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-£•*
              Presented to the
Long Island Historical Society,
            By  Mrs. ENOS;
         FOR THE  ENLARGEMENT OF  THE
   Medical  Department  in  its Library.
            In Memory of her Husband,
      DE WITT C. ENOS,  M.D.
                 WHO DIED
             December \\th,  1868.
    THIS BOOK HAS BEEN LOANED
               by the
Long  Island  Historical Society
          to the Library of the
 Medical Society  of the County of Kings
               1901 

/*'
1  A
k 


NATIONAL LIBRARY OF MEDICINE




         Bethesda, Maryland 
*> 
 
AN
ELEMENTARY  SYSTEM
OF
i*1)i»sfoi*0jKff+
         By JOHN BOSTOCK, M.D.

            F.R.S. L.S. AND H.S. M.R.I.

MEM. AND V. PRES. OF THE GEOLOGICAL, MEM. AND" LATE V. PRES. OE
 THE MEDICAL AND CHIRURGICAL, AND MEM. OF THE ASTRONOMICAL
 SOCIETIES OF LONDON";  MEM. AND LATE PRES. OF THE EDINBURGH
 MEDICAL SOCIETY; HON. MEM. OF THE LITERARY AND PHILOSOPHICAL
 AND OF THE HISTORICAL SOCIETIES OF NEW YORK J LECTURER IN CHE-
 MISTRY AT GUY'S HOSPITAL; PROFESSOR OF PHYSIOLOGY IN THE LIV-
 ERPOOL ROYAL INSTITUTION, &.C. &C.
           VOL. I.  .^flfr ISUfy
                    HISTORICAL
                      •socieru
          BOSTON:
WELLS AND LILLY—COURT-STREET.-
1825. 
4
^
 
PREFACE.
  When we reflect upon the distinguished share which
our countrymen have borne  in  improving the know-
ledge of the animal ceconomy, it may appear not a lit-
tle remarkable, that we have no original work in  our
language which contains a  systematic and  connected
view of modern physiology.  My object in the follow-
ing pages is to endeavour to supply this deficiency, by
presenting  the student with a concise view of the pre-
sent state of the science, embracing an account of the
most important facts  and  observations, as well  as of
those theories  and hypotheses which  have been  the
most generally received, or have  been sanctioned by
the authority of the most eminent names.  As my de-
sign is to furnish an elementary treatise, my first  aim
has been perspicuity, both in language and in  arrange-
ment ; and although it  has not been  my intention to
produce what  may be styled  a popular work, yet I
conceive that it contains  so  little of what  is strictly
technical, as to be  generally intelligible to those who
are not conversant with the  medical  sciences.  View-
ing it, however, in  connexion with  its appropriate ob-
ject, I have endeavoured,  in all cases, not merely to
afford the  student  a  digested abstract of  the present
9tate of our information on the various topics which it
embraces,  but by referring him to  the iources whence 
IV
PREFACE.
I have derived my information, to enable him to ex-
amine for himself how far I have given a correct ac-
count of them, and to assist  him in pursuing  the inves-
tigation of any part in which he may feel  more parti-
cularly interested.  And I may  here remark that in no
instance have I given a reference to any book which  I
have  not myself  examined, and  that in order to facili-
tate the progress of those who may be disposed to fol-
low me in this track, I  have appended  a list of  the
works that have  been consulted, with the dates of  the
editions employed.
   With respect to references, the plan which I have
proposed to myself has been to  indicate, in  all instan-
ces, the original sources of my materials, while, at  the
same  time, I have avoided filling my pages with a mul-
titude of quotations, which could afford  no  additional
authority to the subject in question.  On one  point  I
profess myself to have exercised all the care of which
I was capable, in scrupulously assigning  to  each  indi-
vidual the share of merit which justly belongs to him
in the discovery of facts or  the formation of  theory.
During the progress of information, and while know-
ledge is rapidly advancing, it not unfrequently happens
that the same fact is discovered, or  the same train of
reasoning  developed, by different individuals entirely
independent of each other;  but where the priority of
publication is clearly proved, we ought to be cautious
in admitting any claims that  are subsequently brought
forwards, while all  instances of that disingenuousness
which aims at suppressing the names of preceding wri-
ters, for the purpose of procuring a surreptitious cele-
brity, cannot be too severely reprobated.  But to  the 
PREFACE.                    V
credit of  the  English be it  said, that such examples
are among them extremely  rare.  It is impossible  to
peruse the various scientific and medical journals of the
metropolis without observing, that so far from keeping
back the  various discoveries that are made  in  other
countries, one of their first objects is to obtain priority
of infprmation on these topics, and it is truly gratifying
to observe with what quickness and accuracy it is trans-
mitted to us from  the  various parts of the continent.
   1 feel it incumbent upon me to make some  observa-
tions upon the portion of the work which I have de-
voted to  the  consideration  of physiological  theories.
When we call to mind the  fate  of  those which have
hitherto been given to the world, how even the  most
elaborate of them, and those which appeared to be the
best founded, have been  successively discarded, and
given place to some new speculation, v\ hich has, in  its
turn, shared the fate of  its predecessors,  we might  be
tempted to regard the whole as undeserving of any
share of our attention.   But, although the truth of the
foregoing  statement cannot  be denied, still, 1  appre-
hend, the subject possesses  many claims  upon us.  It
might be  sufficient to allege that  the theories of  emi-
nent physiologists form a curious  part of the history of
the science, that they  mark the progress of knowledge,
and exhibit, in an interesting point of view, the  opera-
tions of the mind in its  attempts to  arrive at truth.
It can surely never  be considered as an   unimportant
or trifling pursuit,  to inquire  how such men as  Haller
and Hunter reasoned, or by what mode of investigation
they were led to the discovery of the truths which im-
mortalize  their name«. 
VI
PREFACE.
  And further, although no one in the present day ean
be insensible to the comparative value which ought to
be attached to facts and to opinions, still they are often
so intimately blended together that it is  extremely
difficult to separate them, and this is more especially
the case in the  study of physiology, where, from obvi-
ous causes, it is much less easy to  make observations,
or to perform experiments that may lead to unexcep-
tionable results, than when we operate upon inanimate
matter.  Even  the most unfounded, and, as we  now
conceive them,  the most absurd theories of the chemi-
cal and mathematical physiologists of the seventeenth
century, were, to a certain extent, derived from what
at that period was called experiment, and which satis-
fied  the minds of the learned men of the  age, yet  if
we except the  simple detail of anatomical observation,
there  is perhaps  scarcely a single statement  against
which  we should  not now be disposed to offer some ob-
jections.  And  there is  another circumstance which
renders it necessary for the student  to  be made ac-
quainted with  the  most noted theories of the older
writers, that without this knowledge their works would
be  unintelligible;  for such complete possession  had
these topics taken of their minds, that we can scarcely
peruse a single  page  without meeting with some  the-
ory,  either expressed or  implied, which is intimately
connected no less with their observations  than  with
their reasoning*.
  And I shall further advocate the cause of theory,  as
being a direct means, and that a very important  one,
of acquiring a knowledge of  facts.  In prosecuting our
investigations we  are necessarily guided by some object. 
PREFACE.
Vll
and  this  is,  in most cases,  a preconceived hypothesis,
which we wish either to put to the test of experiment,
or to inquire how  far it can  be reconciled with the
structure  of  the body  or the operation of  its functions.
This is the natural process  by which information  is ac-
quired ; the  errors into which we  have so frequently
fallen do not consist in the  legitimate employment of
hypothesis, but in our being so much influenced by it,
as to  " mistake the scaffold  for  the  pile,"  to regard a
train of reasoning in  the same  light with a deduction
from  facts.   Who that  has attended to  the state of
chemical science  for  the  last 50 years can  reasonably
doubt that its progress was  prodigiously accelerated by
the formation of  the   Lavoisierean theory,  by classing
the insulated facts in a systematic form, by generalizing
the conclusions that appeared to be fairly derived from
them,  by introducing a uniform  nomenclature, and by
discarding a  mass of antiquated opinions and phraseolo-
gy ?  Yet this edifice,  so beautiful in  its separate parts,
and  which  seemed so consistent  as a whole,  and so
firmly connected  together,  appears destined to fall be-
fore the  powerful genius  of Davy; its strong  holds
have  been assailed, and it totters to its very base.
  One of the prevailing errors of  the present day I
conceive to be a fondness for constructing new arrange-
ments, and for introducing new terms into all the phy-
sical sciences.  This is, no  doubt,  partly owing to the
rapid increase of information, which, to  a certain ex-
tent,  produces a  necessity  for change of  both system
and of language;  but the  innovations have been carried
to a most unreasonable length.   Indeed  this is so  much
the case, that, in some departments, the attention is 
Vlll
PREFACE.
almost entirely engrossed by the study of nomenclature,
while in consequence of  the variety of denominations
that are given to the same object, and the number of
technical  terms  with  which  the  memory  becomes
charged, we defeat  our very end  and object, which is
to produce a uniformity of names, and a greater sim-
plicity in our designation of things.  In the following
work it has been  my aim to form an arrangement,
which shall be no further technical  than is absolutely
necessary  for announcing  the subjects as they succes-
sively fall  under our notice; scarcely a single new term
is-introduced, while, with a very few exceptions, I have
employed  the old terms in their most generally receiv-
ed  acceptation,  and have endeavoured always to use
them precisely in the same sense,
  Although I am not sensible  that I have omitted any
reasonable means for rendering my work complete, yet
I am fully aware that,  after all  the  pains that I have
bestowed  upon it, it must contain many parts that re-
quire correction, both with respect to the statement of
facts and  the inferences that  are deduced from them.
It is, in  a  great measure, from this consideration that I
have determined to publish it in separate volumes, in
order that I might be able, in the second volume, to
correct  the errors  and supply the  deficiences which
should be pointed out  as occurring  in the first.  And
I beg to  remark upon  this  subject, that I shall pay
every attention  to  the criticisms that  are made upon
the work, and  shall thankfully avail myself of all the
information that I can  obtain from this source.
   I cannot conclude these remarks  without adverting
to the great advantage which I  have derived in the 
PREFACE.
IX
prosecution of this work from the very extensive and
valuable library of the Medical andChirurgical Society.
When we reflect  upon  its  recent  date,  and  bear  in
mind that  it was  established by a few private indivi-
duals, depending for  its support solely upon the sense
of its utility, we cannot  estimate  too highly the public
spirit of those who were the most active in its original
formation.   To the survivors  it is  a sufficient reward
to witness the success of their labours, but I trust that
I shall  be pardoned  for introducing in this connexion
the name of  Dr.  Marcet, among whose claims to the
gratitude of his profession, perhaps the very conside-
rable share which he had  in  the establishment of the
Medical and Chirurgical Society, must be considered
as the most important.*

  * I am aware that it is  seldom proper to obtrude upon the pub-
lic feelings of a personal nature, yet I shall  hope for the indul-
gence of my  readers  if I offer  my testimony to the distinguished
merits of my much valued and  ever to be lamented friend.  His
character has been so justly delineated by the elegant and correct
pen of Dr. Roget, that 1  can do no more than  give my warm as-
sent to the sentiments expressed  in his memoir, an assent sanction-
ed by an unreserved and confidential intimacy of  twenty-eight
years.
t 
 
Content®*
                                                      PAGE
 Introductory  Observations    -                           1
 Definition of Physiology    -      -      -      -           1
 Sketch of the History   -----       i
 Hippocrates        ..-_-.    i
 Aristotle        -      -      -      -      -      -       3
 Galen      -       -      -      -   •   -      -      -    3
 State of the Science after his Death    -                     5
 Chemical and Mechanical Sects    -     ■ -      -      -    6
 Origin of the Vitalists; Stahl    -                           6
 Hoffmann   -------8
 Boerhaave     ------       8
 Haller.......9
 Cullen.......9
 Hunter      -------   10
 Bichat   -       -      -      -      -      -      -      H
 Plan of the Work ; Division of the functions into contractile
   and sensitive     -      -      -      -      -      -12
 Connexion between the sensitive and intellectual functions      13


                      CHAPTER I.

 OF MEMBRANE      -      -       -      -      -      -15
 The body composed of solids and fluids  -      -      -      15
 Remarks upon the  systematic  arrangements of the subjects
   of physiology ------      16
 Membrane; its extent, composes the basis of the body     -   17
 To what substances the term is applied  -      -      -      19
 Mechanical structure of membrane ;  opinion of Haller ;  cel-
   lular web    ------      20
 Membrane composed of fibres      -       -      -      -   20
 Continuous all  over the body                               20
 Boerhaave's hypothesis of the  structure of membrane ; re-
   futed by Haller  ------   21
 Ultimate  fibre thought to be vascular                        22
 Nature of the ultimate fibre ; its size      -      -      -   23
Fontana's account of the membranous fibre     -      -      24
Properties of membranous matter ; elasticity      -      -   25
Membrane does not  possess spontaneous contractility    -      26 
xu
CONTENTS.
                                                        PACE
Vis cellulosa of Blumerrbach       -      -      -          27
Tone of Bordeu and Bicbat                                 28
Sensibility of membrane ; errors of the ancients ;  old opera-
   tion of lithotomy      -----      29
Membrane the most simple  of the organized bodies -      -   31
Organization defined;  physical, physiological   -       -      31
Opinions of Dumas and Cuvier; remarks   -      -      -   33
Chemical  nature of membrane ; Haller's opinion       -      34
Culien's ; experiment? of Fourcrov, of I Jatchett    -      -   35
Albumen the basis of membrane ; pontains  jelly,  mucus, and
   water;  effect of the water      -      -      -      -   37
Ultimate elements of membrane                             38
Effect of chemical re-agents       -      -      -      -   39
Chen»;cal relations of jelly;  relation of jelly to albumen -      40
Hatchett's experiments     -      -      -      -      -   41
Species of membrane; Cellular texture, Haller's account of    41
Comnriun-cahons between its cells; Emphysema    -      -   42
W. Hunter's account of the  cellular texture    -       -       43
Borden's; Bichat's; remarks on Bichat's  account   -      -   44
Form of the cells       -----       46
Properties of the cellular texture ; chemical composition   -   47
Membranes : their texture                                  49
Bichat's arrangement; mucous; serous; fibrous     -          49
Chemical composition    -----      53
Tendons and ligaments; cartilages  -      -                 53
Life  of these parts, in  what  it consists                        55
Mode of their growth       -      -      -      -      -   56
The skin ; epidermis; its pores; vessels, &c.; effect of pressure  57
Corpus mucosum   -       -      -      -      -      -   62
Colour of the skin; nature of the colouring matter; Albinos ;
  cause of this variety      -      -      -      -      -   63
Cutis;  its nerves, papillae,  blood-vessels; minute  texture;
  properties       -       -      -      -      -      -67
Structure of the papillae  -----      69
Chemical composition of the cutis  -      -      -      -   70
Nails, &c.       -       -       -      -      -       .       71
Hair;  Vauquelin's analysis  -      -      -      -      -   72


                      CHAPTER II.

Of bone        ----._       75
    § 1. Form and Structure of Bone       -      -      -    75
Description of bone     -----       75
Arrangements of the bones  -      -      -      -      -    76
Mechanism of the upper and lower extremities                77
Articulations; joints  -       -  N   -      -      -      -    78
Structure of bone; observations of Herissant   -       -       80 
CONTENTS.
xm
PAGE
Texture of the Membrane ; Bichat's opinion      "-      -    81
Compact and cellular part; uses of each       -       -        82
Texture of bone, fibrous ; direction of the fibres   -           84
Physical properties    -----        85
    §2. Chemical  composition ef Bone   . -      -      -    85
Phosphate of lime ; albumen   -                            85
Oil and Marrow; their  uses       -      -      -           87
    § 3. Formation of Bone    -      -       -               88
Ossification; Haller's hypothesis; remarks upon it -      -    89
Progress of ossification  -----        91
Howship's observations   -      -      -      -      -    92
Successive changes in the structure of the bone       -        92
Origin of the earth ; how deposited ? how organized ?    -    93
Mode of prosecuting the inquiry                            94
Duhamel's hypothesis     -      -      -      -           97
Effect of madder on bone      -                            97
Ossification a case of secretion    -      -      -           98
Reparation of bone ; how effected ?    -       -       -        99
    §4. Vital properties of Bone  -      -      -      -   101
Diseases of bone      -                                   102
State of the earthy matter -      -      -      5      -   102


                      CHAPTER III.

Of muscle  -       __£»-.   105
    § 1. Form and Structure of Muscles        -              105
Description of muscles     ._,*--   105
Their vessels and nerves      -                           106
Minute structure; observations of Leeuwenhoek   -      -   107
Of Muys and  others    -       -      -       -       -       107
Thought by some to  be vascular;  to have transverse fibres   110
Prochaska's account       -      -      -      -      -   111
Fontana's      -      -       -      -       -       -       113
Carlisle's -       -       -      -      -      -      -   113
Muscular and nervous fibres thought to be identical   -       114
Muscular coats     -       -      -      -      -      -116
Uses of the two structures     -      -       -       -       116
Bichat's arrangement of muscles  -      -      -      -   117
Colour of muscles      -       -      -       -       -       117
Composition of muscles; cellular substance       -          118
Albumen, jelly, extract, osmazome, salts       -       -       119
    & 2. Chemical relations of muscle      -      -          120
Action of sulphuric acid ; of nitric acid -       -       -       120
Formation of adipocire  ; nature of adipocire      -      -   122
Yellow acid     -      -       -      -       -       -       123
Spontaneous formation  of adipocire       -      -      -   124 
XIV
CONTENTS.
PAGE
    § 3. Properties of muscles      -       *       -      "   12?
1.  Physical properties  -      -      -       -       -       J25
Extensibility; elasticity    -       -       -       "          J*J}
2.  Vital properties; contractility      -       -       -       l*jj
Reasons for the name     ...                  128
Muscular contraction described        -       -       -       13U
Is the specific gravity affected ? Blane's experiments; Car-
  lisle's        -       -      -      -       "       -       {30
Is the blood expelled ?             -       -       -      '   \iQ
Nature of contractility        ~      ~       ~       ~       \tZ
Contractility confounded with Elasticity    -       -      '    ti
Difference between them     -                            J34
Relaxation;  phenomena of relaxation     ...   135
Replacement of the parts     -      -            •  -       J3"
Bichat's opinion   -                                    *   iqq
Nature of stimulants  -       -      -       -       **       j3°
Stimulants do not act mechanically        -       -      -   139
Tonicity; probably depends upon  elasticity    -       -       140
Bichat's different kinds of contractility     -       -      -   141
Sensibility of muscles; HaHer's opinion       -       -       142
Bichat's.......\f
Effect of habit  -       -       -       -      -       -       143
     §4.  Use of muscles  -       -       -       -#     -    143
Do.es all spontaneous motion  depend upon contractility ?       144
Case of the iris        -----       145
Vita propria of Blumenbach       -                         I45
     § 5.  Mechanism of muscles       -      -       -       146
Borelli's account  of muscular action       -       -       -    147
Illustration of muscular motion        -      -      -       147
Loss  of power from the  nature of the lever       -       -    148
Power sacrificed to convenience       -                     148
Increase of velocity       -       -      -       **       -    149
Loss  of power from oblique position of the muscles   -       150
Saving of the quantity of contraction     -       -       -    150
Extent of action increased      -       -      -      -       I50
Loss of power from the  composition of forces     -       -    151
From the oblique insertion of the  tendons     -      -       152
 From the ends acting against each other  -       -       -    152
 Saving of muscular power     -       -      -      -       1^3
 Saving of muscular contraction    -                         I53
 Contractility a specific  property       -      -       -       1&3
 Remarks on animal mechanism    -                         I55
 Force of muscular contraction  -       -      -       -       *55
 Its velocity ; its extent   -      -              -      "   1^6
      §6.  Hypotheses of muscular contraction   -       -       157
 Hypotheses of contraction         -       -       -      -   lo7
 What is the efficient cause of contraction ?            -       I58 
CONTENTS.
XV
                                                        PACE
No mechanical cause adequate    -      -      -       -    159
Various unfounded hypotheses;  Borelli's      -      -       159
Stuart's; chemical hypothesis;  electrical -      -           159
Keill's hypothesis      -                                   160
Prochaska's; Hales's observations; Blane's hypothesis    -    162
General remarks       -                                   164
Cause of contractility      -                                165
Caloric;  electricity ; oxygen; chemical composition ; Hum-
  boldt's experiments   -      -      -      -      -       166
Contractility connected with the chemical condition of the
  muscle, and the coagulability  of the  fibrin      -       -    169
General remarks on the chemical hypothesis  -      -       171
Contractility supposed  to depend upon structure ; upon at-
  traction  -      -       -      -      .      _       -172
General conclusion     -      -      -      .      .       174

                      CHAPTER  IV.

Of  the nervous system   -      -      -      -       -    175
     §  1.  Description of the nervous system    -      -       176
Description of the brain ; membranes, ventricles -       -    177
Division  into cerebrum and  cerebellum;  into the  two he-  '
  mispheres   -       -      -      .      .      .       J77
Cortical and medullary matter    -      -      -       -    178
Spinal cord     -       -      -      .      .      _       j-yo,
Nerves    -      -       -      .      .      .       -179
Intercostal nerve       -      -      .      .      _       jgQ
Relation  between the brain and nerves    -      -       -    180
Opinion of Gall; of Tiedemann       -      -      .       j 81
Ganglia    -------    181
Distribution of the nerves      -      -      .      .       *Q2
Great quantity of blood sent to  the brain  -      -       -    183
Minute structure of the brain ; its fibres-      -      -       184
Decussation of the fibres  -      -      -      -       -    185
Microscopical observations  on  the brain ; by Prochaska ;
  the Wenzels; Bauer       -      -      .      .       igg
On  the nerves; by Monro; Fontana; Soemmering; Reill    188
Chemical properties of brain ; experiments of Fourcroy «md
  Vauquelin      -       -      -      .      .       -    190
     § 2.   Vital powers or faculties of the nervous system, and
            the mode of their operation  -      -      -       192
Sensibility;  not necessarily connected with contractility       193
Remarks upon the terms employed       -                  193
Sensibility defined ; relation of sensation to perception        194
Mode of action of the nervous system     -                   196
1st. Impressions on the organs of sense       -      .        197
Illustration oi the touch  and the sight     -      -       -    197 
XVI
CONTENTS
                                                        PAOB
2d.  Re-action of the brain    -      -       •       -       198
Illustrated by voluntary motion   -       •*•      -      -    199
Two modes of sensibility     ...       -       199
How • '«* the nerves act ?  -----    200
Hypothesis of the nervous fluid       -                      201
Of vibrations     .-_.•-    202
Of electricity         .....       203
    §3.  Use of the nervous system        ...    206
1st. To maintain a connexion  with the external world         206
2d.  To unite the body into one whole     ...    206
Vegetable life        ....       -       207
That of th*' lower classes of animals      ...    208
Is there a sensorium commune ?                             209
In man, situated in the brain     -                          209
More extended in the lower animals   -                      210
Functions of the spinal cord      -                         210
Effect  of injury of ihe brain   -                             211
Is volition confined to the brain ?  -      -       -       -    212
Doctrine of the Stahlians      -                             212
Exclusive seat of perception      ...       -    213
Particular hypotheses; membranes; pineal gland  ^  -       214
Researches of the moderns; first,  observing the  effects of
  injury or disease        -----    216
Of hydrocephalus      -----       218
Second, attempting to trace the nerves to their origin         219
Do different parts of the brain serve for different purposes ?
  Hypothesis of Willis    -      -       -       -       -   220
Philip's classification of the nervous functions          -       221
Observations of Flourens and Rolando     -                  222
Bell's  experiments on the nerves;  Magendie's        -       224
Bell's  division of the nerves into  two classes       -       -   225
General conclusion     -----       226
Comparative examination of the human brain      -       -   228
Proportion of the brain to the nerves  -      -       -       229
Of the cerebrum to the cerebellum        ...   230
Of the cerebrum to the medulla oblongata    -       -       230
Organization of the brain   -----   231
Use of the ganglia     ...      -       -       231
     §  4.   Connexion between the muscular and nervous systems   232
Introductory remarks      -       -'      -       -       -   232
Question stated;  Doctrine of Haller-,  of Ihe neurologists     234
Arguments of the Hallerians       -                         235
1st. Contractility not in proportion to  the nerves      -       235
2d. Contractility of separated  part         -                  235
3d. Acephalous  foetuses       ...       -       236
4th. Zoophytes w;thout nerves    -                         236
5th. Heart acts before the nervous system   -       -       237 
CONTENTS.
XV11
 Other arguments •  contraction of fibrin by Galvanism     -    238
 Reply of the neurologists      -                            239
 General diffusion of nerves       -                         239
 Case of the heart considered  -                            240
 Of the contractility of separated part9     ...    240
 Of acephalous foetuses         -      -      .      _    .   241
 Comparative size of the brain and spinal cord     -       -    242
 Propagation of contractility    -                            242
 Case of the zoophytes considered  -                         242
 Direct arguments of the neurologists  -      -      -       243
 Inferences  respecting the nerves of the heart      -       -    243
 Stimulants  act  through  the nerves ;  experiments of Smith     244
 Sedatives act through the nerves -           -      -       245
 Mental operations alffect the muscles      ...    245
 Experiments of LeGallois; of Philip  -      -      -       246
 General observations;  question confined to certain  cases
   only     -       -       -       .      .       .       -    248
 Distinction between voluntary and involuntary muscles        249
 Independent contractility exercised by  inroluntary muscles     250
 Experiments on stimulants not generally applicable    -       251
 Conclusion         ------    252
     §5.   Arrangement  of the functions        -      -       253
 General observations      -                                 253
 Arrangement of Dumas; of Richerand;  of Bichat; of Cuvier    254
 Objections and remarks        ....       256
 Functions  arranged into  contractile,  sensitive,  and intel-
   lectual   -----..    251
 First class ; circulation  ; respiration  ; &c.     -      -       257
 Connexion between them   -                                 259
 Functions of the inferior animals      -       -       -       260
 Second class; sensitive  functions    -             -      -    261
 Third class; intellectual functions     -       -      -       262


                       CHAPTER  V.

 Of the Circulation       -                            -   264
     §  1. Introductory remarks   -                            264
On the connexion of the functions  and their relative im-
   portance        ------   265
Relation of the heart  and brain        -              -       265
Heart formed before the brain     ....   266
Action of the heart  independent of the  brain  -       -       267
     § 2.  Description of the heart and its appendages       -   268
Description of the heart      -                            269
Nomenclature of the cavities of the heart        -      -    269
Use of the heart      .....       270
r 
win
CONTENTS.
                                                         pAb*.
Arteries;  membranous coats;  muscular coat      -      -   271
Veins.......272
Course of the blood; the circulatiou double       -      -   272
Nomenclature employed       -                            273
Progress of the blood through the heart and vessels      -   273
    § 3.  History of the  discovery of the circulation      -       274
Opinions of the Ancients; of Servetus,  Colombo,  and Ce-
  salpini   -------   275
Discovery of Harvey   -----       275
Reception of Harvey's  doctrine   .       -       -          276
Proofs of the circulation       -                            277
1st. Observations on the heart of a living animal  -      -   277
2d.  Microscopical observations on the vessels   -       -       277
3d.  Mechanism of the valves      -                         278
4th. Operation of transfusion  -      _       -       -       278
Opinions entertained respecting the  operation     -      -   279
5th.  Effect of wounds of the vessels   -                     280
6th. Of ligatures   -       -      -       -       -      -   281
Relation between the two circulations        -       -       281
Illustrations trom  pathology ;  examples    ...   282
    § 4.  Circumstances connected with  the mechanism of the
           heart       -       -       -       -      -       284
Size of the cavities ------   284
Form and  strength of the  ventricles    -                     285
Order of time in which the parts of the heart contract        286
Do the cavities expel all their contents ?  -                  287
Period of a complete circulation; Blumenbach's estimate     287
Systole and diastole of  the heart       -       -      -       288
No communication between the ventricles       -       -   289
Controversy of Vesalius and Dubois    -                     290
Liquor pericardii   ------   290
Size of the heart      -       -       -       -      -       291
Change of its figure during contraction    -        -       -   291
Beating of the heart   -                             -      292
Foetal circulation; general remarks       -                 293
Peculiarities of the  foetal  circulation    ...      294
Placenta;  foramen ovale ;  Ductus venosus et  arteriosus      294
Use of these parts        -                                295
Physical  cause of the change from  the foetal  state to the
  state after birth        -                                296
Mechanism of the foetal circulation     -                     296
Sabatier's hypothesis          -                            297
Developement of the parts        ....   298
Comparative anatomy of the circulatory organs       -      298
In mammalia and birds     ....       -   299
Amphibia      -       .       .       .                    299
Fish                      -              .                  301 
CONTENTS.
XI \
                                                         I'AGK
Remarks on the terms employed      -      -      -      3°1
General remarks   ------   302
    §5. V ital properties and actions of the heart      -      303
Sensibility; nerves of the heart;  their use       -       -   393
To convey perceptions of disease     -                    304
To indicate mental emotions       -                        3"5
Contractility of the heart      .      -      -      -      306
Cau*e of the contraction of the heart;  opinions of the  An-
   cients ; of Sylvius,  of Senac   -              -       -   30ti
Cause of the constancy of the  heart's motion  -      -      307
Willis's hypothesis       -      -       -       -       -    308
Doctrine of Stahl; rem irks upon it; objections      -       309
Structure of the fibres of the heart        -       -       -   310
Regularity of the  heart's motion ;  opinion of Bellini; of
   Baglivi;  of Haller  -----      312
     § 6 Action and properties oj the vessels       -       -   313
Sensibility of the vessels       ...       -      314
Contractility of the vessels        -       -       -       -   314
Opinion of Haller     -----      314
Hypothesis of Cullen     -----   315
Action of the capillaries       -                            3i6
Inequality in the  distribution of the blood  -       -       -   316
Hunter's experiments  ; remarks upon them    -       -      317
Parry's experiments     -       -       -                  31o
Opinions of Bicbat; Berzelius ; Young        *       -      319
Experiments of Verchuir; Philip; Thomson;  Hastings      320
Observations of Philip and Hastings       -       -          321
General conclusions      -           ...      322
Structure and offices of the veins  -      -      -       -   323
Cause of the pulse ; Bichat's opinion   -      -       -      323
Parry's experiments ; remarks    -      -      -       -   324
     §7.  Efficient causes of the circulation      -       -      325
 Contractility of the heart; of the capillaries     -       -   326
 Effect of the elasticity of the  vessels   -      -       -      326
 Pressure of the muscles upon  the veins   -      -       -   326
 Effect ot derivation ;  hypothesis of Wilson ;  of Carson         327
 Remarks ;  elasticity of the heart                            330
 No actual source of power       -                         331
 Causes which retard the motion of the blood  -       -       332
 Application of hydraulics to the circulation       -       -    333
 Use of mathematical reasoning in physiology  -       -       333
 Calculations of the force  of the heart, by  Borelli; by Keill;
    account of his experiments     -                         334
 Remarks       -      -      -      -       -       '       33£
 Hales's experiments; remarks    -                         -wo
     §8.0/ Inflammation     -                            337
 Phenomena of inflammation       -       -       -       -    337 
XX
CONTENTS.
                                                        FAt.t
Proximate cause      .....      338
Hypothesis of Boerhaave   -----   338
OfCullen......339
Of Allen  -------   340
General remarks      .....      341


                      CHAPTER VI.

Of the Blood    ...---   343
    § 1. Remarks on the progress of animal chemistry   -      313
Improvements of the French ;  Rouelle, Fourcroy, Berthollet   344
Of the English ; of Berzelius  -      -      -      -      346
Modern method of analysis       -                        346
    § 2. Nature and properties of the blood -      -       -   347
Description of the blood      ....      348
Spontaneous coagulation   -----   348
Extrication of caloric ; Gordon's experiment  -      -      348
    § 3. Fibrin   -       -      -      -      -       -   349
Circumstances affecting the spontaneous coagulation; effect
   of rest ;  of air     -      -      -      -      -      350
Experiments of Hewson ;  of Hunter      ...   351
Polypous concretions  -      -      -      -             352
Effect of the gases ------   352
Circumstances retarding the coagulation       -      -      353
Specific gravity of crassamentum  -      -      -       -   353
Haiitus -------      353
Cause of the coagulation of the fibrin     -                 354
Circumstances which prevent it                            354
Life of the blood  ------   355
Buffy coat     ------      357
Cause of its formation ; opinion of Hewson ; of Hunter; of
   Hey -------      358
Fibrin assists in repairing  injuries -                        359
Sympathetic powder   -----      359
Union of divided parts     -                               360
Operation of Taliacotius      -      -       -      -      361
Home's and Bauer's observations  -      -      -       -   361
    § 4. Red particles -----      363
Leeuwenhoek's account    -                               363
Hewson's account     -                                  364
Hunter's ; Torre's; Monro's ; Cavallo's; Young's  -       -   365
Size of the globules   -                                  367
Chemical properties       -                               368
Berzelius's experiments       -                           368
Iron in the blood ; Menghini's experiments        -       -   368
Colour of the blood ; Brande's experiments    -      -      369 
CONTENTS.
XXI
                                                        PAGF.
Vauquelin's experiments   -       -      -      -      -   371
Effect of air  upon the blood;  observations of Lower; of
  Cigna ; of Priest;ey   -----       372
Home and Bauer's observations on the globules   -      -   373
    § 5. Serum        -----       375
Properties of serum       -       -          **          -   375
Coagulation by heat    -----       376
Separation of the serosity  -----   376
Remarks on the  coagulalion of the serum     -       -       376
Effect of chemical re-agents       -      -      -      -   377
Properties of coagulated albumen      ...       377
Cause of the coagulation   -----   378
Hypothesis of Thomson ; of Brande    -                    378
Chemical relations of albumen; uncoagulated ; coagulated -   379
    § 6. Serosity      -                            -      380
Properties of serosity      -                                380
Contains no jelly      -----      381
Uncoagulable matter      -----   381
Opinion of Berzelius; of Brande       -                    382
Salts of the blood; examined by Marcet  -                 383
By Berzelius   ------      384
Use of the salts    ------   384
Sulphur in the blood   -----      385
Ultimate analysis of the blood      ...       -   3*55
     § 7. Different states of the blood   -                    386
Effects of disease  -      -      -      -              -   386
Arterial and venous blood; their colour; their temperature;
   capacity for heat    -----      387
Humoral pathology       -       -       -       -   x    -   388
Controverted by Baglivi;  by Cullen   -                    389
Account of successive  discoveries respecting the blood    -   390
Galen's opinions      -----      391
Harvey's; Lower's; Malpighi's;  Senac's   -       -       -   392
Observations of  Prevost and  Dumas   ...      394
Conclusion -------   395 
 
ELEMENTS
or
PHYSIOLOGY. 
/ 
INTRODUCTORY OBSERVATIONS.
   The term Physiology, according to its original mean-
ing, is  nearly  synonymous with  Natural  Philosophy;
but it has for  a long time been always usec[.in a more
limited sense,  and restricted to that branch of science
which  treats  of the functions  of the living  animal
body, and of the powers by which these functions are
exercised.*
   Notwithstanding the value which must have been at
all times attached to the  study of  the animal body,
both  as holding the first rank  in the  scale  of natural
objects, and as being intimately connected with  the
various  departments of medicine, its  functions were
seldom made a distinct object of investigation until the
beginning of the last century.   Although the writings
of  the  ancient physicians, and  of the  earlier  among
the moderns, abound in physjological speculations, they
are rarely  brought forwards  in a connected or sys-
tematic form;  so that we are  obliged to  collect  our
knowledge of their tenets more from a number of scat-
tered fragments, that are  dispersed through works on
medicine and pathology, than from treatises expressly
devoted to the subject.
   Hippocrates may be regarded as the father of phy-
siology as well as of medicine, although from the more
complicated nature of the  former, the actual advances

  * Some of the Germans have lately employed the more correct
term biology, as designating the science, which essentially consists
in the  knowledge  of those properties which distinguish  animate
from inanimate matter
               1 
2                   Hippocrates.
which he made in it were  probably not very consider-
able.   We observe in his writings  many  traces of the
Pythagorean philosophy, but, at the same  time, we
meet  with a large proportion of what is original, or, at
least,  what has not  been traced  to any  other source.
One of his leading tenets is the existence of a principle
which he styles nature (<pt/<nS), and to which he ascribes
the direction and superintendence of all our corporeal
actions and movements.  To  this  principle he attri-
butes  a species of intelligence, and  conceives that one
of its  most  important offices is to  attach  to the  body
what  is  beneficial, and to reject from it what would
prove injurious ;—an hypothesis which, although ex-
pressed in different ways, and clothed in  a more or less
mysterious form,  has continued to be a  popular doc-
trine  to  the present day.  Besides this nature, which
is regarded as the prime agent, there are other subor-
dinate principles  or faculties (3t/»aps$) which  especially
operate in the production of the various functions.
   With  respect  to the body, he  conceives it  to be
composed  of  three kinds of substances, solids, fluids,
and spirits, which are themselves formed  by the com-
bination  of  the  four primary elements.   The  nature
of  the body is supposed to  be materially affejcted by
the nature of the four  elements  which enter into its
composition; as  well as by the four qualities of  hot,
cold,  moist, and dry ; which, by their respective  com-
binations and  proportions, produce the four tempera-
ments.   These are considered  as  original predisposi-
tions  existing in  the body, influencing both  its  mental
and corporeal  character, arid  laying a foundation  for
the diseases to which the individual is more especially
liable.   In his account of the different functions  of the
body, although  we observe  many marks of  sagacity
and acuteness, yet there is much that is inaccurate and
erroneous.  His acquaintance with  the minute structure
of  parts was limited; but little was  known of the nature
»f the external agents which affectthe corporeal organs; 
                   Aristotle.'—Galen.                  3

while the use of the  organs themselves  was  derived
from  vague conjecture or false  analogy.  Hippocrates
also  adopted  the  mysterious opinions of Pythagoras
respecting the occult power of  particular  numocrs;
and he believed that the stars exercise an influence over
the operations of the body.*
   Little  or no  advance was  made in the  science  of
physiology from  the time of Hippocrates  to  that  of
Aristotle.  The genius of Aristotle and the course in
which it was directed were,  in  many respects, well
adapted for the  improvement of  this science.   He
appears to have been the first among the ancients who
advanced comparative anatomy and natural  history to
any considerable  degree  of perfection; and while  he
enjoyed great advantages for  obtaining information on
these topics, he cultivated these advantages with much
assiduity.  Hence  he  acquired  an extensive acquaint-
ance  with natural  objects,  and may be considered as
having made an actual advance in our knowledge of the
animal  ceconomy,  although  perhaps  less than  might
have  been expected  from the means of information
which he enjoyed, and the powers of mind which he
displayed on other topics.
   After the death of  Aristotle  we  have another long
interval, during which no progress was  made in physio-
logical science, when  it received  a new  impulse from
the genius of Galen.  A considerable share  of  the
celebrity which  this extraordinary character  attained
is derived from  his  physiology.  When we compare
his treatise " On the Use of the  Parts of  the Body"
with any work on  the same subject published before
his time, we cannot but  admire the superiority of  his
information and the ingenuity with which he applies it
to the explanation of the animal  ceconomy.  Yet  on

  * The best view of the Physiology and Pathology of Hippocrates,
which are every where blended together, is contained in his trea-
tise " De Natura Hominis."  Opera a Foesio, t. i. p. 22-.—-231. 
4
Galen.
both these points he is not  without  considerable defi-
ciencies and  inaccuracies ; his physiology is frequently
founded upon fallacious principles; and in  his applica-
tion  of such  as are more correct, he displays more of
what may be termed  ingenuity, than of that cautious
discretion which is  so  necessary in the investigation of
any intricate point connected with the actions of vitality.
  Galen  was a warm admirer and encomiast of Hippo-
crates ; he professed to agree with him in all his funda-
mental doctrines, and  to  aim at little more than to
elucidate and amplify his principles.   But although he
sets out from the same point, he soon deviates into a
more intricate path; and he becomes  so  involved in
abstruse  and complicated hypothesis, that we are no
longer able to trace the simplicity of the original in the
refined speculations of his commentator.  He assumes
the four  elements  and the  four qualities; but in his
application of them either to physiology or to patho-
logy,  he  introduces so many minute  distinctions and
intricate  combinations, as to give a new aspect to the
doctrine.  The real merit of Galen, however, consists
in his knowledge of anatomy and in  his acquaintance
with the  minute structure of parts, in which he made
very considerable advances  upon his  contemporaries.
The diligence  which  he displayed on  these points is
worthy of our warmest applause; yet the  encomiastic
flattery of his followers, by the excess to  which they
carried their admiration, has perhaps somewhat tended
to diminish his reputation.   From many circumstances
connected with the history of the age, as well as from
the candid confession  of Galen  himself, we may con-
clude  that  he rarely, if ever,  dissected  the human
subject;  but that he examined the bodies of apes, and
of other  animals the  most  nearly resembling it; and
from these,  by making what he deemed  the proper
allowances,  he  draws up his descriptions.   But  his
zealous disciples would not admit of what they thought
an imperfection in the  works of  their master: and to 
Chemical and Mechanical Sects.
3
such an extent did they carry this principle, that  they
even considered it  as  more  probable that the human
body should have undergone a permanent change in its
anatomical structure, than that Galen could have  com-
mitted an error.
   The  superior  talents of Galen, and the unrivalled
reputation which he obtained,  seemed  to  repress all
further efforts for the improvement  of physiological
science ; and his immediate successors, regarding him as
beyond the  reach  of competition} were satisfied with
implicitly adopting his opinions,  without  attempting to
inquire into their correctness, or to extend their appli-
cation.   The spirit of the  times but too  powerfully
coincided with this feeling.   The Roman empire began
to exhibit unequivocal marks of decline  : in every de-
partment of literature there  was a deficiency of genius,
and nothing  more  was now  attempted than to imitate
the standards of excellence which had adorned  the
preceding age.   But Rome, even in its most splendid
period, had bestowed little attention upon the physical
sciences ; and the  efforts which were now  made were
altogether  imperfect and unavailing.   Nor  was  the
revival of letters  in the 15th  century, which roused
the intellectual  powers, after a dead repose of nearly
 1000 years,  productive of the  same benefit to physio-
logy as to many other departments of science.   From a
variety of causes, partly perhaps of an incidental nature,
 and  partly  depending  upon the limited  knowledge
 which  was then possessed of the powers and properties
 of natural bodies,  the  physiologists of that period fell
 into the error of ascribing the phenomena of life to the
 operation of the laws which influence inanimate matter.
 Hence arose the contending sects of the chemists  and
 the mathematicians; the former accounting for all the
 operations  of the animal ceconomy by the  chemical
 action  of the components of the body upon each other,
 the latter by the  principles of mechanics.   It is not
 necessary,  in the  present  day, to enlarge upon  the 
6
Stahl.
waste of genius and the misapplication of experimental
research, which originated from this fatal error; it may
be  sufficient  to remark, that although important facts
were occasionally brought to light, and many elaborate
investigations were instituted, from which  some valua-
ble information may be deduced, yet that not one single
hypothesis was proved, nor one single principle estab-
lished, of all those upon which so much labour and
learning  were bestowed.
  While the chemical and mechanical sects were thus
dividing the opinions  of  the  most learned men of the
age, a new  doctrine  was  gradually rising  up,  which,
although in the first instance it was equally remote from
the principles oi true  science, yet after having received
a number of successive purifications,.it at length appear-
ed in a more  correct form, and occasioned the complete
overthrow of both the  contending  parties.   For this
revolution we are indebted principally to Stahl.  This
distinguished  character  was brought  up in the school
of  the chemists; but being possessed  of  a  powerful
understanding, he soon deserted  he tenets of his pre-
ceptors, from a  full  conviction  of  their futility.  He
was forcibly impressed with the difference between the
changes which the components of the body experience
during life, and what  would take  place in the same sub-
stances  under other  circumstances.   Hence he  con-
cluded that when they form a part of the living system,
they  must be possessed of some additional principle,
that counteracts the  effects that would otherwise be
produced.  To  the   agent  which  thus  opposes the
physical  powers  of   matter, and to  which  the body
owes its  vital properties, he gave the  name of anima.
He conceived it to possess powers of a specific  nature,
and he especially attributed  to it a species  of intelli-
gence  which enables it to act the  part of a rational
agent, and to superintend all our corporeal operations.*

  * Tbeor. Med. ver.;  Physiol, sect,  i, mem. 3.  § 13.  It may
afford a topic for literary  discussion, how far Stahl borrowed his 
Stahl.
7
  To Stahl, therefore,  we must ascribe  the merit of
clearly  perceiving the  inadequacy of  the  actions  of
either chemical  or  mechanical  causes  to explain  the
phenomena of life,  a truth which we  now  regard as
incontrovertible,  and which, obvious as  it  appears, had
been overlooked  or  disregarded  by the  most  acute  and
learned  of his  predecessors.  But afier having  thus
established a firm basis for his hypothesis, he  was led
astray  by  the  fashionable  metaphysics  of the  day.
Instead of  investigating the nature of the animal func-
tions, and  ascertaining the laws  which direct them, he
deemed it sufficient  to refer them  all  to  an hypothe-
tical  principle,  which he invested with powers accom-
modated  to his  purpose.  In its  general aspect  the
anima of Stahl may seem to hear a near relation to the
$wts of  Hippocrates; but  there  is this  essential differ-
ence  between them, that  Hippocrates  employs  his
term merely as a general expression of the facts, where-
as Stahl considers his hypothetical principle as some-
thing distinct from  the  body, which actually produces
its  powers and faculties.  But although the hypothesis
of  the  anima  was  in itself gratuitous  and altogether
objectionable,  it  had the  good  effect  of turning  the
attention to the phenomena more immediately connect-
ed  with life,  of  enabling  us  to  trace  their  connexion
with the  other  operations  of  nature, and ascertaining
more correctly the laws by which they are respectively
governed.  This progress  was  indeed attended  with
much difficulty, and  the advances  which were  made in
it were very gradual; but it is the correct plan of pro-
ceeding, and  that which must eventually lead to  the
true  theory of animal life, and to the just principles of
physiology.

notions from Vanhelmont, whose hypothetical agent,  which he
named archeus, bears a  near resemblance to  the anima.  But I
should be disposed to refer  Stahl's doctrine to Hippocrates, with
whose writings he must have been conversant. 
&               Hoffmann.'--Boerhaave.
   When knowledge  is acquired by slow degrees, and
truth is not elicited until after many unsuccessful efforts,
it is  not  easy to assign to  each individual the exact
share which  he contributed to the progress of improve-
ment, or to ascertain precisely  in what proportion his
exertions  may have conspired to  the  final result.  In
the present instance I am disposed to attribute a  con-
siderable share  of  merit to Hoffmann, who although a
hasty and multifarious, rather than  a correct anoj con-
sistent writer, seems to have been one of the earliest
who entertained correct notions respecting the general
principles  and  objects of  physiology.   He had the
sagacity to perceive that much  of what Stahl ascribed
to the operation of his anima, might be  more correctly
attributed  to the action of the nervous system; and he
appears to have been  among the first  who duly esti-
mated the importance of this part of  our  frame in the
vital  operations.*
   Contemporary with Stahl and  Hoffmann  was Boer-
haave,  a man perhaps equal to them in  the general
powers of his mind, or, if he possessed  less genius and
originality, he was superior in judgment and information.
No one ever enjoyed greater fame as a teacher;  and
from this  circumstance, as well  as from their  intrinsic
merit, his  doctrines acquired a degree of ascendancy
over  the  public mind  which had, perhaps, not  been
equalled since the  time  of  Galen.  But the genius of
the age was  not favourable to the continued dominion
of any  hypothesis; and as  the  theory of Boerhaave
wanted the substantial support of facts,  its celebrity
did not long  survive  its founder.  He was a professed
eclectic; he  selected from  all preceding writers  what

  * Hoffmann's writings occupy no less than six large folios, and
as he is generally deticient in arrangement, it  is  no easy task to
select those parts which may exhibit the clearest view of his doc-
trines.  His great work, " Medicina Rationalis Systematica," con-
tains many remarks upon the nervous system,  which show how
much importance he attached to it. See particularly lib. i. sec. 3. 
DTaller.—Cullen.
9
appeared to be valuable in their  respective systems,
and endeavoured to mould the materials thus collected
into one  harmonious whole.   Hence his system was the
result  rather of learning  than  of information;  and
although it indirectly tended to the detection  of error,
it induced a state of mind which led to its own downfal.
  But whatever advances may have  been made until
this period in physiological science, they  will appear of
small amount when compared with the mass of  know-
ledge which burst upon us about the middle of the last
century,  and for which we are principally indebted  to
Haller.  This celebrated man is, in every  point  of
view, entitled to the appellation of the father of modern
physiology,  whether  we  regard  the  unremitting assi-
duity  with  which he cultivated  the science, or the
actual  advancement which he effected.   Every circum-
stance of talent, character, and situation, conspired to
promote his great object.   In  learning,  in industry, in
discrimination, he has seldom been excelled ; he  devot-
ed a large portion of his  life to the cultivation of phy-
siology, while his rank and  fortune gave every facility
to his exertions.   What, however, more especially enti-
tles him to the  highest commendation, is the method
which he introduced  and established, of investigating
the phenomena  of the living body solely by observation
and  experiment, and  keeping hypothesis entirely  in
subjection to  these two leading principles.   So power-
ful an  effect indeed have his influence  and example pro-
duced, that, since his time, the science has  assumed
altogether a new aspect; and from the publication of
his " Elements," we may date the commencement of a
new era in physiology.
   This great monument of learning  ai d industry was
still  in progress when Cullen entered upon his career ;
a man of a very different turn of mind, yet  one whp
was eminently useful  in this department of knowledge.
He  excelled in general views  rather than in minute
researches ;  and, without adding  many new  facts  t«
              2 
10
Hunter.
 our previous stock of information, he arranged  into a
 very beautiful and interesting system  those of which
 we were already in possession.  iFew persons have con-
 tributed more than Cullen  to sweep away the useless
 rubbish of antiquity; and there  is a spirit of philoso-
 phical  scepticism  that  pervades  his writings,  which
 happily coincided with the inquiring genius of the age
 in which  he flourished.
   Among the authors who have  been  most successful
 m the  cultivation  of physiology, we  must class John
 Hunter.  He possessed a remarkable share of boldness
 and originality of conception; his mind was equally ar-
 dent and  acute; and  to  these qualities  he added the
 most patient industry in  tlie investigation of na'ure un-
 der every aspect in which  she presents herself  to our
 notice.   The  high  situation which he held in this me-
 tropolis, both  as a practitioner and a teacher,  and the
 noble memorial of his talents, which is deposited in the.
 College of Surgeons, have conspired to  raise his repu-
 tation to the  highest  pitch of celebrity.   In  the ex-
 planation of the operations of life, he professed to pro-
 ceed entirely  upon  the result  of  observation and expe-
 riment; but, in this respect, he exhibited a singular ex-
 ample of self-deception, for his  writings are, in  fact,
 full of hypothesis and abound with  theories expressed
 or implied ; hence he  has unhappily introduced  into
 physiology a kind of metaphysical language, which has
 certainly tended to impede  the progress of science, by
 substituting new expressions for new ideas :  thus  lead-
 ing us to suppose  that we  had gained  an addition to
 our knowledge, when, in fact, we were only employing
 new  forms of speech.  There is, however, no one since
 the time of Haller to whom  the science is more indebted
 for new facts than to  Hunter ; and urTon these his fame
will be amply supported when his speculations are for-
gotten.   In his physiological hypotheses, Hunter makes
perpetual reference to the existence and operations of
 what  he calls  the  vital  principle.   It is not easy, on 
Bichat.                    Al
many occasions, to  determine how far  his expressions
aie to be received  in a literal,  or how  far in a meta-
phorical  sense,  but many of them strongly  resemble
the Stahlian doctrine,  of an  intelligent  principle, con-
n cted with the body, directing  its  motions,  and pre-
serving it from  injury  or  destruction.   In his explana-
tion of the functions and operations of the living animal,
he  not  unfrequently  confounds  physical  with  final,
causes, and attributes to the specific effects of life, ac-
tions  that ought to  be  referred to the  powers belong-
ing to inanimate matter.
  Among the modern physiologists there is no one who
has more  just claim  to  our  attention than  Bichat,
whether we regard him as an observer of facts, or an
improver of  theory.   In the  course of a short life he
acquired an accurate and extensive knowledge of ana-
tomy, and made many discoveries in this  department
of science, which seemed to have been so entirely pre-
occupied  by his predecessors.   In his views of the ani-
mal  ceconomy, he proceeded  upon the  principles of
correct philosophy ;  he regarded the vital functions as
of a description essentially different from any other na-
tural phenomena,  and diligently applied himself to ob-
tain an accurate knowledge of them,  to observe their
relation to each other, and to arrange them  according-
ly.   His  classification will, indeed, in many of its parts,
appear too refined, and his speculations to  savour too
much of  metaphysical  subtilty ; but we  must regard
him as having possessed an unusual share of genius and
acuteness, and as  having made very considerable  addi-
tions to the stock of  physiological knowledge.
   This slight sketch  of the labours of preceding  phy-
siologists will tend to point out  both  the cause of the
imperfection of the science and the method  of advanc-
ing it.   We find that for a long  course of years, every
one who attempted  to explain the operations of the
animal ceconomy, employed   only those powers which
belong to inanimate matter;  and that, at a later peri- 
ifi
Plan of the Work.
od, when the inadequacy of  this mode  became appa-
rent, instead of inquiring into the actual nature of  the
specific powers of vitality, it was deemed  sufficient to
have recourse to certain  hypothetical principles,  de-
rived from false analogies or from the mistaken philo-
sophy of the age.  The more correct opinions of  the
present day, for which we  are in a great  measure in-
debted  to  the sagacity of Haller, have  led us to  con-
clude that  all the appropriate actions of the living  sys-
tem may be referred to the  two classes  of motion  and
feeling;  and that these depend upon  two  principles
inherent in the body, contractility and sensibility,—the
one seated in the muscular fibre, the other in  the ner-
vous matter.  To the action of one or other  of  these
principles,  every  corporeal  change  may be ultimately
referred; and it is through  their immediate operation
that all the functions are performed.  Hence we have
a foundation for an arrangement of  the  functions  into
contractile and sensitive, to  which I propose to adhere
in the following work ;  and for reasons  which will be
hereafter more fully  detailed, I shall  begin  with the
former class.  The functions which  belong to this divi-
sion are, the circulation of the blood, respiration, animal
temperature, secretion, digestion,  assimilation, absorp-
tion, and generation.
   But, before I  proceed to  the individual  functions,  it
will be necessary to give an  account of  the nature of
the two powers  of contractility and sensibility, and of
the organs by which  they are exercised—the muscles
and the nerves.   It will be  also found advantageous to
premise a description of membrane and bone, because
these substances constitute,  as it wrere, the basis of the
body ;  and without some knowledge of their nature, it
would  be difficult to comprehend the operation of the
muscles and the nerves, or  the connexion which  they
have with  the system at large.
   After reviewing in succession the various contractile
functions, I shall proceed to the other  great  division, 
Plan of the Work.
13
the sensitive.   These  comprehend what are common-
ly styled the five  senses—sight,  hearing, smell, taste,
and touch;  and besides these are other classes of  sen-
sations, which appear  equally specific, although  from
the mode  in which they  operate,  or the organ by
means of which  they are  exercised, their distinct na-
ture has not been  so  generally recognised.  Of these,
some  of the most important are the sensation that at-
tends muscular contraction, that of heat and cold, and
that of hunger.
   The connexion between the corporeal and  mental
part of our  frame  is so intimate, that it is impossible to
acquire a complete knowledge of the one, without pay-
ing some attention to the other.  There is  a very im-
portant class of phenomena of an intermediate, or per-
haps, more  properly, of a compound nature, where an
effect upon  either a contractile or a sensitive  function
is succeeded by some intellectual operation,  or where
an intellectual  operation produces a change in the ac-
tion of the corporeal  organs.  Some of the more im-
portant of these will be briefly noticed;  and although
it will be my object to encroach as little  as possible
upon  the province of the metaphysician, 1 shall be un-
avoidably led io consider  some of  those  topics which
are only indirectly connected with physiology ; of this
description  are the effects of association,  habit, imagi-
nation, sympathy,  and  volition.
   A very curious  subject  connected  with  the animal
ceconomy, which must engage a share  of our attention,
respects the causes which produce  the differences be-
tween individuals, both those which more immediately
affect  the external form, giving rise to the varieties of
the  human species,  as  they  are  termed, and  those
which seem to depend more upon the internal actions
of the system, constituting  the  temperaments.   This
subject will naturally lead us to notice the curious sub-
ject of craniology; and, connected with  this,  1   shall
venture to offer some  observations upon the much con- 
14               Plan of the Work.
troverted question, of the nature of the connexion be-
tween the intellectual faculties, and the organ by which
they are exercised.  In  the last place,  I  shall make
some  remarks upon the natural progress of the animal
body, from the commencement of its existence through
its state of maturity, to its decline, and final dissolution,
by which its component parts fall into decay, and its
appropriate powers are at first impaired and ultimately
destroyed. 
        ELEMENTS
               OF

PHYSIOLOGY.
                    CHAP,  h

                  <©f JHcmtraur*

   Whetc we examine the structure and composition of
the animal body,  the most obvious division of its com-
ponent  parts is into solids  and fluids; the  first being
fixed and  permanent in their nature,  and  affording the
basis by which the general form is determined; while
the latter are lodged  inappropriate receptacles,formed
by the solids, are generally in motion, or are undergoing
some  obvious  changes  in  their quantity or quality.
The science of anatomy, which professes to describe
the mechanical structure of the body, and the physical
relation which  its parts bear  to each other, is  princi-
pally concerned with the solids; while both the solids
and the fluids  are equally the  province of the physio-
logist, whose business it is to study the nature of all the
substances that  enler  into  the animal  frame.   The
solids,  as  being the  most durable part  of  the  fabric,
and as forming the  organs necessary to  prepare the
fluids, and to apply them when prepared to their dif-
ferent uses, seem to offer themselves as the first objects
of our attention ; although, upon a more minute exa-
mination, we may find the fluids to be of no less impor-
tance in our ceconomy, as either by the intervention of 
IS       The Body composed of Solids and Fluids.

external agems,  or by the action of their components
upon each  other, they are,  in most  cases, the  media
through which those operations are effected, which are
essential to life.   It must, however, be remarked, that
the terms solid and fluid, as applied to the components
of the  body, are rather  relative than positive ;  there
is scarcely any part so solid,  which  may not by desicca-
tion  or by  mechanical compression be  rendered still
more compact;  and  most of what have been  called
animal fluids are  composed of water, containing different
species of solid matter imperfectly dissolved, or merely
in  a state of mechanical diffusion.  The principal varie-
ties  of solids, considered in  relation to their form and
structure,*  are  the  bones,  with their appendages, the
cartilages and  the ligaments, the muscles with the ten-
dons, the membranes of all descriptions, the  various
kinds  of sacs  and vessels,  the  fat, and the  cerebral
matter.   If we  arrange  the solids of the  body  with
regard to their  chemical composition, and to  the uses
which they serve in the animal ceconomy, we may place
them  under five divisions :—the  osseous matter, the
membranous, the muscular, the  adipose, and the cere-
bral ;t and  we may say, in general  terms, that the com-

  * The  method  of viewing the animal body as composed  not
merely of a number of organs, but each organ as itself composed
of a  variety of textures, which are more or less common to the
different orgnns, appears to have originated with Dr. C. Smyth, as
illustrative of the phenomena of inflammation,  it was carried to a
much greater degree of minuteness by Bichat, who extended it to
all parts of the body, and employed it as a leading principle of his
systematic arrangement.  It must  no doubt be regarded as one of
the greatest  improvements that  have been  introduced  into  our
science ; but I have not formally adopted it in the following pages,
because  the elementary nature of this work seemed scarcely to
render it necessary ; while, at the same time, it  might have led
to  useless and tedious repetitions.  The reader may,  however,
observe that the general principle is always held in view, and is,
in many cases, directly referred to.
  t M. Beclard reduces the primitive classes of organized solids to
three:—the cellular, the nervous, and the muscular; his division
of cellular comprising the osseous, the membranous, and the adipose 
Arrangement of the Solids.
17
  parative  degrees of their solidity or  fixedness are in
  the  above  order.   I shall  not,  however, follow this
  arrangement in the description of the solids, as the plan
  which I  propose to adopt in the following  pages  is
  founded rather upon  the functions  which the body
  exercises, than upon its composition.   I propose to give
  an account  of both the solids and the fluids, as  I succes-
  sively treat of the  functions  of  those parts in which
  they exist in the greatest quantity or the most perfect
  state ; in consequence however of its general diffusion
  through all the organs of the  body, it will be found
  convenient to commence with the membranous matter.*
     Membrane is the  most simple in its  structure of any
  of the organized parts of the  body ; it  is the  most
  extensively diffused,  and exists in the greatest  propor-
  tion.  The coverings, not only of the body at  large,
  but  of each of its individual  parts,  both internal and
  external, are  principally composed of  membrane; and
^ it lines all the  cavities  in which the  different  organs
  are  situated.   It constitutes the main bulk of the bones,
  and determines their  figure;  the  earthy matter upon
  which their strength and hardness depend, being depo-
  sited in  a tissue of membranous cells.   Membrane also
  enters into the structure  of muscles, not only affording
  them an external sheath, in  which they are each  of
  them enclosed, but the same matter is also interposed

  of the above arrangement.  Add. a l'Anat. Gen. de Bichat, p.  2.
  This is likewise the arrangement of Cuvier;  see Diet, des Scien.
  Nat. " Animal."
     *  I have not thought  it expedient to adopt  any of the  arrange-
  ments of the subjects of physiology, which have been formed with
  so much  labour and ingenuity by  some of the modern French
  writers;  those, for example, of Dumas, Bichat, Rrcherand, and
  Magendie.  The  object of these authors appears to have been to
  produce a system which should be equally applicable to physiology
  and  to anatomy ; but it  may be doubted whether their plans have
  not become complicated and unnatural, in proportion as they are
  rendered more comprehensive.  For some useful remarks on this
  subject, see Ed. Med. Journ. r. xv. p. 565,
                  3 
18
Extent of Membrane.
 between their fibres, separating them into bundles, to
 which it, in like manner, affords a distinct covering, and
 these into still smaller bundles, until it appears at U:iij;th
 to envelop each  individual  fibre.   The  membranous
 matter composes  very  nearly the  whole bulk  of the
 tendons, by  which the  muscles  are attached  to the
 bones; of the ligaments, by which the bones  and other
 solid parts are  connected to each  other; and  of the
 cartilages,  which form the basis  of many parts of the
 body,  supplying the place of bone, and  which also
 cover  the ends of the bones, and assist in the  formation
 of the joints.   It also enters  very largely into the com-
 position of the  hair, the nails, and other similar parts
 connected  with the  surface.  It  likewise  composes
 what is called the cellular texture,—a series of  cells or
 interstices, which  extends over a great portion of the
 body, fills up its intervals, and serves to unite the dif-
 ferent  parts  to each other.  Membranous  matter  is
 the  chief ingredient  in  the glands, both those  which
 are attached  to  the absorbent system, and those which
 are appropriated to the office of secretion.  The brain
 is also enveloped in a covering of membrnne; and it is
 probable that the nerves are composed of a series  of
 fibres  enclosed  in membranous  sheaths, analogous  to
 those of the muscles.  The pouches or sacs, which are
 found in different parts of the body, such as the stomach
 and  the bladder, are almost entirely composed of mem-
 brane ; and what  perhaps  must be  regarded  as the
 most important of all the purposes  which  it  serves,
 this substance composes the principal part of  the  tubes
 or vessels  with  which the animal body is so plentilully
 furnished.
  From this  account of the extent and distribution  of
 membrane, we find that it must exceed in  quantity all
 the other  solids of the body  taken together, and that
 it enters as a principal ingredient into almost every part
 of the animal frame, the enamel of the teeth being, as
we are informed, the only solid  in  which it cannot be 
            Membrane the basis of the Body.          ,19

detected.*  This  is  indeed  so completely  the  case,
that were it  possible to  remove the earth from the
bones, the muscular fibre, the nervous matter, and the
fat  from  the  soft  parts, to empty the  vessels and to
evaporate the fluids generally, the size and figure of
the body  would remain nearly unchanged.  Membrane
may therefore be considered as the connecting medium
between the different parts of the body by which they
are  held  together, the basis  to which  they  are all
attached,  and the mould in which the particles of the
other kinds of matter are deposited.!
  It  will appear  from these  observations  upon the
extent of  membrane, that I employ the term in rather
a more comprehensive  sense than ordinary ; and that
I include under it, not only what have  been usually
called membranes,  but the whole  of the  substance
which possesses the same mechanical structure and the
same chemical properties.   What I have 6tyled mem-
branous matter nearly coincides with the white parts of
the older anatomists,—the cellular texture of Haller,
the tissu  muqueux  of Bordeu,^  and the tela mucosa of
Blumenbach ;§  the first of these terms was, however,
used  in a  vague  manner, without  any very  distinct
appropriation;  and Haller's, Bordeu's, and Blumen-
bach's appear objectionable, as  they are derived from
hypothetical  opinions respecting the nature  of this
substance, which are probably not altogether correct.
  The mechanical structure of membrane, as it exists
in the different  parts  of the  body, has been minutely
examined by various anatomists, and was particularly
attended  to by Jialler.  He  described it as composed
of a  vast assemblage of  lines or fibres, in their state
of ultimate division too small to  be  perceived by the
eye, but which, by the union of a sufficient number of

  * Blumenbach's  Physiol. § 22.  See Hatchett, Phil. Trans, for
1799,  p. 328.
  t Cuvier, Tab. El. p. 25.
  } Recherches sur le Tissu Muqueux.       § Physiol. § 21. 
29
Structure of Membrane.
them, are formed either  into larger  visible  fibres, of
into  plates, according to the structure of the parts in
which they are  situated   He  was at much pains to
detect  this fibrous structure in all the organs of the
body, and to show that the membranes, however dif-
fering in their apparent texture, or whatever degree
of firmness they possessed, were all  resolvable  into
the same substance.  This he  calls cellular web; and
although his idea of its structure  may not be entirely
correct, yet he made considerable advances  upon the
knowledge of his predecessors.*
  All the solid  parts of  the body,  he  supposes, by
mechanical division or by  maceration in water, may be
made to assume the fibrous appearance.  In its most
simple  state  the fibre is  to be regarded as a straight
line, and by the approximation of these lines, in dif-
ferent  directions with respect  to  each other,  all the
various forms  are produced that  enter  into the com-..
position  of the  animal body.   He further conceives,
that the greatest  part  of the  solids, in their primary
State of aggregation, compose plates with interstices
between them, and that the most compact membranous
body  consists of  this texture  in  a condensed state.
Whether the  tendons and ligaments ever actually pos-
sessed the mechanical structure of thts-eellular texture
may be  reasonably doubted;  but it appears that, by
proper  methods, a structure somewhat resembling it
may be  exhibited in parts that  are  naturally of the
densest  consistence.
  The  uninterrupted continuity of the .membranous
matter,  all over  the body,  was  one o|*tf he discoveries
of Haller.  He employed  much  accurate dissection,
and instituted  many experiments,  to prove this point;
but it  is now so generally  admitted,  as  to  render it
unnecessary to  adduce any  arguments  in its  favour.
It follows indeed as the  direct consequence  of the
* El. Physiol, lib. i. § %: 
Boerhaave on  the Structure of Membrane.      21
 new which we have taken of membrane,  regarding it
' as  the  basis  of the whole  body, into  which  all  the
 other parts  are moulded, by which they are  at  the
 same time enclosed, and  which  serves the purpose of
 connecting them together into one whole.*
    The  idea  which was entertained  by Boerhaave
 respecting the structure  of  membrane, is in itself so
 improbable,  and seems so contrary to the evidence of
 the senses, that it is surprising it should have been so
 generally received ;t and may serve as one among other
 proofs of the unlimited confidence which was formerly
 placed in all his opinions.  He supposed that the sim-
 ple fibres, or the smallest into  which it is possible to
 conceive them to be divided, by their union, compose a
 membrane of the  first  order or series, which, when
 coiled up, will form a vessel of the first order or series.
 These vessels,  by being  placed in  contiguity or being
 interwoven together, form a membrane of the second
 order or series, which is again coiled up  into  a vessel
 of the second  order;  a third series of membranes and
 vessels is then formed, and others in succession, until
 they acquire a sufficient  magnitude to be visible to the
 naked eye.   According* to  this  hypothesis  it  follows,
 that, except  the earth  of the  bones,  no  part  of the
 body is  properly solid  but the  coats  of vessels; and
 that, all the fibres which are cognizable by the senses,
 are only a  congeries of vessels  arranged in these
 ascending orders.J   It is scarcely necessary to observe,
 that this hypothesis is entirely gratuitous, that  there is

    * El. Physiol, lib. i. § 1,2; and Prim. Lin. c.  1, § 1—13.
    t See Haller's Phys. lib. i. § 3, for a long list of authors who
 adopted it.
    \ Although this may appear to be  the fair deduction  from the
 expressions that are employed by Boerhaave, it must be acknow-
 ledged that we do not find the doctrine laid down by him so expli-
 citly as might be expected, from the statement of Haller, or even
 of Van Sweiten.   See the references to Boerhaave, given by Hal-
 ler ; Van Sweiten's Com. on Aph. 39; also Gorteri Med. Con>
 pen'd. § 1—5, and fig. 1, 5, 14—21. 
2<2
Hypothesis refuted by fialler.
no foundation for these regular gradations of vessels
and membranes, and that the actual degree of vascu-
larity of the different parts is infinitely varied.   Both
from  the effect of injections and from microscopical
observations, we may conclude not only that membrane
generally is much less vascular than the  muscular parts,
but that different membranes differ very much  in this
respect from each other; and  it even appears,  that
there are large portions of membrane which are with-
out vessels of any description.
  For the  refutation of the  hypothesis of Boerhaave,
we  are  indebted to Albinus,* and still more to Haller;
but in accomplishing this object, Haller probably went
too far into the opposite extreme ; for he is disposed
to regard some of the  ultimate parts of which the so-
lids are composed, as unorganized/!"  This opinion he
seems to have adopted, partly from an idea that a vas-
cular  structure  is essential  to organization, and  partly,
because, in the division of  the larger fibres into those
that are more  minute, we must at length  arrive  at a
fibre which is too small to admit of any further subdi-
vision.  But this latter objection is rather metaphysi-
cal  than physiological, and refers more to the fineness
of our instruments,  than to the actual state of the parts,
while the  former is an assumption without proof, and
will probably be found to be incorrect.  ,
  The  idea that vascularity is essential to organization,
or rather,  that in  descending from larger to  smaller
parts,  organization and vascularity must cease  at  the
same  time, has  been generally entertained by the most
eminent modern  physiologists.  It seems to have  ori-
ginated, in  a great  measure,  from the skilful injections
of Ruysch,J who proved by his  preparations, that  ma-
ny of the white parts of the  body,  as they  were term-
ed,  which were thought by the  ancients to be entirely

  *  Acad. Annot lib. iii. c. 1.       1 Prim. Lin. c. 1, § 16.
  ^  See Albinus ubi supra.    '* 
Fibre thought to be Vascular.
23
without  blood, possessed numerous vessels demonstra-
ble to the  eye.   Wm. Hunter, in his strictures upon
the doctrine of Haller, adopts this opinion ;  he always
speaks of organization as synonymous with vascularity,
and  takes  it for granted, in reference to  the minute
structure of the  body, that  where there is no circula-
tion  there is no  life.*   An error of a similar  kind for-
merly prevailed  respecting the  distribution of the
nerves ;  for as sensation  was admitted to be an appro-
priate quality of  the living  body, it was  assumed  that
no living part could be without sensation ;  and of course,
that the smallest parts into which an organized  body
could be conceived to be divisible, were nervous fila-
ments/!*   But  there is  reason to believe,  that both
these notions  ate incorrect; and although our views
must be, to a' certain extent, hypothetical, when we
venture  to describe the structure of parts that are too
small to  be visible, yet  we may at least  form  a  plausi-
ble conjecture  upon the subject.
   We may agree with Haller in conceiving, that there
is an actual  solid fibre, the  basis of  the whole animal
frame, to which  the vessels are superadded as distinct
appendages, but  we cannot admit the existence of the
inorganic concrete, which he describes as filling up the
spaces between the fibres."}"   The fibre itself,  although
not essentially  vascular, we must suppose to be a regu-
larly organized  body, composed of particles bearing a
certain relation to each  other, and possessed of certain
specific properties.   By the conjunction of these fibres,
membranes of  all forms are produced, and among oth-
ers the vessels;  but the Coats of these vessels  are com-
posed of fibres that are themselves without an internal
cavity, and  have  no kind of circulation  through their

  * Med. Obs. and Inq. v. ii. p. 27.
  t Boerhaave, Inst. § 301 ; Praelect. § 440; see also Bell's Anat.
v. i. p. 404.
  I Prim.  Lin. c. i. passim.         . 
24                 Size of the Fibre.
substance.   With respect to the question, how these
ultimate fibres, which are without vascularity, can be
said to possess life, I conceive it to be a dispute about
words.*  If a certain assemblage of  parts, when taken
as a whole,  exhibits  vital functions, we may say  that
every individual portion  of it is alive, although the im-
agination may form a conception of its ultimate parts,
as not  being possessed of any characteristic of life.
   In the present state' of our  knowledge it is perhaps
impossible  to  make any  estimate of the size of the ul-
timate fibres of membrane. The current opinion among
the physiologists of the  last  century was in favour of
its being almost inconceivably minute; an opinion, which
was  partly founded  upon the microscopical  observa-
tions of Leeuwenhoek and others, and partly  upon the
hypothetical train of reasoning of which 1 have already
given an account.  Haller speaks of it as a geometri-
cal line, or as possessing length without any  sensible
thickness;  and  to give  an idea of its  minuteness,  he
observes, that there are  animals so small, that the most
powerful glasses are barely sufficient to  render them
visible to the  eye, yet these animals contain a compli-
cated set of organs, each of which possesses a  fibrous
structure.*  It may, however, be reasonably doubted,
whether the  ultimate fibre be of the same size in all
animals; and, upon  the whole, it is rather  probable
that in  the  human subject it possesses  a  magnitude,
which is more within the limits of our comprehension.
   We are indebted to Fontana for a number of micro-
scopical observations on  membrane;  and although it is
necessary to receive such observations with great cau-
tion, in consequence of the numerous errors and decep-
tions to which they are  liable,"!" yet his remarks are so

   * El. Phys. lib. i. § 1.
   t If in this, or in other parts of the following work, I may ap-
pear to speak in a disparaging manner of the labours of those who
have devoted their time to microscopical investigations into the mi-
nute structure of the  components of the body, I beg to observe, 
Properties of Membrane.               25
 candid, and what he describes is so credible, that I am
 disposed to place some confidence in them.  By using
 glasses of  moderate powers, he  found that a  compact
 tendon was composed of a number of flattened plates,
 which he calls the primitive fasciae, and which  are con-
 nected together  by cellular  substance of  a more  lax
 texture.  By maceration, or mechanical division, these
 fuscice were found to be made up of cylinders, in  the
 f-M -n of solid threads of a spiral or waved form:* these,
 we  are expressly told, are neither hollow nor vascular;
 homogeneous in their consistence, and of the same size
 in all the parts of the same animal.   These  primitive
 cylinders or tendinous threads are  about the T3W of an
 inch in diameter ;  they form a  large portion  of  the
 substance  of  the  whole body, and, according  to  the
 opinion which  was prevalent when  Fontana wrote, to
 which  we  have already alluded, he calls them non-or-
 ganic.t  These observations,  as far as they can be  de-
 pended upon, entirely oppose the vascular hypothesis
 of the  Boerhaavian school,  and present a much more
 rational and intelligible  idea of the construction of  the
 ultimate parts  of the animal fabric.
   The properties which more  especially  belong  to
 membrane,  are  cohesion,  flexibility, extensibility, and
 elasticity.  It will be  unnecessary to enlarge  upon  the
 importance of these properties in  a system like that of
 the   living body,  in which great strength is necessary,

 that it is done in no degree upon individual, but entirely  upon ge-
 neral, consideration-.   An  historical detail of the errors into which
 this instrument has led even those who have been the most skilful
 in its application, would have the effect of inducing us to  place but
 little confidence in hypotheses and speculations that are derived from
 objects which can only be  detected by the use of high magnifiers.
  * The observations of Monro would, however, lead us to sup-
pose that this spiral or waved appearances is an optical deception.
Obs. on the Nervous System, c. xxii. pi. 35, et seq.
  t Sur les Poisons, t. ii. p. 222, et seq.; pi. 6, fig. 1, 2, 3, 4, b 5
pi. 7, fig. 1, 2.
                4 
\
 26             Membrane not contractile.

 together with lightness and a capacity for free motion,
 and where the parts  are perpetually varying in their
 bulk and relative position.
   Of these properties, elasticity may, in some degree,
 be regarded as the specific quality of membranous mat-
 ter ;  as it appears to be the only  one of the  constitu-
 ents of the animal body which possesses it.  The mus-
 cular fibre is flexible, and is capable of being extended,
 but it does not appear that  it is properly elastic.   As
 we advance in our subject, we shall  be more able to
 estimate  the advantages  to  be derived from  this pro-
 perty : at present I  shall briefly notice,  that it  is  an
 essential  agent in the  action  both  of the arteries and
 of the thorax, so that it is of prime importance in the
 functions  of circulation and  of respiration.   In some in-
 stances it co-operates  with  the muscles  in  the motion
 of the joints,  and it is frequently employed to restore
 the situation of a part that  has been previously moved
 by muscular contraction from its natural position.
   Besides the above properties,  which are universally
 admitted  to belong to  membranous  matter,  but which
 it possesses in common with other natural  bodies, some
 physiologists  have ascribed to it  qualities  of a more
 specific or  appropriate nature.   Many of the modern
 French writers, as Bichat*  and Richerand,t have sup-
 posed that the different forms  of  membrane  have a
 degree of spontaneous contractility and sensibility con-
 nected with,  or inherent  in  them;  but  this opinion
 seems to be derived  from  the idea that  contractility
 and sensibility are necessarily attached to  every part
 of a living body,  and  to  membrane  among the rest.
 So far as the opinion depends upon any general princi-
 ple concerning the nature  of a living body, 1 shall think
it sufficient  to  refer to the  observations  which were
 made above, respecting the  connexion  between life and

      * Traite des Memb.  p. 54; Anat. Gen. t. i. p. 116.
     t Elem. de Physiol, t. i. p.  48. 
Blumenbacfi9s Vis Cellulosa.            27
vascularity.   And as to the facts which have been ad-
duced to prove this point,  I conceive them to be alto-
gether  inconclusive.   The  alleged  instances,  where
pure membrane is  supposed  to exhibit marks of  con-
tractility, are either of a very dubious kind, and so ob-
scure as to afford no sufficient ground  for any theoret-
ical deduction, or, when they are more obvious and de-
cisive, they appear to be easily referable to the effects
of elasticity.   Of this kind are the  shrinking of a cavi-
ty that  has been preternaturally distended, the retrac-
tion of a tense  membrane when suddenly cut across,
and the collapse of tubes or sacs of various kinds, upon
the removal of some extraneous force that had stretch-
ed them beyond  their  ordinary size ; but in  all these
cases we see nothing more than  the operation of  the
elastic power of the membranes, modified  by their sit-
uation, or by the nature  of  the parts'connected with
them.
   Professor Blumenbach  ascribes to membrane a  spe-
cific? power, which he calls contractility, or vis cellulosa ;
but  he  employs  the  term  contractility in a peculiar
sense, and expressly distinguishes  it from the moving
power  of the  muscular  fibre.*  The  contractility of
Blumenbach consists in  the  contraction  which mem-
brane is occasionally observed to exercise,  when it has
been over-distended, and  the  stretching force is with-
drawn, and, like the cases mentioned above, may be re-
ferred to elasticity. The  principal example of it which
he adduces is  the action of  the cellular  substance in
propelling the  serous  exhalation into the  lymphatic
vessels—an operation  which is very obscure, and  with
the nature of which we are too little acquainted for us
to make it the basis of an hypothesis.
   Under the title of tone or tonic power, the Stahlians
formerly described a peculiar property as  belonging to
membrane; and this term has been lately employed in
* Instit. Physiol. § 40, 59. 
28
Tone of Borden and Bichat.
the same way by Bordeu* and Bichat.f  Bordeu  de-
scribes the tonic power as that  property of the cellular,
or, as he styles  it, the mucous  texture,  by which each
of the separate  cavities or cells of which it is composed
acts  upon all those around it, and keeps them in a state
of equilibrium  or  of uniform  distention.   Bichat  ex-
pressly states, that what  he terms the  tonic power of
membranes exists in  all the  three species into which
he divides these bodies: the mucous,  the  serous, and
the fibrous;  the instances, however, which he adduces
of its effects are not very explicit.   This, as well as the
tone of Bordeu, appears  to  be very similar to the vis
cellulosa of Blumenbach ;  and  it seems probable, that
as far as they depend upon any one power,  they may
all be referred to the action  of elasticity.
   With  respect to the sensibility of membrane, consid-
ered as a matter of  fact, independent of any specula-
tion  concerning  the nature of  organization or vitality,
the opinions  of  physiologists have been various; and
it  was especially the subject  of a  warm  controversy,
about the middle of the last  century,  between Haller
and  Whytt.J  As is often the case in  points of this na-
ture, the question has been decided by  a kind of com-
promise ; it  is generally admitted with Haller, that
simple membrane is insensible  in its healthy  and natu-
ral state, but that  it is liable to inflammation, and that
it then becomes  sometimes exquisitely painful.§  The

  * Recherches sur le Tissu Muqueux, § 70.
  t Traite" des Membranes, p. 62, 101, 133.
  | Haller, Mem. sur la Nature Sens, et' Irrit. des Part, and Op.
Min. t. i.;  Whytt's  Essay on Sensibility and  Irritability, and  Ap-
pendix.
  We are  informed by Wilson, Lectures on the Bones, p. 44,  that
the doctrine of the  insensibility of the periosteum and various other
membranous bodies, while in their healthy  state, was taught by
Wm.  Hunter in his lectures,  as early as the year 1746, which was
previous to the publications of Haller on this subject.
  § Bichat, Anat. Gen. t. i. p. 119; Blumenbach, Physiol. § 210. 
Opinion of the Ancients.
29
cause of this fact, the excessive degree of pain, which
is excited by disease  in parts that are, at other times,
without sensation, is perhaps not altogether understood.
We may remark concerning it, that one  effect of in-
flammation is to enlarge the bulk of the inflamed  part,
and the  pain is generally in proportion to the difficulty
with which the part  admits of this extension.   A high
degree of inflammation may exist in loose cellular tex-
ture, and we may be scarcely sensible of its existence,
while  the inflammation of the  periosteum of the small-
est bone, as of a  tooth, of the sclerotic coat of the eye,
or of the tense membrane  about the  finger nail, will
be  almost intolerable.  In these  cases we shall  proba-
bly always  find, that  even if the inflamed part be with-
out nervous filaments, which  give  it sensibility, still
that there  are some  branches of nerves immediately
contiguous  to it, which  in consequence of the firmness
of all the neighbouring parts, are pressed upon  and ir-
ritated,  while the blood-vessels  connected with them
are in  a  state of plethora; for it seems to be a general
law of the animal ceconomy, that  no  cause is more  pow-
erful in  producing  pain than a certain degree of  pres-
sure upon a nerve, while its  sensibility is  augmented
by  an  unusual determination of blood.
  It is probable that much error and confusion took
place on the  subject  of the sensibility of  membrane,
among the anatomists and  physiologists,  after  the re-
vival of  letters,  in consequence of  their blind venera-
tion for the ancients.   Hippocrates, who had  but  an
imperfect knowledge of the existence and use of nerves,
confounded them, or  at least placed them in  the same
class, with  the tendons,  from some  similarity in their
visible structure and appearance, and  having  observed
very serious effects to ensue from injuries  of  the pro-
per nerves, he laid it down as a maxim, that tendons
and other membranous parts are among the most sen-
sible organs of the body.*  This erroneous opinion ma-

  *  Foesii, (Econ. Hipp. " Newpey."  See also Pliny, Hist. Nat. lib. 
se
Operation of Lithotomy.
terially influenced, not  only physiological speculations,
but medical and  surgical practice, even as  late as the
middle of the last century,  long after  the distinction
between nerves  and  tendons was thoroughly under-
stood.   Even Boerhaave fully subscribed  to this doc-
trine, in which he is warmly seconded  by his  learned,
but obsequious commentator,  Van Sweiten ;*  and the
influence of the old  hypothesis upon our language may
still be observed  in the present day.f
  John Bell, in his usual animated and impressive man-
ner, describes the dreadful effects which this opinion,
concerning the great sensibility of membrane, formerly
produced in the operation of lithotomy.J  As the blad-
der princfpally consists of membrane, it was agreed by
all the learned operators, for a succession of  ages, that
it would be improper  to cut or  divide  any part  of it;
and, therefore, in order to extract the calculus, a  varie-
ty of instruments were  employed for the purpose, as it
was said, of  dilatation, but which,  in  fact, caused the
most cruel laceration of  the organ  itself and of the
neighbouring parts.   It is truly astonishing to observe,
how the weight  of authority  bore down  the clearest
dictates of reason, and the most decisive results  of ex-
perience; and  how  the most obvious facts were  warp-
ed and misconstrued, before mankind would  submit to
prefer the evidence of their  own senses to the mere
hypothetical opinions of the ancients.
  From these  remarks it will appear, that except bone,
membrane may be  regarded as  the most simple in its

vii. c. 20; Le Clerc, Hist, de  la Medecine, liv. iii. c. 3, § 5; and
Haller, Mem. sur les Part. Sens, et Irrit. t. i. p.  19;  and Opera Mi-
nora, t. i. p. 411.
  * Aphorismus 164; and comment, in eund.
  t  Stuart argues with much ingenuity to prove, that tendons and
nerves are the continuation of the same substance, differing mere-
ly in the mechanical arrangement  or  disposition of their parts.
Diss, de Struct, and Mot. Mus. C. vii.
  | Surgery, v. ii. sect.  3. 
Organization defined.               31
properties of all the  organized parts of the body.  By
this expression, I must  be understood to mean, that the
properties which  belong to it, are likewise found in
many other  natural objects.  Cohesion necessarily be-
longs to all  solids, while flexibility, extensibility,  and
elasticity are possessed  by  many vegetable and some
mineral  substances, and also by dead  animal  matter ;
whereas spontaneous contractility  and sensibility are
the exclusive properties  of  the  living body.   We are,
however, as  much  unacquainted with the  intimate na-
ture and immediate cause of the properties of mem-
brane  as of  contractility and sensibility,  only we are
much more familiar with these operations.
   As I have several  times made use of the term orga-
nization, and shall  frequently have  occasion to employ
it in the subsequent  parts of this work, it may be de-
sirable to give  a clear explanation  of it.   In  its  most
extensive  acceptation,  it may be regarded as nearly
synonymous with the word arrangement, signifying that
the parts of  the organized body are placed according
to some specific structure visible to the eye.   Thus the
serum of the blood, when coagulated and dried,  in its
chemical  and  mechanical properties,  almost  entirely
agrees with membranous matter, yet in its texture it is
obviously different.   We say that the  serum is not or-
ganized, because its texture is perfectly homogeneous, it
is cut or broken with equal  facility  in every direction;
whereas, in a tendon, which  is organized, there is  a re-
gular distribution of the particles in  a specific form, and
according to  a determined arrangement.   The term is
not so generally applied  to  mineral  substances, yet in
reality crystallization seems to be analogous to  this kind
of physical  organization.  It is  doubtful whether the
term can with propriety be  applied to any fluid ;  and
if, for  reasons which will hereafter appear, it should
be  applied to the fibrin of  the blood, still the greater
part of the animal  fluids can have no title to it.  It is
a question which we cannot  perhaps very  easily deter- 
 o2            Physiological Organization.

 mine, whether any of the solids  are not organized.  I
 have already considered this point  with respect to the
 ultimate  fibres of membrane, but  it may still be  sup-
 posed to  be  the  case  with some other of the compo-
 nents of the  body ; for example, with the earth of the
 bones, which has been conceived to be  merely deposit-
 ed in cells of membranous matter, upon which its form
 entirely depends.  This  point we shall examine  more
 fully when I come to treat upon  bone ; and as we  ad-
 vance  in  the subject,  we  shall more  accurately learn
 what substances are organized, and  what are to be con-
 sidered as composed of unarranged  particles, or rather,
 if there be any which  fall  under this description.
   But besides this kind  of physical  organization,  the
 word is employed by physiologists in a more restricted,
 but at the same time in a  more correct sense, when it
 is applied to  a system, composed of a number of indi-
 vidual parts,  possessing each of them appropriate pow-
 ers and functions, but all conducive to the existence and
 preservation  of the whole.   An animal body is thus
 said to be  organized, or  to consist of a number of  or-
 gans or instruments.   A vegetable, in  like manner, is
 an organized  body, consisting of separate parts, as the
 roots,  the sap vessels, and the leaves, each   of them
 constituting a distinct organ or instrument for  perform-
 ing some appropriate action, yet all composing  one con-
 nected system.  It is  this species of physiological  or-
ganization which  properly distinguishes animate from
 inanimate  matter; and where  we are able to ascertain
 its existence,  it may be regarded as a sufficient charac-
 teristic of the presence of life.
   From these  observations, it will  appear that mem-
brane has a  perfect organization, although one which
is  more simple than that  of some  other parts of  the
body, as being possessed of fewer powers, and  made up
of fewer  component parts. Some  writers, especially
of the French school, seem to regard organization as ne-
cessarily connected with contractility and  sensibility ; 
               Cuvitr's Opinion—Remarks*.            S3

and to consider those parts which are neither contrac-
tile  nor sensitive, as inorganic.   I have  already refer-
red to the opinion of Fontana on this point, and a simi-
lar kind of doctrine is maintained by Dumas ; he speaks
of  the  cellular substance as being slightly organized,
and even calls it  a kind of  inorganic sponge ;*  and a
Similar  doctrine seems almost necessarily to follow from
the view  which Bordeu  takes of the subject.1
   The  opinion of the learned naturalist Cuvier respect-
ing  the nature of organization,  is, on the  contrary,
somewhat more restricted than the one which I have
adopted.   He  conceives it to be essential  to an organ-
ised body that it be composed of both solids and fluids,
the latter being the media through which its functions
are performed, and the former being necessary to con-
tain the fluids.!  This view of the subject is probably
correct, so far  as respects any organized being of which
we are able to ascertain the independent existence ;
but when we attempt to conceive of the ultimate parts
of which  it consists, we must at length arrive at a solid
fibre, which  contains  no fluids, and which  is, however,
composed of regularly arranged particles.
   With respect to the essential distinction between or-
ganized and unorganized bodies, this author points out
the following circumstances : their structure, the mode
in which   they are originally produced, that  in which
they are supported, and  that by which they  are finally
destroyed.   With respect to structure, I have already
remarked, that it is  essential to an organized body to
be composed of separate  parts, which  are  heterogene-
ous and dissimilar to each other, yet which all combine
together to form  one whole; whereas the parts of a
simple unorganized body are homogeneous, so that into
whatever  number  of  portions it  is divided, still  each
portion  may retain every property of the  whole mass,

           * Principes de Physiol, t. ii. p. »
           t Regne Animal, t. i. p. 11. 15.
               5 
34         Chemical Composition ofMcmhrane.

and constitute a perfect existence.   Its individual parts
have  no relation to  each other except those of cohe-
sion and physical attraction; whereas the components
of an organized body possess  numerous relations of a
more  complicated .nature, each having its appropriate
and specific  powers, which  enable  them  to  form a
whole, to the perfection of which every individual part
is necessary.   As to the production, support, and de-
struction  of  organized  bodies, and  the way in  which
they differ from the  same operations in those that are
without  organization, we shall be  able to  enter with
more  advantage upon these topics, when we  have made
ourselves acquainted with the functions to which they
are respectively subservient.
   Having now considered the structure and  physical
properties of membrane, I must proceed to give an ac-
count of its chemical composition and the effect of che-
mical re-agents upon it.   So  very  imperfect  was the
knowledge  of animal  chemistry, even as late as the
time of Haller and Gullen, that they supposed all the
soft  parts to  consist of  the same  substance, differing
only in  its mechanical  arrangement.   Haller had an
opinion, that membrane, being the least complicated
part  of the body, consisted principally of  the simple
fibres, which  served as a kind of  basis to the whole
system, and that the fibre itself was composed of earthy
particles cemented by gluten.*  The discoveries of the
pneumatic chemists, and especially  of the French, who
have  assiduously cultivated this department of science,
proved that  Haller's opinion is fallacious, and that earth
is not an essential constituent  of membrane.   His hy-
pothesis of the connecting gluten is equally gratuitous,
and  is  quite  contrary to  the more correct notions  of
modern chemistry.  The particles of membrane, as well
as those which compose any other solid, are held toge-
ther by their attraction for each other, not  by any con-
* JC1. Phys. lib. i. sect. 1. 
          Haller9s Opinion.—Cuvierfs Opinion.         .»:)

necting medium.   It appears indeed  that  membrane
acts mechanically in uniting the different parts of the
body, and in maintaining the proper form of those sub-
stances, which  are  of so delicate  a  consistence, as not
to be able to preserve themselves in a compact state,
for want of a greater degree of cohesion  between their
particles.   The soft pu.p of the neives, for example,
and  the adipose  matter, seem  'o  be retained in  their
present form, merely by the membrane  in which they
are  imbedded ; but this is quite independent of the
consistence or structure  of the  membrane itself.
   Although Cullen had no direct share in the great re-
volution in the  doctrines of chemistry which commenc-
ed about sixty years ago, yet his  notions  on this, as on
most other topics to which he paid any attention, were
much more correct than those  of his predecessors. He
pointed out the mistake of Haller respecting the basis
of the body being formed of solid particles united by a
cementing material, and maintained, on  the contrary,
that the  simple fibre  is an  homogeneous  compound;
but, with  the exception of the bones, he  conceives this
compound, which he calls the animal mixt, to be of the
same nature  in all the different parts of the  body.*  So
little indeed  was he acquainted with the  constitution of
animal matter, that he expressly says, we know  nothing
of it, except that it consists of some  concreting sub-
stance united to water,  and that the differences which
it exhibits.in various parts  of the  body are merely ow-
ing  to the  proportion  which  the  connecting  matter
bears to the water.  When we  recollect  that Cullen
formed his  opinions on  physiology before we  were
made acquainted  with the gaseous  bodies which enter
into the composition of nnimal  matter,  and that the
only method then employed for its  analysis  was simple
combustion or  destructive distillation,  we ought not  to
be surprised  at the incorrect opinions which he  enter-
tained upon the subject.
* Inst, of Med. § 10, 13- 
 S6             Experiments of Fourcroy.

