this  chapter  will  be  to  study  the  complex 
motor  apparatus,  consisting  of  an  elaborate  system  of  skeletal 
muscles,  on  the  co-ordinated  action  of  which  depend  the  loco- 
motor  movements,  i.e.  the  different  forms  of  displacement  of  the 
body  as  a  whole.  These  are  distinguished  from  the  partial  move- 
ments or  displacements  of  the  limbs,  by  which  the  relations  of  the 
different  mobile  parts  of  the  body  are  altered.  In  the  former  the 
base  of  the  body  is  displaced ;  in  the  latter  it  may  remain  immobile. 

In  the  study  of  these  motor  functions  the  physiologist's  task  is 
to  a  large  extent  linked  with  that  of  the  anatomist.  It  is,  in  fact, 
impossible  to  form  a  clear  conception  of  the  mechanism  of  a  move- 
ment carried  out  by  the  active  participation  of  many  different 
muscles  without  first  knowing  the  points  of  attachment  of  each 
muscle  as  well  as  the  form  and  articulation  of  the  bones,  which  act 
passively  as  the  levers.  But  while  the  anatomist  is  occupied  more 
particularly  with  the  mechanical  action  of  each  muscular  unit,  the 
physiologist  supplements  this  by  the  synthetic  study  of  the  co- 
ordination of  the  various  muscular  forces  which  combine  in  the 
accomplishment  of  each  separate  motor  act. 

96 


CHAP,  ii   MECHANICS  OF  LOCOMOTOR  APPARATUS      97 

I.  Historical  investigation  into  the  action  of  the  muscles  on 
the  skeleton,  aiid  the  mechanism  of  posture  and  locomotion,  com- 
menced with  Borelli's  classic  De  motu  animalium,  published  in 
1680.  The  writings  of  Barthez  (1798)  and  of  Gerdy  (1832)  con- 
tain no  real  advance  on  the  work  of  Borelli.  Poisson  (1833) 
first  attempted  to  calculate  the  work  which  a  man  performs  in 
walking.  Eeal  progress  in  this  direction  was  made  in  the  classical 
publication  of  W.  and  E.  Weber,  Die  Mechanik  der  menschlichen 
Gehwerkzeuge,  which  appeared  in  1836.  The  second  half  of  the 
nineteenth  century  brought  many  anatomical  studies  on  the  form 
of  the  articular  surfaces,  and  the  significance  of  the  ligaments,  the 
articular  capsules,  fascia,  etc.,  more  especially  from  Henke,  Langer, 
and  H.  Meyer.  Among  standard  works  Duchenne's  Pliysiologie 
des  mouvements  deserves  mention,  owing  to  the  positive  character 
of  the  research  and  the  accuracy  of  the  descriptions,  although  it 
does  not  compare  in  originality  with  the  epoch-making  researches 
of  Borelli  and  the  Webers.  After  the  application  of  the  graphic 
methods,  more  particularly  by  Marey  and  Carlet  (1872),  the  study 
of  locomotion  was  carried  to  greater  perfection.  Still  greater 
advances  were  made  after  instantaneous  photography  had  been 
applied  to  the  study  of  the  successive  phases  of  movement  in  man 
and  other  animals,  first  by  Muybridge,  subsequently  by  Marey 
(1882)  and  his  successors  with  more  perfect  kinernatographic 
methods. 

As  a  preliminary  we  require  a  general  notion  of  the  structure 
of  the  bones,  the  passive  organs,  and  the  action  of  the  muscles, 
which  are  the  active  organs  of  movement. 

Taken  as  a  whole,  the  bones  may  be  regarded  as  rigid  organs 
in  comparison  with  the  forces  which  act  on  them  during  the 
movements  of  the  body.  The  ribs  are  an  exception  to  this  rule, 
since  (Vol.  I.  p.  407)  they  undergo  a  slight  degree  of  flexion  and 
torsion  round  their  long  axis  during  thoracic  inspiration. 

To  the  student  of  animal  mechanics  the  histological  structure 
of  the  bones,  which  is  more  particularly  of  morphological  interest, 
appeals  less  than  their  architecture,  which  is  such  as  to  combine 
the  greatest  amount  of  rigidity  with  the  greatest  possible  lightness, 
as  first  pointed  out  by  H.  Meyer  in  1867.  All  the  long  bones 
are  hollow,  which  does  not  lessen  their  rigidity,  since  a  hollow 
cylinder  presents  the  same  resistance  to  pressure  and  traction  as  a 
solid  cylinder  of  the  same  'diameter  and  identical  material.  The 
marrow  which  fills  the  bony  cavity  contributes  to  the  comparatively 
light  weight  of  bone,  since  it  is  rich  in  fat.  The  trabeculae  which 
constitute  the  spongy  part  of  the  extremities  of  the  long  bones  are 
so  arranged  as  to  support  the  surfaces  destined  to  bear  the  greatest 
pressure. 

The  application  of  this  mechanical  principle  is  to  be  found  in 
all  bones,  but  it  is  specially  obvious  in  the  femurs. 

VOL.  in  H 


98  PHYSIOLOGY  CHAP. 

The  head  of  the  femur  is  united  obliquely  by  its  neck  to  the 
shaft  of  the  bone,  at  an  angle  which  usually  diminishes  during  the 
period  of  growth  under  the  influence  of  the  weight  of  the  body,  and 
varies  in  the  adult  from  110°  to  140°.  In  the  shaft  of  the  femur, 
which  is  by  far  the  larger  portion,  the  compact  bone  forms  a  tube 
with  thick,  solid  walls,  filled  with  marrow  which  is  largely  fat. 


Fin.  M. — Section  through  the  end  of  a  femur.     (Zaaijnr.) 

But  at  the  upper  end  of  the  femur,  including  the  head,  neck, 
and  trochanters,  in  consequence  of  the  obliquity  of  the  head  to  the 
longitudinal  axis  of  the  bone  the  conditions  for  obtaining  the 
necessary  strength  become  extremely  complex,  since  the  compact 
substance  of  the  tube  extends  (Fig.  64)  into  a  system  of  lamellae 
arranged  fanlike  so  as  to  support  the  surfaces  destined  to  bear  the 
greatest  pressure. 

It  should  be  noted  that  when  from  pathological  conditions,  for 


ii          MECHANICS  OF  LOCOMOTOE  APPARATUS         99 

instance,  articular  anchylosis,  and  after  amputations  or  resections, 
the  mechanical  requirements  to  which  the  bones  naturally  conform 
are  changed,  the  systems  of  lamellae  of  the  spongy  substance  alter 
considerably. 

The  enlargements  usually  presented  at  the  ends  of  the  long 
bones,  the  ridges,  tuberosities,  and  spines  are  for  the  purpose  of 
giving  the  muscles  large  and  adequate  surfaces  of  attachment. 

The  bones  of  which  the  skeleton  is  made  up  are  united  rigidly 
together,  or  in  such  a  manner  as  to  permit  a  more  or  less  extensive 
displacement  and  movement  on  each  other.  The  bones  united  by 
sutures  (sytiarthroses),  as  those  which  compose  the  cranium,  are 
perfectly  immobile  ;  those  united  by  means  of  cartilages  (synchon- 
droses) are  semi-mobile,  or  admit  of  very  limited  movements.  Such 
are  the  syrnphyses  of  the  pubis  and  innominate  bone  and  the 
synchondroses  of  the  ribs  and  vertebrae.  Finally,  the  bones 
united  by  articular  capsules  are  semi- mobile  (ampliiartlirose}, 
mobile  (artlirose),  or  very  mobile  (diarthrose*),  according  to  the 
form  of  the  articulation.  The  articulations  of  the  carpal  and 
tarsal  bones  belong  to  the  first  category  ;  the  elbow,  knee,  and  ankle 
to  the  second ;  the  shoulder  and  hip-joints  to  the  last. 

In  all  these  true  articulations  the  heads  of  the  bone  are  covered 
with  a  layer  of  cartilage,  to  the  edges  of  which  the  fibrous  articular 
capsule,  which  connects  the  two  bones  and  surrounds  the  articular 
cavity,  is  attached.  Each  capsule  is  covered  internally  by  a  pave- 
ment epithelium  which  extends  over  the  joint  cartilage,  and 
secretes  the  synovia,  a  colourless,  transparent,  viscous  fluid,  formed 
by  the  mucous  metamorphosis  of  the  epithelium,  which  is  destined 
to  lubricate  the  articular  surfaces  and  enable  them  to  move  easily 
one  upon  the  other. 

Externally,  fibro-elastic  ligaments  strengthen  the  capsule,  and 
prevent  or  limit  to  a  greater  or  less  extent  the  movements  of  the 
articular  heads. 

From  the  physiological  point  of  view,  articulations  can  be 
subdivided  into  the  classes  proposed  by  A.  Fick.  The  first 
comprises  the  synchondroses  (ribs  and  vertebrae)  and  the 
arnphiarthroses  (joints  between  the  tarsus  and  carpus).  In  these 
articulations  the  bony  surfaces  never  change  their  relations, 
and  can  only  be  fixed  or  moved  to  a  limited  extent  by  the 
elasticity  of  the  interpolated  fibro-cartilages,  or  pericapsular  liga- 
ments. The  bones  thus  united  are  in  stable  equilibrium,  to  which 
they  return  immediately  when  any  external  cause  which  has 
displaced  them  from  their  normal  position  ceases  to  act.  The 
arthroses  and  diarthroses  form  the  second  class,  as  the  articular 
surfaces  change  their  relations  while  moving.  The  bones  thus 
articulated  are  in  unstable  equilibrium,  that  is,  they  remain  in 
whatever  position  they  are  placed  by  external  causes,  until  this  is 
removed  by  some  force  working  in  the  opposite  direction.  A 


100  PHYSIOLOGY  CHAP. 

comparatively  slight  force  is  consequently  able  to  produce  move- 
ments of  the  bones. 

In  articulations  of  the  second  class  (arthroses  and  diarthroses), 
which  more  especially  concern  us,  the  bones  have  articular  heads 
which  are  approximately  cylindrical  or  spherical  in  shape.  The 
former  constitute  the  hinge  joints  which  move  in  a  single  axis ; 
one  of  the  articular  surfaces  is  concave,  the  other  convex.  Both 
are  shaped  like  a  section  of  a  cylinder,  or  more  exactly  like  a  cone, 
an  ovoid,  or  an  ellipse.  The  articulations  of  the  elbow,  knee, 
and  ankle  belong  to  this  class.  In  the  second  class  of  articula- 
tions with  round  heads,  the  bones  can  rotate  round  a  single  axis, 
as  in  the  humero-radial  and  the  atlanto-epistropheal  joints,  or 
round  many  axes,  as  in  the  ball-and-socket  joints,  represented  by 
the  scapulo-humeral  and  the  hip-joints. 

From  these  articulations  with  one  or  many  axes,  we  must 
distinguish  the  articulations  with  two  axes  at  right  angles  to 
one  another,  represented  by  the  saddle  joints  and  the  con- 
dyloid  joints.  The  articular  saddle  surfaces  are  convex  in  one 
direction  and  concave  in  the  plane  vertical  to  it.  Such  is 
the  joint  between  the  metacarpal  bone  of  the  thumb  and  the 
trapezium  bone  of  the  carpus,  which  permits  not  only  of  flexion 
and  extension,  but  also  of  adduction  and  abduction  in  two  almost 
perpendicular  axes.  The  joint  between  the  radius  and  the  bones 
of  the  carpus,  which  permits  the  flexion  and  extension  of  the 
hand,  and  its  abduction  and  adduction  in  two  axes  vertical  to 
each  other,  is  also  a  condyloid  bi-axial  articulation. 

In  most  articulations  the  surfaces  of  the  bones  are  not  in 
complete  apposition.  There  is  only  a  small  area  of  contact 
between  the  head  of  the  femur  and  the  hollow  of  the  acetabulum, 
because,  as  Konig  showed,  their  surfaces  are  not  geometrically 
complementary.  The  gap  between  the  articular  surfaces  where 
there  is  no  direct  contact  is  filled  either  by  the  synovia  or  by 
introflexion  of  the  capsular  membrane  due  to  external  pressure. 
These  capsular  introflexions  always  have  excrescences  known  as 
synovial  villosities,  which  are  rich  in  vessels  and  lined  with 
epithelium,  to  which  the  formation  of  synovia  is  mainly  due. 
There  are  consequently  no  true  articular  cavities. 

However  small  the  area  of  contact  of  the  articular  heads, 
it  was  formerly  supposed  that  it  was  invariably  present,  but 
Konig  found  an  exception  in  the  scapulo-humeral  articulation. 
On  dissecting  frozen  subjects  he  discovered  that  there  was 
always  a  layer  of  congealed  synovia  between  the  two  articular 
surfaces. 

An  important  but  difficult  question  is,  what  forces  intervene 
to  resist  displacements  of  the  articular  surfaces  ?  E.  Weber 
attributed  this  to  atmospheric  pressure  only.  He  saw  that  if  all 
the  muscles  surrounding  the  hip-joint  in  a  suspended  corpse 


ii          MECHANICS  OF  LOCOMOTOR  APPARATUS       101 

were  divided,  and  the  capsular  membrane  and  accessory  ligaments 
of  the  articulation  were  then  cut  oft*  the  head  of  the  femur  remained 
in  the  acetabulum,  and  was  not  apparently  displaced.  In  this 
case  the  entire  weight  of  the  lower  limb  is  effectively  supported 
by  atmospheric  pressure,  which  is  equivalent  to  admitting  that 
a  column  of  air  the  height  of  the  atmosphere  and  section  equal 
to  that  of  the  acetabular  cavity,  would  be  heavier  than  the  lower 
limb,  which  weighs  about  22  kgrms.  Weber  tried  a  control  ex- 
periment. On  the  same  subject  he  made  a  small  opening  from 
the  internal  surface  of  the  pelvis  to  the  acetabulum,  and  allowed 
the  air  to  enter  into  the  joint ;  the  head  of  the  femur  no  longer 
remained  in  the  cavity,  and  the  limb  fell  directly  the  air  was 
admitted,  because  the  contact  of  the  articular  surfaces  at  the 
point  of  perforation  was  not  so  intimate  as  at  the  edges  of  the 
acetabulum,  where  there  is  a  cartilaginous  ring  which  exactly  fits 
the  head  of  the  femur,  and  consequently  the  air  rapidly  penetrated 
between  the  surfaces. 

It  is,  however,  known  that  the  results  of  these  experiments  are 
not  applicable  to  other  articulations :  if  the  fingers  are  stretched 
by  a  traction  of  not  more  than  500  grrns.,  the  articular  surfaces 
of  the  rnetacarpal-phalaugeal  joints  come  apart.  The  separation 
produces  a  characteristic  sound,  and  the  articular  capsule  and 
surrounding  tissue  are  intraflected  to  fill  the  space  left  by  the 
displacement  of  the  surfaces  of  contact. 

Besides  the  atmospheric  pressure,  the  contact  of  the  articular 
surfaces  is  aided  by  the  ligaments  which  are  attached  chiefly  to 
the  capsule.  This  is  apparent  in  the  amphiarthrosis  of  the  carpus 
and  tarsus,  which,  owing  to  the  shortness,  strength,  and  tension 
of  the  accessory  ligaments  which  strengthen  the  capsules  as  well 
as  to  the  complex  and  irregular  form  of  the  articular  surfaces,  are 
movable  only  to  a  very  limited  extent.  In  the  arthroses  and 
diarthroses,  on  the  contrary,  which  are  more  freely  movable,  the 
capsules  and  ligaments  serve,  not  to  keep  the  articular  heads  in 
contact,  but  rather  to  limit  the  movements.  In  fact  they  are  not 
tense  when  the  muscles  are  at  rest,  but  are  thrown  into  tension 
when  the  moving  limb  reaches  a  certain  extreme  position.  In 
order  to  understand  the  mechanism  of  the  articulations  in  general, 
it  is  also  necessary  to  take  into  consideration  the  tone  and  state 
of  contraction  of  the  muscles  which  surround  the  joints.  Even 
in  the  resting  state  the  muscles  are  never  so  relaxed  in  the  normal 
individual,  as  not  to  contribute  to  the  support  of  the  joints.  The 
articular  contact  is  opposed  by  the  weight  of  the  limb,  as  well  as 
by  the  pressure  at  which  the  synovial  juice  is  secreted,  which 
cannot  be  less  than  that  at  which  the  blood  circulates  in  the 
capillaries  of  the  synovial  tissue.  And  there  must  always  be 
equilibrium  between  these  antagonistic  forces.  It  is  not  possible 
to  calculate  exactly  to  what  extent  atmospheric  pressure  helps  to 


102  PHYSIOLOGY  CHAP. 

support  a  joint  and  keep  its  articular  surfaces  in  contact,  although 
it  is  undeniable  that  this  pressure  is  a  considerable  factor. 

Owing  to  their  conformation  the  joints  and  the  soft  parts 
which  surround  them  (muscles,  capsules,  ligaments)  not  only 
serve  to  connect  the  segments  of  the  limbs,  but  also  limit  their 
movements.  Thus  the  olecranon  of  the  ulna  during  the  extension 
of  the  forearm  comes  in  contact  with  the  dorsal  surface  of  the 
humerus,  and  prevents  further  extension.  The  same  function 
is  exerted  by  the  so  -  called  ligaments  of  arrest ;  the  lateral 
ligaments  of  the  knee-joint,  which  run  from  the  internal  and 
external  condyles  of  the  femur  to  the  internal  condyle  of  the 
tibia  and  the  head  of  the  fibula,  are  stretched  during  the  extension 
of  the  leg,  and  limit  this  movement  to  180°. 

II.  The  discussion  on  the  physiology  of  muscle  in  Chapter  I. 
refers  particularly  to  bundles  of  parallel  fibres  of  uniform 
length,  in  which  the  total  action  represents  the  sum  of  the 
actions  of  each  fibre.  But  muscles  with  parallel  fibres  like 
the  sartorius  and  the  frog's  hypoglossus  are  rare ;  the  structure 
of  the  muscle  is  usually  less  simple.  In  addition  to  long  muscles 
and  short  muscles,  cylindrical,  and  spindle-shaped,  and  flat  muscles, 
anatomists  distinguish  fan-shaped  muscles,  semipennate  muscles, 
and  pennate  muscles,  according  to  the  direction  of  the  fibres,  the 
form  of  the  tendons,  and  the  manner  in  which  the  muscle  bundles 
are  inserted. 

In  fan-shaped  muscles  the  different  parts  may  act  separately 
or  all  together.  The  deltoid  is  a  classical  example.  This  muscle 
raises  the  arm  forward,  backward,  or  from  the  side,  according 
as  only  the  front  or  back  portion  or  the  whole  acts.  In  the 
latter  case  the  movement  (as  occurs  when  several  forces  act 
simultaneously  in  different  directions)  follows  the  diagonal  given 
by  the  parallelogram  of  the  forces,  which  causes  the  arm  to  be 
raised  in  the  lateral  plane. 

Semipennate  and  pennate  muscles  are  more  common.  In 
these  a  tendon  penetrates  deep  into  the  belly  of  the  muscle,  and  the 
muscular  fibres  run  out  from  it  obliquely  in  one  or  more  directions. 
In  such  muscles  the  line  of  junction  of  the  points  of  attachment 
does  not  coincide  with  the  direction  of  the  fibres,  and  when  the 
whole  muscle  contracts,  the  effect  is  the  sum  of  the  values, 
calculated  for  each  fibre  separately.  The  gastrocnemius,  the 
biceps,  and  brachialis  anticus,  and  the  flexors  for  the  arm,  are 
examples  of  pinnate  muscles. 

Generally  speaking,  in  muscles  with  parallel  fibres,  the 
diameter  and  cross -section  is  proportional  to  their  strength, 
while  their  length  is  proportional  to  the  range  of  the  movements 
they  can  produce.  But  in  pennate  muscles  the  strength  and 
range  of  the  movements  cannot  be  deduced  from  their  section 
and  apparent  length :  there  are  short  muscles  which  appear  to  be 


ii          MECHANICS  OF  LOCOMOTOE  APPARATUS       103 

long,  thick  muscles  which  appear  thin.  The  energy  these  are 
capable  of  developing  is  measured,  not  by  the  area  of  the  section 
vertical  to  their  long  axis  (anatomical  section),  but  by  the  area 
of  a  section  vertical  to  the  direction  of  the  bundles  of  fibres 
(physiological  section) ;  and  the  range  of  their  action  is  measured, 
not  by  their  anatomical  length,  but  by  their  physiological  length, 
i.e.  the  mean  length  of  the  muscle  bundles  of  which  they  consist. 

All  muscles  are  not  inserted  into  the  bones.  The  fibres  of  the 
visceral  organs — as  the  heart,  bladder,  intestines,  uterus,  as  well  as 
the  circular  fibres  of  the  oral,  pyloric,  and  anal  sphincters — are 
only  inserted  into  one  another  or  into  the  surrounding  soft  parts. 

Other  muscles  are  attached  to  the  bone  by  one  end,  and 
terminate  at  the  other  in  soft  parts,  either  on  the  skin  or  in  the 
raucous  membrane.  Such  are  the  azygos  uvulae,  the  levator 
palati,  the  muscles  of  the  face,  the  stylo  -glossus,  the  stylo- 
pharyngeus,  etc.  The  muscles  of  the  face  exert  a  mutual  traction, 
making  equilibrium  with  the  symmetrical  muscles  of  the  other 
side ;  when  the  muscles  on  one  side  of  the  face  are  paralysed,  the 
mouth  consequently  becomes  oblique. 

All  the  other  skeletal  muscles  are  composed  of  straight  fibres, 
the  two  ends  of  which  are  generally  inserted  into  tendons  of 
greater  or  less  length,  by  which  they  are  attached  to  two  distinct 
bones  of  the  skeleton.  The  majority  of  the  muscles  cross  only 
one  joint,  that  is,  they  are  attached  by  their  two  ends  to  two 
contiguous  bones,  and  are  therefore  uni- articular  muscles. 
Certain  muscles,  however,  cross  two  or  more  articulations,  and 
are  attached  to  more  or  less  distant  bones  :  these  are  bi-  or  multi- 
articular  muscles.  The  anterior  brachial  muscle  is  uni-articular, 
the  semi-tendinous  is  bi-articular,  as  well  as  the  long  head  of  the 
biceps  and  certain  muscles  of  the  leg.  In  these  cases  the  muscles 
and  tendons  are  unusually  long,  and  as  they  can  shorten  con- 
siderably are  able  to  move  two  or  more  articulations  simultaneously. 

When  two  bones  are  connected  by  a  movable  articulation,  and 
a  muscle  passes  from  one  to  the  other,  this  forms  a  lever.  The 
skeleton  is  built  up  of  a  vast  number  of  levers,  the  movements 
of  which  combine  among  themselves  in  the  most  various  and 
complex  forms.  The  centre  of  gravity  of  each  limb  represents 
the  point  of  application  of  the  resistance,  that  is  the  weight  of 
the  bony  lever,  of  the  soft  parts  by  which  this  is  covered,  and 
of  any  extrinsic  load  which  may  be  carried  by  the  limb.  The 
point  of  insertion  of  a  muscle  or  muscles  upon  the  movable 
segment  represents  the  point  of  application  of  the  force.  Finally, 
the  fulcrum  of  the  lever  is  represented  by  the  articular  surface 
of  the  moving  bone  upon  the  articular  surface  of  the  fixed  bone, 
or  by  the  ground,  or  any  other  fixed  support  on  which  the 
limb  rests. 

It  is  rare  to  find  that  one  of  two  interarticulated  bones  is 


104 


PHYSIOLOGY 


CHAP. 


absolutely  rigid  and  the  other  movable ;  much  more  frequently 
both  the  bones  are  movable,  but  in  different  degrees.  The  muscle 
or  muscles  attached  to  the  two  bones  exert  in  contraction  an 
equal  traction  upon  the  two  points  of  insertion  and  tend  to  dis- 
place the  two  bones  equally,  but  since  the  resistances  opposed  to 
the  displacement  of  the  two  bones  differ,  it  follows  that  they  are 
unequally  displaced.  The  distinction  of  fixed  and  movable  in- 
sertions of  a  muscle  really  has  only  a  very  relative  value.  As  a 
rule,  however,  one  of  the  muscular  insertions  is  less  displaced 
than  the  other,  generally  that  which  is  nearer  the  axis  of  the 
trunk,  or  the  root  of  the  limb. 


FIG.  65. — A,  Flexor  movements  of  forearm  for  contraction  of  anterior  brachial,  which  causes 
backward  rotation  of  arm  in  scapulo-humeral  articulation.  (O.  Fischer.)  B,  Extensor  move- 
ments of  forearm  produced  by  triceps,  and  associated  with  forward  rotation  of  arm  in 
scapulo-humeral  articulation.  (O.  Fischer.)  The  two  diajn'ams  represent  an  experiment  made 
on  a  mechanical  model. 

To  demonstrate  the  mobility  of  the  points  of  insertion  of  the 
muscle,  Fischer  (1895)  employed  a  wooden  model  to  represent 
the  humerus  and  ulna  articulating  together,  flexed  by  contrac- 
tion of  the  anterior  brachial  muscles,  and  extended  by  the  con- 
traction of  the  triceps.  He  found  that  the  movement  of  flexion 
is  associated  with  the  backward  displacement  of  the  humerus,  and 
the  movement  of  extension  with  its  forward  displacement  (Fig. 
65,  A,  B). 

The  relation  between  the  movements  of  the  shoulder  and  of 
the  elbow  joints  which  occur  in  consequence  of  the  contraction 
of  the  flexor  or  extensor  muscles  of  the  elbow  varies  when  the 
mass  of  the  limb  is  increased.  If,  for  instance,  a  weight  is  held 
in  the  hand,  and  the  elbow  is  flexed,  the  movement  at  the  shoulder 
is  increased. 


II 


MECHANICS  OF  LOCOMOTOE  APPAEATUS       105 


These  statements  refer  not  merely  to  the  flexor  and  extensor 
muscles  of  the  forearm,  but  have  a  general  value.  When  the 
knee  is  bent,  not  only  does  the  leg  move  backward,  but  the  thigh 
bends  simultaneously  forward.  Generally  speaking,  it  may  be 
stated  that  a  uni-articular  muscle  produces  a  movement  in  the 
neighbouring  articulation  in  the  opposite  direction  to  that  which 
occurs  in  the  articulation  lying  between  its  points  of  insertion. 

The  whole  of  the  force  on  the  muscles 

is  not  utilised  in  the  movements  of  the  ^ 

skeleton.  This  occurs  only  in  the  case 
when  the  insertion  of  the  muscles  is 
approximately  at  right  angles  to  the  bone, 
as  in  the  masseters  which  are  able  to  em- 
ploy their  full  strength  in  bringing  the 
jaws  together.  But  the  great  majority 
of  the  muscles  are  inserted  more  or  less 
obliquely,  the  direction  of  their  fibres 
forming  a  more  or  less  acute  angle  with 
the  principal  axis  of  the  bone.  In  all 
these  cases  a  great  part  of  the  traction 
force  of  the  muscle  is  lost  in  the  move- 
ment. This  disadvantage  is  frequently 
diminished  by  the  fact  that  many  bones 
have  prominences  at  the  point  of  attach- 
ment of  the  muscles  over  which  the  tendons 
of  the  muscles  pass  as  over  a  pulley,  and 
become  attached  to  the  bone  at  a  favour- 
able angle. 

In  every  case,  whatever  the  form  and 
size  of  the  angle  of  insertion  of  a  muscle 
upon  the  bone,  it  is  possible  by  resolving 
the  total  traction  force  into  its  components, 
according  to  the  law  of  the  parallelogram 
of  forces,  to  estimate  how  much  is  utilised 

T       i       .  ,  ,  •  ,  •  Fio.  t>6. — Diagram  of  the  resolu- 

m    displacing    the    moving    bone,  Supposing          tion   ofi  muscular   force   into 

the  other  bone  to  be  rigid. 

Let  it  be  supposed  that  AC  and  AB  in 
Fig.  66  represent  the  long  axes  of  two  bones,  which  are  movable 
round  the  axis  A  perpendicular  to  the  plane  of  the  figure ;  that 
MM'  are  the  points  of  insertion  of  a  muscle,  M  being  fixed,  M' 
movable ;  lastly,  that  the  line  M'D  represents  the  total  traction 
force  of  which  the  muscle  is  capable.  If  we  resolve  the  line  M'D 
into  its  two  components  M'E  and  M'F,  which  are  vertical  to  each 
other,  then  M'E  represents  the  force  utilised  by  the  muscle  in 
moving  the  joint  A,  called  by  mechanicians  the  moment  of  force, 
while  M'F  is  the  amount  of  force  that  is  spent  in  pressing  the  two 
articular  surfaces  at  A  against  one  another,  so  as  to  render  the 


its  components.     Explanation 
in  text. 


106 


PHYSIOLOGY 


CHAP. 


articulation  more  solid.  The  more  obtuse  the  angle  BAG  formed 
by  the  two  bones,  the  smaller  will  be  the  components  M'E,  i.e.  the 
force  utilised  in  the  movement.  The  smaller  this  angle  becomes, 
the  greater  will  be  the  proportion  of  the  force  employed  in  the 
movement. 

Since  movable   bones  may  be   regarded   as   levers,    the   laws 

which  govern  the  action  of 
levers  can  be  applied  to  them. 
When  the  object  is  to  attain 
considerable  speed  rather  than 
have  great  force,  the  force  is 
applied  to  the  shorter  arm  of 
the  lever ;  when,  on  the  con- 
trary, a  high  resistance  has  to 
be  overcome,  and  less  speed 
of  movement  is  required,  the 
force  is  applied  to  the  longer 
arm.  In  the  animal  body  the 
arm  of  the  lever  to  which  the 
force  is  applied  is  shorter  than 
that  which  causes  resistance, 
i.e.  the  majority  of  the  muscles 
are  inserted  nearer  the  articu- 
lations than  is  the  centre  of 
gravity  of  the  movable  part. 

This  arrangement  is  advan- 
tageous for  the  speed  of  the 
movement,butdisadvantageous 
owing  to  loss  of  force.  The 
loss  is,  however,  compensated 
by  the  fact  that  a  less  amount 
of  muscular  shortening  is  re- 
quired to  effect  a  given  range 
of  movement  (Fig.  67). 

It  is  important  to  note  that 
during  movement  the  length 
of  the  arm  to  which  the  force 
applied,    and    that    which 


FIG.  C7. —  Diagram  showing  the  various  degrees  of 
muscular  shortening  required  for  a  given  move- 
ment, according  as  the  lever  arm  varies  for 
Eower  and  for  the  load.  (Luciani.)  When  the 
iver  AC  rotating  on  the  axis  A  reaches  AC",  the 
muscle  MM  only  shortens  slightly  (Mm'),  because 
the  lever  arm  AM  i.s  shorter  than  that  of  the 
load  MC ;  the  muscle  MM',  on  the  contrary,  has 
to  shorten  much  more  (to  Mm")  to  execute  the 
same  movement,  because  the  arm  AM'  is  much 
longer  than  that  of  the  load  M'l '. 


IS 


carries  the  weight,  often  vary 
in  proportion  with  the  range  of 
the  movement,  so  that  the  load  diminishes  during  work.  When, 
for  instance,  the  body  is  raised  from  the  bent  knee,  this  movement 
is  accompanied  by  the  unloading  of  the  muscles  which  actively 
extend  the  knee.  In  this  position  the  arm  that  carries  the  load 
is  represented  by  the  horizontal  distance  of  the  axis  of  the  knee- 
joint  from  the  line  of  gravity  of  the  body,  i.e.  from  the  perpen- 
dicular taken  from  its  centre  of  gravity.  During  the  rise  this 


ii          MECHANICS  OF  LOCOMOTOK  APPARATUS       107 

distance  becomes  gradually  less,  and  iu  the  erect  posture  is  almost 
negligible.  On  the  other  hand,  the  working  line  of  the  quadriceps 
muscle  which  extends  the  knee  remains  at  approximately  the  same 
distance  from  the  axis  of  the  knee-joint  during  the  movement. 

III.  Leaving  the  study  of  the  various  positions  that  may  be 
assumed  and  the  different  movements  that  may  be  performed 
by  each  part  of  the  skeleton,  we  must  here  confine  ourselves  to 
studying  the  different  postures  and  movements  of  the  body  as  a 
whole  in  progression. 

In  both  standing  and  walking  the  position  and  the  displace- 
ment of  the  centre  of  gravity  and  of  the  line  of  action  of  gravity 
of  the  whole  body  are  of  great  importance. 

Every  part  of  the  body  gravitates  according  to  the  vertical 
line  that  falls  from  it  to  the  earth.  This  infinite  number  of 
perpendiculars  which  only  meet  at  the  centre  of  the  earth,  and 
niay  therefore  be  regarded  as  parallels,  may  be  replaced  by  one 
single  perpendicular  line  representing  the  sum  of  the  component 
forces ;  this  is  known  as  the  line  of  gravity.  Whatever  position 
is  assumed  by  the  body,  so  long  as  it  preserves  the  same  form, 
the  lines  of  gravity  corresponding  with  each  posture  intersect 
at  the  same  point  which  is  known  as  the  centre  of  gravity. 

In  all  bodies  which  are  not  geometrical  in  form  and  consist 
of  a  heterogeneous  mass,  the  centre  of  gravity  can  only  be  deter- 
mined by  experiment.  This  is  done  by  suspending  the  body  by  a 
cord  successively  in  two  different  positions ;  the  directions  of  the 
cord  prolonged  through  the  body  give  two  lines  of  gravity,  and 
the  point  at  which  they  intersect  is  the  centre  of  gravity.  The 
exact  determination  of  the  centre  of  gravity  of  the  human  body 
is  much  more  difficult,  since  it  is  not  a  rigid  body,  and  undergoes 
changes  of  form. 

Borelli  (1679)  and  the  Webers,  starting  from  the  assumption  that 
in  well-formed  individuals  the  line  of  gravity  must  lie  in  the  median 
sagittal  plane,  or  the  plane  of  symmetry  of  the  body,  attempted 
merely  to  ascertain  the  height  of  the  centre  of  gravity,  that  is,  its 
distance  from  the  sole  of  the  foot  and  apex  of  the  head,  without 
defining  its  position  on  the  transverse  vertical  plane.  For  this 
purpose  they  laid  a  man  on  his  back  upon  a  board  supported  on 
a  metal  wedge,  and  placed  the  whole  in  equilibrium  like  the  arms 
of  a  balance.  The  vertical  plane  perpendicular  to  the  length  of 
the  body  through  the  wedge  that  supports  the  board  must  pass 
through  the  centre  of  gravity.  They  found  that  this  plane  was 
nearer  the  crown  of  the  head  than  the  sole  of  the  foot.  If  the 
total  height  of  a  man  be  taken  as  1000,  the  centre  of  gravity 
would  be  found  at  570  from  the  sole  and  at  430  below  the  crown. 

These  observations  were  controlled  by  Harless  and  by  Meyer, 
who  found  values  that  did  not  vary  more  than  3  per  cent  from 
those  of  the  earlier  observers.  Harless  found  that  in  woman  the 


108 


PHYSIOLOGY 


CHAP. 


centre  of  gravity  is  placed  lower  than  in  man  ;  in  children,  on  the 
contrary,  it  is  higher,  owing  to  the  relatively  greater  or  less 
development  of  the  pelvis. 

In  order  to  ascertain  the  centre  of  gravity  in  the  antero- 
posterior  plane  of  the  body,  Meyer  placed  a  naked  subject  in  the 
erect  and  rigid  posture,  and  then  made  him  bend  forward  on  the 
front  of  his  feet  and  his  heels  as  far  as  possible  without  falling. 
By  means  of  a  plumb  line  he  determined  the  lines  of  gravity  in 
the  two  most  extreme  postures,  and  the  points  of  intersection  of 


Fin.  68.  —  Normal  position.  (Braune  ami 
Fischer.)  In  this  position  the  centres  of 
rotation  of  the  principal  articulations  fall 
in  the  same  vertical  plain-  indicated  by  the 
line. 


FIG.  60.  —  Military  position  or  "stand  at 
ease."  (Braune  and  Fischer.)  In  this 
position  the  centres  of  rotation  for  the 
lower  limbs  lie  behind  the  vertical  line  that 
passes  through  the  centre  of  gravity. 


these  lines  in  the  body  represent  its  centre  of  gravity  in  the  given 
erect  and  rigid  posture. 

More  recently  Braune  and  Fischer  have  applied  the  same 
method  to  the  dead  body  frozen  and  extended  on  its  back  upon  a 
board.  The  rigid  and  invariable  form  of  the  body  enabled  them 
to  determine  exactly  the  point  of  intersection  of  three  perpen- 
dicular lines  of  gravity  obtained  by  successively  suspending  the 
body  in  three  different  positions. 

According  to  Weber  the  centre  of  gravity  of  the  whole  body 
in  the  erect  position  is  at  about  the  level  of  the  sacral  promontory  ; 
according  to  Meyer  it  lies  at  about  the  upper  border  of  the  second 
sacral  vertebra  inside  the  spinal  canal ;  according  to  Braune  and 
Fischer  it  is  considerably  farther  forward,  at  the  level  of  the  upper 
border  of  the  third  sacral  vertebra. 


ii          MECHANICS  OF  LOCOMOTOE  APPAEATUS       109 

The  centre  of  gravity  of  the  trunk  may  lie  determined  on  the 
dead  subject  in  the  same  manner  after  exarticulating  all  the 
limbs.  It  lies  in  the  plane  between  the  lower  extremity  of 
the  sternum  or  the  ensiform  cartilage  and  the  tenth  dorsal 
vertebra,  and  in  a  vertical  transverse  plane  that  passes  somewhat 
behind  the  axes  of  rotation  of  the  heads  of  the  femurs.  We  shall 
presently  see  the  importance  of  this  fact. 

The  position  of  the  centre  of  gravity  for  the  whole  body  is 
important  in  determining  the  positions  of  more  or  less  stable 
equilibrium  of  the  body.  Braune  and  Fischer  denned  the  normal 
erect  posture  (Normdl-Stdlung}  as  that  in  which  the  axes  of 
rotation  of  the  principal  articulations  fall  in  the  same  vertical 
transverse  plane  as  the  line  of  gravity  (Fig.  68).  From  this 
they  distinguish  the  military  or  "  stand-at-ease  "  position  (Bequeme 
Hal  tuny}  in  which  the  line  of  gravity  falls  4  cm.  in  front  of 


FIG.  70. — The  base  of  support  and  the  line  of  gravity  in  different  postures.  At  A  tin1  base  of 
support  is  represented  by  the  area  <>''<•'/,  and  </  is  the  point  through  which  the  line  of  gravity 
passes  ("attention  attitude").  At  B  the  base  of  support  comprises  ulinl,  i/  being  the  point 
through  which  the  line  of  gravity  passes  ("normal  position"). 

the  line  of  junction  of  the  articular  heads  of  the  femurs  (Fig.  69). 
In  the  first  posture  the  line  of  gravity  falls  near  the  posterior 
margin  of  the  base  of  support ;  in  the  second  it  falls  considerably 
more  forward  (Fig.  70).  Obviously  this  last  posture  represents  a 
more  stable  condition  of  equilibrium. 

In  each  different  posture  assumed  by  the  body  resting  on  the 
soles  of  both  feet  there  is  a  new  displacement  of  the  centre  of  gravity 
(Fig.  71).  If  the  individual  carries  a  weight  he  is  constrained  to 
modify  his  position  because  the  system  is  thrown  out  of  equilibrium, 
unless  the  centre  of  gravity  lies  within  the  common  base  of 
support.  If  the  load  is  placed  on  the  back  he  must  lean  forward, 
if  the  weight  is  placed  in  front,  backward.  If  a  weight  is  held  up 
with  the  right  arm  the  body  inclines  to  the  left ;  if  with  the  left 
arm,  to  the  right.  Heavier  weights  can  be  borne  on  the  head,  as 
then  the  normal  posture  of  the  trunk  may  be  but  little  changed, 
and  the  line  of  gravity  little  displaced,  but  the  centre  of  gravity 
is  raised,  which  renders  the  equilibrium  less  stable,  though  the 
base  of  support  is  unchanged. 


110 


PHYSIOLOGY 


CHAP. 


In  order  to  increase  the  base  of  support  and  to  obtain  more 
stable  equilibrium  it  is  only  necessary  to  set  the  feet  further  apart 
upon  the  ground.  This  is  often  done  where  the  erect  posture  has 
to  be  long  maintained. 

From  these  forms  of  symmetrical  vertical  posture  we  must  dis- 
tinguish the  asymmetrical  vertical  posture,  in  which  almost  the 
whole  weight  of  the  body  falls  upon  one  leg,  the  other  being 
slightly  flexed  and  placed  in  advance.  In  this  posture  (Jianchee] 
the  line  of  gravity  falls  through  the  extended  limb  which  supports 


FIG.  71.— Displacement  of  centre  of  gravity  in  postures  a,  &,  c.    (Braune  and  Fischer.) 
Centres  of  gravity  shown  as  black  dots  on  the  vertical  lines. 

the  body,  and  the  trunk  consequently  inclines  towards  this  side. 
The  different  forms  of  this  posture,  which  is  very  natural  and 
instinctive,  are  determined  by  the  angle  formed  by  the  longi- 
tudinal axes  of  the  two  limbs  or  by  the  distance  between  the 
two  soles  of  the  feet. 

IV.  We  should  next  consider  briefly  the  mechanism  of 
equilibration  in  the  different  postures  of  the  human  body,  but 
must  here  confine  ourselves  to  the  horizontal  posture,  the  sitting 
posture,  and  the  common  erect  attitudes. 

The  horizontal  posture  is  the  easiest  to  maintain  because 
it  unites  as  completely  as  possible  the  two  conditions  of  stable 
equilibrium,  i.e.  an  extensive  base  of  support,  and  the  maximum 
approximation  of  the  centre  of  gravity  to  it.  As  muscular  con- 


ii          MECHANICS  OF  LOCOMOTOE  APPAEATUS       111 

tractions  are  not  necessary  for  maintaining  equilibrium  in  lying 
down,  that  is  therefore  the  position  of  rest  and  sleep.  We  may 
distinguish  between  the  sternal,  sterno-costal,  lateral  and  dorsal 
postures.  This  last  is  almost  confined  to  man,  as  in  no  other 
vertebrate  is  the  back  sufficiently  flat  to  support  the  weight  of  the 
body  conveniently. 

In  the  sitting  posture,  if  the  trunk  is  leaning  against  the  back 
of  the  seat,  all  the  muscles  are  in  repose,  except  the  elevators  of 
the  head  which  keep  it  in  the  vertical  position.  In  fact,  in 
sleeping  while  seated  the  head  drops  forward  towards  the  chest, 
which  shows  that  the  centre  of  gravity  for  the  head  is  placed  in 
front  of  the  occipito-atlantoid  articulation. 

When  seated  on  a  stool  with  no  support  for  the  back,  the  base 
of  support  is  represented  by  the  line  that  connects  the  outer 
margins  of  the  sciatic  tuberosities  and  of  the  feet  which  rest  on 
the  ground.  In  order  to  maintain  the  centre  of  gravity  of  the 
head  and  trunk  within  this  base,  it  is  necessary  to  obtain  the 
antero-posterior  balance  by  the  alternate  activity  of  the  dorsal, 
the  lumbar,  and  the  psoas-iliac  muscles. 

In  the  erect  posture,  with  the  two  feet  set  square,  the  centre 
of  gravity  of  the  body  is  brought  much  higher  from  the  base  of 
support,  and  this  base  is  much  smaller;  it  would  therefore  be 
natural  to  assume  that  a  much  greater  muscular  force  would  be 
necessary  to  preserve  equilibrium.  Meyer,  on  the  contrary, 
demonstrated  that  in  the  most  comfortable  erect  posture,  the 
muscular  activity  necessary  to  preserve  equilibrium  is  small,  as  this 
is  due  principally  to  the  tension  of  the  ligaments,  especially  the 
ileo-femoral  ligaments. 

As  its  articulations  are  mainly  synchondroses,  the  vertebral 
column  may  be  regarded  as  an  elastic  bar,  capable  of  supporting 
the  entire  weight  of  the  head,  trunk,  and  upper  limbs.  It  has 
various  curvatures ;  it  is  convex  forwards  in  the  cervical  and 
lumbar  regions,  and  concave  in  the  thoracic  and  sacral  regions 
(Fig.  72).  It  is  wholly  immobile  in  the  sacral  region  owing  to  the 
fusion  of  the  vertebrae,  but  little  movable  and  flexible  in  the 
lumbar  region,  much  more  mobile  and  flexible  in  the  dorsal 
part,  and  in  the  cervical  region  it  is  remarkably  flexible  in  all 
directions.  The  neck  muscles  fix  the  head,  and  therefore  make 
the  cervical  spine  relatively  rigid. 

The  line  of  gravity  of  the  trunk  and  head  in  the  easy  (or 
military)  position  shown  in  Fig.  69  falls  behind  the  line  of 
junction  of  the  ileo-femoral  articulations.  The  trunk  would 
primarily  fall  back,  but  for  the  resistance,  as  Meyer  showed,  of  the 
strong  ligament  which  runs  from  the  anterior  inferior  iliac  spine 
to  the  anterior  intertrochanter  line  of  the  femur ;  the  balancing 
of  the  trunk  on  the  heads  of  the  femur  is  chiefly  due  to  the 
elastic  tension  of  this  ileo-femoral  ligament,  but  this  is  aided  by 


112 


PHYSIOLOGY 


CHAP. 


the  alternate  activity  of  the  psoas-iliac  muscles,  which  tend  to 
bend  the  trunk  forward,  and  the  dorsal  and  lumbar  muscles,  which 
tend  to  incline  it  backward. 

The  common  line  of  gravity  of  the  head,  trunk,  and  thighs,  also 
passes  behind  the  knee-joints;  and  some  arrangement  is  necessary 

when  the  individual  is  in  the  upright 
posture  to  prevent  falling  backwards 
owing  to  flexion  of  the  knees.  This  is 
provided  for  by  the  tension  of  the  ileo- 
fernoral  ligaments  which  rotate  the 
femora  inwards,  and  thus  prevents  the 
slight  external  rotation  which  is  neces- 
sary for  the  flexion  of  the  knees.  The 
hip-  and  knee-joints  are  thus  both  fixed 
by  the  weight  of  the  trunk,  which 
throws  the  ileo-femoral  ligaments  into 
tension.  Owing  to  this  mode  of  fixation 
of  the  knee-joints,  the  active  interven- 
tion of  the  extensor  quadriceps  muscle 
is  not  necessary,  and  indeed  the  patellar 
ligament  does  not  seem  to  be  more  tense 
in  the  vertical  posture  than  in  other 
positions. 

The  line  of  gravity  of  the  whole  body 
falls  on  the  ground  in  a  plane  somewhat 
anterior  to  the  line  between  the  two 
tibio-astragalic  articulations,  and  the 
body  tends  to  fall  forwards.  This  is 
avoided  by  the  fact  that  the  plane  of 
flexion  in  this  joint  is  very  oblique  with 
that  of  the  other  side ;  the  two  planes 
of  flexion  form  an  angle  of  60°  open  to 
the  front.  In  order  that  flexion  at 
these  two  joints  should  be  possible,  it 
is  therefore  necessary  for  the  two  knees 
to  be  moved  apart  from  each  other,  and 
flexed.  When  flexion  of  the  knees  is 
prevented,  falling  forward  owing  to 
flexion  of  the  tibio-astragalic  articula- 
tions is  also  prevented.  As  the  fixation 
of  the  hip-joint  determines  the  fixation  of  the  knee,  the  fixation 
of  this  joint  leads  to  the  fixation  of  the  ankle.  Here  again  the 
gastrocnemius,  soleus,  posterior  tibial,  and  posterior  peroneal 
muscles  also  take  part  in  maintaining  fixation. 

The  tarsal  and  metatarsal  bones,  which  constitute  the  skeleton 
of  the  foot,  form  an  arch  which  rests  on  the  ground  by  the 
tuberosity  of  the  heel,  and  the  heads  of  the  first  and  fifth  meta- 


Fio.  72. — Curve  normally  presented 
by  the  anterior  median  profile  of 
the  vertebral  column  in  the 
military  posture.  (G.  H.  Meyer.) 
it,  tuberculum  anterius  of  atlas  ; 
b,  lower  border  of  6th  cervical 
vertebra ;  c,  upper  border  of  9th 
dorsal  vertebra  ;  /,  lower  border 
of  2nd  lumbar  vertebra  ;  p,  pro- 
montorium  ;  s,  symphysis  ossium 
pubis ;  d,  angle  of  3rd  sacral 
vertebra  ;  e,  coccyx. 


ii          MECHANICS  OF  LOCOMOTOE  APPARATUS       113 

tarsal  bones.  Owing  to  the  strength  of  the  plantar  ligaments 
the  arch  of  the  foot  can  carry  heavy  weights  without  giving  way. 
Flat  foot,  owing  to  abnormal  relaxation  of  these  ligaments,  is  un- 
favourable to  the  maintenance  of  equilibrium  in  the  erect  posture 
and  in  walking. 

Owing  to  the  formation  of  the  skeleton  and  the  arrangement 
of  its  ligaments,  the  erect  posture  can  therefore  be  maintained 
with  a  comparatively  slight  expenditure  of  muscular  energy. 
But  when  it  is  necessary  to  remain  standing  for  a  long  time, 
an  asymmetrical  posture  is  generally  preferred,  in  which  the 
main  part  of  the  weight  of  the  body  is  thrown  on  one  leg,  while 
the  other  is  held  in  a  forward  and  semi-flexed  position. 

Vierordt,  by  an  extremely  simple  graphic  method,  registered 
the  oscillations  of  the  head  in  different  positions,  with  the  object 
of  determining  the  most  natural  posture,  i.e.  that  which  induces 
the  least  fatigue  and  provides  the  greatest  stability  of  the  body. 
The  method  consisted  in  attaching  a  pen  to  the  head  by  a  suitable 
cap,  which  traced  on  a  paper  fixed  horizontally  from  above  the 
oscillations  of  the  principal  axis  of  the  body  in  different  postures, 
each  being  maintained  for  three  minutes.  He  found  that  the 
antero-posterior  and  lateral  oscillations  are  considerably  greater 
in  the  symmetrical  military  posture  than  when  the  weight  was 
thrown  upon  one  leg  (asymmetrical).  The  latter  posture  is 
accordingly  the  most  natural,  and  preference  is  given  to  it  in 
sculpture  and  painting. 

According  to  Vierordt  the  advantages  of  the  asymmetrical 
posture  are  as  follows  :— 

(a)  Greater  rigidity  of  the  hip-  and  knee-joints,  due  to  almost 
the  whole  weight  of  the  body  falling  on  the  limb  which  serves 
as  support ;  this  produces  increased  tension  of  the  ligaments, 
particularly  of  the  ileo-femoral. 

(&)  The  calf  muscles  of  only  one  side  are  active,  and  less 
work  is  thrown  upon  these  than  in  the  symmetrical  posture. 

(c)  The  advanced  limb,  which  does  not  bear  the  weight  of  the 
body,  exerts  a  slight  pressure  on  the  ground,  so  that  when  the 
quadriceps  extensor  of  the  knee  comes  actively  into  play  to  hinder 
the  body  from  falling  forwards,  it  works   under  favourable  con- 
ditions.     In  the  symmetrical  posture,  on  the  contrary,  the  calf 
muscles  on  both  sides  work  under  a  heavy  load  to  attain  the 
same  end. 

(d)  The  appreciation  of  pressure  by  the  sole  of  the  advanced 
limb,  and  the  muscle  sense  generally,  are  under  the  most  advan- 
tageous conditions  in  the  asymmetrical  posture,  so  that  oscillations 
of  the  centre  of  gravity  are  more  readily  perceived,  and  promptly 
compensated  by  muscular  reaction. 

And,   as   in    the   asymmetrical  attitude,  the   muscles   of   one 
limb    only    become    fatigued,    it    is    possible    to    remain    longer 
VOL.  Ill  I 


114 


PHYSIOLOGY 


CHAP. 


standing,  by  throwing  the  weight  of  the  body  alternately  on  the 
two  feet. 

V.  In  locomotion  there  is  a  great  and  more  or  less  rapid  dis- 
placement of  the  centre  of  gravity  of  the  body  and  its  base  of 
support.  The  movements  performed  by  man  in  different  forms 
of  locomotion  are  extremely  complicated.  But  the  principles  of 
mechanics  by  which  we  have  explained  the  maintenance  of 
equilibration  help  to  solve  the  fundamental  problems  of  human 
locomotion. 

The  ordinary  forms  of  locomotion  are  walking  and  runniny. 

In  both  the  body  is  thrown 
forward  by  the  rhythmic  and 
alternate  muscular  contractions, 
specially  by  the  muscles  of  the 
lower  limbs.  In  walking  the 
body  never  leaves  the  ground, 
but  in  running  the  whole  body 
is  momentarily  in  the  air. 

According  to  the  description 
of  the  Webers  the  lower  limbs 
are  alternately  active  in  walk- 
ing ;  while  the  one  which  is 
applied  to  the  ground  sustains 
the  entire  weight  of  the  body 
and  throws  the  centre  of  gravity 
forward,  the  other  swings  pass- 


ively. 

Each  step  begins  with  plac- 

ment  of  the  step.     (Kick.)    a,   passive  right  ing  the  active  limb  with  its  Sole 

leg  winch  touches  ground  with  big  toe  only;  on     the     ground,     the     foot     and 
db,    left    foot    with    whole    sole    resting    on  ,~ 

ground;   c,  centre   of  rotation  for  hip-joint;  knee     being      SOlliewhat     flexed, 
IKY/,  rectangular  triangle,  in  which  the  passive  -\      ,  i  -i  ,         p     ,  i          1,1 

limb  forms  the  hypotenuse,  the  ground  and  ailQ     1116     Weigilb     01  DOCly 

catheter'  accor(lin8  to  the  falls  on  the  sole,  while  the 

passive  limb  lies  behind  with 
its  great  toe  on  the  ground.  At  this  stage  the  centres  of  the 
femoral  heads  and  the  extremes  of  the  two  limbs  form  a  rect- 
angular triangle  with  the  ground,  two  sides  being  formed  by  the 
active  limb  and  the  ground,  and  the  hypotenuse  by  the  passive 
limb  (Fig.  73). 

In  the  next  stage  of  the  step,  the  knee  of  the  active  limb 
is  extended  and  the  heel  raised,  throwing  the  centre  of  gravity 
forward  and  slightly  raising  it,  while  at  the  same  time  the  passive 
leg  is  lifted  from  the  ground  and  swung  forwards  till  it  once 
more  touches  the  ground  and  takes  the  weight  of  the  body. 

According  to  the  Webers  each  step  in  walking  may  be  con- 
sidered as  a  movement  of  falling  forward,  which  is  arrested  by 
advancing  the  passive  limb  and  throwing  the  weight  upon  it. 


S  a! 

FIG.  73. — Position  of  lower  limbs  at  commence 


II 


MECHANICS  OF  LOCOMOTOE  APPARATUS       115 


In  order  to  swing  forward  without  hitting  the  ground  the 
passive  lirub  must  shorten  slightly.  But  according  to  the  Webers' 
theory  this  is  not  due  to  contraction  of  the  flexors  of  the  thigh 
or  knee,  for  the  lower  limb  may  be  regarded  as  a  compound 
pendulum  which  in  oscillating  becomes  slightly  flexed  at  its 
articulations.  Eecent  investigation  has,  however,  modified  much 
in  this  theory. 

It  is  not  correct  to  say  that  the  limb  lifted  from  the  ground 
and  swinging  forwards  is  totally  passive.  Duchenne,  by  his 
clinical  observations,  demonstrated  the 
necessity  in  regular  walking  of  the 
active  intervention  of  the  flexors  of  the 
thigh,  the  tensor  fasciae,  the  psoas-iliac 
and  the  sartorius  muscles  to  shorten 
the  limb  and  avoid  contact  with  the 
ground  during  the  swing.  Marey,  too, 
showed  that  the  swing  of  this  limb 
could  not  be  regarded  as  passive,  since 
it  consists  in  a  progressively  acceler- 
ated movement,  and  must  therefore  be 
associated  with,  and  partly  dependent 
on,  muscular  force. 

In  order  to  obtain  a  more  exact  idea 
of  the  complex  movements  of  walking, 
the  way  the  feet  are  lifted  and  set 
down,  and  the  position  assumed  by 
the  limbs  at  their  principal  articula- 
tions in  each  phase  of  the  step,  graphic 
and  chronophotographic  methods  must 

hp  rp^nrrprl    in  FIG.  74.— Pedestrian  in  exploring  si s 

which  record  the  pressure  applied 
to    the    ground    upon    a    portable 

Marey   and    Carlet   were    the    first    who        apparatus.    (Marey.) 
applied    the    graphic    method    to    the    study 

of  the  complex  movements  of  walking  and  running.  Of  the  different 
instruments  which  Marey  invented,  the  most  important  are  the  shoes,  which 
register  the  pressure  applied  to  the  ground  by  the  individual  who  walks  or 
runs.  The  sole  of  these  shoes  contains  an  air-chamber  communicating  by  a 
tube  with  a  recording  tambour,  which  writes  upon  a  portable  revolving 
cylinder,  held  in  the  hand  of  the  individual  who  performs  the  experiment 
(Fig.  74).  The  air-chamber  lies  in  the  front  part  of  the  sole,  near  the  end 
of  the  metatarsus.  Accordingly  it  only  registers  the  pressure  exerted  upon 
the  anterior  part  of  the  foot  (Fig.  75).  Carlet  obtained  better  tracings  by  em- 
ploying soles  with  two  intercommunicating  air-chambers  placed  one  lu-ar 
the  heel,  the  other  near  the  front  of  the  metatarsus. 

Along  with  these  tracings  of  the  pressure  exerted  by  the  feet  while 
resting  on  the  ground,  Marey  and  Carlet  registered  the  vertical  oscillations 
of  the  head,  or  the  horizontal  oscillations  of  the  pelvis  (Figs.  75,  79),  by 
means  of  special  tambours. 

The  chronophotographic  method  which  Marey  applied  to  walking 
consists  in  recording  on  one  fixed  plate  the  successive  images  of  a  person 
walking.  The  photographic  apparatus  has  a  lens,  and  a  man  is  made  to 


116 


PHYSIOLOGY 


CHAP. 


walk  past  a  black  ground  with  a  white  net  on  his  back  which  is  vividly 
illuminated  by  direct  sunlight.  While  he  walks  a  rotating  apparatus  lets 
light  into  the  camera  obscura  at  regular  intervals.  At  each  instantaneous 
exposure  an  image  of  the  subject  in  different  postures  is  thrown  upon  the 
successive  parts  of  the  plate  (Figs.  82  and  84).  In  order  to  obtain  more 
images  at  each  cycle,  and  at  the  same  time  to  avoid  the  confusion  resulting 
from  their  superposition,  Marey  invented  the  ingenious  method  of  partial 


Km.  7-j.  —  Curve  of  walking.     (Marry.)     />,  movements  of  right  foot  ;  5,  of  left  foot  ; 

II,  vertical  oscillations. 


which  consists  in  suppressing  the  images  of  the  left  side  of 
the  body,  photographing  only  the  right  half  of  the  walker.  For  this 
purpose  the  left  half  is  clothed  in  black,  the  right  in  white  (Fig.  76). 
The  figures  of  each  step  can  similarly  be  multiplied  in  walking  or  run- 
ning by  increased  simplification  of  the  images.  For  this  the  subject  is 
clothed  entirely  in  black,  six  brilliant  metal  buttons  being  placed  on  the 
head  and  over  the  articulations  of  the  shoulder,  elbow,  thigh,  knee,  and  foot,  as 
well  as  five  shining  bands  over  the  bone  of  the  arm,  forearm,  thigh,  leg, 
and  edge  of  the  foot  (Fig.  77).  By  photographing  the  subject  as  he  walks 
forward  strongly  illuminated  by  the  sun,  the  chronophotogram  is  obtained, 
as  shown  in  Fig.  78,  where,  for  the  sake  of  simplification,  the  tracing  of  the 


Fiii.  76.— Photographs  of  right  half  of  body  of  a  subject  walking  slowly  iiasl  the  camera.     (Marey.) 

head  is  omitted,  since  it  shows  only  vertical  oscillations  which  are  perfectly 
comparable  at  every  step  with  those  of  the  dots  on  the  shoulder  and  thigh, 
as  shown  on  the  figure. 

A  later  improvement  on  Marey's  method  was  introduced  by  Braune  and 
Fischer,  who  substituted  for  the  dots  and  metal  bands  on  the  black  coat  of 
the  subject,  upright  Geissler's  tubes,  connected  with  the  conducting  wires 
of  a  circuit  which  included  a  big  Ruhmkorf  induction  apparatus.  The 
circuit  was  interrupted  at  equal  intervals,  which  lasted  O0383  parts  of  a 
second.  By  photographing  the  subject  as  he  wralked  not  only  along  a  plane 
parallel  with  the  sensitive  plate  but  also  along  other  planes,  Fischer  was 


II 


MECHANICS  OF  LOCOMOTOK  APPARATUS       117 


able  to  construct  a  curve  of  the  movements  of  various  joints  and  of  the  head, 
as  also  of  the,  movements  of  the  trunk,  etc. 

Fig.  80  is  a  diagram  of  the  cycle  of  walking  constructed  by  Zimmerman 
from  tlie  dmmophotographs  of  Fischer. 

The  tracing  (Fig.  79)  obtained  by  Carlet  with  his  exploring 
shoes  shows  that  in  the  usual  mode  of  walking  the  heel  is  first 
applied  to  the  ground,  then  the  whole  sole  of  the  foot,  and  lastly 
the  ball  of  the  toes  only ;  that  the  time  during  which  both  feet 
are  on  the  ground  is  less  than  half  the 
period  that  each  alone  rests  on  it ;  that 
the  time  of  the  rise  and  swing  of  one 
leg  is  always  shorter  than  that  of  the 
opposite  limb.  Carlet  demonstrated  by 
the  same  method  that  the  pressure  exer- 
cised by  the  foot  upon  the  ground  during 
a  step  is  not  equal  to  the  weight  of  the 
body,  but  that  in  the  last  stage  of  the 
step  an  additional  pressure  dependent 
on  the  muscular  forces,  which  raises  the 
body  and  propels  it  forward,  is  added. 
According  to  Carlet  the  additional  incre- 
ment of  pressure  varies  with  the  length 
of  the  steps  and  never  exceeds  20  kgrms. 

The  length  of  the  step  depends  on 
the  length  of  the  lower  limbs  and  the 
degree  in  which  the  knee  of  the  limb 
which  bears  the  weight  of  the  body  at 
the  commencement  of  the  step  is  flexed. 
Fig.  73,  which  shows  diagrammatically 
the  position  of  the  lower  limbs  at  the 
commencement  of  the  step,  makes  it 
plain  that  the  length  of  step  can  only 
increase  when  the  length  of  the  hypo- 
tenuse (i.e.  the  length  of  the  extended 
limb)  is  increased,  or  when  the  flexion 
of  the  knee  of  the  limb  on  which  the  weight  of  the  body 
falls  is  increased.  People  who  have  long  legs  and  long  feet 
naturally  take  longer  steps  than  short  people ;  and  if  they  walk 
together  the  latter  are  obliged  to  quicken  their  step  by  a  voluntary 
effort ;  this  is  done  by  increasing  the  flexion  of  the  knee  and 
dropping  the  centre  of  gravity.  If  the  knee  is  kept  rigid  and 
extended,  only  very  short  steps  are  possible,  and  a  greater  expendi- 
ture of  energy  than  usual  is  required. 

It  is  also  possible  to  vary  the  rate  of  the  step,  which  depends 
on  the  duration  of  the  application  of  one  or  both  feet  to  the  ground, 
that  is,  on  the  forward  swing  of  the  inactive  limb.  The  duration  of 
the  double  application  depends  on  the  will ;  the  more  hurried  the 


ing.  ChronophotograpMc  method. 
(Marey.) 


118 


PHYSIOLOGY 


CHAP. 


gait,  the  shorter  it  becomes,  and  according  to  the  Webers  in  very 
rapid  walking  its  duration  is  reduced  to  zero,  i.e.  one  leg  is  raised 
as  soon  as  the  other  touches  the  ground.  This,  however,  is  contra- 
dicted by  Carlet,  who  found  a  brief  period  in  which  both  feet  were 
on  the  ground,  even  in  the  most  rapid  gait.  The  rate  of  swing 
of  the  relatively  passive  limb  depends  on  the  stature  or  the  length 
of  limb.  The  shorter  the  limb,  the  more  rapid  the  swing. 

The  speed  of  walking  depends  upon  the  length  and  duration 
of  the  steps,  i.e.  the  distance  traversed  in  the  time  unit.    Numerous 


FIG.  78. — Chronophotograph  of  walking  ;  shows  the  successive  positions  taken  up  by  the  joints 
"and  bones  of  the  limbs  in  the  step.     (Marey.) 

experiments  of  the  "Webers  show  that  as  an  individual  increases 
the  length  of  his  steps  their  duration  diminishes,  so  that  when 
walking  at  full  speed  the  duration  of  the  steps  is  minimal  and  their 
length  maximal.  This  can  be  verified  from  the  figures  given  by 
the  Webers  in  the  following  table :— 


Duration  of  Step 
in  Seconds. 

Length  of  Step 
in  Millimetres. 

Speed  of  Walking 
in  Metres  per  Sec. 

0-335 

851 

2-397 

0-417 

804 

1-928 

0-480 

790 

1-646 

0-562 

724 

1-288 

0-604 

668 

1-106 

0-668 

629 

0-942 

0-846 

530 

0-627 

0-966 

448 

0-464 

1-050 

398 

0-379 

This  law  of  the  inverse  ratio  between  length  and  duration  of 
steps  only  holds,  according  to  Marey,  up  to  a  certain  point.    When 


II 


MECHANICS  OF  LOCOMOTOE  APPARATUS       119 


the  number  of  steps  exceeds  150  per  minute,  i.e.  when  the  duration 
of  the  step  becomes  less  than  0'4  second,  the  speed  of  walking 
does  not  increase  because  the  length  of  step  diminishes. 

The  force  of  walking  depends  on  the  extensor  muscles  of  the 
thigh,  leg,  and  foot. 

Fig.  80  gives  an  exact  idea  of  the  position  of  the  principal 
articulations  not  only  of  the  lower  limbs,  but  also  of  the  upper 
limbs  and  the  head  at  the  different  moments  of  the  step  cycle. 


123      4      567      g-     91011 


T23     4       567 


Fi<:.  79. — Tracings  of  the  pressure  applied  to  the  ground  in  walking.  (Carlet.)  I'd,  right  foot; 
P*.  left  foot;  Or,  vertical  oscillations;  On,  horizontal  oscillations.  1,  2,  3  =  period  of  double 
application;  3,  4,  5  =  period  of  single  application;  l-7  =  period  of  application  of  left  foot; 
5-11  =  period  of  application  of  right  lout  ;  1-3  and  5-7  =  application  of  heel  of  left  or  right  foot ; 
4-5  and  8-'.i  =  application  of  point  of  left  or  liuht  foot. 

The  cycle  begins  at  the  instant  in  which  the  left  leg  is  raised 
from  the  ground  and  swings  forward,  while  the  heel  of  the  right 
leg  rests  upon  the  ground. 

Each  step  is  divided  into  10  successive  phases  of  equal  duration, 
and  at  every  10th  phase  the  right  leg  is  in  the  position  originally 
occupied  by  the  left,  and  vice  versa.  From  the  1st  to  the  5th 
phase,  which  include  the  first  half  of  the  step,  the  left  knee 
becomes  flexed,  while  the  right  becomes  extended,  so  that  the  thigh 
and  shoulder  joints  (represented  by  the  junctions  of  the  black  and 
red  lines)  and  the  vertex  of  the  head  (represented  by  the  big  dots 
marked  on  the  upper  part  of  the  figure)  are  somewhat  raised. 
From  the  6th  to  the  10th  phase,  which  include  the  second  half  of 

i  1 


120 


PHYSIOLOGY 


CHAP. 


the  step,  the  left  leg  is  extended  forward  till  the  heel  touches  the 


o 

~~. 


to 

5 


30 

a 


o 

S 


00 


ground,  while  the  right  leg  first  rests  upon  the  ground  with  the 


ii          MECHANICS  OF  LOCOMOTOE  APPARATUS       121 

whole  sole  of  the  foot,  but  later,  as  the  heel  rises,  on  the  point  of  the 
foot  only.  In  the  first  half  of  the  step — owing  to  the  extension 
of  the  right  knee — there  is  an  upward  vertical  oscillation  of  the 
hip,  shoulder,  and  head  ;•  while  in  the  second  half  of  the  step  there 
is  a  downward  movement  owing  to  forward  flexion  of  the  right 
ankle,  and  parti}7  also  of  the  knee  on  the  same  side.  So  that  at 
each  step  there  is  a  douhle  vertical  oscillation  of  the  hip,  shoulder, 
and  head,  as  clearly  shown  by  the  figure.  According  to  the  Webers 
these  vertical  oscillations  attain  a  height  of  32  mm.,  according  to 
Carlet  of  37  mm.,  in  persons  of  average  height,  during  fairly  rapid 
walking;  they  increase  in  proportion  to  the  length  of  the  steps. 

Besides  these  vertical  oscillations,  the  top  of  the  head  and  the 
shoulders  and  hips  show  lateral  horizontal  oscillations  during 
walking,  which  are  very  apparent  on  looking  down  from  a  height, 
for  instance  from  a  window,  upon  a  person  walking  in  the  street. 
While  the  vertical  oscillations  coincide  with  the  length  of  a  step, 
the  horizontal  oscillations  correspond  to  the  double  steps  or  a  whole 
step  cycle.  These  lateral  horizontal  oscillations  reach  their  maximum 
at  the  same  moment  as  the  vertical  oscillations.  In  the  diagram 
of  Fitj.  80  the  maximal  lateral  oscillation  therefore  falls  to  the 

O 

right  at  the  5th  phase,  and  the  maximum  of  lateral  oscillation  to 
the  left  at  the  15th  phase.  The  further  apart  the  limbs  are  in 
walking,  the  more  pronounced  are  these  lateral  oscillations,  which 
evidently  depend  upon  the  degree  of  abduction  at  which  the  feet 
are  planted  upon  the  ground. 

The  oscillations  of  the  shoulders  and  hips  round  a  vertical  axis 
should  also  be  noted ;  these  accompany  the  lateral  oscillations  of 
the  trunk.  At  each  step  the  leg  that  is  moving  forward  is  accom- 
panied by  a  forward  movement  of  the  hips  and  a  backward  move- 
ment of  the  shoulders,  i.e.  a  slight  twist  of  the  trunk  round  a 
vertical  axis.  This  torsion  may  be  so  exaggerated  as  to  become 
very  apparent,  but  it  is  present  to  a  slight  extent  even  in  normal 
walking,  especially  in  women  with  a  large  pelvis.  The  forward 
movement  of  the  hips  is  also  due  to  the  swing  forward  of  the 
lower  limb  of  the  corresponding  side  and  the  active  contraction  of 
the  lumbar  muscles ;  the  backward  inclination  of  the  shoulders  is 
produced  by  the  swing  forward  of  the  upper  limb  of  the  opposite 
side,  which,  according  to  Duchenne,  is  not  purely  passive,  as  it 
depends  partly  on  contraction  of  the  deltoid  muscle.  Fig.  80  shows 
plainly  that  while  the  left  leg  swings  forwards,  the  right  arm 
becomes  more  and  more  flexed  at  the  elbow,  and  is  raised  and 
advanced.  This  torsion  of  the  trunk  and  active  oscillation  of  the 
upper  limbs,  which  balance  the  body,  increase  in  rapid  walking. 

These  simultaneous  and  opposite  movements  of  the  upper  and 
lower  limbs  in  the  ordinary  gait  of  man  correspond  with  the 
alternate  movement  of  the  four  limbs  in  the  ordinary  gait  of  the 
quadrupeds. 


122  PHYSIOLOGY  CHAP. 

Lastly,  it  should  be  noted  that  the  torsion  of  the  trunk  is 
always  accompanied  (particularly  in  hurried  walking  and  climbing) 
by  a  rhythmical  forward  movement  of  the  trunk  and  head  at  each 
stride.  This  movement,  which  overcomes  the  resistance  of  the  air 
and  economises  the  power  of  the  limbs  by  throwing  the  centre  of 
gravity  forward,  is  probably  the  effect  of  the  activity  of  various 
muscles,  especially  of  the  ilio-psoas. 

VI.  After  this  account  of  the  complex  mechanism  of  walking 
there  is  little  to  add  in  regard  to  running.  As  we  have  already 
pointed  out,  the  two  feet  are  never  on  the  ground  at  the  same 
moment  in  running,  and  one  foot  never  comes  in  contact  with  the 
ground  till  the  other  has  been  raised  from  it ;  the  entire  body  is 
consequently  suspended  for  a  moment  in  the  air.  This  is  shown 
by  the  tracing  taken  with  the  exploring  shoes  (Fig.  81).  It  can 
also  be  seen  with  instantaneous  photographs  upon  a  fixed  plate, 


FIG.  81. — Curves  nf  luiiniim,  traced  with  m-onliim  shoes.  (Matey.)  D,  movements  of  rijjlit  font  : 
S,  movements  of  left  tout  :  n.  \n  t  iciil  oscillations.  The  ai'plieation  of  the  foot  to  the  ground 
lie-ins  at.  the  moment  at  which  tin-  cuive  tises;  its  removal,  at.  the  moment  at  wliich  tin- 
curve  drops. 

when  the  exposures  occur  at  a  rhythm  corresponding  with  that  of 
the  two  phases  of  the  step  in  running  (Fig.  82). 

This  essential  difference  between  walking  and  running  depends 
upon  the  fact  that  in  running  the  extension  of  the  limb  upon  the 
ground  and  of  forward  displacement  of  the  body  is  more  marked, 
so  that  the  body  is  thrown  forward  and  raised  from  the  ground. 
During  the  moment  while  the  body  is  unsupported  in  the  air  the 
two  legs  swing  forward.  The  leg  which  gives  the  forward  impulse 
is  a  little  behind  during  the  swing,  and  a  little  forward  while  the 
other  leg  touches  the  ground. 

The  contact  of  each  foot  on  the  ground  is  shorter  in  running 
than  in  walking,  and  its  duration  is  inversely  proportional  to  the 
force  with  which  each  foot  is  applied  to  the  ground ;  this  increases 
with  the  rate  of  running.  The  frequency  of  contact  increases 
with  the  pace,  but  only  within  certain  limits,  beyond  which  the 
space  covered  in  a  certain  time  depends  more  on  the  length  of  the 
steps  than  on  their  number. 

The  absolute  duration  of  the  period  in  which  neither  foot  is  on 
the  ground  varies  very  little  with  the  variations  of  the  speed  of 
running ;  but  its  relative  duration  increases  considerably,  since, 


ii          MECHANICS  OF  LOCOMOTOH  APPARATUS       123 

as  was  said  above,  the  duration  of  the  contact  diminishes  with 
increased  speed. 

In  order  to  form  a  true  conception  of  the  mechanism  of 
running  it  is  very  instructive  to  ascertain  the  exact  moment  at 
which  the  vertical  oscillations  of  the  body  reach  their  maximum 
upward  excursion.  The  Webers  held  that  this  occurred  as  the 
body  is  projected  upward  and  forward  by  the  force  of  the  impulse 
given  by  the  rapid  extension  of  the  limb  in  contact  with  the 
ground.  Marey's  tracings  show,  on  the  contrary,  that  the  body 
attains  the  maximum  of  its  vertical  ascents  as  one  foot  conies  to 


FIG.  82.— Instantaneous  photograph  of  running— on  a  fixed  plate.     (Marey.) 

the  ground.  As  shown  by  curve  0,  Fig.  81,  the  head  begins  to 
rise  at  the  moment  at  which  the  foot  touches  the  ground,  and 
reaches  its  maximum  height  midway  through  the  period  of 
contact,  after  which  it  descends  and  reaches  its  minimum  at  the 
moment  when  the  foot  leaves  the  ground,  and  before  the  other 
foot  comes  into  contact  with  it,  i.e.  during  the  phase  of  suspension. 
This  proves  that  the  suspension  is  due  essentially  not  to  the 
sudden  extension  of  the  leg  but  to  its  subsequent  flexion,  which 
suddenly  withdraws  it  from  the  ground  after  giving  the  upward 
and  forward  thrust  to  the  body. 

Both  the  leg  on  the  ground  and  also  the  swinging  leg  are 
much  more  active  in  running  than  in  walking.  The  muscles  of 
the  upper  limbs  also  contribute  to  the  forward  thrust  of  the  body, 
since  they  oscillate  alternately  with  the  homologous  lower  limbs. 

The  torsion  of  the  trunk  round  a  vertical  axis  and  inclination 


124  PHYSIOLOGY  CHAP. 

of  the  shoulders  are  less  marked  in  running  than  in  walking.  On 
the  other  hand  the  inclination  of  the  trunk  forward  in  the  first 
period  of  the  contact,  and  backward  in  the  second  half,  is  much 
more  pronounced  in  running. 

The  speed  of  running,  according  to  the  statement  of  the 
Webers,  may  exceed  4'5  m.  per  second ;  anything  beyond  these 
limits  can  only  be  kept  up  for  a  short  distance. 

Galloping  differs  from  walking  and  running,  in  which  there  is 
a  regular  alternation  of  the  movements  of  the  limbs  on  the  two 
sides,  which  are  placed  on  the  ground  at  regular  intervals. 
Galloping  deserves  a  short  mention,  although  it  is  not  a  normal 
form  of  locomotion  in  man.  According  as  the  gallop  to  the 
right  or  to  the  left  is  imitated,  the  right  or  left  foot  is  put  forward 
at  each  step,  like  a  galloping  horse.  In  Fig.  83,  which  represents 


Fio.  83. — Tracing  of  galloping  to  the  right.     (After  Marey.)    D,  movements  of  right  foot; 
N,  of  left  foot ;  0,  vertical  oscillations. 

a  tracing  obtained  by  Marey  with  recording  shoes,  four  phases  can 
be  distinguished  in  the  gallop.  The  left  foot,  the  more  posterior, 
firsb  touches  the  ground  with  a  firm  and  prolonged  pressure ; 
while  the  left  foot  is  still  on  the  ground  the  right  foot  is  placed  in 
a  more  advanced  position  (double  contact),  but  with  less  and 
shorter  pressure ;  the  second  contact  is  at  once  followed  by 
elevation  of  the  left  foot  (simple  contact) ;  and  finally  conies  the 
rise  of  the  right  foot  also  (suspension),  which  lasts  a  perceptible  time 
before  the  tap  of  the  left  foot  begins  the  second  cycle.  Line  0  of 
the  figure  shows  that  the  two  taps  are  followed  by  two  slight 
elevations  of  the  head,  followed  in  turn  by  two  depressions,  most 
of  which  coincide  with  the  phase  in  which  the  whole  body  is 
unsupported  in  the  air. 

Jumping  consists  essentially  in  the  rapid  and  energetic 
extension  of  one  or  both  lower  limbs,  preceded  by  a  pronounced 
flexion,  by  which  means  the  body  is  thrown  upward  and  forward. 
The  mechanism  of  jumping  varies  considerably  according  to  its 
purpose. 

Chronophotographs  on  a  fixed  plate  of  the  successive  positions 
of  an  individual  who  is  jumping  over  a  hedge  or  ditch  (Fig.  84) 
show  that  during  the  spring  and  the  upward  and  forward  thrust 


ii          MECHANICS  OF  LOCOMOTOK  APPAEATUS       125 

of  the  body,  the  movement  is  much  more  rapid  than  in  coming 
down  again.  While  rising,  the  arms  are  pushed  forward  in  order 
to  raise  the  centre  of  gravity  and  increase  the  impulse  in  the 
direction  of  the  leap ;  during  the  descent,  on  the  contrary,  they 
are  thrown  back  to  lessen  the  momentum  of  the  body  at  the 
moment  at  which  it  touches  the  ground.  As  soon  as  the  feet 
come  in  contact  with  the  ground  the  knees  are  flexed  to  lessen 
the  counter-blow  and  the  shock. 

In  order  to  understand  the  essential  features  of  the  different 
gaits  which  we  have  been  discussing  the  diagram  suggested  by 
Marey  is  useful.  In  this  the  duration  of  the  contacts  of  the  right 
foot  is  shown  by  white  lines,  of  the  left  foot  by  shaded  lines,  the 
duration  of  the  elevation  of  either  limb  in  the  air  by  the  iuter- 


FIG.  84.— Instantaneous  photographs  of  a  long  jump — on  fixed  plate.     (Mai^y.) 

veiling  black  area.  It  is  a  kind  of  simplified  notation,  less 
complete  than  that  of  the  graphic  method  because  it  does  not 
indicate  the  pressure  exercised  by  the  foot  upon  the  ground  and 
its  variations ;  but  it  is  much  clearer  and  shows  at  a  glance  the 
fundamental  difference  between  the  different  gaits  (Figs.  85,  86). 
This  form  of  notation  is  almost  indispensable  in  differentiating  the 
various  gaits  of  quadrupeds. 

VII.  Swimming  differs  from  terrestrial  locomotion  inasmuch  as 
the  body  does  not  rest  on  the  ground,  but  is  immersed  in  water, 
which  is  a  fluid  medium. 

The  body  floating  in  water  may  be  compared  to  a  body 
resting  upon  a  supporting  plane,  formed  by  the  buoyancy  of  the 
fluid.  This  is  due  to  a  great  number  of  parallel  forces  which 
act  vertically  from  below  upward  on  the  lower  surface  of  the 
swimming  body.  The  resultant  of  these  forces  is  called  the  centre 
of  buoyancy,  which  corresponds  to  the  centre  of  gravity  of  the 
liquid  mass  displaced.  The  floating  body  may  thus  be  regarded  as 


126 


PHYSIOLOGY 


CHAP. 


suspended  by  its  centre  of  buoyancy,  and  to  be  in  equilibrium  it  is 
necessary  that  the  centre  of  gravity  and  the  centre  of  buoyancy 
shall  be  on  the  same  vertical  plane.  And  for  the  equilibrium  to 
be  stable  the  centre  of  gravity  of  the  floating  body  must  be  below 
the  centre  of  buoyancy.  Ships  are  all  constructed  on  this 


Fio.  S5.—  Diagram  of  four  different  gaits,  from  man.     (After  Marey.)     1,  walking  on  Hat  ground  ; 
2,  walking  uphill  and  upstairs  ;  3,  running  ;  4,  fast  running. 

principle,  i.e.  so  that  their  centre  of  gravity  shall  be  as  low  as 
possible  in  comparison  with  the  centre  of  buoyancy.  The  same 
principle  has  recently  been  applied  to  dirigible  airships  and 
aeroplanes. 

On  an  average  the  human  body  as  a  whole  is  heavier  than  fresh 
water  (I/O  10),  but  its  gravity  differs  little  from,  and  is  even  some- 
what less  than,  that  of  salt  water.  While  lying  on  his  back,  so 


Fio.  86.— Diagram  of  galloping  and  jumping.     (Marey.)    1,  galloping  to  the  left ;  2,  to  the  right ; 
3,  series  of  rhythmical  jumps  on  both  feet ;  hops  on  right  foot  alone. 

that  only  his  mouth  and  nose  are  above  the  water,  an  adult  man 
(especially  if  very  fat)  can  easily  float  on  the  sea,  if  he  keeps  all 
his  muscles  relaxed.  Thin  people,  however,  whose  average  specific 
gravity  is  rather  higher  than  that  of  salt  water,  are  unable  to 
float  in  the  supine  position  without  the  help  of  slight  impulsive 
movements  of  the  feet,  produced  by  rhythmical  extension  of  the 
legs.  In  order  to  move  in  this  position  it  is  necessary  to  supple- 


ii          MECHANICS  OF  LOCOMOTOK  APPARATUS       127 

ment  the  movements  of  the  legs  by  slight  rowing  movements  with 
the  arms. 

Swimming  with  the  abdomen  downwards  is  more  difficult, 
either  because  the  centre  of  gravity  is  above  the  centre  of  dis- 
placement or  because,  as  the  head  and  neck  are  out  of  water,  the 
weight  of  the  body  is  consequently  greater  than  that  of  the  water 
displaced. 

The  mechanism  of  swimming  consists  essentially  in  exercising 
pressure  upon  the  water  rhythmically  from  above  downwards,  and 
from  before  backwards  with  the  surface  of  the  hands  and  feet,  so 
as  to  cause  a  reaction  of  the  water  displaced,  which  is  able  to  raise 
the  body,  prevent  it  from  sinking,  and  impel  it  forward  in  the 
required  direction. 

The  details  of  the  mechanism  of  swimming  have  been  little 
studied  since  graphic  methods  cannot  be  applied,  and  chrono- 
photography  is  difficult.  Moreover,  swimming  is  not  natural  to 
man,  but  is  an  art  which  he  learns  and  perfects  by  practice. 
Accordingly  there  is  no  fixed  and  constant  mode  of  swimming, 
and  the  movements  of  the  upper  and  lower  limbs  adopted  by 
different  swimmers  are  not  exactly  alike.  Generally  speaking, 
there  is  an  initial  thrust  forward  on  the  surface  of  the  water  by  a 
rapid  extension  and  adduction  of  the  legs,  on  which  the  water  is 
displaced  backwards  and  toward  the  bottom  by  the  feet,  producing 
a  reaction  which  raises  the  body  of  the  swimmer  and  jerks  it 
forward.  This  movement  of  the  lower  limbs  is  accompanied  with 
a  forward  thrust  of  the  arms,  which  are  brought  together  in  front. 
The  arms  are  then  moved  outwards,  backwards,  and  slightly 
downwards,  this  being  perhaps  more  efficacious  in  swimming 
than  the  initial  movement  of  the  lower  limbs.  This  movement 
is  associated  with  retraction  and  abduction  of  the  legs,  which 
completes  the  natatory  cycle. 

If  the  swimming  movements  are  too  strong  and  rapid,  they 
are  fatiguing  and  of  little  use.  Both  hands  and  feet,  which  act  as 
the  blades  of  an  oar,  press  on  the  water  with  the  maximum  available 
surface,  and  return  to  the  starting  position  with  a  slower  move- 
ment, and  at  the  same  time  present  the  smallest  possible  surface 
to  the  water. 

BIBLIOGRAPHY 

BORELIJ.     De  motu  animalium,  etc.     Rome,  1680. 

ED.  and  W.  WEBER.     Mechanik  der  menschlichen  Gehwerkzeuge.     Guttingen,  1836. 
DUCHENNK..     Phys.  des  mouvements,  1867. 
CARLET.     fitude  sur  la  locomotion  humaiiie,  1872. 
MAREY.     La  machine  animale,  1879. 

G.  H.  MEYER.     Die  Statik  und  Mechanik  des  menschlichen  Knochengeriistes,  1873. 
PETTIGREW.     La  locomotion  chez  les  animaux,  1874. 
A.  FICK.     Hermann's  Handbuch  der  Physiol.,  I.,  1879. 

W.  BRAUNE  and  0.  FISCHER.     Abhandlungen  der  rnath.-phys.  Klasse  der  konig. 
sachs.  Gesellsch.  der  Wissenschat'ten,  1885-1904. 


128  PHYSIOLOGY  CHAP,  n 

MAREY.     Developpement  de  la  methode  grafique  par  1'emploi  de  la  photographic. 

Paris,  1885.     Le  mouvement,  1894. 

0.  FISCHER.     Arch.  f.  Anat.  und  PhysioL,  Anat.  Abt.,  1S96. 
R.    DU   BOIS-REYMOND.     Ergebnisse  d.    PhysioL,    II.,   Part  ii.,  1903.     (Contains 

many  references. )    Spezielle  Muskel physiologic  oder  Bewegungslehre.     Berlin, 

1903. 

Recent  English  Literature  :— 

SHERRINGTON.      Remarks  on  the  Reflex  Mechanism  of  the   Step.     Brain,   1910, 

xxxiii.  1. 
GRAHAM  BROWN.    The  Intrinsic  Factors  in  the  Act  of  Progression  in  the  Mammal. 

Proc.  Roy.  Soc.,  London,  1911,  B.  Ixxxiv.  308. 
GRAHAM   BROWN.     Note  on  the  Movements  of  Progression  in  Man.     Journ.   of 

PhysioL ,  1912,  xlv.  p.  xvii. 
GRAHAM    BROWN.      Dynamic    Principles   involved    in    Progression.      Brit.   Mt>d. 

Journ.,  1912,  ii.  285. 


CHAPTER   III 

PHONATION    AND    ARTICULATION 

CONTENTS. — 1.  General  observations  on  the  fundamental  characters  of  sounds, 
and  their  formation  by  different  musical  instruments.  2.  Structure  of  larynx  as 
a  musical  instrument  ;  functions  of  laryngeal  muscles.  3.  Nerves  and  centres  of 
phonation.  4.  Mechanical  conditions  for  the  production  of  laryngeal  sounds  ; 
function  of  different  parts  of  the  phonatory  system.  5.  Principal  characteristics 
of  the  singing  voice.  6.  Difficulties  and  natural  imperfections  of  singing. 
7.  The  vowel  system  in  phonetic  language.  8.  Theory  of  physical  nature  of 
vowel  tones.  9.  System  of  semivowels  or  sounding  consonants,  middle  consonants 
and  mute  consonants.  10.  Composition  of  syllables  and  words.  11.  Writing,  or 
graphic  language.  Bibliography. 

BOTH  in  animals  and  man  movement  may  be  regarded,  broadly 
speaking,  as  the  external,  conscious  or  unconscious,  manifestation 
of  the  mental  state.  But  it  is  essential  to  discriminate  between 
the  movements  which  betray  only  instinct  and  feeling,  and  the 
expressional  movements  which  are  the  means  of  intellectual 
communication. 

These  expressional  movements  and  attitudes  taken  as  a 
whole  constitute  natural  language,  and  are  of  special  artistic  and 
psychological  interest.  From  the  physiological  point  of  view 
they  present  no  difficulties ;  they  can  be  explained  on  simple 
anatomical  principles,  and  by  the  general  laws  of  mechanics, 
which  were  discussed  in  the  last  chapter. 

The  natural  language  and  the  vocal  expression  of  animals 
constitute  our  only  objective  basis  for  the  construction  of  a 
comparative  psychology.  This  language  consists  of  gestures, 
ejaculatory  sounds  or  noises,  and  physiognomic  attitudes,  which 
are  partly  imitative  (onomatopoeic)  and  to  a  far  larger  extent 
instinctive,  developed  according  to  the  laws  of  heredity  and 
atavism.  In  this  language  there  is  nothing  conventional ;  it  is 
intelligible  to  all,  without  instruction  or  effort.  Without  such 
a  language  animals  would  be  unable  to  herd  together,  unite  in 
families  and  societies,  defend  themselves  from  their  enemies, 
migrate  in  flocks  at  certain  seasons,  etc. 

As  a  general  rule  it  may  be  said  that  natural  language  is 
most  complete  in  the  more  intelligent  animals.  In  different 

VOL.  Ill  129  K 


130  PHYSIOLOGY  CHAP. 

animals,  again,  different  organs  or  parts  have  the  task  of  expression. 
In  the  higher  mammals  it  is  the  face  which  by  the  mobility  of 
its  muscles  lie  trays  most  expression,  and  in  many  mammals — but 
not  in  man — the  ears  contribute  greatly  to  expression  by  their 
varied  movements ;  the  nose,  lips,  and  mouth  play  a  considerable 
part  in  physiognomy.  In  some  animals,  again,  the  movements  of 
the  tail  and  feet  are  significant.  Lastly,  the  different  postures  of 
the  body  as  a  whole  play  a  great  part  in  expression.  Painters, 
sculptors,  actors,  all  make  special  studies  of  the  natural  language, 
both  in  animals  and  man.  They  devote  themselves  to  observing 
and  minutely  analysing  postures  and  deciphering  their  psycho- 
logical significance,  in  order  to  reproduce  them  effectively  in 
works  of  art  or  dramatic  representations. 

I  Hit  the  chief  means  by  which  the  animal  expresses  its  feelings, 
wants,  and  passions  is  the  voice,  i.e.  the  inarticulate  or  scarcely 
articulate  sounds  and  noises  which  are  characteristic  of  different 
species. 

In  deaf  mutes  the  language  of  gesture  attains  a  high  develop- 
ment, and  is  able  to  fulfil  all  the  needs  of  social  life.  But  under 
normal  conditions  the  mimetic  language  of  man  is  almost  always 
accompanied  by  phonetic  language,  or  speech,  and  merely  serves 
to  reinforce  and  elucidate  expression. 

Voice  production  is  not  the  direct  effect  of  muscular  activity, 
but  is  due  to  the  vibrations  produced  in  a  particular  apparatus, 
the  larynx,  which  is  a  true  musical  instrument.  Nevertheless,  as 
it  is  muscular  contraction  which  produces  the  degree  of  tension 
in  the  vocal  cords  that  is  essential  to  the  formation  of  the  different 
sounds,  the  study  of  phonation  (speech)  is  closely  connected  with 
the  study  of  movements. 

The  formation  of  words,  i.e.  articulate  speech,  is  a  more 
complex  process,  which  is  not  limited  to  the  larynx,  but  also 
depends  on  the  production  of  non-musical  noises  by  the  current 
of  expired  air  as  it  passes  through  the  pharynx,  buccal  cavity, 
and  nasal  fossae.  Consequently,  laryiigeal  phonation  is  not  in- 
dispensable to  conversation,  any  more  than  verbal  articulation  is 
necessary  to  singing.  It  is  possible  to  whisper  without  using 
the  vocal  cords,  and  to  sing  vocally  without  words. 

I.  Since  the  voice  is  an  acoustic  phenomenon  with  musical 
characters,  the  organ  which  produces  it  may  be  considered  as  a 
musical  instrument.  In  order  to  understand  its  function  in 
speech,  it  is  well  to  glance  briefly  at  the  fundamental  principles 
of  the  production  and  characteristics  of  tones  in  general. 

All  elastic,  solid,  fluid,  or  gaseous  bodies  are  capable  of 
vibrating  so  as  to  produce  auditory  sensations,  that  is,  tones  or 
noises.  A  tone,  according  to  Helmholtz,  is  any  auditory  sensation 
produced  by  regular  rhythmical  vibrations ;  a  noise  is  a  sensation 
due  to  irregular  and  non-rhythmical  vibrations. 


in  PHONATION  AND  ARTICULATION  131 

Simple  sounds  or  tones  are  composed  of  pendular  vibrations, 
i.e.  to-and-fro  movements  of  the  vibrating  molecules  which  follow 
the  same  laws  of  motion  as  a  pendulum.  These  vibrations  only 
differ  in  amplitude  and  duration  :  the  amplitude  is  directly  pro- 
portional to  the  loudness  of  the  sounds  ;  the  duration  is  inversely 
proportional  to  the  number  of  vibrations  per  second,  on  which  the 
pitch  of  the  sound  depends.  The  form  of  the  pendular  vibrations 
is  constant  and  invariable.  They  can  be  graphically  recorded 
by  making  a  tuning-fork  trace  its  vibrations  on  a  revolving 
cylinder. 

Helmholtz  distinguishes  "simple  tones"  or  sounds  (Ton)  from 
"  compound  tones  "  (.Klang),  which  are  an  aggregate  of  the  simple 
tones  produced  by  simple,  pendular  vibrations.  While,  the  form 
of  vibration  in  simple  tones  is  always  the  same,  that  of  compound 
tones  varies  considerably,  and  depends  on.  the  algebraic  sum  of  the 
component  tones.  The  deepest  of  these  tones  is  called  the  prime 
tone,  and  the  rest  are  the  harmonics,  or  over-tones.  The  vibration 
frequency  of  the  prime  tone  to  that  of  the  partial  tones  is  in  the 
ratio  of  1  :  2  :  3,  etc. 

The  number  of  partials  which  make  up  a  compound  tone,  and 
their  relative  strength,  differs  considerably  for  different  musical 
instruments,  even  when  the  prime  tone  is  the  same.  This  difference 
gives  rise  to  the  quality  (timbre,  Klangfarbe]  of  a  note,  which 
depends  on  the  particular  form  of  the  vibration  of  the  tone,  due  to 
the  relative  number  and  strength  of  its  harmonic  overtones. 

A  compound  tone  can  be  resolved  into  its  partial  tones  by 
means  of  resonators.  All  sounding  bodies  have  their  own  note  ; 
when  made  to  vibrate,  they  invariably  give  out  a  note  of  a  certain 
pitch,  which  corresponds  with  a  certain  frequency  of  vibration  per 
second.  When  the  surrounding  air  transmits  to  the  sounding 
body  a  number  of  vibrations  corresponding  to  its  proper  note,  it 
begins  to  vibrate  in  unison.  When,  on  the  contrary,  the  vibration 
frequency  does  not  correspond  with  the  frequency  of  its  own  note, 
it  remains  at  rest,  or  vibrates  very  feebly.  Given  a  series  of  hollow 
metal  chambers  (resonators)  tuned  to  different  notes  of  the  musical 
scale,  it  is  possible  to  analyse  compound  tones  into  their  partials. 
When  one  ear  is  stopped,  and  the  other  is  applied  to  the  aperture 
of  a  resonator,  each  resonator  reinforces  its  own  note  and  cuts 
out  all  the  rest  (Helmholtz).  Konig's  manometric  flame  method, 
described  in  text-books  of  physics,  renders  visible  the  partials 
contained  in  a  compound  tone. 

Another  mode  of  analysing  complex  sounds  is  based  on  the 
phonautographic  curves  traced  by  means  of  the  thin  membranes 
used  in  phonographs  with  a  very  light  lever,  or  a  small  mirror 
that  reflects  a  beam  of  light  011  to  a  travelling  sensitive  surface 
(Hermann's 


Musical    instruments    can    be    classified    according    to    the 


132  PHYSIOLOGY  CHAP. 

way  in  which  their  sounds  are  produced  ;  the  principal  forms  are 
stringed  instruments,  wind  instruments,  and  reed  pipes. 

In  stringed  instruments  the  notes  produced  by  the  vibrations 
of  the  strings  are  enormously  reinforced  by  the  resonance  boxes. 
The  pitch  varies  with  the  length,  tension,  density,  and  thickness 
of  the  stretched  string. 

The  frequency  of  vibration  per  second,  on  which  the  pitch 
depends,  is  inversely  proportional  to  the  length  of  the  string.  A 
string  vibrating  over  its  whole  length  gives  out  the  deepest  note  ; 
if  the  length  is  halved,  the  frequency  of  vibration  is  doubled,  and 
the  pitch  is  raised  an  octave ;  with  a  third  of  its  length  the 
frequency  will  be  three  times  as  great,  i.e.  a  twelfth,  and  so  on. 

The  frequency  of  vibration  varies  directly  as  the  square  root 
of  its  stretching  force.  In  order  to  raise  by  an  octave  the  pitch 
of  the  note  given  by  the  string,  the  tension  would  require  to  be 
increased  four  times. 

The  frequency  of  vibration  varies  inversely  as  the  mass  of  unit- 
lengths  of  the  string.  Thicker  and  heavier  strings  vibrate  less 
rapidly  and  therefore  have  a  deeper  tone. 

Wind  instruments  differ  from  stringed,  since  the  air  is  here  the 
resonant  body,  and  the  walls  of  the  pipe  in  which  the  air  vibrates 
affect  only  the  timbre,  i.e.  the  number  and  strength  of  the  partials. 
The  pitch  of  the  fundamental  tone  depends  on  the  dimensions  of 
the  pipe,  and  the  strength  of  the  blast  of  air  passing  through  its 
aperture.  The  narrower  and  shorter  the  pipe,  the  higher  is  the 
pitch ;  the  greater  the  tension  of  the  vibrating  air  molecules,  the 
more  rapid  are  the  vibrations,  and  the  higher  the  frequency  per 
second. 

Eeed  instruments  (oboe,  clarinet,  bassoon)  only  differ  from 
other  wind  instruments  by  the  fact  that  their  aperture  is  not 
fixed  and  constant,  but  is  formed  of  two  vibrating  tongues,  which 
rhythmically  enlarge  and  reduce  the  opening  by  which  the  air 
penetrates  into  the  tube.  According  to  Helruholtz  the  vibrations 
of  the  tongues  are  pendular,  and  they  can  only  give  out  simple 
tones.  The  compound  tones  of  these  instruments  depend  on  the 
vibration  of  the  air  in  the  pipes ;  the  tongues  merely  regulate  the 
entrance  of  the  air  blast  by  rhythmically  alternating  the  diameter 
of  the  opening,  which  breaks  up  the  column  of  air  into  a  series  of 
rapid  blasts. 

Instruments  with  rigid  tongues  must  be  distinguished  from 
those  with  soft  or  membranous  tongues,  which  are  represented  in 
brass  instruments  (trumpets,  horns,  etc.)  by  the  lips  of  the  performer. 
In  these  instruments  the  number  of  the  vibrations  is  inversely 
proportional  to  the  length  and  diameter  of  the  vibrating  membrane, 
and  directly  proportional  to  its  tension  and  elasticity  and  to  the 
strength  of  the  air-current  thrown  into  vibration.  The  width  of 
the  aperture  does  not  appear  to  influence  the  pitch  of  the  note 


Ill 


PHONATION  AND  AKTICULATION 


133 


produced  by  membranous  tongues,  but  its  formation  is  easier 
in  proportion  as  the  slit  is  narrower.  The  extra  tubes  which 
form  the  body  of  these  instruments  have  a  great  influence  on  pitch 
and  timbre ;  the  tones  become  deeper  as  the  body  is  longer,  but 
never  drop  an  octave  as  is  the  case  in  instruments  with  rigid  lips. 
As  a  musical  instrument  the  larynx  has  many  points  of 
resemblance  with  tongued  instruments.  The  formation  of  laryn- 
geal  sounds  depends  on  the  passage  of  air  through  a  slit  (opening 
of  the  glottis)  which  is  rhythmically  altered  in  width  by  the 
vibration  of  membranous  tongues  (the  vocal  cords)  so  as  to  break 
up  the  air  blast  that  passes  through  it.  The  wind-pipe  is  formed 
by  the  bronchi  and  trachae, 
as  in  brass  instruments  ;  the 
sounding -pipe  or  resonator 
by  the  cavities  lying  above 
the  glottis,  i.e.  the  larynx  and 
pharynx,  the  mouth  and  the 
nose.  On  the  other  hand 
the  vocal  apparatus  is  dis- 
tinguished from  all  tongued 
musical  instruments  by  the 
fact  that  the  vocal  cords 
which  represent  the  tongues 
can  change  at  any  moment 
in  length,  breadth,  diameter, 
and  tension,  even  independ- 
ently of  the  pressure  of  the 

air    blast  which    thrOWS    them    Fl°-  S7.— Laryngeal  cartilages,   seen   from    behind. 

(Henle.)  t,  thyroid  cartilage:  Cs,  i.'l,  its  superior 
and  inferior  horns;  Pm,  Pr,  processus  muscnlus 
and  vocalis  of  arytenoid  cartilage  ;  co,  cartilage 
of  Santorini  ;  <•;•,  cricoid  cartilage. 


cr 


into  vibration. 

A  clear  idea  of  the  con- 
struction   of    the    larynx    is 
essential    in    order   to   understand    the    complex    mechanism   of 
phonation. 

II.  The  larynx  consists  of  a  cartilaginous  skeleton  which  is  only 
partially  ossified.  The  laryngeal  cartilages  are  united  by  fibrous 
membranes,  ligaments,  small  articular  capsules,  and  by  a  series  of 
small  muscles,  which  constrict  or  dilate  the  glottis,  stretch  or  relax 
the  vocal  cords,  and  regulate  the  thickness  of  their  vibrating 
portions. 

The  cricoid  cartilage  is  shaped  like  a  signet  ring  with  its  narrow 
part  forward,  and  its  face  backward.  Its  lateral  surface  articulates 
with  the  inferior  cornua  of  the  thyroid  cartilage.  The  two 
cartilages  can  rotate  round  the  horizontal  axis  of  these  articular 
surfaces,  the  anterior  surface  of  the  thyroid  may  be  displaced 
forwards  and  downwards,  or  the  front  part  of  the  cricoid  cartilage 
may  be  pushed  up  towards  the  thyroid.  The  triangular  bases  of 
the  two  arytenoid  cartilages  articulate  at  the  upper  margin  of  the 

K  1 


134 


PHYSIOLOGY 


CHAP. 


cricoid  plate  on  both  sides  of  the  median  line  by  oval  saddle-shaped 
joints,  which  allow  of  their  rotation  on  their  base,  and  the  dis- 
placement of  the  base  inward  or  outward.  The  stout  crico- 
arytenoid  ligament  controls  the  back  to  front  movement  of  the 
arytenoids.  At  the  summit  of  the  latter  comes  the  articulation  of 
the  two  little  cartilages  of  Santorini  (Figs.  87,  88,  89). 

The  thyroid  cartilage  is  attached  to  the  hyoid  bone,  which  lies 
above  it,  by  a  fibrous  membrane,  the  thyro-hyoid  (known  in  its 
middle  portion  as  the  ligamentuni  thyreo-hyoideum  lateralis),  and 
by  the  lateral  thyro-hyoid  ligament,  which  runs  from  the  superior 
cornua  of  the  thyroid  to  the  great  cornua  of  the  hyoid.  By  means 


-Cs 


Pi — 3 


FIG.  88.—  (Left.)    t,  thyroid,  and  cc,  cricoid  cartilages,  from  the  side.    (Henle.) 

FIG.  89. — (Right.)  Laryngeal  cartilages  divided  through  the  median -sagittal  plane,  and  viewed 
from  within.  (Henle.)  /,  thyroid  cartilage  ;  Cs,  its  upper  horn  ;  Pi',  processus  vocalis  of 
arytenoid  ;  co,  cartilage  of  Santorini ;  er,  cricoid  cartilage. 

of  these  membranes  and  ligaments  the  whole  larynx  can  be  drawn 
upwards. 

Behind  the  thyro-hyoid  membrane  is  the  epiglottis,  which  is 
attached  below  the  thyro-epiglottidean  ligament  to  the  median 
notch  of  the  thyroid,  and  projects  into  the  pharyngeal  cavity  in  the 
form  of  a  tongue  which  is  folded  back  in  swallowing  and  forms  a 
lid  for  the  upper  opening  of  the  larynx  (Figs.  90,  91,  92). 

On  both  sides  of  the  free  portion  of  the  epiglottis  the  mucous 
membrane  forms  a  fold  that  unites  the  upper  margin  of  this 
cartilage  with  the  cartilages  of  Sautorini.  In  the  depth  of  this 
aryteiio-epiglottidean  fold  there  is  a  group  of  mucous  glands  and  a 
nodule  known  as  the  cuneiform  cartilage,  or  cartilage  of  Wrisberg. 
The  aryteno-epiglottidean  fold  limits  the  upper  opening  of  the 
larynx  ;  it  is  oval  in  form  and  is  inclined  backwards  and  downwards. 

The  laryngeal  cavity  narrows  into  the  glottis  or  rima  glottidis. 


Ill 


PROBATION  AND  AKTICULATION 


135 


Here  the  mucous  membrane  forms  on  each  side  two  thick  trans- 
verse ridges  which  extend  from  the  base  of  the  epiglottis  backwards 
to  the  vocal  processes  of  the  arytenoids.  The  two  upper  ridges  are 
known  as  the  false,  and  the  two  lower  as  the  true  vocal  cords.  The 
former  project  less  towards  the  median  line  of  the  glottis  than  the 
latter.  Between  the  true  and  false  vocal  cords  are  two  recesses, 
known  as  the  ventricle  of  Morgagni  (Fig.  94). 

The  elastic  fibres  of  the  submucosa  are  highly  developed  in  the 


fas 


tat 


J.f- 


FIG.  90. —Laryngeal  cartilage  with  fascia,  ligaments,  and  insertions  of  certain  muscles.  (Henle.) 
Oli,  hyoid  bone;  e,  epiglottis;  Cs,  superior  horn  of  thyroid  cartilage;  he,  hyo-epiglottic 
ligament ;  Jitl,  lateral  hyo-thyroid  ligament ;  tr,  cartilage  tritica  ;  tc,  thyro-epiglottie  cartilage  ; 
ca,  crico  -  arytenoid  cartilage:  tas,  tai,  superior  and  inferior  thyro  -  arytenoid  ligaments; 
Cap',  Cap",  insertions  of  posterior  crico-arytenoid  muscle  ;  Lp,  insertion  of  laryngo-pharyngeal 
muscle. 

true  vocal  cords,  and  form  compact  bands  which  run  through  their 
whole  length ;  they  are  wedge-shaped  in  cross-section,  and  covered 
by  a  layer  of  non-ciliated  pavement  epithelium.  In  the  false  vocal 
cords  the  elastic  connective  tissue  is  much  less  abundant,  and  the 
mucous  membrane  that  covers  it  is  rich  in  adenoid  tissue,  which  is 
even  more  plentiful  in  the  laryngeal  ventricles  and  on  the  posterior- 
inferior  surface  of  the  epiglottis.  The  mucous  membrane  of  these 
parts  soon  becomes  oedematous  from  accumulation  of  lymph  in  the 
lymph-spaces,  which  may  obstruct  respiration  and  cause  suffocation 
by  closure  of  the  glottis. 

Owing  to  their  elasticity  the  true  vocal  cords  extend  and  con- 
tract without  falling  into  folds,  and   their   delicate  free  edges, 


136 


PHYSIOLOGY 


CHAP. 


which  are  thrown  into  vibration  by  the  expiratory  blast,  remain 
regular. 

The  two  true  vocal  cords  which  extend  from  their  anterior 
insertion  on  the  thyroid  to  the  vocal  processes  of  the  arytenoids, 
into  which  they  are  inserted  posteriorly,  form  the  pars  vocalis  of 
the  glottis,  the  average  length  of  which  in  the  adult  male  is  18 '2 
mm.  according  to  Miiller,  17'5  mm.  according  to  Harless,  in  the 
female  12'6  mm.  according  to  Miiller,  13-5  mm.  according  to  Harless. 
The  posterior  part  of  the  glottis,  which  is  7 -8  mm.  long,  and 


FK;.  91.— Larynx  from  behind,  after  removing  a  portion  of  the  aryepiglottidean  fold  and  upper 
posterior  portion  of  left  thyroid  cartilage.  (Henle.)  Taep,  thyro-ary-epiglottidean  muscle  ; 
Cap,  posterior  crico - ary tenoid  muscle;  A,  arytenoid  muscle;  x,  kerato - cricoid  muscle; 
kcps,  posterior,  superior,  kerato-crieoid  ligament ;  co,  cartilage  of  Santorini ;  *,  mucous  glands 
iu  tlie  aryepiglottic  fold. 

extends  from  the  posterior  ends  of  the  vocal  cords  to  the  intra- 
arytenoid  fold,  is  bounded  by  the  arytenoids,  and  is  known  as  the 
rirna  glottidis  respiratoria  or  intercartilaginea. 

The  laryngeal  muscles  dilate  and  constrict  the  glottis,  and 
extend  and  relax  the  vocal  cords.  These  effects  for  the  most,  part 
depend  not  on  the  action  of  a  single  muscle,  but  on  the  co-ordinated 
play  of  several,  which  makes  it  harder  to  obtain  any  exact  know- 
ledge of  the  function  of  each  separate  muscle  when  they  are 
working  together. 

The  two  posterior  crico-aryteuoid  muscles  are  the  chief,  if  not 
the  only  dilators  of  the  glottis ;  owing  to  their  attachments 
and  the  oblique  course  of  their  fibres  they  rotate  the  bases  of  the 


Ill 


PHONATION  AND  AKTICULATK  >X 


137 


arytenoids  round  their  vertical  axis,  and,  therefore,  draw  the  two 
muscular  processes  of  the  arytenoids  down  and  back,  and  con- 
sequently further  from  the  median  line,  and  at  the  same  time 
raise  the  two  vocal  processes.  Isolated  contraction  of  these 
muscles  must  therefore  abduct  the  vocal  cords  and  dilate  the  rima 
glottidis ;  their  paralysis  must,  on  the  other  hand,  produce  in- 
spiratory  dyspnoea  owing  to  abnormal  constriction  of  the  rima,  but 
it  does  not  cause  appreciable  disturbance  of  phonation. 

The   constriction  of   the   glottis   is   produced  chiefly   by    the 

Oh 


.} tr 


cl 


FIG.  M.—  Larynx  and  hyoid  bone,  from  the  front.  (Henle.)  Oh,  hyoid  bone;  litl,  lateral  hyo- 
thyroid  ligament ;  if,  cartilage  tritica  ;  htm,  median  hyo-thyroid  ligament ;  ct,  crieo-thyroid 
ligament;  Pp,  inferior  extremity  of  palato-pharyngeal  muscle;  Th,  thyro-hyoid  muscle;  Cir, 
erico-thyroid  muscle  divided  into  three  bundles  ;  the  vertical  bundle  on  the  left  side  has  been 
removed  to  show  the  crico-thyroid  ligament  i:t. 

transverse  arytenoid  muscle,  which  runs  between  the  outer 
posterior  borders  of  the  arytenoids,  and  by  contracting  draws  the 
two  bases  of  these  cartilages  towards  the  middle  line,  and  their 
mesial  surfaces  together,  so  that  the  intercartilaginous  glottis 
is  closed.  When  this  muscle  is  divided  in  any  animal,  the 
posterior  portion  of  the  glottis  remains  fully  open. 

Other  muscles  also  are  concerned  in  the  active  closure  of  the 
glottis  ;  they  co-operate  with  the  transverse  arytenoids  to  form 
a  kind  of  laryngeal  sphincter.  Among  these  are  the  thyro- 
aryepiglottidean,  and  the  thyro-arytenoid  muscles.  The  two  first 
run  from  their  point  of  attachment  on  the  inner  surface  of  the 
thyroid  obliquely  backwards  over  the  two  posterior  surfaces  of 


138 


PHYSIOLOGY 


CHAP. 


the  arytenoids,  where  they  cross  in  the  median  line,  and  then 
run  along  in  the  aryteno-epiglottidean  fold  to  be  inserted  in 
the  base  of  the  epiglottis.  The  two  latter  start  from  the  lower 
part  of  the  internal  angle  of  the  thyroid,  and  turn  backwards 
and  upwards  to  the  muscular  processes  of  the  arytenoid.  The 
chief  function  of  these  muscles  is  to  constrict  the  glottis,  and 
reinforce  the  transverse  arytenoid  muscle. 

The  lateral  crico-arytenoid  muscle  also  aids  in  the  abduction 
of  the  vocal  cords.     This  muscle  runs  obliquely  from  behind  and 


CO 


£M cap 


Fin.  93.  — Side  view  of  larynx,  utter  exarticula- 
tion  and  removal  of  left  plate  of  thyroid 
cartilage.  (Henle.)  Sat,  articular  surface  of 
thyroid  with  cricoid  ;  (jap  and  ( 'al,  crico- 
arytenoid  muscles,  posterior  and  lateral  ; 
co,  cartilage  of  Santorini,  below  which  the 
arytenoid  and  thyro-epiglottidean  muscles 
(Fig.  91)  are  seen  in  profile. 


ct 


Fie.  94. — Frontal  section  of  larynx,  the  anterior 
half  viewed  from  behind.  (Henle.)  t,  thyroid; 
cr,  cricoid  ;  a,  plica  ary-epiglottica ;  Taep, 
thyro-ary-epiglottidean  muscle ;  Toe  and 
Tai,  thyro-aryitenoid  muscles,  external  and 
internal :  1,  tubercle  of  epiglottis  ;  2,  3,  ven- 
tricle ;  4,  plica  thyreo-arytaenoidea  superior 
or  false  vocal  cord;  5,  plica  thyreo-ary- 
taenoidea inferior,  or  true  vocal  cord. 


above,  forward  and  downward,  viz.  in  the  opposite  direction  to  the 
posterior  crico-arytenoid  or  abductor  of  the  glottis. 

The  tension  of  the  vocal  cords  is  especially  due  to  the  crico- 
thyroid  muscles,  which  in  contracting  raise  the  front  part  of  the 
cricoid  towards  the  thyroid,  and  depress  the  posterior  part  of 
the  cricoid  and  consequently  of  the  two  arytenoids  which  rest 
upon  it  (Longet).  The  effect  of  this  rotation  of  the  cricoid  on 
its  transverse  horizontal  axis  is  to  increase  the  distance  between 
the  points  of  insertion  of  the  vocal  cords  and  thus  to  stretch 
them.  In  order  that  the  vocal  cords  may  be  stretched,  it  is  necessary 
that  the  two  arytenoid  cartilages  should  be  firmly  fixed,  so  that 


Ill 


PHONATION  AND  AETICULATION 


139 


Tae 


Tan 


they  cannot  be  drawn  forward.  This  is  effected  by  the  combined 
action  of  the  dilatators  and  constrictors  of  the  glottis,  viz.  the 
posterior  crico-arytenoids  (dilatators),  the  transverse  and  oblique 
arytenoids,  the  external  thyro-arytenoids,  and  the  lateral  crico- 
arytenoids  (constrictors).  If  the  posterior  crico-arytenoids  alone 
contracted  with  the  crico-thyroids,  the  vocal  cords  would  be 
stretched  and  abducted  and  the  glottis  dilated.  But  it  is 
essential  for  the  formation  of  sounds  that  the  cords  shall  be  not 
only  tense,  but  also  approximated  to  each  other,  so  that  they  can  be 
thrown  into  vibration  by  the  expiratory  air-current.  These  two 
conditions  are  realised  when  the  constrictors  of  the  glottis  are 
thrown  into  action  simultaneously  with  the  dilatators. 

According  to  C.  Meyer  and  Griitzner,  the  genio-hyoid  and 
thyro-hyoid  muscles  con- 
tribute to  the  tension  of 
the  vocal  cords,  as  they 
raise  the  thyroid  upwards 
and  forwards  in  the  direc- 
tion of  the  chin,  and  sup- 
plement the  action  of  the 
crico- thyroid  muscles  by 
which  the  rotation  of  the 
crico- thyroid  articulations 
round  the  transverse  hori- 
zontal axis  is  effected. 

The  relaxation  of  the 
vocal  cords  is  due  to 
simple  elastic  reaction 
when  the  extensor  muscles 
cease  to  act.  Active  re- 
laxation of  the  cords  can, 

however,  be  produced  by  the  internal  thyro-arytenoids,  which 
are  perhaps  the  most  important  muscles  for  phonation.  They 
are  triangular  muscles,  which  extend  with  the  vocal  cords  from 
the  inner  angle  of  the  thyroid  to  the  vocal  processes  of  the 
arytenoids,  but  some  of  their  bundles  are  inserted  in  the  elastic 
substance  of  the  cords.  When  these  muscles  contract  they  pro- 
duce an  opposite  effect  to  the  crico-thyroids,  and  bring  the  vocal 
processes  of  the  arytenoid  nearer  to  the  thyroid,  which  relaxes 
the  cords.  But  it  is  conceivable  that  contraction  of  the  isolated 
bundles  inserted  into  the  elastic  tissue  of  the  cords  may  produce 
tension  of  some  parts  and  relaxation  of  others. 

It  is  very  probable  that  the  true  function  of  the  internal 
thyro-arytenoids  in  phonation  is  to  regulate  the  tension  and 
thickness  of  the  vibrating  portion  of  the  vocal  cords,  by  which 
a  rapid  succession  of  tones  of  different  pitch  is  made  possible. 

The   internal   thyro-arytenoids   almost   always   co-operate    in 


Km.  '.15.— Transverse  section  of  larynx  through  bone  of 
arytenoid  cartilages.  (Henle.)  t,  thyroid  ;  PC,  pro- 
cessus  vocalis  of  arytenoid  ;  .?//,  sinus  pyriformis ; 
Th,  section  through  thyro-hyoid  muscle;  A,  ary- 
tenoid muscle;  Toe,  Tai,  thyro  -  arytenoid  muscles, 
internal  and  external ;  Taep,  thyro-ary-epiglottidean 
muscle  ;  *,  anterior  cord  of  glottis. 


140 


PHYSIOLOGY 


CHAP. 


phonation  with  other  laryngeal  muscles.  If  we  assume  that 
during  contractions  of  the  muscles  which  stretch  the  vocal  cords, 
the  internal  thyro-arytenoids  which  tend  to  relax  them  are  also 
contracting,  it  is  easy  to  understand  the  functions  of  the  latter, 
which  regulate  the  delicate  changes  in  position  of  the  larynx 
and  vocal  cords  necessary  in  a  gradual  succession  of  tones  that 
differ  little  in  strength  and  pitch  from  each  other.  The  feeling 
of  tension  in  the  larynx  in  singing  with  the  chest  register  fully 

open  shows  that  in  singing  all 
the  laryngeal  muscles  may  be 
more  or  less  active,  and  that  the 
formation  of  different  musical 
notes,  gradations  of  their  pitch, 
and  rise  and  fall  in  the  scale, 
depend  on  the  delicate  co-ordina- 
tions of  their  activity,  and  par- 
ticularly on  the  internal  thyro- 
arytenoids,  which  are  in  direct 
and  intimate  relation  with  the 
vibrating  vocal  cords,  and  have 
justly  been  named  the  "  vocal 
muscles." 

III.  The  nerves  to  the  larynx 
are  the  two  laryngeal  branches 
of  the  vagus  (Fig.  96).  The 
superior  laryngeal  certainly  con- 
tains more  sensory  than  .motor 
fibres  ;  the  former  are  distributed 
by  the  rainus  internus  to  the 
mucous  membrane  of  the  larynx 
FIG.  96.  —  Laryngeal  nerves  from  behind,  and  to  the  laryngeal  muscles  as 

(Sappey.)l,  Superior  laryngeal  nerve;  2,  its  flUvp(,      nf     mnqmilflv      cprmp  •  rhp 

external  branch ;   3,  4,  5,  twigs  to  mucous  HDrCS  UlUSCUJdl      SenbC  ,  tilt 

membrane  of  larynx  ;  6   filaments  that  con-  motor     fibres     paSS     through  the 
nect   lett    superior    and    interior    laryngeal 

nerves;  7,  same  nn  the  right:  8,  8,  inferior  ramUS    externUS   to   innervate    the 

laryngeal  nerves;   !>,  branches  to  posterior  ,1  -j  -i  ,1  i 

cricp-arytenoid    muscles;    10,    branch    to  Cl'lCO-thyrOld  mUSClCS,  partly  alSO 

arytenoid  muscle  ;  11,  12,  branches  to  crico-  t-Uc   qr-irfemnirl  rnnenlp 
aryteiioid  and  thyro-arytenoid  muscles.  B  dry  ten  O.  SOie. 

The  inferior  laryngeal,  or 

nervus  recurrens,  is  a  purely  motor  branch  which  supplies  all 
the  muscles  of  the  larynx  except  the  crico-thyroid. 

As  Claude  Bernard  observed  complete  aphonia  in  cats  after 
extirpation  of  the  spinal  accessory,  it  was  generally  held  that 
the  motor  fibres  of  the  larynx  came  from  the  ramus  interims 
(accessorius  vagi)  of  this  nerve,  although  they  ran  in  the  vagus. 
But  the  later  work  of  Grabower  (1890)  showed  that  the  motor 
branches  to  the  larynx  originate  in  the  vagus,  and  more 
particularly  from  its  lower  roots. 

Section  of  both   laryngeal   nerves   produces  relaxation  of  all 


in  PHONATION  AND  ARTICULATION  141 

the  muscles  of  the  larynx,  so  that  the  vocal  cords  assume  the 
position  of  elastic  equilibrium  as  in  the  dead  body.  Under 
these  conditions  the  glottis  is  moderately  open,  in  the  form  of 
mi  isosceles  triangle,  with  the  angle  of  the  apex  towards  the 
attachments  of  the  vocal  cords  on  the  inner  surface  of  the  thyroid. 
Contraction  of  the  laryngeal  muscles  is  therefore  not  required 
to  hold  the  glottis  open,  as  it  must  be  in  respiration.  Laryngo- 
scopic  observations  show,  however,  that  during  quiet  respiration 
when  no  voluntary  influence  is  exerted  upon  the  laryngeal 
muscles  the  glottis  is  more  widely  open  than  after  death.  In 
quiet  respiration  the  glottis  has  an  average  width  of  14  mm.  in 
the  adult  man,  and  about  11  mm.  in  a  woman,  while  on  the  dead 
subject  it  is  about  5  mm.  and  4  mm.  respectively.  This  striking 
difference  shows  that  in  life  the  posterior  crico-arytenoid  muscle 
is  kept  continuously  in  a  state  of  semi-contraction  by  the  reflex 
or  automatic  tonic  activity  of  a  centre,  which  acts  exclusively 
or  predominatingly  upon  those  fibres  of  the  recurrens  which 
innervate  the  abductors  of  the  vocal  cords. 

In  many  animals  this  tonic  contraction  of  the  abductors  of 
the  glottis  varies  with  the  rhythm  of  the  respiratory  muscles ; 
at  each  inspiration  the  glottis  dilates,  and  at  each  expiration 
it  is  slightly  constricted.  In  man,  however,  laryngoscopical 
observation  shows  that  during  quiet  breathing  these  respiratory 
oscillations  of  the  glottis  do  not  occur  in  the  great  majority  of 
cases  (Sernon),  and  only  appear  during  forced  or  dyspnoeic 
respiration  (see  Vol.  I.  p.  421). 

After  section  of  the  recurrent  laryngeal  nerve  this  respiratory 
rhythm  ceases,  and  the  cords  take  up  the  paralytic  position  of 
moderate  separation  which  is  seen  after  death. 

Section  of  one  recurrent  nerve  alone  deforms  the  glottis  owing 
to  disappearance  of  the  tone  of  the  muscles  on  the  paralysed  side, 
which  brings  the  vocal  cord  of  that  side  nearer  the  median  line. 
This  deformation  or  asymmetry  of  the  glottis  increases  during 
forced  respiration. 

The  most  important  effect  of  section  of  the  recurrent  nerves  is 
the  aphonia  first  described  by  Galen.  Total  loss  of  the  voice  is 
not,  however,  constant.  Haller,  J.  Miiller,  Magendie,  and  others 
noted  that  many  dogs  continue  to  bark  after  section  of  the 
recurrent  nerves,  while  others  are  still  capable  of  emitting  high 
notes,  especially  when  suffering  acute  pain.  Longet  confirmed  this 
fact,  and  found  that  the  power  of  uttering  high  sounds  was  ob- 
served only  in  dogs  a  few  months  old,  in  which  the  tension  of  the 
vocal  cords  produced  by  the  action  of  the  crico-thyroid  muscles, 
which  are  not  paralysed  by  section  of  the  recurrent  nerves, 
suffices  for  the  formation  of  high  sounds,  the  inter-cartilaginous 

O  t  O 

portion  of  the  glottis  not  being  fully  developed,  owing  to  the  almost 
total  absence  of  the  vocal  processes,  so  that  the  cords  are  kept 


142  PHYSIOLOGY  CHAP. 

sufficiently  close  together,  even  when  the  arytenoid  muscles  are 
paralysed. 

Stimulation  of  the  peripheral  branch  of  a  recurrent  nerve 
brings  the  cord  of  the  same  side  nearer  the  median  line  than  does 
simple  section  of  this  nerve,  while  stimulation  of  both  recurrent 
nerves  causes  the  cords  to  come  together  and  the  glottis  to  close. 
So  that  normally  the  effect  of  the  recurrent  nerves  which  contain 
fibres  for  both  the  abductors  and  the  adductors  of  the  glottis  is 
domiiiantly  on  the  dilatators ;  when,  on  the  other  hand,  they  are 
stimulated  artificially  the  effect  on  the  adductors  of  the  glottis  pre- 
dominates. The  explanation  of  these  phenomena  seems  to  be  as 
follows :  Normally,  only  those  fibres  of  the  recurrent  nerves  which 
are  connected  with  a  centre  intimatelv  related  with  the  bulbar 

b 

respiratory  centre  exert  a  constant  tonic  influence  which  maintains 
the  inspiratory  dilatation  of  the  glottis ;  when,  on  the  contrary,  the 
two  recurrent  nerves  are  artificially  excited,  all  the  laryngeal 
muscles  concerned  in  voluntary  phonatioii  (except  the  anterior 
crico-thyroids)  contract,  and  the  contraction  of  the  adductors 
consequently  predominates. 

Section  of  the  superior  laryngeal  nerve  on  one  or  both  sides 
does  not  appreciably  affect  the  glottis,  but  it  makes  the  voice 
raucous  and  prevents  the  formation  of  high  notes  owing  to  the 
loss  of  function  of  the  crico-thyroid  muscles  which  keep  the  cords 
in  tension.  Longet  demonstrated  that  the  peculiar  harshness 
which  ensues  on  paralysis  of  the  superior  laryngeal  nerve  depends 
wholly  on  its  external  branch,  which  gives  fibres  to  the  crico- 
thyroid.  Isolated  section  of  this  nerve  produces  the  same  effect 
as  section  of  the  whole  nerve.  He  found,  too,  that  the  hoarseness 
of  the  voice  can  be  made  to  disappear  by  bringing  the  cricoid 
artificially  nearer  the  thyroid ;  it  is  therefore  obviously  due  solely 
to  relaxation  of  the  vocal  cords.  After  cutting  the  internal 
branch  of  the  inferior  laryngeal,  Longet  could  detect  no  appreci- 
able change  in  the  animal's  voice,  and  electrical  stimulation  of 
this  branch  produced  no  effect  on  the  laryngeal  muscles,  though 
Magendie  held  that  the  ramus  interims  contains  motor  fibres  for 
the  arytenoid  muscle. 

The  centres  of  the  laryngeal  fibres,  both  those  which  maintain 
the  laryngeal  respiratory  rhythm  and  those  which  control  phona- 
tion,  lie  in  the  bulb  or  medulla  oblongata. 

The  centre  for  respiratory  rhythm  is  closely  connected  with 
the  respiratory  centre,  but  is  distinct  and  independent  of  it.  We 
saw  that  the  glottis,  during  quiet  respiration,  is  kept  constantly 
dilated  by  the  tonic  action  of  the  recurrent  nerves.  Semon  and 
Horsley,  experimenting  on  cats,  further  showed  that  stimulation 
of  the  upper  portion  of  the  floor  of  the  fourth  ventricle  produces 
marked  widening  of  the  glottis,  but  the  thoracic  respiratory  move- 
ments continue ;  the  bulbar  centre  for  the  laryngeal  respiratory 


in  PHONATION  AND  ARTICULATION  143 

movements  can  therefore  be  excited  independently  of  the  centre 
for  the  thoracic  respiratory  movements.  Unilateral  stimulation 
of  this  centre  invariably  produces  bilateral  effects,  i.e.  abduction 
of  both  vocal  cords  and  widening  of  the  glottis. 

The  movements  of  phonation  have  also  a  separate  centre  in  the 
bull).  After  separating  the  brain  from  the  bulb,  Vulpian  was  able 
renexly  to  elicit  cries,  as  though  the  animal  still  reacted  to  the 
painful  effects  of  stimulation.  Semon  and  Horsley  on  stimulating 
the  ala  cinerea  and  upper  margin  of  the  calamus  scriptorius, 
obtained  energetic  closure  of  the  glottis,  or  adduction  of  both 
vocal  cords,  when  the  animal  was  not  too  profoundly  narcotised. 

Since  phonation  is  a  voluntary  act,  perfected  by  practice,  it  is 
regulated  by  special  cortico- cerebral  centres  which  control  the 
action  of  the  bulbar  laryngeal  centres. 

The  cortical  centres  in  the  Macacus  monkey  lie  in  the  lowest 
part  of  the  pre-central  or  ascending  frontal  convolution ;  and  in 
doo-s,  in  the  lowest  part  of  the  pre-crucial  part  of  the  sigmoid 
gyrus.  Electrical  stimulation  of  this  area,  in  either  hemisphere, 
produces  adduction  of  both  vocal  cords  which  lasts  as  long  as  the 
stimulation  (Semon  and  Horsley).  But  if  this  is  unduly  pro- 
tracted the  need  of  breathing  causes  a  pronounced  dilatation 
of  the  glottis,  which  momentarily  interrupts  its  closure. 

In  man  the  area  of  phonation  and  articulate  language  is  far 
more  developed  ;  it  lies  at  the  foot  of  the  third  frontal  convolution, 
and  acquires  a  much  higher  functional  significance  in  the  left 
hemisphere  than  in  the  right.  This  important  subject  will  be 
discussed  more  fully  in  Chapter  IX. 

Extirpation  of  both  cortical  speech  centres  does  not  paralyse 
the  glottis  in  animals.     After  unilateral  extirpation  stimulation 
of  the  centre  in  the  other  hemisphere  produces  the  same  effect- 
closure  of  the  glottis — as  was  previously  obtained. 

Unduly  strong  or  protracted  stimulation  of  the  cortical  centre 
of  phonation  may  induce  an  epileptic  attack  which  begins  in  the 
vocal  cords,  and  then  spreads  to  the  muscles  of  the  face,  neck,  and 
limbs.  The  scream  with  which  ordinary  epileptic  attacks  begin 
probably  depends  on  the  initial  excitation  of  this  centre  in 
the  cortex. 

IV.  Ferrein  (1741)  was  the  first  who  attempted  acoustic 
experiments  on  the  excised  larynx  of  recently  killed  dogs,  by 
bringing  the  walls  of  the  glottis  artificially  together,  and  blowing 
forcibly  through  the  trachea. 

Johannes  Miiller  (1839)  successfully  resumed  the  study  of  the 
formation  of  sounds  in  the  larynx  of  dead  bodies.  He  fixed 
threads  to  the  two  arytenoid  cartilages  so  that  he  could  alter 
the  width  of  the  glottis  by  bringing  them  more  or  less  closely 
together,  and  produced  different  degrees  of  tension  in  the  vocal 
cords  by  pulling  the  thyroid  cartilage  forward  by  weights. 


144  PHYSIOLOGY  CHAP. 

The  trachea  was  connected  to  a  bellows,  and  the  different 
pressures  at  which  the  air  traversed  the  glottis  were  measured 
by  a  manometer. 

With  this  method  Miiller  carried  out  a  long  series  of  experi- 
ments which,  though  less  valuable  to-day  owing  to  the  laryngo- 
scopical  observations  now  made  on  the  living  subject,  were  of 
epoch-making  importance  in  the  history  of  physiology.  When 
the  cords  were  brought  together,  their  tension  being  unchanged, 
the  laryngeal  sounds  became  higher ;  on  moving  the  cords  apart, 
the  sounds  were  deeper.  With  increased  tension  of  the  cords,  the 
note  could  be  raised  two  octaves.  With  increased  air  pressure,  the 
tension  of  the  cords  being  unchanged,  the  strength  and  pitch  of 
the  laryngeal  note  could  be  raised  a  fifth.  Lastly,  he  found  that 
everything  above  the  true  vocal  cords  could  be  removed  without 
altering  the  pitch  of  the  sounds,  and  that  the  office  of  the  accessory 
tube,  the  pharyngo-buccal  and  nasal  cavities,  was  limited  to 
altering  the  pitch. 

J.  Miiller  first  constructed  an  artificial  larynx  with  one  or  two 
membranous  tongues  of  elastic  material  or  arterial  wall  stretched 
across  the  mouth  of  a  wooden  pipe,  011  which  he  studied  the 
mechanical  conditions  for  the  production  of  sound  and  of  variations 
in  pitch,  strength,  and  timbre.  But  in  his  conclusions  he  fell  into 
the  same  error  as  Ferrein,  who  first  compared  the  vocal  cords  to 
the  strings  of  a  violin,  and  regarded  their  vibrations  as  the  primary 
source  of  the  sounds,  the  air  blast  as  the  bow  which  threw  them 
into  vibration,  and  the  thorax  and  lungs  as  the  hand  that  moves 
the  bow.  Miiller  supported  this  theory,  even  after  W.  Weber  had 
demonstrated  by  his  classical  experiments  that  the  sounds  of 
tongued  instruments  are  essentially  due  to  explosions  of  air,  viz. 
to  the  periodic  increments  and  decrements  of  pressure  as  it  passes 
through  the  slit  that  lies  between  the  vibrating  tongues. 

Direct  observation  on  the  living  subject  of  the  position  of  the 
glottis  during  the  formation  of  sounds  was  an  immense  advance 
in  the  study  of  the  mechanism  of  the  laryngeal  sounds. 

Magendie  (1816)  was  the  pioneer  in  this  research.  He 
recognised  that  it  is  necessary  for  the  emission  of  vocal  sounds 
that  the  arytenoids  and  vocal  cords  be  brought  together, 
while  the  opening  of  the  inter-cartilaginous  glottis  does  not 
prevent  the  formation  of  sounds.  His  method  consisted  in 
exposing  the  glottis  in  dogs  by  an  incision  between  the  hyoid 
bone  and  thyroid  cartilage.  The  same  method  was  adopted  by 
the  surgeon  Malgaigne  (1831),  who  corrected  certain  errors  in 
Magendie's  observations,  and  showed  that  only  the  pars  niena- 
branacea  of  the  glottis  is  concerned  in  voice  formation. 

The  human  glottis  has  also  been  directly  observed  in  persons 
who  have  attempted  suicide  by  cutting  the  throat  above  the  vocal 
cords  (Mayo,  1883,  and  others).  Such  observations  confirm  the 


Ill 


PHONATION  AND  AKTICULAT ION 


145 


fact  that  there  is  adduction  of  the  vocal  cords  in  the  formation 
of  sounds,  so  that  the  glottis  assumes  the  form  of  a  slit. 

The  discovery  of  the  laryngoscope  by  the  famous  singing- 
master  Manuel  Garcia  (1854)  made  it  possible  to  observe  the 
human  glottis  directly  under  normal  conditions,  during  the 
emission  of  laryngeal  sounds  of  different  pitch. 

The  original  laryngoscope  used  by  Garcia  was  a  simple  metal  mirror 
fixed  to  a  handle  at  a  suitable  angle.  After  warming  it  gently  over  a  spirit 
lamp  to  prevent  the  deposition  of  moisture,  it  was  introduced  into  the  isthmus 
of  the  fauces,  so  that  a  beam  of  light  could  be  thrown  on  to  the  glottis,  which 
thus  becomes  visible  to  the  observer,  who  is  looking  into  the  mirror.  The 


FI0.  07.— Examination  of  larynx  by  laryngoscope,  u,  b,  two  metal  mirrors  ;  illuminated  by  a  lamp, 
which  is  reflected  from  a  mirror  with  a  central  aperture  which  is  fixed  in  front  of  the 
observer's  eye. 

latter  may  be  directly  illuminated  by  sunlight,  which  was  Garcia's  original 
method,  or  by  a  lamp  at  the  side  of  the  observer  in  front  of  which  a  large 
lens  is  placed  to  increase  the  strength  of  the  illumination  ;  or  by  a  lamp 
placed  behind  the  shoulder  of  the  person  observed,  which  illuminates  a 
concave  mirror,  and  reflects  a  beam  of  light  upon  the  mirror  of  the  laryngo- 
scope. The  observer  watches  the  latter  through  a  central  aperture  in  the 
concave  mirror  (Fig.  97). 

Oertel  employed  a  rapidly  intermittent  illumination  by  placing  a  Mach's 
stroboscopic  disc  in  front  of  the  lamp.  It  is  then  possible  to  follow  the 
vibration  of  the  vocal  cords  by  direct  vision. 

Szimanowsky  obtained  instantaneous  photographs  of  the  glottis  during 
the  production  of  the  different  tones  by  substituting  a  photographic  apparatus 
for  the  eye  of  the  observer. 

The  whole  of  the  laryngeal  vestibule  cannot  be  seen  simultaneously  on 
the  laryngoscopic  mirror,  but  by  moving  the  mirror  it  is  possible  to  see  the 
different  parts  in  succession  (Fig.  98). 

Laryngoscopical  observation  shows   that  voice   production  is 
VOL.  in  L 


146 


PHYSIOLOGY 


CHAP. 


preceded  by  closure  of  the  whole  glottis,  or  of  the  pars  mem- 
branacea  (Fig.  98).1  Now  the  emission  of  tones  coincides  with 
the  rapid  opening  and  vibration  of  the  vocal  cords  by  the  blast  of 
air  forced  through  the  glottis  by  the  expiratory  muscles.  The 
vibrations  of  the  cords  are  not  limited  to  their  narrow  margins, 
but  extend  more  or  less  through  their  entire  mass.  At  the  same 
moment  the  epiglottis  is  somewhat  raised,  particularly  in  high 
notes  ;  the  aryteno-epiglottidean  folds  are  stretched ;  and  the  false 
vocal  cords  are  drawn  slightly  nearer  together  and  stretched,  but 
they  do  not  vibrate.  At  the  same  moment  the  whole  larynx 
becomes  more  or  less  firmly  fixed  by  the  action  of  the  extrinsic 
muscles  (thyro-hyoid,  sterno-thyroid,  pharyngeal,  etc.),  and  rises 
with  the  emission  of  the  high  notes,  and  falls  with  the  low  notes. 
During  the  production  of  high  notes  the  tongue  contracts 
energetically,  the  tip  being  drawn  back,  and  the  base  lifted.  The 
soft  palate  is  raised  towards  the  posterior  wall  of  the  pharynx, 


FIG.  '.is.  — Positions  of  glottis  previous  to  production  of  the  voice. 

and  the  pillars  of  the  fauces  approximate  and  narrow  its  opening. 
In  deep  notes,  on  the  contrary,  the  tongue  contracts  slightly  and 
remains  flat ;  the  soft  palate  is  raised,  and  the  pillars  of  the  fauces 
move  apart.  But  the  most  important  of  all  these  changes  in  the 
voice-producing  apparatus  are  the  vibration  of  the  vocal  cords 
and  the  form  of  the  membranous  glottis,  which  varies  considerably 
with  the  pitch,  intensity,  and  register  of  the  voice. 

In  order  that  the  vocal  cords  should  vibrate,  it  is  necessary 
for  the  air- current  passing  through  them  to  be  at  a  certain 
pressure,  sufficient  to  displace  them  from  their  position  of 
equilibrium.  In  a  case  of  tracheal  fistula  in  a  woman,  Cagnard- 
Latour,  by  fitting  a  manometer  into  the  mouth  of  the  fistula,  was 
able  to  measure  the  pressure  of  the  blast  of  air  during  the 
production  of  sounds  of  different  pitch.  He  found  a  pressure  of 
160  mm.  H20  necessary  for  sounds  of  medium  pitch,  of  200  mm. 
for  high,  and  of  945  mm.  for  the  highest  notes.  Griitzner 
obtained  approximately  the  same  figures  in  a  young  man  on 
whom  tracheotomy  had  been  performed. 

Adduction   of   the   vocal   cords   and   narrowing  of  the  glottis 

1  This  is  not  in  agreement  with  some  later  observations. — F.  A.  W. 


in  PHONATION  AND  ARTICULATION  147 

obstructs  the  passage  of  air,  and  increases  the  pressure  in  the 
trachea  necessary  for  throwing  the  vocal  cords  into  vibration. 
The  loss  of  voice  when  the  trachea  is  opened  depends  on  the  fall 
of  the  pressure  of  the  expiratory  air  below  the  minimum  necessary 
for  the  vibration  of  the  vocal  cords. 

But  the  pressure  of  the  expiratory  air  would  in  itself  produce 
no  musical  effect  if  the  vocal  cords  were  not  thrown  into  a  proper 
degree  of  tension  by  their  tensor  muscles.  As  we  have  seen, 
paralysis  of  the  anterior  crico-thyroid  muscles  makes  the  voice 
hoarse,  and  hinders  the  formation  of  high  tones. 

The  following  general  laws  of  the  mechanism  of  the  production 
of  laryngeal  sounds  may  be  deduced  from  experiments  on  animals 
and  observations  on  man  :— 

(a)  The   membranous  glottis  is   the  exclusive  seat  of  voice 
production.     Lesions  of  the  vocal  cords  render  voice  production 
impossible. 

(b)  The  vocal  cords  acting  as  membranous  tongues  are  thrown 
into  vibration  by  the  pressure  of  the  expiratory  blast,  and  vibrate 
synchronously  with  the  air-current.     The  vibrations  of  the  vocal 
cords  certainly  produce  a  note,  but  its  intensity  is  very  low,  hardly 
to  be  compared  with  that  of  the  tones  arising  from  the  larynx. 
The  true  sounding  body  is  the  air,  but  the  vibrations  of  the  air 
are  determined  by  the  vibrations  of  the  vocal  cords. 

(c)  The  vibrations  of  the  air  which  are  started  in  the  glottis 
are  transmitted  to  the  mass  of  air  lying  below  as  well  as  above 
the  vocal  cords.     The  vibrations  of  air  in  the  windpipe,  bronchi, 
and  lungs  are  communicated  to  the  thoracic  wall,  and  can  easily 
be  detected  by  applying  the  hand  to  the  chest.     This  resonance 
of   the  chest  must  certainly  produce  increased  intensity  of  the 
laryngeal  notes,  though  it  is  difficult  to  appreciate  its  importance. 

(d)  The  resonator  proper  consists  of  the  parts  lying  above  the 
vocal  cords,  the  laryngeal  vestibule,  and  upper  portions  of  the 
pharynx,  mouth,  and  nose.     It  is  on  the  vibrations  of  the  air  in 
this  tube  that  the  special  qualities  which  characterise  the  human 
voice  depend.     The  necessary  coincidence  between  the  vibration 
of  the  vocal  cords  and  that  of  the  air  in  the  resonator  is  obtained 
by  the  varying  tension  of  the  walls,  and  the  alterations  in  length, 
breadth,  and  shape  of  the  cavity,  by  upward  and  downward  move- 
ments of  the  larynx,  and  alterations  of  the  tongue,  soft  palate, 
pillars  of  fauces,  cheeks,  and  lips. 

(e)  Moro-agni's  ventricles  are  of  little  importance  as  resonators, 
but  they  give  space  for  the  free  vibration  of  the  vocal  cords,  and 
produce  a  secretion  by  which  the  laryngeal  mucous  membrane  is 
kept  moist. 

(/)  The  false  vocal  cords  can  alter  the  form  of  the  laryngeal 
vestibule  by  their  approximation  towards  the  middle  line,  and 
thus  change  the  character  of  the  tone  produced  by  the  vibrations 


148  PHYSIOLOGY  CHAP. 

of  the  true  vocal  cords.  It  is  doubtful  whether  they  can  act  as 
dampers  by  dropping  to  the  level  of  the  true  vocal  cords. 

(g)  The  function  of  the  epiglottis  in  voice  production  is  also 
uncertain.  But  the  positions  it  takes  up  must  certainly  contribute 
to  altering  the  character  and  quality  of  the  voice. 

(A)  Abundant  proof  of  the  great  influence  on  the  character  of 
the  voice  of  the  different  forms  which  may  be  assumed  by  the 
pharyngo-buccal  cavity  owing  to  the  various  positions  of  the  soft 
palate,  tongue,  and  lips,  will  be  shown  when  we  come  to  discuss 
language  and  particularly  the  formation  of  the  vowels. 

V.  The  sounds  produced  by  the  human  voice  are  all  comprised 
in  the  interval  of  three  and  a  half  octaves,  or  a  little  more,  but  no 
one  individual  possesses  such  an  extensive  vocal  range.  Few 
indeed,  and  only  after  long  practice,  succeed  in  acquiring  a  range 
of  even  three  octaves,  and  in  these  rare  cases  the  end-notes  of  the 
scale  are  deficient  in  strength  and  clearness.  The  average  compass 
of  a  well-developed  singer  seldom  exceeds  two  octaves. 

The  range  of  voice  within  the  limits  of  the  two  octaves 
depends  principally  upon  the  dimensions  of  the  larynx,  which 
differs  considerably  in  the  sexes.  In  either  sex  musicians  dis- 
tinguish three  different  varities — soprano,  mezzo-soprano,  and 
contralto,  for  the  female  voice ;  tenor,  baritone,  and  bass,  for  the 
male  voice.  The  soprano  voice  is  about  an  octave  higher  than 
the  tenor ;  the  contralto  about  an  octave  above  the  bass.  A  few 
notes  between  G  and  F  of  the  third  octave  of  the  piano  are 
common  to  baritone  and  soprano.  The  table,  p.  149,  shows  the 
range  of  voice  usually  met  with  in  different  singers.  Opposite 
each  note  is  the  number  of  simple  vibrations  which  correspond 
to  it  according  to  the  international  concert  pitch  a1  =  435  (see 
Chap.  V.  of  Vol.  IV.). 

At  puberty  there  is  a  rapid  development  of  the  larynx  which 
alters  the  range  of  the  voice.  Owing  to  the  elongation  of  the 
cords  the  voice  generally  falls  an  octave  in  the  male  and  about 
two  notes  in  girls.  A  boy's  soprano  voice  usually  changes  to  a 
tenor,  an  alto  to  a  baritone.  While  changing,  the  voice  becomes 
harsh,  uneven,  and  guttural ;  this  is  due  to  a  transitory  hyperaernia 
and  swelling  of  the  vocal  cords  which  accompanies  the  growth  of 
the  whole  organ. 

In  eunuchs  the  voice  of  childhood  is  usually  retained,  but  it 
becomes  stronger  and  fuller. 

The  upper  limit  of  the  vocal  tones  is  reached  at  about  the  age 
of  eleven  years.  Children's  voices  may  reach  the  highest  notes  of 
the  fifth  octave,  which  are  very  seldom  attained  by  the  highest 
sopranos. 

The  range  of  a  child's  voice  varies,  according  to  Engel,  from 
three  whole  toues  to  two  full  octaves.  Paulsen  (1895)  found  on 
examining  a  large  number  of  children  that  the  compass  of  the 


III 


PHONATION  AND  ARTICULATION 


149 


voice  in  the  sixth  year  was  about  an  octave,  by  eleven  it  was 
twice  as  great,  by  fourteen  still  more  extended.  Girls'  voices 
reach  their  widest  range  at  the  thirteenth,  boys'  voices  at  the 
fourteenth  year. 

In  advanced  life  the  upper  tones  gradually  weaken,  and 
ultimately  disappear.  A  soprano  voice  nearly  always  turns  into 
a  mezzo-soprano,  and  a  tenor  often  becomes  a  baritone.  These 
changes,  unlike  those  of  puberty,  come  on  gradually,  and  are  due 
to  loss  of  elasticity,  caused  by  calcification  of  the  laryngeal 


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1-1O 

129 

122 
103 
96'5 

86 
81 

cartilages,  which  begins  about  middle  age,  and  increases  with  old 
age.  The  thyroid  ossifies  first ;  then  the  cricoid ;  much  later  the 
arytenoids.  In  old  age  the  compass  of  the  voice  shrinks,  and  its 
resonance  diminishes  and  becomes  tremulous,  owing  to  retrogressive 
changes  in  the  neuro-muscular  apparatus  of  the  larynx  and  the 
expiratory  muscles. 

Voices  differ  not  only  in  their  relative  position  in  the  scale,  but 
also  in  quality  or  timbre.  Just  as  it  is  easy  to  distinguish  the  tone 
of  a  basso  concerto  from  a  violoncello,  and  that  of  a  clarinet  from 
an  oboe,  so  a  practised  ear  can  distinguish  a  bass  from  a  baritone 
or  tenor,  and  a  contralto  from  a  soprano,  even  when  they  are 
singing  the  same  notes. 

Generally  speaking,  "  bright "  voices  can  be  distinguished  from 


150 


PHYSIOLOGY 


CHAP. 


"  dull "  voices,  while  others  are  "  full,"  i.e.  of  medium,  normal 
timbre.  With  bright  timbre  the  larynx  is  raised,  the  resonance 
cavity  is  short,  the  mouth  wide  open,  the  glottis  constricted ;  with 
dull  timbre  the  larynx  is  lowered,  the  resonance  tube  long,  the 
oral  opening  constricted,  the  glottis  rather  wider.  The  difference 
in  quality  is  most  distinct  if  the  same  note  is  sung  with  the  two 
vowels  A  and  U. 

It  is  an  important  fact  that  the  voice  can  be  varied  in  the 
same  individual  by  altering  the  position  of  the  vocal  organ. 
When  the  scale  is  sung  from  the  lowest  to  the  highest  note  the 
voice  retains  the  same  quality  between  certain  limits,  the  pitch 
only  being  altered.  But  in  rising  gradually  to  higher  notes  the 
voice  is  not  only  raised  hut  also  changes  in  quality.  The  voice  is 
usually  divided  into  three  registers,  in  analogy  with  the  registers 
of  an  organ  :  these  are  the  chest  register,  the  middle  register,  and 
the  head  register,  or  falsetto. 


A  B 

Fie.  9; i. — Aperture  of  glottis  during  emission  of  low  notes  (A),  and  liigh  notes  (B), 

with  chest  register. 

Laryngoscopical  observations  show  that  each  register  corre- 
sponds to  a  particular  position  of  the  larynx,  which  is  constant  for 
all  notes  comprised  in  that  register,  the  tension  of  the  cords  alone 
being  altered  according  to  the  height  of  the  notes.  In  passing 
from  one  register  to  another  the  position  of  the  larynx  changes 
abruptly. 

The  exact  positions  of  the  larynx  in  correspondence  with  the 
different  vocal  registers  is  a  subject  of  discussion  among  the 
laryngologists. 

It  is  generally  admitted  that  in  the  chest  register  the  vocal 
cords  vibrate  over  their  whole  length ;  the  aperture  of  the  glottis 
is  elliptical  and  wide  or  narrow,  according  to  the  pitch  of  the 
sounds  ;  the  intercartilaginous  portion  of  the  glottis  is  also  more  or 
less  widely  open  ;  and,  lastly,  the  vibrations  of  the  cords,  which  can 
be  clearly  seen  by  the  laryngoscope,  are  transmitted  to  the  chest 
walls,  hence  the  name  of  "  chest  "  register  (Fig.  99). 

In  singing  with  a  head  register,  or  falsetto,  the  vocal  cords  are 
shorter  and  narrower;  the  intercartilaginous  portion  of  the  glottis 
is  completely  closed ;  the  membranous  glottis,  on  the  contrary,  is 


Ill 


PHONATION  AND  AETICULATION 


151 


open,  Itut  only  in  the  middle  part,  where  it  forms  a  comparatively 
wide  space  through  which  the  expired  air  can  readily  escape 
(Garcia) ;  this  produces  greater  resonance  in  the  pharyngo-huccal 
cavity,  and  vibrations  of  the  cranial  bones  (hence  "head"  voice); 
the  false  vocal  cords  are  tensely  stretched,  and  approach  the  true 
cords,  or,  according  to  some  authors,  actually  come  into  contact 
with  them;  the  vibrations  of  the  cords  are  only  visible  in  the 
most  forward  part  of  their  free  edges  (Fig.  99«)-  Other  observers., 
on  the  contrary,  state  that  in  the  head  register  the  glottis  is  open 
in  its  entire  length,  although  it  is  reduced  to  a  linear  slit  (French). 
Possibly  all  singers  do  not  employ  the  same  laryngeal  mechanism 
in  the  different  registers. 

Among  the  contradictory  interpretations  of  the  fundamental 
differences  between  the  chest  register  and  the  head  register,  that 
of  Lehfeldt  (1835)  found  wide  acceptance,  and  was  adopted  by 


Fit;.  99a. — Aperture  of  glottis  during  emission  of  lii.^h  notes  (C),  with  chest  register  ;  and  of 
highest  notes  (D),  with  head  register.     (Mandl.) 

Job.  Miiller  and  many  other  physiologists.  He  assumed  that  in 
the  falsetto  voice  only  the  free  edges  of  the  vocal  cords  are  thrown 
into  vibration,  while  in  the  chest  voice  the  whole  of  the  cords 
vibrate.  Bonders  held  that  in  the  chest  register  the  musculus 
vocalis  (internal  thyro-aryteuoid),  being  contracted  and  tense, 
participates  in  the  vibrations  of  the  cords,  and  that  its  weight 
drags  down  the  pitch.  In  the  falsetto  register,  on  the  other  hand, 
as  the  musculus  vocalis  is  relaxed,  the  vibratory  movement  is  con- 
fined to  the  edges  of  the  cords;  the  pitch  consequently  becomes 
higher  owing  to  the  reduction  of  the  vibrating  mass.  The  relaxa- 
tion of  the  musculus  vocalis  accounts  for  the  comparative  breadth 
of  the  glottis  and  the  more  rapid  absorption  of  the  reserve  air,  as 
well  as  the  more  marked  fatigue  and  greater  vibration  of  the  head. 
After  Oertel's  laryngoscopical  observations  (1882)  by  Mach's 
stroboscope  method  (intermittent  illumination  of  the  glottis)  this 
theory  lost  ground,  and  was  gradually  replaced  by  another, 
according  to  which,  when  the  falsetto  voice  is  produced,  nodal  lines 
are  formed  in  the  vocal  cords  parallel  to  their  free  borders.  The 
increased  height  of  the  falsetto  notes  is  therefore  due,  not  to 


152  PHYSIOLOGY  CHAP. 

decreased  depth  and  breadth  of  the  vibrating  portion  but  to  the 
subdivision  of  the  vocal  cords  into  two  vibrating  sections,  by  a 
nodal  line  which  runs  parallel  with  their  edges.  When  the 
musculus  vocalis  is  tense  and  contracted  like  the  edge  of  the  cord 
in  which  it  is  embedded,  it  vibrates  with  them,  and  this  prevents 
the  formation  of  nodal  points,  and  the  chest  voice  consequently 
results. 

The  change  from  the  chest  register  to  falsetto  is  on  this  new 
theory  due  principally  to  the  relaxation  of  the  musculus  vocalis. 
This  change  is  usually  easier  and  less  apparent  in  women  than  in 
men. 

The  singer's  art  is  largely  directed  to  equalising  the  resonance 
and  timbre  of  the  voice  in  different  notes  of  the  scale,  so  as  to  pass 
smoothly  from  one  register  to  another.  Many  important  exercises, 
again,  aim  at  facility  in  altering  the  strength  of  a  tone  without 
changing  its  pitch — i.e.  at  singing  crescendo  and  decrescendo.  The 
strength  of  the  laryngeal  notes  depends  on  the  amplitude  of  the 
vibrations  of  the  vocal  cords,  due  in  its  turn  to  the  pressure  of  the 
expiratory  current.  But  when  the  position  of  the  glottis  and  the 
tension  of  the  vocal  cords  remain  unchanged  it  is  possible  by 
increasing  the  pressure  of  the  air-blast  to  raise  the  height  of  a 
tone  a  fifth  ;  consequently,  to  produce  a  crescendo  on  the  same  note 
there  must  be  a  compensatory  alteration  of  the  vocal  cords  in  order 
to  preserve  the  same  number  of  vibrations.  Compensation  in  the 
opposite  direction  is  necessary  to  produce  a  decrescendo.  These 
compensations  are  obtained  by  decrease  or  increase  of  the  tension 
in  the  vocal  cords  (relaxation  or  contraction  of  the  crico-thyroid 
muscles),  or  by  increase  or  decrease  in  the  mass  of  the  vibrating 
parts  (contraction  or  relaxation  of  the  musculus  vocalis).  Laryngo- 
scopical  observation  confirms  sometimes  the  one,  sometimes  the 
other  interpretation.  Both  are  difficult  adjustments,  which  are 
easily  executed  even  by  experienced  singers,  and  are  only  learned 
by  long  practice. 

"  Expression  "  depends  on  these  modulations  of  the  strength  of 
a  note  without  altering  its  pitch.  No  musical  instrument  is  better 
adapted  than  the  larynx  to  give  expression  in  singing,  for  the 
larynx  is  a  living  instrument,  brought  into  direct  relation  with  the 
emotional  and  motor  centres  of  the  performer  by  means  of  its 
sensory  and  motor  nerves. 

VI.  The  power  of  utilising  the  larynx  as  a  musical  instrument 
is  not  common  as  a  natural  endowment,  not  only  because  few  people 
possess  the  range,  volume,  and  quality  of  voice  that  is  indispensable 
for  singing,  but  also  because  many  people  do  not  understand  the 
right  use  of  the  larynx  as  a  musical  organ,  though  every  one  is  more 
or  less  capable  of  using  it  as  an  organ  of  speech. 

In  former  days,  particularly  towards  the  end  of  the  eighteenth 
century,  the  difference  between  the  singing  voice  and  the  speaking 


ni  PHONATION  AND  ARTICULATION  153 

voice  was  much  discussed.  The  voice  used  for  speaking  is 
commonly  held  to  be  different  from  that  used  in  singing.  But 
this  is  a  mistake.  In  compass  the  only  difference  is  that  the  tones 
used  in  speaking  are  generally  comprised  within  half  an  octave, 
while  those  employed  in  singing  extend  over  two  octaves.  A  more 
important  difference  lies  in  the  fact  that  in  speaking  many  sounds 
(consonants)  are  used,  so  that  the  tones  and  the  intervals  between 
the  tones  are  not  so  plain  as  in  singing.  There  are  not  therefore 
two  different  voices  but  rather  two  modes  of  using  the  same  voice  ; 
dramatic  recitation  and  lyrical  declamation  stand  midway  between 
speaking  and  singing. 

Owing  to  these  differences  between  the  singing  voice  and  the 
speaking  voice,  mistakes  in  the  correct  pronunciation  of  words,  and 
in  the  true  intonation,  modulation,  and  accentuation  of  phrases 
and  periods,  are  often  tolerated  in  speaking  because  they  are  less 
offensive  ;  in  singing,  on  the  contrary,  false  intonation  and  wrong 
notes  produce  a  sense  of  discomfort  which  is  unbearable  to  the 
trained  ear. 

Longet  distinguishes  three  different  causes  for  the  very  common 
failure  to  sing  in  tune,  which  amounts,  in  some  cases,  to  a  total 
incapacity  :— 

1.  The  individual  "  has  no  ear,"  i.e.  his  sense  of  hearing  is  not 
acute  enough  to  enable  him  to  distinguish  between  the  different 
tones.     No   one  with    this   defect   can   sing.      In   fact,  auditory 
sensations  are  at  least  as  necessary  to  the  adequate  function  of  the 
organ  of  phonation   as   are  visual  and  tactile  sensations  in  the 
movements  of  the  body  and  limbs.      The  actual  development  of 
the  voice  is  dependent  on  the  functioning  of  the  organ  of  hearing ; 
dumbness  is  associated  with  congenital  deafness,  and  is  almost 
always  due  to  lack  of  auditory  sensations  and  not  to  defects  in  the 
voice-producing  apparatus. 

2.  The  individual  does  not  sing  well  because  his  tone-memory 
is  defective,  i.e.  notes  do  not  leave  clear  and  distinct  traces  in  his 
memory,  from  which  he  can  easily  revive  the  corresponding  tones. 
He  is  quite  capable  of  singing  in  tune  to  an  instrument,  or  with 
other  true  singers,  but  when  left  to  himself  he  cannot  hit  or  keep 
up  the  correct  note,  and  is  aware  that  he  sings  out  of  tune.     In 
these  cases  the  musical  memory  can  be  developed  gradually  by 
careful   training,  so  that   the    faults  in   singing  are   reduced   or 
disappear. 

3.  The  individual  cannot   sing   correctly  because  his   larynx 
cannot  produce  true  notes  in  response  to  volitional  impulses.     lAhis 
not  uncommon  peculiarity  is  due  not  to  anomalous  conformation 
of  the  larynx,  but  to  some  imperfection  of  the  nervous  mechanism 
by   which   the   tactile   and   muscular  sensations  are    transmitted 
centripetally  to  the  centre,  or  the  motor  impulses  centrifugally  to 
the  laryngeal  muscles. 


154  PHYSIOLOGY  CHAP. 

The  ability  to  sing  depends  not  on  the  construction  of  the 
larynx,  but  on  the  possession  of  the  proper  nervous  mechanism,  by 
which  both  the  auditory  sensations  and  the  tactile  and  muscular 
sensations  are  capable  of  guiding  the  volitional  impulses  in  such  a 
way  that  these  are  promptly  and  accurately  transmitted  to  the 
corresponding  muscles.  Congenital  delects  in  these  nervous 
mechanisms  can  also,  to  some  extent  at  least,  be  overcome  by  long 
and  steady  practice,  just  as  a  violin  player  is  able  in  a  wonderful 
way  to  cultivate  the  nervous  mechanisms  which  move  the  muscles 
of  his  hands.  A  perfect  singer  is  not  born,  but  trained,  as  a 
concert  player  is  developed  after  long  practice  ;  but  of  course  in 
either  case  a  favourable  congenital  predisposition  is  indispensable 
to  the  mastery  of  the  art. 

It  is  possible  by  minute  and  careful  analysis  of  the  voice  to 
detect  comparative  correctness  or  faults  of  its  formation,  as  well  as 
of  the  different  notes  of  the  musical  scale  which  it  is  able  to 
produce. 

A  voice  is  "  true "  when  the  vibration  numbers  of  its  notes 
correspond  exactly  to  their  place  on  the  scale ;  it  is  "  false  "  when 
the  vibration  numbers  are  greater  or  less  than  those  of  the  notes. 
Rising  (crescenti)  voices  are  the  more  usual ;  falling  (calandi)  voices 
less  common,  except  in  a  singer  whose  voice  is  worn  out.  It  is 
often  the  case  that  certain  notes  are  false,  while  others  are  in  tune. 
Minor  keys  are  more  difficult  to  sing  correctly  than  major  keys. 

Hen  sen  by  Konig's  manometric  flames,  Kliinder  by  the 
phonautographic  method  which  records  the  vibrations  of  the 
original  tone  and  the  note  sung  in  unison  with  it,  made  interest- 
ing researches  on  the  accuracy  of  the  voice.  They  discovered  that 
it  is  very  difficult  to  hold  a  note  with  a  constant  number  of 
vibrations  for  a  given  time.  Owing  to  positive  or  negative 
variations  in  the  tension  of  the  vocal  cords,  the  truest  voices 
fluctuate  in  vibration  frequency  above  and  below  the  normal 
mean.  The  mean  error  for  any  particular  note  is  not  more  than 
0'35  per  cent ;  but  in  holding  on  a  note,  or  in  singing  crescendo 
or  diminuendo  it  may  amount  to  1*54  per  cent,  owing  to  the 
difficulty  of  compensation,  even  in  the  larynx  of  a  professional 
singer  with  long  practice,  in  forming  and  holding  on  the  notes. 
This  slight  natural  imperfection  of  the  voice  in  keeping  on  the 
notes  is  due  not  to  want  of  ear,  but  to  the  larynx  and  its  vocal 
muscles  (thyro-arytenoid  muscles),  which  are  incapable — no  matter 
how  much  they  are  exercised — of  keeping  up  the  exact,  degree  of 
tension  required  for  the  several  notes  of  the  scale,  without  slight 
periodic  variations.  The  slight  imperfections  in  the  formation 
and  emission  of  tones,  perceptible  even  in  expert  singers,  depend 
more  on  the  ear  than  on  the  larynx,  and  are  due  to  defective 
sharpness  in  the  memory  traces  of  the  respective  tones. 

VII.  Articulate  language  is  limited  to  man,  and  is  one  of  the 


in  PHONATION  AND  AETICULATION  155 

highest  faculties  by  which  he  is  distinguished  from  the  rest  of 
the  animal  kingdom.  From  the  physical  point  of  view  it  consists 
in  a  series  of  special  expiratory  and  sometimes  inspiratory  sounds 
produced  in  the  resonance  cavity  of  the  pharynx,  mouth,  and  nose, 
which  may  be,  but  need  not  be,  combined  with  the  laryngeal 
tones.  In  talking  aloud  the  laryngeal  tones  are  combined  with 
the  pharyugo-buccal  sounds  into  articulate  speech,  but  in  whisper- 
ing, i.e.  speech  without  voice,  there  are  no  laryngeal  tones.  It  is 
even  possible  to  speak  sotto  voce  without  a  glottis,  as  after  loss  of 
the  larynx  by  surgical  operation.  The  resonator  is  therefore  of 
fundamental  importance  to  the  formation  of  words,  while  in 
singing  it  is  of  secondary  importance. 

The  vocal  apparatus  has  rigid  parts,  such  as  the  hard  palate 
and  nostrils,  and  mobile  parts,  such  as  the  lips,  tongue,  and  soft 
palate.  It  is  the  changes  in  form  of  the  resonating  cavity  due  to 
the  movements  of  these  soft  parts  which  give  rise  to  the  different 
articulate  sounds.  Sometimes  these  changes  do  not  interrupt  the 
continuity  of  the  vocal  instrument ;  at  other  times  they  constrict 
or  close  it,  rendering  the  escape  of  the  expired  air  difficult  or 
impossible.  This  constriction  or  occlusion  may  occur  in  certain 
regions,  as  in  the  glottis,  in  the  isthmus  of  the  fauces,  between  the 
soft  palate  and  dorsum  of  the  tongue,  between  the  hard  palate  or 
alveolar  arches  and  the  tip  of  the  tongue,  or  at  the  lips.  These 
are  known  as  the  regions  of  articulation. 

The  number  of  elementary  sounds  which  in  different  combina- 
tions build  up  a  language  or  dialect  is  limited,  but  it  varies 
considerably  in  different  languages  and  dialects.  The  sounds  are 
distinguished  as  vowels  and  consonants  in  the  grammar  of  every 
language.  The  value  of  this  distinction  has  been  much  discussed, 
and  many  erroneous  definitions  have  been  made,  showing  that 
there  cannot  be  any  absolute  difference  between  vowels  and 
consonants,  by  which  they  can  invariably  be  recognised.  One 
group  of  consonants,  in  fact,  has  the  character  of  vowels,  and 
these  sounds  are  frequently  referred  to  as  the  semi- vowels. 

Speaking  generally,  it  may  be  said  that  the  vowels  are  laryn- 
geal sounds,  which  assume  their  specific  character  in  the  resonating 
cavity  owing  to  the  predominance  there  of  one  or  two  tones  of  a 
given  pitch.  The  consonants,  on  the  contrary,  are  sounds  which 
are  almost  invariably  formed  in  the  resonating  cavity,  and  may 
or  may  not  be  combined  with  laryngeal  tones. 

The  vowel  a  (ah)  is  often  regarded  as  the  foundation  from 
which  all  the  other  vowels  may  theoretically  be  derived.  It  does 
in  fact  represent  a  laryngeal  sound  as  little  modified  as  may  be 
by  the  resonating  cavity,  which  remains  as  widely  open  as  possible. 
C.  Hellvvag  in  his  Deformatione  loquelae  (1781)  distinguishes  three 
typical  vowels,  which  produce  the  maximal  difference  to  the  ear. 
These  three  are  the  only  vowels  found  in  hieroglyphs,  and  in 


156  PHYSIOLOGY  CHAP. 

Indian,  Gothic,  and  Arabic  writing.  They  are  i  (ee\  a  (ah),  u  (00). 
All  other  vowels  used  in  modern  languages  and  dialects  are  inter- 
mediate, and  are  derived  from  these  three  typical  vowels. 

The  system  of  distinct  vowels  used  in  different  languages  and 
dialects  is  represented  in  the  following  diagram  of  Briicke  (after 
Hellwag)  :— 

A 

Ae       A° 

Ea       Aoe       O 

E         E°        O        0 

I          Iu  U1  U 

The  angles  of  the  triangle  are  occupied  by  three  typical  vowels ;  at 
the  sides  and  within  the  triangle  are  the  intermediate  vowels,  many 
of  which  are  not  represented  in  written  language  by  special  signs. 

The  mouth  takes  up  a  definite  position  for  each  vowel  according 
as  it  is  pronounced  aloud  or  whispered.  These  positions  of  course 
differ  most  for  the  three  typical  vowels. 

As  shown  by  Fig.  100  the  larynx  is  most  raised  at  i  (ee),  the 
lips  are  drawn  back  and  the  oral  aperture  is  widened  transversely, 
the  teeth  are  brought  close  together,  and  the  tongue  is  raised 
from  the  floor  of  the  mouth  and  brought  near  the  palate  so  as 
to  leave  only  a  narrow  opening  for  the  air.  With  u  (oo),  on  >the 
contrary,  the  larynx  is  lowered  as  far 'as  possible,  the  oral  aperture 
is  brought  forward  and  constricted,  the  lips  forming  an  almost 
circular  opening,  owing  to  contraction  of  the  orbicularis,  and  the 
tongue  is  dropped  towards  the  floor  of  the  mouth  and  raised 
behind  towards  the  soft  palate.  Lastly,  with  a  (ah)  the  vocal 
tube  has  a  length  intermediate  between  i  (ee)  and  u  (oo),  the 
larynx  is  least  displaced,  the  mouth  is  wide  open  and  rounded, 
and  the  whole  tongue  is  drawn  back  towards  the  floor  of  the 
mouth  so  as  to  form  a  funnel-shaped  cavity. 

Certain  authors  distinguish  a  (ah,)  as  pharyngeal,  i  (ee)  as 
palatal,  u  (oo)  as  velar  (Fig.  100),  but  these  terms  have  little 
physiological  value.  The  phonic  characters  of  the  different  vowels 
depend  essentially  on  the  position  and  special  form  of  the  whole 
resonance  cavity,  and  not  merely  on  the  different  regions  in  which 
it  becomes  constricted. 

In  the  intermediate  vowels  the  different  movable  parts  of  the 
resonator  take  up  intermediate  positions :  e  (eh),  ea  (e  =  let),  ae 
(a  =  hat)  are  formed  between  i  (ie)  and  a  (ah) ;  o  (oh),  oa  (  =  or), 
a°  (6  =  shot)  between  u  (oo)  and  a  (ah). 

The  pure  vowels  are  pronounced  with  the  soft  palate  raised, 
and  the  nasal  cavities  more  or  less  completely  closed  (Fig.  100). 
When  the  soft  palate  is  not  raised  the  vowel  has  a  nasal  sound, 
and  if  the  nostrils  are  closed  this  is  intensified,  because  the  air 
in  the  nasal  cavity  is  better  able  to  vibrate  in  unison  with  the 
air  of  the  pharyngo-buccal  cavity. 


Ill 


THONATION  AND  AETICULA.TION 


157 


In  pronouncing  the  fundamental  vowel  a  (ah),  where  the 
oral  aperture  is  maximal,  the  soft  palate  is  least  raised 
(Czermak) ;  011  dropping  from  a  to  the  end-vowels  u  and  i  the 
soft  palate  is  raised  and  the  nasal  cavity  more  perfectly  closed 
in  proportion  as  the  oral  cavity  is  constricted.  This  agrees  with 
the  fact  that  a,  o,  e  are  easily  rendered  nasal,  which  is  difficult 
for  i  and  u. 

The  complete  series  u  (oo) . . .  a  (oh) ...  i  (re)  corresponds  to 


FIG.  100. — Shape  of  oral  cavity  in  the  production  of  the  three  fundamental  vowels  (Grutzner.) 

the  progressive  rise  in  pitch  when  the  vowels  are  pronounced  with 
the  ordinary  breath.  Although  the  several  vowels  can  be  pro- 
nounced on  different  musical  notes  it  is  very  difficult  to  enunciate 
u  clearly  in  the  highest  soprano,  and  i  in  the  deepest  bass. 

U...  i  really  represent  the  vowel -limits.  In  uttering  these 
the  canal  is  most  constricted ;  at  u  the  opening  of  the  lips  is 
narrowest,  at  i  the  oral  cavity  is  smallest,  owing  to  the  rise  of 
the  tongue  which  divides  it  into  two.  Beyond  these  limits  the 
character  of  the  vowel  sounds  is  obscured,  and  approximates  to 
that  of  the  consonants. 


158  PHYSIOLOGY  CHAP. 

The  fact  that  the  vowel  limits  are  reached  when  the  resonating 
cavity  is  most  restricted,  and  blocks  the  passage  of  the  air,  agrees 
with  the  fact  that  it  is  impossible  to  sing  u  and  i  very  long  and 
loud  like  the  other  vowels.  According  to  Wolf  u  can  only  be 
heard  distinctly  at  280  paces,  i  at  300,  while  a  is  quite  audible  360 
paces  distant. 

On  the  other  hand  the  vibrations  of  the  walls  of  the  resonance 
cavity  produced  by  the  vibration  of  the  air  is  maximal  with  the 
vowels  u  and  i,  minimal  with  a.  On  stopping  the  ears,  u  and  i 
sound  very  loud  to  the  ear,  a  much  less  so.  On  applying  the  palm 
of  the  hand  to  the  head,  the  cranial  bones  are  felt  to  be  vibrating 
at  u,  still  more  strongly  at  i,  and  not  at  all  at  a,  e,  o.  This  fact  has 
been  utilised  in  teaching  deaf  mutes  to  pronounce  i,  which  they  find 
the  most  difficult. 

The  diplitliongs  should  not  be  confused  with  the  intermediate 
vowels.  Grunmaeh  erroneously  regards  a,  u,  o  as  diphthongs ;  in 
our  opinion  it  is  more  correct  to  define  them  with  Goidanich,  as 
organic  alterations  of  the  normal  vowels.  All  the  intermediates 
represent  special  vowel  sounds  due  to  special  positions  of  the  phona- 
tory  apparatus.  In  diphthongs,  on  the  contrary,  as  Brticke  noted, 
there  is  a  rapid  passage  from  the  position  of  one  vowel  to  that  of 
the  next,  the  first  being  almost  always  accentuated.  In  the 
diphthongs  au  (  =  how),  ai  (  =  high'),  etc.,  the  first  vowel  functions 
as  the  sonant,  the  second  as  a  consonant. 

VIII.  The  formation  of  the  different  vowels  is  thus  funda- 
mentally due  to  the  special  positions  assumed  by  the  pharyugo- 
buccal  cavity  acting  as  a  resonator,  and  we  next  have  to  determine 
the  physical  nature  of  the  vowels,  i.e.  the  partial  tones  of  which 
they  are  composed,  and  the  relations  of  intensity  on  which  their 
timbre  or  quality  depends.  This  problem  is  more  complicated 
than  appears  at  first  sight. 

Generally  speaking,  the  sound  of  any  musical  instrument  is 
a  compound,  in  which  one  fundamental  tone,  the  deepest  and 
strongest,  and  several  harmonic  over-tones,  weaker  in  proportion 
as  their  pitch  is  higher,  can  be  distinguished.  But  this  theory  is 
not  applicable  to  the  human  voice,  especially  not  to  the  complex 
sounds  in  which  we  can  distinguish  the  specific  characters  of  the 
different  vowels.  This  is  evident  from  the  following  facts  :— 

(a)  The  different  vowels  can  be  recognised  even  when  they  are 
whispered,  that  is,  uttered  without  any  laryngeal  voice. 

(&)  The  different  vowels  can  be  uttered  either  in  speaking  or 
singing  to  the  same  musical  note. 

(c)  Any  vowel  may  be  sung  to  different  notes  of  the  scale,  and 
recognised  for  each  note. 

These  three  points  suggest  that  the  complicated  laryngeal 
sounds  acquire  their  special  vowel  character  from  the  pharyngo- 
buccal  cavity,  which  acts  as  a  resonator,  and  reinforces  certain 


in  PHONATTON  AND  AETICULATION  159 

partials,  while  others  are  excluded,  according  as  it  assumes  the 
position  for  saying  or  singing  one  or  other  of  the  vowels. 

The  earliest  experiments  on  the  physical  nature  of  vowel  tones 
were  made  by  Willis  (1829),  and  Wheatstone  (1837),  who  con- 
structed a  theory  of  vowel  tones  which  remained  unnoticed  for 
twenty  years.  Douders  (1857)  first  showed  clearly  that  the  cavity 
of  the  mouth  for  different  vowels  is  tuned  to  different  pitches.  It 
forms  a  resonator  which  can  be  tuned  to  the  different  sounds 
characteristic  of  different  vowels. 

In  order  to  ascertain  the  tones  which  characterise  the  several 
vowels,  Donders  cut  out  the  laryngeal  sounds  which  usually 
accompany  them,  by  whispering  them  one  after  the  other ;  under 
these  conditions  sounds  are  produced  in  which  the  ear  can  re- 
cognise a  definite  pitch  in  the  dominating  tone,  which  varies  for 
the  different  vowels,  but  is  approximately  constant  in  all  persons 
of  the  same  sex  and  age.  These  sounds  are  caused  by  the  air-blast 
in  the  oral  cavity,  where  the  tones  are  reinforced  so  that  it  is 
possible  to  recognise  the  different  vowels,  although  they  are 
wreaker  than  the  normal  voice.  In  speaking  or  singing  the 
sounds  given  out  by  the  resonator  are  associated  with  the  laryngeal 
sounds,  and  the  specific  partials  of  the  different  vowels  are  greatly 
reinforced,  and  give  the  laryngeal  sounds  their  characteristic 
timbre. 

In  his  classical  work  Die  Lehre  von  den  Tonempfindungen 
Helmholtz  placed  his  theory  of  vowel-tones  on  a  strict  scientific 
basis,  and  extended  Bonders'  hypothesis.  According  to  Helmholtz 
"  the  vowels  of  speech  are  in  reality  tones  produced  by  membranous 
tongues  (the  vocal  cords)  with  a  resonance  chamber  (the  mouth) 
capable  of  altering  in  length,  width,  and  resonant  pitch,  and  hence 
capable  also  of  reinforcing  at  different  times  different  partials  of 
the  compound  tone  to  which  it  is  applied."  J 

In  order  to  determine  what  partial  tones  of  the  mouth  cavity 
give  their  vowel  character  to  the  laryngeal  tones  Helmholtz 
employed  a  more  accurate  method  than  that  of  Donders.  He 
struck  tuning-forks  of  different  pitch,  and  held  them  before  the 
open  mouth  arranged  for  the  pronunciation  of  each  vowel  in  turn. 
The  pitch  of  the  fork  which  then  sounded  loudest  gave  the  proper 
tone  to  which  the  mouth  was  tuned.  Helmholtz  found  that  the 
pitch  of  the  vowels  rises  progressively  from  u  (oo)  to  a  (ah)  and 
from  a  (nil}  to  i  (ee).  In  u,  o,  a  he  only  distinguished  a  single 
note  ;  in  ae,  e,  i,  oc,  u'  two  different  notes,  because  the  mouth  cavity 
is  divided  in  the  pronunciation  of  these  vowels  by  the  rise  of  the 
tongue  (Fig.  101).  He  maintained  that  the  vowel  notes  are  the 
same  in  men,  women,  and  children.  The  least  change  in  the 
position  of  the  oral  cavity  modifies  the  quality  of  the  tone,  and 
thus  gives  rise  to  the  intermediate  vowels  which  are  so  common 

1  Sensations  of  Tone,  Helmholtz,  tr.  Ellis  from  3rd  ed.,  p.  153,  1875. 


160 


PHYSIOLOGY 


CHAP. 


in  the  Franco-Italian  and  Anglo-Saxon  languages.  This  fact, 
according  to  Helmholtz,  explains  why  the  vowel  tones  as  fixed 
by  Bonders — and  also  by  Merkel,  Auerbach,  Krinig,  and  other 


n                      f    : 

• 
»• 

9- 

r 

> 
*- 

f- 

—  v,  — 

VL  •»               * 

rrr\r       i     f 

vy              1 

f 

9 

y         d     0     A     A 
* 

E  r  < 
i 

'. 
[) 

T 

ri 

FIG.  101.—  Pitch  of  vowels  according  to  Helmholtz. 

later  observers — differ  in  certain  respects   from  those  which    he 
obtained. 

He  finally  concluded  that  "  vowel  qualities  of  tone  consequently 
are  essentially  distinguished  from  the  tones  of  most  other  musical 
instruments  by  the  fact  that  the  loudness  of  their  partial  tones 


FIG.  102. — Kcinig's  apparatus  for  illustrating  the  quality  of  vowel  tones  by  a  manometric  flame. 
Above,  the  figure  shows  a  section  of  Konig's  manometric  capsule  and  the  rubber  membrane 
which  divides  the  stream  of  gas  from  the  air  of  the  tube  that  is  sung  into. 

does  not  depend  upon  the  numerical  order,  but  upon  the  absolute 
pitch  of  those  partials."  l 

Helmholt/    attempted  to  demonstrate  the  correctness    of   his 
view  by  synthetically  combining  the  tones  of  certain  tuning-forks 

1  Page  172,  Ellis'  tr.,  q.v. 


Ill 


PHONATION  AND  ARTICULATION 


1G1 


in  his  well-known  vowel  apparatus.  He  obtained  the  sound  of  u  (oo) 
by  combining  the  fundamental  tone  I1  \vith/&2 ;  the  sound  of  u  (oh) 
by  combining  the  same  fundamental  tone  with  &3 ;  the  sound  of  a 
(ah)  by  combining  bl  with  I4.  He  was,  however,  unable  to  repro- 
duce the  highest  tones  of  e  (ch)  and  i  (re)  by  the  tuning-forks. 

The  vowel  tones  were  also  studied  by  Ko'nig  with  the  aid  of 
his  mauometric  flame  apparatus  (Fig.  102).  This  method  is  very 
useful  in  analysing  the  complex  nature  of  the  vowel  tones,  since  it 
shows  the  difference  in  the  form  of  sound-wave  not  only  for  the 


IT 


Fio.  103.— Flame  pictures  of  the  vowels  a  (ah),  o  (oh),  u  (oo),  in  three  different  keys. 

separate  vowels,  but  for  the  same  vowel  at  a  different  pitch.  The 
duration  of  the  wave-periods  is,  however,  the  same  for  the  different 
vowels  sung  to  the  same  note  (Fig.  103).  The  alteration  of  the 
form  of  the  wave  while  the  period  is  constant  must  be  due  to  the 
superposition  of  tones  developed  in  the  mouth,  characteristic  of 
the  vowels  upon  the  tones  emitted  by  the  larynx.  But  it  is  not 
possible  from  the  simple  wave-form  shown  by  the  flames  to 
determine  the  number,  pitch,  and  strength  of  the  partial  tones 
from  which  the  different  sung  vowels  result. 

Hallock  (1896)  employed  a  method  founded  on  that  of  Ko'nig. 
He  connected  eight  resonators  in  harmonic  series  with  as  many 
Konig's  man  om  etric  capsules,  sang  a  vowel  in  front  of  them,  and 
then  photographed  the  reflection  of  the  flames  in  a  mirror.  From 

VOL.  Ill  M 


162  PHYSIOLOGY  CHAP. 

these  photographs  the  partials  present  in  any  vowel  tone  within 
the  range  of  the  resonators  could  be  detected. 

Edison's  invention  of  the  phonograph  (1877),  and  its  perfection 
by  himself,  by  Graham  Bell  and  others,  reopened  the  whole 
question  of  vowel  tones,  to  which  Fleeming-Jenkm,  Ewing, 
Hermann,  Hensen,  Pipping,  Boeke,  Lloyd,  M'Kendrick,  and  others, 
have  contributed  in  the  controversy.  The  chief  question  has  been 
whether  each  word  has  an  absolute  or  a  relative  pitch,  and  whether 
on  changing  the  prime  tone  to  which  a  vowel  is  sung,  its  principal 
over-tones  change  too,  as  is  the  case  with  ordinary  musical  instru- 
ments ;  or  whether  the  height  of  the  partial  tones  which  give  the 
vowel  its  character  always  remains  the  same,  independent  of  the 
pitch  of  the  prime  tone  to  which  it  is  sung. 

The  method  employed  for  solving  this  difficult  problem  con- 
sisted in  taking  graphic  tracings  of  the  vowel  sounds,  or  vowel 
phonograms,  and  then  analysing  the  complex  curves  of  these 
sounds  into  the  simple  curves  of  the  component  tones  by  means  of 
Fourier's  theorem. 

Bonders  (1870)  first  applied  the  phonautograpli  of  Leon  Scott 
to  the  investigation  of  vocal  phonograms.  In  1878  Fleeming- 
Jenkin  and  Ewing  employed  Edison's  tin-foil  phonograph  for 
this  purpose,  although  it  was  too  imperfect  to  produce  the  sounds 
of  all  the  vowels  clearly.  These  authors  came  to  the  conclusion 
that  both  relative  and  absolute  factors  entered  into  the  composition 
of  the  vowels — an  intermediate  theory  already  accepted  by 
Auerbach  and  by  Helmholtz  in  later  editions  of  his  book. 

Hermann  took  up  the  subject  about  1890,  by  the  improved 
wax-cylinder  phonograph,  and  photographed  the  curves  by  a 
beam  of  light,  reflected  from  a  small  mirror  attached  to  the 
vibrating  disc  of  the  phonograph.  The  curves  thus  obtained, 
representing  the  wave  forms  of  the  vowel  tones,  were  then 
analysed  by  Fourier's  method. 

Hermann  found  that  the  phonograph  only  reproduces  the 
sung  vowels  accurately  when  the  cylinder  rotates  at  the  same 
rate  as  that  at  which  they  were  recorded,  and  that  the  quality 
of  a  vowel  varies  considerably  with  the  rate  of  the  cylinder. 
He  maintains  the  fixed-pitch  theory,  and  states  that  there  is 
for  each  vowel  a  characteristic  tone  which  he  terms  the  formant. 
He  further  assumes  (and  in  this  his  theory  differs  from  all  others) 
that  the  formant  need  not  necessarily  be  a  partial  tone  of  the 
fundamental.  The  pitch  of  the  formant  may  vary  considerably ; 
with  the  same  prime  it  may  vary  in  certain  cases  as  much  as 
several  semitones.  Fig.  104  shows  in  musical  notation  the  pitch 
of  the  vowel  according  to  Hermann. 

Pipping's  results  in  the  main  agree  with  those  of  Hermann. 
He  collected  and  analysed  the  vowel  curves  by  means  of  Hensen's 
gramograph. 


Ill 


PHONATION  AND  AKTICULATION 


163 


Sauberschwartx  with  Griitzner  (1895)  investigated  the  subject 
by  an  ingenious  application  of  the  laws  of  the  interference  of 
sounds.  The  vowels  were  sung  into  the  mouthpiece  of  a  long 
tube,  to  which  other  short  tubes  of  definite  length  were  attached. 
By  closing  the  outer  end  of  certain  of  these  tubes  various  partials 
could  be  extinguished  by  interference,  and  the  listener  at  the 
other  end  of  the  tube  observed  an  alteration  in  the  quality  of 
the  vowel.  Sauberschwartz,  generally  speaking,  supports  Hermann. 

Later  researches  by  Boeke,  M'Kendrick  and  others  added 
new  facts  to  the  analysis  of  vowel  sounds.  At  the  Fifth 
International  Physiological  Congress  at  Turin,  Hensen  stated 
that  the  resonance  tones  of  the  oral  cavity  arranged  for  the 
pronunciation  of  different  vowels  are  variable  within  certain 
limits,  as  had  been  established  by  Pipping.  But  he  also  showed 
that  the  pitch  of  the  laryngeal  tones  produces  a  rise  in  the  oral 
resonance  tones.  At  a  they  may  rise  from  940  to  1175  ;  at  o 


1 

! 

1 

j   j 

L 

J 

i 

i 

™ 

• 

-#• 

ff 

j 

—  j  — 

~]r  *  — 

i 

—  J  —  5^  — 
™ 

^ 

ln\ 

i 

v  Is 

* 

t                  -A- 

f 

u  o 

FIG.  104. — Pitch  of  the  vowels  according  to  Hermann. 

from  498  to  552  double  vibrations.  The  problem  of  vowel  sounds 
is  therefore  more  complicated  than  was  supposed,  and  still  awaits 
its  final  solution. 

In  conclusion,  Bonders'  theory,  which  assumes  that  the  oral 
cavity  is  tuned  for  each  vowel  to  a  tone  of  fixed  and  unalterable 
pitch,  whatever  the  fundamental  laryngeal  note  to  which  it  is 
sung,  is  certainly  too  restricted.  Each  vowel,  however,  undoubtedly 
has  one  or  more  predominating  partial  tones,  formed  by  the  oral 
cavity,  on  which  the  specific  character  of  that  vowel  depends.  Since 
the  form  of  the  mouth  varies  with  the  individual  and  the  race,  and 
the  positions  it  assumes  in  different  dialects  and  even  in  different 
individuals  in  the  pronunciation  of  the  several  vowels  are  not 
and  cannot  be  identical,  it  is  easy  to  see  why  the  formants  of 
any  vowel  are  not  identical  in  all  cases.  They  approximate, 
however,  in  certain  common  characters,  by  which  it  is  possible 
to  identify  a  vowel,  however  differently  it  may  be  formed  by 
different  individuals.  It  is  also  certain  that  the  resonating 
cavity  varies  very  little  when  a  musical  scale  is  sung  to  a  single 
vowel.  The  ear  is  always  able  to  recognise  the  vowel  sung, 
whatever  its  pitch ;  each  vowel,  however,  has  a  special  register 
in  which  its  quality  is  best ;  the  soprano  is  best  adapted  to  the 


164  PHYSIOLOGY  CHAP. 

end- vowel  i,  the  bass  to  the  end-vowel  u.  Finally,  the  clearness 
and  purity  of  vowel-formation  varies  considerably  in  different 
languages.  It  is  generally  admitted  that  the  sung  or  spoken 
vowels  are  purest  in  the  Italian  tongue,  and  least  so  in  English. 
Italians,  moreover,  prefer  the  fundamental  vowel  sounds  a,  i,  u, 
which  He  at  the  extremes  of  the  natural  system ;  they  also  admit 
the  middle  vowels  e  and  6,  b  and  6  (open  and  closed),  but  reject 
all  other  intermediate  vowels.  The  English,  on  the  other  hand, 
not  only  prefer  these,  but  have  further  developed  a  whole  series 
of  vowels  characterised  by  imperfect  formation,  which  makes 
them  very  difficult  to  recognise  and  classify. 

IX.1  It  is  difficult  to  draw  up  any  rational  classification  of 
consonants.  The  most  satisfactory  would  be  based  on  their 
objective,  physical  nature,  but  we  have  no  means  for  the  physical 
analysis  of  elementary  consonant  sounds,  such  as  enables  us  to 
determine  the  physical  nature  of  musical  tones.  Hermann  found 
himself  at  a  loss  after  some  introductory  experiments.  We 
can  only  fall  back  on  the  physiological  classification,  which 
is  founded  on  the  mode  of  producing  the  consonant  sounds  and 
their  subjective  acoustic  character. 

Hermann  made  a  primary  division  of  consonants  into  two 
groups,  voiced  and  voiceless,  according  as  the  sounds  formed  are 
accompanied  by  laryngeal  tones  or  not.  Voiced  consonants  are 
much  more  numerous  than  voiceless  consonants ;  they  are  sub- 
divided into  semivowels,  or  liquids  (which  can  function  either  as 
consonants  or  vowels,  and  can  be  pronounced  alone,  independent 
of  other  vowel  sounds),  and  sounding  consonants. 

It  is  indispensable  to  the  perfect  formation  of  vowel  sounds 
that  the  pharyngeal  cavity  should  be  closed  off  from  the  nasal 
fossae.  When  this  does  not  take  place,  the  quality  of  the  vowels 
alters  and  they  become  nasal,  since  the  expiratory  current  passes 
through  the  nose  as  well  as  the  mouth.  On  closing  the  nostrils 
the  nasal  character  is  intensified  and  may  be  more  prolonged. 
This  nasal  quality  characterises  the  French  language,  but  is  also 
present  in  Italian,  Spanish,  and  all  other  languages. 

The  nasal  vowels  an,  en,  6n  represent  the  transition  between 
the  vowels  and  the  liquids  or  semivowels. 

The  semivowels  are  in,  n,  ng,  I,  and  r.  They  have  the 
character  of  vowels  because  they  are  always  uttered  with  the 
voice,  i.e.  they  are  accompanied  by  vibrations  of  the  glottis 
(except  when  whispered),  and  sometimes  carry  the  accent,  when 
they  function  as  pure  vowels.  They  approximate  to  consonants 
because  they  are  pronounced  with  the  mouth  partly  or  entirely 
closed,  and  in  the  majority  of  cases  the  accent  does  not  fall  on 
them,  so  that  they  mostly  play  the  part  of  consonants. 

1  This  section  has  been  considerably  abridged    from  the  Italian  text,   which 
contains  more  detail  than  is  required  by  the  physiological  student. — ED. 


Ill 


PHONATION  AND  ARTICULATION 


165 


The  sounds  in,  n,  n<j,  constitute  a  distinct  group  of  nasal 
semivowels  (rhinophones)  characterised  by  the  expulsion  of  the 
expired  air  through  the  nose,  where  the  laryngeal  tone  acquires 
a  characteristic  resonance,  while  the  mouth  is  closed  in  a  definite 
position.  For  m  the  mouth  is  closed  with  the  lips  pressed 
together  (labial  articulation).  For  n  the  oral  cavity  is  generally 
closed  by  applying  the  tip  of  the  tongue  to  the  upper  alveolar 
arch  (alveolar  articulation)  or  to  the  hard  palate  (palatal  articu- 
lation) (Figs.  105  and  106).  In  ng  (represented  in  Sanskrit 
by  a  special  symbol)  the  mouth  is  closed  by  the  approxi- 


Fio.  105. — Articulation  of  >i". 
(Luciani  and  Baglioni.) 


FIG.  106. — Articulation  of  gna. 
(Luciani  and  Baglioni.) 


Impression  left  by  the  tongue  stained  by  cocoa  powder  previous  to  articulation. 

mation  of  the  dorsum  of  the  tongue  to  the  soft  palate,  either 
more  to  the  front  (when  preceded  by  e  and  i  as  in  Engel, 
thing}  or  more  to  the  back  (if  preceded  by  a  and  o,  as  in 
Wange,  long]. 

The  semivowels  /  and  r  are  distinguished  from  these  nasal 
sounds  by  the  fact  that  their  resonance  comes  from  the  mouth, 
and  not  from  the  nasal  cavities  which  are  closed  by  elevation 
of  the  soft  palate.  Several  kinds  of  I  can  be  distinguished 
according  to  the  seat  of  articulation,  the  most  usual  being  formed 
by  bringing  the  tip  and  lateral  edges  of  the  tongue  into  contact 
with  the  alveolar  and  dental  arches,  while  the  air  escapes 
through  two  lateral  openings  between  the  premolars  (Fig.  107). 

M  i 


166 


PHYSIOLOGY 


CHAP. 


This  is  the  so-called  alveolar  I  used  in  most  European  languages. 
Besides  this  there  is  also  an  apical  I,  which  is  easily  formed  by 
applying  the  tip  of  the  tongue  to  the  hard  palate,  above  the 
alveolar  border.  This  is  the  /  of  the  English  will,  well,  hall, 
etc.  It  is  also  found  in  Norwegian  and  Polish. 

r  differs  from  /  because  the  tip  of  the  tongue  is  rapidly  and 
intermittently  applied  to  the  palate,  which  gives  a  vibratory 
character  to  the  laryngeal  tone.  The  labial  r  (brr)  is  not  in 
written  language,  but  is  often  formed  by  children,  and  is  also 
an  interjection  e.g.  to  express  cold.  In  Germany  coachmen  use 


FIG.  107. — Articulation  of  Za. 
(Luciani  and  Baglioni.) 


FIG.  108.— Articulation  of  glia. 
(Luciani  and  Baglioni.) 


it  to  stop  their  horses.  Gael  states  that  it  occurs  in  the  language 
of  the  savages  on  an  island  near  New  Guinea.  The  most  common 
forms  of  the  anterior  and  alveolar-palatal  are  formed  by  vibrating 
the  tip  of  the  tongue  against  the  dental  and  alveolar  arches, 
and  by  applying  it  in  the  apical  position  to  the  hard  palate. 
The  velar  or  uvular  r,  formed  by  applying  the  dorsum  of  the 
tongue  to  the  uvular  portion  of  the  soft  palate,  is  less  vibrant, 
and  is  known  as  the  French  r  because  it  is  characteristic  of  that 
language.  Lastly,  there  is  a  laryngeal  r  caused  by  the  tremulous 
closure  of  the  glottis,  with  a  deep,  soft  tone  as  in  the  English 
girl,  bird,  or  the  higher  and  harsher  gli  of  Arabic. 

The  physical  nature  of  the  semivowels  has  not  been  determined, 
owing  to  the  difficulties  which  their  study  presents.  According 
to  Hermann  and  Matthias  there  are  formants  in  the  sounds 


Ill 


PHONATION  AND  AKTICULATION 


1G7 


m,  n,  I,  which  can  be  recognised  in  phonautographic  curves.  The 
phonograms  of  r,  according  to  Hensen  and  Winckler,  exhibit 
a  rhythmical  crescendo  and  decrescendo  like  the  modemto  beats  of 
a  musical  tempo. 

Consonants  proper  are  distinguished  from  semivowels  in  being 
invariably  composed  of  sounds,  while  the  accent  never  falls  on 
them,  i.e.  they  never  act  as  syllabic  sonants.  They  form  two 
subgroups,  according  as  they  are  accompanied  by  distinct  laryngeal 
tones,  or  not ;  the  first  are  called  sounding  (or  median)  consonants, 


FIG.  109. — Articulation  of  da  and  gia. 
(Luciani  and  Baglioni.) 


Km.  110.— Articulation  of  co  and  ga. 
(Luciani  and  Baglioni.) 


the  second  mutes.      Both  may  be   subdivided  into   occlusives   or 
explosives,  and  fricatives  or  spirants. 

Explosive  consonants  are  produced  by  the  sudden  opening  of 
the  oral  cavity,  owing  to  the  pressure  of  the  expiratory  air. 
Their  formation  accordingly  involves  the  closure  of  the  pharyngo- 
buccal  cavity  at  a  certain  point,  in  which  sense  only  they  are 
occlusive  or  dosing  sounds.  Some  authors  maintain  that  they 
should  be  called  explosive  when  followed  by  a  vowel  or  semivowel 
(as  in  ba,  pi,  de,  te,  bra,^>la,  dro,  knu),  and  occlusive  when  preceded 
by  a  vowel  or  semivowel  (ab,  ip,  ed,  ot,  arb,  alp,  ord,  onk).  But 
this  a  fallacy.  Every  one  can  demonstrate  that  even  when 
preceded  by  vowels  or  semivowels,  the  characteristic  sound  of  an 
explosive  consonant  is  heard,  not  at  the  closure,  but  at  the 
reopening,  of  the  cavity  which  has  been  momentarily  closed. 


168 


PHYSIOLOGY 


CHAP. 


Fricative  consonants  are  produced  by  sounds  of  friction  as 
the  expiratory  current  passes  through  the  constricted  oral  cavity, 
and  are  consequently  continuous  or  liquid  sounds  like  the  semi- 
vowels, unlike  the  explosives  which  are  instantaneous. 

The  explosive  consonants  b,  d,  g;,  g",  are  formed  with  the 
glottis  open,  and  may  be  preceded  and  accompanied  by  a  laryngeal 
tone ;  in  p,  t,  c',  k,  the  glottis  is  fully  closed,  and  the  expulsion  of 
the  air  is  not  accompanied  by  vibrations  of  the  vocal  cords. 

The  labials  &  and  p  are  always  formed  by  the  opening  of  both 
lips.  In  the  alveolars,  </,  <f,  t,  c'  the  position  of  the  tongue  varies  ; 


FIG.  111.— Articulation  of  i  and  en'. 
(Luciani  and  Baglioni.) 


FIG.  112. — Articulation  of  jet. 
(Luciani  and  Baglioni.) 


hence  their  sound  differs  more  or  less  noticeably.  The  same  holds 
for  the  palatals  ga  and  k  (Figs.  109,  110). 

Fricative  or  spirant  consonants  are  formed  when  the  expiratory 
blast  of  air  is  driven  with  a  certain  force  through  a  confined 
passage.  Unlike  the  explosives  the  fricatives  are  preceded,  not 
By  the  closure,  but  simply  by  the  constriction  of  the  pharyngo- 
buccal  cavity.  They  may  or  may  not  be  accompanied  by  laryngeal 
tones,  i.e.  may  be  voiced  or  voiceless,  w,  v,  the  French  and  Italian 
j,  are  pronounced  with  the  voice ;  /,  the  German  ch  and  sell,  and 
French  ch,  without  the  voice ;  with  or  without,  s,  z  and  the 
English  tli.  Grammarians  term  the  sounding  s  and  z  lenes,  and 
the  mute  s  and  z  fortes.  But  the  true  physiological  difference  is 
that  the  former  are  accompanied  by  laryngeal  sounds. 

The  only  consonant  which  is  necessarily  voiceless  is  h ;  it  may 


Ill 


rHONATION  AND  AETICULATION 


109 


be  tennis,  due  to  the  slight  sound  that  accompanies  the  opening 
of  the  glottis  previous  to  the  utterance  of  a  vowel  (spiritus  lenis 
of  the  Greeks,  aleph  of  the  Hebrews,  hamze  of  the  Arabs),  or 
t'ortis  (spiritus  asper,  Greek;  he,  Arabic).  The  latter  sound  is 
'absent  in  Italian,  but  exists  in  many  languages  (harp,  house, 
Hans}.  The  mute  h  is  sometimes  represented  (as  a  historical 
reminder)  in  Italian,  French,  and  English,  but  is  frequently 
omitted  in  written  language. 

In   pronouncing   s   the   constriction  is  usually  produced   by 
contact  of  the  lateral  edges  of  the  tongue  with  the  entire  dental 


]•'!<•.  113.— Articulation  of  sa.     (Griitzner.)  FK;.  114.—  Articulation  of  scia.    (GriitziuT.) 

Impression  left  by  the  tongue  stained  with  carmine  previous  to  articulation. 

arcade,  except  the  small  anterior  median  space  opposite  the  two 
incisor  teeth  (Fig.  113) ;  the  sound  is  due  to  the  escape  of  air 
through  this  narrow  passage. 

The  English  tk  is  formed  by  applying  the  tip  of  the  tongue 
above  the  lower  incisors  till  it  lightly  touches  the  lower  lip 
(interdental  articulation). 

Both  s  and  th  may  be  pronounced  without  the  voice  (thick, 
thing},  or  with  the  voice  (those,  that).  The  mute  th  corresponds 
to  6a  and  the  sounding  th  to  8a  of  modern  Greek. 

The  fricative  which  the  Germans  write  sch,  the  French  ch, 
and  the  Italians  sci,  is  distributed  through  all  known  languages, 
and  is  really  a  simple  consonant,  although  in  a  few  languages 
(Sanskrit,  Hebrew/ Cyrillian  and  Glagolitic  dialects  of  Slav)  it 


170  PHYSIOLOGY  CHAP. 

is  expressed  by  a  special  sign.  It  is  not,  in  fact,  a  series  of  sounds, 
but  a  single  continuous  sound  very  similar  to  s,  formed  by  con- 
striction of  different  parts  of  the  oral  cavity.  It  is  due  to 
application  of  the  lateral  edges  of  the  tongue  to  the  hard  palate, 
alveoli,  molar  teeth,  allowing  an  escape  of  air  through  a  median 
passage  between  the  tip  of  the  tongue  and  palate,  which  is  wider 
and  more  posterior  than  in  s  (Figs.  113,  114). 

X.  The  words  of  a  language  result  from  the  different  combina- 
tions of  the  elementary  sounds  we  have  been  dealing  with— 
vowels,  semivowels,  sounding  and  mute  consonants.  One  or  two 
vowels,  alone  or  accompanied  by  semivowels  or  consonants  so  as 
to  make  a  continuous  phonetic  unity,  form  the  so-called  syllables. 
The  phonetic  continuity  of  the  syllable  depends  on  its  being 
pronounced  in  one  uninterrupted  breath,  which  is  only  possible 
when  its  elements  are  capable  of  fusion  or  agglutination.  When 
the  successive  sounds  are  not  capable  of  agglutination,  so  as  to 
be  uttered  in  a  single,  continuous,  expiratory  effort,'  a  short 
interruption  or  pause  (the  hiatus)  is  interposed  between  them,  by 
which  the  sound  is  divided  into  two  or  more  syllables. 

The  coherence  of  two  vowels  forms  a  diphthong ;  when  they 
make  a  single  syllable,  i.e.  fuse  together  so  that  the  voice  is 
not  interrupted  in  the  rapid  transition  from  the  position  for  the 
first  to  that  for  the  second  vowel ;  when,  on  the  contrary,  two 
vowels  follow  without  agglutinating,  so  that  the  voice  is  interrupted 
in  passing  from  one  to  the  other,  they  do  not  form  part  of  the  same 
syllable  and  do  not  constitute  a  diphthong  (aid,  poetry}.  The 
division  of  two  normally  agglutinated  vowels  by  the  interposition 
of  a  hiatus  is  known  as  diuresis ;  the  fusion  of  two  separate  vowels 
which  form  part  of  two  successive  syllables,  as  synaresis.  Tn  the 
first  case  one  of  the  syllables  is  made  into  twTo,  in  the  second  two 
syllables  are  fused  into  one. 

More  frequently  the  syllable  consists  of  one  vowel  or  diphthong 
and  one,  two,  or  three  semivowels  or  consonants,  and  vice  versa. 
Two  laws  must  be  observed  for  the  adhesion  of  a  vowel  with 
semivowels  and  consonants :  (a)  Vowels  readily  adhere  to  semi- 
vowels, imperfectly  to  explosives  and  fricatives;  (£)  Both 
semivowels  and  consonants  agglutinate  perfectly  with  vowels  to 
form  single  syllables. 

The  combination  of  several  syllables  constitutes  polysyllabic 
words,  in  which  the  phonetic  unity  is  interrupted  once  or  oftener, 
according  as  it  consists  of  two  or  more  syllables.  The  break 
is  produced  by  the  discontinuity  of  the  outgoing  expiratory 
blast  due  either  to  occlusion  or  narrowing-  of  the  resonating 

o  o 

cavity  at  some  point  along  its  course — glottis,  soft  palate,  hard 
palate,  or  lips.  The  interruption  may  be  more  or  less  appreci- 
able according  as  it  is  more  or  less  prolonged,  and  is  not  always 
a  complete  silence,  but  may  be  a  light  aspiration — the  tennis 


in  PHONATION  AND  AKTICULATION  171 

h,  or  spirit-us  lewis  of  Greek — which  is  not  usually  marked  in 
writing. 

In  each  syllable  accent  and  yuaiUity  have  to  be  distinguished. 
"  Accent "  means  the  loudness  and  pitch  of  tone  with  which  the 
.syllable  is  pronounced.  In  syllables  which  consist  of  one  or  two 
vowels  combining  with  one,  two,  or  three  semivowels  or  consonants, 
the  accent  falls  on  the  sound  which  is  uttered  in  the  strongest 
and  highest  voice  :  this  is  the  sonant  of  the  syllable.  The  rest 
of  the  elements  associated  with  the  sonant  and  pronounced  in  a 
weaker  and  lower  voice, — whether  vowels,  semivowels,  sounding 
consonants,  or  dumb  consonants — form  the  consonants. 

ir»rd  accent,  again,  must  be  distinguished  from  syllabic  accent; 
it  falls  on  those  syllabic  sonants  which  are  pronounced  in  the 
loudest,  highest  voice.  Physiologically  the  accent  may  be  suit- 
divided  as  pJton-ic  and  tonic  according  to  its  strength  or  pitch. 
Practically  this  distinction  is  rarely  made,  because  the  accent 
generally,  depends  on  the  higher  pitch  at  which  the  syllable  is 
uttered. 

The  "  quantity  "  of  the  syllables  depends  on  their  brevity  or 
length,  i.e.  the  physiological  duration  of  the  expiratory  breath  in 
which  they  are  uttered,  which  varies  according  to  the  different 
vowels,  semivowels,  and  consonants.  In  Greek  and  Latin  the 
quantity  of  the  syllable  was  regularly  distinguished  and  used  as 
the  base  of  metric  poetry.  Modern  languages  attach  little  weight 
to  the  quantity — i.e.  brevity  or  length — of  the  syllables,  since 
this  is  dominated  by  the  accent,  which  has  become  the  base  of 
modern  metrical  poetry.  Even  when  imitating  classical  metres 
we  emphasise  the  accent,  not  the  length  of  the  syllables — a 
splendid  example  of  this  being  the  work  of  the  Italian  poet, 
Carducci. 

The  combination  of  syllables  leads  to  the  formation  of  sentences 
which  are  divided  by  pauses  of  different  length,  marked  in  writing 
by  commas,  semicolons,  etc.  The  words  of  which  they  consist  are 
variously  accentuated.  There  is  also  a  sentence  accent,  which 
falls  on  the  words  we  emphasise  in  speaking,  and  sometimes 
underline  in  writing.  The  pitch  of  the  ordinary  speaking  voice 
varies  within  the  limits  of  a  half-octave.  In  European  languages 
the  different  tones  of  the  language  colour  the  phrases  and  alter 
their  expression.  Correct  diction  and  accent  is  a  special  gift  with 
which  different  individuals  are  very  variously  endowed.  This 
may  not  make  their  speech  more  intelligible,  but  it  certainly 
renders  it  more  effective  and  agreeable. 

XI.  The  development  of  speech  in  children  closely  follows 
their  anatomical  development  and  the  physiological  exercise  of 
the  speech  organs.  They  begin  by  vocalising,  and  utter  high- 
pitched  vocal  sounds,  i,  a,  e,  which  constitute  the  cries  and  in- 
articulate sounds  of  infancy.  The  child's  first  articulate  utterances 


172  PHYSIOLOGY  CHAP. 

are  those  that  are  most  easily  formed,  viz.  semivowels  and  labial 
consonants  ( pa,  ba,  ma,  Iru,  Ira,  pra\  which  require  only  a  single 
action  of  the  lips  that  are  perfectly  formed  from  birth  and  capable 
of  function.  A  little  later  conies  the  formation  of  the  alveolar 
consonants  (da,  to)  winch  cannot  be  uttered  till  the  jaws  are  well 
developed  and  the  teeth  protruding.  The  palatals  and  volars  are 
acquired  later,  1  toth  because  they  are  harder  to  form,  and  because 
the  development  of  the  soft  palate  is  completed.  Ca  (ka)  is  easier 
than  ga,  which  does  not  occur  in  primitive  languages,  as  g  was  a 
later  modification  of  c.  The  ga  sound  is  often  replaced  by  children 
with  ta.  The  semivowel  r  is  harder  to  pronounce  than  m,  n,  and 
/.  Many  children  and  adults  lisp,  i.e.  are  unable  to  utter  the 
alveolar  r,  and  substitute  I  for  it. 

Up  to  a  certain  point  there  is  a  parallelism  between  the 
ontogenetic  and  phylogenetic  development  of  language  in  the 
different  races.  Some  primitive  languages  are  very  rich  in  vowels  ; 
but  after  a  certain  point  of  development  they  employ  many 
consonants.  Up  to  the  present  there  has  been  no  comprehensive 
study  of  the  development  of  primitive  idioms,  but  it  may  be  stated 
generally  that  languages,  like  individuals,  evolve  until  they  reach  a 
certain  point  of  development,  after  which  they  suffer  a  slow  but 
persistent  transformation,  for  worse  or  for  better. 

It  is  well  known  that  the  dialects  of  savage  races  may  undergo 
such  modifications  in  the  course  of  a  few  years  that  they  are 
hardly  recognisable.  Writing  and  written  language  play  an 
important  part  in  checking  or  hindering  the  natural  tendency  of 
every  language  to  transformation,  but  this  is  largely  promoted 
by  contact  between  the  several  dialects  and  vernaculars,  as  well 
as  by  intercourse  between  peoples  who  employ  different  idioms. 

The  great  historical  transformation  of  Latin  into  the  modern 
Romance  languages  may  perhaps  be  taken  as  an  illustration  of  the 
above.  Even  before  the  fall  of  the  Roman  Empire  it  was  favoured 
by  the  predominating  influences  of  the  unlettered  popular  dialects 
during  the  early  part  of  the  Middle  Ages,  over  the  fixed  idiom  of 
the  Latin  Codices.  The  metamorphosis  took  place  more  rapidly 
in  France  than  in  Italy,  which  was  the  centre  of  Roman  civilisation. 
And  French  literature  was,  for  this  very  reason,  nearly  two 
centuries  ahead  of  Italian  literature. 

But  while  written  literature  may  check  the  natural  evolution 
of  a  language,  it  can  never  arrest  it,  for  its  development  is  the 
work  of  the  people,  not  of  the  writers.  This  is  plain  from  the 
discrepancy  between  any  language  in  the  strict  sense,  and  its 
literature--*.^  between  spoken  and  written  language.  The 
difference  is  greatest  in  the  English  language,  in  which  the  written 
or  printed  words  are  not  so  much  a  symbolic  representation  of  the 
different  tones  and  sounds  of  which  they  are  built  up,  as  mere 
mnemonic  signs — a  little  plainer  and  more  expressive  than  the 


in  PHONATION  AND  AETICULATION  173 

hieroglyphics  of  the  ancients.  Among  the  different  Teutonic 
idioms  the  German  language  is  the  most  faithfully  represented  in 
its  writing. 

Of  the  Neo-Latin  languages,  French  has  certainly  retained  its 
archaic  form  in  writing  more  closely  than  the  others ;  because  the 
evolutionary  transformations  of  the  language  spoken  by  the  people 
were  not  adopted  in  the  written  form,  owing  to  the  prejudices  of 
the  grammarians.  In  Italian  and  Spanish,  on  the  contrary,  the 
written  language  is  a  more  faithful  transcript  of  the  pronunciation. 

BIBLIOGRAPHY 

For  this  subject  the  student  may  consult  articles  by  JON.   MULLER,  LONGET, 
GRUTZNER  (iu  Hermann's  Handbuch),  BRUCKE,  GAD  and  HEYMAN.S,  SCHAEFKK. 

The  principal  Monographs  and  Memoirs  are  :— 

LISKOVIUS.     Phys.  d.  Menschl.  Stimnie,  1846. 

HARLESS.     Art.  Stimnie  i.  d.  Wagners's  Handwort.  d.  Physiol.,  1853. 

LEPSIUS.     Das  allgemeine  liuguistische  Alphabet.     Berlin,  1855. 

DONPER.S.     Arch.  f.  d.  holland.  Beitrage  f.  Nat.  u.  Heilk.,  1857. 

CZERMAK.     Der  Kehlkopfspiegel,  etc.     Leipzig,  1860. 

THAI*SING.     Das  natiirliche  Lautsystem.     Leipzig,  1863. 

MKRKEL.     Anat.  u.  Physiol.  d.  menschl.  Stimni-  und  Sprachorgans,  1856.     Antro- 

pophonik.     Leipzig,  1857.     Physiol.  d.  menschl.  Sprache.     Leipzig,  1866. 
FOURNIE.      Physiologic  de  la  voix  et  de  la  parole.      Paris,  1866. 
RUMPELT.     Das  natiirliche  System  d.  Sprachlante.     Halle,  1869. 
KONIG.     Annal.  d.  Physik,  vii. ,  1876;  cxxxxvi. ,  1872. 

SIEVEKS.     Grundziige  der  Lautphysiologie.     Leipzig,  1879.     (Now  in  its  5th  ed.) 
BUUECKE.     Grundziige  d.   Physiol.  u.   Systematik  d.  Sprachlaute.     Wien,  1836. 

(Now  in  its  5th  ed.) 

GAVARRET.  Phenomenes  physiques  de  la  phonation  et  de  1'audition.  Paris,  1877. 
HELMHOLTZ.  Die  Lehre  von  den  Tonempfindungen.  Braunschweig,  1877. 

(Tr.  by  Ellis  from  3rd  ed.,  1875.) 
AUERBACH.     Ann.  d.  Physik,  iii.,  1878. 
GARCIA.     Mem.  sur  la  voix  humaiue,  1855-1861-1878. 
SCHNEEBELI.     Arch,   des  sc.  phy.  et  nat.  i.,  1879. 