   The experiments of Hales, who obtained large quan-
 tities of fixed air, as it was then termed, from urinary
 calculi, am' afterwards those  of Priestley, who procur-
 ed azote from the muscular fibre, by  means of the ni-
 tric acid, may be considered  as  among the  earliest
 which  ihrew any light upon the real nature  of animal
 substances ;  but for the first regular analysis  of them,
 and, especially, for the first attempt to distinguish their
 different species, and  to show the  nature  and  propor-
 tion, both of  their primary compounds and of their ul-
 timate  elements, we  are principally indebted to the
 French.  Fourcroy early devoted  himself to the de-
 partment of  animal chemistry, and  enriched it with
 many important discoveries;  but  his  opinions  are not
 to be  regarded as, in all  instances,  entirely correct.
 This is the  case with  respect  to membrane.   Finding
 that a large, and as it seemed, an indefinite quantity of
 jelly could be extracted by  boiling from many mem-
 branous bodies, he was disposed to regard membrane
 as essentially  composed of jelly, or, at  least,  as differ-
 ing from it rather in its physical, than in its  chemical
 properties.   Speaking of the different textures,  the
 cellular, tendinous, ligamentous, &c, which  he class-
 es together, under the head of membranous  or white
 parts,  as possessing  the same chemical  constitution,
 he  informs us  that they dissolve entirely in  boiling
 water, and form with  it, while it remains hot,  a viscous
 fluid, which, when cold, concretes into  a transparent
 and  tremulous jelly.*   This statement is erroneous in
 two respects; in the first place, there is probably no
 single article of these  enumerated by Fourcroy, which
 is completely soluble in water when boiling under  the
 ordinary atmospheric pressure ; and, secondly, although
jelly, in a greater or less proportion, may probably be
 procured from all of  them, yet they differ very much
 in the quantity which they contain;  and there  are some

  * System of Chem. Knowledge, by Nicholson, vol. ix. p. 319, et
alibi. 
            Albumen the Basis of Membrane.          37

in which it forms only a small proportion of their solid
contenK
  We are indebted to Mr. Hatchett for a much more
correct view of the subject; from his experiments  we
learn,  that  what may be considered as  the basis of
membranous matter is a substance, which, in its chemi-
cal  properties, is identical with the albumen of the egg,
when in a state of coagulation.*  Albumen  naturally
exists in the form of an adhesive fluid, miscible in  wa-
ter,  but when subjected  to  a temperature  of  about
165°, it experiences a remarkable change in  its physi-
cal  properties.  By the operation of heat it is convert-
ed into a solid, which is no longer capable of  beingdis*
solved in water; and if after coagulation it be gradu-
ally exposed to a higher temperature, it is  reduced to
a firm semi-transparent body, very  similar  to some of
the more compact  varieties of membrane.
  But although albumen  appears to be  the  essential
part of membrane,  that which gives it its general form
and determines its  peculiar  texture,  yet it probably al-
ways contains jelly, and in some cases, even much more
copiously than the albumen itself. Jelly is very soluble
in water, especially when heated; it is thus separated
from the albumen,  and by the evaporation  of the  wa-
ter, may be obtained in a state of purity.   One of the
most striking  characteristics of jelly is  the  property
which it exclusively possesses, when united to a quan-
tity of water, of being dissolved  by  heat, and again be-
coming concreted  by cold,  without, as it appears, un-
dergoing any change in its chemical constitution.
   Another substance which  appears to enter into  the
constitution  of membrane,  or is at  least  frequently
found connected with it, is  animal mucus.  This,  like
jelly, is soluble in  water, but it  does not possess  the
property of gelatinization, and it differs  from jelly  in
many of its chemical relations.   Animal mucus appears
* Phil. Trans, for 1800, p. 399, et alibi 
 38          Ultimate Elements of Membrane.

 to be nearly related to albumen; and  indeed the con-
 stituent upon which its characteristic properties princi-
 pally depend, would seem to be a mere modification of
 this substance.
   A considerable  proportion  of both  the  bulk and
 weight of membrane, as well as of all  the other soft
 parts, consists of water;  and it has been supposed by
 many  eminent  physiologists  that  upon the relative
 quantity of the water and  the solid matter depend ma-
 ny of  the morbid changes of the body,  as well  as the
 natural varieties in the constitution and temperament
 of different individuals.  Boerhaave  entered largely into
 these speculations ; they were refined upon, with much
 ingenuity,  by his  pupil  and successor Gaubius,* and
 were,  to a certain extent, adopted even  by Cullent-
 Membrane, when no longer forming a  part of the vital
 system, is capable of having its properties much affect-
 ed by the  quantity  of water with which it is combined;
 and  there are some facts connected  with  pathology and
 the  practice  of medicine, which would lead  us to con-
 ceive, that the elasticity, and perhaps even the density,
 of some of the external parts of the body ma^ be influ-
 enced by being exposed to warmth  and moisture.  But
 there is always great difficulty  in applying these me-
 chanical explanations to the living body ; and when we
 reflect how many mistakes have occurred on  the sub-
ject, we must feel the necessity of proceeding with the
greatest caution.
   With respect to the ultimate  chemical elements of
 which membrane is composed, we find  that, like other
 animal substances, it consists essential') of oxygen, hy-
drogen,  carbon, and azote.   It has been  observed that
membrane  is  less disposed to undergo the putrefactive
fermentation  than any of  the soft parts of the animal
body, from which circumstance, as well as from the re-
lation which  it bears to jelly, it  has  been supposed to
* Instit. Pathol. § 150—168.
t Inst. § 13. 
Chemical Relations of Jelly.
39
contain a less proportion of azote than  the muscular
fibre ;  an opinion  which appears to be sanctioned by
the analysis of Gay-Lussac and Thenard.*  The great-
er fixedness of membrane, or its less disposition to  be-
come  putrid,  may  be  immediately  attributed  to a
stronger attraction between its  particles, or it may  de-
pend merely upon its containing but a small portion of
either blood or fat, substances which  have  always a
powerful tendency to decomposition.  The more dense
varieties of  membrane  contain  less water than  many
other of the solids of the  body, and this may be  one
reason  why they are less disposed  to  putrefy; as we
invariably find that moisture favours decomposition.
   By the assistance of heat membranous matter is so-
luble in the  mineral  acids ; its  combination with  the
sulphuric and muriatic acids is  not attended with  any
peculiarly interesting phenomena, but the effects which
are produced by the nitric are  more remarkable ;  the
membrane  is partly dissolved  and  partly decomposed,
and several  new compounds are  produced, which will
be more fully described  when  I treat expressly upon
the analysis of animal substances.   Membrane  is also
soluble in the pure  fixed  alkalies,  and  a  saponaceous
fluid is formed,  which  has been  employed,  in some
instances,  instead of the  coarser  kinds of soap, made
in the  usual process, by  the combination of alkali and
oil.   Membrane  has a  strong  affinity for the  tanning
principle;  by uniting with a  portion  of tan, it  is con-
verted  into a dense, flexible,  elastic  substance, little
 susceptible of putrefaction, which,  under certain  mo-
difications,  forms the basis of leather.

   * Children's Thenard, p.  357 ; Thenard, Traite de Chimie, iv.
 204
   The following are the results of Thenard's analysis:
               Carbon       Oxygen     Hydrogen       Azote.
 Fibrin  .  .   .  53.365  .  .   19.8 5  .   .  7.021  .  . 19.934
 Albumen  .   .  52 883  .  .  23.872  .   .  7.540  .  .  15.705
 Jelly   .  .   .  47.881  .  .  27.207  .   .  7.914  .  . 16.98^ 
40                 Relation to Jelly.
   The jelly, which enters so largely into the composi-
 tion  of some kinds of membrane,  has also  a strong
 attraction for the tanning principle, and forms with it a
 substance, which appears in its chemical properties to
 be very similar to that produced by tan and the proper
 basis of membrane, the albumen.  B it it  necessarily
 differs  in  its  mechanical consistence, as the jelly, at
 least in the form in which it is  usually employed, is
 dissolved in water, and of course  without any regular
 organization of its particles, or even any adhesion be-
 tween them.  The mineral  acids and the pure alkalies,
 when assisted by heat, readily dissolve jelly, but nothing
 very interesting or important results from their combi*
 nation;  the compound  of  jelly and  alkali does  not
 appear  to  possess that saponaceous  property which
 exists in the compound of albumen and alkali.*
   It  appears  from the  analyses of MM. Gay Lussac
 and  Tnenard, referred to above, that jelly, as well as
 albumen, contains less azote than the muscular fibre;
 and they also found  that the  proportion  of oxygen in
jelly is considerably greater than in either of the other
two substances.   It is probably upon this circumstance,
 as Well as  upon  its less  compact  mechanical  constitu-
tion, that the greater tendency of jelly to pass into the
acid state depends; and  hence it is that jelly has been
generally considered to be less completely animalized
than the other soft parts of the body; for one of the
characters which distinguish  animal  from vegetable
substances  is, that the former evolves an alkali, and the
latter an acid, during their spontaneous decomposition.
As, however, there are some animal bodies that become
acid, so there  are some vegetables that become  alka-
line, and are found to  contain azote.   These may be
considered as  forming, on each  side, the  connecting
link between two of the great kingdoms of nature.
  An interesting experiment  was performed by Mr.
- Phil. Trans, for 1800, p. 379. 
Physiological Relation.              41
 Hatchett, which tends to illustrate the difference be-
 tween the chemical constitution of albumen and jelly :
 he found that if coagulated albumen be immersed for
 some time in diluted nitric acid, at the  temperature of
 the atmosphere,  it is gradually converted into a sub-
 stance resembling jelly*   We may suppose  thai, :n
 this case, the nitric acid parts with a portion of its oxy-
 gen to the albumen, and  consequently,  that jelh  is to
 be regarded as  differing from  albumen  in  containing
 a greater proportion of oxygen;  an  opinion wLk--* is
 supported by the analyses of Gay-Lussac andThcinivi.
   The  physiological relation which  subsists between
jelly and albumen is no less deserving of our attention.
 It is ascertained, that if we examine the same mem-
 branous  parts  at different ages,  those of the young-
 animal will be found to contain a greater proportion of
jelly, and those of the older of albumen.   It is on this
 account  that the parts of young animals, such as the
 foot of the calf, are principally employed in the pre-
 paration of jelly as an article of diet;  and every one
 must be  acquainted  with  the difference between the
 soups formed from veal and from  beef,  in the  greater
 proportion of jelly contained in the former.  We thus
 perceive that the young animal, not only in its physical
and  mental powers,  but even in  its chemical constitu-
tion, is less completely possessed of the characteristics
of the animal than when it has arrived at a more mature
age.  As we advance in the  subject, we shall find that
the same observation applies to other parts of the cor-
poreal frame besides the membranous matter.
   Having described the structure, properties, and com-
position  of membranous matter in general, I now pro-
ceed to give a more particular account of some of the
different  forms  under  which it exists.  I  shall confine
myself at present to those  species of membrane which
are dispersed  in  various situations through the body.
* Phil. Trans, for 1800, p. 385. 
42       Species of Membrane.—Cellular Texture.

and are connected with all  the  different  parts  of it;
as it will be more convenient to reserve for their appro-
priate'places the account of  those bodies that contain
some other ingredients superadded to  the membrane,
which  gives  them their distinguishing qualities, as the
bones and the muscles, and  likewise those that, in con-
sequence  of their  peculiar  organization, serve for the
purpose  of some specific function, as the blood-vessels
and the glands.
  The first species of membranous matter that I shall
notice is  the cellular  texture, as  it is  the most exten-
sively diffused, and is that which  has been conceived to
form the basis  of all the  rest,  or to constitute,  as it
were,  the original structure, from which the others
have all been produced.   Many  of the modern physio-
logists have paid attention to this  substance, but Bergen
would  appear  to  be the first author  who explicitly
states  the fact of  its general diffusion,* while we are
indebted to Haller for  a number  of experiments and
observations, which form the correct foundation  of all
that we  now  know  respecting it.  According to this
author, the cellular texture is found  in nearly  every
part of the body,  being  contiguous to each separate
organ, frequently entering into their substance, and con-
necting their different parts with each  other.  It is, in
short, the substance which fills up the spaces that exist
between every other part, which preserves them all in
their proper  situation,  prevents  them  from  unduly
pressing  upon  each  other,  or interfering with  their
motions or functions  of any kind.  The description of
it  which  was given  by Haller,  and which has been
generally admitted by subsequent anatomists, is, that it
consists of an irregular assemblage of  plates that cross
each other in various directions,  forming a kind of net-
work, and leaving a  series  of irregular cells.t   Many

  * De Membrana Cellulosa, in Haller. Disp. Anat. t. 3, p. 79, et
seq.; Bergen's Essay is dated 1732.
  t EI. Phys. lib. i. sect.  2. 
          Hunter's Account of Cellular Texture.        43

circumstances prove that these cells communicate  with
each  other.   Thus  when air  or fluid of any kind is
introduced into a part of this texture, it may be diffused
all over the body, without employing such a degree of
force  as can be supposed sufficient to produce a rupture
of the membrane  itself.   It is  this inflation of the cel-
lular texture by air that produces  the disease of  em-
physema, where, generally in consequence of an  acci-
dental injury, a preternatural  opening  having  been
formed between the vesicles  of the  lungs  and some
part of the  cellular  substance  contiguous to them, a
portion of the air which is received in inspiration passes
into this  texture.*  In some of these  cases the whole
body  has been puffed  up  in the  most extraordinary
degree, and  the patient  has actually been  destroyed
by suffocation.  The fluid of anasarca, which is depo-
sited in the same cells, although less moveable and less
penetrable than air, is also liable to pass from one part
of the body to another,  in obedience to  the laws of
gravity,  from the trunk to the  extremities,  and again
from  the extremities to  the trunk, according  as the
posture of the  patient has  been erect or horizontal.
And,  to a certain degree,  this is likewise the case  with
collections of pus,  although, from  well-known circum-
stances attending its formation, the transmission of this
substance along the cells  is less general and less exten-
sive than in the former instances.
   A valuable addition to  the knowledge which Haller
gave  us respecting the cellular  texture was made by
W. Hunter,  who first clearly pointed out a difference
in the nature of the eivities that are  contained in this
substance, both «n respect to the  communication with
each  other and to the uses for which they are destined/!'
The adipose matter, which is dispersed over most  parts

  * This effect is distinctly noticed by Bergen, p. 85,  as a decep-
tion practised by beggars and by butchers.
  t Med. Obs. et Inq. v. ii. p. 26, et seq. 
44
Borden's.
of the body, is contained in the cellular texture ;  and
Hunter's observations go to establish the fact, that the
fat is not lodged indiscriminately in all of them, but that
it  has peculiar colls destined for its reception, which do
not communicate with each other, and which are dis-
tinct from those that contain  the air in emphysema or
l'ie water of anasarca.  These particular cells he calls,
from trie;r contents, adipose, in opposition  to the gene-
ral ones, which he calls reticulated.   It is  not pretend-
ed i  it any  difference can be detected in the appear-
ance or visible  structure  of these  two kinds of cells;
but the difference  between  them is conceived to be
sufficiently proved by their situation and their contents.
The parts of the  body,  where the fat is  principally
accumulated, are  not the same  with those  which are
the most subject  to anasarca; and  it is also observed,
that fat never passes from one  cell to another in the
way that air and  water do, but that each portion of fat
always remains stationary in the same  cell in which it
was originally lodged.  The opinion of Hunter, although
it can scarcely be said to be demonstrated by any direct
anatomical proof, is generally admitted to be correct,
as it coincides with all our pathological and physiologi-
cal observations, and is most consonant to our notions of
the nature  of fat,  and the relation which  it bears to
the other parts of the system.*
   An account of the  structure and  properties of the
cellular texture was  made the  subject of a separate
publication  by Bordeu, but  his description does not
possess that degree of accuracy which  can give much
weight to his opinions.  He entitles it the mucous tex-
ture, from an hypothesis which he formed of its origin.
He speaks of it  as consisting of fibres that are enve-
loped in a stratum of mucus, so as to compose a spongy
texture, without  any regular figures;  and  it  may be

  * M. Beclard has offered some additional circumstances in favour
of this opinion, p. 15. 
Remarks on Bichat.                45
inferred, that he regards it  as  almost  without organ-
ization.*
  The latest writer who has described  the mechanical
structure of the cellular substance is Bichat; and it is
the more deserving of notice, as it professes to be the
result  of  careful  observation,  and  differs, in  some
respects, from that of  his predecessors.  He informs
us that if we  accurately examine  a  portion of the
cellular texture, we shall  perceive it to be composed
of extremely thin plates,  with  a number of fine fila-
ments  crossing  them.   That the eye  is not able  to
trace any thing further than these plates and filaments;
that the plates  do not exhibit  any  appearance of a
fibrous structure, or, in fact, of any  specific organiza-
tion, and that the  filaments  seem incapable  of  more
minute subdivision.  It may  be  inferred  from his  ex-
pression, that this is an account of what we are able to
detect by the naked eye.   The filaments he supposes
to be exhalent and absorbent vessels; but this conclu-
sion is deduced, not from  any thing of a vascular struc-
ture which was discoverable  in them, but simply  from
the circumstance, that there  must be an apparatus  for
exhalation and absorption, somewhere  connected with
these cells ;  and unless these  filaments  perform this
office, we are ignorant by what means it is  effected.
Although the plates do not possess any visible organi-
zation, yet the author argues that they are organized,
upon the general  principle,  that  every part  must  be
so which is connected with the  living body.f
   It is  perhaps to be regretted, that such an accurate
observer  as  Bichat did  not employ the microscope,
before he  had given  so decided an  opinion upon  the
structure of  these  parts;  for if  we  are  to  form  any
speculations  upon the subjects  of  minute anatomy,
there can  be no doubt that,  by the cautious use of this

            * Recherches sur le Tissu Muqueux.
            t Anat. Gen. t. i. p. 106, et seq. 
46
Form of the Cells.
instrument, we may be enabled  to discover parts that
cannot otherwise be  detected.   The necessity for an
organ may be regarded as a proof of its existence, but
it  is a species of reasoning which we should employ
with great reserve.   It  seems very  certain, that the
cavities of the cellular  texture, at  least those which
Wm. Hunter  calls  reticular,  always contain more or
less of an albuminous fluid, which is,  in some  way, se-
parated from  the blood; and  it is equally certain, that
this fluid would  accumulate  in them, were it not  re-
moved from time to  time, by an operation, which can
be performed by no method with which we are  ac-
quainted, except by the action of the  absorbents.   We
may then say, that the cavities  are  provided  with an
exhaling and absorbing apparatus, but beyond this  we
are not able to proceed.   Blood-vessels are  seen  pass-
ing through the  cellular  texture  in  various  directions,
part of which we may presume are  expended in sup-
port of the  substance  itself;   and  there  are  also
branches of nerves found in it, but they appear rather
to be crossing it, in  order  to be distributed to some
other parts, than to be destined for the use of the tex-
ture itself.
   With respect to the form of the cavities, we have
no accurate  knowledge.   All the writers  who have
described them since Haller, speak of the cells as hav-
ing an  irregular  or indeterminate figure, and generally
compare them to those of a sponge.   But this illustra-
tion, although it is commonly referred to, and is men-
tioned  even by Cuvier,* cannot be considered  as  very
appropriate, except so far as  regards  their  free com-
munication with  each other.   The cavities of a sponge
are of  a tabular form, whereas  it may be  presumed
that those of the substance  in question are rather nar-

  * Tab. Elem. p. 25.  This learned naturalist, in the Diet. Scien.
Nat. article " Animal," describes  the cellular texture as consisting
of a number of small plates irregularly thrown together, and form-
ing small communicating cell? 
             Properties of Cellular Texture.          47

row spaces with  acute  angles, the sides of which are
flattened, and, when not  forcibly expanded, we  may
suppose, to be in contact.
  Some physiologists have indeed  gone so far as  to
deny altogether the existence of any cellular arrange-
ment, and  to assert  that  the appearance  of cavities,
which  is  produced by  injecting air or fluid into this
texture, depends not  upon any cavities previously ex-
isting there,  but upon the substance  itself being so soft,
and at the same time so tenacious, as to admit of hav-
ing its parts distended and forced asunder, in the same
way as  if we  inject air  or  fluid into  a mass of softened
glue.*   But, notwithstanding  the respectability  of the
authors who have advanced this opinion, I think it is
clearly  contrary to the  obvious conclusion which would
be  drawn by an unbiassed  observer  of the various
states of this texture, which appear  to me totally diffe-
rent from what would  take place upon the supposition
of its being a uniform mass,not to insist upon the theo-
retical objection  of any part  of the body consisting of
unorganized matter.
   I have anticipated the greatest part of what might
be said on the properties of  the cellular texture in my
remarks  on  membrane  generally.   Notwithstanding
the opinion of many very eminent  physiologists,  I am
not disposed to admit of its possessing  either  contrac-
tility or sensibility ; but it exhibits  more marks of vi-
tality, or rather, it  is  more intimately  connected with
the functions of  the  system at large than some other
species of membranous matter.  It is  especially liable
to be the seat of inflammation, and in consequence of
the laxity of its texture, is frequently the depository
of large collections of  pus.   The theory of inflamma-
tion is  a subject that  must  occupy our attention  in a
subsequent part of  the  work; at  present it  may be
remarked, that an essential and obvious feature of this
* «ee Beclard, p. 19—23. 
4 b               Chemical Composition.
process consists in  those  vessels which generally con-
tain only a colourless fluid, becoming so far enlarged as
to  admit of the red particles of  the  blood, that this
change occurs in the vessels  of the cellular  texture,
and that probably the seat of  it is in the exhalents of
the part.   It is stated  that the cellular  texture pos-
sesses the power of  speedily renewing itself,  after it
has been wounded or destroyed; and that in the pro-
cess of  the healing of wounds, or repairing injuries of
any kind, it is this part  which is first formed, or which
first recovers  itself; and  it has  also  been supposed
that it is the cellular substance which is first produced
in the development of  the embryo; but this opinion
is derived from no  very accurate  discrimination of
the nature of the  substance, and is to be regarded as
at least very problematical.
   The chemical composition of  the cellular  texture,
like that of membrane in general, has been thought to
consist, in a great  measure, of jelly.  I have  already
referred to Fourcroy's  account of it, but  it  appears
that he had not a sufficiently correct idea of the nature
of jelly, or at least of the distinction between jelly and
the animal substances which the most nearly resemble
it.   Bichat says that boiling  water first hardens and
afterwards dissolves  the   cellular  texture; but this
statement is made in  a  loose manner, and  it  may be
doubted how far it  was the result of direct  experi-
ment.*  Nearly a similar account of the chemical com-
position of the  cellular  texture is  given  by Cuvier;t
but, like that of Bichat, it is stated incidentally, and is
to  be  considered rather as  a  commonly received
opinion, than as one explicitly  adopted  by  this learn-
ed  naturalist.
   The next species  of  membranous matter  which  I
^hall notice are  the bodies that are especially  denomi-
* Anat. Gen. t. i. p. 111.
f Regne Anim. t. i.  p. 2C 
Mucous Membranes.
49
nated  membranes, to  which  the generic term was
originally applied.  They consist of thin semi-transpa-
rent sheets or plates, which generally form the  coats
or coverings of  some  other  parts,  and  which  differ
from the cellular texture in the  greater continuity of
their structure.   Haller, in  conformity with his  gene-
ral doctrine on this subject, supposed that the proper
membranes,  like  all the other  white parts, consist
merely of condensed  cellular  substance;  and he was
at much pains to  prove this point, by examining  them
after they  had been macerated in water for a long
time, and were approaching to a  state of decomposi-
tion.*  To a certain extent  this idea  is well  founded,
but,  as a matter of fact, independent of any  specula-
tion  on their origin or the mode of their formation, it
does not  appear  that the  whole substance of  mem-
branes can be resolved  into this texture ;  for although
there may  be a considerable quantity of it  attached to,
or connected with them, still  there  appears  to be a
solid basis, which is no  longer capable of  further sub-
division into more  minute  plates.  The proper  mem-
branes form the  subject  of a  very elaborate publica-
tion  by Bichat, in which he has  arranged them into
different classes, has  minutely examined the structure
and  functions of each, and pointed out their connexion
with the other parts of the  system.  His work con-
tains many interesting details, and deserves to be care-
fully studied;  yet I  think that his distinctions are
sometimes  too refined, and that  his  opinions are  occa-
sionally rather ingenious than just.   But there is  a real
foundation  for the division which  he makes  of  mem-
branes into  the  three  kinds  of mucous, serous, and
fibrous; of  these  1 shall give  some account in suc-
cession.
  The mucous membranes  are named from the  pecu-
liar  semi-fluid  substance with which their surface is
  * El. Phys. lib. i. sect. 3.
7 
50
Mucous Membranes.
covered, proceeding from numerous small glands that
are imbedded in them. This kind of membrane always
lines those cavities which are disposed in the form of
irregular  passages, or canals, that open to the  atmo-
sphere, and are connected with the skin at their extre-
mities.  Of these, the principal are the mouth, the nos-
trils, the oesophagus, and the intestines, composing the
great system of the digestive organs, and  those con-
nected with  the  urinary  organs,  and  the  uterine
system.  These membranes are attached  to the parts
which they cover by a smooth and dense surface, while
their external surface is  soft and pulpy, and generally
irregular  from numerous projections of various kinds,
which differ according to the uses for which the part
is destined.   According to Bichat they are divisible in-
to distinct layers ;* but this seems scarcely compatible
with the account which  he gives of their organization,
and with the  idea which is  commonly entertained of
their texture ; so that it is  probable  that  the  layers
which have been supposed to be detached  from these
membranes were merely portions of condensed cellular
substance, by which they were connected to the  sub-
jacent parts.   The mucous membranes are  the  imme-
diate seat  of some important functions : in the  mouth
and nose, they constitute the organs of taste and smell;
in the stomach, of digestion ; and in the  intestines, of
the assimilation of the food, and the separation of the
nutritive from the fcecal part.   On  this account they
differ from most membranous bodies, in being  plenti-
fully supplied with blood-vessels and nerves, as well as
in possessing  an  extensive apparatus of glands and ab-
sorbents.   As I  shall have occasion to enter more par-
ticularly upon these points, when I treat upon the dif-
ferent functions that  are connected with the  mucous
membranes, I shall at present only remark concerning
them, that unlike most of the membranous bodies, they
exhibit, in a  high degree, the powers of vitality, and
* Traite des Mem. art. ii. § 3. 
Serous Membranes.
51
 are intimately connected with all the general actions of
 the system.
   The second species of membranes, the serous, differ
 materially from the mucous in their seat, their texture,
' and  their properties.  They are always found in close
 cavities that do not communicate with the atmosphere,
 as those  of the  thorax, and the abdomen ; they form
 coats for most of the individual organs which are essen-
 tial to  the animal ceconomy, as the heart, the lungs,
 and the different abdominal viscera, and they  frequent-
 ly afford  an external covering  for  those parts Avhich
 are  lined internally with a mucous  membrane.   The
 serous  membranes  in their texture are dense, smooth
 and compact, comparatively thin, but of considerable
 strength in proportion to their bulk, and are not divisi-
 ble  into  any  regular layers; they  have their surface
 always moistened with a fluid which  exhales from them,
 as is supposed, in the gaseous state.  No glandular ap-
 paratus has been detected in them, and on this account
 the fluid has  been ascribed rather to a kind of infiltra-
 tion through  small pores, than to what can properly be
 called  secretion.  Although  in some states of disease
 the exhaled fluid accumulates in cavities that are lined
 with  serous  membranes, forming different  species of
 dropsies, in health it is always removed as fast as it is
 generated, proving  that the absorption exactly  keeps
 pace with the exhalation.  We have, therefore, a clear
 manifestation of the effect of these two processes; and
 yet we are not able to detect  the apparatus  by which
 they are carried on, a circumstance which, I conceive,
 is unfavourable  to  the  opinion  of Bichat, that the fila-
 ments of the cellular texture are a system of exhalent
 and absorbent vessels.   The specific use of  the serous
 membranes,  as consisting of a smooth surface, which is
 always lubricated  by an albuminous fluid, is to give a
 capacity for  the free motion of  the parts which they
 enclose  upon each other, at the same time  that they
 are prevented from adhering together, to which, from 
52
Fibrous Membranes.
their frequently being  in close contact, they would be
liable, without the intervention of this fluid.   The se-
rous membranes have scarcely any vessels of sufficient
size to convey red  blood, and  have very few, if  any,
nerves ; they are therefore without sensibility, and ex-
hibit only in a low degree the general powers of vita-
lity.   They possess a  considerable share of  elasticity
and expansibility, but are not properly contractile, nor
do  they manifest any properties except  those  which
are common to every part of the body.
  The third class of membranes, the fibrous, are nam-
ed from their  obvious texture, as consisting of a visible
assemblage of fibres, united into a continuous extended
surface.   They differ  from both the former kinds in
not being moistened by any fluid, but in their  general
aspect they are more similar to the serous, being dense,
thin, and smooth, although, according to their situation,
and the  uses  which they serve, they are more  varied
in their form and consistence.  Among the most impor-
tant of the fibrous  membranes  are the  periosteum,
which surrounds the  bones;  the dura  mater, which
lines the skull; the aponeuroses, those membranous ex-
pansions which surround certain  muscles and  separate
them  from each other; the capsules of the joints, and
the sheaths of  the tendons.   The structure   of these
bodies is distinctly and obviously fibrous, and they seem
to possess a texture which is more dissimilar to  the
cellular than any which we have yet examined.   The
fibres, so far  as we are able to separate them by ma-
ceration  or by dissection, appear to  be  strong dense
cords, without  blood-vessels, nerves,  glands, or specific
apparatus of any kind, and of course they are possessed
of no  properties  but those which belong to every  part
of the body.   Their use in the animal ceconomy is  prin-
cipally mechanical;  to enclose soft substances and pre-
serve them  in their proper form, to separate  them
from  each other, and  to keep them in their  relative
position. 
      Chemical Composition.—Tendons and Ligaments.   53

  The chemical composition of the proper membranes
is similar to that of the membranous matter generally ;
they  consist of a basis  of albumen, united to  different
portions of jelly and mucous.  It is stated, that in pro-
portion to the density of their texture, is the quantity
of albuminous basis compared to that of the other in-
gredients.   The  fibrous membranes consequently con-
tain little else but albumen, while the mucous, at least
some  of the more delicate of them, are nearly soluble
in water.   The membranes  contain no earth, and only
a very small quantity of any saline matter;  in an ex-
periment  of  Mr. Hatchett's, 250 grs. of bladder left a
residuum  of no more than *02 gr.*
   The chemical  composition of these  bodies, as is the
case with membranous  substances generally, differs ac-
cording to the age of the subject from which they are
procured ; in young animals they contain more jelly,
while, as  age advances, the proportion of albumen  is
increased.
   Tendons and ligaments are bodies that nearly resem-
ble the fibrous membranes in their minute texture and
their chemical composition.   It was upon tendons that
Fontana's observations  were made ; and even with the
naked eye  we can easily observe their structure, as
consisting  of longitudinal fibres, lying parallel to  each
other, and closely united together.  It is generally ad-
mitted that no nerves are sent to them, that  they pos-
sess very few  if any blood-vessels, and no organs  have
been detected in them  for the purpose either ef secre-
tion  or  absorption.   Their  principal use is to connect
the muscles with  the bones, and to serve as cords  or
ropes to transmit  the action  of the muscles to a distant
point, and in doing this, their operation appears to  be
entirely  mechanical.  The ligaments, in their texture,
nearly resemble  tendons ; they are, like them,  com-
pact, strong, and flexible bodies, but they are  generally
* Phil. Trans, for 1799, p. 333. 
54
Cartilages.
more dense in  their consistence, and their fibrous tex-
ture is  generally less  distinctly marked.  They have
no nerves,  but they have a few  blood-vessels distribut-
ed to them, and they appear to possess somewhat more
connexion with the vital powers of the system.  Their
use  is sufficiently expressed by their name ;  they are
principally employed in connecting the bones with each
other,  particularly about  the articulations.   In their
chemical composition,  tendons and ligaments nearly re-
semble the more compact membranes ;  their basis ap-
pears to be coagulated albumen, united to different pro-
portions of jelly and mucus ; they contain no earth, and
only a minute quantity of saline  matter.
  Cartilages are bodies which, in  many respects, near-
ly resemble ligaments, although they differ from them
in some important particulars.  It is not easy to per-
ceive any  fibrous texture in them;  on  the contrary,
their obvious appearance is that of an uniformly dense,
membranous matter, not extensible, but highly clastic.
Their use is to cover  the ends of  the'bones, especially
about the  joints, where, for the purpose of motion, a
smooth  and firm surface is required ;  and in many parts
they supply the place of  bone,  where strength  is  ne-
cessary  together with a degree of flexibility, as about-
the  thorax,  the  trachea, and oesophagus.   They arc
described by the most  correct anatomists as being with-
out visible  vessels  or nerves.*  They appear to consist
principally of albumen, with little, if  any jelly  and  mu-
cus ; it is said that a portion of earthy matter is always
found in them, which Dr. Davy estimates  at -2|7 of
their weig;ht,t but Mr. Hatchett  does  not consider  it
as essential to their constitution.^  Cartilages  appear
tonold  a kind  of intermediate  place between mem-

  *  Haller, El. Phys. 29, 4, 27.   Soemmering de Corp. Hum. Fab.
t. i. § 27.
  t  Monro's Outlines, v. i.  f. 68.
  | Phil. Trans, for 1799,  p. 331. 
Life of these parts.
55
brane and bone, a circumstance to which  I  shall have
occasion to recur when I come to treat upon this latter
body.
  I  have stated that the  fibrous membranes, the ten-
dons, and the cartilages,  possess neither blood-vessels
nor nerves ;  that they are  not  furnished with any or-
gans that we can detect, for the purpose either of se-
cretion or  absorption; and that they  do not exhibit
any  of the appropriate powers of vitality, being neith-
er contractile nor sensitive ; it may then be asked, how
are  they connected with the  vital  system,  or in what
sense  are we to  regard them as possessing life?  The
question, I acknowledge,  is one that cannot be easily
answered, and which may perhaps be thought to turn
rather upon the  definition  which we give  of  certain
words and expressions than  upon  any absolute facts
that we can adduce.   I have already mentioned, that
some eminent physiologists conceive  life to be always
 necessarily connected with vascularity and with sensi-
 bility; and these writers do not hesitate to call the
 dense membranes and the tendons dead or inanimate,
 seeming to regard them as only mechanically attached
 to the more vital parts.*   But to this opinion  it may
 be objected, that there is no portion of the body which,
 as far as we  can judge, has not  a regularly  organized
 structure, and that this can only be produced by the
 operation of some vascular action, probably analogous
 to secretion, by  which the matter that composes them
 may be deposited, particle  by   particle, in its proper
 situation.  We shall also learn, as  we  advance in the
 subject, that every part  of the body is liable to decom-
 position, and is probably removed in process of time,
 particle  by particle, in a manner precisely the reverse
 of that in which it was  formed, and that this process
 can only be effected  by  the  absorbent system.  Al-
 though therefore we  are  not  able  to  detect either a
* Carlisle, in Phil. Trans, for 1805, p. 12, &c. 
56                Mode of growth.
secretory or an absorbent apparatus in these parts, yet
we have sufficient  proof of their existence, and they
must be considered as constituting the medium through
which their vitality is preserved, and which connects
them with  the other parts of the living system.
   Some writers, especially of the French and  German
schools, have indeed attempted to explain how this ad-
dition and subtraction of matter may be produced with-
out the  intervention of vascular action,  and have not
hesitated to compare it to the  effect of mere attrac-
tion, similar to what occurs  in  the  formation  of crys-
tals.  Linnaeus, who was too fond of fanciful analogies
between things that had  little real resemblance, has,
in some degree-, contributed to this opinion by his well-
known aphorism, which he employed to distinguish be-
tween  the  three  kingdoms of nature.   He says that
minerals grow, vegetables grow and live, animals grow,
live, and move.*   But  between  the  growth of mine-
rals and that of animals there  is this essential  differ-
ence, that crystallization consists merely  in the apposi-
tion of particle to  particle, by which the substance has
its bulk increased, but without those parts that are  al-
ready formed having their arrangement, in any way,
altered or changed.  The consequence of which is, that
if a crystal be broken into a  number  of parts,  each
part forms  as perfect a crystal as the larger one; and„
on the  contrary, if a small crystal be placed in a saline
solution, where it  may receive  additional matter, the
small crystal will differ from  the larger one simply  in
its bulk.   But this is not the case with a  membrane
or a tendon.  If we compare  the corresponding parts
in a young  animal  and  in one that  is fully  grown, we
shall find that the  latter is not merely increased in size,
or has received an addition of new matter at its exter-
nal surface, but that every individual part of  it is of a
diSlerent size, and  is differently  connected with the ad-
* Philos. Botan. Introd. 
Skin.                      57
joining parts from  what it was originally; so that it is
demonstrable to the  eye, that the small tendon could
never have acquired the  size  of the  large one, until
the former had had all its particles gradually removed,
and new particles deposited in their place.  This sub-
ject  will be considered more fully when I come to treat
upon absorption;  it is  noticed at present for the pur-
pose  of   explaining  the difference  between  animal
growth  and  the  mere increase  of bulk which consti-
tutes crystallization.   The proper answer to the ques-
tion proposed seems therefore to be,  that the life of
these parts consists  in their being under the influence
of those actions by which the growth  of  the  body is
effected and its organization preserved.
   All animals, except those  of the simplest structure,
possess an outward covering, which connects their parts
too-ether, protects them from  injury, and  prevents  the
too  powerful impression of  the external agents  to
 which  they  are  exposed.   In  the   human  species,
 and in those classes of animals that are the most near-
 ly allied to it  in  their structure and organization,  this
 part is called the skin ; and I have classed it among the
 membranous  bodies, because, although it possesses some
 characters peculiar to itself,  it agrees with the  mem-
 branes in  many of its properties, both anatomical, phy-
 siological, and chemical.*  The skin  has  been divided
 by anatomists into distinct layers, or rather  into  dis-
 tinct organs, which possess peculiar structures and func-
 tions ;  the principal of which are the epidermis, or cu-
 ticle ; the rete mucosum; and the cutis, or true skin.
   Of these the epidermis is the external  covering.  It
 is a thin semi-transparent body,  adhering uniformly to
 the parts on which it is laid, and closely applied to all
 their inequalities.  It does  not possess any  blood-ves-
 sels or nerves that  can be  detected, it exhibits no

   *  See Bonn de Cont. Mem., who perhaps carries the analogy be:
 tween the skin and the other membranes too far.
               8 
5$                    Epidermis.
marks of sensibility, and  seems  to have but little con-
nexion with the vital powers of the system.  It is fre-
quently destroyed from various accidents, and is quick-
ly reproduced, without causing  any material derange-
ment, or any sensible change  in the functions of  the
subjacent parts.   With respect to its minute structure,
we are informed,  that it consists of a thin expansion, in
which no specific  texture of any kind  can be perceiv-
ed ;  for the laminated or scaly  appearance, which was
thought by  Leeuwenhoek,* and  some of  the older
writers, to be natural to  it, appears to be  the  effect
either of disease, or of mechanical violence.  In some
parts, indeed, where it is thicker  than  ordinary, it is
capable of an imperfect division into layers; but these
do not seem  to possess any  very distinct line of sepa-
ration, and are irregular and not well defined/1*   Some
physiologists have considered it  as  a substance  merely
spread over the surface, like a crust or film, and sup-
posed it to be formed  by exudation from the cutane-
ous vessels,"]: while both Bichat and  Cuvier seem inclin-
ed to regard it as  without any regular  arrangement of
its parts, and possessed of no visible organization.§
   As the cutaneous perspiration issues from the great-
est part of the surface  of the body,  it follows that the
epidermis must be furnished with pores or passages of
some kind  for its  transmission ; yet, with the exception
of Bichat,|J anatomists  have confessed themselves  un-
able to detect these passages.   Indeed, one of the most

  * Arcana Naturae, p. 205.
  t Bichat, Anat. Gen. t. ii. p. 749, et seq.; Gordon's Anat. p. 327.
  % Winslow, Anat. sect. 7, § 2, 140; Haller, El. Phys. 12, 1. 12;
Meckle in Cruickshank on Ins. Persp. p. 10, 27
  § Anat. Gen. t. ii. p. 752, 757 ; Tab. Elem. p. 55; see also Law-
rence's Lect. p. 274;  Gordon more decidedly states it to be " truly
inorganized or non-vascular."  Anat. p. 239.
  t| Ubi supra, p. 746; see also Winslow ubi supra, 147-9;  and
Bonn, § 6. 
Its Ports.
W
remarkable properties of this part is its power of re-
taining fluids of all kinds, and preventing their escape
from the surface.  It is well known that it retains, for
some time, the matter that is discharged from the cutis
by a blister; and those who are  conversant  with dis-
sections must have observed how much less rapidly the
surface dries up when it is  not deprived of its cuticle*
Various explanations of this fact have been proposed;
Winslow and Bonn suppose  that when the epidermis i3
detached from the cutis, a portion of the latter adheres
to the former, which mechanically closes up the pores;
Albinus and Meckle,  that  it  transudes through  the
substance of the cuticle ; Bichat  conceives  that  the
pores pass through in  an oblique direction, and, conse-
quently, that their sides are pressed together when the
body  is distended ; while the observations of Cruick-
shankt would lead us to conclude that the epidermis is
possessed of a kind of elasticity  which  tends  to close
the pores, unless they are   forcibly kept open by the
passage of some fluid through them.   Perhaps none  of
these suggestions entirely  removes the difficulty; we
may, however, go so far as  to remark, that the matter
of perspiration, being discharged in the form of vapour,
is enabled to pass through very minute pores;  and that
the epidermis, when removed from the part  to  which
it is attached, will shrink, and thus close up any open-
ings which it possessed while in  its natural situation.^
   There has  been  as much difficulty respecting the

  * Chevalier's Lectures, p. 116.
   t Cruickshank, p. 13, et seq.
  I Mr. Chevalier's recent publication contains an account of some
observations which he has made upon  this part, which lead us to a
new, and, as it appears,  a more probable  account  of its functions
than any which had been previously proposed. He conceives it to
be composed of " an infinite number  of small velamina regularly
arranged," so as to form  ";a bibulous and exquisitely hygrometrical
covering"  Lectures on the general  Structures of  the Human
Body, p? 133, pi. 2. fig. 1— 6. 
6o
Vessels.
vessels that secrete or convey the  matter of perspira-
tion as the openings by  which it is discharged.  Wra.
Hunter conceived  that  he was able to detect  them
merely by  separating  the epidermis  from the  cutis,
when  they might be seen  passing from one to the oth-
er, like the fine  threads of a spider's web,*  but this
idea is not countenanced by the observations of subse-
quent  anatomists.t   Bichat, indeed, speaks  of the ex-
halants that pass from the cutis to  the epidermis  as
being sufficiently visible  ;J on  this point,  however,  as
well as respecting the  pores of the  epidermis,  it is
difficult to  reconcile his  descriptions  with  those  of
other  observers of acknowledged accuracy.   We are,
therefore, still left in doubt,  both respecting  the  or-
ganization of the epidermis, and its connexion  with the
other  parts of the  system: yet there  are  many facts
which  show that this  connexion exists.  The facility
with which the epidermis  is  reproduced, when it has
been destroyed, is alone  a  sufficient proof of this point,
for the reproduction can  only take place in consequence
of a regular deposition of particles from vessels appro-
priated to the purpose.  And its own structure, when
considered as  a whole, exhibits evident marks of what
may be termed organization ;  for although  it is difficult
to see  any thing of this  kind,  when we examine only
small portions of it, yet we observe that there are par-
ticular parts  of the body  where  the  epidermis is  al-
ways thick, and  other parts where it  is always thin,
and this obviously connected with the uses  of  these
parts.§ It is  also liable  to a visible change in  its struc-
ture from various morbid  causes, so as necessarily  to
imply  a connexion  with the  vascular system;  from

  * Med. Obs. and Inq. v. ii. p. 52, pi. 1, fig.  1, 2.
  t Gordon, p 239; See Ruysch, Adv.  Anat.  3, 8 ;  and the Stric-
tures of Albinus, Acad. Annot. 7, 3.
  \ Anat. Gen. t. iv. p. 746.
  § Albinus, Acad. Annot. lib. 1, p. 27; Winslow ubi supra, 143, 
Effect of Pressure.              61
which we may infer that this is the case at other times,
although the minuteness of the parts prevents us  from
discovering it.   The analogy  of  the  inferior animals
leads us to the same view of the subject, for the scales
of fish, the thick folds with which the elephant is cover-
ed, and other similar substances, are properly produc-
tions of the epidermis, or are analogous to  what we
consider as the epidermis in the  human subject.*  As
far as its chemical composition has  been examined,  it
seems to consist almost entirely of albumen.
   There  is a circumstance with respect to the epider-
mis which  deserves to be noticed ; its property of  being
thickened  by pressure.   I have already remarked, that
it is naturally thicker in certain parts  of the  body,  as
in the soles of the feet, and  the  palms of the hands ;
and we find that, in these situations, the natural thick-
ness is increased by exercise, especially if long continu-
ed, and not too considerable.  The final cause of this
change is very obvious; and it  affords one  instance,
among many  others, of  that  admirable adaptation of
the organs to their appropriate  uses*,  by  which they
are not only fitted for  performing certain  actions, but
are endued with the  power  of accommodating them-
selves to  incidental circumstances.   But the physical
cause of this change of structure  is not so easy to com-
prehend, and we are scarcely in  possession of any facts
 which can enable  us to explain satisfactorily the  mode
 in which it is produced.   It may, perhaps, be referred
 to an increased action  that is  excited in the  secretory
 vessels of the cutis, analogous to  some other operations
 of the body, where an  increase  of vascular action in a
 part promotes its natural functions; but  this explana-
 tion is not without its difficulties, and is, at least, entire-
ly conjectural/!"

   * Blumenbach's Pbys. §  177, note.
   t This supposition would accord with Bonn's idea of the forma-
 tion of the epidermis, as composed by the  continuation of  the 
63
Corpus Mueosum.
   The nature of  the next layer of the  integuments,
which lies under the epidermis, has been much contro-
verted.   Its existence was first announced by Malpighi,
who described it as a stratum of soft matter, disposed
in the form of fibres, crossing each other in various di-
rections, which  was  situated  between  the epidermis
and the cutis.*  Some of  the modern anatomists have
conceived it  to be merely  a thin layer of pulpy matter,
without any distinct reticulated  structure ;t while Bi-
chat,  whose acuteness always entitles  his opinions to
great  attention, altogether doubts its  existence  as  a
proper membrane, and  supposes that what Malpighi
saw and described is nothing  more than a net-work of
extremely delicate vessels, which, after having  passed
through the  cutis, ramify on the surface in  all direc-
tions/}:  There are, however, high authorities in favour
of  the original  opinion of Malpighi, some, at least, of
which appear to be derived from original observation.§
Cruickshank, who has  examined  the skin with great
accuracy,  speaks of the rete mueosum as a substance,
of the existence of which he entertained no doubt, and
which might be easily detected in all  individuals, and
even  in some of the internal parts  of the body.|j  We
have  a still more recent account  of it by Dr.  Gordon,
who,  after controverting the opinion of Bichat, informs
us that it  was easy to demonstrate  the  existence of  a
distinct membrane, between the  cutis and epidermis, in
the Negro, but that it was not to be  found  in the Eu-

cutaneous vessels, united together by the fluid which exudes  from
them, § 7.
  * Opera  Post. p.  28, et alibi.
  t Blumenbach, de Gen. Hum. Var. § 42; et Physiol. § 180.
  \ Anat. Gen. t. ii. p. 665.
  § Albinus, Acad.  Annot. lib.  1,  c. 1, passim; Ruyscb, Advers.
Anat. 3, 8.
  II On Insens.  Persp. p. 3, et seq. p. 22, 36, et alibi. 
Colour of the Skin.
6S
ropean.*  It is difficult to decide between such  high
authorities ; the evidence in favour of the existence of
this body seems, however, so strong as scarcely to allow
us to doubr upon the point; but we may, at the same
time, coincide so far with Bichat as to suppose that the
reticulated texture, which Malpighi described, consists
rather of a network of vessels ramifying on the surface
of the cutis, than forming a part of the  corpus mueo-
sum itself.t
   Malpighi announced this  body as being the part from
which the colour of the  skin proceeds;  and, whatever
opinion we may entertain respecting its structure  or its
nature, it seems to be generally admitted, that neither
the epidermis nor the cutis are  the  proper seat of co-
lour, but that this  depends upon something which  is
situated between them.   In the Negro  it is  black,  in
the Chinese it is yellow, in  the  aboriginal American  of
a copper colour, while in the  European it  possesses
different shades of red  and  olive,  more  or  less ap-
proaching  to whiteness/f  These different shades  of
the  skin afford a presumption in  favour of the exist-
ence of the corpus mueosum, or  of something corres-
ponding to  it: neither the  epidermis nor the cutis  of
the  Negro,  when separately examined, are black ; nor
does it appear that there is any difference in the colour
of the blood, so that their  complexion would seem ne-
cessarily to depend  upon something  not contained  in
the  vessels, and  distinct from  the other  integuments.
Besides the general question respecting the existence of
the  corpus mueosum,  it  has been asked,  what is the
exact nature of the colouring matter? is it inherent in

   *  Anat. p. 242; see also Lawrence's Lect. p. 276; and Beclard,
p. 272.
   t For a perspicuous account of the opinions of the modern ana-
tomists respecting this organ, I may refer to a valuable paper in
the Ed  Med. Journ. v. 18, p. 247.
   X Blumenbach, de Gen. Hum. Var.  Physiol. § 181. 
64               Effect of Solar Light.
the substance, or is it something superadded to it ?  It
has been asserted that the  colouring matter  may be
dissolved or suspended in water, and it has been com-
pared to the  pigmentum  nigrum  of  the eye,  or,  by
others, to the oily  matter  which gives the peculiar  co-
lour to the hair; but it is  premature  to  form  conjec-
tures about the nature of  a substance the existence of
which is still doubtful.*
  The dark colour of the  skin in the inhabitants of the
torrid zone  has  been popularly ascribed to the influ-
ence of the sun upon the surface of the body,t but  the
tinge produced on the skin  by  exposure  to   a  bright
light  appears to have no connexion  with the perma-
nent colour of the negro.    The  blackest complexions
are not found  in  the  hottest regions, and there  are
some considerable  tribes,  nearly  under the  equator,
whose skin is whiter than that  of many Europeans.f
Besides,  the  brovvnness   produced by the sun  is  not
transmitted from parents  to  their offspring,  whereas
the children of negroes are  equally black in whatever
climate they are born, and their complexion  is not al-
tered by any  number of  generations; while  we find,
on the contrary,  that after  three or four successive
stages, the original  colour,  whether white or  black, is
almost  entirely obliterated by  the  union  of parents
from different varieties.  It has not  been ascertained
upon what  part of the integuments the sun acts, whe-
ther upon the epidermis,  the corpus  mueosum, or the

  * It would appear to be this part  that is the immediate seat of
the peculiar colour which is produced by  the internal use of nitrate
of silver, as I have observed that where,  in consequence of scars,
the  epidermis  and  cutis adhere together,  the surface has  not
acquired the tinge.  In a patient in Guy's Hospital, who had been
repeatedly scarified, and had the skin blackened by the nitrate, the
marks of the scarificator exhibited the appearance of white lines.
  t  Buffon's Nat. Hist, by Wood,  t. iii. p. 405.
  X  Haller, El. Phys.  12. 1. 14;  Blumenbach's Phys. Elliotson's,
note, p. 112.  Laurence's Leer. p. 291. 
Albinos.
65
 cutis; but it is probably  upon the epidermis, because
 we  are informed that the tan of the skin may be re-
 moved by blisters.
   As connected with the account of the corpus mueo-
 sum, it will be  proper  to  notice a  singular variety,
 which occasionally occurs, where the skin  is entirely
 without colour.   In  the complexion of  the fairest Eu-
 ropean female, there  is  always  a  mixture  of red  or
 brown, but  in  these  individuals, who  from their ap-
 pearance have  obtained the name of albinos, the skin
 is of a dead  pearly  whiteness.  In almost all persons
 there is a correspondence between  the shade of the
 skin and that of the  hair and eyes, and  this is found to
 be the case in the albino, for the hair is perfectly white,
 and the eye  is without that  substance which gives the
 various colours  to the iris.   From the relations of tra-
 vellers, it may be supposed  that albinos are more fre-
 quent in some parts of the world  than  in  others, and
 especially among the  Africans and  Indiana, but they
 are not very uncommon in all the temperate countries
 of Europe.   This peculiarity appears in both the sexes,
 and has a tendency to become hereditary, but its origin
 is entirely unknown.*
   The term  Albino is  derived  from  the  Portuguese,
and was  applied by them to individuals  whom  they
 found on the coast of Africa, that in every respect re-
 semble  the negroes, except in their colour.   The same
 description of persons has been  also found  in  the isth-
 mus of Darien, and in some of the oriental  isles,  and so
 numerously as to have induced some  writers to con-
 ceive that they formed  distinct  tribes ;t but for this
 opinion there appears to have been no foundation.  In

  * It would appear from the  following passage in Pliny that this
 variety was observed among the ancients.  " In  Albania gigni
 quosdam glauca oculorum acie, a oueritie statim canos, qui noctu
 plusquam interdiu cernant."  Nat. Hist.  lib. vii. cap. 2.
  * See Buffon, v. iii. p. 328,344,  and 419
                      9 
66
Cause of this variety.
this part of the world we have sufficient proof that the
albino is an accidental  variety,  although,  as  was re-
marked above, with some tendency to propagate  itself
when it has been once produced.  Besides the white-
ness of the  skin  and  the peculiar appearance of the
iris, which is of a bright rose colour, the eye  is so sen-
sible to light, that  the  individual  is scarcely able to
keep it  open in the sunshine, although in the shade or
the dusk of the evening, the vision seems to be per-
fect.
  Buffon, according to  his  usual  speculative manner,
attributes this peculiarity to an effort of  the  constitu-
tion to assume, what  he calls, the primitive colour of
nature,  which he supposes  was white, and which has
been changed, by various circumstances, into the shades
which it now exhibits.*   Saussure  has  given  us an ac-
curate and interesting account of two albinos that  were
born at  Chamouni,t but it is to  a conjecture  of Blu-
menbach's that we  are indebted for our knowledge of
the cause.  He conceived that the pink colour of the
eye and its delicate sensibility  depend upon the ab-
sence of the pigmentum nigrum, the black  mucous sub-
stance which is  spread over the posterior part of the
organ.   The conjecture of Blumenbach was complete-
ly verified by Buzzi of Milan, who  had an  opportunity
of dissecting the eye of an  albino, and found it  to be
entirely without  the  pigmentum  nigrum,   He  after-
wards examined the skin, and  he found that the corpus
mueosum  was either entirely wanting, or  at least that
it was perfectly white, so as to escape  his observation,
and he naturally attributes the absence of coIoi.t in the
surface  to the state of this  part.  We may therefore
conclude that the same cause  operates  upon  the eye
and the skin, that the redness of the one and the white-
ness of  the other depend upon the same physical de-
fect in their organization, and  that  it is derived  from

  * v. hi. p. 422.     t Voyages  dans les Alpes, § 1037—1043, 
Nerves of the Skin.
67
the parent, although we are entirely  ignorant of what
it is in their constitution or habits which can  give rise
to this peculiar condition  in  their  offspring.  Albinos
have  been born in different climates and countn s, and
under circumstances that have no point of resemblance,
to which we can, with any probability, refer the phe-
nomena.*
   Under the  corpus  mueosum lies the cutis, or true
skin,  a body  of considerable thickness, tough, flexible,
extensible, and  elastic, of a dense  texture,  composed
of a number of small  fibres or plates,  closely interwo-
ven and firmly  united together.  Its external surface
is compact and smooth, while the internal  is more loose
and irregular; it is  connected to the parts below it by
the cellular texture, and it passes  into  this  substance
by  almost insensible degrees.   Besides this, which con-
stitutes the proper basis of the cutis,  or as it has been
termed,  the corium, there is attached to it a very ex-
tensive  system of nerves, blood-vessels,  and absorbents,
which are dispersed over  every part  of  it with  the
greatest minuteness. The sensibility of the skin differs
very  much in its different parts, but in  its general ex-
tent it may be considered as  possessing  the most acute
degree of feeling of any of the structures  of  which the
body  is composed ;  and it  is accordingly   observed in
surgical operations,  that the  most severe  pain is expe-
rienced during the division of the  skin.   Its external
surface,  when  examined  by  a microscope, is found to
be  rendered unequal by little eminences or projections.
These, which  have obtained the name  of papillae, are
supposed to contain each  of them the small  branch of
a nerve,  of which they constitute  the ultimate  ramifi-
cations,  and seem to be the immediate  seat of the  or-
gan of touch, as well  as of all the other  sensations

  * Brewster's Enc.  Art. Albino; Nich. Journ. v. xix. p. 81 ; Law-
rence's Lect. p. 281, et seq.  For some inter tiling observations on
white varieties of animals, see Hunter on the Anim. QEcon. p. 243,
et seq. 
68
Minute texture.
  which reside in the surface of the body.   They are the
  most easily detected, and are supposed to be the most
  numerous, in those organs which have the most * xqui-
  site sensibility, whether it  be that  of touch  general-
  ly, as in the points  of  the fingers, or in other organs,
  where  there exists  some sensation of a more specific
  kind.   The blood-vessf Is,  with which  the  skin  is so
  plentifully furnished, ramify  in  all directions over its
  surface, forming  innumerable  plexuses, and probably
  producing that appearance which Malpighi mistook for
 a  reticula"ted  membrane.  These  vessels render the
 skin one of the most vital parts of the body, subject to
 a variety  of diseases,  and  intimately connected with
 various  functions, especially with those of animal tem-
 perature, secretion, and absorption.
    With  respect  to the minute texture  of the skin,
 Ha. er describes it  as  being  the  same with  that of
 men branes  generally;   he says  it  is  composed  of
 threads  and plates, which are  short, interwoven,  and
 closely  adhering  together,  the external part  being
 more dense, and the interior gradually passing into the
 cellular  texture.*   The account which Bichat gives of
 it is essentially the same,  except that he conceives it
 to  be composed entirely  of threads  or fibres,  which
 are interwoven  together in all directions, leaving spaces
 between them of various forms and  sizes.t  This struc-
 ture may be easily detected  by  maceration  in  water,
 when the tissue of fibres may be  seen, with the inter-
 stices or areolae, through which the hairs, vessels, and
 nerves probably pass, and by which they are support-
 ed.   Tne^y do not seem,  however,  to pierce through
 the skin  in a straight direction, but  to pursue a  ind-
ing course, so that it is very difficult to perceive the
actual pores through  which  they  have  proceeded.J
The srnail cells  or cavities under the skin, formed by

  * El. Phys. 12. 1.2.        t Anat. Gen. t. ii. p. 658, et seq.
                X Gordon's Anat.  p. 232. 
PapUlae.
69
the membranous plates or bands which connect it with
the parts below, are generally filled with fat, and there
are also connected with certain  parts of  the skin,  a
number of sebaceous glands, which secrete an oily fluid,
that is  probably of a  specific  nature different from
the fat.
  The properties of the cutis must be considered under
two points of view ; those which are  attached to it as
composed of a membranous basis, which gives  the skin
its  general form and  consistence ; and  those which
belong to the system  of  nerves and  vessels* that are
connected  with this hasis.  The properties of this basis
are probably the same  with those of the other kinds of
membranous matter, and are altogether of a mechanical
nature ;  it  possesses cohesion,  flexibility, extensibility,
and  elasticity  in an eminent degree.  In  addition to
these,  some  writers*have ascribed to it contractility,
and what they have called tonicity, but I conceive that
this  has been  done without sufficient foundation, and
that the facts which have been adduced,  are either of
a very dubious nature, or are  more properly referred
to the effects of elasticity.
  We conclude  partly from analogy and partly from
observation,  that the papillae  contain the ultimate ter-
minations of the  nerves, and are the immediate seat of
the sensation which resides in the skin.  In all parts
of the body it is found that the sensibility of the nerves
resides principally, if not entirely, in their extremities,
where they are either divided into extremely minute
filaments,  or spread out into  a  thin  expansion.   In
what degree the microscopical observations that have
been made upon the cutaneous nerves enable us to trace
them irito the papillae  is perhaps a little doubtful; but
so far as they can be depended upon, they  lead to the
opinion, that this is their ultimate destination.   Besides
the nervous filament, the papillae are supposed to con-
tain, each  of them, a  minute  branch of an artery and
a corresponding vein, together with an exhalent and an 
70
Chemical Composition of the  Cutis.
 absorbent; but the  existence of these latter vessels
 appears  to  be derived rather  from conjecture than
 from actual observation.   It is  however certain that
 the skin is the seat  of an  extensive system  of exhala-
 tion and  absorption, although it may be very difficult
 to  determine the actual termination  of  the  vessels, or
 the exact apparatus by which these  functions are per-
 formed.  With respect to the properties of the  cutis,
 considered  in  its  most extensive relations,  we  may
 therefore conclude that, in addition to the mechanical
 qualities  mentioned  above, it possesses those  imme-
 diately  dependant upon nerves and  blood-vessels, but
 that  it is without  contractility, which is  exclusively
 attached  to the muscular fibre.
   Although  the chemical composition of the cutis has
 been  much  attended to by the  modern experimental-
 ists, our  knowledge concerning  it is still  imperfect.
 The best English  systematic writers, as  Aikin, Brande,
 Henry, Murray, Thomson, and Ure, describe it as con-
 sisting chiefly of jelly, and the same opinion appears to
 be  generally adopted  by the French chemists.   Mr.
 Hatchett, whose researches on these subjects are pecu-
 liarly valuable, also regards the  skin  as being princi-
 pally  composed of a  kind of jelly, although  of a more
 dense consistence and less soluble nature than ordinary.
 Seguin,  who  has paid particular attention to the chemi-
 cal composition of  the skin, in  connexion  with  the
 process of tanning, enters  more  minutely into the sub-
ject, and supposes that it consists of  two parts, which
 differ in  their chemical, as well as in  their  physical
 properties: a texture of interlacing fibres, which form
 its  basis; and  a semifluid  matter  mechanically inter-
posed between them.   The fibrous part he  considers
 to be nearly similar  to the muscular fibre,  and to be
formed  of an oxidated jelly, and the semifluid matter
 to be  of a mucous or gelatinous nature.*  The idea of

       * Fourcroy's System by Nicholson, v. ix. p. 353. 
Nails* $c.                    71
the  fibre  consisting of oxidated jelly appears to be
quite hypothetical, and as far as  we have  any light
thrown upon the subject by experiment,  I  should be
led to the opposite conclusion, that the jelly is more
oxidated than the fibrous part  of the skin.   Upon  the
whole it is probable that the fibrous  part of the skin,
which constitutes its proper substance or basis, is com-
posed of albumen, like the other membranous bodies,
and  that it has  intermixed with it a quantity of matter,
of a different chemical nature, which we may suppose
to be a compound of jelly and  mucus.
   There is a class of bodies connected with the exter-
nal surface of almost  all animals, which, although very
various in their shape  and appearance,  are analogous
to each other in their origin and their chemical com-
position.   They may  be divided into two varieties, the
first consisting  of  nails, claws, hoofs, scales,  &c.;  the
second of hairs, bristles, wool, quills, and feathers. The
first may be considered as weapons of defence or pro-
tection ; they are either productions of the  skin, or at
least they are so intimately connected with it, that  it is
often difficult to detect the evact  line of demarkation
between  them.   They  are  generally considered  as
more immediately attached to  the  epidermis ; and it  is
observed, that, in some  instances, they occupy the place
of this body, lying directly upon the cutis, and not hav-
ing any thing exterior to  them.*   We may frequently
 {jerceive  in  this class  of  bodies a kind  of fibrous or
 aminated texture,  although this entirely disappears in

  * The nails in  particular are described by anatomists as being
actually a production of the  epidermis of the finger; and in proof
of this it is stated,  that by maceration, the nail may be removed
along with the  epidermis.   Haller, El. Phys  12.  1. 15; Winslow,
sect.  vii. 192 ;  Albinus, Acad.  An.  lib. ii. c. 15.  But these two
bodies differ so  much, both in their  structure and in the manner
in which they are connected with the contiguous parts, that I con-
ceive it would be more proper to say, that the nail occupies the
place of the epidermis, and that they adhere firmly together at
their junction, than that they constitute the same organ. 
72
Hair.
 those  that are  the most dense,  when they become
 nearly homogeneous.  They are chiefly composed of
 albumen, with different proportions of jelly and mucus.
    Hair and feathers differ materially from the bodies
 just described, both  in their  origin and their structure ;
 they proceed from  a  kind of bulb  or root,  which is
 situated  below the cutis, through which they  pass, and
 project beyond its external surface.   They consist es-
 sentially oT  an external  tube  and  an internal  pulp.
 In hair the tube  is very delicate, and is entirely  filled
 with the pulp;  in the  quili the  tube is firmer, and the
 internal  part is proportionably much  smaller  in quan-
 tity.   Although  hair seems  so smooth to  the touch,
 we are informed  by  Bichat,* that it actually  possesses
 an imbricated or bristled texture,  the  processes all
 pointing in one direction, from the root to the tip, ana-
 logous  to the feather  part of the quill, and  that it is
 upon this structure that the operation of felting  depends,
 in  which the hairs are mechanically entangled together,
 and retained in this  state  by the inequalities on  their
 surface.f   Next  to  the bones,  hair is said to be the
 most indestructible  of the constituents of the body;
 and there are accounts of  its having been found in old
 tombs,  after all the soft parts had entirely disappeared.
 The hair of different individuals differs considerably in

  * Anat. Gen. t. iv. p. 787.
  t There is, however,  reason to doubt the existence of  these
 bristles,  which, it appears, have never been detected by the most
 powerful microscope; see  Leeuwenhoek's figure in Phil. Trans.
 No. 140; Fontana on Poisons, tab. i. fig.  1 ; and  the  plates in
 Hooke's  Micographia, pi. iii. fig. 2; also Young's Nat.  Phil. v. ii.
 p. 190.   Dr. Fleming, Phil,  of Zool. v. i p. 88.; and the author of
 the  art. " Anatomy," in Dr.  Brewster's Enc. v. i. p. 842  ; describe
 the  hairs as being conical, tapering from the root to the tip.   Dr.
Gordon, Anatomy, p. 444, conceives them to be solid, and the same
idea was maintained  by  Hooke.   The different  opinions which
microscopical observers have held on this point, which it might be
supposed could have been so easily decided, afford a useful  illus-
tration of the degree of  confidence which we ought to place in
 -nch observations. 
Vauquelin's analysis.
73
its thickness, being, as it is  said, from ^ to j^ of an
inch in diameter; and it is no less variable in its other
physical properties, some kinds  being much more dense
and elastic than others, a circumstance which, according
to Mr. Hatchett, depends upon the proportion of jelly
which it contains.
   We  are indebted to  Vauquelin  for an  elaborate
analysis of hair, from which we learn, that it  consists
principally of an animal matter, united to a portion of
oil,  which  seems to contribute to  its flexibility  and
cohesion.  Besides  this  there is another substance of
an oily nature, from which the specific colour of  the
hair is derived, and there  are  also small portions of
iron, manganese,  sulphur, and  the phosphate and car-
bonate of lime.*   The animal matter, which constitutes
nearly the whole bulk  of  the  hair,  is  conceived   by
Vauquelin to be a species of mucus ; but Mr. Hatchett
has more correctly designated it as  being chiefly albu-
men, united to  a small  quantity  of jelly.   Vauquelin
found that the colouring matter  of hair is destroyed  by
acids ; and suggests that when it has suddenly changed
its colour and  become  white,  in consequence of  any
great  mental agitation, it is owing to the production of
an acid in the  system ; but this idea seems very hypo-
thetical, and I  conceive it more  probable that the effect
depends upon the sudden stagnation of the vessels which
secrete the colouring matter, while the absorbents con-
tinue  to act and remove  that  which already exists/f

  * Ann. Chim. t. Iviii. p. 41.
  t I have suggested an  explanation of the fact upon the supposi-
tion that it is an actual occurrence ; but although every  one must
have heard of numerous instances of the hair becoming suddenly
grey, I do not find any cases related where it happened under the
immediate observation of the narrator; and when we reflect upon
the manner in which the hair grows, by protrusion from the bulb,
it is certainly difficult to  conceive how, when once grown, its phy-
sical  properties can be  changed.  The existence of the disease
called Plica Polonica, which might seem an analogous circumstance,
is now generally disbelieved.  Among the  older writers we meet
                  10 
74
Properties.
As the  colour  of the  hair seems  to depend  upon a
peculiar kind of oil, and as there is often a correspon-
dence between  the colour of the hair and the skin, it
has been supposed that  the colouring  matter of the
corpus  mueosum must, in like manner, be of an oily
nature;  the conjecture is not without plausibility, but
it  has not been confirmed  by any direct facts or experi-
ments.
   In their natural  state all these  bodies are without
sensation, and  they possess no  visible blood-vessels;
but under certain circumstances, they are subject  to a
species  of inflammation, when vessels may be detected,
at least in some  of them, and  they become  acutely
sensitive.  The painful sensations  in  this  case ap-
pear  to proceed,  not  from any nerves that are dis-
tributed to the  organs   themselves,   but   from the
increased bulk  of  the  part, as produced by the state
of inflammation  pressing  upon and  irritating  some
contiguous nerves,  in  the same  manner as in the in-
flammation of the ligaments and  tendons.   An obvious
use of hair, in  the inferior  animals, is to protect the
body from external cold, but except on the head, this
cannot be considered as applying to  the human spe-
cies, nor can we  easily conceive what  is its object  in
our ceconomy; yet it  is  contrary to our ideas of the
nature of things to suppose that what is so constantly
found to exist should  not  be formed for some useful
purpose.

with narratives, apparently well authenticated, where the  hair is
said to have continued to grow after death, and even to attain an
extraordinary length, but, upon whatever evidence they may appear
to  rest, we may safely conclude that there is some fallacy or inac-
curacy in the statement. 
Of Bone.
75
                    CHAPTER II.


                       €>t JUonr.

    In treating of bones I  shall first give an account of
  their external form, their internal structure, and  their
  physical  properties; afterwards  we shall  examine
  their chemical composition; in the third place I  shall
  inquire  into the mode of their formation; and  shall
  conclude with some remarks upon the nature of  their
  connexion with  the other  parts of  the living system.

            § 1.  Form and  Structure of Bone.

    With  the general form  and appearance  of bones
  every one is  sufficiently familiar;  they are hard and
  inflexible  bodies,  without contractility or sensibility,
  very little subject tb decay, and are perhaps the  only
  substances to which the  term solids strictly  applies.
  They serve as a defence and support to the soft parts,
.  either affording them a case, in which they are  lodged
  and protected from injury, as   in  the instance  of the
  brain and lungs; or as pillars to which the more flexi-
  ble and delicate organs may be attached and  kept in
  their relative position, as particularly takes  place  with
  respect  to  the muscles.  The bones are also fixed
  points against which the  muscles  re-act; when  they
  commence their contractions,  they form a system of
  cylindrical levers, by  which all the movements  of the
  body are effected; and they likewise very essentially
  contribute to these movements, by the share  which
  they have in  the  formation of the joints;  so that, in
  conjunction with the muscles, they  constitute the prin-
  cipal organs of the important  function of locomotion.
  In man and the higher orders of animals the bones are 
76"         Description of Bone.—Arrangement.

generally speaking  in  the  interior  of the body; and
even when they approach towards the surface, are al-
ways covered by muscles  or membranes; but  in the
Crustacea, the testaceous  mollusca,  and  in certain in-
sects,  the  bones  compose  an external case  within
which  all the soft parts are contained.
  The larger  bones are nearly uniform in  different
individuals,  but there is some  irregularity among the
smaller ones, so that the total number of bones in the
skeleton is not always the  same ; in general, however,
they amount to about 260,* exhibiting every variety of
figure  and size, according to the structure and uses  of
the particular parts in which  they are  found.   They
may be arranged  into  three classes—the long  round
bones,  the broad flat  ones,  and the short bones ap-
proaching more or less to the square form ; to the first
class belong the bones  of  the upper and lower extre-
mities, to the second class  those of the  skull, and  to
the third the vertebrae.  These three kinds of bones,
as we  shall afterwards find, differ not  merely in their
external shape, which may  be conceived to be an inci-
dental  circumstance and one of little  importance, but
likewise in  the  more essential points of the  mode  of
their growth and  their mechanical structure.   They
are also distinguished by the uses which  they serve  in
the animal  ceconomy.  The long bones are more imme-
diately adapted for  the purposes  of  motion, either
enabling us to shift  our position from place to  place,
constituting what is termed locomotion,  or to  act upon
other bodies that are contiguous to us, as is especially
the case with the hands and arms;  the  flat bones ob-
viously serve for  the  protection  of  the soft  parts;
while  the  third class of bones are usually  found  in
those organs, where  it was necessary to unite in the
same part a considerable degree of  strength with the
capacity for free motion.

  * Soemmering, Corp. Hum. Fab. § 12.  Boyer, Anatomie, t. i. p.
12. Monro's Outlines, v. i. p. 12. 
    Mechanism of the Extremities:—Upper and Lower.  77

   It would be foreign to  the purpose of this work to
enter upon a description of the forms or  uses of the
individual bones, but it  may be proper to make a  few
observations upon the beautiful mechanism  of this part
of the animal fabric, and to show how admirably each
of its individual  organs is  adapted to its particular use.
For this purpose we may take the  example of the up-
per and lower extremities.   In the  human  subject the
arms are  obviously intended, not for support, but for
acting upon contiguous bodies.  They are therefore so
attached to the  trunk as to be easily applied to them
in all directions, the upper part admitting of free  mo-
tion,  and  at  the same  time  possessing  considerable
strength, while the extremity of the limb is composed
of a great number of smaller bones, that have less mo-
tion upon  those  immediately connected with them, yet
the whole  assemblage constituting an apparatus which
is capable of executing all the various movements  that
are necessary for the purposes of life, with a degree of
precision and velocity that would be almost inconceiva-
ble, were  we not &o familiar with its operations.   The
arm is so placed as to be applied the most easily to the
objects  that  are before  us  and nearly on the same
level; the joints of the elbow  and  wrist are obviously
fitted for  the same purpose ;  while  the  structure of
the hand and fingers points them out as the organs of
what has been called prehension, and as being singular-
ly adapted for examining  the texture and figure of the
bodies that are within  our reach.
   The lower  extremities  are equally  fitted  for  their
specific object,—the support  of  the body  and its va-
rious progressive motions.   They are strong pillars so
placed as  to bear its weight in the  most advantageous
manner; the foot is so adjusted to  the  leg as to form
a firm basis, while  its  smaller parts possess that de-
gree of motion upon each other, which assists in the
changes of position, without admitting of that variety
of complicated actions that are observed  in the hand, 
78
Articulations.
 which, in the foot, would have been not  only  useless
 but even injurious, as necessarily diminishing the  sta-
 bility of the body.*   Without  going into  a more  mi-
 nute detail, it  may be asserted, that if a skeleton  was
 to  be  found of  an anknown animal, with extremities
 formed like those of man, we  should be at no  loss to
 decide concerning its general habits ; that it was essen-
 tially a biped,  that its body was  intended  to  be kept
 in the erect position, that it was neither a flying  nor
 an  aquatic animal, but that  its  natural  abode was  the
 surface of the earth.   Nothing  therefore can  be more
 unfounded than the speculations of those metaphysical
 physiologists, on the one hand,  who,  for the purpose of
 assimilating the human form and  functions to those of
 the monkey, have conceived that man was naturally  a
 quadruped, nor of those, on  the contrary, who consider
 the latter  animals  as bipeds.  Technically speaking,
 they are  quadrumanous,t their extremities all possess-
 ing the characters which  point  them out as instruments
 of prehension.                               ,
  The  form and structure of the articulations  are
 among the most interesting parts of  the animal cecono-
 my.  According to the language  of anatomists, every
 part where two bones are  connected  together is de-
 nominated an articulation, whether they admit of  any
 degree of motion upon each other, or are  firmly fixed
 together ;J but I shall only notice in this  place those
 articulations which are moveable, where the bones are
united  by ligaments, or other membranous  bodies of  a
 flexible nature, so as to be capable of changing their

  *  Cuvier, Lemons, t. i. p. 473, &.c.  Bichat, Anat. Descript. t. i.
 p. 284, et seq.  Blumenbach,  de  Gen. Hum. Var.  § 5, 10.   Mr.
 Abernetby's third  Physiological Lecture contains many interesting
 observations on the bones and joints.
  t  Buffon, v. x. p. 15.  Cuvier, Tabl. El. p. 94.
  JSabatier, Anat. t. i. p. 20.   Boyer, Anat. t. i. p. 55.  Bichat.
 Anat. Gen. t. ii. p. 174. 
Joints.                     79
direction or relative position.   The moveable articula-
tions present a great variety of forms, which have re-
ceived appropriate technical names, but  they may  be
generally referred  to two principal classes,—the ball
and socket, and the  hinge.  In the  ball  and socket
joint the moveable body is furnished with a round end,
which plays  in a  corresponding hollow  in the fixed
bone;  while in the  hinge both are furnished with pro-
cesses and depressions, which are mutually adapted to
each other.   The hip-joint is an example of the first,
and the  elbow of the second  species of articulation ;
it is obvious that the first admits of a rotatory motion
in all directions, while the second  is capable  of beino*
moved in two directions only.
  Although the general form  of the  articulation may-
be observed in the  solid  body of the  bone itself,  yet
in most cases  cartilage materially contributes to the ac-
curate completion of these parts, and the whole extent
of the articulating surface is always covered  with  this
body.   Many obvious advantages arise from  this con-
struction.   The  smoothness of the cartilage, as well
as its elastic nature, admits of a more easy  motion than
could have existed if the two hard substances had been
in immediate  contact, while,  at the  same time,  the
parts are less liable to injury  from violent concussion,
than if they had  possessed a more rigid  texture.   In
order to facilitate motion, by diminishing  friction,  the
joints are enclosed in a membranous bag, filled  with a
dense lubricating fluid, called synovia,  which  is always
interposed  between the moveable  extremities.  To
complete the  mechanism of  these  parts,  they are pro-
vided  with a suitable  apparatus of ligaments,  which
serve to keep the bones in their relative situations,  and
to regulate the motions  of the joints,  so as to  prevent
their displacement,  except under circumstances  of ex-
traordinary violence.  To enter into a  description of
the ligaments, or indeed of any of  the individual joints
would  be to encroach upon the province of the anato- 
80          Texture of the membranous part.

mist, I shall only further observe on this subject, that
in no part of the body is  the adaptation of means to
ends more apparent ■ than in  the  construction  of  the
joints and the apparatus connected with them.*
   The mechanical  structure of bone formed a part of
the investigations of Malpighi, and he is considered as
having been the first who announced that its basis con-
sists of an animal matter, the texture  of which resem-
bles that of the cellular substance/I"  The experiments
of Duhamel proved, that the animal matter,  under  cer-
tain circumstances, assumed a laminated appearance ;J
but we  ac# indebted to Herissant for  the  important
fact, that bone contains an earthy matter, and that
many of its specific properties depend upon  this ingre-
dient.   He  distinctly states  that bone is   essentially
composed of two substances,—the one a cartilaginous
basis or  parenchyma, which gives the general form to
the part; the other a peculiar earthy matter, which is
deposited in the cartilaginous basis, and is the  cause of its
hardness.§ This may be demonstrated by digesting bone
in diluted muriatic acid, so as to dissolve the earthy mat-
ter without acting upon the membrane, when we  pro-
cure a substance,  retaining its former bulk  and shape,
but converted into  a soft, flexible, and elastic body. In
this process we have removed the  earth, and left the
membrane, and by burning the  bone we may reverse
the operation, for we may suffer all the animal matter
to be consumed, while the earth  is left untouched, pre-
serving, in a great measure, its former texture.
   The general  opinion among modern  anatomists re-
specting the structure of bone, and the manner in which

  * An interesting example of this kind has been lately pointed out
by Mr. Earle, in the structure of the spine in certain  birds.  Phil.
Trans, for 1822, p  576.
  tAnat  Plant p. 19.
  + Mem. Acad, for the years 1739, 1741, 1742,  1743, passim.
  §Mcm. Acad, for 1758, p. 322. 
BichaVs Opinion.
81
its membranous part is arranged, is, that like the other
soft solids, it is essentially composed  of fibrous laminae
or plates, which  are so connected together, as to form
by their intersection a series of cells, analogous to those
of the cellular texture, in which the earth is deposited.
Gagliardi conceived that  the plates were held together
by small processes, like nails, the form of which he mi-
nutely describes ;*  but this  has not been confirmed by
subsequent  observations, and seems to have  been a
mere fanciful  conjecture.  Bichat has even denied the
existence of the  laminated structure of  bone,  and has
endeavoured to show that all the facts and experiments
which seem to demonstrate  its presence are fallacious,
and depend,  either upon the peculiar   mode in which
the bone has been  treated   by  the operator,  or upon
some other cause, which  induces the laminated appear-
ance, although the  laminae  did not previously exist.t
To a certain extent the opinion of Bichat may be cor-
rect.  By a kind of loose analogy, which is so often in-
troduced into all  departments of science, the substance
of bone  has been described  as consisting of regular con-
centric rings, like  those that  compose  the trunks of
trees; an analogy that was  probably  derived  from the
hypothesis  of  Duhamel  respecting the formation of
bone, which will  be presently noticed.   These concen-
tric layers certainly do not exist,;}; but I think it equal-

  * Anat. Ossium, passim, and  fig.  2.  This treatise would appear
to exhibit one of those remarkable cases of self-deception, which
are occasionally met with, even in the palpable science of anatomy.
Probably in the same light  we must regard the account given by
Havers of the longitudinal and transverse pores; see his Ostologia,
§35—37.  Havers's description is, however, partly sanctioned by
the authority of the elder Monro. Anatomy  of the  Bones and
Nerves, p. 13.
  t Anat. Gen. t. ii. p. 155, et seq.   Cheselden says, " Nor are the
parts of bones disposed into visible lamellae, stratum super stratum,
as many have painted."  Osteographia, Introd.
  J The mechanical structure  of the membranous part of bone has
been elaborately developed by Scarpa, who  has detailed a series
                  II 
82
Compact and Cellular Parts.
\y certain that the  membrane of bone is composed of
plates, very similar in their general form and  disposi-
tion to  those of the cellular  texture, and it is probable
that the earthy matter is inserted between these plates,
and thus is  likewise disposed to assume the laminated
structure.   The proof  of this structure will  appear
when we come to consider the  internal  conformation
of bone, and the appearances  which it  exhibits when
partially decomposed.*
   When a bone is divided  longitudinally,  so as to dis-
close its internal  structure,  we  observe  its different
parts to exhibit a variety of  appearances,  especially
with respect to  the greater or less  compactness of its
composition.   These varieties  have been reduced  to
two,—the hard or compact, and the alveolar or spongy.
Generally speaking,  there is no  bone which does not
exhibit both of these textures, the compact forming its
external, and  the  spongy  its internal part.  The long
bones consist of a  hollow cylinder of compact matter,
including a quantity  of  the spongy substance ; but the
proportion of  the  two varies  much in  the different
parts of the same bone.   The  shank  or body of the
bone consists  principally of the compact with but little
of the cellular matter, while the extremities or  heads
of these bones are principally composed of the cellular

of accurate observations on it in its various states of growth and
disease, as well as by subjecting it to the  action of chemical re-
agents.   He very satisfactorily refutes the idea of the membranous
part of bone being composed of a series of regular concentric la-
minae.  See his essay De Penit. Oss Struct, p. 16, et alibi.
  * As we may presume that the earthy part of the bone is mould-
ed into its appropriate form by the membrane into which it is de-
posited, we may judge of the structure of the latter by that of the
former, which from its firmer consistence it is more easy to ascer-
tain.  Now whether we examine the bone during its formation in
the foetal state, or after it has had its membrane destroyed by the
action of fire, we find the earth to assume the appearance of fibres,
which, when the  bone is perfected, have a  tendency to a laminated
arrangement. 
Uses of each.                  80
matter with only a thin crust of the compact substance.
It has been asserted, although I  do not find that the
experiment has been  accurately made, that equal cy-
linders of the same bone, taken from different parts of
their length, contain  the same absolute quantity of so-
lid fibres, but differently disposed.   The flat bones ge-
nerally consist of an external covering of the hard sub-
stance on each of their surfaces, with a layer of the
spongy matter interposed between them;  while, in the
short bones, the disposition and proportion of the two
kinds of  texture is more  irregular.   In the large bones
of the extremities, where the  structure is seen  to the
most advantage, the  compact substance is found to be
a completely solid body  scarcely exhibiting any visible
arrangement, either  fibrous or laminated; but, as we
proceed  towards the  inner part, we find the substance
to be less and less dense, until, at length, it becomes
completely cellular,forming what have been termed the
cancelli.   In the centre  of the bone there is  scarcely
any  of the  spongy matter, and a considerable hollow
space is  left, which is filled up with a  series  of  mem-
branous  cells, in which  the  marrow is lodged :  some
writers have called this  the  reticulated part of the
bone.
   I  have been thus particular in  describing the struc-
ture of the long bones in order to show how admirably
the arrangement of their parts is  adapted to the pur-
poses for which they  are destined.  Their extremities
are  the  fixed points  from  which the  muscles  re-act,
and  where greater space  was required for the inser-
tion  of the tendons ; their diameter  is, on this account,
considerably increased, and their osseous matter is dis-
posed in nearly an equal degree  through their  whole
substance; while, in the middle of  the bone, which is
more exposed to external violence, and where nothing
was  wanting but mere strength, the bony plates  are all
consolidated together  into a compact dense ring, leaving
the centre nearly hollow.   This form of the part, as 
*4
Texture of Bone fibrous.
consisting of a  quantity of compact matter  disposed
round  a central  cavity, has  the  important  effect  ox
increasing the strength  of  the bone without adding to
its weight.  The  resistance of a cylindrical body to a
force applied  transversely  may be  mathematically de-
monstrated to be increased in proportion to its diame-
ter,  so  that the  same  number of fibres,  placed as it
were round the  circumference of a circle, produce a
stronger bone than if they  had been all  united in the
centre, and the diameter of it had been proportionably
diminished.*   We accordingly find that   the  hollow
cylindrical  bones are always  placed in those parts of
the body where the power of resisting external force
was  an important object ; but  where, at the same time,
it  was very desirable not to add unnecessarily to their
weight.
   Although the hard external part  of the bone is a
perfectly compact body, in which we can scarcely per-
ceive any trace  of  a  specific  organization, yet there is
reason  to conclude that  it is made up  of fibres and
plates similar to those of the spongy or  cancellated
part, and differing iVo...j  it  principally  in  its greater
degree of condensation.   When  we exa-i^ne  a bone
during the process of ossification,t we find that those
parts which afterwards become the most  completely
solidified  are  of an evident fibrous  texture; and  we
observe the fibres to become  more and more numerous
as the process advances, and  to adhere more  and more
closely together, until, at length, the substance becomes
perfectly compact.  And  when a bone is subjected to
any  operation, by which its substance  is decomposed,
and  its texture destroyed,  as  by calcination,  by mace*
ration  in diluted  acids, or  by long exposure  to  the
atmosphere, it always  exhibits a laminated  or  fibrous

   *  Monro, Anatomy of the Bones and Nerves, p. 21; Porterfield,
in Ed. Med. Essays, v. i. p.  112.
   t  Albinus, Icon.  Oss. Foetus, tab. 1, fig. 1, 2. 
Chemical Composition.               85
appearance,  and shows a  tendency  to  separate into
longitudinal portions.  Besides, the transition from the
compact to tiie  spongy part of the  bone is not  marked
by any decided  limits, but thej pass into  each other by
insensible degrees, so as to  show that there is no essen-
tial difference between them.
   The  direction of the fibres is found to vary, in the
three  kinds  of bones,  according  to their  respective
forms;  in the  round  cylindrical  bones  they are  long,
and  lie parallel to each other,—in  the  flat bones they
generally  exhibit a radiated  structure,—while  in the
short bones their direction is more irregular, depending,
in each particular  case, upon  the figure  of the bone to
which they belong.
   In its physical properties, bone is the most simple of
any  of the components of  the body.   Membra-jae, as  I
remarked on a  former occasion, is not possessed of any
properties that are peculiar  to the living system, and
which  do not  belong to  many other substances;  but
bone, when in its most perfect state,  is neither flexible,
extensible, nor  elastic, and, in short, has no mechanical
properties but those which belong to every kind of solid
matter.

           § 2. Chemical Composition of Bone.
   The chemical nature  of bone v/rc ve»*v imperfectly
understood unm aou,  r :*y •*"»*»rs ago.   It had, indeed,
been discovered by Herissant  to uc  <-.     ^.'Und of an
animal and an earthy  substance, but nothing was known
respecting the  exact nature of cither of its ingredients.
Gahn seems to have been  the first  who discovered that
 the earth was  the phosphate of lime;* an earlhj salt,

   *  The claim of Gahn to this discovery, which  was long doubtful,
is, at length,  fnJIy  established  by  Berzelius.  See Progress  of
Animal Chemistry, p. 76.
   The more accurate researches of contemporary chemists, and
 especially of Mr. Hatchett, MM. Fourcroy and Vauquelin, and Prof.
Berzelius, have discovered that the  earth of bone  is less simple 
36
.1 tint men.
which is insoluble in water,  bears a high temperature
without  being decomposed,  so as to give to bone the
property of resisting, in a remarkable degree, most of
the external agents to which it is exposed, and to ren-
der  it the  most durable of any organized  body with
which we are acquainted.   Accordingly the bones  of
animals are found in a  tolerably perfect state after  a
lapse even of many centuries,  and after having been
exposed to all the  revolutions to which the surface of
the  earth is incident.   Indeed, from  the  discoveries
which have  been lately  made  by the modern geologists,
we are induced to believe that bones still remain, which
have existed long before any traditionary or historical
records  of which we are in possession, and when the
earth was peopled  by animals of a different kind from
any  of its  present inhabitants.*
   The nature of the animal  matter of bones was still
longer in being understood, and we are indebted to Mr.
Hatchett for our knowledge  on this subject.   He found
it  to possess all the characters  of condensed albumen,
the substance  which I  have already mentioned as the
basis of membranous matter of all descriptions.  Of
the  different species of these  bodies, it  appears  the
most nearly to resemble  cartilage ;  and, from  the
observations that have  been  made on the original for-
mation of bone, it is reasonable to conclude that it  is
identical with  this  substance.   Besides the solid animal

than  was  previously supposed to  be the case.  Besides the  phos-
phate of lime, which forms nearly 82 per cent, of the weight  of
the earth, it contains,  according to Berzelius, the fluate and the
carbonate of lime  with the phosphates of magnesia and soda.
Thomson's Chem. v. iv. p. 485.   The analysis indicates a consider-
able excess of lime above that necessary to saturate the acids ; and
the same  excess, although in a little different proportion, is indi-
cated by the experiments of Mr.  Dalton ; Manchester iVlem. v. iii.
ser.  2d, p. 5; this, however, as  he observes, may, perhaps, be
owing to a quantity of carbonic acid being driven off by the calci-
nation.
   *  Clift in Phil. Trans, for 1823, p. 84. 
Oil and Marrow.
87
matter, bones contain a quantity of jelly, which may be
extracted from them by boiling,* and we find that  this
jelly is much more abundant in the bones of young than
of old animals.  Before the experiments of JVIr. Hatch-
ett,  the same erroneous  opinion  was  entertained re-
specting the animal matter  of bones as of  membrane,
that it consists of jelly, an opinion which is maintained
even by Bichatt and Cuvier,J as well as by other emi-
nent  physiologists,  whose  works  are  of recent date.
Perhaps this may be the case with some of the bones
of very young animals; but, with respect  to the per-
fect bones  of the  adult, it is certain  that, unless  the
water be applied under a degree  of compression so as
to raise its temperature  much  above the  ordinary
boiling  point, as takes place  in Papin's digester, a small
portion only of the  bone  will be dissolved.
   Besides the marrow which occupies the central cavi-
ties  of some of  the larger bones, the pores  and can-
celli of the  bone itself contain a  kind of  oily matter,
which has been thought to differ from marrow merely
in possessing a greater degree of fluidity.§   The mar-
row is said to be lodged in a series of membranous cells
which, like those in which the fat is deposited, do not
communicate with each other;  while, from the  obser-
vations that have been lately made by Mr. Howship,
it seems probable that what has been called the oil of
bones is  deposited in  longitudinal  canals  that pass
through the solid substance of the bone through  which
its vessels are transmitted.||

  * Proust in Journ. Phys. v. liii. p. 227 ; Berzelius on  Animal
Chem. p. 78; see also Ann. Phil. v.  xii. p. 106, for the process
employed at Geneva for procuring jelly from  bone ; but, as is re-
marked by the editor, it is the substance alone to which the term
•• gelee" is applied that we are to consider as jelly.
  f Anat. Gen. t. ii. p. 160, et seq.
  | Tab. Elem. p. 32 ;  Legons, t. i. p.  103.
  § Boyer, Anat. t. i. p. 38.
  I| Med. Chir. Trans, v. vii. p. 393, et seq. 
88
Their use.
   Many conjectures have been formed concerning the
use of the marrow and  the  oil  of  bones,  but they  all
seem to  be  unsatisfactory.   The  general opinion of
physiologists about the time of Boerhaave and Haller
was, that the oil served to render the bones less brittle,
and  that the  marrow was deposited  in  the centre to
be carried   into the  body   of the  bone,  and  diffused
through  its substance, as it  was required for this pur-
pose.  Even the most approved of the moderns, as Sa-
batier and Boyer, seem still to attach some importance
to this hypothesis, for it is  stated  by them, although,
perhaps, with less confidence  than by their predeces-
sors.*  As to the oil, it does not appear that  it could
have the effect  which has  been assigned  to it under
any circumstances, and  it  is  still less  probable  when
considered  in its actual  relation to  the bones,  because
it appears that the oil which is  found in them, is rather
lodged in separate cavities  than  mixed   up  with the
earthy matter, or diffused through the  substance  of
the bone generally.   But after discarding the  old hy-
pothesis, we have little that  is more satisfactory to
offer in its room ; the only  plausible  conjecture  that I
can form is, that the  marrow and the oil of bones serve
the same purposes  in  the  animal ceconomy with the
other oily secretions ; and, as it was desirable for the
bones to be either hollow, or filled  with a substance
which should not add much to their weight, advantage
was  taken of this circumstance to employ them  as de-
posits or reservoirs for adipose matter.t   With respect
to the use of the fat generally, this will  be treated of
hereafter.
              § 3. Formation of Bone.