OERTEL.     Ueber  d.  Median,  des  Brust-  und  Falsett-Register.     Stuttgart,  1882. 
BELL,  A.  M.     Sounds  and  their  Relations.     London,  1882. 
TECHMER.       Phouetik.       Leipzig,     1880.       International    Zeitschr.    f.    allgemeine 

Sprachwissensch.  i.,  1884. 

SWEET.     A  Primer  of  Phonetics.     Oxford,  1890. 
SEMON.     Brit.  Med.  Journ.     London,  1886. 
FRENCH.     Verhamll.  d.  intern.  Congr.     Berlin,  1890. 
STORN,  J.     Englische  Philologie.     Leipzig,  1892.     (Vol.  i.  contains  a  critical  review 

of  all  the  important  works  on  phonetics  published  between  1840  and  1880.) 
WYLLIE.     Disorders  of  Speech.  1894. 
PIPPING.     Zeitschr.  f.  Biol.,  xxvii.,  xxxi.,  1890-94. 
BREYMANN,  H.     Die  phon.  Literatur  von  1876-1895.     Leipzig,  1897. 
HERMANN.     Arch.  f.  d.  ges.  Physiol.  Ixi.,  1895  ;  Ixxxiii.,  1900. 
HALLOCK.     Am.  Ann.  Photogr.  '  1896. 

FLEEMING-JENKIN  and  EWING.     Trans.  Roy.  Soc.  Edin.  vol.  xxxviii.,  1897. 
HENSEN.     Arch.  ital.  de  biol.,  1901. 
ROUSSELOT.      Principes   de    pnonetique    experimental e.      Paris,   1897-1901.      Les 

Modifications  phonetiques  du  langage.  Paris,  1891. 
G.  ASCOLI.  Archivio  glottologico  italiano,  vol.  i.,  1873. 
SCRIPTURE,  E.  W.  Elements  of  Experimental  Phonetics.  New  York  and  London, 

1902. 
JESPERSEN,  0.     Lehrbuch  d.  Phon.     Leipzig,  1904. 


174  PHYSIOLOGY  CHAP,  in 

SCRIPTURE,  E.  W.     Speech  Curves.     Washington,  1906. 

PANCONCELLI-CALZIA.     Bibliographia  phonetica.     (Published  regularly  since  1906 

in  Medizinisch-piidagogische  Monatschrift  f.  d.  Sprachheilkunde.     (References 

to  recent  works  on  phonetics). 
PASSY,  P.     Expose  des  principes  de  1'association  phon.  internationale.     Leipzig, 

1908. 

GUTZMANN,  H.     Phys.  d.  Stimme  u.  Sprache.     Brunswick,  1909. 
LUCIANI,  L.     Par  la  ritbrnia  ortografica  (Estr.  Atti  d.  Soc.  it.  per  il  progr.  delle 

Scienze— iv.  Riunione.     Naples,  ottobre  1910. 
LUCIANI,   L.     Di    una   ril'orma  ortografica   basata  sulla  fonetica  fisiologica   (Estr. 

Rivista  pedagogica,  a.  iv.,  v.  i.,  1910). 
GOIDANICH,  P.  C.     Rivista  pedagogica,  3rd  year,  vol.  ii.     Modena,  1910.     Archivio 

glottologico  italiano,  vol.  xvii.,  1910.     Miscellanea  di  studi  in  onore  di  Attilio 

Hortis.     Trieste,  1910. 
POIROT,  J.     Die  Phonetik  (Hb.  d.  phys.  Methodik  di  R.  TIEGERSTEDT,  iii.  Bd.  vi. 

Abt.).     Leipzig,  1911. 

Recent  English  Literature  : — 

MOTT,  F.  AV.     The  Brain  and  the  Voice  in  Speech  and  Song.     London  and  New 

York,  1910. 
AIKIN,  \V.  A.     The  Voice — An  Introduction  to   Practical  Phonology.     London, 

1910. 


CHAPTER   IV 

GENERAL   PHYSIOLOGY   OF   THE   NERVOUS    SYSTEM 

CONTENTS. — 1.  Structural  elements  of  the  nervous  system.  Theory  of  in- 
dependent neurones,  or  continuity  of  neuro-fibrils.  2.  Conditions,  laws  and 
phenomena  of  conduction  in  nerve.  3.  Rate  of  conductivity  :  diphasic  character 
of  the  impulse  arousing  it.  4.  Metabolism  of  nerve  ;  electromotive  phenomena 
during  rest  and  excitation  :  demarcation  current,  action  current.  5.  Excitation 
of  nerve.  Natural  stimuli  and  artificial  (chemical,  mechanical,  electrical)  stimuli. 
6.  Factors  in  life  and  death  of  nerve  :  conditions  of  excitability.  7.  Polar  effects 
of  constant  current  ( electro tonus) :  correlative  changes  in  excitability  and  con- 
ductivity. 8.  Excitatory  action  of  electrical  currents.  Laws  of  excitation. 
9.  Theories  as  to  origin  of  nerve  activity.  10.  General  functions  of  nerve-centres. 
Ganglion  cells  and  central  fibrillary  network.  Bibliography. 

THE  Nervous  System,  which  is  the  real  centre  of  the  functions  of 
animal  life,  controls  the  activities  of  the  organs  of  involuntary— 
or  vegetative — life,  as  well  as  those  of  the  muscles.  By  means  of 
the  sensory  mechanisms  it  correlates  the  several  organs  among 
themselves,  and  brings  the  organism  as  a  whole  into  relation  with 
the  external  world,  while  it  is  able  by  means  of  the  motor 
mechanisms  to  vary  these  relations  and  adapt  them  to  change  of 
circumstances. 

In  order  that  it  may  fulfil  these  important  functions,  the 
nervous  system  is  built  up  of  morphological  elements  which 
establish  a  functional  link  between  the  different  organs,  inde- 
pendent of  their  juxtaposition  or  distance,  and  control  the 
circulation  of  the  tissue  fluids,  so  that  when  a  given  change  takes 
place  in  one  part,  other  phenomena  necessarily  ensue  in  other 
remote  parts,  e.g.  in  the  skin  and  the  muscles,  the  mucous 
membrane  and  the  glands,  etc.  It  is  the  nervous  system  that 
presides  over  those  complex  relations  between  distant  organs 
which  the  ancients  termed  "sympathies."  It  represents  the 
physiological  unity,  the  reciprocal  dependence  of  parts,  on  which 
the  psychological  unity,  expressed  in  the  phenomena  of  the  ego  or 
consciousness,  is  founded. 

The  most  elementary  organisms,  while  they  possess  no  differ- 
entiated nervous  and  muscular  systems,  nevertheless  exhibit 
essential  animal  characteristics  of  sensibility  and  motility,  albeit 

175 


176  PHYSIOLOGY  CHAP. 

in  a  rudimentary  and  ill-defined  form :  to  explain  this  fact  we 
must  assume  a  common  protoplasmic  basis  for  both  these 
elementally  functions  and  those  evolved  in  the  more  perfect 
organisms  'by  gradual  morphological  and  functional  differentiation 
intfc  %r?e**nervous  and  muscular  systems. 

The  organs  of  the  nervous  system,  of  which  the  general 
physiology  will  be  considered  in  this  chapter,  represent  the  highest 
grade  of  morphological  and  functional  differentiation,  both  in  the 
ontogenetic  development  of  the  individual  and  in  the  phylogenetic 
development  of  the  lowest  forms  of  the  animal  kingdom. 

I.  The  nervous  system  in  man  and  other  vertebrates  consists 
of:  (a)  a  compact  mass — the  cerebrospinal  axis;  (&)  nerves  which 
are  given  off  from  this  axis — the  cerebral  and  spinal  nerves — and 
distributed,  by  successive  division,  into  smaller  and  smaller  bundles 
and  branches,  to  nearly  all  the  organs  and  tissues  of  the  body ; 
(c)  a  vast  number  of  ganglia  or  nervous  nodes,  intercalated  along 
the  course  of  the  nerves  at  greater  or  less  distance  from  the  cerebro- 
spinal  axis,  many  of  which  form  two  lateral  chains,  and  constitute 
the  splanchnic  or  great  sympathetic  system. 

To  the  naked  eye  the  nervous  system  consists  of  two  dissimilar 
substances — the  white  matter  and  the  f/rey  matter.  Under  the 
microscope  both  are  seen  to  be  made  up  of  fibres  and  nerve- 
cells,  the  fibres  predominating  in  the  white  matter,  the  cells  in 
the  grey. 

Apart  from  their  minute  histological  structure,  the  nerve-cells 
of  the  cerebrospinal  axis  and  ganglia  have  long  been  regarded  as 
the  central,  and  the  nerve-fibres  as  the  peripheral,  parts  of  the 
I  system.  The  cells  more  particularly  serve  the  storage,  elaboration, 
I  transformation,  and  development  of  the  specific  energies  of  the 
system ;  the  fibres  more  especially  conduct  and  transmit  these 
energies  from  the  periphery  to  the  centre  (centripetal  or  afferent 
nerves),  and  from  the  centre  to  the  periphery  (centrifugal  or  efferent 
nerves).  The  inclination  to  differentiate  between  the  physiological 
functions  of  the  ganglion  cells  and  of  the  nerve  fibres,  which  are 
filiform  processes  of  the  cells,  became  more  definite  after  the 
discovery  of  the  telegraph  by  Morse  (1837),  which  to  many  minds 
suggested  a  parallel  between  the  functions  of  the  nervous  system 
and  the  telegraphic  installation  of  a  State.  The  cells  were  com- 
pared to  the  telegraph  apparatus,  the  fibres  to  the  conducting 
wires,  the  cerebrospinal  axis  to  the  great  central  telegraph  station, 
the  conglomerated  ganglia  of  the  sympathetic  system  to  the  inter- 
mediate exchanges,  the  peripheral  ganglia  to  the  local  offices  of 
country  towns  and  villages. 

But  despite  the  apparent  analogy  between  the  two  systems, 
which  both  consist  of  distant  apparatus  brought  into  direct  relation 
by  conducting  wires,  there  are  huge  internal  differences  in  the 
nature  and  function  of  the  elements  of  which  the  two  systems, 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    177 

respectively,  are  composed.  The  physiological  data  we  are  about 
to  discuss  will  emphasise  these  differences. 

In  reviewing  our  present  knowledge  of  the  minute  structure  of 
the  histological  elements  of  the  nervous  system,  it  should  be  noted 
that  the  data  are  all  comparatively  recent.  Notwithstanding  the 
number  and  ability  of  the  investigators  and  the  delicacy  and 
variety  of  the  methods  employed,  the  facts  are  not  yet  sufficiently 
clear  and  unequivocal  to  admit  of  the  construction  of  any  universal 
and  authoritative  morphological  theory. 

The  first  exact  account  of  the  existence  of  specific  nerve-cells 
dates  from  1833,  when  Ehreuberg  described  the  cells  of  the  spinal 
ganglia  of  the  frog.  In  1838  Eemak  first  discovered  in  the 
sympathetic  of  vertebrates  that  the  nerve-fibres  are  a  prolongation 
of  the  processes  of  the  cells,  which  was  confirmed  in  1842  by 
Helmholtz  and  Hannover  on  invertebrates.  Deiters  was  the  first 
to  demonstrate,  in  a  monograph  published  after  his  death  by 
Schultze  (1863),  that  two  different  kinds  of  processes  can  be 
distinguished  in  the  central  nerve-cells — nerve-fibres  proper,  and 
protoplasmic  processes.  He  proved  the  continuity  of  the  former 
with  the  axis-cylinders  of  medullated  nerve-fibres,  but  left  the 
destination  and  physiological  function  of  the  latter  undetermined. 

Gerlach  in  1871,  by  the  gold  chloride  method,  demonstrated 
the  existence  in  the  grey  matter  of  the  cerebrospinal  axis  of  a 
diffuse  fibrillary  network,  which  he  interpreted  as  the  result  of 
an  anastomosis  or  concrescence  of  the  finest  ramifications  of  the 
protoplasmic  processes  of  the  ganglion  cells.  To  this  he  ascribed 
the  important  function  of  bringing  the  ganglion  cells  of  the  central 
mass  of  the  nervous  system  into  direct  interrelation. 

In  1873  Golgi  discovered  his  method  of  staining  nerve-cells  and 
fibres  black  with  salts  of  silver  which  led  to  a  great  advance  in  our 
knowledge  of  the  minute  structure  of  the  nervous  system.  He 
showed  that  at  a  certain  distance  from  the  cells  the  nerve  pro- 
longations or  axons  give  off  collateral  rami  which  branch  from  the 
trunk,  mostly  at  a  right  angle.  Like  Gerlach  he  admitted  the 
existence  of  a  diffuse  network  of  nerve-fibrils  which  conduct  the 
excitation ;  but  denied  that  it  was  formed  by  the  dendritic 
ramifications  of  the  protoplasmic  processes,  which  he  held  to  be 
simple  nutrient  paths  from  the  cell  body,  with  free  endings. 
Golgi  maintained  that  the  ganglion  cells  were  united  by  a  fibrillary 
network  formed  of  the  finest  ramifications  of  the  axis-cylinders. 

Subsequent  researches  made  by  Eamon  y  Cajal  after  1888,  with 
Golgi's  methods,  led  this  author  to  deny  the  existence  of  any  such 
diffuse  fibrillary  network :  Cajal  concluded  that  both  the  dendrites 
and  the  axons  terminate  free  ;  and  that  each  ganglion  cell,  with 
the  whole  of  its  protoplasmic  and  axis-cylinder  processes,  represents 
an  elementary  organism  in  itself,  connected  with  the  others  not  by 
anastomosis  nor  continuity,  but  by  simple  contact  or  contiguity. 

VOL.  1IT  N 


-13 


mm 


,  j 


R 


B 


II 


c 


FIG.  115. — A,  Bipolar  nei  ve-cell  with  poles  prolonged  into  medullated  nerve-fibres.  (Rey  and 
Retzius.)  The  cut  in'  cell  is  invested  with  the  neurilemma.  li  R,  nodes  of  Ranvier. 
B,  Portions  of  two  nerve-tibres  stained  with  osinic  acid  (from  a  yonm;  rabbit);  diagrammatic, 
425  diameters.  (Schafer.)  R  R,  nodes  of  Ranvie.r,  with  axis :  cylinder  passing  through  ; 
a,  neurilemma ;  c,  nucleus  and  ]irotoplasm  lying  between  the  neuiilemma  and  the  medullary 
sheath.  C,  Mednllated  nei  vr-liln  i-  treated  with  osmic  acid.  (Rey  and  Retzius.)  E,  node  of 
Ranvier ;  K,  nucleus.  The  myelin  of  the  medullary  sheath  is  incompletely  interrupted  so  as 
to  form  conico-cylindrical  segments. 


CH.IV  GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM  179 

Cajal's  observations  found  general  support  and  were  repeated 
and  confirmed  by  Ko Hiker,  Lenhossok,  and  van  Gehuchten  with 
Golgi's  method ;  by  Eetzius,  Biedermanu,  and  others  with 
Ehrlich's  method  (intra  vitn-m,  staining  with  methylene  blue). 

Waldeyer  gave  the  name  of  neurone  (from  vtvpov,  point  of 
contact  of  many  nerve  threads)  to  the  elementary  units  of 
which  the  nervous  system  is  built  up,  which  term  found  great 
favour  with  the  neurologists,  and  contributed  not  a  little  to 


Kl'..  11(1. — Phylogenetic  and  onto^enetic  development  of  neurones  with  loiix  axons  from  pyramidal 
cells  of  cerebral  cortex.  (Ramon  y  Cajal.)  The  upper  series  represents  the  phylogenetic 
development  of  these  cells  :  .4,  in  fro;; ;  Jl,  newt ;  (.',  rat ;  D,  man.  The  lower  series  shows  the 
ontogenetic  development  of  the  neuroblasts  of  those  cells  in  live  successive  phases,  a,  b.  c,  "'.  e. 

popularise  the  "  neurone  theory "  in  the  medical  world.  The 
protoplasmic  processes  were  termed  dendrites,  the  nerve  process 
neurite,  axon,  or  axis-cylinder.  The  dendrites  differ  from  the 
axons  in  various  structural  characters,  some  of  which  had  been 
described  by  Deiters,  others  were  discovered  by  Golgi  with  his 
method.  In  many  neurones  the  dendrites  exhibit  minute  lateral 
processes — spines  or  gemmules — along  their  course  which  are 
never  seen  on  the  axons. 

Some  nerve-cells  are  wholly  destitute  of  dendrites,  e.g.  the 
typical  cells  of  spinal  ganglia  and  the  corresponding  ganglia  of 
the  cranial  nerves.  On  the  other  hand  some  nerve-cells  have  no 

N  1 


180 


PHYSIOLOGY 


CHAP. 


\ 


true  axis-cylinder  process,  e.g.  those  of  the  stratum  granulosum  of 
the  olfactory  bulb.  The  cells  of  the  spinal  ganglia  of  Teleosteans  and 
the  cells  of  the  cochlear  ganglion  are  bipolar  or  bineural,  i.e.  have 
two  axons  (Fig.  115,  A),  and  in  the  molecular  layer  of  the  cerebral 
cortex,  according  to  Ramon  y  Cajal,  Eetzius,  and  others,  there 
are  nerve -cells  with  two  or  three  axons.  Veratti,  however, 
contests  this  statement,  and  gives  a  totally  different  interpreta- 
tion to  the  data  on 


which     it 
According 


is     based, 
to    Gokri 


o  o 

the  cells  of  the  cere- 
bral cortex  which  give 
origin  to  the  so-called 
pyramidal  tracts,  and 
still  more  those  of  the 
ventral  horns  of  the 
spinal  cord,  have  long 
axis-cylinder  processes 
which  give  off  col- 
lateral rami,  while 
they  preserve  their 
individuality  for  a 
long  distance  ;  the 
latter  are  continued 
in  the  ventral  root- 
fibres  of  the  spinal 
nerves  (Fig.  116). 
The  cells  of  the  dorsal 
horns  of  the  cord,  on 
the  contrary,  and 
many  cells  in  the  grey 
matter  of  the  large 

FIG.  117.— Large  ceUs  with  short  axons.    Golgi  s  second  type,  6 

found   in   the  nuclear  layer  of  the   cat's  cerebellum,   high  Cerebral    Centres,    have 

magnification.     (Golgi.)    In  order  to  distinguish  the  proto-  •,         ,             •              -i  •      •> 

plasmie  processes  from  the  nerve  processes  or  axis-cylinders,  SllOr  b     aXIS  -  Cylinders, 

the  former  are  printed  in  black,  the  latter  with  their  rami-  ,,7  V,  i  r-  l-i         v  o  T>  o  o  f  a  A  1  \T 

tications  in  red.  11V 

divide  and  subdivide, 

and  soon  lose  their  individuality  (Fig.  117).  It  is,  however,  very 
doubtful  whether  the  presumably  different  functions  of  these 
various  forms  of  neurones  are  connected  with  the  morphological 
differences  indicated  by  the  appearance  of  their  axis-cylinders. 

The  neurone  theory,  which  regards  the  elementary  components 
of  the  nervous  system  as  morphologically  distinct,  is  not  based 
on  any  conclusive  evidence.  Even  after  the  observations  of 
Ramon  y  Cajal  and  his  numerous  adherents,  Golgi  and  his  pupils 
still  insisted  on  the  theory  of  a  diffuse;  nervous  network,  formed 
of  the  collateral  rami  given  off  from  the  axons  in  the  vicinity 
of  the  ganglion  cells.  Golgi  demonstrated  this  diffuse  nervous 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    181 

network  more  particularly  in  certain  parts  of  the  central  nervous 
system,  e.g.  the  fascia  dentata  of  the  hippocampus  (Fig.  118) 
and  the  cerebellar  cortex  (Fig.  119). 

The  neurone  theory,  on  the  other  hand,  harmonises  perfectly 
with  the  embryological  observations  of  His  (1887),  who  believed 


Fin.  IIS.  —Fascia  dentata  of  pes  hippocampi  major.  (Golgi.)  Between  the  processes  coming  from 
the  upper  layer  of  nerve-cells  and  the  lower  of  nerve-fibres  there  is  an  intervening  zona  reticulari.s 
composed  of  nerve-libres  which  interlace  repeatedly,  so  that  they  lose  their  individuality  and 
constitute  what  Golgi  calls  the  diffuse  nerve  network. 

that  he  had  demonstrated  the  genesis  of  the  nerve  elements  from 
the  special  germinal  cells  of  ectodermal  origin,  which  are  inter- 
posed between  the  epithelial  cells  of  which  the  walls  of  the 
primitive  neural  tube  are  composed.  A-polar  and  rounded  in 
an  early  stage,  they  subsequently  become  piriform ;  next  they 
send  out  a  nerve  process  and  become  uni-polar ;  finally  the 
dendrites  appear  also  (Fig.  116,  a,  b,  c,  d,  e].  During  their  growth 

N  2 


182 


PHYSIOLOGY 


CHAP. 


the  neuroblasts  gradually  move  away  from  the  wall  of  the  neural 
canal  towards  the  exterior.  Many  of  them  remain  in  the  central 
grey  matter ;  others  wander  out  to  form  the  cerebrospinal  ganglia, 
sympathetic  ganglia,  etc. 

But  this  theory  of  His,  in  so  far  as  it  conceives  the  nerves 
to  be  only  appendages  of  the  ganglion  cells,  is  contradicted  by 
the  observations  of  Balfour,  Beard,  Dohrn,  Kupfer,  and  Eaffaele 


FIG.  IIP. — Cerebellar  cortex  showing  relations  between  the  small  cells  of  the  molecular  layer  and 
the  body  of  Pnrkinje's  cells.  (Golgi.)  The  nerve-fibres  descending  from  the  small  cells  of  the 
molecular  layer  partially  embrace  the  large  body  of  the  Purkinje  cells,  partially  pass  between 
these,  and  then  subdivide  repeatedly  belowjthem  to  form  another  diffuse  network 

on  fishes,  and  the  more  recent  work  of  Bethe,  Paladiuo,  Fragnito, 
and  Capobianco  on  chick  embryos.  According  to  these  observers 
the  axis  -  cylinders  of  the  peripheral  nerves  and  of  the  white 
matter  of  the  central  organs  are  not  (from  the  histogenetical 
point  of  view)  composed  of  prolongations  of  the  axons  and 
dendrites  of  the  ganglion  cells,  but  are  derived  from  the  fusion 
of  many  cells  arranged  in  series,  and  only  contract  relations  with 
the  ganglion  cells  at  a  later  time.  The  problem  is  still  unsolved, 
since  some  authors  (Harrison  in  the  first  place)  confirm  the 
view  of  His,  while  others  take  the  polygenetic  theory  as  proven. 


iv    GENERAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    183 

Whatever  the  value  of  these  conflicting  statements,  and  how- 
ever certain  it  is  that  during  their  histogenetic  development 
the  constituent  elements  of  the  nervous  system  are  morphologi- 
cally distinct  and  independent,  it  is  far  from  proved  that  in 
fully  developed  tissues  the  so-called  "  neurone "  represents  a 
true  morphological  unit,  and  is  not  a  fusion  of  many  elements, 
or  syncytiutn  ;  nor  that  these  neurones  do  not  enter  into  close 
relation  by  direct  continuity  of  their  protoplasmic  substance ; 
nor,  lastly,  is  the  idea  of  a  diffuse  fibrillary  network  which,  both 
in  the  central  grey  matter  and  at  the  periphery,  knits  the  several 
neurones  into  a  single  unitary  system,  comparable  with  the 
vascular  system,  by  any  means  excluded. 

This  modern  view  of  the  minute  structure  of  the  nervous 
system  is  founded  on  the  work  of  Apathy,-  Bethe,  Nissl,  and 
others,  who,  by  new  methods  of  staining,  have  brought  out  new 
facts  which  are  in  more  or  less  open  contradiction  with  the 
neurone  theory.  We  must  confine  ourselves  to  a  brief  survey  of 
the  principal  data  supplied  by  these  researches. 

While  the  method  used  by  Golgi  and  his  numerous  followers 
in  the  study  of  the  minute  structure  of  the  nervous  system  has 
added  greatly  to  our  positive  knowledge  in  this  difficult  subject, 
it  is  by  no  means  the  best  adapted  to  show  up  the  microscopic 
structure  of  the  nerve-cells  and  processes.  With  too  intense 
impregnation  with  silver,  both  cells  and  processes  are  stained 
uniformly  black.  In  order  that  this  method  may  bring  out  the 
fine  structure  of  the  body  of  the  nerve -cell,  as  in  the  figures 
obtained  by  Golgi,  it  is  necessary  to  make  repeated  experiments, 
for  which  no  general  rules  can  be  given. 

Again,  there  is  grave  reason  to  suspect,  on  the  strength  of  the 
facts  established  by  Apathy  for  the  nervous  system  of  the  leech, 
that  the  silver  method  which  only  shows  up  certain  elements  of  the 
system,  leaving  the  rest  unstained  and  therefore  undifferentiated,  is 
inadequate  for  the  demonstration  of  the  finest  ramifications  of  the 
dendrites  and  axis-cylinders.  We  have  seen  that  Golgi  himself 
pointed  out  that  the  free  endings  discovered  by  Ramon  y  Cajal, 
upon  which  the  whole  neurone  theory  is  based,  are  not  indisput- 
able, but  result  from  an  inherent  defect  in  the  method  of  staining. 

In  1871,  in  describing  the  ganglion  cells  of  the  spinal  cord, 
Max  Schultze  recognised  the  fibrillary  nature  of  their  protoplasm 
and  of  the  protoplasmic  and  nerve  processes.  Both  in  fresh 
preparations  and  in  those  treated  with  osmic  acid,  he  observed 
distinct  fibrils  which  run  in  various  directions  through  the  cell 
body,  giving  it  the  appearance  of  a  network  or  reticulum,  and 
are  in  direct  connection  with  the  elementary  fibrils  of  which  both 
the  axons  and  the  dendrites  are  composed.  He  further  assumed 
the  existence  of  a  finely  granular  substance,  which  fills  the 
inter  fibrillary  spaces. 


184 


PHYSIOLOGY 


CHAP. 


This  point  of  view  was  adopted  by  Erik  Miiller,  Boll,  Schwalbe, 
and  Eanvier,  and  was  subsequently  carried  further  by  Flemming 
(1895),  who  on  staining  with  hamiatoxylin  described  independent 
fibrils  in  the  dendrites  which  were  continued  into  the  cell  body, 
though  he  could  not  trace  them  distinctly  into  the  centre  of  the 
cell,  where  they  seemed  to  anastomose  to  form  a  network. 

The  theory  of  the  fibrillary  nature  of  the  protoplasm  of  the 
nerve-cells  was  disputed  by  v.  Lenhossek,  but  it  was  adopted  and 
defended  by  Dogiel,  Donaggio,  Becker,  Marinesco,  Held,  and 
Lugaro.  In  1896,  Donaggio,  with  a  special  method  of  elective 


FIG.  120. — Peripheral  network  of  nerve-cells  from  flop's  spinal  conl.     (Dona.ugio.) 

staining,  observed  and  described  a  fibrillary  network  that  per- 
vades both  the  interior  and  the  periphery  of  the  nerve-cells,  and 
in  which  the  fibrils  from  the  surrounding  tissue  terminate 
(Fig-  120). 

Lugaro  (1897)  convinced  himself,  with  the  same  haeniatoxylin 
method  as  Flemniing  employed,  of  the  fibrillary  structure  of  the 
spinal  ganglion  cells  of  dogs  poisoned  with  arsenic,  which  totally 
destroyed  the  chromatic  substance  at  the  periphery  of  the  cell 
body.  The  fibrils,  according  to  Lugaro,  anastomose  among  them- 
selves, forming  a  very  delicate  reticulum  in  certain  types  of  cells, 
a  coarser  network  in  others.  He  made  analogous  observations 
upon  the  cells  of  the  nerve-centres  of  animals  subjected  to  ex- 
perimental hyperthermia. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    185 
Levi,  Luo-aro's  collaborator,  obtained  similar  results  from  the 

O 

ganglion  cells  of  frogs  during  hibernation,  in  which  state  the 
chromatic  subtance  is  very  scanty,  so  that  the  achromatic  fibrillary 
part  is  more  conspicuous. 

The  existence  of  fibrils  in  the  nerve-cell  and  its  processes  may 
be  regarded  as  fully  established  by  Apathy's  work  on  the  nervous 
system  of  the  Anellidac  (1897).  He  demonstrated  definite  fibrils 
by  a  special  method  of  staining  the  ganglion  cells  with  gold 
chloride.  As  shown  by  Fig.  121,  these  fibrils  penetrate  from  the 
dendrites  into  the  cell  body,  where  they  form  a  wide -meshed 
network,  and  then  collect  into  a  single  bundle,  and  leave  by  the 
axis-cylinder.  The  fibrillary  network  (Apathy)  assumes  different 


FIG.  121. —  <i;t]r_li'>n  cell  of  ventral  cord  of  Lmnliriciit,  showing  an  endoeellular  fibrillary  network, 
which  is  continuous  with  the  afferent  fibrils  of  the  dendrites,  and  with  one  larger,  effVii-nt 
fibre  of  the  axon.  (Apathy.) 

forms  according  to  the  nature  of  the  ganglion  cells.  The  small 
fibres  brought  out  by  the  gold  stain  are  shown  to  be  bundles  of 
very  delicate  elementary  fibrils,  which  escape  observation  owing 
to  their  size  and  the  inadequacy  of  the  staining  methods.  These 
are  the  conducting  elements  proper  of  the  nervous  system. 

Any  one  who  has  studied  the  preparations  obtained  with 
Apathy's  method  must  admit  that  they  exhibit  astonishingly 
clear  details  of  structure,  which  may  be  of  fundamental  import- 
ance to  physiology.  At  the  same  time  it  must  be  remembered 
that  Apathy's  positive  results  relate  solely  to  the  nerve-cells  of 
the  lower  animals  (Hirudo  and  Lumbricus),  and  that  in  spite 
of  prolonged  experiments,  nothing  exactly  corresponding  has  so 
far  been  obtained  in  vertebrates. 

Bethe,  in  a  series  of  interesting  observations  (1897-1890), 
endeavoured  by  other  special  methods  of  elective  staining  of  the 


186 


PHYSIOLOGY 


CHAP. 


fibrils  to  extend  to  vertebrates  the  morphological  facts  and  con 
ceptions  which  Apathy  developed  for  Anellidae.  According  to 
Bethe  the  fibrils  in  the  ganglion  cells  remain  independent, 
without  anastomosing  among  themselves  to  form  a  network, 
except  in  the  cells  of  the  spinal  ganglia,  in  which  he  found  the 
network  to  consist  of  coarser  fibrils,  with  larger  meshes,  than  had 
been  observed  by  other  methods.  Bethe's  fibrils  pass  in  every 
direction  from  one  process  to  another,  and  between  different 
branches  of  the  dendrites. 

Golgi  also  investigated  the  minute  structure  of  the  nerve-cell 


JSlPii  Jim 

^ 

~ 


Fie.  1:22. — Kibrillary  ut-twoik  of  a  fell  of  the  do^'s  spinal  curd,  obtained  by  Dona.u.uio  with 
his  spi'dal  mi-thud  uf  fli-cth>-  staining. 

after  his  classical  work  on  the  general  structure  of  the  nervous 
system  referred  to  above.  His  own  publications  and  those  of 
his  pupil  Veratti  (1898-1900)  demonstrated  for  almost  every 
form  of  nerve-cell :  («)  an  endocellular  reticulum ;  (&)  a  fibrillary 
structure  of  the  peripheral  zone  of  the  cell;  (c)  a  kind  of  peri- 
cellular  network. 

The  nature  and  function  of  the  endocellular  reticulum  are 
still  undetermined.  As  between  the  two  hypotheses  now  in  the 
field,  according  to  which  it  is  either  a  nervous  network  (Apathy) 
or  a  system  of  nutritive  canaliculi  (Holmgren),  Golgi  does  not 
attempt  to  decide. 

The  nervous  character  of  the  fibrils  which  constitute  the 
fibrillary  structure  of  the  peripheral  zone  of  the  ganglion  cell 


iv    GENERAL  PHYSIOLOGY  OF  NERYOUS  SYSTEM    187 


:i 

3 

o 

p 


is  proved  by  their  continuity  with  the  axis-cylinder 
process.  Golgi  has  hitherto  failed  to  discover  any 
relation  between  these  peripheral  fibrils  and  the 
endocellular  reticulum,  which  appears  to  be  an 
argument  in  favour  of  Holmgren's  hypothesis, 
although  Golgi's  reluctance  to  accept  this  inter- 
pretation is  easily  understood. 

The  pericellular  network  described  by  Golgi 
for  different  cells  of  the  cerebellum,  cerebrum,  and 
spinal  cord  consists,  in  his  opinion,  of  neuro-keratiu, 
and  he  believes  its  function  to  be  one  of  insulation, 
as  he  considers  it  entirely  different  to  and  distinct 
from  the  diffuse  nervous  network  described  above. 

This  fibrillary  network  on  the  surface  of  the 
nerve -cells  is  admirably  shown  up  by  Bethe's 
method,  and  probably  corresponds  with  the  peri- 
pheral network  observed  by  Donaggio  and  by  Cajal 
in  1896. 

Donaggio   obtained    excellent    preparations   of 
vertebrate  nerve-cells  by  his  special  method.     As 
seen  in  Fig.  122,  the  cells  are  not  only  penetrated 
at  the  periphery  by  longitudinal  fibrils  which  pre- 
serve their  individuality  without  anastomosing,  as 
stated  by  Bethe,  but  in  addition  a  great  number  of 
fibrils  can  be  seen  which  are  directed  to  the  centre 
of  the  cell,  and  there  divide  minutely  to  form  a 
dense  network  which  is  not  stained  by  Bethe's  and 
Golgi's  methods.      The  fibrillary  network 
nected  on  the  one  side  with  the 
fibrils  that  penetrate  from  the 
dendrites,    on    the    other   with 
the  fibrils  that  form  the  axis- 
cylinder. 

Donaggio's  more  recent  pre- 
parations (1904)  show  still  more 
plainly  that  the  fibrils  of  which 
the  axis  -  cylinder  is  composed 
are  derived  directly  from  the 
endocellular  fibrillary  network 
(Fig.  123).  The  mode  of  origin 
varies  according  to  two  cellular 
types,  indicated  by  Donaggio. 

On  tracing  out  the  course  of 
a  sensory  fibre,  Apathy  found 
that  it  breaks  up  within  the 
central  nervous  system  into  an 
elementary  fibrillary  network  (JElementargitter),  which  suggests 


is  con- 


I!*'"'' 


188  PHYSIOLOGY  CHAP. 

the  diffuse  nervous  network  of  Gerlach  and  Golgi,  inasmuch  as 
it  is  continuous  with  the  fibrils  that  enter  from  the  periphery, 
and  those  which  leave  in  the  axis  of  the  single  process  of  the 
nerve-cells  of  Hirudo.  The  filaments  of  this  network  are  therefore 
in  direct  continuity  with  the  sensory  or  motor  fibrils  that  enter  and 
leave  the  ganglion  cells,  and  which  form  the  intracellular  fibrillary 
network  referred  to  above.  All  the  ganglion  cells  are  thus  directly 
connected  among  themselves  by  the  continuity  of  the  fibrils,  which, 
according  to  Apathy,  are  the  essential*  elements  of  nerve  con- 
ductivity. At  the  periphery  of  the  system  again,  both  in  the 
epithelial  cells  and  in  the  sensory  cells  and  muscles,  the  fibres 
never  exhibit  free  endings  but  anastomose  among  themselves  to 
form  a  network,  in  the  same  way  as  the  arteries  and  veins  form  a 
single  continuous  system  by  means  of  the  capillary  network. 

Bethe  confirmed  Apathy's  results  in  the  most  essential  points, 
for  vertebrates  as  well  as  for  invertebrates,  by  another  method,  viz. 
elective  staining  of  the  fibrils.  He  finds  that  very  different  re- 
lations prevail  in  different  classes  of  animals  between  the  ganglion 
cells  and  the  fibrils.  In  Arthropoda  the  extracellular  fibrillary 
network  is  well  developed,  while  comparatively  few  h'brils  enter  or 
leave  the  ganglion  cells  to  form  an  intracellular  network.  In 
vertebrates,  on  the  other  hand,  most  of  the  fibrils  pass  through  the 
cell,  without  forming  a  network  within  it ;  on  the  contrary  an 
extracellular  network  is  formed  by  the  anastomosing  of  the  fibrils 
that  surround  the  cell. 

This  last  statement  of  Bethe's  is  contradicted,  as  we  have  seen, 
by  the  most  recent  work  of  Golgi,  Donaggio,  and  Semi  Meyer, 
which  shows  that  the  methods  employed  by  Bethe  bring  out 
only  the  coarser  fibrils,  leaving  the  more  delicate  intra-  and  peri- 
cellular  fibrils  unstained.  Bethe,  on  the  strength  of  his  own 
observations,  and  of  an  experimental  argument  which  we  shall 
examine  below,  reduces  the  importance  of  the  ganglion  cells,  and 
holds  them  to  be  mere  stations  for  the  passage  and  reinforcement 
of  the  nerve  current,  while  the  central  activity  of  the  system  is 
developed  outside  the  cell  in  the  intercellular  elementary  network 
of  the  grey  matter ;  Donaggio,  on  the  contrary,  holds  that  the 
cell  probably  represents  the  true  centre  for  the  reception  of  the 
excitatory  impulse  and  for  its  synthesis  and  transformation. 

As  regards  the  theory  of  the  unitary  structure  of  the  nervous 
system  of  vertebrates,  Held  supports  Bethe  in  essentials,  on  the 
strength  of  his  own  observations ;  Golgi,  Veratti,  Donaggio  main- 
tain an  absolute  reserve ;  Semi  Meyer  and  Lugaro,  while  they 
admit  the  importance  of  Bethe's  observations,  deny  that  these  prove 
the  applicability  to  vertebrates  of  Apathy's  results  for  inverte- 
brates, so  as  to  overthrow  the  neurone  theory,  according  to  which 
the  relation  of  the  separate  elements  of  the  system  is  merely  one 
of  contact.  Lugaro  admits  as  a  possibility,  in  regard  to  the  question 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    189 

of  inter-neuronal  anastomosis,  that  the  nature  of  the  connection 
between  the  elements  of  the  system  may  have  developed  in  two 
opposite  directions  in  the  course  of  phylogenetic  evolution.  He 
accepts  the  theory  of  Apathy  for  invertebrates,  but  maintains  that 
of  Ramon  y  Cajal  for  vertebrates,  so  long  as  the  continuity  of  the 
fibrils  which  compose  the  central  and  peripheral  elementary  net- 
work is  not  positively  demonstrated. 

The  most  emphatic  and  certainly  one  of   the   most   reliable 
supporters   of    the   theory  of  Apathy  and   Bethe,  for   both    in- 


FIG.  124. — Two  cells  from  ventral  horn  of  human  spinal  cord.  (Nissl's  method.)  The  chromatic 
sul .stance  is  collected  into  small  masses,  which  give  a  speckled  appearance  to  the  cytoplasm. 
Each  cell,  besides  the  nucleus  and  nucleolus,  contains  a  distinct  mass  of  stainable  granules. 

vertebrates  and  vertebrates,  is  Nissl,  although  his  own  work  does 
not  refer  specially  to  the  fibrillary  structure  of  the  nervous 
system.  In  1893  he  discovered  the  existence  in  many  ganglion 
cells  of  peculiar  granules  which  stain  with  basic  aniline  dyes, 
particularly  with  rnethylene  blue  and  toluidine  blue.  These— 
which  are  now  generally  referred  to  as  Nissl's  granules  or  chromato- 
phile  granules — are  present  in  small  masses  throughout  the  body 
of  the  cell  and  in  the  larger  dendrites  (Fig.  124). 

Nissl  holds  that  since  the  fibrillary  nature  of  the  achromatic 
part  of  the  ganglion  cell  has  been  established,  the  theory  of  the 
nerve  unit  (neurone*)  is  no  longer  tenable.  He  concludes,  on  the 
strength  of  the  researches  of  Apathy,  Bethe,  and  Held,  which 


190 


PHYSIOLOGY 


CHAP. 


demonstrated  the  fusion  of  the  axis -cylinder  fibrils  into  an 
intracellular  elementary  network,  that  the  nervous  system  is 
constructed  of  ganglion  cells  and  of  a  fibrillary  nerve  substance, 
the  latter  being  a  specifically  differentiated  cell  protoplasm, 
present  in  the  cells  as  fibrils,  and  outside  them  as  grey  matter, 
which  last  apparently  consists  of  a  close  and  very  delicate 
network  of  elementary  fibrils.  So  that  Nissl,  like  Bethe,  considers 
the  grey  matter  to  be  the  most  important  constituent  of  the 
nervous  system. 

Another  method,  which  brings  out  the  fibrillary  character  of 
the  nerve-cells,  is  that  discovered  by  Ramon  y  Cajal ;  it  depends 
on  the  reduction  of  silver  nitrate,  and  is  known  as  the  photo- 
graphic method.  According  to  Golgi  the  results  obtained  by 
it  are  of  the  utmost  importance  and  are  easy  of  demonstration. 


FIG.  125. — Tin  cr  nri  \v-cells  and  processes  showing  presence  and  course  of  neuro-tibrils. 
Rtimon  y  Cajal's  photographic  method. 

Cajal's  method  (Fig.  125)  shows  up  every  detail,  so  that  the 
course  of  the  fibrils  can  be  followed  both  within  the  cell  body 
and  in  the  processes.  Among  its  other  advantages  is  the  fact 
that,  unlike  any  that  preceded  it,  it  brings  out  the  fibrillary 
structure  of  the  nerve  elements  during  their  earliest  development. 
Jaederholm,  nevertheless,  remarks  with  regard  to  the  signifi- 
cance and  theoretical  value  of  these  histological  observations : 
"  In  my  opinion  the  reticular  formations  within  the  cells  must 
be  regarded  as  artificial  products  due  to  agglutination.  Such  a 
reticular  formation  may  be  simulated,  because  the  cytoplasm, 
coagulated  in  the  form  of  a  network,  stains  along  with  the 
fibrils ;  this  happens  most  frequently  with  Donaggio's  method  ; 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    191 

less  often  with  that  of  Cajal,  more  rarely  still  with  those  of 
Bethe  and  of  Bielschowsky." 

It  is  curious  and  instructive  to  note  that  while  for  Ramon 
y  Cajal  (1908)  the  results  obtained  by  his  method  and  its 
modifications  afford  a  positive  proof  of  the  neurone  theory — since 
he  has  never  been  able  to  convince  himself  of  the  existence  of 
anastomosing  intercellular  fibrils — for  Golgi  (1910)  none  of  the 
data  adduced  in  regard  to  the  anatomical  structure  of  the  nervous 
system  offer  a  definite  proof  either  of  the  theory  of  independent 
cell-units  (neurones),  or  of  the  unitary  fibrillary  theory. 

Nevertheless,  from  the  present  state  of  our  knowledge,  Golgi 
rejects  the  view  according  to  which  the  nerve-cell  is  deposed, 
and  the  chief  functional  value  attributed  to  the  fibrils.  "  I 
should  feel  as  though  I  were  breaking  faith  if  I  faltered  in 
my  firm  conviction  that  the  nerve-cells  are  the  central  organs 
of  the  specific  psychical  and  sensory  activities  which  we  ascribe  to 
the  nervous  system,  provided  we  admit  that  they  too  come  under 
the  concept  that  is  valid  for  the  whole  of  the  cell  theory,  viz. 
that  the  nerve-cells,  while  endowed  with  a  certain  autonomy, 
are  more  or  less  dependent  on  their  anatomical  and  functional 
inter-relations.  It  is  hardly  necessary  to  point  out  that  this 
statement  does  not  entirely  exclude  the  participation  in  psychical 
and  sensory  actions  of  all  the  other  factors  that  enter  into  the 
complex  organisation  of  the  nervous  system. 

"  In  regard  to  the  functional  mechanism  of  the  nerve  elements, 
far  from  being  able  to  accept  the  idea  of  the  independence 
implied  in  the  concept  of  the  neurone,  I  can  but  once  more  state 
my  conviction  that  the  nerve-cells  exhibit  collective  activity, 
in  the  sense  that  larger  or  smaller  groups  of  them  exert  a 
collective  action  upon  the  peripheral  organs,  through  bundles  of 
fibres  and  through  the  diffuse  nervous  network.  This  concept  of 
course  includes  that  of  the  analogous  opposite  action  in  regard 
to  sensory  functions. 

"  However  much  my  position  may  conflict  with  the  view  of 
separate  anatomical  units,  I  cannot  renounce  the  idea  of  a 
unitary  action  of  the  nervous  system,  nor  feel  disturbed  if  this 
brings  me  back  to  the  earlier  conception  of  the  mode  in  which 
the  nervous  system  functions." 

Golgi's  views  on  the  functional  activity  of  the  central  nervous 
system,  which  are  based  on  anatomical  investigations,  and  parti- 
cularly on  the  existence  of  a  diffuse  nervous  network,  are,  how- 
ever, opposed  to  the  best-established  facts  of  the  physiology  of  the 
sense  organs.  They  are  more  particularly  at  variance  with  the 
authentic  and  easily  demonstrated  observations  of  isolated  con- 
duction and  perception  of  tactile  sensations  at  various  points 
of  the  skin,  and  of  elementary  retinal  sensations,  which  we 
shall  discuss  in  treating  of  the  physiology  of  these  sense  organs. 


192  PHYSIOLOGY  CHAP. 

In  1885  Golgi  wrote  at  the  beginning  of  his  celebrated  mono- 
graph :  "  As  regards  the  central  organs  of  the  nervous  system, 
the  main  task  of  modern  anatomy  must  be  to  answer  the 
most  pressing  of  the  problems  propounded  by  physiology."  The 
neurone  theory,  while  it  harmonises  with  the  cell  theory,  un- 
doubtedly corresponds  best  with  the  postulates  of  physiology, 
although  it  is  far  from  solving  them  all  adequately. 

Whatever  the  final  solution  of  this  important  controversy 
as  to  the  structure  and  mode  of  activity  of  the  central  and 
peripheral  nervous  systems,  it  must  be  admitted  that  the  wealth 
of  physiological  facts  that  have  accumulated  in  this  important 
field  have  developed  quite  independently  of  the  prevailing  theories 
of  their  exact  constitution.  If  the  contents  of  the  present 
chapter  are  considered  without  prejudice — and  we  recommend 
them  more  particularly  to  the  attention  of  histologists,  it  must 
be  admitted  that  the  physiology  of  the  nervous  system  is  far 
in  advance  of  its  anatomy. 

II.  In  discussing  the  general  physiology  of  the  skeletal 
muscles  we  saw  that  they  are  normally  thrown  into  activity 
by  the  agency  of  their  nerves  alone ;  when  these  are  cut,  all 
movement  instantly  ceases.  Nerves  are  no  less  excitable  than 
muscles ;  but  while  in  muscle  active  reaction  to  stimuli,  i.e. 
"excitation,"  is  apparent  as  contraction  or  relaxation,  the  active 
response  of  the  nerve  is  not  visible,  but  consists  in  the  simple 
transmission  or  conduction  of  the  excitation  from  the  point 
stimulated  to  the  end-organ.  The  excitability  of  nerve  is  therefore 
manifested  in  its  conductivity,  i.e.  its  capacity  for  transmitting 
the  effect  of  local  stimulation  at  one  point  along  its  entire 
length.  The  excitatory  impulse  in  muscle  is  also,  as  we  know, 
propagated  along  the  muscle  fibres  by  physiological  conduction, 
but  conductivity  assumes  a  special  development  in  the  nerve, 
and  may  be  considered  as  its  specific  function,  depending  on 
the  particular  differentiation  and  constitution  of  its  protoplasm. 
Nerve  conduction  consists  not  in  the  propagation  of  fluid 
or  gaseous  materials,  as  was  formerly  supposed,  but  in  the 
transmission  of  excitation,  that  is,  of  the  active  state  of  the  nerve 
substance,  the  conditions,  laws,  and  characteristics  of  which  we 
must  now  investigate. 

The  fundamental  condition  of  conductivity  in  a  nerve-fibre 
is  its  anatomical  continuity  and  integrity.  If  after  dividing  a 
mixed  nerve  the  two  ends  are  brought  into  perfect  contact,  we 
obtain  physical  continuity,  but  not  the  anatomical  continuity 
which  is  imperative  for  conduction ;  stimuli  applied  above  the 
section  are  not  transmitted  in  an  efferent  direction  to  the  muscles, 
nor  those  sent  in  below  in  an  afferent  direction  to  the  centres. 
An  effect  identical  with  that  of  section  is  produced  by  crushing, 
cauterisation,  scalding,  and  by  the  action  of  certain  poisons, 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    193 


n 


I 


localised  to  one  point  of  the  nerve.  Lastly,  as  was  known  to 
the  ancients,  the  simple  tying  of  a  nerve  prevents  physiological 
conduction  along  its  fibres. 

Fontana  (1797)  was  the  first  who  observed  that  the  gradual 
compression  of  a  nerve  may  abolish  its  conductivity  without  any 
concomitant  excitatory  phenomena.  But  the  subsequent  experi- 
ments of  E.  H.  Weber,  Schiff,  and  others,  threw  doubt  upon  his 
conclusions.  They  found  that  the  paralysis  due  to  compression  of 
the  nerve  is  preceded  by  a 
state  of  increased  excita- 
bility of  the  nerve  and 
motor  phenomena  in  the 
muscle.  The  subject,  which 
is  important  to  clinical 
medicine,  was  methodically 
investigated  by  Liideritz 
(1881),  Zederbaum  (1883), 
and  Efron  (1886),  who  con- 
firmed the  observations  of 
Schiff.  They  saw  that  when 
the  compression  of  the  nerve 
has  not  been  too  severe,  nor 
too  prolonged,  its  conduc- 
tivity may  be  gradually  re- 
established. According  to 
Liideritz,  gradual  compres- 
sion abolishes  conductivity 
first  in  motor  and  later  in 
sensory  fibres ;  but  this 
observation  was  contra- 
dicted by  Zederbaum  and 
Efron.  In  their  experi- 
ments on  the  nerves  of 
amphibia  and  of  mammals, 
these  authors  noted  that 
a  pressure  of  some  hundred 
grammes  is  always  required  before  conductivity  is  abolished. 

These  experiments  were  resumed  by  Ducceschi  (1900)  in 
Ewald's  laboratory  by  another  method,  i.e.  compression  of  a  very 
limited  area  of  the  nerve  by  means  of  a  silk  thread  (about  0'3 
mm.  thick) ;  this  is  passed  round  the  nerve  as  it  lies  upon  a 
metal  plate  through  two  small  holes  made  in  the  latter,  so  that  it 
can  be  gradually  drawn  down  by  a  weight  (Fig.  126). 

By  means  of  this  little  apparatus  Ducceschi  succeeded  in 
diminishing  or  abolishing  conduction  in  the  frog's  sciatic  by  the 
compression  caused  by  a  weight  of  a  few  grammes,  without  any 
preceding  signs  of  excitation,  as  already  observed  by  Fontana. 

VOL.  in  0 


FIG.  12G. — Apparatus  for  measurable  compression  of 
frog's  nerve  by  a  silk  thread.  (Uucceschi.)  1,  metal 
plate  pierced  with  two  small  holes  ;  «,  sciatic  nerve  ; 
/,  silk  thread  ;  b,  balance  to  carry  weights  ;  »•,  support 
moved  by  screw  v  to  allow  the  weight  to  be  applied 
gradually. 


194 


PHYSIOLOGY 


CHAP. 


He  saw  that  conductivity  returned  a  few  seconds  after  the  pressure 
was  removed,  provided  it  had  not  been  excessive  nor  unduly  pro- 


Fni.  127. — Myograms  of  frog's  gastrocnemius  (1)  with  electrical  stimulation  ;  (2)  with  break  shocks 
at  an  interval  of  4  sees.  (Ducceschi.)  In  both  tracings  a  weight  was  applied  at  ^  the  value 
being  marked  in  grammes  ;  at  -^-  the  compression  ceased. 

longed  (Fig.  127).  If,  while  the  frog's  gastrocnemius  was  being 
tetanised  by  an  interrupted  current  applied  to  the  sciatic,  the 
nerve  was  compressed  below  the  point  of  excitation,  the  trans- 
mission of  the  impulses  was  partially  inhibited,  and  the  almost 


FIG.  128. — The  marks  on  these  tracings  correspond  to  those  of  the  preceding  figure. 
At  b  and  c  the  nerve  was  tetanised. 

tonic  contraction  of  the  muscle  was  transformed  into  a  clonic 
contraction  (Fig.  128).  The  effects  of  graduated  compression  on 
conductivity  differed  according  as  chemical,  mechanical,  or  electrical 


iv    GENEKAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    195 

stimuli  were  employed,  owing  probably  to  their  different  intensity. 
When  excitation  from  chemical  stimuli  (glycerol  or  hypertonic 
salt  solution)  was  no  longer  able  to  pass  the  compressed  point, 
excitation  from  mechanical  stimuli  was  able  to  get  through  ;  when 
the  latter  was  blocked  by  the  compression,  electrical  stimuli  were 
still  effective  (Fig.  129).  It  is  an  interfering  fact  that  reflex 
spinal  excitation  is  arrested  by  a  minimal  degree  of  compression 
such  as  blocks  the  transmission  of  chemipal  stimuli. 

A  frog's  nerve  ceases  to  conduct  when  its  diameter  is  reduced 
to  one-third  or  one-fourth  of  the  normal ;  it  then  becomes  trans- 
parent, as  the  fluid  contained  in  the  myelin  sheath  is  pushed  back 
above  and  below  the  point  of  compression.  Histological  inspection 
of  the  nerve  compressed  by  a  silk  thread  shows  that  there  is 
no  blackening  of  the  myelin 
sheath  by  osinic  acid  near  the 
point  of  compression,  but  the 
axis-cylinder  (the  conducting 
element)  is  reduced  in  size. 

After  D  ucceschi,  Signorina 
Calugareanu  (1901)  experi- 
mented iu  Dastre's  laboratory, 
by  a  somewhat  different 
method,  on  the  effects  of 
mechanical  compression  of 
the  nerve  of  the  electrical 

Organ    Of    Torpedo,    the    frog's     Fio.  129.— The  very  rapid  contractions  at  the  begin- 

•    ,•  -i   ,1  11  •,>  ning  of  the  tracing  were  due  to  chemical  stimula- 

SCiatlC,  and  the  rabbit  S  VagUS.          tion  with  glycerol,  applied  to  the  upper  part  of 

She  also  obtained  diminution       the  nerve-   At  ^  the  nerve  was  compressed  by 

P  i        ,•     .,  •.I  25  grms.     At  </  it  was  stimulated  above  the  point 

01    COlldllCtlVlty    WltbOUt    any          of  compression  with  break  shocks. 

previous  rise  of  excitability, 

and    found    that    the    injurious    influence    of    compression    was 

not  manifested  immediately,  but  after  a  certain  time  (about   1 

minute). 

Bethe,  too  (1903),  studied  the  effect  of  compression  on  frog's 
nerve  by  a  method  similar  to  that  of  Ducceschi,  with  reference 
more  particularly  to  the  histological  changes.  He  found  that  by 
a  degree  of  compression  which  did  not  abolish  conductivity  to 
electrical  stimuli  the  axis-cylinder  may  be  considerably  reduced 
in  diameter,  at  the  cost  not  of  the  neuro- fibrils  which  compose  it, 
but  of  the  perifibrillar  substance  (or  neuroplasin).  According  to  his 
calculations  the  amount  of  perifibrillar  substance  in  the  normal 
fibre  is  to  that  of  a  compressed  fibre  which  is  still  capable  of  con- 
ducting, as  654 :  1.  This,  he  says,  proves  that  conductivity  is  a 
function  of  the  neuro-fibrils  and  not  of  the  perifibrillar  substance. 
Bethe  further  noted  that  when  the  nerve-fibres  are  rendered 
incapable  of  conducting  by  compression,  they  also  lose  their 
capacity  for  primary  staining,  i.e.  staining  with  basic  dyes  in  the 


\ 


\ 


196  PHYSIOLOGY  CHAP. 

fresh  state,  or  when  dehydrated  only, — which  returns  when  con- 
ductivity is  re-established. 

One  of  the  most  important  facts,  which  may  rank  as  a  funda- 
mental law  of  nerve  conduction,  is  that  each  fibre  of  a  nerve 
conducts  the  excitatory  impulse  from  the  periphery  to  the  centre, 
or  from  the  centre  to  its  terminal  ramifications,  without  spread  of 
the  excitation  by  contact  to  the  neighbouring  fibres.  In  the  case 
of  a  mixed  nerve  the  motor  fibres  can  be  excited  along  their 
course  without  simultaneously  producing  sensations,  or  the  sensory 
fibres  without  simultaneous  production  of  movements.  The  most 
convincing  proof  of  isolated  conduction  of  the  active  state  in 
individual  fibres  is  afforded  by  the  delicacy  of  localisation,  both  of 
movements  and,  still  more,  of  sensations.  It  is  possible  to  stimulate 
the  small  bundle  of  fibres  that  form  the  motor  roots  of  the 
sciatic  separately  so  as  to  produce  localised  contractions  in  the 
individual  muscles  or  portions  of  muscles  which  they  innervate, 
without  diffusion  of  the  impulse  to  the  whole  group  of  muscles 
that  are  thrown  into  action  by  stimulating  the  trunk  of  the  sciatic. 
The  excessively  delicate  localisation  of  tactile  sensations,  the 
sharpness  of  outlines  and  shading  of  colours  in  visual  images, 
would  be  quite  impossible  if  each  fibre  of  a  peripheral  or  optic 
nerve  were  not  an  isolated  conductor. 

This  localisation  of  movements  and  sensations,  with  which  we 
are  all  familiar,  has  so  far  received  no  mechanical  explanation.  It 
has  been  thought  on  good  evidence  that  the  sheaths,  and  particularly 
the  myelin  sheath,  are  mainly  responsible  for  the  complete  insula- 
tion of  the  axis-cylinder ;  but  the  fact  that  this  insulation  holds 
good  for  the  non-medullated  nerve-fibres  as  well  leads  one  to 
conjecture  that  it  is  a  property  inherent  in  the  axis -cylinder, 
though  we  are  ignorant  of  the  cause  to  which  it  is  due.  That 
insulated  conduction  does  not  depend>  on  the  medullary  sheath 
is  further  proved  by  the  fact  established  by  Ducceschi,  that  when 
the  frog's  sciatic  is  so  compressed  as  to  rupture  the  sheath  without 
blocking  the  conductivity  of  the  nerve,  isolated  contraction  of  the 
separate  muscles  of  the  foot  can  be  obtained  by  stimulating  single 
branches  of  the  lumbro-sacral  plexus. 

The  new  theory  of  the  minute  structure  of  the  nervous  system, 
according  to  which  the  axis-cylinder  and  the  dendrites  are  con- 
sidered not  as  elementary  nerve-fibres  but  as  bundles  of  separate 
fibrils  forming  an  elementary  network,  naturally  raises  the  question 
whether  the  law  of  insulated  conduction  is  applicable  to  the  pro- 
cesses (dendrites  and  axons)  of  the  ganglion  cells  as  a  whole,  or 
to  the  individual  fibrillary  elements  of  which  these  seem  to 
consist.  It  must  be  confessed  that  science  is  not  yet  ready  to 
solve  this  problem,  which  needs  a  more  complete  knowledge  of 
their  anatomical  relations.  We  can  only  say  that  many  ramifica- 
tions of  nerve-fibres  are  merely  dissociations  of  distinct  fibrils 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    197 

united  into  bundles,  and  that  the  true  ramifications  of  the  con- 
ducting elements  probably  exist  only  in  the  terminal  and  peripheral 
organs,  where  distinction  and  localisation  of  the  physiological 
effects  of  the  excitation  transmitted  along  the  conducting  filaments 
is  no  longer  necessary. 

Another  fundamental  fact  of  nerve  conduction  is  what  William 
James,  the  psychologist,  termed  the  forward  direction.  Conduction 
is  normally  centripetal,  i.e.  from  the  periphery  to  the  centre  in 
sensory  fibres  and  afferent  fibres  in  general,  and  centrifugal,  from 
centre  to  periphery,  in  the  motor  fibres  and  efferent  fibres  in 
general.  Again,  when  the  nerves  are  artificially  stimulated  along 
their  course,  the  effect  is  expressed  in  movement  for  motor  nerves, 
in  sensation  for  the  sensory.  We  shall  see,  in  fact,  in  discussing 
the  physiology  of  the  special  nerve  roots,  that  on  stimulating  the 
central  stump  of  a  root  that  contains  motor  fibres  only  all  sensory 
reaction  fails,  and  on  stimulating  the  peripheral  stump  of  a  root 
containing  only  sensory  fibres  no  motor  reactions  are  obtained. 

This  fact  at  first  sight  justifies  the  conjecture  that  sensory 
nerves  can  only  conduct  the  excitation  in  an  afferent  direction 
when  excited  along  their  course,  and  motor  nerves  only  in  an 
efferent  direction,  as  though  there  were  some  valvular  mechanism 
which  allows  the  transmission  of  the  impulse  in  one  direction  and 
blocks  it  in  the  other.  Certain  experimental  facts,  however,  show 
this  hypothesis  to  be  untenable,  and  indicate  that  nerves  in 
general,  when  artificially  excited  at  any  point  of  their  course,  are 
capable  of  conducting  in  both  directions,  but  the  effect  is  manifested 
only  at  the  centre  for  sensory  nerves,  and  at  the  periphery  for 
motor  nerves. 

The  best  argument  for  double  conduction  appears  from  the 
study  of  the  electrical  phenomena  that  accompany  the  excitation 
of  nerve.  This  will  be  discussed  in  a  separate  section.  When  a 
nerve  is  stimulated  midway,  while  the  two  ends  are  joined  up  to 
two  galvanometers,  the  so-called  negative  variation  is  seen  on 
both.  This  occurs  not  only  with  a  mixed  nerve,  which  contains 
both  sensory  and  motor  fibres,  but  also,  as  Du  Bois  Reymond 
pointed  out,  with  a  nerve  which  contains  only  motor  (efferent) 
fibres,  e.g.,  the  ventral  spinal  roots. 

Gotch  and  Horsley  repeated  and  varied  this  experiment,  both 
with  efferent  and  afferent  nerves.  They  divided  a  ventral  root  of 
the  sciatic  plexus  in  the  cat ;  connected  it  with  a  highly  sensitive 
galvanometer,  and  then  excited  the  trunk  of  the  sciatic.  A  double 
reaction  followed — -of  the  muscles  of  the  limb,  which  proved 
centrifugal  conduction  in  the  motor  fibres,  and  of  the  galvano- 
meter, which  showed  centripetal  conduction  in  the  same  motor 
fibres.  Similar  effects  were  obtained  with  sensory  nerves.  On 
exciting  a  dorsal  root  and  connecting  the  central  end  of  the 
divided  sciatic  with  the  galvanometer,  the  negative  variation 


198  PHYSIOLOGY  CHAP. 

appeared,  which  is  a  proof  of  centrifugal  conduction  in  the  sensory 
fibres. 

Many  other  attempts  have  been  made  to  demonstrate  the 
possibility  of  reversal  of  the  normal  passage  of  excitation  along  a 
nerve.  Schwann  divided  the  sciatic  of  a  frog,  and  allowed  the 
two  ends  to  unite.  He  then  stimulated  the  sensory  roots  of  the 
nerve,  and  saw  that  its  excitation  produced  no  contraction  in  the 
muscles  of  the  limb.  From  this  he  concluded  against  the  theory 
of  conduction  in  a  double  direction,  since  it  seemed  to  him  im- 
probable that  each  afferent  or  efferent  fibre  of  the  two  stumps 
should  be  able  to  unite  with  a  fibre  of  its  own  kind.  But  the 
fact  that  normal  sensibility  and  motility  is  recovered  after  nerve 
section  shows  that  what  Schwann  thought  so  impossible  really 
does  take  place.  His  experiments,  which  Steinbriick  confirmed  in 
1838,  do  not  therefore  overthrow  the  theory  of  conduction  in 
both  directions. 

Bidder  (1841)  attempted  to  connect  the  peripheral  end  of  the 
hypoglossal  (motor  nerve)  with  the  central  end  of  the  lingual 
(sensory  nerve),  but  he  only  managed  to  unite  trunks  of  the  same 
kind,  as  in  Schwann's  experiments.  Union  of  heterouomous 
stumps  was,  however,  obtained  by  the  subsequent  experiments 
of  Gluge  and  Thiernesse  (1859),  Philipeaux  and  Vulpian  (1860), 
Roseuthal  (1864),  and  Bidder  himself  (1865).  It  was  found  that 
when  the  two  nerves  above  mentioned  had  united,  stimulation  of 
the  lingual  produced  movements  of  the  tongue,  and  stimulation 
of  the  hypoglossal  (united  to  the  central  end  of  the  lingual)  elicited 
signs  of  pain. 

These  results  seemed  to  be  positive  evidence  for  conduction  in 
I  both  directions ;  subsequent  researches,  however,  proved  them 
capable  of  a  different  interpretation.  The  symptoms  of  pain  when 
the  hypoglossal  was  stimulated  can,  according  to  Arloing  and 
Tripier,  be  interpreted  as  a  phenomenon  of  recurrent  sensibility  in 
the  stump  of  the  hypoglossal,  and  the  movements  of  the  tongue 
on  stimulating  the  lingual  may,  according  to  Vulpian's  last  work, 
depend  on  excitation  of  the  fibres  of  the  chorda  tympani,  which  is 
an  efferent  nerve.  If,  on  the  other  hand,  the  hypoglossal  on  one 
side  be  cut  so  that  it  degenerates  completely,  and  the  peripheral 
stump  of  the  freshly  divided  lingual  nerve  is  then  excited,  a  slow 
contraction  of  the  tongue  follows,  which  is  due  to  the  chorda 
tympani  and  is  accompanied  by  vascular  dilatation.  The  mechanism 
of  this  phenomenon  is  very  obscure,  since  the  chorda  tympani  has 
no  direct  anatomical  connection  with  the  tongue  muscles,  and 
produces  no  motor  effect  under  normal  conditions,  i.e.  when  the 
hypoglossal  is  uninjured.  So  that  none  of  these  experiments  are 
of  any  account  for  the  question  of  double  conductivity  in  nerve. 

Nor  can  any  greater  value  be  assigned  to  the  experiments  which 
Paul  Bert  carried  out  on  rats  by  suturing  the  tip  of  the  tail  to  the 


iv    GENERAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    199 

skin  of  the  back,  and  dividing  it  when  healed  close  to  the  root. 
As  he  elicited  signs  of  pain  on  exciting  this  inverted  tail,  he 
concluded  that  conduction  in  the  nerve  had  been  reversed.  But 
till  we  know  what  phenomena  of  degeneration  and  regeneration 
take  place  in  the  nerve,  after  transplanting  the  tail,  it  is  impossible 
to  give  any  positive  explanation  of  the  results  of  this  experiment, 
and  it  cannot  be  invoked  in  favour  of  the  law  of  double  conduction. 

Kiihne  (1859)  attempted  by  another  method  to  prove  con- 
duction in  both  directions.  He  divided  the  broad  end  of  a  freshly 
dissected  frog's  sartorius  into  two  strips  with  scissors,  and  found 
that  mechanical  stimulation  of  one  of  the  strips  produced  h'brillary 
contractions  which  were  not  confined  to  the  segment  of  muscle 
that  was  directly  excited,  but  spread  also  to  the  strip  that  had 
not  been  excited.  According  to  Klihne  this  phenomenon  can  only 
be  explained  on  the  assumption  that  the  excited  and  non-excited 
segments  of  muscle  contain  nerve-fibres  which  come  from  the 
bifurcation  of  the  axis-cylinders  of  the  principal  nerve.  The 
excitation  is  transmitted  centripetally  in  the  nerves  of  the  first 
strip,  and  then  spreads  centrifugally  to  the  nerves  of  the  second 
strip. 

Babuchin  repeated  this  experiment  on  the  electrical  organ  of 
Malapterwrus  which  has  a  single  gigantic  many-branching  nerve- 
fibre.  He  found  that  excitation  of  a  single  twig  of  this  fibre 
suffices  to  produce  a  discharge  of  the  whole  electrical  organ. 

Hermann  attached  great  importance  to  these  experiments  of 
Ktihne  and  Babuchin  as  evidence  for  the  law  of  conduction  in 
both  directions.  Other  authorities,  on  the  contrary,  make  strong 
objections,  for  which  we  have  not  space,  particularly  as  Kiihne, 
in  a  memoir  of  1886,  published  a  long  series  of  new  experiments 
on  the  pectoral  and  gracilis  muscles  of  the  frog  which  lend  them- 
selves better  to  the  solution  of  the  problem. 

If  the  pectoral  muscle  of  the  frog  is  divided  as  shown  in  Fig. 
130,  by  leaving  a  bridge  (Z~]  which  carries  the  nerve  and  a  few 
muscle  fibres,  mechanical,  chemical,  or  electrical  stimulation  of 
this  bit  of  tissue  will  cause  the  whole  of  the  remainder  of  the 
preparation  (J/)  to  contract.  This  contraction  is  not  fibrillary  as 
in  the  sartorius,  but  diffuse  and  simultaneous  in  all  the  fibres  of 
the  muscle,  so  that  it  can  be  graphically  recorded  and  shown  to 
exhibit  the  characteristics  of  a  single  twitch.  The  experiment  of 
Fig.  131  is  still  more  decisive.  It  shows  that  retrograde  con- 
duction of  the  nerve  impulse  along  the  motor  fibres  may  also 
occur  between  two  parts  of  the  same  muscle  (K  and  L],  united 
only  by  the  nerve  (&),  on  stimulating  one  portion  of  the  nerve  (Z), 
so  that  any  direct  intervention  of  the  muscle  fibres  in  causing 
the  phenomenon  is  excluded. 

Kiihne  ascertained  by  a  minute  histological  examination  of 
the  nerves  of  the  frog's  pectoral  and  gracilis  muscles  that  the 


200 


PHYSIOLOGY 


CHAP. 


dichotomous  branchings  of  the  nerve-fibres  occur  principally  at 
the  points  at  which  the  nerve  enters  the  muscle,  and  in  the 
extramuscular  part  of  the  same  nerve.  This  dichotomous  division 
of  the  nerve-fibres  is  brought  about  by  the  separation  of  the  fibrils 
of  which,  according  to  Schultze,  the  axis-cylinders  are  composed. 
Hence  the  experiments  of  Kiihne  not  only  yield  a  direct  proof 
of  double  conductivity,  but  they  also  imply  that  the  isolated  con- 
duction which  Johannes  Miiller  showed  to  be  a  property  of  the 
axis-cylinder  does  not  hold  as  between  the  fibrils  of  which  each 
axis-cylinder  is  composed. 

Kiihne  employed  the  same  method  to  demonstrate  unequivocally 
that  the  paralysing  action  of  curare  is  localised  in  the  end-plates 
of  the  muscular  nerves,  and  does  not  spread  to  the  motor  fibres 


Z 


... 

1'lUv 

rTXiF 

I 
ft 

I   ^ 

p"   ' 

f               ! 

i           '    L 

N 


FIG.  130. — Killing's  experiment  on  frog's  pectoral 
muscle.  -Y,  iirrvt-  which  supplies  the  right 
half  (in)  of  the  muscle  ;  the  left  half  is  cut 
away  leaving  only  the  bridge  Z,  which  con- 
tains the  part  of  the  nerve  that  is  mechanic- 
ally stimulated. 


PIG.  131. — Kiihne's  experiment  on  the  gracilis 
muscle.  N,  nerve  that  gives  off  branches 
to  the  two  separate  parts  of  the  muscle 
A'  and  L  and  to  the  bridge  of  muscle  Z, 
which  is  mechanically  excited. 


(see  Chapter  I.).  He  employed  the  gracilis  muscle  of  the  frog, 
which  can  be  divided  by  a  ligature  into  two  portions,  in  only  one 
of  which  the  poisoned  blood  circulates.  The  muscle  thus  treated 
can  be  cut  so  that  the  nerve  forms  the  only  connection  between 
the  curarised  and  non-curarised  portions  (Fig.  132).  Under  normal 
conditions  the  mechanical  stimulus  applied  at  N,  Z,  or  K  pro- 
duces a  contraction  of  the  entire  muscle  according  to  the  law 
of  the  backward  conduction  of  excitation ;  but  in  the  curarised 
muscle  mechanical  stimulation  of  the  nerve  at  N  and  at  k  will 
only  cause  contraction  of  the  part  K,  i.e.  the  non-curarised  portion 
of  the  muscle,  the  same  effect  being  produced  by  exciting  the 
branches  /  and  I'  of  the  curarised  portion.  This  proves  that  the 
nerve-fibres  have  not  been  paralysed  by  the  curare,  since  con- 
duction in  a  centripetal  direction  takes  place  in  them,  as  under 
normal  conditions. 

It  may  be  argued  logically  from  the  law  of  double  conduction 
that  the  motor  and  sensory  nerves  do  not  differ  fundamentally  in 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    201 


their  internal  constitution.  That  under  normal  conditions  the 
former  conduct  centrifugally  and  the  latter  centripetally  depends 
not  ou  any  intrinsic  difference,  but  on  the  specific  nature  of  the 
organ  with  which  they  are  related  at  the  centre  or  the  periphery, 
and  to  which  they  transmit  the  excitation.  If  experimental  efferent 
excitation  of  sensory  nerves  and  afferent  excitation  of  motor 
nerves  produces  no  perceptible  motor  or  sensory  effects,  there  must 
at  the  peripheral  end  of  the  former  and  central  end  of  the  latter 
be  some  apparatus,  as  to  the  nature  of  which  we  are  entirely 
ignorant,  which  hinders  the  excitation  from  being  propagated,  as 
a  system  of  valves  determines  the  direction  of  flow  of  a  current. 
There  is  thus  no  intrinsic  contradiction 
between  the  law  "  of  the  forward  direc- 
tion of  normal  excitations  "  and  that  "  of 
the  double  direction  of  experimental 
Vexcitation,"  i.e.  such  as  is  artificially 
produced  along  the  course  of  the  nerve. 
Intimately  connected  with  this  law 
is  the  other  which  Hermann  (1879) 
termed  "law  of  the  constant  effect  of 
nervous  excitation."  Whether  a  nerve 
be  excited  at  its  end  or  at  any  point 
along  its  course,  the  effect  on  the  organ 
of  reaction  is  invariably  the  same,  viz. 

I    muscular  movement  for  motor  nerves, 

sensation  for  sensory  nerves.  The  local-  Fio.  132. -Kuime's  experiment 
isation  and  character  of  the  muscular 
movement  are  determined  not  by  the 
site  of  stimulation,  but  by  the  number 
of  fibres  excited  and  their  peripheral 
distribution  to  the  muscle.  So,  too, 
the  location  and  specific  quality  of 
the  sensation,  e.g.  pressure,  heat,  and 
pain,  which  occurs  on  stimulating  a  sensory  cutaneous  nerve 
at  any  point,  is  identical  with  that  produced  by  the  action 
of  natural  stimuli  upon  the  end-organ  in  the  skin.  The  most 
striking  example  that  can  be  adduced  in  proof  of  this  law  is  that 
observed  when  a  limb  has  been  amputated.  "  When  the  member  to 
which  a  nerve  trunk  is  distributed,"  says  Johannes  Miiller,  "  is 
removed  by  amputation,  the  stump  of  the  nerve  which  contains 
the  whole  of  the  shortened  nerve-fibres  is  capable  of  the  same 

\sensations  as  if  the  amputated  limb  were  still  present.  This 
persists  all  through  life."  If  the  stump  becomes  inflamed,  such 
persons  complain  of  sharp  pains  in  the  entire  lost  limb.  Upon 
recovery  they  have  the  same  sensations  that  normal  people  feel  in 
a  healthy  limb,  and  there  is  often  a  persistent  sensation  of  itching, 
or  discomfort,  which  appears  to  be  localised  in  the  limb  that  no 


frog's  graeilis  muscle,  halt' of  which 
had  been  poisoned  with  curare  and 
then  severed,  so  that  only  the 
nerve  was  left  as  a  connecting 
bridge.  N,  nerve  that  gi\es 
branches  to  the  poisoned  L  and 
non  -  poisoned  K,  halves  of  the 
muscle  ;  k,  connecting  bridge  ; 
Z,  nerve -muscle  biidgr  that  is 
mechanically  excited. 


202  PHYSIOLOGY  CHAP. 

longer  exists.  Many  persons  eventually  become  accustomed  to 
these  sensations,  and  cease  to  notice  them ;  but  they  surge  up 
again  when  attention  is  focussed  upon  them,  and  are  often  felt 
distinctly  in  the  fingers,  sole  of  the  foot,  or  hand.  The  sensation 
is  more  acute  when  pressure  is  exerted  on  the  stump. 

The  symptoms  of  anaesthesia  dolorosa  are  no  less  important 
to  the  demonstration  of  the  peripheral  projection  of  sensations. 
Traumatic  paralysis  from  compression  or  section  of  a  nerve  trunk, 
in  which  more  or  less  extensive  cutaneous  areas  become  totally  in- 
sensitive to  the  strongest  stimuli,  though  the  patient  still  complains 
of  intense  pain  in  them  owing  to  the  irritable  state  of  the  nerve 
trunk,  is  not  infrequent.  In  surgery,  division  of  the  nerve  may 
fail  to  cure  neuralgia,  as  it  merely  interrupts  the  conduction  of 
external  peripheral  excitations  to  the  centre,  but  cannot  suppress 
the  conduction  of  central  irritation  in  the  nerve,  which  gives 
origin  to  sensations  projected  to  the  periphery  similar  to  those 
produced  by  extrinsic  local  stimulation. 

The  phenomenon  of  the  peripheral  projection  of  sensations  can 
easily  be  demonstrated  under  normal  conditions  by  mechanical 
excitation  of  one's  own  ulnar  nerve  in  the  groove  of  the  internal 
condyle  at  the  elbow,  where  it  is  accessible ;  this  produces  a  prick- 
ing in  the  palm  and  back  of  the  hand,  and  in  the  third  and  fourth 
fingers.  Pressure  on  the  infraorbital  nerve,  where  it  issues  from 
its  foramen,  produces  pricking  at  many  points  of  the  cheek  and 
upper  lip. 

III.  Johannes  Miiller  in  1844  declared  the  problem  of  the 
velocity  of  nerve  conduction  to  be  insoluble,  and  compared  it  with 
that  of  light.  "  The  time,"  he  writes,  "  in  which  a  sensation 
passes  from  the  exterior  to  the  brain  and  spinal  cord,  and  thence 
back  to  the  muscle  so  as  to  produce  a  contraction,  is  infinitely 
small  and  immeasurable."  Only  six  years  later,  in  1850, 
Helmholtz  was  able  by  exact  physical  methods  to  determine  the 
rate  of  propagation  in  a  frog's  nerve,  and  to  demonstrate  that  it 
is  infinitely  slow  in  comparison  with  the  propagation  of  physical 
energy.  Electricity  traverses  a  space  of  464  million  metres  in  a 
second,  light  300  million,  sound  332  metres;  the  excitatory 
impulse  in  nerve,  on  the  contrary,  is  transmitted  at  a  rate  so 
much  lower  that  it  may  be  compared  with  the  speed  of  a  loco- 
motive or  the  flight  of  an  eagle. 

The  first  exact  measurement  of  the  velocity  of  conduction  in 
nerve  was  made  by  Helmholtz  on  a  frog's  nerve-muscle  preparation 
(Fig.  3).  If  the  time-interval  between  the  stimulation  of  the 
nerve  and  the  contraction  of  the  muscle  (latent  period)  is  measured, 
it  is  found  to  be  greater  when  the  motor  nerve  is  stimulated  at  a 
point  remote  from  the  muscle  than  when  it  is  stimulated  near  the 
muscle.  The  difference  in  the  time-interval  is  also,  carteris  paribus, 
proportional  to  the  length  of  nerve  between  the  two  points  excited. 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    203 

From    the  difference  in   time  and   the  length    of  the    nerve   as 
measured  the  rate  of  conductivity  is  easily  calculated. 

Helmholtz  employed  two  methods  for  determining  the  time  that  elapses 
between  the  (electrical)  stimulation  of  the  nerve  and  the  reaction  of  the  muscle. 
The  first  method,  invented  by  Pouillet,  consists  in  measuring  the  duration 
of  an  electrical  current,  sent  through  a  galvanometer  at  the  moment  of  excit- 
ing the  nerve,  and  interrupted  at  the  moment  at  which  the  muscle  contracts 
(for  details  of  the  application  of  this  method  see  Biedermann).1  The  second 
method,  employed  after  Helmholtz  by  all  physiologists,  is  a  special  applica- 
tion of  the  graphic  method.  The  times  of  nerve  excitation  and  muscle  con- 
traction are  recorded  by  a  myograph  on  the  smoked  paper  of  a  drum  or  plate, 
which  is  moving  very  rapidly,  the  time  being  marked  on  the  same  surface 
by  means  of  a  tuning-fork.  The  difference  in  time  can  thus  be  measured 
exactly  between  the  first  stimulation  of  the  nerve  close  to  the  muscle  and  the 
commencement  of  the  muscular  contraction,  and  the  second  stimulation 
farther  from  the  muscle  and  commencement  of  the  second:  contraction. 
When  the  times  of  the  two  successive  stimulations  are  recorded  at  the  same 
point  of  the  revolving  drum  (as  in  Fig.  133),  the  distance  between  the  initial 


Fir..  133. — Velocity  of  nerve  conduction,  as  measured  by  Marey  on  himself.  1,  myogram  traced  on 
exciting  the  nerve  close  to  the  muscle  ;  2,  myogram  on  exciting  the  nerve  30  cms.  from  the 
muscle  ;  D,  time  tracing  from  a  tuning-fork  at  250  double  vibrations  per  second.  The  interval 
between  the  two  contractions  occupies  about  2-5  vibrations,  corresponding  to  O'Ol  sec.  in 
which  the  impulse  traverses  30  cms.  =  30  m.  per  second. 

point  of  the  two  contractions  is  all  that  is  required  to  calculate  the  rate  of 
conductivity,  when  the  length  of  nerve  between  the  two  points  of  excitation 
is  known. 

From  an  average  of  the  experiments  made  by  Helmholtz  on 
the  frog's  nerves  the  velocity  of  nerve  conduction  was  found  to  be 
27'25  metres  per  second,  which  is  much  less  than  the  velocity  of 
the  propagation  of  sound  in  air,  but  greater  than  the  propagation 
of  the  contraction  wave  in  the  muscle  of  the  same  animal,  this 
being,  as  we  have  seen,  about  1  metre  per  second. 

Helmholtz  and  Baxt  also  determined  the  rate  of  conductivity 
in  the  motor  nerves  of  man.  They  recorded  the  myograms  of  the 
thumb-muscle  upon  a  rotating  cylinder  by  placing  a  sensitive 
lever  on  the  thenar  eminence,  and  exciting  the  median  nerve 
either  in  the  axilla  or  near  the  wrist  joint,  through  the  previously 
moistened  skin.  The  rate  obtained  was  somewhat  higher  than  for 
frog  nerves,  i.e.  30-35  in.  per  second. 

Helmholtz  and  many  other  investigators  have  also  attempted 
to  determine  the  rate  at  which  the  impulse  is  propagated  in  the 

1  Electro-Physiology,  English  translation  by  F.  A.  Welby,  1896,  ii.  59. 


204  PHYSIOLOGY  CHAP. 

sensory  nerves  of  man,  but  the  resulting  data  are  discordant  and 
unconvincing.  The  method  consists  in  determining  the  reaction- 
time  to  tactile  sensations  sent  in  at  two  points  on  the  skin  of  the 
arm,  at  different  distances  from  the  centres.  As  soon  as  the 
subject  perceived  the  sensation  he  pressed  a  button  which  marks 
the  moment  of  reaction  upon  a  revolving  cylinder.  It  was 
formerly  assumed  that  the  reaction-time  for  two  approximately 
identical  sensations,  evoked  at  two  points  of  the  skin  at  different 
distances  from  the  centres,  differed  only  in  proportion  to  the 
different  length  of  nerve  through  which  the  impulse  has  to 
pass  before  reaching  the  centres.  The  discrepancy  of  results 
obtained  by  various  experimenters,  which  ranges  from  26  to  more 
than  100  m.  per  second,  however,  shows  that  the  lost  time  at 
the  centres,  where  the  afferent  excitation  is  transformed  into  a 
motor  impulse  passing  down  the  efferent  nerve,  must  vary  con- 
siderably, according  to  the  site  of  stimulation,  the  state  of  fatigue 
and  degree  of  attention  of  the  subject,  with  other  less  appreciable 
conditions.  It  is  probable,  judging  from  other  experiments  to  be 
described  later,  that  the  rate  of  conductivity  is  the  same  in 
sensory  nerves  as  in  motor. 

Considerable  differences  in  rate  of  conductivity  are  found  in 
the  lower  animals,  and  even  in  different  kinds  of  nerve  in  the 
same  animal.  Fredericq  and  van  de  Velde  found  for  the  nerves 
of  the  claw  of  the  sea-crab  a  velocity  varying  from  6  to  12  metres 
per  second  when  the  temperature  varied  between  19°  and  20°  C. 
v.  Uexkiill  found  variations  of  O'4-l  m.  per  second  for  the  nerves  of 
the  mantle  of  Cephalopoda ;  Chauveau  found  in  the  vagus  fibres 
that  innervate  the  smooth  muscle  cells  of  the  oesophagus  of  large 
mammals  a  velocity  averaging  8'2  rn.  per  second,  while  in  the 
vagus  fibres  that  innervate  the  striated  muscles  of  the  larynx  it 
averaged  66'7  m.  per  second.  According  to  Chauveau -this  rate 
is  not  uniform  for  all  parts  of  the  nerve,  but  falls  in  the  parts 
nearest  the  muscle. 

From  some  of  Gotch's  work,  again,  it  seems  highly  probable 
that  the  rate  of  transmission  of  the  motor  impulse  is  much  lower 
in  the  terminal  branches  of  the  nerve  than  it  is  in  the  principal 
trunks.  In  experiments  on  the  electrical  organ  of  Malapterurus, 
in  which  a  gigantic  nerve-fibre  terminates  in  a  very  free  arborisa- 
tion, he  measured  the  difference  of  latent  period  obtained  on 
exciting  the  organ -directly  or  through  the  nerve,  and  found  that  a 
non-negligible  fraction  of  time  (0'003-0'005  per  second)  was  lost 
in  the  transmission  of  the  impulse  along  the  twigs  of  the  nerve. 
On  repeating  the  experiments  of  Babuchin  on  the  same  nerve 
(see  p.  199)  to  see  if  the  retrograde  centripetal  conduction  of 
the  impulse  proceeded  at  the  same  rate  as  the  centrifugal,  his 
results  led  him  to  conclude  that  the  velocity  of  conduction  did  not 
alter  with  the  ascending  or  descending  direction  of  the  impulse. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    205 

The  influence  of  temperature  on  rate  of  conduction  in  nerve  is 
very  apparent.  Helmholtz,  experimenting  with  the  motor  nerves  I 
of  frog,  found  that  their  conductivity  diminished  considerably 
on  cooling,  and  increased  on  warming  to  25°  C.  Gotch  and 
Macdonald  made  a  careful  research,  exciting  the  same  nerve  at 
regular  intervals  with  minimal  or  nearly  minimal  stimuli.  They 
found  that  on  cooling  the  nerve  to  5°  C.  the  muscular  response 
diminished  or  disappeared,  while  on  warming  it  to  35°  C.  it  was 
increased  and  became  maximal.  So  that  cooling  diminishes  not 
only  the  velocity  of  conduction,  but  the  intensity  of  the  effect  trans- 
mitted by  the  nerve  as  well ;  heating  produces  the  opposite  effect. 

Helmholtz  and  Baxt  further  observed  that  both  the  rate  of 
conduction  and  the  intensity  of  the  effect  transmitted  vary 
with  alterations  in  the  strength  of  the  stimulus.  This  result, 
obtained  on  the  brachial  nerve  of  man,  was  confirmed  by 
Vintschgau  for  the  motor  nerves  of  frog,  and  by  Fick  for  the  non- 
medullated  nerves  of  Anodonta.  It  was,  however,  always  disputed 
by  Rosenthal  and  Lautenbach,  and  it  is  in  any  case  doubtful 
whether  it  applies  to  mechanical  and  chemical  excitation  as  well 
as  to  electrical  stimuli.  It  should  further  be  noted  that  the 
shortened  latent  period  obtained  on  stimulating  the  nerve  with  a 
stronger  induction  current  may  be  apparent  only,  which  is  due 
to  the  fact  that  in  this  case  the  current  spreads  further  and 
stimulates  points  of  the  nerve  which  lie  nearer  to  the  muscle. 

We  shall  later  discuss  the  alterations  in  the  conductivity  of 
the  nerve  caused  by  electrotonus. 

Fr.  W.  Frohlich  (1904),  in  studying  the  oxygen  demand,  and 
the  effects  of  narcosis  on  the  frog's  sciatic  (infra],  showed  by  the 
myographic  method  that  the  rate  of  transmission  of  the  nervous 
impulse  undergoes  a  local  diminution  during  asphyxia  and 
narcosis  in  the  part  of  the  nerve  affected,  and  that  this  became 
more  marked  in  proportion  to  the  length  of  nerve  involved.  This 
delay  in  conduction  is  perceptible  even  in  a  state  of  narcosis  or 
asphyxia  in  which  conductivity  seems  by  other  methods  to  be 
unaltered. 

According  to  Ch.  Richet  the  experimental  results  arrived  at 
by  the  various  authors  as  to  the  velocity  of  transmission  of  the 
excitation  or  active  state  of  the  nerve  may  be  summarised  as 
follows  :— 

(r/,)  In  the  frog  the  mean  velocity  of  the  nervous  vibration  (as 
he  terms  the  active  or  excited  state  of  the  nerve)  is  from  20  to 
26  m.  per  second. 

(&)  In  warm-blooded  animals  this  velocity  is  30-34  m.  per 
second. 

(c)  It  varies  with  a  number  of  factors,  particularly  with  the 
temperature. 

It  is  not  identical  in  every  part  of  the  nerve. 


206  PHYSIOLOGY  CHAP. 

From  these  facts  we  derive  the  important  conclusion  that 
fthe  internal  excitatory  process,  or  active  state  of  the  nerve, 
Us  transmitted  at  a  rate  that  is,  comparatively  speaking,  so  low 
that  it  must  undoubtedly  consist  in  a  physico-chemical  change  of 
the  living  substance  of  the  axis  cylinder,  propagated  by  contiguity 
from  one  part  to  the  next.  The  conduction  of  excitation  in  the 
nerve  is  analogous  to  the  transmission  of  excitation  in  the  muscle, 
although  it  occurs  much  more  rapidly.  We  may  assume  with 
Pfliiger  that  potential  energy  is  liberated  during  activity  in  nerve 
as  in  muscle,  this  chemical  process  being  propagated  from  segment 
to  segment  till  it  reaches  the  muscle,  where  it  excites  the 
mechanical  process  of  contraction  just  as  the  spark  of  a  match 
produces  an  explosion  when  it  reaches  the  powder  in  a  mine. 

As  in  muscle  so  in  nerve,  it  can  be  proved  that  excitation 
is  a  diphasic  cyclic  process,  whatever  concept  be  formed  of  the 
hitherto  unknown  chemical  changes  aroused  by  the  stimulus. 
Just  as  in  muscle  the  phase  of  relaxation  follows  the  phase  of 
contraction,  and  the  whole  cycle  of  muscular  excitation  results 
from  these  two  factors,  so  in  nerve  the  active  state  results,  as  can 
be  demonstrated,  from  a  physico-chemical,  presumably  katabolic, 
change,  followed  after  a  brief  interval  by  the  opposite  (anabolic) 
change,  which  represents  the  return  of  the  protoplasm  of  the 
nerve  to  the  molecular  equilibrium  proper  to  the  resting  state. 
Our  physiological  analysis  of  the  phenomena  of  excitation  will 
yield  constant  confirmation  of  this  law. 

IV.  We  have  seen  that  the  excitation  or  active  state  of  a 
muscle  is  expressed  in  three  orders  of  effects ;  in  mechanical, 
chemical,  and  electrical  phenomena.  The  active  state  of  a 
nerve  induced  by  various  stimuli  is,  on  the  contrary,  so  far  as  we 
know,  expressed  solely  by  alteration  of  its  electrical  potential. 

The  chemical  composition  of  the  axis-cylinder  (the  only  really 
and  specifically  active  part  of  a  nerve)  is  totally  unknown  to  us. 
Under  the  microscope  it  gives  the  xanthroproteic  reaction  and 
other  indications  of  a  protoplasmic  character.  From  this  single 
fact  we  may  conclude,  with  Foster,  that  there  is  a  generic 
analogy  between  the  chemical  composition  of  the  active  sub- 
stance of  muscle  and  that  of  nerve,  and  conjecture  that  the 
transmission  of  excitation  along  the  nerve-fibre  is  accompanied 
by  chemical  changes  similar  to  those  which  take  place  in  the 
muscle  fibre.  It  is,  however,  certain  that  the  nutritive  exchanges 
and  metabolic  phenomena  which  are  theoretically  probable  in 
nerve  must  be  extremely  small,  since  it  has  so  far  been  impossible 
to  obtain  any  direct  demonstration  of  them. 

A.  D.  Waller,  starting  from  the  observation  (which  we  shall 
discuss  below)  that  there  is  a  relation  between  the  functional 
capacity  of  the  nerve  and  the  variations  produced  experimentally 
in  the  CO.,  content  of  the  surrounding  atmosphere,  concludes  that 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    207 

the  nerve  produces  carbonic  acid  during  its  activity ;  but  there  is 
so  far  no  direct  demonstration  of  this  fact.  It  has,  indeed,  as  we 
shall  see,  been  demonstrated  of  late  years  by  the  school  of  Verworn 
(H.  v.  Baeyer,  Fr.  W.  Frohlich)  that  the  nerve  requires  a  supply 
of  oxygen  to  keep  up  its  vitality.  Thunberg  succeeded  in 
measuring  the  quantity  of  oxygen  absorbed  and  of  carbonic  acid 
given  off.  But  no  one  has  yet  proved  that  this  respiratory  gas 
exchange  depends  directly  upon  the  state  of  rest  or  activity  of 
the  nerve.  Funke  found  that  the  normally  alkaline  reaction  was 
converted  into  an  acid  reaction  in  a  nerve  treated  with  strychnine, 
owing  to  its  exaggerated  activity,  but  this  observation  has  not 
been  confirmed  by  other  workers.  Rohmann,  who  experimented 
on  the  nerves  of  the  electrical  organ  of  Torpedo,  using  acid  fuchsin 
as  his  reagent,  failed  to  obtain  any  positive  result. 

The  exceedingly  slow  character  of  nerve  metal  lolisrn  can  also    , 
be  detected  in   the  fact  that,  unlike  the  grey  matter,  which  is 
irrigated  by  a  rich  network  of  blood  capillaries,  the  vascularisa- 
tion   of  nerve  is  very  little  developed.     But  the  best  argument,  of 
which  we  shall  give  experimental  proof  later  on,  is  the  fact  that 
nerve,  unlike  the  nerve-centres,  is  practically  inexhaustible,  i.e.  it 
shows  no  visible  signs  of  fatigue,  even  when  thrown  into  a  state  I 
of  activity  for  several  hours. 

Thermal  phenomena,  again,  such  as  are  due  to  katabolic 
processes,  are  very  small  and  insignificant  in  the  active  nerve. 
Schiff  found  a  slight  increase  in  heat  development  when  he 
applied  the  thermo-electric  pile  to  nerve.  But  the  same  method 
yielded  negative  results  in  the  hands  of  other  expert  observers 
(Helmholtz,  Heidenhain).  Nor  did  Rolleston  arrive  at  any 
positive  result  with  Callender's  extremely  sensitive  method. 

It  seems  impossible  to  doubt  that  metabolism  is  very  low  in 
nerve-fibre,  even  after  strong  and  persistent  stimulation,  which 
evidently  means  that  the  work  the  nerve  has  to  perform  is 
inconsiderable.  Both  when  the  excitation  is  propagated  from  the 
periphery  to  the  centre  (afferent  nerves)  and  when  it  travels  from 
the  centre  to  the  periphery  (efferent  nerves),  the  nerve  only  needs 
to  send  a  slight  impulse,  a  tiny  spark,  to  the  end  -  organ  with 
which  it  is  connected  in  order  to  effect  a  vigorous  process  and 
marked  explosion  of  energy,  owing  to  the  great  irritability  of 
that  organ. 

Yet,  however  slight  it  may  be,  the  process  of  excitation  and 
conduction  in  the  nerve-fibre  must  involve  a  certain  consumption 
of  energy.     That  the   products  of  chemical  dissociation  and  the 
correlative  development  of  heat  are  not  demonstrable  even  after 
strong  and  protracted    stimulation,   suggests    that   the    chemical  i 
dissociation  is   rapidly  compensated  by  a    process  of   restitution.  ' 
Gad,  in  •  formulating  this  notion  more  precisely,  assumes  that  the 
restitution  of  the  substance  that  has  been  altered  by  excitation 


208  PHYSIOLOGY  CHAP. 

in  any  part  of  a  nerve  is  accomplished  instantaneously  at  the 
expense  of  the  next  part,  and  that  upon  this  the  propagation  of 
the  excitatory  impulse  depends. 

An  indirect  proof  of  this  theory  is  afforded  by  the  study  of 
the  electrical  phenomena  exhibited  by  nerve  in  the  state  of  rest 
and  of  activity,  which  need  only  a  brief  description,  since  they  are 
almost  exactly  identical  with  those  already  discussed  for  muscle 
(vide  Chapter  L,  sec.  XL,  p.  68). 

The  discovery  of  the  so-called  current  of  rest  in  nerve  was 
made  by  du  Bois-Beymond  (1845).  Any  bit  of  nerve  cut  out 
of  the  body  presents  approximately  the  same  electromotive 
phenomena  as  muscle,  and  these  may  be  summed  up  as  follows  :— 

(a)  Two  symmetrical  points  on  the  longitudinal  surface  and  of 
the  two  cross-sections  of  a  nerve  are  as  a  rule  iso-electric,  i.e. 
equipotential. 

(6)  Two  points  at  different  distances  from  the  sections  show  a 


FIG.  134. — Diagram  <>f  demarcation  currents  in  a  length  of  mixed  nerve  excised  from  the  animal. 
Direction  ni  currents  indicated  by  arrows;  e,  physiological  equator  at  the  centre  of  the  bit 
of  nerve. 

difference  in  potential,  in  the  sense  that  the  point  nearest  the 
cross -section  is  electrically  negative,  on  the  galvanometer,  as 
compared  with  the  other  point. 

(c)  Generally  speaking,  the  surface  of  a  transverse  section  is 
negative  to  the  natural  or  longitudinal  surface,  and  the  greatest 
difference  in  potential,  i.e.  the  maximum  deflection  of  the  galvano- 
meter needle,  is  obtained  on  placing  one  unpolarisable  electrode 
on  the  cut  surface  and  the  other  on  the  middle  of  the  longitudinal 
surface. 

The  diagram  in  Fig.  134  is  a  representation  of  these  pheno- 
mena. They  are  all  comprised  under  the  general  law  that  in 
i  excised  nerve  the  longitudinal  surface  represents  the  positive  pole 
'  or  anode,  and  the  transverse  surface  the  negative  pole  or  kathode. 

The  currents  that  can  be  led  off  to  a  galvanometer  from  an 
artificial  cross-section  and  from  any  given  point  of  the  natural 
longitudinal  surface  of  a  nerve,  decline  rapidly,  especially  in 
warm-blooded  animals.  In  the  frog's  sciatic  the  value  of  the 
current  may  fall  by  one-half  in  two  to  four  hours,  especially  in 
summer.  But  the  difference  of  potential  may  increase  again,  and 
the  current  may  regain  its  original  force,  if  a  new  section  is  made 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    209 

near  the  first.  This  fact  seems  to  us  important,  because  it 
corroborates  Engelrnarm's  theory  that  the  strength  of  the  current 
corresponds  with  the  intensity  of  the  lesion  in  the  injured  nerve, 
and  that  this  process  of  injury  is  arrested  at  the  next  node  of 
Ranvier.  It  also  gives  support  to  Hermann's  theory  that  the 
uninjured  cell  elements  are  incapable  of  developing  electromotive 
phenomena,  and  that  the  critical  points  of  demarcation  between 
the  healthy  tissue  and  that  injured  by  the  section  are  determined 
by  these  nodes. 

Nerves  that  are  wholly  dead  are  incapable  of  giving  currents. 
Any  lesion  of  a  nerve  along  its  course,  by  cauterising,  crushing, 
compression,  etc.,  renders  it  negative  to  the  normal  parts.  Local 
changes  of  temperature  in  the  nerve,  if  insufficient  to  produce 
structural  lesions  (e.g.  up  to  30°  C.),  give  rise  to  electromotive 
phenomena,  the  heated  tissue  becoming  positive  to  the  normal 
tissue,  as  occurs  in  muscle. 

It  may  be  deduced  from  all  these  facts  that  the  electrical 
phenomena  of  resting  nerve  depend  on  the  negativity  (on  the 
galvanometer)  of  the  altered  or  injured  portions  of  the  fibres,  in 
relation  to  the  uninjured,  which  justifies  the  name  of  demarcation 
currents  given  by  Hermann. 

The  strength  of  the  demarcation  currents  does  not  appear  to 
be  in  strict  relation  with  the  area  of  cross-section.  The  frog's 
sciatic  gives  a  more  vigorous  current  ( =  O'02-O'Oo  volt)  than  a 
large  nerve  of  the  horse  or  monkey  ( =  O'OOS  volt  according  to 
Biedermaiin).  This  is  probably  due  to  the  varying  resistance  and 
susceptibility  of  the  nerve  to  external  agents.  It  may  be  affirmed 
in  general  that  every  cause  which  decreases  the  functional  capacity 
of  the  nerve  must  also  diminish  the  intensity  of  its  demarcation 
current. 

An  important  fact  discovered  by  different  observers,  both  for 
vertebrates  and  invertebrates,  is  that  non-niedullated  fibres  yield 
greater  differences  of  potential  and  therefore  larger  currents  than 
medullated  fibres,  independently  of  their  sectional  area.  From 
this  it  may  be  inferred  that  the  seat  of  the  electrical  phenomena  \ 
is  not  the  medullated  sheath  but  the  axis-cylinder  of  the  nerve. 

Another  remarkable  fact  is  that  while  in  a  mixed  nerve- 
composed  of  afferent  and  efferent  fibres — the  two  transverse 
sections,  or  two  points  equidistant  from  these  upon  the  longi- 
tudinal surface,  are  equipotential  when  connected  with  the 
galvanometer,  this  is  not  the  case  for  nerves  composed  of  one 
kind  of  fibre  only — afferent  or  efferent.  The  central  cross-section 
of  an  afferent  nerve  (e.g.  a  dorsal  root  of  a  frog's  spinal  nerve)  is 
negative  to  the  peripheral  cross-section,  but  the  central  cross- 
section  of  an  efferent  nerve  (e.g.  the  electrical  nerve  of  Torpedo)  is 
positive  to  the  peripheral  cross-section  (Fig.  135).  In  these  cases 
the  equator  is  not  equidistant  from  the  two  cross-sections,  but 

VOL.  Ill  P 


210  PHYSIOLOGY  CHAP. 

lies  nearer  the  peripheral  section  in  the  afferent  nerve,  nearer  the 
central  section  in  the  efferent  nerve. 

This  phenomenon,  discovered  by  Du  Bois-Eeymond  and 
confirmed  by  Fredericq,  Mendelssohn,  and  others,  indicates  that 
efferent  nerves  are  traversed  by  an  ascending,  afferent  nerves 
by  a  descending  axial  current.  This  is  the  only  objective 
difference  known  at  present  between  the  two  categories  of  nerves, 
which  are  alike  in  structure  and  in  their  capacity  for  conducting 
in  both  directions. 

According  to  the  latest  work  of  Weiss  (1904),  the  potential 
difference  between  two  cross-sections  of  nerve — the  axial  current 
—is  due  solely  to  an  anatomical  cause,  the  unequal  distribution 
of  the  connective  tissue.  The  more  connective  tissue  present, 
the  less  the  potential  that  can  be  led  off",  owing  to  the  resulting 
short  circuit.  The  contrary  direction  of  the  axial  current  in 
efferent  and  afferent  nerves  might  also  be  the  result  of  unequal 
arrangement  of  the  connective  tissue. 


/ 


Centrifugal  nerve.  Centripetal  nerve. 

Fio.  135.— Diagram  of  axial  currents  in  centripetal  and  centrifugal  nerves.     (Du  Bois-Eeymond.) 
c,  central  end  ;  ;<,  peripheral  end  ;  e,  physiological  equator. 

The  discovery  of  the  current  of  rest  or  demarcation  current 
was  immediately  followed  by  that  of  the  current  of  action,  i.e. 
the  electromotive  phenomena  produced  by  stimulating  a  nerve, 
which  correspond  perfectly  with  those  already  noticed  for  muscle. 
In  nerve  as  in  muscle  the  current  of  action  is  manifested  as  the 
negative  variation  of  the  demarcation  current.  If  a  current  from 
one  end  of  the  divided  sciatic  of  the  frog  is  led  off  to  the  galvano- 
meter, it  is  reduced  or  abolished  on  exciting  the  other  end  with 
a  tetanising  current.  When  stimulation  ceases,  recovery  of  the 
original  state  is  manifested. 

Du  Bois-Keymond's  phenomenon  of  the  negative  variation  can 
also  be  demonstrated  with  chemical  stimuli  (Griitzner),  mechanical 
stimuli  (Hering),  and  physiological  stimuli  (Gotch  and  Horsley) 
for  both  afferent  and  efferent  nerves.  It  is  seen  in  afferent 
nerves  when  the  peripheral  stump  of  the  dorsal  root  of  a 
mammalian  spinal  nerve  is  connected  with  the  galvanometer, 
either  the  peripheral  nerve  or  the  sensory  nerve-endings  of  the 
skin  being  excited  at  a  distance.  It  is  seen  in  efferent  nerves  on 
leading  off  the  central  end  of  the  ventral  root,  or  sciatic,  to  the 
galvanometer,  and  exciting  the  ganglion  cells  of  the  cord  or  the 


iv    GENERAL  PHYSIOLOUY  OF  NEIiVOUS  SYSTEM    211 

cerebral  cortex  directly,  or  reflexly,  liy  stimulation  of  the  central 
end  of  the  sciatic  of  the  opposite  side. 

The  discovery  of  these  electrical  phenomena,  which  are  the 
constant  corollary  of  nerve  stimulation,  signalled  a  considerable 
advance  in  the  general  physiology  of  nerve,  since  they  are  the 
only  external  manifestation  known  of  the  transition  from  the 
state  of  rest  to  that  of  activity. 

The  negative  variation  of  the  current  of  rest  depends  on  the 
fact  that  the  excited  point  of  the  nerve  becomes  for  the  moment 
the  seat  of  a  negative  electrical  potential  which  is  transmitted 


lii 


Ether 

FIG.  136.— Photograph  of  electrical  variations  produced  by  rhythmical  tetanisatiun  nf  an  excised 
nerve.  (A.  I>.  Waller.)  The  stimulations  were  sent  in  at  intervals  of  a  minute.  After  applying 
ether  (black  line)  the  electrical  responses  were  suspended  for  about  5  min.,  after  which  they 
recommenced  and  became  more  vigorous  than  before. 

along  the  nerve  as  a  diphasic  wave,  in  complete  analogy  with  what  \ 
we  have  seen  for  muscle. 

The  strength  of  the  negative  variation  is  up  to  a  certain 
limit  proportional  to  the  intensity  of  stimulation  (Waller).  It 
is  a  more  reliable  measure  of  the  impulse  in  a  motor  nerve  than 
the  height  of  the  muscular  contraction  which  the  impulse  induces. 
In  fact  the  maximum  degree  of  muscular  excitation  is  evoked 
with  a  strength  of  stimulus  less  than  that  required  for  the 
maximum  degree  of  nervous  excitation.  When  the  maximal 
muscular  contraction  is  already  obtained,  it  is  still  possible  to 
increase  the  value  of  the  negative  electrical  variation  by  increasing 
the  strength  of  stimulation. 

The    negative    variation    alters    with    the    excitability    and    \ 
conductivity  of  the  nerve ;    it  is  abolished  or  decreased  by  any 


212 


PHYSIOLOGY 


CHAP. 


factor  that  lowers  functional  activity ;  on  the  other  hand  it  is 
effectively  reinforced  by  all  stimuli  that  promote  activity.  On 
warming  the  nerve  to  35-40°  C.  the  duration  of  the  negative 
variation  diminishes ;  it  is  prolonged  by  cooling  the  nerve  to 
5°  C.  Lowering  the  temperature  also  delays  the  propagation  of 
the  negative  variation. 

Waller  studied  the  course  of  electromotive  phenomena  in 
nerve  by  photographing  the  galvanometer  deflections  in  a  long 
series  of  rhythmical  tetanisations.  These  records  give  valuable 
indications  in  regard  to  the  effect  of  anaesthetics,  salt  solutions, 
alkaloids,  gases,  etc.,  when  applied  directly  to  a  length  of  excised 
nerve.  He  concluded  as  follows  : — 


Chloroform 


Fio.  137.—  Photograph  as  before.     (Waller.)    The  figure  shows  that  after  applying  chloroform  to 
the  nerve  (black  line)  the  electrical  reactions  are  permanently  abolished. 

(a)  Anaesthetics  (ether  and  chloroform)  temporarily  abolish 
the  current  of  action  and  the  excitability  of  the  nerve.  The 
return  of  the  action  current  after  inhibition  by  ether  is  invariably 
followed  by  a  secondary  augmentation  :  its  suppression  by  chloro- 
form is  not  only  more  prolonged,  but  may  be  permanent  if  the 
dose  is  too  strong  (Figs.  136  and  137). 

(5)  Oxygen,  nitrogen,  hydrogen,  nitrous  oxide,  carbonic  oxide, 
have  no  appreciable  effect  upon  the  current  of  action ;  on  the 
other  hand,  carbon  dioxide  in  small  quantities  (e.g.  4  per  cent,  as 
in  expired  air)  increases  it ;  in  larger  percentages  carbon  dioxide 
acts  exactly  like  ether  (Figs.  138  and  139). 

(c)  Potassium  salts  have  a  decidedly  depressing  influence ; 
sodium  salts  are  less  depressing.  Calcium  and  strontium  salts, 
on  the  contrary,  increase  the  current  of  action. 


iv    GENERAL  PHYSIOLOGY  OK  NEEVOUS  SYSTEM    213 


(d)  Among   the   alkaloids,  aconitine  and    veratrine   iu    1   per 
cent   solutions   rapidly  abolish   the   current   of  action  ;    curariue, 


FIG.  138. — Photograph.     (Waller.)    To  show  primary  excitation  of  the  nerve  by  a  small  amount  of 

CO-2  applied  between  the  two  white  lines. 


digitaline,  and   morphine  diminish  its  activity;    strychnine   in- 
creases it ;  atropine  and  aconitine  are  inert. 

(e)  Protracted  tetanisation  increases  the  current  of  action,  i.e. 


CO-j 

FIG.  139.— Photograph.  (Waller.)  Shows  that  a  large  amount  of  CO»,  acting  on  the  nerve 
during  the  light  band,  at  first  suspends  the  electrical  reactions  of  the  nerve  and  then  has  a 
secondary  exciting  action. 

has  an  effect  similar  to  that  of  CO.,  in  small  doses  (Eig.  140). 
Eroin  this  fact  Waller  argues  that  tetanisation  of  nerve  is 
accompanied  by  a  development  of  C02. 


214  PHYSIOLOGY  CHAP. 

These  conclusions  (as  Boruttau  pointed  out)  are  partially 
based  upon  the  theoretical  fallacy  that  the  magnitude  of  the 
galvanometer  swing  is  an  exact  measure  of  the  strength  of  the 
current  of  action.  This  is  not  correct.  The  magnitude  of  the 
galvanometer  deflection  is  a  result  not  merely  of  the  strength  of 
the  current  but  also  of  its  duration.  Admitting  that  the  cessation 
of  deflections  on  the  galvanometer  indicates  the  disappearance  of 
the  action  current,  it  is  not,  on  the  other  hand,  legitimate  to 
assume  that  an  increase  in  these  deflections  must  represent  an 
increase  of  the  action  current  and  a  rise  of  excitability.  To  study 
the  period  of  the  current  of  action  it  is  necessary  to  employ  the 
capillary  electrometer,  the  oscillations  of  which  can  be  photographed. 


Fin.  140. — Photograph.  (Waller.)  Shows  that  prolonged  tetanisation  of  the  nerve 
(at  T  from  a.  to  <o)  has  the  same  exciting  action  on  the  electrical  vuiiutions  of 
the  nerve  as  a  small  amount  of  COo. 

Boruttau  and  Frohlich  (1904)  were  able,  by  this  method,  to  show 
that  the  action  current  in  the  nerve  treated  with  alcohol,  ether, 
chloroform,  and  carbonic  acid  really  suffers  a  decrement — the 
amount  of  which  is  in  ratio  with  the  strength  of  the  stimulus 
and  the  length  of  the  injured  tract.  The  change  in  the  period 
of  the  excitatory  wave  is  localised  in  the  part  of  the  nerve 
that  is  affected ;  while  the  diminution  in  the  current  of  action, 
once  set  up,  affects  the  normal  parts  of  the  nerve  as  well. 
The  increase  in  the  galvanometer  deflection  observed  by  Waller 
as  an  after-effect  depends  not  upon  increased  excitability,  but 
upon  increased  duration  in  time  of  the  excitatory  wave,  which  is 
due  to  delay  in  the  process  of  recovery. 

The  negative  variation  depends  not  only  upon  the  intensity  of 
the  stimulus  but  also  upon  the  strength  of  the  current  of  rest  led 
off  to  the  galvanometer.  It  is  more  vigorous,  as  the  anode  is 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    215 

nearer  the  centre  of  the  longitudinal  surface  of  the  nerve,  when 
the  kathode  is  on  the  cross-section.  Moreover,  many  conditions 
that  affect  the  demarcation  current  in  one  direction  or  the  other 
affect  the  action  current  in  the  same  way.  Non-medullated  nerve- 
fibres,  which  yield  a  more  pronounced  demarcation  current,  also 
exhibit  a  stronger  action  current.  In  non-medullated  fibres 
the  mere  opening  or  closing  of  a  constant  current  indicates  on 
the  galvanometer  a  diminution  in  the  difference  of  potential  present 
in  the  resting  state,  while  a  tetanising  current  (i.e.  a  succession 
of  stimuli  of  given  frequency)  is  required  to  obtain  the  same  effect 
in  rnedullated  fibres.  This  is  because  in  medullated  nerve  the 
intensity  of  the  electrical  phenomenon  is  too  low  for  the  passage 
of  a  single  wave  of  the  action  current  to  act  upon  the  galvano- 
meter. But  it  can  be  demonstrated,  as  in  muscle,  that  the 
uniform  negative  variation  shown  by  the  galvanometer  during 
the  tetanising  stimulation  of  a  nerve  is  the  effect  of  a  series  of 
discontinuous  electrical  changes  which  have  the  same  rhythm  as 
the  stimulus  sent  into  the  nerve. 

Bernstein  (1867)  demonstrated  this  with  his  differential 
rheotome,  by  which  the  galvanometer  circuit  is  rhythmically  closed 
for  the  briefest  period  at  regular  intervals  which  coincide  with 
each  stimulation.  He  found  that  the  negative  variation  starts  at 
once  in  the  part  excited,  that  it  is  propagated  along  the  nerve  at 
the  same  rate  as  the  excitation  (27  in.  per  second  at  15°  C.) ;  lastly, 
that  it  remains  a  very  short  time  at  each  point  of  the  nerve 
(0'0007  sec.),  corresponding  to  a  wave-length  of  about  18  mm. 

Wedensky  adopted  the  telephone  to  render  the  rapid  successions 
of  the  currents  of  action  perceptible  to  the  ear  on  tetanising  the 
frog's  sciatic.  When  connected  with  the  nerve  that  is  being 
tetanised,  the  telephone  gives  the  sound  that  corresponds  with  the 
number  of  induction  shocks  from  the  exciting  current.  When 
the  strength  of  the  shocks  is  increased,  the  sound  in  the  telephone 
is  also  strengthened  till  it  reaches  a  maximum,  after  which  no 
further  increase  of  current  strength  increases  the  effect  in  the 
telephone.  If  the  nerve  is  killed  by  ammonia  every  sound  in  the 
telephone  ceases. 

Gotch  and  Burch,  by  substituting  a  highly  sensitive  capillary 
electrometer  for  the  galvanometer,  were  able  not  only  to  demon- 
strate the  discontinuous  character  of  the  electrical  changes 
produced  by  faradisation  of  the  nerve,  but  also  to  photograph  the 
action  currents,  as  shown  by  the  oscillations  of  the  mercury 
meniscus  in  the  capillary.  By  this  method  they  found  that  the 
negative  variation  reached  its  maximum  in  O'OOl  sec.,  and  lasted 
longer  when  the  temperature  was  lower.  Further,  on  comparing 
the  curves  of  the  capillary  electrometer  with  those  obtained  from 
currents  of  known  strength,  they  found  that  the  negative  variation 
may  amount  to  0'03  volt  at  5 J  C. 


216  PHYSIOLOGY  CHAP. 

On  experimenting  with  a  bundle  of  six  frogs'  sciatics,  cooled 
to  5°  C.  in  order  to  delay  the  transmission  of  the  wave  of  the 
current  of  action,  Hermann,  with  the  rheotome,  succeeded  in  show- 
ing its  diphasic  character,  i.e.  the  negative  phase  is  followed  by  a 
positive  phase  which  is  different  in  form,  but  of  the  same  algebraic 
value  (Fig.  141).  This  was  confirmed  by  Boruttau  for  the  non- 
niedullated  nerves  of  Octopus  and  Elf  clone,  in  which  the  rate  of 
conductivity  is  very  low.  Gotch  and  Burch  photographed  the 
diphasic  wave  in  frog's  nerve,  with  reduced  velocity  of  conduction, 
on  the  capillary  electrometer. 

The  diphasic  character  of  the  electromotive  effects  of  rhythmi- 
cal tetanisation  can  easily  be  seen  in  Waller's  galvanometer 
photographs.  The  curves  show  that  the  negative  phase  is  often 


PIG.  141. — Diagram  of  diphasic  variation  of  electrical  potential  at  two  points  of  a  nerve  after  a 
single  excitation,  measured  by  the  rheotome.  (Hermann.)  The  curves  a  b  c — d  e  f  show 
respectively  the  electrical  variations  from  the  points  proximal  and  distal  to  the  electro"  Irs. 
The  diphasic  curve  traced  by  the  coarser  lines  results  from  the  algebraic  sum  of  the  preceding. 
The  spaces  filled  by  cross  lines,  which  represent  the  two  phases  of  the  wave,  are  approximately 
equal  according  to  Hermann. 

followed  by  a  positive  phase,  directly  the  stimulation  ceases.  The 
positive  phase  is  seen  particularly  in  cooled  nerve,  and  in  nerves 
injured  by  preparation,  or  by  long  soaking  in  normal  saline.  The 
negative  phase  is  most  evident  after  prolonged  tetanisation  and 
the  action  of  a  small  amount  of  C02  (Figs.  138  and  140). 

As  for  muscle,  so  for  nerve,  it  is  highly  probable  that  the 
negative  phase  of  the  current  of  action  may  be  the  expression  of 
a  katabolic  or  disintegrative  process,  and  the  positive  phase,  of  an 
anabolic  or  reintegrative  process. 

After  all  that  has  been  said  of  the  current  of  action  it  is 
natural  to  regard  it  as  the  external  sign,  and  to  a  certain  extent 
the  measure,  of  the  active  state  of  a  nerve,  i.e.  of  its  excitation. 
But  it  must  not  be  thought  that  the  electrical  phenomenon  con- 
stitutes the  whole  or  the  essential  part  of  excitation.  In  the 
present  state  of  our  knowledge  we  must,  while  holding  the  current 
of  action  to  be  concomitant  with  the  active  state  of  the  nerve, 
keep  the  two  phenomena  distinct ;  since,  as  we  shall  see,  the 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    217 

electrical  variation  can  be  manifested  after  the  excitability  of  tbe 
nerve  has  entirely  disappeared. 

V.  The  term  stimulus,  as  applied  to  nerve,  covers  every  agent 
capable  of  translating  its  excitability  into  action — as  directly 
expressed  in  the  external  sign  of  the  current  of  action,  by  which 
the  physical  change  of  tbe  nerve  is  manifested.  The  indirect 
subjective  proof  of  nerve  excitation  is  sensation,  when  the  stimulus 
acts  upon  our  sense  orga.ns :  consciousness  of  the  voluntary 
impulse  when  it  proceeds  from  the  higher  centres.  The  indirect 
objective  proof  is  a  simple  muscular  contraction  when  the  stimulus 
acts  upon  the  motor  nerves, — a  reflex  muscular  contraction  when 
it  acts  on  the  sensory  nerves.  In  most  of  the  work  done  upon 
nerve  the  reaction  of  the  muscle  has  been  taken  as  the  index  of 
activity,  so  that  the  results  for  the  most  part  apply  only  to  motor 
nerves. 

We  must  distinguish  between  natural  and  artificial  nerve 
stimuli.  Nerve,  like  muscle,  is  excitable  at  every  point  of  its 
course  by  a  great  number  of  stimulating  agents  of  varying 
character  (chemical,  thermal,  mechanical,  electrical).  Normally, 
however,  sensory  nerves  and  afferent  nerves  in  general  are  always 
excited  from  the  sense-organs  with  which  their  peripheral  termina- 
tion is  in  relation ;  and  motor  nerves  and  efferent  nerves  in 
general  are  always  excited  from  the  central  organ  from  which  they 
take  origin.  Moreover,  the  peripheral  organ  of  sensory  nerves  is 
normally  excited  exclusively  by  external  stimuli  of  a  definite 
character,  which  are  therefore  known  as  specific  stimuli.  As  we 
shall  &ee  later  in  describing  the  sense-organs,  their  nerve-endings 
are  so  constituted  that  they  are  highly  susceptible  to  the  influence 
of  stimuli  which  would  be  powerless  to  excite  the  nerves  themselves 
at  the  different  points  of  their  course. 

For  this  reason  the  natural  stimuli  for  the  respective  sense- 
organs  are  also  termed  adequate  stimuli ;  they  are  adapted  to  the 
specific  constitution  of  the  sensory  nerve-endings  which  they 
stimulate.  The  adequate  stimulus  for  the  optic  nerve  is  light, 
which  alone  can  excite  retinal  nerve-endings ;  the  adequate 
stimulus  for  the  auditory  nerve  is  sound,  which  alone  can  excite 
the  nerve-endings  of  the  organ  of  Corti,  etc. 

Motor  nerves,  again,  are  normally  excited  by  specific  stimuli, 
produced  by  the  (reflex  or  automatic)  activity  of  the  ganglion  cells 
of  the  central  organ  from  which  they  originate,  and  on  which 
they  are  morphologically  and  functionally  dependent. 

The  fact  that  naturally  every  nerve  is  excitable  only  at  one 
of  its  ends  (peripheral  or  central),  and  only  to  a  definite  kind  of 
stimulus,  is  one  of  the  most  admirable  adaptations  of  the  animal 
organisation,  and  prevents  that  chaotic  disorder  in  the  activity  of 
the  whole  system  which  would  occur  if  the  nerves  were  excitable 
at  every  point  of  their  course  by  different  external  and  internal 


218  PHYSIOLOGY  CHAP. 

factors,  e.g.  the  tissue  fluids  by  which  they  are  irrigated,  and 
which  regulate  their  metabolism. 

Although  under  physiological  conditions  excitation  never 
occurs  along  the  course  of  a  nerve,  it  is,  as  we  have  seen,  excitable 
at  any  point,  when  acted  on  by  an  artificial  stimulus  of  sufficient 
strength.  Its  excitability  is  indicated  by  the  minimal  intensity 
of  the  effective  stimulus,  when  the  latter  can  be  measured  with 
sufficient  accuracy.  Speaking  generally,  we  may  say  that  the 
minimal  intensity  of  effective  stimulus  is  less  for  nerve  than  for 
muscle,  which  shows  that  nervous  excitability  is  greater  than 
muscular  excitability,  and  that  the  two  forms  of  excitability  have 
a  different  organic  substrate. 

Of  the  many  external  agents  which  throw  a  nerve  into  activity 
when  applied  experimentally,  electrical  and  mechanical  stimuli 
are  usually  adopted :  the  former  because  they  are  easily  graduated 
and  do  little  harm  to  the  integrity  of  the  nerve ;  the  latter 
because  their  action  can  be  localised  to  the  point  of  application. 
Thermal  and  chemical  stimuli  are  less  used,  because  they  are 
not  easy  to  graduate  and  are  more  or  less  harmful. 

(«)  Little  need  be  said  in  regard  to  thermal  stimuli.  The 
intrinsic  temperature  of  an  animal  (homoiothermic  or  poikilo- 
therrnic)  does  not  act  as  a  stimulus  on  the  nerve,  but  regulates 
the  normal  degree  of  its  excitability. 

Nor  does  abnormal  rise  or  fall  of  general  or  local  temperature 
as  a  rule  act  as  a  stimulus  when  it  occurs  gradually ;  it  merely 
modifies  the  excitability  of  the  nerve.  The  rapid  heating  of  a 
frog's  motor  nerve,  by  dipping  it  into  water  at  38°  0.,  or  bathing 
any  given  point  with  the  same,  may,  according  to  Valentin,  excite 
a  muscular  twitch  without  causing  local  death  of  the  nerve.  But 
this  observation  was  not  confirmed  by  Eckhard,  who  found  that 
contractions  were  only  produced  by  a  temperature  of  66-68°  C., 
i.e.  when  the  rise  of  temperature  was  so  great  as  to  destroy  the 
structure  of  the  nerve  or  permanently  alter  it.  According  to 
Valentin,  a  rapid  fall  of  temperature  to  -  5°  C.  also  excites  a  nerve, 
though  gradual  freezing  produces  neither  excitation  nor  final  loss 
of  excitability. 

The  later  work  of  Kosenthal,  Afanasieff,  Griitzner,  and  others 
was  directed  more  to  the  influence  of  temperature  upon  the  ex- 
citability and  conductivity  of  nerve  than  to  its  stimulating  action. 
It  is  true  that  when  the  temperature  rises  above  35°  C.  or  sinks 
to  -  4°  C.,  signs  of  excitation  often  ensue,  but  this  fact  can  be 
interpreted  either  as  meaning  that  stimuli  that  are  normally  inert 
become  effective  in  consequence  of  the  rise  of  excitability,  or  that 
the  too  acute  rise  or  fall  of  temperature  develops  specific  stimuli 
of  a  mechanical  or  chemical  nature. 

In  regard  to  the  stimulating  action  of  abnormal  temperatures 
along  the  course  of  a  sensory  nerve,  E.  H.  Weber  observed  on 


iv    GENERAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    219 

man  that  a  few  seconds  after  plunging  the  elbow  into  water  at 
the  temperature  of  melting  ice,  a  painful  sensation  is  produced 
over  the  whole  cutaneous  area  served  by  the  ulnar  nerve,  and  later 
a  sensation  of  insensibility,  which  is  undoubtedly  due  to  diminished 
conductivity  in  the  cooled  portion  of  the  nerve. 

(&)  Many  soluble  chemical  substances  act  as  stimuli  when 
applied  to  an  exposed  nerve.  But  the  excitatory  effects  which 
they  induce  are  irregular  in  character,  and  in  all  probability 
their  action  depends  either  on  the  removal  of  water  from  the 
nerve,  or  on  the  specific  action  which  they  exert  upon  its 
molecular  state;  or  again  upon  the  alteration  or  death  of  the 
nerve  at  the  points  of  contact. 

When  a  motor  nerve  is  left  to  dry,  its  excitability  rises  at 
first ;  this  is  followed  by  a  state  of  excitation  expressed  in  a  suc- 
cession of  small  muscular  twitches,  or  irregular  tetanus ;  lastly, 
there  is  loss  of  excitability  and  conductivity.  Up  to  a  certain 
point  these  effects  are  stronger  in  proportion  to  the  length  of 
nerve  exposed  to  desiccation.  They  vary  also  in  different  nerves, 
and  in  different  parts  of  the  same  nerve.  If  instead  of  dehydrat- 
ing the  nerve  it  is  bathed  in  distilled  water,  the  opposite  phenomena 
occur ;  there  is  depression  amounting  to  total  loss  of  excitability. 

It  is  certain  that  some  organic  substances  act  as  stimuli 
when  applied  to  nerve,  by  abstracting  water  from  it.  Such,  e.g., 
are  glycerol,  urea,  the  sugars,  which  stimulate  motor  nerves  more 
vigorously  in  proportion  as  they  are  more  concentrated.  As 
regards  the  action  of  urea,  Buchner  noted  that  its  prolonged 
application  is  not,  as  is  the  case  with  other  chemically  exciting 
substances,  followed  by  loss  of  vitality  in  the  nerve. 

Nearly  all  the  neutral  salts,  if  applied  for  some  minutes  to  a 
nerve,  act  as  stimuli  with  an  intensity  approximately  proportional 
to  their  concentration ;  too  strong  a  solution  rapidly  inhibits  or 
destroys  the  excitability  of  the  nerve  (Griitzner). 

In  order  to  obtain  salt  solutions  perfectly  comparable  in  their 
effects,  Griitzner  employed  equimolecular  and  not  equivalent 
solutions,  i.e.  solutions  containing  the  same  percentage  doses  of 
salts.  For  the  different  sodium  salts  the  scale  of  excitatory  action 
is  NaF,  Nal,  NaBr,  Nad.  The  molecular  weights  of  these  salts 
are  in  an  ascending  order :  NaF,  41'9  ;  NaCl,  58'3  ;  NaBr,  102'7 ; 
Nal,  1494;  and  the  percentage  content  of  the  equimolecular 
solutions  is  NaF,  4-2;  NaCl,  5-8;  NaBr,  10'2;  Nal,  14-9.  From  this 
we  may  conclude  that  abstraction  of  water  is  not  the  sole  factor 
that  determines  the  excitatory  action  of  a  salt,  but  that  this 
further  depends  upon  the  specific  action  of  the  chemical  com- 
pound upon  the  nerve.  Griitzner  demonstrated  the  same  for  the 
salts  of  potassium,  caesium,  rubidium,  barium,  strontium,  and 
calcium. 

Grlitzner's  experiments  on  afferent  nerves  with  these  salts  are 


220  PHYSIOLOGY  CHAP. 

interesting.  In  view  of  the  uncertainty  of  the  results  when 
reflexes  were  taken  as  the  index  of  excitability  it  occurred  to 
him  to  utilise  the  burning  sensation  felt  on  applying  equimolecular 
salt  solutions  to  a  cut  on  the  finger.  With  sodium  salts  his  results 
were  as  follows:  with  Nal  (14'9  per  cent)  sensation  is  aroused 
after  5  sees.;  with  NaBr  (10'2  per  cent),  after  10  sees.;  with  NaCl 
(5-8  per  cent),  after  15  sees.  Sensory  nerves  are  accordingly  stimu- 
lated in  the  same  order  as  motor  nerves.  But  on  vising  potassium 
salts  Griitzner  observed  an  interesting  difference  in  the  reaction  of 
motor  and  sensory  nerves.  These  salts  have  only  a  slight  stimulat- 
ing effect  on  motor  nerves,  but  act  very  powerfully  on  sensory 
nerves ;  for  the  latter  potassium  chloride  is  the  most  active, 
sodium  chloride  is  the  least  active  of  all.  This  important  point 
can  be  demonstrated  by  the  following  experiment.  If  the  sciatic 
plexus  of  an  anaesthetised  frog  is  divided  on  both  sides,  and 
a  solution  of  KC1  applied  to  the  central  end  of  one  plexus  and 
the  peripheral  end  of  the  other,  reflex  movements  are  seen  in  the 
anterior  limbs  and  trunk,  while  no  contractions  appear  in  the 
muscles  of  the  excited  posterior  limb ;  on  repeating  the  experi- 
ment with  NaCl,  movements  are  seen  in  the  muscles  of  the 
directly  excited  limb,  while  movements  of  the  reflexly  excited 
muscles  only  appear  after  an  interval.  This  difference  can  be 
interpreted  to  mean  that  KC1  is  better  able  to  excite  in  the 
afferent  direction,  i.e.  to  awaken  the  activity  of  the  central  organs, 
while  NaCl  is  more  able  to  excite  along  efferent  paths,  i.e.  to  stir 
up  the  activity  of  the  peripheral  end-plates.  Moriggia,  on  the 
contrary,  found  that  NaCl  (04  per  cent)  excited  the  sensory  and 
not  the  motor  fibres. 

The  results  of  experiments  on  the  excitatory  action  of  the 
basic  compounds  do  not  agree.  Eckhard  and  Kiihne  observed  that 
even  very  weak  solutions  (01  per  cent)  of  NaOH  and  KOH  were 
exciting^  to  motor  nerves ;  Griitzner,  on  the  contrary,  found  that 
their  stimulating  action  was  very  weak,  while  larger  doses  had  a 
destructive  effect.  Ammonia  kills  the  nerve  without  exciting  it. 

Inorganic  acid  compounds  in  general  have  a  stimulating  action 
proportional  to  their  chemical  avidity.  Griitzner  found  that 
nitric  and  hydrochloric  acid  stimulated  in  \veaker  solutions  than 
sulphuric  acid.  The  organic  acids  excite  only  in  concentrated 
solutions,  and  some  of  them  (e.g.  oxalic  acid)  destroy  the  vitality 
of  nerve  without  exciting  it. 

The  salts  of  the  heavy  metals  again  affect  the  vitality  of 
nerve,  without  any  previous  stage  of  excitation,  but  according  to 
Eckhard  and  Kiihne,  zinc  chloride,  zinc  sulphate,  and  ferric 
chloride  are  exceptions  to  this  rule. 

(c)  Every  one  knowrs  that  mechanical  factors,  e.g.  compression, 
shock,  crushing,  pulling,  cutting,  puncture,  produce  excitation 
when  they  act  on  nerve  at  a  certain  rate  and  with  a  certain 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    221 

energy,  since  they  induce  pain  in  sensory  nerves  and  muscular 
twitches  from  motor  nerves.  Slight  pressure  or  traction  may 
temporarily  increase  the  excitability  of  nerve,  but  it  is  sometimes 
possible,  by  slow  but  continuous  mechanical  action,  to  destroy  con- 
ductivity and  excitability  in  a  nerve  without  any  perceptible 
previous  excitation.  Paralysis  of  the  brachial  plexus  has  been 
noted  clinically  as  resulting  from  the  constant  use  of  crutches, 
and  paralysis  of  the  recurrent  laryngeal  nerve  is  often  due  to  its 
compression  by  an  aneurism. 

Physiologists     have     devised     various     means    of     applying 


FIG.  142. — Induction  coil.     (Dn  Bois-Reymonrl.) 

mechanical  action,  which  has  the  great  advantage  of  being 
perfectly  -easy  to  localise,  as  a  nerve  stimulus.  The  simplest 
method  is  that  of  rapid  section  of  the  nerve  with  scissors.  For 
the  quick  repetition  of  mechanical  stimuli,  Du  Bois-Reyrnond  used 
a  little  toothed  wheel  that  compressed  successive  portions  of  the 
nerve.  Heidenhain  employed  a  small  hammer  arranged  so  that  it 
always  tapped  a  fresh  bit  of  the  nerve.  A  similar  tetanomotor 
was  employed  by  Wundt  and  perfected  by  Tigerstedt,  which  acted 
for  a  given  time  upon  the  same  point  of  the  nerve.  Langendorff 
substituted  a  vibrating  tuning-fork  for  the  hammer.  Finally  von 
Uexkiill  (1895)  invented  a  rigid  hammer  which  tapped  the  nerve 
as  it  lay  over  a  very  soft  pad,  so  that  it  was  possible  to  stimulate 
the  same  point  for  a  long  time  without  injuring  the  nerve ;  this 


222 


PHYSIOLOGY 


CHAP. 


produced  a  form  of  stimulation  very  similar  to  faradisation,  with 
the  advantage  of  eliminating  all  the  errors  due  to  spread  of  the 
stimulus  to  other  parts  of  the  nerve. 

A  highly  special  form  of  stimulation  is  obtained  by  rapidly 
removing  the  compression  applied  to  the  nerve.  But  in  this  case 
it  is  not  certain  that  there  is  true  mechanical  excitation  ;  more 
probably  the  muscular  reaction  depends  on  the  recovery  by  the 
nerve  of  its  normal  fluid  content,  which  had  been  altered  by  the 
previous  compression  ;  this  gives  rise  to  a  demarcation  current 
which  excites  the  nerve. 

(d)  The  best  excitant  of  nerve,  as  of  muscle,  with  the  strongest 
analogy  to  physiological  excitants  is  undoubtedly  the  electrical 
current,  of  which  the  efficacy  as  a  stimulus  was  demonstrated  by 
Galvani  and  Volta. 


\ 


Flu.  143.—  Dnnir 


l  iunl  ]>u  Bois-Reymoml 


The  electrical  stimulus  most  employed  is  the  induced  current, 
generated  in  a  secondary  circuit  by  the  make  and  break  of  the 
current  which  passes  through  the  primary  circuit  of  an  induction 
coil  (Fig.  142).  It  can  be  perfectly  graduated,  is  capable  of 
yielding  a  comparatively  high  electromotive  force,  is  of  brief 
duration,  and  develops  very  rapidly.  The  regular  series  of  make 
and  break  shocks,  or  of  alternating  break  and  make  shocks,  from 
Du  Bois-Reymond's  sliding  induction-coil  is  generally  known  in 
the  laboratory  as  the  tetanising  current. 

The  direct  application  of  the  constant  galvanic  current  from 
a  cell  (Fig.  143)  has  the  disadvantage,  owing  to  its  prolonged 
passage,  of  producing  electrochemical  changes  in  the  tissues  greater 
than  those  due  to  other  methods  of  stimulation.  This  inconveni- 
ence can  be  reduced  to  a  minimum  -by  employing  very  brief 
currents  in  alternating  directions.  It  is  also  easy  by  means  of  a 
rheochord  to  regulate  the  intensity  and  exactly  measure  the 
electromotive  force  of  the  current  employed  as  stimulus.  Later  on 


iv    GENERAL  PHYSIOLOGY  OF  NKliVOUS  SYSTEM    223 

we  shall  examine  the  effects  of  galvauic  currents  upon  nerve  in 
full  detail. 

We  have  already  seen  (p.  19)  that  alternating  currents  of 
high  frequency  (Hertz  waves)  and  sufficient  intensity  to  light 
an  electric  lamp  have  no  stimulating  action  upon  nerve  or  muscle, 
probably  because  they  paralyse  conductivity  (D'Arsonval). 

The  currents  from  a  telephone  are  also  capable  of  stimulating 
nerve.  Hiirthle  succeeded  in  exciting  a  frog's  nerve  by  the  sounds 
of  a  heart  beating  into  a  telephone. 

Lastly,  the  physiological  electromotive  phenomena  of  the 
electrical  organs  of  Torpedo  (Marey),  as  well  as  the  intrinsic  currents 
of  voluntary  muscles  of  the  heart  and  the  nerve  itself,  can  also 
be  used  as  nerve  stimuli  (Hering). 

Whatever  the  nature  of  the  agent  employed  as  stimulus,  the 
excitation  which  it  discharges — given  constant  excitability  in 
the  nerve — is  dependent  both  on  the  intensity  of  the  stimulus 
and  on  the  rapidity  with  which  its  action  begins  and  ceases,  as 
well  as  on  its  mode  of  action  on  the  nerve.  It  is  generally  agreed 
that  the  efficacy  of  a  stimulus  depends  within  certain  limits  upon 
its  intensity.  But  the  method  by  which  this  law  is  deduced  from 
the  muscular  reaction,  direct  or  reflex,  is  inaccurate.  Waller 
demonstrated  (supra)  that  the  only  physical  measure  of  the 
activity  of  a  nerve  is  its  electrical  variation,  which  is  manifested 
even  when  the  stimulus  is  so  weak  that  it  fails  to  evoke  any 
muscular  contraction,  and  which  increases  with  the  increase  in  the 
strength  of  the  stimulus,  even  when  the  muscular  reaction  is 
already  maximal. 

The  relations  between  the  excited  state  and  the  mode  of 
stimulating  the  nerve  have  been  studied  particularly  for  electrical 
currents.  When  applied  to  motor  nerves  (Ritter  and  others) 
these  produce  a  maximum  effect  at  the  moment  of  incidence  and 
of  disappearance,  and  evoke  a  contraction  only  at  the  instant  of 
making  and  breaking  the  current,  and  not  during  its  passage, 
provided  there  are  no  rapid  positive  and  negative  alternations 
of  its  strength.  On  the  basis  of  these  facts  Du  Bois-Reymond 
formulated  the  law  that  currents  stimulate  in  virtue  not  of  their 
absolute  intensity  but  of  the  rapidity  with  which  they  arise  and 
disappear,  or  at  which  their  intensity  increases  or  diminishes.  No 
universal  value  can,  however,  be  ascribed  to  this  law.  The 
reaction  of  the  muscle  is  not  an  exact  index  of  the  state  of 
activity  of  the  nerve.  Both  during  and  after  the  passage  of  a 
current,  while  the  muscle  is  inactive,  important  changes  are  going 
on  in  the  nerve,  which  are  not  always,  but  only  in  given  cases, 
transmitted  to  the  muscle.  Further,  under  certain  conditions,  the 
closure  and  opening  of  an  electrical  circuit  connected  with  the 
nerve  will  evoke  a  true  tetanus  instead  of  simple  contractions. 
Lastly,  in  sensory  nerves  there  is,  not  only  at  the  make  and  break 


224  PHYSIOLOGY  CHAP. 

but  also  during  the  passage  of  the  current,  a  continuous  sensation 
which  is  the  subjective  sign  of  an  excited  state  of  the  nerve. 

It  should  be  noted  that  besides  the  influence  of  the  ascend- 
ing or  descending  direction,  to  which  we  shall  refer  below,  the 
current  is  most  efficacious  when  passed  longitudinally  through  the 
nerve,  least  when  passed  transversely  across  it  (Galvani,  Albrecht). 
Finally,  the  exciting  action  increases  with  extension  of  the  intra- 
polar  length  (Pfaff,  v.  Humboldt). 

VI.  The  efficiency  of  external  stimuli  varies  in  the  first  place 
with  the  excitability  of  the  nerve,  which  differs  very  much  not 
only  in  different  classes  of  animals,  but  also  in  different  nerves  of 
the  same  animal,  in  different  fibres  of  the  same  nerve,  and,  accord- 
ing to  some  investigators,  even  in  different  parts  of  the  same  fibre. 
Kitter  and  Eollett  were  the  first  to  note  that  on  exciting  a  frog's 
sciatic  with  a  current  of  minimum  intensity  the  abductors  and 
flexors  of  the  foot — i.e.  the  muscles  innervated  by  the  peroneal 
nerve — were  thrown  into  contraction ;  while  the  adductors  and 
extensors — i.e.  the  muscles  innervated  by  the  branches  of  the  tibial 
—were  only  excited  by  stronger  currents.  This  same  holds  good 
for  the  flexor  and  extensor  nerves  of  the  toad  and  rabbit,  and  can 
be  shown  not  only  with  electrical  but  also  with  mechanical  and 
chemical  stimuli.  In  the  frog's  vago-sympathetic  trunk  the 
inhibitory  fibres  are  excited  by  weaker  currents  than  the  acceler- 
ators. Excitation  of  the  nerve  of  the  crab's  claw  with  a  very 
weak  current  (see  p.  35)  causes  the  abductor  of  the  claw  to 
contract ;  with  stronger  currents  this  muscle  relaxes  and  the 
adductor  contracts.  Weak  currents  usually  suffice  to  excite 
nerves,  but  the  nerve  of  the  electrical  organ  of  Malaptcrurus  is 
excitable  to  strong  currents  only,  and  is  almost  inexcitable  to 
chemical  stimuli.  Probably  there  are  no  two  nerves  in  the  same 
animal  with  identically  the  same  degree  of  excitability. 

At  first  sight  the  degree  of  excitability  in  different  parts  of  the 
same  nerve  appears  to  vary.  If  a  motor  nerve,  e.g.  the  frog's 
sciatic  recently  divided  from  the  spinal  cord,  is  excited  at  different 
points  nearer  to  or  farther  from  the  muscle,  the  reaction  of  the 
muscle  is  seen  to  be  more  vigorous  in  proportion  as  the  stimulation 
is  more  remote.  Pfliiger  explained  this  fact  (first  observed  by 
Budge)  on  the  hypothesis  that  the  nervous  excitation  produced  by 
the  stimulus  increased  like  an  avalanche  on  its  way  to  the  muscle. 
But  this  interpretation  was  at  once  disputed  by  Heidenhain,  and 
subsequently  by  Fleischl,  Griitzner,  Tigerstedt,  and  others.  The 
phenomenon  must  be  due  to  the  increase  of  excitability  caused  in 
the  upper  part  of  the  sciatic  by  the  injury  due  to  the  section.  When 
the  nerve  remains  as  far  as  possible  under  normal  conditions,  it  is 
found  to  be  equally  excitable  in  its  different  parts  to  chemical 
(v.  Fleischl)  and  mechanical  stimuli  (Tigerstedt).  The  excitatory 
impulse  is  more  probably  weakened  than  reinforced  during  its 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    225 

propagation  through  the  nerve,  owing  to  the  resistance  encountered. 
I'ucceschi  in  fact  saw  that  on  compressing  the  frog's  sciatic  lightly 
by  his  method  (Chap.  IV.  p.  I',).0.)  near  the  muscle,  and  then 
tetanising  it  with  an  induced  current  alternately  near  the  point 
of  compression  and  at  the  central  end  of  the  nerve,  the  conduction 
of  the  impulse  to  the  muscle  ceased  earlier  from  the  more  distant 
points  of  excitation  than  from  those  nearer  to  the  muscle. 

Whatever  the  degree  of  excitability  in  the  different  nerves,  it 
can  survive  for  a  long  time,  independently  of  the  circulation.  If 
care  be  taken  to  avoid  desiccation  and  too  sudden  changes  of 
the  normal  temperature,  the  medullated  fibres  of  mammalian 
nerves  are  capable  of  preserving  their  excitability  for  many  hours, 
and  those  of  the  frog  for  many  days,  even  when  the  circulation 
has  been  entirely  arrested. 

The  functions  of  nerves  are  usually  supposed  to  be  very 
unstable  and  readily  altered  by  slight  causes.  But  it  is  easy  to 
demonstrate,  on  the  contrary,  that  nerve,  owing  to  its  low  meta- 
bolism and  specific  differentiation,  represents  a  form  of  living  proto-  i 
plasm  which  is  endowed  with  peculiarly  high  resistance  to  noxious  \ 
influences.  It  is  possible  to  experiment  for  a  long  time  with  a 
mammalian  nerve,  after  it  has  been  isolated  for  a  considerable 
distance  from  the  surrounding  tissues  and  its  circulation  cut  off, 
without  loss  of  its  normal  functions,  provided  it  remains  covered 
and  protected  from  heat  and  cold,  and  that  circulation  is  normal 
in  the  central  and  peripheral  organs  with  which  it  is  connected. 
After  occluding  the  aorta  of  a  rabbit,  the  sciatic  (according  to 
Frederic*  [)  is  capable,  on  electrical  stimulation,  of  causing  the 
corresponding  muscles  of  the  leg  to  contract,  even  after  an  interval 
of  half  an  hour.  After  three-quarters  of  an  hour  the  contractions 
cease  for  indirect  stimulation,  while  the  direct  excitability  of  the 
muscles  still  persists.  This  is  due  not  to  exhaustion  of  the  nerve, 
but  to  loss  of  conductivity  in  the  motor  end-plates.  In  fact  even 
w I it'ii  the  muscles  have  lost  their  excitability  the  nerves  are  still 
alive  and  capable  of  excitability  and  conductivity,  as  is  shown  by 
the  negative  electrical  variation. 

The  most  striking  demonstration  of  the  vital  resistance  of 
nerve  is,  however,  its  comparative  non-fatigability. 

When  a  motor  nerve  is  excited,  the  muscle  apparently  becomes 
fatigued  long  before  the  nerve.  This  was  demonstrated  by 
Bernstein  in  the  following  experiment : — Make  two  preparations  of 
the  frog's  sciatic ;  cut  them  high  up  so  as  to  separate  them  from 
the  spinal  cord,  to  exclude  sensations  and  reflexes  :  tetanise  the 
two  peripheral  stumps  simultaneously  with  the  same  induced 
current,  and  at  the  same  time  pass  a  strong  constant  current  in 
the  ascending  or  descending  direction  through  one  of  the  two 
sciatics  below  the  point  tetanised  :  this — by  a  polarising  process 
known  as  electrotonus,  which  we  shall  presently  study — inhibits  the 

VOL.  Ill  (> 


226  PHYSIOLOGY  CHAP. 

excitability  and  conductivity  of  the  nerve,  so  that  the  transmission 
of  excitation  to  the  muscle  is  prevented.  The  muscles  of  the  first 
sciatic  will  then  be  thrown  into  tetanus  which  lasts  for  some 
minutes  and  gradually  dies  away,  while  the  muscles  of  the  second 
(polarised)  sciatic  remain  absolutely  quiet.  In  order  to  show  that 
the  absence  of  tetanus  in  the  first  case  is  not  due  to  fatigue  or 
exhaustion  of  the  nerve,  it  is  only  necessary  to  break  the  polaris- 
ing current  which  blocks  the  second  nerve.  The  corresponding 
muscles  are  at  once  thrown  into  tetanus  of  the  same  vigour  and 
duration  as  that  of  the  other  side,  showing  that  the  nerve  had 
preserved  its  excitability  intact  during  the  protracted  stimulation. 

Schiff  in  1858,  by  a  method  similar  to  that  of  Bernstein,  arrived 
at  the  same  conclusion  as  to  the  great  resistance  of  nerve  to  fatigue. 
He  applied  the  electrodes  of  a  very  weak  battery,  the  circuit  of 
which  was  closed  instantaneously  every  two  seconds  by  the 
pendulum  of  a  clock,  to  the  distal  stump  of  the  frog's  sciatic,  and 
obtained  a  muscular  twitch  at  each  closure.  If  the  electrodes  of 
a  strong  tetanising  induction  current  were  then  applied  to  the 
central  end  of  the  nerve  the  rhythmical  contractions  were  replaced 
by  a  tetanus  that  died  out  gradually,  till  finally  it  ceased  altogether, 
on  which  the  muscle  no  longer  reacted  either  to  the  intermittent 
shocks  of  the  battery  or  to  the  induced  tetanising  current. 
Under  these  conditions  it  would  seem  as  though  the  nerve  were 
exhausted,  but  proof  to  the  contrary  was  shown  in  the  fact  that 
directly  the  tetanising  current  was  interrupted  the  rhythmical  con- 
tractions reappeared.  To  explain  this  fact  Schiff'  assumed  that  the 
induced  current  produces  a  negative  excitation,  which  was  able  to 
neutralise  the  effect  of  the  intermittent  shocks. 

Wedensky  (1884)  improved  on  the  methods  of  Bernstein  and 
Schiff,  and  confirmed  and  extended  their  researches.  He  tetanised 
the  sciatic  with  an  induced  current  of  given  strength  and  frequency 
till  the  phase  of  apparent  exhaustion  was  reached.  On  then  re- 
ducing the  intensity  and  frequency  of  the  current  the  tetanus 
reappeared,  showing,  according  to  Wedensky,  that  the  nerve  was 
not  exhausted,  but  acted  as  an  inhibitory  nerve.  The  experiment 
can  be  repeated  many  times  upon  the  same  nerve,  always  with 
the  same  result. 

This  "  paradoxical  "  phenomenon,  viz.  that  a  stronger  or  more 
frequent  stimulus  produces  less  effect  than  a  weaker  or  less  frequent 
stimulus,  was  satisfactorily  interpreted  by  F.  B.  Hofmann,  who  in 
1902-4  undertook  a  series  of  accurate  investigations  into  muscular 
tetanus  from  indirect  stimulation.  He  refers  it  to  fatigue  of 
the  end-organs.  The  excitability  of  these  is  depressed  after  each 
stimulation  :  recovery  takes  place  after  an  interval  which  is  longer 
in  proportion  with  the  strength  of  the  preceding  excitation  and 
the  degree  of  fatigue.  If  the  stimuli  are  too  strong,  and  follow 

O  O' 

too  rapidly,  there  is  no  recovery,  and  in  excitability  ensues  ;  if  the 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    227 

stimulus  is  weakened,  or  made  less  frequent,  the  reaction  reappears. 
Under  normal  conditions  these  effects  of  fatigue  are  manifested 
only  in  muscle  and  particularly  in  the  motor  end-plates ;  but  we 
shall  see  that  under  special  circumstances  the  nerve  trunk  too  may 
exhibit  similar  paradoxical  phenomena,  so  that  the  experiments 
of  Sclriff  and  Wedensky  cannot  be  taken  as  a  positive  proof  of 
the  non-fatigability  of  nerve. 

The  experiment  of  Bowditch  (1885)  is  simpler  and  less 
ambiguous.  After  curarising  a  cat,  using  artificial  respiration, 
he  divided  the  sciatic  and  tetanised  for  a  long  time  with  an  in- 
duction current,  which  produced  no  effect  upon  the  muscles  of  the 
leg,  owing  to  the  paralysis  of  the  motor  end-plates.  After  two  to 
three  hours  of  artificial  respiration  the  paralysis  induced  by  the 
curare  wears  off,  the  animal  gradually  recovers,  and  the  effects  of  the 
excitation  of  the  sciatic  appear  in  the  form  of  an  irregular  tetanus. 
Lambert  substituted  atropine  for  curare,  and  was  able  to  show  the 
non-fatigability  of  the  secretory  fibres  contained  in  the  chorda 
tympani.  After  many  hours  of  ineffectual  stimulation  of  the 
nerve  the  sub-maxillary  gland  began  to  secrete  as  the  poison 
disappeared  gradually. 

A  more  direct  proof  of  the  relative  inexhaustibility  of  nerve 
was  given  by  Wedensky  with  the  galvanometer  and  telephone. 
He  showed  that  the  electrical  phenomena  (negative  variation) 
characteristic  of  functional  activity  undergo  no  perceptible  altera- 
tion after  protracted  stimulation ;  and  that  two  nerves  excised 
from  the  body,  one  being  at  rest,  the  other  exposed  to  prolonged 
stimulation,  perished  simultaneously. 

These  researches  as  a  whole  show  that  nerve  fibres,  unlike 
other  parts  of  the  central  and  peripheral  nervous  system,  exhibit 
no  signs  of  exhaustion,  even  after  protracted  activity  :  the  fact  that 
a  nerve  is  still  capable  of  reacting  to  direct  stimulation  after  the 
response  of  the  muscle  had  ceased  proves — as  Waller  pointed  out 
—that  the  organs  which  connect  the  nerve  with  the  muscle,  i.e. 
the  motor  end-plates,  are  much  more  easily  fatigued  than  the 
muscle  and  nerve.  It  is  probable  that  the  waste  products  developed 
by  the  muscle  during  tetanus  have  some  significance  in  the 
production  of  exhaustion  in  the  end-plates,  as  they  may  exert 
a  toxic  action  on  the  motor  nerve -endings  similar  to  that  of 
curare  (Abelous). 

This  relative  inexhaustibility  is  not,  however,  characteristic  of 
all  nerves.  Garten  (1903)  discovered  a  non-medullated  nerve 
(olfactory  of  pike)  which  readily  becomes  fatigued.  On  stimulat- 
ing it  with  a  series  of  induction  currents  at  brief  intervals,  the 
action  current — observed  by  the  capillary  electrometer — diminished 
after  a  few  stimulations,  but  it  increased  again  after  a  pause. 
Even  niedullated  frog's  nerve  under  abnormal  conditions  manifests 
phenomena  which  cannot  be  interpreted  otherwise  than  as  fatigue 

Ql 


228  PHYSIOLOGY  CHAP. 

effects.       Fr.  W.   Frohlich   (1904),  who   made   a   long  series   of 
accurate  observations   on   this   question,  saw  that,  at   a   certain 
stage  of  narcosis  or  asphyxia  of  the  nerve,  phenomena  of  apparent 
inhibition  set  in  which  are  perfectly  analogous  to  those  described 
by  Wedensky,  and  which  Hermann  referred  to  fatigue  of  the  end- 
organs.     This  paradoxical  state,  in  which  very  strong  and  frequent 
stimuli  are  less  effective  than  weaker  and  less  frequent  stimuli, 
can  only  be  interpreted  in  these  experiments  as  fatigue  of  the 
part  of  the  nerve  which  is  exposed  to  narcosis  or  asphyxia.     Such 
manifestations   of  fatigue  do  not  appear  in  nerve  under  normal 
\  conditions,  because  the  consumption  of  living  matter  is  minimal, 
I  and  recovery  is  extraordinarily  rapid.     They  are  manifested  only 
'  when  the  restitution  processes  are  much   retarded  by  toxic  or 
other  pathological  influences. 

Although  under  normal  conditions  nerve  is  practically  inex- 
haustible to  prolonged  artificial  stimuli,  so  long  as  these  do  not 
alter  its  substance,  its  specific  activities  (excitability  and  con- 


Fio.  144.— Griinliagen's  experiment  on  the  effect  of  COo  on  a  limited  portion  of  a  frog's 
sciatic  nerve.     Explanation  in  text. 

ductivity)  may  progressively  diminish  and  eventually  disappear 
when  it  is  deprived  of  the  essential  conditions  of  its  existence. 

Since  nerve  in  atmospheric  air  shows  no  signs  of  fatigue  even 
after  protracted  activity,  the  question  naturally  arose  as  to  how 
far  its  functions  depend  upon  the  supply  of  oxygen,  and  how 
much  they  are  altered  when  indifferent  or  toxic  gases  are  sub- 
stituted for  atmospheric  air.  The  earlier  investigations  of  Banke 
and  of  Ewald  (1867-69)  are  inconclusive ;  they  were  incomplete 
and  yielded  little  result. 

Ranke  stated  that  a  nerve  (frog's  nerve-muscle  preparation) 
suffers  no  injury  in  an  atmosphere  of  carbonic  acid,  and  that  it 
keeps  its  excitability  longer  in  an  atmosphere  of  hydrogen  than 
in  one  of  oxygen.  Ewald  was  unable  to  discover  any  difference 
in  the  period  of  declining  excitability,  whether  the  nerve  was 
immersed  in  oxygen  or  hydrogen,  or  was  in  vacuo.  He  concluded 
that  its  vitality  is  independent  of  its  oxygen  supply. 

The  experiment  in  which  Grlinhagen  allowed  carbonic  acid  to 
act  not  upon  the  entire  nerve-muscle  preparation  of  the  frog,  but 
only  upon  a  limited  portion  of  the  nerve,  is  more  important.  For 
this  purpose  he  introduced  the  nerve  of  the  frog's  leg  into  a  glass 


iv    GENEEAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    229 

tube  which  served  as  a  gas  chamber,  and  plugged  the  ends  with 
china  clay  saturated  with  isotonic  salt  solution.  By  using  two  pairs 
of  electrodes  he  was  able  to  excite  both  the  part  of  the  nerve  that 
was  being  treated  with  CO.,  and  the  more  proximal  part  outside 
the  gas  chamber  (A  and  B  of  Fig.  144).  At  a  certain  time  after 
passing  the  current  of  C02  into  the  gas  chamber,  stimulation  of 
the  nerve  at  point  A  produced  only  a  feeble  response,  which 
gradually  disappeared  altogether;  while  stimulation  at  point  B 
was  still  fully  effective.  The  impulse  starting  at  B  can  therefore 
be  transmitted  along  the  portion  A  of  the  nerve,  in  which  excit- 
ability has  been  depressed  or  abolished.  This  important  experi- 
ment is  complementary  to  Waller's  researches  on  the  effects  of 
CO.,  on  the  electromotive  response  of  nerve  (Figs.  138,  139),  and 
proves  that  excitability  and  conductivity,  while  closely  associated, 
behave  on  artificial  excitation  as  two  distinct  properties  of  the 
nerve. 

Griinhagen's  experiments  were  continued  by  Luchsinger,  and 
more  particularly  by  Piotrowski,  who  extended  them  to  anaes- 
thetics, and  endeavoured  to  differentiate  the  action  of  the  latter 
upon  the  excitability  and  the  conductivity  of  nerve,  by  means 
of  various  forms  of  electrical  and  mechanical  stimuli.  He  con- 
cluded as  follows : 

(a)  Carbon  dioxide  and  carbon  monoxide  gases  always  produce 
a  marked  depression  of  excitability  in  the  intoxicated  segment 
without  injuring  conductivity. 

(&)  Alcohol  vapour  causes  an  initial  rise  of  both  excitability 
and  conductivity  :  later  on  the  second  decreases  more  rapidly  than 
the  first,  until  a  stage  is  reached  in  which  excitations  aroused 
above  the  intoxicated  portion  are  no  longer  conducted,  although 
the  nerve  is  still  perfectly  excitable  at  that  point. 

(c)  Ether  and  chloroform  depress  both  excitability  and  con- 
ductivity, but  affect  the  former  more  rapidly  and  fundamentally 
than  the  latter.  Chloroform  attacks  the  vitality  of  nerve  more 
powerfully  than  ether,  so  that  its  effects  may  become  permanent. 
Gotch  also  confirmed  these  results. 

(cT)  In  all  these  experiments  conductivity  returns  more  rapidly 
than  excitability,  when  the  action  of  these  gases  upon  the  nerve 
is  stopped. 

The  results  of  these  and  many  similar  experiments  are 
obviously  unsatisfactory,  and  are  far  from  giving  any  clear  idea  of 
the  relations  between  excitability  and  conductivity  in  nerve.  The 
work  in  Verworn's  laboratory  of  his  pupil  Fr.  W.  Frohlich  (1903) 
has  thrown  more  light  on  this  subject.  Frohlich  found  that  on 
anaesthetising  or  asphyxiating  a  tag  of  nerve  its  excitability 
diminishes  gradually  and  almost  evenly,  while  conductivity — i.e. 
excitability  of  the  more  central  and  uninjured  parts  of  the  nerve — 
is  at  first  unaltered,  and  then,  when  the  excitability  has  fallen  to 

Q  2 


230 


PHYSIOLOGY 


CHAP. 


a  certain  point,  suddenly  disappears.  Recovery  takes  place  in  the 
same  way  ;  excitability  gradually  rises,  while  conductivity  suddenly 
returns  in  its  former  proportions  as  soon  as  the  excitability  has 
risen  to  its  normal  level  (Fig.  145). 

Von  Baeyer  (1902),  in  Verworn's  laboratory,  carried  out 
another  series  of  researches  on  the  effect  of  oxygen  and  the  in- 
different gases  (nitrogen  and  hydrogen)  upon  the  vitality  of  nerve. 
By  means  of  Griinhagen's  method,  which  he  improved  in  certain 
details  (Figs.  146  and  147),  he  established  the  following  results, 
which  are  complementary  to  those  of  his  predecessors  : 


200 


0 


10 


15 


20 


25 


30 


35 


FIG.  145. —  Diagram  to  show  changes  of  excitability  and  conductivity  in  a  motor  nerve  under  the 
influence  of  anaesthetising  and  asphyxiating  agents  upon  a  limited  portion.  (Fr.  W.  Frohlich.) 
The  abscissa  line  shows  the  time  in  minutes  ;  the  ordinates,  the  distance  in  mm.  of  the  coils  at 
which  the  minimal  stimulus  (single  induction  shock)  takes  effect. 

(a)  Under  the  direct  asphyxiating  influence  of  the  indifferent 
gases,  the  excitability  of  nerve  disappears  in  three  to  five  hours. 
On  substituting  oxygen  for  these  gases,  normal  excitability  returns 
after  three  to  ten  minutes. 

(&)  The  physiological  conductivity  of  the  nerve  is  also  abolished 
by  the  asphyxiating  gases,  and  recovered  on  adding  oxygen. 

(c)  Asphyxia — loss  of  excitability  and  conductivity — spreads 
along  the  nerve  in  a  centrifugal  direction  according  to  the  Hitter  - 
Valli  law  (infra) ;   functional  recovery  when  oxygen  is  supplied 
seems,  on  the  contrary,  to  be  propagated  in  a  centripetal  direction. 

(d)  On  raising  the  temperature  of  the  nerve  to  42-47°  C.  the 
indifferent  gases  produce  asphyxia  in  twenty  to  sixty  minutes.     If 
the  temperature  be  then  lowered  again  to  that  of  the  surrounding 


iv    GENERAL  PHYSIOLOGY  OF  NEKVOUS  SYSTEM    231 


atmosphere,  and  the  current  of  indifferent  gases  continued  for 
twenty-five  minutes,  the  nerve  does  not  recover.  P>ut  if  oxygen  is 
passed  through  the  gas  chamber  there  is  a  preceptible  recovery  in 
three  to  six  minutes,  which  becomes  complete  in  a  few  moments. 

These  results  show  that  the  vitality  of  nerve  depends  on  a 
definite  supply  of  oxygen.  Its 
comparative  inex  haustil  tility 
under  normal  conditions  is  due 
to  the  fact  that  at  ordinary 
temperature,  in  presence  of 
atmospheric  air,  it  obtains  all 
the  oxygen  essential  to  its 
functions.  As  we  have  seen, 
both  v.  Baeyer  and  Frohlieh 
demonstrated  unmistakable 
phenomena  of  nerve  -  fatigue 
in  an  atmosphere  deprived  of 
oxygen. 

Von  Baeyer's  experiments 
were  extended  and  completed 
by  Fr.  W.  Frdhlich  (1903),  who 
found  that  asphyxiated  and 
anaesthetised  nerve  is  incap- 
able of  recovery  by  assimilating 
oxygen,  confirming  the  results 
of  Hans  Winterstein  for  nerve- 
centres  (infra'}.  Frohlich  then 
studied  the  effects  of  duration 
of  oxygen  supply  on.  the  re- 
covery of  asphyxiated  nerve. 
With  prolonged  passage  of 
oxygen  he  found  an  initial 
rise  of  excitability  up  to  the 
normal  height;  a  further  supply 
of  oxygen  produced  no  further 
rise  of  excitability,  but  in- 
creased the  duration  of  a  second 
asphyxia. 

Von  Baeyer's  experiments 
were  repeated  by  Boas  (1904), 

\vho  placed  the  nerve  in  an  atmosphere  of  pure  hydrogen  and 
in  vacua,  with  the  same  results. 

Thunberg  (1904)  showed  that  the  consumption  of  oxygen  and 
production  of  carbonic  acid  in  nerve  can  be  demonstrated  directly 
by  chemical  analysis.  By  means  of  a  micro-respiratory  method  he 
was  able  to  measure  oxygen  intake  and  carbonic  acid  output  from 
excised  bits  of  rabbit's  nerve. 


FIG.  146. — Von  Baeyer's  method  of  demonstrating 
the  effect  of  gases  on  a  length  of  nerve.  «,U-tul>e 
ending  in  a  bulb  with  a  little  water  to  saturate 
the  gas  passing  through  it ;  the  tube  is  enclosed 
in  a  kind  of  water-bath  by  which  tin- 1  i-mp.'iature 
of  the  gas  can  be  raised  as  desired  ;  b,  gas 
chamber  into  which  the  nerve  is  introduced 
through  the  side  aperture  <',  and  where  it  can 
be  excited  by  means  of  platinum  electrodes 
soldered  in  at  <l  ;  e,  vent  for  gas  ;  /,  rubber  cork 
through  which  the  bulb  of  a  thermometer  can 
be  introduced  into  the  chamber. 


232 


PHYSIOLOGY 


CHAP. 


Another  important  condition  of  the  vitality  of  nerve  lies  in 
its  anatomical  continuity  and  connection  with  its  central  organ. 
A  long  series  of  well-established  facts  proves  that  when  this 
connection  is  interrupted  its  normal  nutrition  and  morphological 
structure  are  altered,  as  well  as  its  excitability. 

When  a  nerve,  e.g.  sciatic,  is  divided  at  any  point  of  its  course, 
there  is  at  first  a  considerable  rise  in  excitability,  particularly  near 
the  point  of  section  (Rosenthal),  which  is  due  to  the  electromotive 
changes  developed  there  (demarcation  current).  This  rise  dies 
away  after  a  certain  time,  and  gives  place  to  a  gradual  decrease, 
and,  finally,  the  total  loss  of  excitability  in  the  nerve. 

According  to  a  law  formulated  by  Valli  and  confirmed  by 
Bitter  the  depression  and  loss  of  excitability,  both  in  the  excised 


FIG.  147.— Gas  chamber  of  v.  Baeyer's  apparatus,  with  unpolarisable  brush  electrodes  instead 
of  those  shown  in  preceding  figure.  The  letters  ?ill  e\,  il\,  e\,  J\  have  the  same  meaning  as 
b,  <;  d,  K,  /in  previous  figure. 

0 

nerve  and  in  that  which  is  only  divided,  begin  at  the  proximal  end 
and  progress  centrifugally  towards  the  periphery.  Experiment 
shows  in  fact  that  when  excitability  is  exhausted  in  the  proximal 
parts  the  nerve  is  still  capable  of  excitation  in  more  peripheral 
regions.  Complete  disappearance  of  excitability  in  the  entire 
trunk  of  the  sciatic  occurs  four  days  after  section  in  the  clog 
(Longet),  two  days  in  the  rabbit  (Eanvier),  two  days  and  a  half 
in  the  pigeon  (Waller).  In  poikilothermic  animals  in  general 
excitability  lasts  much  longer ;  it  varies  considerably  with  the 
season  and  with  the  general  conditions  of  nutrition  in  the  animal 
experimented  on.  In  the  frog,  during  the  winter  season,  the 
excitability  of  the  cut  sciatic  persists  for  thirty-three  days  after 
section  (Brown-Sequard). 

Before  this  gradual  depression  and  loss  of  excitability  in  the 
centrifugal  direction  is  completed,  a  characteristic  degenerative 
change  begius  in  the  divided  nerve,  which  is  coupled  after  a  few 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    233 


days  with  an  opposite  regenerative  process.  This  finally  leads  to 
the  gradual  recovery  of  function  in  the  nerve,  and  so  of  sensibility 
and  motility  in  the  region  which  it  innervates. 

These  morphological  studies  of  the  degeneration  and  re- 
generation of  nerves  severed 
from  their  centres  were 
begun  by  Steinbriick  (1838), 
Nasse  (1839),  Giinther  and 
Schon  (1840) ;  but  they  only 
acquired  significance  after 
the  discovery  of  the  so-called 
trophic  centres  of  the  spinal 
roots  by  Augustus  Waller  iu 
1852. 

We  must  here  confine 
ourselves  to  a  summary  of 
the  changes  produced  by 
severing  the  fibres  of  a  mixed 
peripheral  nerve  from  their 
trophic  centres.  Two  to  four 
days  after  section  the  whole 
peripheral  part  of  the  nerve 
and  a  short  length  of  its 
central  portion  (according  to 
Engemiann  to  the  nearest 
node  of  Ranvier,  but  accord- 
ing to  other  authors  as  far 
as  the  second  or  third  node) 
begins  to  undergo  a  process 
of  degeneration,  which  is 
easily  traced  under  the  micro- 
scope, and  which  leads  to  the 
disintegration  of  the  fibres. 
It  is  usually  held  that  the 
degenerative  process  does  not 
advance  progressively  from 
the  seat  of  the  lesion  towards 
the  periphery,  but  that  it 
appears  simultaneously 
throughout  the  whole  distal 


FIG.  148. — Degeneration  and  regeneration  of  nerve- 
libres.  (Ranvier.)  A,  rabbit's  sciatic  four  days 
after  section;  B,  C,  the  same  fifty  hours  after 
section ;  D,  fibre  stained  with  carmine  only,  to 
show  axis  -  cylinder  ;  F,  (~f,  pigeon's  fibres  three 
days  after  section  ;  H,  two  fibres  of  rabbit's  vagus 
six  days  after  section  ;  J,  lymph  cell  from  inter  - 
tibrillary  connective  tissue,  containing  ingested 
globules  of  myelin.  Throughout  the  figure,  n,  n, 
are  nuclei ;  x,  x,  myelin  broken  up  by  increase 
of  the  protoplasm  ;  etc,  axis  -  cylinder  ;  K,  L,  re- 
generation of  nerve-fibres  ;  H,  of  rabbit's  vagus 
seventy-two  days  after  section  ;  L,  of  rabbit's 
sciatic  ninety  days  after  section  ;  e,  conical  ending 
of  white  matter  of  central  end  of  the  nerve  ;  s, 
sheath;  na,  new  axis -cylinder.  L  shows  two 
globules  of  myelin  left  over  from  the  degeneration 
of  the  old  fibre. 


portion.    The  rapidity  of  the 
degenerative  process  is  greater  in  young  than   in   old  animals, 
in   strong   than   in  weak,  in  warm-blooded   than   in    the   cold- 
blooded. 

The   most  apparent  change  occurs   in    the   myelin  sheath  of  , 
the   fibres,    which   undergoes   progressive   fragmentation    till   it 
is  reduced  to  small  irregular  lumps  or  drops.     Along  with  this 


234  PHYSIOLOGY  CHAP. 

morphological  alteration  there  is  n  chemical  metamorphosis  of 
the  rnyelin  which,  probably  owing  to  the  formation  of  fat,  now 
stains  black  with  osmic  acid,  after  the  nerve  lias  been  mordanted 
in  a  chrome  solution.  Marchi's  method  of  distinguishing  between 
the  healthy  and  the  degenerated  nerve-fibres  is  based  on  this 
chemical  change  of  the  myelin  sheath  (Fig.  148,  A-J"). 

Many  hold,  on  the  strength  of  Eanvier's  studies,  that  the 
fragmentation  and  fatty  degeneration  of  the  myelin  is  accom- 
panied by  a  multiplication  of  the  nuclei  of  the  neurolemma, 
and  increase  of  its  protoplasm,  which  interrupts  the  continuity 
of  the  medullary  sheath.  The  axis-cylinder,  too,  is  broken  up 
by  the  same  process  as  the  myelin,  i.e.  by  increase  of  the 
protoplasm  at  the  level  of  the  nuclei  of  the  interannular  segments. 
But  according  to  the  recent  and  more  accurate  work  of  Bethe 
and  Monckeberg  the  degenerative  alteration  of  the  axis-cylinder 
precedes  the  other  changes,  and  takes  place  pari  passu  with  the 
diminution  and  loss  of  excitability  in  the  nerve.  First,  the 
fibrils  of  the  axis-cylinder  stain  less  readily ;  next,  they  fuse 
into  a  compact  cord,  which  looks  knotted  in  places,  and  also 
shows  large  fusiform  nodules ;  lastly,  they  break  up  and  then 
dissolve  into  a  detritus  of  colourless  granules.  The  acute  period 
of  the  degenerative  process  is  followed  by  a  slow  fetage,  in  which 
the  products  of  disintegration  are  absorbed  (by  phagocytosis  ?) 
so  that  they  entirely  disappear  after  three  to  four  weeks.  When 
clear  of  the  degeneration  products  the  fibres  of  the  nerve  are 
seen  as  strands  filled  with  large  fusiform  elements,  which  are 
derived  from  the  cells  of  the  neurolemma.  What  part  do  these 
spindle-shaped  elements  play  in  the  regeneration  of  the  nerve  ? 

The  regenerative  process  in  the  divided  nerve  proceeds  to  a 
large  extent  along  with  the  degenerative,  to  which  it  is  the  active 
reaction,  directed  to  the  morphological  and  functional  recovery 
of  the  injured  nerve. 

There  are  two  principal  theories  to  explain  the  process  of 
nerve  regeneration,  which  are  related  to  the  two  fundamental 
conceptions  of  the  morphological  structure  of  the  nervous 
system  discussed  earlier  in  this  chapter. 

In  correspondence  with  the  neurone  theory,  many  authors 
hold  that  the  regeneration  of  the  axis-cylinders  in  the  peripheral 
end  of  the  cut  nerve  is  due  exclusively  to  an  outgrowth  of  the 
axis-cylinders  of  the  central  end.  These  increase  in  size,  become 
bulbous  at  their  extremities,  and  send  out  fibrils  in  a  centrifugal 
direction,  which  pierce  the  cicatricial  tissue  that  has  united 
the  two  stumps,  and  then  penetrate  the  old  neurolemmal  sheaths, 
or  grow  along  them  until  they  reach  their  peripheral  termination. 
Ranvier,  Vanlair,  Strobe  are  the  chief  promoters  of  this  theory 
(Fig.  148,  K,L}. 

The   other   conception  of  the  regenerative   process   in   nerve 


iv    GENEEAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    235 

corresponds  with  the  theory  which  regards  a  ganglion  cell  and 
its  processes,  not  as  a  morphological  and  functional  unit,  but 
as  a  syncytium,  i.e.  the  result  of  the  fusion  of  a  number  of 
neuroblasts  arranged  in  a  chain.  On  this  hypothesis  the  cells 
of  the  neurolemma  represent  the  residues  of  the  neuroblasts 
from  which  the  nerve -fibres  originated,  and  after  section  of 
the  nerve  they  reassume  their  character  of  neuroblasts  by 
multiplying  and  hypertrophying  in  the  form  of  spindle-shaped 
embryonic  cells,  and  regenerate  the  nerve-fibre  discontinuously 
and  simultaneously  in  the  different  parts  of  the  cut  nerve.  This 
theory  is  supported  by  Benecke,  Tizzoni  and  Cattani,  Huber, 
v.  Biingner,  Galeotti  and  Levi  in  particular,  and  it  has  been 
reinforced  by  recent  morphological  and  experimental  observations 
of  Bethe. 

Bethe,  unlike  the  earlier  workers,  prevented  the  two  stumps 
of  the  divided  sciatic  in  dogs  and  rabbits  from  joining,  and 
examined  the  peripheral  stump  six  to  nine  months  later  by 
physiological  and  histological  methods.  When  the  experiment 
was  carried  out  on  adult  animals  he  noted  an  increase  of 
protoplasm  in  the  neurolemma,  with  differentiation  into  an 
axial  filament  and  a  peripheral  sheath,  but  was  unable  to  detect 
fibrils  in  the  former  or  niyelin  in  the  latter.  The  nerve  was 
thus  partially  regenerated,  but  was  found  on  stimulation  to  be 
inexcitable  and  incapable  of  conducting. 

Bethe  obtained  different  results  on  experimenting  with  young 
animals,  in  which  the  regenerative  capacity  of  the  tissues  as 
a  whole  is  much  greater.  Of  four  young  dogs  and  one  rabbit 
operated  on  he  observed  in  3  cases  not  only  complete  morpho- 
logical regeneration,  but  also  functional  recovery  of  the  isolated 
peripheral  nerve  (i.e.  one  not  reunited  with  the  central  stump). 
On  stimulating  with  induced  currents  that  were  too  weak  to 
produce  direct  excitation  of  the  muscle,  the  leg  muscles  were  seen 
to  contract  freely. 

Laugley  and  others,  however,  objected  to  Bethe's  conclusions 
that  this  was  not  a  true  autogenous  regeneration  of  the  nerves, 
and  that  the  regeneration  of  the  peripheral  stump  must  depend 
on  its  uniting  with  the  central  end  of  other  adjacent  nerves 
that  had  been  divided  in  the  operation.  The  .tendency  mani- 
fested even  by  nerves  that  are  situated  at  a  distance,  and  that 
supply  other  muscles,  to  unite  with  the  peripheral  ends  of  cut 
nerves,  so  as  to  re-establish  the  conductivity  of  the  fibres,  is 
in  fact  very  marked.  This  enigmatical  fact,  that  nerve  -fibres 
emero-in^  from  the  centre  and  in  normal  connection  with  it 

o       o 

grow  towards  peripheral  organs  that  have  been  denervated,  has 
been  attributed  by  some  neurologists  who  deny  autogenous 
regeneration  to  a  kind  of  neurotaxis,  i.e.  to  the  capacity  of 
denervated  organs  to  attract  the  nerve-fibres  that  grow  towards 


236  PHYSIOLOGY  CHAP. 

the   periphery   (perhaps   by  chemical  stimuli  deriving  from  the 
degenerative  processes). 

Some  remarkable  experiments  have  recently  been  carried  out 
upon  the  embryos  of  various  cold-blooded  animals  with  a  view 
to  solving  the  origin  of  nerve  -  fibres.  The  results  cannot, 
however,  be  taken  as  conclusive  for  either  theory.  Such  are  the 
experiments  of  Braus  and  Banchi  (1905),  who  transplanted  limb 
buds  into  the  bodies  of  tadpoles,  and  the  observations  of  0. 
Schultze  (1904-5)  on  the  histogenesis  of  the  peripheral  nerves 
in  tadpoles.  These  yield  data  that  decidedly  favour  the 
autogenous  theory.  On  the  other  hand,  Harrison  (1904-6)  found 
in  amphibian  larvae  that  after  excising  the  neural  crest,  from 
which  all  the  cells  of  Schwann  for  sensory  and  motor  nerves  are 


FIG.  149. — Diagrammatic.  Regenerative  changes  at  the  central  end  of  a  nerve-fibre,  close  to  the 
section.  (Perroncito.)  a,  normal  axis-cylinder  composed  of  a  bundle,  of  fibrils;  b,  swelling, 
from  or  above  which  the  regenerating  fibres  grow  out ;  c,  portion  of  axis-cylinder  undergoing 
degenerative  changes,  close  to  the  section  ;  <l,  d",  young  fibrils  sprouting  from  the  axon,  which 
leave  the  nerve-fibre  through  the  neurolemma  ;  d',  new  fibres  running  backward  in  a  spiral  ; 
e,  fi  Oi  Q'I  9">  ''i  h',  h",  different  forms  of  buds  and  regenerating  fibres. 

derived,   the  axis -cylinders  still   develop,    but   remain    destitute 
of  sheaths. 

When,  in  1900,  it  was  still  possible — in  the  absence  of  specific 
histological  tests — to  question  the  existence  of  the  regeneration 
of  axis-cylinders  in  cut  nerves,  Purpura  examined  them  with 
Golgi's  silver  nitrate  method  and  obtained  decisive  results.  At  the 
extremity  of  the  central  stump  of  a  divided  nerve,  between  the 
normal  medullated  fibres,  he  observed  the  presence  of  nude  axis- 
cylinders  that  stained  black  and  were  associated  with  a  number 
of  ramifying  varicose  nerve  -  fibrils,  of  a  markedly  embryonic 
character.  These  fibrils  invaded  the  cicatricial  tissue  between 
the  two  stumps,  running  through  it  in  all  directions,  and 
interlacing  in  a  most  complex  fashion.  At  a  later  period  the 
peripheral  stump  is  also  invaded  by  fine  branching  nerve-fibrils, 
which  differ  from  those  which  run  in  the  scar  by  following  a 
longitudinal  course  between  the  residues  of  the  old  degenerated 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    237 

fibres.  Purpura  holds  that  the  newly  found  fibrils  come  from 
the  central  end  of  the  nerve,  and,  in  fact,  from  the  old  axis- 
cylinders.  At  a  later  stage,  in  place  of  the  fibrils  and  arranged 
like  them,  bundles  of  medullated  nerve-fibres  are  found  in  the 
cicatrised  tissue  and  in  the  peripheral  stump. 

Lastly,  A.  Perroncito  (1908)  made  a  careful  histological  study 
of  the   regeneration  of  cut  nerves,  using  particularly  Ramon  y 
Cajal's  photographic   method.     He    too   concluded    that   the  re-    . 
generation  of  nerve-fibre  is  exclusively  the  work  of  the  central    \ 
stump.     He   brought  out  the  remarkable  fact  that,  regenerative 
changes  in  the  fibrils  occur  within  a  few  hours  of  the  injury  in 
the  central  end  of  cut  nerve,  far  more  rapidly  than  was  formerly 
supposed.     The  regenerative  process  is  manifested  by  a  numerous 


FIG.  150.— Three  nerve-fibres  from  central  end  of  do.^'s  sciatic  at  different  periods  after  section. 
The  axon  shows  different  forms  of  regenerating  fibrils.  (Perroncito.)  The  upper  fibre  comrs 
from  a  nerve  divided  six  hours,  the  centre  fibre  seventeen  hours,  the  lowest  fibre  forty-eixht 
hours  previous  to  preparation. 

and  varied  formation  of  fibrils,  derived  from  the  central  stumps 
of  the  axis-cylinders  which  had  degenerated  for  a  greater  or  less 
distance  (but  never  more  than  a  few  millimetres)  from  the  point 
of  section.  This  degeneration  ceases  at  a  point  of  the  fibre  which 
does  not,  according  to  Perroncito  but  contrary  to  the  opinion  of 
others,  correspond  with  a  node  of  Ranvier:  at  this  point  the 
end  of  the  axis -cylinder  a  few  hours  after  section  exhibits  a 
fusiform  or  cylindrical  swelling,  in  which  a  fibrillary  structure 
is  quite  apparent  (Fig.  149).  The  formation  of  new  fibres,  most 
of  which  as  they  grow  advance  towards  the  periphery,  proceeds 
rapidly  from  this  swelling  or  the  part  of  the  axis  -  cylinder 
immediately  above  it.  Some  force  their  way  through  the  neuro- 
lemma  into  the  old  fibres.  All  of  them  exhibit  characteristic 
bulbous  or  spiral  endings  (Fig.  150).  Twenty-four  hours  after 
the  lesion,  in  young  animals,  these  regenerated  prolongations  have 
already  passed  the  confines  of  the  old  central  stump,  and  penetrated 


238 


PHYSIOLOGY 


CHAP. 


the  blood-clot  of  the  wound  and  the  clumps  of  leucocytes  found 
at  the  extremity  of  the  central  stump  of  the  cut  nerve. 

During  the  third  or  fourth  days  after  section  the  process  of  re- 
generation proceeds  no  less  rapidly ;  the  central  end  is  surrounded 
by  a  mass  of  newly  formed  connective  tissue  which  is  permeated 


%-,  #fefeg§S5=3S?%S 


'r*    'i-«f>-<   •  '-     -•  it  Jf  ^.'  ~  •    f^f~i-~f-^m.7 — -v^ 


^^^s^^^^^^^^^^^s^^^ 


FIG.  151.  —  Extreme  end  of  central  stump  and  portion  of  cicatrix  (semi-diagrammatic)  twenty 
days  after  section.  (Perroncito.)  The  regenerated  fibrils  from  the  nerve-fibres  of  the  central 
stnmp  in  the  first  zone  of  the  cicatrix  interlace  and  run  in  all  directions  ;  in  the  next  zone  they 
niaUf  a  number  of  spiral  formations  ;  lastly,  they  form  a  fibrillary  interlacement  like  a  network, 
which  fills  flip  middle  part  of  the  cicatrix.  This  apparent  network  again  gives  rise,  in  the 
outer  part  of  the  cicatrix,  to  slender  bundles  of  new  fibrils,  which  run  singly  in  the  longitudinal 
direction,  and  begin  to  reconstitute  the  peripheral  part  of  the  divided  nerve. 

in  all  directions  by  a  great  number  of  new  fibres  that  run  mainly 
along  the  axis  of  the  old  nerve.  Twenty  to  thirty  days  after  the 
section  the  regenerating  fibres  travelling  towards  the  peripheral 
stump  are  once  more,  to  a  large  extent,  made  up  into  definite 
bundles,  while  the  spiral  regenerative  formations  have  attained 
their  maximal  development  (Fig.  151).  Thus  we  have  an 


iv    GENEEAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    239 

anatomical  recovery  of  the  cut  nerve,  since  the  newly  formed 
nerve-fibres,  after  passing  through  the  cicatrised  tissue  and 
repeatedly  dividing  into  branches,  rejoin  the  peripheral  stump 
and  run  through  it,  between  the  old  degenerating  fibres.  The 
newly  formed  nerve-fibres,  including  even  the  most  delicate,  are 
invariably  continuous  from  the  outset,  as  if  there  were  no 
formation  of  nerve-fibres  other  than  those  coming  from  the 
central  stump  of  the  cut  nerve. 

Perroncito  observed  that,  while  the  functional  recovery  of  the 
nerve  was  intimately  connected  with  the  scar  formation,  it  may, 
under  certain  conditions,  be  independent  of  it.  He  saw,  for 


FIG.  152. — Dog  in  which  all  the  IUTVCS  of  the  right  hind-leg  were  destroyed.     After  some  months 
it  showed  no  defect  in  progression.     (Purpura.) 

example,  that  the  conduction  of  electrical  excitation  reappears 
earlier  in  the  peripheral  part  than  at  the  scar,  which  would 
explain  Bethe's  experimental  results.  He  brings  out  the  fact  that 
functional  recovery  is  not  exclusively  and  necessarily  associated 
with  anatomical  regeneration  since  it  can  be  simulated  by  the 
existence  of  collateral  nerve  paths. 

Sometimes,  particularly  in  young  animals,  Purpura  noticed  a 
rapid  and  more  or  less  complete  functional  recovery,  which  he 
attributed  to  a  process  of  collateral  compensation.  In  all  cases 
in  which  he  observed  slow  functional  recovery  he  attributes  this 
to  regeneration  of  the  nerve-fibres.  To  ascertain  whether  the 
more  rapid  recovery  is  due  to  collateral  paths,  Purpura  operated 
on  puppies  by  cutting  all  the  nerves  to  the  hind -limb,  and 
obtained  complete,  though  retarded,  return  of  function,  i.e.  of 
perfect  co-ordination  in  walking,  as  partially  shown  in  Fig.  152. 

In    addition    to    his    experimental    investigations    into    the 


240 


PHYSIOLOGY 


CHAP. 


functional  recovery  of  a  cut  and  sutured  nerve,  Purpura  made 
some  interesting  clinical  applications  of  his  conclusions  on  nerve 
regeneration.  He  demonstrated  the  possibility  of  recovery  of 
function  on  crossing  two  different  nerves.  In  a  patient  affected 
with  facial  paralysis,  which  resisted  medical  treatment  (Fig.  153), 
he  made  a  crossing  of  the  outer  branch  of  the  spinal  accessory 
nerve  with  the  facial  (May  1909).  Forty  days  after  the  operation 
a  slight  correction  of  the  facial  asymmetry  was  perceptible ;  after 
two  and  a  half  months  it  was  practically  cured  (Fig.  154).  At  the 
close  of  1909  the  invalid  besun  to  exhibit  associated  movements 

o 


FIG.  153.— Complete  paralysis  of  left  facial  nerve  previous  to  operation.     (Purpura.) 

of  the  shoulder  and  the  muscles  innervated  by  the  facial.  In  the 
early  months  of  1910  the  movements  were  associated  when  they 
were  sharp  and  sudden,  but  the  patient  was  able  to  dissociate 
them  when  she  fixed  her  attention  on  them.  By  the  second  half 
of  that  year  she  was  always  able  to  dissociate  them. 

More  recently  (1910)  Modena  instituted  histological  investiga- 
tions with  Donaggio's  method  upon  the  regenerative  phenomena 
in  divided  nerve,  and  his  results  agree  fundamentally  with  those 
of  Purpura  and  Perroncito. 

VII.  Special  interest,  from  both  the  theoretical  and  the 
practical  standpoint,  attaches  to  the  study  of  the  changes  which 
the  nerve  undergoes  when  any  part  of  it  is  exposed  to  the  action 
of  a  constant  current.  These  changes  appear  as  physical  electro- 
motive and  physiological  phenomena,  and  consist  in  profound 
alterations  of  the  excitability  and  conductivity  of  the  nerve. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    241 


The  former  were  discovered  in  1.843  by  Du  Bois-Reymond,  who 
gave  the  name  of  electrotonus  to  the  special  electrical  state  produced 
by  the  passage  of  a  galvanic  current,  in  both  the  intrapolar  and 
the  extrapolar  parts  of  a  nerve.  The  latter,  which  were  accurately 
described  by  Pfliiger  in  1859,  are  more  properly  termed  electro- 
tonic  alterations  of  the  excitability  and  conductivity  of  nerve. 
Both  these  effects  are  in  reality  manifestations  of  the  chemical 
phenomena  of  electrolysis  and  polarisation. 

We  know  that  the  passage  of  a  galvanic  current  through  a 
moist  conductor  is  accompanied  by  phenomena  of  electrolysis  and 


FIG.  154. — Correction  of  the  facial  paralysis  two  and  a  half  months  after  the  crossing  of  the 
external  branch  of  the  spinal  accessory  with  the  facial.     (Purpura.) 

dissociation,  which  reach  their  maximal  development  at  the 
points  of  entry  and  exit  of  the  current,  i.e.  at  the  electrodes. 
When  the  current  passes  through  a  moist  conductor,  the  presence 
of  electrolytes  (i.e.  the  molecules  of  a  neutral  salt  in  solution) 
renders  the  fluid  acid  at  the  anode  and  alkaline  at  the  kathode 
owing  to  the  transport  of  the  acid  negative  ions  to  the  positive  pole, 
and  of  the  basic  positive  ions  to  the  negative  pole  of  the  current. 
If  after  a  prolonged  passage  of  current  through  the  fluid  the 
electrodes  are  disconnected  with  the  cell  and  connected  to  a 
galvanometer,  a  so-called  "  polarisation  current "  is  seen  in  the 
opposite  direction  to  the  polarising  current ;  this  is  due  to  the 
accumulation  of  positive  ions  at  the  kathode  and  negative  ions  at 
the  anode  of  the  polarising  current. 

Since  nerve  is  a  moist  conductor,  the  passage  of  a  galvanic 

VOL.  Ill  R 


242 


PHYSIOLOGY 


CHAP. 


current  through  it  must  be  accompanied  by  these  polarisation 
phenomena. 

When  metal  electrodes  are  applied  to  a  nerve,  the  principal 
seat  of  polarisation  is  the  surface  of  contact  of  the  electrodes 
with  the  fluids  of  the  nerve,  which  is  therefore  called  external 
polarisation.  The  intensity  of  this  polarisation  can  be  reduced 
by  employing  currents  of  very  brief  duration  (induced  currents), 
alternating  in  direction,  and  of  approximately  equal  strength 
(sinusoidal  currents).  It  can  be  practically  abolished  by  using 
unpolarisable  electrodes  (see  Fig.  45,  p.  71). 

When  a  current  is  passed  through  a  nerve  by  means  of 
unpolarisable  electrodes,  so  that  external  polarisation  is  abolished, 
internal  polarisation,  so-called,  will  still  be  manifested;  it  is 
specially  conspicuous  in  nerves  with  medullated  fibres,  and  arises 
from  their  peculiar  structure.  In  this  case,  too,  the  electrolytic 


Nerve. 


Anelectrotonic. 
current. 


Polarising 
current. 


Katelectrotonic 
current. 


FIG.  155.— Diagram  of  electrotonic  currents,  to  show  polarising  current  thrown  into  median 
portion  of  an  exposed  nerve;  anelectrotonic  current  led  on'  to  galvanometer  from  anodal 
portion  ;  katelectrotonic  current  led  off  to  galvanometer  from  kathodal  portion  of  the 
nerve.  (Waller.) 

effects  of  the  passage  of  current  are  more  pronounced  at  the 
poles,  i.e.  at  the  points  of  entrance  (anode)  and  exit  (kathode]  of 
the  current,  whence  they  spread  with  diminishing  intensity,  not 
only  in  the  intrapolar,  but  also  in  the  extrapolar  parts  of  the 
nerve.  The  displacement  of  the  electrolytic  products  or  ions  in 
the  direction  of  the  poles  during  closure  of  the  current  is  shown 
in  the  intrapolar  tract  by  a  rise  of  electrical  resistance  (diminished 
current  intensity)  and  in  the  extrapolar  tracts  by  electrical 
currents  which  are  in  the  same  direction  as  the  polarising  current 
when  led  off  to  the  galvanometer  (Fig.  155).  These  currents  are 
known  as  anelectrotonic  currents  in  the  extrapolar  tract  corre- 
sponding to  the  anode,  and  katelectrotonic  currents  in  the  part 
corresponding  to  the  kathode. 

The  strength  of  the  electrotonic  currents  increases  with  the 
strength  of  the  polarising  current,  with  diminished  distance 
between  the  galvanometer  electrodes  and  those  of  the  cell,  lastly, 
with  increased  length  of  the  intrapolar  tract.  They  do  not 
appear  when  the  polarising  current  is  passed  transversely  through 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    243 

the  nerve ;  when  the  nerve  is  tied,  bruised,  or  its  physiological 
conductivity  in  any  way  interrupted ;  and  when  the  nerve  is 
degenerated,  exhausted,  or  dead. 

Anelectrotonic  are  stronger  than  katelectrotonic  currents ;  the 
former  gradually  increase  during  the  passage  of  the  polarising 
current,  while  the  latter  gradually  decline.  On  cooling,  both 
decline  to  the  point  of  total  disappearance.  The  maximum 
intensity  of  the  electrotonic  currents  may  exceed  that  of  the 
demarcation  currents  by  more  than  twenty-five  times. 

Electrotonic  currents  alter  in  direction  when  the  polarising 
current  is  reversed ;  they  persist  during  the  whole  time  of  the 
passage  of  the  polarising  current,  and  their  intensity  decreases 
along  the  extrapolar  tracts  in  proportion  with  the  distance  from 
the  poles.  These  characters  distinguish  the  electrotonic  currents 
sharply  from  the  action  currents,  which,  as  we  have  seen,  are 
constant  in  direction,  and  arise  from  the  active  state  or  excitation 


rdh 

LJ 


FIG.  156.— Diagram  of  the  electrotonic  currents  which  summate  algebraically  with  the 
demarcation  currents  in  a  length  <>t'  rxcised  nerve.     (Luciani.) 

of  the  nerve,  independently  of  the  nature  of  the  stimulus,  and  of 
the  direction  of  the  exciting  current  when  an  electrical  stimulus 
is  employed. 

When  the  polarising  current  is  sent  into  an  excised  nerve,  from 
which  demarcation  currents  can  be  led  off  to  the  galvanometer, 
these  summate  algebraically  with  the  electrotonic  currents,  which 
are  accordingly  reinforced  if  in  the  same  direction  as  the  demarca- 
tion currents, — weakened  or  reversed,  if  the  latter  are  in  the 
opposite  direction  (see  Fig.  156).  These  phenomena  were 
formerly  known  as  the  positive  and  negative  phases  of  electrotonus, 
an  unfortunate  expression  as  the  electrotonic  phenomena  are 
entirely  independent  of  the  demarcation  currents. 

The  fundamental  phenomena  of  electrotonus  can  be  reproduced 
on  very  simple  models.  As  early  as  1863  Matteucci  observed 
that  the  electrotonic  currents  in  both  intrapolar  and  extrapolar 
portions  of  the  nerve  can  be  demonstrated  in  all  essential 
particulars  if  the  galvanic  current  is  led  through  a  platinum  wire 
surrounded  by  a  porous  sheath  saturated  with  fluid,  instead  of 
through  a  nerve.  Hermann,  Griinhagen,  Hering  confirmed 
Matteucci's  observations  by  means  of  slightly  different  models. 


244  PHYSIOLOGY  CHAP. 

Hermann's  model  consists  of  a  glass  tube  containing  a  platinum 
wire,  which  makes  a  good  conducting  axis.  The  tube,  closed  at 
the  ends,  is  rilled  with  a  saturated  solution  of  zinc  sulphate,  which 
forms  a  moist,  less  well-conducting  sheath  for  the  axis.  A  pair  of 
zinc  electrodes  are  fastened  to  the  tube,  which  are  in  contact  with 
the  solution,  and  serve  as  the  polarising  and  galvanometer  contacts. 
The  electrolytic  polarisation  which  takes  place  during  the  passage 
of  the  current  between  the  surface  of  the  metallic  core  and 
the  solution,  and  drives  the  kathodic  ions  towards  the  anode  and 
the  anodic  ions  towards  the  kathode,  generates  a  resistance  to  the 
passage  of  the  current  through  the  intrapolar  portion  by  which 
its  longitudinal  diffusion  in  the  extrapolar  parts  is  promoted. 

Both  in  the  nerve  and  in  Hermann's  model,  polarisation  or 
post-electrotonic  currents  are  produced  on  breaking  the  polarisa- 
tion circuit.  These  are  opposite  in  direction  to  the  electrotonic 
currents,  and  are  due  to  the  accumulation  of  ions  with  the  opposite 
charge  at  either  pole  of  the  battery.  The  reversal  of  current  at 
the  close  of  electrotonus  was  demonstrated  on  nerve  by  Pick,  but 
according  to  Hermann  it  is  definite  only  in  the  anelectrotonic 
region. 

Notwithstanding  the  analogy  between  the  electrotonic  pheno- 
mena in  nerve  and  those  which  can  be  reproduced  in  the  core- 
model,  there  is  no  doubt  that  the  former  depend  not  only  upon 
physical  conditions,  but  also  upon  the  anatomical  and  physiological 
integrity  of  the  nerve. 

Biedermann  pointed  out  the  differences  between  the  electrotonic 
phenomena  in  normal  and  in  etherised  nerve.  In  a  normal  nerve 
traversed  by  a  polarising  current  the  extrapolar  electrotonic  effects 
from  two  points  ecpuidistant  from  the  poles  are  not  equal  on  the 
galvanometer.  In  one  case  Biedermann  found  that  anelectrotonus, 
as  expressed  by  the  deflection  of  the  galvanometer  needle,  was 
equal  to  46  and  katelectrotonus  to  a  deflection  of  25 ;  on 
increasing  the  strength  of  the  polarising  current  he  obtained 
anelectrotonus  of  96,  katelectrotonus  of  60.  On  etherising  the 
nerve  these  differences  disappeared ;  with  the  first  current  the 
galvanometer  deflection  was  24  in  both  the  anodic  and  the 
kathodic  region  ;  with  the  second  current  it  was  68  for  the  former, 
66  for  the  latter.  Biedermann  took  these  results  obtained  with 
etherised  nerve  to  be  the  expression  of  the  physical  electrotonus 
due  to  polar  electrolytic  effects,  and  those  obtained  with  normal 
nerve  to  be  the  expression  of  physiological  electrotonus  due  to 
special  vital  conditions  which  make  anelectrotonus  more  pro- 
nounced than  katelectrotonus.  He  further  showed  that  the  effects 
of  anelectrotonus  spread  over  a  larger  area  in  normal  than  in 
etherised  nerve. 

These  observations  of  Biedermann  are  supported  by  Waller, 
who  found  that  anaesthetics,  and.  all  agents  in  general  that 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    245 

influence  the  electrical  reaction  of  nerve,  are  also  capable  of 
temporarily  suppressing  electrotonus. 

Besides  the  electrotouic  phenomena  strictly  so-called,  polarising 
currents  evoke  other  parallel  specific  changes  of  excitability  and 
conductivity  in  both  the  intrapolar  and  the  extrapolar  portions  of 
the  nerve.  We  owe  our  knowledge  of  the  principal  phenomena 
of  this  subject  to  Pfliiger,  who  followed  up  the  earlier  researches 
of  Bitter,  Nobili,  Matteucci,  Valentin,  and  Eckhard.  The  main 
facts  in  regard  to  the  electrotonic  changes  of  the  excitability  of 
nerve  are  as  follows  :— 

(«)  The  passage  of  a  constant  current  through  a  nerve  causes  a 


s.c. 


Fio.  157.— Diagram  to  show  electrotonic  modifications  of  excitability,  according  to  ascending  or 
descending  direction  of  polarising  current.  (Waller.)  p.c.,  polarising  current ;  s.c.,  exciting 
current  :  HI.,  muscle.  In  the  upper  diagram  the  direction  of  the  polarising  current  is  ascending, 
and  excitability  is  therefore  lowered  in  the  anelectrotonic  region  ;  in  the  lower  diagram  the 
direction  of  the  polarising  current  is  descending,  and  excitability  is  therefore  raised  in  the 
katelectrotonic  region  of  the  nerve. 

rise  of  excitability  at  the  kathode  and  a  fall  of  excitability  at  the 
anode. 

(&)  These  changes  in  excitability  are  most  marked  at  the  poles, 
but  they  also  spread  into  the  intra-  and  extra-polar  regions, 
Crowing  weaker.  There  is  in  the  intrapolar  portion  an  indifferent 
point,  at  which  excitability  remains  unaltered. 

(c)  When  the  current  that  sets  up  electrotonus  ceases  the 
alterations  of  excitability  are  reversed;  the  kathodic  region 
becomes  less  excitable,  the  anodic  region  more  so. 

The  nerve -muscle  preparation  of  the  frog  is  generally  used 
in  experimental  demonstration  of  these  electrotonic  changes  in 
excitability.  According  as  the  polarising  current  is  passed  in  an 
ascending  or  a  descending  direction  through  the  nerve,  the 
anelectrotonic  or  katelectrotonic  region  will  be  found  nearer-  the 
muscle.  In  order  to  show  that  excitability  is  depressed  in  the 
former  and  raised  in  the  latter,  the  nerve  is  excited  near  the  anode 
or  kathode  respectively,  either  by  an  induction  current  (as  in  Fig. 


246 


PHYSIOLOGY 


CHAP. 


157)  or  with  mechanical  or  chemical  stimuli.  The  strength  of 
the  muscular  response,  recorded  on  a  revolving  cylinder,  is  found 
to  be  diminished  when  the  nerve  is  stimulated  in  the  region  of  the 
anode,  increased  when  excited  near  the  kathode. 

A  curve  of  the  katelectrotonic  and  anelectrotonic  alterations 
of  excitability  corresponding  with  the  kathodic  and  anodic  regions 
can  be  constructed  by  comparing  the  muscular  responses  obtained 
by  exciting  different  parts  of  the  anodic  and  kathodic  regions. 
The  form  and  height  of  the  negative  and  positive  excursions  of 
this  curve  alter,  according  to  Prluger's  comprehensive  researches, 
with  the  strength  of  the  polarising  current,  and  the  degree  of 
excitability  of  the  nerve  experimented  on.  It  is  further  found 
that  when  the  polarising  current  is  weak  the  indifferent  point  in 
the  iutrapolar  tract  lies  near  the  anode,  and  in  proportion  as  the 


FIG.  loS. — Diagram  of  electrotonic  changes  of  excitability  in  the  infra-  and  extra-polar  portions  of 
the  nerve.  (Pfliiger.)  a,  position  of  anode  ;  /,-,  position  of  kathode  ;  a,  k,  intrapolar  portion. 
The  three  curves,  j/j,  //.,,  i/:i,  represent  the  electrotonic  effects  of  weak,  medium,  or  strung 
currents.  The  .points,  .1],  .1-.',,  ,>.,.  show  the  relative  position  of  the  indifferent  points  with  tin- 
three  currents.  The  portions  of  the  curves  below  the  abscissa  express  the  anelectrotonic 
diminution  of  excitability  ;  the  portions  of  the  curves  that  rise  above  the  abscissa  express  the 
katelectrotonic  increase  of  excitability. 

strength  of  the  current  increases  it  shifts  towards  the  kathode. 
All  these  facts  are  represented  in  the  diagram  of  Fig.  158. 

Griinhagen's  researches  show  that  both  the  kathodic  rise  and 
the  anodic  fall  of  excitability  occur  at  the  poles  without  any 
appreciable  delay  after  closure  of  the  circuit.  The  electromotive 
effects  due  to  polarisation,  on  the  contrary,  appear  in  the  im- 
mediate vicinity  of  the  poles  at  an  interval  of  O001  sec.  after 
closure  of  a  very  brief  current. 

On  the  strength  of  the  facts  at  present  known  the  electro- 
motive effects  and  electrotouic  alterations  of  excitability  appear 
not  to  be  strictly  synchronous.  But  seeing  the  parallelism  of  the 
two  classes  of  phenomena,  it  is  natural  to  surmise  that  there  is  a 
close  connection  between  them,  and  probably  a  relation  of  cause 
and  effect. 

The  alterations  of  excitability  that  occur  on  breaking  the 
polarising  circuit  must  be  regarded  as  the  effects  of  recovered 
equilibrium  in  the  nerve.  The  anodic  rise  and  kathodic  fall  of 
excitability  begin  at  the  poles  and  spread  thence  to  the  peri- 


iv     GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    247 

pheral  regions.  The  anodic  effect  is  more  pronounced  than  the 
kathodic. 

Conductivity  is  also  affected  by  the  passage  of  the  polarising 
current.  When  the  central  portion  of  a  nerve  is  excited  by  an 
electrical  stimulus  of  minimal  intensity,  and  the  galvanic  current 
then  passed  through  its  peripheral  part,  the  muscular  reaction 
diminishes  or  fails  altogether.  This  effect  persists  for  a  short  time 
after  opening  the  current. 

The  electrotonic  decrease  of  conductivity  is  greater  in  propor- 
tion to  the  strength  and  duration  of  the  polarising  current.  It 
appears  to  be  associated  with  the  fall  of  excitability  at  the  anode 
on  closing  the  circuit,  which  is  not  compensated  by  the  rise  of 
excitability  and  conductivity  at  the  kathode.  This  can  be 
demonstrated  as  follows :  A  polarising  current  is  sent  through  the 


s.c. 


FIG.  159. — Diagram  of  tripolar  application  of  polarising  current  to  nerve.  (Danilewsky.) 
s.c.,  exciting  current ;  m,  muscle  ;  a,  k,  lateral  electrodes  joined  together,  connected  with 
kathode  ;  c,  central  electrode  connected  with  anode. 

frog's  nerve-muscle  preparation  by  means  of  three  electrodes  (as 
shown  in  Fig.  159),  the  two  side  electrodes  being  connected  with 
the  kathode  of  the  cell  and  the  middle  electrode  with  the  anode. 
In  this  case  the  katelectrotonic  effect  prevails  over  the  auelectro- 
tonic,  because  the  kathodic  region  is  more  extended  than  the  anodic. 
If  a  point  of  the  nerve  remote  from  the  muscle  be  now  excited  the 
response  of  the  muscle  is  greater  than  usual,  owing  to  the  kat- 
electrotonic rise  of  excitability  and  conductivity.  If  the  experi- 
ment is  reversed  by  putting  two  positive  electrodes  at  the  sides 
and  one  negative  in  the  middle,  the  opposite  result  appears,  i.e. 
the  response  of  the  muscle  is  less  than  normal,  owing  to  the 
preponderance  of  anelectrotonus  over  katelectrotonus. 

The  polar  electrotonic  changes  affect  not  only  the  amplitude 
of  the  reaction,  but  also  the  velocity  of  conduction.  On  closing 
the  polarising  circuit  there  is  acceleration  at  the  kathode  and 
delay  at  the  anode,  except  where  the  effects  at  the  two  poles  are 
in  perfect  equilibrium,  when  the  rate  of  conduction  remains 


243 


PHYSIOLOGY 


CHAP. 


unaltered.  The  reversed  polar  changes  on  opening  the  circuit 
also  affect  the  rate  of  conductivity ;  in  the  region  in  which 
excitability  is  increased  conductivity  is  also  accelerated. 

All  these  data  in  regard  to  the  polar  effects  of  the  constant 
current  are  founded  on  experiments  specially  made  on  frogs'  nerves. 
Many  workers  since  Helmholtz  have  attempted  to  reproduce  the 
same  electrotonic  phenomena  upon  man,  but  the  results  have  been 
variable  and  uncertain.  Waller  and  De  Watteville  alone  succeeded 
in  showing  that  electrotonus  follows  the  same  laws  in  man  as  in 
other  animals,  the  only  difference  being  that  the  polar  changes  are 
less  marked  with  different  modes  of  sending  in  the  current. 

VIII.  In  speaking  of  the  polar  changes  of  excitability  and 
conductivity  in  nerve  during  the  passage  of  a  constant  current 
we  have  confined  ourselves  to  the  excitatory  influence  of  this 
current  upon  the  nerve  at  make  and  break,  i.e.  when  its  action 
upon  the  nerve  begins  and  ceases.  These  excitatory  effects  are 
expressed  in  the  muscular  contractions  that  occur  at  these  two 
moments.  According  to  the  strength  of  the  polarising  current, 
and  its  ascending  or  descending  direction  in  the  nerve,  it  is 
possible  to  obtain  break  as  well  as  make  contractions,  or  break  or 
make  contractions  only.  The  regular  order  in  which  these  signs 
of  nervous  excitation  occur,  and  the  explanation  of  their  occurrence 
by  the  laws  of  electrotonus,  constitute  what  is  known  as  "  Pfliiger's 
law  of  contractions,"  as  in  the  following  table : — 


Ascending  Direction. 

Descending  Direction. 

Strength  of 

Gum-lit. 

Closing. 

Opening. 

Closing. 

Opening. 

Weak 

Weak  contrac- 

Weak contrac- 

tion 

tion 

Medium 

Strong  con-         Weak  contrac- 

Strong  con- 

Weak contrac- 

traction                    tion 

traction 

tion 

Strong 

Weak  contrac-        Strong  con- 

Strong  con- 

Weak contrac- 

tion 

traction 

traction 

tion 

Very 

Strong  con- 

Strong con- 

strong 

traction 

traction 

These  experimental  data,  which  together  constitute  the  Law  of 
contractions,  are  expressed  in  the  diagram  of  Fig.  160. 

The  results  obtained  with  weak  and  moderate  currents  are 
readily  interpreted  if  we  assume  with  Pfliiger  that  they  depend  on 
rise  of  excitability  in  the  nerve  at  the  kathode  (katelectrotouus), 
which  takes  place  so  abruptly  on  closure  of  the  circuit  that  it 
causes  excitation,  no  matter  what  the  direction  of  the  current  may 
be.  The  anodal  rise  of  excitability  which  occurs  on  opening  the 
circuit,  owing  to  the  disappearance  of  anelectrotonus,  is  less 
effective  than  the  kathodal  rise  at  closure.  This  explains  why  the 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    249 

break  of  weak  currents  produces  uo  excitation,  and  why  at  break 
the  contraction  is  relatively  less  marked  with  moderate  currents 
than  it  is  at  make. 

The  excitation  caused  by  stimulating  with  strong  or  very 
strong  currents  requires  a  more  elaborate  explanation.  In  this 
case,  also,  the  nerve  is  excited  at  the  kathode  at  make  and  at  the 
anode  at  break  of  the  circuit.  The  excitation,  moreover,  increases 
in  proportion  to  the  strength  of  the  current.  But  for  a  motor 

Ascending  cmivnts  Descending  currents 

t  ! 


Wrak  r  I  -  SAS  \  \  Weak 


Medium  I  I  5MB  SHfi   9  '  Medium 


Strung  C  \  SM  5BS  BBB  1  Strong 


strong  strong 


t  I  t  1 

Make  Break  Make  Break 

Fi(3.  160. — Pfliiger's  Law  of  Contractions. 

nerve,  the  kathodal  excitation  at  make  with  an  ascending 
direction  of  current  must,  in  order  to  reach  the  muscle,  pass 
through  the  auodal  region,  in  which — as  we  have  seen — con- 
ductivity is  greatly  depressed.  This  explains  why  in  such  a 
case  the  make  contraction  is  either  very  feeble — with  strong 
currents,  or  fails  altogether — with  very  strong  currents.  So,  too, 
the  anodal  excitation  at  break,  in  order  to  reach  the  muscle, 
must  with  a  descending  current  traverse  the  kathodal  region,  in 
which  (owing  to  the  disappearance  of  katelectrotonus)  conductivity 
is  much  diminished.  This  explains  the  weak  contraction  that 
appears  at  break  of  strong  descending  currents,  and  which  may 
fail  altogether  when  very  strong  currents  are  employed. 


250  PHYSIOLOGY  CHAP. 

The  same  law  of  contraction  applies  to  sensory  or  afferent 
nerves.  In  this  case  the  reflex  muscular  response  is  taken  as 
the  measure  of  excitation  in  the  nerve.  Here  the  results  must 
of  course  be  inverted,  the  reflex  contractions  excited  from  sensory 
nerves  with  ascending  and  descending  currents  following  the 
law  of  motor  nerves  for  the  descending  or  ascending  currents 
respectively. 

The  expressions  adopted  in  the  formula  of  the  law  of  con- 
traction, of  weak,  medium,  strong,  or  very  strong  currents,  have 
only  a  relative  value,  since  the  local  phenomena  of  excitation  due 
to  polar  changes  depend  not  only  on  the  strength,  direction,  and 
duration  of  the  current,  but  also  on  the  initial  excitability  and 
the  length  of  nerve  traversed  by  the  current.  It  has  been  shown 
that  polar  electrical  stimulation  is  more  effective  as  the  electrodes 
are  further  apart,  because  the  changes  in  the  equilibrium  of  the 
nerve  are  so  much  the  more  difficult  to  compensate. 

All  the  phenomena  of  Pfliiger's  law  come  off  equally  well  with 
tripolar  excitation  of  the  nerve,  as  in  Fig.  160.  The  nerve  is  even 
more  sensitive  to  this  form  of  stimulation,  probably  owing  to  the 
larger  area  of  the  intrapolar  tract,  so  that  currents  which  were 
ineffective  with  ordinary  bipolar  contacts  may  become  effective. 

There  may  be  exceptions  to  Pfliiger's  law  owing  to  the  influence 
of  accessory  factors.  Such  are  the  local  alterations  of  excitability 
due  to  the  effect  of  temperature,  to  salt  solutions,  to  interference  or 
coincidence  of  the  polarising  current  and  the  demarcation  current, 
etc.  When,  for  instance,  the  kathode  is  close  to  the  section  in  a 
freshly  divided  nerve,  a  break  contraction  can  be  obtained  not 
only  with  medium,  but  also  with  weaker  currents/  which  are 
usually  ineffective.  This  is  because  in  such  a  case  the  descending 
break  current  summates  with  the  demarcation  current,  which  is 
also  descending.  When,  on  the  contrary,  the  two  currents  are 
opposite  in  direction,  the  effects  are  neutralised.  It  can,  in  fact, 
be  demonstrated  experimentally  that  a  vigorous  demarcation 
current  is  able  to  annul  the  exciting  action  of  a  weak  polarising 
current  in  the  opposite  direction  (Hering). 

The  polarisation  after-effect,  which  appears  in  the  nerve  after 
the  passage  of  a  polarising  current  of  sufficient  strength  and 
duration,  may  both  at  make  and  at  break  render  another  current 
in  the  same  direction  effective  when  the  latter  is  too  weak  to 
produce  any  excitation  alone.  The  break  contraction  resulting 
in  this  case  may  be  taken  as  a  proof  of  the  fact  that  the  disappear- 
ance of  anelectrotonus  is  as  capable  of  arousing  excitation  as  the 
appearance  of  katelectrotonus. 

The  polarisation  after-current  on  the  passage  of  a  strong 
polarising  current  may  itself  cause  a  prolonged  excitation 
expressed  by  the  persistent  contraction  of  the  muscle.  This 
phenomenon  is  known  as  Ritter's  opening  tetanus.  It  is  seen 


iv    GENEEAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    251 


with  an  ascending  polarising  current,  and  depends  upon  excitation 
at  the  former  anode,  as  is  also  proved  by  the  fact  that  division  of 
the  nerve  in  the  intrapolar  tract  during  tetanus  is  not  enough  to 
abolish  it. 

The  closing  contraction  of  a  polarising  current  may  also, 
under  special  conditions  of  exaggerated  local  excitability  of 
nerve,  be  transformed  into  a  closure  tetanus  when  the  direction 
of  the  current  is  descending.  This  phenomenon  evidently 
depends  on  persistence  of  kathodal  excitation. 

Waller  and  De  Watteville  (1882)  devoted  much  time  to 
verifying  Pfltiger's  law  for  man.  The  study  of  the  polar 
phenomena  on  man  presents  special  complications,  owing  to  the 
presence  of  the  tissues  by  which  the  nerve  is  surrounded.  In  the 
frog's  nerve  the  polarising  current  is  applied  directly,  the  poles 
being  set  far  enough  apart  to  keep  the  kathodal  and  anodal 


FIG.  161. — Diagrams  to  show  the  spread,  or  concentration,  of  a  polarising  current  that  enters  or 
leaves  the  skin  by  a  series  of  points  above  a  nerve,  over  which  the  anode  (A)  or  kathode  (A")  of 
a  battery  is  applied.  (Waller.) 

influences  distinct.  In  man,  on  the  contrary,  the  current  must 
be  sent  in  through  the  skin,  and  before  reaching  the  nerve  it  has 
to  pass  through  all  the  tissues  which  lie  above  it.  Peripolar 
regions  are  thus  formed  more  or  less  extensively  round  the  poles, 
which  make  it  futile  to  apply  the  two  electrodes  to  the  same 
nerve,  since  the  kathodal  and  anodal  regions  cannot  be  kept 
distinct,  nor  can  the  direction  of  current  strictly  speaking  be 
called  ascending  or  descending.  It  is,  therefore,  necessary  to 
employ  Chauveau's  method  of  unipolar  stimulation,  in  which 
one  electrode  is  placed  upon  the  skin  above  the  nerve  and  the 
other  applied  to  a  distant  point  of  the  body.  When  the  anode 
is  applied  to  the  nerve,  the  current  enters  by  a  series  of  points, 
over  a  considerable  length  of  the  nerve,  and  leaves  by  another  no 
less  extensive  series  of  points  (Fig.  161  A).  The  former  constitute 
the  anodal  polar  region,  the  latter  the  kathodal  peripolar  region. 
When,  on  the  contrary,  the  kathode  is  applied  to  the  skin  over 
the  nerve,  the  opposite  phenomena  occur  (Fig.  161 K).  The 
current  which  is  widely  diffused  in  the  body  is  thus  concentrated 
at  the  points  of  exit  from  the  body  which  form  the  kathode.  Its 


252 


PHYSIOLOGY 


CHAP. 


density  is  therefore  greater  in  the  kathodic  polar  than  in  the 
anodic  peripolar  region. 

As,  therefore,  the  excitations  and  make  contraction  arise  at 
the  kathode,  and  the  excitation  and  break  contraction  at  the 
anode,  Waller  says  that  when  a  current  strong  enough  to  produce 
contraction  at  break  as  well  as  at  make  is  employed  for  unipolar 
stimulation  (anodal  or  kathodal)  the  kathodal  closure  contraction 
is  the  strongest ;  the  kathodal  opening  contraction  the  weakest. 
The  anodal  closure  contraction  is  less  strong  than  the  kathodal, 
and  the  anodal  opening  contraction  is  less  weak  than  the  kathodal. 

If  instead  of  using  strong  currents,  unipolar  stimulation 
commences  with  a  weak  current  that  is  gradually  strengthened, 
the  contractions  (auodal  and  kathodal  closure  and  opening)  appear 
in  the  following  order :— 


Weak  current 

Kathodal 

closure  contrac- 

tion 

Medium  current 

Kathodal 
closure  contrac- 

Anodal closure 
contraction 

Anodal  opening 
contraction 

Strong  current 

tion 
Kathodal 
closure  contrac- 
tion 

Anodal  closure 
contraction 

Anodal  opening 
contraction 

Kathodal 
opening 
contraction 

This  order  of  contractions  constitutes  what  Waller  calls  the 
"  law  of  contraction  in  man,"  which  may  be  interpreted  as  follows : 

The  fact  that  the  kathodal  make  contraction  is  the  first  to 
appear  with  weak  currents,  and  is  the  strongest  of  all  the  reactions 
with  medium  and  strong  currents,  is  due  to  its  dependence  upon 
the  katelectrotonus  that  arises  in  the  polar  regions,  i.e.  upon  the 
most  effective  form  of  stimulus  in  the  most  favourable  region. 
The  appearance  of  the  kathodal  break  contraction  with  strong 
currents  only,  while  it  is  the  weakest  of  all  the  reactions,  is  due 
to  its  dependence  upon  the  disappearance  of  katelectrotonus  in 
the  peripolar  region,  i.e.  on  a  less  effective  form  of  stimulus  in 
the  less  favourable  region.  That  the  anodal  make  contraction 
usually  precedes  the  anodal  break  contraction  can  be  explained  by 
the  fact  that  the  former  depends  on  the  appearance  of  katelectro- 
tonus in  the  peripolar  region,  the  latter  on  the  disappearance 
of  katelectrotonus  in  the  polar  region.  At  other  times,  indeed 
(Waller),  this  order  may  be  inverted,  and  the  anodal  break  con- 
traction may  precede  the  anodal  make  contraction.  This  anomaly 
is  only  an  apparent  deviation  from  the  law,  and  depends  on  the 
relative  density  of  current  in  the  two  regions,  due  to  the  nature 
of  the  tissues  that  surround  the  nerve. 

According  to  Waller,  the  latent  period  of  the  break  contraction 
in  man  is  constantly  about  0'05  sec.,  i.e.  it  is  extremely  long  in 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    253 

comparison  with  the  very  variable  latent  period  1'or  the  frog.  It 
is  also  a  striking  fact  that  when  strong  currents  are  used  con- 
tractions not  only  appear  at  make  and  break  of  the  current,  but 
there  is  frequently  a  tonic  contraction  or  galvanotonus  during  the 
whole  time  the  current  is  passing. 

The  law  of  contraction  in  man  is  of  great  practical  importance 
in  differentiating  between  normal  and  morbid  states  of  the  nerves, 
as  with  the  latter  the  above  reactions  may  be  deficient  or  absent, 
owing  to  depression  or  abolition  of  excitability  and  conductivity. 

The  so-called  reaction  of  degeneration  is  clinically  of  great 
interest.  It  occurs  when  the  muscle  and  nerve  degenerate, 
either  from  pathological  processes  in  the  trophic  centres,  or 
because  the  connections  of  the  latter  with  the  muscles  have  been 
interrupted  (neuritis,  compression  and  injury  of  the  nerves). 

Two  principal  forms  of  the  reaction  of  degeneration  can  be 
distinguished :  Erb's  reaction,  and  reaction  at  a  distance. 

(ft)  Erlfs  reaction  is  characterised  by  a  primary  phase  of 
increased  galvanic  excitability,  with  loss  of  direct  and  indirect 
faradic  excitability.  Later  on,  galvanic  excitability,  too,  disappears 
in  the  nerve,  and  the  contractions  obtained  on  exciting  the  muscle 
directly  become  slow,  prolonged,  and  irregular,  and  are  most 
marked  on  closure  at  the  anode  or  positive  pole ;  with  the 
advance  of  the  degenerative  process  stronger  and  stronger 
currents  are  required  to  excite  the  muscle,  till  finally  all  trace  of 
electrical  excitability  disappears. 

(&)  Reaction  at  a  Distance. — The  reaction  to  which  Ghilarducci 
(1895)  gave  this  name  is  constantly  exhibited  under  the  same 
pathological  conditions  as  Erb's  reaction.  To  demonstrate  it  the 
large  electrode  (indifferent  electrode)  is  placed  as  for  Erb's  reaction 
on  the  sternum  or  nape  of  the  neck ;  but  instead  of  applying  the 
exploring  electrode  to  the  surface  of  the  muscle  as  for  Erb's 
reaction,  it  is  placed  below  it  at  a  distance  so  much  the  greater 
from  the  peripheral  extremity,  as  the  tendon  of  the  muscle  to  be 
explored  is  shorter  and  the  patient  more  delicate  (e.g.  to  examine 
the  deltoid  in  children  of  less  than  a  year  old  the  exciting 
electrode  is  placed  upon  the  back  of  the  hand). 

"  Reaction  at  a  distance  "  is  distinguished  from  "  Erb's  reaction  " 
by  the  following  characteristics  :— 

(a)  The  muscular  contractions  constantly  predominate  at  the 
closure  of  the  negative  pole  ; 

(ff)  They  are  manifested  with  currents  three  to  four  times 
weaker  than  those  required  to  make  the  muscle  contract  with 
direct  excitation ; 

(y)  They  persist  long  (three  to  four  years)  after  every  trace 
of  electrical  excitability,  as  tested  by  classical  methods,  has 
disappeared. 

Reaction  at  a  distance  is  thus  of  far  greater  importance  than 


254  PHYSIOLOGY  CHAP. 

Erb's  reaction,  since  it  survives  for  a  long  time,  and  is,  in  ad- 
vanced stages  of  disease,  the  sole  means  of  proving  the  existence  of 
degenerative  processes. 

In  order  to  determine  more  exactly  what  changes  in  the  con- 
ductivity of  nerve  accompany  the  electrotonic  alterations  of 
excitability,  Novi  with  Brugia  (1890)  carried  out  a  series  of 
investigations  on  the  latent  period  by  direct  stimulation  of  motor 
nerves  in  a  state  of  electrotonus.  These  experiments  were  per- 
formed on  the  exposed  sciatic  of  the  dog  by  Chauveau's  unipolar 
method.  A  second  series  of  investigations  was  made  by  Brugia 
on  man  with  the  object  of  determining  the  degree  in  which  the 
electrotonic  alterations  of  excitability  affect  the  conductivity  of 
motor  nerves  left  in  normal  relation  with  the  surrounding  tissues. 
The  results  are  as  follows  :— 

(".)  In  the  isolated  nerve  of  the  dog  anelectrotonus  produces  a 
considerable  delay  in  the  rate  of  transmission ;  katelectrotonus,  on 
the  contrary,  accelerates  the  transmission  of  excitation,  excepting 
for  strong  currents,  when  it  is  retarded,  though  to  a  less  extent 
than  for  anelectrotonus. 

(&)  In  the  nerve  of  man  left  in  its  normal  relations  with  the 
surrounding  tissues,  both  katelectrotonus  and  anelectrotonus,  but 
the  latter  more  especially,  produce  a  considerable  delay  in  the 
rate  of  conductivity. 

(c)  In  the  nerve  both  of  dog  and  man  a  progressive  increase 
in  polarisation  increases  the  latent  period  proportionately;   but 
while  a  certain  degree  of  anelectrotonus  blocks  the  conduction  of 
the  impulse  completely,  katelectrotonus  may  become  very  pro- 
nounced before  it  abolishes  the  conductivity  of  the  nerve. 

(d)  While  the  delay  in   the  muscular  response  ends  almost 
simultaneously  with  the  cessation  of  katelectrotonus,  there  is,  on 
the  contrary,  both  in  dog  and  man,  a  very  long  interval  before  the 
nerve  regains  its  full  conductivity  in  anelectrotonus. 

(V)  Increased  strength  of  stimulus  has  hardly  any  effect  on  the 
anelectrotonised  nerve,  while  it  compensates  the  difficulty  of  con- 
duction for  the  nerve  produced  by  katelectrotonus. 

(/)  In  nerves  which  have  begun  to  degenerate,  i.e.  in  the  state 
in  which  faradic  and  galvanic  excitability  are  merely  diminished, 
the  electrotonic  delay  in  conduction  is  more  pronounced  than 
under  normal  conditions ;  at  a  more  advanced  stage  of  degenera- 
tion even  katelectrotonus  is  capable  of  prolonging  the  latent 
period,  and  all  the  various  phenomena  of  electrotonus  are  slower 
and  more  feebly  developed. 

IX.  How  far  is  it  possible  from  the  whole  of  the  facts  before 
us  to  construct  a  general  theory  of  the  genesis  and  intrinsic 
mechanism  of  nervous  activity  ?  Before  replying  to  this  question 
we  must  review  the  various  hypotheses  that  have  been  brought 
forward. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    255 

It  is  hardly  necessary  to  mention  the  grossly  mechanical  con- 
ception of  the  early  physicians,  who  compared  the  influence  of  the  \ 
nerves  upon  the  muscles  to  the  pulling  of  hell  wires  in  order 
to  ring  them. 

Another  hypothesis  that  now  seems  little  less  puerile,  although 
under  various  forms  it  prevailed  for  centuries,  was  that  hy  which 
the  nerves  were  regarded  as  hollow  tubes  or  canals,  within  which 
circulates  a  fluid,  or  a  more  or  less  ethereal  and  mystical  gas,  that 
conveys  the  movements  ordered  by  the  brain  and  the  sensations 
from  the  sense  organs,  and  received  various  names  according  to 
the  epoch  and  school  of  thought  (spi-ritus  mtalis  or  animalis, 
pneuma,  fluidum  nerveum,  etc.).  The  paralysis  produced  by 
ligation  of  a  nerve  was  explained  as  the  necessary  effect  of  the 
arrest  of  the  fluid  that  circulates  in  the  nerve  tubes. 

At  a  much  later  time  physicians  conceived  the  conduction  of 
neural  activity  as  a  phenomenon  analogous  to  the  imdulatory  \ 
transmission  of  a  mechanical  impulse  through  an  elastic  medium, 
the  nerves  being  regarded  either  as  vibrating  cords  or  as  being 
composed  of  a  number  of  minute  elastic  particles  which  transmit 
their  oscillations  one  to  another  (Robinson,  1630).  The  theory  of 
an  imponderable  nervous  fluid  was,  however,  more  plausible  and 
found  more  favour.  Especially  after  the  phenomena  of  frictional 
electricity  and  the  laws  of  its  propagation  became  known  many 
physicians  thought  they  could  compare  activity  in  the  nerve  to 
that  of  an  electrical  apparatus.  Hausen  (1743)  and  de  Sauvages 
(1744)  were  the  first  who  upheld  the  electrical  nature  of  nervous 
activity.  Haller  criticised  this  hypothesis,  holding  it  to  be 
unfounded  and  contradicted  by  two  important  experimental  facts 
— absence  of  insulation  of  the  nerves,  and  the  paralysing  effects  of 
tying  the  nerve. 

It  was  not  till  Walsh  (1773)  had  pointed  out  the  electrical 
nature  of  Torpedo  shocks,  and  Galvani  had  discovered  animal 
electricity,  that  the  hypothesis  of  the  electrical  nature  of  nervous 
activity  became  more  widely  known  and  accepted,  and  it  has  [ 
only  acquired  the  definite  position  of  a  scientific  theory  within 
recent  years. 

The  hypothesis  of  absolute  identity  between  electricity  and 
neural  activity  received  a  fatal  blow  when  Helmholtz  (1850) 
demonstrated  by  exact  physical  methods  that  conduction  in  the 
nerve  proceeds  at  an  incomparably  slower  rate  than  electrical  con- 
ductivity (see  p.  203).  Nevertheless  it  appears  highly  probable 
from  the  work  on  animal  electricity  done  by  Nobili,  Matteucci, 
and  particularly  by  Du  Bois-Reymond  on  the  negative  variation 
of  the  nerve  current  and  the  phenomena  of  electrotonus  (1843), 
that  electrical  energy  does  play  a  part  in  nervous  conduction, 
although  under  a  different  form  from  that  assumed  in  the  theory 
of  their  identity. 


\ 


256  PHYSIOLOGY  CHAP. 

In  order  to  account  for  the  complex  of  phenomena  comprised 
under  the  term  "animal  electricity,"  Du  Bois-Eeymond  pro- 
pounded his  molecular  theory,  according  to  which  the  nerve 
contains  a  large  number  of  peripolar  electrical  molecules,  arranged 
in  regular  order.  But  this  theory,  which  now  has  only  historical 
interest,  seems  neither  acceptable  nor  necessary  after  the  rigorous 
criticism  of  data  which  led  Hermann  to  formulate  the  ((Iteration 
theory, — accepted  by  most  physiologists.  Du  Bois-Eeyrnond  failed 
to  show  how  his  molecular  theory  could  account  for  the  intimate 
mechanism  of  the  conduction  of  excitation  along  the  nerve. 

To-day  it  is  almost  universally  admitted  (supra,  p.  200)  that 
the  conduction  of  excitation  is  caused  by  a  physico-chemical  pro- 
cess in  the  living  matter  of  the  axis-cylinder,  which  is  propagated 
from  one  segment  to  another  like  a  spark,  one  segment  or  portion 
of  the  fibre  being  excited  by  the  next,  as  though  the  state  of  the 
active  portion  acted  as  a  stimulus  upon  the  inactive. 

This  schematic  conception  of  neural  conductivity  obviously 
connotes  the  theory  that  the  two  physiological  attributes  of  nerve, 
excitability  and  conductivity,  are  fundamentally  only  different 
expressions  of  one  single  property.  For  if  we  assume  the  con- 
duction incited  by  an  external  stimulus  to  be  due  to  the  fact  that 
the  active  state  of  the  excited  segment  acts  as  an  internal  stimulus 
for  the  next  segment,  then  conductivity  must  obviously  be  con- 
ceived as  a  particular  form  of  excitability,  and  the  existence  of 
the  first  is  not  admissible  without  the  second. 

Tbis  theory  has  been  opposed  by  a  wbole  series  of  facts,  which 
seem  to  show  that  under  certain  conditions  conductivity  can  be 
diminished,  or  even  abolished,  without  perceptible  injury  to 
excitability,  and  vice  versa  (see  p.  229  for  the  local  influence  of 
anaesthetics  upon  nerve) ;  and  that  under  many  other  experimental 
conditions  the  rise  or  fall  of  the  two  properties  are  not  parallel, 
(see  p.  245,  katelectrotonic  and  anelectrotonic  alterations  of 
excitability  and  conductivity).  Nor  can  we  absolutely  deny  the 
contention  of  van  Deen,  Schitf,  and  others,  that  the  central  nervous 
system  contains  fibres  endowed  with  perfect  physiological  con- 
ductivity (aesthesodic  and  kinesodic  fibres),  which  are  entirely 
devoid  of  excitability  to  any  artificial  stimuli.  But  even  if  well 
established  these  facts  do  not  prove  that  excitability  and  con- 
ductivity cannot  co-exist ;  at  most  they  show  that  different  nerve 
fibres,  or  the  same  fibres  under  different  experimental  conditions, 
present  great  variations  of  susceptibility  to  various  stimuli  and 
their  respective  modes  of  action.  It  is  quite  probable,  as  Hermann 
pointed  out,  that  adequate  internal  stimuli  normally  find  more 
favourable  conditions  of  excitation  and  conduction  in  nerve  than 
do  the  artificial  external  stimuli  which  are  foreign  to  physiological 
life.  In  this  connection  the  work  of  Gotch  and  Macdonald  on 
the  influence  of  temperature  upon  the  excitability  and  con- 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    257 

ductivity  of  nerve  should  lie  remembered.  They  confirm  the 
preceding  results  of  Helmholtz,  Grlitzuer,  and  other  authors,  and 
show  that  conduction  must  be  an  effect  of  excitation  because  it 
varies  with  variations  of  temperature  in  correspondence  with  the 
rise  or  fall  of  excitability. 

An  exhaustive  theory  of  nervous  activity  would  have  to  define 
iu  what  the  physico-chemical  alterations  of  the  fibre  that  we 
term  "  excitation "  consist,  and  how  they  are  propagated  to 
adjacent  segments,  which  is  the  process  of  "  conduction."  We 
are  far  from  any  such  theory.  We  can  only  affirm  that  the  active 
state  of  the  point  of  nerve  stimulated  is  intimately  associated 
with  its  electrical  negativity,  and  the  conduction  of  excitation 
with  the  wave-like  propagation  of  this  negativity,  i.e.  the  current 
of  action.  Since  the  electrical  stimulus  is  among  the  most 
powerful  excitants  of  neural  activity,  and  is  an  important  factor 
in  excitability,  it  seems  probable  that  the  action  current  of 
nerve  is  no  mere  accessory  pheno- 
menon, but  that  it  is  the  im- 
mediate cause  of  the  conduction 
of  the  excitatory  impulse.  ... 

According  to  Hermann  this 
conduction  may  be  explained  on 
the  assumption  that  anelectro- 
tonus  is  produced  at  the  excited 

„  ,         Fie.  1132. — Diagram  of  conduction  in  nerve. 

Spot,    111    COUSeqiience    OI    external  (Hermann.)    For  explanation  see  text. 

stimulation,  and   katelectrotonus 

in  the  adjacent  segments.  Hermann's  hypothesis  is  illustrated 
iu  the  diagram  (Fig.  162),  in  which  KK  represents  the  axial 
substance,  HHHH  the  sheath  of  the  nerve-fibre,  pqrs  the  segment 
of  nerve  stimulated.  The  lines  of  demarcation  (ps,  qr)  between  the 
excited  segment  and  the  adjacent  non-excited  segments  present  two 
electromotive  surfaces,  owing  to  the  negative  electrical  potential  of 
the  former,  which  generate  currents  in  both  directions,  as  indicated 
by  the  diagram.  According  to  Hermann  these  currents  must  be 
of  enormous  strength,  seeing  the  microscopic  interval,  and  conse- 
quent minimal  resistance,  between  the  two  electromotive  surfaces. 
They  are  therefore  capable  of  producing  in  the  auodal  zone  (aa,  aa) 
an  anelectrotonus  which  throws  the  substance  of  the  nerve  into 
rest,  and  in  the  kathodal  zone  (cc,  cc)  a  katelectrotonus  of  sufficient 
intensity  to  excite  it.  In  this  way  the  excitatory  impulse  is  trans- 
mitted along  the  nerve. 

Yet  even  on  these  assumptions  we  have,  as  Hermann  confesses, 
no  perfect  theory  of  conduction  in  the  nerve.  His  hypothesis 
seems  probable  from  the  fact  that  his  core-model,  consisting  of  a 
platinum  wire  surrounded  by  a  solution  of  copper  sulphate,  is 
able  (according  to  Hermann  and  Samways  and  Boruttau)  to 
exhibit  electrotonic  currents,  which  advance  in  wave  form  like  the 

VOL.  in  s 


258  PHYSIOLOGY  CHAP. 

action  current  of  the  nerve.  To  demonstrate  this  fact  it  is  only 
necessary  to  send  a  polarising  current  of  brief  duration  through 
the  model,  and  to  lead  off  from  more  or  less  distant  points  by  the 
galvanometer  electrodes.  Electrotonic  currents  make  their  appear- 
ance at  a  time  when  the  polarising  circuit  has  already  'been  broken. 
How  these  waves,  which  are  analogous  to  the  action  currents  of 
nerve,  can  be  generated  in  the  artificial  conductor  is  still  obscure. 
The  apparent  similarity  of  the  two  phenomena  is  interesting,  and 
justifies  the  conjecture  that  conduction  of  the  impulse  in  nerve 
consists  in  the  spreading  in  wave  form  of  a  physico-chemical 
molecular  process,  comparable  with  that  observed  on  the  core- 
model.  This  hypothesis  agrees  better  with  the  known  facts  of  the 
velocity  of  transmission  of  the  nerve  impulse  (which  we  have  seen 
to  be  about  40  m.  per  second)  than  any  other  theory,  on  which 
the  active  state  of  nerve  is  assumed  to  be  a  chemical  modification 
accompanied  by  metabolic  phenomena. 

Biedermanu  objected  to  the  hypotheses  of  Hermann  and 
Boruttau  that  conduction  of  excitation  is  a  general  property, 
common  to  many  tissues  very  different  from  nerve.  In  some  of 
these  tissues  conduction  takes  place  from  cell  to  cell,  e.g.,  in  ciliated 
epithelial  cells,  in  hydroid  colonies,  in  the  cells  of  cardiac  muscle, 
etc.  Yet,  as  Boruttau  remarks,  in  these  cases  cited  by  Biedermann 
the  transmission  of  the  impulse  can  be  measured  by  millimetres 
or  centimetres  per  second.  These  phenomena  are  in  a  different 
category  from  those  manifested  in  the  homogeneous  elementary 
fibrils  of  the  axis-cylinder,  in  which  the  velocity  may  reach  60  rn. 
per  second. 

On  the  other  hand  it  must  be  pointed  out  that  nerves  have 
recently  been  found  in  invertebrate  animals  with  a  comparatively 
sluggish  rate  of  conduction,  while  many  gradual  transitions  exist 
between  the  most  rapid  conduction  of  vertebrate  nerves  and  that 
of  other  tissues,  so  that  there  is  no  justification  for  assuming  a 
fundamental  difference  in  the  process  of  nerve  conduction.  As 
we  have  seen,  the  latest  investigations  on  asphyxia  and  fatigue  in 
nerve  have  proved  that  its  metabolism,  however  small,  is  by  no 

i  means  a  negligible  factor,  and  must  be  taken  into  account  in 
any  comprehensive  theory  of  nervous  activity.  The  chemical 
theory,  which  refers  the  conduction  of  the  excitatory  impulse  in 
nerve,  like  that  in  all  other  tissues  of  the  body,  to  the  propaga- 
tion of  a  process  of  chemical  change,  and  regards  the  electrical 
phenomena  solely  as  accessory,  is,  therefore,  at  least  in  theory,  as 
acceptable  as  the  purely  physical  theory. 

Of  late  the  theory  of  axial  conduction  seems  to  be  yielding 
more  and  more  to  modern  concepts  of  physico- chemistry,  by 
which  the  bio-electric  phenomena  are  referred  to  the  principle  of 
concentration  cells  (Ostwald,  Tschagowetz,  Macdonald,  Oker-Blom, 
Bernstein,  and  others).  Nernst  and  Zeynek  (1899),  on  the  strength 


iv    GENERAL  PHYSIOLOGY  OF  NEKVOUS  SYSTEM    259 

of  certain  analogies,  proposed  the  theory  that  every  excitation  of 
living  matter  (conceived  as  ;i  system  of  semipermeable  membranes) 
induces  change  in  the  concentration  of  the  ions,  and  that  the 
resulting  concentration  currents  set  up  conduction  in  the  nerve. 
In  this  way,  as  pointed  out  by  Boruttau  (1904),  it  is  possible  to 
reconcile  the  two  opposite  theories,  physical  and  chemical,  by 
assuming  that  conduction  in  the  nerve  depends  upon  the  electrical 
currents  produced  by  chemical  metabolism. 

This  theory,  which  Verworn  has  also  (1906)  accepted,  presents 
the  further  advantage  of  not  being  confined  to  nervous  tissue,  since 
it  is  applicable  to  all  other  tissues  of  the  body. 

X.  We  have  seen  that  the  function  of  the  nerve-fibre  is  to 
conduct  excitation.  Under  normal  conditions  the  excitatory 
impulse  never  arises  in  the  fibres,  hence  they  are  not  capable  of 
transforming  or  reinforcing  the  impulses  transmitted,  either  from 
the  periphery  (centripetal  or  afferent  nerves),  or  from  the  centres 
(centrifugal  or  efferent  nerves).  The  excitability  of  nerve-fibres 
is  rather  a  condition  of  their  conductivity  than  an  autonomous 
property.  But  when  the  centripetal  impulse  has  reached  the 
central  grey  matter  the  afferent  impulse  is  transformed  into  an 
efferent  impulse.  This  transformation  consists  not  in  a  simple 
reversal  of  direction  of  the  impulse,  but  in  a  discharge  of  fresh 
energy,  in  which  there  is  often  a  marked  disproportion  between 
the  afferent  and  the  resulting  efferent  impulses.  When,  e.g.,  a 
foreign  body  comes  in  contact  with  the  glottis,  a  loud  fit  of 
coughing  is  reflexly  excited.  This  indicates  that  the  stimulation 
of  a  few  sensory  fibres  is  able  in  the  centres  to  produce  spread  of 
excitation  to  the  motor  fibres  of  all  the  expiratory  muscles.  There 
is  thus  in  the  centres  an  explosion  of  fresh  energy,  comparable  to 
that  discharged  in  the  muscle  when  the  excitation  reaches  the 
end-plates  along  the  motor  nerves. 

The  transformations  which  the  afferent  impulses  undergo  in 
the  centre  can  also  be  expressed  as  a  diminution  or  inhibition  of 
pre-existing  activities.  The  foreign  body  which  provokes  reflex 
couo-hincr  when  it  touches  the  glottis  does  not  merely  throw  the 

O  O  O  */ 

motor  centres  of  the  expiratory  muscles  into  activity,  but  it 
simultaneously  inhibits  the  activity  of  the  inspiratory  muscles. 
Every  co-ordinated  reflex  presents  this  double  action  of  afferent 
impulses  on  the  central  organ.  The  afferent  impulses  are  also 
capable  of  setting  up  processes  which  lead  to  the  facilitation 
(Balinung] l  of  other  reflex  acts. 

While  conductivity  is  the  fundamental  physiological  function    v 
of  the  peripheral  nerve-fibres — since  we  have  no  proof  that  these     \ 
modify  impulses   during  conduction, — excitability  is   the    funda- 
mental function   of  the  nerve-centres,  so  that  a  weak  impulse 

1  BahnuiKj  has  been  variously  rendered  in  English  as  facilitation,  reinforcement, 
canalisation,  augmentation. — Tu. 


260  PHYSIOLOGY  CHAP. 

may  set  up  a  vigorous  and  widespread  reaction,  with  great  ex- 
penditure of  energy. 

As  we  know  nothing  of  the  physiological  process  which  is  the 
material  basis  of  nerve  excitation,  we  are  a.  fortiori  ignorant  of 
the  physiological  process  which  underlies  the  excitation  of  the 
centres.  It  can  only  be  said  that  from  the  subjective,  psycho- 
logical point  of  view,  it  may  be  distinguished  as  conscious  and 
unconscious,  according  as  it  is  accompanied  or  unaccompanied  by 
changes  in  the  ego  and  the  state  of  consciousness.  From  the 
objective  physiological  point  of  view  it  may  be  either  reflex  or 
automatic,  i.e.  evoked  by  impulses  that  reach  the  centre  from  the 
periphery  by  afferent  paths,  or  by  such  as  arise  within  the  centre 

itself,  and  are  sent  out  peri- 
pherally to  the  motor  apparatus. 
Both  reflex  and  automatic  acts 
may,  of  course,  be  either  con- 
scious or  unconscious. 

We  have  so  far  always 
spoken  of  centres  or  of  central 
grey  matter  in  contrast  to  the 
peripheral  nerve-fibres,  but  this 
general  expression  includes  two 
quite  distinct  structures,  the 
ganglion  elements  or  nucleated 
nerve  -cells,  and  the  extra- 
cellular fibrillary  network. 
Here,  again,  the  question  crops 
up  :  is  the  central  process  (re- 


Fio.   163.—  One  of   the   unipolar  n<>rve-cdls   that    Hex       Or      automatic, 

"liS:  )°f  U"'  '  or  unconscious)  seated  in  the 

ganglion  cells  or  in  the  extra- 

cellular network  of  fibrils  ?  From  the  morphological  point  of  view 
the  matter  is  still  —  as  we  have  seen  —  sub  judice  (pp.  180  et  seq.}\ 
but  we  must  now  review  the  physiological  arguments  that  bear  on 
one  or  the  other  of  these  hypotheses. 

In  support  of  the  opinion  that  the  ganglion  cell  is  only  a 
trophic  centre,  a  reservoir  for  the  nerve  currents,  while  the  central 
activity  of  the  system  develops  outside  the  cell,  in  the  elementary 
neuro-fibrillary  network  of  the  grey  matter,  Bethe  (1897-8)  adduced 
an  experiment  made  upon  Carcinus  maenas,  a  crayfish.  The 
muscles  of  the  antennae  of  this  crustacean  are  innervated  by 
neurones  which  (as  shown  by  the  diagram,  Fig.  163)  recall  the 
unipolar  cells  of  the  spinal  ganglia  of  mammals.  At  a  considerable 
distance  from  the  pear-shaped  cell  body  the  nerve  process  divides 
into  two  branches,  one  of  which  is  in  connection  with  the  dendrites 
of  other  neurones  or  neuropile,  and  forms  the  cellulipetal  path, 
the  other  runs  to  the  muscles  of  the  antennae  and  forms  the 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    261 

cellulifugal  path.  After  isolating  the  cephalic  ganglion  that 
innervates  the  second  pair  of  antennae,  Bethe  frequently  succeeded 
in  completely  removing  the  part  which  contains  the  bodies  of  the 
ganglion  cells,  so  that  not  one  of  them  was  left  connected  with  the 
neuropile  and  the  peripheral  nerve  processes.  Twelve  to  twenty- 
four  hours  after  the  operation  he  found  that  the  tone  of  the  muscles 
of  the  antennae  was  normal ;  the  reflexes  excited  by  contact  were 
carried  out  normally,  or  even  exaggerated  ;  and  on  applying  re- 
peated slight  stimuli  which  were  individually  insufficient  to  induce 
a  reflex,  they  summated,  and  eventually  discharged  a  reflex.  On 
the  second  day  from  the  operation,  however,  the  reflex  excitability 
was  diminished,  the  movements  of  the  antennae  became  smaller  and 
slower;  finally,  on  the  third  to  fourth  day  they  ceased  altogether, 
even  to  the  strongest  stimuli,  the  antennae  remaining  drooping  and 
relaxed  as  if  their  nerve  had  been  divided.  From  these  results 
Bethe  concluded  that  the  ganglion  cells,  i.e.  the  nucleated  portions 
of  the  neurones,  are  not  essential  to  reflex  phenomena ;  and  that 
muscular  tone,  co-ordinated  reflexes,  and  summation  of  stimuli, 
may  persist  even  after  removal  of  the  ganglion  cells,  as  if  the 
excitations  passed  directly  from  the  neuropile  to  the  motor  nerve 
of  the  antennae,  as  indicated  by  the  arrow  on  the  diagram.  The 
early  disappearance  of  functional  activity  after  removal  of  the 
ganglion  cell  is  due  to  the  loss  of  its  trophic  action  upon  the 
entire  neurone. 

In  the  unipolar  neurones  of  vertebrates,  as  in  those  of  the  spinal 
ganglia,  the  cell  body  appears  to  be  a  collateral  appendage  to  the 
paths  of  physiological  conduction,  and  there  is  reason  to  doubt 
whether  the  excitations  naturally  pass  through  it,  and  if  it  is  inter- 
calated on  the  paths  followed  by  the  physiological  impulses.  This 
hypothesis,  already  raised  by  Nansen  and  by  Ramon  y  Cajal,  seems 
probable  not  only  from  Bethe's  experiments,  but  also  from  those  of 
Steinach,  who  endeavoured  to  bring  about  the  degeneration  of  the 
frog's  spinal  ganglia  by  cutting  off  their  blood-supply.  Under  such 
conditions  he  observed  that  reflexes  could  be  obtained  on  exciting 
the  sensory  nerves  as  long  as  ten  to  fourteen  days  after  the 
operation,  although  under  the  microscope  it  could  be  seen  that  the 
ganglion  cells  had  undergone  a  more  or  less  profound  degeneration. 
But  Verworn  rightly  points  out  that  this  experiment  is  of  no  great 
value  because  the  exact  degree  to  which  degeneration  must  be 
pushed  before  the  cells  are  rendered  incapable  of  conducting  has 
not  been  determined  by  histological  examination.  Stomach's  experi- 
ment does  not  therefore  exclude  the  possibility  that  the  impulses 
normally  pass  through  the  ganglion  cells. 

Greater  importance  must  be  attached  to  the  experiments  on 
whether  the  afferent  impulses  conducted  by  the  sensory  nerves 
are  delayed  in  passing  through  the  spinal  ganglion  or  not.  Exner 
(1897)  was  the  first  to  state  that  there  was  no  delay.  His  experi- 


262  PHYSIOLOGY  CHAP. 

inents,  which  contradicted  those  of  Wundt,  who  had  previously 
found  a  delay  of  0'02  sec.,  were  repeated  by  Moore  and  Eeynolds 
(1898)  at  Schiifer's  instigation.  They  cut  all  the  bundles  of  a  dorsal 
spinal  root  in  the  frog,  except  one,  and  recorded  the  reflex  time  of 
a  muscular  contraction  on  exciting  first  the  remaining  bundle  of 
the  root  and  then  the  nerve  before  its  entrance  into  the  ganglion. 
They  found  that  the  latent  period  did  not  vary  perceptibly,  which 
led  them  to  conclude  that  the  afferent  excitations  traversing  the 
sensory  paths  do  not  pass  through  the  body  of  the  ganglion  cells, 
the  true  function  of  which  is  trophic. 

But  can  this  conclusion  from  the  spinal  ganglion  cells  be 
properly  extended  to  all  ganglion  cells  of  the  grey  matter  of  the 
central  nervous  system  of  vertebrates  1  Can  we  from  the  physio- 
logical standpoint  unreservedly  accept  the  theory  of  Apathy  and 
Bethe  that  the  diffuse  network  of  nerve  fibrils,  which  appears  to 
be  the  universal  and  essential  medium  of  the  reciprocal  relations 
between  the  different  fibres  and  the  ganglion  cells,  represents  the 
true  and  only  substrate  of  the  central  neural  phenomena  1 

Possibly  our  knowledge  is  not  yet  enough  advanced  to  be  able 
to  give  a  decisive  and  final  reply  to  this  question.  But  it  is  closely 
related  to  the  question  of  the  specific  energies  called  out  by  the 
excitation  of  the  different  sensory  nerves.  What  is  the  true 
material  basis  of  specific  energy  ?  Why  does  the  optic  nerve  in- 
variably respond  by  visual  sensations  and  the  auditory  nerve  by 
sensations  of  sound,  whatever  the  nature  of  the  stimulus  that 
affects  them  ?  Does  this  depend  on  the  specific  nature  of  the 
neurones  in  toto,  i.e.  on  the  peripheral  conducting  paths  as  well  as 
the  centres  ;  or  are  all  conducting  nerve-fibres  essentially  identical 
in  character,  and  is  the  substrate  of  specific  energy  represented  by 
the  peripheral  and  central,  sensory  and  motor  connections  of  the 
nerves  ?  Most  physiologists,  particularly  those  who  have  studied 
the  general  physiology  of  nerve  (among  them  Du  Bois-Eeymond 
and  Hermann)  are  in  favour  of  the  latter  view. 

Still  there  are  not  wanting  supporters  of  the  opposite  theory, 
who  assign  to  the  individual  fibres  (sensory  and  motor,  rnedullated 
and  non-medullated)  a  qualitatively  different  functional  nature 
(Griitzner  and  others).  Bering  (1899),  on  the  strength  more 
particularly  of  his  studies  on  the  physiology  of  the  senses,  declared 
emphatically  against  the  doctrine  of  the  identity  of  nerve  functions, 
and  assumed  instead  that  the  individual  neurones  differed  not  only 
by  their  different  place  in  the  system,  but  also  by  the  qualitatively 
different  nature,  innate  or  hereditary,  of  their  activity. 

Whatever  the  final  solution  of  this  difficult  problem,  it  is 
certain  that  the  mode  in  which  the  central  grey  matter  reacts 
to  direct  or  indirect  stimulation  presents  certain  characteristic 
peculiarities  by  which  it  is  distinguished  from  the  peripheral 
nerves. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    263 

The  grey  matter  of  the  centres  is  capable  of  reacting  by  pro- 
longed excitation  to  a  simple  stimulus,  e..g.  the  prick  of  a  pin. 
Thus  Birge  observed  that  the  rat's  spinal  cord  reacted  by  simple 
twitches  to  puncture  of  the  white  matter  and  by  a  regular  tetanus 
to  puncture  of  the  grey  matter.  Again,  the  frog's  spinal  cord 
responds  by  prolonged  excitation  to  single  induction  shocks 
(Marchand).  According  to  Baglioni  and  Fienga  the  motor 
elements  of  the  ventral  horn  exhibit  the  same  property  as  the 
frog's  spinal  cord,  of  reacting  to  single  stimuli  by  tetaniform 
excitation. 

Another  charactistic  property  of  the  grey  matter  is  that  it 
reacts  more  effectively  to  frequent  and  weak  stimuli  than  to 
stronger  and  less  frequent  shocks.  Kronecker  and  Nicolaides,  on 


FIG.  Ki4. — Reflex  movement  of  frog's  leg  after  electrical  stimulation.  (Stirling.)  The  lower  line 
marks  seconds  ;  the  middle  line  the  duration  of  the  stimulation  ;  the  upper  line  the  reflex 
movement  preceded  by  small  preliminary  contractions. 

stimulating  the  vasomotor  centre,  obtained  feeble  effects  with 
strong  but  infrequent  induction  shocks,  while  with  moderate  but 
more  frequent  shocks  of  the  same  current  the  effect  was  much 
more  pronounced.  The  same  appears  in  reflex  stimulation  of  the 
spinal  cord ;  break  induction  shocks  of  a  given  strength  induce 
reflex  movements  more  rapidly  in  proportion  to  their  frequency 
(Stirling).  With  this  property  is  intimately  associated  that  of 
summation  of  stimuli  possessed  in  a  striking  degree  by  the  grey 
matter ;  this  gives  the  character  of  a  high  tension  discharge  to 
the  reaction.  Sanders -Ezn  with  chemical  stimuli,  Stirling  with 
electrical  stimuli,  applied  to  the  skin  of  the  decerebrated  frog, 
obtained  small  preliminary  contractions  and  then  a  vigorous 
contraction,  which  is  succeeded  by  a  period  of  exhaustion,  necessary 
to  the  formation  of  a  new  charge  (Fig.  164). 

Lastly,  artificial  excitation  of  the  grey  matter  shows  that  it  has 
the  faculty  of  transforming  the  rhythm  of  the  stimulation  into  a 
different  and  characteristic  rhythm  of  its  own.  This  is  seen  from 


264  PHYSIOLOGY  CHAP. 

the  investigations  of  Kronecker  and  Stanley-Hall,  quoted  on  p.  21 
(Fig.  13). 

Baglioni  showed  in  a  preliminary  series  of  researches  (1900), 
carried  out  especially  upon  the  spinal  cord  of  the  frog,  that  it  is 
possible  to  differentiate  between  the  individual  elements  of  the 
central  substance  by  their  reactions  to  certain  poisons.  He  started 
from  the  observation  that  strychnine  and  phenol  have  the  common 
property  of  increasing  the  reflex  excitability  of  the  spinal  cord  to 
an  enormous  extent,  but  the  disturbances  they  produce  are  dis- 
tinct. While  strychnine  poisoning  causes  tetanic  spasms  in  all  the 
muscles  of  the  body  so  that  co-ordinate  movements  become  im- 
possible, phenol  poisoning  does  not  abolish  co-ordinated  movements, 
but  these  are  interrupted  by  rapid  clonic  contractions  which  produce 
constant  attacks  of  tremor  in  different  muscles. 

Baglioni  referred  these  fundamental  differences  to  the  different 
point  of  attack  of  the  two  poisons  upon  the  spinal  cord.  He 
found  that  if  carbolic  acid  were  applied  to  the  cells  in  the  dorsal 
or  posterior  part  of  the  cord,  while  the  ventral  cells  were  spared, 
clonic  contractions  of  the  limbs  appeared ;  but  if  strychnine  was 
subsequently  applied  to  the  same  region,  it  failed  to  elicit  tetanic 
action.  These  and  other  experiments  led  Baglioni  to  conclude 
that  the  action  of  strychnine  is  confined  to  the  cells  of  the  dorsal 
part  of  the  cord  (sensory  or  co-ordinating  ganglion  cells  of  the 
dorsal  horn),  while  phenol  has  a  selective  action  upon  the  cells  of 
the  ventral  part  of  the  cord  (motor  ganglion  cells  of  the  ventral 
horn). 

In  subsequent  researches  upon  other  animals  Baglioni  (1904-9) 
confirmed  and  amplified  the  theory  of  the  elective  action  of 
strychnine  and  phenol  upon  specific  central  cells,  and  claimed 
that  it  is  a  physiological  method  by  which  the  existence  of  sensory 
central  elements  reacting  to  strychnine  and  of  motor  elements 
reacting  to  phenol  can  be  readily  detected.  He  also  found  that  the 
central  nervous  system  of  invertebrates  contains  elements  that  react 
to  one  or  the  other  of  these  two  poisons.  In  Cephalopoda  the 
ganglion  stellatuin  of  the  mantle  consists  of  ganglion  cells,  which 
react  exclusively  to  the  action  of  phenol  and  cause  clonic  spasms 
in  the  muscles  innervated  by  them,  while  they  are  entirely  unaffected 
by  strychnine,  which,  on  the  other  hand,  attacks  the  higher  central 
ganglia  of  the  head,  and  produces  tetanic  convulsions  similar  to 
those  seen  in  vertebrates.  Fr.  W.  Frohlich  (1910)  confirmed  and 
amplified  Baglioni's  work  on  Cephalopoda. 

In  the  higher  vertebrates  also  (dogs),  strychnine  and  carbolic 
acid  exhibit  an  elective  exciting  action  on  the  different  ganglion 
cells.  Baglioui  and  Magnini  (1909)  noticed  the  remarkable  fact 
that  strychnine,  besides  picking  out  cells  in  the  dorsal  region  of 
the  cord  and  bulb,  will  also  attack  the  ganglion  cells  of  the 
excitable  zone  of  the  cerebral  cortex,  and  excite  them  to  activity. 


iv    GENEEAL  PHYSIOLOGY  OF  NEEVOUS  SYSTEM    265 

More  recently  (1909)  Baglioni  has  brought  forward  other 
experimental  arguments  in  support  of  the  theory  of  the  elective 
action  of  these  two  poisons,  and  emploj^ed  the  cerebrospinal  axis  of 
the  toad,  which,  unlike  that  of  the  frog,  can  be  completely  isolated 
and  removed  from  the  vertebral  cavity  owing  to  the  great  length 
of  its  cauda  equina.  It  allows  all  the  operative  handling 
necessary  for  the  complete  isolation  of  the  cerebrospinal  axis, 
which  in  the  frog  involves  serious  lesions  and  even  death  of  the 
central  substance,  since  this  is  extremely  sensitive  to  the  least 
mechanical  injury.  In  the  central  preparation  of  the  toad  (Fig.  166) 
it  is  comparatively  easy  to  apply  small  wads  of  cotton  wool  soaked 
in  strychnine  or  carbolic  acid  to  the  dorsal  or  ventral  surface  of 
the  lumbo-sacral  enlargement,  which  contains  the  centres  of  reflex 
activity  for  the  posterior  limbs.  It  is  found  that  strychnine  pro- 
duces increased  reflex  excitability  and  tetanic  spasms  when  applied 
to  the  dorsal  surface  of  this  part,  while  it  is  inert  when  placed  in 
direct  contact  with  the  ventral  surface.  Vice  versa,  carbolic  acid, 
in  a  weak  solution  (Ol  per  cent)  increases  reflex  excitability  and 
produces  clonic  convulsions  when  applied  to  the  ventral  surface, 
while  it  has  no  such  effect  when  brought  into  direct  contact  with 
the  dorsal  surface.  By  this  means  Baglioni  also  demonstrated 
the  presence  of  central  elements  on  the  dorsal  surface  of  the  bulb, 
which,  under  the  local  action  of  strychnine,  induce  tetanus  in 
the  posterior  limbs. 

Baglioni  confirmed  the  interpretation  already  given  by  Claude 
Bernard  of  the  origin  of  the  tetanic  spasms  observed  during  the 
action  of  strychnine.  The  essential  cause  is  the  abnormal  increase 
of  reflex  excitability  produced  by  strychnine,  owing  to  which 
minimal  peripheral  sensory  stimuli,  which  are  incapable  under 
normal  conditions  of  inducing  reflex  contractions,  are  now  adequate 
to  excite  all  the  centres  of  the  cord  which  they  affect,  to  the  point 
of  exhaustion.  If  after  severing  the  spinal  cord  from  the  bulb  the 
whole  of  the  dorsal  roots  are  cut  (as  was  also  seen  in  1893  by 
H.  E.  Hering),  or  if  every  peripheral  stimulus  from  the  skin  and 
the  higher  sense  organs  is  artificially  eliminated  by  placing  the  frog 
in  a  suitable  medium,  strychnine  will  kill  the  animal  without  pro- 
ducing any  tetanic  spasms.  While  the  stimuli  from  the  skin  and 
external  sense-organs  induce  the  primary  contraction  of  all  the 
muscles  of  the  body,  it  is  the  secondary  stimuli  coming  from  the 
end  organs  seated  in  the  muscles  and  tendons  stimulated  by  the 
muscular  twitches  that  reflexly  incite  the  subsequent  tetanic  con- 
vulsions, till  the  temporary  or  final  fatigue  of  central  activity  is 
brought  about. 

That  under  normal  conditions  the  spinal  cord  is  not  capable  of 
reacting  by  a  prolonged  series  of  tetanic  contractions  to  faradic 
stimuli  applied  to  afferent  fibres  is  due  to  the  fact  that  after  each 
single  excitation  the  central  elements  are  thrown  into  a  refractory 


266  PHYSIOLOGY  CHAP. 

period  or  time  of  recovery,  which  lasts  Q'25-0'5  sec.,  during  which 
they  are  incapable  of  transmitting  impulses  to  the  motor  elements 
of  the  ventral  half  of  the  cord.  The  latter,  on  the  contrary,  are 
still,  under  normal  conditions,  able  to  react  to  a  series  of  stimuli 
thrown  in  in  rapid  succession,  which  evokes  tetanic  contractions  of 
the  corresponding  muscles. 

Finally,  in  another  series  of  researches,  Baglioni  studied  the 
action  of  many  derivatives  of  phenol,  and  saw  that  while  some  of 
these,  such  as  the  di-  and  tri-phenols,  have  the  same  exciting  action 
as  carbolic  acid,  others  produce  an  initial  depression  ;  others,  again, 
like  benzoic  and  salicylic  acids,  have  no  action  on  the  nerve- 
centres. 

From  these  observations  as  a  whole,  as  well  as  from  the  varying 
capacity  of  resistance  to  asphyxia  shown  by  the  individual  parts  of 
the  cerebrospiual  axis,  it  is  obvious  that  there  are  fundamental 
differences  between  the  peripheral  and  central  nervous  systems, 
and  also  between  the  different  elements  of  the  central  system— 
functional  differences  that  certainly  cannot  be  reconciled  with  the 
theory  of  equivalence  or  physiological  identity  of  all  the  elements 
that  make  up  the  nervous  system. 

Unlike  the  peripheral  nerves,  the  central  grey  matter  has 
a  very  active  metabolism,  and  is  therefore  highly  vascular.  In 
this  connection  Fritsch  made  an  important  observation  to  the 
effect  that  the  large  ganglion  cells  of  the  nuclei  of  origin  of 
the  vagus  and  trigeminus  nerves  in  Lophius  piscatorius  are 
traversed  by  a  network  of  capillaries  which  is  essential  to  their 
nutrition. 

The  need  of  a  blood-supply  for  the  function  of  the  nerve- 
centres  is  shown  by  the  effects  of  blocking  the  vessels  which  supply 
them.  A  diminished  flow  of  blood  to  the  brain  by  rapid  compres- 
sion of  the  two  carotids  suffices  to  abolish  consciousness,  and  in 
many  cases  produces  a  fainting  fit,  owing  to  the  incapacity  of  the 
grey  matter  to  function,  due  to  anaemia.  Stenson's  experiment 
(cited  elsewhere)  that  compression  or  ligation  of  the  abdominal 
aorta  of  the  rabbit,  is  quickly  followed  by  paralysis  of  the  hind 
limbs,  shows  that  anaemia  of  the  spinal  cord  makes  the  ganglion 
cells  incapable  of  function. 

Fredericq  repeated  Stenson's  experiment  011  dogs  in  order  to 
determine  more  accurately  the  time  required  to  produce  motor  and 
sensory  paralysis.  Fifteen  to  twenty  seconds  after  the  occlusion 
of  the  aorta  there  was  a  transitory  motor  excitation  of  the  muscles 
of  the  limbs,  followed  by  motor  paralysis  which  became  total  in 
30-40  sees.  During  this  time  the  sensibility  of  the  lower  limbs 
is  unaltered ;  it  is  only  after  90  sees,  that  hyperaesthesia  followed 
by  anaesthesia  sets  in,  which  becomes  total  about  3  mins.  after 
occluding  the  aorta.  If  the  compression  or  the  ligature  is  removed, 
sensibility  returns  after  5-10  mins.,  and  motility  somewhat  later. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    267 

If  the  block  is  kept   up  for  longer,  uo  functional  recovery  takes 
place. 

These  facts,  showing  that  the  individual  ganglion  cells  present 
different  resistances  to  anaemia,  are  confirmed  by  Landergren's 
work  on  the  phenomena  of  acute  asphyxia.  As  shown  in  Fig.  165, 
four  stages  can  be  distinguished  in  acute  asphyxia.  In  the  first 
stage  there  is  a  brief  rise  of  activity  in  the  vasornotor  bulbar 
centre.  When  the  activity  of  this  centre  ceases  the  excitation 
of  the  vagal  cardiac  centre  reaches  its  maximum.  The  course  of 

i.  n.  in.  iv. 

Period  of  general    Period  of  suspended     Period  of  exagger-     Final  period  (pre- 
rxcitation.  respiration.  ated  respiration.  mortal). 


Fir..  165. — Diagram  of  vital  resistance  of  some  nerve-centres  to  asphyxia.  (Landergren.)  Tlie 
continuous  curved  line  indicates  the  functional  excitation  and  subsequent  paralysis  of  the 
bulbar  vasomotor  centre  ;  the  dotted  line,  the  functional  state  of  the  centre  for  the  cardiac 
vagus  ;  the  broken  line,  the  state  of  activity  of  the  respiratory  centre  ;  the  dotted  and  broken 
line  (with  which  the  life  of  the  animal  expires)  indicates  the  functional  state  of  the  spinal 
and  vasomotor  centres. 

the  excitation  of  the  respiratory  centre  was  not,  owing  to  a  long 
pause  in  respiration,  completely  represented,  but  it  appears  to 
coincide  approximately  with  that  of  the  bulbar  cardiac  centre. 
The  last  to  be  thrown  into  excitation  are  the  spinal  vasomotor 
centres,  the  activity  of  which  continues  even  when  the  function  of 
the  other  centres  is  abolished. 

That  the  metabolism  of  the  nerve-cell  is  highly  active  in  com- 
parison with  the  very  low  metabolism  of  the  nerve-fibre,  appears 
not  only  indirectly  from  the  fact  that  the  nucleated  portion  of  the 
cell  is  the  trophic  centre  of  the  entire  neurone,  as  we  saw  in 
discussing  Wallerian  degeneration  (see  pp.  233  ct  srq.'),  but  also 
and  more  directly  from  the  observation  of  Marinesco,  that  under 
certain  normal  or  morbid  conditions  of  the  ganglion  cells  there  is 


268  PHYSIOLOGY  CHAP. 

a  gradual  disintegration  of  the  chromatic  substance  of  Nissl's 
granules  (see  Fig.  124,  p.  189),  which  spreads  uniformly  over  the 
cell  protoplasm.  This  process  (known  as  chromatolysis}  is  accom- 
panied by  a  swelling  of  the  cell,  with  lateral  displacement  of  the 
nucleus,  followed  later  by  a  diminution  in  the  volume  of  the  cell, 
and  the  partial  or  total  disappearance  of  the  chromatic  substance. 

In  studying  the  cytological  changes  in  the  nerve-cell  after 
prolonged  work,  Lambert,  Eegnat,-  and  Mann  saw  that  the  nerve- 
cell  diminishes  in  size  and  that  the  chromatic  substance  is 
disintegrated  and  gradually  disappears,  but  Nissl,  on  repeating 
these  observations,  obtained  unconvincing  results,  though  he 
observed  a  certain  diminution  of  the  chromatic  substance. 

Clearer  and  more  definite  results  ensue  on  severing  the  axon 
from  the  cell,  as  shown  by  the  investigations  commenced  by  Nissl, 
and  continued  in  particular  by  Lugaro,  Marinesco,  and  Van 
Gehuchten.  The  first  signs  of  chromatolysis  in  the  cell  were 
observed  twenty-four  to  forty-eight  hours  after  section  of  a 
motor  nerve.  The  chromatolytic  process  goes  on  for  about  fifteen 
days,  when  the  cell  is  reduced  to  a  rounded  mass  destitute  of 
Nissl's  granules.  The  chromatolysis  begins  near  the  point  of  exit 
of  the  axis-cylinder,  then  invades  the  perinuclear  portion  of  the 
cell,  next  the  more  peripheral  part,  and  lastly  the  dendrites. 
After  twenty  to  twenty-four  days  the  process  of  regeneration  sets 
in ;  it  progresses  very  slowly,  and  is  complete  in  about  three 
months. 

Alterations  in  the  sensory  cells  after  section  of  the  peripheral 
nerve  were  studied  by  Lugaro,  Fleming,  Cox,  and  others.  On 
cutting  the  spinal  root  between  the  ganglion  and  the  cord,  Lugaro 
found  few  signs  of  chromatolysis  in  the  cells  of  the  ganglia.  Van 
Gehuchten  and  Nelis,  on  the  contrary,  observed  chromatolysis  in 
the  cells  of  the  jugular  ganglion  after  section  of  the  vagus.  It 
differed  only  in  not  being  followed  by  a  process  of  reintegration,  so 
that  after  about  three  months  the  cells  had  almost  entirely  dis- 
appeared. Nissl  noted  the  same  result  in  certain  motor  cells  also, 
and  Schafer  in  the  cells  of  Clarke's  column,  after  section  of  the 
direct  cerebellar  tract.  This  ascending  or  retrograde  degeneration 
after  section  of  the  nerve  is  a  valuable  help  in  localising  the  centre 
connected  with  given  nerve  paths  (Gudden's  method). 

It  is  easy  to  understand  that  all  portions  of  the  processes 
separated  from  the  nucleus  degenerate,  since  the  nucleus  is  the 
centre  of  nutrition  for  the  entire  neurone :  it  is  more  difficult  to 
explain  the  cause  of  chromatolysis  and  the  degeneration  of  the  cell 
body  after  the  severance  of  a  part  of  the  axon.  The  disintegra- 
tion and  degeneration  described  by  Van  Gehuchten  for  certain 
sensory  cells  are  probably  due  to  the  loss  of  function,  after  inter- 
ruption of  the  paths  by  which  peripheral  excitations  normally 
reach  the  cell.  But  this  explanation  is  not  applicable  to  the 


iv    GENERAL  PHYSIOLOGY  OF  NEIIVOUS  SYSTEM    269 

phenomena  of  degeneration  in  motor  cells,  since  their  afferent 
path  remains  intact.  According  to  SchaTer  the  explanation  is  that 
after  section  of  the  axis -cylinder,  its  end  must  tirst  undergo 
chemical  and  electrical  alterations,  under  the  influence  of  inflam- 
mation and  cicatrisation,  which  keep  the  cell  in  an  abnormal  state 
of  protracted  excitation.  In  fact  we  have  seen  that  chromatolysis 
accompanies  exaggerated  activity  of  the  nerve. 

Chromatolysis  may  also  result  from  the  action  of  certain 
poisons,  e.g.,  arsenic,  lead  acetate,  bromides,  antipyrine,  cocaine, 
strychnine,  alcohol,  some  bacterial  toxines  (rabies,  tetanus,  etc.). 

A.  Monti  concludes  from  a  long  series  of  observations  that 
chromatolysis  of  nerve -cells  is  frequent,  and  is  definite  and 
constant  in  cases  of  disturbed  metabolism.  On  comparing 
preparations  made  by  Nissl's  and  by  Golgi's  method,  Monti  came 
to  the  conclusion  that  there  is  an  almost  exact  correspondence 
between  chromatolysis  and  degeneration  of  the  dendrites.  Both 
are  observed  in  nutritional  disturbance  of  the  nerve -cell.  This 
correlation  between  the  alteration  of  the  dendrites  and  those 
of  the  chrornatophile  substance  agrees  with  Golgi's  idea,  that  the 
protoplasmic  processes  play  an  important  part  in  the  nutrition  of 
the  nerve-cell. 

Donaggio  found  that  while  the  chromatic  substance  is  readily 
destroyed  by  pathogenic  causes,  the  intracellular  reticulum  offers 
an  enormous  resistance.  It  is,  on  the  other  hand,  profoundly 
injured  when  the  pathogenic  agent  is  combined  with  the  action  of 
cold. 

The  subject  of  metabolism,,  or  the  material  exchanges  in  the 
nerve  -  centres,  has  only  been  approached,  largely  by  indirect 
methods,  of  late  years.  It  is  a  priori  evident  that  in  the  central 
masses  of  the  nervous  system,  as  in  the  other  tissues  and  organs, 
the  specific  functions  are  intimately  bound  up  with  the  successive 
phases  of  katabolism  and  anabolism,  in  which  the  discharge  or 
accumulation  of  energy  takes  place. 

The  fact  that  of  all  the  tissues  the  central  nervous  system 
offers  most  resistance  to  loss  of  weight  in  fasting  shows  its 
predominance  and  its  capacity  for  keeping  the  energy  required  for 
its  functions  constant,  by  drawing  its  nutriment  from  all  the 
other  tissues.  This  is,  however,  no  argument  for  assuming  that 
the  chemical  work  which  accompanies  the  activity  of  the  nerve- 
centres  is  necessarily  very  active. 

The  earliest  researches  on  the  metabolism  of  nerve-centres 
was  confined  to  establishing  the  variations  in  the  chemical 
reactions.  While  the  white  matter  preserves  its  alkaline  reaction 
to  litmus  for  a  comparatively  long  time  after  death,  the  reaction 
of  the  grey  matter  in  warm-blooded  animals  changes  so  rapidly 
that  it  becomes  acid  almost  immediately  after  death.  For  some 
time  this  was  supposed  to  be  the  vital  reaction  of  the  grey  matter 


270  PHYSIOLOGY  CHAP. 

(Gscheidleu).  Langendorff  (1885)  first  demonstrated  that  grey 
matter  also  is  alkaline  to  litmus  intra  vitam,  and  that  the  acid 
reaction  sets  in  after  cutting  off  the  blood -supply,  and  may 
disappear  again  if  the  circulation  is  re-established  promptly.  The 
observation  that  in  the  frog  rise  of  temperature,  strychnine 
poisoning,  or  any  cause  that  increases  metabolism  accelerates  the 
appearance  of  the  acid  reaction,  led  Langendorff  to  conclude  that 
the  formation  of  acid  is  due  to  vital  processes,  the  products  of 
which  are  eliminated  under  normal  conditions  by  the  blood  stream. 

We  owe  our  first  detailed  knowledge  of  the  metabolic  pro- 
cesses that  go  on  in  the  nerve-centres  to  the  researches  of  Verworn 
and  his  pupils  (1900-3).  The  method  used  by  Verworn  in  his 
experiments  on  frogs  consisted  in  replacing  the  blood  circulation 
by  an  artificial  circulation  of  various  fluids.  This  artificial 
circulation,  in  the  form  either  of  a  constant  stream  or  of  a 
rhythmically  intermittent  current  similar  to  that  of  the  normal 
circulation  by  means  of  a  small  pressure  pump  (Winterstein, 
Baglioni),  was  introduced  through  a  glass  cannula,  inserted  in  the 
aorta,  near  the  heart.  After  passing  through  the  whole  vascular 
system  the  fluid  left  the  body  again  at  the  cardiac  orifices,  which 
were  opened  so  as  to  allow  the  circulating  fluid  to  escape  through 
them.  Verworn  used  strychuinised  frogs  for  experiment  because 
their  increased  excitability  made  it  possible  to  obtain  a  more  exact 
and  easy  demonstration  of  the  changes  in  reflex  activity  caused  by 
the  influence  of  various  experimental  factors.  Briefly  stated,  his 
results  are  as  follows  :— 

If  the  blood  of  a  strychninised  frog  is  replaced  by  physiological 
saline  previously  deprived  of  its  oxygen  by  boiling,  before  the 
circulation  is  started,  the  tetanic  spasms  that  occur  at  every 
contact  gradually  diminish  and  are  separated  from  each  other  by 
increasingly  long  pauses  of  inexcitability,  till  finally  no  reaction 
can  be  aroused.  On  then  circulating  the  oxygen-free  saline  there 
is  a  slight  initial  recovery,  which  can  only  be  explained  by  the 
washing  away  of  the  toxic  products  of  metabolism  that  have 
accumulated.  The  recovery  thus  obtained  is,  however,  incomplete 
and  of  short  duration.  If,  on  the  other  hand,  the  salt  solution  is 
replaced  by  well-oxygenated  defibrinated  blood,  there  is  soon  a 
complete  recovery  shown  by  strong  and  protracted  tetanic  spasms. 
What  constituent  of  the  blood  is  responsible  for  this  complete 
recovery  of  the  normal  excitability  ?  Verworn  found  that  the 
recovery  was  practically  the  same  when  salt  solution  fully 
saturated  with  oxygen  was  circulated  instead  of  blood,  while 
blood  serum  deprived  of  oxygen  was  totally  ineffective.  This 
shows  that  the  restorative  action  was  due  not  to  organic  nutritive 
materials,  but  solely  to  the  oxygen. 

On  the  strength  of  these  results  Verworn  distinguishes  two 
fundamentally  different  factors  in  the  paralysis  of  the  centres,  viz. 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    271 

fatigue  due  to  the  accumulation  of  the  toxic  products  of  meta- 
bolism, and  exhaustion  due  to  consumption  of  the  supply  of 
oxygen.  The  former  can  be  eliminated  by  mechanical  washing, 
the  latter,  on  the  contrary,  only  by  a  fresh  supply  of  oxygen  to  the 
centres.  The  paralysis  caused  by  these  two  factors  together 
produces  what  Verworn  terms  work-paralysis. 

Verworn  attributes  fatigue  to  the  production  and  accumulation 
of  carbonic  acid,  more  particularly  on  the  strength  of  Winterstein's 
experiments.  This  author  found  that  C02  at  a  high  concentration 
is  able  to  exert  a  markedly  paralysing  action  on  the  centres,  and 
inhibits  the  appearance  of  the  strychnine  spasms. 

By  the  method  of  artificial  circulation  Winterstein  endeavoured 
to  decide  whether  this  narcosis,  since  it  is  capable  of  suspending 
excitatory  processes,  is  able  to  check  the  restorative  action  of  oxygen 
also.  He  experimented  as  follows  :— 

A  strychniuised  frog,  asphyxiated  by  the  circulation  of  oxygen- 
free  salt  solution,  was  anaesthetised  by  the  circulation  of  salt 
solution  containing  a  narcotic  (chloroform,  ether,  alcohol,  carbonic 
acid).  Oxygenated  blood  mixed  with  the  same  narcotic  was  then 
circulated.  Under  these  conditions  there  was  of  course  no 
recovery  of  the  centres,  on  account  of  the  narcosis.  But  on 
circulating  normal  saline  to  remove  the  drug  there  was  still  no 
recovery  of  central  excitability,  because  the  asphyxiated  nerve- 
centres,  which  had  been  deprived  of  oxygen,  were  unable,  owing 
to  the  action  of  the  narcotic,  to  utilise  it  when  offered  them. 
Narcosis  thus  suspends  not  only  the  katabolic  but  also  the  anabolic 
processes.  Fr.  W.  Frohlich  observed  an  analogous  effect  on  peri- 
pheral nerve  (supra,  p.  231).  This  important  fact  is  explained 
by  the  latest  work  of  Winterstein  (1905)  as  a  direct  arrest  of 
the  oxidation  processes  by  narcotics,  represented  in  the  lower 
organisms  by  an  extraordinary  fall  in  the  consumption  of  oxygen 
during  narcosis. 

In  another  series  of  researches  Winterstein  studied  the  special 
state  of  the  nerve-centres  known  as  heat  paralysis.  When  a  frog 
is  warmed  in  a  thermostat,  all  reactions  disappear  after  a  period 
of  general  excitation,  owing  to  a  paralysis  of  the  nerve-centres 
which  passes  off  if  the  animal  be  cooled  again  in  time.  Winterstein 
found  this  heat  paralysis  to  be  closely  related  to  the  oxygen 
supply  of  the  centres.  If  a  frog  which  is  in  a  condition  of  heat 
paralysis  be  cooled  in  an  atmosphere  free  of  oxygen,  or  if  its 
blood  be  replaced  by  cold  physiological  saline  containing  no 
oxygen,  the  animal  is  unable  to  recover  from  the  paralysis. 
Recovery,  on  the  contrary,  takes  place  when  there  is  sufficient 
oxygen.  It  follows  that  heat  paralysis  must  be  a  form  of  asphyxia, 
due,  according  to  Winterstein,  to  the  fact  tliat  either  the  store  of 
oxygen  in  the  centres  or  their  oxidative  processes  are  insufficient 
for  the  excessive  demand  produced  by  the  heat. 


272  PHYSIOLOGY  CHAP. 

Further  advance  in  the  general  physiology  of  the  nerve- 
centres  was  made  by  Baglioni  (1904)  with  his  method  of  isolating 
the  spinal  cord.  This  method  is  much  simpler  than  that  of 
artificial  circulation,  and  avoids  the  lesions  caused  by  protracted 
artificial  circulation,  which  readily  induce  oedema  and  lower  the 
vitality  of  the  nerve  -  centres.  Baglioni's  method  consists  in 
dissecting  out  the  spinal  cord  by  removing  the  dorsal  halves  of 
the  vertebrae,  and  separating  it  from  the  rest  of  the  body,  so  that 
it  is  only  attached  by  the  sciatic  nerve  and  plexus  to  the  leg, 
which  can  be  stimulated  and  used  as  the  index  of  excitability 
on  one  or  both  sides.  On  applying  mechanical  or  electrical 
stimuli  to  the  skin,  reflex  movements  are  produced  in  the  leg, 
since  the  spinal  centres  have  not  been  injured  by  the  operation. 
Baglioni  finds  that  on  placing  this  preparation  in  an  atmosphere 
of  pure  oxygen,  or  in  physiological  saline  saturated  with  oxygen, 
it  survives  and  preserves  perfect  reflex  activity  for  twenty-four 
to  forty-eight  hours.  The  oxygen  tension  of  atmospheric  air  is 
not  enough  to  maintain  its  vitality  for  more  than  two  hours  at  a 
temperature  of  18-20°  C.,  as  the  oxygen  can  only  be  absorbed 
from  the  dorsal  surface  of  the  cord — the  ventral  surface  being 
covered  by  the  anterior  half  of  the  vertebrae.  Reflex  action 
disappears  in  a  much  shorter  time,  in  about  three-quarters  of  an 
hour,  if  nitrogen  is  substituted  for  oxygen,  and  more  rapidly  in 
proportion  as  the  temperature  is  higher. 

This  experiment  indicates  even  more  plainly  than  the  last  the 
great  oxygen  hunger  of  the  nerve-centres  and  their  capability  of 
surviving  for  a  comparatively  long  time  with  their  circulation  cut 
off  and  with  no  supply  of  organic  nutrient  materials.  The  need 
of  oxygen,  which  greatly  exceeds  that  of  the  peripheral  nerves,  is, 
according  to  other  experiments  of  Baglioni,  a  characteristic  property 
of  the  central  nervous  system,  not  only  in  vertebrates,  but  in  in- 
vertebrates also. 

Wiuterstein,  Baglioni,  and  Fienga  subsequently  found  that  it 
was  possible  to  isolate  the  frog's  cord  still  more  completely  by 
lifting  it  almost  entirely  out  of  the  vertebral  canal.  Total 
isolation  of  the  cerebrospinal  axis  is  thus  possible  in  the  toad 
(Baglioni,  1908),  owing  to  the  great  length  of  the  cauda  equina, 
which  allows  of  the  necessary  manipulation  in  freeing  the  cerebro- 
spinal axis  from  its  connections  without  serious  injury.  Fig.  166 
gives  the  photograph  of  such  a  preparation  from  the  toad. 

Winterstein  (1906)  carried  out  a  series  of  quantitative 
estimations  of  the  gaseous  metabolism  of  the  frog's  isolated  spinal 
cord  by  means  of  Thunberg's  microspirometer,  which,  as  shown  on 
p.  231,  makes  it  possible  to  measure  the  carbonic  acid  given  off  and 
the  oxygen  absorbed,  thus  giving  the  respiratory  quotient  for  small 
organs  and  animals.  He  concludes  that  the  asphyxial  paralysis 
of  the  centres  is  due,  not  to  the  consumption  of  the  reserve 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    273 

oxygen,  but  to  an  accumulation  of  products  of  metabolism,  wbicb 
have  a  paralysing  action  and  are  easily  oxidisable,  so  that  a 
proportional  amount  of  oxygen  is  consumed  in  neutralising  them. 


Fn;.  Itiij. — Central  preparation  of  toad.  (Bullion!.)  The  posture  of  the  lower  liinlis.  uliirli  arc 
exhausted  by  recent  reflex  activity,  differs  from  that  in  a  living  preparation.  The  dm-sal  surface 
of  the  spinal  cord  is  shown. 

He  further  found  that  the  spinal  cord  under  these  conditions 
consumes  about  250-350  cmm.  of  oxygen  per  gramme  per  hour, 
its  respiratory  quotient  being  always  less  than  unity. 

Two  years  previous  to  Verworn,  Ducceschi  (1898)  had  made 
VOL.  in  T 


274  PHYSIOLOGY  CHAP. 

use  of  the  method  of  artificial  circulation  in  estimating  the 
results  produced  in  the  spinal  centres  of  batrachians  by  salt 
solutions  at  different  concentrations.  He  found  that  the  solution 
best  adapted  to  maintain  the  functions  of  the  spinal  centres  was 
one  containing  from  0'6  to  1  per  cent  sodium  chloride.  Hypertonic 
solutions,  which  contain  more  than  1*5  per  cent  sodium  chloride, 
cause  motor  paralysis  after  a  brief  period  of  motor  excitation 
(tetanus,  clonic  spasms),  while  hypotonic  solutions,  which 
contain  less  than  0'6  per  cent  sodium  chloride,  cause  depression 
and  loss  of  excitability,  but  less  rapidly  and  without  any  previous 
phase  of  increased  excitability.  Since  hypertonic  solutions 
withdraw  water  from  the  nerve-centres,  and  hypotonic  solutions 
cause  excess  of  fluid  or  oedema  in  them,  these  experiments  of 
Ducceschi  show  the  importance  of  water  for  the  metabolism  of 
the  ganglion  cells. 

Morawitz  subsequently  worked  at  the  same  subject  with 
Verworn,  and  arrived  at  the  following  conclusions  which  confirm 
and  partly  extend  those  of  Ducceschi :  (a)  If  distilled  water  is  cir- 
culated through  a  strychniuised  frog,  excitability  soon  disappears 
altogether,  to  reappear  on  circulating  a  physiological  saline 
solution.  (6)  Great  loss  of  water  from  the  cord  owing  to 
artificial  circulation  of  a  hypertonic  solution  (2-5  per  cent  sodium 
chloride)  increases  the  reflex  excitability  in  the  frog  till  it 
resembles  strychnine  poisoning,  (c)  If  more  water  is  added  to 
that  contained  in  the  nerve  elements,  excitability  diminishes. 
Everything  therefore  tends  to  show  that  the  excitability  of  the 
ganglion  cells  depends  to  a  large  extent  on  their  water  content. 

Battelli  extended  Ducceschi's  experiments  to  the  artificial 
circulation  of  warm-blooded  animals  (guinea-pigs)  in  order  to 
study  the  influence  of  water,  of  certain  inorganic  salts,  and  of 
glucose  upon  the  nutrition,  and  therewith  the  excitability  of  the 
nerve-centres. 

The  following  seem  to  us  to  be  among  the  most  important 
of  his  results :  (a)  Artificial  circulation  of  a  deoxygenated  salt 
solution  prolongs  to  some  extent  the  duration  of  reflex  excitability, 
which  only  lasts  70  sees,  after  tying  the  aorta.  (&)  A  physiological 
solution  saturated  with  oxygen  increases  the  duration  of  the 
reflexes  for  a  variable  but  not  very  prolonged  period,  (c)  A 
mixture  of  sodium  chloride  and  calcium  chloride  solution  saturated 
with  oxygen  gives  a  marked  and  constant  increase  in  the  reflexes. 
(d)  Potassium  and  magnesium  salts,  neutral  sulphates  and 
phosphates  are  tolerated  by  the  centres,  but  do  not  increase  the 
duration  of  the  reflexes,  (e]  If  the  artificially  circulated  fluid 
has  even  a  moderately  alkaline  reaction  due  to  the  carbonate, 
bicarbonate,  or  phosphate  of  sodium,  the  vitality  of  the  centres  is 
rapidly  abolished.  (/)  A  deoxygenated  solution  of  sodium  or 
calcium  causes  only  a  slight  prolongation  of  the  functions  of  the 


iv    GENERAL  PHYSIOLOGY  OF  NERVOUS  SYSTEM    275 

nerve-centres.  The  chief  result  of  Battelli's  experiments  is  that 
calcium  salts  appear  to  be  essential  to  the  gaseous  exchanges 
between  the  circulating  fluid  and  the  nerve-centres. 

Some  recent  experiments  of  Sabbatani  also  confirm  the 
importance  of  calcium  to  the  normal  functions  of  the  centres  of 
the  cerebral  cortex. 

Baglioni  (1904)  further  instituted  a  series  of  experiments  on 
his  preparation  of  the  frog's  isolated  spinal  cord,  with  the  object 
of  determining  the  conditions  under  which  salt  solutions  are  able 
to  maintain  the  reflex  activity  of  the  nerve-centres.  In  particular 
he  investigated  the  importance  of  sodium  chloride,  and  found  that 
it  cannot  be  replaced  by  any  other  substance,  e.g.  glucose,  glycerol, 
asparagine,  etc.,  or  by  potassium  or  lithium  chloride  at  equal 
concentration.  Sodium  chloride  can  only  be  replaced  to  a  certain 
extent  by  other  salts  of  sodium  (bicarbonate,  nitrate). 

If  the  isolated  spinal  cord  is  placed  in  an  isotonic  solution 
which  contains,  e.g.,  glucose  instead  of  sodium  chloride,  its  reflex 
excitability  disappears  after  a  certain  time  (two  to  five  hours 
according  to  the  surrounding  temperature),  and  returns  again  if 
the  preparation  be  immediately  plunged  into  a  solution  containing 
0'6-0-9  per  cent  sodium  chloride.  Peripheral  nerves  react  in  the 
same  way. 

Lastly,  it  must  be  noted  that  Herlitzka  (1909)  instituted  a 
series  of  researches  with  artificial  circulation  through  the  bulbar 
centres  of  the  frog,  in  order  to  determine  the  chemical  conditions 
of  the  artificial  solutions  which  are  able  to  maintain  their 
activity.  Among  other  points,  he  finds  that  a  series  of  organic 
substances,  such  as  glucose,  glycerol,  and  urea,  added  to  normal 
saline  enable  the  centres  to  survive  for  a  comparatively  long  time. 
He  attributes  the  action  of  these  substances  to  their  solubility  in 
lipoids. 

BIBLIOGRAPHY 

The  student  will  find  copious  references  to  the  early  literature  of  this  subject  in 
HERMANN'S  Text-book  of  Physiology,  and  to  the  later  in  those  of  SOHAFER  and 
NAGEL. 

Morphology  of  Nervous  System  :— 

WALHEYER.     Deutsche  med.  "VVochenschr.,  1891. 

RAMON  Y  CA.JAL.     Revista  de  cientias  medicas  de  Barcelona,  nuras.  16,  20,  22,  23, 

1892.     Arch,  di  fisiol.  vol.  v.,  1908. 

NISSL.     Allgem.  Zeitschr.  f.  Psychiatric,  vol.  xlviii.,  1892. 
APATHY.     Mitteil.  a.  d.  zool.  Station  zu  Neapel,  1897. 
BETHE.      Arch.    f.    mikrosk.    Anat.,    1897.       Morphol.    Arbeiten   von    Schwalbe, 

vol.   viii.,   1898.     Biol.   Centralblatt,   xviii.,   1898.     Arch.    f.  mikrosk.   Anat. 

vol.  Iv.,  1900.     Allg.  Auat.  u.  Physiol.  d.  Nervensystems.     Leipzig,  1903. 
ROBERTSON.     Brain,  Part  Ixxxvi.,  1899. 
GOLGI.     Boll,  della  Societa  Med.  Cliir.  di  Pavia,  1898-99.    Verhandl.  d.  anat.  Ges. 

XIV.  zu  Pavia,  1900.     Arch,  di  fisiol.  vol.  iv.,  1907.     Atti  della  Soc.  ital.  p.  il 

progresso  d.  scienze,  III.  Riunione,  1910. 
DONAGGIO.     Riv.  sper.  di  freniatria,  1896,   1900,  1904,  1905,  1908.      Int.  Congress 

of  Physiology.     Turin,  1901;  Brussels,  1904. 


276  PHYSIOLOGY  CHAP. 

PURPURA.  Bollettino  della  Society,  medico-chirurgica  di  Pavia,  1901.  Rendiconti 
del  K.  Istituto  Lombardo  di  Scienze  e  Lettere,  serie  ii.  vol.  xxxiv.,  1901. 
Archives  italicnnes  de  biologie,  fasc.  xxxv.,  1901.  Arcliivio  ed  atti  della 
Soeieta  italiana  di  Chirurgia,  1909.  Arcliivio  ed  atti  della  Soeieta  italiana  di 
Chirurgia,  1911. 

PERRONCITO,  A.  Mem.  del  R.  Istituto  Lombardo  di  Sc.  e  Lett;  ;  Classe  delle  Sc. 
mat.  e  nat.  vol.  xx.,  1908. 

VERWORN,  W.     Zeitschr.  f.  allg.  Physiol.  vol.  vi.,  1906. 

MODENA.     Bull,  dell'  Ace.  medica  di  Roma,  1910. 

Excitability  and  Conductivity  of  Nerve  :  — 

HELMHOLTZ.     Arch.  f.  Anat.  u.  Phys.,  1850-52. 

GRUTZNEU.     Pfliiger's  Archiv,  vol.  xxviii.,  1882. 

ZEDERBAUM.     Du  Bois-Reymond's  Arch.,  1883. 

KUHNE,  W.     Zeitschr.  f.  Biologie,  1886.      Ueber  die  Wirkung  des  Pfeilgiftes  auf 

die  Nervenstiimme.     Heidelberg,  1886. 
GOTCH  and  HORSLEY.     Phil.  Trans.,  1891. 
BERNSTEIN.     Untersuchungen  iiber  den  Erregungsvorg.  im  Nerven-  u.  Muskel- 

system,  1891. 

WEDENSKY.     Pfliiger's  Archiv,  vol.  Ixxxii..  1900. 
DUCCESCHI.     Pfliiger's  Archiv,  vol.  Ixxxiii.,  1900. 
FRUHLICH,  FR.  W.     Zeitschr.  f.  allg.  Physiol.  vol.  iii.,  1904. 
THHRNER,  W.     Ibidem,  vol.  viii.,  1908. 

Electrophysiology  of  Nerve  : — 

MATTEUCCI.     Traite  des  phenomen.es  electro-phys.  des  animaux.     Paris,  1844. 
Du  BOIS-REYMOND.     Untersuchungen  liber  thier.  Electr.     Berlin,  1848. 
PFLUGER.     Untersuchungen  iiber  die  Physiol.  des  Electrotonus.     Berlin,  1859. 
BERNSTEIN.    Untersuchungen  iiber  den  Erregungsvorgang  im  Nerven-  und  Muskel- 

system,  1871. 
WUNDT.      Untersuchungen  z.    Median,    d.    Nerv.    u.    Nervencentren.      Stuttgart, 

1876. 

TIGERSTEDT.     Mitt.  v.  physiol.  Lab.  in  Stockholm,  vols.  i. -iii.,  1882-85. 
BIEDERMANN.     Elektrophysiologie.    Jena,  1895.     (English  Trans,  by  F.  A.  Welby, 

1896). 
HERMANN.     Pfliiger's  Archiv,  vols.   vi.,   vii.,   viii.,   xxx.,   xxxi.,   xxxiii.,   xxxv., 

Ixii.,  1872-98. 

WALLER.     On  Animal  Electricity.     London,  1897. 
GOTCH  and  BURCH.     Proc.  Roy.  Soc.  London,  vol.  Ixiii.,  1898. 
BORUTTAU.    Pfliiger's  Archiv,  vols.  Iviii.,  Ixiii.,  Ixvii. ,  Ixxi.,  Ixxxiv.,  cv.,  1894-1904. 

General  Physiology  of  Nerve-Centres  :— 

NISSL.     Allg.  Zeitschr.  f.  Psychiatrie,  1892. 

LUGARO.     Rivista  di  pat.  nervosa.     Firenze,  1896. 

MARINESCO.     Presse  medicale,  1897.     Arch.  f.  Physiol.,  1899. 

DUCCESCHI.     Sperimentale,  Iii.,  1898. 

WINTERSTEIN.      Du  Bois - Reyinond's  Arch.,   1900;   Supp*-      Zeitschr.   f.    allgem. 

Physiol.  i. ,  1901  ;  v.,  1905  ;  vi.,  1906. 
VON  BAEYER.     Zeitschr.  f.  allgem.  Physiol.  i.,  1901. 
BATTELLI.     Journal  de  physiol.  et  de  path,  gen.,  1900. 
VERWORN.      Du  Bois  - Reymond's  Arch.,    1900;    Supp*-      Die   Biogenhypothese. 

Jena,  1903. 
BAGLIONI.      Du  Bois -Reymond's  Arch.,  1900.     Zur  Analyse  der  Reflexfunktion. 

Wiesbaden,  1907.     Zeitschr.  f.  allg.  Physiol.  ix.  and  x.,  1909. 
HERLITZKA,  A.     Arch.  d.  fisiol.  vol.  vii.,  1909. 

Recent  English  Literature  :— 

KEITH    LUCAS.      Temperature  Co-efficient  of  the  Rate  of  Conduction  -in  Nerve. 

Journ.  of  Physiol.,  1908,  xxxvii.  112. 
BRODIE  and  HALLIBURTON.    Heat  Contraction  in  Nerve.    Journ.  of  Physiol.,  1904, 

xxxi.  473. 


iv    GENEKAL  PHYSIOLOGY  OF  NEKVOUS  SYSTEM    277 

ADRIAN.       On    the   Conduction   of    Subnormal    Disturbances  in    Normal    Nerve. 

Journ.  of  Physiol.,  1912,  xlv.  389. 
MKEK  and  LEAPER.     On  the  Effects  of  Pressure  on  the  Conductivity  in  Nerve  and 

Muscle.     Amer.  Journ.  of  Physiol.,  1911,  xxvii.  308. 
KKITH  LUCAS.     On  the  Sunimation  of  Adequate  Stimuli  in  Muscle  and  Nerve. 

Journ.  of  Physiol.,  1910,  xxxix.  461. 
GOTCH.     The  Delay  of  the  Electrical  Response  of  a  Nerve  to  a  second  Stimulus. 

Journ.  of  Physiol.,  1910,  xl.  250. 
ADRIAN  and  LUCAS.     On  the  Summation  of  a  Propagated  Disturbance  in  Nerve 

and  Muscle.     Journ.  of  Physiol.,  1912,  xliv.  68. 
KEITH  LUCAS.     On  the  Refractory  Period  of  Nerve  and  Muscle.    Journ.  of  Physiol., 

1909,  xxxix.  331. 
SCOTT.     On  the  Relation  of  Nerve  Cells  to  Fatigue  of  their  Nerve  Fibres.     Journ. 

of  Physiol.,  1906,  xxxiv.  145. 

HALLIBURTON.     Biochemistry  of  Nerve  and  Muscle.     London,  1904. 
ALCOCK  and  LYNCH.      On   the   Relation   between   the   Physical,    Chemical,   and 

Electrical  Properties  of  the  Nerves.     Journ.   of  Physiol.,  1910,  xxxix.  402  ; 

and  1911,  xlii.  107. 

SCOTT.     On  the  Metabolism  and  Action  of  Nerve  Cells.     Brain,  1905,  xxvii.  506. 
KEITH  LUCAS.      On  the  Recovery   of  Muscle  and  Nerve  after  the  Passage  of  a 

Propagated  Disturbance.     Journ.  of  Physiol.,  1910,  xli.  368. 
ADRIAN.     Wedensky  Inhibition  in   Relation  to  the  "  All-or-None"   Principle   in 

Nerve.     Journ.  of  Physiol.,  1913,  xlvi.  384. 
HEAD,  RIVERS,  and  SHERREX.     The  Afferent  Nervous  System  from  a  New  Aspect. 

Brain,  1905,  xxviii.  99. 
HEAD  and   RIVERS.      A  Human   Experiment   in  Nerve  Division.     Brain,   1908, 

xx  xi.  323. 


CHAPTER  V 

SPINAL   CORD   AND    NERVES 

CONTENTS. — 1.  Grey  and  white  matter  of  the  spinal  cord.  2.  Extra-  and  intra- 
spinal  nerve-cells  ;  their  connections  with  the  root-fibres  and  tracts  which  ma.ke 
up  the  spinal  columns.  3.  Spinal  roots.  Bell-Magendie  law  of  localisation  of 
sensory  and  motor  tracts.  Waller's  law  of  degeneration  after  section.  4.  Func- 
tional relations  between  afferent  and  efferent  roots.  5.  Segments]  arrange- 
ment of  .spinal  roots.  6.  Reflex  activity  of  segments  of  cord  ;  shock  after  section 
of  cord.  7.  Short  and  long  spinal  reflexes;  laws  of  reflex  spread.  8.  Genesis  of 
spinal  reflexes  ;  central  factors  that  inhibit  or  promote  them.  9.  Tonic  and 
automatic  functions  of  spinal  cord  ;  "  knee-jerk"  or  patellar  reflex.  10.  Trophic 
functions  of  spinal  cord.  11.  Sensory  functions  and  Pfliiger's  "spinal  soul." 
1'2.  Spinal  cord  an  instrument  of  the  brain  ;  spino-cerebral  and  cerebro-spinal 
paths  of  conduction.  13.  Localisation  of  principal  spinal  centres  ;  phenomena  of 
spinal  deficiency  (dogs  with  amputated  cord,  Goltz).  Bibliography. 

BlCHAT  distinguished  two  main  parts  of  the  nervous  system, 
the  Cerebrospinal  System  and  the  Splanchnic  or  Sympathetic 
System.  The  first  regulates  the  relations  between  the  organ- 
ism and  the  external  world  and  presides  over  the  functions 
of  animal  life;  the  second  controls  the  relations  between  the 
respective  organs,  and  presides  over  the  functions' of  vegetative 
(or  visceral)  life.  Acceptable  as  this  dualistic  conception  of 
the  nervous  system  may  be  in  the  abstract,  it  should  be  clearly 
recognised  that  it  goes  too  far,  and  gives  rise  to  error  in  the 
localisation  and  definition  of  the  boundaries  between  the  two  parts 
of  the  system.  The  cerebrospinal  axis  is  not  completely  detached 
from  the  sympathetic  system.  While  the  two  are  quite  distinct 
at  the  periphery  to  which  both  are  distributed,  they  intermix  in 
the  central  nervous  system  and  fuse  into  a  single  system.  The 
cerebrospiual  axis  controls  the  functions  of  animal  life,  but  is  not 
thereby  excluded  from  the  control  of  the  visceral  organs  also ;  on 
the  other  hand,  the  sympathetic  does  not  represent  the  entire 
nervous  system  of  visceral  life,  but  only  that  part  of  it  which  lies 
outside  the  cerebrospinal  axis.  It  may  thus  be  treated  as  the 
part  of  the  latter  which  is  distributed  in  the  form  of  gangliated 
plexuses  to  the  visceral  organs.  Experimental  analysis  shows 
fundamentally  the  same  nervous  mechanisms  in  the  ganglia  of  the 
sympathetic  as  exist  in  the  spinal  cord. 

278 


CHAP.  V 


SPINAL  COED  AND  NEEVES 


279 


I.  The  spinal  cord, 'which  occupies 
the  whole  extent  of  the  vertebral  canal 
in  the  early  months  of  foetal  life,  ex- 
tends in  the  adult  from  the  foramen 
occipitale  magnum  to  the  lower  edge 
of  the  first  lumbar  vertebra,  and  has 
an  average  length  of  45  cm.  (Fig.  167). 

There  is  a  corresponding  segment 
or  metamere  of  the  spinal  cord  with 
two  pairs  of  nerves  connected  with  it 
for  each  segment  of  the  vertebral 
column.  But  the  metamerism  of  the 
roots  must  be  distinguished  from  the 
metamerism  of  the  cord.  The  former 
is  a  true  and  perfect  metamerism, 
because  each  pair  of  nerves  (neuromcrc') 


FIG.  167. — Diagrammatic  view  from  before  of  spinal  cord 
and  medulla  oblongata,  including  the  roots  of  tin? 
s]iinal  and  some  of  the  cranial  nerves,  and  on  one  side 
the  gangliated  chain  of  the  sympathetic.  (All™ 
Thomson.)  J.  The  spinal  nerves  are  enumerated  in 
order  on  the  right  side  of  the  figure.  Br,  brachial 
plexus  ;  Or,  anterior  crural ;  0,  obturator ;  and  Sc,  great 
sciatic  nerves,  coming  off  from  lumbo-sacral  plr.xus  ; 
X,  X>  filum  terminale;  a,  b,  c,  superior,  middle,  and 
inferior  cervical  ganglia  of  the  sympathetic,  the  last 
united  with  the  1st  thoracic,  il  :  <l' ,  the  llth  thoracic 
ganglion  ;  I,  the  12th  thoracic  (or  1st  lumbar) ;  below 
ss,  the  chain  of  sacral  ganglia. 


is  in  relation  at  the  periphery  with 
definite  and  circumscribed  portions  of 
groups  of  muscles  (myomeres)  and 
cutaneous  areas  (dermatomeres},  as  we 
shall  see  in  discussing  the  peripheral 
distribution  of  the  spinal  nerves.  In 
the  spinal  cord,  on  the  other  hand, 
metamerism  is  reduced  to  its  lowest 
terms.  Originally  independent,  during 
phylogenetic  and  ontogenetic  evolution 
the  spinal  segments  (myelomeres)  have 
fused, and  their  functions  have  mingled. 
What  remains  of  their  primary  inde- 
pendence is  confined  to  the  intimate 
functional  connection  that  exists  in 
carrying  out  the  simplest  reflex  acts 
between  the  ventral  and  the  dorsal 
roots  of  the  same  spinal  segment. 

Fig.  168  shows  the  natural  appear- 
ance of  a  segment  of  the  cord,  with 
the  corresponding  pair  of  spinal  nerves 


Cl 


Hr 


IS*-' 


a 


J2 


ss) 


280 


PHYSIOLOGY 


CHAP. 


issuing  from  it  by  two  distinct  roots.  The  ventral  root  consists  of 
a  larger  number  of  slender  bundles  ;  the  dorsal  root  contains  a 
smaller  number  of  thicker  bundles.  The  roots  on  the  two  sides 
are  never  perfectly  symmetrical.  The  ventral  roots  (excepting 
those  of  the  first  cervical  pair)  are  as  a  whole  smaller  than  the 
dorsal  roots  and  probably  contain  a  smaller  number  of  fibres. 
This  was  in  fact  determined  by  Birge  on  two  frogs,  in  which  the 
dorsal  roots  contained,  respectively,  3781  and  5335  fibres,  and  the 
ventral  roots  3528  and  4283  fibres. 


FIG.  168. — Different  views  of  a  portion  of  the  spinal  cord  from  the  cervical  region  with  the  roots  of 
the  nerves.  Slightly  enlarged.  (Allen  Thomson.)  In  A  the  anterior  or  ventral  surface  is 
shown,  the  ventral  nerve-root  of  the  right  side  having  been  divided  ;  B,  view  of  the.  right  side  ; 
C,  the  upper  surface  ;  D,  nerve-roots  anil  ganglion  from  below.  1,  ventral  median  tissm  r  ; 
•2,  dorsal  median  fissure;  3,  ventro  -  lateral  impression,  over  which  the  bundles  of  the 
ventral  nerve-root  are  seen  to  spread  (too  distinct  in  figure) ;  4,  dorso-lateral  groove,  into  which 
the  bundles  of  the  dorsal  root  are  seen  to  sink  ;  5,  ventral  root ;  5',  in  A,  ventral  root  divided 
and  turned  upwards  ;  ii,  dorsal  root,  the  fibres  of  which  pass  into  the  ganglion,  6'  ;  7,  united 
or  compound  nerve  ;  7',  dorsal  primary  branch,  seen  in  A  and  D  to  be  derived  partly  from 
ventral,  partly  from  dorsal  root. 

In  vertebrates  the  length  of  the  individual  segments  of  the 
spinal  cord  is  not,  as  a  rule,  equal  to  the  height  of  the  correspond- 
ing vertebrae ;  it  usually  decreases  from  above  downwards,  so  that 
the  length  of  the  spinal  cord  only  amounts  to  three-quarters  that 
of  the  vertebral  canal.  The  successive  roots  in  descending  series 
have  therefore  a  more  oblique  longitudinal  course,  and  travel 
farther  before  they  reach  the  corresponding  intervertebral  foramina. 
The  lower  part  of  the  vertebral  canal  merely  contains  a  mass  of 
nerve-roots  known  as  the  cauda  cquina. 

The  cervical  enlargement  of  the  cord,  which  comprises  the 
reoion  of  the  roots  that  make  up  the  brachial  plexus,  is  largest  at 


SPINAL  CORD  AND  NEEVES 


281 


the  height  of  the  5th  and  6th  cervical  vertebrae  and  ends  at  the  level 
of  the  2nd  and  3rd  thoracic  vertebrae.  The  lumbo-sacral  enlarge- 
ment, which  comprises  the  segments  that  send  roots  to  the  lumbo- 
sacral  plexus,  begins  at  the  level  of  the  10th  dorsal  vertebra  and  is 
largest  at  the  level  of  the  12th.  Next  comes  the  conus  wcdulhiris, 
which  terminates  at  the  level  of  the  1st  or  2nd  lumbar  vertebra 
in  the  hlum  terminate,  by  which  the  cord  is  attached  to  the 
coccyx. 

The  cord  as  a  whole  is  enclosed  in  a  sheath  (thcccC)  formed  of 
a  dense  fibrous  membrane,  the  dura  mater,  which  is  attached  to 


Ml 


KK..  li'i'.i.—  Diagrammatic  transvrisr  section  of  spinal  cord.  (Er-l>.)  o,  tissur:>  longitudinalis  ventralis ; 
h,  f.  1.  dorsal;  e,  ventral  column;  rf,  lateral  column;  e,  dorsal  column;  ./,  t'linieulus  .Lji-acili.s  ; 
ij,  fimiculus  cuneatus ;  h,  ventral;  t,  dorsal  root;  k.  central  canal;  /,  suleus  intermedius 
dorsalis:  «i,  ventral  horn;  H,  dorsal  horn;  o,  traetus  intermedio  -  lateralis ;  <',  lu-ni/essus 
ivt  ienlaris  ;  a,  wliite  or  ventral  commissure;  r,  grey  or  dorsal  commissure;  s,  Clarke's 
column  or  coliimiia  vesicularis. 

the  periosteum  that  lines  the  interior  of  the  vertebral  canal. 
Enclosed  in  the  dura  mater,  the  cord  is  protected  against  external 
pressure,  and  readily  gives,  without  undue  strain,  to  the  twisting 
and  displacement  caused  by  the  movements  of  the  vertebral 
column.  In  fact  there  is  a  space  between  the  dura  mater  and  the 
cord,  filled  with  a  lymphatic  fluid  known  as  the  cc rebro spinal  fluid, 
which  is  continually  formed  as  fast  as  it  diffuses  through  the 
lymphatic  spaces  in  the  spinal  roots. 

Inspection  of  a  transverse  section  of  the  spinal  cord  (Fig.  169) 
shows  the  arrangement  of  the  central  grey  matter  and  the 
peripheral  white  matter,  but  comparison  of  a  series  of  transverse 
sections  made  at  different  levels  (Fig.  1*70)  shows  that  different 
regions  present  special  characteristics  and  variations  in  form, 


282 


PHYSIOLOGY 


CHAP. 


and  in  the  relative  quantity  of  grey  and  white  matter,  particularly 
in  the  region  of  the  cervical  and  lumbar  enlargements. 

By  means  of  Otto  Stilling's  table  of  planirnetric  measurements 
of  the  cross-sections  of  single  spinal  roots,  of  the  grey  and  white 
matter,  and  of  the  different  bundles  at  the  level  at  which  each  root 


FIG.  170.— Transverse  section  of  spinal  cord  at  dim-rent  heights.  (W.  R.  Cowers.)  Twice  the 
natural  si/e.  The  letters  and  numbers  indicate  the  position  of  each  section;  Co,  at  level1  of 
fnrry.U'Ml  nerve;  Sac.4,  of  4th  sacral;  L3,  of  3rd  lumbar,  and  so  on.  The  grey  substance  Is 
shaded  dark,  and  the  in-i  vc-erlls  within  it  are  indicated  by  dots. 

emerges,  Woroschiloff  constructed  the  diagrammatic  curve  of 
Fig.  171,  iu  which  the  abscissa  represents  the  points  at  which  the 
roots  emerge,  while  the  ordinates  indicate  the  sectional  areas  of 
the  grey  matter,  the  roots,  and  the  different  columns  (dorsal, 
lateral,  ventral).  The  first  curve  (<jr]  shows  the  increase  of  grey 
matter  near  the  lumbar  and  cervical  enlargements.  The  second 


SPINAL  CORD  AND  NEKVES 


283 


curve  (nr)  shows  that  the  sectional  areas  of  the  spinal  roots  also 
increase  at  the  two  enlargements,  so  that  there  is  a  certain  ratio 
between  the  number  of  the  root-fibres  and  the  amount  of  grey 
matter  in  the  corresponding  segments  of  the  cord.  The  three  last 
curves  (pc,  Ic,  ac)  show  that  the  white  matter  of  the  cord, 
particularly  that  of  the  lateral  and  dorsal  columns,  gradually 
increases  in  bulk  from  below  upwards. 

The  nerve-cells  are  not  uniformly  distributed  in  the  grey 
matter,  but  are  collected  into  groups  which  occupy  definite  and 
approximately  constant  positions  in  the  different  regions,  in  which 
they  form  columns  of  cells.  The  largest  ganglion  cells  are  in  the 
ventral  part  of  the  ventral  horn.  They  increase  in  number  at  the 
level  of  exit  of  each  ventral  root,  especially  in  the  thoracic  region 
of  the  cord,  which  indicates  its  metameric  origin.  They  also 


FIG.  171.— Diagram  to  show  relative  and  absolute  size  of  sections  of  the  grey  matter,  white 
columns,  and  spinal  roots  at  different  levels  of  the  spinal  cord.  (After  Woroschiloff.)  The 
sections  of  the  different  roots  (w.r.),  grey  matter  ((jr.),  and  lateral,  dorsal,  and  ventral  columns 
(I.e.,  p.i.:,  «.<•.)  are  represented  by  curves,  their  common  abscissa  beiu.u  intersected  by  ordinates, 
each  of  which  corresponds  to  a  pair  of  spinal  nerves.  In  the  ordinates  each  mm.  of  rise  above 
the  abscissa  line  corresponds  to  about  1  sq.  mm.  area  of  section. 

increase  in  number  in  the  two  enlargements,  parallel  with  the 
increased  size  and  number  of  fibres  of  the  ventral  roots  in 
these  parts. 

Another  group  of  cells,  distinct  from  the  preceding,  is  found 
in  the  lateral  horn,  mainly  in  the  thoracic  segments,  where  the 
lateral  horn  appears  as  a  distinct  formation.  Its  cells  are  smaller 
than  those  of  the  preceding  group,  and  are  generally  spindle- 
shaped,  with  their  larger  axes  directed  towards  the  apex  of  the 
horn. 

The  two  dorsal  grey  horns,  again,  have  at  their  base,  particularly 
in  the  thoracic  region,  a  well-defined  oval  group  of  ganglion  cells, 
which  are  smaller  than  those  of  the  ventral  horn.  This  is  the 
so-called  columna  vesicularis  or  Clarke's  column.  In  the  cervical 
segments  and  lower  part  of  the  lumbar  cord  it  is  represented  by 
the  cervical  nucleus  and  the  sacral  nucleus  of  Stilling  respectively. 
And  in  other  parts  of  the  spinal  cord  there  are  found  the  so-called 


284  PHYSIOLOGY  CHAP. 

solitary  cells,  which  from  their  form  and  character  must  be  also 
regarded  as  belonging  to  this  group. 

The  chief  characteristic  by  which  the  cells  of  the  grey  matter 
of  the  cord  are  distinguished  from  those  of  the  inter-vertebral 
and  sympathetic  ganglia  is  the  branching  of  their  processes  into  a 
vast  number  of  very  fine  filaments,  similar  to  the  ramifications  of 
the  delicate  fibrils  by  which  the  axis-cylinders  of  the  peripheral 
nerves  terminate  in  the  tissues. 

The  nerve-fibres  of  the  columns  of  the  white  matter  of  the 
cord  have  medullated  sheaths,  but  no  sheath  of  Schwann.  They 
vary  considerably  in  diameter ;  the  largest  are  in  the  ventral 
roots  and  outer  parts  of  the  lateral  columns ;  those  of  the  dorsal 
roots  and  columns  are  smaller ;  smaller  still  those  of  the  anterior 
commissure  and  the  parts  of  the  lateral  columns  near  the  grey 
matter. 

The  general  direction  of  the  fibres  is  transverse  in  the  roots, 
longitudinal  in  the  columns,  oblique  in  the  commissures,  but  in  the 
grey  matter  the  medullated  fibres  interlace  in  all  directions,  both 
individually  and  when  collected  into  bundles,  while  its  fine  non- 
medullated  fibres  form  an  inextricable  felt-work. 

The  white  matter  is  traversed  by  a  number  of  radial  septa, 
along  which  the  marginal  vessels  penetrate  into  the  cord.  These 
septa  consist  of  neuroglia  which  also  supports  the  medullated 
nerve-fibres  in  a  loose  network  and  forms  a  denser  net  in  the 
grey  matter.  The  neuroglia  is  particularly  rich  in  the  substantia 
gelatinosa,  which  surrounds  the  central  canal  of  the  cord  and 
covers  the  cap  of  the  dorsal  horn.  It  is  epiblastic  in  origin, 
and  as  it  consists  of  keratin,  it  is  very  resistant  to  artificial 
digestion. 

II.  As  the  minute  structure  of  the  cord  and  the  still  unsettled 
questions  of  anatomy  are  not  the  business  of  the  physiologist,  we 
must  confine  ourselves  to  such  facts  as  are  more  particularly  of 
physiological  interest. 

One  of  the  best-established  anatomical  facts  is  that  the  fibres 
of  the  ventral  roots  represent  the  processes  or  axis-cylinders  of 
ganglion  cells  that  lie  in  the  grey  matter  of  the  ventral  horn  of 
the  same  side  (Deiters,  1865).  Some  of  these  root  fibres,  however, 
pass  through  the  ventral  commissure  and  form  connections  with 
the  cells  of  the  ventral  horn  on  the  opposite  side. 

The  fibres  of  the  dorsal  roots,  on  the  contrary,  are  not  directly 
connected  with  the  cells  of  the  dorsal  horn,  but  are  processes  of  the 
spinal  ganglion  cells.  These  cells  usually  have  a  single  process,  which 
divides  after  a  short  course  into  two  branches,  one  of  which  passes 
to  the  periphery  through  the  spinal  nerves,  while  the  other  branch 
passes  to  the  cord  as  the  dorsal  or  posterior  root.  Almost  all  the 
fibres  of  this  root  divide  on  reaching  the  cord  (Eamon  y  Cajal  and 
Kolliker)  into  two  main  branches,  one  ascending,  the  other 


SPINAL  COED  AND  NEEVES 


285 


descending  in  the  dorsal  column  and  the  region  round  the  dorsnl 
horn  (Fig.  172).  Both  these  branches  give  off  collaterals  at  fairly 
close  intervals,  which  run  towards  the  grey  matter,  penetrate  it, 
and  ramify  around  its  cells.  Some  of  these  collaterals  run  to  the 
cells  of  the  ventral  horn  on  the  same  side ;  others  enter  into 
direct  relation  with  the  cells  of 
Clarke's  column  or  the  solitary 
cells  of  the  dorsal  horn. 

To  summarise  the  facts  most 
essential  to  physiology  :  The  fibres 
of  the  peripheral  nerves  which 
emerge  by  the  ventral  roots  have 
their  cells  of  origin  in  the  ventral 
horn  of  the  cord,  and  those  which 
enter  by  the  dorsal  roots  originate 
not  from  the  cells  of  the  cord,  but 
from  the  spinal  ganglia.  In  the 
grey  matter  of  the  cord  the  nerve- 
tibres  of  the  two  roots  are  closely 
related,  so  that  transmission  of  the 
excitations  from  one  root  to  the 
other  is  possible,  either  by  simple 
contact  between  the  ends  of  the 
neurones,  or  by  the  anastomosis  of 
the  neurones  among  themselves 
into  a  common  fibrillary  network. 
Lastly,  the  nerve-fibres  which  make 
up  the  dorsal  white  column  of  the 
cord  are  the  prolongation  of  the 
peripheral  fibres  that  enter  by 
the  dorsal  roots ;  but  the  fibres 
that  constitute  the  ventro-lateral 
columns  are  independent  of  the 
peripheral  neurones. 

Investigations  on  the  embryo- 
logical  development  of  the  spinal 
cord,  pathological  observations  on 
spinal  diseases  in  man,  and  the 
effects  of  partial  sections  of  the 
cord  in  animals,  have  yielded  the 
highly  important  result  that  the  columns  which  make  up  the 
white  matter  of  the  cord  are  not  uniform  masses  of  nerve-fibres,  but 
can  be  subdivided  into  well-differentiated  bundles  or  tracts.  The 
enibryological  investigations  of  Flechsig  led  to  the  very  important 
conclusion  that  the  development  of  the  myelin  sheath  does  not 
take  place  simultaneously  on  all  the  longitudinal  fibres  of  the 
spinal  cord,  but  it  occurs  earlier  in  certain  bundles  or  tracts  of 


FIG.  172.— Longitudinal  section  of  dorsal 
column  of  spinal  cord  of  chick  on  eighth 
day  of  incubation.  (Ramon  y  Cajal.) 
Shows  the  course  of  five  entering  fibres 
of  dorsal  root,  and  some  longitudinal 
fibres  of  ventral  column.  A,  A,  fibres  of 
dorsal  root;  B,  bifurcation  of  one  in 
form  of  Y  ;  C,  D,  origin  of  collateral 
branches  ;  B,  fibres  of  Qoll's  tract,  also 
giving  oft' collaterals. 


286 


PHYSIOLOGY 


CHAP. 


fibres   than   in  others,  as  partially  shown   in  Fig.   173.     By  this 
means  certain  tracts  can  be  distinguished. 

Corresponding  results  are  obtained  from  the  study  of  the 
ascending  and  descending  degenerations  observed  in  cases  of  spinal 
disease,  or  experimentally  produced  in  animals.  In  cases  of  hemi- 
plegia  from  cerebral  apoplexy  complete  degeneration  of  the  pyram- 
idal tract  is  seen  in  the  cord  (Fig.  174).  After  transection  of  an 
upper  thoracic  segment  (Fig.  175)  descending  degeneration  of  both 
pyramidal  tracts  can  be  followed  to  the  lumbo-sacral  cord,  and 
ascending  degeneration  of  the  columns  of  Goll  and  the  cerebellar 

O  O 


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FIG.  173. — Section  of  spinal  curd  of  new-born  animal.  The  pyramidal  tracts  which  are  not  yet 
m\  i-linated  an-  rli-ar  and  transparent.  The  pyramidal  tracts  of  the  ventral  column  extend  to 
the  periphery  of  tin-  ventral  lateral  column.  (Edin^vr.)  ll'ni-;el-ZotiK  =  root-zone ;  Grenz- 
scliicht  =  limiting  layer;  KleinKirnseitenstrang-Bahn=d.\'KC\  cerebellar  tract;  Seitenstrtiity- 
Vorderstrang-Grwndbiindel=groiui<l  bundle  of  lateral  and  ventral  column. 

tracts  through  the  cervical  segments.  Other  ascending  and 
descending  degenerations  are  observed  with  other  diseases,  or  as 
the  result  of  injuries  or  experimental  lesions. 

The  methodical  study  of  cross-sections  of  the  different  segments 
of  the  cord,  both  in  cases  of  pathological  or  experimental  degenera- 
tion and  in  the  embryonic  cord  at  different  periods  of  develop- 
ment, has  made  it  possible  to  distinguish  the  two  categories  of 
fibres  in  the  white  columns.  The  first  consists  of  tracts,  the 
sectional  area  of  which  increases  continuously  from  below  upwards 
by  constant  addition  of  new  fibres.  In  the  second  the  tracts  do 
not  increase  from  below  upwards,  but  vary  in  diameter  in  different 
regions  according  to  the  bulk  of  the  corresponding  spinal  roots. 
The  bundles  in  the  first  group  represent  the  long  conducting 
paths,  spino-cerebral  and  cerebro-spinal,  which  directly  connect 


V 


SHNAL  COED  AND  NEEVES 


287 


the  different  segments  of  the  cord  with  the  brain,  or  the  different 

regions  of  the  brain  with 

the  cord.    The  bundles  in 

the  second  group,  on  the 

other  hand,  are  the  short 

intraspinal  ascending   or 

descending   paths   which 

connect  together  different 

elements   of  the  cord   at 

different  levels. 

We  must  glance  at 
the  principal  facts  in 
regard  to  the  nature  and 
relations  of  the  main 
tracts  in  the  two 
groups  :— 

(a)  The  pyramidal 
tracts  are  composed  of 
the  axis-cylinders  of  cells 
in  the  Eolandic  area  of 
the  cerebral  cortex.  They 
pass  through  the  internal 
capsule,  cerebral  ped- 
uncle, and  pyramids  of 
the  medulla  oblongata, 
where  most  of  the  fibres 
decussate  before  descend- 
ing in  the  form  of  a 
compact  bundle  in  the 
dorsal  portion  of  the 
lateral  column  (crossed 
lateral  pyramidal  tract). 
A  small  number  of  these 
fibres  which  do  not  cross 
in  the  bulb  descend  on 
both  sides  of  the  ventral 
median  i fissure  as  the 
direct  pyramidal  tract 
described  by  Tiirck  ;  this 
usually  ends  about  half- 
way down  the  thoracic 

COrd.        The    fibres    Of    the    FIG.    174.  — Secondary     de-     FIG.  17">.— Sre.m.lary  ascend- 

.  j    -,  p/,       scending  degeneration  due        ins;    and    descending    de- 

pyraniiual    tracts    give   Oil        to  a  lesion  in  left  cerebral         generations  due  to  lesions 

pnl'htpri'h        nlrrncr        thpir        licniisi.liere.    (After  Erb.)         of    upper    thoracic    cord. 

(After  Sti  mnpell.) 

course,     which     arborise 

around  the  cells  of  the  ventral  roots,  so  that  each  fibre  is  able 

to  convey  excitations  to  a  series  of  cells  which  are  distributed 


c— 


288  PHYSIOLOGY  CHAP. 

along  the  different  segments  of  the  ventral  grey  matter.  It  is 
probable  that  some  at  least  of  the  collaterals  of  the  direct 
pyramidal  tract  decussate  in  the  cord,  and  pass  to  the  opposite 
side  through  the  ventral  commissure,  before  they  enter  into 
relation  with  the  cells  of  the  ventral  roots. 

As  shown  by  Fig.  174  the  pyramidal  fibres  undergo  a  descend- 
ing degeneration,  but  this  never  extends  to  the  fibres  of  the 
ventral  roots  so  long  as  the  cells  of  the  ventral  horn  remain 

intact. 

(b)  Two  bundles  can  be  traced  from  the  lateral  column  to  the 
cerebellum :  one,  described  by  Marchi,  undergoes  descending 
degeneration  after  extirpation  of  the  same  side  of  the  cerebellum 
(direct  ventro-lateral  cerebellar  tract);  the  other,  described  by 
Flechsig,  degenerates  in  the  ascending  direction,  after  lesions  of 
the  lateral  part  of  the  cord  (direct  dorso-lateral  cerebellar  tract). 

The  former,  as  shown  by  Fig.  176,  occupies 
in  dogs  the  ventral  three-fourths  of  the 
veutro-lateral  column,  and  also  dips  in- 
wards in  front  of  the  crossed  pyramidal 
tracts.  [More  recent  investigations  have 
proved  that  it  does  not  take  origin  in 
the  cerebellum,  but  from  cells  of  the  brain- 
stern  that  lie  immediately  Ventral  to  it., 
no.  i76.-section  of  s,,inai  cord  and  chiefly  from  Deiter's  nucleus.— ED. ] 
(inmiiai  region)  of  dog,  killed  ^\IQ  direct  ascending  cerebellar  tract 

three  months  alter  removal  of  -,i-,r-\     •       i  •       i-  • 

right  half  of  cerebellum,      (rig.     l/o)    IS     better     knOWll  ;     it    llCS    in 

LMsahaded^thdotr  the  dorsal  margin  of  the  lateral  column, 

and  increases  in  size  as  it  ascends,  till  on 

reaching  the  sides   of  the   bulb  it  passes  through   the   restiform 
body  to  the  median  lobe  of  the  cerebellum. 

The  fibres  of  Flechsig's  cerebellar  tract  originate  from  the  cells 
of  Clarke's  column  on  the  same  side,  and  therefore  degenerate 
upwards. 

(c)  Gowers  identified  another  important  tract,  which  occupies 
an  irregular  area  in  the  lateral  column  in  front  of  the  direct  cere- 
bellar tract  and  the  crossed  pyramidal  tract,  and  is  known  as  the 
ventro-lateral  ascending  bundle  (Fig.  177).  This  tract  grows  larger 
as  it  ascends;  it. can  be  followed  into  the  bulb  and  pons  Varolii. 
After  lesions  of  the  lumbar  segments  it  undergoes  ascending 
degeneration.  Its  cells  of  origin  are  probably  in  the  dorsal  horn. 
We  shall  return  to  the  significance  of  this  bundle  in  considering 
the  effects  of  partial  transverse  section  of  the  cord. 

(d~)  Each  dorsal  column  contains  two  bundles,  which  are 
separated  anatomically  by  a  septum  from  the  middle  of  the 
thoracic  region  upwards :  the  funiculus  gracilis  or  column  of  Goll 
occupies  the  medial  dorsal  part,  and  the  funiculus  cuneatus  or 
tract  of  Burdach  the  lateral  part  of  the  column.  We  have 


SPINAL  COED  AND  NERVES 


280 


already  said  that  the  fibres  of  the  dorsal  columns  are  the  direct 
continuation  of  the  dorsal  roots,  which  originate  in  the  cells  of 
the  spinal  ganglia.  The  fibres  of  the  tract  of  Goll  are  small 
in  diameter,  and  many  of  them,  instead  of  entering  the  grey 
matter  of  the  cord,  run  as  far  as  the  medulla  oblongata,  where 
they  terminate  in  a  special  nucleus  of  grey  matter  (nucleus  of 
the  funiculus  gracilisj.  The  tract  of 
Burdach  consists  of  larger  fibres  which 
send  numerous  collaterals  to  the  grey 
matter,  and  penetrate  into  it  after  a  longer 
or  shorter  course,  coming  into  intimate 
relation  with  the  cells  of  Clarke's  column. 
Both  these  tracts  undergo  ascending  de- 
generation after  section  or  compression  of 
the  cord,  or  severance  of  the  dorsal  roots. 
Goll's  tract,  which  is  myelmated  later, 
contains  the  longer  paths  which  arise 
from  the  lumbo-sacral  and  lower  thoracic 
roots ;  while  Burdach's  tract,  for  the  most 
part,  consists  of  short  intraspinal  paths, 
with  longer  fibres  derived  from  the  higher 
thoracic  and  cervical  roots,  which  do  not 
enter  the  tract  of  Goll,  and  terminate  in 
the  nucleus  of  the  funiculus  cuneatus  or 
nucleus  of  Burdach  in  the  bulb.  Thus 
the  two  bundles  of  the  dorsal  column  are 
composed  principally  of  exogenous  fibres 
or  spino-cerebral  paths  of  conduction,  but 
they  also  contain  endogenous  fibres  or 
intraspinal  paths. 

(e)  The  endogenous  intraspinal  fibres 
are  represented   mainly  by  the   portions 
of  the  white  matter  adjacent  to  the  grey. 
Such  is  probably  the  character  of  the  zone  Fio.  ivT.-As^ndm,^  degeneration 
of  fine  fibres  which  fills  the  area  between 
the  ventral  and  dorsal  horns,  termed  by       cowers,  after 
Sherrington   and   Grlinbauni   the   lateral 
limiting  layer  (Fig.  178,  I.  n.  5).     But  a 

certain  number  of  intraspinal  fibres  with  a  short  course  are  inter- 
spersed among  the  fibres  of  the  crossed  pyramidal  tract.  They 
are  distinguished  from  the  latter  by  their  earlier  myelination,  and 
by  the  fact  that  they  do  not  degenerate  with  them  (Miinzer). 

The  so-called  ground  bundle  of  the  ventro- lateral  column 
occupies  a  sectional  area  that  varies  with  the  area  of  the  grey 
matter.  Probably  many  of  its  fibres  are  interspinal  and  serve  to 
connect  the  grey  matter  of  different  segments  of  the  cord. 

The  ventral  zone  of  the  dorsal  column  consists  of  fibres  whose 


the 


cord   at    the    1st   liiinluii1 
m^nt.     (Gowers.) 


VOL.  Ill 


u 


290 


PHYSIOLOGY 


CHAP. 


cells  lie  in  the  dorsal  horn ;  they  do  not  degenerate  with  the  other 
parts  of  the  same  columns,  and  are  probably  also  endogenous 
internuncial  fibres. 

Certain  cells  of  the  intraspinal  system  have  axis -cylinders 
that  cross  with  those  of  the  other  side,  through  the  dorsal  white 
commissure. 

(/)  In  addition  to  the  cells  which  are  the  trophic  centres  for 
the  fibres  of  the  ventral  roots  and  the  white  matter,  the  grey 
matter  of  the  cord  also  contains  numerous  fibres,  which  traverse 
it  in  every  direction,  forming  a  close  plexus.  Many  of  these  are 
collaterals  of  the  long  and  short  paths  of  the  white  matter.  The 
observations  of  Sherrington  and  of  G.  Mingazzini  show  that  some 

A  B 


Km.  178. — Section  through  A,  cervical,  B,  lumbar  cord,  to  show  approximate  limits  of  the  respective 
systems  of  the  spinal  cord,  as  shown  by  embryological  research,  and  principally  from  prepara- 
tions of  secondary  degeneration  in  one  or  other  of  the  systems.  (Edinger.)  la,  pyramidal 
tract  of  lateral  column  ;  1,  pyramidal  tract  of  ventral  column  ;  2,  ground-bundle  of  ventro- 
lateral  bundle;  3,  ventro-lateral  cerebellar  tract;  4,  dorsal  cerebello-spinal  tract;  f),  external 
limiting  layer  of  grey  matter ;  0,  column  of  Burdach  ;  7,  column  of  Goll ;  8,  zone  of  entry  of 
roots  ;  9,  ventral  area  of  dorsal  columns. 

of  them  degenerate  after  ablation  of  the  Eolandic  area  of  the 
cerebral  cortex,  as  a  result  of  degeneration  of  the  pyramidal  tracts. 

Schiff  assumed  long  conducting  tracts  for  sensations  of  pain 
in  the  grey  matter ;  but  nowadays  only  short  paths  are  recognised 
in  it.  Painful  impulses  may  traverse  the  fibres  of  the  grey 
matter,  but  they  emerge  after  a  short  course  and  run  up  the 
lateral  columns  of  the  opposite  side,  probably  in  the  region  of  the 
tract  of  Gowers. 

III.  From  the  standpoint  of  general  physiology  the  spinal 
cord  may  be  regarded  as  a  highly  complex  organ — or,  better,  a 
series  of  intimately  connected  segmental  organs — which  receives 
all  the  excitatory  impulses  arising  at  the  periphery,  except  from 
the  head,  by  centripetal  paths,  and  reflects  them  directly  by 
centrifugal  paths,  or  else  conducts  them  farther  to  the  central 
stations  of  a  higher  order,  situated  in  different  regions  of  the 
brain.  Nearly  all  spinal  acts,  strictly  so-called,  present  under 


v  SPINAL  CORD  AND  NERVES  291 

normal  conditions  the  character  of  reactions  induced  by  external 
influences,  in  the  form  of  movements  which  are  adapted  to  adjust 
the  organism  temporarily  to  its  environment.  In  a  word,  the 
reflex  act  is  the  elementary  nervous  process  that  underlies  the 
most  complex  activities  of  the  spinal  system.  Many  of  the  spinal 
acts  commonly  termed  automatic  or  spontaneous,  since  they  appear 
to  be  independent  of  external  influences,  are  classed  by  other 
authors  among  reflex  actions,  the  distinction  between  reflex  and 
automatic  acts  having  varied  at  different  periods  and  in  different 
schools.  To  this  we  shall  return  later. 

The  first  question  before  entering  on  the  study  of  the  spinal 
reflexes  is  to  determine  whether  sensation  and  movement  depend 
on  separate  nerve-fibres  or  not,  i.e.  are  the  sensory  impulses  from 
the  periphery  to  the  cord  conducted  by  the  same  fibres  as  those 
which  conduct  motor  impulses  from  the  cord  to  the  muscles  ? 

From  remote  antiquity  it  has  been  assumed  that  the  sensations 
and  the  movements  of  animals  depend  on  distinct  nerve-fibres. 
Herophilus  and  Erasistratus,  as  well  as  Galen,  affirmed  this  from 
their  clinical  observations,  and  from  the  varying  effects  of  injury, 
which  abolished  now  sensibility,  now  motility,  and  by  irritating 
the  former  produced  pain,  or,  by  exciting  the  latter,  convulsions. 
"  There  are  nerves,"  said  Galen,  "  to  the  muscles  and  others  to  the 
skin :  when  the  former  are  affected,  movement  is  abolished,  when 
the  latter,  sensibility." 

The  next  question  is  whether  the  motor  and  sensory  nerves 
enter  and  leave  the  cord  together  or  separately.  Starting  from 
the  anatomical  fact  that  the  spinal  nerves  emerge  by  two  distinct 
roots  from  the  cord,  Walker  (1809)  was  happily  inspired  to 
attribute  different  functions  to  these  roots.  But  as  he  made  no 
experiments  he  fell  into  the  error  of  attributing  sensation  to  the 
ventral,  and  motor  functions  to  the  dorsal  roots.  In  the  same 
year  the  celebrated  naturalist  Lamarck  hit  on  the  same  idea, 
but  did  not  actually  determine  the  function  of  either  root.  The 
first  experimental  research  in  this  matter  was  made  by  Charles 
Bell  (1811).  But  as  he  worked  with  freshly  killed  rabbits  he 
was  unable  to  establish  the  function  of  the  dorsal  roots,  and 
merely  succeeded  in  demonstrating  the  motor  nature  of  the  ventral 
roots.  Convincing  proof  of  the  different  functions  of  the  two  roots 
was  not  forthcoming  for  another  ten  years,  when  it  was  afforded 
by  the  work  of  Magendie,  Job.  Miiller,  Panizza,  Longet,  and 
Claude  Bernard. 

In  1822  Magendie  discovered  that  cutaneous  sensibility  is 
abolished  in  the  regions  supplied  by  the  fibres  coming*  from 
divided  dorsal  roots,  while  it  is  unimpaired  when  the  ventral  roots 
are  cut.  He  exposed  the  posterior  portion  of  the  cord  in  very 
young  dogs,  divided  the  lumbar  and  sacral  dorsal  roots  on  one 
side,  and  closed  up  the  wound.  At  first  the  limb  on  the  operated 


292  PHYSIOLOGY  CHAP. 

side,  besides  being  insensitive,  appeared  to  be  completely  paralysed; 
but  after  a  few  minutes  distinct  movements  were  visible.  In 
other  experiments  Magendie  cut  the  ventral  roots  on  one  side 
and  left  the  dorsal,  when  he  noted  that  the  corresponding  limb, 
while  totally  immobile  and  flaccid,  preserved  its  sensibility  intact. 
He  concluded  that  the  posterior  roots  were  more  especially 
connected  with  sensibility,  the  anterior  roots  more  particularly 
with  movement. 

Magendie's  experiments  were  the  necessary  complement  to 
those  of  Bell,  who  affirmed  nothing  as  to  the  sensory  properties 
of  either  root.  The  merit  of  this  discovery  is  undoubtedly  shared 
by  both  investigators. 

On  repeating  and  varying  his  experiments,  Magendie  did  not 
always  obtain  such  clear  results  as  the  above,  and  he  published 
his  doubts  with  commendable  scientific  integrity.  But  they  were 
soon  removed  by  the  subsequent  experiments  of  other  workers  on 
animals  more  easily  operated  on  than  dogs.  The  most  classical 
demonstration  of  the  Bell  -  Magendie  law  was  given  by  Joh. 
Miiller  on  the  frog,  in  which  it  is  possible  to  expose  the  entire 
cord  without  serious  functional  depression.  Mltller's  frog,  familiar 
to  every  student  of  physiology,  shows  on  one  side  complete 
paralysis  of  movement  with  intact  sensibility,  on  the  opposite 
side  complete  paralysis  of  sensibility  with  intact  movements, 
when  all  the  ventral  roots  are  cut  on  the  one  side,  all  the  dorsal 
on  the  other. 

The  complete  evidence  for  the  Bell -Magendie  law  may  be 
summed  up  as  follows  :— 

(a)  On  exciting  or  dividing  a  ventral  root,  there  is  a 
localised  contraction  in  the  muscle  or  muscles  innervated  by 
that  root.  (&)  The  same  effect  is  obtained  on  stimulating  the 
peripheral  stump  of  the  same  ventral  root  by  any  stimulus, 
(c)  No  effect,  on  the  contrary,  is  obtained  when  the  central  stump 
is  stimulated.  (YZ)  Motor  paralysis  of  the  whole  limb  follows  on 
section  of  all  the  ventral  roots  that  innervate  its  muscles. 
(e)  Signs  of  pain  (cries,  or  more  or  less  diffuse  reflex  movements) 
are  obtained  on  exciting  or  dividing  any  dorsal  root.  (/)  The 
same  effect  is  produced  by  exciting  the  central  stump  of  the  same 
divided  root.  (#)  Excitation  of  the  peripheral  stump  has  no  effect. 
(Ji)  After  cutting  all  the  dorsal  roots  that  innervate  a  limb  it  is 
found  to  be  totally  insensitive. 

The  Bell-Magendie  law  holds  for  every  class  of  vertebrate.  It 
was  established  for  batracians  by  the  experiments  of  Joh.  Miiller, 
Panizza,  and  Fodera  ;  for  birds  by  those  of  Panizza,  Moreau,  and 
Schiff ;  for  fishes  by  those  of  Wagner,  Stannius,  and  Moreau. 

This  original  formula  had  to  be  revised  as  soon  as  it  became 
clear  that  the  nerves  of  the  sympathetic  system,  which  serve  the 
visceral  organs,  have  as  much  a  spinal  origin  as  the  somatic  sensory 


v  SPINAL  CORD  AND  NERVES  293 

and  motor  nerves.  Besides  the  motor  nerves  to  skeletal  muscles, 
the  motor  nerves  to  plain  muscle  (intestine,  excretory  ducts,  bronchi, 
vessels),  the  secretory  nerves,  the  inhibitory  or  dilatator  nerves, 
etc.,  must  all  be  taken  into  consideration.  All  these  nerves  were 
included  in  the  common  category  of  centrifugal  or  efferent  nerves. 
On  the  other  hand,  besides  the  nerves  of  general  or  specific  sense, 
the  excitation  of  which  produces  conscious  sensations,  other  nerves 
that  transmit  impulses  from  the  periphery  to  the  centres,  and  do 
not  evoke  any  appreciable  sensation,  had  to  be  recognised.  Both 
these  groups  of  nerves  were  included  in  the  general  category  of 
centripetal  or  afferent  nerves.  The  most  general  and  compre- 
hensive formula  for  the  Bell-Magendie  law  must  therefore  run  : 
the  ventral  roots  contain  only  centrifugal,  the  dorsal  roots  only 
centripetal  fibres. 

The  first  experiments  of  Bell,  Magendie,and  J.  Miiller  contain  no 
positive  demonstration  of  this  new  and  more  comprehensive  formula 
of  the  law  of  the  spinal  roots.  Yet  (as  already  discussed  in  Vol.  I. 
Chap.  X.)  the  results  of  experiments  by  Cl.  Bernard,  Schiff, 
Pniiger  on  vaso-constrictor  nerves,  of  Dastre,  Morat,  Gaskell  on 
vaso-dilatators,  of  Luchsinger  on  the  secretory  sweat  nerves,  which 
are  all  localised  in  the  ventral  roots,  agree  perfectly  with  it. 

Other  investigations,  however,  showed  that  the  Bell-Magendie 
law  in  its  wider  formula  is  not  universally  valid,  but  admits  of 
certain  exceptions.  According  to  the  work  of  Strieker  and  his 
pupils,  the  vaso-dilatators  to  the  posterior  extremities  are  contained 
in  the  4th  and  5th  dorsal  lumbar  roots  of  the  dog,  and  the  corre- 
sponding fibres  for  the  anterior  limbs  run  in  the  dorsal  roots  of 
the  brachial  plexus.  According  to  Steinach  the  motor  fibres  to 
the  oesophagus,  stomach  and  intestine,  including  the  rectum,  are 
contained  in  the  dorsal  roots  of  the  3rd- 6th  spinal  nerves  in 
the  frog.  This  was  disputed  by  Horton-Smith,  who,  however, 
admitted  that  he  had  found  motor  fibres  to  the  skeletal  muscles  in 
the  dorsal  roots  of  the  frog.  These  exceptions  to  the  law  agree 
with  the  histological  observations  of  Lenhossek  and  Ramon  y  Cajal, 
who  found  that  the  dorsal  roots  contain  centrifugal  elements,  i.e. 
some  cells  of  the  ventral  horn  send  out  their  axis-cylinders  by  the 
dorsal  roots. 

Magendie  was  the  first  to  point  out  from  certain  of  his  experi- 
ments that  the  dorsal  roots  sometimes  contain  motor  fibres,  and 
the  ventral  roots  sometimes  contain  sensory  fibres.  Owing  to 
these  contradictory  facts  the  value  of  the  law  of  the  functions  of 
the  roots  was  disputed  for  some  time ;  but  the  difficulty  dis- 
appeared when  Longet  and  then  Bernard  demonstrated  that  the 
sensibility  of  the  anterior  roots  was  only  an  apparent  exception  to 
the  Bell-Magendie  law.  The  sensory  elements  of  the  anterior 
root  really  corne  from  the  dorsal  root,  and  only  pass  through 
the  ventral  to  supply  the  sensory  innervation  of  the  nieninges. 


294  PHYSIOLOGY  CHAP. 

Demonstration  of  this  phenomenon,  which  Longet  termed  recurrent 
sensibility,  was  given  in  the  following  experiments  :— 

(a)  If  the  ventral  root  be  cut,  and  the  two  stumps  are  then 
stimulated,  sensory  effects  are  obtained  from  the  peripheral  end 
only,  while  excitation  of  the  central  stump  produces  no  effect. 

(&)  If  a  dorsal  root  be  cut,  the  sensibility  of  the  corresponding 
ventral  root  disappears  entirely,  whether  this  be  cut  or  not. 

Claude  Bernard  discovered  that  in  order  to  obtain  a  good 
demonstration  in  the  dog  of  the  sensibility  of  the  ventral  roots,  it 
is  necessary  to  wait  about  an  hour  after  exposing  the  cord.  If  the 
sensibility  of  the  roots  is  tested  immediately  after  the  vertebral 
canal  has  been  opened,  it  is  always  found  that  the  dorsal  roots 
alone  respond  to  stimulation.  This  fact  is  incontestable,  but  the 
explanation  given  by  Bernard  appears  to  us  incorrect.  He  assumes 
that  the  recurrent  sensory  fibres  of  the  ventral  roots  become 
insensitive  owing  to  the  shock  of  the  operation,  and  recover  their 
sensibility  with  rest.  But  under  normal  conditions  not  only  the 
ventral  roots  through  which  the  recurrent  fibres  pass,  but  also  the 
meninges  of  the  cord  to  which  they  are  distributed,  are  insensitive 
like  all  serous  membranes,  and  they  become  sensible  to  pain  only 
when  inflammation,  due  to  exposure  to  the  air  and  other  influences, 
sets  in.  Hence  we  may  conclude  that  the  fibres  that  run  back 
from  the  dorsal  to  the  ventral  roots  to  be  distributed  to  the 
meninges  belong  to  that  category  of  centripetal  nerve-fibres  that 
abound  in  all  visceral  organs,  and  are  normally  devoid  of  con- 
scious sensibility  ;  excitation  of  these  only  passes  the  threshold 
of  consciousness  to  arouse  sensations  of  pain  under  conditions  of 
irritation  or  inflammatory  reaction. 

Bernard  further  demonstrated  that  division  of  the  mixed  nerve 
trunk  at  a  certain  distance  from  the  union  of  the  two  spinal  roots 
abolishes  the  sensibility  of  the  ventral  root,  in  the  same  way  as 
after  division  of  the  dorsal  root.  This  fact  proves  that  the  point  at 
which  the  recurrent  fibres  turn  ceutripetally  is  not  at  the  junction 
of  the  roots,  but  in  the  nerve  plexuses  or  more  peripherally. 

Bernard  further  believed  that  he  had  demonstrated  that  the 
sensibility  of  each  ventral  root  was  dependent  solely  on  the  corre- 
sponding dorsal  root,  and  not  on  other  adjacent  sensory  roots,  but 
the  subsequent  researches  of  Arloing  and  Tripier  show  that  recur- 
rent fibres  may  pass  from  a  sensory  to  other  sensory  roots. 

The  existence  of  recurrent  centripetal  fibres  in  the  ventral 
roots  makes  it  highly  probable  that  centrifugal  fibres  may  emerge 
from  the  ventral  roots  to  run  back  in  the  dorsal  roots  to  innervate 
the  muscle  cells  that  occur  in  the  interior  or  on  the  surface  of 
the  cord  (vasomotor  fibres).  Vulpian,  on  exciting  the  peripheral 
stump  of  a  ventral  root,  was  unable  to  detect  any  visible  alteration 
of  circulatory  conditions  at  the  surface  of  the  cord,  but  this  negative 
result  is  possibly  due  to  the  fact  that  the  vasomotor  nerves  of  the 


v  SPINAL  CORD  AND  NERVES  295 

cord,  like  those  of  the  hrain,  have  a  long  course  in  the  sympathetic 
chain  and  plexuses,  after  which  they  re-enter  by  the  spinal  roots 
of  a  region  higher  or  lower  than  that  under  observation. 

An  indirect  proof  of  the  Bell-Magendie  law  is  afforded  by  the 
Wallerian  degenerations  that  take  place  in  the  two  spinal  roots 
after  section.  As  we  saw  in  the  last  chapter  (see  p.  232),  when 
a  mixed  nerve  is  divided  the  peripheral  part  that  is  severed 
from  the  centre  degenerates,  while  the  proximal  part  connected 
with  the  centre  remains  unchanged  for  a  long  time,  and  may  grow 
and  regenerate  the  cut  nerve.  Waller  found  that  after  section  of 
the  dorsal  root  (between  the  spinal  ganglion  and  the  cord)  the 
central,  but  not  the  peripheral  part  degenerates  ;  after  section  of 
the  ventral  root,  on  the  contrary,  the  peripheral,  but  not  the 
central  part  degenerates.  So  that  the  afferent  fibres  of  the 
posterior  root  have  their  trophic  centre  in  the  cells  of  the  spinal 
ganglion,  and  the  efferent  fibres  of  the  ventral  root  have  their 
trophic  centre  in  the  cells  of  the  grey  matter  of  the  cord.  This 
observation  agrees  with,  and  therefore  confirms,  our  physiological 
knowledge  of  the  dissimilar  character  of  the  fibres  which  constitute 
the  two  roots. 

Wallerian  degeneration  also  confirms  the  phenomenon  of 
recurrent  sensibility.  Schiff  (1850)  was  the  first  to  see  that 
after  cutting  the  ventral  root  certain  fibres  in  the  central  stump 
degenerate,  while  a  corresponding  number  in  the  peripheral  stump 
remain  intact.  Since  these  are  recurrent  fibres,  it  is  clear  that 
those  which  are  separated  from  their  trophic  centres  in  the  central 
stump  degenerate,  while  those  which  are  left  in  connection  with 
their  centre  in  the  peripheral  stump  remain  intact. 

Wallerian  degeneration  also  confirms  the  fact  that  a  certain 
number  of  centrifugal  (vaso-dilatator)  fibres  emerge  with  the  dorsal 
roots.  If  this  is  a  genuine  exception  to  the  Bell-Magendie  law, 
section  of  the  dorsal  roots  should  give  rise  to  a  form  of  degeneration 
which  is  not  in  strict  correspondence  with  Waller's  law,  i.e.  there 
must  be  some  intact  fibres  in  the  central  stump  and  some 
degenerated  fibres  in  the  peripheral  sturnp.  Different  authors, 
however,  obtained  different  results  by  this  method.  Vejas,  Max 
Joseph,  Gad,  Morat  and  Bonne  obtained  positive  results  as  above  ; 
Sherrington,  Singer  and  Miinzer,  Gabri,  on  the  other  hand,  found 
the  central  stump  completely  degenerated,  and  the  peripheral  stump 
intact,  precisely  according  to  Waller's  law.  In  order  to  settle  the 
controversy,  Tarulli  and  Panichi  (1902)  resumed  the  study  of  the 
degenerations  consequent  on  section  of  the  dorsal  roots,  and  made 
a  number  of  experiments  on  different  parts  (cervical,  dorsal,  and 
lumbar)  of  the  dog's  cord.  The  degenerations  were  followed  out 
by  the  method  of  Marchi  or  of  Weigert-Pal,  both  on  cross-sections 
of  the  root-stumps  and  on  teased  bundles  of  nerves,  in  order  to 
study  the  fibres  lengthways.  The  result  was  constant ;  in  the 


296 


PHYSIOLOGY 


CHAP. 


peripheral  stumps  of  the  cervical  and  thoracic  dorsal  roots  there 
were  a  very  few  degenerated  fibres,  and  in  the  central  stump  a 
corresponding  number  of  healthy  fibres.  But  in  the  lumbar  dorsal 
roots  more  fibres  were  degenerated  in  the  peripheral  stump  and 
more  were  intact  in  the  central  stump  (Fig.  179). 

Hence  the  degeneration  method  confirms  this  exception  to  the 
Bell-Magendie  law,  as  a  few  dorsal  root- fibres,  especially  in  the 
lower  lumbar  segments,  have  a  centrifugal  course,  and  take  origin 
either  from  Kainon  y  Cajal's  dorsal  root  cells  or  from  the  cells  in 
the  ventral  horn,  while  all  the  rest  have  their  trophic  centre  in 
the  spinal  ganglion. 

IV.  Numerous  physiological  and  clinical  facts  show  that  there 


Fio.  179.— A,  transMTsi'  section  of  central  end  of  7th  dorsal  lumbar  root  of  dog,  showing  degenera- 
tion of  most  of  the  fibres  (black  discs)  with  very  few  healthy  fibres.  13,  transverse  section  of 
piTipln-ral  i-iid  of  same  root,  showing  contrary  appearance.  (From  preparations  made  by 
Tarulli  and  Panichi  with  Marchi's  method.) 

is  a  close  relation  between  sensation  and  movement,  and  that  the 
functions  of  the  two  spinal  roots,  while  distinct,  are  not  inde- 
pendent of  one  another. 

The  influence  that  the  dorsal  roots  exercise  upon  the  spinal 
efferent  neurones  can  be  shown  in  various  ways  by  observing  the 
reaction  of  the  skeletal  muscles.  Brondgeest  (1860)  was  the  first 
who  noted  relaxation  or  atony  of  the  flexor  muscles  of  the  frog's 
thigh  after  cutting  the  dorsal  roots  of  the  lumbar  plexus.  Harless, 
on  stimulating  the  frog's  sciatic  with  a  weak  induction  current, 
before  and  after  section  of  the  same  roots,  found  the  constant 
effect  of  division  to  be  diminished  excitability  in  the  nerve. 

Cyon  (1865)  first  experimented  directly  on  the  spinal  roots, 
and  demonstrated  that  the  integrity  of  the  dorsal  roots  is  indis- 
pensable to  the  normal  excitability  of  the  corresponding  ventral 
roots.  Section  of  the  former  produces  a  depression  of  excitability 
in  the  latter. 


v  SPINAL  CORD  AND  NERVES  297 

Von  Bezold  and  Uspensky  contested  Cyon's  results,  since  they 
were  unable  to  verify  any  constant  influence  of  the  dorsal  upon 
the  ventral  roots.  According  to  these  authors,  the  fact  recorded 
by  Cyon  is  rarely  met  with ;  in  the  majority  of  cases  excitability 
remains  unaltered ;  sometimes,  indeed,  it  is  temporarily  increased. 

This  last  feature  was  constantly  observed  by  Marcacci  in 
Dastre's  laboratory.  He  divided  all  the  spinal  roots  in  the  frog 
with  the  exception  of  one  pair.  On  then  cutting  the  dorsal  root 
of  this  pair  he  found  that  an  induced  current  that  was  previously 
inadequate  to  evoke  a  response  now  threw  the  muscles  innervated 
by  the  remaining  ventral  root  into  contraction. 

Bemiondo  and  Oddi  (1890),  under  our  direction,  resumed  the 
experimental  study  of  this  subject  on  the  dog.  They  abolished 
the  influence  of  the  dorsal  root,  not  only  by  section,  but  also  by 
the  local  application  of  cocaine,  which  produces  temporary  paralysis 
without  excitation.  Under  these  conditions  they  constantly  found 
a  marked  depression  of  excitability  in  the  corresponding  ventral 
root,  which  no  longer  reacted  to  the  minimal  stimuli  that  had 
previously  been  effective. 

In  a  new  series  of  experiments  (1896)  Polimanti  returned  to 
this  subject,  and  sought  to  determine  the  influence  exercised  on  a 
ventral  root,  both  by  the  dorsal  roots  of  the  same  pair  and  by 
those  of  other  pairs  (above  or  below)  on  the  same  or  the  opposite 
side.  Generally  speaking,  he  confirmed  and  extended  the  results 
of  Belmondo  and  Oddi,  and  found  that  on  dividing  the  dorsal 
roots  there  is  constantly  a  marked  depression  of  excitability  in 
the  corresponding  ventral  root.  The  same  result  was  often 
obtained  on  testing  the  reciprocal  influence  of  two  roots  of 
different  spinal  pairs,  on  the  same  or  the  opposite  side.  But  there 
was  a  marked  difference  between  the  results  of  Belmondo  and 
Oddi  and  those  of  Polimanti  as  regards  the  effects  of  mechanical 
or  electrical  stimulation  of  the  divided  dorsal  roots.  The  first 
authors  found  that  on  stimulation  of  the  dorsal  roots  the  excita- 
bility of  the  ventral  roots  was  almost  invariably  increased  above 
the  normal ;  Polimanti  in  most  cases  obtained  the  opposite  result, 
i.e.  depression  of  excitability,  which  he  held  to  be  a  reflex  inhibition, 
probably  caused  by  the  excessive  strength  of  the  stimulus.  But 
he  did  not  deny  that  under  normal  conditions  a  slow  and  quiet 
wave  of  excitation  passes,  as  assumed  by  Cyon,  from  the  dorsal  to 
the  ventral  root,  by  which  its  excitability  is  maintained  and  on 
which  the  tone  of  the  skeletal  muscles  depends. 

In  proof  of  the  reinforcing  action  of  the  dorsal  upon  the 
ventral  roots,  it  is  only  necessary  to  study  the  motor  effects  of 
dividing  the  former.  If  one  dorsal  root  alone  is  divided  no  very 
obvious  effects  ensue,  because  the  influence  of  adjacent  roots 
readily  compensates  the  functional  deficiency.  But  if  several 
sensory  roots  are  cut,  e.g.  all  those  which  supply  the  sensory 


298  PHYSIOLOGY  CHAP. 

innervation  for  a  posterior  limb,  the  movements  of  this  limb,  while 
not  abolished,  will  be  altered  in  a  characteristic  manner. 

Panizza  (1835),  who  first  performed  this  experiment,  noted 
that  the  movements  of  the  apaesthetic  limb  were  uncertain  and 
showed  the  characteristics  termed  by  us  dysmetria,  i.e.  failure  to 
measure.  In  movements  of  flexion,  for  instance,  the  limb  was 
carried  too  far  up  and  out.  Stilling  (1842)  confirmed  Panizza's 
observations  and  ascribed  to  the  dorsal  roots  the  maintenance  of 
muscular  tone  by  transmitting  to  the  centres  a  knowledge  of  the 
state  and  position  of  the  muscles.  Cl.  Bernard  (1858)  pointed  out 
that  the  frog  made  little  use  of  its  leg  muscles  when  the  influence 
of  the  sensory  roots  was  cut  out.  A  very  accurate  description  of 
the  movements  of  the  apaesthetic  leg  of  the  frog  has  recently  been 
given  by  the  younger  Hering.  Among  various  phenomena  he 
noted  the  following  as  characteristic :  when  the  animal  jumps  it 
takes  up  its  normal  position  first  with  the  intact  and  then  with 
the  apaesthetic  limb,  and  in  bringing  the  latter  back  to  the 
ordinary  position  raises  it  unduly  (Hebphdnomen).  When  the 
posterior  roots  are  divided  on  both  sides,  the  frog  makes  lower  and 
less  extensive  springs. 

The  effects  of  dividing  the  dorsal  roots  in  the  dog  were 
exhaustively  studied  by  Baldi  (1885),  who  kept  the  animals  alive 
for  a  long  time.  On  cutting  the  afferent  roots  of  a  hind-limb  the 
leg  in  which  sensibility  is  paralysed  is  not  used  in  walking  during 
the  first  days ;  it  seems  incapable  of  supporting  the  weight  of  the 
body,  is  kept  semi-flexed  at  the  thigh-  and  knee-joints,  and  is  rarely 
completely  extended.  Later  the  animal  begins  to  use  it  in  walking, 
but  in  an  abnormal  manner ;  it  is  lifted  too  high  and  thrown 
either  too  far  forward  or  too  far  back.  After  cutting  the  afferent 
roots  of  the  last  three  cervical  nerves  and  the  first  thoracic  on  one 
side,  the  animal  limps,  holding  the  insensitive  leg  up  off  the 
ground.  After  a  few  days  the  leg  may  be  used  in  walking,  but 
the  foot  gives  way  and  the  animal  stumbles  and  falls.  Sub- 
sequently the  gait  improves,  but  then  trophic  disturbances  of  the 
limb  in  which  sensation  is  lost  set  in.  Bilateral  section  of  the 
afferent  roots  of  the  lumbo-sacral  plexus  makes  the  animal 
incapable  of  using  the  posterior  half  of  its  body,  which  is  dragged 
passively  along  by  the  anterior  part  as  if  paralysed.  On  lifting 
the  animal  up,  the  hind-limbs  perform  alternate  flexor  and  extensor 
movements.  Eventually  the  hind-limbs  succeed  in  supporting  the 
weight  of  the  trunk  up  to  a  certain  point,  but  the  knees  often 
knock  together  and  give  way. 

The  effects  of  dividing  the  dorsal  roots  of  the  monkey,  accord- 
ing to  Mott  and  Sherrington  (1895),  are  even  more  striking. 
When  all  the  afferent  roots  of  a  limb  are  cut  it  is  used  neither  in 
walking  nor  climbing,  and  only  comes  into  play  with  very  energetic 
movements  of  the  corresponding  normal  limb.  When  the  monkey 


v  SPINAL  CORD  AND  NERVES  299 

wishes  to  reach  an  object  with  a  limb  in  which  only  the  sensibility 
of  the  skin  of  the  hand  is  preserved,  its  movement  is  irregular  and 
zig-zag,  and  it  often  grasps  objects  lying  near  the  thing  to  which 
the  movement  was  directed. 

According  to  H.  Munk,  who  tested  these  results  o'f  Sherrington 
and  Mott  by  experiments  on  the  macaque  monkey,  on  cutting  the 
dorsal  roots  of  one  arm  the  immobility  of  this  limb  is  not  so 
complete  as  was  asserted  by  the  above  authors.  It  is  only  the 
movements  normally  observed  on  stimulating  the  afferent  nerves 
of  the  limb  that  disappear ;  the  other  movements  seem  to  be 
difficult  and  temporarily  or  permanently  impaired  in  proportion 
as  the  excitability  of  the  central  organs  from  which  they  are 
evoked  is  diminished,  owing  to  the  suppression  of  the  excitations 
that  normally  reach  them  by  the  sensory  paths. 

Bickel  (1897)  observed  that  the  effects  of  severing  the  afferent 
paths  in  the  dog  are  greatly  aggravated  by  lesions  of  the  labyrinth. 
A  similar  effect  is  also  obtained  by  cutting  out  the  retinal 
sensations. 

H.  E.  Bering,  Sherrington,  and  Bickel  all  agree  that  mechanisms 
exist,  more  particularly  in  the  cerebral  hemispheres,  which  are 
capable  of  compensating  the  loss  of  afferent  control  in  animals 
with  paralysed  sensibility.  Bickel  and  Jacob  (1900)  saw  that 
the  disturbance  of  gait  in  dogs  that  have  lost  sensibility  in  the 
hind-limbs  gradually  diminishes  in  time  till  it  disappears.  "  If 
after  this  compensation  has  been  established  the  senso  -  motor 
zones  of  the  cerebral  cortex  in  relation  with  the  hind-limbs  are 
destroyed,  the  ataxic  disturbances  reappear,  and  are  again  compen- 
sated slowly  and  feebly — never  to  the  former  extent."  Merzbacher 
(1902)  found  the  same  on  the  frog. 

The  experiments  of  Trendelenburg  (1906)  on  pigeons,  in  which 
the  dorsal  roots  of  various  regions  of  the  cord  had  been  cut,  agree 
fundament  illy  with  the  above.  Bilateral  section  of  the  dorsal 
roots  which  innervate  the  wings  crippled  the  animals  permanently 
for  flight,  while  bilateral  section  of  the  dorsal  roots  for  the  legs 
caused  permanent  incapacity  for  standing.  After  unilateral  section 
of  the  same  roots  a  great  difference  is  seen  in  the  behaviour  of  the 
wings  and  the  feet,  as  this  operation  does  not  interfere  with  normal 
flight,  signs  of  dysmetria  being  perceptible  only  in  certain  reflexes 
(abnormal  lifting  of  the  wing),  but  unilateral  section  of  the  lumbo- 
sacral  roots  produces  marked  ataxia,  which  at  first  hinders  both 
standing  and  walking.  The  animal  only  learns  to  use  its  limbs 
again  by  degrees,  the  disturbances  of  innervation,  particularly  in 
locomotion,  being  plainly  shown  by  an  abnormal  raising  of  the 
leg,  analogous  to  the  Hebphanomen  which  Hering  described  for 
the  frog.  The  reason  for  this  dissimilar  behaviour  of  the  wing 
and  the  leg  lies  in  the  fact  that  the  wings  are  as  a  rule  innervated 
simultaneously,  so  that  sensory  impulses  passing  to  the  centres  on 


300  PHYSIOLOGY  CHAP. 

one  side  only  can  regulate  the  movements  of  both  wings ;  while 
the  legs  which  come  into  play  alternately  have  each  an  independent 
regulating  mechanism.  The  compensatory  phenomena  observed 
after  operating  on  oue  leg  are  undoubtedly  due  to  sensations 
coining  from  the  sound  leg.  If  this  also  is  operated  on  the  power 
of  standing  is  permanently  lost.  The  labyrinth  takes  an  important 
part  in  these  phenomena  of  compensation :  if  it  is  destroyed  on 
both  sides,  compensation  disappears  and  never  fully  returns. 
The  cerebrum,  on  the  other  hand,  has  no  influence  in  compensating 
these  motor  disturbances. 

Trendelenburg's  results  agree  with  those  obtained  by  other 
experimenters  on  other  animals.  His  observations  differ  in  one- 
important  respect  from  those  previously  recorded,  viz.  while 
bilateral  section  of  the  dorsal  roots  of  the  legs  causes  muscular 
atony  of  those  limbs,  so  that  they  hang  flaccid,  bilateral  section  of 
the  dorsal  roots  that  innervate  the  wings  does  not  induce  loss  of 
their  muscular  tone,  so  that  when  at  rest  they  keep  approximately 
the  normal  position  of  flexion — folded  and  raised  on  to  the  back— 
and  neither  hang  flaccid  nor  trail  the  feathers  on  the  ground. 
The  tone  of  the  muscles  to  which  this  posture  of  the  wings  is  due 
does  not  disappear  even  if  the  anterior  brain  is  removed,  or  the 
labyrinth  destroyed.  Trendelenburg  concluded  that  the  tone  of 
the  wings  is  not  reflex  in  origin.  In  some  control  experiments 
Baglioni  (1907),  however,  noted  that  the  insensitive  wing  does  not 
behave  at  all  like  the  normal  wing.  Even  if  the  apaesthetic  wing 
does  not  hang  or  trail  on  the  ground  when  the  pigeon  stands  erect 
or  walks,  like  the  wing  paralysed  by  section  of  all  its  motor  and 
sensory  nerves,  it  certainly  does  not  oppose  the  same  degree  of 
resistance  to  passive  movements  as  a  normal  wing,  nor  is  it  raised 
and  lowered  immediately  like  the  normal  wing.  The  insensitive 
wing  is,  therefore,  deficient  in  muscular  tone.  In  order  to  explain 
why  the  apaesthetic  wing  does  not  betray  its  atonic  condition  in 
the  erect  posture  or  in  walking,  Baglioni  suggests  that  the  sensa- 
tions coming  from  the  leg  renexly  excite  tonic  contraction  of  the 
wing  muscles,  so  that  these  are  raised  on  to  the  back  and  do  not 
trail  along  the  ground. 

V.  The  mode  in  which  the  fibres  of  the  spinal  roots  tire  dis- 
tributed after  passing  through  the  nerve  plexuses  to  the  skin  and 
subcutaneous  tissues,  and  particularly  to  the  muscles,  is  of  more 
than  merely  anatomical  interest.  It  is  intimately  associated  with 
the  simplest  reflex  functions  of  which  the  individual  segments  of 
the  cord  are  capable ;  it  has  further  a  practical  interest,  as  from 
our  knowledge  of  it  it  is  possible  from  motor  and  sensory  functional 
disturbances  to  deduce  conclusions  as  to  the  localisation  of  circum- 
scribed lesions  of  the  cord  or  the  spinal  roots. 

Anatomy  tells  us  little  of  the  special  peripheral  relations  of  the 
sensory  and  motor  fibres  that  emerge  from  each  pair  of  roots.  In 


v  SPINAL  COED  AND  NERVES  301 

fact  the  spinal  nerves  intermix  so  freely  along  their  course  in  the 
plexuses  (cervico-dorsal,  lumbo-sacral  plexuses)  that  it  is  necessary 
in  order  to  ascertain  the  peripheral  distribution  of  each  sensory 
and  motor  root  to  resort  to  the  emhryological  method,  or  the 
physiological  methods  of  section  and  excitation,  or  the  pathological 
method  of  degeneration  combined  with  clinical  observations. 

Apart  from  observations  by  the  older  anatomists  (Reil,  Monroe, 
Scarpa,  Sommering),  Schroder  van  cler  Kolk  (1847)  was  the  first 
to  occupy  himself  with  the  peripheral  distribution  of  the  spinal 
roots.  He  assumed  that  the  branches  of  the  mixed  nerves  in 
general  are  distributed  so  that  the  sensory  ramifications  terminate 
in  the  region  of  the  skin  lying  immediately  over  the  muscles 
innervated  by  the  motor  fibres  of  the  same  nerve. 

Starting  from  this  concept,  Eckhard  (1849)  studied  on  the  frog 
the  relations  between  the  peripheral  terminations  of  the  dorsal  and 
ventral  roots  that  innervate  the  hind-limbs.  He  found  Schroder's 
law  to  be  true,  but  not  entirely  accurate,  since  the  sensory  fibres 
do  not  exactly  supply  the  cutaneous  areas  over  the  muscles 
innervated  by  the  corresponding  motor  fibres.  In  order  to  discover 
the  distribution  of  the  sensory  roots  in  the  skin,  he  divided  all 
the  dorsal  roots  save  one,  and  then  ascertained  which  area  of 
the  skin  still  preserved  its  sensibility.  In  this  way  he  dis- 
covered that  each  root  provides  sensibility  to  a  definite  and 
continuous  region  of  the  skin,  and  that  these  regions  more  or  less 
overlap  one  another.  To  determine  the  distribution  of  the  motor 
roots,  he  experimented  with  electrical  excitation  of  one  alone,  after 
section  of  the  rest,  and  found  that  it  only  threw  certain  of  the 
muscles  of  the  limb  into  contraction.  This  corrected  an  observa- 
tion made  by  Kronenberg  (1836)  under  Johannes  Miiller's 
direction.  He  attributed  to  the  plexus  a  protective  function 
against  fatigue,  and  assumed  that  the  stimulation  of  a  single  root 
forming  part  of  the  plexus  was  able  to  throw  all  the  muscles  of 
the  limb  into  contraction. 

Eckhard's  results  were  controlled  by  Koschewnikoff  (1868),  C. 
Mayer  (1869),  and  more  recently  by  Sherrington  (1893),  without 
substantial  modification.  Peyer  (1854)  and  Krause  (1865) 
obtained  similar  results  on  the  rabbit. 

But  in  all  these  researches  the  leading  motive  that  was  to 
combine  the  scattered  facts  into  one  system  was  wanting,  viz.  the 
extension  of  the  idea  of  segmentation — metamerism — to  the  peri- 
pheral distribution  of  the  sensory  and  motor  roots.  Tiirck  (1856) 
first  detected  a  segmental  arrangement  in  the  cutaneous  areas 
supplied  by  the  sensory  roots.  He  divided  the  dorsal  roots  one  by 
one  in  the  dog,  and  determined  the  peripheral  distribution  of  each 
by  observing  the  zone  of  insensibility  to  touch  and  pain  that 
ensued  in  the  skin.  He  thus  discovered  the  cutaneous  root  areas 
for  the  whole  of  the  dog's  body,  and  showed  that  a  part  of  each 


302  PHYSIOLOGY  CHAP. 

zone  acquired  its  sensibility  almost  exclusively  from  the  corre- 
sponding dorsal  root,  while  the  remainder  owed  its  sensibility  both 
to  its  proper  root  and  to  those  adjacent  to  it.  The  cutaneous 
root-zones  or  segments  of  the  neck  and  trunk,  according  to  Tiirck, 
are  arranged  in  series  and  girdle  the  body  like  rings,  which  start 
from  the  spinous  processes  of  the  vertebrae  and  reach  the  ventral 
median  line  in  a  direction  almost  vertical  to  the  axis  of  the  body. 
The  root  areas  for  the  skin  of  the  limbs  appeared  to  Tiirck  to 
be  irregular  in  form,  which  in  his  day  was  found  difficult  to 
interpret. 

Although  commended  by  Ludwig  in  the  second  edition  of  his 
Text-book,  Tiirck's  memoir  passed  almost  unnoticed,  the  morpho- 
logical theory  of  metamerism  not  being  yet  sufficiently  developed. 

The  modern  view  of  the  segmental  distribution  of  the  ventral 
roots  was  led  up  to  by  the  work  of  Ferrier  and  Yeo  (1881)  on  the 
motor  roots  of  the  brachial  plexus  in  the  monkey  ;  the  almost 
contemporaneous  work  of  Paul  Bert  and  Marcacci  on  the  roots  of 
the  him  bo-sacral  plexus  in  the  dog  ;  that  of  Forgue  and  Lauuegrace 
(1884)  on  the  roots  of  the  brachial  and  lumbo-sacral  plexuses  of 
the  dog  and  monkey ;  lastly,  that  of  Polimanti  (1894)  on  the 
brachial  and  lumbo-sacral  plexuses  of  the  dog,  rabbit,  and  cat. 
The  separate  excitation  of  each  of  the  ventral  roots  that  combine 
to  form  these  plexuses  invariably  resulted  in  a  synergic  movement, 
co-ordinated  to  a  definite  purpose,  so  that  there  is  in  the  individual 
ventral  roots  a  functional  systematisation  of  movements. 

The  memoir  of  Forgue  and  Lanuegrace  is  the  most  important 
from  the  segmental  point  of  view.  These  authors  recognised  that 
each  root  contributes  to  the  innervation  of  an  always  identical 
series  of  muscles,  so  that  in  animals  of  the  same  species  the 
distribution  is  approximately  constant.  When  a  functional  varia- 
tion occurs  it  is  small,  and  the  innervation  acquired  or  lost  by 
any  root  is  borrowed  from,  or  passed  on  to,  the  root  immediately 
adjacent  to  it,  and  not  to  a  more  distant  root.  In  opposition  to 
the  other  authors  cited,  Forgue  and  Lannegrace  assumed  that 
while  the  excitation  of  an  entire  root  does  produce  a  combined 
movement,  this  combination  is  accidental  and  not  functional,  so 
that  normally,  in  carrying  out  any  movement,  the  will  must  excite 
the  synergic  fibres  of  several  roots,  and  not  of  one  root  alone. 
They  showed  no  reason  why  this  should  be  the  case,  but  it 
harmonises  with  the  histological  fact  of  the  multiplicity  of 
collateral  rami  from  the  fibres  of  the  pyramidal  bundle,  which 
penetrate  the  grey  matter  at  different  levels  and  enter  into  relation 
with  the  cells  of  the  ventral  horn  in  different  segments. 

The  theory  of  the  metameric  distribution  of  the  sensory  and 
motor  roots,  now  generally  admitted,  rests  to  a  large  extent  upon 
the  exhaustive  experiments  of  Sherrington  (1893)  on  the  sensory 
roots,  of  Kisien  Russell  on  the  motor  roots  of  the  monkey,  and  on 


v  SPINAL  CORD  AND  NERVES  303 

the  morphological  work  of  Bolk  on  both  motor  and  sensory  roots 
in  man. 

If  we  summarise  the  complicated  results  of  these  three  authors 
under  a  few  heads,  and  for  the  moment  pass  over  certain  divergences 
which  will  be  discussed  below,  it  may  be  said  that  :— 

(«)  There  is  a  true  segmentation  of  the  body-surface  (Sherring- 
ton's  segmental  skin-field)  as  well  as  a  true  segmentation  of  the 
muscles,  which  both  correspond  with  the  metamerism  of  the  spinal 
roots.  There  are  certain  exceptions  to  the  strict  parallelism 
between  the  segmental  innervation  of  the  skin  and  of  the 
muscles  assumed  by  Schroder  van  der  Kolk,  particularly  in  the 
extremities,  where  during  phylogenetic  and  ontogenetic  evolution 
the  muscle  segments  often  become  more  or  less  displaced  in 
relation  to  the  segmental  skin-fields. 

(6)  While  the  skin  segments  (Bolk's  dermatomes)  form  con- 
tinuous fields,  the  muscle  segments  (Bolk's  myotomes)  are  com- 
pounded of  portions  of  several  muscles.  Their  metameric 
arrangement  is  less  striking  than  in  the  dermatomes,  but  can 
easily  be  demonstrated. 

(c)  The  metameric  arrangement  of  the  dermatomes  and 
myotomes  in  the  neck  and  trunk  is  ring-shaped ;  at  the  ex- 
tremities it  seems  to  be  more  complicated,  but  is  intelligible  from 
the  ernbryological  development  of  these  organs. 

(d~)  Each  derniatorne  is  partially  covered  by  the  adjacent,  which 
immediately  precedes  and  follows  it  in  the  serial  arrangement 
(cranio-caudal  direction).  This  fact,  already  known  to  Eckhard 
and  Tiirck,  has  been  termed  by  Sherrington  overlapping.  Whether 
a  similar  overlapping  occurs  among  the  myotomes  is  at  present 
unknown. 

(0)  The  sensory  inuervation  of  the  muscles  follows  their 
metamerism,  not  that  of  the  skin.  The  metamerism  of  the  pilo- 
rnotor  nerves  is  almost  parallel  with  that  of  the  skin.  The 
vasomotor  innervation  of  the  skin  also  corresponds  approximately 
with  the  dermatomes. 

These  facts  from  the  work  of  Sherrington,  Risien  Russell  and 
Bolk  give  an  almost  complete  schema  of  the  metamerism  of  the 
skin  and  muscles  (Fig.  180).  There  are,  of  course,  divergences 
that  seem  a  priori  inevitable  in  view  of  the  difference  of  species 
(man  and  monkey)  and  of  method  (physiological  and  morpho- 
logical) under  which  the  data  were  collected. 

Kocher's  attempt  (1896)  to  determine  the  segmental  skin- 
fields  for  man  solely  by  deductions  from  clinical  data  was  a 
failure.  A  series  of  publications  by  the  Dutch  neurologist 
Winkler  and  his  pupils,  Beyermann,  Coenen,  Langelaan,  Van 
Rynberk,  show  that  the  clinical  data  accord  well  with  the  diagrams 
of  Sherrington  and  of  Bolk. 

Wichmann    has    recently    collected     from     modern     clinical 


304 


PHYSIOLOGY 


CHAP. 


literature  (Thorburn,  Kocher,  Gowers,  Starr,  Eclinger,  Leyden, 
Goldscheider,  Striimpell,  Jacob,  etc.)  a  series  of  observations  on 
the  segmental  innervation  of  muscle  whicb  agree  witb  the  fore- 
going experimental  and  morphological  facts. 

The  main  defect  of  Kocher's  diagram,  and  also  of  that  suggested 
by  the   American    neurologist  Allen    Starr,  is  in  the  nietameric 


FIG.  180. — Metameric  distribution  or  transverse  segmentation  of  cutaneous  areas  <>f  sensibility  of 
human  body,  drawn  with  the  limbs  in  the  position  of  their  embryonic  growth.  (Diagram  con- 
structed by  Luciani  from  Bolk's  data.)  The  series  of  derma  tomes  which  successively  correspond 
to  the  cervical,  lumbar,  and  sacral  roots  is  indicated  by  different  degrees  of  shading. 

division  of  the  limbs.  Without  giving  sufficient  attention  to  the 
special  character  of  the  embryological  development  of  the  limbs, 
they — Starr  more  particularly — represented  the  dermatomes  as 
running  from  the  vertebral  column  to  the  limbs  in  uninterrupted 
zones,  narrow  in  the  middle  and  somewhat  expanded  at  the  ends. 
Bolk's  schema,  on  the  contrary,  corresponds  perfectly  with  our. 
knowledge  of  the  embryological  development  of  the  limbs.  The 
arrangement  of  the  der-matomes  in  the  upper  limb  (Fig.  180)  is  in 
the  following  order  in  the  cranio-caudal  direction  :  shoulder,  outer 


SPINAL  CORD  AND  NERVES 


305 


side  of  upper  arm,  radial  side  of  forearm,  hand,  ulnar  side  nf 
forearm,  inner  side  (lower  in  figure)  of  upper  arm,  axilla.  The 
segments  4,  5,  6,  1C  are  separated  from  the  segment's  8C,  ID  by 
a  line  corresponding  to  the  axis  of  the  limb.  There  is  a  similar 
arrangement  in  the  lower  limb.  If  we  consider  the  embryo- 
logical  development  of  the  limb  as  shown  in  the  diagram  (Fig. 
181)  it  is  easy  to  see  how  this  arrangement  originated.  At  a 
the  limb-buds,  formed  chiefly  by  a  lengthening  of  the  nietameres 


-  1 

4 

$ 

6 

7 

8 

/ 

z 

/ 

I 

a  A] 

i 

_J 

/ 

FIG.  181. —  Diagram  of  embryonic  development  of  tipper  limbs  from  the  metameres  UC,  !>,  6,  7,  8, 
ID.  (Bolk.)  a,  1),  (.-,  d,  e, /show  the  successive  phases  of  the  growth  cone  of  the  limU^wing 
to  the  lengthening  of  the  metameres  destined  for  the  upper  limb,  and  its  displacement  from 
the  middle  line  of  the  body. 

7  and  80,  begin  to  appear ;  at  b  and  c  these  metameres,  separated 
by  the  axis  of  the  limb,  begin  to  extrude  from  the  median  line  of 
the  body ;  at  d  and  c  the  nietameres  5  and  QC  and  ID  are  also 
displaced  from  the  median  line  and  form  part  of  the  cone  of 
growth  ;  finally  at  /  the  arrangement  and  distribution  of  the 
metameres  of  the  limb  is  the  same  as  those  of  the  adult  individual. 
(  Granting  this  arrangement  of  the  skin  and  muscle  segments, 
we  next  have  to  consider  their  constitution  and  functions  separately. 
With  the  exception  of  a  few  small  muscles  of  the  vertebral 
column,  which  receive  their  motor  fibres  from  one  ventral  root 
alone,  all  the  other  muscles  of  the  human  body  are  supplied  by 


VOL.  Ill 


x 


306  PHYSIOLOGY  CHAP. 

fibres  from  more  than  one  root,  i.e.  they  are  polymeric,,  belonging 
to  many  myotomes.  On  the  other  hand,  each  myotome  contains 
portions  of  several  muscles.  The  actual  muscles,  derived  from  the 
fusion  of  several  monomcric  units,  may  be  classed  in  three  groups  : 
(«)  Muscles  that  remain  monomeric,  with  a  single  function. 
Among  these  are  the  small  vertebral  muscles  above  referred  to. 

O 

(5)  Polymeric  muscles  with  a  simple  function,  as  the  rectus 
abdomiuus,  which  is  innervated  by  the  5th-12th  thoracic  roots; 
the  tendinous  bands  seem  an  evidence  of  the  fusion  of  the  eight 
segments  of  which  the  muscle  is  composed. 

(c)  Polymeric  muscles  with  complex  functions.  Most  of  the 
skeletal  muscles  belong  to  this  category. 

When  a  muscle  thus  receives  fibres  from  two  ventral  roots, 
does  the  stimulation  of  one  of  these  roots  produce  total  contraction 
of  the  muscle  ?  Sherrington  replies  in  the  affirmative ;  he  even 
maintains  that  it  is  not  necessary  to  stimulate  the  whole  of  the 
root ;  it  suffices  to  excite  any  one  of  the  filaments  or  rootlets 
which  compose  the  root,  as  it  passes  through  the  dural  sac,  in 
order  to  throw  the  entire  muscle  into  contraction.  Eisieu  Russell 
contradicts  this  emphatically,  and  affirms  that  stimulation  of  a 
single  root  of  a  polymeric  muscle  only  throws  a  portion  of  it  into 
contraction.  This  is  obviously  the  case  for  the  sartorius  muscle. 
Whatever  the  final  solution  of  this  controversy,  it  is  certain  that 
although  a  myotome  may  be  a  complex  of  muscle  fibres  which 
have  only  a  single  function,  it  is  far  more  frequently  found  that 
the  muscular  complex  of  the  myotome  contains  elements  with 
antagonistic  functions.  In  this  case  it  is  evident  that  the  same 
ventral  root  must  contain  separate  fibres  for  both  functions. 
Thus  Martin  and  Hartwell  observed  in  the  dog  a  rhythmically 
alternating  functional  activity  of  the  motor  root  which  innervated 
the  antagonistic  internal  and  external  intercostal  muscles. 

The  physiological  unit  of  cutaneous  metamerism — the  drrwa- 
tome — has  recently  been  the  subject  of  a  careful  experimental 
study  by  Winkler  and  Van  Rynberk.  They  found  that  the 
dermatome  consists  of  two  areas,  one  central,  the  other  marginal. 
The  former  is  capable  of  maintaining  sensibility  even  when  all 
overlapping  is  abolished  by  section  of  the  neighbouring  posterior 
roots ;  the  latter,  on  the  contrary,  is  not  capable  of  subserving 
sensibility  without  the  co-operation  of  the  overlapping  dermatomes 
(Fig.  182,  A). 

The  sensibility  of  the  central  and  marginal  areas  of  the 
dermatome  is  not  uniform,  but  varies  in  degree  at  different  points. 
Three  spots  can  be  distinguished  in  the  dermatome  at  which 
innervation  and  therefore  sensibility  are  maximal.  One  of  these 
lies  near  the  dorsal  median  line,  the  second  near  the  lateral  line, 
the  third  near  the  ventral  median  line,  as  shown  in  the  diagram. 
From  these  points,  at  which  it  is  most  acute,  sensibility  diminishes 


V 


SriNAL  CORD  AND  NERVES 


307 


gradually  to  the  surrounding  and  the  more  peripheral  parts  of  the 
dermatome.  These  areas  correspond  with  the  points  at  which  the 
cutaneous  nerves  enter  the  skin. 

In  another  series  of  experiments  Winkler  and  Van  Rynberk 
attempted  to  decide  the  question  whether  the  four  or  five  rootlets, 
which  make  up  each  dorsal  root,  have  a  localised  or  a  diffused 


c  F 

Fio.  182.—  Diagram  of  dermatomes  of  the  trunk  of  the  body.  (Winkler  and  Van  Rynberk.)  All 
six  diagrams  show  a  central  area  shaded  dark  and  a  marginal  area  shaded  light  ;  d,  median  dorsal 
linn;  J,  lateral  line  ;  v,  ventral  median  line  ;  ^t,  centre  of  maximal  dorsal  innervation  ;  +,  centre 
of  maximal  lateral  innervation.  A  shows  the  complete  form  of  the  central  area,  which  is  isolated 
only  in  the  most  successful  operations  ;  in  B,  C,  D,  E  there  is  an  increasing  reduction  of  the 
st-nsiiry  central  area  owing  to  greater  traumatic  lesions  or  to  partial  section  of  the  roots  ;  at  F 

tin;  whole  dermatome  is  insensitive  save  the  first  area  marked  *  ***  which  corresponds  to 
the  point  of  maximal  dorsal  iniiPi  vatiun  known  as  the  ultima  m  muricii*  of  the  dermatome. 


distribution  in  the  dermatome.  Their  results  showed  that  partial 
transaction  of  the  root  has  the  same  effect  as  a  complete  section, 
except  that  the  central  area  of  complete  insensibility  is  reduced 
as  indicated  in  Fig.  182.  The  diagrams  B,  C,  D,  E  show  the 
various  degrees  of  restriction  of  sensory  area  shown  in  such  cases. 
During  the  period  of  shock  after  the  operation  a  few  points  only 
may  be  found  near  the  median  dorsal  line  (diagram  F),  in  which 
sensibility  persists  in  the  midst  of  an  analgesic  area.  This  point, 


308  PHYSIOLOGY  CHAP. 

which  coincides  with  the  maximum  of  dorsal  innervation  (diagram 
A  at  point  #),  was  termed  by  Winkler  and  Van  Rynberk  the 
"  ulti'iiiU'in  moricns  "  of  the  dermatome. 

These  observations,  as  a  whole,  bring  out  the  important 
physiological  fact  that  the  function  and  distribution  of  the  root 
filaments  is  diffuse,  and  not  localised,  in  the  segmental  skin-field. 

The  same  authors  also  endeavoured  to  estimate  the  precise 
extent  to  which  overlapping  of  the  dermatonies  takes  place. 

By  a  series  of  ingenious  measurements  and  calculations 
Winkler  and  Van  Rynberk  ascertained  that  the  overlapping  of  the 
central  areas  amounts  to  one-third  near  the  dorsal  median  line ; 
to  two-ninths  near  the  lateral  line ;  while  in  the  ventral  median 
line  they  do  not  come  into  contact.  If  the  marginal  zone  is  also 
taken  into  consideration,  the  total  overlapping  of  the  derrnatomes 
appears  at  no  point  to  be  less  than  half,  so  that  every  point  on 
the  skin  must  be  simultaneously  related  to  two  dermatomes,  i.e. 
it  is  innervated  from  two  dorsal  roots.  This  observation  holds 
for  the  trunk :  in  the  region  of  the  limbs  the  dermatonies  are 
more  compressed,  and  the  overlapping  is  therefore  greater. 

These  central  areas  of  the  dermatomes  are  important,  more 
particularly  when  brought  into  relation  with  the  clinical  facts 
observed  by  Head  (1893).  He  describes  areas  of  cutaneous 
hyperalgesia  met  with  in  many  visceral  diseases,  particularly 
those  of  the  intestines.  He  observed  great  constancy  in  their 
localisation  and  extension,  and  that  in  these  particulars  they 
correspond  with  the  eruptive  zones  of  Herpes  zoster.  Since  it 
is  known  that  this  cutaneous  eruption  is  only  the  external 
symptom  of  an  acute  infectious  inflammation  of  one  or  more 
spinal  ganglia,  it  was  natural  to  assume  that  the  herpetic  eruption 
would  follow  the  cutaneous  metamerism,  the  more  so  as  Sher- 
rington  had  already  noted  that  the  sympathetic  innervation  of 
the  skin  coincides  approximately  with  it.  Head  considers  the 
cutaneous  hyperalgia,  which  is  symptomatic  of  internal  disease,  to 
be  the  peripheral  expression  of  irritation  in  a  spinal  segment. 

The  only  serious  objection  to  this  hypothesis  is  that  none  of 
Head's  zones  overlap  like  the  dermatonies.  It  is  probable  that 
the  zones  of  Head,  like  the  herpetic  eruption,  occur  only  within 
the  central  areas  of  Winkler  and  Van  Rynberk,  where  overlapping, 
as  we  have  seen,  takes  place  to  a  much  smaller  extent  than  for 
the  whole  dermatome.  In  this  way  it  is  possible  to  refer  an 
important  series  of  obscure  clinical  facts  to  the  system  of  cutaneous 
segmentation. 

Another  phenomenon  pointed  out  by  Langelaan  (1900)  must 
be  mentioned  in  connection  with  cutaneous  metamerism.  He 
discovered  that  a  whole  system  of  lines  and  areas  exists  in  the 
skin  of  normal  persons,  which  may,  in  comparison  with  the  rest 
of  the  skin,  be  termed  hyperalgesic.  For  example,  021  pricking 


V 


SPINAL  COED  AND  NEEYKS 


309 


the  arm  in  various  places  lightly  with  a  pin  a  subject  of  ordinary 
intelligence  is  able  to  indicate  accurately  that  in  certain  lines 
and  areas  the  painful  sensation  is  felt  far  more  acutely  than  in 
adjacent  regions.  This  cannot  depend  on  differences  of  pressure 
in  the  pricking,  for  if  the  experiment  be  repeated  at  different 


p. 


Ki',.  is". — Hyperalgesic  liands  and  areas  in  skin  of  upper  limb 
(A),  lower  limb  (B),  and  thorax  (C)  of  a  normal  individual. 
(Langelaan.) 

times  and  on  various  subjects,  the  hyper- 
algesic points  are  found  fixed  and  well 
defined.  On  tracing  the  hyperalgesic 
points  with  a  dermographic  pencil  upon 
the  skin  of  his  subjects,  Langelaan  found 
that  they  combined  into  definite  fields 
and  lines,  which  coincide  with  the  limit- 
ing lines  of  Bolk's  dermatomes  (Fig. 
183,  A,  B,  C). 

The  hyperalgesic  lines  seem  to  corre- 
spond with  those  points  at  which  the 
dermatomes  overlap ;  on  the  back  of  the 
hand  and  the  palm  where  some  of  the 
dermatomes  (6,  7,  86',  1Z>)  fuse  they  form  a  definite  area,  not  a 
line,  as  seen  at  A  in  the  above  figure. 

It  is  worth  noting  that  under  certain  pathological  conditions, 
e.g.  in  Tabes  dorsalis,  these  hyperalgesic  lines  and  fields  become 
pronounced  and  more  easy  to  demonstrate  than  under  normal 
conditions. 


310  PHYSIOLOGY  CHAP. 

In  order  to  obtain  a  more  constant  and  readily  measurable 
stimulus,  Coenen  has  tested  Langelaan's  discovery  by  means  of 
an  Erb's  electrode  with  three  seconds  application  of  weak  induced 
currents.  In  an  area  limited  to  the  ulnar  surface  of  the  forearm 
he  showed  that  the  skin  is  more  sensitive  near  the  axis  of  the 
limb,  and  that  the  subject  felt  pain  here  with  a  current  that  was 
unperceived  in  the  neighbouring  regions. 

VI.  As  was  stated  above,  the  real  and  perfect  metamerism 
of  the  spinal  roots  is  only  seen  in  the  segmeutal  arrangement  of 
the  cell  columns  of  the  ventral  horn  of  grey  matter.  This  fact 
fully  bears  out  the  physiological  view  that  the  spinal  cord 
represents  a  series  of  central  organs  (myelomeres),  which  are 
intimately  connected,  and  are  more  or  less  unitary  in  their 
functions. 

The  predominating  function  of  the  niyelomeres  is  "  reflex 
activity."  This  term,  borrowed  from  the  physicist — who  speaks 
of  the  reflection  of  light  and  heat  rays — corresponds  ill  with  the 
physiological  phenomena  which  it  is  intended  to  connote.  In 
the  widest  sense  any  immediate  reaction  of  a  living  and  excitable 
element  to  an  external  stimulus  may  be  called  a  reflex  act.  In 
a  narrower  sense,  however,  as  applied  to  the  nervous  system, 
the  reflex  act  is  the  involuntary  transformation  of  a  centripetal 
into  a  centrifugal  nerve  impulse,  by  means  of  a  central  organ, 
represented  by  a  group  of  ganglion  cells.  We  say  "involuntary 
transformation  "  to  distinguish  the  reflex  act  from  the  voluntary 
act,  which  may  also  follow  on,  and  be  evoked  by,  an  afferent 
impulse. 

Typical  examples  of  common  reflex  actions  are :  sneezing  on 
stimulation  of  the  nerves  of  the  nasal  mncosa,  coughing  from 
stimulation  of  the  glottis,  swallowing  from  contact  of  fluids  or 
solids  with  the  isthmus  of  the  fauces,  contraction  of  the  pupil 
to  light,  movements  of  the  arm  or  leg  on  tickling  the  armpit  or 
sole  of  the  foot,  etc.  Every  one  knows  that  these  movements  are 
involuntary — for  although  the  will  can  check  them  to  a  certain 
extent,  it  cannot  inhibit  them  —and  that  they  may  be  conscious 
or  unconscious,  since  they  may  occur  in  the  waking  or  the 
sleeping  state. 

But  in  experiments  upon  animals  it  is  difficult  to  distinguish 
"  reflex "  acts  from  the  "  voluntary "  acts  which  result  from 
conscious  sensations.  In  order  to  establish  the  purely  reflex 
nature  of  spinal  acts  the  influence  of  the  will  is  cut  out  in 
animals,  either  by  narcosis,  or  by  decapitation  or  removal  of  the 
cerebrum.  None  of  these  methods,  however,  seem  to  us  adequate. 

The  first  method  is  founded  on  the  fact  that  narcotics  (opium, 
chloroform,  ether)  suspend  the  psychical  activities  first,  without 
loss  of  excitability  or  conductivity  in  the  lower  nervous  elements. 
But  according  to  the  best  auto-observations  in  chloroform  narcosis, 


v  SPINAL  COED  AND  N  KJiVES  311 

the  abolition  of  sensation  and  volition  takes  place  gradually,  and 
is  not  complete  till  the  narcosis  has  been  carried  so  far  as  to 
inhibit  the  movements  that  we  consider  "  reflex "  because  they 
are  excited  by  external  stimuli. 

The  second  method  is  founded  on  the  assumption  that  the 
psychical  functions  are  localised  exclusively  in  the  brain.  Uut 
this,  as  we  shall  see,  is  far  from  certain.  It  is  doubtful  whether 
the  spinal  cord  severed  from  the  cerebrum  may  not  also  be  capable 
of  function  as  an  organ  of  sensation,  albeit  an  imperfect  one,  and 
whether  the  excitation  of  its  afferent  nerves  may  not  avail  to 
excite  traces  of  consciousness  and  motor  impulses,  since  there  is  a 
choice  of  efferent  paths  by  which  the  excitation  can  be  transmitted 
to  the  peripheral  motor  organs. 

Hence  it  is  not  possible  in  studying  the  functions  of  the  spinal 
cord  to  make  a  sharp  distinction  between  purely  reflex  and 
voluntary  acts,  since  there  is  no  objective  sign  by  which  a  clean 
line  of  separation  can  be  drawn  between  them.  The  purposive,  or, 
as  Goltz  calls  it,  the  responsive,  character,  or  property  of  carrying 
out  movements  directed  to  a  given  end,  is  common  to  both  reflexes 
and  voluntary  actions,  as  appears  from  the  experiments  made  on 
cold-  as  well  as  on  warm-blooded  animals. 

We  are  therefore  constrained  to  make  an  objective  study  of 
the  characteristics  and  manifestations  of  the  reflex  acts  which  the 
spinal  cord  is  able  to  carry  out  independently  of  the  brain. 

Whytt  (1750)  was  the  first  who  demonstrated  that  the  agency 
of  a  central  organ  is  necessary  for  the  transmission  of  excitations 
from  afferent  to  efferent  nerves.  As  soon  as  the  grey  matter  of 
the  cord  is  destroyed  every  reflex  movement  ceases.  The  same 
author  showed  that  reflex  action  does  not  depend  on  the  integrity 
of  the  cord  as  a  whole,  but  that  an  isolated  segment  suffices  for  the 
reaction.  If  in  the  decapitated  frog  the  cord  is  divided  at  the 
level  of  the  fifth  spinal  nerves,  reflexes  in  both  the  fore-  and  the 
hind-limbs  are  obtained  on  exciting  the  skin.  The  reflex  centre 
for  the  former  is  located  in  the  ventral  enlargement,  for  the 
latter  in  the  dorsal  enlargement  of  the  cord.  A  striking 
example  of  a  vigorous  and  sustained  reflex  in  the  frog,  first 
noticed  by  Spallauzani,  is  the  sexual  clasp,  which  persists  after 
dividing  the  cord  above  and  below  the  two  large  nerves  of  the 
brachial  region  (second  and  third  cervical  pairs).  The  lizard's  tail, 
like  that  of  the  eel,  can  be  divided  into  a  number  of  pieces,  each 
of  which  preserves  refiex  activity  for  some  time.  The  lumbo- 
sacral  region  of  the  cord  can  be  longitudinally  split  up  into  two 
halves,  each  of  which  is  capable  of  reflex  movements  so  long  as 
the  grey  matter  is  left  intact.  The  functional  capacity  of  isolated 
parts  of  the  spinal  cord  is  the  physiological  evidence  of  its 
metamerism.  In  the  higher  warm-blooded  animals  the  function 
of  the  segments  is  obscured  by  the  phenomena  of  shock,  which 


312  PHYSIOLOGY  CHAP. 

inhibits  the  activities,  not  merely  of  the  parts  directly  injured, 
but  also  of  the  more  remote  parts  which  have  not  received  direct 
injury.  Even  when  contusion  or  traction  is  as  far  as  possible 
avoided,  a  transection  can  suspend  all  activity  in  the  cord  for  a 
certain  time. 

Marshall  Hall  first  gave  the  name  of  "  shock  "  to  this  temporary 
depression  or  total  inhibition  of  the  nervous  functions  after 
mechanical  injury  to  any  part  of  the  system.  Goltz  held  the 
phenomena  of  shock  to  be  due  exclusively  to  inhibition,  but  this 
is  doubtful.  If  the  mechanical  lesion  is  regarded  as  a  powerful 
stimulus,  then  shock  may  be  conceived  as  exhaustion  of  excitability 
in  the  elements  involved.  As  by  transection  of  the  cord  the 
lower  part  is  suddenly  severed  from  the  higher  centres,  we  may 
hold  with  Foster  that  the  phenomena  of  shock  which  it  exhibits 
may  arise  partly  from  the  withdrawal  of  the  stream  of  influences 
which  reached  it  while  still  connected  with  the  rest  of  the  system, 
and  that  these  phenomena  subsequently  disappear  as  the  cord 
becomes  adapted  to  the  new  conditions  and  learns  to  function 
independently. 

Amongst  "  laboratory  animals,"  monkeys  exhibit  spinal  shock 
at  its  maximum  after  transection  of  the  cord  (Sherrington).  The 
fact  should  be  noted  that  the  shock  appears  to  take  effect  in  the 
aboral  direction  only.  After  high  cervical  transection,  the  effects 
of  shock  are  more  severe  in  the  fore-limbs  than  in  the  hind ;  for 
an  hour  or  so  it  may  be  difficult  to  elicit  a  reflex  by  any  kind  and 
any  strength  of  stimulus. 

In  the  dog  this  functional  depression  usually  wears  off  in  about 
five  weeks  after  a  brachial  transectiou.  In  man  transection  of 
the  cord  profoundly  disturbs  the  functions  of  the  skeletal  muscles, 
and  to  a  certain  extent  those  of  the  viscera,  as  in  monkeys. 

G-oltz  assumed  that  the  phenomena  of  shock  may  persist  for 
months  in  the  isolated  part  of  the  cord.  Sherrington,  on  the 
other  hand,  inclines  to  think  that  the  true  shock  phenomena 
pass  off  much  more  rapidly,  and  are  succeeded  by  permanent 
functional  alterations,  which  in  many  ways  resemble  a  recrudescence 
of  shock.  These  are  probably  caused  by  "  isolation-dystrophy " 
due  to  the  withdrawal  from  the  spinal  nerve-cells  of  the  influences 
they  are  accustomed  to  receive  from  higher  parts  of  the  nervous 
system.  In  any  case,  it  is  certain  that  the  phenomena  of  functional 
depression  due  to  transection  of  the  cord  are  more  pronounced  and 
permanent  in  man  and  in  the  ape  than  in  the  dog  and  rabbit, 
while  they  are  quite  transitory  in  the  frog  and  other  cold-blooded 
vertebrates.  The  increasing  gravity  of  shock  in  ascending  the 
vertebrate  scale  is  probably  due  to  the  increasing  influence  of  the 
great  projection  system  of  the  brain  on  the  motor  organ  in  the 
higher  animals.  The  relative  insignificance  of  shock  in  the 
visceral  system,  and  slight  differences  in  the  animal  scale  in  this 


v  SPINAL  CORD  AND  NERVES  313 

respect,  indicate  "  the  extent  to  which  the  reactions  of  the  visceral 
musculature  and  some  of  the  reactions  of  the  skeletal  musculature 
accessory  thereto  are  normally  unconnected  with  higher  conscient 


nervous  organs. 


"  i 


Sherrington's  observations  on  monkeys,  after  cervical  tran- 
section,  are  very  important.  The  motor  root-cells  that  do  not 
respond  to  stimulation  of  the  skin  react  perfectly  to  excitation  by 
the  pyramidal  paths  at  the  cut  end  of  the  cord  ;  weak  stimulation 
of  the  central  ends  of  the  afferent  root  readily  evokes  reflex  move- 
ments, though  far  stronger  stimuli  fail  absolutely  when  applied  to 
the  skin  and  afferent  nerve  trunks. 

VII.  When  a  stimulus  applied  to  any  sensory  area  of  the  body 
evokes  a  reaction  of  the  muscles  belonging  to  the  same  or  to 
adjoining  segments  of  the  cord,  the  reaction  is  termed  a  short 
spinal  reflex;  when,  on  the  contrary,  the  stimulus  evokes  a 
reaction  on  the  musculature  of  a  more  or  less  distant  uietauiere, 
the  spinal  reflex  is  termed  long.  Short  spinal  reflexes  are,  as  a 
rule,  more  easily  and  readily  elicited  because  they  have  less 
resistance  to  overcome. 

Sherrington  makes  the  following  statements  as  to  the  intra- 
spinal  irradiation  in  short  spinal  reflexes  :— 

1.  The  degree  of  reflex  spinal  intimacy  between  afferent  and 
efferent  spinal  roots,  i.e.  the  facility  with  which  the  reflex  is  dis- 
charged,   varies    directly    as    their    segrneutal    proximity.       The 
excitation  of  a  central  end  of  a  severed  thoracic  root  evokes  with 
special  ease  contraction  of  muscles,  or  parts  of  muscles,  innervated 
by  the  corresponding  motor  roots,  and  next  easily  muscles  inner- 
vated  by   the   next  adjacent   motor  roots.     The   spread  of  short 
spinal  reflexes  in  many  instances  seems  to  be  rather  easier  tail  ward 
than  headward. 

2.  Taken  generally,  for  each  afferent  root  there  is  in  its  own 
segment  a  reflex  motor  path  of  as  low  resistance  as  any  open  to  it 
anywhere.     In  other  words,  each  single  afferent  root,  or  a  single 
filament  of  it,  evokes  a  special  reflex  movement  with  a  minimal 
stimulus. 

3.  The  different  motor  mechanisms  for  the  skeletal  musculature 
lying    in    the    same    spinal    segment    exhibit    markedly    unequal 
accessibility    to    the    local  afferent   impulses.     So   that  in   many 
animals  it  is  easier  to  arouse  reflex  contraction  of  the  flexors  of  the 
homonymous  knee  and  the  extensors  of  the  coutralateral  than  of 
the  extensors  of  the  homonymous  and  the  flexors  of  the  contra- 
lateral  knee,  although  the  respective  motor  fibres  may  be  contained 
in  the  same  efferent  root. 

4.  When    a  spinal    reflex    discharge  is  prolonged,   it   usually 

1  Sherrington,  Sc/tafcr's  Text-Book  of  Physiology,  1900,  vol.  ii.  p.  849. 


314  PHYSIOLOGY  CHAP. 

involves   antagonistic   sets   of    motor   cells   alternately,   e.g.    the 
alternate  movement  of  flexion  and  extension. 

5.  The  groups  of  motor  nerve -cells   contemporaneously  dis- 
charged   by    spinal    reflex    action    innervate    synergic    and    not 
antergic  muscles. 

6.  The  reflex  movements  that  may  be  elicited  in  and  from  any 
one   spinal  region  exhibit  much  uniformity  despite    considerable 
variety  of  the  locus  of  incidence  of  the  exciting  stimulus.     Approxi- 
mately the  same  movement,  e.g.  in  the  hind-limb  flexion  of  the 
three  great  joints,  will  result,  whatever  piece  of  the  limb  surface 
be   irritated.     The    seat    of   incidence  of   the  stimulus  will  only 
influence  the  movement  in  so  far  that  the  flexion  will  tend    to 
occur  predominantly  at  that  joint,  the  flexor  muscles  of  which  are 
innervated  by  motor  cells  segment  ally  near  to  the  entrance  of  the 
afferent  fibres  from  the  particular  piece  of  skin  which  is  the  seat  of 
application  of  the  stimulus. 

The  laws,  or  rather  the  rules  which  govern  the  course  of  irradia- 
tion in  long  spinal  reflexes,  were  formulated  by  Pfliiger  in  1853. 
They  can  be  stated  as  follows  :— 

(a)  Law  of  homonymous  conduction  for  unilateral  reflexes.  If 
a  stimulus  applied  to  a  sensory  nerve  provokes  muscular  move- 
ments solely  on  one  side  of  the  body,  that  side  is  without  exception 
that  which  is  the  seat  of  application  of  the  stimulus.  This 
statement,  as  already  known  to  Johannes  Miiller,  does  not 
completely  express  the  facts.  For  instance,  when  the  tail  is 
touched  on  one  side,  it  is  in  many  animals,  from  the  fish  to  the 
mammal,  moved  towards  the  opposite  side,  i.e.  the  reflex  is  dis- 
charged by  the  musculature  of  the  side  opposite  to  the  seat  of 
excitation. 

(&)  Law  of  the  bilateral  symmetry  of  the  reflex  action.  When 
the  excitation  evokes  movements  on  both  sides,  those  muscles  of 
the  opposite  side  first  come  into  play  which  are  symmetrical  with 
those  already  excited  in  the  homonymous  half  of  the  cord.  This 
statement,  although  true  of  a  number  of  instances,  fails  to  conform 
with  fact  in  many  others.  The  important  crossed  reflex  from  the 
hind-limb  of  the  bird  and  mammal  does  not  conform  to  it,  and 
Luchsinger  observed  on  narcotised  dogs  that  excitation  of  a  front 
limb  evokes  reflexes  from  the  hind -limb  on  the  opposite  side. 
This  crossed  reflex,  which  occurs  very  frequently  in  mammals 
(Sherrington),  is  probably  connected  with  the  co-ordination  of  the 
spinal  centres  for  progression. 

(c)  Law  of  unequal  intensity  of  bilateral  reflexes.  When 
excitation  of  a  sensory  nerve  elicits  bilateral  reflexes  of  unequal 
intensity,  the  side  of  stronger  contractions  is  always  homonymous 
with  the  seat  of  application  of  the  stimulus.  This  law  also 
.suffers  exceptions.  The  abduction  of  the  tail  from  the  side 
stimulated,  referred  to  above,  and  the  "  torticollis  "  reflex  towards 


v  SPINAL  COED  AND  NEEVES  315 

the    opposite  side    from   that    excited,  are    examples    of   reflexes 
opposed  to  this  law. 

(fZ)  The  irradiation  of  reflexes  spreads  more  easily  towards  than 
away  from  the  medulla  oblongata,  i.e.  downwards  from  the  cranial 
nerves,  upwards  from  the  spinal  nerves.  When  the  excitation  of 
a  sensory  cranial  nerve  spreads  reflexly  to  a  motor  nerve,  this 
nerve,  according  to  Piiuger,  is  at  approximately  the  same  level  in 
the  central  organ  as,  or  lower  but  never  higher  than,  the  sensory 
nerve.  If  the  excitation  spreads  farther  the  direction  of  irradiation 
is  always  downwards,  towards  the  bulb.  Thus  on  exciting  the 
optic  nerve  the  pupil  contracts,  i.e.  the  impulse  passes  from  the 
optic  to  the  oculomotor  nerve,  and  thence,  from  above  downwards, 
towards  the  bulb.  In  the  cord,  on  the  other  hand,  the  motor  nerve 
first  excited  is  at  the  same  level  as  the  sensory  root  through  which 
the  excitation  passes,  but  when  the  reHex  spreads  the  path  of 
irradiation  is,  according  to  Pfliiger,  always  upwards,  towards  the 
bulb.  Thus  excitation  of  the  finger  evokes  reflexes  in  the  cervical 
region  of  the  cord,  and  on  spreading,  the  excitation  passes  through 
the  cervical  cord  to  the  nuclei  of  the  spinal  accessory,  vagus,  etc., 
and  not  to  the  thoracic  and  lumbar  parts  of  the  cord.  It  is  only 
after  reaching  the  bulb  that  the  excitation  is  able  to  spread  down- 
wards to  the  lumbo-sacral  region. 

This  law  is  the  most  disputed  of  all,  as  it  presents  the  most 
exceptions.  It  contradicts  the  observations  of  Sherrington,  who 
observed  in  mammals  that  in  the  majority  of  instances  irradiation 
spreads  more  easily  down  than  up  the  cord.  It  is  easier  to  obtain 
reflex  movements  of  the  limbs  and  tail  by  excitation  of  the  skin  of 
the  pinna  than  the  reverse ;  it  is  more  difficult  to  elicit  a  move- 
ment of  the  lore-limb  by  excitation  of  the  hind-limb  than  the 
reverse. 

Sherrington  endeavoured  to  determine  the  salient  features  of 
long  intraspinal  reflexes  in  normal  mammals  and  in  those  in  which 
the  cord  is  severed  from  the  brain.  The  animal  is  supported 
freely  from  above  with  its  spinal  axis  horizontal,  so  that  the 
attitude  of  the  limbs  is  determined  by  gravitation.  On  exciting 
different  areas  of  skin  under  these  conditions,  he  found  that 
certain  areas  discharge  reflexes  to  the  skeletal  musculature  more 
easily  than  others.  These  areas  are  the  soles,  the  palms,  the 
pinnae,  the  tail,  the  perineal  region ;  and  with  the  exception  of 
the  last  these  areas  are  those  which  possess  the  greatest  range  of 
motility.  Irradiation  from  these  reflexigenous  areas  takes  place  in 
a  definite  order.  If,  e.g.,  in  the  cat  with  isolated  cord  (Sherrington's 
"  spinal  cat ")  the  left  hind-limb  is  stimulated,  movement  is  excited 
in  that  leg,  which  spreads  to  the  tail,  then  to  the  right  hind-limb, 
lastly  to  the  left  fore-limb.  If  the  left  fore-limb  is  stimulated,  the 
movement  spreads  thence  to  the  left  hind-limb,  the  tail,  the  right 
hind-limb,  and  lastly  the  right  fore-limb.  If  the  left  pinna  be 


316  PHYSIOLOGY  CHAP. 

stimulated  the  irradiation  is  from  left  hind-limb  to  left  fore-limb, 
tail,  right  hind-limb,  right  fore-limb. 

Generally  speaking,  we  may  accept  Sherrington's  statement 
that  the  reflexes  from  spinal  animals  are  very  analogous  to  those 
obtained  from  normal  animals.  The  latter  of  course  exhibit 
greater  variability  in  their  reflex  reactions.  The  long  spinal 
reflexes  are  generally  more  variable  and  less  constant  than  the 
short  reflexes. 

From  this  discussion  it  will  be  seen  that  Pfliiger's  laws  now 
have  little  more  than  a  historical  interest,  owing  to  the  exceptions 
discovered  to  them.  If  any  general  rules  for  the  origin  and  spread 
of  reflexes  are  to  be  formulated  it  is  all-essential  to  take  their 
"biological  significance"  (Langendorff)  into  account,  as  deduced 
from  the  fact  that  they  almost  always  represent  a  reaction  co- 
ordinated to  a  given  end,  and  useful  to  the  organism  as  a  whole. 

Bagiioni  (1904-7),  who  analysed  the  reflexes  that  can  be 
obtained  from  the  "spinal  frog"  after  the  bloodless  severance  of 
the  medulla  oblongata  (compression  by  a  clamp),  when  the  animal 
can  survive  for  a  long  time,  was  able  to  demonstrate  that  different 
retiex  mechanisms  exist  potentially  in  the  spinal  cord,  the 
manifestation  of  which  depends  not  so  much  upon  the  seat,  the 
intensity,  and  the  duration  as  upon  the  nature  of  the  peripheral 
stimulus.  Gentle  pressure  with  the  finger  or  other  blunt  object 
on  the  sole  of  the  foot  excites  an  extensor  reflex  of  the  hind- 
liinb  with  spread  of  the  toes  of  the  same  foot,  so  that  the  web 
presses  against  the  impinging  finger  (plantar  reflex).  Painful 
stimulation  (e.g.  electrical,  chemical,  mechanical,  pricking  with  the 
point  of  a  pin,  or  compression  with  forceps)  of  the  same  point  of 
the  skin  evokes  the  opposite  reflex,  i.e.  flexion  of  the  hind-limb 
and  contraction  of  the  web,  so  that  the  foot  is  moved  always  from 
the  stimulus  and  the  limb  drawn  up  to  the  body. 

Similar  reflexes  have  been  demonstrated  by  Sherrington  (1904) 
on  the  "spinal  dog,"  by  Bagiioni  and  Matteucci  (1909)  on  the 
"spinal  pigeon,"  and  by  G.  Cesana  (1911)  on  rats  after  the  three 
first  days  of  life.  (In  the  earliest  hours  of  life  the  rat  always 
responds  by  a  movement  of  flexion  (Cesana).) 

On  the  strength  of  these  facts  Bagiioni  distinguishes  two 
classes  of  reflex  actions:  those  due  to  abnormal  injurious  stimuli, 
and  those  due  to  normal  (biological  or  functional)  stimuli. 

(</.)  In  the  first  class  the  reflex  movements  are  in  proportion  to 
the  strength  and  duration  of  the  stimuli.  If  these  are  weak  or  of 
short  duration,  the  reflex  aims  at  removing  the  point  of  the  body 
abnormally  stimulated ;  if  they  are  strong  or  protracted,  this 
movement  is  succeeded  by  more  complicated  reflexes  directed  to 
remove  the  obnoxious  stinmlus. 

(&)  The  reflexes  of  the  second  class  are  in  relation,  not  with  the 
strength  or  duration,  but  with  the  nature  of  the  stimulus,  which  is 


v  SPINAL  CORD  AND  NERVES  .".IT 

not  an  injurious  factor  from  which  the  animal  must  escape,  but  a 
condition  favourable  to  the  normal  development  of  useful  functions. 
Thus  the  plantar  reflex  is  a  rellex  which  the  animal  usually  carries 
out  in  walking  or  leaping.  It  represents  the  extensor  reaction 
of  the  limb  applied  to  the  ground  for  the  purpose  of  raising  the 
body. 

The  reflexes  of  the  second  category  do  not  for  the  most  part 
spread  to  different  muscles,  like  the  reflexes  of  the  first  class,  when 
the  strength  or  duration  of  the  stimulus  is  increased;  they  behave, 
on  the  contrary,  more  as  if  they  conformed  to  the  "  all  or  nothing  " 
law  of  the  heart. 

Finally  Baglioni  has  brought  out  the  fact  that  reflexes  of  the 
first  class  are  usually  produced  by  injurious  electrical  or  chemical 
stimuli  such  as  Pfliiger  employed.  To  evoke  reflexes  of  the  second 
category  it  is  necessary  to  use  adequate  stimuli,  and  to  apply  them 
to  the  peripheral  sense  organs  which  normally  receive  them,  and 
•not  to  exposed  nerve  trunks. 

VIII.  The  nature  of  any  reflex  movement  is  determined  by 
the  quality,  intensity,  and  seat  of  the  stimulation,  and  lastly  by 
the  state  of  the  centres  that  participate  in  the  reflex. 

All  the  different  modes  of  cutaneous  stimulation  (electrical, 
mechanical,  thermal,  chemical)  are  capable,  even  when  they  induce 
painful  sensations,  of  evoking  spinal  reflexes.  The.  form  of  the 
movement  may  differ,  however,  with  the  nature  of  the  excitation. 
For  instance,  the  tail  of  the  eel,  according  to  Pfluger's  experiments, 
moves  towards  a  tactile  stimulus,  and  away  from  a  painful 
stimulus.  Certain  special  reflexes  only  come  off  with  specific 
stimuli ;  gentle  patting  of  the  skin  of  a  dog's  flank  may  cause  a 
rhythmical  scratching  movement. 

It  is  easier  to  evoke  a  reflex  by  weak  mechanical  stimulation 
of  the  skin  than  by  strong  induction  shocks  applied  directly  to  a 
nerve  trunk.  Faradisation  of  the  central  end  of  a  muscular  nerve, 
for  instance,  has  much  less  effect  on  respiratory  rhythm  and  on 
blood  pressure  than  the  stimulation  of  a  cutaneous  nerve :  in  the 
first  case  there  is  a  fall,  in  the  second  a  rise,  of  blood  pressure. 
Excitation  of  the  dorsal  roots  induces  reflexes  more  easily  than 
stimulation  of  the  peripheral  nerve-endings  in  the  skin ;  but  in 
the  second  case  the  reaction  is  more  like  an  ordinary  co-ordinated 
movement,  while  in  the  first  it  resembles  a  reflex  spasm.  This 
shows  that  in  mammals  the  spinal  roots  are  less  a  functional  than 
a  purely  morphological  complex  ;  the  functional  combinations  of 
the  root  filaments  are  first  formed  in  the  nerve  plexuses. 

The  character  of  the  reflex  is  also  influenced  by  the  intensity 
of  the  stimulation,  independently  of  any  change  in  the  nature  of 
the  afferent  impulse.  A  weak  stimulus  evokes  a  reflex  reaction 
that  is  transmitted  to  a  few  efferent  fibres ;  a  stronger  stimulus 
causes  the  reflex  to  spread  to  many  efferent,  fibres.  But  there  is 


318  PHYSIOLOGY  CHAP. 

no  strict  relation  between  strength  of  stimulus  and  extent  and 
duration  of  reflex.  According  to  Slier rington,  the  reflex  arc  some- 
times behaves  like  cardiac  muscle,  which  responds  to  stimuli  by 
maximal  contractions  or  not  at  all  (supra^).  In  any  case  it  is 
certain  that  the  internal  conditions  of  the  reflex  arc  have  more 
influence  upon  the  degree  of  the  reaction  than  the  strength  of 
external  stimulus. 

The  seat  of  stimulation  is  an  important  factor  in  determining 
the  character  of  the  reflex  movements.  The  reflexes  evoked  by 
stimulating  the  viscera  are  different  from  those  excited  by 
cutaneous  stimulation  ;  these,  again,  vary  greatly  according  to  the 
point  stimulated.  This  fact  is  easily  demonstrated  on  the  spinal 
decerebrated  frog.  The  constancy  of  the  various  reflex  reactions 
obtained  on  exciting  different  points  of  the  frog's  skin  (by  bits  of 
paper  saturated  with  acidulated  water)  tends  to  show  the  existence 
of  a  functional  mechanism  in  the  cord  in  which  the  character  of 
the  reflexes  is  determined  by  the  spatial  position  of  tbe  spot  at 
which  the  excitation  arises.  This  is  true,  not  only  for  cutaneous 
sensations,  but  also  for  those  which  originate  from  the  sensory 
nerves  of  the  muscles,  tendons,  and  joints,  and  serve  to  identify 
the  position  of  the  limbs  in  consciousness. 

Lastly,  the  character  of  the  reflexes  depends  to  a  great  extent 
on  the  intrinsic  conditions  of  the  cord,  i.e.  the  state  of  excitability 
and  conductivity  of  the  spinal  centres.  Reflex  excitability  can  be 
raised  or  lowered  by  the  action  of  specific  toxic  substances ;  it  is 
depressed  or  abolished  by  anaesthetics,  particularly  with  chloro- 
form :  reinforced  by  convulsants,  especially  strychnine.  Various 
diseases  that  involve  the  spinal  cord  produce  a  rise  or  fall  in  reflex 
excitability,  like  poisons,  so  that  the  reflexes  are  exaggerated  or 
abolished. 

The  functional  condition  of  the  spinal  centres  is  chiefly 
dependent  on  the  circulation  and  the  respiration.  A  spinal  frog 
in  which  the  circulation  is  arrested  by  tying  the  heart,  or  tbe 
blood  is  replaced  by  an  isotonic  salt  solution,  reacts  to  cutaneous 
stimulation  for  about  half  an  hour  if  the  temperature  is  low ;  for 
a  shorter  time  with  a  higher  temperature.  In  the  spinal  rabbit, 
according  to  Sherrington,  the  reflexes  do  not  last  more  than  a 
minute  after  the  arrest  of  circulation  at  the  normal  temperature. 
But  if  the  animal  had  previously  been  cooled,  the  reflexes  may 
persist  much  longer.  Both  anaemia  and  asphyxia,  before  they 
abolish  the  reflexes,  cause  temporary  exaggeration,  shown  by  a  rise 
of  blood  pressure,  contraction  of  the  bladder,  erection  of  hairs,  and 
convulsive  movements. 

In  addition  to  these  variations  of  reflex  excitability  and  con- 
ductivity in  the  spinal  centres,  which  are  produced  by  coarse 
alterations  in  their  physiological  conditions,  we  must  take  into 
consideration  the  other  more  delicate  changes  in  the  state  of  the 


v  SPINAL  COED  AND  NERVES  319 

said  centres,  due  to  the  transient  physiological  processes  known  as 
inhibition  and  facilitation  (Bahnung). 

The  reflex  actions  of  a  spinal  segment  depend,  not  only  on  the 
excitations  that  reach  it  by  the  respective  afferent  paths,  but  also 
on  influences  from  other  portions  of  the  nervous  system.  These 
influences  may  be  of  such  a  character  as  to  moderate  or  depress 
its  activity,  or  they  may  augment  it.  In  the  first  case  there  is 
inhibition,  in  the  second  facilitation,  of  the  reflex. 

Inhibition,  first  discovered  by  the  Webers  in  the  action  of  the 
excited  vagus  on  the  heart,  was  applied  to  the  physiology  of  the 
nervous  system  by  Setschenow  (1863).  He  observed  that  the  frog 
deprived  of  its  whole  brain  developed  stronger  reflexes  and  reacted 
to  weaker  stimuli.  But  if  the  cerebral  hemispheres  alone,  without 
the  optic  lobes  and  remainder  of  the  brain,  were  extirpated,  the 
reflexes  were  not  much  affected.  If,  finally,  the  optic  lobes  of  the 
decerebrated  frog  were  stimulated,  e.g.  with  a  crystal  of  salt,  it  was 
•seen  to  withdraw  its  foot  from  the  acidulated  water  much  later 
than  the  normal  frog.  Setschenow  concluded  that  the  mesen- 
cephalon  is  an  inhibitory  organ  for  spinal  reflexes. 

Inhibitory  reflexes  were  subsequently  obtained  from  other 
parts  of  the  brain,  and  also  from  the  cord  itself,  by  direct  or  reflex 
excitation. 

In  the  higher  mammals,  where  the  cord  contains  long  cortico- 
spinal  paths,  the  brain  has  a  marked  inhibitory  influence  upon  the 
spinal  reflexes,  and  these  are  facilitated  by  the  removal  of  the 
cortex  or  transection  of  the  cortico- spinal  paths.  Both  in  the  dog 
and  in  the  ape  this  phenomenon  is  easily  verified  a  short  time 
after  the  operation,  i.e.  when  the  spinal  exaltation  is  due  to  the 
onset  of  Wallerian  degeneration,  which  acts  as  a  continuous 
irritant  of  the  spinal  tissue.  That  the  brain  can  function  as  an 
inhibitory  organ  for  the  spinal  reflexes  appears  from  the  everyday 
experience  that  we  can  sometimes  voluntarily  arrest,  at  other 
times  delay,  more  often  modify  certain  reflexes,  e.g.  micturition, 
defaecation,  coughing,  sneezing,  etc. 

Another  well-established  fact  is  that  excitation  of  one  part 
of  the  cord  is  able  to  inhibit  the  reflex  activity  of  other  parts. 
This  is  seen  particularly  from  the  experiments  of  Goltz.  If  in  the 
spinal  frog  the  sciatic  nerve  is  stimulated  electrically,  no  reflex  is 
evoked  by  applying  acidulated  paper  to  the  skin.  The  arrest  of 
the  frog's  heart  by  rhythmically  tapping  the  intestines  does  not 
come  off  if  the  foot  is  pinched  at  the  same  time.  The  spinal  snake 
makes  rhythmical  pendulous  movements  which  cease  when  its 
body  is  lightly  touched.  Micturition  already  in  progress  can  be 
interrupted  in  a  spinal  dog  by  pinching  the  hind-foot  or  tail.  In 
the  spinal  cat  suspended  horizontally  with  relaxed  limbs  stimula- 
tion of  the  skin  of  one  foot  causes  drawing  up  of  the  homonymous 
and  extension  of  the  contralateral  limb;  when  both  feet  are 


320  PHYSIOLOGY  CHAP. 

stimulated    simultaneously  the  extensors   are  inhibited  and  the 
flexors  of  both  sides  are  thrown  into  contraction. 