  There are few subjects  in  physiology that have  af-
forded more scope for speculation and hypothesis than

  * Sabatier, Anat. t. i. p. 16 ; Boyer, Anat. t. i. p. 40.
  t Mr. Wilson, in* his Lectures on  the Skeleton, entertains the
 *me idea  respecting the use of the marrow, p. 48, et seq. 
Holler's Hypothesis.
89
the origin of bone, or the manner in which the process
of ossification is accomplished.    The  ancients, who
were ignorant of the nature of bone,  could not be ex-
pected to form  any  accurate  notions on this subject,
and  they accordingly satisfied themselves  with saying,
that there was present in  the fluids  an ossific matter
which became  condensed, as  some thought, by the
operation of animal heat,  some by the  evaporation of
its watery parts, or, according  to others, by mere pres-
sure.  But these  opinions, and many  others equally
vague and gratuitous, were  refuted by  the  modern phy-
siologists,  and  particularly  by  Haller  and  Albinus.*
Haller made  a number of minute observations  upon
this  point, which,  although they did  not lead him to
a perfect  knowledge of  the subject, at least enabled
him to avoid  the gross  errors  of his predecessors.
His  opinion was that as the  growth of the body ge-
nerally depends  upon the  arterial blood, so that of
each of its individual organs  is immediately effected
by  an impulse  given to  the vessels  of  the part,  by
which an  additional quantity  of fluid is carried  to it;
and  that,  in consequence, either of some  provision of
the system, or of some  occasional exciting cause of a
more mechanical nature,  the action of particular arte-
ries  is augmented at certain periods  of life so  as to
cause their successive developement.  With respect to
the  bones, his  idea was that  the  osseous particles
being, as  he  styles them, of a gross  nature, the small
arteries  of  the  foetal  bones are not  capable  of  re-
ceiving them.   At a certain period,  however, as the
heart acquires  more  force,  it  propels   its contents
more powerfully, and thus distends  the   vessels, and
enables  them to receive the earthy particles.  But,
after a certain quantity  has  been deposited, and the
bone has  acquired   a certain degree of firmness, its

  * See Acad. Annot. lib. vii. c. 6, for a sketch of the opinions of
the earlier anatomists upon the  nature and formation of bone, as
well as for the author's own views upon the subject.
               12 
90
Remark upon it.
rigidity resists  further distention; and, at length, by
the continued  addition  of  the  osseous  matter, the
whole becomes solidified, and concretes into a perfect
bone.*
  Many objections  present themselves   against  this
hypothesis,  both when it is  considered, in its'general
outline  and  in its detail.   It is altogether of too me-
chanical a  nature,  and  attributes  all thaee changes
to a  mere alteration in the  diameter of the vessels,
which probably depend upon some action immediately
connected with the functions of life.  If we descend to
particulars, we may  ask what became of the osseous
matter  before  the  arteries  of the  future  bone were
sufficiently capacious to receive  it ?  The arteries  of
the bone begin to convey the earthy particles- before
they  are large enough to admit the red particles  of
the blood, so that,  from the very  earliest  period  of
foetal  existence, we  have arteries which  are obviously
larger than those that are sent to the bones when they
begin to  acquire  their earthy matter; why, then, we
may ask, was not this matter  deposited in these larger
arteries'?  and,  in  short, according  to this mechanical
yiew  of the  subject,  what  prevents the whole  body
from becoming ossified, as each separate artery, or sys-
tem of arteries, acquires sufficient magnitude to  admit
the passage  of these gross particles?  On  this,  how-
ever,  as on  many other topics  in physiology, it is ex-
tremely easy to overthrow the  hypotheses  of others,
but very difficult to  substitute more  correct or consis-
tent ones in  their place; and, on the subject now un-
der consideration,  I confess that I am not in  possession
of any adequate means of explaining the difficulty. Un-
der these circumstances, I shall proceed to give a brief
description of the  phenomena that attend  the process of
ossification ;  and, without attempting to reduce them to
a regular theory, I shall offer some remarks upon them,

  * El. Phys. 29. 4. 23, et seq.; Op. Min. t. ii. p. 595, &c. 
Progress of Ossification.
91
and shall endeavour to show how far they can  be re-
conciled with the other operations of the  animal ceco-
nomy, and how far they must be admitted to be inex-
plicable.   And I  must here  remark, that although I
have thought it necessary to be explicit  in my objec-
tions to Haller's  hypothesis  of ossification, yet I am
fully disposed to  allow him  every degree of merit for
the accuracy of his statements; for it is to his treatise
on the formation  of bone* that we are indebted for the
first, as well as some of the* best observations that we
possess upon the  subject.
   When we examine the foetus,  in  the earliest stages
of its existence, as soon as we are able to observe the
rudiments of its future  limbs, and the different  parts
which are destined to compose the skeleton,  we are
able to trace the figures of some of  the  larger bones,
but they-appear  to be composed of a matter which is
perfectly soft or semi-fluid, contained in a delicate mem-
brane.  By degrees  the  parts acquire  more  consist-
ence, and the membrane  becomes  more  dense,  until
they gradually assume  the appearance and exhibit the
properties of cartilage.   This  cartilage,  which is  at
first transparent  and colourless, after some time exhi-
bits opake whitish spots  on different parts of its sur-
face, which,  when examined by  the microscope, are
found to consist of a number of  delicate lines; these
increase in size and in density, and at length red points
are seen to be dispersed  through them, indicating that
the blood-vessels of the  part are sufficiently capacious
to admit the passage of the red globules through them.
From this period, which, according to Blumenbach, is,
in the  human subject, about  the  seventh or eighth
week after conception,!  the earthy matter is copious-
ly deposited in its appropriate  cells; the parts,  which

   * Exper. de Ossium Form, in Oper. Min. t. ii. p.  460, &c.;
 556, &c.
   t Inst. Phys. § 642. 
•92
Howship*s  Observations.
were at first soft and  afterwards elastic, now become
hard and rigid, so that the blood seems to be scarcely
capable of forcing  a passage through its vessels, com-
pressed as  they are by  the  dense matter which accu-
mulates round them in all directions, and either entire-
ly obliterates them, or at least greatly diminishes their
number and capacity.
   From Mr. Howship's  elaborate observations on  the
process of  ossification, which seem to have  been con-
ducted with so much accuracy, it might appear doubt-
ful, whether the first deposition of  phosphate of lime
is not anterior to the formation of the cartilage, for he
informs us that, in the  long bones, the first appearance
of osseous matter is a short  hollow  cylinder, which is
said to exist before any cartilage  can  be distinguished,
and  which  is conjectured to be secreted by  the vessels
of the periosteum.*  Before, however, we  can admit
this  inference, we must decide in what sense the term
cartilage is to be employed;  and  it must be  proved
that the soft matter, in  which this osseous  cylinder is
formed, is not  itself the future cartilage, merely in a
soft  state, united  to  a  large  proportion of water.  At
all events there seems as  much  propriety in assuming
the previous existence  of the cartilage as of the peri-
osteum, which is conceived to act  so  important a part
in  the process, and which does not appear  to be  dis-
tinctly visible at this early period.
  During this deposition of bony matter another very
important operation is  going  forwards.  The cartilage,
which is destined  to become the basis  of  the future
bone, is homogeneous  in its   texture,  and contains no
cavities of any kind, but while the different parts of it
are changed in  their chemical composition its mechani-
cal structure undergoes an equal  alteration.   In pro-
 ortion as  the secretory arteries deposit the proper
 one, the absorbents carry  off  the  cartilage ; but al-

  * Med. Chir. Tr. v. vi. p. 263, et seq.; v. vii. p. 387, et seq.. 
How Organized,
93
  though their action corresponds in point of  time, they
  differ as to  the seat of their operations, the  greater
  quantity of osseous matter being deposited  on the out-
  er surface of the bone,'while the absorption is carried
  on at the centre, so  that when the external  part of the
  bone acquires its proper degree of hardness,  the interior
  is either formed into a complete cavity or into the loose
_ cellular substance that has  been described.  In con-
  templating this very  curious metamorphosis,  the  fol-
  lowing questions, among  many others that might  be
  asked,  present themselves to  us.  What is the origin
  of the  phosphate  of lime, which gives the  bones' their
  solidity ?  Is it received into the system of the mother
  along with her food, or have her organs of  assimilation
  or secretion the power of generating this earthy Salt?
  Supposing the  lime to be received into the circulation,
  what  cause determines it to pass into those particular
  arteries that go to the  bones, and how is it  disposed of
  at other  times, before  and after the period of ossifica-
  tion?  Then  if we  conceive the earthy matter  to be
  present in the blood, and to be conveyed  by the  ves-
  sels to its proper destination, how  is it deposited by
  the arteries?   Is it poured  out from their  extremities,
  is it deposited from  their  sides,  or does it remain
  lodged in them, so  as  in fact to convert  the  arteries
  themselves into the  osseous fibre?   Each  of  these
  opinions  has had  its supporters, and it would  perhaps
  be difficult to  adduce any decisive argument either for
  or against any one  of them; but upon the  whole  it is
  the most agreeable to the general  actions  of  the  ani-
  mal ceconomy to adopt the idea that the phosphate of
  lime is poured out from the extremities of the vessels.
    But although it seems, on many  accounts, the  most
  agreeable to the  laws of the animal ceconomy, to  sup-
  pose  that  the minute arteries pour  out  the earthy
  matter from their extremities, yet there are some cir-
  cumstances respecting the  mechanical mode in  which
  the operation  is effected, which it is not easy to  recon- 
94      Alteration of structure in the Membranes.

cile to this supposition.   We may conceive that from
some  unknown cau^e the  arteries of certain parts of
the cartilage  acquire  a  disposition  to deposit  the
earthy matter which they contain, yet how can these
depositions acquire the  particular  form  which  they
exhibit ?  They do not seem  to  follow the  direction
of the arteries which accompany them in their course,
but they  sometimes assume  the radiated structure,
branching off from a common centre, or at  other times
compose masses of* parallel  lines,  shooting  out  in a
course.contrary to that of the vessels  which are  sup-
posed to carry the  materials for their  formation.   If
we might  be permitted  to indulge a conjecture  upon
the subject, it would seem as if certain portions of the
cartilage acqnired an affinity for the earthy matter, and
that when the deposit  began to be formed, it received
accessions of new matter in consequence of the affinity
between the particles  of the  phosphate of lime  pro-
ducing a species of crystallization.
   And  here  again  a   new series of questions occurs.
What is the nature of  the texture  in which the earth
is deposited ?  The cartilage previously appears with-
out any cavities; are the solid particles then simply
interposed between the particles  of  the membrane  as
it were incidentally? or  is  a  space formed  for their
reception, in consequence of a portion  of the animal
matter  being removed  by the  absorbents precisely  at
the same  time that the  earthy matter is conveyed  to
it?   Is the  original cartilage entirely  removed, and
new animal matter deposited in its place, possessed of
a different arrangement  of its parts? or is there some
chemical  change going  forwards in it, by which the
membrane has  both  its form and  its  composition
changed at the  same time?   To  these questions we
are, I conceive, unable to return  any  satisfactory an-
swers;  yet until they  are solved, it is obviously impos-
sible  to form a perfect theory  of ossification.
   In order to  investigate the subject, and to throw 
Mode of Prosecuting the Inquiry4
95
any real light upon  the nature  of  the effect that is
produced, we must first of all inquire, what is the exact
nature of the animal matter that occupies the place of
the future bone or composes its basis.   Some  physiolo-
gists, as Haller,  Sabatier,  and  Boyer,* have stated
that it  is gelatinous,  while others, as Bichat,t have
called it mucilaginous ; but both these terms,  we may
presume, were  employed  in  a vague sense,  referring
more to the physical properties and consistence of the
substance, than to its chemical  nature, which it  is pro-
bable was never accurately examined, nor indeed was
the knowledge of animal chemistry  sufficiently advanc-
ed to enable the earlier writers  to  obtain any correct
knowledge on this point.  Even Bichat, when he styles
it mucilaginous,  does not appear to have affixed  any
other meaning to the  word, than that of a semi-fluid
substance^ possessed of a certain degree of  tenacity  ;
for the  proofs which he brings in support of his posi-
tion are altogether inadequate.   As  far as we are able
to form an opinion on a point in which we are  entirely
guided  by conjecture, it is more probable that the first
rudiment of the bone is gelatinous  than mucilaginous.
We find that all  the membranous parts of young  ani-
mals contain a considerable  quantity of jelly,  and that
as they advance  in life  the proportion of jelly gradual-
ly diminishes, while  that of  the albumen, which con-
stitutes  the  proper  membrane, is increased.  Besides,
mucilage appeals, in all cases, to be  the  product of
glandular secretion, and we have no proof of the exist-
ence of any organs of this description connected with
the foeta! bones.
   In its second, or what has been  called its cartilagi-
nous state, I am not aware that any  direct experiments
have been performed upon its  chemical nature ; but as

  * Haller, EI.  Pbys. xxix. 4, 23.  Sabatier,  Anat.  t.  i. p. 13;
Boyer, Anat. t. i. p. 40;  see also Gibson in Manch. Mem. v. i. new
series, p. 151.
  t Anat. Gen. t. ii. p. 189. 
^
 9$         Mode of Prosecuting the Inquiry.

 it is then in a condition which admits of more minute
 examination, and  exists  in  much  larger quantity,  we
 are better acquainted with its physical  properties, and
 there  is  reason to suppose that the substance  which
 occupies the situation of  the future bone, is nearly of
 the same chemical nature with the membranous matter
 that afterwards enters into its composition.   Still, how-
 ever, the mechanical disposition of its  parts differs so
 much in the two states, that  it seems  most  probable,
 and is most analogous  to  the usual operations of  the
 system, that the first  cartilage should  be  entirely  re-
 moved, and  that a new deposition of animal matter
 should  take place.   We are  not  able to determine
 precisely what is the  nature of the change  which indu-
 ces the partial opacity of the cartilage  in those  places
 which afterwards  become  the centres of ossification,
 whether it  be merely a greater condensation of  the
 part, or the abstraction of a portion of the water con-
 tained in it, or whether it be the commencement of the
 actual deposition of the osseous matter.
-*■  The next thing that we observe is  the  presence of
 the vessels carrying red blood, a  circumstance  which
 must no doubt depend upon an increased local action;
 but what is the immediate cause of this, or what con-
 nexion it has  with the  previous condition of the carti-
 lage, is altogether unknown.  I have  already pointed
 out  the difficulty of explaining the  manner in  which
 the deposition of the  earthy matter is  brought  about,
 and  indeed enough  has  been said to  prove that   al-
 though we are acquainted  with the different steps of
 the operation, and with the order in which they suc-
 ceed each other, we are scarcely able, in a single case,
 to decide upon their efficient cause, or to point out.  any
 connexion between them.
   In considering the formation of  bone, and especially
 the immediate source whence its component parts  are
 derived,  it may be  proper to notice an hypothesis, 
Effects of Madder on Bone.            97
which for some  time enjoyed a considerable share of
celebrity, and which although at present discarded,
deserves to be mentioned as having led to some impor-
tant  facts  on the  subject.   Duhamel,  an ingenious
French naturalist, had formed an  opinion, that  the suc-
cessive layers or annual  rings of woo£^tvhich are form-
ed in the trunks of trees, are deposited from the inner
bark, or rather that the inner bark of each  year is,
during the following season, converted into the albur-
num, or the external layer  of the proper wood.  This
hypothesis he endeavoured to extend to the bones,  and
for this purpose devised  a set  of experiments, which
were prosecuted with much diligence.   It had been
discovered,*  that when an animal has  had  madder
mixed with  its food, the bones  become  tinged with a
reddish  colour.  He accordingly gave madder  to an
animal for a certain  period, then  omitted it for some
time, and afterwards again  resumed its use, when upon
examining the bones after  this plan had been pursued,
he informs us that they exhibited  alternate rings of a
red  and white colour, corresponding to the times when
the  animal had used the madder  or omitted  it.   His
conclusion was that the  bones are formed of concentric
laminae or rings, which  are deposited from the perios-
teum or investing membrane;  and the  results  of his
experiments, as  he  reported  them, were generally
conceived to afford decisive evidence of the truth of his
hypothesis.   Mr. John Bell shrewdly  remarks, that
when speculators perform  experiments, they generally
find  exactly what they  desired  to find,  and so  it ap-
pears to have  been  with  Duhamel.  We are now as-
sured that the succession of differently coloured rings
which. Duhamel described, could  have no existence, or

  * Haller, El. Phys.  xxix. 4, 26 ; see also Duhamel in Mem,
Acad, for  1739; and Gibson,  in Manchester Mem. vol. i. new
series, p. 146.
13 
98          Ossification  a Case of Secretion.

that if  any thing resembling them  took place, it could
have no connexion  with the periods during which the
madder had been given or withheld.  The hypothesis
was indeed  very satisfactorily controverted by Haller,
who, at the same time, gave the proper explanation of
the phenomenon, supposing that it  depended upon the
affinity which exists between the colouring matter, and
the phosphate  of lime ;t this  opinion Rutherford has
since  confirmed by direct experiment,^ and has correct-
ly referred it to the general principle  by which colour-
ing matters are peculiarly  disposed to unite to earthy
salts, a principle upon which the operation of mordents
in the art of dyeing depends.
   On the  subject  of ossification,  I shall only further
remark, that its  immediate  cause  appears  to  be un-
known, but that,  in its  general  nature, it may be con-
sidered  as  analogous  to those  operations which we
ascribe to the function of secretion, where the arteries
possess the power of either separating particles already
existing in  the  blood, and appropriating  them to some
specific  purpose, or  of forming new combinations, which
may be afterwards  separated and employed in different
ways.  The only circumstance that is peculiar to this
case is, that the secreting process is confined to a limit-
ed period of our existence ;  that it commences without
any assignable cause ; and when it  has  proceeded for
a certain length of  time, and supplied  the wants of the
system,  it ceases in  a way which is equally inexplicable.
When we come hereafter to treat more particularly
upon the growth of the  body,  and the gradual deve-
lopement of its different organs, we shall observe this
adjustment of its physical condition to the circumstances

  * El. Phys. xxix. 4. 33—36.
  t § 26.
  t Blake on the Teeth, p. 138, et seq.  It is not a little remark-
able that  Hunter fell into the error of supposing that the madder
attaches itself to  the animal matter of the bone, and not to its
earthy part.  Home's Lect. on Comp. Anat. p. 64. 
                   Reparation of Bone.                99

 in which it is placed, not only as respects the whole
 system, but in each of its individual  parts; and we shall
 find, with regard to  the  bones in particular, that they
 receive their perfect form, and  complete constitution,
 in the order which is the best adapted  to the situation
 of the animal.  As to the cause which determines these
 effects to be  produced at certain periods of our exist-
 ence, we can say little more than that we find it to  be
 a matter of fact.  It is a part of the general constitu-
 tion of the animal system, that,  at regular times,  cer-
 tain changes should take place without our being able
 to assign any  physical cause for them.   In the present
 case, the final cause is sufficiently obvious; at the com-
 mencement of our existence, softness and flexibility are
 absolutely requisite,  and  hardness would be  injurious,
 while,  as the necessity for resisting external  violence
 gradually arises, the  capacity for resistance is  propor-
 tionabiy produced.
   The power which the constitution possesses of re-
 pairing bones when  accidentally  injured, is, perhaps,
 more wonderful in its operation than that which origi-
 nally produced  them, as  it exhibits, in a more remark-
 able  manner, that mutual adjustment of the different
 corporeal actions, and the adaptation of  it to fortuitous
 circumstances, which distinguishes the animal machine
 from all mechanical  contrivances.   Not  only  do  we
 find that if a bone be completely divided the fractured
 ends are quickly cemented together, and rendered as
 firm as  before the injury; but even, after a considera-
 ble portion of the bone has been removed, a new piece
 is generated to supply the deficiency.
   A similar kind of controversy subsisted, for a long
time, respecting the  reparation of bone as concerning
its original formation.   The  older  writers supposed
that the soft  mucus  or jelly,  which is  effused in the
first instance, was condensed by heat or pressure into  a
hard gluten, which formed the uniting substance.* This
* Boerhaave, Aphor. 343, &c. cum comment. Sweiten, 
100                  How effected.

they called callus, and conceived that it always retained
its membranous  state, and was  never  converted  into
proper bone.   Some  physiologists supposed that  this
callus was immediately produced from effused and co-
agulated blood, and others that it was derived from the
periosteum  of  the old  bone.   It  is  now,  however,
generally understood that the process by which bone is
repaired is very  similar to that by which it is originally
produced;  the arteries  of the  divided bone* throw
out a soft matter,  called lymph, the nature of which
has not been  exactly  ascertained ;t this becomes  gra-
dually converted into cartilage,  or rather, perhaps, is
replaced by it, after being itself previously  absorbed;
the earth of bone is  then deposited  in  this cartilage,
and the cartilage either  removed, or new  moulded,  in
the manner which was described above.  But what  is
the immediate cause  by  which this change is effected,
why the arteries  throw out  this substance, how  it  is
moulded  into its proper form, whence  the supply  of
earth  is derived just  at the  exact period  when it is
required for the  wants of the system, are questions that
have not yet been satisfactorily answered.   The hypo-
theses that have been formed upon the subject have
been, in some cases, the  mere expression of  the fact  in

  * From the experiments of Mr, Wood, it would appear, that the
vessels which are principally  concerned in this process are, in the
first instance,  those  which belong to the internal membrane of the
bone.  Manch. Mem. v. iii.  new series,  p. 275,  et seq.   This
opinion, as well as the other  modern doctrines respecting the
reparation  of bone, allowing for some inaccuracy  in the  terms
employed, necessarily depending upon the imperfect state of che-
mical science, may be found in the writings of Haller; see Op. Min.
t. ii. p. 477, et alibi;  see also Scarpa de Oss. Struct, p. 31.
  t We should be induced by analogy to conclude that the matter
effused, in this case, is coagulated  albumen ; but I  believe  it has
not been made the subject of distinct experiment.   Mr. Dowler's
experiments prove  that fibrine enters into the composition  of the
buffy coat of the blood, and probably of the fluids which are poured
out in the adhesive inflammation  of the  soft parts.  Med. Chir.
Trans, v. xii. p. 86, et seq. 
               Vital Properties of Bone.            10 j

different words; in others, the substitution of the final
for the efficient cause;  or they  have proceeded upon
the assumption of some imaginary agent created by the
fancy of the writer to  meet the  present  emergency.
We  cannot doubt that there is a proper efficient cause
for this, as well as for every other change which occurs
in the system; and that,  were  our knowledge of the
animal ceconomy complete, we should be able to refer
it to the general laws by which the body is directed.
At present, however, our acquaintance with the minute
operations of nature is  extremely limited, and we are
only retarding the  advancement of science by prema~
ture attempts at explaining them.

     § 4. Connexion of Bone with the living system.

   Having now taken a view of the structure of bones,
of their physical properties and chemical composition,
and  made some remarks upon the mode of their growth
and  formation, it  remains to consider the nature of
their connexion with the system at large, and the  pro-
perties  which they possess, as forming a part of a living
organized body.   I have  already remarked, that bone,
in its most  perfect state, possesses few blood-vessels,
compared with many  other  structures;  it  does not
seem that  any nerves are sent  to it, and we  judge of
the  presence of the absorbents, rather from  observing
effects  which can be ascribed to no other cause,  than
from being able actually to demonstrate their existence.
Bone is, consequently, devoid of sensibility, and is also
equally  without  contractility;  it partakes only  in a
small degree of the general action of the system, and
its changes  of all kinds  are effected slowly, and often in
an almost imperceptible  manner.   Yet,  like all other
organized parts, we have reason to suppose that every
portion  of  it is  connected with both the arterial and
the absorbent systems,  and that, in process of time,
 each particle is removed, and fresh ones deposited  in 
10S
Slate of the earthy Matter.
their place.  This  gradual exchange  of  old  for  new
matter is proved by the phenomena which attend the
growth of bone.*   A solid organized body cannot grow
by the distension of its parts, or by the accretion of  new
matter to its external surface,  but by the gradual re-
modelling of the whole.   If the  secreting vessels be
supposed to act more powerfully than the absorbents,
the new matter is either conveyed more rapidly, or in
greater quantity, than  the  old matter is  removed,  so
that the bulk of the whole is ultimately increased, and
yet the  operation is effected  so  gradually,  that  the
general form of the bone and the relation of its differ-
ent parts to each other are not materially  altered.
   These observations refer to the bones in their healthy
state.   When labouring under disease, they  exhibit
very unequivocal marks of vitality, being subject to af-
fections  which  are precisely similar to the inflamma-
tion, swelling, and suppuration of the soft parts, making
allowance for the difference of their mechanical struc-
ture.   And although healthy bone is insensible, yet, in
some  of its diseased states,  it becomes exquisitely pain-
ful ; and, in this case, it may be presumed  that the sen-
sation arises, not from  any  nerves actually sent to the
bone itself, but  from its increased bulk and firm  tex-
ture distending the nerves that are  distributed upon
the contiguous  parts, as takes  place  with respect  to
dense membranes of all descriptions.
   The same general observations, with respect to  the
nature of  their vitality, will  apply to  the bones as  to
the cartilages and the tendons; but there is one point

  * The experiments of Duhamel, on the effect of madder upon
the bones, were generally supposed to afford the most direct proof
of this interchange of particles, even by those who admitted the
hypothesis  of the concentric layers  to be imaginary.  But the
experiments and reasoning of Mr. Gibson have shown that the
removal of the red matter depends upon the serum, which circu-
lates through the vessels of the bones abstracting the colour  from
the phosphate by its superior attraction for it.  Manchester Mem
v. 1. new series, p. 160. 
               State of the earthy Matter.            103

respecting  it, which  appears to  present an additional
source of difficulty ;  are we to consider the earthy mat-
ter as organized and possessed of life ? Perhaps, at the
first statement of  this question,  every one will be  dis-
posed to deny the possibility of life being attached to
an earthy salt, and, in a general sense, the objection is
valid.  But when we come to consider the  subject in
its  most  minute  relations, it will not be easy  to point
out any  essential  difference  between  the earthy and
the animal matter which enters  into the constitution of
bone.  They  are both derived from the blood, and de-
posited by vessels connected with the arterial system;
they both possess a specific determinate arrangement;
and they are both, after a certain period,  taken up  by
the absorbents, and  again carried into the mass of cir-
culating fluids.  It is  not improbable that, before they
are either of them expeiled from the system, or are
again applied to any other use in it, they undergo de-
composition,  and that part  of their elements may be
employed in forming new compounds, while the remain-
der may be rejected by some of  the excretory passa-
ges.  I should be  inclined, therefore, to say, that the
phosphate of lime, while forming a part of an organiz-
ed  body, is alive, because  the bone is so generally; but
the phosphate of  lime, or its elements, while  they are
circulating in  the  blood, or passing off by the kidney,
or alimentary canal,  cease  to be so, in the same'man-
ner as the carbon which is expired from the lungs, or
the mucus which is expelled from the mouth, are not
considered as being alive,  although they may,  perhaps,
a short time before, have been  employed in the  com-
position of a muscle  or a nerve.   This view of the sub-
ject will  lead us to reject  the mechanical idea which
has been  entertained  by  some  physiologists,  that the
earthy matter of  the bones is simply deposited in the
interstices of the membrane, and has its particles kept
together merely by the cells in which they are lodged.
I conceive that the earthy particles have an affinity for 
104      Does it form a Part of the living System ?

each other, and perhaps  for the membrane, by which
they are combined in a form that belongs to them, as
necessarily as to any of the soft parts, although it pro-
duces in them a peculiar arrangement, which may not
be found in any other substance. 
Of Muscle.
105
                   CHAPTER III.

                     <©f JHuiscle.

   The next  subject which we are  to consider is  the
 muscles,  and I  shall arrange  what I have to say re-
 specting  them under six heads.  I shall first  describe
 the form and structure  of  muscles; second, their che-
 mical composition; in the third place, their properties;
 fourth, their  uses ; fifth, their mechanism; and lastly,
 I shall  offer  some remarks upon the  hypotheses that
 have been formed  to explain their action.

          § 1.  Form and Structure of Muscles.

   Muscles constitute what  we call the flesh  of animals,
 but although  these terms are now by every (jne regard-
 ed as synonymous,  the older authors made a distinction
 between  what  they styled the flesh, and  the fibrous
 part, regarding this latter only as the proper organ  of
 motion ; and it was not until the  middle of  the seven-
 teenth century that this error was rectified by Steno.*
 In their usual form, muscles are composed of masses of
 fibres,t lying  parallel to each other, intermixed with a
 quantity of membranous matter, a  structure which  is
 visible  to the naked  eye,  and may be rendered more
 apparent  by cutting  the muscle transversely, and ma-

  * De Muse. Obs. Specimen in Mangeti Bib. An. t. ii. p. 518, et
 seq.
  t Croone appears to have been the first physiologist who had a
distinct idea of the fibrous structure of muscles, and that muscular
motion depends upon the contraction of the fibres.  We learn from
Eloy, Diet. Hist. " Croone," that he published a treatise, " de Ra-
tione Motus Muscul." in 1664 ; see also ActaErud. for 1682 ; PhiJ.
Trans. 1681, Phil. CoL No. II. p. 22.
                 14 
106
Structure of Muscles.
 cerating it, for some time, in hot water, or in alcohol.3'
 The whole muscle is enclosed  in a membranous sheath,
 which covers it  in  every part, except where its ends
 are  attached to  the  bones.   We  observe  that  the
 fibres  are disposed  into small bundles,  called  lacerti,
 each of which is also enclosed in a sheath of membrane,
 and  that  these bundles are divisible into  still smaller
bundles, apparently without  any limit,  except what
 arises from the imperfection of our  instruments.
   Although the fibres of many of the muscles appear
to be of  considerable length, yet it has been  doubted
 whether  this be  actually the  case, or whether what
 appears to be one continuous fibre may not, in reality,
 be made up of a number of smaller ones that are con-
 nected  at their extremities;  the authorities for each
 of these  opinions are  nearly  balanced,  but, perhaps,
 those for the continuity of the  fibre may, upon  the
whole,  preponderate.  The  fibre  is represented  by
 many writers as  exhibiting a wrinkled or waved ap-
pearances but there is reason to doubt whether  this
 De its natural state, and  whether it  may not depend
upon the condition in which it  is found, when it  is exa-
mined after death, and  detached from the neighbour-
ing parts.  In most muscles, the  centre is  thicker than
the rest,  and  appears  to contain more fibres;  this  is
called  the belly ; hence it gradually diminishes  in size
to the extremities, one or  both of which terminate in a
membranous  body, which  is either a tendon, or an ex-
panded  membrane, called  an aponeurosis, according  to
the situation  of the muscle, and its connexion with the
neighbouring organs.  There are considerable intersti-
ces between  the muscles, which are occupied  by fat
and cellular texture, and in these intervals a safe lodg-

  * For a most correct delineation of the disposition and direction
of the fibres of the different  muscles  connected with the trunk  of
the body, I may refer to Prof. Tiedemann's very beautiful lithogra-
phic plates of the arteries; a work which is no  less admirable as
a specimen of art than of anatomical accuracy. 
Nerves.
107
ment is afforded for the trunks of the blood-vessels and
nerves.  Most of the large muscles are situated  near
the surface, covering the  bones, and filling up the spa-
ces between them, so as  to produce the general form
and  outline  of  the body.  Besides the  aponeuroses,
which are  attached to the muscles, and the membran-
ous sheaths wrhich cover them externally, and  inclose
their lacerti, expanded membranes are often found en-
tering into the body of the muscle, and dividing them
into  separate portions.  All these varieties of mecha-
nical structure are obviously adapted to the uses of the
individual muscles in which they are found, and there
is no part of the animal ceconomy which exhibits more
of this kind of adaptation than the  muscular system.
   With the exception of some of the  viscera, muscles
are  more  plentifully supplied with arteries than any
other  parts of the body; they are distributed  among
the fibres in numerous branches, which continue  to sub-
divide with so much minuteness, as at length to become
no longer visible.   The capillary veins are equally,  or
even more numerous than the arteries, and form a com-
plete  vascular net-work ; the contents of  which are
gradually discharged into larger and larger vessels, un-
til the blood at length arrives at .the main trunks.  The
veins that  belong  to  the  muscles are remarkable  for
the number of valves which  they contain.  The  ulti-
mate termination of the blood-vessels, or the manner
in which the  arteries are connected with the veins, is
not  very accurately ascertained ;  but  this  is a  point
which will be considered with more propriety hereaf-
ter.
   The apparatus of nerves, which is sent to the mus-
cles, is very considerable ;  and especially to those which
are under the control of the will, being greater in pro-
portion to their size  than  to any other part of the
body, except  the  organs  of the senses.  The nerves
that  belong to the voluntary   muscles  proceed almost
exclusively from the  brain itself, or from  the  spinal 
108
Minute Structure^
cord, whereas the muscular coats of the viscera are,
for the most part, supplied immediately from the gan-
glia.  The former are so much  more numerous than
the latter, that, according to the remark of Haller, the
nerves that  go to the thumb are more in quantity than
those that  supply the  whole  substance of the liver.
There are many curious circumstances connected with
the distribution of the  nerves, and the course which
they take, as, for  example,  where a nerve runs for a
considerable distance, as if for the express purpose of
supplying a  particular muscle, which might  have  re-
ceived its  nerves from a nearer source ; and where
two or more nerves come to  the same  muscle when
there is no apparent reason, from the structure of  the
part, why any one of them alone might not have been
sufficient.* It has been thought that each separate fibre,
or, at least,  each  of  the smallest  bundles  into which
the fibres are arranged, contains one  of  the ultimate
branches of an  artery and a nerve ; our actual observa-
tions scarcely  enable  us to  decide upon this point,
but there is some reason to suppose that it may be the
case.
   I have now been  describing the structure  of mus-
cles as it appears to the naked eye,  but many anato-
mists have attempted, by the aid of the microscope, to
ascertain the nature of the ultimate fibre, as it has been
called,  or that which is no  longer capable  of further
subdivision  without a breach of its substance.   As is ge-
nerally the  case  in microscopical observations, the de-
scriptions that have been given  by these writers are
very various, both as to the size and  the  form of the
ultimate fibre ; and there is  also a  wTant of  uniformity
in the terms which they have employed to express the
gradations of the component parts of the muscle, which

   * These and other apparent anomalies of a similar  kind are ex-
 plained by the very ingenious hypothesis of Mr. C, Bell.  See  Phjl>
 Trans, for 1821, p. 398, et seq. 
Observations of Leeuwenhoek, Muys, Qc.      109
apparently  increases  the  discordance of  their state-
ments.
  Leeuwenhoek, who  is celebrated for the early use
which he made of the microscope  in  anatomical re-
searches, describes the ultimate filament  as  being al-
most inconceivably minute, some thousands of them uni-
ting to form one visible fibre.   We learn from him that
the  ultimate  fibres   are  serpentine and cylindrical
bodies, lying parallel to each other; that they are of
the same figure in all animals, but differ  considerably
in their size.  He states that their  size  bears no pro-
portion to that of the animal to which  they belong ;
and that even, in some instances,  the smallest animals
have the largest fibres ; as, for example, the fibres of
the frog are said to be larger than those of the ox.*
   Muys, an industrious Dutch anatomist, was engaged,
for several years, in investigating the minute structure
of muscles, and his description, in many respects, agrees
 with Leeuwenhoek's, except that he supposes the ulti-
 mate  filament to be always of the same size.  He im-
 agines that the fibres are distributed into regular gra-
dations or series, and  that the smallest fibrils of  which
 the last series is composed,  are some hundred   times
 less than the finest hair, a proportion  larger indeed
 than that assigned by Leeuwenhoek, yet still too mi-
nute to permit us to form any conception of it.    Many
 other accounts of the structure of muscles  have been
 published from time to time; some  anatomists describ-
 ed them  as  being straight,  others  zig-zag or waved,
 and others wrinkled or knotted :  some  as being solid
 and others hollow,  while many eminent physiologists
 have  conceived that they are jointed, and consist of a
number  of parts, connected together like  a  row of
beads.t   Borelli, a learned  and ingenious Italian, well

   * Arcana Naturae, p. 43, et seq.
   t Haller, El. Phys. xi. 1, 3—6;  Soemmering, Corp. Hum. fab. t.
 iii. § 14; Prochaska, de Came Mus. p. 19, et seq. 
110
Thought to be vascular.
known for his elaborate work on muscular motion, an-
nounced that the fibre consists of a  series  of hollow
rhomboidal vesicles, and deduced from this structure  a
theory of muscular contraction, which he supported by
a long train of mathematical problems,  and while ma-
thematical reasoning was fashionable  in  physiology, his
demonstrations  were conceived to be incontrovertible.
A peculiar  modification  of Borelli's opinion was pro-
posed by Stuart,  who thought that  the muscular fibre
was composed of a string of vesicles, immediately form-
ed from the substance of the nerves, which he conceiv-
ed was  similar to that  of the  tendons,  and that these
vesicles  were covered by a net-work of blood-vessels.*
  Another opinion  entertained respecting  the nature
of the muscular fibre was,  that it  is entirely composed
of vessels, either possessing some peculiar structure, or
consisting of the small branches of arteries.  This  hy-
 gothesis, which appears to have been first broached by
 [ooke, was adopted by many learned physiologists, es-
pecially  those of  the mechanical sect,  and was made
the basis of some of their speculations concerning mus-
cular contraction.  A number of facts  were  adduced
in its support, but they may  all  be explained by  the
numerous vessels which   are  dispersed through  the
muscles, without  having recourse to the  supposition
that the fibre itself has a  vascular structure.!   Many
celebrated names, and  among others those of Willis^

  * Dis. de Mot. et Struct. Mus. c. 8.
  The idea of the vesicular structure of the muscular fibre was em-
braced by Hooke, in part at least from  his own observations, and
was at first admitted by  Leeuwenhoek,  although he afterwards,
upon further examination, retracted it.  It appears to have  been
previously employed by Croone as the basis of  his  hypothesis of
muscular contraction, and was adopted  for the same purpose by
Keill and Stuart, yet notwithstanding the sanction of so many learn-
ed names, it seems to be totally void of foundation.  See Leeuwen-
hoek, Arcan. p. 43, 54, and 58.  Phil. Trans. Phil. Col. No.  v. p.
152, and No. vii. p. 188, April 18, 1682.
  t  See Carlisle, Phil. Trans, for 1805, p. 7.
  + De Motu Muscul. p. 46. 
Prochaska9s Account.
Ill
and Baglivi,*  are  attached  to  an erroneous opinion,
that  besides  the  longitudinal fibres, muscles possess
transverse fibres, crossing the others at right angles, and
that these are  important  agents in muscular action.
This diversity of  opinion  has in part arisen from the
uncertainty  which attends all microscopical  observa-
tions, and in  part, no doubt, from  the state  of mind
with which the observers made their inquiries, biassed
by a favourite notion, and anxious to discover some ap-
pearances which might support their hypotheses.  The
sagacity of Haller perceived the futility of these fanci-
ful  opinions, and his  authority  greatly contributed  to
effect their downfal.  Since  his time  the  subject  has
been examined by Prochaska, an able anatomist of Vi-
enna, by the Abbe Fontana, by Sir A.Carlisle, and Mr.
Bauer.   We  meet  likewise  with a  great number of
valuable remarks  on the muscles, and on the mode of
their actions in the writings  of  Bichat, who, although
he  has  not added  any absolutely new facts or observa-
tions, has arranged the  knowledge which we possess on
the subject with much  ingenuity, so as to present many
parts of it under a novel and interesting aspect.   If his
classification should appear  too  minute and  intricate,
and some of his opinions rather subtile than well found-
ed, still there is in them much that  is extremely im-
portant both to the anatomist and the physiologist.
  Prochaska, in entering upon his work, proposes  a no-
menclature of  the component  parts  of  the muscle,
which  professes to be  derived  from  the actual struc-
ture of the parts.   To  the larger divisions of the  mus-
cles he  applies the old  term of  lacerti, using  it  in  the
same sense with Haller and other preceding anatomists;
the term fibre he restricts  to the  smallest divisions of
the lacertus, which can be easily separated by mecha-
nical means,  while the still more  minute parts, which
are only to be detected by the use of glasses, he calls
the threads or filaments.   He informs us that each of
the fibres, as  well as the  lacertus, is inclosed in a pro-
* Opera, p. 399. 
lis
Prochaska9s Account.
per membranous sheath, but  it does not  appear that
this is the case with the filaments, a number of which
are invested in one common sheath, and are connected
together by a fine web of cellular texture.   The fibre,
when properly prepared, and  separated from all extra-
neous matter, he conceives to be of the same thickness
through the whole  of its extent,  and continuous from
one end of the muscle to the other, not  as Haller and
many other anatomists  have  supposed,  consisting of a
number of smaller fibres connected together by their ex-
tremities. Leeuwenhoek, Muys, and most other preced-
ing writers  had described the  fibres as being cylindric-
al, but Prochaska  says  that  they are obviously of  an
irregular polyhedral form, and that they are generally
flattened, being thicker in  one direction than the other.
The fibres are not always of the same diameter,  they
differ in different  animals, and  likewise  in different
parts  of the  same animal, and he also observes that
they  are smaller in young subjects, and increase  in
size as  the body increases in bulk generally.   These
circumstances, as  he remarks, render it very  difficult
to institute  any  very  accurate  comparison  between
the size  of the fibre  in different animals, and render
Leeuwenhoek's  observations  on   this  point  very
doubtful.
  With respect to the ultimate fibres, or,  as he styles
them, the filaments, their shape  and extent is said  to
be similar to that of the larger fibres, being flattened
polyhedrons, reaching the  whole length  of the muscle.
They differ, however, from the proper fibre in being
always of the same  magnitude, and this he estimates,
nearly as Muys had done, at about one-fiftieth part the
size of the red globules of the blood.  As the  fibres
are of different diameters, the number  of filaments
contained in each fibre  must  be necessarily different,
varying from 100 to 400 or  500.   The filaments are
solid and homogeneous ; when  prepared for examina-
tion they have a number of depressions or wrinkles  o$ 
Carlisle's Account.
113
their  surface, which gives them a waved appearance,
and, when viewed in a  certain direction,  makes them
appear somewhat serpentine or zig-zag, but these de-
pressions  he conceives are produced by the blood-ves-
sels,  nerves, and membranous bands which crossed
them.*
  The account which Fontana gives us of his microsco-
pical  observations on the ultimate muscular fibre, is-, on
the whole, not very different from that of Prochaska.
By the use of  a fine needle he divided  the muscular
fibre  into small filaments, which seemed to be incapa-
ble of further subdivision ; these he calls the primitive
fleshy filaments, and some hundreds of  them  unite to
compose  what he denominates a primitive fleshy fasci-
culus  or bundle, by which he probably means the same
division that Prochaska simply  calls a fibre.  The pri-
mative filaments are described  as solid cylinders, mark-
ed externally with transverse  lines  or  bands at equal
distances; the filaments lie parallel to each other, and
are not twisted together, as is the case with the primi-
tive  filaments of membrane;  and  from  this  circum-
stance he says that the two parts may,  at all times, be
distinguished from each other.   The extreme branches
of the blood-vessels and nerves, although so plentifully
distributed  through the muscles, do not seem to enter
into the  substance of the filaments, nor  even of the
primitive fasciculi.  The smallest vessels capable  of
containing red blood, is  about three  times larger than
the muscular filament, and the smallest  nerve about
four  times larger than the smallest blood-vessel, so that
there is no difficulty in detecting them when they are
mixed with the filaments.t
   The observations of  Sir A.  Carlisle  differ, in many
respects, from those of preceding writers, especially of
Prochaska  and Fontana.  He describes  the  ultimate

      * De Carne Musculari, p. 25, et seq.
      t Sur les Poisons, t. ii. p. 228 ; vol. vi. fig. 6, 7, 9.
                 15 
114       Muscles and Nerves thought identical.

fibre, by which he  appears to mean the filament of the
above authors, as  " a solid cylinder, the covering of
which is a reticular membrane, and the contained part
a pulpy substance  regularly granulated,  and of  very
little cohesive power when dead."  He speaks of it as
what may be  very easily detected by  a microscope,
and as not being so extremely minute as had been pre-
viously  conceived,  but he prudently declines stating its
actual size.   The  extreme branches of the blood-ves-
sels and nerves are  seen ramifying on the  surface of
the membrane inclosing the pulp, but we are not able
to trace them into the body of  the fibre.  There is,
upon the whole, a simplicity  and clearness in this de-
scription which inclines  me to place confidence  in it,
but,  at  the same time, it would be  desirable that the
observations  should be repeated and confirmed, as the
authority  of  some of the anatomists wrho differ from
him  is too respectable to be hastily abandoned.*
   The  account which Mr. Bauer gives us of the mus-
cular fibre differs considerably from that  of either Pro-
chaska, Fontana, or Carlisle. In examining the globules
of the blood  with  his  high magnifiers, he  found that
these bodies, when deprived of their colouring matter,
were of the  same diameter with  the ultimate muscular
fibre, and that the fibre was in fact composed  of a
series of  the globules arranged  in straight lines.  He
confirmed his observations by  a subsequent experiment,
in which, by  a certain degree of maceration, he suc-
ceeded  in reducing a muscle, first, into a number of fibres
of the  same diameter with the  globule, and,  by con-
tinuing  the operation, into the globules themselves; the
size  of  the globule, when deprived of its colouring mat-
ter,  and consequently that of the  muscular fibre, he
estimates at  svso of an inch in diameter.t
   Among the more  noted hypotheses that have been

   * Phil. Trans, for 1805, p.  6.
   ' Phil. Trans, for 1818, p.  174, 175;  pi. 8. fig. 4, 5, 6. 
*
           Muscles and Nerves thought identical.        115

 formed respecting  the nature of muscles, independent
 of their visible appearance, I must not omit to mention
 one  which prevailed very  generally  about 50  years
 ago, and was  zealously defended by  Cullen, that mus-
 cles are, to use his own expression, the moving extre-
 mities of nerves.*  The fibres of the muscle  are sup-
 posed to be continuous  with those of  the  nerve, and to
 be absolutely the same substance, but that they expe-
 rience a change  in their structure, so that when the
 nerve is converted into muscle it loses  the  power of
 communicating feeling,  and  acquires that  of  producing
 motion.  This doctrine of Cullen's seems  to have been
 the result  of the physiological speculations that he had
 formed respecting  the nature  of  life.   Following up
 the idea of Hoffmann, that the animal functions exhibit
 phenomena of a specific kind, which cannot be referred
 to any other powers  in nature,  he classed  them to-
 gether under the denomination of vital;  and as both
 sensation and  spontaneous motion were obviously to be
 placed among the vital operations,  he hastily conclud-
 ed that they  must proceed from the action of the same
 organs.  In answer to  this hypothesis I think it suffi-
 cient to observe, that substances which differ in  their
 appearance and  structure, as well as in their physical
 and chemical  properties,  can have no claim to be re-
 garded as identical.  And  with the same remark I may
 dismiss an analogous speculation, that muscle and tendon
 are the same  substance, differing only in the more con-
 densed state of the latter ; an opinion which was trans-
 mitted from the ancients,  embraced by Boerhaave and
 his disciples, was adopted by Albinus, who studied the
 muscles with such minute  attention, and  was in short
so generally admitted,  even in the middle of  the last
century, that  Hallert and Sabatierf scarcely ventured
to give a decided opposition to it.

        * Instit. § 29, 94.         t EI. Phys. ii.  1, 18.,
                J Anatomie, t. i. p. 242. 
116
Use of these Structures.
      Besides the bodies which I have described above,*to
   which the name of muscles has been generally applied?
   muscular fibres appear under a different form, and one
   which is less obvious to the eye, but Avhich is no less
   necessary to the existence of the animal.   I  refer to
   those structures, where fibres, which appear essentially
   to resemble those of the proper  muscles,  are attached
   to membranous expansions, composing what have been
   called muscular coats.   These muscular coats are con-
   nected with the hollow cavities that exist in  different
   parts of the body,  in  the  form  cither of pouches or
   cylinders, and are destined for the transmission or lodg-
   ment of various bodies  of  a soft or fluid consistence,
   and which propel  their contents by  means of  these
   fibres.   The mechanical  structure of  the muscular
   coats is considerably different from  that of the proper
   muscles;  the fibres  are much shorter, and instead of
   lying parallel, as is always the case with  the  muscles,
   they seem to be  interlaced or twisted together, and,
   according to Prochaska*sometimes even to anastomose
   or bifurcate.*  The fibreg  of the  muscular coats do
   not' exhibit  that division into lacerti  or  bundles,  nor
   have they the regular belly  or tapering extremities of
    the others.  Their immediate  attachments  are also
   different; the  proper  muscles have one  of their ends
   jat least  terminating in a tendon or fibrous membrane,
   while the muscular  coats are attached to membranes
•  that exhibit less of the fibrous and more of the cellular
    texture.
      The uses of these two classes  of  bodies are likewise
    very different.  The  proper muscles are  always de*
    signed to produce the motion of some part of the body,
    by altering its relative  position  with respect  to  the
    other parts, while the motions that are caused by the
    fibres of  the muscular  coals are  designed  to operate
    solely upon the contents of  the  organ to which they
Tab. 6, fig. 2 and 3. 
Colour of Muscle.
117
belong, and consist in a number of small contractions,
in each of which a few fibres only act at the same time.
And these two kinds of organs differ moreover in the
connexion which they have  to the other parts of the
living system, and particularly to the nerves; for while
most of  the proper muscles are supplied with nerves,
either from the brain itself or  from the spine, which
may be regarded as an immediate appendage to the
brain,  or are, many of them, more or  less  dependant
upon the will,  the muscular coats are, in most cases,
supplied from the ganglia,  and their action is  entirely
involuntary.
   From this  difference  in  their structure and proper-
ties  most anatomists have restricted the term muscle
to the regular  masses of parallel fibres;  but Bichat
applies it  generally to both of them. The proper
muscles, as being the media through which we  observe
the operation of both sensation and motion, those  qua-
lities which are essential and appropriate to animal ex-
istence, he styles muscles  of animal life, while the oth-
er class he calls  the muscles of organic life, in conse-
quence of their being destined  principally for these or-
gans, which serve for the support  of the individual, but
which  do not present so  obviously the phenomena  of
sensation  and motion.*   The  correctness  of Bichat's
names depends  upon that of his peculiar theory of vi-
tality,  which will be examined hereafter ; I shall there-
fore adhere to the  former nomenclature, and when I
speak  of muscle in the abstract I  must be  understood
to refer solely to the larger masses of parallel fibres,
while  to  the others I shall apply the usual term  of
muscular coats.
   In man and the more perfect animals muscles gene-
rally possess  a reddish brown colour, but  this seems
not to  be essential to them,  as by sufficient  ablution  in
water, or by maceration  in alcohol, they may be de-
* Anat. Gen. t. ii. p. 400. 
118
Cellular Substance.
  rived of it, and be  rendered nearly  white,  without
  aving their texture  apparently altered.  As their co-
 lour is most  considerable in animals with red blood, it
 has been usually attributed to a quantity of red blood
 remaining  attached  to the fibres, either extravasated
 through  them, or  simply contained in the vessels;  but
 Bichat  endeavours to show that this is not the case,
 and  that the colour  depends  upon some foreign sub-
 stance that is combined with the fibre.   He founds his
 opinion upon the circumstance, that in the same animal
 some of  the muscles are always much redder than oth-
 ers,  and yet  they do not appear to have  a  greater
 quantity of blood sent to  them, and also that in differ-
 ent classes of animals  the colour of the muscles does not
 appear  to  correspond with the  quantity of red blood
 circulating through  their vessels.*  But whatever be
 the  nature of  the colouring matter, we may conclude
 that it is not necessary to the constitution of the fibre
 or to its  specific properties; for some of the muscular
 parts that  are the most contractile are of the lightest
 colour.   Generally, however, the red  colour  prevails
 in the voluntary muscles,  and  it has also been observed
 that in those which are naturally coloured, the shade
 becomes deeper in  proportion to the degree in which
 the muscle is exercised, t
   Besides the  membranous substance, which seems to
 enter into the  necessary structure of a muscle, which
 envelopes its fibres and lacerti  and  forms  its  sheath,
 determining its figure and preserving it in  its proper
 position,  there is  likewise a quantity of cellular  sub-
stance of a more loose texture  interspersed through the
body  of the muscle, and filling up the cavities between
its separate parts.   This is similar to the cellular  sub-
stance which enters so  largely into the composition of
the body generally, and like it appears to be intended

  * Anat. Gen. t. ii. p. 327.
  t Home's Lect. on Comp. Anat. p. 81, et seq.
I 
Albumen, Jelly, Extract, Osmazome.       119
 to contain both fat  and the peculiar albuminous fluid.
 It  has been  conceived that, besides the  proper fat
 which is lodged in its appropriate cells, muscles contain
 a quantity of oil  of a more fluid  consistence, which is
 intimately united  with them, and  serves to lubricate
 them, to assist their movements, and  to prevent their
 adhesion;  but this opinion is rather founded upon con-
 jecture and the supposed utility of the substance,  than
 upon any  experiments  which have directly proved its
 existence.
   A quantity of albumen, of jelly, and of the peculiar
 substance  called extractive  matter, may be procured
 from the muscles by boiling, but it does not appear that
 these form any essential part of their substance, ancbit
 is doubtful whether the jelly be always  present in the
 muscles of the adult.  In young animals it appears that
 the muscles, as well as  the membranes and  bones, con-
 tain a considerable  quantity of jelly, but as they  ad-
 vance in age  this jelly disappears, and is replaced by
 albumen.  When muscles are digested in warm water,
 a quantity of saline matter is separated from them, but
 it is doubtful whether this be attached to the muscular
 fibres themselves, or be merely lodged in the different
 vessels  that pass through them ;  the former however
 appears the more probable supposition, because, as far
 as it has been  examined, it would seem  not to be  the
 same combination of salts which exists in the blood.
  When the muscular fibre has been macerated for a
 sufficient length of time, and is cleared, as much as pos-
 sible, from all extraneous matter, we obtain  it in a pure
 state.   It is nearly white, without much  taste or smell,
 and if it be kept free  from  moisture, it  will remain a
 long time without undergoing decomposition or experi-
 encing any change.*  If the water which has been em-
 ployed in the maceration, and which contains albumen,
jelly, extract, and various salts,  be evaporated to drv-
* Fourcroy's System, by Nicholson, v. ix. p. 335. 
120
Chemical Relations of Muscle.
ness, and then treated with alcohol, the extract  alone
is dissolved, and by the evaporation of the alcohol, may
be obtained in  apure state.   This substance was  dis-
covered  by M. Thouvenel;  it has a brown colour, an
acrid taste, and an  aromatic odour, is soluble both in
water and in alcohol, and would seem to be  the  ingre-
dient which gives the specific flavour to the flesh of
different animals, and especially to be the part which
forms  the  brown crust on roast  meat.   M. Thenard
has given the name of Osmazome  to the substance.*
  The  salts that are contained in  muscular flesh or
connected with  it,  are principally the phosphates of
soda, ammonia,  and  lime, and the carbonate of lime.
For the discovery of  the phosphate and carbonate of
lime .we are  indebted to Mr. Hatchett.t   Fourcroy
and Vauquelin inform us  that they have detected  sul-
phur  and potash in  muscles,^  and Prof. Berzelius the
muriate, phosphate, and lactate of soda ;§ but perhaps
there is still some uncertainty respecting the nature of
the salts, and the  mode  in which  they exist when en-
tering into the constitution of the  muscle.

      § 2.  The Chemical Composition ofJMuscle.

  The muscular fibre, in  its pure state, is readily acted
upon by  various  chemical re-agents.   Most of  the
stronger acids and  the caustic alkalies dissolve it; but
it will not  be necessary to enter  into a detail  of the
phenomena that  occur with any of  these, except with
the sulphuric and the nitric acids.  By digesting the
fibre with sulphurio acid, and then removing the  acid
by carbonate of lime, M.  Braconnot converted it into a

  * Chimie, t. iii. p. 759 ; Berzelius, however, does not think this
substance to be a distinct proximate principle.  See his View of
Animal Chem. p. 82.
  t Phil. Trans, for 1800, p. 395.       $ Ann. Chim.t. lvi. p. 43.
  5 Thomson's Chem. v. iv. p. 474. 
Chemical Relations of Muscle.
121
 peculiar kind  of extractive  matter, from which,  by
 means of alcohol, he procured  a substance named leu-
 cine, in consequence  of its white colour; this, by the
 action of  nitric acid, is converted into what is  called
 nitro-leucic acid.*   By the nitric  acid  fibrine is partly
 decomposed and partly dissolved, while a quantity of
 gas is disengaged, consisting principally of azote, united
 to about one-tenth of its bulk of carbonic acid.  The
 same kind of gases are produced  by other animal sub-
 stances,  when they are treated  with nitric acid, but the
 muscular fibre differs from  most of them in extricating
 a larger proportion of azote, indicating that a greater
 quantity of this substance enters  into its  composition.
 As this is the element which prevails in animal bodies,
 and  particularly distinguishes their chemical composi-
 tion  from that of vegetables, muscles are said to be the
 most completely animalized part of the body ; and it
 is worthy of observation, that  in the same degree as
 the animal constitution differs from the  vegetable in its
 chemical constitution, it acquires, at  the same time, its
 most characteristic  physiological  properties.   It is ge-
nerally understood that the muscles of the animals with
red  blood, which  possess the greatest variety of func-
 tions, and enjoy them  in the most  perfect state, contain
 more azote than those of  fish or reptiles ; and  that in
 animals of  the same species, those of adult age contain
 more azote  than the same animal  soon after birth.
This is one among several instances where it would ap-
pear that  the full developement  of  the animal func-
tions  is  necessarily connected with a certain  chemical
constitution; but although  this  appears to be a matter
©f fact, we are not authorized  to conclude,  with some
 modern  physiologists, that the vital powers are the ne-
cessary result of a peculiar chemical  mixture.
   When the action of  nitric acid  upon the muscular
fibre is  promoted  by heat, the muscle is quickly dis

         * Ann. Chim. et Phys. t. xiii. p.  118, et seq.
              16 
122
Formation of Adipocire.
solved in large quantity, the fluid assumes a deep  yel-
low colour and acquires a degree of unctuosity,  while,
at the same time, there is  a rapid escape of gas,  con-
sisting principally of a  mixture  of  azote and carbonic
acid, together  with a quantity  of nitrous gas.   Alter
the acid has dissolved a considerable portion of the
fibre,  globules  of oil appear on the  surface ;  these,
when the fluid cools, assume a concrete form, and are
found to be a substance of  a  peculiar nature, which,
from possessing properties intermediate between those
of  fat and wax, has obtained  the name of adipocire.
Portions of the  oxalic and malic  acids are also formed,
and besides these several other substances are contain-
ed  in the fluid, and some, as it appears,  of a peculiar
nature, generated by the action of the nitric acid upon
the  muscular fibre.
  The substances which result from the  mutual  action
of nitric acid and fibrine, have been minutely examined
by  Fourcroy and Vauquelin, and appear to be  both
numerous and complicated  in their  relations to each
other.  Besides the gases that are disengaged, and the
oxalic and malic acids that are left in the  fluid, it  would
appear, that at least  three  other new substances  are
produced; a peculiar fatty  or adipocirous  substance,
an acid, which from its colour has been called the  yel-
low acid, and a substance nearly  approaching to  a re-
sin  in its properties, which  possesses an  intensely  bit-
ter taste.*   Professor Berzelius, however, throws some
doubt upon the  nature  of these two  latter substances,
as distinct chemical products, and seems more disposed
to consider them as being merely combinations of  the
nitric acid with  different  portions   of  the  muscular
fibre.t  The subject indeed still  remains in some  de-
gree of obscurity; yet it appears probable that  a  por-
tion both of the acid and of the fibre is decomposed,

           * Ann. Chim. v. Ivi. p. 37.
           \ Medico-Chirurg. Trans,  v. iii. p. 205. 
Spontaneous Formation of Adipocire.
123
and that the substances generated by the  decompose
tion of the fibre contain a larger proportion of hydrogen
and perhaps also of oxygen, with less azote and carbon,
than the muscle  in its original state.
  There are several reasons which lead to the opinion,
that the concrete fat or adipocire, which is formed by
the action of nitric acid upon muscular fibre, differs in
its constitution from the fibre itself, in consequence of
the addition of  oxygen  and the abstraction of azote
and carbon.  With respect to the  yellow substance,
which appears to be the result of some further change
in the composition of the  muscular fibre,  we are not
sufficiently acquainted  with its nature, nor indeed have
we yet  that exact knowledge of its properties in its
uncombined state, for us to decide upon  its  composi-
tion, or the relation which it bears to the adipocire or
the entire fibre.   Analogy, however, would lead us to
conjecture that  this is a  still further remove from the
muscular fibre, and that the  abstraction of still  more
carbon, and the  addition of more oxygen, than what is
sufficient  to  convert  muscular  fibre  into adipocire,
would convert adipocire into the  yellow  resin.   But
this is a point which  must be  determined by future
experiment.                          • L   »       1
  There is a very peculiar change which the muscle
undergoes in its chemical composition, under certain
circumstances, which was,  in the first instance, effected
spontaneously, but which  has been since  imitated by
various  artificial processes.  There was  an  immense
burial-ground in Paris, called La Cimetiere  des Inno-
cens, which, in consequence of some improvements that
were going forwards, it was determined to remove.
This place had  been  the receptacle for a considerable
part  of the population of  Paris for several  centuries.
The  number of burials was supposed to be some thou-
sands annually;  the  bodies were deposited in pits en-
trenches about 30 feet deep, each capable of holding
from 12 to 1500 bodies, which were then covered with 
124             Formation of Adipocire*

a few feet of earth, so that the whole area, occupying
about 7000 square yards, was converted  into a  mass,
consisting principally  of animal  matter, rising several
feet above the natural level of the soil.  Upon opening
the ground  for the  purpose of removing this prodi-
gious collection of dead bodies, they were found to be
entirely altered in their nature and appearance. What
had formerly composed  the  soft  parts  of the body
was converted into  an  unctuous  substance, of a grey
colour, and of a peculiar but not very offensive odour.
According to their position in the pits, and the  length
of time they  had been  deposited, the  bodies had  un-
dergone this  transformation in a  more  or less perfect
manner.   The transformation  was  found  to  be most
complete  in those bodies that were nearest the  centre
of the  pits; and when  they had been buried about
three years, and in these  cases, every part, except  the
bones,  the hair, and the nails, seemed to have lost all
their specific properties, and to have acquired those of
this peculiar substance.*
   We are indebted to Thouretf  for an interesting  de-
tail of  the circumstances that attended this opening of
the burial-ground, and to Fourcroy for a chemical ana-
lysis of the peculiar  substance into  which  the  bodies
were converted.  By subjecting it to the action of  the
appropriate chemical re-agents, he  found  it  to be  a
saponaceous  compound, consisting of ammonia  united
to adipocire, the same substance which is  produced by
the action of nitric acid upon muscle.   When the  adi-
pocire  was freed from the ammonia, and obtained  in a
state of purity, it  was  found very nearly to  resemble
spermaceti, both in  its  physical  and chemical cha-
racters.J

      * See also Home in Phil. Trans, for 1813, p. 149.
      t Journ. de Phys. t. xxxviii. p. 249.
      X Ann. Chim. t. iii. p. 120; t. v. p. 154; t. viii. p. 17. 
              Physical Properties of Muscle.         125

  It was afterwards found that this conversion of mus-
cular flesh into adipocire might be produced  by other
means besides that of  inhumation ; mere immersion in
cold water, especially  in a slow running stream,  com-
pletes the  operation  much  more speedily  than the
spontaneous decomposition which was carried  on in the
burial-ground at Paris; and the action of diluted nitric
acid is still more rapid;  but  in this case a portion  of
the acid adheres to the adipocire, of which  it is very
difficult entirely to deprive it.*  On account of its re-
semblance to spermaceti it was  proposed to establish
a manufacture of adipocire, from the carcases of such
animals as were not proper for food; and  attempts  of
this kind have been actually made, both  in this country
and  in  France, but in both cases without success, in
consequence, as it appears, of the difficulty of entirely
removing from the adipocire  its unpleasant smell and
dingy colour.   From observing what takes place, when
the conversion of  muscle into adipocire  is  effected  by
means of diluted nitric acid, we may conclude that this
substance  differs  from  the  muscular  fibre, in  con-
taining less carbon and azote  and more hydrogen and
oxygen.

             § '3.   Properties  of Muscle.

   I now come, in  the third place, to give an account of
the properties of  the  muscular fibre, and these I shall
arrange  under the heads  of  physical and vital;  the
first comprehending those  which are connected  with
its mechanical form, its  structure, and its  obvious ex-
ternal characters;  the second comprising its  powers as
forming part of a  living organized body.   With respect
to the first class of properties, those which I  have de-
nominated physical, there is some difficulty in precise-

  * See Gibbes, in Phil. Trans, for 1794, p. 169; and for 1795,
p. 239. 
126          Physical Properties of Muscle.
 )y ascertaining their nature, in consequence of the closo
 attachment which there is between the muscular fibre
 and the membranous matter,  so as to render it  impos-
 sible to separate one from the other without  altering,
 or rather entirely destroying, its  texture.  It  seems,
 however,  reasonable  to conclude that the  muscular
 fibre possesses all the  properties that belong  to mem-
 brane, although  not in the same degree.   The  muscu-
 lar fibre is cohesive, but much less so than membrane,
 while its  flexibility is perhaps  greater; it  is  highly
 extensible,  and  perhaps elastic.   Its  extensibility is
 probably equal to that of membrane;  indeed, in most
 instances,  they are  brought  into  action  at  the same
 time, and must necessarily exist in the same degree, as
 the two substances are so intimately connected together;
 but I am not  acquainted with  any experiments that
 have been expressly made upon this point.  There is
 a considerable difference between the  extensibility  of
 the proper muscles and that of the muscular coats; the
 former are much limited in this respect by their local
 position, and  their  connexion with the  neighbouring
 parts, while the muscular coats, from  their structure,
 possess almost an  indefinite power in this respect, and
 frequently exhibit very remarkable  instances  of  it.
 The change in the size of the uterus, the stomach.
 and the bladder,  from  their most contracted  to their
 most  extended states, is well known to every one; and
 although, in these cases, it is  not certain in  what de-
 gree the membrane and the muscular fibre individual-
 ly partake in  these changes, yet  it is reasonable  to
 conclude  that  it  belongs to them both nearly  in an
 equal degree.
  There  is considerably more  doubt  respecting the
 elasticity of the muscular fibre; for although  the pro-
 per muscles, and  still more the muscular coats, exhibit
decisive marks of elasticity, yet here it is impossible to
sav  how much  of this belongs  exclusively to the fibre,
and how much it  has in common with  the membrane. 
Vital Properties.—
Contractility.
127
The soft and yielding nature of the fibre, when detach-
ed from the membrane, would not indicate any great
degree of elasticity •*  and as Soemmering remarks,t the
almost total  absence of this property in the fibre after
death  would lead us to the same conclusion, yet there
are some  phenomena which render  it probable that
the fibre is possessed of this quality in a certain degree.J
To the elastic nature  of the muscles generally, as con-
sisting of a compound of fibre and membrane, I should
refer the natural contraction of Whytt ;§ those actions
which Cullen, and  many physiologists since  his  time,
have  called  tone, or  tonicity,  and  which Bichat has
classed  under  the  head of contractility from texture,
in which, after a part has been distended by any cause,
when the  distending force is withdrawn,  it  gradually
recovers  its natural  form and  dimensions.   But  this
point will be considered more fully hereafter.
  But all these physical properties of muscle are little
worthy of our attention, compared to its vital proper-
ties, or  those  which  it possesses as  forming a part  of
a living organized body, giving  rise to a class of pheno-
mena, which we consider as essentially connected with
life, and the cessation  of which indicate that its  com-
plete extinction has taken place.  Of these properties,
by  far the most important and interesting, if not the
only one, is that which has been styled by many modern
physiologists irritability, but to  which 1 have preferred
giving the name of contractility.   It  may be defined,
that power which the muscular fibre possesses of dimi-
nishing  its  length,  or  of  contracting  and shortening
itself.   From  a very  extensive range  of facts and ana-

  * See Carlisle, in Phil.  Trans, for 1805, p. 3.
  t Hum. Corp. Fabrica, t. iii. § 5.
  + The crassamentum of the blood, when obtained in  a fibrous
state, is in some degree elastic ; but although it agrees with the
muscular  fibre in its chemical properties, it probably differs in it*
mechanical organization.
  § Essay on Vital and Invol. Motions, sect. 1, § 3. 
 128            On the term Contractility.

 logics we  conclude that this  power is never exercised
 without the agency of some direct independent cause,
 to  which  the  name  of stimulant  has been applied;
 and we arrive at this conclusion, not merely from the
 general principle, that every effect in nature must have
 its  appropriate cause, or that every event is preceded
 by some other event, which stands to it in the relation
 of a cause, but from  actually  observing, that when we
 see muscular contraction take  place, and have an oppor-
 tunity of examining all the previous circumstances, we
 can  assign the exact  event which has  produced the
 contraction.  It  must,  however, be  admitted,  on the
 other hand, that the  stimulants,  or the causes  of con-
 traction, are as  different  as  possible from  each other
 in their nature ;  and  in  fact,  as  far as  we can judge,
 have not any single property  in  common, except  that
 now under consideration, of producing the  contraction
 of the muscular  fibre.
  Since the time of Haller, who had the merit of first
 clearly comprehending the nature and extent  of this
 property, and strictly  pointing out its effects, the term
 irritability has been  generally applied to  it.*   Thi6
 word was,  I believe, first used in  physiology by Glisson,
 an  ingenious English  anatomist,  who  lived  about the
end of the seventeenth century, and who entertained
 some opinions on the subject of muscular action,  that
 were to a certain extent correct, and were a consider-
 able advance upon the knowledge of his predecessors/!"
 Although I feel a great objection to alter the language
 of science  unnecessarily, yet,  in the present  instance, a
 necessity for  the  proposed change exists.   In the first
 place,  irritability is a term employed  both  in  physio-
logy, in pathology, and in ethics,  and in each of these

  *  Mem. sur la Nature Sens, et Irrit. des Parties du Corps Ani
 mal, mem. 1, sect. 2.
  t See particularly his treatise, "  De Ventriculo," c. v. in Man
 geti Biol. Anat. t. i. p. 80, et seq. 
Reasons for the term.
129
sciences in a different  sense.  In  physiology it simply
designates a certain faculty in  the muscular fibre ; in
pathology it signifies a peculiar condition of the vital
powers  generally,  and of  their  relation  to  external
agents ;  and in ethics it expresses  a certain state of  the
temper  and feelings.   Then  with respect  to  physio-
logy alone irritability is objectionable, because it was
employed by  Haller  and  his disciples  to express  a
peculiar  property,  which is necessarily connected with
an hypothesis, not the  mere contractility  of the muscu-
lar fibre, but the  way in which the contraction is pro-
duced, or rather  implying the nature of the cause as
well as the effect; and although I am  disposed to  think
that the hypothesis of Haller is correct, yet it is still
but an hypothesis;  and the influence  of language over
opinion is so great, that it is  always desirable to  avoid
those  phrases  which  may, even  unconsciously,  affect
our judgment  on such topics.  The term contractility
has  the advantage of simply expressing  the fact,  its
use  has been sanctioned by several eminent physiolo-
gists, and although it may be perverted or improperly
applied, it seems  in itself to be unobjectionable.*
   In considering the subject of contractility, it will  be
proper to begin by giving an  account  of  muscular con-
traction, describing its phenomena and direct effects,
then those of the relaxation  of the muscles, and I shall
afterwards make  some remarks  upon stimulants, or the
agents which  act upon the  fibre.   Relaxation is the
natural state of  the muscle,  or that condition which it
affects, when not  acted  upon by  any external cause.
Upon the application of a stimulant its contraction com-
mences ; its  surface,  which  was  before  smooth, now
                                                  «
  * Blumenbach uses it in a different sense, to express the re-action
of the cellular texture, making it synonymous with his vis cellulosa.
Some of the French physiologists employ it in a more general way
to express every motion of any part of the body.  Fournier, Art.
" Contractility," Diet, des Scien. Med., defines it to be the motion
of which all parts of the body are capable except the nerve?
            T7 
 13©    Specific Gravity of Muscles during Contraction.

 becomes furrowed and wrinkled, its belly swells  out
 and  grows hard and firm to the touch,  while the ends
 approximate, and the whole muscle is rendered thicker
 and  shorter.*  This is an account of the general effect
 of contraction, but many questions present themselves
 when  we  minutely  consider  the  operation.  It  has
 been a subject both of theory and experiment, whether
 the specific gravity of a muscle be increased during its
 contraction,  or whether  the  fibres gain  in thickness
 precisely what they lose in length ;t an inquiry which,
 as will be seen  hereafter,  is  not a subject of  mere
 curiosity, but is connected with the theory of contrac-
 tion, or the intimate  nature of the operation  by which
 it is  produced.
  Some experiments were performed by the  older
 anatomists, and especially by Glisson, which seemed to
  rove  that the muscle was altogether diminished in
  ulk during contraction ; and experiments of a similar
 kind have been more lately made by Sir G. Blane and
 Sir A. Carlisle.   Sir G. Blane, however, was led from
 his  results to  conclude  that  the absolute bulk of a
 muscle, and of course its specific gravity, is not changed
 during contraction.   He enclosed a living eel in a glass
 vessel filled with water, the neck of which was drawn
 out into a fine tube ; then  by a wire introduced into
 the vessel  he irritated the tail of the  animal so as to
 produce strong contraction, during which he observed
 that the water in the tube remained stationary.   He
also compared the two sides of a fish, one of which had
 been crimped, and thus brought into  a  state of strong
 contraction, the  other left in its natural condition, and
 he states that he found their specific gravity to be  the
 same.   On the contrary,  when he tried the  effect of
extension on  a vegetable substance, as  caoutchouc, its
specific gravity was diminished by being stretched out,
but it recovered its former density when it contracted.J

  * Haller, EI.  Phys. xi. 2, 17—20.          t Ibid. § 22.
  1 Select Dissert, p. 239—241. 
Is the Blood expelled?
131
  Sir A.  Carlisle tried an experiment upon a man's
arm, analogous to that  of  Sir G. Blane on the  tail of
the eel, but with a different result.  The  arm  was
immersed in a jar of water, with which a barometrical
tube was  connected, and when the muscles were made
to contract strongly, the level of the water was raised
in the tube, showing that  the bulk of the muscles was
increased by contraction,  while  at the same time he
informs us that the specific  gravity  was  increased;
and he states that the  same change  occurs in crimped
fish.*  Probably, however,  experiments  of this  kind
do not admit of a very decisive result, because we may
suppose that while one set  of  muscles  is contracted,
another set is  relaxed, and that besides the  simple
effect of  contraction, there  may be  a  displacement of
parts, or  some  alteration in their arrangement, which
may affect the  bulk of the limb, without there being
any absolute change  in the density of the muscular
fibre itself.t
    It has  likewise been a subject of controversy whe-
ther the  quantity of blood  in muscles be diminished
during their contraction.   Most of  the earlier writers
supposed it to be the case, and this  opinion was adopt-
ed by the Boerhaavians,f but it may be inferred that
they were influenced rather by hypothesis than by ac-
tual observation; for as it was the general opinion that
the muscles were  rendered smaller by contraction,  it
was concluded  that a portion of their blood mustb e
squeezed out.   We are indeed, as a proof of this, told

   * Phil. Trans, for 1805,  p. 22, 23.
   t The experiments of Sir Everard Home, on the increased size
of muscles during contraction, only prove that  their bulk is increas*
 ed in one direction. Lect.  on Comparative Anatomy, p. 33. Mr,
 Herbert Mayo, by employing the heart of a dog, has obviated the
 objections which exist against the experiments of Sir G. Blane and
 Sir A. Carlisle; he finds the bulk to remain precisely the  same
 during the states of contraction and relaxation.  Anat. Comment
 p.  12.
    t Boerhaave, Instit. § 401. 
132
Nature of Contractility.
by Winslow,* and some of the most respectable anato-
mists of his age, that the muscles become paler during
contraction, and again resume their colour when relax-
ed ;  and this was particularly  stated to be the  case
with the heart of the frog, and  that of the chick dur-
ing incubation ; but, as Haller remarks, this effect does
not depend   upon the blood being expelled from  the
substance of  the muscles of the heart, but from the ca-
vity  of the ventricles, the heart  in  these animals being
so transparent  as to permit the colour of  its  contents
to be  perceived externally.!   The  opinion that the
blood is expelled has been more lately adopted by Bi-
chat, but  his reasons for  it do not  appear of  much
weight.  He principally insists  upon  the  well-known
fact, that during the operation of  drawing blood  from
the arm, the flow is increased by contracting the mus-
cles ;J  but the  additional quantity  of blood that is ex-
pelled in  this  case is not derived  from the capillary
vessels dispersed through the fibres, but from the larg-
er venous trunks, which  are pressed upon by the  swel-
ling  out of the bellies of the muscles.   Sir A. Carlisle
also  adopts the same  opinion, but rather upon general
grounds, than  as derived  from any  decisive  experi-
ments ; he only states, in a loose way, that the muscles
become pale during contraction,§ without alleging any
proof of the  fact; and it may be remarked, that  if, as
he supposes, the absolute size of the muscle be increas-
ed  by contraction,  it  does not seem  likely that the
quantity of blood in it will be diminished.
   The nature of muscular contractility, or the relation
which it bears to the other powers of matter, has been
a subject of  long and learned discussion, yet until very
lately it was entirely  misunderstood.  Now, indeed, that
we are become familiar  with the  conception of it, as a

  * Anatomy, sect. 3, art. 1, § 48.       t El. Pbys. xi. 2, 21.
  X Anat. Gen. t. ii. p. 378.
  § Phil. Trans, for 1805, p.  27. 
Confounded with Elasticity.           133
property of a specific  nature, inherent in the muscular
fibre  and peculiar  to it, it seems  scarcely possible to
conceive of any quality  that  possesses more distinct
characters.   Yet, although Glissin, Baglivi, and others,
made  some  approaches to a correct view of the  sub-
ject, it remained involved in much obscurity until the
time  of Haller.   This  great  physiologist,  however,
clearly pointed  out its nature, marked its specific dif-
ferences, and announced  it as being exclusively attach-
ed to  the  muscular  fibre ;  and  what, perhaps, should
be regarded as the most  important of all his numerous
discoveries, and  the one  which had the greatest effect
in promoting our knowledge of  the animal ceconomy,
he showed in what respects the phenomena of muscu-
lar contractility differ from those of nervous sensibility,
and  referred them  respectively to their  appropriate
causes.*  Even the  most learned and judicious of his
immediate  predecessors  or  contemporaries, as  Hoff-
mann, Boerhaave, and Cullen,  were not  sufficiently
aware  of  this distinction, and perpetually  confounded
their effects.!   But what is a still greater, and, as it
now  appears, a  less  pardonable  error,  they had  not
learned to distinguish  between contractility and elasti-
city :  they  referred many of the effects of  the former
to the operations of the  latter; and  also endeavoured
to  account for them entirely upon mechanical  princi-
ples, such  as are alone applicable  to elastic bodies.
Yet  the difference between these two powers is  most
obvious and essential.  Elasticity always depends  upon
simple re-action, and is never  the  source of actual pow-
er ; it merely restores, in a contrary direction, the force
which had been impressed ; and even, when acting to
the greatest advantage, the  effect which it  produces

  * El. Phys. xi. 2, 4, et seq. ; Mem. sur les Part. Sens, et Irrit.
Op. Min. t. i. p. 329.
  t Even the acute and accurate  Bichat has not clearly perceived
the distinction, and to this cause may be  ascribed much of the ob-
scurity and intricacy which we occasionally find in his works 
 134       Difference of Contractility and Elasticity.

 can never be  greater than  the amount of the cause,
 and the re-action can  never  take  place as long as the
 cause  continues  to  be applied.   Thus the force with
 which a steel  spring recoils,  even supposing it to  be a
 perfect elastic, is only equal to that which is required
 to bend it, and as long as the force remains applied, it
 is impossible for  the recoil to take place.*
  But in muscular  contraction we observe a very dif-
 ferent train of events.   The mechanical effect is  infi-
 nitely greater  than  the mechanical cause producing it,
 and indeed bears no physical proportion to it, while at
 the very time  the cause is  applied,  and  is acting
 with all its force, the  re-action  commences and far sur-
 passes the force  of  the agent.f   But what is still  more
 decisive against  the doctrine, that contractility is only
 a modification of elasticity, is, that the most  consider-
able effects of muscular action are  frequently produced
 without any mechanical cause at all, where the  agent
 is of a kind which has no relation to any of the mere
physical properties of matter.   No fact in the whole
range of natural  phenomena occurs more frequently to
 our observation,  yet such is the devoted attachment to
theory  which takes possession of the mind, and so diffi-
cult is  it to shake  off established errors, that all the
mathematical physiologists attempted to explain  mus-
cular  contraction by the laws of mechanical  impulse.
 We can scarcely review, without  a feeling of humilia-
tion, the absurd hypotheses which were  invented  by
the most learned men of the  age, and were  brought
forwards, with all the aid of geometrical demonstration,
 and enforced by  a string  of problems, theorems, corol-

  * J. Hunter appears to have been one  of the first physiologists
who very clearly distinguished elasticity from contractility.  Trea-
 tise on the Blood, p. 105, 106.
  t Fordyce, in Phil. Trans, for 1788, p.  25, observes, that if the
inside of the heart  be  slightly scratched by a needle, it will con-
 tract so strongly as  to  force the point of the needle into its sub-
 stance. 
Relaxation.
135
laries, and lemmas.  To all this learned trifling it  is
sufficient to reply, that a mechanical force, of an indefi-
nite  extent, is frequently produced without the inter-
vention of  any mechanical cause whatever, and  must
therefore be referred to a  principle of a totally differ-
ent nature.
  One of the most remarkable circumstances respect-
ing contractility is,  that in all muscular action, however
powerful  the stimulant be that is  applied, still  after
some time the  effect ceases, and the muscle becomes
relaxed.*   And this succession of alternation after con-
traction occurs,  even although the stimulus continues to
be  applied.   This we perpetually observe in all our
experiments upon  muscles, with either mechanical  or
chemical substances;  it likewise takes place in all the
natural operations  of the system, and is to be  observ-
ed, in a very remarkable degree, in the muscles  that
are under the control of the will.   In performing any
voluntary action, where the mental energy continues to
be exercised with equal, or even with greater power,
although  our very  existence immediately depended up-
on it, we  find ourselves unable to persevere in the ac-
tion  beyond  a  certain length of time.  The  muscles
that  have  been contracted become, what is  termed,
exhausted,! and a certain period is necessary to elapse
before they are again capable of being stimulated  or
excited into action.  In a majority of instances we may
observe a degree of correspondence between the sub-
sequent exhaustion and  the previous stimulation, but

   * Cullen's Instit. § 108.
   t The term exhausted is here employed as the one in common
use, without any reference to the hypothesis from which it origi-
nated, because a word did not occur which might convey a more
simple expression  of the fact.  On this subject the reader may  pe-
ruse with advantage Dr. Park's remarks in the Quart. Journ. v. ii
p. 228. 
 136              Replacements of Parts.

 many causes interfere to  prevent  these two  circum-
 stances from bearing an exact ratio to each other.*
   The phenomena  which  attend  upon the relaxation
 of a  muscle are precisely the  reverse  of those  of its
 contraction:  the belly  becomes  soft, its  swelling sub-
 sides, and  the  wrinkles  disappear  from  its  surface ;
 the force of  contraction  no longer existing, the ends,
 not being drawn together,  recede, and the whole re-
 sumes its  natural state.   Relaxation is generally conr
 ceived to be  merely a passive effect,  and to consist sim-
 ply in the absence of contraction, but when parts have
 been displaced by contraction there  is a  necessity for
 some absolute  power to  brin^ them  back to their  for-
 me** situation.  This power is,  in most cases,  that of
 tho antagonist muscles.  The  muscular system is so ar-
 ranged that,  in most parts  of  the body, one muscle or
 set of muscles  has another  muscle  or set of muscles
 which act in  precisely  a contrary direction, and is in-
 tended to  produce precisely  the  opposite effect;  one
 muscle draws a part to the right hand, another to the
 left;  one muscle raises it, another  depresses  it,  and
 when either  muscle has been in action, it generally hap-
 pens  that the opposing muscle then  acts and produces
the contrary  effect.   Besides  the  antagonist  muscles,
another counteracting force, which is often useful in re-
 placing parts, is elasticity.   Muscles are frequently so
situated that  when they contract  they move someelas-

  * It may, I think, be questioned, whether exhaustion ever takes
place in cases of simple contractility, or whether it be not confined
to those, in which the sensibility of the nerves has been called into
 action.  We are indebted to Dr.  Wollaston for  an interesting  ob-
servation, which renders it probable that the state of exhaustion,
 or rather the alternation of contraction and relaxation,  is much
more rapidly produced than is commonly supposed.  He founds his
opinion upon a peculiar vibratory sound which is perceived when
 the finger is inserted into the ear with a moderate degree of force.
 This acute philosopher conceives that,  in this case, the voluntary
 effort, although apparently continuous, " consists in reality of a
great  number  of  contractions repeated at extremely short inter-
 vals."  Phil. Trans, for  1810, p. i'. 
Bichat's  Opinion.
137
tic  membranous  body, or not unfrequently a quantity
of elastic  membranous matter enters into their  own
composition, which, when the fibres relax, re-acts and
restores the parts to its natural position.  Examples of
this kind occur ii» the muscles about the thorax and the
larynx, where the muscles  are connected  with carti-
lages, which are  compressed or distended according to
circumstances, and which immediately re-act when the
contraction ceases.  A third  means by which muscles
are replaced after contraction is the force of gravity :
it not unfrequently happens  that the action of a  mus-
cle  has the effect of raising  up some part and sustain-
ing it without support, and of course, when the muscu-
lar  contraction ceases,  the  part falls down by its own
weight.  This frequently occurs in the motions of the
extremities.  The hollow  muscles  and  the muscular
coats are  excited to contract by some substance which
distends their cavities; the act  of contraction, by dis-
charging  the  distending substance, removes  the excit-
ing cause, and relaxation naturally ensues.
   But although relaxation  has  generally been  consi-
dered as simply  a passive state, in  which  the muscle
merely ceases to act, and where it  is brought into  its
ordinary condition by other agents,  the  contrary doc-
trine has  been  occasionally maintained; and as it has
found a supporter in Bichat, it may  be necessary to no-
tice it.  He conceives that relaxation is in part at least
an active  effect, and that it consists  in something more
than the mere cessation of contraction.   He founds his
opinion,  as it appears  to  me, upon very insufficient
grounds of reasoning; the only fact  which he adduces
is, that if the heart   be grasped  during  its diastole, it
may be felt to press  with considerable force upon the
hand.*  But this is too vague an experiment on which
to build an opinion of so much consequence. The heart
is a remarkably  complicated organ  with  regard to its
  * Anat. Gen. t. ii. p. 468.
18 
138
Nature of Stimulants.
mechanism, and as we  shall afterwards find, when we
come to treat upon its motions, there are many circum-
stances respecting it which require  to be taken into
consideration.
   I have  already remarked  upon  the  multifarious na-
ture  of stimulants,  as they  have  been called, those
agents which possess the specific power of exciting the
muscular fibre to contraction.   It  has been  asserted,
and is indeed literally  true, that  every body  in exist-
ence is a stimulant  to  the  muscular fibre, because,  in-
dependently of  any other  quality,  the  mere contact of
a material substance  produces this effect.  Stimulants
have  been arranged in various ways,* but perhaps the
most  convenient and comprehensive is into  the three
heads of mechanical, chemical, and what we may term
vital.    Mechanical  impulse of all kinds, beginning with
the slightest touch  that is  capable  of  being perceived,
and proceeding to a degree of  violence  short of that
which absolutely destroys  the texture of the  part, are
of the first class; a great variety of chemical substan-
ces that have few properties in  common, as alcohol,
acids, alkalies, metallic salts, and many vegetable acrids,
are of the second class; while  in the third  we may
place those agents that seem  to operate  immediately
upon  the vital powers without producing any apparent
physical change in  the part,  as the electric fluid, and
particularly that  modification  of it  which constitutes
galvanism.  Independent  of any external agents, the
muscles are thrown into the  strongest contractions by
a variety  of nervous affections which  arise from inter-
nal causes, and above all from the  act of volition.  By
a process  which will probably always remain inexplica-

  * See Smith, de Mot. Mus. p. 32.  Blumenbach, § 52, divides
them into chemical, mechanical, and  mental;  Blane into internal
and external, arranging them according to the situation where they
are applied rather than the mode  of their action.  Select Diss.
p. 245. 
Specific Stimulants.
139
ble, we no sooner will the motion of any muscle than
it obeys the summons with promptness and  accuracy.
  It is a remarkable circumstance connected with  the
effect of stimulants upon the  muscular fibre,  that par-
ticular sets of fibres are specifically acted upon by par-
ticular stimulants, and this without any difference that
we can discover in  the fibre itself, or any thing in the
nature of the stimulant which could  enable  us to pre-
dict the result.   Thus certain substances taken into the
stomach produce the healthy action of this organ, and
cause its fibres to exercise their vermicular motion, so
as in due time to propel its contents into the intestines,
while others instantly excite  the  violent action of vo-
miting.  Substances which have  passed through  the
stomach without producing  any particular effect  upon
its fibres,  when  they  arrive at  the  intestines, throw
 these  organs  into  strong  contractions.   In  the same
 way the urine acts specifically  upon  the bladder, cer-
 tain sapid substances upon  the salivary  glands, and in
 short  there  is scarcely one among the muscular coats,
 or among the system of  muscular  fibres, that contri-
 bute to the  production of the organic  functions, which
 have not some  specific or characteristic property  of
 this kind.  In the proper  muscles, those which  serve
 for motion, the effect  of  stimulants is more uniform,
 and may, for the most part, be referred  to the ratio of
 quantity.
   Concerning the specific nature of contractility, it is
 most  remarkable that it should  be called  into action
 by  such a variety  of agents,  and  I know of no method
 of explaining this  singularity.   The effect  of all the
 substances is,  however, the same in kind;  or if there
 should be any  difference in this  respect,  it is in the
 proportionate degree of  their  intensity and their dura-
 tion,  or their subsequent  and  secondary operation on
 the system.   This great variety in the  nature of the
 stimulating agents affords an additional proof of the ab-
 solute impossibility of accounting  for muscular action 
140
"Tonicity.
upon any mechanical principles; for  it not only seems
to be equally affected by the two great powers  of me-
chanic impulse and chemical  attraction, but  by mere
mental impressions, which, as far as we can judge, have
no resemblance to any of the properties of matter.
  Besides contractility, or the proper Hallerian irrita-
bility, the muscular fibre has been supposed to possess
another specific  or peculiar quality, which  has been
called tone or tonicity.  I have already remarked that
Cullen, as well as many of  the  modern physiologists,
have insisted upon this property of muscle; and it  is a
term which is very extensively employed in  pathology,
but in  this case  apparently with  little precision, and
probably without any decided meaning being  attached
to the use of it.  Physiologists have  attempted to  de-
scribe it  more accurately, and it  has been  illustrated
by  the  retraction which a  muscle  exhibits   when  its
fibres are divided transversely, or  by the drawing up
of one side of the face  when the muscles of the other
side have become paralyzed, and by other similar  oc-
currences.  It seems,  therefore,  to  be a contraction
which the muscular fibre exhibits when  not under the
influence  of  any distending force, which takes place
without the intervention of any external stimulant, is
slow in its operation and limited in its extent,  and is not
subject  to the alternations  of relaxation.*  Although,
therefore, both its direct and its ultimate effect  be con-
traction, yet, in every respect, it  differs from the pro-
per contractility which has  been described above, and
I conceive has no connexion with  it.  Such  a power
undoubtedly  exists in  the muscles, but  it  is  by no
means certain whether it ought  to be  referred to the
proper  muscular fibres or  to the  membranous matter
to which they are attached. There are many circum-
stances  which seem to  render  it probable that all the
soft solids of the body are  kept in  a state of moderate
* Fordyce, in Phil. Trans, for 1788, p. 30, et seq, 
             Different kinds of Contractility.          HI

distention, and that when this distention  is removed,
the parts slowly contract, but in a manner which more
resembles the re-action of an elastic body than the con-
traction of the muscular fibre, and  I should therefore
refer it either to the elasticity of the membranous mat-
ter, or to that of the  muscular  fibre itself, and not in
any  degree  to  its  proper   contractility,  to  which  it
seems to have no analogy.   Haller accurately discrimi-
nates the power  of  contraction,  which  the  muscular
fibres possess in  common with  all  other  matter,  and
which he calls the general   contractile  power or  the
dead force, from  its  proper  irritability, as differing both
in its seat, its mode of action, and  its  effects.*  This
general contractile power or dead force  seems evident-
ly to be the  operation of elasticity, and I conceive that
there is nothing in the phenomena that have  been as-
cribed to tonicity, which may not be  referred to  the
same power.
   Among  the different modifications of  contractility
which are  pointed out by Bichat. I regard that which
he styles contractility  from  structure in  the same point
of view, as an effect of  elasticity, whether residing  in
the membrane or in the proper fibre, but  as having no
relation to the Hallerian irritability, of  which, indeed,
he appears to be  himself well aware.   I  shall not at
present follow this author through  all his complicated
arrangement of the  different species of contractility,  as
the propriety of his divisions depends very much upon
his general  views concerning the nature of life, which
will  be better understood when we are further advanc-
ed in our subject.
   Besides  the specific  property of irritability,  many
physiologists ascribe  to  the  muscular fibre a degree  of
sensation, and even  Haller himself, to   whom so much
merit is due for  the sagacity with  which he has dis-
criminated between the powers of the muscles and the
* El. Phys. xi. 2, 1—3. 
142
Sensibility of Muscles.
nerves, employs expressions from which it might be
conceived  that he considers the vis nervea as an actual
property of the muscular fibre itself,  as well as its  irri-
tability, or vis incita, as he styles it.*    The vis nervea
of Haller is that power in the  muscular fibre which
enables it to receive impressions conveyed to it by the
nerves, but this supposed vis  nervea ought not to be
regarded as a function of its contractility, for in fact it
is nothing more than  the power  which  the fibre  pos-
sesses  of receiving the impressions that are made upon
it, so as to cause it to contract,  the  impressions  that
are conveyed to it by the nerves being only one among
the other  stimulants  which produce its contractions.
Bichat supposes  that the muscular fibre possesses  pro-
per  and inherent sensibility, but the  muscular sensibi-
lity differs from the vis  nervea  of Haller, as Bichat
ascribes to muscles an actual  degree of  feeling which
does not seem  to differ essentially from the sensibility
residing in the  nerves.   The  doctrine which  was so
warmly contended for  by the antagonists of Haller,
and  which may,  perhaps, be  regarded  as the  most
popular at the  present time, is in its  essence precisely
the  reverse of this  opinion, although they  are  fre-
quently confounded together.  According  to the neu-
rologists, as they have been termed, where a stimulant
acts  upon the muscular fibre,  the  immediate  action is
not upon the fibre itself, but always,  in  the  first in-
stance, upon the nervous filaments connected  with it;
but the further discussion of this  question, as well as
the nature of sensibility itself,  and the distinction  be-
tween this power and  contractility,  must be  referred
to the  chapter  on the nervous system.
  I must remark  in this place,  although the subject
will be more fully considered  hereafter,  that muscular
contractility is much influenced by  many of those facul-
ties or functions which seem to be  intermediate   be-
*E1. Phys. xi. 2, 15. 
Use of Muscles.                 14S
tween the corporeal  and mental  parts of our frame.
Thus the power of volition is exercised most conspicu-
ously in every  thing which is connected with muscular
contractility, and indeed is the grand theatre on which
its effects are manifested. The operations of habit and
of sympathy are also sufficiently obvious, and in many
cases, as I shall afterwards have occasion to point out,
these effects appear to be the result of the immediate
action of the muscular fibre itself,  independently of the
intervention of the nervous influence.

                § 4.  Use of Muscles.

   Having given an account of  the form  and structure
of muscles,  of their  chemical composition  and their
properties,  I now proceed to consider  their uses.  The
general  use of the  muscles is sufficiently obvious; they
are  the  grand  organs of motion, both of that by  which
the  body is moved from place to  place, constituting
loco-motion; that by which  each  of its separate parts
is moved, when we act upon the contiguous bodies in
our  intercourse with  the external world; and that by
which many of the various minute actions are perform-
ed,  which are  essential to the exercise of the vital func-
tions.  In short  muscular motion  seems to be concern-
ed in almost every operation that is  produced, either
by the system at large or by its individual parts.  All
 these effects are brought about  by the simple act of
 contraction, or that by which the fibres  shorten them-
 selves,  and by approximating  the ends of the mus-
 cles, draw  together  the  parts to which the ends are
 attached.  Nor is  the operation of  the muscular coats
 less important than that of the proper  muscles, although
 it is less obvious to the eye. Here the fibres, not being
 collected together into large  masses, which act simul-
 taneously,  the result of their contraction  is not the
 movement of  any  particular part,  but  they  act, as it
 were, fibre by fibre, producing in the organ to which 
144
Is all Spontaneous Motion contractile ?
they are attached a peculiar kind of undulatory, or, as
it has been termed,  vermicular motion, from its resem-
blance to the crawling of the  worm,  which serves to
keep their contents in a slate of perpetual  agitation, to
mix  them intimately together, and ultimately to  pro-
duce their expulsion.
  The particular operation of the muscular coats  will
be more fully  explained  when we come to that  part
of our subject which treats of those functions that de-
pend immediately  upon  their action ; but before we
quit  this subject it  will be necessary  to inquire into  a
point, which has often  been discussed, whether all the
spontaneous motions that are observed in the body are
to be referred to contractility,  under one  or other of
its species? We know that both elasticity and gravity
are the cause of motion in the  body, but they  are suf-
ficiently  distinct from contractility ;  the  question is,
therefore,  whether motions  which do  not appear to
depend upon any of the  usual physical powers of  mat-
ter are all  to be referred  to contractility ? The  diffi-
culty which exists in this case is, that there are certain
very obvious motions of particular parts, where no  mus-
cular fibres have been detected, and yet where the
quantity of motion and the size of the part is  so consi-
derable, that we might have  supposed that the  fibre
would have possessed  a sensible  magnitude.   One of
the most remarkable examples of this kind, and what
has generally been  adduced as that by which the con-
troversy must be ultimately  decided, is  the  Iris. In
this  part, which is not very minute, and in which the
motions  are very rapid and considerably extensive, no
muscular fibres have been  detected;  for  although
many  eminent  anatomists and  physiologists  have, at
different times, announced their existence, the latest
and  best observations appear to decide in the negative.
How, therefore, is the iris moved ?  There is nothing
in its action analogous to elasticity, and nothing which
can  arise from the  force of gravity.  Blumenbach has 
Muscularity of the Iris.
145
attempted to solve  this difficulty by saying  that the
iris and some other parts, which  are in the same pre-
dicament,  possess a  peculiar  power, which he  calls
their vita propria, and that  this  is the cause of their
contraction.*  But when we come to consider this hy-
pothesis, it  will appear to be merely a form of speech
which throws no light upon the  phenomena or upon
their cause, and does not  tend to generalize analogous
facts, but which forms a part of that system of obscure
causes which is too often had recourse to by physiolo-
gists, when  they  are at  a loss for  a rational explana-
tion.   Nothing, however, can be  more injurious to the
progress of science than  this  method  of substituting
new words for  new  ideas, and of advancing hypothe-
ses which,  when we come to examine into their real
foundation, must be regarded as merely verbal.  I have
no hesitation in confessing that there are many parts of
physiology which  are yet unexplained, and the motions
of the  iris  I conceive to  be one  of these.!  Upon the
whole, however, when we perceive any motions which
seem, in all respects, to agree with  those which are the
evident result of  muscular contraction,  it  may  not  be
unreasonable to conjecture that they depend upon the
same cause,  even although  we are not  able to detect
the apparatus by  which they are produced.

   * Inst. Phys. § 42 and 273.
   t  Since the above  was written the  question respecting the mus-
 cular fibres of the iris is decided in the affirmative by the microsco-
 pical observations of the  accurate and indefatigable Mr Bauer;
 Phil. Trans,  for 1822, p. 78.  See also the still later observations
 of Mr. Jacob, Med. Chir. Trans, v. xii p.  514.  I may remark that
 his exquisitely beautiful engravings do not appear  on all points
 quite to correspond with the magnified figures of Mr. Bauer. Ber-
 zelius also informs us that the  iris has all  the chemical characters
 of muscle ;  View of Animal Chemistry, p.  86.  Another considera-
 tion which  might be  alone sufficient to prove the muscularity of
 the iris, is deduced  from the fact, that in certain individuals  the
 motion  of this part  is under the control  of the will; we are in-
 formed by Dr. Roget that tbis is the case with his eye. Travers's
 Synopsis of the Diseases of the Eye, p. 72.
                19 
146             Mechanism of Muscles.
             J 5.  Mechanism of Muscles.

   In considering the  mechanism of muscles, we must
 bear in mind that  their action consists essentially in the
 approximation  of  their extremities, in consequence  of
 the shortening  of  their fibres, and  that the immediate
 effect  of this is to move  any body to which the ends
 are  attached.  It, however,  generally  happens  that
 one  of the ends is connected with some  fixed point,
 while the other is much more moveable, and of course
 the bone or other solid body which is attached to it is
 moved in  the same manner.  In order to promote the
 symmetry  of form and the facility of motion,  we find
 that, in many cases, the flesh of the muscle itself is not
 inserted into the  body which is to be  moved, one or
 both of the ends terminating in membrane, which, ac-
 cording to  the situation or use of  the  part, is either
 condensed  into a strong cord, constituting a tendon, or
 spread out into a membranous expansion.
   Although a \ery slight  knowledge of the structure
 and functions of the body  would render it obvious that
 the  muscles are the great instruments of its motions,
 yet no accurate conception of the mode in which they
 operate seems  to  have been entertained  before the
 publication of Borelli's celebrated work on animal mo-
 tion.*  This  writer very ingeniously referred  the  ac-
 tions of the muscles upon the bones and solid parts, to
 the effect  of a mechanical  power acting upon a lever.
 He reduced his doctrine to a  mathematical form, pur-
sued his idea through all the organs of the body, and
clearly explained the mode in which every individual
action  is produced, in a most elaborate and minute de-
 tail.!  Winslow may also be  mentioned  as among the

  * De Motu Animalium.
  t Although Borelli has been generally supposed to have  esta-
blished his theory  of the mechanism of muscular motion, it may be 
             Illustration of Muscular Motion.          I AT

first of  those who presented  a clear and correct  idea
of the  subject, which, although posterior  to  that  of
Borelli, may, in some respects, be considered as deserv-
ing of  even more commendation, because it  has the
merit of not being clogged with any fanciful hypothe-
sis, which  is  unfortunately the case with that of the
former  writer.
   The  fixed points  of the body, from  which  motion
commences, or against which the muscles re-act when
they begin their contractions, are generally the bones,
and the motions  are  performed by the intervention of
joints.   Considering the bones, therefore, as being act-
ed upon by the muscles after the manner of levers, the
part where the  muscle or tendon is inserted into the
bone will represent the power, the joint the fulcrum,
and the part that is moved  constitutes  the  weight.
Writers on mechanics have divided levers into three
kinds, according  to the relative position of  their three
essential parts;  the  weight, the  power, and  the ful-
crum.   Those of the  first kind have the fulcrum in the
centre ; in those of  the second kind the weight  is in
the centre;  while in the third the power is in the cen-
tre ; the bones are of this last description, in which the
power is placed  between the fulcrum and  the weight.
The motion of the fore-arm may be taken as an exam-
ple of the effect of muscular contraction and the man-
ner in which it is produced.  When we wish to raise a
weight by bending  the elbow joint, it  is  effected  by
muscles situated below the shoulder, which have ten-
dons inserted into the top of the  bone of the -fore-arm

proper to remark that it  has been called in question by Barthez.
See Art. " Barthez" in Suppl. to Encyc. Brit.; also Journ. de Phys.
t.  xlvii. p. 271. 
148
Loss of Power.
near the  elbow.*   Let A B represent  the fore-arm,
     A

     0
G
  B D the  shoulder-bone, D the muscle, E the  tendon,
  C the insertion of the tendon into the  fore-arm, and B
  the elbow-joint.  The  contraction of the muscle tends
  to approach C to D,  which, as D is a fixed point, is ef-
  fected by bending the joint B, raising up the point C,
  and consequently any weight G which  may be attach-
  ed to it.   The consideration of  the manner in which
  the muscle  acts in this case, proves that the mechanism
  of the animal body is calculated to produce a great loss
  of absolute  power.   It is an established position in me-
  chanics,  that in  the action of  levers, the power is to
  the weight  as the distance between the weight  and the
  fulcrum is to the distance between the power  and the
  fulcrum.  In the present case,  therefore, the power of
/ the muscle  is to the effect produced by it as A B is to
  C B ; and supposing C B to be  one-twentieth  of  the
  length of A B, one-twentieth only of the power of the
  muscle is exerted in raising the weight, the  rest is ex-
  pended in acting against the disadvantage of the posi-
  tion.   We  shall, however, find it to be a general fact,
  or, as it is termed, a law of the animal ceconomy, that
  muscular power is  always sacrificed to convenience.
  Had the object been to raise the weight with the least
  possible  power, the muscle  would have been placed on
  the.fore-arm, and the  tendon  inserted into the lower
  part  of the shoulder-bone, but in this case the awk-
  wardness of the  limb would  have much  more  than
  counterbalanced  the supposed advantage  of the saving
  of  muscular power.   The remark applies with  still
  greater  force  to the  fingers.   At  present they  are

       * Winslow, sect. 3. art. 5; and Mem. Acad, for 1720. 
                   Velocity gained.                149

moved by the contraction of muscles placed on the fore-
arm, and are connected to them by long delicate ten-
dons which pass over the wrist and hand.  But if  this
order had been  reversed, and the flesh of the muscle
had  been placed on the  fingers, the hand would have
been almost useless from its clumsy form.
   Another important advantage which arises from the
present construction of the muscles, as consisting of le-
vers, where the power is situated near the fulcrum is,
that we acquire a great degree of velocity.  Let W P F
represent the bone of the fore-arm, in which W is the
weight, P the power, and F the fulcrum.  Let us sup-
pose that the elbow-joint is  moved so as to bring the
fore-arm into the position A B F.  From the centre F
draw the arcs A W and  B  P, and  it will appear, that
while the power is passing through the small arc B P,
the weight is describing the large arc A W.   Now the
arcs are"5to each other as the radii W F and P F, and
the arcs are  passed over in the  same time, the veloci-
ties will therefore be as the lines  W F and P F, or in
this case as 20 to I.  Paley judiciously remarks that
there  are  many more cases  in which it is  useful to
raise a small weight rapidly than a large one slowly.*
   Besides  the loss of power which is occasioned by the
nature of the lever,  in consequence of the power being
applied nearer the fulcrum than the  weight;  there are
other circumstances in the  construction  of muscles
which  produce the  same  effect, by which there is  a
* Natural Theology. 
    /

150   Loss of Power from Oblique Position of Muscles.

very considerable expenditure of absolute power; but
in this, as in the former case, this loss of power  is al-
ways attended with some very obvious advantage.  Most
of the  muscular fibres are so placed as to act  oblique-
ly, and it was well known that by this arrangement a
quantity  of  power is  lost, in proportion to  the degree
in which the direction of the fibres differs from that of
the moving  body.   But what  we in this case lose in
power  we gain in the saving of the quantity of con-
traction.   Let A and  C be two fixed points, and let B
be some moveable point, which is to be brought down
to D.   If it were done  by a straight  line, passing  in a
perpendicular direction  B C, it would  be necessary that
the fibre should contract  equal to half its length,  sup-
posing B D to be equal  to DC ; whereas the same ef-
fect  will be brought  about by the oblique  line A B,
contracting through the space E B  only, which is  evi-
dently a less  proportion  of its length, E B  being  less
than A F by E F.  It is  obvious that  the  antagonist
muscles will be less stretched, that  there will be a less
displacement  of parts, a less degree  of pressure upon
the vessels  and nerves,  and  that less  distention  and
straining of  the membranous matter will  ensue, the
smaller is the degree of contraction of the fibres,  and
the less alteration the muscle consequently experiences
in its general  form.   In pursuance of the same princi-
ple we may remark that the extent of action in a mus-
cle  is necessarily in  proportion to  the length  of  the
fibre, for it is obvious that a long fibre will have to di- 
From Composition of Forces.           151
minish in a less proportion than a shorter one to pro-
duce the same degree  of absolute contraction.*
  A third  source of loss of  power depends upon the
situation of the muscles with respect to each other, an
action being seldom performed without the concurrence
of two or  more  muscles  to  the same effect.   In this
case,  not only the fibres must act in an oblique  direc- \
tion, but the action of each of the muscles must, in some
measure, oppose  each  other.  Here is a loss of power
from  what is styled by mechanicians the  composition
of forces,  but, as in all the former instances, the pre-
sent construction is attended with many important ad-
vantages.  When two or more muscles act upon the
same point, the effect  will be to draw  the  body in  the
diagonal ;  and  we consequently have it in our power
to alter the direction of the motion with  great  ease
and accuracy,  by throwing, at pleasure, a little more
or  less energy into one or other of the  muscles,  and
drawing the body into any of the intermediate  posi-
tions.   Thus  a  great variety of motions may be pro-
duced by two muscles only, and the body is less liable
to feel fatigued in any one part by the exertion being,
as  it were, diffused through a larger space, and a less
quantity of it being required at each single point.
   A  fourth circumstance connected with the  mechani-
cal construction  of  muscles, which proves a source of
 the loss of power is, that the tendon is  generally in-
 serted into the  bone  at an acute angle, whereas, in or-
 der  that the power should  have operated to the most
 advantage, it ought to have  acted upon the lever in a
 perpendicular direction.   Upon the  same principle,
 power is also lost by  having the muscular fibres insert-
 ed  obliquely into the tendons; but although power is
 thus sacrificed,  it is obvious that the present  arrange-
 ment is much more commodious; and indeed, in many
 cases it would have been impossible for the muscles to
• Winslow's Anat. sect. 3, art. 1, § 51. 
152
Saving of Power.
have acted perpendicularly upon the bones, or to have
been differently inserted into the tendons without a to-
tal change in the form and arrangement of all  the body.
  A fifth cause by which  muscular power is lost arises
from the  circumstance of the two ends of  the muscle
pulling against each other.  This is obviously the case
where  both ends are  moveable, and where one end is
fixed, as much force is expended on  this  as  on  the
moveable extremity, and before this latter can produce
any effect, it must counteract the resistance offered by
the former, and in this case exactly half its mechanical
power  is lost  before the motion commences.   Besides
what have  been mentioned, physiologists have  pointed
out other circumstances which, in like manner, cause a
ldss of  absolute power, but where this loss either ne-
cessarily arises from  the nature of muscular  contrac-
tion, is essentially connected with the form of the body,
or is compensated by some obvious advantage.
  Amidst so many examples, where muscular power is
expended for the purpose of producing some important
benefit to the  system, there are a few instances of a
contrary kind, where the parts  are  evidently formed
for  the purpose  of assisting muscular  action.  The
heads of the bones into which the tendons are insert-
ed, not  unfrequently swell out into a rounded  projec-
tion, by which means the muscles act upon the  bone at
a less oblique angle, and this we observe to take place
more particularly  in  those cases where the greatest
exertion of muscular power  is required, as in the  mus-
cles of the trunk and the lower extremities.   For the
same purpose  some bones are provided with processes
of considerable length, which seem to be solely intend-
ed for the insertion of  muscles, and the same  appears
to be the principal object of the small detached bones,
which are occasionally found near the joints, as the pa-
tella and the sesamoid  bones.   These,  however, can
only be regarded as exceptions to the general rule, and
in all cases we  perceive the operation  of the principle 
            Contactility a specific Property.          153

which  was  stated above, that the quantity of  power
employed appears to have been no object in the con-
struction of  the body, but that it is always sacrificed,
without any reserve, either to general convenience, to
the symmetry of the form, to the gaining of velocity,
or to the savins: of the extent  of contraction.   The ad-
vantages which arise from the velocity of our  move-
ments, from the facility with  which we can alter their
direction, and  from the connexion of the muscles to the
moving points, by means of tendons, which, like ropes,
serve  to convey the force from  the point where it is
actually generated,  to  the part where it  is wanted to
be employed,  are so obvious  as  to require no  further
illustration.  It is not,  however, so evident what is the
advantage  to  be gained by the  saving of contraction,
yet so much attention appears to have been bestowed
upon this point, that we  must suppose there  to have
been some urgent reason for it.  As the intimate nature
of muscular contraction is itself unknown, it is scarcely
to be expected that  we should be able to give a satis-
factory solution  of this difficulty  ; for it does not obvi-
ously depend,  like the  former circumstances, upon any
general  principles of  mechanics, but upon something
specific in the nature of muscular contraction.  I shall,
however, hazard a conjecture upon the subject, after
premising that it is merely to  be regarded as such, and
must therefore be maintained  no longer than it appears
to be countenanced by the phenomena, or serves satis-
factorily to  explain  them, without violating any esta-
blished principle or well-ascertained facts.
   The only conception that we  can form of the con-
traction of the muscular fibre  is, that it consists in the
approximation of the  individual  parts of which it con-
sists, whether it be  of the whole fibre, or of some of
its  constituents, which give it its  specific  properties.
This attraction does not seem to bear any resemblance
to the attraction of gravity, or to that of chemical affi-
nity, the  one  operating upon large masses of matter, 
154
Illustration of the Process.
the other  upon the separate particles  of  which they
are composed.   The contraction  of  the fibre appears
to differ from them  both in its causes and in its pheno-
mena, and  we  may  therefore suppose that it is essen-
tially different in its  general laws and modes of action.
The force  of the  attraction of gravitation increases as
the distances decrease, and  this is probably the  case
with chemical attraction, but it would appear that the
attraction of contractility has not this property,  or at
least that  this  property, if it exist, is counteracted  by
other circumstances.  Of  these  circumstances  one is
sufficiently obvious, the re-action of  the membranous
matter attached to the muscular fibre.   Whether this
be the only cause, or whether there  be others that op-
erate, whether the attraction between  the particles of
the  muscular fibre  increase with the decrease of  dis-
tance, whether it be the  same at all  distances, or whe-
ther it may not even decrease in the direct ratio of the
distances,  are  questions  that it is entirely beyond  our
power to answer.   But this is certain, that as the par-
ticles approximate,  the  membranous  matter  will  be
compressed or  bent out of its ordinary situation,  and
that this compression  will increase as the  distances di-
minish ; that, therefore,  as the degree of contraction
increases, a greater force  will be required to continue
it, and still more to go on augmenting it.
   As an illustration of the nature of  the process, we
may conceive of  two bodies differently electrified so
placed, that when they act upon each  other they may
compress a spiral  spring.   Let them be brought within
the sphere of their mutual attraction, we may suppose
that a certain quantity of electricity will be  necessary
to cause them  to commence their  approach to  each
other, and that  as they  advance, and  the mechanical
resistance  of the spring becomes greater,  they are un-
able to proceed  without  a  new accession of electric
fluid, and  the nearer they approach the greater quan-
tity will be requisite.  This  supposition or conjecture 
Force and  Velocity of Contraction.
155
would  reduce the effects of muscular  contractility to
an attraction  between  the  individual particles of the
fibres,  which  is counteracted by the elasticity of the
membranous  matter that  is connected with  them.
Whether this attraction, like that of gravity, increases
as the  distances decrease,  and is  counteracted  in its
operation merely  by the elastic nature of the mem-
brane, is a point upon which I do not pretend to offer
any  opinion.  We can only say that  the  membrane
must be compressed, and in proportion to the increase
of compression so will be the necessity for an increase
of power to continue the contraction.
   In speaking of the animal fabric  we are obliged to
employ terms derived from the workmanship of  other
bodies.  We  therefore speak of the sacrifice of power
and  of its expenditure, as we should  do in a  machine of
any  description, where the object  of the  engineer is
to oeconomize labour.   But no idea  of this  kind ought
to attach to our conception of the human body, where
a certain construction of parts was  adopted,  as  being
the  most useful for all the purposes of  life, and those
powers are assigned to it which are necessary for pre-
serving it in  its proper condition.  Muscular contrac-
tility is one of these powers, and of course  the proper
quantity was given for the due  performance  of the
functions that depend upon it.
   Having given an account of the mechanism of muscles
and  the nature of  their  operation, it  remains for me
to make some  remarks upon  the force, the  velocity,
and  the extent of this power.   From the observations
that have been made above, upon  the quantity of force
that is expended in order to produce a certain effect,
we  may conclude that the  absolute force of  muscular
contraction, the power which the fibres actually  exert,
is exceedingly  great.  The mechanical physiologists,
and  especially Borelli, attempted to estimate the degree
of this force, and  although we cannot place implicit
confidence in their estimates, as they proceed, in some 
156
Its Extent.
 measure, upon hypothetical  and erroneous principles,
 yet we may allow that they are sufficiently correct to
 assure us that it exceeds very much any idea that we
 should have previously formed respecting it.  Accord-
 ing to his estimate the flexor muscles of the  thumb
 possess a power equal to nearly 4,000 lbs. which may
 be considered as at least  100 greater than the actual
 power which  they are capable of exercising.*
  There  are many  cases in  which  the velocity  of
 muscular  contraction is  no  less remarkable  than  its
 force.   As an example of this  the  muscles connected
 with the organs of speech are  often adduced, where,
in rapid enunciation, the number of distinct contractions
 that take  place, in order to form certain combinations
 of vocal sounds,  is  very great,  each word, or rather
 each  syllable, requiring several  different contractions,
which must  succeed each other in rapid  succession,
 with proper intervals between them.  The motions of
 the muscles connected with the fingers, in playing upon
 musical instruments, is no less remarkable, for here
 the contractions  are generally greater in extent, and
 therefore   must  proceed  with  proportionably  more
velocity, although they do not  succeed each other so
rapidly as those of the vocal organs.
  The extent of muscular contraction, or the degree
in which any particular muscle  is capable of shortening
itself, has not been very accurately ascertained.   In
the proper muscles it has been thought that the fibres
never diminish to more than  one-third of their natural
length, and even this must be considered as a remark-
 able case.   In the muscular coats indeed the contrac-
 tion of the whole substance  is much greater, but then
it is not ascertained  what portion of it belongs to the
 proper fibre and wrhat to the membrane.   It has been
 remarked that some of the lower tribes of animals, as

  * Prop. 126 ; the estimate of Borelli is, however, conceived by
Pemberton to  be considerably exaggerated.—See Introduction to
Cowper's Myotomia Reformata. 
               Hypotheses of Contraction.           157

the polypi and the actiniae, appear to contract  their
limbs to a much greater degree, and there  is every
reason from analogy to believe that they are  provided
with organs for the purpose  of  motion,  which may be
considered as  muscular; but scarcely enough  is known
concerning their nature to enable us to employ them as
the basis of any calculation that we may form upon
the subject.

       § 6. Hypotheses of muscular Contraction.

   After this account of the structure of the  muscular
fibre, of its chemical nature, its properties,  uses, and
mechanism, I come,  in the last  place, to consider the
hypotheses that  have been invented  to  explain  its
action.   Two  distinct  questions here  present them-
selves ; first, What is the efficient cause of the contrac-
tion of the fibre, or by what physical cause  is it  pro-
duced ?  and  secondly,  What is  the cause of contrac-
tility, or of that property of the fibre which  produces
contraction ? These questions have generally  been con-
founded together, or have been considered as  involving
only one subject of inquiry, and  yet I apprehend  they
are clearly distinct, and that we  may conceive it possi-
ble to  afford  a satisfactory answer to one  of them,
without our being able to  solve the other.   We may
perhaps discover something in the mechanical  construc-
tion of the fibre,  in  the arrangement of its  particles,
or in the mode in  which its constituents are connected
to each other, which may  explain to us the  reason of
their alternate contraction and relaxation,  upon  the
application of the appropriate  exciting cause ; or,  on
the  contrary,  without being able  to accomplish this
object,  we may perceive the correspondence   between
the operation  of  some external circumstance and the
action of contractility, which will warrant us in regard-
ing this as the cause of the effect.  Both the above
questions are highly interesting,  but they  are unfortu-* 
158
Efficient cause of Contraction.
nately both  of them of very difficult solution.  With
respect to the efficient cause of muscular contraction it
may be remarked generally,  that  every  attempt  to
account for it on the principles of mere mechanics must
be obviously abortive, because in the operation of the
muscles we have  an  actual generation of  power.   In
the best contrived machinery we have only the existing
power applied in  a  new  direction,  better  adapted for
some  particular object;  but  power is never  actually
generated.   In those engines which  act from the mere
force  of gravity,  what we gain in  power we lose in
velocity, or the reverse ;  and when from the re-action
of an elastic body, as from the recoiling  of a spring,
there seems to be a real production of power, the effect
thus apparently produced is no greater than was origin-
ally employed in compressing it, and its effect is neces-
sarily limited to a short period, for  when this power is
expended all motion ceases.  On this account it will  be
unnecessary for us  to  enter into any detail  of those
hypotheses which attribute muscular contraction to any
mechanical construction of the  fibre  ; as that of Borelli,
who supposed  that it  consisted of a series of rhom-
boidal vesicles, which were  in  some way  made to ex-
pand when the muscle contracted, and to collapse when
it was relaxed, an hypothesis  which he laboured with
much care  and supported by a long train of mathema-
tical reasoning.  Or the  hypothesis of Steuart, which
is framed with a great appearance of learning and geo-
metrical precision, and  which supposes that the muscu-
lar fibre is  composed of a-string of vesicles formed of
the substance of the nerves, which during  muscular
action are  inflated by the ingress of the nervous fluid.
But it is sufficient to remark concerning them, that the
whole rests upon a  supposition which is  not counte-
nanced  by a  single  direct fact,  and that should we
admit the  vascular form  of the fibre, we are still as
much at  a loss as at first to know in what manner it
becomes distended, and shall have to call  in some new 
Various Hypotheses.
159
agent  to  perform this  part of the  operation.  Nor
shall we find a better explanation of the efficient cause
of muscular contraction by having recourse to any che-
mical  operation, such as the production  of a gaseous
body,  which was a favourite notion with the physiolo-
gists of the  seventeenth century, who supposed that
there was an effervescence excited in the muscle.  This
effervescence was attributed  to various causes;  by
some to the  mixture  of an acid and an  alkali, which
were imagined to be  brought together in some myste-
rious manner, while others, and those among the  most
learned and ingenious men  of the age, such as Willis,
Bellini, Mayow, and Keill, ascribed it to a fermentation
or effervescence excited by a union of the particles of
the  muscular fibre with the  nervous fluid, or  with
some  etherial  spirit   contained in the blood.  When
electrical phenomena began to be  attended to, it was
supposed  that  the fibres of the muscle  might be dis-
posed  in such a manner as to form  a kind  of battery,
which  should produce contraction  by its  explosions;
and after  the  discovery of  galvanism,  an elaborate
attempt was made by  Valli of Pisa,  to account for
muscular action  by supposing that the muscles consisted
of an  arrangement of parts analogous to that  of the
elements of the galvanic pile.*   It will be  quite unne-
cessary to enter upon any formal examination of these
hypotheses, which are now completely discarded; it is
sufficient to observe concerning them that they  are not
supported  by any foundation of facts,  that  they  have
scarcely any analogies in their  favour, in  short, that
they were purely gratuitous,  and  could never  have
been  tolerated,  had   not the  mind been disposed to
listen to any thing which promised to throw the smallest
ray of light  upon a  subject that was involved in so
much obscurity.

  * Experiments on Animal Electricity,  with their Application to
Physiology, by L. Valli.  See Brit. Crit. for Mar. 1794.   Jour, de
Phys. t.  xli. contains several letters of Valli on the subject. 
160
Keill's Hypothesis.
   There is, however, one hypothesis which it may be
 proper to notice, not from  its intrinsic excellence, or
 from its giving us  any  real insight into  the nature of
 muscular contraction, but as  affording a curious fact in
 the history of science, and one which it  may be useful
 to relate, in order to impress upon our minds  the  dan-
 ger which even  the most  learned men incur,  when
 they permit themselves to confound a train of reason-
 ing with a deduction of  facts.   I  refer to  the  theory
 which was formed  by Keill  to  explain  the nature of
 muscular  contraction.  Keill wras  a  man  of considera-
 ble talents, a  profound  mathematician, and a zealous
 cultivator of  the  various departments of medicine  and
 physiology.    In  forming his  theory  he set out by
 adopting the  notion of Borelli, that the muscular fibre
 consists of rhomboidal vesicles, resembling  a  string of
 bladders, which communicate with each  other.  When
 these vesicles are inflated, provided at the  same time
 that their substance be  not actually  distended, it is ob-
 vious that the total length of the fibre will  be dimi-
 nished, and hence that the whole  muscle will be short-
 ened.  Now  the  blood  and the  animal spirits were
 made the agents to produce  this  distention, and in
 proof of this  idea it  was stated,  that  upon the tying
 up of the artery  and nerve  that lead to a muscle,  the
 part loses its  power of contraction.  But this inflation
 may be accomplished in two ways, either by a greater
quantity of blood and  animal  spirits  being sent  into
the vesicles, or by the quantity previously in them be-
ing rarified and thus made to occupy a greater space;
and after  deliberately considering both  these  points,
and weighing their  respective probabilities  with much
acuteness  and  ingenuity, a decision is made in favour of
 the latter supposition.   Nor is there  less ingenuity
displayed  in the mode in which  this rarefaction is sup-
 posed to be brought about.   It is stated  that the blood
 contains  a great  quantity of air  mechanically mixed
 with its fluid  particles, which by various means may be 
Keill's Hypothesis.               161
separated from it, and caused to  assume the  elastic
state.   In  some way,  which does not indeed  seem  to
be  very thoroughly explained, this air gets into the
vesicles, and  is kept there  in a state of compression,
the elasticity of the air being balanced exactly  by the
strength of the vesicles.   If however we could suppose
any other substance to enter the vesicles, which might
cause the particles of the  air to  acquire a  great  in-
crease of their elasticity, the vesicles  must become dis-
tended, and this effect is conceived to be brought about
by a quantity of the nervous fluid coming into contact
with  the air.   When these two  bodies  are  mixed  to-
gether, a sudden increase of bulk  is  the consequence,
the vesicles are quickly distended, and the muscle pro-
portionably shortened.
  Having  thus  explained the manner in which  muscu-
lar contraction is produced, which, as the author trium-
phantly observes, is accomplished  without having  re-
course  to  any  chemical  hypothesis of fermentation,
effervescence, or precipitation, we  are  next  to explain
how these  minute vesicles can, by their action, produce
such prodigiously great effects.   And here we have a
long and very abstruse train  of  mathematical reason-
ing, founded upon the  principle, that if a bladder by its
inflation will  raise a  certain weight, by dividing the
bladder into a number of smaller ones connected  to-
gether, we diminish the capacity of the cavity without
diminishing the  extent of its  contraction,  so that the
same bulk  of gas will raise a much greater weight than
if it  had been  all contained in one  bladder.   Proceed-
ing upon this  principle,  we  may diminish the size of
the bladders and increase their number to an  indefinite
extent,  and thus, with only a given quantity of gas, we
may produce an unlimited effect.   Thus if a bladder of
a certain size  will cause a muscle to shorten itself  to
the extent  of an inch, if the bladder be divided into
100 parts, and these be disposed  in a straight line, the
contraction will still be equal to an inch, but the quan-
               21 
162
Prochaska9s Hypothesis.
  tity of actual inflation and the force required to pro-
  duce  it,  will be  10,000 times  less than  when  the
  single bladder is employed.*  It is not a little curious
  to observe  how much acuteness is displayed in con-
  structing  the several  parts  of  this hypothesis, what
  advantage is taken  of  the  various circumstances that
  appear to favour it, and how the supposed objections
  that might  be  urged  against  it  are  repelled;  yet I
  need not say that the whole fabric is destitute of the
  slightest foundation, that it all rests  upon a set of gra-
  tuitous positions, that  have not  the least  ground  of
  probability for their support, and that, on this account,
  all  the ingenuity  manifested  in  the finishing of. the
 subordinate  parts is completely misapplied.
   There is  much more  simplicity and less violent  im-
 probability in the hypothesis  of  muscular contraction
 that  was advanced by Prochaska, although,  I fear,  we
 must  admit  that  it  is equally  without  foundation.
 From his explanation of the structure  of the muscles
 he concludes that the minute  branches of the arteries
 are every  where connected with  the ultimate  muscu-
 lar filaments, that they  creep about them, and  cross
 them  in all directions.  Hence he argues that when
 these vessels are rendered  turgid by an accession of
 blood, in passing  among  the  filaments they must bend
 them  into  a serpentine  form,  and thus diminish their
 length, and that of the muscle  generally.!
   In  connexion with  this hypothesis  of Prochaska's I
 think it not improper to notice a microscopical obser-
 vation of Hales's, which although it may have been
 perverted by the causes which are so apt  to affect  all
 observations  of this  kind, comes from too respectable
 a quarter  to be entirely neglected.   He  informs us
 that when he viewed the  muscles of a  frog with  a
powerful lens, he observed the fibres lying parallel  to
* Keill, Testamina, No. V,
t De Carn. Mus. § 2, c. i. 
Blane's Hypothesis.
1G3
each other, with  the  blood running up and down be-
tween each fibre  in the small capillary arteries.   If
the muscle was then made  to contract, to use his own
expression, " the scene is  instantly changed from pa-
rallel fibres to serieses of rhomboidal pinnula?,  which
immediately disappear as soon as the muscle ceases,to
act."*  We  may  easily conceive that an  appearance
similar to what Hales describes would follow from the
shortening of the  fibres and the necessary contraction
of all the parts connected  with them, but  it does not
throw any light upon  the nature of the operation, nor
does it enable us to judge  whether the fibres or the
vessels were  the  prime  agents in the  production  of
the change.
  The only other opinion which I shall notice on this
subject is  the one that was brought forward  a few
years  ago  by Sir  G. Blane, and  that  indeed  more  in
the form of a conjectural speculation, than of a formal
hypothesis.  As he was  led from his experiments  to
conclude that  the actual  bulk of the muscle  is not
altered during its  contraction, but that  it gains in thick-
ness exactly what it loses  in length, he observes that
we may account for this change by supposing that the
muscle is made up of  particles of an oblong form, and
that when the  muscle  is contracted, the long diameter
of the particle is removed  from a perpendicular into a
transverse  direction.!  This speculation has certainly
the advantage over Keill's, in containing a much smaller
number of assumptions, but its foundation is equally
gratuitous, and, like that  of Prochaska, seems totally
inadequate to produce the effect in question.
  After such melancholy  examples of failure before
our eyes, it will not be expected that I should attempt
to unravel a mystery,  which has hitherto remained in
such impenetrable obscurity.   It may, however, be de-

               * Statical Essays, vol. ii. p. 59.
                t Select Dissert, p. 243 
164
General Remarks.
sirable to state in what degree  the efficient cause of
muscular contraction is a legitimate object of inquiry,
and towards what points we  ought particularly to di-
rect our attention.  In the first  place, the  simple act
of contraction must  consist in the approximation of the
particles of which the fibre is composed, and this may
be brought about  in various  ways.  The  fibre itself
may be condensed in its whole substance, or it may be
bent or folded up into a  kind  of zig-zag form, or the
attraction  between some  of its parts  may cause the
whole to be corrugated, thus shortening it in its perpen-
dicular  direction without producing any actual conden-
sation.  We  have,  however, no  proof  either from the
evidence of our  senses, or from  any correct deduction
of reasoning of any  specific structure or constitution of
the fibre which  can, in any degree, explain the manner
in which this approximation is effected.  It is not like-
ly that any further  discovery can  be  made  upon this
subject by the aid of microscopes, for it appears that
there is a limit to the employment of  high magnifiers,
beyond  which the  liability  to ocular  deception  is so
great as  to counterbalance any supposed  advantage
from the increased  magnitude of the object.   If, there-
fore, any additional  information  can ever be acquired
on this point, it  is more likely that it  will be done by
observing the effects  produced on the whole  muscle,
and by tracing the analogy between these effects  and
other natural phenomena, than  by the mere examina-
tion of the separate  fibres.   And if we are  unable to
account for the approximation of the particles, still less
are we able to explain why the various things which
we call stimulants, so extremely  heterogeneous in their
nature, and which  have no  other common property,
should all coincide  in  producing the same  effect upon
the fibre.   This is so unlike the operation of any other
physical cause with which we are  acquainted, that we
must for the  present  consider  it  as an  ultimate fact,
one of those mysteries in nature  which daily present 
                Cause of Contractility.             165

themselves to our observation, but which elude all out-
attempts to refer them to any more general principle.
  The other inquiry  which I  proposed, what is the
cause of contractility, remains involved in as much ob-
scurity as the one  we  have  been considering.  The
attempts that have  been made to explain it  are  not less
numerous than  in the former case, nor can they be con-
sidered as more fortunate,  although they  may proba-
bly  appear  less palpably  absurd.  Before we enter
upon the inquiry it  will be proper to have  a clear and
explicit statement of  its object, a circumstance which
is always necessary in philosophical  investigations, but
which seems to be particularly  so   in  this instance,
where several  hypotheses  have been advanced, which
in fact appear to be no more than mere verbal expla-
nations, or  peculiar expressions  which do not convey
any  distinct idea to the mind.  Our object  is to inquire
whether, when a muscle contracts in consequence of
the  application of   a stimulus, this event is uniformly
preceded by any other event, so that  the latter may
stand to the former in the relation of its cause.  This
necessary antecedent to contraction may be something
of a peculiar and specific kind, or it  may be referable
to some of the other agents in nature.  If it be of the
former description, we  are to prove  that it is governed
by appropriate laws, that cannot be referred to any
other power, and we are to  point out in what this spe-
cific difference consists.  If it be  found to belong  to
any  of the known agents, we are to prove the reality
of this  connexion, to  show that the effect never takes
place without  the  presence of this supposed agent, that
when this  agent  is  present  the  power  of contraction
continues,  and that an increase  or  diminution in the
quantity or force of the agent is always attended by a
corresponding  increase or diminution of  the contractile
power.
   It will be necessary for us to examine more in de-
tail  the hypotheses that have been formed to account 
166             Cause of Contractility.
 for the cause of contractility, than those concerning the
 efficient cause of contraction,  because while  the latter
 have been all nearly discarded  and are  generally ne-
 glected, the former are many of them of modern growth,
 are maintained by many living authors,  are daily re-
 ferred  to  by physiologists end  pathologists, and are
 made the foundation of many topics both of specula-
 tion and of practice.  We may  arrange  these  hypo-
 theses under two divisions ; first, those which ascribe
 muscular contractility to the presence of some extra-
 neous agent or power superadded to  the animal body;
 or, secondly,  those which ascribe it  to some peculiar
 state or function  of the  body itself.  The  idea  that
 contractility  depends upon the presence of free  caloric
 may be adduced as an example of the first, and, as an
 instance of the second,  the opinion   that contractility
 necessarily results from  a peculiar chemical composi-
 tion of the muscular fibre.   The first class of  hypo-
 theses will not detain us long, because they have been
 brought forward in a less formal shape, and because,
 being less clogged with obscure speculations, and being
 of a more palpable nature,  they  are  more easy to re-
 fute.   Because it  was observed  that there  is  a con-
 nexion between the  temperature  of an animal and the
 degree of its contractility, some physiologists have con-
 ceived that contractility depended  immediately upon
 caloric,  or  the matter of  heat interspersed in  an un-
 combined state between the fibres.   Others,  perceiv-
 ing how  remarkably the  muscles are affected by the
 electrical fluid, supposed  that this was the immediate
 cause of muscular contractility, and  set themselves to
 invent different modes in which what  they  styled ani-
 mal electricity might be  generated.   With  respect to
 both these hypotheses we may  remark  that caloric
 and the electric fluid are  found to be very powerful
 stimulants to  the fibre, and  it would appear, with re-
spect to the first of them, that a certain range of tem-
 perature is necessary for the existence of  the contrac- 
Various Hypotheses.
167
tile state.  Another opinion concerning the  cause of
contractility, which must be placed in our first division,
was fashionable a few years ago, according to which
the immediate cause of this property was ascribed to
oxygen.   It w:is conceived that oxygen is absorbed by
the lungs during respiration, is  carried by the arterial
blood to the muscles, and gives  them their contractile
power.  It was imagined that  in various states of the
system, and from various incidental causes, oxygen was
absorbed  and carried to the muscles in very different
quantities, and that in  proportion to the quantity their
contractility was increased or diminished.  This specu-
lation, which appears  to 'have  been  first  formally
brought  forwards  by  Girtanner* and  was zealously
adopted  by Beddoes, was applied  by him very exten-
sively to pathology, and was made  the foundation of
some supposed improvements in the practice of medi-
cine.   For a short  time this doctrine  obtained a con-
siderable share of popularity, but  when the  first  im-
pression  of novelty had subsided,  and  its real merits
began to be canvassed, it was found to  be built upon a
set of entirely gratuitous positions, and  was almost uni-
versally  abandoned.   It has,  however,  lately found a
supporter in M. Richerand, a writer more remarkable
for a popular air which he gives to his works, and for
the liveliness of his  imagination, than for the  correct-
ness of his judgment.  He  adds to it   the  additional
speculation, that the union of the  oxygen in the arte-
rial blood and the elements of the muscle  is  brought
about by the  nervous  fluid,  which produces an  effect
something like that of the electric spark.!
   In the second class of hypotheses  that have been
formed to account  for contractility,  there  is one that
has been detailed with a considerable degree of mi-

  * Journ. de Phys. t. xxxvii. p. 139.
  t Elements of Physiol. § 163; see also Blumenbach's Inst, by
Elliotson,  § 50, 54. 
168           Humboldt's  Experiments.
 nuteness, and  has had a  great variety of argument,
 and even experiments, adduced in  its  favour; I refer
 to that  which  ascribes  contractility  to the chemical
 composition of the  fibre.  It is  found that a certain
 proportion  of chemical  elements composes a body en-
 dowed with certain properties, and  whenever the ele-
 ments are put  together in  a  proper proportion, these
 properties are the necessary result.   Thus, a  certain
 proportion  of sulphur and oxygen forms sulphuric acid,
 a substance which possesses a set  of qualities  neces-
 sarily belonging  to  it: it  is  a  heavy, unctuous, acid
 fluid, and we may correctly say,  that  these properties
 are necessarily attached  to its chemical composition.
 The  same  reasoning is   applied  to  the  muscular
 fibre; this  body  is  composed of carbon, hydrogen,
 azote, and  oxygen, which  all of them exist in a cer-
 tain proportion, and   when they are  united  together
 they  form  the  body which we call a muscular fibre,
 which possesses a certain  set  of  physical and che-
 mical properties,  and also the physiological  proper-
 ty  of contractility.  Contractility  is  said,  therefore,
 to  be as  much  the  necessary result of the chemical
 elements  which compose  the fibre,  as  acidity is  of
 the compound  of  oxygen and sulphur  which composes
 sulphuric  acid.  In  order  to prove  this  hypothesis
 by  experiment,  an attempt has been  made to show,
 that if  by any means an alteration  be  made  in the
 proportion of the  elements  of  which   the   fibre is
 composed,  without, at  the  same time, destroying its
 texture, or  its  physical  properties, a corresponding
change  is  brought   about in its  contractile  power.
Humboldt particularly  directed his  attention  to this
point, and endeavoured to  demonstrate that  a very
slight  change in the chemical composition of the mus-
cle  entirely  destroys  its  contractility,  while, by  re-
storing  the  original  composition of  the muscle, the
contractility is also restored.  As oxygen is the most
variable of  the  components of the  muscular fibre, or 
     Contractility connected with Chemical Composition.  169

at least that which is  the most easily added and sub-
tracted from it,  by means of chemical re-agents, his
experiments  chiefly consisted  in observing the effects
of this  substance upon contractility,  and  by employ-
ing galvanism as a test of the presence  of the con-
tractile power, he found  that it  was perceptibly af-
fected by very slight variations in the proportion of
the chemical elements  of the muscle.*   There are
some interesting  experiments  that lead to the same
conclusion in the thesis of Smith,!  a work which, in
consequence of its peculiar destination, has  been little
known to the public,  but which  contains  more  valua-
able and interesting matter than many bulky volumes
that have  acquired a high degree of celebrity.   The
experiments  were  performed  about  the  year  1766,
long before the chemical  theory  of  contractility was
thought of.   Their immediate object is  to show  the
effect of chemical agents  in increasing or diminishing
the power which the muscles possess of being affected
by stimulants of  various kinds, and in some cases their
operation was such as rather  to  indicate  a change in
the composition of the muscle  than merely  in its con-
tractility.
  A train of reasoning has been brought  forwards by
the  chemical physiologists, in favour of their views of
contractility, derived  from the state of the muscular
fibre  after  death, which is found to  differ very much
according to  the  mode in  which life has been destroy-
ed.  If an animal in full health be  suddenly killed, the
muscles are firm  and rigidly contracted,  and they  re-
main a long time without undergoing the  process of
decomposition ;  whereas, on the contrary, if death en-
sue  after violent exercise, if  it be caused by lightning
or electricity, or by the operation of some kinds  of poi-

  * Experiences sur le Galvanisme, &c. par Jadelot; also Ann
Chim. t. xxii. p. 51 ; Journ. Phys. t. xlvi. p. 465 ; t. xlvii.  p. 65.
  t Test. Phys. Inaug. de Actione Musculari, Appendix.
              22
«, 
170 v
General Remarks.
sons,  the muscles are  relaxed and soft, have  lost all
their  contractility, and  much  sooner become  putrid;
and it is  found that in all instances these two states or
conditions correspond to each other, viz. the degree of
contractility remaining in the muscle and its tendency
to putrefaction.  As the decomposition of the substance
of a muscle is obviously a chemical operation, and as it
thus  appears to be  so intimately connected with  its
contractility,  it was concluded  that contractility is  the
necessary result of a peculiar combination of chemical
elements.  This  argument  in favour of the chemical
theory has been  also  extended to the connexion  that
has been observed  between the  contractility of  the
muscular fibre and the coagulability of the fibrin of the
blood.  The greatest part,  if not  all  those circumstan-
ces which affect  the  contractility of the muscle,  are
found to produce a proportionate and  corresponding
effect upon  the  coagulation of the  fibrin.  But  the
fibrin of  the  blood, it is said, is a mere chemical  com-
pound ;  any change in its coagulability must therefore
depend upon an alteration in its chemical constitution,
and as  the  muscular fibre exactly resembles it in its
chemical composition, and as there is a strong similari-
ty between their respective properties of contractility
and coagulability, so it is inferred that the former must
likewise  depend  upon a  chemical combination.   For
the facts respecting the blood we are  principally in-
debted to J. Hunter, who, however, brought them for-
wards with a very different, and even a directly oppo-
site, viewr, to  prove that the blood, in consequence of
its exhibiting properties so  analogous to those  belong-
ing to the muscular fibre, is the appropriate  seat of vi-
tality.  This hypothesis will be discussed in  its proper
place  ; but in the mean time I may remark,  that what-
ever conclusion we form  concerning Hunter's specula-
tion .on the life  of the blood, still it  indicates an  inti-
mate  and necessary relation between its physiological
and its chemical properties. 
Other Hypotheses.              171
  It would appear then, upon the whole, that  there
are some "Striking  facts and strong analogies in favour
of the chemical hypothesis, and they certainly go so far
as to prove that there is a very intimate connexion be-
tween  the chemical  composition of  the fibre and  its
contractile power.   But they do not prove any thing
besides this; they demonstrate that a connexion exists
between the two  circumstances, not that  one is  the
cause of the other.  Indeed there is an obvious  and
well-known fact which is decisive against this  supposi-
tion.  A muscle immediately after death has the same
chemical composition  as during life, yet if life be com-
pletely extinguished, contractility is  gone and can never
be  restored.   If it be said that a chemical change in
the muscle commences immediately after  death, but
that it is too slight to be delected, I reply that a change
which is imperceptible cannot be adduced as the foun-
dation on which to build  an hypothesis.  And were it
even proved that this alleged change did exist, it might
still be objected that the progress  of chemical decom-
position bears no  proportion  to  the alteration in the
state of the contractile power, the former commencing
very slowly, and by almost imperceptible degrees; the
latter proceeding  rapidly, and in a short time having
arrived at the utmost change which  it  ever experien-
ces.  Besides,  although it be a  less direct argument
against the chemical  hypothesis,  and  one that is mere-
ly analogical, yet it possesses considerable weight, that
although there are many substances that possess near-
ly the  same chemical  composition with the  muscular
fibre, yet no other body in nature exhibits any proper-
ty which is at all  similar to  contractility;  it  does not,
indeed,  resemble  any other quality in  nature, and al-
though  exclusively attached to a substance composed
of certain chemical elements, it seems more natural to
suppose  that it is superadded to these elements, than
necessarily resulting from their combination.
  Another opinion respecting the  cause of contractile 
172               Other Hypotheses.
ty, which has  been frequently brought forwards, al-
though scarcely in the form of a regular hypothesis, is,
that this property depends upon the mechanical struc-
ture of the  fibre.   We observe a body possessed of a
very peculiar  arrangement,  unlike every other in  na-
ture, and  possessed of an equally peculiar property,  it
is therefore concluded that the property is the neces-
sary result of the peculiar structure or arrangement of
the  parts of which the body is composed.   But  the
answer that was  made  to the chemical theory  applies
to this with still more force ;  that long after the con-
tractile power  is extinguished by death the  structure
remains unaltered, and as any material  alteration in
this respect would be of a more palpable nature  than
the former, so  we may conclude, with more confidence,
that it has not  taken place.*
  Many  physiologists  of  the  first eminence,  among
whom we  may include  Haller and Cullen, when en-
deavouring  to  account for the cause of contractility,
have  thought  it sufficient to say, that this  attraction
between the particles of the fibre, which causes it to
contract, is nothing more than  a peculiar mode  or spe-
cies of the attraction which subsists between the parti-
cles of all matter.  And this appears  to be nearly the
opinion of Fordyce, when he ascribes contractility to
what he calls the attraction of life,! and of those phy-
siologists  who  speak of  it as an attraction depending
upon the operation of the vital principle.  Many facts
and experiments have  been  adduced  in favour of the
hypothesis  of  attraction, which all tend to show that
there exists a greater degree of cohesion between the
particles of the muscular fibre during life than imme-
diately after death, and before we can conceive that it

  *  This view of the subject may derive some confirmation from
the fact discovered by Hunter, that a muscle may have its fibres
much  shortened  without  any diminution of its  contractility,
Home's Lect. p. 40.
  t Phil. Trans, for 1788, p. 25 
General Remarks.
173
has experienced any material change in its chemical or
physical constitution.  Observations of this kind occur
not unfrequently in  the  writings of the older physiolo-
gists ;  among the  moderns Sir G. Blane attempted to
prove  this diminished  cohesion by a direct experiment
on  the  muscles  of the  thumb,*  and remarks of the
same  kind have  been  made by  Carlisle! and by Bi-
chat.;}; With a view to the same conclusion it has been
observed, that when a muscle is ruptured during life it
is the  tendinous  part  which  is disposed to give way,
while, on  the contrary, after death the fleshy  part is
always weaker than the tendon.§  Although  perhaps
it is  impossible to  perform any very decisive  experi-
ments  upon this subject, yet we admit the truth of the
position, that during  muscular action  the particles of
the fibre are more strongly attracted  together, and in-
deed the very nature of the operation implies that this
must be  the  case.  We must also bear in mind  that
mechanical violence  is itself a stimulus, and that in con-
sequence of the admirable arrangements  of the animal
ceconomy,  the very circumstance,  which would other-
wise tend to disorganize the muscles,  has  the  immedi-
ate effect of preventing this disorganization from taking
place.   Yet,  although we admit the existence  of this
increased attraction  as an  actual fact, it affords no  ex-
planation of the cause of contractility.  The hypothe-
sis, when stripped of the peculiar language in which it
is conveyed,  amounts to nothing more  than the  expres-
sion of the fact in new terms, for still the fundamental
difficulty remains, what it is which determines  the at-
traction  between the particles of matter to exert their
power in this  peculiar manner and under these pecu-

  * Blane's Select Dissert, p. 237.
  t Phil. Trans, for 1805, p. 3; the author remarks that the di-
minished cohesion after death occurs only in the direction of the
fibre.
  X Anat.  Gen. t. ii. p. 398.
  § Carlisle, in Phil. Trans, for 1805, p. 4. 
174
General Conclusion.
liar circumstances.   I have, therefore, no hesitation in
concluding that, in the present state of our knowledge,
contractility  ought  to  be  regarded as  the  unknown
cause of known effects, a quality attached to a particu-
lar species of matter possessed of properties  peculiar
to itself, and which  we  are  not able to refer  to any
general principle. 
Nervous System.
175
                    CHAPTER  IV.


               <©f the  Jierljous System,

   In the last  chapter  I gave an account  of one of  the
appropriate powers of the animal body, contractility,
and of the organs by which it  is exercised ; I now pro-
ceed to the other  property that belongs exclusively to
animal  life,   sensibility.*   As  contractility  is always
attached to the  muscular fibre, so sensibility is always
attached to the nervous system ; it is found in no  other
part; and wherever the nervous matter can  be traced,
sensibility, in a greater or less degree, may always be
detected.

  * One of the objections that were urged above against the use
of the word irritability to designate  the appropriate power of the
muscles, applies to sensibility as expressing the power attached to
the nervous system,  that besides its technical and physiological
sense,  it is frequently employed in  a general way  to indicate a
peculiar state of the feelings or character.  Were I to venture to
introduce  a new term, 1 should propose that of sensitivity, which
might bear the same relation to the  nervous system,  that contrac-
tility does to the muscular.  M. Cuvier, in his  report on the expe-
riments of M. Flourens, which will  be more  particularly  noticed
hereafter, remarks  upon the  ambiguity which, in the French lan-
guage, attaches  to the word " sensible ;" this term being applied to
a body capable either of receiving, of producing, or of conducting
sensations.  In  English, part of the  difficulty may be removed by
employing the word " sentient" in the first, and " sensitive" in the
third of these cases; but we have still a fourth, and that the  most
ordinary use of the word sensible, as expressing the state of the
intellectual powers.  Tbis paper contains many valuable observa-
tions upon the  importance of a correct nomenclature in the  science
of physiology.   As an illustration of the inaccurate or indeterminate
mode in which the terms connected with this subject are employed,
I may remark that  Helvetius supposes the  mind,  " la  faculty de
penser," to be entirely  composed  of " sensibilite physique" and
memory; De l'Esprit, dis. 1, ch. 1 ;  while Richerand conceives
that there may be sensibility independent of the presence of nerves;
Physiol. Inst. p. 22. 
176             Description of the Brain.
   In treating upon this subject I must begin by a brief
description of the  nervous system,  and its  anatomical
structure, together with its  physical and chemical pro-
perties.   I shall, in the second  place, consider its vital
powers or faculties, and the mode  of their operation,
and this will  naturally lead me to make some observa-
tions upon the use of the nervous system.   I shall next
inquire into  the  nature of the  connexion that subsists
between  the  muscles and the nerves, and I shall endea-
vour to distinguish  between  their effects upon the ani-
mal ceconomy in general,  and upon the different parts
of  which it is composed.   When we have  thus taken
a view of both  the powers which characterize animal
existence, we shall be prepared for forming a classifi-
cation of  the functions,  ascertaining in  what  degree
they depend  upon the muscular or the nervous systems,
and what is the  nature of the relation that they bear
to  each other.*

        § 1.  Description of the JVervous System.

   The nervous system consists  of four  principal parts
or organs;  the brain,  the  spinal cord, the nerves, and
the ganglia.!  The brain  is  a body of a pulpy consis-

  * Willis may be considered as the first among the moderns who
investigated with much success  the structure and functions  of the
nervous system.  Boerhaave paid comparatively but little attention
to it: Haller again studied it with much minuteness; and since his
time we may select the names of Vic-d'Azyr, Soemmering, the
Wenzells, and Drs.  Gall and  Spurzheim,  whose labours  on this
subject have been peculiarly valuable.  The late investigations of
Dr. W. Philip,  of Mr.  C. Bell, and of M. Magendie, fully entitle
them to a place in the above list.   An interesting, and, so far as I
am able to judge, a very accurate abstract of the successive disco-
veries that have been made on the subject of the brain and nerves
is given by Sprengel, Hist, de ia Med.  t. iv. sect. 12, c. 4.
  t  It may be proper to remark, that whenever the terms " nervous
system," u nervous matter," " nervous power," Sac. are employed,
without any addition or restriction, they are to be understood in a
general sense, as including or referring to all the four parts men-
tioned above. 
Description of the drain.
177
  tence, resembling a  soft coagulum, filling the  hollow
  bone called the skull,  which gives  the form  to the
  head.   It is of  an extremely irregular figure, having a
  number of projections  and depressions,  corresponding
  partly to the irregularities of the skull, and partly pro-
  duced by convolutions and  cavities in the brain itself.
  it is covered externally with various membranes, of
  which the most important  are  two,  an  external one,
  thick and dense, which  lines the skull, and an internal
  one, more thin and delicate, which closely invests  the
  central mass, and follows its surface into all its depres-
  sions and cavities.   To  these the older anatomists owe
  the names  of the Dura and  Pia Mater,  in conformity
  to a whimsical  hypothesis,  that these  two  were  the
  origin of all  the other membranes of the body.  The
  internal cavities of the  brain, which are called  ventri-
  cles, are lined with a serous membrane, secreting an
  albuminous  fluid, which,  in  the healthy state  of  the
  organ, is removed  by  absorption as rapidly as it is
  produced, but which  is  occasionally collected  in consi-
  derable quantity, giving rise to  the formidable disease
  of hydrocephalus.
   Scarcely  any thing is  known with respect to the
 use of the different  projections and depressions  of the
 brain;  but  there are two  points connected  with its
 form, that it is  important  to notice,  as  they seem to
 throw some  light upon  its  physiology and the nature
 of its functions.  These  are, first, the division of the
 encephalon or cerebral  mass, into the cerebrum, or
 brain properly so called, and the cerebellum, or  lesser
 brain;  and secondly,  its division into the two  hemi-
 spheres.   The  greater  part of the  nervous matter
 within  the  skull composes the proper brain or cere-
 brum ;  it occupies the whole of  the upper part of the
 head, and is separated by a dense membrane from the
 lesser brain, except at the common basis of both, where
 thej are united.   There is  a dense membrane, pro-
jecting directly downwards  to a considerable depth, 
178          Cortical and  Cineritious Fart.
 from the upper part of the  skull,  and extending from
 the fore to the back part  of the head, which divides
 the brain into the two hemispheres as they have been
 called ; the cerebellum is  likewise divided by a similar
 membrane into two hemispheres.
   When we cut into the interior of the brain, we find
 it to be composed of two substances, that differ in their
 colour and consistence ; these have  obtained the  names
 of the cortical or cineritious, and the medullary matter.
 The cortical, as its name imports, is on the outside, and
 is of a reddish-brown colour; it is obviously of a softer
 consistence than the medullary part, and it leaves by
 desiccation a smaller  quantity of solid  residuum.  In
 the  foetus it is considerably less firm, and at this period
 it bears a larger proportion  to the medullary matter
 than it  does  in the   adult.   It  evidently contains a
 greater number of blood-vessels;  and  more  may be
 brought into view, when it is examined  by the micro-
 scope.  On this account it was conceived by Ruysch to
 be  composed  entirely  of  blood-vessels,  with the con-
 necting cellular membrane, an opinion which was at one
 time very generally  adopted, and to  which  Haller
 inclines,*  although  the mere  inspection  of  the part
 would seem  to prove  its  inaccuracy.   Malpighi sup-
 posed that he had  detected a  glandular structure in
 this  portion of the brain,!  an  idea which was embraced
 by many eminent anatomists, and which may be thought
 to receive some confirmation from the  microscopical
 observations  that have been lately made upon  this
 organ.J

  * El. Phys. t. x. 1, 12.
  t  Exer. de Cerebro, in Mangeti Bib. Anat. vol. ii p. 56.
  | The medullary matter, both from its aspect and relative posi-
 tion,  is generally considered as constituting the  nervous substance
 in its most perfect state ; and Drs.  Gall and Spurzheim have con-
jectured that the use of the cineritious is to form or secrete  the
 medullary part.  Recherches sur le Systeme Nerveux, § 2.   The
 particular facts from which  they derive their hypothesis are^rthat 
Nerves.                    179
  To the base of the skull, connected with the  brain
by the intervention of the medulla oblongata, is attached
what has been commonly called the spinal marrow, but
which has been more correctly termed by Gordon the
spinal cord.   Like  the brain  it is  enclosed  in  mem-
branes, it possesses both cineritious and medullary mat-
ter, although their respective position is reversed; it
has a longitudinal furrow, dividing it imperfectly into
two halves, analogous to the hemispheres of the brain.
   To the lower part of the brain, or rather  perhaps,
according to the  more  accurate researches of the
modern anatomists,  to  the  medulla  oblongata, are at-
tached  a number of small white cords,  called nerves,
composed of medullary  matter, possessing a distinct
fibrous  structure, and enclosed in sheaths of membrane.
These  principally pass from the  brain  to  the  organs
of  the  external senses, and bodies  of a similar kind
pass from the spinal cord to the  muscular parts; the
former have  been called  the cerebral,  the latter the
spinal or vertebral nerves;  both of  them are disposed
in  pairs, and  proceed in corresponding directions to the
two sides of  the body.  At their  commencement from
the brain or spinal cord,  anatomists generally  reckon
nine pair of the former nerves and thirty of the latter,
but they soon  divide  into  numerous branches,  which
are distributed to all parts of the body.   In their pas-
sage they frequently anastomose or communicate with
each other, and these communications are sometimes
so numerous and intricate as to form a complete net-
 work,  to  which the name of plexus has been applied.

 the nerves appear to be enlarged when they pass through  a mass
 pf cineritious matter, and  that masses of this substance are depo-
sited on all the parts of the spinal cord where it sends out nerves.
 Prof. Tiedemann,  however, remarks, in opposition to the above
 opinion, that in the foetus,  the medulla is formed before the cortex,
 and he limits the use of the latter to the conveyance of the arterial
 blood which may be necessary to support the energy of the perfect
 nervous matter.  Med.  Repos. vol. xv.  p.  315.   See also Magen-
 die, PhysioL t. i. p. 162. 
180
Relation of the Brain and Nerves.
From these plexuses new nerves originate, which seem
to  be  independent  of  those which  produced  them.
When the nerves arrive at their ultimate destination,
they  generally ramify into small  branches, which  be-
come  more and more minute, until they seem at length
to be melted down  into a kind  of pulp, and are no
longer visible  to the  eye.*
  In  speaking of  the relation which  subsists between
the brain and  the  nerves, it has been  usual to describe
the latter as  derived from  the former, or as produc-
tions  of its  substance.   This manner of  viewing  the
subject  probably  arose, in  some measure, from  the
hypothesis of the animal spirits, which were supposed
to be  lodged in a  series of tubes, that served as  a  re-
ceptacle for them, and  conveyed them to all parts of
the body.!  And even since the doctrine of the animal
spirits has  been called  in  question, the same kind of
language is maintained, and the nerves  are spoken of,
in a vague  way, as fibres actually continued from those


  * Besides these two classes of nerves, the cerebral and the spinal,
there is one nerve, or set of nerves, that appears to hold an inter-
mediate relation between the  two, or to  have a direct connexion
with both the brain and the spinal cord ; this is  the intercostal
nerve,  with  its  ramifications.  Some  nervous twigs that descend
from the brain unite with the  branches that are sent off from the
spinal  cord ;  these form series  of ganglia on  each side  of the
spine,  from which numerous nerves proceed that  are distributed
over all the thoracic and abdominal  viscera.  From the  way in
which the intercostal nerve is composed, it would seem adapted to
combine the influence of all the parts of the nervous system, and to
afford  a supply of this influence  to each individual organ,  which,
in this way, have a direct nervous communication, and it  is from
this circumstance that its  popular name of sympathetic is derived.
It must, however, be  remarked, that both the anatomical  and the
physiological relation  which this nerve bears to the other  parts of
the system have been  the subject of much discussion.  See Bichat
sur la  Vie et  la Mort,  p. 249 et seq.; also Beclard, p. 61,  and Mr.
Shaw's Strictures upon Bichat in Lond. Med. Journ. t. xlix. p.  456.
Richerand has some good observations upon this part of the nervous
system, Phys. t. i. p. 108.
  t Monro on the Nervous System, p. 24. 
Ganglia.
181
of the medulla of the brain.  Of  late, however, the
directly contrary opinion has been  advanced  by Drs.
Gall and Spurzheim, that the brain is an appendage to
the spinal cord, or  that  it is to be regarded as a kind
of large tubercle or ganglion, connected with it, in the
same way as  other  ganglia are connected  with the
        i            •           i    *  rrii •    *     C
nerves that are contiguous  to them.    Itns  view oi
the  subject  has been  ingeniously defended by  Prof.
Tiedemann, by  a reference  to  the progressive deve-
lopement of the nervous system in the foetus, in which
we  find that the  spinal  cord  is  formed  before the
brain, and also by the analogy of the inferior animals,
where, as we pass on from the  most perfect organiza-
tion to that which is less so, the brain disappears be-
fore the spinal cord.!   Perhaps  this is more a  verbal
distinction than an actual difference  in the conception
of the object, for when anatomists speak of the nerves
as being productions of the  brain, they probably mean
no more than that the brain is the centre to which the
affections of the nervous  system  are to be referred,
employing the phrase rather in a physiological, than in
an anatomical sense.
   The ganglia  are small  knots or masses of  nervous
matter, which  are situated along  the  course  of the
nerves, generally where two or three of them form an
angle, and  especially in  the different  parts  of the
thorax and abdomen.  They are composed  of a mix-
ture of two substances, which appear analogous to the
cineritious and medullary matter of the  brain;  they
are of a redder colour and are more copiously supplied
with arteries  than the  nerves; they  are also of  a

   * Recherches sur le Systeme Nerveux, sect. 1.
   t Medical Repos. v. xv. p. 310.  From some later observations
made by Tiedemann and Serres on the developement of the nervous
system in the human foetus, we learn that  the spinal cord is the
part which is first formed, afterwards the medulla oblongata, then
the cerebellum, and lastly the cerebrum.  Beclard, add. a Bichat,
p. 4 1. 
182           Distribution of the Nerves.
firmer consistence, and are covered with a denser mem-
brane.   Anatomists are  generally agreed  that  the
nerves which  proceed  from a  ganglion  are  larger
than those which enter into it, as if, in their  passage
through  it, they  had  received an additional quantity
of matter.*  With respect to their texture we are  in-
formed  by Monro,! and  the account  which has been
more lately  given by ScarpaJ  is fundamentally  the
same, that the filaments  of  the different nerves which
compose the  ganglion  proceed individually without  in-
terruption, but that they  are  all  twisted  together into
an irregular bundle, and  that filaments from different
nerves are united in  the formation of  a new nerve.
In this way it would appear that  a mechanical connex-
ion is established between the parts that receive their
nerves from  the ganglia, and we may presume that
this will  contribute to a sympathy between their ac-
tions.^
   With  respect to the  distribution  of the nerves it
may be remarked, that the greatest  part of the ner-
vous matter  is sent to the organs of  sense and  of  vo-
luntary motion, that the viscera  are  much more spar-
ingly supplied  with nerves,  the glands have still fewer,
while some  of the  membranous parts appear to be
entirely   without   them.||   Generally  speaking   the
nerves which supply the organs  of sense seem to  pro-
ceed immediately from the base  of the  brain, or
rather from  the medulla oblongata, while the muscles
receive their nerves  from  the spinal cord; but there

   * Haller, EI. Phys.  x. 6, 11.  Soemmering, Corp. Hum. Fab. t
iv. § 157.
   t On the Nervous  System, c. 19.
   X De Nervorum Gangliis,  § 6, 7, et alibi, tab. 2.
   § We have a very full abstract of all  that refers to the ganglia in
 Johnstone's " Essay," with a  copious list of references.
   )| Haller, El. Phys. x. 6, 9. Soemmering, Corp. Hum. Fab.  t. iv.
 § 131. Blumenbach's Inst. Phys. § 210. 
        Great  Quantity of Blood sent to the Brain.    18S

are some exceptions to this rule.   There is much more
irregularity with respect to the course of the nerves
that go to the viscera; they generally take  their im-
mediate origin from some of the  ganglia and plexuses
that form part of the intercostal system, and they are
connected with each  other in a  great variety of ways,
apparently  for the purpose of producing a direct ner-
vous communication between all the viscera, as well as
between each viscus  and the other parts  of  the body.
It is worthy of notice that  the  nervous system gene-
rally,  including  the  brain,  the  spinal  cord,  and all
their ramifications, is so  disposed, that  if the  body be
divided  into  two  lateral  halves, by a plane   passing
perpendicularly through its  centre, the nerves of the
two parts will be almost exactly similar to each other,
while, at the same  time, they are  so united by plexuses
and anastomoses of various  kinds, as to ensure  a  com-
plete connexion beUveen the two  parts and  an entire
correspondence of  their sensations.
   A circumstance connected with the anatomical struc-
ture of the brain that deserves  to be noticed is the
great quantity of blood  which is  transmitted to it by
the arteries.  Haller  made  a calculation, from whicn
he concluded, that  one-fifth of all  the blood sent out
of the left  ventricle of the heart is carried to the
head, although the weight of the  brain in the human
subject be not more  than one-fortieth of that of the
whole body.*   This estimate has  been thought to be
too large, but even if we reduce the quantity of blood
to one-tenth, according to the idea of Monro,! it will
be a very  great  over-proportion.  There  are many
curious contrivances, connected  with  the  circulation
through the head, for preventing this great quantity
of  blood from  producing any  injurious effects  upon
the brain by its pressure or its  unequal distribution,

         * El. Phys. x. 5, 20.
          t On the Nervous System, p. 3. 
184
Fibres of the Brain.
in consequence cither of its stagnating in the vessels, or
being too  violently propelled  through  them, but  the
description of these  is rather  the  province of  the
anatomist  than  the   physiologist.   Many conjectures
have  been formed respecting  the use of this  great
quantity of blood, and it gives a degree  of  plausibility
to an opinion, which was entertained by Hippocrates,*
that the brain has some analogy to a secreting organ.
It has been conceived that one  use of  the  ventricles,
as well as  of the  various internal convolutions of  the
brain, is to afford a more extended  surface, by which
the blood-vessels may enter its substance at a greater
number of points, and consequently, in smaller quanti-
ty at any one part, while, at the same time,  they  are
more firmly supported in their passage  by the greater
quantity of investing membrane.!
  Both  the  chemical and the physical properties of
the  nervous  matter  are  obviously peculiar  to  itself,
unlike  what we meet with in any other of  the con-
stituents of the body, but  wherever it is found it exhi-
bits  nearly the same properties.   Its general  appear-
ance is too well  known  to require any description,  but
there is  one  circumstance which has lately been  the
subject of  much discussion, how far it is to be  consider-
ed as being composed of proper fibres.   It is generally
agreed that the medullary part of the brain, when  ex-
amined in its most  perfect and recent state, especially
after it has been artificially hardened or condensed by
the action  of  heat  or certain  chemical substances,  if it
be carefully scraped with a blunt  instrument, exhibits
the  appearance  of fibres of  considerable  magnitude,

  * De Glandulis, Opera, t. i. p. 272, 1. 17.
  t The conjecture  of Sir Everard Home is not without plausibili-
ty, that the fluid which the ventricles contain, varying in its quan-
tity, may serve to equalize  internal pressure.  Phil.  Trans, for
1814  ; p. 471, and for  1821, p. 32. 
                   Fibres of the Brain.                I8fi

with furrows between them.*   These furrows or striae
are, for the most part, placed in such  a direction as to
converge towards the base of the brain, and it has been
a question, whether these fibres merely unite, forming
what are  termed  commissures, or whether they actu-
ally cross each other, and pass  onto the opposite sides
of the  body.    That this decussation takes  place  with
respect to some at  least of  the fibres, near the  union
of the  cerebrum and  cerebellum,  is an opinion of an-
cient date,! and has occasionally  been announced  in
modern times, as the direct result of anatomical obser-
vation ; but for its full establishment and clear demon-
stration we may consider  ourselves  as indebted to Drs.

  *  Haller, EI. Phys. x. 1, 13.  Cullen's Phys. § 29.  The fibrous
structure of the brain was the  foundation of a great part of  Des-
cartes' hypothetical opinions respecting the animal spirits.
  t For the opinions that have been entertained on this point from
the time of Aretaeus to the present day, see Soemmering de bas.
Enceph., p. 19 ; also Dr. Cooke's elaborate work on Nervous Dis-
eases, v. ii. p. 109. It is remarkable  that the question concerning
the decussation of the fibres of the optic nerves appears still  to be
undecided, although it is a part which, from its size and situation,
might have been  supposed peculiarly favourable for the  purpose.
See Vicq. d'Azyr, p. 51, pi.  17, fig. 1, No. 32.  *
  In the number of the  Lond. Med. and Phys. Journ. which is just
published, for Dec. 1823, we have a brief account of some experi-
ments on this subject by Treviranus.  Upon examining the  optic
nerves,  after their consistence has been hardened by the action of
alcohol, he finds  that a  part of the fibres pass on from their origin
to the retina of the same side, while those of the interior and low
er portion of the nerves appear to unite together, but it could not
be perceived that any of them actually crossed.  It may, perhaps,
not be going too  far to infer that the  same structure may exist  in
the  central  parts of the brain, and  that the greatest part of the
fibres of tbis organ may simply unite or be brought into close  ap-
position.  I  ought to apologize  for offering an opinion  upon  an
anatomical question, but 1 had the good fortune to be present  at
some examinations of the brain which were made  by Dr. Spurz-
heim, and the impression produced upon  my mind was that  com-
paratively tew of the fibres could  be actually seen to decussate : it
is impossible  to  speak  too  highly of the dexterity of his opera-
tions.
                 24 
186       Microscopical Observations on the Br am.
 Gall and Spurzheim.*   Still, however, the quantity of
 fibres which can be seen to decussate, is so small com-
 pared to the whole mass of cerebral matter, as to leave
 some doubt whether it  be sufficient to explain all  the
 pathological  consequences that  have  been  deduced
 from it.  1 allude to the well-known fact,  that an inju-
 ry inflicted on one side of the brain exhibits its effects
 on the opposite  side of the body, proving,  at all events,
 the transmission of the nervous influence in this parti-
 cular direction,  whatever may be  the  physical struc-
 ture  of the  organ.  The  spinal cord, as  vyell  as  the
 brain, possesses  a fibrous texture, although, as it would
 appear, less distinct than the brain, and it  differs from
 the brain in the  effects resulting from disease or injury,
 which are  generally observed to produce  paralysis  on
 the same side of the body with that on which the  in-
 jury  has been inflicted.!
   Of late years  we have had many microscopical obser-
 vations on the minute structure of the brain.   Prochas-
 ka, by employing  a powerful lens,  found it to  be com-
 posed of a pulp, containing a number of small globules
 or rounded particles; the  pulp itself appeared to con-
 sist of  flocculi,* likewise  formed of  globules, connected
 together by fine cellular  substance, the ultimate glo-
 bules being of a tolerably firm consistence, and  about
 eight  times less than the  red particles of  the  blood.J

  * See especially their sixth sect, and the observations made up-
 on it by the members of the Institute, who were selected to report
 on their memoir; from this, and from various papers which were
published in  consequence  of the controversy that ensued on  the
originality of the observations  of Drs. Gall and  Spurzheim,  we
may conclude that the  connecting fibres had been occasionally  ob-
served by anatomists, but that the circumstance had been little at-
tended to, and was not an opinion at that time generally received.
  t See Monro on the Nervous  System, c. 9 ; also Yelloly, in Med.
Chir. Trans, t. i. p.  187, et seq.  ; this valuable paper evinces  the
uncertainty which prevails even among the first anatomists respect-
ing a matter of fact  apparently of easy determination.
  J Op. Min. t. i. p. 342. 
Microscopical Observations on the Bravn.       187
These observations, in their more essential parts, have
been confirmed by the still more recent and elaborate
examination of the Wenzels, who, by using higher mag-
nifiers, detected more clearly the constitution  of the
brain, as composed of a series of these small globules^
which were apparently of a cellular texture, and which
constituted the  whole solid mass  of  the  organ*   It
may seem remarkable that neither Prochaska nor the
Wenzels could perceive any specific difference between
the minute structure of the medullary and the  cineri-
tious  matter,  as we can scarcely doubt that the  latter
is more vascular, and  it may be inferred to be so from
the  observations of  Mr. Bauer, who confirms the ^ex-
istence  of the globules, and remarks that they are dis-
posed  in  lines, so as  to give  the brain its fibrous ap-
pearance.  We are further informed by him, that the
diameter of the globules varies from st-jo  to-ronr of  an
inch,  the general size being -j»Vv; they  are  both  larger
and in greater proportion  in the medullary, than in the
cortical  part of the brain.!
   According  to Sir Everard Home these globules are
connected together by a peculiar  gelatinous substance,
which he conceives to act a very  important part in the
animal  ceconomy. He goes so far as to state that " there
can be  no doubt that the communication of sensation
and volition,  more or less, depends upon it;" he even
regards it as  the very essence of life, and, referring to
Hunter's  doctrine  of the materia  vitae,  he remarks,
" this grand  idea  of  Mr. Hunter's, M. Bauer,  by his
discovery of this transparent  mucus, has realized.";);

   * De  Structura Cerebri, p. 24, et seq.
   t Phil. Trans, for 1818, p. 176 ;  and for 1821, p. 27, et seq.
   X Phil. Trans, for 1821, p. 32, 33.  It may appear not a little
remarkable, that so zealous and intelligent a disciple of the Hun-
terian school, and one whose pursuits  and acquirements so well
qualify him for judging of its tenets, should have  thus broached
the most direct system of materialism that has been given to  the
world.  I  shall have occasion hereafter to atate  the arguments 
188      Microscopical Observations on the Nerves.

  The  fibrous structure of the nerves is  said  to  be
more obvious than that of the medulla of the  brain.
Monro* and Fontana! have examined the nerves with
the microscope, and have described them as being com-
posed of a number of longitudinal cylinders, connected
together  by cellular substance, which, like the muscu-
lar fibres, may be divided into portions that  are more
and more minute, until at  length we arrive at the pri-
mitive or ultimate nervous filament.   This,  according
to the latter  of  these authors, is about  twelve  times
greater than the  fleshy fibre, and may be easily distin-
guished  from it  by its  texture, as well  as by its size.
It is of a waved or tortuous form, and is composed  of
a cylindrical  canal, containing a viscid  pulpy matter,
evidently different from, the substance of  the canal  it-
self.  Monro  describes the ultimate   nervous filament
as a brownish pulpy matter, surrounded by a number
of white transparent  bands, but it would seem that this
appearance of bands was  merely an optical deception,
produced by the  effect  of light acting upon the  waved
surface of the cylinder.^   In speaking of the shape of
the  nerves  I  have employed the  term  cylindrical, in
conformity with  the  account which  is usually given of
them,  but we are informed  by Soemmering,  who must
be regarded  as one of the highest authorities, that they
are of a conical form, the apex being at the part where
they are sent off from the brain, or that they gradual-
ly increase in diameter as they proceed from their  ori-
gin to the organs for which they are destined.^   With

which have induced  me  to adopt the immaterial hypothesis, but
the example and authority of  Sir Everard Home should certainly
operate as a strong motive with  those who embrace this view of
the subject for exercising perfect candour towards their opponents.
  * On the Nervous System, c. 13, and Tab. 13, fig. 1—14.
  t Sur les Poisons, t. ii. p. 18, et seq. pi. 3 et 4.
  X On the Nervous System, c.  13 and 22; See  Soemmering,
 §138.
  § Corp. Hum. Fab. t. iv. § 144 
         Microscopical Observations on the Nerves.      189

respect to the general structure of the nerves it may
be  further remarked, that  the intercostal nerve  and
the par vagura are said to differ from the other nerves
in the disposition of their fibres, which, instead of being
straight and parallel, are irregularly connected to each
other and twisted together.*
  The ultimate nervous fibre, as described by Fonta-
na,  is however very much smaller than the fibres that
seem to compose the  substance of the brain, when  we
scrape it with a blunt instrument; so that if we are to
believe in the reality of both these  formations, and to
suppose that the minute structure of the brain is simi-
lar  to that of the nerves, we must conjecture that the
visible striae  or fibres  of the  brain are  analogous to
the lacerti or larger masses that enter  into the  com-
position  of the  muscles, and  that,  were  their con-
sistence sufficiently solid, they might  be  resolved in-
to smaller primitive fibres, like those that are found
in the muscles.   This view of the subject seems to re-
ceive some confirmation from the observations of Reill
on the nerves, which, as they are among the latest, so
likewise are  probably  to be regarded  as among the
best that we possess upon the subject.    He describes
these bodies as composed of  very fine  filaments, that
seem to differ in thickness, from that of a hair to  the
finest fibre of silk.   These filaments are each of them
enclosed in a delicate sheath,  called neurilema, and in
their course down the nerve they divide, subdivide, and
unite again, in  the most varied  manner,  producing a
perfect connexion among themselves in every  part.   A
number of these filaments forms a larger bundle or fas-
ciculus, which is  always enclosed in its  sheath or neu-
rilema, and these fasciculi divide and unite in the same
way with the primitive filaments.   Most of the nerves
consist of several of these fasciculi, although there are
nerves which contain only  a single one, and perhaps
* Wilson's Lectures on the Skeleton, p. 7. 
190
Chemical Properties of the Brain.
  some of the smallest consist only of an individual fila-
  ment.   The different filaments, as well as the fasciculi,
  are tied together by the substance  which forms  their
  sheaths, and the  same  body  seems to compose the ge-
  neral ^sheath or covering of  the whole nerve, present-
  ing altogether  a structure which is considerably  analo-
  gous  to  that of the muscle.*
    For our  knowledge of the chemical  composition of
  nervous matter we are  indebted, in the first  instance,!
 to Thouretf and Fourcroy,§  who gave  us some impor-
 tant information respecting it, and what they left im-

   * De Structura  Nervorum, c. 1—4, and plates.   Mr. Mayo has
 conferred an obligation upon the student of anatomy, by presenting
 him with  a translation or abstract of many of Reill's treatises, with
 the accompanying plates. These, which are in some measure to
 be regarded in the light of diagrams or plans of the brain, are cha-
 racteristic and expressive, but they appear to me to exaggerate
 the fibrous structure of the parts, even after they  have undergone
 the action of the  chemical re-agents by which their substance is
 hardened, and  their natural divisions rendered more distinct.  In
 speaking of the anatomical structure of the nerves it may be pro-
 per to advert to the curious experiments of Dr. Haighton on the
, re-production  or reparation of nerves.  Phil. Trans, for 1795, p.
 190 et seq.  It appears from them  that after a nerve has been com-
 pletely divided, and its functions totally suspended, it gradually re-
 sumes  its  powers,  and the ends are found to be connected by the
 formation  of a  new substance.   We  should not previously have sus-
 pected that a part possessed  of such delicate functions could have
 been so easily  restored, or that the newly formed portion, which is
 obviously  different from the other parts of the nerve, would have
 proved adequate tp perform the office of the organ in its original
 state.
   t It  will be amusing, and may not be altogether uninstructive, to
 the student of animal chemistry to peruse Lemery's account  of the
 chemical analysis of the brain, written about  the commencement of
 the last century: Course of Chemistry, p. 506....10.  Lemery was
 an intelligent and industrious experimentalist, to whom the science
 lies under considerable obligations.
   X Journ. de  Physique, t. xxxviii. p. 334.   Thouret particularly
 pointed out the circumstance of the little comparative tendency of
 cerebral matter to undergo decomposition, p. 329.
   § Ann. Chim. t.  xvi. p. 282. 
Chemical Properties of the Brain.
191
perfect has been more lately supplied  by Vauquelin.*
The general result of these experiments  is that the
medullary  matter is a peculiar chemical compound, un-
like any other of the constituents of the body; that in
some respects  it resembles  a  saponaceous substance,
being miscible with water, and forming with it an emul-
sion, which remains for a long  time without being de-
composed.  Fourcroy was not able to procure any pro-
per oil  from  the cerebral  substance, nor to obtain any
decisive indication  of the  presence of oil  as entering
into  its composition, but Vauquelin has found in it two
species of adipose,  or rather sdipocerous matter, which
are soluble in  alcohol;  likewise  the  peculiar animal
principle which  is  called osmazome,  together with a
quantity of albumen,  a small quantity  of  phosphorus,
and some salts.   The albuminous matter is capable of
being partially  coagulated both by heat and by  acids,
but either it is in a state of combination, which gives it
specific properties, or it is an essentially different kind
of albumen from that which exists in the blood.   The
action of nitric acid upon brain is considerably  diffe-
rent from  that which it exerts upon most other animal
substances, in disengaging from it little or no azote ; the
gases which  it  evolves being  principally  nitrous and
carbonic acids.   If brain be gradually  heated, a great
proportion of  its  weight,  especially  of  the  cineri-
tious part, is evapdrated in the form of water, so that
the solid matter which is left amounts to no more than
about  one-fourth of the whole ; this forms a half-solid
friable mass, which may be again reduced to an emul-
sion by the addition of water.   If alcohol be digested
upon dried brain, a part of it  is converted into  a sub-
stance  very  like spermaceti, but it does not appear in
wliat way this  change is  effected.  Pure  potash dis-
solves brain, and disengages from it a  large quantity of
ammonia,  and ammonia is also evolved from the solu-
* Ann. Chim. t. Ixxxi. p. 37. 
192
Sensibility.
tion of brain in nitric acid, when it is much concentrat-
ed. A quantity of carbonaceous matter is left in these
processes, and the same takes place from the action oi
sulphuric acid.   Brain is found to contain a quantity of
saline matter, which, however,  seems to be less than
in many other of the  components of  the  body; it
consists principally of the phosphates of lime, soda, and
ammonia.

§ 2.  Vital  Powers or faculties of the  Nervous System,
           and the Mode of their Operation.

   When we consider the brain and nerves, as forming
a part of the living  system, our first  inquiry  must be,
what  properties they possess  in common with the other
organs of the body, and what powers they  have that
are peculiar to themselves.   The  answer to this ques-
tion may be anticipated from  what has  been  already
stated ; of the  two specific powers that distinguish liv-
ing from dead matter, spontaneous motion  and sensa-
tion, the first is confined entirely to the  muscles, while
the latter is equally  confined  to the brain and nerves.
When  a nerve is acted upon  in such  a manner as that
its appropriate power is excited, motion  is not necessa-
rily produced,  nor any other visible  change  but the
animal  feels.  On the  other  hand,  there  are many
cases  in which  motion is  produced .that  is unattended
with sensation; of this kind  are most of the minute
operations   that  compose  the  internal functions, of
which, in a state of health,   we are perfectly  uncon-
scious, and which are only known to us  by their effects.*

  * The separation of the two vital powers is well exemplified in
the very interesting experiments of Mr. Brodie on the action of
poisons on the animal system. Phil.Trans, for 1811, p. 178, et seq.
We learn from them that certain substances have the effect of de-
stroying the sensibility and the power over the voluntary muscles,
while the action of the heart and of the organic  functions appears
to be affected only, as it were, in an indirect manner.   The same
distinction is  still more amply and  extensively established by the 
Sensibility.                   193
These  two powers,  therefore, motion and sensation,
although in a  great number of instances they are con-
nected together, being  reciprocally the cause of each
other,  are not, however, necessarily connected, either
of them may exist separately, and  when they are con-
nected it is not in any  regular proportion.   We con-
clude,  therefore, that  it is  the office of  the  nervous
system to produce sensation, but the way in which this
is accomplished, on the  succession of changes by which
it is immediately  preceded, we shall  find  it extremely
difficult to  ascertain.   With  respect to  the  relation
which  the  different  parts bear to each other,  it has
been generally  supposed  that the brain is the  centre
of  the nervous system,  or that part to which all the
others are  subservient,  and that the nerves receive im-
pressions from external  objects and transmit these im-
pressions to the brain,  where they become  sensible to
the mind, constituting perceptions.*  This view of the

experiments  of Dr Philip,  to  which frequent reference  will be
made in the  subsequent  parts of this work.   A similar conclusion
may be  drawn from an experiment of M. Magendie's on the effect
of prussic acid.  Quart. Journ. v. iv. p. 350.
  * I have ventured to employ the terms " sensation" and "per-
ception" in a sense somewhat different from their  ordinary accep-
tation, but by so doing it appears to me that we avoid part of the
obscurity which attaches to the subject.   Sensation  is generally
used to express the effect produced on the sensorium by an impres-
sion transmitted to it by  a nerve, whereas I  think it will be found
more convenient to extend it to all the actions of the nervous sys-
tem.  It will, therefore,  include both the organic and animal sensi-
bility of Bichat, and the nervous and sensorial powers of Dr. Philip,
while perception,  as 1 would propose to use the term, constitutes
a mode or species of sensation, and is the result of the latter of
these only, corresponding, to a certain extent, with  Bichat's ani-
mal sensibility, and more nearly with Dr.  Philip's sensorial power.
Quart. Journ. v. xiii. p. 97.   The  "sentiment" of Magendie and
some other French writers, is nearly synonymous with " percep-
tion."  Physiol,  t. i. p.  142; and  Bichat uses the word " tact" in
nearly the same sense.  Sur la Vie, &c.  p. 83.  Legallois, how-
ever, employs the word "sentiment;' as  correlative to " mouve-
ment," expressing nervous  ..ction -jrencrally, p. 2, et alibi.  The
                 2fi 
194                  Sensibility.
subject is, in the main, correct, although  the experi-
ments and discoveries of the modern  anatomists have
led to some modifications which must be noticed.
   All questions respecting the action  of  the nervous
system are involved in much  obscurity, which, in some
measure,  attaches to the nature of  the subject.  Al-
though we have found that  there  are many difficulties
connected with the complete understanding of muscu-
lar contraction, yet we may form a plausible conjecture
concerning its mode of action, and can distinctly trace
its operation from its commencement in the fibre to its
effect on the part that is moved.   We do not indeed
see how the  action  of the  stimuli that  are applied
should cause the particles of  the fibre to approximate,
but we can clearly see the connexion between the ap-
proximation of the particles and the consequences that
ensue.  In the nervous system, however,  we have no
phenomena of this kind  to guide our reasoning,  and
although we can prove that  the nerves are the  media
by which external impressions are  conveyed to the
brain, we are totally  at a loss to account for  the  man-
ner in which the conveyance is managed.
   In  proportion to the deficiency of  our knowledge
upon  any topic, so is generally the  obscurity of our
language, and the  terms which  we  employ,  when
speaking of the nervous system and its actions, being
originally metaphorical,  and being  used  in different
senses on different occasions, increase  the  difficulty  of

circumstance  of applying the same term to a different faculty from
that to which it had been appropriated by physiologists of so much
eminence as Bichat and Philip, is of itself an objection to my no-
menclature, but I know  of no other method of  expressing my
meaning clearly, unless by the invention of some new term, to which
I feel  a still stronger objection.  Locke, Essay, b. ii. ch. 1,  § 3, and
the other modern metaphysicians,  so far  as I am acquainted with
their works, make sensation a mode of perception, the difference
between the terms referring rather to some difference in the degree
in which the understanding is affected, than in the  part of the ner-
vous system which is called into action. 
Sensibility.
195
obtaining accurate ideas upon the  subject.   The word
sensibility, which is  employed  by physiologists to  ex-
press the peculiar  power  of  the nervous system, is
applied in common language  to a  certain state of the
mind or  character,  so that  before  we employ  it in
scientific discussions  we must  begin  by discarding  our
accustomed associations.*   Physiological sensibility may
be defined, the power which the  nervous  system  pos-
sesses of receiving and transmitting certain  impressions,
and producing corresponding changes in the sensorium,
but it is essential  to  notice  that these  two operations'
are not necessarily connected together, or  that it  is no
necessary part of this sensibility for  these  impressions
to be perceived by  the  mind,  or to  become  percep-
tions.!  In  what  particular  cases these  powers  are
exercised separately,  or  where nervous action is  not
succeeded by perception, will be considered hereafter.

  *  See note in p. 175.
  t Although the existence of sensation without perception has
been  admitted  by various  physiologists,  especially by Cullen,
Whytt, and Bichat, the subject has generally been rendered some-
what obscure, either in  consequence of the hypotheses that have
been connected  with it,  or the terms that  have been employed.
Cullen uses the word " sensation" in a sense  considerably different
from the one  proposed  above, but, it must  be  admitted, that on
this, as on every other occasion, he expresses himself with great
perspicuity.   Institutions,  § 32, 36,  et alibi.  Bichat has involved
the subject in his complicated doctrine of the two vital  principles,
one serving for organic, the other for animal  life. Scarpa  cor-
rectly defines " simple sensation" to  be  nervous action which is
not attended with consciousness.  Tab. Neur § 21. The subject
is clearly stated by Dr. Park; he, however, substitutes the term
«reflexion" for  " perception;" but  I prefer the latter as being
less metaphorical  Quart.  Journ. v. i. p. 155, et seq.  Richerand cor-
rectly divides sensibility into perceptibility, and into  sensation with-
out perception;  but he afterwards describes this latter too vaguely,
as being common to every thing that has life, and being diffused
through both animals and vegetables.   El.  Physiol, by De Lys,
p. 27.  The existence of nervous action without perception is one
of the points which Mr. C. Bell establishes as marking the differ-
ence between his divisions of the nerves.  Phil. Trans, for 1821. 
196
Action  of the Nervous  System.
but the  possibility of  the  occurrence  is generally  ad-
mitted.*
   Assuming it, therefore,  as  an established  fact, that
the brain and nerves are the  primary  seat of sensibili-
ty, we   must  inquire  into  the  mode  by  which  this
faculty  operates.   The  operation  we shall find to be
of two kinds ; the first  depending  upon the action  of
external bodies on  the  nervous  system, the  second
upon the  re-action  of  the  nervous  system itself  on
some of the corporeal organs.!  The  body is furnished
with  certain instruments, denominated organs of sense,
consisting essentially of two parts, a peculiar conforma-
tion  of  an  organized substance, which  is specifically
adapted to receive and modify certain impressions, and
a quantity of nervous  matter suitably  disposed  for the
reception of the impressions after they have been thus
modified.   The nervous  matter that belongs to the

  * If a  new term be thought necessary to express the power
which certain parts of the nervous system possess of exciting per-
ceptions,  the analogy of our  language would suggest perceptivity ;
but I have not ventured to introduce either this term or sensitivity
into the text.  M. Richerand has employed the  word " perceptibi-
lite" in the same sense.   El. Physiol, t. i. p. 44.
  t In an ingenious experimental essay by M. Fleurens, of which
we have an analysis by  Cuvier,  Ann. Chim.  et  Phys. t. xx. the
author appears to regard  these rather as  two distinct powers of
the nervous system, than as different modes of the operation of the
same power; and probably this  opinion will be found to be correct.
But until  we have a larger body of facts, or some of a more decisive
nature, it must be considered rather as a verbal distinction, than
as one derived from an accurate knowledge of nervous action, and
which affords us any new ideas upon the subject  We may,  how-
ever, observe that the recent investigations of Mr. C. Bell lead us
to a conclusion very similar to that of M. Fleurens, as  we find that
different nerves, or at least  different nervous filaments, are con-
cerned in these operations.  A remarkable instance of the degree
in which  the judgment  is perverted by  preconceived hypothesis
occurs in the writings  of Baglivi, a physiologist of genius and
originality, who supports the doctrine, that the proper  sensibility
of the nerves resides in  their membranous coats.  De Fibra
Motrice Spec. lib. i. cap. 5, corol. 4. 
Illustrations.                 197
organs of sense is connected by  nerves to the brain,
and these nerves possess the power of conveying the
impressions along their course  to this organ, where
they produce perceptions.   In this operation there are
three distinct stages, the  original  impression  on the
sentient nervous extremities,* the  transmission of the
sensation along the trunk of the nerve, and the recep-
tion of it by the  brain; and it may be laid  down  as a
point, proved by  the most  ample  deduction  of  facts,
that an external impression cannot  be perceived by
the mind, without going through the  successive  steps
of this process.
  One of the most important of  the external senses is
the touch; it is extended over a great part of the sur-
face of  the body,  but its  most delicate seat is the
points  of  the fingers.   When  a  substance  presses
upon the finger, some peculiar change is induced upon
the expansion of nervous matter, which is connected
with the cutis; a certain effect is  immediately propa-
gated along  the  nerves that lead from  the hand  to
the brain,  and a third change  is  then  produced  in
the brain itself.   That  these three successive changes
are all concerned in the operation  is proved  by daily
experience, in which we find that  if either the  organ
itself be  injured,  the  nerve  be  interrupted in its
course,  or the brain be  in  any way deranged, the
proper  effect does not follow from the application of
the impression.   The example of  the eye, another  of
the organs of sense, may be adduced, as  affording a
still clearer conception of  the subject,  the impressions
of sight being of  a more  distinct  and  specific  kind
than those  derived  from the  touch.   The eye is an
optical  instrument, consisting  of  a lens,  which  is
adapted for receiving  the rays of light,  and bringing
them into a proper state for forming an impression on
the  retina,  an expansion  of nervous  matter, that is
* Cullen's Physiol. § 29, 30. 
198
Illustrations.
situated at its posterior  part.  The action of the lens
upon the rays of light is entirely mechanical, and differs
in no respect from the effect that is produced upon them
by  a transparent substance of  the same shape and
density.  The nervous expansion at  the back of the
eye  is connected  with the optic nerve, and this commu-
nicates directly with the  under part of the brain.  Now
it is  found as necessary for vision  that the nerve should
be in a  perfect state  as the eye  itself, and we always
find, that although  both the eye and  the  nerve be
perfect, if the brain  be diseased, the correct perception
of sight is not excited.   We' cannot,  indeed, perform
direct experiments upon  those organs of the  external
senses that  are  situated  in the  immediate vicinity of
the brain, as the  eye and the ear, in consequence of
the  short course  of  their  nerves, and   the  impossi-
bility of coming  into contact with them, without de-
ranging parts immediately essential to life ;  but there
are many pathological facts which prove the necessity
for the entire state both  of the organ of sense and the
communicating nerve.  Blindness and loss of  hearing
are  as certainly  produced by an affection of the optic
and  auditory nerves, or  by any circumstance which
prevents them from  performing  their accustomed  ac-
tions, as by a disease of the  eye and the  ear itself, and
without  any physical derangement of  the  part,  we
have frequent  examples, where  mere  pressure upon
the nerves  produces  the  same effect, and where,  upon
the removal of  the pressure, the  faculties of the organ
are again restored.
  The second mode in which the nervous system ope-
rates is  by its re-action on some of the  organs of the
body, an operation which, with  respect  to the succes-
sion  of events, is the reverse of the one which has been
described above.   Of the actions of this description
one of the  most  important to our existence, and the
most frequently exercised, is the  faculty of  voluntary 
V
Re-action of the Brain.             199
motion.  Here the affection originates in the brain, in
which some  change takes  place;  this is transmitted
down the  nerve into  the muscle, where an effect is
produced on the fibre, which causes it to contract, and
in this, as in the former case, all the  three stages are
equally essential.   I do not at present enter into any
discussion concerning the nature of  these changes, but
propose merely to point out the order of their  succes-
sion, and their dependence upon each other.  Now, in
this instance, in consequence of the  space which inter-
venes between the parts where the .action commences
and terminates,  we have the most ample means of ob-
serving the necessity of the  integrity of the nerve as
the medium of communication.   If the nerve be divid-
ed in its course we may exert the volition, and produce
the necessary change in the brain, but no motion will
ensue in the muscle; at  the same time  our own feel-
ings will not indicate to us that any thing has occurred
out of the  ordinary course of events,  and we are  only
aware of  the  defect  by finding ourselves unable to
produce the  desired  contraction.   And we have  it in
our power to prove that, in  this case, the defect does
not depend upon the  morbid  condition of the  muscle,
because if  we irritate the nerve just  below the  point
where it is divided, we find that the  muscle will  con-
tract, in the same manner as if a similar kind of irrita-
tion had been  applied to  the nerve in  its entire  state.
We may also extend the  same kind of trial  to the
brain, for  by  irritating the upper part of  the nerve,
above its division, we shall  have a  sensation produced
in the brain, similar to what would have followed the
application of the same stimulus to the remote extremi-
ty of the nerve.
   We perceive that the two modes in which the pow-
er of sensibility operates, so far  as the order of the
phenomena is  concerned, are exactly the  reverse of
each other, but that the same parts are called into action, 
200             How  do the nerves act?

and are equally connected together*   We  may  then
conclude that sensibility  is  the appropriate and exclu-
sive faculty of the nervous system, and that it has two
distinct modes  of  action,  the one  originating from ex-
ternal  impressions, which are propagated from the ex-
tremities to  the centre,  the  other depending upon a
change in the brain itself, which  proceeds  in the con-
trary direction, from  the centre of the nervous system
to its extreme parts.   Besides these physical functions
of the  nervous  system, there  are others, which either
belong to it, or are,  at least, always connected with it,
of an intellectual or  moral kind,  which constitute the
science of metaphysics; so  far,  however, as they are
attached to the corporeal frame  or affect its  functions,
they will be considered in  a subsequent part  of the
work.
   Having ascertained that  the nervous system  is the
organ of sensibility, either as proceeding from external
impressions carried along the nerves to  the  brain,  or
transmitted by   them in  the contrary direction,  from
the brain to the voluntary muscles, our next subject of
inquiry must be, in what manner is this  operation  ef-
fected ?   The  question may ' be  thus  stated in direct
terms.   When an impression made upon an  organ of
sense is transmitted  by a nerve to the brain, or when
the exercise of volition is communicated  to the nerve,
so as  to produce  the corresponding  effect  upon the
muscle, what change does the nerve experience, or in
what  way  is it  acted  upon, so as  to admit of this trans-
mission?   Three hypotheses have been invented to
account for this power  of the nerves;  the  one which
is the oldest, and has been the most generally received,
is that the brain and nerves are provided with a cer-
tain fluid, called the animal spirits,  which serve as the

   * This remark must be understood in a general sense only, as
from some recent  discoveries there is reason to conclude, that these
two powers or operations are actually  exercised  by different por-
tions of nervous matter. 
            Hypothesis of the Nervous Fluid.         201

medium of communication between the different parts
of the nervous system; the second supposes that  this
transmission is effected by means  of the vibrations or
oscillations of the particles  of the nervous matter it-
self ;  while the third ascribes the action of the nerves
to the operation of electricity.
   The hypothesis of the  animal spirits is popularly as-
cribed to Descartes, and he may, perhaps, be consider-
ed  as the person who reduced  it  to  a  regular form,
and contributed, by his authority, to its general recep-
tion, although traces of it may be  found in the writings
of Hippocrates*  The principal ground of  this hypo-
thesis seems to have  been  the idea that the brain is a
secretory organ, an idea which was suggested by the
great quantity of blood sent to it, and by some supposed
resemblance in its structure to other secreting glands.!
Yet, as nothing cognizable  by the  senses is produced
by  it, it was concluded that  it must secrete  something
of a subtile or etherial nature, peculiarly suited to the
performance of the functions which belong to the brain,
and which are so unlike  those of other material sub-
stances.   It must be recollected, that  about two cen-
turies ago, every thing that could  not be otherwise ex-
plained was referred  to the agency of some kind of re-
fined spirit, an idea which appears to have been origi-
nally derived from the alchemists,  and, after  being in-
corporated with  the metaphysics of the age, gave  rise
to a long train  of mysticism.  Almost every  philoso-
pher of that period adopted more or less of these  no-
tions.   Newton's ether is well known to  have proved
an abundant source of speculation to multitudes of those
who called themselves his followers, and who seem un-
fortunately to have copied almost  the only error which
this great man committed.  Upon  this slender founda-

  * On this point it will be sufficient to refer to the learned work
of Dr. Good, v. ii. p. 22. et seq.
  t Descartes, Tractatus de Homine, 6 14,
                     26 
202                   Of Vibrations.
  tion was built the  hypothesis of  the nervous fluid,  or
  the animal spirits,  as they have been termed ; yet their
  existence was assumed as an ascertained fact, and even
  their different affections and  diseases were  spoken of
  with as much confidence  as  if  the authors  had been
  treating upon something which was the immediate ob-
 ject of their senses, and  with which they  were per-
 fectly familiar.*   The  doctrine of  the animal  spirits
 has likewise  become a  subject of  popular belief, and
 has given rise to  a  variety of  expressions,  that are
 every day employed in  our common language.   There
 does not, however, appear  to be the least shadow of
 proof of  their existence, either from experiment  or ob-
 servation; there is no analogy  in  their  favour, the
 structure and physical  properties of the nerves do not
 seem  adapted to  the office  that  has  been assigned
 them ;  and,  in short, the whole is an hypothesis entire-
 ly unfounded and quite gratuitous.!