Inhibition  of  a  spinal  centre  through  other  centres  probably, 
according  to  Sherrington,  plays  a  great  part  in  the  co-ordination  of 
the  spinal  acts.  In  fact,  his  researches  show  that  the  contraction 
of  any  group  of  muscles  is  usually  accompanied  by  the  inhibition 
of  the  antagonist  group.  The  tension  of  the  muscle  in  consequence 
of  its  contraction  mechanically  excites  its  sensory  apparatus 
(inusculo-tcridinous  organ  of  Golgi)  and  thus  reflexly  depresses  the 
tone  of  the  antagonist  muscle.  On  faradising  the  central  end  of 
the  nerve  of  the  femoral  biceps  of  the  cat  the  effect  of  this 
stimulation  on  the  extensor  muscles  of  the  knee  is  shown  by  their 
elongation  and  the  temporary  diminution  of  the  patellar  reflex. 


FIG.  184. — Myograms  of  weak  tonic  contraction  of  m.  extensor  communis  of  toes.  (Verworn.) 
The  arrows  indicate  the  times  at  which  there  is  reflex  inhibition  of  tone  after  crushing  the 
antagonist  muscles.  The  curves  are  reduced  to  §. 

If  the  flexor  muscle  of  the  leg  is  detached  from  its  insertion  and 
then  stretched  or  compressed,  there  is,  as  with  electrical  stimulation, 
a  relaxation  of  the  extensor  muscle  of  the  knee  and  a  weakening 
of  the  knee-jerk.  To  confirm  these  effects,  which  Sherrington  calls 
reciprocal  innervation  of  antagonist  muscles,  Verworn  performed 
the  following  experiment  on  the  dog :  he  isolated  the  branch  of 
the  peroneal  nerve  by  which  the  m.  extensor  lougus  communis  of 
the  foot  is  innervated,  detached  this  muscle  from  its  insertion,  and 
connected  it  with  a  recording  apparatus,  after  fixing  the  limb  by 
a  plaster  bandage.  On  stimulating  the  nerve  at  regular  intervals 
of  one  second,  he  obtained  a  tracing  of  approximately  equal  con- 
tractions. On  pinching  the  flexor  muscles  with  a  large  forceps 
during  this  periodical  stimulation  he  obtained  a  temporary  fall  in 
the  level  of  the  contractions,  which  indicates  a  reflex  depression  of 
the  tone  in  the  muscle  due  to  the  mechanical  excitation  of  its 
antagonist  (Fig.  184). 


v  SPINAL  COIU)  AND  NKKVKS  321 

The  iiihiltition  due  to  direct  or  indirect  excitation  of  a  spinal 
centre  is  usually  quite  transient  in  decerebrated  animals.  When 
the  stimulation  is  sufficiently  prolonged,  the  inhibition  is  followed 
by  a  functional  rise,  which  accords  well  with  the  alternating  clonic 
character  of  the  muscular  reactions  in  decerebrated  animals. 

Transection  of  the  cord  also  induces  inhibition  in  its  caudal 
segments,  which  is  more  pronounced  in  the  segments  nearest  the 
section  and  gradually  declines  in  the  more  remote  segments.  This 
is  plain  from  Eoseuthal's  experiments  (1873).  He  showed  that 
the  latent  time  of  the  reflex  evoked  in  the  frog's  hind-limb  by 
stimulating  the  skin  of  the  opposite  limb  is  longer  in  low  than 
in  high  transection.  Bickel  at  a  later  date  (1898)  proved  on  the 
frog,  salamander,  and  tortoise  that  the  reaction  time  is  longer 
when  the  cord  is  cut  below  the  brachial  plexus  than  when  it  is 
divided  immediately  below  the  medulla  oblongata.  Further,  De 
Boeck  (1887)  found  that  a  stronger  stimulus  was  needed  to  excite 
a  reflex  in  the  rabbit  when  the  cord  was  divided  than  when  the 
section  lay  above  the  spinal  bulb. 

The  opposite  effect,  facilitation  or  augmentation  (Bahnuny} 
of  the  spinal  reflexes,  was  first  pointed  out  by  Exner  in  1882. 
He  saw  in  the  rabbit  that  on  simultaneously  stimulating  the 
cortical  centre  for  a  given  muscle  of  the  leg  and  a  point  on  the 
skin  of  the  leg  by  which  the  same  muscle  was  excited,  the  reflex 
contraction  was  more  energetic  than  when  the  cortex  alone,  or 
the  skin  alone,  was  excited.  On  reducing  the  strength  of  the 
cutaneous  stimulus  till  it  became  subliminal,  it  was  made  efficient 
again  when  a  cortical  stimulus  was  applied  two  seconds  pre- 
viously. Adequate  skin  stimuli  similarly  rendered  subliminal 
cortical  stimuli  effective.  When  both  stimuli — taken  singly — were 

O     v 

subliminal,  each  made  the  other  efficient  if  the  interval  between 
them  did  not  exceed  one-eighth  of  a  second. 

Sherrington  gives  other  instances  of  reflex  facilitation.  He 
states  that  the  reflex  excited  from  an  afferent  root  of  a  spinal 
animal  by  a  given  minimal  stimulus  can  be  evoked  by  a  weaker 
stimulus  when  other  adjacent  roots  are  previously  excited. 

In  1905  he  analysed  the  fundamental  characteristics  of  a 
specific  reflex  in  the  dog,  the  "scratch  reflex."  On  applying 
certain  stimuli  within  a  wide  saddle-shaped  zone  of  the  skin  on 
the  back  and  flanks  (Fig.  185)  of  a  dog,  after  high  thoracic  tran- 
sectiou,  the  hind-leg  on  the  same  side  executes  a  scratching  move- 
ment. This  movement  is  produced  by  flexion  of  the  hip,  knee, 
and  ankle,  which  is  rhythmically  repeated  about  four  times  a 
second.  The  sensory  nerve-endings  which  discharge  the  reflex 
(the  "  receptors  ")  lie  on  the  surface  of  the  skin  and  seem  to  be  in 
close  relation  with  the  hair  follicles.  The  reflex  can  be  evoked  by 
mechanical  stimuli — rubbing  the  skin  or  lightly  pulling  the  hair- 
as  well  as  by  electrical  excitation — weak  faradic  currents,  constant 

VOL.  m  Y 


322 


PHYSIOLOGY 


CHAP. 


currents,  and  alternating  currents  of  high  frequency.  The  reflex 
consists  in  a  series  of  short  rapid  contractions  of  the  flexors  of  the 
hip,  the  frequency  of  which  is  independent  of  that  of  the  excitation. 
The  reflex  path  runs,  as  shown  by  the  method  of  successive  sections, 
in  the  external  part  of  the  lateral  column. 

The  chief  characteristic  of  this  reflex  is  that  one  and  the  same 
reaction  can  be  elicited  from  a  comparatively  large  sensory  area 
(Sherrington's  receptive  field),  so  that  a  whole  series  of  afferent 
(sensory)  mechanisms  are  in  connection  with  the  same  efferent 
(motor)  mechanism. 

"  At  the  commencement  of  every  reflex  arc,"  Sherrington  writes, 
"  is  a  receptive  neurone  extending  from  the  receptive  surface  to 
the  central  nervous  organ.  This  neurone  forms  the  sole  avenue 
which  impulses  generated  at  its  receptive  point  can  use  whitherso- 


FIG.  185. — Receptive  field  for  scratch  reflex  in  dog  with  complete  cervical 
transaction.     (Sherrington.) 

ever  be  their  destination.  This  neurone  is  therefore  a  path 
exclusive  to  the  impulses  generated  at  its  own  receptive  point,  and 
other  receptive  points  than  its  own  cannot  employ  it. 

"  But  at  the  termination  of  every  reflex  arc  we  find  a  final 
neurone,  the  ultimate  conductive  link  to  an  effector  organ,  muscle, 
or  gland.  This  last  link  in  the  chain,  e.g.  the  motor  neurone, 
differs  obviously  in  one  important  respect  from  the  first  link  of 
the  chain.  It  does  not  subserve  exclusively  impulses  generated  at 
one  single  receptive  source,  but  receives  impulses  from  many 
receptive  sources  situate  in  many  and  various  regions  of  the  body. 
It  is  the  sole  path  which  all  impulses,  no  matter  whence  they 
come,  must  travel  if  they  are  to  act  on  the  muscle-fibres  to  which 
it  leads.  .  .  . 

"  Eeflex  arcs  show,  therefore,  the  general  features  that  the 
initial  neurone  of  each  is  a  private  path  exclusively  belonging  to  a 
single  receptive  point  (or  a  small  group  of  points) ;  and  that  finally 
the  arcs  embouch  into  a  path  leading  to  an  effector  organ ;  and 


v  SPINAL  CORD  AND  NKliVKS  323 

that  their  final  path  is  common  to  all  receptive  points  wheresoever 
they  lie  in  the  body,  so  long  as  they  have  connection  with  the 
effector  organ  in  question.  The  terminal  path  may,  to  distinguish 
it  from  iuternuncial  common  paths,  be  called  tin-  Jinal  common 
path.  The  motor  nerve  to  a  muscle  is  a  collection  of  final  common 
paths."  1 

Given  this  special  arrangement  of  the  various  elements  which 
constitute  a  reflex  arc,  a  series  of  important  theoretical  conclusions 
capable  of  explaining  the  phenomena  of  facilitation  and  inhibition, 
as  seen  in  the  reciprocal  action  of  the  various  reflexes,  can  be 
deduced.  It  is  obvious  that  when  several  receptors  connected  with 
the  same  common  path  are  simultaneously  excited,  their  individual 
effects  must  be  either  summated  so  as  to  reinforce,  or  neutralised 
so  as  to  inhibit,  according  as  the  reflexes  which  they  separately 
excite  harmonise  or  are  incompatible.  Sherrington  terms  the 
former  "  allied,"  the  latter  "  antagonist,"  reflexes.  He  has  demon- 
strated a  series  of  such  reflexes  on  the  dog,  which  were  either 
allied  to,  or  inhibitory  of,  the  "  scratch  "  reflex. 

IX.  It  is  a  vexed  question  whether  the  spinal  cord  is 
capable  of  automatic  as  well  as  reflex  activity.  The  rhythmic 
respiratory  movements  that  may  persist  after  dividing  the  bulb 
are  of  a  doubtful  character  (Vol.  I.  p.  502).  The  tone  of  the 
sphincters  and  of  the  blood-vessels,  which  we  discussed  in  the 
physiology  of  digestion  and  circulation  (Vol.  II.  Chaps,  III.  and  VI., 
Vol.  I.  Chap.  X.),  is  probably  due  to  the  action  of  constant  or 
frequently  repeated  extrinsic  stimuli.  The  tone  of  the  common 
skeletal  muscles  in  the  resting  state,  which  undoubtedly  depends 
on  spinal  tonus,  is  again  not  automatic  but  reflex  in  character,  as 
conies  out  plainly  from  Brondgeest's  experiments.  If  the  sciatic 
of  one  hind-limb  be  divided  in  a  spinal  frog  suspended  vertically, 
the  flexor  muscles  of  that  limb  are  relaxed,  while  those  of  the 
opposite  limb  are  slightly  contracted.  This  shows  that  the  tone  of 
the  flexor  muscles  of  the  hind-limb  prevails  over  those  of  the 
extensor  muscles  after  removal  of  the  brain,  and  that  this  muscular 
tone  depends  on  spinal  tonicity.  If  instead  of  cutting  the  sciatic 
its  posterior  roots  are  divided  (Cyon),  the  tone  of  the  flexors  also 
disappears.  This  shows  that  the  tone  of  the  spinal  centre  is  not 
automatic  but  reflex,  i.e.  it  depends  on  a  continuous  wave  of 
excitation  which  flows  through  the  sensory  fibres  to  the  centre, 
and  thence  back  to  the  muscles. 

Chloroform  and  ether,  like  transection  of  the  afferent  roots, 
abolish  the  tone  of  the  spinal  cord. 

The  tonic  influence  of  the  afferent  roots  seems  not  to  be 
derived  exclusively  from  the  sensitive  cutaneous  surface,  as  Brond- 
geest  assumed.  In  fact  it  persists  in  the  frog  even  when  the  whole 

1  Sherrington,    The  Intcyrative  Action  of  the  Nervous  System,  London,   1906. 
pp.  115  and  116. 


324 


PHYSIOLOGY 


CHAP. 


of  the  skin  has  been  removed,  according  to  Moinmsen.  There 
must,  therefore,  be  other  paths  of  excitation  besides  the  cutaneous 
nerves,  probably  from  the  sensory  nerve-endings  in  the  muscles 
and  tendons. 

Since  the  spinal  tone  that  governs  muscular  tone  is  reflex, 
not  automatic,  it  may  be  asked  whether  it  depends  exclusively 
upon  the  afferent  excitations  and  is  a  constant  quantity,  or  can 


FIG.  186. — Tracings  of  homulateral  reflexes  of  hind-limb  of  marsh  tortoise,  obtained  with  uniform 
and  rhythmically  recurrent  stimuli.  (Fano.)  To  avoid  confusion  between  the  separate  reflexes 
by  (superposition  of  the  curves,  a  special  mechanical  contrivance  was  fitted  by  which  the 
writing-point  was  removed  from  the  drum  at  a  given  moment  after  stimulation.  The  points  of 
stimulation  are  marked  below  the  series  of  curves,  and  the  time  in  ^},n  sec.  The  vertical 
lines  that  coincide  with  each  stimulation  were  ruled  with  a  T  square  to  show  the  reaction-time. 
Tracings  reduced  by  J. 

vary  automatically,  independent  of  any  extrinsic  influence,  in 
consequence  of  periodic  oscillations  or  variations  in  the  excitability 
and  metabolism  of  the  central  organ  ? 

Fano  (1903)  from  a  systematic  study  of  the  reflex  movements 
of  the  marsh  tortoise  (Umi/s  palustris)  adduced  experimental 
evidence  for  the  last  view.  He  invented  an  apparatus  by  which 
the  animal  could  be  excited  at  regular  intervals  by  faradic  break 
shocks  of  constant  strength,  the  reflex  reactions  being  recorded  at 
regular  distances  on  a  smoked  drum.  He  proved  that  the  motor 
reactions  are  not  uniformly  vigorous,  but  exhibit  continuous 


SriNAL  COED  AND  NERVES 


325 


irregularly  periodic  oscillations.  The  curves  of  Fig.  186  represent 
this  phenomenon.  The  time  marking,  obtained  from  a  tuning 
fork  of  100  vibrations  per  second,  and  the  exact  moment  of 
stimulation,  are  recorded  below  the  muscle  tracings.  By  measur- 
ing the  distance  between  the  single  stimuli  and  the  corresponding 
reactions,  the  latent  period  of  the  latter  is  arrived  at.  Another 
interesting  fact  then  comes  out,  that  besides  the  irregular  periodic 
oscillations  in  the  amplitude  of  the  reactions,  there  are  similar 
oscillations  in  the  reaction  time. 

Fano's  experiments  demonstrate  that  the  automatic  variations 
of  special  excitability  above  described,  which  give  a  character  of 
irregular  oscillating  periodicity  to  the  spinal  tone  in  the  tortoise, 


FIG.  187. — Tracing  a.s  in  last  figure,  after  cervical  transection  of  the  cord.    (Fano.) 

depend  on  influences  coming  from  the  brain,  particularly  from 
the  medulla  oblongata.  These  periodic  oscillations  diminish  when 
by  removing  the  fore-brain  the  inhibitory  influence  of  the  mid- 
brain  is  unchecked.  If  the  optic  lobes  are  also  destroyed,  so  that 
the  automatic  activity  of  the  bulb  is  given  free  rein,  the  oscilla- 
tions once  more  become  very  conspicuous  and  far  exceed  those 
observed  under  normal  conditions.  After  dividing  the  thoracic 
cord  they  diminish  considerably  in  the  hind-limbs ;  after  cervical 
transection  they  decrease  in  the  fore-limbs  (Fig.  187). 

Fano's  observations  give  further  confirmation  of  the  inhibitory 
influence  of  the  optic  lobes  already  referred  to  (p.  319),  and  of  the 
automatic  activity  of  the  spinal  bulb,  to  be  discussed  in  the  next 
chapter.  These  automatic  oscillations  of  the  excitability  of  the 
cord  are  merely  the  spread,  almost  one  might  say  the  reflection,  of 
those  more  marked  waves  that  occur  in  the  bulb,  the  existence  of 


326 


PHYSIOLOGY 


CHAP. 


which  was  deduced  by  us  as  early  as  1879  from  the  critical  analysis 
of  periodic  respiration  (Vol.  I.  p.  492). 

Langendorff  (1905)  has  recently  confirmed  Fano's  observations 
for  the  oscillations  of  intensity  in  the  reflex  movements  of  the 
tortoise.  But  he  was  unable  to  admit  their  dependence  on 
impulses  from  the  bulb,  since  they  persisted  after  high  tran- 
section  of  the  cord.  Scheven  in  the  rabbit  noticed  analogous 
oscillations  of  the  patellar  reflex,  which  is  evoked  by  the  rhythmical 
application  of  single  mechanical  stimuli  (M///YA). 

According  to  Gr.  Cesana  (1911),  in  the  new-born  rat  oscillations 
in  the  height  of  the  reflex  contractions  are  seen  from  the  earliest 


A 


f 


Fin.  iss.  —  Knee-jerk.  A,  the  dotted  line  indicates  the  movement  produced  l>y  lapping  the 
palellar  tendon:  B,  the  same  obtained  by  a  hammer  when  it  does  not  occur  readily  in  the 
usual  way. 

days  of  life,  and  these,  contrary  to  what  occurs  in  the  adult,  persist 
even  after  transection  below  the  medulla  oblongata. 

The  phenomenon  of  "  knee-jerk,"  first  studied  by  Westphal  and 
by  Erb,  is  strictly  related  to  the  tone  of  the  skeletal  muscles. 

When  the  limb  is  hanging  with  all  the  muscles  at  rest  a  light 
blow  on  the  patellar  ligament  with  the  hand,  or  better  with  a 
small  hammer,  evokes  a  sharp  contraction  of  the  quadriceps  cruris 
and  an  extension  of  the  knee  (Fig.  188).  Similar  effects  are  seen 
in  other  muscles  on  mechanically  exciting  the  muscles  and  tendons 
or  the  periosteum,  but  the  knee-jerk  is  the  most  typical  and  the 
best  studied. 

The  indispensable  condition  for  the  appearance  of  the  knee-jerk 
is  some  tension  or  tone  in  the  muscle.  The  stimulus  which  evokes 
the  reaction  consists  in  a  gentle  but  sudden  passive  increase  of 
this  tension. 


v  SPINAL  COED  AND  NEEVES  327 

The  true  reflex  character  of  the  patellar  reflrx  or  tendon 
phenomenon  is  not  universally  admitted.  According  to  Brissaud, 
Eulenberg,  Mac  William,  Waller,  Gowers,  and  others,  the  time 
elapsing  between  the  mechanical  stimulation  and  the  muscular 
reaction  is  too  brief  for  a  reflex  (via  afferent  root,  cord,  and  motor 
root  cells),  and  corresponds  approximately  to  the  latent  period  in 
direct  electrical  excitation  of  the  muscle,  as  shown  by  the  curve  of 
Fig.  189. 

But  its  reflex  nature  was  clearly  brought  out  by  Sciamanna 
(1900)  in  some  ingenious  experiments  on  a  patient  with  marked 
exaggerations  of  the  knee-jerk  on  the  right  side  ;  the  right  vastus 
iuternus  muscle  also  contracted  reflexly  when  the  patellar  tendon 
on  the  left  side  was  tapped.  By  means  of  the  graphic  method  he 
showed  that  the  direct  and  reflex  contractions  of  the  leg  excited  and 


FKI.  189. — Comparison  of  latent  period  in  (1)  a  direct  contraction,  (2)  the  tendon  phenomenon, 
(3)  a  reflex  contraction.     On  the  rabbit.    (Waller.) 

those  of  the  opposite  side  differ  perceptibly  in  the  time  lost  from 
the  moment  of  stimulation. 

Scheven's  latest  experiments  in  Langendorffs  laboratory  are 
also  decidedly  in  favour  of  the  reflex  nature  of  the  knee-jerk.  In 
the  rabbit  he  compared  the  latent  period  in  direct  electrical 
stimulation  of  the  muscle  and  after  mechanical  stimulation  of  the 
patellar  tendon.  His  method  enabled  him  to  record  the  moment 
of  stimulation  with  great  accuracy  in  both  cases,  while  he  avoided 
the  usual  errors  due  to  inertia  of  the  lever.  On  direct  stimulation 
of  the  muscle  he  found  the  latent  period  to  be  on  an  average 
O'Oll  sec.,  while  in  the  knee-jerk  it  amounted  to  0-022  sec.,  i.e. 
nearly  double  the  former.  This  is  excellently  shown  in  Fig.  190, 
in  which  the  upper  line  (d.s.)  gives  the  curve  of  the  m.  extensor 
cruris  with  direct  stimulation ;  the  lower  (r.s.),  which  starts  much 
later  from  the  abscissa,  shows  the  mechanically  excited  reflex 
contraction  of  the  same  muscle. 

Scheven  also  recorded  a  long  series  of  patellar  reflexes  evoked 
by  rhythmical  stimuli,  with  the  object  of  establishing  the 
influence  of  specific  conditions  of  stimulation  on  the  height 


328  PHYSIOLOGY  CHAP. 

of  the  reflex  contractions.  He  saw  that  even  with  perfect 
equality  of  stimulation  periodical  variations  in  the  height  oi 
the  contractions,  corresponding  to  those  which  Fauo  observed 
on  the  tortoise,  were  always  present.  He  attributed  these  to 
corresponding  variations  in  the  excitability  of  the  spinal  centres. 
Fatigue  was  practically  excluded  under  Scheveu's  experimental 
conditions.  In  one  experiment  he  recorded  some  900  reflex 
contractions,  excited  at  intervals  of  one  second,  without  fatigue, 
as  noted  by  Treves  in  his  experiments  on  man,  with  the  ergograph 
(Chap.  I.  p.  51).  The  height  of  the  contractions  increased  in 
direct  ratio  with  the  height  from  which  the  hammer  dropped  to 
arouse  the  reflex,  and  rose  rapidly  at  first  and  then  more  slowly  to 
the  maximum  when  the  height  of  drop  was  about  30  cm.  On 


FKJ.  1!'0.  -Comparison  of  contraction  from  extensor  muscle  of  raliliit's  leg  to  direct  electrical 
stimulation  (il.x.),  and  reflex  mechanical  stimulation  (/•.*.).  (Scheven.)  Tunin.n-foi  k  100 
vibrations  per  second. 

further  increasing  the  drop  the  height  of  the  twitch  declined, 
probably  owing  to  inhibition  caused  by  the  strong  excitation  of 
the  afferent  cutaneous  nerves.  Specially  important  is  the  fact  that 
the  height  of  the  contraction  depended  to  a  large  extent  upon  the 
stimulation  frequency ;  the  smaller  the  interval  between  two 
stimuli,  up  to  a  certain  point,  the  higher  was  the  contraction. 
This  is  undoubtedly  an  effect  of  summation  of  stimuli,  and  as 
summation  is  a  property  of  the  nervous  centres  (see  last  chapter) 
this  fact  also  testifies  strongly  to  the  reflex  nature  of  the  knee-jerk. 
Whether  the  knee-jerk  be  regarded  as  a  reflex  or  not,  it  is  in 
any  case  dependent  on  the  integrity  of  a  spinal  reflex  arc — the 
afferent  limb  of  which  conducts  from  the  sensory  organs  in  the 
muscle  itself  and  its  appendages — to  which  is  due  the  tone  or  state 
of  tension  in  the  latter  during  rest.  If  the  afferent  nerves  of  the 
muscle  or  its  motor  or  sensory  roots  are  divided,  the  knee-jerk  is 
abolished ;  while  it  persists,  and  may  even  be  increased,  if  all  the 


v  SPINAL  CORD  AND  NERVES  329 

other  afferent  nerve  paths  to  the  limb  are  severed.  The  integrity 
of  the  reiiex  arc  seems  a  necessity,  either  because  the  stimulus 
mechanically  excited  from  the  patellar  ligament  traverses  this  arc 
in  order  to  throw  the  muscle  into  contraction,  or  because  it  main- 
tains the  mild  tonic  tension  in  the  muscle  which  is  the  sine  qua 
non  of  the  slight  passive  extension — this  again  acting  on  the 
muscle  as  a  direct  stimulus.  The  dependence  of  the  knee-jerk  on 
the  excitability  of  the  spinal  centres  is  also  shown  by  the  fact  that 
it  is  favoured  by  the  waking  state  and  by  voluntary  activity ;  it 
is  depressed  during  sleep,  anaesthesia,  and  spinal  anaemia ;  and  it 
is  abolished  by  the  inhibitory  excitation  of  the  afferent  nerves  of 
the  antagonist  muscles  (Sherrington — supra). 

Speaking  generally,  it  may  be  said  that  the  patellar  reflex 
faithfully  follows  the  oscillations  in  spinal  excitability,  showing 
now  a  rise  and  now  a  fall.  Hence  it  may  almost  be  taken  as  a 
very  delicate  physiological  indicator  of  the  tone  of  the  nerve- 
centres  in  general,  and  those  of  the  cord  in  particular.  In  this 
lies  its  great  clinical  value.  Its  disappearance  is  a  characteristic 
symptom  in  locomotor  ataxy ;  its  exaggeration  is  indicative  of  those 
descending  processes  of  degeneration  in  the  cord  which  are  associated 
with  the  pronounced  exaggeration  of  muscular  tone,  clinically  known 
as  spasticity. 

Experimentally  the  knee-jerk  has  been  the  object  of  much 
study,  and  some  of  the  experiments  bear  directly  on  the  physio- 
logy of  the  spinal  cord.  The  conditions  which  intensify  the 
reflex  are  :  electrical  excitation  of  the  central  end  of  the  sciatic  on 
the  opposite  side  ;  stimulation  of  the  skin  or  mucous  membrane 
0-2-04  sec,  before  the  jerk  is  elicited  ;  a  flash  of  light ;  a  sudden 
sound  preceding  the  jerk  by  0'2-0'3  sec.  ;  two  taps  on  the  tendon 
at  a  short  interval ;  lastly,  rest,  food,  etc.  Other  conditions  depress 
or  abolish  the  phenomenon  either  immediately  or  after  a  brief  re- 
inforcement ;  as  local  fatigue  of  the  extensor  muscles,  general 
fatigue,  local  anaemia  produced  by  an  Esmarch's  bandage,  arrest 
of  circulation  in  the  lumbar  region,  inhalation  of  chloroform  or 
ether,  etc. 

Sherrington  says  that  in  the  monkey  spinal  transection  usually 
abolishes  the  jerk  for  a  week  or  so.  In  the  dog  and  cat  it  can  be 
evoked  in  a  quarter  of  an  hour  or  less  from  the  time  of  the  opera- 
tion, while  Barbe  stated  that  he  obtained  the  phenomenon  in  man 
immediately  after  decapitation.  On  the  other  hand,  complete 
destruction  of  the  cord  in  the  thoracic  region  usually  seems  to 
abolish  the  knee-jerk  permanently. 

The  reflex  spinal  mechanism  connected  with  the  knee-jerk  of 
each  side  is  unilateral  and  lies  in  its  own  half  of  the  cord.  As 
shown  by  the  diagram  (Fig.  191),  the  reflex  centre  in  the  monkey 
lies  in  the  fourth  and  fifth  lumbar  segments  (chiefly  the  fourth  in 
man).  If  the  cord  be  split  in  the  median  sagittal  plane  the  jerk 


330 


PHYSIOLOGY 


CHAP. 


4L  (3)  ' 
5L(4)  " 
6L(5) 


on  either  side  is  not  impaired.  Spinal  transaction  and  transection 
at  the  junction  of  diencephalon  or  mesencephalon  increase  the 
briskness  of  the  jerk,  and  after  ablation  of  the  Eolandic  cortex,  on 
one  side,  the  contralateral  knee-jerk  usually  becomes  more  brisk. 
Jeudrassik  noticed  that  a  voluntary  movement  of  the  arm  at  the 
time  the  knee-jerk  is  being  elicited  augments  it  ;  and  that  if  the 
jerk  is  very  feeble  it  may  be  reinforced  by  making  the  patient 
interclench  his  fingers  and  pull  them  apart  strongly  (Jendrdssik's 
grip).  This  is  probably  due  to  the  fact  that  con- 
traction  of  the  arm-muscles  relaxes  the  muscles  of 
the  leg,  and  thus  cuts  out  the  tone  by  which 
the  patellar  reflex  is  inhibited.  According 
to  Bowditch  and  Warren,  the  effect  is  most 
marked  when  the  patellar  tap  is  delivered 
0'2-0'6  sec.  after  the  voluntary  move- 
uient  of  the  arm. 

X.  In  close  association  with  the 
tonic  action  of  the  spinal  centres  is 
the  trophic  action  which  they 
exert  upon  other  centres  and 
upon  the  peripheral  tissues. 
We  have  already  reviewed 
the  arguments  which 
underlie     the     Wal- 
lerian    doctrine   that 

Or    nll~ 
nnvHrrn 
P 
Ol      the      nCUTOne 

.1 
represents    the 

trmihip    ppntrp  nf 
HOpIl 

all     ifq    ^lrnpp^sPc! 

(\L1.       JLLO        \JL  WV-'C/OO^O. 

. 

We  kllOW  further 
,  i  •  .-i 

that  in  the 
central  nervous 
system  the  normal  trophic  influence  is  exerted  in  the  same 
direction  as  the  physiological  conduction  of  excitation  ;  it  is  the 
sensory  neurones  that  control  the  nutrition  of  the  motor  neurones, 
and  not  the  reverse.  On  interrupting  the  relations  of  inter- 
dependent groups  of  nerve-cells,  there  is  arrest  of  development 
(agenesis)  if  the  growth  of  parts  is  still  incomplete,  secondary 
atrophy  if  development  is  already  perfect.  After  section  of  the 
sensory  roots  not  only  do  their  central  ends  degenerate,  but  trophic 
changes  may  be  seen  in  the  corresponding  motor  root  cells 
(Warrington,  1897). 

In  this  connection  we  must  confine  ourselves  to  the  group  of 
well-known  phenomena  which  show  that  the  spinal  nerves  and 
their  centres,  as  well  as  the  centres  of  the  brain,  are  to  some  extent 


FIG.  11H.—  Diagram  to  show  nervous 
mechanism  of  knee-jerk.  (Sherring- 
ton.)  4L-18,  4th-7th  lumbar  and 
1st  saci'al  roots  of  Modulus;  the 
corresponding  roots  in  man  are 
numbered  in  brackets  (the  7th 
lumbar  pair  in  monkey  corresponds 
to  1st  sacral  in  man);  cr.n.,  crural 
nerve  ;  sc.m.,  sciatic  nerve  —  afferent 

.,  ,.         L     j       -,  ,      ,  ,       ,      .. 

paths  indicated  by  dotted  lines, 
etterent  by  broken  lines  ;  m.ext,  ex- 
tensor  muscle  ;  m.flex,  flexor  muscle. 


v  SPINAL  COED  AND  NEEVES  331 

capable  of  profoundly  modifying  the  nutritive  condition  of  other 
tissues,  from  which  it  has  been  attempted  to  build  up  the  theory 
of  the  existence  of  a  special  category  of  nerves,  with  the  function 
of  directly  regulating  the  metabolism  and  nutrition  of  the  tissues, 
—the  so-called  trophic  nerves.  We  must  examine  the  data  lief  ore 
testing  the  theoretical  value  of  the  conclusions  based  on  them. 

According  to  Louget,  Mayo  (1823)  was  one  of  the  first  who 
called  attention  to  the  fact  that  after  lesions  of  the  trigeminal 
nerve  the  conjunctiva  of  the  eye  becomes  inflamed,  the  cornea 
ulcerated,  and  the  face  on  the  side  of  the  lesion  oedematous. 
Similar  clinical  observations  were  made  by  other  observers.  First 
Fodera,  then  Magendie  and  Longet,  reproduced  these  changes 
experimentally  on  rabbits,  by  intercranial  section  of  the  trigemiuus 
with  a  special  hooked  knife.  In  addition  to  panophthalmitis 
Bernard,  Biitner,  and  Eollet  subsecpuently  noted  ulcerations  of  the 
lips  and  buccal  cavity. 

Magendie  (1824)  observed  that  when  the  section  was  made 
above  the  Gasserian  ganglion,  the  dystrophic  changes  in  the  eye 
set  in  more  slowly  or  were  entirely  absent,  while  they  inevitably 
appeared  if  the  lesion  involved  the  ganglion.  Bernard  (1868) 
confirmed  these  results  from  his  clinical  observations.  Longet 
attributed  the  alterations  in  the  eye  after  lesions  of  the  Gasserian 
ganglion  to  the  simultaneous  injury  to  the  sympathetic  filaments 
that  pass  from  the  carotid  branch  of  the  superior  cervical  ganglion 
to  the  Gasserian  ganglion,  but  Bernard  does  not  support  this  view. 
In  his  opinion  the  extirpation  of  the  superior  cervical  ganglion 
delays  the  trophic  disturbances  in  the  eye  after  section  of  the 
trigeminus,  by  increasing  the  circulation  and  augmenting  the 
vitality  of  the  eye  and  its  resistance  to  the  post-operative  causes 
of  the  dystrophy. 

Sinitzin's  experiments  (1871)  confirmed  and  extended  those 
of  Bernard.  On  piercing  with  a  glass  thread  the  cornea  of  a  rabbit 
in  which  the  superior  cervical  ganglion  had  previously  been  ex- 
tirpated, there  was  usually  no  inflammatory  reaction ;  whereas 
the  same  operation  performed  on  the  other  eye  caused  extensive 
conjunctivitis  with  iritis,  and  sometimes  panophthalmitis.  Section 
of  the  trigeminus  produced  no  corneal  ulceration  when  the  superior 
cervical  ganglion  had  been  destroyed  shortly  before  or  immediately 
after.  Lastly,  the  eye  troubles  caused  by  section  of  the  trigeminus 
rapidly  cleared  up  if  the  ganglion  was  excised. 

These  results,  contradicted  by  Eckhard  and  by  Senftleben 
(1873),  were  confirmed  by  Spallitta  in  Marcacci's  laboratory  (1894) 
by  some  successful  experiments  on  dogs,  which  he  sums  up  as 
follows : — 

(a)  Lesions  of  the  Gasserian  ganglion  constantly  induce  the 
trophic  lesions  of  the  eye  already  described  by  Fodera  and 
Magendie  and  confirmed  by  later  observers. 


PHYSIOLOGY  CHAP. 


Previous  destruction  of  the  superior  cervical  ganglion 
prevents  the  trophic  changes  which  result  from  injury  of  the 
Gasserian  ganglion  alone. 

(c)  When    disturbances    appear  in   the   eye   after   the   double 
operation,  they  are  constantly  recovered  from. 

(d)  Animals  from  which  the  Gasserian  ganglion  alone  is  removed, 
and  those  in  which  this  lesion  was  preceded  by  destruction  of  the 
superior  cervical  ganglion  present  totally  dissimilar  symptoms  in 
the  eye,  independent  of  whether  the  trophic  alterations  are  present 
or  not. 

Schiff,  Mantegazza,  Vulpiau,  studied  the  after-effects  of  tran- 
section  of  the  spinal  nerves  to  the  limbs.  After  dividing  the  sciatic 
and  crural  nerves,  Schiff  found  in  the  adult  dog,  cat,  and  frog  that 
three  to  six  months  after  the  operation  the  bones  of  the  operated 
limb  were  smaller  than  those  of  the  normal  limb.  Mantegazza 
and  many  others  afterwards  drew  attention  to  the  muscular  atrophy 
which  appears  after  sensory  and  motor  paralysis  of  the  limb.  In 
two  to  three  weeks  the  muscle  fibres  begin  to  atrophy,  and  after 
some  months  or  years  they  are  converted  into  a  tissue  resembling 
connective  tissue.  Loss  of  excitability  goes  parallel  with  the 
atrophy,  and  the  electrical  reaction  of  degeneration  appears. 

Bidder  noted  that  a  few  weeks  after  section  of  the  nerves  to 
the  salivary  glands  these  become  about  half  the  size  of  the  healthy 
glands  on  the  opposite  side.  Nelaton  emphasised  the  clinical  fact 
that  the  testis  atrophies  after  section  of  the  spermatic  nerves. 
On  dividing  this  nerve  in  animals,  sparing  the  blood-vessels  of  the 
spermatic  cord  and  the  vas  deferens  as  far  as  possible,  Obolensky 
saw  that  the  testis  dwindled  in  two  to  three  weeks,  and  almost  dis- 
appeared after  four  months.  Histological  examination  showed  that 
the  glandular  tissue  had  almost  disappeared,  and  was  replaced  by 
connective  tissue  and  fat.  When,  on  the  contrary,  the  spermatic 
nerves  are  spared  and  the  vas  deferens  is  divided,  there  is  no 
apparent  change  in  the  testis. 

In  Baldi's  experiments  (1889)  in  our  laboratory,  on  the  effects 
of  section  of  the  afferent  or  efferent  roots  in  dogs  he  paid  particular 
attention  to  the  trophic  changes  in  the  skin.  Clinical  observation 
had  already  shown  that  the  diseases  of  motor  and  sensory  nerves 
are  accompanied  by  alterations  in  the  nutrition,  not  only  of  muscle, 
but  of  other  peripheral  tissues  as  well;  cutaneous  ulceratiou,  for 
instance,  is  particularly  frequent  after  lesions  of  the  peripheral 
nerves.  In  order  to  investigate  the  origin  of  this  dystrophy,  Baldi 
operated  on  a  series  of  dogs,  cutting  in  some  the  dorsal,  in  others 
the  ventral,  roots,  which  subserve  the  sensibility  or  the  motility, 
respectively,  of  an  entire  fore-  or  hind-limb,  on  one  or  both  sides. 

The  first  effect  in  the  limb  that  has  become  completely 
insensitive  is  neuro-paralytic  hyperaemia,  shown  in  the  rise  of 
temperature  and  reddening  of  the  skin.  This  is  very  transient, 


v  SPINAL  COED  AND  NEliVKS  .",.",:', 

and  disappears  after  a  few  days,  even  before  the  complete  healing 
of  the  spinal  wound. 

As  soon  as  the  wound  is  healed,  and  the  animal  begins  to 
move  about,  an  abnormal  erosion  of  the  nails  is  noticed,  followed 
shortly  after  by  loss  of  hair  on  the  dorsum  of  the  foot  and  by 
some  excoriation.  If  the  animal  is  left  to  itself  an  ulcer  soon 
forms  that  involves  the  derma  and  subjacent  tissues,  the  capsules 
of  the  joints  open,  and  the  phalanges  and  even  the  metatarsal 
bones  fall  off.  To  prevent  this,  or  to  heal  the  lesions,  it  is 
necessary  to  keep  the  insensitive  limb  constantly  in  bandages.  In 
dogs  with  bilateral  transaction  of  the  sensory  roots  of  the  lumbo- 
sacral  region  the  cutaneous  alterations  set  in  more  rapidly.  After 
this  operation  the  animal  cannot  retain  either  faeces  or  urine,  so 
that  precautions  must  be  taken  to  prevent  irritation  from  these 
sources.  Immediately  after  the  operation  the  rectal  mucosa  and 
the  penis  are  slightly  relaxed  and  markedly  hyperaemic ;  but  in 
time  the  hyperaemia  disappears  and  the  parts  are  apparently  normal. 
Before  long,  however,  erythema,  ulcerations,  ,and  other  lesions  of 
the  tissues  of  the  limbs  set  in,  and  become  incurable  unless  treated 
with  the  greatest  care. 

The  effects  of  dividing  the  motor  roots  to  a  hind-limb  differ 
little  from  the  above.  Essentially  different,  however,  are  the 
effects  of  simple  transection  of  the  cord  between  the  last  dorsal 
and  the  first  lumbar  vertebrae,  as  repeatedly  carried  out  by  Goltz. 
After  the  shock  effects  have  disappeared  and  the  wound  has 
healed,  these  animals  exhibit  no  dystrophic  changes  in  the  tissues 
of  the  limbs,  although  in  progression  they  drag  either  the  perineum 
or  one  or  the  other  hip  on  the  ground,  and  pull  the  posterior  parts 
of  the  trunk  along,  since  it  receives  no  voluntary  impulses. 

If  in  dogs  in  which  the  dorsal  roots  or  ventral  roots  of  one 
hind-limb  are  cut  the  hair  of  both  hind-legs  is  shaved  off  in  two 
corresponding  areas,  the  hair  in  the  limb  operated  on  takes  more 
than  twice  as  long  to  regain  its  original  length,  and  the  new  coat 
is  thinner  and  poorer  than  that  of  the  normal  limb.  The  nails, 
too,  grow  more  slowly  in  the  limb  operated  on  than  in  the  normal 
limb.  If  croton  oil  is  smeared  upon  symmetrical  areas  of  both 
limbs,  the  blister  appears  twenty-four  hours  later  in  the  operated 
leg,  and  the  new  epidermis  forms  a  fortnight  later  than  in  the 
healthy  limb. 

Under  the  microscope  the  skin  of  the  insensitive  limb  is 
seen  to  be  much  atrophied  and  the  Malpighian  layer  sometimes 
disappears. 

Various  hypotheses  have  been  put  forward  to  account  for  these 
trophic  disturbances  consequent  on  nerve  lesions.  The  following 
are  among  the  more  general  and  widely  accepted  :— 

(«)  The  dystrophic  effects  are  produced  by  the  neuro-paralytic 
hyperaemia  which  sets  up  disorders  of  nutrition  in  the  tissues ; 


334  PHYSIOLOGY  CHAP. 


They  depend  on  external  trauma  or  irritation,  against  which 
the  operated  animal  is  no  longer  able  to  protect  itself; 

(c)  They  depend  on  both  these  factors,  since  the  neuro-paralytic 
hyperaemia  makes  the  tissues  more  vulnerable  to  external  injuries  ; 

(d~)  They  depend  on  loss  of  the  influence  of  the  nerves  which 
regulate  the  nutritive  processes  and  metabolism  of  the  tissues. 

The  first  hypothesis,  supported  by  Fodera,  Magendie,  Longet,  is 
clearly  controverted  by  the  experimental  results  of  Bernard, 
Sinitziu,  and  Spallitta,  which  show  that,  on  the  contrary,  under 
special  conditions,  hyperaemia  may  even  promote  the  nutrition  of 
the  tissues.  Moreover,  the  hypothesis  takes  no  account  of  the 
fact  that  hyperaemia  is  a  transitory  phenomenon  and  that  the 
trophic  lesions  often  make  their  first  appearance  after  it  has 
disappeared. 

The  second  theory,  first  propounded  by  Snellen  and  Bonders, 
is  based  on  the  fact  that  after  section  of  the  trigemiual  or  of  the 
facial  nerve  the  panophthalmitis  could  be  warded  off  for  six  to  ten 
days  if  the  eye  were  artificially  protected  from  injury  or  irritation 
by  particles  of  dust.  It  was  severely  shaken  by  the  experiments 
of  Meissuer,  who  observed  panophthalmitis  after  a  partial  lesion  of 
the  trigeminus  which  had  not  entirely  destroyed  the  sensibility  of 
the  cornea,  On  the  other  hand,  Baldi's  observations  show  that 
even  if  traumatic  irritation  is  often  a  necessary  factor  in  trophic 
disturbance  it  is  not  sufficient  of  itself  to  cause  it.  It  must 
therefore  be  assumed  that  parts  which  are  deprived  of  their  inner- 
vation  exhibit  a  lower  resistance  or  greater  vulnerability,  so  that 
they  can  be  injured  by  slight  irritants  that  do  not  affect  tissues  to 
which  the  nerves  are  intact. 

In  what,  then,  does  this  lessened  resistance  or  greater  vulner- 
ability in  the  denervated  tissues  consist  ?  Schiff  explained  the 
pauophthalmitis  consequent  on  section  of  the  trigeminus  by  the 
third  of  the  hypotheses  enumerated  above,  and  held  that  the 
lowered  resistance  of  the  eye  results  from  the  neuro-paralytic 
hyperaemia,  owing  to  which  particles  suspended  in  the  air, 
which  do  not  injure  the  normal  eye,  become  the  cause  of 
panophthalmitis. 

This  theory,  too,  is  in  direct  contradiction  with  the  experiments 
of  Sinitzin  and  Spallitta.  After  ablation  of  the  superior  cervical 
ganglion  the  neuro-paralytic  hyperaemia  of  the  eye  should  be  more 
pronounced  than  that  which,  according  to  Schiff,  sets  in  after 
simple  lesion  of  the  trigeminus.  But  the  trophic  disturbances  in 
the  eye  may  be  altogether  absent.  Schiff's  view  is  moreover 
inadequate  to  explain  Baldi's  interesting  observations  on  the 
retarded  growth  of  hair  and  nails,  and  the  slow  regeneration  of  the 
epidermis  and  cicatrisation  of  wounds  in  a  limb  with  sensory 
paralysis.  It  is  evident  that  these,  as  well  as  the  atrophy  of  the 
muscles  and  other  tissues,  including  the  skin,  are  the  effects  of  loss 


v  SPINAL  COED  ANT)  NERVES  335 

of   the  trophic  influence   of  the   nerves  and   their  corresponding 
centres. 

But  this  trophic  influence  must  not  be  taken  in  the  sense 
previously  suggested  by  Meissuer  and  Samuel,  viz.  that  there  is 
a  special  category  of  trophic  nerves  and  centres,  entirely  distinct 
from  the  sensory  and  the  motor,  whose  function  is  the  direct 
control  of  metabolism  and  nutrition  of  the  tissues,  independently 
of  both  the  blood  and  lymph  circulation,  and  of  the  new  conditions 
of  functional  paralysis  set  up  in  the  tissues  after  the  section  or 
lesion  of  their  respective  nerves.  Any  such  hypothesis,  besides 
being,  unsupported  by  experimental  facts,  is  contrary  to  the  spirit 
of  the  cell  theory,  according  to  which  the  function  of  living 
cells  is  inseparable  from  their  nutrition,  because  every  excitation 
necessarily  has  an  altered  metabolism  for  its  material  basis. 
When  the  function  of  a  cell  or  organ  is  under  the  direct  and 
absolute  influence  of  another  cell  or  organ  (as  the  muscle  depends 
upon  the  nerve),  then  the  latter  by  controlling  the  function  must 
also  indirectly  control  the  nutrition  of  the  former. 

XI.  In  discussing  the  spinal  reflexes  we  saw  that  there  is  a 
certain  relation  between  the  sensory  surface  stimulated  and  the 
reflex.  In  a  spinal  (or  bulbo-spinal)  animal  direct  stimulation 
of  the  central  end  of  a  large  nerve  only  evokes  a  spasmodic  unco- 
ordinated reflex,  in  which  muscles  of  different  or  even  antagonistic 
function  are  simultaneously  thrown  into  action ;  on  stimulation  of 
a  sensory  surface,  on  the  contrary,  the  combination  of  the  muscles 
thrown  into  play  is  much  more  complex,  and  the  reflex  is  repre- 
sented by  a  true  co-ordinated  motor  act,  in  which  not  only  do 
many  muscles  take  part,  but  there  is  an  evident  harmony  between 
the  strength,  duration,  and  precise  moment  of  the  contraction  of 
each  muscle  that  participates  in  the  action.  In  fact,  the  expression 
"  co-ordinated  muscular  act "  means  that  the  whole  movement  is 
directed  towards  the  attainment  of  a  useful  effect  in  the  most 
profitable  manner,  and  that  the  muscular  reaction  is  perfectly 
adapted  to  the  stimulus,  so  that  there  is  an  ideal  teleological 
relation  between  them. 

Grainger  (1837)  seems  to  have  been  the  first  who  pointed  out 
that  the  reflex  spinal  movements  excited  by  cutaneous  stimuli 
were  defensive  in  character,  and  apparently  directed  to  the  purpose 
of  removing  the  stimulus. 

The  most  classical  example  of  these  defence  reflexes  of  force  is 
seen  in  the  spinal  or  bulbo-spinal  frog.  The  crouching  position 
that  it  naturally  assumes  shews  that  the  spinal  centres  are  in 
continuous  activity,  because  a  paralysed  animal  stays  in  any 
position  given  to  it.  If  the  leg  is  pinched,  it  is  drawn  away  as 
though  to  escape  from  a  painful  impression.  If  a  bit  of  paper 
soaked  in  dilute  sulphuric  or  acetic  acid  is  applied  to  any  point 
of  its  skin,  the  frog  performs  a  whole  series  of  movements,  which 


336  PHYSIOLOGY  CHAP. 

are  perfectly  co-ordinated  to  the  eiid  of  removing  the  obnoxious 
stimulus. 

Besides  these  defensive  acts,  there  are  other  co-ordinated 
reflexes  in  the  spinal  frog  connected  with  the  reproductive 
functions.  Goltz  observed  that  whenever  a  decerebrated  male 
frog  is  gently  stroked  on  the  skin  of  its  back,  it  croaks  as  if  to 
express  pleasure.  In  the  breeding  season  if  the  back  of  a  female 
frog,  or  even  the  finger  of  the  observer,  is  placed  in  contact  with 
the  skin  of  the  thorax  of  the  male,  the  fore-limbs  clasp  the  object 
strongly  and  persistently,  as  in  the  normal  sexual  embrace. 

In  mammals,  too,  it  is  possible  to  observe  co-ordinated  reflexes 
in  portions  of  the  cord  that  are  entirely  separated  from  the  brain, 
for  instance  in  the  lumbar  enlargement,  after  transection  in  the 
thoracic  segments.  Ten  days  after  the  operation,  when  the  effects 
of  "  shock  "  have  quieted  down,  the  animal  will  pass  urine  only 
when  the  bladder  is  full,  or  when  the  skin  of  the  perineum  is 
tickled.  So  too,  it  only  defaecates  or  performs  movements  of 
defalcation  when  the  anal  orifice  is  tickled,  and  during  expulsion  of 
the  faeces  it  lifts  its  tail  and  shifts  and  flexes  its  hind-limbs  as  if  try- 
ing not  to  soil  itself.  If  the  skin  of  the  animal  is  lightly  stimulated 
in  the  sacral  region,  the  foot  on  the  same  side  makes  rhythmical 
movements  of  alternate  flexion  and  extension,  as  it  normally  does 
in  scratching.  If  the  penis  is  excited  by  masturbatory  manipula- 
tions the  phenomena  of  erection  and  spermatic  ejaculation  follow, 
associated  with  movements  or  postures  of  the  hind-limbs  that 
express  voluptuous  sensations. 

These  and  other  phenomena  admirably  described  by  Goltz  and 
his  pupils  are  co-ordinated  reflex  actions,  designed  to  satisfy  a 
want  or  to  protect  some  part  of  the  body  from  injurious  stimuli. 
In  other  less  frequent  cases  the  motive  of  the  reflex  seems  to  be 
preservation  of  the  individual  while  the  part  is  sacrificed.  This 
interesting  group  of  phenomena  were  investigated  by  Fredericq, 
and  termed  by  him  autolomy.  More  particularly  in  certain 
insects  (grasshoy>pers),  crustaceans,  arachnids,  echiuoderms,  if  a 
limb  is  mechanically  or  chemically  stimulated,  it  suddenly  breaks 
and  drops  off,  so  that  the  animal  is  able  to  escape  from  the  pursuer. 
The  same  phenomenon  is  also  seen  in  certain  vertebrates,  as  in  the 
blind-worm  and  green  lizard,  which  readily  part  with  their  tails 
to  escape  capture.  The  fracture  of  the  limb  or  tail  is  effected  by 
a  violent  reflex  contraction  of  certain  muscles  by  a  mechanism 
which  is  not  fully  known.  Since  the  phenomena  of  autotomy 
persist  in  decapitated  animals  they  witness  to  a  solidarity  of 
action,  almost  one  might  say  a  personality  of  the  spinal  cord  when 
it  is  separated  from  the  cerebrum. 

Even  in  the  absence  of  external  stimuli,  the  spinal  animal 
sometimes  carries  out  complex  actions  which  differ  little  from 
those  of  the  intact  animal.  It  is  an  ancient  observation  that 


v  SPINAL  CORD  AND  NERVES  3:(»7 

fowls  can  fly  directly  after  decapitation.  Tarchanoffs  observations 
on  ducks  are  more  interesting.  After  trausection  of  the  cord 
between  the  4th  and  5th  cervical  vertebrae  they  can  perform  a 
long  series  of  perfectly  regular  swimming  movements  in  the  water, 
both  with  the  feet  and  the  wings.  But  if  placed  on  a  table  they  are 
incapable  of  standing  upright,  although  they  execute  regular 
alternating  movements  of  walking  with  their  legs. 

In  man,  too,  complex  co-ordinated  reflexes  of  defence  have 
been  observed  in  cases  of  contusion  or  dislocation  of  the  cord  in 
the  cervical  or  thoracic  region.  Marshall  Hall  describes  a  man 
whose  cord  was  crushed  at  the  neck  by  a  fall.  There  was  complete 
motor  and  sensory  paralysis  of  the  lower  half  of  the  body,  but 
when  stimulated  either  with  painful  mechanical  stimuli,  or  with 
hot  water,  or  by  tickling  the  soles  of  the  feet,  the  lower  limbs 
moved  with  great  vigour  as  if  the  patient's  cord  felt  the  pain  or 
was  aware  of  the  tickling. 

The  fully  co-ordinated  defensive  movements  carried  out  in 
sleep  (e.g.  in  response  to  bites  of  fleas  or  mosquitoes),  and  many 
quite  unconscious  movements  made  during  the  waking  state, 
while  the  attention  is  otherwise  occupied,  are  similar,  and  should 
probably  be  classed  among  the  purely  spinal  co-ordinated  reflexes. 

All  these  instances  illustrate  the  great  complexity  of  the 
spinal  reflexes — a  complexity  that  cannot  be  explained  by  the 
simple  spread  of  excitation  from  the  afferent  nerves  into  adjacent 
nerve-cells. 

An  adequate  theory  of  reflexes  must  throw  light  on  the  process 
by  which  the  centripetal  or  afferent  excitation  becomes  centrifugal 
or  efferent ;  it  must  tell  us  why  the  reflex  is  sometimes  confined 
to  a  few  muscles,  and  at  other  times  spreads  to  more  muscles  in 
various  combinations ;  why  the  efferent  impulses  travel  along 
certain  paths  and  not  others ;  lastly,  how  the  co-ordination  and 
adaptation  of  the  reflexes  to  the  nature  and  localisation  of  the 
stimulus  is  attained.  At  present  we  can  only  give  vague  and 
inadequate  replies  to  these  questions,  though  a  few  hypothetical 
but  certainly  ingenious  attempts  have  been  made  towards  a  partial 
solution  of  the  problem  on  the  basis  of  the  neurone  theory. 

The  greater  or  less  irradiation  of  reflexes  and  the  laws  by 
which  they  are  governed,  are  generally  explained  by  the  more  or 
less  direct  and  easy  communication  between  the  sensory  and 
motor  neurones  concerned ;  or  the  greater  or  less  conductivity 
along  the  paths  formed  by  the  fibrillary  networks  in  the  grey 
matter. 

It  is  harder  to  explain  the  adaptation  of  the  reflex  to  the 
stimulus.  In  this  connection  the  fact  is  usually  cited  that  habit 
facilitates  the  transmission  and  association  of  actions  that  were 
difficult  in  the  first  place,  which  is  possibly  due  to  improved  con- 
ductivity along  the  paths. 

VOL.  in  z 


338  PHYSIOLOGY  CHAP. 

But  these  and  other  more  detailed  mechanical  explanations  of 
co-ordinated  reflexes  adapted  to  stimuli  seem  inadequate  to  account 
for  the  variety  of  the  modes  in  which  a  brainless  frog  reacts  to 
different  forms  of  stimulation.  Some  authors  have  maintained, 
on  the  strength  of  these  observations,  that  the  spinal  cord  itself, 
as  the  continuation  of  the  brain,  is  also  a  seat  of  psychical 
functions,  and  look  upon  these  complex  reactions  as  the  expression 
of  a  rudimentary  consciousness  and  volition  in  the  cord,  persisting 
even  after  it  has  been  severed  from  the  cerebrum. 

This  doctrine  is  contrary  to  the  old  metaphysical  axiom  of 
the  absolute  unity  and  immateriality,  and  consequent  indivisi- 
bility of  the  ego  or  soul.  This  axiom,  which  the  earlier  spiritual- 
istic philosophy  accepted  as  dogma,  is,  however,  easily  controverted 
by  experimental  physiology.  The  divisibility  of  the  "  ego "  as 
a  sentient  principle  is  demonstrated  by  the  fact  that  a  numerous 
class  of  the  lower  animals  are  propagated  by  fission,  and  are  able 
to  multiply  by  division  into  the  segments  or  metameres  of  which 
they  consist  (Vol.  I.  p.  84).  Each  segment  is  capable  of  forming  an 
entity  with  the  same  sensorial  capacity  as  the  complete  individual 
of  which  it  was  a  part.  Hence  it  is  not  only  legitimate,  but 
scientifically  necessary,  to  inquire  whether,  on  dividing  the 
cerebrospinal  axis  in  the  higher  animals,  consciousness  can  be 
divided  also.  The  answer  to  this  difficult  and  possibly  still 
insoluble  problem  lies  in  arguments  from  analogy,  based  on  the 
experimental  facts  that  indirectly  witness  to  the  psychical 
capacity  of  the  spinal  cord. 

We  conclude  that  a  living  being  is  capable  of  awareness  of 
itself  and  of  the  world  without  it ;  of  controlling  its  own  actions 
by  will,  of  having,  in  fact,  a  "soul,"  only  from  the  resemblance 
between  our  own  conscious  actions  and  those  that  it  presents. 
Thus  from  the  cogito  ergo  sum,  which  is  the  direct  intuitive  proof 
of  our  own  consciousness,  we  recognise  the  same  in  our  fellow-men, 
then  by  induction  in  the  higher  animals,  and  lastly  in  the  lower 
animals  also. 

Is  the  adaptation  to  end  which  characterises  the  movements 
of  decapitated  animals  enough  to  convince  us  that  their  spinal 
cord  is  capable  of  feeling  and  volition  ?  Evidently  not,  because 
all  the  mechanisms  of  the  animal  economy  are  adapted  to  obvious 
ends ;  coughing  cleanses  the  air  passages ;  vomiting  empties  the 
stomach  of  injurious  matters  ;  contraction  of  the  pupil  modifies 
the  effects  of  light ;  winking  of  the  eyelids  removes  dust  particles 
from  the  cornea ;  intestinal  peristalsis  sends  on  the  faeces,  etc.  etc. 
These  co-ordinated  mechanisms  have  come  about  by  a  slow  process 
of  natural  selection,  according  to  Darwin ;  by  an  evolutionary 
automatic  process  of  unknown  character,  according  to  Nageli ; 
more  simply,  they  represent  fossilisation  of  psychical  functions, 
having  been  built  up  step  by  step  from  voluntary  actions,  which 


v  SPINAL  COED  AND  NEEVES  339 

by  long  practice  became  as  it  were  materialised  and  automatic, 
and  were  transmitted  by  inheritance.  Evidence  for  the  organisa- 
tion of  what  were  at  the  outset  voluntary  acts,  lies  both  in  the 
fully  unconscious  co-ordinated  reflexes,  which  we  are  able  to  carry 
out  not  merely  in  sleep  but  also  in  the  waking  state,  and  in  the 
fact  that  many  complex  actions  that  were  voluntary  at  first  (e.g. 
walking,  reading,  piano-playing,  etc.)  become,  after  long  practice, 
mechanical,  and  are  carried  out  with  perfect  regularity  without 
the  intervention  of  the  will  or  the  least  effort  of  attention. 

In  order  to  judge  objectively  of  the  psychical  or  mechanical 
character  of  a  given  spinal  reaction,  it  is  necessary,  according  to 
Pfliiger  and  Auerbach,  to  see  if  it  varies  from  one  moment  to 
another  with  the  variations  in  external  relations.  If  the  individual, 
when  prevented  from  carrying  out  a  given  movement  adapted  to 
the  removal  of  an  obnoxious  stimulus,  employs  another  action 
directed  to  the  same  end,  this  proves  it  to  be  possessed  of  sentient 
functions,  because  from  one  moment  to  the  next,  without  any  pre- 
existent  mechanism,  organised  by  long  practice,  it  knows  how  to 
modify  or  change  the  character  of  the  reaction,  so  as  to  adapt 
it  to  the  required  end.  Evidence  of  such  a  capacity  is  brought 
forward  by  these  authors.  They  observed  that  a  decerebrated 
frog,  when  a  drop  of  acid  falls  on  its  right  flank,  or,  better,  when 
a  bit  of  paper  soaked  in  acid  is  applied  to  it,  always  uses  its  right 
leg  to  wipe  away  the  irritant.  If  the  right  leg  is  amputated,  it 
first  makes  ineffective  efforts  with  the  stump,  and  then  employs 
its  left  leg.  If,  after  amputating  the  right  leg,  the  acid  is  applied 
to  the  right  side  of  the  back,  the  frog  again  makes  ineffectual 
attempts  with  the  stump,  and  then  stops.  But  on  applying  the 
acid  to  the  left  side  of  the  back  also,  the  frog  uses  its  left  foot  to 
wipe  itself  on  the  left  as  well  as  on  the  right  side. 

Pfliiger  insisted  on  these  phenomena  as  evidence  that  the 
spinal  cord  of  the  frog  is  capable  of  at  least  rudimentary  psychical 
functions.  According  to  other  authors,  on  the  contrary,  these 
actions,  besides  being  rare  and  generally  incomplete,  are  capable 
of  a  purely  mechanical  explanation.  The  fact  that  when  the 
limb  which  the  animal  uses  for  removal  of  the  cutaneous  stimulus 
has  been  amputated,  the  limb  of  the  opposite  side  is  resorted  to 
for'  the  same  purpose  after  ineffective  attempts  with  the  stump,  is 
held  to  mean  that  the  local  excitation,  owing  to  the  longer  contact 
of  the  stimulus  on  the  skin,  has  become  more  intense,  and  has 
spread  from  one  half  of  the  cord  to  the  other.  But  if  Pfliiger's 
description  is  studied  in  all  its  significant  details,  this  mechanical 
explanation  is  obviously  inadequate. 

Foster,  on  the  other  hand,  points  out  that  spontaneous  move- 
ments (automatic  movements  proper),  such  as  occur  in  the  entire 
absence  of  external  stimuli,  are  never  seen  in  the  spinal  frog. 
This  fact  appears  to  him  irreconcilable  with  the  existence  of  any 


340  PHYSIOLOGY  CHAP. 

active  consciousness  in  the  cord,  that  is,  of  an  uninterrupted 
sequence  of  psychical  processes  and  transitional  states,  as  though 
an  internal  stimulus  were  perpetually  acting  on  the  central  organ. 
He  therefore  inclines  to  attribute  to  the  cord  a  sort  of  transitory, 
discontinuous  consciousness,  which  only  surges  up  in  response  to 
stimuli  of  a  certain  intensity,  and  maintains  that  our  complete 
consciousness,  and  that  which  we  attribute  inductively  to  the 
higher  animals,  is  merely  the  perfect  development  of  this  rudi- 
mentary spinal  consciousness. 

"  We  may,  on  this  view,"  Foster l  writes,  "  suppose  that  every 
nervous  action  of  a  certain  intensity  or  character  is  accompanied 
by  some  amount  of  consciousness,  which  we  may,  in  a  way, 
compare  to  the  light  emitted  when  a  combustion  previously  giving 
rise  to  invisible  heat  waxes  fiercer.  We  may  thus  infer  that  when 
the  brainless  frog  is  stirred  by  some  stimulus  to  a  reflex  act,  the 
spinal  cord  is  lit  up  by  a  momentary  flash  of  consciousness  coming 
out  of  darkness  and  dying  away  into  darkness  again  ;  and  we  may 
perhaps  further  infer  that  such  a  passing  consciousness  is  the 
better  developed  the  larger  the  portion  of  the  cord  involved  in  the 
reflex  act  and  the  more  complex  the  movement." 

Though  direct  confirmation  of  Foster's  hypothesis  on  the 
nature  of  the  spinal  psychical  functions  is  wanting,  it  appears  to 
us  to  be  logical  and  generally  admissible.  Those  who  take  the 
manifestations  of  perception  and  memory  as  the  distinguishing 
signs  of  consciousness,  and  absolutely  deny  the  psychical  character 
of  co-ordinated  reflexes,  do  not  reflect  that  the  spinal  cord  is  not 
claimed  as  the  seat  of  the  higher  intellectual  functions,  but  only  as 
that  of  a  simple  rudimentary  intelligence  due  to  the  synthesis  of  a 
small  group  of  elementary  sensations.  The  approach  of  a  dog  on 
hearing  its  own  name,  the  return  of  a  hungry  animal  to  the  place 
where  it  is  accustomed  to  find  food,  are  conscious  acts  of  perception 
involving  a  process  of  memory.  Of  course  nothing  of  the  sort  can 
be  observed  in  a  "  spinal  "  animal.  According  to  Goltz'  ex- 
periments, if  two  frogs,  one  normal,  the  other  spinal,  are  placed  in 
water  and  the  vessel  is  gradually  heated,  the  normal  frog  makes 
movements  to  escape  from  the  water  when  the  temperature  rises 
to  35°  C. ;  the  spinal  frog,  on  the  contrary,  makes  no  attempt  to 
avoid  the  danger,  and,  provided  the  rise  of  temperature  be  gradual, 
will  let  itself  be  boiled  without  effort  to  escape.  If,  on  the  other 
hand,  the  spinal  frog  is  thrown  into  water  already  heated  up  to 
35°  C.  it  will  at  once  make  lively  movements,  which  must, 
according  to  Goltz,  be  regarded  as  unconscious  reflexes,  because 
they  did  not  appear  under  the  former  conditions  of  experiment. 
But  from  our  point  of  view,  these  facts — even  if  they  show  that 
the  spinal  frog  exhibits  no  sign  of  perception  and  memory — do 
not  exclude  the  possibility  of  its  possessing  transitory  flashes  of 

1  Foster,  Text-Book  of  Physioloyy,  1897,  part  iii.  p.  983. 


v  SPINAL  COED  AND  NEKVES  341 

consciousness,  arising  from  a  psychical   synthesis  of   elementary 
sensations. 

Lastly,  many  of  those  who  see  in  the  co-ordinated  spinal 
reflexes  inherited,  instinctive,  but  unconscious  acts,  do  not 
recognise  that  in  admitting  these  they  implicitly  admit  a  sort  of 
fossil  intelligence  for  the  cord, — i.e.  to  adopt  Bering's  felicitous 
expression — unconscious  memory  of  primitive  psychical  processes. 
The  entire  i "  soul "  of  a  brainless  Amphioxus  is  a  spinal  soul. 
How  much  of  this  soul  persists  as  such,  and  how  much  (to  repeat 
the  metaphor)  in  a  fossil  state,  in  the  spinal  cord  of  the  higher 
vertebrates  ?  The  future  must  decide. 

At  first  sight  it  would  seem  as  though  the  most  complex  of 
the  spinal  reflexes  that  are  independent  of  the  brain  and,  in  our 
opinion,  indicate  a  rudimentary  spinal  intelligence,  should  be 
more  numerous,  more  striking,  and  better  elaborated  in  the  higher 
animals  with  a  more  developed  nervous  system.  The  contrary, 
however,  is  the  fact ;  these  higher  spinal  reflexes  predominate  and  1 
are  more  vigorous  and  pronounced  in  the  lower  vertebrates.  This  • 
of  course  may  be  due  to  the  greater  solidarity  between  the 
different  segments  of  the  system  in  the  higher  vertebrates,  and  the 
greater  control  exerted  by  the  brain  over  the  spinal  mechanism, 
owing  to  the  development  of  the  long  spino-cerebral  and  cerebro- 
spinal  conducting  paths  which  are  totally  absent  in  the  lower 
vertebrates. 

XII.  The  long  conduction  paths  which  run  from  the  cord  to 
the  brain  and  from  the  brain  to  the  cord,  constitute  so  many  inter- 
central  reflex  arcs,  by  means  of  which  the  spinal  mechanisms  of 
the  higher  vertebrates  are  brought  into  direct  functional  com- 
munication with  the  cerebral  mechanisms.  It  is  through  these 
long  conducting  paths  that,  with  the  development  of  definitely 
conscious  sensations  and  voluntary  movements,  the  spinal  cord 
ceases  to  be  a  collection  of  autonomous  centres  and  becomes  an 
instrument  of  the  brain. 

We  have  seen  that  the  cord  is  capable  of  executing  perfectly 
co-ordinated  reflex  movements.  In  voluntary  movements  impulses 
descending  from  the  brain  throw  the  same  spinal  mechanisms  into 
play  as  are  concerned  in  the  execution  of  the  spinal  reflexes 
excited  by  impulses  conducted  from  the  periphery  along  the 
afferent  nerves.  Indeed,  since  reflex  movements  differ  from 
voluntary  in  nothing  except  the  exciting  agent,  it  would  be 
irrational  to  suppose  that  they  depend  on  two  separate  central 
mechanisms. 

Marshall  Hall's  theory,  which  distinguished  the  spinal  reflexes 
from  the  voluntary  movements  by  assuming  an  excito -motor  system 
consisting  of  fibres  separate  from  those  of  sensation  and  voluntary 
motion,  has  long  been  abandoned.  The  anatomy  of  the  cord  shows, 
as  we  have  seen,  that  the  same  neurones,  by  coming  into  relation 


342  PHYSIOLOGY  CHAP. 

through  their  collaterals  with  the  cells  of  the  ventral  roots,  are 
excito-motor,  and  belong  to  the  spinal  reflex  arcs ;  and  by  sending 
ax  oils  cere!  >ral  wards,  act  as  sensory  nerves,  and  are  part  of  a  cere- 
bral reflex  arc.  On  the  other  hand,  the  peripheral  motor  neurones 
function  as  involuntary  or  reflex  fibres  when  they  react  to  stimuli 
received  through  the  dorsal  roots,  and  as  voluntary  motor  nerves 
when  excited  by  the  pyramidal  tracts. 

Thus  the  cells  of  the  spinal  mechanisms  are  not  merely  in 
relation  with  local  functions  of  the  cord,  but  also  send  impulses  to 
the  cerebral  nerve-cells  and  receive  others  from  them  in  turn. 
The  phylogenetic  evolution  of  the  nervous  system  goes  pari  passu 
with  an  ever-increasing  development  of  the  long  spi no-cerebral 
and  cerebro-spinal  conducting  paths.  The  pyramidal  tract,  which  in 
the  higher  vertebrates  represents  the  complex  of  the  long  cerebro- 
spinal  motor  conducting  paths,  increases  gradully  in  bulk  and 
attains  its  maximal  development  in  man.  The  direct  ventral 
pyramidal  tract  only  appears  in  man,  and,  according  to  Sherrington, 
in  the  ape.  In  rats  and  guinea-pigs,  according  to  Lenhossek,  the 
pyramidal  tracts  are  small  and  run  in  the  dorsal  columns  :  while 
in  rabbits,  cats,  dogs,  they  pass,  according  to  Spitzka,  through  the 
lateral  columns,  after  decussating  in  the  medulla  oblongata.  In 
the  cat  (Boyer),  in  the  dog  (Muratoff),  in  the  monkey  (Mellus  and 
Sherrington),  and  sometimes  in  man  also  (Pitres),  there  is  a  small 
direct  lateral  pyramidal  tract,  as  the  bulbar  decussation  is  not 
always  complete.  In  the  lower  vertebrates  (amphibia,  reptiles,  and 
also  birds),  it  is  probable  that  there  are  no  cortico-spinal  nor  long 
centripetal  tracts,  such  as  are  present  in  the  higher  vertebrates 
with  a  well-developed  cerebral  cortex. 

It  is  essential  to  bear  in  mind  the  varying  development  and 
course  of  the  cerebro-spinal  and  spino-cerebral  conducting  tracts 
in  different  classes  of  vertebrates,  in  order  to  avoid  the  error  which 
the  older  physiologists  fell  into,  when  they  applied  the  data 
obtained  from  the  physiological  effects  of  partial  transections  of 
the  cord  in  the  lower  vertebrates  to  human  physiology. 

We  have  seen  that  complete  transection  of  the  cord  produces 
paraplegia  by  interrupting  all  the  conduction  paths.  We  must, 
therefore,  confine  ourselves  to  studying  the  effects  of  partial 
spinal  transection  upon  the  motility  and  sensibility  of  the  more 
caudal  parts,  by  experiments  on  the  vertebrates  nearest  to  man, 
as  well  as  from  the  simpler  and  least  equivocal  clinical 
observations. 

Clinical  cases  of  cerebral  lesions  taught  us  long  since  that  the 
motor  and  sensory  paths  decussate  in  the  cerebro-spinal  axis. 
Haemorrhage  in  the  right  brain  causes  motor  and  sensory 
paralysis  of  the  left  half,  and  when  in  the  left  brain,  of  the  right 
half  of  the  body.  Brown-Sequard,  however,  records  certain 
exceptions  to  this  rule,  which  can  be  explained  either  by  an 


v  SPINAL  COED  AND  NERVES  343 

anomalous  failure  of  the  conducting  paths  to  decussate,  or  by  a 
double  decussation.  Clinical  cases  have  in  i'act  been  dm-.ribed  in 
which  the  one  or  the  other  had  occurred.  But  these  exceptions 
are  rare. 

Does  this  decussation  occur  in  the  brain,  in  the  bulb,  or  in  the 
cord  I  The  interhemispherical  commissure,  the  so-called  corpus 
eallosiim,  contains  simple  paths  of  interhemispherical  association, 
and  is  not  related  to  cerebro-spinal  conducting  paths.  The 
majority  of  the  motor  cerebro-spinal  fibres  which  form  the 
pyramidal  tracts  cross  in  the  bull),  while  many  of  the  fibres 
which  do  not  cross  here  (direct  ventral  and  lateral  pyramidal 
bundles)  decussate  in  the  cord,  passing  from  one  side  to  the  other 
by  the  white  and  grey  commissures.  In  any  case  a  partial  spinal 
decussation  of  the  motor  paths  is  established,  both  by  histological 
facts  and  by  bilateral  descending  degeneration  of  the  direct  and 
crossed  pyramidal  tracts  after  unilateral  traumatic  injury  or 
pathological  lesions  of  the  cord  (W.  Miiller,  Charcot,  Pitres,  and 
others). 

The  decussation  of  the  sensory  paths  is  known  to  occur  partly 
in  the  so-called  interolivary  region  of  the  bulb,  above  and  dorsal 
to  the  decussation  of  the  motor  pyramidal  tracts ;  but  certain 
collaterals  of  the  medullated  fibres  of  the  dorsal  roots  also  cross 
through  the  anterior  commissure.  It  may  therefore  be  stated  in 
general  terms  that  anatomical  facts  show  that  the  long  motor  and 
sensory  conduction  paths  cross  from  one  side  to  the  other,  to  a 
small  extent  in  the  cord,  to  a  much  larger  extent  in  the  brain-stem. 

The  effects  of  unilateral  section  of  the  cord  must  now  be  con- 
sidered in  more  detail. 

Few  problems  in  the  physiology  of  the  nervous  system  have 
been  more  discussed,  and  the  results  and  interpretation  differ 
widely. 

Galen  was  the  first  who  performed  and  attempted  to  follow  up 
the  total  or  partial  transection  of  the  cord  (probably  on  monkeys), 
and  it  is  astonishing  to  see  how  closely  his  results  agree  with  the 
most  recent  observations. 

Many  workers  took  up  this  subject  in  the  early  half  of  the 
nineteenth  century,  but  after  the  first  experiments  of  Fodera 
(1823),  Schops  (1827),  J.  van  Been  (1838),  Valentin  (1839), 
Stilling  (1842),  Budge  (1842),  Eigenbrodt  (1848),  the  only  authors 
who  published  repeated  communications  upon  it  were  Brown- 
Sequard  in  France  and  M.  Schiff  in  Germany  and  Italy. 

Brown-Sequard's  theory,  which  was  accepted  by  most  physio- 
logists and  quoted  in  nearly  all  text-books  of  the  physiology  and 
pathology  of  the  nervous  .system,  may  be  summed  up  in  the 
following  propositions :  (a)  Nearly  all  the  motor  fibres  cross  in  the 
medulla  oblougata,  very  few  in  the  cord ;  (6)  nearly  all  the  sensory 
paths  cross  in  the  cord,  very  few  in  the  medulla  oblongata. 


344  PHYSIOLOGY  CHAP. 

The  experimental  basis  of  this  theory  consisted  in  the  fact  that 
after  hemisection  of  the  cord  there  is,  according  to  Brown-Sequard, 
direct  motor  and  crossed  sensory  paralysis.  The  former  is  asso- 
ciated with  slight  paralysis  of  the  opposite  side ;  the  latter  is 
accompanied  not  by  hypoaesthesia,  but  by  hyperaesthesia  on  the 
side  of  the  section.  Many  clinical  cases  of  unilateral  spinal  lesions 
confirm  the  results  of  these  hemisection  experiments  performed  on 
various  vertebrates. 

But  it  can  be  objected  to  Brown-Sequard's  experimental  results 
that  the  animals  were  under  observation  for  too  short  a  time  : 
that  the  sensory  changes  was  frequently  tested  directly  after  a 
severe  operative  trauma ;  that  there  was  no  microscopic  control  of 
the  operations ;  lastly,  that  Brown-Sequard's  own  description  of 
some  of  the  results  of  his  experiments  contradict  his  conclusions, 
and  rather  suggest  that  each  half  of  the  cord  contains  sensory 
fibres  from  both  halves  of  the  body.  It  is  evident  that  he  allowed 
himself  to  be  influenced  in  his  experimental  observations  by  the 
preconceived  ideas  which  he  had  formed  from  his  clinical  observa- 
tions. The  latter,  again,  are  far  from  invariably  confirming  his 
conclusions,  and  in  many  cases  the  seat  of  the  lesion  has  not  been 
exactly  localised  by  anatomical  examination. 

Schiff,  too,  occupied  himself  in  detail  with  the  effects  of  spinal 
hemisection.  In  his  experimental  observations  (as  we  learn  from 
his  most  reliable  pupil  and  successor  A.  Herzen)  he  was  always 
guided  by  the  following  rules : 

(1)  If  a  function  is  found   to   persist  immediately,  or  a  few 
minutes  or  hours,  after  the  transection  of  a  part  of  the  cord,  this 
is  a  definite  proof  that  it  is  independent  of  the  part  divided,  and 
is  connected  with  other  parts  that  have  not  been  injured. 

(2)  If  under  these  conditions  there  is  a  loss  of  function,  this 
does  not  prove  relation  between  this  function  and  the  injured  part, 
unless  the  loss  persist  for  weeks  and  months  after  the  operation, 
till  cicatrisation  is  complete,  the  effect  of  shock  entirely  worn  off, 
and  the  animal  as  far  recovered  as  the  operative  lesion  permits. 

Under  these  irreproachable  criteria,  Schiff  arrived  at  the 
following  results  from  his  experiments  on  unilateral  transection 
of  the  cord : 

(a)  At  whatever  level  one  half  of  the  cord  is  divided,  a  series 
of  phenomena,  some  transitory,  others  permanent,  can  be  seen. 
The  former  consist  in  a  diminution  of  pain  sensibility  on  the 
opposite  side,  which  may  amount  to  total  analgesia ;  various  motor 
disturbances  on  both  sides ;  frequently  hyperaesthesia  to  pain  of 
the  injured  side,  associated  with  vascular  dilatation.  The  only 
permanent  symptom  is  the  abolition  of  tactile  sensibility  on  the 
side  of  the  lesion  in  all  the  more  caudal  parts. 

(6)  After  transection  of  the  whole  spinal  cord  with  the 
exception  of  the  posterior  columns  in  the  thoracic  region,  there  is 


v  SPINAL  COED  AND  NERVES  345 

persistence  of  tactile  sensibility,  while  sensibility  to  pain  is  wholly 
abolished. 

(c)  The  converse  experiment,  that  is  section  of  the  posterior 
columns  only,  while  the  rest  of  the  spinal  cord  is  left  intact,  pro- 
duces immediate  and  permanent  loss  of  tactile  sensibility,  while 
pain  sensibility  persists. 

(rf)  Section  of  the  ventro-lateral  columns  does  not  abolish 
tactile  or  pain  sensibility. 

(V)  Two  lateral  hemisections,  right  and  left,  at  different  levels, 


Fin.  102. — Seetiun  of  ventral  and  thoracic  columns  with  nearly  the  whole  of  the  j;rey  matter  in 
rabbit — level  of  last  dorsal  vertebra.     (Woroschiloff.) 

at  a  certain  distance  from  one  another,  reduce  sensibility  to  pain 
on  both  sides,  while  tactile  sensibility  is  entirely  abolished. 

(/)  Median  longitudinal  section  of  the  lumbar  cord  at  the 
level  at  which  the  nerves  to  the  lower  extremities  pass  out, 
diminishes  sensibility  to  pain,  while  tactile  sensibility  and  motility 
remain  intact. 

From  these  experiments  Schiff  formulated  the  following 
theoretical  conclusions  :  Tactile  sensibility  is  carried  to  the  brain 
by  the  fibres  of  the  dorsal  columns  on  the  same  side,  which,  there- 
fore, do  not  cross  in  the  cord ;  pain  sensibility  is  transmitted  by 
the  grey  matter  of  both  sides,  but  chiefly  through  the  opposite 
side ;  motor  impulses  are  transmitted  by  the  grey  matter  and  by 
the  ventro-lateral  columns ;  the  ventro-lateral  columns  do  not 
transmit  sensory  impressions. 


346 


PHYSIOLOGY 


CHAP. 


Subsequent  research,  especially  by  Miescher  (1870),  Nawrocki 
(1871),  Woroschiloff  (1874),  iu  Ludwig's  laboratory,  led  to  results 
which  absolutely  contradicted  Schiff's  conclusion  that  the  lateral 
columns  do  not  transmit  sensory  impressions. 

Woroschiloff,  who  made  all  his  experiments  on  rabbits,  found 
that  after  dividing  the  dorsal  and  ventral  columns  and  the  whole 
of  the  grey  matter  in  the  lower  thoracic  region,  the  transmission 
of  sensory  and  motor  impulses  was  mot  affected ;  after  section  of 
the  two  lateral  columns,  on  the  contrary,  both  are  abolished,  and 
all  reflex  relations  between  the  posterior  and  anterior  portions  of 


FIG.  193. — Section  of  both  lateral  columns  and  of  a  lateral  portion  of  both  horns  of  the  grey 
matter — level  of  last  dorsal  vertebra.     (Woroschiloff.) 

the  body  are  minimal  (Figs.  192,  193).  From  these  experiments 
he  concluded  that  the  lateral  column  contained  both  motor  and 
sensory  paths. 

From  a  subsequent  study  of  the  effects  of  transection  of  the 
cervical  cord  of  the  rabbit,  Woroschiloff  (1878)  obtained  similar 
results,  and  demonstrated  that  the  sensory  and  motor  paths  for 
the  fore-limbs  also  run  in  the  lateral  columns.  The  motor  paths 
lie  principally  on  the  same  side,  the  sensory  on  the  side  opposite. 

This  last  assertion,  which  agrees  with  Brown-Sequard's  theory, 
is  contradicted  by  some  important  later  experiments  on  higher 
mammals  (dogs,  monkeys),  which  tend  to  show  that  the  conduct- 
ing paths  for  sensibility  only  cross  to  a  minor  extent  in  the  cord. 

Among  these  experiments  those  of  Mott  (1892)  on  the  effect 
of  heuiisection  of  the  cord  in  monkeys  deserve  special  attention. 


SPINAL  CORD  AND  NERVES 


347 


He  found  paralysis  of  voluntary  movement  in  the  limbs  on  the 
side  of  the  section,  which  passes  off  to  a  great  extent,  and  defective 
sensibility  on  the  same  side,  which  diminishes  on  the  return  of 
motility.  Mott  also  observed  on  the  operated  monkey  the  symptom 
known  as  allocliciria  for  pain,  and  perhaps  also  for  tactile  sensi- 
bility ;  when  a  point  of  the  skin  of  the  limb  on  the  side  of 


c 


D 

Fii;.  194. — Ascending  degenerations  after  spinal  hriiiisrrtinn  .in  "monkey.  (Mutt.)  D,  .site  of 
complete  hemisection  of  left  side,  between  5th  and  (3th  thoracic  vertebrae  ;  C,  transverse 
.sect  inn  immediately  above  the  level  nf  the  operation;  B,  section  at  level  of  4th  thoracic 
\eitebra  ;  A,  section  at  level  of  6th  cervical  vertebra.  The  degenerations,  as  shown  by  the 
lighter  parts  of  the  photograph,  extend  to  the  tract  of  Goll,  the  direct  eerebellar  tract  of 
Flechsig,  and  the  ventro-lateral  tract  of  Cowers. 

the  lesion  is  stimulated  the  animal  refers  the  sensation  to  the 
honionymous  point  on  the  opposite  side.  The  return  of  the  motor 
functions  takes  place  more  rapidly  for  bilateral  associated  than  for 
unilateral  movements;  flexion  reappears  before  extension;  the 
movements  of  the  ankle-joint  before  those  of  the  knee  and  foot : 
the  movements  of  the  fingers  recover  only  very  imperfectly. 

The  following  conclusions  may  be  drawn  from  Mott's  work  as 
a  whole ;  the  sensory  paths  do  not  cross  directly  after  they  enter 
the  spinal  cord ;  the  paths  of  cutaneous  sensibility  in  general,  and 


348  PHYSIOLOGY  CHAP. 

perhaps  of  muscular  sensibility  as  well,  only  pass  along  the  same 
side  of  the  cord,  while  the  paths  for  pain  or  thermal  sensibility 
pass  along  both  sides. 

According  to  Mott's  observations,  the  ascending  degenerations 
after  hemisection  of  the  cord  are  sharply  limited  to  the  side  of  the 
operation,  as  shown  by  the  photograph  reproduced  in  Fig.  194. 
From  this  he  concluded  that  the  greater  part  of  the  crossed  fibres 
which  conduct  pain  and  thermal  sensibility  must  undergo  an 
interruption  in  the  grey  matter  of  the  cord  before  they  pass  to 
the  opposite  side. 

The  importance  of  Mott's  observations  lies  essentially  in  their 
contradiction  of  the  theory  of  Brown-Sequard,  which  held  its  own 
for  so  many  years  in  physiology  and  medicine,  and  in  their  having 
led  Brown-Sequard  in  the  last  months  of  his  working  life  (1894) 
to  renounce  his  old  theory  of  the  decussation  of  sensory  paths  in 
the  cord. 

Almost  simultaneously  with  Mott,  and  while  still  ignorant  of 
his  important  publication  (1893),  we  investigated  on  dogs  the 
immediate  and  remote  effects  of  lateral  hemisection  of  the  cord, 
which  were  published  by  Bottazzi  in  1895,  together  with  a  critical 
review  of  the  subject,  and  some  new  experiments  of  his  own.  It 
is  interesting  to  note  the  almost  complete  accordance  of  our  own 
conclusions  from  dogs  with  those  previously  published  by  Mott 
from  experiments  on  the  monkey. 

After  transection  of  the  right  half  of  the  lower  thoracic  cord, 
we  observed  («.)  immediate  paralysis  of  the  right  hind-leg  passing 
into  a  state  of  persistent  paresis,  and  temporary  paresis  of  the  left 
hind-leg  ;  (6)  obvious  ataxy  of  the  right  hind-leg  which  became 
more  pronounced  and  definite  as  the  motor  paralysis  diminished ; 
(c)  serious  disturbance  of  tactile  sensibility  in  both  hind-legs  im- 
mediately after  the  operation,  which  disappeared  in  the  left  leg  with 
the  period  of  irritation,  but  persisted  though  greatly  diminished 
in  the  right ;  (d)  diminution  of  pain  and  thermal  sensibility  in 
both  hind-limbs,  but  much  more  pronounced  in  the  right  leg. 

True  hyperaesthesia  was  not  observed  in  any  of  the  dogs  we 
operated  on,  but  the  reflexes  were  increased  in  the  right  hind-leg 
after  the  period  of  irritation.  The  ascending  degenerations  seen 
in  our  dogs  involved,  as  in  Mott's  experiments,  the  column  of 
Goll,  the  direct  cerebellar  tract  of  Flechsig,  and  the  ventro-lateral 
tract  of  Gowers. 

In  1891  Gotch  and  Horsley  brought  forward  another  clear 
and  quite  original  experimental  proof  of  the  theory  that  the 
majority  of  centripetal  impulses  pass  through  the  same  half  of  the 
spinal  cord  as  that  to  which  they  were  carried  by  the  dorsal  roots. 
After  hemisection  of  the  lower  thoracic  region,  they  examined  the 
current  of  action  in  the  various  columns  of  the  cord  on  stimulation 
of  the  sciatic  nerve.  The  maximal  galvanometer  deflection  was 


v  SPINAL  COED  AND  NEEVES  349 

obtained  from  the  dorsal  columns,  and  next  from  the  lateral 
columns  of  the  same  side. 

The  difficulty  of  examining  and  interpreting  the  phenomena 
due  to  partial  transaction  of  the  spinal  cord,  particularly  the 
different  disturbances  of  sensibility,  becomes  much  less  when  the 
observations  are  made  upon  man  in  cases  of  spinal  disease,  or  local 
traumatic  lesions  of  the  cord.  On  the  other  hand  such  disease  or 
injury  is  rarely  sharply  circumscribed  to  one  part  or  one  entire 
half  of  the  cord,  so  that  the  symptoms  necessarily  vary  and  their 
value  is  impaired. 

In  lesions  confined  to  one  half  of  the  cord,  Kocher  (189G) 
found  that  the  motor  disturbances  do  not  differ  from  those 
observed  after  hemisection  in  the  higher  animals.  There  is  total 
homolateral  paralysis  which  diminishes  in  time  and  is  eventually 
reduced  to  a  slight  paresis.  The  sensory  disturbances  consist  in 
homolateral  hyperaesthesia  to  contact  and  to  pain,  and  in  many 
cases  to  heat  and  cold,  which  also  involves  the  deeper  tissues,  as 
movement  of  the  limbs  is  very  painful.  On  the  side  opposite  to 
the  lesion  there  is  as  a  rule  diminished  sensibility,  which  is  marked 
or  slight,  according  to  the  extent  and  severity  of  the  spinal  lesion. 
Sometimes  every  form  of  sensibility  is  abolished ;  more  frequently 
tactile  sensation  remains  and  pain  sensation  is  reduced,  with  or 
without  diminished  sensibility  to  heat  and  cold.  But  these  dis- 
turbances of  sensibility,  whether  direct  or  crossed,  are  not 
permanent,  as  the  homolateral  hyperaesthesia  and  the  contra- 
lateral  anaesthesia  or  different  dissociated  hypoaesthesias  disappear. 

It  is  thus  obvious  that  Brown-Sequard's  syndrome  is  seen  in 
the  majority  of  cases  of  unilateral  lesions  of  the  cord. 

None  of  the  interpretations  so  far  put  forward  to  explain  the 
clinical  homolateral  hyperaesthesia  and  controlateral  anaesthesia 
have,  however,  reconciled  these  with  the  experimental  observations 
on  the  higher  mammals.  Serious  objections  can  be  brought 
against  the  old  doctrine  of  the  spinal  decussation  of  sensory  paths, 
the  chief  of  which  are  as  follows :  (a)  simple  puncture  of  the 
dorsal  cord  induces  homolateral  hyperaesthesia,  with  motor  and 
vasoniotor  paralysis ;  (&)  hemisection  of  the  thoracic  cord  along 
with  transection  of  the  opposite  side  of  the  cervical  cord  does  not 
affect  the  sensibility  of  the  two  lower  extremities ;  (c)  the  homo- 
lateral  hyperaesthesia  is  more  marked  than  the  coiitralateral  anaes- 
thesia, which  varies  greatly  both  in  man  and  animals,  and 
frequently  bears  no  relation  to  the  seat  of  the  lesion ;  (rf) 
Galen's  experiment  of  dividing  the  decussating  fibres  only  by 
median  longitudinal  section  of  the  lumbar  enlargement  does  not 
abolish  but  only  diminishes  sensibility. 

Owing  to  these  objections  Brown-Sequard  gave  up  his  view 
that  the  anaesthesia  results  from  interruption  of  the  crossed 
sensory  paths,  and  regarded  it  as  an  inhibitory  phenomenon,  and 


350  PHYSIOLOGY  CHAP. 

the  hyperaesthesia  as  a  phenomenon  of  dynamogeny,  without 
asserting  that  these  two  terms  gave  any  final  solution  of  the 
problem,  which  it  must  be  admitted  is  still  totally  obscure. 

More  recently  (1902)  Borchert,  in  H.  Muuk's  laboratory,  made 
further  experiments  on  the  effects  of  dividing  the  dorsal  columns 
in  dogs  at  different  levels  of  the  cord,  and  investigated  the  disturb- 
ances of  tactile,  painful,  and  muscular  sensibility  in  the  limbs. 
His  experiments,  controlled  by  microscopic  examinations,  showed 
that  after  section  of  the  dorsal  columns,  not  only  painful,  but  also 
tactile  and  muscular  sensibility  (consciousness  of  position  of  limbs) 
persisted,  so  that  there  was  still  some  power  of  localisation. 

This,  according  to  Borchert,  disposes  of  Schiif's  theory  that 
tactile  impulses  can  only  be  conducted  by  the  long  tibres  of  the 
dorsal  columns,  while  it  eliminates  the  contradiction  in  the  results 
observed  on  man  and  on  the  dog.  Just  as  man  is  still  capable 
after  degeneration  of  the  dorsal  columns,  as  in  tabes  dorsalis,  of 
perceiving  tactile  stimuli,  so  the  dog  is  not  insensitive  to  them 
after  experimental  division  of  the  same  columns. 

It  follows  that  tactile  sensations  must  be  transmitted  by  the 
short  intraspinal  afferent  paths,  and  that  destruction  of  the  dorsal 
columns  (Borchert)  causes  not  a  qualitative,  but  only  a  quantitative 
diminution  of  sensibility. 

Finally  we  must  refer  to  the  work  of  Petren  (1902),  who  made 
a  careful  synthetic  review  of  clinical  cases,  particularly  those  with 
unilateral  lesions  of  the  cord  due  to  traumna,  spondylitis,  syringo- 
myelia,  etc.  He  concludes  that  tactile  sensibility  (pressure) 
follows  two  paths  in  the  cord  :  the  one,  the  long  uncrossed  path  of 
the  dorsal  columns ;  the  other  associated  with  the  paths  of  the 
other  forms  of  cutaneous  sensibility.  The  latter  (pain,  tempera- 
ture) first  pass  through  the  dorsal  horn  of  the  same  side,  and  then 
cross  the  median  line.  For  the  hind-limbs  this  decussation  is 
completed  by  the  level  of  the  first  lumbar  segment,  or  at  latest  the 
twelfth  thoracic  segment,  never  lower  down.  After  crossing,  these 
paths  run  upwards  in  the  external  half  of  the  lateral  column,  but 
in  the  higher  segments  they  reach  its  median  half,  so  that  there 
is  within  the  lateral  column  a  gradual  displacement  of  fibres  from 
without  inwards.  These  sensory  paths  probably  correspond  with 
part  of  the  fibres  of  the  tract  of  Gowers. 

According  to  Petren,  a  unilateral  lesion  of  the  cord,  when  not 
too  low  down,  only  produces  crossed  anaesthesia.  This  assumes 
two  forms :  either  pain  and  thermal  sensibility  are  altered,  while 
tactile  sensibility  remains  normal ;  or  all  forms  of  cutaneous  sensi- 
bility are  modified.  These  are  the  only  types  found,  the  first 
being  the  most  common.1 

1  EDITORIAL  NOTK. — The  question  of  sensory  conduction  in  the  cord  can  evi- 
dently be  definitely  settled  only  by  observations  of  the  sensory  disturbances  pro- 
duced by  local  spinal  lesions  in  man,  as  in  man  alone  is  it  possible  to  investigate 


v  SPINAL  CORD  AND  NEKVES  351 

XIII.  We  have  seen  that  although  the  spinal  cord  is  only  the 
instrument  of  the  1  train  in  the  execution  of  voluntary  movements, 
it  may  exhibit  activity  independently  of  the  higher  centres  in  the 
so-called  reflex  movements. 

We  have  further  seen  that  the  spinal  reflexes  vary  not  only 
with  the  strength  of  stimulus  and  the  excitability  of  the  centres, 
but  also  with  the  site  of  the  stimulus.  It  is  therefore  necessary 
to  ascertain  what  part  of  the  cord  is  concerned  in  individual 
spinal  reflexes,  i.e.  what  is  the  localisation  of  their  spinal  centres. 

These  problems  are  difficult  to  solve,  and  little  progress  has 
yet  been  made  in  this  direction.  The  spinal  cord,  as  we  have  seen, 
consists  of  a  series  of  segments  or  myelomeres  which  are  intimately 
connected,  and  more  or  less  linked  together  into  a  functional 
solidarity,  so  that  the  different  reflex  centres  cannot  be  distin- 
guished by  separating  them — apart  from  the  shock  this  produces. 

It  is  certain  that  there  are  reflex  centres  which  are  more  or 
less  scattered  throughout  the  spinal  axis,  so  that  we  cannot  speak 
of  their  localisation  in  any  given  region  or  segment  of  the  cord. 
Such  are  the  spinal  vasomotor  centres  and  the  centres  for  sweat 
secretion  discussed  in  Vol.  I.  p.  363  et  seq.,  Vol.  II.  p.  495  et  seq., 
and  the  reflex  centres  which  maintain  a  tonic  and  trophic  influence 
upon  the  muscles  and  the  other  tissues,  as  discussed  in  the  present 
chapter. 

In  regard  to  the  localisation  of  the  motor  (muscular)  centres 
in  the  cord,  it  was  formerly  supposed  that  there  was  a  distinct 
separation  between  them,  according  to  their  functions  (i.e.  specific 
extensor  centres,  flexor  centres,  etc.).  Eecent  research  has  not, 
however,  confirmed  this  hypothesis.  Lapinsky  (1903)  published 
a  series  of  experiments  on  dogs  and  rabbits  with  the  object  of 
determining  if  there  were  definite  centres  in  the  cord  for  the 
separate  groups  and  segments  of  the  musculature  of  the  limbs. 
He  usually  employed  Gudden's  method,  and  examined  the  retro- 
orade  degeneration  which  occurs  in  the  nerve-cells  after  section  of 

D  O 

accurately  the  state  of  the  various  forms  of  sensibility.  But  as  opportunities  of 
accurately  correlating  the  clinical  symptoms  and  the  site  of  the  lesion  are  rare,  a 
final  conclusion  can  be  reached  only  by  such  extensive  investigations  as  can  be 
scarcely  possible  to  any  one  clinician.  On  the  other  hand  accurate  clinical 
observations  on  suitable  cases,  even  when  the  site  and  extent  of 'the  lesion  cannot 
be  verified,  can  at  least  show  how  the  various  components  of  sensation  are  grouped 
and  arranged  in  their  passage  through  the  cord.  The  later  observations  of  many 
writers,  as  Petren,  Rothmann,  and  especially  of  Head  and  his  collaborators,  justify 
the  following  conclusions  : — Pain  and  thermal  sensibility  are  conducted  through 
the  opposite  ventrolateral  columns  ;  two  paths  are  open  to  tactile  stimuli,  one 
in  the  homolateral  dorsal  column,  the  other  in  the  opposite  ventrolateral  column 
in  the  neighbourhood  of  the  pain  and  thermal  paths  ;  the  faculty  of  localisation  is 
spatially  associated  with  the  tactile  impressions  in  the  cord  ;  the  dorsal  columns 
convey  uncrossed  the  impulses  that  subserve  the  sense  of  position  and  the  appre- 
ciation of  movement,  the  recognition  of  size,  shape,  form,  and  weight,  the  appre- 
ciation of  vibration  and  the  discrimination  of  simultaneous  contacts  (Weber's 
compasses). 


352  PHYSIOLOGY  CHAP. 

their  axis-cylinder.  Lapinsky's  results  contradicted  the  conclusions 
of  previous  workers  that  the  motor  centres  of  the  cord  are  segment- 
ally  arranged  in  correspondence  with  the  respective  segments  of  the 
liinbs  they  innervate.  The  cord  has  no  compact  columns  of  cells, 
but  merely  solitary  groups  at  different  levels  with  no  definite 
boundaries.  Still  less  is  it  possible,  he  says,  to  demonstrate  special 
centres  for  the  flexors  and  extensors  or  for  the  adductors  of  the 
thigh.  The  cells  with  these  functions  lie  at  different  levels  of  the 
cord  and  belong  to  the  groups  which  simultaneously  supply  their 
antagonist  muscles.  So,  too,  the  idea  that  each  muscle  has  its 
special  centre  is  contradicted  by  the  fact  that  every  muscle  receives 
nerve -fibres  from  several  ventral  roots,  and  that  each  of  the 
larger  muscles  has  centres  in  several  different  groups  of  cells.  No 
experiments  have  yet  succeeded  in  demonstrating  distinct  centres 
in  the  cord  for  separate  muscles,  or  groups  of  muscles  with  the 
same  function. 

Owing  particularly  to  Goltz,  who  made  a  prolonged  study  of 
the  effects  of  complete  transection  of  the  cord  in  the  lower  thoracic 
region,  we  are  able  to  divide  the  spinal  reflex  centres  into  two 
groups:  those  seated  in  the  lurnbo-sacral  part  of  the  cord  and 
those  in  the  cervico-thoracic  part.  The  two  enlargements,  lumbar 
and  cervical,  may  physiologically  be  regarded  as  two  lower  or 
subordinate  brains,  which  preside  over  the  sum  of  the  reflex  acts 
of  which  these  two  parts  of  the  cord  are  capable. 

The  lower  or  lurnbo-sacral  part  of  the  cord  contains  the  centres 
for  the  following  special  reflexes  :— 

(a)  The  centre  for  movements  of  the  posterior  (lower)  limbs; 
as  we  have  seen,  it  is  possible  in  the  "  spinal "  dog  with  suitable 
stimulation  of  the  skin  to  evoke  all  the  reflex  acts  of  which 
the  lower  part  of  the  animal's  trunk  is  capable. 

(&)  The  ano-spinal  centre  (Vol.  II.  p.  372). 

(c)  The  vesico-spinal  centre  (Vol.  II.  p.  474). 

((/)  The  centre  for  erection,  the  geuito-spinal  centre,  and  the 
ecbolic  or  utero-vaginal  centre  (which  we  shall  discuss  in  the 
chapter  dealing  with  the  functions  of  the  male  and  female  genital 
systems  ;  see  Vol.  V). 

The  upper  or  cervico-thoracic  region  of  the  cord  contains  :— 

(«)  The  centre  for  movements  of  the  anterior  (upper)  limbs. 

(&)  The  spinal  centres  for  the  respiratory  movements  (Vol.  I. 
p.  447). 

(c)  The  spinal  centres  for  the  cervical  sympathetic,  the  vaso- 
motor  and  secretory  fibres  of  which  run  principally  to  the  head. 
The  so-called  cilio-spinal  centre,  or  dilatator  of  the  pupil,  dis- 
covered by  Budge,  extends  from  the  lower  half  of  the  cervical  cord 
to  the  level  of  the  third  thoracic  segment.  Electrical  excitation 
of  this  segment  region  produces  mydriasis,  like  the  excitation  of 
the  cervical  sympathetic. 


v  SPINAL  COED  AND  NERVES  353 

(<f)  The  accelerator  spinal  centres  for  the  heart  are  in  approxi- 
mately the  same  region  as  the  cilio-spinal  centre  (Vol.  I.  p.  .'!oGj. 

From  this  enumeration  it  is  plain  that  not  only  the  nerve- 
centres  for  the  organs  of  animal  life,  but  to  some  extent  those  of 
the  visceral  function  also  lie  in  the  spinal  cord. 

Since  the  innervation  of  the  organs  of  visceral  life  is  supplied 
directly  by  the  sympathetic  ganglion  system,  a  final  and  interesting 
problem  here  presents  itself.  Are  the  functions  of  the  sympathetic 
system  subordinate  to  those  of  the  spinal  centres,  or  can  they 
subsist  independently  of  them  ? 

To  solve  this  question  it  is  necessary  to  study  the  immediate 
and  remote  effects  of  ablation  of  the  cord.  Previous  to  the 
remarkable  results  obtained  by  Goltz  and  Evvald  in  1896,  such  a 
research  would  have  been  impossible.  They  first  demonstrated 
that  dogs  can  survive  for  many  months  in  a  good  state  of  health 
after  repeated  removal  of  parts  of  the  cord  from  below  up  to  the 
cervical  region ;  so  that  the  opinion  previously  maintained  by 
every  one — that  in  warm-blooded  vertebrates  the  cord  is  absolutely 
indispensable  to  life,  as  the  regulator  of  the  nutritional  processes, 
the  vascular  tone,  and  the  thermal  equilibrium  of  the  organism- 
is  fallacious. 

As  we  have  already  seen  (p.  330),  after  simple  section  of  the 
dorsal  roots  of  the  spinal  nerves  the  tissues  that  become  insensitive 
are  more  liable  to  injury  than  before.  This  is,  of  course,  most 
marked  in  the  posterior  part  of  the  dog  with  amputated  cord. 
Patches  of  decubitus,  pustules,  erythema,  oedema,  especially  near 
the  genital  organs  and  anus,  are  extremely  likely  to  appear ;  but 
these  cutaneous  lesions  can  be  avoided  or  cured  by  constant  and 
scrupulous  cleanliness.  By  degrees,  however,  the  skin  of  the  cord- 
less animal  gradually  acquires  an  increasing  resistance  to  external 
injurious  influences. 

Even  more  important  to  the  survival  of  these  animals  is  the 
avoidance  of  a  fall  in  the  blood  temperature,  which  is  liable  to 
occur  directly  after  simple  transection  of  the  cord,  by  enclosing 
the  animal  in  a  chamber  with  double  metal  walls,  between  which 
warm  water  is  continually  circulated. 

The  persisting  activities  in  the  posterior  part  of  the  animal 
that  has  lost  its  thoracic  and  lumbo-sacral  cord  are  far  more 
numerous  than  would  be  anticipated  a,  priori  from  what  we  have 
learned  experimentally  with  regard  to  the  functions  of  the  spinal 
cord.  The  immediate  effects  of  removal  of  the  cord  are  principally 
due  to  operative  shock.  After  a  few  months  they  diminish 
sufficiently  to  give  a  clear  idea  of  the  great  physiological  im- 
portance of  the  sympathetic  ganglion  system,  in  so  far  as  it  is 
capable  of  acting  on  the  organs  and  tissues  of  vegetative  life, 
independently  of  the  spinal  system. 

Directly  after  ablation  of  the  thoracic  and  lumbo-sacral  cord, 

VOL.  in  2  A 


354  PHYSIOLOGY  CHAP. 

the  external  sphincter  of  the  anus  is  entirely  relaxed ;  but  after  a 
few  months  (as  already  shown  in  Vol.  II.  p.  372)  it  regains  its 
tone.  It  reacts  to  mechanical  traction,  to  injections  of  cold 
water,  to  induced  currents ;  it  may  also  recover  the  rhythmical 
automatic  contractions — independent  of  external  stimuli — which  it 
manifests  after  simple  division  of  the  cord  from  the  higher  centres. 
From  these  facts  Goltz  and  Ewald  concluded  that  the  anal 
sphincter,  in  addition  to  the  cerebral  and  spinal  centres,  possesses 
peripheral  sympathetic  ce'ntres,  which  possibly  lie  in  the  depth 
of  the  muscle. 

Unlike  the  sphincter,  which  also  consists  of  striated  muscle, 
all  the  striated  skeletal  muscles  atrophy.  First  they  lose  their 
faradic,  next  their  galvanic  excitability,  lastly,  they  become 
inelastic  and  are  reduced  to  bundles  of  connective  tissue.  The 
bones  also  alter  and  become  brittle.  The  digestion,  which  is 
disturbed  during  the  first  days,  becomes  normal  again  in  the 
course  of  a  few  weeks.  Defaecation  takes  place  regularly  once  or 
twice  a  day,  and  the  faeces  are  natural  in  appearance.  The  urine 
is  clear,  free  from  sugar  and  albumin.  The  bladder,  which  is 
paralysed  for  the  first  days,  gradually  recovers  its  functions,  and 
after  a  few  months  evacuates  the  urine  collected  in  it  periodically 
and  spontaneously,  and  when  evacuation  has  taken  place  the 
animal  remains  dry  for  hours. 

A  pregnant  bitch,  a  few  hours  after  extirpation  of  94  cm.  of 
cord,  gave  birth  to  five  puppies,  one  of  which  was  left  to  her  to 
suckle,  which  she  did  perfectly.  The  puppy  sucked  all  the 
mammae  in  turn,  and  even  the  last  pair,  which  were  entirely 
deprived  of  spinal  innervation,  yielded  an  abundance  of  milk. 

The  tone  of  the  blood-vessels  in  the  dog  that  has  lost  its  cord 
recovers  completely  in  a  few  days.  The  temperature  of  the 
clenervated  posterior  limbs  becomes  the  same  as  that  of  the 
anterior,  which  are  still  innervated  by  the  spinal  nerves  from  the 
cervical  region.  From  this  it  can  be  seen  that  the  vascular  tone 
does  not  depend  exclusively  upon  the  bulb  and  cord,  as  was 
formerly  supposed,  but  that  even  under  normal  conditions  the 
sympathetic  ganglion  system  must  have  an  enormous  influence 
over  it. 

One  sciatic  nerve  was  divided  in  a  dog  that  had  lost  the 
lumbo-sacral  part  of  its  cord  ;  at  first  there  was  a  marked  difference 
in  the  diameter  of  the  vessels  and  the  temperature  of  the  paralysed 
hind-limbs,  but  after  a  few  days  these  differences  disappeared. 
On  stimulating  the  skin  of  the  posterior  part  of  the  cordless 
animal,  it  is  not  possible  reflexly  to  influence  the  vessels  at  remote 
parts  of  the  skin,  but  all  stimuli  have  the  same  local  effect  in  the 
posterior  as  in  the  anterior  part  of  the  animal.  Unipolar  ex- 
citation by  induced  currents  produces  pallor  of  the  prolapsed 
inucosa  of  the  rectum,  and  heat  and  cold  affect  the  cutaneous 


v  SPINAL  CORD  AND  NERVES  355 

\vssds  of  the  hind-limbs  in  the  same  way  as  those  of  the  fore- 
liinlis. 

Owing  to  this  local  excitability  of  the  cutaneous  vessels,  the 
cordless  animal  is  capable  of  maintaining  its  normal  blood 
temperature  during  marked  oscillations  of  the  external  tempera- 
ture, and  though  it  is  necessary  to  keep  it  in  a  chamber  with 
constant  temperature  immediately  after  the  operation,  this  pre- 
caution becomes  unnecessary  in  a  few  weeks. 

At  the  season  for  changing  the  coat,  a  marked  difference  is 
seen  in  the  hair  of  the  anterior  and  posterior  parts  of  the  body ; 
in  the  former  it  is  new  and  glossy,  in  the  latter  it  is  dull  and 
lifeless,  and  conies  out  at  the  least  pull. 

From  these  phenomena  as  a  whole  we  must  conclude  that 
the  cord  is  not  absolutely  indispensable  to  life  in  warm-blooded 
vertebrates,  but  that  it  is  important  to  the  visceral  functions. 

The  absence  of  the  spinal  centres  is  responsible  for  the  low 
energy  with  which  these  functions  are  carried  out  under  the 
exclusive  influence  of  the  sympathetic  system,  and  the  great 
instability  in  the  health  and  vitality  of  the  cordless  animal,  which 
requires  constant  care,  and  easily  falls  ill  and  succumbs  to 
slight  causes. 

The  closure  of  the  anal  sphincter  in  a  dog  in  which  the  cord 
is  simply  transected  is  tirmer  than  after  removal  of  the  cord,  and 
the  rhythmic  reflex  contractions  of  the  anus  that  are  easily  seen 
in  the  "  spinal "  animal  are  exceedingly  rare  in  the  "  sympathetic  " 
animal. 

Even  more  striking  is  the  diminished  energy  of  the  vesical 
functions  in  the  cordless  animal ;  the  bladder,  moreover,  is  often 
infected,  and  most  of  the  animals  die  of  cystitis  and  pyelo- 
nephritis. Only  in  rare  cases  has  it  been  possible  to  cure  the 
cystitis  when  it  has  once  set  in. 

Digestive  disorders,  again,  are  very  dangerous  to  the  animal 
that  has  lost  its  cord. 

Finally,  in  the  cordless  animal  thermal  regulation  is  only 
possible  with  limited  variations  of  the  external  temperature. 

These  important  observations  of  Goltz  and  Ewald  on  the 
symptoms  produced  by  removal  of  the  spinal  cord  enable  us  to 
appraise  the  value  of  the  early  doctrine  (see  p.  278),  by  which  the 
sympathetic  system  was  held  to  preside  over  the  functions  of 
visceral  life.  Undoubtedly  all  such  activities  may  subsist  and 
function  in  a  comparatively  normal  fashion  after  removal  of  all 
spinal  influence.  The  office  of  the  spinal  system  in  regard  to  the 
functions  of  visceral  life  seems  to  consist  in  endowing  these 
functions  with  greater  energy,  and  in  conferring  greater  stability 
and  more  solid  equilibrium  on  the  general  constitution  of  the 
animal. 


356  PHYSIOLOGY  CHAP 

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pat.,  1863,  1868-69. 

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MARTIXOTTI.     Arch.  f.  Anat.  und  Physiol.,  1890,  Suppl*- 
GOTCH  and  HOKSLEY.     Croonian  Lecture,  1891. 
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BoTTAZzr.     Rivista  di  freniatria.     Reggio  Emilia,  1895. 
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Tonic  and  Trophic  Functions  of  Spinal  Cord  :  — 

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MAGENDIE.     Journal  de  physiol.  exp.,  t.  iv.,  1824. 

SCHIFF.     Morgagni,  1864. 

LONGET.     Traite  de  physiologic,  1868. 

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WALLER,  A.  D.     Journ.  of  Physiology,  1890. 

SHERRINGTON.     Journal  of  Physiology,  1892. 

SPALLITTA.     Arch,  di  oftalm.  dell'  Angelucci,  1894. 

GOLTZ  and  EWALTI.     Pfluger's  Archiv,  1896. 

FANO.     Atti  dei  Lincei,  1902. 

Localisation  of  Spinal  Centres  :— 
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SHERRINGTON.  A  Mammalian  Spinal  Preparation.  Journ.  of  Physiol.,  1909, 
xxxviii.  375. 

BROOKS.  The  Effects  of  Lesions  of  the  Dorsal  Nerve  Roots  on  the  Reflex  Excit- 
ability of  the  Spinal  Cord.  Amer.  Journ.  of  Physiol.,  1910,  xxvi.  212. 

WARRINGTON  and  GRIFFITHS.  On  the  Cells  of  the  Spinal  Ganglia,  and  on  the 
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SHERRINGTON.  The  Proprioceptive  System  in  its  Reflex  Aspect.  Brain,  1906, 
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SHERRINGTON.  Plastic  Tone  and  Proprioceptive  Reflexes.  Quart.  Journ.  of  Experi- 
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SHERRINGTON.  On  Reciprocal  Innervation  of  Antagonistic  Muscles.  Proc.  Roy. 
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SHERRINGTON.  Reflex  Inhibition  as  a  Factor  in  the  Co-ordination  of  Movements 
and  Postures.  Quart.  Journ.  of  Experiment.  Physiol.,  1913,  vi.  251. 


358  PHYSIOLOGY  CHAP,  v 

SHKRRIXOTUN.     Further  Observations  on  the  Production  of  Reflex  Stepping  l>y 
Combination  of  Reflex  Excitation  and  Reflex  Inhibition.     Journ.  of  Physiol., 

1913,  xlvii.  196. 

SHERRINGTON.     Reciprocal  Innervation  and  Symmetrical  Muscles.     Proc.  Roy.  Soc., 

London,  1913,  B.  Ixxxvi.  219. 
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Proc.  Roy.  Soc.,  London,  1913,  Ixxxvi.  233. 
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SHERRINGTON.     Some  Comparisons  between  Reflex  Inhibition  and  Reflex  Excita- 
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Roy.  Soc.,  London,  1912,  B.  Ixxxv.  289. 
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CHAPTER   VI 

SYMPATHETIC    SYSTEM 

CONTENTS. —  1.  Anatomy  and  histology  of  fibres  and  ganglia  of  sympathetic 
system.  2.  Peripheral  distribution  of  sympathetic  system  to  the  organs  which  it 
innervates.  3.  Physiological  arrangement  of  constituent  parts  of  sympathetic 
system  ;  origin  and  course  of  efferent  fibres.  4.  Origin  and  course  of  att'en-nt 
fibres.  5.  Function  of  peripheral  ganglia.  Bibliography. 

THE  Sympathetic  System,  while  intimately  connected  with  the 
cerebrospinal  axis,  differs  from  it  in  many  respects,  especially  in 
its  peripheral  distribution.  This  is  evident  from  the  important 
researches  of  Laugley,  to  whom  we  are  chiefly  indebted  for  our 
knowledge  of  this  subject. 

Just  as  the  lunibo-sacral  part  of  the  cord  is  able  to  function 
after  it  has  been  separated  from  the  cervico-thoracic  segments,  so 
the  sympathetic  system  is  able  to  recover  and  maintain  certain  of 
its  functions — at  least  for  a  time  and  under  given  conditions  of 
existence  and  nutrition — after  extirpation  of  those  segments  of  the 
spinal  cord  with  which  it  is  anatomically  connected  (Goltz). 

On  account  of  this  property,  by  which  the  system  which 
controls  the  visceral  and  involuntary  functions  of  the  body  is  : 
distinguished  from  the  spinal  nerves  that  innervate  the  somatic 
organs  and  depend  wholly  on  their  connections  with  the  central 
nervous  system,  Langley  has  proposed  to  replace  the  term 
Sympathetic  System  by  the  more  physiological  title  Autonomic 
Nervous  System.  But  since  this  autonomy  is  incomplete,  and 
there  are  close  anatomical  and  physiological  relations  between  the 
visceral  system  and  the  cerebrospinal  axis,  it  seems  more  con- 
sistent to  retain  the  older  nomenclature. 

In  discussing  the  functions  of  the  visceral  organs  in  the  first 
two  volumes  we  laid  stress  on  the  physiological  importance  of 
individual  parts  of  the  sympathetic  system ;  in  tiie  present 
chapter  we  have  to  deal  with  this  system  as  a  whole  and  with  its 
general  characteristics. 

I.  The  sympathetic  nervous  system  consists  of  a  highly  com- 
plex arrangement  of  ganglia,  nerve-fibres,  and  nerve-plexuses, 
which  are  distributed  to  the  different  regions  of  the  bod)-. 

359 


3GO  PHYSIOLOGY  CHAP. 

Anatomically  the  following  parts  can  be  distinguished  :— 

A.  Two  nerve  cords,  running  along  the  ventral  surface  of  the 
vertebral  column,  from  the  atlas  to  the  coccyx,  which  are  segmentally 
interrupted  at  given  points  in  their  course  by  nodes  or  ganglia, 
and    are    known    as    the    gangliated    cords    of    the   sympathetic 
(Fig.  167,  p.  279).      Each  is  subdivided  into  cervical,  thoracic, 
lumbar,  and  sacral  portions. 

The  cervical  part  has  three  ganglia  :  superior,  middle,  and 
inferior.  The  thoracic  part  contains  eleven  or  twelve  ganglia,  the 
first  two  or  three  of  which  are  usually  united  into  a  single  ganglion 
the  stellate  ganglion — while  the  lumbar  and  sacral  parts  have 
five  or  sometimes  only  four  ganglia  each.  The  ends  of  the  two 
chains  converge  and  unite  behind  the  coccyx  in  a  small  single 
node,  the  so-called  unpaired  coccygeal  ganglion  of  Walter. 

Each  of  these  ganglia,  which  Gaskell  termed  vertebral  or  lateral 
from  their  position,  gives  off  three  branches  :  (a)  fibres  which 
connect  the  ganglion  with  the  neighbouring  spinal  nerves  (rami 
conimimicantes).  Of  these,  there  are  two  classes  :  the  white  rarni, 
which  consist  principally  of  myelinated  nerve-fibres ;  and  the  grey 
rarni,  composed  mainly  of  non-medullated  fibres.  These  are  the 
!  only  paths  by  which  the  sympathetic  system  is  united  to  the 
cerebrospmal  axis.  (6)  Branches  which  connect  the  several 
ganglia  among  themselves,  and  consist  partly  of  medullated, 
partly  of  non-medullated,  fibres,  (c)  Branches  that  either  run 
directly  to  the  peripheral  organs  or  to  ganglia  of  the  sympathetic 
system,  which  lie  more  peripherally. 

B.  The  large  plexuses  of  the  sympathetic,  which  innervate  the 
viscera  and  lie  distal  to  the  ganglion  chain  near  the  large  blood- 
vessels.    They  consist  of  a  network  of  nerve-fibres,  which  arise  for 
the  most  part  in  the  gangliated  cord,  but  partly  also  from  the 
vagus  and  from  ganglia  within  the  plexus.     The  most  important 
are  :  the  cardiac  plexus  ;  the  caeliac  plexus,  also  called  from  its 
radiate    appearance   the    solar  plexus,  which  is   the    largest  and 
richest  in  the  body,  and  is  formed  principally  of  the  splanchnic 
nerves  from  branches  given  off  by  the  5th  or  6th  to  the  9th  or 
10th  thoracic  ganglia;  and  the  hypjjgastricjDlexus. 

Gaskell  gave  the  name  of  prc-vertebral  or  collateral  to  the 
ganglia  of  the  large  plexuses  to  distinguish  them  from  those  of 
the  ganglion  chain,  which  he  termed  vertebral  or  lateral.  Besides 
these  ganglia  smaller  groups  of  cells  lie  more  peripherally  along 
the  course  of  the  different  nerve  trunks,  before  these  enter  the 
visceral  organs  they  innervate  ;  Gaskell  termed  these  ganglia  of 
the  third  order  terminal  ganglia. 

C.  Besides  the  sympathetic   system   proper,  there   are   other 
central  and  peripheral  nervous  structures  with  similar  functional 
properties,    which    must    be    discussed    along    with    it.      Langley 
includes  in  the  sympathetic  system  all  the  nerves  and  ganglia 


VI 


SYMPATHETIC  SYSTEM 


361 


which  supply  the  unstriated  muscles  of  the  body  (vessels,  digestive 
tract,  excretory  ducts,  hair  follicles),  the  myocardium,  and  the 
secretory  nerves  to  the  glands,  in  contradistinction  to  the  parts 
of  the  nervous  system  which  innervate  the  striated  skeletal 
muscles.  But  this  division  by  peripheral  distribution  is  not 
always  possible ;  in  some  parts  of  the  gut  (e.g.  in  the  upper  parts 
of  the  oesophagus  and  end  of  the  rectum)  striated  muscle  fibres 
are  controlled  by  the  sympathetic  system. 

Langley  divides  the  entire  Sympathetic  or  Autonomic  System 


FIG.  195.—  Two 


cells  I've  mi  fi-vvical  ganglion  of  cat.     Golgi's  incMioil.     Highly 
(v.  Kolliker.)    ?*,  axon. 


niagnified. 


into  three  parts  :  (a)  the  sympathetic  in  the  strict  sense  of  the 
term;  (&)  the  cnni'ml  system  (mesencephalic  and  bulbar),  which 
supplies  the  eye,  upper  part  of  the  digestive  tract,  heart,  and  lungs  ; 
(c)  the  S((-cral  system,  which  innervates  the  lower  parts  of  the 
digestive  tract,  the  bladder,  and  the  genital  organs.  We  shall 
frequently  return  to  this  classification. 

In  its  minute  structure  the  sympathetic  system  presents  the 
same  constituent  elements  as  the  rest  of  the  nervous  system,  viz. 
nerve-fibres,  ganglion  cells,  and  a  complicated  fibrillary  network 
around  the  ganglion  cells  which  probably  originates  in  the  pro- 
cesses of  the  nerve-fibres.  The  single  nerve-fibres  unite  into  nerve 
trunks,  while  the  ganglion  cells  and  network  of  fibrils  accumulate 
at  certain  points  along  their  course. 


362 


PHYSIOLOGY 


CHAP. 


The  cells  of  the  sympathetic,  unlike  those  of  the  bulbar  and 
spinal  ganglia,  are  for  the  most  part  multipolar  and  smaller  and 
almost  uniformly  round  (Fig.  195).  Stohr  distinguishes  three 


Motor 


IVricellular  network 


Capsule 


Sensory  spinal 
nerve-fibre 


Sympathetic  (?) 
fibre 


Section  through 
-  peiirapsular 
network 

Surface  view  of 
"    perk'Hpsular 
network. 


Sti-llate  cell 


Nerve  process 


Lamellar 
capsule 


Fio.  196.— Diagrammatic.     Elements  of  two  sympathetic  ganglia.     (Stohr.)    1,  2,  3,  cells  of 

first,  second,  and  third  type. 

types  of  ganglion  cells  (Fig.  196)  to  which  no  distinctive  function 
can  at  present  be  attributed. 

The  nerve-fibres  are  of  two  kinds.  The  first  are  ordinary 
medullated  nerve-fibres,  which  are  found  in  the  white  rami 
communicantes ;  these,  which  connect  the  spinal  cord  and  the 
sympathetic,  originate  in  the  cells  of  the  lateral  horn  of  the  cord, 
and  conduct  to  the  ganglia  of  the  lateral  chain. 


vi  SYMPATHETIC  SYSTEM  363 

The  second  variety  are  the  so-called  fibres  of  IJemak,  which 
have  no  niyelin  sheath  and  present  a  grey  appearance.  They  are 
derived  from  the  cells  of  the  sympathetic  ganglia,  and  connect 
these  with  the  peripheral  organs. 

The  general  rule  that  the  white  (myelinated)  fibres  of  the 
sympathetic  system  descend  from  the  spinal  cord  (efferent  paths) 
or  ascend  to  the  cord  (afferent  paths)  and  thus  belong  entirely  to 
the  cerebrospinal  axis,  while  the  grey  (non-medullated)  fibres 
spring  from  the  sympathetic  ganglia  and  belong  to  the  sympathetic 
system  in  the  narrower  sense,  is,  according  to  Langley,  liable  to 
exceptions.  For  example,  he  says  that  the  nerves  of  the  sym- 
pathetic ganglia  which  innervate  the  muscles  of  the  feathers  in 
birds  are  all  myelinated. 

II.  The  peripheral  organs  supplied  by  the  fibres  of  the  sym- 
pathetic have  already  been  discussed  in  the  preceding  volumes,  but 
may  here  be  recapitulated  :— 

(a)  The  sphincter  of  the  iris  and  pupil,  contraction  of  which 
diminishes  the  size  of  the  pupil. 

(&)  The  ciliary  muscles,  contraction  of  which  relaxes  the  zonule 
of  Zinu  and  accommodates  the  eye  for  near  objects. 

Both  these  muscles  are  innervated,  as  are  most  of  the  striated 
muscles  of  the  eye,  by  the  third  cranial  nerve  ;  but  the  fibres 
destined  for  these  unstriated  muscles  are,  unlike  those  for  the 
other  muscles,  interrupted  in  a  peripheral  ganglion,  the  ciliary 
ganglion,  like  all  sympathetic  fibres  ;  accordingly,  they  must  be 
included  in  the  sympathetic  system. 

(c)  The  dilatator  pupillae,  the  functional  antagonist  of  the 
sphincter  of  the  pupil,  contraction  of  which  widens  the  pupil. 

(rf)  The  plain  muscle  fibres  found  in  the  orbital  tissues, 
Tenon's  capsule,  and  the  eyelids,  which  enlarge  the  palpebral 
fissure,  protrude  the  eyeball  and  retract  the  eyelids.  In  some 
animals  there  are  also  muscle  fibres  in  the  nictitating  membrane 
in  the  internal  angle  of  the  orbit,  contraction  of  which  retracts 
this  membrane. 

(f)  The  musculature  of  the  blood-vessels  of  the  eye,  which 
when  contracted  constricts  the  blood-vessels  of  the  conjunctiva, 
iris,  etc.  The  lachrymal  glands  also  receive  fibres  from  the 
sympathetic,  which  on  stimulation  cause  a  secretion  of  tears. 

All  these  nerve -fibres  spring  from  the  superior  cervical 
ganglion.  We  shall  later  discuss  their  connections  with  the 
spinal  cord. 

Next  to  the  sympathetic  fibres  that  supply  the  eye  come  those 
which  are  distributed  to  the  surface  of  the  body  to  innervate  the 
plain  muscle  fibres  of  the  various  organs  of  the  skin.  These 
are  :— 

(a)  The  muscle  fibres  of  the  cutaneous  vessels,  contraction  of 
which  constricts  the  vascular  lumen  and  diminishes  the  amount 


364  PHYSIOLOGY  CHAP. 

of  blood  circulating,  producing  pallor  aud  coldness  in  the  corre- 
sponding cutaneous  regions ;  their  relaxation  has  the  opposite  effect. 

(/3)  The  muscle  fibres  of  the  hair  follicles,  whose  contraction 
produces  "goose  skin."  The  study  of  the  innervation  of  these 
organs,  which  are  specially  developed  in  the  cat,  provided  Langley 
with  a  means  of  determining  the  arrangement  and  distribution 
of  the  sympathetic  fibres.  He  found,  however  (1904),  that  in  this 
animal  the  conditions  were  more  complex  than  in  the  other 
mammals,  as  there  are  two  sets  of  antagonist  muscles,  one  of 
which,  the  more  powerful,  prevails  over  the  other  in  artificial 
stimulation,  and  causes  depression  of  the  hairs,  while  the  other 
causes  their  erection.  In  man,  owing  to  the  retrogression  of 
the  piliferous  system,  the  muscles  of  the  hair  follicles  are  of  no 
great  importance.  Erection  of  the  hairs  produces  "  goose  skin  " 
after  stimulation  by  cold  and  in  certain  emotions,  as  fear,  etc. 

(y)  The  ducts  of  certain  cutaneous  glands,  e.g.  the  mammtiry 
glands,  are  provided  with  contractile  elements,  which  are  con- 
trolled by  the  sympathetic  system. 

The  different  glands  of  the  skin,  in  particular  the  sweat  glands 
and  sebaceous  glands,  are  also  innervated  by  the  sympathetic. 

The  second  large  and  important  province  governed  almost 
exclusively  by  the  sympathetic  system  includes  the  visceral 
organs  in  the  strict  sense,  viz.  the  organs  of  circulation  (heart, 
blood-  and  lymph-vessels) ;  and  the  digestive  system,  both  its 
unstriated  muscles — on  which  the  co-ordiuated  movements  of  the 
stomach  and  intestines,  defalcation,  micturition,  etc.,  depend — and 
its  secretory  glands. 

On  the  following  page  is  Langley 's  Table  l  with  a  few  minor 
alterations.  It  sums  up  the  various  functions  of  the  sympathetic 
system  in  its  widest  sense. 

III.  The  first  problem  to  be  studied  in  the  physiology  of  the 
sympathetic  nervous  system  is  its  intimate  structure,  the  origin 
and  course  of  its  nerve-fibres,  and  the  relations  in  which  these 
stand  with  the  several  ganglia. 

As  we  know,  two  different  experimental  methods  can  be 
utilised  in  tracing  the  course  of  the  nerve-fibres ;  one  anatomical, 
based  on  Waller's  law  (p.  233),  according  to  which  the  part  of 
the  nerve  that  is  severed  from  its  trophic  centre  degenerates ; 
the  other,  physiological,  based  on  the  phenomena  which  appear 
on  exciting  the  central  or  peripheral  end  of  the  cut  nerve,  or  the 
functional  disturbances  seen  after  the  cutting,  cooling,  poisoning, 
etc.,  of  the  nerve. 

We  must  first  consider  the  origin  and  course  of  the  efferent 
nerve-fibres  (motor  or  secretory). 

The  only  path  followed  by  the  nerve-fibres  which  connect  the 
cerebrospinal  axis  with  the  ganglion  chain  of  the  sympathetic, 

1  Langley,  Ergebnisse  der  Physiologic,  1903,  Jahrgang  ii.  Abteihmg  ii.  p.  830. 


VI 


SYMPATHETIC  SYSTEM 


365 


Mid-brain 
autonomic 


Bulbar 
autonomic 


Sacral 
a  titonomic 


Effects  of  stimulating  the  mid-bram, 

luillar  ami  s;ici-;il  mil  i  ni'iniir  l 


Contraction  of  iris 
Contraction  of  ciliary  muscle 


Inhibition  of  heart,  and  of 
vessels  of  mucous  membranes 
of  head 

Motor  and  inhibitory  effects  on 
smooth  musculature  of  gut 
from  oesophagus  to  descend- 
ing colon 

Motor  and  inhibitory  effects  on 
muscles  of  trachea  and  lungs 

?  Secretion  of  gastric  glands, 
liver,  and  pancreas 


Inhibition  of  arteries  of  rectum, 
anus,  and  external  generative 
organs 

Contraction  of  smooth  muscula- 
ture of  descending  colon, 
rectum,  and  aiius 

Inhibition  of  smooth  muscles  of 
anus 

Contraction  of  bladder 

Inhibition  (?  contraction)  of 
urethra 

Inhibition  of  muscles  of  external 
generative  organs 


nl'  si  imllhlt  ini;  till-  s.VIII- 
]i:itlir1  1C    IIITNPS. 


Contraction  of  dilator  of  iris 
Contraction  of  unstriated  orbital 

muscle 
Contraction  of  arteries  of  eye 

Acceleration  of  heart  and  con- 
traction of  blood-vessels  in 
mucous  membranes  of  head 

Inhibitory  and  motor  effects  on 
smooth  musculature  of  gut 
from  oesophagus  to  descend- 
ing colon 

?  Secretion  of  gastric  glands, 
liver  and  pancreas 

Contraction  of  vessels  of  gut 
from  oesophagus  to  descend- 
ing colon 

?  Contraction  of  vessels  of  lung 

Contraction  of  vessels  of  abdom- 
inal viscera 

Contraction  of  musculature  of 
spleen,  ureters  and  internal 
generative  organs 

Contraction  of  smooth  muscles, 
and  arteries  of  skin 

Secretion  of  cutaneous  glands 

Contraction  of  arteries  of  rectum, 
anus,  and  external  generative 
organs 

Inhibition  and  contraction  of 
smooth  musculature  of  de- 
scending colon,  rectum,  and 
anus 

Inhibition  and  contraction  of 
bladder 

Contraction  (?  inhibition)  of 
urethra 

Contraction  of  muscles  of 
external  generative  organs 


is  through  the  rami  coinrnunicantes.  We  have  seen  (p.  292,  et  seq.) 
that  the  Bell-Magendie  law  holds  good  for  the  sympathetic  fibres, 
except  that  the  vaso-dilator  fibres  to  the  fore-  and  hind-limbs,  in 
the  dog  at  least,  leave  the  cord  by  dorsal  and  not  by  ventral  roots. 
The  remaining  efferent  fibres  of  the  sympathetic  system  run  in 
the  ventral  roots,  and  beyond  the  spinal  ganglia  join  the  fibres 
of  the  dorsal  roots,  with  which  they  run  for  a  short  course, 
forming  the  so-called  spinal  nerves.  These  give  oft'  branches  at 
different  intervals,  including  the  rami  communicantes,  first,  the 
white,  later  or  more  peripherally  the  grey  rami.  In  some  cases, 
however,  the  white  and  grey  rami  arise  at  approximately  the 
same  point  of  the  spinal  nerve,  and  unite  in  a  common  trunk. 


366  PHYSIOLOGY  CHAP. 

The  rami  communicantes  branch  from  a  mixed  spinal  nerve,  and 
are  themselves  mixed  nerves,  containing  both  afferent  and  efferent 
fibres. 

Gaskell  (1886)  was  the  first  to  make  an  exact  study  of  the 
structure,  distribution,  and  function  of  the  sympathetic  nerve- 
fibres.  As  in  the  dog  the  fibres  that  issue  from,  the  cells  of  the 
spinal  cord  are  myelinated,  and  as  all  the  medullated  fibres  which 
connect  the  cord  with  the  ganglion  chain  run  in  the  white  rami, 
he  concluded  that  the  majority  of  the  fibres  that  pass  from  the 
cord  to  the  sympathetic  must  traverse  the  white  rami.  As  he 
further  established  that  in  the  dog  the  white  rami  emerge 
exclusively  between  the  2nd  thoracic  and  2nd  lumbar  roots,  it 
follows  that  the  region  of  the  cord  between  these  segments  is 
the  only  part  that  gives  origin  to  sympathetic  fibres. 

Isolated  stimulation  of  the  white  rami  communicantes  usually 
presents  insuperable  difficulties,  because  they  run  along  with  the 
grey  fibres.  In  order  to  demonstrate  the  efferent  fibres  which 
unite  the  cord  and  the  sympathetic  it  is  usual  to  stimulate  the 
entire  spinal  nerve  above  the  point  of  exit  of  the  rami  communi- 
cantes. The  results  of  Claude  Bernard,  Langley,  Sherrington, 
etc.,  fully  agree  with  Gaskell's  conclusions.  Only  those  spinal 
nerves  which  give  origin  to  white  rami  communicantes  are  capable, 
on  artificial  stimulation,  of  exciting  the  organs  innervated  by  the 
sympathetic.  The  cervical  nerves,  which  have  no  white  rami, 
are  incapable  of  any  such  action.  Bernard  (1862)  found  nerve- 
fibres  able  to  dilate  the  pupil  in  the  1st  thoracic,  and  not  in  the 
8th  cervical  nerve ;  Sherrington  (1892)  observed  the  same  on 
the  ape ;  and  Langley  (1897)  found  in  the  cat,  rabbit,  and  dog 
that  the  1st  thoracic  is  the  highest  nerve  capable  of  a  sym- 
pathetic reaction  on  excitation. 

Analogous  results  were  obtained  from  experiments  on  the 
lower  spinal  nerves.  Langley  and  Anderson  (1895)  obtained  no 
sympathetic  reaction  on  stimulating  the  spinal  nerves  below  the 
lowest  lumbar  nerve  that  has  a  white  ramus.  In  the  dog  this  is 
the  3rd  or  4th,  in  the  cat  the  4th  or  5th,  in  the  rabbit  the  5th,  and 
occasionally  the  6th,  in  man  probably  the  2nd  or  3rd  lumbar  nerve. 

The  results  obtained  by  the  degeneration  method  agree  fully 
with  the  excitatory  results.  Section  of  those  ventral  roots  that 
give  no  sympathetic  reaction  on  stimulation  causes  no  degeneration 
in  the  medullated  nerve-fibres  of  the  rami  communicantes.  This 
holds,  e.g.  in  Langley 's  demonstration  on  the  cat  (1896),  for  the 
ventral  roots  of  the  6th  and  7th  lumbar  nerves,  or  the  sacral  and 
coccygeal  nerves.  As  Langley  remarks,  this  is  the  more  remark- 
able seeing  that  in  the  cat  the  rami  which  apparently  originate 
in  the  6th  lumbar  nerve  may  contain  over  300  medullated  nerve- 
fibres.  It  follows  that  these  fibres  must  originate  in  the  higher 
spinal  nerves ;  most  of  them,  in  fact,  degenerate  after  transection 


vi  SYMPATHETIC  SYSTEM  367 

of  the  thoracic  and  higher  lumbar  nerves,  which,  when  stimulated, 
yield  a  sympathetic  reaction  (supra). 

Langley  concludes  that  the  .sympathetic  nerve-fibres  take  origin 
from  a  limited  region  of  the  cord,  and  reach  the  white  rami 
couinumicantes  as  medullated  fibres.  This  region  is  the  same  as 
that  from  which  the  nerves  to  the  trunk  emerge,  and  lies  between 
the  regions  from  which  the  nerves  for  the  fore-  and  hind-limbs 
originate,  though  overlapping  them  to  a  certain  extent.  The 
exact  limits  of  the  sympathetic  origin  vary  slightly  in  animals  of 
the  same  species. 

According  to  recent  researches  (Gaskell,  Mott,  Sherrington, 
Onuf  and  Collins,  Anderson,  Scaffidi,  Hering)  the  spinal  cells 
from  which  the  efferent  sympathetic  fibres  spring  lie  in  the  lateral 
horns,  and  contribute  the  so-called  intermedia- lateral  tract  of 
Lockhart  Clarke. 

If  we  follow  the  sympathetic  fibres  along  the  white  rami 
communicantes  in  the  peripheral  direction  we  meet  in  the  first 
place  the  lateral  or  vertebral  ganglia.  This  opens  up  the 
important  question  as  to  the  relations  between  the  fibres  of  spinal 
origin  and  the  elements  of  these  ganglia,  more  particularly  the 
ganglion  cells. 

If  the  sympathetic  fibres  behaved  like  the  other  efferent  fibres 
of  the  body,  they  would  pursue  an  uninterrupted  course  to  the 
organs  which  they  innervate.  We  shall,  however,  find  a  funda- 
mental difference  in  this  respect  between  the  two  classes  of  nerve- 
fibres,  as  was  first  established  by  Langley. 

The  two  methods  commonly  employed  to  determine  the  peri- 
pheral course  of  the  fibres — observation  of  the  effects  of  stimulation 
and  study  of  the  degenerations  after  division — are  not  suit- 
able for  this  purpose.  No  salient  qualitative  difference  has  been 
observed  in  the  effects  of  exciting  the  sympathetic  fibres  above 
and  below  the  ganglion.  And  the  degeneration  method,  however 
valuable  elsewhere,  is  not  applicable  to  the  sympathetic  system 
because  its  fibres  are  largely  non-medullated,  and  that  method  is 
based  on  the  degeneration  of  the  rnyelin  sheath  (Langley). 
Observation  of  a  nerve-fibre  that  was  medullated  as  far  as  the 
ganglion,  and  non-niedullated  afterwards,  might  lead  to  the  false 
induction  that  the  fibre  terminated  in  the  ganglion,  since  the 
process  of  degeneration  cannot  be  followed  beyond  that  point. 
Nevertheless  the  experiments  with  this  method  have  yielded 
results  that  agree  with  those  we  are  now  about  to  consider. 

Langley  discovered  and  elaborated  a  third  method,  which  is  of 
the  utmost  importance  in  determining  the  different  nerve  paths,  and 
the  constitution  of  the  sympathetic  system.  This  is  the  nicotine 
method,  based  on  the  property  that  nicotine  has  of  paralysing  the 
ganglion  cells  of  the  sympathetic  system,  or  more  probably  their 
synaptic  junctions,  while  leaving  the  fibres  unaffected. 


368  PHYSIOLOGY  CHAP. 

Hirschniann  (1863)  observed  that  nicotine  has  a  paralysing 
action  on  the  sympathetic  system ;  in  the  rabbit  the  intravenous 
injection  of  nicotine  abolished  the  effects  of  stimulating  the 
cervical  sympathetic.  But  the  methodical  application  of  this 
discovery  is  due  to  Langley  and  Dickinson  (1889-90).  They 
established  the  fact  that  stimulation  of  the  nerve  roots  that  give 
off  sympathetic  fibres  is  totally  ineffective  after  injecting  nicotine 
into  the  circulation  of  a  rabbit  or  cat.  From  this  they  concluded 
that  at  some  point  of  the  system  nicotine  blocks  the  transmission 
of  the  excitations  passing  towards  the  periphery.  But  when  the 
nerve-fibres  behind  a  ganglion  (i.e.  peripheral  to  it)  are  excited,  all 
the  effects  observed  previous  to  the  injection  of  nicotine  can  be 
obtained,  showing  that  the  point  attacked  by  the  poison  lies  within 
the  ganglion.  This  conclusion  is  confirmed  by  the  fact  that  the 
local  application  of  a  dilute  solution  of  nicotine  (about  0'5  per 
cent)  to  the  ganglia  produces  the  same  effect. 

The  importance  of  this  method  may  be  illustrated  by  one  of 
Langley's  experiments.  Stimulation  of  the  sympathetic  immedi- 
ately below  the  stellate  ganglion  produces,  as  is  well  known, 
contraction  of  the  blood-vessels  as  well  as  other  changes  in  the 
fore -limb  and  shoulder,  and  vaso-constriction,  dilatation  of  the 
pupil,  and  other  effects  in  the  head.  After  the  application  of  a 
dilute  solution  of  nicotine  to  the  ganglion,  stimulation  of  the  sym- 
pathetic below  it  produces  no  effect  in  the  fore -limb  or  shoulder, 
but  the  usual  effects  in  the  head,  while  the  effects  of  stimulation 
on  this  side  of  the  ganglion  are  unaltered.  This  shows  that  the 
sympathetic  fibres  that  supply  the  fore-limb  are  connected  with 
the  cells  of  this  ganglion,  while  those  that  supply  the  head  pass 
through  the  ganglion  uninterrupted.  On  the  other  hand,  if  a 
dilute  solution  of  nicotine  is  applied  to  the  superior  cervical 
ganglion  and  its  accessory  ganglion,  stimulation  of  the  sympathetic 
below  the  stellate  ganglion  produces  no  effects  in  the  head ;  all  the 
fibres  that  pass  through  the  stellate  ganglion  to  supply  the  head 
must  therefore  be  connected  with  the  cells  of  the  superior  cervical 
ganglion  or  its  accessory  ganglion. 

Langley  made  similar  experiments  on  other  portions  of  the  sym- 
pathetic system,  and  also  on  the  related  bulbar  and  sacral  nerves, 
and  came  to  the  general  conclusion  that  every  efferent  fibre  of  the 
sympathetic  system  which  runs  from  the  cord  in  a  white  ranius 
communicans  ends  without  exception  in  a  vertebral  (lateral)  or 
pre-vertebral  (collateral)  ganglion,  where  it  enters  into  direct 
relations  with  a  ganglion  cell,  which,  by  its  non-medullated 
process,  transmits  the  impulse  which  it  receives  from  the  medullated 
fibre  towards  the  periphery. 

Langley  distinguishes  the  nerve-fibres  that  end  in  the  ganglion, 
i.e.  2)re-ganglionic,  from  those  which  originate  in  the  cells  of  the 
ganglion  itself,  or  post-ganylionic.  Von  Kolliker  preferred  the 


vi  SYMPATHETIC  SYSTEM  369 

names  of  pre-cellnlai-  and  post-cellular  fibres,  or  called  them  viscero- 
motor  fibres  of  the  first  and  second  order.  Langley  objected  that 
"  a  pre-ganglionic  fibre  is  post-cellular,  in  relation  to  the  nerve- 
cell  from  which  it  arises  " ;  while  the  second  term  is  too  limited, 
as  it  does  not  include  the  secretory  fibres.  We  therefore  adopt 
Langley's  nomenclature. 

The  nicotine  method  is  not  conclusive  since  the  action  of 
nicotine  differs  in  different  cases.  In  certain  animals,  as  the  dog, 
it  has  hardly  any  effect ;  in  different  animals  of  the  same  species, 
again,  or  in  different  sympathetic  regions  in  the  same  animal,  it 
acts  differently.  The  splanchnic  system,  for  instance,  is  more 
resistent  to  its  action  than  the  cervical  sympathetic.  The  paralytic 
phenomena  are  usually  preceded  by  phenomena  of  excitation.  In 
birds  nicotine  excites  and  causes  erection  of  the  feathers  without 
paralysing  the  ganglia. 

The  results  of  the  nicotine  methods  were  substantially  confirmed 
by  Langendorff  (1891-92),  who  saw  that  in  the  period  immediately 
preceding  the  animal's  death  stimulation  of  the  fibres  that  run  to 
the  superior  cervical  ganglion  and  the  ciliary  ganglion  fails  to 
produce  any  effect  long  before  the  nerves  that  emerge  from  these 
ganglia  become  inexcitable. 

To  sum  up,  we  may  conclude  that  the  efferent  sympathetic 
fibres  issuing  from  the  cord  never — like  the  motor  fibres  to  the 
skeletal  muscles — run  uninterruptedly  to  the  organs  innervated ; 
they  terminate,  after  a  longer  or  shorter  course,  in  a  ganglion. 
Some  end  in  the  first  ganglion  they  encounter ;  others,  on  the 
contrary,  pass  through  several  ganglia  before  reaching  their 
terminal  station — on  their  way  they  may  send  collaterals  to  a 
great  number  of  different  cells.  There  is  only  one  break  in  the 
efferent  sympathetic  path,  since  the  post-ganglionic  fibres,  according 
to  Langley,  always  run  without  further  interruption  to  the  peri- 
pheral organs  which  they  supply. 

The  great  majority  of  the  post-ganglionic  fibres  from  the 
ganglia  of  the  lateral  chain  run  back  in  the  grey  rami  to  the 
corresponding  spinal  nerves,  or  to  the  next  higher  or  lower  spinal 
nerve,  to  innervate  the  peripheral  organs  served  by  the  sympathetic, 
in  the  regions  to  which  these  spinal  nerves  are  distributed  (skin 
system).  Where  the  spinal  nerves  innervate  segnaentally  distinct 
regions,  for  instance  in  the  trunk  and  neck,  the  skin  fields 
supplied  by  the  grey  rami  do  not  overlap  at  all,  or  only  by  about 
1-2  mm.  But  in  regions  in  which  the  spinal  nerves  form  plexuses, 
the  areas  innervated  by  the  various  grey  rami  do  overlap  to  a  large 
extent,  as  can  readily  be  demonstrated  by  producing  sweat 
secretion  of  a  cat's  pad  by  stimulating  the  grey  rami  of  different 
spinal  nerves. 

According  to  Langley,  the  stellate  and  the  superior  cervical 
ganglion  not  only  give  off  post-ganglionic  fibres  to  the  corre- 

VOL.  in  2  B 


370  PHYSIOLOGY  CHAP. 

spending  spinal  nerves,  \\hich  then  pass  to  the  skin,  but  also  send 
fibres  to  the  viscera  (heart,  lungs  and  their  blood-vessels,  salivary 
glands).  These  two  ganglia  therefore  give  oft"  visceral  as  well  as 
cutaneous  fibres. 

The  prevertebral  or  peripheral  ganglia  supply  the  viscera 
exclusively,  and  send  no  fibres  to  the  spinal  nerves  (Langley).  The 
inferior  cervical  ganglion  sends  fibres  to  the  heart :  the  different 
ganglia  oi'  the  solar  plexus  serve  the  abdominal  viscera ;  the 
inferior  mesenteric  ganglion  sends  fibres  to  the  lower  part  of  the 
gut  and  the  urogenital  system. 

Langley  brings  out  the  striking  fact  that  the  ganglia  of  the 
sympathetic  system  nowhere  have  a  special  arrangement  according 
to  their  function ;  the  cells  are  not  divided  into  groups  with 
special  functions,  viz.  for  the  contraction  or  the  relaxation  of  the 
unstriated  muscles  of  the  gut  or  arteries.  The  ganglia  are  rather 
cell  groups,  whence  the  nerves  run  out  to  special  regions  to  inner- 
vate the  whole  of  the  organs  controlled  by  the  sympathetic  in 
that  region  indiscriminately. 

Fig.  197  illustrates  diagrammatically  the  origin,  course,  and 
peripheral  distribution  of  the  fibres  of  the  sympathetic  system. 

IV.  Our  present  knowledge  of  the  course  and  functional  signi- 
ficance of  the  afferent  fibres  of  the  sympathetic  system  is  compara- 
tively scanty  and  incomplete.  Every  one  knows  that  the  visceral 
organs  are  sensitive,  as  violent  stimuli  can  evoke  pain,  but  under 
normal  conditions,  the  movements  of  the  gut, of  the  iris,  the  secretory 
processes,  etc.,  do  not  affect  consciousness, — in  other  words  the 
afferent  impulses  that  ebb  and  now  in  the  sympathetic  system  do 
not  usually  pass  the  threshold  of  consciousness.  That  such  im- 
pulses exist  may  safely  be  affirmed  on  the  strength  of  the  facts 
before  us,  for  histology  has  demonstrated  the  presence  of  special 
sensory  end -organs  in  the  viscera,  particiilarly  the  so-called 
Pacinian  corpuscles,  which  abound,  for  instance,  in  the  cat's 
mesentery. 

What,  then,  do  we  know  of  the  origin  and  course  of  the 
afferent  sympathetic  paths,  and  their  relations  to  the  sympathetic 
ganglia  ?  Do  all  organs  supplied  with  efferent  sympathetic  fibres 
possess  afferent  fibres  as  well  ?  Do  the  afferent  sympathetic  fibres, 
like  the  efferent,  undergo  a  break  in  their  passage  through  the 
ganglia  ?  The  answers  to  these  important  questions,  which  are 
essential  for  a  clear  understanding  of  the  complex  structure  of  the 
sympathetic  system,  will  be  found  in  Langley 's  review  of  the 
experimental  work  on  this  subject  (1903). 

In  this  connection  it  is  useful  to  separate  the  sympathetic 
system,  in  the  narrower  sense,  from  the  two  other  functionally 
related  autonomic  systems,  the  bulbar  and  the  sacral.  While 
these  two  supply  afferent  fibres  to  all  the  peripheral  organs  to 
which  they  send  efferent  fibres,  the  same  only  holds  for  the 


VI 


SYMPATHETIC  SYSTEM 


371 


i  G  vert. 


G  so/ 


-V-£ 


FIG.  107.  —Diagram  of  thf  IIPI  \-o\is  elements  wliii-h  make  up  the  sympathetic  or  splanchnic  sy^teni. 
(  Ba-liuiii.)  ];.  1; .  >pinal  con  I  :  It. 11'.,  ilursal  rool  :  •  H"..  ventral  root  ;  *p.\'.,  spinal  nerve;  r.o., 
white  raiuus  conimunicans  :  /.•:..  ,,'rey  ranius  eommunicans  ;  f,'..sV.,  lateral  chain  ;  G.vert.,  ganglia 
»t'  lateral  chain  (vertebral  ganglia) ;  '/..-"/.,  si  il.-n-  .^anxlioii :  p.  G.,  peripheral  ganglia  (t.-iminal) ; 
H.nt'-a.inf.,  inferior  mesfiitfi  ic  u m.^lion  ;  D.  intestun'  :  Ji  lilailder.  The  l^it  Md.-nt  t  he  figure 
shows  the  peripheral  cutaneous  system  (.4f.,  arterial  walK  ;  Ar.,  erectoi  mu^rl<-s  of  hairs; 
<//•..  gland  cells);  the  ri.u'lit  .irives  tin-  peripheral  splanchnic-  system  (.-If.,  arterial  walls;  dr., 
gland  cells;  P,  Pacinian  corpuscles).  The  afferent  paths  and  cells  are  black  ;  the  efferent  pre- 
ganglionic(intra-central).  bin*-  ;  tin-  ••M'-i'Mit  post-ganglionic  paths  and  cells,  red. 

2  B  1 


372  PHYSIOLOGY  CHAP. 

sympathetic  to  a  limited  extent,  viz.  for  the  visceral  organs.  The 
remainder  receive  their  afferent  fibres  direct  from  the  spinal  nerves 
and  not  from  the  sympathetic  by  the  grey  rarni.  After  section  of 
the  grey  rami  Langley  found  that  only  one  or  two  fibres,  which 
apparently  terminated  close  to  the  vertebral  column,  degenerated 
in  the  central  end,  and  stimulation  of  the  central  end  evoked  no 
reflex.  So  that  if  the  walls  of  the  blood-vessels  in  the  skin  and 
limbs,  or  the  plain  muscle  and  cells,  or  the  ducts  of  the  glands 
receive  afferent  fibres,  these  must  run  in  the  spinal  nerves  from 
the  periphery  to  the  cord,  without  passing  through  the  ganglion 
chain  of  the  sympathetic.  The  same  is  true  of  the  head  also,  in 
which  the  sympathetic  sends  its  efferent  nerves  into  the  province 
of  the  bulbar  (autouomic)  nerves ;  and  perhaps  also  for  the  lower 
part  of  the  gut,  where  in  the  same  way  it  enters  the  region  inner- 
vated by  the  sacral  system. 

The  afferent  innervation  of  the  viscera  is  quite  different.  The 
majority  of  the  afferent  fibres  of  the  thoracic  organs,  as  well  as  of 
the  stomach,  intestine,  mesentery,  etc.,  electrical  stimulation  of 
which  causes  pain,  run  in  the  sympathetic  nerve  trunks  and  not 
in  the  vagus.  It  has  long  been  known  that  excitation  of  the 
vagus  below  the  diaphragm  produces  little  or  no  pain  in  animals. 

The  afferent  sympathetic  fibres  come  from  the  same  spinal 
nerves  as  the  efferent  fibres,  that  is,  in  man  from  the  first  thoracic 
to  the  second  or  third  lumbar.  Like  the  efferent  fibres,  they  pass 
through  the  white  rami  communicantes.  Their  peripheral  course 
is,  however,  quite  different,  for  while  the  efferent  paths  are  inter- 
rupted in  their  passage  through  the  ganglion,  so  that  a  pre-  and  a 
post-ganglionic  part  can  be  distinguished  in  them,  this,  so  far  as 
we  know,  is  not  the  case  for  the  afferent  neurones.  The  latter, 
both  in  their  mode  of  origin  and  their  subsequent  peripheral 
course,  behave  like  the  rest  of  the  afferent  neurones  in  the  body, 
ascending  as  medullated  fibres  to  the  intervertebral  ganglia,  where 
they  have  their  trophic  centre,  and  from  which  they  run  in  the 
dorsal  roots  to  the  cord. 

There  is  obviously  no  reason  to  suppose  that  the  afferent  fibres 
belonging  to  the  cutaneous  organs,  which  run  with  the  spinal 
nerves,  without  entering  the  ganglia  of  the  sympathetic  chain, 
behave  differently  from  other  afferent  fibres.  And  we  have  direct 
experimental  evidence  that  the  sympathetic  afferents  which 
supply  the  visceral  organs  for  the  most  part  have  their  trophic 
centre  in  the  intervertebral  ganglia.  The  proof  is  that 
section  of  the  mixed  spinal  nerves,  immediately  below  the 
spinal  ganglion,  causes  all  or  nearly  all  the  fibres  of  the  white 
rami  to  degenerate,  while,  on  the  contrary,  section  of  the  lateral 
strand  of  the  sympathetic  or  of  the  two  splanchnics  produces  no 
degeneration  of  the  fibres  of  the  white  rami. 

The  same  is  true  of  the  sacral  nerves.     In  the  cat,  for  instance, 


vi  SYMPATHETIC  SYSTEM  373 

the  pelvic  nerve  contains  upwards  of  1000  afferent  fibres,  and  after 
cutting  the  sacral  roots,  Langloy  ami  Anderson  found  that  only 
about  half  a  dozen  of  these  fibres  were  not  degenerated  in  the 
nerve.  Langley  concludes  that  of  the  thousands  of  afferent  nerve- 
h'bres  running  from  the  viscera  to  the  cord,  not  more  than  a  dozen 
or  so  have  their  trophic  centres  in  the  peripheral  ganglia,  these  in 
all  probability  being  either  post-gauglionic,  medullated,  or  recurrent 
afferent  fibres. 

V.  Having  discussed  the  origin  and  course  of  the  afferent  and 
efferent  fibres  of  the  sympathetic  system,  and  acquired  a  general 
idea  of  its  structure,  there  remains  the  most  important  question  of 
all,  the  significance  and  functions  of  the  sympathetic  ganglia. 

Are  we  to  regard  these  masses  of  ganglion  cells  as  portions  of 
the  cerebrospinal  axis  which  have  been  displaced  to  the  periphery, 
but  are  still   endowed  with  the  functions  of  the  centres  ?     The 
earlier  anatomists  seemed  to  incline  to  this  view  when  they  gave 
the  name  of  cerebrum  dbdominale  to  the  solar  ganglion.     We  have 
learned   that   the  fundamental  property   of  the  central    nervous  , 
system  lies  in  its  capacity  for  subserving  reflex  acts,  so  in  order  to  ! 
decide  this  question  we  must  ascertain  whether  the  ganglia  of  the 
sympathetic  system  are  capable  of  subserving  reflexes. 

From  the  above  conclusions  on  the  course  of  the  afferent  fibres 
of  the  sympathetic,  any  such  possibility  must  a  priori  be  excluded, 
seeing  that  all  or  nearly  all  the  afferent  paths  run  without  inter- 
ruption to  the  spinal  ganglia,  and  never  enter  into  direct  relations 
with  the  sympathetic  ganglia.  The  excitations  which  they  trans- 
mit must  therefore  reach  the  centres  of  the  cerebrospinal  axis 
before  they  can  be  reflected  again  to  the  periphery. 

This  logical  conclusion  is  apparently  contradicted  by  a  series 
of  observations  which  seem  to  show  that  under  certain  conditions 
the  spinal  ganglia  may  function  as  true  reflex  centres.  Cl. 
Bernard  (18G4)  was  the  first  to  describe  these  phenomena.  After 
dividing  the  lingual  nerve  above  the  point  at  which  it  emerges 
from  the  chorda  tympani,  and  thus  cutting  off  all  connection  with 
the  central  nervous  system,  he  artificially  stimulated  the  peripheral 
end  of  the  lingual  nerve,  and  saw  an  abundant  secretion  from  the 
submaxillary  gland.  We  have  already  recorded  the  experiments 
of  Sokowin  who  observed  that  after  cutting  off  all  direct  com- 
munication with  the  spinal  cord,  stimulation  of  the  central  end 
of  the  hypogastric  nerve  induces  contraction  of  the  bladder  on 
the  opposite  side.  This  observation,  subsequently  confirmed  by 
Nussbaum,  Nawrocki  and  Skabitschewski,  and  others,  was  inter- 
preted to  imply  that  the  inferior  mesenteric  ganglion  was  able  to 
function  as  a  reflex  centre. 

Other  similar  facts  were  observed  in  the  sympathetic  nervous 
system  by  Langley  and  Anderson.  They  saw  on  repeating  the 
experiment  of  Sokowin  that  stimulation  of  the  hypogastric  also 

•2  B  2 


374  PHYSIOLOGY  CHAP. 

produced  contraction  of  the  internal  anal  sphincters,  ischemia  of 
the  rectal  mucosa,  slight  pallor  of  the  cervix  and  body  of  the 
uterus  on  the  opposite  side,  etc.  Laugley  (assisted  partly  by 
Anderson)  obtained  similar  results  for  the  pilomotor  muscles  and 
the  cutaneous  blood-vessels  in  the  thoracic  and  lumbar  regions. 

But,  according  to  Laugley,  none  of  these  reactions,  in  which 
excitation  of  the  central  end  of  a  sympathetic  trunk  after 
separation  from  the  higher  centres  causes  motor  or  secretory 
effects,  are  true  reflexes.  His  arguments  and  interpretation  will 
be  better  understood  by  giving  a  specific  example  :— 

If  the  lateral  strand  of  the  sympathetic  be  cut  in  the  cat 
immediately  above  the  7th  lumbar  ganglion,  and  the  central 
(cranial)  end  stimulated,  erection  of  the  hairs  with  contraction  of 
the  blood-vessels  will  be  seen  in  the  cutaneous  regions  innervated 
by  the  4th  and  5th  lumbar  roots.  The  same  effects  may  be 
obtained  many  days  after,  when  sufficient  time  has  elapsed  for  the 
degeneration  of  afferent  nerve-fibres  with  trophic  centres  below  the 
level  of  section.  It  follows  that  the  excitation  in  this  case  is  not 
conducted  by  fibres  whose  trophic  centres  lie  in  the  lower  portion 
of  the  sympathetic.  If  the  nerve -roots  of  the  4th  or  5th 
lumbar  ganglion  are  now  cut  the  reaction  described  disappears 
after  five  days.  We  must,  therefore,  conclude  that  the  excitation 
was  transmitted  by  pre-ganglionic  efferent  fibres. 

This  striking  fact  that  the  supposed  reflex  ceases  on  degenera- 
tion of  the  pre-ganglionic  fibres  is,  according  to  Langley,  common 
to  all  so-called  "  sympathetic  reflexes  "  hitherto  described. 

The  only  possible  explanation  he  can  find  is  that  each  pre- 
ganglionic  fibre  divides  into  several  collaterals,  and  sends  branches 
to  different  ganglia.  Stimulation  of  the  central  end  of  one  of 
these  fibres  causes  an  excitation  that  is  at  first  propagated  back- 
wards along  the  cut  fibre,  and  then  to  another  twig,  until  it 
reaches  the  ganglion  which  gives  origin  to  the  post-ganglionic 
fibres  that  evoke  the  reaction.  In  other  words,  this  is  a  similar 
process  to  that  described  by  Klihne  in  his  experiments  on  the 
conduction  of  motor  nerve  in  both  directions.  Langley  has 
proposed  to  call  this  special  phenomenon  by  the  name  of  pseudo- 
reflexes  or  pre-ganglionic  axon  reflexes.  Fig.  198  is  a  diagram 
of  the  course  of  the  excitation  as  compared  with  a  true  reflex. 
Langley  utilised  these  pseudo- reflexes  for  the  purpose  of  ex- 
perimentally determining  which  pre-ganglionic  fibres  are  connected 
with  different  ganglia. 

He  concludes  :  "  In  my  opinion  none  of  the  '  apparent '  reflexes 
of  the  autonomic  ganglia  depend  on  a  reflex  mechanism  similar  to 
that  which  subserves  reflexes  in  which  the  central  nervous  system 
is  concerned,  as  in  no  case  is  an  afferent  fibre  concerned  in  the 
process." l 

1  Langley,  Ergelnissc  dcr  Physiologic,  1903,  Jahrgang  ii.  Abteil.  ii.  p.  859. 


VI 


SYMPATHETIC  SYSTEM 


375 


Another  argument  adduced  by  Schultz  against  the  view  that 
the  sympathetic  ganglia  act  as  true  reflex  centres  is  that  stimula- 
tion of  both  post-ganglionic  and  pre-ganglionic  fibres  has  the  same 
effect  ;  and  that  no  summation  can  be  seen  from  the  latter,  such  as 
is  observed  in  the  central  nervous  system. 

Intimately  connected  with  the  functional  importance  of  the 
sympathetic  ganglia  is  the  question  whether,  after  separation  from 
the  cerebrospinal  axis,  they  are  capable  of  sending  tonic  impulses 
to  the  peripheral  organs  which  they  innervate.  This  point,  too, 
has  received  various  answers. 

The  simplest  method  of  solving  it  evidently  consists  in 
severing  the  pre-ganglionic  fibres  on  one  side  of  the  body,  and  the 
post-ganglionic  on  the  other,  or  in  extirpating  the  whole  ganglion. 
As  the  results  can  be  compared  on  the  two  sides  of  the  body  it 
should  be  easy  to  deduce  the  influence  exercised  by  the  ganglia 


& 


FIG.  198. — Mechanism  of  action  in  pseudn-,  or  pre-ganglionic  axonal,  and  true-  reflexes.     (Langley.) 
A,  true  reflex ;  B,  pseudo-reflex  ;  .C,  common  diagram  for  A  and  H. 

alone,  apart  from  the  cerebrospinal  axis.  The  cervical  sympathetic, 
and  the  superior  cervical  ganglion  which  has  a  dilatator  action  on 
the  pupil,  are  well  adapted  for  this  experiment,  but  the  results 
obtained  by  various  authors  (Budge,  Braunstein,  Langendorff, 
Kowalewsky,  Schultz)  disagree.  According  to  the  three  first,  the 
pupil  is  contracted  for  some  hours  to  one  or  two  days  after  the  ex- 
tirpation of  the  cervical  ganglion,  which  implies  that  the  ganglion 
really  has  a  tonic  dilatator  action,  on  suppression  of  which  the 
pupil  contracts.  But  when  the  influence  of  the  ganglion  is 
removed  without  irritation  no  difference  is  observed  in  the  width 
of  the  pupils. 

Similar  researches  have  been  made  on  the  ciliary  ganglion. 
This  ganglion  normally  exerts  a  tonic  action  on  the  sphincter 
papillae,  which  is  maintained  reflexly  by  the  light  that  impinges 
on  the  retina,  and  excites  the  ganglion  by  way  of  the  optic 
nerve  and  mesencephalon.  Section  of  both  optic  nerves  in  an 
animal  causes  dilatation  of  the  pupil ;  according  to  Schultz  and 
Lewandowsky  the  ciliary  ganglion  has  no  influence  on  this,  for 


376  PHYSIOLOGY  CHAP. 

the  pupil  is  not  further  dilated  if  the  nerves  to  the  sphincter  are 
cut  on  one  side  or  the  other  of  the  ganglion. 

Accordingly  it  is  not  possible  to  demonstrate  that  either  the 
superior  cervical  ganglion  or  the  ciliary  ganglion  have  any 
constant  tonic  influence.  Still  less  can  this  be  proved,  as  Langley 
says,  for  the  other  peripheral  ganglia  of  the  sympathetic.  Nor 
is  this  surprising  seeing  that  all  the  known  tonic  influences 
exerted  by  the  central  nervous  system  invariably  take  place 
reflex ly,  while  the  sympathetic  ganglia  are  unable,  as  we  have 
seen,  to  subserve  reflexes  independently  of  the  cerebrospinal  axis. 

As  the  sympathetic  ganglia  are  therefore  incapable  of  suit- 
serving  reflex  acts  and  of  maintaining  tone  apart  from  the  central 
nervous  system,  what  is  their  function  ?  It  must  be  confessed 
that  in  the  actual  state  of  knowledge  a  complete  answer  is  not 
possible.  That  their  function  is  of  importance  is  beyond  doubt, 
because  the  animal  economy  has  no  superfluous  or  useless  elements  ; 
and  observations  are  not  wanting  to  show  that  the  removal  of  a 
ganglion  is  by  no  means  without  injurious  effects.  Thus,  if  the 
cervical  sympathetic  is  cut  on  the  one  side,  and  the  superior 
cervical  ganglion  is  removed  on  the  other,  the  pupil  on  this  side 
gradually  becomes  larger  than  that  of  the  other  side,  (Langendorff's 
paradoxical  dilatation  of  the  pupil).  There  is  no  satisfactory 
explanation  of  this  phenomenon,  but  it  shows  the  influence  of  the 
ganglion. 

Langley  holds  that  the  sympathetic  ganglia  are  centres  of  re- 
inforcement for  the  central  nervous  system,  and  if  separated  from 
the  latter  lose  their  capacity  for  carrying  out  their  functions.  But 
it  must  be  remembered  that  the  peripheral  ganglia  are  capable  of 
surviving  for  years  after  their  separation  from  the  cerebrospinal 
axis,  and  of  reacting  to  poisons,  or  to  internal  secretions  of  the  body, 
as  those  coming  from  the  glandular  substance  of  the  paraganglia, 
which  (see  Vol.  II.  Chap.  I.)  seem  from  recent  researches  to  have  a 
special  affinity  for  these  sympathetic  nerve-cells. 

Schultz  too  suggested  that  the  ganglia  may  be  relays,  in  which 
excitations  coining  from  the  higher  centres  by  way  of  the  pre- 
ganglionic  fibres  are  reinforced. 

In  addition  to  this  vague  and  far  from  well-grounded  hypothesis 
that  the  peripheral  ganglia  of  the  sympathetic  are  relays  for  re- 
inforcement, another  theory  as  to  their  function,  based  on  their 
special  structural  relations,  has  been  put  forward.  Bidder  and 
Volkmann  (1842)  pointed  out  that  the  number  of  the  nerve-fibres 
issuing  from  a  ganglion  (Langley 's  post-ganglionic  fibres)  exceeds 
the  number  of  fibres  entering  it  (pre-ganglionic  fibres) ;  this  also 
agrees  with  the  observation  referred  to  above,  that  one  pre-ganglionic 
fibre  may  form  relations  with  a  number  of  peripheral  ganglion 
cells.  These  facts  suggest  that  one  function  of  the  ganglia  may  be 
to  enlarge  the  field  of  distribution  of  the  impulses  carried  towards 


vi  SYMPATHETIC  SYSTEM  377 

the  periphery  by  the  pre-ganglionic  fibres,  since  by  the  ganglia 
intercalated  along  the  course  of  these  fibres  the  excitation  of  a  lew 
pre-ganglionic  may  be  transmitted  to  a  large  number  of  post- 
ganglionic  fibres. 

Hofmann  (1904)  held  that  the  ganglia  of  the  sympathetic  may 
be  co-ordinating  centres  in  the  course  of  the  efferent  paths.  He 
tried  to  support  this  view  by  the  fact  that  stimulation  of  the  1st 
or  2nd  thoracic  nerve  produces  a  general  dilatation  of  the  whole 
pupil,  while  excitation  of  the  separate  ciliary  nerves,  on  the  con- 
trary, produces  a  partial  dilatation  of  certain  sectors  of  the  pupil. 
The  pre-ganglionic  fibres  of  each  thoracic  nerve  must  therefore 
influence  the  whole  iris,  while  the  post-ganglionic  fibres  of  the 
long  ciliary  nerves  can  only  innervate  a  portion  of  its  musculature. 
From  these  observations  Hofmann  concluded  that  the  ganglion 
cells  whence  the  post-ganglionic  fibres  issue  are  united  by  com- 
missural  fibres  so  as  to  form  a  true  co-ordinating  centre. 

Langley,  however,  who  had  concluded  against  these  inter- 
gangliar  commissural  fibres,  obtained  opposite  results  on  repeating 
Hofmann's  experiments.  He  found  that  stimulation  of  the  separate 
small  bundles  which  make  up  the  three  thoracic  nerves  produced 
contraction  of  only  one  part  of  the  dilatator  pupillae.  He  further 
saw  that  the  effects  of  stimulating  the  post-ganglionic  fibres  as 
they  leave  the  ganglion  are  practically  identical  with  those 
obtained  from  stimulation  of  separate  bundles  of  the  pre-ganglionic 
fibres  before  they  enter  the  ganglion.  In  both  cases  excitation  of 
a  few  fibres  suffices  to  produce  maximal  dilatation  of  the  whole 
pupil.  But  if  too  few  fibres  are  excited,  then  in  both  cases  either 
a  weak  general  dilatation,  or  a  dilatation  of  part  only  of  the  pupil 
results.  From  this  he  concluded  that  the  spread  of  the  pre- 
ganglionic  excitations  is  due  not  to  co-ordination  in  the  ganglion, 
but  to  the  fact  that  the  post-ganglionic  fibres  anastomose  and 
mingle  in  the  preterminal  plexus. 

On  comparing  the  functions  of  the  sympathetic  ganglia  with 
those  of  any  part  of  the  central  nervous  system  it  seems  from 
these  facts  that  they  are  most  comparable  with  the  functions  of 
the  motor  ganglion  cells  of  the  ventral  horn  of  the  cord.  The 
motor  cells  of  the  ventral  horn  have  also  no  intracommissural 
fil  ires :  their  sole  task  is  to  transmit  the  impulses  that  reach  them 
from  the  central  sensory  elements  by  their  efferent  processes, 
which,  like  the  post-ganglionic  fibres  of  the  sympathetic,  run 
uninterruptedly  to  the  peripheral  organs  which  they  innervate. 
The  pre-ganglionic  fibres  are  comparable  with  the  intracentral 
association  fibres,  which  bring  the  various  centres  into  inter- 
communication, e.g.  the  long  pyramidal,  or  short  intraspinal 
paths,  which  unite  the  afferent  with  the  efferent  mechanisms,  and 
like  the  pre-ganglionic  fibres  enter  into  relation  by  means  of 
collaterals  with  a  number  of  motor  cells  in  the  ventral  horn. 


378  PHYSIOLOGY  CHAP. 

Comparative  physiology  gives  instances  of  peripheral  motor 
ganglia  which  are  quite  analogous  to  those  of  the  sympathetic 
system,  e.g.  the  stellate  ganglion  of  the  Cephalopoda  (Baglioni, 
1903). 

This  short  chapter  on  the  functions  of  the  sympathetic  nervous 
system  must  not  be  concluded  without  pointing  out  that  all  the 
arguments  which  Langley  and  other  experimental  physiologists 
bring  forward  to  show  that  the  peripheral  ganglia  of  the  sym- 
pathetic are  incapable  of  functioning  as  true  reflex  centres  apply 
only  to  the  vertebral  or  prevertebral  ganglia,  and  cannot  be 
extended  to  the  still  more  peripheral  nervous  system,  which,  in 
the  form  of  ya.ngliated  plexuses,  is  intimately  related  to  the 
muscular  elements,  as  fche  intrinsic  ganglion  system  of  the  heart 
and  blood-vessels,  Auerbach's  plexus  in  the  gastro-intestinal  walls, 
etc.  In  Chaps.  IX.  and  X.  Vol.  I.,  and  Chap.  IV.  Vol.  II.,  we 
reviewed  the  experimental  facts  from  which  it  may  be  concluded 
that  these  nerve  organs  are  capable,  even  when  separated  from 
the  cerebrospinal  axis,  of  provoking  true  reflex  acts,  the  so-called 
periplieral  reflexes. 

Unless  we  admit  these  peripheral  reflexes  and  recognise  their 
great  importance,  it  is  impossible  to  explain  the  astonishing 
results  observed  by  Goltz  and  Ewald  after  ablation  of  the  spinal 
cord  in  dogs,  which  were  discussed  in  the  concluding  paragraphs 
of  the  last  chapter  (pp.  352  et  seq.'). 


BIBLIOGRAPHY 

MAYER,  S.     Hermann's  Handbuch  der  Physiologic,  vol.  ii.     Leipzig,  1879. 

GASKELL.     Journ.  of  Physiol.,  vol.  vii.,  1886. 

v.  Kc'JLLiKEii.     Handbuch  der  Gewebelehre,  vol.  ii.     Leipzig,  1896. 

BOTTAZZI,  F.     Riv.  di  patol.  nervosa  e  mentalc,  1897. 

LANGLEY.     Schafer's  Textbook  of  Physiology,  vol.  ii.,  1900. 

LANGLEY.     Ergebnisse  des  Physiol.,  ii.,  Part  ii. ,  1904. 

LANGLEY.     Brain,  vol.  xxvi.,  1903. 

LANGLEY.     Journ.  of  Physiology,  vols.  xxx.  and  xxxi.,  1905. 

LEWANDOWSKY.     Die  Funktionen  des  zentralen  Nervensystems.     Jena,  1907. 

SCHULTZ,  P.     Nagel's  Handbuch  der  Physiologic,  vol.  iv.,  1909. 

These  works  contain  numerous  other  references. 

Recent  English  Literature  :— 

LANGLEY  and  OHBELLI.  Observations  on  the  Sympathetic  and  Sacral  Autonomic 
Systems  of  the  Frog.  Journ.  of  Physiol.,  1910,  xli.  450. 

LANGLEY  and  ORBELLI.  The  Sympathetic  Innervation  of  the  Viscera.  Journ.  of 
Physiol.,  1910,  xl.  p.  Ixii. 

ANDERSON.  Paralysis  of  Involuntary  Muscle  with  Special  Reference  to  "  Para- 
doxical Contraction."  Journ.  of  Physiol.,  1903,  xxx.  290. 

LANGLEY  and  MAGNUS.  Movements  of  the  Intestine  before  and  after  Degenerative 
Section  of  the  Mesenteric  Nerves.  Journ.  of  Physiol.,  1905-6,  xxxiii.  34. 

ELLIOTT.  The  Innervation  of  the  Bladder  and  Urethra.  Journ.  of  Physiol., 
1906-7,  xxxv.  367. 


vi  SYMPATHETIC  SYSTEM  379 

ELLIOTT.  Imiervation  of  the  Adrenal  Glands.  Journ.  of  Physiol.,  1913,  xlvi. 
285. 

ELLIOTT.  Control  of  the  Suprarenal  Glands  by  the  Splanchnic  Nerves.  Journ. 
of  Physiol.,  1912,  xliv.  374. 

BAKKINCTOX.  The  Nervous  Mechanism  of  Micturition.  Quart.  Journ.  of  Experi- 
ment, Physiol.,  1914,  viii.  33. 

BRUCE.      Vasodilator   Axon   Reflexes.      Quart.   Journ.    of  Experiment.    Physiol., 

1913,  vi.  339. 

EDWARDS.  A  Study  of  the  Anatomy  and  the  Vasomotor  Phenomena  of  the 
Sympathetic  Nervous  System  of  the  Turtle.  Amer.  Journ.  of  Physiol., 

1914,  xxxiii.  229. 


CHAPTER   VII 

THE   MEDULLA   OBLONGATA    AND    CEREBRAL   NERVES 

CONTENTS. — 1.  General  anatomy  of  the  brain  :  the  medulla  oblongata.  2.  Motor 
functions  of  hypoglossus  nerve.  3.  Vago  -  accessory  group  ;  motor  functions 
of  eleventh  nerve.  4.  Different  functions  of  vagus  nerve.  5.  The  glosso- 
pliaryngeal  exclusively  a  nerve  of  taste.  6.  Functions  of  the  facial  and  acoustic 
nerves.  7.  Functions  of  the  oculoineter  and  trigeminal  nerves.  8.  The  medulla 
oblongata  as  a  motor  centre.  9.  The  medulla  oblongata  as  the  central  organ 
of  locomotion  and  posture.  10.  The  medulla  oblongata  as  a  sensory  centre. 
Bibliography. 

IN  the  lower  vertebrates  the  spinal  cord  alone  suffices,  as  we  have 
seen,  for  the  regulation  of  all  the  functions  of  animal  life.  The 
lowest  vertebrate,  Amphioxus,  possesses  only  a  spinal  cord  divided 
into  rnetameres,  the  higher  of  which,  according  to  Kupffer'a 
recent  work,  represent  a  rudimentary  brain,  although  they  have  as 
yet  acquired  no  functional  importance  greater  than  or  different  to 
the  other  metanieres  (Steiner).  In  the  series  of  Craniota,  on  the 
contrary,  the  constituent  parts  of  the  brain  are  added  to  the  spinal 
cord  by  the  progressive  development  of  the  organism.  In  man, 
the  highest  member  of  the  animal  scale,  the  brain  is  so  highly 
i  developed  that  the  spinal  cord  seems  in  comparison  to  be  merely 
its  appendage. 

I.  From  the  physiological  point  of  view  the  brain  may  be 
divided  into  parts,  corresponding  with  those  which  can  be  dis- 
tinguished at  an  early  stage  of  its  development. 

At  the  head  end  of  the  primitive  neural  tube  the  first  signs  of 
the  brain  appear  as  three  dilatations,  which  are  transformed  into 
vesicles,  destined  later  to  form  the  cerebral  ventricles.  The  anterior 
and  posterior  vesicles  each  divide  into  two,  while  the  median 
vesicle  remains  undivided.  The  three  primary  cerebral  vesicles 
thus  form  five  secondary  cerebral  vesicles,  which  again  give  rise 
from  before  backwards  to  :— 

(ft)  The  fore-brain  or  prosencephalon.  In  the  embryo  this  is 
represented  by  the  1st  secondary  vesicle,  which  is  originally  very 
small  and  afterwards  grows  out  laterally,  forming  the  hemispherical 
diverticula.  In  the  adult  it  is  represented  by  the  brain  proper  or 

380 


CHAP,  vii  THE  MEDULLA  OBLONGATA  381 

cerebral  hemispheres.  Each  hemisphere  consists  of  the  cortex,  and 
the  caudate  and  lenticular  nuclei  which  constitute  the  corpus 
stria  turn. 

(&)  The  'tween-brain  or  thalamencephalon.  In  the  embryo  this 
is  represented  by  the  2nd  cerebral  vesicle,  the  lateral  walls  of  which 
thicken  and  form  the  optic  thalami.  The  third  ventricle  lying 
between  the  thalami  represents  the  1st  primary  cerebral  vesicle. 

(c)  The  mid-brain  or  mesencephalon  is  formed  by  the  thicken- 
ing of  the  walls  of  the  3rd  embryonic  vesicle.     Its  ventral  part 
forms  the  cerebral  peduncles,  the  dorsal  part  the  optic  lobes  or 
corpora  bigemina  of  the  lower  vertebrates,  the  corpora  quadrigemina 
of  mammals.     The  aqueduct  of  Sylvius  by  which  the  third  and 
fourth  ventricles  communicate  is  the  remains  of  the  embryonic 
mesencephalic  vesicle. 

(d)  The  hind-brain  or  metencephalon  develops  from  the  4th 
secondary  vesicle.     The  thickening  of  the  ventral  wall  gives  rise 
to  the  pons  Varolii,  of  the  dorsal  walls  to  the  cerebellum.     The 
fourth  ventricle   or   sinus   rhomboidalis   is    the  remains   of  the 
embryonic  vesicle. 

(e)  The  medulla  oblongata  or  myelencephalon  is  derived  from 
the  5th  secondary  vesicle,  the  ventral  portion  of  which  enlarges  to 
form  the  bulb  or  medulla  oblongata,  while  the  dorsal  part  remains 
a  simple  epithelial  layer  adherent  to  the  pia  mater  which  covers 
the  sinus  rhomboidalis. 

In  order  to  form  an  idea  of  the  very  unequal  development  of 
the  five  embryonic  segments  in  the  brain  of  the  adult,  the  corre- 
sponding parts  of  Figs.  199  and  200  should  be  compared.  The  first 
represents  the  brain  of  a  human  embryo,  at  two  and  a  half  months  ; 
the  second,  the  adult  brain.  It  will  be  seen  that  in  the  foetus  the 
thalamencephalon  and  mesencephalon  are  relatively  very  large, 
while  in  the  adult  the  cerebrum,  and  after  it  the  cerebellum,  are 
largest,  and  the  corpora  quadrigemina  are  relatively  small. 

Anatomical  text-books  should  be  consulted  for  the  external  form 
and  internal  structure  of  the  brain  :  here  we  must  confine  our- 
selves to  such  anatomical  details  as  are  necessary  to  the  study  of 
its  physiology. 

The  spinal  bulb,  which  is  the  subject  of  the  present  chapter,  is 
the  intracranial  prolongation  of  the  spinal  cord,  hence  the  name 
medulla  oblongata.  Owing  to  its  vital  importance,  and  the 
multiplicity  of  its  functions,  it  is  quite  one  of  the  most  important 
parts  of  the  nervous  system.  The  complexity  of  its  structure 
indicates  the  complexity  of  its  functions. 

It  is  conical  in  form,  with  the  base  above,  at  its  junction  with 
the  pons,  and  a  truncated  apex  below,  continuous  with  the  spinal 
cord.  As  shown  by  Fig.  201,  the  cerebral  nerves  from  the  hypo- 
glossal  (12th)  to  the  abducent  (6th)  issue  from  the  ventral  and 
lateral  surfaces  of  the  bull  >. 


382 


PHYSIOLOGY 


CHAP. 


C.q. 


olf 


\ 


Fio.  199.— Sagittal  section  of  the  brain  of  a  2^  months' foetus.  (His.)  5  diameters.  Abovi'.  in  I  lie 
right,  the  medial  surface  of  the  left  cerebral  hemisphere  ;  the  wide  cavity  of  the  third  ventricle 
is  limited  above  and  in  front  by  a  thin  lamina  ;  below,  the  iiifuiidibulnm  and  pituitary  body. 
The  thalamus  occupies  the  lateral  and  upper  part  of  the  cavity  ;  in  front  and  below  is  the 
foramen  of  Monro  ;  behind  the  thalamus  another  depression  which  opens  into  the  slit  of  the 
external  geniculate  body  ;  ulf,  olfactory  lobe  ;  ?>,  pituitary  body  ;  c.q.,  corpus  quadrigeminum  ; 
cli,  cerebellum  ;  m.o.,  medulla  oblongata. 


Pio.  200.—  Right  half  of  the  brain  divide<l  by  a  vertical  antero-posterior  section  (from  various  sources 
and  from  nature).  (Allen  Thomson.)  £.  1,  -2,  3,  3n.,  36  are  placed  on  convolutions  of  the 
cerebrum ;  4,  the  fifth  ventricle,  and  above  it  the  divided  corpus  callosum ;  5,  the  third 
ventricle;  5',  pituitary  budy;  il,  corpora  quadrigemina  and  pineal  sland  ;  +,  the  fourth 
ventricle;  7,  pons  Varolii  ;  8.  medulla  oblon^ata  ;  :',  ceiebellum;  I,  the  oltaetory  bullj;  II, 
right  optic  nerve  ;  III,  right  3rd  nerve. 


VII 


THE  MEDULLA  OBLONGATA 


383 


Certain  bundles  of  nerve-fibres  from  the  spinal  columns  pass 
through  the  medulla  and  pons,  and  on  reaching  the  ventral  part 


Fir;.  201.  — View  from  before  of  medulla  oblongata,  pous  Varolii,  crura  cerebri.  and  other  central 
portions  of  the  encephalon.  (Allen  Thomson.)  Natural  size.  On  right  side  the  convolutions 
of  the  central  lobe  or  island  of  Reil  have  been  left,  with  a  small  part  of  the  anterior  cerebral 
convolutions  ;  on  left  side  these  have  been  removed  by  an  incision  carried  between  the  thalamus 
options  and  the  cerebral  hemisphere.  I',  olfactory  tract  cut  short  and  lying  in  its  groove  ; 
II,  left  optic  nerve  in  front  of  the  commissure;  II',  right  optic  tract;  Th,  cut  surface 
of  the  left  thalamus  options  ;  C,  central  lobe  or  island  of  Reil ;  Sy,  fissure  of  Sylviusi; 
X.  X.  anterior  perforated  space;  e,  external,  i,  internal  corpus  geniculatum  ;  Ji,  hypophysis 
cerebri  or  pituitary  body  ;  tc,  tuber  cinereum  with  infundibulum  ;  a,  one  of  the  corpora 
albicantia  ;  P,  cerebral  peduncle  or  crus  ;  III,  close  to  left  oculomotor  nerve;  X,  posterior 
perforated  space.  The  following  letters  and  numbers  refer  to  parts  in  connection  with 
the  medulla  oblongata  and  pons:  PV,  pons  Varolii;  V,  greater  root  of  5th  neive;  +,  lesser 
or  motor  root;  VI,  6th  nerve;  VII,  facial;  VIII,  auditory  nerve;  IX,  glossopharyngeal ; 
X,  pneumogastric ;  XI,  spinal  accessory;  XII,  hypoglossal ;  67,  suboccipital  or  1st  cervical 
nerve  ;  /in.  pyramid  ;  o,  olive  ;  rl,  ventral  median  fissure  of  spinal  cord,  above  which  the 
decussation  of  the  pyramids  is  represented;  c<i.  ventral  column  of  cord  ;  r,  lateral  tract  of 
bulb  continuous  with  i7,  the  lateral  column  of  the  spinal  cord. 

of   the  mid-brain   divide  into  two  large  bundles — the  cerebral 
peduncles  —  which  penetrate   into  both   hemispheres.      On   this 


384 


PHYSIOLOGY 


CHAP. 


account  many  anatomists  give  the  name  brain-stem  to  those  parts 
of  the  medulla  and  pons  which  are  the  direct  continuation  of  the 
spinal  cord  (Fig.  202). 

The  pyramidal  tracts — as  we  saw  in  the  last  chapter — decussate 


FIG.  202. — View  of  medulla  oblongata,  pons  Varolii,  crura  cerebri,  and  central  parts  of  encephalon 
from  right  side.  (Allen  Thomson.)  The  corpus  striatum  and  thalamus  options  have  been 
preserved  in  connection  with  the  central  lobe  and  crura  cerebri,  while  the  remainder  of  the 
cerebrum  has  been  removed.  St,  upper  surface  of  corpus  striatum  ;  Th,  back  part  of  tha- 
lamus options  (pulvinar) ;  (',  placed  on  the  middle  of  the  five  or  six  convolutions  constituting 
the  central  lobe  or  island  of  Reil,  the  cerebral  substance  being  removed  from  its  circumference  ; 
>'//,  tissure  of  Sylvius,  from  which  these  convolutions  radiate,  and  in  which  are  seen  the  white 
striae  of  the  olfactory  tract ;  I,  the  olfactory  tract  divided  and  hanging  down  from  the  groove 
in  the  convolution  which  lodges  it;  II,  optic  nerves  a  little  way  in  front  of  the  chiasma  ; 
a,  right  corpus  albieans  with  tuber  cinereum  and  infundibulum  in  front  of  it ;  h,  hypophysis 
or  pituitary  body  ;  e,  external,  i,  internal  corpus  geniculatum  at  back  part  of  optic  tract;  P, 
peduncle  or  crus  of  cerebrum;  III,  right  oculo-motor  nerve;  p,  pineal  gland;  q,  corpora 
quadrigemina  ;  IV,  trochlear  nerve  rising  from  r,  valve  of  Vieussens.  The  following  numbers 
and  letters  n-fer  chiefly  to  parts  in  connection  with  medulla  oblongata  and  pons  :  V,  on  pons 
Varolii  above  right  nervus  trigeminns  ;  .s,  superior,  m,  middle,  in,  inferior  peduncle  of  cere- 
bellum cut  short;  VI,  6th  nerve;  VII,  facial  nerve;  VIII,  auditory  nerve;  IX,  glosso- 
pharyngeal  nerve  ;  X,  opposite  cut  end  of  pneumogastric  nerve  ;  XI,  uppermost  fibres  of 
spinal  accessory  nerve;  XII,  hypoglossal  nerve  ;  jxi,  pyramid;  o,  olive ;  ar,  arciform  fibres  ; 
/,  lestiform  body;  //•,  tubercle  of  Rolando;  ca,  ventral,  cp,  dorsal,  cl,  lateral  columns  of 
spinal  cord  ;  (7,  '<"/,  ventral  and  dorsal  roots  of  1st  cervical  nerve. 

in  the  lower  part  of  the  bulb,  turning  sharply  ventralwards  to 
form  the  ventral  or  anterior  pyramids.  By  this  decussation  (Figs. 
203  and  204)  the  ventral  horns  become  detached  and  separated 
from  the  rest  of  the  grey  matter. 


VII 


THE  MEDULLA  OBLONGATA 


385 


The  long  fibres  of  the  columns  of  Goll  and  Burdach  terminate, 
on  reaching  the  lower  part  of  the  bulb,  in  two  grey  nuclei,  one 
lying  \vithiu  the  column  of  Goll  (Fig.  203  Ny},  the  other  externally 
within  the  column  of  Burdach  (Fig.  204  JVc).  As  the  central 
canal  approaches  the  dorsal  surface  of  the  bulb,  these  nuclei 
enlarge,  till  just  above  the  decussation  of  the  pyramids  they  form 
the  prominences  termed  the  clavae  (Fig.  205,  n.g.,  n.c.)  from  the 
ventral  surfaces  of  which  the  arcuate  fibres  emerge,  and  turn 


FIG.  203.— Transverse  section  of  medulla  <>M<nii:;it.-i  in  MI-  the  decussation  of  the  pyramids.     (Henle. 
FPH,  pyramidal  tract;  C<jn,  ventral  horn  ;  Fa',  rest  ,of  ventral  horn  ;  A";;,  nucleus  of  funiculus 
gracilis  ;  <j,  substantia  tft'latinosa  ;  XI,  spinal  accessory. 

forwards  and  inwards  towards  the  median  raphe,  where  they  cross 
with  those  of  the  opposite  side.  So  that  above  and  dorsal  to  the 
motor  or  pyramidal  decussation  is  the  sensory  decussation  of  the 
fibres  of  the  fillet  of  Eeil  or  lemniscus  niedialis,  which  lies  im- 
mediately dorsal  to  the  pyramids. 

The  sensory  fibres  of  the  lateral  column  of  the  cord,  which  lie 
closely  related  to  Gowers'  tract,  do  not  decussate  but  continue  to 
ascend  through  the  lateral  zone  of  the  medulla ;  they  pass  by  the 
lateral  nucleus  of  the  bulb,  and  eventually  join  the  mesial  fillet  in 
the  upper  portion  of  the  medulla  or  in  the  pons. 

The  cerebellar  tracts  of  the  lateral  columns  pass  through  the 
restiform  body  or  the  inferior  cerebellar  peduncle,  and  terminate 
in  the  cerebellar  cortex. 

VOT,.  in  2  c 


386 


PHYSIOLOGY 


CHAP. 


The  grey  matter  of  the  cord  is  continuous  with  that  of  the 
medulla,  but  its  shape  in  the  cross-section  is  considerably  altered 
by  the  motor  and  sensory  decussations,  and  by  the  appearance  of 
the  fourth  ventricle.  This  takes  place  in  the  upper  half  of  the 
bulb,  where  the  dorsal  columns  separate,  the  grey  commissure 
disappears,  and  the  central  canal  opens  out  to  form  the  fourth 
ventricle  or  fossa  rhornboidalis  (Figs.  207,  208). 


FIG.  204.— Transverse  section  of  medulla  oblongata  in  the  region  of  the  most  caudal  roots  of  the 
hypoglossus.  Decussation  of  pyramids  almost  complete.  (Henle.)  Nc,  nucleus  of  funiculus 
cuneatus  ;  XII,  hypoglossal.  Other  indications  as  in  preceding  ligure. 

When  the  central  canal  opens  out,  the  grey  matter  that 
surrounded  it  in  the  cord  comes  to  lie  in  the  floor  of  the  ventricle, 
so  that  the  part  that  was  formerly  ventro-lateral  (representing  the 
base  of  the  ventral  horn  of  the  cord)  becomes  internal  or  medial, 
and  the  homologue  for  the  dorsal  horn  becomes  external  and  lateral. 
The  nuclei  of  origin  and  termination  of  the  cranial  nerves  lie  in 
this  grey  matter,  which  is  formed  by  the  breaking  up  of  the 
motor  and  sensory  columns  of  the  spinal  cord. 

There  are  other  grey  nuclei  in  the  bulb  that  are  not  represented 
in  the  cord.  After  the  nuclei  of  the  columns  of  Goll  and  Burdach 
already  alluded  to,  the  most  important  is  the  nucleus  of  the  olivary 


VII 


THE  MEDULLA  OBLONGATA 


387 


body,  which  is  a  thin  wavy  lamella  of  grey  matter,  witli  its  opening 
or  hilus  towards  the  median  line  ;  it  receives  a  bundle  of  fibres 
(olivary  peduncle)  which,  after  crossing  the  raphe  and  decussating 
with  those  from  the  opposite  side  (Fig.  206),  passes  to  the  restiform 
body  or  the  inferior  cerebellar  peduncle.  When  there  is  atrophy 
or  agenesia  of  one  cerebellar  hemisphere  (Gudden),  or  after  extirpa- 
tion of  one  lateral  half  of  the  cerebellum  (Luciani),  atrophy  of  the 


c.c 


I 
k. ,  SL^vi  i^-V)  v'^fflSaaeKS      / 


n.c. 


n.am. 


a,-m.f. 


n.a  r 


FIG.  206. — Section  of  medulla  oblongata  at  about 
the  middle  of  olivary  body.  (Schwalbe.)  f. 
f.l.a.,  anterior  median  fissure :  //."/•.,  nucleus 
:n  riformis ;  p,  pyramid  ;  XII,  bundle  of 
hypoglossal  nerve  emerging  from  surface;  at 
b  it  is  seen  coursing  between  the  pyramid 
and  the  olivary  nucleus  o  ;  f.a.e.,  extemal 
arcuate  fibres;  n.l.,  nucleus  lateralis ;  a, 
arcuate  fibres  running  towards  restiform 
body,  partly  through  substantia gelatinosa  0, 
partly  superficial  to  descending  root  of  5th 
nerve  a.  V.  ;  X,  bundle  of  emerging  vagus 
root;  f.r.,  formatio  reticularis  ;  C.r.,  em  pus 
restiforme,  beginning  tn  be  formed  chiefly  by 
arciform  fibres,  superficial  and  deep;  n.c., 
nucleus  cuneatus  ;  n.fi.,  nucleus  gracilis; 
t,  attachment  of  the  ligula  ;  ,/X,  fiuiiculus 
solitarius  ;  »X,  n\',  two  parts  of  the  vagus 
nucleus;  mXII,  hypoglossal  nucleus;  n.t.. 
nucleus  of  funieulus  teres;  n.'iiu..  nucleus 
ambiguus  ;  r,  raphe;  A,  continuation  of 
ventral  column  of  cord  ;  o',  u",  accessory 
olivary  nuclei ;  p.o.l.,  pedunculus  ulivae. 

olive  on  the  opposite  side  is  constantly  seen,  which  proves  that 
there  are  crossed  relations  between  the  olives  and  the  two  halves 
of  the  cerebellum.  At  the  dorsal  and  medial  surfaces  of  the 
principal  nucleus  of  the  olives,  there  are  two  accessory  olivary 
nuclei,  dorsal  and  medial.  They  probably  have  the  same  physio- 
logical value  and  the  same  relations  with  the  cerebellum  as  the 

O 

principal  olivary  nucleus. 


FIG.  205.— Section  of  medulla  oblongata  in  the 
region  of  the  superior  pyramidal  decussation. 
(Schwalbe.)  }.  a.ni.f.,  ventral  median  fissure; 
/.a.,  superficial  arcuate  fibres  emerging 
from  fissure;  py.  pyramid;  n.ur.,  nucleus 
of  arcuate  fibres  ;  /.a.1,  deep  arcuate  fibres, 
becoming  superficial ;  o,  lower  end  of  olivary 
nucleus  ;  o',  accessory  olivary  nucleus  ;  n.l., 
nucleus  lateralis  ;  f.r.,  formatio  reticularis  ; 
/.a.2,  arcuate  fibres  proceeding  from  formatio 
reticularis  ;  n,  substantia  gelatinosa  Rolandi ; 
i.i.V.,  descending  root  of  5th  nerve;  n.c., 
nucleus  cuneatus  ;  n.c.',  nucleus  cuneatus 
externus ;  /.c.,  funieulus  cuneatus;  11.11., 
nucleus gracilis ;./>/.,  funieulus gracilis;  »>.  »/../., 
dorsal  median  fissure ;  c.c.,  central  canal, 
surrounded  by  grey  matter,  in  which  are 
H.X1,  nucleus  of  spinal  accessory.  /t.XII, 
nucleus  of  hypoglossal;  x.d.,  superior  pyra- 
midal decussation. 


388 


PHYSIOLOGY 


CHAP. 


Particular  mention  should  be  made  of  the  formatio  reticularis 
which  occupies  the  entire  central  part  of  the  bull)  (Figs.  205  and 
206) ;  it  consists  of  nerve-fibres  that  cross  in  every  direction,  and 
form  a  network.  The  longitudinal  bundles  are  intersected  by  the 
transverse  or  arcuate  fibres  that  traverse  the  raphe  obliquely. 
Between  the  fibres  there  is  a  considerable  number  of  nerve-cells, 
mostly  of  a  large  size.  These,  according  to  Deiters,  send  their 
processes  downwards,  and  their  dendrites  horizontally.  The 
formatio  reticularis  may  be  regarded  as  a  special  form  of  the 

ordinary  grey  matter 
in  which  the  cells  are 
irregularly  scattered, 
and  form,  as  Kolliker 
says,  a  diffuse  nucleus. 
It  is  probable  that  the 
main  functions  of  the 
bulb  depend  on  these 
central  multipolar  ele- 
ments of  the  formatio 
reticularis  (Edinger) ; 
the  great  physiological 
significance  of  the  bulb 
also  appears  from  the 
fact  that  it  contains  the 
nuclei  of  origin  of  most 
of  the  efferent  cerebral 
nerves,  as  also  the  ter- 
minal nuclei  of  most 
of  the  afferent  cerebral 
nerves.  The  nuclei  of 
the  hypoglossal,  spinal 
accessory,  vagus,  and 


„  1  „  a  nil  a 

centre  of  the  cerebellum  ;    6,  fillet  at  side  of  the  crura     g  1  O  S  S  O   -  pliai 

cerebri  ;   7,  lateral   grooves  of  crura  cerebri  ;   8,  corpora 

quadrigemina. 


FIG.  207.—  The  three  pairs  of  cerebellar  peduncles.  (Sappey, 
after  Hirsehtield  ami  Leveille.)  On  left  side  the  three 
cerebellar  peduncles  have  been  cut  short;  on  right  side 
the  hemisphere  has  been  cut  obliquely  to  show  its  con- 
nection with  the  superior  and  inferior  peduncles.  1, 
median  groove  of  fourth  ventricle  ;  2,  same  groove  at  the 
place  where  the  auditory  striae  emerge  from  it  to  cross 
the  floor  of  the  ventricle  ;  3,  inferior  peduncle  or  restiform 
body;  4,  funiculus  gracilis  ;  5,  superior  peduncle  —  on 
right  side  the  dissection  shows  the  superior  and  inferior 
peduncles  crossing  each  other  as  they  pass  into  the  white 

lie  entil'elv  with- 
n    i 

in  the  bulb;  those  of  the 
acoustic,  facial,  and  trigeminal  nerves  lie  partly  in  it,  partly  in  the 
pons  ;  those  of  the  oculomotor  and  trochlear  nerves  are  found 
in  the  grey  matter  that  surrounds  the  aqueduct  of  Sylvius  in  the 
raid-brain. 

The  origins  of  the  motor,  and  terminations  of  the  sensory, 
nerves  are,  as  we  have  seen,  systematically  arranged  in  the  spinal 
cord,  so  that  they  can  be  identified  at  a  glance.  In  the  medulla, 
on  the  contrary,  all  segmental  regularity  is  lost  ;  the  motor 
and  sensory  elements  here  form  irregular  groups  that  make  it 
impossible  from  their  relative  positions  to  recognise  their  functions. 

Of  the  twelve  pairs  of  cerebral  nerves  the  1st  and  2nd,  i.e. 
the  Olfactory  and  Optic  nerves,  are  so  different  from  the  others  in 


VII 


THE  MEDULLA  OBLONGATA 


389 


str 


to. 


their  origin  and  mode  of  development  that  it  seems  advisable  to 
study  them  separately,  in  discussing  the  olfactory  and  visual 
senses.  Embryologically,  they  are  not,  like  the  other  cranial 
nerves,  mere  prolongations  from  the  walls  of  the  primitive  neural 
tube,  but  vesicles  that  have  budded  out  from  that  tube,  the  lumen 
being  subsequently  obliterated. 

The  apparent  origin  of  the  ten  remaining  pairs  from  the  3rd 
to  the  12th  is  readily  seen  from  a  glance  at  the  base  of  the 
brain  (Fig.  201).  Their  real  origins  lie  in  more  or  less  elongated 
.nuclei,  which  extend  from  the  caudal  end  of  the  bulb  to  the 
cranial  end  of  the  ventral  wall  of  the  Sylvian  aqueduct.  Fig. 
209  gives  an  approximate  idea  of  their  positions. 

II.  The  nucleus  of  origin  of  the  Hypoglossus  consists  in  a  long 
column  of  grey  matter  in  the  im- 
mediate vicinity  of  the  median  line. 
It  begins  at  the  level  of  the  striae 
acusticae,  and  ends  a  few  millimetres 
below  the  tip  of  the  calamus  scrip- 
torius ;  its  total  length  is  approxi- 
mately that  of  the  olive.  Below,  it 
occupies  a  ventral  position  in  respect 
of  the  spinal  canal  (Fig.  205,  n.XII) ; 
above,  where  the  spinal  canal  opens  to 
form  the  rhomboid  sinus,  it  assumes  a 
dorsal  position  (Fig.  206,  ?^.XII). 

The  nucleus  of  the  hypoglossus 
consists  of  a  group  of  large  ganglion 
cells,  enclosed  in  a  line  nervous  net- 
work (Fig.  210);  their  axis-cylinders 
run  ventralwards  through  the  formatio 
reticularis  and  emerge,  as  a  series 
of  little  bundles,  between  the  olive 
and  the  pyramids.  Eoller's  nucleus  of  small  cells,  as  shown  in 
the  figure,  is  not  an  accessory  nucleus  of  the  hypoglossus,  but 
belongs  to  the  diffuse  nucleus  of  the  formatio  reticularis. 

Morphologically  speaking,  the  hypoglossal  is  not  a  simple 
nerve,  but  a  compound  one,  formed  by  the  union  of  at  least  three 
ventral  roots  fused  into  a  single  'trunk,  as  may  be  seen  from  a 
study  of  its  root  filaments.  In  all  probability  it  originally  had 
a  corresponding  dorsal  root  on  the  type  of  the  spinal  nerves,  and 
this  has  in  fact  been  described  as  an  anatomical  variation  in  the 
ox,  dog,  pig  (C.  Mayer),  in  the  cat  (Vulpian),  and  also  in  man 
(Vulpian,  Chiarugi).  Complete  or  partial  disappearance  of  dorsal 
roots  during  phylogenesis  can  also  be  seen  in  the  first  spinal 
nerves  in  reptiles  and  birds.  In  adult  man,  more  often  than  in 
other  mammals,  the  dorsal  roots  of  the  1st  cervical  nerve  are 
rudimentary,  which,  as  Chiarugi  rightly  remarks,  is  a  proof  of  the 

2  C  i 


Flu.  20S. — Aiitei  inr  boundary  (floor)  of 
fourth  ve utricle.  (Schafer.)  Natural 
size,  in.s.,  median  sulcus  ;  .-'/,  striae 
acusticae.  marking  Limit  between 
pontine  part  of  ventricle  ami  medul- 
lary part  of  calamus  sr-riptorius ; 
Lr.,  lateral  recess  ;  i.f.,  inferior 
(posterior)  fovea  ;  a.c.,  ala  cinerea  ; 
t.a.,  tri.u'onuin  acustici  ;  s.f.,  superior 
(anterior)  fovea,  close  to  lateial 
margin  of  superior  part  of  ventricle. 


390 


PHYSIOLOGY 


CHAP. 


tendency  of  the  first  segment  of  the   trunk  to  become  modified 
according  to  the  type  of  the  occipital  segments. 


B 


FIG.  200. — Diagram  to  show  situation  of  chief  nerve-nuclei  and  terminations  of  cranial  nerves  in 
medulla  oblongata  and  pons  near  floor  of  fourth  ventricle.  Twice  the  natural  size.  A,  from 
behind  ;  B,  profile  view  of  right  half,  the  medulla  and  pons  being  supposed  to  lie  transparent. 
The  efferent  or  motor  nuclei  are  coloured  red,  the  afferent  or  sensory  nuclei,  blue.  In  A  the 
motor  nuclei  are  represented  on  right  side  only,  the  sensory  on  the  left.  Ill,  IV,  oculomotor 
and  trochlear  nucleus;  I'd,  descending  root  of  5th  nerve;  1's,  so-railed  sensory  nucleus  of 
5th;  l'a,  ascending  root  of  5th;  I'm,  motor  nucleus  of  5th;  VI,  nucleus  of  abdncens; 
VII,  nucleus  of  facial  ;  ?tVII,  root  of  facial  curving  round  abducens  nucleus  ;  VIII,  inner  or 
dorsal  nucleus  of  auditory  ;  VIII',  outer  or  ventral  nucleus  of  audit' ay  ;  IX.  X.  vm;n-<_;losso- 
pharyngeal  nucleus ;  na,  nucleus  ambiguus.  accessory  or  efferent  vago-glosso-pharyngeal 
nucleus;  XI,  nucleus  of  spinal  accessory;  XII,  nucleus  of  hypoglossal ;  XII',  issuing  roots 
of  hypoglossal. 

At  its  origin  the  hypoglossal  is  an  exclusively  motor  nerve. 
This  was  recognised  by  Galen,  who  in   Book  VIII.  cap.  v.  "  de 


VII 


THE  MEDULLA  OBLONGATA 


391 


usu  port  in  in;'  classed   this  nerve  among  the  "  <luri    ct  motor  i." 
Boerhaave  opposed  this  correct  view  aud  described  it  as  a  nerve  of 
taste,  since  it  is  the  only  nerve  to  the  tongue.     Willis  recognised 
its  motor  nature,  but  also  attributed  a  gustatory  function  to  it— 
a  theory  that  was  generally  followed  until  Panizza  (1834)  first 


s8KB*rofofi 

-%6e:w«iv.ySKtV   t  >!;• 


•-•'-• 


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„•'        librae,  propna* 


£ ., tfuoleua  XII 


Fibroe  offer-ante 


-  -  ffaclaif  SI  Rotter. 

-  -  -forrtuXII. 


FIG.  210.—  Frontal  snrtion  tlirough  hypoglossal  nucl'-ns.     (Koch.) 


demonstrated  experimentally  that  the  old  Galenic  concept  that  it 
is  exclusively  motor  was  accurate. 

The  observations  of  H.  Mayo,  Magendie,  and  Longet,  who 
stated  that  section  or  simple  mechanical  stimulation  of  the  hypo- 
glossal  above  the  hyoid  bone  is  painful,  cannot  be  disputed.  But 
this  sensibility  is  due  to  the  fact  that  it  anastomoses  with  fibres 
of  the  vagus,  of  the  lingual  branch  of  the  5th  nerve,  and  of  the 
three  upper  cerebral  nerves.  Cl.  Bernard  also  found  that  the 


392  PHYSIOLOGY  CHAP. 

peripheral  end  of  the  cut  hypoglossal  was  sensitive,  which  he 
attributed  to  recurrent  twigs  of  the  lingual. 

Panizza  gave  an  exhaustive  description  of  the  effects  of 
bilateral  division  of  the  hypoglossal  in  dogs,  all  of  which  depend 
on  the  paralysis  of  the  tongue  muscles.  The  animal  is  no  longer 
capable  of  lapping  up  liquids  with  its  tongue,  nor  of  swallowing 
solids  after  masticating  them,  unless  the  alimentary  bolus  drops 
into  the  pharynx  passively  when  the  head  is  held  up.  If  during 
the  movements  of  the  head  and  jaws  the  tip  of  the  tongue  projects 
from  one  or  other  corner  of  the  mouth  it  remains  there,  for  the 
animal  is  incapable  of  drawing  it  back.  If  the  tongue  is  bitten 
during  mastication,  the  animal  gives  a  cry  of  pain,  showing  that 
painful  sensibility  is  unaffected.  If  a  drop  or  two  of  concentrated 
solution  of  quinine,  which  has  a  very  bitter  taste  but  no  smell, 
is  dropped  on  the  tongue,  the  animal  shakes  its  head  and  lips 
violently  and  makes  agitated  movements  of  mastication,  as  if  to 
get  rid  of  an  unpleasant  sensation.  This  proves  that  the  sense  of 
taste  is  preserved. 

Electrical  stimulation  of  the  peripheral  end  of  the  divided 
hypoglossal  provokes  contractions  of  all  the  muscles  of  the  tongue, 
except  the  palato-glossal  and  pharyngo-glossal.  The  fibres  of  the 
three  first  cervical  nerves,  which  anastomose  with  the  hypoglossal, 
are  distributed  to  the  thyro-hyoid  and  genio-hyoid  muscles. 

Hypoglossal  paralysis  in  man  confirms  the  results  of  experi- 
ments on  dogs;  the  effects  are  purely  motor.  In  bilateral 
paralysis  the  tongue  cannot  move  in  the  mouth ;  hence  there  are 
disturbances  in  speaking  and  singing,  slow  mastication,  and  great 
difficulty  in  swallowing  owing  to  the  incapacity  of  the  tongue  to 
drive  the  food  into  the  pharynx  ;  tactile  and  pain  sensibility  are 
unaltered,  but  taste  is  slightly  blunted  as  the  tongue  cannot 
manipulate  the  food. 

In  unilateral  hypoglossal  paralysis  the  tongue  is  higher  on 
the  paralysed  than  on  the  healthy  side,  owing  to  loss  of  tone  in 
these  muscles;  the  tip  of  the  tongue  is  deflected  towards  the 
healthy  side,  which  is  somewhat  shortened  by  the  physiological 
tone  of  the  non-paralysed  longitudinal  fibres.  When,  on  the 
contrary,  the  tongue  is  protruded  from  the  mouth,  it  is  twisted 
towards  the  paralysed  side,  owing  to  the  one-sided  action  of  the 
genio-giossus,  which  from  the  direction  of  its  fibres  draws  the 
healthy  half  of  the  tongue  towards  the  median  line.  In  this 
unilateral  paralysis  of  the  tongue,  speech,  mastication,  and  degluti- 
tion are  but  slightly  affected. 

A  few  months  after  experimental  transection  or  paralysis  of 
one  hypoglossus,  the  muscular  atrophy  of  the  paralysed  half  of  the 
tongue  becomes  very  pronounced. 

III.  Scarpa,  Bischoff,  and  many  others  regarded  the  10th 
and  llth  nerves,  i.e.  the  Vagus  and  the  Spinal  Accessory,  as  one 


VII 


THE  MEDULLA  OBLONGATA 


393 


single  cerebral  nerve,  in  which  the  vagus  represents  the  dorsal  or 

sensory  root,  and  the  accessory  the  ventral  or  motor  root.    Certainly 

the  mode  of  origin  of  the  vagus  presents  analogies  with  the  origin 

of  the  dorsal  roots  of  the  spinal  nerves.     Its  primary  root  possesses 

a  ganglion  (root  or  jugular 

ganglion)  which  is  connected 

with   the  bulb  by  a  series 

of   rootlets,  and  recalls  the 

ganglion  of  a  dorsal  spinal 

root.      The   vagus  contains 

both     sensory    and     motor 

fibres.     Fig.  209  shows  that 

it    has    two    nuclei    in    the 

bulb,    a    larger    sensory 

nucleus  lying  under  the  ala 

cinerea,  and  a  smaller  motor 

nucleus  which  it  shares  with 

the  9th  cerebral  nerve,  and 

which     is     known     as    the 

nucleus  ambiguus. 

On  the  other  hand,  we 
learn  from  histology  and 
embryology  that  the  spinal 
accessory  nerve  arises  with 
ventral  spinal  roots.  Its 
internal  or  bulbar  portion 
(accessory  properly  so- 
called)  unites  with  the  vagus 
beyond  the  ganglion,  as  if 
it  were  a  motor  root  (Fig. 
211). 

Whatever  the  morpho- 
logical value  of  the  theory 
which  assumes  the  vagus- 
accessory  to  be  a  single 
nerve,  it  is  very  convenient 
from  the  physiological  point 
of  view  to  consider  the  llth 
and  10th  cerebral  nerves 
together. 

The  accessory  of  Willis 
is  an  exclusively  motor  nerve, 
which  originates  (Fig.  209) 
from  a  column  of  cells  placed  dorso-laterally  to  the  hypoglossal 
nucleus,  and  extends  into  the  spinal  cord  to  the  5th  cervical 
segment,  in  which  it  forms  part  of  the  grey  matter  of  the 
lateral  horn.  From  this  nucleus  the  fibres  emerge  in  a  series 


FIG.  211.  —  Diagiam  of  roots  and  communicating  branches 

of  vagus  ami  neighbouring  nerves.  (Sappey,  after 
Hirschfeld  ami  Leveillr.)  1,  facial  nerve  ;  2,  glosso- 
pharyngeal  with  pnti-n.-al  ganglion  ;  2',  connection  of 
digastric  branch  of  facial  with  glossopharyngeal 
nerve  ;  a,  vagus,  with  its  t\vn  ganglia  ;  4.  accessory; 
5,  hyp"gli>>-al  :  <\  >up>-iior  cervical  ganglion  of  sym- 
pathetic ;  7,  7,  loop  of  union  between  tiist  two 
cervical  nerves;  S,  carotid  branch  of  *yiiipatli>'t  ii-  ; 
li,  tympanic  nerve  gh>- n  ntt'from  petrosal  ganglion:  HI, 
its  carotid-tympanic  ti laments;  11,  twigtoEu.stachian 
tube;  12.  twig  t»  fen>->tia  vestibuli  ;  13,  branch  to 
fenestra  cochleae;  14,  small,  15,  large,  superficial 
petrosal  nerve;  10.  optic  ganglion;  17,  auricular 
l.ianch  of  vagus  ;  IS.  connection  of  accessory  with 
vagus  ;  Hi,  union  of  liyin.igln-.sal  with  1st  cervical 
m-iYc;  20,  union  between  sterno-mastoirt  branch  of 
accessory  ami  that  of  .ml  <•'•] -viral  nerve  ;  21.  pliaiyn- 
geal  plexus  ;  22,  superior  laryng-eal  nerve  ;  23.  ex- 
t>-riiiil  laryngi-al  ;  24,  mMiUe  cervical  ganglinii  of 
sympathetic. 