   * Haller devotes no less than ten pages of his great work,  El.
 Phys. x. 8,  11—16, to learned discussions respecting the nature of
 this imaginary  agent,  inquires  whether it  be albuminous,  spiritu-
 ous, acid, sulphureous,  aeriform,  or etherial, and concludes that it
 bears a resemblance to what has been termed the spiritus rector
 of plants, a substance nearly as little understood as the one which
 it is intended to illustrate.  The respect which must always attach
 to whatever comes from Haller's pen prevents those reflections
 which we might be inclined "to  make on the occasion,  and we are
 induced rather  to lament the low state of physical  science when
 he wrote, than  to impute to him any deficiency of judgment. Stu-
 art, in his learned dissertation, on the structure and action of mus-
 cles, thus defines the nervous fluid ;  " tenuissimum, dulcissimum,
 mobilissimum, et minime cohoerens, aut coagulationi obnoxium san-
 guinis."  C. v.  § 13.  Its existence is advocated by Sabatier, t.  iii.
 p. 224, and  Boyer, t. iii. p. 311.   Plenk devotes  a  section  to the
 description of its physical properties, many of which, however,  it
 must be allowed are negative ;  Hydrologia, p. 49.  It is indirectly
 admitted even  by Cuvier, Regne Anim.  t. i. p. 31, and more di-
 rectly by  Dr. Good, v. iii. p. 24—27.
  t Does not the curious fact which  has been established   in the
late controversy respecting the effect of dividing the eighth pair of
nerves, that the nervous influence may  be transmitted  along a di-
vided nerve, even when the parts are one-fourth of  an inch asun- 
Of  Vibrations.
203
    The hypothesis of vibrations had  been  imperfectly
  stated by many  of the earlier physiologists, but it was
  so much  detailed  and  embellished  by Hartley, as  to
  be,  by  common consent, connected  with  his name.*
  According to this doctrine  the action of  the nerves
  consists in a vibration of the  particles  of  which  they
  are composed,  by which impressions  are  transmitted
  along them, and conveyed  to and  from  the   brain  in
  perception and volition  respectively.!  This  hypothe-

  der, afford  a direct argument against the idea of this influence de-
 pending upon the passage of a subtile  fluid?  See Quart. Journ. v.
 xi. p. 325, and v. xii. p. 17.
   * The hypothesis of vibrations was very explicitly  laid down
 by N. Robinson, who  published his treatise on the  spleen some
 years before Hartley's " Observations" appeared ; to the general
 idea of the vibratory action of the nerves  he also subjoins the ad-
 ditional  speculation  of the " machinulae," which bear a close re-
 semblance  to  the " vibratiuncles."  New system  of the spleen,
 &c. p. 1, c.  7.   Some of the French  metaphysicians,  especially
 Condillac, preceded  Hartley  in  supporting the doctrine of vibra-
 tions ; Condillac's work  on  the  senses was published  about two
 years before Hartley's.
   t Strictly speaking the hypothesis of vibrations should be sub-
 divided into the opinions  of those who  suppose that the particles of
 the medullary matter itself are the agents, or that there  is diffused
 or dispersed through them a subtile ether which acts the sole or
 the principal part.   Hartley adopts the supposition of the interme-
 diate action of the ether, p. 21, and by thus encumbering his hy-
 pothesis  with this imaginary agent  deprives it of its only recom-
 mendation,  that of simplicity   If we could conceive how the ether
 can receive all the various modifications of external  impressions,
 and transmit them to  the nervous  particles,  there would be no diffi-
 culty in dispensing with the operations of the ether.   Dr. Young's
 view of the subject coincides, in a considerable degree, with Hart-
 ley's, except that for the  hypothetical ether he substitutes the elec-
 tric fluid.  See Med. Lit. p. 99, 100 ; and Lect. v. i. p. 740. Blumen-
 bach  more  directly and explicitly admits the plausibility " of the
 doctrine  of a nervous fluid, which is  thrown into oscillatory vibra-
 tions by the action of stimulants ;" and as if not satisfied with the
 two hypotheses, he argues in favour  of the similarity of nervous
 action and the elective influence.   Nor does he stop even here, but
goes on to state that by the oscillations of tbis ether, Hartley " very
ingeniously explains the association of ideas, and again, by the as-
sistance of this, most  of the functions of the  animal faculties." Phy- 
:i)4                 Of Electricity.
sis has  the advantage over that of the animal  spirits,
inasmuch as it does not  assume  the existence  of  any
imaginary agent, but it may perhaps be questioned whe-
ther it possesses any other recommendation.   We have
no more direct  evidence of  the vibration of the ner-
vous matter than of the fluid of the Cartesians, and we
may remark that the general  aspect and structure of
the nerves  appear perhaps less adapted  to  vibration
than to secretion.   The principal arguments that have
been adduced in favour  of the Hartleian  hypothesis
are certain facts, in which it seems that when an im-
pression has been  made upon  an organ  of sense,  the
effect is continued  for some  time after the  impressing
cause is removed, and  that  it  gradually  subsides  in a
way which was thought most analogous to a vibratory
motion.*   The facts to which  I refer occur particular-
ly with respect to  the sense  of sight, and will  be de-
tailed when I  come to give an account of this faculty,
and I shall  defer to that part of the work the  further
consideration  of the hypothesis  of  vibrations, as its
merits will  be better understood when  we have made
ourselves more fully acquainted  with the  nature of
the external senses.
  The  electric hypothesis is of modern origin, and has
indeed scarcely yet been brought forward in an  arrang-

siol. § 226.  It cannot  but excite some surprise  to observe the fa-
cility with which so eminent a physiologist and naturalist becomes
involved in such an intricate tissue of unfounded speculations.  His
judicious and intelligent commentator, Dr. Elliotson, very candidly
admits the futility of the whole train  of deductions.  See his note
in loco.  With respect to the hypothesis  of vibrations I may re-
mark, that the fact alluded to above, of  the transmission of the
nervous influence through the interval between the parts of a di-
vided nerve, seems more  decisive  against this speculation than
against that of a nervous fluid.  The solution of continuity must
certainly put  an effectual barrier to the propagation  of the vibra-
tory or oscillatory action.
  * Hartley on  Man,  c. i. §  1, prop.  3,  et seq.; Belsham,s Ele
ments, c. iii. § 4. 
Qf Electricity.                    205
 ed  and  methodical  form.   It principally rests  upon
 various experiments  that  have  been made by Dr.  W.
 Philip, and other English physiologists, to elucidate the
 laws of the nervous system, in which it appeared that
 when a nerve  was  divided, so as entirely to intercept
 the transmission of its  action, the  place of  the nerve
 might be supplied by a galvanic apparatus*   The fur-
 ther examination of  this  hypothesis must be likewise
 deferred,  until we have had an opportunity of  consid-
 ering more minutely  the nature  of  the facts  on which
 it is supported, especially those connected with  the
 functions of secretion  and digestion.!

  * Valli's speculations on the  action of the two  metals upon the
parts of living animals led him to assert the identity of electricity
and of the nervous fluid.   Journ. de Phys. t. xli. passim. The same
opinion is, to a certain extent, countenanced  by Dr. Young, Lect.
v. i. p. 740, and was formed previously to the experiments of Dr.
Philip.  Mr. Abernethy goes still further ; for he seems  strongly
inclined to regard some subtile  fluid, analogous to electricity, not
merely as the prime agent  in sensation, but as even  constituting
 the essence of life  itself:  singular as it may appear, we find  this
 highly respectable and intelligent writer sliding into materialism,
at the very  time  when he  is directing the  force  of his genius
against this doctrine.  See Lectures on Hunters Physiol, p. 26,30,
35, 80, et alibi.   It is scarcely necessary to observe that metaphy-
sically speaking, the subtile  or etherial  agents that are called into
aid in our explanation of the vital phenomena, are as truly mate-
rial as the densest stone or metal.
  t^Although the full consideration of this hypothesis is deferred
until we come to that part of the work which treats mo're imme-
 diately of the facts from which  it is derived, I  may anticipate the
 discussion so far as to remark, that, before  the electric hypothesis
 can be considered as proved, two points must be demonstrated ;
 first, that every function of the nervous  system may be performed
by the substitution of electricity for the action of the nerves;  and
 secondly, that all the nerves admit of this substitution.  We must
 not rest satisfied with its apparent action upon the stomach, which
is at best a  dubious case, as  far as the operation  of the nerves is
 concerned ; we must show that volition can be transmitted by the
 electric fluid, and  that this fluid is  equally  capable of stimulating
 the neryes of the involuntary, as of the voluntary  muscles. 
206            Use of the Nervous System.
            § 3.  Use of the Nervous System.

   The uses of the nervous system, the subject which
 we  are  next to consider, may be resolved into two;
 first, to maintain our connexion with the external world,
 by receiving external impressions and producing volun-
 tary motions : and seconaly, to unite the different parts
 of the animal frame into one whole.*
   Although it is possible  to  conceive of a  kind of inde-
 pendent existence being carried on, at least for a limit-
 ed space of time, in which the animal should be cut off
 from all surrounding objects, and in which the exercise
 of his funcjrions should be confined to the simple  con-
 tinuance of life, this state of insulation could not be long
 maintained, and even while it lasted  would be  attend-
 ed with the suspension of  all those circumstances which
 render  life  desirable.  We are, at  every instant, re-
 ceiving impressions from  the  objects which surround
 us, some of them for the immediate purpose of supply-
 ing our corporeal frame with  the materials necessary
 for  its support, and  others acting more directly upon
 the  mental faculties, and  producing a species  of re-ac-
 tion upon some of the organs of the body,  by which we
 are led to accomplish those objects, which are scarcely
 less  essential  to our present state  of existence, than
 what contributes to its  immediate  physical  support.
 Now in consequence of  its  power  of receiving  and
 transmitting  the impressions of  external  objects, the
 nervous system is the great apparatus  by  which these
 effects are accomplished.
   Nor is  the second use of the nervous system less im-

  * The researches of Mr. C. Bell  lead to the conclusion that these
two functions of the nervous system are  exercised by different de-
scriptions of nerves ; the first by certain cerebral and spinal nerves,
which pass directly from the brain or spinal cord to the  organ
which receives the  impression ; the second  by those which  pass
from  one organ to another, including what he terms the  superad-
 ded system of nerves 
Vegetable Life.
207
 portant, that of uniting the various parts of the animal
 frame into  one connected whole.   The different func-
 tions which depend upon contractility, such as the cir-
 culation, respiration, and  digestion, have all  no doubt a
 necessary connexion with each other.   The circulation
 could not be carried on unless the digestion produced
 the materials of which the blood is composed ; respi-
 ration must cease unless the heart propelled the blood
 through the lungs; and digestion can only be perform-
 ed by the blood  being conveyed to the minute arteries
 of the stomach, after  it has received its proper action
 in the lungs.   But  still, if we may use the expression,
 the dependance of these functions upon each other is a
 kind of mechanical dependance.   We may conceive of
 a being that should have all these operations going for-
 ward, according to their respective laws, yet that there
 should be no consciousness of identity, and no connexion
 between these operations, except the physical relation
 which they bear to each other.  If, for example, we
 could, by a  mechanical  operation, propel  the  blood
 along the  arteries, and, at the same time, by artificial
 means, produce the alternate motions of the lungs, we
 might imagine it  possible to procure a supply of arte-
 rial blood,  which,  when conveyed to  the stomach,
 might act there so as  to cause this organ to digest the
 substances contained in it, and to prepare from them a
 quantity  of nutritive matter for the purpose of sangui-
 fication.
  Probably the life of vegetables consists in this  kind
 of physical  connexion  between the different functions,
 in which, by  mechanical and chemical actions alone,  a
 succession of changes takes place merely depending up-
 on  the physical operation of various external agents.
 This may be considered as nearly coinciding with  the
 organic life of Bichat.*   In the  supposed case of the
animal, as stated  above, if we only conceive a force to
'■" * Sur la Vie et la Mort, p. 3. 
208            Lower Classes of Animals.

be applied, so as to set the fluids in motion, we might
imagine  the  rest to be  accomplished by the ordinary
properties of matter, exercising its attractions and affi-
nities,  as the different substances are brought within
the sphere of their mutual action.   But still the being
would  be no  more than a species of  automaton, with-
out homogeneity and destitute of consciousness.   The
nerves, on the  contrary, pervade every part, and give
to the whole set of organs and functions a necessary
vital dependance upon each other, so as to bestow up
on the animal the feeling of  individuality, and to con-
nect all its operations without any visible change in its
structure and composition.  A great part of the scien-
ces of medicine and of pathology consists in tracing the
operation of this  nervous connexion between the diffe-
rent, parts of the body, and observing the effects which
are propagated  to distant  organs  or functions by the
affection of any single  organ or function.  And this
connexion is not  of that kind which we may denomi-
mate physical, where the change is extended to remote
parts in consequence of an alteration in the mechanical
or chemical constituents of the body, but it is to be re-
ferred  to that  sympathetic   connexion  between  the
parts, which can be accounted for upon no other prin-
ciple but the operation of the nervous energy.
  The information which we gain by investigating the
anatomy of different kinds of animals, and comparing
them with the  human  subject, confirms and illustrates
this idea of the use of the nervous system.  It is re-
marked by Blumenbach, that in the cold-blooded ani-
mals, where the size of the  brain bears only a  small
proportion to that of  the nerves  proceeding from it,
there is much less sympathy between the different or-
gans  and functions of the body, while, at the same time,
each separate part possesses  a greater share of indivi-
dual vitality.   This we see exemplified in the length of
time during which life  remains attached to their limbs
when divided from the body,  the power which some of 
Sensorium  Commune.
&t)9
them possess of re-producing parts that have been re-
moved, and, as we descend lower in the scale of orga-
nization, the still more extraordinary power of being
multiplied, like vegetables, by mechanical division*
  This view of the subject will serve, in a great mea-
sure, to answer  a  question, which was formerly the
subject of much controversy among physiologists, whe-
ther there be, what has been termed, a sensorium com-
mune, a part  of the nervous system, from  which voli-
tion originates, and to which all impressions are refer-
red or conveyed, before they excite perceptions.  The
question has  been proposed in  another form, although
essentially of  the same import, whether, when an im-
pression be made upon an organ of sense, as, for exam-
ple, upon the eye, the  perception exists in the eye or
the brain? Is the last change which takes place, imme-
diately previous to perception, an action of the nervous
matter that is connected  with  the eye or of  the brain
itself? The general result of  our experience leads us
to  conclude that there is a common centre of percep-
tion, and that in the human species it exists exclusively
in  the brain.!
   The proof of the existence of a common sensorium
depends upon the facts  that  have  been  referred to
above, where impressions made upon an organ of sense
are not followed by a perception, provided  the nervous
communication  between  the  organ and the  brain  be
destroyed or  injured.   And the same conclusion seems
to  be  confirmed by a series  of facts  the reverse of
these, where, when an effect has been  produced upon
the brain, similar, as  we may suppose, to  one which

  * Blumenbach, Specim. Physiol, p. 20;  Ebel, Observ. Neur. in
Ludwig, Scrip. Neur. t. iii. p.  152.
  t The word brain is here employed in its most extensive sense,
to signify all the parts of the nervous  system  except the nerves
and the spinal  cord.  We have some  reason to suppose that the
medulla oblongata is more immediately essential to certain nervous
operations than either the cerebrum or cerebellum.
                 27 
210          Functions of the  Spinal Cord.

had, on some former  occasion, been transmitted  to  it
from an organ of sense, it has excited the idea of an
external impression, although the organ of sense may
have been  destroyed.   This is the  case  with persons
who, after  having arrived at maturity, have had the
eyes entirely destroyed, yet  such individuals continue
to dream of visible  objects, and arc  able to recall visi-
ble ideas with  perfect facility.  It is  partly also upon
the  principle  of the  actions of the  brain  producing
effects similar to those that  follow from impressions
upon the extremities of the nerves, that we account for
the  mistaken perceptions that are  experienced  after
the loss  of  a limb, which  are frequently not to be dis-
tinguished  from  those  that  formerly  existed  in the
part.*
   In man, as has just been  stated,  the sensorium ap-
pears to be exclusively confined to the brain, but as we
descend  in  the scale  of beings, to those  whose  func-
tions, and especially whose nervous functions, are less
perfect,  it would appear  that the sensorium is  more
extended.   In  some of the amphibia we  may conjec-
ture that the spinal  cord partakes with the brain  in all
its faculties,  and, as  we advance to animals that have a
still simpler  organization, the brain entirely disappears,
and the spinal  cord  seems to be substituted in  its place.
There is, however, reason to doubt  whether, in this
case,  the animal  possesses  any degree of  what can
properly be  called  perception, and  whether the sole
object of its nervous system may not be to convey im-
pressions from  one part to another,  which are neces-
sary for  the  functions  of the animal, but which do not
excite any ideas of consciousness.
  * Porterfield on the  Eye, v. i. p. 364.  The peculiar feelings
experienced by those who have lost a limb, which is described by
the author as  occurring in his  own person, probably depends in
part upon another cause, the comparison which they make between
the sound and the mutilated extremity ; an individual who was born
without legs, or who had lost both of them in infancy, would never
have these false perceptions. 
Effect of Injury of the Brain.          £11
  The same kind of communication by means of nerves,
which we have found to be necessary with respect  to
the brain, is equally so with respect  to the spinal cord,
which may be regarded as a common centre for the
greatest  part of the nerves that supply the muscles  of
voluntary motion.   When the spinal cord  is compressed
or  divided in any part, the limbs  that are  supplied
with nerves which branch  off from it below the  injury,
are palsied.  If the injury take place near the lower
extremity of the spine, the lower limbs  alone become
insensible, and, as none of the functions essential to life
are affected, the patient lives with all his faculties and
powers unimpaired, except that of loco-motion.  The
nearer to the  head the  injury  is situated, so much
more exten-ive  is  the  derangement of the  different
functions; and  there are  cases  upon record, where,
after a dislocation or fracture of some of  the cervical
vertebrae, all power has been lost over  the voluntary
muscles,  and the functions  of the abdominal and  tho-
racic viscera have been nearly suspended, yet, for the
short time that  life  was  capable of being continued
under these circumstances,  the cerebral  functions and
the mental faculties have remained in a sound state.
  Considering, therefore,  the  brain as  the centre  of
perception, it necessarily follows, that an injury to this
organ is attended with a diminution or loss of sensation
to the whole  system, although each of  the organs  of
sense and motion may be  individually in  a sound state.
This  is proved by our  daily experience  of the  effects
of external  violence  upon  the  brain, and of various
diseased  states, either of the nervous matter  itself,  or
of other bodies in its vicinity, such as tumours of the
skull, thickening of its  membranes, or effused fluids of
any kind, pressing  upon the surface of the  brain  or
contained within  its cavities.  One  of  the most fre-
quent causes of the loss of nervous  power is pressure,
and this may take place without any permanent injury
to the part compressed, for we frequently observe that 
212
Fs  Volition confined to the Brain?
when  the pressure  is  removed the organ resumes its
ordinary functions.*
   A question has been asked respecting the organs of
voluntary  motion, which is analogous to  the one  that
has been noticed above respecting the organs of sense.
When we exercise our volition,  and produce muscular
contraction, is the first effect of volition some change in
the brain itself, or does the will act immediately upon
the muscles? The question may perhaps be regarded
as merely  a verbal one, or  at least  as involving more
of a metaphysical than a physical inquiry, and it must
be acknowledged that, like many others connected with
the nervous system, it  is  one to  which we are unable
to give  a  decisive  answer.   Analogy  is,  however,
strongly  in favour of  the  opinion  that  some  change
ensues in  the  brain itself,  and that  this  change is the
cause  of  a subsequent change  in the  nerve, and this
again  of  the  change  in  the muscle.   The  division of
the communicating  nerve  produces the  same  loss of
voluntary power that it does of perception, and although
the process be  reversed, as to the order in which  the
parts are  affected,  each separate  step in the  process
may be supposed to  be  equally essential in the one
case as in the other.-
  Although this mode of reasoning has been generally
adopted  by the modern  physiologists, a  contrary doc-
trine  was  maintained by many of the writers of the
last century, and especially by the Stahlians.   It was
conceived  to be a necessary consequence of their hypo-

  * The case  of the  Parisian  beggar, which has been brought
forwards to explain the nature of sleep, Hartley on  Man,  v. i. p.
46, although it  does not correctly apply to  that state, is a good
illustration  of the  effect of pressure  in producing a temporary
abolition of the nervous functions.  To the same cause may pro-
bably be referred, in part at least,  the coma which was  observed
to ensue in the experiments of M. Rolando upon deep-seated injuries
of the brain, which must  have been necessarily attended with  a
considerable effusion of blood in the interior of the organ.  Magen-
iie, Journ. de Physiol, t. iii. p. 95, et seq. 
Perception confined to  the Brain.         213
thesis, respecting the connexion  between the muscular
and the nervous systems, that the soul, as they termed
it, is  co-existent with the  different  parts of the  body,
and is extended  through all  the organs  of sense and
the  parts subservient  to motion.   The  disciples  of
Stahl supposed the soul to act directly upon every part
of the body, and to be  immediately concerned in  every
vital function, whereas the opponents of this doctrine
maintained that the soul acts only upon  the brain, and
is immediately concerned in the sensitive and intellec-
tual functions alone.*   I  shall have occasion to state
my objections to the Stahlian hypothesis  hereafter, but
I may remark in this place, that even  were  it  to  be
admitted, the above consequence does not necessarily
follow from it.
  We have now, therefore, proceeded so far as to con-
clude that the brain is  the common centre of the ner-
vous system, to which all  the impressions of  external
bodies on the extremities of  the nerves are  referred,
and from which originate all the actions that  are exe-
cuted by  the  organs under  the control   of the  will.!
Physiologists, however, have not  been  satisfied with
assigning  the  brain  generally as the  sensorium com-
mune ; they  have been anxious to find  out some par-
ticular portion of it which might be regarded as  the
more  essential organ to which all the rest are subser-
vient.  The investigation is a curious one, and, although
it may have been rendered ridiculous by the  whimsical
opinions  to  which it has given rise, it is  in itself  a legi-
timate object of inquiry.  It may be regarded as  essen-
tially the same, although  expressed in more correct

  * See Haller, El. Phys. x. 8, 24.
  t Haller, El. Phys. x. 8, 23—25.  The  agency of the brain is
here extended to every operation of the nervous system in which
either perception or volition is concerned ; in simple nervous ac-
tion, as for example, in that which is carried on  between the diffe-
rent abdominal viscera, we have no evidence that any parts are
concerned except the nerves themselves. 
£14
Hypothesis of the Pineal Gland.
 language, with the discussion which occupied so much
 of the attention of  the older metaphysicians and phy-
 siologists  respecting the  seat  of  the soul, by  which
 word, so  far  as they had any accurate notions upon
 the  subject,  they  appear  to  have  intended  to ex-
 press the organ of  perception and  volition, or  rather
 that material  organ to which these faculties are at-
 tached, or through which  they  operate.   There are
 many circumstances with respect to the structure and
 organization of the  brain, which have led to the suppo-
 sition, not only  that its various parts must each of them
 exercise some peculiar function, but that certain por-
 tions of it possess the  specific  powers of  the nervous
 system in a  much greater degree  than  others.  The
 fibrous or striated appearance of the brain, which has
 been lately so much attended to by anatomists, seems also
 to lead to the same conclusion, as the uniform direction
 of these striae and their regular disposition, converging
 to certain parts of the cerebral mass, would induce us
 to regard them as  analogous to the fibres which com]
 pose the nerves,  and  intended to convey  the nervous
 influence to  some particular organ, which is more es-
sentially or necessarily concerned in perception.
  It would  be an unprofitable waste of time to relate
 the various  notions that have been entertained upon
 this  subject,  as they are, for  the most  part, purely
 hypothetical, and destitute even of a shadow of proof.
 It may be proper, however, to notice an opinion that
 prevailed at one time among some  eminent physiolo-
gists, that the immediate  seat  of  perception is not in
the  brain itself,  but  in  the investing membrane,  an
 opinion evidently connected with the  mistaken hypo-
thesis derived from the ancients, respecting the sensi-
bility of membrane  generally, to which I have already
had  occasion to  refer,  and  which, as we shall after-
wards find, was applied  to many  other  parts  of the
animal economy.  There is also another opinion on this
subject that may be noticed, but certainly more in con- 
Hypothesis of the Pineal Gland.           215
 sequence of  the celebrity of the name to  which it is
 attached, and to the favourable reception which it ex-
 perienced among  men  of science,  than of its  intrinsic
 merit.   I allude to  tiie idea of Descartes, who pointed
 out the pineal gland as the peculiar organ of the ner-
 vous functions, or, as it was termed, the seat  of  the
 soul.*   The  pineal  gland  is  a small  projection at  the
 basis of the brain, which,  in  many respects,  is curiously
 organized,  and appears to be carefully protected from
 external injury.   It was  therefore  conjectured that it
 must serve some  important  purpose, and  this conjec-
 ture appeared to be confirmed  by  the circumstance
 that, upon  examining the brains of certain idiots, they
 were found to  contain a  quantity  of earthy matter.
 This sand was supposed to be an extraneous substance
 which, from  accident  or  disease,  was  lodged  in  the
 part, and impeded its  functions, and, a connexion thus
 appearing to exist between  a disease of this part and
 an imperfection in the  nervous powers, it  was conclud-
 ed to be the  immediate seat of these faculties.  There
 was some plausibility in this reasoning.   But Descartes,
 although a man who  very effectually  promoted  the
 progress of knowledge, lived before the full establish-
 ment of the  inductive  method of  philosophizing.   He
 neglected to inquire into the natural state of the gland ;

  * Tractatus de Homine, pars Quinta. This organ is thus describ-
 ed by Muraltus ;  " Hsc  (glandula pinealis) radicibus quatuor, ali-
 quando binis,  aliquando unica, insignibus medullaribus, i. e. nervis
 omnibus  in compendio junctis suffulcitur : haec omnium objectorum
 motusexcipit: anima in  hac sola per hos motus sensilia externa, et
 omnes ideas, quae a sensibus proficiscuntur, apprehendit, tanquam
in centro, &c."   Clavis Medicinae, p. 508, (1677.)  A perspicuous
 abstract  of Descartes' system may be found in Sprengel, Hist, de la
 Med. t. v. sect. 5, ch. 4.   He informs us, contrary to  what is com-
 monly related, that the  existence of earthy matter in  the pineal
gland was first detected  by  Huet.  For the form of the organ and
its connexion  with the other parts of the brain, see  Vicq d'Azyr,
pi. 8, fig. 1, Nos. 17, 18; pi. 12,  No. 14; pi. 13, No. 14;  pi.  14,
No. 20 ;  pi 16, No. 45.   This splendid performance must be ad-
mitted to supersede every other reference. 
210           Effect of Injuries or Diseases.

it has been since found that, in the  adult  human sub
ject, earthy matter is always present in it, and indeed
composes a considerable part of its substance.*
  The investigation of the particular seat of nervous
sensibility  has been  diligently  prosecuted by some of
the modern  anatomists,  and they have  undoubtedly
proceeded upon  a more correct plan, if they have not
been more successful in  their result.   They have not
been satisfied with mere  conjecture,  but, in order to
discover this  supposed seat of sensibility,  they  have
adopted  two modes of inquiry.
  According to the first they have examined the brain
after it has  been injured  by accident  or  disease, and
have noticed  what effects have  been  produced  upon
its faculties;  whether the destruction of any particular
part has been followed by the loss of any particular
faculty;  or whether  there is any one part, the destruc-
tion of which seems  to be necessarily  connected with
the total loss of the  sensitive functions.   But although
many  accurate  examinations  have  been  made, and
many curious facts that bear upon this  point have been
brought forward,! nothing very  important  seems to
have been established, except that the medullary mat-
ter in general is more sensible than the  cortical.   It
seems likewise  to be proved that the sensibility of the
medullary part itself increases as we  proceed nearer
to the centre of the brain, where we also find a  much
more  elaborate system  of organization,  and a  much
greater variety of separate parts, all of which we may

  * Blumenbach's Physiol, p.  125 ; and Comp. Anat. by Lawrence.
p. 296.  Soemmering, De acervulo cerebri dissertatio, in Ludwig,
Scrip. Neur. t. iii. p. 322.  An analysis is given of the earthy mat-
ter, but it is not sufficiently' accurate to enable us to ascertain its
nature ; they seem to indicate that it contains lime, and it is stated
that  the oxalic acid enters into its composition, p. 337.  See also
Soemmering, Fab.  Hum.  Corp. t. 4,  § 52,  et  Wenzel de  Struct.
Penit. Nerv. p. 316.
  t Haller, El. Phys. x. 7, 22. 
Effect of Injuries or Diseases.           217
fairly conclude serve some  appropriate  purpose con-
nected  with the nervous powers.  Indeed  the result of
our examination of the  brain,  after it has  been injured
or diseased, is that it is capable of undergoing a much
greater  degree  of  disorganization  in its mechanical
structure, than could previously have been supposed
compatible  with the maintenance of its functions, with-
out  their being very  materially  affected.   With re-
spect t^the more external  portion  of the brain, it is
well known that it may be pierced or cut, or even that
large masses of it may  be removed without any very
material effect  being produced upon  the  perceptive
faculties,* and we frequently find that large abscesses
are formed in it, or  tumours and excrescences of vari-
ous kinds, which,  if  they do  not compress the remain-
ing part  of  the brain, seem to produce little injury to

  * This was very remarkably exemplified in the experiments of
M. Legallois and Dr.  Philip, and in some that have been made
more  lately by M. Flourens, of which we  have  an analysis by
Cuvier,  Ann. Chim. et Phys. t. xx.  Sir Everard  Home's experi-
ence leads him to a  conclusion still more singular,  that  all the
functions of the brain remain after the destruction  of the whole of
its medullary matter.  Phil. Trans, for 1821, p. 31.  See likewise
Monro on  the Brain,  p.  38, with  the references; and  Diet, des
Scien. Med. Art. " Hydrocephale," p. 243, et alibi, by Itard.  This
is also the inference that we are  to draw  from  an amusing, al-
though not very scientific paper in the  Edinburgh  Review, vol.
xxiv. p.  434;  if we adopt implicitly all  the statements that are
brought forward in this  article, it would  be very difficult to assign
any use  for the brain.  Of the two most  remarkable cases quoted,
that taken from  Dr. Quinn, it may be remarked,  is  vaguely and
briefly related, and is moreover anonymous.  On Dropsy of the
Brain, p. 104.  The other case, which was very minutely describ-
ed by Dr. Heysham, is,  on many accounts, deserving of our atten-
tion, and serves to show  in a remarkable manner the independence
of the contractile functions  upon the nervous system, but  it does
not throw much light  on the connexion between the brain and the
sensitive functions.  I may be allowed to observe that the reason-
ing of Dr. Hull would have  been more perspicuous had the terms
employed been used in a more definite manner; the essay is, how-
ever, a  valuable collection  of facts  Manchester  Mem. vol. v.
p. 47*'
                   28 
218
Of Hydroceplialus.
its functions.   There are also many curious  and well
authenticated pathological  facts on  record, where dif-
ferent parts of the medulla  of  the  brain  have  been
destroyed, and even those which,  from their  situation
with respect to the organs of sense, might have been
supposed  the  most  essential, and  yet the   nervous
powers have remained nearly in their ordinary state.
   The facts that have been observed with resriect  to
hydrocephalus bear  immediately  upon this  question,
and  lead  to  conclusions  that  are  very  unexpected.
When the  water  collects  in the  ventricles  that are
near the base of  the brain, if the skull yields  to the
distend ha force from within, and  the pressure  be not
too suddenly applied, the bones separate and  the skull
becomes enlarged to an immoderate size.   When the
head is examined after death, the cavity of the skull
is found to  be filled  with a  fluid, surrounded  by  a
kind of bag of cerebral matter.   Until lately it was
assumed as an obvious and well ascertained fact, that,
in  these cases, a considerable part  of the brain was
actually removed  by  the  absorbents,  but  even  if,
according  to the statement  of Dr. Gall and  some  of
the  continental  anatomists,  the  substance   of the
'brain is  not  actually  diminished,  still  its  texture and
organization  must  be   very  materially   deranged.*

   * The opinion, that in those cases of hydrocephalus  where the
skull allows of the extension of the size of the head, and the con-
sequent formation of a large central cavity, the substance  of the
brain is not actually removed, but  has only the relative situation
of its parts  changed, was maintained  by Sir Everard Home,
probably before it had been promulgated by the continental anato-
mists.  In the Phil. Trans, for  1814,  p. 474, after  giving an
account  of a case in which the head had acquired an enormous
size, while the mental faculties were but little impaired, he adds,
" .The cerebrum is made up of thin convolutions of medullary and
cortical substance, surrounding the two lateral ventricles, which are
unfolded when the cavities of these ventricles  are enlarged, and
in this unfolded state the functions  belonging  to this part of the
organ can be carried on."  As the brain  in this case was not ex-
 amined, we may infer that the above conclusion was derived from 
         Attempts to trace the Nerces to one  Spot.     219

From the gradual way in which the symptoms of the
disease  manifest themselves, we may be  certain  that,
for a long  time before death, the  head  must  have
been nearly in the same  state  in  which it  is found
upon dissection, yet the faculties, both  physical and
intellectual, have   remained  in  tolerable  perfection,
and  the patient has rather suffered from  general  indis-
position, and from  the inconvenience  of an  unwieldy
head, totally disproportioned to the rest  of the body,
than from a  defect  of the  powers of the nervous
system.*
   Another method which has  been employed in order
to ascertain the  seat  of the  sensorium commune, is
to endeavour to trace  up the nerves  of the  different
organs  of  sense to  one spot within the  brain,  which
might  be  considered as  their origin.   But  although
this  plan has  been attempted  by  the  most skilful
anatomists, it  has  not been  successful;  many of the
nerves  may indeed be  traced up to the base of the
brain,  or to some   part  immediately connected with
the  medulla  oblongata, but   this  cannot  be  accom-
plished  with respect to the whole of them.   It would
appear, therefore, that no  anatomical centre of this

dissections of morbid brains that had been previously made, and it
will hence afford us another instance in which Sir Everard Home
has anticipated Drs. Gall and Spurzheim in what has been supposed
among the most novel of their doctrines.  Some remarks are made
by Morgagni oh this subject, Book I,  letter  12, art.  13, et  seq.
which show that he had a somewhat similar idea, although pro-
bably less precise than that of. Sir Everard Home.  He speaks of
"the substance of the cerebrum itself" adhering to the skull  "in
the form of  a membrane ;"  of " the brain being  extended  almost
to the thinness of  a membrane ;" but,  at the same time, he con-
ceives that there  are many cases  where  the  brain is actually
destroyed.  It does not exactly appear  whether he thought the
loss of the sensitive and intellectual  functions  were  in proportion
to the actual destruction of the brain.
  * Dr. Male has detailed one of the .most remarkable cases of this
kind  which we have on record in  the Ed. Med. Journ. v. ix. p.
398. 
 ■120       Uses of Different Parts of the Brain.

 kind has  yet been  detected,  and when  we  find that
 the accurate  Soemmering, as  the   result  of his  re-
 searches,  has fixed upon  the  halitus, or fluid in the
 ventricles, as the  primary seat of sensibility,* we can
 scarcely expect that it ever will be discovered.
   And besides  the  difficulties, both pathological and
 anatomical,  which we  have found in our attempts to fix
 upon any  spot within the  cerebral mass  as the  imme-
 diate seat of the  perceptive faculties, there are some
 circumstances  which  lead us to  doubt  whether any
 organ of this kind actually exists.   There are certain
 considerations which have  induced many physiologists
 to conclude  that, although  the brain is to be regarded
 as the  common sensorium, yet  that the expression
 can  only  be  employed  in  a  general way, when  we
 speak of the cerebrum and cerebellum  as contrasted
 with the  nerves and  spinal  cord.   An opinion has
 long prevailed that different portions of the brain are
 subservient  to  different offices,  as, for example, that
 some are  more peculiarly  connected with the organs
 of sense,  some  with  voluntary  motion,  and  others
 with the different  vital functions.   Willis was  among
 the first who distinctly pointed out certain phenomena
 that were  supposed to lead to this conclusion.  His
 idea was,  that  the cerebrum  or proper  brain is the
 organ  of  the  perceptions derived  from  the external
 senses, and of voluntary motion, while the cerebellum

  * He admits that every  part of  the brain has been injured,
 without any  corresponding injury having been perceived in its
 functions, and he, at the same time, objects to  the doctrine that
 all the brain  in its whole extent is to be regarded as the seat of
 the mental powers.  Fab. Hum. Corp. t. 4, § 98.   Hence he con-
 ceived himself reduced to the dilemma of fixing upon the fluid of
 the ventricles as the appropriate organ of the noblest faculty which
 is possessed  by man.  In § 59, he says, " peculiare organum sen-
sorii communis  si ponere fas est, vel si propria sedes sensorio com-
 muni in cerebro est, haud sine veri quadam specie  hoc in humore
 (ventriculorum) quaeri debet."  On this subject see Sprengel, Inst.
 Med. t. ii. p.  237, et seq. 
Uses  of different Parts of the Brain.       221
 is the source of the  involuntary  and vital  functions.*
 This  opinion,  which  was  embraced  and zealously
 defended by Boerhaave, and many  of his disciples,!
 was derived partly from observations and experiments
 on the effects of injuries to  the two parts of the cere-
 bral  mass  respectively, and partly  from  the investi-
 gations of comparative anatomy; but although many
 curious coincidences were pointed out, yet  the objec-
 tions against the  hypothesis that were adduced  by
 Haller and  others  were  so  decisive,! as to prove  that
 it is unfounded.§
   But although it may  be  admitted  that we have
 not succeeded in our  attempts to  appropriate different
 parts of the cerebral mass  to different nervous func-
 tions, either according to  the arrangement of  Willis,
 or of  any other which  has been proposed since his
 time, still there are certain  considerations which  may
 lead us to suspect  that  this appropriation  may actu-
 ally exist.   And on this question we  may derive some
 important  information  from  the  experiments  of M.
 Legallois and Dr. Philip, and the  discussion  to  which
 they have given rise.  It  appears to be  fully  esta-
 blished by these physiologists, and more particularly
 by Dr. Philip, who has stated his opinion  with more
 precision and accuracy  than M.   Legallois, that the
 action  of the  nerves  is different  from,  and  inde-
 pendent of,  that of the brain.  He accordingly assigns

  * Cerebri Anat. c. 15, p. 74.
  t Boerhaave,  Instit.  § 401,  415.  See also Haller, El. Phys.
 iv. 5. 8.
  X El. Phys. x. 7,  36.
  § Dr. Philip, whose experimental investigations have given him
 the means  of forming a correct opinion on this subject,  concludes
 that the division of the cerebral mass into cerebrum and cerebellum
 has no relation to the voluntary and involuntary muscles, but may
 rather refer to some distinction between  the different sensorial
functions.  Exper.  Enq. p. 108.  The late investigations by M.
Fleurens seem to show  that the cerebrum is the more immediate
seat of perception, and the cerebellum of volition. 
222   Philip's Classification of the Nervous Functions.

to  them different denominations, styling them respec-
tively the  nervous and sensorial powers.*   It appears
that the former of these consists simply in the  transmis-
sion of certain effects by means of the nerves  from one
part of the  system to  another, in which  the brain is
not necessarily concerned, and that consequently they
are not  referrible  to the  common   sensorium.   Our
inquiry, therefore, will  be limited to Dr. Philip's sen-
sorial power, which  he supposes to be  composed of
the  functions  of  perception!  and  volition.    Now
there is at least  no  improbability in  the  supposition,
that these  functions,  which  appear  to be so  clearly
distinct  in   their  nature  and  operation, might  be
attached to different parts of the  brain,{  and perhaps

  * Enquiry, p. 186.  Phil. Trans, for  1815, p. 90.
  t Or, as he terms it, sensation ; see note in p. 193.
  X A very elaborate train  of experiments  has been  lately per-
formed  on this subject by M. Fleurens, of  which we  have an
abstract by M.  Cuvier.  M. Fleurens'proposed to  discover from
what part of the brain irritation  may be  propagated to the mus-
cles, to what part sensation extends, proceeding from the  extremi-
ties towards the centre, and what is the immediate seat  of volition
when it is exercised in effecting muscular contraction.  He endea-
voured to ascertain these points by gradually removing  successive
portions of the  brain and noticing the effects of each removal,
when he was led to conclude that the two first of these, or,  as we
may regard them, the centres of irritation and of sensation, are in
the medulla oblongata, at the  part where  the tubercula quadri-
gemina are attached  to it.   We are Informed  that the great mass
of the cerebrum and cerebellum are  not immediately  concerned
either in muscular irritation or in sensation ; they appear, however,
to be necessary to perception, especially the former, which  is also
supposed to be the immediate seat  of memory and intellect.  The
effect of removing the cerebellum was to destroy  the voluntary
power over the muscles ; the animal appeared to retnin  its volition,
but  had  lost the capacity of exercising it.  M Cuvier speaks in
high terms of  commendation of the paper  of M.  Fleurens, and
it must be confessed  that if  the experiments be confirmed, they
will lead to very important views respecting the  nervous func-
tions.   Ann. de Chim.  et  Physique,  t.  20.   Shortly after  the
publication of  the  above abstract,  M. Magendie published a
detail of a series  of  experiments,  very closely resembling those 
      Philip's Classification of the Nervous Functions.  22S

some  confirmation  of  this  opinion  may be derived
from some of his experiments, in  which  the two func-
tions of the sensorial power were not always affected
in the same  degree  bv the  same  application to the
brain, or by the same mechanical  injury to its structure.
Possibly we  may go so far as to  conjecture that while
the perceptive faculties have their common centre in
the medulla oblongata  or  its appendages, volition has
a more extended connexion with the brain, a conjec-
ture which may derive some  support from the  more
intellectual nature  of this latter faculty.   So far as we
are able  to come to any conclusion upon so intricate a
subject, it  would   appear  that the  brain  itself is the
more immediate  seat of the  proper  intellectual facul-
ties, or that it is through this part of the nervous sys-
tem that the mind acts upon the  physical organs.  But
the further consideration of  this question, as well as
the doctrine of craniology, will be referred to a subse-
quent part of the work.*

of M. Fleurens, which  had been performed twelve years  before
by M. Rolando.  They appear, indeed, to have been even more deci-
sive, and to have been made upon a greater variety of animals, than
those  of M. Fleurens.   They were, I believe, entirely unknown
in this country, and seem to have been nearly so in France ; and
it must be acknowledged that this coincidence, where we have no
ground for suspecting  any  unfair claim  to originality on the part
of M. Fleurens, must  tend  very  materially to, strengthen our
confidence in the accuracy of the results.  The  principal circum-
stance in which the conclusions of M. Rolando  differ from those
of M. Fleurens is, that whereas the latter physiologist considers
the cerebellum to be  the regulator, as he terms it, of the volun-
tary motions, M. Rolando regards it  as  the origin  of  them, thus
more completely separating the primary seat of perception from
that of volition.  Magendie, Journ. de Physiol, t. iii. p. 95, et
seq. See some observations upon the  subject  by M. Magendie,
p. 153.
  * It may be worthy of remark, that Sir Everard Home has given
his  sanction and authority to the doctrine of craniology in the most
explicit manner, although the mode of  reasoning upon which he
founds  his opinion may appear somewhat questionable.   Phil.
Trans, for 1821, p. 31. 
 224       Bell and Magendie's Experiments.

   Although  we  have  so little certain knowledge re-
 specting the exact parts of the brain, which may serve
 as the respective centres of  the two functions of per-
 ception and volition, some very interesting experiments
 have been lately  made by Mr. Bell and M. Magendie,*
 which confirm the  opinion that had been advanced by
 physiologists as a plausible conjecture,  that the trans-
 mission of these  two powers  from the extremities to
 the brain, or from the  brain  to the extremities, is ef-
 fected by different nerves, or at least by different ner-
 vous filaments.   The  nerves  that  proceed  from  the
 spine have a double  origin,  or are composed of two
 nerves, one  proceeding from  the  anterior,  and  the
 other  from  the posterior part  of the cord.   Now,  it
 has been found by direct experiment, that the  parts to
 which the nerves are sent are deprived of motion and
 sensation respectively, according as the anterior or pos-
 terior  roots of the  nerves are divided.  From this se-
 paration of the functions of the nerves, and the appro-
 priation of each function  to a specific organ,!  we gain
 an analogical argument for the  same kind of separation
 in the brain, and  this conjecture would  appear to be

  * I have associated the name of M. Magendie with that of Mr.
 Bell as  the discoverer of the fact referred to in the text; but,  in
justice to Mr. Bell, it is necessary to  state, that his experiments
 were clearly antecedent to those of M.  Magendie, although M.
 Magendie might have been unacquainted with them.  On this sub-
ject the papers of Mr. Shaw furnish  very decisive evidence, and
 should be perused, as well for this as for the other valuable matter
 which they contain,  connected with  the  double function of the
 nerves.  See Lond. Med. Journ. v. xlviii p.  343, and 457 ;  v.
 xlix. p. 449.  It is always a painful task  to notice what may ap-
 pear like disingenuousness, especially in those whose attainments
 are of a superior order ; such a reflection cannot, however, but be
 suggested by the perusal  of a late memoir of  M. Magendie's in
 Ann. de Chim. et Phys. t. xxiii. p. 429.
  t This separation of the nervous functions has been extended by
 M. Magendie to the two pillars of which the spinal cord is com-
 posed.  Journ. de  Physiol, t. iii. p.  153. 
BeWs Division of the Nerves.
225
sanctioned by the experiments of M. Fleurens and M.
Rolando.
  A very interesting  series of  facts has  been lately
brought forwards by Mr. Bell respecting the functions
of the nerves, which  throws considerable  light upon
their mode of  action and  their connexion  with  the
other parts of the system.   There are certain circum-
stances in the anatomical structure and the distribution
of the nerves  which led to  the  arrangement of them
into two  classes,  and which indicated that they each
serve different purposes in the animal ceconomy.  From
the situation of these two sets of nerves with respect
to their origin  and to each other, Mr. Bell has given
them the names of symmetrical or original, and irregu-
lar or superadded.   The first  set,  which  might  per-
haps be called more appropriately, the general nerves,
consist of the  fifth pair of the cranial and all the spinal
nerves; they  have double  roots, one  of which is  con-
nected  with  ganglia;  they pass  laterally  to  the  two
halves of the body, the two sides having no connexion
with each other,  and they are distributed to all the
muscular parts that are  under  the control of the  will.
They appear to be  the organs of perception and  voli-
tion, deriving, as we may  conjecture, these two func-
tions from their double  roots.  These we may regard
as that part  of the nervous system  which serves the
purpose of establishing our connexion with the exter-
nal world.
   Mr. Bell's second set  of nerves proceed by single
 roots from the  base of the medulla oblongata, or the
 parts immediately connected with it;  they procee d in
 a much more irregular  manner than the former, and
 are distributed  to all the organs which are concerned,
 either directly  or indirectly, in the function of respira-
 tion.  From  this  circumstance they have  received the
 denomination of respiratory  nerves, as well as that of
 superadded or  irregular.   Their course  is designated
 by this last term, as they  pass from one organ to ano- 
226
General Conclusion.
 ther in the most intricate  manner, connecting  them to-
 gether, passing across the general  nerves,  occasionally
 uniting with them, and forming the connecting link be-
 tween the two  halves of the body.    These nerves are
 not under the control of the will, and are  not capable
 of exciting perception ; they are, therefore, furnished
 only with the faculty of transmitting the nervous influ-
 ence, or with what Dr.  Philip styles nervous  power,
 in  opposition  to sensorial.   Some very curious and im-
 portant  pathological  deductions  have been made  by
 Mr. Bell, from  the new  views which he has  given us
 on the subject of the nerves, and we have  also a num-
 ber of additional remarks by Mr. Shaw, which confirm
 and illustrate  Mr. Bell's doctrines,  and give us reason
 to  expect that they may be applied with great advan-
 tage to the practice  of medicine and  surgery.*
   The result  of our observations  upon the  nervous
 system and its functions is,  that it has two distinct pow-
 ers,  that of  receiving  and transmitting impressions,
 which is exercised by the  nerves and spinal cord, and

  * See Bell, in  Phil. Trans, for  1821, p.  398, et seq.;  also Phil.
 Trans, for 1822,  p. 284, et seq.; and Shaw, in Quart. Journ. v.
 xiii. p. 120; and Med.  Chir. Trans, v.  xii. p. 105; Lond. Med.
 Phys. Journ. v. xlviii. p.  343, and 457; v. xlix. p. 449.  Experi-
 m&te similar in their nature to  those of Mr. Bell have been per-
 formed by Mr. Mayo, but with a different result, so far as the re-
 spective powers of the nerves are concerned, and their relation to
 the  faculties of perception and voluntary motion.   Comment, p.
 107, et seq.; and part 2, p. 2, et seq.  It is to  be  regretted that
 such discrepancies  should arise, but where  truth is the only object
 of the inquirer, they will be in no long time  reconciled  by multi-
plying our observations and experiments.   Since the above was
written two papers  of Mr. Bell's have appeared in the Phil. Trans.
for  1823, p. 166, and 289, in which he has made a beautiful appli-
cation of his principle to  illustrate the respective  offices of the
different nerves that are sent to the eye and the parts immediately
connected with it.  The acute mind of J.  Hunter enabled, him to
detect the general  principle  of the specific powers of different
nerves when sent to the same organ, Animal  Economy, p. 262, but
the  merit of demonstrating the truth of the  principle, and of its
successful application, rests with Mr. Bell. 
General Conclusion.
007
that of perception  and volition,  which is more immedi-
ately exercised  by the brain.*  Upon this  principle
Blumenbach has arranged the organs of these functions
into the two  classes of sensorial,  comprehending  the
brain  and its immediate appendages, and the nervous.
properly  so called,  including the nerves, the  plexuses,
and the ganglia.!   The sensorial organs are the exclu-
sive seat  of the  powers of perception and volition,  and
of the  intellectual  faculties,  while the  office of  the
nerves is  to serve as media of communication  between
the common centre and the  organs of sense and  mo-
tion.}

  * Dr. Philip, in Quart. Journ. v. xiv. p. 93.
  t Instit. Physiol. § 198.
  X What is stated in the text is, perhaps, all that we are warrant-
ed in concluding  from  the facts which  are at present clearly ascer-
tained ; but it is almost impossible to proceed so far without form-
ing some conjectures,  or proposing some queries respecting what
remains still to be discovered   Mr, Bell's first  set of nerves, i. e.
the fifth cranial and the spinal, possess the function  of communi-
cating both perception and volition, and as they arise from  double
roots, it is not unreasonable to infer, that the two  roots serve re-
spectively for the two powers.  But these nerves are  distributed
both to the voluntary muscles, and to the skin and the internal sur-
faces ;  has  any  anatomical  difference been detected between the
nerve of the two orders of parts,  the one possessing  the  double
function, the other  merely serving for the transmission of percep-
tion ?  Mr.  Bell's second division of nerves, the irregular, are not
capable of communicating either perception or volition, but serve
to transmit  the nervous influence from one  part to another; it in-
cludes what he names  the respiratory nerves and the intercostal
system, and is connected in an indirect manner only with the brain,
while it is principally  to these nerves that the ganglia  are  attach-
ed.  Are these nerves capable of  transmitting their influence  in
both directions ?  Is it probable, that besides their ordinary office,
these nerves, on certain occasions, are capable of conveying per-
ceptions, and that the ganglia are the parts to which the percep-
tions are referred,  for example, the  perceptions of internal dis-
eases 1   Besides  these two classes of nerves, we have a third kind,
those appropriated  for specific perceptions, as the optic, the olfac-
tory, &c.; What is  there peculiar in  their anatomical structure?
Do not the  mere perceptive parts of the first class belong to this di-
vision ?  Have not  the nerves  of  the  surfaces more  analogy,  at 
228      Comparative Examination of the Brain.

   The great superiority of the intellectual faculties of
man over those  of  other animals,  has induced anato-
mists to investigate  whether there be any thing in his
anatomical structure which would seem to account for
this superiority.   The great  size of the  human brain,
compared to that of other animals, was noticed by the
ancients, and Aristotle laid it down as a  general  prin-
ciple,  that  the faculties which  were  referred to  this
organ  were  in proportion to its size, compared  with
that of  the  whole  body.  This rule holds good  with
respect to many  of  the domestic animals, which were
the best known  to  the ancients, and  upon which we
may presume that their observations were made.   For
example, the brain of a man, according to  the calcula-
tion  of Monro, is four times  that of an  ox, although,
upon  an average, the body  of  the ox is  six times  the
size of the human body.*   But there are many excep-
tions to this  rule.  It has  been found by  the accurate
researches of the modern anatomists, that  in some of
the mammalia, the proportion of the size of the brain
to the  body is equal to that of the human subject,! and
that there are certain species of birds  in  which  the
proportional size is  even  greater.  It further appears
that some animals, which are remarkable for the com-
parative perfection of their sensorial powers, have the
brain  below the  average size,  as  the horse  and  the

least in  their functions, with  these  nerves, than with those which
transmit volition ?  What relation do the nerves that convey simple
sensations of pleasure and pain  bear to the other parts of the ner-
vous system ?   The  further consideration of many of these points
obviously belongs to  a subsequent  part of the work.  In order to
avoid circumlocution it might be convenient to give the names pf
simply sensitive, perceptive, and motive, to the three kinds of
nerves,  according as  they respectively serve for the offices of the
mere transmission of nervous  influence,  for perception, and for
voluntary motion.
  * On the Nervous System, p. 25.
  t Bufl'on, v. ix. p. 247, says that the brain of the seal is larger in
proportion to the body of the animal than that of the human subject. 
         Comparative Examination of the Brain.     229

elephant.  In man, the  ratio of the weight of the
brain to that of the whole body has  been stated at  an
average at about ^, in the  dog it is about ris, in the
horse _^, in the elephant ^-  only, while, on the con-
trary, in several of the small singing birds, and particu-
larly in the canary, the  brain is above the average of
man, being as much as T>T,* and Ebel mentions a kind of
simia, where the proportion is even T\.\
   But an observation  has been  made by Soemmering,
to which hitherto  no  exception has  been found, that
the perfection of the  sensitive functions  does not de-
'pend upon the absolute size of the brain, nor upon its
proportion to the  body at large, but  upon the propor-
tion between the size  of the brain and the aggregated
bulk of the nerves that proceed from it ;J  or, according
to Blumenbach's nomenclature,  between  the sensorial
and the nervous  organs.   As  an illustration  of this
position the example  of the horse is cited; the abso-
lute size of the  brain of the  horse  is only  about half
the size of the human  brain,  while the mass of  the
nerves of the horse at their origin,  is no less than  ten
times larger than that  of  man.  And as  we pursue
 our researches into comparative anatomy, we find that
we  are able, in  most cases at least,  to trace a corres-
pondence  between the  perfection  of the  respective
functions  and the  physical condition of the organs.
 Most of the inferior animals  have larger nerves, and
possess some of the nervous functions in a much more
 acute state than man,  but man decidedly excels them
 all in the  comparative size of the brain and in the per-
 fection of his intellectual functions.

   * Cuvier, Lee,. d'Anat.  Comp. t. ii. p.  149,  et seq. See also
 Lawrence's Lect. p. 19J.
   t  Observ. Neurol, ex Anat. Comp. in Ludwig, Scrip. Neur. t.
 iii. p. 150.
   X  Corp. Hum. Fab. t. iv. §92; de  Basi  Enceph.  p. 14.  Law-
 rence's Lectures, p.  192,  et  seq.  Blumenbach's  Comp. Anat. by
 Lawrence, p. 292. 
 230      Comparative Examination of the Brain.

    Ever since the time of  Willis the  proportion of the
 cerebrum to the cerebellum is a point  that has  been
 attended to by anatomists, as marking a difference in
 the degree of perfection of the nervous system, and it
 has been asserted, that the proportion of the cerebrum
 to the cerebellum is greater in  man  than in any other
 animal.   But although this  holds  good  in most in-
 stances,  it appears from  Cuvier that there are some
 exceptions, and,  as  is  often the case in comparative
 anatomy, we find that in those points where man differs
 most from other  animals, there are some species of
 simiae which resemble the human subject.  In man the
 weight of the cerebrum is to that of the  cerebellum as
 nine to one, in the dog as eight to one, in the horse as
 seven to one, in the  cat as six to one,  in the sheep as
 five to one, while, on the contrary, in a certain  species
 of monkey, the proportion is as much as  fourteen to
 one.* It may seem somewhat remarkable  that although,
 in the higher classes of animals, we find a general ratio
 between the perfection of the nervous system and the
 large size of the cerebrum, compared with that of the
 cerebellum, yet when  we descend lower in the scale,
 we meet  with some cases in which  the  cerebellum is
 entirely wanting.   In these cases,  however, the gene-
 ral form  of the brain differs so much from that of man,
 and the animals that resemble him, that it is not easy
 to say what are the parts most analogous to  each other,
or  to what portions of the brain the different appella-
tions ought to be applied.
   Another comparison has been instituted, which gives
a more constant superiority to the human subject, the
proportionate  size of  the  cerebrum  to  the medulla
oblongata, although, in this instance,  as well as in the
former,  the simiae are found  to be more analogous to
man than to any other animals.!

  * Lee. d'Anat. Comp. t. ii. p. 152, et seq.  Blumenbach's Comp.
Anat. by Lawrence, p.  312.
  t Lee. d'Anat. Comp. t. ii. p. 152, et seq.   The dolphin forms 
Use of the Ganglia.
231
  All these comparative observations are deserving of
attention, but we may remark concerning them, that
we  might, a priori, expect the powers of the (nervous
system  to depend as much,  at least, upon the perfec-
tion of  its organization, as upon its mere bulk, or upon
the proportion between the  size  of its different parts.
It does  not appear that any very  accurate comparative
observations  have been made upon the minute struc-
ture of  the brain in the different classes of animals, nor
perhaps ought we to expect to be able  to discern any
visible difference between them ; but it is well  known
that the greatest variety exists in their  general figure
and anatomical  structure, and although  we  are  very
frequently unable to trace the connexion between the
configuration of  parts and their respective functions, we
may reasonably infer that such a connexion actually
exists.
  The  only further  observations that I shall offer on
the comparative uses  of the different  parts  of the
nervous system  are  concerning the  appropriate office
of  the  ganglia.   From the  mode in which  they are
composed, it  appeared a natural conclusion,  that one
office which they perform is to produce  a more com-
plete connexion and  sympathy between the sensations
of  distant  parts; but this,  as far  as appears,  might
have been  accomplished  by the simple union  of the
nervous filaments, as  occurs in  the  plexuses, without
the additional apparatus which we observe in the gan-
glia : some eminent anatomists, as Winslow, Willis, and
Vieussens, supposed  them to be small brains, or inde-
pendent sources of nervous power  and central spots,
to  which  perceptions  are referred.  This opinion is
embraced by Richerand* and by Cuvier,! and a doc-

the only exception to this rule among the animals upon which ob-
servations have been made.
  * Physiologie, t. i. p. 108.
  t Leg. d'Anat. Comp. Intr. p. 26.  The author remarks that the
ganglia are larger and more numerous when the brain is deficient
in size. 
232    Connexion between the Nerves and the Muscles.

trine essentially similar is maintained by Bichat,* who
conceives them to be the nervous centres of the orga-
nic functions.   Lancisi had  a fanciful notion that they
promoted  the  flow  of the animal  spirits  along the
nerves, by a kind of  muscular action ;f  Johnstone sup-
posed that their use is  to render the organs  which
derive  their  nerves  from  them independent  of the
wilhj  and it  has been  lately  conjectured  that their
office is to recruit the nerves that pass through them,
or to add to their substance, in the same  manner that
the cortical part of the  brain  has been conceived  to
generate  the  medulla.  Dr. Philip considers the  gan-
glia as secondary sources of nervous influence, the spe-
cific office of which is to receive supplies of it from all
parts of the  brain and spinal cord, and  transmit this
collected influence to the organs where it is required.^
But  the difficulty which  has been already  alluded  to
occurs  in  this  hypothesis,  that this  combination  of
nervous influence, so far as  we know, might  have been
accomplished  by the mere  union of the  nervous fila-
ments.||  Upon the whole  I apprehend we must ac-
knowledge that the specific office of the ganglia has
not been discovered.

§ 4.  Connexion  between  the  Muscular and  Nervous
                      Systems.

  Having  considered the properties and uses of the
nervous system, I proceed to inquire into  the nature of
the connexion between the  nerves and  the muscles, or,

  * Anat. Gen. t. i. p. 200; t. ii.  p. 405.
  t Morgagni, Ad vers. Anat. pars 5, p. 113.
  X Essay on the Ganglia, p. 19.
  § Enquiry, p. 170, et seq.; Phil. Trans, for 1815, p. 436 ; Quart.
Journ. v. xiii. p. 266.
  || For a concise  view of the  various opinions  that have been
entertained upon this subject, see Soemmering, Corp. Hum. Fab.
6  161. 
Question stated.
233
more generally, between  sensation and motion.   After
Haller had clearly established  the difference  between
the two essential properties of animal life, contractility
and sensibility, and pointed out their mode of action, it
was  universally admitted  that the former of  them  is
the immediate cause  of motion and the latter of sensa-
tion.   It was  obvious that motion was, in many cases,
necessarily accompanied by sensation, but the question
then  arose, whether  it was so in  all  instances.  The
solution  of  this question was attended with many diffi-
culties, and  eventually gave rise to one of the most ani-
mated controversies  that  ever took place in  physiolo-
gy, and  which, although  no longer pursued with  any
degree of acrimony, subsists  to the present day.
   The point at issue may  be thus stated.   When a
stimulant acts upon a  muscular fibre, so as to produce
contraction, does it act immediately upon the  fibre it-
self, or does it not always  act through the intervention
of a nerve ?  The nerves are the organs of sensation,
when, therefore, a muscle receives the impression of a
stimulant, is not this  impression always, in the first in-
stance, received upon the nervous matter distributed
through the muscle,'and the impression then  transfer-
red  from the nerve to the muscular fibre ? Haller and
his disciples thought  the  intervention of the nerve not
to be necessary,  but supposed that the irritability of
 the  muscle, as they termed it, was, in many cases  at
 least, alone concerned, and that consequently stimulants
 were capable of acting upon the  fibre itself.   His op-
 ponents, of whom Whytt was one of the most active
 and zealous, supported the contrary doctrine, and main
 tained that the muscular fibre is merely an  organ of
 motion, that it is incapable of  receiving impressions
 from external objects,  and  never contracts,  except
 through the  intervention  of the nervous power * Thio
 hypothesis  was embraced by many of the French writ-

   *  On Vital and Involuntary Motions, sect. i. p. 10, et alibi.
                 30 
234
Arguments of the Hallerians.
crs, particularly by Senac, who became one of its most
able defenders, as well as by the colleagues of Whytt,
Cullen  and Monro;  and it was  the doctrine generally
embraced in  the University of Edinburgh,  then ap-
proaching to  its  most  splendid period of  reputation.*
The term irritability, which had  been originally used
by  Glisson in a physiological sense, and had been adopt-
ed  by  Haller, was employed  by the  two parties in a
somewhat different meaning, a  circumstance which it is
necessary to bear in  mind  in examining the  merits of
the  controversy.   By Haller it is intended to express
the power inherent in the muscular fibre (its vis incita)
of being excited  to contraction on the application of a
stimulant; according  to Whytt it  means  the faculty
which the muscular  fibre possesses of receiving impres-
sions transmitted to it from the nerves.   The experi-
ments and arguments that have been adduced in  this
controversy, in support of the two opposite  opinions,
have filled  many volumes ; I shall only have  it in my
power  at present to  notice a few of the leading  facts
that  have been  stated, and the general scope of the
reasoning that has been employed.!

  * Willis, who was  one  of the first that minutely attended to the
operations  of the nervous system, conceived that all  motion de-
pends upon, or originates in, the nerves, and that the nerves of the
voluntary and involuntary organs are derived from the cerebrum
and cerebellum respectively.  Mayow, Boerhaave, and other emi-
nent physiologists of the latter part of the  seventeenth and the be-
ginning of the eighteenth century, adopted Willis's hypothesis, and
it may be considered as  the prevailing opinion until  the time of
Haller.
  t  A well-digested and  correct state of the hypotheses that pre-
vailed on this subject before the time of Haller, and of his own
doctrines, will  be found in a report made  to the French  Institute
on the experiments of Legallois by Percy, Humboldt,  and Halle.
See Ed. Med. Journ.  v. x. p. 207 ; and Philip, in Quarterly Journ.
v. xiii. p. 98 ; also Dr. Cooke's introduction to his valuable treatise
on nervous diseases.—M. Cabanis, an eloquent and acute  writer,
and the nature of whose  work might be supposed to lead him to a
degree of logical accuracy, has, notwithstanding, chosen to regard
this controversy as merely a verbal one, but I believe that I shall 
Arguments of the Hallerians.
235
   The great argument of Haller was an appeal to the
anatomical structure and obvious powers of the animal
body.   He made a distinction between the contractile
and  the sensitive organs, and he endeavoured  to point
out to what parts of the system these terms were res-
pectively  applicable.*   He pointed  out  some which
were extremely  contractile, but were only scantily sup-
plied with nerves, and it was found generally, that the
contractility of  parts did not bear any ratio to their
sensibility, or to the quantity of nerves sent to them.
The  example  of the  heart was adduced in proof  of
this  position.   Indeed  so little sensitive is  this organ,
not merely in  its sound, but even in its  morbid state,
that there are many well-known instances, where it is
found  to  have undergone great alteration in its struc-
ture, to have  had its parts condensed by the effect  of
inflammation,  or even destroyed by  suppuration, and
yet no pain has been felt, and nothing unusual has been
experienced except a sense of oppression, and  this not
depending so much  upon the condition of the heart  it-
self, as upon the difficulty which it  had in  transmitting
the blood along the arteries.
   In the second  place it was urged as a powerful argu-
ment in favour of the Hallerian doctrine, that muscular
parts remain contractile  for a long time after they are
removed  from the  body, and when their  communica-
tion with the  brain  is of course destroyed.!  This is
especially the case  with  respect to the heart, which in
frogs and in  cold-blooded animals generally, for  many
hours  after its separation from the body, will still con-
tract on the application  of a stimulant; but how,  it  is
asked, can the  nervous system be  concerned in this
case, since the centre of the sensibility is removed ?

be justified in stating that he has completely misunderstood the na-
ture of the  argument.  See  Rapports du Phys. et Mor.  de l'hom
me, t. i. p. 90, 91, (2e edit.)
  * Mem sur les Part. Sens, et Irrit.  Opera Minera, t,  i. p. 239.
  t Haller sur les Part. Sens, et Irrit. t. i. p.  48, et seq. 
236
Arguments of the Hallerians.
   A third set of facts, which were supposed to be still
more in favour of his doctrine, was brought  forwards
by Haller, consisting of the accounts of foetuses that
were born with imperfect brains, or  even altogether
without heads, and yet had grown to their full size in
the uterus,  and after  birth exhibited many marks of
contractility, being capable of moving their limbs upon
the application of stimuli, of evacuating the contents of
the bladder and intestines, and, in short, of exercising
the accustomed  functions, as far as was consistent with
their imperfect  organization.   Indeed it would appear
that, if we could have supplied the materials for diges-
tion, life  might  have  been prolonged to  an indefinite
period.   This point  has been lately insisted upon by
Dr. Philip, in his essay on the connexion between  the
muscular and the nervous powers.   From  some expe-
riments that  were performed by Legallois  on this sub-
t'ect, it seemed  to be proved, that the  motion of the
 leart was independent of the brain,yet that there was
a necessary connexion  between the heart and the spinal
cord.*  But  the experiments of  Dr. Philip have de-
monstrated,  that the spinal  cord is no more necessary
than the brain for the motion of the heart.   He found
that the total destruction both of the brain  and  the
spinal cord did not prevent the contraction of the heart
from proceeding in its ordinary manner, provided its oth-
er connexions with the system were duly maintained ;
he |ikewise adduces  cases, apparently well authenticat-
ed, of foetuses born in a state of  maturity, where  the
spinal cord, as well as  the brain, was totally wanting.!
   In the fourth place, the Hallerian doctrine has been
supposed by some physiologists to receive very powerful
support from the  constitution of  the lower classes of
animals, such as the  Actiniae, and others of the larger

  * Sur le Principe de la Vie, p. 138, et seq. et alibi.
  t Philip's Enq. p. 62.   Lawrence, in Med. Chir. Trans, v. v. p.
168, et seq. 
Arguments of the Hallerians.
237
zoophytes, which are of considerable size, and are en-
dowed with a great degree of contractile power, yet in
which the most  minute  researches have not been able
to detect a nervous system.   The limbs of these ani-
mals contract upon  the application of a stimulant, and
of course the contraction is brought  about without the
intervention of nerves, but  as it appears to be precise-
ly similar to  that of animals that have  a nervous  sys-
tem,  so we  may conclude  that in both  cases the pro-
cess is conducted in the  same manner, and according to
the same general laws.
   A fifth argument in favour of the  Hallerian doctrine
has been derived from the order of  time in which the
different parts of the body  come into existence and ac-
quire their full powers.   By minute observations made
upon the foetus, and more especially  upon the chick  in
ovo, during the earliest  periods of their existence, we
learn that the formation  of the heart precedes that  of
the  brain; that the first distinct indication of life is a
small beating point, the  punctum saliens, as it has been
called,* which afterwards becomes  the  muscular sub-
stance  of the ventricles, from  this  the large  vessels
gradually expand, and it is not until  after some  time
that the  brain becomes  organized.!  The  successive
periods at which the functions of the parts respective-
ly commence  their  actions agree wi'h these observa-
tions.   The  contractions of  the heart" proceed with
perfect regularity long before we can trace any sign  of
the  operations  of the nervous system, and we find a
great variety of involuntary muscular motions perform-
ed in the most perfect manner immediately after birth,
while it seems necessary that a considerable length  of

  * Harvey de Generatione.  Exerc. 17.
  t From the recent observations of Sir K.  Home we learn, that
the rudiments of the brain and spinal cord are  visible before the
heart, but it may be argued,  that the nervous system is at ths pe-
riod incapable of performing  any of its functions.  Phil. Trans, for
1822, p. 342. 
238      Contraction of the Fibrin by Galvanism.

time should elapse before any of the nervous functions
are capable of being exercised.*
   Besides the above  arguments, all of which seem to
be derived from legitimate grounds of reasoning, other
considerations have been adduced in favour of the Hal-
lerian doctrine, which are either in themselves of less
weight, or have been since  superseded by more cor-
rect scientific investigations.  These, it will not be ne-
cessary to notice, except indeed that derived from the
analogy of  vegetables, which Haller himself seems to
have regarded as of considerable  force.   Plants, he
said, exhibit evident marks of irritability, they possess
spontaneous motion,  and obey  the operation of stimu-
lants,  yet they are without nerves,  so  that we have
here a case  in which  irritability exists independent of
a nervous system.   But this  is  certainly an attempt to
explain what is obscure by  something which  is still
more so; we know less  of  vegetable  than of  animal
life, and when we speak  of  the irritability  of  vegeta-
bles, we employ a metaphorical  expression to denote
a quality with the nature of which we are totally un-
acquainted.
   I must not omit to mention an argument, that would
have great weight in  favour of the independent  con-
tractility of  the muscular fibre,  were the fact on which
it  is founded fully established.  I allude to some  expe-
riments which were performed in  Italy a  few  years
ago, on the application of galvanism to the fibrin of the
blood  immediately after coagulation,  in which it was
stated  that a contraction was  produced  in this substance
similar to that of the  muscular  fibre.   The strong ana-
logy which exists between  the  properties  of  the two
kinds of fibrin would no  doubt  go far to demonstrate,
that if contraction could be  produced  without  the in-
tervention of nerves  in  the  one  case,  it  might be so
likewise in  the other.   Unfortunately, however, the
* Haller, El. Phys. iv. 4. 28 
Reply of the Neurologists.
239
fact in  question is  not sufficiently authenticated; the
experiment, when  performed in  this country, has not
succeeded, and  although a negative  experiment is not
to be considered as of itself of equal  force with a posi-
tive one, yet, upon the  whole, the  preponderance of
evidence  seems to be against the contractility of the
fibrin of the blood.*
   Powerful and  direct  as the arguments  may seem
which were adduced by Haller and his disciples, in sup-
port of the  doctrine of the independent  action of the
muscular  fibre, the neurologists have not been remiss
in replying to them, and  they  have  further supported
their side of  the question by arguments,  which, by
many physiologists, have been even thought more con-
vincing.   In opposition  to Haller they have  likewise
appealed to the anatomical structure of the body, and
have  particularly insisted upon  the general diffusion of
nervous matter through the substance of  the  muscles.
Although we are not able to trace the nerves to their
extreme ramifications, yet it is contended that they are
in fact distributed  to  each individual  fibre, for when
we insert into a muscular part the finest point of a nee-
die, if it be only  sufficient to produce a contraction, it
will excite a corresponding sensation.  Indeed some of
the ablest defenders  of  this side  of  the  question, and
particularly  Smith, seem disposed to rest the issue of
the question upon this sole point, whether it  be possi-
ble to discover any part which i<- contractile, and which
is, at the same  time, not furnished  with  nerves.   It
seems,  however, impossible to  put it to the test of di-
rect experiment, for although we might have it in our
power  to obtain the muscular fibre in a separate state,
and might even,  by  the diagnostic characters pointed

  * See also Berzeliu« on the progress of animal chemistry, p.
20, where we are informed that the  apparent contraction of fibrin
upon the application of electricity depends  upon the shrinking of
the body connected with its coagulation; it is not improbable that
the process may be promoted by electricity. 
240             Reply of the Neurologists.
out  by Fontana, accurately  distinguish  between  the
muscular and  the nervous  filaments, yet in employing
the mechanical means necessary for their separation,
all  their vital properties would be  unavoidably extin-
guished.   With respect  to the  heart and the other
parts which are scantily supplied with nerves, and yet
possess a great degree of contractility, it  was  said that
in these cases, the quantity of nerve, although small, is
in proportion to the nature of the  stimulant,  and the
degree of effect required, and, in short, that the nerves
of the heart are adequate  to the action of the organ.
Then  it is  argued  that the  heart  is  furnished  with
nerves, although  small,  and if they  are not employed
in producing its contraction, for what purpose  are  they
destined ?
  With respect  to the  power which individual  mus-
cles possess of retaining their  contractility  when sepa-
rated from the body, the neurologists certainly appear
to have been much puzzled to account for the pheno-
mena, and they were  reduced to  the  necessity of
adopting the  opinion, which appears to involve a gross
inconsistency, that  the sentient  principle is divisible*
or rather that there  is no  sensorium commune.   This
inconsistency  they could only  escape  by adopting the
Stahlian hypothesis of the  soul being co-extended  with

  *  Whytt on Sensibility  and Irritability, part 2, § 2.   On  Vital
and Involuntary Motions, § 14.   We may remark how directly the
opinions of this learned physiologist lead to materialism,  at the very
time that he is arguing against this doctrine ; a striking  example of
the  inconsistencies into which we fall when  we attempt to investi-
gate topics that are  beyond our comprehension, and a powerful
motive for exercising the utmost candour towards those who differ
from us on such abstruse points.  Mr. Herbert Mayo, who is  in ge-
neral remarkabi? for the correctness of his phraseology, may be
cited as an illustration of the same  sentiment.  In his observations
upon this much agitated question, he  uses the expression, " mind
and matter are logically distinct substances," thus controverting his
own position in the very enunciation of it.  The candid and  philo-
sophical reflections with which he concludes the chapter cannot be
too highly commended. Anat. Comment,  p. 8, 9. 
Reply  of the Neurologists.            241
the body* as they termed it, or that the different parts
of the  body were able  individually  to perceive  the
effect  of stimuli  applied to  them.  Senac explicitly
states  it as his opinion, that the nerves and spinal cord
possess all the  properties of  the  brain, only in a less
degree, and that they are capable, for a limited time,
of performing all  its  functions-!  According to the hy-
pothesis of the  animal spirits,  which was then general-
ly adopted, he conceives that  the  spinal cord and even
the ncrvos are capable of generating these spirits, and,
in short, that the  whole nervous system is, to a certain
extent, the seat of perception-!   The same kind of
reasoning  was  applied  to repel  the  arguments that
were  drawn  from  the existence  of foetuses without
heads, in which case it was said that  the seat of sensi-
bility was only  in  part removed,  and that what was
left in the  spinal cord, the nerves, and  the ganglia, was
still competent to carry  on all  the  functions which are
exercised by these imperfect beings.
   In connexion with this argument it  has  been observ-
ed that the size of the brain and the spinal cord, in the
different classes of animals, bears no proportion to each
other;  on  the contrary, as we descend to the less per-
fectly organized classes, the brain diminishes,  and at
length entirely disappears, while  the spinal cord is in-
creased in  size,  as if for  the purpose of supplying  the
place of the brain.   These  facts  are well  known, but
the inference to be drawn from them is  not  so clear.
Before  we can form an  hypothesis to account for  the
action of the nervous  system, derived from  observa-
tions on the  comparative  anatomy of  the inferior  ani-

  * See Stuart de  Motu Muscul. § 5.
  t This appears to be the opinion likewise of Scarpa; speaking
of the nerves generally,  he says that they possess a power inde-
pendent of the  brain, and cites the cases of acephalous foetuses in
proof of this point.  Tabulae Neur. § 22.
  X Sur le Cceur, liv. 4. c. viii.
                 31 
242            Reply of the Neurologists.
mals, we must previously make ourselves acquainted
with the nature of their functions, which we have many
reasons for supposing to be very  different  from those
of the human species.   The acephalous foetuses, which
have been employed to show the independence of the
muscles  upon, the  nervous system,  have been also
brought  forward  to prove the  independence  of the
nerves upon the  brain, for it is said that, in these cases,
the nerves are perfectly formed, or  even sometimes
larger than natural, as  if intended to  supply  the defi-
ciency of the brain.  But here again, although we may
admit the anatomical facts, the conclusion does not ne-
cessarily follow from them, for in these instances there
is no unequivocal evidence of the existence of any func-
tions, which  the Hallerians conceive to be exclusively
attached to the brain as distinct from the nerves, and
although the nerves exhibited their natural appearance,
and seemed to  possess a perfect  anatomical structure,
we have no means of ascertaining in what degree they
were capable of exercising their appropriate  functions.
   The uniformity of the action of  the different fibres
of which the muscle consists, or what  has been termed
the general consent of all its parts,  has been regarded
by some of the neurologists as an argument  of much
weight in favour  of their doctrine.   If only one fibre
be irritated,  the whole muscle instantly  contracts, but
how can this contraction be propagated from fibre to
fibre except by means of nerves?  This argument, how-
ever, implies a  knowledge  of the  intimate  nature of
muscular contractility  which  we are not. entitled to
assume,  and it can only be regarded as endeavouring
to explain a difficulty by the adoption of an  hypothe-
tical principle, which itself stands in need of proof.
   The argument in favour of the  Hallerian hypothesis,
drawn from the  absence of nerves in the zoophytes,
was answered by asserting that we are not sufficiently
acquainted with the structure  of these animals to make
it the foundation of our reasoning, and  it was  even 
          Direct Arguments of the Neurologists.       243

alleged that the same argument might be employed to
prove  the existence of contractility without the muscu-
lar fibres; for a proper fibrous structure can no more
be  perceived in these animals than a nervous system.
In the same  manner  it  was stated that the order of
time  in  which the  different parts  are  formed, was  a
subject involved in too much obscurity to permit us to
employ it in our reasoning.  It was said that the heart
might  be sooner visible  than the  brain, in consequence
of  its  motion, of its consistence, and its other sensible
properties,  but that it  is impossible for us to  decide
which of the parts is  actually first brought  into exist-
ence.*
   So far  I  have attempted to give an abstract  of the
manner in  which  the  neurologists replied to the rea-
soning of the Hallerians;  they  have  also employed
direct arguments  in support  of their opinions, which
must now  be stated.   But before  I  enter upon  this
subject I may remark concerning  the  heart, which, as
it appears,  has been appealed to  by the supporters of
both sides of the  question, as a proof of tneir respec-
tive doctrines, that the  structure of the nerves of this
organ  has itself been  a subject of controversy  among
anatomists,  and has given rise to much learned discus-
sion and  minute  investigations.   According  to  Soem-
mering! the nerves sent to the heart are much smaller
in proportion to the size of the organ than  to any other
muscle, and  it was even  contended by  Behrens,! that
these  nerves are not destined for  the muscular  part of
the organ, but for its large vessels, while,  on the con-
trary, we  have the no less  respectable  authority of
ScaiyaJ in support of  the opinion that the heart  is

   * See note in p. 237.         t  Corp. Hum. Fab. t. iii. § 32.
  t Dissert, qua demon. Cor Nervis carere.
   § Tabulae  Neurologicae Card. Nerv. &c.  These may be consi-
dered as, in all respects, probably the best anatomical plates that
were ever published.   They are admirably expressive of the sub-
ject, without the gaudiness of the French engravers, who appear
to aim principally at  effect, or the  tameness of the English, who
seem to think of little else except economy. 
244
Arguments of the Neurologists.
 furnished  with nerve? in the  same  manner with the
 other muscles  of the body.*   Until the  anatomical
 question respecting the nerves of the  heart be decided,
 it will be impossible to  build any  physiological  hypo-
 thesis upon them, but  the  comparatively  insensitive
 state  of the  heart is admitted by every one, and may
 be adduced as an objection to the doctrine of the neu-
 rologists, even  were the existence of its nerves fully
 established.
   The argument which  was brought forwards by the
 neurologists with  the most confidence was derived from
 experiments made with artificial stimulants,  the object
 of which was to show that  in  a great number of the
 most  unequivocal cases   they act  upon the  muscles
 through the intervention of the nerves.   The experi-
 ments of Smith are some of the earliest,  as well as the
 most decisive that were  performed  on  this subject,!
 and he found that exactly the same effects  were pro-
 duced, whether the stimulant was applied to the fibres
 themselves, or to the nerve that is distributed through
 them.J  This he observed  to obtain with  respect to
 all the different kinds of stimulants, mechanical as well
 as chemical, and in these cases  it is easy  to detach the
 nerve  from the  surrounding  parts, so that the applica-
 tion may be made to it  in the  most unexceptionable
 manner.  The experiments that have been more lately
 made  with galvanism tend  to the  same conclusion.
 Here,  when a muscle is completely separated from the
 body, except by the  intervention of a nerve, contrac-
 tions are excited by  transmitting the  electric influence

  * See also Senac's work on the  Heart,  liv. i.  ch. 7, where we
have a minute detail of the observations of various anatom sts and
physiologists previous to his publication, and liv. iii. ch. 8, § 5.
  t From a MS. copy of Cullen's Lectures on Physiology, of which
I am in possession, it appears that it was chiefly upon the authority
of Smith's experiments, that he derived his hypothesis of the iden-
tity of the muscular and nervous fibres.
  X De Motu Musculari, passim. 
Arguments of the Neurologists.         245
 through the  nerve,  and it  is always found that if  a
 trunk of a nerve form part of a circuit, it is  not the
 muscles in the  neighbourhood of the nerve  that are
 excited, but  those to  which the nerve is ultimately
 distributed, however distant they may be.
   By reversing the nature  of the  experiment the re-
 verse effect was produced.   If instead  of applying  a
 stimulant we make use of  a sedative,  such as opium
 or laurel water, and immerse the nerve  in it, the mus-
 cles to which the nerve is sent lose their contractility
 as entirely as if the sedative had been applied  to the
 muscular fibres  themselves.   Facts of this kind are so
 well substantiated as  to admit of no contradiction, and
 they  undoubtedly seem to disprove one part of Haller's
 doctrine, that opium  and other narcotics, when they
 affect the muscular power, operate through the  inter-
 vention of  the  blood-vessels and not of the  nerves.
 Now  it is  said that we have certain  evidence  of the
 intervention of the nervous power in a great variety of
 cases, it is  therefore  a reasonable and  fair inference
 that the same intervention exists in all cases, and that
 muscular contraction never ensues from the application
 of a stimulant except through the medium of a  nerve.
   But the facts  which have been generally thought the
 most  decisive against Haller are those  in which  we
 observe the muscular power to be affected by mental
 operations, such as the passions,  and this is observed
 to be especially the  case with  respect  to  the  heart.
 the organ which had  been selected by the Hallerians,
 as one that  acted independently of the riervnis power,
 and was even thought  to be entirely  without  nerves.
 And  besides  the observations that have been  made
 upon  the body, while in a state of health, numerous
 pathological occurrences daily present  themselves to
us, where the contractility of the muscles is obviously
 influenced by the state  of the nervous  system,  or by
 agents  which can  only operate through  its  means.
 Other considerations  of less weight  or  founded upon 
£46       Experiments of Legallios and Philip.
 less certain grounds, have been urged  by the neurolo-
 gists, but what I have stated seems to me to constitute
 the most  important part of their reasoning,  and so
 convincing did  it  appear, that  their  hypothesis  has
 been continually gaining ground, until it came to be
 almost universally adopted.*
   The  opinion- of physiologists on this disputed ques-
 tion were much influenced in favour of the hypothesis
 of the neurologists by the very elaborate  and ingenious
 train of experiments which were performed by Legal-
 lois, to  which I have already had occasion  to refer.
 Haller had shown that the heart can continue its action
 when it is detached  from the nerves that proceed to it
 directly from  the  brain, and  had thence  concluded
 that it is not under the influence of the nervous system.
 Legallois, however,  endeavoured to prove, that if, be-
 sides the  removal  of the brain, we also destroy the
 spinal cord, the motion of the heart immediately ceases,
 and thus, by establishing, as he conceived, a necessary
 connexion  between  the action of the heart  and  the
 spinal cord, he controverted  the argument  that  had
 been deduced by Haller in favour of the  independent
contractility  of the  muscles.   The  experiments  by
which Legallois supported his opinion were apparently
so direct and unequivocal, as to gain very general assent
to his doctrine, and  were supposed completely to sub-
vert  that cf  Haller, when the subject was  taken up
by  Dr.  Philip, who,  by repeating and modifying  the
experiments of Legallois, detected a source of fallacy
in them, which, as  far as this  question is concerned,
entire'y destroys their value, and subverts the  conclu-
sion which had been drawn from them.  Legallois  had
announced that when the spinal cord is destroyed, every

  * See  Dr. Alison's remarks in the Quarterly Journal, v. ix. p.
 106; also the Report made  to the French  Institute, referred to
 above, p. 293. Cuvier says, that the objections to Haller's doc-
trine are every  day becoming more apparent.  Lee. d'Anatomie
 comp. Intr. p. 22. 
Of Philip.
247
  art of  the body loses its contractility, but Dr. Philip
  iscovered that this is only the  case when the cord is
destroyed suddenly ; on the contrary, when the destruc-
tion is effected slowly and gradually, he found that the
heart was capable of continuing  its contraction,* and
hence he infers the correctness of Haller's doctrine  of
the inherent contractility of the muscular fibre.   And,
indeed, if we allow the accuracy of Dr. Philip's results,
respecting which  there appears no reason to entertain
any doubt, they afford  us the most direct confirmation
of Haller's doctrine of muscular contractility being a
faculty  which  exists  independently of nervous  sensi-
bility.!
   Besides establishing the general fact, that the  heart
retains its contractility after it has been separated both
from the  brain and the spinal cord, Dr. Philip perform-
ed some further experiments for the  purpose of prov-
ing that the contractile power of the muscles is inde-
pendent of the nervous influence.   The experiments
consisted  in employing  the corresponding muscles of
the two extremities of an animal, the nerves of one of
which were divided, while  those of the other remain-

   *  Experimental Enquiry, p. 88 and 97.
   t In order to obtain a clear and  comprehensive knowledge of
the experiments and reasoning which were adduced in the course
 of this discussion, which may be considered as among the most
curious and important that ever engaged the attention of physiolo-
gists, the following works should be carefully perused.  Legallois5
work, " Experiences sur le Principe de la Vie," which contains
 his  original experiments; Dr. Philip's two  papers in the Phil.
 Trans, for 1815, in which he  urges his objections to Legallois' con-
 clusions, and states  the main facts on  which he founds his own
 opinion ; his " Experimental Enquiry into the L>»ws of the Vital
 Functions ;" and his series of papers m the Quarterly Journal, v.
 xiii. and xiv. consisting of his general conclusions and a digested
 summary of his doctrines.  A very correct and elegant summary
 of the experiments of M. Legallois and Dr. Philip, and the conclu-
 sions which may be deduced from them, is given by Dr. Roget in
 the supplement to the Encyclopaedia Britannica, article " Physio-
 logy."
I 
'248
General Observations.
ed entire.   Both the sets of muscles were then thrown
into strong contractions by the direct application of a
stimulant, when  it  was  found that the  extremity  in
which the nerves were  left entire  lost its contractile
power as soon or sooner  than  that in which the nerves
were divided.*  This  result  appears  fully to justify
Dr. Philip's conclusion, that contractility is an inherent
power of the muscles, and  does  not depend upon any
thing which is conveyed  to them through the media of
the nerves.!  About the same  time when Dr.  Philip
was  engaged in his experiments  to prove the indepen-
dent contractility of the heart, some valuable observa-
tions upon the same  subject were  made by Mr. Clift,
which led him  to  the  same  conclusion.   They  were
made on the carp, and  it was found the heart  of this
animal  is capable  of supporting its contractility for
some hours  after  its complete  separation from the
brain and spinal  cord.f
   In concluding the review  of this controversy we
may observe, that, on arguing upon this subject, wri-
ters  in general have not sufficiently attended to a point
which was very explicitly  stated by  Haller  himself,
that the question is  not   whether the nerve generally
intervenes between the action of the stimulant and the
contraction of the muscle, but wrhether  its intervention
can,  in  any instance, be  dispensed  with.§  I have al-
ready had occasion to describe  the process by  which

  * Experimental Inquiry, p. 99.
  t Phil. Trans, for 1815, p. 89.
  X Phil. Trans, for 1815.  The  important and decisive  experi-
ments of Mr. Brodie, which  have been already  referred  to,  al-
though performed with a somewhat different  object, bear very
directly upon this point.  Phil.  Trans, for 1811,  p. 36, et seq.
See also Mr. Mayo's Comment, p. 16.
  § Whytt, a writer of considerable  acuteness and information,
argues upon the principle, that as the intervention, of the nervous
system is necessary for the  performance of certain muscular
motions, it must  be  so in all cases. See the Essay on  Vital and
Involuntary Motions, pac;;im. 
           Voluntary and Involuntary Motions.       249

volition is propagated from the  brain down the nerve
to the muscle,  and in all  these  cases it is sufficiently
obvious that the  action of the  nerve is  an essential
part of the process.  And this is not only the  case in
all  voluntary motions, but  also in all those  motions,
either voluntary or involuntary, where the stimulant is
not directly applied  to the part  that  is  ultimately
moved.  Here the transmission of the effect is always
through the nerve, and it appears, moreover,  that in
many  instances it  is impossible  to produce the  same
effect in any way, except by means of the nerve.  A
great number, however, of the most important actions
of the body are performed in consequence of the direct
application  of  stimulants  to  the part  that is to be
moved.  Of this  description  are the vital functions
generally, where  different  substances,  partly as it ap-
pears by their mechanical  bulk, and partly by certain
specific properties, cause the contraction  of the muscu-
lar fibres  to which they are  applied.   These opera-
tions are most of them involuntary, apparently placed
out of the direct influence of the nervous system, and
seem  to be  examples of the  excitement of muscular
contraction in consequence of the direct  application of
a  stimulus.   We  accordingly find that  this question
has been much embarrassed  by not attending  to the
difference between the  voluntary and  the  involuntary
muscles, a difference which was seldom adverted  to by
the earlier physiologists, although not  totally unknown
to them.  This difference will be more fully explained
when we discuss more particularly the nature of voli-
tion ;  but I  may remark in this place, that although
there are certain muscles that act habitually in  both
ways, and others which may, on certain  occasions, act
in a manner different from that which appears to be
their ordinary mode,  yet that there is  a  decided  diffe-
rence between  the two classes, and that this distinction
depends, in a considerable  degree, upon  the quantity
of nerve that is sent to them, and  the  source  whence
               32 
 250 Independent Contractility refers to Involuntary Motions.

 the  nerves  are derived.  The organs of voluntary
 motion are  more  plentifully  supplied with nerves, and
 they are derived  more or less directly from the  brain
 and  the spinal  cord, while  the  involuntary  muscles
 have fewer nerves, and those, for the  most  part, pro-
 ceeding  immediately  from   the intercostal nerve,  or
 from some of the  numerous  ganglia  with  which it  is
 connected.*   The ordinary motions of these parts are
 not only  independent of volition, but they  are  without
 consciousness, which always attends the contractions of
 the voluntary muscles, and  they may  be generally said
 to want those characteristic circumstances  which mark
 the intervention of the nervous system,  or which indi
 cate it to have  any connexion  with or co-operation  in
 the effect produced.
   In discussing  this question  we are therefore  entirely
 to discard  the  consideration of the voluntary  muscles,
 and to disregard all  the  experiments that  have been
 performed upon them, as it  is  admitted on all  hands
 that they are placed under  the direct control of the
 nervous  system.!   The only subjects of  controversy

   * Bichat, Anat.  Gen. t. ii. p. 405 ; see  also Johnstone  on the
 Ganglia, sect. 2.
   t Dr. Philip, with his usual clearness and sagacity, has  pointed
 out the difference  which exists between  the voluntary and the
 involuntary muscles with  respect to  the cause which stimulates
 them into action.   This, in the former, he states to be the act of
 volition alone;  but this limitation,  I conceive, to be liable to cer-
 tain, exceptions, although it is obvious that the will is their appro-
 priate and ordinary stimulant.  See "Enquiry," p.  101.   If we
 refer to the classification of the nerves which is stated above, we
 should say  that the voluntary muscles possess both perceptive and
 motive nerves,  the  involuntary muscles possess no motive  nerves,
 and it is probable that  their nerves  are principally the simply sen-
sitive, with a small proportion however of the perceptive.  This
 consideration may lead to the conjecture, that the electric  fluid is
 not capable of acting upon the  nerves which serve for the purpose
 of simple sensation, but  that both  the perceptive and the  motive
 nerves are  under its influence.  It  is not probable  that  the small
degree of perception which the involuntary muscles possess is not
employed in their ordinary action, but serves only to convey to us 
  Independent Contractility refers to Involuntary Motions. 251

are the involuntary muscles, and here the fact  seems
to  be, that we have  on one  side  the most  decisive
proof  that these  muscles, such for  example  as the
heart, can act  when entirely cut off from all connexion
with  the nervous  system,  while, on  the contrary, we
have no less decisive  proof that they are capable of
being  influenced by causes which can  only  operate
through the intervention of the nerves.   This appa;
rent difficulty may  be removed, as Dr. Philip has clear-
ly shown, by making a  distinction between the  ordina-
ry and the extraordinary action of these parts.  Under
ordinary circumstances  the  heart contracts merely  by
the stimulus of the blood, in consequence of the inhe-
rent contractility of its  fibres, but  upon  certain  occa-
sions it is liable to  feel  the influence  of  passions and
other mental emotions,  which can only be  conveyed to
it through the intervention  of the nerves.*  What de-
termines  the operation  of these extraordinary circum-
stances, and how they are connected  with the involun-
tary muscles, will be the subject of future  considera-
tion ; but in the  mean time the facts must be admitted,
and they seem to offer  an easy explanation of the diffi-
culty which has so long embarrassed  this question.
   By not attending to this  distinction between the vo-
luntary and involuntary muscles, the  greatest part of
the experiments  on the artificial application of  stimu-
lants,  which had been regarded as  among the most
decisive arguments in  favour of the  doctrine of the
neurologists, will be found  to  be totally  irrelevant to
the question.   In the experiments  of this kind the ap-
plication has generally  been made  to  the  voluntary
muscles, which are not  properly the subject of the con-
troversy.   If, on the contrary, the involuntary muscles

the knowledge of any unnatural or morbid state of the parts, and
that the ganglia are the centres to which these perceptions are
referred ?
  * Exper. Enq. p. 79. 
252 Independent Contractility refers to Involuntary Motions.

be employed, we shall obtain  results that favour the
Hallerian hypothesis.   From  obvious causes it is not
so easy to perform  experiments on  the involuntary as
on the voluntary muscles, but upon the whole it seems
tolerably well established  that the nerves which sup-
ply these parts are  not  affected  by the application of
artificial stimuli, or rather v ill  not admit  of the trans-
mission of the effect to distinct  muscles, in  the same
manner with the nerves  that go  to  the  involuntary
muscles.   The experiments with  the galvanic appara-
tus, which are the   most easily performed, lead to this
conclusion, either that the involuntary muscles are ab-
solutely incapable of being stimulated by the applica-
tion of electricity to the  nerves, or at least in so small
a degree as.  bears  no  proportion  to the  size  of  the
nerves, or to  the contractility  of the  part  when  the
stimulus is applied  directly  to its substance.*
   The final result  of  the controversy appears there-
fore to be in favour of the doctrine of Haller, although
in admitting it we are obliged to introduce certain mo-
difications, which did not enter into his original  hypo-
thesis.!

  * i Dr the effect of galvanism  on  the  involuntary muscles, see
my Essay on Galvanism, n.  49 ■ iuichat,  sur la Vie et la Mort, p.
120:  Bichat, indeed, states the results of his experiments in a ge-
neral way only, yet  we  may  regard his statement as sufficient to
prove the different effect produced on the two kinds of muscles;
also Dr. Paris's observations  on the effect of electricity on the
action of the heart, Med. Juris, v. ii. p. 32.  I must, however, ob-
serve that  Dr.  Park, arguing from the same  premises, is led to
form an opposite conclusion.  Quart-Journ. v. ii. p. 233.  Because
it has been found  in these  experiments that the involuntary mus-
cles are very slightly affected  by the galvanic influence, he con-
tends that there is  no  specific difference between them and the
voluntary muscles.  But in  answer to  the objection of this intelli-
gent physiologist, I reply, that the extremely delicate sensibility of
the one class, and the small share of it  possessed by the other,
bears no proportion  to  the  quantity of nerves respectively sent to
them,  and can only be explained upon the supposition of some es-
sential difference in the  properties of the nerves themselves, or in
their relation to the  muscles.
  t Philip's Enquiry, p. 103, 
Arrangement of the Functions.
258
         § 5.  Arrangement of the Functions.