394  PHYSIOLOGY  CHAP. 

of  filaments  along  the  lateral  column  of  the  cord  and  the  bulb 
below  the  vagus. 

The  external  or  spinal  portion  of  the  accessory,  after  passing 
out  by  the  jugular  foramen,  is  directed  backwards,  and  perforates 
the  sterno-mastoid  and  trapezius  muscles,  where  it  forms  a  plexus 
with  branches  of  the  cervical  nerves.  Division  of  the  external 
branch  therefore  produces,  not  total,  but  only  partial  paralysis 
of  these  muscles.  According  to  Longet,  if  the  animal,  after  bi- 
lateral section  of  the  external  branch  of  the  accessory,  is  made  to 
run,  it  soon  becomes  breathless,  not  being  able,  on  account  of  the 
partial  paralysis  of  the  steruo-mastoid  and  trapezius  muscles,  to 
elevate  the  thorax  sufficiently  and  dilate  the  lungs. 

The  internal  bulbar  branch  of  the  accessory,  after  joining  the 
trunk  of  the  vagus,  sends  part  of  its  fibres  into  its  pharnygeal 
branch,  while  the  rest  anastomose  with  the  vagus  trunk,  so  that  it 
is  impossible  to  distinguish  them  anatomically,  and  recourse  must 
be  had  to  physiological  tests. 

Bischoff  (1832)  was  the  first  who  maintained,  on  the  basis  of 
certain  experiments  on  goats,  that  intracranial  bilateral  section  of 
all  the  root  bundles  of  the  spinal  accessory  paralyses  the  muscles 
of  the  larynx,  as  after  section  of  the  recurrent  nerves  (see  pp.  140 
et  seq.}.  Longet  (1841),  Morgan ti  (1843),  confirmed  the  results  of 
Bischoff,  and  suggested  for  the  bulbar  part  of  the  accessory  the 
name  of  nervus  vocalis. 

Cl.  Bernard  introduced  a  new  method  of  extirpation  of  the 
whole  of  the  accessory  nerve  by  pulling  it  out  with  a  stout  forceps 
as  it  emerges  from  the  jugular  foramen.  The  operation  is  easy 
in  rabbits  and  cats,  but  difficult  in  adult  dogs.  After  bilateral 
destruction  of  this  nerve  the  respiratory  movements  of  the  glottis 
cease;  according  to  Bernard,  the  glottis  remains  open  in  the 
normal  position,  while  after  section  of  the  two  recurrent  nerves 
the  glottis  becomes  constricted  by  adduction  of  the  vocal  cords, 
leaving  such  a  narrow  fissure  that  the  animal  is  in  danger  of 
suffocation.  Bernard  concluded  that  the  fibres  which  adduct  the 
vocal  cords  are  distinct  from  the  respiratory  nerves  which  widen 
the  aperture  of  the  glottis.  The  former  come  from  the  roots  of  the 
accessory,  the  latter  from  the  roots  of  the  vagus,  but  both  are 
contained  in  the  recurrent  nerves. 

Bernard's  views  were  contested  by  Longet,  Schiff,  Heidenhain, 
and  others,  who  maintained  that  the  effects  on  extirpating  the 
accessory  and  dividing  the  recurrent  nerves  were  identical. 

A.  Waller  (1856)  and  Burckhard  (1867)  supported  the  theory 
that  the  motor  fibres  of  the  recurrent  nerves  come  from  the 
accessory  by  the  fact  that  in  rabbits,  after  section  of  the  nerve, 
many  or  all  the  recurrent  fibres  degenerate.  Although  these 
results  all  agree  with  Longet's  theory,  other  experimenters  bring 
forward  facts  that  are  diametrically  opposed  to  it. 


vii  THE  MEDULLA  OBLONGATA  395 

In  1840  Volkinann,  in  collaboration  with  Bidder,  denied,  on 
the  strength  of  a  number  of  experiments,  that  intracranial 
stimulation  of  the  roots  of  the  accessory  influences  the  laryngeal 
muscles ;  the  opposite  results  obtained  by  Longet  with  galvanic 
excitation  of  these  roots  were  due  to  spread  of  the  stimulus  to 
neighbouring  roots  of  the  vagus.  Van  Keinpen  and  Stilling 
(1863),  Navratil  (1871),  obtained  the  same  negative  results. 
Schech  (1873),  on  the  contrary,  extirpated  both  accessories  iu 
puppies,  and  showed  by  a  series  of  laryngoscopical  observations 
that  both  vocal  cords  were  paralysed  in  the  cadaveric  position, 
with  complete  aphonia,  as  already  stated  by  Bernard. 

Eeceut  work  on  the  innervation  of  the  larynx  has  been  directed 
to  solving  the  two  questions :  (a)  what  difference  is  there  between 
the  effects  of  dividing  the  recurrent  nerves  and  extirpating  the 
accessory  ?  (b)  do  the  motor  nerves  to  the  larynx  come  from  the 
accessory,  the  vagus,  or  from  both  these  nerves  { 

The  experiments  of  Wagner  in  Halle  (1890-91)  on  cats,  rabbits, 
and  dogs  demonstrated  that  the  section  of  a  recurrent  nerve  at 
once  produces  marked  adduction  of  the  corresponding  vocal  cord 
and  consequent  asymmetry  of  the  glottis,  and  that  section  of  both 
the  recurrent  nerves  produces  either  closure  of  the  glottis  by  com- 
plete bilateral  adduction  of  the  vocal  cords  and  necessitates 
tracheotomy  to  prevent  the  animal  from  dying  of  asphyxia,  or  a 
pronounced  adduction  of  the  cords  which  reduces  the  glottis  to  a 
mere  fissure.  In  all  cases,  after  dividing  the  recurrent  nerves 
there  is  immobility  of  the  vocal  cords.  This  fact  agrees  with 
Bernard's  observations. 

The  adduction  of  the  cords  and  narrowing  of  the  glottis  does 
not,  however,  depend  on  the  action  of  the  muscles  innervated  by 
the  recurrent  nerve,  but  on  that  of  the  crico- thyroid  muscles 
which  are  innervated  by  the  superior  laryngeal;  in  fact,  it  dis- 
appears immediately  after  section  of  this  nerve  and  the  glottis 
assumes  the  cadaveric  position.  If  after  section  of  the  recurrent 
nerves  the  glottis  is  observed  daily,  it  is  seen  that  after  a  few  (two 
to  six)  days  the  vocal  cords  pass  from  the  median  position  of  com- 
plete adduction  to  the  cadaveric  position  of  moderate  abduction, 
in  which  they  remain.  These  facts  agree  with  the  observations  of 
Longet,  Schiff,  and  others  in  opposition  to  Bernard. 

•It  was  more  difficult  to  decide  the  question  of  the  origin 
of  the  motor  laryngeal  fibres  contained  in  the  recurrent  nerves. 
Grabower  solved  this  problem  by  the  research  which  he  carried 
out  under  Gad's  direction  (1889).  Using  cats,  clogs,  and  rabbits, 
he  demonstrated  plainly  that  the  accessory  has  no  part  in  the 
motor  innervation  of  the  larynx,  which  is  supplied  by  the  4th 
to  6th  lower  rootlets  of  the  vagus.  These  same  lower  roots  of  the 
vagus  also  contain  the  sensory  fibres  for  the  larynx. 

In   his   experiments   on    the    accessory    Grabower    employed 


396  PHYSIOLOGY  CHAP. 

different  methods :  division  of  the  root  fibres  within  the  cranium ; 
section  of  the  nerve  directly  it  has  left  the  jugular  foramen  ; 
Bernard's  method  of  tearing  the  nerve  out.  All  the  experiments 
carried  out  with  the  first  two  methods  constantly  gave  negative 
results ;  the  normal  movements  of  abduction  and  adduction  of  the 
vocal  cords,  in  both  respiration  and  phonation,  are  in  no  way  altered. 
On  the  other  hand,  tearing  the  nerve  out  from  the  jugular  foramen 
always  produced  in  rabbits  immobility  of  the  vocal  cords  in  the 
cadaveric  position,  on  the  side  operated  on ;  this  depends  on  the 
intimate  anatomical  relations  between  the  accessory  and  the  lower 
root  filaments  of  the  vagus,  which  are  torn  out  with  the  accessory. 
Grabower  demonstrated  that  in  rabbits,  as  in  cats  and  dogs,  the 
motor  and  sensory  innervation  of  the  larynx  is  due  to  these  root- 
lets of  the  vagus,  as  intracranial  section  of  them  produces  motor 
and  sensory  paralysis  of  the  larynx  on  that  side.  When,  on  the 
contrary,  he  destroyed  the  upper  roots  of  the  vagus,  leaving  the 
lower  roots  intact,  there  was  no  disturbance  of  the  normal  functions 
of  the  vocal  cords. 

Grossmann,  under  Exner's  direction,  obtained  practically  the 
same  results  as  Grabower,  and  almost  simultaneously.  He 
specially  investigated  the  effects  of  intracranial  electrical  excita- 
tion of  the  single  rootlets,  both  of  the  vagus  and  the  accessory,  in 
rabbit.  Like  Grabower,  he  found  that  while  stimulation  of  the 
roots  of  the  accessory  produced  no  motor  effect  on  the  vocal  cords, 
that  of  the  separate  roots  of  the  vagus  produced  strong  adduction 
or  abduction  of  the  corresponding  vocal  cord,  or  more  or  less 
extensive  contraction  of  almost  all  the  laryngeal  muscles. 

Since  these  experimental  facts  have  overthrown  the  theory 
which  ascribed  the  innervation  of  the  larynx  to  the  internal 
branch  of  the  accessory,  the  question  arises  if  the  theory  of  the 
origin  of  the  inhibitory  cardiac  fibres  of  the  vagus  from  the 
accessory  can  be  retained.  As  we  have  seen  (Vol.  I.  p.  329), 
Waller  (1856)  based  this  hypothesis  on  his  observation  that  the 
cardiac  fibres  of  the  vagus  degenerated  and  the  inhibitory  effects 
of  stimulation  ceased  after  extirpating  the  accessory.  Schiff, 
Heidenhain,  Vulpian,  and  Jolyet  confirmed  his  results.  But  after 
Grabower  had  proved  that  some  roots  of  the  vagus  are  (constantly 
in  rabbit)  torn  away  with  the  roots  of  the  accessory  by  this 
method  of  extirpation,  both  these  observations  lost  their  value  as 
evidence.  On  the  other  hand,  Gianuuzzi  was  unable,  in  rabbits 
fourteen  days  after  extirpation  of  the  accessory,  to  demonstrate 
complete  loss  of  the  inhibitory  action  of  the  vagus.  While 
Heidenhain,  Vulpian,  and  Jolyet  found  acceleration  of  cardiac 
rhythm — the  necessary  effect  of  abolishing  the  tonic  action  of  the 
inhibitory  fibres — after  destroying  the  accessory  Schiff  and  Eckhard 
obtained  negative  results. 

If  the  bulbar  roots  of  the  accessory  therefore  have  no  influence 


vii  THE  MEDULLA  OBLONGATA  397 

on  the  laryngeal  muscles  and  heart,  what  muscles  do  they  inner- 
vate? The  effects  of  intracranial  excitation  of  the  roots  of  the 
accessory  must  be  investigated  in  order  to  solve  this  problem. 
The  results  obtained  by  Bentz  and  Longet  from  their  experiments 
on  dogs  suggest  that  the  chief  part  of  the  pharyngeal  muscles  are 
innervated  by  the  accessory ;  Ghauveau,  on  the  contrary,  experi- 
menting with  horses,  only  obtained  a  contraction  from  the  upper 
part  of  the  first  pharyngeal  constrictor.  More  interesting,  because 
probably  applicable  to  man,  are  the  later  experiments  of  Beevor 
and  Horsley  (1888)  upon  monkeys;  they  obtained  contraction  of 
the  levator  palati,  azygos  uvulae,  and  a  large  part  of  the  muscula- 
ture of  the  pharynx,  by  stimulating  the  roots  of  the  accessory  after 
rapid  extirpation  of  one  cerebral  and  cerebellar  hemisphere. 

IV.  We  have  already,  in  previous  chapters  of  this  book,  referred 
to  the  various  and  important  functions  of  the  Vagus  or  10th  nerve 
(formerly  misnamed  "  pueumogastric  ").  Now,  therefore,  we  need 
only  summarise  them,  and  add  such  experimental  facts  as  we  have 
not  had  the  opportunity  of  discussing  elsewhere. 

The  branches  of  the  vagus  are  of  course  distributed  to  the 
head,  neck,  thorax,  and  abdomen,  i.e.  to  many  different  visceral 
and  somatic  organs  (Fig.  212). 

01.  Bernard  and  others  demonstrated  the  existence  of  sensory 
roots,  but  after  giving  off  the  superior  laryngeal,  the  proportion  of 
sensory  fibres  in  the  vagus  trunk  is  small,  especially  in  rabbits. 
The  inferior  laryngeal  consists  for  the  most  part  of  motor  fibres. 

The  branches  of  the  vagus  contain  fibres  with  various 
functions  :  — 

(a)  The  sensibility  of  the  posterior  part  of  the  meninges  is  due 
to  the  meningeal  branch,  which  leaves  the  jugular  ganglion  and 
accompanies  the  posterior  branch  of  the  meningeal  artery.  It  is 
probable  that  the  vomiting  in  meningitis  is  reflexly  produced  by 
the  excitation  of  this  branch  of  the  vagus. 

(&)  The  sensibility  of  the  pinna  and  external  auditory  meatus 
is  partly  supplied  by  the  auricular  branch,  which  also  conies  from 
the  jugular  ganglion. 

Irritation  of  the  area  innervated  by  the  auricular  nerve  may 
produce  reflex  vomiting  and  coughing,  as  well  as  reflex  contraction 
of  the  vessels  of  the  ear  (Snellen,  Loven). 

(c)  The   pharyngeal   branch   or   branches   that  run  from  the 
ganglion  nodosum  to  form  the  pharyngeal  plexus  contain  sensory 
fibres  for  the  mucous  membrane  of  the  pharynx,  and  motor  fibres 
for  the  three  pharyngeal  constrictors.     Both  these  come  into  play 
in  deglutition  and  vomiting. 

(d)  The  mucous  membrane  of  the  posterior  part  of  the  tongue, 
epiglottis,  and  larynx  (especially  the  part  above  the  glottis)  owes  its 
excessive  sensibility,  by  which  the  least  mechanical  stimulus  evokes 
repeated  fits  of  convulsive  coughing,  to  the  sensory  fibres  of  the 


398  PHYSIOLOGY  CHAP. 

vagus  contained  iu  the  superior  laryugeal.  The  special  sensory 
and  motor  functions  of  the  two  laryngeal  nerves,  the  nerves  of 
phonation,  are  dealt  with  in  Chap.  III.  of  this  volume. 

(e)  The  mucous  membrane  and  plain  muscle  fibres  of  the 
trachea,  bronchi,  and  pulmonary  alveoli  are  innervated  by  the 
pulmonary  branches  of  the  vagus,  which  form  the  pulmonary 
plexus.  The  important  part  played  by  the  afferent  and  efferent 
fibres  of  the  pulmonary  branches  of  the  vagus  in  the  innervation 
of  the  respiratory  apparatus  is  discussed  in  Vol.  I.  Chap.  XIII. 

(/)  The  function  of  the  branches  of  the  vagus  that  form  the 
cardiac  plexus  (inhibitory  fibres,  depressor  nerve,  etc.)  in  control- 
ling the  action  of  the  heart  has  been  dealt  with  in  Vol.  I.  Chap.  IX. 

(#)  The  importance  of  the  oesophageal,  gastric,  and  caeliac 
plexuses  of  the  vagus  has  already  been  discussed  in  other  chapters, 
particularly  in  Chap.  III.  4,  9,  and  11,  and  IV.  7,  of  Vol.  II.  (also 
in  Chap.  VI.  of  this  volume). 

In  order  to  obtain  a  clear  and  accurate  idea  of  the  vital 
importance  of  the  vagi,  in  regulating  circulation,  respiration,  and 
digestion,  we  need  only  examine  the  effects  of  dividing  them  on 
both  sides  in  the  neck.  This  study  was  inaugurated  by  Valsalva, 
Morgagni  (1740),  Legallois  (1812);  continued  more  particularly 
by  Traube  (1846),  Cl.  Bernard  (1858),  M.  Schiff  (1867);  and 
resumed  more  recently  by  Vanlair  (1893),  A.  Herzen  (1894), 
Pawlow  (1910),  Nicolaides  (1901),  Gomez  Ocaiia  (1903).  The 
results  can  be  briefly  summarised.  Section  of  both  vagi  in  the 
neck  produces  maiiy  disturbances,  which  lead  more  or  less  rapidly 
to  the  death  of  the  animal.  Rabbits  generally  die  in  twenty 
to  thirty-six  hours,  dogs  in  four  to  five  days,  fowls  in  six  to 
seven  hours.  In  young  animals  death  takes  place  in  thirty  to 
sixty  minutes  after  vagotoniy  with  symptoms  of  acute  asphyxia, 
owing  to  total  paralysis  of  the  laryngeal  muscles,  and  almost 
complete  closure  of  the  glottis  by  the  passive  adduction  of 
the  vocal  cords.  This  is  due  to  paralysis  of  the  posterior  thyro- 
arytenoid  muscles  which  dilate  the  glottis,  and  to  the  fact  that  the 
pars  interarytaenoidea  of  the  glottis  is  incompletely  developed, 
and  its  lips  are  almost  entirely  destitute  of  membrane.  Legallois 
found  that  in  young  animals  simple  section  of  the  recurrent  nerves 
suffices  to  produce  death  by  asphyxia ;  but  if,  after  cutting  the 
vagi  free,  pulmonary  ventilation  is  supplied  by  tracheotomy,  young 
animals,  like  adults,  are  capable  of  surviving  longer. 

The  cause  of  death  of  adult  animals  after  bilateral  section  of 
the  vagi  is  very  complex. 

It  is  generally  accepted  that  the  section  or  ligation  of  one 
vagus  only  in  mammals  or  man  is  well  borne  in  the  majority  of 
cases,  the  disturbances  of  cardiac  rhythm,  respiratory  rhythm,  and 
digestive  functions  being  readily  and  speedily  compensated.  But 
if  the  other  vagus  be  simultaneously  divided,  the  consequent  trachy- 


vii  THE  MEDULLA  OBLONGATA  399 

cardia  and  dyspnoea  may  become  so  marked  that  the  animal  dies 
in  a  few  hours,  owing  merely  to  the  cessation  in  the  control  of 
respiration  and  circulation.  In  fact  no  lesion  of  the  internal 
organs  sufficient  to  account  for  death  can  be  detected  by  post- 
mortem examination. 

In  other  cases  the  animals  survive  the  double  vagotomy  for  a 
longer  period,  and  death  is  due  to  hepatisation  of  the  lungs,  particu- 
larly of  the  upper  lobes,  or  to  haemorrhage  or  hyperaemia  with 
diffuse  oedema  of  the  lungs  and  excess  of  mucus. 

Like  the  panophthalmia  after  section  of  the  trigeininal  nerve 
(see  pp.  330  e,t  seq.},  the  pneumonia  that  follows  vagotomy  was  long 
regarded  as  a  proof  that  the  vagi  contained  fibres  with  a  trophic 
influence  on  the  pulmonary  tissue.  Traube  was  the  first  who 
threw  doubt  on  this  theory.  He  noted  after  double  vagotomy 
difficulty  in  swallowing,  owing  to  the  paralysis  of  the  glottis  and 
oesophagus  ;  bits  of  food,  saliva,  or  buccal  mucus  may  consequently 
get  into  the  air  passages  or  stick  in  the  oesophagus  and  give  rise 
to  frequent  regurgitation,  in  which  particles  may  penetrate  through 
the  open  glottis  into  the  lungs,  and  there  set  up  inflammation. 

Again,  apart  from  the  penetration  of  irritating  substances  by 
the  air  passages,  the  pulmonary  lesions  consequent  on  double 
vagotomy  may  be  explained  by  the  following  facts  :— 

(a)  Vagotomy  causes  motor  and  sensory  paralysis  of  the  larynx, 
trachea,  the  bronchi,  and  pulmonary  alveoli,  which,  besides  produc- 
ing pulmonary  emphysema  and  catarrh  of  the  bronchi,  suppresses 
coughing  and  favours  irritation,  not  only  by  foreign  bodies,  but 
also  by  the  mucus  secreted  by  the  bronchi. 

(b)  The   acute    dyspnoea    consequent    on    double    vagotomy 
hinders    the    pulmonary    circulation,    and    eventually    produces 
marked    pulmonary   congestion    with    haemorrhage    and    oedema, 
even  independently  of  the  vasomotor  paralysis  of  the  lung  which 
was  insisted  on  by  Schiff  and  Herzen,  but  for  which  there  is  no 
direct  evidence. 

When  an  interval  of  several  months  intervenes  between  the 
section  of  the  first  and  second  vagus,  so  that  the  nerve  first  divided 
is  able  to  regenerate,  dogs  not  infrequently  survive  double  vagotomy 
(Vanlair),  but  not  rabbits  or  guinea  pigs  (Beaunis).  It  is,  how- 
ever, difficult  to  decide  what  length  of  time  must  elapse  between 
the  first  and  second  vagotomy,  in  order  to  ensure  regeneration  and 
therefore  survival.  Vanlair's  dogs  died  one  to  eight  days  after  the 
second  vagotomy  \vhen  the  first  had  been  made  four,  six,  seven 
months  or  even  a  year  previously.  But  as  one  dog  survived 
when  the  second  vagus  was  cut  ten  months  after  the  first,  he 
concluded  that  at  least  ten  to  twelve  months  were  essential  for 
complete  regeneration  of  the  vagus  first  divided. 

Later  work  has  proved,  however,  that  independently  of  the 
regeneration  of  the  nerve  first  divided,  dogs  may  survive  for 


400  PHYSIOLOGY  CHAP. 

months  when  the  second  vagotomy  follows  within  a  few  months 
after  the  tirst  (Her/en,  Pawlow).  Herzen  succeeded  in  keeping 
them  alive  by  making  a  gastric  fistula  through  which  he  fed  the 
vagotomised  animal,  so  as  to  avoid  pneumonia.  Pawlow  obtained 
still  better  results  by  supplementing  the  gastric  with  the  double 
oesophageal  fistula,  as  described  in  his  experiments  on  sham 
feeding  (Vol.  II.  p.  108). 

The  experiments  of  Nicolaides,  however,  proved  that,  without 
artificial  help,  a  strong  dog  can  survive  the  second  vagotomy 
performed  immediately  after  the  wound  of  the  first  operation  has 
healed.  At  the  Physiological  Congress  at  Turin  (1901)  he  showed 
two  large,  robust,  and  healthy  dogs,  in  which  the  vagi  and  sym- 
pathetics  had  been  divided  in  the  neck  in  two  successive  sittings 
at  a  few  days'  interval,  ten  months  and  nineteen  months  earlier. 
These  animals  were  well  nourished  and  ate  well,  swallowing  large 
pieces  of  meat  without  difficulty.  Phonation,too,had  been  recovered. 
The  post-mortem  examination,  made  before  a  committee  of  the 
Congress,  showed  that  the  two  vagi  had  not  regenerated,  and  their 
peripheral  ends  were  seen  under  the  microscope  completely  de- 
generated. There  is  at  present  no  evidence  to  explain  how  these 
two  dogs  succeeded  in  compensating — perfectly,  to  all  appearance 
—the  disturbances  of  respiratory  and  cardiac  rhythm,  of  phonatiou, 
and  of  the  mechanical  and  secretory  activities  of  digestion. 

Still  more  marvellous  is  the  survival  of  other  dogs  in  which 
double  vagotomy  was  performed  in  one  sitting.  Among  the 
various  cases  recorded  by  the  younger  Herzen  (1897)  the 
most  interesting  is  that  presented  by  Boddaert  to  the  "  Societe* 
de  Medecine  de  Gand  "  (1877).  A  strong  bitch  survived  double 
simultaneous  vagotomy  for  three  months  and  six  days.  During 
the  first  week  it  seemed  depressed,  and  vomited  the  milk  and  water 
swallowed ;  tachycardia  and  dyspnoea  were  marked.  During 
the  second  week  improvement  set  in,  and  the  animal  ate  freely 
without  vomiting.  The  vomiting  decreased  further  during  the 
first  and  second  months,  and  the  animal's  strength  returned  pro- 
portionately. At  the  end  of  the  second  month  its  respiration 
frequency  was  14,  and  its  pulse  132  per  minute.  In  the  last 
week  of  its  life  its  nutrition  was  again  disturbed,  and  its  strength 
gradually  diminished.  The  post-mortem  examination  revealed 
emphysema  of  the  upper  lobes  of  the  lung  and  broncho-pneumonia 
of  the  right  lower  lobe,  though  microscopic  examination  failed  to 
discover  any  traces  of  food  or  buccal  epithelium.  The  two  stumps 
of  the  vagus  had  united  again,  but  it  was  obviously  too  early  for 
any  complete  regeneration. 

Gomez  Ocaiia,  again,  at  the  International  Congress  of  Medicine 
at  Madrid  (1903),  presented  a  large  strong  dog  which  had  survived 
bilateral  section  of  the  vago  -  sympathetic  in  the  neck,  per- 
formed some  three  months  earlier.  After  twelve  days  the  normal 


vii  THE  MEDULLA  OBLONGATA  401 

relations  between  respiratory  and  cardiac  rhythm  returned.  But 
when  shown  at  the  Congress  the  animal  was  still  incapable  of 
making  any  sounds,  and  vomited  frequently,  though  well  nourished 
and  in  good  spirits.  After  anaesthetising  it  with  ether  and 
chloroform,  Pawlow  and  Steward  exposed  the  two  nerve  trunks, 
which  were  found  to  be  already  united  by  cicatricial  tissue,  but 
not  regenerated,  since  strong  electrical  stimulation  below  the 
point  of  section  did  not  affect  the  rhythm  of  the  heart,  although 
above  that  point  it  produced  acceleration  of  the  respiratory  rhythm. 

Both  Boddaert's  case  and  that  of  Gomez  Ocana  show  that, 
although  important,  the  functions  of  the  vagus  nerves  are  not 
absolutely  indispensable  to  life.  How  the  disorders  of  respiratory 
and  cardiac  rhythm,  of  deglutition  and  of  phonation,  which  neces- 
sarily result  from  double  vagotomy  can  be  compensated  remains  a 
mystery. 

V.  The  Glosso-pharyugeal  or  9th  cerebral  nerve  leaves  the 
medulla  oblongata  by  two  roots,  one  of  which,  the  motor,  arises 
along  with  the  vagus  from  the  nucleus  ambiguus,  the  other,  which 
is  sensory,  has  its  terminal  nucleus  above  that  of  the  vagus,  on  the 
floor  of  the  fourth  ventricle,  in  the  ala  cinerea  (see  Fig.  204).  It 
is  therefore  a  mixed  nerve,  and  may  be  regarded  as  a  metarneric 
homologue  of  a  spinal  pair.  In  its  passage  through  the  jugular 
foramen,  along  with  the  vagus  and  accessory,  it  bears  two  small 
ganglia,  the  jugular  and  petrosal,  which  have  unipolar  cells  like 
the  spinal  ganglia.  The  petrosal  ganglion  gives  origin  to  the 
tympanic  branch  (Jacobson's  nerve),  which  connects  the  glosso- 
pharnygeal  with  other  nerves  at  the  base  of  the  skull  (Fig.  211). 

In  passing  through  the  neck  the  glosso-pharyngeal  gives  off  a 
pharyngeal  branch,  a  tonsillar  branch  which  also  innervates  the 
mucous  membrane  of  the  pillars  of  the  fauces  and  the  soft  palate, 
and  lingual  branches  that  supply  the  circumvallate  and  foliate 
papillae  of  the  mucous  membrane  over  the  posterior  two-thirds  of 
the  tongue  (Fig.  212). 

Before  the  publication  of  Panizza's  classical  memoir,  Experi- 
mental Researches  on  Nerve  (1834),  Fodera,  Mayo,  and  Magendie 
had  maintained  that  the  sense  of  taste  was  subserved  entirely  by 
the  lingual  branch  of  the  tris;eminal.  Panizza  was  the  first  who 

O  t? 

demonstrated  that  the  glosso-pharyngeal  is  the  taste  nerve,  just 
as  the  Lingual  branch  of  the  trigeminal  is  the  tactile  nerve,  and 
the  hypoglossal  the  motor  nerve,  for  the  tongue. 

Panizza's  assertion  of  the  exclusively  gustatory  character  of 
the  glosso-pharyngeal  was  at  once  contested  by  Joh.  Miiller  and 
his  pupil  Kornfeld,  who  believed  this  nerve  to  be  of  little  import- 
ance for  taste,  that  sense  being  served  by  the  lingual  nerve,  as 
Magendie  stated.  Other  physiologists  came  to  the  same  conclusion 
(Hall  and  Braughtou,  Wagner,  Valentin,  Staniiius)  on  repeating 
Panizza's  experiments  ;  and  others  recognised  the  glosso-pharyngeal 

VOL.  Ill  2  D 


402 


PHYSIOLOGY 


CHAP. 


as  the  principal  nerve  of  taste,  but  asserted  that  the  lingual  branch 
of  the  trigeminal  possessed  the  same  function.     Alcock  (1839),  in 


FIG.  212.— Distribution  and  connections  of  vagus  nerve  on  left  side  in  neck  and  upper  part  of 
thorax.  (Sappey,  from  Hirschfeld  »nd  Leveille.)  i.  1,  vagus  nerve  ;  2,  ganglion  of  its  trunk  ; 
3,  bulbar  part  of  accessory  ;  4,  union  of  vagus  with  hypoglossal ;  5,  phary  ngeal  branch  of  vagus  ; 
li,  superior  laryngeal  nerve  ;  7,  external  laryngeal  ;  8,  communication  of  external  laryngeal 
nerve  with  superior  cardiac  branch  of  sympathetic  ;  9,  recurrent  or  inferior  laryngeal ;  10, 
superior,  and  11,  inferior  cervical  cardiac  branches;  12,  13,  posterior  pulmonary  plexus;  14, 
lingual  branch  of  mandibular  nerve  ;  15,  distal  part  of  hypoglossal  nerve  ;  16,  glosso-pharyngeal 
nerve  ;  17,  accessory  nerve,  uniting  by  its  inner  branch  with  the  vagus,  and  by  its  outer  passing 
into  the  sterno-mastoid  muscle  ;  18,  2nd,  19,  3rd  and  20,  4th  cervical  nerves  ;  21,  origin  of  phrenic 
nerve  ;  22,  23,  5th,  6th,  7th,  8th  cervical  nerves,  forming  with  the  1st  thoracic  the  brachial 
plexus  ;  24,  superior  cervical  ganglion  of  sympathetic  ;  25,  middle  cervical  ganglion  ;  26,  inferior 
cervical  ganglion  united  with  1st  thoracic  ganglion  ;  27,  28,  29,  30,  2nd,  3rd,  4th,  and  5th 
thoracic  ganglia. 

% 

an  important  series  of  experiments,  maintained  that  the  gustatory 
fibres  run  in  the  glosso-pharyngeal  and  the  lingual  and  palatine 
branches  of  the  trigeminus,  and  that  the  spheno-palatine  ganglion 


vii  THE  MEDULLA  OBLONGATA  403 

and  the  chorda  tympaiii  are  of  no  importance  for  the  sense  of 
taste,  since  they  can  be  extirpated  or  divided  without  disturbing 
it.  Guzot  and  Cazalis  (1839)  concluded  from  their  researches 
that  the  lingual  was  the  tactile  and  gustatory  nerve  for  the  anterior 
three-fourths  of  the  tongue.  Eeid  (1839)  added  that  after  bilateral 
section  of  the  glosso-pharyngeal  the  sense  of  taste  was  sufficiently 
well  preserved  to  distinguish  bitter  substances. 

On  the  other  hand,  01.  Bernard  (1843)  found  that  after 
dividing  the  facial  nerve  in  the  cranial  cavity,  or  cutting  the 
chorda  in  the  tympanic  cavity,  the  taste  sense  is  altered  in  the 
anterior  part  of  the  tongue,  because  savours  are  less  promptly 
recognised  than  on  the  side  not  operated  on. 

Biffi  and  Morganti  (1846),  after  unilateral  section  of  the 
chorda,  failed  to  confirm  the  difference  in  the  sense  of  taste  on 
the  two  halves  of  the  tongue.  It  further  appeared  from  their 
experiments  that  the  glosso-pharyngeal  is  the  nerve  of  taste  for 
the  palate,  fauces,  and  posterior  two-thirds  of  the  tongue,  while 
the  lingual  branch  serves  its  anterior  third. 

Duchenne  (1860)  brought  evidence  in  favour  of  Bernard's 
theory  of  the  presence  of  taste  fibres  in  the  chorda  tympani  by 
exciting  them  electrically  through  the  external  auditory  meatus. 
This,  according  to  Duchenne,  produces,  in  addition  to  sensory 
phenomena,  a  metallic  taste  in  the  anterior  two -thirds  of  the 
tongue ;  while  electrical  stimulation  of  the  lingual  nerve,  on  the 
other  hand,  does  not  produce  any  sense  of  taste. 

According  to  Schiff  (1867),  the  taste  fibres  for  the  anterior 
part  of  the  tongue,  which  leave  the  bulb  with  the  second  branch 
of  the  trigerninal,  run  to  the  spheno-palatine  ganglion,  thence  by 
the  Vidian  nerve  to  the  geniculate  ganglion  of  the  facial,  and 
finally  join  the  trunk  of  the  inferior  maxillary  nerve,  or  run  in 
the  facial  to  the  chorda  tympani,  and  thence  to  the  lingual.  This 
theory,  however,  is  at  variance  with  the  fact  established  by  Alcock, 
and  subsequently  confirmed  by  Prevost,  that  the  extirpation  of  the 
spheno-palatine  ganglion  produces  no  perceptible  alteration  in 
taste. 

Lussana  and  Inanzi  (1862)  fell  back  on  Bernard  and  Duchenne's 
hypothesis.  They  maintained  that  the  taste  fibres  to  the  anterior 
part  of  the  tongue  come  from  the  facial  or  the  intermediary  nerve 
of  Wrisberg,  and  pass  to  the  geniculate  ganglion,  thence  by  the 
facial  trunk  to  the  chorda  tympani  and  to  the  lingual.  In  addition 
to  his  experimental  data,  Lussana  based  his  view  upon  clinical 
cases  of  paralysis  of  the  trigeminus  without  loss  of  taste  on  the 
anterior  part  of  the  tongue,  and  of  paralysis  of  the  facial  nerve 
or  lesions  of  the  chorda  tympani  in  man,  with  abolition  of  taste 
in  this  region.  To  this  it  was  objected  that  in  facial  paralysis 
the  sense  of  taste  disappears  from  the  tip  of  the  tongue  only  if 
the  lesion  lies  between  the  geniculate  ganglion  and  the  exit  of  the 


404  PHYSIOLOGY  CHAP. 

chorda,  and  not  when  it  involves  the  trunk  of  the  nerve  proximal 
to  the  ganglion. 

If  the  taste  fibres  for  the  anterior  part  of  the  tongue  come 
neither  from  the  trigeniinal  nor  the  facial,  they  may  be  derived 
indirectly  from  the  glosso-pharyngeal,  through  Jacobson's  nerve, 
or  from  the  small  superficial  petrosal  which  unites  the  glosso- 
pharyngeal  with  the  facial.  This  opinion,  which  is  well  estab- 
lished from  the  anatomical  point  of  view,  was  confirmed  by  Carl 
(1875)  from  accurate  observations  on  himself.  He  noticed  that 
the  left  anterior  part  of  his  tongue  was  entirely  deficient  in  sensi- 
bility to  taste.  He  had  no  affection  of  the  facial  or  trigeniinal 
nerves,  but  from  early  youth  had  suffered  from  left  otorrhoea  with 
almost  complete  destruction  of  the  tympanum.  His  left  chorda 
tympani  seemed  to  be  healthy,  since  its  secretory  and  sensory 
fibres  reacted  immediately  to  excitation.  The  loss  of  taste  in  the 
anterior  part  of  the  tongue  must  be  due  therefore  to  injury  to 
other  branches  of  the  tympanic  plexus.  He  concluded  that  the 
taste  fibres  of  this  region  came  from  the  petrosal  ganglion  of  the 
glosso-pharyngeal,  ran  in  the  tympanic  branch  (Jacobson's  nerve) 
to  the  tympanic  plexus,  and  thence  by  the  small  superficial  petrosal 
nerve,  to  the  otic  ganglion  and  the  lingual  nerve ;  or  partly  to  the 
geniculate  ganglion,  and  so  by  the  chorda  tympani  to  the  lingual. 

Von  Urbantschitsch  (1876)  took  the  same  view  as  Carl,  on  the 
strength  of  his  clinical  observations,  and  held  that  taste  fibres 
run  through  the  tympanic  plexus,  which  is  connected  by  Jacob- 
son's  nerve  with  the  glosso-pharyngeal.  This  theory,  while  not 
confirmed  directly  by  experiment,  seems  the  most  acceptable.  It 
readily  explains  the  cases  of  trigeminal  paralysis,  and  those  in 
which  the  facial  is  injured  by  a  lesion  of  the  trunk  above  the 
geniculate  ganglion  without  noticeable  disturbance  of  the  sense  of 
taste.  If  we  accept  this  conclusion,  it  confirms  Panizza's  original 
statement  that  the  function  of  taste  is  served  exclusively  by  the 
glosso-pharyngeal  nerve. 

Another  question  not  yet  fully  cleared  up  is  whether  the  fibres 
of  the  glosso-pharyngeal  subserve  only  taste,  or  tactile  and  pain 
sensibility  also,  in  the  parts  which  they  supply.  Panizza  held 
that  the  intracranial  mechanical  stimulation  of  the  glosso- 
pharyngeal  produces  no  sensations  of  pain,  but  others,  including 
Longet,  deny  this.  On  the  other  hand,  no  conclusion  in  favour 
of  the  thesis  that  the  9th  is  exclusively  a  taste  nerve  can  be 
drawn  from  the  fact  that  pain  sensibility  persists  in  the  tongue, 
fauces,  and  anterior  surface  of  the  epiglottis,  after  section  of  the 
glosso-pharyngeal.  Volkmann  found  that  after  this  operation 
irritation  of  the  posterior  part  of  the  tongue,  fauces,  and  pharynx 
no  longer  cause  reflex  nausea  and  vomiting;  but  this  might 

O  O    '  O 

obviously  depend  on  loss  of  the  taste  sense  in  this  region  rather 
than  on  paralysis  of  tactile  or  pain  sensibility.     In  fact,  after 


vii  THE  MEDULLA  OBLONGATA  405 

section  of  the  trigeminal,  which  certainly  sends  sensory  and 
tactile  fibres  to  the  isthmus  of  the  fauces,  the  vomiting  reflexes 
persist. 

Another  experimental  argument  favours  the  idea  that  the 
centripetal  fibres  of  the  9th  nerve  are  exclusively  for  taste.  We 
know  how  intimate  a  relation  exists  between  gustatory  sensations 
and  reflex  salivation,  and  Ludwig  and  Eahn,  on  stimulating  the 
central  end  of  the  divided  glosso-pharyngeal,  obtained  a  more 
abundant  secretion  of  saliva  than  on  exciting  the  lingual.  After 
bilateral  section  of  the  trigeminal  nerve  in  the  cat  there  is  an 
abundant  secretion  of  saliva  if  the  animal  is  given  milk  made 
bitter  with  quinine.  This  does  not  occur  on  the  other  hand  after 
bilateral  section  of  the  glosso-pharyngeal.  All  these  facts  seem  to 
us  to  favour  Panizza's  theory. 

The  motor  fibres  of  the  9th  cranial  nerve  supply  the  stylo- 
pharyngeal  muscle  and  the  superior  constrictor  of  the  pharynx 
(Volkmann  and  Klein).  These  muscles  come  into  action  during 
the  deglutition  reflexes,  which  are  readily  excited  by  stimulating 
the  base  of  the  tongue  towards  the  isthmus  of  the  fauces. 

The  tympanic  or  Jacobson's  branch,  which,  as  we  have  seen, 
conducts  the  taste  fibres  by  an  indirect  path  to  the  anterior  part 
of  the  tongue,  also  contains  secretory  fibres  for  the  parotid  gland 
(Vol.  II.  p.  76). 

VI.  The  8th  nerve  has  two  roots ;  one,  the  medial  or  anterior, 
forms  the  Vestibular  nerve,  which  pierces  the  bulb  on  the 
inner  side  of  the  restiform  body  and  ends  in  the  nucleus  in  the 
floor  of  the  fourth  ventricle ;  the  other,  the  lateral  or  posterior 
branch,  forms  the  Cochlear  nerve,  which  passes  round  the  resti- 
form body,  where  it  has  a  special  nucleus  (Fig.  213).  These  are 
two  distinct  nerves,  arising,  like  the  dorsal  roots  of  the  spinal 
pairs,  from  peripheral  ganglia ;  the  first  from  the  vestibular 
ganglion  or  ganglion  of  Scarpa;  the  second  from  the  spiral 
ganglion  of  the  cochlea. 

According  to  Horbaczewsky  the  vestibular  and  cochlear  nerves 
run  separately,  from  their  origin,  in  the  sheep  and  horse.  After 
section  of  the  vestibular  branch  in  the  sheep  (Biehl)  and  in 
pigeons  (Wallenberg)  there  is  ascending  degeneration  of  the 
medial  roots,  which  extends  as  far  as  the  corresponding  nucleus. 
After  removing  the  semicircular  canals  alone  in  pigeons  the  same 
degeneration  results ;  but  after  extirpation  of  the  cochlea  only  the 
lateral  root  degenerates  as  far  as  its  nucleus  (Forel,  Onufrowicz, 
Baginski,  Deganello). 

The  central  relations  of  the  vestibular  and  cochlear  nerves  are 
still  doubtful;  the  former  is  specially  connected  with  the  cere- 
bellum, the  latter  with  the  cerebrum. 

We  shall  discuss  the  functions  of  these  two  nerves,  which 
together  make  up  the  8th  cerebral  nerve,  in  detail,  in  treating  of 


406 


PHYSIOLOGY 


CHAP. 


To  cerebellum 


C.L.R 


VIII    M 


the  sense-organs ;  here  we  need  only  say  that  the  physiological 
expression,  acoustic  nerve,  applies  only  to  the  cochlear  branch  and 
not  to  the  whole  nerve,  since  the  vestibular  branch  has  nothing 
to  do  with  hearing.  With  the  earliest  experiments  of  Flourens 
(1828-30),  who  may  be  called  the  founder  of  the  physiology  of  the 
semicircular  canals,  the  important  fact  became  evident  that  all 
lesions  or  injuries  of  the  labyrinth  are  followed  by  specific  motor 
disorders  without  loss  of  hearing ;  while  deafness  without  motor 
disturbance  is  the  effect  of  destroying  the  cochlea.  To  prove  that 
the  organs  innervated  by  the  vestibular  nerve  have  quite  a 

different  function  from  the 
cochlea,  we  may  cite  the 
facts  adduced  by  Bateson 
(1890),  Kreidl  (1895),  Lee 
(1898),  and  others,  showing 
that  fishes,  which  have  no 
cochlea,  have  no  proper 
sense  of  hearing,  i.e.  they 
do  not  react  to  ordinary 
sound  vibrations.  When 
fish  are  excited  by  ex- 
plosions or  other  loud  noises 
this  cannot  be  due  to  stimu- 
lation of  the  labyrinth, 
because  approximately  the 
same  reactions  are  ex- 
hibited when  the  labyrinth 
has  been  removed.  These 
sounds  therefore  excite  the 
tactile  sense  in  fishes — the 
auditory  sense,  as  we  shall 
presently  see,  being  only  a 
specialisation  of  this. 
Doubt  was,  however,  cast  on  these  experiments  on  hearing  in 
fishes  by  Parker  (1903).  He  noted  that  certain  kinds  of  fish, 
although  devoid  of  cochlea,  reacted  to  the  vibration  of  a  violin 
string,  or  even  to  the  note  of  a  tuning-fork  transmitted  through 
water,  by  modifications  in  the  movements  of  their  fins  and  their 
respiratory  rhythm.  According  to  Parker,  these  reactions  dis- 
appear almost  entirely  on  destroying  the  labyrinth. 

As  the  two  branches  of  the  8th  nerve  are  analogous  to  two 
dorsal  spinal  roots,  so  the  7th  cerebral  nerve — the  Facial — corre- 
sponds to  a  large  ventral  root,  or  more  properly  to  the  union  of  a 
number  of  such  roots.  It  takes  origin  in  the  lower  part  of  the 
pons  from  a  nucleus  of  large  ganglion  cells,  which  lies  at  about 
the  level  of  the  6th  nerve,  and  somewhat  higher  and  more 
ventral  than  the  nucleus  of  the  vestibular  branch  of  the  8th 


FIG.  213. — Plan  of  roots  of  acoustic  nerve.  (Thane.) 
The  outline  represents  a  section  at  the  junction  of 
the  bulb  with  the  pons  :  VIII.M,  vestibular  division  ; 
vm.LjCochlear  division  of  auditorynerve;  N.  vin.  ACC, 
accessory  nucleus  ;  G.L.R.,  lateral  nucleus  ;  N.VIII.D, 
dorsal  nucleus  ;  AV,  bulbo-spinal  root  of  5th  nerve. 


VII 


THE  MEDULLA  OBLONGATA 


407 


nerve  (Fig.  209).  Its  fibres  first  pass  medialwards  and  dorsal- 
wards  to  form  a  loop  round  the  nucleus  of  the  abducens,  and  then 
turn  ventral-  and  lateralwards  to  emerge  at  the  upper  end  of  the 
bulb  (Fig.  214).  The  facial  nerve  enters  the  internal  auditory 
meatus  along  with  the  8th  nerve,  but  separates  from  it  at  the 
bottom  of  the  meatus  to  enter  the  aqueduct  of  Fallopius,  which 
it  leaves  on  the  lower  surface  of  the  skull  by  the  stylo-mastoid 
foramen  (Fig.  215).  The  facial  is  accompanied  by  the  nervus 
intermedius  of  Wrisberg. 

During  its  course  through  the  Fallopian  canal  the  facial  gives 


FIG.  214.— (Left.)  Plan  of  origins  of  fith  and  motor  root  of  7th  cerebral  nerves.  (Thane,  adapted 
from  Schwalbe.)  The  outline  represents  a  transverse  section  of  the  lower  part  of  the  pons,  on 
to  which  the  course  of  the  facial  nerve  is  projected;  vi,  6th  nerve;  N.VI,  its  nucleus;  vn, 
facial  nerve  ;  VILA,  ascending  portion  of  its  root,  supposed  to  be  seen  in  optical  section  ; 
N.VII,  its  nucleus  :  so,  superior  olive;  AV,  sensory  or  bulbo-spinal  root  of  5th  nerve;  VIII.M, 
mesial  root  of  acoustic  nerve. 

FIG.  215. — (Right.)  Facial  nerve  in  its  canal,  with  its  connecting  branches,  etc.  (Sappey,  after 
Hirschfeld  and  Leveille.)  f.  The  mastoid  and  a  part  of  the  petrous  bone  have  been  divided  nearly 
vertically,  and  the  canal  of  the  facial  nerve  opened  in  its  whole  extent  from  internal  meatus  to 
stylo-mastoid  foramen  ;  the  Vidian  canal  has  also  been  opened  from  the  outer  side  ;  1,  facial 
nerve  in  first,  horizontal  part  of  its  course ;  2,  its  second  part,  turning  backwards  ;  3,  its 
vertical  portion  ;  the  nerve  at  its  exit  from  stylo-mastoid  foramen  ;  5,  geniculate  ganglion  ; 
6,  large  superficial  petrosal  nerve  ;  7,  spheno-palatine  ganglion  ;  8,  small  superficial  petrosal 
nerve;  9,  chorda  tympani ;  10,  posterior,  auricular  branch  cut  short;  11,  branch  to  digastric 
muscle ;  12,  branch  to  stylo-hyoid  muscle  ;  13,  twig  uniting  with  glosso-pharyngeal  nerve 
(14  and  15). 

off  two  branches  to  the  tympanum,  the  smaller  of  which  innervates 
the  stapedius  muscle,  the  other — which  is  the  chorda  tympani— 
passes  through  the  tympanic  cavity  and  unites  with  the  lingual 
branch  of  the  trigeminal  to  run  partly  to  the  sub-maxillary 
ganglion,  partly  to  the  front  part  of  the  tongue.  Branches  run 
from  the  geniculate  ganglion  through  the  large  superficial  petrosal 
nerve  to  the  spheno-palatine  ganglion,  from  which  the  palatine 
branches  emerge  to  supply  the  muscles  of  the  soft  palate,  parti- 
cularly the  azygos  uvulae  and  the  levator  palatini.  On  leaving 
the  skull  the  facial  sends  branches  to  the  external  muscles  of  the 
ear,  the  stylo-hyoid  and  the  posterior  belly  of '  the  digastric.  At 


408 


PHYSIOLOGY 


CHAP. 


the  posterior  border  of  the  masseter  the  facial  trunk  divides  into 
many  branches,  which  are  distributed  to  all  the  muscles  of  the 
face,  to  the  buccinator  and  the  platysma  inyoides  (Fig.  216). 

After  some  incomplete  experiments  by  Bellingeri,  Charles  Bell 
(1821)  demonstrated  that  the  facial  is  an  exclusively  motor  nerve. 


Fin.  216.— Superficial  distribution  of  facial,  trigeminal,  and  other  nerves  of  head.  (Sappey,  after 
Hirschfeld  and  LevcilK-.)  f.  Facial  nerve— I,  trunk  of  facial  nerve  after  its  exit  from  stylo- 
mastoid  foramen  ;  2,  posterior  auricular  branch;  3,  filament  of  great  auricular  nerve  uniting 
with  foregoing  ;  4,  occipital  branch  ;  5,  auricular  branch  ;  6,  twig  to  superior  auricular  muscle  ; 
7,  nerve  to  digastric,  8,  that  to  stylo-hyoid  muscle  ;  9,  superior  or  temporo-facial  division  of  the 
nerve;  10,  11,  temporal  branches  ;  12,  malar;  13,  14,  buccal;  15,  inferior  or  cervico-facial 
division  of  the  nerve  ;  16,  mandibular  ;  17,  cervical  branch.  Fifth  nerve— IS,  auriculo-temporal 
uniting  with  facial,  giving  anterior  auricular  and  parotid  branches,  and  ascending  to  temporal 
region;  19,  20,  supra-orbital;  21,  lachrymal;  22,  infra-trochlear  ;  23,  facial  twig  of  zygomatic ; 
•24,  superficial  branch  of  naso-ciliary ;  25,  infra-orbital ;  26,  buccal,  uniting  with  branches  of 
facial ;  27,  mental.  Cervical  nerves— 28,  great  occipital ;  29,  great  auricular  ;  30,  31,  small 
occipital ;  32,  superficial  cervical. 

He  proved  that  after  section  of  this  nerve  the  sensibility  of  the 
face  was  unaffected,  while  the  facial  muscles  were  paralysed.  After 
him,  many  other  physiologists  confirmed,  completed,  and  corrected 
his  observations,  either  by  experimental  section  or  by  electrical  and 
mechanical  excitation  of  the  trunk  of  the  facial  and  its  branches. 


vii  THE  MEDULLA  OBLONGATA  409 

VII.  The  cerebral  nerve  which  presents  the  strongest  analogy 
to  a  spinal  pair  is  certainly  the  Trigemiual  or  Trifacial,  with  its 
sensui T  root  connected  with  the  semilunar  or  Gasserian  ganglion, 
and  its  single  motor  root  which  unites  with  one  division  of  the 
sensory  root  to  form  a  mixed  nerve. 

Both  the  larger  sensory  and  the  smaller  motor  root  of  the 
trigeminus  issue  from  the  side  of  the  pons,  where  the  transverse 
fibres  of  the  latter  pass  into  the  middle  cerebellar  peduncle  (Fig. 
201).  The  motor  fibres  arise  in  a  nucleus  of  large  cells  at  the 
level  of  the  upper  portion  of  the  fourth  ventricle  ;  they  are  joined 
by  a  bundle  of  fibres  known  as  the  descending  or  mesencephalic 
root,  which  springs  from  a  long  slender  column  of  cells  in  the 
central  grey  matter  of  the  aqueduct  of  Sylvius  (Fig.  209).  The 
fibres  of  the  sensory  root  run  in  part  direct  to  the  upper  nucleus, 
which  lies  lateral  and  ventral  to  the  motor  nucleus.  The  greater 
number  turn  spiualwards  through  the  pons,  into  the  bulb  and  cord, 
to  the  level  of  the  4th  cervical  segment ;  they  terminate  among 
the  cells  of  the  substantia  gelatinosa  Eolandi  (descending  or  bulbo- 
spinal  root  of  the  5th  nerve). 

Distal  to  the  Gasserian  ganglion  the  trigeminus  divides  into 
its  three  great  branches  :  the  ophthalmic,  the  superior  maxillary, 
and  the  inferior  maxillary  (Fig.  217). 

The  ophthalmic  division  is  the  smallest  of  the  three  sensory 
branches  which  arise  from  the  unipolar  cells  of  the  semilunar 
ganglion.  It  supplies  branches  to  the  dura  mater  and  tentorium, 
to  the  eyeball  and  lachrymal  gland,  to  the  mucous  membrane  of 
the  nose  and  the  conjunctiva  of  the  eyelids,  to  the  skin  of  the  tip 
of  the  nose,  upper  eyelid,  forehead,  and  of  the  anterior  portion  of 
the  scalp.  The  ciliary  gland  is  connected  with  it. 

The  superior  maxillary  nerve,  with  the  sphenopalatine  ganglion 
(Meckel's  ganglion)  which  is  attached  to  it,  sends  branches  to  the 
skin  of  the  cheeks  and  anterior  part  of  the  temples,  the  lower 
eyelid,  the  side  of  the  nose  and  the  upper  lip ;  also  to  the  upper 
teeth  and  mucous  membrane  of  the  nose,  upper  part  of  pharynx, 
antrum  of  Highmore  and  posterior  ethmoid  sinuses,  and  the  soft 
palate ;  finally  to  the  tonsils,  uvula,  and  glands  of  the  buccal 
cavity. 

The  inferior  maxillary  or  mandibular  nerve,  which  is  the 
largest  of  the  three  branches  of  the  trigeminal,  is  a  mixed  nerve 
owing  to  its  union  with  the  motor  root.  Its  sensory  branches  are 
distributed  to  the  side  of  the  head  and  external  ear,  the  external 
meatus,  lower  lip  and  lower  part  of  the  face.  It  also  gives  sensory 
branches  to  the  larger  part  of  the  tongue,  to  the  mucous  membrane 
of  the  cheek,  gums,  and  lower  teeth,  to  the  salivary  glands,  the 
articulation  of  the  jaw,  the  dura  mater,  the  cranium,  and  the 
mucous  membrane  lining  the  mastoid  sinuses.  The  otic  and  sub- 
maxillary  ganglia  are  intimately  connected  with  the  mandibular 


410 


PHYSIOLOGY 


CHAP. 


nerve.  Bellinger!  gave  the  name  of  masticator  nerve  to  the 
motor  root  because  it  is  distributed  to  the  masseter,  temporal,  and 
the  two  pterygoid  muscles,  but  it  also  gives  branches  to  the 
mylo-hyoid,  the  anterior  belly  of  the  digastric,  tensor  palati,  and 
the  tensor  tympani. 

Charles  Bell  (1821)  first  affirmed  that  the  gaugliated  root, 
the  5th  nerve,  was  the  sensory  nerve  of  the  face,  but  it  was 
Fodera  (1823)  who  first  performed  intracranial  section  of  the 


FIG.  217.— Diagram  of  brandies  of  fifth  pair.  (After  a  sketch  by  Charles  Bell.)  J.  1,  Small  root 
of  5th  nerve  ;  -2,  large  root,  passing  forwards  into  the  semilunar  ganglion  ;  3,  placed  on  the 
bone  above  the  ophthalmic  nerve,  which  is  dividing  into  the.  frontal,  lachrymal,  and  naso- 
ciliary  brandies,  the  latter  connected  with  the  ciliary  ganglion  ;  4,  placed  on  the  bone  close  to 
foramen  rotundum,  marks  the  maxillary  division,  which  is  connected  below  with  the  splieno- 
palatine  ganglion,  and  passes  forwards  to  the  infra-orbital  foramen  ;  5,  placed  on  the  bone  over 
the  foramen  ovale,  marks  the  mandibular  nerve,  giving  off  aurieulo-temporal  and  muscular 
branches,  and  continued  by  inferior  dental  to  lower  jaw,  and  by  lingual  to  tongue  ;  a,  sub- 
maxillary  gland,  with  sub-maxillary  ganglion  placed  above  it  in  connection  with  lingual  nerve  ; 
6,  chorda  tympani ;  7,  facial  nerve,  issuing  from  stylo-mastoid  foramen. 

trigeminal  on  rabbits,  and  saw  that  sensibility  was  abolished  in 
all  the  external  parts  of  the  face,  and  on  the  mucous  membrane 
of  the  nose,  cheeks,  and  tongue.  Fodera's  observations  were  con- 
firmed and  amplified  by  H.  Mayo,  Magendie,  Eschricht,  and 
others. 

Unilateral  paralysis  of  the  motor  root  of  the  trigeminus 
paralyses  the  masticator  muscles  of  the  same  side,  so  that  in 
mastication  the  jaw  is  pulled  towards  the  paralysed  side  and  the 
teeth  of  the  upper  and  lower  jaws  no  longer  meet  accurately. 


vii  THE  MEDULLA  OBLONGATA  411 

We  have  already  dealt  fully  with  the  trophic  disturbances  of 
the  eye  after  intracranial  section  of  the  5th  nerve  (Chap.  V.  p.  330). 

The  6th  cerebral  nerve — the  Abducens  or  External  Oculo- 
motor— is  distributed  solely  to  the  external  rectus  muscle  of  the 
eye.  Its  fibres  arise  from  a  small  nucleus  lying  in  the  floor  of 
the  fourth  ventricle,  immediately  above  the  striae  acusticae  (Fig. 
209).  They  issue  in  the  form  of  a  flattened  bundle  from  the  lower 
edge  of  the  pons,  external  to  the  pyramid.  On  paralysis  of  this 
nerve  the  eyeball  deviates  inwards,  owing  to  preponderance  of  the 
antagonistic  internal  rectus  muscle  (convergent  strabismus). 

The  4th  or  Trochlear  nerve  is  the  smallest  of  the  cerebral 
nerves.  It  arises  in  an  elongated  nucleus,  a  prolongation  of  the 
nucleus  of  the  3rd  nerve,  which  lies  in  the  ventral  grey  matter 
of  the  aqueduct  of  Sylvius  at  the  level  of  the  posterior  quadri- 
geminal  bodies  (Fig.  209).  Its  fibres  bend  around  the  aqueduct 
and  enter  the  superior  medullary  velum  where  they  decussate 
completely  with  those  of  the  opposite  side.  After  a  long  intra- 
crauial  course  this  nerve  is  distributed  exclusively  to  the  superior 
oblique  muscle.  After  section  or  paralysis  of  the  trochlear  the 
outward  and  downward  rotation  of  the  eveball  is  lost,  so  that 

V 

there  is  an  upward  and  inward  squint — in  the  direction  of  the 
nose — owing  to  the  unantagonised  action  of  the  inferior  oblique 
nerve. 

The  3rd  or  Oculomotor,  the  largest  of  the  motor  nerves  to 
the  eyeball,  arises  in  a  nucleus  in  the  grey  matter  of  the  aqueduct 
of  Sylvius,  under  the  anterior  quadrigeminal  body  (Fig.  209). 
After  passing  through  the  tegmentum  the  nerve  emerges  at  the 
inner  border  of  the  cerebral  peduncle  at  the  upper  margin  of  the 
pons  (Fig.  201).  It  innervates  all  the  external  muscles  of  the 
eye  except  the  external  rectus  and  the  superior  oblique,  which 
are  supplied  by  the  6th  or  4th  nerves,  that  is  the  superior, 
inferior,  and  internal  rectus  muscles,  the  inferior  oblique  and  the 
levator  palpebrae.  The  branch  that  innervates  the  inferior  oblique 
muscle  sends  fibres  to  the  ciliary  ganglion ;  the  short  ciliary 
nerves  which  spring  from  this  penetrate  the  bulb  in  the  form  of 
minute  filaments,  and  innervate  the  sphincter  iridis  and  ciliary 
muscle. 

VIII.  As  a  central  organ  the  Medulla  Oblongata  has  an 
importance  far  greater  than  that  of  any  other  part  of  the  nervous 
system.  When  the  bulb  is  severed  by  a  transverse  section  from 
the  rest  of  the  brain  many  important  functions  are  preserved 
which  are  immediately  abolished  when  the  section  falls  between 
the  bulb  and  the  spinal  cord.  These  are  the  functions  of  the 
cerebral  nerves  which  emerge  from  and  have  their  centres  in  the 
bulb,  but  in  addition  certain  spinal  functions  become  paralysed 
because  their  dominating  and  co-ordinating  centres  lie  in  the 
bulb. 


412  PHYSIOLOGY  CHAP. 

The  activity  of  the  bulbar  centres  is  for  the  most  part  deter- 
mined by  peripheral  excitations  that  reach  them  by  afferent  paths 
(reflex  centres),  but  it  is  sometimes  evoked  by  rhythmic  or  tonic 
internal  central  excitations  (automatic  centres).  Their  normal 
function  depends  on  their  structure  and  on  the  normal  gas 
exchanges  kept  up  by  circulation  and  respiration.  Asphyxia, 
rapid  anaemia,  rise  of  blood  temperature  from  any  cause  excites 
and  finally  exhausts  the  bulbar  centres. 

In  discussing  the  visceral  functions  we  dealt  with  the  bulbar 
centres  by  which  they  are  controlled,  that  is,  those  which  regulate 
cardiac  activity,  vasomotor  tone,  respiratory  rhythm  and  digestion, 
consequently  we  need  only  now  consider  their  more  general 
functions. 

In  the  bulb,  and  intimately  connected  with  the  respiratory 
centre,  there  is  a  centre  which,  when  excited,  produces  general 
convulsions  or  spasms.  It  has  long  been  known  that  excitation 
of  the  bulb  by  any  kind  of  stimulus  readily  induces  general  con- 
vulsions. Acute  asphyxia,  rapid  ligation  of  the  two  carotids  and 
vertebral  arteries,  rapid  bleeding,  or  compression  of  the  veins  of 
the  neck  so  as  to  produce  a  cerebral  congestion  all  conduce  to 
more  or  less  general  cramps  or  convulsions  (Kussmaul  and  Tenner, 
Landois,  Hermann,  and  others)  by  interruption  of  the  normal 
exchanges.  If  the  interruption  develops  slowly  the  animal  may 
perish  from  asphyxia  without  any  previous  convulsions. 

Kussmaul  and  Tenner  believed  that  they  had  demonstrated 
the  integrity  of  the  bulb  to  be  an  essential  condition  for  the 
appearance  of  general  convulsions,  because  general  convulsions  no 
longer  set  in  in  rabbits  after  separation  of  the  bulb  from  the  cord. 
Destruction  of  the  nceud  vital  of  Flourens  was  sufficient  to  cause 
the  animal's  immediate  death  without  convulsions.  If  it  were  kept 
alive  by  artificial  respiration  with  the  bellows,  no  abrupt  suspension 
of  gas  exchanges,  however  produced,  was  capable  of  evoking  such 
excitation  of  the  spinal  cord  as  to  cause  general  convulsions. 
Hence,  they  concluded,  there  must  be  a  centre  in  the  bulb  whose, 
excitation  is  indispensable  for  producing  spread  of  convulsions  to 
all  the  muscles. 

Freusberg  (1875),  however,  with  dogs  saw  that  even  in  the 
"  spinal "  animal  the  hind-limbs  and  tail  were  convulsed  during 
acute  asphyxia,  though  to  a  less  degree  than  when  the  bulb  remained 
connected  with  the  cord.  Baglioni  and  Carincola  (1911)  confirmed 
Freusberg's  observations  on  pigeons.  They  also  found  that  these 
symptoms  of  excitation  did  not  occur  if  all  the  posterior  roots  had 
previously  been  divided.  They  are  not,  therefore,  according  to 
Baglioni,  due  solely  to  increased  venosity  of  the  blood,  as 
Freusberg  surmised,  but  are  partly  due  to  sensory  excitations 
carried  from  the  periphery  by  the  posterior  roots. 

Nothnagel,  by  direct  excitation  of  the  rabbit's  bulb,  endeavoured 


vii  THE  MEDULLA  OBLONGATA  413 

to  ascertain  the  extent  of  the  centre  which  gave  rise  to  these 
general  convulsions.  According  to  him  it  extends  from  the  bulb 
to  the  mid-brain.  But  Owsjaunikow  (1875)  was  able  by  a  better 
method  to  show  that  in  the  rabbit  the  centre  on  which  the  spread 
of  the  convulsions  depends  is  seated  in  the  lower  third  of  the 
bulb,  and  has  an  area  of  some  6  mm.,  measured  from  the  tip  of 
the  calamus.  He  evoked  the  spasm  by  reflex  stimulation  of  the 
bulb,  using  electrical  stimulation  of  a  hind-limb  of  the  rabbit. 

After  dividing  the  bulb,  by  a  transection  6  mm.  above  the  tip 
of  the  calamus  scriptorius,  it  was  possible  with  a  given  strength  of 
stimulus  to  provoke  reflex  movements  in  the  four  limbs  of  the 
animal ;  but  if  the  section  of  the  bulb  were  made  lower  down,  the 
convulsions  were  only  partial,  on  one  or  both  sides. 

It  seems  to  us  probable  that  while  in  the  higher  vertebrates 
the  formatio  reticularis  normally  presides  over  respiratory  rhythm, 
under  abnormal  conditions  the  excitation  that  affects  it  directly  or 
reflexly  may  spread  to  other  skeletal  muscles.  On  this  theory  the 
collection  of  motor  cells  scattered  over  this  region  would  deserve 
the  physiological  name  of  general  motor  centre. 

IX.  The  medulla  oblougata  and  pons  Varolii  have  other 
important  functions. 

We  know  that  the  movements  of  locomotion  are  started  by 
voluntary  impulses,  but  once  set  going  they  can  be  continued 
mechanically,  without  attention  on  the  part  of  the  subject.  This 
shows  that  the  organs  which  execute  and  co-ordinate  the  move- 
ments of  walking  are  anatomically  distinct  from  those  which 
control  the  voluntary  impulses  proper.  That  man  and  many  other 
vertebrates  do  not  walk  from  birth,  and  need  a  long  education  to 
acquire  the  power,  is  due  to  the  fact  that  at  birth  the  nerve- 
centres  which  subserve  locomotion  are  incompletely  developed. 

Physiological  experiments  show  that  the  centre  for  progression 
lies  in  the  bulbo-pontine  region.  Eedi  (1810)  first  observed  that 
land  tortoises  can  crawl  after  the  brain  has  been  removed.  Fontana 
confirmed  this  observation,  but  Eolando  failed,  probably  because 
he  extirpated  the  bulb  also.  Fano  repeated  the  experiments  with 
marsh  tortoises  in  our  laboratory  (1884).  He  found  that  if  the 
entire  brain,  with  the  exception  of  the  bulb,  were  destroyed  these 
animals  began,  after  a  short  time,  to  exhibit  unwonted  locomotor 
activity,  either  continuous  or  periodical,  and  accompanied  by 
movements  of  the  neck  and  tail.  The  front  limbs  became  more 
active  than  the  hind-limbs.  The  curve  of  progression  shows  that 
such  animals  do  not  move  in  a  straight  line,  but  follow  an  irregular 
course,  and  sometimes  make  circus  movements  in  one  or  the  other 
direction,  not  apparently  due  to  any  asymmetry  of  lesion  (Fig. 
218).  Locomotion  is  periodical,  not  continuous,  when  the  tortoise 
was  not  properly  awake  from  its  winter  sleep,  when  much  blood 
had  been  lost  at  the  operation,  or  when  the  central  activities  are 


414  PHYSIOLOGY  CHAP. 

depressed  from  any  cause.  The  number  of  steps  in  each  locomotor 
period  bears  no  proportion  to  the  successive  pauses,  as  we  noted 
in  the  analogous  phenomena  of  periodic  cardiac  and  respiratory 
rhythm  (Vol.  I.  Chaps.  IX.  and  XIII.).  These  and  other  facts  for 
which  we  have  no  space  are  evidence  in  favour  of  the  fundament- 
ally automatic  nature  of  the  activity  of  the  locomotor  centre. 

Fano  tried  to  localise  the  centre  for  progression  in  tortoises  by 
Owsjanuikow's  method  of  successive  sections  of  the  bulb.  He 
found  it  was  limited  to  its  lower  third,  and  that  it  thus  coincides 
with  the  localisation  of  the  centre  for  general  reflexes  in  the 


FIG.  218.— Curve  of  progression  of  clecerebrated  tortoise,  which  had  a  brush  dipped  in  anilin  solution 
fastened  to  its  tail.  (Fano.)  The  curve  is  reduced  to  T£n.  The  arrows  show  the  direction  of 
tin-  movement ;  the  small  breaks,  the  points  at  which  the  animal  stopped. 

rabbit.  To  us,  however,  it  seems  more  probable  that  the  lower 
third  of  the  bulb  is  related  to  the  true  locomotor  centre  as  the 
nceud  vital  of  Flourens  is  to  the  true  respiratory  centre — this,  as 
we  have  seen,  being  far  more  extensive,  and  probably  including 
the  whole  region  of  the  formatio  reticularis. 

The  bulb  is  necessary  not  only  for  walking  but  also  for  active 
posture,  that  is,  the  capacity  for  remaining  in  a  given  posture  or 
attitude,  and  resuming  it  when  passively  disturbed.  In  order  to 
take  up  or  maintain  its  natural  pose,  the  animal  must  throw  a 
number  of  muscles  into  activity.  The  tendency  to  take  up  a 
normal  attitude  seems  more  marked  in  the  lower  than  in  the 
higher  vertebrates. 

We  know  from  the  experiments  of  Renzi,  Vulpian,  and  more 


vii  THE  MEDULLA  OBLONGATA  415 

recently  Steiner,  that  after  excision  of  the  whole  of  the  brain, 
except  the  hulb,  fish  can  swim  and  maintain  their  normal  position 
with  the  back  uppermost.  The  decerebrated  frog,  according  to 
the  well-known  experiments  of  Golt/,  remains  motionless  in  the 
normal  position ;  it  responds  by  a  series  of  regular  springs  to 
slight  stimuli,  and  if  thrown  on  to  its  back  turns  over  again  to 
recover  its  normal  position.  Toads  differ  from  frogs  only  in  the 
fact  that  after  decerebration  they  creep  about  periodically  like 
land  tortoises.  The  latter,  according  to  Fano,  also  try  to  resume 
the  normal  position  when  placed  on  their  backs ;  after  remaining 
motionless  for  some  time  the  animal  extends  its  neck,  makes  a 
lever  of  its  jaws  against  the  ground,  and  agitates  its  limbs  so 
forcibly  as  to  rotate  its  body  on  the  long  axis,  which  brings  it 
back  to  the  normal  position.  Not  invariably,  but  in  most  cases, 
these  repeated  efforts  attain  their  object :  sometimes  the  decerebrate 
tortoise  turns  over  almost  as  quickly  as  the  normal  animal. 
Similar  facts  are  observed  in  birds  and  mammals.  Both  pigeons 
and  young  rabbits  after  removal  of  the  brain  as  low  as  the  pons 
stand  upright  and  walk  if  stirred  up.  Even  without  external 
stimuli  they  move  about  periodically  like  tortoises,  but  as  soon  as 
the  pons  is  destroyed  or  injured,  standing  and  walking  become 
impossible. 

The  recent  experiments  of  Baglioni  (1909)  have  proved  the 
existence  in  the  toad  of  true  sensory  centres  in  the  dorsal  region 
of  the  upper  third  of  the  bulb,  which  preside  over  the  movements 
of  the  hind-limbs  and  possibly  of  the  fore-limbs  as  well.  He 
isolated  the  cerebrospinal  axis  of  the  toad  (Fig.  166)  and  found 
that  electrical  and  mechanical  stimulation  of  this  region  not  only 
evoked  movements  of  the  limbs,  but  is  capable,  under  the  influence 
of  a  local  application  of  strychnine,  of  profoundly  modifying  the 
reflex  acts  evoked  from  the  hind-limbs  by  peripheral  stimuli. 

Magnini  and  Bartoloniei,  who  experimented  under  Baglioni's 
guidance  upon  dogs,  found  that  the  local  application  of  strychnine 
to  different  parts  of  the  dorsal  surface  of  the  bulb  provoked  various 
effects,  as  hyperaesthesia  and  paraesthesia  in  the  peripheral  dis- 
tribution of  the  cranial  sensory  nerves,  particularly  the  fifth  pair, 
spontaneous  muscular  contractions,  spasms  of  different  muscles 
of  the  face  and  neck,  dyspnoea,  vomiting,  disturbances  in  gait, 
erection  of  penis.  Assuming  that  strychnine  acts  electively  upon 
the  sensory  central  elements,  these  results  are  in  favour  of  the 
hypothesis  that  there  are  in  the  bulb,  and  particularly  in  its  dorsal 
part,  centres  which  are  mainly  sensory.  This  conclusion  agrees 
with  the  other  results  obtained  by  these  observers,  viz.  that  local 
application  of  weak  solutions  of  carbolic  acid — which  stimulates 
motor  elements  (p.  264) — produces  hardly  any  effects. 

X.  Are  all  these  highly  complex  automatic  actions  and  re- 
flexes of  which  bulbo-spinal  animals  are  capable  accompanied  by 


416  PHYSIOLOGY  CHAP. 

consciousness  or  not  ?  The  same  question  arose  with  reference  to 
the  spinal  cord  (pp.  335  et  seq.),  and  the  student  must  refer  to  the 
arguments  there  discussed. 

Flourens,  in  the  first  edition  of  his  work  on  the  Nervous  System 
(1823),  stated  that  the  cerebral  hemispheres  are  the  exclusive  seat 
of  all  sensation  and  volition,  and  consequently  of  all  intellectual 
activity.  But  it  was  pointed  out  by  Cuvier,  in  his  report  to 
the  Academic  des  Sciences  (1842)  on  Flourens'  work,  that  this 
conclusion  was  not  a  logical  deduction  from  experimental  observa- 
tions, from  which  on  the  other  hand  it  was  logical  to  conclude  that 
the  cerebral  hemispheres  are  the  only  centres  through  which 
sensations  can  reach  consciousness.  Flourens  accordingly,  in  the 
2nd  edition  of  his  work  (1842)  modified  his  conclusions  by  stating 
that  "1'animal  qui  a  perdu  ses  lobes  cerebraux  n'a  pas  perdu  sa 
sensibilite ;  il  la  conserve  tout  entiere.  II  n'a  perdu  que  la 
perception  de  ses  sensations  ;  il  n'a  perdu  que  1'intelligence." 

Johannes  Miiller  also  argued  from  the  experiments  of  Flourens, 
Magendie,  and  Desmoulins,  that  the  medulla  oblongata  was  "  der 
Sitz  des  Empfinduugsvermogens."  He  believed  that  the  bulbo- 
spinal  animal  has  lost  its  memory  and  power  of  reflection  and 
attention,  but  that  it  continues  to  feel,  and  to  react  to  sensations 
by  complex  movements  which  are  not  mere  reflex  phenomena. 

Longet  pointed  out  in  his  classical  treatise  that  the  bulb  and 
pons  contain  sensitive  and  insensitive  parts  as  well  as  motor  and 
non-motor  parts,  and  affirmed  that  the  pons,  besides  being  the 
conductor  for  afferent  sensory  impressions  and  voluntary  motor 
impulses,  must  be  a  centre  of  special  activity,  owing  to  the  large 
amount  of  grey  matter  contained  in  it.  According  to  Longet  it  is 
especially  in  the  pons  that  the  centre  of  general  sensibility  and 
the  locomotor  centre  are  seated.  In  claiming  for  the  pons  a  sort 
of  sensorium  commune  Longet  relied  particularly  on  the  fact  that 
rabbits,  mice,  and  dogs,  in  which  the  whole  of  the  brain  except  the 
bulbo-pontine  region  has  been  destroyed,  respond  by  repeated 
cries  expressive  of  pain,  accompanied  by  convulsive  movements, 
when  a  limb,  tail,  or  ear  is  strongly  excited.  Owing  to  their  varied 
and  persistent  character  Longet  does  not  believe  that  these  cries 
can  be  simple,  unconscious,  reflex  acts,  but  regards  them  as  the 
expression  of  pain  really  felt  by  the  animal. 

Vulpian  came  to  the  same  conclusion  after  repeating  and  con- 
firming Longet's  experiments.  He  added  an  observation  that 
seems  to  us  important.  If  the  whole  of  the  brain,  including 
the  pons,  is  destroyed  in  a  young  rabbit,  it  responds  to  each 
stimulus  by  a  brief,  single,  invariably  uniform  cry,  which  has  no 
significance  or  expression,  but  resembles  the  sounds  made  by 
certain  toys  when  squeezed  at  one  particular  spot.  If,  on  the 
other  hand,  the  pons  is  also  left  intact,  the  animal  responds  to 
stimulation  by  one  or  more  prolonged  cries  which  undoubtedly 


vii  THE  MEDULLA  OBLONGATA  417 

express  pain,  and  are  perfectly  similar  to  those  which  the  intact 
rabbit  makes  when  sharply  stimulated. 

These  sensory  phenomena  observed  in  animals  after  removal  of 
their  fore-  and  mid-brains  are  analogous  to  those  observed  in  man 
during  chloroform  narcosis.  Chloroform  probably  abolishes  the 
excitability  of  the  cerebral  hemispheres  before  it  acts  upon  the 
lower  centres  of  the  brain ;  incompletely  chloroformed  subjects 
often  utter  distressing  cries,  contort  the  face  as  if  suffering  pain, 
and  writhe  under  the  surgeon's  knife  in  a  way  that  convinces 
every  one  present  that  these  are  no  mere  reflex  acts,  but  a  true 
expression  of  pain,  although  on  waking  they  declare  that  they 
have  fel  t  nothing.  "  Notre  conviction  profonde "  (adds  Longet) 
"  est  qu'il  y  a  eu  sensation  de  douleur,  et  que  son  souvenir  seul  a  fait 
defaut.  .  .  .  Dansl'etat  de  demi-sommeil,  que  d'idees  aussi  traversent 
notre  cerveau  et  qui,  1'instant  d'apres,  nous  echappent ! " 

This  theory  of  "  ~bulbo-pontine  consciousness  had  and  still  has 
many  opponents  who  would  localise  all  psychical  functions  ex- 
clusively to  the  cortex  of  the  cerebral  hemispheres,  and  treat 
the  phenomena  described  by  Joh.  Miiller,  Longet,  and  Vulpian  as 
being  purely  unconscious  reflexes.  The  obstacles  to  a  clear  and 
incontestable  solution  by  experiment  are  enormous  and  perhaps 
insuperable. 

In  our  opinion  more  value,  as  evidence  for  a  sensorium  in  the 
spinal  bulb,  attaches  to  the  observations  on  lower  vertebrates  (frog, 
toads,  tortoises)  described  above.  When,  e.g.,  the  tortoise  thrown 
on  its  back  makes  all  the  associated  movements  of  the  normal 
animal  with  head  and  limbs  in  order  to  resume  its  habitual 
position,  it  is  natural  to  ask  what  can  be  the  nature  of  the  strong 
external  stimuli  which  are  able  reflexly  to  discharge  the  entire 
complex  of  simultaneous  and  successive  muscular  actions  which 
the  animal  performs  with  singular  dexterity,  after  remaining  for 
some  time  motionless  with  its  head  and  limbs  withdrawn  into  the 
carapace.  It  seems  to  us  clear  that  in  this  case  we  are  in  the 
presence  not  of  externally  evoked  reflex  (Actions,  but  of  central 
instinctive  actions  (i.e.  such  as  are  acquired  by  habit  and  trans- 
mitted by  heredity)  which  cannot  fail  to  be  accompanied  by  a 
certain  degree  of  consciousness. 

BIBLIOGRAPHY 

Structure  of  Medulla  Oblongata :  see  recent  text-books  of  Histology  of  the 
Nervous  System,  including  those  of  EDINGEK,  v.  GEHUCHTEN,  BEOHTEREW,  and 
the  standard  text-books  of  anatomy. 

Physiology  of  the  Cranial  Nerves  :  a  full  bibliography  will  be  found  in  the 
classical  text-books  of  Joh.  MULLER,  LONGET,  and  HERMANN  (vol.  ii.,  Special 
Nerve-Physiology,  by  Prof.  S.  Meyer). 

Among  the  most  important  Monographs  are  : — 
BELL,  CH.     An  Exposition  of  the  Natural  System  of  Nerves,  1824. 
PANIZZA,  B.     Ricerche  sperimentali  sopra  i  nervi,  ecc.     Pavia,  1834. 

VOL.  Ill  2  E 


418  PHYSIOLOGY  CHAP,  vn 

MAGENDIE.     Lecons  sur  les  fonct.  du  syst.  nerv.     Paris,  1839. 

BKKXARD,  CL.     Arch.  gen.  denied.,  1844. 

BIFFI  and  MORGANTI.     Ann.  univ.  di  ined.     Milan,  1846. 

BUDGE.     Neue  raed.  Zeitschr.,  1847. 

WALLER,  A.     Gaz.  raed.  de  Paris,  1856. 

BERNARD,  CL.     Lecons  sur  la  physiol.  et  la  pathol.  du  syst.  nerv.     Paris,  1858. 

MEISSXKR.     Zcitschr.  f.  rat.  Med.,  1867. 

ADAMUK.     Centralbl.,  1870. 

LrssANA.     Gazz.  ined.  ital.,  1871. 

BODDAEKT,  R.      Ann.  de  la  Soc.  de  Mud.  de  Gand,  1877. 

DUVAL.     Soc.  de  Biol.,  1878. 

VULTIAN.     Comptes  rendus,  1880. 

GI.EY,  E.     Soc.  de  Biol.,  1887. 

GROSSMAN N.     Sitxungber.  d.  Wiener  Akad.,  1889. 

GRAP.OWKK.     Centralbl.  f.  Physiol.,  1890. 

SCHIFF.     Gesamin.  Beitr.  z.  Physiol.  iii.     Lansanne,  1896. 

Motor  and  Sensory  Functions  of  Medulla  Oblongata  and  Bulbo-Pontine  Tract, 
in  addition  to  text-books  by  Joh.  Miiller  and  Longet,  see  :— 

FLOURKXS.     Kech.    expi-rim.    sur  les  propr.    et  les   fonct.  du  syst.   nerv.     Paris, 

1842. 

GOLTZ.     Function,  d.  Nervenzentr.  d.  Frosches.     Berlin,  1863. 
VULPIAN.     Lemons  sur  la  physiol.  gen.  et  comp.  du  syst.  nerv.     Paris,  1866. 
OWSJANXIKOFF.     Bericlite  d.  K.  Siichs.  Gesellsch.  d.  Wissensch.,  1875. 
FRETSUKIM;.     Arch.  f.  exper.  Pathol.  u.  Pharniak.  vol.  iii.,  1875. 
FANO.     Pubbl.  del  R.  1st.  di  studi  sup.     Florence,  1884. 
BATESON.     Journal  of  the  Marine  Biological  Association  of  the  United  Kingdom, 

1890. 

KIJKIIM,.     Piliiger's  Archiv,  1895. 
LEE.     American  Journ.  of  Physiol.,  1898. 
PARKER.     Fiscli.  Connn.  Bull.,  1903. 
BAGLIONI.     Zeitschr.  f.  allg.  Physiol.  ix.,  1909. 
MAGNIXI  and  BAUTOLOMEI.     Arch,  di  fisiol.  viii.,  1910. 

Recent  English  Literature  :  — 

MATHISOX.     The  Effects  of  Asphyxia   upon   the   Medullary  Centres — Vasomotor 

Centre.     Journ.  of  Pliysiol.,  1911,  xlii.  283. 
SOLLMANN  and    PiLrHEU.      Reactions  of  the   Vasomotor  Centre  to  Section  and 

Stimulation  of  the  Vagus  Nerves.     American  Journ.  of  Physiol.,  1912,   xxx. 

303. 
MUSSEX.     Note  on  the  Movements  of  the  Tongue  from  Stimulation  of  the  Twelfth 

Nucleus,  Root,  and  Nerve.     Brain,  1909,  xxxii.  206. 
GUSHING.     The  Taste  Fibres  and  their  Independence  of  the  Nervus  Trigeminus. 

Johns  Hopkins'  Hosp.  Bull.,  1903,  xiv. 
DAVIES.     Functions  of  the  Trigeminal  Nerve.     Brain,  1907,  xxx.  219. 


CHAPTER   VIII 

THE    HIND-BRAIN 

CONTENTS. — 1.  Anatomy  of  hind-brain  :  afferent  and  efferent  tracts  of  the  three 
cerebellar  peduncles.  2.  Preliminary  observations  on  cerebellar  functions.  3.  Dy- 
namic phenomena  immediately  incident  on  removal  of  cerebellum.  4.  Cerebellar 
ataxy  in  dogs  and  monkeys  after  removal  of  half  the  cerebellum.  5.  Cerebellar 
ataxy  after  total  removal  of  cerebellum.  6.  Cerebellar  ataxy.  7.  The  cerebellum 
as  the  centre  of  equilibrium  ; »  8.  And  the  co-ordinating  organ  of  voluntary 
movements  ;  9.  And  the  organ  of  subconscious  sensations,  exercising  constant 
reinforcing  action  upon  the  other  nerve-centres.  10.  Localisation  of  cerebellar 
functions.  Bibliography. 

IN  discussing  the  medulla  oblongata  we  were  obliged  to  include 
the  poiis  Varolii,  which,  both  in  its  structure  and  its  functions, 
is  the  continuation  of  the  bulb.  Embryclogically,  however,  while 
the  medulla  oblongata  arises  from  the  5th  secondary  vesicle,  the 
pons  and  cerebellum  originate  in  the  4th  secondary  vesicle,  and 
form  respectively  the  ventral  and  dorsal  parts  of  the  Hind-brain 
or  Mesencephalon. 

I.  The  Hind-brain  is  more  developed  in  mammals  than  in  other 
classes  of  vertebrates.  Both  the  ventral  and  the  dorsal  portions 
present  new  and  special  formations  which  do  not  exist  in  lower 
vertebrates — the  pons  properly  so-called,  the  middle,  cerebellar 
peduncles,  and  the  lateral  cerebellar  lobes.  The  pons  consists 

of    a.    nroipr'.fiincr     mass    nf    fibvps    witli     an     nKlimiQ     omi^a/-.     XTTU^U 


ERRATUM 

Page  419,  par.  1,  line  7,  for  "  Mesencephalon"  read  "  Metencephalon. " 


nets,  uesiufs  a  meuian  ioue  or  vermis, 
lateral  lobes  or  cerebellar  hemispheres,  which  do  not  exist,  or  are 
rudimentary,  in  the  lower  vertebrates.  This  increased  develop- 
ment of  the  hind-brain  in  mammals  is  counterbalanced  by  a  con- 
siderable relative  reduction  in  the  mid-brain,  in  comparison  with 
that  of  the  lower  vertebrates. 

419 


420 


PHYSIOLOGY 


CHAP. 


In  transverse  sections  of  the  brain  stem  at  the  level  of  the 
pons,  the  ventral  part,  or  pons  proper,  must  be  distinguished  from 
the  dorsal  part  or  tegmentum,  which  is  the  continuation  of  the 
bulb.  The  former  contains  the  transverse  fibres  which  pass  to  the 
middle  peduncles ;  the  most  superficial  lie  over  the  pyramids,  the 
deeper  pass  partly  between  the  pyramidal  fibres,  partly  dorsal  to 
them  ;  reaching  the  middle  line  they  decussate  with  the  fibres  from 
the  other  side  (Fig.  219).  The  grey  matter  of  the  pous  contains 


a.V 


O.S. 


FIG.  219.--Sec.tion  across  lower  part  of  pons.  (Stilling  and  Sehwalbe.)  jii/,  pyramidal  bundles  con- 
tinued up  from  medulla  ;  po,  transverse  fibres  of  pons  passing  from  middle  cms  of  cerebellum, 
before  (/in-)  and  behind  (/'O1)  chief  pyramidal  bundles  ;  t,  deeper  transverse  fibres,  constituting 
trapezium  ;  the  grey  matter  between  the  transverse  fibres  is  not  represented  in  this  or  in  the 
following  figures  ;  r,  raphe  ;  o.s.,  superior  olivary  nucleus  ;  n.V,  bundles  of  ascending  roots  of 
5th  nerve,  enclosed  by  prolongation  of  grey  substance  of  Rolando;  VI,  6th  nerve;  TO. VI, 
its  nucleus;  VII,  facial  nerve;  Vll.a,  ascending  portion  of  facial  root;  TO. VII,  its  nucleus; 
VIII,  superior  root  of  auditory  nerve ;  TO. VIII,  part  of  nucleus  of  Deiters  ;  V,  section  of  vein. 

small  multipolar  nerve-cells  scattered  among  the  superficial  and 
deeper  bundles  (Fig.  220). 

The  dorsal  part  of  the  pons  represents  the  continuation  of  the 
formatio  reticularis  and  grey  matter  of  the  bulb,  but  it  also  con- 
tains a  more  definite  and  compact  mass  of  grey  matter,  known  as 
the  superior  olivary  nucleus,  as  well  as  the  nuclei  of  the  5th,  6th, 
and  7th  cerebral  nerves. 

The  cerebellum  or  dorsal  part  of  the  mesencephalon  occupies 
the  posterior  fossa  of  the  skull :  its  median  portion  forms  the  roof  of 
the  fourth  ventricle  (Fig.  221).  Between  the  two  superior  peduncles 
this  roof  is  completed  by  the  velum  medullare  superius,  or  valve 


VIII 


THE  HTND-BEAIN 


421 


of  Vieussens,  which  extends  to  the  corpora  quadrigemina  and  the 
roof  of  the  aqueduct  of  Sylvius  (Fig.  200). 

Most  anatomists  distinguish  a,  verm  is  or  median  lobe  and  two 
hemispheres,  or  lateral  lobes,  in  the  cerebellum.  Bolk  (1902), 
however,  on  the  basis  of  accurate  investigation  and  patient  phylo- 
genetic  comparison  of  many  mammalian  cerebella,  demonstrated 
that  this  organ  is  divided  not  in  the  sagittal  but  in  the  transverse 


V.IV. 


*  •  '•    -•     -;  -'.-       .  ••  :'  Pf£*$?'  -^k    '"•*-<'#  I/ /y  'I'^vf     ''•*•-'*>-'  •         ~    '  *^-»-z£J"*^aii?*~"  *       i    ~' 

1  '  •"  •      .  • '    '4-KaT**       ir~jBrt~jf?7  j's~'''&'*^'j'  Tt  -~V     '*I^T%  •  ••         ' '     '    V  "'^      v*TjF      ""    * 


:^  fPS-W^ciSTS^:'-:.xJ^3^f;>-,  r, 

Si'  ">5;;»  -.• --Ci«^.  •;:-  -^^ScrsiK- 


FIG.  220.  -  Transverse  section  of  pons  Varolii  through  origin  of  auditory  nerve.  (Schafer.)  From  a 
photograph.  Magnified  about  -1  diameters.  J".  1 V.,  fourth  ventricle ;  c,  white  matter  of  cerebelhir 
hemisphere  ;  r.il.,  corpus  dentatvim  cerebelli  ;  //.,  flocculus  ;  c.r.,  corpus  restiforme  ;  R.,  Roller's 
ascending  auditory  bundle;  D,  Deiters' nucleus  ;  VIII,  issuing  root  of  auditory  nerve  ;  VIII.  d., 
dorsal  nucleus;  VIII.  v.,  ventral  (accessory)  nucleus  of  auditory  ;  it.ti:,  small-celled  nucleus 
traversed  by  fibres  of  trapezium  ;  tr.,  trapezium  ;  /.,  fillet  ;  ii.l.li.,  posterior  longitudinal  bundle  ; 
./'.;•.,  formatio  n-ticularis  ;  ('.a.,  ascending  root  of  .5th;  s.g.,  substantia  gelatinosa  ;  s.o.,  upper 
olive;  VII.,  issuing  root  of  facial;  H.V1I.,  nucleus  of  facial;  VI.,  root  bundles  of  abducens  ; 
py.,  pyramid  bundles;  n.p.,  nuclei  pontis. 

direction.  According  to  the  Dutch  anatomist,  the  cerebellum  of 
mammalia  presents  one  uniform  type  ;  despite  any  variations  from 
this,  there  is  always  a  deep  primary  sulcus  which  usually  extends 
to  the  white  matter,  and  divides  the  cerebellum  into  an  anterior 
and  a  posterior  part  (Fig.  222). 

In  man  the  anterior  lobe  of  Bolk  includes  the  so-called  vermis 
superior  (lobulis  centralis  and  lingula),  the  monticulus  and  the 
lobus  quadratus  anterior.  This  anterior  lobe  forms  a  single  un- 
paired median  organ. 


422 


PHYSIOLOGY 


OHAP. 


The  posterior  lobe  of  Bolk  is  larger  and  includes  all  the  rest  of 
the  cerebellum.  It  can,  however,  be  subdivided  into  four  lobules, 
two  median  and  two  lateral. 

(a)  The  first  of  the  two  median  lobules,  called  lobulus  simplex 
by  Bolk,  becomes  so  wide  in  man  that  anatomists  had  distinguished 
in  it  a  declivium  or  median  part,  and  the  lobus  quadratus  superior 
or  lateral  parts.  To  this  Bolk  restores  the  character  of  a  single 
median  unpaired  lobule. 

(&)  The  second  of  the  median  lobules  is  the  lobulus  medianus 
posterior  of  Bolk,  the  so-called  verjnis  inferior.  The  single,  un- 
paired character  of  this  organ  is  admitted  by  every  one. 

(c)  The  two  lateral  lobules  were  termed  lobuli  complicate  by 


12 


lobe  ;  7,  pons  Varolii ;  8,  middle  peduncle  of  cerebellum  ;  9,  medulla  oblongata  ;  10,  11,  anti-run- 
part  of  great  horizontal  fissure  ;  1'2,  13,  smaller  and  larger  roots  of  fifth  pair  of  nerves  ;  14,  sixth 
pair;  15,  facial  nerve;  16,  pars  intermedia;  17,  auditory  nerve;  IS,  glosso-pharyngeal ;  19, 
pneumogastric  ;  20,  spinal  accessory  ;  21,  hypoglossal  nerve. 

Bolk,  and  include  the  remainder  of  the  cerebellum.  While  the 
other  lobes  develop  in  an  antero-posterior  line,  so  that  the  inter- 
lamellar  sulci  all  have  a  transverse  or  oblique  direction,  the 
development  in  the  lobuli  complicati  follows  a  twisted  or  spiral 
line,  and  the  interlamellary  sulci  consequently  run  in  irregular  and 
even  opposite  directions.  The  schematic  type  which  Bolk  gives 
for  this  lobule  results  from  two  loops  back  to  back  joined  by  an 
isthmus  that  runs  parallel  with  the  median  line.  In  the  human 
cerebellum  there  is  an  enormous  development  of  the  parts  con- 
tained in  the  first  loop,  which  includes  the  lobuli  semilunaris, 
gracilis,  and  cuneiformis  of  the  anatomists ;  the  isthmus  is  formed 
by  the  tonsils  ;  the  whole  of  the  rest,  which  is  rudimentary,  consists 
of  the  flocculus. 

This  new  morphological  and  phylogenetic  view  of  the  cere- 


viii  THE  HTND-BEAIN  423 

belluin  is  interesting,  because  it  is  reasonable, — as  Bolk  showed  in 


V.cac. 


B 


Fir,.  222.— Views  of  upper  (A)  and  lower  (B)  surfaces  of  Imman  cerebellum.  Natural  size.  From 
photographs.  (Sriiafer.)  The  plate  also  shows  Bolk's  divisions  into  lobules,  in  different  colours. 
The  light  yellow  is  Bolk's  anterior  lobe  ;  dark  yellow,  simple  median  lobule  on  upper  surface, 
and  posterior  median  lobule  on  lower  surface  of  cerebellum;  the  red  shows  the  two  lateral 
lobules  which  Bolk  calls  .•um^oinc/— of  which  the  deeper  red  tonsils  and  flocculi  also  form 
part.  In  A  :  ?.c.,  lobulus  centralis  ;  n.l.c.,  ala  lobuli  centralis  ;  m,  culmen  monticuli ;  J.m., 
lobus  culminis  ;  d.,  clivus  ;  ?.<•?.,  lobus  clivi ;  l.cac.,  lobus  cacuminis  ;  l.t.,  lobus  tuberis  ;  s.p.-c., 
suk-iis  post-centralis  ;  s.pr.-d.,  sulcus  pre-clivalis  ;  s.p.-d.,  sulcus  post-clivalis  ;  f.li.,f.h.,  lissura 
horizontalis  magna.  In  B:  I,  lingula ;  I.e.,  lobus  centralis  ;  a.l.c.,  all  lobuli  centralis;  s.p.-c., 
sulcus  post-centralis  ;  r.rn.s.,  velum  rnedullare  superius  ;  p.s.c.,  pedunculus  cerebelli  superior  ; 
p.c.,  pedunculi  cerebelli  medius  et  inferior  ;  n.,  nodulus  ;  r.m.i.,  velum  medullare  inferius  ;  p.fl., 
pedunculus  flocculi;  rf.,  flocculus ;  «.,  uvula;  n/n.,  amygdala;  >py,  pyramis ;  l.lii:,  lobus 
biventralis;  1. 1:,  tuber  valvulae  sen  posticum;  l.t.,  lobus  postero-inferior ;  /.f/)'.1,  lobulus 
niacilis  anterior  :  ?."/.-,  lobulus  -lacilis  ]«.st>-i  ior  ;  s.pr.-gr,,  sulcus  pre-gracilis  ;  s.i.-qr.,  suleus 
intra-gracilis  :  s.p.-gr.,  sulcus  post-gracilis  ;  f.li.,  tissura  horizontalis  ma-na.  The  vallecula  has 
been  somewhat  opened  out  to  display  the  parts  of  the  lower  worm. 

his  masterly  work  on  the  Mammalian  Cerebellum,  1904-6, — by 

2  E  i 


424 


PHYSIOLOGY 


CHAP. 


correlating  the  relative  development  of  different  lobes  in  different 
mammals  with  the  degree  of  functional  development  of  certain 
groups  of  muscles,  to  argue  in  favour  of  a  physiological  connection 
—a  functional  relation --between  the  central  and  peripheral 
variations.  Bolk's  ingenious  inductions,  taken  as  the  starting- 
point  of  new  physiological  researches,  have  led  to  certain  positive 
results  in  regard  to  functional  localisation  in  the  different 
cerebellar  lobules. 

As  regards  the  structure  of  the  cerebellum,  we  must  confine 
ourselves    to   certain   general   statements,   referring   for    minute 


culm-en 


Sulfuspost-  centr-alis 

loiuLus  cert-trellis 

li.ngu.la. 


• 

;<;-- '  ^RgSO? 

l^^r^^^sA^ 


ventricu.lu.3 
IV 

Fie..  LJi'3. — Median  section  of  vermis.     Light  yellow,  Bolk's  anterior  lobe  ;  dark  yellow, 

the  two  median  lobules. 

details  to  recent  text-books  on  the  anatomy  and  histology  of  the 
nervous  system. 

If  a  section  is  made  through  the  cerebellum  in  the  median 
sagittal  line,  it  is  seen  to  consist  of  a  central  white  substance 
covered  by  a  uniform  layer  of  grey  cortical  matter  (Fig.  224).  The 
lamellar  or  foliated  aspect  of  the  surface  of  the  cerebellum  is  pro- 
duced by  the  terminal  branches  of  the  so-called  "  arbor  vitae," 
covered  with  grey  matter. 

Each  lamella  shows  in  section  a  central  zone,  of  white  matter, 
and  a  cortex  of  grey  matter  consisting  of  two  layers,  one  of  which 
is  termed  granular  because  it  contains  small  nerve-cells  which 
look  like  granules  with  low  magnification,  the  other  molecular 
owing  to  its  appearance  under  the  microscope.  Between  the  two 
layers  there  is  a  layer  of  large  nerve-cells,  known  as  the  cells  or 
corpuscles  of  Purkinje  (Fig.  224). 


VIII 


THE  HIND-BKAIN 


425 


The  medulluted  fibres  of  the  white  matter  appear  continuous 
with  the  three  peduncles  which  unite  the  cerebellum  with  the 
brain -stem. 

Lying  in  the  white  matter,  near  the  roof  of  the  fourth 
ventricle,  are.  four  masses  or 
nuclei  of  grey  matter  of 
different  sizes,  which  are 
symmetrically  arranged  on 
either  side  of  the  organ. 
The  most  medial  is  known 
as  the  nucleus  of  the  roof 
(nucleus  fastigii) ;  the  most 
lateral  is  the  nucleus  den- 
tatus,  also  known  as  the 
corpus  olivare  cerebelli,  from  b 
its  great  resemblance  to  the 
olive  of  the  bull.).  The  two 
small  nuclei,  respectively  the 
nucleus  giobosus  and  emboli- 
formis,  are  accessory  nuclei 
lying  between  the  two  pre- 
ceding (Fig.  225). 

From  the  physiological 
point  of  view  it  is  important 
to  form  a  clear  picture  of  the 
relations  of  the  cerebellum 
to  the  rest  of  the  nervous 
system,  by  identifying  the 
afferent  and  efferent  paths 
that  pass  through  the  three 
cerebellar  peduncles. 

The  fibres  of  the  superior 
peduncles  (crura  ad  cere- 
brum) arise  for  the  most 
part  in  the  cells  of  the 
dentate  nuclei ;  they  run 
forwards  to  the  mesence- 
phalon,  decussate  almost  , 

'  Fio.  224.— Section  of  cortex  of  cerebellum.     (Sankey.) 

Completely  beneath    the    COr-         a,  pia  mater  ;&,  external  layer  ;e,  layer  of  corpuscles 

Jf    •  •  j  of  Purkinje ;    d,  inner  or  granule  layer ;    e,  white 

pora  quadrigemma,  and  ter-       matter. 

inmate  in  the    nuclei    rubri 

of  Stilling,  which  lie  in  the   tegmentum  of   the   mid-brain   near 

the  regio  subthalamica.     From  the  cells  of  the  red  nuclei  fibres 

run  out  to  the  optic  thalami. 

In  addition  to  these  efferent  fibres  the  superior  cerebellar 
peduncles  also  contain  a  few  afferent  fibres  (Mingazzini),  which 
probably  arise  in  the  thalami,  pass  through  the  red  nuclei  without 


426 


PHYSIOLOGY 


CHAP. 


interruption,  and  decussate  on  the  way  to  the  superior  cerebellar 
peduncles. 

After  complete  extirpation  of  one-half  of  the  cerebellum — 
which  we  first  performed  successfully  on  dogs — March!  found  by 
his  method  almost  total  degeneration  of  the  red  nucleus  on  the 
opposite  side  and  only  partial  degeneration  of  the  red  nucleus  on 
the  same  side  (Fig.  226).  The  decussation  of  the  superior  central 
peduncles  is  therefore  not  complete,  though  nearly  so. 

According  to  the  Dejerines,  the  red  nucleus  does  not  degenerate 


r?,.  globe  sits 


pll-iS        '   -  vvlfi' 


FIG.  225.— Section  across  the  cerebellum  and  medulla' oblongata,  showing  position  of  nuclei  in 
white  matter  of  cerebellum.  (Stilling.)  J.  fl.rf.,  nucleus  dentatus  cerebelli ;  s,  band  of 
fibres  ilri -ivrd  ,from  restiform  body,  partly  covering  dentate  nucleus  ;  s.c.ji.,  commencement 
i  if  superior  cerebellar  peduncle  ;  com',  com",  eommissural  fibres  crossing  in  median  white  matter. 

with  unilateral  cerebellar  lesions  that  involve  the  cerebellar  cortex 
only,  and  not  the  dentate  nuclei,  which  proves  the  origin  in  these 
nuclei  of  the  fibres  that  run  to  the  red  nuclei. 

Marchi's  method  clearly  shows  that  the  superior  cerebellar 
peduncle  is  largely  composed  of  efferent  fibres  of  cerebellar  origin. 
According  to  Eamon  y  Cajal,  the  axis-cylinders  of  the  cells  of 
the  dentate  nucleus  can  be  followed  into  this  peduncle,  which 
also  receives  a  few  fibres  from  the  cerebellar  cortex.  As  the 
fibres  emerge  from  the  cerebellum  many  of  them  give  off  large 
collateral  branches,  which  form  a  descending  bundle  that  passes 
through  the  substantia  reticularis  grisea,  and  gives  fibres  to  the 
nuclei  of  the  cerebral  nerves  (Cajal). 


VIII 


THE  HIND-BEAIN 


427 


The  middle  peduncles  (crura  ad  ponteni)  are  largely  composed 
of  afferent  fibres  to  the  cerebellum,  which  arise  in  the  cells  of  the 
pontine  nuclei.  They  cross  in  the  median  line  of  the  pons  and 
terminate  in  the  cerebellar  cortex  of  the  opposite  side.  Since  the 
cells  of  these  crossed  ponto-cerebellar  fibres  are  in  relation  with 
the  final  ramifications  of  the  fibres  which  have  their  origin  in  the 
cortex  of  the  frontal  and  temporal  lobes  of  the  brain,  it  follows 
that  each  cerebral  hemisphere  is  indirectly  connected  with  the 
opposite  half  of  the  cerebellum  on  the  opposite  side  by  these  fronto- 
temporo-pontine  paths  (Fig.  227,  «,  &). 

According  to  Eamon  y  Cajal,  efferent  fibres  from  Purkinje's  cells 


/.;•  {I;!.;  ^X    '    4 

.' >  i.,-:.t.  '  •       .   *f -. .-  •' 


FIG.  226. — Sections  of  dog's  mesencephalon,  showing  degenerations  following  extirpation  of  right 
half  of  cerebellum.  (Marchi's  method.)  A,  section  at  level  of  nucleus  of  origin  of  3rd  nerves  ; 
a,  a,  red  nuclei  of  Stilling,  that  to  the  left  much  degenerated,  that  to  the  right  less  so  ;  b, 
fibres  of  3rd  nerves  degenerated  on  the  side  of  the  extirpation  ;  d,  posterior  longitudinal 
bundle  terminating  in  the  nucleus  of  the  3rd  nerves  ;  e,  pes  pedunculi ;  /,  inferior  bundle  of  fillet 
of  Reil  coursing  to  corpora  quadrigemina.  B,  corresponding  section  at  superior-  corpora  quadri- 
gcmina  ;  n,  «,  red  nuclei,  as  above;  b,  posterior  longitudinal  bundle;  c,  optic  tract  partially 
degenerated  on  the  side  of  the  extirpation  ;  d,  inferior  bundle  of  fillet  of  Reil  running  near  the 
corpora  geniculata  to  the  corpora  qnadrigemina  ;  e,  pes  of  cerebral  peduncle. 

also  run  through  the  middle  peduncles,  cross  in  the  pons,  and  then 
descend  in  the  lateral  column  of  the  cord  to  terminate  round  the 
motor  cells  of  the  ventral  horn.  According  to  Marchi  and  Mingazzini, 
some  of  these  efferent  fibres  run  to  the  pontine  nuclei,  thence 
fibres  arise  which  ascend  vertically  through  the  cerebral  peduncle 
on  the  opposite  side.  By  these  indirect  cerebello-cerebral  paths 
the  cerebellum  can  influence  the  cerebrum  on  the  opposite  side 
(Fig.  227,  c,  d).  Finally,  according  to  Bechterew  and  Mingazzini, 
fibres  of  the  middle  peduncle,  which  arise  in  the  cerebellar  cortex, 
cross  the  raphe  of  the  pons,  run  up  its  sides,  and  end  in  the 
formatio  reticularis  (Fig.  227,  e,f). 

The    inferior    peduncles    (crura   ad    medullam)    contain    both 
afferent  and  efferent  fibres,  the  former  predominating.     The  fibres 


428 


PHYSIOLOGY 


CHAP. 


ascending  from  the  cord  must  be  distinguished  from  those  which 
take  origin  in  the  medulla  oblongata. 

The  "afferent  spinal  fibres  run  in  the  lateral  columns  of  the. 
cord  ;  these  are  the  direct  cerebellar  tracts  of  Flechsig,  which 
ascend  through  the  restiform  body  to  the  vermis  of  the  cerebellum. 
The  fibres  of  these  bundles  spring  for  the  most  part  from  the  cells 
of  Clarke's  column  on  the  same  side,  and  as  the  collaterals  of  the 
posterior  roots  run  to  these  cells  there  is  thus  au  indirect  connec- 
tion between  the  dorsal  roots  and  the  cerebellum.  But,  according 
to  Edinger,  Obersteiner,  and  Thomas,  there  is  also  a  direct  connec- 
tion between  the  posterior  roots  and  the  cerebellum,  as  certain 
fibres  of  the  posterior  column  turn  dorsalwards  and  lateralwards  as 
external  posterior  arcuate  fibres,  and  join  the  restiform  body,  to 
run  with  the  fibres  of  Flechsig's  bundle  to  the  vermis. 

From  certain  observa- 
tions of  Ferrier  and 
Turner  it  seems  probable 
that  the  nuclei  of  the 
posterior  columns  also 
send  fibres  to  the  cere- 
bellum via  the  restiform 
body,  but  this  has  not  yet 
been  proved. 

A  larger  proportion  of 
the  fibres  of  the  inferior 
cerebellar  peduncle  come 
from  the  bulb  than  from 
the  cord.  Atrophy  of 
the  inferior  olive,  associ- 
ated with  atrophy  of  the  opposite  side  of  the  cerebellum, — as  first 
described  by  Meynert  and  confirmed  by  subsequent  observers- 
shows  that  there  is  a  crossed  relation  between  the  inferior  olive 
and  the  cerebellum,  by  way  of  fibres  that  ascend  through  the 
restiform  body.  Other  fibres  spring  from  the  cerebellar  cortex 
and  descend  to  the  olive  of  the  opposite  side  ;  in  fact,  after  uni- 
lateral cerebellar  extirpation  there  is  a  considerable  atrophy  of  the 
inferior  olive  of  the  opposite  side  (Fig.  228,  a,  &). 

According  to  Edinger,  a  bundle  of  afferent  fibres,  which  he 
terms  the  direct  sensory  cerebellar  tract,  takes  origin  in  the  main 
nucleus  of  the  acusticus,  the  nucleus  of  Deiters,  and  the  nucleus  of 
Bechterew,  and  ascends  through  the  internal  segment  of  the 
inferior  cerebellar  peduncle  to  the  cerebellum,  where  it  ends  in 
the  nucleus  fastigii  and  the  nucleus  globosus  (Fig.  229).  This 
bundle  is  joined  by  fibres  from  the  trigemiiius,  vagus  and  accessory 
nuclei.  As  the  fibres  of  the  vestibular  nerve  terminate  in  the 
vestibular  nucleus  there  is  thus  an  indiiect  relation  between  the 
semicircular  canals  and  these  internal  nuclei  of  the  cerebellum. 


Fio.  227.— Plan  of  afferent  and  efferent  paths  that  run 
through  the  middle  cerebellar  peduncle  to  establish 
reciprocal  relations  between  the  cerebellum  and  the. 
cerebrum.  (Mingaxzini.) 


VIII 


THE  HIND-BRAIN 


429 


The  efferent  cerebello-spinal  fibres  that  leave  by  the  lower 
cerebral  peduncle  are  represented  by  the  direct  ventro-lateral 
bundle  of  Marchi,  the  course  of 
which  has  been  well  illustrated 
by  Thomas.  The  fibres  of  this 
bundle  pass  through  the  inner 
segment  of  the  corpus  restiforme 
between  the  cells  of  Bechterew's 


Fin.  228. —  Plan  of  olivo-cerebellar  paths,  a; 
cerebello  -  olivary,  b  ;  cerebello  -  spinal, 
crossed,  <;  <l,  and  direct,  e,  which  accompany 
the  pyramidal  tracts.  (Mingazzini.) 


Fie.  229.— Plan  of  direct  sensory  cerebellar 
paths  (Edinger),  running  froTii  Deiters'  D, 
and  Bechterew's  7J,  nucleus  of  vestibularis  v, 
to  nucleus  fastigii  t,  and  nucleus  globosus  g. 


and  Deiters'  nuclei,  run  through  the  formatio  reticularis  in  the 
neighbourhood  of  the  inferior  olive,  and  pass  into  the  ventro- 
lateral  marginal  zone  of  the  cord  without  decussation.  After 
unilateral  extirpation  of  the  cerebellum  there  is  descending 
degeneration  of  this  bundle,  as  far  as  the  lumbar  region,  which 
decreases  from  above  downwards  (Fig.  230). 


C 

FIG,  230.— Sections  of  spinal  cord.  A,  lumbar;  B,  thoracic;  C,  cervical,  after  extirpation  of  right 
half  of  cerebellum  in  dog.  Showing  degeneration  of  Marchi's  antero-lateral  tract  on  same  side 
as  the  extirpation.  <i,  efferent  spino-cerebellar  bundle  degenerated  on  right  side  as  far  as  the 
lumbar  section,  while  on  the  left  side  the  degeneration  is  slight,  partial,  and  does  not  extend 
beyond  the  cervical  section.  The  bundle  thus  includes  nearly  the  whole  border  of  the  ventro- 
lateial  eiilumn  ;  at  '/  it  takes  in  part  of  the  pyramidal  tract;  at  c  it  comprises  the  area 
in  which  lies  the  anterior  portion  of  Flechsig's  cerebellar  tract;  at  d  some  fibres  of  the 
ventral  roots  are  also  degenerated. 

It  seems  probable  from  the  observations  of  Thomas  that 
Marchi's  bundle  springs,  like  the  fibres  of  the  superior  cerebellar 
peduncle,  from  the  dentate  nucleus,  and  that  the  degeneration  of 


430 


PHYSIOLOGY 


CHAP. 


these  two  fibre-systems  is  in  proportion  with  the  injury  of  that 
nucleus.  Lesions  of  the  nucleus  fastigii  produce  no  degeneration 
in  the  cord. 

Besides  Marchi's  bundle,  another  efferent  cerebello-spinal  tract, 
mostly  crossed,  but  to  a  small  extent  direct,  has  been  described 
by  Mingazzini,  Pick,  and  others.  The  crossed  portion  leaves  the 
internal  segment  of  the  restiforin  •  body,  enters  the  raphe  as 
internal  arcuate  fibres,  joins  the  external  ventral  arcuate  fibres 
of  the  opposite  side,  and  enters  the  pyramidal  tract  (Fig.  228,  c,  d}. 

The  few  uncrossed  fibres 
pass  as  external  ventral 
arcuate  fibres  and  join 
the  pyramid  tract  on  the 
same  side  (Fig.  228,  c}. 
It  is  evident  that  the 
crossed  portion,  since  it 
decussates  again  with  the 
contralateral  pyramid, 
joins  each  lateral  half 
of  the  cerebellum  and  of 
the  same  side  of  the 
cord,  and  that  the  small 
uncrossed  portion,  which 
also  decussates  with  the 
homolateral  pyramid, 
establishes  a  relation  be- 
tween each  lateral  half 
of  the  cerebellum  and 
the  opposite  side  of  the 
cord.  This  is  clear  from 
Fig.  231. 

II.  The  experimental 
determination  of  the 
functions  of  the  cere- 
bellum is  one  of  the 
most  difficult  problems  in  the  physiology  of  the  central  nervous 
system.  We  devoted  many  years  (1884-91)  to  experiments 
in  the  solution  of  this  question.  Previous  investigators  had 
confined  themselves  almost  without  exception  to  ascertaining 
the  immediate  effects  of  lesion  or  partial  removal  of  the  cere- 
bellum or  its  peduncles.  Eolando  (1809)  contented  himself 
with  destroying  half  or  the  whole  of  the  cerebellum  in  different 
mammals,  and  giving  a  summary  description  of  the  effects  on 
the  same  day,  without  taking  any  trouble  to  keep  the  animals 
alive.  Fodera  (1823)  and,  shortly  after,  Flourens  (1824-42) 
observed,  particularly  in  birds,  the  immediate  effects  of  small  suc- 
cessive ablations  of  increasingly  deeper  layers  of  the  cerebellum. 


FIG.  231.— Diagram  to  show  crossed  (a)  and  direct  (b)  cere- 
bello-spinal paths  which  accompany  pyramidal  tract  p, 
and  are  in  relation  with  the  cells  of  the  ventral  horn 
ca,  from  which  the  motor  roots  ra  emerge  to  inner- 
vate the  muscles  m.  (Mingazzini.) 


vin  THE  HIND-BIUIN 

Stu<lv  of  (lie  remote  cl't'ects  was  only  attempted  very  inadequately 
liy  Flourens,  and  always  on  birds.  Magendie  (1828),  Serres 
(1826),  and  Bouillaud  (1827)  in  their  experiments  followed  more 
or  less  on  the  lines  of  Eolando,  Fodera,  and  Flourens.  After 
several  years,  experiments  on  the  cerebellum  were  resumed  by 
N.  Schiff  (1858-59),  Brown-Sequard  (1859-60-61),  R.  Wagner 
(1858-1860),  Dalton  (1861),  Lussana  (1862),  Leven  and  Ollivier 
(1862-63),  Vulpian  (1866),  Weir  -  Mitchell  (1869),  Nothnagel 
(ISTl),  Ferrier  (1878),  and  others. 

At  the  outset  of  our  own  researches  on  the  cerebellum  it 
seemed  to  us  advisable  to  extend  our  study  to  the  higher  mammals, 
dogs  and  monkeys,  in  which  the  organ  is  more  developed,  but 
which  till  then  had  rarely  been  employed  for  experiments  on 
account  of  the  supposed  technical  difficulties. 

Our  principal  experiments  may  be  divided  into  three  series, 
viz.  investigation  of  animals  after  removal  of  the  lateral  half  of 
the  cerebellum,  of  the  vermis,  and  of  the  whole  or  almost  the 
whole  of  the  organ. 

Before  describing  the  results  it  seems  advisable  to  make  a  few 
preliminary  remarks  for  the  guidance  of  the  student:— 

(tf.)  Whatever  the  extent  or  degree  of  the  cerebellar  lesion, 
whether  it  be  symmetrical  or  asymmetrical,  unilateral  or  bilateral, 
complete  or  incomplete,  the  resulting  symptoms  are  disturbances 
of  voluntary  movement. 

(ft)  Unilateral  lesions  of  the  cerebellum  produce  disturbances 
chiefly  on  the  same  side  of  the  body;  while  the  effects  of  re- 
moving the  so-called  motor  region  of  a  cerebral  hemisphere  are 
mainly  crossed,  i.e.  on  the  opposite  side  of  the  body  to  that 
operated  on. 

(c)  Whatever    the   nature    of  the   cerebellar    lesion,  the   true 
phenomena   of  deficiency,  i.e.  those  due  directly  to  loss   of  the 
cerebellum,  are  preceded  by  a  brief  period  of  functional  exaltation ; 
while  in  lesions  of  the  cerebrum  the  phenomena  of  deficiency  are 
constantly  preceded  by  a  period  of  functional  inhibition.     To  be 
rigorously    objective,   we   will  refer   to   the  immediate  effects   of 
ablation    of   the    cerebellum   as    "dynamic   phenomena,"   leaving 
undecided    the    question  of   whether    they   are  produced   by  the 
irritation  of  the  operative  traumatism  or  by  the  sudden  cessation 
of  the   influence   of  the   cerebellum  upon  other  portions  of   the 
nervous  system. 

(d)  To  the  phenomena  of  cerebellar  deficiency  of  the  second 
period   there  succeeds  a  third  series  of  effects,  which  we  have 
termed  "  compensatory  phenomena  "  ;  these  are  due  to  the  activities 
of  portions   of  the  cerebellum  that  are    left  intact,  or   of  other 
cerebral  centres.     In  the  first  case  there  is  organic  compensation, 
which  consists  in  the   gradual  diminution   of  the  phenomena  of 
deficiency ;  in  the  second  case  there  is  functional  compensation, 


432  PHYSIOLOGY  CHAP. 

which  consists  in  abnormal  movements  directed  to  meeting  and 
partially  compensating  the  effects  of  deficiency. 

(V)  The  phenomena  of  cerebellar  deficiency,  in  association  with 
the  processes  of  functional  compensation,  make  up  a  syndrome  or 
characteristic  complex  of  phenomena,  which  has  long  been  known 
by  the  generic  name  of  cerebellar  ataxy.  It  is  the  task  of 
physiology  to  make  as  exact  an  analysis  as  possible  of  the 
individual  elements  that  go  to  form  this  ataxy,  with  the  object  of 
distinguishing  the  phenomena  due  to  loss  of  cerebellar  innervation 
from  those  due  to  the  instinctive  or  voluntary  compensatory  acts, 
which  are  directed  to  nullifying  the  effects  of  the  former. 

(/)  As  each  lateral  half  of  the  cerebellum  is  connected  mainly 
with  the  corresponding  half  of  the  body,  it  is  obvious  that  the 
symptoms  of  unilateral  cerebellar  extirpation  must  be  greater  on 
the  side  of  the  operation  than  on  the  opposite  side.  Hence, 
comparison  of  the  two  halves  of  the  body  in  an  animal  from 
which  one-half  of  the  cerebellum  was  removed  is  equivalent  to 
comparing  two  animals  of  the  same  species,  age,  and  constitution, 
one  of  which  is  in  full  enjoyment  of  its  cerebellar  innervation,  the 
other  almost  entirely  deprived  of  it. 

III.  If  not  too  deeply  anaesthetised  or  enfeebled  by  bleeding 
during  the  operation,  dogs  show  signs  of  distress  and  agitation 
immediately  after  complete  removal  of  one-half  of  the  cerebellum. 
The  animal  also  presents  pleurothotonus  or  curvature  of  the 
vertebral  axis  to  the  side  operated  on,  tonic  extension  of  the 
anterior  limb  on  the  same  side,  with  clonic  movements  of 
the  three  other  limbs ;  rotation  of  the  neck  and  head  towards  the 
healthy  side,  slight  nystagmus  and  squint  with  inward  and  down- 
ward deviation  of  the  eye  on  the  side  operated  on,  and  downward 
and  upward  of  the  eye  on  the  healthy  side ;  and  rotation  round 
the  long  axis  of  the  body  in  the  same  direction  as  that  of  the 
neck  and  head  (i.e.  from  the  side  operated  on  to  the  healthy  side 
if  the  animal  is  looked  at  in  front,  from  the  healthy  side  to  the 
operated  side  if  it  is  viewed  from  behind). 

The  immediate  dynamic  phenomena  after  total  removal  of  the 
cerebellum  are  agitation,  unrest,  and  cries  from  the  animal ; 
opisthotonus,  or  backward  curving  of  the  vertebral  axis,  par- 
ticularly of  the  neck  and  head  ;  tonic  extension  of  both  fore-limbs, 
with  alternating  clonic  movements  of  hind-limbs ;  bilateral  con- 
vergence of  the  eyes  ;  and  tendency  to  stagger  and  fall  backwards. 

These  symptoms  may  seem  more  simple  than  those  which  follow 
unilateral  destruction,  but  they  are  really  the  same  dynamic 
disturbances  spread  over  both  sides.  Opisthotonus  is  substituted 
for  pleurothotonus ;  tonic  extension  of  both  limbs  for  tonic 
extension  of  one  limb,  regression  and  falling  backward  for  rotation 
on  the  long  axis. 

After  destruction  of  the  vermis  and,  generally  speaking,  after 


viii  THE  HIND-BRAIN  433 

incomplete  bilateral  or  unilateral,  symmetrical  or  unsymmetrical 
injuries,  the  dynamic  phenomena  are  more  irregular,  both  in  their 
nature  and  extent.  In  all  cases  the  dynamic  phenomena  approxi- 
mate more  nearly  to  those  of  unilateral  or  total  extirpation, 
according  as  the  peduncles  of  one  side,  or  those  of  both,  were 
similarly  affected. 

The  immediate  dynamic  symptoms  persist  for  a  few  days— 
usually  eight  to  ten — if  the  wound  remains  aseptic ;    the   tonic 
spasms  diminish  in  strength  and  duration,  and  become  transformed 
into  clonic  and  oscillatory  movements. 

The  first  symptom  to  disappear  is  the  rotation  011  the  long 
axis,  or  tendency  to  fall  and  topple  backwards  (which  usually 
lasts  only  four  to  five  days).  The  last  to  disappear  is  the  pleuro- 
thotonus  or  opisthotonus,  which  remain  evident  for  a  number  of 
days  if  the  animal  is  suspended. 

As  the  tonic  spasm  disappears  and  the  movements  become 
merely  clonic  and  tremulous,  the  animal's  attempts  to  hold  itself 
upright  and  to  walk  gradually  become  more  effective.  Dogs,  as 
a  rule,  regain  the  power  of  floating  and  swimming  before  they 
become  able  to  walk. 

In  monkeys,  with  the  exception  that  there  is  tonic  flexion  of 
the  fore-limbs  instead  of  tonic  extension,  the  dynamic  symptoms 
are  identical  with  those  described  in  dogs;  but  they  are  less 
intense  and  of  shorter  duration,  so  that  the  phenomena  of  cerebellar 
deficiency  are  more  plainly  seen  after  a  very  few  days,  when  every 
trace  of  the  forced  movements  disappears. 

The  exact  interpretation  of  the  origin  and  nature  of  the 
dynamic  phenomena  is  one  of  the  most  difficult  problems  we  meet 
in  the  physiological  study  of  the  cerebellum,  and  is  so  far  unsolved. 
The  feature  which  has  more  especially  claimed  the  attention  of 
experimenters  from  Pourfour  du  Petit  (1710),  Lafargue  (1838), 
Magendie  (1839),  Schiff  (1849),  Longet  (1878),  to  the  workers  of 
the  present  day  is  the  rotation  of  the  animal  on  its  own  longitudinal 
axis.  Does  this  depend  on  the  irritation  of  the  fibres  of  the 
cerebellar  peduncles  by  the  operative  injury  or  on  the  sudden 
removal  of  the  influence  of  one-half  of  the  cerebellum  upon  the 
rest  of  the  nervous  system  ? 

In  our  Monograph  upon  the  Cerebellum  we  declared  for  the 
former  view,  which  was  already  held  by  Brown-Sequard,  Vulpian, 
Weir-Mitchell,  and  others,  and  characterised  as  irritative  all  the 
dynamic  symptoms  that  predominate  immediately  after  removal 
of  portions  of  the  cerebellum,  as  Goltz  had  given  the  name  of 
inhibitory  to  those  which  ensue  directly  on  cerebral  ablation. 
This  view  is  supported  by  the  following  arguments  :— 

(«)  They  correspond  with  the  degree  of  operative  injury  and 
with  the  appearance  of  inflammatory  and  infective  processes  in  the 
wound. 

VOL.  in  2  F 


434  PHYSIOLOGY  CHAP. 

(&)  They  predominate  in  the  side  exclusively  or  mainly 
affected,  and  appear  to  be  more  pronounced  and  varied  in  pro- 
portion as  the  lesion  is  deeper  and  extends  farther  towards  the 
cerebellar  peduncles. 

(c)  When  the  peduncles  are  partly  degenerated,  in  consequence 
of  previous  removal  of  the  vermis,  the  later  destruction  of  a 
lateral  lobe  only  produces  slight  and  transient  irritative 
symptoms. 

Ferrier,  however,  showed  that  when  there  is  actual  irritation 
or  inflammation  in  the  cerebellum  the  dynamic  phenomena  are 
very  different  from  what  we  had  described.  He  found  that  when 
a  lateral  lobe  of  the  cerebellum  was  partially  cauterised  so  that 
the  adjacent  parts  were  irritated,  rotation  took  place  in  exactly 
the  opposite  direction  to  that  which  we  observed  after  removal  of 
one  side  of  the  cerebellum. 

We  had  never  performed  cauterisation  experiments  on  the 
cerebellum  as  they  appeared  unsuitable  for  eliciting  clear  and 
unequivocal  physiological  facts,  but  on  repeating  Ferrier's  experi- 
ment on  a  number  of  animals  we  convinced  ourselves  of  the 
accuracy  of  his  observations.  We  found  that  more  or  less  pro- 
found cauterisation  of  the  cortex  of  a  cerebellar  lobe  on  one  side 
gave  rise  to  symptoms  that  were  almost  exactly  the  opposite  of 
those  seen  after  its  removal.  The  disquiet  and  cries  of  pain  are 
absent — the  animal  rather  appearing  depressed  and  subdued; 
the  pleurothotonus  to  the  injured  side  is  replaced  by  slight 
pleurothotonus  to  the  normal  side ;  the  tendency  to  rotate  and 
actual  rotation  round  the  long  axis  from  the  operated  towards  the 
healthy  side  is  replaced  by  a  tendency  to  rotate  in  the  opposite 
direction,  i.e.  from  the  healthy  towards  the  operated  side. 

On  what  does  this  reversal  of  effects  depend  ?  The  question  is 
still  undecided.  In  reply  to  Ferrier  we  advanced  the  hypothesis 
that  the  cauterisation  of  the  cerebellum  irritates  the  adjacent 
parts  as  well,  including  the  dura  mater,  which  is  a  sensory 
membrane  capable  of  producing  symptoms  of  reflex  inhibition  on 
excitation.  This,  however,  is  not  an  adequate  explanation.  Are 
the  pleurothotonus  and  rotation  in  the  opposite  direction  to  be 
referred  to  the  preponderance  of  inhibitory  effects  on  the  operated 
side  or  to  exaggerated  activity  on  the  healthy  side  ?  A  recent 
experiment  on  dogs  indicates  that  it  depends  on  both  these  factors. 
We  observed  that  if  before  cauterising  the  cerebellum  on  one  side 
the  two  halves  of  the  cerebellum  were  divided  1  >y  a  median  sagittal 
section,  the  animal  appeared  subdued  with  pleurothotonus  to  the 
cauterised  side,  and  a  slight  tendency  to  rotate  towards  the 
healthy  side.  Next  day  the  animal  was  quiet ;  it  lay  on  the  flank 
of  the  cauterised  side,  and  if  forcibly  placed  on  the  opposite  side 
made  a  half-turn  to  recover  this  position,  but  showed  no  tendency 
to  rotate  on  its  axis ;  if  held  up  there  was  pleurothotonus  to  the 


VIII 


THE  HIND-BRAIN  435 


cauterised  side,  Imt  no  rotation  of  its  head  towards  the  sound 
side. 

Mechanical  excitation  of  one-half  of  the  cerebellum  can  also 
evoke  motor  reactions  predominating  in  the  muscles  of  the 
opposite  side.  Nothnagel  observed  in  1876  that  puncture  of  the 
vermis  with  a  tine  needle  on  one  side  of  the  median  line,  or  of  one 
cerebellar  hemisphere,  produced  pleurothotonus  or  curvature  of 
the  vertebral  column  to  the  opposite  side,  with  rotation  of  the 
head  in  the  same  direction,  i.e.  opposite  to  that  observed  after 
removal  of  one-half  of  the  cerebellum.  But  reactions  also  occur 
in  the  fore-limb  and  facial  muscles  of  the  excited  side.  Lewan- 
dowsky  and  J.  Munk  confirmed  these  results;  they  found  that 
tine  needles  must  be  used  in  order  to  evoke  them,  because  with 
coarser  lesions  the  irritative  symptoms  are  mingled  with  those  of 
the  paralysis  and  produced  quite  different  phenomena. 

Sergi  repeatedly  found  that  simple  section  of  the  lower  and 
internal  portion  of  a  cerebeilar  hemisphere,  including  a  part  of 
the  peduncles,  produces  a  tendency  to  rotate,  or  actual  rotation,  in 
a  direction  opposite  to  that  which  we  observed  after  unilateral 
cerebellar  extirpation,  and  comparable  with  the  effects  of 
cauterisation. 

Electrical  stimulation  of  one-half  of  the  cerebellum  (Lewan- 
dowsky,  1903)  gave  parallel  results.  Weak  induced  currents 
produced  restlessness  and  consecutive  movements  that  suggested 
that  the  animal  was  suffering  from  vertigo.  Stronger  currents 
produced  a  forced  position  towards  the  side  opposite  that  excited 
(right  pleurothotonus  when  left  side  is  excited);  movements  of 
facial  muscles  and  horizontal  nystagmus  of  the  head ;  falling  of 
the  animal  to  the  right  if  excited  on  the  left,  and  rotation  in  the 
opposite  direction  to  that  observed  after  unilateral  extirpation. 
Lewandowsky,  of  course,  assumed  that  there  was  true  irritative 
rotation  in  his  case,  and  that  ours  was  due  to  paralytic  rotation. 

On  the  other  hand,  Pagano  (1902),  working  in  Marcacci's 
laboratory,  found  that  merely  injecting  a  few  drops  of  1  per  cent 
solution  of  curare  into  one  cerebellar  hemisphere  in  dogs  produced 
violent  epileptiform  reactions — mainly  of  the  muscles  of  the  same 
side,  and  especially  various  rotatory  movements — ten  to  fifteen 
minutes  after  injection. 

Two  general  propositions  can  be  positively  stated,  without 
danger  of  contradiction,  in  regard  to  the  rotation  round  the 
longitudinal  axis  that  is  constantly  seen  after  destruction  of  one- 
half  of  the  cerebellum  :— 

(a)  Predominance  of  the  functional  activity  of  the  cerebral 
centres  of  one  side  is  a  necessary  condition  for  forced  rotations, 
and  the  afferent  disturbance  (vertigo)  due  to  the  sudden  upset  of 
functional  equilibrium  is  its  immediate  cause. 

(&)  The  rotation  phenomenon  and  the  forced  movements  and 


436  PHYSIOLOGY  CHAP. 

positions  in  general  which  follow  immediately  on  the  cerebellar 
lesions  (whether  they  are  regarded  as  effects  of  irritation  of  the 
fibres  of  the  peduncles  and  of  the  extra-cerebellar  cells  with  which 
those  are  connected,  or  whether  they  are  referred  to  the  paralysis 
or  disturbance  of  cerebellar  functions  by  the  lesion)  must  not  be 
regarded  either  as  the  converse,  or  as  an  exaggeration,  of  the  defect 
phenomena  that  appear  in  the  second  post-operative  period. 

That  vertigo  is  the  true  cause  of  forced  movements  and, 
generally  speaking,  of  the  dynamic  phenomena  of  the  first  post- 
operative period  is  directly  confirmed  by  clinical  cases  of  cerebellar 
disease,  in  which  vertigo  is  a  very  frequent  symptom.  But  the 
indirect  evidence  afforded  by  the  behaviour  of  monkeys  with 
lesions  of  the  cerebellum  is  also  most  striking  ;  they  soon  learn  to 
avoid  rotation  on  their  long  axis  by  clutching  the  surrounding 
objects  with  their  hands.  If  set  upon  the  bare  ground  they 
support  not  only  their  trunk  but  also  their  head  on  it.  Further, 
the  fore-limb  of  the  operated  side  is  abducted  as  far  as  possible, 
and  the  animal  remains  indefinitely  motionless  in  this  position  in 
order  to  avoid  vertigo. 

The  disturbance,  produced  either  by  irritation  of  the  peduncular 
fibres  or  by  the  sudden  disequilibration  of  the  functional  activities 
of  the  two  sides  by  the  sudden  paralysis  of  one,  may  produce 
vertigo.     On  the  other  hand,  we  know  that  independent  of  any 
cerebellar  lesion  similar  rotatory  vertigo  with  actual  rotation  on  the 
longitudinal  axis  may  be  produced  in  dogs,  either  by  section  of  the 
vestibular  nerve  (Bechterew)   or   by  a  unilateral  lesion   of  the 
inferior  olive  (Probst).     As  the  relations  of  the  vestibular  nucleus 
and  the  olive  with  the  cerebellum  are  known,  it  might  be  assumed 
that  here  also  the  disturbance  of  cerebellar  influence  comes  into 
play  in  producing  the  rotation  phenomenon.     But  even  when  the 
cerebellum  has  been  totally  removed  it  is  still  possible  to  produce 
galvanic  vertigo  in  dogs  (Purkinje  and  Hitzig)  which  proves  that 
vertigo  may  arise  without  active  participation  of  the  cerebellum. 
There  is  evidence  which  tends  to  show  that  the  rotary  phenomena 
which  accompany  vertigo  depend  actually  neither  on  the  cere- 
bellum nor  on  the  brain-stem,  but  solely  on  the  so-called  motor 
zone  of  the  cerebrum.     In  this  connection  the  symptoms  described 
by  Pagano  after  injections  of  curare  are  of  great  interest.     If  the 
motor  zone  (sigmoid  gyrus)  is  excited  on  the  side  opposite  the 
cerebellar  hemisphere  into  which  curare  is  injected,  no  localised 
movements  of  this  side  result,  and  the  rotation  of  the  body  round 
the  longitudinal  axis  occurs  in  the  opposite  direction.     Complete 
removal  of  the  motor  zone  on  both  sides  entirely  suppresses  both 
the  general  convulsions  and  the  partial  tonic  contractions ;  only 
an  increase  in  muscular  tone  is  perceptible,  particularly  in  the 
muscles  of  the  injected  side. 

This  series  of  facts  shows  that  the  dynamic  phenomena  of  the 


vin  THE  HIND-BEAIN  437 

early  post-operative  period  are  associated  with  a  form  of  vertigo, 
and  that  they  are  neither  the  converse  to,  nor  an  exaggeration  of, 
the  defect  phenomena  of  the  second  post-operative  period,  because 
they  are  not  fundamentally  due  to  excessive  activity  nor  to 
paralysis  of  the  cerebellum. 

The  explanation  of  the  dynamic  phenomena  of  the  first  period 
is  still  a  mystery;  it  is  very  doubtful  how  far  they  depend  on 
irritation  or  paralysis  of  the  cerebellar  peduncles.  It  is  incon- 
testable, and  in  our  opinion  clearly  proved,  that  it  is  impossible 
at  present  to  argue  from  these  phenomena  in  regard  to  the  normal 
functions  of  the  cerebellum.  If  in  our  1891  Monograph  all 
these  dynamic  phenomena  of  the  early  post-operative  period  were 
referred  on  the  strength  of  ablation  experiments  to  irritation,  on 
the  other  hand  we  avoided  the  more  serious  error  of  assuming 
them  to  be  the  converse  of  the  true  phenomena  of  cerebellar 
deficiency.  Indeed,  we  have  repeatedly  noted  that  phenomena  of 
irritation  prevail  in  the  muscles  of  the  fore-limbs  and  neck,  and 
phenomena  of  deficiency  in  the  muscles  of  the  hind-limbs  and 
vertebral  column. 

IV.  As  the  dynamic  phenomena  of  the  first  period  disappear, 
the  symptoms  which  depend  on  loss  of  the  cerebellar  functions 
become  more  and  more  prominent.  These,  as  we  have  already 
said,  constitute  the  syndrome  which  is  known  as  cerebellar  ataxy. 

The  dog,  after  removal  of  half  its  cerebellum  and  as  the  early 
dynamic  phenomena  are  disappearing,  is  so  weak  in  the  muscles 
of  the  limbs  on  the  operated  side,  particularly  the  hind-limbs, 
that  at  first  sight  they  appear  paralysed.  In  order  to  move  from 
one  place  to  any  other,  it  is  obliged  to  crawl  on  the  buttock  of 
the  operated  side,  the  principal  effort  being  made  with  the  muscles 
of  the  healthy  side.  This  inability  to  stand  upright  and  walk 
may  last  four  weeks.  During  this  time,  however,  if  the  animal 
can  lean  the  flank  of  the  operated  side  against  a  wall,  it  is  able 
to  stand  upright  and  make  regular  steps.  Further,  if  thrown 
into  water,  it  keeps  itself  quite  well  on  the  surface,  maintains 
its  equilibrium,  and  swims  with  perfect  co-ordination.  But  if 
its  method  of  swimming  be  carefully  watched,  it  is  seen  that  it 
cannot  keep  the  trunk  perfectly  horizontal,  but  the  operated  side 
lies  constantly  deeper  in  the  water  than  the  normal  side.  More- 
over, the  animal  is  unable  to  swim  in  a  straight  line,  and 
constantly  makes  circus  movements  to  the  sound  side. 

The  interpretation  of  these  facts  is  obvious.  The  animal  is 
incapable  of  standing  on  its  feet  and  walking  unless  it  can  find 
support  on  the  operated  side,  because  the  weakness  of  the  limbs 
on  that  side  is  so  great  that  they  cannot  bear  the  weight  of  its 
body.  It  succeeds  in  swimming  well,  because  the  water  supports 
the  weight  of  the  body.  In  swimming,  its  healthy  side  is  higher, 
and  it  continually  turns  towards  this  side,  because  t*he  move- 


438  PHYSIOLOGY  CHAP. 

ments  and  the  thrusts  in  the  water  with  the  limbs  of  the  healthy 
side  are  more  vigorous  and  energetic  than  those  on  the  operated 
side. 

The  animal  gradually  learns  to  make  more  and  more  successful 


123  4  5 

FIG.  232. — Tracings  of  footprints  during  ordinary  progression.  From  live  normal  dogs.  (Luciani.) 
The  prints  of  the  fore-legs  are  represented  by  small  circles,  those  of  the  hind-legs  by  triangles. 
The  prints  of  the  left  leg  are  distinguished  from  those  of  the  right  by  a  black  dot  in  the  centre 
of  the  circles  and  triangles.  The  traces  of  the  right  and  left  feet  are  united,  respectively,  by 
lines.  Each  25  mm.  corresponds  to  1  in.  1,  Shows  the  elegant  gait  of  a  young  poodle ;  2,  the 
clumsy  gait  of  a  bitch  weighing  (JOOO  grins.  ;  3,  a  young  dog  weighing  2700  grms.  ;  4,  a  young 
dog  of  2980  grms.  ;  5,  the  reeling  gait  of  a  bitch  weighing  5400  grms. ,  which  was  completely 
blind  owing  to  enucleation  of  the  eyeballs. 

efforts  at  standing  upright  and  walking,  till  at  last  it  succeeds. 
At  first  it  falls  constantly  to  the  side  of  the  operation,  owing  to 
the  giving  way  of  the  limbs  on  that  side  and  consequent  loss  of 


vni  THE  HIND-BEAIN  439 

equilibrium ;  after  a  time  it  i'alls  less  frequently.  This  gradual 
restitution  of  function  is  only  to  a  small  extent  due  to  organic 
compensation,  and  depends  far  more  upon  functional  compensation, 
on  the  gradual  acquisition  of  new  acts  and  movements,  which  are 
capable  of  compensating  the  effects  of  cerebellar  deficiency,  and  of 
preventing  loss  of  equilibrium  and  the  tendency  to  fall  towards 
the  injured  side.  By  the  curving  of  the  vertebral  column  the 
weight  of  the  hind  part  of  the  body  is  thrown  towards  the  affected 
side,  and  thus  falls  chiefly  on  the  opposite  hind-limb,  i.e.  the  hind- 
limb  unaffected  by  the  operation.  By  abduction  of  the  fore-limb 
it  widens  the  basis  on  which  the  body  rests,  lowers  its  centre  of 
gravity,  and  makes  the  passive  flexion  of  the  fore-limbs  in  the 
various  joints  more  difficult. 

Eeproduction  of  the  footprints  gives  a  record  of  these  com- 
pensating processes  and  a  more  minute  analysis  of  the  gait.  The 
normal  tracing  of  the  dog's  ordinary  walk  is  not  always  perfectly 
equal  and  regular,  but  varies  not  only  with  the  age  and  size  of 
the  individual,  but  also  with  its  race,  as  shown  in  the  examples 
of  Fig.  232.  To  understand  this  tracing  it  must  be  remembered 
that  the  ordinary  step  of  the  dog  is  made  by  alternate  setting 
down  and  lifting  up  the  two  diagonal  pairs  of  feet,  and  that  both 
the  setting  down  and  the  lifting  up  of  the  fore-limbs  precedes 
those  of  the  hind-limbs,  so  that  four  distinct  taps  occur  at  regular 
intervals,  as  can  be  proved  by  listening  when  the  animal  walks 
upon  a  wooden  floor. 

If  we  examine  the  tracing  of  the  footsteps  of  a  bitch  in  which 
the  right  half  of  the  cerebellum  had  been  completely  extirpated, 
it  is  seen  to  be  very  different  from  the  normal  (Fig.  233).  Tracing 
b  was  taken  two  months  after  the  operation ;  the  animal  held  the 
principal  axis  of  its  body*  curved  to  the  right  and  oblique  to  the 
direction  of  progress,  so  that  the  limbs  of  the  right  side  were 
more  raised  and  abducted  than  in  the  normal,  and  the  left  limbs 
adducted.  It  shows  this  alteration  in  the  gait  very  plainly, 
especially  in  the  marked  displacement  to  the  right  of  the  foot- 
prints of  the  hind-limbs,  the  varying  length  and  force  of  the  step, 
and  the  irregularity  of  the  two  lines  which  join  the  prints  of  the 
fore-paws,  which  normally  are  almost  parallel.  A  year  after  the 
operation  tracing  c  was  taken  from  the  same  bitch,  and  showed 
greater  regularity  of  gait,  although  the  displacement  to  the  right 
of  the  footprints  of  the  hind-limbs  still  persisted,  though  it  is  less 
pronounced.  After  blindfolding  the  animal's  eyes  tracing  d  was 
taken,  and  shows  that  the  gait  was  not  much  altered  from  that 
with  the  eyes  open ;  but  the  direction  of  progress  was  uncertain, 
the  steps  shorter,  and  the  fore-limb  more  abducted.  Tracing  e 
was  taken  a  few  minutes  after  the  subcutaneous  injection  of 
30  cgrms.  of  morphine  hydrochlor.  and  shows  exaggeration  of  all 
the  above  anomalies  in  the  animal's  gait. 


440  PHYSIOLOGY  CHAP. 

When  the  dog  with  half  a  cerebellum  has  succeeded,  after 
repeated  attempts,  in  avoiding  falling-  to  the  injured  side  by 
appropriate  compensatory  acts,  it  also  becomes  able  to  avoid 
forced  circus  movements  towards  the  healthy  side  in  swimming ; 
it  is  able  to  keep  to  a  straight  line,  and  to  turn  towards  the 
operated  side.  For  this  purpose  it  adopts  the  same  device  in 


PIG.  233.— Tracings  of  the  gait  of  a  bitch  weighing  5150  grins,  after  complete  extirpation  of  the 
right  half  of  the  cerebellum.  (Luciani.)  6,  tracing  taken  two  months  after  the  operation  ; 
c,  over  a  year  from  the  operation  ;  d,  after  a  year  with  eyes  bandaged  ;  e,  after  a  year  when  the 
animal  had  previously  received  morphia. 

swimming  as  in  walking,  that  is,  curvature  of  the  vertebral 
column  towards  the  defective  side,  which  enables  it  to  use  the 
lumbo-sacral  part  of  its  trunk  as  a  rudder.  It  compensates  the 
stronger  action  of  the  limbs  of  the  sound  side  by  an  appropriate 
degree  of  vertebral  curvature,  and  swims  in  a  straight  line  or  even 
turns  towards  the  defective  side. 

One  of  the  main  results  of  our  studies  on  the  cerebellum  is 
that  we  have  shown  it  to  be  possible,  and  even  easy,  to  separate 
the  phenomena  of  cerebellar  deficiency  from  the  phenomena  of 


VIII 


THE  HIND-BKAIN 


441 


functional  compensation,  that  is,  the  instinctive  and  voluntary 
acts  above  described,  by  which  the  animal  tries  to  repair  the 
effects  of  loss  of  cerebellar  function.  As  soon  as  the  so-called 
motor  zone  of  the  cerebrum  is  destroyed  on  one  or  both  sides  the 
animal  with  a  half  cerebellum  loses  for  a  long  time,  or  for  ever, 
the  newly  acquired  capability  of  holding  itself  upright,  and 
walking  without  falling  towards  the  affected  side. 

When  the  motor  region  of  the  left  cerebral  hemisphere  was 
removed  from  the  bitch  with  the  half  cerebellum  which,  fourteen 
months  later,  gave  the  tracings  in  Fig.  233,  she  once  more  lost 


A  B 

FIG.  234. — Brain  of  the  bitch  from  which  the  preceding  tracings  were  taken.  (Luciani.)  A,  upper 
surface,  showing  absence  of  right  half  of  cerebellum  and  of  left  sigmoid  gyrus.  B,  lower  surface, 
shows  diminution  of  right  half  of  pons  and  of  left  pyramid. 

the  power  of  standing  upright  and  walking,  because  the  limbs  of 
the  right  side  could  not  support  the  weight  of  the  body.  Twenty 
days  after  the  cerebral  operation  she  succeeded,  by  leaning  her 
right  side  against  a  tree,  in  raising  herself  on  her  four  legs.  But 
as  soon  as  she  tried  to  leave  this  support  she  fell.  She  was,  how- 
ever, able  to  swim  well  to  the  right,  and  even  in  a  straight  line, 
notwithstanding  the  curvature  of  the  vertebral  column  to  the 
right,  because  the  strokes  of  the  left  limbs  on  the  water  were 
much  stronger  than  the  right.  About  six  months  after  the  last 
operation  she  could  once  more  walk  without  support,  but  still 
fell  not  infrequently  to  the  right.  In  walking  she  held  the 
axis  of  her  body  very  obliquely  to  the  direction  she  was  going  in, 
and  even  more  curved  to  the  right  than  at  the  time  when  tracing 
I  was  taken.  When  blindfolded  she  did  not  attempt  to  walk, 


442  PHYSIOLOGY  CHAP. 

ami  if  forced  to  move,  she  fell  to  the  right,  owing  to  the  limbs 
of  the  right  side,  in  which  muscular  and  cutaneous  sensibility 
were  altered,  giving  way.  If  thrown  into  water  in  a  pool,  she 
swam  properly  with  eyes  open  or  blindfolded,  with  well-coordinated 
movements,  but  with  the  right  side  deeper  in  the  water  than  the 
left.  She  died  from  severe  and  repeated  epileptic  attacks,  live 
months  after  the  second  operation.  When  the  brain  was  removed 
from  the  body  both  lesions  were  found  to  be  complete  (Fig. 
234,  A,  B). 

In  this  case  the  inability  to  stand  upright  and  to  walk,  after 
ablation  of  the  motor  zone  on  the  side  opposite  that  of  the  cerebellar 
operation,  was  not  complete  and  permanent.  The  partial  re- 
education of  the  animal,  notwithstanding  the  marked  alteration 
in  motility  and  sensibility  of  the  right  limbs,  was  undoubtedly 
due  to  the  compensatory  function  of  the  right  motor  zone,  which 
had  been  left  intact.  In  other  cases,  in  fact,  when  the  animals 
were  deprived  of  half  the  cerebellum  and  both  motor  zones,  we 
obtained  permanent  loss,  not  only  of  maintaining  the  erect  posture 
and  of  walking,  but  of  swimming  also. 

The  phenomena  of  cerebellar  deficiency  exhibited  by  the  animal 
with  a  half  cerebellum,  particularly  in  the  limbs  of  the  operated 
side,  must  be  analysed  more  accurately.  Let  us  again  refer  to  the 
bitch  from  which  the  tracings  in  Fig.  233  were  taken. 

Prior  to  the  extirpation  of  the  right  half  of  the  cerebellum 
this  animal  had  been  trained  to  sit  up  for  a  long  time  on  its  hind 
legs.  After  the  operation  it  lost  this  power,  and  had  not  regained 
it  fourteen  months  later.  When  food  was  brought  to  the  animal 
and  held  above  its  head,  it  stood  upright,  but  fell  suddenly,  owing 
to  the  flexion  of  the  right  hind-leg.  When  it  was  made  to  draw 
a  weight  tied  to  its  tail,  the  greater  expenditure  of  force  required 
in  walking  caused  it  to  fall  frequently  to  the  affected  side.  When 
a  clamp  was  applied  to  the  lobe  of  the  left  ear  the  animal  tried  to 
remove  it  by  appropriate  movements  of  the  left  fore-limb  ;  but  if 
the  same  clamp  was  placed  on  the  ear  of  the  side  operated  on,  the 
animal  never  attempted  to  use  the  limb  of  that  side,  but  contented 
itself  with  vigorously  shaking  its  head,  which  frequently  caused  it 
to  lose  its  balance  and  fall  to  the  right.  To  these  and  other 
similar  phenomena  of  cerebellar  deficiency  we  gave  the  name  of 
asthenia :  muscular  asthenia  due  to  nervous  asthenia,  the  direct 
consequence  of  loss  of  the  influence  of  the  homolateral  half  of  the 
cerebellum. 

Other  phenomena  prove  that  this  asthenia  is  always  closely 
associated  with  a  definite  diminution  of  the  normal  tone  of  the 
muscles — i.e.  of  the  degree  of  their  active  tension  during  rest— 
which  must  exert  a  considerable  influence  on  the  contractions  and 
relaxations  of  the  muscles,  particularly  as  regards  the  form,  degree, 
and  duration  of  these  processes. 


vin  THE  HIND-BRAIN  443 

When  the  bitch  that  had  lost  the  right  half  of  its  cerebellum 
was  held  up  by  its  flanks  in  the  air,  the  muscles  of  the  right  hind- 
limb  were  seen  to  be  more  relaxed  than  those  of  the  opposite  side, 
as  in  the  hind -leg  of  Brondegeest's  frog,  after  section  of  the 
posterior  spinal  roots.  On  lifting  the  soles  of  the  animal's  feet 
with  the  palm  of  the  hand,  greater  resistance  to  passive  flexion 
was  felt  in  the  leg  of  the  healthy  side  than  on  the  side  operated 
on ;  the  latter,  indeed,  could  be  flexed  beyond  the  normal  limit, 
that  is,  farther  than  the  limb  of  the  sound  side.  If  the  animal 
was  watched  while  feeding  in  the  upright  position,  with  its  limbs 
separated  to  widen  the  base  of  support  and  its  whole  attention 
given  to  its  food,  it  was  noticed  repeatedly  that  the  legs  of  the 
injured  side  gradually  gave  way,  so  that  the  animal  would  have 
lost  its  equilibrium  and  fallen  to  this  side,  if  it  had  not  become 
aware  of  its  danger  in  time  to  recover  its  equilibrium  by  suitable 
compensatory  movements. 

The  tendency  of  the  animal  to  fall  towards  the  operated  side 
during  the  early  days  after  removal  of  one-half  of  the  cerebellum 
is  evidently  related  to  the  passive  flexion  of  the  limbs  when 
it  is  intent  on  its  food.  On  watching  carefully,  it  is  evident 
that  the  fall  is  due,  not  to  the  irregular  position  of  the  injured 
limbs,  but  to  the  unexpected  relaxation  of  the  muscles,  which  the 
animal  has  not  yet  learned  to  guard  against. 

Another  more  easily  observed  phenomenon  may  in  our  opinion 
be  referred  to  the  too  sudden  relaxation  that  follows  the  contraction 
of  the  muscles,  owing  to  diminution  of  their  tone.  We  noticed  in 
our  bitch  that  the  limbs  of  the  operated  side  were  lifted  higher 
than  the  normal,  as  if  she  had  to  mount  up  little  steps,  and 
that  she  set  them  down  more  forcibly  on  the  ground,  and  thus 
made  more  noise  on  the  wooden  floor.  It  appears  to  us  highly 
probable  that  the  abnormal  elevation  is  the  effect  of  the  too  rapid 
relaxation  of  the  extensors  of  the  limbs  during  the  contraction  of 
the  flexors,  and  the  stamp  the  effect  of  the  too  rapid  relaxation  of 
the  flexors  while  the  extensors  contract.  We  shall  return  to  this 
phenomenon  in  order  to  discuss  other  and  less  probable  interpreta- 
tions of  it. 

To  this  group  of  symptoms,  which  are  intimately  connected 
with  and  yet  distinct  from  asthenia,  we  gave  the  name  of  atonia, 
which  has  met  with  general  acceptance. 

A  third  group  of  symptoms  may  be  added  to  asthenia  and 
atonia  if  the  mode  in  which  the  contractions  are  carried  out  is 
carefully  observed.  In  normal  limbs  the  contractions  of  the 
muscles  are  gradual  and  sustained  in  character,  that  is  without 
interruption  of  continuity,  without  trembling  or  oscillation,  and 
with  perfect  fusion  of  their  elementary  impulses.  When  lying 
down  in  its  kennel  the  animal,  after  removal  of  half  its  cerebellum, 
only  differs  from  the  normal  animal  by  a  slight  and  almost  con- 


444  PHYSIOLOGY  CHAP. 

stant  trembling  of  the  head,  which  in  this  posture  is  the  only 
unsupported  part  of  the  body,  its  position  being  maintained  by  the 
active  contraction  of  the  muscles  of  the  neck.  When  the  animal 
stands  it  can  be  seen  that  the  tremor  is  not  limited  to  the  head, 
but  involves  the  whole  body,  which  oscillates  slightly  either  in  the 
transverse,  oblique,  or  diagonal  direction.  When  it  moves  slowly 
this  tremor  is  exaggerated;  the -movements  of  the  limbs  on  the 
operated  side  and  of  the  vertebral  column  show  a  characteristic 
defect  in  continuity  and  stability,  owing  to  the  intermittent  nature 
of  the  contractions,  as  though  the  summation  of  single  impulses 
were  imperfect.  This  defective  co-ordination  and  unsteadiness  is 
known  to  clinicians  as  titubation,  since  it  gives  the  impression 
that  the  patient  hesitates  to  decide,  or  has  difficulty  in  transmitting 
the  voluntary  impulse  to  the  muscles. 

This  titubation,  however,  disappears  when  the  animal  spon- 
taneously, or  compulsorily,  accelerates  its  gait.  No  signs  of 
ataxy  are  then  perceptible  other  than  those  which  depend  on 
hemiasthenia  and  hemiatonia,  and  on  the  abnormal  compensatory 
acts  by  which  the  animal  endeavours  to  escape  the  effects  of  these. 
This  proves  that  the  tremulousness  does  not  depend  on  delay  in 
the  development  of  the  voluntary  impulses,  or  on  difficulty  of 
transmitting  them  to  the  muscles ;  but  solely  on  the  incomplete 
summation  of  the  single  impulses,  owing  to  which  the  movements 
become  slightly  tremulous. 

On  the  other  hand,  the  tremor  increases  and  assumes  the 
character  of  marked  rhythmical  oscillations  when  the  animal  eats 
some  favourite  food.  There  are  also  true  pendulum  movements  of 
the  head  in  the  diagonal  direction,  due  to  the  alternate  functional 
predominance  of  its  depressor  and  levator  muscles,  which  are 
partially  transmitted  over  the  whole  trunk.  The  animal  is  unable 
to  check  or  arrest  them,  so  that  its  nose  may  hit  the  bottom  of 
the  dish  or  the  floor  on  which  the  food  is  placed. 

To  this  group  of  phenomena,  which  includes  tremor,  titubation, 
and  rhythmical  oscillating  movements,  we  gave  the  name  of  astasia 
for  the  sake  of  brevity  and  owing  to  their  probable  common 
origin. 

The  ataxy  in  apes  deprived  of  half  their  cerebellum  is 
fundamentally  identical  in  its  main  features.  Generally  speaking, 
compensation  sets  in  more  rapidly  and  in  a  very  varied  form  in  these 
animals.  We  have  already  seen  that  monkeys  can  overcome  the 
effects  of  vertigo  soon  after  the  operation.  On  the  disappearance 
of  the  dynamic  disturbances  they  are  almost  always  able  to  avoid 
falling  to  the  affected  side ;  in  walking  the  limbs  of  this  side  are 
strongly  abducted ;  in  sitting  upright  they  support  themselves  by 
placing  one  or  both  hands  to  the  ground  or  by  holding  on  to  the 
leg  of  a  table.  They  can  also  avoid  the  swaying  of  the  head  and 


vni  THE  HIND-BRAIN  445 

trunk,  which  miffht  cause  them  to  fall  when  the  hands  are  used 

o 

for  eating,  by  resting  the  head  firmly  on  the  ground  or  against 
a  wall. 

But  these  artifices,  which  the  monkey  can  use  in  consequence 
of  the  higher  development  of  its  motor  centres,  do  not  obscure  the 
signs  of  cerebellar  deficiency,  which  are  even  more  striking  than 
in  the  dog. 

The  asthenia  of  the  limbs  on  the  injured  side  is  expressed,  in 
addition  to  the  signs  already  described  in  dogs,  in  the  less  use 
which  the  animal  makes  of  them  ;  when  a  favourite  fruit  is  offered, 
the  monkey  always  grasps  it  with  the  hand  of  the  sound  side. 

This  is  not  due  to  paresis  of  the  limbs  of  the  operated  side,  for 
when  the  animal  is  suspended  in  the  air  by  a  sling  round  its 
trunk,  and  one  of  the  feet  is  brought  near  a  small  table,  the  latter 
is  strongly  grasped  with  both  hands.  By  pulling  gradually  on  a 
dynamometer  which  is  fixed  to  the  sling,  while  the  ape  is  fastened 
in  this  way  to  the  leg  of  the  table,  it  is  possible  to  measure  the 
force  by  which  the  animal  holds  the  table  ;  also  it  will  be  noticed 
that  first  the  hand  of  the  operated  side  and  then  that  of  the  sound 
side  gives  way. 

The  atonia  is  shown  by  the  fact  that  when  the  monkey  is  on  all 
fours  on  the  ground,  in  the  horizontal  position,  the  affected  side 
hangs  lower,  owing  to  the  defective  tone  in  the  muscles  of  the 
limbs  on  that  side.  Sometimes  there  is  slight  ptosis  of  the  upper 
eyelid  of  the  injured  side,  and  a  drawing  over  of  the  mouth  towards 
the  healthy  side,  when  the  animal  shows  its  teeth  in  biting  its 
food. 

Finally,  the  astasia  that  is  expressed  in  tremor,  titubation,  and 
rhythmical  oscillation  is  more  marked  in  the  monkey  than  in  the 
dog.  Monkeys  show  tremor  not  only  of  the  head,  but  unmistak- 
ably in  both  the  fore-  and  the  hind-limb  of  the  operated  side, 
whenever  these  are  employed. 

Patrizi  (1904),  to  render  the  atonia,  asthenia,  and  astasia  more 
distinct,  recorded  graphically  both  simple  twitches  and  tetanic 
contractions  of  the  muscles  of  the  normal  and  the  operated  side 
in  doss,  after  removal  of  one-half  of  the  cerebellum.  His  observa- 

O     ' 

tions  show  that  muscles  deprived  of  the  influence  of  the  cerebellum, 
and  excited,  directly  or  reflexly,  with  electrical  stimuli,  in  an 
animal  that  has  been  immobilised  but  not  anaesthetised,  present 
curves  which  differ  from  those  of  the  normal  side,  owing  to 
diminution  of  tone,  lower  functional  energy,  more  rapid  fatigue, 
and  the  incomplete  fusion  of  the  elementary  twitches  from  which 
the  contraction  as  a  whole  results. 

On  anaesthetising  the  animal  to  eliminate  the  normal  tone  of 
the  muscles  the  myograms  of  the  limbs  on  the  healthy  side 
resemble  those  obtained  without  narcosis  from  the  limbs  of  the 
decerebellated  side.  From  these  results  Patrizi  was  led  to  con- 


446  PHYSIOLOGY  CHAP. 

elude  thab  the  asthenic  and  astatic  phenomena  are  intimately 
connected  with  the  atonic  symptoms ;  this  agrees  well  with  our 
conception  of  the  physiology  of  the  cerebellum. 

A  general  fact  to  which  there  has  been  no  exception  in  our 
numerous  experiments  on  dogs  and  monkeys  is  that  the  phenomena 
of  deficiency  consequent  on  complete  unilateral  extirpation  of  the 
cerebellum  are  limited  exclusively  to  the  neuro-muscular  system ; 
sensation  is  not  disturbed. 

We  more  particularly  investigated  the  tactile  and  muscular 
sense. 

On  merely  touching  a  normal  dog  while  it  is  eating,  or  while 
its  eyes  are  bandaged,  or,  better,  while  it  is  suspended  in  the  air  by 
means  of  a  sling  with  the  limbs  hanging  down  (Hitzig's  method), 
it  shows  by  a  swift  movement  of  reaction  that  it  has  noticed  the 
contact.  If  the  tactile  sensibility  of  the  decerebellated  dog  is 
tested  in  the  early  post-operative  period,  when  the  animal  is  still 
incapable  of  standing  or  walking,  the  reactions  to  contact  are 
usually  absent  in  the  limbs  both  of  the  operated  and  of  the  normal 
side,  and  there  may  be  no  reactions  to  slight  painful  sensations  of 
any  kind,  particularly  upon  the  operated  side. 

But  if  the  examination  is  repeated  three  to  four  weeks  after  the 
operation,  at  the  time  when  the  locomotor  ataxy  is  at  its  maximum, 
the  reactions  to  contact  never  fail ;  only  they  occur  with  a 
perceptible  delay  on  the  operated,  as  compared  with  the  normal,  side. 
Finally,  during  the  period — which  may  last  over  a  year — in  which 
the  cerebellar  ataxy  is  final  and  permanent,  with  no  prospect  of 
improvement,  the  animal  reacts  to  slight  contacts  with  equal 
promptness  on  either  side.  This  shows  that  unilateral  removal  in 
the  cerebellum  does  not  disturb  tactile  sensibility. 

It  is  more  difficult  in  animals  to  make  any  exact  investigation 
of  the  so-called  "  muscular  sense  "  —by  means  of  which  we  are  aware 
of  the  position  of  our  limbs,  the  direction  of  active  and  passive  move- 
ments in  the  same,  and  the  degree  of  tension  or  resistance  opposed 
to  muscular  contraction,  without  the  aid  of  tactile  sensibility  and 
vision.  Of  these  different  forms  or  qualities  of  muscular  sense,  the 
first,  which  conveys  the  sense  of  the  position  of  the  limbs,  is  easy 
to  examine  in  dogs.  When  a  normal  dog  with  its  eyes  bandaged 
is  kept  upright  on  a  table,  and  any  one  of  the  four  limbs  is  brought 
into  an  unnatural  position,  e.g.  when  the  dorsal  surface  of  the  foot 
is  placed  in  contact  with  the  table,  the  limb  is  brought  back 
instantly  to  the  normal  position  ;  if  one  of  the  four  legs  is  left 
unsupported,  by  letting  it  hang  over  the  edge  of  the  table,  the 
animal  at  once  draws  it  up  and  puts  it  back  on  the  table. 

In  the  dog  after  removal  of  half  the  cerebellum  it  is  impossible 
to  carry  out  this  experiment  successfully  while  the  animal  is  still 
unable  to  stand  on  its  legs,  and  therefore  to  react  to  unaccustomed 
postures,  even  when  perfectly  aware  of  them.  When  it  begins  to 


viii  THE  HIND-BRAIN  447 

walk,  and  tin-  cerebellar  ataxy  is  pronounced,  the  animal  does  not 
always  correct  the  abnormal  positions  in  which  its  limbs  are 
placed,  and  when  it  does  there  is  a  certain  delay  in  the  limbs  of 
the  side  operated  on,  as  compared  with  the  normal  side.  Ducceschi 
and  Sergi  drew  attention  to  the  fact  that  during  this  period  the 
dog  with  half  a  cerebellum  in  many  cases  does  not  correct  the 
abnormal  postures  given  to  the  limbs  of  the  operated  side,  and 
sometimes,  though  more  rarely,  not  even  those  of  the  limbs  on  the 
healthy  side,  in  which  there  is  no  reason  to  suspect  any  disturb- 
ance of  the  muscular  sense. 

If,  lastly,  the  muscle  sense  is  investigated  during  the  long 
period  in  which  the  cerebellar  ataxy  has  become  stationary  and 
permanent,  anomalous  positions  of  the  limbs  of  the  operated,  as 
well  as  of  the  sound,  side  are  corrected  as  in  normal  dogs. 

These  facts  show  that  absence  of  the  cerebellum  is  com- 
patible with  integrity  of  the  muscle  sense.  It  is  evident  that  the 
frequent  failure  to  react  in  the  early  stage  and  afterwards  has  no 
value  as  evidence  of  sensory  disturbance  ;  in  this  kind  of  research 
the  maxim  that  one  well-estal  dished  positive  proof  is  worth  more 
than  any  number  of  negative  proofs  holds  good. 

If  the  behaviour  of  a  dog  in  which  the  cortex  of  one  side  of 
the  so-called  sensory -motor  area  (sigmoid  gyrus)  has  been  removed 
is  compared  with  that  of  the  dog  with  only  half  a  cerebellum, 
the  conclusion  that  the  muscular  sense  is  seriously  disturbed  in 
the  former  and  has  not  perceptibly  suffered  in  the  latter  is 
inevitable.  In  both  the  defect  phenomena  disappear  in  time,  but 
in  the  former  the  failure  to  correct  the  abnormal  postures  of  the 
limbs  persists  for  months,  while  in  the  latter  it  disappears  entirely 
as  soon  as  the  animal  has  acquired  the  power  of  walking,  although 
extreme  ataxia  persists. 

But  the  most  cogent  proof  of  the  integrity  of  the  muscular 
sense  in  decerebellated  dogs  is  the  retention  of  power,  when  the 
animal  lies  at  rest,  of  scratching  the  skin  of  the  abdomen,  thorax, 
and  neck  with  one  or  both  hind-feet,  with  perfect  adaptation  to 
the  purpose  of  removing  disagreeable  stimuli.  This  is  such  a  common 
occurrence  that  it  may  altogether  escape  the  careless  observer. 
But  this  action,  on  the  one  hand,  necessitates  integrity  of  cutaneous 
sensibility,  and  on  the  other  capacity  for  rightly  exciting,  directing, 
measuring,  and  therefore  being  aware  of  muscular  contractions — in 
a  word,  integrity  of  the  muscle  sense. 

V.  A  critical  analysis  of  the  ataxia  due  to  unilateral  lesions  of  the 
cerebellum  will  greatly  facilitate  our  task  of  analysing  the  second 
typical  form  of  cerebellar  ataxy — that  which  results  from  bilateral 
lesions.  Speaking  generally,  the  absence  of  the  whole  cerebellum 
produces  the  same  symptoms  as  the  loss  of  one-half,  only  they 
affect  both  sides,  and  do  not  predominate  in  one  alone. 

This  spread  of  the  defect  phenomena  to  both  sides  produces  a 


448  PHYSIOLOGY  CHAP. 

peculiar  form  of  motor  ataxy,  which  has  been  well  described  as 
"  drunken  gait "  —a  name  which  suggests  itself  at  once  to  every 
one  who  sees  an  animal  attempt  to  walk  for  the  first  time  after 
removal  of  its  cerebellum.  A  careful  analysis  of  this  reeling  zig- 
zag gait  shows  that  it  results  from  the  same  factors  which  we 
distinguished  in  the  gait  of  animals  with  a  half-cerebellum,  i.e. 
from  asthenia,  atonia,  and  astasia,  and  from  compensatory  pro- 
cesses, which  are  not,  however,  limited  to  one  side,  but  involve 
both. 

On  the  disappearance  of  the  dynamic  phenomena  of  the  early 
post-operative  period,  the  dog  remains  for  a  certain  time  incapable 
of  standing  on  its  feet  and  sustaining  the  weight  of  its  own  body. 
At  each  attempt  to  get  up  it  falls  now  on  one  side  and  now  on 
the  other.  Later  it  begins  to  rise  on  the  fore-limbs  only,  because 
the  hind-limbs  flex  at  each  attempt  to  stand  up. 

That  this  inability  of  the  animal  to  assume  and  maintain  the 
upright  posture  is  due  solely  to  asthenia,  atonia,  and  astasia,  and 
not  to  inability  to  co-ordinate  its  movements,  nor  to  deficient 
equilibrium,  is  proved  by  the  fact  that  during  this  period  the 
animal  is  able  to  swim  as  well  as  any  normal  dog. 

At  a  later  period  the  animal  manages  to  rise  gradually,  and  to 
take  a  few  steps,  but  it  frequently  falls  to  one  side  or  the  other, 
owing  to  the  flexion  of  the  limbs,  particularly  the  hind -legs, 
which  are  always  the  weakest.  In  the  upright  position  it  is  never 
still  for  a  moment,  and  always  seeks  the  support  of  a  wall  in  its 
first  attempts  at  walking.  It  is  only  later  that  it  gradually  learns 
to  walk  without  support  and  to  fall  less  often  and  less  suddenly, 
till  at  last  it  avoids  this  altogether. 

This  functional  restitution  is  only  to  a  minimal  extent  due  to 
organic  compensation ;  it  depends  fundamentally  upon  functional 
compensation.  We  must  carefully  examine  the  form  and  the 
effects  of  these  compensatory  processes,  because  it  is  these  that 
give  its  most  characteristic  feature  to  cerebellar  ataxy. 

These  compensatory  processes  consist  mainly  in  exaggerated 
abduction  of  the  four  limbs  in  walking.  This  widens  the  base  of 
support  and  lowers  the  animal's  centre  of  gravity,  making  it  less 
liable  to  fall ;  at  the  same  time  the  swaying  of  the  body  increases, 
as  this  is  a  reaction  to  the  resistance  which  its  feet  encounter  from 
the  ground  (Fig.  79,  p.  119). 

The  decerebellated  animal  cannot  use  the  muscles  of  the 
vertebral  column  to  compensate  its  symptoms,  as  they  are  atonic 
and  asthenic  on  both  sides ;  this  contributes  to  the  horizontal 
oscillations  and  frequent  alternating  displacements  of  the  animal's 
centre  of  gravity  to  right  and  left.  The  not  uncommon  cross- 
ing 'of  the  fore-limbs,  so  that  the  right  foot  is  set  down  to  the 
left  and  the  left  foot  to  the  right  side,  is  undoubtedly  a  com- 
pensatory adaptation,  intended  to  obviate  the  effects  of  these 


viii  THE  HIND-BRAIN  449 

exaggerated  horizontal  oscillations.  It  can  easily  be  understood 
that  it'  the  animal's  trunk  is  inclined  to  the  left  and  the  centre  of 
gravity  displaced  to  that  side,  while  the  right  fore-limb  is  raised, 
then,  in  order  to  recover  equilibrium,  the  limb  must  he  put  down 
obliquely  to  the  left,  so  that  it  crosses  with  the  leg  of  this  side; 
the  contrary  must  take  place  if  while  the  left  leg  is  raised  the 


FIG.  235.— Tracings  of  gait  of  a  bitch  wei.u'hinj,'  0!>75  jjrnis.  in  which  the  cerebellum  had  been  almost 
completely  removed  by  three  operations.  (Luciani.)  ft,  tracing  obtained  two  and  a  half 
months  after  final  operation  ;  c,  eleven  months  after;  r',  the  same  with  eyes  blindfolded. 

trunk  is  suddenly  inclined  to  the  right  while  the  left  leg  is  raised. 
This  interpretation  is  confirmed  by  the  fact  that  crossing  of  the 
fore-limbs  almost  always  occurs  when  the  animal  tries  to  alter  its 
direction,  as  shown  by  the  tracings,  of  the  footprints  (Fig.  235). 
In  this  case  it  curves  its  cervical  spine  to  the  right  or  left,  so  that 
the  left  fore-limb  crosses  with  the  right,  or  the  right  fore-limb 
with  the  left,  to  avoid  loss  of  equilibrium  and  the  danger  of 
falling. 

So  that  when  in  the  decerebellated  animal  there  is  a  marked 

VOL.  in  2  G 


450  PHYSIOLOGY  CHAP. 

displacement  of  the  centre  of  gravity  to  one  or  the  other  side  as 
it  walks,  it  can  recover  its  equilibrium  either  by  exaggerated 
abduction  or  by  exaggerated  adduction  of  the  fore-leg,  propor- 
tionate to  the  degree  of  displacement  and  the  stage  of  the  step  at 
which  it  occurs,  whether  at  the  moment  of  dropping  or  raising  one 
or  the  other  fore-limb.  The  gait  of  the  drunken  man,  at  least  in 
mild  intoxication,  also  results  from  depression  of  the  energy  and 
tone  of  the  nervous  system  (Schmiedeberg,  Bunge) ;  by  facilitat- 
ing the  flexion  of  the  limbs  under  the  weight  of  the  body  this 
produces  abnormal  involuntary  lateral  displacements  of  the  centre 
of  gravity,  which  the  individual  compensates  by  exaggerated 
abduction  or  adduction  of  the  limbs. 

The  movements  of  the  decerebellated  dog  are  not  indeed  the 
best  adapted  to  the  object  of  preserving  equilibrium  and  recovering 
it  when  menaced,  with  a  minimal  expenditure  of  energy.  We 
have  seen  that  the  animal  with  half  a  cerebellum  lifts  the  limbs  of 
the  injured  side,  particularly  the  fore -limbs,  higher  than  the 
normal  and  stamps  them  more  firmly  on  the  ground.  This 
peculiarity,  to  which  we  gave  the  name  of  motor  dysmetria,  and 
which  is  well  described  by  the  term  "  hen's  gait,"  is  seen  on  both 
sides  in  dogs  after  removal  of  the  cerebellum.  Whatever  the 
explanation  of  this  dysmetria,  it  undoubtedly  expresses  an 
imperfect  functioning  of  the  peripheral  organs  whose  task  it  is  to 
effect  compensation,  so  that  the  animal  wastes  part  of  its  energy 
uselessly.  We  have  already  shown  how  this  may  be  interpreted 
as  the  simple  effect  of  atony  of  the  leg-muscles,  owing  to  which 
there  is  a  too  rapid  relaxation  of  the  extensors  when  the  flexors 
are  contracting  and  a  too  rapid  relaxation  of  the  flexors  while 
the  extensors  are  contracting.  So  long  as  this  hypothesis  has  not 
been  experimentally  disproved,  we  cannot  include  dysmetria  in  the 
fundamental  elementary  symptoms  of  cerebellar  deficiency  which 
consist  in  atonia,  asthenia,  and  astasia.  But  we  shall  return 
later  on  to  this  disputed  point. 

The  cerebellar  ataxy  of  monkeys  which  have  lost  both  sides 
of  their  cerebellum  only  differs  from  that  of  dogs  in  the  more 
varied  form  of  the  compensatory  processes,  owing  to  their  greater 
activity. 

During  the  period  in  which  the  monkeys  are  unable  to  stand 
upright,  and  are  compelled  by  the  functional  incapacity  of  their 
hind-limbs  to  drag  the  body  along  the  ground,  they  can  clamber 
on  to  the  furniture  by  means  of  their  fore -limbs,  which  are 
always  less  asthenic  than  the  hind.  Even  long  after  the  operation 
the  monkey  is  incapable  of  standing  erect  and  of  walking  in  the 
vertical  position  on  its  hind-legs  only,  as  it  not  infrequently  does 
under  normal  conditions. 

Again,  the  dorsal  curvature  of  the  back,  due  to  atony  of  the 
extensor  muscles  of  the  vertebral  column,  is  more  pronounced 


vm  THE  HIND-BRAIN  451 

in  monkeys  than  in  dogs,  so  that  in  the  tracing  the  foot- 
prints of  the  hind -limbs  always  fall  in  front  of  those  of  the 
fore-limbs  (Fig.  236).  The  animal  deviates  from  side  to  side  in 
walking,  making  an  undulating  line,  and  if  it  falls  to  right  or  left 
this  is  always  due  to  the  giving  way  of  one  or  both  hind-limbs, 
in  which  atony  is  predominant.  In  comparison  with  a  normal 
monkey,  it  moves  more  slowly,  and  from  time  to  time  feels  obliged 
to  rest,  sitting  on  its  buttocks. 

The  astasia  is  most  prominent  in  the  neck,  but  spreads  more 
or  less  to  all  the  other  muscles,  as  shown  by  the  slight  trembling 
of  the  limbs  each  time  they  are  used  for  isolated  movements,  as 
to  carry  fruit  to  the  mouth,  to  catch  the  insects  in  the  hair,  etc. 

In  monkeys,  too,  the  limbs  are  raised  unduly  in  walking 
(dysmetria),  owing  to  disturbed  functions  of  the  organs  charged 
with  the  compensatory  processes.  This  dysmetria  is  certainly 


FIG.  236.— Male  Macacus  in  which  nearly  the  whole  of  the  cerebellum  was  extirpated  at  one 
sitting.  (Luciani.)  b,  tracing  obtained  one  and  a  half  months  after  the  operation  ;  c,  tracing 
taken  after  a  yeai . 

not  sensory  in  origin,  because  cutaneous  and  muscular  sensibility 
are  not  found,  with  the  various  methods  of  investigation  which 
can  be  employed  on  animals,  to  be  appreciably  disturbed.  If 
total  extirpation  of  the  cerebellum  is  performed  on  an  animal 
which  has  previously  been  deprived  of  the  signioid  gyri,  which 
contain  the  senso-motor  area,  or  if,  vice  versa,  these  are  excised 
in  an  animal  that  has  already  lost  its  cerebellum,  it  remains 
for  the  rest  of  its  life  incapable,  not  only  of  walking,  but 
even  of  supporting  itself  for  a  few  moments  in  the  erect  posture. 
This  depends  less  on  the  fact  that  the  motor  defect  phenomena 
are  much  greater  in  this  case,  because  those  which  depend  on  the 
absence  of  the  cerebellum  sum  up  with  the  others  which  are  due 
to  deficiency  of  the  two  cerebral  areas,  than  on  the  removal  of  the 
sigmoid  gyri,  which  disturbs  cutaneous  and  muscular  sensibility ; 
the  animal  consequently  loses  the  power  of  compensation  by  which 
it  widens  its  base  of  support  to  save  itself  from  falling. 

Between  the  two  extreme  typical  forms  of  cerebellar  ataxy 
described,  which  are  due  to  the  total  or  almost  total  absence  of  half 


452  PHYSIOLOGY  CHAP. 

or  the  whole  of  the  cerebellum,  there  are  a  number  of  intermediate 
forms,  due  to  partial  and  more  or  less  extensive,  symmetrical,  or 
asymmetrical  lesions  of  this  organ,  which  can  more  often  be 
observed  because  it  is  much  easier  to  keep  alive  animals  with 
partial  mutilations  of  the  cerebellum. 

The  most  important  difference  between  the  typical  forms  of 


Fio.  237. — Gait  of  a  bitch  of  6000  grms.  in  which  the  two  lateral  halves  of  the  cerebellum 
were  divided  by  a  vertical  cut,  much  of  the  grey  matter  of  the  vermis  being  lacenttrd. 
(Luciani.)  a,  tracing  before  the  operation  ;  b,  four  days  after  operation  ;  c,  live  days  after  ; 
d,  a  month  after ;  c,  two  months  after. 

ataxy  described  above  and  these  intermediate  forms  consists  in 
the  fact  that  while  the  former  improve  but  little,  and  persist 
throughout  the  animal's  life,  the  latter  improve  progressively 
until  they  become  latent,  i.e.  there  is  a  true  organic  compensation, 
which  gradually  makes  the  various  forms  of  functional  compensation 
superfluous. 

The  tracings  in   Fig.   237  were  taken  from  an  adult  bitch  in 


vin  THE  HIND-BRAIN  453 

which  the  cerebellum  had  been  divided  in  the  median  line  by  a 
small  knife  and  a  hook,  so  that  a  considerable  part  of  the  grey 
matter  of  the  vermis  was  destroyed. 

Tracing  a  represents  the  animal's  normal  gait ;  four  to  five  days 
after  the  operation  tracings  b  and  c  were  taken,  which  show  marked 
al  id  action  of  both  fore-  and  hind-limbs,  in  order  to  widen  the  base 
of  support,  thus  making  it  easier  to  maintain  the  equilibrium  and 
avoid  falling  on  one  side  or  the  other.  The  steps  are  also  seen  to 
be  shorter  in  comparison  with  the  normal;  to  cover  the  same 
distance  10  steps  were  taken  in  a,  14  in  b,  13  in  c.  Tracing  d 
was  made  one  month,  and  tracing  e  two  months,  after  the 
operation,  when  the  improvement  in  walking  is  evident  and  the 
gait  so  nearly  normal  that  no  one  could  distinguish  it  without 
comparing  the  tracings. 

In  another  bitch  we  excised  the  whole  of  the  median  lobe  or 
vermis,  without,  however,  exposing  the  floor  of  the  fourth  ventricle, 
as  the  uvula  was  left  partly  uninjured.  Tracing  b  of  Fig.  238, 
taken  ten  days  after  the  operation,  when  the  dynamic  phenomena 
had  not  entirely  ceased,  shows  very  grave  locomotor  disturbances  ; 
the  steps  are  extremely  short  and  it  was  found  on  listening  that 
the  taps  of  the  feet  on  the  floor  occurred  at  irregular  intervals ; 
each  fore-leg  frequently  crosses  that  of  the  opposite  side,  but  the 
hind-limbs  do  not  cross.  Owing  to  the  strong  lateral  oscillations 
of  the  vertebral  column  the  direction  of  progression  is  curved,  and 
often  a  zigzag,  and  the  distance  between  the  print  of  each  lateral 
pair  of  feet  varies,  which  produces  a  marked  disturbance  of 
co-ordination.  Two  days  later,  when  the  dynamic  disturbances 
had  disappeared,  tracing  c  was  taken,  which  shows  a  surprising 
improvement  in  the  gait,  and  a  week  later  tracing  d,  which  differs 
little  or  not  at  all  from  the  normal.  Tracing  d'  with  the  animal 
blindfolded  was  obtained  on  the  same  day,  and  shows  how  little 
influence  vision  has  upon  the  gait.  A  month  later  the  gait  is 
approximately  the  same,  as  shown  by  tracing  e.  Tracing  e, 
obtained  after  a  hypodermic  injection  of  morphia,  shows  that  its 
action  upon  the  nervous  centres  causes  the  partial  reappearance 
of  the  ataxic  phenomena. 

All  our  researches  lead  to  the  important  conclusion  that  organic 
compensation  of  partial  lesions  is  dependent  on  the  remaining 
portions  of  the  cerebellum,  i.e.  on  parts  with  the  same  functional 
character  as  the  part  extirpated,  and  that  compensation  ensues  so 
much  the  faster  and  to  a  greater  extent,  in  proportion  as  the  part 
destroyed  is  small  in  comparison  with  the  portions  left  intact  and 
able  to  function. 

A  valuable  confirmation  of  this  analysis  of  the  ataxy  due  to 
more  or  less  complete  extirpation  of  the  cerebellum  in  dogs  was 
given  by  Langelaan  (1907)  in  his  admirable  description  of  a  case 
of  congenital  cerebellar  ataxy  in  a  young  cat,  which  he  examined 


454 


PHYSIOLOGY 


CHAP. 


by  physiological  tests  during  life  and  with  histological  methods 
after  its  death.  While  alive  the  animal  exhibited  all  the  defect 
phenomena  which  we  described  under  the  heads  of  asthenia, 
atonia,  and  astasia,  particularly  in  its  hind-limbs.  These  defect 
phenomena  were  associated  with  compensatory  phenomena,  as 
pronounced  abduction  of  the  fore-  and  hind-limbs.  Langelaan 


FIG.  238. — Tracings  of  gait  from  a  bitch  weighing  5395  grms.  which  had  been  deprived  of  the  median 
eriebellar  lobe.  (Luciani.)  a,  tracing  nine  days  after  operation;  c,  eleven  days  after;  d, 
nineteen  days  after  ;  d',  the  same,  on  blindfolding  the  animal ;  «,  a  month  after ;  e',  the  same 
after  hypodermic  injection  of  morphine. 

carefully  examined  sensation  without  discovering  any  disorder ; 
the  muscle-sense,  which  he  tested  minutely,  was  almost  normal. 
At  the  post-mortem  examination  he  observed  a  marked  atrophy 
of  the  whole  cerebellum,  which  involved  only  the  cortical  elements 
(granular  layer  and  layer  of  Purkinje's  cells) ;  while  the  central 
nuclei  and  those  of  Deiters  and  Bechterew  were  normal  in  form 
and  structure.  In  addition  to  the  atrophy  of  the  cerebellar  cortex 


vin  THE  HIND-BRAIN  455 

there  was  an  associated  atrophy  of  certain  systems  of  fibres  of  the 
cord  and  bulb. 

VI.  As  long  ago  as  1879  Nothnagel  pointed  out  that  the 
symptoms  of  disease  of  no  other  part  of  the  brain  are  so  uncertain 
as  in  the  cerebellum.  Even  to-day  loose,  inaccurate,  and  con- 
tradictory clinical  observations  only  tend  to  make  any  general 
conception  of  the  functions  of  the  cerebellum  difficult.  The 
reasons  for  this  failure  of  clinical  and  experimental  observations 
to  agree  are  numerous,  and  must  be  understood  by  the  physiologist 
who  wishes  to  avail  himself  of  clinical  observation. 

In  the  first  place,  the  material  for  clinical  observation  of 
diseases  of  the  cerebellum  is  not  plentiful.  In  1899  Adler 
published  a  brief  review  of  124  of  the  best  observed  cases  from 
the  literature  of  the  ten  years  preceding.  To  this  survey  we  need 
only  add  the  few  cases  published  between  1898  and  the  present 
day. 

In  these  statistics  cases  of  tumours  of  various  kinds  pre- 
dominate largely  over  all  other  forms  of  disease ;  atrophy  and 
agenesia  are  less  frequent ;  still  less  common,  haeniorrhagic  foci, 
softening,  abscesses  ;  rarest  of  all,  traumatic  and  surgical  lesions. 

A  highly  important  fact  which  impresses  every  one  who 
studies  clinical  cases  of  cerebellar  diseases  is  that  in  some  of  them 
the  disease  remains  obscure  or  latent  during  life  and  is  not 
suspected  before  the  post-mortem  examination.  Our  Monograph 
of  1891  showed  that  certain  of  the  cases  described  as  "latent" 
were  so  only  to  the  extent  that  the  accentuated  form  of  dysmetria 
of  movements — which  many  of  the  older  and  some  of  the  modern 
clinicians  hold  erroneously  to  be  the  most  characteristic  sign  of 
cerebellar  disease,  and  which  are  fallaciously  termed  "  disturbances 
of  co-ordination  "  —were  wanting.  But  in  other  cases  there  could 
be  no  doubt  that  the  lesions  of  the  cerebellum  presented  no 
symptoms. 

If  these  cases  of  comparative  or  total  absence  of  the  essential 
phenomena  of  cerebellar  deficiency  are  investigated  one  by  one;  it 
will  be  found  that  they  are  all  instances  of  agenesia,  viz.  a  more 
or  less  complete  congenital  defect  or  arrested  development  of  the 
organ,  dating  back  to  embryonic  life,  or  of  sclerosis  or  atrophy, 
which  are  the  final  outcome,  of  circumscribed  encephalitis  with  a 
slow  course. 

Mingazzini  has  recently  made  a  fresh  investigation  of  all  the 
earlier  and  recent  cases  of  agenesia  and  atrophy  of  either  half 
or  the  whole  of  the  cerebellum,  and  came  to  the  following  con- 
clusions :— 

(a]  Agenesia  of  half  the  cerebellum  usually  runs  its  course 
without  any  symptoms  whatsoever. 

(I)}  Unilateral  cerebellar  atrophy  remains  latent,  when  only 
the  superficial  cortex  is  affected. 


456  PHYSIOLOGY  CHAP. 

(c)  When  the  unilateral  atrophy  involves  the   cortex   of  the 
involuted  folia,   but  not  the  deeper  parts,  slight  and  not  very 
characteristic  motor    disturbances   result ;    there   is   merely  slow 
progression  and  a  tendency  to  make  backward  steps. 

(d)  Only  when  the  atrophy  involves  the  whole  of  one-half  of 
the  cerebellum   is   the   characteristic  drunken  gait  and  manifest 
asthenia  of  the  muscles  on  the  affected  side  to  be  seen. 

(e)  Incomplete   bilateral    agenesia    of  the    cerebellum    seldom 
runs  its  course  without  symptoms.     This,  however,  occurred  in  a 
case  described  by  Ingels,  in  which  the  weight  of  the  cerebellum 
was  reduced  to  ^V  of  the  normal.     But  in  the  majority  of  cases 
there  is  ataxia  with  a  greater  degree  of  astasia,  or  pronounced 
ataxia — particularly  in  the  lower  limbs — with  general    asthenia 
and  astasia,   which   may   appear  in   the  hands  and  arms  in  the 
form  of  tremor. 

(/)  In  bilateral  sclerotic  atrophy  the  main  symptoms  of 
cerebellar  deficiency  are  seldom  absent.  Tin-  most  constant  are: 
swaying  in  the  upright  position  (astasia),  which  compels  the 
patient  to  widen  his  base  of  support  to  avoid  falling ;  a  zigzag 
gait  like  that  of  a  drunken  man,  which  is  sometimes  accompanied 
by  marked  diminution  of  power  (asthenia)  in  the  lower  limbs— 
rarely  in  the  upper — so  that  the  patient  is  obliged  to  support 
himself  by  the  walls,  seats,  or  a  friendly  arm  to  avoid  falling. 

These  facts,  derived  from  a  critical  examination  of  this  group 
of  clinical  cases — which  is  certainly  the  most  important  from  the 
physiological  point  of  view — not  only  agree  with  those  obtained 
experimentally  by  ourselves  in  dogs  and  monkeys,  but  are  a 
useful  complement  to  them. 

The  cases  of  agenesia  that  run  a  latent  course  seem  to  us  of 
the  highest  value,  because  they  show  that  if  a  partial  arrest  of 
development  takes  place  in  the  cerebellum,  such  organic  adaptations 
may  come  about  in  the  cerebral  system  as  a  whole  as  can  wholly 
or  partially  compensate  the  cerebellar  deficiency. 

The  cases  of  atrophy  which  present  no  symptoms  during  life,  or 
only  such  as  are  slight  and  not  characteristic,  agree  perfectly  with 
the  experimental  fact  that  more  or  less  complete  organic  com- 
pensations may  occur  with  surprising  rapidity  after  incomplete 
mutilations,  symmetrical  or  asymmetrical,  of  the  cerebellum  in 
dogs  and  monkeys. 

Evidently  when  cerebellar  disease  develops  very  slowly,  it  may 
attain  a  considerable  severity  without  any  visible  symptoms,  since 
the  effects  of  deficiency  are  obscured  or  repaired  by  simultaneous 
organic  compensation  in  proportion  as  they  make  their  appearance. 

It  is  also  plain  that  the  process  of  organic  compensation  by  the 
intact  parts  of  the  cerebellum  can  only  take  place  imperfectly  in 
cases  of  bilateral  agenesia  or  atrophy,  when  the  healthy  and  func- 
tioning part  of  the  organ  is  reduced  to  a  minimum. 


vni  THE  HTND-BEATN  457 

Less  convincing  from  the  physiologist's  point  of  view  is  the 
larger  group  of  clinical  cases  of  various  kinds  of  tumours  in 
one  or  other  part  of  the  cerebellum,  which,  in  addition  to  more 
or  less  extensive  destruction  of  normal  tissue,  compress  the 
adjacent  organs,  beyond  the  limits  of  actual  disease,  particularly 
the  pons  and  medulla.  It  is  a  priori  evident  that  in  these 
cases  the  fundamental  phenomena  of  cerebral  deficiency  are 
masked  and  to  some  extent  replaced,  by  irritation  or  paralytic 
phenomena,  in  proportion  with  the  more  or  less  acute  course  of 
the  disease  and  the  extent  and  degree  of  the  compression  exerted 
by  the  tumour  on  the  surrounding  parts. 

The  mechanical  effects  of  compression  are  easy  to  recognise. 
The  crossed  hemiplegia  and  hemiparesis1  seen  in  certain  cases  of 
tumour  of  one  lateral  half  of  the  cerebellum  certainly  depend  on 
the  compression  which  the  tumour  exerts  on  the  motor  paths  in 
the  pyramidal  fibres  of  the  same  side  before  they  cross.  The 
homolateral  paralysis  of  one  or  more  cerebral  nerves  by  which  the 
syndrome  of  cerebellar  tumours  is  sometimes  complicated  is  due 
to  the  same  cause. 

The  symptoms  which  physicians  regard,  not  without  reason,  as 
the  irritative  effects  of  cerebellar  tumours  are  more  frequent,  more 
numerous,  and  more  varied. 

One  of  the  most  general  is  intermittent  or  continuous  headache, 
which  may  be  localised  in  the  forehead  or  temples,  more  often  in  \ 
the  occiput,  particularly  close  to  that  part  of  the  cerebellum  which  ' 
is  the  seat  of  the  tumour. 

Vertigo  in  its  various  forms  is  another  symptom  by  which  the 
clinical  picture  of  cerebellar  tumours  is  frequently  complicated. 
Some  regard  it  as  an  essential  feature  of  cerebellar  diseases ;  the 
characteristic  syndrome  of  ataxy  would  thus  be  only  an  effect  of 
vertigo.  We  learn,  however,  from  clinical  observation — which  is 
in  this  case  of  the  utmost  value  since  it  relates  to  a  subjective 
phenomenon — that  ataxy  may  be  present  without  the  faintest  sign 
of  vertigo ;  that  this  is  almost  invariably  associated  with  irritative 
and  conrpressive  lesions  of  the  cerebellum,  and  is  absent  in  all 
degenerative  and  destructive  lesions  ;  finally,  that  vertigo  is  not  an 
exclusive  symptom  of  cerebellar  diseases,  but  is  very  frequently 
associated  with  diseases  of  other  parts  of  the  central  and  peri- 
pheral nervous  systems. 

Vomiting  is  not  uncommonly  associated  with  headache  and 
vertigo,  and  may  depend  on  the  compression  of  the  bulb  or 
on  the  irritation  which  spreads  to  the  posterior  corpora  quadri- 
"•riuina,  where  there  is  a  centre  for  the  contractions  of  the  stomach. 

O  ' 

The  forced  movements  and  attitudes  by  which  vertigo  is 
constantly  accompanied  in  animals  have  usually  been  observed 
in  clinical  cases  of  compressive  and  irritative  lesions,  involving 
one  cerebellar  hemisphere.  Eotation  and  circus  movements  are 


458  PHYSIOLOGY  CHAP. 

exceedingly  rare  ;  more  frequently  there  is  an  irresistible  tendency 
to  incline  sideways  or  backwards,  with  curvature  of  trunk  or  neck, 
strabismus,  nystagmus,  etc.,  so  that  the  patient  is  incapable  not 
only  of  walking,  but  also  of  holding  himself  upright. 

Cases  of  cerebellar  tumours  are  not  infrequently  complicated 
by  epileptiform  attacks,  which  may  be  general  and  widespread,  as 
in  ordinary  epilepsy,  or  partial  and  limited  to  certain  groups  of 
muscles,  as  in  Jacksonian  epilepsy.  But  in  cerebellar  atrophy  of 
long  standing  these  epileptiform  fits  are  even  more  frequent ; 
epilepsy  cannot  therefore  be  purely  and  simply  the  effect  of 
compression  exerted  by  the  tumours. 

In  tumours  with  a  rapid  course  this  complex  of  symptoms 
predominates,  and  partly  or  wholly  masks  the  fundamental 
phenomena  of  cerebellar  deficiency.  But  in  most  cases  the 
asthenic,  atonic,  and  astatic  symptoms  described  in  animals  that 
have  lost  part  or  the  whole  of  the  cerebellum  are  associated  to  a 
greater  or  less  degree  with  symptoms  due  to  compression  or 
irritation  of  the  adjacent  organs. 

With  the  exception  of  cases  of  agenesia  and  partial  atrophy 
with  a  slow  course  which  may  remain  entirely  latent,  the  gait  in 
the  vast  majority  of  cases  of  cerebellar  disease  due  to  large  or  small, 
symmetrical  or  asymmetrical  lesions  (tumours,  haemorrhagic  foci, 
abscesses,  etc.)  is  what  clinicians  term  staggering,  uncertain,  and 
reeling  like  that  of  the  slightly  inebriated — this  is  the  synthetic 
expression  of  cerebellar  ataxy.  As  in  a  drunken  person,  the 
oscillations  of  the  body  and  continual  irregular  displacements  of 
the  centre  of  gravity  represent  the  effects  of  functional  deficiency, 
while  the  separation  of  the  feet  in  walking,  the  inclination  to  left 
or  right,  the  hurried  step  forward  or  stumble  back,  and  the  use  of 
the  arms  as  a  counterpoise,  are  compensatory  acts  intended  to  widen 
the  base  of  support,  lower  the  centre  of  gravity,  and  re-establish 
equilibrium  which  is  threatened  in  one  direction  or  the  other. 

In  asymmetrical  or  unilateral  lesions  of  the  cerebellum  the 
tendency  to  fall  is  in  the  majority  of  cases  towards  the  side  of  the 
lesion  (seven  times  out  of  ten,  Adler) ;  in  bilateral  symmetrical 
lesions  the  tendency  is  usually  to  fall  backwards.  Exceptions  to 
this  rule,  while  conflicting  from  the  clinical  point  of  view,  have  no 
scientific  value. 

One  important  clinical  result  is  that  the  motor  disturbances  in 
cerebellar  patients  are  always  far  more  marked  in  the  lower  limbs 
than  in  the  upper — as  is  the  case  to  a  marked  extent  in  animals. 
In  rare  cases  there  is  a  certain  amount  of  ataxia  in  the  upper 
limbs,  which  is  shown  in  an  incapacity  for  carrying  out  delicate 
movements  with  the  hands. 

Still  more  important  is  the  fact  clinically  noted  by  Nothnagel, 
Monakow,  and  others  that  in  cerebellar  patients  the  ataxy  of  the 
lower  limbs  disappears  completely  when  the  patients  are  lying  in 


viii  THE  HIND-BRAIN  459 

bed.  In  this  position  of  stable  equilibrium  they  are  capable  of 
carrying  out  any  movement  rapidly  and  completely.  It  is  rare  to 
find  that  one  or  the  other  leg,  if  raised,  trembles  slightly  or 
makes  shaky  or  disconnected  movements.  "When  the  patient 
lies  on  his  back  in  bed,"  writes  Nothnagel,  "  the  leg-movements 
are  made  quickly  and  certainly ;  the  subject  has  a  clear  idea  of 
their  position  and  manages  to  place  one  limb  actively  in  exactly 
the  same  place  to  which  the  other  has  been  brought  passively." 

This,  which  agrees  perfectly  with  experimental  observations, 
proves  that  cerebellar  patients — like  decerebellated  animals — retain 
on  the  one  hand  the  complete  ability  to  co-ordinate  their  move- 
ments, on  the  other  the  integrity  of  the  muscular  sense,  that  is, 
full  consciousness  of  the  position  of  the  limbs  in  space,  both  during 
rest  and  in  muscular  activity. 

It  is  curious  to  note  that  while  v.  Monakow  expressly  admits 
that  "  the  phenomena  of  cerebellar  ataxy  in  man  coincide  in 
essentials  with  the  observations  made  upon  animals,"  he  expressly 
denies  that  asthenia  and  atonia  are  essential  factors  in  clinical 
cerebellar  ataxy. 

But  it  is  only  necessary  to  glance  through  the  cases  collected 
by  Adler  (1899),  the  majority  of  which  were  tumours  in  one  or  other 
part  of  the  cerebellum,  to  see  that  asthenia,  expressed  in  the  words 
"  weakness  "  or  "  paresis  "  of  the  muscles  of  the  legs,  was  expressly 
noted  in  a  great  number  of  cases.  The  most  striking  are  11  cases 
of  tumour  of  one  cerebellar  hemisphere  in  which  muscular  weak- 
ness, or  even  a  distinct  hemiparesis,  was  noted  definitely  in  the 
homolateral  side.  In  6  other  cases  where  there  is  no  reference 
to  the  strength  of  the  limbs  it  is  stated  that  the  gait  was  unsteady 
and  uncertain,  and  that  the  patient  had  a  tendency  to  fall,  or  did 
fall,  towards  the  side  in  which  the  tumour  lay.  In  8  cases,  lastly, 
it  was  noted  that  the  patient  was  unable  to  stand  or  walk,  owing 
merely  to  irritative  phenomena  and  vertigo. 

In  denying  the  occurrence  of  atonia  v.  Monakow  repeated 
Ferrier's  objection  that  the  tendon-phenomenon  or  knee-jerk  was 
exaggerated,  according  to  Eisien  Russell,  in  animals  after  opera- 
tions on  the  cerebellum.  He  admits  that  Gowers,  Jackson,  and 
Dercum,  on  the  strength  of  clinical  observations,  ascribed  a  marked 
influence  on  muscular  tone  to  the  cerebellum.  "  But,"  he  adds, 
"  if  observations  on  the  absence  of  patellar  reflex  where  there  are 
circumscribed  lesions  of  the  cerebellum  are  not  wanting,  in  other 
cases  of  cerebellar  tumour  the  tendon  reflexes  are  normal.  It  is 
certain  that  depression  of  muscular  tone  involving  loss  of  the 
patellar  reflex  is  very  inconstant  in  cerebellar  affections  in  man. 
Luciani  assumes  that  the  alteration  in  tone  is  so  delicate  that 
clinicians  do  not  succeed  in  detecting  it.  He  himself,  however 
(as  Terrier  justly  points  out),  has  neglected  the  very  method  which 
physicians  adopt  in  every  case  for  testing  the  tone  of  the  muscles, 


460  PHYSIOLOGY  CHAP. 

viz.  examination  of  the  tendon  reflex,  so  that  the  essential  basis 
of  his  atonia  is  wanting."  To  this  argument  we  replied  to  Ferrier 
in  1895 :  "  No  one  has  ever  demonstrated  that  the  tone  of  the 
muscles  bears  any  relation  to  the  reflexes  that  can  be  evoked  by 
mechanical  stimulation  of  their  tendons.  I  fail  to  see  why  a 
certain  degree  of  atony  should  diminish  or  remove  the  tendon 
reflex  ;  it  even  seems  to  me  that  it  may  exaggerate  this  reflex — if 
not  in  force  certainly  in  its  range.  It  is  a  fact  that  exaggeration 
of  the  knee-jerk  or  patellar  reflex  is  commonly  noted  by  physicians 
in  cases  with  cerebellar  lesions,  apart  from  the  contracture  of  the 
paralysed  limb.  Since  Terrier  stated  that  after  removal  of  the  cere- 
bellum the  patellar  reflex  in  his  monkeys  was  grossly  exaggerated 
after  a  few  months,  he  was  logically  bound  to  conclude  either  that 
the  tendon  reflexes  are  in  no  way  related  to  the  muscular  tone,  or 
that  the  absence  of  the  cerebellum,  far  from  producing  atonia  as  I 
maintain,  induces,  on  the  contrary,  hypertonia  or  exaggeration  of 
muscular  tone." 

Terrier,  and  later  v.  Monakow,  did  not  dispute  the  facts  on 
which  we  founded  the  theory  of  astasia.  He  agreed  with  us  that 
the  lack  of  stability  or  firmness  in  the  limb,  both  in  different 
positions  and  in  movement,  is  seen  particularly  on  the  side  of  the 
lesion ;  that  it  is  not  confined  to  the  muscles  of  the  trunk  and 
limbs,  but  extends  to  all  the  muscles ;  and  lastly,  that  it  is 
expressed  in  tremor,  unsteadiness,  and  also  in  dysmetria  of  the 
movements  of  the  limbs,  despite  the  functional  compensation  of 
which  the  voluntary  motor  centres  are  capable.1 

In  conclusion,  it  follows  that  in  the  simplest  and  most  typical 
cases  the  clinical  symptoms  of  diseases  of  the  cerebellum  in  no 
way  contradict  the  experimental  observations.  When  the 
principal  atonic,  asthenic,  and  astatic  symptoms  of  cerebellar 
deficiency  are  absent  or  indefinite,  it  should  be  remembered  that 
the  partial  deficiency  of  the  organ  may  be  more  or  less  perfectly 
adjusted  by  a  process  of  organic  compensation.  In  cases  in 
which  the  cerebellar  disease  runs  an  acute  course,  and  is  accom- 
panied by  vertigo  and  irritative  phenomena,  these  naturally  pre- 
dominate, and  may  disturb  the  co-ordination  of  movements  so 
much  as  to  render  the  erect  posture  and  locomotion  impossible. 

1  Mingazzini  lias  unhappily  replaced  the  term  astasia  by  that  which  seems  to 
him  more  correct  of  dystasia  or  dysbasia,  by  which  he  means  the  difficulty  which 
cerebellar  patients  find  in  standing.  He  has  evidently  not  grasped  that  the  astasia, 
or  want  of  stability  refers  to  all  voluntary  muscles  and  not  merely  to  the  muscles 
of  the  lower  limbs,  neck  and  back,  which  are  specially  concerned  in  the  erect 
posture  and  in  locomotion. 

This  change  in  nomenclature,  trifling  as  it  seems,  may  well  be  a  source  of 
ambiguity,  obscurity,  and  confusion  in  the  physiology  of  the  cerebellum  ! 

Less  mischievous,  but  equally  useless,  is  the  substitution  for  atonia  and  asthenia 
of  hypotonia  and  hyposthenia  which  some  clinicians  think  more  appropriate,  as 
though  it  were  not  obvious  that  the  lack  of  tone  and  energy  in  the  muscles  must 
be  understood  in  a  relative  sense,  just  as  anaemia  signifies  not  complete  deficiency 
but  comparative  poverty  of  amount  of  blood  circulating. 


VIII 


THE  HIND-BRAIN  461 


VII.  The  hypotheses  of  the  functions  of  the  cerebellum  have 
developed  in  three  different  directions.  The  first  incorrect  ideas 
of  Rolando  (1809-28)  were  modified  by  Luys,  Dalton,  and 
Weir-Mitchell,  and  after  our  own  prolonged  experimental  studies 
assumed  a  definite  form,  in  which  the  cerebellum  is  regarded  as  an 
organ  of  subconscious  sensation,  which  exerts  a  continuous  rein- 
forcing action  upon  the  other  nervous  centres,  and  on  which  the 
normal  tone  of  the  muscles  depends.  The  theory  deduced  from 
the  experiments  of  Flourens  (1842),  who  localised  in  the  cere- 
bellum the  faculty  of  co-ordinating  the  movements  of  posture  and 
locomotion,  was  most  fully  set  forth  by  Lussaua  (1862),  who  con- 
sidered the  cerebellum  as  the  centre  of  muscular  sense.  Lastly, 
according  to  the  hypothesis  propounded  by  Magendie  (1825)  solely 
on  the  strength  of  the  forced  movements  of  rotation  and  retro- 
pulsion  after  lateral  lesions  or  symmetrical  destruction  of  the 
cerebellar  substance,  the  cerebellum  is  an  organ  for  maintaining 
the  equilibrium  of  the  body  in  the  erect  posture  and  in  walking.  I 
This  hypothesis  was  further  developed  in  the  work  of  Terrier  (1876), 
Bechterew  (1884-96),  Thomas  (1897),  Stefani  (1887-1903),  and 
others,  who  promulgated  various  conceptions  of  the  intervention 
of  the  cerebellum,  in  the  equilibration  and  orientation  of  the  body 
in  space. 

Investigation  of  this  last  theory  is  especially  important,  because 
it  leads  to  the  discussion  of  the  physiological  relations  between 
the  cerebellum  and  the  labyrinth,  the  peripheral  sense-organ 
served  by  the  vestibular  nerve,  which  we  have  seen  to  be  connected 
with  the  cerebellum  by  means  of  the  nucleus  of  Deiters. 

This  is  not  the  place  to  discuss  the  complex  physiological 
doctrine  of  the  end-organs  of  the  vestibular  nerve,  or  labyrinth, 
which  must  be  dealt  with  along  with  the  other  sense-organs.  It 
has  been  experimentally  demonstrated  that  the  nerve-endings  of 
the  semicircular  canals  and  saccules  of  the  vestibulum  constitute 
an  extremely  delicate  organ  of  sense,  necessary  to  the  preservation 
of  equilibrium  and  the  orientation  of  the  body  in  space.  Here  we 
need  only  insist  on  the  fact  which  is  of  predominant  importance 
for  the  physiology  of  the  cerebellum,  that  the  proximal  and 
remote  phenomena  consequent  on  unilateral  and  bilateral  destruc- 
tion of  the  labyrinth  resemble  in  no  slight  degree  those  which 
appear  after  the  unilateral  or  bilateral  ablation  of  the  cerebellum. 

Flourens,  who  was  the  first  to  propound  a  •  theory  of  the 
function  of  the  labyrinth  (1824-30),  recognised  the  analogy  between 
the  motor  disorders  consequent  on  lesions  of  the  semicircular 
canals  and  those  which  follow  cerebellar  ablations.  The  further 
investigations  of  Goltz  (1869-79)  confirmed  and  extended  the 
likeness  between  the  effects  of  the  two  operations.  Lastly,  Ewald 
(1887,  1889-92),  who  investigated  the  more  remote  residual 
phenomena  due  to  uni-  and  bi-lateral  ablation  of  the  labyrinth, 


462  PHYSIOLOGY  CHAP. 

brought  out  clearly  the  almost  complete  identity  of  these  with  the 
fundamental  phenomena  of  cerebellar  deficiency. 

We  must  confine  ourselves  to  stating  that  the  main  symptoms 
due  to  defect  of  the  labyrinth  are  —  according  to  the  minute 
observations  of  Ewald  —  abnormal  relaxation  of  the  affected 
muscles,  diminished  energy  during  activity,  and  diminished  pre- 
cision of  the  movements  in  which  they  are  concerned.  All  the 
special  symptoms  which  animals  without  a  labyrinth  present  in 
comparison  with  normal  animals  can  easily  be  interpreted  as  the 
effects  of  atonia  during  repose,  and  of  asthenia  and  astasia  during 
muscular  activity. 

The  symptoms  of  the  early  post -operative  period  are  also 
phenomena  of  deficiency,  as  recognised  by  Flourens,  and  are 
accordingly  of  the  same  character  as  the  residuary  symptoms  of 
the  later  period.  This  appears  from  Ewald's  work,  and  still  more 
obviously  from  the  researches  of  Gaglio  (1889)  on  the  effect  of 
cocainisation  of  the  membranous  labyrinth.  When  cocaine  is 
applied  to  the  divided  semicircular  canals  all  the  motor  disturb- 
ances consequent  on  the  lesions  persist,  while  if  the  canals  are 
intact  it  produces  for  a  period  of  thirty  to  sixty  minutes  the  same 
effects  as  result  from  cutting  or  destroying  them. 

The  difference  in  the  motor  disturbances  in  animals  a  short 
time  and  a  longer  period  after  loss  of  the  labyrinth  is  only 
quantitative,  and  is  due  to  the  intervention  of  compensating 
phenomena.  Ewald  showed  that  after  almost  total  disappearance 
the  motor  disorders  consequent  on  destruction  of  the  labyrinth 
reappeared  after  removing  the  motor  zone  of  one  cerebral  hemi- 
sphere, and  return  in  their  original  intensity  and  persist  after 
removing  both  motor  regions,  so  that  the  parallel  is  almost 
complete  between  our  studies  on  the  cerebellum  and  those  of 
Ewald  on  the  labyrinth. 

The  fact  that  the  motor  disorders  produced  by  destruction  of 
the  labyrinth  are  phenomena  of  deficiency  led  Ewald  to  conclude 
that  these  peripheral  sense-organs  normally  send  a  continuous 
excitation  to  the  nerve-centres,  which  reaches  the  muscles  reflexly, 
keeps  up  their  tone,  and  thus  makes  their  normal  function 
possible. 

What  are  the  centres  through  which  the  labyrinth  reflexly  keeps 
up  muscular  tone  ?  Owing  to  the  great  resemblance  between  the 
phenomena  of  labyrinthine  and  cerebellar  deficiency,  it  seems 
legitimate  to  conclude  that  the  labyrinth  exerts  its  tonic  action 
on  muscle  through  the  cerebellum.  Ewald,  however,  is  not 
in  favour  of  this  conclusion,  on  the  strength  more  particularly  of 
the  experiments  of  his  pupil  Lange,  who  demonstrated  that  in 
pigeons  which  had  been  deprived  of  their  cerebellum  some  time 
previously  lesions  of  the  labyrinth  induced  the  same  character- 
istic phenomena  as  were  observed  when  the  cerebellum  was  intact, 


viii  THE  HIND-BEAIN  463 

and  that  in  pigeons  which  had  some  time  previously  lost  their 
labyrinth  the  removal  of  the  cerebellum  was  followed  by  incapa- 
bility of  standing,  and  all  other  disorders  noted  when  this 
operation  is  performed  on  the  normal  pigeon.  But  in  a  later 
critical  study  (1903)  Stefani  rightly  points  out  that  if  the 
phenomena  of  labyrinthine  deficiency  can  be  evoked  on  de- 
cerebellated  animals,  this  only  shows  that  this  sensory  organ 
influences  not  merely  the  cerebellum,  but  other  centres  also ; 
and  if  the  phenomena  of  cerebellar  deficiency  appear  in  animals 
that  have  no  labyrinth,  this  means  that  cerebellar  activity  is 
maintained  not  merely  by  the  impulses  coining  from  the  labyrinth, 
but  also  by  those  other  multiple  afferent  paths  which  anatomy 
has  shown  to  be  directly  or  indirectly  in  relation  with  the 
cerebellum. 

In  order  to  bring  out  the  special  physiological  importance  of 
the  vestibular  nerve,  in  so  far  as  it  is  related  to  the  cerebellum 
and  concerned  in  its  functions,  Stefani  refers  to  his  earlier  ex- 
periments with  Weiss  (1877),  which  showed  degenerative  alteration 
of  Purkinje's  cells  in  the  cerebellum  of  pigeons  after  destruction  of 
the  semicircular  canals.  Since  this  result  was  not  confirmed  by 
other  observers,  Stefani  (1899)  induced  his  pupil  Deganello  to 
repeat  these  experiments  with  the  methods  of  Marchi  and  Nissl. 
These  new  researches  not  only  confirmed  the  preceding  results, 
but  brought  out  other  degenerative  changes  in  the  bulb,  which 
are  highly  interesting  for  both  anatomy  and  physiology. 

Since  Purkinje's  cells  are  the  principal  element  of  the  cerebellar 
cortex,  a  localised  degeneration  round  these  in  all  the  lamellae, 
on  one  or  both  sides,  as  occurs  after  unilateral  lesions  >  of  the 
labyrinth  (according  to  Stefani  and  Deganello),  can  only  mean 
that  the  activity  of  the  cerebellum  is  due  mainly,  if  not  exclusively,  1 
to  the  impulses  transmitted  from  the  labyrinth. 

While  fully  agreeing  with  Stefani's  facts,  we  are  unable  to 
subscribe  to  the  theory  which  regards  the  cerebellum  as  the  organ 
for  equilibration  and  orientation  of  the  body  in  relation  to  its 
environment.  Neither  the  cerebellum  nor  the  labyrinth,  in  so  far 
as  it  is  in  relation  with  the  cerebellum  and  influences  its  activity, 
has  this  special  function,  though  undoubtedly  both  combine  with 
other  centres  to  preserve  equilibrium  and  orientate  the  body 
in  space.  Ewald,  who  is  the  most  competent  authority  on  the 
physiology  of  the  labyrinth,  expressly  admits  that  the  continuous 
reflex  action  of  the  labyrinth  on  muscular  energy  and  tone  is 
the  main  function  of  this  organ,  and  that  in  virtue  of  this  rein- 
forcing action  (which  may  oscillate  more  or  less  according  to  the 
displacement  of  the  centre  of  gravity  of  the  body)  the  labyrinth 
participates  in  the  complex  functions  of  orientation  and  equilibrium. 

Goltz  (1870)  held  the  labyrinth  to  be  the  organ  for  perception 
of  the  position  of  the  head,  and  fundamentally  important  to 


464  PHYSIOLOGY  CHAP. 

equilibrium,  and  he  considered  the  motor  disturbances  which 
follow  lesions  of  the  semicircular  canals  to  be  the  effect  of  defective 
or  fallacious  sensations  of  the  position  of  the  head,  due  to  sup- 
pression or  alteration  of  the  normal  displacements  and  oscillations 
of  the  pressure  of  the  endolymph  in  the  semicircular  canals,  by 
which  the  ampullar  nerve-endings  are  excited.  It  was,  however, 
demonstrated  by  Cyou  (1897)  and  confirmed  by  Gaglio  that  under 
certain  experimental  conditions  the  endolymph  may  be  entirely 
drained  away  without  producing-  any  disturbance  of  equilibrium. 

At  the  same  time  Cyon's  hypothesis  that  the  semicircular 
canals  are  the  peripheral  organ  of  space -perception  is  unproved, 
as  will  be  shown  in  Chapter  II.  of  the  next  volume.  As  Gaglio 
aptly  observes,  "  We  explore  space  with  all  our  senses,  and  it  is 
the  sum  of  the  impressions  which  they  make  on  our  nerve-centres 
that  arouses  in  us  the  consciousness  of  relation,  of  the  position  of 
equilibrium,  and  of  the  movements  of  our  body  in  respect  to  the 
environment." 

The  principal  function  of  the  labyrinth  is — in  Ewald's  ex- 
pression, already  used  by  Hogyes — its  tone,  by  which  muscular 
tone  is  reflexly  controlled  ;  and  no  other  hypothesis  is  needed  to 
explain  the  motor  disorders  consequent  on  section  or  destruction 
of  the  semicircular  canals.  The  disturbance  •  of  the  muscular 
functions  is  so  prominent  that  Ewald  and  many  others  before  and 
after  him  have  called  attention  to  it,  and,  as  Gaglio  remarks,  it 
is  this  which  has  led  the  observer  so  far  from  the  truth. 

If  we  examine  the  theories  of  the  physiology  of  the  cerebellum 
we  find  the  same  fallacy.  Abstract  ideas  of  equilibration,  orienta- 
tion, co-ordination,  for  a  long  while  prevented  attention  from 
being  directed  to  the  essential  phenomena. 

In  1886  Ferrier,  starting  from  the  fact  that  the  activity  of 
the  cerebellum  persists  intact  after  removal  of  the  cerebral  hemi- 
spheres, declared  that  organ  to  be  independent  of  consciousness 
and  will,  although  he  held  it  to  be  normally  associated  with  the 
activity  of  the  fore-brain,  since  disturbances  of  equilibrium  in  a 
given  direction  will  under  normal  conditions  provoke  conscious 
or  voluntary  efforts  of  a  compensatory  character  in  the  opposite 
direction.  The  same  adjustments  effected  by  the  cerebellum  may 
therefore  be  carried  out  by  the  fore -brain  independently  of  it. 
The  effects  of  cerehellar  lesions  were  designated  by  Ferrier  paralysis 
of  reflex  adjustments,  and  are  to  be  carefully  distinguished  from 
paralysis  of  spinal  and  cerebral  reflexes,  which  never  results  from 
uncomplicated  cerebellar  lesions ;  so  that  in  1886  Ferrier  looked 
on  the  cerebellum  merely  as  a  centre  in  which  a  very  complex 
mechanism  for  unconsciousequilibrationwa,sdevelopQd  during  phylo- 
genetic  evolution.  But  as  the  cerebrospinal  axis  already  in  itself 
contains  mechanisms  which  are  capable  of  reacting  to  each  displace- 
ment of  the  equilibrium  of  the  body  by  appropriate  instinctive 


vin  THE  HIND-BEAIN  465 

or  voluntary  reflexes  of  a  compensatory  character,  capable  of 
replacing  the  body  in  the  normal  position  of  equilibrium,  it  is 
obvious  that  equilibration  of  the  hody  in  space  is  not  a  specific 
function,  attributable  to  this  or  that  part  of  the  system,  but  a 
complex  /unction,  dependent  on  the  intimate  organisation  and 
functional  harmony  of  the  system  as  a  whole. 

The  i  IK  K  if  that  cerebellar  ataxy  is  not  due  to  defective  equi- 
libration in  space,  but  to  the  asthenic,  atonic,  and  astatic  neuro- 
muscular  state,  is  the  fact  that  then1  is  a  period  or  stage  of 
cerebellar  ataxy  during  which  the  animal  is  incapable  of  walking 
or  falls  at  every  step,  although  it  is  still  quite  capable  of  floating 
and  swimming  perfectly  in  the  water — where  equilibration  is 
much  more  difficult -- without  losing  its  equilibrium,  and  of 
regaining  it  promptly  if  it  is  lost,  and  further  of  readily  altering 
its  direction  by  appropriate  compensatory  acts  in  order  to  get 
near  the  edge  of  the  basin  and  climb  out  (Luciani). 

In  order  to  discredit  this  observation,  it  was  suggested  that 
"  the  movements  required  in  swimming  in  water  are  not 
necessarily  so  exact  as  those  of  walking  "  (Murri).  Obviously  the 
everyday  fact  has  been  overlooked  that  every  normal  person 
knows  how  to  walk,  while  many  have  never  learned  to  swim  and 
cannot  keep  themselves  afloat  in  water  without  drowning. 

The  publication  of  our  Monograph,  The  Cerebellum  (1891),  had 
an  undoubted  influence  011  Ferrier.  In  reviewing  our  work 
(Neurological  Society  of  London,  1894)  he  no  longer  spoke  of  the 
cerebellum  as  an  organ  of  equilibration,  nor  as  a  collection  of 
unconscious  centres  of  reflex  action  destined  to  come  into  play  to 
restore  the  equilibrium  of  the  body  as  soon  as  it  is  menaced  in 
any  given  direction.  He  admitted,  on  the  contrary,  that  the  cere- 
bellum exercises  a  constant  influence  (directly  or  through  the 
other  cerebrospinal  centres)  upon  the  motor  systems  of  the 
animal  machine,  adding  that  "  even,  however,  if  we  assume  that 
this  is  the  true  formula  for  the  influence  of  the  cerebellum  it  still 
remains  to  be  determined  how  its  activity  is  called  into  play  and 
brought  to  bear  on  the  muscles,  either  in  association  with  the 
cerebrum  or  independently."1 

In  his  earlier  work  Stefani  applied  Goltz'  theory  of  the  semi- 
circular canals  to  the  cerebellum,  and  maintained  that  "  the  cere- 
bellum may  be  regarded  as  an  organ  which  utilises  the  impulses 
sent  out  from  the  semicircular  canals  to  acquaint  the  animal 
with  the  position  of  its  head  in  relation  to  the  environment." 
The  decerebellated  animal  is  not  able  to  keep  its  head  in  the 
normal  position  because  it  has  lost  consciousness  of  its  position. 
When  it  wants  to  carry  out  some  movement  its  head  oscillates  in 
all  directions  and  the  centre  of  gravity  is  displaced  to  one  or 
the  other  side,  while  the  animal  reacts  to  these  displacements  by 

1  Ferrier,  Brain,  1894,  vol.  xvii.  p.  37. 
VOL.  Ill  2  H 


466  PHYSIOLOGY  CHAP. 

appropriate  compensation  movements  directed  to  the  maintenance 
of  its  equilibrium  which  cause  the  irregularity  of  its  gait. 

In  a  later  publication  (1903)  Stefani  came  back  on  his  old 
theory,  and  recognised  that  it  was  inadequate,  and  that  "  in  the 
actual  state  of  our  knowledge  the  best  hope  of  completing  it  lies 
in  blending  it  with  the,  theory  of  Luciani,  who  regards  the 
cerebellum  as  the  centre  of  muscular  tone.  Luciani  has  demon- 
strated the  existence  of  a  cerebellar  tone,  Ewald  the  existence  of  a 
labyrinthine  tone.  To  complete  the  two  theories  and  fuse  them 
into  one  we  need  only  assume  that  the  cerebellar  tone,  as  demon- 
strated by  Luciani,  arises  in  the  labyrinth,  and  is  therefore  adapted 
to  the  requirements  of  equilibration  and  orientation,  as  already 
suggested  by  Dreyfuss  in  Germany  and  Gaglio  in  Italy." 

It  is  not,  however,  a  matter  of  indifference  whether  the  cere- 
bellum is  termed  the  organ  of  equilibrium,  or  of  orientation,  or  of 
tone.  The  tonic  reflex  activity  controlled  by  the  cerebellum  is 
not  merely  exerted  on  the  muscles  that  function  during  posture 
,  and  locomotion,  but  it  extends  more  or  less  to  all  the  skeletal 
muscles  whatever  their  function.  In  moving  the  eyes,  in  speaking 
or  singing,  in  writing,  playing  the  piano,  sitting  down,  in  all  these 
actions  there  must  certainly  be  intervention  of  the  tonic  influence 
of  the  cerebellum,  although  the  resulting  movements  are  quite 
different  in  character  from  those  of  equilibration.  Again,  when 
standing  and  walking  the  cerebellum  intervenes  less  as  the  organ 
for  preserving  equilibrium  than  as  the  organ  which  regulates  the 
tone  and  contraction  of  the  muscles  to  the  right  extent  and  in  the 
proper  combination.  Stefani  is  unfortunate  in  citing  Gaglio  in 
support  of  his  hypothesis ;  for  the  latter  expressly  denies  Goltz' 
theory  that  the  head  possesses  a  special  sense  of  equilibrium  in 
the  labyrinth,  "  since  the  general  conditions  of  sensibility  which 
control  the  sense  of  equilibrium  in  other  parts  of  the  body  must 
suffice." 

VIII.  In  The  Cerebellum  (1891)  we  made  a  comparison  between 
the  primitive  rudimentary  theory  of  Eolando  and  that  of  Flourens, 
and  expressed  the  following  opinion,  which  we  still  hold  to  be 
legitimate  :  "  Eolando  looked  upon  the  disturbance  of  co-ordination 
as  the  effect  of  partial  destruction  of  the  cerebellum,  owing  to 
which  there  was  unequal  and  irregular  transmission  of  the  normal 
influence  of  the  cerebellum  to  the  different  parts,  and  he  erroneously 
characterised  the  asthenia  as  paralysis.  Flourens  fortunately 
avoided  this  error ;  he  expressly  defines  as  weakness  what  Rolando 
termed  paralysis,  but  erred  in  regarding  not  this  weakness  but 
the  inco-ordination  of  movements  as  the  main  symptom  of  the 
loss  of  the  specific  function  of  the  cerebellum.  In  an  animal 
deprived  of  its  cerebellum,  he  says,  '  tons  les  mouvements  partiels 
subsistent  encore ;  la  co-ordination  seule  de  ces  mouvements  est 
perdue.' 


vni  THE  HIND-BRAIN  4G7 

"Rolando's  error  was  easily  corrected  by  more  careful  observa- 
tions ;  that  of  Flourens  opens  a  false  track  to  subsequent  workers, 
and  has  become  a  serious  obstacle  to  advance  in  the  physiology  of 
the  cerebellum.  Rolando's  view  led  him  logically  to  the  other  error 
of  considering  the  cerebellum  as  an  organ  subservient  to  sensation 
(through  the  agency  of  the  medulla  oblongata)  or  to  the  will  (through 
the  agency  of  the  cerebral  hemispheres) ;  the  mistake  of  Flourens 
led  him  to  create  an  abstract  and  fictitious  entity,  the  principle  of 
co-ordination  or  regulation  of  complex  movements  or  postures,  as 
represented  by  the  various  forms  of  locomotion  or  position — a 
principle  localised  in  the.  cerebellum,  and  independent  of  the 
cerebrum,  as  the  function  of  the  latter  remains  intact  after  removal 
of  the  cerebral  hemispheres. 

:'  However  fallacious  and  poorly  founded,  Eolando's  theory 
in  itself  is  clear,  definite,  and  complete  in  fundamentals,  while 
that  of  Flourens  is  obscure,  imperfect,  and  unintelligible,  since  it 
is  impossible  to  picture  in  what  the  supposed  co-ordinating  or 
regulating  functions  of  the  cerebellum  can  influence  locoinotor 
movements,  which  are  willed  by  the  cerebrum  and  carried  out  by 
the  medullary  axis ;  nor  how  this  regulation  can  take  place  when 
once  the  functional  independence  of  the  cerebrum  and  cerebellum 
has  been  admitted." 

Lussana,  who  considered  the  cerebellum  as  the  centre  of 
muscular  sense,  offered  an  explanation  of  the  phenomena  of  cere- 
bellar  deficiency  described  by  Flourens  that  was  ingenious  in  its 
simplicity. 

'  For  a  long  time  "  (he  wrote  in  1862)  "  the  importance  of  this 
(muscular)  sense,  through  which  the  muscles  effectively  carry 
out  their  voluntary  movements,  has  been  recognised.  It  will 
suffice  to  quote  two  physiologists  of  undoubted  authority,  Bell  and 
Panizza.  The  former  recognises  that  by  sensory  impressions  we 
can  appreciate  the  degree  of  contraction  of  our  muscles,  and 
are  able  by  this  means  to  regulate  their  activity  in  proportion 
to  the  resistance  which  we  have  to  overcome.  In  1834  Panizza, 
who  described  ataxia  after  section  of  the  dorsal  spinal  roots, 
wrote :  The  influence  of  the  will  on  the  muscles  that  are  partially 
deprived  of  sensibility  is  feeble  and  uncertain,  because  they  no 
longer  feel  and  are  no  longer  felt." 

"  The  muscular  sense  "  (adds  Lussana)  "  is  par  excellence  the 
main  factor  in  co-ordinating  voluntary  movement ;  its  central 
organ  is  the  cerebellum.  Far  more  important  and  indispensable 
than  the  cutaneous  sense,  the  muscular  sense  serves  in  animals  to 
make  known  the  resistance  met  with,  and  in  voluntary  movements 
to  regulate  the  forces  of  contraction  by  which  the  muscle  is  able 
to  overcome  it.  ... 

•  Without  the  cerebellum  the  animal  no  longer  feels  the  solidity 
of  the  earth  on  which  it  rests  in  standing  and  walking,  nor  the 


468  PHYSIOLOGY  CHAP. 

resistance  of  the  medium  in  which  it  flies  or  swims ;  it  does  not 
recognise  the  impenetrability  of  the  objects  which  obstruct  its 
course  ;  it  does  not  feel  the  weight  of  the  body  it  has  to  carry  ;  this 
is  the  physiological  explanation  of  the  disturbance  of  voluntary 
movement  described  by  Flourens.  '  Le  cervelet,'  says  this  author, 
'  est  le  siege  exclusif  du  principe  qui  co-ordonne  les  mouvements 
de  locomotion.'  The  true  function  of  the  cerebellum,  in  short,  is 
the  muscular  sense." 

Undoubtedly  Lussana's  theory  is  an  ingenious  completion 
and  development  of  that  of  Flourens,  save  for  his  assumption 
that  the  cerebellum  is  not  the  seat  of  any  sensation.  His  hypo- 
thesis is  so  lucid  that  it  might  find  general  acceptance  were 
not  one  thing — direct  experimental  evidence  for  it — lacking. 
As  a  matter  of  fact,  the  occurrence  of  the  staggering  and  reeling- 
gait,  and  other  locomotor  disorder  in  decerebellated  animals  or 
in  diseases  of  the  cerebellum  is  not  enough  to  establish  loss  or 
disturbance  of  muscular  sense,  because  the  normal  regularity  of 
the  movements  does  not  depend  exclusively  upon  the  muscle  sense. 

In  1903  a  pupil  of  Munk — Lewaudowsky — again  assumed 
the  cerebellum  to  be  the  centre  for  muscular  sense,  and  claimed 
that  the  phenomena  of  cerebellar  ataxy  consist  in  disorders  of 
co-ordination. 

As  we  have  already  given  definite  proof  that  both  in  animals 
after  removal  of  the  cerebellum  and  in  disease  of  this  organ  in 
man  the  muscular  sense  is  not  in  any  way  altered,  it  is 
unnecessary  to  discuss  this  hypothesis  again.  But  the  position 
taken  up  by  Lewandowsky  may  detain  us  for  a  moment. 

He  agrees  that  the  generic  term  ataxy  does  not  express  a 
unitary  concept,  but  is  simply  a  complex  represented  by  certain 
disorders  of  movements,  or  motor  paralysis.  "  If,"  he  adds,  "  a 
definite  concept  were  attached  to  the  term  ataxy,  there  would 
be  no  ground  for  dispute  as  to  what  is  meant  by  cerebellar  ataxy." 
Again,  when  we  say  that  the  animal  or  man  whose  cerebellum 
is  affected  has  an  uncertain,  reeling,  swaying  gait,  similar  to  that 
of  a  drunkard,  we  express,  not  a  single  phenomenon,  but  a 
complex,  which  may  be  split  into  a  number  of  components. 

What  are  the  simple  components  of  cerebellar  ataxy  for 
Lewandowsky  ?  He  verih'es  the  occurrence  of  astasia,  atonia, 
and  neuro- muscular  asthenia,  which  we  have  described  and 
demonstrated  in  various  ways.  He  recognises  the  atonia  by  the 
fact  that  the  limbs  of  decerebellated  animals  can  be  flexed  or 
extended  not  only  more  readily  than,  but  also  beyond  the  range 
of,  the  normal.  He  also  describes  asthenia,  but  does  not  admit 
that  it  is  due  to  defect  of  the  stkenic  action  of  the  cerebellum. 
He  assumes  that  the  complex  movements  only  appear  less 
energetic  because  the  synergic  and  co-ordinated  actions  of  all 
the  muscles  that  come  into  play  in  the  various  voluntary  move- 


VIII 


THE  HIND-BEAIN  469 

are  lacking  in  decerebellated  animals ;  in  a  word,  asthenia 
is  for  him  a  result  of  disturbance  of  the  co-ordination  of  the 
movements. 

As  evidence  for  this  loss  of  co-ordination  Lewandowsky 
adduces  the  phenomenon  which  wre  described  minutely  under 
the  name  of  dysmetria,  as  expressed  in  the  so-called  hen's  gait. 
Lewandowsky  regards  this  symptom,  which  can  also  be  seen  after 
section  of  the  dorsal  spinal  roots  and  in  tales  dorsalis,  as  all- 
important.  Asthenia,  atonia,  ataxia,  fall  into  the  second  place ; 
they  are  not  fundamental  phenomena  of  cerebellar  ataxy,  but 
are  merely  secondary  to  dysmetria  and  to  the  imperfect  co- 
ordination of  the  voluntary  movements,  which  in  its  turn  is  due 
to  disturbance  of  the  muscular  sense  ! 

"Luciani,"  he  adds,  "has  not  been  able  to  clear  up  the 
symptoms  in  cerebellar  ataxy,  because  he  overlooks  one  effect  of 
cerebellar  lesions  which  we  should  place,  in  the  first  rank— 
i/ffi'i-ofions  of  the  muscular  sense.  While  Luciani,  after  thousands 
of  experiments,  has  never  ol (served  disturbances  of  the  muscle 
sense,  we,  on  the  contrary,  say  that  every  motor  trouble  due  to 
cerebellar  lesions  is  accompanied  by  it." 

This  view,  which  is  denied  by  most  authoritative  observers, 
compels  Lewandowsky  to  admit : 

(a)  That  the  cerebellum  is  not  the  only  central  organ  of 
muscular  sense,  as  the  cerebral  cortex  also  participates  : 

(&)  That  it  does  not  represent  an  intermediate  station  on  the 
paths  of  muscular  sensibility  running  to  the  brain,  but  that  there 
are  direct  paths  between  the  cerebrum  and  the  spinal  cord,  which 
are  unconnected  with  the  cerebellum; 

(c)  That  there  is  both  conscious  and  subconscious  regulation  of 
movement  by  the  muscular  sense;  that  the  cerebrum  attends  to 
conscious  regulation,  while  the  cerebellum  has  no  other  task 
than  that  of  controlling  and  directing  the  subconscious  move- 
ments ! 

But  these  conclusions  invalidate  all  his  previous  statements  : 
if  the  cerebellum  is  not  the  seat  of  conscious  sensations,  cerebellar 
ataxy  obviously  cannot  be  a  sensory  ataxy  like  that  which  is 
seen  after  section  of  the  roots  and  in  tabes,  nor  is  the  cerebellum 
a  centre,  for  the  muscle  sense.  If  the  spino-cerebral  sensory 
paths  are  unconnected  with  the  afferent  spino-cerebellar  paths,  it 
is  clear  that  decerebellated  animals  cannot  exhibit  disturbance  of 
the  muscle  sense,  since  the  spino-cerebral  paths  that  transmit 
the  impressions  of  the  state  of  the  muscles  to  the  cerebral 
centre  are  intact;  it  is  accordingly  absurd  to  assume  that  the 
dec.erebellated  animal  does  not  perceive  and  correct  abnormal 
positions  of  its  limbs,  if  it  be  once  admitted  that  the  cerebellum 
is  not  the  seat  of  conscious  sensations. 

It   must   be   admitted    that   dysmetria   of  movement  can   be 


470  PHYSIOLOGY  CHAP. 

variously  interpreted.  In  1883  Schiff  considered  it  to  lie  one 
of  the  essential  elements  which,  along  with  asthenia,  make  up 
the  syndrome  of  cerebellar  ataxy.  But  he  rejected  the  hypothesis 
that  dysmetria  depends  on  defective  co-ordination,  as  Lewaud- 
owsky  holds,  nor  did  he  regard  it  as  an  effect  of  the  loss  of  the 
inhibitory  action  of  the  cerebellum,  as  assumed  by  Budge  in 
1841  and  by  Wagner  in  1858 ;  he  attributed  it  to  irregularity  in 
the  reinforcing  action  transmitted  from  the  remaining  portion  of 
the  cerebellum  to  the  group  of  muscles  which  come  into  play  in 
the  different  complex  voluntary  actions.  Babinski,  who  accepted 
this,  called  it  cerebellar  a-syneryy. 

Schiff's  view  seems  acceptable  in  cases  of  incomplete  extirpa- 
tion or  pathological  states  of  the  cerebellum,  but  in  cases  of 
complete  extirpation  of  one  lateral  half,  or  of  the  whole  cere- 
bellum, his  interpretation  is  not  adequate.  It  must  further  be 
added  that  dysmetria  is  not  constant  in  all  cases  of  cerebellar 
lesion ;  even  in  clinical  cases  it  is  a  rare  symptom. 

As  already  stated,  it  is  probably  due  to  idonia  of  the  muscles 
of  the  limbs,  owing  to  which  there  is  a  too  rapid  relaxation  of 
the  extensors  when  the  flexors  contract,  and  a  too  rapid  relaxa- 
tion of  the  flexors  when  the  extensors  contract.  Lewandowsky 
did  not  admit  this  simple  explanation,  according  to  which 
dysmetria  is  a  natural  consequence  of  atonia. 

IX.  We  must  now  consider  the  function  of  the  afferent  im- 
pulses that  reach  the  cerebellum  from  the  numerous  afferent 
paths,  and  the  influence  of  those  it  transmits  to  its  efferent  paths. 
These  are  the  main  'problems  on  the  solution  of  which  the 
physiology  of  the  cerebellum  has  to  rest. 

One  of  the  most  striking  and  really  fundamental  facts  bearing 
on  these  problems,  which  finds  confirmation  both  in  physio- 
logical experiment  and  in  clinical  observations,  is  that  profound 
alterations  and  absolute  loss  of  the  cerebellum  do  not  paralyse 
either  sensation  or  volitional  movement,  although  it  has  been 
clearly  demonstrated  that  this  organ  is  related  by  its  afferent 
paths  to  the  peripheral  sense-organs  (especially  the  cutaneous, 
muscular,  and  labyrin thine  senses),  and  by  its  efferent  paths  to  the 
peripheral  apparatus  for  voluntary  movements.  While  lesions  of 
other  cerebrospinal  centres  result  in  true  paralysis — complete  or 
incomplete — of  sensation  and  motion,  cerebellar  deficiency  is  shown 
in  simple  neuro-muscular  atonia,  asthenia,  astasia. 

In  order  to  explain  these  differences,  we  are  naturally  led  to 
make  certain  conjectures,  which  are  in  no  way  at  variance  with 
anatomical  facts,  and  which  harmonise  well  with  physiological 
research  as  a  whole  :— 

(a)  That  the  cerebellum  with  its  appendages  constitutes  a 
small  and  comparatively  independent  system  in  itself,  so  that  its 
removal  interrupts  no  important  conducting  paths,  centripetal  or 


vin  THE  HIND-BRAIN  471 

centrifugal,  between  the  brain  and  the  peripheral  organs  of  sensa- 
tion and  motion ; 

(b)  That  it  has  no  field  of  action  of  its  own,  i.e.  belonging  to 
itself  exclusively,  which   is  not  equally  at  the  service  of   other 
centres  of  the  cerebrospinal  system ; 

(c)  That  it  is  not  a  sensory  centre  properly  so  called,  as  the 
sensory  impressions  which  reach  it  by  special  afferent  paths  arouse 
no  conscious  sensations,  but  normally  remain  subliminal,  below 
the  threshold  of  consciousness  ; 

(d)  That  under  the  special  conditions  in  which  its  activity  is 
concerned,  it  may  be  regarded  as  a  small  coadjutant  system  to 
reinforce  the  great  cerebrospinal  system. 

In  agreement  with  the  recent  morphological  and  phylogenetic 
investigations  of  Bolk,  there  is  ample  physiological  demonstration 
that  the  cerebellum  is  a  single  unpaired  organ,  each  portion  of 
which  has  the  same  function  as  the  whole.  In  fact  the  loss  of 
the  vermis  may  be  repaired,  i.e.  organically  compensated,  by  the 
lateral  lobes,  and  after  various  cerebellar  lesions,  symmetrical 
or  asymmetrical,  circumscribed  or  diffuse,  the  phenomena  of 
deficiency  differ  not  in  their  nature  and  character,  but  solely  in 
intensity,  extent,  and  duration,  and  by  their  more  or  less  marked 
influence  on  the  muscles  of  one  or  other  side  of  the  body.  Our 
own  investigations  proved  clearly  and  decisively  that  unilateral 
mutilations  have  a  predominantly  homolateral  effect,  i.e.  much 
more  marked  on  the  muscles  of  the  same  side,  and  not  only  on  the 
muscles  that  subserve  posture  and  locomotion,  but  on  all  the 
voluntary  muscles  and  in  particular  on  the  muscles  of  the  lower 
or  posterior  limbs,  and  on  the  muscles  that  fix  the  vertebral 
column. 

If  the  principal  effects  of  cerebellar  deficiency  consist  in  atonia, 
asthenia,  and  astasia,  it  follows  logically  that  the  coadjutant  or 
reinforcing  influence  that  the  cerebellum  normally  exerts  upon  the 
rest  of  the  system  consists  in  a  tonic,  sthenic,  and  static  neuro- 
muscular  effect  by  which— 

(a)  The  degree  of  tension  at  which  the  neuro-muscular  organs 
remain  during  functional  pause  or  rest  is  increased  (tonic  action) ; 

(6)  The  energy  developed  during  the  various  voluntary,  auto- 
matic, and  reflex  actions  is  increased  (sthenic  action) ; 

(c)  The  rhythm  of  the  elementary  impulses  of  which  these  acts 
are  made  up  is  accelerated,  and  their  normal  fusion  and  regular 
continuity  is  maintained  (static  action). 

If  it  be  once  allowed  that  dysmetria  of  movement  is  a  constant 
phenomenon  of  cerebellar  deficiency ;  if,  as  Lewandowsky  has 
maintained,  dysmetria  is  one  of  its  essential  and  necessary  phenomena, 
and  not  a  simple  result  of  atonia  or  astasia,  then  we  must  add  a 
fourth  factor.  The  tonic,  sthenic,  static  effects  must  be  supple- 
mented by  an  adaptive  action,  on  which  the  range,  precision,  and 


472  PHYSIOLOGY  CHAP. 

adaptation  to  end  of  the  several  voluntary,  automatic,  and  reflex 
acts  must  depend. 

Can  the  cerebellum  exert  an  adjusting  effect  on  the  functions 
of  the  motor  organs  without  being  an  organ  of  conscious  sensation  ? 
We  need  not  hesitate  to  reply  to  this  question  in  the  affirmative, 
since  all  the  elements  of  the  nervous  system,  not  excluding  those 
of  the  sympathetic,  are  usually  credited  with  this  adaptive  capacity, 
which  may  in  a  wide  sense  lie  termed  the  regulating  or  co-ordinating 
faculty  ?  By  what  mechanism  is  this  exerted  ?  Unless  we  accept 
with  Flourens  an  abstract  co-ordinating  or  regulating  function  in 
the  cerebellum,  the  only  alternative  is  that  the  precision  and 
accurate  range  of  movement  result  from  the  precision  and  accurate 
adaptation  of  its  tonic,  sthenic,  and  static  influence. 

The  first  fact  that  strikes  every  one  who  investigates  the 
intrinsic  differences  in  the  three  main  physiological  functions  of 
the  cerebellum  is  that  they  are  so  much  akin,  so  intimately 
connected  in  their  origin,  that  it  is  practically  impossible  to 
consider  them  separately  and  apart.  Astasia,  in  which  the 
deficiency  of  static  action  is  expressed,  is  usually  held  to  be  a 
natural  effect  of  asthenia  (Tremitus  a  debilitate);  asthenia,  by 
which  the  loss  of  sthenic  effect  in  the  activity  of  the  muscles  is 
expressed,  appears  to  be  related  to  the  atonia  observed  during  their 
repose.  As,  however,  it  is  very  difficult  to  demonstrate  the  relative 
degree  of  the  three  phenomena  in  decerebellated  animals,  and  as 
it  is  not  only  atonia  or  asthenia  or  astasia  that  is  the  most 
pronounced  or  obvious  symptom  in  such  animals,  it  may  be 
assumed — as  we  said  in  1891 — that  there  are  only  three  different 
extrinsic  manifestations  of  a  single  process,  though  there  may  be 
no  constant  relation  between  their  relative  intensities. 

In  addition  to  the  tonic,  sthenic,  and  static  functions,  which 
may  collectively  be  referred  to  as  the  "action  of  reinforcement," 
the  cerebellum  normally  exercises  a  direct  or  indirect  trophic 
action  on  the  organs  with  which  it  is  in  relation.  Direct  trophic 
influence  is  demonstrated  by  the  degeneration  and  sclerosis  that 
follow  ablation  of  the  cerebellum,  as  shown  by  the  work  of  Luciani 
and  Marchi,  and  that  of  Mingazziiii,  Turner  and  Ferrier,  Thomas, 
Probst,  and  others.  Indirect  trophic  action  is  seen  specially  in  the 
muscular  changes  observed  in  cerebellar  ataxy,  the  retarded  growth 
of  the  cutaneous  elements,  particularly  in  the  skin,  and  the  lowered 
resistance  of  decerebellated  animals  to  the  injurious  action  of 
external  agents,  so  that  they  succumb  to  disease  more  readily 
than  the  intact  animal,  and  have  a  shorter  life  in  comparison. 

The  trophic  and  functional  influences  obviously  represent  the 
two  sides — internal  and  external — of  one  and  the  same  physio- 
logical process,  the  intimate  nature  of  which  is  unknown  to  us, 
and  of  which  we  perceive  only  the  most  striking  and  obvious 
effects. 


vin  THE  HIND-BE AIN  473 

Both  tlu1  trophic  and  the  tonic  influences  are  continuously 
excited  by  the  duvet  and  indirect  paths  that  carry  impulses  to 
the  cerebellum  from  the  cutaneous,  muscular,  and  labyrinthine 
sense-organs.  Of  these  afferent  paths  that  serve,  the  activity  of 
the  cerebellum,  particular  importance  attaches  to  the  vestibular 
nerve,  which  transmits  tonic  impulses  from  the  labyrinth  by  way 
of  the  nucleus  of  Deiters,  as  demonstrated  by  Ewald,  Gaglio, 
Stefani,  and  Deganello.  It  must  be  abmitted  that  the  demonstra- 
tion of  the  special  influence  which  the  labyrinth  exerts  on  the  , 
functions  of  the  cerebellum  is  the  only  new  fact  of  real  importance  \ 
that  has  been  added  to  the  physiology  of  this  organ. 

X.  In  conclusion  we  must  recapitulate  the  new  morphological 
theory  of  the  cerebellum,  which  Bolk  has  constructed  on  the  basis 
of  an  interesting  phylogenetic  and  ontogenetic  comparison  between 
the  brains  of  different  mammals  and  man. 

From  the  phylogenetic  point  of  view,  the  cerebellum  of  all 
mammals  consists  of  two  lobes,  one  anterior,  the  other  posterior, 
divided  by  a  primary  sulcus.  The  anterior  lobe  always  forms  a 
single  unpaired  median  organ;  the  posterior  lobe  is  subdivided 
into  four  lobules,  two  median  and  two  lateral,  which  are  separated 
by  secondary  sulci. 

From  the  ontogenetic  point  of  view,  Bolk  distinguishes  four 
centres  of  development,  two  median  and  two  lateral,  characterised 
by  varying  rapidity  of  growth,  during  which  the  lobular  arrange- 
ment of  the  adult  cerebellum  is  determined  by  means  of  numerous, 
mainly  transverse  sulci. 

On  studying  the  developmental  variations  of  the  single  lobes 
or  lobules  of  the  cerebellum  in  different  mammals,  Bolk  noted  a 
more  or  less  definite  relation  between  them  and  the  degree  of 
functional  development  of  special  groups  of  muscles  ;  this  led  him 
to  attribute  the  functional  control  of  special  muscular  complexes 
to  certain  lobules. 

We  must  confine  ourselves  to  the  main  features  of  the 
functional  localisations  in  different  lobules  of  the  cerebellum, 
based  on  the  ingenious  deductions  made  by  Bolk  from  his  morpho- 
logical studies. 

He  starts  from  the  fact  that  in  certain  movements  the 
muscles  on  both  sides  come  into  action,  and  in  other  parts  of 
the  body  the  muscles  of  one  side  are  capable  of  the  most  complex 
movements,  while  those  of  the  other  side  may  remain  altogether 
inactive. 

The  head  and  neck  are  certainly  included  among  the  former. 
In  the  head  are  the  external  muscles  of  the  eyes,  the  masticator 
muscles,  the  mimic  facial  muscles,  the  lingual,  pharyngeal,  and 
laryngeal  muscles,  which  nearly  always  function  bilaterally.  In 
the  neck,  again,  the  muscles  that  effect  the  various  movements  of 
the  head  enter  into  bilateral  activity.  The  muscles  of  both  the 


474  PHYSIOLOGY 


CHAP. 


head  and  neck  must,  according  to  Bolk,  be  influenced  by  the  two 
separate  median  segments  of  the  cerebellum. 

In  the  upper  and  lower  limbs  the  case  is  different.  We  know 
that  each  limb  is  able  in  man  to  execute  a  great  variety  of  more 
or  less  complex  movements,  independently  of  the  limb  on  the 
opposite  side.  But  this  independence  is  not  always  complete  and 
absolute.  Learners  of  the  piano  and  violin  have  by  practice  to 
overcome  great  difficulties  in  order  to  render  the  muscles  of  the 
two  sides  independent,  and  to  avoid  the  simultaneous  contraction 
of  the  homologous  muscles  of  the  upper  limbs.  Bolk  infers  from 
this  that  in  order  to  regulate  the  movements  of  the  limbs  there 
must  be  three  distinct  centres  in  the  cerebellum :  one  unpaired 
for  synergic  bilateral  movements  ;  two  paired  for  the  dissociated 
movements  of  each  limb. 

Finally  the  trunk  muscles  specially  employed  in  the  respiratory 
movements,  and  in  equilibration  during  the  erect  posture  and  in 
locomotion,  must,  according  to  Bolk,  be  represented  in  the  cere- 
bellum by  one  unpaired  median,  and  two  lateral  centres. 

Which  cerebellar  lobes  represent  these  hypothetical  centres 
that  can  be  distinguished,  according  to  Bolk,  in  the  cerebellar 
cortex  ?  He  begins  by  pointing  out  that  the  lobes  and  lobules  of 
the  cerebellum,  as  above  indicated,  are  really  arranged  one  above 
the  other,  like  the  corresponding  muscular  areas  of  the  body.  On 
the  basis  of  this  correspondence  we  may  assume  that  :— 

(a)  The  lobulus  anterior  contains  the  centres  for  the  muscles 
of  the  eye,  jaw,  face,  tongue,  pharynx,  larynx,  that  is,  all  the 
muscles  of  the  head  region  ; 

(b)  The  lobulus  simplex  contains  the  centre   for   the   muscles 
of  the  neck  ; 

(c)  The  upper  part  of  the  lobulus  medianus  posterior  represents 
the   median   centre   for   the   associated   movements    of  the   two 
extremities  ; 

(d)  Each  of  the  lobuli  ansiformes  or  paramediani  contains  the 
lateral  centres  for  the  dissociated  movements  of  the  two  limbs, 
the  crus  prirnum  being  more  exactly  the  centre  for  the  fore  or 
upper  limbs,  the  crus  secundum  and  lobulus  paramedianus  that  for 
the  hind  or  lower  Limbs  ; 

(e)  The  lower  part  of  the  lobulus  medianus  posterior  includes 
the  centres  for  the  respiratory  and   perineal  musculature ;   the 
formatio  vermicularis  the  centres  for  the  trunk  muscles ;  and  the 
lobulus  petrosus  the  centre  for  the  muscles  of  the  tail. 

This  arrangement  is  represented  in  Bolk's  diagram  of  the 
mammalian  cerebellum,  which  is  reproduced  in  Fig.  239. 

According  to  Bolk  this  hypothetical  functional  localisation  in 
the  cerebellum  is  confirmed  by  correlation  of  the  development  of 
the  lobes  and  lobules,  respectively,  in  different  mammals  with  the 
functional  development  of  the  corresponding  groups  of  muscles. 


VIII 


THE  HIND-BKAIN 


475 


For  an  exact  description  of  these,  the  student  must  refer  to  Bulk's 
original  monograph. 

We  shall  now  see  how  far  Bolk's  inductions — founded  on  com- 
parative anatomy — have  been  confirmed  by  physiological  experi- 
ment, either  by  the  method  of  electrical,  mechanical,  and  chemical 
stimulation  of  different  parts  of  the  brain,  or  by  the  removal  of 
single  segments. 

After  Hitzig  and  Fritsch  had  demonstrated  the  possibility  of 
localising  certain  motor  centres  in  the  cerebral  cortex  by  electrical 
stimulation  (Chap.  X.)  Ferrier  (1879)  made  use  of  this  method, 
not  merely  in  developing  the  theory  of  cerebral  localisation,  but 
also  in  attempting  to  extend  it  to  the  cerebellar  cortex.  The 


f'JoFfilfttS 

'  formatio    vermicularis 

FIG.  239.— Diagram  of  lobules  of  mammalian  cerebellum.  (After  Bolk,  simplified  by  van  Ryriberk.) 
Left  side  of  figure  gives  Bolk's  new  terms  for  the  lobules  ;  right  side,  the  probable  localisation, 
according  to  Bolk,  of  the  relation  in  different  mammals  between  lobular  development  and 
the  functional  development  of  different  groups  of  muscles. 

motor  effects  which  Ferrier  obtained  by  faradisation  of  various 
points  of  the  surface  of  the  cerebellum  in  the  ape  consisted  in 
associated  movements  of  the  eyeball  to  the  right  or  left,  upward 
or  downward,  according  as  the  stimulus  was  applied  to  the  right 
or  left  half,  or  to  the  anterior  or  posterior  part  of  the  median 
lobe  of  the  cerebellum.  Movements  of  the  head,  as  well  as  certain 
abrupt  movements  of  the  limbs  on  the  side  excited,  were  often 
associated  with  those  of  the  eyes. 

Ferrier's  results  were  not,  however,  confirmed  by  Mendelsohn 
with  induced  currents.  Ferrier  employed  such  strong  currents 
that  they  may  have  spread  to  adjacent  regions,  as  the  corpora 
quadrigemina,  pons,  bulb. 

Nothnagel  (1876)  performed  a  number  of  experiments  on 
rabbits  with  mechanical  stimulation,  by  running  a  needle  into 
different  points  of  the  cerebellar  cortex.  Among  the  effects  of 


476  PHYSIOLOGY  CHAP. 

this  stimulation  he  noted  rhythmical  movements  of  one  fore-limb, 
movements  of  mastication,  arching  of  back,  etc.  But  these  effects 
were  not  exactly  localised,  although  Nothnagel  affirmed  a  certain 
relation  between  the  points  at  which  the  needle  was  inserted  and 
the  reaction. 

Pruss  (1901)  attributed  much  importance  to  the  direction  of 
the  currents  (ascending,  descending,  transverse)  in  the  results 
obtained  by  electrical  stimulation  of  the  cerebellar  cortex.  The 
conclusions  he  arrived  at  in  regard  to  cerebellar  localisation 
would  be  highly  important  if  they  could  be  accepted.  But  he 
himself  states  that  the  currents  which  he  employed  to  provoke  the 
reactions  described  were  excessive. 

Negro  and  Eosaenda  (1907)  repeated  these  experiments  upon 
the  rabbit's  cerebellum  with  moderate  faradic  currents.  On 
stimulating  the  area  which  corresponded  approximately  to  the 
crus  p/'i in  tun  of  Bolk,  they  obtained  unilateral  contractions  of  the 
facial  muscles  and  anterior  limb,  which  were  sometimes  isolated, 
sometimes  associated.  Only  when  the  current  was  unduly  strong 
did  the  reactions  extend  to  the  muscles  of  the  two  sides.  With 
unipolar  stimulation  they  obtained  more  accurate  localisation  ol 
the  facial  and  fore -limb  muscles,  and  found  that  the  facial 
centre  lies  more  forward  than  the  centre  for  the  fore -limb. 
Both  lie  somewhat  internally,  but  their  exact  position  was  not 
determined. 

Horsley  and  Clarke  (1908),  in  a  series  of  researches  carried 
out  with  more  accurate  methods,  were  able  to  demonstrate 
that  the  stimulation  had  to  be  of  enormously  greater  strength  to 
obtain  motor  reactions  in  faradising  the  cerebellar  cortex  than 
was  required  to  excite  the  cerebral  motor  centres;  and  that 
even  strong  currents  are  not  effective  when  the  method  of 
bipolar  excitation  is  employed.  They  came  to  the  conclusion  that 
the  cerebellar  cortex  is  practically  inexcitable ;  that  when  motor 
reactions  are  obtained,  these  are  due  to  spread  of  the  stimulus 
to  the  subjacent  nuclei  of  grey  matter  (dentate  nucleus,  roof 
nucleus,  Belters'  nucleus,  etc.),  and,  finally,  that  the  results 
obtained  by  previous  observers  were  attributable  to  some  fallacy. 

Pagano  (1904)  investigated  cerebellar  localisation  by  means  of 
chemical  stimuli,  and  employed  minute  interstitial  injections  of  a 
solution  of  curare,  because — as  previously  noted  by  Tillie — this 
poison  has  a  decidedly  exciting  action  upon  the  nerve-centres. 

He  succeeded  in  mapping  out  four  distinct  motor  centres  in 
the  cerebellum  f<  >r  the  muscles  of  different  regions  :— 

(a)  A  paired  centre  for  the  fore-limb,  lying  near  the  crus 
primum  of  Bolk. 

(&)  A  paired  ^centre  for  the  hind-limb,  near  the  crus  secundum. 

(c)  An  unpaired  centre  for  the  muscles  of  the  neck,  lying  in 
the  lobulus  simplex. 


VI 11 


TTIE  HIND-l'.ftAIN  477 


(d~)  All  unpaired  centre  for  the.  muscles  oi'  the  back,  in  the 
lowest  part  of  the  lobulus  medianus  ])osterior. 

These  results  approximate  closely  to  Bolk's  diagram  of  localisa- 
tion ;  hut  the  inadequacy  of  Pagano's  method  for  any  exact 
determination  of  the  cerebellar  centres  may  be  concluded  both 
from  the  inconstancy  and  the  variability  of  the  reactions  excited 
by  the  curare  at  the  different  points  of  injection,  and  from  bis 
own  observation  that  a  deep. injection  of  curare  into  the  lobus 
anterior  causes  violent  excitation  of  almost  all  cerebral  centres, 
with  varied  sensory  and  motor  manifestations  termed  by  Pagano 
psychic  strychninism  or  motor  delirium,  which  rapidly  caused  the 
death  of  the  animal. 

These  studies  of  the  effect  of  poisons,  applied  to  the  cerebellum, 
were  continued  in  our  laboratory  by  Magnini  under  Baglioni's 
guidance  (1910).  Baglioni's  previous  work  had  proved  that  local 
application  of  weak  solutions  of  carbolic  acid  affect  electively 
the  motor  elements  of  the  spinal  cord,  and  solutions  of  strychnine 
the  sensory  elements  of  the  whole  nervous  system  (p.  264  et  seq.~). 
It  was  therefore  hoped  that  by  employing  these  two  poisons  as 
chemical  stimuli  of  the  cortex  and  deep  parts  of  the  cerebellum, 
it  might  be  possible  to  obtain  facts  of  importance  for  the  theory 
of  cerebellar  localisation. 

But  the  results  were  disappointing,  though  they  brought  into 
prominence  symptoms  which  demonstrated  the  specifically  different 
nature  from  the  corresponding  elements  of  the  cerebrospinal  axis 
of  the  afferent  and  efferent  elements  of  the  cerebellum. 

Carbolic  acid,  applied  to  the  cms  primum  and  secundum  of 
the  cerebellum,  in  any  strength  of  solution  (T3-6  per  cent  on 
discs  of  filter  paper)  has  no  immediate  effect.  This  means  that 
the  cerebellar  cortex,  so  far  as  we  know,  either  contains  no  motor 
elements,  or  these  are  specifically  different  in  character  from  the 
spinal  motor  elements. 

Strychnine,  when  applied  to  the  lobulus  medianus  posterior, 
lobulus  parainedianus,  or  crus  secundum,  either  to  the  surface  or  by 
injection,  produces  no  special  symptoms,  according  to  the  various 
regions  excited,  but  only  more  or  less  general  movements  of  the 
head,  neck,  trunk,  and  limbs  of  the  side  homolateral  with  the 
stimulation.  Application  by  discs  of  filter  paper  either  produces 
no  effect  or  mere  twitches  of  the  facial  muscles.  Superficial 
injections  merely  lead  to  raising  of  the  fore -leg  on  the  same 
side,  blepharospasm,  salivation  with  rhythmical  movements  of  the 
jaw,  tonic  contraction  of  the  two  limbs  on  the  homolateral  side, 
with  tactile  hyperaesthesia  of  the  skin  of  the  homolateral  side  of 
the  face. 

These  results,  while  they  do  not  disprove  the  concept  of 
localisation  in  the  cerebellum,  give  no  decisive  argument  in  favour 
of  it.  The  amount  of  strychnine  used  to  evoke  these  phenomena, 


478  PHYSIOLOGY  CHAP. 

of  excitation  (1-2  per  cent  solutions)  far  exceeded  that  required  to 
evoke  the  typical  spasms,  when  applied  to  the  excitable  zones  of 
the  cerebral  cortex  and  the  dorsal  horn  of  the  cord.  The  more  or 
less  diffuse  symptoms  of  irritation  are  similar  to  those  produced 
by  applying  the  poison  in  minute  doses  to  adjacent  parts  of  the 
bulb.  It  is  probable  that  the  effects  observed  are  due  to  the 
spread  of  the  poison  to  the  centres  in  the  dorsal  surface  of  the 
bulb,  and  consequently  that  the  afferent  elements  of  the  cerebellum 
are  different  in  their  nature  from  those  of  the  cerebrospinal  axis. 

The  same  negative  results  were  obtained  by  Beck  and  Bikeles 
(1912)  on  repeating  these  experiments  with  superficial  application 
of  carbolic  acid  and  strychnine. 

More  exact  results  in  accordance  with  the  theory  of  cerebellar 
localisations  were  to  be  expected  from  the  method  of  partial  and 
localised  extirpation  of  the  different  segments  of  the  cerebellum. 

Our  studies  on  the  cerebellum  aimed  specially  at  formulating 
the  general  function  of  this  organ  on  an  experimental  basis,  and 
Iwere  confined  to  analysis  of  the  components  of  the  ataxy  con- 
/  sequent  on  more  or  less  complete  extirpation  of  one  half,  or  of  the 
so-called  vermis,  or  of  the  entire  cerebellum.  "  From  our  researches 
as  a  whole,"  we  wrote  in  1891,  "it  is  plain  that  the  different 
segments  of  the  cerebellum  all  have  the  same  function.  In  fact, 
the  loss  of  the  median  lobe  may  in  great  measure  be  repaired,  i.e. 
organically  compensated,  by  the  lateral  lobes ;  and,  generally 
speaking,  whatever  the  cerebellar  mutilation,  symmetrical  or 
asymmetrical,  circumscribed  or  extensive,  the  defect  phenomena 
do  not  differ  intrinsically,  but  only  in  intensity,  extent,  and 
duration,  and  in  their  more  or  less  greater  incidence  on  one  or 
other  side  of  the  body.  .  .  .  We  cannot,  therefore,  regard  the 
cerebellum  as  a  collection  of  functionally  distinct  or  different 
centres  in  the  sense  that  each  of  its  segments  is  in  more  or  less 
intimate  or  direct  relation  with  a  special  group  of  muscles,  or  is 
designed  for  functions  of  different  character." 

Nevertheless,  our  investigations  resulted  in  one  definite  fact 
which  paves  the  way  to  the  theory  of  cerebellar  localisation,  viz. 
that  in  dogs  or  monkeys  the  influence  of  each  lateral  half  of  the 
cerebellum  is  mainly  direct,  that  is,  is  exerted  principally  on  the 
muscles  of  the  same  side.  Rolando's  rudimentary  experiments 
established  the  same  fact,  and  long  before  Rolando,  in  1749,  the 
celebrated  physician,  Giovanni  Bianchi  of  Rimini,  had  formulated 
the  same  theory  011  a  clinical  observation,  as  we  learn  from 
Bilaiicioni's  interesting  historical  notice  (1908). 

Ferrier  (1876)  observed  a  fact  which  has  a  certain  value  in 
relation  to  the  theory  of  cerebellar  localisation.  He  found  that, 
after  the  extirpation  of  the  anterior  portion  of  the  vermis,  monkeys 
showed  a  tendency  to  fall  forwards ;  after  extirpation  of  the 


VIII 


THE  HIND-BRAIN 


479 


posterior  part  of  the  vermis,  the  tendency  was  to  fall  backwards. 
Thomas  (1897),  on  the  contrary,  found  a  special  relation  in  dogs 
between  the  vermis  and  the  muscles  of  the  anterior  portion  of  the 


.-•  fv 


'•--.//> 


L  ans 


FIG.  240.— Lobular  division  of  dog's  cerebellum.    (Bolk.) 

trunk,  and  between  the  hemispheres  of  the  cerebellum  and  the 
muscles  of  its  posterior  portion. 

But  it  was  van  Eynberk  who  first  provided  an  experimental 
basis  for  the  theory  of  cerebellar 
localisation,  taking  as  his  guide 
Bolk's  work  on  the  comparative 
anatomy  of  the  mammalian  cere- 
bellum. 

He   attempted   to    test   Bolk's 
inductions  experimentally  by  cir- 
cumscribed extirpations  of  certain    '*>•?  *"• 
lobules,  and  to  this  end  performed     \     ,-,, 
numerous     experiments     in     the 
Physiological    Institute    in    Rome 

*/  o 

(1904-8).      As   all  his  work  was 

carried  out  on  the  dog  it  is  useful 

in  the  two  accompanying   figures 

to  reproduce  a  diagram  of  the  dog's 

cerebellum    divided    into    lobules 

according  to  Bolk  (Fig.   240),  as 

well  as  a  sagittal   section,  which 

allows    us    to    compare    depths    of 

the    inteiiobar    and    interlobular 

sulci,  and  the  varying  size  of  the  lamellae  of  which  the  lobules  are 

composed  (Fig.  241). 

The  new  facts  established  by  van  Ryuberk  may  be  grouped  as 
follows  :— 

(a)  After  the  total  or  partial  extirpation  of  the  lobulus  simplex 


;.  241. — Sagittal  section  of  dog's  cere- 
bellum to  show  depth  of  sulci.  The 
abbreviations  on  both  these  figures  refer 
to  the  diagram  of  Fig.  -J3'.'. 


480  PHYSIOLOGY  CHAP. 

the  animal  presents  side-to-side  oscillations  of  the  head,  which  are 
evidently  due  to  astasia  of  the  muscles  of  the  neck.  Both  at  rest 
and  in  walking  the  animal  exhibits  rhythmical  oscillations  of  the 
head  from  one  side  to  the  other  similar  to  the  sign  a  man  makes  for 
no.  This  symptom  can  be  observed  for  a  week,  or  even  a  month, 
but  owing  to  organic  compensation  it  becomes  less  and  eventually 
disappears. 

(b)  Immediately  after  the  more  or  less  complete  extirpation 
of  the  crus  primum  a  characteristic  symptom  makes  its  appear- 
ance.    As  the  animal  lies  quiet,  or  when  the  trunk  is  cautiously 
raised  by  placing  one  hand  below  the  thorax,  at  each  mechanical 
or   auditory  stimulus   the   front  paw  of  the  side  oper.itrd  on  is 
raised  upward  and  backward  to  the  level  of  the  ear  by  flexion  of 
the  knee.     The  paw  remains  rigid  for  a  moment  in  that  position, 
and  then  falls  gradually,  but  the  same  movement  recurs  after  each 
stimulus.    This  obviously  dynamic  or  irritative  phenomenon,  which 
recalls  the   military   salute,  only  lasts   three   to   seven   days  and 
gradually  disappears.     When  the  animal  subsequently  begins  to 
walk  there  is  seen  to  be  considerable  dysmetria  in  the  movements 
of  the  fore-limb,  which  is  due  to  the  atonia  of  the  muscles  of  the 
limb,  and  lasts  a  longer  or  shorter  time  according  to  the  extent 
and   depth   of  the  lesion.      But   these   symptoms,  too,  disappear 
owing  to  organic  compensation. 

(c)  After  the  localised  extirpation  of  the  crus  secoiidum,  parti- 
cularly when  the  genu  by  which  this  lobule  is  connected  with  the 
lobulus  paraniedianus  is  also  excised,  no  dynamic  phenomena  are 
ever  observed,  but  only  simple  asthenia  of  the  muscles  of  the  hind- 
limb  on  the  same  side,  owing  to  which  the  limb  readily  Hexes 
under  the  weight  of  the  trunk.     When  the  extirpation  includes 
the  two  crura  of  the  lobus  ansii'ormis,  there  is  hen's  gait,  combined 
with  obvious  asthenia  and  atonia  of  the  two  limbs  on  the  side 
operated  on,  which  becomes  less  and  disappears  more  slowly  by 
compensation. 

(d)  The  extirpation    of   the    lobulus    paraniedianus    produces 
rotation  on  the  longitudinal  axis,  associated  with  pleurothotonus  to 
the  side  operated  on.     According  to  van  Eynberk  these  dynamic 
phenomena,  in  which  the  musculature  of  the  trunk  plays  a  special 
part,  are  not  seen  after  localised  extirpation  of  the  lobus  para- 
niedianus.    When  in  addition  to  this  lobule  the  two  crura  of  the 
lobus    ansiforniis   are   excised,   the  resulting  symptoms   strongly 
resemble  those  of  unilateral  removal  of  the  whole  cerebellum,  but 
they  are  more  perfectly  compensated. 

(e)  After  the  isolated  extirpation  of  the  anterior  part  of  the 
lobulus  medianus  posterior,  which  van  Eynberk  termed  lobule  S 
from  its  configuration,  no  abnormal  symptoms  appear.    When  the 
crus  primum  is  also  extirpated  the  symptoms  which  this  produces 
are  exaggerated,  but  eventually  they  are  fully  compensated. 


vin  THE  HIND-BKAIN  481 

These  effects  of  the  extirpation  of  lobules  of  the  cerebellum 
obtained  by  van  Kynberk  were  continued — at  least  in  essentials— 
by  the  researches  of  Pagano  (1904),  Marassini  (1905-6),  Luna 
(1907),  Hulshoff  Pol  (1909),  and  Binnert  (1908). 

The  results  obtained  on  dogs  were  continued  by  a  series  of 
fresh  researches  by  van  Kynberk  and  Vincenzoni  (1908)  on  the 
sheep's  cerebellum,  in  which  the  S  lobule  is  more  developed  than 
in  dogs.  In  sheep,  too,  excision  of  the  paramedian  lobule  causes 
rotation  round  the  long  axis  of  the  animal. 

Eothmann's  experiments  on  monkeys  (1910-11)  harmonise  well 
with  the  localisations  indicated  by  Bolk.  He  further  found  that 
in  dogs  the  extirpation  of  the  lower  part  of  the  anterior  lobule 
disturbs  phonation  (barking),  and  also  produces  noticeable  dis- 
turbances in  the  movements  of  the  tongue  and  jaws.  These  results 
were  not,  however,  confirmed  by  Grabower  (1912). 

As  a  whole,  these  experimental  facts  to  a  large  extent  confirm 
the  inductions  of  Bolk,  and  are  the  first  positive  indication  of 
localisation  in  the  cerebellum.  There  is  no  experimental  control 
for  the  less  accessible  parts  of  the  cerebellum ;  it  has  been 
impossible  to  study  the  effects  which  follow  on  local  extirpation 
of  the  whole  anterior  lobe-- which,  according  to  Bolk,  must 
influence  the  muscles  of  the  head — and  of  the  formatio  reticularis, 
which  must  be  in  relation  with  the  caudal  and  spinal  muscles. 

These  results  agree  perfectly  with  the  general  theory  of  the 
function  of  the  cerebellum  as  stated  above,  and  there  is  no  necessity 
for  reviving  Flourens'  old  hypothesis.  By  his  morphological 
studies  Bolk  has  suggested  to  other  investigators  this  new  develop- 
ment of  cerebellar  physiology,  according  to  which  the  several 
lobules  of  the  cerebellum  have  a  more  intimate  or  direct  relation 
with  special  groups  of  muscles ;  on  the  other  hand  the  function  of 
reinforcement  is  everywhere  the  same  in  the  cerebellum,  and 
defect  of  any  of  the  lobules  can  be  met  by  organic  compensation 
in  the  lobules  that  remain. 

One  of  the  most  important  results  of  the  analysis  of  cerebellar 
ataxy  produced  in  dogs  by  the  unilateral  or  bilateral  ablation  of 
the  cerebellum  is  the  sharp  separation  of  the  symptoms  of  cere- 
bellar deficiency  from  those  vi  functional  compensation  ;  the  latter 
are  the  purposive  and  voluntary  acts  by  which  the  animal  succeeds 
in  obviating  the  effects  of  deficient  or  lost  cerebellar  innervation. 

Directly  the  sigmoid  gyrus  of  one  or  both  cerebral  hemispheres, 
which  contains  the  greater  part  of  the  voluntary  motor  centres,  is 
destroyed,  the  animal  which  has  lost  half  or  the  whole  of  its 
cerebellum  loses  again  for  a  time,  or  permanently,  the  power  of 
maintaining  the  erect  posture  and  of  walking  (p.  440). 

In  reviewing  the  facts  which  show  that  the  compensation  of 
cerebellar  ataxy  is  dependent  on  the  motor  zone  of  the  cerebrum, 
a  new  series  of  problems  is  at  once  presented  to  the  physiologist. 

VOL.  Ill  2  I 


482  PHYSIOLOGY  CHAP. 

The  solution  of  these  is  important  to  the  general  physiology  of 
the  cerebellum  and  the  functional  localisation  within  it,  since 
they  not  only  afford  new  evidence  for  the  reinforcing  action  of  the 
cerebellum  upon  the  cerebrospinal  axis,  but  further  throw  light 
on  the  mechanism  by  which  the  motor  area  of  the  brain  gradually 
becomes  capable  of  compensating  the  effects  of  cerebellar  deficiency. 
The  most  important  problems  raised  are  :— 

(a)  What  change  occurs  in  the  normal  excitability  of  the 
cerebral  motor  area  of  dogs  that  have  previously  been  deprived  of 
half  or  the  whole  of  their  cerebellum  ? 

(6)  Is  electrical  stimulation  of  the  cerebellum  capable  of  alter- 
ing the  threshold  value  of  the  motor  area  ? 

(c)  Is  there  a  definite  functional  relation  between  the  cerebellar 
lobules  that  have  been  electrically  excited  and  the  centres  in  the 
central  motor  area,  the  excitability  of  which  is  affected  ? 

We  instituted  experiments  directed  to  solving  the  first 
question,  and  published  the  results  in  our  Monograph  (1891). 
In  dogs,  some  months  after  the  removal  of  half  or  of  the 
whole  cerebellum,  excitability  was  increased  in  both  motor 
areas  of  the  cerebral  cortex,  both  to  electrical  and  to  mechanical 
stimulation.  In  two  dogs  in  which  one-half  of  the  cerebellum 
had  been  extirpated  a  year  previously,  both  sigmoid  gyri  containing 
the  motor  centres  for  the  limbs  were  removed.  During  the 
operation  the  mechanical  excitation  of  these  centres  produced 
intense  and  general  reactions  in  both  limbs,  which  were  equal  on 
the  two  sides.  In  a  third  dog,  which  had  lost  the  median  and 
right  lateral  lobe  of  the  cerebellum  fourteen  months  earlier,  the 
same  results  were  obtained  with  faradisation  of  the  two  motor 
areas.  Cortical  excitability  was  increased  on  both  sides,  and  we 
were  unable,  even  with  weak  induced  currents,  to  provoke  move- 
ments limited  to  one  limb ;  they  were  always  diffuse  and  involved 
either  the  two  limbs  of  the  opposite  side  or  all  four  limbs. 

This  increased  excitability  of  the  cerebral  motor  centres  agrees 
perfectly  with  our  explanation  of  the  compensation  of  cerebellar 
deficiency,  as  due  to  an  exaggerated  functional  activity  initiated 
by  their  greater  excitability. 

In  1893  Russell  obtained  a  diminution  of  excitability  of  the 
motor  area  of  the  cerebral  cortex  in  dogs  and  apes  some  weeks 
after  removal  of  the  opposite  half  of  the  cerebellum. 

This  result  is  a  new  argument  in  favour  of  our  theory  that  the 
cerebello-cerebral  relations  are  principally  crossed,  so  that  the 
reinforcing  action  which  each  half  of  the  cerebellum  exerts  on  the 
cerebral  motor  centres  mainly  affects  those  of  the  opposite  side. 
On  the  other  hand  it  can  readily  be  understood  that  the  ablation 
of  one-half  of  the  cerebellum,  by  eliminating  this  reinforcement, 
must  in  the  early  period — which  may  last  for  some  weeks- 
produce  a  diminution  in  the  excitability  of  the  motor  centres  of  the 


viii  THE  HTND-BEAIN  483 

opposite,  cerebral  hemisphere,  and  it  is  only  later,  after  some 
months,  that  the  exaggerated  voluntary  efforts,  directed  to  the 
mechanical  compensation  of  the  cerebellar  deficiency,  may  or  can 
produce  an  increase  in  the  excitability  and  functional  efficiency 
of  the  centres. 

We  controlled  Eussell's  experiments  in  two  monkeys  some 
months  after  the  extirpation  of  the  right  half  of  the  cerebellum, 
and  in  a  dog  only  seventeen  days  after  the  same  operation.  The 
excitability  of  the  left  cerebral  motor  area  was  diminished  only  at 
certain  points,  while  at  others  it  appears  either  unaltered  or 
increased,  in  comparison  with  the  right  motor  area.  Not  being 
able  at  the  time  to  give  an  adequate  interpretation  of  this  equivocal 
result,  we  confined  ourselves  to  bringing  it  into  relation  with  the 
fact  that  the  anatomical  and  functional  relations  between  the 
cerebellum  and  cerebrum  are  mainly  but  not  exclusively  crossed. 

Gilberto  Eossi  eventually  cleared  up  the  matter  by  publishing 
two  brief  but  important  experimental  observations  in  1912,  which 
were  obtained  with  all  possible  technical  precautions. 

The  immediate  effect  of  hemi-extirpatioii  of  the  dog's  cerebellum 
is  a  diminution  of  excitability  in  the  motor  cortical  area  on  the 
opposite  side,  as  compared  with  that  on  the  same  side  as  the 
extirpation.  This  diminution  can  be  seen  during  the  whole  of 
the  period  in  which  the  phenomena  of  deficiency  persist.  The 
establishment  of  compensatory  phenomena  is,  on  the  contrary, 
accompanied  by  a  definite  increase  of  excitability  in  the  motor 
area  of  the  opposite  side,  as  compared  with  the  side  of  the 
extirpation. 

These  new  experimental  data  are  a  direct  proof  of  the  re- 
inforcing action,  for  the  most  part  crossed,  which  the  cerebellum 
exercises  upon  the  cerebrum,  while  they  further  show  that  voluntary 
effort  suffices  to  repair  and  to  compensate  the  phenomena  of 
deficiency,  by  raising  the  excitability  of  the  cerebral  motor  cortex. 

On  investigating  the  effect  of  simultaneous  stimulation  of  the 
cerebral  and  cerebellar  cortex,  Eossi  found  that  faradic  stimuli 
applied  to  the  cortex  of  one  lateral  half  of  the  cerebellum  in 
all  the  lobes  explored — crus  primum,  crus  secundum,  lobulus 
paramedianus — raised  the  excitability  of  the  cerebral  cortex  on 
the  opposite  side.  That  is,  no  motor  reaction  was  induced,  but 
the  threshold  of  excitation  of  the  central  motor  area  of  the 
opposite  side  was  lowered,  which,  by  facilitating  the  motor  effects, 
made  previously  inefficacious  currents  effective.  On  the  other 
hand,  faradisation  of  the  same  parts  of  the  cerebellum  on  one  side 
caused  no  appreciable  modification  in  the  excitability  of  the 
cerebral  cortex  on  the  same  side.  Very  weak  faradic  currents 
produce  these  effects,  during  slight  narcosis  of  the  animal.  In 
profound  narcosis  the  stimulation  of  the  cerebellum  is  ineffective. 
These  new  experimental  observations  published  by  Eossi 

2  I  1 


484  PHYSIOLOGY  CHAP. 

confirm  the  relative  inexcitability  of  the  cerebellar  cortex  already 
demonstrated  by  Horsley  and  Clarke,  but  at  the  same  time  they 
partially  elucidate  the  mechanism  of  the  reinforcing  action  of 
the  cerebellum  on  the  cerebrum.  On  the  other  hand  they 
contribute  nothing  to  the  theory  of  cerebellar  localisation,  which 
rests  upon  a  totally  different  order  of  facts.  To  settle  the  question 
of  functional  localisation  in  the  cerebellum  by  the  method  of 
simultaneous  stimulation  of  the  cerebellum  and  cerebrum  would 
require  a  long  series  of  delicate  experiments  (on  which  Eossi  is  at 
present  engaged)  on  the  effect  upon  the  excitability  of  the 
corresponding  motor  centres  of  the  cerebral  cortex,  of  stimulating 
the  separate  cerebellar  lobes. 

BIBLIOGRAPHY 

The  most  important  publications  on  the  Cerebellum  are  : — 

ROLANDO.     Saggio  sopra  la  vera  struttura  del  cervello.     Sassari,  1809  ;  Turin,  1823. 

MAGENDIE.     Precis  elemeutaire  de  physiologic.     Paris,  1825. 

BOUILLAUD.     Arch.  gen.  de  med.  xv.     Paris,  1827. 

ANDRAL.     Clinique  med.  v.     Paris,  1833. 

FLOURENS.     Recherches   experimentales    sur    les    proprietes   et   les    fonctions   du 

systeme  nerveux  dans  les  animaux  vertebres.     Paris,  1842. 
DALTON.     Amer.  Journ.  of  Med.  Sciences.     1861. 
WAGNER.     Journ.  de  physiol.  de  Brown-Sequard,  iv.,  1861. 

LUSSANA.     Ibidem,  v.,  1862.     Fisiologia  e  patologia  del  cervelletto.     Padua,  1897. 
LEVEN  and  OLIVIER.     Arch.  gen.  de  med.,  1862-63. 
LUYS.     Arch.  gen.  de  med.,  1864. 

WEIR-MITCHELL.     Amer.  Journ.  of  Med.  Sciences,  1869. 
LONGET.     Traite  de  physiologic.     Paris,  1873. 
HITZIG.     Untersuchungen  liber  das  Gehirn.     Berlin,  1874. 
FERRIER.     Functions  of  the  Brain,  1876. 
NOTHNAGEL.       Centralbl.    f.    med.    Wiss.,    1876.      Virchow's    Arch.    Ixiii.,    1877. 

Topische  Diagnostik  der  Gehirnkrankheiten.     Berlin, 1879. 
LUCIANI.     II  Cervelletto.     Florence,  1891.     Rivista  sp.  di  freniatria,  xviii.,  1892  ; 

xxi.,  1895.     Archives  italiennes  de  phys.  xxi.,  1894. 

MARCHI.     Sull'  origine  e  decorso  dei  pednncoli  cerebellari.     Florence,  1891. 
LANGE.     Pfliiger's  Archiv,  1.,  1891. 

EWALD.     Untersuchungen  iiber  das  Endorgan  d.  N.  octavus.     Wiesbaden,  1892. 
RUSSELL  RISIEN.     Phil.  Trans.  Roy.  Society  of  London,  v.  185,  1894.      British 

Med.  Journal,  1894. 

FERRIER  and  TURNER.     Phil.  Trans,  v.  185,  1894. 
SCHIFF.     Recueil  des  niemoires  physiologiques,  vol.  iii.,  1896. 
BECHTEREW.     Arch.  f.  Anat.  u.  Physiol.,  1896. 
THOMAS.     Le  Cervelet.     Paris,  1897. 
MONAKOW.     Nothnagel's  Spez.  Pathologic,  ix.,  1897. 

ABLER.     Die  Symptomatologie  der  Kleinhirnerkrankungen.     Wiesbaden,  1899. 
DEGANELLO.     Arch,  delle  scienze  med.  xxiv. ,  1900. 
DREIFUSS.     Pfliiger's  Archiv,  Ixxxi.,  1900. 
PROBST.     Arch.  f.  Psych,  u.  Nervenkrankh.  xxxv.,  1902. 

LEWANDOWSKY.      Arch.  f.  Anat.  u.  Physiol.,  1903.     Das  Kleinhirn.     Jena,  1907. 
GAGLIO.     Arch,  per  le  scienze  med.  xxiii.,    1899.      Arch.  ital.  de  biol.  xxxviii. 

1903. 

STEFANI.     Atti  del  R.  1st.  veneto,  Ixii.,  1903. 
DUCCESCHI  and  SERGI.     Arch,  di  fisiol.  del  Fano,  i.,  1904. 
PATRIZI.     Memorie  della  R.  Ace.  di  scienze,  lettere,  ed  arti  in  Modena,  1905. 
H.  MUNK.     Sitzungsber.  d.  k.  preussischen  Akad.  d.  Wissensch.,  1906-7. 
LANGELAAN.     Verh.  d.  k.  Akad.  van  Wetensch.  te  Amsterdam,  1907. 


vni  THE  HIND-BKAIN  485 

A.  MUURI.     Lczioni  di  clinica  medica.     Milan,  1908. 

G.  MlNGAZZlNl.     Lezioni  di  anatomia  clinica  dei  centri  nervosi.     Milan,  1908. 

Theory  of  Functional  Localisation  of  Cerebellum  :— 

PRUS.     Arch,  polonaises  des  sciences  biol.  et  med.  i.,  1901. 

BULK.     Morpliol.  Jahrbuch,  xxxi.,  1902.     Psychiatrische  en  neurol.  Bladen,  1902. 

Monatsschr.   f.    Psychiatric    und    Neurologic,    xii.      Verh.    d.    k.  Akad.   van 

"Wetensch.  te  Amsterdam,  i.,  1905  ;  ii.,  1905.     Das  Zerebellum  der  Saugetiere. 

Jena,  1906. 
VAN  RYNBERK.      Archivio  di  fisiologia  di  Fano,  i.,  1904  ;    ii.,   1904.      Archives 

intern,  de  physiologic,  v.,  1907.      Folia  neuro-biologica,  i.,  1908.     Ergebnisse 

der  Physiologic,  VII.  Jahrgang,  1908  ;  VIII.  Jahrgang,  1912. 
PAGANO.      Rivista  di  pat.  nervosa  e  mentale,    vii.,    1902  ;    ix.    1904.     Archives 

intern,  de  physiologic,  ii.,  1904.     Archives  italiennes  de  biologie,  xliii.,  1905. 
MARASSINI.      Archivio  di  fisiologia  di  Fano,  ii.,   1905.      Archives  italiennes  de 

biologie,  xlvii.,  1907. 
LUNA.      Ricerche    fatte   nel   laboratorio   di   anat.    normale    di    Roma   e    in   altri 

laboratori  biologici,  xii.,  1906. 
HORSLEY  and  CLARKE.     British  Med.  Journ.,  1906. 
HORSLEY  and  BOUCHE.     Ibidem,  1907. 
NEGRO  and  ROSAENDA.      Giornale  della  R.  Ace.  di  Med.  di  Torino,  xiii.,  1907. 

Archivio  di  psichiatria,  med.  legale  e  antr.  criminale,  xxviii.,  1907. 
VINCENZONI.     Archivio  di  farmacologia  sperimentale  e  scienze  affini,  vii.  1908. 
BINNERTS.     Academisch  proefschrift.     Amsterdam,  1908. 
LOURIE.     Neurologisches  Zentralblatt,  Leipzig,   1908.      Pfliigers  Archiv.      Bonn, 

1910. 

HORSLEY  and  CLARKE.     Brain.     London,  1908. 

HULSHOFF  POL.     Psych,  en  neurologische  Bladen.     Amsterdam,  1909. 
MAGNINI.     Arch,  di  fisiologia  del  Fano,  vii.,  1910.  . 
ROTHMANN.     Neurol.  Zentralblatt.     Leipzig,  1910-11. 
ROTHMANN  und  KATZENSTEIX.     Ibidem,  1911. 
BAUER   and   LIEDLER.       Arbeiten   aus   dem   neurol.    Institute    aus    der   Wiener 

Universitat,  1911. 

BECK  and  BIKELES.     Pfliigers  Archiv,  1911.     Zentralblatt  f.  Physiol.,  1912. 
GRABOWER.     Arch.  f.  Laring.  und  Rhinologie,  xxvi.,  1912. 
G.  Rossi.     Archivio  di  fisiologia,  x.  p.  251,  1912.     Ibidem,  x.  p.  389,  1912. 

Recent  English  Literature  :— 

HORSLEY  and  CLARKE.     On  the  Intrinsic  Fibres  of  the   Cerebellum,  its  Nuclei 

and  its  Efferent  Tracts.     Brain,  1905,  xxviii.,  13. 
HORSLEY  and  CLARKE.     The  Structure  and  Function  of  the  Cerebellum  examined 

by  a  new  Method.     Brain,  1908,  xxxi.  138. 

SHERRINGTON.     The  Integrative  Action  of  the  Nervous  System.     London,  1906. 
HORSLEY  and  MAC-NALTY.      On  the   Cervical  Spino-bulbar  and    Spino-cerebellar 

Tracts,  and  on  the  Question  of  Topographical  Representation  in  the  Cerebellum. 

Brain,  1909,  xxxii.  237. 


CHAPTER   IX 

MID-BRAIN    AND   THALAMENCEPHALON 

CONTENTS. — 1.  General  structure  of  the  mesencephalon.  2.  The  thalamen- 
cephalon.  3.  Effects  of  total  extirpation  of  fore-,  inter-,  and  mid-brain  in  fishes  ; 
4.  In  amphibia ;  5.  In  birds  ;  6.  In  mammals.  7.  Effects  of  stimulating  the 
mesencephalon.  8.  Effects  of  extirpating  the  corpora  quadrigemina  alone. 

9.  Effects  of  dividing  the  whole  or  half  the  brain-stem  at  level  of  the  mid-brain. 

10.  Effects  of  incomplete  or  total  removal  of  optic  thalami.     Bibliography. 

I.  THE  Mid-brain  (mesencephalon)  arises  from  the  median  primary 
vesicle  of  the  embryonic  brain,  which  is  interposed  between  the 
hind -brain  (pons  and  cerebellum)  and  the  inter -brain  (optic 
thalamus).  Of  the  cerebral  vesicles  this  is  the  one  that  under- 
goes least  alteration  during  development.  The  changes  consist 
principally  in  a  simple  thickening  of  its  walls  and  subsequent 
restriction  of  the  cavity,  which  is  transformed  into  the  aqueduct 
of  Sylvius.  In  the  lower  vertebrates  it  attains  a  more  or  less  con- 
spicuous development ;  but  in  mammals  its  comparatively  pre- 
cocious development  is  arrested  very  early,  and  in  man  it  develops 
least  of  the  five  original  parts  of  the  brain. 

The  mid-brain  is  usually  divided  into  two  parts  :  one  ventral— 
the  cerebral  peduncles ;  the  other  dorsal — comprising  the  corpora 
quadrigemina  which  in  lower  vertebrates  are  also  known  as  the 
optic  lobes. 

The  ventral  portion  of  the  mid-brain  is  divided  into  two  parts 
by  the  substantia  nigra  of  Sommerung,  the  ventral  of  which  is 
termed  the  pes  or  crusta  of  the  peduncle,  the  dorsal  the  tegmentum 
(Figs.  242,  243). 

The  first  is  the  continuation  of  the  pyramidal  fibres  of  the  pons 
and  bulb,  with  the  addition  of  other  longitudinal  fibres  which 
corne  from  the  fore-brain ;  the  second  is  the  continuation  of  the 
formatio  reticularis,  with  the  addition  of  much  grey  matter  and  of 
white  fibres,  some  of  which  represent  the  continuation  of  the 
superior  cerebellar  peduncles.  The  crura  of  the  peduncles  are 
separated  from  one  another ;  the  two  tegmerita,  on  the  contrary, 
are  united  in  the  median  plane  along  the  raphe,  and  extend 
dorsally  on  the  side  of  the  aqueduct  into  the  corpora  quadrigemina. 

486 


CHAP,  ix  MID-  AND  INTEE-BEAIN  487 

Viewed  in  section  the  base  of  the  peduncles  is'crescentic  in  form  ; 
the  bundles  of  which  it  is  composed  are  separated  by  prolonga- 
tions of  the  pia  mater.  The  pyramidal  bundles  of  the  cord,  medulla, 
and  pons,  are  the  largest  element,  and  occupy  the  median  part,  of 
the  cms  of  the  peduncles.  They  arise  from  the  Eolandic  or  central 
region  of  the  cerebral  cortex,  pass  through  the  internal  capsule, 
and  run  to  the  nuclei  of  origin  of  the  motor  nerves  in  the  pons, 
bulb,  and  cord.  The  external  or  lateral  segment  of  the  pes  is 
formed  of  bundles  which  are  the  prolongation  of  the  lateral 
bundles  of  the  poiis ;  these  take  origin  in  the  occipito-temporal 
regions  of  the  cerebral  cortex,  and  terminate  in  the  cells  of  the 
nuclei  of  the  pons  which  give  rise  to  the  fibres  that  form  the 
ponto-cerebellar  path.  The  internal  median  segment  of  the  pes 
is  composed  of  fibres  which  develop  late  as  compared  with  those  of 
the  pyramidal  bundle ;  they  pass  through  the  anterior  portion  of 


FIG.  242.— Outline  of  two  sections  across  the  mesencephalon.  Natural  size.  (Schafer.)  A,  through 
inferior  pair  of  corpora  quadrigemina  ;  B,  through  superior  pair,  cr,  crusta  ;  s.n.,  substantia 
nigra ;  t,  tegmentum ;  s,  Sylvian  aqueduct  with  central  grey  matter ;  c.q..  grey  matter  of 
quadrigeminal  bodies  ;  l.g,,  lateral  groove  ;  p.L,  posterior  longitudinal  bundle ;  il.V,  descending 
root  of  5th  nerve;  s.c.p.,  superior  cerebellar  peduncle;  /,  fillet.  The  dotted  circle  in  B 
indicates  the  tegmental  nucleus. 

the  internal  capsule,  and  come  from  ^he  prefrontal  region  of  the 
hemisphere. 

The  substantia  nigra  consists  of  pigmented  cells  and  nerve- 
fibres  of  which  the  destination  is  unknown.  They  form  the 
ventral  stratum  of  the  tegmentum,  which  contains  much  grey 
matter,  consisting  of  scattered  nerve-cells  intersected  by  longi- 
tudinal, transverse,  oblique  and  arcuate  fibres,  which  give  the 
same  appearance  to  the  lower  part  of  the  mesencephalon  as  the 
formatio  reticularis  of  the  bulb  or  pons  (Fig.  228).  Besides  the 
scattered  bundles  of  longitudinal  fibres,  we  have  to  consider 
the  dorsal  longitudinal  bundle,  the  superior  cerebellar  peduncles, 
and  the  fillet  of  Eeil  (Fig.  244;.  The  first  arises  from  the  nuclei 
of  the  motor  cerebral  nerves,  and  especially  from  the  3rd,  4th,  and 
6th  pairs ;  the  second,  as  we  have  seen,  decussate  near  the  red 
nucleus  of  Stilling,  and  pass  to  the  ventral  portion  of  the  optic 
thalamus ;  the  fillet  originates  principally  in  the  nuclei  of  the 
dorsal  columns  of  the  opposite  side,  and  comes  into  relation  with 
the  corpora  quadrigemina  and  optic  thalamus. 

The  aqueduct  is  surrounded  by  a  layer  of  grey  matter,  which 

2  I  2 


488 


PHYSIOLOGY 


CHAP. 


is  the  prolongation  of  that  which  lines  the  floor  of  the  fourth 
ventricle.  In  addition  to  many  scattered  cells,  the  grey  matter  of 
the  aqueduct  contains  the  cell  columns  which  give  origin  to  the 
roots  of  the  3rd,  4th,  and  the  descending  root  of  the  5th  nerve 
(Fig.  208). 

The  posterior  corpora  quadrigemina  consist  almost  entirely  of 


' 


FIG.  243. — Transverse  section  across  mid-brain,  through  inferior  corpora  quadrigemina.  Magnified 
about  3 J  diameters.  From  a  photograph.  (Schafer.)  ST.,  dorsal  quadrigeminal  groove  (sulcus 
longitudinalis)  ;  c.i/.p.,  corpus  quadrigeminum  posterius  ;  str.l.,  stratum  lemnisci ;  c.yr.,  central 
grey  matter  ;  n.lll,  IV,  oculo-motor  nucleus  ;  d.V.,  descending  root  of  6th  nerve  ;  p.l.b.,  posterior 
longitudinal  bundle;  f.r.t.,  formatio  reticularis  tegmenti ;  d,  tl',  decussating  fibres  of  tegmentum; 
s.c.j).,  decussating  fibres  of  superior  cerebellar  peduncles;  /,  upper  fillet;/',  lower  or  lateral 
fillet;  p.p.,  pes  pedunculi ;  s.??.,  substantia  nigra  ;  g.i.p,,  interpeduncular  grey  matter;  Sy, 
Sylvian  aqueduct. 

grey  matter  (Fig.  243).  The  cells  which  they  contain  are  in 
connection  with  the  endings  of  the  fibres  of  the  lateral  fillet, 
which  arise  from  the  nucleus  cochlearis  of  the  auditory  nerve 
on  the  opposite  side.  In  correspondence  with  this  intimate 
relation  of  the  posterior  corpora  quadrigemina  with  the  nucleus 
of  I the  cochlear  nerve,  it  is  in  mammals  only --which  have  a 
well -developed  auditory  apparatus  —  that  the  posterior  corpora 
quadrigemina  appear  as  distinct  prominences.  Other  vertebrates, 


IX 


MID-  AND  INTER-BKAIN 


489 


including  birds,  bare  only  corpora  bigeinina  (optic  lobes),  wbicb 
probably  represent  tbe  anterior  pair. 

The  anterior  quadrigeminal  bodies  are  less  prominent,  but 
longer  and  darker,  than  the  posterior  (Fig.  229).  A  small  bundle 
of  white  fibres,  which  emerges  from  the  lateral  edge  of  the  nucleus 
and  runs  towards  the  corpus  geiiiculatum  externum,  is  a  part  of  the 
optic  nerve.  Fibres  also  spring  from  the  cells  of  the  grey  matter 

'  • 


-t 


^Ki/'^M 

!:lll&^il£ 


FIG.  244. — Section  across  miil-bi-ain,  through  superior  corpora  quadrigeinina.     Magnified  about  3J 
diameters.      From  a   photograph.      (Schafer.)     Sy,   Sylvian  aqueduct ;   r.p.,   posterior    com- 
missnre;  fil.pi.,  glandula  pincalis  ;  c.q.a.,  grey  matter  of  one  of  superior  corpora quadrigemina 
i'. 1,1. in.,  corpus  geniculatum  mesiale  ;  e.g.!.,  corpus  geniculatum  laterale  ;   tr.ojit.,  optic  tract 
p.p.,  pes  pedunculi ;  p.I.b.,  posterior  longitudinal  bundle;  /.,  upper  fillet;  r.n.,  red  nucleus 
H.III,  nucleus  of  3rd  nerve  ;  III,  issuing  fibres  of  3rd  nerve  ;  l.p.p.,  locus  perforatus  posticus. 

of  these  eminences,  and  terminate  in  the  nuclei  of  the  3rd  and  4th 
pair,  where  the  fibres  of  the  posterior  longitudinal  bundle  also  end. 
Impulses  from  the  optic  nerve  can  thus  readily  be  reflected  to  the 
nuclei  of  the  nerves  that  innervate  the  muscles  of  the  eye. 

II.  The  Inter  -  brain  (thalamencephalon)  originates,  as  we 
have  seen,  in  the  2nd  secondary  vesicle  of  the  embryonic  brain. 
The  optic  thalami  are  the  thickening  of  the  walls  of  this  vesicle, 
the  cavity  of  which  shrinks  in  the  adult  to  the  third  ventricle. 


490 


PHYSIOLOGY 


CHAP. 


Viewed  from  above  the  optic  thalami  are  two  large  oval  masses 
of  grey  matter,  which  are  covered  by  a  thin  sheet  of  white  fibres. 
At  the  anterior  end  a  mass  known  as  the  tuberculum  anterius 
projects  into  the  lateral  ventricle,  and  is  covered  with  the 


FIG.  245. — View  from  above  of  third  ventricle  and  part  of  the  lateral  ventricles.  (Henle.)  The 
lirain  has  been  sliced  horizontally  immediately  below  the  corpus  callosum,  and  the  fornix  and 
velum  interposition  have  been  removed.  Tho,  thalamus  opticus  ;  7's,  its  anterior  tubercle; 
Pr,  pulvinar  ;  Com,  middle  commissure  stretching  between  the  two  optic  thalami  across  middle 
of  third  ventricle ;  Cf,  columns  of  fornix ;  On,  pineal  gland  projecting  downwards  and 
backwards  between  superior  corpora  quadrigemina  ;  St,  stria  terminals  ;  Cs,  nucleus  caudatus 
of  corpus  striatum  ;  Vsl,  ventricle  of  septum  lucidum  ;  CcW,  section  of  genu  of  corpus  callosum  ; 
Pen,  pineal  peduncle  ;  Tfo,  pineal  stria;  Cop,  posterior  commissure. 

epithelium  that  lines  this  cavity.  At  the  posterior  and  mesial 
end  a  still  more  conspicuous  prominence,  known  as  the  pulvinar, 
extends  over  the  quadrigemiual  bodies  and  partially  covers  them 
(Fig.  245). 


IX 


MID-  AND  INTER-BEATN 


491 


At  the  ventral  part  of  the  posterior  end  of  the  optic  thalamus 
are  two  oval  prominences,  the  corpora  geniculata.  The  corpus 
geiiiculatuin  internum  is  the  smaller  ;  it  is  connected  with  the 
posterior  quadrigeminal  body  hy  a  bundle  of  medullated  fibres 
known  as  the  •  brachium  posticum.  The  corpus  geuiculatum 
externum  or  laterale  lies  directly  below  the  pulvinar,  and  is  con- 
siderably larger;  it  receives  the  external  root  of  the  optic  tract, 
and  is  united  to  the  anterior  quadrigeminal  body  by  a  bundle  of 
medullated  fibres  known  as 
the  brachium  antieum. 

A  frontal  section  of 
the  optic  thalamus  shows 
that  the  grey  mass  of 
which  it  is  composed  is 
divided  into  three  distinct 
nuclei  by  a  medullary 
layer :  an  internal  nucleus, 
lying  between  this  layer 
and  the  third  ventricle  ;  an 
external  nucleus  between 
the  internal  nucleus  and 
the  so-called  internal  cap- 
sule ;  and  an  anterior  or 
superior  nucleus  which 
corresponds  to  the  anterior 
tubercle  of  the  thalamus 
(Fig.  247). 

A  horizontal  section 
through  the  thalamus 
shows  the  same  three 
nuclei  (internal,  external, 
anterior)  under  another 
aspect  (Fig.  247). 

The  optic  thalamus  at 
its  lower  and  external  surface  is  in  direct  relation  with  the 
bundles  of  fibres  coming  from  the  upper  end  of  the  peduncle. 
These  are  the  fibres  of  the  superior  cerebellar  peduncle;  fibres 
which  arise  from  the  cells  of  the  red  nucleus ;  the  fibres  of  the 
dorsal  longitudinal  bundles ;  and  part  of  the  fibres  of  the  median 
lemniscus  or  fillet  of  Reil. 

Other  fibres  connect  the  optic  thalamus  with  the  nuclei  of  the 
corpus  striatum.  These  take  origin  partly  in  the  caudate  nucleus, 
partly  in  the  lenticular  nucleus.  They  cross  the  genu  and  posterior 
segment  of  the  interior  capsule,  and  penetrate  the  lateral  border  of 
the  thalamus.  Larger  bundles  issue  from  the  ventral  surface  of 
the  lenticular  nucleus,  and  enter  the  ventral  surface  of  the  thalamus. 
The  fibres  that  unite  the  thalamus  to  the  cerebral  cortex  spring 


FIG.  246.—  Mesencephalon  and  its  relations.  (Testut.) 
1,  third  ventricle  ;  2,  epiphysis  or  pini'al  gland  ;  3, 
trigonum  habenulae ;  4,  posterior  end  of  optic  thalamus ; 
5,  external ;  6,  internal  geniculate  bodies ;  7,  optic 
tract  with  its  two  roots  ;  8,  anterior ;  9,  posterior 
corpora  quadrigemina ;  10,  anterior ;  11,  posterior 
brachium  of  corpora  quadrigemina ;  12,  pons ;  13, 
valve  of  Vieussens  ;  14,  superior  cerebellar  peduncles  ; 
15,  trochlear  nerve ;  16,  lateral  bundle  of  isthmus 
cerebri ;  17,  fourth  ventricle ;  18,  middle  cerebellar 
peduncles  ;  19,  inferior  cerebellar  peduncles. 


492 


PHYSIOLOGY 


CHAP. 


from  its  different  portions,  and  spread  like  a  fan  into  the  centrum 
ovale.  They  are  grouped  into  three  principal  1  amdles.  The  anterior 
bundle  emerges  at  the  frontal  end  of  the  thalamus,  runs  through 
the  anterior  segment  of  the  internal  capsule,  and  spreads  to  the 
cortex  of  the  frontal  lobe.  The  posterior  bundle  arises  in  the 
pulvinar  and  corpus  geniculatum  exteruuni,  follows  an  antero- 

posterior  course,  crosses  the 
hindmost  segment  of  the 
external  capsule,  and  spreads 
out  to  the  cortex  of  the 
occipital  lobe  (optic  radia- 
tion of  Gratiolet).  The  in- 
ferior bundle  starts  from  the 
mesial  and  ventral  parts  of 
the  thalamus,  runs  obliquely 
lateralwards,  passes  along 
the  ventral  surface  of  the 
lenticular  nucleus,  and 
finally  ends  in  the  cortex 
of  the  temporal  lobe  and 
insula  (ansa  peduncularis  of 
Gratiolet). 

It  is  important  to  deter- 
mine the  origin,  course,  and 
termination  of  the  optic 
nerves,  and  their  connection 
with  the  mid -brain,  thala- 
•mus,  and  cerebrum.  The 
fibres  that  make  up  each 
optic  nerve  arise  from  the 
ganglion  cells  of  the  retina. 
They  emerge  from  the  eye- 
ball a  little  mesial  to  the 
posterior  pole,  and  enter  the 


Fio.  24 


Thalamencephalon  and  its  relations.  Frontal 
section  through  grey  commissure.  (Testut.)  a, 
frontal  portion  of  lateral  ventricle  ;  h,  its  inferior 
horn  ;  c,  third  ventricle ;  d,  Sylvian  fissure ;  e, 
optic  tract  ;  /,  gyrus  hippocampi.  1,  lamina 
incdullaris  interna  of  optic  thalamus  ;  2,  lamina 
medullaris  externa  ;  3,  internal ;  4,  external ;  5, 
superior  nucleus  of  optic  thalamus ;  6,  caudate 
nucleus  ;  6',  its  lower  end  ;  7,  7',  lenticular  nucleus  ; 
8,  claustrum  ;  9,  external  capsule ;  10,  internal 
capsule  ;  11,  pes  pedunculi ;  12,  substantia  nigra  ; 
13,  stratum  dorsale  of  regio  subthalamica  ;  14,  zona 
incerta  ;  15,  nucleus'  of  Luys  ;  16,  anterior  end  of 
red  nucleus  ;  17,  great  commissure. 


cranium   through   the  optic 


foramen.  Directly  after 
entering  the  skull  both  optic 
nerves  unite  in  the  chiasma,  in  which  more  than  half  the  fibres 
decussate,  and  thence  pass  to  the  posterior  part  of  the  optic 
thalamus  or  pulvinar  under  the  name  of  the  optic  tract. 

Experimental  physiology  and  pathological  anatomy  show 
clearly  that  each  optic  nerve  contains  two  distinct  bundles  of 
fibres :  one  direct,  which  remains  on  the  side  in  which  it  takes 
origin,  and  a  crossed  bundle,  which  decussates  in  the  chiasma  to 
pass  to  the  other  side.  The  fibres  of  the  direct  bundle  come  from 
the  external  or  temporal  third  of  the  retina ;  those  of  the  crossed 
bundle  from  the  two  inner  or  nasal  thirds.  The  dividing  line 


IX 


MID-  AND  INTEE-BEAIN 


493 


9 


between  these  two  retinal  zones  corresponds  to  a  vertical  plane 
through  the  t'ovea  eentralis  or  yellow  spot  of  the  retina  (Fig.  249). 
Besides  these  two  handles  Samelsohn  (1882)  distinguishes  a  third 
-macular — bundle  that  includes  the  tibres  from  the  macula  lutea, 
the  seat  of  central  or  direct  vision. 
The  macular  bundle  again  divides 
into  two  groups  of  tibres :  one 
direct,  which  remains  on  the  same 
side  ;  one  crossed,  which  decussates 
in  the  chiasma  and  passes  to  the 
other  side.  Fig.  250  shows  the 
position  and  direction  of  the  three 
bundles  which  make  up  the  optic 
nerve. 

Partial  decussation  of  the  fibres 
of  the  optic  nerves  is  constant  in 
man  and  in  the  ape,  but  it  is  not 
general  in  the  vertebrate  series. 
The  existence  of  the  direct  bundle 
seems  to  be  associated  with  binocu- 
lar vision,  since  in  animals  whose 
eyes  are  directed  sideways,  so  that 
binocular  vision  is  impossible,  e.g. 
in  birds  and  fishes,  there  is  total 
decussation  of  the  optic  fibres. 
This  rule,  however,  has  certain  ex- 
ceptions :  in  the  rabbit,  dog,  and 
cat  there  is  a  partial  crossing, 
though  less  than  in  monkeys  and 
man,  but  in  the  mouse  and  guinea- 
pig,  according  to  Singer  and 
Miinzer,  decussation  is  complete. 
And  in  some  birds,  e.g.  the  owl,  in 
which  vision  is  binocular  owing 
to  the  position  of  the  eyes,  de- 
cussation is  still  complete. 

As  shown  in  Fig.  250,  the 
chiasma  also  contains  in  its  pos- 
terior parts  commissural  fibres, 
which  are  not  connected  with  the 
optic  nerves  and  eyes,  but  pass  from  the  internal  geniculate  body 
of  one  side  to  that  opposite ;  these  constitute  Gudden's  commissure, 
the  function  of  which  is  quite  unknown. 

The  optic  tract  runs  obliquely  backwards,  and  after  passing 
around  the  cerebral  peduncle  divides  into  two  branches  of  unequal 
size  (Figs.  189, 190,  pp.  327,  328).  The  lateral  branch  contains  all 
the  optic  fibres  of  the  direct,  crossed,  and  macular  bundles  ;  a  large 


FIG.  248.— Horizontal  section  of  left  hemi- 
sphere. (Flechsig.)  1,  anterior;  2,  pos- 
terior limb  ;  3,  genu  of  internal  capsule  ; 
4,  nucleus  lenticularis  ;  5,  nucleus  cauda- 
tus  ;  6,  optic  thalamus  ;  7,  anterior  horn 
of  lateral  ventricle;  8,  its  posterior  or 
occipital  horn ;  9,  septum  lucidum  and  its 
central  cavity  ;  10, 11,  fornix  ;  10',  corpus 
callosum ;  12,  claustrum ;  13,  external 
capsule;  14,  insula  ;  15,  Sylviuu  tissuif. 


494 


PHYSIOLOGY 


CHAP. 


part  of  these  fibres  terminate  in  the  external  geniculate  body ; 
others  which  pass  ventrally  and  laterally  to  the  geniculate  body 
enter  the  pulvinar ;  other  less  numerous  fibres  take  a  more 
medial  direction  and  reach  the  anterior  corpus  quadrigendnum. 
The  finer  internal  branch  of  the  optic  tract  is  the  continuation 
of  Gudden's  commissure,  and  therefore  contains  no  optic  fibres 
properly  so-called.  It  enters  the  internal  geniculate  body,  and 
through  it  reaches  the  posterior  quadrigeminal  body. 

III.  The  mid  -  brain  and  inter  -  brain  are  the  parts  of  the 
central  nervous  system  which  from  their  situation  in  the  higher 
animals  have  been  least  satisfactorily  studied  by  ordinary  physio- 
logical methods.  The  results  of  researches  on  the  lower  animals, 

in  which  the  methods  of  ablation 
succeed  fairly  easily,  are  not 
directly  applicable  to  mammals 
and  man,  in  which  these  segments 
of  the  brain  probably  have  a  less 
important  or  different  physio- 
logical value,  owing  to  the  pre- 
ponderating importance  and 
influence  of  the  other  centres, 
especially  the  cerebrum  and  the 
cerebellum. 

Owing  to  the  incomplete  and 
not  infrequently  incoherent  and 
contradictory  results  of  experi- 
ment, we  must,  therefore,  confine 
ourselves  to  a  critical  discussion 
of  the  most  definite  fundamental 
facts. 

The  observations  on  the  effects 
of  total  extirpation,  either  of  the 

fore -brain  alone,  or  of  the  inter-  and  hind -brain  in  different 
classes  of  vertebrates,  are  most  important  to  the  physiology  of 
these  three  parts  of  the  brain.  Certainly  they  do  not  exactly 
define  the  functions  of  the  individual  centres  contained  in  the 
parts  that  are  destroyed  or  preserved;  but  they  undoubtedly 
place  us  in  a  position  to  form  a  general  conception  of  their  physio- 
logical significance.  The  functions  lost  depend  on  the  segments 
destroyed ;  the  functions  that  remain,  on  the  surviving  segments. 
Arnpliioxus,  the  lowest  type  of  vertebrate,  has  no  true  brain, 
but  the  anterior  end  of  the  cord  is  slightly  enlarged  owing  to  the 
presence  of  a  sinus  ovalis  which  is  continued  into  the  vertebral 
canal.  This  represents  a  rudimentary  brain,  which  does  not 
differ  essentially  in  structure  from  the  rest  of  the  cord,  since  it 
consists  of  internal  white  matter  and  an  outer  layer  of  nerve- 
fibres  that  run  longitudinally. 


FIG.  249. — Comparative  extent  of  the  retinal 
areas  connected  with  the  direct  and  crossed 
bundles  of  the  optic  nerve,  in  fundus  of 
left  eye.  (Testut.)  n,  nasal  portion 
connected  with  the  crossed ;  t,  temporal, 
with  the  direct  bundle  ;  re,  x,  separating 
line  between  the  two  portions.  1,  sclerotic ; 
2,  choroid  ;  3,  retina  ;  4,  pupil ;  5,  fovea 
centralis  and  yellow  spot. 


IX 


MID-  AND  INTER-BE  AIN 


495 


Steiner  (1885)  divided  Amphioxus  into  two  transverse  halves, 
cephalic  and  caudal ;  both  parts  fall  immediately  to  the  bottom 
of  the  vessel,  and  lie  motionless,  but  if  after  a  few  minutes  the 
two  parts  are  stimulated  mechanically,  each  begins  to  move  with 
perfect  regularity,  maintaining  its  equilibrium  and  always 
advancing  head -end  forward.  If  the  animal  is  divided  into 
three  or  four  segments,  each  of  these,  after  a  suitable  interval, 
responds  by  locomotor  movements  to  external  stimuli.  Steiner 
concluded  from  these  observations  that  Amphioxus  consists  of  a 
number  of  metameres  which  in  no  way  differ  physiologically, 
and  that  it  has  no  true  brain  or  controlling  centre  for  general 
movements. 

Danilewsky  obtained  somewhat  different  results  from  his  later 


FIQ.  250. — Diagram  of  decussation  of  optic  nerve-fibres  in  chiasma.  (Vialet.)  1,  optic  nerve  on 
left ;  1',  on  right  side  ;  2,  1',  optic  tract  on  left  and  right  side  ;  a,  direct ;  6,  crossed  bundle  ; 
e,  macnlar  bundle,  partly  crossed,  partly  direct ;  d,  Gudden's  commissure. 

experiments.  After  bisecting  the  animal,  he  saw  that  the  anterior 
half  was  capable  of  executing  spontaneous  rhythmical  extension 
and  flexion  movements,  but  not  true,  locomotion ;  the  posterior 
half,  on  the  contrary,  remained  motionless  for  a  long  time.  Arti- 
ficial stimulation  elicited  motor  reactions  more  readily  from  the 
head  than  from  the  tail  end. 

When  the  head  is  cut  off,  spontaneous  movements  cease ;  the 
animal  remains  one  to  two  days  motionless  unless  artificially 
stimulated.  The  reflex  movements  are  normal  but  weak,  and 
excitability  seems  more  depressed  than  in  the  anterior  part  of  the 
divided  animal. 

From  these  and  similar  observations,  Danilewsky  concluded 
that  the  so-called  "  brain "  of  Amphioxus  contains  the  centres 
for  voluntary  movement,  that  is,  controlling  centres  for  all  the 
other  segments  of  the  neuraxon. 

In  fishes  in  general  the  brain  is  but  little  developed.      In 


496 


PHYSIOLOGY 


CHAP. 


Cyclostomes  and  Teleosteans  the  cerebral  mantle  consists  of  a  single- 
layer  of  ectodermal  cells. 

According  to  Steiner  no  disturbances  in 
the  movements  are  seen  after  excising  the 
fore-brain  of  Squalius  cephalus,  a  teleostean 
(Fig.  251);  the  animal  moves  as  though  it 
were  intact.  If  offered  a  living  worm  it 
chases,  catches,  and  swallows  it.  If  a  bit 
of  string  of  much  the  same  size  is  thrown 
into  the  water,  the  animal  comes  up  in  the 
same  way,  but  turns  off  lief  ore  catching  it, 
or  rejects  it  from  its  mouth.  It  is  able  to 
select  its  food,  and  recognises  its  companions 
that  have  not  been  operated  on.  Steiner's 
experiments  show  that  ablation  of  the  fore- 
^ner^SSSn:  brain  iii  this  class  of  fish  produces  no 


2) 


FIG.   251. — Brain  of  Sqtudius 


noticeable  disturbance ;   we  may,  therefore, 

brain ;  D,  myelencephalon     conclude     that      the      parts      of      the      liei'VOUS 

system  remaining  intact  suffice  for  the  com- 
plete execution  of  all  the  higher  nervous  functions. 

These  are  certainly  represented  in  the  mid-  and  'tweeii-brain. 
When  the  optic  lobes  are  excised,  according  to  Steiner,  the  animal 
loses  its  power  of  maintaining  equilibrium,  and  lies  on  its  side,  or 
back,  motionless,  with  relaxed  fins. 
But  the  return  of  spontaneous  move- 
ment, some  time  after  the  operation,  is 
not  excluded  :  Steiner  did  not  continue 
his  observations  long  enough. 

According  to  Sterner,  removal  of 
the  anterior  brain  in  Selachians,  as 
in  the  dog-fish  (Scyllium  canicula, 
Fig.  252),  causes  immobility  for  many 
hours  and  even  days,  unless  the  animal 
is  artificially  stimulated.  Bethe  was 
unable  to  confirm  this  observation, 
as  he  found  that  removal  of  the  fore- 
brain  did  not  abolish  spontaneous 
movements.  The  animals  certainly 
no  longer  feed  spontaneously,  but  FlG.  252.-Bram  ot 
this  is  due  not  to  ablation  of  the 
fore-brain,  but  to  destruction  of  the 
olfactory  lobes,  as  is  proved  by  the 
fact  that  excision  of  the  latter  alone 
produces  the  same  effect.  On  the 
other  hand,  attentive  observation  of  the  normal  dog-fish  shows 
that  it  is  largely  guided  by  the  sense  of  smell  in  seeking  its  food ; 
the  Squalius,  on  the  contrary,  by  the  visual  sense. 


(Steiner.)  en,  nasal  capsule;  bo, 
olfactory  bulb:  A,  prosencephalon; 
A',  optic  thalami  or  'tween-brain  ;  P>, 
optic  lobes  or  mid-brain  ;  C,  meten- 
cephalon  or  hind-brain  ;  D,  myelen- 
cephalon or  bulb,  from  which  the 
vagus  nerve  emerges. 


ix  MID-  AND  INTEK-BKATN  497 

Even  when  the  mid -brain  as  well  as  the  'tween -hrain  is 
destroyed,  there  is,  according  to  Bethe,  no  disturbance  of  the 
spontaneous  movements ;  the  dog-fish  is  still  capable  of  perfectly 
equilibrated  movements,  which  differ  in  no  way  from  those  of  the 
normal  animal. 

Marked  disorders  of  movements  only  appear  after  removal  of 
the  mid-  and  hind-brain;  the  results  of  Steiuer,  Loeb,  and  Bethe 
all  agree  on  this  point.  The  roof  of  the  mid-brain  is  not 
concerned  in  the  movements,  and  it  can  be  extirpated  on  one  or 
both  sides  without  producing  any  motor  disturbance,  but  accord- 
ing to  Steiuer  the  animal  no  longer  reacts  to  light  stimuli. 

O  •         i  » 

Removal  of  the  ventral  part  of  the  mid-brain,  on  the  contrary, 
produces  constant  motor  disturbances,  which  are  specially  marked 
after  unilateral  section. 

If  the  whole  of  the  right  side  is  divided  at  the  posterior  edge  of 
the  mid-brain,  the  animal  swims  directly  after  the  operation  in 
circular  progression  to  the  left.  Sometimes  these  circus  move- 
ments are  associated  with  rotation  round  the  long  axis. 

After  total  separation  of  the  mid-  and  hind-brain,  the  animal 
usually  exhibits  circus  movements  to  either  side,  but  if  the  lesion 
is  quite  symmetrical,  it  advances  in  a  straight  line,  and  turns  and 
changes  its  direction  only  on  coming  in  contact  with  the  vessel 
walls.  Moreover,  it  changes  from  the  horizontal  plane  into  an 
oblique  or  vertical  direction  only  under  external  stimulation,  and 
during  such  change  it  may  for  a  time  take  up  the  abnormal 
position  with  its  back  downwards,  though  finally  it  turns  over 
briskly  to  assume  the  abdominal  position.  To  conclude,  the  dog- 
fish without  its  mesencephalon  executes  perfectly  normal  swimming 
movements,  but  has  difficulty  in  altering  the  direction  of  its 
movements,  while  orientation  in  space  is  affected  but  not  lost. 
According  to  Bethe,  Steiner  is  mistaken  in  stating  that  the  animal 

O  " 

is  incapable  of  spontaneous  movements  under  these  conditions,  and 
that  artificial  stimuli  are  necessary  to  rouse  it  to  locomotion. 

IV.  We  must  next  consider  the  effects  of  destroying  the  brain 
in  Ampliilia,  and,  first  of  all,  in  the  frog  (Fig.  25.':!). 

Goltz1  assumed  (1869)  that  absence  of  voluntary  locomotor 
movements  was  the  most  important  point  in  which  the  animal 
that  had  lost  its  fore -brain  differed  from  the  intact  animal. 
Obviously,  however,  he  excised  the  optic  thalanius  or  mid-brain 
together  with  the  fore-brain.  When  the  functions  of  these  two 
separate  parts  of  the  brain  are  distinguished,  as  was  achieved  by 
Goltz'  pupil  M.  Schrader  (1887),  the  results  are  very  different,  for 
if  the  optic  thalami  are  interfered  with  as  little  as  possible  the 
animal  differs  in  no  respect  from  the  intact  animal.  The  frog 
moves  spontaneously,  even  when  placed  in  an  unnatural  position ; 

1  In  his  monograph,  "  JBeitrage  zur  Lehre  von  den  Funktionen  dcr  Nervenzentrcn 
des  Frosches." 

VOL.  Ill  2  K 


498 


PHYSIOLOGY 


CHAP. 


swims  normally  ;  buries  itself  at  the  beginning  of  winter;  if  slowly 
lowered  by  a  screw  adjustment  into  water  begins  to  swim  at  once 
like  an  intact  frog ;  and  is  capable  when  the  hibernating  season  is 
over  of  feeding  itself  like  a  normal  frog,  by  catching  the  flies  that 
come  into  its  vessel. 

That  the  senses,  particularly  vision,  remain  intact  in  the  frog 
after  removal  of  the  fore-brain  had  already  been  demonstrated  by 
Desmoulins,  Magendie,  Longet,  and  others,  though  Flourens  stated 
the  contrary.  When  stimulated  to  move,  these  animals  are 
capable  of  avoiding  the  obstacles  they  meet.  Blanschko  repeated 

these  researches  under  H.  Munk 
(1880),  and  found  that  the  frog 
deprived  of  its  hemispheres  is 
capable  of  adapting  its  move- 
ments to  different  positions, 
and  to  the  size  and  nature  of 
obstacles,  and  to  vary  them 
suitably  when  the  power  of 
moving  is  interfered  with,  or 
the  position  of  the  obstacles 
changed.  Such  frogs  are  not 
merely  not  blind  in  any  ab- 
solute sense,  but  they  are  not 
even  "psychically  blind";  they 
retain  not  only  sensations  but 
also  perceptions  and  visual 
images  like  the  intact  frog. 
The  other  senses  are  also  un- 
affected, with  the  exception,  of 
course,  of  the  sense  of  smell, 

Fit-.    253. -Frog's    brain  —  enlarged    four    times.      sillCe       this       depends       Oil       the 
(Loeb.)      G.C.,  prosencephalon ;    Th.O.,    optic     f.lfflp^-m,v    Vmlllcl     whinli    nvp    PY 
thalanms:   Lnb.  opt.,  optic  lobes;   P. C.,  cere-       uiaGtOiy  IDS,   WHICH    aiC    6X- 

beiium,  showing  medniia  obiongata  below,    tirpated  with  the  fore-brain. 

whence  issue  the  cranial  nerves.  TTT-I 

When  the  optic  tlialaim  are 

totally  destroyed  as  well  as  the  hemispheres,  the  animal,  according 
to  Schrader,  remains  motionless,  but  this  state  of  depression 
partially  wears  off.  If  the  animal  is  examined  some  months 
after  the  operation,  at  the  close  of  the  winter  sleep,  when  the 
lesion  is  perfectly  healed,  it  is  seen  that  on  gradually  lowering  it 
by  means  of  the  screw  into  water  it  does  not  swim  as  when  the 
hemispheres  alone  are  removed,  but  floats  motionless  on  the 
surface.  On  repeating  Goltz'  experiment,  in  which  the  animal  is 
made  to  walk  up  and  down  an  inclined  plane  (Fig.  254),  the 
frog  without  a  mid-brain  moves  its  head  only,  and  makes  no 
attempt  to  climb  up  ;  if  the  plane  is  too  much  sloped  the  creature 
crawls  down  instead  of  up,  viz.  behaves  in  a  manner  exactly 
opposite  to  that  of  the  frog  that  has  lost  its  hemispheres  only. 


IX 


MID-  AND  INTER-BRAIN 


499 


The  effects  of  excising  the  whole  of  the  mid-braiu  again  differ 
slightly,  according  to  Schrader,  from  the  results  obtained  by  Goltz 
and  Steiner.  When  the  medulla  oblongata  is  uninjured  by  this 
operation,  the  mutilated  frog  preserves  its  quack -reflex,  and  the 
characteristic  swim-reflexes,  the  centre  for  which  lies  not  in  the 
optic  lobes  (Goltz  and  Steiner),  but  in  the  bulb.  But  if  the 
animal  is  left  undisturbed  without  external  stimulation,  the  sup- 
pression of  the  spontaneous  movements,  according  to  Schrader, 
is  even  more  definite  and  complete  than  when  only  the  fore-  and 
mid-brain  are  removed.  Evidently  this  depends  not  on  the 
removal  of  the  mid-brain  as  held  by  Goltz  and  Steiner,  but  on  the 
functional  depression  of  the  locomotor  centre  in  the  bulb,  due  to 


FII;.  254. — Goltz'  experiment  on  frog  deprived  of  its  cerebral  hemispheres,  and  made  to  climb  up 
and  down  an  inclined  plane.  On  the  left  the  frog  is  seen  ascending  an  inclined  board  ;  in  the 
(.entre  it  has  climbed  to  the  top  of  the  upright  board;  on  the  right  it  is  coming  down  the 
opposite  slope. 

operative  traumatism.  As  early  as  1883  Fano  demonstrated  that  if 
the  experiment  were  repeated  on  the  toad  (Bufo  viridis),  which  is 
very  near  the  frog  in  the  zoological  scale,  but  is  far  more  resistent 
and  less  excitable,  a  similar  result  is  obtained  as  with  the  marsh 
tortoise  (see  p.  413).  After  destroying  the  whole  mid -brain 
(including  of  course  the  'tween-  and  fore-brain),  automatic  loco- 
motion can  be  seen  in  this  animal  as  readily  as  in  the  tortoise. 
But  while  in  the  latter  the  locomotor  movements  may  be  con- 
tinuous, in  the  toad  they  are  nearly  always  periodic,  viz.  in  the 
form  of  groups  of  locomotor  movements  separated  by  pauses. 
Toads,  like  tortoises,  when  deprived  of  the  mid-brain,  recover  their 
normal  position  by  appropriate  movements  if  turned  over  on 
the  back. 

Fano's  studies  on  the  marsh  tortoise  are  of  great  importance, 
as  regards  the  results  of  removing  the  fore-  and  mid-brain.  They 
may  be  summarised  as  follows :  Removal  of  the  cerebral  hemi- 
spheres (Fig.  255)  does  not  apparently  deprive  the  animal  of 
any  of  the  faculties  attributed  to  the  fore  -  brain.  It  moves 


500 


PHYSIOLOGY 


CHAP. 


spontaneously,  sees  quite  well,  avoids  obstacles,  responds  ade- 
quately to  the  impressions  it  receives,  and  behaves  in  all  respects 
like  the  normal  tortoise.  The  only  difference  is  that  it  moves 
slower,  is  less  lively,  and  shows  less  initiative.  Still  its  actions 
are  certainly  not  merely  reflex,  and  probably  arise  in  the  optic 
thalami.  Fano,  in  fact,  demonstrated  not  only  by  removal  of 
the  hemispheres,  but  also  by  stimulation  of  the  thalami,  that 
the  latter  play  a  considerable  part  in  the  evolution  of  the 
voluntary  acts.  The  optic  thalami,  like  the  cerebral  hemispheres, 
react  to  electrical  stimulation  by  groups  of  locomotor  movements 
which  have  all  the  character  of  voluntary  movements,  which 
is  not  the  case  on  electrical  stimulation  of  other  parts  of  the 
nervous  system. 

When  the  optic  thalami  as  well  as  the  hemispheres  are  excised 
in  a   tortoise,-  the   constant    result  is  that    spontaneous    activity 

ceases,  and  the  animal  becomes  absolutely 
motionless.  It  remains  for  days  in  the 
position  in  which  it  is  placed  without 
manifesting  any  reaction.  Its  spon- 
taneous activity  is  not  abolished,  but 
merely  inhibited,  by  the  mid-brain,  for 
we  have  seen  that  on  removing  the  latter 
automatic  locomotion  reappears. 

On    the   strength    of    these    results, 
which  were  confirmed  by  Bickel,  Fano 
credited  the  mid-brain  with  a  continuous 
inhibitory    action    upon    the  automatic 
the  medulla.     According  to 
central    mechanism   of    the 
movements   of    the    tortoise 

the 


.A 


Fin.  '25'>. — Brain  of  Kmys 

seen  in  situ,  after  removing  the 
top  of  the  skull.  (Fano.)  A, 
prosencephalon  ;  B,  inescnceplia- 
lon  ;  (.',  metencephalon  ;  D,  my- 
elencephalon. 


centres  of 

Fano,    the 

voluntary 

consists  in  inhibition  by  the  fore-  and  'tween -brain  of 
constant  tonic  inhibition  exerted  by  the  mid-brain.  So  soon  as 
the  fore-brain  depresses  mesencephalic  inhibition  in  voluntary 
activity,  the  automatic  activity  of  the  bulb  spreads  along  the 
efferent  paths  determined  by  heredity  or  acquired  by  habit, 
making  use  of  the  spinal  mechanisms  and  the  energy  accumulated 
therein.  This  schematic  concept  undeniably  agrees  with  the 
phenomena  exhibited  by  the  marsh  tortoise ,  but  its  applicability 
to  other  amphibia  and  reptiles,  and  still  more  to  other  classes  of 
vertebrates,  is  very  doubtful. 

V.  Eolando  (1809)  first  observed  the  effects  of  removing  the 
cerebral  hemispheres  in  birds,  but  he  confined  himself  to  observa- 
tions made  shortly  after  the  operation.  Flourens  (1822)  used 
his  experiments  on  pigeons  as  the  basis  of  his  general  theory  of 
the  functions  of  the  cerebral  hemispheres.  He  experimented  on 
other  classes  of  vertebrates  with  the  single  object  of  controlling 
and  generalising  from  the  data  acquired  on  pigeons,  which 


ix  MID-  AND  INTER-BRAIN  501 

became  the   starting-point  of  all   subsequent  researches   on  the 
cerebral  centres  down  to  the  present  day. 

According-  to  the  classical  description  of  Flourens,  the  pigeon 
deprived  of  its  cerebral  hemispheres  is  an  animal  condemned  to 
perpetual  dreamless  sleep.  None  of  its  senses  are  active ;  it 
remains  motionless  wherever  it  is  placed;  it  never  moves 
spontaneously,  and  stays  in  the  sleeping  posture  (Fig.  256).  If 
stimulated  it  seems  to  wake,  opens  its  eyes,  shakes  its  wings, 
moves  a  little,  and  then  relapses  into  slumber.  If  thrown  into 
the  air  it  flies,  but  fails  to  avoid  obstacles.  It  retains  the  capacity 
of  keeping  its  equilibrium  both  while  standing,  and  in  moving 
when  stimulated.  It  has  completely  lost  the  faculty  of  feeding 


FIG.  256. — Pigeon  deprived  of  its  cerebral  hemispheres  in  position  described  by  Flourens. 

(From  a  photograph  by  Dalton.) 

by  itself,  so  that  it  will  starve  in  front  of  a  heap  of  corn.  It 
shows  no  fear  when  any  one  approaches  or  threatens  it,  nor  any 
inclination  for  the  other  sex.  It  digests  well  when  fed,  and  can 
consequently  survive  for  a  long  time.  It  digests  sleeping;  and 
only  makes  a  few  aimless  steps  occasionally,  owing  to  fatigue  in 
the  legs.  In  short,  the  pigeon  that  has  lost  its  fore-brain  has  lost 
all  its  perceptions,  all  its  instincts,  all  its  intellectual  faculties. 

But  none  of  the  physiologists  who  repeated  Flourens'  experi- 
ment were  able  to  convince  themselves  of  the  accuracy  and 
constancy  of  his  description,  nor  that  the  ablation  of  the  hemi- 
spheres sufficed  to  produce  total  abolition  of  sensation  in  general, 
and  more  particularly  of  vision  and  hearing.  They  found  that 
pigeons  with  no  hemispheres  were  capable  of  avoiding  obstacles 
when  they  moved,  of  following  the  movements  of  a  lighted  candle 
with  their  head,  of  starting  violently  at  loud  noises,  as  the  report 
of  a  pistol — in  a  word,  gave  obvious  signs  of  seeing  and  hearing. 


502  PHYSIOLOGY  CHAP. 

In  this  connection  the  experiments  of  Magendie  (1825),  Bouillaud 
(1850),  Longet  (1847),  Keuzi  (1863),  and  Lussana  and  Lemoigne 
(1871)  are  highly  important.  It  was  the  observations  of  these 
authors  as  a  whole  that  laid  the  foundation  of  the  generally 
accepted  psychological  distinction  between  crude  sensations  or 
simple  psychical  impressions  on  the  central  sense-organs,  and  per- 
ceptions or  sensations  elaborated  by  the  intellectual  centres  and 
referred  to  the  external  world.  The  former  are  also  termed 
unconscious  or  passive  sensations,  the  latter  conscious  or  active 
sensations.  Only  the  last  are  dependent  on  the  cerebral  hemi- 
spheres, while  the  first  depend  on  the  thalamencephalon,  mid- 
brain,  the  pons,  medulla  oblongata,  and  cord. 

To  explain  the  discrepancy  between  the  results  of  Flourens 
and  those  of  Magendie,  Longet  and  Eenzi,  it  is  not  enough  to 
insist  on  the  inhibitory  effects  of  traumatism,  since  we  know  that 
Flourens — unlike  Eolando — succeeded  in  keeping  decerebrated 
pigeons  alive  for  a  long  time  and  in  observing  them  for  months. 
Clearly  he  must  have  excised  the  whole  or  greater  part  of  the 
optic  thalami  which  represent  the  'tween-brain,  along  with  the 
hemispheres.  Longet  was  the  first  who  attached  great  importance 
to  the  exact  delimitation  of  the  cerebral  lesions,  and  he  obtained 
animals  deprived  of  their  hemispheres  only,  without  injury  to  the 
optic  thalami. 

H.  Munk  (1883)  resumed  the  experiments  on  pigeons,  with 
the  object  of  deciding  the  old  controversy  between  Flourens,  who 
concluded  that  the  pigeon  deprived  of  its  cerebral  lobes  "  a  perdu 
tous  ses  sens,"  and  his  successors,  who  held  with  Cuvier  "que 
les  lobes  cer^braux  sont  le  receptacle  ou  toutes  les  sensations 
preunent  une  forme  distincte,  et  laissent  des  souvenirs  durables." 

As  we  shall  presently  see,  H.  Munk  in  his  experiments  on 
dogs  and  monkeys  came  to  the  conclusion  that  the  destruction  of 
certain  segments  of  the  cerebral  cortex  produced  total  blindness 
in  these  animals.  If  what  happens  in  dogs  can  also  be  observed 
on  birds,  Munk  thought  it  certain  that  complete  extirpation 
of  both  hamispheres  must  produce  results  similar  to  those  so 
excellently  described  by  Flourens,  who  alcne  had  made  observa- 
tions on  completely  decerebrated  birds.  The  error  would  then, 
according  to  Munk,  lie,  not  with  Flourens,  but  with  his  successors, 
by  whom  the  cerebral  hemispheres  of  the  pigeons  were  only 
destroyed  incompletely.  This  operation  is  more  difficult  than 
any  other  to  carry  out  accurately  on  account  of  the  uncontrollable 
haemorrhage. 

Eighty  per  cent  of  Munk's  pigeons  perished.  Of  the  twenty- 
five  that  survived,  four  only  were  found  at  the  post-mortem  to 
have  been  completely  operated  on.  These  had  been  subjected  to 
repeated  experiments  for  months  after  the  operation.  They  were 
totally  blind,  and  behaved  exactly  as  Flourens  described.  If 


ix  MID-  AND  INTEK-BEATN  503 

l>l;iced  on  the  edge  of  a  table  they  often  went  over  it  and  fell  to 
the  ground.  They  stumbled  against  obstacles;  the  brightest 
light  anil  blackest  dark  produced  no  effect  other  than  a  pupil 
reaction  (myosis  or  inydriasis).  If  flung  into  the  air  they  always 
fluttered  down,  and  on  reaching  the  ground  continued  to  flap 
their  wings  for  some  time  before  they  became  quiet ;  they 
blundered  against  obstacles  during  their  flight,  and  if  this  was 
impeded,  tumbled  to  the  ground. 

In  seeking  to  account  for  the  disparity  between  these  results 
of  Munk  and  those  previously  described  with  no  less  care  by 
Longet,  we  were  led  to  think  (1885)  that  the  four  pigeons 
examined  by  Munk  had  become  blind  from  the  effects  of  degenera- 
tion descending  to  the  thalami  and  optic  lobes,  which  Munk  did 
not  examine  directly.  It  is  certain  that  the  more  recent  experi- 


Fio.  -257. — A,  brain  of  normal  pigeon — from  nature,  enlarged  \.  a-c,  brain  of  a  pigeon  in  which 
Schiuder  had  extirpated  both  hemispheres,  sparing  the  optic  thalami  and  optic  lobes— also 
magnified  J.  a,  from  behind  ;  li,  from  front ;  c,  from  the  side. 

merits  of  Schrader  (1889),  due  to  the  effects  of  total  destruction 
of  the  cerebral  hemispheres  of  pigeons,  accurately  performed,  pro- 
duced a  perfectly  different  set  of  symptoms  from  that  described 
by  Munk. 

Schrader  lost  75  per  cent  of  the  animals  operated  on,  fourteen 
pigeons  survived.  Many  of  these  were  killed  after  four  months, 
after  they  had  been  closely  and  frequently  examined.  Some  died 
in  the  fourth  or  fifth  week  with  signs  of  progressive  weakness, 
probably  the  effect  of  descending  degeneration.  The  post-mortem 
examination  performed  by  Recklinghausen  showed  completely 
successful  ablation  of  the  hemispheres  with  no  lesion  of  the  optic 
thalami. 

In  the  first  three  to  four  days  after  the  operation,  according 
to  Schrader,  there  is  the  condition  of  sleep  and  absolute  immobility 
described  by  Eolando  and  Flourens.  After  this  period  the  animals 
begin  to  move  about  in  the  laboratory,  very  slowly  at  first  and 
quicker  by  degrees  till  they  recover  their  normal  gait.  This 
active  movement  cannot  be  ascribed  to  traumatic  irritation,  since 


504  PHYSIOLOGY  CHAP. 

the  periods  of  activity  alternate  regularly  with  those  of  rest  and 
quiet  sleep  during  the  night. 

From  the  outset  these  spontaneous  movements  are  guided  by 
visual  sensations,  for  the  animals  are  capal  >le  of  avoiding  obstacles 
of  any  kind  as  perfectly  as  normal  pigeons.  The  movements 
are  regulated  perfectly  by  tactile  sensations,  and  all  changes  of 
equilibrium  are  exactly  compensated.  Sounds  and  noises,  on  the 
contrary,  have  no  influence  on  the  course  of  the  movements, 
although  hearing  is  not  lost,  since  the  sound  of  striking  a  match 
makes  the  pigeon  start. 

The  brainless  pigeon  can  easily  be  inhibited  in  its  movements. 
If  it  is  touched  lightly,  or  taken  up  and  set  down  again,  it  will  at 
once  throw  its  head  back,  ruffle  its  feathers,  and  sleep. 

By  special  experiments  it  has  been  shown  that  the  decerebrated 
pigeon  is  capable  of  making  definite  purposeful  movements. 
When,  for  instance,  it  is  set  on  a  perch  that  hardly  supports  its 
feet,  6  feet  above  the  floor  of  an  empty  room,  it  decides  after 
long  hesitation  to  fly,  and  drops  to  the  ground  in  a  gentle  curve. 
If,  again,  a  horizontal  support  is  placed  at  the  same  height  a 
few  yards  away,  the  bird  much  sooner  resolves  to  leave  its  uncom- 
fortable perch,  and  flies  to  the  firmer  support.  If  a  stool  is  then 
set  a  yard  away  from  the  bough,  the  pigeon  drops  first  on  to  the 
stool  and  then  to  the  ground.  But  while  capable  of  flying  down, 
it  never  attempts  to  fly  up.  It  seems  doubtful  whether  it  is  able 
to  feed  itself. 

The  brainless  pigeon  shows  by  its  voice  and  movements  that 
it  is  capable  of  sexual  excitation,  but  it  is  indifferent  to  the 
presence  of  the  female.  Nor  does  she  in  turn  trouble  about  the 
young  birds  that  surround  her  and  follow  her.  Decerebrated 
pigeons  are  equally  destitute  of  the  sense  of  fear;  their  move- 
ments are  governed  by  the  size,  form,  situation  of  surrounding 
objects,  but  to  these  themselves  they  remain  entirely  indifferent, 
whether  they  be  animate  or  inanimate,  friend  or  foe. 

In  conclusion,  it  can  be  affirmed  from  Schrader's  observations 
that  the  fore-brain  of  the  pigeon  is  neither  a  sensory  nor  a  motor 
centre,  since  its  total  absence  causes  neither  loss  of  movement  nor 
of  sensation.  But  the  decerebrated,  as  compared  with  the  normal, 
pigeon  shows  marked  defects  which  are  most  readily  explained 
as  the  loss  of  memory  impressions  of  previous  sensations,  owing 
to  loss  of  intelligence  properly  so-called.  All  the  actions  of 
pigeons  without  fore-brains,  however  varied  and  complex,  show  a 
regular  and  definite  direction.  They  have  the  character  of  the 
responsive  movements  of  Goltz,  that  is,  they  are  to  a  large  extent 
determined  reflexly  by  the  excitations  which  come  from  the 
periphery  to  the  sensory  centres  of  the  thalami,  optic  lobes,  and 
medulla  oblongata.  As  a  whole,  they  give  an  idea  of  the  very 
important  functions  dependent  on  the  remaining  portions  of  the 


ix  MID-  AND  INTEE-BEAIN  505 

brain.  In  the  absence  of  adequate  researches,  it  is  not  at  present 
possible  to  distinguish  which  portion  of  these  functions  belong  to 
the  'tween-] train,  hut  it  may  be  assumed  with  great  probability 
that  Flourens'  classical  description  of  the  pigeon  destitute  of 
sensation  and  spontaneous  movements  corresponds  with  what  is 
observed  when  the  inter  -  brain  is  destroyed  along  with  the 
fore-brain.  Certain  observations  made  by  Schrader  on  pigeons 
in  which  ablation  of  the  hemispheres  was  associated  with  very 
extensive  lesions  of  the  optic  thalami,  tend  to  confirm  this  opinion. 
He  found  that  under  these  conditions  the  animal  collided  with 
obstacles,  and  was  unable  promptly  to  correct  slight  passive  dis- 
placements of  the  extremities. 

VI.  The  effects  of  total  destruction  of  the  cerebrum  in  small 
mammals  was  frequently  investigated  by  Flourens  ;  but  it  was 
reserved  for  later  observers  to  give  an  accurate  account  of  them. 

On  this  point  again  the  results  obtained  by  H.  Munk  are  in 
fundamental  contradiction  with  those  of  other  workers.  He 
experimented  on  rabbits,  guinea-pigs,  and  rats.  The  first, 
according  to  Munk,  survive  at  most  two  days ;  guinea-pigs  and 
rats  four  days.  Death  is  not  due  to  inanition,  because  they  lose 
only  7  to  20  per  cent  of  their  weight ;  but  to  inflammatory  reaction 
and  progressive  softening  of  the  remaining  parts  of  the  brain. 

In  the  first  stage  the  decerebrated  animal  remains  motionless 
and  passive  like  Flourens'  pigeons.  In  the  second  stage  the 
animal  makes  a  few  rare  isolated  movements,  occasionally  a  few 
steps  to  left  or  right.  Eespiration  is  quicker  and  deeper,  and 
after  a  few  hours  the  animal  begins  to  walk.  The  third  stage  is 
characterised  by  periodic  walking,  such  as  Fano  described  in  the 
brainless  tortoise.  In  rabbits,  guinea-pigs,  and  rats,  when  deprived 
of  the  prosencephalon,  the  pupil  reflexes  persist  but  the  animals 
are  not  otherwise  affected  by  light.  In  walking  they  collide  with  ^ 
every  obstacle  they  meet,  go  straight  ahead  without  altering  their 
course,  and  run  up  against  the  wall  of  the  room,  or  fall  off  the 
table,  in  short,  they  show  complete  lack  of  the  visual  sense. 

Widely  different  and,  as  regards  vision,  exactly  contrary 
results  were  obtained  by  Christian!  in  rabl  >its  after  excision  of  the 
cerebral  hemispheres,  including  the  corpora  striata,  but  sparing 
the  optic  thalami.  Directly  after  the  operation  the  animal 
remains  motionless,  but  it  escapes  if  excited.  If  kept  awake  it  is 
capable  of  spontaneous  movement,  but  relapses  into  sleep  if  left  \ 
alone.  In  provoked  or  spontaneous  movements  nothing  abnormal 
occurs ;  the  animal  avoids  obstacles  without  touching  them  with 
its  nose,  and  is  even  capable  of  jumping  up  and  climbing  without 
stumbling.  Obviously,  therefore,  its  movements  are  guided  by 
the  sense  of  vision. 

If  in  addition  to  the  prosencephalon  the  thalamencephalon 
also  is  extirpated  or  profoundly  injured,  Christian!  noted  that  the 


506 


PHYSIOLOGY 


CHAP. 


rabbit  is  not  capable  of  maintaining  equilibrium  either  in  standing 
or  in  walking. 

The  observations  on  rabbits  and  other  small  mammals  were 
only  made  during  one  to  two  days,  beyond  which  he  was  unable  to 
keep  them  alive.  They  are  important  as  showing  that  the  motor 
and  sensory  functions  which  persist  can  be  carried  out  independently 
of  the  parts  of  the  brain  that  were  destroyed,  but  they  do  not 
permit  us  to  ascertain  how  far  the  loss  of  function  is  due  to 
removal  of  the  organs,  or  to  the  effects  of  operative  traumatism. 

All-important  and  unique  in  the 
Literature  of  the  subject  are  the  re- 
searches and  observations  of  Goltz 
(1892)  on  three  brainless  dogs  which 
he  succeeded  in  keeping  alive  for  some 
time.  The  first  lived  fifty-seven  days, 
the  second  ninety-two  days,  the  third 
was  killed  by  bleeding  after  eighteen 
months.  The  right  hemisphere  was 
destroyed  in  a  single  operation ;  the 
left  in  three  operations ;  the  frontal 
and  parietal  lobes  were  first  removed, 
next  the  temporal  lobe,  and  lastly  the 
occipital. 

In  the  third  decerebrated  dog,  on 
which  Goltz  made  minute  observa- 
tions which  he  carefully  recorded,  the 
post-mortern  examination  by  Schrader 
showed  as  follows  (Fig.  258) :  medulla 
oblongata  and  cerebellum  perfectly 
normal,  but  the  pyramids  had  dis- 
appeared ;  the  left  anterior  quad- 
rigeiniiial  body  was  much  flattened, 

FIG.  258.— Brain  from  Goltz  celebrated  «  ,  ,  .    , 

"brainless  dog."    (Explanation  in    shrunken,     soitened,     and     greyisn- 

yellow  in  colour,  and  the  left  pos- 
terior quadrigeminal  body  showed  the  same  change  to  a  slight 
degree.  The  rest  of  the  left  fore-brain  with  the  optic  thalamus 
measured  1'7  cm.  in  length;  it  consisted  of  a  softened  greyish 
mass,  which  was  mainly  the  remains  of  the  corpus  striatum 
and  thalamus.  The  remains  of  the  right  fore -brain  with  the 
thalamus  of  that  side  measured  3  cm.  in  length.  Besides  the 
degenerated  portions  of  the  corpus  striatum  and  thalamus,  a  soft 
brown  residue  of  the  cornu  Ammonis  could  be  seen.  The  right 
optic  nerve  was  smaller  than  the  left  and  grey  in  colour,  while 
the  colour  of  the  left  was  normal. 

The  phenomena  manifested  by  Goltz'  "brainless  dog"  are 
therefore  characteristic  of  an  animal  deficient  not  only  in  the 
entire  cortex  of  the  fore-brain,  but  also  in  a  large  part  of  the 


ix  MID-  AND  INTER-BRAIN  507 

basal  ganglia  and  a  lesser  extent  of  the  corpora  quadrigemina. 
The  phenomena  of  deficiency  observed  in  this  animal  cannot  be 
attributed  exclusively  to  the  fore -brain,  but  are  partly  due  to 
damage  of  the  thalaniencephalon  and  mid -brain  as  well.  To 
summarise  the  phenomena  observed  by  Goltz  :— 

On  the  third  day  from  the  last  cerebral  ablation,  the  animal 
began  to  walk  of  itself  in  the  room.  Its  capacity  for  locomotion 
increased  rapidly,  so  that  after  a  month  it  was  able  to  climb  a 
plane  sloping  20°  without  difficulty. 

After  a  few  months  there  was  marked  disturbance  of  nutrition, 
with  progressive  emaciation  of  the  posterior  half  of  the  body.  By 
means  of  careful  feeding,  however,  this  progressive  emaciation  was 
partially  repaired  and  arrested,  though  the  stability  of  movement 
which  the  animal  exhibited  a  few  weeks  after  the  last  operation 
did  nou  return. 

According  to  Goltz,  the  cause  of  this  emaciation  was  to  be  attri- 
buted partly  to  the  fact  that  the  animal  moved  continually  within 
its  cage,  so  that  its  intervals  of  rest  and  sleep  were  less  than  in 
normal  dogs ;  partly  also  to  imperfect  thermal  regulation,  which 
made  it  give  off  more  heat  than  the  normal.  Otherwise  it  slept  ' 
curled  up  like  a  normal  dog ;  it  breathed  more  rapidly  when  kept 
in  a  heated  atmosphere,  and  shivered  and  trembled  in  a  cold  place. 

Digestion   was   normal ;    there  was   no   foul  smell   from  the  \ 
mouth,  and  the  faeces  were  normal  in  colour  and  consistency.     The 
urine  never  contained  sugar  or  protein  after  the  first  few  days 
from  the  final  operation. 

During  the  eighteen  months  of  observation  the  animal  never 
evinced  any  sign  of  sexual  desire. 

After  emaciation  was  arrested  the  animal  moved  fairly 
steadily  on  uneven  ground ;  but  it  readily  slipped  on  a  smooth 
floor,  though  it  was  capable  of  recovering  itself  without  aid.  It 
never  walked  on  the  dorsa  of  its  feet.  If  its  limbs  were  placed  in 
an  abnormal  position,  it  reacted  at  once  so  as  to  correct  this.  If 
it  was  placed  upright  on  a  table  and  the  support  suddenly  with- 
drawn from  one  leg  by  pulling  away  a  leaf  of  the  table,  the  leg 
dropped  a  little,  but  was  at  once  drawn  up  without  loss  of 
equilibrium.  After  hurting  one  of  its  hind-legs,  it  trotted  about 
on  the  three  sound  limbs,  and  spontaneously  held  up  the  injured 
one.  These  phenomena  showed  that  the  muscular  and  cutaneous 
senses  were  not  entirely  lost  after  destruction  of  the  hemispheres. 

Although  the  regulation  of  the  movements  was  maintained, 
the  animal  was  never  capable  of  finding  the  place  at  which  any 
one  had  touched  it.  II',  for  instance,  its  left  hind-leg  was  pulled, 
it  turned  its  head  sharply  to  the  point  of  contact,  and  tried  to 
snap,  but  seldom  succeeded  in  reaching  the  hand. 

The  sense  of  touch  was  considerably  blunted.  On  blowing 
through  a  glass  tube  between  the  hairs  of  the  dorsuni  of  the  foot  or 


508  PHYSIOLOGY  CHAP. 

near  the  nose  the  animal  did  not  react,  hut  the  inside  of  the  ear 
remained  sensitive  to  this  stimulus.  The  animal  reacted  vigorously 
to  stronger  stimuli,  and  awakened  if  asleep.  If  pinched  or  pricked 
at  any  point  of  the  skin  while  wandering  about,  it  showed  annoy- 
ance by  its  movements  and  voice,  or  by  biting. 

The  sense  of  taste  remained  ;  if  offered  two  portions  of  meat  in 
two  dishes,  one  dipped  in  milk,  the  other  in  solution  of  quinine 
sulphate,  it  chewed  and  swallowed  the  first,  and  rejected  the 
second  after  taking  it  into  its  mouth  and  biting  it. 

The  sense  of  smell  was  of  course  absent,  since  the  olfactory 
lobes  had  been  destroyed,  but  the  nasal  branches  of  the  trigeminus 
sufficed  to  produce  a  reaction  in  presence  of  ammonia  vapours, 
and  sneezing  with  tobacco-smoke. 

The  sense  of  hearing  was  much  reduced ;  the  blare  of  a 
trumpet  was  required  to  arouse  it  from  sleep. 

In  regard  to  vision  it  was  noticed  that  the  pupils  of  both  eyes 
contracted  sharply  to  light,  and  if  a  flash  of  light  from  a  dark 
lantern  was  suddenly  turned  on  the  animal  in  the  dark,  it  shut 
its  eyes  and  turned  its  head  away.  On  the  other  hand,  it  was 
unable  to  avoid  obstacles  by  sight.  The  fixed  stare  of  its  expres- 
sionless eyes  lasted  unchanged  till  death,  even  when  threatening 
gestures  were  made  or  a  cat  or  rabbit  was  brought  in  front  of  its 
eyes.  Still,  according  to  Goltz,  it  could  not  be  termed  wholly 
blind,  as  it  shut  its  eyes  and  turned  its  head  aside  in  presence  of 
light. 

The  intelligence  of  the  animal  was  very  much  reduced.  It 
remained  mute  and  indifferent  alike  to  caresses  and  threats.  Yet 
it  did  not  lose  its  sense  of  hunger  and  instinct  to  feed.  When 
hungry  it  moved  about  in  its  cage,  put  its  tongue  out  rhythmically, 
and  made  mastication  movements  with  its  jaws.  If  set  on  a  table 
with  a  dish  of  milk  and  pieces  of  meat  near  its  nose,  it  began  at 
once  to  lap,  chew,  and  swallow  with  evident  satisfaction,  like  an 
ordinary  dog.  In  proportion  as  the  stomach  filled,  the  mastication 
movements  became  slower,  and  finally,  when  it  had  taken  500 
grins,  flesh  and  290  grms.  milk,  it  left  off  eating.  The  animal  was 
incapable  of  finding  the  way  to  its  food ;  if  the  meals  had  not  been 
placed  in  front  of  its  nose  it  would  have  died  of  inanition  in  the 
presence  of  abundance  of  food,  like  Flourens'  pigeon. 

Goltz'  dog,  accordingly,  differs  from  the  decerebrated  fishes 
and  frogs  of  Steiner  and  Schrader,  which  captured  worms  and 
flies  ;  but  it  must  not  be  forgotten  that  in  this  animal,  not  only 
was  the  fore-brain  absent,  but  almost  all  the  thalamencephalon, 
and  part  of  the  mid-brain  as  well.  "  A  dog  with  intact  'tween- 
brain  and  normal  optic  nerves  would  undoubtedly  exhibit  more 
phenomena  than  our  dog,  notwithstanding  the  loss  of  the  cerebral 
cortex  and  corpora  striata  "  (Goltz). 

This  prediction  has  been  verified  by  the  work  of  Eothmann, 


ix  MID-  AND  INTEE-BEAIN  500 

given  iu  one  of  his  earliest  communications  to  the  Medical  Society 
of  Berlin  in  1911.  He  exhibited  a  dog  operated  on  at  two 
sittings,  two  years  and  three  months  previously,  the  two  cerebral 
hemispheres  being  completely  removed  with  the  exception  of 
certain  parts  of  the  base,  which  had  to  be  spared  in  order  not  to 
damage  the  chiasma  and  optic  tract. 

After  becoming  emaciated,  it  recovered  its  initial  weight  of  12 
kgrms.  It  began  to  walk  after  two  days ;  in  a  couple  of  weeks  it 
could  feed  itself.  Its  mode  of  barking  and  eating  was  perfectly 
normal.  After  a  few  months  it  was  capable  of  walking  and 
running.  When  teased  by  pinching  it  tried  to  bite;  but  quieted 
down  when  its  head  was  stroked.  The  sense  of  position  was  not 
completely  lost  in  the  limbs,  but  when  set  on  a  table  with  one  leg 
hanging  down,  it  did  not  attempt  to  bring  it  back  into  a  normal 
position.  Although  it  appeared  to  be  blind  it  had  regained  the 
winking  reflex  by  the  end  of  the  second  week,  and  when  a  sound 
was  made,  it  turned  its  head  back  and  pricked  up  its  ears. 
Mental  activity  was  not  entirely  absent ;  Eothmann  saw  the  proof 
of  this  in  the,  fact  that  the  dog  learned  to  adapt  its  movements  to 
the  oblong  form  of  its  cage.  He  concluded  that  the  lower  centres 
are  capable,  by  daily  practice  and  education,  of  co-ordinated 
movements  directed  to  an  end,  and  of  assuming  eventually  part  of 
the  activities  which  normally  belong  to  the  fore-brain. 

Eothmann  has  not  yet  published  his  complete  work,  giving  the 
post-mortem  description  of  the  brain  and  a  detailed  account  of  the 
symptoms,  which  are  (indispensable  in  making  a  comparative  study 
between  this  animal  and  Goltz'  dog. 

Goltz'  observations  show  that  the  most  important  phenomena 
of  deficiency  observed  after  the  destruction  of  the  brain  are  the 
loss  of  all  the  manifestations  or  expressions  from  which  we  draw 
conclusions  as  to  the  memory,  reflection,  and  intelligence  of  the 
animal.  All  the  sensory  and  motor  functions  essential  to  life, 
save  those  of  seeking  food,  may  be  executed,  even  if  imperfectly, 
1  >y  the  surviving  centres.  The  dog  without  a  fore-brain  is  capable 
of  feeding  itself  when  the  food  is  presented  to  it ;  of  moving  with 
tolerable  regularity,  under  the  guidance  of  muscular  and  cutaneous 
sensations ;  possibly  also  of  sight  and  hearing  when  the  thalam- 
encephalon  and  mid-brain  are  intact ;  and  of  passing  alternately 
from  the  waking  to  the  sleeping  state  like  the  normal  dog.  The 
prosencephalou  is  not  necessary  in  any  absolute  sense  for  all  these 
functions,  most  probably  because  their  highest  representation 
is  in  other  parts -- particularly  in  the  thalamencephalon  and 
mesencephalon. 

Flechsig  holds  everything  Goltz  observed  in  the  dog  to  be 
partially  true  of  man  also.  He  saw  a  new-born  infant,  in  whom 
only  the  basal  parts  of  the  brain,  including  the  posterior  corpora 
quadrigemina,  existed,  while  the  hemispheres,  thalami,  and  anterior 


510  PHYSIOLOGY  CHAP. 

corpora  quadrigemina  were  absent.  The  child  only  lived  a  day 
and  a  half.  During  this  time  it  cried  and  showed  signs  of  dis- 
comfort, and  when  the  skin  was  pinched,  its  cries  and  associated 
movements  of  the  limbs  became  more  marked.  Heubner  observed 
a  human  anencephalous  infant  that  lived  sixteen  days,  and  behaved 
exactly  like  a  normal  child  of  the  same  age. 

Normal  new-born  infants  who  have  no  intellectual  psychical 
activities  cry,  like  Goltz'  dog,  when  they  are  hungry  or  distressed ; 
after  being  suckled  and  laid  comfortably  to  rest  they  become  quiet 
and  sleep.  Dements,  again,  and  low-grade  microcephalic  idiots  are 
comparable  to  the  brainless  dog ;  they  are  men  without  a  brain, 
who  have  no  intellect  or  memory,  but  who  nevertheless  possess 
sensory  and  motor  capacity.  Their  special  senses  persist ;  they 
experience  sensations  of  hunger  and  thirst,  and  their  acts  are 
directed  to  satisfying  their  needs ;  they  react  to  painful  sensations 
by  movements  of  defence  and  cries  of  distress.  It  is  therefore 
evident  that  profound  dementia,  i.e.  the  complete  absence  of  the 
higher  psychical  faculties,  does  not  necessarily  imply  loss  of  the 
lower  faculties. 

In  monkeys,  too,  the  fore-brain  has  been  removed  by  Karplus 
and  Kreidl  (1912)  at  the  Physiological  Institute  of  Vienna. 
Macacus  rheus  bears  the  complete  extirpation  of  one  hemisphere 
well.  In  a  few  hours  it  is  able  to  assume  the  sitting  posture  in 
its  cage — and  to  feed  itself  by  means  of  the  limb  of  the  side  operated 
on.  The  whole  of  the  opposite  side  shows  grave  disturbances  in 
movement  and  sensation,  but  a  large  part  of  these  disappear  in 
the  course  of  a  few  weeks.  For  months,  however,  the  monkey 
feeds  itself  almost  exclusively  with  the  hand  of  the  side  operated 
on ;  only  when  this  is  prevented  does  it  use  that  of  the  opposite  side. 

After  the  extirpation  of  the  second  hemisphere  the  results  were 
less  successful ;  only  two  monkeys  survived  for  two  weeks.  The 
extremities,  which  were  paretic  after  the  first  operation,  were 
moved  more  freely  and  frequently  after  the  second  than  the  limbs 
of  the  other  side.  The  monkeys  were  alternately  in  a  state  of 
waking  and  sleeping ;  the  sleep  lasted  longer  than  the  waking 
period,  during  which  they  opened  their  eyes,  moved,  and  reacted 
freely  to  various"  stimuli.  The  movements  of  the  head  and  eyes 
are  normal,  those  of  the  limbs  much  altered.  One  of  the  animals 
a  few  days  after  the  second  operation  succeeded  in  assuming  the 
sitting  posture  with  its  head  erect,  in  eating  with  the  hand  that 
had  become  paretic  after  the  first  operation,  and  in  suspending 
itself  for  some  minutes  to  the  bars  of  the  cage,  after  which  it  shut 
its  eyes,  bent  its  head,  and  relapsed  into  the  sleeping  state. 

Light  stimuli  caused  the,  pupil  to  contract  but  produced  no 
other  reaction.  Strong  auditory  stimuli  roused  the  monkey 
from  sleep,  and  when  awake  it  produced  not  only  reflex  move- 
ments of  the  ears,  but  also  movements  of  the  head  and  of  the 


ix  MID-  AND  INTER-BRAIN  511 

limbs.      Tactile    stimuli  evoked  complex   movements  as  well  as 
simple  reflexes. 

It  would  be  of  the  greatest  interest  to  obtain  a  long  survival 
after  complete  decerebration  in  monkeys,  in  order  to  see  how 
far  the  phenomena  of  deficiency  can  actually  be  modified. 

H.  Munk  put  forward  a  number  of  ingenious  objections  to 
the  effect  that  all  the  phenomena  described  by  Goltz  in  the 
brainless  dog  can  be  explained  as  simple  reflexes,  not  necessarily 
accompanied  by  any  psychical  activity.  He  holds  that  the  sense 
centres  by  which  we  are  normally  brought  into  relation  with  the 
external  world  are  protected  against  the  abnormal  and  injurious 
effects  of  certain  peripheral  stimuli  by  a  mechanism  which  evokes 
ordinary  reflex  movements,  unaccompanied  by  sensations,  which 
ward  off  or  remove  the  stimuli  from  the  nerve-endings,  while  at 
the  same  time  they  can  arouse  sensations  so  that  conscious  and 
voluntary  movements  co-operate  to  the  same  purpose.  These 
common  protective  movements,  whose  reflex  centres  lie  below  the 
fore-brain,  persist  in  the  dog  without  cerebral  hemispheres. 

In  the  next  chapter  we  shall  return  to  Munk's  theory.  Here 
we  need  only  point  out  that  Goltz  declines  to  consider  the 
brainless  dog,  which  sleeps  when  replete,  is  restless  when  its  meal 
is  delayed,  and  tries  to  bite  the  hand  that  teases  it,  as  a  mere 
reflex  machine,  an  insensitive  automaton.  If  these  complex  acts 
are  unmistakable  signs  of  wants,  feelings,  sensations  in  the 
normal  dog,  why  are  they  less  so  in  the  dog  without  a  cerebrum  ? 
Munk  and  those  who  agree  with  him  show  a  tendency  to 
limit  the  material  basis  of  psychical  phenomena  as  much  as 
possible,  and  to  ascribe  them  solely  to  the  cerebral  cortex,  perhaps 
with  the  object  of  facilitating  the  solution  of  certain  problems. 
Nevertheless  the  riddle  of  the  "  psyche  "  remains,  whatever  theory 
of  sensibility  and  consciousness  is  accepted. 

The  theory  of  Loeb — one  of  the  most  distinguished  of  Goltz' 
pupils — comes  very  near  that  of  Muuk.  Starting  from  Munk's 
position  that  consciousness  is  a  function  of  memory,  because  when 
memory  is  lost,  as  in  fainting,  deep  sleep,  and  in  stupor  due 
to  certain  poisons,  consciousness  is  simultaneously  suspended, 
Loeb  concludes  that  the  prosencephalon  is  indispensable  to 
memory,  and  consequently  that  the  brainless  animal  is  an 
automaton  entirely  destitute  of  personality  or  consciousness,  but 
he  adds  a  reservation  which  does  not  seem  important  in  view  of 
the  experimental  observations  of  Schrader  and  Goltz.  Loeb 
shrinks  from  going  so  far  as  to  assume  that  the  fore-brain  is  the 
organ  of  consciousness.  "The  organ  of  consciousness  may  well 
be  the  whole  brain  or  the  whole  of  the  central  nervous  system  so 
long  as  it  is  connected  with  the  fore-brain,  and  the  latter  may 
be  indispensable  only  in  the  activity  of  memory  associations." 
A  critical  examination  of  this  theory  would  take  us  too  far 


512  PHYSIOLOGY  CHAP. 

from  our  subject.  It  is  only  necessary  to  remark  that  there  is 
this  difference  between  the  views  of  Munk  and  Loeb.  Accord- 
ing to  Munk,  the  brainless  animal  has  lost  all  its  senses,  including 
sight  and  hearing,  as  assumed  by  Floureus.  Loeb,  on  the  contrary, 
does  not  deny,  but  even  confirms,  the  observations  of  Schrader  on 
pigeons  and  of  Goltz  on  the  brainless  dog,  but  he  holds  that  these 
animals,  while  more  or  less  guided  reflexly  by  sensory  impressions, 
have  no  trace  of  consciousness,  because  they  are  destitute  of 
associative  memory. 

So  long  as  there  is  no  evidence  to  the  contrary  it  may  be 
maintained  that  brainless  animals  are  in  a  state  of  severe  dementia 
because  they  have  lost  memory  and  perception,  but  are  capable, 
of  elementary  internal  and  external  sensations,  by  which  their 
automatic  and  reflex  movements  are  regulated. 

At  a  later  point  we  shall  discuss  this  question,  and  endeavour 
to  differentiate  between  the  concepts  of  perception  and  of  sensation. 

VII.  To  determine  the  functional  importance  of  the  mesen- 
.cephalon  and  thalameucephalon  we  need  only  sum  up  briefly  the 
results  of  the  other  experiments  by  which  it  has  been  attempted 
to  excite  or  destroy  these  parts  separately,  in  order  to  examine 
the  effects  and  deduce  conclusions  as  to  their  functions. 

Direct  stimulation  of  the  roof  of  the  mid-brain,  which  is 
represented  in  birds,  amphibians,  reptiles,  and  fishes  by  the  optic 
lobes  or  corpora  bigemina,  in  mammals  by  the  corpora  quadri- 
gemina,  gives  positive  results  to  electrical,  mechanical,  chemical, 
and  thermal  excitation. 

In  the  frog,  electrical  excitation  of  the  optic  lobes  produces  a 
movement  of  the  head  towards  the  opposite  side  and  upwards, 
and  sometimes  also  provokes  quacking.  According  to  Wilson,  the 
beats  of  the  heart  are  slowed  also.  Chemical  stimulation,  as  by 
a  crystal  of  sodium  chloride  applied  to  the  optic  lobes  of  the 
frog,  prolong  the  latent  period  of  the  movements  evoked  by  the 
cutaneous  excitations ;  sometimes  there  is  complete  inhibition  of 
reflexes,  particularly  if  the  cutaneous  stimulus  is  of  a  painful 
rather  than  a  tactile  character  (Setschenow). 

The  optic  lobes  of  amphibia  contain  centres  which  control  the 
sexual  clasp.  Albertoni  demonstrated  on  toads  and  Tarchanoff 
on  tadpoles  that  mechanical  stimulation,  as  pricking  with  a  pin, 
squeezing  with  a  forceps,  of  the  optic  lobes  at  once  ends  the  clasp, 
while  the  same  stimuli  applied  to  the  hemispheres  and  optic 
thalariii  have  no  effect  011  it.  They  interpret  these  observations 
as  meaning  that  there  are  inhibitory  centres  of  the  clasp  in  the 
optic  lobes,  which  are  thrown  into  activity  by  the  mechanical 
stimuli.  According,  on  the  contrary,  to  Baglioni  (1911)  from 
his  recent  experiments  on  toads,  these  are  not  inhibitory  centres 
but  true  excitatory  centres  of  the  clasp,  which  are  in  tonic  activity 
during  the  embrace,  and  are  profoundly  injured  and  put  out  of 


ix  MID-  AND  INTEK-BRAIN  513 

action  by  mechanical  stimuli,  to  which  the  centres  are  highly 
sensitive.  He  found,  in  fact,  that  on  employing  electrical  ex- 
citation, which  is  more  easily  graduated  and  less  destructive 
than  these  injurious  stimuli,  the  clasp  is  never  interrupted,  but 
is  actually  strengthened.  On  the  other  hand  the  local  application 
of  an  anaesthetic,  e.g.  stovaine,  to  the  dorsal  surface  of  the  optic 
lobes  is  followed  by  interruption  of  the  embrace. 

In  birds  electrical  stimulation  of  an  optic  lobe  causes  dilatation 
of  the  pupil  on  the  opposite  side ;  the  head  is  also  raised,  and 
various  movements  are  made  by  the  wing  on  the  opposite  side, 
and  by  both  feet  (Ferrier). 

Kschischkowski  has  recently  (1911)  in  our  laboratory  employed 
Baglioni's  method  of  specific  chemical  stimuli  (strychnine  and 
carbolic  acid)  applied  locally,  in  order  to  discover  the  nature  of 
the  central  elements  which  constitute  the  superficial  layers  of  the 
optic  lobes  in  the  pigeon.  He  found  that  the  application  of 
strychnine  and  picrotoxiu  caused  contraction  of  the  skeletal 
muscles  of  the  fore-  and  hind -limbs  and  of  the  neck  on  the 
opposite  side.  It  is  only  when  the  poison  is  applied  in  larger 
quantities  or  to  a  greater  surface  (1-2  sq.  mm.)  that  contractions 
of  the  homolateral  muscles  with  circus  movements  towards  the 
same  side  occur.  These  phenomena  of  excitation  set  in  a  few 
seconds  after  the  application  of  the  stimulus  and  last  for  some 
minutes.  Since  the  application  of  carbolic  acid  has  no  effect,  we 
may  conclude  that  the  elements  of  the  superficial  layer  of  the 
optic  lobes  are,  in  relation  to  this  chemical  stimulus,  of  the  same 
character  as  the  central  elements  of  the  dorsal  half  of  the  cord, 
as  well  as  the  cells  in  the  excitable  cortex  of  the  dog,  since  these 
also  have  the  specific  property  of  reacting  to  strychnine  and 
picrotoxin  and  not  to  carbolic  acid,  which,  on  the  other  hand, 
produces  a  reaction  from  the  motor  cells  of  the  ventral  horn  (see 
above,  pp.  264  et  seq.}. 

In  mammals  faradisation  of  the  anterior  quadrigeminal  body 
produces  pupillary  dilatation  on  the  opposite  side,  and  at  a  later 
stage  on  the  same  side  also,  and  conjugate  deviation  of  the  eyes 
upward  and  towards  the  opposite  side,  with  retraction  of  the  ear 
and  angle  of  the  mouth.  The  same  stimulus  applied  to  the 
posterior  quadrigeminal  body  produces  erection  of  the  ear  on  the 
opposite  side  and  emission  of  cries. 

Adamlik  succeeded  in  producing  different  co-ordinated  move- 
ments of  the  eyes  when  he  excited  various  points  of  the  anterior 
quadrigemiual  bodies  in  the  dog.  After  a  vertical  section  in 
the  median  plane  the  reaction  only  involves  the  eye  of  the  side 
excited. 

Terrier,  experimenting  on  monkeys,  obtained  similar  reactions 
to  those  seen  in  dogs.  Unilateral  electrical  excitation  of  the 
anterior  quadrigeminal  body  produces  wide  dilatation  of  the 

VOL.  Ill  2  L 


514  PHYSIOLOGY  CHAP. 

opposite  pupil,  followed  shortly  by  that  of  the  pupil  on  the  same 
side,  with  pronounced  opening  of  the  lids  and  raising  of  the 
eyebrows.  The  eyes  turn  up  and  towards  the  opposite  side  ;  the 
head  moves  in  the  direction  of  the  eyes ;  and  the  ears  are  lowered. 
If  the  excitation  is  prolonged  the  tail  is  raised,  the  lips  spread 
out,  the  jaws  close,  the  angles  of  the  mouth  are  drawn  back  as 
far  as  possible ;  the  upper  limbs  are  flexed  at  the  elbow-joint, 
adducted  and  drawn  back.  If  the  excitation  is  continued, 
complete  opistothomis  results. 

Excitation  of  the  posterior  quadrigeminal  bodies  in  monkeys 
produces  the  same  effects,  but  there  is  further  emission  of  sounds 
of  a  character  varying  with  the  duration  of  the  stimulus.  The 
motor  effects  which  are  at  first  confined  to  the  opposite  side 
subsequently  extend  to  both  sides. 

It  is  not  easy  to  ascertain  the  value  or  physiological  significance 
of  these  experiments  on  the  corpora  quadrigemina  with  the 
excitation  method.  The  motor  effects  of  electrical  excitation  may 
depend  on  the  transmission  of  the  stimulus  to  the  motor  tracts 
or  to  subjacent  centres.  At  the  same  time  they  are  evoked  by 
very  weak  currents,  which  are  hardly  perceptible  at  the  tip  of  the 
tongue.  Other  forms  of  excitation  which  are  incapable  of  spread- 
ing may  also  produce  the  same  effects  under  certain  conditions. 

The  phenomena  produced  by  excitation  of  the  corpora  quadri- 
gemiua  are  undoubtedly  reflex  in  character,  that  is,  they  depend 
on  the  transmission  of  an  active  state  from  the  sensory  centres 
to  the  motor  centres  or  tracts.  The  effects  of  momentary  stimula- 
tion of  the  mesencephalon  strongly  resemble  the  movements  of 
repulsion  that  take  place  when  an  object  is  suddenly  brought  near 
the  eyes,  which  makes  it  probable  that  the  excitation  gives  rise 
to  subjective  luminous  sensations,  and  this  reflexly  discharges  the 
reaction  movements. 

Trismus,  contraction  of  the  facial  muscles,  and  opistothonus, 
which  ensue  on  strong  and  protracted  stimulation  of  the  quadri- 
geminal bodies,  may  be  looked  on  as  symptoms  or  manifestations 
of  pain.  The  dilatation  of  the  pupil  is  a  phenomenon  of  the  same 
character,  since  we  know  that  it  occurs  with  every  sudden  excita- 
tion of  the  sensory  nerves.  So,  too,  the  cries  of  distress  due  to 
excitation  of  the  posterior  quadrigeminal  bodies. 

Danilewsky  demonstrated  that  electrical  stimulation  of  the 
deep  layers  of  the  corpora  quadrigemina  produces  a  marked 
increase  in  arterial  pressure,  which  is  associated  with  retardation 
and  reinforcement  of  the  heart-beat.  Eespiration  is  disturbed 
too,  expiration  in  particular  being  exaggerated.  Probably  these 
effects  are  due,  at  least  in  part,  to  transmission  of  the  electrical 
stimulus  to  the  subjacent  cerebral  peduncles. 

Valentin  and  Budge  found  that  electrical  excitation  of  the 
corpora  quadrigemina  also  affected  the  viscera,  producing  con- 


ix  MID-  AND  INTEE-BEAIN  515 

tractions  of  the  stomach,  intestine,  and  bladder.  Hlasko  stated 
more  definitely  that  there  is  a  centre  in  the  posterior  corpora 
quadrigemina  for  the  contraction  of  the  stomach  which  induces 
vomiting.  When  these  bodies  are  destroyed  vomiting  is  no  longer 
produced  by  apomorphine.  Frequently  repeated  vomiting  may 
occur  in  dogs  in  which  the  quadrigeminal  bodies  have  been 
partially  injured,  and  therefore  irritated,  during  extirpation  of  the 
anterior  vermis  of  the  cerebellum.  After  three  or  four  days  the 
vomiting  ceases,  probably  owing  to  the  cessation  of  the  irritation. 

VIII.  The  anatomical  relations  of  the  optic  tracts  with  the 
optic  lobes  and  anterior  corpora  quadrigeniina  show  that  these 
ganglia  are  of  supreme  importance  in  vision.  But  the  clearest 
and  most  unmistakable  demonstration  of  the  different  centres 
that  are  in  direct  relation  with  the  optic  nerves,  and  therefore 
function  in  vision,  is  given  after  extirpation  of  one  eyeball  in 
young  animals  and  in  man ;  this  produces  atrophy  and  partial 
agenesis  of  the  anterior  quadrigeminal  body  and  the  external 
geniculate  body  on  the  opposite  side,  as  well  as  of  the  optic 
thalamus  and  cortex  of  the  occipital  lobe,  while  the  posterior 
quadrigemiual  body  and  internal  geniculate  body  are  spared. 
Evidence  for  this  is  shown  by  the  experiments  and  clinical 
observations  of  Pauizza,  Svan,  Gudden,  Ganser,  Forel,  and  v. 
Monakow. 

Mayer,  Flourens,  and  Budge,  experimenting  on  pigeons  and 
dogs,  first  pointed  out  that  the  destruction  of  the  optic  lobes  and 
corpora  quadrigemina  produced  loss  of  vision  and  immobility  of 
the,  pupils.  They  noticed  that  these  effects  are  crossed,  that  is, 
unilateral  destruction  produces  paralytic  effects  on  the  retina 
and  iris  of  the  eye  on  the  opposite  side.  Longet,  Eenzi,  Stefani, 
and  Miiuzer  and  Wiener  confirmed  these  observations ;  but  found 
that  the  blindness  consequent  on  destruction  of  the  optic  lobes 
was  not  complete.  Lussana  and  Lemoigne  stated  that  total  blind- 
ness, at  least  for  a  few  days  after  the  operation,  occurred  only 
after  destruction  of  the  anterior  corpora  quadrigemina,  and  that 
amblyopia  only  resulted  from  destruction  of  the  posterior  quadri- 
geminal bodies.  They  further  held  that  paralysis  of  the  pupil 
ensued  only  when  these  parts  were  seriously  injured.  Many 
observers  found  that  unilateral  ablation  of  the  quadrigemiual 
bodies  produced  circus  movements,  but  they  do  not  agree  as  to 
whether  such  movements  were  towards  the  healthy  or  the  operated 
side.  Ataxia  and  disorders  of  equilibrium  were  further  observed 
after  destruction  of  the  quadrigeminal  bodies,  but  they  are  not 
unilateral  and  do  not  persist;  probably  they  depend  on  injury 
of  the  adjacent  or  subjacent  parts.  The  same  holds  good  for 
functional  disturbances  of  the  internal  ocular  muscles,  which 
possibly  depend  on  injury  of  the  nucleus  of  origin  of  the  oculo- 
motor nerve. 


516  PHYSIOLOGY  CHAP. 

"  Stefani  described  the  effects  of  destroying-  both  lobes  of  the 
pigeon  as  follows :  "  After  recovery  from  the  destruction  of  the 
optic  lobes,  they  only  show  disturbance  of  vision,  relative  not  absolute 
blindness,  perfectly  comparable  to  that  which  follows  the  removal 
of  the  cerebral  hemispheres  in  these  animals.  The  pigeon  does 
not  fly  away  when  I  stretch  out  my  hand  to  take  it  tip,  nor  does 
it  peck  at  the  corn  in  front  of  it  though  hungry ;  but  it  is  able 
to  fly  and  to  avoid  obstacles,  drops  down,  perches  on  objects,  or 
flies  to  the  ground  like  the  healthy  pigeons ;  while  the  pigeons 
blinded  by  removing  their  eyes  remain  motionless,  and  when  forced 
to  move  only  blunder  against  obstacles." 

The  experiments  of  Jappelli  and  Sgobbo  (1900),  who  destroyed 
the  corpora  quadrigemina  in  dogs  by  the  ingenious  method  of 
introducing  a  small  galvano-cautery  like  a  flexible  sound,  ending 
in  a  tiny  platinum  loop,  into  the  space  between  the.  dura  mater 
and  the  cerebellum,  are  specially  important.  With  this  instrument 
they  succeeded  in  obtaining  a  clean  and  sharply  defined,  more  or 
less  complete  removal  of  one  or  other  quadrigeminal  body  on  one 
side,  which  was  aseptic  and  spared  the  other  tissues.  They  kept 
the  animals  alive  till  the  resulting  symptoms  were  fixed  and 
permanent,  and  correlated  these  permanent  symptoms  with  the 
degree  and  locality  of  the  lesion.  In  this  way  they  formed  very 
definite  conclusions  as  to  the  functions  of  the  corpora  quadri- 
gemiua,  which  partially  confirmed  those  of  the  earlier  observers, 
partially  corrected  them,  and  added  new  results  that  harmonised 
\vell  with  the  most  recent  morphological  investigations.  We  may 
sum  up  the  conclusions  of  this  important  work,  keeping  as  closely 
as  possible  to  the  terms  in  which  they  were  formulated  by 
Sgobbo : — 

(a)  Visual  disturbance  in  the  eye  of  the  opposite  side  results, 
not  only  from  lesions  of  the  anterior  quadrigeminal  body,  as  many 
authors  suppose,  but  also  from  injury  to  the  posterior  body,  as 
had  been  previously  noted  only  by  Lussana  and  Lemoigne  and 
Bechterew. 

(6)  This  disturbance  consists,  not  in  blindness,  but  in  diminu- 
tion of  vision  (amblyopia)  in  the  whole  visual  field  of  the  eye 
on  the  opposite  side.  This  agrees  with  the  observations  of  Serres, 
Renzi,  and  Stefani. 

(c)  Lesions  of  the  posterior  quadrigeminal  body  also  produce 
auditory  disturbances  (deafness  and  dullness  of  hearing)  in  the 
ear  of  the  opposite  side,  associated  with  paresis  of  the  external  ear 
muscles.  This  observation  is  new,  not  having  been  made  by  any 
previous  authors.  It  agrees  with  the  effects  of  electrical  stimula- 
tion of  the  posterior  quadrigeminal  body,  which,  as  we  see,  causes 
movements  of  the  ear  on  the  opposite  side,  and  cries. 

(d}  The  corpora  quadrigemina  do  not  contain  centres  for  the 
movements  of  the  eyeball  as  other  authorities  supposed.  After 


ix  MID-  AND  INTEE-BKAIN  517 

lesions  (if  these  bodies  motor  disturbances  in  the  eye  were  either 
totally  absent  or  appeared  only  when  the  lesion  was  so  extensive 
as  to  involve  the  grey  matter  that  surrounds  the  Sylvian  aqueduct. 
Hesen  and  Volkers  and  Bechterew  came  to  the  same,  conclusion. 
This  contradicts  the  views  of  Terrier  and  of  Adamiik,  who  con- 
cluded from  the  excitation  method  that  the  anterior  1  todies  con- 
tained special  centres  for  the  conjugate  movements  of  the  eyes. 

(e)  Nor  do  the  quadrigemina  contain  the  centre  for  the  move- 
ments of  the  iris,  disturbance  of  the  latter  being  only  seen  when 
the  lesion  extends  to  the  oculo-motor  nucleus,  i.e.  when  it  involves 
the  grey  matter  that  surrounds  the  aqueduct  of  Sylvius.  Lussana 
and  Lemoigne  and  Bechterew  also  assumed  that  the  centre  for 
the  iris  was  not  situated  in  the  corpora  quadrigemina,  but  lay 
deeper. 

(/')  Circus  movements,  paresis  or  paralysis  of  the  limbs,  and 
disturbances  of  equilibrium  appear  as  transitory  phenomena  when 
the  lesion  is  limited  to  the  corpora  quadrigemina.  They  must 
therefore  depend  on  the  excitation  or  destruction  of  the  subjacent 
or  surrounding  parts.  Circus  movements  which  are  usually 
towards  the  side  of  the  lesion  are  due  to  the  hemiparesis,  and 
disappear  as  the  latter  wears  off;  the  movements  towards  the 
opposite  side  depend  on  the  excitation  of  the,  subjacent  pyramidal 
fibres  and  are  quite  transient. 

Sgobbo  follows  up  his  series  of  experiments  on  dogs  by  a  critical 
review  of  the  clinical  cases  described  by  various  authors  in  which 
post-mortem  examination  showed  lesions  limited  to  one  or  other  or 
both  of  the  corpora  quadrigemina,  with  a  view  of  ascertaining  the 
functions  of  these  ganglia  in  man. 

After  minutely  analysing  the  complex  symptomatology  of  these 
cases,  he  came  to  the  general  conclusion  that  both  isolated  lesions 
of  the  anterior  and  posterior  corpora  quadrigemina  and  lesions 
involving  both  these  bodies  failed  to  produce  any  constantly 
appreciable  alteration  in  vision  or  hearing.  It  is  possible  that  in 
proportion  as  the  prosencephalon  acquires  a  greater  importance  in 
the  zoological  scale  the  functional  importance  of  the  mesencephalon 
in  general,  and  of  the  quadrigemina  in  particular,  may  diminish. 
For  the  better  solution  of  this  question  it  is  desirable  that  a 
methodical  series  of  experiments  should  be  carried  out  upon  the 
corpora  quadrigemina  of  monkeys,  which  come  nearest  to  man  in 
the  relative  development  of  these  segments  of  the  brain. 

IX.  The  function  of  the  centres  of  grey  matter  which  lie  deep 
in  the  mid-brain  and  cerebral  peduncles  is  very  obscure  and  un- 
certain. It  is  only  known  that  lesions  of  the  mesencephalon 
produce  forced  movements  as  their  immediate  consequence. 
Sherrington  (1896)  described  some  important  effects  of  sections  of 
various  extent,  at  the  level  of  the  mid-brain.  In  the  monkey  he 
contirmed  the  fact  that  section  in  front  of  the  mid-brain  leaves 


518  PHYSIOLOGY  CHAP. 

voice-production  intact,  while  section  behind  it  abolishes  phonation. 
He  further  observed  a  cataleptic  condition  in  monkeys  after  section 
in  front  of  the  mesencephalon ;  reflex  movements  are  carried  out 
with  extreme  slowness,  and  the  attitudes  assumed  or  passively 
given  are  long  sustained.  He  holds  it  probable  that  the  tonic 
spasms  of  epilepsy  are  due  to  excitation  of  the  brain-stem,  which 
agrees  with  Ziehen's  view  that  they  are  subcortical,  while  the 
clonic  spasms  are  cortical  in  origin.  Verworn  (1898)  showed  that 
after  decerebration  it  is  much  easier  to  evoke  the  state  of  forced 
immobility  known  as  hypnosis  in  the  pigeon. 

Sherrington  (1898)  described  the  persistent  tonic  spasm  that 
occurs  in  certain  groups  of  muscles,  after  section  of  the  brain  in 
front  of  the  corpora  quadrigemina,  as  decerebrate  rigidity.  This 
symptom  appears  in  apes,  dogs,  cats,  rabbits,  and  guinea-pigs. 
The  contracted  groups  of  muscles  are  the  retractors  of  the  head 
and  neck,  the  muscles  of  the  tail,  the  extensors  of  the  elbow,  knee, 
shoulder,  and  ankle.  The  foot  and  hand  are  but  little  concerned, 
the  ringers  and  toes  not  at  all.  In  kittens  this  spasm  may  last 
four  days  with  little  interruption.  When  it  ceases  it  can  easily  be 
evoked  again  by  passive  movements  of  the  corresponding  joints. 
At  first  the  spasm  assumes  the  form  of  tonus ;  subsequently  it 
becomes  a  tremor.  In  narcosis  it  dies  down,  and  reappears  as  this 
passes  off. 

The  spasm  depends  on  the  integrity  of  the  dorsal  spinal  roots. 
In  fact  it  does  not  appear,  or  only  imperfectly,  in  the  limits  to 
which  the  dorsal  roots  had  been  cut  some  days  previously,  and 
it  disappears  if  they  are  divided  after  it  has  set  in. 

During  the  state  of  decerebrate  rigidity,  stimulation  of  various 
points  of  the  central  nervous  system  or  of  certain  peripheral 
nerves  elicits  reflexes  which  consist  in  relaxation  of  the  contracted 
muscles  and  contraction  of  the  antagonists.  Prolonged  stimulation 
sometimes  results  in  rhythmical  flexion  and  extension  of  the  four 
limbs,  which  by  their  co-ordination  recall  the  complex  of  move- 
ments present  in  quadruped  progression  (Chap.  VII.  et.  seq.~). 

After  hemisection  of  the  'tween  brain  the  same  rigidity 
appears,  but  it  is  far  more  marked  on  the  side  of  the  lesion 
(Sherrington).  The  whole  course  of  the  effects  of  hemisection  of 
the  mid- brain  has  been  described  by  Probst  (1904). 

Probst  experimented  on  cats.  After  dividing  the  right  half  of 
the  mid-brain  midway  between  anterior  and  posterior  corpora 
quadrigemina,  he  noticed  the  phenomena  which  maybe  summarised 
as  follows  :— 

Immediately  after  section  on  the  right  side  there  is  curvature 
of  the  body  and  head  to  the  left  side,  with  tonic  contraction  of  the 
musculature  of  the  left  side  of  the  neck.  The  pupils  are  con- 
stricted slit-wise,  and  after  half  an  hour  horizontal  nystagmus  may 
be  seen  in  the  left  eye  alone.  The  jaws  are  closed,  and  there  is 


IX 


MID-  AND  INTEE-BEAIN 


519 


tonic  contracture  of  the  left  limbs.  If  the  left  hind-leg  is  passively 
stretched,  it  remains  extended  while  the  right  goes  hack  to  its 
former  position.  The  animal  lies  on  the  left  side. 

An  hour  and  a  half  after  the  operation  the  animal  lies  in  the 
position  shown  in  Fig.  259,  with  its  head  turned  to  the  left  between 
the  two  hind-limbs  which  are  extended  forwards.  The  right  fore- 
leg makes  constant  swimming  movements ;  the  left  limbs  are 
motionless. 

The  animal  keeps  up  this  forced  position  during  the  first  three 
days  after  the  operation.  The  myosis  diminishes,  the  nystagmus 
ceases.  Both  motility  and  sensibility  are  greatly  diminished  on 
the  left,  and  it  is  necessary  to  feed  the  animal  artificially. 

On  the  seventh  day  the  animal  makes  attempts  to  stand  but 


FIG.  250. — Forced  curvature  in  cat  to  the  left,  after  section  of  ri^ht  side  of  mid- 
brain  and  cerebral  peduncle.     (Probst.) 

falls  to  the  left.  The  left  limbs  are  paretic  and  anaes- 
thetic, and  are  only  moved  reflexly.  The  two  pupils 
are  equal  and  react  to  light. 

On  the  ninth  day  the  animal  begins  to  walk  in  a  circular 
direction  to  the  left,  but  falls  after  a  few  steps.  It  begins  to 
support  itself  also  on  the  left  fore-leg,  and  can  now  turn  its  head  to 
the  right. 

On  the  eleventh  day  it  can  walk  for  a  short  distance,  leaning 
against  the  wall. 

On  the  thirteenth  day  it  walks  better,  but  always  in  a  circular 
direction  to  the  left;  it  frequently  crosses  its  fore-limits.  It  has 
regained  the  sensibility  of  the  left  limits;  but  does  not  correct  the 
abnormal  position  assumed  by  these  limbs.  It  eats  spontaneously. 

On  the  twentieth  day  it  still  presents  circus  movements  to  the 
left,  but  is  able  to  jump  off  a  chair.  When  called,  it  can  turn  its 
head  to  the  right,  but  still  keeps  up  the  forced  position  of  the  head 
to  the  left. 


520  PHYSIOLOGY  CHAP. 

On  the  twenty-first  day  both  motor  zones  of  the  cerebral 
cortex  were  exposed  and  stimulated  by  electrical  currents.  On 
exciting  the  left  sigmoid  yyrus  single  contractions  were  evoked, 
as  well  as  epileptic  fits  confined  to  the  right  side.  On  exciting 
the  right  sigmoid  gyrus  weak  currents  only  elicited  contractions 
of  the  left  ear  and  left  facial  muscles.  Very  strong  currents 
evoked  weak  contractions  of  the  left  limbs,  but  never  epileptic 
attacks. 

From  these  facts  observed  after  unilateral  trausection  of  the 
entire  mid-brain  of  the  cat  it  is  clear  that  there  is  never  total 
paralysis  of  sensation  and  motion  in  the  opposite  half  of  the 
animal.  After  three  weeks  it  regains  its  capacity  of  walking  and 
jumping ;  the  forced  postures  and  movements  seen  directly  after 
the  operative  act  improve  progressively,  and  the  sensory  disorders 
improve  rapidly. 

Apart  from  the  special  cases  we  have  been  considering,  it  may 
be  stated  in  general  terms  that  the  intensity  of  the  symptoms  of 
unilateral  section  of  the  mid-brain,  including  the  cerebral  peduncle, 
depend  on  whether  the  transection  is  complete  or  not.  One  effect 
of  the  coutralateral  motor  paresis  is  the  circus  movement  of  the 
animal,  which  is  generally  to  the  opposite  side,  sometimes  also  to 
the  side  of  the  lesion ;  in  the  first  case,  which  is  the  rule,  the 
curvature  of  the  spinal  axis  predominates — in  the  second,  the 
greater  extension  of  the  limbs  of  the  operated  side,  in  comparison 
with  the  paretic  limb  of  the  opposite  side,  prevails. 

In  the  monkey,  and  more  particularly  in  man,  the  effects  are 
greater.  Clinical  cases,  no  less  than  experiments  on  animals, 
enable  us  to  form  an  idea  of  the  importance  of  the  cerebral 
peduncle,  inasmuch  as  it  contains  the  sensory  and  motor  cerebro- 
spinal  conducting  paths.  In  correspondence  with  the  localisation 
and  extent  of  lesions  of  the  peduncle  there  is  crossed  motor, 
sensory,  or  mixed  paralysis,  partial  or  complete. 

X.  The  physiology  of  the  optic  thalami  leaves  much  to  be 
desired.  This  is  due  in  great  measure  to  the  difficulty  of  attacking 
these  masses  of  grey  matter  without  damaging  the  surrounding 
organs.  The  method  proposed  and  carried  out  by  Lo  Monaco  in 
our  laboratory  undoubtedly  indicates  considerable  progress  from 
the  point  of  view  of  technique.  It  consists  in  the  partial  transec- 
tion of  the  corpus  callosum,  which  produces  no  apparent  disturb- 
ance, and  separation  of  the  two  hemispheres  so  as  to  expose  the 
thalami,  in  order  to  excite  them  or  remove  them  entirely  or  in  part. 

Contrary  to  the  vie\vs  of  other  authors,  electrical  or  other 
stimulation  of  the  thalami  causes  neither  painful  sensation  nor 
motor  reaction,  provided  the  stimulation  does  not  spread  to  the 
cerebral  peduncles  nor  the  anterior  quadrigeminal  bodies  (Ferrier, 
Lo  Monaco).  The  effects  of  the  destruction  or  removal  of  the 
thalami  varies  according  to  different  experimenters,  and  according 


ix  MID-  AND  INTER-BRAIN  521 

to  the  operative  methods  employed  and  the  greater  or  less  lesions 
of  the  adjacent  parts. 

The  anatomical  connections  of  the  thalami  with  the  other 
portions  of  the  1  train  (pp.  489  ct  seq.)  throw  sufficient  light  on 
this  difficult  suhject.  Anatomical  research,  particularly  the  most 
recent  work  of  Dejerine  and  of  Roussy,  has  proved  that  every  part 
of  the  cerebral  cortex  receives  nerve-fibres  from  the  optic  thalamus. 
On  the  other  hand,  the  thalamus  sends  no  fibres  to  the  cerebral 
peduncle  or  to  the  bulb  and  spinal  cord;  after  destruction  of  the 
thalamus  no  degeneration  is  seen  either  in  the  motor  (pyramidal 
tracts)  or  the  sensory  (lemniscus)  paths. 

The  atrophy  of  the  thalamus  that  follows  excision  of  the 
opposite  eyeball  (Panizza,  J.  Svan)  shows  the  extreme  importance 
of  the  thalamus  in  vision.  In  the  lower  vertebrates  the  corpora 
bigemina  represent  the  principal  station  reached  by  the  fibres  of 
the  optic  nerve ;  but  in  the  higher  vertebrates  the  thalamic  visual 
centres  are  always  larger  in  proportion  to  those  of  the  mid-brain 
(Gudden,  v.  Mouakow,  Edinger,  and  others).  Of  the  four  masses 
of  grey  matter  into  which  the  mammalian  thalamus  is  divided,  it 
is  the  hindmost,  the  pulvinar,  which  directly '  receives  the  optic 
fibres ;  and  the  pulviuar  and  the  external  corpus  geniculatum  give 
origin  to  the  paths  to  the  occipital  region  of  the  cortex  and  the 
angular  gyri  (v.  Monakow,  Vialet,  Ferrier,  and  Turner),  which — as 
we  shall  see  iii  the  next  chapter — represent  the  cortical  centres 
of  vision. 

Many  fibres  of  the  mesial  fillet  (lemniscus)  terminate  in  the 
lateral  nucleus  of  the  thalamus,  and  penetrate  especially  into  its 
ventral  and  posterior  parts  round  the  centre  median  of  Luys.  As 
we  know,  this  represents  the  continuation  of  the  dorsal  columns  of 
the  spinal  cord,  and  perhaps  also  Gowers'  tract ;  in  a  word,  the  long 
spino-cerebral  sensory  paths. 

From  the  lateral  grey  matter  of  the  thalamus,  fibres  run  to  the 
parietal  and  mesial  regions  of  the  cortex ;  those  to  the  Rolandic 
area  receive  their  medullary  sheath  very  early,  towards  the  ninth 
month  of  foetal  life.  The  fibres  that  run  from  the  anterior  part  of 
the  thalamus  to  the  frontal  region  of  the  cortex  are  late  in  acquir- 
ing their  sheath  (fourth  month  after  birth).  A  large  system  of 
fibres  that  develops  early  unites  the  thalamus  to  the  nuclei  of 
the  corpus  striatum,  that  is,  the  caudate  nucleus  and  lenticular 
nucleus.  Lastly,  the  thalamus  receives  fibres  from  the  superior 
cerebellar  peduncle,  either  directly  or  through  the  red  nuclei. 

These  anatomical  considerations  as  a  whole  naturally  lead  to 
the  conclusion  that  the  thalamus  is  a  great  sensory  centre,  to 
which  a  number  of  centripetal  paths  from  different  sensory  organs 
converge,  and  from  which  they  spread  out  to  the  different  regions 
of  the  cerebral  cortex.  Broadly  speaking,  apart  from  exaggeration 
and  fancies,  this  was  the  theory  sustained  by  Luys  (1865-76) 


522  PHYSIOLOGY  CHAP. 

on  the  basis  of  anatomical  and  clinical  observations.  Ferrier  (1878) 
adopted  this  same  point  of  view,  partially  on  the  strength  of  an 
experiment  on  a  monkey.  After  dividing  the  thalamus  in  this 
animal  by  an  incandescent  wire  introduced  through  the  occipital 
lobe,  he  noted  among  other  less  definite  phenomena  cutaneous 
hemianaesthesia  on  the  opposite  side,  blindness,  and  pupillar 
dilatation,  from  which  he  concluded  that  the  thalami  are  centres 
in  which  the  sensory  paths  converge  and  are  interrupted  before 
radiating  to  the  cortex.  He  remarked  that  if  the  thalami  are  the 
relay  centres  for  the  sensory  tracts,  it  follows  that  lesions  of  these 
ganglia  must  produce  an  alteration  in  the  various  forms  of 
sensibility.  This  fact  seems  to  be  better  demonstrated  by  the 
study  of  clinical  cases  than  by  experiments  on  animals.  Many  of 
the  cases  described  by  Luys  are  not  conclusive,  since  they  are 
tumours ;  but  certain  cases  of  simple  softening,  confined  more  or 
less  clearly  to  the  thalami,  are  very  important  from  the  physio- 
logical point  of  view. 

Among  the  most  valuable  and  best  described  clinical  cases  is 
one  of  Hughlings-Jackson's  (1875).  The  post-mortem  examination 
showed  a  considerable  depression  on  the  posterior  half  of  the  right 
thalamus.  On  sectioning  it  was  found  to  be  softened  and  greyish- 
yellow  in  colour.  The  softening  did  not  extend  beyond  the  limits 
of  the  thalamus  into  the  white  matter  of  the  hemisphere  and 
peduncle,  and  its  anterior  half  and  the  posterior  half  of  the  corpus 
striatum  were  intact.  No  other  lesions  could  be  found  in  the 
brain.  The  symptoms  obviously  present  in  life  with  this  well- 
defined  lesion  of  the  optic  thalamus  were  as  follows:  Weakness 
of  movements  on  the  left  side,  especially  in  the  leg,  marked 
diminution  of  tactile  sensibility  on  the  left,  diminution  of  smell 
or  at  least  of  ordinary  sensibility  of  left  nostril,  slight  diminution 
of  taste  in  left  half  of  tongue,  doubtful  loss  of  hearing  in  left  ear, 
and  finally,  left  hemianopsia  in  both  eyes,  i.e.  blindness  of  right 
hall'  of  both  retinae  (bilateral  homonymous  hemianopsia). 

Experimental  researches,  when  uncomplicated  by  lesions  of 
other  parts,  partially  confirm  the  results  of  clinical  observation. 

The  prolonged  researches  of  Lo  Monaco  (1898-1911)  led  to 
the  conclusion  that  of  the  effects  of  partial  or  total,  unilateral  or 
bilateral  extirpations  of  the  thalami,  the  symptoms  of  visual 
deficiency  are  the  most  prominent  both  from  their  gravity  and 
their  persistence. 

Lesions  limited  to  the  internal  or  external  part  of  one  thalamus 
produce  very  marked  amblyopia  of  the  eye  on  the  opposite  side, 
while  the  eye  of  the  side  operated  on  shows  no  alteration  to 
ordinary  tests.  This  amblyopia  is  not  permanent,  but  gradually 
disappears  within  a  few  weeks.  No  defect  of  the  other  special 
senses  can  be  observed,  but  there  is  a  diminution  of  tactile  and 
painful  sensibility  on  the  skin  of  the  opposite  side.  The  circus 


ix  MID-  AND  INTEE-BKAIN  523 

movements  noted  by  Magendie,  and  the  hemiplegia  described  by 
other  authors,  do  not  occur,  though  there  is  diminution  of  muscular 
power  on  the  opposite  side.  These  symptoms  disappear  after  a 
few  days. 

When  the  unilateral  ablation  involves  the  posterior  part  of 
tin-  thalamus  or  the  pulvinar  there  seems  to  be  total  blindness  of 
the  eye  on  the  opposite  side,  which  apparently  persists  as  long  as 
the  animal  survives.  When  the  excision  of  the  pulvinar  is  bi- 
lateral the  dog  appears  to  be  blind  in  both  eyes ;  immediately 
after  the  operation  its  behaviour  is  similar  to  that  of  a  dog  in 
which  both  eyeballs  have  been  removed,  but  there  is  not  absolute 
permanent  blindness.  In  fact,  the  animals  had  hardly  recovered 
from  the  operation  when  both  began  to  walk,  and  they  soon  learned 
to  orientate  themselves,  to  recognise  the  objects  near  them,  and 
thus  to  avoid  them  in  walking. 

Among  Lo  Monaco's  experiments  great  importance  attaches 
to  that  performed  on  a  dog  in  which  the  pulvinar  was  destroyed 
on  both  sides,  causing  atrophy  of  the  corpora  quadrigemina  and 
the  external  geniculate  bodies.  In  this  animal  there  were  obvious 
visual  disturbances  that  persisted  during  the  eleven  months  that 
it  survived. 

The  dog  exhibited  a  graver  disturbance  of  vision  than  the 
psychical  blindness  due  to  extirpation  of  both  cortical  visual 
centres,  but  less  than  the  blindness  that  results  from  extirpation 
of  both  eyeballs. 

In  addition  to  visual  disturbances  there  is,  according  to  Lo 
Monaco,  a  unilateral  or  bilateral  affection  of  taste  in  dogs  deprived 
of  the  pulviuar  on  one  or  both  sides,  shown  by  the  fact  that  one  or 
other  half  of  the  tongue,  or  the  entire  taste  surface,  is  insensitive 
to  the  bitterness  of  a  saturated  solution  of  quinine. 

The  sense  of  smell  is  also  disturbed  in  dogs  that  have  lost  their 
pulvinar ;  they  only  perceive  the  odour  of  meat  when  it  is  placed 
near  their  nostrils,  while  a  dog  blinded  by  extirpation  of  the  eyes 
recognises  it  at  a  much  greater  distance. 

Lo  Monaco  found  painful,  thermal,  and  muscular  sensibility 
intact  in  dogs  after  removal  of  the  pulvinar.  After  destruction  of 
the  mesial  or  anterior  nucleus  of  the  thalamus,  on  the  contrary, 
tactile  sensibility  and  muscular  energy  are  reduced  on  the  contra- 
lateral  side ;  but  not  permanently,  as  no  trace  of  diminution  can 
be  recognised  after  a  few  days.  The  circus  movements  to  the 
opposite  side  are  only  seen  during  the  first  days  after  the  operation, 
and  evidently  depend  on  the  prevailing  action  of  the  muscles  of  the 
side  operated  on,  or  of  the  side  on  which  the  thalamus  is  more  pro- 
foundly and  extensively  injured. 

Anatomical  examination  of  the  brains  of  the  dogs  whose 
thalamus  was  operated  on  by  Lo  Monaco  almost  entirely  confirms 
the  functional  lesions  observed  during  life.  In  a  case  of  removal 


524  PHYSIOLOGY  CHAP. 

of  the  anterior  part  of  the  thalamus  the  peripheral  visual  paths 
(tract,  chiasrna,  optic  nerves)  were  found  to  be  completely  normal ; 
but  there  was  partial  degeneration  of  the  optic  radiations  of 
Gratiolet,  which  run  from  the  thalamus  and  external  geniculate 
body  to  the  cortex  of  the  occipital  globe.  On  the  other  hand,  in 
the  cerebrum  of  the  dog  killed  a  year  after  the  bilateral  destruction 
of  the  pulvinar,  degeneration  could  be  seen  both  in  the  peripheral 
and  central  visual  paths.  In  the  peripheral  paths  the  internal 
side  of  the  tract  was  degenerated,  and  in  the  central  there  was 
partial  degeneration  of  the  bundle  of  Gratiolet,  which  was  more 
pronounced  in  its  lower  third.  None  of  the  experiments  on  more 
or  less  extensive  unilateral  or  bilateral  extirpation  of  the  thalamus, 
on  the  contrary,  showed  any  such  degenerations  in  the  sensory 
paths  of  the  fillet,  which  agrees  with  the  fact  that  the  disturbances 
of  cutaneous  and  muscular  sensibility  observed  during  life  were 
transient.  This  tends  to  some  extent  to  modify  the  prevailing 
anatomical  concepts  of  the  relations  of  the  sensory  paths  with  the 
thalamus,  and  the  too  extensive  interpretations  given  to  the 
symptoms  observed  in  Hughlings- Jackson's  case. 

If  the  localisation  of  function  in  the  several  nuclei  of  the 
thalami  and  the  complex  of  sensory  and  psychical  functions 
carried  out  by  the  thalami  is  still  uncertain,  we  know  at  least— 
from  the  researches  of  Lo  Monaco,  in  particular — that  the  pulvinar 
is  of  great  importance  in  vision,  and  also  participates  in  the 
functions  of  taste  and  smell.  On  the  other  hand,  it  would  appear 
that  the  sensory  and  motor  disturbances  observed  in  the  early 
post-operative  period,  specially  after  destruction  of  the  anterior 
nucleus,  are  simple  effects  of  interruption  of  the  thalarno-cortical 
and  cortico-thalamic  fibres. 

There  are  clinical  facts  in  favour  of  the  view  that  the  thalami 
exercise  an  influence  on  the  mimetic  or  emotional  manifestations. 
But  these  are  inconstant  phenomena,  the  origin  of  which  has  not 
yet  been  fully  cleared  up. 


BIBLIOGRAPHY 

The  following  are  among  the  most  important  of  the  recent  works  : — 

GOLTZ.     Beitriige  zur  Lehre  von  den  Functiouen  der  Nervenzentren  des  Frosches. 

Berlin,  1869. 

HUGHLINGS-JACKSON.     Reprints  of  London  Hospital  Reports,  1875. 
FKRRIEK.     Functions  of  the  Brain,  1876. 
FANO.     Arch,  italiennes  de  biologie,  1883. 
FANO.     Pubbl-.  del  R.  Istituto  di  Studi  Sup.  in  Firenze,  1884. 
FANO.     La  Salute.     Genoa,  1885. 

CHRISTIANI.     Zur  Physiologic  des  Gehirns.     Berlin,  1885. 
STEINEK.      Die    Functionen   des    Zentralnervensystems    and    ilire    Phylogenese. 

Brunswick,  1885-88. 

BECHTEREW.     Virchow's  Arch.,  1887-88. 
SCHRADER,  M.     Pttiiger's  Archiv,  1887  and  1889. 


ix  MID-  AND  INTEK-BRAIN  525 


Mrxu,    H.      i'hor   die    Funktioiien    des   Grosshivns.      Gesammelte 

1890.     Sitzungsbi-r.  d.   K.  preuss.  Akad.  d.  Wiss.  zu  Berlin.     Jahrg.  1881-89. 

l)u  Bois-Reymond's  Arch.,  1884. 
M<IXAKO\V.     Arch.  1'.  Psychiatric.     1888-92. 
(i.n.TZ.      Pfluger's  Archiv,  1884-88-92. 
VIA  LET.     Centres  cerebraux  dc  la  vision.      Paris,  1893. 
Lo  MONACO.     Rivista  di  patologia  nervosa  e  mentale.     Florence,  1897. 
SHERRINGTON.     Phil.  Trans.     London,  1896-98. 

YERWORN.     Beitriige  zur  Physiol.  d.  Zentralnervensy  stems.     Jena,  1898. 
JAITELLI.     R.  Ace.  Med.  Chir.  di  Napoli,  1898. 
FEIIUIER  and  TURNER.     Phil.  Trans.     London,  1898. 
I'.KTHE,  A.     Piliiger's  Archiv,  1899. 

SGOBBO.     II  Manicondo  moderno.     Nocera  Inferiors,  1900. 
DEJERINE,  J.     Anatomic  des  centres  nerveux.     Paris,  1907. 
Lo  MONACO.     Sulla  fisiol.  dei  talaini  ottici,  Raccolta  di  lavori  di  iisiologia  e  scienze 

affini  pel  giubileo  del   prof.   Luciaiii.     Milan,  1900.     Atti  della  R.  Ace,  dei 

Lincei,  1910. 

PROBST.     Jahrbiicher  f.  Psych,  u.  Neurol.,  1904. 
ROUSSY,  G.     La  Couche  optique.     Paris,  Steinheil,  1907. 
BAGLIONI.     ZentralM.  f.  Physiol.,  1911. 
KSCHSCHKOWSKI.     Zentralblatt  f.  Physiol.,  1911. 
ROTHMANN.     Berl.  mecl.  Gesellsch.,  June  1911. 
KARPLUS  and  KREIDL.     Wiener  klinische  Wochenschrift,  1912. 

Recent  English  Literature  :  — 

GRAHAM  BROWN.     On  Postural  and  Non-Postural  Activities  of  the  Mid-brain. 

Proc.  Royal  Soc.,  1913,  B.  Ixxxvii.  145. 
SACHS.     On   the   Structure   and    Functional    Relations   of   the   Optic   Thalamus. 

Brain,  1909,  xxxii.  95. 


CHAPTEE   X 

THE   FORE-BEAIN 

CONTENTS. — 1.  General  anatomy  of  telencephalon.  2.  Structure  of  the  cerebral 
cortex  or  pallium.  3.  History  of  cerebral  localisation.  4.  Excitable  zone  of  the 
cerebral  cortex  ;  localisation  in  dog,  monkey,  man.  5.  Physiological  analysis  of 
motor  reactions  of  cerebral  cortex.  6.  Inhibitory  reactions.  7.  Organic  reactions 
of  cortical  origin.  8.  Epilepsy  from  cortical  excitation.  9.  The  sensory-motor 
area,  deduced  from  effects  of  partial  or  total  destruction  of  excitable  cortex.  10. 
Functions  of  basal  ganglia  or  corpora  striata  (caudate  and  lenticular  nuclei). 
11.  Visual  area.  12.  Auditory  area.  13.  Olfactory  and  gustatory  areas.  14. 
Association  areas  ;  division  of  cortex  into  thirty-six  areas,  according  to  Flechsig's 
embryological  method.  15.  Physiological  analysis  of  speech  disorders  of  cerebral 
origin.  16.  General  theory  of  the  psycho  -  physical  functions  of  the  brain. 
Bibliography. 

I.  THE  Fore-brain  (prosencephalon,  telencephalon,  brain  proper) 
represents  in  man,  as  in  all  vertebrates,  the  most  bulky  segment  of 
the  central  nervous  system.  It  originates  in  the  primary  cerebral 
vesicle,  from  which  at  an  early  stage  the  two  diverticuli,  which  are 
known  in  the  adult  as  the  lateral  ventricles,  develop,  while  the 
central  portion  of  the  vesicle  is  reduced  to  the  small  cavity  of  the 
third  ventricle.  The  walls  of  this  cavity  develop  progressively  in 
the  vertebrate  series,  and  become  the  cerebral  hemispheres. 

The  primary  vesicle  thickens  at  the  base,  where  a  large  mass, 
which  ernbryologists  call  the  basal  lobe,  develops.  Its  anterior 
portion,  from  which  the  fibres  of  the  olfactory  nerve  emerge,  is 
destined  to  constitute  the  olfactory  apparatus ;  the  posterior  part 
is  of  a  considerable  size,  and  forms  the  so-called  corpus  striatum. 
These  masses  are  afterwards  separated  by  a  fissure  from  the  more 
conspicuous  segment  of  the  vesicle,  the  walls  of  which  thicken 
comparatively  late,  and  form  the  mantle  of  the  brain  or  pallium. 
Fig.  260  is  a  good  representation  of  the  several  parts  or  segments 
of  the  human  1  >rain  in  its  early  period  of  development.  Its  various 
parts  are  more  or  less  developed  in  all  mammals,  both  during 
embryonic  life  and  after  development  has  been  completed. 

In  the  bony  fishes  the  pallium  is  represented  merely  by  an 
epithelial  layer ;  in  the  cyclostomes  the  side  walls  alone  begin  to 
thicken ;  in  certain  species  of  selachians  an  enlargement  takes 

526 


CHAP.  X 


THE  FOEE-BRAIN 


527 


place  in  the  lateral  and  frontal  walls ;  in  amphibia  and  reptiles 
the  pallium  is  entirely  composed  of  nerve  substance;  in  birds  and 
especially  in  mammals  it  reaches  a  much  higher  development  than 
all  the  other  brain  segments  together;  and  finally,  in  man  it 
attains  the  enormous  development  represented  by  the  cerebral 
hemispheres. 

It  is  noticeable  that  while  the  development  of  the  pallium  of  the 
fore-brain  proceeds  pari  2^ssu  with  the  higher  psychical  activity 
of  the  animal,  the  olfactory  apparatus  and  corpus  striatum  (which 
develop  from  the  basal  lobe  of  the  embryonic  brain)  present,  like 


FIG.  260. — Median  section  through  brain  of  a  human  embryo  in  fifth  week.     (His.) 

all  the  other  segments  of  the  cerebrospinal  axis,  comparatively 
little  difference  throughout  the  whole  scale  of  vertebrates. 

The  olfactory  apparatus  in  the  human  foetus  of  two  to  four 
months  appears  in  the  form  of  a  hollow  protuberance  from  the  fore- 
1  »rain  ;  but  during  development  its  walls  thicken  till  the  cavity  is 
completely  obliterated.  In  the  adult  it  is  possible  to  distinguish 
(Fig.  261) :- 

(a)  The  olfactory  bulb,  which  rests  on  the  lamina  cribrosa  of  the 
ethmoid  and  receives  through  its  pores  the  fibres  of  the  olfactory 
nerves  that  originate  in  the  nasal  mucosa ; 

(&)  The  olfactory  tract,  which  divides  into  two  divergent  roots  ; 

(c)  The  olfactory  area,  in  which  the  median  or  grey  roots  of  the 
tract  arise ; 

(d)  The  posterior  olfactory  lobule,  formed  from  that  part  of  the 


528 


PHYSIOLOGY 


CHAP. 


cerebral   cortex    which    appears    on    the    surface   of   the  anterior 
perforated  space. 

The  corpus  striatum  arises  from  the  base  of  the  telencephalon 
in  the  cavity  of  the  cerebral  vesicles.  Its  position  is  invariable 
from  the  tishes  to  man.  Since  it  is  covered  by  the  pallium  it 
cannot  lie  seen  in  the  intact  brain;  in  teleosteans  only,  in  which 
the  pallium  is  composed  of  a  thin  membrane,  it  is  visible,  and 
composes  the  entire  fore-brain.  The  fish's  brain,  according  to 
Edinger,  may  be  morphologically  compared  with  a  human  brain  in 


L.t. 


G.s. 


Ch. 


FIG.  261.— Olfactory  lobe  of  human  brain.  (His.)  Kv,,  olfactory  bulb;  T,  tract;  Tr.n.,  trig-one; 
R,  rostrum  of  corpus  callosum  ;  p,  peduncle  of  corpus  callosnm,  passing  into  U.S.,  gyms 
subcallosus  (diagonal  tract,  Broca);  Br,  Brora's  area  ;  F.p.,  tissnra  pnnia  ;  F.x.,  lissura  serotina  ; 
' '."..  position  of  anterior  commissure  ;  L.t.,  lamina  terminalis  ;  '  //.,  optic  chiasma  ;  T.o.,  oj)tic 
tract;  ?>.<>//.,  posterior  olfactory  lobe  (or  anterior  perforated  spare);  m.r.,  mesial  root;  /.»•., 
lateral  runt  of  tract. 

which  the  hemispheres  have  been  excised  but  the  corpus  striatum 
left ;  to  show  this  it  is  only  necessary  to  draw  a  section  of  the 
fore-brain  of  a  bony  fish  within  the  diagrammatic  outline  of  a 
human  brain.  As  shown  in  Figure  262,  the  fibres  of  the  corpus 
striatum  lie  in  the  region  occupied  in  mammals  by  the  anterior 
part  of  the  internal  capsule  (cf.  Fig.  247,  p.  492).  In  the  lower 
vertebrates  (fish,  amphibia,  reptiles)  the  pallium  is  little  or  not 
at  all  developed  as  compared  with  the  basal  ganglion;  in  birds, 
although  the  mantle  is  developed,  the  basal  ganglia  always 
forms  the.  main  part  of  the  fore-brain;  in  mammals  lastly,  and 
particularly  in  man,  owing  to  the  enormous  development  of  the 
pallium,  the  basal  ganglia  become  a  purely  secondary  part  of 
the  brain. 


X 


THE  FORE-BKA1N 


529 


In    the 


higher 


vertebrates  (birds  and  mammals)  the  basal 
ganglion  undergoes  a  further  subdivision;  the  fibres  which 
descend  from  the  pallium  traverse  it,  dividing  it  into  a  lateral  or 
extraveutricular  and  a  medial  or  intraventricular  segment.  The 
first  is  generally  known  as  the  lenticular  nucleus  ;  the  second  as 
the  caudate  nucleus  (Figs.  245,  246,  247).  Both  these  nuclei  of  the 
corpus  striatum  are  united  by 
fibres  to  the  nuclei  of  the  optic 
thalamus. 

The  caudate  nucleus  of  the 
human  brain  is  pear-shaped 
with  the  larger  end  anteriorly, 
it  lies  in  the  wall  of  the  anterior 
horn  of  the  lateral  ventricle. 
Its  ventricular  surface  is 
covered  by  a  layer  of  ependyma 
and  of  ciliated  epithelium.  The 
mass  of  the  ganglion  consists 
of  a  reddish  -grey  substance; 
the  microscope  shows  nerve- 
cells  generally  pigmeiited  in 
the  adult,  most  of  which  are 
small  and  belong  to  Golgi's 
second  type  with  short  axis- 
cylinder  processes  running  in 
various  directions,  some  into 
the  internal  capsule  (Marchi). 

The  lenticular  nucleus  is 
separated  from  the  caudate 
nucleus  by  the  layer  of  white 
matter  which  forms  the  in- 
ternal capsule.  It  is  only 
visible  in  sections  of  the  hemi- 
sphere (Fig.  263),  in  which  it 
appears  lens  -shaped.  It  is 
smaller  at  both  ends  than  the 
caudate  nucleus.  Two  white 
lines  or  medullary  laminae  divide  it  into  three  zones,  the  outer 
of  which,  the  largest  and  dark  red  in  colour,  is  known  as  the 
putamen  ;  the  two  inner,  of  a  yellower  tint,  are  known  as  the 
globus  pallidus.  Anteriorly  these  two  nuclei  of  the  corpus 
striatum  are  united  by  their  bases,  and  come  into  contact  below 
with  another  nodule  of  grey  matter,  the  nucleus  amygdalus,  which 
in  its  turn  is  continuous  with  the  grey  matter  of  the  cortex. 
The  cells  of  the  lenticular  nucleus  contain  yellow  pigment,  and  as 
a  whole  resemble  those  of  the  caudate  nucleus,  but  many  of  them 
belong  to  Golgi's  first  type  —  i.e.  they  have  long  axis-cylinders. 


FIG.  2li'2. — Frontal  section  through  1'ore-lirain  of  a 
teleostean,  Corrina  nii/ni,  din-ctcd  obliquely 
behind  and  down.  Round  this  the  outline  of 
a  mammalian  cerebrum  is  drawn,  to  show  the. 
relations  between  tin-  basal  ganglia  and  the 
pallium.  (Edinger.) 


VOL.  in 


2  M 


530 


PHYSIOLOGY 


CHAP. 


The  nuclei  of  the  corpus  striatum  are  connected  by  nerve- 
fibres  ;  other  fibres  run  to  adjacent  parts  of  the  internal  capsule, 
to  the  corona  radiata  and  to  the  cortex. 

The  internal  capsule  is  the  mass  of  white  fibres  situated 
between  the  lenticular  nucleus,  caudate  nucleus,  and  the  optic 
thalamus  (Fig.  263).  In  front,  behind,  and  above  it  is  continuous 

with  the  white  matter  of 
the  hemispheres,  and  is 
composed  of  fibres  that 
spread  out  like  a  fan- 
whence  the  name  corona 
radiata.  Below,  the  fibres 
of  the  internal  capsule  and 
corona  radiata  are  con- 
tinuous with  the  pes  of  the 
cerebral  peduncle.  In  hori- 
zontal sections,  as  in  Fig. 
263,  the  internal  capsule 
presents  a  knee,  the  anterior 
and  posterior  segments  join- 
ing at  an  angle  of  about 
120°.  Clinical  observations 
have  led  to  the  conclusion 
that  the  fibres  running  in 
the  middle  third  of  the 
internal  capsule,  i.e.  those 
along  the  globus  pallidus 
of  the  lenticular  nucleus, 
are  in  connection  with  the 
part  of  the  cerebral  cortex 
which  we  know  as  the  motor 
area ;  those  of  the  anterior 
third  with  the  prefrontal 
region ;  and  those  of  the 
posterior  third  with  the 
temporo-occipital  regions  of 
the  cortex. 

The  localisation  in  the 
internal  capsule  of  the  fibres 
from  the  nuclei  of  the  corpus  striatum,  the  optic  thalamus,  the 
subthalamic  region,  and  the  cortex  of  the  opposite  hemisphere, 
through  the  great  interhemispherical  commissure  of  the  corpus 
callosum,  is  not  exactly  known. 

The  cerebral  mantle  in  the  higher  vertebrates,  particularly  in 
man,  comprises  the  greater  part  of  the  mass  of  the  cerebral 
hemispheres;  it  is  divided  by  the  sulcus  longitudinalis  and  united 
by  the  corpus  callosum. 


FIG.  263.  —Horizontal  section  through  part  of  cerebral 
hemisphere.  (Schiifer,  after  Shattock.)  Natural 
size.  The  section  is  viewed  from  below  ;  V.Z.,  lateral 

ventricle,  anterior  horn;  c.c.,  corpus  callosum  ; 
s.l.,  septum  lucitlum  ;  a./.,  anterior  pillars  of  fornix  ; 
v3,  third  ventricle;  tli,  optic  thalamus;  st,  stria 
terminalis  ;  c,  nucleus  caudatus,  and  «./.,  nucleus 
lenticularis  of  corpus  striatum;  i.e.,  internal  capsule; 
</,  its  knee  or  genu ;  n.c.,  tail  of  nucleus  caudatus 
appearing  in  descending  horn  of  lateral  ventricle ; 
cl,  claustvum  ;  /,  island  of  Reil. 


THE  FORE-BRAIN 


531 


Each  hemisphere  presents  an  outer  convex  surface  lying  in 
the  vault  of  the  skull;  a  Hat  inner  or  mesial  surface  forming  one 
side  (if  the  longitudinal  sulcus ;  and  an  irregular  lower  surface  in 
which  there  is  the  deep  fissure  of  Sylvius.  As  shown  by  Figs. 
264,  265,  266,  all  three  surfaces  'of  the  cerebral  hemispheres 
present  numerous  fissures  or  sulci,  marking  out  as  many  smooth 
and  winding  projections,  the  convolutions  or  gyri.  The  surface 
of  the  brain  is  enormously  increased  by  this  folding  into  sulci 
and  irvri.  The  extent  of  the  infolded  surface  is  estimated  at 

o*/ 

double  that  of  the  visible  surface. 

The  membranes  that  envelop  the  brain  resemble  those  of  the 


Fir;.  204.-  External  aspect  of  left  cerebral  hemisphere.     The  names  of  the  gyri  and  lobules  are 
marked  in  Roman  type  ;  those  of  the  sulci  and  fissures  in  italics. 

spinal  cord  in  structure.  The  pia  mater,  which  is  very  rich  in 
vessels,  dips  down  into  the  bottom  of  the  sulci,  while  the  arachnoid 
passes  from  one  convolution  to  the  next  without  penetrating  between 
them  ;  the  whole  floats  in  the  sac  of  the  dura  mater. 

The  primary  sulci,  which  are  seen  in  the  foetal  human  brain 
and  in  adult  apes,  must  be  distinguished  from  the  secondary  sulci ; 
the  former  divide  the  hemispheres  into  lobes,  the  latter  subdivide 
the  lobes  into  gyri  or  convolutions. 

The  primary  sulci  are  the  Sylvian  fissure  (fissura  cerebri 
lateralis),  the  sulcus  of  Rolando  (sulcus  centralis),  and  the  parieto- 
occipital  sulcus.  The  lobes  formed  by  these  sulci  are  the  frontal, 
temporal,  parietal,  occipital,  and  central  (or  island  of  Reil).  The 
convolutions  of  each  lobe  are  shown  with  their  names  in  the  three 
diagrammatic  figures. 


532 


PHYSIOLOGY 


CHAP. 


Like  the  rest  of  the  brain,  the  cerebral  hemispheres  consist  of 
white  and  grey  matter.  The  former  occupies  the  internal  part, 
where  it  forms  the  so-called  medullary  centre ;  the  second  forms 
the  superficial  layer,  known  as  the  grey  cerebral  cortex. 

The  white  matter  of  the  cerebral  hemisphere  consists  of 
medullated  fibres,  which  are  generally  smaller  than  those  of 
the  cord.  They  may  be  grouped  into  three  principal  systems 
according  to  their  course  :— 

(a)  Commissural  or  transverse  fibres,  which  unite  the  two 
hemispheres ; 

(&)  Projection  fibres,  that  run  from  the  brain -stem  to  the 
hemispheres,  or  vice  versa ; 


Fio.  265.— Median  longitudinal  section  through  adult  brain.  The  posterior  parts  of  the  thalamus, 
cerebral  peduncles,  etc.,  have  been  removed,  so  as  to  expose  the  inner  surface  of  the  temporal 
lobe. 