   These observations  upon the connexion which sub-
sists between the action of the muscles and the nerves
will enable us to decide upon the plan which we ought
to adopt  in  the  arrangement of  the functions.  The
older  physiologists, and  many of the most  eminent
among the  moderns,  have classed  them  under the
three  divisions of animal, vital, and natural; the  first
signifying those which  are specifically attached to ani-
mal existence, such as  immediately depend upon  sensi-
bility and contractility, including   the various forms  of
sensation and spontaneous motion ; the  vital, denoting
those that are directly concerned in the continuance of
life, such as the action  of the heart and lungs ; and the
third class, the natural, intended to express those which
are not necessary  for  the immediate  continuance  of
life, but which serve to maintain the body in its proper
condition, and to support all the   other functions;  in
this class  are  placed digestion, secretion, and absorp-
tion.   There  is a foundation for this  division, but it is
in some respects faulty, especially  in there  not  being
any precise  limits between the two latter classes, the
vital and the natural;  and with respect to the nomen-
clature of the whole it is  obviously incorrect.  In the
first place, every one of the functions may be  strictly
ealled animal, for in every one of them the  operation
either of sensibility  or of contractility is immediately
concerned.  The animal functions are also strictly en-
titled to the appellation of vital, for not only are they
directly essential  to  the support  of life, but they are
likewise the most characteristic of its  presence;  with
respect to the term natural, as applied to any descrip-
tion of functions, it is clearly without any specific mean-
ing.
   Several new  classifications  of  the  functions  have
been lately proposed in France by physiologists, whose 
254
Of Dumas and Richer and.
 works, although  of various characters,  have each of
 them obtained a  considerable share of reputation ; of
 these the most important are Dumas,  Richerand, Bi-
 chat, and Cuvier.  The  first of these writers, whose
 productions are more distinguished by  the popularity
 of their  style  than  by sciei.tific research, divides the
 functions into four classes; in the first he places those
 which serve  to connect the  individual  with  external
 objects,  under which  he  includes nearly the  same
 operations, which in the old arrangement were styled
 the animal functions, spontaneous motion, sensation, and
 the action of the  external senses.   In the second  class
 he places the functions which maintain the body in its
 natural condition,  considering it as a compound of solids
 and fluids, possessing the  properties of  cohesion, con-
 sistency,  and temperature; here are placed the circu-
 lation, respiration, and the faculty  of generating heat.
 The third class contains those functions, the object of
 which is to preserve the composition of the body, and
 the properties immediately connected with it; among
 these are digestion, assimilation, sanguification,  secre-
 tion, and absorption.  In the fourth  class are placed the
 functions which refer to the connexion that subsists be-
 tween different individuals, as well  those which serve
 for the continuance of the  species, as those which con-
 nect mankind together by their moral agencies.   Con-
 sidered as a physiological arrangement, the plan of Du-
 mas is decidedly bad ; the second and third classes are
 separated by a distinction  which is not easy to compre-
 hend, and the functions which are  placed together in
 the  last class, whatever connexion they may have in a
 metaphysical sense,  have  no  physical  connexion with
 each other.
   Richerand's method is  much  more simple;  he di-
vides the functions  into two classes only ; those  that
 are subservient to the  preservation of  the individual,
and  those that are subservient to the preservation of
the species.  But  this arrangement is not derived from 
Of Bichat.
255
any natural principle of classification, and  it  presents
the practical objection  of throwing almost all the func-
tions  into one  of the divisions.  Bichat, in this  as  in
most  other cases, has disregarded, in a great measure,
the opinions of his predecessors, and  founded  his sys-
tem upon a new principle, which appears more philo-
sophical, although  not  without considerable objections.
He places all  the  functions in two classes, to  which
he gives the names of animal and organic, the first coin-
ciding nearly with the  animal functions of  the older
physiologists; the organic embracing both  their vital
and natural functions.  The author himself character-
izes his animal functions as  those which distinguish the
living animal from all other beings, those which enable
him to maintain his connexion  with the external world,
originating from, or immediately consisting  in, the fa-
culties of sensation and locomotion.  The organic func-
tions  are those which  serve for  the support  of the
body  individually, without  any reference to surround-
ing objects, which are performed  by certain organs
that  are similar, or at least  analogous to what  we find
in every being that is possessed of organization.  This
division is preferable to the old one,  in being more sim-
ple, and in not attempting to discriminate between the
vital and natural  functions,  which are  so closely con-
nected together.   But  I conceive that it is not unex-
ceptionable, either with respect  to  the  actual nature
of the functions, or to the  names  by which  they are
designated.   All the functions  are  properly animal, for
they  are all sufficiently  distinct, both  in their prime
cause and their phenomena, from  any which  are  ex-
ercised by vegetables, and they are  all entitled to the
name of organic, for  the brain  and muscles are as pro-
perly organs of sensation and motion  as  the heart and
lungs are of the circulation and the respiration.
  The  arrangement of  Cuvier  may  be regarded  as
compounded of those of Richerand  and Bichat.  He
divides the  functions into three classes—animal, vital. 
256             Objections and Remarks.
 and generative ;  the first coinciding with the functions
 so named by Bichat, and the second being also similar
 to his organic functions, except in separating those that
 are  subservient to  generation.   This method labours
 under the same objections with that of Bichat, although
 it is perhaps somewhat improved by the separation of
 the  generative functions, which could not with proprie-
 ty be included under the  organic, according to the de-
 finition  which he gives  of them.*
  Besides  the objections that have  been urged  to
 these different arrangements, considered  individually,
 there is one that attaches to  them generally, as well
 as to all the others  that have been proposed, that they
 do not make a sufficient distinction between the  func-
 tions immediately resulting from  the action of  the ner-
 vous system, as forming one of the constituents  of the
 body, and the njental or intellectual operations.   The
 brain is indeed the instrument of  the mind, or the me-
 dium through which the mind acts, yet  it does not ne-
 cessarily follow that the mind is  to  be regarded as a
 quality  or property  of the brain.   But whatever  may
 be our opinion upon this point, we maty without hesita-
 tion  assume that  the functions  which  result from the
immediate  action of the brain and nerves are altogeth-
er so different from  those of the  mind or intellect, that
notwithstanding the  connexion which subsists between
them, they should be placed  in distinct classes.   Per-
haps one cause why writers  on  physiology have not
made separate classes of these two orders of functions
may be, that they supposed   the former of them only
to be the proper objects  of  their attention, and that
the  mental or intellectual  powers  belonged exclusively
to the science of  metaphysics.   This,  however, is no
ground for  employing a defective  arrangement,  and it

  * It may be worthy of observation that Cuvier, who  is  so emi-
nently distinguished for  his sagacity in  classification and arrange-
ment, should have described sensibility and muscular contractility
n* both of them functions of the nerves.  Regne Anim. p. 33. 
     Functions arranged into ContractUef Sensitive, 8{c.  257

may be farther remarked, that although the object of
metaphysics be very different from  that of physiology,
yet the operations of mind and body are so intimately
connected together, and the  one  part of our frame has
so much power over the other, that no system of phy-
siology can be perfect, in which the  mental  faculties
are entirely disregarded.
   The mode of viewing the subject which appears to
me the  most correct, is to regard contractility and sen-
sibility as the two primary  attributes  of animal life,
each equally characteristic of it and peculiar to it, and
each performed by its appropriate organs.  The func-
tions depend upon the  exercise of  these  powers, and
although probably in all cases they are both  of them
exercised, yet generally one of  them seems to be the
principal agent,  or the prime origin of the ensuing ope-
ration;  we may consequently divide them into the con-
tractile  and  sensitive  functions,  or those  which more
directly belong to contractility and to sensibility, and
which of course serve  respectively for motion and sen-
sation, and to these  two  classes, according to the re-
marks that have been  made  above, must be added the
third class of the intellectual functions.
   The contractile functions  must be considered in the
first place, as being  the  most  independent, and what
may be  regarded as  the  prime cause of the others, for
we have seen that the muscular system can act with-
out the  intervention of the nervous, but that the ner-
vous is directly dependant upon the  muscular.   The
heart and the involuntary muscles continue to  contract,
and the limbs remain sensible  to the impression of sti-
mulants, after the brain and spinal cord are totally de-
stroyed, but if  the  circulation and the respiration be
stopped,  the nervous  power is  immediately  extin-
guished.
   Among the contractile functions, the  essence of which
consists in motion, the first in point of importance, and
the one which may  be regarded  as the most necessary
              33 
258              Contractile Functions.
 to the direct support of life, and to the indirect main-
 tenance of  all the rest, is the circulation.   In all  ani-
 mals, whose functions and mode of existence bear any
 considerable analogy or resemblance to the human sub-
 ject,  we observe  that  the fluid which serves for  the
 support of  the system, and from which the  materials
 for its nutrition  are immediately derived, is kept in
 continual motion.  In  the  more perfect  animals  the
 great  source of  motion in the  circulating fluid  is the
 heart, but as we  descend  in the scale of  organization,
 the heart becomes of less  relative importance, and a
 part of its power is supplied by the action of the great
 vessels, until at length we arrive at an order of animals,
 where its power  is entirely superseded by that of the
 large arteries,  while in  the  lowest tribes, which possess
 any thing analogous to a sanguiferous system, the large
 arteries themselves are not to  be distinguished, nor  is
 there any regular progression of the fluids, and we can
 observe nothing more than a general oscillatory motion
 in them, which appears to be equally extended through
 all parts of  the body.   It must, however,  be observed,
 that the perfection of the circulating system does not
 hold an exact ratio with that of the organization gene-
 rally.   Many insects that  have  various distinct organs,
 and a variety of delicate functions, have no circulating
system,* and the  office of the heart and arteries is sup-
 plied  by parts  which act upon a  different principle.
   Next to the circulation,  in point of importance, comes
the respiration, the function by  which the fluid that  is
carried along the vessels  is adapted for the  purposes
of life, by a certain change which it experiences from
the action of the air.   This function, in some form or
other, is probably exercised by  all classes of  animals.
The same kind of complicated mechanism, which exists
in the higher orders, is not indeed found in  a  great
number of the inferior  tribes,  but  in  them  we may

      * Lamark,  Hist, des Anim. sans Verteb, Intr. p. 149. 
Contractile Functions.
253
 trace something which is to be regarded as a substitute
 for it, or as supplying its place, by  enabling the air to
 produce its appropriate action on the nutritive  fluid.
 After these two functions, one by  which the blood is
 carried to all  parts of the body, and the other by which
 it acquires its vital properties, we come to those of ca-
 lorification, secretion, digestion,  including assimilation
 and sanguification,   and   absorption,  functions which
 serve, in some  way  or other,  for  the  continuance of
 the action of the animal machine, and which preserve
 all its parts in their proper condition, without, however,
 being essential to  the immediate  support of life.  In
 this class  we may  place  the function  of generation,
 which, although one  of the most inexplicable of all the
 operations that  are performed by the animal powers,
 and acting in a  specific manner,  of which we have no
 other example,  may be considered as essentially con-
 sisting in secretion-
   Alt hough I have spoken of some of these functions
 as being more essential to life  than the  others, still,
 when we take a general survey of the  animal ceconomy,
 we find that they are all of them intimately connected
 together, acting, as it were, in a kind of circle.   The
 circulation has been stated to be the prime cause of all
 the rest,  for  it is  that which carries to every part of
 the body the fluid  which endows it with its vital proper-
 ties and  its appropriate powers.   The heart, however,
 would be incapable  of  fulfilling its functions were not
 its  fibres furnished  with   a  regular  supply of blood,
 which has been  carried through the lungs, and is acted
 upon  by the air in the  process of respiration, which
 transmission of  blood through the lungs is itself effect-
 ed by  the  action  of  the  heart.   If we conceive the
 heart and lungs, or some organ equivalent to them, to
 be in  action, so  that the blood may  receive its proper
alteration from  the air, and may be carried to all parts
of the body, we have the  essentials of life, and are in
possession of  those  functions by  wWch existence may 
260
Functions of the inferior Animals.
be maintained, and the individual preserved, for a cer-
tain length of time, in a  perfect  condition.  Both the
solids and the fluids of the body are, however, in a con-
stant state of  change.  One essential office of  respira-
tion is to discharge a  quantity of carbonaceous matter
from  the lungs, and the blood,  after  it  has passed
through the vessels, is incapable of continuing its office
without a supply of fresh materials.   The heart itself,
the great source of all  the motions  of the body,  and
the centre  of the  circulating  system,  would  lose  its
powers, were  not its substance gradually renewed, and
the waste that  is  thus  going  forwards from  various
causes counteracted  by the functions of digestion and
assimilation.   But for the performance of  these func-
tions it is  necessary that  certain substances should be
separated from  the mass of blood, constituting the pro-
cess of secretion, and, after the future nourishment is
prepared and  elaborated, absorption  is necessary  to
carry it to its  proper receptacles.   All these functions
are therefore  as necessary for the continued support of
the body, as  the circulation and respiration  are for its
momentary  existence, but they are so in a less direct
manner, and are connected more through  the medium
of certain mechanical  and physical changes, than in con-
sequence of any changes which seem immediately con-
nected with the specific powers of the system.
   These remarks on the relative importance of  the
different functions  must be  understood only  as  they
regard man  and those  animals that the  most  nearly
resemble  him  in their organization.  As we examine
the various classes with respect to each other, taking
in the  whole of the  scale, from the most perfect to
those that are'the least so, we observe a very different
order to prevail respecting the connexion between the
functions and  their  relative  degrees  of importance.
Beginning from the human species, and descending  by
a gradual progression, we  find that the  intellectual
functions  are  thfe  first  that  disappear, the sensitive 
/
                 Sensitive Functions.               261

also become fewer in number or more contracted in
their  operations, and, according to the opinion of the
most  learned naturalists,  many of the lowest tribes of
animals are entirely without a nervous system, and in
consequence are deprived of the powers that depend
upon  it.   Among the contractile functions, the circula-
tion, which we have considered to be the most impor-
tant in  man, is the one which is first found to be want-
ing among the lower animals; the organs of respira-
tion,  secretion, absorption, and  generation, gradually
become less and less distinct,  until at length  they can
be no longer  traced, while  the  last  that remain are
those  of  digestion, although  there is a considerable
number of animals  in whom no distinct apparatus even
for digestion  can be detected.   The  power of produc-
ing their  species  is also  absolutely  essential to  ani-
mal existence, but the manner in  which this  is accom-
plished in the most simple animals is totally different
from  the  function of generation as  exercised by the
more  complicated,  and in the former no distinct organ
for this  purpose  can  be  discovered.   According to
Lamark,  who has  minutely  attended to the  grada-
tions  of animal  existence, the organs of the several
functions,  when considered with respect to  their  rela-
tive necessity  for the absolute  support of life, and the
universality of their occurrence, will  stand  in the fol-
lowing order; the organs of digestion, those of respi-
ration, of motion, of generation, of perception, " senti-
ment," and lastly of the  circulation.*
  The  sensitive functions may be divided  into  two
classes; first,  those which originate  in the  action of
the external  agents  upon the  nervous system,  and,
secondly, those of a reverse kind, which depend  upon
the re-action of the nervous system upon these agents.
In  the  first of these  divisions are included  what we
call the external  senses,  the sight,  hearing,  taste,
* Anim. sans Verteb. t. i, p. 360, 
262             Intellectual Functions.
 smell and  touch, and  in  the  same  division must be
 placed the sensation of hunger, that of temperature,
 and some others, which have not been correctly discri-
 minated from general feeling, but which  possess specific
 characters.  In the second class, those functions which
 depend  upon the re-action of the nervous  system on
 external  bodies,  we must  place  volition, and  to the
 same class  we may also refer instinct, association, sym-
 pathy, habit, and some other  faculties  of  a  similar
 kind, which appear to hold, as it were, an intermediate
 rank between the  corporeal  actions and  those of a
 purely intellectual  nature.   As the functions which
 compose  the first of these classes  may be all referred
 to a species of perception,  so the latter may be consi-
 dered as more  or  less analogous  to volition; in the
 former, the effect upon the nervous  system, whatever
 it be, is  propagated  upwards from  the  extremities to
 the centre, in the latter it proceeds in the opposite
 direction, from the  centre  to  the  extremities of  the
 body.
   The intellectual  functions  form  the third   class;
 these  are a less direct object of physiology than the
 two former, yet many of them are so closely  connected
 with  the  physical changes  of  the  body  as to require
 some degree of notice in a  system  which professes to
 give a complete view of the animal ceconomy.  These,
 although  intimately,  and, as it would appear, necessa-
 rily connected  with  the nervous system, are,  at  the
 same time,  so different in their phenomena  and their
 characters from any of the  properties of matter, that
 I conceive we are warranted in the conclusion that they
 originate from an  essentially different  source, and  are
 of  an  essentially  different  nature.   Whatever  hypo-
 thesis, however, we may adopt upon  the subject,  it is
 obvious that they possess  the  power of acting upon
 matter, and that they exercise a very extensive influ-
ence over the animal  body, and so far as  this  influence
extends, it  will fall  under  our  department to investi- 
Intellectual Functions.             263
gate its nature and to trace its effects.   Among these
intellectual operations, which  possess a  decided action
upon the corporeal frame, we must place the passions,
and in the same  class we may regard that compound of
mental and  physical  influences, from   which  results
what we call temperament and character.   We hence
proceed to functions of a  more  purely intellectual
kind,  which, as they recede from the  corporeal,  and
advance towards the mental part of our frame, are less
within our  province, and belong more to the moralist
or the metaphysician. 
264             Introductory Rs-tyarks.
                  CHAPTER V.

                 <Df tfie Circulation.

           § 1.  Introductory Observations.

   I  have now described in succession  the principal
ingredients of which the body is composed ;  the mem-
branous matter, the bones,  the  muscles,  and the  ner-
vous substance ; and I have likewise given an account
of the two general  properties which distinguish ani-
mals from all other beings, contractility and sensibility.
I must now proceed to the different functions which
are individually exercised by the particular  organs  of
the body, which,  all  of them, consist either in motions
brought  about  by  the  contraction  of  the  muscular
fibres, in sensations  produced by  the appropriate  ac-
tions of the nervous system,  or in peculiar affections  of
certain parts  of this system, which are connected with
the various intellectual operations.   According to the
arrangement which I proposed  in  the last chapter, I
shall begin with the contractile functions,  those which
more immediately depend upon the contractility of the
muscular  fibre, because  they seem  to  be  the  most
essential  to the  existence  of the  animal frame, and
because we conceive ourselves to be better acquainted
with their nature,  and  regard  them as  being more
analogous to  the other  powers of  matter, than the
functions  which  depend  upon the  operations of the
nervous system.
   I have already made  some  remarks upon the con-
nexion  of the  functions  with each  other, and  upon
their relative  importance to  the support of  animal
existence, and  we are  led  to conclude, that  in  the
higher orders  of organized beings, the  circulation of 
               Connexion of the Functions.           265

 the blood  seems  to  be,  as  it were,  the main spring
 of  all the rest,  that from  which  they derive their
 origin, and which is the most essential to the  well-be-
 ing of the whole.  Respiration, in  the  most  perfect
 animals, is, indeed, as essential to their existence as the
 circulation, but, if we  may be allowed the expression,
 it is only incidentally necessary, inasmuch  as by respi-
 ration we  produce that  change in  the  blood which
 gives the heart its power of contraction.  It  appears
 to follow as a direct consequence of Mr.  Brodie's  inte-
 resting experiments,  that  if the blood had its specific
 change induced upon it by any other means, or were
 it exposed to the action of the air in any other manner
 than  by passing  through  the lungs, all  the functions
 would go  on  as  at  present without  interruption*
 whereas, if the circulation be impeded or suspended,
 every part of the system, and every one of the func-
 tions, immediately  feel  the  effect.  This observation
 is, however, strictly applicable only to  a part, although
 that a large part, of the animal kingdom.   As  1 have
 remarked above, there is a numerous class, and  that
 possessed of a considerably complicated organization,
 which has no circulation of the blood,  and yet in these
 the nutritive fluid is acted upon by the air in a  way
 which may be regarded as  analogous to respiration.
But the general structure of these animals, and the na-
 ture of their functions, bear so little  analogy to that of
 man,  as not to allow of their being compared to each
 other, or  considered as  merely  occupying different-
 gradations in the same scale.
  With respect  to the other contractile functions,  I
 may remark that, however necessary a certain tempe-
 rature may be to the existence of what are called the
 warm-blooded animals,  who,  being generally immersed
 in a medium  colder  than themselves, require some

           * Phil. Trans, for 1811, p. 36, et seq.
34 
266
Heart first formed.
apparatus for generating or evolving  caloric, in order
to supply this deficiency, yet this  may, in like  man-
ner, be  regarded  as rather  incidental  than essential,
and what is  more dependant upon  the peculiar cir-
cumstances in which they are placed, than upon any
thing  necessarily connected with the support  of life.
The functions of digestion, absorption, and secretion,
are evidently still  less subservient to mere existence,
their object being  either to  supply  materials for the
growth  and  mechanical  support of the body, or  to
mould and fashion its form,  while generation  is  obvi-
ously  unconnected  with the life  of the  individual,
and is  only  useful  as  a  means of perpetuating the
species.
   If we take into  consideration the relative impor-
tance of the contractile and sensitive functions, or  of
the heart  and the  brain,  as  being the  respective
centres  of each, so far  as regards mere animal  exist-
ence,  we shall also be led  to decide  in favour of the
former.  In  the  higher  orders of animals  indeed,
where  there is  the  greatest  number, and the most
perfect development of the  organs and functions, the
brain and the heart  may, at  the  first view, appear  to
be equally  essential, not  only  to  the  continuance  of
their  full  powers, but  even of life itself.  Upon a
more accurate  examination  of  the subject, however,
we shall find that the heart is the centre, not of the
contractile powers  alone,, but  of  the  whole  of the
corporeal frame,  a  conclusion  to which we  are led,
both by anatomical  researches,  and by the nature  of
the powers and  functions respectively exercised by
these parts.
   When we  attempt to trace the progress of an orga-
nized being, from  its earliest stage of existence to  its
full maturity, the  first appearance that  we  observe  of
any arrangement of parts  consists in  the rude sketch
of what is afterwards to become the  organs of circula-
tion.  We are informed by  Harvey, who accurately 
       Action of the Heart independent of the Brain.    H6t

observed the gradual  development of  the  different
parts of the embryo  in the chick during  incubation,
that the first appearance of distinct organization was a
beating  point, punctum  saliens,  as  he expresses  it,*
which was the rudiment of the future heart, and which
preceded the formation of the other parts of the body,
being visible for some  time before he could discern any
trace of the brain. The existence of acephalous foetus-
es affords a further confirmation of  the same opinion;
as these beings  are absolutely without brains, so  it  is
certain  that they cannot possess any share  of those
powers which are derived solely from this  organ; yet
they have grown to their full size in the  uterus, and
have even lived  for some time  after they have  been
expelled from it, and their death has  appeared to  be
owing,not to any physical impossibility to the continuance
of life, but to their not being able to effect those chan-
ges which are, as it were, incidentally necessary to the
continuance of an existence  of  any considerable  dura-
tion.  For example, a  regular supply of nutritious  mat-
ter is essential to the support of life;  this can only be
supplied by the introduction of food into the  stomach,
and food can only be received into the stomach by the
act of deglutition, but this act, at least in  the higher
order of animals, cannot  be  performed without the  in-
tervention of the nervous sytem.
   Then with respect to the dependance of these two
parts upon each other, the view which has been taken
of the nature of their powers, and the manner in which
they are exercised, lead us to the same opinion.   The

  * Quarto itaque die si inspexeris........punctum sanguineum
aaliens emicat.  De Gener. Exer. p. 17. Haller observed the pul-
sation of the heart at a considerably earlier period ;  see Comment.
de Form. Cord, in Op. Min. t. ii. p. 101, and Comment, de Form.
Pulli, c. 9.   " Deinde hora 42 e*t cor vidi et aortam, et motum
vertiginosum quasi,  sagittaeque similem, sanguinis  rubiginosi ex
corde sursum projecti, iterumque relabentis."  Op. Min. t. ii. p,
369.  See note in p. 2*7. 
268              Description of the Heart.

very existence  of the brain, as composing part of  the
substance of the body,  necessarily implies the convey-
ance of the blood or some analogous fluid for its forma-
tion  and  support,  while, on the contrary, it  does  not
appear that the mechanical contraction of  the heart,
or the  means,  whatever they may  be, by which  the
fluid is carried  to  the  brain, is  necessarily connected
with the  exercise   of  any  sensitive  function.  These
considerations,  and others of a similar kind, both  ana-
tomical and physiological, all conduce to  the conclusion,
that we  must regard  the heart as the  centre of  the
whole  corporeal frame, the fountain of  life, which  is
designed to pour out its vital streams to  every part of
the sy tern, and to unite the various,functions, however
different in their nature and operations, into one  har-
monious whole.*

   § 2.  Description of the Heart and its Appendages.

   The organs of circulation may be divided into three
parts, as connected with their structure  and their uses,
the heart, the arteries, and the veins.   The  heart is a
hollow muscle,  composed of masses of strong longitudi-
nal fibres, forming  an  irregular cone,  and leaving an in-
ternal  cavity.  The outside of the  heart is covered
with a firm membrane, and the internal cavity is lined
with the same substance, the muscular part is copious-
ly supplied with blood-vessels,  but its nerves are consi-
dered  as few in number in proportion to its bulk.!   It

  * Soemmering has adduced various considerations, which appear
conclusive as to the point, that the nervous  system is not necessa-
ry to the mere continuance of life. Corp. Hum.  Fab. t. iv. § 87.
The same doctrine is the necessary deduction from the decisive
experiments of Mr. Brodie and of Dr. Philip, which have been al-
ready referred to, and is confirmed by some experiments that  are
related in the posthumous work of my much  respected  preceptor,
Dr. Marshall, Anatomy of the Brain, p. 249, et seq.; and likewise
by those of Mr.  Mayo, Comment, p. 16.
  t Vide Supra, p. 243. 
Description of the Heart.             269
is suspended from its base by the great  blood-vessels,
which form the main trunks of  the  sanguiferous  sys-
tem, and it  is enclosed in a membranous bag called the
pericardium ; it is situated in the left side of the fore-
part of the  thorax, resting upon  the diaphragm.  The
interior of  the heart is unequally divided, by a  strong
muscular septum, into two distinct cavities, called ven-
tricles, which have no direct communication with each
other; there are  also  two membranous  bags  at the
base  of  the heart, called auricles, forming in  all four
separate cells, each of the auricles communicating with
its corresponding ventricle,  but the auricles, as well as
the ventricles, having  "no direct communication with
each other.  Although the auricles may  be considered
as membranous bodies  compared  with ventricles, yet
they are furnished with numerous fibres, and possess the
power of contraction.
   In  describing the different parts of the heart,*  it  is
customary to speak of its right and left sides, and of
the  right and left  auricle and ventricle, but it  is well
known  that the terms  are not  correctly applicable to
the situation of these cavities in the human body, which,
as far as its situation is concerned, are  more accurately
designated  by  the words anterior and  posterior.  The
terms right and  left were  originally employed  by the
ancients  in consequence of  their dissecting brute ani-
mals, in which the heart is placed differently from what
it is in the  human subject, and  corresponds  generally
with the terms that were employed.    This affords one
proof, among  many others  of  a  similar nature, that
when Galen and his successors  described the  anatomy
of man, their descriptions were  borrowed, at least in a
great  measure, from  the different  species  of simia?,
which, in consequence  of the superstition and prejudi-
ces of the  age, they were obliged to substitute for the

   * Perhaps  one  of the most ample and correct anatomical descrip-
tions of the heart will be found in Bichat's Anat. Des. t. iv. p. 87,
et seq.; see also Boyer, Anat. t. iv. p. 277. 
270
Arteries.
human body.*   With respect to the  names which we
attach to the cavities of  the heart, perhaps, upon  the
whole,  the most  unexceptionable  terms, ana   those
which are  the least likely to  lead to any erroneous
conceptions, are pulmonic and  aortic, those which are
usually called  right  being immediately subservient to
the pulmonic, and those called  left to the aortic circu-
lation.
  The use  of  the heart, as forming a part of the cir-
culating system, is to receive  the blood from the veins
and to propel it again through the arteries ;  this is ac-
complished by the contraction  of  its fibres, by which
the  cavities of the  heart are* diminished in  size, and
their contents  necessarily forced  out.   The  simple
diminution of the cavities, and the mere pressing out of
the  blood, would not, however, be sufficient for  the
purpose of the circulation; for it is not only necessary
that the blood be moved, but that it be moved in the
right direction.  For this purpose the heart  is furnish-
ed with an elaborate mechanism of valves, which are
attached to the orifices of the ventricles and the mouths
of the  arteries, and which are  so  constructed, that
when the heart contracts, and  the blood is forced  out,
the current is  necessarily propelled in the proper di-
rection.
  When  the  blood  leaves the heart it  is  sent with
considerable force into the large trunks of the arteries;
these vessels  soon begin to ramify in different  direc-
tions to all parts of  the body,  until at length  they are
reduced to vessels too small to be traced by the eye or
even by the microscope.   The arteries, which perform
this office of conveying the blood from the heart, are
flexible, elastic  tubes,! principally composed of  mem-

  * Haller, El. Phys. t. iv. 2. 3.
  t  It may be necessary  to observe that,  according to the obser-
vations of the most accurate anatomists, the arteries are not per-
fectly cylindrical, but conical, the narrower end of the cone being
situated towards the heart.  Hunter on the Blood, p. 168, et seq. 
Arteries.
271
branous  matter  formed into distinct layers, and com-
posing what have been called the coats of the arteries.
Of these membranous coats anatomists usually describe
two, as possessing  a sufficiently determinate structure
to be  easily distinguished from each other; the outer
one  partaking more of the nature of the cellular tex-
ture, and  therefore called  the cellular  coat ;*  and an
inner  membrane, white, firm, and  smooth, possessing
more of the physical properties of tendon.   In conse-
quence of the erroneous notions  which  formerly pre-
vailed on the  subject of the  white parts of the body,
to which I have already alluded, this latter was named
by the older writers the nervous coat, a name which
has still been applied to it by some of the moderns, but
it is sufficiently designated by the  name of the interior
or innermost coat.
   Between these  membranous coats is situated a stra-<
turn of transverse  fibres,  which have been  termed the
muscular coat: this has been supposed, like other mus-
cular  parts, to possess a contractile power,  and to give
the  artery the capacity of alternately contracting and
relaxing, thus  assisting the  heart  in the propulsion of
the  blood.!  To this alternate change in the  capacity
of the arteries the pulse has been commonly  ascribed,
and the sense of pulsation  which the artery gives to
the  finger, when applied to certain parts of the surface
of the body, has been  supposed  a sufficient  proof of

   *  Some anatomists have been disposed to regard this outer coat
as merely a continuation of the cellular substance which is conti-
nued over all the body, and connects together its different parts,
and have therefore conceived it to be not essential to the existence
of the  proper arterial structure,  an opinion which I am disposed to
consider as correct, but I have thought it desirable to employ, for
the present, the ordinary phraseology.  See some judicious obser-
vations in a Review ofBeclard's Additions  to Bichat; Ed.  Med.
Journ. t. xviii. p. 258.
   f The  nature of these transverse fibres, and the question whe-
 ther they are properly entitled to the appellation of muscular, and
possess a proper contractile  power, will be  considered hereafter. 
272               Circulation double.
 the existence of the arterial  dilatation, but this point
 will be considered more fully hereafter.   The mouths
 of the two great arteries, which receive  the  blood as
 it is projected respectively from the two  ventricles of
 the heart, are each of them  furnished with a system
 of valves, by means of which, when the blood  once en-
 ters the arteries, it cannot return  into the  heart, but is
 necessarily forced towards the extremities.
   When the blood has been transmitted  by  the arte-
 ries over all  parts of the body, it  is returned again to
 the  heart  by the veins,  being first received by  their
 minute  extremities, and  carried from smaller to larger
 branches, contrary to  what takes place in  the  arteries,
 until at length it arrives at the large trunks, and is pour-
 ed from them into the heart.   The veins are membra-
 nous tubes like the arteries, but they differ from these
 in possessing a less firm texture, in  being nearly with-
 out the transverse fibres, and  in  having a  number  of
 valves in different parts  of their  course ; whereas the
 arteries have no valves except  at their  commence-
 ment.
  After this brief and general sketch of the organs of
 circulation, the next object will be  to trace the blood
 through its whole progress,  beginning  at  one  part of
 the circuit, and following it until it arrives again at the
 same point.  But before I enter upon the  description,
 I must observe that the blood in fact makes two  cir-
 culations before.it absolutely completes its course, being,
 between the  two, brought back again to the heart, al-
 though  not to the same part of this organ.  This double
circuit  depends upon the circumstance,  that  by the
circulation  of the blood two distinct objects are obtain-
ed ; by one of them the blood is sent into the lungs, and
is there exposed to the action of  the atmospheric air,
by which its  properties are changed, and it is adapted
to the support of life.  The blood, having thus acquir-
ed its specific vital properties, is returned to the heart,
and is again sent out from this organ, along another set 
Course of the  Blood.
273
of vessels, to all  parts of the body, except to the cells
of the lungs, through which it had been transmitted in
its former circuit.   These two circuits have been dis-
tinguished by  different appellations; from the extent
of their course they have  sometimes  been called  re-
spectively the  lesser  and  the greater circulation :  or
perhaps more appropriately, from the parts  to  which
they are sent,  the  first  has  been called the pulmonic
and the latter  the aortic or svstemic circulation.* The
organs of the circulation  have  also  been  divided into
the arterial and  the venous parts, as depending upon
the structure of  the vessels and the  mechanical  pur-
poses which they respectively serve.  They have like-
wise been divided  into the  parts  containing the red
and the black blood,  a division which proceeds more
upon  physiological than upon  anatomical principles, and
does not entirely coincide  with  the former.  We shall
find it convenient to use each of these divisions on cer-
tain occasions,  employing one  or other of them accord-
ing to the objects in view, or the particular point which
we wish to illustrate.
   In  tracing the progress  of the blood  through the
heart and along  the arteries and veins, I shall begin
With that part where  it  is  returned  by the systemic
veins, or those which belong  to the greater or general
circulation, into  the  right auricle  of the  heart.  From
the right auricle it  is  poured into the right ventricle ;
when  the ventricle becomes distended to a certain ex-
tent, its fibres contract, and its cavity  being thus consi-
derably diminished, a  proportionate  quantity  of the
fluid which it contains is expelled.  There is a valve,

  * These are the  terms employed by Dr. Barclay in his " New
Anatomical Nomenclature," p. 176, a work which is justly entitled
to the praise of ingenuity, but I think the proposed alterations are
most of" them unnecessary, and on that account very undesirable.
The partial adoption of a new  language  in any department of  sci-
ence tends to embarrass the memory, and the general adoption of
it would have the serious objection of rendering the old standard
authors, in a great measure, unintelligible.
               35 
274
History of the Circulation.
 or set of valves, which, from its  figure, as consisting of
 three  principal divisions,  has been called tricuspid, at-
 tached to the passage between the auricle and the ven-
 tricle, and so constructed, that, by  the  contraction  of
 the ventricle, it closes up this orifice, and  prevents the
 blood  from returning into the auricle, so that  it  is ne-
 cessarily  sent  forwards  into  the  pulmonary  artery,
 which likewise opens into the  right ventricle.   The
 pulmonary artery  carries the blood through the  lungs,
 in a way  which will be  more particularly described
 hereafter, along the lesser or pulmonic circulation; and,
 after  it has undergone its appropriate change from the
 action of the air, it is  returned into the left auricle by
 the pulmonary veins.   The same  mechanical  process
 occurs in the left side of the heart  as  I have just de-
 scribed with  respect  to  the right; the ventricle con-
 tracts, a valve at its mouth,  which, from  its consisting
 of two principal divisions,  is called the  mitral valve,
 prevents the blood from returning into the auricle, and
 it is accordingly propelled into the  aorta, the great sys-
 temic artery.   When the  blood  has once  entered the
 artery, it is prevented from flowing back into the heart
 by a set  of valves called sigmoid or semilunar, placed
 at the mouth of the vessel, so  that  any motion  which
 is afterwards impressed  upon  it, after it  once  enters
 the aorta,  either by the succeeding portions of blood
 sent from the heart, by the action of the vessels  them-
selves, or by any extraneous cause, must  all have the
 effect  of  carrying the blood forwards from the  heart
into the  veins, then from the smaller  veins  into the
vena cava, the main trunk  of  the  systemic veins, and
finally  depositing it in the right auricle.

   § 3.  History of the Discovery of the  Circulation.

  A slight and  casual observation   of the phenomena
of the  living body was sufficient to prove that the blood
i* perpetually in motion, but the nature of this motion. 
History of the Circulation.
273
or the course which it pursues,  was  unknown to the
ancients.*  They had  many chimerical and unfounded
opinions upon the subject, which it  is not necessary to
detail, although some of them were sanctioned by high
authorities.   As a specimen of their notions it may be
sufficient to  state,  that  they considered the principal
office of the arteries to be that of conveying air or some
kind of spirits to and  from the heart, while the veins
carried the blood;  that the fluids moved along the ves-
sels in one direction during the day, and in the contrary
direction during the  hours of sleep,  and various doc-
trines  of a similar  kind  were maintained, either deriv-
ed from incorrect or imperfect observations,  or found-
ed totally upon mere unauthorized hypotheses.
   Some  approaches to the  true theory of the circula-
tion were made by Servetus, or Servede, the celebrated
victim of  Calvinistic  intolerance,  and afterwards by
the  Italian anatomists,  Colombo and Cesalpini,  who
flourished in the sixteenth century.  It appears  that
they  had each of them  a pretty correct idea  of the
passage of the blood through the lungs, along the  less-
er circulation, and  were even aware of its  being acted
upon by the air, during this part  of its course,  but, in
other respects, their view of the subject was complete-
ly erroneous.!  The honour of the  grand discovery of
the circulation, the greatest that was ever made  in ana-
tomy  or physiology, is due to  our  illustrious country-
man, Harvey.   He completed the discovery about the
year 1620,  but, with  a  rare degree of philosophical
forbearance, he spent eight years in digesting and ma-
turing his ideas, when they were at length given to the
world in a short tract, written with remarkable clear-
ness   and perspicuity, which is  well characterized by
Aikin, " as  one of the most  admirable examples of a

   * For an account of the opinions of the older anatomists on this
subject, see Senac's Treatise on the Heart, Introd. p. 68, et seq.
   t Haller, El. Phys. iv. 4. 17 ; Sabatier, Anat. t. ii. p. 255, 
 2;6     •       Histgry of the Circulation.

 series  of arguments, deduced from observation and ex-
 periment, that ever appeared on any  subject."*
  The manner in which this discovery was received by
 the public forms a curious and interesting occurrence in
 the  history of philosophy.  Harvey, for some  time,
 scarcely made a single convert, and an excessive clamour
 was  excited against him, for having called in  question
 the revered authority of the ancients.  He fortunately
 lived in a country  which had been favoured with  the
 light of the reformation, otherwise it is not  impossible
 that he might have shared  the fate of Galileo, for some
 of his antagonists, when they found themselves foiled in
 argument,  did not scruple to  raise  against him  the
 weapons of superstition and prejudice, insinuating that
 his  new doctrines  would tend to subvert the credit of
 the  scriptures, and thus undermine the foundations of
religion and morality.   After  some time, however, it
 was  found  that Harvey's  theory was  true,  and  his
opponents  then commenced a different plan of attack.
They  asserted that the doctrine of the circulation,
which  had  been  brought forwards by him as a new
discovery, was well known to the ancients, and passages
 were quoted and warped in a thousand ways to prove
the allegation.  It is asserted that, for some years, he
even suffered in  his  professional practice  from  the
prejudice  excited  against  him;  but  by  degrees the
merits  of his discovery began  to be appreciated, and
he lived long enough to witness  the  triumph of  truth
over the cavils of ignorance.
  Harvey's doctrine  of the  circulation is now so uni-
versally admitted, that it  might seem unnecessary to
adduce any formal train of reasoning in its  support.
It may, however, be useful to review  the nature of
the  arguments that were  employed, as many of  them
consist of curious matters of fact, and throw consider-
able  light  upon the structure  and properties of the

  * See Harvey de Motu Cordis  et Sanguinis Circulo. 
Proofs of the  Circulation.             %77
sanguiferous system.  If we open the chest of a cold-
blooded animal, and bring the heart into view, we may
observe its alternate contraction and dilatation proceed
with great regularity.*   For a  short space  of time the
heart lies  at rest, and suffers itself to be distended with
blood, then it is  suddenly seen to rise up  on its basis,
to shorten its fibres, and to expel its contents.   During
this process it strikes  the ribs, and produces what we
call the beating of the heart, which does not depend, as
is sometimes imagined, upon the distention of the heart
from the blood which is received into  it, but, according
to  the  ingenious suggestion of W.  Hunter, upon the
injection of the blood into the curve of the aorta tend-
ing, to  a certain degree, to straighten  this part, and to
raise up the apex of the heart by which it is brought
into contact with the ribs.!
   The passage of the blood along the arteries and the
veins was first demonstrated to the eye by the experi-
ment of Malpighi,! who, by applying the  microscope
to  the  web of a frog's foot, or  other transparent mem-
branous part, enabled us to behold the interesting spec-
tacle of the arteries rapidly  projecting the blood in suc-
cessive waves towards their extremities, where it  was
received by the veins and returned in  a uniform stream
by their trunks.   It must, however, be acknowledged,
that this  experiment,  although  a peculiarly  beautiful

   * Harvey, Exer. 1, cap. 2.
  t J. Hunter on the Blood, p. 146, note.  Harvey was well aware
that the striking of the heart against the ribs did not depend upon
its  distention, p. 30.
   X Malpighi informs us that he  saw the circulation of the blood,
by  means of the microscope, in the membranous part of the lungs
and the mesentery.  See his  Second  Epistle " de  pulmonibus,"
addressed to Borelli; it is dated 1661j see also Boerhaave, Prpe-
lect. ab  Hallero, notae ad § 160.  Leeuwenhoek first saw the cir-
culation by  the microscope, as it seems, in the year  1698; he
observed it in a bat's wing, a tad-pole, and a fish's tail; Hoole's
Leeuwenhoek, p. 90, et seq.; also Epistola, p. 49, where, in a
letter to Heinsius, Oct. 1698, he  describes his observations on the
circulation in microscopic eels.                        ♦ 
278
Transfusion.
one, can scarcely be regarded as proving more than the
mere passage of the  blood through the arteries and
the veins, and the circumstance of the  pulsation being
oonfined  to the former of these vessels, for the rapid-
ity of its motion, and  the interlacing of the vessels
with each other, scarcely permit the eye to detect the
exact progress which it follows.
   From  an inspection of the mechanism of the valves,
we perceive that it is impossible for the  blood to return
from the ventricle into the auricle, because, when this
fluid endeavours to escape, the first effect is to raise up
the vElve which was floating upon its  surface,  and  to
apply it closely  to the passage which  leads from the
ventricle to the auricle.  There is, however, no obsta-
cle to the entrance of the blood into the arteries, and
we accordingly find that they become  distended with
blood.   From various causes, which will be more par-
ticularly  examined hereafter, the artery then contracts,
but the valves which are at its mouth are so construct-
ed as to prevent the  blood from getting back into the
heart,  so that it must be necessarily carried forwards
into the minute branches of the arterial system.
   The curious operation called transfusion proves the
course of the circulation to be  from the arteries into
the veins.  In  this  operation, which seems  to have
been invented, or at least perfected by Lower about
the year 1660, the artery  of  one  animal is connected
by a  tube with  the vein of another  animal, when we
find that the  first is gradually  emptied  of its  blood,
while the second  is brought into  a state of plethora.
If an opening be made at the same time in the veins  of
the second animal, the blood originally belonging  to it
will escape, and thus the fluid in the vessels generally
will be changed.  At the time when these experiments
were  made  diseases  were commonly supposed  to de-
pend upon some morbid qualities residing in the blood,
and as the operation of transfusion held out a method
of changing this fluid at pleasure, it was hailed as a 
Transfusion.
279
most important  means of  restoring the  health, and,
repugnant as it appears to the feelings, some individuals
actually submitted to  have  the  blood  of  lambs  or
calves transmitted into their vessels, for the purpose of
being cured of certain diseases, or having their vigour
renovated when it was exhausted by old age.
   It does not belong to my present  object to  notice
the  operation, except  so far  as  it  may  illustrate the
theory of  the  circulation, otherwise it  would be  amus-
ing to  recount the extravagant  expectations  that were
formed  respecting its  probable  advantages.  Lower
himself, who was  a man  of science, and possessed of a
clear  and philosophical  turn  of mind, seemed to re-
gard the discovery as a  new era in  the healing art,*
and it was warmly patronized by other learned persons,
who might be supposed  less apt  to be biassed  in  its
favour.  But  the first experiments of the  kind that
were performed upon the human subject  ended fatally,
and  although the advocates for  the practice endeavour-
ed to show that these unfortunate events were not ne-
cessarily connected  with the act of transfusion, yet it
excited  so much alarm, and  appeared  altogether so
disgusting and shocking an operation, that it was pro-
hibited  in  France by  an  act  of the   legislature,  and
everywhere soon fell into complete neglect.!

   * De Corde, c. 4;  Boerhaave, Prael. ab Haller, not. ad § 160.
   t The following papers give an account of some of the first expe-
riments  that were  performed on this subject.  Phil. Trans. No.
19, p. 352, (1666.)  A general  notice of the  fact of transfusion
having been performed before the Royal Society in London and at
Oxford.  No. 20, p. 353.   A more full detail  of the  experiment.
No.  25,  p.  449, (1767.)   An  account of further experiments.
No. 26, p. 479   The operation is performed at  Paris.   No. 27,
p. 490.  The  operation is performed at  Pisa, by Fracassi.  No.
28, p. 517.  Account of Bond's case at Paris,  the  first human sub-
ject on whom the operation was performed; it ended fatally  No.
30, p. 557.  The operation was  performed in  London on a human
subject by Lower and King. No. 32, p. 617, (1668.)   Denys per-
forms the operation at Paris on a maniac; the disorder is supposed
fo be relieved ;  the  operation is repeated and ends fatally.  No. 
280               Wounds of the Vessels.
   A fifth argument that was advanced  as a  proof of
the circulation being from  the  arteries  into the veins
is  derived from the  effects  of wounds of the  vessels.
It  Was observed  that when an artery was cut  or divid-
ed, the part nearest to the  heart projected  a  stream
of blood, and that comparatively little  fluid was  poured
out from the other end, while the reverse was observed
to take place with respect to the veins when they were
wounded;  here  the  flow of blood  was  from  the part
more remote from the heart.  Although this statement
is  in the  main true, and is  naturally explained  by the
course which  the blood is known to follow, yet  it must

36, p. 710.  A particular account of the above  case.   No. 54, p.
1075, (1669.)  Further  particulars of the  case.   See also Senac's
Treatise on the Heart, Intr. p. 92.—From  this time the operation
appears to have  been entirely laid aside, until it was  again intro-
duced by Dr. Blundell, who has given us  a minute detail of his
experiments, and of the method of performing the operation.  He
has established the  important  point, that the blood of an animal of
the same species may be safely and easily transfused,  but that  if
the blood of a different kind of animal be employed, great disorder
of the functions is occasioned, and death generally ensues.  Med.
Chir. Trans, v. ix. p. 56.  The experiment was tried  upon the
human  subject, and, so far as  the operation was concerned, with
success.   Ibid. v. x. p. 296.—The curious fact, that the transfusion
of the blood of an  anima! of a different species proves  fatal, has
been since observed by MM. Prevost and Dumas ; they once men-
tion  Dr.  Blundell's name,  but no  one would suspect, from the
perusal of their memoir, that he had anticipated them in the most
important of their conclusions.  Bibl. Univ, t. xvii. p.  215.  The
results  of the experiments of Dr. Blundell, and of MM. Prevost
and Dumas, would appear to be scarcely consistent with the fol-
lowing statement by M. Magendie; Physiol, t.  ii. p. 342.  " J'ai
eu occasion d'en (experiences) faire un certain  nombre, et je n'ai
jamais vu que l'introduction du sang d'un  animal dans les veines
d'un autre eut des inconveniences graves, meme quand on augmente
beaucoup, par ce tnoyen, la quantite  de sang."—Numerous refer-
ences to cases or treatises on transfusion may be  found in Plouquet,
" Chirurgia Infusoria et Transfusoria ;" we may  remark, however,
that here, as well as in other parts of this learned performance,
the value of the work  is  diminished in  consequence of subjects
being incorporated, which have rather a technical or verbal, tha^
 a  real connexion. 
Ligatures.
281
be considered rather as affording an illustration of the
subject, than as any very direct proof.
  A much more  decisive argument  is offered by  the
effect of ligatures placed upon  the  vessels;  here it
was  observed that if the artery be tied, so that the
stream  of blood  along it  be  interrupted, the part
between the heart  and the ligature  becomes turgid,
while the  part beyond the ligature is  comparatively
emptied of blood.  A ligature upon a vein has exactly
the  contrary effect; here the part between the com-
mencement of the vessel and the ligature is rendered
turgid, while the  part  between the ligature and the
heart becomes flaccid.
  Two other arguments in proof  of  the  circulation
have been adduced, even by writers of the first emi-
nence, the  power  which  we  have of filling  all the
vessels  of the  body by injecting a fluid into  one of
them, and the fact  well known  to  physiologists,  that
when certain medicinal substances are introduced into
the  veins,  they are carried  into the general circula-
tion, and are found to exercise their  specific action
upon certain glands  or  other organs of the  body, in
the  same  manner as if they  had  been received into
the  stomach by the mouth.* These two circumstances,
however, can afford only a general proof of  the motion
of the  blood through  the vessels,  and of their mere
communication with each other, without showing the
nature  of  the   blood's  motion,  or the  manner in
which this communication  is effected.
   All the circumstances which have been enumerated)
the  inspection  of the heart of  a cold-blooded animal;
the  application of a microscope to  a transparent mem-
brane, the mechanism of the valves, the  operation of
transfusion, the effect of wounds of the vessels and the
action of ligatures, when taken in connexion with each
other,  may  be  considered as proving very decisively

          * Soemmering, Hum. Corp. Fab. t. v. § 40.
                 36 
 282           Illustrations from Pathology.

 that  the course of the  blood is from the  heart along
 the  arteries, and through the veins back to the heart;
 but it still remains  to prove in what manner the sys-
 temic and  the  pulmonic circulations are  related  to
 each other.  This  is very  satisfactorily demonstrated
 by the  mechanism of the heart and  especially that of
 its valves.  We  find that  there  is  no direct passage
 between  the right and  left sides of the  heart, that
 when the blood is in either of the auricles, it must  be
 transmitted into  the  corresponding ventricle, that the
 tricuspid and mitral valves will not permit  it to return
 into   the  auricles, and, therefore, that  the pulmonic
 ventricle, when it contracts, must  necessarily force the
 blood into the pulmonary artery, while the aortic ven-
 tricle can propel  it only  into the aorta.
   In  speaking of the proofs of the circulation I have
 hitherto taken no  notice  of a train of  phenomena
 which daily offer themselves to our  notice, and which
 are generally  regarded  as  affording very direct and
 decisive proofs of the course  of the blood.   I allude
 to the appearances which are frequently  found in  the
 dissection  of  subjects who have died of diseases  of
 the sanguiferous system.   These,  however, are rather
 to be considered  as illustrations of the true theory,  or
 as confirmations of  it,  than  as actual  proofs, and
 although  they may occasionally assist us in investigat-
 ing the nature of  the   uses  which  the blood serves
 in the animal ceconomy,  yet, as they belong more  to
 pathology  than  to  physiology, it  would  be  scarcely
 consistent with the object of  this work to enter into
 any minute detail of them.
   1 shall  merely  state in general terms, that when  an
 obstruction occurs to  the passage of the  blood along
 any  part  of its  course, a turgescence  is  produced
behind the  obstruction,  just in the   same  manner  as
from  the application of a ligature.    We occasionally
 observe  individuals in whom we  have reason to sup-
 pose  that the blood  does  not experience  its specific 
              Illustrations from Pathology.          285

change  by the action of the  air in the lungs, and, on
examining their bodies after death, we find that from
some malconformation of the heart or its appendages,
the blood had been transmitted immediately from the
right to the  left side  of this  organ, without  passing
through  the pulmonary vessels.  It  not  unfrequently
happens that a great arterial or venous trunk becomes
obliterated  by some accident, or may have been  defi-
cient in  the original formation of the body, and we
then find that the branches are increased to an unusu-
al size to supply the deficiency, and that they are given
off in such situations as to correspond with  the  theory
which has  been  laid   down.  These examples may
serve as specimens  of the  nature of the illustrations
of the true  theory of the circulation, which are afford-
ed by morbid anatomy and  pathology.
   We may now be considered as having  established
the  general fact of the circulation and the path which
the  blood pursues, but there are several circumstances
connected with this function which require to be more
minutely examined, either  as  having  formerly  been
the  subject of controversy, as points  about which a
difference  of  opinion  still  exists,  or as  tending to
illustrate some of the operations of the animal  ceco-
nomy, and  to explain the  uses of  its different parts.
In the first place I shall mention the circumstances of
a more mechanical nature, connected  with the struc-
ture and organization of the heart and its appendages,
directly affecting its motion or  its action upon the
blood, considered merely as an hydraulic machine.  I
shall afterwards notice some points that are more im-
mediately connected with  its action as  a vital organ,
particularly those  that  depend upon  its contractility.
Lastly I shall give an account of various circumstances
connected with the arteries and the veins, which I have
hitherto not  noticed, or adverted  to  only in  an indi-
rect or cursory  manner.   In pursuance of this plan
 it will be my object to  intrude as little as possible upon 
 '554         size of the  Cavities of the Heart.

 the  province  of  the  anatomist, and to make  use of
 the facts deduced from his science only so far as they
 immediately  lead  to   any  important   physiological
 conclusions.

           § 4.   Mechanism of the. Heart*

   We  have  seen that the substance of the heart  is
 composed of the parietes  of  two  cavities, called ven-
 tricles, to which  two others are attached, called auri-
 cles,  making in  all four cavities,  through  which the
 blood is progressively carried from  one  to the other in
 succession.   In describing  the   heart  it  has been  a
 point  warmly contested  by  anatomists  what  is  the
 relative size of these cavities ; whether they have all
 exactly the same  capacity, or whether they differ from
 each  other in this  respect.   As to the auricles, per-
 haps  the point can scarcely be  determined  with per-
 fect accuracy,  as  it is  not easy to assign  the precise
 limits where the  large  veins may be said  to  terminate
 and the auricles to commence.   It  is,  however, gene-
 rally  admitted that the  right auricle  is considerably
 more capacious than the left,  and  Haller assigns their
 proportions as  about seven  to five.!  The limits of the
 ventricles are better defined, both in consequence of
 their  more compact form, and of the valves  which are
 attached to  both their orifices; yet it is  remarkable
 that  very  different opinions  have been entertained
 respecting their  size, a point  which one should have
supposed might have been  easily subjected to a direct
 and precise experiment.  Most of the older anatomists
 have  described  the right  ventricle as  considerably

  * For the most ample account of  every thing that  respects the
mechanism and structure of the heart, the reader may be referred
 to the learned work of Senac, liv. 1 and 3, a writer no less to be
admired for the extent of  his information, than for the  candour
with which he comments upon the opinions of others.
  t El. Phys", iv. 2. 17. 
Form and Strength of the Ventricles.       285
  larger than the left, and even Haller  admits that this
  difference of  size  exists,* but there seems to be good
  reason for doubting the  correctness  of  the opinion.
  Sabatier  examined  this  point very  accurately, and
  his  conclusions have been since generally acquiesced
  in.   He admits that when we examine the heart after
  death, the right, or  pulmonic cavities, are frequently
  found much  more capacious  than the  aortic,  but  he
  conceives that  this  difference did not exist during life,
  and that it is occasioned by the manner in which  the
  circulation terminates  in  the last  moments of exist- ■
  ence.  From causes which  will  be more particularly
  described hereafter, in  the  act  of death  the blood
  necessarily  becomes  accumulated  in  the  pulmonic
  cavities of the  heart, while it is, from the same cause,
- almost  entirely expelled  from  the  aortic  cavities;
  hence the latter become contracted, while the  former
  are proportionably dilated,  and the comparative weak-
  ness of  the muscles of the  pulmonic ventricle  still
  further contributes to produce this  effect, and  permits
  the  dilatation  to take  place.  It appears, therefore,
  that we are to regard the two ventricles of the heart,
  during the  life of  the  animal, as  possessing nearly
  equal capacities.!
    But whatever may be the  fact respecting the size of
  the  two  ventricles,  they differ very obviously  from
  each other  in their  form and in the  strength of the
  masses  of muscular fibres which compose  their sides.
  The left ventricle, or that  which communicates direct-
  ly with the systemic circulation, is much stronger than
  the  other : it  lies  more nearly in the  centre  of the
  heart, and gives the general  form to the organ, while
  the right, or pulmonary ventricle, lies, as it were, upon

    * El. Phys. iv.  3. 3;  Lower, p. 36, endeavoured to prove that
  the capacity of the ventricles is equal, but  his opinion was not
  generally adopted.
    t Sabatier, Anat. t. ii. p. 241. and t. iii. p. 373; Mem. Acad, for
  1774. 
286        Form and Strength of the Ventricles.
the systemic, like an appendage attached to the heart,
and has  much  thinner and weaker parietes.   Accord-
ingly, when we  divide the heart by a transverse  inci-
sion across the  two ventricles, we find that the section
of the left ventricle is nearly a circle, while that of the
right  exhibits a  semilunar figure.   This difference in
the strength of the ventricles is  necessarily connected
with  the offices  which  they  respectively perform, or
with the  degree  of force which they exercise in  the
parts  of  the circulation to which they are immediately
destined.   The right  or  pulmonic ventricle has merely
to propel the blood through the lungs, while the  left
has to  transmit  it to every other part of the  body.
The resistance  which the blood has  to overcome in its
passage  through the  vessels depends upon a combina-
tion of several circumstances, which  will be considered
hereafter, but  there  can be  no doubt of the general
fact respecting  the  difference of  resistance opposed to
the blood at its entrance into the two circulations, and,
by ascertaining the relative  quantity of fibres which
belong to each  of the  cavities, we might form an esti-
mate  of the amount of the force respectively exercised
by them.  The same difference of strength exists in
the auricles as in the  ventricles, the  right  being  consi-
derably weaker than the left; Haller conceives that the
former possesses only one-third the strength of the lat-
ter.*
  Another  subject, which has given rise to much  dis-
cussion, is the exact order of  succession in which  the
different parts of the heart contract.   It is obvious that
each auricle  must  contract before  its  corresponding
ventricle, but it has been questioned whether any of
these  events are  synchronous, or whether they do not
each of them occur in succession.  It is now, however,
very generally admitted,  that  the parts of  the same
description  contract precisely  at the same  point of
* El. Phys. iv. 3. 2. 
Period of a Circulation.              287
time, as the two  auricles and the two ventricles; that
the contraction of the auricles exactly alternates with
that of the ventricles, and  that the contraction of the
arteries is synchronous with that of the auricles.  This
opinion was warmly contested,  about the  middle of
the last century,  by Lancisi and Nicholls,  who had each
of them  some  peculiar notions on this subject, which,
however, it is not necessary to particularize, as they are
now entirely discarded.
   Every part of the blood passes through all the four
cavities of  the heart in the course of a complete cir-
culation ; it therefore necessarily follows, that if all the
cavities contract  an equal  number of times  during the
same interval, they must project the  same quantity of
blood, and consequently, if they differ in size, that  a
portion of  the contents of the larger  of them will not
be expelled. With respect to the ventricles it appears
that their  size is nearly equal, and that, at each  con-
traction, they are  nearly emptied; but it is probable
that this is not the  case  with the auricles,  and if the
right be so much larger than the left, as has been stat-
ed above,  it is obviously impossible that this can be the
case.  Indeed, from the form of  the auricles it would
appear that the  contraction of their  fibres  cannot en-
tirely obliterate  their cavities.  It is also probable that
when the  auricles  contract, a part of their  contents
will be forced back into  the mouths of the great veins,
as there is no valve situated between the vein  and the
auricle by which the reflux of the blood can be  pre-
vented.*
   Calculations have been formed of the length of time
which the heart occupies in performing its motion, and
of the quantity of blood which is expelled by each con-
traction.   This quantity of course varies in  different

   * Haller,  El. Phys. iv. 4. 10.  For some interesting observations
on the mechanism of the heart, see Home's Lect. on Comp. Anat.
p. 47. 
288          Systole and Diastole of the Heart.

individuals, and in the same individual at different times,
and  there are practical difficulties which  prevent us
from arriving at complete certainty on  these  points.
Professor Blumenbach's estimate may be taken as a fair
average ;  according to this the heart is supposed to ex-
pel two ounces of blood at each contraction ; the whole
mass of blood is reckoned at 33lbs.* and the number of
pulsations are taken at  seventy-five in a minute.  Pro-
ceeding upon  these data we shall  find that the blood
shall complete its circulation, or that  the whole of it
shall have passed through the heart in about two mi-
nutes and a  half, and  that  a mass of fluid equal to the
blood would be carried through the heart twenty-four
times in an hour.  It must, however, be observed that
the different portions of blood complete the circulation
in very different periods of time, partly depending up-
on the length of the course which  they have to follow,
and  partly upon  the degree of resistance which they
meet with.   When the-blood is  sent  into the aorta it
soon begins to pass into the different arterial branches
that are connected with the great trunk; a part circu-
lates only through the  muscles of  the  heart, another
portion takes a longer  circuit through the chest,  and
others through such as  are more extended, until a part
of the blood  is carried to those organs that  are  most
remote from the heart.
  It has been stated that the  auricles and ventricles
are filled and  emptied  alternately, so  that there is no
period in  which the whole of the  heart is  either  full
or empty, but,  as the substance of the  ventricles  is
much more considerable than that  of the auricles, and
as the former belong more particularly to the heart it-
self,  the terms systole and diastole of the  heart  are ap-
plied to the contraction and dilatation of the ventricles

  * Mr. Good has collected the various estimates which have been
formed of the  amount of the whole mass of blood;  he concludes
the most probable quantity to be between  thirty and forty pounds.
Study of Med. v. ii. p. 11. 
        No Communication between the Ventricles.      289

respectively, and are of course reversed with  respect
to the auricles.   I have before observed that the pul-
sation of the  heart, which we feel when  the  hand is
placed upon  the ribs, depends not  upon any increase of
bulk which  the ventricles experience by the  injection
of the blood  into them, but upon the effort which they
make to expel  their contents, or  rather by the  injec-
tion of the  blood  into the arteries ;  the  beat of  the
heart therefore occurs during the systole  of the ven-
tricles, and is contemporary  with  the  diastole of  the
auricles.
   In describing the structure of the heart it has been
already stated that, in the adult and perfect  state of
this organ, there  is no direct communication  between
its  right and left sides, i.  e. between the two  auricles
and the two ventricles.   As a general principle, no
point in  anatomy is  better established than this fact,
and it is one which admits of an easy and satisfactory
proof.  With  respect to the auricles, however,  the
position must be taken with  some  limitations,  as it ap-
pears that the passage between them, which  exists in
the foetus, called the foramen ovale, which I shall have
occasion to describe more fully hereafter,  is sometimes
not entirely  closed even long after the period  of infan-
cy.*  With respect to  the ventricles,however, the fact
may  be stated without exception, and yet such was the
force of prejudice, and the  bigoted attachment  to hy-
pothesis, that  men of  learning were not  wanting  who
affirmed the existence  of certain passages  or pores be-
tween  the ventricles,  which they asserted  that they
were able to detect, and even professed to  demonstrate
to  others,!  In this, as well as  in  many similar  cases,

  * Sabatier says, it always remains open ; see also Blumenbach's
Comparative Anatomy, by Lawrence, § 159, note (C).
  t Haller, El. Phys. iv. 3. 13.  Soemmering, Corp. Hum. Fab. t.
v. § 27 ; Sabatier, Anat. t. ii. p. 235.  The existence of such pas-
sages was first  announced by Vieussens and Thebesius;  they  were
received by Ruysch,  Lancisi, and  others of the first eminence ;
                 37 
290
Liquor Pericardii.
 it is not easy to decide, whether such persons were the
 dupes of their own credulity or wished to impose upon
 others, but it must tend to impress upon our minds the
 important truth, that even the most  direct testimony
 is always to be received  with distrust,  when the facts
 related are themselves incredible.
   There is a still more remarkable example of the bi-
 goted attachment to certain opinions, and, especially,
 when they were sanctioned by the authority of the an-
 cients,  connected with this part of the subject, which
 it may not  be uninstructive to  relate.   Vesalius,  the
 great restorer of anatomy after the dark ages, perceiv-
 ed that the description of the vessels of the  heart which
 was left by Galen, did not correspond to what he found
 in the human subject, but resembled this part  in apes
 and  monkeys; from this circumstance he very  natural-
 ly concluded that Galen  used these  animals in  his  dis-
 sections.   A learned  French anatomist  and professor,
 Du  Bois,  better  known under  his latinized name of
 Sylvius, who was a warm advocate  for  the ancients,
 and  a violent antagonist of Vesalius, in his zeal to repel
 the accusation, seriously maintained  the  position, that
 the human form had undergone  a change  in its struc-
 ture  since the age of Galen, and that  formerly  the
 vessels were distributed as  he described them.*
   The heart, as I remarked above, is  enclosed in a
 membranous bag or pouch, called, from its situation, the
 pericardium ; it is lined with a serous membrane, which,
 like  other parts of the same structure,  has a  serous
 fluid  perpetually  discharged  from its surface.  This
 fluid, the liquor pericardii, is sometimes  found to exist
 in considerable quantity,  to  the amount  of  several
 ounces; so  large a quantity, however, is evidently the

they were afterwards called in question by Duverney, and finally
disproved by Senac and Sabatier.  See  Sabatier, Anatomie, t. iii.
p. 410.
  * Haller, El. Phys. iv. 2. 7.  Du Bois extends this argument to
fhe intermaxillary bone. Lawrence's Lectures, p. 17 t 
Change of Figure.
291
effect of disease, but it is a question, about which there
have been very warm and even very acrimonious dis-
putes,  whether any perceptible quantity of the liquor
pericardii exists during life and  in the state of health.*
Perhaps the'question can scarcely yet be considered as
completely decided;  if we argue from the analogy of
what occurs  in other close cavities that are furnished
with a serous membrane,  we should  conclude  that, in
the natural state of the parts, there is no fluid present,
but that as fast as it is discharged by one set of vessels
it  is taken  up by another.  W hen, however, these
actions do not correspond, when either the discharge is
too  rapid or  the removal  too slow, an accumulation
must take place.
  A circumstance respecting the  mechanical structure
of the heart, which may be worth noticing, is  the dif-
ference of its size in different individuals; this difference
is  indeed much  more  considerable  than might  have
been suspected,  for  we are  informed by anatomists,
that the heart is, in  some individuals, double the size
it  is in others, and this has not been  observed  to bear
any  proportion to the general bulk of the body.  The
heart of the foetus always bears a  greater proportion
to the  whole body than  that of the  adult; as the
growth advances  this disproportion is diminished, but
it is  not entirely removed until the body attains its full
size.  It has also been  observed, that the proportion
between the parts of the heart  is different in the foetus
from what  it is  in the  adult;  the  auricles are larger
than the ventricles, and the aortic  side  of  the heart
generally is larger than the pulmonic; but these points
will  be considered  more particularly in  the account of
the foetal circulation.
   The heart is essentially  a muscular organ, and when

  * Haller, El.  Phys. iv. 1. 19, 20.  Soemmering, Corp.  Hum.
Fab.  t. v. § 6.   Sabatier, Anat. t. ii. p. 217.  Bell's Anat. v. ii. p.
52, et seq. 
°-92               Change of Figure.

it  contracts it acts, like other  muscular organs, by
shortening its  fibres, and in this way it diminishes^ the
capacity of its cavities.   The general fact  is demon-
strable  to the eye, when we  lay open the thorax of  a
cold-blooded animal, and may be directly inferred both
from the structure of  the valves  and from the  actual
effects  which  are produced.   There  has,  however,
been much controversy upon this subject, although one
that is apparently so clear and perspicuous ;  the great
point in dispute is, whether the ventricles are diminish-
ed  in both their  dimensions, whether, by the act of
contraction, their sides are not brought nearer together
without their  being diminished in length, or even whe-
ther the  heart is not  actually lengthened  during its
systole.  This opinion, which at one  time  had  very
powerful  advocates, seems to have  arisen  partly from
some hypothetical notions about the  pulsation of the
heart,  or the manner  in  which it is enabled to strike
the ribs during its systole; but by occular examination,
by  direct  experiments  made upon  the heart,  and by
considering the manner in  which the valves perform
their office, it is now generally admitted that the cavi-
ties of the ventricles are diminished  in every direction.*
  With respect to the striking of the  heart against the
ribs, this, like  almost every other circumstance connect-
ed  with its mechanism, has given rise to considerable
discussion, although the cause which has been already
assigned for it,! the sudden injection of blood into the
aorta, and its consequent effort to straighten its curva-
ture, will probably be considered as  sufficient to explain
the phenomena.   Other causes,  however, have  been
pointed out, either as  more  satisfactory, or at least as
conspiring  with  this to  produce the effect;  among
others, Sabatier has endeavoured to* prove that, when

  * Sabatier, Anat.  t. ii. p. 229; Bichat,  Anat. Descrip.  t. iv. p.
113.
  t  See p. 277. 
Foetal Circulation.
293
the ventricles contract, a portion of the blood that was
contained in them is necessarily  forced behind  the
valves into the auricles, and in this way contributes to
push the heart forwards against the fore-part  of  the
thorax.*
   While the future animal is still retained in the ute-
rus of its mother, it is obviously placed under very dif-
ferent circumstances,  with respect to all surrounding
agents, from what it is after that period.  It is entirely
secluded from the air, which is afterwards so essential
to its existence, it is incapable of receiving any nourish-
ment through the usual course of the digestive organs,
it is constantly immersed in a high  temperature,  and
has no opportunity of employing either the muscles of
loco-motion, or any of those that are  connected with
the exercise of the external senses.   In short, it may
then  be regarded  as forming a part of the mother;
from her it derives its nourishment, its heat, and all
those powers necessary for the  support of that kind of
life  which  it possesses.   Still,  however, to  a  certain
extent, its organs are developed, and acquire the form
and properties which they are  afterwards to possess,
although with certain modifications and  adaptations to
present circumstances, so as to  afford a  most remark-
able example of what has been called prospective  con-
trivance,!  or that adjustment of means to ends, which
respects not merely the present condition of the being,
but that which  it is  afterwards to assume.   This  spe-
cies of adjustment is more peculiarly remarkable with
respect to the circulation of the blood, for we  have it
directed in a different course from that which it after-
wards pursues, we have.even vessels employed which
are  obliterated after birth,  while the  whole is so  con-
nected with the mother, that her system supplies what
is deficient in that  of  the embryo,  and  completely
ministers to all its wants.   Both as constituting in itself

   * Anatomie, t. ii. p. 230.      t Paley's Natural Theology. 
294
Ductus Venosus 8f Arteriosus.
 a very interesting part of physiology, and as tending to
 illustrate the functions of the adult, we may consider
 the foetal circulation as a subject well deserving of our
 attention.*
   The most important point in which  the state of the
 foetus differs from the same animal after  birth is its
 seclusion from the atmospheric air, from which it fol-
 lows, in the first place, that- the lungs are incapable of
 exercising  their appropriate functions, or  of inducing
 the  specific  change  in  the  state of  the  blood, and
 secondly, that this change  of the  blood, so far as it is
 required for foetal existence, must be  effected  by the
 mother.   In order to  accomplish this  purpose, a large
 part of  the  blood, which in the animal after birth is
 carried through the lungs, forming the lesser or  pul-
monic  circulation, is  in  the foetus diverted from this
 channel, and passes directly into the left, or aortic side
 of  the heart.  This  diversion in the  course  of the
blood is a necessary consequence  of the state of the
foetus, both with respect to its posture  and the relative
development of its organs, and is likewise an expedient
adapted  to the circumstances in which it  is situated.
In order to supply the place of the lungs, or to execute
the office which they are incapable of performing, the
blood is carried  into the placenta,  where it is so acted
upon  by the  blood of the mother, as to experience a
change analogous to that which, after  birth, it under-
goes in  the  lungs.  It  is  carried to  this organ and
brought  back from it  by a set of  vessels  which exist
only before birth, and which are necessarily destroyed
by the act of leaving the uterus,  at the  very instant
when they become no longer of any use.
  But in appending the supplementary or  extraneous
set  of vessels to the ordinary circulating system,  it
happens that  the blood, after it has  experienced its
specific change, is returned to the  foetus in the course
* Senac, liv. 3. ch. 9, 10, 11. 
Use of these Parts.
295
of the venous part of the circulation.  It is, however,
obviously unnecessary  for it  to complete its course in
this  direction,  and probably by so doing it would lose
some  part of  that specific quality which  it was the
office of the placenta to impart to it.  On  this account
a passage exists between the two auricles, called the
foramen ovale, through which a part of the blood that
is brought into the pulmonic auricle is directly convey-
ed into the systemic auricle, without  passing into the
pulmonic ventricle, as well as two additional vessels  or
ducts, which belong exclusively to the foetal circulation.
By one of  these  a  part  of the blood is immediately
brought back to the heart,  soon  after its  return from
the placenta, without passing through any  part of the
venous circulation, which it would  otherwise  have  to
perform in  order to  arrive at  that  organ;  by the
other, a part of the blood  which  has  arrived at the
right or pulmonic ventricle, and is propelled into the
mouth  of the  pulmonic artery, is carried directly into
the  aorta, thus escaping the whole  of the pulmonic
circulation, as well as  the passage through the left  or
aortic cavities of the heart.
  The first of these temporary or supplementary ves-
sels, as they may be styled, is named  the ductus veno-
sus; the second, the ductus arteriosus; names, which
it may be remarked, are  rather anatomical than phy-
siological, being derived from the  parts to which they
are connected, not from  the offices which they  per-
form.   In fact they are  both to be regarded as arte-
rial vessels, for their purpose is to convey, by a short
track, the blood, after  it has been changed in the pla-
centa, to the main trunk  of the  aortic  system.   In
short, the mechanism  of  the  foetal  heart all tends
to one object, to reduce what in  the adult  is a double
organ, or at least  an  organ consisting of  two sets  of
parts, which, although  placed in  contact, serve two
different purposes,  to  a  single organ, or  to an organ,
the parts of which may conspire  to one object onlv. 
296       Mechanism of the Foetal  Circulation.

The foetus is in the state  of those animals  that are
without lungs, and therefore before birth onl^so much
blood is sent to them  as  may  be  sufficient for their
growth, and may prepare  them  for being employed
after the animal acquires  the capacity of breathing
when it leaves the uterus.
   In the course of  this  work many opportunities will
occur of illustrating  the nature of the functions by the
difference between the adult and the fcetal organs;  at
present we shall only further remark,  that  although
we are fully acquainted with the  nature of the differ-
ence in the mechanical structure of  the parts, and the
change  which they experience at birth,  we are  per-
haps scarcely able,  in every period,  to  trace  out the
actual or immediate cause by  which the  change  is ef-
fected.   We,  however, understand it sufficiently  to
perceive that it is accomplished by a system of contri-
vances at once simple and effectual.  The first act of
inspiration, which  is immediately connected  with the
introduction of the infant into its new state of existence,
necessarily causes  the blood  to pass through the pul-
monic vessels in greater quantity than  before birth,
and-we may infer that  this  new direction which the
blood then assumes  produces  all  the changes  in the
vessels, expanding those  parts which were before small
and only  imperfectly pervious,  while  it diverts the
blood from those that are no longer  useful, and which,
therefore, by their own elasticity, shrink up and finally
become obliterated.
   All the peculiarities of the  fcetal circulation evident-
ly tend to one  object, to  bring the blood, after it has
been changed in the placenta, more directly into the
systemic artery, but it   is  not so evident what is the
use  of each particular part  of the additional apparatus.
It may  be asked, why may not the whole change have
been effected by means  of  the  foramen  ovale or the
ductus arteriosus alone, as the object of both of them
appears to be precisely the same ?   Part of  the diffi- 
Sabatier's Hypothesis.
297
culty which has  attached to this subject is  certainly
owing to the incorrect notions which, until lately, were
entertained respecting the  use of the lungs and  the
function of respiration,   Although  the  older writers
had some imperfect idea of the connexion between  the
passage of the blood through the lungs and a  chemical
change in the composition of the air, yet the  chief ob-
ject of respiration was conceived to be mechanical,  and
of course there could be no correct conception of  the
use of the placenta as a substitute for the  lungs. What-
ever purposes the pulmonic circulation may be suppos-
ed to serve, it is obvious that it is unnecessary for  the
foetal state, but that it becomes necessary the  very mo-
ment that the animal,  by leaving  the uterus, acquires
an independent existence, and must therefore perform
by its own  organs  those  functions which were before
exercised by  the organs of  the  mother.   Yet we may
readily conceive the difficulty there would be  in effect-
ing this change, without, at the same time, producing
a great derangement in the mechanical structure of  the
parts concerned, and that it would be desirable to em-
ploy every method for rendering this transformation
as easy as possible.   Perhaps,  then,  it may be  re-
garded as  a  sufficient  reason for the present  construc-
tion of the body,  that   this change  would  be  more
readily effected by  having the current of blood divid-
ed into two streams, instead of the whole of it  going
through one channel, so that the use of the ductus ar-
teriosus, in addition  to the foramen ovale, is simply to
facilitate the transmutation from the fcetal to the respi-
ratory state, by increasing the  number- of  parts con-
cerned, and  therefore  rendering a  less mechanical
change necessary in any one direction.
  Although I think  it  quite useless to advert  to  many
of the  speculations  and  discussions  that have taken
place on the  subject  of  the foetal circulation, there
is one hypothesis that may be mentioned, principally
on  account of the individual by whom it was  ad-
                      38 
298   Comparative Anatomy of the Circulatory Organs.

vanced.  Sabatier, whose name has been so frequently
referred to as one of the most accurate and judicious
of the anatomists who have particularly directed their
attention to the  investigation of the structure and me-
chanism  of the  heart, has taken much pains to prove
that the object of the foramen ovale is not simply to
permit a part of the blood  to pass directly from the
pulmonic to the  aortic auricle, but to keep the  two cur-
rents   of  blood that proceed  from  the  two  great
branches of the vena cava separate  from each other,
to send that part of it which comes from the vena cava
superior into the pulmonic ventricle,  while the  blood
from  the vena cava inferior is transmitted through the
foramen ovale into the aortic  ventricle.* But in spite of
the authority by which the hypothesis is supported, I
must  acknowledge that  I think it  very fanciful and al-
together inadmissible.
   It has been stated  by those who have  minutely at-
tended to the gradual development of the  parts  in the
fcetal state, that in the first stages of existence the two
sides  of the heart are nearly  of the same strength and
form, but by  degrees the aortic  ventricle,  in   conse-
quence of the greater force which it has to exert, ac-
quires its superior strength and thickness.  This is ana-
logous to other  well-known facts in the animal cecono-
my, where a muscular part acquires additional strength
by action, a provision which  is attended with  the most
beneficial results, and is one  of the most beautiful ex-
amples of the adaptation of means to ends with  which
we are acquainted :  the efficient cause of this change
will be considered hereafter.
   The great importance of  the circulation, considered
as the regulator of the  whole animal machine, and the
connexion which it has   with  all  the  other functions,
renders it desirable for us to  view it in all its  relations,

   * Anat. t. ii. p. 224, and t. iii. p. 387;  Mem. Acad for  1774, p.
 198.   , 
Amphibia.                   299
and to examine  it under every different circumstance
in which it presents itself to our inspection.   It may,
on  this  account, be useful to make some observations
upon  the comparative  anatomy of the organs of circu-
lation, at least in those animals whose general structure
is so similar or analogous to the human, as to enable us
to establish a comparison between them.  Of the two
great divisions into which  the whole animal kingdom
has been arranged by  Cuvier, the animals  with and
without vertebra?, I shall refer only  to  the former, as
the structure and ceconomy of the latter differ so ma-
terially  from man, as not  to throw any  light upon  the
subject  now under consideration.   We haj^e seen that
an  essential part  of the circulation in  the human frame
is the circumstance of its being double, or of the blood
being carried twice  through  the  heart  in each com-
plete  circuit, once for the  purpose of its being acted
upon  by the air  which is received into  the lungs, the
other, in order to transmit it, when thus  acted upon, to
all  parts of the body.
  The  animals  possessed  of  vertebrae  have been di-
vided into the four classes of mammalia, birds, reptiles
or amphibia, and fish.  The circulatory  organs of all
the animals that belong  to  the two first  classes are es-
sentially the same with those in man; they consist of a
heart divided into two ventricles, to which two auri-
cles arc appended ;  to these the arteries and veins  are
so attached, that the blood pursues its complete course
along the  two circulations, as in the human subject,  the
differences depending only upon some variations in the
shape or position of the   parts, the order and disposi-
tion of the vessels, or the structure of the valves.
  The  third class, the reptiles or amphibia, although
they differ from  the other vertebrated animals suffi-
ciently  to be placed in a  ceparate division, differ also
considerably among themselves, so as to be defined al-
most  as much by negative, as by positive  characters.
The organs of the circulation are less uniform in this 
500
Amphibia.
 than in the other classes, and it is perhaps not a little
 remarkable, considering the great attention which has
 been bestowed upon comparative anatomy, and the fa-
 cilityWith which animals of this description may be
 procured, that anatomists do not altogether coincide  in
 the  account which they give of the circulatory organs
 of the same animal.  Without descending, however,  to
 minute particulars, which would be foreign to my ob-
 ject, it will be sufficient  to state as a general fact, that
 the  heart of the amphibia  consists either of only one
 ventricle, or of  two ventricles which  freely communi-
 cate with each other, so as, physiologically considered,
 to be  equivalent to one.  The number of auricles de-
 pends  upon the construction of the ventricular part  of
 the  heart;  where there is a  single ventricle there is
 but  one auricle, and where there is a double ventricle
 there are two auricles.   In all these animals, however,
 there  is only a single large  artery proceeding from the
 heart, which serves both for the pulmonic and the sys-
 temic  circulation, and the  essential peculiarity of the
 circulatory organs of these  animals consists  in the pul-
 monic  circulation being merely  an appendage to the
 systemic circulation.  After the great  artery, which
 may be regarded as analogous to the aorta of the mam-
 malia and birds,  has left the heart, it divides into two
 main branches, by one of which a  part  of the blood is
 carried to the lungs, while the other part goes through
 the arteries that are distributed  over all the parts  of
 the body. These two portions of blood are united in the
 heart,  and, after being  mixed  together,  are again ex-
 pelled through  the  great artery.   It appears, there-
 fore, that whatever be   the office of the lungs, a part
 only of the blood is transmitted  through them during
 each circuit, and that although there are two sets  of
 vessels, yet  that  each  portion  of the  blood passes
 through one  circulation  only each  time  that it leaves
 the heart.*
  * Blumenbach's Comp. Anat. by Lawrence, p. 241, with note (E)
containing the references to Cuvier. 
General Observations.
sot
  The  circulation  of the blood is  effected in fishes,
the fourth great class of the vertebrated animals, in a
different and more simple  manner.  Here the  heart
consists of only one auricle  and one ventricle; all the
blood, as it  returns from the veins, is  brought back
into the auricle, is poured from this into the ventricle,
and from the ventricle  into  the great  artery, which
carries it  to the branchiae or gills, the organ which  in
fish corresponds  to the  lungs  of  breathing  animals.
The  single  heart in fish may therefore  be considered
as corresponding to the pulmonic heart  of the  mam-
malia and birds.  After  the blood  has  traversed the
gills,  and  undergone  the specific  change from the
action of the air that is suspended or dissolved in the
water in which the animals  are immersed, it  is again
collected  into  a  main arterial  trunk;  from this it is
sent to all  parts of  the body, and is  again  brought
back  into the auricle by the  veins.   Here every part
of the blood is exposed to the action of the air  through
each  circuit, but in  consequence of the smaller pro-
portion of blood in fishes, and the more scanty supply
of air, the  mutual action of the air and the blood, or
the degree of effect produced by this action, is  much
inferior  to  what  it is in  animals furnished with
lungs.*
   While  I  am upon  this part  of  the  subject it may
be necessary to make an observation upon the  terms
single and double circulation, which I have frequently
had occasion to  employ, and which have not always
been  used by authors in the same sense.  According
to what I conceive to be the most correct acceptation
of the phrase double circulation, it  should be applied
to that construction of the  heart and its appendages,
where there are two cavities which do  not communi-
cate with each other, except through the medium of
one of  the  circuits, as in the two first  classes of ani-
* Monro on Fishes, p. 14, et. seq. 
302              General Observations.

mals.  By a single  circulation, on  the contrary, we
should understand that which consists of a heart  with
only two cavities, where the  blood, when it has once
left this  organ, does not return to it  until  it has  com-
pleted its  passage  through all the vessels,  as is the
case  in  fishes.  The amphibia will hold  a  middle
place between the two,  part  of  the blood being car-
ried through only one circuit, while another  part of it
goes through both the lungs and  the body generally.
   This concise sketch of the comparative anatomy of
the  circulatory organs proves  to us both the impor-
tance of  the function, and  its intimate connexion  with
respiration, so much so as to justify the assertion, that
a primary object of  the  circulation is to propel the
blood through the lungs or some  equivalent organ,
where it  may receive the  influence of the  air, and
have a certain specific change  wrought upon it, which
is  a necessary requisite to the performance of its other
offices.   It will  also appear from these remarks, that
the use of the heart is entirely mechanical,  that it  is
an apparatus  by which  the blood  is propelled along
a  series of vessels, by means of  the alternate  contrac-
tion  and  dilatation of a  muscular receptacle.   The
mechanism of  the  heart  is all directed to this object,
that is, to the propulsion of the  fluid with  the  due
degree of  force and in the proper  direction, and  upon
this  principle we may explain the  action  of all  its
separate  cavities, valves, and  other appendages, and
show how any variation which occurs with respect to
them in  the different classes of animals  are  adapted
to the general structure  and  functions  of  the  indi-
vidual.   Where  the  quantity of blood is large in pro-
portion to  the  size  of  the  body,  and  where  it  is
necessary that it  should  receive the full  influence of
the air,  there  are  two complete circulations, and of
course two muscular bags  to  send  it along  the  two
sets  of vessels, the relative strength of which is pro-
portionate  to the resistance which they have  to over- 
           Sensibility.  Nerves of the Heart.        803

come.   Where  the quantity of blood is  smaller, and
where a less degree of change is induced upon  it by
the  air, we  have,  according  to  circumstances,  either
only a  single circulation,  or  one of an  intermediate
kind, and we find  that  the mechanism of the  heart
and  its absolute power are always exactly adapted to
the circumstances of each particular case.  We have
here only one principal  muscular cavity, or,  if  there
be a greater number,  they have  a free communication
With each other, while  we find that the number of
auricles, whether  one or  more,  is in  like manner
adapted to the number  and disposition of the  great
veins, so as the most readily to receive the blood from
them, and convey it into the ventricle  in the manner
which best  admits  of their  effectually performing the
alternate actions  of contraction and dilatation.

   § 5.  Vital Properties and Actions of the Heart.

   Having  now  made ourselves acquainted with the
mechanism of the heart, we shall proceed, in the next
place, to consider  its  vital properties, which in this,
as in every other part of the body, are two, contrac-
tility and sensibility.  I have  already had occasion to
enter  upon  the  question, how far  the  heart possesses
proper sensibility,  and we  have seen  that  on this
point a great difference  of opinion  still exists,  among
those  who  might be  supposed   the  best qualified to
judge concerning it, both  with  respect  to  the actual
facts, and to the  inferences  that may be  deduced from
them.   What  I  am disposed to regard as the most
probable conclusion, in the present state of our know-
ledge, is, that the heart has but a small share of sen-
sibility ; that when it acts  in its ordinary manner, it
produces no sensation ;  that it  is not under  the con-
trol of the will; that  the nerves distributed to  it are
less numerous than those which  are  sent  to other
parts  containing the same number  of muscular fibres 
304
Their  Use.
and  that, both from their  origin  and their texture,
they are more analogous to  the nerves which supply
the muscular coats of the viscera, than to those which
are distributed over  the proper muscles.
   Still, however, the  heart  is supplied  with  nerves,
although  perhaps scantily,  and we are naturally led
to inquire  what is their use.   To this question we
must seek for a reply rather from a consideration of the
uses of the nervous  system generally, than  from any
individual facts which we  have it  in  our  power to
adduce on this  particular  topic.   The uses  of the
nervous system have been stated above to  be two; to
connect us with the  external  world, and to  unite the
different parts of the  system with each  other,  so as
to form  it into one  connected whole.   The first of
these objects is effected through the  medium of the
organs of the external  senses only,  and does  not apply
to the  heart; we are therefore to look to  the second
to explain the  point now  under consideration.   We
may suppose that one important use which the nerves
of the heart serve, as well  as  those of all the other
internal viscera, is to indicate to us  any injury or dis-
ease of  the  organs, of which, as  they  are removed
from our view, we  might  be  unconscious, were not
the parts endued with the  faculty of  feeling  pain.
To this explanation,  as applied  to the heart,  an objec-
tion  may indeed be urged, that  it not unfrequently
becomes the subject of disease, and  even in a  very
considerable  degree, without  our  experiencing  any
direct  sensation  of pain, so that  we  become sensible
of the morbid condition of the organ more from  some
indirect circumstances connected with the state of the
circulation,  or of some of  the other functions, than
from  any indication of it depending upon the sensa-
tion excited in the heart itself. On  the  other  hand,
however, we are aware that there are certain affections
of the  heart, as induced either  by  injuries or disease,
in which it is sensible to pain  or uneasiness, and  per- 
Their Use.
305
haps all that we are able to say, in the present case, is,
that the degree of sensation which the heart possesses
is in proportion to the quantity of nerves sent to it,
and is adequate to the wants of the system.
  There is another  use which may  be assigned to  the
nerves of  the  heart, although it may belong more to
the moral  than to the physical part of our frame.  We
have  already had occasion to remark, that although the
heart  in its  ordinary action is independent of  the ner-
vous system, yet that on certain occasions it  is  liable to
be  influenced through it.   This is  especially the  case
with respect to mental emotions, which frequendy pro-
duce or are attended by  some  change in the state of
the circulation, either quickening or retarding the  ac-
tion  of the  heart,  or affecting the quantity of blood
propelled by each pulsation.  Hence, according to the
nature of  the  emotion, a greater or less  quantity of
blood  will  be sent to the surface of  the body, and in no
part will the effect  of this change  be more apparent
than in the face.  The countenance, therefore, as indi-
cated  by the state of the circulation, becomes the index
of the mental emotions, and  as it is  not under  the con-
trol of the will, it frequently points out what is actual-
ly passing in the mind, in a manner which can neither
be falsified nor concealed.   There are many important
effects which are produced upon the various functions,
as well contractile as sensitive, by an occasional increase
or diminution of the circulation, as  indirectly  effected
by the nerves of the heart; but these will be consider-
ed more fully hereafter.
  With respect to the other vital function of the heart,
its  contractility, there are not the  same difficulties as
with respect to its sensibility, since its most obvious and
characteristic property is  its constant motion  and  the
readiness with  which it obeys the action of various sti-
mulants.   The contractility of the muscular fibres of
the heart is  indeed  the main spring of the animal  ma-
chine,  considering it as an apparatus adapted for  the
                39 
306               History of Opinions.
 purpose of spontaneous motion ;  for the direct office of
 the heart, and  the immediate effect of  its contraction,
 is to propel the blood through the two circulations, in
 one of which it undergoes a certain necessary change,
 while in the other it is sent, after being changed, to all
 parts of the body, giving to each of them their specific
 powers and capacities for action.  Many  causes have
 been assigned for  the  power by which  this great  ma-
 chine  is  primarily  moved.   The ancients, who  could
 conceive of no proper  mechanical cause for so great an
 effect, had  recourse to many mysterious  agencies  and
 fanciful  hypotheses.   They imagined that  the  heart
 contained a species of innate fire, or a kind of ethereal
 or subtile spirit, which produced its motion, but they
 did not condescend to give any minute description of
 the  manner in  which the  subtile  fluid acted.  The
 learned  Dutch Professor, Sylvius, who is noted  as  the
 founder of the chemical sect in medicine, accounted for
 the motion  of the  heart in  a way which was perhaps
 more  intelligible, although certainly not more correct.
 He ascribed it to an effervescence excited by  a mixture
 of the different kinds of  blood, one of which possessed
 an  acid  and  the other an  alkaline nature, and  many
 other equally absurd ideas prevailed until the publica-
 tion of Senac's valuable treatise on the heart.*
   This judicious physiologist properly attributed  the
 power by which the circulation  is  carried on entirely
 to  muscular  contractility, residing principally in  the
 heart, and showed that by the blood being poured into
 its cavities,  and  causing a certain degree of  distention
of its fibres, the heart is stimulated to contraction, and
 by this act expels its contents.!   The stimulating cause

  * For a sketch of the opinions of his predecessors and for a full
 exposition of his own doctrine, see Senac, liv. 4. c. 7. 8. 9."
  t Among the physiologists who attributed the#>ntraction of the
heart to the stimulus of the blood, some ascribed it to certain spe-
 cific properties in this fluid, which acted upon the fibre, others to
 their distention only.   Those  who adopted the former  opinion 
              Constancy of the Heart's.Motion.           307

being thus removed, the heart relaxes, but, in the mean
time, a portion of blood  has been propelled  along the
arteries and  veins  into the auricles, and is ready to  be
poured into  the  ventricles immediately upon their re-
laxation.   They  therefore again become distended, are
again  excited to contract, and again propel  the  fluid
along the vessels, and this alternation proceeds as long
as life  continues.   It is frequently observed that, even
in human contrivances, the most important effects  are
produced by the most simple  means, and the observa-
tion applies to the  present case.   Yet simple and intel-
ligible as is the general doctrine of the circulation, there
are  many interesting and difficult points concerning it,
which we are not  yet able to answer or comprehend
to our entire satisfaction.*
   The most  important subject connected with the mo
tion of the heart, and one which has given rise to much
controversy,  is the inquiry into the cause of its regula-
rity and constancy.   What, it  has been asked, can  en-
able the  heart to proceed for years together, without
fatigue, pulsating at equal intervals, and propelling the

were  much puzzled to account for the different effects of the two
kinds of blood in the two ventricles.
  * Some  experiments are stated to have been made by Mr. Bro-
die, which appear to oppose the doctrine of Senac.   He emptied
the heart of its blood and found that  it still contracted and relaxed
alternately, hence he concludes that the action depends upon some
influence transmitted to it, in the same manner as with respect to
the diaphragm, and  not upon the blood in its cavities. See Cooke
on Nervous Diseases,  Introd.  p. 61.  Whatever comes from Mr.
Brodie's pen must be received with attention, but until the experi-
ments are given more in detail, it would be premature to  specu-
late upon the consequences that may be deduced from them.  We
have likewise  a similar statement made by Mr. Mayo, Comment.
p. 16, from which he concludes that the alternations of contraction
and relaxation in the heart depend upon something in its structure ;
in Mr. Mayo's experiment the effect  was produced after the organ
was separated from the brain and spinal cord.   May we refer it to
the elasticity of the  heart, causing an alternation of action like the
vibrations of a metallic rod ?  Can this elasticity and the action rer
suiting from it stimulate the muscular fibres? 
                                         /

308         Constancy of the Heart9s Motion.

same quantity of  blood ?  The hypotheses that have
been advanced to answer this question are,  as usual,
very numerous.  Willis, who may be regarded as the
first physiologist that was fully sensible of the import-
ance of the nervous system in the animal ceconomy, ad-
vanced an opinion, which, for  some time, was very ge-
nerally received, that  the nerves of the heart, as well
as of all the organs of  the body which are in constant
motion, are derived  from a different part of  the brain
from the nerves of those organs which are only called
into occasional action.   It must be admitted that  there
are certain facts which countenance the idea, that the
voluntary and involuntary muscles derive their nerves
from different  sources, but it is doubtful how far this
will apply to the  heart, and even were it proved, al-
though it might tend to generalize the fact,  still it would
not solve the difficulty.  Willis's doctrine,  however,
had many adherents ; among others, Lancisi, who pub-
lished  an elaborate treatise upon the heart, adopted it,
and laboured to  remove all  the objections  that had
been urged  against it,  and  in short it remained,  for  a
long time, the most approved hypothesis with the me-
chanical  physiologists,  and with those who  were the
most conversant with  the anatomical structure of the
body.  Many other  opinions  were occasionally started,
which  it will not  be necessary to notice, but  there  is
one which has had so  extensive an influence over the
science of physiology,  that it must not be passed  over
in silence ;  I refer to the doctrine of Stahl, who ascrib-
ed the regularity  of the heart's  motion to the anima,
or soul, which resides in man, and superintends his ac-
tions, and which, knowing the fatal effects that would
ensue from the interruption of so important a function,
is careful always to preserve it in a proper state  of ac-
tion.*

  * The last  defender of  the pure Stahlian doctrine appears to
have been Nicholls;  see his treatise " De Anima Medipa."  But 
Stahlian Doctrine.
309
   The  doctrine of a superintending intelligent princi-
 ple, residing in the body, seems to have originated from
 Vanhelmont, who gave it the name of archeus ; Stahl
 refined  upon  Vanhelmont's notion, and applied  it  to
 many parts of the animal ceconomy, under the appella-
 tion of anima,  and it has borne a distinguishing share in
 the hypotheses of many learned physiologists, down to
 the present time, under the title of the vital  principle,
 spirit  of animation, and various other names.   An agent
 of  this  kind,  although not so distinctly brought  into
 view as by Stahl and some of his  immediate followers,
 forms a leading feature  in the writings of  John Hun-
 ter;!  and many of Darwin's speculations, when divest-
 ed  of  their  poetical  garb, can only be referred to the
 same  class.  But I have no hesitation in saying,  that
 nothing can be more contrary  to the spirit of true  phi-
 losophy, than to assume the existence of an intelligent
 agent, of which we are entirely unconscious, or to ad-
 duce,  as the cause of certain effects in  the body, a pow-

 even as modified by Whytt and those physiologists who have  been
 designated by the title of semi-animists, it involves us in the great-
 est inconsistencies.  Whytt maintains the identity of the vital and
 the  sentient principle, or of life and intellect, and argues that  a
 considerable part  of the actions of the body are effected by mental
 operations, of which we are essentially inconscious.  On Vital and
 Involuntary Motions, §11.
  t  Although it is an  ungracious task to dwell upon  the errors of
 great men, yet the very circumstance of their celebrity is a reason
 why we should be more especially put upon our guard against the
 mistakes into which they may have occasionally fallen.  This is
 perhaps in no  one instance more necessary than with respect to
 John Hunter.  After giving his reasons for dissenting from the ex-
 planations that  had been previously given of the alternate action
 of the  heart, he subjoins  his own.  " The alternate contraction
 and  relaxation of the heart constitutes a part of the circulation ;
 and  the whole takes place in consequence of a necessity, the con-
 stitution demanding it, and  becoming the stimulus;  it is rather
 therefore the want of repletion which makes a negative impres-
 sion on the constitution, and becomes the stimulus, than the imme-
 diate impression of something applied to the heart." On the Blood,
p. 149. 
310
Remarks upon it.
er of which we  have no knowledge or intimation, ex-
cept as a commodious method of  solving the  present
difficulty.
  The  Stahlian doctrine, in  all its ramifications, and
under  every form  in which it  has  been  exhibited,
seems to have originated, partly from  the want of an
accurate discrimination between the physical  and the
final causes of the  operations of the body, and partly
from an indistinct conception of the difference between
the agency  of the first great cause of  all things, and
the secondary or  physical cause, into which  alone  it
is the proviuce of natural  philosophy to inquire.   It
affords no explanation of the physical  cause,  or the
nature of any phenomenon, to say that  the Supreme
Being has thought fit to order it so ; the object of our
researches is  to examine, to which of the great  laws
that are impressed upon matter, the action in question
can be referred.   But we are always unwilling to con-
fess  our ignorance, and  are  never satisfied  without
attempting to  explain every  thing  that  passes before
us.   In the  present instance  the only answer that we
can give to the proposed question is one that is  in itself,
in some measure,  an acknowledgment  of our imper-
fect  acquaintance  with  the subject.  We know that
distention excites a muscle to contract, and that when
a muscle  has  contracted  relaxation  ensues.   In the
present case, therefore, we  can  only  say, that in the
formation  of  our  body the  degree of contractility
bestowed  upon  the  heart, the quantity of distention
which  it receives from the blood, the  size and  texture
of the arteries which are to  transmit the blood, and
the quantity of resistance which it has to overcome,
are all so  nicely  balanced, that each,  particular action
is retained in due  subjection  to the  rest, and contri-
butes to form one  harmonious wdiole.
  Admitting the  justice  of  this  remark, which  is
indeed merely the expression  of an obvious matter  of
fact, it remains for us to inquire,  what  is the  specific 
                Structure of the Heart.             311

mechanism by  which  this action is accomplished,  or
whether we can observe  any  thing  peculiar in the
structure  of the heart, or  the disposition of its  parts,
which would seem to  adapt it  to this state  of  conti-
nued  action.   It must  be  confessed  that  on this point
we have but little assistance from  the researches  of
anatomy,  at least there are  no facts  with which we
are acquainted that can afford us a satisfactory solu-
tion of the difficulty.   I have already adverted  to the
nerves of the heart, which, both with respect to their
quantity,  their origin,  and  perhaps also their  mode
of distribution, seem to differ from the nerves of the
voluntary muscles.   And with respect to the muscu-
lar fibres of  the  heart, it   has  been observed, that
both  in  their  form  and their  mode  of  connexion
with each other, they likewise differ from the  volun-
tary  muscles.  Instead  of  an   assemblage  of long
and comparatively straight  fibres, disposed  in  the
form  of separate bundles, each  of them  enclosed in a
sheath of cellular substance,  and  the  whole furnished
with  a coating of the same, the  muscular fibres of the
heart are disposed in  an irregular  manner,  they are
not divided into distinct parcels, and they have but
little  cellular  substance  attached  to them.*   This
peculiar form and composition of the muscular part of
the heart seems, however, to refer rather to its mecha-
nical  action than to any peculiarity in its vital powers.
The  long and straight lacerti of the muscles  of  volun-
tary  motion are  fitted to produce  the  contraction of
these parts in one direction only, whereas the irregular
interlacing of  the  fibres of  the heart obviously serve
to promote  the contraction  of  this  organ  in  every
direction, so as to diminish  its  size  in  all  its dimen-
sions.   There is no muscular part  which is  possessed
of the  same kind  of action  with  the heart, and which
is possessed  of nearly the  same degree of power, so

          * Soemmering, Hum. Corp. Fab. t. v.  § 29. 
312
Regularity of the HearVs Motion.
as to require an equal quantity  of muscular fibres to
be concentrated in one point; but it would appear that
a similar structure of the muscular  matter exists in
the stomach and the bladder, and  that some approach
to it will be found in all  those hollow  muscles, where
the  contractile  force  is exercised in  more than  one
direction.   This structure, however,  throws no light
upon the nature of the vital powers of the heart,  nor
does it, in  any degree, tend to  explain  the difficulty
in which this point seems to be involved.
  The regularity  of  the heart's motion, or the per-
fectly uniform manner  in which the different steps of
the process follow each other, proceeding in the same
order and occupying the same space of time, is  a  cir-
cumstance still  more  worthy of  our  admiration than
its constancy,  and  was accordingly  regarded by  the
earlier  anatomists  and   physiologists  as  something
almost beyond the powers  of the  human  mind  to
comprehend or  explain.   The  mathematicians  were
not,  however, wanting in their attempts to solve  the
problem, and  Bellini,  who in  the application of his
general  principles was  appalled  by  no difficulties,
endeavoured to account for  it by supposing that the
auricles and ventricles of the heart were to be regarded
as antagonist muscles  so  arranged,  that when one set
of them  contracted  the other  necessarily relaxed.
Baglivi, whose premature death  must excuse many of
his  errors, formed  an  ingenious, although  fanciful
hypothesis, according  to which  he accounted for the
phenomena in question upon the  idea  that the  alter-
nate contraction and relaxation of the ventricles pro-
ceeded from a  corresponding alternation of pressure
on certain parts of the  nervous system,  by  which
their energy,  and consequently  the contractile power
of the muscles, was alternately repressed and excited.
A mechanical  theory  something  like  this  was  main-
tained by Boerhaave,  but it will not  be necessary to
examine it in  detail, for this, and some other refined 
Action and Properties of the Vessels.       313
speculations of the same description, were completely
overthrown by Haller.   He reduced the  regularity of
the motion of the heart to the simple effect of stimuli,
acting successively upon  a series of contractile organs,
the mechanism  of  which is  so arranged, that  each
part,  when  relaxed, receives the stimulus  from  the
contiguous parts, is then  roused to contraction,  and
by this act transmits  the stimulating body to the next
cavity, which is  then in a state of relaxation and pre-
pared for its reception.

   §  6.  Action and Properties of the Blood-vessels.

   We are now to  proceed to the  third of  the  topics
which I pointed out as  requiring  our  attention,  the
structure and actions of the  arteries  and veins.    We
have  hitherto considered the blood-vessels  merely in
the light of tubes  appended to the heart,  receiving
the fluid  that is propelled into them by this organ,
an<}p transmitting it  from one set  of  cavities  to  the
other.  We must now regard them in a  further point
of  view,  not simply  as  mechanical  agents, acting
like  the parts of an hydraulic machine, but  as vital
agents,  endued with the properties of  living matter,
and forming parts of an organized system.  Although
nothing can appear more reasonable than this doctrine
in the abstract,  yet there are few topics in physiology
which  have  been   the  subject of  more controversy
than  the  exact" nature  of  the  vital powers of  the
blood-vessels, and  the consequent  share which they
have  in  the circulation of th£, blood.   The mechani-
cal physiologists, as  might be  expected from  their
system, regarded them  as  mere  tubes,  subject  to no
laws  but  those of mechanical   impulse,  and  even
some of the latest and most esteemed of the moderns
do not  admit them  to  possess either contractility or
sensibility. 
314
Contractility'—'Opinion of Haller.
   As to the latter quality, it  is generally agreed that
 the  blood-vessels  possess no proper sensibility in their
 healthy  and  natural  state,   being,  in  this  respect,
 analogous to many other parts of the body which are
 principally   composed  of  membranous  matter,  and
 are not subject to the control of the will.   How far
 the  blood-vessels  resemble  the   other  membranous
 parts in the capacity of feeling  pain, while suffering
 from inflammation or any  other  morbid state, is  a
 question  which  appears  to   have   been  but  little
 attended to ;  analogy would induce  us to suppose that
 they possessed sensibility under  these  circumstances,
 and I know of no facts  which would lead us  to a con-
 trary conclusion.
   But the great controversy respecting the vital pow-
 ers of the blood-vessels  has been concerning their con-
 tractility, or rather that of the arteries, and this ques-
 tion has been resolved into another,  which is intimately
 and necessarily connected with it, whether the arteries
 possess  any muscular fibres, or whether  the transvMse
 fibres, which  have been usually called the  muscular
 coat, are  justly entitled to that denomination.  That
 the larger arteries actually possess a certain assemblage
 of fibres, placed in a transverse direction, is  admitted
 by the concurrent testimony of all  anatomists, but there
 has been a great difference of opinion respecting their
 nature and properties, or the  effect which they pro-
 duce in  the animal ceconomy.
  The  contractile  power of  the  arteries was  very
 warmly discussed by the anatomists of  the   last cen-
 tury, and  was  one of those points  on  which  Haller
 exercised  all his talents, both  anatomical and  physiolo-
gical.   To a  certain extent he was the advocate for
 the muscularity of the arteries ; he regarded the trans-
 verse fibres as clearly muscular; he, indeed,  admitted
 that he could not exhibit their contraction by the appli-
cation of  the appropriate stimuli, but he adduced  a
variety of considerations to prove  that the contraction 
Hypothesis of Cullen.
315
 of the arteries was an important  agent in the  circula-
 tion of  the blood.*  The  contractility of the arteries
 was warmly advocated  by Whytt! and Senac,J and
 may be regarded as forming the basis of Cullen's cele-
 brated hypothesis of the action of the  vessels.  This
 hypothesis, which had so much influence over the gene-
 ral doctrines  of  pathology, as  to introduce a  totally
 new theory of some of the most important parts of the
 science, although not invented,§ was so far modified and
 arranged by Cullen, as to possess a merit far superior
 to  that  of  mere  originality.   The Galenic doctrine of
 the humoral pathology had been already called in ques-
 tion by Baglivi and others,  and the  hypothesis of the
 solidists had begun to make  some  progress in public
 estimation.   But  it  was rather from the weakness  of
 the old  theory than from the  consistency or force  of
 the new one,  that this  change of opinion is  to  be
 ascribed, for it must be acknowledged that the opposers
 of  the humoralists had been  much  more successful in
 controverting  their antagonists than  in proving the
 superiority  of  their own doctrines.   Cullen was not
 satisfied with completing  the destruction of the  ancient
 edifice, but aspired to the honour of erecting a new one
 in its place, and consequently he did not think it suffi-
 cient   merely to state  in  general terms that  the vital

  * El. Phys. ii. 1. 7; ii. 1. 13;  iv.  4. 32; vi. 1. 39; Memoires
 sur la Nature Sens, et Irrit. des  Part, du Corps Animal, mem. 2,
 sect. 11; his treatises " De Sanguinis Motu," " De Part. Corp.
 Hum. Sent, et Irrit." and " Responsio," in Opera Minora, t. i.  On
 no topic is the candour and caution of this great man more appa-
 rent than in what relates to the muscularity of the arteries.
  t Whytt's works, On the Circulation of the Fluids in the very
 small vessels of Animals; and Observations on Sensibility  and Irri-
 tability, part ii. sect. 1.
  X Traite du Coeur, liv. 5, ch. 3.
  § The  doctrine of the vital action of the vessels was  perhaps
 first distinctly announced by Stahl, and was very explicitly stated
by Gorter, but so combined with erroneous opinions as to lose
 much of its value.  See Med. Compend. t. i. tract. 17. 
316
Action of the Capillaries.
actions of the body,  and the changes which it expe-
riences, depend upon the solids,  but  he proceeded to
point out tne agents by which these changes are effect-
ed, and these he determines to be the minute ramifica-
tions  of  the  arterial  system,  or,  as  they have  been
named from their size, the capillary vessels.
   The action of the capillary  vessels has, since the
time of Cullen,  been generally  regarded  as the great
agent in all the vital  actions of  the  body, either phy-
siological  or  pathological, by which  any permanent
changes  are  produced in  its  form  or  composition.
This  point we shall  have  abundant  opportunities of
illustrating in the account of the different functions as
they will  successively fall under our review, and with
respect to the circulation in  particular,  there  seems
every  reason to conclude, that  it is very materially
influenced by the  capillaries, not merely as one of the
means employed to propel the blood  along the vessels
in its  ordinary course, but as the power by  which all
the subordinate changes in the state of the circulation
are principally or entirely effected.
   With respect to the share which the arteries them--
selves have  in  the  motion of  the  blood, this acute
physiologist remarks, that  if  the motion  of the blood
depended entirely upon the impetus impressed on it
by the heart, its  force  and velocity  in  the  different
parts of the body must,  at all  times,  bear the same
ratio  to  each other.   If  the quantity and velocity of
the  blood in any  two corresponding  parts, as  in the
two arms, for example,  be the same,  provided the
arteries  be mere  membranous  tubes, the  momentum
of the blood  in the  two arms  must always be  pre-
cisely similar, and this will continue  to  be the  case,
whatever be the  strength or velocity of the  heart's
motion, and however these may vary  at different times.
   But we do not  observe this constant ratio  to exist;
on the contrary, the relative momentum  of the blood
in the different parts of the body is always varying, 
Hunter's Experiments.
317
so that the  quantity of blood and  the velocity with
which it moves are perpetually altered, both from the
effect of external stimuli, and from a number of inter-
nal causes.   This variable state  of  the momentum of
the  arterial  system  may  be  regarded as a decisive
proof of the  vital action of the vessels, and it  may be
considered as almost a necessary consequence, that this
action must consist in alternate contraction and dilata-
tion, and it is at least  highly probable, that the contrac-
tion  is effected by a muscular structure.*
   An elaborate  set of experiments  was performed by
Hunter,  the  object  of  which  was  to distinguish  be-
tween the  elastic and the muscular power of the
arteries,  in which the existence of this latter appeared
to be fully established.  The  experiments proceeded
upon the principle that the  arteries  possess both  a
proper contractile and  an elastic power, that the for-
mer of  these  ceases with life,  but  that the latter
remains as long as the parts retain their structure and
composition.   An animal was  bled to death, by which
the arteries  are brought into a state of complete con-
traction ; portions of them were then taken and  slit
open longitudinally,  and were distended  by a given
weight in the transverse direction.   After some time
the  weight was removed, and they were then left  at
liberty to resume their  natural size,  when  it was found
that they had undergone a certain degree  of contrac-
tion, but  less than that which  they possessed  before
the experiment.  They were measured in their three
states, of ordinary contraction,  of greatest distention,
and  of medium contraction;  it  was  argued  that  the
difference between their original size  and  the greatest
distention  of which they were capable, was the mea-.
sure of the sum of their muscular and elastic contrac-i
tion, while the* degree in which  they  recovered them-*
selves after  the distention was  the measure of their
* Thomson's Lectures on Inflammation, p. 66. 
318
Parry's Experiments.
 elastic force only, because after death this power alone
 could be supposed  to  remain in them,  the muscular
 power necessarily ceasing with the  cessation of life.
 By the weights that were employed, and by the degree
 of distention that was  produced, Hunter endeavoured
 to estimate the exact relation  which these forces bore
 to each other in the different vessels, or in the different
 parts  of  the vessels upon which  he performed  his
 experiments.*
   Although I conceive there are various  circumstances
 which will prevent us from arriving at  any great degree
 of accuracy in  the  estimates  that  are  deduced from
 experiments of  this  description, yet the  principle upon
 which they were  performed I  believe  to  be correct,
 and they  may be  considered  as certainly establishing
 the general fact,  that  the arteries possess  a proper
 contractile, as well as an elastic power.   We may also
 be allowed to depend  upon them  so far as to admit
 that they afford evidence of the general distribution of
 these  respective forces; viz. that the larger arteries
 possess a greater proportion of the  elastic,  and  the
 smaller of  the  muscular power, a conclusion  which
 coincides with Cullen's speculations.
   A number of experiments,  essentially  resembling
 those of Hunter, and which appear to have been per-
formed with great  care, were made by  the late Dr.
Parry, and  have been  lately repeated  and  extended
by his son;  from these,  as  well  as  from various con-
siderations connected with the subject, they arrive at
a conclusion which, in its most important features, may
be regarded as coinciding with that  which  we have
obtained from other sources.!   He, indeed, conceives
that the fibres which compose the middle coat of the

r * Hunter on the Blood, p. 124, et seq.; see Hewson's Exp. Enq.
v. ii. p. 14, for a confirmation of the principles upon which the
above experiments were conducted.
  t See Dr. Hastings's remarks on Dr. Parry's experiments, in his
 Treatise on the Mucous Membrane, p. 20, 36, &c. 
Opinion of Bichat.                sig
  artery are not properly muscular, because he supposes
  they cannot be  made to contract upon the application
  ot  those stimulants which produce contraction in proper
  muscles ; but he admits of a certain vital action in these
  parts, allowing a considerable degree of contraction of
  the arteries, necessarily connected with the life of  the
  part, and which is a distinct property from what  the
  vessels possess as elastic tubes;  to this power he gives
  the name of tonicity.*
    But although  so many circumstances, both physiolo-
 gical and pathological, tended to favour  the doctrine of
 the contractility  of the  vessels, still it remained defec-
 tive in its  most important point, that  the transverse
 fibres could not  be made to contract  upon the applica-
 tion of  stimulants.   It  had, indeed, been  generally
 assumed, from their appearance and texture, that these
 fibres  were muscular, but Haller's experiments  were
 unfavourable to  this opinion,! and it was strenuously
 opposed by Bichat, both upon anatomical and physical
 considerations.^   We are  also  informed by Berzelius

   *  On the Arterial Pulse, p. 52, et seq.
   t  Albinus, describing the anatomical appearance of the  parts,
 without any  regard to physiological hypotheses, says, that*the'
 transverse fibres of the  large arteries do not resemble  either
 muscle or tendon.   Acad. Annot. lib. 4, c. 8, p. 32, 33.
   X  Anat. Gen. t. 1, p. 272, et seq.   Nysten endeavoured to prove
 the correctness of Bichat's opinion, by showing that the  aorta is
 not sensible to the stimulus of galvanism.  Recherches de Physiol.
 p. 325, et seq.  It must, however, be remarked, that the aorta was
 not the part of the arterial system where contractility is supposed
 to reside,  and that  we have experiments which lead to the con-
 trary conclusion, although, perhaps, not so decisive  as Nysten's.
 We must remark also, that Bichat supposes the contraction of the
 capillaries to be independent of the heart.  Sur la Vie et Mort, p.
 134.  Lerminier, the writer of the article "Circulation," in the
 Diet, des Scienc. Med. argues, that the circular fibres are not mus-
 cular, nor the  arteries contractile; but he restricts the term artery
 to the larger  vessels, and supposes the capillaries to be  distinct
from either the arteries or veins; it does not, however, appear to
me that any advantage is gained by this innovation, and it is not
pretended that any precise  limit can be fixed where this change
 takes place. 
320         Experiments of Verschuir, Philip,
that  the chemical  analysis of these  transverse fibres
differs from that of the proper muscles,* and the same
statement is made by Dr. Young.!  But  the objection,
although proceeding from such  high authority, will
probably not  be thought absolutely decisive, when we
reflect  upon the decided marks of contractility which
is manifested  by many of the lower classes of animals,
as the Actiniae, the substance of  which  is at  least  as
unlike that  of the muscles of warm-blooded  animals,
as the  transverse fibres  of the  arteries can  be con-
ceived  to be.J
  But all the arguments of a general nature that have
been adduced in this question are of little weight com-
pared to the  direct experiments which have been per-
formed since  the time of Haller, and which appear un-
equivocally to prove that the arteries possess a power
in every respect analogous to, or  rather identical with,
that  of the  proper  muscular fibre.  Experiments of
this  description were  performed by Verschuir  shortly
after those of Haller; they are related with much ap-
parent  candour and  accuracy, and seem  to prove very
decidedly that the  larger arteries contract upon  the
application  of the ordinary stimulants,§  but, from  the
high  and almost  overwhelming   authority of  Haller,
they appear to have been but little attended to, and to

  * View of Animal Chemistry, p. 25.      t Med. Lit. p. 501.
  X Dr. Young appears almost to afford a reply to his own objec-
tion, for  at the termination of the paragraph  he  maintains that a
part may be muscular which does not contain fibrin, and he adduces
the case  of the crystalline lens in support of his opinion.   He sup-
poses these fibres possess considerable elasticity.  Med. Lit. p. 502.
Dr. Jones, who, it  may be presumed, had made  himself familiar
with  the  appearance of these  parts, very decidedly pronounces
them to  be muscular; at the  same time  he says  that they possess
considerable elasticity.  Treatise on  Haem.  p.  2.  Sir Everard
Home observes, that the thin membranous coat of the hydatid pos-
sesses contractility, although its structure is so different from that
of the muscles.  Lect. on Compar. Anat.  p. 30.
  § De Arter. & Ven. Vi. irrit. p. 20. 25. and 81. 
*>
'Thomson, and Hastings.
321
have made scarcely  any impression on  the opinions of
physiologists.
   The results  of Verchuir's experiments have been
amply  confirmed by the successive  investigations  of
Dr. Philip, Dr. Thomson, and Dr. Hastings.   Dr. Phi-
lip placed the web of the frog's foot in the microscope,
and distinctly saw the capillaries contract upon the app-
lication of those  stimulants which produce the contrac-
tion  of the muscular  fibre* The same effect is describ-
ed as having been the result  of Dr. Thomson's experi-
ments ;! and it would appear that, in  both these cases,
the  appearances were so obvious and decisive, as  to
admit of no question  as to their reality, and scarcely of
any doubt as to  the cause producing them.  This con-
clusion  has been recently confirmed  by  Dr.  Hastings,
and  he has  farther  extended his experiments  to  the
large arterial trunks, and even to the veins,!  an(^  nas
observed  in them, as well as  in the arteries, the most
clear evidence of their contraction upon  the  applica-
tion  of various   stimulants, both chemical and  mecha-
nical^
   And  besides the direct result of  experiment, there
are  other circumstances  stated by Dr.  Philip,  which
are scarcely less  decisive in favour of the contractility
of the  arteries.   He informs us that he  distinctly ob-
served  the circulation in  the smaller vessels to continue
for some  time  after  the  heart was removed from  the
body,||  and  the  same observation was  made  by  Dr.
Hastings,H an  effect which must necessarily have  de-
pended upon the action of the vessels themselves.  Dr.

  * On Febrile Diseases, (3d ed.) v. ii. p. 17, et seq.; Med. Chir.
Trans, v. xii. p. 401, et seq.
  t Lectures on Inflammation, p. 83.
  X The contraction of the veins was .observed by Verschuir.
  § Treatise on the Mucous Membrane, Introd. p. 24—28, 50—58,
61—64.
  || Enquiry, ex. 24, 62,  63. Quart. Journ. xiii. 107.
  r Introd. p. 51.
              11 
 •>22               General Conclusion.
                                             i
 Philip further informs us that the motion of the blood
 in the capillaries is influenced by stimulants applied to
 the central parts of the nervous system,* which must
 depend upon the  capillaries  possessing a proper con-
 tractile power, similar  to that of the muscular fibre.!
   It appears, therefore, that we are  fully warranted
 in  the  conclusion that  the arteries possess  a  proper
 contractile  power, and  it is to be presumed that  this
 power  resides in  their  transverse fibres.   It appears
 likewise to be established,  that this contractile  power
 is principally seated in the  capillary arteries, while the
 large trunks and the veins, although not destitute of it,
 possess it in a less degree.  Indeed  every fact with
 which  we  are  acquainted respecting the  mechanism
 and functions of the sanguiferous system, lead us to the
 same conclusion, that the  large arteries are to  be  re-
 garded as canals transmitting the blood from the heart,
 where  it receives its  great impulse, into  the  smaller
 branches,  and  that it is  principally  in  these  smaller
 branches  that it exercises  its various functions.  We
 are therefore to  consider the large trunks in the light
 of a mechanical or hydraulic system, and the  capilla-
 ries as physiological  or  vital organs.   It may  be  re-
 marked that  this  distinction, which is of the  greatest
 importance, has seldom been clearly laid down by phy-

  * Enquiry, p. 291, 292.
  t An indirect argument of considerable importance in favour of
 the contractile power of the arteries may, I  think, be drawn from
 the occurrence of cases in which the heart has been either altoge-
 ther wanting or completely defective in its structure, of which a
 well-marked instance  is recorded by Mr. Brodie, Phil. Trans, for
 1809, p. 161, et seq.   We have  a decisive instance of the same
kind mentioned by Hewson, Exp. Enq. v. ii. p. 15.   We may con-
clude, in these cases, that the arteries must have been the compen-
sating organs ; and it is more agreeable to the general  principles
of the animal ceconomy to suppose that they were endued with an
 additional portion of  their natural power, than that a completely
new function was imparted to them. 
Cause of the Pulse.
siologists* and that to this neglect may be  attributed
at least a part of that ambiguity which has so long pre-
vailed respecting the properties of the arterial system.
   With respect to the properties of the veins there is
much less difference of opinion  than with respect to the
arteries.  It is generally  admitted that the veins exhi-
bit the transverse  fibres  in small quantity only, or are
nearly destitute of that part which is analogous to the
middle coat of the  arteries, and are consequently to be
regarded as little more than mere  elastic tubes.  Their
office is to return  the  blood to the heart after it has
completed all its functions in  the different organs, and
has either expended that ingredient which gives it the
power of acting upon the constituents of the body, or
has acquired some addition which renders it  inert or
noxious.   The action of the veins is therefore entirely
mechanical, and  the blood is transmitted by them to
the auricles upon  hydraulic principles, in a way which
will be considered hereafter.   With respect  to  their
structure, so far as their physiological  properties arc
concerned, it is only necessary  to remark, that all the
large veins which pass along the muscles are furnished
with valves so placed as to prevent the regurgitation
of the blood towards the commencement of the  ves-
sels ;  the use of these valves, and the reason why they
are confined to certain veins alone, will  be further con-
sidered when we treat  of  the powers by which  the
circulation is effected.
   Before we quit this part  of our subject it will be ne-
cessary to  make some  observations upon the  peculiar
affection of the arteries which is denominated the pulse.
It is well known that if-the finger be  applied with a
moderate degree of force to certain of the arteries, a
degree of pressure or increased resistance is experien-
ced  by the finger during the instant of the systole of

  * From this censure I must except the anonymous author in the
Edin. Med. Journ. to whose judicious  papers I  have so frequently
had occasion to refer. 
324
Parry's Experiments.
 the  heart, or that period when the  heart  propels n^
 contents into the arterial trunks.  This constitutes the
 pulse; and until lately it  was always  conceived to de-
 pend upon the dilatation of the vessels produced by
 the increased quantity of blood that was projected into
 them during the  contraction  of the ventricle.  The
 acuteness of  Bichat led him to doubt whether the di-
 latation of  the  artery actually existed, or even if this
 were the case, whether it was sufficient to  account for
 the phenomena,  and he was disposed to refer it rather
 to a  change in the position of  the artery, produced by
 the sudden  impetus of the jet  of blood into it,  analo-
 gous to the effect on the neck of the aorta, by which
 the apex of the heart  is raised up and  made to  strike
 on  the thorax.   Still,  however, the  bulk of  physiolo-
 gists  continued to attribute the pulse to the dilatation
 of the artery, until Dr. Parry instituted an experimen-
 tal  inquiry into the subject, the  result of which was to
 show that not the  smallest dilatation  can be perceived
 in the larger  arteries when they are laid bare  during
 life, nor does he  believe that there is any degree of
 displacement  or  unbending of the artery,  which  can
 account for the effect that is produced upon the finger.*
 He ascribes  the pulse to " impulse of  distention from
 the systole of the left ventricle given by the blood, as
 it passes through any part of an artery contracted with-
 in its natural diameter."   This view of  the subject ap-
 pears to me to be correct; at the same time we may
 remark that it does not  fundamentally alter our  idea
 of the  nature of  the pulse,  or the relation which its
 phenomena bear  to the other  parts of  the system, or
to the use that is  made of it in pathology.   According
 to this doctrine we must regard the  artery as an elas-

  *  We are, however, informed by Dr. Hastings, that the alter-
nate dilatation and contraction of the larger arteries was sufficient-
ly obvious to himself and his friends ;  it is implied, although not so
stated, that this alternate action corresponded to or was connected
with the pulse.   Treatise on the Mucous Membrane, p. 31, note. 
Cause of the Circulation.             325
  tic and distensible  tube, which is at all times filled, al-
  though with the contained fluid  not in an equally con-
  densed state, and that the effect produced on  the fin-
  ger depends upon  the  amount of this condensation, or
  upon the  pressure which it exercises upon the vessel
  as determined  by the degree in  which it is capable of
 being compressed.   Upon this  principle we can easi-
 ly account for  the different conditions of the pulse,
 and the relation which each of them bears to  the ac-
 tion of the heart, whether it expels a larger or  a smal-
 ler quantity of blood, whether \i is sent out of the ven-
 tricle with a greater or  less force, whether the con-
 traction be performed in  a longer or shorter space of
 time, and other points  of this nature, the consideration
 of which belongs more especially to the science of pa-
 thology.*

        § 7.   Efficient Causes of the  Circulation.

   In considering this subject, we shall inquire first, into
 the nature and  operation of these causes, and, secondly,
 into their amount or the degree of  their effect.   The
 causes themselves may  be arranged under the heads
 of vital and mechanical, those which belong  to the or-
 gans as parts  of the living body, and those which they
 possess when regarded  merely as a  system of  elastic
 tubes or membranous  cavities.  The  vital   powers of
 the constitution may be all reduced to the single effect
 of muscular contractility, by  which, as has  been so
 often remarked, the size  of the  cavity is diminished,
 and the contents necessarily  pressed  out.   This  is a
 real source  of  power in which  motion is  generated
 which did  not  previously exist,  and the ventricles of
 the  heart are the main  spring from  which   this force
 proceeds. A similar source of motion appears likewise

  * For some judicious observations upon this subject see  an arti-
cle in the Journal of Medical Science, No. 38. 
 326             Pressure of the Muscles.

 to originate in the arteries, especially in their capillary
 extremities, by which they produce an actual addition
 to the motion of the sanguiferous system, subsidiary to
 that of the heart.  The power of the artenes is, how-
 ever, entirely subservient  to  that  of the  heart, and
 much  inferior to it  in quantity, for we find  that the
 pulsations of  every   part  of  the  arterial  system, al-
 though situated at such various distances from the cen-
 tre, are all synchronous, and contemporary  with the
 contraction of the ventricles.   Hence it  appears that
 the impulse which  is given to the  blood in  the trunks
 of the great  arteries  is propagated  to  the remotest
 parts of the system,  and that they  are immediately
 Drought into  their state of distention.
  It was a point which was much contested by the ear-
 lier physiologists, especially by those of the  mechanical
 sect, whether the elasticity  of  the vessels promoted
 the flow of the blood  through  them.  As a question
 concerning the mere quantity  of power, we  apprehend
 there can be no  doubt of  its  insufficiency, because it is
 a principle which is  now generally  admitted, that sim-
 ple elasticity is not a source of power, but only a means
 of distributing the power generated by other causes in
 a new direction. Although, therefore, the present con-
 stitution of the blood-vessels  is much more  convenient
 and more conducive  to the well-being of  the animal
 ceconomy than a set  of rigid  tubes  would  have  been,
 their  membranous coats are not to be considered as, in
any degree, contributing to the actual power by which
the blood is propelled along them.
  Among the mechanical  causes which promote the
circulation of the blood there  is one which is generally
supposed  to  be considerably  efficacious, especially in
 the venous part  of the circulation, the pressure which
 the muscles, during their contraction, exercise upon the
veins.   Whenever a muscle contracts, so as  to have its
ends brought nearer  to each  other, its belly  is propor-
tionably increased in thickness, and it  is evident that in 
Derivation.
327
this change of form all the tubes that pass through the
muscles, or in contact with them, will  be compressed.
When this compression is exercised upon an artery, its
operation will be rather to retard than to promote the
flow of the blood, in consequence of its diminishing the
capacity of the  vessels,  and rendering them less able
to yield to  the  distending force  of the heart; but in
the veins any effect of  this kind will  be much more
than  compensated,  in consequence of the  numerous
valves which these vessels contain.   As  the veins are
less firm or dense  than the arteries, and  are generally
so situated as to be  more subject to be acted upon by
the muscles, it follows that the effect of external pres-
sure will be experienced in a greater degree  than by
the arteries, and therefore that the  balance  will be
considerably in favour  of the transmission of the blood
towards the heart.   The use of these valves is suffi-
ciently obvious from their form, and it is still further
proved by the circumstance, that those veins alone are
furnished  with  them  which  accompany the muscles,
especially those  of the extremities, while  the veins be-
longing to  the internal  viscera,  and those  connected
with the system of the hepatic circulation, are not pro-
vided with them.
   There is a mechanical cause which has been pointed
out as contributing to  the circulation of the blood, to
which the  name of  derivation  is applied.  When the
ventricles  have  contracted,  and have  expelled  their
contents into the arteries, they relax, and by this means
become again increased, and  consequently  a vacuum
Avould be produced in  them,  were it not that they are
immediately filled by the flowing in of  the blood from
the contiguous auricles.  The fluid in this case  is sup-
posed to leave the auricle, not from the muscular  con-
traction of this organ,  but from  its necessarily flowing
into that part where there is the least pressure.   The
effect of derivation,  as influencing the circulation of the
blood, is a circumstance  which seems to have escaped 
328
Hypothesis of Carson
the older physiologists; it is mentioned,  although ob-
scurely, by Haller, but was  first brought forwards in a
clear and definite manner  by  Dr.  Wilson, in a short
essay, which contains some ingenious speculations, con-
nected with much of what is incorrect, both as to mat-
ter of fact and the inferences  that  are deduced from
them.   After remarking upon the insufficiency of the
force of the  heart to propel the blood  through the
whole course of the  circulation, he goes so far  as to
state that the heart  is not  the organ of the motion of
the blood, and that it even  acquires no actual  addition
of motion in passing through the heart.  The sole, or
at least by far the most important power of the  heart,
according to this author, is its faculty of absorbing the
blood from  the veins, which it does upon the principle
of an exhausting machine ;  by  throwing out  the blood
from its cavities a space is left into  which the contents
of the  veins arc immediately discharged, because there
is the least  resistance in this direction.*
   The views which had been thus imperfectly opened
by Dr.  Wilson have  since been more fully disclosed by
Dr. Carson.  In an  elaborate dissertation, in which he
very fully discusses  the nature and extent of the  pow-
ers of  the circulating system,  he  so far coincides with
the generally received opinion, as to conceive  that the
contractile  force of the   heart  transmits  the blood
through the arteries, and even into the extremities of
the veins,  but  that   this  vis a, tergo,  as  it is  termed,
would not be competent to  complete  its return into
the right auricle. To accomplish this object Dr. Car-
son has recourse to  what he terms  the  power of suc-
tion, which, on the principle suggested by Dr. Wilson,
impels the  venous blood into the  cavities of the heart,
to fill  up the vacuum which would otherwise be  form-
ed there.   This diminution of  resistance to   the en-
trance  of the venous blood into the heart  is brought
* Wilson's Enquiry, p. 9, 11, 16, 35. et alibi. 
Hypothesis of Carson.
329
about in two ways:  it is supposed that the construc-
tion or disposition of the muscular fibres of the ventri-
cles is of that kind, that when they relax, the  organ is
necessarily dilated, a circumstance which depends upon
the fibres being twisted, so as to give to  the  parietes
of both the  ventricles a shape scpewhat resembling
that of the figure 8.   A still  more powerful  agency,
however, he  conceives to be derived from the action of
the lungs.  These, it is supposed, are always in a state
of forced distention, and would consequently collapse by
the pressure of  the  atmosphere,  were  they  not con-
tained  in a  rigid  case which  secludes them from  its
operation.  In one part, however, where the membranes
of the  heart are  connected with the pleura, the walls
of the  thorax are merely membranous, and are  there-
fore subject  to the influence of this external pressure,
which, acting through the  intervention of the  pericar-
dium, keeps  its cavities in a state of dilatation, and, as
the external surface of the heart  is always in contact
with the internal surface of the pericardium, the auri-
cles must also of course be kept distended, except when
they contract by their vital energy.   Hence, what
may be termed the natural condition of both the auri-
cles  and venticles is a state of dilatation, so that imme-
diately after each of them  have  completed their sys-
tole, and relaxation ensues, they  become again dilated,
and  necessarily receive  the  blood which is contiguous
to them in  the  veins, as the  valves will prevent the
return of that which has once passed through them.*
I conceive the general conclusions of Dr. Carson to be
fully established, so far  as respects the inadequacy of
the contraction of the heart  and arteries to return the
blood to the right auricle, and also the actual existence
of the principle of  derivation, by  which  the venous
blood  is poured into  the auricle and ventricle, because
it meets with less resistance in this quarter than in any
* Carson's Inq. pp. 97, 108, 117, et alibi.
    42 
330
Remarks.
other direction.   I am, however, disposed to doubt the
validity of some parts of his reasoning, while there are
certain  positions which appear to be  decidedly incor-*
rect.  In  the latter predicament I consider the alleged
condition  of the lungs, as being always retained  in  a
state of forced distention, a point which I shall discuss
more at large when I treat upon the function  of respi-
ration,  while among the doubtful positions  may be
placed the  supposed  dilatation of the  heart  by the
mere relaxation of its fibres.   If we  conceive of the
relaxation of a set of fibres of this description, as form-
ing the  parietes of a double  cavity, it will have the
effect of leaving this cavity in  what may be termed  a
passive  state, so as readily to yield to any distending
force from  without; but this  is  merely a negative
effect, and will  not account  for the  entrance of the
fluid into it  without some other more active principle.
This I conceive to be  a  mechanical cause  depending
upon the structure of the heart, as consisting of a sub-
stance which possesses a great  degree  of elasticity, so
that when its cavity is diminished by the contraction of
the muscular fibres, as  soon  as the contractile power
ceases to  operate, the  elastic  force comes into play,
and tends  to bring it back to its former shape.   We
may form a clear idea of the operation of this suppos-
ed principle by regarding the heart in  two  ways, first,
as consisting of a flexible and inelastic bag similar to  a
moistened bladder; and,  afterwards, as composed of  a
bag of similar dimensions formed of caoutchouc.   We
may imagine that each of these has the  same appara-
tus of muscular fibres; when the first  of them is filled
with  blood, the  muscular fibres  contract, reduce its
size, thereby expelling its contents, and leave the bag
in a collapsed state;  whereas, in the second case, after
the fibres  have contracted and expelled the blood, the
elastic nature of the  organ  causes it to  resume its
rounded form, and to  leave a cavity nearly  as conside-
rable as  before  the  operation.  This cavitv will of 
Conclusion.
SZl
 course be  immediately filled by any fluid which is in
 contact with it:  and in the case of the heart the blood
 that is in the auricles, without any action on  their part,
 will immediately flow into the ventricles, and will itself
 be succeeded in  the auricles, by an equal quantity of
 blood  from the  veins.   We have, perhaps, no very
 decisive experiments or observations to prove that this
 is actually  the state of things with respect to the heart,
 but it appears very  probable that it is so, at  least to a
 certain extent,  and therefore I do not hesitate  to enu-
 merate derivation, or, as  it  might be more correctly
 and  less hypothetically termed, the  elasticity  of the
 heart itself, as among those  causes  which assist in the
 circulation  of the blood.*
   Contrary, however, to what  appears to be the opi-
 nion  of those who have treated on this subject, I can-
 not admit that  the principle of derivation is an actual
 source of power,  or  that there is any generation of mo-
 tion produced by it.   Like other forces which depend
 upon elasticity, it is to be regarded solely as giving a
 new  direction to a power previously existing, the origin
 of which, in this case, is the contractility of the ventri-
 cles.   It may indeed be regarded as  a very beautiful
 contrivance for equalising  the force  employed in the
 circulation,  and for transferring, as it  were, part  of it
 from  the  commencement to the  termination  of  the
 passage of  the blood along the  vessels;  but I  appre-
 hend that precisely as much power as is gained by the
 influx of the blood from the  auricles  into the  ventri-
 cles,  must have been previously exercised by the mus-

  * See Dr. Hastings's observations upon Dr. Carson's hypothesis,
 Treatise on  the Mucous Membrane, p. 8, et seq., and Philip in
 Med. Chir. Trans,  xii. 397, et seq.  It is to this elasticity of the
heart that we may refer a certain degree of re-action which it
appears to exert during its diastole, and which M. Magendie ob-
serves is something more  than a mere passive operation.  Physiol.
 t. ii. p. 329.   The  same  opinion, as has been stated above, p. 173,
 Was maintained by Bichat. 
 532        Causes which retard the Circulation.

 cles of the ventricle in overcoming the increased resis-
 tance caused by the increased elasticity of its substance.
 We may conclude therefore that the efficient causes of
 the circulation of the blood are the contractility of the
 muscular fibres of the heart, that of the capillary arte-
 ries, and external  pressure upon the veins, principally
 produced by the contraction of the muscles.
   After considering the causes  or  powers which pro-
 mote the flow of the  blood along the vessels, it will be
 necessary to take a cursory view of those which  tend
 to retard it.  These are very numerous, and some of
 them very considerable ; they may  be all referred to
 the head of mechanical causes, because  any circum-
 stance which tends to diminish the vital energy of the
 heart or arteries acts merely in a negative manner, di-
 minishing the effect of their contractility.  The most
 important  of the mechanical  causes which retard  the
 motion  of  the  blood are  the following; the physical
 composition and structure  of the vessels, as  being  im-
 perfectly elastic, flexible,  pursuing  a winding  course,
 ramifying into branches which go  off at considerable
 angles from the trunks, the branches occasionally unit-
 ing, by  which the streams of blood meet each other in
 opposite directions, and the circumstance of the  sum of
 the areas of all the branches being greater  than  that
 of the main trunk.   The  resistance  which the blood
 already in  the vessels  opposes to the  entrance  of  any
 fresh quantity is the cause of a  prodigious expenditure
 of power,  while the nature of the blood itself, as being
 a thick and tenacious fluid, its adhesion to the sides of
 the vessels, and the friction which it  must experience
 in passing along so extensive a  system of tubes, afford
 other causes of the loss of power, the amount of which
 must be very great.   Those  who are versed  in  the
 laws of hydraulics will perceive the reality of all these
 causes  of  retardation, and will be  aware that they
 operate independently of the vital  power of the or-
gans, acting upon  them as they would on a system of 
         Application  of Mathematics to Physiology.     333

 tubes possessed of  the same physical  properties, but
 without any of  those  functions which  are peculiar to
 the living  animal.
   When we consider how much the powers of hydrau-
 lics are concerned in the  circulation, we cannot be sur-
 prised that the mechanical  physiologists,  who applied
 their science to many points of the animal (economy to
 which it had so little relation, should  have bestowed
 unusual attention upon every  circumstance connected
 with the action of  the heart, and the  motion of the
 blood along the vessels.   We shall accordingly find
 that some  of their  most elaborate calculations were
 directed to this subject,  and that they bestowed upon
 it no less attention  than  upon the  cause and nature of
 muscular contraction.  Upon the whole, the result of
 their labours has been almost as unfortunate in this as
 in the former case, for although  the data are less ob-
 scure, as far as concerns the nature of the powers em-
 ployed, yet  we are  totally unable to  ascertain the
 amount both of the powers which promote and those
 which retard the circulation of the blood.
   With respect to mathematical  reasoning in general,
 it must be admitted that,  when it  is cautiously applied,
 it has enabled  us  to arrive at  physiological  truths,
 which we  perhaps  could not  have attained  by any
 other method, and  which are beyond  the reach  of
 actual observation.   But  when we call in the aid  of
 mathematics to  assist us in our researches, it is of the
 utmost  importance  to ascertain that our data be well
 founded, and that we are  not misled by  false analogies,
 or by the  mis-application of principles which may be
 in themselves correct.  But  the  mechanical physiolo-
 gists fell into the fatal errors of assuming principles
 which were incorrect, of  adopting data  which were  of
 doubtful authority, and of applying  them  in an incor-
rect manner.
  To relate all  the theories, hypotheses, and calcula-
tions that have been formed upon the  subject of tho 
334
Keill's Experiments.
 circulation, would be an idle expense of time and labour,
 but it may be proper to give an account of some of the
 attempts that have been made to estimate the force of
 the heart, because they were conceived  by  men  emi-
 nent  for their learning and ability, and afford an excel-
 lent specimen of  the  method of reasoning  that  was
 fashionable at the time when  they flourished.
   Borelli,  proceeding upon  his hypothesis, that the
 power of muscles is  in proportion to their weight, esti-
 mated that the force 01 the heart is equal to the enor-
 mous sum of 180,0001b.   Keill perceived the extrava-
 gance of Borelli's calculation,  and attempted to arrive
 at the truth by a more complicated  process.  He set
 out by the position that the force of the  heart produ-
 ces two effects; it expels a quantity of blood from its
 cavities,  and communicates motion to the contents of
 the arteries.  He  first attempted to estimate the quan-
 tity  of blood thrown  out of  the heart by each of its
 contractions ; and  by taking the diameter  of the aorta,
 be  could then calculate the  velocity  with  which it
 passes along this  vessel.  He  found the  quantity of
 blood to  be  about two ounces, the area of the great
 vessel to be about three-fourths of a square inch, and
 he conceived that  the actual contraction of the ventri-
 cle would occupy  about the two-hundredth part of a
 minute.  Hence he  found that the  blood  sent into the
 aorta yvould compose a cylinder of about  eight inches
in length, and be  driven along with a velocity of  156
feet in a  minute.   In producing this velocity  the heart
has not only to  expel  the blood, but to overcome all
the resistances in the vessels, and the next step was to
ascertain their amount.  For this purpose he opened a
living animal, and  laid bare the iliac artery and vein.
Now  he argued that all the blood which  passes through
any artery must be returned by the corresponding vein
in the same time, but with a different degree of force;
the arterial blood  has to overcome all the resistances
which occur in the course of the circulation, the venous 
Remarks upon them>
335
blood possesses only the force which remains after the
resistances have been overcome.  He opened the iliac
vein and received all the  blood that flowed out in ten
minutes, and afterwards he opened the artery and re-
ceived the blood that flowed out during the same length
of  time, when he found  that  the quantity of blood
which he obtained from the artery was to  that from
the vein as seven and a half to three, or as two and a
half to one.  He therefore concluded that the first of
these numbers may be regarded as the measure of the
velocity which the blood receives from the full  force
of the heart; and the second, the velocity with which
it moves after it has overcome all the obstacles which
it meets with in its passage through the vessels.  Pro-
ceeding upon this principle, the velocity  in the aorta,
without the resistances, are estimated at  390 feet in a
minute, or nearly six feet and a half in a second. From
this datum, by means of  the Newtonian theorem, he
estimates the force which is necessary to  move a given
column of blood, with a known velocity in a given time,
and this he determines to be five ounces and a half, or
about half a million of times less thanj;he  calculation
of  Borelli.
   We  cannot but give the merit of ingenuity to Keill's
reasoning, but it is obviously incorrect in many particu-
lars.   In the first place, a great mass of resistance  is
opposed  to the blood at its entrance into  the aorta,
which  must have been  overcome before it arrives at
the iliac artery, on which Keill made the experiment.
In  the  second place, the quantity of blood which flows
from a divided  vessel is  no measure of what passes
through it  at offer times, as on the  principle of deri-
vation,  blood  will be sent from all   the  neighbouring
vessels to a part where the resistance is removed.  In
the third place, we are not certain that the same quan-
tity of blood is returned by what are  called the corres-
ponding veins; and it is  also probable that, in Keill's
experiments,  a greater quantity than ordinary would 
336
Hales's Experiments.
pass off by the veins, in consequence of the anastomo-
ses that veins have with each other.  But it is  unne-
cessary  to dwell  any  longer upon these objections,
enough  having been  said to show  that  the  estimate
does not afford even an approximation  to truth.
   The only other  calculation of this kind which I shall
notice, is that of Hales. Hales was  remarkable for the
purity and integrity of  his character, and his ardour in
philosophical researches, and he  bestowed a large part
of his time on experimental inquiries into the nature of
vegetable and animal bodies.  He had too much  can-
dour to  be blindly  devoted to any sect, but the genius
of the age in which he lived was so decidedly in favour
of the employment of mathematical reasoning in every
department  of philosophy, that he entered  very fully
into all  the views of  his predecessors  respecting the
mechanical  powers of  the  sanguiferous  system.   He
attempted to estimate the relative force of the  arte-
ries and veins by inserting tubes  into the great vessels
near the heart, and observing the comparative height
to which the blood was impelled into them.   This he
found to vary in different experiments, but it was al-
ways considerably greater in the arteries than in the
veins, upon an average, as about  ten to one.  In order
to ascertain  the absolute force of the heart, Hales in-
serted tubes into the aorta, soon after it leaves the left
ventricle,  when he found the column of blood raised in
the tube to be of  such a height, that by comparing it
with the cavity from which it was  projected, and tak-
ing into account the time and the area of the vessel,
the force  of the heart would be about 50lb.*  Perhaps
Hales's  estimate  may  not  be very remote from the
truth, yet there are many points in  which it is defec-
tive, even regarding the heart as  an hydraulic machine;
and it is  obvious,  that when we consider  contractility
as a variable power, depending upon a number of cau-
* Statical Essays, v. ii. p. 38, 40. 
               Phenomena of Inflammation.           357

  ses connected with life, which it is impossible to appre-
  ciate,  we  shall  be convinced  of  the futility of such
  calculations.  Hales's  works, however, contain much
  important  information, the direct result of experiment,
  which will always render them a valuable magazine of
  tacts for the philosophical inquirer into the actions of
  the sanguiferous system.


                 § 7.   Of* Inflammation.

    Before I quit  the  subject of the circulation it may
 be proper  to  offer a  few  remarks on the nature of
 inflammation,  a  point  indeed more immediately con-
 nected  with pathology, but yet of  considerable impor-
 tance considered  in  its  physiological  relations.  The
 phenomena of  local inflammation, to which I mean
 principally  to confine my observations, vary according
 to the structure and functions of the part affected, yet
 there are some circumstances which may be considered
 as common  to all cases, of which the four following are
 considered  the most essential,—redness, heat, pain, and
 swelling.*   It is generally agreed that the  capillaries
 are the  immediate seat of  the  inflammatory  action,
 and that when any change occurs in the  large vessels,
 it is to be attributed to  a  secondary  or consequential
 operation, originating from the  affection of  the  minute
 arteries.  All  the four  symptoms mentioned above,—
 redness, heat,  pain, and swelling, may  be attributed to
 one primary cause, an increase in the size of the minute
 vessels, by which  they are enabled to admit of more
 than the ordinary quantity of blood  to be received into

  * Cullen's First Lines, § 235; Thomson's Lectures on Inflamma-
 tion, p. 42; see also,  J. Hunter's Treatise on the  Blood, c 3, a
 portion of this celebrated work which  cannot be  too carefully
 studied, both  for its valuable  observations and for  its profound
insight into the operations of the animal ceconomy; yet even here
 we have to lament the metaphysical subtilties in which the author
is occasionally involved.
            43 
338            Hypothesis of Boerhaave.
them,  but a great diversity--of opinion has prevailed
concerning the mode in which the  blood is conveyed
or retained there, or concerning what has been termed
the proximate cause of inflammation.
  After the vital power of the vessels had been estab-
lished  by  Stahl  and his disciples,  the phenomena  of
local inflammation were referred to this action,  and  as
all the natural operations of the arterial system seemed
to be augmented during this state, so it followed, almost
as an obvious consequence, that inflammation essential-
ly consists in  increased  action of the  capillaries.*   A
strong objection to this supposition was, however, quick-
ly perceived, that the effect of the vital action of the
vessels is  contraction, while, as we observed above, the
very essence of  inflammation consists in an increase  of
thecapacity of the vessels.  But the ingenuity of the
physiologists was not baffled by this difficulty ; various
means  were invented to  accommodate  the theory  to
the facts, depending upon the presence of some obsta-
cle which the blood was conceived  to meet with in  its
passage through the vessels, which, at the same time,
was not  incompatible  with their increased diameter.
Boerhaave attributed  the obstruction to a change  in
the  texture  of the blood itself,  by which  it  became
more  thick  and  viscid,  acquiring,  what  he called, a
state of lentor, and to this lentor he added the further
hypothesis, that the increased action of the  arteries
forces  the larger  particles of  the  blood into vessels,
which, in their natural  condition,  are too  small  to
receive them.   This constitutes the  error loci of  the
mathematical physiologists, and by the lentor and error
loci were the phenomena of local inflammation explain-
ed by Boerhaave and his numerous disciples,!  until this,

  * For a  clear and candid statement of the opinions which have
been entertained  upon the state of the blood-vessels in inflamma-
tion, I may refer the reader to Dr. Thomson's Lectures on Inflam-
 mation, p  61—75; and  Hastings's Treatise on the Mucous Mem-
brane of the Lungs, p. 67, et seq.
   t Aphor. 110, 122, 370, et seq. cum Sweiten. Comment. 
Of Cullen and Allen.
8S9
 like  most of their other speculations, was assailed by
 the powerful genius of Cullen.   In place of the mecha-
 nical  doctrine  of Boerhaave,  Cullen substituted   his
 favourite  hypothesis of spasm ;* for he admitted  the
 increased  action  of the vessels in  local inflammation,
 while he was aware, that  without some counteracting
 circumstance, this increased action  would  produce e£
 fects totally inconsistent with  the actual phenomena.!
 We shall, however, find, upon  due  reflection, that  the
 spasm  of Cullen is  equally  unfounded, and perhaps
 even less intelligible, than the  lentor and error loci of
 the Boerhaavians ; and accordingly  his explanation  has
 been generally regarded as incomplete, yet since   his
 time no regular  attempt  has  been  made to reconcile
 the increased action of the vessels with their enlarged
 diameters.
   In this dilemma a totally different view of the ques-
 tion has been taken,  according to  which local inflam-
 mation is to be attributed to a diminished action of  the
 capillaries.   This hypothesis,  which  appears to have
 been originally  proposed by Vacca, an Italian physiolo-
 gist,  about  the middle  of the last  century,  was first
 brought forwards in a  clear  and  consistent form   by
 Mr. Allen, who, for some years, lectured in Edinburgh
 on the  animal ceconomy ; it was adopted  by Dr. Wilson
 PhilipJ: who performed  a series  of  experiments  in
 support of it, and  has  been since  embraced  by  Dr.
 Parr,§ Dr. Thomson,|| and Dr. Hastings.1T

  * First Lines, § 244, et seq.
  t Haller was quite  aware that an increased action of the arteries
 must have  a  tendency to diminish their capacity, and employed
 this consideration as  an  argument against the  muscularity of the
 capillaries.
  X Wilson on Febrile Diseases, v. iii. p. 15—73.
  § Dictionary, Article " Inflammation."
  || Lectures on Inflammation, p. 70
  IT On the Mucous Membrane,  p. 71, et seq.  Dr. Thomson  and
Dr. Hastings likewise supported  the hypothesis by numerous expe-
riments.  Although Philip, Thomson, and Hastings, agree in  the 
340
Of Allen.
   According  to  Mr.  Allen's hypothesis, the  redness,
 heat, pain,  and  tumour,  are  to  be  ascribed to  the
 increased quantity of  blood which the vessels contain
 in consequence of their relaxed state; the symptoms,
 therefore, which had  been usually attributed to exces-
 sive action he ascribes to this partial stagnation of the
 fluids, together with  a kind  of struggle between the
 loss  of  power in  the  part, and the unusual stimulus to
 which it is thus subjected.  Although this doctrine of
 the proximate  cause of inflammation may, at first view,
 seem  to counteract our  established notions upon  the
 subject, yet  it will, I think, be found upon examination
 to be  more consistent in all  its parts, and  to accord
 better with  the various phenomena both  of  pathology
 and of physiology, than any  of  the speculations which
 had preceded  it, derived from the principle of increased
 action combined with  obstruction.   And indeed if we
 take  into account  that the exact seat of the inflamma-
 tory action is not visible to the eye, and that, according
 to the hypothesis  of Dr.  Hastings, the state of active
 inflammation consists  in  an   increased action  of  the
 larger arteries, while the capiharies are in their natural
 state,*  it  will approximate this  hypothesis, at  least as
 to all pathological  and  practical consequences,  pretty

 main point, that inflammation essentially  consists in diminished
 action of the  capillary arteries, they differ  respecting the actual
 state of the vessels.   Dr Philip supposed that the constant effect
 of inflammation is to dilate the vessels, and  to diminish  the  velo-
city of their contents.  Treatise on Febrile Diseases, v. iii. p. 15,
et seq.; also Preface  to 4th ed. p.  vii.; and Med. Chir.  Trans, v.
xii. p. 407.  Dr. Thomson concludes that the velocity is sometimes
increased and sometimes diminished ; Lect. on Inflammation, p. 89;
while  Dr. Hastings adopts the  opinion of Dr. Philip, that in the
 proper inflammatory  state, the velocity  of the fluids  is always
 retarded ; on the  Mucous  Membrane, p. 91, et alibi.   It may be
 worth noticing, that the article " Inflammation," in the Diet, des
 Scien. Med., written by Boyer in 1818, contains no account of either
 the hypothesis or experiments of the English physiologists : inflam-
 mation is referred, according  to the old doctrine, to the increase
 of vital action.
  * On the Mucous Membrane, p.  106. 
                  General Remarks.               341

nearly to  the old doctrine.   But I must add,  that I
think we are not arrived at that degree of knowledge
on the subject which  will enable us  to form a decisive
opinion respecting it.   Waving, therefore, the regular
discussion of the hypothesis, I shall conclude  by  a  few
observations which may be of some use to those  who
are inclined to investigate the proximate cause of in-
flammation with more minuteness..
  Although we  may conceive that  the  phenomena of
inflammation are as readily explicable upon the hypo-
thesis of diminished  as of increased contractility of
the capillaries, yet it  appears to me that both the ex-
citing causes of  this affection  and  the treatment coin-
cide more with the idea of excessive than of defective
action.  All those circumstances which  we are usually
in the  habit of considering as stimulants excite inflam-
mation; and where the same effect is brought  about
by sedatives, or by agents  of  a more doubtful opera-
tion, still we can  generally perceive  the existence of
what has been termed re-action, which is the immediate
precursor of the change in the state of  the circulation.
In the same way the remedies for inflammation appear
to me  more adapted  to  remove  or relieve  an  excess
than a defect of vital  energy, as  for this purpose, ex-
cept under  peculiar circumstances,  we always  apply
either direct or indirect sedatives, and find stimulants
to be as injurious as the others are  beneficial.  From
these considerations I am induced to recur to the for-
mer idea of increased action being the proximate cause
of inflammation, or at least as being  essential  to it, and
to inquire whether there be no correct method of com-
bining a state of increased action with distention  of the
vessels.  This, it is obvious, must  be accomplished by
obstruction in some form or other, either arising from
the nature of the fluid, or from the  difficulty with  which
it leaves the vessels after it  has  entered into  them.
Now, although we may agree with  Cullen that Boer-
haave  adduced no sufficient  proof of the existence of 
342
General Remarks.
 his lentor and error loci, yet  it does not follow that no
 alteration in the condition of  the  blood  exists.  May
 we not conceive, that  by the  inflammatory action  the
 proportion of fibrin  is  increased, or that  the  fibrin al-
 ready present  acquires a greater  tendency to coagu-
 late ?   That the solid contents generally  of the  blood
 are augmented, either by an increased quantity being
 thrown into the vessels, or a portion  of the more fluid
 part being removed ?  May not some new  arrange-
 ment take place with respect to the  globules, so that
 they may coalesce or be  more strongly  attracted   to-
 gether?  Or, without having recourse to  any specula-
 tions of this kind, may we not conceive it  possible, that
 if the  minute arteries are  contracting more vigorously
 than ordinary, their relaxation  will be proportionably
 great,  so as  to allow  of the different parts  of the blood,
 as the fibrin and the globules, to be admitted  into ves-
 sels  which  are generally impervious  to them, and
 which, when once entered, from the vis a tergo on  the
 one hand, and  from  the  decreasing  diameter  of  the
 vessels as they  divide into small branches  on the other,
 are forcibly detained, and produce all  those symptoms
 which  seem to  originate from mechanical  obstruction?
 These considerations  are  thrown  out rather to show
 what may be conceived as a possible occurrence, than
from the idea of our  possessing any evidence  of their
 actual  existence.  They may, however, show that  we
 have not a sufficiently  intimate acquaintance with the
subject to enable us to decide peremptorily respecting
the proximate cause of inflammation. 
Progress of Animal  Chemistry.          343
                  CHAPTER  VI.

                    m the ttlootr.

 § 1.   Remarks on the Progress of Animal  Chemistry.

   After the description of the course which the blood
 follows in the  circulation, and  of the mechanism by
 which its motion is produced and regulated, I must now
 proceed to consider those functions by which  its phy-
 sical and chemical properties are changed, so as to be-
 come  subservient to  the growth  and nutrition of the
 body.   The blood is, however, a fluid of a  very com-
 pound nature, the different constituents of  which are
 possessed of peculiar properties, and are retained in a
 state of combination,  in  many respects, unlike that of
 any other substance with which we are acquainted. It
 will therefore be  desirable, before  we proceed to  the
 other functions, to give some account of the nature and
 properties of the blood ; to this I shall prefix a few
 remarks upon the history and present state  of animal
chemistry.
   During  the earlier part of  the  eighteenth  century,
when chemistry first began to assume a scientific form,
and when the experimentalist proposed to himself some
definite and  intelligible object of inquiry, the analysis
of animal and vegetable substances naturally attracted
a share of his  attention.   The mode  of examination
which was then adopted was indeed little calculated to
throw any light upon  the subject,  for it consisted al-
most entirely in submitting the substances to the pro-
cess of distillation at  a  high  temperature, by which
their primary compounds  or proximate principles were
entirely destroyed, and either converted into new com-
pounds, which did not previously exist, or resolve^ into 
344         Progress of Animal Chemistry.
 their ultimate elements.   Many of these latter were of
 a gaseous  or volatile  nature, and  from the operator
 being, at  that  period, ignorant of  the properties, or
 even of the existence of such bodies, they were  suffer-
 ed to escape, and were  totally disregarded, while the
 solid or fluid products  that were obtained were, in all
 cases, nearly similar to each other, and  conveyed no
 idea of the nature of the substance from which they
 were procured.   They principally  consisted  of a car-
 bonaceous  residuum, with a quantity of empyreumatic
 oil and ammonia, which two latter substances were ge-
 nerated during the process.
   The first radical improvement in  animal analysis con-
 sisted in substituting the action of various re-agents for
 this method of destructive distillation, an improvement
 for which we are principally indebted to the French,
 and especially to some  members of  the Royal Acade-
 my of Sciences,  who, about the middle of the last cen-
 tury, were led to investigate the composition of organ-
 ized bodies, and  soon perceived the little benefit that
 had been derived from the former method of proceed-
 ing:.  One of the most active of  those who  were en-
gaged in this new pursuit was  Rouelle ; he subjected
 the  substances  which   he wished  to analyze to the
action of alcohol, acids, alkalies, and other powerful re-
agents; he noticed  the effect  of simple exposure to
the atmosphere,  he examined  the  changes  produced
by temperature  and  moisture,  and,  at the same time,
carefully watched the progress of spontaneous decom-
position.   Neumann of Berlin,  and some other of the
German chemists, proceeded upon the same plan with
Rouelle and  his  associates,  and,  at a somewhat  later
period, Macquer and Baume  materially contributed to
our  knowledge  of this department of  chemistry by
their publications.  Hitherto it had been  little attend-
ed to in this country;  Hales  indeed made the impor-
tant discovery, that a permanent gas was obtained from 
Progress of Animal Chemistry.           345
various animal substances by distillation* but it  was an
insulated fact, the nature of which was  not understood,
so that it  led to no further improvement; and it was
not until the  establishment of the pneumatic chemis-
try, as it  has been called,  for  which we are so much
indebted to Black, Cavendish,  and Priestley,! that the
nature of  the results could  be  understood, or the  true
method  of  analysis  be  clearly comprehended.  The
experiments of Priestley, in which he  obtained azotic
gas by treating animal substances  with nitric acidjcon-

  * He informs us, that he obtained  " a considerable quantity of
permanent arr"  from  blood, fat, and various other animal substan-
ces, and more  especially  from  urinary calculi.  Stat. Ess. v. i. p
173, 193, (1769.)  Scheele's  Experiments on Calculus were publ
fished in  1776 ; see Marcet on Calculous Disorders, p. 63.
  t It was from the latter of these philosophers that I received my
first instruction  in chemistry,  and I cannot mention his name with-
out offering to his memory my grateful tribute  of respect and ad-
miration.   His merit as a chemical discoverer of the first order is
so generally acknowledged, that it may appear almost unnecessary
to enlarge upon it, yet  I  believe that few  persons who  have not
particularly  attended to the subject are aware of the full  extent of
our obligation.  Those who are disposed to investigate this point
should peruse his original six volumes of experiments,  and com-
pare the  information  which they contain with the chemical publi-
cations which immediately preceded them. In originality, in quick-
ness of apprehension, and in diligence, he has probably never been
surpassed ;  but  1 conceive that  his judgment  was by no  means
equal  to  his genius,  for,  although we are astonished with the va-
riety and extent of his discoveries,  we are not unfrequently sur-
prised  at the futility of his hypotheses and the weakness of the ar-
guments by which he defends them.   So far as  I am capable of
forming an opinion, the same  character will  apply to  his  other
publications.   Of his strictly theological works I do not profess to
judge ; but two of his most  elaborate performances,  which were
intended for general use, the " Disquisitions," in which he attempts
to identify the  phenomena of mind with those  of matter, and the
" Letters to  a Philosophical Unbeliever," the object of which is to
prove that the credibility  of supernatural  events  rests  upon the
same grounds with that of the ordinary operations of nature while
they abound with ingenious remarks and original conceptions ap-
pear to me to be both of them founded upon fallacious principles.
  X Priestley's experiments, in which  he procured " phlogisticated
air" by the action of nitric acid on animal  substances, were pub-
                      44 
346
Modern Analysis.
 stituted a very important  advance in our  knowledge,
 but we must admit that  it was chiefly by the labours
 of the French, and especially by those of Fourcroy and
 Berthollet,* that the foundation was laid of the  cor-
 rect information which we at  present possess on this
 subject.   Latterly,  indeed,  the English have  had at
 least an equal share  in  promoting the  science of ani-
 mal chemistry ; I have already had occasion repeated-
 ly to refer to the  labours  of  Mr. Hatchett, and, in ad-
 dition to his name,  we may select those of Wollaston,
 Pearson,  Marcet,  Henry,  Prout, Brande, J.  Davy,
 Thomson, and Ure.   In France, those who are at  pre-
 sent the most distinguished in this department are Vau-
 quelin,  Guy-Lussac,  Thenard, Chevreul, Proust, and
 Bouillon la  Grange ;  and we  must not omit  to acknowl-
 edge the great obligation  under which we lie  to Swe-
 den, formerly in  the person  of  Scheele, and  now in
 that of Berzelius,  whose genius and assiduity have ren-
 dered him almpst equally  illustrious in every branch of
 chemistry.!
   The method at present employed in  the  examina-
 tion of animal substances  may  be considered as com-
 bining three distinct sets of operations.   The first con-
 sists in noticing the  effect of external agents upon the
 substance in question, and  observing  its spontaneous
, changes ; the second depends upon  the  application of
 re-agents, which  are used either in the way of tests,
 to indicate the existence  of  particular elements or pri-

 lished in 1775. Experiments on Air, v. ii. p. 145, et seq. (Original
 series  of six volumes.)  Fourcroy says  that Berthollet discovered
 azote in animal substances in 1784.  System, v. ix. p. 42,
   * See Berthollet's Memoirs on the analysis of Animal Substances;
 Mem. Acad, for 1785 ; also Journ. de Phys. t. xxviii. p. 272,  et t.
 xxix. 389.
   t For a sketch of the progress of animal chemistry, see Four-
 croy's System, v. ix. p. 33—56 ; and Berzelius's essay expressly on
 this subject.   It is much to be regretted that these writers should
 have entirely omitted to give any particular references to  the ex-
 periments or opinions which they detail. 
Coagulation of the Blood.
347
mary compounds, or as menstrua, which, by their spe-
cific affinities, may separate the  elements  or primary
compounds from  each other; while  the  third  set of
operations are to be regarded  as, in some measure, a
return to the original plan of  destructive  distillation,
but with this very essential difference, that, in the  mo-
dern analysis, we carefully collect  all the gaseous  and
volatile matter, and by ascertaining its  nature and  the
amount of its  elements, we estimate the  nature  and
amount of the compounds  into which they previously
entered as constituents.   We procure,  for example, a
certain quantity of carbonic acid gas and of water,  and
we know the proportion of carbon, oxygen, and hydro-
gen,  which  they respectively  contain ; the azote  re-
mains uncombined and is collected in the gaseous state,
so that we are able to  ascertain the  amount and rela-
tive proportion of the elements which entered into the
constitution  of the  substance analyzed.   This method
of discovering the nature of a body, by resolving it  into
other bodies of known composition, was first practised,
although in rather  a rude manner,  by Fourcroy  and
Vauquelin;  it  was afterwards very much improved by
MM. Gay-Lussac and Thenard,  and still more so by
Prof. Berzelius and Dr. Prout, from whose science  and
skill it has arrived  at a very great degree of  perfec-
tion.*

      § 2.  Nature  and  Properties  of the Blood.

  I shall now  revert to  our  more immediate  object,
the nature and properties of the blood.   After describ-
ing this fluid in its entire state, I shall give an account

  * For an account  of the modern analysis of animal substances,
see Thenard's "Traite," t. 4; Children's Translation of the same,
containing much valuable  additional matter; an Essay by Berze-
lius, in the 4th and 5th vols, of Annals of Philosophy ; Dr. lire's
paper in Phil. Trans,  for 1822; and the various papers of Dr,
Prout, in the Med. Chir. Trans, and the Annals of Philosophy. 
348
Extrication of Caloric.
of the primary compounds,  and  proximate principles,
into which it may be separated, either by its spontane-
ous changes,  or by  the application  of re-agents.  In
the next place I shall notice some of the  alterations
that are brought  about in  the  bjood by the  natural
functions of the system or by the effects of disease, and
I shall conclude by  some  observations upon the opin-
ions that have been successively  entertained respecting
its various constituents.
   Blood,  when first drawn  from the vessels, is an  ad-
hesive fluid, of an homogeneous consistence, of a speci-
fic gravity of  about 1*050,  in man and the more per-
fect animals of a red colour,  of  a slightly saline  taste,
and, in the human subject, of the temperature of about
98°.   Soon after  it  leaves the vessels, if it be suffered
to remain at rest, it begins  to  coagulate; and as this
process  advances, it  will be  found to separate into two
distinct  parts,  so that we at length obtain a red mass
floating  in a yellowish fluid:  the red part is called  the
clot or crassamentum,  and the  fluid  part the serum.
In venous blood, which is generally employed in  these
experiments, the average  period of coagulation is said
to be about seven minutes.  The proportion of  the
two constituents has been variously estimated ;  it is not
easy to  obtain any accurate  result, because the  separa-
tion is by no means  complete, a portion  of the serum
always remaining attached to the clot; and by attend-
ing to the state of the blood, we find that  the  propor-
tion  varies  considerably  in  different individuals,  and
even  in the same individual at different times.   It  has
been  stated, as a general  average, that the crassamen-
tum amounts to about one-third   of the weight of  the
serum,  and  perhaps this may  not be  far from  the
truth.
   As the fluid of  warm-blooded animals,  when first
drawn from the vessels,  possesses  a temperature con-
siderably greater than that   of  the atmosphere,  it  has
been  made the subject  of experimental inquiry, what 
Crassamentum.
349
is the rate of  the cooling of the blood, compared to
that of water raised to the  same  temperature.  The
greater viscidity of the blood must necessarily tend to
retard the escape of  heat from it, but,  besides this, it
has been conceived that the coagulation of the fibrin,
like other processes in which a fluid is  converted into
a solid, should cause the absolute extrication of caloric.
Fourcroy relates an experiment, in which, during the
formation of  the clot,  the  thermometer rose  no less
than 11°,* but  as  the particulars were not mentioned,
and  as  the  result  appeared to be in contradiction to
some facts adduced by Hunter!  and others, the conclu-
sion was  not generally admitted.   Fourcroy's experi-
ment has, however, been confirmed by some  that have
been lately performed by Gordon,  in which the effect
of coagulation in  evolving caloric was  rendered most
evident, by moving the thermometer, during the forma-
tion of the clot, first   into the coagulated,  and after-
wards into the  fluid part  of the blood, when he found
that by  this means he could detect  a difference of 6",
and that  the difference  remained perceptible for 20
minutes after the process had commenced.  In repeat-
ing the experiment upcn blood, drawn from a person
labouring under  inflammatory  fever,  the rise of the
thermometer wTas no less than 12°!  I conceive, there-
fore, that this point may be considered as established,
that during the coagulation of fibrin a quantity of calo-
ric is extricated,  thus proving that fibrin has a less ca-
pacity for heat in its coagulated than in its uncoagulated
state.

                    § 3.   Fibrin.

   The crassamentum, when removed from the  serum,
generally appears under the form of a soft solid, of

      * Ann. de Chimie, t. vii. p.  147, from 20° to 25° R.
      t Hunter on the Blood, p. 27.
      X Annals of Philosophy, v. iv. p. 139. 
350
Fibrin.
such consistence as to bear cutting with a knife :  it fre-
quently assumes a fibrous appearance, and when it has
been coagulated under particular circumstances,  it may
be converted into an  irregular net-work, consisting alto-
gether of fibres, of a greater or less degree of fineness,
according to the manner in which the process has been
conducted.   The best method of exhibiting this  fibrous
appearance  is to stir the blood, as it flows from the ves-
sel, with  a bunch of twigs, or to receive it into a bottle,
and shake it during its coagulation, but it  must  be ob-
served, that if the motion  be too considerable, the clot
is altogether prevented from forming.   The coagulum
which has been produced in the usual  manner, while
the blood is at  rest,  may  also be deprived  of  its red
colour by repeated ablution in water, thus showing that
the colouring matter is only mechanically mixed with
the fibrin,  and  not  retained  there by  any chemical
affinity.  When the  fibrin is thus procured  in a pure
state, it is found to  be a  solid  of  considerable consis-
tence, elastic and tenacious, and in  its general  aspect,
as well as in its chemical relations, very similar  to  the
pure  muscular fibre, although we have reason  to sup-
pose that it differs from it in  its minute  organization.
It has been designated by  several  names—coagulable
lymph, gluten,  fibre  of the  blood,  and fibrin; this last
appellation  was given  to  it by the French chemists,
and will  be  adopted in this work,  as being the most
characteristic and appropriate.
   It is obviously upon the fibrin that the formation
and separation of  the clot depends, thus  producing
what has been termed the spontaneous coagulation of
the blood, in opposition to the  other kinds  of coagula-
tion, which  are effected by  the application of heat, or
of some  chemical re-agent.  A change  so singular in
its nature could not  but excite  great  attention among
physiologists, and  numerous observations  and  experi-
ments have been made to account for  its  occurrence,
or to discover  what  circumstances  tended  to promote 
Effect of Rest and Air.
351
 or retard it.  The  two  most obvious circumstances
 which might be supposed to operate, as constituting
 the chief difference between the condition of the blood
 while in  the  vessels, and  after it  is  discharged  from
 them, are rest and exposure to air.   I  have already
 alluded to the effect of agitating the  blood;  it is well
 known, that  if the fluid, as it is discharged from the
 vessels, be briskly stirred about for some time, the pro-
 cess of  coagulation is entirely prevented  from taking
 place, either in consequence of a more complete union
 of its parts with each other, which prevents  their fu-
 ture separation, or from the fibrin,  after it has been for
 some time discharged from the blood, losing this pecu-
 liar property, by which its particles  are  attracted to-
 gether.    It is probable that both these causes may
 operate, but  I am not acquainted with any facts which
 can enable us to determine which of them has the most
 powerful effect.
   With   respect  to  the influence of air upon the
 spontaneous coagulation of the blood, we have not yet
 arrived at any very positive conclusion.  Many experi-
 ments were performed on  this subject by Hewson, and
 although  they are not sufficiently decisive, nor always
 uniform in their results, yet they lead to  the  opinion,
 that the presence of air promotes coagulation.*  Hun-
 ter opposed the doctrine of Hewson,! but  his experi-
 ments and arguments go no further than to show, that
 air is not  essential to the  process;  a  point which was
 fully admitted by Hewson, and which follows immedi-
 ately from his"  experiments.   This circumstance  is
 proved by the fact, that coagulation  not  unfrequently
 takes place in the vessels or cavities of the body, where
 the blood must be completely excluded from  the air;
 and indeed this change has been found to exist,  to a
certain degree, during life,  as  the polypous concretions

  * Experimental Enquiries, p. 20.    t On  the Blood, p. 22. 
552                 Of the Gases.
that are occasionally found in different cavities of the
body, and  which from the previous  symptoms, as well
as from their appearance and texture, must, at least in
some cases, have existed before death, are chiefly com-
posed of fibrin.  Many of the wonderful  stories that
are recorded, and  sometimes on very good authority,
of worms  being found in the chambers of the heart, the
arch of the aorta, the sinuses of the brain, or the large
veins, must be explained upon the supposition, that the
spectators have  been deceived  by  portions of coagu-
lated fibrin, in the  form of long strings, possessing some-
what of the shape  and  form  of  worms,  to which a
lively  imagination  and  a fondness  for the marvellous
have added  the  other properties of these animals.
   Besides the action of the atmosphere generally on
the coagulation of  the  fibrin, experiments have been
made upon the effect of its constituent parts taken se-
parately,  and also of  other  gases  ; but although the
examination has been  pursued with considerable dili-
gence, the results are not so decisive as might perhaps
have been expected.   It must, however, be confessed,
that in performing experiments of  this kind, much ma-
nual dexterity is requisite, and that there are a variety
of circumstances, connected with the  state of  the at-
mosphere itself, the manner in which the blood flows
from the  body,  the kind of vessel in which it is  receiv-
ed, the temperature and other  conditions of the gas in
question,  and the manner in  which it is  brought into
contact with the blood, all of which may produce a no-
table difference in the result.   We find, therefore, that
although  some  respectable authors would lead us to
suppose that oxygen retards  the progress of coagula-
 tion, and  that it is promoted by carbonic acid and some
 other of the unrespirable  gases, yet  we are  informed
 by Sir H. Davy, that he could not  perceive any diffe-
 rence in  the  period  of  the  coagulation of  venous
 blood when it was exposed to azote, to nitrous gas, to 
Circumstances  retarding Coagulation.        353
oxygen,  to  nitrous oxide, to carbonic acid, to hydro-
carbon, or to atmospheric air.*
   I have mentioned above that the spontaneous coag-
ulation of the fibrin is prevented by sufficient agitation,
and the same effect is produced by the addition of cer-
tain neutral salts.  Hewson, to whom  we  are  princi-
pally  indebted for these facts, found that the sulphate
and muriate of soda and the nitrate  of  potash were
among the most powerful salts in this respect, so much
so, that if we add to a portion of blood rather less than
one-twentieth of its weight of any one of them  the co-
agulation does not take place.   On what this depends
we are  entirely ignorant; it would  not  appear to be
upon any tendency in the salt employed to dissolve the
fibrin, because the neutral salts do not possess this pro-
perty, at the same time that potash, which is the pro-
per solvent of fibrin, has less power in retarding its co-
agulation.  Besides the neutral salts, the  mere dilution
of blood with a sufficient quantity of water will effec-
tually  prevent its  spontaneous  coagulation.  We are
informed  by Crawford, that when blood is mixed with
twelve times its bulk of water, no  coagulation was ob-
served to take place for several hours,! an effect which
may perhaps be explained merely by the particles being
removed to so great a distance from each other, as  to
be placed beyond the reach of their mutual attraction.
   Among the changes which attend the coagulation of
the fibrin, I may  remark that its specific gravity is said
to be increased  by  this  process ;  but  this is  a point
which it must be difficult to ascertain, in consequence
of the serum  and the red globules which  are  always
mixed with the clot, besides  that  the firmness  of  the
clot, and  consequently its specific gravity,  differ very
much in different cases.  Haller, as it  would  appear
upon  the authority of  Jurin, states that the specific

       * Researches on Nitrous  Oxide,  p. 380.
       " On Animal Heat, p. 278.
              45 
354             Cause of Coagulation.
gravity of the crassamentum is 1*126,* the serum being
only 1*030;! but the fact  which was long since observ-
ed by Boyle, that the crassamentum floats in the serum,
so as to  preserve  the  surface  of  the two nearly on a
level, would seem to show that they cannot differ much
in their specific gravity.
   Much has been written about what is termed the
hahtus of the blood, or the vapour which arises from
it when it is first drawn from  the  body.  Plenk, who
has paid the most attention  to it, calls  it  gas animale
sanguinis; he conceives it to be composed of hydrogen
and carbon, and that it  produces many important effects
in the animal ceconomy .J  But I  believe that this opi-
nion is altogether unfounded, as the halitus is nothing
more than the aqueous vapour, which necessaril) arises
from a fluid considerably warmer  than  the air in con-
tact with it, and which, during its evaporation, carries
up a very minute quantity of animal, and perhaps even
of saline matter.§
  The cause of the coagulation of the fibrin has never
been satftfactorily explained : it is a phenomenon which
does  not exactly  resemble any other with which we
are acquainted, and  the operation  of external agents
upon it is not so well  marked  as to enable us to  refer
it to any general operation of  the physical  properties
of matter.   What renders the  subject more difficult is,
that there are some circumstances which affect the
coagulation of the  blood in a manner that we are  quite
unable to explain.   Many causes of sudden death  have
this effect;  lightning and  electricity;  a  blow upon the
stomach, or  injury to the brain; the bites of venomous
animals, such as  the viper and  the  rattle-snake;  some
acrid vegetable poisons, as laurel-water;  also excessive
exercise, and even violent mental emotions, when they

  * El. Phys. v. 2, 5.           t v. 3, 1.
  I Hydrologia, p. 42.          § Fourcroy, Syst. v. ix. p. 185. 
Life of the Blood.
355
 produce the sudden extinction of life, prevent the usual
 coagulation of the blood from taking place.*
   A singular coincidence has  been observed in  these
 cases between the want of coagulability in the fibrin of
 the  blood, and  the  diminution of contractility in the
 muscles after death.   They are all found in a state of
 relaxation, incapable of being excited by ihe accustom-
 ed stimuli; and it has been  further observed that the
 body is disposed to run rapidly  into the state of decom-
 position.  These facts appear to identify,  at least to a
 certain  degree,  the  property of muscular contraction
 with that  of the coagulation of the fibrin, and this iden-
 tity is further supported by  considering that the che-
 mical composition of fibrin is similar to that of muscle.
 For the knowledge of this relation between the coagu-
 lation of the  blood and the contraction of the muscles
 we are principally indebted to Hunter,  whc noticed it
 with much attention,  and built upon it some of his  fa-
 vourite physiological speculations.  It  is indeed proba-
 ble that we may trace to this source his celebrated hy-
 pothesis of the  life of the  blood, a doctrine which is
 founded upon the principle that a fluid  is capable of
 organization,  and that it may possess functions either
 identical with, or very similar  to those which are the
 most characteristic of the living animal solid.  Accord-
 ing to this  hypothesis  the blood is suppt >ed not merely
 to be the substance which  gives  life to the animal,  by
 carrying to all parts what is necessary for their support
 and  preservation, but that it  is  properly itself an orga-
 nized living bod\, and even  the peculiar seat in which
 the vitality of the  whole system  resides.!   The ques-
 tion  of the life of the blood cannot be fully examined,
 until we  are further advanced in our view of the ani-
 mal ceconomy, and especially, until I have endeavour-
ed to define the manner in which  the  term life ought
to be employed.   But I may remark,  that  even were
* Hunter on the Blood, p. 76.
t Hunter on the Blood, p. 7S. 
S56
Remarks.
 the Hunterian doctrine of the life of the blood  to be
 fully established, it would not offer any explanation of
 the cause  of its coagulation;  for  the  same difficulty
 still remains, in what manner the presence of life ope-
 rates  so as  to produce  either the coagulation of the
 blood or the contraction of the muscles.
   Perhaps the most obvious and consistent view of the
 subject is  that  the fibrin has a natural  disposition  to
 assume the solid form, when  no  circumstance prevents
 it  from exercising this inherent tendency.   As it is gra-
 dually added  to the blood, particle by particle,  while
 this fluid is in a state of agitation in the vessels,  it has
 no opportunity of concreting; but when  it is  suffered
 to lie at rest, either within or without the vessels, it is
 then able to exercise its natural  tendency.   In this  re-
 spect the coagulation of the fibrin of the blood  is very
 analogous to the  formation of organized solids in gene-
 ral, which only exercise  their property  of concreting
 or coalescing  under certain  circumstances, and  when
 those  causes, either chemical  or  mechanical,  which
 would  tend to prevent the operation, are not in action.
 Upon this principle we  shall  be induced  to regard the
 coagulation of the blood  as  analogous  rather  to the
 operation  by which the  muscular fibre  is originally
formed, than  to that by which its contractile power is
 afterwards occasionally called into action;  for, notwith-
 standing the  relations pointed out by Hunter, we shall
 find that the operations are essentially different  in two
 very important particulars—in the  causes  which pro-
duce them, and in  the subsequent  state of the  parts.
 The causes of muscular contraction,  as we have already
 had occasion to observe,  are exclusively stimulants  of
 various kinds, but  it does not appear that any  one  of
 these, numerous and various as they are, has the small-
 est effect in  promoting  the  coagulation  of  the blood.
 With respect to the subsequent  state of the parts,  in
 the muscle contraction  is always  succeeded by  relaxa-
tion, whereas nothing at all resembling this ever occurs 
Buffy Coat.
357
 in the blood ;  the fibrin, when  once formed,  remains
 unchanged as long as it retains its chemical composition.
 Upon the whole, therefore, although we must  acknow-
 ledge the validity of the facts  pointed  out  by Hunter,
 we are at present scarcely prepared to form them into
 a consistent theory;  and  we  must  content ourselves
 with  the simple statement, that the fibrin of the blood
 and  the  muscular  fibre possess,  the former  the  pro-
 perty of coagulation, and the latter that of contraction,
 which are acted upon in  the same manner by various
 circumstances, although we are not able, in these cases,
 to perceive the relation of cause and effect.*
   Before  I dismiss the  subject of the  coagulation of
 the fibrin, I must advert to a circumstance which  is
 of great  importance in the practice of medicine, that
 the nature and appearance of the coagulum vary very
 much according to the state of the  bod\. at the  time
 when the blood  is drawn.  The  most important of
 these  variations consists in what is  called the  size, or
 buffy   coat of  the blood,  a term employed to denote
 that state of  the crassamentum, when  the upper part
 of it  contains  no red  particles, but  exhibits a  layer of
 a buff-coloured substance, lying  on the  top of  the red
 clot.   This buffy coat is generally  formed when  the
 system is  labouring under inflammatory  fever,  and
 when, according to the modern doctrines of pathology.
 there  is  supposed to be an increased action of  the ar-
 teries.  The  immediate  cause of this  appearance in
 the crassamentum is  obvious;  the  globules, or  other
 matter which  give it the red  colour, begin to  subside
 before the coagulation is completed, so  that the upper
 part of the clot  is left without them.  The  remote

  * Upon  the same  principle which  induced me to notice John
 Hunter's hypothesis of the action of the heart, I shall quote his
 opinion respecting the coagulation of the blood.  « My opinion is
that it coagulates from an impression: that is, its fluidity under
such circumstances being improper, or no longer necessary, it co-
 agulates to answer now the  necessary purpose  of soliditv "  On
the Blood, p. 25.                                 J' 
,358         Opinions respecting its Formation.

cause of the buffy coat is not yet ascertained, although
many  experiments  have  been  made to  discover  it.
Hewson thought that the  fibrin  became specifically
lighter, and, of course, the red  particles comparatively
heavier, whence  they would be disposed to sink to the
lower  part of the clot; jie also  thought that the  blood
coagulated  more slowly.*   Hunter was inclined  to ac-
count for the appearance by  the  firmer coagulation of
the fibrin, as it were, squeezing out the red particles :
but this  would scarcely explain why the upper part of
the clot  alone is left without them.  Hey's opinion is
perhaps  better founded,  that by the increased  action
of the  vessels the different  constituents of the  blood
are more intimately  mixed together,!  while Dr.  Davy
opposes the  opinion of Hewson as to the  fact of the
slower coagulation  of inflamed blood-!  From  some
experiments that were performed  on the  composition
of the buffy  coat by Mr. Dowler, it  appears that it
contains  a very large proportion of serum,§ and  this,
by diminishing its viscidity, will more readily  allow  of
the subsidence of  the red particles.  It is, however,
not improbable that  Hunter's  opinion is in  part cor-
rect, for we find  that  the clot of inflamed  blood  obvi-
ously  possesses a firmer  texture  than  in its ordinary
state, so that sometimes, in  consequence of the con-
traction of the clot,  after it has begun to form, the
surface has a depression  in the centre, forming  what
is called the cupped state of the coagulum.   And here
we  have another analogy between the blood and the
muscles; for  there are several circumstances  which
lead us to  conclude, that the  force of muscular con-

  * Experimental Enquiries, p. 39, 59, et alibi.
  t Observations on  the Blood, p. 10,  19, et alibi.
  X Phil. Trans, for  1822, p. 271.
  § Med. Chir. Trans,  v. xii. p. 91.  Hewson conceived that the
buffy coat is composed of fibrin, but that in inflammation the fibrin
acquires a thinner consistence,  p. 34, 45, et alibi. 
Sympathetic Powder.
359
traction  through  the system generally is increased in
inflammatory fever.*
  It is probably  upon  the fibrin  that  the property
which the blood  possesses of repairing the injuries of
the  solids principally depends, a  property which af-
fords us one of the most  interesting examples of the
resources of the animal  ceconomy, while, at  the same
time, it very  forcibly illustrates  the slow progress of
medical information, when the mind has once  received
an impulse  in a wrong  direction.   Every one  who is
acquainted  with the  history of surgery is  acquainted
with the  sympathetic powder, which, about  the mid-
dle of the seventeenth century, engaged the notice and
received  the sanction of the most learned men of the
age.  This celebrated  remedy derived its  virtues not
from its  composition,  but  from the mode of its  appli-
cation, for it was not to be applied to the wound, but
to the weapon by which the wound was inflicted; the
wound  was ordered  to  be  merely closed  up, and was
taken  no further care  of.!   Most  men  of sense,  in-
deed,  ridiculed the   proposal, but after being  fully
tried,  it  was  found  that  the sympathetic  mode of
treating wounds was more successful  than those  plans
which proceeded  upon what were considered  scientific
 firinciples ;  and it continued to gain ground  in the pub-
 ic estimation, until at length some innovator  ventured
to try the experiment of  closing  up the  wound with-
out  applying  the sympathetic powder to  the  sword.
Wiseman, who wrote about fifty or sixty  years after
the  introduction of this mysterious  operation  by Sir
Kenelm Digby, in describing the  importance  of keep-

  * It may not be uninteresting to peruse the account which Sy-
denham gives of the buffy coat of the crassamentum of the blood
in pleurisy  ; his observations will be commonly found to  be correct,
although his  hypotheses are too often fallacious.  Observ. circa
Morb. Acut. Hist. § 6, c. 3.
  t See " A  late Discourse, &c." by  Sir K. Digby, a  treatise
which admirably  exemplifies the mode of philosophizing that wai
fashionable in the earlier part of the seventeenth century. 
360
Re-union of Divided Parts.
 ing the divided  parts in close union, says,  " for  here
 nature  will truly act her part, by  the  application of
 blood and  nourishment  to both sides indifferently, and
 finish  the  coalitus  without  your  further  assistance.
 And this is that  which gives such credit to the sympa-
 thetic  powder."*
   Although  we  are  now  well  acquainted  with  the
 general facts respecting  the re-union of divided parts,
 yet there  is much obscurity  concerning the exact mode
 of the operation.   We find  that when two  newly cut
 surfaces, which  were  not  previously  connected,  are
 laid in  close apposition, and  the air carefully excluded,
 they will unite, and when the  operation is  performed
 under favourable circumstances, the trace of  the wound
 is scarcely  perceptible, either in  the structure or func-
 tions of the part.   What will appear  more  wonderful
 is, that parts  of different structures are capable of con-
 tracting this close  union, the arteries, veins, and even
 the  nerves, becoming connected, each  to each; and to
 add still further  to  the marvellous aspect of these
 operations,  we  cannot avoid giving  our assent to the
 fact, that portions of the  body, which had been entire-
 ly cut off,  or even of a different  body,  if  speedily ap-
 plied to a recently divided surface,  will unite  and re-
 tain their functions.!   Although, in a great majority of
 instances, we shall find ourselves in the  right, if we
 disbelieve   the  wonderful talcs that we  find  in  the
 works of the older writers, yet our scepticism may be
 carried  too far;  and accordingly  it is now  admitted,

  * Chir. Treat, b. 5, c. 1, p. 342.
  t J. Hunter caused the spur9 of a young cock to adhere to the
 comb of another cock, and  the testicles were found to become
united to the internal  cavities of other animals.  He remarks,
" The most  extraordinary of all  the  circumstances respecting
union, is by removing a part of one body and aft'?rwarils uniting
it to some other part of another, where, on one side, there can be
no assistance given to the union, as the divided or separated partis
hardly able to do more than  preserve  its own living principle, and
accept of the  union."  Treatise on the Blood, p. 20fi. 
                Re-union of Divided Parts.             361

  that  the operations of  Taliacotius, or  Tagliacozzi,  a
  name which could not until  lately be  admitted into a
  serious discussion, were  founded upon  correct princi-
  ples.   It appears, indeed, that a  process of an analo-
  gous nature had  been long practised in India, and  has
  been  introduced into this country,  with complete suc-
  cess, by  Mr. Carpue.
    As I have already stated, we have reason to believe
  that  the fibrin is the intermedium by which the  pro-
  cess is effected, yet I confess  that I know of no rational
  method in which  we can explain the successive steps
  of  the operation.  We   may, indeed,  conceive of the
  divided end of an artery, which belongs  to the cut sur-
 face nearest  the heart, discharging a  portion  of its
 fibrin, which may coagulate, and form a  basis, or nidus,
 as it has been termed, through which  the current of
 blood  may afterwards  form  a new channel;  but  in
 what  way  this  stream is to discover  the ends of  the
 arteries of the other  surface, by  what  power it is to
 enter  them, how  these  insulated  parts  are to propel
 their  blood into the veins, and lastly, how the veins of
 the divided part are  to transmit their contents into the
 veins of the body, are questions that at present, 1 ap-
 prehend, we are not able to answer.*
   A curious series of  facts relative to the coagulation
 of the blood, and to the  mode  in which portions of
 coagulum  acquire an organized  structure,  has been
 lately  brought forwards by Sir Everard  Home, princi-
 pally derived  from  the   microscopical observations of
 Mr. Bauer.   It is stated that a  quantity of carbonic
 acid is always present in the blood, that, during  its

   * It may be amusing to observe the uses which are ascribed to
 the crassamentum of  the  blood by  Plenk, a writer of extensive
 information and general accuracy.   The  uses that he points out
 are three ;  1. (to employ his own words) " sanguini ruborem con-
 ciliat;" 2.  by the gravity of its metallic ingredients, it irritates
 the heart and arteries more effectually than the  lighter particles
 of serum ;  3. at the same  time it imparts  motion to the lighter
particles of the serum.
                      4fi 
362           Re-union of Divided Parts.
coagulation,  this  acid  is  extricated, and  that by its
extrication it forms linear  passages or tubes in the sub-
stance of the blood, into which the vessels of contiguous
parts are elongated,  and which become the rudiments
of the future arteries.   It would appear that the serum
is the  nidus  in  which these tubes are formed, as they
are said to be altogether independent of the globules,
which are supposed to be the more immediate consti-
tuents of the fibrin.   It is  not expressly stated whethe^
the tubes are themselves  converted into blood-vessels,
or whether  they only afford spaces in which vessels
are formed, nor does it seem quite clear what connexion
the spontaneous coagulation of the fibrin has with the
production of  the tubes.   Without calling in question
the accuracy of Mr. Bauer's observations, it  may be
remarked,  concerning the  hypothesis that  is deduced
from them,  that the formation of regular  tubes could
not be the  result of the  extrication of gas in a viscid
fluid, the formation of the tubes must therefore be the
result  of a tendency in  the fluid  in question to  assume
an  organic  arrangement.  The  observations  of  Mr.
Bauer are  valuable,  as showing the mechanical struc-
ture which the blood exhibits, during  the  process by
which it becomes organized, but, I apprehend,  they
throw no further light upon the operation.*  We  can-
not be surprised that so subtile a property as that by
which the  blood  is enabled  to acquire an organic ar-
rangement should be destroyed by its being subjected
to the action of the air-pump.!