(c)  Association  or  arcuate  fibres,  that  unite  neighbouring  or 
remote  parts  of  the  cortex  of  the  same  hemisphere. 

The  cerebral  cortex  varies  between  2  and  4  mm.  in  thickness, 
according  to  the  region  and  to  age.  On  examination  with  the 
naked  eye  in  a  vertical  section,  it  is  seen,  not  to  be  uniform,  but 
to  consist  of  a  series  of  parallel  layers,  alternately  white  and  grey, 
the  number  of  which  varies  in  different  regions  (Baillarger,  1840) 
(Fig.  267).  This  variation  in  the  colour  shows  that  the  structure 
of  the  cortex  is  not  uniform,  as  is  also  confirmed  by  microscopical 
examination. 

II.  The  form  and  arrangement  of  the  nerve-cells  vary  with 
the  varying  depth  of  a  convolution ;  there  are  different  more  or 
less  well-defined  layers,  which  are  not  always  distinct,  and  do  not 


X 


THE  FOEE-BEAIN 


always  correspond  with  those  visible  to  the  naked  eye.  Usually 
tin-re  may  be  distinguished  (Meynert  and  Eamoii  y  Cajal) : 
(a)  a  superficial  molecular  layer ;  (&)  one  or  two  layers  of  large 
and  small  pyramidal  cells ;  (c)  one  or  two  layers  of  polymorphic 
and  spindle-shaped  cells.  A  marked  difference  is  to  be  seen  in 
the  various  regions  of  the  cortex  in  the  form  and  size  of  the 


FIG.  266.— Gyri  at  the  base  of  the  brain.     Diagrammatic.     The  chiasma  is  turned  backwards. 

nerve-cells,  and  in  the  depth  and  delimitation  of  the  different  layers. 
In  the  central  convolutions,  adjacent  to  the  sulcus  of  Rolando, 
some  of  the  deeper  pyramidal  cells  assume  comparatively  gigantic 
proportions,  as  first  noted  by  Betz  and  Bevan  Lewis,  but  this  is 
not  observed  in  the  cortex  of  the  occipital,  temporal,  or  frontal 
lobes,  in  which  the  place  of  the  giant  cells  is  largely  occupied 
by  the  smaller  pyramidal  cells  and  by  small  angular  cells. 

To  Brodmaun   belongs   the  credit   of  having  recently  (1909) 


534 


PHYSIOLOGY 


CHAP. 


drawn  attention  to  the  structural  characters  of  the  cerehral 
cortex,  by  study  of  the  arrangement  and  morphological  characters 
of  the  cells  which  constitute  its  various  layers.  By  long  and 
patient  comparison  of  the  different  areas  of  the  pallium  he  has 
arrived  at  results  which  are  of  great  interest,  and  which  can  be 
summarised  as  follows  :— 

According  to  Brodmann,  the  fundamental  type  of  the  cerehral 
cortex,  from  which  all  the  other  secondary  types  are  differentiated 
during  foetal  development  (from  the  seventh  month),  consists  of 
six  layers  which  may  be  clearly  recognised,  and  are  formed  by 
three  strata  rich  in  cells  alternating  with  three  layers  poorer  in 
cells  (Fig.  268).  The  first  and  sixth  of  these  strata  are  constant 
in  all  cortical  regions  of  the  adult  human  brain  and  all  mammals. 
Others,  on  the  contrary,  as  the  second  and  fourth  granular  layers, 
vary  greatly  and  may  disappear  in  many  regions  of  the  adult 

human  1  train;  the  remaining 
layers,  the  third  and  fifth, 
present  an  intermediate  grade 
of  variability. 

This  structural  six -layer 
type  is  not  permanent;  'in 
many  regions  it  is  more  or 
less  transitory.  The  numerous 
secondary  structural  types  that 

i.        ZU(  .   oruuiUiia       Ul         lid  CUlrtl       (JUll  V  vjiuunJiio.  -.  -.  ,  _ 

(Baillarger.)     Approximately  natural  ^  size.  ^  1,      develop    IrOlll     it    lOrill     almost 

nine-tenths  of  the  entire  cortex 
of  the  adult  human  brain. 

These  secondary  types  may 
in  their  turn  be  grouped  into  two  great  categories  :— 

(a)  Homotypical  cortical  formations,  in  which  the  structure  is 
fundamentally  unchanged,  the  six  layers  persisting  (Fig.  269). 
The  greater  part  (about  three-quarters)  of  the  cortex  of  the  human 
brain  comes  under  this  category.  The  numerous  types  which  it 
comprises  are  distinguished  from  each  other  by  the  varying 
characters  of  the  several  cell  layers.  These  characters  are  par- 
ticularly the  depth  or  thickness  of  the  cortex,  the  size  of  the  cells, 
and,  above  all,  the  numerical  richness  of  the  cells  which  make  up 
the  different  layers. 

(&)  Heterotypical  cortical  formations,  which  lose  their  funda- 
mental structure  during  ontogeuetic  development,  either  because 
the  layers  increase  in  number,  as  in  the  case  of  the  cortex  of  the 
calcarine  fissure  (Fig.  270),  or  because  some  of  the  original  six 
layers  disappear  (Fig.  271). 

We  said  that  some  nine-tenths  of  the  whole  cortex  of  the 
adult  human  brain  belong  structurally  to  the  fundamental  type  of 
the  six  cellular  layers,  either  because  they  retain  it  throughout  life, 
or  because  they  exhibit  it  in  some  stage  of  development.  The 


Fio.     267.  —  Sections    of     cerebral    convolutions. 


show  the  six  layers  usually  seen  in  the  cortex 
with  the  naked  eye  ;  2,  appearance  of  a  section 
of  a  convolution  from  the  neighbourhood  of  the 
calcarine  fissure. 


x  THE  FORE-BRAIN  535 

remaining  tenth  port,  which  never  even  during  embryonic  develop- 
ment presents  a  six-layer  structure,  includes  the  cortex  of  the 
olfactory  Imlh,  hippocampus,  dentate  fascia,  etc.  These  portions 
were  termed  het&rogenetic  cortical  areas  hy  Brodniann  in  contra- 
distinction to  the  former,  which  he  termed  homogenetic  cortical 
areas. 

The  various  cortical  regions  differ  from  one  another  both  in 
the  characters   of  the  cell  layers  and   in   the  characters   of  the 


.  ' 

Fir,.  268. — Transverse  section  of  cortex  of  calearine  lissun-  from  a  human  foetus  of  eight  months. 
Cortical  region  in  which  the  fundamental  cytotectonic  primitive  type  of  six  layers  (to  right) 
is  directly  continuous  at  the  point  indicated  by  arrows  with  the  eight-layered  cytotectonic 
type  proper  to  the  grey  matter  of  the  area  striata  of  the  calearine  fissure.  (Brodmann.)  The 
respective  layers  are:  I,  lamina  zonalis  ;  II,  lamina  granularis  externa ;  III,  lamina  pyramid- 
alis  ;  IV,  lamina  granularis  interna  ;  IVa,  sublamina  granularis  int.  superficialis  ;  IVb,  sub- 
lamina  granularis  intermedia  (Stria  Gennari  s.  Vicq  d'Azyri);  TVc,  sublamina  granularis  int. 
profunda ;  V,  lamina  ganglionaris ;  VI,  lamina  multiformis ;  Via,  sublamina  triangularis  ; 
VI'j,  sublamina  fusiformis. 

nerve -fibres  they  contain,  and  in  studying  the  latter  different 
structural  types  can  also  be  distinguished ;  Brodmann  has  studied 
the  mydo-architecturc  of  the  cerebral  cortex  as  well  as  its  cyto- 
architccturc.  To  enter  into  details  would  exceed  the  limits  of 
our  subject,  and  we  can  only  refer  the  student  to  Fig.  272,  which 
shows  diagrammatically  the  combined  results  of  the  study  of  the 
cells  by  Golgi's  and  Nissl's  methods,  and  of  the  nerve-fibres  by 
Weigert's  method  (0.  Vogt). 

On  the  basis  of  the. results  obtained  from  studying  the  cyto- 


536 


PHYSIOLOGY 


CHAP.  X 


architecture  of  the  different  parts  of  the  cerebral  cortex,  Brodmann 
plotted  out  the  entire  cortical  surface  into  fifty -two  areas  (Fig. 
273  a,  b)  which  he  grouped  into  eleven  regions  or  principal  fields ; 
the  postcentral,  precentral,  frontal,  insular,  parietal,  temporal, 
occipital,  cingular,  retrosplenial,  hippocampal,  olfactory.  In  this 
way  he  obtained  a  surface  localisation,  a  sort  of  geographical  chart, 
of  the  cerebral  cortex.  The  definition  of  the  different  areas  is 


Ilia 


Hlb 


>1I1 


•   :. 


•••.."''-•••     •       ....'.   •   '.  •  •''•     ,•       .'   '••     .  • 


FIG.  269.  — Cy  totectonio  type  of  cortex  of  occipital  lobe  of  adult  man,  in  which  the  fundamental 
type  of  six  layers  persists.    (Brodmann.)    Magnification  60  diameters. 

possible  owing  to  the  fact  that  the  structural  peculiarities  char- 
acteristic of  each  area  are  sharply  limited  (Fig.  268),  so  that  it 
is  tolerably  easy  in  serial  sections  to  recognise  and  fix  the  limits 
which  mark  off  each  area  from  the  adjacent  regions. 

The  special  importance  of  Brodmann's  regional  subdivision  for 
the  physiologist  and  neurologist  is,  as  he  clearly  brings  out,  that 
while  the  greater  number  of  the  fields  thus  defined  have  as  far 
as  is  known  no  connection  with  actual  physiological  functions, 
some  of  the  areas,  and  precisely  those  which  are  characterised  by 


I 

'i    /  ;• 

•X    4 

• 

1  .;. 

it  .>.  -  .• 

»vv. 

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•  A*  "°-    «'. 

-»: 

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ill 

£: 

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«.  •  ..  :/ 

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IVb- 


'     .     f'  '    I  r  •  •  ', 


FIG.  270. — Cytotectonic  type  of  area  striata 
of  calcaiiii"'  tissure  of  adult  man.  (Brod- 
mann.) Magnified  (i6  diameters. 


FIG.  271. — Gifranto-pyrainidal  eytotectonic  ty]»' 

zone  of  adult  man.  The  t,wo  more  superlicial  layers 
are  not  reproduced.  (Brodmann.)  Figs.  270,  271, 
272  have  all  the  same  magnification  of  66  diameters, 
and  show  the  different  sizes  of  the  cells  and  layers  in 
the  different  regions  of  the  cortex. 


538  PHYSIOLOGY  CHAP. 

conspicuously  differentiated  structure  (heterotypical  formations), 
coincide  with,  or  are  directly  related  to,  the  regions  whose  functions 
are  known  from  experimental  physiological  research  or  clinical 
observations.  These  areas  are  especially :  the  giganto-pyramidal 
area  (field  4  of  Broclmann)  characterised  by  the  presence  of  giant 
pyramidal  cells  (Fig.  272),  which  occupies  the  precentral  region 
and  coincides — as  we  shall  see  later — with  the  excitable  or  motor 
area  ;  and  the  striated  area  of  the  calcarine  fissure  (field  17)  in  the 
occipital  region  (Fig.  270),  characterised  by  increase  of  the  cellular 
layers  and  the  presence  of  large  numbers  of  small  cells,  which 
includes  the  visual  zone. 

III.  The  effects  of  complete  destruction  of  the  telencephalon  in 
different  classes  of  vertebrates,  as  discussed  in  the  last  chapter, 
showed  that  the  view  of  those  authors  who  maintain  that  all  the 
functions  and  acts  of  conscious  psychical  life  are  localised  ex- 
clusively in  this  chief  segment  of  the  brain  has  not  been  confirmed, 
nor  can  it  be  confirmed  by  the  physiological  methods  at  our  dis- 
posal. There  is,  however,  no  doubt  that  the  fore-brain  is  the  seat 
of  all  the  higher  mental  activities,  particularly  the  formation  of 
images,  their  association  and  calling-up  in  memory,  and  their 
expression  in  complex  voluntary  acts — in  a  word,  the  highest 
phenomena  of  the  intellect. 

A  critical  review  of  the  theories  that  have  prevailed  as  to  the 
material  mechanism  and  seat  of  psychical  phenomena  was  published 
by  Soury  (1899),  from  a  wide  point  of  view,  and  with  great  wealth 
of  detail.  To  use  the  author's  happy  expression,  it  comprises  the 
natural  history  of  the  human  mind,  and  could  not  therefore 
possibly  be  summarised  in  the  limits  of  the  present  volume. 
Enough  to  say  that  from  Alcmeon  of  Croton  (500  B.C.),  who  seems 
to  have  been  the  first  who  looked  on  the  brain  as  the  central  organ 
of  the  soul,  to  Franz  Joseph  Gall  (1810-18),  who  first  conceived 
the  brain  as  a  collection  of  organs  corresponding  to  different 
mental  faculties,  innumerable  hypotheses  have  been  formulated  to 
account  for  the  intimate  relations  between  physiological  function 
and  psychical  activity — i.e.  between  body  and  soul.  Of  these 
hypotheses,  both  in  classical  and  in  modern  times,  that  which 
regards  the  brain,  or  a  part  of  it,  as  the  material  substrate 
necessary  to  the  activity  of  the  mind,  has  certainly  predominated. 
This  theory,  however,  only  reached  its  complete  expression  with 
Gall. 

Haller  (1708-77)  regarded  the  white  matter  of  the  brain,  not 
the  grey  cortex,  which  he  thought  insensitive  to  stimuli,  as  the 
seat  of  sensation  and  the  source  of  movement.  He  did  not  allow 
that  different  psychical  functions  could  be  assigned  to  particular 
provinces  of  the  brain,  because  the  nerves  of  the  sense  organs  are 
connected  with  different  points  of  the  brain,  and  have  no  special 
seat  in  the  sensorium  commune,  that  is  in  the  white  brain  matter. 


X 


THE  FOEE-BEAIN 


539 


Frochaska  (1749-1820)  made  notable  progress  in  defining  the 
seat  of  mental  phenomena.     He  held  the  brain  in  general  to  he 


iV    'v   ^ 

,  • »  ' k  *  • :. 


>*•>•  r.v  w  ^: 


..  -.     .    •  I      .  .  •        « 

.'  )•  ,'•  :•<  iJ  '-j  •" 

' 


/.'I'    M*          '• 


Fio.  27'2. — Diagram  to  show  tlu-  layers  of  cells'andjfibres  in  tlie  grey  matter  of  the  human  cerebra 
cortex,  according  to  three  histological  methods  :  (a)  Golgi ;  ('-/)  Nissl  ;  (r)  Weigert.     (O.  Vogt.) 

the  organ  of  thought,  but  believed  it  not  improbable  that  the 
different  acts  of  intelligence  have  distinct  organs  in  the  brain. 


540 


PHYSIOLOGY 


CHAP. 


Prochaska  accounts  for  the  dreams  of  sleep  on  the  supposition  that 
the  organ  of  perception,  which  is  dulled  in  sleep,  is  distinct  and 
perhaps  remote  from  the  organ  of  ideation. 

Bichat  (1771-1802),  on  the  contrary,  returned  partially  to  the 
older  view.  Every  kind  of  sensation  has  its  centre  in  the  brain, 
but  the  brain,  is  never  affected  by  the  passions ;  the  organs  of 
organic  life  and  the  sympathetic  ganglia  are  the  exclusive  seat  of 
the  latter.  Lesions  of  the  liver,  stomach,  spleen,  intestines,  heart, 


FIG.  273  «. —External  surface  of  brain.  Representation  of  cortical  areas  according  to  the  cyto- 
architecture  of  the  grey  matter  in  man.  (Brodmann.)  In  this  and  the  next  figure  the 
different  areas  are  marked  by  numbers  and  various  other  signs.  Such  are  area  4,  distinguished 
by  large  black  dots,  which  is  the  giganto-pyramidal  area  (motor  zone) ;  and  area  17,  marked  by 
small  black  points,  the  area  striata  (visual  zone). 

etc.,  produce  a  variety  of  affections  which  cease  when  the  cause  is 
removed.  Fear,  for  instance,  arises  from  the  stomach,  choler  from 
the  liver,  goodness  from  the  heart,  joy  from  the  intestines. 

Yet  more  astonishing  is  the  theory  put  forward  by  the  great 
anatomist  Sommering  in  1796,  which  is  to  some  extent  a  return 
to  the  ideas  of  Herophilus  and  Galen,  who  localised  the  seat  of  the 
pneuma  psychikon  in  the  cerebral  ventricles.  During  his  anatomical 
studies  on  the  real  origin  of  the  cranial  nerves,  he  was  struck  by 
the  1'act  that  nearly  all  terminated  in  the  walls  of  the  cerebral 


X 


THE  FOKE-BRAIN 


541 


ventricles,  where  they  are  Lathed  by  the  serous  fluid  of  these 
cavities.  This  led  him  to  conclude  that  this  fluid  (aqua  ventri- 
culorum  cerebri}  is  the  single  medium  of  nervous  activity,  the 
sensorium  commune,  the  organ  and  seat  of  the  soul. 

Sommering  dedicated  his  treatise,  Ueber  das  Organ  der  Seele, 
to  Kant  in  order  to  obtain  that  great  philosopher's  opinion  upon 
his  hypothesis.  Kant's  reply  is  worthy  of  him,  and  is  of  peculiar 
interest  in  view  of  his  bent  to  scepticism.  He  a  priori  rejects  the 
idea  that  the  soul,  which  can  only  lie  limited  by  time,  can  be 


FIG.  273  6. — Internal  surface  of  brain.    Cortical  areas  according  to  cyto-architecture  of  grey  matter 

in  man.     (Brodmann.) 

spatially  localised.  From  the  physiological  point  of  view  only  the 
site  of  the  sensorium  commune  can  be  considered,  that  is,  the  organ 
which  makes  possible  "the  association  of  all  sensory  representa- 
tions in  the  mind."  This  sensorium  commune  is  not  the  seat  of 
the  soul,  but  it  is  the  immediate  organ  of  the  soul,  on  the  one 
hand  isolating  the  nerves  which  terminate  there  so  as  to  keep  the 
sensations  distinct,  on  the  other  establishing  a  perfect  community 
between  them.  Can  this  seusorium  be  represented  by  the  water 
of  the  cerebral  ventricles,  as  assumed  by  Sommering  ?  The  great 
difficulty  in  admitting  this  hypothesis  is — according  to  Kant— 
that  the  water,  being  a  fluid,  cannot  be  organised,  and  without 
organisation  no  matter  can  serve  as  the  immediate  organ  of  the 


542  PHYSIOLOGY  CHAP. 

soul.  In  conclusion  therefore  (and  this  is  the  pith  of  Kant's 
metaphysical  comment  on  Sommering's  hypothesis)  it  is  not 
impossible  for  the  physiologist  to  make  the  collective  unity  of  all 
the  sense  perceptions  in  a  common  organ  intelligible,  though  he 
who  attempts  to  solve  the  problem  of  the  seat  of  the  soul  is 
handling  the  impossible,  and  may  be  confronted  with  the  words  of 
Terence,  "  Incerta  haec  si  tu  postules  ratione  certa  facere,  nihilo 
plus  agas,  quam  si  des  operam  ut  cum  ratione  insanias." 

These  remarks  are  necessary  to  the  correct  appreciation  of  the 
physiological  value  of  the  work  of  Gall  and  his  pupil  and  collab- 
orator Spurzheim,  the  founders  of  the  theory  of  cerebral  localisa- 
tion. They  were  the  first  who  brought  out  the  importance  of  the 
grey  matter  of  the  cerebral  cortex  in  general,  and  of  the  ganglia  of 
the  nervous  system,  which  they  considered  to  be  the  origin  of  the 
nerves  and  the  organ  of  nutrition  of  the  white  matter.  The 
nervous  system  as  a  whole  results  from  the  association  of  several 
separate  systems,  each  of  which  has  a  different  function.  All 
these  systems,  however,  are  united  by  means  of  commissures. 
There  is  accordingly  no  common  centre  for  all  sensations,  all 
thoughts,  all  volitional  impulses.  Unity  results  from  the  harmony 
of  the  individual  functions  brought  about  by  the  commissures. 

Again  the  cerebral  hemispheres  are  divisible  into  as  many 
pairs  of  particular  organs  as  the  distinct  functions  which  they  sub- 
serve. Intellectual  phenomena  depend  exclusively  upon  the  cere- 
brum, and  its  convolutions  are  "  the  organs  of  the  mind."  Gall 
excludes  the  sense  organs  from  any  direct  participation  in  the 
phenomena  of  the  intellect.  They  do  not  develop  in  proportion 
with  intelligence,  in  fact  the  larger  number  of  them  even  stand 
in  inverse  ratio  with  it.  Taste  and  smell  are  more  developed  in 
lower  mammals  than  in  man ;  vision  and  hearing  are  more  acute 
in  birds  than  in  mammals.  The  cerebrum  alone  develops  in  direct 
proportion  with  intelligence.  The  loss  of  one  or  more  senses  does 
not  diminish  intelligence,  which  may  persist  even  after  the  loss  of 
all  the  senses. 

Gall,  however,  did  not  confine  himself  to  the  consideration  of 
the  cerebrum  as  the  substrate  of  mental  phenomena ;  he  conceived 
a  psychological  system,  in  which  the  intellect  or  psychical  person- 
ality of  man  is  divided  into  a  sum  of  arbitrary  heterogeneous 
faculties,  each  independent  of  the  other,  and  each  represented  in  a 
special  province  of  the  cerebral  cortex. 

Gall's  so-called  phrenology  started  with  the  observation  made 
in  his  schoolboy  days,  when  he  noticed  that  some  of  his  fellow- 
students  who  had  a  remarkable  memory  for  words  had  prominent 
eyes ;  this  led  him  to  conclude  that  the  faculty  of  verbal  memory 
was  localised  in  that  part  of  the  frontal  lobe  which  lay  above  and 
behind  the  orbital  cavity. 

If  the  capacity  for  learning  easily  by  heart  is  associated  with 


x  THE  FOEE-BKAIN  543 

such  an  external  peculiarity,  why  should  not  other  mental  faculties 
when  they  are  markedly  developed  be  associated  with  special 
humps  or  prominences  on  the  surface  of  the  skull  ?  This  generalisa- 
tion gave  rise  to  the  subsequent  researches,  based  on  more  or  less 
fantastic  or  subjective  ideas,  from  which  Gall  and  Spurzheim  con- 
structed the  new  science  of  phrenology.  Its  aims  were  study  of 
the  most  prominent  mental  faculties  and  predominating  moral 
characteristics  of  different  individuals ;  crauioscopic  observation 
of  the  form  and  varying  development  of  the  several  regions  of  the 
cerebral  cortex  ;  and  direct  examination  of  the  brain  after  death— 
in  the  hope  of  determining  the  seat  of  the  different  faculties. 

Although  Gall  was  a  good  observer,  as  shown  by  his  valuable 
contributions  to  the  anatomy  of  the  brain,  and  although  the 
fundamental  facts  from  which  he  started  were  correct,  he  lost  all 
critical  sense  in  his  eager  attempt  to  solve  his  phrenological 
problems,  and  accepted  wholly  illusory  appearances  for  reality. 
This  did  not  prevent  his  theory,  with  Spurzheim's  modifications 
and  additions,  from  obtaining  a  great  following. 

When  Floureus  published  his  researches  on  the  physiology  of 
the  brain  (1822),  he  conferred  a  great  benefit  on  science  by  rooting 
out  the  intruding  phrenological  system. 

He  admitted  with  Gall  that  the  cerebrum  alone  was  of  direct 
importance  to  intelligence ;  but  absolutely  rejected  the,  idea  that 
different  regions  of  the  cerebral  cortex  could  be  relative  to  different 
intellectual  functions.  He  found  it  possible  to  extirpate  very 
extensive  portions  of  the  cerebral  hemispheres  without  producing 
loss  of  their  functions,  and  saw  that  a  very  small  portion  of  the 
brain  sufficed  for  the  exercise  of  its  functions.  But  as  larger 
portions  were  removed  all  the  functions  became  gradually  weaker, 
and  were  entirely  lost  when  the  destruction  exceeded  a  certain 
limit.  Consequently  the  cerebral  lobes  must  be  concerned  as  a 
whole  in  the  exercise  of  their  functions. 

When  one  perception  is  lost,  he  says,  all  the  rest  go  too ;  if  one 
faculty  disappears,  all  the  others  vanish.  There  is  therefore  no 
definite  seat  for  the  different  perceptions.  The  capacity  for 
perceiving,  judging,  or  willing  anything  is  located  at  the  same 
place  as  that  of  perceiving,  judging,  willing  some  other  thing,  and 
this  faculty  is  therefore  one,  and  is  essentially  located  in  a  single 


organ. 


This  rejection  of  central  localisation  seemed  to  be  the  last  word 
on  the  relations  of  the  brain  to  the  mind.  But,  as  the  last  chapter 
si  towed,  later  researches  into  the  effects  of  cerebral  ablation  in  the 
different  classes  of  vertebrates  proved  that  this  theory,  on  which 
all  psychical  functions  are  exclusively  localised  in  the  cerebral 
hemispheres — which  is  still  maintained  by  Muiik  and  to  a  certain 
extent  by  Loeb, — does  not  agree  with  the  facts,  and  is  definitely 
contradicted  by  the  behaviour  of  the  lower  vertebrates  after  the 


544  PHYSIOLOGY  CHAP. 

removal  of  the  fore-brain.  The  only  part  of  Gall's  theory  which 
Floureus  accepted  unreservedly  is  that  which  modern  research  has 
proved  untenable.  On  the  other  hand,  the  great  merit  of  Floureus 
as  the  pioneer  in  cerebral  physiology  is  indisputable.  But  he  went 
too  far  in  his  work  of  destruction ;  it  is  one  thing  to  show  that 
Gall's  localisations  are  unfounded,  and  another  to  deny  absolutely 
all  localisation  of  the  intellectual  functions  in  the  brain. 

The  most  recent  researches  show  plainly  that  there  is  a  nucleus 
of  truth  in  phrenology.  All  portions  of  the  cerebral  hemispheres 
have  not  the  same  functions ;  distinct  areas  of  the  cerebral  cortex 
are  concerned  in  different  sense  perceptions,  in  different  ideas  and 
memories,  and  in  the  various  voluntary  impulses.  But  the  new 
theory  of  cerebral  localisation  is  quite  different  from  that  proposed 
by  Gall,  and  has  been  gradually  developed  upon  a  scientific  and 
experimental  basis. 

G.  K.  Bouillaud  (1825),  a  follower  of  Gall,  published  a  memoir 
called  "  Clinical  researches  to  demonstrate  that  loss  of  speech 
corresponds  with  lesions  of  the  anterior  lobules  of  the  brain,  and 
to  confirm  Gall's  opinion  on  the  seat  of  the  organ  of  articulate 
language."  In  this  memoir,  which  is  of  great  historical  importance, 
he  describes  the  symptoms  of  aphasia  as  observed  by  himself  in  a 
series  of  cases,  in  some  of  which  he  was  able  to  make  a  post- 
mortem examination,  and  to  show  that  in  all  the  lesion  involved 
the  orbital  part  of  the  frontal  lobe.  He  drew  the  following  general 
conclusion  from  his  clinical  and  anatomo-pathological  observa- 
tions :  The  human  brain  has  an  important  function  in  the 
mechanism  of  a  great  number  of  movements ;  it  regulates  such  as 
are  under  the  control  of  the  intelligence  and  the  will.  There  are 
many  special  organs  in  the  brain,  each  of  which  governs  special 
movements.  The  organs  for  the  movements  of  speech  are  directed 
by  a  distinct  and  independent  brain  centre,  which  lies  in  the 
anterior  lobes.  Loss  of  speech  is  due  either  to  loss  of  memory  for 
words,  or  to  loss  of  the  muscular  movements  from  which  speech 
results.  Loss  of  speech  does  not  imply  loss  of  the  movements  of 
the  tongue  as  an  organ  of  mastication  and  deglutition  of  food,  nor 
loss  of  taste — which  suggests  that  the  tongue  has  three  distinct  con- 
nections in  the  brain.  Many  nerves  have  their  origin  in  the  brain  ; 
those  which  innervate  the  muscles  that  co-operate  in  the  produc- 
tion of  speech  originate  in,  or  at  least  necessarily  communicate 
with,  the  anterior  lobes. 

A  little  later  (1836)  M.  Dax,  who  was  probably  unaware  of 
Bouillaud's  important  memoir,  communicated  a  series  of  clinical 
cases  which  demonstrated  that  disorders  of  spoken  language  are 
constantly  associated  with  a  lesion  of  the  left  cerebral  hemisphere. 
A  new  memoir  pointing  out  the  same  constant  coincidence  was 
presented  to  the  Academic  de  Paris  (1863)  by  Dax  fils,  when  it 
was  badly  received  by  Lelut,  but  defended  by  Bouillaud. 


x  THE  FORE-BRAIN  545 

Bouillaud  observed  that  a  certain  number  of  acts,  c.y.  writing, 
drawing,  painting,  fencing,  were  carried  out  with  the  right  hand. 
They  are.  associated  and  co-ordinated  movements  which  imply 
activity  of  a  particular  cerebral  organ,  a  given  centre  for  sensation, 
motion,  and  special  memory,  which  is  undoubtedly  seated  in  the 
left  hemisphere.  Why,  he  asked,  should. we  not  be  left-brained  for 
the  movements  of  articulation  also  ? 

This  acute  conjecture  was  confirmed  by  Paul  Broca,  who 
showed  more  definitely  than  Gall,  Spurzheim,  Bouillaud,  and  Dax 
that  the  true  site  of  the  special  organ  of  verbal  articulation  lies  in 
the  left  hemisphere  of  the  human  brain. 

In  1861  Broca  presented  a  first  memoir  to  the  Anthropological 
Society  of  Paris,  in  which  he  stated,  on  the  basis  of  certain  of  his 
clinical  cases,  that  lesions  of  the  lower  segment  of  the  third  frontal 
convolution  of  the  left  hemisphere  (the  so-called  pars  opercularis  or 
Broca's  convolution)  involved  loss  of  the  faculty  of  speech — aphemia 
or  aphasia.  This  he  showed  to  be  the  seat  of  the  cerebral  organ  of 
verbal  articulation,  or  more  precisely  of  the  memory  of  a  certain 
kind  of  co-ordinated  movements  necessary  for  the  articulation  of 
speech.  In  fact,  in  cases  of  lesions  of  this  convolution  the  memory 
of  words  is  not  lost,  nor  are  the  nerves  and  muscles  that  come  into 
play  in  phonation  and  spoken  language  paralysed  ;  it  is  only  the 
memory  of  verbal  articulation  that  is  affected. 

Broca  was  fully  aware  of  the  capital  importance  of  his  discovery 
as  the  foundation-stone  of  a  new  theory  of  cerebral  localisation  in 
opposition  to  the  doctrine  of  Flourens.  "We  now  know,"  he  says, 
"that  all  the  parts  of  the 'brain  properly  so-called  have  not  the 
same  functions,  that  all  the  convolutions  represent,  not  a  single 
organ,  but  many  organs  or  groups  of  organs,  and  that  there  are 
large  distinct  regions  of  the  brain  which  correspond  to  the  large 
regions  of  the  mind."  According  to  Broca,  the  new  theory  must  be 
built  up  upon  normal  anatomy  and  pathology,  because  a  physio- 
logical system  that  is  not  based  on  definite  anatomical  facts  cannot 
withstand  criticism. 

Another  French  anatomist  and  anthropologist,  P.  Gratiolet 
(1861),  had  a  yet  clearer  conception  of  the  modern  theory  of 
cerebral  localisation,  though  his  view  was  obscured  by  doubts  and 
contradictions,  as  appears  from  the  following  extract  :— 

:'  It  is  legitimate  to  assume  that  there  are  as  many  distinct 
regions  in  the  cerebral  hemispheres  as  there  are  different  organs 
of  sensation  at  the  periphery  of  the  body.  Thus  we  have  the 
brain  of  the  eye,  the  ear,  and  so  on;  and  in  each  of  these  brains  it 
would  be  easy  to  locate  a  memory  and  an  imagination.  But  where 
are  we  to  locate  general  intelligence  ?  If  there  were  several  organs, 
several  brains,  of  what  use  would  they  be  to  one  another?  How, 
for  instance,  could  the  brain  of  the  ear  assist  the  brain  of  the  eye  ? 
The  anatomical  conditions  of  these  associations  and  of  this  synergy 

VOL.  in  2  N 


546  PHYSIOLOGY  CHAP. 

lie  perhaps  in  the  numerous  commissures,  which,  since  they  unite 
all  the  convolutions  of  a  hemisphere  in  the  most  perfect  manner, 
determine  the  fundamental  unity  of  the  hrain.  Is  the  intellect 
seated  simultaneously  in  the  centrum  ovale  and  the  layers  of  the 
cortex,  or  is  it  seated  in  the  latter  exclusively  ?  I  doubt  whether 
in  the  physiology  of  the  intellect  it  is  possible  to  neglect  the 
centrum  ovale  with  safety.  Admitting,  however,  that  the  intellect 
has  the  whole  brain  for  its  organ,  it  is  not  activated  at  all  points 
of  the  brain  in  the  same  way." 

This  statement  of  Gratiolet,  as  was  opportunely  pointed  out  by 
Soury,  contains  almost  the  whole  general  modern  theory  of  the 
localisation  of  cerebral  functions,  which  has  developed  in  quite  a 
different  direction  from  that  of  the  older  phrenology.  The  latter 
pictured  the  brain  as  divided  into  so  many  independent  organs, 
intended  for  very  complex  functions.  The  new  theory,  on  the 
contrary,  endeavours  to  determine  the  varying  importance  of  the 
different  parts  of  the  'brain  in  so  far  as  they  receive  centripetal 
projection  paths  coming  from  the  different  sense-organs,  centrifugal 
projection  paths  along  which  the  different  voluntary  impulses  are 
transmitted  to  the  muscles,  and  commissural  and  association  paths 
which  bring  the  separate  fields  of  action  into  close  connection. 
The  highest  and  most  complex  psychical  functions  are  not  localised 
in  these  cortical  fields,  but  are  conditioned  by  the  associative 
elements,  in  so  far  as  these  co-operate  in  making  the  brain  into  a 
\  single  organ.  The  individual  acts  of  the  mind  result  from  the 
different  combinations  of  the  intellectual  functions  of  the  separate 
cortical  areas. 

IV.  From  these  introductory  remarks,  though  brief  and 
incomplete,  it  will  be  readily  seen  that  the  theory  of  sensory 
and  motor  cerebral  localisation  was  already  formulated  in  the 
abstract,  and  only  called  for  experimental  evidence  and  better 
definition,  when  Hitzig  aud  Fritsch  (1870)  published  their  first 
memoir, "  On  the  electrical  excitability  of  the  brain,"  which  formed 
the  brilliant  opening  of  a  new  chapter  in  cerebral  physiology. 

All  the  most  experienced  experimenters — Magendie,  Longet, 
Matteucci,  Van  Deen,  Budge,  Schiff — believed  that  the  nerve- 
centres  of  the  cerebrospinal  axis  in  general,  and  of  the  cerebral 
hemispheres  in  particular,  were — unlike  the  peripheral  nerves— 
iuexcitable  to  different  kinds  of  stimuli  applied  directly  either  to 
the  grey  or  to  the  white  matter.  Fritsch  and  Hitzig  were  the 
first  who  demonstrated  the  fallacy  of  this  belief.  They  found,  and 
this  was  their  chief  discovery,  that  a  portion  of  the  convexity  of 
the  cerebral  hemispheres  of  the  dog  is  motor,  that  is,  it  reacts 
by  muscular  movements  to  the  direct  application  of  a  galvanic 
current,  while  the  other  portion  is  iuexcitable  to  this  stimulus. 
On  exciting  with  weak  currents  the  resulting  contractions  are 
limited  to  certain  groups  of  muscles  on  the  opposite  side  of  the 


X 


THE  FOKE-BRAIN 


547 


body;  with  stronger  currents  the  reaction  spreads  to  more. 
muscles,  not  only  on  the  opposite,  hut  also  ou  the  same  side  of  the 
hody.  The  mere  displacement  of  the  electrodes,  or  moving-  them 
away  from  each  other,  is  enough  to  alter  the  form  or  extent  of 
the  reaction.  Lastly,  if  the  electrodes  are  moved  still  further 
from  each  other,  or  the  current  strengthened,  epileptiform  con- 
vulsions set  in  which  rapidly  involve  all  the  muscles. 

Hitzig  and  Fritsch  gave  the  name  of  centres  to  those  areas  of 
the  cerebral  cortex   which,  when   excited  with    a   weak    current, 
induce  reaction  in  a  limited  group   of  muscles   on   the   opposite 
side.    The  position  of  these  centres 
is  approximately  constant  in  the 
dog,  taking   into    account  the 
different  conformation  of  the  sulci 
in     different     races.        They     are 
grouped    round    the   sulcus   cruci- 
atus,  which    limits   the   so-called 
sigmoid  convolutions  in    the   dog, 
and    also    extend   to    the  anterior 
part  of  the  second  external   con- 
volution, as  shown  in  Fig.  274. 

The  excitable  area  of  Fritsch 
and  Hitzig  includes  the  centres  for 
the  movements  of  the  adductors, 
flexors,  and  extensors  of  the  limbs 
on  the  opposite  side,  as  well  as  the 
centres  which  control  the  move- 
ments of  the  face,  head,  and  neck. 
They  evoked  contractions  of  the 
muscles  of  the  back,  tail,  and 
abdomen,  on  exciting  points  of 
the  brain  surface  lying  between 
those  defined  as  centres,  but  were 
unable  to  determine  satisfactorily 
any  circumscribed  point  from  which  each  of  the  above  movements 
could  be  separately  excited.  They  stated  that  the  whole  of  the 
cerebral  surface  behind  the  centre  for  the  facial  muscles  was 
absolutely  insensitive  to  the  strongest  electrical  excitation. 

The  galvanic  current  is  not,  however,  the  most  appropriate 
stimulus  for  the  purpose  for  which  it  was  employed  by  Hitzig 
and  Fritsch.  Every  closure  or  opening  of  the  current  produces 
an  electrolytic  change  in  the  cerebral  surface  at  the  points  of 
contact  of  the  electrodes,  which  rapidly  depresses  and  abolishes 
excitability.  This  is  not  the  case  if  faradic  currents  are  employed, 
and  these  can  moreover  be  readily  varied  so  as  to  adapt  them  to 
the  varying  excitability  of  the  motor  points  of  the  cerebral  cortex. 

Ferrier  (1873-1875),  in  determining  the  excitable  points  of  the 


FIG.  274.— Cortical  motor  centres  of  dog, 
according  to  first  experiments  by  Hitzig 
and  Fritsch.  A,  centre  of  neck  muscles  ; 
+  ,  of  extensor  and  adductor  muscles  of 
anterior  limb;  +,  of  flexors  and  rotators 
of  anterior  limb;  {{,  of  muscles  of  posterior 
limb  ;  Q,  of  muscles  of  the  face.  The  two 
hemispheres  belong  to  two  different  kinds 
of  dogs. 


548  PHYSIOLOGY  CHAP. 

cerebral  cortex,  used  the  currents  from  the  secondary  coil  of  Du 
Bois-Keymond's  sliding  inductorium,  coupled  with  a  Daniell  cell, 
and  succeeded  in  localising  more  centres,  and  in  extending  the 
excitable  zone,  in  the  dog  (Fig.  275).  This  was  a  marked  advance, 
not  only  as  regards  specialisation  of  the  reactions,  but  also  as  to 
their  form.  Terrier's  observations,  in  fact,  bring  out  clearly  that 
the  motor  reactions  evoked  on  faradisation  of  the  cerebral  surface 
have  a  marked  character  of  purpose,  that  is,  they  are  perfectly 
analogous  to  the  various  movements  co-ordinated  to  a  given  end 
which  the  animal  voluntarily  performs  under  normal  conditions 
of  life.  These  are  not  obtained  with  galvanic  currents,  which 
induce  sudden  contractions  of  given  groups  of  muscles  at  each 


Fir;.  275. — Cortical  motor  centres  of  dog  according  to  Ferrier.  1,  opposite'  hind-limb  fuh;inn-<l  ; 
3,  tail  moved  laterally  ;  4,  retraction  and  adduction  of  opposite  hind-limb ;  5,  protraction  of 
opposite  fore-limb  with  elevation  of  shoulder;  7,  closure  of  opposite  eye,  and  movement  of 
eye-l>alls;  8,  retraction  and  elevation  of  opposite  angle  of  mouth;  9,  opening  of  mouth  and 
movements  of  tongue;  10,  retraction  of  angle  of  mouth  owing  to  contraction  of  platysma  ; 
11,  elevation  of  an^le  of  mouth  and  side  of  face,  with  closure  of  eye ;  12,  opening  of  eyes  witli 
dilatation  of  pupils  ami  movements  of  eyes  and  head  to  opposite  side  ;  13,  movement  of  eyes  to 
opposite  side  ;  14,  pricking  or  sudden  retraction  of  opposite  ear;  15,  torsion  of  nostril  on  same 
side  ;  10,  elevation  of  upper  lip  and  dilatation  of  nostrils. 

opening  and  closure,  which  have  not  the  perfect  association  and 
succession  characteristic  of  normal  voluntary  acts. 

Working  with  Tamburini  (1878)  we  brought  some  new  facts 
to  light,  in  regard  both  to  specialisation  of  the  reactions  from  the 
various  excitable  areas  in  the  dog,  and  to  their  extent  and 
location  in  different  individuals  and  in  both  hemispheres  in  one 
animal.  It  is  not  accurate  to  say  that  the  excitable  areas  which 
Hitzig  termed  centres  have  an  approximately  constant  position 
in  different  dogs,  and  it  is  a  mistake  to  assume  with  Ferrier  that 
they  are  symmetrical  in  the  two  hemispheres  of  the  same  animal. 
Not  only  may  the  centres  for  the  front  limbs  be  grouped  in  two 
distinct  areas,  capable  of  provoking  two  opposite  reactions,  but 
a  similar  specialisation  can  more  frequently  be  demonstrated  also 
in  the  region  concerned  with  the  movements  of  the  hind-limb. 
Lastly,  not  only  does  the  excitability  of  the  centres  vary  with  the 


THE  FOEE-BEAIN 


549 


different  experimental  conditions  to  which  the  animal  is  exposed 
(derive  of  narcosis,  haemorrhage  during  the  operation,  hyperaemia 
or  isrliat'inia  of  the  cortex),  but  the  excitability  of  Hie  different 
centres  of  the  same  animal  also  varies,  as  well  as  the  extent  of 
the  areas  which  each  occupies.  This  is  shown  diagram  matically 
in  Fig.  276. 

A  new  fact  which  we  discovered  in  18*78  is  that  the  motor 
centres  for  the  limbs  of  the 
dog  are  not  limited  to  the 
surface  of  the  postcruciate  part 
of  the  sigmoid  gyrus,  but  ex- 
tend into  the  portion  of  the 
cortex  that  dips  into  the  sulcus, 
which  we  found  to  be  about 
three  times  as  extensive  as  the 
excitable  area  on  the  surface. 
When  an  induced  current  is 
applied  by  suitably  protected 
electrodes,  reactions  of  the 
hind-limb  on  the  opposite  side 
arc  obtained  when  the  elec- 
trodes are  placed  on  the  most 
internal  and  median  part  of 
the  introtiected  cortex;  and  re- 
actions <  if  the  opposite  fore- limb 
(in  exciting  the  outer  part  of 
the  cortex. 

Later  on  (1883)  we  found 
that  the  cortex  within  the 
sulcus  cruciatus  of  the  dog  is 

excitable,  not    merely  tO  faradic     FIG.  276.— Asymmetrical  localisation  of  the  motor 
!     .  .          i  i  i         •  centres    in    the    postcruciate 

stimulation,  but  also  to  mechani- 
cal stimuli.  To  demonstrate  this 
it  is  necessary  to  divide  the 
arachnoid  that  unites  the  two 
edges  of  the  cruciate  sulcus, 
avoiding  the  vein  that  passes 

through  it,  and  to  introduce  a  metal  probe  with  sharp  edges 
carefully  through  the  opening,  and  pass  it  along  the  sulcus  so 
as  to  scrape  the  introflected  cortical  surface.  The  usual  com- 
plex motor  reactions  of  the  muscles  of  the  limbs  on  the  opposite 
side  will  be  at  once  obtained;  those  of  the  posterior  limbs  on 
scraping  the  inner  and  deeper  part,  and  of  the  anterior  limbs 
on  scraping  the  outer  and  superficial  part  of  the  introflected 
cortex.  The  reactions  do  not  differ  from  those  obtained  with 
electrical  stimulation,  but  they  are  usually  less  vigorous,  and 
after  being  once  elicited,  do  not  recur  on  repeating  the  stimulus, 


postcruciate  part  of  clod's 
sigmoid  gyrus.  (Lnciani  and  Tainlmrini.)  a, 
abduction  and  flexion  of  posterior  limb  of 
opposite  side  ;  a',  elevation  and  advance  of  same 
limb;  6,  abduction  and  elevation  of  oppn^iti' 
fore-limb;  V,  flexion  of  forearm  on  arm  with 
movement  of  opposite  shoulder  ;  b",  retraction 
and  adduction  of  opposite  fore-limb;  c,  move- 
ments of  head  and  neck. 


550  PHYSIOLOGY  CHAP. 

since  this  partially  destroys  the  nervous  tissue  and  abolishes  its 
excitability. 

The  mechanical  excitability  of  the  cortex  in  the  depths  of  the 
cruciate  sulcus  is  no  accidental  or  exceptional  fact ;  it  can  invari- 
ably be  demonstrated  in  all  dogs  in  which  the  electrical  excitability 
of  the  superficial  cortical  centres  is  well  preserved. 

All  previous  observers  found  the  superficial  cortex  of  the 
sigmoid  gyrus  inexcitable  to  mechanical  stimuli.  In  very 
exceptional  cases  only  Hitzig  (1877)  observed  movements  of  one 
limb  during  the  removal  of  the  corresponding  centre.  It  is  prob- 
able that  the  normal  mechanical  excitability  of  the  motor  centres 
of  the  cortex  is  easily  exhausted,  long  before  the  electrical  ex- 
citability, by  mere  exposure  of  the  surface  to  the  air.  The  cortex 
in  the  cruciate  sulcus,  on  the  contrary,  keeps  its  excitability 
longer. 

The  action  of  chemical  stimuli  on  the  cerebral  cortex  produces 
different  effects.  Landois  (1891)  found  that  on  sprinkling  the 
motor  zone  of  the  dog  with  various  constituents  of  urine  clonic 
convulsions  set  in  after  a  long  latent  period,  which  lasted  a  longer 
or  shorter  time  and  were  more  or  less  generalised  all  over  the 
body.  Maxwell  (1906)  observed  that  these  symptoms  of  excitation 
are  due,  not  to  stimulation  of  the  ganglion  cells  of  the  cortex, 
but  to  osmotic  or  chemical  excitation  of  the  nerve-fibres  in  the 
subjacent  white  matter,  which,  as  we  know  from  other  experiments 
on  nerve  (see  p.  219),  react  to  these  stimuli. 

But  in  another  series  of  experiments  he  found  that  certain 
chemical  substances,  like  creatine,  act  directly  upon  the  elements 
of  the  cortical  grey  matter.  In  fact,  the  application  of  creatine, 
solid  or  strongly  concentrated,  to  the  cortex  is  followed  after 
rather  a  long  latent  period  by  clonic  and  tonic  contractions, 
while  the  injection  of  creatiue  solutions  into  the  depth  of  the 
white  matter,  and  steeping  the  motor  nerve  trunks  in  saturated 
solution  of  the  same  substance,  fails  to  evoke  signs  of  reaction. 

Baglioni  and  Magnini  (1909)  worked  out  the  effects  of  different 
chemical  substances  (acetic,  citric,  carbolic,  glyceric  acids,  urea, 
sodium  chloride,  sodium  sulphate,  strychnine,  picrotoxiu,  and 
curare)  when  applied  to  the  excitable  zones  of  the  cerebral  cortex 
of  the  dog.  After  exposing  the  motor  zone  and  determining  the 
threshold  of  the  faradic  excitability  of  a  given  centre,  they  applied 
the  chemical  substance,  and  employed  the  threshold  of  faradic 
excitability  to  ascertain  the  stimulating  or  depressing  action  of 
the  chemical  substance  employed,  independent  of  the  direct  motor 
reactions  which  it  produced. 

From  their  results  they  were  able  to  divide  the  chemical 
substances  which  affect  the  centres  in  the  motor  zone  into  two 
distinct  groups. 

(«)  The  first  includes  the  acids  employed,  and  glucose,  urea, 


X 


THE  FORE-BRAIN 


551 


chloride  and  sulphate  of  sodium.  In  very  weak  solutions  these 
have  no  effect  on  the  faradic  excitability  of  the  cortex  ;  while  in 
stronger  concentrations,  or  solid,  they  almost  constantly  lower  the 
excitability.  In  minimal  doses  they  do  not  include  spontaneous 
spasms  or  clonic  contractions;  in  comparatively  strong  doses,  on 
the  contrary,  they  induce  paralytic  symptoms,  which  are  evidently 
due  to  the  chemical  destruction  of  the  nerve  elements. 

(ft)  The  second  group  includes  strychnine  and  picrotoxin.     In 
minimal   doses    these   substances   immediately  raise    the   faradic 


Fio.  277. — Surface  of  left  hemisphere  ot  < '<  rm-  I'm.  278. — Upper  surface  of  hemispheres  of 

fitli'i'iiK.     (Kerrier.)  I'fri'iijiillii.-ita.     (Kerrier.) 

1,  Opposite  hind-limb  advanced  as  in  walking;  2,  movements  of  thigh,  leg,  and  foot  ;  3,  move- 
ments of  tail;  4,  retraction  and  adduction  of  opposite  arm;  5,  forward  extension  of  opposite 
arm  and  hand  ;  a,  b,  r,  <1,  single  and  combined  movements  of  lingers  and  list ;  (5,  supination  and 
llexion  of  f ore -arm  ;  7,  contraction  of  zygomatic  muscles  with  retraction  and  elevation  of  angle 
of  mouth  ;  8,  elevation  of  ala  of  nose  and  upper  lip  ;  !>,  10,  opening  of  mouth,  advance  of  lips, 
protrusion  and  retraction  of  tongue  ;  11,  retraction  of  opposite  angle  of  mouth  ;  12,  wide  opening 
of  eyes,  dilatation  of  pupils,  movement  of  eyes  and  head  to  opposite  side ;  13,  13',  movement  of 
ryes  to  opposite  side,  with  upward  or  downward  deviation  and  contraction  of  pupils  ;  14,14', 
pricking  of  opposite  ear,  with  rotation  of  eyes  and  head  to  opposite  side,  wide  dilatation  of  pupils. 

excitability  of  the  excitable  areas,  and  after  a  very  1  rief  latent 
period  of  from  a  few  seconds  to  1-2  minutes  produce  the  localised 
movements  similar  to  those  observed  on  faradic  excitation  of  the 
centres,  but  the  movements  are  repeated  rhythmically,  at  the  rate 
of  about  40-50  per  minute,  for  a  longer  or  shorter  time  (25-35 
mins.)  in  the  form  of  characteristic  tic-like  movements,  whether 
the  animal  is  fixed  to  the  apparatus,  or  suspended  by  the  back,  or 
left  free  on  the  ground. 

Probably   curare    should    also    be    included    in    this   class    of 
the  chemical  substances  which  are  capable  of  directly  exciting  the 


PHYSIOLOGY 


CHAP. 


ganglion  cells  of  the  cortex.  Sergi  (1902)  observed  phenomena 
analogous  to  the  above  on  applying  curare  to  the  cortex  of  the 
guinea-pig;  Baglioni  and  Magnini  noted  an  increase  of  faradic 
excitability,  expressed  by  a  drop  in  the  threshold  of  excitability. 

That  the  action  of  these  specific  poisons  (strychnine,  picro- 
toxin,  curare)  is  exerted  electively  on  the  cortical  ganglion  cells, 
and  does  not  spread  to  the  nerve-fibres  of  the  corona  radiata, 
is  demonstrated  by  the  fact  that  both  the  increase  in  faradic 
excitability  and  the  rhythmical  contractions  disappear  immediately 


FIG.  279.— Plan  of  li-l't  hemisphere  in  Macacus  brain.     External  surface.    (Horsley  and  SchalVr.) 

and  for  ever  so  soon  as  the  poisoned  area  of  the  cortex  is  excised 
or  damaged  by  other  poisons. 

The  fact  that  carbolic  acid,  which  picks  out  the  motor  cells  of 
the  ventral  horn  of  the  spinal  cord,  has  no  action  nor  depressing 
effect  on  the  cortex  led  Baglioni  and  Magnini  to  conclude  that 
the  ganglion  cells  of  the  cortical  motor  zone  are  not  of  the  same 
nature  as,  and  cannot  be  identified  with,  the  motor  cells  of  the 
cord  through  which  they  indirectly  exert  their  motor  effect,  and 
should  rather  be  compared  with  the  cells  of  the  dorsal  horn  of  the 
spinal  cord  in  their  property  of  reacting  to  strychnine. 

Later  work  on  the  dog's  brain  added  to  the  number  of  excit- 
able centres.  H.  Krause  (1884),  on  applying  electrical  stimuli  to 
an  area  lying  somewhat  external  to  and  in  front  of  Terrier's  point 


X 


THE  FORE-BRAIN 


553 


12,  observed  movements  of  deglutition  and  partial  or  total  con- 
strietion  of  the  glottis  and  larynx  associated  with  contract-ion  of 
the  muscles  of  the  neck,  of  the  superior  constrictors  of  the  pharynx, 
levatores  veli-palatini,  glosso-palatini,  and  tongue — in  a  word,  the 
muscles  which  come  into  play  in  deglutition  and  phonation. 

The  internal  interhemi spherical  surface  of  the  brain,  while  less 
known  (perhaps  because  more  difficult  to  explore),  also  contains 
excitable  areas,  although  these  have  not  been  localised  and  defined 
with  sufficient  accuracy.  Lo  Monaco  found  that  the  fore-part  of 


MOVEMENTS  OFFLEX|ON    AT 

TOES  AND    KNEE         EXTENSION. 
AT 


FIG.  280.—  Plan  of  left  hemisphere— 


Internal  surface.     (Horsley  and 


the  marginal  convolution  contains  the  continuation  of  the  sensory 
motor  /one  of  the  external  surface. 

Ferrier  first  applied  the  method  of  faradisation  to  determining 
the  excitable  area  in  the  lower  apes  (Macacus  cynomolgus).  He 
found  that  it  extended  over  a  larger  surface  than  in  the  dog;  in 
addition  to  the  two  central  or  Rolandic  convolutions  it  comprises 
the  angular  gyrus,  a  portion  of  the  upper  tempero-sphenoid  con- 
volution, and  part  of  the  first  and  second  frontal  convolutions. 
As  shown  by  Figs.  277  and  278,  a  larger  number  of  centres  for 
given  movements  of  different  muscular  groups  can  lie  identified  in 
this  species  of  ape. 

For  descriptive  purposes,  Beevor  and  Horsley  (1887-88) 
divided  the  excitable  zones  of  the  cerebral  cortex  of  Macacus  into 


554  PHYSIOLOGY  CHAP. 

fields  or  areas  (Figs.  279  and  280) :  (a)  the  area  connected  with 
movements  of  the  head  and  eyes ;  (&)  that  connected  with  move- 
ments of  the  face,  including  those  of  the  mouth,  cheeks,  and 
larynx  ;  (c)  that  related  to  the  movements  of  the  upper  limhs ; 
(d)  that  for  movements  of  the  lower  limbs  ;  (e)  that  connected 
with  movements  of  the  trunk  and  tail.  These  areas  are  not  limited 
by  sulci  or  other  structural  features ;  so  they  are  not  distinct,  as 
would  appear  from  the  diagram,  but  merge  gradually  one  into 
another.  When  the  faradic  stimulus  is  moderate  and  falls  1  letween 
the  limits  of  one  of  the  areas,  the  reactions  are  confined  to  a  single 
region ;  when  the  stimulus  is  strong  and  protracted  the  reactions 
spread  into  the  neighbouring  regions ;  when  the  stimulus  falls  at 
the  point  of  transition  between  two  areas,  muscular  reactions  can 
be  elicited  from  both  regions  by  even  a  moderate  excitation. 

On  stimulating  different  points  of  the  five  areas  above  enumer- 
ated, Beevor  and  Horsley  obtained  a  further  specialisation  of  the 
reactions  shown  on  the  two  figures  reproduced.  These  intra- 
regional  localisations  are  more  definite  and  pronounced  in  propor- 
tion as  the  areas  are  wider  and  the  reactions  more  circumscribed. 
This  holds  especially  for  the  movements  of  the  fore-limbs  and  the 
face.  The  reactions  usually  permit  of  distinction  into  a  relative 
area  and  a  small  principal  area  or  focal  point,  on  stimulating 
which  the  given  movement  results  with  greater  promptness  and 
precision.  The  movement  is  rarely  simple,  e.cj.  flexion  or  extension 
of  the  thumb;  more  frequently  complex  movements  result,  simul- 
taneously or  in  succession.  The  reactions  obtained  most  constantly 
and  promptly  may  be  termed  primary  movements  in  distinction 
from  the  secondary  which  occur  rarely. 

The  most  salient  characteristic  of  these  reactions — as  Ferrier 
first  pointed  out — is  their  purposive  co-ordination,  as  though  they 
were  evoked  by  an  act  of  volition.  The  impression  made  is  that 
the  voluntary  movements  most  frequently  carried  out  by  these 
animals  are  those  most  readily  obtained  by  electrical  stimulation 
of  the  cortex.  Thus,  on  stimulating  certain  points  of  the  area  for 
the  arm,  it  is  easy  to  elicit  a  series  of  prehensile  movements ;  011 
stimulating  certain  lower  points  of  the  area  for  the  face,  a  series  of 
complex  mastication  movements  is  obtained,  which  are  character- 
istic of  Macacus.  When  the  reaction  elicited  by  electrical  stimula- 
tion is  not  co-ordinated,  it  can  often  be  shown  that  the  surface  of 
the  brain  is  in  a  condition  of  abnormal  excitability,  which  causes 
excitation  to  spread. 

The  results  which  Beevor  and  Horsley  (1890)  obtained  by 
faradising  the  cerebral  cortex  of  an  orang-outang,  and  those  from 
the  wider  experiments  of  Grlinbaum  and  Sherriugton  (1901-3)  on 
anthropoid  apes,  are  of  great  interest,  since  the  configuration  of  the 
anthropoid  brain  is  closely  allied  to  that  of  man. 

Beevor  and  Horsley  found  that  the  complex  excitable  areas  of 


x  THE  FORE-BRAIN  555 

the  cortex  of  the  orang  do  not  overlap  like  those  of  the  lower  apes 
(Macacus,  Cerco^ithcrus),  hut  are  separated  here  and  there  by 
intermediate  areas  which  are  inexcitable  even  to  strong  currents. 
The  sum  of  the  excitahle  areas  is  relatively  smaller  in  the  orang 
than  in  the  lower  apes.  In  tact  the  first  frontal  convolution  and  the 
upper  part  of  the  postcentral  convolution  were  inexcitable ;  in  the 
fronto-parietal  lohe  the  whole  of  the  precentral  convolution,  an  area 
in  front  of  the  precentral  sulcus,  the  lower  two-thirds  of  the  post- 
central  convolution,  and  the  portion  of  the  marginal  gyrus  which  is 
continuous  with  the  superior  end  of  the  precentral  were  excitahle. 

Griinbauni  and  Sherrington  obtained  somewhat  different  results 
from  their  experiments  on  sixteen  individuals  of  different  species 
— orangs  (Opithaecus  satyr  us),  gorillas  (Troglodytes  gorilla?),  and 
chimpanzees  (Troglodytes  nigcr  and  Troglodytes  calvus).  For 
stimulating  the  cortex  they  preferred  the  method  of  unipolar 
faradisation,  hy  which  the  excitable  areas  can  be  more  precisely 
differentiated. 

They  found  in  each  of  the  animals  examined  that  the  motor 
areas  were  present  all  along  the  precentral  convolution  (Fig.  281), 
and  continued  into  the  cortex  that  dips  into  the  central  or 
Rolandic  sulcus,  and  the  other  secondary  sulci  by  which  this  is 
limited.  Probably  the  excitable  area  buried  in  the  sulci  equals,  if 
it  does  not  exceed,  that  which  is  uncovered.  The  anterior  limit 
of  this  area  is  not  sharp,  and  retreats  towards  the  central  sulcus 
when  the  excitability  of  the  cortex  is  depressed.  The  posterior 
limit,  on  the  contrary,  is  sharper  and  more  constant,  and  reaches 
the  floor  of  the  central  sulcus  along  its  entire  length,  with  the 
exception  of  its  upper  and  lower  portions.  In  none  of  the  animals 
examined  were  there  excitable  areas  in  the  postcentral  convolution. 
Sometimes,  and  only  with  strong  faradisation,  weak  and  indefinite 
reactions  were  evoked,  which  are  not  comparable  with  those 
obtained  from  the  true  motor  area.  Still  it  can  be  seen  that  the 
motor  effects  of  faradising  the  several  points  of  the  precentral 
convolution  with  weak  currents  are  facilitated  by  the  simultaneous 
faradisation  of  the  points  lying  at  the  same  level  of  the  post- 
central  convolution.  The  student  is  advised  to  note  this  fact, 
which  may  solve  the  contradiction  between  the  results  of  Beevor 
and  Horsley  and  those  of  Grunbaum  and  Sherrington  as  regards 
the  excitability  of  the  postcentral  convolution. 

The  entire  surface  of  the  island  of  Reil  is  inexcitable  even  to 
strong  currents.  On  the  mesial  surface  of  the  hemispheres  the 
excitable  area  is  small  in  extent  (Fig.  282).  It  does  not  reach  the 
sulcus  calloso-marginalis.  Certain  points  near  this  fissure  may 
evoke  weak  movements  of  the  shoulder,  trunk,  hand,  and  finger ; 
but,  according  to  Grunbaum  and  Sherriugton,  it  is  uncertain 
whether  these  are  of  the  same  character  as  those  evoked  from  the 
true  motor  zone. 


556 


PHYSIOLOGY 


CHAP. 


In  the  cortex  of  the  frontal  lobe  Griinbaum  and  Sherrington, 
like  Beevor  and  Horsley,  found  a  large  area  completely  separated 
from  the  motor  zone  of  the  Eolandic  area,  faradisation  of  which 
produces  conjugate  deviation  of  the  eyes.  The  lower  extremity  of 
the  occipital  lobe,  and  the  region  lying  around  the  lips  of  the 
calcarine  fissure,  are  excitable  to  faradisation  ;  conjugate  movements 
of  the  eye!  »alls  may  be  also  elicited  from  here.  Griinbaum  and 


Anus 


Abdomen 

Chest 


Fingers 
c$  thumb \_ 


^e^  /  CidLre 
Nose     of  JAW. 


Opening 
ofj&w.        Vocal 
cords. 


Salcus  centralis. 


FIG.  281.— External  surface  of  brain  of  orang,  showing  excitable  areas. 
(Griinbaum  and  Sherrington.) 

Sherrington,  however,  hesitate  to  include  this  region  with  the  true 
motor  area  represented  by  the  Eolandic  area. 

The  two  figures  281  and  282  give  approximately  the  localisation 
of  the  areas  for  the  face,  fore-limbs,  trunk,  and  hind-limbs,  as  well 
as  the  differentiation  of  the  excitable  points  contained  in  each 
area.  Among  these  are  centres  for  the  special  movements  of  the 
ears,  nostrils,  palate  (acts  of  sucking  or  mastication),  vocal  cords, 
muscles  of  thorax,  abdomen,  pelvis,  and  of  anal  and  vaginal  orifices. 
The  faradisation  of  certain  points  produces  not  motor  but  inhibitory 
effects  similar  to  those  described  by  Sherrington. 

These  results  of  the  experiments  of  Griinbaum  and  Sherrington 
on  anthropoid  apes  differ  from  those  observed  by  Beevor  and 


THE  FOBE-BEAIN 


557 


Horsley,  since  they  found  that  the  motor  area,  docs  not,  extend  to 
the  postcentral  convolution,  hut  is  contincd  to  the.  whole  extent  of 
the  precentral  and  the  introflexed  cortex  of  the  Eola,ndie,  sule.us, 
and  that  the  excitable  areas  of  which  it  consists  are  not  separated 
from  one  another  by  intermediate  inexcitahle  spots,  hut  partially 
overlap  at  the  margins,  forming  a  true  continuous  excitable  /one, 
like  that  observed  on  the  lower  apes. 

It  is  remarkable  that  the  topographical    distribution    of   the 
cortical  centres  for  the  musculature  of  the  different  regions  of  the 


Sale.  Central.       A  nu3,  * 


SuLc.  caUcso 


Sulc.precen  Cr  marg. 


SuLc.parlfto 
occip. 


Sidc.calcarin 


FIG.  282. — Internal  or  mesial  snrfac.fi  of  brain  of  oraiiy,  showiny  excitable  amis. 
(Grunbanm  and  Sherrington.) 

body  lies  within  fairly  exact  limits  along  the  precentral  con- 
volution, from  below  upward,  in  the  segmental  bulbo-spinal  order 
(Fig.  281). 

In  man,  too,  observations  have  been  made  with  the  object  of 
mapping  out  the  topography  of  the  excitable  areas  of  the 
cortex.  The  first  attempts  were  made  by  the  American  surgeon 
Bartholow  and  the  Italian  neurologist  Sciamanna.  Bnt  the  data, 
obtained  were  scanty,  since  only  very  circumscribed  areas  of  the 
cortex,  exposed  by  surgical  operations,  were  excited.  More 
recently,  owing  to  the  progress  of  cerebral  surgery,  the  Eolandic 
region  of  the  human  brain  has  often  been  exposed  in  cases  of 
epilepsy,  and  excited  by  the  same  faradisation  methods  as  are 
employed  in  dogs  and  monkeys.  The  most  important  results 
were  obtained  by  Ferrier  in  four  individuals  (1890),  by  Horsley 


558  PHYSIOLOGY  CHAP. 

and  Beevor  in  six  (1890),  and  by  Bechterew  in  tbree  adolescents 
suffering  from  idiopathic  epilepsy  (1899). 

The  general  conclusions  arrived  at  by  Becbterew,  from  the 
results  of  his  predecessors  as  well  as  of  his  own  researches,  are  as 
follows  :— 

(a)  The  general  arrangement  of  the  motor  centres  in  man 
coincides  approximately  with  that  observed  in  the  lower  apes 
(Macacus,  C'ercopithecus}.  In  fact,  according  to  Bechterew,  they 
include  both  the  central  or  Rolandic  convolutions,  besides  the 
adjacent  regions  of  the  frontal  convolutions. 

(&)  The  centres  for  the  lower  limits  lie  in  the  upper  segment  of 
the  postcentral  convolution;  the  centres  for  the  upper  limbs  lie  in 
the  median  segment  of  the  two  central  convolutions ;  immediately 
below  these  are  the  centres  for  the  thumb  and  fingers,  and  finally 
the  centres  for  the  face  lie  in  the  lowest  segment  of  the  two  central 
convolutions. 

(c1)  The  centres  for  the  lateral  movements  of  the  head  and  eyes 
correspond,  as  in  the  monkey,  with  the  posterior  segment  of  the 
second  frontal  and  probably  extend  to  the  adjacent  regions 
as  well. 

(d")  The  centres  for  the  musculature  of  the  back  lie  on  the 
surface  of  the  precentral  convolution,  above  the  centres  for  the 
upper  limit,  and  probably  extend,  as  in  the  monkey,  to  the  adjacent 
mesial  surface  of  the  hemisphere. 

(e)  In  man,  as  in  the  monkey,  there  are  special  centres  for  the 
thumb  and  fingers,  which  lie  immediately  below  the  motor  centres 
for  the  upper  limbs. 

(/)  As  in  monkeys,  the  several  cortical  centres  above 
enumerated  are  separated  in  man  by  tracts  of  inexcitable  cortex 
(Bechterew). 

This  last  observation  merely  echoes  the  results  obtained  by 
Beevor  and  Horsley  on  the  orang,  which  were  contradicted  by  the 
later  and  more  numerous  experiments  of  Griinbaum  and  Sherrington 
on  various  species  of  anthropoid  apes.  The  supposed  isolation  of 
centres  noted  by  these  authors  pro)  >al  >ly  depends  upon  a  depression 
of  the  normal  excitability  of  the  cortex,  due  either  to  excessive 
narcosis  or  to  the  prolonged  exposure  of  the  cerebral  surface, 
owing  to  which  only  the  focal  areas  of  the  different  centres  remain 
excitable,  while  the  peripheral  borders,  by  means  of  which  these 
centres  are  connected  and  partially  overlap,  have  completely  1<  »st 
their  excitability.  Sherrington's  observation  that  the  anterior 
limit  of  the  excitable  zone  of  the  anthropoid  apes  is  indefinite,  and 
becomes  displaced  backwards  towards  the  central  sulcus  as  the 
cortical  excitability  is  lowered,  is  in  favour  of  this  hypothesis. 
In  this  class  of  research  a  positive  result  is  invariably  more 
valuable  than  a  negative  result. 

An  important  correction  of  Bechterew's  conclusions  is  offered  by 


X 


THE  FORE-BRAIN 


559 


F.  Krause's  recent  and  numerous  experiments  on  localisation  of  the 
motor  area  in  the  human  lirain  by  means  of  unipolar  faradisation. 
His  results  coincide  perfectly  with  those  of  Sherrington  for 
anthropoid  apes,  in  so  far  that  they  demonstrate  the  inexeitability 
of  the  postcentral  convolution,  and  limit  the  human  motor 
cortical  area  to  the  precentral  gyrus.  He  further  succeeded  in 
differentiating  more  fully  the  excitable  points  corresponding  to 
different  movements  of  the  upper  limb  and  face  (Fig.  283). 

There  can  be  no  doubt — although  there  is  no  direct  evidence— 
that  the  excitable  area  of  the  human  brain  also  extends  to  the 


-r 


Fio.  283. — Electrically  excitable  region  of  human  cortex.  (F.  Krause.)  The  black  dots  on  the 
surface  of  the  precentral  convolution  indicate  the  different  motor  centres  ;  /,  sulcus  centmlis 
or  fissure  of  Rolando  ;  n.  extension  and  internal  rotation  of  foot ;  li,  elevation  and  abduction  of 
arm  ;  c  and  rf,  flexion  of  knee  ;  c,  ulnar  flexion  ;  /,  palmar  flexion  ;  ;/,  radial  flexion  ;  /(,  dorsal 
flexion  of  hand  ;  i,  p,  q,  r,  movements  of  thumb ;  I,  flexion  ;  in,  extension  of  four  fingers  ;  n, 
extension  ;  o,  flexion  of  index  finger;  s,  extension  of  little  finger;  t,  eyelid  of  opposite  side  ;  », 
movements  of  buccal  angle  ;  r,  of  zygomatic  muscle  and  levator  of  upper  lip  ;  .c,  c  if  niassfl  ITS  ; 
y,  of  external  pterygoid  muscle. 

introfiexed  cortex  that  dips  into  the  lips  of  the  Kolandic  sulcus,  as 
has  been  well  demonstrated  in  the  anthropoid  apes. 

Some  authors  have  contended  that  a  stronger  current  is  required 
to  elicit  motor  effects  in  man  and  in  the  anthropoid  apes  than  in 
the  lower  animals,  and  that  in  man  it  is  more  difficult,  owing  to 
spread  of  the  excitation  to  the  subjacent  centres,  to  arouse  epilepti- 
form  convulsions  by  electrical  stimulation  of  the  cortex.  Both 
these  statements  were  contradicted — by  Griinbaum  and  Sherrington 
for  the  anthropoid  apes,  and  by  Bechterew  and  Krause  for  man. 

V.  These  experimental  observations  on  the  topography  of  the 
excitable  areas  of  the  brain  surface  in  the  higher  vertebrates 
represent  the  development  of  the  important  discovery  of  Hitzig 


560  PHYSIOLOGY  CHAP. 

and  Fritsch.  They  afford  a  general  experimental  proof  of  the 
functional  specialisation  of  different  regions  of  the  cerehral  cortex, 
while  telling  us  nothing  definite  about  the  function  of  the  excitable 
as  compared  with  the  non-excitable  areas. 

The  objections  raised  against  the  value  of  the  results  obtained 
by  electrical  stimulation  of  the  cortex  do  not  all  stand  criticism 
and  analysis.  Carville  and  Duret,  Onirnus,  Dupuy,  and  others 
showed  experimentally  that  the  electrical  currents  applied  to  the 
cortex  spread,  more  or  less  in  proportion  to  their  intensity,  both 
superficially  and  deeply  beyond  the  area  between  the  electrodes. 
They  concluded  that  the  motor  reactions  aroused  by  electrical 
excitation  of  the  cortex  are  not  sufficient  proof  either  of  its 
excitability  or  of  functional  localisation,  since  they  may  be 
interpreted  as  the  effect  of  spread  of  current  toward  the  basal 
ganglia,  pons,  and  bulb,  where  there  are  nerve  elements  that  are 
readily  excitable. 

But  it  must  be  remembered  that  :— 

(a)  The  motor  reactions  confined  to  given  groups  of  muscles 
can  also  be  obtained  with  mechanical  stimulation,  which  does  not 
spread,  but  remains  strictly  localised  to  the  regions  directly 
involved  (Luciani). 

(//)  The  effects  of  electrical  excitation  are  quite  definite.  The 
slightest  shift  in  the  position  of  the  electrodes  produces  quite  a 
different  reaction  ;  so  soon  as  they  are  applied  to  the  anterior 
frontal  or  occipital  regions  all  reaction  ceases,  even  when  the 
strength  of  the  stimulus  is  greatly  increased  (Hitzig,  Ferrier). 

(c)  The  convolutions   of  the  island  of  Keil,  though   they  lie 
immediately  above  the  corpus  striatum,  are  absolutely  inexcitable, 
while  the  central  or  Rolandic  convolutions,  which  are  more  remote 
from  the  basal  ganglia,  yield  with  the  same  current  very  definite 
reactions  varying  at  different  points  of  the  gyri  (Ferrier,  Griinbaum, 
and  Sherrington). 

(d)  If  the  cortex  of  the  postcruciate  portion  of  the  sigmoid 
gyrus  of  the  dog,  which  contains  centres  from  which  the  muscles 
of  the  limbs  on  the  opposite  side  can  be  excited,  lie  cut  with  a 
sharp  knife,  leaving  the  incised  strip  in  position,  the  usual  reactions 
are  no  longer  obtained  on  electrical  stimulation,  although  electrical 
conductivity  has  not  been  altered  by  the   incision  (Luciani  and 
Tamburini). 

(e)  If  after  destruction  of  the  excitable  centres  for  the  dog's 
limbs  the  subjacent  white  matter  is  excited,  the  usual  reactions 
are  obtained  ;    but  if  at  the  end  of  a  few  days  the  brain  is  again 
exposed,  and  the  current  applied  to  the  bottom  of  the  wound,  no 
reaction  will    lie    obtained,  although    the   physical    conditions  of 
electrical  diffusion  are  unchanged  (Albertoni  and  Michieli). 

(/)  The  cortical  grey  matter  which  yields  motor  reactions  on 
application  of  an  electrical  current  is  truly  excitable ;  it  is  not 


X 


THE  FOEE-BEAIN 


5G1 


merely  a  physical  conductor  of  the  current  to  the  white  matter  of 
the  centrum  ovale,  but  its  elements  are  physiologically  excited, 
and  through  them  the  excitation  is  transmitted  to  the  nerve-fibres 
(Frangois-Franek  and  Pitres). 

This  last  fact  can  be  demonstrated  experimentally  by  comparing 
the  motor  reactions  evoked  on  exciting  the  cortex  and  those 
obtained  on  exciting  the  subjacent  white  matter  with  the  same 
current. 

After  diligent  research  Frangois-Franek  and  Pitres  (1878-79) 
established  the  fact  that,  generally  speaking,  the  white  matter 
is  less  excitable  than  the  grey.  If,  after  ascertaining  the 
minimal  current  capable  of  pro- 
ducing a  given  movement  by 
stimulation  of  the  cortex  the  grey 
matter  is  excised,  and  the  same 
current  applied  to  the  white 
matter  lying  immediately  below  A 
it,  the  reaction  is  no  longer 
obtained.  It  is  necessary  to  in- 
crease the  strength  of  the  current 


can 


be 


FIG.  284. — Lost  time  in  muscular  contraction 
on  exciting  the  cortical  centre  M,  and  the, 
underlying  white  matter  M'.  (Frangois- 
Franck  and  Pitres.)  The  middle  line  shows 
the  time  in  J-JTJ  sec.  The  lower  line  marks 
the  application  of  the  stimulus.  In  A  the 
lost  time=Tijir  sec.  ;  in  B=-Tr>Tf  sec. 


before     the     movement 
evoked  again. 

On  the  other  hand,  the  excit- 
ability of  the  cortex  under  the 
action  of  certain  toxic  substances 
is  more  easily  lost  than  the  ex- 
citability of  the  white  matter ; 
this  is  seen  after  chloral  narcosis. 
While  the  dog  lies  in  the  chloral 
narcosis,  even  the  strongest 
stimulation  of  the  cortex  fails 
to  elicit  any  muscular  response, 
while  stimulation  of  the  subjacent  white  matter  is  still  effective, 
even  with  comparatively  weak  currents.  This  fact,  first  observed  by 
Frangois-Franck  and  Pitres,  and  confirmed  by  Eichet,  Bubnoff  and 
Heidenhain,  and  de  Varigny,  is  of  great  theoretical  importance. 
It  seems  to  show  that  the  cortical  substance  rendered  inexcitable 
by  chloral,  may — while  preserving  its  physical  conductivity- 
oppose  an  insurmountable  barrier  to  the  transmission  of  the 
stimulus  applied  to  its  surface. 

Another  important  fact  brought  out  by  Frangois-Franck  and 
Pitres  is  the  delay  in  the  muscular  reaction,  which  is  perceptibly 
greater  when  the  cortex  is  electrically  stimulated  than  when  the 
electrical  stimulus  is  applied  to  the  centrum  ovale.  To  avoid 
experimental  errors,  or  reduce  them  to  a  minimum,  in  demonstrat- 
ing this  fact  it  is  necessary  to  operate  on  one  and  the  same  animal 
by  simultaneously  exciting  a  region  of  the  cortex  and  an  adjacent 

VOL.  Ill  2  0 


562 


PHYSIOLOGY 


CHAP. 


portion  of  the  centrum  ovale  in  the  same  hemisphere,  or  better 
in  symmetrical  regions  of  the  two  hemispheres.  Fig.  284  is  a 
tracing  showing  the  intervals  between  the  moment  at  which  the 
current  passes  and  the  moment  at  which  the  reaction  commences 
on  exciting  the  cortex  and  the  centrum  ovale.  As-  will  be  noted, 
the  difference  is  not  insignificant;  in  this  instance  it  amounts  to 
y-§^  sec.,  but  in  other  cases  it  may  attain  y-g-^  sec.  Bubnoff  and 
Heidenhain,  who  operated  on  dogs  under  morphia,  even  obtained  a 
difference  of  Vrnrtr  8ec- 

Tins  marked  delay  in  response  when  the  cortex  is  excited 
shows  that  the  cortical  grey  matter  is  not  merely  a  passive  inert 
conductor  to  the  subjacent  white  matter.  It  receives  the  stimulus, 


FIG.  285. — Tracing  <>t'a  voluntary  contraction  of  the  opponens  pollicis  taken  at  a  known  vdncily 
of  the  recording  cylinder.  (Schafer.)  Shows  the  elementary  vibrations  that  make  up  the 
contraction. 

elaborates  it,  and  enters  into  the  active  physiological  state  known 
as  excitation,  which  Pfliiger  proved  to  occur  on  the  direct  or  reflex 
excitation  of  the  grey  matter  of  the  spinal  cord. 

To  obtain  a  clear  idea  of  the  active  state  or  physiological  ex- 
citation of  the  cortex,  it  is  useful  to  compare  the  character  of  the 
muscular  contractions  evoked  by  the  voluntary  impulse  with  those 
produced  by  electrical  excitation  of  the  cortex. 

On  recording  the  voluntary  contraction  of  any  muscle  (e.g.  the 
opponens  muscle  of  the  thumb),  by  some  suitable  myographic 
method,  the  resulting  curve  shows  undulations  which  are  fairly 
regular  as  to  rhythm,  though  irregular  in  amplitude,  with  a 
frequency  of  10-12  per  second  (Fig.  285).  Horsley  and  Schafer 
showed  this  variation  to  be  fairly  constant  in  the  same  individual, 
but  variable  in  different  subjects  (from  8  to  13  contractions  per 
second),  provided  the  resistance  the  muscle  encounters  in  contract- 


X 


THE  FOKK-l'.UAIN 


563 


ing  is  very  slight.  The  subsequent  work  of  Griffiths  brought  out 
the  fact  that  when  this  resistance  increases  there  is  a  corresponding 
increase  in  the  frequency  of  contraction,  up  to  15-18  per  second. 
When  the  resistance  is  protracted  and  fatigue  supervenes  the 
frequency  diminishes.  As  shown  by  Fig.  286,  an  outstretched  arm 
holding  a  weight  shows  the  same  rhythm  of  contraction  as  a  single 
muscle. 

We  may  thus  say,  with  Schafer,  that  the  average  frequency  of 
the  discharges  which  produce  a  voluntary  contraction  is  from 
10  per  second,  with  a  possible  increase  to  20  per  second,  when  the 
resistance  opposed  to  the  contraction  is  excessive.  These  facts 
harmonise  well  with  those  given  by  Eichet  for  tremor,  viz.  10-11 
contractions  per  second.  They  also  agree  with  the  fact  that  it  is 
impossible  to  speak  or  sing  more  than  eleven  syllables  or  to  play 
more  than  eleven  musical  notes  per  second.  The  cortical  cells 


Fin.  2S(i.—  Vibrations  of  outstretched  arm  holding  ;i  weight  of  about  six  kilos.     (W.  Griffiths.) 
Tin1  spaces  between  the  vertical  lines  represent  intervals  of  one  sec. 

thrown  into  activity  during  these  voluntary  acts  cannot  discharge  at 
a  greater  rapidity  than  this.  The  most  elementary  psychical  acts 
of  the  cortical  cells  have  therefore  a  mean  duration  of  y^  sec.  ; 
but  it  is  probable  that  practice  and  certain  favourable  conditions 
may  shorten  this  duration. 

Let  us  pass  on  to  examine  the  characters  of  the  motor  reactions 
artificially  obtained  by  electrical  excitation  of  the  excitable  points 
of  the  cerebral  cortex,  and  see  if  they  differ  from  those  of  voluntary 
action. 

Frangois-Franck  and  Pitres  (1878-79)  stated  that  stimulation 
of  the  motor  cortex,  like  that  of  the  motor  tracts  of  the  cerebro- 
spinal  axis,  gives  rise  to  a  series  of  contractions  the  rhythm 
of  which  corresponds  exactly  to  that  of  the  stimulus  adopted,  just 
as  in  the  stimulation  of  a  peripheral  nerve.  If  the  cortex  of  the 
excitable  zone  is  stimulated  5,  10,  20,  40  times  per  second,  the 
number  of  contractions  which  make  up  the  muscular  response  will 
be  5,10,  20,  40  per  second ;  above  40  per  second  the  single  contrac- 
tions fuse  to  form  a  perfect  tetanus.  This  last  statement,  which  is 


564 


PHYSIOLOGY 


CHAP. 


too  absolute,  was  subsequently  modified  by  the  authors  themselves, 
who  found  that  the  ascending  line  of  a  cortico-muscular  tetanus  is 
invariably  notched,  the  fusion  of  contractions  not  being  always 
complete  if  the  stimuli  are  sent  at  a  rate  sufficient  to  produce 
tetanus  when  applied  to  the  muscle  or  its  motor  nerve. 

The  later  work  of  Horsley  and  Schiifer  (1886)  led  to  more 
exact  results,  which  are  to  some  extent  directly  contradictory  of 
the  statements  of  Fran^ois-Franck  and  Pitres.  In  experimenting 


FIG.  2S7. — Myographic  curves  from  hamstring  of  monkey.  (Horsley  and  Schnfer.)  A,  natural 
contraction  (voluntary);  B,  contraction  caused  by  excitation  of  cortical  leg  centre  by  rapid 
induced  currents. 

on  monkeys,  dogs,  cats,  and  rabbits  they  found  that  when  the 
excitable  zone  of  the  cortex  was  stimulated  with  faradic  currents  of 
a  frequency  of  10-12  per  second  the  muscle  reacted  with  rhythmical 
contractions  of  the  same  rhythm  as  the  current.  But  this 
synchronism  ceases  when  the  frequency  of  stimulation  exceeds 
that  limit ;  the  contraction  curve  no  longer  shows  fusion  of 
the  contractions,  that  is,  complete  tetanus,  but  it  reproduces  the 
rhythmical  oscillations  of  voluntary  movements  (Fig.  287). 

From  these  results  as  a  whole  it  seems  reasonable  to  conclude 
that  the  active  state  aroused  in  the  cells  of  the  cortex  by  direct 
artificial  stimulation  is  analogous  to,  if  not  identical  with,  the 


x  THE  FOEE-BEAIN  565 

active    state    into    which    it    is    thrown    physiologically    during 
voluntary  activity. 

VI.  Besides  the  motor  reactions  we  must  take  into  considera- 
tion the  inhibitory  functions  of  the  cortex,  of  which  little  is  at 
present  known. 

The  discussion  in  the  last  chapter  of  the  effects  of  cerebral 
extirpation  shows  that  the  fore-brain  possesses  inhibitory  functions. 
Goltz'  brainless  dog,  which  moved  constantly  in  its  cage  so  long 
as  it  was  awake  and  not  overcome  by  fatigue  and  sleep,  reminds  us 
of  the  continuous  movement  characteristic  of  certain  forms  of 
dementia.  This  abnormal  and  aimless  work  may  be  regarded  as  a 
natural  effect  of  the  loss  of  the  inhibitory  powers  of  the  brain.  In 
agreement  with  this  is  the  fact  observed  by  Goltz  that  a  whole 
series  of  special  characteristic  reflexes  can  be  evoked  in  the  brain- 
less dog,  which  are  not  obtained  with  the  same  promptness,  facility, 
and  constancy  in  the  normal  dog  (in  which  the  brain  is  capable  of 
inhibition).  We  have  seen  that  the  ablation  of  the  cerebrum  in 
mammals  at  first  produces  a  state  of  rigidity  or  tonic  contraction 
in  certain  muscular  groups  of  the  trunk  and  limbs  which  is  an 
exaggeration  of  the  normal  muscular  tone,  retiexly  produced  by 
influences  which  reach  the  centres  by  the  ordinary  afferent  paths 
and  are  transmitted  to  the  muscles  by  the  motor  paths.  We  saw 
that  after  section  of  one  side  of  the  brain-stern  the  exaggeration  of 
t<  >ne  and  rigidity  is  produced  in  one  half  of  the  body  only,  because 
it  is  only  in  one  half  that  the  inhibitory  influence  of  the  higher 
centres,  which  normally  moderates  the  reflexes  that  determine  the 
tone  of  the  muscles,  is  lost. 

It  is  evident  that  the  inhibitory  influence  of  the  brain  may  be 
exercised  1  >y  the  will,  as  well  as  its  excitatory  function.  We  are 
able  at  will  not  only  to  throw  muscles  into  contraction,  but  also 
to  restrict  or  arrest  their  activity.  We  continuously  exert  a 
regulating  control  over  our  reflex  movements  when  we  are  awake ; 
we  are  able  to  reinforce,  moderate,  or  even  arrest  them.  Does 
this  inhibition  depend  on  the  interruption  of  the  activity  of  the 
cortical  motor  centres,  or  on  a  positive  activity  which  opposes  the 
impulses  of  these  centres  and  suppresses  their  effects  ?  What  is 
the  mechanism  of  this  inhibition  ?  Are  there  in  addition  to  the 
motor  centres  and  nerves  other  inhibitory  cortical  centres  and 
nerves?  Or  are  the  same  motor  mechanisms  capable  of  two 
opposite  forms  of  excitation?  These  questions  are  entirely  suit 
j  a  dice,  for  it  is  possible  to  offer  different  solutions  of  them,  with 
experimental  evidence  in  support  of  each.  We  must  confine 
ourselves  here  to  recording  the  best-established  facts. 

Bubnoff  and  Heidenhain  (1881),  after  they  had  determined  the 
motor  area  in  the  dog,  recorded  the  contractions  of  the  extensor 
muscle  of  the  toes  on  a  revolving  cylinder.  Any  strong  excita- 
tion of  the  foot  throws  this  muscle  into  reflex  contraction.  If, 


566  PHYSIOLOGY  CHAP. 

during  contraction,  the  skin  of  the  foot  is  gently  stroked,  or  the 
motor  area  tetanised  with  a  small  current,  the  muscle  relaxes,  and 
the  contraction  disappears  entirely  or  partly  (Figs.  288,  289). 
These  tracings  show  that  the  state  of  activity  of  the  motor  centres 
of  the  cortex  which  is  elicited  by  strong  stimulation  may  be 
abolished  by  a  subsequent  peripheral  or  central  stimulation  of  an 
exceedingly  mild  character,  which  in  the  resting  state  of  the 
centres  would  lie  incapal  >le  of  producing  any  obvious  effect. 

Brown-Sequard  (1884)  on  exciting  the  non-motor  region  of  the 
cortex  of  dogs  and  rabbits  with  strong  currents  was  able  to  abolish 
the  excitability  of  the  motor  area  for  some  minutes.  He  termed 
the  part  of  the  cortex  which  does  not  react  by  movements  to 


FIG.  288.— Inhibitory  effects  of  reflex  excitations.  (Bubnoff  ;m<l  Heidenliain.)  a  represents  a 
reflex  contraction  of  the  muscle,  a  /3,  caused  by  rubbing  the  skin  of  the  belly  ;  at  y'  there  is  a 
rapid  relaxation,  •/  y,  caused  by  tactile  stimulation  of  the  skin  of  the  leg  ;  at  S  the  contracture 
2>  &'  is  reinforced  after  lirm  pressure  of  the  leg;  at  e  the  muscle  relaxes  suddenly  and 
completely,  e  e',  after  gently  stroking  the  skin  of  the  leg. 

stimulation,  inhibitor}/  ;  he  denied  its  inexorability,  and  held  it  to 
be  capable  of  activity,  and  of  transmitting  excitation  to  other 
centres,  along  the  association  fibres,  so  as  to  inhibit  their  functional 
activity. 

With  a  view  to  localising  the  inhibitory  activity  of  the  cortex, 
Libertini  (1895)  endeavoured  to  determine  the  reflex  time  of  the 
muscles  in  the  dog's  limbs,  before  and  after  destroying  certain  seg- 
ments of  the  brain.  He  found  that  a  few  days  after  the  excision 
of  one  or  both  pre-frontal  lobes  there  was  a  marked  shortening  of 
the  reflex  time  of  the  muscles  of  the  fore-limb.  The  same  effect 
is  not  obtained  or  only  to  a  much  less  extent,  after  excising  one  or 
both  occipital  lobes,  and  does  not  occur  after  excision  of  the 
temporal  lobe.  The  reflex  time  of  the  muscles  of  the  hind-limb 
undergoes  no  perceptible  variation  before  and  after  the  operation. 


x  THE  FOBE-BKAIN  567 

Fano  determined  the  variations  of  the  reflex  time  after 
faradising  the  cortex.  He  observed  that  on  exciting  the  pre- 
froutal  lobe  for  five  seconds  by  an  induction  current  (so  strong  as  to 
produce  epileptoid  convulsions  when  applied  to  the  motor  area), 
there  was  invariably  a  depression  of  excitability  in  the  cerebro- 
spinal  centres,  lasting  about  three  minutes.  In  fact  during  this 
time  if  the  skin  of  the  fore-limb  of  the  opposite  side  were  excited 
by  a  break  current,  so  as  to  provoke  a  reflex  contraction  from  the 
subjacent  muscles,  there  was  a  reduction  in  the  height  of  the 
myographic  curve,  and  a  striking  lengthening  of  the  reflex  period, 
that  is  the  contrary  effect  to  that  observed  by  Libertini  after 
excision  of  the  pre-frontal  lobe. 


FIG.  289. — Inhibitory  effect  of  weak  cortical  stimulation.  (Bubnoff  and  Heidenhain.)  At  «  the 
muscle  contracts,  a  a',  after  the  application  of  a  strong  galvanic  current  to  the  cortical  centre  ; 
at  b  there  is  a  stronger  contraction,  b  V,  after  a  second  excitation  with  same  current ;  after 
the  slow  relaxation,  b'  <.•',  the  muscle  is  suddenly  elongated,  c'  c,  by  the  action  of  a  w.-ak 
galvanic  current  on  the  same  centre. 

Simultaneously  with  Fano,  this  cerebrospinal  inhibition  was 
demonstrated  by  Oddi  by  a  different  method.  He  applied  to  the 
5th  ventral  lumbar  root  a  pair  of  electrodes,  connected  with  a 
sliding  induction  coil  and  a  metronome  which  served  as  an  inter- 
rupter, so  that  the  nerve  could  he  rhythmically  excited.  The 
rhythmic  contractions  of  the  gastrocnemius  muscle  were  recorded 
on  a  rotating  drum.  After  exposing  the  brain  under  a  suitable 
degree  of  narcosis,  he  stimulated  the  cortex  of  the  pre-frontal  lobes 
of  the  side  opposite  to  the  excited  spinal  root  with  another  induced 
current,  and  noted  profound  changes  of  an  inhibitory  character  on 
the  curves  of  the  rhythmical  contractions  of  the  gastrocnemius 
(Fig.  290).  These  inhibitory  effects  ensued  after  a  fairly  long 
period  of  latent  excitation,  and  continued  for  some  time  after  the 
application  of  the  stimulus  to  the  cortex  had  ceased.  On 


568 


PHYSIOLOGY 


CHAP. 


faradising  the  pre-frontal  cortex  on  the  same  side  as  the  root 
experimented  on,  a  weaker  inhibitory  effect  could  also  be  observed 
(Fig.  291).  When,  on  the  contrary,  the  occipital  lobes  of  either 
side  were  excited,  even  with  very  strong  currents,  no  appreciable 
alteration  in  the  tracing  could  be  detected. 

These  researches  show  that  inhibitory  effects  from  cortical 
excitation  can  be  transmitted  not  only  to  the  muscles  of  the  fore-, 
but  also  to  those  of  the  hind-limbs. 

Neither  the  experiments  of  Fano  nor  those  of  Oddi,  however, 
demonstrate  that  special  inhibitory  centres,  antagonistic  to  the 
motor  centres,  are  contained  in  the  cortex  of  the  pre-frontal  lobe. 
The  stimulus  required  to  elicit  inhibitory  effects  from  this  is  always 
stronger  than  that  which  elicits  motor  reaction  when  the  excitable 


1 


RS  iJ 


UUlWIMIUUlJUWm 


uuuuui 


Flo.  2'JO. — Inhibitory  effect  of  faradisinj;  pre-frontal  lobe  upon  contractions  of  gastrocriemius 
muscle  of  opposite-  side',  excited  by  rhythmical  stimulation  of  the  fifth  motor  lumbar  root. 
(Oddi.)  The  middle  line  shows  the  be^innin^  ami  end  of  the  cortical  excitation;  the  lower- 
line  indicates  the  rhythmical  excitation  of  the  spinal  rout. 

area  is  stimulated.  The  pre-frontal  lobe  contains  no  definite 
and  well-marked  areas  from  which  prompt  and  facile  inhibitory 
effects  can  be  obtained.  Oddi  further  observed  that  faradic 
currents  applied  to  the  pre-frontal  lobes  after  a  marked  inhibition 
give  rise  to  epileptic  fits,  probably  because  the  stimulus  is  trans- 
mitted to  the  motor  area.  All  this  tends  to  the  conclusion  (after 
Bubnoff  and  Heidenhain,  as  above  cited)  that  the  centres  contained 
in  the  so-called  motor  area  are  capable  of  both  motor  and  in- 
hibitory reactions. 

Sherrington  (1893-95)  and  H.  E.  Bering  and  Sherrington  (1897) 
demonstrated  that  the  faradisation  of  certain  points  of  the  cortex 
lying  in  the  motor  area  may,  besides  contraction,  produce  relaxa- 
tion or  depression  of  tone  in  the  antagonist  muscles.  This  effect  is 
obtained  not  on  stimulating  the  same  point  of  the  cortex  which 
produces  contraction,  but  on  applying  the  stimulus  to  the  area 
which  produces  the  contraction  of  the  antagonists.  There  would 


THE  FOKE-BKAIN 


569 


therefore   seem   to   be,  at  all   events  for   this  form  of  inhibition, 
distinct  paths  for  motor  and  for  inhibitory  impulses. 

Among  the  most  classical  examples  of  this  so-called  reciprocal 
innervation  of  the  antagonist  muscles,  is  that  which  Sherriugton 
discovered  for  the  muscles  of  the  eye-ball.  If  in  the  cat  or 
monkey  the  oculo-rnotor  and  the  trochlear  nerves  of  the  left  side 
are  cut  so  that  only  one  muscle,  the  external  rectal,  remains  active 
in  the  eye  of  this  side,  and  the  area  in  the  frontal  or  the  occipital 
lobe  which  normally  produces  conjugate  movements  of  both  eyes 
to  the  right  (Fig.  281)  is  then  faradised,  there  will  lie  a  deviation 
to  the  right  not  only  of  the  normal  right  eye  owing  to  the  con- 
traction of  the  right  external  rectus,  but  also  of  the  paralysed 


FIG.  291. — Weaker  inhibitory  effect  after  faradising  the  pie-frontal  lobe  on  same  side  as  the  ga.stru- 
cnemius  that  is  making  the  tracing.  (Oddi.)  The  three  lines  correspond  to  those  of  the  previous 
figure. 

left  eye  owing  to  relaxation  of  the  left  external  rectus.  By  a 
similar  experiment,  after  section  of  the  sixth  abducens  nerve,  an 
inliibitory  action  on  the  right  internal  muscle  of  the  operated 
eye  can  be  demonstrated,  associated  with  contraction  of  the 
internal  rectus  of  the  normal  eye. 

Another  example  of  reciprocal  innervation  may  be  seen  in  the 
extensor  and  flexor  muscles  of  the  extremities.  In  chloroform 
and  ether  narcosis  there  is  a  stage  during  which  a  state  of  flexion 
or  tonic  extension  of  the  extremities  can  be  observed.  If  in  a 
monkey  in  this  state  the  cortical  areas  which  determine  the  con- 
traction of  the  flexors  are  faradised,  relaxation  of  the  extensors 
can  lie  distinctly  perceived  if  the  muscles  are  felt  with  the  hand. 
If  the  cortical  areas  of  the  extensors  are  faradised,  while  the  flexor 
muscles  are  held  in  the  hand,  relaxation  of  these  muscles  can  be 
distinctly  felt. 


570  PHYSIOLOGY  CHAP. 

Similar  effects  to  those  obtained  by  the  direct  stimulation  of 
the  cortex  result  both  from  stimulation  of  the  nerve  fibres  of  the 
corona  radiata,  after  removal  of  the  grey  matter,  and  from  reflex 
stimulation,  due  to  excitation  of  sensory  nerves  on  their  end- 


organs. 


These  and  other  similar  facts  have  led  some  authors  to  the 
conclusion  that  on  stimulation  of  the  cortex  there  is  always,  along 
with  contraction  of  certain  muscles,  relaxation  of  their  antagonists, 
and  that  under  normal  conditions  there  is  never  synchronous  con- 
traction of  antagonistic  muscles.  The  later  observations  of  E.  du 
Bois-Eeymond  (1902)  show  plainly  that  the  relaxation  of  certain 
muscles  during  the  contraction  of  their  antagonists  is  not  a  general 
specific  law  ;  that  there  is  a  whole  series  of  facts  which  are  opposed 
to  this  so-called  "  law,"  and  generally  speaking  that  the  inhibitory 
effects  are  not  confined  to  the  antagonist  muscles,  but  may  also 
extend  to  other  muscles  of  any  function.  While  admitting  the 
accuracy  of  the  inhibitory  phenomena  described  by  Sherrington 
and  others,  there  is  no  necessity  for  undue  generalisation. 

VII.  In  addition  to  motor  and  inhibitory  effects  on  the 
voluntary  muscles  the  stimulation  of  the  excitable  area  of  the 
cortex  produces  effects,  also  motor  or  inhibitory,  in  the  organs  of 
vegetative  life. 

It  is  a  matter  of  common  observation  that  emotional  states  of 
different  kinds  are  associated  with  respiratory,  circulatory,  and 
secretory  changes.  Since  the  discovery  of  Hitzig  and  Fritsch, 
a  number  of  experimenters  have  tried  to  localise  the  centres 
of  these  special  reactions  in  the  cortex  by  the  usual  method 
of  faradic  stimulation,  but  these  attempts  have  not  led  to  any 
such  precise  localisation  as  in  the  case  of  the  voluntary  move- 
ments. Generally  speaking,  it  may  be  stated  that  the  electrical 
excitation  of  any  point  of  the  so-called  motor  area  may  excite 
respiratory,  cardiac,  or  secretory  effects.  But  there  is  no 
specific  localisation  for  these  reactions,  only  a  diffuse  localisation 
which  extends  all  over  the  area  which  is  known  to  be  excitable. 
Beyond  this  zone  cortical  stimulation  is  ineffective,  when  moderate 
currents  incapable  of  provoking  convulsive  attacks  are  used. 

Electrical  stimulation  of  the  motor  area  in  the  dog  produces 
(Danilewsky,  Bochefontaiue,  Frangois-Franck,  and  Pitres)  some- 
times acceleration,  sometimes  retardation  of  the  respiratory  rhythm, 
independently  of  the  exact  point  of  stimulation,  and  rather  in 
relation  to  the  strength  of  the  stimulus.  Bechterew  obtained 
similar  results,  while  others  described  special  inspiratory  and 
expiratory  effects  on  exciting  fixed  and  definite  points  of  the 
motor  zone. 

The  differences  noted  by  the  various  experimenters  probably 
depend  on  the  degree  of  anaesthesia  of  the  animal,  perhaps  also 
on  the  nature  of  the  anaesthetic.  Under  chloral,  Eichet  observed 


x  THE  FOEE-BEAIN  571 

that  OH  exciting  different  points  of  the  cortex  there  was  respira- 
tory arrest. 

Faradisation  of  one  point  of  the  pre-frontal  lobe,  that  is,  of  the 
cortex  lying  in  front  of  the  motor  area,  also  produces  arrest  of 
respiration  in  the  inspiratory  phase,  preceded  by  acceleration  of 
rhythm  (H.  Munk).  At  other  points  on  the  inferior  surface  of  the 
same  lol  >e  it  produces  arrest  of  respiration  in  the  expiratory  phase, 
also  preceded  by  acceleration.  These  effects  were  obtained  not 
only  on  dogs  but  also  on  monkeys. 

The  subsequent  work  of  W.  G.  Spencer  showed  that  the 
inspiratory  effects  obtained  on  exciting  the  cortex  of  the  inferior 
surface  of  the  pre-frontal  lobe  are  apparently  connected  with  the 
olfactory  function. 

Lastly,  Langelaan  and  Beyermaim  (1903)  claimed  to  have 
discovered  on  the  dog  an  area  lying  at  the  extremity  of  the  siguioid 
gyms,  where  the  coronary  fissure  meets  the  pre-Sylvian,  the 
electrical  excitation  of  which  with  very  weak  faradic  currents 
produces  respiratory  acceleration,  followed  by  inspiratory  arrest. 
On  the  basis  of  clinical  observations  they  hold  that  a  similar 
centre  also  exists  in  man  at  the  base  of  the  second  frontal  convolu- 
tion near  the  pre-central  gyrus. 

After  the  discovery  of  Hitzig  and  Fritsch,  Schiff  showed  that 
faradisation  of  the  motor  zone  may  produce  cardiac  and  vascular 
effects.  Many  subsequent  observers  have  continued  the  study  of 
this  subject.  Danilewsky  found  that  on  exciting  Hitzig's  centre 
for  ocular  movements  in  the  curarised  dog,  blood  pressure  was 
raised  owing  to  vase-constriction  and  slowing  of  cardiac  rhythm. 
Bochefontaine,  who  also  operated  on  curarised  dogs,  observed  that 
the  circulatory  effects  were  obtained  from  the  whole  motor  area, 
from  a  much  more  extensive  surface  than  was  assumed  by 
Danilewsky.  These  reactions  consist  in  a  marked  increase  of 
arterial  pressure  with  delay  in  cardiac  rhythm.  The  pressor 
effect  is  sometimes  preceded  by  a  depressor  effect,  the  former  is 
probably  due  to  the  predominance  of  vascular  spasm,  the  latter  to 
predominance  of  cardiac  inhibition. 

Eichet  found  that  faradisation  of  the  anterior  part  of  the 
sigmoid  gyrus  in  particular  produced  circulatory  effects ;  a  short 
stimulation  sufficed  to  produce  a  marked  rise  of  arterial  pressure, 
after  a  long  latent  period ;  the  pressor  effect  persists  for  a  very 
long  period ;  and  finally  the  excitability  of  the  cortex  disappears 
after  quite  moderate  stimulation,  every  reaction  ceasing,  even  to 
maximal  currents. 

Franeois-Franck  and  Pitres  made  a  minute  analysis  of  the 
circulatory  reactions  to  cerebral  faradisation.  In  order  to  separate 
the  effects  on  the  vessels  from  those  on  the  heart,  they  atropinised 
the  animal  or  cut  the  vagi.  They  saw  that  ill  operated  dogs 
cortical  excitation  produced  a  marked,  gradual  rise  of  arterial 


572 


PHYSIOLOGY 


CHAP. 


pressure,  followed  by  a  regular  drop  to  the  normal,  and  even  below 
it.  The  pressure  curve  is  comparable  with  that  obtained  under 
identical  conditions  of  suppression  of  moderating  influences,  on 
direct  or  reflex  excitation  of  the  bulbo-spinal  centres.  Only  very 
rarely  does  cortical  excitation  produce  a  depressor  effect  due  to 
vascular  dilatation ;  it  is  probable  that  the  brain  may  produce 
active  dilatation  of  limited  vascular  regions,  and  does  not  sensibly 
affect  the  general  arterial  pressure. 

These   vascular    changes    due    to   cortical   excitation    are    not 


Fir;.  292.— Opposite  effect  upon  volume  of  kidney  (rul.ll.)  and  arterial  pressure  (P.C.)  of  cortical 
excitation  (.shown  on  lower  line).  (Francois-Franok  and  Pitres.)  Arterial  pressure  rises  from 
130  to  260  mm.  Hg.,  while  the  volume  of  the  kidney  diminishes.  As  the  animal  was  atropinised, 
the  excitation  does  not  affect  cardiac  rhythm,  and  the  pressor  effect  in  this  case  evidently 
depends  on  the  contraction  of  the  vessels,  both  superficial  and  deep  or  visceral. 

elicited  from  the  whole  of  the  brain  surface ;  unless  very  strong 
currents  capable  of  producing  epileptic  attacks  are  used,  fara- 
disation of  the  anterior  frontal,  inferior  lateral,  and  posterior 
occipital  regions  are  ineffective.  Vaso-motor  effects  are  constant 
on  stimulating  the  motor  area ;  whatever  point  of  this  region 
is  excited  the  vasomotor  reaction  is  general  and  bilateral ;  it  is 
not  more  pronounced  in  the  limb  that  corresponds  with  the  centre 
excited,  nor  in  the  superficial  than  in  the  deep  vessels  (Fig.  292). 
It  is  probable  that  vascular  response  can  be  produced  from  the 
excitable  area  of  the  cortex  in  proportion  as  this  contains  afferent 
paths  to  the  vasomotor  centres  of  the  bulb ;  the  vascular  reactions 


x  THE  FORE-BRAIN  57:5 

due  to  stimulation  of  the  cortex  are  similar  to  those  excited  rcflexly 
from  the  cutaneous  or  mucous  sensory  surfaces. 

The  effects  on  the  heart  of  cortical  stimulation  are  very  variable, 
according  to  Francois  -  Franck  and  Pitres ;  acceleration  and 
retardation  of  rhythm  appear  irregularly  in  the  course  of  a  single 
experiment,  independently  of  the  seat  of  stimulation.  This  con- 
stantly occurs  on  applying  currents  capahle  of  provoking  epileptic 
fits  in  animals  that  are  in  light  narcosis.  During  the  tonic  phase 
of  the  epileptic  attack  there  is  thus  a  more  or  less  marked  slowing 
of  cardiac  rhythm  (from  150  to  110  beats  per  minute),  while  during 
the  clonic  stage  the  rhythm  is  accelerated  (e.g.  rises  from  125  to 
250  beats  per  minute).  In  curarised  animals  too,  in  which  the 


Fir,.  293.— Voluntary  acceleration  of  cardiac  rhythm  with  no  change  in  the  respiration.  Observa- 
tion made  i  >n  a  young  man  by  Patrizi.  The  arrow  indicates  the  commencement  of  the 
voluntary  effort  to  accelerate  the  beat  of  the  heart.  The  upper  line  is  the  tracing  of  thoracic 
respiration  by  Marey's  /i»c»i/n»/nij</i  ;  the  lower,  the  pulse  tracing  from  the  left  hand,  taken 
with  Luciani's  ralHnn-trif  ijlin'e. 

convulsions  of  the  voluntary  muscles  are  eliminated,  the  same 
cardiac  reactions  can  be  seen  on  strong  cortical  excitation. 

Changes  of  cardiac  rhythm  can  also  be  observed  on  moderate 
cortical  excitation  of  brief  duration,  which  is  incapable  of  producing 
epileptic  seizures.  In  these  cases  the  effect  consists  in  regular 
acceleration  or  retardation  of  rhythm.  The  form  of  the  reaction 
is  independent  of  the  site  of  the  stimulation  in  the  motor  area, 
and  seems  to  depend  more  upon  the  intensity  of  the  stimulus : 
inhibition  is  usually  due  to  sudden,  strong  excitation,  acceleration 
to  rnild  and  prolonged  stimuli. 

In  respect  of  these  cardiac  reactions  the  excitable  surface  of 
the  brain  may  again  lie  compared  to  a  sensitive  surface,  and  there 
is  no  reason  for  assuming  that  the  motor  area  contains  special 
moderator  and  accelerator  centres  for  the  heart. 


574  PHYSIOLOGY  CHAP. 

The  afferent  paths  from  the  cortex  to  the  cardio-motor  bulbo- 
spinal  centres  by  which  changes  in  the  frequency  and  intensity  of 
the  cardiac  rhythm  are  produced,  are  normally  excited  reflexly  by 
emotions,  by  excessive  work,  by  the  tension  of  the  muscles,  and  by 
variation  in  respiration.  But  there  may  exceptionally  lie  percept- 
ible acceleration  or  diminution  of  the  cardiac  rhythm  associated 
with  a  simple,  direct  voluntary  impulse,  without  obvious  change  in 
the  respiratory  rhythm  (Tarchanoff,  Patrizi)  (Fig.  293). 

From  the  effect  of  the  emotions  on  the  secretions  and  specially 
on  salivation  and  perspiration,  on  the  muscle  cells  innervated  by 
the  sympathetic,  on  the  skin,  the  alimentary  tract,  and  the 
urinary  system,  it  is  highly  probable  that  artificial  stimulation 
of  the  cortex  also  produces  similar  effects.  In  fact,  Bochefontaine 
first,  and  after  him  many  other  observers,  found  that  faradisation 
of  the  motor  area  in  the  dog  produced  a  now  of  saliva  from  the 
salivary  glands  of  both  sides.  Changes  in  sweat  secretion  were 
not  observed.  In  experimental  epilepsy  Franc, ois-Franck  and 
Pitres  found,  both  in  the  goat's  foot  and  the  dog's,  that  drops  of 
sweat  were  exuded  during  the  convulsions,  and  Adamkiewicz, 
in  cases  of  partial  epilepsy  in  man,  noted  abundant  perspiration 
in  the  skin  of  the  limb  that  was  convulsed. 

The  observations  of  Bochefontaine  and  others  on  gastric, 
biliary,  and  urinary  secretions  gave  no  definite  results.  But 
Bochefontaine,  Francois  -  Franck  and  Pitres,  Bechterew  and 
Mislawsky,  and  Sherrington,  obtained  more  positive  vesical  re- 
actions on  exciting  different  points  of  the  motor  area.  According 
to  von  Pfungen  (1906),  the  movements  of  the  gut  can  also  be 
influenced  by  cortical  stimulation. 

VIII.  Intimately  connected  with  the  study  of  the  motor 
effects  obtained  on  cortical  faradisation,  are  the  epileptiform 
convulsive  phenomena  which  are  often  produced  when  the  currents 
employed  are  unduly  strong  or  applied  for  too  long  a  time,  or 
when  the  cerebral  cortex  is  abnormally  excitable.  Hitzig  and 
Fritsch,  who  discovered  the  excitability  of  the  cortex,  first  pointed 
out  this  fact,  and  recognised  that  the  epileptic  attacks  began 
with  convulsions  of  the  muscles  corresponding  to  the  centre  first 
excited,  and  afterwards  spread  to  other  muscular  groups.  Shortly 
before  their  discovery,  however,  Hughlings  Jackson  had  concluded 
from  the  clinical  study  of  epileptiform  convulsions  localised  to 
certain  groups  of  muscles  that  certain  forms  of  epilepsy  depend 
on  lesions  of  cortical  centres  which  produce  periodical  discharges 
(discharging  lesions)  in  the  direction  of  the  corpus  striatum.  The 
observations  of  Hitzig  and  Fritsch  and  of  Ferrier  (187-i)  may  be 
taken  as  experimental  confirmation  of  Jackson's  theory. 

The  epileptic  convulsions  obtained  on  cortical  faradisation 
differ  from  simple  motor  reactions  because  they  persist  and 
sometimes  increase  after  the  stimulus  has  ceased,  and  because  of 


x  THE  FORE-BRAIN  575 

their  tendency  to  spread  to  adjacent  groups  of  muscles  till  they 
become  general,  as  if  the  stimulus  only  discharged  an  excitatory 
process  which  develops  independently  of  external  stimuli. 

The  epileptic  discharge  due  to  cortical  faradisation  always 
liegins  in  the.  muscular  group  which  corresponds  to  the  cortical 
motor  centre  stimulated.  According  to  the  strength  and  duration 
of  the  stimulus,  or  the  excitability  of  the  centre  stimulated,  it 
may  remain  limited  to  a  single  group  of  muscles,  or  extend  to 
all  the  muscles  of  one  half  of  the  body,  or  involve  the  muscles  of 
both  sides. 

The  epileptic  discharge  follows  a  certain  order  in  spreading, 
which  almost  always  corresponds  to  the  anatomical  arrangement 
of  the  motor  centres  in  the  cortex.  This  fact,  which  is  brought 
out  by  the  observations  of  Ferrier,  Luciani  and  Tamburini,  and 
Unverricht,  proves  that  the  spread  of  the  attack  depends  on  the 
propagation  of  the  active  epileptic  state  from  the  cortical  centre 
directly  excited  to  the  contiguous  centres  in  the  motor  area. 

It  is  important  also  to  note  the  mode  in  which  the  epileptic 
attack  spreads  from  one  half  of  the  body  to  the  other.  According 
to  the  observations  of  Unverricht,  which  were  confirmed  by 
Francois- Franck  and  Pitres,  the  epileptic  attack  always  invades 
the  other  half  of  the  body  in  a  typical  and  constant  manner,  no 
matter  where  the  fit  may  start.  After  involving  all  the  muscles 
of  one  side  in  the  ascending  or  in  the  descending  order,  the  attack 
invariably  spreads  to  the  other  side  in  the  ascending  order,  viz. 
from  the  muscles  of  the  posterior  to  those  of  the  anterior  limb,  and 
from  there  to  the  muscles  of  the  neck,  face,  etc.  This  rule  for  the 
spread  of  the  convulsions  in  experimental  epilepsy,  holds  good  also 
with  very  rare  exceptions  for  the  spread  of  the  convulsions  of 
epilepsy  in  man. 

The  duration  of  each  experimental  fit  varies  from  a  few  seconds 
to  two  or  more  minutes.  Sometimes  after  the  attack  is  over,  it 
recurs  spontaneously  after  a  brief  pause ;  at  other  times  the 
animal  may  pass  into  a  true  epileptic  state  (status  epilepticus),  in 
which  the  convulsions  diminish  or  become  more  severe,  but  do  not 
cease  entirely.  The  animal  of  course  becomes  exhausted  and  dies 
after  a  few  hours. 

It  is  interesting  to  note  that  both  in  simple  epileptic  seizures, 
and  in  recurrent  attacks,  or  in  the  epileptic  state,  the  muscles  are 
not  all  equally  involved  in  the  convulsions.  This  agrees  with  the 
fact  that  the  excitability  of  the  various  cortical  motor  centres  is 
not  uniform,  but  varies  in  different  individuals  and  in  the  same 
individual  at  different  periods  of  the  experiment.  Often  indeed  a 
current  of  moderate  strength  will  not  elicit  an  attack  when  applied 
to  one  focus,  while  a  weak  current  will  suffice  to  provoke  the 
attack  if  applied  to  another  centre. 

According   to    Unverricht,  the  body-temperature   rises  from 


576  PHYSIOLOGY  CHAP. 

1°  to  2°  C.  during  an  attack  of  epilepsy;  and  in  the  epileptic  state 
the  temperature  may  reach  44°  0.  The  rise  of  temperature  during 
the  fits  is  certainly  in  relation  with  the  intensity  and  spread  of 
the  muscular  convulsions. 

When  the  cerebral  cortex,  either  from  individual  predis- 
positions, or  from  special  conditions  due  to  the  operation,  is  in  a 
state  of  abnormally  increased  excitability,  an  epileptic  attack  may 
be  retiexly  excited  by  stimulation  of  a  sensory  nerve  (Franeois- 
Franck).  Under  ordinary  conditions  stimulation  of  the  inex- 
citable  parts  of  the  brain  cannot  induce  an  epileptic  attack,  but 
if  the  motor  area,  i.e.  the  whole  or  certain  of  the  excitable  parts 
are  in  a  state  of  hyper-excitability,  owing  to  exposure  to  the  air  or 


FIG.  ~2'.H.-  .17,  epileptoid  lit,  tracing  from  muse,  extensor  CTiiris.  (FianQois-Franck  and  Pitres.) 
TliH  fit  falls  into  three  periods  ;  1,  a  tniiii-  period,  corresponding  to  the  duration  of  the  electrical 
excitation  K  ;  2,  at  (lie  close  of  cortical  stimulation,  the  tetanic  condition  is  reinforced  ;  3,  the 
I'lnnii-  period,  in  which  the  muscle  gradually  relaxes. 

to  previous  stimulation,  application  of  the  faradic  current  to  the 
cortex  of  the  occipital  or  parieto- temporal  lobe  (i.e.  to  points 
more  or  less  remote  from  the  motor  area)  may  also  evoke  an 
epileptic  fit.  Does  this  fact  depend  on  physical  conduction  of  the 
current  to  the  hyper-excitable  region,  or  have  areas  become  hyper- 
excitable  which  do  not  normally  respond  to  artificial  stimuli  ? 
The  latter  supposition  agrees  with  the  fact  that  spontaneous 
epilepsy  (whether  idiopathic  or  Jacksouian)  is  generally  preceded 
by  a  sensory  aura  which  varies  in  character,  and  is  evidently  due 
to  excitation  of  different  sensory  areas  of  the  cortex.  It  is  im- 
portant to  note  that  in  Jacksonian  seizures,  unlike  even  the 
mildest  form  of  idiopathic  epilepsy,  the  attack  is  accompanied  by 
a  disturbance,  but  never  by  complete  loss,  of  consciousness. 

By  means  of  a  tracing  on  a  rotating  drum  from  one  muscle  of 
a  limb,  Frangois-Franck  and  Pitres  were  able  to  investigate  the 
muscular  phenomena  of  the  epileptic  fit  produced  by  electrical 


x  THE  FORE-BBAIN  577 

excitation  of  the  motor  area.  They  observed  that  the  attack  con- 
sists of  two  phases,  a  tonic  and  a  clonic  stage.  As  shown  in  Fig. 
294,  the  tonic  phase  persists,  and  reaches  its  maximum  after  the 
cessation  of  tetanisation ;  the  clonic  phase  lasts  longer,  and  is 
characterised  by  violent,  but  less  frequent  and  irregular,  muscular 
contractions.  The  tonic  phase  may  be  altogether  absent,  especi- 
ally it'  the  animal  is  deeply  under  the  anaesthetic ;  then  the  con- 
tractions are  very  pronounced,  and  the  intervals  between  them 
increase  as  the  muscle  relaxes. 

These  facts  were  confirmed  by  Horsley  and  Schafer  in  both 
dogs  and  monkeys.  According  to  Charcot  partial  epileptic  attacks, 
which  he  terms  vibratory,  because  they  consist  of  simple  clouic 
spasms  definitely  separated  from  one  another,  can  be  observed  in 
man.  In  idiopathic  epilepsy,  on  the  contrary,  according  to  Brown- 
Sequard,  the  initial  tonic  phase  is  never  absent. 

We  have  already  considered  the  organic  changes  (respiratory, 
cardiac,  vascular,  secretory,  visceral,  etc.)  which  accompany  epi- 
leptic seizures.  Franc,ois-Franck  first  analysed  these  minutely  by 
means  of  the  graphic  method,  and  demonstrated  that  the  epileptic 
organic  effects  can  be  elicited  without  convulsions  of  the  voluntary 
muscles  when  the  cerebral  cortex  of  a  curarised  dog  is  electrically 
stimulated  with  strong  currents,  under  artificial  respiration. 

Besides  faradisation  of  the  brain,  the  development  of  spontaneous 
epileptic  fits  may  be  observed  in  animals  in  which  a  part  of  the 
cortex  has  been  destroyed.  This  fact  affords  experimental  con- 
firmation of  Jackson's  clinical  observations.  The  first  four  cases 
of  epilepsy  in  dogs  after  extirpation  of  part  of  the  motor  area  were 
described  by  Hitzig.  He  did  not  discuss  the  pathogenesis  of 
epilepsy ;  but  confined  himself  to  the  simple  statement  that  lesions 
of  the  cerebral  cortex  may  induce  epilepsy. 

While  experimenting  on  the  brain,  we  frequently  had  oppor- 
tunities of  observing  various  forms  of  epileptic  convulsions  which 
developed  spontaneously,  under  different  conditions,  in  dogs  and 
monkeys  after  previous  operations  on  the  cerebral  cortex,  and  are 
significant  in  the  pathogenesis  of  epilepsy.  We  published  a 
Memoir  in  1878  in  which — after  a  critical  examination  of  the 
different  cases  of  epilepsy  due  to  lesions  of  the  cortex — we  put 
forward  a  general  theory  of  the  cortical  origin  of  epilepsy,  whether 
Jacksonian  or  idiopathic,  and  stated  that  the  motor  area  of  the 
cerebral  cortex  represents  the  central  organ  of  epileptic  con- 
vulsions. Direct  or  indirect  excitation  of  this  area  due  to  any 
cause  is  the  essential  factor  of  the  epileptic  seizure.  The  excita- 
tii  in  of  the  bulb  is  probably  an  accessory,  complementary  factor, 
which  is  not  indispensable.  Shortly  stated,  the  following  are  the 
arguments  in  favour  of,  and  opposed  to,  this  theory  :— 

(a)  When  the  epilepsy  develops  in  animals  after  partial 
destruction  of  the  motor  area  on  one  side  the  tonic-clonic  con- 

VOL.  in  2  P 


578  PHYSIOLOGY  CHAP. 

vulsions  do  not  involve  all  the  muscles  of  the  opposite  side ;  they 
merely  involve  the  muscular  groups  of  which  the  centres  are 
intact,  while  those  groups  of  which  the  centres  have  been  excised 
escape. 

(6)  After  destruction  of  the  whole  motor  area  on  one  side, 
faradisation  of  the  subjacent  white  matter,  even  with  the  strongest 
currents,  may  fail  to  elicit  true  epileptic  convulsions,  though  these 
are  readily  evoked  when  the  stimulation  is  applied  to  the  cortex 
of  the  motor  area  (Francois-Franck  and  Pitres,  Fig.  295). 

(c)  Occasionally,  however,  when  the  motor  area  on  one  side  has 
been  extirpated,  electrical  stimulation  of  the  subjacent  white 
matter  may  give  rise  to  epilepsy.  But  in  this  case  the  convulsions 


A  B 

YIG.  295. — Curves  from  a  dog's  musclf  i>roilurp<l  l>y  strong  excitation. 

begin  not  in  the  muscles  of  the  opposite  side  of  the  body,  but  in 
those  of  the  side  excited.  This  shows  that  excitation  of  the  white 
matter  produces  the  attack  not  through  the  bulb,  but  by  trans- 
mission of  the  excitation  along  association  paths  to  the  motor  area 
of  the  other  hemisphere  (Bubnoff  and  Heidenhain.) 

(d)  This  is  confirmed  by  the  fact  that  after  bilateral  extirpa- 
tion  of  the   motor    zone   electrical    stimulation   of  the   subjacent 
medullary  substance  invariably  fails  to  excite  an  epileptic  attack, 
no  matter  how  strong  the  current  (Bubnoff  and  Heidenhain). 

(e)  If  after  incomplete  extirpation  of  the  motor  area  on  one 
side  the  portion  left   intact  be   stimulated,  diffuse  epileptic  con- 
vulsions   may  involve    all   the    muscles,    with    the    exception    of 
the    groups    represented    in    the    area    that    had    been    destrovrd 
(Uuverricht). 

(/)  If  during  the  initial  phase  of  an  epileptic  attack  produced 
by  laradising   the    motor  area  the  sigmoid  gyrus  of   the   dog  is 


x  THE  FORE-BRAIN  579 

excised,  the  attack  can  immediately  he  arrested  (H.  Munk).  In 
the  early  stage  of  an  epileptic  attack  it  is  not  infrequently  possihle 
by  extirpating  the  centre  of  one  extremity  to  prevent  the  spread 
of  the  convulsion  to  that  limb,  though  the  rest  of  the  body  is 
violently  convulsed.  In  other  cases  it  is  possible  by  prompt  ablation 
of  the  whole  motor  region  on  one  side  to  arrest  the  convulsions  on 
the  opposite  side  of  the  body,  or  on  both  sides.  In  other  cases 
when  the  general  convulsions  have  reached  their  maximum 
development  destruction  of  the  whole  motor  region  of  one 
hemisphere  fails  to  arrest  them  (Bubnoff  and  Heidenhain,  Novi 
and  Luciani,  Roseubach  and  Dauillo). 

(g]  The  hypodermic  injection  of  2  mgrms.  of  picrotoxin,  or 
14  rngrms.  of  sulphate  of  quinine  per  kgrm.  of  the  animal,  produces 
in  dogs  and  cats  vomiting,  salivation,  and  muscular  contractions  in 
the  form  of  tremors  or  twitches  of  the  muscles  of  the  face,  neck,  and 
trunk,  extending  subsequently  to  the  muscles  of  the  fore-limbs  and 
then  to  the  hind -limbs.  These  isolated  twitches  become  more 
vigorous  and  frequent  until  the  animal  cries,  loses  consciousness, 
falls  on  one  side,  and  is  seized  with  a  general  epileptic  attack  in 
which  the  tonic  phase  of  a  few  seconds  is  followed  by  a  clonic 
phase  of  one  to  five  minutes.  If  the  drug  is  again  administered  to 
the  same  animal  a  few  days  after  excision  of  the  motor  area  on 
one  side,  the  isolated  twitches  of  the  muscles  of  face,  trunk,  and 
limits,  which  precede  the  general  epileptic  attack,  are  much  weaker 
on  the  opposite  side  of  the  body.  Moreover,  during  the  fit  the 
convulsions  are  more  marked  in  the  muscles  of  the  operated  side 
and  less  strong  in  the  muscles  of  the  opposite  side  (Rovighi  and 
Santini). 

(h)  If  potassium  bromide  is  administered  to  dogs  for  several 
.days  in  succession  the  electrical  excitability  of  the  cortex  is  so 
much  reduced  that  even  strong  currents  fail  to  produce  an 
epileptic  attack,  and  when  successive  or  lethal  doses  of  quinine  are 
injected  epilepsy  is  not  evoked  (Albertoni).  The  same  negative 
result  is  seen  on  injecting  a  dose  of  picrotoxin  sufficient  under 
normal  conditions  to  cause  an  epileptic,  attack  (Rovighi  and 
Santini).  Inhalation  of  ether  and  chloroform  also  moderates  and 
sometimes  inhibits  the  convulsions  produced  by  poisoning  by 
picrotoxin  and  quinine  (Rovighi  and  Santiui). 

Certain  objections,  which  we  will  examine  critically  in  detail, 
were  made  to  these  arguments  which  undoubtedly  indicate  or  even 
prove  the  cortical  origin  of  epilepsy  :— 

(a)  Spontaneous  epileptic  convulsions  almost  invariably  develop 
in  animals  after  previous  operations  on  the  cortex,  not  only  when 
the  motor  area  of  one  or  the  other  side  has  been  extirpated,  but 
also  after  removal  of  non-motor  regions  (Luciani).  This  con- 
troverts the  theory  that  the  motor  area  is  the  central  organ  of 
epilepsy  (Vizioli,  Morselli).  Electrical  stimulation  of  non-motor 

2  P  l 


580  PHYSIOLOGY  CHAP. 

regions,  as  the  cortex  of  the  occipital  lobe,  may  also  produce 
epilepsy  (Unverricht,  Framjois-Franck),  arid  it  might  be  supposed, 
and  was  in  fact  assumed  by  some,  that  in  these  cases  the  epileptic 
attack  develops  independently  of  the  motor  area. 

But  these  two  groups  of  arguments  lose  all  value  as  against 
the  origin  of  epilepsy  in  the  cortical  m<  >tor  area,  if  we  admit  that 
in  all  these  cases  the  state  of  excitation  started  in  a  sensory  area 
must  necessarily  be  transmitted  to  the  motor  region  before  the 
epileptic  attack  can  occur.  This  is  directly  proved  by  the  work 
of  Rosenbach  and  Danillo ;  they  found  that  electrical  stimulation 
of  the  occipital  lobe  no  longer  produced  an  epileptic  attack  after 
the  entire  motor  area  of  the  homonymous  side  had  been  destroyed, 
or  if  a  narrow  band  of  grey  matter  were  excised  between  the  motor 
area  and  the  excited  occipital  area.  They  further  found  that  if 
the  excited  occipital  area  were  separated  by  an  incision  after  the 
attack  had  already  set  in,  this  did  not  cease,  though  it  was  always 
arrested  if  the  motor  area  was  removed  at  the  proper  time. 

(/3)  Complete,  bilateral  epileptic  attacks  can  be  evoked  by 
exciting  the  motor  area  of  one  side  after  previous  destruction  of 
the  motor  area  of  the  opposite  side  (Albertoni,  Fraucois-Franck 
and  Pitres).  But  this  fact  does  not  controvert  the  cortical  origin 
of  epilepsy,  and  even  confirms  it,  as  it  proves  that  in  the  bilateral 
spread  of  the  epileptic  attack  the  epileptogenous  excitation  often, 
if  not  always,  diffuses  to  the  motor  centres  of  the  bull)  (or  bulbo- 
spinal  tract),  which  may  be  considered  as  the  accessory,  comple- 
mentary, though  indispensable  factor.  Unverricht's  observations 
agree  with  this  interpretation.  He  saw  that  the  bilateral  attack 
caused  by  excitation  of  the  motor  zone  on  one  side  is  frequently 
not  of  equal  intensity  on  the  two  sides.  While  the  muscles  of  the 
side  opposite  that  excited  are  in  dome  convulsions  the  muscles  of 
the  same  side  are  in  tonic  contraction,  or  contract  clonically  in 
the  same  rhythm,  but  less  strongly  than  those  of  the  opposite  side. 
From  this  he  concluded  that  the  essential  part  of  the  epileptic 
attack  consists  in  primary  muscular  convulsions,  the  indispensable, 
conditions  of  its  appearance  being  the  integrity  of  the  cerebral 
motor  area. 

(y)  A  complete  section  of  the  corpus  callosum  of  the  cat  does 
not  prevent  the  onset  of  a  bilateral  epileptic  attack  after  electric 
stimulation  of  the  motor  area  of  one  side  (Frangois-Frauck  and 
Pitres).  But  this  fact  does  not  positively  exclude  the  interpre- 
tation offered  by  Bubnoff  and  Heidenhain,  that  the  excitation 
may  be  transmitted  from  one  hemisphere  to  the  other,  since  the 
commissural  fibres  of  the  corpus  callosum  have  not  been  proved 
to  be  the  sole  and  exclusive  connecting  paths  between  the  grey 
matter  of  the  two  hemispheres.  In  any  case  the  bilateral  spread 
of  the  tit  may  be  explained  by  the  active  intervention,  in  a 
secondary  and  subordinate  manner,  of  the  bulbo-spiual  centres. 


x  THE  FORE-BKAIN  581 

(5)  Some  poisons,  particularly  absinthe,  produce  convulsive 
attacks  similar  to  those  excited  by  electrical  stimulation  of  the  cor- 
tex, when  they  are  introduced  into  the  circulation.  These  attacks 
are  also  seen  in  animals  in  which  the  brain-stem  is  completely 
severed  from  the  brain  (Magnan).  Injection  of  a  few  drops  of 
tincture  of  absinthe  produces  inexcitability  of  the  cerebral  cortex, 
with  the  simultaneous  onset  of  violent  epileptic  seizures  due  to 
the  excitation  of  the  bulbo- spinal  centres  (Francois -Franck). 
Apart  from  these  experiments  we  know  from  Owsjannikow's 
work  that  the  bulb  contains  a  centre  for  common  direct  or  reflex 
convulsions,  a  sort  of  motorium  commune  (Chap.  VII.  pp.  411-13). 
According  to  Horsley  and  Schiifer  epileptiform  convulsions  can 
sometimes  be  observed  after  strong  and  protracted  stimulation  of 
the  spinal  cord,  when  the  cord  has  been  separated  from  the  bulb. 

These  facts  undoubtedly  prove  that  diffuse  epileptiform  con- 
vulsions may  be  evoked  by  exciting  the  whole  of  the  bulbo-spinal 
centres,  either  with  circulating  poisons,  or  by  vigorous  and 
diffuse  stimulation,  independently  of  the  brain  or  of  the  excitability 
of  the  cerebral  motor  cortex.  It  seems,  however,  illogical  to 
compare  these  convulsive  phenomena  with  genuine  epileptic  fits : 
they  have  not  the  clinical  characters  of  epileptic  seizures  which 
invariably  begin  with  symptoms  of  cortical  disturbance,  i.e.  complete 
loss  or  disturbance  of  consciousness,  and  convulsive  spasms  limited 
to  one  group  of  muscles.  If  the  epileptogenic  excitation  spreads 
to  the  lower  centres  before  the  fit  becomes  general,  this  does  not 
destroy  the  fact  that  the  essential  origin  of  both  Jacksonian  and 
idiopathic  epilepsy  lies  in  the  cerebral  cortex. 

IX.  The  attempt  to  discover  the  physiological  significance  of 
the  so-called  "centres"  contained  in  the  excitable  area  of  the 
cortex  has  produced  a  long  series  of  works,  giving  a  minute 
description  of  the  immediate  and  remote  effects  of  partial  or  total 
destruction  of  this  area. 

The  majority  of  the  experiments  have  been  made  on  dogs. 
If  the  whole  of  the  excitable  zone  on  one  side,  e.g.  the  left  hemi- 
sphere, is  excised,  the  animal  as  soon  as  it  comes  out  of  the 
anaesthetic  has  complete  paralysis  of  the  right  side.  It  lies  on 
this  side  with  its  four  limbs  flexed.  If  the  limbs  are  stretched 
passively,  it  only  draws  the  left  ones  back.  It  walks  with 
difficulty,  turning  to  the  left,  to  which  side  its  neck  and  head 
are  also  bent,  and  often  falls  owing  to  flexion  of  its  right  limits, 
which  are  frequently  placed  with  the  dorsum  of  the  foot  on  the 
ground.  The  muscles  of  the  right  half  of  the  face,  which  has  the 
immobility  of  a  mask,  are  also  paretic.  It  does  not  react  to  any 
abnormal  position  in  which  the  right  limbs  may  be  placed; 
sensibility  to  pain  is  somewhat  blunted,  and  tactile  sensibility 
seems  almost  lost  on  the  right  side. 

This    motor  hemiplegia    and    disturbance    of    cutaneous   and 


582  PHYSIOLOGY  CHAP. 

muscular  sensibility  persists  for  a  few  hours  after  the  operation, 
but  then  passes  off  gradually,  and  almost  entirely  disappears 
after  a  few  days,  so  that  it  is  difficult  without  careful  investigation 
to  distinguish  between  the  operated  and  the  intact  animal. 

Evidence  for  these  facts  is  given  by  Carville  and  Duret, 
Albertoni  and  Michieli,  Lussana  and  Lemoigne,  and  Luciani  and 
Tamburini. 

The  symptoms  described  by  Goltz  after  complete  extirpation 
of  the  whole  anterior  half  of  the  dog's  left  hemisphere,  which 
certainly  included  more  than  the  whole  of  the  excitable  area  on 
that  side,  are  more  characteristic  and  detailed.  At  first  there 
was  complete  motor  and  almost  complete  sensory  hemiplegia  of 
the  whole  of  the  right  side.  After  a  few  days  the  animal  improved 
to  the  extent  of  walking  without  falling,  but  showed  a  tendency  to 
turn  to  the  right,  and  weakness  and  uncertainty  in  the  movements 
of  the  limbs  of  that  side.  If  placed  on  a  table  the  animal  fell 
easily,  and  then  beat  the  air  with  its  right  limbs,  as  already 
noted  by  Hitzig.  In  gnawing  bones,  pieces  readily  fall  out  of 
the  right  side  of  the  mouth,  as  Schiff  had  already  observed.  If 
the  animal  had  been  trained  to  give  its  right  paw  when  invited, 
before  the  operation,  it  would  now  only  give  the  left. 

According  to  Goltz  the  sensory  disorders  are  even  more 
important  than  the  motor.  The  disturbance  of  muscular  sense, 
as  recognised  by  Hitzig,  is  unmistakable,  but  the  disturbance  of 
tactile  sensibility  is  110  less  striking,  although  the  power  of 
recognising  contacts  on  the  right  half  of  the  body  is  not  entirely 
lost,  as  was  erroneously  assumed  by  Schiff. 

JSfo  less  important  is  the  description  given  by  Goltz  of  the 
effects  of  bilateral  extirpation  of  the  entire  anterior  half  of  the 
hemispheres  to  about  7  mm.  in  front  of  the  chiasma.  On 
recovering  consciousness  a  few  hours  after  the  operation  the 
animal  makes  futile  attempts  to  stand.  It  cannot  swallow  or 
lap  milk,  but  has  to  be  artificially  fed  for  several  weeks.  The 
power  of  standing  and  walking,  in  a  very  shaky  way  at  lirst  and 
afterwards  more  and  more  steadily,  is  regained  before  the  power 
of  feeding  itself.  About  two  months  after  the  operation  the  defect 
phenomena  become  almost  stationary. 

Although  the  animal  has  recovered  its  power  of  standing 
upright,  walking,  running,  jumping,  these  actions  are  awkward 
and  imperfect.  The  hind-legs  drag,  and  it  slips  easily  on  a  smooth 
floor,  but  can  rise  alone.  If  the  bilateral  lesion  is  tolerably  sym- 
metrical, it  is  able  to  walk  in  a  straight  line,  or  to  right  or  left, 
according  to  its  needs  ;  but  if  the  lesion  is  very  unsymmetrical,  it 
leans  to  the  side  most  injured,  although  it  may  turn  to  the  opposite 
side.  There  is  no  muscular  paralysis,  and  sensibility  is  not  lost  in 
any  part  of  the  body,  but  there  is  a  marked  hyperaesthesia  of  the 
skin,  recalling  that  described  by  Brown-Sequard  after  spinal  liemi- 


x  THE  FOEE-BEAIN  583 

section  (Chap.  V.  pp.  .'->41  et  *eq.).  Notwithstanding  this  cutaneous 
hyperaesthesia,  the  animal  cannot  use  its  muscles  in  carrying  out 
certain  voluntary  acts.  It  i'eeds  clumsily  and  dirtily  like  a  pig, 
making  unusual  associated  movements  hoth  with  its  limbs  and 
with  its  jaws  and  tongue.  It  can  only  pick  up  a  hone  with  its 
mouth  after  many  attempts  and  with  great  trouble,  and  is  quite 
incapable  of  holding  it  between  the  front  paws,  like  a  normal  dog, 
to  gnaw  it.  If  accustomed,  before  the  operation,  to  giving  its  paw, 
the  power  of  doing  so  seems  entirely  lost.  If  a  piece  of  meat  is 
offered  to  it  so  that  the  long  axis  of  the  head  has  to  be  raised  to 
90°,  the  animal  is  incapable  of  making  this  movement ;  it  opens 
and  shuts  its  mouth  in  the  direction  of  the  food  without  power 
to  take  it,  or  to  direct  the  position  of  the  head  so  that  the  meat 
should  drop  into  its  mouth. 

Another  interesting  result  of  Goltz'  researches  is  that  dogs 
whose  anterior  cerebral  lobes  have  been  extensively  mutilated  on 
both  sides  lose  the  power  of  voluntarily  controlling  the  reflexes, 
the  centres  of  which  lie  in  the  bulbo-spinal  axis.  Goltz  described 
a  series  of  characteristic  reflex  movements  which  are  almost 
constant  in  normal  dogs  on  gently  exciting  the  skin  in  certain 
regions,  and  he  observed  that  these  reflexes  not  only  persisted  but 
were  exaggerated  in  dogs  that  had  been  operated  on.  In  relation 
to  this  diminished  power  of  voluntary  inhibition,  expressed  in  the 
apparent  rise  of  reflex  excitability,  is  the  fact  pointed  out  by 
Goltz  that  dogs  after  removal  of  the  anterior  part  of  the  hemispheres 
become  more  impulsive  and  aggressive.  Animals  that  had  been 
docile,  quiet,  and  affectionate,  became  difficult  to  manage,  ill- 
tempered,  and  abnormally  restless  after  the  operation,  and  continued 
so  for  mouths,  till  progressive  emaciation  led  to  death. 

These  facts  show  that  the  symptoms  of  sensory-motor  paralysis 
or  paresis  directly  due  to  extirpation  on  one  or  both  sides  of  the 
anterior  parts  of  the  hemispheres  diminish  gradually  till  they 
disappear  to  a  large  extent.  The  residual  defect  phenomena 
persist  till  death,  and  consist  in  the  animal's  imperfect  capacity  for 
acquainting  itself  with  the  position  and  form  of  objects  by  means 
of  the  muscular  and  cutaneous  senses,  for  using  its  muscles  as 
in  the  normal  performance  of  certain  voluntary  acts,  and  ifor 
voluntary  inhibition.  We  shall  presently  return  to  this  pheno- 
menon in  order  the  better  to  define  it  from  the  psycho-physiological 
point  of  view. 

Having  thus  examined  the  effects  of  total  destruction  of  the 
part  of  the  brain  which  contains  the  excitable  area,  we  must  next, 
by  the  method  of  electrical  stimulation,  investigate  the  effects  of 
extirpating  the  cortex  only  of  certain  of  the  lobules  or  centres  into 
which  it  can  be  divided. 

Munk  divided  the  excitable  area — which  he  termed  the 
"sensory  sphere"  because  he  regarded  it  as  the  seat  of  tin' 


584 


PHYSIOLOGY 


CHAP. 


perceptions  and  representations  of  skin  and  muscle  sensibility — into 
seven  distinct  regions,  corresponding  to  the  different  parts  of  the 
opposite  side  of  the  body  with  which  each  is  related,  as  already 
demonstrated  by  electrical  excitation.  He  distinguished  the 
centres  of  the  anterior  limb  (D,  Fig.  296),  of  the  posterior  limb 
(0),  of  the  head,  face,  and  tongue  (E),  of  the  eyes  (F),  of  the  ears 
(Gf),  of  the  neck  (IT),  and  of  the  back  (J).  As  shown  by  the  figure, 
these  seven  regions  occupy  the  whole  of  the  anterior  part  of  the 
outer  surface  of  the  hemispheres:  they  do  not  form  islands  like 


FIG.  296. — Dog's  brain  from  above  and  from  the  side,  marked  out  into  Munk's  "sensory  spheres." 
A,  A,  visual  sphere  ;  A',  focal  region  of  visual  sphere,  excision  of  which  produces  psychical 
blindness;  It,  I:,  auditory  sphere;  J",  focal  region  of  auditory  sphere,  excision  of  which 
produces  ps\chic;al  deafness;  C-J,  sensory  area;  < ',  of  tore-leg;  D,  of  hind-leg ;  E,  of  head  ; 
F,  of  the  eye's  ;  G,  of  the  ears  ;  H,  of  the  neck  ;  ./,  of  the  trunk. 

Ferrier's  excitable  centres,  but  come  into  contact  with  one  another 
though  they  are  separated  by  fairly  sharp  borders.  Any  lesion 
in  the  sensory  sphere  must,  according  to  Munk,  result  in  disturb- 
ance of  perceptions  and  representations  of  corporeal  sensibility, 
differently  localised  according  to  the  seat  and  extent  of  the  injury. 
Slight  lesions  only  produce  loss  of  tactile  and  motor  representa- 
tions ;  graver  lesions  involve  loss  of  representations  of  position  also; 
still  more  serious  injury  involves  loss  of  representations  of  pressure 
or  contact.  As  the  paralytic  effects  disappear  there  is  recovery 
first  of  simple  representations  and  then  of  the  more  complex  ; 
the  representations  of  pressure  return  first,  next  those  of  position, 
lastly,  the  tactile  and  motor  representations. 


x  THE  FORE-BRAIN  585 

As  a  concrete  instance  of  these  effects,  we  may,  according  to 
Munk,  describe  the  symptoms  due  to  total  excision  of  the  centre 
for  the  tore-limb  in  the  left  hemisphere  (D,  Fig.  296).  During 
the  tirst  three  to  five  days  after  the  operation  these  are  as 
follows  :— 

(a)  Loss  of  appreciation  of  contact  and  pressure  on  the  skin  of 
I  In'  /'i</ht  fore-limb. — When  one  of  the  left  extremities  or  the  right 
hind-limb  is  lightly  touched  with  the  ringer  or  the  point  of  a 
needle,  the  dog  reacts  at  once  by  slight  movements  or  tries  to  bite, 
or,  if  the  prick  is  deep,  draws  away  its  limb  from  the  unpleasant 
stimulus.  When,  on  the  contrary,  the  skin  of  the  right  fore-limb 
is  stimulated  in  the  same  way  the  dog  takes  no  notice  ;  it  only  draws 
the  limb  back  when  it  is  firmly  pressed  or  pricked,  and  the  animal 
neither  looks  round  nor  attempts  to  bite,  showing  that  the  reaction 
is  only  reflex. 

(b)  Loss  of  appreciation  of  the  position  of  the  same  limb. — The 
fore-limb  can  lie  placed  in  any  abnormal  position,  it  may  be  adducted, 
abducted,  pulled  forward  or  backward,  the  dorsum  of  the  foot  may 
be  placed  on  the  ground,  the  several  joints  flexed  or  extended  ;  the 
dog  does  not  correct  its  abnormal  posture  and  remains  indifferent  to 
it  until  it  begins  to  walk  again.  In  the  case  of  the  other  three 
legs,  on  the  contrary,  the  animal  corrects  the  abnormal  positions 
promptly. 

(c)  Loss  of  motor  representations  of  the  right  fore-limb. — This 
limb  is  capable  not  only  of  reflex  movements,  but  also  of  move- 
ments associated  with  those  of  the  other  three  limbs,  as  in  walking, 
running,  and  jumping.     But  the  animal  does  not  understand  how 
to  use  the  limb  separately.     If  it  had  been  taught  before  the  opera- 
tion to  give  its  right  paw  when  desired,  it  is  only  able  afterwards 
to  give  the  left ;  it  can  no  longer  scratch  itself,  or  hold  a  bone  or 
piece  of  meat  with  its  right  foot,  but  only  with  the  left ;  if  placed 
on  a  table  with  the  right  leg  hanging  over  the  edge,  the  animal, 
though  aware  of  the  danger  of  falling,  does  not  draw  back  its  leg 
for  support. 

(d)  Loss  of  tactile  representations  in  the  right  fore-limb. — The 
operated  dog  is  capable  of  walking,  running,  jumping,  and  of  the 
rhythmical  alternation  and  association  of  movements  in  the  four 
limbs ;  in  a  word,  the  coarse  mechanism  of  the  complicated  move- 
ments is  preserved,  but  the  finer  regulation  of  these  movements 
is  lost  in  the  right  fore-limb.     When  the  animal  walks  it  is  evident 
that  the  movements  of  this  limb  are  not  properly  graded  either  in 
lifting  it  or  moving  it  forward,  or  in  planting  it  on  the  ground.     At 
times  the  animal  rests  on  the  dorsum  of  the  foot,  and  easily  slips 
on  a  smooth  surface ;  in  fact,  it  cannot  use  the  limb  with  the  same 
accuracy  and  precision  as  the  other  three  legs,  owing,  says  Munk, 
to  lack  of  tactile  representations. 

He    defines    these    disturbances    as  "psychical    paralysis    of 


586  PHYSIOLOGY  CHAP. 

sensibility  and  motion."  They  diminish  gradually,  and  by  the 
second  week  the  dog  begins  to  recognise  contacts  on  the  skin  of 
the  right  fore -leg.  The  gait,  too,  improves.  After  four  weeks 
only  a  certain  defect  in  the  isolated  movements  of  this  limb  can  be 
perceived,  with  a  slight  lack  of  precision  and  dexterity  in  the  com- 
plicated movements  of  locomotion.  Even  these  small  disturbances, 
however,  have  disappeared  ten  weeks  after  the  operation. 

Very  different  are  the  effects  of  total  or  partial  removal  of  the 
excitable  area  of  the  cortex  in  the  ape.  Goltz  described  a  Macacus, 
in  which  the  cortex  of  the  frontal  and  parietal  lobes  of  the  left 
hemisphere  was  destroyed  by  two  operations.  This  monkey  was 
kept  under  observation  for  eleven  years.  Completely  hemiplegic 
immediately  after  the  operation,  after  a  few  months  it  was  only 
hemiparetic  in  all  the  muscles  of  the  right  side.  In  slow  walking 
it  used  both  feet  and  the  left  hand,  while  the  right  hand  was 
generally  held  up  in  the  air.  In  scratching  and  for  grasping  the 
food  offered  to  it,  it  always  used  the  left  hand. 

The  clumsy,  imperfect  manner  in  which  the  right  limbs  were 
used  in  walking,  jumping,  and  climbing,  showed  that  cutaneous 
and  muscular  sensibility  were  affected.  In  fact,  the  ape  did  not 
recognise  slight  contacts  on  the  skin  of  the  right  limbs,  while  the 
same  contacts  were  readily  appreciated  on  the  left.  But  the  skin 
of  the  right  side  was  not  entirely  insensitive  ;  moderate  pressure  on 
the  right  paw  was  plainly  felt  by  the  animal,  which  showed  that  it 
was  able  to  localise  it. 

The  inability  to  use  the  right  hand  in  isolated  purposive  acts 
depends  partially  on  the  blunting  of  cutaneous  sensibility.  If  the 
monkey  is  offered  a  large  apple  which  it  cannot  hold  with  the  left 
hand  alone,  it  uses  the  right  hand  as  well  to  lift  it  to  its  mouth. 
If  the  left  hand  is  held  while  the  monkey  is  offered  a  piece  of  sugar, 
it  stretches  out  its  right  hand  slowly,  evidently  overcoming  some 
resistance  to  the  voluntary  impulses.  By  repeated  efforts  it  can 
learn  once  more  to  give  its  right  hand  and  make  a  military  salute 
with  it ;  but  the  use  of  the  right  hand  always  remains  a  difficulty. 
Some  effort  is  evidently  required  to  extend  the  fingers  completely 
and  grasp  objects  with  them,  which  implies  a  commencing  con- 
tracture  of  their  muscles.  The  great  difference  in  the  power  of  using 
the  two  hands  is  shown  by  the  following  experiment :  if  the  monkey 
is  set  on  a  table  and  its  left  hand  held  while  some  cherries  are 
thrown  down  in  front  of  it,  the  animal  will  carefully  and  clumsily 
use  its  right  hand  to  take  them  one  after  another  and  put  them 
in  its  mouth.  But  as  soon  as  the  left  hand  is  liberated  it  uses  it 
with  astonishing  dexterity  to  catch  up  the  fruit. 

These  observations,  as  a  whole,  show  that  the  excitable  area  is 
more  important  in  the  monkey  than  in  the  dog  for  the  normal 
control  of  the  muscles.  Years  after  the  operation,  residual 
phenomena  of  deficiency  are  recognisable  in  apes  as  a  slight  degree 


X 


THE  FOEE-BEAIN 


587 


<>!'  motor  paresis  and  a  certain  blunting  of  cutaneous  and  muscular 
sensibility. 

Munk's  experiments  refer  particularly,  to  the  effects  of  isolated 
extirpation  of  several  regions  of  bis  sensory  sphere,  which  are 
somewhat  differently  localised  in  monkeys  and  in  dogs  (Fig.  297). 
His  results  are  a  complete  contrast  to  those  described  for  dogs ; 
the  defect  phenomena  in  the  different  forms  of  cutaneous  and 
muscular  sensibility  are  perfectly  localised  to  the  parts  of  which 
the  centre  had  been  destroyed.  Just  as  the  movements  produced 
by  stimulation  of  different  regions  of  the  Eolandic  area  are  due 


FIG.  297. — Mattmis  brain  from  above  ami  from  the  side,  showing  the  respective  sensory  areas 

as  in  last  figure.     (From  H.  Munk.) 

to  awakening  of  the  sensations  which  normally  accompany  such 
movements,  so  the  motor  paralysis  consequent  on  extirpation  of 
these  regions  is,  according  to  Munk,  due  to  loss  of  the  same  sensa- 
tions. Again,  after  transaction  of  the  dorsal  roots  of  a  limb  its 
voluntary  motility  is  largely  reduced  or  abolished  (Pani/zi,  Baldi). 
It  follows  logically  from  Munk's  theory  that  after  total  extirpation 
of  any  one  of  his  sensory  areas,  for  instance  area  D,  there  must  be 
total  loss  of  cutaneous  and  muscular  sensibility  in  the  fore-limb  on 
the  opposite  side.  Yet  this  is  not  shown  either  by  his  own  experi- 
ments, or  by  those  of  his  numerous  opponents. 

Schafer  states  positively  that  in  the  monkey  careful  and 
complete  removal  of  the  entire  region  of  the  cortex,  which  on 
stimulation  produces  movements  of  the  hind-limb  of  the  opposite 
side  (area  0  of  Munk),  may  not  be  followed  by  any  obvious 
sensory  paralysis,  although  the  limb  loses  its  power  of  voluntary 
movement.  The  extirpation  of  the  cortex  can  be  shown  to  be 
complete  by  the  fact  that  on  exciting  an  epileptic  lit  by  electrical 
stimulation  of  other  areas  of  the  cortex,  the  hind-limb  of  the 


588  PHYSIOLOGY  CHAP. 

opposite  side  takes  no  part  in  it.  A  similar  fact  was  demonstrated 
by  Fload  for  the  motor  area  of  the  face  (area  E  of  Munk). 

According  to  Schafer  there  may  be  complete  paralysis  of 
voluntary  movements  on  the  opposite  side,  with  no  appreciable 
loss  of  sensibility,  not  merely  after  removing  the  cortex  of  a 
single  motor  area,  but  also  when  nearly  the  whole  of  the  motor 
cortex  has  been  extirpated  in  the  monkey.  This  was,  however, 
contradicted  by  the  observations  of  other  workers,  particularly 
those  published  by  ourselves  in  1885,  which  were  fully  confirmed 
by  Mott  in  1894  Both  our  results  and  those  of  Mott  indicate 
that  a  more  or  less  extensive  lesion  of  the  Eolandic  area  is  always 
followed  by  more  or  less  complete  motor  paralysis,  associated 
with  an  appreciable  degree  of  defective  sensibility  in  the  limbs. 
Schafer's  criticism  of  the  methods  which  Mott  employed  for 
testing  sensibility  in  the  monkey  does  not  appear  to  us  to  detract 
from  the  value  of  Mott's  interpretation,  which  for  the  rest  agrees 
with  the  exhaustive  researches  of  Goltz. 

At  the  same  time  we  accept  Schafer's  conclusions  that  the 
motor  paralysis  present  after  removal  of  the  cortex  of  the 
Eolandic  area  of  the  monkey  cannot  be  interpreted,  with  Munk, 
as  entirely  due  to  loss  of  sensibility.  Logically  speaking,  the 
Eolandic  area  cannot  lie  denned  as  sensory  or  motor,  but  must 
be  regarded  as  sensory-motor.  Motor,  because  it  represents  that 
portion  of  the  cortex  which  is  directly  connected  by  efferent  or 
projection  fibres  with  the  lower  motor  centres  of  the  mid-brain, 
bulb,  and  cord,  and  because  impulses  for  voluntary  motor  activity 
and  the  first  phase  of  this  activity  originate  here;  sensory, 
because  the  voluntary  acts  are  guided  and  controlled  1  >y  cutaneous 
and  muscular  sensations,  so  that  the  parts  of  the  cortex  in  which 
they  originate  must  be  intimately  connected  with  the  perceptual 
centres  for  these  sensations ;  sensory -motor,  because  the  dis- 
turbances incident  on  the  destruction  of  the  Eolandic  area  are 
neither  exclusively  motor  nor  exclusively  sensory. 

Another  more  specific  objection  may  lie  raised  to  Munk's 
theory.  He  assumes  a  constant  relation  between  the  lesion  or 
destruction  of  each  sensory  region,  and  the  seat  and  extent  of  the 
disturbance  of  cutaneous  and  muscular  sensibility.  Our  own 
researches  with  Seppilli  (1885)  both  on  dogs  and  monkeys  failed 
to  confirm  this  view,  which  is  obviously  opposed  by  facts  derived 
from  objective  observation.  It  is  practically  impossible  to  define 
the  limits  of  the  single  centres  of  the  excitable  area,  and  to 
localise  the  effects  of  their  destruction  in  one  cutaneous  region  or 
to  one  group  of  muscles.  Removal  of  the  cortex  from  any  one  of 
the  areas  which  responds  to  electrical  stimulation  by  movements 
confined  to  a  single  part  of  the  opposite  side  of  the  body  produces 
paralytic  effects  which  predominate  in,  but  are  not  entirely 
confined  to  that  part,  as  they  also  spread  more  or  less  to  adjacent 


X 


THE  FOEE-BEAIN 


589 


This  shows  that  even  it'  the  electrical  method  is  a 
v;ilua,l»le  means  of  localising  the  foci  of  maximal  excitability  it  is 
worthless  for  defining  the  total  area  of  each  centre.  These  areas 
probably  radiate  out  from  the  foci,  overlapping  and  partially 
fusing  with  the  adjacent  centres  of  other  regions  of  the  body,  so 
that  it  is  impossible  to  destroy  them  separately. 

Lastly,  it  must  be  noted  as  a  serious  objection  to  Hunk's 
theory  that  the  paralytic  phenomena  which  he  described  are 
transient  and  disappear  almost  completely  in  a  few  weeks,  even 
when  the  cortex  has  been  entirely  removed  from  the  corresponding 
sensory  regions.  How  are  we  to  explain  this  fact  without 


FIG.  L".I*.     Sriis.ii  y-motor  ami  of  human  cerebral  cortex.     The  cortex  of  the  paracentral  lobe  of  the 
mesial  surface,  which  is  nut  visible  in  the  figure,  also  forms  part  of  the  sensory-motor  area. 

admitting  the  existence  of  other  sub-cortical  centres,  able 
vicariously  to  assume  the  psychical  functions  of  the  centres  that 
have  been  destroyed?  But  if  this  theory  be  accepted,  Munk's 
hypothesis,  which  confines  all  psychical  functions  to  the  cortex,  is 
overthrown. 

One  point  remains:  granting  the  mixed  sensory  and  motor 
character  of  the  excitable  area  of  the  cortex,  are  we  to  assume 
that  in  this  area  the  sensory  elements  are  completely  mingled 
with  the  motor  as  first  suggested  by  Tamburini  in  1876,  or  are 
they  partially  mingled  and  partially  separate  ? 

The  localisation  in  the  human  brain  of  that  area  of  the  cortex 
which  is  in  relation  with  voluntary  movement  is  dependent  more 
on  a  series  of  clinical  and  anatomo-pathological  observations  than 
on  electrical  stimulation  of  the  cortex.  Many  reliable  authors 


590  PHYSIOLOGY  CHAP. 

held  that  the  motor  zone  of  the  cerebral  cortex  of ,  man  has 
approximately  the  same  extent  as  that  of  the  inferior  apes,  and 
comprises  both  the  central  or  Kolandic  convolutions  and  the  para- 
central  lobe  and  foot  of  the  frontal  convolutions.  This  view  is 
supported  by  positive  and  negative  cases.  Whenever  there  is 
paralysis  of  voluntary  movement  of  cortical  origin,  localised  to 
one  half  of  the  body,  the  post  -  mortem  examination  shows  a 
destructive  lesion  in  this  region  of  the  opposite  hemispheres,  while 
lesions  of  other  parts  of  the  cortex  are  not  accompanied  by  any 
obvious  paralysis  of  voluntary  movement  during  life. 

As  regards  the  division  of  the  human  motor  area  into  different 
centres  corresponding  with  the  different  muscular  groups,  clinical 
observation  agrees  with  the  results  of  physiological  experiment  on 
monkeys  (Fig.  298).  The  paralysis  of  the  muscles,  the  centre  of 
which  has  been  destroyed,  is  usually  complete,  and  diminishes  in 
adults  less  readily  than  in  monkeys,  showing  that  in  man  the 
motor  area  is  of  more  importance  than  in  monkeys  in  the 
execution  of  voluntary  movements,  just  as  it  is  more  important  in 
monkeys  than  in  dogs.  In  man,  too,  it  can  sometimes  be  shown 
that  a  muscle  which  is  incapable  of  carrying  out  any  isolated 
voluntary  contraction  preserves  its  power  of  acting  in  association 
with  other  muscles. 

Contracture  is  seen  more  readily  in  man  than  in  the  monkey. 
It  consists  in  a  state  of  hypertonus  of  the  paralysed  muscles,  due  in 
all  probability  to  suppression  of  the  inhibitory  impulses  which  the 
spinal  centres  habitually  receive  from  the  cerebral  cortex,  while 
the  tonic  influences  constantly  flowing  to  these  centres  from  the 
cerebellum  persist.  It  can  be  seen  in  man,  and  to  a  lesser  degree 
in  monkeys,  that  in  hemiplegia  from  cerebral  lesions  exaggera- 
tion of  spinal  reflexes  is  associated  with  contracture,  while  in 
paraplegia  from  total  transverse  lesions  of  the  cord  contractures 
never  occur,  and  the  spinal  reflexes  are  diminished  or  abolished. 

So  far  the  most  reliable  observers  agree.  But  when  it  comes 
to  confirming  by  clinical  and  anatomo- pathological  observation 
the  conclusions  obtained  from  animals  in  regard  to  the  localisation 
of  cutaneous  and  muscular  sensibility  in  the  cortex,  there  is 
much  controversy. 

In  their  first  publications  (1877-79)  Charcot  and  Pitres  cited  a 
series  of  cases  of  cortical  motor  paralysis  in  which  cutaneous  and 
muscular  sensibility  remained  perfectly  intact.  Tripier  (1880) 
was  the  first  who  maintained  from  his  own  clinical  observations 
that  the  motor  area  of  the  Kolandic  region  is  at  the  same  time  a 
sensory  zone,  because  lesions  of  it  produce  disturbances  of  motility 
and  sensibility.  Petrina  (1881),  Exner  (1881),  Lisso  (1882),  main- 
tained the  same  view.  In  a  subsequent  clinical  study  (1883), 
Charcot  and  Pitres  opposed  this  tendency.  While  admitting  the 
force  of  the  clinical  facts  adduced  by  Tripier  and  other  observers 


x  THE  FORE-BRAIN  591 

they  thought  it  an  exaggeration  to  assume  that  destructive  lesions 
of  the  motor  area  are  invariably  accompanied  by  disturbance 
of  sensibility.  In  their  final  publication  (1895),  which  gives  a 
very  lucid  summary  of  the  results  of  clinical  observations  as  a 
whole,  they  came  to  the  following  conclusion  :— 

"Paralysis  <  if  cortical  origin  may  be  accompanied  by  disturbances 
df  cutaneous  and  muscular  sensibility,  but  these  sensory  troubles 
which  are  sometimes  associated  with  the  motor  paralysis  are  in 
no  constant  and  inevitable  relation  with  the  lesions  of  the  motor 
zone.  The  cortical  motor  centres  of  the  Rolandic  area  are  not 
therefore  sensory-motor  organs." 

Luciani  and  Seppilli  (1885)  concluded  after  a  critical  ex- 
amination of  47  clinical  cases  that: — "There  is  a  vast  area, 
including  the  anterior  part  of  the  frontal  lobe,  the  temporal 
lobe,  and  the  occipital  lobe,  which  is  in  no  relation  with 
cutaneous  and  muscular  sensibility.  As  disease  of  the  posterior 
parts  of  the  three  frontal,  the  two  ascending  or  central  convolu- 
tions, the  paracentral  lobule  and  the  two  parietal  gyri  produces 
disturbances  of  cutaneous  and  muscular  sensibility,  we  rightly 
ascribe  a  sensory  function  to  them,  and  regard  them  as  belonging 
to  the  centre  of  cutaneous-muscular  sensibility  in  man.  As  we 
can  see,  this  centre  is  more  extensive  than  the  so-called  motor 
area,  since  in  addition  to  the  Rolandic  convolutions  it  also  com- 
prises the  two  parietals  and  the  posterior  portions  of  the  three 
frontal  c<  mv<  ilutions. 

"  Disturbance  of  cutaneous  sensibility  may  occur  unaccompanied 
by  any  alteration  of  muscular  sensation.  On  the  other  hand,  in 
three  of  our  cases  there  was  disturbance  of  the  muscle -sense 
without  paralysis  of  movement  and  with  no  alteration  of  cutaneous 
sensibility,  so  that  it  seems  as  if  in  man  the  areas  of  the  brain 
surface,  lesions  of  which  produce  alteration  of  movement  and  dis- 
turbance of  muscular  and  cutaneous  sensibility,  are  not  identical." 

Mills,  too  (1890-1901),  asserted  that  many  cases  had  been 
published  in  which  there  were  lesions  of  the  motor  area  with  no 
disturbance  of  sensibility.  In  several  cases  of  lesions  of  the  cortex 
of  the  Rolaudic  area  after  the  surgical  extirpation  of  tumours, 
careful  examination  of  the  patient  showed  that  sensibility  was 
intact. 

In  his  review-  of  the  whole  clinical  literature  Schafer  (1900) 
stated  that  the  cases  of  more  or  less  circumscribed  lesions  in  the 
h'olandic  area,  in  which  sensibility  was  not  disturbed,  amounted 
to  66  per  cent. 

Von  Monakow  (1902)  from  his  most  recent  observations  con- 
firmed the  conclusion  of  Luciani  and  Seppilli.  He  states  expressly 
that  lesions  of  the  cortex  of  the  precentral  gyrus  occasionally,  I  >ut  not 
always,  nor  permanently,  cause  alterations  of  sensibility  associated 
witli  motor  paralysis  or  paresis.  On  the  other  hand,  he  states 


592 


PHYSIOLOGY 


CHAP. 


that  in  recent  years  a  large  number  of  cases  of  true  disturbance, 
of  sensibility  have  been  published,  with  complete  absence  of  henii- 
plegic  symptoms,  due  to  extensive  destructive  lesions  of  the 
parietal  lobe,  while  the  cortex  of  the  precentral  gyrus  was  intact. 
The  latter  must  therefore  be  the  true  motor  area,  as  shown  by  the 
experiments  of  Sherrington  and  Krause  on  anthropoid  apes,  and 
on  man  by  the  electrical  method  (see  Fig.  281,  p.  556;  Fig.  283, 

p.  559). 

These  recent  positive  cases  quoted  by  Cox,  Mills,  Eedlich, 


POT 


POT 


A 


por 


Fir,.  299.— Diagram  of  projection  and  association  areas.  (From  Flechsi^.)  >'£,',  sensory-motor 
area;  V,  visual  area;  .•!,  auditory  area;  F,  frontal  association  area;  /,  association  area  <>1 
insul'a;  POT,  parieto-oceipito-temporal  association  area. 

Spiller,  and  Oppenheim,  are  supported  by  another  series  of  older 
negative  cases,  described  by  Bastian,  Dana,  Heuschen,  Dejeriue, 
and  others,  which  confirm  the  same  theory.  So  that  from  clinical 
data  we  are  forced  to  conclude  with  Monakow  that  hemiplegia 
of  cortical  origin  may  occur  without  hemianaesthesia,  and  henii- 
anaesthesia,  particularly  with  disturbance  of  muscular  sense, 
without  true  hemiplegia.  Cortical  hemiplegia  GC  hemiparesis  is 
almost  always  associated  with  a  lesion  of  the  precentral  con- 
volution, and  the  hemianaesthesia  or  hemihypoaesthesia  is 
associated  with  lesions  of  the  convolutions  that  lie  behind  the 
central  or  Eolandic  sulcus. 

Monakow,    too,    applied    the    term  sensory-motor   sphere  to  a 


THE  FORE-BRAIN 


593 


more  extended  region  than  the  Rolandic  area  of  the  human  1  train  ; 
this  he  terms  the  ceutro-parietal  region,  which  includes,  in  addition 
to  the  two  central  convolutions  and  the  supramarginal  gyrus,  the 
anterior  part  of  the  upper  and  lower  parietal  lohes.  Within  this 
extensive  centro-parietal  region  lie  both  the  cortical  terminations 
of  the  neurones  of  cutaneous  and  muscular  sensibility  and  the 
nerve-cells  in  which  voluntary  movement  is  initiated.  But  the 
sensory  elements  are  not  completely  mingled  with  the  motor  ; 


POT 


V- 


Fn 


t.  300.— Plan  of  projection  and  association  centres.  (After  Flechsig.)  N/-.',  sriisory-motor  area  ; 
I",  visual  area;  A,  auditory  area;  F,  frontal  association  area;  /,  association  area  of  insula; 
POT,  parieto-occipito-temporal  association  area  ;  0,  olfactory  area. 

the  former  extend  more  particularly' behind  the  central  sulcus,  the 
latter  lie  almost  completely  in  front  of  it. 

This  theory  agrees  fairly  well  with  Flechsig's  observations, 
which  are  founded  on  the  myelination  of  the  projection  fibres  of 
the  corona  radiata  during  embryonic  development  and  the  first 
months  of  extra-uterine  life.  He  states  that  the  centro-parietal 
zone  extends  backward  to  the  posterior  border  of  the  post-central 
convolution  and  the  paraceiitral  lobule;  forward,  to  the  frontal 
convolutions,  reaching  the  operculum  below,  and  the  corpus 
callosum  at  the  medial  surface  (Figs.  299,  300).  According  to 
Flechsig,  the  origins  of  the  pyramidal  tracts  do  not  spring 
uniformly  from  the  whole  of  this  centro-parietal  zone  and  in 

VOL.  in  2  Q 


594  PHYSIOLOGY  CHAP. 

direct  relation  with  the  sensory  endings,  but  lie  chiefly  in  the 
paracentral  lobule,  the  precentral  gyrus,  the  introflexed  cortex  of 
the  Rolandic  sulcus  (fissure),  and  the  posterior  segment  of  the  first 
frontal  convolution.  According  to  Flechsig's  later  conclusions 
(1904),  the  sensory -motor  zone,  properly  so-called,  lies  only  within 
the  Rolandic  fissure  ;  the  convexity  of  the  precentral  convolution 
is  almost  purely  motor,  and  the  convexity  of  the  post-central 
convolution  is  almost  purely  sensory.  This  also  agrees  with  the 
fact  that  the  giant  pyramidal  cells  are  very  few  in  the  cortex  of 
the  post-central  convolution  (Brodmann).  But  Flechsig's  diagram 
seems  to  us  incorrect,  as  it  makes  the  boundary  between  the 
mixed  zone  and  the  sensory  and  motor  zones,  and  between  these 
and  the  inexcitable  frontal  and  parietal  limiting  zones,  too  sharp 
and  distinct. 

X.  The  functions  of  the  sensory-motor  area  of  the  cerebral 
cortex  are  intimately  connected  with  those  of  the  sub-cortical  grey 
nuclei  which  are  situated  toward  the  base  of  the  cerebral  hemi- 
sphere, the  principal  being  the  so-called  corpora  striata,  i.e.  the 
caudate  and  lenticular  nuclei.  As  shown  by  Fig.  263  (p.  530),  the 
caudate  nucleus  is  the  medial,  intra-ventricular  portion,  the 
lenticular  the  lateral  extra- ventricular  part  of  the  corpus  striatum. 
The  two  nuclei  are  separated  from  each  other  by  a  layer  of  white 
fibres — the  so-called  internal  capsule — which  are  continuous  with 
the  fibres  of  the  white  matter  of  the  hemispheres  and  spread  out 
like  a  fan  in  the  direction  of  the  cortex  (corona  radiata  of  Eeil). 
The  two  nuclei,  however,  are  not  completely  separated,  as  there 
are  a  number  of  small  bridges  of  grey  matter,  particularly  in  the 
anterior  limb  of  the  capsule,  which  unite  them. 

From  the  phylogenetic  and  ontogenetic  point  of  view  the  basal 
ganglion  or  corpus  striatum  precedes  the  formation  of  the  mantle 
or  pallium,  and  constitutes  the  base  of  the  telencephalon  or  fore- 
brain,  which  develops  from  the  first  secondary  vesicle.  From  this 
fact  it  may  be  concluded  with  probability  that  the  functions  of  the 
two  principal  nuclei  of  the  corpus  striatum  in  mammals  and  man 
do  not  differ  essentially  from,  and  are  of  the  same  order  as,  those 
of  the  cerebral  cortex. 

A  number  of  clinical  and  anatomo-pathological  observations  on 
man  have  proved  that  an  apoplexy  which  injures  the  fibres  of  the 
middle  third  of  the  internal  capsule  produces  sensory  and  motor 
hemiplegia  on  the  opposite  side  of  the  body,  showing  that  the 
fibres  of  this  segment  of  the  capsule  are  in  connection  with  the 
sensory -motor  area  of  the  cortex.  On  the  other  hand,  experiments 
on  animals  have  shown  that  total  extirpation  of  this  area  pro- 
duces degeneration  of  the  whole  of  the  pyramidal  tract  in  the 
middle  third  of  the  capsule.  Lastly,  it  is  proved  by  anatomy  and 
experiment  that  the  fibres  of  the  anterior  segment  of  the  capsule 
are  in  connection  with  the  prefrontal  region  of  the  pallium, 


x  THE  FOKE-BKAIN  595 

and  those  of  the  posterior  segment  with  the  temporo- occipital 
region. 

Besides  these  fibres  whicli  unite  the  cerebral  cortex  with 
subcortical  centres  the  internal  capsule  contains  many  other 
bundles:  as  those  which  unite  the  corpus  striatum  with  the 
thalamus  and  those  which  connect  the  cortex  with  the  thulamus. 
lleference  should  be  made  to  the  most  recent  text-books  of  the 
anatomy  of  the  nerve-centres  for  the  origin,  arrangement,  and 
course  of  this  very  complex  system  of  projection  and  association 
fibres. 

The  nuclei  of  the  corpus  striatum,  unlike  those  of  the  optic 
thalamus,  are  not  in  close  connection  with  the  cerebral  cortex. 
This  was  clearly  brought  out  by  Gudden  (1872),  who  found  that 
after  extirpation  of  the  sigmoid  gyrus  in  the  dog  there  is  marked 
atrophy  of  the  thalamus,  while  the  caudate  nucleus  and  putamen 
undergo  only  a  slight  diminution  in  size  (Biauchi  and  d'Abundo). 
Many  of  the  projection  fibres  that  run  from  the  corona  radiata  to 
the  internal  capsule  also  run  through  the  corpus  striatum,  but  are 
connected  with  it  only  by  slender  collaterals,  the  principal  branches 
running  to  the  grey  matter  of  the  thalamus,  pons,  bulb,  and  cord. 
This  different  relation  in  which  the  cortex  stands  to  the  corpora 
striata  which  form  part  of  the  prosencephalon,  and  to  the  optic 
thalami  which  belong  to  the  diencephalon  or  'tween  brain, 
harmonises  with  the  theory  which  holds  the  basal  nuclei  to  be  an 
integral  and  complementary  part  of  the  cortical  system  in  general, 
and  particularly  of  the  sensory-motor  sphere. 

The  physiological  significance  of  the  basal  nuclei  was  the 
subject  in  the  past  of  very  discordant  hypotheses,  'which  were 
either  pure  speculation  or  were  based  on  inadequate  anatomical, 
clinical,  and  experimental  observations,  which  need  not  now 
concern  us.  Disease  confined  to  the  grey  matter  of  the  caudate 
and  lenticular  nuclei,  without  lesions  of  the  fibres  of  the  internal 
capsule,  are  rare,  and  not  always  properly  observed  and  described 
in  the  patient's  lifetime.  Experimental  lesions  of  these  nuclei, 
owing  to  their  position  and  connections,  inevitably  involve  damage 
to  'surrounding  parts.  This  explains  why  the  physiology  of  the 
corpora  striata  is  still  rudimentary. 

It  is  possible  indirectly  to  form  an  approximately  correct 
conception  of  the  functions  of  the  corpora  striata,  by  comparing 
the  defect  phenomena  which  ensue  on  extensive  extirpation  of  the 
cerebral  cortex  of  the  dog,  including  the  whole  sensory -motor 
area,  with  those  seen  after  complete  destruction  of  the  cortex  and 
also  of  the  corpora  striata.  In  our  1878  memoir  (with  Tamburini) 
on  the  sensory -motor  area  of  the  dog,  we  put  forward  the. 
hypothesis — in  order  to  account  for  the  partial  and  fairly  rapid 
compensation  of  the  paralytic  symptoms — that  the  basal  ganglia 
were  capable  of  vicariously  assuming  the  functions  of  the  excised 

2  Q  l 


596  PHYSIOLOGY  CHAP. 

cortical  region.  In  our;  1885  monograph  (with  Seppilli)  on  cerebral 
localisation,  we  supported  this  view  by  observations  on  a  dog  in 
which  the  whole  of  the  corpus  striatum  and  anterior  part  of 
the  thalamus  were  destroyed  on  one  side,  in  addition  to  the 
excitable  area.  In  this  case  the  usual  motor  and  sensory  defect 
phenomena  of  the  opposite  side  persisted  for  more  than  nine 
months  after  the  operation,  which  is  never  the  case  when 
the  operation  involves  the  cortex  only,  or  the  whole  anterior 
half  of  the  brain  is  destroyed,  as  shown  by  the  classical  ex- 
periments of  Goltz.  In  all  these  cases  the  paralytic  symptoms 
are  so  slight  after  a  few  days  or  weeks  that  they  seem  to  have 
entirely  disappeared  unless  they  are  carefully  sought  for.  It 
seems  to  us  therefore  legitimate  to  conclude  that  the  basal  ganglia 
have  the  same  function  as  the  sensory-motor  zone  of  the  cortex,  and 
that  the  greater  persistence  and  severity  of  the  defect  symptoms 
in  the  dog  were  due  to  the  destruction  of  both  the  corpora  striata 
and  the  cortex. 

Direct  experimental  investigation  of  the  basal  ganglia  was  first 
attempted  by  Nothnagel  on  rabbits  (1876),  by  the  injection  of  a 
few  drops  of  chromic  acid,  and  by  a  trochar  from  which  blades 
could  be  projected,  which  he  inserted  through  the  interhemispheri- 
cal  fissure  into  the  third  ventricle ;  on  turning  it  round  he 
destroyed  the  head  of  the  caudate  nucleus.  Among  his  observa- 
tions the  fact  is  worthy  of  notice  that  an  irritative  lesion  of  the 
head  of  this  nucleus,  which  he  called  nodus  cursurius,  produces  in 
the  animal  an  irresistible  tendency  to  run.  This  fact  was  confirmed 
by  Fournier  and  by  Ifezek,  but  denied  by  Schwohu  and  Eckhard. 

After  injections  of  chromic  acid  into  the  anterior  half  of  the 
lenticular  nucleus,  Nothnagel  noted  paralysis  of  the  muscles  of 
the  limbs,  without  perceptible  alteration  of  sensibility  to  pain. 
Carville  and  Duret  (1875),  011  repeating  the  experiments  on  the 
caudate  and  lenticular  nuclei,  observed  hemiplegia  of  the  opposite 
side,  which  was  more  serious  when  the  internal  capsule  was 
badly  injured.  They  surmised  that  Nothnagel,  by  using  chromic 
acid,  had  also  injured  the  capsule. 

Johannsen  (1885),  on  faradic  excitation  of  the  lenticular 
nucleus,  observed  first  tonic  contractions  and  then  clonic  twitches 
in  the  muscles  of  the  opposite  side,  sometimes  of  the  same  side 
also.  He  noted  that  these  epileptoid  effects  occurred  also  when 
the  excitable  cortex  was  partially  destroyed ;  and  they  were 
consequently  independent  of  spread  of  the  current  to  the  cortical 
motor  area.  The  epileptoid  attacks  were  more  diffuse  on  exciting 
the  middle  and  inner  third  of  the  lenticular  nucleus ;  and  more 
confined  to  special  groups  of  muscles  when  the  posterior  segment 
of  the  nucleus  is  excited. 

Baginski  and  Lehmann  (1886)  in  studying  the  functions  of  the 
caudate  nucleus  used  an  aspirator,  connected  with  a  thin  glass 


x  THE  FOEE-BEAIN  597 

tube  introduced  through  ;i  small  aperture  in  the  skull;  on  remov- 
ing part  of  the  caudate  nucleus  by  this  means  they  observed 
symptoms  of  sensory  and  motor  defect  on  the  opposite  side,  but 
only  of  short  duration.  They  also  observed  a  rise  of  the  animal's 
temperature,  for  several  days,  to  40°,  an  effect  previously  noted  by 
Sachs,  Ott,  and  Eichet. 

Sgobho  (1892)  again  employed  Nothnagel's  trochar  to  destroy 
the  caudate  or  the  lenticular  nucleus  alone,  or  the  motor  area,  or 
the  motor  area  and  basal  ganglia.  But  his  notes  of  the  experiments 
leave  much  to  be  desired ;  he  neglected  sensory  changes  altogether. 
Still  he  noted  the  interesting  fact  that  simultaneous  lesions  of  the 
motor  zone  and  the  corpus  striatum  produce  paralytic  symptoms 
which  are  more  serious  and  last  longer  than  those  due  to  lesions 
of  one  of  these  parts  only. 

Sellier  and  Verger  (1898)  succeeded  in  destroying  small 
portions  of  the  basal  ganglia  without  damaging  the  surrounding 
parts,  by  means  of  bipolar  electrodes  covered  so  as  to  insulate 
them  except  at  the  points.  In  a  dog  thus  operated  on  and  killed, 
after  forty-one  days,  they  noted  partial  hemiplegia  of  the  opposite 
side,  which  persisted  till  death;  tactile  hemianaesthesia,  which 
diminished  after  the  third  week ;  total  loss  of  muscular  sense, 
and  normal  sensibility  to  pain.  Examination  of  the  brain  revealed 
a  focus  the  size  of  a  pea  in  the  head  of  the  caudate  nucleus, 
and  spreading  to  the  anterior  segment  of  the  internal  capsule. 
This  excellent  experiment  demonstrates  that  the  symptoms  due 
to  lesions  of  the  caudate  nucleus  are  identical  with  those  conse- 
quent on  ablation  of  the  senso-motor  zone. 

Pagano  (1906)  by  the  exciting  action  of  injections  of  curare, 
which  he  had  already  employed  on  the  cerebellum,  attempted  to 
sin  »w  the  special  importance,  in  his  opinion,  of  the  caudate  nucleus 
as  "  the  seat  of  physiological  mechanisms  which  serve  the  ex- 
pression of  the  emotions."  When  curare  is  injected  into  the  inner 
half  of  the  anterior  and  median  third  of  the  head  of  the  caudate 
nucleus  it  excites  symptoms  which  suggest  fear ;  injected  into 
the  posterior  third  it  gives  rise  to  symptoms  of  anger  ;  lastly,  when 
it  stimulates  the  outer  part  of  the  anterior  third  of  this  nucleus 
marked  visceral  phenomena  are  seen.  But  the  injection  of  curare 
by  Pagano's  method  is  manifestly  inadequate  for  exact  localisation; 
and  the  psycho-motor  agitation  which  results  gives  rise  to  such 
complex  phenomena  that  any  physiological  analysis  of  them  would 
be  exceedingly  difficult. 

Lo  Monaco's  experimental  extirpation  of  the  head  of  the  caudate 
nucleus  through  the  inter-hemispherical  sulcus,  after  section  of  the 
corpus  callosum,  represent  the  most  exact  contributions  to  this 
subject  (Chap.  IX.  p.  520).  In  four  dogs  which  survived  long  enough 
to  allow  investigation  of  the  effects  and  their  course,  the  symptoms 
were  constantly  and  exclusively  those  of  motor  and  sensory  defect 


598  PHYSIOLOGY  CHAP. 

on  the  opposite  side,  with  little  or  no  difference  from  those  due  to 
ablation  of  the  excitable  area  of  the  cortex.  All  four  animals  died 
in  violent  attacks  of  epilepsy,  one  after  about  three  months,  the 
other  three  a  month  or  rather  more  after  the  operation. 

Lo  Monaco's  attempts  to  extirpate  the  lenticular  nucleus  more 
or  less  completely  were  less  successful  and  conclusive,  since  this 
involves  removal,  simultaneously,  or  by  a  preceding  operation,  of 
a  considerable  area  of  cortex  from  the  parietal  and  temporal  lobe, 
and  thus  produces  partial  loss  of  sight  and  hearing.  In  certain 
experiments  of  partial  destruction  of  the  lenticular  nucleus  with- 
out injury  to  the  internal  capsule,  the  sensory  and  motor  symptoms 
are  similar  to  those  that  follow  destruction  of  the  head  of  the 
caudate  nucleus. 

We  may,  therefore,  conclude  from  the  results  obtained  by 
various  physiological  methods  that  the  functions  of  the  two  nuclei 
of  the  corpus  striatum  do  not  differ  from  those  of  the  sensory- 
motor  area  of  the  cortex. 

The  clinical  and  anatomo-pathological  facts  that  can  throw 
light  on  the  physiology  of  the  corpus  striatum  in  man  are  scanty, 
but  highly  important,  as  they  confirm  and  partially  supplement 
the  incomplete  results  of  experiment. 

Charcot  (1876)  assumed  that  when  lesions  of  the  caudate  and 
lenticular  nucleus  are  confined  to  these  parts,  and  do  not  involve 
the  capsule,  they  either  run  a  latent  course  or,  if  motor  paralysis 
ensues,  it  is  invariably  slight  and  transitory. 

Nothnagel  (1877),  on  the  other  hand,  held  that  concomitant 
lesions  of  the  capsule  were  not  necessary  to  produce  complete 
or  incomplete  motor  paralysis,  as  was  also  believed  by  Gowers 
and  Oppenheim.  To  account  for  the  disappearance  of  the 
symptoms,  he  assumed  that  the  function  of  one  nucleus  may  be 
supplemented  by  the  homonymous  nucleus  on  the  opposite  side, 
or  that  the  lenticular  of  one  side  may  be  supplanted  by  the 
caudate  of  the  same  side,  or  vice  versa.  This  strengthens  the 
view  that  the  two  nuclei  have  the  same  function. 

Von  Monakow  distinguishes  the  effects  of  haemorrhagic  lesions 
from  those  of  softening.  The  latter  for  the  most  part  run  a  latent 
course;  the  former,  on  the  contrary,  produce  a  typical  hemiplegia 
that  gradually  disappears,  which  he  believed  to  be  due  to  com- 
pression of  the  capsule.  Brissaud  (1895)  held  the  same  opinion. 

Mingazzini  (1908),  from  the  observations  of  nine  lesions 
limited  to  the  lenticular  nucleus,  demonstrated  unmistakably 
that  motor  paresis  of  one  whole  side  of  the  body,  usually  accom- 
panied by  diminution  of  muscular,  painful,  tactile  and  thermal 
sensibility,  is  the  symptom  most  frequently  observed  during  life. 
Mingazzini  has  no  doubt  that  special  motor  paths  run  from  the 
lenticular  nucleus  (putamen)  to  the  internal  capsule,  in  association 
with  the  pyramidal  tract. 


x  THE  FOBE-BEATN  599 

Both  experimental  research  on  animals  and  clinical  lads  from 
man  therefore  support  the  conclusion  that  the  functions  of  the, 
corpus  striatum  are  homologous  with  those  of  the  sensory-motor 
area  of  the  cerebral  cortex. 

XL  The  localisation  of  the  area  of  the  cortex  which  serves 
the  perception  and  memory  of  visual  images  has  excited  much 
discussion. 

The  earliest  anatomical  studies  for  the  purpose  of  ascertaining 
which  portion  of  the  cerebral  cortex  was  in  relation  with  the  optic 
nerve,  and  therefore  with  vision,  are  those  of  B.  Pauizza  (1855). 
When  Hitzig  (1874)  announced  that  the  lesions  of  one  posterior 
portion  of  the  dog's  hemisphere  produced  blindness  on  the  opposite 
side  with  paralytic  dilatation  of  the  pupil,  he  was  unaware  that 
the  same  fact  had  been  observed  many  years  previously  by 
Panizza. 

In  his  book  on  the  functions  of  the  brain  (1875),  Terrier 
localised  the  cortical  centre  of  vision,  extirpation  of  which  produces 
blindness  in  the  eye  of  the  opposite  side  (Figs.  296,  297, 
pp.  584,  587),  in  the  angular  gyrus  of  the  monkey,  and  the 
corresponding  region  of  the  second  external  convolution  in  dogs, 
cats,  and  rabbits. 

In  his  first  communications  on  the  visual  sphere  of  the  cortex 
(1877-78),  H.  Munk  maintained  that  after  bilateral  removal  of  the 
cortex  in  area  A'  of  the  dog  (Fig.  296),  characteristic  disturbances 
of  vision  occurred,  which  he  termed  psychical  blindness.  In  this 
condition  the  animal  can  see,  but  no  longer  recognises  the  objects 
which  it  sees,  i.e.  it  receives  visual  sensations  but  has  lost  the 
memory  of  previous  visual  images.  If  the  whole  of  the  occipital 
lobe  is  destroyed  (A  A'  A,  Fig.  296),  then,  according  to  Munk,  the 
blindness  is  not  only  psychical,  but  absolute  and  permanent,  which 
he  terms  cortical  Uindness.  In  monkeys,  too,  the  visual  sphere  lies 
in  the  occipital  lobes.  Partial  lesion  of  the  latter  produces  more 
or  less  complete  psychical  1  ilindness,  extirpation  of  a  whole  occipital 
lobe  produces  bilateral  homonymous  hemianopsia,  namely,  blindness 
of  the  two  halves  of  the  retina  of  the  operated  side ;  removal  of 
both  occipital  lobes  leads  to  total  and  permanent  cortical 
blindness. 

In  the  following  year  (1879)  we  found  with  Tamburini  that 
the  visual  centre  in  dogs  is  not  confined  to  the  cortex  of  the 
occipital  lobe,  but  spreads  forwards  to  the  frontal  region;  in 
monkeys  it  includes  the  angular  gyrus  in  addition  to  the  cortex 
of  the  occipital  lobe.  We  first  demonstrated  that  not  only  in 
monkeys,  but  also  in  dogs,  the  visual  zone  of  one  side  is  in 
relation  with  both  retinae,  and  not  merely  with  the  retina  of  the 
opposite  side.  But  the  bilateral  homonymous  hemianopsia  or 
total  blindness  which  results  from  excision  of  the  visual  area  on 
one,  or  on  both  sides,  is  neither  absolute  nor  permanent,  even  if,  in 


GOO  PHYSIOLOGY  CHAP. 

the  monkey,  the  whole  of  the  occipital  lobe  and  the  angular  gyms 
of  one  or  of  both  sides  be  extirpated.  Terrier  and  Yeo  (1880) 
came  to  approximately  the  same  conclusions  in  a  further  series  of 
researches  on  the  monkey. 

On  the  other  hand,  Munk,  in  subsequent  communications 
(1880-81),  developed  his  famous  theory  of  the  projection  of  the 
different  segments  of  the  retina  on  different  areas  of  his  visual 
sphere  in  dogs.  According  to  this  theory  the  central  area  A' 
corresponds  with  the  macula  lutea,  or  retinal  area  of  distinct 
vision  of  the  eye  of  the  opposte  side ;  the  more  external  portion  of 
A  with  the  outer  segment  of  the  retina  on  the  same  side ;  the 
more  internal  portion  of  A  with  the  inner  segment  of  the  retina 
on  the  opposite  side :  the  anterior  half  of  the  visual  sphere  is 
related  to  the  upper  halves  of  the  two  retinae,  and  its  posterior 
half  to  the  lower  halves  of  both  retinae.  According  to  Munk, 
therefore,  it  is  possible  in  dogs  to  produce  blindness  of  any  sector 
of  each  retina  by  extirpating  the  corresponding  cortical  area  in 
the  visual  sphere.  This  partial  blindness  will  be  permanent,  just 
as  the  total  blindness  is  permanent  after  complete  extirpation 
of  both  visual  spheres.  He  sought  to  apply  the  same  theory  to 
monkeys,  but  admitted  that  his  attempts  were  not  conclusive. 

Undoubtedly  if  this  theory  of  the  projection  of  the  retina  on 
the  visual  sphere  of  dogs  had  been  founded  on  reliable  experi- 
mental facts,  it  would  constitute  the  finest  discovery  in  the  physio- 
logy of  the  cerebral  cortex.  But  the  subsequent  researches  of 
Loeb,  Goltz,  and  particularly  of  Luciani  and  Seppilli,  who  methodic- 
ally re-tested  Munk's  theory,  failed  to  substantiate  it. 

It  is  certain  from  our  own  experiments  with  Seppilli  (1885) 
that  obvious  visual  disorders  occur  in  dogs  not  only  after  extirpa- 
tion of  the  occipital  lobe,  but  also  after  removing  any  other 
extensive  portion  of  the  cortex,  including  the  frontal  lobes,  that  is, 
the  region  furthest  from  Munk's  visual  sphere.  This  agrees  with 
the  previous  experiments  of  Goltz,  Luciani  and  Tamburini,  Hitzig, 
Lautenbach,  and  others.  But  on  closer  consideration  of  the  effect 
on  the  visual  function  of  destruction  of  the  different  portions  of 
the  brain,  there  is  seen  to  be  an  important  difference :  the  visual 
disorders  that  result  from  destruction  of  the  frontal  and  temporal 
lobes  are  transitory,  while  those  that  follow  removal  of  the 
occipital  and  parietal  lobes  are  permanent — the  former  do  not 
appear  unless  the  frontal  or  temporal  area  destroyed  is  consider- 
able— the  latter  can  easily  be  seen  when  only  a  small  portion  of 
the  cortex  of  the  parieto-occipital  lobes  is  removed.  This  fact 
shows  plainly  that  the  localisation  of  the  visual  centre  of  the  dog- 
in  the  cortex  of  the  occipital  lobe  is  mere  speculation.  Un- 
doubtedly the  cortex  of  the  parietal  lobe  also  forms  an  integral 
part  of  this  centre,  which  must  spread  even  beyond  its  limits, 
though  it  is  not  possible  to  determine  the  exact  boundaries. 


x  THE  FORE-BRAIN  G01 

Another  indisputable  fact,  in  which  our  results  agree  perfectly 
with  Munk,  is  that  in  dogs  extensive  extirpation  of  one  occipital 
lobe  at  once  produces  bilateral  IK  anonymous  hemianopsia,  which  is 
somewhat  more  extensive  in  the  eye  of  the  opposite  side  than  in 
the  homolateral.  This  proves  that  each  visual  centre  is  in  direct 
relation  with  the  more  extensive  nasal  segment  of  the  retina  on 
the  opposite  side,  and  with  the  less  extensive  temporal  segment 
of-  the  retina  on  the  same  side.  Contrary,  however,  to  Munk's 
theory,  our  experiments  further  bring  out  the  following  un- 
mistakable facts : — 

(a-)  Jfemiopic  defects  result  not  only  after  extensive  and 
complete  destruction  of  one  occipital  lobe,  but  also  after  extensive 
removal  of  the  cortex  of  either  the  parietal  or  the  temporal  lobe. 
This  fact  shows  that  in  the  dog  the  visual  centre  is  not  confined  to 
the  occipital  lobe,  but  also  spreads  in  the  cortex  of  adjacent  lobes. 

(6)  Partial  bilateral  extirpation  (outer  or  inner,  in  front  or 
behind)  of  the  occipital  lobes  never  produces  definite  symptoms 
of  partial  blindness,  but  always  more  or  less  marked  visual 
disturbances  distributed  over  different  segments  of  both  retinae. 
This  observation  confutes  the  theory  of  retinal  projection  on  to 
the  cortex. 

(c)  Neither  the  hemiopic  defects  due  to  extensive  unilateral 
extirpations  of  the  occipital,  parietal,  and  temporal  regions  of  the 
cortex,  nor  the  visual  disturbances  spreading  over  the  whole 
retinal  field,  which  occur  after  bilateral  extirpations  limited 
to  these  regions,  are  permanent,  but  both  gradually  disappear. 
The  hemianopsia  is  transformed  by  degrees  into  hemiamblyopia ; 
the  diffuse  blindness  into  diffuse  amblyopia  of  the  whole  retina  ; 
lastly,  the  aniblyopia  symptoms  gradually  diminish  to  phenomena 
of  simple  psychical  blindness,  more  or  less  severe  and  complete. 
These  facts  are  directly  opposed  to  the  theory  of  absolute  and 
permanent  cortical  blindness. 

The  above  observations,  published  in  1885,  were  substantially 
confirmed  in  1903  by  Shinkichi  Iniamura  in  an  important  series 
of  researches  carried  out  in  Exner's  laboratory  at  Vienna.  He 
admitted  that  the  occipital  lobe  must  stand  in  closer  relation  with 
the  visual  function  than  other  parts  of  the  cerebral  cortex.  The 
anatomical  researches  of  v.  Monakow  and  Probst  show  that  the 
occipital  cortex  is  in  direct  connection  with  the  subcortical  visual 
centres  (external  corpus  geniculatum,  pulvinar  and  anterior  quad- 
rigeminal  body).  Imamura  was  able  with  Marchi's  method  to 
follow  descending  degenerations  from  the  occipital  cortex  to  the 
subcortical  visual  centres,  while  this  degeneration  is  absent  when 
the  frontal  lobes  are  destroyed. 

Contrary  to  Munk's  view,  and  in  accordance  with  the  state- 
ments of  Loeb,  Hitzig,  and  Luciani,  Imamura,  after  extirpating 
any  portion  of  the  occipital  lobe,  always  found  hemianopsia  and 


602  PHYSIOLOGY  CHAP. 

hemiamblyopia  of  the  side  opposite  to  the  injured  hemisphere, 
which  were  transient  and  only  lasted  from  eight  to  twenty  days. 

Imamura  confirmed  the  observations  of  Luciani,  Loeh,  and 
Hitzig,  that  when  the  visual  disturbances  due  to  removal  of  one 
portion  of  the  cortex  have  disappeared,  they  reappear  in  an 
aggravated  form  and  in  both  eyes  after  a  second  symmetrical 
lesion  of  the  other  hemisphere. 

Lastly,  in  a  final  series  of  researches,  Imamura  also  divided 
the  corpus  callosum ;  he  confirmed  Lo  Monaco's  observation  that 
this  produces  no  appreciable  effects  in  intact  dogs,  and  he  found 
that  if  this  operation  is  succeeded  by  unilateral  extirpation  of  any 
region  of  the  convex  surface  of  the  brain,  the  usual  visual  disturb- 
ances that  follow  show  no  tendency  to  disappear  even  within  two 
months.  He  further  saw  that  if  the  corpus  callosum  is  cut  in 
dogs  in  which  the  symptoms  of  cortical  extirpation  had  been 
compensated,  the  visual  troubles  reappear  and  persist.  This 
demonstrates  the  importance  of  the  corpus  callosum,  as  it  contains 
the  paths  through  which  compensation  of  the  hemiamblyopia  due 
to  unilateral  lesions  takes  place. 

The  experimental  conclusions  obtained  from  the  dog  are  in 
evident  contradiction  with  those  obtained  experimentally  from 
the  monkey,  and  particularly  with  the  anatomical  and  clinical 
observations  of  Hun,  Heuschen,  Flechsig,  and  Niessl,  on  man, 
which  limit  the  visual  sphere  to  the  middle  and  lower  surface  of 
the  occipital  lobe,  precisely  to  the  so-called  calcarine  area,  in  which, 
according  to  the  extensive  histological  researches  of  Brodmann, 
the  cortex  assumes  a  quite  characteristic  structure  (zona  striata 
of  Brodmann). 

A.  Tschermak  (1905)  initiated  a  new  series  of  researches, 
intended  to  settle  these  differences  and  to  determine  the  special 
importance,  in  dogs  as  well,  of  the  region  homologous  with  the 
calcariue  area. 

On  stimulating  the  medial  posterior  surface  of  the  dog's  brain, 
and  particularly  the  cortex  lying  round  the  sulcus  recurrens 
superior,  which  is  homologous  with  the  calcarine  fissure  of  the 
monkey  and  of  man,  Tschermak  obtained  co-ordinated  movements 
of  the  eyes ;  on  excising  the  cortex  of  that  area,  he  produced 
hemianopsia  and  loss  of  the  eye-reflexes  on  the  opposite  side.  He 
saw  that  these  symptoms  diminished,  but  did  not  entirely  dis- 
appear, even  after  a  long  period.  Finally,  he  found  descending 
degeneration  to  the  sul  (cortical  visual  centres  from  the  area 
destroyed.  Consequently  in  the  dog  the  visual  sphere  is  localised 
to  the  medial  surface  of  the  hemispheres,  in  the  region  homologous 
with  the  calcarine  area.  The  parieto-occipital  convexity  may  repre- 
sent the  association  zone  in  the  dog,  as  suggested  by  Flechsig. 

Fr.  Kurzveil  (1909),  working  under  Tschermak's  guidance, 
confirmed  his  results,  and  stated  that  the  alterations  in  vision  and 


THE  FORE-BRAIN 


603 


eye-reflexes  (especially  marked  on  the  outer  half  of  the  visual 
Held  of  flie  eye  of  the  side  opposite  that  in  which  the,  calcarine 
region  had  been  destroyed)  persisted  almost  unaltered  for  over  a 
year.  He,  too,  was  able  with  Marchi's  method  to  detect  a 


B 


FIG.  301. — The  dotted  region  of  the  occipital  lobe  indicates  the  extent  of  the  area  striata  on  the 
superior  surface,  A;  inferior  surface,  li  ;  and  mesial  or  internal  surface,  C,  of  dog's  brain. 
(Campbell.) 

degeneration  descending  towards  the  antero-  lateral  part  of  the 
pulvinar,  in  the  dogs  operated  on.  Lastly,  after  extirpating  the 
eye  of  a  new-born  puppy,  he  found  hypoplasia  of  the  calcarine 
region  on  the  opposite  side  when  development  was  complete. 
Panizza,  many  years  before,  had  described  the  same  hypoplasia— 


604  PHYSIOLOGY  CHAP. 

not  localised,  however,  to  the  calcarine  region,  but  diffuse  all  over 
the  controlateral  occipital  lobe. 

Minkowski  (1911)  continued  the  work  of  Tschermak  and 
Kurzveil.  Starting  from  the  localisation  and  extent  of  the  strintt.1 
area,  as  described  by  Campbell  on  the  upper,  middle,  and  inner 
surfaces  of  the  occipital  lobe  of  the  dog's  brain  (Fig.  301),  he 
attempted  to  show  that  the  destruction  of  this  area  on  one  side 
produces  amaurosis  or  permanent  blindness  in  the  temporal  three- 
fourths  of  the  visual  field  of  the  opposite  side,  while  there  is 
transitory  amaurosis  in  a  small  nasal  portion  of  the  homolateral 
visual  field.  From  this  he  concludes  that  the  visual  sphere 
coincides  perfectly  in  the  dog  with  the  area  striata,  and  that  the 
greater  part  (over  three-fourths)  of  each  retina  is  represented  in 
the  area  striata  of  the  occipital  lobe  of  the  opposite  side,  and  the 
small  remaining  part  in  the  area  striata  of  both  sides,  mainly, 
however,  on  the  hoinonymous. 

Bilateral  removal  of  the  striate  area,  according  to  Minkowski, 
produces  total  and  permanent  blindness.  He  states  that  dogs 
thus  operated  on  for  ever  lose  not  merely  perceptions  but  also 
simple  ocular  reflexes  to  luminous  stimulation,  with  the  exception 
of  the  pupil  reflex. 

The  sub-cortical  optic  centres  alone  cannot  therefore,  according 
to  this  author,  subserve  even  the  simplest  visual  reflexes. 

We  may  ignore  Minkowski's  other  statements  and  confine 
ourselves  to  the  consideration  of  this  conclusion,  which  he  has 
confidently  described  in  much  detail.  It  is  so  diametrically 
opposed  to  our  own  results  that  we  immediately  instituted  an 
experimental  control  by  three  different  students  in  our  laboratory. 
Up  to  the  present  the  results  of  excising  Campbell's  striate  areas 
on  both  sides,  in  three  young  dogs,  have  been  in  contradiction  with 
the  statement  which  Minkowski  uses  as  the  basis  of  his  entire 
theory  of  the  visual  sphere  in  dogs. 

During  the  first  days  after  the  operation,  the  three  dogs  which 
had  been  deprived  of  Campbell's  striate  area  on  both  sides  were 
not  merely  not  blind,  but  were  not  even  amblyopic.  They  were 
capable,  in  walking,  of  avoiding  contact  or  collision  with  the  walls 
surrounding  them,  the  legs  of  chairs,  or  other  furniture  in  the 
vicinity.  They  never  stumbled  against  obstacles  placed  on  the 
floor  of  the  room,  both  irregularly  and  sometimes  in  lines  and 
close  to  each  other,  so  that  the  dogs  might  easily  have  knocked 
them  over  in  passing  between  them,  if  their  vision  had  been  ever 
so  slightly  affected.  It  was  amazing  to  see  how  often  they  got  by 
without  stumbling  against  any  of  the  obstacles. 

Such  a  flagrant  contradiction  between  Minkowski's  statement 
and  our  own  observations  was  quite  unexpected.  To  test  it  we 
killed  the  three  dogs  in  order  to  make  sure  by  examination  that 
the  whole  of  the  area  striata  had  been  destroyed  on  both  sides. 


x  THE  FOEE-BEAIN  G05 

It  was  found  that  in  each  of  the  three  animals  the  cortical  lesion 
had  not  extended  at  all  points  to  the  limits  assigned  by  Campbell 
to  the  area  striata,  while  at  others  it  had  exceeded  them.  A 
small  area  in  the  front  and  deeper  parts  of  the  lower  surface  of 
the  area  which  lies  on  the  tentorium  escaped,  while  on  its  upper 
and  mesial  surface  the  lesion  extended  somewhat  further  inwards 
towards  the  parietal  lobe. 

The  failure  to  destroy  the  whole  of  the  area  striata  is,  however, 
quite  inadequate  to  explain  the  discrepancies  in  the  results, 
particularly  if  we  remember  that,  according  to  Minkowski,  there 
is  a  projection  of  the  retinal  element  on  to  the  visual  cortex ;  the 
anterior  region  of  the  area  striata  would  correspond  with  the 
upper  segment  of  the  retina,  the  posterior  region  with  its  lower 
segment.  Since  the  portion  of  the  area  striata  remaining  intact 
corresponds  only  with  about  the  twentieth  part  of  the  total  area, 
it  is  easy  to  see  that  if  Minkowski's  theory  were  correct  there 
must  have  been  absolute  and  permanent  blindness  of  nineteen- 
twentieths  of  both  retinae,  which  would  readily  have  been  detected 
in  our  careful  and  repeated  investigations. 

It  has  not  therefore  been  demonstrated  that  the  area  striata 
represents  the  whole  of  the  visual  sphere,  or  is  more  than  its  focal 
area.  This  doubt  is  borne  out  by  careful  examination  of  the 
microscopical  preparations  in  our  laboratory  with  the  best  technical 
methods  available.  Till  the  contrary  is  proved,  we  are  not  justified 
in  assuming  that  there  is  not  in  dogs  a  definable  area  of  the  cortex 
with  a  structure  similar  to  that  of  the  calcarine  region  of  the 
human  brain. 

Further,  it  is  indisputable  that  the  whole  of  the  visual 
functions,  including  the  visual  reflexes,  are  not  localised  in  the 
cortex,  and  that  part — the  most  elementary — of  them  are  subserved 
by  sub-cortical  centres.  It  is  impossible  to  overlook  the  results 
<  ii'  our  earlier  researches  which  demonstrated,  in  dogs  as  well  as 
in  the  macaque  monkey,  that  the  blindness  incident  on  bilateral 
extirpation  of  the  occipital  lobe  is  temporary;  and  that  it 
becomes  reduced  in  a  few  days  to  an  amblyopia  which  gradually 
disappears  till  the  symptoms  are  merely  those  of  psychical 
blindness,  in  which  the  animals  see,  but  fail  to  recognise  the 
objects  which  they  see.  All  this  was  confirmed  by  Lo  Monaco ; 
he  found,  after  removing  the  two  occipital  lobes  in  bulk,  that  the 
blindness  was  neither  absolute  nor  permanent  in  his  dogs,  and 
only  became  so  after  the  subsequent  operative  destruction  of  the 
optic  thalami. 

Evidently  Minkowski  was  led  away  by  the  preconceived  ideas  : 
(«)  that  the  visual  sphere  was  confined  to  and  strictly  localised 
in  the  area  striata;  (b)  that  all  the  visual  functions  had  their 
centre  in  the  cerebral  cortex. 

If  these  two  propositions  were  generally  applied  to  the  different 


606 


PHYSIOLOGY 


CHAP. 


qualities  of  sensations,  it  would  have  to  be  admitted  that  all 
mental  activities  from  the  most  complex  to  the  simplest,  including 
the  visual  reflexes,  must  have  their  seat  in  the  cerebral  cortex — a 
conclusion  that  contradicts  all  that  has  been  set  forth  in  the 
previous  chapters  as  to  the  functions  of  the  cerebrospinal  axis. 

Let  us  see  if  Minkowski's  theory  is,  partly  at  any  rate, 
applicable  to  the  visual  centres  of  the  monkey.  Munk,  as  we 
have  seen,  left  his  researches  incomplete  as  regards  the  visual 
sphere  in  apes.  The  sole  fact  which  he  demonstrated,  and  which 
we  fully  confirmed,  was  that  bilateral  homonymous  hemianopsia 
occurs  after  extirpation  of  a  whole  occipital  lobe.  But  while  he 
took  this  to  be  a  permanent  symptom,  we  showed  that  it  is 
temporai'y,&n&  that  it  may  be  reproduced  by  successive  operations 

on  the  same  hemisphere.  This  proves 
that  in  monkeys,  too,  the  visual 
sphere  extends  beyond  the  limits  of 
the  occipital  lobe.  Munk  did  not 
adduce  a  single  experiment  in  sup- 
port of  his  hypothesis  of  retinal 
projection  on  the  cortex,  or  show 
that  partial  extirpation  produces 
partial  blindness  of  one  or  the  other 
portion  of  the  retina. 

The  experiments  on  the  cortical 
visual  sphere  of  the  monkey  were 
continued  by  Schafer  and  Sanger- 
Brown  in  1888.  Extirpation  of  one 
occipital  lobe  (Fig.  302)  produces 
bilateral  homonymous  hemianopsia 
in  monkeys :  extirpation  of  both 
occipital  lobes  produces  total  blind- 
ness, which,  however,  is  not  permanent  if  these  lobes  alone  are 
injured.  To  produce  permanent  blindness  it  is  necessary  that 
the  lesion  should  extend  beyond  the  occipital  lobes,  particularly 
on  the  inner  and  lower  surface,  and  include  part  of  the  cortex 
of  the  temporal  and  parietal  lobes  (Fig.  303).  Contrary  to 
Ferrier  and  Yeo,  Schafer  and  Sanger-Brown  exclude  the  cortex 
of  the  angular  gyrus  from  the  visual  area.  The  hemiopic 
symptoms  sometimes  seen  after  removal  of  the  cortex  from 
that  gyrus  disappear  after  a  few  days,  and  may  depend  on  shock 
extending  to  the  contiguous  occipital  lobe.  But  this  interpreta- 
tion will  not  hold  in  view  of  the  fact  established  by  us,  that  the 
residual  disorders  of  vision  due  to  extirpation  of  the  occipital 
lobes  become  aggravated  after  injury  of  the  angular  gyri. 

Schafer  and  Sanger-Brown  accepted  projection  from  the  retina 
on  the  cortical  centre  of  vision  in  monkeys,  which  Munk  already 
held  for  dogs.  But  in  the  monkey  central  vision — i.e.  the  area 


Fir:.  302. — Brain  of  Mtwiwus  from  which 
one  occipital  lobe  had  been  entirely 
removed,  but  the  angular  gyrus  left 
intact.  (Scha'IVr  and  Sanger-Brown.) 


X 


THE  FORE-BRAIN 


607 


of  the  centre  of  vision  corresponding  with  the  macula  lutea — 
lies  (in  the  inner  or  mesial  surface  of  the  occipital  lobe ;  the 
scheme  proposed  by-  Munk  for  dogs  is  not  therefore  directly 
applicable  to  monkeys.  These  authors  did  not  test  the  effects 
of  partial  destruction  of  the  visual  area  ;  they  merely  relied  on 
the  reactions  to  electrical  excitation,  which  varied  in  different 
parts  of  the  area. 

It  must,  however,  he  remembered  that  electrical  stimulation  of 
the  angular  gyrus,  which — according  to  Schafer  and  Sanger-Brown 
—is  not  comprised  in  the  visual  area,  also  produces  movements  of 
the  eye -balls.  It  should  further  be  added  that  in  1895,  after  the 
publication  of  Henschen's  clinical  researches,  Panichi  repeated 
the  experiments  on  the  macaque  monkey  in  gur  laboratory,  with 


Ki<;.  303. — Maracus  brain  viewed  from  above,  A,  and  from  below,  B.     Both  occipital  lobes  and,  on 
the  under  surface,  part  of  the  temporal  lobes  bad  been  cut  away.     (Schafer  and  Banger-Brown.) 

quite  different  results  from  those  of  Schafer  and  Sanger-Brown. 
He  not  only  confirmed  the  fact  that  the  visual  area  of  monkeys 
cannot  be  restricted  to  the  occipital  lobes,  but  his  results 
confute  the  view  that  the  focus  of  central  vision  is  seated  in  the 
cortex  of  the  calcarine  fissure,  cuneus,  and,  generally  speaking,  of 
the  mesial  surface  of  the  occipital  lobe.  So  that  the  visual  area 
of  monkeys  has  not  been  finally  determined. 

According  to  Brodrnann,  the  area  striata  of  the  lower  apes 
extends  from  the  calcarine  region  over  almost  the  whole  lower, 
mesial,  and  external  surface  of  the  occipital  lobe.  But  not  even 
by  accepting  Minkowski's  view  that  the  visual  sphere  coincides 
with  the  area  striata  is  it  possible  to  explain  the  fact  that 
after  the  bilateral  destruction  of  the  whole  occipital  lobe  the 
blindness  which  ensues  is  not  permanent.  A  fresh  series  of 
experiments  directed  to  the  solution  of  this  problem  is  necessary. 

As  regards  the  visual  area  in  man,  it  may  at  once  be  stated  on 
the  strength  of  a  large  number  of  clinical  cases  that  the  lesions  of 


608  PHYSIOLOGY  CHAP. 

one  occipital  lobe  produce  bilateral  visual  disturbances  which  are 
hemiopic  in  character  ;  the  halves  of  the  two  retinae  corresponding 
to  the  side  of  the  injured  occipital  lobe  are  blind  (homonymous 
bilateral  hemianopsia).  The  perimetric  observations  made  in 
some  of  these  cases  show  that  the  line  of  demarcation  between  the 
blind  and  the  seeing  parts  of  the  retina  does  not,  as  a  rule,  pass 
through  the  fixation  point,  but  to  its  blind  side,  i.e.  the  fovea  is 
not  comprised  in  the  hemiopic  lesion. 

Clinical  evidence  in  many  cases  seems  to  show  that  the  visual 
area  of  man  is  better  defined  and  less  diffuse  than  in  monkeys,  as 
in  the  latter  it  is  more  restricted  than  in  dogs.  Not  a  few  clinical 
cases,  moreover,  indicate  that  it  is  lesions  of  the  inner  or  mesial 
surface  of  the  occipital  lobe  which  cause  the  most  serious  dis- 
turbances of  vision. 

Henschen  (1892)  maintained  on  the  basis  of  his  clinical  and 
anatomo-pathological  researches  that  the  visual  area  of  the  human 
brain  is  confined  to  the  cortex  of  the  calcarine  fissure,  but  critical 
examination  of  the  arguments  on  which  he  based  this  theory 
shows  that  the  visual  centre  cannot  be  contained  within  such 
narrow  limits.  He  has  not  cited  a  single  case  that  is  anatomically 
sound,  in  which  a  lesion  sharply  limited  to  the  calcarine  area 
produced  total  and  permanent  hemianopsia.  In  all  cases  so  far 
published  of  cortical  hemianopsia  there  were  more  extensive 
lesions,  both  of  the  mesial  surface  and  of  the  convex  surface  of 
the  occipital  lobe. 

According  to  Dejerine  and  Vialet  (1893)  the  cortical  visual 
centre  of  man  occupies  the  whole  extent  of  the  mesial  face  of  the 
occipital  lobe,  limited  in  front  by  the  parieto-occipital  fissure, 
above  by  the  upper  border  of  the  hemisphere,  below  by  the  lower 
border  of  the  third  occipital  gyrus,  behind  by  the  occipital  pole. 
But  lesions  of  the  cortex  of  the  three  external  occipital  convolutions 
can  also  produce  hemianopsia,  as  proved  by  Turner  (1895)  and 
Pick  (1896).  Crispolti  (1902)  concluded  from  a  critical  survey  of 
155  clinical  cases  that  the  cuneus  is  of  chief  importance  for  vision, 
the  lingual  and  fusiform  gyri  of  less,  but  that  the  cortex  of  the 
outer  surface  of  the  occipital  lobe,  i.e.  of  the  three  occipital  con- 
volutions, is  also  part  of  the  visual  centre. 