  * Phil. Trans, for 1818, p. 181, et seq.; for  1820, p. 2.
  t Since the  above was  written Dr. Davy  has  published the
result of some  experiments on the subject, from which, as well as
from other considerations, he concludes that Sir Everard Home's
hypothesis is so far unfounded as  respects the existence of car-
bonic acid in the blood.   Dr. Davy remarks, that the gas observed
by Mr. Bauer  is probably azote, implying his belief that gas of
some kind or other is contained in the blood.  His experiments
would,  indeed, lead to the opinion, that there is no gas in recent
blood.  Phil. Trans, for  1823. p. 506.  But. on the contrary, the 
Leeuwenhoeck's Account.
363
   With respect to  the chemical  properties  of  fibrin
 it is  sufficient to remark, that they appear exactly to
 resemble those of the muscular fibre;  it is acted upon
 in the same  manner  by nitric acid and the other re-
 agents, so as to be fully entitled to the appellation of
 liquid flesh, which was bestowed upon it  by the  older
 physiologists.   For  the first correct  account of  the
 chemical relations  of fibrin we are indebted  to Four-
 croy, Vauquelin, and  Berthollet;  it  has  been lately
 examined by  Berzelius,  whose  experiments  may be
 regarded as the most correct that we possess upon the
 subject.*

                 § 4.  Red Particles.

   After having described  the fibrin, I  proceed to  the
 other constituent of the  crassamentum, the red parti-
 cles or globules.!  These, from the singularity of their
 appearance and organization, have attracted an unusual
 share of attention, and have been the  subject of almost
 innumerable observations and experiments.   Soon after
 the   microscope was  introduced into  anatomical  re-
 searches, these peculiar bodies were observed by Mal-
 pighi, and they  were  afterwards more minutely  exa-
 mined by Leeuwenhoek.   They were at first described
 simply as globules floating in the  serum, and giving the
 blood its red colour,  but as observations were  multi-
 plied, errors  and absurdities  were  advanced  in an
 almost equal  proportion.   Leeuwenhoek  himself in-
 vented a fanciful  hypothesis,  which  had a long and

 existence of carbonic acid in blood, or at least the fact that  carbo-
 nic acid may be disengaged from blood, by merely removing the
 atmospheric pressure, seems to be established by Vogel, Ann. Phil.
 v. vii. p. 57; and by Mr. Brande, Phil. Trans, for 1818,  p. 181.
  * Med Chir. Trans, v. iii. p. 200.
  t I have retained the  ordinary description  of the clot, as com-
posed  of fibrin and the red globules, although some late experi-
ments, of which an account is given below,  throw a degree of
doubt upon its accuracy. 
364
Hewson's Account.
 powerful influence  over the most  enlightened  physio-
 logists, that the red particles of the blood  were com-
 posed  of  a series  of globular  bodies  descending  in
 regular gradations; each of the red particles was sup-
 posed to be made up of six  particles of serum, a par-
 ticle  of scrum  of six  particles of lymph, &c*  1 his
 hypothesis, for which  there really does  not  appear to
 be the  slightest foundation, was so suited  to the mecha-
 nical  genius of the age, that it  was generally adopted
 without any examination of its truth,  received as the
 basis  of many  learned speculations in  that  and the
 succeeding age, and even formed a leading feature in
 the pathological speculations of Boerhaave.  The  fu-
 tility  of the doctrine was  exposed  by  Lancisi  and
 Senac,  but it still maintained its ground  until the time
 of Haller.   When  objects can  only  be  detected  by
 highly magnifying lenses,  it is so extremely  difficult  to
 avoid being  misled  by ocular deceptions, that  all de-
 scriptions of this kind  are to  be  received  with the
 greatest caution.  The necessity of this caution is suffi-
 ciently  proved by the  discordant accounts,  respecting
 the red globules of the blood, that  have been given by
 different observers, who could have no apparent motive
 for intentionally imposing  upon  their readers.
   Next to the observations of Leeuwenhoek, those  of
 Hewson were the most elaborate, and had at least the
 appearance of  great accuracy.   He describes the red
particles as consisting of a solid centre, surrounded by
a vesicle filled  with  a  fluid.  He informs us, that  by
adding  water  to them they swell out,  the   surround-
ing vesicle becomes  thinner, and at  length bursts, and

  * For  an account  of Leeuwenhoek's supposed discoveries re-
specting the constitution of the globules, see Martine, in Ed. Med,
Ess. v. ii. p. 74, &c.; the whole of this Essay is well worth perus-
ing, as a curious specimen of the  mode of prosecuting physiolo-
gical inquiries, that was pursued by  the learned mathematicians
about a century ago.  The  earliest of Leeuwenhoek's papers ap-
pears to be in the Phil. Trans, for 1674, No. 23. 
Hunter's Account.
365
 leaves  no trace behind;  the whole substance of the
 particles is soluble in water, and imparts to it their red
 colour.   It appears also that those animals which have
 white or rather colourless blood, possess particles which
 are supposed to be similar in  their general form and
 organization to those of the  red-blooded animals;  we
 are likewise informed that they  are of  different sizes
 in different animals, and that their size  bears no ratio
 to  that of the animal  from which  they  are taken, as,
 for example,  they are said to be  of  the  same size  in
 the ox  and the mouse, larger in birds, and  to be the
 largest in the skate ; in  birds, amphibia, and in insects,
 they are elliptical, but, excepting in  their  form,  they
 resemble those of the  human subject.   We  have an
 account of some singular  changes that  are  produced
 upon their colour  and  form by various chemical  re-
 agents, especially by some saline bodies.  Alkalies and
 acids, when moderately  strong, first  corrugate the ve-
 sicle, and afterwards seem to  dissolve  or  decompose
 the whole of the globules; nitre has  the property of
 considerably heightening the  colour, so as to convert it
 to a bright red, while, on the contrary, there are some
 other substances by which their colour is destroyed
 without changing their form.*
  Hunter, who made  many observations on these bo-
 dies,  differs  essentially  in  his  account of  them  from
 Hewson.  He is silent respecting the central nucleus
 and the investing vesicle ;  there are some animals in
 which he could not discover any globules, as  the silk-
 worm and the lobster, and he never observed them, in
 any case, to  assume the elliptical form,  described  by
 Hewson.  He does not  regard them as properly solid
 bodies,  but as liquids  possessing a central attraction,
 which  determines  their figure;  a  circumstance that
might identify them with substances of an oily nature,

  *  Phil. Trans, for 1773, p. 303, et seq.; Tab. 12,  Also Exper.
Enq. v. iii. ch. 1. 
366
Founds Account.
were it not stated, on the other hand, that the globules
are miscible with water, and that they always preserve
the same size, and are never disposed to run together
or coalesce.*                                     .
  The globules of the blood have  been also examined
by the Abbe Torre, by Monro, and more lately by Dr.
Young.   Torre supposed them to be  flattened annular
bodies, or like rings composed  of a number of separate
parts  cemented  together;!  to Monro they exhibited
the appearance of circular flattened  bodies like  coins
with a dark  spot  in  the centre,  which he conceived
was not  owing to a perforation, as Torre had imagined,
but only to a depression.!  Some  remarks were  pub-
lished on the subject  by Cavallo, who conceived  that
all these appearances were deceptive, depending  upon
the peculiar modification of the rays of light, as affect-
ed  by the form  of the particle, and he concludes that
they are in fact  simple  spheres.§  But  the  account
which Dr. Young has  recently given  of these  bodies,
fo a certain extent,  coincides  with  the description of
Hewson.  He remarks that if the globules be viewed
by a strong light, they will appear like simple transpa-
rent spheres, but  that if we examine them by a confined
and diversified light, we shall be better able to ascer-

  * On the Blood, p. 40, et seq.  Mr. Bauer, however, found that
when the investing vesicle is removed, the nuclei are disposed to
unite together, and upon this  property the formation of the muscu-
lar fibre depends.  Phil. Trans  for  1818, p. 176.  MM. Prevost
and Dumas, in like manner, suppose  that the  crassamentum of the
blood, in the act of its spontaneous  coagulation, is formed by the
central globules adhering together in the form of fibres.   Ann.
Chim. et  Phys. I. xxiii. p. 51.
  t Phil.  Trans, for 1765, p. 252, et seq.
  X We must not omit noticing the result of Prof Amici's examina-
tion of the globules, as given us in the Edin. Med. and Surg. Journ.
vol. xv. p. 120.  It may afford curious matter  for speculation to
those who place much confidence in microscopical observations;
it is, however, proper to observe  that the statement does come
directly from the author himself
  § Medical  Properties of Factitious Airs, p. 237, et seq. 
Size of the Globules.
387
 tain their real figure and  structure.   The particles of
 the  blood of the skate, from their size and distinctness,
 are  the most  proper for this kind of  examination,  and
 he found their form to be like that of an  almond, but
 less  pointed and a little flattened;  they consist  of an
 external envelope containing a central  nucleus.  This
 nucleus is independent of  the substance with which it
 is surrounded, for when  this latter has been  removed
 or destroyed, the nucleus still  appears  to  retain  its
 original form.   The nucleus is much  smaller  than  the
 part surrounding it,  being  only about  one-third  the
 length and one-half the breath of the whole particle.
 We are informed that the entire particle of the  hu-
 man blood is not  larger than  the central part  of  the
 particle of the  skate.  Dr.  Young found that the par-
 ticle in the  human subject is flattened, and has  a  de-
 pression in the centre, somewhat as was described by
 Monro, but much less in degree.*         *
   There has  been as  much  difference  of opinion  re-
 specting the size, as the form of these particles. With-
 out recurring to the older and less correct observations,
 it may be  sufficient  to  give  those of Dr.  Young,
 Captain  Kater,  and  Mr Bauer; Dr.  Young! and Cap-
 tain  Katerf both agree that the particles of the hu-
 man blood  are  between ^oVe and tcw  of an inch in
 diameter, or taking the medium, rsirs of  an inch.  Mr.
 Bauer supposes them to be  considerably  larger; in
 their entire state he estimates them at -rrm of an inch,
 and  even when  they have lost their external part,  the
 nucleus is said to be 2^ of  an inch in diameter ;§ it is
 not stated whether the observations of Dr. Young and

  * Med. Liter, p.  545.  Mr. Bauer has observed that the form of
 the globules of the skate is oval during the life of the  animal, but
becomes flattened after its death ;  this circumstance may perhaps,
in some measure, tend to reconcile the discordant statements  that
we meet with on this subject.  Phil. Trans, for 1818, p. 174.
  t Med. Liter, p.  555.      J Phil. Trans, for 1818, p. 187.
  § Phil. Trans, for 1818, p. 173. 
368
Iron in the Blood.
Captain Kater were made  upon the entire globule, or
upon the central  part only.   These estimates unfortu-
nately differ so much from each other, as to throw a
considerable doubt  upon their correctness; but, upon
the whole, I feel disposed  to assent  to the statements
of Dr. Young and Captain  Kater, from  their  coinci-
dence with each other, although made with a different
kind of apparatus*
  The composition and  chemical  properties  of  these
bodies still remain  the  subject of controversy, for al-
though they have engaged the attention of some of the
most acute of the modern chemists,  the results which
they have obtained are so discordant,  that we  cannot
deduce any consistent or decided conclusion from them.
This, in  some  measure, depends upon the  difficulty
which there is  in  procuring  them in a  separate state;
there appears to be no method of detaching them from
the serum in which they are  enveloped, without at the
same  time dissolving at least their  external covering,
and  perhaps affecting the consistence of the  whole.
The experiments of Berzelius are the  most elaborate,
and  probably those  on  which  we ought  to place the
most confidence ;  but I  think it  may  be objected to
them, that according to the method which he adopted,
the external  part of the globule  would  be removed,
while  the  nucleus  would  be necessarily mixed  with
some of the other ingredients of the  blood.  His result
is, that these particles do not materially differ  from the
other parts of the blood, except in their colour, and in
the circumstance  of a quantity of the red  oxide  of iron
being found among their ashes after#j£mbustion.!
  The discovery  of  iron in the bloocr%>pears to have
been originally made by  Menghini4 and has been fully

  * Cavallo states that the particles varied in size, the larger being
0003 and the smaller 0004 of an inch in diameter, p. 249.
  t Med. Chir. v. iii. p 212, et seq.
  X Menghini's Memoir (Bonon. Comment, t. ii. pars 2, p. 244, et
seq.) gives an account of a prodigious number  of experiments 
Iron in the Blood.                  3QS
confirmed by late observers, although they have differ-
ed very  much both concerning  the amount of the iron
and the  state  in which  it  exists.   Menghini himself,
and some of  the  earlier  chemists,  seem  to  have  very
much over-rated it;  Fourcroy's  account does not ena-
ble  us to ascertain the quantity of  it in the blood  with

which he performed on the blood of various animals, as well as other
animal substances.   Most of the experiments are related only in a
summary manner, but some of them  are  detailed with more mi-
nuteness.   In the first series  he used  five  ounces (2400 grains) of
the blood of a dog, and by calcination  he obtained 24 grains of re-
siduum, to which he applied a magnet, and found very nearly the
whole  to be attracted by it.   The calx consisted of  two kinds of
particles;   the one,  " splendidiores,"  which were the most easily
attracted;   the other, " colore  ad crocum  martis vergentes," also
magnetic,  but less so than the  former, p.  245, 246.   As the Bolo-
nese Commentaries  may not  be accessible to  every one, I shall
transcribe an experiment that was made upon human blood.   " Hu-
mani enim sanguinis globulos unius librae  vehementissimo igne di-
midiam horam vexavimus : vexatos ebullire primum aliquantisper,
turn  ex improviso flammulam  emittere conspeximus.  Erat haec
eaerulea ad inslar earum rerum sulphurcarum,  qure solitae sunt ad-
hiberi  ad transmutandum ferrum in chalybem.  Metus fuit ne emis-
sa flammula, cum materiam omnem absumeret, curiositatem quoque
nostram eluderet.  Quapropter subsidentem in vase materiem illico
supra porphyritem Lellius effudit.  Haec granorum 28 ponderis in-
venta est. • Hanc postea cum supra eburneum planum extendissem,
in grandiuscula quaedam corpora, inter quae unum  eminuit figura
subrotundum, magnitudine ceteris praecellens, granum  parvuli cice-
ris adaequans, offendi.  Periclitari hinc, volui an ad cultrum mag-
neticum omnia accederent; accesserunt autem super ea velocitate,
qua solet ferrum purissimum.   Porro corpusculum illud, quo cete-
ris magnitudine praestabat, discissum et fractum, intus cavum, ni-
tentibus lineis distinctum, figura, duritie, et colore ubicunque simil-
limum fuso ferro,  mediocris lentis auxilio cognovimus." p. 260,
261.  On  this subject it will only  be necessary  to  remark that
Menghini's paper affords one instance out  of many others, written
at that  period,  where we may be assured that  the facts as stated
cannot  be true,  yet where it is  not  easy to assign the source of
fallacy, or  to determine  in what degree  the experimentalist was
himself deceived or wished to deceive others.   Plenk, Hydrol. p.
38, says that Rhades discovered  the  iron  in  the blood.   In 25
pounds of blood,  the average  quantity in a man, he found two
drachms of oxide of iron.   Vauquelin says that Lemery discovered1
'*<•   Ann. Chim. et Phys. t. i. p. 9.
             47 
370
Colour of the Blood.
any degree of accuracy,* but we are informed by Ber-
zelius, that the colouring matter of the blood, separat-
ed from the other  part, leaves one-eightieth of an  in-
combustible residuum, of which rather more than one-
half is an  oxide of  iron.!
  We have hitherto been unable  to ascertain  in what
state  this  iron exists; it  would appear  not  to be in the
form  of any of the known salts of this metal, because,
before the blood has  been calcined, we cannot detect
the iron  by the tests which  usually  indicate  its pre-
sence, yet its solubility  in the  serum,  on the  other
hand, would seem  to favour the opinion of its possess-
ing  something analogous to the saline state.  Berzelius
has performed many experiments on this point, but  his
conclusion is merely a negative  one,  that he has  been
unable to combine  the serum with any salt of  iron, so
as to  produce a compound similar to the  colouring mat-
ter of the blood-!
  The existence of iron in the globules of  the blood is,
however, clearly  proved;  whatever  difficulty  there
may be in determining the state in which it exists, and
from  the property  which iron  possesses  of colouring
the substances with which it is  united, it has generally
been  supposed  that the iron gives  the blood its red
colour.   We are not, 1 apprehend, in possession of any
facts  by which  this opinion  can  be either  decisively
proved or disproved, but I  think it may  be admitted
as a  probable presumption.. It  has indeed  been op-
posed by  some writers of high authority;  of these one
of the first, both in point of  time and of respectability,
is Wells.§  But  his experiments  seem  to me only to
prove that the colour of the blood is not occasioned by

  * System, t. ix. p. 207.      t Med. Chir. Trans, v. iii. p. 215.
  X Med. Chir. Trans,  v. iii.  p. 221.  Fourcroy and Vauquelin an-
nounced, as the result  of direct experiment, that the iron of the
blood  was  in the state of sub-phosphate, but  Vauquelin has since
retracted this opinion.   Fourcroy's System, v.  ix. p. 207, 208.
  & Phil. Trans, for 1797, p. 416, et seq. 
Vanquelin's Experiments.
371
any salt of iron, or  of iron  in  such a  state as  to be
affected by the ordinary tests, which is admitted to be
the case.   Mr. Brande has also attempted to  prove
that the colour of the  blood  does not depend upon
iron,* because he found the indications of the presence
of iron to be as considerable in  the parts of the blood
that are without colour as in the globules themselves;
and indeed his  results  would  rather tend to prove that
the quantity of iron in the blood is too  minute to pro-
duce any effect in it,  than  to explain its action on the
different component parts of this fluid.   But with re-
spect to the quantity of iron, I may remark that they
are at  variance with the later and apparently more
elaborate  experiments of Berzelius.
   A series of experiments have been lately performed
on the colouring matter of the blood by  M. Vauquelin,
which he  regards  as confirming  the conclusion of Mr.
Brande.  They consisted  in digesting the  crassamen-
tum in diluted  sulphuric acid, which dissolves a portion
of the albumen and fibrin, together  with  the colouring
matter, which  last is thrown down separately from the
solution by ammonia.  The  colouring matter subsides
from the  fluid, and, by  sufficient  washing, may be ob-
tained, as it is supposed,  in a pure  state; if it be then
diffused through water it produces a fluid of a purplish
colour,  in which the presence of iron is not indicated by
the usual  tests, while  they readily detect it in the fluid
from  which the colouring matter has subsided.!  But
I apprehend that  this cannot be considered as deciding
the point; for we  may observe that after the crassa-
mentum  has been subjected to the action of these  re-
agents, the constitution and chemical properties  of  its
component parts will  be considerably altered, so as not
to afford  us any  certain indication of  their previous
state.   Besides, although the precipitate that is formed

  * Phil. Trans, for 1812, p. 90, et seq.   »
   t Ann. Chim. et Phys. t. i. p. $. 
372          Effect of Air upon the Blood.
 upon the addition of the  ammonia be a substance of a
 purple colour,  we do not  seem  to have any evidence
 that it is composed of the red  particles as  they natu-
 rally exist in the blood ; and  we may further remark
 that the experiments of M. Vaucjuelm differ essentially
 from those of  Mr. Brande, inasmuch as Mr. Brande's
 results tend to prove the almost total absence of iron
 in the blood.
   One of the most remarkable properties  of  the red
 globules is the change which is effected in their colour
 by the action of  the  different  gases.   Lower noticed
 the greater brightness of  the upper and external part
 of the clot, when exposed to  the air, and attributed it
 to its proper cause,* but the mathematical  doctrines,
 which were so  prevalent about  this period,  led to a
 different explanation  of the fact.   Cigna  of Turin,
 about 60 years ago, revived the  doctrine  of Lower,
 and confirmed  it by some  ingenious experiments, but it
 is remarkable that he afterwards almost  abandoned  his
 own  hypothesis.!   The  subject  was  then taken  up
 by Priestley, and  he  not only fully  established  the
 point, that  the  bright  rgd colour  of the external
 part  of  the  crassamentum  depends upon  the action
 of the  atmosphere, but  he proved that  it  is owing
 to the oxygenous part of the air alone, and  that car-
 bonic  acid  and  azote   have  precisely the  contrary
 effect, reducing bright scarlet blood to the purple co-
lour.:!;  We  have every  reason  to suppose  that  it  is
 the red  particles of the  crassamentum  on  which the
 air more particularly acts,§ and as these  would ap-

  * De Corde, c  iii  p. 178.
  t Priestley on Air, v. iii. p. 357, et seq.
  { Ibid. p. 363, et seq.
  § We learn from Berzelius, that " blood, in which the colouring
 matter is still contained, absorbs oxygen  gas very quickly, when
 out of the body and shaken in atmospheric air ;....on the other hand,
serum, when destitute of colouring matter, does not change the at-
 mospheric air before it begins to putrify."  View of Animal Che-
 mistry, p. 36. 
Globules of the Blood.              373
 pear to differ in  their chemical constitution from the
 other constituents of  the  blood,  principally in the
 iron  which  they   contain, it seems  a natural, conclu-
 sion  that  the  iron,  however  minute  in quantity, is
 the  agent by  means of  which the  blood  acts  upon
 the  atmosphere.   Of this,  however,  it  is admitted
 that  we  have  no decisive  proof, and  that until we
 know in  what state  the iron  exists  in  the  blood, we
 can   form no  more  than  a  conjecture  on  this  point.
   Both  from the  microscopical  observations  and the
 experiments  of various  kinds  that  have been  made
 upon the red  particles,  it would seem  probable that
 their colouring  ma'ter  is  principally or entirely seat-
 ed  in  their external  covering,  and  that the central
 nucleus itself is  without  colour.  From this  circum-
 stance it  had been generally supposed  that the par-
 ticles  were soluble in water, but  Dr.  Young  informs
 us that  it  is  merely  the  envelope,  which  contains
 the colouring matter, that  is  so, and  he  points out
 a  method by which  the  central nucleus may  be pro-
 cured, retaining its perfect  form in  water,  after the
 red  part  has been dissolved.*
   Besides the  oidinary  globules  of  the  blood, Mr.
 Bauer has given us an  account of another  species of
 globules, which  would appear to be essentially different
 from  the  former, both in  their nature and properties,
 and in the relation which  they bear  to the other con-
 stituents of the blood.  He first detected them in the
 serum, where he  observed them to  be actually  gene-
 rated while the fluid  was under examination.  Minute
 spots made their appearance, which gradually  increas-
 ed in bulk, until some of them attained the size of the
globules of the blood  when deprived of their colouring
 matter.   We are  informed that these globules are ge-
nerated in serum after  it  has been removed from the
vessels for some days; it  would appear, therefore, to
* Med. Lit. p. 347 
374
Lymph Globules.
be independent of any property in the fluid that is con-
nected with vitality, or its  tendency to organization.
Similar appearances were detected in  pus, which is
stated to be, in the  first instance, an homogeneous fluid,
and that globules gradually make their  appearance in
it.  It does not appear that the  serum is actually com-
posed of these globules, but that they are formed from
its constituents.   Sir Everard Home gave them  the
name of lymph globules.*
  Mr. Bauer  afterwards observed these lymph glo-
bules in the coagula of an aneurysm,  where they exist
along with the  ordinary blood globules, the lymph glo-
bules being in greater proportion in the  older coagula,
until it appeared that the oldest were almost entirely
composed  of them.  The globules in   these  coagula
were rrcs  of an inch in  diameter, and were supposed
to be the same  that had been previously  observed in
the serum.  The buffy coat  of  inflamed blood  is said
to consist almost entirely  of these lymph globules, a
circumstance which appears somewhat inconsistent with
the  fact  previously noticed, of their  being found in
greater abundance  in  old  coagula, and  with a remark
which is subsequently  made, that in tumours, the firm-
er and older  parts are  principally composed  of the
lymph globules, and the more recent principally of the
ordinary blood globules.   From  some  of Mr. Bauer's
observations it might be  inferred that  these lymph
globules are merely the ordinary blood  globules de-
prived of their envelope  of colouring matter, but there
are  other  facts stated which seem incompatible with
this idea.!
   It is not impossible that these  lymph globules may
be the origin of Leeuwenhoek's descending series, and
 it affords us a  striking illustration of the  mode in which
 microscopical observations may be warped and accom-

       * Phil. Trans, for 1819, p. 2, et seq.
       t Phil. Trans, for 1820, p. 2, et seq. 
Coagulation of Serum.
375
 modated to a preconceived theory, even by a person of
 skill, science, and integrity.

                     § 5.   Serum.

   After this account of the crassamentum of the blood,
 we now proceed to the serum, or the fluid part which
 is left  after the separation of  the clot,  in consequence
 of the  spontaneous coagulation of the  fibrin.  Serum
 is a transparent, hom< geneous liquid, of a light straw
 colour, a saline taste, and an adhesive  consistence. Its
 specific gravity varies in different subjects, but it is al-
 ways greater than that of water; the average is  pro-
 bably about  1.025.*   It converts blue  vegetable  co-
 lours to green, thus  proving that it  contains a quantity
 of uncombined  alkali, and  besides  this it is  found to
 hold in solution various earthy and  neutral salts.   Its
 most remarkable and characteristic property is its co-
 agulation by heat:  we find  that  when the  serum  of
 the  blood is exposed to a temperature of 160°,! it be-
 comes white and opake, and acquires  a  firm consist-
 ence.   In this state  it exactly  resembles  the white of
 the  egg, when hardened by boiling,  and is found to be
 essentially the same with this substance, whence it  has
 obtained the name  of albumen.   Although the whole
 of the serum appears to be  converted into a solid mass
 by the  process  of coagulation,  yet,  if the albumen be
 cut into small pieces, and placed  in the mouth  of a
 funnel, a fluid drains from  it, which  is  called  the  se-

  * Marcet, in Med. Chir. Trans,  v. iii.  p. 363.
  t Dr. Thomson quotes Cullen as st-iting  that the coagulation or
 albumen takes place at 165°, but Without any particular reference;
 Cullen,  in his  "Institutions,'' p. 206,  fxes the degree at 156.
 Fourcroy, in his " System," v. ix.p. 190, iixes it at 75 C. i. e. 167
 F.; while in Ann. Chim. t. vii. p. 156, he names 55 R i. e. 155*75
 F.; 160 is the degree assigned by Henry,  Children, Brande, and
 Ure. MM. Prevost and Dumas, in tome recent experiments, state
the degree to be " autour de 70 Cent." i. e. 158 F. Ann. Chim, et
 Phys. t. xxiii. p. 53. 
376             Coagulation of Serum.
rosity of the blood.   The separation  of  the  serosity
may be  further promoted by washing the coagulated
albumen in hot water,  and after this process has been
continued for a sufficient length  of time, the albumen
is  left pure, united  only with a  quantity of  water;
this, by the application  of a  moderate heat, may be
expelled, when the substance  assumes  the appearance
of a scmitransparent solid, both  in its  physical  and
chemical properties similar to the  harder varieties of
membrane, except that it does not exhibit any appear-
ance of an organized  structure.
   The coagulation of albumen is  an operation which
must  be  regarded as  essentially  different  from  the
spontaneous coagulation  of the  fibrin, although they
are both designated by the same appellation, inasmuch
as they are produced  by totally different means; the
one by mere rest,  which has no  effect  upon  the other,
while, on the contrary,  heat, which does  not  produce
the  concretion  of the  fibrin,  immediately converts
albumen into the solid form.  The texture also  of the
coagulum is different in  the two  cases ; the fibrin has a
tendency to arrange  its  particles in a specific  manner,
so as to present the appearance  of an  organized body,
but nothing of this kind  takes place  with  respect to
the albumen;  it simply concretes into a mass of an
uniform  consistence,  in  which  the albumen remains
united to the water that previously held it in  solution.
   Besides heat, there are other  agents which are said
to coagulate albumen;  alcohol, acids, metallic  salts,
and tan, and, according to the curious discovery  of Mr.
Brande,  it may be also effected by the negative wire
in the interrupted galvanic circle.  But I apprehond,
that in these cases, although the  whole  or  a  part of
the  albumen  is  converted into the  solid  form, the
operation is  very  different from that  of heat.  Some
of these agents, as alcohol, and  perhaps the  stronger
mineral  acids, produce  their effect by  abstracting a
portion of the water which  held  the albumen in solu- 
Cause of the Coagulation.            S77
 tion, while tan and the  metallic salts unite  with the
 albumen and  form a compound  which is  insoluble  in
 water, and consequently  separates from the fluid, thus
 producing an  effect,  which  should rather be  styled
 precipitation than coagulation.
   Albumen which has  been coagulated by heat, to
 which  I shall at present confine my remarks, differs  in
 many respects from albumen before it has undergone
 this  change.   Besides its conversion  from the fluid to
 the  solid  form, many of its  physical properties are
 altered, and it is differently acted upon  by  chemical
 re-agents, especially by water, in which it is no longer
 soluble.  The efficient cause  of the coagulation  of
 albumen  is a  question that  has  been frequently  dis-
 cussed, but  hitherto, I  conceive, without much success.
 We are informed that  the specific gravity of albumen
 is not affected  by the process, so that we  may conclude
 it does not depend upon condensation ; nothing is added
 to it, and nothing is abstracted from it;  for  although
 Scheele endeavoured to prove that there was a fixation
 of the matter of heat, and Fourcroy, in his vague way,
 attributes it to the absorption of oxygen,  we do  not
 find  that there  is any  foundation for  this opinion.
 We learn indeed from the experiments of Carradori,
 that  the coagulation takes place  as readily when the
 contact of air  is prevented,  as  when the  albumen is
 exposed to the atmosphere ; and  he likewise informs
 us that  the  substance  experiences no  change of bulk
 during  the operation.*  We  can only, therefore,  ac-
 count for it upon the supposition of some change which
 the figure or nature of  its particles have  experienced,
 by which their relation to each other  is altered, with-
 out their being brought nearer together, or, as far as
we can  perceive,  being arranged in any specific manner
analogous to organization.   But we  are  unable to

                 * Ann. Chim, t. xxix.
           48 
578
Clvemical Properties of Serum.
explain what is the nature of this new relation, or what
are the means by which it is effected.
  Dr.  Thomson supposes that the process of coagula-
tion is  analogous to the  change  which takes  place in a
solution of silicated  potash, when it  is saturated with
muriatic  acid, where the acid  gradually detaches  the
potesh from the silex, which being thus left at liberty,
unites  with a portion of  the  water and forms a  gelati-
nous mass.*   But it  may be objected to Dr. Thomson's
hypothesis, that the  case he adduces is one of an inter-
change of chemical  elements,  which in fact produces
a precipitation,  but  which is brought  about  so slowly,
that the  precipitated body becomes united to a portion
of water, instead of being thrown down separately, as
it would  be  under ordinary  circumstances.  With re-
spect to albumen, however,  we have no evidence that
any chemical change takes place among its constituent
parts, or that any thing analogous to precipitation exists.
  Mr. Brande employs a  method  of explaining  the
phenomenon which is somewhat different.  He regards
liquid  albumen as a solution of solid albumen in alkali,
and  upon this principle  he  endeavours to show  how
the action of the galvanic apparatus, of alcohol, and of
acids,  coagulate albumen  by abstracting  the  alkali.!
But  I  think I have proved  by direct experiment, that
the  quantity of alkali in albumen is much too minute
to retain it  in solution, and that the alkali may  be
neutralized and the  albumen still retain its fluid form ;J
besides I  do  not perceive how  this explanation applies
to the action of caloric.  Upon the whole  I  am  dis-
posed  to regard the  coagulation of albumen by heat as
an effect  entirely sui generis, as one  which at present
we are not able to refer to any  general principle.
  The most important chemical properties of albumen,

        *  System, v. v. p. 409.
        t Phil. Trans, for 1809, p. 373, et seq.
        X  Med. Chir. Trans, v. ii. p.  173, 174. 
              Chemical Properties of Serum.          379

while in its liquid form, are its solubility in  water, and
the precipitates which it forms with the mineral  acids,
tan, and a variety of metallic salts.  Of the acids,  the
muriatic is supposed to combine with it the most readily,
and is therefore employed as one of the most delicate
tests  of its presence in a substance  where  we suspect
it to exist.  Tan forms with  albumen a dense  precipi-
tate,  of a tough  consistence,  and insoluble in  water.
A variety  of the  metallic salts  precipitate albumen,
and, like the acids, serve as very delicate tests  of its
presence ; of these probably the corrosive sublimate,
or the bichloride of mercury, is the  most delicate, and
at the same time the most discriminative, as it appears
to have no action  upon any other of the animal sub-
stances which enter into the composition of the albu-
minous fluids.
  The chemical  relations of coagulated albumen, as I
have already remarked, differ materially from those of
this substance before  coagulation.  It then becomes
completely insoluble in water, unless by heating  the
water under strong compression it be raised to a tem-
perature considerably above the boiling point, and then
it would appear that the albumen is rather decomposed
than dissolved.  Coagulated albumen is  partially solu-
ble in sulphuric acid,  but one of its most  interesting
chemical relations is that which  was described by Mr.
Hatchett, where he found that by digesting it for some
time in diluted nitric acid, it is  converted into a sub-
stance which possesses the physical and  chemical pro-
perties of jelly.   If the nitric acid be applied in a con-
centrated state, and the action be assisted by heat,  the
albumen is dissolved,  and the fluid assumes a yellow
colour,  which is  changed into a  deep orange  by  the
addition of ammonia, a change which may be employed
as a test of the presence of albumen in the solution.*

  * Phil. Trans, for 1800, p. 385 ;  for a good view of the  chemi-
cal relations of albumen, both in its uncoagulated and in its coagu-
lated state, see Thomson's System, v. iv. p. 406. 
380         Serosity.'—-Does not contain Jelly.

The caustic mineral alkalies  act  readily  upon  solid
albumen, and  form with  it a saponaceous fluid, which
may be substituted  for some of the coarser  kinds of
soap in various manufacturing processes.

                    § 6.   Serosity.

  The portion of the serum which remains  fluid  after
the albumen has been coagulated by heat, and which
may be obtained either by washing the coagulum with
water, or  by  simply suffering  the  fluid part  to  drain
from  it,  is  called the serosity.  Compared  with the
other constituents of the blood,  it exists only in  small
quantity, and  is generally so connected with the  albu-
men,  that  it  was some  time before it attracted any
attention;  and partly on this account, and partly  from
its being a  compound substance, consisting  of several
ingredients, it  was not until very lately that any correct
notions were  entertained  respecting it.  Its existence
as a substance  distinct from the  albumen  appears to
have been  first announced by Butt, in a thesis published
at Edinburgh  in 17G0;* its properties were still further
developed   by Cullen in  his  " Institutions,"! and  it
afterwards became the subject of more minute chemical
examination in  France,  by Fourcroy and Vauquelin,|
and by Parmentier  and  Deyeux.§  The most impor-
tant point  which the  French  chemists stated, as the
result  of their experiments, is the discovery  of a quan-
tity of gelatine, or animal jelly, in the  serosity, which
was said to constitute the bulk of the  animal matter
contained  in it,  and to which  it owed  its specific  pro-
perties.  The account  which was given of this sub-
stance, especially by Parmentier and Deyeux, was so
much  in  detail, and  altogether bore  so  much the

  * De Spontanea Separatione Sanguinis, p. 53, et seq.
  t § 247—253.
  X Ann. Chim. t. vi. p.  181 ; and  t. vii. p. 157.
  § Journ. de Phys. t. xliv. p. 439, 9. 
Uncoagnlable Matter.              381
appearance of accuracy, that every one acquiesced in
their statement, and  not  only  was  jelly always con-
sidered by systematic chemists to be one  of  the con-
stituents of the blood, but means were pointed out  for
ascertaining its  proportion, and  many  important phy-
siological  speculations were derived  from its supposed
agency in the animal ceconomy.*
  During a course of experiments on the nature of  the
animal  fluids, in which  I was  engaged in the  years
1805 and liJOfi, I examined  the serosity of the blood,
but was unable  to detect the smallest quantity of jelly
in it,  or in any  other of the albuminous fluids, so that
I was led to conclude that jelly never exists as a consti-
tuent of the blood.!   This discovery  has been since am-
ply confirmed by Prof. Berzelius, Dr. Marcet, and jfylr.
Brande, so that notwithstanding  the  high authority
and the weight of experiment  by which the contrary
opinion appeared to be supported,  we may certainly
decide  that  the blood  contains no  gelatine.   At  the
same time, however, that I made  the above experi-
ments,  I found that the  serosity contains a quantity of
animal  matter, and that this  matter is not albumen,  but
it was  difficult  to  ascertain  any other than  negative
characters for it, as it is always united with a quantity
of soda, and with a variety  of other salts, from which
I know of no method of separating it, without its being,
at the same time, decomposed.   To this substance  Dr.
Marcet has applied the  name of muco-extractive mat-
ter ;! I have preferred styling it the uncoagulable mat-
ter of  the  blood,  as a term expressive  of  its most
characteristic and  distinctive  property.  So  far as  I
have been able  to ascertain  its  nature, it is not coagu-

  * Sprengel, a writer of extensive information, and generally of
great accuracy, describes the jelly of the  blood in the following
terms; "namoue gelatina, quam continet (serum) in frigore dun-
taxat coit, nequaquam vero in aestu."  Inst. Med. t. i. p. 381.
  t Med. Chir. Trans, v. i. p. 71, et seq.
  X Ibid. v. ii. p. 364. 
 382              Opinion of Brande.
     t
 lable by heat, or by any other means; it is not affected
 by corrosive sublimate, or by tan,  which are the ap-
 propriate tests  of  albumen  and of jelly respectively,
 but it is copiously  precipitated by  the muriate of tin,
 and still more  so by the acetate of lead.  These re-
 agents  have indeed been supposed  to act rather upon
 the salts contained in  the serosity than upon the ani-
 mal matter, but the presence of this latter may be un-
 exceptionably indicated by  nitrate of silver;  this does
 not produce any immediate change  upon it, and if  it
 be kept in  the  dark, remains for a  long  time without
 alteration,  but upon exposure to light, communicates
 to it a black colour, as it does to animal  matter gene-
 rally.
   Although, I think,  there is sufficient  proof of the
 existence of this  peculiar  substance in  the  serosity,
 and of  its being a proximate animal principle different
 from any other  of the constituents of the blood, yet a
 contrary opinion has been maintained by Mr. Brande.
 Mr. Brande principally  resting upon  the fact,  that
 when the serosity is exposed to the  action of the gal-
 vanic apparatus, a  quantity of coagulum, apparently
 similar  to  albumen, is collected  round the  negative
 wire, supposes  the animal  matter in this part of the
blood to be  merely albumen,  held  in  solution by an
 alkali   But  1  think,  from the manner in which he
 performed  his experiment,  it will be found,  that the
serosity  upon which  he  operated was in. an impure
state, and that it still contained a quantity of  albumen,
which  was separated  by the action of the apparatus.
Besides, I found by direct experiment,  that if the al-
kali in the  serosity be  neutralized, and  even if there
be an excess of  acid, still there is no tendency to co-
agulation manifested  by  the animal  matter  which  it
contains, under circumstances which would immediate-
ly have produced this effect in an equally  concentrated
 solution of  albumen.
  Prof. Berzelius entertains a different opinion respect- 
Salts of the Blood.-
Experiments of Marcet.
383
ing the nature of the animal  matter in  serosity.  He
says,  'it is clear  that Dr. Marcet's  extractive matter
is the impure  lactate of soda."*  It would seem that
he conceives,  that  a part  of the soda of the  blood,
which had been  supposed by other  physiologists to be
in a caustic state, is in combination with the lactic acid,
and that this salt is united  to a portion of  animal mat-
ter.  I do not,  however,  find that he  has distinctly
stated what  are  the properties of this animal  matter,
which is combined  with the  lactate of soda,  whether
he considers it to be a  portion of the albumen which
remains  attached to it,  or  something of a specific  na-
ture.   Although,  therefore,  we  may admit, upon  his
authority,  the  existence of the  lactic  acid, or of the
lactate of  soda in the  blood, I do not think  that this
affords any objection to  the proofs that have been  ad-
duced by Dr. Marcet  and myself of the uncoagulable
matter as forming one of its essential constituents.
   The only remaining  ingredients  of the blood are
the  various salts that are found in it, which, although
they  might in one  sense be  regarded as extraneous
substances, yet  they are so constantly present, and so
nearly in the same proportion under all circumstances,
that  we must  regard them as an essential part  of it.
They appear to  have  been first  distinctly noticed by
Guglielmini;! they were examined  with considerable
skill  and  accuracy  by  Rouelle,^ and since his  time
have   been frequently  made  the subject of examina-
tion,  but for the  latest  and  most correct  account of
them we are indebted to Dr. Marcet and Prof. Berze-
lius.
   Dr. Marcet, after coagulating the albumen and wash-
ing out the serosity  from it, evaporated the solutit n

  * Med. Chir. Trans, v. iii. p. 231 ; Progress of Animal Chem.
p. 16.
  t Opera, 1. ii. de Sanguinis Natura, sect. 52.
  X Journ. de Medecine, t. xlvi. p. 65, et seq. (1776.) 
§84                Use of the Salts.

thus obtained, and incinerated the residuum, by which
means he  obtained  the  saline  matter in a  separate
state; it was found to amount  to rather  more  than 9
grains in  1000  grains  of serum.   Of these  9 grains
about 6i were muriate  of soda, combined with a small
quantity of muriate of  potash,  about li of the subcar-
bonate of  soda,  with  minute quantities of the sulphate
of potash, and the  phosphates  of  lime, iron, and mag-
nesia.*   There  is  reason  to suppose  that the soda
which Dr.  Marcet obtained  in the  state of  a subcar-
bonate exists in  the  blood  in the caustic  state.  Prof.
Berzelius's analysis of  the  salts of  the  serum agrees
with  Dr. Marcet's very  nearly in the quantity of  the
muriates,  which he estimates  at  6 grains from 1000
grains of the serum; the absolute amount of  the soda
we cannot ascertain,  as he  only gives it as  existing in
the form of an impure lactate, and with respect to the
other  salts,  the sulphate  of potash and the  earthy
phosphates,  he supposes  that they did not previously
exist in the blood, but were generated during the pro-
cess of combustion.!  The difference of  opinion which
thus appears between  two chemists of so much emi-
nence renders it very desirable that the experiments
should be  carefully repeated, that the existence of the
lactic acid may  be confirmed,  and a further  examina-
tion made  of the animal  matter which forms the basis
of the serosity.f
   Since  we find that a certain  quantity of saline mat-
ter is constantly present  in the blood, as  well  as in all
the other albuminous  fluids, we  are  naturally led  to

  * Med. Chir. Trans, v. ii. p. 370.
  t Med. Chir. Trans, v.  iii. p. 231.  See also Dr. Prout, on the
salts in albumen ovi, in Phil. Trans, for 1822, p. 385.
  X Sir Everard Home,  in dissecting an aneurysmal tumour, found
a mass of crystals, which were analyzed  by Mr.  Faraday, and are
stated  to have been " sulphate of lime,  with muriate and phos-
phate  of soda," which,  it is added, are " salts usually met with in
the blood."  Phil.  Trans, for  1820, p. 3. 
Ultimate Analysis.
385
conclude, that these salts perform some useful purpose
m the animal  ceconomy, yet  we  are at a loss  to say
what this purpose can be.  It has  been  conjectured
that they may stimulate  the nerves  of  the heart, and
thus  contribute  to  the contraction of its  muscular
fibres,*  that  they may  aid in the operation of the
secreting organs, or  that they may contribute to the
process  of digestion,  but these suppositions are all gra-
tuitous.
   Sulphur has been enumerated among the constituents
of  the blood, but  its existence  would appear  to be
rather problematical.   The  only direct  proofs  that
have been  brought  of  its  presence is the effect  of
serum in tarnishing  silver, when heated in contact
with it, and  the fact mentioned  by  Vogel, that when
serum is beginning to decompose, a gas exhales from
it which has the  property of blackening  the acetate
of lead.!
   Although  the animal  substances  which  enter  into
the  composition of the  blood possess properties, both
chemical and  physical,  which are sufficiently charac-
teristic to distinguish them from  each other, yet they
may all  be  resolved  into  the  same ultimate  elements,
«—carbon, oxygen, hydrogen, and azote.   MM.  Gay
Lussac and  Thenard have endeavoured to ascertain
the  respective proportion  in  which  these elements
exist in albumen, in fibrin, and in jelly,  but the results
can scarcely be regarded as more than approximations
to the truth.   They  are as follows :
                  Albumen/   Fibrin.       Jelly.
       Carbon____52*883____53*36____47*881
       Oxygen.... 23*872.... 19*685.... 27-207

  * Whytt's Works, p. 26.
  t Ann. Chim. t. lxxxvii. p. 215.  Berzelius objects  to the opinion
that sulphur is a  constituent  of the blood, but admits  that it is so
of the albumen ; View of Animal Chemistry, p.  17.  This state-
ment appears so singular, that I suspect  there must  be some inac-
curacy in the translation.
                   49 
38b
Different  States of Blood.
                  Albumen.      Fibrin.      Jelly.
       Hvdrogen..  7*54....   7*021....  7*914
       Azote  .... 15*705.. ..  19*934.... 16*998*

         § 7.   Different States of the Blood.
   We have a few experiments, but those  not very sa-
tisfactory, upon the relative composition  of  the blood
in the  different periods  of life, and in different morbid
conditions of the body.   From these we may be  per-
haps authorized  to  draw the  inference,  that  the  pro-
portion of azote  increases as age  advances,  and as co-
inciding with this opinion, that  there is  more fibrin in
the blood of the adult than in  that of the infant. Four-
croy informs us that he found  the blood of  the fcetus
to contain no fibrin, but in its  stead a gelatinous  sub-
stance, which was not  redened by the  contact of  the
air, and also that there  were no phosphoric salts in it.!
We may probably admit the general fact, but the im-
perfect state of  animal chemistry when   these experi-
ments  were performed  will not allow us to  place  im-
plicit confidence  in  the  statement.   Pathologists have
minutely  described  the  different appearances  which
the blood exhibits in different  diseases, and  the altera-
tion which takes place  in its  physical  properties;  but
we have scarcely a single fact  on which  we can rely,
that indicates  any  decided  difference in  its chemical
constitution-!

  * Thenard, Chim. t. iii. p. 523, 528, 534. Notwithstanding the
ingenuity of the process which was  employed by MM. Gay Lussac
and Thenard, and their known skill  and address  in conducting ex-
periments, it appears that the method which they adopted does not
admit of perfect accuracy, and we accordingly find that every sub-
sequent attempt to discover the ultimate elements  of organized
substances differs more or less from  those that  have preceded it.
For the objections to this process (which appear to be valid) the
essays of Prof. Berzelius in Ann. Phil. v. iv. p. 402, et. sejj. and of
Mr. Daniell  in Children's Thenard, p.  358, et  seq.  may be con-
sulted.
  t Ann. Chim. t. vii. p. 162.
  t Berzelius has mentioned some minute circumstances in which 
Arterial and Venous.
387
   There is, however, one change of great importance,
 which  the  blood experiences in  its  passage  along the
 circulation, that from  the arterial to the venous state.
 The most obvious character which  distinguishes these
 two kinds of blood is  their colour, which,  in the large
 trunks  of  the  systemic arteries, is  a bright scarlet,
 and in  those of the corresponding veins a purplish  red.
 With respect to the other circumstances in which they
 differ, it is commonly stated that venous blood coagu-
 lates more  slowly than arterial, and that it contains less
 fibrin, but that its  specific  gravity is  greater; I  con-
 ceive, however, that- these points are  not very accu-
 rately ascertained.
   Although the relative temperature of  arterial  and
 venous blood is a matter of fact, which one should have
 supposed might have  been  easily learned by  a simple
 experiment, yet it seems to be still undetermined,  at
 least we have  precisely  opposite accounts  given by
 those who have professed to relate the results of their
 own experiments.  Upon the whole the weight of au-
 thority seems to be in  favour  of the  temperature  of
 the  arterial  being greater  than  that  of the venous
 blood.   Dr. Davy, in  his experiments, which are the
 latest and probably the  most correct  that we  possess
 upon the subject, always found  the temperature of the
 blood in the large arteries to be a degree  or a degree
 and a half  higher than in the corresponding veins.*

 human blood differs  from that of the  ox, and from these is led  to
 the conclusion that the latter, notwithstanding the nature of its
 food, contains more azote than the former.   Med. Chir. Trans, v
 iii. p  229.
  * Phil. Trans, for 1814, p. 596, 597. Crawford, p. 273, says
 that the  arterial  blood which he employed in his experiments was
 102°, the venous 99-|', and it may be inferred that this difference
 existed while the two fluids remained in their respective vessels.
 Plenk s*ays, generally, that the temperature of the blood is about
 96°, and that  the arterial  blood is warmer than the venous.  Hy-
 drologia, p. 32.   The results of the experiments of Mr. Coleman
 and Sir A. Cooper were, that the venous blood had a temperature
superior to that of arterial blood; but t his  apparent  discrepancy 
388
Humoral Pathology.
  A still more important difference is the one  which
Dr. Crawford laboured so much to establish, the great-
er capacity for heat of the arterial than of the venous
blood;  this  he estimates  to  be  in the proportion of
eleven and a half to ten, and it was upon this fact that
he founded  his theory of animal heat;  but as  this sub-
ject  will necessarily claim our attention in a subsequent
part of the  work, I shall defer  for the present the
farther consideration of  these experiments, and  of the
value which is to be attached to  them.    The  change
of the blood from its venous to its arterial state being
effected during its passage through the lungs, when it
is exposed to the  action of the atmosphere, is  so inti-
mately connected  with the subject of respiration, that
we shall  be  more  able to estimate the nature and
amount of this change when we have inquired into the
nature of this function.
  Many calculations have been  formed  of  the  total
quantity of blood  in the  body, but  as  the  data  upon
which they have  proceeded are  extremely uncertain,
so the conclusions have  been widely different  and,  of
course, the greatest part of them  remote  from the
truth.  Perhaps, upon the whole, the estimate which
would seem the nearest  approximation is that of  Hal-
ler,  who supposes  that the blood may constitute about
one-fifth  of the weight of  the  adult body,  the pro-
portion of  the fluids being greater in youth and di-
minishing as age advances.   A body weighing one hun-
dred and fifty pounds would  therefore  contain  about
thirty pounds of blood, and of  this it is supposed that
three-fourths or more are in the  veins,  and one-fourth
only in the  arteries.*

may perhaps  be  reconciled by the statement subsequently made,
that although, when the heart was first examined, the blood in the
right ventricle was the warmer of the two, yet after remaining for
some time exposed to the air, the relative temperature of the two
was altered, in consequence, as was supposed, of the greater specir
fie heat of the arterial blood.  Coleman on Respiration, p. 36.   .
  * El.  Phys. v. 1, 3 
Opposed by Baglivi.
389
   The  great importance of the  blood in the animal
ceconomy, as the source whence  all the  parts of the
body derive  their immediate  support,  and new matter
is obtained to repair the waste occasioned by the exer-
cise  of  our various functions,  induced  the earlier phy-
siologists to regard this fluid as the prime seat and di-
rect cause of all diseases.   This doctrine is  tacitly as-
sumed  by  Hippocrates, and  was  strenuously  insisted
upon and greatly amplified by Galen, who laid it down
as the basis of all his elaborate hypotheses, that changes
in the state of the  blood were the cause of every  de-
viation from  health, and likewise, that an original dif-
ference in the  nature of the fluids gives rise to  those
different conditions  of the constitution called  tempe-
raments.  This doctrine,  which obtained the name of
the humoral  pathology, was generally  adopted  by Ga-
len's successors, and maintained its ground, without ev-
er being called in question, for many centuries.   Even
after the chemist had subverted most  of  Galen's dog-
mas, and had  produced a total  revolution in  medical
practice, the blood was  still regarded  as the origin of
diseases, and  they were ascribed to an acid, an alka-
line, a watery, a saline, a  putrid, or some other imag-
inary condition of the fluids.   The mathematical phy-
siologists were likewise, for the most part, humoralists,
and  ascribed diseases  to some change  in  the condition
of the  particles of  the   blood, connected with their
weight, size, viscidity, or  other qualities, which  might
be supposed to affect their motion along the vessels.
   The  first regular Opposition which was  made to the
humoral pathology was  by Baglivi, who maintained, in
a very unequivocal manner, that disease more frequent-
ly originates in the solids  than  in  the fluids, and that
anv change in these latter is to be regarded as an effect
and  not as a cause.*   The premature  death of Baglivi

  * The doctrines of Baglivi will  be found in his treatise " De
Fibra Motrice," a work which exhibits a powerful and original ge-
nius, but still struggling with the shackles of authority. 
390
And Cullen.
prevented him from extending and  maturing his ideas
in the way which might have been expected from the
early promise of his talents,  and it  must  be admitted
•that some of his prominent doctrines  are  fanciful  and
unfounded.   From this time, however, the solids were
more or less regarded  as  influencing the  state  of the
constitution,  until  the humoral  pathology  received  its
most  formidable attack from Cullen.   Since his  time
the doctrine  of  solidism may be considered as forming
the prevailing tenets  of the medical schools, and is the
one to which we usually have recourse for  our explana-
tion of the phenomena of  the animal ceconomy, which
are supposed to be connected with its  morbid changes.
Upon the whole, I conceive, there can be little doubt,
that both our  original temperaments and our subse-
quent diseases are  more affected by the condition and
properties of the muscles and the nerves,  than  by any
physical or chemical  differences  in  the  nature  of the
blood;  yet,  I apprehend,  that the solidists have gone
too far in asserting that there is no original difference
in the state of the fluids.   When we consider the vari-
ous sources from which the chyle is derived, we might
rather suppose  that  it would vary in  its properties in
different cases,  than  that  it should possess a constant
uniformity, nor are we in possession of any experiments
sufficiently decisive to authorize us in asserting that this
absolute uniformity exists.   This question will,  how-
ever,  be discussed more  fully when  we come to the
functions of digestion and assimilation.
                                41
    § 8. Successive discoveries respecting  the Blood.

   From the great  number  of individuals who  have
treated  of the  blood,  pathologists, physiologists,  and
chemists, and from the erroneous opinions which were
so long entertained respecting it, it necessarily  follows
that very different accounts  have  been given  of the
nature of its component parts, and that the same sub- 
History of Opinions.  Galen.
391
stance has frequently received different denominations.
It will therefore be desirable  to give a brief sketch of
what may be called  the natural  history of the blood,
to notice the  successive  discoveries that  have  been
made concerning  it,  and  to point  out  the differences
that have existed in  the opinions of some of  our most
distinguished writers on this  subject.*  It will not  be
requisite for our present purpose to trace the progress
of opinion  beyond  the period of  Galen;  more espe-
cially, as there is some reason to conclude that his doc-
trines were fundamentally the same with  those of his
predecessors.  He supposed that  the blood essentially
consisted of four parts, to which jie gave the  names of
gore  or blood properly  so called,  phlegm,  bile, and
black bile.!  It is  not very easy  to  determine  what
substances he intended to designate under these terms,
nor,  except as  a matter of mere curiosity, is it a ques-
tion  of  any importance, as we know that his opinions
are erroneous.  It is  probable,  however,  that  under
the  denomination of  a<^«, which  has been translated
cruor or sanguis,  he proposed to designate the crassa-
mentum or clot,  that  the term  (pteyp* was  applied to
the serum,  and that  of black  bile  to the red globules
at the lower part of the clot,  which, in consequence of
being secluded from the air,  had  acquired a dark co-
lour.   With respect  to the mm °r  bile, as one of the
constituents of the blood, it seems probable that  its ex-
istence  was assumed,  rather because this substance was
separated by the liver, and was therefore supposed to
have been  previously  in  the  blood,  than  from  there
being any distinct part to which  the name  could be
appropriated.

  * I  shall here beg leave to refer to an essay published in  the
first volume of the Med. Chir. Trans., where some points respect-
ing the natural  history of the blood are discussed more at large
than is consistent with the nature of the present work.
  t For a learned account of the opinions of the ancients and the
earlier of the moderns respecting  the constitution of the blood, I
may refer to an essay by Martine,  Ed. Med. Essays, vol. ii. p. 67. 
 392              Malpighi.—Senuc.

   Erroneous as these opinions were it does not appear
 that  any material correction of them took place until
 the time of Hcirvey, who,  about the middle of the
 seventeenth century, described the spontaneous separa-
 tion of the blood into the crassamentum and the serum.*
 He is also supposed to have been  the first  who gave
 an account of the coagulation of the albumen  by  heat,
 but I conceive that his claim to the discovery is very
 dubious, and am more disposed to  give the merit of  it
 to Lower, who describes  it  in a  much  more  correct
 and unequivocal manner.!  At the same time Malpighi
 materially advanced our knowledge respecting  the na-
 ture of  the  crassamentum, which  he found to consist
 of a white fibrous substance,  united to a red colouring
 matter; he also saw the red  particles, which were af-
 terwards so  minutely examined by Leeuwenhoek, and
 he likewise, to a certain extent, understood the nature
 of the buffy coat which forms  upon  the  blood drawn
 during inflammatory fever.   I have already had  occa-
 sion to  give  an  account  of  the fanciful  speculations
 whicj^ Leeuwenhoek  formed respecting  the red glo-
 bules, as well as of the discovery of iron in the blood,
 and the discussion respecting its state of combination,
 and the effect  which it has in producing the red colour
 of the blood.   After  much  discussion respecting the
 structure of  the red particles,  Dr. Young appears to
 have  at length decided this point by showing that the
 colour of the  blood  is produced  by a vesicle which
surrounds a colourless  globule, while the still later ob-
servations of Mr. Bauer, to which, may be added those
of MM. Prevost and  Dumas, render it probable that
these  central globules  compose the fibrin.
  We are indebted to Senac for some advance in our
knowledge of  the serum,  which he distinctly remarks
as being similar to the white of the egg,  and, at the
same  time, points  out  the circumstances in which it
* De Generatio, Ex. 52.
t De Corde, p. 6. 
Jelly of the Blood.
39a
 iiffers from jelly.  As far as I have been able to learn,
it was he who brought into general use the terms se-
rosity and coagulable lymph,  the first being applied to
the serum generally, and  the latter to the crassamen-
tum, the simple  term lymph having been before given
to the serum.   About the  middle  of  the last century
there was very considerable confusion in the names ap-
plied  to the different  parts of the blood,  partly from
imperfect notions of the substances that  were described,
and  partly  from  different  writers describing the same
substance under  different names, or applying the same
name to different substances.   This was the case with
the word serosity,* which was  first applied to the se-
rum at large, but was afterwards restricted by Cullen
to that part of  it which is not coagulated by heat.!
Cullen appears  to have been  the first  who introduced
the term gluten,! as  applied  to what had been before
called  by  Senac the  coagulable lymph, and  by Gug-
lielmini, with more propriety, the fibre  of the blood.
   It was about this  time that we first hear of the jelly
or gelatine  of the blood, but both the terms employed,
and the properties by which it was designated, are so
vague, that it is  impossible  to draw any correct conclu-
sion from them as to what  the writers intended to de-

  * The earliest work in which  I have met with the term " sero-
site" is  in an essay of Lemery's in  Mem. Acad, for 1729, on the
Action of Borax on  the  Animal Fluids.   It was applied by him to
the serum; it  was  used in the same sense by  Senac and by Rou-
elle; Journ. de Med. t.  xl. p. 68,  1773.  By some of the French
physiologists it is applied to the different species of dropsical fluids,
or any aqueous secretion or excretion from the blood;  see an ela-
borate  article,  " Serosite"," by M.  Villerme, in Diet,  des Scien.
Med.
  t There has been the  same diversity in the use of the word cru-
or; the ancients appear to have understood by it the  red blood
generally, and it is used in this sense by Guglielmini, de Sang. §
44; Haller, El. Phys. v. 2. 8, 9, and Cullen, Inst. § 249,  apply it to
the crassamentum, while Blumenbach restricts it to the red globules;
Tnst. by Elliotson, p. 6.
  t Institutions § 4. c. ii
               50 
394
Jelly of the Blood.
scribe.   The jelly of the blood was, however, in the
year 1790, explicitly announced by  MM.  Fourcroy and
 Vauquelin,  and  four years afterwards  a  very detailed
account of  it was given  by MM. Parmentier arid Dey-
eux,  in which  the method of  procuring  it and its dis-
tinctive properties were  laid  down with a degree  of
minuteness that  appeared to remove all  doubt on the
subject.  I  have  had occasion, however, to point out
the  error that  has prevailed on this subject, and, at the
same time, to observe,  that although  we can  have no
doubt about the non-existence  of jelly  in the serosity,
yet we have been unable to ascertain exactly  what is
the nature  of the animal matter which enters  into its
composition.*

  * A very  interesting series of observations and experiments
have been lately made upon the blood by MM. Prevost and Dumas,
which present us  with an idea  of its nature and  constitution that
is, in some respects, different from the  one generally  adopted.
They regard the blood as essentially composed of serum, holding
in suspension a quantity of red particles, which consist of central
colourless globules enclosed in a coloured vesicle.  When the fluid
is drawn from the vessels, the central globules, in consequence, as
it may be inferred,  of the  loss of their envelope, are attracted
together, and disposed to arrange  themselves in lines  or fibres,
thus forming the basis of the clot or crassamentum.  These fibres
mechanically entangle in the network which they form  a quantity
 of the serum and of  the colouring matter, which, by simple drain-
ing, or by sufficient ablution in water, may be removed from them.
What we then procure is pure fibrin ; they therefore identify this
substance with the central globule, and the clot generally with the
 entire particle.  1 may observe that Berzelius always  considers
 the fibrin and the  red globule's as distinct proximate principles ;
 Progress of  Animal Chem. p.  16, 23, 46.   The  colouring matter
is said to be  a compound  of a  peculiar animal substance and the
 peroxide of iron :  water possesses the property of breaking down
 these vesicles and detaching them from their nuclei, but does not
 dissolve them. The authors do not appear to  have examined the
 nature of this animal matter, nor to  have made any  particular
 observations upon the state  or quantity of the iron. They have
 not entered  into any detail of the chemical relations of the albu-
 men, they only state that various re-agents act upon it in the same
 manner as upon fibrin.  Tbe existence of  the uncoagulable matter
 i-s recognized and  is characterized as a substance soluble both in 
Conclusion.
395
   The general conclusions that we may form respect-
ing the nature of  the blood are, that  it is a compound
fluid, consisting of several ingredients  of various phy-
sical  and chemical  properties,  dissolved,  or at  least
suspended, in a large quantity of water.  Of these the
fibrin  and the  colouring  matter  are disposed to unite,
to separate partially from the water, and  to form the
crassamentum or clot, to  which the iron is  also  attach-
ed.   The albumen,  the  uncoagulable  matter, and the
salts,  remain in  a state  of solution in  the water, and
compose the serum; by  heat the  albumen is rendered
solid,  and  may, in  this  way,  be  detached  from the
serosity, which consists of a portion  of  water holding
in solution  the uncoagulable matter and the salts.   By

water and in alcohol, and precipitated  by the  salts of lead ; they
suppose, with Berzelius, that  it is combined with lactate of soda.
  But the most important part of the researches of these gentlemen
consists in some very valuable experiments upon the proportional
quantity of globules contained in  the  blood of different kinds of
animals, and  of different parts of the sanguiferous  system  in the
same animal.  As they appear to bear an exact  ratio with the tem-
perature of the  animal,  1 shall defer giving a particular account of
them until we arrive at the subject of animal  heat.  I shall only
anticipate  so far as to state, that the higher is the  natural tempe-
rature of the animal, the greater, is the proportion of particles in
the blood, and that arterial contains a greater proportion of them
than venous  blood.  They afterwards entered into  a very curious
investigation respecting the changes which the  blood experiences
in animals who have had the  kidneys  extirpated ; the  result was,
that notwithstanding the loss of these organs, the urea was formed
and might be detected  in  the blood; but I shall  postpone the
farther consideration of this  subject to the chapter on  secretion.
Ann. Chim et Phys. t. xxiii p. 50, et seq. and p. 90, et seq.
  The authors do not refer to any  of Sir Everard  Home's  papers
on the  blood, a circumstance  which is to  be regretted, as it would
have been interesting to have learned how far their microscopical
observations agreed with those of Mr. Bauer   We may, however,
remark upon the coincidence between their account of the fibrin
and Mr. Bauer's description  of the origin  of the muscular fibre.
It would scarcely be supposed, from the  perusal of these papers,
that many of the  most  curious particulars respecting the globules
of the  blood which they have detailed,  had  been  observed long
before  by Hewson. 
S9b'
Conclusion.
slow evaporation part of the salts may be procured in
the crystalline form, but  the whole of the saline mat-
ter can only be obtained by  calcining the residuum
after evaporation, when the animal matter is consumed,
and the neutral  and earthy salts left behind, although
probably in a different state of combination from what
they originally possessed. 
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 Lerminier, in Diet, des Scien. Med.
 Linnaeus, Philosophia Botanica   -
London Medical and Physical Journal  -
Lower de  Corde      -
Ludwig, Scrip. Neur.  -
                              M.

 Magendie, in Ann. de Chim. et Phys. t. xxiii.
 --------, in Quart. Journ. v. iv.
 ---*----, Journal de Physiologie
 --------, Physiologie     -
 Male, in Edinburgh Medical Journal, v. ix.
 Malpighi, Opera      -
 Manchester Memoirs (2d edit.)   ...
 Mangetus, Bibliotheca Anatomica
 Marcet, in Med. Chir. Trans, v. ii. iii.
 ------on Calculous Disorders   -
 Marshall on the Anatomy of the Brain
 Martin, in Edin. Med. Essays, v. ii.
 Mayo's Anatomical and Physical Commentary
 Medical and Physical Journal    ...
 Medical Observations and Enquiries (4th edit.)
 Medical Repositorj'   -
 Medico-Chirurgical Transactions
 Memoires de I'Academie Royale des Sciences
 Menghini, in Bonon. Comment, t. ii.
Monro, (Primus) Anatomy of the Bones and Nerves.
------(Secundus) on the Nervous System  -
.----------------on Fishes    -
Par.  1815-
     Lond.
     Haye
 Lugd. Bat.
 Lugd. Bat.
7, for 1764.
     Lond.
       Par.
     Lond.
Vien.
Lond.
Amst.
 Lips.
1819
1729
1708
1719

1798
1812
1720
1755
1799,
1669
1791
-, (Tertius) Outlines of Anatomy
Morgagni, Adversaria Anatomica
--------on the Seats of Diseases by Alexander
Mnraltus, Clavis Medicinae   -
                51
Par,	. 1821
Par.	1816
Lond.	1687
Lond.	1789-
- Genev.	1699
Lond.	1819
Lond.	1815
Lond.	1822-
Lond.	1799-
Lond.	1776-
Lond.	1814-
Lond.	1810-
Par.	1701-
ves. Edin.	1758-
- Edin.	1783
- Edin.	1785
Edin.	1813
Lugd. Bat.	1741
Lond.	1769
- Tigur.	167"
 
102
LrST  OF REFERENCES.
                             N.

Nicholls de Anima Medica.....Lond-  W6
Nicholson's Journal......Load.  1802-
Nysten, Recherches de Physiologie    -     -     -     Par.  1811

                             P.

Paley's Natural Theology.....Lond.  1807
Paris and Fonblanque on Medical Jurisprudence   -   Lond.  1823
Park, in Quart. Journ. v.  i. ii.
Parmentier, in Journal de Physique, t.  xliv.
Parr's Medical Dictionary.....Lond.  1809
Parry on the Arterial Pulse      ...     -   Bath,  1816
-----'s (C. H.) additional Experiments      -     -   Bath,  1819
Philip, Experimental Enquiry (2d edit.)     -     -   Lond.  1818
-----, in Med. Chir. Trans v. xii.
-----, in Phil. Trans, for 1815.
-----, in Quart. Journ. v. xiii. xiv.
Philosophical Transactions of the Royal Society of London.
Plenk, Hydrologia......Vien.  1794
Plinius, Naturalis Historia, a Gronovio      -    Ludg. Bat.  1669
Plouquet, Literatura Medica     ...     -    Tub.  1808-
Porterfield, in Edinburgh Medical Essays, v. i.
----------on the Eye.....Edin.  1759
Prevost, in Ann. de Chim. et Phys. t. xxiii.
------, in Bibliotheque Universale, t. xvii.
Priestley's Experiments on Air   -                  Lond.  1774-
--------------------abridged       -             Brim.  1790
Prochaska de Came Musculari   ...     -    Vien.  1778
---------de Structura Nervorum     -              Vind.  1779
Proust, in Journ. Phys. t. liii.
Prout, in Ann. Phil. v. 14, 15, 16; v. 4, 2d ser.
-----,  in Med. Chir. Trans, v. viii. ix.  xii.
-----,  in Phil. Trans, for 1822.



Quarterly Journal of Science    ....   Lond.  1816-
Quin on Dropsy of the Brain    -                  Lond.  1790

                             R.

Reil de Structura Nervorum     -               Hal. Sax.  1796
Richerand, Elemens de Physiologie (3me edit.)   -    Par.  1804
---------'s Physiology by*De Lys    -    -    -   Lond.  1812
Robinson on the Spleen.....Lond.  1729
Roget, in Suppl. to Encyc. Britan.
Rouelle, in Journal de Medicine, t. xl. xlvi.
Ruysch, Opera.......Ams.  1737 
LIST  OF REFERENCES.                 40.:
s.
 Sabatier, Anatomie......Par. 1781
 -----—, in Mem. Acad. Scien. for 1774.
 Sandifort, Thesaurus......Rot. 1768-
 Saussure, Voyages dans les Alpes     -    -    -    Gen. 1787
 Scarpa de Structura Ossium      -    -    -    -    Lips. 1799
 ------de Nervorum Gangliis    ...    -    Mut. 1779
 ------, Tabulae Neurologicae     ...    -    Tic. 1794
 Scheele's Chemical Essays      -                 Lond. 1788
 Senac, Traite du Coeur.....Par. 1783
 Shaw, in London Medical Journal, v. xlviii. xlix.
 ----,  in Med. Chir. Trans, v. xii.
 ----,  in Quart. Journ.  v. xiii.
 Smith  de Actione Musculari      -                 Edin. 1767
 Soemmering de Acervulo Cerebri, in Ludwig, t. iii.
 ----------de Base Encephali, in Do. t. ii.
 —-------de Corporis  Humani Fabrica    -    -   Traj. 1""94
 Sprengel, Histoire de la Medicine     -              Par. 1815
 --------, Institut. Medicae.....Amst. 1810-
 Spurzheim (et Gall) sur le Systeme Nerveux     -    Par. 1809-
 Stahl,  Theoria Medica  Vera     -                  Hal. 1737
 Steno  de Musculis, in Mangetus, Bibl. Anat.
 Stuart  de Motu et Structura Musculari      -     -   Lond. 1738
 Sydenham, Opera    -              -     -   Lugd. Bat. 1726

                             T.

 Teidemann, in Med. Repos. v. xv.
 ---------, Tabulae Arteriarum  -                  Carls. 1822
 Thenard on Chemical Analysis, by Children      -   Lond. I 819
 -------, Traite (|e  Chimie      -                   Par. 1821
 Thomson's (Dr. J.) Lectures on Inflammation     -   Edm. 1813
 ---------(Dr. T.) System of Chemistry (5th edit.)  Lond. 1817
 -----------------, in Phil. Trans, for It09.
 Thouret, in JouumI de  Physique, t. xxxviii.
 Torre, in  Phil. Trans, for  1765.
 Travers on Diseases of (he Eye  -    -     -     -   Lond. 1820
 Treviranus, in London  Med. Journ.

                             U.

Ure's Dictionary of Chemistry   -                  Lond. 1821
----, in Phil. Trans, for 1822.
Valli, in Journ. de  Phys. t. xii.
Van Sweiten, Comment, in Boerhaave Aphor.     -  L. Bat. 1742- 
104
LIST  OF REFERENCES.
Vauquelin, in Ann. de Chim. t. vi. vii. Ivi. Iviii. Ixxxi.
--------, in Ann. de Chim. et Phys. t. i.
Verschuir de Arter. et Ven. vi Irrit.   -     -    -   Gron. 1766
Vicq. d'Azyr, Traite d'Anatomie      -     -    -    Par- 1786
Villarme, in  Diet, des Scien. Med.
Vogel,  in Ann. de Chim. t. lxxxvii.
-----,  in Ann. de Chim. et Phys. t. vii.

                             W.

Wells,  in Phil. Trans, for 1797
Wenzel, de  Structura Cerebri    -    -     -    -    Tul. 1812
Wlivtt's W-rks.......Edin. 1768
Will;?.  Or>-ra.......Gen. 1776
W.'U'u-'s "(Dr. A ) Fr.-juiry into the Circulation    -   Lond. 1774
-------(jH.m■•-.'; Lectwes on the Bones    -    -   Lond. 1720
-------(Dr. Pi.iiip'l on Febrile Diseases   -    - Winch. 1801
Wm-iow. in  Mfjm. Acad. Scien. for !720.
-------'s Anatomy, by Douglas (5th edit )  -    -   Lond. 1763
Wiseman's Chirurgical Treatises      ...   Lond. 1686
Wollastoo, in Phil. Trans,  for 1C10.
Wood,  in Manchester Mem. v. iii. (2d edit.)
Yelloly, in Med. Chir. Trans, v. i.
Young's Lectures on  Natural Philosophy   -     -   Lond. 1807
........- Medical Literature      -                  Lond. 1813
i 
INDEX-
                                                         PACK
 Adipocire, account of  -       -       -       -       -      122
 ----------natural formation of          -      -      -   124
 Adipose cells, William Hunter's account of    -       -       43
 Air, effect of on the coagulation of the blood     -      -   351
 Albinos, account of            -              -       -       65
 Albinus's remarks on the Epidermis referred to   -           62
 -----------------on Ossification  referred to   -       -       89
 -----------------on the Structure of Membrane  -           22
 Albumen, coagulation of       -                            376
 Albumen of the Blood, account of -       -      -      -   376
 •        the Basis of Membrane       -                      37
 --------, Thenard's analysis of    -       -      -      -    38
 Allen's  hypothesis of Inflammation     ...      340
 Amici's observations on the particles of the blood referred to  365
 Amphibia, account of the Circulation of                     299
 Animal  Spirits, hypothesis of                               201
 Animal  Substances, account of their analysis   -       -      344
 Aristotle, account of his opinions                              3
 Arteries, description of        -                            271
 Articulations, description of       -       -      -           78

                              B.

 Baglivi  opposed the Humoral Pathology       -       -      389
 -------s doctrine of the Action of the Heart referred to  -   312
 Bauer's account of the Blood  -                            373
 --------------of the Muscular Fibre    -      -       -   113
 --------------of the Structure of the Brain  -       -      186
             - of the Structure of the Iris      -      -   145
 Beddoes's hypothesis of muscular contraction referred to      167
Bell (C.)  on the Functions of the  Nerves    -     -       -   225
Bell's (J.) remarks on the supposed Sensibility of Membrane   30
Bellini's doctrine of the action of the Heart referred to   -   312
Bergen  on the Structure of Cellular Substance  referred to      41
Berzelius's account of the Earth of Bones       -      -     85
------------------of the Particles of the Blood              ?6P 
  106                       INDEX.

                                                         PACK
  Berzelius's account of the Salts of the Blood      -      -   384
  ---------------of the Pi-rosity of the Blood      -       383
  Bichat, account of his doctrines in Physiology    -      -    11
     —'s------of the Cellular Texture       -       -        45
  ------------of the Corpus Mueosum   -       -      -    62
  ,------------of Hair       ...       -        72
  ------------of the Pulse       -       -       -      -   323
  ------arrangement of the Membranes        -       -        49
  ----------------------Muscles       -       -      -   117
  ■      remarks on the EpiJermis referred to  -       -        57
 ------———- on the Colour of Muscles -       -      -   117
 -------------on Contractility       -       -       -       141
 -------------on the Relaxation of Muscles     -          137
 -------------on the Structure of Bones     -       -        80
 Birds, account of their Circulation -                         299
 Blane's Experiments on Muscles       -       -       -       130
 -      Hypothesis of Muscular Contraction       -       -    163
 Blood, account  of      -       -       -  ■     -       -       348
 ------Buffy coat of      -      -       -       -           349
 -----  Course  of in the Circulation   -       -       -       272
 ------Difference between Arterial and Venous  -       -    387
 ------Life of the, Hunter's  Hypothesis of   -       -       355
 ------Quantity of in  the body   -                         388
 ------  Spontaneous coagulation of           -       -       348
 Blumenbach's account of Albinos         -      -           67
 ■------------------of  Membrane  -                      27
 -----------Arrangement of the Nervous Functions     -    230
 ------------Estimate of the Period of the  Circulation       287
 ------------Vita Propria, account of   -       -       -    145
 Boerhaave, Account of his doctrines in Physiology    -        8
 ---------'s Account of Membrane        -      -       -    20
 ----------Hypothesis of Inflammation       -      -      338
 Bone, account of  -       -       -       -      -       -    75
 ■----Chemical composition of        ...       35
 ----Diseases  of referred to                                102
 ----Vital properties of                                    101
 Bonn s Remarks on the EpHermis        -       -      -    58
 Bordeu's account of Membrane        -                      44
 Borelli on the action of Muscles   -       -      -          147
-----'s Estimate of the Force of the Heart   -      -      334
--------------------------of Muscular Contraction  -   155
 ------on the Structure of Muscles   ...      108
Bostock's experiments on the  Serosity of the  Blood      -   381
Braconnot's experiments on Muscle referred to        -      121
Brain and Heart, how connected together         -      -   265
---- description of -        -       -      .      .       177
 ---- proportion of in different Animals   -       -       -   228 
INDEX.
407
Brande s experiments on the Coagulation of Albumen         376
■-----------------on the Colouring matter of the Blood   369
r---;-------------on the Serosity of the Blood       -   382
Brodie's Remarks on the action of the Heart referred to      307
Buffon's Remarks on Albinos referred to                      66
Butt's Remarks on the Serosity of the blood      -      -   380

                              C.

Cabanis' Opinion  on the Relation of Irritability and Sensi-
  bility referred to           -      -       -      -      235
Caloric  supposed to be the cause of Contractility  -      -   166
Callus of Bone, account of                                  99
Capacity for Heat of Arterial and Venous Blood  .-      -   387
Capillary Vessels,  Remarks upon their Action        -      316
Carlisle's Account  of Muscle      -      -      -      -   11$
------- Experiments on Muscles     -       - .     -      130
Carson's Remarks on the Motion of the Blood    -      -   328
Cartilages, account of  -       -      _      _      -      54
Cellular Texture, account of            -      -           41
-------Web, Haller's account of                           20
Chemical Hypothesis of Musculai Contractility    -      -   167
--------Sect of Physiologists, account of    -       -      -   5
Cheselden's account of the Structure of Bone referred to      83
Chevalier's Observations on the Epidermis referred to    -    58
Circulation, Account of        -                           264
---------Causes of    -      -       -      -       -   326
---------Comparative Anatomy of the Organs of   -      298
--------— Cause  of                                      272
Clift's Observations on Muscular Action referred to    -      247
Coagulation of Albumen, account of                        376
-------------------- cause  of     -       -      -      377
------------the Blood, account of      -      -       -   348
----■-----------------cause of                          354
Colour  of the Skin, seat of       -       -      -           63
Contractile Functions, general account of      -      -       12
Contractility, account of  -      -       -      -          127
----------cause of -       -      -       -      -      166
----------of the Blood Vessels, remarks upon  -      -   314
----------of the Heart, remarks upon       -      -      306
Contraction, Muscular, account of -                        128
------------------hypotheses of  -       -      -      157
Corpus Mueosum, account of      -      -      -      -    62
Crassamentum, account of                                 356
Croone's observations on the Structure of Muscles referred
   to '     -       -      -      -       -      -      -10b
Cruickshank's remarks on the Epidermis referred to  -       58 
/408
INDEX.
                                                        PAGE
Cullen, account of his opinions in Physiology                   9
-------'s hypothesis of Inflammation   ...      339
--------opposition to the Humoral Pathology    -      -   390
—-----remarks on the Action of the Vessels  -      -      316
               on Membrane     -       -       -      -    35
 Cutis, account of                                           67
 Cuvier's account oi Cellular Texture referred to  -       -    46
 ——— remarks on the Functions of the Nervous System   230
 ---------------on Organization     -                      33

                              D.

 Dalton's experiments on the Earth of Bones referred to         85
 Daniell's Observations on the ultimate Analysis of organized
   Bodies referred to                                       386
 Davy's (Dr. J.)  observations on the Temperature of  the
   Blood       ------       307
 Derivation, effect of upon the Circulation    -            -   327
 Descartes' hypothesis of Animal Spirits, account of   -       201
 --------------------of the Use of the Pineal Gland      -   215
 Diastole of the Heart, account of     -      -      -       288
 Dowler's experiments on the Buffy Coat of .the Blood     -   357
 Duhamel's account of Bone referred to       -      -        80
 ---------hypothesis of the Formation of Bone, account of    97
 Dumas' experiments on  the Blood referred to     -       -   394
 Dumas' remarks on the  organization of Membrane referred
   to   -      -      -       -      -      _      .        33

                              E.

 Earle's observations on the Spine of certain Birds referred
   to   ------      .        80
Elasticity, how different  from Contractility        -       -   133
Electrical hypothesis of ftervous action referred to    -       203
Electricity  supposed to be cause of contractility    -       -    167
Epidermis,  account of -       -      -      -      -        57
Extremities, account of their Mechanism  -       -       -     77

                              F.

Feathers, account of                                        72
Fibre,  Membranous, remarks upon  -       -      -       -    20
-----Muscular, account of    -      -      -      .       105
"~—;-----------circumstances affecting its contractility        169
Fibrin, chemical  properties of            -       -       -    361
------circumstances affecting the coagulation of     -        170
------description of     -       ...          350
       effect of in repairing injuries   -       -       _       359 
l-MDfA.                       409
                                                         PACK
 Fibrin, Thenard's Analysis of     -       -       -       38, 385
 Fibrous Membranes, account of                             49
 Fish, account of their Circulation -       -       -      .   301
 Fleurens' account of his experiments on the Brain    -      222
 Fluids of the Body, remarks upon        -       -      -    15
 Foetal Circulation, account of  -       -       -      -      293
 -----Heart, account  of   -       -       -       -      -   291
 Fontana's account of Membranes      ...       24
 —---------•---of Muscles     -       -       -          113
 ---------------of Nerves   -       -       -      -      188
 Foramen Ovale, account of       -                         294
 Fourcroy's account of Adipocire       -      -      -      123
 ---------remarks on the Blood of the  Foetus referred to    386
 ----------------on the chemical  composition of Nervous
                       Matter     -       -       -      -   186
 ----------------on the Iron in the Blood   -      -      368
 Functions, arrangement of -       -       -       -      .   253
 --------  relative importance of                           259
 Fourcroy's remarks on the Analysis of Animal Substances     346

                              G.

 Gagliardi's account of  Bone referred to       -       -        81
 GahVs account of the  Earth of Bone referred to  -           85
 Galen's description of  the Blood Vessels referred to   -       290
 ------opinions in Physiology, account of                     3
 ■       opinions respecting the Nature of the Blood   -       391
 ------Pathology referred to    -       -       -       -   388
 Gall on the development of the Nervous System      -       180
 ----on the Use of the Cortical part  of the Brain        -    178
 Ganglia, account of    -       -      -       -       -       181
 -------hypothesis concerning the use of        -       -    231
 Gases, effect of upon the Coagulation of the  Blood    -       352
 Gaubius's opinion respecting Membrane referred to       -     38
 Gay-Lussac and Thenard's analysis of Animal Substances       38
 ———--------------- analysis of the Blood   -       -    385
 Gibson's observations on Bone referred to     -       -       102
 Gritanner's hypothesis  of Muscular Contractility referred to   167
 Glisson's remarks on Irritability referred to    -       -       128
 Good's remarks on the Nervous System referred to       -   202
 Gordon's account of  the Corpus Mueosum referred to  -      63
 Guglielmini's observations on the  Salts of the Blood referred
  to   -------      384

                              H

Hair,  account of   -       -       -      -      -       -    72
Hales's experiments on Animal Substances referred to        3J£
                52 
110
INDEX.
                                                        PAGE
Hales's experiments on the Force of the Heart   -      -   336
------observations on the Contraction of Muscles    -      163
Halitus of the Blood, account of          -       -      -   353
Haller's account of Membrane         -       -       -     29, 34
---------------of the Membranes       -       -      -    49
--------------- of the Skin    -       -       -       -       67
------doctrines in Physiology, account of       -      -     9
------idea of the chemical composition of Membrane         34
------hypothesis of Ossification, account of     -      -    89
------ remarks on the Action of the Heart    -       -      312
--------------on the Cellular Texture  -       -      -    42
--------------on the connexion between the muscles and
                 the  nerves      -                         232
--------------on Contractility       ...      128
—-----------on the Contractility of the Arteries      -   235
Hartley's hypothesis of Vibrations, account of -       -      202
Harvey's discovery of the Circulation, account of        -   275
--------opinion  respecting the Blood referred to    -      392
Hastings's experiments on the Contractility of the Arteries    321
Hatchett's account of the chemical composition of Bone       86
____________________________________________of Hair  -    72
--------------------------------------------of Membrane  37
Havers's account of the Structure of Bone referred to    -    81
Heart and Brain, how  connected       ...      265
-----account of  its Contractility        -                  306
-------------of  its Mechanism       -                     284
      beating of,  how produced   -       -      -      277, 292
■-----change of Figure during Contraction    -      -      291
-----description of                                      268
-----remarks upon the Nerves of    -       -      -   243, 303
--------------upon the Sensibility of    -      -      -   303
--------------upon the Size of       -       -      -      291
--------------upon the Use of   -       -      -      -   270
Herissant's account of Bone referred to                       80
Hewson's account of the red Particles  of the Blood      -   364
---------remarks on the Coagulation of the Blood    -  351, 353
----------------on the cause of the  Buffy Coat -      -   358
Hev's remarks on ditto        ....      359
Hippocrates, account of his doctrines in Physiology      -      2
-----------'s opinion  respecting  Membrane referred to        30
Hoffmann, account of his opinions in Physiology  -      -      8
Home's observations on the Coagulation of the Blood  -      361
------------------on the Structure of the Brain       -    187
------opinion respecting Craneology  referred to     -      223
------------- respecting the Use of  the Ventricles of the
                Brain referred to     -       -      -       184
Hewship's  cc&unt tf the Structure of Bone referred  to  -     87 
INDEX.
Ill
                                                         I'At. K
Howship's observations on Ossification -      -      -        92
Humboldt's experiments on Contractility  -       -       -    168
Humoral Pathology, account of       ...       388
Hunter, (John) account of his doctrines in Physiology     -     10
------'s---- experiments  on the Muscularity of the  Ar-
                 teries    -      -      -       -       -    317
-----------remarks on the Coagulation of the Blood   170, 351
-----------on the Action of the Heart -       -       -    309
------------on the red Particles of the Blood      -       365
Hunter (William), his idea of Organization  referred to    -     22
-----'s--------remarks on the Beating of the Heart       358
----------------------on the Cellular Texture      -     43
----------------------on the Epidermis  -      -        59
Hydraulics, principles of applied  to  the Circulation       -    333
Hydrocephalus, state of the  Brain in   -      -      -       218

                              I.

Inflammation, account of  -
——-------, effect of on Membrane  -
Intellectual Functions, remarks upon
Intercostal nerve, account of  -
Involuntary muscular motions how different
Iris, remarks upon its action
Iron in the Blood, observations on the
Irritability, muscular, remarks upon

                              J.

Jelly, one of the constituents of Membrane       -      -    37
---- of the  Blood, remarks upon the  -       -      -       381
----, Thenard's  Analysis of     -       -      -      -    38
Joints, account of                                          78

                              K.

Kater's observations  on the size of the Globules of the
   Blood       ------       .jG7
Keill's estimate of the force of the Heart -      -      -    3.34
------hypothesis of muscular contraction     -      -       160

                   9         L\
Leeuwenhoek's account of the Epidermis referred to     - '    57
----.--------------------- Particles  of  the  Blood  re-
                                ferred  to       -      -    363
.--------------------—-—-■ Muscular Fibre referred to     107
.——-------— observations on the Circulation referred to     278
Legallois' experiments on the Brain referred to       -       221
             -   337
                  29
                  13
                 180
from voluntary    249
                 145
                 368
                 127 
U2
INDEX.
                                                         I'AliJ.
  Legallois' experiments on muscular action referred to     -   246
  Lemery's remarks on the Serosity of the blood referred to   393
  Leucine, account of       -       -      -      -       -   121
  Ligaments, account of -       -       -       -      -       53
  Ligatures on the Blood-vessels, effect of   -      -       -   281
  Linnaeus's distinction of the three kingdoms  of nature re-
   ferred to       ------    56
  Liquor Pericardii, account of  -       -       -      -      290
 Lower performed the operation of Transfusion    -       -   278
 -----'s remarks on the colour of the Blood referred to      372

                              M.

 Madder, effect of upon the Bones  -       -      -           97
 Magendie's observations on the functions of the nerves       224
 Malpighi's account of the Corpus Mueosum referred to    -    62
 -----------------Structure of Bone referred to       -    80
 -------- observations on the Blood referred to      -       392
 -------------------------Circulation  referred to    -   277
 Mammalia, account of their Circulation       -       -       299
 Marcet's experiments  on the Salts of the Blood    -       -   884
 -----------------------Serosity of the Blood    -       381
 Marrow, account of       -----    87
 Martine's remarks on the constitution of the Blood referred
  to       -------   363
 Mechanical Sect of Physiologists, account of  -       -         5
 Meckle's remarks on the Epidermis referred to    -       -    59
 Membrane, chemical composition of   -      -       -        34
 ---------, description of-      -      -       -       -17
 ---------, meaning of the term      -      -       -        19
 ---------, physical properties of -      -      -       -    25
          , ultimate analysis of                              38
 Membranes, account of    -       -      -      -       -    41
 Menghini's experiment on the Iron in the Blood       -      368
Monro's account  of the nerves referred to -      -       -   188
------remarks on the ganglia referred to    -       -       182
Muco-extractive  matter of the Blood     -                 381
Mucous Membrane, account of -      -      -       -       49
Mucus, one of the constituents of Membrane     -       -   38
Muscles, account of    -       -      -      -       -       105
------, chemical composition of  -                         143
Muscular coats, account of     -      -      -       -       n6
■         Contraction, account  of  -      -      -       -   127
      — and Nervous systems, how connected        -      232
Muys's observations on the Muscles referred to   -       -   107 
INDEX.
413
                              N.

  ,._ ..                                                    pAGE
  j\ails, account of      -       -       -      -      -       71
  Nerves, description of           -      -      -      -    179
  ------, observations on their action   ...       225
  ------ of the Heart, remarks upon      -      -      243,  303
  Nervous and Muscular systems, how connected       -       232
  -------Fluid, hypothesis of                               201
  --------Matter, chemical composition of     -      -       190
  --------System, account of      -      -      -      -    175
  "---------------, mode of its action   -      -      -       196
 ---------------, use  of          -      -      -      -    206
 Neurologists, account of  their doctrine        -      -       239

                              O.

 Organization, remarks upon      -      .      _        22, 30
 Osmazome, account of        -       -      -      .       119
 Ossification,  remarks upon        -      -      -      -    88
 Oxygen, supposed to be the cause of Contractility     -       167

                              P.

 Papillae of the skin, account of   -      -      -        67, 69
 Parmentier and  Deyeux's observations on the  Serosity of
   the Blood  referred to          -       -       -      ~    380
 Parry's account of the Pulse referred to      -      -       324
 -------experiments on the  contractility of the arteries re-
          ferred  to            -       -      -      -       318
 Particles of the Blood, account of -      -      -      -    363
 Perception defined     -       -       -      -      -       193
 Paricardium, account of   -       -      -      -      -    290
 Pineal Gland, Descartes' hypothesis concerning       -       214
 Philip's experiments on the Brain, account of            -    221
 -------------------------Contractility of the arteries re-
                             ferred to   -       -      -    320
 ———-------------on Muscular action referred to   -       246
 .------hypothesis of Inflammation        ...    349
 -------remarks on the Functions of the Brain        -      221
 ---------------------Use of the Ganglia        -       -    231
 Physiology, definition of                                     1
 ----------, sketch of the  History of      -       ...      2
 Placenta, account of   -       -      -       -       -       294
 Plenk's remarks on the Halitus of the Blood      -       -    353
 Plexuses of the Nerves, account of            -       -      239
 Pores of the  Skin, account of    -      -       -       -     58
Power lost in Muscular action  -                           148 
414
I N DEX.
                                                        PAGE
Prevost and Dumas' experiments on the Blood    -      -   394
Priestley's experiments on the Blood referred to  -      -   372
____._______________________composition  of animal sub-
                              stances referred to   -   36,345
                     -, remarks upon    -                  345
Prochaska's account of Muscles referred to    -      -       HI
.-----------hypothesis of Muscular contraction   -      -    162
___________remarks on the Minute Structure of the Brain     186
Pulse, account of                                           ~^



Quadrumanous Animals referred to    •  -      -       -     78

                             R.

Reil's observations on the structure of Nerves -       -       190
Relaxation of Muscles, account of  -      -      -       -    135
Retarding causes of the Circulation referred to -       -       332
Richerand's hypothesis of Contractility referred to        -    167
___________remarks on the properties of Membrane   -        26
Roget's observations on  the motions of the Iris   -       -    145
Rolando's experiments on the Brain referred to       -       222
Rouelle's experiments on animal Chemistry referred to   -    344
__________________----- the Blood referred to       -       384
Rutherford's experiments on Bone referred to     -            98
Ruysch's observations on the Brain referred to        -       236

                              S.

Sabatier's remarks on the size of the Ventricles   -       -    285
Salts, their effect on the coagulation of the Blood      -       353
Salts of the Blood, account of      -                         383
Scarpa's account of the  Structure of Bone referred to  -        81
——- remarks on the Nerves referred to       -       -   241
-----------------------------of the Heart referred to     244
Sedatives, mode of their operation        ...   245
Segum's account of the  Skin   -                             70
Senac's account of the action of the Heart -      -       -   306
------opinion respecting the Blood referred to      -      393
------remarks on the Nervou> Functions referred to   -   241
 Sensation, remarks upon the Seat of   -       -       -      209
 Sensibility defined  -       -       -       -      -      -192
---------of Membrane, opinions concerning -      -        29
 -----------Muscles, account of  -       -      -           142
 -----------the Heart, remarks upon        -       -       303
 Sensitive Functions, remarks upon -       -      -       -13 
INDEX.
415
Sensorium Commune, remarks upon   -       -       -      209
Serosity of the Blood, account of  -      -      -      380, 393
Serous Membranes, account of -       -       -       -       49
Serum of the Blood, account of    -      -      -      -   375
Shaw's remarks on the  Functions of the Nerves       -      224
Skin, account of the       -      -      .      .      -    57
Smith's experiments on Contractility referred to      -      169
                      Stin.U'r'.nts referred to    -      -   244
Smyth's remarks on the Structures of the Body       -       16
Scemmering's remarks on the Nerves referred to -      -   188
---;-----------------on the Nervous Functions referred to  229
Solidists, doctrines of, referred to  -      -      -      -   385
Solids of the Body, arrangement of, by Beclard       -       15
Soul, inquiry into the seat of     -      -      -          2i4
Spinal cord, account of -      -      -       .      -      179
Stahl, account of his doctrines in Physiology                   6
----'s---------the Action of the Her*rt      -       -      309
----hypothesis respecting the Nerves referred to       -   181
Steno's account of the muscles referred to     -      -      105
Stimulants, account of     -      .      .      .      -   138
----------, remarks on the  mode of their action       -      244
Structures of the body, arrangements of the      -      -    15
Sulphur in the Blood, remarks upon   ...      385
Sylvius's controversy with Vesalius referred to    -       -   289
Sympathetic powder, account of                           359
Systole of the Heart, account of   -       -      -       -   288

                              T.

Tendons, account of       -      -       -      -      -    53
Thenard's analysis of organized substances    -      -       38
Thenard's ultimate analysis of the Blood  -                 385
Thomson's (Dr. J.) experiments on the contractility of the
                     arteries referred to     -      -      321
------------------hypothesis of Inflammation   -      -   340
----------(Dr. T.) remarks on the coagulation of Albumen  378
Tiedemann's remarks on the Brain referred to       -      179
--------------------------development  of  the Nervous
                             System referred  to       -   181
Tone of Muscles referred to   -      -       -      -      140
Transfusion, account of   -      -      -      -      -   278

                              1;.

IJre's experiments on Animal Analysis referred to -      -   3«i-. 
416
INDEX.
                              V.
                                                         PAGE,
 Valli's hypothesis of Muscular Contraction referred to    -   160
 Valves of the Heart, account of                             278
 Van Sweiten's  remarks on the Sensibility of Membrane re-
   ferred to       ------    3u
 Vascularity, how far connected with organization      -        22
 Vauquelin's analysis of Hair, account of   -       -       -    72
-----------remarks on the Chemical Composition of ner-
                            vous matter referred to    -   271
 -------------------------Colouring Matter of the  Blood
                            referred to -       -       -   371
 Veins, account of                                      277, 323
 Vesalius's remarks on Galen referred to  -       -       -   289
 Verchuir's experiments on the contractility of the arteries
   referred to   -       -      -       -              -       320
 Vessels, sanguiferous, account of  -       -       -       -   313
 Vibrations of the nerves, hypothesis  of -      -       -       202
 Voluntary  motion,  account of     -      -       -       -   198
 ---------  motions  compared to involuntary   -       -       249

                             W.

 Water, its supposed effect upon Membrane        -       -    37
 Wells's remarks on the Colouring Matter  of the Blood -       369
 Wenzel's observations on the  Structure  of the Brain       -   187
 Whytt's remarks on the action of the Heart referred to       310
 ———-----------------connexion between  the  muscular
                         and nervous systems referred to    234
 ----------------------Sensibility of Membrane referred to    29
 Willis's remarks on the  Action of the Heart referred to   -   307
 ---------------------Functions of the Brain referred to     220
 Wilson's remarks on the Circulation       -                  353
 Winslow's remarks on the  contraction of the Muscles   -       131
 -----------------------Epidermis referred to   -       -    57
 Wiseman's remark  on the  Sympathetic Powder referred to    360
 Wood's remarks on the  reparation of bone referred to    -   100

                             Y.

 Yelloly's observations on the Spinal  Cord  referred to      -   186
 Young's observations on the Particles of the Blood  -       -   366
END OF  VOL. I- 
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