Monakow  came  to  the  same  conclusions  (1897-1902)  when 
he  referred  the  visual  sphere  of  man  to  the  three  occipital  con- 
volutions, the  entire  cuneus,  the  lingual  lobule,  and  the  descending 
gyrus,  in  addition  to  the  calcarine  region  which  forms  its  most 
important  part.  Bernheimer  (1900),  with  the  myelination 
method,  arrived  at  the  same  conclusions.  Flechsig  (1901),  by  the 
same  method,  located  the  central  focus  of  vision  in  the  calcarine 
fissure,  and  the  margins  of  the  cuneus,  the  lingual  lobule,  and  the 
cortex  of  the  external  occipital  pole  ;  but  he  admitted  that  it  also 
extended  beyond  these  limits  (V,  Figs.  299,  300). 


x  THE  FORE-BRAIN  609 

Against  Henschen's  localisation,  Monakow  brought  out  the  fact 
that  in  cases  of  blindness  acquired  in  infancy,  with  total  degenera- 
tion of  the  optic  nerves,  the  cortex  of  the  calcarine  fissures  does 
not  suffer  a  greater  reduction  of  volume  than  the  cortex  of  the 
external  convolutions  of  the  occipital  lobe. 

Henschen  tried  to  adapt  Munk's  theory  of  retinal  projection 
to  the  visual  sphere.  According  to  Henschen  the  upper  quadrants 
of  the  retina  are  represented  in  the  upper  border  of  the  calcarine 
fissure,  the  lower  quadrants  in  its  lower  border.  Against  this 
view  it  may  be  observed  with  Monakow  that  in  cases  of  bilateral 
hemianopsia  of  cortical  origin  in  man,  there  is  persistence  of 
central  or  macular  vision  even  when  the  calcarine  region  as  well 
as  the  introflexed  cortex  in  this  fissure  are  affected.  This  proves 
that  the  focus  of  distinct  central  vision  cannot  be  limited  to 
a  restricted  cortical  area.  Both  Sachs  and  Bernheimer  reject  the 
theory  of  Munk  and  Henschen  that  the  macula  lutea  is  repre- 
sented in  a  circumscribed  area  of  the  visual  sphere. 

Lesions  of  the  occipital  lobes  not  only  produce  hemianopsia, 
but  may  also  be  associated  with  special  psychical  disorders, 
characterised  by  alterations  of  the  visual  representations.  These 
disturbances  differ  in  form  and  degree,  from  a  slight  difficulty  in 
rightly  interpreting  visual  images  to  genuine  psychical  blindness 
similar  to  that  observed  in  monkeys  after  removal  of  both  occipital 
lobes,  which  when  the  symptoms  of  blindness  and  amblyopia  have 
passed,  recover  vision  completely,  but  continue  incapable  of 
recognising  the  objects  which  they  see.  The  symptoms  which 
characterise  psychical  blindness  in  monkeys  may  be  illustrated  by 
the  following  experiment :  if  some  grapes  or  bits  of  dried  fig  are 
scattered  on  the  table  with  lumps  of  cork  of  the  same  size,  the 
ape  which  has  lost  both  its  visual  spheres  is  incapable  of  dis- 
tinguishing them  by  vision ;  it  picks  them  up  indifferently,  one 
after  the  other,  but  retains  the  grapes,  while  it  rejects  the  cork 
directly  it  is  taken  into  the  mouth. 

The  same  obtains  in  typical  cases  ot  psychical  blindness  in 
man.  Although  the  individual  sees  to  a  certain  extent,  and 
stereognostic  vision  is  preserved,  he  is  not  capable  of  identifying 
the  objects  he  sees,  even  when  familiar  in  everyday  life.  Psychical 
blindness  is  a  very  complex  disturbance,  which  depends  on  various 
components.  It  is  not  exclusively  dependent  on  the  partial  lesion 
of  the  visual  sphere,  but  may  occur  when  some  of  the  association 
paths  by  which  the  visual  cortex  is  brought  into  relation  with 
other  cortical  regions  are  interrupted. 

A  special  form  of  incomplete  psychical  blindness  seen  in  man 
is  the  so-called  word  blindness  which  was  first  reported  by 
Kussmaul  (1877).  It  is  characterised  by  inability  to  comprehend 
the  significance  of  printed  or  written  words,  although  the  power  of 
expressing  ideas  in  speech  or  writing  is  retained.  The  individual 

VOL.  in  2  R 


610  PHYSIOLOGY  CHAP. 

affected  with  word  blindness  sees  the  letters  and  words,  and  can 
even  copy  them;  but  he  is  incapable  of  reading  them,  combining 
them  together,  or  understanding  them.  In  cases  in  which  the 
visual  field  is  examined  by  the  perimeter,  it  is  found  that  word 
blindness  is  sometimes  independent  of  any  change  in  the  field, 
and  at  other  times  is  associated  with  a  concentric  contraction 
of  the  field,  or  with  hemianopsia. 

Word  blindness  leads  us  to  assume  that,  there  is  in  the  brain  a 
region  for  the  perception  of  the  graphic  signs  of  speech  and  the 
memory  of  them,  which  are  necessary  to  the  understanding  of 
their  significance.  But  in  which  part  of  the  brain  is  this  special 
centre  for  the  visual  perception  of  words  located  ?  The  fact  that 
word  blindness  can  exist  independently  of  any  alteration  in  the 
visual  field,  shows  that  the  centre  for  verbal  visual  perceptions 
lies  beyond  the  sphere  of  vision  properly  so  called.  But  the  fact 
that  it  may  be  associated  with  hemianopsia,  or  a  concentric 
restriction  of  the  visual  field,  leads  us  to  conclude  that  this  centre 
must  lie  contiguous  to  the  centre  of  vision  proper.  There  are 
cases  of  word  blindness  on  record  in  which  the  post-mortem 
examination  showed  a  lesion  of  the  second  left  parietal  convolu- 
tion; this  includes  the  angular  gyms,  which  in  our  opinion 
represents  the  anterior  portion  of  the  visual  area  of  man. 

XII.  Less  experimental  work  has  been  done  on  the  localisa- 
tion of  the  auditory  area,  no  doul  >t  1  tecause  the  sense  of  hearing  is 
less  easy  to  examine  in  animals  than  vision. 

Ferrier  (1875)  was  the  first  to  point  out  that  the  centre  of 
auditory  sensation  is  represented  in  the  ape  by  the  cortex  of  the 
first  temporal  convolution,  and  by  the  corresponding  region  of  the 
third  external  convolution  in  dogs  (cf.  points  14,  15,  Figs.  275, 
276).  In  fact,  this  part  of  the  temporal  lobe  alone  responds  to 
electrical  stimulation  by  very  definite  reactions :  by  movements  of 
the  ear  muscles  on  the  opposite  side,  while  the  eyes  open  widely,  the 
pupils  dilate,  and  the  eyes  and  head  are  suddenly  turned  to  the 
opposite  side,  as  if  the  animal  were  surprised  by  some  unexpected 
sound  on  that  side.  To  confirm  this  interpretation  Ferrier 
cauterised  the  temporal  convolution.  If  the  lesion  was  confined 
to  one  side,  the  monkey  continued  to  react  to  auditory  sensations, 
by  moving  its  head  if  any  one  called  it,  'but  if  the  ear  of  the 
operated  side  were  plugged  with  wool,  it  seemed  no  longer  aware 
of  sounds.  After  bilateral  lesions  of  the  upper  temporal  con- 
volution the  monkey  no  longer  reacted  to  certain  auditory  stimuli 
which  under  normal  conditions  excite  attention.  The  deafness 
assumed  by  Ferrier  is  obviously  an  erroneous  interpretation  of  the 
symptom.  All  subsequent  investigation  has  shown  unmistakably 
that  the  auditory  centre  is  not  confined  to  the  area  indicated  by 
Ferrier,  but  its  focal  area  is  probably  represented  by  that  centre. 

H.  Munk  (1878-81)  stated  that  when  area  B  of  the  temporal 


x  THE  TORE-BRAIN  (ill 

lulu1  (Fig.  296)  was  destroyed  <m  both  sides  in  dogs,  it  produced 
a  disturbance  of  hearing  which  he  termed,  psychical  ilrufncss,  its 
characteristic  being  that  although  the  animal  hears,  i.e.  lias 
auditory  sensations,  it  has  lost  the  perceptions  and  memory  of  the 
auditory  images  perceived  in  its  preyious  life.  This  is  a  more 
correct  interpretation  of  the  effects  described  by  Terrier  as  due  to 
destruction  of  the  upper  temporal  convolutions;  the  monkey  was 
not  deaf,  for  it  reacted  to  a  sudden  sound,  but  it  did  not  respond 
to  calls  nor  to  friendly  addresses. 

Munk's  psychical  deafness  is  a  transient  phenomenon,  which 
gradually  disappears,  so  that  after  a  few  days  the  operated  can 
hardly  he  distinguished  from  the  normal  animal.  But  if  the 
whole  of  the  temporal  lobe  is  destroyed  on  both  sides  by  sub- 
sequent operations,  the  psychical  deafness  is  transformed  into 
absolute  and  permanent  deafness,  which  Munk  terms  cortical 
deafness. 

Our  experiments  with  Tamburini  (1879),  and  particularly 
those  with  Seppilli  (1885),  brought  out  new  and  interesting  facts. 
They  proved  that  the  auditory  centre  cannot  be  restricted  to  the 
limits  laid  down  hy  Terrier,  nor  those  assumed  by  Munk.  It 
spreads  more  or  less  beyond  the  confines  of  the  temporal  lobe : 
above,  towards  the  parietal  and  occipital  region ;  behind,  towards 
the  gyrus  hippocampi,  and  mesially,  towards  the  cornu  Ammonis. 

Unilateral  extirpation  of  the  auditory  sphere  causes  bilateral 
disturbance  of  hearing,  principally  in  the  ear  of  the  opposite  side. 
When  the  effects  of  extirpation  of  the  auditory  sphere  on  one  side, 
e.g.  the  right,  have  subsided,  and  the  opposite  auditory  sphere  is 
then  destroyed,  not  only  is  auditory  disturbance  produced  on  the 
right,  but  the  deafness  of  the  left  ear  which  had  disappeared 
returns.  This  fact  was  unmistakable  in  six  dogs  under  our  own 
observation.  Here  we  have  experimental  proof  that  the  cerebral- 
ward  paths  that  come  from  the  cochlear  nuclei  undergo  in- 
complete decussation  like  the  optic  nerves ;  and  that  neither  the 
crossed  paths  nor  the  direct  are  related  to  distinct  portions  of  the 
auditory  centres,  but  both  spread  more  or  less  uniformly  through- 
out these  centres. 

The  effects  of  more  or  less  extensive  extirpations  of  the 
auditory  sphere  consist  in  a  more  or  less  grave  affection  of  hearing, 
which  never  amounts  to  complete  deafness.  This  auditory  dis- 
turbance is  transitory  and  due  to  the  shock  of  the  operation ;  as 
it  disappears,  the  signs  of  partial  psychical  deafness  appear  more 
and  more  clearly,  as  seen  by  the  animal's  failure  to  appreciate  the 
value  of  sounds,  noises,  and  calls,  although  it  shows  signs  of  hear- 
ing them. 

Bilateral  extirpation  of  the  auditory  centres  produces  more 
serious  effects,  even  when  incomplete.  At  first  the  disturbance  of 
hearing  may  amount  to  total  deafness ;  but  this  soon  becomes 


612  PHYSIOLOGY  CHAP. 

partial ;  there  is  only  a  dulness  of  hearing  that  gradually  diminishes 
till  nothing  remains  1  >ut  the  more  or  less  marked  signs  of  psychical 
deafness. 

These  results  confute  Munk's  theory  of  cortical  deafness. 

We  experimented  almost  entirely  upon  dogs,  Schafer  and 
Sanger-Brown  (1888)  on  monkeys.  In  h've  macaques  they 
removed  or  destroyed  the  upper  temporal  convolution  on  both 
sides,  and  in  one  they  completely  removed  both  temporal  lobes. 
The  last  operation  for  a  time  produced  a  state  approximating  to 
idiocy,  but  hearing  was  not  abolished  in  any  of  the  animals, 
perhaps  not  even  diminished,  since  the  inconstancy  of  reaction  to 
sounds  may  be  interpreted  as  a  sign  of  simple  psychical  deafness. 

These  results  agree  with  our  own  observations  on  the  dog,  and 
obviously  strengthen  the  theory  that  the  seat  of  auditory  per- 
ception is  not  confined  to  the  cortex  of  the  temporal  lobe,  but 
spreads  to  the  adjacent  regions  as  well. 

That  the  focal  area  of  auditory  perception  lies  in  the  upper 
temporal  convolution  seems  probable  from  the  results  of  electrical 
stimulation,  and  from  Flechsig's  observations  as  to  the  time  at 
which  the  myelination  of  its  fibres  takes  place  (Fig.  300),  and 
from  v.  Monakow's  anatomical  observations.  The  cortex  of  the 
temporal  lobe,  and  particularly  that  of  the  first  convolution, 
according  to  v.  Monakow,  is  in  direct  communication  with  the 
internal  geniculate  body,  which  in  its  turn  is  related  to  the 
posterior  quadrigeminal  1  todies,  and  these  are  connected  with 
the  cochlear  nerve  by  the  lateral  lemniscus  and  certain  fibres  of 
the  formatio  reticularis. 

The  results  of  clinical  and  anatorno -pathological  observations 
on  the  auditory  sphere  of  the  human  brain  are  interesting. 
Generally  speaking,  they  are  definitely  in  favour  of  the  theory 
which  we  brought  forward  with  Seppilli  in  1885. 

A  fact  which  seems  to  be  of  special  importance,  because  it  is 
at  variance  with  Munk's  cortical  deafness,  is  the  absence  in 
medical  literature  of  any  description  of  cases  of  deafness  or  marked 
loss  of  hearing  in  one  or  both  ears  when  the  autopsy  shows 
clearly  and  conclusively  that  there  was  a  destructive  lesion, 
exclusively  localised  to  the  cortex.  Clinical  observation  brings 
out  a  no  less  important  positive  fact — that  lesions  of  the  cortex 
of  the  temporal  lobes  produce  a  curious  mental  disorder  during 
life,  characterised  by  the  fact  that  the  patients,  while  perfectly 
aware  of  the  least  sound  or  noise,  are  incapable  of  understanding 
the  significance  of  the  words  they  hear.  Wernicke  (1874)  first 
described  this  condition,  which  he  termed  sensory  aphasia,  because 
he  took  it  to  be  an  affection  of  the  paths  of  auditory  speech. 
Kussmaul  (1876)  after  a  more  profound  analysis  regarded  it  as  an 
incomplete  form  of  psychical  deafness,  and  called  it  word  deafness, 
which  finds  its  complement  in  the  word  blindness  above  described. 


x  THE  FORE-BRAIN  613 

We  collected  (1885)  20  cases  of  word  deafness  from  clinical 
and  anatomo- pathological  observations,  which  on  examination 
yielded  some  important  tacts  showing  that  the  region  injured  in 
word  deafness  is  the  first  and  part  of  the  second  left  temporal 
Convolution. 

Two  other  clinical  facts  prove  the  functional  connection 
between  the  left  temporal  lobe  and  the  auditory  paths  of  speech: 
(a)  the  cases  recorded  of  lesions  of  the  right  temporal  lobe 
unaccompanied  in  life  by  word  deafness ;  (b)  lesions  of  the  left 
temporal  lobe  in  left-handed  individuals,  which  were  unaccompanied 
by  word -deafness.  There  are  authentic  cases  of  left -handed 
persons  in  whom  destruction  of  the  left  convolution  of  Broca  was 
not  betrayed  by  any  disturbance  of  speech.  The  predominance 
of  the  left  brain  in  right-handed  people  is  replaced  by  predomin- 
ance of  the  right  brain  in  the  left-handed. 

To  confirm  the  theory  that  the  central  focus  of  the  auditory 
components  that  subserve  acoustic  perceptions  and  ideas  lies  in 
the  first  temporal  convolution,  the  fact  may  be  adduced  that 
defective  development  of  the  temporal  lobes,  particularly  of  the 
first  temporal  convolution,  as  compared  with  the  rest  of  the  brain 
has  frequently  been  noted  at  the  post-mortem  examination  of 
individuals  who  were  deaf-mutes  from  birth. 

XIII.  Comparatively  few  investigations  have  been  made  upon 
the  cortical  localisation  of  the  olfactory  and  gustatory  centres. 

Ferrier,  starting  from  the  anatomical  fact  that  there  is  a 
direct  connection  between  the  olfactory  tract  and  the  gyms 
hippocampi  (subiculum  cornu  Ammonis),  regards  this  region— 
without  defining  its  limits — as  the  olfactory  centre.  Electrical 
excitation  of  the  subiculum  both  in  dogs  and  monkeys  (15,  Fig. 
275)  produces  movements  of  sniffing  in  the  nostril  of  the  same 
side,  as  though  the  animal  perceived  a  strong  smell.  This  effect, 
which  is  not  obtained  from  any  other  region  of  the  cortex, 
strengthens  the  presumption  that  the  hippocampal  region  forms 
part  of  the  olfactory  area. 

It  is  probable,  according  to  Ferrier,  that  the  gustatory  centre 
is  contiguous  with  or  lies  very  near  the  olfactory.  He  believes 
it  is  localised  in  the  lower  extremity  of  the  second  temporal 
convolution,  since  electrical  stimulation  of  this  region  sometimes, 
but  not  always,  provokes  movements  of  the  tongue  and  jaw,  as 
th<  nigh  the  animal  perceived  a  sensation  of  taste. 

Ferrier  tried  to  support  his  hypothesis  by  destroying  this 
region,  in  order  to  see  if  symptoms  of  loss  of  taste  and  smell 
resulted.  But  the  effects  were  few  and  uncertain  :  he  found  that 
extensive  destruction  of  the  upper  temporal  region  in  the  ape 
might  in  addition  to  auditory  disturbance  produce  signs  of 
affection  of  smell  and  taste.  With  more  extensive  cauterisation 
of  both  temporal  lobes,  so  as  to  destroy  the  whole,  of  it,  inclusive 


614 


PHYSIOLOGY 


CHAP. 


of  the  hippocampus,  he  obtained  temporary  abolition  of  smell  and 
taste,  in  addition  to  loss  of  touch  and  hearing.  None  of  these 
experiments  —  as  Ferrier  expressly  points  out — can  define  the 
exact  limits  of  the  centre  of  taste  and  smell ;  but  he  believes  that 
the  olfactory  area  is  quite  distinct  from  the  area  that  reacts  to 
electrical  stimulation. 

Our  experiments  on   dogs  (1885)  confirm   the  importance   of 
the   hippocampal   region   for  the   olfactory  sense.      They  further 


Fie;.  304.— External  surface  of  right  hemisphere  of  female  infant  54  cm.  long,  still-born  a  month 
before  normal  period  of  foetal  maturity.     (Flechsig.)    The  explanation  refers  to  this  and  the 

following  ligure. 

The  figures  on  this  and  the  following  illustration  indicate  the  chronological  order  in  which  the 
til ni's  lying  below  the  different  cortical  area  become  myelinated  ;  the  letters  show  the  order  of 
myelination  of  different  segments  of  the  same  area.  The  dotted  surface  shows  the  distribution 
of  iinyelination,  which  is  approximately  the  same  as  that  observed  in  male  infants  of  a  month 
old.  The  temporal  lobe  is  pressed  downwards,  so  as  to  open  the  Sylvian  fissure  and  make  visible 
the  convolutions  of  the  island  of  Reil.  The  elementary  fields  become  myelinated  in  the  following 
imler:  1,  lamina  perforata  anterior,  trigonum  olfactorium  (invisible  in  both  figures);  2,  lolmlN 
paracentralis,  upper  third  of  the  two  central  convolutions  ;  '2b,  median  third  of  posterior  central 
convolution  and,  later,  the  corresponding  convex  segment  of  the  pie-central  (motor  area);  3, 
septum  lucidum ;  4tt,  4&,  gyms  hippocampi ;  5,  lips  of  calcarine  fissure,  occipital  pole,  gyms 
ilcM-endens  ;  ii,  gyrus  fornicatus  ;  7,  1st  temporal  convolution;  7",  upper' part  of  posterior  con- 
volution of  island;  8,  foot  of  1st  frontal;  Sb,  subjacent  part  of  gyrus  fornicatus;  ti,  supeiim 
segment  of  cuneus ;  10,  inner  surface  of  temporal  pole  ;  11,  transverse  convolution  of  frontal  lobe, 
orbital  portion  of  3rd  frontal;  IL.',  gyrus  siibangularis  ;  13,  gyrus  supra-angularis  ;  14,  14b,  1st 
temporal ;  15,  15b,  1st  frontal,  particularly  the  inner  sin-face  and  anterior  part  of  gyrus  fornicatus  ; 
Iti,  1st  parietal;  17,  17ft,  areas  round  field  5;  18,  ISb,  foot  of  2nd  and  3rd  frontal;  I'.i,  gyrus 
.-iiprainarginalis ;  20,  3rd  occipital;  21,  posterior  segment  of  1st  parietal;  22,  greater  part  of 
island;  23,  gyrus  occipito-temporalis  ;  24,  2nd  occipital;  25,  small  posterior  inferior  portion  of 
gyrus  fornicatus  (omitted);  26,  at  base  of  frontal  lobe  (omitted);  27,  median  segment  of  3nl 
hontal;  28,  polar  portion  of  1st  frontal  (omitted);  20,  rest  of  gyms  supramarginalis  (omitted) ; 
30  (erroneously  marked  35),  upper  part  of  2nd  frontal;  31,  over  field  12  (omitted);  32,  lower  part. 
of  island;  33,  portion  of  gyrus  fornicatus  lying  below  praecuneus  ;  34.  gyrus  angularis  ;  35,  inner 
surface,  of  frontal  lobe  ;  36,  2nd  and  3rd  temporal  convolution. 

show  that  the  pes  hippocampi  major  or  the   cornu  Ammonis  is 
an  important  part  of  the  olfactory  centre. 


THE  FORE-BILUX 


615 


This  research  was  continued  by  Fasola  with  a  view  to 
determining  the  physiological  value  of  the  cornu  Ainmonis,  which 
is  a  special  part  of  the  cerebral  cortex.  Fasola  showed  that  in 
dogs  the  cornu  Ainmonis  is  concerned  not  only  with  the  olfactory 
sense,  but  also  with  vision  and  hearing.  It  is  a  part  of  the  brain 
in  which  a  partial  fusion  of  different  sensory  centres  takes  place, 
such  as  we  showed  in  the  parietal  lobe  of  dogs. 

H.  Munk  records  the  case  of  a  dog  which  became  blind  after 
the  destruction  of  the  occipital  cortex,  and  which  seemed  to  have 
also  lost  the  sense  of  smell.  On  making  sections  it  was  found 


. '  mf  Y  . 

\  'y*&::£-:;.:   \ 


\ 


FIG.  30"). — Internal  surface  of  left  hemisphere  of  same  infant. 

that  the  entire  hippocampus  on  both  sides  was  transformed  into 
a  thin-walled  cyst. 

Hughlings  Jackson  and  Beevor  observed  a  case  of  tumour  of 
the  right  hippocampal  convolution,  in  which  the  patient  had 
subjective  olfactory  sensations. 

Flechsig,  too,  by  investigating  the  myelination  of  the  fibres 
during  development,  succeeded  in  mapping  out  a  cortical  field  in 
the  hippocampal  region  which  lie  held,  in  agreement  with  these 
few  physiological  and  clinical  observations,  to  represent  the 
olfactory  centre  (Figs.  304,  305).  It  is  probable,  however,  from 
anatomical  facts  that  this  centre  is  not  entirely  confined  to  the 
hippocampal  region.  The  researches  of  Meynert,  Brown,  Golgi, 
and  others  show  that  in  the  human  brain  the  olfactory  tract  has 
three  roots,  the  outer  of  which  ends  in  the  hippocampal  convolution, 


616  PHYSIOLOGY  CHAP. 

the  middle  in  the  anterior  perforated  substance,  the  inner  in  the 
frontal  extremity  of  the  gyrus  corporis  callosi. 

Brown  (1879)  concluded  from  his  comparative  anatomical 
observations  that  there  were  three  distinct  olfactory  centres.  By 
a  series  of  careful  anatomical  observations,  Golgi  discovered  thaL 
the  fibres  of  the  olfactory  tracts  are  in  close  relation  with  the 
cells  of  the  grey  matter  of  the  frontal  lobes  with  which  they 
come  in  contact. 

The  localisation  of  the  taste-centre  is  at  present  wholly 
unknown.  Flechsig  supposes,  without  any  convincing  evidence, 
that  the  sense  of  taste  is  connected  with  the  anterior  part  of  the 
gyrus  fornicatus.  But  his  latest  researches  on  myelination  have 
failed  to  confirm  this  hypothesis. 

XIV.  A  glance  at  Figs.  304  and  305  (Flechsig),  which  repre- 
sent the  excitable  areas  of  the  cortex,  shows  that  they  extend  over 
about  one-third  of  the  surface  of  the  human  brain  ;  they  are  united 
by  projection  fibres  descending  through  the  internal  capsule  with 
the  mid-brain  and  the  bulbo-spinal  axis,  which  constitute  the 
cortical  sensory  and  motor  centres.  We  are  so  far  unable  to 
determine  the  specific  function  of  the  remaining  two-thirds  of  the 
cerebral  cortex,  which  is  termed  latent  because  stimulation  of  it 
gives  rise  to  no  reaction,  and  its  excision  to  no  permanent  sensory 
or  motor  disturbance.  We  only  know  that  in  man  as  well  as  in 
animals  extensive  destruction  of  these  inexcitable  areas  depresses 
intellectual  activity,  proportionately  with  the  extent  of  the  lesion, 
but  similar  effects  occur  after  destruction  of  the  excitable  areas, 
in  addition  to  the  sensory  or  motor  paralysis  or  paresis. 

Embryological  observations,  particularly  the  work  of  Flechsig 
(1880-1904),  have  thrown  much  light  on  this  difficult  subject. 
Flechsig' s  method  of  studying  the  human  brain  during  embryonic 
development  consists  in  ascertaining  at  what  period  different 
bundles  of  fibres  that  make  up  the  corona  radiata,  or  the  so-called 
centrum  ovale,  acquire  their  myelin  sheaths.  The  myelination 
of  any  bundle  of  fibres  is  complete  when  the  nerve  elements  which 
it  contains  have  reached  their  functional  maturity.  This  maturity 
is  attained  at  different  times  by  different  bundles,  which  are 
connected  with  different  cortical  fields.  In  order  to  bring  out 
the  successive  advance  of  myelination,  Flechsig  employed  Weigert's 
method,  which  stains  all  the  myelinated  fibres,  but  leaves  the 
non-myelinated  fibres  uncoloured.  He  found  that  in  the  human 
hemisphere  myelination  begins  at  the  fifth  month  of  foetal  life 
and  continues  till  the  fourth  month  of  extra-uterine  life. 

The  law  of  myelogenesis  as  formulated  by  Flechsig  assumes 
that  functionally  equivalent  fibres  become  myelinated,  that  is, 
attain  their  maturity,  simultaneously,  and  fibres  of  different 
functional  value  become  myelinated  at  different  periods.  So  that 
by  studying  its  myelogenesis  the  brain  may  be  divided  into  a 


x  THE  FOEE-BKAIN  617 

number  of  parts,  each  representing  a  special  centre  of  psyc.ho- 
physical  activity,  which  are  fairly  easy  to  localise,  although  their 
limits  are  not  clearly  marked,  and  overlap. 

According  to  Flechsig  the  myelogenetic  cortical  fields  may  be 
grouped  either  from  their  anatomical  structure — i.e.  as  the  pro- 
jection or  the  association  hi  ires  predominate  they  are  either 
sensory  and  motor  centres,  or  association  centres ;  or  from  the 
emhryological  standpoint — i.e.  from  the  date  of  their  myelination 
they  may  lie  classed  as  primary,  intermediary,  and  terminal  regions. 

Flechsig's  sensory  and  motor  centres  which  possess  mainly 
centripetal  and  centrifugal  projection  nitres,  are  those  which  we 
have  already  discussed ;  they  are  marked  in  Figs.  299,  300,  by  the 
/ones  of  red  dots.  The  association  centres,  in  which  the  arcuate 
fibres  that  unite  different  points  on  the  cortex  predominate  over 
the  projection  fibres,  are  contained  in  the  pre-frontal,  the  extensive 
temporo-parieto-occipital,  and  the  insular  regions  (convolutions  of 
the  island  of  Keil).  As  we  have  seen,  Flechsig's  association  areas 
include  the  whole  of  the  inexcitable  cortex. 

In  his  latest  embryological  studies  (1904)  Flechsig  divides  the 
cerebral  cortex  into  thirty-six  elementary  myelogenetic  fields. 
The  greater  part  of  these  medullary  areas  myelinate  before  birth, 
and  represent  primary  fields  which  are  the  most  important 
anatomically  and  physiologically,  because  the  foetus  at  term 
already  receives  stimuli  from  without,  and  is  beginning  to  elaborate 
them  as  the  intellect  develops.  During  the  first  month  of  extra- 
uterine  life — foetal  post-maturity  as  it  is  termed  by  Flechsig — the 
process  of  myelination  extends  to  the  intermediate  fields.  At  the 
commencement  of  the  second  month  myelination  of  the  terminal 
fields  sets  in,  and  may  be  completed,  as  far  as  the  main  nerve- 
fibres  but  not  their  collaterals  are  concerned,  at  the  close  of  the 
fourth  month  of  extra-uterine  life. 

For  this  text-book  Figs.  304,  305  will  suffice  to  give  an  idea  of 
the  final  results  reached  1  >y  Flechsig  in  his  division  of  the  cerebral 
cortex  into  thirty-six  different  areas  of  myelination  ;  the  functional 
significance  of  only  a  few  has  been  determined. 

Certain  objections  were  raised  against  Flechsig's  theory  by 
Dejerine,  0.  Vogt,  Sachs,  v.  Monakow,  Hitzig  and  others,  but  these 
have  neither  confuted  the  observations  on  which  it  is  based  nor 
diminished  its  importance.  Dejerine  was  the  first  to  argue  that 
the  whole  of  the  cerebral  cortex,  including  probably  the  island  of 

O       JL  i/ 

Reil,  possesses  projection  fibres  that  pass  through  the  capsule. 
The  projection  fibres  from  the  association  centres  seem,  however, 
to  be  few  in  number,  and  it  has  not  been  demonstrated  that  all 
projection  fibres  subserve  sensory  and  motor  conduction :  it  may 
be  their  function  to  associate  the  cortical  fields  with  the  sub- 
cortical  centres,  since  we  have  no  ground  for  denying  psychical 
ideative  functions  to  the  latter,  and  for  attributing  these 


618  PHYSIOLOGY  CHAP. 

exclusively  to  the  cortex.  Dejerine  recognised  that  the  pre-frontal 
lobe,  which  represents  an  association  area,  contains  a  bundle  of 
projection  fibres  running  to  the  thalamus,  and  particularly  to  its 
nucleus  interims.  In  the  parietal  lobe  again,  and  especially  in  the 
angular  gyrus,  there  are,  according  to  Dejerine,  projection  fibres 
that  run  to  the  pulvinar  and  posterior  part  of  the  lateral  nucleus 
of  the  thalamus,  which  degenerate  after  lesions  of  those  regions  of 
the  cortex.  These  are  projection  fibres  whose  function  is  not  to 
conduct  sensory  and  motor  impulses,  but  to  associate  the  cortical 
with  the  sub-cortical  psychical  centres. 

Monakow,  on  the  other  hand,  observed  that  the  sensory  and 
motor  centres  are  also  provided  with  association  fibres,  and  indeed 
contain  more  association  than  projection  fibres.  But  even  if  we 
accept  the  accuracy  of  this  fact,  which  Flechsig  denies,  it  does  not 
follow  that  the  structural  difference  between  the  projection  centres 
and  association  centres  is  not  sufficiently  marked  to  enable  them 
to  be  readily  distinguished  and  identified  by  simple  embryological 
features.  There  is,  of  course,  no  absolute  difference  between  the 
two  classes  of  centres,  but  merely  a  relative  and  gradual  difference. 
It  would  be  a  mistake  if  the  terms  sensory  and  'motor  centres  on 
the  one  hand  and  purely  psychical  centres  on  the  other  were  taken 
to  exclude  all  representative  or  ideative  capacity  from  the  former. 
But  it  is  only  reasonable  to  suppose — at  least  it  is  a  probable 
hypothesis — that  the  latter  have  more  important  psychical  functions 
than  the  former. 

This  hypothesis  appears  to  be  supported  by  comparative 
anatomy  and  physiology,  which  show  that  the  surface  of  the  in- 
excitable  association  centres  of  the  cerebral  cortex  increases 
progressively  in  proportion  as  the  intelligence  of  the  animal  rises. 
In  the  lower  mammals,  as  the  rodents,  there  are  no  association 
centres,  and  consequently  the  sensory  and  motor  centres  are  in 
contact ;  in  carnivora  the  association  centres  are  little  developed 
and  hard  to  identify  by  Flechsig's  method ;  they  increase  con- 
siderably from  the  lower  apes  to  the  anthropoids;  and  finally  in 
man  they  extend  over  the  greater  part  of  the  cerel  >ral  cortex. 

If  we  study  the  chronological  order  in  which  the  nerve-fibres 
of  the  different  cortical  fields  become  myelinated,  as  shown  in 
Figs.  299,  300,  we  find  another  argument  in  support  of  the  view 
that  the  association  centres  have  a  higher  psychical  function  than 
the  sensory  and  motor  centres.  Myelination  in  fact  commences 
with  the  ascending  cortical  afferent  fibres  which  reach  the 
sensory  areas  of  the  cortex :  next  the  cortico-motor  bundles 
descending  from  the  motor  cortical  centres  become  myelinated; 
and  lastly  the  arcuate  fibres,  which  serve  to  bring  the  different 
cortical  fields  into  inter -communication,  obtain  their  myelin 
sheaths.  The  association  centres  are  ontogenetically  the  last 
to  attain  anatomical  maturity,  for  the  very  reason  that  they  have 


x  THE  FOEE-BEAIN  019 

higher  psychical  functions,  which  develop  later,  even  in  the  phylo- 
genetic  series. 

We  must  now  see  if  this  finds  much  or  little  support  from  the 
physiologist  and  the  clinician.  Of  course  there  is  no  question  of 
discriminating  any  functional  difference  in  the  various  areas  of  the, 
cortex  which  mature  at  different  periods  of  foetal  development 
and  make  up  the  so-called  association  centres  :  we  are  still  far  from 
this  even  after  Brodmaim's  careful  work  on  the  structure  of  the 
different  parts  of  the  cerehral  cortex.  It  is  only  the  psycho- 
physiological  importance  of  the  association  areas  as  a  whole  that 
can  he  briefly  indicated. 

It  has  often  been  assumed,  from  Gall  to  the  latest  obseners, 
that  the  frontal  lobes,  or  at  least  their  non-excitable  or  pre-frontal 
portions,  which  attain  a  much  higher  development  in  man  than 
in  the  lower  vertebrates,  are  the  special  seat  of  the  intellectual 
faculties.  Leaving  aside  theoretical  preconceptions  and  hypotheses, 
no  one  who  has  been  long  occupied  with  the  effects  of  partial 
destruction  of  the  brain  in  dogs  or  monkeys  can  fail  to  note  the 
insignificance  and  brief  duration  of  the  symptoms  presented  by 
animals  after  removal  of  the  pre-frontal  lobes.  Neither  from 
Munk's  experiments  nor  our  own,  nor  from  those  of  Horsley  and 
Schafer,  does  it  appear  that  after  destruction  of  the  pre-frontal 
lobes  the  dog  and  the  ape  differ  in  any  obvious  way  from  intact 
animals,  in  regard  to  their  intelligence. 

The  alterations  of  character  described  by  Goltz  in  animals 
after  removal  of  the  front  half  of  both  hemispheres  are  very 
striking:  they  lose  the  power  of  inhibiting  their  reflexes,  they 
become  abnormally  restless  and  uneasy,  and  though  formerly 
docile  and  affectionate,  become  intractable  and  ill-tempered.  But 
it  is  evident  that  most  of  these  psychical  changes  are  due  to 
destruction  of  the  sensory-motor  area,  and  that  little  can  be 
referred  to  the  destruction  of  the  pre-frontal  region. 

L.  Bianchi,  following  on  Hitzig  and  Wundt,  maintained  that 
the  frontal  lobe  is  "  the  organ  for  the  physiological  fusion  of  all 
the  sensory  and  motor  products  elaborated  in  other  regions  of  the 
cortex — the  organ  of  conscious  synthesis  of  the.  main  factors  of 
mental  life — the  region  in  which  are  stored  the  greatest  available 
number  of  memory  images,  upon  which  the  whole  of  the  psychical 
personality  depends." 

Physiological  experiment,  however,  shows  clearly  that  the 
functions  thus  attributed  to  the  pre-frontal  lobe  are  not  real.  The 
monkey  deprived  of  pre-frontal  lobes,  which  Bianchi  showed  at  the 
International  Congress  of  Medicine  in  Eome,  1894,  manifested  no 
perceptible  mental  alteration,  in  the  opinion  of  the  Committee 
appointed  to  examine  it.  Horsley  and  Schafer  frequently  noted 
that  the  pre-frontal  region  maybe  removed  without  producing  any 
obvious  symptom. 


620 


PHYSIOLOGY 


CHAP. 


Sciamanna's  observations  at  the  Clinic  of  Psychiatry  in  Rome, 
are  more  interesting;  in  1905,  at  the  International  Congress  of 
Psychology  in  Rome,  he  exhibited  two  monkeys  (Macacus 
cynomolgus),  from  which  he  had  removed  the  pre-frontal  lobes  the 
year  In- lore. 

Previous  to  the  operation  the  animals  had  been  under  the 
observation  of  Sciamanna  and  his  assistants,  who  had  studied  their 
habits  and  characters,  the  reactions  they  gave  to  various  kinds  of 


Fin.  :;or,.  —  A,  <lia;;]arii  <>t'  visual  sphere,  which  als {tends  over  to  tli"  cortex  of  the  im-sial  ami 

inferioi  surface,  which  is  nut  seen  in  the  figure.     B,  anditoiy  *]>II«TH  of  dog's  cerebral  cortex. 

(  I.M-iani.) 

stimuli,  the  complex  purposive  acts  which  they  performed,  e.g. 
feeling  for  sugar  in  the  pocket  of  their  keeper,  looking  at  them- 
selves in  a  mirror,  etc.  After  recovering  from  the  shock  of  the 
operation,  there  was  no  appreciable  change  in  their  behaviour; 
they  continued  to  perform  all  the  actions  learned  during  the 
period  of  observation,  as  before. 

A  committee  consisting  of  Professors  Fleehsig,  Henschen  and 
Fano  reported  of  these  apes:  There  were  no  paretic  or  spastic 
symptoms,  and  no  exaggeration  or  defect  in  the  usual  motor 
activity  of  the  monkeys.  They  did  not  assume  abnormal  positions 
during  rest;  their  attention  was  attracted  by  any  new  object. 


THE  FOEE-BRAIN 


621 


They  showed  a  lively  interest  in  a  mirror  placed  before  them; 
they  were  greedy  for  fruit  and  still  more  for  sugar,  which  they 
sought  in  the  pocket  where  they  had  learned  to  tind  it;  they  were 
on  good  terms  with  their  attendant,  and  behaved  differently  to 
the  people  they  knew  and  to  strangers.  If  disturbed  by  threats 
or  noises  they  tried  to  escape  as  far  as  possible;  but  allowed 
themselves  to  be  touched  and  caressed;  they  never  showed  un- 
reasonable fear  or  an^er. 


Fie;.  307. — C,  olfactory  spln-rc  ;  D,  .somo-urstln't  ic  "i  M 'usury-motor  spline  of  iln-'.s  cerebral  rm  tex. 

Diagrammatic.     (Luciani.) 

After  killing  both  monkeys  under  chloroform,  the  Committee 
examined  their  brains.  It  seemed  at  first  as  if  but  little  of  the 
frontal  lobes  had  been  removed,  but  from  an  accurate  report 
published  by  Cerletti,  the  frontal  pole,  which  is  pronounced  and 
bulges  forward  in  the  macaque,  was  entirely  absent,  while  the 
rest  of  the  pre-frontal  lobe  was  occupied  by  cicatricial  tissue,  so 
that  in  both  monkeys  the  whole  of  the  pre-frontal  lobes  had  been 
thrown  out  of  function. 

Clinical  experience  also  militates  against  the  theory  which 
ascribes  special  value  in  regard  to  mental  functions  to  the  pre- 
frontal  lobes.  Many  cases  have  been  described  in  which  lesions 
of  the  anterior  frontal  region  have  not  been  accompanied 


622  PHYSIOLOGY  CHAP. 

by  psychical  symptoms.  Welt  (1888)  compared  59  cases  of 
different  lesions  of  the  frontal  lobes:  only  in  12  cases  was 
there  any  mental  disturbance  or  change  of  character.  Recent 
observations  have  contributed  nothing  in  support  of  the  old 
.hypothesis  that  intelligence  depends  particularly  upon  the  pre- 
frontal  lobes.  Eoncoroni  (1911),  from  a  careful  review  of  the 
most  recent  clinical  cases,  concludes  that  lesions  of  the  pre-frontal 
lolies  do  not  produce  motor  paralysis  nor  sensory  alterations,  the 
most  characteristic  symptoms  being  impulsiveness  or  irritability, 
a  tendency  to  irrelevant  witticisms,  amnesia  in  regard  to  particular 
words  and  acts,  alterations  in  handwriting,  apraxia,  ataxy,  and 
alterations  or  loss  of  the  power  of  performing  certain  voluntary 
acts.  The  absence  of  sensory  and  motor  symptoms  with  lesions 
in  the  pre-frontal  lobes  agrees — according  to  Eoncoroni — both  with 
the  experimental  facts  and  with  the  cytotectonic  observations  of 
Brodmann,  as  well  as  with  the  anatomical  relations  of  the 
pre-frontal  lobe.  Eoncoroni  in  conclusion  declares  against  the 
hypothesis  that  the  highest  intellectual  faculties  are  located  in 
the  pre-frontal  lobes. 

When,  on  the  other  hand,  we  consider  Flechsig's  great  posterior 
association  area  we  see  at  once  that  both  physiological  evidence 
and  the  facts  of  morphology  and  anthropology  point  to  the  special 
importance  of  this  region  in  mental  functions. 

Gk>ltz'  experiments  upon  dugs  in  which  the  whole  posterior 
half  of  the  hemispheres  were  removed  are  of  great  importance  in 
estimating  the  value  of  subsequent  investigations.  He  saw  that 
dogs  which  were  lively  and  active  before  this  operation  became 
quiet  and  apathetic.  Even  more  striking  than  this  change  of 
character  was  the  marked  diminution  of  intelligence :  the  animals 
behaved  as  if  they  were  imbecile  or  demented. 

We  observed  practically  the  same  signs  of  grave  mental 
disturbance  in  dogs  from  which  the  whole  cortex  of  the  parietal 
lobe,  or  the  parieto-occipital,  or  the  parieto-temporal  region,  was 
removed.  Removal  of  these  regions  leads  to  serious  disturbance 
of  all  sensory  function,  while  lesions  of  no  other  part  of  the 
cerebral  cortex  of  the  dog  produce  such  complex  effects,  which  of 
course  imply  profound  mental  degradation. 

On  comparing  the  four  diagrams  representing  the  visual, 
auditory,  tactile,  and  gustatory  spheres  in  the  dog  (Luciani  and 
Seppilli,  Figs.  306,  307,  A,  B,  C,  D),  it  is  at  once  evident  that  each 
sensory  sphere,  besides  its  own  area,  overlaps  and  partially  fuses 
with  those  around  it.  This  common  area  is  the  parietal  lobe, 
more  precisely  Munk's  ^'sphere  (Fig.  296),  which  we  regarded  as 
the  most  important  region  of  the  dog's  hemisphere,  as  the  centre 
of  centres,  on  which  the  normal  association  of  percepts  and  their 
memory  images  depend. 

The   recent   work   of   0.   Kalischer    (1907)  on    the    psychical 


x  THE  FOEE-BEAIN  623 

functions  of  the  auditory  and  visual  sphere  of  the  dog,  affords 
new  evidence -in  support  of  this  hypothesis.  He  educated  certain 
dogs  to  swallow  pieces  of  meat  only  on  hearing  a  given  sound, 
and  not  to  touch  them  at  sounds  of  a  different  pitch.  These 
animals  retained  the  capacity  for  recognising  the  "dinner-sound" 
even  when  the  cortex  of  both  temporal  lobes  had  been  destroyed. 
This  shows — according  to  Kalischer — that  these  complex  reactions 
(which  certainly  cannot  be  identified  with  simple  reflex  acts)  may 
take  place  in  the  absence  of  the  sensory  auditory  area,  provided 
the  subcortical  auditory  centres  are  present  and  are  functionally 
intact. 

Kalischer  taught  other  dogs  to  touch  their  food  only  in 
brilliantly  lighted  surroundings,  and  not  to  take  it  in  a  dim  light. 
This  habit  was  also  preserved  after  removal  of  both  occipital  lobes 
(Munk's  visual  sphere),  proving,  according  to  Kalischer,  that  the 
power  of  recognising  differences  of  luminous  intensity  does  not 
depend  on  integrity  of  Munk's  cortical  visual  centres.  On  the 
other  hand,  the  power  of  recognising  differences  in  colour  depends 
on  the  integrity  of  the  cortical  visual  sphere.  Kalischer  showed 
in  a  recent  series  of  experiments  (1909)  that  dogs  that  were 
accustomed  to  take  pieces  of  meat  only  when  light  of  a  given 
colour,  e.g.  red,  was  let  into  the  room,  and  not  to  touch  them  when 
the  light  was  a  different  colour,  entirely  lost  the  power  for  recog- 
nising the  "  dinner-colour"  after  removal  of  both  occipital  lobes. 

These  ingenious  experiments  should  be  controlled.  They  do 
not  controvert  the  generally  accepted  theory  that  the  highest 
mental  functions  of  perception,  memory,  association,  are  seated  in 
the  sensory  spheres  of  vision  and  hearing.  They  rather  tend  to 
support  the  hypothesis  that  these  spheres  are  not  sharply  limited 
to  the  cortex  of  the  temporal  and  occipital  lobes,  but  extend 
upward  and  forward  towards  the  parietal  lobe. 

Experimenting  with  monkeys,  Horsley  and  Schafer  confirmed 
the  predominating  importance  of  the  posterior  regions  of  the 
hemispheres  in  relation  to  psychical  functions.  They  stated  that 
a  condition  of  idiocy  was  more  readily  produced  in  the  ape  by 
removing  extensive  regions  of  the  temporal  lobes  on  both  sides 
than  by  cutting  off  the  pre-frontal  region  completely  by  an  incision. 

The  most  striking  evidence  of  the  psychical  importance  of 
Flechsig's  posterior  association  area  is,  however,  derived  from 
clinical  and  anthropological  observations.  Clinical  data  show 
that  external  lesions  of  the  cortex,  particularly  if  bilateral,  are 
capable  of  producing  mental  disorders  or  diminution  of  intelligence, 
whatever  their  situation.  But  it  is  a  fact  that  the  most  common 
and  serious  of  such  disorders  depend  on  lesions  localised  in  this 
area.  Failure  of  the  ideative  faculty,  mental  confusion,  dementia-, 
obvious  symptoms  of  psychical  blindness  and  deafness,  are  more 
or  less  characteristic  symptoms  of  bilateral  destructive  lesions  of 


624  PHYSIOLOGY  CHAP. 

the  parietal,  temporal,  and  occipital  lobes.  According-  to  Flechsig, 
in  fact,  it  is  in  this  region  that  the  greater  part  of  man's  intellectual 
inheritance  is  stored  up,  and  the  visual,  auditory,  tactile,  and 
olfactory  images  associated  into  higher  mental  products. 

R.  Wagner  concluded  from  his  comparative  anthropological 
studies  on  the  brains  of  highly  intelligent  persons,  and  of  those  of 
mediocre  or  low  intellect,  that  the  degree  of  development  of  the 
intellectual  faculties  depends  on  the  wealth  and  depth  of  the 
sulci,  that  is,  on  the  surface  area  of  the  cerebral  cortex,  rather 
than  on  the  weight  or  total  volume  of  the  brain.  This  tends  to 
support  the  view  that  the  intellectual  faculties  are  not  located 
in  any  one  part  of  the  brain,  but  depend  on  the  organ  as  a 
whole,  and  develop  in  proportion  with  the  grey  matter  of  the 
cortex. 

But  after  a  more  minute  analysis  of  the  development  of  the 
several  regions  of  the  cerebral  cortex,  Eiidinger  (1882)  noted  the 
important  fact  that  the  parietal  convolutions  are  extraordinarily 
well  developed  in  men  of  high  intelligence,  as  compared  with 
ordinary  individuals  and  the  lower  human  races.  He  was  able  to 
obtain  eighteen  brains  of  people  with  different  claims  to  eminence, 
among  them  Dollinger,  Bischoff,  Lasaulx,  and  Liebig.  In  examin- 
ing these  he  was  specially  struck  by  the  exceptional  development 
of  the  convolutions  and  fissures  of  the  parietal  lobe,  which  gives 
this  region  quite  a  different  aspect  from  that  of  the  brains  of 
uncultured  persons.  The  study  of  the  skulls  of  Kant,  Gauss, 
Dirichlet  also  showed  marked  development  of  the  parietal  region. 
In  the  skulls  of  Bach  and  of  Beethoven,  which  have  been 
studied  by  His  and  by  Flechsig,  there  was  a  marked  development 
of  the  posterior  regions  of  the  brain  (parieto-occipito-temporal) 
and  the  Rolandic  region,  while  the  pre -frontal  lobes  were  of 
only  comparatively  insignificant  dimensions.  The  brain  of  the 
astronomer  Gylden,  examined  by  Eetzius,  showed  considerable 
development  of  the  parietal  lobe,  especially  of  the  angular  gyrus. 
In  Helmholtz'  brain,  according  to  Hansemann,  the  pre-cuneus 
and  parietal  region  included  between  the  angular  gyrus  and 
the  upper  temporal  gyrus  were  remarkable  in  size.  Eaffaelle's 
cranium,  studied  by  Mingazzini  in  an  authentic  chalk  drawing  at 
Urbino,  shows  a  striking  contrast  between  the  modest  height  of 
the  forehead  and  great  expansion  of  the  occipital  and  parietal 
lobes.  The  skulls  of  Gauss  and  Richard  Wagner,  according  to 
His  and  Flechsig,  on  the  contrary  exhibit  a  striking  development 
not  only  of  the  posterior  association  area,  but  also  of  the  anterior 
or  pre-frontal  association  area  of  Flechzig. 

On  the  other  hand,  S.  Sergi  (junior),  in  a  recent  study  of  the 
brain  of  the  various  human  races  (1909),  has  brought  out  the  fact 
that  the  development  of  the  frontal  lobe  is  not  in  ratio  with  the 
degree  of  intellectual  development,  and  that  the  highest  races  are 


x  THE  FOKE-BEAIN  625 

characterised  by  predominating  development  of  the  parietal  and 
occipital  lobes. 

XV.  To  form  a  more  adequate  idea  of  the  complexity  of  the 
intellectual  processes,  we  may  briefly  examine  the  most  typical 
forms  of  disturbance  of  speech. 

In  a  wide  sense  speech — or  language — covers  the  sum  of 
all  the  means  which  man  employs  to  express  his  thoughts. 
Language  is  mimetic,  phonetic,  graphic  (see  Chap.  III.),  according 
to  the  nature  of  the  signs  employed — gestures,  words,  writing. 

Apart  from  mimetic  language  (which  is  the  means  of  com- 
munication for  deaf-mutes,  phonetic  and  graphic  language  have  a 
historical  development  in  the  race  as  in  the  individual.  Com- 
parative philologists  endeavour  to  reconstruct  the  phylogenesis  of 
language ;  psycho-physiological  observations  of  the  manner  in 
which  the  child  learns  gradually  to  speak,  read,  and  write,  reveal 
the  mode  of  development  of  language  in  the  individual.  Poverty 
of  language  indicates  poverty  of  ideas  in  primitive  peoples  as  in 
children  ;  wealth  of  language  is  the  gauge  of  civilisation  for  the 
most  advanced  nations,  as  for  the  most  gifted  and  most  highly 
developed  minds. 

The  spoken  or  written  word  is  the  symbolical  representation  of 
the  idea,  which  is  necessary  in  order  to  express  it,  or  communicate 
it  to  others.  The  highest  organs  of  ideation,  while  intimately 
connected  with,  are  entirely  distinct  and  separate  from,  the  organs 
of  speech.  In  fact,  serious  mental  disturbance  may  coexist  with 
perfect  integrity  of  phonetic  and  graphic  speech.  On  the  other 
hand,  psychological  analysis  and  clinical  observations  show  that 
the  mechanism  by  which  ideas  are  clothed  in  verbal  symbols  is 
very  complex,  and  involves  the  intervention  of  three  associated 
centres  :  the  centre  for  the  motor  images  of  words  ;  the  centre  for 
phonetic  verbal  images ;  the  centre  for  visual  verbal  images.  The 
first  (Fig.  308)  is  Broca's  centre,  which  occupies  the  foot  of  the 
left  third  frontal  convolution ;  the  second  is  Wernicke's  centre 
seated  in  the  left  first  temporal  convolution  and  supramarginal 
gyrus ;  the  third  lies  in  the  occipito-parietal  lobe  near  the  visual 
area — according  to  Dejeriue  it  is  placed  in  the  left  angular  gyrus. 

These  three  centres  together  form  an  area  peculiar  to  the 
human  brain,  the  so-called  speech  centre,  comparable  to  the 
sensory-motor,  visual,  auditory  and  other  areas  which  we  have 
been  discussing.  But  unlike  these  the  speech  centre  is  single  or 
unilateral ;  it  lies  in  the  left  hemisphere  in  right-handed  people, 
in  the  right  hemisphere  in  the  left-handed.  This  asymmetrical 
unilateral  development  of  the  central  organs  of  speech  is  purely 
functional  and  not  morphological,  for  the  right  hemisphere  presents 
the  same  structure  and  connections  as  the  left.  The  different 
functional  importance  of  the  two  hemispheres  in  speech  evidently 
depends  on  the  larger  and  almost  exclusive  use  which  the  right - 

VOL.  in  2  s 


626 


PHYSIOLOGY 


CHAP. 


handed  make  of  the  left  brain,  and  the  left-handed  of  the  right 
brain,  during  the  years  of  education,  in  learning  to  speak,  read, 
write,  and  in  performing  finer  and  more  skilled  work.  It  is  there- 
fore reasonable,  and  well-confirmed  by  clinical  evidence,  that 
lesions  of  the  normal  speech  centres  may  be  functionally  com- 
pensated by  the  symmetrical  area  of  the  opposite  side.  This 
functional  compensation  or  substitution  is  effected  more  readily 
and  completely  in  children  than  in  adults.  Gowers  and 
Mingazzini  sustain  that  in  the  state  of  infancy  the  central  speech 
mechanisms  are  bilateral  or  at  least  more  equally  distributed 


FIG.  308.— Area  for  speech  and  its  three  centres  for  verbal  images.  (Dejerine.)  A,  Wernicke's 
centre,  for  auditory  verbal  images  ;  B,  Broca's  centre,  for  motor  verbal  images  ;  PC,  centre  for 
visual  verbal  images. 

between  the  two  hemispheres  than  in  adults.  But  in  adults,  too, 
according  to  the  consensus  of  clinical  evidence,  there  must  be 
considerable  difference  in  individuals ;  Gowers,  Brans,  and  Collier 
state  that  in  right-handed  people  the  left  hemisphere  has  no 
monopoly  in  speech.  Hughlings  Jackson,  Bastian,  and  Byrom 
Bramwell,  also  on  the  strength  of  clinical  observations,  have 
assigned  the  function  of  premeditated  speech  to  the  left  hemi- 
sphere and  the  simpler  function  of  automatic  speech  to  the  right 
hemisphere. 

Severe  lesions  of  Broca's  convolution  cause  aphasia,  that  is 
loss  of  the  power  of  speech,  owing  not  to  paralysis  of  the  nerves 
and  muscles  thrown  into  action  during  phonation,  but  to  abolition 
of  the  memory  of  a  certain  order  of  co-ordinated  movements 
necessary  to  the  articulation  of  words.  The  intelligence  of  the 


x  THE  FOEE-BKAIN  627 

patient  remains  intact ;  he  understands  what  is  said  or  read  to 
him,  and  remembers  what  he  previously  learned.  His  vocal 
organs  are  also  normal,  but  he  is  unable  to  speak,  though  he  can 
sing  vocally,  laugh,  and  express  emotions  by  his  voice.  His 
auditory  and  verbal  images  are  preserved,  along  with  visual 
images  of  objects  and  the  images  of  written  words.  He  can  also 
write  intelligently  when  the  lesion  is  limited  to  Broca's  con- 
volution, and  mimetic  language  is  perfectly  retained.  Sometimes 
he  continues  the  use  of  Yes  and  No  and  a  few  other  words,  as 
exclamations.  Under  certain  emotional  conditions,  but  not 
always  at  will,  he  is  able  to  enunciate  words — a  proof  that  the 
right  hemisphere  too  is  to  some  extent  concerned  with  motor 
speech,  as  maintained  by  Gowers. 

Broca's  theory  has  been  attacked  in  recent  years  by  P.  Marie, 
who  declares  that  Broca's  convolution  does  not  take  part  in  any 
way  in  the  complex  function  of  speech.  To  support  this  he 
invokes  a  large  number  of  clinical  cases  of  motor  aphasia  with  all 
the  symptoms  we  have  described,  in  wrhich  a  post-mortem  examina- 
tion showed  the  left  third  frontal  convolution  to  be  absolutely 
intact.  He  also  cited  a  second  clinical  series  in  which  motor 
aphasia  was  absent,  while  examination  revealed  isolated  destruction 
of  Broca's  lobule. 

Marie's  cases  do  not,  however,  invalidate  Broca's  theory.  If 
carefully  considered,  it  will  be  found  that  they  are  not  irreconcilable 
with  that  theory,  as  was  shown  by  Mingazzini  (1908). 

Clinical  experience  teaches  that  more  or  less  transitory  motor 
aphasia  may  be  due  to  the  shock  or  disturbing  effect  of  a  focal 
lesion  which  indirectly  affects  the  function  of  the  elements  of 
Broca's  convolution.  Mingazzini  records  a  case,  observed  by 
Panegrossi,  of  a  patient  affected  with  paralysis  of  the  right  arm, 
who  for  several  days  entirely  lost  his  speech,  though  able  to  under- 
stand questions ;  he  only  began  to  articulate  certain  words  clearly 
a  few  days  before  his  death.  The  autopsy  revealed  a  softening  in 
the  middle  part  of  the  pre-central  convolution,  while  Broca's 
convolution  was  intact.  The  functions  of  the  latter  were  evidently 
affected  solely  by  circulatory  disturbances,  and  oedema  due  to  the 
haemorrhagic  focus,  which  was  beginning  to  subside  shortly  before 
the  patient's  death. 

In  other  cases  the  motor  aphasia  may  be  due  to  arteritis  or 
thrombosis  of  the  arterial  branches  that  supply  Broca's  con- 
volution. In  a  case  of  right  hemiplegia  associated  with  motor 
aphasia,  Mingazzini  and  Marchiafava  found  on  post-mortem 
examination  arteritis  and  partial  thrombosis  of  the  left  Sylvian 
artery,  with  an  enormous  red  softening  which  involved  the 
lenticular  nucleus,  external  capsule,  and  the  pyramidal  region  of 
the  internal  capsule,  without  disturbance  of  Broca's  convolution  on 
either  side. 


628  PHYSIOLOGY  CHAP. 

It  should  be  noted  in  conclusion  that  the  post-mortem  integrity 
of  Broca's  organ  in  persons  who  had  suffered  from  motor  aphasia 
may  be  more  apparent  than  real,  unless  a  careful  microscopical 
examination  has  been  made.  Marie's  cases,  in  which  there  was 
no  motor  aphasia  despite  destruction  of  Broca's  convolution  in 
right-handed  patients,  are  not  irreconcilable  with  the  generally 
accepted  theory,  as  slowly  developing  changes  in  the  opercular 
portion  of  the  third  left  convolution  may  be  associated  with  a 
progressive  functional  development  of  the  corresponding  right  con- 
volution, which  is  the  motor  centre  for  articulate  speech  in  left- 
handed  persons. 

The  fact  that  in  young  persons  motor  aphasia  due  to  lesions 
of  Broca's  centre  quickly  disappears  was  used  by  Mingazzini  as 
an  argument  in  favour  of  Gowers'  theory,  which  assumes  that 
up  to  a  certain  age  both  hemispheres  co-operate  in  the  formation 
of  the  motor  images  of  speech,  and  that  the  function  of  the  right 
brain  is  only  later  transferred  to  the  left  hemisphere  in  right-handed 
people,  and  vice  versa  in  the  left-handed. 

If  we  accept  this  hypothesis  there  is  no  difficulty  in  assuming 
that  in  certain  individuals,  particularly  in  the  ambidextrous, 
the  function  of  speech  may  be  distributed  throughout  life 
in  an  approximately  equal  degree  to  both  hemispheres,  so  that 
even  a  sudden  lesion  of  one  does  not  abolish  speech  (Mingazzini). 
This  theory,  which  invalidates  Marie's  arguments,  is  supported 
by  all  the  clinical  cases  of  motor  aphasia,  due  to  destruction  of 
the  left  centre  of  Broca,  in  which  speech  gradually  returns  after 
a  longer  or  shorter  interval.  The  following  case  reported  by 
Oppenheim  (1909)  is  of  great  importance  as  a  physiological 
experiment  on  man.  In  a  patient  in  whom  Broca's  centre  had 
been  exposed,  motor  aphasia  occurred  each  time  the  brain  was 
compressed,  and  disappeared  when  the  pressure  was  removed. 

Lesions  of  Wernicke's  centre  produce  word  deafness',  those 
of  the  cortex  of  the  occipital  lobe  or  angular  gyrus  word  blindness. 
The  centres  of  auditory  and  visual  word  memory  are  not 
equally  important  in  the  mechanism  of  speech ;  obviously  the 
former  preponderates.  The  child  learns  to  speak  by  exercising  its 
auditory  perceptions.  As  the  association  paths  that  connect  the 
auditory  word  centre  with  the  motor  word  centre  become  developed 
it  makes  its  first  attempts  to  talk,  and  speech  gradually  becomes 
more  perfect  as  the  cortical  and  sub-cortical  centres,  and  paths 
and  peripheral  organs  of  speech,  attain  full  development. 

Lesions  of  the  subcortical  paths  and  peripheral  organs  produce 
disturbance  of  articulation  or  dysarthria,  but  the  capacity  for 
internal  or  mental  speech  then  remains  intact.  Lesions  of  Broca's 
and  Wernicke's  centres  may  produce  alterations  on  the  sensory 
side  of  speech,  and  total  or  partial  incapacity  for  phonetic 
expression  (aphasia  or  dyspliasia?)  with  more  or  less  disturbance 


x  THE  FOEE-BEAIN  629 

of  internal  speech.  "The  auditory  images,"  writes  Dejerine,  "are 
the  first  to  be  formed ;  they  are  the  most  deeply  traced  and  always 
control  the  processes  of  internal  language;  the  motor  images  of 
articulation  next  form  very  rapidly,  and  unite  closely  with  the 
auditory  images.  The  union  of  these  two  contributes  the  first 
and  indispensable  basis  of  internal  language.  At  a  much  later 
stage  the  child  learns  to  attach  the  visual  image  of  words  to  the 
auditory  and  motor  images  of  articulation.  .  .  ." 

In  reading  the  child  gradually  learns  to  connect  the  sounds  of 
the  words  it  already  knows  with  graphic  characters,  the  meaning 
of  which  is  at  first  unknown  to  it.  At  the  same  time  or  shortly 
after,  it  learns  to  write,  i.e.  to  reproduce  written  or  printed 
characters,  which  reinforces  in  its  memory  the  intimate  connection 
between  the  phonetic  images  primarily  acquired  and  the  newly- 
learned  graphic  images  which  correspond  with  them. 

Hence  in  all  who  are  able  to  read  and  write,  the  mechanism  of 
language  is  more  complicated  than  in  the  uneducated.  It  depends 
on  the  harmonised  activity  not  only  of  the  auditory  and  motor 
word  centres,  but  also  of  the  visual  word  centre.  But,  in  both 
educated  and  uneducated,  speech  depends  essentially  upon  the  \ 
co-ordination  of  word  sounds  with  word  motor  images ;  verbal  i 
images,  even  in  those  whose  visual  memory  is  exceptionally 
developed,  only  play  a  subordinate  part  in  speech,  in  so  far  as 
they  are  intimately  connected  with  phonetic  symbols.  The 
scientific  proof  of  this  lies  in  the  fact  that,  while  there  are 
numerous  clinical  cases  in  which  word  deafness,  from  lesions 
confined  to  the  auditory  centre,  is  associated  with  loss  or  disturb- 
ance of  speech,  i.e.  with  aphasia  or  dyspliasia — which  Weruicke 
terms  sensory  to  distinguish  it  from  the  motor  aphasia  due  to 
destruction  of  Broca's  centre — there  are  no  cases  on  record  of 
word  blindness  due  to  lesions  confined  to  the  visual  sphere,  in 
which  the  patient  was  incapable  of  speaking.  Kussmaurs  word 
blindness  is  characterised  by  inability  to  read  and  write  from 
dictation,  i.e.  alexia  and  agraphia,  and  is  not  associated  with 
aphasia  or  dysphasia  if  the  lesion  is  limited  to  the  visual  sphere. 

This  theory  of  the  absolute  functional  preponderance  of  the 
auditory  centre  in  the  mechanism  of  speech  is  at  variance  with 
the  view  of  Charcot,  who  classed  individuals  into  auditive,  visual, 
and  motor,  according  as  they  depended  chiefly  on  the  auditory 
word  centre,  the  visual  word  centre,  or  the  motor  word  centre  in 
speech.  But  on  Charcot's  theory  no  one  can  be  a  visual  who  is 
unable  to  read,  and  before  learning  to  read  it  is  necessary  to 
be  an  auditive.  We  must  assume,  in  order  to  explain  the 
change  into  a  visual,  that  the  practice  of  reading  intensifies 
memory  of  written  characters  so  much  that  it  becomes  easier  to 
evoke  graphic  images  than  verbal  sounds. 

It  is  more  difficult,  on  this  theory,  to  understand  how  auditives 


\ 


630  PHYSIOLOGY  CHAP. 

can  become  motor,  i.e.  how  speech,  which  was  originally  dependent 
on  the  auditory  word  centre,  is  later,  in  certain  individuals, 
associated  with  the  motor  word  centre,  which  may  thus  alone 
subserve  it.  The  motor  word  centre  is  so  connected  with  the 
auditory  word  centre  that  it  is  inconceivable  that  any  separate 
education  can  make  it  predominant  over  the  latter. 

Among  the  most  characteristic  forms  of  speech  disturbance 
due  to  lesions  of  the  cerebral  cortex,  is  that  which  has  been  well 
described  as  verbal  amnesia,  since  it  is  clinically  quite  distinct  from 
verbal  deafness.  In  the  one  there  is  more  or  less  complete  loss  of 
memory  of  the  auditory  images  of  speech ;  in  the  other  it  is 
merely  the  power  of  recalling  such  images  that  has  gone.  While 
the  patient  suffering  from  word  deafness  cannot  understand  spoken 
language  and  is  incapable  of  speaking,  the  patient  with  verbal 
amnesia  understands  perfectly,  and  without  hesitation,  whatever 
is  said  to  him ;  and  he  can  pronounce  every  word  easily ;  but  his 
speech  is  more  or  less  hesitating  and  unintelligible,  as  he  cannot 
recall  a  large  number  of  words,  particularly  proper  names  and 
substantives.  "  The  idea  is  there,  but  the  word  fails,  although 
articulation  is  not  defective "  (Kussmaul).  "  The  idea  does  not 
call  up  the  word,  but  the  word  can  always  reawaken  the  idea,  for 
the  patient  can  repeat  and  understand  the  word  which  is  suggested 
to  him,  and  which  corresponds  with  the  idea  he  wants  to  express  " 
(Tamburini).  The  auditory  and  motor  word  centres  are  capable 
of  reacting  to  the  external  stimuli,  but  have  become  incapable  of 
reacting  to  the  internal  stimuli  of  ideational  activity. 

Many  authors  have  confused  amnesia  with  word  deafness,  and 
maintain  that  they  differ  only  in  degree.  It  is  true  that  word 
deafness  necessarily  involves  amnesia ;  but  their  co-existence  is 
not  absolutely  inevitable,  for  verbal  amnesia  may  be  present 
without  a  trace  of  word  deafness. 

Even  if  both  forms  imply  a  lesion  of  the  auditory  area, 
pathological  anatomy  proves  their  different  localisation.  In  cases 
of  pure  verbal  amnesia  Wernicke's  centre,  i.e.  the  posterior  part 
of  the  left  first  temporal  convolution,  is  not  involved,  but  only  the 
left  inferior  parietal  lobe,  as  was  seen  in  typical  cases  described 
by  Banti,  Cornil,  Kussmaul,  Broadbent,  and  others. 

XVI.  The  new  and  fundamental  principle  which  Flechsig 
introduced  into  the  physiology  of  the  brain  consists  essentially,  in 
the  distinction  which  he  made  between  the  sensory  and  voluntary 
motor  centres,  which  are  united  by  afferent  and  efferent  fibres 
with  the  peripheral  sensory  and  motor  organs,  and  the  psychical 
centres  properly  so-called,  which  are  connected  by  endogenous  or 
intra- central  association  fibres  among  themselves  and  with  the 
different  sensory  centres.  According  to  Meynert  and  Weruicke 
the  "  sensory  spheres  "  included  the  whole  of  the  cerebral  cortex  ; 
each  of  them  was  connected  with  the  rest  by  endogenous,  and 


x  THE  FOBE-BBAIN  631 

with  the  periphery  by  exogenous  fibres.  Their  functional  synergy 
depended  on  the  central  continence  of  these  sensory  spheres,  which 
rendered  the  cerebrum  the  single  organ  of  intelligence.  Munk's 
general  hypothesis  of  the  psycho-physiological  functions  of  the 
brain  is  based  upon  this  schema  of  Meynert  and  Wernicke. 

According  to  our  own  theory,  which  is  based  on  experimental 
work  on  dogs,  the  several  sensory  centres  overlap  in  a  common 
area  to  which  we  gave  the  name  of  "  centre  of  centres."  Flechsig, 
too,  admits  that  there  is  no  absolute  line  of  demarcation  between 
his  cortical  projection  fields,  which  include  the  sensory  and  motor 
areas,  and  the  association  jields.  Between  the  one  and  the  other 
Flechsig  sees  the  same  relations  as  exist  between  sensibility  and 
intelligence  "  which,  while  theoretically  separable,  are  really 
intimately  associated."  Niliil  est  in  intellectu  quia  prius  fuerit  in 
sensibus.  Without  the  sensory  centres,  the  intellectual  centres 
would  be  ab  initio  incapable  of  producing  ideas  or  representations  ; 
1  H  ith  normally  act  and  react  together,  work  for  the  same  ends,  and 
aim  at  the  same  results.  The  material  supplied  by  the  sensations 
is,  so  to  speak,  elaborated  in  the  intellectual  centres.  The 
functions  of  the  one  represent  the  receptive  phase,  those  of  the 
other  the  reactive  phase  of  the  mental  process.  The  former  (to 
adopt  the  classical  language  of  Aristotle)  constitute  the  passive 
intellect,  the  latter  the  active  intellect. 

It  was  the  clinicians — arguing  from  the  symptoms  of  aphasia 
—who  first  postulated  the  existence  of  an  ideational  centre  in  the 
cortex  distinct  from  the  centres  for  verbal  images  (auditory,  visual, 
articulative).  The  fact  that  there  may  be  total  loss  of  the  use  of 
words  with  no  apparent  disturbance  of  intelligence  is  the  most 
cogent  argument  that  the  word  and  the  idea  are  formed  in- 
dependently of  one  another,  in  different  areas  of  the  cerebral 
cortex.  But  it  was  only  from  the  studies  of  Flechsig  that  this 
hypothetical  ideational  centre  acquired  a  localisation,  though  still 
indefinite  and  vague.  It  is  evident  that  it  must  lie  in  the  associa- 
tion fields,  more  particularly  in  those  contained  within  the  parieto- 
occipito-temporal  area  of  Flechsig. 

The  distinction  between  sensory -motor  and  psychical  areas  of 
the  cortex  is  intimately  connected  with  an  important  question 
of  the  general  theory  of  Memory.  Is  the  seat  of  primary  precepts 
or  sensory  images  identical  with  or  different  from  that  of  the 
secondary  representations  or  the  secondary  sensory  images,  evoked 
by  a  simple  effort  of  memory  ?  If  the  first  hypothesis,  which  has 
been  formulated  by  Bibot  and  other  psychologists,  and  accepted 
unconditionally  by  physiologists  and  clinicians,  be  admitted  it 
follows  that  the  sensory  centres  on  which  perception  of  the 
external  world  depends  are  at  the  same  time  the  seat  at  which  the 
memory  images  must  be  formed  and  stored  up,  but  we  are  unable 
to  picture  or  to  comprehend  their  nature.  If  we  accept  the  second 


632  PHYSIOLOGY  CHAP. 

alternative,  we  must  assume  that  "  the  sensory  and  motor  centres 
serve  only  for  immediate  and  ever  new  reactions,  of  which  they 
preserve  no  impressions — that  the  enduring  or  incomplete  memory 
of  events  which  affect  the  projection  centres  are  stored  up  in 
other  centres — that  the  images  of  things  are  perceived  at,  one  point 
and  retained  at  another  .  .  ."  (Tanzi). 

This  hypothesis  seems  to  us  to  be  an  arbitrary  interpretation 
of  Flechsig's  theory.  Prior  to  the  distinction  of  the  cerebral 
cortex  into  projection  fields  and  association  fields,  when  the  brain 
was  simply  held  divisible  into  sensory  and  motor  spheres,  it  was 
natural  to  assume  that  the  memory  of  sense  impressions  was 
distributed  all  over  the  cerebral  cortex.  That  the  association 
fields  are  the  exclusive  seat  of  memory,  and  that  the  projection 
fields  which  are  in  the  most  immediate  connection  with  the 
peripheral  sense  organs  are  incapable  of  preserving  the  impressions 
and  percepts,  is  a  necessary  consequence  of  Flechsig's  theory. 

The  occurrence  of  blindness  of  cortical  origin  without  loss  of 
the  power  of  evoking  visual  images,  does  not  prove  (as  stated  by 
Tanzi)  that  the  centre  of  visual  memory  is  distinct  and  separate 
from  the  area  of  visual  sensibility.  When  we  consider  that  visual 
memory  may  theoretically  be  divided  into  functionally  distinct 
components,  as  the  special  memories  of  luminosity,  colour,  form, 
dimensions,  etc.,  it  seems  legitimate  to  assume  that  the  lesions 
which  produce  cortical  blindness  do  not  destroy  the  whole  visual 
fields,  and  do  not  therefore  blot  out  the  whole  of  the  visual 
memory  stored  in  the  cortex. 

No  argument  in  fact  prevents  us  from  assuming  that  all 
cortical  areas,  not  excluding  those  in  most  intimate  relation  with 
the  peripheral  sense  organs,  are  the  seat  of  special  memories  and 
contain  the  traces  of  previous  percepts  and  representations;  that 
these  impressions,  organically  distributed  over  countless  elements, 
are  in  more  or  less  close  inter-relationship,  and  are  capable  of 
associating  or  combining  in  a  thousand  different  ways. 

This  theory  of  memory  agrees  perfectly  with  the  results  of 
psychological  analysis  of  perceptions  in  contrast  to  simple 
sensations ;  a  perception  results  from  the  synthesis  of  a  sensory 
image  with  the  mnemonic  traces  left  by  preceding  sensations.  The 
sensory  centres  of  the  cortex  which  are  the  seat  of  perception  are 
accordingly  capable  of  retaining  memory  impressions. 

On  the  other  hand  there  can  be  no  doubt  that  the  greater 
number  of  the  nerve  elements  concerned  with  memory  must  be 
sought  in  the  association  areas  of  the  cortex.  The  physiological 
proof  of  this  is  the  amnesia  of  varying  kind  and  degree  produced 
by  alterations  of  these  areas.  The  psychological  proof  lies  in 
the  analysis  of  representations,  in  so  far  as  these  result  from 
association  of  the  multiple  and  varied  memory  images  which  arise 
in  distant  and  distinct  areas  of  the  cortex. 


x  THE  FOKE-BKAIN  633 

In  considering  the  theory  of  memory,  it  is  important  to 
determine  what  are  the  stimuli  which  are  able  to  revive  the 
memories  retained  in  the  ganglion  cells  of  the  cortex  and  to  re- 
invoke  the  images  in  the  form  of  representations.  In  this  psycho- 
physiological  process  special  importance  is  usually  ascribed  to 
internal  stimuli,  which  act  upon  the  sensory  organs,  constantly 
excite  memories,  and  bring  all  the  latent  energies  of  the  mind  into 
play.  But  internal  stimuli  coming  from  the  vegetative  organs 
through  the  sympathetic  system  to  the  cerebral  cortex,  where  they 
excite  bodily  sensations  and  instincts  in  consciousness,  must  be 
of  almost  equal  importance  to  mental  activity.  The  brain  is 
consequently  the  meeting-place  for  impressions  from  the  outer 
world  and  for  those  that  originate  within  the  organism.  Both  these 
channels  excite  the  psychical  centres  centripetally  and  the  motor 
system  ceutrifugally. 

The  association  between  the  sense  centres  and  those  of  instinct 
give  an  emotional  tone  to  the  perceptions,  and  thereby  increase 
their  dynamic  efficiency.  The  associations  between  the  exterior 
and  interior  sensory  centres  and  the  psychical  areas  proper 
serve  the  idealisation  of  the  images  and  determine  the  exchange  of 
action  and  reaction  between  the  sensations  and  instinct,  and  the 
intellect.  It  is  in  the  struggle  between  impulse  and  inhibition 
that  actions  acquire  an  ethical  character.  The  greater  the 
functional  energy,  and  the  more  perfect  the  inhibition  and  control, 
so  much  the  more  will  reason  prevail  over  emotion. 

By  its  investigations  into  the  material  conditions  of  human 
activity,  physiology  allies  itself  with  the  moral  sciences.  In  the 
twentieth  century  it  will  pursue  the  scientific  analysis  of  psycho- 
physical  phenomena  without  preconception  or  prejudice.  It  will 
not  be  hampered  as  in  the  past  by  animus  to  the  concept  of 
the  soul,  nor,  on  the  other  hand,  will  it  fail  to  recognise  that 
psychical  development,  even  on  the  ethical  side,  depends  to  a 
large  extent  upon  the  somatic  substrate. 

The  more  science  succeeds  in  revealing  the  nature  of  life  in 
general,  and  of  the  human  mind  in  particular,  the  stronger  and 
clearer  will  be  our  scientific  faith  that  behind  this  world  of 
appearances  there  lies  a  world  of  reality,  in  comparison  with 
which  human  consciousness  and  human  knowledge  •  are  but  as  a 
shadow. 

BIBLIOGRAPHY 

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of  the  Brain,  see  : — 

SOURY,  J.     Le  Systeme  nerveux  central.     Paris,  1899. 

The  principal  Physiological  Monographs  relating  to  the  Theory  of  Cerebral 
Localisation  are  : — 

HITZIG.     Untersuchungen  liber  das  Gehirn.     Berlin,  1874.     Gesammelte  Abhand- 
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634  PHYSIOLOGY  CHAP. 

FERRIER.     Functions  of  the  Brain.     London,  1876. 

LUCIANI  and  TAMBURINI.     Sni  centri  psicomotori  e  psicosensori  corticali.     Reggio 

Emilia,  1878-79. 

LUCIANI  and  SEPPILLI.     Le  Localizzazioni  funz.  d.  cervello.     Naples,  1885. 
FRANgois-FiiANCK.     Les  Fonctions  motrices  du  cerveau.     Paris,  1887. 
BEEVOR,  HORSLEY,  SCHAFER.     Phil.  Trans.,  1887,  1888,  1890. 
GOLTZ.     Arch.  f.  d.  ges.  Phys.,  1884-99. 
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Akad.  d.  Wissensch.,  1892-1901. 

GRUNBAUM  and  SHERRINGTON.     Proc.  Royal  Society,  Ixix.  and  Ixxii.,  1901,  1903. 
IMAMURA.     Pfliiger's  Archiv,  c.,  1903. 
TSCHERMAK.     Zentralbl.  f.  Pliys.,  xix.,  1905. 
KURZVEIL.      Pfliiger's  Archiv,  cxxix. ,  1909. 
v.  MONAKOW.     Uber  den  gegenwiirtigen  Stand  der  Frage  nach  der  Localisation  in 

Grosshirn.     Ergebnisse  der  Physiologie,  I.,  III.,  VI.,  1902,  1904,  1907  (contains 

a  bibliography  of  the  literature  of  this  subject). 
KKAUSE,  F.     Berl.  klin.  Wochenschrift,  1908. 
MAXWELL,  S.  S.     Journal  of  Biological  Chemistry,  ii.  and  iii.,  1907.     Archivio  di 

fisiologia,  vi.,  1909. 

BAGLIONI,  S.,  and  MAGNINI,  M.     Archivio  di  fisiologia,  vi.,  1909. 
Lo  MONACO.     Memorie  della  R.  Academia  dei  Lincei,  1910. 
KALISCHER,  0.     Berichte  d.  Kgl.  Preuss.  Akad.  d.  Wiss.     Berlin,  1907.     Arch.  f. 

(Anat.  u.)  Physiol.,  1909. 

MlNKOWSKl,  M.     Pfliiger's  Archiv,  cxli.,  1911. 
UCTOMSKY,  A.      tlber  die  Abhangigkeit  der  kortikalen  motorischen  Reaktionen 

von  zentralen  Nebeueinwirkungen.     Petersburg,  1911. 

ROTHMANN.     Berlin,  mediz.  Gesellsch.,  1911.     Folia  Neurobiologica,  vi.,  1912. 
KARPLUS  and  KREIDL.     Wiener  klinischen  Wochenschrift,  1912. 

The   most   important   of  the   Clinical    Monographs    on   Sensorial    Motor   and 
Linguistic  Localisation  quoted,  as  above,  by  v.  Monakow,  are  : — 

BROCA.     Bull,  de  la  soc.  anatornique.     Paris,  1861-63. 

BASTIAN.     On  the  Various  Forms  of  Loss  of  Speech,  1869. 

WERNICKE.     Der  aphasische  Sintomencomplex.     Breslau,  1874. 

NOTHNAGEL.     Topische  Diagnostik  d.  Gehirner.     Berlin,  1879. 

EXNER.     Local,  d.  Func.  in  d.  Grosshirnriude  d.  Menscheu.     Vienna,  1881. 

KUSSMAULL.     Storungen  der  Sprache,  1885. 

GOWERS.     Diseases  of  the  Brain.     London,  1885. 

BANTI.     Lo  sperimentale.     Florence,  1886. 

CHARCOT.     Progres  med.,  1888. 

DEJERINE.     Semaiue  med.,  1884.     Compt.   rend,  de  la  Soc.  de  Biol.     Paris,  1891. 

Revue  de  psych.,  1898. 
HENSCHEN.     Klin.  u.  anat.  Beitr.  z.  Path.  d.  Gehirns.     Upsala,  1890-92. 

-  CHARCOT  and  PITRES.     Les  Centres  moteurs  corticaux  chez  I'honinie.     Paris,  1895. 
V.  MONAKOW.     Gehirnpathologie.     Wien,  1897. 

PITRES.     Progr.  med.,  1898.     Revue  de  Med.,  1899. 
TAMBURINI.     Riv.  di  freniatria.     Reggio  Emilia,  1903. 
OPPENHEIM.     Neurol.  Centralbl.,  1909. 
RONCORONI.     Rivista  di  pat.  nervosa  e  mentale,  xvi.,  1911. 
G.  MIRGAZZINI.     Folia  neuro-biologica,  vii.,  1913. 

The  principal  Monographs  relating  to  the  Anatomy  and   Embryology  of  the 
Human  Brain  and  the  Association  Centre  are  :— 

-  DEJERINE.     Anatomie  des  centres  nerveaux.     Paris,  1895. 

FLECHSIG.  Gehirn  und  Seele.  2nd  ed.,  Leipzig,  1896.  Die  Localisation  der  geistigen 
Vorgange.  Leipzig,  1896.  Les  Centres  de  projection  et  d'association  du 
cerveau  humain.  Congr.  intern,  de  med.  Paris,  1900.  Einige  Bemerkungen 
iiber  die  Untersuchungsmethoden  der  Grosshirnrinde,  insbesondere  des 
Menschen.  K.  Siich.  Gesellsch.  d.  Wissensch.  z.  Leipzig,  1904.  Arch.  f.  Anat. 
(u.  Physiol.),  1905. 

G.  MINGAZZINI.  Lezioni  di  anatomia  clinica  dei  centri  nervosi,  Unione  tipografica 
editrice.  Turin,  1908. 


x  THE  FOEE-BEAIN  635 

K.  BRODMANN.     Vergleichende  Localisationslehre  der  Grosshirurindc.      Leipzig, 
1909. 

Cortical  Pathogenesis  of  Epilepsy  :— 

HUGHLINGS  JACKSON.     A  Study  of  Convulsions.     London,  1870. 

FIUTSOH  and  HITZIG.     Arch.  f.  Anat.  u.  Physiol.,  1870. 

FERRIEU.     West  Riding  Luii.  Asyl.  Rep.     London,  1873. 

LUCIANI.     Riv.  sp.  di  freniatria.     Reggio  Emilia,  1878.     Arch.  ital.  per  le  malattie 

nervose.     Milano,  1881. 

ALBEKTONI.     Ann.  univ.  di  med.     Milano,  1879. 
BUBNOFF  and  HEIDENHAIN.     Pfliiger's  Archiv,  xxvi.,  1881. 
FRANCOIS-FRANCK   and   PITRES.      Art.    "Encephale,"    Diet.    enc.    des    sciences 

medicales,  xxxiv.     Paris,  1882.     Arch,  de  physiol.  norm,  et  path.,  1883. 
ROVIGHI  and  SANTINI.     Sulle  conv.  epil.  per  veleni.     Firenze,  1882. 
Novi.     Lo  Sperimentale,  1885. 
ROSENBACH.     Neurol.  Centralbl.,  1889. 
UNVERRICHT.      Arch.  f.  Psych,  u.  Nervenkr.,    1886.      Deutsch.    Arch.   f.   klin. 

Med.,  1889. 

SEPPILLI.     Riv.  sp.  di  fren.     Reggio  Emilia,  1886. 
SORIENTE.     L'Etiologia  e  la  patogenesi  dell'  epilessia.     Naples,  1895. 

Recent  English  Literature  : — 

CAMPBELL.     Histological  Studies  in  Cerebral  Localisation.     London,  1905. 
GORDON  HOLMES  and  PAGE  MAY.     OH  the  Exact  Origin  of  the  Pyramidal  Tracts  in 

Man  and  other  Mammals.     Brain,  1909,  xxxii.  1. 
HORSLEY.     The  Functions  of  the  so-called  Motor  Area  of  the  Brain.     Brit.  Med. 

Journ.,  1909,  ii.  125. 
BASTIAN.     The  Functions  of  the  Kinaesthetic  Area  of  the  Brain.     Brain,  1909, 

xxxii.  327. 
GRAHAM  BROWN  and  SHERRINGTON.     Observations  on   the  Localisation   of  the 

Motor  Cortex  in  the  Baboon.     Journ.  of  Physiol.,  1911,  xliii.  209. 
MOTT,  SCHUSTER,   and  SHERRINGTON.     Motor  Localisation  in  the   Brain  of  the 

Gibbon  correlated  with  a  Histological  Examination.     Proc.  Royal  Soc.,  1911, 

Ixxxiv.  67. 
MOTT.     Progressive  Evolution  of  the  Visual  Cortex  in  Mammalia.     Lancet,  1904, 

ii.  1555. 
BEYERMANN  and  LANGELAAN.     Localisation  of  a  Respiratory  and  Cardio-Motor 

Centre  in  Cortex  of  the  Frontal  Lobe.     Brain,  1903,  xxvi.  81. 
BOLTON.     Functions  of  the  Frontal  Lobes.     Brain,  1903,  xxvi.  215. 
GUSHING.     Note  on  the  Faradic  Stimulation  of  the  Post-Central  Gyrus  in  Conscious 

Patients.     Brain,  1909,  xxxii.  44. 
HEAD  and  HOLMES.     Sensory  Disturbances  from  Cerebral  Lesions.     Brain,  1911, 

xxxiv.  102. 


INDEX   OF   SUBJECTS 


Abducent  nerve,  411 
Absinthe,  convulsions,  581 
Absolute  force,  muscle,  47 
Acetabulum,  100 
Acid,  carbolic,  v.  Phenol 

carbonic,  v.  Carbon  dioxide 

lactic,  muscle,  38,  39 

uric,  muscle,  38 
Acids,  nerve  stimuli,  220 
Acoustic  nerve,  roots,  406 
Action  current,  muscle,  77 

nerve,  210 
Activity,  muscular,  84 

neural,  254 

Aeroplane,  centre  of  gravity,  126 
Aesthesodic  nerve  fibres,  256 
Agenesis,  cerebellum,  455 

nerve  cells,  330 
Agraphia,  629 
Ala  cinerea,  vagus,  393 
Alcohol,  gait,  450 
Alexia,  629 
"  All  or  nothing  "  heart,  13 

reflexes,  317 

Allocheira,  spinal  hemisection,  347 
Amblyopia,  quadrigeminal  lesion,  516 

thalamic  lesion,  522 
Ammonia,  nerve,  220 
Amnesia,  630 
Amphiarthroses,  99 
Amphioxus,  brain,  380 

sinus  ovalis,  494 

"spinal  mind,"  341 
Anabolic  nerves,  82 
Anabolism,  protein,  45 
Anaesthesia,  417 
Anaesthesia  dolorosa,  202 
Anaesthetics,  convulsions,  579 

knee-jerk,  329 

nerve,  211,  212 

spinal  cord,  323 
Anelectrotonic  current,  242 
Anencephaly,  509,  510 
Anisotropy,  muscle,  27 
Anodonta,  nerve  conduction,  205 
Ano-spinal  centre,  352 
Ansa  peduncularis,  492 


Antagonism,  muscle,  35 
Anthropoids,  cortical  localisation,  554 
Ape,  cerebellar  ablation,  444 
Aphasia,  544,  545,  612,  626 
Aphonia,  140 

Aplysia,  oesophageal  rhythm,  32 
Aqueduct,  of  Sylvius,  488 
Arachnoid,  531 
Arbeitssammler,  65,  66 
Area,  auditory,  592,  610 

calcarine,  602 

gustatory,  613,  616 

motor,  594 

olfactory,  527,  613 

sensory-motor,  592 

striata,  602,  603,  604 
dog,  604 
monkey,  607 

visual,  592,  599,  606 
Areas,  architectural,  cerebrum,  536,  540 

association,  592,  616,  618,  632 

hyperalgesic,  308 

projection,  592 
Arm,  movements,  104 
Arsenic,  ganglion  cells,  184 
Arthroses,  99 
Articulation,  155 
Articulations  (joints),  99 
Ash,  muscle,  41 
Asphyxia,  nerve,  231 

nerve  centres,  267,  270 
Association  centres,  592,  616,  618,  632 
Association  fibres,  cerebrum,  532 
Astasia,  cerebellar,  444 
Asthenia,  cerebellar,  442 
Asynergy,  cerebellar,  470 
Ataxy,  cerebellar,  432,  437 

spinal,  298 

tabetic,  469 
Atony,  cerebellar,  443 

spinal,  300 

Atrophy,  cerebellum,  455 
Auditory  area,  dog,  611,  620 
man,  612 
monkey,  610,  612 

nerve,  405 
Aura,  epileptic,  576 


637 


638 


PHYSIOLOGY 


Auricle,  oscillations  of  tonus,  32 
Autonomic  nervous  system,  359 
Autotoniy,  336 
Avalanche  theory,  224 
Axis-cylinder,  179 
Axon,  179 
reflexes,  374 

Balmung,  259 

Barium  salts,  nerve,  219 

Bibliography,  bulb,  417 

cerebellum,  484 

cerebral  localisation,  633 

locomotion,  127 

mid -brain,  524 

muscle,  94 

nerve,  276 

nervous  system,  275 

spinal  cord,  356 

.sympathetic  system,  378 

voice,  173 

Bird,  decerebrate,  500 
Blindness,  cortical  and  psychical,  599 
Blood-vessels,  afferent  nerves,  372 
Bones,  mechanics,  97,  103 
Brain,  amphibia,  497 

Amphioxus,  495 

bibliography,  634 

corvina  nigra,  529 

development,  380 

embryo,  527 

fish,  528 

foetal,  382 

membranes,  531 

psychical  functions,  543 

Scyllium  canicula,  496 

inhibition  of  spinal  reflexes,  319 

Squalius  cephalus,  496 

teleosteau,  and  human,  529 

tortoise,  500 

Brain-stem,  transection,  517 
Bromides,  epilepsy,  579 
Bulb,  380  et  seq. 

consciousness,  416 

convulsions,  581 

grey  matter,  386 

olfactory,  527 

phenol,  415 

posture,  414 

sensory  centres,  415,  416 

spinal  reflexes,  325 

strychnine,  415 
Bundle,  dorsal  longitudinal,  487 

macular,  493 

Caesium  salts,  nerve,  219 
Calamus  scriptorius,  389 
Calcarine  area,  vision,  602 
Calcium  salts,  nerve,  219 

nerve  centres,  275 
Calomel,  electrode,  72 
Caloric  yield,  muscle,  67 
Canaliculi,  neural,  186 


Canals,  semicircular,  461  ct  scq. 
Capillary  electrometer,  72 
Capsule,  internal,  530,  594 
Carbon  dioxide,  muscle,  41 

nerve,  228 

Carcinus  maenas,  unipolar  neurone,  260 
Cardio-accelerator  centres,  spinal,  353 
Cardiogram,  80 
Carnine,  muscle,  38 
Cartilages,  laryngeal,  133 
Cassida  equestris,  muscle,  29 
Catalepsy,  mid-brain  lesion,  518 
Catgut,  contraction,  90 
Cauda  equina,  280 
Caudate  nucleus,  529,  596 
Cells,  nerve,  176,  178 
Centre,  ano-spinal,  352 

cardio-accelerator,  353 

cilio-spinal,  352 

convulsaut,  412 

ideational,  631 

of  centres,  622,  631 

of  gravity,  109,  126 

phonation,  143 

speech,  545,  625 

vesico-spinal,  352 
Centres,  association,  592,  616,  618,  632 

bulbar,  412 

centre  of,  622,  631 

cerebellar,  474,  476 

cortical,  538  et  seq. 

cortical  inhibitory,  565,  566 

laryngeal,  142 

phonation,  143,  553 

projection,  592 

psychical,  616 

respiratory,  352,  412 

secretory,  bulbar,  405 
cortical,  574 
spinal,  352 

thalamic  visual,  521 
Centrum  ovale,  excitation,  561 
Cephalopoda,  velocity  of  nerve  impulse, 

204 

Cercopithecus,  cortex  cerebri,  551 
Cerebellar,  asynergy,  470 

ataxy,  437,  450,  458,  465 

centres,  474 

cortex,  182 

deficiency,  442 

disease,  455  et  scq. 

dysmetria,  450,  460,  470 

gait,  449 

lesions,  431  et  seq. 

localisation,  474,  479 

peduncles,  388,  419,  425,  427,  428 

tracts,  288,  428 

vertigo,  435,  436 
Cerebellum,  419-484 

agenesis,  455 

astasia,    asthenia,    atonia,    442,    443, 
444 

atrophy,  455 


INDEX  OF  SUBJECTS 


G39 


Cerebellum,  bibliography,  484 
co-ordination,  406 

curare,  4:.!f»,  436,  476 

disease,  4f>f>  ft  w//. 

equilibration,  461 

excitation,  435 

i'oived  inoveinents,  432 

functions,  430,  461 

lien's  jf ait,  450 

labyrinth,  461 

lesions,  431  ct  seq. 
man,  458 

lobes,  421 

lobules,  479 

localisation,  474 

muscular  sense,  446,  467 

nuclei,  425 

olivary  connexions,  387,  428 

ontogeny,  473 

orientation,  466 

phenol,  477 

phylogeny,  473 

reinforcement,  483 

sense  organs,  473 

static  function,  471 

sthenic  function,  468,  471 

structure,  424 

strychnine,  477 

surface,  422 

tactile  and  muscular  sense,  446 

tonic  function,  471 

tracts  from  cord,  428 

tract  to  cord,  429,  430 

trophic  function,  472 

tumours,  457 

uncrossed  connexions,  478 
Cerebral  gyri  and  sulci,  531    ' 

hemispheres,  531 

localisation,  538  ct  seq. 
bibliography,  633 

vesicles,  380 
Cerebrospiual  fluid,  281 

preparation,  272,  273 
Cerebrum,  526  et  seq. 

abdominale,  373 

anatomy,  526 

area  striata,  602,  603,  604,  607 

association  areas,  592,  616,  618,  632 

auditory  area,  592,  610 

Brodmann's  areas,  533,  536,  540,  594 

calcarine  area,  602 

cerebellar  lesion,  435,  441,  481,  483 

cortex,  531  et  seq. 

cyto-architectural  areas,  536,  540 

gustatory  area,  613 

lesions,  581  et  seq. 

motor  areas,  546  ct  seq. 

muscular  sense,  582 

myelination,  614,  616 

olfactory  area,  527,  613 

projection  areas,  592 

sensory-motor  area,  592 

visual  area,  592,  599,  606 


Ghost  register,  150 

Chiasma,  optic,  492 

Chimpanzee,  cortical  localisation,  555 

Chorda  tympani,  taste,  403 

Chordograms,  91,  92 

Chloral,  cortex  cerebri,  561,  570 

Chromatolysis,  268 

Ciliary  ganglion,  375 

Cilio-spinal  centre,  352 

nerves,  366 

Cinchonidiiie  ("quinine"),  579 
Circulation,  cortex,  571 
Circus  movements,  quadrigeminal  lesion, 

517 

Clavae,  bulb,  385 
Clot,  muscle,  36,  37 
Cocaine,  muscle,  87 
Coccygeal  ganglion,  360 
Cochlear  nerve,  405 
Collateral  ganglia,  360 
Collaterals,  177,  285 
Column  of  Burdach,  288 

of  Clarke,  283 

of  Goll,  288 

of  Tiirck,  287 

Comniissural  fibres,  cerebrum,  532 
Commissure,  Guddeu's,  493 

optic,  492 
Compensation,    cerebellar   lesions,    439, 

448,  452 
Conduction,  nerve,  192  et  seq. 

spinal  ganglion,  261 

spinal  reflexes,  314 
Consciousness,  bulbo-pontine,  415 

decerebrate,  511 

spinal,  337 

Consonants,  155,  164,  167 
Constant  current,  peripolar  effects,  251 

polar  effects,  245,  251 
Contraction,  catgut,  90 

idio-muscular,  5,  24 

muscle,  7 

mechanism,  85 
secondary,  77 

Pfliiger's  law,  25,  248,  251 

surface  tension,  94 
Contraction  wave,  muscle,  21,  23,    28, 

29 

Contracture,  muscle,  31,  33,  50 
Conus  medullaris,  281 
Convulsions,  absinthe,  581 

anaesthetics,  579 

bulbar  centre,  412 
Co-ordination,  cerebellum,  466 

reflexes,  320 

sympathetic,  377 
Cords,  vocal,  135 
Core  models,  nerve,  243,  257 
Cornea,  Gasserian  ganglion,  331 
Corpora  bigemina,  489 
lesion,  516 

geniculata,  491 

quadrigemina,  488,  513,  515 


640 


PHYSIOLOGY 


Corpora  quadrigemina,  lesion,  516 

striata,  functions,  594 
Corpus  callosum,  530 

epilepsy,  580 

vision,  602 
striatum,  body-temperature,  597 

development,  528 

functions,  595  et  seq. 

nuclei,  529 
Cortex  cerebelli,  182 

cerebri,    association   areas,    592,    616, 
618,  632 

Brodmann's  areas,  533  ct  seq. 

cells,  534 

centre  of  centres,  622 

cercopithecus,  551 

chemical  excitation,  550 

chloral,  561,  570 

ciuchonidine,  579 

circulation,  571 

contracture,  590 

curare,  552 

cytotectonic  types,  536  et  seq. 

excitable  area,  man,  559 

excitation,  560 

Flechsig's  centres,  630 

frontal  lobe,  619 

inhibition,  565 

kidney,  572 

mechanical  excitation,  550 

motor  areas,  546  et  seq. 

phenol,  552 

picrotoxin,  551,  579 

projection  areas,  592 

reflexes,  583 

rhythm,  562,  564 

schema,  539 

sensation,  582 

sensory-motor  areas,  581  et  seq. 

spinal  reflexes,  319 

strychnine,  264,  551 

viscera,  570 

vision,  599 

Cortical  blindness,  dog,  599 
centres,  538  et  seq. 

dog,  548 

macacus,  552 

orang,  556 

phonation,  143 
deafness,  611 
epilepsy,  574 
latency,  561 
lesions,  581  et  seq. 

dog,  585 

man,  590 

monkey,  586 

sensation,  582,  587 
localisation,  538  et  seq. 

anthropoids,  554 

dog,  547 

man,  557 

monkey,  553 

orang,  554 


Corvina  nigra,  brain,  529 

Crab  claw,  muscle,  35 

Cranial  autonomic  system,  361 

nerves,  388  et  seq. 

nuclei,  390 
Craniota,  380 
Creatine,  muscle,  38 
Creatiniue,  muscle,  38 
Crest,  neural,  nerve  development,  236 
Crura  cerebelli,  388,  425,  427,  487 

cerebi'i,  486 
Curare,  caudate  nucleus,  597 

cerebellum,  435,  436,  476 

cortex  cerebri,  552 

muscle,  4 

nerve-endings,  200 
Current,  axial,  nerve,  210 

demarcation,  muscle,  75 
nerve,  209 

of  action,  muscle,  77 
nerve,  210,  215 

of  injury,  muscle,  76 
nerve,  209,  215 

of  rest,  muscle,  69,  73 

nerve,  208 
Currents,  electrotonic,  242  et  seq. 

post-electrotonic,  244 

thermal,  76 

Curvature,  vertebral  column,  112 
Cytotectonics,  brain,  536  et  seq. 

Deafness,  cortical  and  psychical,  611 
Decerebrate  bird,  500 

dog,  506,  509 

fish,  496 

frog,  497,  498 

monkey,  510 

rabbit,  505 

rigidity,  518 

tortoise,  499 
Decussation,  bul bo-spinal,  342,  343 

optic,  493 
Degeneration,  chromatolytic,  268 

nerve,  232 

spinal,  286  et  seq.,  347 
Deglutition,  centre,  553 
Demarcation  current,  muscle,  75 

nerve,  208 

positive  variation,  82 
Dementia,  510 
Dendrites,  179 
Dermatomeres,  279 
Dermatomes,  303,  306 
Dextrin,  muscle,  38 
Dextrose,  muscle,  38 
Diarthroses,  99 
Digitaline,  muscle,  87 
Diphasic  variation,  muscle,  79 

nerve,  216 
Diphthongs,  170 
Dog,  auditory  area,  611 

motor  area,  547 

olfactory  area,  613,  614 


INDEX  OF  SUBJECTS 


641 


Dog,  visual  area,  509 

Dorsal  longitudinal  bundle,  487 

Dura  mater,  281,  531 

Dynamic    phenomena,    cerebellar,    432, 

433,  437 

Dynamograph,  47 
Dynamometer,  47 
Dysarthria  and  dysphasia,  628 
Dysbasia,  460 

Dysmetria,  298,  450,  460,  470 
Dysphasia  and  dysarthria,  628 
Dyspnoea,  vagotomy,  399 
Dystasia,  460 
Dystrophy,  isolation,  312 
nerve  section,  333 


Ego,  divisibility,  338 
Elasticity,  muscle,  85 
Electrical  stimuli,  222 
Electrocardiogram,  82 

vagus,  83 
Electrodes,  calomel,  72 

uonpolarisable,  71 

polarisation,  241 
Electrometer,  capillary,  72 
Electrophysiology,  muscle,  68  ct  scq. 

nerve,  208  ct  scq. 
Electrotonic  currents,  ether,  244 

excitability,  244 
Electrotonus,  240 
Eledone,  nerve,  216 
Embrace  reflex,  311,  512 
Embryo  brain,  527 
Emys  Europaea,  auricular  tonus,  32 
brain,  500 

palustris,  reflexes,  324 
Energy,  kinetic,  muscle,  45 

source  of  muscular,  42 
Epiglottis,  134 
Epilepsy,  574 

bibliography,  635 

body  temperature,  576 

bromides,  579 

corpus  callosum,  580 

subcortical  factors,  577 

tonus  and  clonus,  577 
Equilibration,  cerebellum,  461 

posture,  110 
Erect  posture,  111 
Ergograms,  49 
Ergograph,  48,  57 
Eunuch,  voice,  148 
Excitability,  electrotonic,  245 

muscle,  3 

nerve,  224 

post-electrotonic,  245 
Excitation,  high  frequency,  19 

law  of,  223 

Excito-motor  system,  341 
Expression,  130 
Extractives,  muscle,  38 
Eye,  extirpation,  visual  cortex,  603 

VOL.  Ill 


Facial  nerve,  406 

distribution,  407 

function,  408 
Facilitation,  259 
Falsetto  register,  151 
Fascia  dentata,  181 
Fat,  in  muscle,  40 
Fatigue,  central,  51,  271 

fasting,  56 

food,  51 

in  vivo,  49 

mental  and  muscular,  50 

muscle,  38,  48,  53,  59 
factors,  59 
temperature,  11 

nerve,  207,  225 

peripheral,  51 

practice,  56 

recovery,  53 

spinal,  50 

Femur,  mechanics,  98 
Fibrin,  proteolytic  products,  45 
Fillet,  bulb,  385 

mid-brain,  487 

optic  thalami,  521 
Fish,  decerebrate,  496 

hearing,  406 
Foot,  mechanics,  112 
Force,'  absolute,  47 
Forced  movements,  432  ct  seq. 
Fore-brain,  development,  526 
Formant  tone,  162 
Formatio  reticularis,  388,  413 
Fractional  heat  coagulation,  muscle,  37 
Frog,  balancing,  498,  499 

decerebrate,  497 
Frontal  lobe,  619 

intellect,  624 

man,  622 
Funiculus  cuneatus,  288 

gracilis,  288 

Gait,  cerebellar,  dog,  438,  449,  451 
man,  458 
monkey,  451 

man,  alcohol,  450 
Galvanometer,  mirror,  70 

string,  73 

Galvanotonus,  251,  253 
Ganglia,  basal,  528 

glossopharyngeal,  401 

spinal,  261,  284 

sympathetic,  360  et  seq. 

vagal,  393,  396 
Gangliated  plexuses,  378 
Ganglion  cells,  180 

function,  260 
Ganglion,  ciliary,  375 

coccygeal,  360 

Gasserian,  331,  409 

inferior  mesenteric,  370 

Meckel's,  409 

nodosum,  396 

2T 


642 


PHYSIOLOGY 


Ganglion,  petrosal,  401 

reflexes,  373 

solar,  373 

sphenopalatine,  403 

spiral,  405 

stellate,  nicotine,  368 

stellatum,    cephalopoda,     strychnine 
and  phenol,  264 

superior  cervical,  branches,  363 

nicotine,  368 
Gas  chamber,  231,  232 
Gases,  muscle,  41 
Gasserian  ganglion,  331,  409 
Gemmules,  179 
Genito-spinal  centres,  352 
Glossopharyngeal  nerve,  401 

functions,  404 

motor  fibres,  405 

salivation,  405 

section,  404 

taste,  401 
Glottis,  135  et  seq. 

phonation,  144 

spinal  accessory,  394 
Glycerol,  nerve,  219 
Glycocoll,  muscle,  38 
Glycogen,  inanition,  39 

muscle,  38,  39 

Gorilla,  cortical  localisation,  555  ' 
Gravity,  centre  of,  107 
Grey  matter,  excitability,  262 

post-mortem  acidification,  270 
summation,  262 
rami,  372 
Gustatory  area,  613,  616 

Harmonics,  131 

Hearing,  cerebrum,  592,  610 

fish,  406 

quadrigeminal  lesion,  516 
Heart,  cortex  cerebri,  573 

equipoteutial  lines,  81 

positive  variation,  82 

voluntary  acceleration,  573 
Heat,  effect  on  muscle,  10,  18,  76 
nerve,  211,  218 

production,  muscle,  59  ct  seq. 

nerve,  207 

Hebphanomen,  298,  299 
Hemianaesthesia,  man,  592 
Hemianopsia,  522,  599,  601,  608 
Hemiplegia,  342,  581,  592 
Hemisection,  spinal  cord,  344 
Hind-brain,  419-485 
Hippocampus,  614 
Horizontal  posture,  110 
Hyperaesthesia,  cortical  lesion,  582 

spinal  lesion,  341 
Hyperalgesia,  cutaneous,  308 
Hypnosis,  decerebration,  518 
Hypogastric  nerve,  373 
Hypoglossal  nerve,  dorsal  root,  389 
functions,  390 


Hypoglossal  nerve,  origin,  389 

paralysis,  392 

recurrent  sensibility,  392 
Hypoxanthine,  muscle,  38 

Ideational  centre,  631 
Idio-muscular  contraction,  5 
Inanition,  muscular  metabolism,  38 

nerve-centres,  269 
Inductorium,  221 
Infancy,  speech  centres,  626 
Inhibition,  cortical,  565 

skeletal  muscle,  35 

spinal,  319 

temperature,  35 
Injury  current,  muscle,  76 

nerve,  208,  215 
Innervation,  larynx,  140,  394 

limbs,  305 

muscles,  303 

overlap,  305 

pharynx,  397 

reciprocal,  320 

skin,  300  et  seq. 
Inogenetics,  muscle,  93 
Inosite,  muscle,  38 
Inotagmata,  90 
Insertion,  muscles,  105 
Intellect,  active  and  passive,  630 

parietal  gyri,  624 

sulci,  624 

Intermediolateral  tract,  367 
Internal  capsule,  530,  594 
Intoxication,  fatigue,  59 
Iron,  muscle,  41 
Irradiation,  reflexes,  315 
Island  of  Reil,  555 
Isometry,  muscle,  14 
Isotony,  muscle,  14 

Joints,  99-102 

Katabolic  nerves,  82 
Katelectrotonic  current,  242 
Kidney,  cortex  cerebri,  572 
Kinesodic  nerve-fibres,  256 
Kinetic  energy,  muscle,  45 
Knee-jerk,  326 

cerebellar  disease,  459 

conditions,  329 

decapitation,  329 

latency,  327 

nervous  mechanism,  330 

reinforcement,  330 

sleep,  329 

spinal  disease,  329 
transection,  329 

Labyrinth,  lesions,  299,  406 

tonus,  464,  466 
Lactic  acid,  muscle,  38,  39 


INDEX  OF  SUBJECTS 


643 


Language,  cortical  mechanism,  625 

evolution,  172 

peripheral  mechanism,  129 

written,  172 
Laryngeal  cartilages,  133,  134 

ligaments,  134 

muscles,  136 

nerves,  14CL394 
centres,  142 
origin,  395 

respiration,  141 
Laryngoscope,  145 
Larynx,  1 33  et  scq. 

innervation,  394 

mechanics,  143 

spinal  accessory,  394 

vagotomy,  399 
Latency,  cortical,  561 

electrotonic,  246 

knee-jerk,  327 

muscle,  8,  9 
Lateral  ganglia,  360 

ventricles,  490 
Law,  Bell-Magendie,  292 

myelogenetic,  616 

of  contractions,  25,  248 

of  nerve  conduction,  197 

of  reflexes,  Pfliiger,  314 

Ritter-Valli,  232 
Lecithin,  muscle,  40 
Lenticular  nucleus,  596 
Levers,  bones,  103 
Life,  internal  and  external,  1 
Ligaments,  99,  101 
Limbs,  centres,  352 

metamerism,  305 

trophic  nerves,  332 
Lingual  nerve,  373 
Load,  muscle  twitch,  13 
Lobe,  frontal,  619 

occipital,  599,  606 

olfactory,  528 

parietal,  624 

temporal,  610 
Lobule,  olfactory,  527 
Lobules,  of  cerebellum,  479 
Localisation,  cerebellum,  474,  479 

cerebrum,  538  et  seq. 
Locomotion,  96-128 

bibliography,  127 

chronophotograms,  116,  117,  118 

gait,  126 

galloping,  124 

jumping,  124 

mechanics,  97 

oscillations,  121 

pace,  118 

pressure,  119 

swimming,  125 

walking,  114 
curves,  116 

work,  97 
Lumbricus,  neurofibrils,  185 


Macula  lutea,  visual  area,  609 
Malapterurus,  velocity  of  nerve  impulse, 

204 

Maltose,  muscle,  38 
Man,  auditory  area,  612 

motor  area,  559 

smell,  615 

visual  area,  607 
Mass,  centre  of,  107 
Masticatory  nerve,  410 
Maximum  work,  52 
Mechanical  stimuli,  220 
Mechanics,  bones,  97 

foot,  112 

larynx, 143 

muscles,  102 

posture,  107 

vertebral  column,  111 
Medulla  oblongata,  380-418 

bibliography,  417 

centres,  412 

posture,  414 

spinal  reflexes,  325 

tracts,  383 
Membranes,  brain,  531 

spinal  cord,  281 
Memory,  340,  509,  545,  599,  631 

unconscious,  341 

verbal,  630 
Mesencephalon,  381,  486-525 

development,  486 

excitation,  512 

lesions,  494  et  seq. 

spinal  reflexes,  319 
Metameres,  Amphioxus,  495 
Metamerism,  bibliography,  356 

limbs,  305 

trunk,  301,  303 
Metencephalon,  381 
Microcephaly,  510 
Micturition,  inhibition,  319 
Mid-brain,  486 

ablation,  fish,  497 
frog,  498 
toad,  499 

bibliography,  524 

hemisection,  518 

lesion,  rabbit,  505 
tortoise,  500 

tortoise,  500 

Moments,  muscular,  105,  106 
Monkey,  area  striata,  607 

auditory  area,  610 

motor  area,  552  et  scq. 

olfactory  area,  613 

visual  area,  606 
Muscle,  1-95 

absolute  force,  47 

acidity,  40,  41 

action  current,  77 

activity,  lactic  acid,  39 

Amici's  line,  27 

anisotropy,  27 


644 


PHYSIOLOGY 


Muscle,  ash,  41 
bibliography,  94 
chemical  energy,  88 
chemistry,  36 
circulation,  5 
clot,  36 

Cohnheim's  areas,  26 
contraction,  7  et  seq. 

optical  changes,  28 
contracture,  31 
curare,  4 
current  of  action,  77 

of  rest,  69,  73 
diphasic  variation,  79 
discs,  91 
disuse,  6 
efficiency,  67 
elasticity,  85 

fatigue,  87 

poisons,  87 
electrical  wave,  93 
electro-physiology,  68 
energy,  42,  93 
excitability,  3 
extractives,  38 
fatigue,  48,  52 

temperature,  11 
fats,  40 
fibres,  26 
fibrils,  27 

fixed  contraction  wave,  28 
fractional  heat  coagulation,  37 
galvauogram,  78 
gases,  41 
heat,  production,  59 

tension,  65 

fatigue,  65 
histology,  2,  25 
inhibition,  35 
injury  current,  76 
inogenesis,  93 
intensity  of  stimulus,  13 
isotony  and  isometry,  14 
kinetic  energy,  45 
Krause's  membrane,  27 
latency,  8,  9 

of  inhibition,  36 
load,  53 

mechanical  work,  46 
mechanism  of  activity,  84 
metabolism,  nitrogenous,  42 

starvation,  38 

work,  39,  40 
nuclei,  25 

optical  properties,  27 
phosphates,  39 
pigments,  38 
plasma,  36 
proteins,  37 
proteogenesis,  45 
proteolysis,  44 
proteose,  37 
quick  and  sluggish  fibres,  10 


Muscle  reaction,  39,  40 

recovery,  12 

red  and  pale,  9,  24 

relaxation,  14,  30,  88 

respiration,  42 

rigor  mortis,  36 

salts,  41 

sarcolemma,  25  , 

sarcomeres,  27 

sarcoplasm,  26 

secondary  contraction,  77 

serum,  36 

simple  twitch,  8 

sound,  19,  31 

staircase  contraction,  11 

survival,  5 

tension,  30 

tetanus,  33 

thermal  currents,  76 

thermodynamic  theory,  89 

thermo-electric  theory,  92 

thermogenesis  and  inogenesis,  93 

tonus,  30 

inhibition,  35 
oscillation,  32 

trophic  influence  of  central  nervous 
system,  6 

twitch,  load,  13,  16 
temperature,  10,  16 
veratrine,  31 

volume,  contraction,  21 

voluntary  contraction,  19 

water  content,  41 

wave,  21,  24 

Weber's  paradox,  86 

work,  diet,  44 
heat,  62.  66,  67 
respiration,  62 
Muscles,  insertion,  105 

laryngeal,  136 

mechanics,  102,  105,  106 

metamerism,  306 

monomeric  and  polymeric,  306 

resolution  of  forces,  105 
Muscular  sense,  cerebellum,  446,  467 

cerebrum,  582 
Musculin,  38 
Musical  instruments,  132 
Myelencephalon,  381 
Myelination,  cerebrum,  614,  616 

spinal  cord,  290 
Myelomeres,  279,  310 
Myoalbumiu,  38 
Myoglobulin,  38 
Myograms,  6 
Myograph,  6,  22 
Myohaematin,  38 
Myomeres,  279 
Myosin,  36,  37 
Myosinogen,  37 
Myotomes,  303 

Narcosis,  310 


INDEX  OF  SUBJECTS 


645 


Negative  variation,  muscle,  77 

nerve,  210 

Nerve,  abducens,  411 
activity,  nature,  254,  256 

i<mir  theory,  259 
alkali,  220 
auabolism,  207 
anaesthetics,  211,  212 
asphyxia,  231 
auditory,  405 
autogenesis,  236 
axial  current,  210 
bibliography,  276 
carbou  dioxide,  228 
cells.  176  et  scq. 

agenesis,  330 

arsenic,  184 

artefacts,  190 

caualiculi,  186 

chromatolysis,  268,  269 

fatigue,  268 

metabolism,  268 

Nissl  granules,  189 

regeneration,  268 
centres,  259  et  scq. 

agenesis,  330 

alkali,  274 

anaemia,  266 

asphyxia,  267,  270 

atrophy,  330 

bibliography,  276 

bulbar,  412 

calcium  salts,  275 

circulation,  266 

facilitation,  259 

fatigue,  271 

heat  paralysis,  271 

inhibition,  259 

metabolism,  266,  269,  271 

perfusion,  274 

poisons,  264 

respiration,  272,  273 

respiratory  quotient,  273 

rhythm,  21,  263 

salts,  274 

spinal,  352  et  scq. 
cochlear,  405 
compression,  193 
conduction,  192,  257,  258 

degeneration,  254 

electrotonic,  247,  254 

oxygen,  205 
core  models,  243,  257 
current  of  action,  210,  211,  215 

of  rest,  208,  209 
degeneration,  232 
diphasic  action  current,  216 
double  conduction,  197,  200 
drugs,  212,  214 
effect  of  salts,  212,  219 
electrical  stimuli,  222 
electrophysiology,  208  et  seq. 
electrotonic  currents,  242 


Nerve,  electrotonus,  240 
excitability,  224 

and  conductivity,  229 

oxygen,  230 
facial,  406 
fatigue,  227,  228 
iluid,  255 

forward  conduction,  197 
galvanic  excitability,  248 
gas  chamber,  231,  232 
gases,  212 

glossopharyngeal,  401 
hypogastric,  373 
hypoglossal,  389 
impulse,  temperature,  205 

velocity,  202,  205 
factors,  205 

wave  length,  215 
inexhaustibility, '207,  225 
isolated  conduction,  196 
lingual,  373 
masticatory,  410 
mechanical  stimuli,  220 
metabolism,  206 
oculomotor,  411 
optic,  492 
oxygen,  207 
polarisation,  242 

after  effect,  250 
post-electrotonic  current,  244 
reaction  of  degeneration,  253 
regeneration,  234 
respiration,  231 
Hitter- Valli  law,  232 
roots,  Bell-Magendie  law,  292 

bibliography,  356 
section  of,  232,  268 
specific  functions,  262 
stimuli,  217 
strychnine,  207 
survival,  225 
syncytium,  235 
temperature,  218 
tetanisation,  213 
thermogenesis,  207 
trigeminal,  409 

taste,  403 

trophic  action,  331 
tripolar  excitation,  250 
trochlear,  411 
trophic  centres,  233 
vestibular,  405 

Nerves,  afferent  and  efferent,  293 
centripetal  and  centrifugal,  293 
cranial,  388 
laryngeal,  140,  394 
trophic,  331 
Nervous    system,    general    physiology, 

175-277 

morphology,  bibliography,  275 
plan,  176 

Neural  crest,  nerve  development,  236 
Neurite,  179 


646 


PHYSIOLOGY 


Neuro  blasts,  182 
Neurofibrils,  183 
Neuromeres,  279 
Neurone  theory,  179,  180,  191 
Neurones,  development,  179 

unipolar,  260 
Neuropile,  260 
Neurotaxis,  235 
Nicotine  method,  367 
Nitrogenous  metabolism,  muscle,  42 
Nodus  cursorius,  596 
Non-polarisable  electrodes,  71 
Nuclei,  corpus  striatum,  529 

cranial  nerves,  390 

optic  thalamus,  491 
Nucleus  anibiguus,  401 

Bechterew's,  428 

caudate,  529,  596 
curare,  597 
lesion,  596 

Deiters',  288,  428 

dentatus,  425 

emboliformis,  425 

fastigii,  425 

globosus,  425 

lenticular,  529 
excitation,  596 
lesion,  596 

red,  426 

Rollers's,  389 

Stilling's,  283 
Nystagmus,  cerebellar,  432 

Occipital  lobe,  vision,  599,  606 
Octopus,  nerve,  216 
Oculomotor  nerve,  411 
Olfactory  apparatus,  527 
area,  527,  613,  614,  621 
lobule,  527 
tract,  527,  615 
trigone,  528 
Olive,  bulb,  387 

cerebellar  tracts,  429 
cerebellum,  387,  428 
vertigo,  436 

Optic  chiasma,  492,  495 
lobes,  bird,  513 

excitation,  512 

frog,  512 

lesion,  516 

phenol,  513 

strychnine,  513 
nerves,  492 
thalami,  490 

cortical  connexion,  521 

excitation,  520 

functions,  521 

hemianopsia,  522 

lesion,  522,  524 

nuclei,  491 

smell  and  taste,  523 

vision,  521,  522 
tract,  493 


Orang-outang,  cortical  localisation,  554 
Orientation,  cerebellum,  466 
Overlapping  nerve  fields,  303 
Over-tones,  131 
Oxidation,  animal,  43 
Oxygen,  muscle,  41 
rigor  mortis,  42 

Pallium,  526 

Panophthalmitis,  trigeminal  section,  331 

Paraplegia,  342 

Parietal  lobe,  intellect,  624 

Pars  opercularis,  545 

Peduncles,  cerebellar,  388,  425,  427,  487 

cerebral,  486 
Peripheral  reflexes,  378 
Pharynx,  innervation,  397,  405 
Phenol,  bulb,  415 

cerebellum,  477 

cortex  cerebri,  552 

optic  lobes,  513 

spinal  cord,  264 
Phonation,  130 

bulbar  centre,  143 

cortical  centre,  553 

glottis,  144,  145 

mid-braiii  lesion,  517 

pressure,  146 

resonance,  147 
Phonophotography,  131 
Phrenology,  542 
Physostigmiue,  muscle,  87 
Pia  mater,  531 

Picrotoxin,  cortex  cerebri,  551,  579 
Pigeon,  decerebrate,  500 
Pigments,  muscle,  38 
Pitch,  sound,  132 
Planimetry,  spinal  cord,  282 
Plasma,  muscle,  36 
Plexus,  brachial,  280,  301 

cardiac,  398 

coeliac,  398 

lumbo-sacral,  280,  301 

oesophageal,  398 

pharyngeal,  397 
pulmonary,  398 
Plexuses,  gangliated,  378 
Pneumonia,  vagotomy,  399 
Polarisation,  after  effect,  250 

electrodes,  241 
Pons  Varolii,  413  el  seq. 
sensibility,  416 
structure,  420 
Post-cellular  fibres,  369 
Post-ganglionic  fibres,  368 
Posture,  cerebellar  lesions,  432 
equilibration,  110 
erect,  111 
expression,  130 
mechanics,  107 
sitting,  110 

Potassium  salts,  muscle,  41 
nerve,  219 


INDEX  OF  SUBJECTS 


647 


Precellular  fibres,  369 
Preganglionic  fibres,  368 
Prevertebral  ganglia,  360 
Progression,  bulbar  centre,  413 
Projection  areas,  cerebrum,  592 

fibres,  cerebrum,  532 

of  sensation,  202 

retino-cerebral,  600 
Prosencephalon,  380,  526-635 
Protein,  lactic  acid,  39 

metabolism  muscle,  43,  45 
Proteogenesis,  muscle,  45 
Proteolysis,  muscle,  44 

products,  45 
Proteose,  muscle,  37 
Pseudo-reflexes,  374 
Psychical  blindness,  dog,  599 
man,  609 

deafness,  611 

functions,  623 

bulbar  and  pontine,  415 
spinal,  311 
Puberty,  voice,  148 
Ptilvinar,  490 

lesion,  523 

vision,  522 
Pyramidal  tracts,  287  et  seq. 

comparative  anatomy,  342 

origin,  593 

Quasi-consciousness,  bulb  and  pons,  415 
Quasi-reflexes,  374 

Kami  communicantes,  365 
Reciprocal  inuervation,  320,  569 
Recitation,  153 
Recurrent  laryngeal  nerve,  140 

sensibility,  294,  392 
Reflex  action,  310  et  seq. 
final  common  path,  323 
receptive  field,  322 
receptors,  321 

arc,  322 

scratch,  321 
Reflexes,  allied,  323 

antagonistic,  323 

axon,  374 

long  and  short,  313 

Pfliiger's  laws,  314 

spinal,  313 

bibliography,  356 

spread,  313 

sympathetic,  peripheral,  378 
Refractory  period,  spinal  cord,  265 
Regeneration,  nerve,  234 
Reinforcement,  cerebellar,  483 

dorsal  spinal  roots,  297 

sympathetic  ganglia,  376 
Relaxation,  active,  30 

muscle,  88 
Resolution,  forces,  105 

tones,  131 
Resonators,  131 


Respiration,  cortical  excitation,  570 

laryugeal,  141 

muscle,  42 

nerve,  231 

Respiratory  centres,  bulbar,  412 
spinal,  352 

quotient,  muscle,  42 
nerve-centres,  273 
Rheochord,  75 
Rhinophones,  165 
Rhythm,  cortex  cerebri,  562,  564 

oesophageal,  Aplysia,  32 

tremor,  563 

Rigidity,  decerebrate,  518 
Rigor  mortis,  36,  42 
Rubidium  salts,  nerve,  219 
Running,  curves,  122 

Sacral  autonomic  system,  361,  372 
Salivary  glands,  trophic  nerves,  332 
Salivation,  glossopharyngeal,  405 
Salts,  nerve  stimuli,  219 
Sarcolemma,  25 
Sarcomeres,  27 
Sarcoplasm,  26,  33 
Sartorius,  contraction  wave,  23 

innervation,  5 
Scratch  reflex,  321 
Secondary  contraction,  77 
Secretion,  cortex  cerebri,  574 
Secretory  centres,  bulbar,  405 

cortical,  574 

spinal,  352 
Segmental  limb  fields,  304 

muscular  fields,  303 

skin  field,  303 
Semivowels,  164 
Sensation,  projection,  202 
Sensory-motor  area,  cortex,  581 

dog,  621 

man,  589 

monkey,  552 
Sensory  sphere,  dog,  583,  584 

macacus,  587 
Sentences,  171 
Serum,  muscle,  36 
Ship,  centre  of  gravity,  126 
Shock,  294,  312,  336,  351,  353 

duration,  312 

inhibition,  312 
Shoes,  recording,  115 
Sigmoid  gyrus,  547 
Singing,  art,  153 
Sinus  ovalis,  amphioxus,  494 
Sitting  posture,  110 
Skin,  innervation,  303  et  seq. 

trophic  nerves,  332 
Sleep,  knee-jerk,  329 
Smell,  pulvinar,  523 
Solar  ganglion,  373 
Sound,  muscle,  19 

physics,  130,  131 
Specific  nerve  energy,  262 


648 


PHYSIOLOGY 


Speech,  625 

centre,  545,  625 
development,  171 

Sphincter  ani,  extra-spinal  centres,  354 
Spinal  accessory,  dyspnoea,  394 

functions,  394 

larynx,  394 

nerve,  392 

nuclei,  393 

animal,  convulsions,  412 
cat,  315 

centres,  rhythm,  324 
Spinal  cord,  278-358 

ablation,  353 

anaesthetics,  323 

ascending  degeneration,  289 

at  birth,  286 

automatism,  323 

bibliography,  356 

Burdach's  tract,  288 

cell  groups,  283 

centres,  351 

cerebellar  lesion,  429 
tracts,  288 

Clarke's  column,  283,  288 

convulsions,  581 

degeneration  from  hemisection,  347 

descending  degeneration,  290 

dorsal  column,  285,  289,  350 
roots,  284,  293,  295,  296 

endogenous  fibres,  289 

fatigue,  50 

Coil's  tract,  288 

Gower's  tract,  288 

grey  matter,  290 

ground  bundle,  289 

hemisection,  344 

lateral  columns,  346 

long  tracts,  341 

membranes,  281 

motor  and  sensory  decussation,  343 

motor  path,  345 

Miiller's  preparation,  292 

myelination,  290 

nerve  roots,  290 

pathic  path,  290,  345 

phenol,  264 

pseudo-psychical  functions,  338 

pyramidal  tracts,  287,  342 

reflex  functions,  310 

refractory  period,  265 

respiration,  272,  273 

SchifF's  criteria,  344 

scratch  reflex,  321 

segmental  relations,  301 

sensory  paths,  350 

Stilling's  nucleus,  283 

strychnine,  264 

tactile  path,  345 

tonic  functions,  323 

tracts,  286  et  scq. 

"  unconscious  memory,"  341 

unilateral  lesions,  man,  349 


Spinal  cord,  vasomotor  nerves,  294 
ventral  zone,  289 
visceral  functions,  354 
white  matter,  284 
dog,  316 
frog,  316,  335 
ganglion,  conduction,  261 
lesions,  dystrophies,  353 

shock,  353 

mind,  amphioxus,  341 
nerve  roots,  280 
nerves,  279,  280 
metamerism,  301 
pigeon,  316 

preparation,  Baglioni,  272 
rabbit,  318 
rat,  316 

reflexes,  circulation,  318 
condition  of  centres,  318 
conduction,  314 
co-ordination,  320,  335 
duck,  337 

facilitation,  319,  321 
inhibition,  319,  321 
irradiation,  315 
man,  327,  337 
stimuli,  316,  317 
symmetry,  314 
tonus,  oscillations,  324 
Staircase  contraction,  11 
Status  epilepticus,  575 
Stellate  ganglion,  cepalopoda,  378 
Stimuli,  experimental,  217,  218 
adequate,  217 
chemical,  219 
electrical,  222 
high  frequency,  223 
mechanical,  220 
specific,  217 
summation,  17 
thermal,  218 
String  galvanometer,  73 
Strontium  salts,  nerve,  219 
Strychnine,  bulb,  415 
cerebellum,  477 
cortex  cerebri,  264,  551 
optic  lobes,  513 
spinal  cord,  264 
Snbstantia  nigra,  487 
Sugars,  nerve,  219 
Sulcus  cruciatus,  547 
Summation,  of  stimuli,  17 
Superior  cervical  ganglia,  corneal  ulcer, 

331 

laryngeal  nerve,  142 
Super-position  of  contractions,  17 
Surface  tension,  contraction,  94 
Survival,  muscle,  5 
nerve,  225 
spinal  cord,  272 
Swimming,  125 
Syllables,  170 
accent,  171 


INDEX  OF  SUBJECTS 


649 


Syllables,  quantity,  171 
Sylvian  aqueduct,  488 
Sympathetic  ganglia,  360  et  scq. 

analogies,  377 

co-ordination,  377 

functions,  373 

tonic  action,  375 
fibivs,  362 

afferent,  370 

analogies,  377 

Bell-Magendie  law,  292,  365 

efferent,  364 

nerves,  distribution,  363 
system,  359-379 

anatomy,  360 

bibliography,  378 

physiological  analysis,  365 

schema,  371 
Synarthroses,  99 
Synchoudroses,  99 
Syncytium,  neural,  183 
Synovia,  99 

Tabes,  ataxy,  469 

hyperalgesia,  309 
Tactile  sense,  cerebellum,  446 
Tambour  myograph,  22 
Taste,  chorda  tympani,  403 

cortex  cerebri,  616 

facial  paralysis,  403 

glossopharyngeal,  401 

nerves,  401 

pulvinar,  523 
Taurine,  muscle,  38 
Tegmentum,  486 
Telencephalou,  526 
Temperature,  corpus  striatum,  597 

muscle,  fatigue,  11 
inhibition,  35 

muscle  twitch,  10 

nerve,  218 

impulse,  205 
Temporal  lobe,  excitation,  610 

lesion,  610 
Tension,  muscle,  work,  65 

heat,  65 

Terminal  ganglia,  360 
Testis,  trophic  nerves,  332 
Tetanomotor,  221 
Tetanus,  muscle,  17 

opening,  25 
Thalamencephalon,  381 

development,  489 
Thelephorus     melanurus,      contraction 

wave,  28 

Thernio-galvanograms,  muscle,  61 
Thermogenesis,  methods,  60 

muscle,  59 

nerve,  207 

Thermometer,  Baudin's,  61 
Thermopile,  muscle,  60 
Timbre,  131 
Titubatiou,  cerebellar,  444 


Toad,  phenol,  and  strychnine,  265 
Tone,  muscular,  see  Tonus 
Tones,  fundamental,  131 

partial,  131 

resolution,  131 

vowel,  158 
Tonus,  muscle,  31 

cerebellar,  466 

labyrinth,  464 

oscillation,  muscle,  33 

spinal,  323 

Tortoise,  decerebrate,  499 
Tract,  Burdach's,  288 

direct  cerebellar,  288 

Coil's,  288 

Gower's,  288 

intermediolateval,  367 

olfactory,  527,  615 

optic,  493 

pyramidal,  287,  342,  593 

Tiirck's,  287 

Tracts,  cerebellar,  288,  385,  428,  430 
Tremor,  rhythm,  563 
Trigemiual  nerve,  409 

distribution,  409 

functions,  410 

paralysis,  410 

roots,  409 

Trigone,  olfactory,  528 
Tripolar  excitation,  250 

polarisation,  247 
Trochlear  nerve,  411 
Trophic  nerves,  331 

function,  cerebellum,  472 
Twitch,  muscle,  8 

Unconscious  memory,  341 
Unipolar  nerve  cell,  conduction,  261 

neurone,  Carcinus,  260 

stimulation.  251 
Urea,  muscle,  38 

nerve,  219 
Uric  acid,  muscle,  38 

Vagotomy,  398 

Vagus  nerve,  392  el  seq. 

branches,  393 

cardiac  fibres,  396 

distribution,  397,  402 

electrocardiogram,  83 

nuclei,  393 

reflex  vomiting,  397 

velocity  of  nerve  impulse,  204 
Valve,  of  Vieusseus,  420 
Variation,  diphasic,  muscle,  79 
nerve,  216 

negative,  77,  210,  215 

positive,  76 

Vasomotor  centres,  spinal,  352 
Velocity,  muscle  wave,  23 

nerve  impulse,  202,  205 
Ventricle,  fourth,  389 

of  Morgagni,  135 


650 


PHYSIOLOGY 


Ventricles,  lateral,  490 
Veratrine,  muscle,  31,  34 
Verrnis,  lesions,  432,  478 
Vertebral  column,  111 

ganglia,  360 
Vertigo,  cerebellar,  435 

galvanic,  436 

olivary,  436 

vestibular,  436 
Vesicles,  cerebral,  380 
Vesico-spinal  centre,  352 
Vestibular  nerve,  405 

section,  405 
Viscera,  afferent  nerves,  372 

cortical  excitation,  570 

innervation,  370 
Visceral  disease,  cutaneous  hyperalgesia, 

308 
Vision,  calcariue  area,  602 

pulvinar,  524 
Visual  area,  599 

dog,  602,  620 

man,  602,  607 

monkey,  606 
Vocal  cords,  135 

pbonatiou,  147 
Voice,  127-174 

bibliography,  173 

compass,  148 

crescendo,  decrescendo,  152 

qualities,  149 

recitation,  153 


Voice  registers,  150 

singing,  148 

Volume-contraction,  muscle,  21 
Vowel  analysis,  160 

sounds,  nasal,  164 

tones,  158,  160 

resonance,  159 
Vowels,  155,  157 

diphthongs,  158 

flame  pictures,  161 

formant  tone,  162 

pitch,  163 

Wave,  contraction,  21 

White  rami,  366 

Word  blindness,  609,  628 

deafness,  612,  628 

memory,  630 
Words,  formation,  170 
Work,  and  metabolism,  muscle,  43 

and  respiration,  muscle,  43 

locomotion,  97 

maximum,  53 

Xanthine,  muscle,  38 

Yellow  spot,  cortical  representation,  609 

Zinc  electrodes,  71 
Zinc  salts,  nerve,  220 
Zones,  cutaneous,  308 


INDEX  OF  AUTHOES 


ABELOUS,  fatigue,  '227 
D'ABUNDO,  corpus  striatum,  595 

optic  thalamus,  595 
AUAMKIEWICZ,  cortex,  secretion,  574 
ADAMUK,    corpora   quadrigemina,    513, 
517 

medulla  oblongata,  418 
ABLER,    cerebellar    lesions,     455,    458, 

459,  484 

ADRIAN,  nerve,  conduction,  276,  277 
AEBY,  contraction  wave,  24 
AFANASIEFF,  nerve,  temperature,  218 
AIKIN,  voice,  174 
ALBERTONI,  epilepsy,  579,  580,  635 

cortical  excitation,  560 
lesion,  582 

optic  lobes,  512 
ALBRECHT,  nerve,  electrical  excitation, 

224 

ALCMEON,  brain,  538 
ALCOCK,  taste,  402,  403 

nerves,  277 

ALDEHOFF,  glycogen,  inanition,  39 
ALDINI,  animal  electricity,  68 
AMICI,  line,  muscle,  27 

muscle  mechanism,  91 
ANDERSON,  hypogastric  nerve,  373 

sympathetic,  367,  368,  378 

white  rami,  366 
ANDRAL,  cerebellum,  484 
ANREP,  muscle  elasticity,  87 
APATHY,  neuronbrils,  185,  262 

neurone  theory,  183,  275 
ARAKI,  lactic  acid,  muscle,  39 
ARISTOTLE,  intellect,  631 
ARLOING,  nerve  conduction,  198 

sensory  roots,  294,  356 
D'ARSONVAL,  electrodes,  71 

high  frequency  excitation,  19 

muscle,  contraction,  94 
energy,  92 
thermopile,  60 
ASCOLI,  semi- vowels,  173 
AUERBACH,  plexus,  378 

spinal  cord,  339 

vowels,  160,  173 


BABINSKI,  asynergy,  470 

BABUCHIN,  nerve  conduction,  199,  204 

v.  BAEYER,  nerve  asphyxia,  230 

oxygen,  206 
BAGINSKI,  corpus  striatum,  596 

8th  nerve,  405 
BAGLIONI,  articulation,  165  ct  seq. 

bulb,  sensory  centres,  415 

cortex  cerebri,  550,  634 

dorsal  roots,  300 

electric  organs,  93 

grey  matter,  263 

medulla  oblongata,  418 

mid-brain,  525 

nerve-centres,  272 
poisons,  264 

nerve  roots,  356 

optic  lobes,  512 

reflexes,  276 

rhinophones,  165 

spinal  asphyxia,  412 
frog,  316 
reflexes,  316 

stellate  ganglion,  cephalopoda,  378 

sympathetic,  371 

BAILLARGER,     cerebral      convolutions, 
534 

cortex  cerebri,  532 
BALDI,  dorsal  roots,  298,  356 

nerve  section,  332 

voluntary  movement,  587 
BALFOUR,  nerve  origin,  182 
BANCHI,  nerve  autogenesis,  236 
BANCROFT,  muscle,  calcium,  95 
BANTI,  speech,  634 
BARBE,  knee-jerk,  329 
BARRINGTON,  micturition,  379 
BARTHEZ,  locomotion,  97 
BARTHOLOW,  cortical  localisation,  557 
BARTOLOMEI,  bulb,  415,  418 
BARZELOTTI,   muscle,    contraction,   21, 

22 

BASLER,  muscle  fibres,  10 
BASTIAN,  cortex  cerebri,  man,  592,  635 

speech,  626,  634 
BATESON,  hearing,  fish,  406,  418 


651 


652 


PHYSIOLOGY 


BATTELLI,  pcrfusion  of  spinal  cord,  274, 

276 

BAUDIN,  thermometer,  61 
BAUER,  cerebellum,  485 
BAXT,  velocity  of  nerve  impulse,  203 

nerve  conduction,  205 
BEAKD,  nerve  origin,  182 
BEAUNIS,  vagotomy,  399 
v.  BECHTEREW,  bulb,  417 

cerebellar  peduncles,  427 

cerebellum,  equilibration,  461,  484 

corpora  quadrigemina,  517 

cortex  cerebri,  bladder,  574 
respiration,  570 

localisation,  man,  558 

mid-brain,  524 

nucleus  of,  428 

spinal  cord,  356 

vertigo,  436 

BECK,  cerebellum,  drugs,  478,  485 
BECKER,  neuroh'brils,  184 
BECLARD,  muscle,  heat,  60 
BECQUEREL,  muscle,  heat,  60 
BEEVOR,  localisation,  man,  558 
monkey,  553,  634 

smell,  man,  615 

spinal  accessory,  397 
BELL,  A.  M.,  sound,  173 
BELL,  C.,  anatomy  of  brain,  356 

facial  nerve,  408 

muscular  sense,  467 

natural  system  of  nerves,  417 

spinal  nerve  roots,  291,  356 

trigeminal  nerve,  410 
BELL,  GRAHAM,  phonograph,  191 
BELLINGERI,  facial  nerve,  408 

trigeminal  nerve,  410 
BELMONDO,  nerve  roots,  297,  356 
BENECKE,  nerve  regeneration,  235 
BENTZ,  spinal  accessory,  397 
BERNARD,  C.,  aphonia,  140 

dorsal  roots,  298 

ganglion  reflexes,  373 

hype-glossal,  391 

muscle,  circulation,  5 
excitability,  4 
respiration,  work,  62 

nerve  roots,  291 

nervous  system,  356,  418 

rami  communicantes,  366 

recurrent  sensibility,  293 

spinal  accessory,  394 

strychnine,  265 

superior  cervical  ganglion,  331 

taste,  403 

vagotomy,  398 

vagus,  397 

BERNHEIMER,  visual  area,  608 
BERNSTEIN,  bio -electricity,  258 

contraction  wave,  23 

muscle,  action  current,  77 
demarcation  current,  75 
physics,  94,  95 


BERNSTEIN,  muscle,  surface  tension,  94 

waves,  93 
nerve,  action  current,  215,  276 

fatigue,  225 
rheotome,  77 
tetanus,  19 
BERT,  P.,  lumbar  plexus,  302 

nerve  conduction,  198 
BETHE,  brain,  fish,  496,  497 
mid-brain,  525 
nerve-cell  function,  260 
nerve,  compression,  195 
degeneration,  234 
origin,  182,  275 
regeneration^  235 
neurofibrils,  186 
BETZ,  cortex  cerebri,  533 
BEYERMANN,  cortex  cerebri,  respiration, 

571,  635 

spinal  skin  fields,  303 
v.  BEZOLD,  contraction  wave,  24 
muscle,  veratrin,  31 
nerve  roots,  297 
Plliiger's  law,  25 
BIANCHI,  G.,  cerebellum,  478 
BIANCHI,  L.,  corpus  striatum,  595 

frontal  lobe,  619 
BICHAT,  brain,  540 
life,  1 

nervous  system,  278 
BICKEL,  ataxy,  299 
inhibition,  321 
mid-brain,  tortoise,  500 
BIDDER,  larynx,  395 
nerve,  conduction,  198 

section,  332 

sympathetic  ganglia,  376 
BIEDERMANN,  crab  claw,  35 
electrophysiology,  94,  276 
electrotouic  current,  244 
muscle  antagonism,  35 
contraction,  93 
current,  76 
muscular  nerves,  36 
nerve  cells,  179 

conduction,  258 
BIEHL,  vestibular  nerve,  405 
BIELCHOWSKY,  nerve  cell,  191 
BIFFI,  taste,  403,  418 
BIKELES,  cerebellum,  drugs,  478,  485 
BILANCIONI,  cerebellum,  478 
BINNERT,    cerebellar    localisation,   481, 

485 

BIRGE,  grey  matter,  263 
spinal  nerve  roots,  280 
BISCHOFF,  muscle,  urea,  42 
spinal  accessory,  394 
vagus,  392 

BLANSCHKO,  decerebrate  frog,  498 
BLIX,  muscle  elasticity,  87 

heat,  66 
myography,  8 
BOAS,  nerve  asphyxia,  231 


INDEX  OF  AUTHOES 


653 


BOCHEFONTAINE,  cortex  cerebri,  bladder, 
574 

circulation,  571 

respiration,  570 

secretion,  574 

BODDAERT,  vagotomy,  400,  418 
BOECK,  muscle,  anisotropy,  27 
DE  BOECK,  spinal  inhibition.  321 
BoiiM,  muscle,  veratrin,  31 

rigor  mortis,  39 
BOEKE,  vowel  analysis,  162 
BOERHAAVE,  hypoglossal,  391 
BOGDANOW,  muscle  fat,  40 
BOLK,  cerebellum,  421,  471,  473,  484 

development  of  limbs,  304 

spinal  metamerism,  303,  356 
BOLL,  neurofibrils,  184 
BOLTON,  frontal  lobes,  635 
BONNE,  spinal  nerves,  295 
BORCHERT,  spinal  cord,  350,  357 
BORELLI,  centre  of  gravity,  107 

de  rnotu  auimalium,  97,  127 

muscle,  configuration,  47 
contraction,  21 
excitability,  3 
BORUTTAU,  core  model,  257 

muscle,  94 

nerve,  activity,  259,  276 

drugs,  214 
BOTTAZZI,  muscle  contraction,  32 

muscle  tonus,  33 
veratrine,  32 

sarcoplasm,  33 

spinal  hemisection,  348,  357 

sympathetic,  378 
BOUCHE,  cerebellum,  485 
BOUDET,  contracture,  31 
BOUILLAUD,  aphasia,  544 

cerebellum,  431,  484 

cerebrum,  502 
BOWDITCH,  "All  or  nothing,"  13 

knee-jerk,  330 

nerve,  inexhaustibility,  227 
BOYER,  pyramidal  tract,  342 
BRAMWELL,  B.,  speech,  626 
BRAUGHTON,  taste,  401 
BRATJNE,  centre  of  gravity,  108 

chronophotography,  116,  127 

posture,  110 

BRAUNSTEIN,  sympathetic  ganglia,  375 
BRAUS,  nerve  autogenesis,  236 
BRECHET,  muscle,  heat,  60 
BREYMANN,  phonetics,  173 
BRISSAUD,  contracture,  31 

corpus  striatum,  598 
BRISSEAU,  knee-jerk,  327 
BROADBENT,  verbal  memory,  630 
BROCA,  aphasia,  545 

speech  centre,  545,  625,  634 
BRODIE,  ruyography,  8 

nerve,  heat,  276 
BRODMANN,  area  striata,  607 

calcarine  area,  602 


BRODMANN,   cortical  architecture,  533, 

536,  594 
localisation,  635 
BRONDGEEST,  spinal  nerves,  296,  356 

spinal  tonus,  323 
BROOKS,  spinal  reflexes,  357 
BROWN,  olfactory  tract,  615 
BROWN,      GRAHAM,      cortex      cerebri, 
baboon,  635 

mid-brain,  525 

progression,  128 

spinal  cord,  358 
BROWN,  SANGER,  auditory  area,  612 

visual  area,  606 
BROWN-SEQUARD,  cerebellar  lesions,  433 

cerebellum,  431 

cortical  inhibition,  566 

epilepsy,  577 

motor  decussation,  342 

muscle,  circulation,  5 

nerve  section,  232 

sensory  decussation,  343 

spinal  cord,  hemisection,  344,  357 
BRUCE,  axon  reflexes,  379 
BRUCKE,  diphthongs,  158 

muscle  fibre,  27 

rigor  mortis,  36 

voice,  173 

vowel  system,  156 
BRUNINGS,  muscle  sound,  21 
BRUGIA,  electrotonus,  254 
BUBNOFF,  cortex  cerebri,  561 

cortical  inhibition,  565 

epilepsy,  578,  635 

spinal  reflexes,  357 
BUCHNER,  chemical  stimuli,  219 
BUDGE,  corpora  quadrigemina,  514 

cortex,  546 

medulla  oblongata,  418 

optic  lobes,  515 

spinal  cord,  343 

sympathetic  ganglia,  375 
v.  BiiNGNER,  nerve  regeneration,  235 
BiiTNER,  fifth  nerve,  331 
BUNGE,  alcohol,  450 

muscle  ash,  41 

BURCH,  nerve,  action  current,  215,  276 
BURCKHARD,  spinal  accessory,  394 
BURDACH,  tract,  288 
BURRIDGE,  muscle,  fatigue,  95 

CAGNIARD-LATOUR,  phonation,  146 
CALUGAREANU,  nerve  compression,  195 
CAMIS,  motor  centres,  358 
CAMPBELL,  area  striata,  603 

cortex  cerebri,  635 
CAPOBIANCHO,  nerve  origin,  182 
CARINCOLA,  spinal  convulsions,  412 
CARL,  taste,  404 
CARLET,  locomotion,  97,  127 

walking,  115 
CARVALHO,  muscle,  32 
CARVILLE,  corpus  striatum,  596 


654 


PHYSIOLOGY 


CARVILLE,  cortical  lesion,  582 

excitation  of  cortex,  560 
CATTANI,  nerve  regeneration,  235 
CAZALIS,  taste,  403 
CERLETTI,  frontal  lesion,  621 
CESANA,  G.,  spinal  oscillations,  326 

spinal  reflexes,  316,  356 
CHANDELON,  muscle  glycogen,  39 
CHARCOT,  corpus  striatum,  598 

cortex,  man,  590,  634 

epilepsy,  577 

speech,  629 

spinal  decussation,  343 
CHAUVEAU,  muscle  circulation,  5 

muscle  elasticity,  87 
energy,  88 

spinal  accessory,  397 

unipolar  stimulation,  251 

velocity  of  nerve  impulse,  204 
CHIAKUGI,  hypoglossal,  389 
CHRISTIANI,  decerebrate  rabbit,  505 

mid-brain,  524 
CLARKE,  LOCKHART,  column  of,  283 

intermedi< 'lateral  tract,  367 
CLARKE,  R.  H.,  cerebellum,  476,  485 
CLAUSIUS,  law  of  thermodynamics,  89 
COENEN,  skin  fields,  303,  356 
COHNHEIM,  areas,  muscle,  26 
COLASANTI,  muscle,  lactic  acid,  40 
COLLIER,  speech,  626 
COLLINS,  sympathetic  origin,  367 
CORNIL,  word  memory,  630 
COWL,  inhibition,  muscle,  36 
Cox,  chromatolysis,  268 

cortex,  man,  592 
CRISPOLTI,  visual  area,  608 
GUSHING,  cortex  cerebri,  635 

taste,  418 

CUVIER,  cerebrum,  416 
CYON,  labyrinth,  564 

nerve  roots,  296,  356 

spinal  tonus,  323 
CZERMAK,  laryngoscope,  173 

vowel  sounds,  157 

DALTON,  cerebellum,  431,  484 
DANA,  cortex,  man,  592 
DANILEWSKY,  amphioxus,  495 

corpora  quadigemina,  514 

cortex,  respiration,  570 

muscle,  heat,  66 

myosin,  37 

tripolar  electrodes,  247 
DANILLO,  epilepsy,  579 
DASTRE,  vasomotors,  293 
DAVIES,  fifth  nerve,  418 
DAX,  M.,  aphasia,  544 
v.  DEEN,  aesthesodic  nerve-fibres,  256 

cortex,  546 

spinal  cord,  343 
DEGANELLO,  cerebellum,  484 

eighth  nerve,  405 

labyrinth,  463 


DEITERS,  formatio  reticularis,  388 

nerve  cells,  177 

nucleus,  288 

spinal  nerve  roots,  284 
DEJEIUNE,  cortex,  man,  592,  634 

mid-brain,  525 

myelogenetic  areas,  617 

optic  thalami,  521 

red  nucleus,  426 

speech  centre,  625 

visual  area,  608 
DEMANT,  muscle  creatine,  38 

rigor  mortis,  39 

DERCUM,  cerebellar  disease,  459 
DESMOULINS,  brain,  frog,  498 

bulbar  sensibility,  416 
DICKINSON,  nicotine  method,  368 
DOGIEL,  neurofibrils,  184 
DOHRN,  nerve,  origin,  182 
DONAGGIO,  chromatolysis,  269 

neurofibrils,  184,  188,  269 
DONDERS,  muscle,  elasticity,  87 

nerve  section,  334 

voice,  151,  173 

vowel  tones,  159 
DREIFUSS,  cerebellum,  484 
Du  BOIS-REYMOND,  E.,  current  of  rest, 
70 

electrophysiology,  276 

electro  tonus,  241 

key,  222 

law  of  excitation,  223 

mechanical  stimuli,  221 

muscle,  contraction,  93 
currents,  70 

muscle  sound,  20 

nerve  axial  current,  210 
current,  208 

pre-existence  theory,  70 

unpolarisable  electrodes,  73 
Du     BOIS-REYMOND,     R.,    antagonist 
muscles,  570 

locomotion,  128 

muscle,  128 
DUCCESCHI,  cerebellar  ablation,  447 

cerebellum,  484 

nerve  centres,  276 
conduction,  193,  276 
excitability,  224 

perfusion  of  spinal  cord,  274 
DUCHENNE,  locomotion,  97,  127 

taste,  403 

walking,  115 

DUMAS,  muscle,  mechanism,  91 
DUPUY,  excitation  of  cortex,  560 
DURET,  corpus  striatum,  596 

cortical  lesion,  582 

excitation  of  cortex,  560 
DUVAL,  bulb,  418 

ECKHARD,  chemical  stimuli,  220 
corpus  striatum,  596 
spinal  accessory,  396 


INDEX  OF  AUTHOES 


655 


ECKHARD,  spinal  nerves,  301 

thermal  stimuli,  218 

trophic  action  of  ganglia,  331 

vagus,  396 

EPINGER,  brain,  anatomy,  356 
fish  and  man,  529 

cerebellar  tracts,  428 

fish  brain,  528 

formatio  reticularis,  388 

sensory  cerebellar  tract,  428 

spinal  cord,  286,  290 

thalamus,  521 
EDISON,  phonograph,  191 
EDWARDS,  sympathetic,  379 
EFRON,  nerve  compression,  193 
EHRENRERG,  nerve  cells,  177 
EHKLICH,  nerve  cell,  179 
EIGENBRODT,  spinal  cord,  343 
EINTHOVEN,  galvanometer,  73 

high  frequency  excitation,  19 

muscle,  physics,  94 
ELLIOTT,  sympathetic,  379 
ENGEL,  voice,  148 
ENGELMANN,  chordograms,  92 

inotagmata,  90 

muscle  energy,  89,  93 
injury  current,  70 

nerve  degeneration,  233 
injury  current,  209 

Pfliiger's  law,  25 

Thelephorus,  28 
ERASISTBA.TUS,  nerves,  291 
ERB,  knee-jerk,  326 

reaction  of  degeneration,  6,  253 

spinal  cord,  281 

degenerations,  287,  357 
ERMAN,  muscle  contraction,  22 
ESCHRICHT,  fifth  nerve,  410 
ESMARCH,  bandage,  329 
EULENBERG,  knee-jerk,  327 
EWALD,  ablation  of  cord,  353 

labyrinth,  461,  484 

muscle  contraction,  22 

spinal  cord,  357 

EWART,  muscle  and  electric  organs,  93 
EWING,  vowel  tones,  162,  173 
EXNER,  "Bahnung,"  321 

cortex,  man,  590,  634 

spinal  ganglion  cell,  261 
reflexes,  356 

FANO,  bulb,  418 

cortical  inhibition,  567 

frontal  lesion,  620 

mid-brain,  toad,  499,  524 
tortoise,  500 

muscle  tonus,  32 

oscillation  of  tonus,  324 

progression,  413 

reflexes,  324 

spinal  cord,  357 

vagus,  electro-cardiogram,  83 
FASOLA,  hippocampus,  615 


FERREIN,  larynx,  143 
FEURIER,  auditory  area,  610 

brachial  plexus,  302 

brain,  monkey,  551 

cerebellum,  431,  484 
disease,  459 
equilibration,  461 
functions,  465 
lesions,  434 

corpora  quadrigemina,  513 

cortex  cerebri,  548 
epilepsy,  574,  635 
excitation,  560 

functions  of  brain,  634 

mid-brain,  524 

olfactory  area,  613 

optic  lobes,  513 
thalamus,  520,  522 

restiform  body,  428 

vermis,  478 

visual  area,  606 
FICK,  isotony  and  isometry,  14 

joints,  99 

locomotion,  127 

muscle,  energy,  88 
heat,  65,  94 
thermodynamics,  89 
veratrin,  31 

nerve  conduction,  205 

post-electrotonic  current,  244 

walking,  114 
FIENGA,  grey  matter,  263 

spinal  preparation,  272 
FISCHER,  0.,  arm  movements,  104 

centre  of  gravity,  108 

walking,  116,  120,  127 
FLECHSIG,  anencephaly,  509 

auditory  cortex,  612 

brain  and  mind,  634 

cerebellar  tract,  288 

cortical  areas,  592 
centres,  630 

frontal  lesion,  620 

hippocampus,  615 

myelogenetic  law,  616 

spinal  tracts,  285 

taste,  616 

visual  area,  602,  60S 
v.  FLEISCHL,  nerve  excitability,  224 
FLEMMING,  chromatolysis,  268 

neurofibrils,  184 
FLOAD,  cortical  lesion,  588 
FLOURENS,  brain,  bird,  500 
frog,  498 

bulb,  418 

cerebellum,  430,  461,  467,  484 

cerebrum,  543 

consciousness,  416 

labyrinth,  406,  461 

optic  lobes,  515 
FODERA,  cerebellum,  430 

fifth  nerve,  331,  410 

spinal  cord,  343 


656 


PHYSIOLOGY 


FODERA,  spinal  nerve-roots,  292 

taste,  401 
FONTANA,  decerebrate  tortoise,  413 

muscle  elasticity,  85 

nerve  conduction,  193 
FORBES,  reflex  rhythms,  358 
FOREL,  corpora  quadrigemina,  515 

eighth  nerve,  405 
FORGUE,  spinal  roots,  302 
FOSTER,  nerve  metabolism,  206 

spinal  frog,  339 
FOURNIE,  voice,  173 
FOURNIER,  corpus  striatum,  596 
FRAGNITO,  nerve  origin,  182 
FRANQOIS  -  FRANCK,       brain,       motor 
functions,  634 

cortex,  circulation,  571 
respiration,  570 

cortical  excitation,  561 
rhythm,  563 

epilepsy,  575,  635 

FRANK,  0.,  muscle,  thermodynamics,  94 
FREDERICQ,  autotomy,  336 

nerve,  axial  current,  210 
centres,  anaemia,  266 
survival,  225 

velocity  of  nerve  impulse,  204 
FRENCH,  falsetto  voice,  151,  173 
FREUSBERG,  bulb,  418 

spinal  asphyxia,  412 
v.  FREY,  muscle,  R.Q.,  42 

twitch  and  tetanus,  33 
FRITSCH,  cortex  cerebri,  546 
epilepsy,  574,  635 

Lophius  piscatorius,  266 
FROHLICH,  FR.,  cephalopod  ganglion,  264 

nerve,  drugs,  214 
excitability,  276 
fatigue,  228 
oxygen,  205,  207 

staircase  contraction,  11 

tetanus,  34 
V.  FtiRTH,  muscle,  chemistry,  94 

rigor  mortis,  37 
FUNKE,  nerve,  strychnine,  207 

GABRI,  spinal  nerves,  295 
GAD,  inhibition  of  tonus,  36 
muscle,  latency,  9 
thermodynamics,  89 
twitch,  16 

temperature,  10 
nerve,  repair,  207 
spinal  nerves,  295 
GAGLIO,  cerebellum,  484 
space-perception,  464 
GALEN,  aphonia,  141 
hypoglossal,  390 
nerves,  291 
spinal  cord,  343 
GALEOTTI,  muscle,  contraction,  94 

physics,  94,  95 
nerve,  regeneration,  235 


GALL,  F.  J.,  brain,  538 

phrenology,  542 
GALVANI,  electrical  excitation,  224 

muscle,  electricity,  68 
GANSER,  corpora  quadrigemina,  515 
GARCIA,  M.,  laryngoscope,  145 

voice,  151,  173 
GARTEN,  nerve  fatigue,  227 
GASKELL,  heart  currents,  82 

sympathetic,  360,  366,  378 
GAVARRET,  phouation,  173 
v.  GEHUCHTEN,  nerve-cells,  178 

nerve-cell  degeneration,  268 
GERDY,  locomotion,  97 
GERLACH,  nervous  anastomosis,  177 
GHILARDUCCI,  reaction   at   a  distance, 

253 

GIANNUZZI,  vagus,  396 
GIERSE,  muscle,  heat,  60 
GLEY,  medulla  oblongata,  418 
GLISSON,  muscle  contraction,  21 
GLUGE,  nerve  conduction,  198 
GOIDANICH,  vowel  sounds,  158,  174 
GOLGI,  cerebellar  cortex,  182 

nerve-cells  and  fibres,  177,  275 

neurone  theory,  180,  188 

olfactory  tract,  615 

pericellular  net- work,  187 

tendon  organ,  320 
GOLL,  tract,  288 
GOLTZ,  ablation  of  cord,  353 

brain,  frog,  497 

bulb,  418 

cortex  cerebri,  634 
vision,  600 

cortical  lesion,  dog,  582 
monkey,  586 

decerebrate  dog,  506 

labyrinth,  463 

mid- brain,  524 

posture,  415 

reflexes,  356 

shock,  312 

spinal  centres,  352,  357 
co-ordination,  335 
frog,  340 
GOTCH,  Malapterurus,  204 

muscle,  action  current,  77 

nerve,  action  current,  210,  215 
conduction,  197,  276 
electrophysiology,  276 
refractory  period,  277 
temperature,  205 

spinal  paths,  348,  357 
GOTSCHLICH,  muscle  reaction,  40 
GOWERS,  W.  R.,  aphasia,  626 

cerebellar  disease,  459 

corpus  striatum,  598 

diseases  of  nervous  system,  356 

knee-jerk,  327 

speech  centres,  626,  634 

spinal  cord,  282 

tract,  288 


INDEX  OF  AUTHOES 


657 


K.i;,  cerebellar  lesions,  481,  485 
larynura.1  nerves,  1-10,  395 

medulla   olilmigata,    418 

GRAINGER,  .-pinal  reflexes,  335 
GiiATioi.KT,  1'. ,  ansa  peduncularis,  492 

eeivbral  localisation,  ;".  l.~> 
CRIFKI  rns,  cortical  rhythm,  563 

spinal  ganglia.  357 
GROSSMANN,     laryngeul     nerves,     396, 

MS 
Gui'MiAi'M,  cortical  excitation,  560 

cortical  localisation.  555,  '!"  I 

spinal  cord,  'JS9 
OiirxnAGEX,  core  model,  1243 

elect  rotonic  latency,  246 

nerve,  CO,,  228 
GRI  rzsEi:,  chemical  stimuli,  219 

muscle  fibres,  10 

muscle,  veratriu,  32 

nerve  current.  210 
excitability,  224,  276 

phouation,  146 

tetanus,  33 

\  ocal  conls,  139 

\  <.wels,  163 

(ii:i  X.MACH,  diphthongs,  158 
GSCHEIDLKX,  grey  matter,  270 
GrDDEN,  commissure,  493 

corpora  qualrigemina,  515 

internal  capsule,  595 

method  of,  268 

olive,  387 

optic  thalamic,  521 
Gf  NTHEU,  nerve  degeneration,  233 
Ci  TZMAXN,  voice,  174 
GUZOT,  taste,  403 

HAGEMAXX,  muscle,  efficiency,  67 
HALL,  taste,  401 

HALL,  MARSHALL,  excitomotor  system, 
341 

shock,  312 

spinal  reflexes,  337,  357 
HALL,  STANLEY,  muscle  sound,  21 
v.  HALLER,  aphonia,  141 

brain,  538 

muscle,  excitability,  3 

neural  activity,  255 
HALLIBURTON,  biochemistry,  277 

heat  coagulation,  37 

muscle,  chemistry,  94 
proteins,  37 

nerve,  heat  contraction,  276 
HALLOCK,  voice,  173 

vowel  analysis.  161 
HAM.MAKSTEN,  muscle,  chemistry,  38 
HANNOVER,  nerve  cells,  177 
HANSEMAXN,  cerebrum,  intellect,  624 
HARLESS,  centre  of  gravity,  108 

spinal  nerves,  296 

tetanus,  19 

vocal  cords,  136 

voice,  173 

VOL.  Ill 


HARRISON,  nerve  development,  236 

nerve  origin,  182 

II  \KTWELL,  antagonist  muscles,  306 
HAUGIITON,  muscle,  absolute  force,  47 
HAUSEN,  neural  activity,  255 
HEAD,  cerebral  lesions,  358,  635 
sensory  zones,  308,  356 

nerves,  277 
spinal  cord,  358 

HEIDENHAIN,  cortex  cerebri,  561 
cortical  inhibition,  565,  566 
epilepsy,  578,  635 
muscle,  heat,  61 
nerve,  excitability,  224 

thermogenesis,  207 
spinal  accessory,  394 

reflexes,  357 
tetanomotor,  221 
tetanus,  19 
vagus,  396 

HELD,  neurofibrils,  184 
neurone  theory,  188 
HELI.WAG,  vowel  sounds,  155 
HELJIHOLTZ,  muscle,  glycogen,  39 
latency,  8 
sound,  20 
thermopile,  61 
waves,  93 
nerve  cells,  177 
excitability,  276 
temperature,  205 
thermogenesis,  207 
superposition  of  contractions,  17 
tetanus,  17 
tones,  131,  173 

velocity  of  nerve  impulse,  202 
vowel  tones,  159 
HENKE,  joints,  97 

muscle,  absolute  force,  47 
HENLE,  bulb,  385 

laryngeal  cartilages,  134 
lateral  ventricles,  490 
HENSOHEN,  cortex,  man,  592 
frontal  lesion,  620 
localisation,  634 
visual  area,  602,  608 
HENSEN,  singing,  154 
voice,  173 
vowel  analysis,  162 
HERING,  E.,  core  model,  243 
muscle  current,  76 
nerve  current,  210 
Pfliiger's  law,  25,  250 
unconscious  memory,  341 
HERING,  H.  E.,  cortical  inhibition,  568 
dorsal  roots,  298 
strychnine,  265 

HEKLITZKA,  nerve  centres,  275,  276 
HERMANN,  bulbar  convulsions,  412 
contraction  wave,  24 
core  model,  243,  257 
muscle,  currents,  70 
diphasic  variation,  80 

2u 


658 


PHYSIOLOGY 


HERMANN,  muscle,  gases,  41 
heat,  65 
physiology,  94 

nerve,  conduction,  199,  201,  257 
diphasic  variation,  216 
electrophysiology,  276 
injury  current,  209 
phonophotography,  131 
semivowels,  166 
thermal  currents,  76 
voice,  173 
vowel  tones,  162 
HEROPHILUS,  nerves,  291 
HERRING,  sympathetic,  origin,  367 
HERTZ,  waves,  223 
HERZEN,  A.,  vagotomy,  398 
HESEN,  corpora  quadrigeiuina,  517 
HEYMANNS,    muscle    twitch,    tempera- 
ture, 10 

HIGHMORE,  antrum,  409 
HILL,  A.  V.,  muscle,  physics,  95 
HIRSCHMANN,  nicotine,  368 
His,  embryo  brain,  527 
foetal  brain,  382 
nerves,  181 
olfactory  lobe,  528 
HITZIG,  cerebellum,  484 
cortex  cerebri,  546 
epilepsy,  574 
vision,  599 

cortical  excitation,  560,  633 
myelogenetic  areas,  617 
vertigo,  436 

HLASKO,  corpora  quadrigemina,  515 
HOFMANN,    F.    B.,    end -plate    fatigue, 

226 

muscle,  94 

sympathetic  co-ordination,  377 
HOLMES,  GORDON,  cerebral  lesions,  358, 

635 

pyramidal  tract,  635 
HOLMGREN,  nerve-cell,  186 
HOPPE-SEYLER,  myohaematin,  38 
HORBACZEWSKY,  eighth  nerve,  405 
HORSLEY,  cerebellum,  485 
cortex,  monkey,  552 
cortical  localisation,  634 

rhythm,  562 
epilepsy,  577 

excitation  of  cerebellum,  476 
glottis,  142 
localisation,  man,  557 

monkey,  553 
motor  area,  635 
nerve,  action  current,  210 

conduction,  197 

spinal  accessory,  397 

convulsions,  581 

paths,  348,  485 

HORTON-SMITH,  spinal  nerves,  293 
HUBER,  nerve  regeneration,  235 
HURTHLE,  muscle  contraction,  30 
nerve,  stimuli,  223 


v.  HUMBOLDT,  muscle  electricity,  68 

nerve,  excitation,  224 
HUN,  visual  area,  602 

IMAMURA,  SHINKICHI,  cortex  cerebri,  634 

vision,  601 

IMBERT,  muscle,  contraction,  94 
INANZI,  taste,  403 
INGELS,  cerebellum,  agenesis,  456 

JACKSON,  HUGHLINGS,  cerebellar  disease, 
459 

epilepsy,  574,  635 

mid-brain,  524 

optic  thalami,  522 

smell,  man,  615 

speech,  626 
JACOB,  ataxy,  299 

myomeres,  304 
JACOBSOX,  nerve,  400 
JAEDERHOLM,  nerve  artefacts,  190 
JAMES,  W.,  conduction,  197 
JAPPELLI,  corpora  quadrigemiua,  516 

mid-brain,  525 
JENDRASSIK,  knee-jerk,  330 
JENKIN,    FLEEMING,    vowel    analysis, 

162,  173 

JENSEN,  muscle,  contraction,  94,  95 
JESPERSEN,  phonetics,  173 
JOHANNSEN,  corpus  striatum,  596 
JOLYET,  spinal  accessory  and  vagus,  396 
JOSEPH,  M.,  spinal  nerves,  295 

KAISER,  muscle  relaxation,  14 
KALISCHER,  auditory   and  visual  area, 

dog,  622,  634 
KANT,  soul  and  brain,  541 
KARPLUS,  cortex  cerebri,  634 

decerebrate  monkey,  510 

mid-brain,  525 

KATZENSTEIN,  cerebellum,  485 
VAN  KEMPEN,  spinal  accessory,  395 
KEY,  nerve  cells,  178 
KLEIN,  pharynx,  405 
KLUNDER,  singing,  154 
KNOLL,  muscle  fat,  40 
KNORZ,  muscle,  absolute  force,  47 
KOCH,  hypoglossal  nucleus,  391 
KOCHER,  spinal  lesions,  349,  357 

spinal  metamerism,  303 
v.  KOLLIKER,  dorsal  roots,  284 

formatio  reticularis,  388 

histology,  356 

muscle,  excitability,  4 
waves,  93 

nerve  cells,  178 

sympathetic  cells,  361 

nerve,  369,  378 
KONIG,  acetabulum,  100 

manometric  flames,  131 

vowel  tones,  161 

VAN  DER  KOLK  SCHRODER,  spinal  roots, 
301 


INDEX  OF  AUTHOKS 


659 


K<)i:\].'Ki.i>.  taste,  401 

Ki'^'HKU  NiKnKF,  spinal  nerves,  301 

KnsTi--.il,  muscle,  absolute  force,  47 

KOWAI.K.WSKY,  pupil,  375 

KuAr.i'KUN,  fatigue,  51 

KKATSK,    F.,    localisation,    man,    559, 

634 
KiiArsK,  H.,  cortical  centres,  552 

iiifiiiliraii'1,  muscle,  27 

metamerism,  301 

muscle  and  electric  organ,  91 
KRATSS,  muscle  glycogen,  39 
KUEIDI,.  bulb,  418 

cortex  cerebri,  634 

decerebrate  monkey,  510 

hearing,  fish,  406 

mid-brain,  525 
vox  KRIES,  muscle  sound,  21 

tetanus,  33 
KROXECKEU,  grey  matter,  263 

muscle,  fatigue,  11 
sound,  21 

tetanus,  18 

KUONEXBERG,  spinal  roots,  301 
KSCHISCHOWSKI,  optic  lobes,  513,  525 
KUHXK,  chemical  stimuli,  220 

gracilis  experiment,  200 

muscle,  electric  organs,  91 
excitability,  4 
pigments,  38 

nerve  conduction,  199,  276 

rigor  mortis,  36 
KfPFFER,  amphioxus  brain,  380 

nerve,  origin,  182 
KURZVEIL,  FR.,  cortex  cerebri,  634 

visual  area,  602 
KUSSMAUL.  alexia,  629 

bulbar  convulsions,  412 

cortex  cerebri,  634 

word  blindness,  609 
deafness,  612 


LAFARGUE,  cerebellum,  433 
LAMBERT,  nerve  cell,  268 

nerve,  inexhaustibility,  227 
LANDERGRBN,  asphyxia,  267 
LANDOIS,  bulbar  convulsions,  412 

cortex,  550 
LAXGE,  cerebellum,  484 

labyrinth,  462 
LANGELAAN,  cerebellar  ataxy,  453 

cerebellum,  484 

cortex,  respiration,  571 

hyperalgesic  areas,  308 

skin  fields,  303,  356 
LAXGENDORFF,     grey     matter, 
mortem  acidification,  270 

mechanical  excitation,  221 

pupil,  375 

spinal  reflexes,  316 
tonus,  326 

superior  cervical  ganglion,  369 
LANGER,  locomotion,  97 


LANGLEY,  autonomic  system,  359,  361, 
365,  368 

axon  reflex,  375 

hypogastric  nerve,  373 

muscle,  receptive  substance,  95 

nicotine  method,  367 

rami  communicantes,  366 

sympathetic  reinforcement,  376 

system,  378 

LANNEGRACE,  spinal  roots,  302 
LAPINSKY,  spinal  centres,  351,  357 
LAULANIE,  muscle  elasticity,  87 
LAUTEXBACH,  cortex,  vision,  600 

nerve  conduction,  205 
LEAPER,  nerve,  pressure,  277 
LEE,  hearing,  fish,  406 

medulla  oblongata,  418 
LEGALLOIS,  vagotomy,  398 
LEHFELDT,  voice,  151 
LEHMANN,  muscle  efficiency,  67 

corpus  striatum,  596 
LEMOIGNE,  cerebrum,  502 

corpora  quadrigemina,  515 

cortical  lesion,  582 
VON  LENKOSSEK,  nerve-cells,  178 

neurofibrils,  184 

pyramidal  tract,  342 

spinal  nerve  roots,  293 
LEPSIUS,  alphabet,  173 
LEVEN,  cerebellum,  431,  484 
LEVI,  nerve  regeneration,  235 

neurofibrils,  185 
LEVY,  myohaematin,  38 
LEWANDOWSKY,  cerebellum,    435,   468, 
484 

pupil,  375 

LEWIS,  BEVAN,  cortex  cerebri,  533 
LIBERTIXI,  cortical  inhibition,  566 
LIEBIG,  muscle  energy,  42 

muscle  reaction,  39 
LIEDLER,  cerebellum,  485 
LILLIE,  muscle,  contraction,  95 
LINGLE,  muscular  tone,  358 
LIPPMAXN,  electrometer,  72 
LISKOVIUS,  phonation,  173 
Lisso,  cortex,  man,  590 
LLOYD,  vowel  analysis,  162 
LOEB,  brain,  fish,  497 
frog,  498 

consciousness,  511 

cortex,  vision,  600 

psychical  functions,  543 
LOMBARD,  fatigue,  50,  95 
Lo  MONACO,  corpus  striatum,  597 

cortical  centres,  553,  634 

optic  thalami,  520,  522,  525 
LONGET,  aphonia,  141 

brain,  frog,  498 

cerebellar  lesions,  433,  484 

cerebrum,  502 

cortex  cerebri,  546 

hypoglossal,  391 

muscle,  excitability,  4 

2  U  2 


660 


PHYSIOLOGY 


LONGKT,  nerve  roots,  291,  356 
nerve  section,  232,  357 
optic  lobes,  515 
pons,  416 

recurrent  sensibility,  293 
singing,  153 
spinal  accessory,  394 
trigeminus,  331 
vocal  cords,  138 
LOURIE,  cerebellum,  485 
LOV^N,  muscle  sound,  21 

vagus,  397 

LucAs,  muscle,  contraction,  95 
myography,  8 
nerve,  conduction,  276 
LUCHSINGER,  Bell's  law,  293 
muscle,  antagonism,  35 

glycogen,  39 
nerve,  excitability  and  conductivity, 

229 

LUCIANI,  active  relaxation,  30 
area  striata,  604 
auditory  area,  611 
centre  of  centres,  622,  631 
cerebellar  ataxy,  465 
extirpation,  426 
gait,  438,  440,  451 
cerebellum,  431,  484 
corpus  striatum,  595 
cortex,  man,  591 
sensation,  588 
vision,  599 

cortical  excitation,  560 
lesion,  582 
localisation,  634 

dog,  548 
dysmetria,  298 
epilepsy,  575,  635 
joints,  106 

muscle,  relaxation,  88 
nerve,  currents,  243 
olfactory  area,  614 
olive,  387 
orthography,  174 
rhinophones,  165 
spinal  hemisection,  348 

nerve,  roots,  356 
word  deafness,  613 
LUDWIG,  glossopharyngeal,  405 
muscle,  circulation,  5 

R.Q.,  42 
taste,  405 

LUDERITZ,  nerve  conduction,  193 
LUGARO,  nerve  centres,  276 
neurofibrils,  184 
nerve-cell  degeneration,  268 
LUNA,  cerebellar  localisation,  481,  484 
LUSSANA,  cerebellum,  431,  461,  467,  484 
cerebrum,  502 
corpora  quadrigemina,  515 
cortical  lesion,  582 
medulla  oblongata,  418 
taste,  403 


Lrvs,  centre  median,  521 
cerebellum,  461,  484 
thalamus,  521 

MACDONALD,  muscle,  structure,  95 

nerve,  concentration  cell,  258 

temperature,  205 

MACDONNEL,  muscle,  glycogen,  39 
MAcDoucALL,  fatigue,  95,  358 

inhibition,  358 
MACH,  stroboscopic  disc,  145 
M'KENDRICK,  vowel  analysis,  162 
MAG-MUNN,  myohaematiu,  38 
MAcNALTY,  spinal  tracts,  485 
MACWILLIAM,  knee-jerk,  327 
MAGENDIE,  aphonia,  141 

brain,  frog,  498 

bulbar  sensibility,  416 

cerebellar  lesions,  433 

cerebellum,  431,  484 
equilibration,  461 

cerebrum,  502 

cortex,  cerebi'i,  546 

fifth  nerve,  331,  410 

hypoglossal,  391 

nervous  system,  418 

phonation,  144 

recurrent  sensibility,  293 

spinal  cord,  357 

nerve  roots,  291,  356 

taste,  401 

MAGGIORA,  fatigue,  50,  95 
MAGNAN,  epilepsy,  581 
MAGNINI,  bulb,  415.  418 

cerebellum,  drugs,  477 
localisation,  485 

cortex,  ccrebri,  550,  634 

strychnine,  brain,  264 
MAGNUS,  intestine,  378 

MALGAIGNE,  glottis,    144 

MANCHE,  muscle  glycogen,  39 

MANDL,  glottis,  loi 

MANGOLD,  muscular  nerves,  36 

MANN,  nerve-cell,  268 

v.  MANSFELT,  muscle  elasticity,  87 

MANTEGAZZA,  nerve  section,  332 

MARASSINI,  cerebellar  localisation,  481, 

485 
MARCACCI,  lumbar  plexus,  302 

nerve  roots,  297 
MARCHAND,  grey  matter,  263 
MARCHI,  caudate  nucleus,  529 

cerebellar  tract,  288,  429,  484 

cerebellum,  426 

method  of  staining  degenerated  nerve, 
234 

Purkinje's  cells,  427 
MARCHIAFAVA,  aphasia,  627 
MARCUSE,  muscle  acidity,  40 
MAREY,  gait,  126 

graphic  method,  128 

locomotion,  97,  128 

muscle  contraction,  22.  24 


INDEX  OF  AUTHORS 


661 


MAKKY,  muscle,  elasticity,  87 
myograph,  22 

velocity  of  nerve  impulse,  203 
walking,  115 
MA i HE,  P.,  aphasia,  627 
M  viiiNKsr,!,    nerve  -  cell,    degeneration, 

268 

nerve  centres,  276 
neurotibrils,  184 

M  \UTIN,  antagonist  muscles,  306 
M  AUIINOTTI,  spinal  cord,  357 
MATHISOX,  asphyxia,  418 
MATTEUCCI,  animal  electricity,  255,  276 
core  model,  243 
cortex,  546 
reflexes,  316 

secondary  contraction,  69,  77 
spinal  nerve  roots,  356 
tetanus,  17 

.MATTHIAS,  semi-vowels,  166 
MAXWELL,  cortex  cerebri,  550,  634 
.MAY,  PAGE,  afferent  path,  358 

pyramidal  tracts,  635 
MAYER,  optic  lobes,  515 
MAYER,  C.,  hypoglossal,  389 

spinal  nerves,  301 

MAYER,  G.  R.,  thermodynamics,  89 
MAYER,  S.,  sympathetic,  378 
MAYO,  fifth  nerve,  331 
glottis,  144 
hypoglossal,  391 
taste,  401 

MI-.KK.  nerve  conductivity,  277 
MEIGS,  muscle,  heat  coagulation,  95 
MEISSNER,  bulb,  418 
nerve  section,  334 
MELLONI,  thermopile,  61 
MELLTIS,  pyramidal  tract,  342 
MENDELSOHN,  excitation  of  cerebellum, 

475 

nerve  axial  current,  210 
spinal  reflexes,  357 
MEKKEL,  vowel  tones,  160,  173 
MERZBACHER,  ataxy,  299 
MEYER,  C.,  vocal  cords,  139 
MEYER,  centre  of  gravity,  108 
locotnotioD,  127 
muscle  mechanism,  91 
MEYER,  G.  H.,  vertebral  column,  112 
MEYER,  H.,  locomotion,  97 
MEYXERT,  cerebellum,  428 
cortex  cerebri,  533 
olfactory  tract,  615 
MICHIELI,  cortical  excitation,  560 

cortical  lesion,  582 
MiES'-'HER,  spinal  cord,  346,  357 
MILLS,  cortex,  man,  591 
MINES,  summation  of  contractions,  95 
M  i  KGAZZINI,  G.,  brain,  634 
cerebellar  agenesis,  455 
lesions,  485 
peduncles,  425 
cerebello-spinal  paths,  430 


MINGAZZIXI,G.,  cerebrum,  intellect,  624 
corpus  striatum,  598 
Purkinje's  cells,  427 
speech  centres,  626,  634 
spinal  cord,  290 
MINKIIWSKI,  cortex  cerebri,  634 

visual  area,  dog,  604 
MISLAWSKY,  cortex,  secretion,  574 
MITCHELL,  WEIR,  cerebellum,  431,  484 
MODENA,  nerve  regeneration,  240,  276 
MHXCKEBERG,  nerve  degeneration,  234 
MHMMSEN,  spinal  tonus,  324 
v.  MONAKOW,  auditory  cortex,  612 
cerebellar  ataxy,  458 
cerebellum,  484 
corpora  qiiadrigemina,  515 
corpus  striatum,  598 
cortex  cerebri,  localisation,  634 

man,  591,  592 
mid-brain,  525 
myelogenetic  areas,  617 
occipital  cortex,  601 
speech,  634 
visual  area,  608 
MONARI,  muscle  creatine,  38 
MONROE,  spinal  roots,  301 
MONTI,  A.,  chromatolysis,  269 
MOORE,     spinal    ganglion    conduction, 

262 

MORAT,  spinal  nerves,  295 
MORAWITZ,  spinal  cord,  274 
MOREAU,  spinal  nerve  roots,  292 
MORGAGNI,  vagotomy,  398 

ventricle,  135 

MORGANTI,  medulla  oblongata,  418 
spinal  accessory,  394 
taste,  403 

MORIGGIA,  nerve,  salts,  220 
MORSELLI,  dynamograph,  48 

epilepsy,  579 

MOSCATELLI,  muscle,  lactic  acid,  40 
Mosso,  ergograph,  48,  95 
fatigue,  intoxication,  59 
Mosso,  U.,  fatigue,  food,  51 
MOTT,  cortex,  localisation,  gibbon,  635 

sensation,  588 
dorsal  roots,  298 
spinal  heniisection,  346,  357 

nerve  roots,  356 
sympathetic,  origin,  367 
visual  area,  635 
voice,  174 

MULLER,  ERIK,  neurofibrils,  184 
MULLER,  G.  E.,  muscle,  energy,  92 
MULLER,  H.,  muscle  waves,  93 
MULLER,  JOHANNES,  aphonia,  141 
bulbar  sensibility,  416 
larynx,  143 
muscle  contraction,  21 
spinal  nerves,  291,  356 
taste,  401 

velocity  of  nerve  impulse,  202 
MULLEII,  W.,  spinal  decussation,  343 


662 


PHYSIOLOGY 


MUNK,  H.,  auditory  area,  610 

brain,  frog,  498 

cerebellum,  484 

cortex  cerebri,  634 
respiration,  571 

cortex,  vision,  599 

decerebrate  pigeon,  502 
rabbit,  505 

dursal  roots,  299 

epilepsy,  579 

mid-brain,  525 

psychical  functions,  54-'! 

sensory  sphere,  583 

spinal  nerve  roots,  356 

word  blindness,  609 

deafness,  610 

MUNK,  J.,  cerebellum,  435 
MUNZER,  optic  decussation,  493 

optic  lobes,  515 

spinal  cord,  289 

nerves,  295 

MURATOFF,  pyramidal  tract,  342 
MURRI,  cerebellum,  465,  484 
MrssKX,  hypoglossal,  418 
MUYBRIDGE,  locomotion,  97 


NAGY  v.  REGECZY,  inhibition  of  tonus, 

36 

NANSEN,  nerve-cell  function,  261 
NASSE,  muscle  glycogen,  39 

nerve  degeneration,  233 
NAVRATIL,  spinal  accessory,  395 
NAWALICHIN,  muscle,  heat,  64 
NAWROCKI,  bladder,  373 

muscle  creatine,  38 

spinal  cord,  346,  357 
NEGRO,  cerebellar  localisation,  476 
NELATON,  nerve  section,  332 
NELLS,  chromatolysis,  268 
NERNST,  nerve  activity,  259 
NEUMEISTER,   physiological   chemistry, 

94 
NICOLAIDES,  grey  matter,  263 

vagotomy,  398 
NISSL,  nerve  cell,  189,  268,  275 

nerve  centres,  276 

neurone  theory,  183 

visual  area,  602 
NOBILI,  animal  electricity,  255 

electrotonic  excitability,  245 

muscle  electricity,  69 
NOTHNAGEL,  bulbar  convulsant  centre, 
412 

cerebellum,  431,  484 
ataxy,  458 
excitation,  435,  475 

corpus  striatum,  596,  598 

cortex  cerebri,  634 
Novi,  electrotonus,  254 

epilepsy,  579,  635 

muscle,  fatigue,  12 
NUSSBAUM,  bladder,  373 


OBERSTEINER.  cerebellar  tracts,  428 
OBOLENSKY,  nerve  section,  332 
OCANA,  GOMEZ,  vagotomy,  398 
ODDI,  cortical  inhibition,  567 

nerve  roots,  297,  356 
OERTEL,  laryngoscopy,  145 

voice  registers,  173 
OKER-BLOM,  concentration  cells,  258 

electrode,  71 

OLLIVIER,  cerebellum,  431,  484 
ONIMUK,  excitation  of  cortex,  560 
ONUF,  sympathetic,  origin,  367 
ONUFROWICZ,  eighth  nerve,  405 
OPPENHEIM,  aphasia,  628,  634 

corpus  striatum,  598 

cortex,  man,  592 
ORBELLI,  sympathetic,  378 
OSTVVALD,  bioelectric  phenomena,  258 

electrode,  71 

OTT,  corpus  striatum,  597 
OWSJANNIKOW,  bulb,  convulsions,  413, 
418,  581 

PAGANO,  cerebellum,  curare,  435,  476, 

485 
localisation,  481 

corpus  striatum,  597 
PALADINO,  nerve,  origin,  182 
PANCONCELLI-CALZIA,  phonetics,  174 
PANEGROSSI,  aphasia,  627 
PANICHI,  spinal  nerves,  295 

visual  area,  607 
PANIZZA,  corpora  quadrigemina,  515 

cortex,  vision,  599 

dorsal  roots,  298 

eye,  cortex  cerebri,  603 

hypoglossal,  391 

medulla  oblongata,  417 

muscular  sense,  467 

nerve  roots,  291,  356 

taste,  401 

voluntary  movement,  587 
PARKER,  hearing,  fish,  406,  418 
PASSY,  phonetics,  174 
PATRIZI,  cerebellar  ataxy,  445 

cerebellum,  484 

heart,  acceleration,  573 

muscle,  fatigue,  95 

hibernation,  10 
PAUKUL,  muscle  fibres,  10 
PAULSEN,  voice,  148 
PAWLOW,  vagotomy,  398 
PERRONCITO,   nerve  regeneration,   237, 

238 

DU  PETIT,  cerebellum,  433 
PETREN,  spinal  lesions,  350,  357 
PETRINA,  cortex,  man,  590 
PETTENKOFER,  muscle,  work,  43 
PETTIGREW,  locomotion,  127 
PEYER,  metamerism,  301 
PFAFF,  electrical  excitation,  224 
PFLUGER,  animal  oxidation,  43 

avalanche  theory,  224 


INDEX  OF  AUTHOES 


663 


I'KI.I  tiKii,  electrotonic  excitability,  245 

law  of  contraction,  25,  248 

laws  of  reflex  action,  314 

muscle  energy,  88 

myograph,  7 

protein  and  work,  43 

spinal  cord,  339,  356 
v.  PFUNGEN,  cortex  cerebri,  gut,  574 
I'liiiJi'K.vrx,  nerve,  conduction,  198 
TICK,  cerebellar  tract,  430 

fibrin  proteolysis,  45 

visual  area,  608 

PILCHEU,  vasomotor  centre,  418 
PIOTUOWSKI,  muscle  inhibition,  35 

nerve,  229 

PIPPING,  vowel  analysis,  162,  173 
PITRES,  cortex,  man,  590,  634 
respiration,  570 

cortical  excitation,  561 
rhythm,  563 

epilepsy,  575,  635 

pyramidal  tract,  342 

spinal  decussation,  343 
POIROT,  phonetics,  174 
POISSON,  locomotion,  work,  97 
POL,  HULSHOFF,  cerebellar  localisation, 

481,  485 

POLIMANTI,  nerve  roots,  297,  302,  356 
PORTER,  spinal  reflexes,  358 
PRAUSNITZ,  muscle  glycogen,  39 
PREVOST,  muscle,  mechanism,  91 

taste,  403 
PROBST,  cerebellum,  484 

mid-brain,  518,  525 

occipital  cortex,  601 

vertigo,  436 

PROCHASKA,  perception,  540 
PRUSS,  cerebellar  localisation,  476,  485 
PURKINJE,  cells,  424 

vertigo,  436 
PURPURA,  nerve  fusion,  240,  276 

nerve  regeneration,  236 

RAFFAELE,  nerve  origin,  182 
RAHN,  glossopharyngeal,  405 
RAMON  Y  CAJAL,  cortex  cerebri,  533 

dentate  nucleus,  426 

dorsal  roots,  284 

nerve  cells,  177,  275 

neurofibrils,  190 

neurone  theory,  180 

Purkinje's  cells,  427 

spinal  nerve  roots,  293 

unipolar  nerve  cell,  261 
RANKE,  fatigue  intoxication,  59 

nerve,  fatigue,  228 
RANVIER,  muscle,  28,  94 
red  and  pale,  9 

nerve  degeneration,  232,  233 
regeneration,  234 

ueurofibrils,  184 

RECKLINGHAUSEN,  cerebellum,  503 
REDI,  progression,  413 


REDLICH,  cortex,  man,  592 
RICGNAT,  nerve  cell,  268 
REID,  taste,  403 
REIL,  fillet,  487 

spinal  nerves,  301 
REMAK,  nerve  cells,  177 
RENZI,  cerebrum,  502 

optic  lobes,  515 

posture,  414 
RETZIUS,  cerebrum,  intellect,  624 

nerve  cells,  178 
REYNOLDS,  spinal  ganglion,  conduction, 

262 

REZEK,  corpus  striatum,  596 
RIBOT,  memory,  631 
RICHARDSON,  myography,  8 
RICHET,  contracture,  31 

cortex  cerebri,  561 
circulation,  571 

crab  claw,  35 

muscle,  excitability,  4 
heat,  59 
physiology,  94 

nerve  conduction,  205 

summation  of  stimuli,  17 

tremor,  563 

RITTER,  nerve,  excitability,  224 
section,  232 

opening  tetanus,  250 
RIVERS,  nerve  section,  277 
ROBE,  spinal  paths,  358 
ROBER,  muscle,  fatigue,  76 
ROBERTSON,  nervous  system,  275 
ROBINSON,  neural  activity,  255 
ROHMANN,  nerve,  torpedo,  207 
ROLANDO,  brain,  birds,  500 

cerebellum,  430,  466,  484 

mid-brain,  413 

sulcus  of,  531 
ROLLER,  nucleus  of,  389 
ROLLESTON,  nerve,  thermogenesis,  207 
ROLLET,  contraction  wave,  28 

muscle,  94 

nerve,  excitability,  224 
RONCORONI,  frontal  lobe,  622 

speech,  634 
ROSAENDA,  cerebellar  localisation,  476, 

485 

ROSENBACH,  epilepsy,  579,  635 
ROSENTHAL,  muscle,  absolute  force,  47 

muscle,  current,  75 
physiology,  94 

nerve  conduction,  198,  205 
temperature,  218 

spinal  inhibition,  321 

reflexes,  357 

ROSSBACH,  muscle  elasticity,  87 
Rossi,  cerebellar  ablation,  483 

cerebellum,  485 
ROTHMANN,  cerebellar  lesions,  481,  485 

cortex  cerebri,  634 

decerebrate  dog,  509,  525 
ROUSSELOT,  phonetics,  173 


664 


PHYSIOLOGY 


ROUSSY,  optic  thalami,  521,  525 
ROVIGHI,  cortex,  drugs,  579 

epilepsy,  635 

RUDINGKU,  cerebrum,  iutellect,  624 
RUMPELT,  phonetics,  173 
RUSSELL,  RISIEN,  cerebellum,  484 
ablation,  482 
disease,  459 

spinal  metamerism,  302,  356 
VAN  RYNBERK,   cerebellar  localisation, 

479,  485 

dermatomes,  306 
skin  fields,  303 
spinal  metamerism,  303,  306,  356 

SABBATINI,  cortex  cerebri,  calcium,  275 
SACHS,  caudate  nucleus,  597 
mid-brain,  525 
myelogenetic  areas,  617 
visual  area,  609 
SALOMONSON,  high  frequency  excitation, 

19 

SAMELSOHN,  macular  bundle,  493 
SAMUEL,  nerve  section,  335 
SAMWAYS,  core  model,  257 
SANDERS-BUN,  grey  matter,  263 
SANDERSON,  BURDON,   muscle  current, 

77 

latency,  9 

SANKEY,  cerebellum,  425 
SANTESSON,  muscle,  work,  15 
SANTINI,  cortex,  drugs,  579 

epilepsy,  635 

SAPPEY,  cerebellar  peduncles,  388 
cerebellum,  422 
laryngeal  nerves,  140 
vagus,  393 

SAROKIN,  muscle  creatine,  38 
SAUBERSCHWARTZ,  vowels,  163 
DE  SAUVAGES,  neural  activity,  255 
SCAFFIDI,  sympathetic  origin,  367 
SCARPA,  ganglion,  405 
spinal  roots,  301 
vagus,  392 

SCHAFER,  auditory  area,  612 
cerebellum,  423 
chromatolysis,  269 
cortex,  man,  591 
monkey,  552 
sensation,  587 
cortical  rhythm,  562 
epilepsy,  577 
fourth  ventricle,  389 
localisation,  634 
mesencephalon,  487,  488 
muscle  contraction,  30 

sound,  21 
pons,  421 

spinal  convulsions,  581 
visual  area,  606 
SCHECH,  spinal  accessory,  395 
SCHENK,  muscle,  fatigue,  58,  95 
SCHEVEN,  patellar  reflex,  326,  327 


SCHIFF,  aesthesodic  nerve-fibres,  256 
bulb,  418 

cerebellum,  431,  433,  484 
cortex  cerebri,  546 
circulation,  571 

idio-muscular  contraction,  5,  24 
nerve  conduction,  193 
fatigue,  226 
section,  332,  334 
thermogenesis,  207 
spinal  accessory,  394 
cord,  290,  357 
hemisection,  344,  357 
nerve  roots,  292,  295,  356 
taste,  403 
vagotomy,  398 
vagus,  396 

SCHIFFER,  muscle,  circulation,  5 
SCHIPILOFF,  C.,  myosin,  37 
SCHMIDT,  muscle,  R.Q.,  42 
SCHMIEDEBERG,  alcohol,  450 
SCHNEEBELI,  voice,  173 
SCHON,  nerve  degeneration,  233 
SCHOPS,  spinal  cord,  343 
SCHRADER,  brain,  frog,  497 

lesion,  503 
mid-brain,  524 
SCHULTZ,  pupil,  375 
quasi-reflexes,  375 
SCHULTZE,  M.,  ganglion  cells,  183 

nerve,  autogenesis,  236 
SCHUSTER,  localisation,  gibbon,  635 
SCHWALBE,  bulb,  387 
neurotibrils,  184 
pons,  420 
SCHWAMMERDAM,  muscle,  contraction, 

21 

SCHWANN,  nerve  conduction,  198 
SCHWOHN,  corpus  striatum,  596 
SCIAMANNA,  frontal  lobe,  620 
knee-jerk,  327,  357 
localisation,  man,  557 
SCOTT,  nerve-cells,  277 
SCRIPTURE,  speech,  173,  174 
SCZELKOW,  muscle,  R.  Q.,  42 
SEEMANN,  muscle  twitch,  16 
SELLIEK,  corpus  striatum,  597 
SEMI-MEYER,  neurofibrils,  188 
SEMON,  glottis,  142 

voice,  173 
SENFTLEBEN,  trophic  action  of  ganglia, 

331 

SEPPILLI,  auditory  area,  611 
corpus  striatum,  596 
cortex,  man,  591 
localisation,  634 
sensation,  588 
vision,  600 
epilepsy,  635 
SERGI,     cerebellar     lesion,     435,     447, 

484 

cortex  cerebri,  curare,  552 
frontal  lobe,  624 


INDEX  OF  AUTHORS 


665 


SKI;  R  us,  cerebi'llum,  431 

corpora  quadrigemina,  516 
SKTSCHKNOW,    inhibition    of    reflexes, 
319,  356 

optic  lobes,  512 
SKWAI.L,  superposition  of  contractions, 

18 
SimiiiKi,  corpora  quadrigemina,  515 

corpus  stria  turn,  597 

mid-brain,  525 
SiiATTurK,  brain,  530 
SHKRRINUTON,  cortex,  secretion,  574 

cortical  excitation,  560 
inhibition,  568 
localisation,  555,  634,  635 

decerebrate  rigidity,  518 

dorsal  roots,  298 

facilitation,  321 

inhibition,  320,  357 

integrative  action,  485 

knee-jerk,  329,  330 

localisation,  634 

metamerism,  301 

mid-brain,  525 

phonation,  517 

pyramidal  tract,  342 

rami  communicantes,  366 

reciprocal  innervation,  320,  357,  569 

shock,  312 

spinal  cord,  289,  290 
metamerism,  302,  356 
nerves,  295,  356 
preparation,  357 
reflexes,  313,  315,  320,  357 
tonus,  357 

stepping,  128,  358 
SIEVEKS,  voice,  173 
SINGER,  optic  decussation,  493 

spinal  nerves,  295 
SINITZIN,  Gasserian  ganglion,  331 

spinal  cord,  357 
SKABIT.SCHEWSKI,  bladder,  373 
SMITH,  MEADE,  muscle  heat,  62 
SMELLEN,  nerve  section,  334 

vagus,  397 

SNYDER,  knee-jerk,  358 
SOKOWIN,  bladder,  373 
SOLLMANN,  vasomotor  centre,  418 
SOLVAY,  muscle  efficiency,  89 
SO.MMEU,  rigor  mortis,  36 
SUMMERING,  brain,  540 

spinal  roots,  301 
SORIENTE,  epilepsy,  635 
SOURY,  brain,  538,  633 

cerebral  localisation,  546 
SOWTOX,  reflex  inhibition,  358 
SPALLANZANI,  embrace  reflex,  311 
SPALLITTA,  trophic  action  of  ganglia, 

331,  357 
SPENCER,    W.    G.,  cortex,  inspiration, 

571 

SPILLER,  cortex,  man,  592 
SPIRO,  muscle,  lactic  acid,  40 


SPITZKA,  pyramidal  tract,  342 
SPURZHEIM,  phrenology,  542 
STANNIUS,  spinal  nerve  roots,  292 

taste,  401 
STARR,  ALLEN,  segmental  limb  fields, 

304 

STEFANI,      cerebellum,      equilibration, 
461,  484 

labyrinth,  463 

optic  lobes,  515 
STEINACH,  spinal  nerves,  293 

unipolar  nerve  cell,  261 
STEINBRUCK,  nerve  conduction,  198 

nerve  degeneration,  233 
STEINER,  amphioxus,  495 
metameres,  380 

brain,  fish,  496,  497 

contraction  wave,  24 

mid-brain,  524 

posture,  414 

STENSEN,  N.,  muscle,  circulation,  5 
STENSON,  nerve  centres,  anaemia,  266 
STERN,  muscle  sound,  21 
STEWARD,  vagotomy,  400 
STILLING,  cerebellum,  426 

dorsal  roots,  298 

pons,  420 

spinal  accessory,  395 
cord,  343 
nerves,  356 
nucleus,  283 

STINTZINQ,  muscle  gases,  41 
STIRLING,  summation  of  stimuli,  263 

tetanus,  18 

STUHR,  sympathetic  ganglia,  362 
STORX,  phonetics,  173 
STRICKER,  vasodilatators,  293 
STROBE,  nerve,  regeneration,  234 
STRUMPELL,  spinal  degeneration,  287 
SVAN,  corpora  quadrigemina,  515 

optic  thalamus,  521 
SWEET,  phonetics,  173 
SZIMANOWSKY,  glottis,  145 
SZYMONOWICZ,  muscle  fibre,  27 

TAMBURINI,  auditory  area,  611 

corpus  striatum,  595 

cortex,  sensory-motor  function,  589 
vision,  599 

cortical  excitation,  560 
lesion,  582 
localisation,  634 

epilepsy,  575 

localisation,  dog,  548 

speech,  634 
TANZI,  memory,  632 
TARCHANOFF,  cortex,  heart,  574 

optic  lobes,  512 

spinal  reflexes,  337 
TARULLI,  spinal  nerves,  295 
TECHMER,  phonetics,  173 
TENNER,  bulbar  convulsions,  412 
TENON,  capsule,  363 


666 


PHYSIOLOGY 


TERENCE,  soul  and  brain,  542 
TESLA,  high-frequency  excitation,  19 
TESTUT,  mesencephalon,  491 

optic  nerve,  494 

thalamencephalon,  492 
THANE,  facial  nerve,  407 

eighth  nerve,  406 
THAUSING,  voice,  173 
THIERNESSE,  nerve  conduction,  198 
THORNER,  W.,  nerve  excitability,  276 
THOMAS,  cerebellar  tracts,  428,  429,  484 

cerebellum,  equilibration,  461 
THOMPSON,  spinal  cord,  358 
THOMSON,  ALLEN,  brain,  382,  383 

nerves,  279,  280 

THOMSON,  W.,  galvanometer,  71 
THORBURN,  spinal  metamerism,  304 
THUNBEUG,  nerve  respiration,  207,  231 
TIGERSTEDT,  muscle  latency,  9 

nerve,  electrophysiology,  276 
excitability,  224 

tetanomotor,  221 

TILLIE,  nerve  centres,  curare,  476 
TIZZONI,  nerve  regeneration,  235 
TRAUBE,  muscle,  protein  metabolism,  43 

vagotomy,  398 
TRENDELENBURG,  ataxy,  299 

atomy,  300 

spinal  nerves,  356 
TIIEVES,  ergograph,  57 

muscle,  fatigue,  52,  95 
TRIPIER,  cortex,  man,  590 

nerve,  conduction,  198 

sensory  roots,  294,  356 
TSCHAGOWETZ,  bioelectricity,  258 
TSCHERMAK,    A.,   cerebral  localisation, 
634 

vision,  dog,  602 
TURCK,  spinal  metamerism,  301 

tract,  287 
TURNER,  cerebellum,  484 

mid-brain,  525 

restiform  body,  428 

visual  area,  608 

UCHTOMSKY,  cortex,  634 

v.  UEXKULL,  mechanical  excitor,  221 

velocity  of  nerve  impulse,  204 
UNVERRICHT,  epilepsy,  575,  578,  634 
v.  URBANTSCHITSCH,  taste,  404 
USPENSKY,  nerve  roots,  297 

VALENTIN,  corpora  quadrigemina,  514 

spinal  cord,  343 

taste,  401 

thermal  stimulus,  218 
VALLI,  muscle  electricity,  68 

nerve  section,  232 
VALSALVA,  vagotomy,  398 
VANLAIR,  nerve,  regeneration,  234 

vagotomy,  398 

DE  VARIGNY,  cortex  cerebri,  561 
VEJAS,  spinal  nerves,  295 


VAN    DER    VELDE,    velocity    of    nerve 

impulse,  204 
VERATTI,  nerve-cells,  180 

neuroh'brils,  186 
VERGER,  corpus  striatum,  597 
VERWORN,  contraction,  94,  95 

hypnosis,  518 

muscle  work,  44 

nerve  activity,  259 
centres,  270,  276 

reciprocal  innervation,  320 

spinal  reflexes,  357 

unipolar  nerve  cell,  261 
VIALET,  optic  chiasma,  495 

visual  area,  525,  608 
VIERORDT,  posture,  113 
VINCENZONI,  cerebellum,  485 
VINTSCHGAU,  nerve  conduction,  205 
VIZIOLI,  epilepsy,  579 
VOGT,  cortex  cerebri,  539 

myelogenetic  areas,  617 
VOIT,  muscle,  contraction,  91 

muscle,  urea,  42 

VOLKERS,  corpora  quadrigemina,  517 
VOLKMANN,  glossopharyngeal,  404 

larynx,  395 

pharynx,  405 

sympathetic  ganglia,  376 
VOLTA,  muscle  electricity,  68 

tetanus,  17 
VULPIAN,  cerebellar  lesions,  433 

cerebellum,  431 

hypoglossal,  389 

medulla  oblongata,  418 

muscle,  heat,  59 

nerve,  conduction,  198 
section,  332 

phonation  centre,  143 

pontine  sensibility,  416 

posture,  414 

vagus,  396 

WAGNER,  cerebellum,  431,  484 

laryngeal  nerves,  395 

spinal  nerve  roots,  292 

sulci,  intellect,  624 

taste,  401 
WALDEYER,  nervous  system,  275 

neurone,  179 

WALKER,  nerve  roots,  291 
WALLENBERG,  vestibular  nerve,  405 
WALLER,  A.,  nerve  section,  232 

spinal  accessory,  394 
nerve  roots,  295 

trophic  centres,  233 

vagus,  396,  418 
WALLER,  A.  D.,  animal  electricity,  276 

Bell's  law,  358 

cardiogram,  80 

dynaniograph,  47 

electrotonic  currents,  242,  245 

electrotonus,  man,  248,  251 

fatigue,  48,  227 


INDEX  OF  AUTHOKS 


667 


W  U.LKI:,    A.    D.,    heart,    equipotential 

lines,  81 

knee-jerk,  327,  357 
muscle,  galvanogram,  78 

\\ork.  46 
myograph,  7 
nerve,  CO.,,  206 

drills,  211 

thermo-galvanograms,  61 
WALSH,  torpedo,  255 
WALTER,  coccygeal  ganglion,  360 
WAUUEN,  knee-jerk,  330 
W  \I;I;IN<;TI»X,  sensory  roots,  330 
DE    WATTEVILLE,    electrotonus,    man, 

248,  251 

WEBER,  E.  H.,  joints,  100 
muscle,  47 
contraction,  21,  85 
elasticity,  86 
nerve,  conduction,  193 

temperature,  218 
WEBER,  E.  and  W.,  centre  of  gravity, 

107 

locomotion,  97,  127 
reflexes,  319 
walking,  114 
WEBER,  W. ,  sound,  144 
WEDENSKY,  muscle  sound,  21 

telephone,  77 
nerve  action  current,  215,  276 

fatigue,  226 
WEISS,  labyrinth,  463 
muscle,  glycogen,  39 

veratrin,  32 

nerve,  axial  current,  210 
WELT,  frontal  lobe,  622 
WERNICKE,  sensory  aphasia,  614,  634 

speech  centre,  625 
WERTHER,  muscle  acidity,  40 
WESTPHAL,  knee-jerk,  326,  357 
WHEATSTONE,  vowel  tones,  159 


WHYTT,  reflex  action,  311 
WICHMANN,  muscle  iields,  303 
WIEDEMANN,  galvanometer,  71 
WIENER,  optic  lobes,  515 
WILLIE,  speech,  disorders,  173 
WILLIS,  hypoglossal,  391 

muscle,  excitability,  3 

vowel  tones,  159 
WILSON,  optic  lobes,  512 
WINKLER,  skin  fields,  303,  306,  356 
WINTEUSTEIN,  muscle  chemistry,  94 

nerve  centres,  271,  276 

rigor  mortis,  42 

WISLICENUS,  muscle  metabolism,  43 
WOLF,  vowel  sounds,  158 
WOLLASTON,  muscle  sound,  19 
WOLLENBERG,  vestibular  nerve,  405 
WORM-MULLER,  thermal  currents,  76 
WOROSCHILOFF,  spinal  cord,  283 

spinal  lesions,  345,  346,  357 
WUNDERLICH,  muscle,  heat,  59 
WUNDT,  frontal  lobe,  619 

muscle,  fatigue,  12 

nerve,  276 

opening  tetanus,  25 

spinal  ganglion  cell,  262 

tetanomotor,  221 

YEO,  brachial  plexus,  302 
muscle  latency,  9 
visual  area,  606 

ZAAIJER,  femur,  98 

ZEDERBAUM,  nerve  conduction,  193,  276 
ZEYNEK,  nerve  activity,  259 
ZIEHEN,  convulsions,  518 
ZIEMSSEX,  muscle,  heat,  60 
ZIM.MEUMANN,  walking,  117 
ZUNTZ,  fatigue,  food,  51 
muscle,  efficiency,  67 


END  OF  VOL.  Ill 


Printed  by  R.  &  R.  CLARK,  LIMITED,  Edinburgh. 


HUMAN    PHYSIOLOGY 

By   PROF.    LUIGI    LUCIANI 

Translated  by  FRANCES   A.   WELBY.      With  a  Preface  by 
Prof.  J.  N.  LANGLEY,  F.R.S. 

In  Five  volumes.      Illustrated.      8vo. 

Vol.      I.  CIRCULATION  AND  RESPIRATION.      iSs.  net. 

Vol.    II.  INTERNAL     SECRETION  —  DIGESTION  —  EXCRETION- -THE 

SKIN.      iSs.  net. 
Vol.  III.   MUSCULAR  AND  NERVOUS  SYSTEMS. 

SOME   PRESS   OPINIONS 
VOL.  I 

LANCET. — "We  offer  a  hearty  welcome  to  the  work  of  the  veteran 
professor  of  physiology  in  Rome,  one  of  the  early  Italian  pupils  of  Ludwig 
and  the  successor  of  Moleschott.  Few  men  have  such  an  all-round  know- 
ledge of  physiology  as  Luigi  Luciani,  or  so  wide  an  outlook  on  physiological 
problems,  both  in  their  modern  and  in  their  historical  aspects.  Moreover, 
this  treatise  will  introduce  to  English  readers  much  of  the  work  done  by 
his  compatriots,  which  is  none  too  well  known  in  either  England  or  America. 
It  is  rather  remarkable  that  the  translation  into  English  of  such  an  all-round 
comprehensive  work  should  have  been  so  long  delayed.  All  the  more, 
therefore,  do  we  congratulate  Miss  Welby  on  the  successful  manner  in  which 
she  has  performed  her  work.  We  wish  this  and  the  succeeding  volumes 
every  success  in  their  English  garb,  and  we  hope  that  the  other  three 
volumes  will  soon  make  their  appearance." 

BRITISH  MEDICAL  JOURNAL. — "The  text-book  is  one  which 
should  be  read  by  those  studying  for  higher  examinations,  and  all  who  wish 
for  a  literary  and  philosophic  treatment  of  the  subject.  Luciani  has  the 
same  lucidity  and  charm  of  style  which  Sir  Michael  Foster  possessed,  and 
his  text-book  fills  almost  exactly  the  place  which  Foster's  text-book  held  in 
English  literature.  Very  good  are  the  admirable  historical  summaries  by 
which  each  subject  is  introduced.  .  .  .  An  excellent  feature  is  the  way  he 
sets  forth  classical  experiments  which  prove  the  points  he  is  discussing. 
He  writes  knowing  that  he  has  breadth  and  room  enough  in  his  four 
volumes,  and  owing  to  this  his  work  gains  enormously  over  the  dull,  un- 
embroidered  one-volumed  text- book.  The  student  could  not  have  a  better 
introduction  to  physiology  than  Luciani's  chapter  on  living  matter. 
Miss  Welby  has  done  her  work  very  well." 


SOME   PRESS  OPINIONS   OF  VOL.    I.— Continued. 

NA  TURE. — "  The  arduous  labour  of  translation  has  been  carried  out 
very  efficiently,  the  English  version  being  clear,  accurate,  and  eminently 
readable.  .  .  .  The  references  to  the  literature  of  the  subject  appended  to 
the  various  sections  of  the  work  form  a  very  useful  feature.  The  editor, 
Dr.  M.  Camis,  has  rendered  these  more  complete  by  the  addition  of  the 
chief  recent  English  and  American  physiological  papers.  These  references 
will  undoubtedly  offer  valuable  guidance  to  senior  students  of  physiology 
desirous  of  extending  their  knowledge  of  physiology  beyond  the  limits  of 
their  text-books.  .  .  .  The  book  is  a  remarkable  achievement,  especially  in 
view  of  the  fact  that  it  is  the  work  of  a  single  author,  and  appears  to  the 
reviewer  to  possess  special  qualities  and  merits,  which  entitle  it  to  a  high 
place  amongst  the  existing  English  text-books  of  physiology." 


VOL.  II 

BRITISH  MEDICAL  JOURNAL.—"  Luciani  is  especially  valuable 
in  giving  the  student  admirable  summaries  of  the  history  of  the  science, 
and  he  writes  with  a  philosophic  grace  and  literary  style  such  as  Michael 
Foster  possessed,  and  which  Miss  Welby  renders  into  English  very  well 
indeed.  .  .  .  We  cordially  recommend  the  perusal  of  this  volume  to  those 
who  are  studying  physiology  with  other  aims  than  the  passing  of  examina- 
tion papers." 

LANCET. — "  The  orderly  statement  of  facts  and  theories  with  reference 
to  digestion  are  most  excellent,  and  the  same  may  be  said  as  regards  the 
functional  processes  of  the  kidneys  and  the  skin.  .  .  .  We  feel  sure  that 
this  volume  will  be  welcomed  by  English  physiologists  and  practitioners  of 
medicine,  as  well  as  by  students  who  are  in  pursuit  of  knowledge  carefully 
sifted  and  pleasantly  presented.  The  translation  does  Miss  Welby  much 
credit." 

EDINBURGH  MEDICAL  JOURNAL.— "  The  various  problems 
are  discussed  in  a  critical  and  judicial  manner,  and  the  growth  of  know- 
ledge in  each  department  is  set  forth  in  a  fashion  which  brings  clearly 
before  the  reader  the  way  whereby  our  present-day  opinions  have  been 
elaborated  and  matured.  The  text  is  thoroughly  up-to-date  in  each  section 
of  the  treatise,  and  presents  the  views  of  the  learned  writer  in  excellent 
idiomatic  English.  The  volume  is  a  further  instalment  of  a  work  that  should 
be  in  the  hands  of  every  one  who  is  interested  in  the  science  of  physiology." 

NATURE. — "The  important  character  of  Prof.  Luciani's  text-book 
was  well  recognised  by  English  readers  when  the  translation  of  the  first 
volume  made  its  appearance.  The  second  volume,  which  has  just  been 
issued,  confirms  this  impression.  The  subject-matter  is  treated,  as  a  rule, 
in  an  interesting  way,  pros  and  cons  on  disputed  points  are  discussed 
intelligently,  and  the  work  of  past  researchers,  though  in  the  main  chiefly 
interesting  to  the  historian,  is  presented  with  great  fulness  and  lucidity. 
The  book  will  prove  a  valuable  asset  to  the  professed  physiologist  and  to 
the  advanced  student." 

LONDON  :  MACMILLAN  AND   CO.,   LTD. 


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